A proposal of a power distortion compensator using a matrix converter

Recently, renewable resource supplies, such as fuel cells, photovoltaic cells, wind power, and engine generators for distributed power systems have been studied intensely. Conventional compensators with switching devices are constructed based on a voltage source inverter using six arms. Therefore, conventional power quality compensators require a large electrolytic capacitor in the DC link part of the equipment. The use of a large capacitor hinders downsizing efforts and the lowering of equipment costs. Direct converters, which do not have a large electrolytic capacitor and an initial charge circuit, can be used to realize downsizing and lowering of equipment costs, when compared with conventional converters. This paper proposes a new application of a matrix converter to a PM generator for power quality compensation, such as reactive power compensation, harmonic current, and power interruption. The novel point of this work is that the matrix converter provides reactive power with harmonic current. Simulated and experimental results confirm that the matrix converter can maintain high performance the same as a conventional active filter and an uninterruptible power supply (UPS). © 2010 Wiley Periodicals, Inc. Electr Eng Jpn, 171(4): 37–44, 2010; Published online in Wiley InterScience ( www.interscience.wiley.com ). DOI 10.1002/eej.20972     

Decentralized secondary voltage control using voltage drop compensator among power plants

This paper deals with the problem of voltage collapse in power systems by presenting a decentralized secondary voltage control. For this purpose the coordination between the joint voltage control available in the generation plants is used to control the voltage level at the transmission system by adjusting a compensation impedance. By using this approach, the generation plants become more sensitive to the system operating and configuration conditions. A sensitivity-based methodology to identify the most effective plants and the impedance value associated is presented. Some examples meant to explore the potential of the methodology are presented and discussed with the help of real systems.     

Optimal control of a hybrid power compensator using an artificialneural network controller

A hybrid power compensator (HPC) consisting of a static VAr compensator and a dynamic compensator needs to be optimally controlled during the compensation of nonlinear loads. The HPC must be controlled to meet minimum requirements in terms of power factor and harmonic distortion, while at the same time minimizing its total cost. The use of an artificial neural network (ANN) to control the HPC amid a very dynamic environment to achieve the above is investigated. A state-space model of the power distribution network together with the HPC forms the basis of evaluation of the mentioned controller. The model was calibrated against actual in-network measurements. The results obtained reveals that the application of an ANN in controlling an HPC is feasible given that the ANN parameters are chosen appropriately     

Decentralized robust adaptive neural dynamic surface control for multi‐machine excitation systems with static var compensator

Focusing on solving the control problem of the multimachine excitation systems with static var compensator (SVC), this paper proposes a decentralized neural adaptive dynamic surface control (DNADSC) scheme, where the radial basis function neural networks are used to approximate the unknown nonlinear dynamics of the subsystems and compensate the unknown nonlinear interactions. The main advantages of the proposed DNADSC scheme are summarized as follows: (1) the strong nonlinearities and complexities are mitigated when the SVC equipment are introduced to the multimachine excitation systems and the explosion of complexity problem of the backstepping method is overcome by combining the dynamic surface control method with neural networks (NNs) approximators; 2) the tracking error of the power angle can be kept in the prespecified performance curve by introducing the error transformed function; (3) instead of estimating the weighted vector itself, the norm of the weighted vector of the NNs are estimated, leading to the reduction of the computational burden. It is proved that all the signals in the multimachine excitation system with SVC are semiglobally uniformly ultimately bounded.     

Hybrid intelligence approach for multi-load level reactive power planning using VAR compensator in power transmission network

This paper formulates and solves a techno-economic planning problem of reactive power (VAR) in power transmission systems under loadings. The objective of the proposed research work is to minimize the combination of installation cost of reactive power sources, power losses and operational cost while satisfying technical constraints. Initially, the positions for the placement of reactive power sources are determined technically. Different cost components such as VAR generation cost, line charging cost etc. are then added in the total operating cost in a most economical way. Finally, the optimal parameter setting subjected to reactive power planning (RPP) is obtained by taking advantages of hybrid soft computing techniques. For the justification of the efficiency and efficacy of the proposed approach the entire work is simulated on two inter-regional transmission networks. To validate the robustness and ease of the soft computing techniques in RPP the responses of benchmark functions and statistical proof are provided simultaneously.     

电力系统电容补偿装置的优化设计

针对电容器的优化分组提出了典型日负荷曲线与经济性分析相结合的电容器优化分组方法.该方法以电容器投资费用与因变电站的无功补偿不足而引起的系统有功损耗费用之和达到最小为优化问题的目标函数,并以此为基础求解电容器的优化分组问题.对实际电力系统电容器分组优化改造的结果表明,以本文提出的优化目标函数为基础的方法具有明显的经济效益,可以提高供电质量和设备的利用率.     

Optimal location of PWM based series compensator in a power system

This paper proposes a new approach for optimal placement of PWM based Series Compensator (PWMSC) in large power systems. The proposed approach is based on the Selective Modal Analysis (SMA) and dynamics index to damp out the inter-area oscillation modes. For this reason, first, SMA is used to calculate the low frequency modes of oscillation, and then Most Dominant Line (MDL) Table based on the dynamic index is proposed which shows the influence of active power flows of the transmission lines on inter-area modes of the power system. The parameters of the PWMSC damping controller are designed by optimization based approach for the purpose of damping inter-area oscillations in practical system. Optimal PWMSC placement is validated by comparing different candidate placements based on the total damping that they provide for system. The effectiveness of the proposed method is demonstrated on the 16-machine five-area power system for various network conditions.     

