A novel induction generator system using bi‐directional PWM converter for small‐scale power applications

This paper presents a deadbeat current control structure for a bidirectional power flow pulse‐width modulation (PWM) converter connected to a stand‐alone induction generator (IG), which works with variable speed and different types of loads. Sensorless control of the IG, meaning stator voltage vector control without a mechanical shaft sensor, is considered to regulate both the IG line‐to‐line voltage and the DC‐bus voltage of the PWM converter. In the proposed system, a newly designed phase locked loop (PLL) circuit is used to determine the stator voltage vector position of the IG. A 2.2 kW laboratory prototype has been built to confirm the feasibility of the proposed method. The proposed cost‐effective IG system with a deadbeat current‐controlled PWM converter and capacitor bank requires only three sensors. Moreover, the required rating of the PWM converter becomes smaller due to the existence of the capacitor bank. © 2006 Institute of Electrical Engineers of Japan. Published by John Wiley & Sons, Inc.     

Sinusoidal current‐tracking control for utility interactive inverter with an LCL filter

A voltage source inverter with an LCL filter is often used for a utility interface to control its output current to a grid side because of its harmonic reduction advantages. The integral compensator is often used to reduce the steady‐state errors. However, there is always a control delay due to sinusoidal variations. This paper proposes a digital sinusoidal compensator which is based on the internal model principle to realize a fast sinusoidal response with no delay. It is based on the internal model principle to realize a response with no deviation for a periodic sinusoidal reference input. It has a simple numerator and a denominator z² ? 2z cosωT + 1 of a transfer function which is equal to the z function of a sinusoidal waveform of the angular frequency ω and the sample time T. Compensator and feedback gains of the inverter are determined by the deadbeat or the optimal control principle. The proposed method is investigated for performances and it is validated through simulation and experimental results by a DSP control system. © 2013 Wiley Periodicals, Inc. Electr Eng Jpn, 183(2): 22–28, 2013; Published online in Wiley Online Library (wileyonlinelibrary.com). DOI 10.1002/eej.22339     

A three‐phase,active power filter with a predictive‐instantaneous‐current PWM controller

One of the most emphasized problems to be solved in power systems in recent years is the line‐current harmonics problem. This is due to the use of diode rectifiers, PWM converters, nonlinear loads, and so on. To reduce or eliminate such current harmonics, an active power filter (APF), which is a sophisticated power electronic converter, has been studied and used in some practical applications. In this paper, we propose and discuss two new control methods for three‐phase shunt APFs: the sinusoidal line‐current control method and the instantaneous‐reactive‐power compensation control method. They are based on pulsewidth prediction control, or a predictive‐instantaneous‐current PWM control. Neither any instantaneous power information nor coordinate transformation is necessary for control. In the sinusoidal line‐current control scheme, the controller governs the switching devices of the APF by using the pulse width that is optimally predetermined at the beginning of every switching period with the sinusoidal current reference. The line currents flow sinusoidally and are in phase with the voltage accordingly. In the instantaneous‐reactive‐power compensation control, the control is performed so that the resultant circuit of the load and the APF is regarded as a time‐variant conductance circuit model. The APF with this control scheme can cancel effectively the instantaneous reactive component produced by the load though the controller is simple. This paper discusses the performance characteristics of the APFs when a three‐phase diode rectifier and an unbalanced load are connected to the line. The practicability of the proposed methods is verified by experiment. © 1999 Scripta Technica, Electr Eng Jpn, 130(3): 68–76, 2000     

A self‐commutated back‐to‐back system and its performance under a single line‐to‐ground fault condition

This paper deals with a self‐commutated BTB (Back‐To‐Back) system for the purpose of power flow control and/or frequency change in transmission systems. Each BTB unit consists of two sets of 16 three‐phase voltage‐source converters, and their AC terminals are connected in series to each other via 16 three‐phase transformers. Hence, the BTB unit uses totally 192 switching devices capable of achieving gate commutation. This results in a great reduction of voltage and current harmonics without performing PWM control. Simulation results verify the validity of the proposed system configuration and control scheme not only under a normal operating condition but also under a single line‐to‐ground fault condition. © 2003 Wiley Periodicals, Inc. Electr Eng Jpn, 143(3): 68–78, 2003; Published online in Wiley InterScience ( www.interscience.wiley.com ). DOI 10.1002/eej.10124     

