Power systems: research trends and futureaustralia.ni.com/sites/default/files/Power systems research...

School of Electrical and Electronic Engineering © Dr. N. Ertugrul

Assoc. Prof. Nesimi ERTUGRUL E’mail: [email protected]

Phone: 8303 5465 University of Adelaide

School of Electrical and Electronic Engineering

Power systems: research trends and future


Power systems

• cover a wide range of diverse applications,

• display distinct electrical behaviors,

• are usually inter related, and

• imply highly nonlinear operating characteristics.


• There is the necessity of electrical isolation and the requirements for the wide frequency bandwidth measurements (resulting in significant restrictions on the accuracy of measurements.

• When considering a sensor, its characteristics needs ot be assessed based on three primary criteria: frequency bandwidth, magnitude of the output signal and electrical isolation.

• The frequency bandwidth of measured signals in power systems usually covers a very wide range (from dc to 10s of kHz).

• A conventional voltage transformer may be sufficient to provide a good electrical isolation amplifiers used to measure high voltages) should also be considered in the calibration tests. It is desirable to make the calibration test for each measurement channels.

In power systems ...


Power systems : the main quantities

The table given below summarise the main quantities that can be measured in power systems with their associated characteristics. Quantity Device Function and Remarks Typical

Bandwidth Typical Input Range

Typical Output Gain

Voltage Differential amplifier For high voltage measurements, but not real electrical isolation

DC to MHz 600V 100V = 1V

Isolation amplifier Safe high voltage measurements

DC - 50 kHz

1000V 100V = 1V

Current Hall-Effect current transducer Detects magnetic field produced by current, available in clamp type or through-hole

50 kHz 10A 10A = 1V

Rogowski coil With a flexible cord suitable for measuring large diameter cables and rotating shafts.

few kHZ 1000A 100A = 1V

Flux Search coil Measures flux produced by currents such as the current flowing in the stator and rotor end-windings

10 kHz 1V Proportional to the number of turns

Vibration Piezoelectric accelerometer Acceleration measurements 20 kHz 2g 1g = 1V Speed Tacho-meter Measures shaft speed directly multiples of

kHz 0rpm >2000rpm

Torque In-line torque transducer

Measures shaft torque directly multiples of kHZ

Up to 50Nm 0.1V/Nm

Force gauge Measures average shaft torque indirectly

below kHZ Up to 100Nm 0.1V/Nm


Power systems cover a wide range of diverse applications.

Application Areas: Rotating electrical machines Renewable energy systems Power electronics Transmission systems Power system stability Power system protection Distributed generation systems Smart grid

New efficient hardware designs, on-line and off-line measurements, data analysis and control !

Power systems applications :


Some of the software tools Matlab Finite Element Analysis PSIM dSpace ....... LabView

Power quality monitoring Transformer condition monitoring Rotating machine monitoring (synchronous, wind )

Software tools used in Power Systems:

Major processes Sensors and signal conditioning Measurements Data storage and display Signal analysis Real-time control Real-time monitoring


Five major LabView based applications are included: Power quality monitoring in power systems Condition monitoring of induction machines A low-cost continuous condition monitoring unit with CompactRIO PC based on-line monitoring system Real time solar array monitoring in remote areas Automated dynamometer test setup Electrical machines tests

They have common characteristics, can easily be extended to other applications and have room for improvement and customization.

Research and Trends


An ideal three-phase ac supply consists of three phase voltages that are 120 degrees out of phase and have identical magnitudes. The three voltages should have sinusoidal waveform characteristic at constant frequency and should be available continuously. Any diversion from these requirements to the level that has an adverse effect on the electric consumers is considered as poor quality, "polluted", of power. Voltage dips (sags), swells, interruptions, switching transients, harmonics, notches or flickers are examples of the most frequent disturbances in power system networks.

“Although it is not easy to estimate accurately the exact cost of the pollution in the quality of the power, poor power quality just in US causes about US$13.3 billion in damage per year.”

A. Power quality monitoring in power systems


• Induction motors are the workhorses of industrialized economies. • It is estimated that in developed countries, they consume nearly half of all electric energy generated. • There are about ten million large (>80kW) induction motors worldwide, which are generally very reliable and require minimum maintenance. However duty cycle, installation, manufacturing factors, and environmental influences can deteriorate and reduce the efficiency of these motors as in the other rotating machines. Unexpected downtime which can significantly increase the running cost or even be catastrophic in mission critical applications. In other cases, the efficiency of the motors may have been reduced due to the presence of various motor faults but the motors may still operate. This kind of failure may have a significant cost if not handled promptly and properly. For example an induction machine, which its efficiency reduced from 80% to 70%, would produce an additional electricity cost of about 14% per year.

