Elysium PRO Titles with Abstracts 2018-19


This paper proposes a family of novel flying capacitor transformerless inverters for single-phase

photovoltaic (PV) systems. Each of the new topologies proposed is based on a flying capacitor principle

and requires only four power switches and/or diodes, one capacitor, and a small filter at the output

stage. A simple unipolar sinusoidal pulse width modulation technique is used to modulate the inverter

to minimize the switching loss, output current ripple, and the filter requirements. In general, the main

advantages of the new inverter topologies are: 1) the negative polarity of the PV is directly connected

to the grid, and therefore, no leakage current; 2) reactive power compensation capability; and 3) the

output ac voltage peak is equal to the input dc voltage (unlike neutral-point-clamped and derivative

topologies, which requires twice the magnitude of the peak ac voltage). A complete description of the

operating principle with modulation techniques, design guidelines, and comprehensive comparisons is

presented to reveal the properties and limitations of each topology in detail. Finally, experimental

results of 1-kVA prototypes are presented to prove the concept and theoretical analysis of the proposed

inverter family for practical applications.

EPRO PE -

001

Common-Ground-Type Transformerless Inverters for Single-Phase Solar Photovoltaic

Systems

Transformerless photovoltaic grid-connected inverters have become more and more popular in the field

of distributed photovoltaic power generation systems due to the advantages on high efficiency, low

cost and small size. However, common-mode currents in the transformerless photovoltaic inverters can

result in serious electromagnetic interference problems and safety issues, which will reduce the

reliability of the photovoltaic inverter systems. In this paper, an improved H5 topology, namely H5-D

topology, is proposed, in which a clamping diode is added on the basis of H5 topology to eliminate the

common-mode voltage fluctuation in H5 topology. Further, the simulation results of the H5-D topology

and H5 topology are given and compared by using PSIM software, especially, on the performance of

common-mode currents suppression. Finally, the experimental prototypes of the H5-D topology and

H5 topology are built and tested, the experimental results validate the advantages of the H5-D topology.

The proposed H5-D topology provides a new practical topology for distributed photovoltaic grid-

connected power generation systems.

EPRO PE -

002

An Improved H5 Topology with Low Common-mode Current for Transformerless PV

Grid-connected Inverter


Soft-switching techniques of transformerless photovoltaic grid-connected inverters (TLI) can

significantly reduce switching losses, as well as soften switching processes. Conventional DC-AC soft-

switching configurations proposed by Dr. Divan are invalid in TLIs because of leakage current problem

(LC). In order to develop soft-switching techniques in TLIs, this paper proposes a new soft-switching

configuration and a procedure to guide the invention of soft-switching TLIs. First, this paper proposes

two basic resonance tanks related to DC bus polarities; then uses these basic tanks to elevate four

popular full bridge type TLIs according to the proposed guideline. As a result, four soft-switching TLIs

are gained. Second, this paper picks obtained soft-switching highly efficient and reliable inverter

concept (HERIC) as example to analyze its soft-switching operation principle and performance. As a

consequence, all active switches of the gained soft-switching HERIC circuit are switched under both

of zero-current turn-on and turn-off conditions; the reverse recovery problem of freewheeling diodes

is alleviated owing to the zero-current turn-off of diodes; meanwhile, the common-mode voltage at the

switching frequency scale is still constant. Finally, some experimental results from a 3-kW universal

prototype at 50-kHz switching frequency are provided to verify the effectiveness of main contributions

of this paper.

EPRO PE -

003

A New Soft-Switching Configuration and Its Application in T

transformerless Photovoltaic Grid-Connected Inverters

Transformerless photovoltaic (PV) inverters are more widely adopted due to high efficiency, low cost,

and light weight, etc. Many novel topologies and their corresponding modulation methods have been

proposed, verified, and put into use, solely focusing on active power injection without leakage current

issues. However, some new grid codes require PV inverters to have the ability of injecting reactive

power into the utility for grid support. In order to map the challenge, an improved hybrid modulation

method is proposed and evaluated for one nonisolated H6 topology as an example. With only simple

modification for switching patterns and phase shift for current reference, the variable reactive power

generation ability with zero crossing distortion is achieved, while the common mode voltage is also

eliminated. The operation modes with the improved hybrid modulation approach are presented in detail

and some design considerations are also provided. Extensive results from a 4-kVA prototype along

with the SMPLIS simulation verify the proposed hybrid modulation method.

EPRO PE -

004

An Improved Hybrid Modulation Method for the Single-Phase H6 InverterWith

Reactive Power Compensation


Grid-tied photovoltaic inverters must fulfill several requirements, including high efficiency and

reduced cost and complexity of the overall system. Hence, transformerless operation is advantageous

in order to achieve the prior requirements. Meanwhile, such operation results in several demerits, such

as the dc current component injection into the grid. This component should be effectively mitigated in

order to avoid some impacts, such as the saturation of the transformers in the distribution network. On

the other hand, limiting this component up to few milliamperes is a challenging issue due to the various

measurement errors. Accordingly, different blocking and measurement techniques have been proposed

and studied to overcome this issue, where some demerits are seen behind each technique such as the

implementation complexity, the common-mode voltage problems, and the high filter requirements.

Moreover, none of them measures the dc component directly, but predicts its value using different

approaches. Hence, this letter proposes a new technique to measure this dc current component with

high accuracy using a coupled inductor combined with a small-range Hall effect current sensor in order

to achieve the lowest possible cost with the highest possible accuracy. The proposed technique is

introduced, analyzed, and tested experimentally to verify its principle of operation. Also experimental

measurement of the dc current component using a 5-kVA transformerless grid-tied voltage-source

inverter is introduced with and without the proposed technique in order to validate its operation.

