Integrated power systems For Continuity Of Electrical power In NAVY

SJCET, Palai Department of Electrical And Electronics

Integrated power systems for continuity of the electrical power supply for Naval Use

Subin Paul GeorgePresented By

Contents

1. Introduction

2. Naval Power System Features

3. Ensuring Continuity of Service

4. Radial & Zonal Distribution

5. Voltage in Naval Power Systems

6. Integrated Power Systems

7. Advantages of Integrated Power

8. References

SJCET PALAI Department Of Elcrtical and Electronics

SJCET, Palai Department of Electrical & Electronics Engineering

• Deals with generation, transmission, distribution and utilization of electric power for Naval use

• Closely related to islanded microgrids

• Key focus of Naval Power System designs are –

– Survivability

– Continuity of the electrical power supply

Introduction

About Naval Power Systems

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Naval Power System FeaturesFeature Description

Variable frequency Frequency cannot be assumed to be constant aboard a ship

Lack of time-scale separation

Principal time constants of controls, machine dynamics, and electric dynamics all fall within the same general range of milliseconds to seconds

Load sharing instead of power scheduling

Both real and reactive power are shared equally among all paralleled generators through the fast exchange of load-sharing information

Short electrical distances The distances on board a ship are short (typically under 350 m), making the load-flow problem insignificant

Load dynamicsMust account for the dynamics of loads caused by propulsion motors, large pumps, pulsed loads, propeller dynamics, and ship dynamics.

Tighter Control Because a ship is relatively small, a higher level of centralized control can be exercised

Ungrounded or high-impedance grounded systems

Naval power systems are designed to enable continued operation with a single line to ground fault.

Physical Environment Vibration, humidity, salinity, and shock of the ship must be accounted for in the design

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– Number of generators and switchboards

– Size of generators and switchboards

– Location of generators and switchboards

– Type of electrical distribution systems to be installed

– Ability to identify and isolate damaged sections of the system

Ensuring Continuity of Service

Important Considerations to Ensure Continuity

Naval power systems are undergoing rapid evolution as the demand for on board electrical power continues to grow.

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Radial & Zonal Distribution

Virtually all U.S. naval ships generate and distribute three-phase 60-Hz electrical power at 440 or 4,160 V

o Traditionally, the U.S. Navy used radial distribution systems

o Provided vital loads with alternate sources of power from different switchboards

o Vital loads are provided with alternate sources of power via longitudinal feeder cables from different switchboards

Traditional / Radial System Zonal Distribution

• Zonal distribution systems introduced to overcome increasing number of vital loads

• Vital loads are provided with alternate sources via shorter transverse feeder cables from port and starboard switchboards

• By replacing long feeder cables with short feeder cables, zonal distribution systems reduce cost and weight

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Traditional radial distribution system

Radial & Zonal Distribution

Fig 1.

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Comparison of Radial and Zonal Distribution

Fig 2. Comparison of Radial and Zonal Distribution

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– when the current requirements for a 440-V bus exceed 4,000 A, a shift to a 4.16-kV distribution system should be considered

– The growth in electrical demand has been met on many ships by employing 4.16-kV generation, and distribution with zonal transformers

Voltage in Naval Power Systems

The choice of voltage for generation and distribution is based on cost

NPS load requirements have grown with the introduction of high-power combat systems and the electrification of auxiliary equipment

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Actual NPS Layout in a Ship

Fig 3. Actual naval power system layout in a ship

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– Propulsion engines are least efficient at low power.

– Using the electric motors can save a considerable amount of fuel when operating at a low speed

– Hybrid Electric Drive (HED) adds a propulsion motor to the gearbox of a mechanical drive propulsion system to allow the electrical distribution system to power the ship at low speeds

– Power is generated and distributed via a 4.16-kV, three-phase, 60-Hz high-power bus

– The 4.16-kV bus is used directly by the propulsion motors and to supply a 1,000-V dc lower-power ship-service bus via a transformer rectifier

Integrated Power SystemsThe Zumwalt (DDG1000) class of destroyers is the first surface combatants with Integrated power system.

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IPSs support high-power mission systems– Future weapons systems will continue to increase demand

for electrical generation capacity– Same infrastructure to be shared for propulsion and weapons

systems– Examples of high-power mission systems include laser

weapons, electromagnetic rail guns (EMRGs), electromagnetic launchers, electronic warfare systems, and high-power radars

Advantages of Integrated Power

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IPSs reduce the number of prime movers

– A typical IPS configuration incorporates four to five prime movers as part of generator sets

– Equivalent nonintegrated configurations would typically use four prime movers for propulsion and three to five generator sets for electrical power generation

– The total reduction in prime movers can contribute to acquisition savings, reduced maintenance costs, reduced volume required for intakes and uptakes, and reduced manpower requirements.


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Fig 4. comparison of mechanical drive system and IPS

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IPSs improve the efficiency of propellers

– The propulsion-shaft line can be simplified with the removal of the traditional Controllable Pitch Propeller (CPP) system.

– As compared to Fixed Pitched Propellers (FPPs), CPPs have a larger hub to hold the apparatus for adjusting pitch

– The volume required for combustion air and exhaust will likely decline because of the reduced number of prime movers

– Can be reduced further if generator sets are located higher in the ship


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Fig 5. Contra-rotation through a traditional propeller, shaft, and pod


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IPSs provide general arrangements flexibility

– Mechanical drive locate prime movers low to align with propeller shaft

– Improve longitudinal separation of propellers to improve survivability without long shaft lines

– Volume for air combustion and exhaust will decline due to reduced number of prime movers and can reduce further if generator sets are located high


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IPSs improve ship producability

– Simpler designs help ship builders to simplify and reduce construction schedule

– Zonal systems shorten cable length, and therefore the reduced cost and time of construction

IPSs support zonal survivability

– When a damage occurs in a particular zone, the undamaged zones do not experience a service disruption

– Facilitates the ship to maintain or restore the ship’s primary missions when experiencing battle damage


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IPSs improve electric power quality of service

– Quality of Service (QOS) is a metric to measure the reliability of electrical power provided by the power system to loads

– QOS is calculated as a mean time between service interruption

– By properly selecting the number and ratings of generator sets and energy storage modules and implementing the QOS concepts in the control system, the power system can be designed with a high QOS

IPSs facilitate fuel-cell integrationSince fuel cells produce electrical power, their integration into the IPS is natural since fuel cells are simply generator sets with special characteristics


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NPS undergo rapid evolution on onboard electrical power

Growth is compunded by increased introduction of pulse loads

and nonlinear random loads.

IPSs prove to be the most economical way of powering loads.

Generating and distributing power at 4.16kV and using zonal

transformers to provide 440Vof ac power to loads.

In future, to achieve the power density and affordability

constraints that will be needed for warships, MVdc will be likely

be employed for power generation and distribution.

Conclusion

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– IEEE Paper – “Naval Power Systems: Integrated power systems for the continuity of the electrical power supply”http://ieeexplore.ieee.org/xpl/articleDetails.jsp?arnumber=7116681

– http://www.globalsecurity.org/military/systems/ship/systems/ips.htm

References

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http://ieeexplore.ieee.org/xpl/articleDetails.jsp?arnumber=7116681


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Integrated power systems For Continuity Of Electrical power In NAVY

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