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     

永磁同步电机模型预测电流控制比较研究

对永磁同步电机的3种模型预测电流控制方案进行了比较研究。传统模型预测电流控制策略在单个采样周期中输出一个电压矢量,选择使价值函数最小的电压矢量输出。双矢量模型预测电流控制策略在单个采样周期中输出2个电压矢量,并分别计算2个电压矢量的作用时间,使输出电压矢量与期望电压矢量更加接近。三矢量模型预测电流控制策略在单个采样周期中输出2个有效电压矢量和一个零矢量,扩大备选电压矢量的覆盖范围,减小电流脉动。为了比较3种控制策略的动、静态性能,进行了对比仿真分析。仿真结果表明,多矢量模型预测电流控制具有良好的动静态性能,与传统模型预测电流控制相比,能有效地减小电流脉动。     

Control of three phase PWM rectifier using virtual flux‐based predictive direct power control and SVM under harmonic conditions

In this paper, a new predictive direct power control algorithm to control the PWM rectifier based on virtual flux (VF) is presented. In this algorithm, supply network and the line inductances are assumed as an induction machine and so virtual flux space vectors are assumed corresponding with the space vector of the network voltages. Instantaneous active and reactive powers and finally convertor average voltage in both stationary and rotating reference frames are calculated by the virtual flux space vector components. The main advantages of the proposed method are low total harmonic distortion of the input current and low ripple in the instantaneous active and reactive powers and direct current‐bus voltage under harmonic distorted condition of the supply voltage in comparison with voltage‐based predictive direct power control (V‐PDPC) method. Proposed VF‐PDPC method with space vector modulation switching strategy was tested in simulations and compared with the V‐PDPC method. Copyright © 2015 John Wiley & Sons, Ltd.     

六相永磁同步发电机占空比模型预测直接功率控制

针对传统六相永磁同步发电机(PMSG)单矢量模型预测直接功率控制(MPDPC)电流谐波大、有功和无功功率波动剧烈的问题,提出了一种占空比合成矢量MPDPC。通过对六相整流器的最大和中大电压矢量进行重构,获得12个合成矢量,实现了对谐波电流的有效抑制。在此基础上,提出在每个周期内同时作用一个合成矢量和零矢量,并根据有功和无功预测无差拍原理计算最优占空比,进一步抑制了有功和无功功率脉动。试验结果表明,所提占空比合成矢量MPDPC可以有效减少电流谐波和功率脉动。     

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     

三相电压型PWM整流器无电流传感器控制策略研究

三相电压型PWM整流器有间接电流控制和直接电流控制两种方式 ,两种控制方式各有优点。根据三相电压型PWM整流器的高频动态数学模型 ,提出了基于开关函数检测的无电流传感器控制策略。该控制策略兼有间接电流控制结构简单 ,成本低和直接电流控制动态响应速度快、限流容易、控制精度高等优点。实验结果验证了控制策略的可行性     

AC voltage and current sensorless control method for three‐phase PWM converter

We present a three‐phase PWM converter without AC voltage and AC current sensors. The phase angle used in the control system is adjusted by using a PLL controller without sensing AC voltage. To prevent overcurrent at startup, the initial phase angle of the source voltage is estimated from the shunt current using a novel strategy. Furthermore, the phase currents can be reconstructed from the shunt current without any modification of the PWM pattern. To reduce the effect of current ripple, the shunt current is sampled twice for every phase in one PWM period and the sample timings are carefully adjusted. All of the proposed control schemes can be implanted using a single chip microprocessor (SH7046, Renesas Tech.). Simulation and experimental results with a 5‐kW prototype confirmed that the schemes worked well. © 2010 Wiley Periodicals, Inc. Electr Eng Jpn, 172(4): 48–57, 2010; Published online in Wiley InterScience ( www.interscience.wiley.com ). DOI 10.1002/eej.20983     

Application of a sinusoidal internal model to current control of three‐phase utility interface converters

Three‐phase voltage‐source converters are used as a utility interface. In such a case, the converter line currents are required to track sinusoidal references synchronized with the utility grid without steady‐state error. In this paper a current control method based on a sinusoidal internal model is employed. The method uses a sine transfer function with a specified resonant frequency, which is called an S compensator. The combination of a conventional PI compensator and an S compensator is called a PIS compensator. The PIS compensator ensures that the steady‐state error in response to any step changes in a reference signal at the resonant frequency and zero hertz reduces to zero. An experiment was carried out using a 1‐kVA prototype of three utility interface converters, a voltage‐source rectifier, an active power filter, and STATCOM. Almost perfect current tracking performance can be observed. © 2004 Wiley Periodicals, Inc. Electr Eng Jpn, 150(3): 54–61, 2005; Published online in Wiley InterScience ( www.interscience.wiley.com ). DOI 10.1002/eej.20064     

电流型变流器在电网电压不平衡时的控制

提出一种电网电压不对称情况下抑制三相脉宽调制(PWM)电流型变流器(CSC)直流输出电流二次谐波、减少网侧电流低次谐波的控制方法.该方法对传统的预测控制进行改进并应用到电网不平衡的三相CSC系统中,获得了良好的控制性能.应用电流空间矢量调制技术,使器件的利用率得到提高.所提出的方法无需电流传感器检测网侧电流,降低了实现成本.实验结果证明所提出的方法是正确、可行的.     