EPRO PE -

005

Coupled-Inductor-Based DC Current Measurement Technique

for Transformerless Grid-Tied Inverters

This paper presents a new diode free freewheeling and common-mode voltage (CMV) clamping

branches for single phase transformerless grid connected photovoltaic (PV) inverter for complete

leakage current elimination and low conduction losses. In the past, various isolation techniques have

been proposed for leakage current elimination in transformerless PV inverters. However, galvanic

isolation only cannot completely eliminate leakage current due to that a resonant path is created by the

switch junction capacitors, which also generate leakage current. The proposed freewheeling branch

consists of four MOSFETs along with a clamping branch, which consists of two MOSFETs and a

capacitor divider. The divider is connected to the DC side of the converter to keep constant CMV in

the freewheeling path. As a result, the improved CMV clamping has been achieved for complete

leakage current elimination. The unipolar sinusoidal pulse width modulation (SPWM) technique and

modified HERIC topology with AC-decoupling for galvanic isolation is adopted for lower conduction

losses. The proposed topology consists of only MOSFET in the freewheeling and clamping path which

provides lower conduction losses compared with diode based topologies. The performances of the

proposed topology in terms of common mode characteristics, leakage current, total harmonic distortion

and conversion efficiency are analyzed and compared with H5, H6, HERIC and HBZBR topologies.

The detail analyses are performed using MATLAB/Simulink and PSIM.

EPRO PE -

006

A high efficiency transformerless PV grid-connected inverter with leakage current

suppression


In this paper, a modified buck–boost grid-connected three-phase photovoltaic inverter is presented. In

the structure of inverter, an inductive dc link is used between the input and output. The merits of the

employed inverter are soft switching and step-up/down conversion without any additional power

converter stage. It is a transformerless inverter with no leakage current issue. Moreover, as a result of

increased switching frequency, it offers output current total harmonic distortion within standard limits.

It uses only one current sensor and there is no electrolytic capacitor in it, which leads to high reliability.

The operating principle is thoroughly explained and a simple control strategy with a new maximum

power point tracking (MPPT) algorithm is proposed. The simulation and experimental results are

provided to verify the behavior of a modified inverter, its control strategy, and the MPPT method.

EPRO PE -

007

A Reliable Three-Phase Transformerless Grid-Connected PV Inverter with Inductive

DC Link

Adding the auxiliary switches to the conventional H-bridge inverter is an effective way to eliminate

the leakage current for transformerless PV systems, such as H5, H6, etc. Inspired by the newly

developed embedded-switch H6 topology, a novel embedded-switch inverter (ESI) is proposed in this

paper for three-phase transformerless PV systems. First, the operation principle and characteristics of

the proposed ESI are analyzed. Second, the common-mode model of the three-phase ESI is established,

based on which the main factors that affect the leakage current are discussed. The finding reveals that

the switching states with conventional modulation strategy result in high-frequency common-mode

voltage, which is the source of leakage current. In order to solve the problem, a new modulation

strategy is presented for ESI to eliminate the high-frequency leakage current. Finally, the time-domain

simulation and the experimental tests are carried out. The results verify the effectiveness of the

proposed solution.

EPRO PE -

008

ESI: A Novel Three-Phase Inverter with Leakage Current Attenuation

for Transformerless PV Systems


In this paper, a new method to calculate the five parameters of the single-diode model of a photovoltaic

cell or panel is presented. This new method takes into account the intrinsic properties of the model

equation and the technique of linear least-squares fitting; so, the computational complexity and costs

are very low. Moreover, the proposed method, named two-step linear least-squares method, is able to

work absolutely blindly with any kind of I-V curve. It does not need initial guesses at all and,

consequently, it is not necessary to know previously any information of any parameter. The proposed

method provides the parameters of the single-diode model just using the coordinates of N points (N ≥

5) of the I-V curve. The results provided by this method in a first stage have the same order of accuracy

of the best documented methods in the field of parameters extraction, but, furthermore, in a second

stage, the best accuracy documented until now is obtained in two important case studies usually used

in the literature as well as in a large-scale I-V curve repository with more than one million of curves.

EPRO PE -

009

Two-Step Linear Least-Squares Method for Photovoltaic Single-Diode Model

Parameters Extraction

A new control approach of integrating a solar photovoltaic (PV) with a battery storage is presented to

a single-phase grid for residential and electric vehicle application. The main purpose of the proposed

work is to feed a continuous power to the grid, thereby enhancing the viability of the battery energy

storage support connected to the system. The charging and discharging of the battery achieve power

leveling and load leveling along with increased reliability of the system. The multifunctional voltage-

source converter acts as an active power filter and performs the harmonics mitigation along with

reactive power compensation. In the proposed system, a unique control is developed for

resynchronization of the grid during reconnection of the grid after the mitigation of a failure. The

overall control of the system is adaptable under various practically occurring situations such as

disconnection of the PV array, the battery, and the grid from the system. The detailed design and control

of the proposed system are presented. The validity of the proposed system is performed through a

laboratory prototype developed for a power rating of 2.2 kW connected to the utility grid. The

performance of the system is found satisfactory under various disturbance, and the recorded results

have been demonstrated.

EPRO PE -

010

Implementation of a Grid-Integrated PV-Battery System for Residential and Electrical

Vehicle Applications


Battery storage controlled by an energy management system (EMS) becomes an enabling technique to

enhance solar farm integration. In this paper, the EMS controls battery storage to shape the fluctuated

photovoltaic (PV) plant output into a relatively constant power and support the peak load. The proposed

integrated design method considers both battery size and EMS impacts on the utility benefits and cost.

The utility benefits include power generation, peak power support, and reduced line losses. The cost

of battery storage is determined by the size and lifetime based on the developed battery models.

Accordingly, the utility revenue change due to the battery storage controlled by EMS can be evaluated.

Therefore, the integrated design of battery size and EMS can be determined by managing the change

of utility revenue to gain economic benefits for the large-scale PV power plant application. Finally, the

lithium-ion phosphate (LiFePO4) battery and lead-acid battery are compared to demonstrate the

proposed method on a utility system model, respectively.

EPRO PE -

011

Integrated Size and Energy Management Design of Battery Storage to Enhance Grid

Integration of Large-Scale PV Power Plants

A grid-connected single-phase transformerless inverter that can operate two serially connected solar

photovoltaic (PV) subarrays at their respective maximum power points while each one of them is

exposed to different atmospheric conditions is proposed in this paper. As two subarrays are connected

in series, the number of serially connected modules within a subarray is reduced to half. Reduction in

the number of serially connected PV modules within a subarray leads to an overall improvement in the

magnitude of power that can be abstracted from a subarray while the modules of the subarray are

exposed to varied atmospheric conditions. The topological structure of the inverter ensures that the

common mode voltage does not contain high-frequency components, thereby reducing the magnitude

of leakage current involved with the solar panels well within the acceptable limit. An in-depth analysis

of the scheme along with the derivation of its small signal model has been carried out. Detailed

simulation studies are performed to verify its effectiveness. A 1-kW laboratory prototype of the scheme

has been fabricated. Detailed experimental validations have been carried out utilizing the prototype to

confirm the viability of the proposed scheme.

