Law Haw

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Papers by Law Haw

Modelling of Charging Control Scheme for QZSI with Battery Topology

Journal of information science and engineering, 2020

Quasi Z-source inverter (qZSI) has been proven to be reliable for inverting DC electricity to AC.... more Quasi Z-source inverter (qZSI) has been proven to be reliable for inverting DC electricity to AC. When compared with conventional two stage DC-AC boost inverter topology, qZSI is a single stage topology which can be simply constructed via connecting a quasi Z-source (qZS) impedance network in series with an H-bridge inverter. This resulted an attractive topology without needing any switching element and resistor in the DC-link. In this paper, the investigation of qZSI with battery topology is extended to regulate its output voltage from a fluctuating DC input source. Through extensive mathematic derivation, a control scheme which comprised of battery current controller, battery management algorithm, and electronic circuit breaker (ECB) algorithm, is proposed to achieve the aforementioned outcome plus ensuring the effectiveness of battery charging and discharging capability as well as prevention of over-charging and over-discharging of the battery according to the DC input voltage level. All theoretical findings are validated with simulation results using Matlab / Simulink software package.

Enhanced decoupling current scheme with selective harmonic elimination pulse width modulation for cascaded multilevel inverter based static synchronous compensator

This dissertation is dedicated to a comprehensive study and performance analysis of the transform... more This dissertation is dedicated to a comprehensive study and performance analysis of the transformer-less Multilevel Cascaded H-bridge Inverter (MCHI) based STATic synchronous COMpensator (STATCOM). Among the shunt-connected Flexible AC Transmission System (FACTS) controllers, STATCOM has shown extensive feasibility and effectiveness in solving a wide range of power quality problems. By referring to the literature reviews, MCHI with separated DC capacitors is certainly the most versatile power inverter topology for STATCOM applications. However, due to the ill-defined transfer functions, complex control schemes and formulations were emerged to achieve a low-switching frequency high-bandwidth power control. As a result, adequate controller parameters were generally obtained by using trial and error method, which were practically ineffective and time-consuming. In this dissertation, the STATCOM is controlled to provide reactive power (VAR) compensation at the Point of Common Coupling (...

Optimisation of Neural Network with Simultaneous Feature Selection and Network Prunning using Evolutionary Algorithm

Journal of Telecommunication, Electronic and Computer Engineering, 2016

Most advances on the Evolutionary Algorithm optimisation of Neural Network are on recurrent neura... more Most advances on the Evolutionary Algorithm optimisation of Neural Network are on recurrent neural network using the NEAT optimisation method. For feed forward network, most of the optimisation are merely on the Weights and the bias selection which is generally known as conventional Neuroevolution. In this research work, a simultaneous feature reduction, network pruning and weight/biases selection is presented using fitness function design which penalizes selection of large feature sets. The fitness function also considers feature and the neuron reduction in the hidden layer. The results were demonstrated using two sets of data sets which are the cancer datasets and Thyroid datasets. Results showed backpropagation gradient descent error weights/biased optimisations performed slightly better at classification of the two datasets with lower misclassification rate and error. However, features and hidden neurons were reduced with the simultaneous feature /neurons switching using Geneti...

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DSP Based Implementation of SHE-PWM For Cross-Switched Multilevel Inverter

2019 IEEE 15th International Colloquium on Signal Processing & Its Applications (CSPA), 2019

Multilevel inverter (MLI) plays a crucial role in medium voltage and high power applications. Whi... more Multilevel inverter (MLI) plays a crucial role in medium voltage and high power applications. While the usages of MLIs are continuously growing in every area of power industries, it also initiates certain challenges that require attention. The increased number of power electronic components is one of the most challenging issues for multilevel inverters. The output power quality and the semiconductor device ratings of the grid connected high power inverters are largely dependent on the number of power components. Thus, it is required to decrease the overall power components as much as possible while designing these inverters. Therefore, this paper proposes a single phase 7-level cross-switched multilevel inverter that can produce higher voltages utilizing lesser power components. In order to further improve the efficiency of this MLI and enhancing its performance, selective harmonic elimination pulse width modulation (SHE-PWM) control technique is implemented. Here, Newton Raphson algorithm is examined to calculate the switching angles for different modulation indices. The fundamental voltage is obtained by solving the equations in such a way that the desired low order harmonics are eliminated. MATLAB Simulink software has been used to perform the simulation while the hardware model was implemented using digital signal processor eZdsp528335.

