Gary Chang

• PhD
• National Chung Cheng University

This paper presents an efficient mixed-integer linear programming approach to unit commitment (UC) in isolated power systems while maintaining frequency stability under loss of generation contingencies. The dynamic frequency constraints considered are formulated using the center of inertia (COI) concept to determine the dominant parameters affectin...

This Task Force paper presents several important aspects on modelling single-phase power electronic converters (PECs) for power system distortion studies in the 2-150 kHz frequency range (also referred to as supraharmonics). The paper summarizes the state of the art and provides a systematic framework for the development of models of the unintentio...

When the inverter-based microgrid (MG) operates in islanded mode, effective frequency regulation and equitable sharing of inverter power output among distributed generators (DGs) require the adoption of suitable control strategies. To simultaneously achieve these objectives in inverter control, this article proposes two methods: a novel adaptive in...

An accurate forecast of the PV output can indispensably enhance the stability of power supply. However, the effectiveness of prediction results highly depends on many factors and the data preparations are also an essential process to be considered. The focus of this paper is to classify PV data types by density-based spatial clustering of applicati...

Wind energy is among the fastest-growing electric energy resources worldwide. As the electric power generated by wind turbines (WTs) varies, the WT-connected bus voltage fluctuates. This paper presents a study on implementing a swarm-based proportional and integral (PI) controller for GTO-STATCOM voltage regulator to mitigate the voltage fluctuatio...

This paper presents an Equilibrium Optimizer (EO)-based method that simultaneously determines locations and sizes of multiple photovoltaic (PV) units for maximizing a distribution system’s PV hosting capacity (PVHC). The proposed method avoids various search-space restrictions seen in recent literature. The constraints in this paper are separated i...

Harmonics, inter-harmonics, and low-frequency (below the fundamental frequency) components produced by nonlinear loads and renewables may cause undesired effects on electric power equipment including overheating, resonance, and voltage flickers. This paper presents a hybrid method for the detection of frequency components of the measured waveform t...

With widespread non-linear loads and the increasing penetration of distributed generations in the power system, harmonic pollution has become a great concern. The causes of harmonic pollution not only include the integer harmonics, but also interharmonics, which exacerbate the complexity of harmonic analysis. In addition, the output variability of...

The papers in this special section examine modeling and simulation methods for the analysis and design of advanced energy conversion systems. Energy conversion lies aEnergyveral fronts including materials, conversion methods, power electronics, and controls have created new opportunities for efficient energy conversion from both the conventional an...

The optimal planning for distributed generations (DGs) associated with photovoltaics (PVs) in the utility-owned distribution system is crucial for increasing high penetration of renewables while against practical system operation constraints. Such PV-DG planning is categorized as a complicated mixed-integer nonlinear programming (MINLP) problem and...

Voltage sags are often manifested as the permanent or incipient faults occurred in the power system because of equipment malfunctions or failures. The incipient faults which are originally self-cleaning faults may repeatedly occur and gradually develop to a permanent fault after its first occurrence. The incipient fault detection is considered as a...

Penetration of grid connected renewable energy systems and smart loads based on power electronics technology has been increasing in low and medium voltage distribution. Power Electronics is a key technology for distribution networks which can transfer electrical power from renewable energy sources to grids or generate regulated frequency and/or v...

Generation output forecasting is a crucial task for planning and sizing of a photovoltaic (PV) power plant. The purpose of this paper is to present an effective model for day-ahead forecasting PV power output of a plant based on deep belief network (DBN) combined with grey theory-based data preprocessor (GT-DBN), where the DBN attempts to learn hig...

Voltage fluctuations caused by rapid reactive power consumption of loads and photovoltaic or wind generator output variations may produce flickers and cause undesired effects on electric power components and human eyes. This paper presents a hybrid approach for voltage fluctuations assessment by using synchrosqueezing transform-based algorithm. The...

In this paper, a DC-coupled hybrid microgrid is investigated and a simulation-based electricity analysis manner by using the OPAL-RT real-time simulation is developed for the discussion of the energy-saving issue on the microgrid. Methodologies include modelling, simulation mechanism, and the development of control strategies are presented, and two...

The frequency range between 2 and 150 kHz has recently gained significant attention, triggered by standardization needs and increased emission in this wide frequency range. This paper gives an overview of the state-of-the-art concerning these so-called supraharmonics, and noticeably indicates the research challenges associated with waveform distort...

The wind power forecast has attracted much attention in recent years because of the significantly increasing number of large-scale integrations of the wind power plants in the electric grid. In this paper, a Gaussian mixture model-based neural network model is proposed to forecast the short-term wind power generation. Actual measured wind power out...