EPRO PE -

012

A Grid-Connected Single-Phase Transformerless Inverter Controlling Two

Solar PV Arrays Operating Under Different Atmospheric Conditions


Solar energy has been the most popular source of renewable energy for residential and semicommercial

applications. Fluctuations of solar energy harvested due to atmospheric conditions can be mitigated

through energy storage systems (ESS). Solar energy can also be used to charge electric vehicle batteries

to reduce the dependence on the grid. One of the requirements for a converter for such applications is

to have a reduced number of conversion stages and provide isolation. The Z-source inverter (ZSI)

topology is able to remove multiple stages and achieve voltage boost and dc-ac power conversion in a

single stage. The use of passive components also presents an opportunity to integrate ESS into them.

This paper presents modeling, design, and operation of a modified ZSI integrated with a split primary

isolated battery charger for dc charging of electric vehicle batteries. Simulation and experimental

results have been presented for the proof of concept of the operation of the proposed converter.

EPRO PE -

013

Modeling, Design, Control, and Implementation of a Modified Z-Source

Integrated PV/Grid/EV DC Charger/Inverter

Battery energy storage systems are often adopted to buffer the difference between the intermittent solar

power and the load demand in power grids. The costs of such photovoltaic (PV) battery systems

increase as the required energy storage increases. In this paper, a new configuration comprising the PV

panels, a series dc electric spring (series ES) and a noncritical load is proposed to reduce the battery

storage capacity of dc microgrids that have substantial PV installations. This arrangement forms a PV-

embedded series dc ES (PVES). An optimization method considering the minimization of electricity

bills of the dc microgrids is included to size the storage capacity and to determine the rating of the PV

that are connected to the series ES. Experiments on a 48-V isolated dc grid and simulations on a 400-

kVA grid-connected dc microgrid have been conducted to verify the storage reduction feature of the

PVES. Both sets of results show that the PVES can tackle the intermittency of the solar power with a

smaller storage capacity than that typically required in dc grids with PV installations.

EPRO PE -

014

A Configuration of Storage System for DC Microgrids


This paper proposes a model for planning isolated microgrids. The goal of the proposed model is to

minimize the investment, operational, and total costs of an isolated microgrid through the full

identification of the system configuration. The model designates the optimal type of microgrid, i.e., ac,

dc, or hybrid ac/dc, and the optimal sizing of both the distributed energy resources (DERs) and the

electronic power converters, if needed. To render this planning approach generic, the model

accommodates a wide variety of DERs, including ac and dc generators, capacitors, and energy storage

systems. The detailed operational criteria of each power apparatus are taken into account in order to

provide reliable operational scenarios. As a means of guaranteeing active and reactive power adequacy

in isolated microgrids, the stochastic nature of generation and demand are also considered. The

proposed model was developed analytically as a mixed integer nonlinear problem so that obtaining

solution optima is thus possible with the use of a deterministic branch-and-bound nonlinear solver. The

validity and effectiveness of the new formulation have been demonstrated through several case studies

involving varied load topologies.

EPRO PE -

015

Optimal Configuration of Isolated Hybrid AC/DC Microgrids

In the present, a power decoupling method without additional component is proposed for a dc to single-

phase ac converter, which consists of a flying capacitor dc/dc converter (FCC) and the voltage source

inverter (VSI). In particular, a small flying capacitor in the FCC is used for both a boost operation and

a double-line-frequency power ripple reduction. Thus, the dc-link capacitor value can be minimized in

order to avoid the use of a large electrolytic capacitor. In addition, component design, of, e.g., the boost

inductor and the flying capacitor, is clarified when the proposed control is applied. Experiments were

carried out using a 1.5-kW prototype in order to verify the validity of the proposed control. The

experimental results revealed that the use of the proposed control reduced the dc-link voltage ripple by

74.5%, and the total harmonic distortion (THD) of the inverter output current was less than 5%.

Moreover, a maximum system efficiency of 95.4% was achieved at a load of 1.1 kW. Finally, the high

power density design is evaluated by the Pareto front optimization. The power densities of three power

decoupling topologies, such as a boost topology, a buck topology, and the proposed topology are

compared. As a result, the proposed topology achieves the highest power density (5.3 kW/dm3) among

the topologies considered herein.

EPRO PE -

016

Development of DC to Single-Phase AC Voltage Source Inverter with

Active Power Decoupling Based on Flying Capacitor DC/DC Converter


To enhance the redundancy and reliability for a distributed generation system, a grid-tied photovoltaic

(PV) generation system based on series-connected module-integrated inverters (SC-MIIs) is presented

in this paper. In the grid-tied SC-MII system, each PV panel is interfaced with an MII with independent

maximum power point tracking to harvest maximum solar energy. The outputs of MIIs are at ac line

frequency and are connected in series to fulfill the voltage requirement in the utility grid. Since the

high step-up power conversion stage in the conventional microinverter is avoided, the grid-tied SC-

MII system is easier to implement and features high efficiency. Meanwhile, a distributed control

strategy for SC-MIIs is proposed, in which the active power sharing among the MIIs depends on the

individual maximum power available from PV panels, while the reactive power of the system can be

regulated by any of the MIIs according to the utility grid command. Simulation and experimental

results verify the feasibility and effectiveness of the proposed system and its corresponding control

strategy.