A Hybrid Active Neutral Point Clamped Inverter Utilizing Si and Ga2O3 Semiconductors: Modelling and Performance Analysis

Micromachines, 2021

In this paper, the performance of an active neutral point clamped (ANPC) inverter is evaluated, w... more In this paper, the performance of an active neutral point clamped (ANPC) inverter is evaluated, which is developed utilizing both silicon (Si) and gallium trioxide (Ga2O3) devices. The hybridization of semiconductor devices is performed since the production volume and fabrication of ultra-wide bandgap (UWBG) semiconductors are still in the early-stage, and they are highly expensive. In the proposed ANPC topology, the Si devices are operated at a low switching frequency, while the Ga2O3 switches are operated at a higher switching frequency. The proposed ANPC mitigates the fault current in the switching devices which are prevalent in conventional ANPCs. The proposed ANPC is developed by applying a specified modulation technique and an intelligent switching arrangement, which has further improved its performance by optimizing the loss distribution among the Si/Ga2O3 devices and thus effectively increases the overall efficiency of the inverter. It profoundly reduces the common mode curr...

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Simplified Sinusoidal Pulse Width Modulation of Cross-switched Multilevel Inverter

2019 IEEE 15th International Colloquium on Signal Processing & Its Applications (CSPA), 2019

Multilevel inverters (MLIs) are playing a major role in every sector of power industries, which i... more Multilevel inverters (MLIs) are playing a major role in every sector of power industries, which is growing significantly over the years. Although multilevel inverters are highly applicable, they have some stern disadvantages that need to be dealt with. Some of the most common issues of MLIs include high usage of electric components, highly complex modulation techniques, presence of harmonics and so on. By keeping all these issues into mind, this paper investigates a single phase cross-switched MLI using abridged electric components. Furthermore, it has described a novel and simplified method of implementing sinusoidal pulse width modulation (SPWM) technique. The investigated MLI and the proposed modulation technique is validated by following both simulation and hardware approach. The simulation is performed using MATLAB Simulink software while the hardware prototype of the whole topology is built using TMS320F28335 digital signal processor (DSP) board.

Noise Level Evaluation on Power Quality Disturbances Classification

2021 International Conference on Green Energy, Computing and Sustainable Technology (GECOST), 2021

The detection of power quality disturbances is currently critical in the smart grid applications ... more The detection of power quality disturbances is currently critical in the smart grid applications due to the bidirectional flow of power supply and demands at the main grid. The disturbance of the power quality may be occurred at utility or customer levels due to the unknown noises created by the parasitic components. Since the power data is in a time-series form, Long short-term memory (LSTM) networks are widely used due to its capability in recognizing temporal behavior from the inputs. This paper aims to study the performance of noise level susceptibility using LSTM network. The noise is inserted to the synthetic PQDs in term of Signal-to-Noise ratio with random noises generated from uniform white Gaussian. These noisy data is used to train and test the performance of LSTM model to understand the noise level interruption as LSTM model is popular to determine useful feature in the temporal domain. This work shows the sensitivity of the LSTM model towards unknown noises that is not seen during training phase. The complexity of harvesting all type of PQDs integrated with noises might be increased in the real-time PQDs classification.

