Shin-Ju Chen

Optimal active-reactive power dispatch using an enhanced differential evolution algorithm

This paper presents an enhanced differential evolution (EDE) algorithm to alternatively solve the optimal active-reactive power dispatch (ARPD) problem. Theoretically, there has a coupling relation between active and reactive power dispatches. However, due to a high X/R ratio existing in the transmission line, the problem of ARPD can then be decomposed into two individual sub-problems by the decoupling concept, i.e., active and reactive power dispatch problems. In this paper, a differential evolution algorithm enhanced by combining variable scaling mutation and ant algorithm was proposed to alternatively solve the ARPD problem in a single simulation run. Due to the superiority in optimization, the EDE method is very adequate to deal with the ARPD problem. The proposed approach has been verified on the IEEE 30-bus 6-generator system. Testing results indicate the proposed EDE was superior to the existing methods in terms of active power loss, operating cost, and convergence time.

Evolving radial basic function neural network for fast restoration of distribution systems

This paper presents an optimal radial basic function (RBF) neural network for fast restoration of distribution systems under different load levels. Basically, service restoration of distribution systems is a stressful and urgent task that must be performed by system operators. In this paper, a RBF network evolved by an enhanced differential evolution (EDE) algorithm is developed to achieve the fast restoration of distribution systems. The proposed scheme comprises training data creation phase and network construction phase. In the training data creation phase, a heuristic-based fuzzy inference (HBFI) method is employed to build the restoration plans under various load levels. Then an optimal RBF network is constructed by the EDE algorithm in the network construction phase. Once the RBF network is constructed properly, the desired restoration plan can be produced as soon as the inputs are given. The proposed method has been verifiedd on a typical distribution system of the Taiwan Power Company (TPC). Results show the proposed method can provide better convergence performance and forecasting accuracy than the existing methods.

FPGA-based digital control for boost converters with power factor correction

A field programmable gate array (FPGA) based digital control for boost power-factor-correction (PFC) converters with average current-mode control (ACC) is implemented in the paper. It is designed to fulfill the international current standards on power factor and input current harmonic distortion of power supplies. The digital control design of the boost PFC converter with ACC is implemented by the kit DE2-70 based on the FPGA Cyclone II EP2C896C6N. The control algorithm is developed using the hardware description language Verilog. A prototype of 350W FPGA-controlled boost PFC converter with 90~130 V in the ac input and 312V in the dc output has been built. The experimental results are provided to verify the high power factor complying with IEC61000-3-2 Class-D and output voltage regulation against the input voltage variation and load change.

Small-signal modeling and controller design of BCM boost PFC converters

In this paper, the small-signal model of a boundary conduction mode (BCM) boost power factor correction (PFC) converter controlled by a peak control current control IC L6561 is derived. Based on the derived mathematical model, a Type II compensator is thus well designed to make the boost converter exhibits the performances of high power factor and output voltage regulation. Finally, a 300 W prototype of the BCM boost PFC converter with IC L6561 is implemented. The performance of high power factor and power efficiency is validated by experimental results. Furthermore, the regulation of output voltage despite the variations of the peak line voltage and load resistances is also verified.

Analysis, modeling and controller design of CRM PFC boost ac/dc converter with constant on-time control IC FAN7530

In this paper, a boost ac/dc converter is controlled by an on-time control IC FAN7530 to operate in critical conduction mode (CRM) and exhibits the capability of high power factor correction (PFC). In order to simplify the steady-state analysis, the operating principle is analyzed by a functional-block-diagram (FBD) method. The component considerations are also presented herein. Additionally, the small-signal model of a CRM PFC boost ac/dc converter with variable switching frequencies is derived. Based on the derived mathematical model, a voltage controller is thus well designed to make the proposed boost ac/dc converter have the performances of high power factor and output voltage regulation. Finally, a 300 W prototype of the CRM PFC boost ac/dc converter with IC FAN7530 is implemented. Its performance of high power factor is thus validated by experimental results. Furthermore, the regulation of output voltage despite the variations of the peak line voltage and load resistance is demonstrated.