Novel three‐phase current‐regulated digital PWM and its behavioral analysis

There have been various studies of PWM algorithms for a three‐phase voltage‐source AC/DC power converter since the analog modulation scheme based on a triangular carrier wave was proposed in the 1960s. The PWM algorithm can be considered the heart of electronic power conversion. With progress in digital technology, there is an increasing need for gate signals to be generated directly by digital ICs, such as MPU, DSP, or FPGA/CPLD. This paper analyzes quantitatively the precision of current control of digital PWM taking account of both the sampling period and the delay time (the latter is inevitably accompanied by a digital procedure). The delay time is shown to have a double effect on the current error. In addition, the paper theoretically derives the conditions for digital PWM to meet the PPCR (Pulse Polarity Consistency Rule, that is, the next gate command moves only to the adjacent ones or commands). So far as the authors know, no paper has presented the mathematical requirements for PPCR taking account of the effect of the delay time of digital PWM. The derived theoretical results are summarized as digital PWM design criteria for a three‐phase PWM converter in order to facilitate practical implementation of the theory, guaranteeing PPCR behavior as well as quantitative accuracy of current regulation. © 2004 Wiley Periodicals, Inc. Electr Eng Jpn, 150(2): 62–77, 2005; Published online in Wiley InterScience ( www.interscience.wiley.com ). DOI 10.1002/eej.10330     

A three‐vector‐based direct power control strategy for three‐phase voltage source PWM converters

For traditional direct power control strategy, there exist high steady‐state power ripples and large current harmonics. To solve this problem, this work proposes a novel three‐vector‐based direct power control strategy for three‐phase voltage source pulse‐width‐modulated (PWM) converters. Different from traditional predictive direct power control strategy, an improved vector table is presented and three voltage vectors are selected, which considers the impact of voltage vectors on the active and reactive power simultaneously. The performance of the three‐phase voltage source PWM converters with the proposed control strategy is investigated and compared with the predictive deadbeat direct power control strategy. Furthermore, the three‐phase voltage source PWM converters have also been tested in the condition of different loads and when voltage unbalance occurs. Simulation and experimental work are conducted. The results conclude that the proposed strategy is of simple structure and fast dynamic response. Besides, it can effectively reduce steady‐state power ripples and current harmonics, improving the performance of the three‐phase PWM converters. Copyright © 2016 John Wiley & Sons, Ltd.     

基于自适应谱线增强器预测的有源电力滤波器无差拍控制方法

为了克服有源滤波器控制中由于A/D采样、数据处理等环节带来的延时,提高控制的实时性,采用一种基于自适应谱线增强器（ALE）预测的有源滤波器无差拍控制方式。通过两次ALE预测得到两拍以后的指令电流参考值,进而由无差拍控制得出逆变器的输出电压,经SVPWM调制后给出IGBT驱动信号,从而实现补偿电流无差拍的跟踪指令电流。理论推导证明了所采用预测算法的鲁棒性在H∞意义上是最优的,仿真和试验验证了该方法的正确性和可行性。     

有源电力滤波器无差拍控制策略的研究

采用了一种检测负载侧与电源侧电流的复合谐波电流检测方法,针对四桥臂拓扑结构的有源电力滤波器(APF),提出了一种新型无差拍控制策略,通过对系统结构的分析建立完整的数学模型,对APF各相输出补偿电流之间的耦合问题进行深入研究并提出相应的解决方法。仿真分析和实验结果验证了复合谐波电流检测算法和无差拍控制策略的有效性和正确性。     

