A voltage-source PWM rectifier-inverter with feedforward control of instantaneous power

In general, diode rectifiers with electrolytic capacitors on the dc side have been used as dc power supplies for voltage-source inverters. Rectifiers of this type, however, cause many problems such as poor power factor and harmonics. Recently, voltage-source PWM rectifier-inverters have been studied to provide the following advantages: (1) harmonic-free on both ac sides; (2) unity power factor on the input ac side; (3) power flow of either direction or power regeneration; (4) reduction of the dc capacitor. However, it is difficult for a conventional voltage-source PWM rectifier-inverter to regulate the capacitor voltage on transient states because it has only a voltage feedback loop. This paper describes a voltage-source PWM rectifier-inverter with feedforward control of instantaneous power. Based on the pq theory, the instantaneous power which is calculated in the control circuit of the inverter is fed forward to the control circuit of the rectifier. The feedforward control of instantaneous power contributes greatly to sufficiently suppress voltage fluctuation of the dc capacitor on transient states. Transient characteristics are discussed, and some interesting experimental results of a laboratory model are shown.     

A current-type PWM rectifier with active damping function

A new control method for current-type pulse-width modulation (PWM) rectifiers which can provide active damping function is presented. This damping function is effective only on the harmonic components of AC input current selectively. Thus steady-state waveform distortion and transient oscillation of the input current are reduced by the active damping effects. The active damping function can be realized by feedback control of an LC filter connected to the AC side of the rectifier, and it does not require any additional components in the main circuits, permitting a simple circuit configuration. The control system of the proposed PWM rectifier is analyzed by using a simple block diagram developed in the present paper. From the analytical results, the influence of the circuit parameters and control delay on the active damping effects and the stability of the operation are clarified to establish the design method. To confirm the effectiveness of the active damping function, some results of basic experiments are included. As an example of application of the active damping function, the proposed rectifier is applied to reduce the harmonic currents generated by conventional rectifiers operating in parallel with the proposed rectifier. Some experimental results in this application are also included     

A high-power-factor PWM rectifier without voltage sensors

Pulsewidth modulation (PWM) control techniques for rectifiers are widely used to improve the source current waveform and the input power factor. Recently, methods to reduce the number of detectors have been studied to simplify the system configuration and control of such rectifiers. It is known that a voltage detector on the ac side can be omitted, though a voltage detector on the dc side is needed for adjustment of the dc output of a PWM rectifier. In this paper, a method for controlling a single-phase rectifier without any voltage sensor is proposed. The ac-side voltage can be estimated from the input-reactor voltage when the ac side of the bridge is short-circuited. The reactor voltage is easily obtained by multiplying the inductance of the reactor by the derivative of the source current measured. The dc side voltage can be estimated by calculating the difference between the source voltage at the beginning of every switching period and the reactor voltage sampled and held in the previous bridge conduction mode. This paper describes the control scheme, its implementation, and the performance characteristics of the rectifier. The usefulness of the rectifier is confirmed by experiment. This method is applicable to various types of PWM rectifiers. © 1997 Scripta Technica, Inc. Electr Eng Jpn, 120(4): 90–96, 1997     

A voltage source PWM rectifier-inverter with feedforward control of instantaneous power

In general, diode rectifiers with electrolytic capacitors on the dc side have been used as dc power supplies for voltage source inverters. This type of rectifiers, however, causes many problems such as poor power factor and harmonics. Recently, voltage source PWM rectifier-inverters have been studied to provide the following advantages; (1) harmonic-free on both ac sides; (2) unity power factor on the input ac side; (3) power flow of either direction or power regeneration; (4) reduction of the dc capacitor. It is, however, difficult for a conventional one to regulate the capacitor voltage on transient states because of having only a voltage feed-back loop. This paper describes a voltage source PWM rectifier-inverter with feed-forward control of instantaneous power. Based on the pq theory, the instantaneous power which is calculated in the control circuit of the inverter is fed forward to the control circuit of the rectifier. The feed-forward control of instantaneous power makes a great contribution to sufficiently suppress voltage fluctuation of the dc capacitor on transient states. Transient characteristics are discussed and some interesting experimental results of a laboratory model are shown.     