EPRO PE -

017

A Distributed Power Control of Series-Connected Module-Integrated Inverters

for PV Grid-Tied Applications

A multiphase quasi-Z-source (qZS) dc-dc converter was proposed for distributed energy generation

applications. It contains single-switch qZS isolated dc-dc cells with a voltage doubler rectifier. These

cells are connected in parallel at the input side and in series at the output side to increase the dc voltage

gain. A dc voltage blocking capacitor in series with the isolation transformer results in resonance that

could be utilized for soft-switching. Two design approaches were proposed: considering phase

shedding dependent on the input voltage and without it. The former targets wide input voltage range

applications, while the latter is better suited for high input current applications. An experimental

prototype rated for 300 W was tested with two types of isolation transformers designed according to

the two presented approaches. It could be used as a PV module integrated converter with wide input

voltage regulation range. The experimental results prove efficiency improvement from the phase

shedding. Resonance frequency variations caused by the utilization of the multilayer ceramic

capacitors and their possible influence on switching losses are discussed.

EPRO PE -

018

Multiphase Quasi-Z-Source DC–DC Converters for Residential Distributed

Generation Systems


Multi-inverter systems have been widely used for grid-connected large-scale centralized photovoltaic

(LSCPV) plants. However, the problem of how time delays affect the stability of digitally controlled

grid-connected LSCPV plants with multi-inverter systems has not been investigated sufficiently. This

paper models a grid-connected LSCPV system as a cascade system and conducts a systematic study of

the relationship between the time delay and the stability of a grid-connected LSCPV system. The

analysis intuitively reveals the influence of the time delay on the stability of the grid-connected LSCPV

system. The impact of the time delay on the stability range of the number of grid-connected inverters

in LSCPV plants is discussed for the first time, and the stability range for a specific time delay is

obtained from the root locus. In addition, considering the damping performance is negatively affected

by the time delay, an improved capacitor-current-feedback active damping method is proposed to

reduce the effects of the delay on the damping region and the robustness against variations in the grid

impedance. Simulations and experimental results are presented to validate the theoretical analysis and

the effectiveness of the proposed delay compensation method.

EPRO PE -

019

Modeling and Analysis of a Digitally Controlled Grid-Connected Large-Scale

Centralized PV System

A single phase grid connected transformerless photovoltaic (PV) inverter, which can operate either in

buck or in boost mode, and can extract maximum power simultaneously from two serially connected

subarrays while each of the subarray is facing different environmental conditions, is presented in this

paper. As the inverter can operate in buck as well as in boost mode, depending on the requirement, the

constraint on the minimum number of serially connected solar PV modules that is required to form a

subarray is greatly reduced. As a result, power yield from each of the subarray increases when they are

exposed to different environmental conditions. The topological configuration of the inverter and its

control strategy are designed so that the high-frequency components are not present in the common

mode voltage, thereby restricting the magnitude of the leakage current associated with the PV arrays

within the specified limit. Further, high operating efficiency is achieved throughout its operating range.

A detailed analysis of the system leading to the development of its mathematical model is carried out.

The viability of the scheme is confirmed by performing detailed simulation studies. A 1.5 kW

laboratory prototype is developed, and detailed experimental studies are carried out to corroborate the

validity of the scheme.

EPRO PE -

020

A Buck and Boost Based Grid Connected PV Inverter Maximizing Power Yield From

Two PV Arrays in Mismatched Environmental Conditions


The growth in installed solar photovoltaic (PV) capacity and the ever-increasing power demand due to

the use of energy-hungry appliances have caused voltage issues. In this paper, a hierarchical dispatch

strategy is proposed for coordinating multiple groups of virtual energy storage systems (VESSs), i.e.,

residential houses with air conditioners, to regulate voltage in low-voltage (LV) grids with high solar

PV penetration. Specifically, the two levels of the proposed model are: 1) in the lower level, VESSs

within each intelligent residential district are controlled locally by individual aggregator; 2) in the upper

level, multiple aggregators are coordinated to achieve voltage regulation through a consensus control

strategy. By exchanging information through sparse communication links, each aggregator shares the

required active power adjustment among all participating groups, without compromising users' thermal

comfort. Simulation result demonstrates that the proposed control scheme can effectively regulate

voltage in LV grids with greater robustness and scalability.

EPRO PE -

021

Coordinated Dispatch of Virtual Energy Storage Systems in LV Grids for Voltage

Regulation

This paper deals with the design and performance analysis of a three-phase single stage solar

photovoltaic integrated unified power quality conditioner (PV-UPQC). The PV-UPQC consists of a

shunt and series-connected voltage compensators connected back-to-back with common dc-link. The

shunt compensator performs the dual function of extracting power from PV array apart from

compensating for load current harmonics. An improved synchronous reference frame control based on

moving average filter is used for extraction of load active current component for improved performance

of the PV-UPQC. The series compensator compensates for the grid side power quality problems such

as grid voltage sags/swells. The compensator injects voltage in-phase/out of phase with point of

common coupling (PCC) voltage during sag and swell conditions, respectively. The proposed system

combines both the benefits of clean energy generation along with improving power quality. The steady

state and dynamic performance of the system are evaluated by simulating in MATLAB-Simulink under

a nonlinear load. The system performance is then verified using a scaled down laboratory prototype

under a number of disturbances such as load unbalancing, PCC voltage sags/swells, and irradiation

variation.

EPRO PE -

022

Design and Performance Analysis of Three-Phase Solar PV Integrated UPQC


Microinverters require high voltage gain capability for interfacing the low dc voltage output of

photovoltaic (PV) module to single-phase ac grid. A two-stage nonisolated inverter is proposed in this

paper, with a first boost stage and a second traditional pulse width modulated grid-tied inverter stage.

The proposed boost stage consists of a coupled inductor added with a voltage multiplier to achieve the

required high voltage gain at high efficiency and to operate over a wide input voltage range. Among

the coupled inductor topologies, adding a clamp circuit is a common solution to limit the voltage spike

caused by leakage inductance. In the proposed converter, the resonance between the coupled inductor

and voltage multiplier is used to address the issue of voltage spike, thereby reducing both component

count and device voltage stress. Detailed analysis and design procedure of the proposed converter is

presented in this paper. Experimental results of a 250-W microinverter are presented to validate the

proposed converter.