Three‐stage multiphase‐switched‐capacitor boost DC‐AC inverter

A closed‐loop scheme of a three‐stage multiphase‐switched‐capacitor boost DC‐AC inverter (MPSCI) is proposed by combining the multiphase operation and sinusoidal‐pulse‐width‐modulation (SPWM) control for low‐power step‐up DC‐AC conversion and regulation. In this MPSCI, the power unit contains two parts: MPSC booster (front) and H‐bridge (rear). The MPSC booster is suggested for an inductor‐less step‐up DC‐DC conversion, where three voltage doublers in series are controlled with multiphase operation for boosting voltage gain up to 2³ = 8 at most. The H‐bridge is employed for DC‐AC inversion, where four solid‐state switches in H‐connection are controlled with SPWM to obtain a sinusoidal AC output. In addition, SPWM is adopted for enhancing output regulation not only to compensate the dynamic error, but also to reinforce robustness to source/loading variation. The relevant theoretical analysis and design include: MPSCI model, steady‐state/dynamic analysis, voltage conversion ratio, power efficiency, stability, capacitance selection, total harmonic distortion (THD), output filter, and closed‐loop control design. Finally, the closed‐loop MPSCI is simulated, and the hardware circuit is implemented and tested. All the results are illustrated to show the efficacy of the proposed scheme. Copyright © 2011 John Wiley & Sons, Ltd.     

Experimental investigation of a speed‐sensor‐less IM drive system under Inverter fault‐tolerant control

This paper proposes an algorithm for fault tolerance of three‐phase, inverter‐fed, speed‐sensor‐less control of a three‐phase induction motor drive system. The fault tolerance of the inverter when one switch is open or one leg of six‐switch inverter is lost is considered. The control of the drive system is based on indirect rotor field‐oriented control theory. Also, the speed estimator is based on model reference adaptive system (using stator current and rotor flux as state variables for estimating the speed). The fault‐tolerant algorithm is able to adaptively change over from a six‐switch inverter to a four‐switch inverter topology when a fault occurs; also, it makes a smooth transition of the motor speed, torque, and current when changing over from a faulty condition to a new healthy status, which is four‐switch three‐phase inverter (FSTPI) topology; thus, the six‐switch three‐phase inverter (SSTPI) topology (pre‐fault status) is almost retained for the medium‐power range of induction motor applications. The proposed algorithm is simulated by using the MATLAB/SIMULINK package. Also, the proposed control system is tested experimentally using a digital signal processor (DSP1104). The obtained results from the simulation model and experimental system demonstrate the performance enhancement and good validity of the fault‐tolerance control for the speed‐sensor‐less induction motor drive system. © 2016 Institute of Electrical Engineers of Japan. Published by John Wiley & Sons, Inc.     

模糊控制在三相PWM整流器无差拍控制中的应用

无差拍电流控制为了补偿控制延时,需要对参考电流进行超前预测,由于参考变化的不确定性,单一的预测算法在不同参考变化情况下可能产生较大的电流超调或者相位滞后。本文通过对三种常用预测算法进行比较分析,得出预测参数与电流超调和相位滞后之间的关系,以此提出一种基于模糊控制的预测算法。该算法针对不同的参考电流变化选择合适的预测参数,折衷考虑电流超调和相位滞后的影响,限制电流超调最大值,优化相位滞后。最后,结合TMS320F2812 数字信号处理器(digital signal processor,DSP)控制平台在三相电压型脉宽调制(pulse width modulation,PWM)整流器上进行实验,验证了理论分析的正确性。     

FPGA‐based implementation for improved control scheme of grid‐connected PV system with 3‐phase 3‐level NPC‐VSI

The large scale penetration of renewable energy resources has boosted the need of using improved control technique and modular power electronic converter structures for efficient and reliable operation of grid‐connected systems. This study investigates the performance of a grid‐connected 3‐phase 3‐level neutral‐point clamped voltage source inverter for renewable energy integration by using improved current control technique. For medium or high‐voltage grid interfacing, the multilevel inverter structure is generally used to reduce the voltage stress across the switching device as well as the harmonic distortion. The neutral‐point clamped voltage source inverter is controlled by using decoupling technique along with the proper grid synchronization via moving average filter–based phase‐locked loop. The moving average filter–based phase‐locked loop is used to reduce the delay in grid angle estimation under balanced as well as distorted grid conditions. A Lyapunov‐based approach for analysing the stability of the system has also been discussed. In this study, the hardware‐in‐loop (HIL) simulation of the control algorithm and the grid synchronization technique is realized using Virtex‐6 FPGA ML605 evaluation kit. The performance of the system is analyzed by conducting a time‐domain simulation in the Matlab/Simulink platform and its performance is examined in the HIL environment. The simulation and the hardware cosimulation results are presented to validate the effectiveness of the proposed control scheme.     