滤波器在单相PWM整流器中的应用

为消除混叠在PWM单相整流器交流电流反馈信号中的高次谐波分量和直流电压控制外环中的2次谐波分量,在交流电流反馈通道中设置低通滤波器,并使用陷波滤波器衰减直流2次谐波分量;通过在建立电流控制系统模型中发现的内环低通滤波器可有效消除混叠的高次谐波信号的方法保障系统稳定,而对截止频率过高将引起反馈信号相移,改变系统中低频特性,进而影响系统稳定性,则给出了滤波器参数的设定要求;采用直流环节中的陷波滤波器,相比低通滤波器不仅易于在计算精度有限的底层控制芯片中实现,同时更有效消除2次谐波分量,保障系统的高输入功率因数和低谐波分量,同时拥有良好的动态特性。相关仿真分析及搭建4.5kVAPWM整流器样机平台的实验结果验证了以上推论。     

A new control strategy for voltage-type PWM rectifiers to realizezero steady-state control error in input current

In this paper, a new simple control strategy for AC input current of voltage-type pulsewidth modulation (PWM) rectifiers which can eliminate the steady-state control error completely is proposed. This control method requires neither the instantaneous value of the supply voltage nor any accurate circuit parameters on the AC side of the rectifier. Thus, a robust operation against the variation of the circuit parameters can be achieved. In the proposed control system, a digital resonant element implemented by a digital signal processor (DSP) is introduced as a feedback controller. The digital resonant element exhibits a function similar to an integrator for the fundamental frequency components. Thus, it can eliminate the steady-state control error of the input current completely, The principle of the proposed control method is discussed, and its effectiveness is shown theoretically. The detailed method of the implementation of the lossless digital resonant element is explained. The effects of the harmonics in the supply voltage on the AC input current waveform are clarified. To confirm the effectiveness of the proposed control method, some experimental results from two laboratory test systems are shown     

Investigation of harmonic currents and power factor on power rectifier circuits with nonequi-PWM and equi-PWM control (inductive load)

Lately, on the power rectifier circuit with semiconductor switching device, PWM control is generally employed for the purposes of reducing the harmonic currents on the dc side and improving the power factor of fundamental wave. In this case, the analysis of the current waveform becomes fairly complex. However, we express the PWM controlled voltage waveform by the step function, and can easily analyze the current waveform. We reported formerly some results of analysis about the waveform and harmonics of the current. In this paper, on the power rectifier circuit to which the nonequi-PWM and equi-PWM control are applied, we exactly calculate the harmonic currents on the dc and ac side, and the power factor by the use of the above analytical results. The characteristics of both control methods are compared on condition that each controlled factor of the load voltage is equal. These results are shown in the calculated charts. The following items can be seen from these charts on the power rectifier circuit: (1) The nonequi-PWM control can let the harmonic currents on the dc side decrease more than the equi-PWM control. But on the contrary, the harmonic currents on the ac side increase. Consequently, when the nonequi-PWM control is applied, the total power factor decreases by the increase of distortion factor of the current on the ac side. (2) The difference between the harmonic currents on the dc and ac side to both of the nonequi-PWM and equi-PWM control increases with the increase of controlled factor of the load voltage. © 1999 Scripta Technica, Electr Eng Jpn, 129(4): 117–125, 1999     

A single-phase PWM current source type converter coupled with an ac chopper

A current source type converter can easily generate a sinusoidal current on the ac side by employing a PWM strategy. In the converter system for a single-phase supply, however, the dc current pulsates because the dc output voltage of the converter contains an ac component with twice the ac supply frequency. The dc current pulsations cause the ac current waveform to be distorted. Although the use of a dc reactor with large inductance reduces the dc current pulsations, the size and the weight of converter equipment including a dc reactor is large. Two-phase rectification using two full-bridge converters and a converter system with an ac chopper circuit has been proposed for elimination of the dc pulsations. In these converters, the number of switching devices comprising the circuit will unavoidably increase. To solve this problem, we propose a novel single-phase current source type converter coupled with an ac chopper circuit and the PWM method. In this circuit, two switching devices in the main bridge are used to form an ac chopper bridge with two added devices and a capacitor. This paper gives the experimental and theoretical waveforms and the steady-state characteristics. The results prove that a smooth dc current and a sinusoidal ac current are obtained, and that a great reduction of the dc inductance can be achieved by using the proposed converter. © 1998 Scripta Technica. Electr Eng Jpn, 123(3): 36–45, 1998     

基于电感电压反馈和输入整形技术的LC滤波器混合阻尼控制

电流型PWM整流器采用LC环节来滤除谐波及帮助器件换流,LC型滤波器呈二阶特性,存在谐振尖峰,且电容阻尼较小,在控制系统存在扰动的情况下,容易引起电流波形畸变和振荡。提出了一种采用输入整形技术和电感电压反馈结合的控制策略,输入整形技术能够有效地抑制小阻尼系统的振荡,电感电压反馈控制能够在外部干扰抑制网侧电流波形畸变。结合两者的优点,可有效地解决电流型脉宽调制整流器网侧电流振荡和畸变。仿真验证了所提出的控制策略能够有效减少电流畸变,增加系统的稳定性,并具有一定工程实用性。     