B. Condition monitoring of induction machines


• Due to the development of low-cost compact reconfigurable devices, it has become possible to develop a reconfigurable device to be used in on-line monitoring of induction motors.

• The idea is to develop a low-cost continuous monitoring unit, called an indicator unit, based on low-cost sensors and a high performance standalone processing system, CompactRIO.

• The major benefits of the continuous monitoring process are: a reduction of the number of unexpected failures due to fault detection at an earlier stage, and elimination of the need for periodic condition monitoring inspections.

• For low and medium voltage motors the typical cost of a motor inspection is about A$500 per motor, and it is common to have these tests on six monthly intervals giving an annual cost of A$1000. Depending on the location, travel costs typically add about 50% to the testing cost resulting in a rough annual inspection cost of about $1,500. This annual cost is of the order of the initial target cost for the indicator unit.

B. Condition monitoring of induction machines A low-cost continuous condition monitoring unit with CompactRIO


The shows data acquisition and processing main tasks in an advanced condition monitoring system. The simple LabVIEW based condition monitoring devices may not cover all tasks shown in the figure, such as the diagnostic function, but it contain a data acquisition task with a multiplexer, a sample and hold function, which can be built from a high speed amplifier and an Analog to Digital Converter (ADC).

B. Condition monitoring of induction machines PC based on-line condition monitoring system


Monitoring technique

Signals Sensors FFT Bandwidth Position

Vibration Acceleration Velocity Displacement

Accelerometer 1-2 g 10 Hz to 1 KHz

Motor drive end and non drive end: axial, radial-horizontal, radial-vertical

Stator Current

Current Current transducers: Hall-Effect type or Rogowski Coils

1,000Hz, 20th harmonics

Clipped to one, two or three phase line supply

Stator Voltage

Voltage Voltage Transformers, Differential Isolation Amplifiers

1,000Hz, 20th harmonics

Clipped to one, two or three phase of supply

Flux Leakage Monitoring

Magnetic Field

Search coil or Hall sensors (external or internal)

mV range, 1,000Hz, 20th harmonics

Non drive-end or motor out board around the shaft

Sensor parameters and positions B. Condition monitoring of induction machines


Summary of sensor signal sampling information B. Condition monitoring of induction machines


C. Real time solar array monitoring system in remote areas

In solar based renewable energy systems, a number of single photo voltaic (PV) cells are usually configured in series and/or in parallel to form an array to increase voltage and current ratings. The PV arrays are also covered with some form protection material and are assembled in a frame to increase their reliability against environmental factors and to simplify installation. As these arrays operate in various regions and environmental conditions, it is necessary to obtain their performances characteristics and to be able accurately predict their energy output. Therefore, rapid improvements in the manufacture of solar panels demand standardized tests to evaluate and compare solar panel performance. As the energy output in a PV array depends upon the level solar insolation and the cell temperature (which both is unpredictable) it is critical to develop an


Electrical motor tests are one of the most time consuming and cumbersome tests due to their non linear operating characteristics and the difficulties of accurate and repeatable loading. The developments in PXI based d data acquisition systems and electronically controlled motor drives however, made such tests relatively easy to implement.

D. Automated Dynamometer Test Setup


E. Electrical machines tests

This test system is also developed to simplify the testing procedures of DC electrical machines using the benefits of LabVIEW and associated data acquisition hardware.


Future research

• Real plug and play systems in power electronics • High level modularity (such as general purpose inverter) • Sensor integration and wireless communications • Synchronised measurements in the main grids • Educational/training tools using general purpose educational

base boards (Elvis): Automated wind and PV testing systems • USB based DAQ and integrated signal generation and

measurement


Biography of Nesimi Ertugrul He received the B.Sc. and M.Sc. degrees in Electrical and in Electronic and Communication Engineering from the Istanbul Technical University, in 1985 and 1989 respectively, and received Ph.D. degree from the University of Newcastle upon Tyne, UK, in 1993. Dr. Ertugrul joined the Adelaide University since 1994, where he is an Associated Professor. His research topics include rotor position sensorless operation of brushless permanent magnet and switched reluctance motors, real-time control of electrical machines, motion control, fault tolerant motor drives, condition monitoring, power quality and power system monitoring, predictive maintenance, power electronics systems and electric vehicles. He also engage in research in the development of interactive computer-based teaching/learning systems involving object-oriented programming and data acquisition. Dr. Ertugrul a member of IEEE and the author of a book titled "LabVIEW for Electric Circuits, Machines, Drives and Laboratories" Prentice Hall, 2002, and and serves on the Editorial Advisory Board for the International Journal of Engineering Education (IJEE).

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