Accurate forecasts of wind speed and wind power generation are essential for the effective operation of a wind farm. This paper presents an improved radial basis function neural network-based model with an error feedback scheme (IRBFNN-EF) for forecasting short-term wind speed and power of a wind farm, where an additional shape factor is included i...

The demand of renewable energy resources has become an important issue for green power generation in many countries. With the increasing photovoltaic generation in the distribution system, voltage fluctuation problems often present in the PV-connected grid affected by the moving cloud shadows. This paper presents a study to evaluate impacts on volt...

This paper presents the implementation of power quality (PQ) analysis platform that can access different venders' PQ meter data being translated to Power Quality Data Interchange Format (PQDIF) files and view the data through a LabVIEW-based graphical user interface. The implemented platform also can manage the retrieved PQ data in a customized dat...

With the increasing use of non-linear loads, the harmonic problems have become of great concerns. One of the solutions to harmonics is the application of shunt active power filters (APFs). The APF reference compensation strategy proposed in this paper adopts the backpropagation neural network (BPNN) to train the control algorithm and calculate the...

Forecasting of wind speed and wind power generation is indispensable for the effective operation of a wind farm and the optimal management of revenue and risks. Hybrid forecasting of time series data is considered to be a potentially effective alternative compared with the conventional single forecasting modeling approaches such as autoregressive i...

This paper presents an improved dynamic voltage-current model of an ac electric arc furnace (EAF) for multiple operation stages and for the study of propagations of voltage fluctuations in a power network associated with the EAF in operating stages. The EAF model is developed based on wavelet-transform and neural-network-based methods by training a...

Energy storage systems for power system applications have currently attracted significant interest and attention as an enabling technology for integrating the growing capacity of distributed energy resources into the electric grid. Energy storage systems can provide a variety of solutions for the enhancement of the operational capabilities of the e...

Energy storage systems (ESSs) provide a variety of solutions to manage the power supply in order to create a more resilient energy infrastructure and bring cost saving to electric utilities and consumers. To help understand the electrical characteristic of the ESSs operate in electric grid, the process of modeling and simulation is thus required. T...

A microgrid usually consists of small-scale of thermal generation sources and other distributed energy resources (DER) such as photovoltaic, wind power, and fuel cells to serve its loads. The microgrid can increase DER penetrations and operation reliability through appropriate control schemes and energy management. When the inverter-based DERs supp...

Drastic variations of reactive power consumed by electric arc furnaces (EAFs) often lead to significant voltage fluctuations at the connecting network bus and yield noticeable flickers of lighting devices as well as cause malfunctions of the electrical equipment. If the flicker severity levels are predictable, corrective solutions such as controls...

This paper presents a review with a concise de-scription and analysis of the fundamentals, characteristics, analytical details, merits, and drawbacks associated with existing methods in frequency and time domain for harmonic analysis in practical power networks. The description and analysis are centered on methods developed in the harmonic domain,...

A microgrid integrates renewable energy and other forms of distributed energy resources (DER) to serve its loads. The microgrid can increase the DER penetration and improve power quality and reliability through appropriate management. Under the normal operation, a microgrid is connected to the utility grid, and each DG provides a preset power to th...

This paper presents a study of applying the equivalent effective voltage concept according to IEEE Standard 1459-2010 for determining reference compensation currents of the three-phase three-wire shunt active power filter in the a-b-c reference frame. The APF reference current calculator is developed and is realized on the DSP board through process...

This paper proposes a discrete wavelet transform (DWT) and radial basis function neural network (RBFNN)-based method for modeling the dynamic voltage-current $(v$–$i)$characteristics of the ac electric arc furnace (EAF). The objective of the study is to develop a complete model of the EAF including different operation stages, and the model can be u...

SUMMARY This paper proposes an efficient method to obtain the equivalent fundamental positive-sequence voltage for determining the shunt active power filter (APF) reference compensation currents, where the source voltage magnitude and phase angle at the fundamental frequency are detected by a simplified adaptive linear combiner neural network. The...

If a blackout occurs in the power system, how to restore the grid as soon as possible during the blackout is always a significant issue for the operation of power system. Taiwan power Company (TPC) is planning to connect the Taiwan Grid with the Penghu Island grid, the two-circuit 59km 161-kV submarine cables between Taiwan and Penghu (T-P-cables)...

The wind resource in Penghu is abundant. According to the operating experience and generation output from the Penghu's Zhong-Tun Wind Farm, the capacity factor is above 47%. Currently, the total installed capacity of wind turbines in Penghu reached 10.2 MW and the highest penetration of wind power can be reached 35%. Therefore, such a high penetrat...