EPRO PE -

023

A Z-Source-Derived Coupled-Inductor-Based High Voltage Gain Microinverter

An inherent problem of solar-energy-powered-small-cell base stations (SBSs) is that the energy

generation of the photovoltaic (PV) cell does not match the energy consumption of the SBS in time. In

this paper, we propose optimizing the PV cell orientation angle to achieve a good match between the

energy generation and consumption profiles on a daily time scale. The optimization is formulated as

an integer linear programming problem. We also derive an expression for the correlation between the

energy generation and consumption profiles to evaluate their general interaction independent of the

exact PV cell or SBS deployment setup. The numerical evaluation of the proposed angle optimization

in a business area in London in summer/winter shows that the optimal PV cell orientation in summer

contradicts the conventional assumption of south facing being optimal in the northern hemisphere.

Instead, a southwest orientation should be chosen in summer due to its ability to shift the energy

generation peak toward the energy consumption peak in the afternoon at an SBS in central London.

This is in accordance with the prediction given by our derived correlation between the solar energy

generation and consumption profiles.

EPRO PE -

024

PV Cell Angle Optimization for Energy Generation-Consumption Matching in a Solar

Powered Cellular Network


Photovoltaic (PV) arrays present non-linear I-V curves, which strongly depend on ambient temperature

and solar insolation. This fact poses a problem in identifying the maximum PV power point. In this

paper, a dc motor is powered by a PV array and an attempt is made to optimize the use of the PV energy

while the DC motor is supplied with suitable current and voltage in order to match its load-speed

characteristics. This is achieved through a dc/dc converter controlled by a fuzzy cognitive network

(FCN), in parallel with an energy storage device (battery), so that the PV energy is always fully

exploitable. The algorithm method uses an FCN and a fuzzy controller, which recognize the maximum

power of the PV array very fast while at the same time, they control the speed of the dc motor, under

different insolation and temperature conditions. The proposed algorithm is validated through the

simulation studies and is proven to be effective.

EPRO PE -

025

A Novel Control Algorithm for DC Motors Supplied by PVs Using Fuzzy Cognitive

Networks

Pollution problems caused by fossil fuels has lead more investigations on renewable energy systems.

Photo-voltaic cells and fuel-cells output low level voltage than required, therefore, high gain dc-dc

converters are used to boost this low voltage. The Z-source converter can be employed as dc-dc

converter to boost the PV panel voltages. It also offers other advantages, such as clamped switched

voltage, high voltage gain, isolation of energy source from the load and positive polarity for output

voltage. Therefore, this is a good choice for high step-up applications. This paper presents analysis of

a novel high stepup z-source based dc-dc converter that has higher voltage gain than the z-source

converter. Furthermore, high efficiency, low device voltage stress and wide voltage gain range make

it a good candidate for photo-voltaic and high voltage step-up applications. The proposed dc-dc

converter is evaluated experimentally for converting 24 V DC input to 300 V DC output at 100 W and

to validate the simulation results.

EPRO PE -

026

A Novel Non-isolated Z-source DC-DC Converter for Photovoltaic Applications


A photovoltaic (PV) energy harvester is proposed, and it adopts the fractional open-circuit voltage

method to track the maximal power point of PV cells. The proposed harvester was designed and

fabricated by using a 0.18-μm 1P6M mixed-signal process. The input voltage of the proposed harvester

may range from 0.5 to 1.1 V, and its measured peak total efficiency is 93.4%. The proposed harvester

is suitable for internet-of-things applications, and the maximal duty cycle it can afford for a device

with a 5-mA load and 20-ms activation time is 50%. To prevent partial-shading issues in photovoltaic

(PV) systems, various kinds of voltage equalizers that virtually unify characteristics of shaded and

unshaded modules have been proposed. Although PV string utilization can be dramatically improved,

PV systems tend to be complex and costly because, in addition to the main converter for string control,

voltage equalizers are separately necessary. This paper proposes the single-switch single-magnetic

pulse width modulation (PWM) converter integrating the voltage equalizer using the series-resonant

voltage multiplier (SRVM) for standalone PV systems. By utilizing a square wave voltage generated

across a filter inductor in a PWM buck converter for driving the SRVM, the main PWM converter and

voltage equalizer can be integrated into a single unit with reducing the total switch and magnetic

component counts, achieving not only system-level but also circuit-level simplifications.

EPRO PE -

027

Photovoltaic Energy Harvester with Fractional Open-Circuit Voltage Based Maximum

Power Point Tracking Circuit

To prevent partial-shading issues in photovoltaic (PV) systems, various kinds of voltage equalizers that

virtually unify characteristics of shaded and unshaded modules have been proposed. Although PV

string utilization can be dramatically improved, PV systems tend to be complex and costly because, in

addition to the main converter for string control, voltage equalizers are separately necessary. This paper

proposes the single-switch single-magnetic pulse width modulation (PWM) converter integrating the

voltage equalizer using the series-resonant voltage multiplier (SRVM) for standalone PV systems. By

utilizing a square wave voltage generated across a filter inductor in a PWM buck converter for driving

the SRVM, the main PWM converter and voltage equalizer can be integrated into a single unit with

reducing the total switch and magnetic component counts, achieving not only system-level but also

circuit-level simplifications. The experimental test using the prototype for three PV modules connected

in series was performed emulating a partial-shading condition. The integrated converter effectively

precluded the partial-shading issues and significantly improved the power available at a load,

demonstrating its efficacy.

EPRO PE -

028

Single-Switch Single-Magnetic PWM Converter Integrating Voltage Equalizer for

Partially Shaded Photovoltaic Modules in Standalone Applications


In this paper, a framework for stability analyses of a typical inverter-based islanded microgrid with

two types of nonlinear loads is presented, namely ideal constant power loads (CPLs), which are the

loads supplied by tightly regulated power electronics converters, and dynamic CPLs, which are used

to represent motor-drive systems with large time constants. The comprehensive dynamic model of the

considered microgrid is first developed, based on which a bunch of small-signal models are deduced

using Taylor expansion made at different stable operating points. Afterward, eigenvalue-theorem-

based stability analysis and parametric sensitivity analysis are successively performed on the obtained

small-signal models to verify the stability of the system, predict the system's unstable regions, and

identify the effects of parameters on the stability boundaries. In the meantime, the impacts of different

kinds of nonlinear loads on the system stability are studied. Hardware-in-the-loop (HIL) real-time

simulation platform of a 30-kVA microgrid, which is mainly formed by a 10-kVA photovoltaic (PV)

system, a 10-kVA wind energy conversion system, a 10-kVA lithium-ion battery energy storage

system, and two CPLs, is established in Typhoon HIL 602 device. The validity of the theoretical results

is verified by real-time simulation results.