Active Harmonic Filtering Using Multilevel H-bridge Inverter Based STATCOM

IOP Conference Series: Materials Science and Engineering, 2019

This paper proposed three-phase multilevel cascaded H-bridge inverter (MCHI) based active harmoni... more This paper proposed three-phase multilevel cascaded H-bridge inverter (MCHI) based active harmonic filtering (AHF) compensator, or refer to as static synchronous compensator (STATCOM), to minimize the harmonic components in a transmission network. There are three main elements to form a STATCOM, namely: control scheme, modulation technique and inverter topology. In this work, the synchronous reference frame (SRF) based controller is designed and implemented to produce the desired modulating signals (i.e., one for each phase) for the pulse width modulation (PWM) module. For simplicity, the carrier based pulse width modulation (CBPWM) with in phase disposition (IPD) technique is employed to generate the pulse trains and drive the three-phase five-level CHI. On the other hand, two threephase non-linear loading conditions, which structured by different transformer winding configurations and power rectifier circuits, are utilized to verify the feasibility of the proposed AHF. The effectiveness and the theoretical prediction of the proposed approach is investigated and validated through simulation studies using MATLAB SIMULINK software package.

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SHE-PWM cascaded multilevel converter with adjustable DC sources control for STATCOM applications

ABSTRACT This paper presents a new variation of the selective harmonic elimination pulse width mo... more ABSTRACT This paper presents a new variation of the selective harmonic elimination pulse width modulation (SHE-PWM) technique applied to cascaded multilevel converter based STATCOM system. The DC voltage levels of the cascaded H-bridge converter are assumed variables, hence increasing the degrees of freedom in the formulation of the problem. This approach allows additional harmonics to be controlled when compared to the existing family of SHE-based multilevel control for the same converter configuration. The proposed modulation method also shows an interesting feature of fixed switching angles across the entire range of the modulation index, which alleviates the problem of online implementation. The proposed method solely relies on the availability of the variable DC voltage levels, which can be obtained by different topologies. For simplicity, a DC/DC buck converter is utilized in this paper to provide a variable DC voltage levels required by the H-bridges of the five-level converter. The STATCOM system is integrated with a current controller along with a voltage control loop for the buck converter to meet the reactive power demand of different loading conditions. The method is further compared with the conventional carrier-based pulse width modulation (CB-PWM) to show its improved characteristics. The effectiveness and the theoretical analysis of the proposed approach and validated through simulation studies.

Cascaded multilevel inverter based STATCOM with power factor correction feature

2011 IEEE Conference on Sustainable Utilization and Development in Engineering and Technology (STUDENT), 2011

The paper investigates the STATCOM system based on five-level cascaded inverter controlled using ... more The paper investigates the STATCOM system based on five-level cascaded inverter controlled using carrier-based pulse width modulation (CB-PWM) technique. In this work, the STATCOM is controlled to provide only the reactive power compensation at the point of common coupling (PCC) when an RL load is connected to the power system at different lagging power factors. The rotating switching scheme is employed for the DC link voltage balancing while the phase angle control scheme is used in the STATCOM main system. A new current reference control method is proposed in this work and the effectiveness and the theoretical prediction of the proposed approach for different loading conditions is validated through simulation studies using MATLAB SIMULINK software package.

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Direct Fast Charging of Electric Vehicle Using Solar Power

2019 7th International Conference on Smart Computing & Communications (ICSCC), 2019

In present, environmental problems which originate from the consumption of fossil fuels caused em... more In present, environmental problems which originate from the consumption of fossil fuels caused emission of polluting gases into the atmosphere creating the need for change in mobility habits in today's daily life. Thus, companies and governments had made strong investments in the automotive sector especially in the development of electric vehicles (EVs) and the technologies associated with them. One of the technical issues that had been highlighted is the fast charging of EV batteries. Particularly, the usage of renewable energy systems to fast charge EV and lower the power demands from the grids are encouraged. This project aims to alleviate the current state of fast charging and environmental problems by proposing a high performance DC-DC boost converter controlled by PI controller. The proposed converter is able to generate different output power level based on the desired preset reference voltage value. For simplicity, EV batteries are being replaced with one resistor as a l...