Single-phase line current compensator based on line current detection

We propose the three-phase active filter designed to control the ripple power based on instantaneous ac line power detection. We show that the proposed system has many excellent features such as simple construction, high accuracy, high efficiency, and so on. In this paper, we apply this control principle to single-phase power line compensators such as active filters and reactive power compensators. In this case, we must control the instantaneous current waveform instead of the ripple components of two-axis quantities of the three-phase current or power. The proposed system can be easily constructed and controlled by merely detecting the ac line side current and the dc side voltage of the PWM converter. The system combines many functions, such as a PWM converter, an active filter, a reactive power compensator, without any modifications. In this paper, we compare the proposed system with conventional systems and confirm the feasibility of the system by simulation and experimental results. © 1998 Scripta Technica, Electr Eng Jpn, 124(1): 65–73, 1998     

Modeling and simulation of ac–dc buck-boost converter fed dc motor with uniform PWM technique

PWM controlled rectifiers can efficiently and economically be employed in low and medium power applications of dc drives and in front-end converters of rectifier–inverter systems while maintaining the advantages of design simplicity and operation reliability of naturally commutated schemes. Due to the high dc voltage that is produced which is greater than the peak voltage of the utility supply, the ac–dc buck-boost converter is especially suited as a front-end power source in variable-speed drive systems to convert the utility supply voltage into a variable dc link voltage where a single-phase or a three-phase utilities power supply is available. In this paper, the dynamic model and steady state equivalent circuit of a single-phase ac–dc buck-boost converter fed dc motor with uniform PWM control is presented. The waveforms of voltage and current, the input and output characteristics of the converter are discussed and verified. Measured, computed and simulated results are shown to be very close and the model is proved to be efficient and accurate.     

State feedback control of current-type PWM AC-to-DC converters

A control method for current-type PWM AC-to-DC converters that realizes a sinusoidal AC input current and unity power factor is discussed in detail. In such converters, an LC filter placed on the AC side may cause a resonant problem, especially in the transient condition. To overcome this problem, state feedback control is introduced, and a control strategy suitable for DC-output current control as well as AC-side current control is proposed. Circuit parameters and feedback coefficients in the AC-side current control system are optimized on the basis of an analysis in which the system is treated as a sampled-data system. A method of investigating parameters in the DC-side current control system is shown. To confirm the effectiveness of the control strategy and the validity of the analytical results, an experimental investigation of the basic characteristics of the system is made. As an example, this system is applied to controlling the current waveform in the reactor. The experimental results for this application are also included     

A control method to realize sinusoidal input and output current waveforms for matrix converters based on PWM

A matrix converter (MC) is a three‐phase AC‐to‐AC direct converter without any energy storage requirement. It is expected to be a next‐generation converter by reason of possibilities of small size and high efficiency. At present, there are some problems preventing it from being used practically. One of the problems is the distortion in the input current. The control methods proposed so far have not realized sufficient reduction of the input current harmonics compared with conventional PWM rectifiers. As a solution to these problems, many approaches have been proposed. In the present paper, an improved PWM method that can achieve both sinusoidal input and output currents simultaneously is considered. In this method, the MC is treated as a controlled voltage source viewed from the load side. On the other hand, it is treated as a controlled current source viewed from the line side. The proposed control method is based on the mathematical expression of the function of the PWM operation of MC. To improve the input current waveform, two line‐to‐line voltages of the three‐phase line are used to control the output current. The output duty ratio of the two line‐to‐line voltages is utilized to improve the input current waveform without affecting the controllability of the output current. In addition, the compensation of the variations in the line voltage and the output current are introduced. In this way, the proposed method can realize the sinusoidal input and output currents. The effectiveness of the proposed control method is confirmed by some experimental results employing a laboratory prototype. © 2007 Wiley Periodicals, Inc. Electr Eng Jpn, 161(1): 66–76, 2007; Published online in Wiley InterScience ( www.interscience.wiley.com ). DOI 10.1002/eej.20242     

A suitable single-phase pulse width modulation current source inverter for utility interactive photovoltaic generation system

A suitable single-phase inverter for the utility interactive photovoltaic generation system is proposed. The single-phase Pulse Width Modulation (PWM) current source inverter has a novel circuit configuration in which an auxiliary branch is added to the normal single-phase bridge circuit. To reduce the size and weight of the dc reactor, a double frequency parallel resonance circuit (LC tank circuit) is inserted in the dc side of the inverter. As a result, the double frequency voltage appearing in the dc side of the inverter due to the pulsation of the single-phase instantaneous power is perfectly suppressed by the tank circuit. The constant dc current without pulsation is supplied from PV array to the inverter. The inverter provides a sinusoidal ac current for domestic loads and the utility line with unity power factor. The virtual maximum power of the PV array can be obtained without any feedback control. In the system, the PV array can play an important role as a current-limiter due to its V-I characteristics. Computed waveforms by simulation are shown. Excellent inverter equipment will be realized that is smaller in size and lighter in weight than is usual for a conventional inverter.     