EPRO PE -

029

Stability Analysis and Parameters Optimization of Islanded Microgrid with Both Ideal

and Dynamic Constant Power Loads

Heat transfer through interfaces in nanostructures is becoming ever more important in functional

nanodevices. The existence of interface between two dissimilar materials overheats nanoelectronics

and impacts heat transfer greatly. It is a challenge how to modulate interface to tailor the thermal

transport properties of nanodevices from the perspective of atomic level. In this brief, we consider how

size and interface strain affect thermal boundary resistance (TBR) as well as thermal conductivity (TC)

of Si/Ge core-shell nanowires (CSNWs) using a thermal kinetic method in terms of atomic-bond-

relaxation correlation mechanism and continuum medium mechanics. We propose a theoretical model

to pursue the underlying mechanism on the TBR and TC that determined on the core or shell thickness,

surface roughness, and interface mismatch. Our approach provides a useful guidance to the theoretical

design and experimental control of epitaxial growth in the radial CSNWs for practice applications.

EPRO PE -

030

Size-Dependent Thermal Boundary Resistance and Thermal Conductivity in Si/Ge

Core–Shell Nanowires


In this paper, a novel framework is proposed in order to evaluate impacts of the uncertain models of

the system components on the voltage regulation problem of the medium-voltage distribution systems.

The investigation focuses on the model uncertainty associated with voltage dependency of loads, power

factor of loads, thermal dependency of lines, shunt admittances of lines and internal resistance of

substation transformer. To this end, firstly, voltage constraints are managed using a centralised voltage

control algorithm (VCA) by relying on the simplified models of the system components. The system

loads and lines as well as the substation transformer are then modelled with the uncertain variables

which are bounded in the predefined ranges. Monte Carlo (MC) simulations are used to create wide

series of scenarios that cover the possible values that the parameters of the system components can

take due to their uncertain nature. The model uncertainty impacts on the voltage regulation problem

are finally evaluated by the load flow calculations considering the scenarios created by the MC

simulations and the set-point obtained by the VCA. The proposed investigation brings useful

information regarding the possible deviations that the node voltages can have due to the uncertain

models of the studied components.

EPRO PE -

031

Impacts of the model uncertainty on the voltage regulation problem of medium-voltage

distribution system

Fiber Bragg gratings (FBGs) present strong advantages for temperature or strain sensing in harsh

radiation environments even if their properties are affected by radiations. The amplitudes and kinetics

of these radiation induced changes depend on numerous parameters, intrinsic or extrinsic to the FBGs

themselves. In this paper, we characterized 40 keV X-ray radiation effects on type I FBGs inscribed in

prehydrogenated SMF-28 from Corning through an ultraviolet laser exposure at 244 nm (cw). We

performed a systematic study of the influence of several FBG manufacturing parameters on their

radiation response up to 100 kGy (SiO2) highlighting radiation-induced Bragg wavelength shifts (RI-

BWS) up to 130 pm (~13°C error for temperature measurements) but no decrease of those FBG

reflectivity. Among the investigated parameters are the duration and temperature (100°C and 300°C)

of the thermal treatments applied post-inscription to stabilize the FBG and to complete the H2

outgassing. For such type of FBG, the device has to be recoated after inscription; we then characterize

the impact of this manufacturing step on the FBG response showing that its recoating with NOA-81

acrylate slightly degrades its radiation resistance. In addition to this study, the influence of two other

parameters have also been characterized: RI-BWS increases with the dose rate in the range 1-50 Gy/s

and a pre-irradiation at 1.5 MGy does not stabilize type I FBG response to a second irradiation.

EPRO PE -

032

Radiation Effects on Type I Fiber Bragg Gratings: Influence of Recoating and

Irradiation Conditions


In this paper a power factor correction (PFC) based Hybrid Resonance Pulse Width Modulation

(HRPWM) fed brushless DC motor (BLDC) drive is proposed, analyzed and tested. In this regard,

small signal and circuit analysis of HRPWM are calculated in resonance frequency, above-and below-

resonance frequency. The control method for regulating DC link voltage is also presented.

Furthermore, speed of BLDC motor is controlled by VSI duty cycle variations. Simulation results

depict unit power factor, low THD and appropriate speed control.

EPRO PE -

033

Power factor correction based Hybrid Resonance PWM fed BLDC drive

This brief proposes a mechanical contact-less speed sensing approach for a pulse width modulation

(PWM) operated permanent-magnet direct current (PMDC) brushed motor. A recently reported semi-

analytical dynamic model which incorporates the space-domain effects, namely slotting-effect and

commutation phenomenon, has been taken into consideration to apply the proposed computational

speed sensing approach. This speed sensing approach is basically an indirect estimation process and

discrete in manner. The proposed method is efficiently applicable at higher range of speed. Zones of

estimations with varying load torque and PWM duty cycle are represented with appropriate responses.

A simulation of the proposed estimation method is applied over the dynamic semi-analytical model of

24 V, 12 teeth-slots, 100 W PMDC brushed motor, and various responses are represented in this brief.

EPRO PE -

034

Mechanical Contact-Less Computational Speed Sensing Approach of PWM Operated

PMDC Brushed Motor


In this paper, a fault-tolerant multiphase multilevel inverter (MPMLI) configuration is proposed based

on the dual inverter concept. This configuration helps to improve the performance of pole-phase

modulated multiphase induction motor (PPMMIM) drive in both normal and switch failure conditions.

Comparing to the existing multilevel inverter topologies for multiphase induction motor (MIM) drives,

the proposed MPMLI configuration requires less number of dc sources and power electronic devices.

The proposed MPMLI configuration is able to sustain under various faulty conditions, which can

improve the reliability of the system. In addition, dc-link utilization (DLU) in low-pole mode is

improved by using space vector pulsewidth modulation (SVPWM). In high-pole mode, carrier-phase-

shifted 3-Φ SVPWM is used for reducing the torque ripple. This MPMLI configuration produces a

multilevel voltage profile across the effective phase in 3-phase 12-pole mode. By maintaining the V/f

ratio constant, the proposed MPMLI-fed MIM drive facilitates a wide range of load torque with half

of the rated speed in faulty condition. This advantage makes it suitable for traction and electric vehicle

applications where reliability and wide range of torque-speed are the major concerns. The performance

of proposed MPMLI-fed 5 hp, 9-φ PPMMIM drive is simulated by finite-element method (FEM) in

ANSYS Maxwell 2-D and experimentally verified by laboratory prototype under normal and faulty

conditions.