Modelling of Charging Control Scheme for QZSI with Battery Topology

J. Inf. Sci. Eng., 2020

Analysis of Electrical Distribution System for Offshore Oil and Gas Platform

2019 IEEE Asia Power and Energy Engineering Conference (APEEC), 2019

The electrical power system of a medium size offshore oil and gas platform is studied by using a ... more The electrical power system of a medium size offshore oil and gas platform is studied by using a power system simulator software, namely ETAP. The load flow and short circuit analyses under various operating conditions are carried out, including normal, service, emergency and black start operation. The operations that generate maximum and minimum fault current magnitudes at the main switchboard and electric submersible pump are calculated, respectively. The protective device coordination is achieved by using the time-current curve tool of ETAP. The component ratings, voltage drop, and protection device setting are evaluated based on the results obtained from these analyses. A modern multifunctional transformer relay is proposed on a 2240kVA 6.6/0.415 kV transformer to provide a comprehensive protection and control. The overcurrent tripping time is reduced by using the combination of instantaneous and time-delay protection functions of the multifunctional transformer relay, hence mit...

The Smart IOT Earth Leakage Circuit Breaker with Transformerless And SMPS Auto Recloser

Earth leakage Circuit Breaker (ELCB) is function as a protection device that shall install either... more Earth leakage Circuit Breaker (ELCB) is function as a protection device that shall install either in industrial or residential protect electrical appliance or user from electrical shock or current leakage. When ELCB fault is detected, mechanical switch trigger the system to trip the circuit breaker. The problem faced by the user are the need to access to distribution box (DB) when tripping occur to turn it on manually. Some home appliance such as computer and alarm system should always connected to supply to prevent data from crashing or system mulfunction. The Smart Internet of Thing (IOT) Earth Leakage Circuit Breaker with Transformerless and SMPS Auto Recloser is proposed in this project to solve the need of always standby near to the DB to turn on after trip. This project has been improved from previous study with some transformation of circuit and prototype design. Transformerless circuit develop on this project eliminated the need of bulky transformer which usually used on lin...

A Hybrid Active Neutral Point Clamped Inverter Utilizing Si and Ga 2 O 3 Semiconductors: Modelling and Performance Analysis

Micromachines, 2021

This article is an open access article distributed under the terms and conditions of the Creative... more

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Deep Analysis of Quasi Z Source Inverter for Batteries Charging and Discharging Capabilities Across All DC Capacitors' Terminals

An energy-stored Quasi Z-source inverter (qZSI) is a single stage topology to smoothen and stabil... more An energy-stored Quasi Z-source inverter (qZSI) is a single stage topology to smoothen and stabilize the fluctuation of DC power produced from the photovoltaic (PV) system. Moreover, qZSI allows to step up the double amount of DC output voltage than its DC input voltage compared to the conventional DC-AC boost converter. The existing topology consists of a battery, H-bridge inverter and a quasi-Z-source (qZS). The proposed control scheme is to control DC-link voltage and battery management to charge and discharge the battery effectively. In addition, the electronic circuit breaker (ECB) algorithm is also proposed to limit the battery from over-charging and over-discharging to protect the battery life. Furthermore, the control scheme and ECB can also maintain the qZSI with battery energy storage system (BESS) to work in continuous conduction mode (CCM) rather than discontinuous conduction mode (DCM). To compare and validate the performance of two different types of energy-stored qZSI...

Lead Compensator Design for Single-Phase Quasi Z-Source Inverter

This paper presents a new control method for single-phase quasi-Z-source inverter (qZSI). At pres... more This paper presents a new control method for single-phase quasi-Z-source inverter (qZSI). At present, trial and error, as well as tuning of traditional proportional integral (PI) controller techniques, are utilized at the aforementioned topology to achieve system stability. Nevertheless, drawbacks of PI controlled based converter/inverter topologies are realized which include slow response speed and poor robust performance compared with the systems uncertainties and exogenous disturbances. In this work, lead compensator in control of the unipolar sinusoidal pulse width modulation (SPWM) qZSI is demonstrated to show its superiority against traditional PI control based on the derived qZSI’s small signal model. The methods to obtain the controllers’ parameters of the lead compensator is also documented in this paper. The effectiveness and the theoretical analysis of the proposed approach are verified through simulation studies for different loading conditions. The simulation demonstrat...

