Yun Seng Lim

Energy Storage System for Mitigating Voltage Unbalance on Low-Voltage Networks With Photovoltaic Systems

The growth of building integrated photovoltaic (BIPV) systems in low-voltage (LV) networks has the potential to raise several technical issues, including voltage unbalance and distribution system efficiency. This paper proposes an energy storage system (ESS) for mitigating voltage unbalance as well as improving the efficiency of the network. In the study, a power system simulation tool, namely PSCAD, is used to model two generic LV networks, BIPV systems and an ESS in order to simulate the performance of the networks with various levels of BIPV penetrations. A control algorithm is developed and implemented in the energy storage model in order to study the ability of the ESS to mitigate network voltage unbalance and reduce losses. Experimental studies are carried out in the experimental small-scale energy zone to investigate the effectiveness of the energy storage system under various levels of PV penetration and load conditions. The simulation and experimental studies carried out clearly show the effectiveness of the ESS in reducing the voltage unbalance factor and improving the efficiency of the two networks considered.

Novel Fuzzy Controlled Energy Storage for Low-Voltage Distribution Networks with Photovoltaic Systems under Highly Cloudy Conditions

AbstractThe amount of small-scaled renewable energy sources is anticipated to increase on the low-voltage distribution networks for the improvement of energy security and reduction of greenhouse gas emission. Malaysia has a high solar irradiance level that is ideal for photovoltaic (PV) systems. However, the growth of the PV systems on the low-voltage distribution networks can create a number of technical issues such as voltage rise, voltage unbalance, and reversed power flow. Usually, these issues happen with little fluctuations. However, these issues tend to fluctuate very rapidly in Malaysia because this region has a very low clear sky index. A large amount of clouds often passes over the country, hence making the incident solar irradiance to be highly scattered and fluctuating. Therefore, the power output of the PV systems fluctuates substantially. To ensure an effective operation of the distribution networks with the PV systems, a novel fuzzy control method is developed and implemented to govern the ...

Colloidal Synthesis of Silicon Nanocrystals Via Inverse Micelles Microemulsion

Abstract We describe here the synthesis and characterization of silicon nanocrystals prepared by using microemulsion technique which involved the formation of inverse micelles. Colloidal systems employing TOAB as the surfactant molecules were used to synthesise nanosized silicon nanocrystals. The initial reaction of silicon tetrachloride, SiCl4 with a strong reducing agent, NaBH4 produced Si nanocrystals with hydrogen terminated surfaces. The surfaces of the nanocrystals were then capped with 1-heptene which protected the silicon nanocrystals from oxidation. The resultant surface passivated silicon nanocrystals suspended in organic solvent were characterized by Fourier transform infrared spectroscopy, photoluminescence spectroscopy and high resolution transmission electron microscopy. This study provided direct evidence of ageing, stability of different surface passivation and the quantum confinement effect in nanosized silicon nanocrystals.

Distributed Energy Storage Systems with an Improved Fuzzy Controller for Mitigating Voltage Unbalance on Low-Voltage Networks

AbstractThe growth of photovoltaic (PV) systems on low-voltage distribution networks can create technical issues such as voltage rise, voltage unbalance, unnecessary neutral current circulation, and reverse power flow. Usually, these happen with little fluctuation. However, they tend to fluctuate seriously because of the low clear sky index in Malaysia and they become more severe when the installation and distribution of single-phase renewable energy sources are rather arbitrary and not monitored by utility companies. To ensure effective operation of distribution networks with PV systems, an improved version of a three-phase fuzzy control algorithm for distributed energy storage (ES) systems is proposed. With this algorithm, distributed energy storage systems can control individual phase voltage to mitigate the voltage unbalance factor effectively, maintaining voltage magnitude without cutting any excess renewable energy. An experimental low-voltage distribution network with two 3.6-kWp PV systems was set...

Methodology for optimizing geographical distribution and capacities of biomass power plants in Sabah, East Malaysia

Purpose – Biomass waste can be used as fuel in biomass power plants to generate electricity. It is a type of renewable energy widely available in Malaysia because 12 million tons of the biomass waste is produced every year. At present, only 5 per cent of the total biomass waste in Sabah, one of the states in Malaysia, is used to generate electricity for on-site consumption. The remaining 95 per cent of the biomass waste has not been utilized because the transportation cost for shifting the waste from the plantations to the power plants is substantial, hence making the cost of the biomass generated electricity to be high. Therefore, a methodology is developed and presented in this paper to determine the optimum geographic distribution and capacities of the biomass power plants around a region so that the cost of biomass generated electricity can be minimized. The paper aims to discuss these issues. Design/methodology/approach – The methodology is able to identify the potential locations of biomass power pl...