EPRO PE -

035

A Fault-Tolerant Multilevel Inverter for Improving the Performance of a Pole–Phase

Modulated Nine-Phase Induction Motor Drive

This paper proposes a novel comprehensive model of a vector-controlled induction motor drive in

positive sequence transient stability simulation (PSTSS) programs. The model is implemented to

approximate the behavior of the point-on-wave drive model, and applied to investigate the dynamic

performance of the advanced drive loads in system-level simulations. This positive-sequence drive

model is developed by reducing the three-phase electrical and control representations into d-q axes

positive-sequence formulations. For the positive-sequence model, the line-side rectifier is interfaced to

the grid through a voltage source with separate d-q axes controls to regulate the power factor of the

drive. The machine-side inverter control system is represented based on rotor flux oriented control.

The dc-link of the drive converter is implemented by employing the average model of the pulse-width

modulated (PWM) converter, and is utilized to integrate the line-side rectifier and machine-side

inverter. The proposed motor drive model is validated by comparing the performance with the electro-

magnetic transient (EMT) point-on-wave drive model. The VAr support capability of the drive load

and system-level simulation are investigated by incorporating the developed model into a composite

load structure in PSTSS programs.

EPRO PE -

036

Modeling of Rectifier-Controlled Induction Motor Drive Load in Transient Stability

Simulation Tools


This paper proposes an improved offset selection method for discontinuous-pulse-width-modulation

(DPWM)-based back-to-back converters to reduce dc-link current ripple. DPWM is introduced to

power converters to diminish the stress on power transistors and prolong their lifespan. However, when

using the DPWM method, the dc-link current ripple is increased in nonswitching regions of the power

transistors. Moreover, in DPWM-based back-to-back converters, the dc-link current ripple reaches its

maximum when the two transistors of both inverters are clamped in opposite directions. Therefore, the

dc-link capacitors endure more stress, resulting in decreased life duration. To overcome this issue, the

switching method should consider the clamping periods, when the current ripple increases. This can be

achieved by modifying the DPWM offset, so that the clamping states of both converters are matched.

The effectiveness of the proposed method is confirmed by both simulation and experimental results.

EPRO PE -

037

DC-Link Capacitor-Current Ripple Reduction in DPWM-Based Back-to-Back

Converters

This paper investigates robust control strategies for wind energy conversion systems with variable-

speed permanent magnet synchronous generators, which are integrated into the grid to provide reliable,

secure, and efficient electrical power. A three-phase grid-side converter without a grid transformer is

connected to the grid using an LCL filter with low resistive losses. In these working conditions, an

instantaneous power PI controller for the outer voltage-loop in the grid-side converter is used to

regulate the DC-link voltage and generate the required currents for the inner current-loop in the grid-

side converter. Two integral-type terminal sliding-mode (TSM) controllers are proposed to control the

active and reactive powers exchanged between the converter and the grid. The switching signals in the

controllers are softened to attenuate chattering. The time-varying gains in the controllers are

constructed to reduce control energy wastage and avoid overestimation of the boundaries of system

uncertainties. Simulated and experimental results validate the proposed method.

EPRO PE -

038

Integral-Type Terminal Sliding-Mode Control for Grid-Side Converter in Wind

Energy Conversion Systems


A speed control of sensorless induction motor (IM) drives at zero and very low frequencies is designed

in this paper. A new adaptive sliding mode observer (SMO) to estimate the stator current, rotor flux,

and rotor speed is proposed. To improve the robustness and accuracy of an adaptive SMO during very

low frequency operation, the sliding mode flux observer uses independent gains of the correction terms.

The gains of current and rotor flux SMOs are designed using Lyapunov stability theory to guarantee

the stability and fast convergence of the estimated variables. A Lyapunov function candidate utilizing

the error of rotor fluxes and speed estimation error is synthesized for speed estimation. Detailed

simulations and experiments are given showing the operation of the sensorless speed control at very

low frequency. The results prove the accuracy and robustness of the proposed adaptive SMO. Also,

comparison results with the state-of-the-art methods prove that the proposed method shows excellent

transient and steady-state speed estimation, particularly at very low and zero frequency operations.

EPRO PE -

039

A New Adaptive SMO for Speed Estimation of Sensorless Induction Motor Drives at

Zero and Very Low Frequencies

A speed control of sensorless induction motor (IM) drives at zero and very low frequencies is designed

in this paper. A new adaptive sliding mode observer (SMO) to estimate the stator current, rotor flux,

and rotor speed is proposed. To improve the robustness and accuracy of an adaptive SMO during very

low frequency operation, the sliding mode flux observer uses independent gains of the correction terms.

The gains of current and rotor flux SMOs are designed using Lyapunov stability theory to guarantee

the stability and fast convergence of the estimated variables. A Lyapunov function candidate utilizing

the error of rotor fluxes and speed estimation error is synthesized for speed estimation. Detailed

simulations and experiments are given showing the operation of the sensorless speed control at very

low frequency. The results prove the accuracy and robustness of the proposed adaptive SMO. Also,

comparison results with the state-of-the-art methods prove that the proposed method shows excellent

transient and steady-state speed estimation, particularly at very low and zero frequency operations.

