Gooi Hoay Beng

Extended boost Z-source inverters

The Z-source inverter has gained popularity as a single-stage buck-boost inverter topology among many researchers. However, its boosting capability could be limited and therefore it may not be suitable for some applications requiring very high boost demanding of cascading other dc-dc boost converters. This could lose the efficiency and demand more sensing for controlling the added new stages. This paper is proposing a new family of extended boost quasi ZSI to fill the research gap left in the development of ZSI. These new topologies can be operated with same modulation methods that were developed for original ZSI. Also they have the same number of active switches as original ZSI preserving the singlestage nature of ZSI. Proposed topologies are analyzed in the steady state and their performances are validated using simulated results obtained in Matlab/Simulink. Furthermore they are experimentally validated with results obtained from a prototype developed in the laboratory.

Charging of electric vehicles and demand response management in a Singaporean car park

Uncontrolled charging of electric vehicles can affect the power system operation and stability. In cities with high population density and with short driving distances like Singapore, car parks bear a high proportion of private vehicles most of the day. These car parks can be regarded as aggregators and control the charging process. Demand response could be used by the car park operators as an additional source of revenue and thus help offset the high installation costs. This paper investigates different charging strategies and demand response management possibilities within a specific car park. Data for arrival times and parking durations are obtained using available statistical information, charging of individual electric vehicles is controlled by the car park operator and effects of demand response management on the total charging cost of the system is analysed.

Thermal effect on State Estimation in microgrids

State Estimation (SE) has played a role as a crucial function of energy management and control system. In the past two decades, researchers have been trying very hard to increase the accuracy of SE by improving the SE algorithms or/and using better meters. Microgrids have been popular today because of the penetration of distributed generators which may include micro-turbines and renewable energy sources and the need to operate the system efficiently. SE algorithms need to be modified to fit the new operating conditions. This paper will discuss how temperature can affect the SE function in microgrids and propose an algorithm to improve the accuracy of the SE results.

Validation of Faster Joint Control Strategy for Battery- and Supercapacitor-Based Energy Storage System

Energy storage system (ESS) is generally used to manage the intermittency of the renewable energy sources (RESs). The proper control strategy is needed to effectively maintain the power balance between the RESs, load demand, and ESS. The conventional control strategy for the hybrid energy storage system (HESS) uses the high-/low-pass filter method for system net power decomposition and the ESS power dispatch. In this paper, a new joint control strategy is proposed for photovoltaic-based dc grid system, with battery and supercapacitor (SC) as a HESS. The new joint control strategy utilizes the uncompensated power from the battery system to increase the performance of the overall HESS. The advantages of the proposed control strategy over the conventional control strategy are faster dc-link voltage restoration and effective power sharing between the battery and the SC. The detailed stability analysis of the proposed control strategy is also presented. The effectiveness of the proposed control strategy over the conventional control strategy is validated with the short-term and long-term experimental studies.

Operation of energy storage system for renewable utilization enhancement

This paper presents the optimal operation of energy storage system (ESS) applied for renewable utilization enhancement. The problem is formulated with stochastic dynamic programming (SDP) framework, which explicitly incorporates the system uncertainties. The transmission network modeling is particularly considered from the viewpoint of Independent System Operator (ISO). The SDP-based operation policy for ESS, renewable and conventional generation dispatch can accurately adapt to hourly uncertainties in wind and load demand. It is demonstrated to considerably increase wind utilization and reduce energy production cost. Additionally, comparison result shows that the proposed SDP model outperforms look-ahead optimization model as a commonly used approach for operation problems under uncertainty.

Single-phase grid-tied photovoltaic inverter to control active and reactive power with battery energy storage device

This paper presents a Photovoltaic (PV) inverter along with a battery energy storage system connected in shunt with the grid. The objective of the proposed control system is to control both active and reactive power exchange between the grid and the load throughout the day, through a Voltage Source Inverter (VSI). Along with the reactive power compensation, it also provides current harmonic compensation to the connected load. A combined PV-battery arrangement is provided through a bi-directional DC-DC converter for uninterrupted power supply.

Three-phase shunt connected Photovoltaic generator for harmonic and reactive power compensation with battery energy storage device

This paper presents a solar Photovoltaic (PV) inverter along with a battery energy storage device in shunt with a three-phase grid. Apart from sharing the load active power, the other objective of the PV-battery integrated system is to provide load harmonic and reactive power compensation throughout the day. The interface between the grid and the PV is carried out through a voltage source converter. The voltage across the DC bus capacitor is regulated to maintain a unity power factor operation of the system, irrespective of changes in solar radiation level or due to change in load. A bidirectional DC-DC converter is employed to charge and discharge the connected battery energy storage device. The performance of the system is analyzed with and without the battery, in order to highlight the importance of battery energy storage system.

Market clearing model for Singapore electricity market incorporating transmission loss

The National Electricity Market of Singapore (NEMS) has been studied for its well-known maturity. This paper aims to present a in-depth analysis of the market clearing model (MCM) of NEMS. The Singapore Market Clearing Model is an assessment tool for the settlement of energy and ancillary services simultaneously. The detailed mechanism and clearing process have been developed by researchers from DNV GL. A mixed-integer linear programming (MILP) framework-based MCM was provided. Based on previous work, a modified MCM incorporating transmission loss is studied in this paper, with emphasis on the locational marginal price (LMP). Numerical analysis is performed to demonstrate how the market clearing model works and examine the impacts of transmission loss on the market clearing process and prices. The results of modified MCM with changing scenarios at the distribution scale are tabulated.

Combination of renewable generation and flexible load aggregation for ancillary services provision

Liberalized markets provide opportunities for load aggregators to reduce their operating cost by participation in the wholesale electricity market. Reduction in operating cost result from shifting flexible loads based on the electricity price and also from incentives paid for ancillary service provision. Increased penetration of distributed renewable generation could help distribution system operators (DSO) reduce energy losses and increase network reliability. On the other hand, variability of renewable sources introduce additional challenges that need to be addressed in order to reduce their adverse effects on the power system. This work proposes an energy management system for aggregation of controllable loads in the distribution system. Local generation uncertainties are considered using model predictive control (MPC). The goal of the controller is to provide a schedule for the controllable loads while considering both local solar photovoltaic (PV) generation and provision of ancillary services. A case study based on the National Electricity Market of Singapore (NEMS) is presented to validate the proposed method.

Optimal PMU placement with local redundancy of conventional measurements

This paper talks about optimal PMU placement problem with consideration of conventional measurements from the angle of robustness of state estimation (SE). Using the Binary Linear Integer Programming method, local redundancy of the existing measurements is considered in the PMU placement strategy. Besides, considering the number of PMUs implemented yearly is limited, a multistage placement strategy is proposed according to the improvements on local redundancy. Case study on IEEE 14-bus system is carried out to show the effectiveness of the method on redundancy improvements in SE.