Energy storage system for peak shaving

Purpose – The main purpose of this study is to provide an effective sizing method and an optimal peak shaving strategy for an energy storage system to reduce the electrical peak demand of the customers. A cost-savings analytical tool is developed to provide a quick rule-of-thumb for customers to choose an appropriate size of energy storage for various tariff schemes. Design/methodology/approach – A novel sizing method is proposed to obtain the optimum size of energy storage for commercial and industrial customers based on their historical load profile. An algorithm is developed to determine the threshold level for peak shaving. One of the buildings at Universiti Tunku Abdul Rahman (UTAR), Malaysia, is chosen for this study. A three-phase energy storage system rated at 15 kVA is developed and connected to the low-voltage electrical network in the building. An adaptive control algorithm is developed and implemented to optimize the peak shaving. Findings – The sizing analysis shows that the customer under th...

Improved performance of PMSM speed responses using a hybrid Fuzzy/ PI controller

This paper presents an improved performance of a Permanent Magnet Synchronous Motor (PMSM) using a hybrid Fuzzy/ Proportional-Integral (PI) controller. Hybrid control has an advantage of integrating a superiority of two or more control techniques for better control performances. A fuzzy controller offers better speed responses for start-up and large reference input changes (large speed error) as compared to a Proportional-Integral controller. Nevertheless, a rules-based fuzzy controller is limited to a particular operating condition. If the nature of the load torque is varied, the steady-state error of the fuzzy logic controller will be significant. The Proportional-Integral controller has good adaptability over load torque variation and can maintain high steady-state accuracy. However, the transient responses are quite poor. This study has incorporated a Fuzzy and PI into the control of PMSM to improve its dynamic speed performances. The simulation is carried out using Matlab Simulink.

Fuzzy-driven energy storage system for mitigating voltage unbalance factor on distribution network with photovoltaic system

The amount of small-scaled renewable energy sources is anticipated to increase on the low-voltage distribution networks for the improvement of energy efficiency and reduction of greenhouse gas emission. The growth of the PV systems on the low-voltage distribution networks can create voltage unbalance, voltage rise, and reverse-power flow. Usually these issues happen with little fluctuation. However, it tends to fluctuate severely as Malaysia is a region with low clear sky index. A large amount of clouds often passes over the country, hence making the solar irradiance to be highly scattered. Therefore, the PV power output fluctuates substantially. These issues can lead to the malfunction of the electronic based equipment, reduction in the network efficiency and improper operation of the power protection system. At the current practice, the amount of PV system installed on the distribution network is constraint by the utility company. As a result, this can limit the reduction of carbon footprint. Therefore,...

A Real-Time Active Peak Demand Reduction for Battery Energy Storage with Limited Capacity

—Battery-based energy storage (BESS) has found to have potential and interest in reducing the peak demand. Over the years, a number of control strategies have been developed for BESS to reduce the peak demand. The control strategies are however complex and confined to simulation evaluation only. The control strategies are also not tested in BESS set-up with limited capacity. A simple and yet comprehensive real-time active peak demand reduction control has therefore been developed and presented in this paper. The real-time active control has been evaluated experimentally using the university building as the site. The performance of the real-time control has been evaluated as compared to the fundamental control as well as the ideal reduction in simulation. Even though the capacity is limited, the results showed superiority and adoptability of the real-time active control as compared to the fundamental control, with peak demand reduction of about 8.64% as compared to 4.24%. The real-time active control also showed higher accuracy of 70.52% towards the ideal reduction result as compared to the fundamental control with only 35.25%.

Evaluating the economic benefits of peak load shifting for building owners and grid operator

The economic benefits of load shifting are investigated in this paper. For building owners, the economic benefits are assessed from the perspective of lower connection charges, lower monthly power charge, lower capital cost, and reduced system losses. The non-financial benefit of improved power quality and reliability is also considered. For the grid operator, it is assessed from the perspective of cheaper generation costs and deferment in system upgrading costs. These benefits are derived from reducing the electrical load variability as a result of load shifting. As the electrical loads are varying constantly, the output of power plants need to be varied to meet the changing load and this reduces the efficiency. Furthermore, the capacity of the electrical power system needs to cater for the peak load, which occurs only for a short duration. Hence, reducing load variability will improve the efficiency and reduce wastage. In this study, it is found that substantial saving is obtained by shifting the top 3% peak load while carbon emission is reduced. The maximum saving obtained by the building owners and grid operator is USD 0.47 and USD 3.59 per kWh.