EPRO PE -

040

A New Tuning Method of Multi-Resonant Current Controllers for Grid-Connected

Voltage Source Converters


Objective: Rotary biventricular assist devices (BiVAD) are mechanical pumps that are implanted in

the left and right ventricles of biventricular failure patients to pump blood and provide mechanical

circulatory support. The objective of this paper was to develop and test a novel sensorless control

algorithm that simultaneously satisfies the objectives of providing physiologic control (BiVAD flows

meet cardiac demand), preventing ventricular suction, and providing balanced left-right (systemic and

pulmonary) flows without the use of implantable flow or pressure sensors in the nonlinear, time

varying, and discontinuous circulatory system. Methods: The control algorithm consists of two gain-

scheduled proportional-integral controllers for left and right ventricular assist devices and only requires

intrinsic pump parameters (speed and power) to maintain differential pump speeds (Δ RPML and Δ

RPMR) above user-defined thresholds to prevent ventricular suction, and average reference pressure

heads (Δ PL, Δ PR) to provide physiologic perfusion and balance left-right-sided flow rates. A model-

based approach with extended Kalman and Golay-Savitzky filters was used to estimate Δ PL and Δ

PR. Efficacy and robustness of the algorithm were evaluated in silico during simulated rest and exercise

test conditions for: 1) excessive Δ PL and/or Δ PR setpoints; 2) rapid threefold increase in pulmonary

vascular or vena caval resistances; 3) transitions from exercise to rest; and 4) ventricular fibrillation.

EPRO PE -

041

Sensorless Physiologic Control, Suction Prevention, and Flow Balancing Algorithm

for Rotary Biventricular Assist Devices

Fractional-slot concentrated-winding (FSCW) permanent magnet synchronous machines, which are

characterised with high power density, fault tolerance and wide constant-power speed range, are

gaining more and more attention in the aircraft starter generator (SG) systems. Nevertheless, the short-

circuit (SC) fault, especially the turn-to-turn SC fault, is the obstruct crux in aviation applications. This

study is aimed to demonstrate the feasibility of FSCW permanent magnet SG (PMSG) in dealing with

turn-to-turn SC fault. The law of FSCW-PMSG SC fault is analysed and verified by finite-element

analysis (FEA), including the influence on turn-to-turn SC current by the number of the shorted turns

and the coil position in the slot. The three-phase current injection control is employed to mitigate the

SC fault in PMSG when a turn-to-turn SC fault occurs. A 24-slot, 16-pole FSCW-PMSG with spoke-

type rotor topology is designed to confirm the ability of inhibiting turn-to-turn SC current without the

risk of irreversible demagnetisation. Both FEA and experimental results are presented, verifying the

effectiveness of the three-phase current injection control in restraining the turn-to-turn SC current for

FSCW PMSG in an acceptable range.

EPRO PE –

042

Three-phase current injection method for mitigating turn-to-turn short-circuit fault in

concentrated-winding permanent magnet aircraft starter generator


PM machine or Permanent magnet synchronous motor (PMSM) is a nonlinear system with

multivariable couplings. To achieve the sensorless control of a PMSM with high inertial load, a

modified current observer, using PI regulator instead of sliding mode switching function, is proposed

in this paper. The modified current observer can solve the chattering and phase delay problem while

still maintaining the robust advantages of sliding mode system in position estimation. In addition, a

new phase-locked loop (PLL) based angle switching strategy is designed to ensure the motor can

smoothly switch from I-F control to closed-loop sensorless vector control in startup stage with a high

inertial load. The simulation and experimental results show that the control system of PMSM with

proposed ideas has fast response speed, accurate rotor position estimation, stable state switching and

good system robustness under high inertia load.

EPRO PE -

043

Sensorless control for surface mounted PM machine with a high inertial load

This paper proposes a method for estimating two inductances and capacitance of an LCL filter,

connected between a converter and a grid. Only the dc-bus voltage and converter phase currents need

to be measured. An excitation signal is fed into the converter voltage reference. The fundamental and

selected harmonic components are removed from the stored identification data to prevent biases in the

parameter estimates. The parameters of the hold-equivalent discrete-time model are estimated

recursively. The inductance and capacitance estimates are calculated from the estimated discrete-time

parameters using the corresponding closed-form model. The proposed method can be added to the

existing converter control algorithms. It can provide the parameter estimates for the converter control.

Further, it can be run occasionally during the normal operation in order to obtain an updated grid

inductance estimate. Experimental results show that the proposed method yields very good parameter

estimates and that it can also detect the changes in the grid inductance.

EPRO PE -

044

Plug-In Identification Method for an LCL Filter of a Grid Converter


This paper proposes a new single-phase five-level converter based on switched capacitor technique.

The capacitor charging in the proposed converter is carried out in a self-balancing form which does not

need closed-loop modulations or additional balancing circuits. The proposed topology is a voltage

booster without using end side H-bridge for changing load voltage polarity. So, switching losses and

total voltage stress of semiconductor components reduce in the proposed converter. The performing

modes of the proposed topology, its modulation scheme, capacitors’ balancing analysis, capacitance

and loss calculations, and also the development of the proposed converter for enhancing the quality of

output voltage waveform are discussed in depth. Moreover, the comparison of the proposed structure

with the other multi-level topologies shows that the proposed converter can reduce the number of

semiconductor elements and the required isolated DC sources. Finally, the simulation and experimental

results validate the appropriate performance of the proposed converter.

EPRO PE -

045

A Five-Level Step-up Module for Multilevel Inverters: Topology, Modulation Strategy

and Implementation

In this paper we consider a discrete-time consensus network, and assume that one of the agents acts as

a leader and injects an input signal to improve the overall dynamics performances, in particular to

increase the speed of convergence to consensus or to achieve finite-time consensus. Two possible

control protocols are proposed and the characteristic polynomials of the resulting closed-loop systems

are determined. These results allow to investigate consensus and finite-time consensus of the overall

systems.

EPRO PE -

046

Leader-Controlled Protocols to Accelerate Convergence in Consensus Networks


Aiming at the chattering problem of conventional sliding mode control systems for dc-dc converters,

a quasi-continuous second-order sliding mode (QSOSM) control scheme for buck converters has been

presented in the paper. It will be shown that the QSOSM controller is practically a continuous function

of the states everywhere except the origin. And thus the chattering problem existing in conventional

sliding mode can be practically solved due to the fact that the states cannot be stabilized to the origin

from engineering point of view. Theoretical analysis also shows that the closed loop system of the buck

converter is globally finite-time stable. Finally, the theoretical considerations have been verified by

simulation and experimentation. Specifically, the comparisons between QSOSM controller and PID

controller show that the former one provides a better robustness.

EPRO PE -

047

Quasi-Continuous Second-Order Sliding Mode Control of Buck Converter

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