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A New Hybrid Multilevel Inverter with Reduced Number of Switches

An inverter converts DC into AC symmetrical square wave output voltage. The symmetrical square wa... more An inverter converts DC into AC symmetrical square wave output voltage. The symmetrical square wave contains infinite number of odd harmonics. When these square wave used for electrical equipments, life of the electrical equipment decreases. So, Multilevel inverter produces higher output voltage levels near the sine wave and corresponding magnitude of harmonics reduced. The conventional MLIs are Cascaded H-bridge five-level MLI and Multistring five-level MLIs, which used PWM techniques, the switching losses are high, efficiency decreases and also cost of switches high. The proposed topology is Hybrid Multilevel inverter with reduced number of switches, the switches operated with fundamental frequency then switching losses are low and efficiency increases. A Hybrid MLI produced higher output voltage levels are seven, nine, eleven, thirteen and fifteen. The THD reduces when increasing the higher output voltage levels. The simulation results shown in the Matlab/simulink 2009b.

The New Topology of Multilevel Inverter with Reduced Number of Switches

In this paper, a new multilevel inverter topology is proposed. This novel topology utilizes the c... more In this paper, a new multilevel inverter topology is proposed. This novel topology utilizes the cascaded feature as well as the isolated DC sources presented in Cascaded H-bridge Multilevel inverter (CHB-MLI) and the clamping diode in Diode Clamped Multilevel Inverter (DC-MLI). With these merits combined, an inverter topology with 18 total component counts had being emerged. This proposed topology could produce up to 17 levels of output according the ratio assigned to its DC sources. Apart from producing greater number of output voltage level with considerably low number of component counts, this study also aims to meet the THD limit set by IEEE standard (i.e 5%) for all voltage application below 69kV. In order to verify the functionality of this proposed topology, it being simulated using Matlab/Simulink using different modulation index. The change in THD percentage, the number of voltage output and RMS voltage are being observed and thoroughly discussed. Lastly, a comparative stud...

A New Symmetric and Asymmetric Step-Up Switched-Capacitor Integrated Multilevel Inverter with Self-Balanced and Inductive Load Capability

2021 International Conference on Green Energy, Computing and Sustainable Technology (GECOST)

This paper introduces a new single-stage extendable MLI, hereafter known as the switched-capacito... more This paper introduces a new single-stage extendable MLI, hereafter known as the switched-capacitor boost multilevel inverter (SCBMLI), which is modified from the circuit structure of quasi Z-source inverter (qZSI). Specifically, the proposed topology consists of the series-parallel combination of multi DC source and switched-capacitor (SC) units plus a conventional full H-bridge (HB). When compared to other hybrid multilevel inverter (HMLI) topologies, this new topology will have the capability to generate 17/25 voltage level or more in symmetrical/asymmetrical DC source configuration to obtain virtually sinusoidal AC output voltage using lesser quantity of separated DC capacitors, IGBT switches, diodes and gate drivers. In addition, the proposed topology can boost up the input DC voltage effectively with self-balancing voltage across all the DC capacitors using binary-asymmetric algorithm. Hence, no AC filter circuit and DC-DC converter will be needed for it to achieve very low total harmonic distortions (THD) and high boost gain. To evaluate the superiority of the proposed topology, extensive simulation studies including frequency change and dynamic load change with highly inductive loading are performed in this work using MATLAB/SIMULINK. Finally, various newly developed topologies are also compared to demonstrate merits of the proposed SCBMLI.

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