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PhD Project Proposals (Power Engineering)

Staff Name: Abhisek Ukil

Email: aukil@ntu.edu.sg

Proposed Research Project (1): Design of Robust LV DC Distribution System and Retrofit ofAC Cables

Description:

Todays electric grid is mostly based on alternating current(AC), as well as the loads. However, recently there has beensignificant increase in direct current (DC) loads in the mediumvoltage (MV:

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PhD Project Proposals (Power Engineering)

Staff Name: Gooi Hoay Beng

Email: ehbgooi@ntu.edu.sg

Proposed Research Project (1): Optimization Algorithm to Determine Demand ResponseManagement (DRM) and Generation Schedule

Description:

When microgrids operate in interconnected mode, they canwork as demand response (DR) aggregators to enticecustomers to participate in DRM. Many small loads, whichhave the capability and intention for participating in DRM, arenot qualified otherwise due to their small capacity. The role ofa DR aggregator is to gather all DR participation requests andrepresent them in the wholesale electricity market as a flexibleentity. Loads in microgrids can be combined together as anequivalent elastic large load for DRM participation. Thedesirable consumption and duration time of the loads, outputsof distributed energy sources and energy storage, electric

vehicles (EVs), and energy exchange between the microgridand upstream grid will be determined by maximizing the profitof the microgrid while considering the volatile market prices ofthe electricity. The objective function is to maximize the totalprofit of the microgrids.When microgrids operate in islanded mode, the desirableconsumption and duration time of the loads, outputs ofdistributed sources and storage, and EVs will be determinedby minimizing the total operating cost of the microgrids. Inislanded mode, the uncertainties introduced by loads, EVsand renewable generation resources will aggravate the powerunbalance between supply and demand. The controllablegeneration resources will need to work harder and may need

to maintain a relatively larger spinning reserve since theycannot fall back on upstream supply should one or moregenerators fail. DRM can play an important role in reliableoperation of the microgrid. It can contribute to frequencyregulation which can alleviate the burden of these controllablegenerators. Like in interconnected mode, DRM can be usedto minimize the total operating cost of the microgrid byreducing the outputs of expensive generating units. This workwill examine how DRM can be optimized for the distributiongrid.

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PhD Project Proposals (Power Engineering)

Staff Name: Gooi Hoay Beng

Email: ehbgooi@ntu.edu.sg

Proposed Research Project (2): Improvement of Power Quality in Microgrids

Description:

The nonlinear unbalanced loads and converter-basedsources make the power quality issues more challengingwhen microgrids operate in either interconnected or isolatedmode. To optimize the utilization of the microgrid and toimprove its operational flexibility, controllability and stability, itis important to compensate the micorgrid with proper reactivepower and to filter off load current harmonics resulted fromnon-linear loads and voltage distortions resulting fromsources and/or converter nonlinearities. Hence, animplementation of flexible AC transmission system (FACTS)controllers in the microgrid to improve the power quality has

gained greater attention. As the most representative memberof the Flexible AC Transmission Systems (FACTS) family,Unified Power Quality Conditioner(UPQC) has more controlvariables compared with those of FACTS devices. It canchange a variety of system parameters during operation. Thismakes the running of the microgrid more flexible.UPQC is the integration of series and shunt active filters,connected back-to-back on the DC side, and they share acommon DC capacitor. The series component of the UPQC isresponsible for mitigation of the supply side disturbances inmicrogrids: voltage sags/swells, flicker, voltage unbalanceand harmonics. It inserts voltages so as to maintain the loadvoltages at a desired level, balanced and distortion free. The

shunt component is responsible for mitigating the currentquality problems caused by the consumer: poor power factor,load harmonic currents, load unbalance, etc. It injects currentsin the AC system such that the source currents becomebalanced sinusoids and in phase with the source voltages.With the modification of the control strategy of series andshunt active converters, UPQC can simultaneously controlpower flow and improve voltage regulation via compensationschemes in microgrids. This can be achieved withoutmodifying the system/hardware topology. Controlrequirements for reactive power compensation/voltageregulation will be investigated for various operating modes,interconnected and isolated modes of microgrids.