一种电动汽车充电系统单相整流有源滤波方法

提出了一种应用于电动汽车一体化充电系统中的单相PWM整流有源滤波的控制方法,以抑制充电中单相整流电路的直流电压二次纹波。在单相电网电压充电时,这种控制方法能通过控制电机驱动器电路,复用其中的两相同时进行单相整流和有源滤波,在实现整流器单位功率因数运行、稳定输出直流电压的同时,减小直流侧电压的二次纹波,减小网侧输入电流的总谐波畸变率。对单相整流直流侧电压二次纹波的产生机理、有源滤波电路的拓扑结构、单相整流和有源滤波的控制原理和方法进行了详细地分析。最后搭建输入电压峰值110 V,输出直流电压220 V,负载等效电阻100Ω的仿真模型,通过仿真和实验结果验证了所提控制方法的可行性。     

A Three-Phase Inverter with Reactive Power Control

A new type of self-commutated inverter for fixed or moderately variable frequency has been developed. The inverter is characterized by an extremely uncomplicated main circuit. In its basic form the inverter contains two converter circuits: a principal converter circuit and an auxiliary converter circuit. The principal converter circuit transfers power from the input dc side to the output ac side, and the auxiliary converter circuit generates an inductive current to balance the reactive current of a three-phase capacitor on the ac side. This capacitor has the combined function of a phase compensator, a filter capacitor, and is also the source of the commutating voltage. Both converter circuits are of the line commutated type, meaning that at power frequencies normal converter thyristors can be employed. This makes it possible to build high-power inverters without series or parallel connected thyristors. All filter reactors are smoothing reactors placed on the dc side of the converter circuits. Thus the inverter has a very good efficiency even at the higher frequencies. The ability of a converter circuit to generate a negative sequence current when unsymmetrically controlled makes the inverter insensitive to unbalanced loads. The transient behavior of the inverter is similar to that obtained from a conventional self-commutated inverter with an output filter.     

一种简化T型滤波器的双馈风力发电整流器

在现今风力发电领域,大多采用双馈变速恒频风力发电机,配合两电平电压型三相PWM整流器以获得较好的并网发电效果.由于PWM整流器会在电网侧产生较大的谐波电流,所以必须采用性价比较好的滤波器进行谐波治理.针对双馈风力发电系统的变流器,提出一种简化滤波器的整流器拓扑结构和控制方法,分析了此方法的优点,并且进行了仿真和实验验证.通过仿真和真实系统运行检验了这种简化滤波器整流器的合理性.     

电容电压反馈的电流型整流器有源阻尼控制研究

三相电流型PWM整流器在交流侧采用LC滤波器来滤除谐波,由于二阶LC滤波器的阻尼系数较小,容易引起网侧电流振荡。为此文中提出滤波电容电压反馈的有源阻尼控制,能够在不消耗有功功率的前提下,有效地滤除网侧电流谐波。通过仿真分析可知,提出的电容电压反馈能抑制网侧电流振荡。     

High-power active filter using LC-tuned filter

Usually, to eliminate the harmonics of transmission lines, LC tuned filters are employed to bypass these harmonic components. However, the elimination ability is limited by its damping resistance. Therefore, active filters composed of high-frequency PWM converters are desirable. In comparison with the LC tuned filters, the cost would be very high even in high-power systems. In this paper, a low-cost and high-power active filters for a dc transmission system is proposed. It has active filter ability as well as low cost for high-power uses. Its main circuit is composed of conventional LC filters in series with square-wave voltage inverters. The voltage of the inverter is controlled to cancel the voltage drop of the internal resistance of the LC filter. Thus the Q-factor of the filter can appear at infinity. Calculation of the harmonic and the control are done by DSP (TMS 32010). In the experimental system and simulations, two three-phase tuned filters, 5th and 7th, are employed. Excellent results under 1 percent distortion voltage are obtained.     

单相电流型PWM逆变技术综述

在分析了传统单相电流型PWM逆变器固有缺陷的基础上,系统地论述了从电路拓扑、控制策略等方面提出的多种解决其缺陷的方案,并给出了设计实例与特点,获得了重要结论。电路拓扑方面的解决方案包括差动双向Boost直流变换器型逆变器、组合式Boost/Buck/Buck-Boost逆变器、附加反激AC-DC能量回馈电路的单相电流型高频环节逆变器等,具有满足Boost变换器控制规律、电路复杂、损耗大等特点;控制策略方面的解决方案包括具有补偿环节的非线性调制控制策略和无源性控制策略等,具有输出波形质量高、储能电感大等特点;电路拓扑和控制策略两方面的解决方案包括输入侧串并联谐振器的单相电流型逆变器、具有储能电感电流限定非线性PWM单周期控制单相电流型逆变器等,具有输出波形质量高、储能电感小、变换效率高等特点。