多机系统励磁的非线性L2增益干扰抑制控制

针对多机电力系统，基于严格耗散理论，提出了一种新的能够实现干扰抑制的励磁鲁棒非线性控制策略，在实现过程中不需要任何线性化方法。对三机系统的仿真结果表明，提出的励磁控制策略可提高电力系统暂态稳定性。     

Parallel voltage sag compensator with reduced capacitance using a boost‐type power factor correction rectifier

A new circuit of parallel‐type voltage sag compensator is proposed in this paper. The proposed voltage sag compensator can reduce the necessary capacity of the energy storage capacitor for compensation by boost‐type power factor correction rectifier charging the capacitor during a voltage sag. As a result the proposed system can reduce the size and maintenance of the apparatus. Copyright © 2004 Wiley Periodicals, Inc. This paper shows the principle and control system of the proposed circuit. Compensation characteristics were demonstrated by simulation and experiment. © 2007 Wiley Periodicals, Inc. Electr Eng Jpn, 159(2): 19–33, 2007; Published online in Wiley InterScience ( www.interscience.wiley.com ). DOI 10.1002/eej.20261     

光伏发电系统的发电机有功和无功功率补偿器

光伏发电系统作为分布式电源,它发出的电能通过逆变器输向电网.目前用于分布式系统的大多数逆变器是运行于单位功率因数电流源型逆变器.如果将电压源型逆变器用电流源型逆变器取代,那么光伏发电系统可以在任何时间发出无功功率.根据瞬时功率的理论,逆变器的无功功率可以通过改变其输出电压幅值控制,而有功功率可以通过调整输出电压相位来控制,且有功功率的供给和无功功率的补偿都可以同步进行.当光照强度弱或者光伏模块无法运行时,光伏系统的无功补偿仍然可以用来提高逆变器利用率.     

无功补偿装置在大型辅机启动中应用

某电厂的临时电源系统接入的是农网,在机组的大型辅机启动时,会产生冲击电流和电压跌落,对地方电网产生不利的影响.提出在电厂辅机启动中应用无功补偿及液组软启动的方案来消减产生的不利影响,该方案能将电机的启动电流限制在要求的范围内.阐述了无功补偿装置的现场布置、辅机启动前容量的确定、无功补偿的作用(可以提高功率因数、减小启动电流、延长设备寿命、改善系统运行电压).     

Controlling chaos and voltage collapse using an ANFIS-based composite controller-static var compensator in power systems

Chaos and voltage collapse exist in power systems due to critical loading and disturbing of energy (DE). These phenomena cause instability in power system operation and must be avoided. In this paper, an ANFIS-based composite controller-static var compensator (CC-SVC) was proposed to control both chaotic oscillations and voltage collapse. The ANFIS-based CC-SVC was proposed because its computation was more efficient than Mamdani fuzzy logic controller. Adaptive network parameters were obtained through a training process. The controller parameters were automatically updated by off-line training. Both chaos and voltage collapse were able to control and suppress effectively by the proposed method. Furthermore, the load voltage was held to a set value by adjusting the supplied reactive power. When the reactive load was increased, the SVC susceptance and reactive power supplied by the SVC also increased. The proposed method was able to maintain the load voltage and to increase the loading margin.     

Efficiency improvement of high‐frequency inverter for wireless power transfer system using series compensator

This paper proposes a wireless power transfer system using a series compensator GCSC (gate‐controlled series capacitor) as a primary side capacitor. The GCSC is a circuit module that functions as a series variable capacitor by controlling semiconductor switches. The advantage of applying the GCSC to the primary side capacitor is that it provides controllability of the output power factor for a high‐frequency inverter. Therefore, optimum operation of the high‐frequency inverter can be achieved irrespective of the coil parameters by controlling the output power factor. Experimental results with a 1 kW laboratory prototype confirmed that the proposed system can achieve optimum operation and high efficiencies of the high‐frequency inverter.     

新型静止无功补偿器稳定系统电压的研究

介绍一种基于PWM技术的新型静止无功补偿器。研究该补偿器在稳定系统电压方面的作用,分别对它在小扰动和大扰动情况下的工作状况进行分析,证明在工作范围内新型静止无功补偿器对系统电压有很大的支撑作用,可有效稳定系统电压。该补偿器具有结构简单、控制方便、响应速度快等特点。采用单机无穷大系统对补偿器进行开环和闭环控制仿真研究,验证该补偿器能维持装设点的电压并提高其电压稳定性。     

Modified static VAR compensator using a large value AC capacitor

To overcome some of the limitations of conventional static VAR compensators (SVCs) which are widely used for reactive power compensation, a modified SVC (MSVC) has been proposed. MSVC uses a large value AC capacitor. The large value AC capacitor is realized using unipolar DC capacitors and power semiconductor devices. Unlike the conventional SVCs, the proposed MSVC does not require additional shunt passive filters for harmonic filtering. MSVC has been verified through analysis and simulation. A practical implementation of MSVC has been realized and tested.     

Robust excitation control design using sliding-mode technique for multimachine power systems

An output feedback controller is proposed to enhance the transient stability of nonlinear multimachine power systems considered as a classical model with flux decay dynamics. Combining high-order sliding-mode techniques with a robust high-order sliding-mode differentiator, a robust decentralized controller is obtained. Numerical results are presented to illustrate the performance of the proposed control scheme and its robustness properties.     

Robust excitation control of multi-machine multi-load power systems using Hamiltonian function method

Using an energy-based Hamiltonian function method, this paper investigates the robust excitation control of multi-machine multi-load power systems described by a set of uncertain differential algebraic equations. First, we complete the dissipative Hamiltonian realization of the power system and adjust its operating point by the means of pre-feedback control. Then, based on the obtained Hamiltonian realization, we discuss the robust excitation control of the power system and put forward an H _∞ excitation control strategy. Simulation results demonstrate the effectiveness of the control scheme.