This work is to examine the design architecture of UPQC andits control schemes.

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PhD Project Proposals (Power Engineering)

Staff Name: Gooi Hoay Beng

Email: ehbgooi@ntu.edu.sg

Proposed Research Project (3): Optimization Algorithm to Incorporate Demand ResponseManagement(DRM) in Generation Control of Microgrids

Description:

When a microgrid operates in interconnected mode, it canwork as a demand response (DR) aggregator to enticecustomers to participate in DRM. The role of a DR aggregatoris to gather all DR participation requests and represent themin the wholesale electricity market as a flexible entity. Loadsin microgrids can be combined together as an equivalentelastic large load for DRM participation. On one hand,microgrids have their own generators and they are moreflexible than traditional DR aggregators. On the other hand,the bid price and amount of DR provided by microgrids aremore difficult to determine. The reason is because the DR

provided by the microgrid is affected by the configuration andoperation mode of the microgrid, the load conditions andoutput power of renewable power generation, and theelectricity market price, etc. Microgrids can get extra profit byproviding DR to large traditional power systems. Bothmicrogrids and neighboring connected power systems canbenefit from the implementation of DRM. DRM should becoordinated with the proper operation of energy storagesystems, electric vehicles (EVs) and distributed resources inmicrogrids.

In islanded mode, the uncertainties introduced by loads, EVsand renewable generation resources will aggravate the power

unbalance between supply and demand. The controllablegeneration resources will need to work harder and may needto maintain a relatively larger spinning reserve since theycannot fall back on upstream supply should one or moregenerators fail. DRM can play an important role in reliableoperation of the microgrid. It can contribute to frequencyregulation which can alleviate the burden of these controllablegenerators. Like in interconnected mode, DRM can be usedto minimize the total operating cost of the microgrid byreducing the outputs of expensive generating units.

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PhD Project Proposals (Power Engineering)

Staff Name: Wang Peng

Email: epwang@ntu.edu.sg

Proposed Research Project: Hybrid AC/DC grids

Description:The research team in EEE School of NTU has set up a hybridAC/DC grid to test and develop various control and integrationtechniques for renewable sources and energy storages.

Staff Name: Zhao Jiyun

Email: jyzhao@ntu.edu.sg

Proposed Research Project (1): High power density power electronics packaging

Description:

With the increase in power dissipation and reduction in thesize for power electronic devices, thermal management isbecoming a critical yet challenging role for the technologyadvances further, especially for the high power density andhigh temperature power electronic devices. The purpose ofthis project is to develop the advanced thermal managementsystems for high power density power electronic devices inorder to improve the performances while save the energy.

Staff Name: Zhao Jiyun

Email: jyzhao@ntu.edu.sg

Proposed Research Project (2):Investigation on the Vanadium Redox Flow Battery EnergyStorage System

Description:

The energy storage is essential in the development of smartgrids and the utilization of the renewable energy resources.The large-scale energy storage have the potential tocontribute to (1) improve energy efficiency and flexibility ofnational electricity grids, through load leveling / peak shaving,and (2) grid stabilization of power derived from renewableenergy based sources. The all-vanadium redox flow batteryenergy storage system (VRB-ESS) has to date shown thegreatest potential for large-scale energy storage applicationswith long cycle life and high energy efficiencies of over 80%in large installations. Using the same element in both half-cells, it prevents cross contamination and has a theoreticallyindefinite electrolyte life. It also exhibits a low cost for largestorage capacities. The proposed project evaluates thefeasibility of VRB-ESS on the building applications throughextensive experimental tests and thorough numericalsimulations. Both the experimental results and themathematical modelling and simulations will make significantcontributions to the VRB-ESS implementation in thedevelopment of green buildings. This project will focus on theVRB applications for buildings by combining with renewableenergy sources.