PWM control of three‐phase to three‐phase matrix converters for reducing the number of commutations

This paper presents a control scheme of three‐phase to three‐phase matrix converters for reducing the number of commutations. The number of commutations during a control period in the proposed control scheme can be reduced to three from four in the conventional control scheme. It can be realized by using the output currents in the calculations of the duty factors. As a result, one of the output line voltage waveforms during a control period consists of two voltage levels with the same sign of the reference. The switching loss and the output voltage harmonics can be reduced. The effectiveness of the proposed control algorithm of the matrix converters has been verified by experiments. © 2009 Wiley Periodicals, Inc. Electr Eng Jpn, 170(2): 60–69, 2010; Published online in Wiley InterScience ( www.interscience.wiley.com ). DOI 10.1002/eej.20824     

Input power factor control of three‐phase to three‐phase matrix converters

This paper presents input power factor control of three‐phase to three‐phase matrix converters. The authors propose three kinds of switching patterns for the matrix converters that can realize an arbitrary input‐power‐factor angle between 0 and 2π and reduce the number of commutations in all three phases to four during the control period. Also, the control range of the output voltage reference in the proposed control scheme is derived. The improvement of the input power factor by using the proposed control algorithm has been verified by experiments. © 2011 Wiley Periodicals, Inc. Electr Eng Jpn, 178(3): 42–52, 2012; Published online in Wiley Online Library ( wileyonlinelibrary.com ). DOI 10.1002/eej.21199     

Performance of Dead‐Time Compensation Methods in Three‐Phase Grid‐Connection Converters

This paper discusses the performance of compensation methods for dead‐time voltage error in voltage‐source grid‐connection pulse‐width modulation converters. The theoretical analysis in this paper reveals the relationship between the voltage error and the current ripples through the converter. The analytical results imply that the voltage error is strongly affected by the amplitude of the current ripples as well as the source power factor. This paper proposes a new compensation method which makes it possible to use two lookup tables to reduce the calculation time in the controller. The compensation characteristics are compared by using a 200‐V 5‐kW three‐phase grid‐connection converter. As a result, conventional approximation‐based compensation methods exhibit an acceptable performance in a restricted power‐factor operation range. In contrast, the turn‐off transition‐based compensation method and the proposed method have a good compensation performance all over the power factor.     

A comprehensive study of space vector pulse‐width modulation technique for three‐phase Z‐source inverters

The space vector pulse width modulation (SVPWM) technique has received much attention for three‐phase Z‐source inverters (ZSIs). The differences and connections between the SVPWM technique for ZSIs and for traditional voltage source inverters have been discussed as well. By selecting different null state and shoot‐through state, three switching patterns with different switching numbers have been studied, and the harmonic spectrums of these three patterns are demonstrated. In this paper, the solutions of maximum boost control and constant boost control methods using SVPWM techniques with less switching actions have been proposed and compared with the carrier‐based strategies. Selected experimental results have been provided to validate the theoretical analysis. This work will be beneficial for understanding the SVPWM concept and modulation techniques of the three‐phase ZSIs. Copyright © 2015 John Wiley & Sons, Ltd.     

A novel robust current control approach using adaptive line enhancer for three‐phase current‐source active power filter

An effective system control method is presented for applying a three‐phase current‐source PWM converter with a deadbeat controller to active power filters (APFs). In the shunt‐type configuration, the APF is controlled such that the current drawn by the APF from the utility is equal to the current harmonics and reactive current required for the load. To attain the time‐optimal response of the APF supply current, a two‐dimensional deadbeat control scheme is applied to APF current control. Furthermore, in order to cancel both the delay in the two‐dimensional deadbeat control scheme and the delay in DSP control strategy, an Adaptive Line Enhancer (ALE) is introduced in order to predict the desired value three sampling periods ahead. ALE has another function of bringing robustness to the deadbeat control system. Due to the ALE, settling time is made short in a transient state. On the other hand, total harmonic distortion (THD) of source currents can be minimized compared to the case where ideal identification of the controlled system can be made. The experimental results obtained from the DSP‐based APF are also reported. The compensating ability of this APF is very high in accuracy and responsiveness although the modulation frequency is rather low. © 2004 Wiley Periodicals, Inc. Electr Eng Jpn, 150(1): 50–61, 2005; Published online in Wiley InterScience ( www.interscience.wiley.com ). DOI 10.1002/eej.20014     

The influence of mistuned motor parameters on vector control performance and on line slip frequency correction strategy for induction machine operated under one‐pulse PWM mode