A simplified cascade current‐source inverter interconnected to a single‐phase three‐wire distribution system and its application to electric energy storage systems with batteries

A novel current source inverter system interconnected to the single‐phase grid is proposed. It has the same construction as the conventional three‐phase current source inverter that is interconnected to the single‐phase three‐wire distribution system. Though the proposed circuit has no output transformer, it can be equivalently performed as the single‐phase double cascade inverter by diverting the pole transformer in the utility system. By controlling the appropriate scheme, the output currents can be obtained as the five‐level waveforms and their distortions can be decreased sufficiently. It is applied to the interactive electric energy storage system with batteries and the basic discharging characteristics are discussed experimentally. © 2004 Wiley Periodicals, Inc. Electr Eng Jpn, 150(2): 50–61, 2005; Published online in Wiley InterScience ( www.interscience.wiley.com ). DOI 10.1002/eej.10380     

A control method for small‐scale DC power systems including distributed generators

This paper describes a DC micro‐grid system interconnecting distributed power generators. The system consists of five generation and control units: a solar‐cell generation unit, a wind‐turbine generation unit, a battery energy‐storage unit, a flywheel power‐leveling unit, and an AC grid‐interconnecting power control unit. The control method is proposed for suppressing the circulating current by detecting only the DC grid voltage. This method brings high reliability, high flexibility, and maintenance‐free operation to the system. The method pays attention to DC output voltage performance of each unit. Each of the power control units and the energy‐storage unit is controlled to act as a voltage source with imaginary impedance. On the other hand, each of the two generation units is controlled to act as a current source. The power‐leveling unit is controlled to act as a current source having the function of frequency selectivity like a high‐pass filter. A 10‐kW prototype system verifies experimentally the validity and effectiveness of the proposed control method for the DC‐grid system. © 2009 Wiley Periodicals, Inc. Electr Eng Jpn, 167(2): 86–93, 2009; Published online in Wiley InterScience ( www.interscience.wiley.com ). DOI 10.1002/eej.20603     

三相四线制有源滤波器的新型无差拍控制

建立了三相四线制有源滤波器的完整数学模型.针对三相四线制有源滤波器,提出了一种基于重复预测型谐波电流观测器的新型无差拍控制方案,以改善有源滤波器的动态性能.详细阐述了新型无差拍控制的原理、控制系统的离散化模型、重复预测型谐波电流观测器的工作原理及保证其稳定工作的充分条件.基于MATLAB/Simulink的有源滤波器控制系统仿真分析表明,所提出的新型无差拍控制方案在保证系统稳态精度良好的同时有效改善了系统的动态响应.     

Analysis and effective controller design for the cascaded H‐bridge multilevel APF with adaptive signal processing algorithms

The cascaded H‐bridge (CHB) multilevel inverter is being recognized as the most suitable topology for high‐power medium‐voltage power quality conditioning applications. This paper presents mathematical modeling and effective controller design methodology for the CHB‐based active power filters (APFs), which achieves dynamic reactive power and harmonic compensation. The most crucial problems in CHB‐APF control are the simultaneous requirements of both accurate harmonic current compensation and the dc‐link voltage stabilization among the H‐bridges, which is the prerequisite for the stable operation of CHB‐APF. To achieve dc‐link stabilization, a novel voltage balancing algorithm is proposed by splitting the dc‐link voltage control task into two parts, namely, the average voltage control and the voltage balancing control, where the sine and cosine functions of the phase angle of the fundamental component of the grid voltage are used, respectively. To ensure accurate phase tracking, a novel phase‐locked loop (PLL) is proposed by using the adaptive linear neural network (ADALINE), where the grid voltage background distortion is also taken into account. The superior performance of the ADALINE‐PLL is validated by comparison with the existing PLLs in literatures. Furthermore, the proportional‐resonant (PR) controller is used for the reference current tracking. A separate ADALINE algorithm is applied for reference current generation (RCG) for the CHB‐APF. The excellent performance of the ADALINE‐based RCG scheme is verified by comparison with the existing RCG schemes, namely, the low‐pass filter approach and the single‐phase p ? qmethod. The experimental results on the three modules CHB‐APF are presented, which verifies the effectiveness of the proposed control algorithms. Copyright © 2011 John Wiley & Sons, Ltd.     