SUMMARY In this contribution, a control strategy in phase coordinates abc is proposed as the reference current generator to be used by the shunt active power filter (APF) compensation device. The development of the proposed reference current generator is described in detail. Its control design is kept simple, and transformation between different fr...

This paper discusses design and application of the multiagent simulation technology aiming to meet smart grid requirements. The difference between multiagent systems and multiagent simulation in smart grid applications is clarified. The state-of-the-art applications of multiagent simulation in power and energy systems are classified based on the si...

Magnitude and duration are important characteristics when performing tracking of voltage variations. Accurate characterization of voltage variations relies much on the precise identification of frequencies of the measured signals. Although the Prony's method can provide high resolution for frequency estimation, the computational burden in the root-...

The purpose of unit commitment (UC) for electric utilities is to determine the optimal thermal unit on/off statuses and their MW generations over the scheduled time horizon. The UC problem is formulated to minimize the total generation cost, while the load demand, reserve requirements, and unit constraints are satisfied. Among the UC constraints, a...

This paper describes the challenges and lessons learned when developing industrial-grade data translators aimed for the interfacing of power-flow programs with Electromagnetic Transients Program-type programs. It has been found that the greatest challenges to overcome include: 1) the lack, in the databases used in power-flow programs, of vital piec...

Precisely forecasting the flicker level is important for drastic voltage fluctuations associated with the rapid reactive power consumptions of electric arc furnace (EAF) loads. This paper presents a prediction model based on grey theory combined with radial basis function neural network (RBFNN) for the forecast of flicker severity caused by the ope...

Overhead lines in a transmission system are the most vulnerable component to natural or human attacks that lead to different severities of faults and create power quality (PQ) disturbances such as voltage sags. The transmission network failure can cause the supply voltage interruptions and significant economic loss. The faulted lines or busses must...

The deployment of ac microgrids including distributed energy resources (DERs) can reduce the investment cost of building new fossil-fuel based power plants, facilitate the carbon-oxide reduction, provide reactive power compensation and frequency regulation, and enhance the system stability. However, some undesired effects such as imbalance, voltage...

A microgrid is associated with a low voltage distribution power network and inherits small modular generation systems and loads that have certain coordinated functions to provide the solution to supply premium power to remote or specific areas. Similar to conventional power systems, the energy management of distributed generation resources (DERs) i...

Unit commitment (UC) is to determine the optimal unit status and generation level during each time interval of the scheduled period. The purpose of UC is to minimize the total generation cost while satisfying system demand, reserve requirements, and unit constraints. Among the UC constraints, an adequate provision of reserve is important to ensure...

Rapid voltage fluctuations in an electric power network may produce significant levels of flickers, which have negative impacts on human eyes and power system components. This paper proposes a grey predictor model for the forecast of the flicker severity level associated with operating a large electric arc furnace load. Actual measured flicker inde...

In this paper, an advanced method based on measured data and neural network for highly nonlinear loads such as electric arc furnaces (EAFs) is introduced. An industrial power system with the EAF load is used for field measurements. Modeling results obtained by the proposed method are then compared with the measured data. It shows that the presented...

A micro grid consists of several distributed generation resources and local loads, which provide the solution to supply premium power to remote or specific areas. To the design of a micro grid, it is necessary to perform computer simulation for the planning and study. Before the actual system is built, all potential responses of the system should b...

Due to the demand of green energy, the number of wind turbines installed has been increased drastically worldwide. Comparing with the traditional utility generation systems, the dynamic characteristic and response of wind farms are totally different. As a result, it is very important to analyze wind generation systems with well-proven simulation to...

This paper introduces three examples of new thinking for addressing the challenges that the power system has to cope with. Such new thinking in combination with new technology will be an important element in the transition to the future electricity network (the "smart grid"). With overload protection it is important to not remove the overloaded com...

In recent years, many countries have started to integrate the power system with more advanced information and communication technologies. With transforming the electrical data to useful information, the stability and reliability of power system operation can be secured. By observing this world-wide trend, it is believed that the development of smar...

The operation of electric arc furnaces (EAFs) with drastic and random voltage-current characteristics creates considerable power quality problems in the connected power network. Because of the nonlinear behaviors of the EAF loads during operations, serious voltage fluctuations have been observed at busses that connect the substation transformer and...

The deployment of ac microgrids including distributed energy resources (DERs) can reduce the investment cost of building new fossil-fuel based power plants, facilitate the carbon-oxide reduction, provide reactive power compensation and frequency regulation, increasing spin reserve, and enhance the system stability. However, some undesired effects s...