In high‐power, high‐speed traction drive systems, the traction motor usually operates under one‐pulse PWM (pulse width modulation) mode (square wave) during high‐speed operation. The constant output voltage in this condition makes the traditional vector control inoperative anymore. In this paper, a modified vector control strategy using open‐loop current control instead of closed‐loop current control is proposed. The modified control strategy is specially designed for an induction motor operating under one‐pulse PWM mode. As the field orientation is greatly affected by the deviation in the parameters, the influence of mistuned rotor time constant and mutual inductance (which are regarded as the most important parameters for field orientation) on the performance of modified vector control is studied comprehensively, including the influence on estimated angle and amplitude of rotor flux, d/q‐axis voltage, and output torque. Subsequently, based on the comparison between the different methods, a new slip frequency correction strategy is proposed to maintain proper field orientation for the modified vector control. The new correction strategy is based on the q‐axis current component error. It is independent of the motor parameters and can be easily realized through minor calculations. The simulation and experimental results show that the proposed slip frequency correction strategy can not only eliminate rotor flux angle error in steady state but also effect rapid torque response during the transient process under one‐pulse PWM mode. © 2014 Institute of Electrical Engineers of Japan. Published by John Wiley & Sons, Inc.     

Direct space vector PWM strategy for matrix converters with reduced number of switching transitions

This paper proposes a novel “Direct Space Vector PWM (Direct SVPWM)” strategy based on the direct AC/AC conversion approach for three‐phase to three‐phase matrix converters. This method allows the sinusoidal input and output waveforms as a major premise, and gives top priority to the improvement of output control performance in motor drive applications, such as providing maximum riding comfort in elevators, etc. Output voltage harmonics, switching losses, and common‐mode voltages can be reduced across the entire voltage region. In addition, the switching count can be reduced even further by fully utilizing the output current detection value. Direct space vectors are first defined, and the method of selecting space vectors is described. Next, the PWM duty calculation technique is explained. Finally, the validity of the proposed method is demonstrated by comparison with the conventional virtual indirect method based on experimental and analytical results. © 2010 Wiley Periodicals, Inc. Electr Eng Jpn, 172(3): 52–63, 2010; Published online in Wiley InterScience ( www.interscience.wiley.com ). DOI 10.1002/eej.20953     

三相电压源型PWM整流器的DSP控制

描述了三相电压源型PWM整流器的工作原理,基于整流器网侧电流矢量推导出同步旋转坐标系下系统的数学模型,给出了一种电流前馈解耦控制算法.同时详细介绍了基于电流前馈解耦的PWM整流器双环控制系统设计方法,并且应用TMS320LF2407A建立了PWM整流器的DSP数字化实验系统.实验结果表明,该整流器能获得单位功率因数的正弦输入电流、稳定的直流输出电压和快速的动态响应.     

三电平PWM整流器直接功率控制

在给出了三电平电压型PWM整流器数学模型的基础上,结合瞬时功率理论,推导了输入有功、无功和整流器矢量的关系,提出了一种应用于三电平PWM整流器的直接功率控制(DPC)方法.该方法不仅能够实现系统对有功、无功的直接控制,而且能够避免矢量切换时相电压、线电压幅值的过高跳变,同时有效地控制了中点电位的平衡.仿真和实验结果表明此方法算法简单,实现了单位功率因数控制,电流谐波小,具有良好的动态和稳态性能.     

The theory of instantaneous power in three‐phase four‐wire systems and its applications

This paper discusses “the p–q theory” and “the cross‐vector theory” in three‐phase four‐wire systems, with the focus on similarities and differences between the two theories. They are perfectly identical if no zero‐sequence voltage is included in a three‐phase three‐wire system. However, they are different in definition of the instantaneous active power and instantaneous reactive power in each phase if a zero‐sequence voltage or current is included in a three‐phase four‐wire system. Based on both theory and computer simulation, this paper leads to the following conclusions: An instantaneous reactive‐power compensator without energy storage components can fully compensate for the neutral current even in a three‐phase four‐wire system including a zero‐sequence voltage or current, when a proposed control strategy based on the p–q theory is applied: However, the compensator cannot compensate for the neutral current fully, when a conventional control strategy based on the cross‐vector theory is applied. © 2001 Scripta Technica, Electr Eng Jpn, 135(3): 74–86, 2001     

基于自适应神经网络观测的无电压传感器PWM整流器功率预测控制

模型预测控制在脉宽调制(pulse width modulation,PWM)整流器上的应用既降低了直接功率控制中的脉振又提高了动态响应速度,但是传统的模型预测功率控制(model predictive power control,MPDPC)中对未来时刻状态量的预测仅依靠模型,对模型参数变化较为敏感,功率预测精度受电压传感器的测量精度和网侧谐波变化的影响明显。为实现整流侧参数的实时辨识和提高整体的预测精度,以实现对功率的精准控制,文中在模型预测功率控制(model predictive power control,MPDPC)的基础上引入自适应神经网络电压观测器,提出基于自适应神经网络观测的无电压传感器PWM整流器功率预测控制(adaptive neural model predictive power control,ANMPDPC)策略。通过构建包含自适应神经网络辨识器和自适应神经网络滤波器的自适应电压观测器,实现网侧电压估计的同时滤除电压高次谐波对其的影响,并将电压观测器与功率二步预测相结合,进一步降低功率脉振,提高系统的响应速度和控制精度。仿真和实验结果表明,所提出的改进策略既实现了无电压传感器下的模型预测控制,又有效抑制了网侧谐波的高频干扰及参数变化对预测精度的影响。