An interleaved ZVS forward converter with series input parallel output structure

An interleaved zero-voltage-switching (ZVS) forward converter for high input voltage and high output current applications is proposed in this paper. The converter consists of two active-clamp forward converter cells in series input and parallel output connection to share the input voltage and output current. The interleaved operation is employed to diminish the current ripple on the output capacitor. The resonant inductance and the output capacitances of switches are utilized to realize the resonance at the transition interval of switches such that the ZVS turn-on operation for all switches can be achieved. All these features make the proposed converter suitable for high input voltage, high output current and high efficiency applications. The operating principle, characteristics and design considerations of the proposed converter are presented. Finally, the experimental results of a prototype converter with an input of 400 V and an output of 24V/20A are provided to verify the validity of the proposed converter.

Deterministic and probabilistic wind power forecasting using a hybrid method

This paper proposes a hybrid method for probabilistic wind power forecasting. The proposed approach consists of data classification, deterministic forecasting and probabilistic forecasting stages. In the data classification stage, a fuzzy k-means clustering algorithm is used to classify the historical time series of wind power into various wind classes. Several support vector regression (SVR) models that correspond to diverse wind speeds are then established to train the collected data in the deterministic forecasting stage. An enhanced harmony search (EHS) algorithm is presented to estimate the parameters for each SVR model. Using the wind speed forecasts given by Taiwan Central Weather Bureau (TCWB) for every three hours, a corresponding forecasting model is then used to produce wind power forecasts for future 3 hours in steps of 15 minutes. To assess the risk that is associated with forecasting errors, an EHS-based quantile regression (QR) method is used to provide the confidence intervals for forecasted values in the probabilistic forecasting stage. During testing on a practical wind power generation systems, the proposed method gives better forecasting accuracy and produces more reasonable confidence intervals than existing methods.

An Intelligence-Based Approach to Optimal Power Flow Control Considering Flexible AC Transmission Systems

This chapter proposes an intelligence-based approach to solve the optimal power flow (OPF) problem considering flexible AC transmission system (FACTS). FACTS plays an important role in dynamic stability and steady-state control of power systems. This chapter aims at the study of steady-state control which determines the optimal location of FACTS devices and their associated values in the transmission lines. To determine the optimal solution of FACTS, this chapter presents an improved differential evolution (IDE) approach to deal with the OPF problem. The IDE uses a variable scaling mutation operation to enhance the global search capability of basic DE. Therefore, it is very appropriate to solve the OPF problem. The proposed method is verified on an IEEE 30-bus 41-transmission line system. Results show that the proposed approach can save more active power transmission loss and provides better convergence performance than the existing methods.

A new interleaved series input parallel output zero-voltage-switching forward converter

A new interleaved soft-switching forward converter is proposed in this paper. Two active-clamp forward converters are connected in series input and parallel output structure to share the input voltage and output current. The output capacitance of switches and the resonant inductance are utilized to realize the resonance at the transition interval of switches such that the zero-voltage-switching (ZVS) operation for all switches can be achieved. The current-doubler rectifier with ripple current cancellation is used to reduce the current stress of the transformer secondary winding. The interleaved PWM operation also diminishes the current ripple in the output capacitor to reduce the size of the output filter. All these features make the proposed converter suitable for high input voltage, high output current and high efficiency applications. The operating principles, steady-state analysis and design considerations of the proposed converter are presented. Finally, experimental results based on a 240 W (12V/20A) prototype are provided to verify the effectiveness of the proposed converter.

Interleaved high step-up DC-DC converter with parallel-input series-output configuration and voltage multiplier module

An interleaved high step-up dc-dc converter is proposed for high voltage gain and high efficiency applications. The configuration is composed of modified two-phase interleaved boost converter with parallel-input series-output connection and a voltage multiplier module stacking on the output side. In the proposed converter, the parallel-input connection is used to share the input current and to reduce the conduction losses, while the series-output connection and voltage multiplier module are employed to obtain the high voltage gain without operating at extreme duty ratio. In addition, the input current ripple is reduced due to the interleaved operation. The voltage stresses on the power switches are greatly lower than the output voltage such that the low-voltage-rated MOSFETs with low conduction resistor are available to reduce the conduction losses and to improve the conversion efficiency. Meanwhile, the output diode reverse-recovery problem is alleviated by the leakage inductance of the coupled inductors. Finally, the experimental results from a 1-kW prototype are provided to validate the effectiveness of the proposed converter.