It is known that rapid voltage fluctuations caused by electric arc furnace loads may generate significant levels of flickers, which have negative impacts to human eyes and power system components. This paper proposes a grey predictor model for the forecast of flicker levels produced by an electric arc furnace load. Actual measured data are adopted...

Voltage stability improvement is an important issue in power system planning and operation. Voltage stability of a system depends on the network topology and settings of reactive compensation devices. This research first proposes an improved voltage stability index (IVSI) for network systems, and then presents an optimization method for reactive co...

This paper proposes an efficient backward and forward sweep algorithm for the three-phase power flow analysis of weakly meshed distribution system. In the backward sweep, the Kirchhoff's circuit laws are firstly used to calculate each line current and the upstream bus voltage of each line or a transformer branch. Next, the linear proportional princ...

This task force paper presents multi-domain tools and their interfacing issues to perform simulations that require expertise in multiple areas of physics, such as electrothermal, electromechanical, electrochemical, and electromagnetic simulations, etc. Features of single multi-domain simulation tools, which are capable of simulating more than one s...

With the increasing attention of energy and environmental issues worldwide, the utilization of renewable energy has become more popular. Because of the advances of wind generation technologies, the MW capacity and the height of a single wind turbine installation have drastically increased. As a result, it is expected that modern wind turbines will...

A microgrid is a hybrid power system consists of several distributed generation resources and local loads, which provide the solution to supply premium power to remote or specific areas. However, some undesired effects are accompanied with their installations and operations, such as imbalance, voltage fluctuation, and harmonics, as well as inter-ha...

This paper presents an effective procedure based on fuzzy logic and the immune algorithm for the placement and sizing of shunt capacitor banks in a distorted power network. In the study, the power-loss index associated with each bus, the root mean square (rms) voltage, the total harmonic voltage distortion at each bus, and the capacitor site suitab...

Electric power produced by renewable energy resources has been increased drastically, where the wind generation plays the dominant role in supplying green energy. Due to the limited available sites for onshore wind farms, offshore wind generation has attracted much attention in recent years. Technical challenges for offshore wind power plants conne...

The electricity production from renewable energy has become more attractive due to the need of green energy. Wind power is a matured market resource in the power grids worldwide. Since the saturation of onshore wind farm installations, it is a trend to develop wind farms in the offshore area in the future. The challenge for offshore wind energy tra...

The operation of electric arc furnaces (EAFs) leads to drastic and random characteristics which may cause considerable power quality problems. In this study, the goal is to detect the major voltage fluctuation source that exists in an electric utility distribution substation which serves several steel-making customers. Because of the nonlinear beha...

Applications of solid-state converters and inverters for adjustable speed drives (ASDs) are popular in industrial systems and lead to a significant amount of harmonic and interharmonic currents being injected into the connected system. This paper presents an accurate analytical approach for the assessment of the harmonic and interharmonic currents...

Selection of a suitable method among various techniques for assessment of harmonic and interharmonic components of a measured voltage or current waveform is not an easy task for the students. A good start is to understand the relationship between the analysis techniques and the measured parameters. In this paper, several commonly used methods for t...

This paper presents simulation results by using Matlab/Simulink for the assessment of harmonic and interharmonic currents generated by the voltage source inverter (VSI)-fed adjustable speed drives (ASDs). In the simulation, the commutation effects caused by source impedance and non-ideal supply voltages are included. The front-end converter, dc lin...

This paper presents application experiences of real-time simulation (RTS) techniques for harmonic and flicker studies of an industrial power system, where the system and nonlinear loads are properly modeled. A PC-cluster-based real-time parallel simulator is implemented under MATLAB/SIMULINK, where the studied system consists of an ac electric arc...

This paper presents a fuzzy-based algorithm for the placement and sizing of shunt capacitor banks in a harmonics-polluted distribution system. In the problem the objective function is the total system power loss and the capacitor installation cost, while the constraints are the rms voltage, the individual and total harmonic voltage distortion limit...

Frequency is an important factor for power system harmonics measurement. Accurate spectral analysis relies much on the correct identification of frequencies of the measured signals. In this paper, several commonly used methods for power system stationary and time-varying harmonics measurement are reviewed and compared according to the aspect of fre...

Frequency is an important indicator for the quality of electric power. Accurate spectral decompositions rely much on the correct identification of frequencies of the measured signals. An efficient procedure that includes a high-resolution Prony-based method in conjunction with the downsampling technique for harmonics and interharmonics detection of...

This paper reviews different methodologies for interfacing time-domain and frequency-domain simulation programs. The main objective for this interface is to obtain the steady-state or transient state of a power network containing linear and nonlinear loads, and the calculation of the corresponding harmonics and the foregoing values for different ty...