有源电力滤波器采样滤波电路的优化设计及鲁棒控制

电流采样电路的设计和电流内环的控制效果是影响有源电力滤波器(APF)补偿精度的两个重要因素。文中首先通过波特图详细分析了电阻和电容参数选取对APF电流内环的影响,提出了一种RC滤波电路的参数设计方法。同时,考虑到控制延时环节不可避免存在,分析了带延时环节的z域无差拍离散控制模型,并讨论了电感值变化对系统鲁棒性的影响。对此,文中提出了一种预测电流控制方法,对采样的电网电压,逆变器输出电流都作了超前一拍预测,减小了延时对系统影响,增强系统的鲁棒性。此外,根据z域内的电流环传递函数对系统进行了稳定性分析,给出了控制参数的选取方法。针对该控制方法,搭建了APF试验样机,实验结果验证了控制策略的有效性和可行性。     

采用APF和SVC改善微网电能质量

采用有源滤波器和静止无功补偿装置联合运行的方式来提高孤立运行的微网电能质量,其中有源滤波器接在分布式电源逆变器出口侧,滤除谐波电流,其电流检测采用ip-iq法,跟踪控制采用无差拍控制与空间矢量脉冲宽度调制的方法;静止无功补偿装置,由晶闸管控制的电抗器和晶闸管投切的电容器组成,安装在微网负荷侧,随负荷需求供给无功,维持负荷侧电压稳定,减小系统网损,并提高电能质量。经实验证明了该联合系统对提高微网电能质量是有效的。     

具有延时补偿的数字控制在PWM整流器中的应用

由零阶保持器及计算时间产生的控制延时是数字控制的主要缺点之一，这会导致系统振荡以至不稳定。为补偿延时，提出了一种基于状态反馈的新方法。该方法没有采用状态观测器，首先建立包含延时影响的PWM整流器的新数学模型，然后采用线性状态反馈，通过配置系统极点，得到新控制器。该方法消除延时影响不仅保证系统稳定而且对给定电流输入可取得无差拍响应。1kW的能量回馈型交流电子负载样机被用于验证新方法。样机采用20kHz的开关频率和TMS320F2812 DSP控制芯片。样机实验验证了理论分析的正确。     

Modeling and control of a cascaded multilevel converter‐based electronic power transformer

Control strategy of a cascaded multilevel converter based electrical power transformer (EPT) in a distribution system with capabilities of low voltage ride‐through and unbalanced load current management is investigated in this study. The mathematical model and decoupled control schemes of the system, including a high‐voltage side control scheme, an isolation‐stage control scheme, and a low‐voltage side control scheme, are presented in detail. A dual current control scheme is introduced to control both positive and negative sequence currents for enhancing the low voltage ride‐through capability of the high‐voltage side cascaded H‐bridge converter. Positive, negative, and zero‐sequence voltages are controlled for the low voltage side three‐phase four‐wire converter in the decoupled control scheme, respectively, for unbalanced load current management. A proportional resonant controller (PRC) is utilized to control the zero‐sequence voltage, while the root locus method is applied in the PRC design. Three‐dimensional space vector pulse width modulation (PWM) switching strategy is then used for the low voltage side converter. Simulation studies were conducted with MATLAB/Simulink to validate the coordinated control strategy. © 2016 Institute of Electrical Engineers of Japan. Published by John Wiley & Sons, Inc.