This letter presents an extended Mayr's equation-based model for the pantograph detachment arc of the high-speed railway traction system. The proposed model is composed of Mayr's model for arc behavior control and time-controlled switches for starting pantograph detachment and reattachment events, which are developed by MODELS language and TACS in...

The widespread application of power-electronic loads has led to increasing harmonic pollution in the supply system. In order to prevent harmonics from deteriorating the power quality, detecting harmonic components for harmonic mitigations becomes a critical issue. In this paper, an effective procedure based on the radial-basis-function neural netwo...

Effective detection of power quality events is an important issue for maintaining reliable operations of power systems. Under different measuring environment, detection methods usually need different requirements. In this paper, the performances of several commonly seen methods for the detection of voltage sags are evaluated and compared.

The widespread application of power electronic loads has led to increasing harmonic pollution in the supply system. In order to prevent harmonics from deteriorating the power quality, detecting harmonic components for harmonic mitigations becomes a critical issue. In this paper, an effective procedure based on the radial basis function neural netwo...

This paper presents an approach of incorporating hardware-in-the-loop simulation and ADALINE for shunt active power filter (APF) design. Even when the three-phase source voltages are unbalanced and/or distorted and supply to a nonlinear load, the described compensation strategy can compensate the harmonic and neutral current, and thus improve the p...

The electromagnetic transient programs (EMTP-like tools) are based on the nodal (or modified nodal) equations that enable an efficient numerical solution and, subsequently, fast time-domain simulations. The state-variable-based simulation programs, such as Simulink, are also used for studying the dynamics of electrical systems. Both the offline and...

Field measurements of voltage and current are the most effective way for characterizing the electric response of an ac electric arc furnace that describes its nonlinear behavior. Sufficient measured information can be adopted to determine the background harmonic level in a power system, to characterize specific sources of harmonics, and to develop...

It is known that artificial neural network is a powerful scheme for function learning and modeling nonlinear loads. However, a direct application of artificial neural network for modeling time-varying loads may lead to inaccuracies. This paper presents an accurate neural-network-based method for modeling the highly nonlinear voltage-current charact...

The effective harmonics estimation for measuring power signals has become an important issue in the power quality assessment. By reviewing those commonly used Kalman filter-based models, some limitations for harmonics estimation can be observed. In this paper an extended real model of Kalman filter combined with a resetting mechanism for accurately...

Wind turbines may cause significant impacts on the power quality of their connected grid. Voltage fluctuations produced by wind turbines are usually due to wind speed variations, power and voltage fluctuations. This paper presents simulations for numerical models of two wind turbine schemes, fixed and variable speed types, by using Matlab/Simulink,...

In this paper an efficient time-domain technique based on Prony's method for the time-varying power system harmonics estimation is proposed. Though the high frequency resolution is the major advantage of Prony's method, the great computational burden with the high estimation order usually makes it only suitable for the off-line analysis. To achieve...

Power quality indices are important parameters to assess the operation of a power system. Though there are many power quality indices defined in the literature, the actual operation status of the system is still difficult to observe in some practical applications with the given indices. In this paper, several commonly used and recently proposed pow...

Voltage fluctuations caused by rapidly changing loads in the power systems may give rise to noticeable illumination flickers of lighting equipment. The voltage flickers can also cause malfunctions in many electric devices. This paper presents a digital implementation of flickermeter in the hybrid time and frequency domains based on IEC standard 610...

Harmonics and interharmonics may introduce operational problems in electrical and electronic equipment. Therefore, monitoring harmonics/interharmonics for improving the power quality is of importance for both electric utilities and their customers. In this paper, a cascaded two-stage adaptive linear element (ADALINE) structure for both harmonics an...

Model-based simulations by commercial simulation packages, such as EMTP/ATP, PSCAD/EMTDC and MATLAB/SIMULINK often provide convenience for testing and analyzing the power quality studies. Nowadays, the real-time simulation techniques are highly developed to enhance the capabilities of traditional off-line simulations. This paper presents the real-t...

In this paper an efficient technique based on Prony's method for the time-varying power system harmonic estimation is proposed. Although the high frequency resolution is the major advantage of Prony's method, the great computational burden with the high estimation order usually makes it only suitable for the off-line analysis. To achieve the fast h...

It is typically time-consuming to obtain the time-domain responses of power system from conventional off-line simulation. With the advanced development in computer technologies, the applications of real-time simulations are introduced to power system studies for enhancing the capabilities of traditional off-line simulations. This paper presents a P...