Fast controller for a unity-power-factor PWM rectifier

This paper presents an analog implementation of a fast controller for a unity-power-factor (UPF) PWM rectifier. The best settling times of many popular controllers for this type of power converter are on the order of a few line cycles, corresponding to bandwidths under 20 Hz. The fast controller demonstrated in this paper can exercise control action at a rate comparable to the switching frequency rather than the line frequency. In order to accomplish this while maintaining unity power factor during steady-state operation, the fast controller employs a ripple-feedback cancellation scheme     

Operating limits of the current-regulated delta-modulatedcurrent-source PWM rectifier

A stand alone, three-phase, delta-modulated, current-source PWM rectifier has been built and has been shown to be capable of operating with near sinusoidal current waveforms, unity power factor. and good DC current regulation. A mathematical model that has been justified against experimental measurements and results from digital simulations is presented. The current waveform distortion limit and the asymptotic stability limit are established. It is shown that the rectifier can operate safely within these limits in the entire range of its power ratings     

Improved frequency characteristics of the randomized PWM boost rectifier

A randomized pulse width modulation (RPWM) algorithm is applied in the control unit of the boost rectifier to achieve improved frequency characteristics in the wide band. First, the introduction of the RPWM switching is reflected in a smaller increase of the total harmonic distortion (THD) factor in the input current. Nevertheless, decrease of the power factor is negligibly small. Second, the power spectrum density (PSD) of the input current is estimated and measured to evaluate the influence of randomization in the high-frequency range. This approach offers an effective and credible prediction method for reduction of conductive electromagnetic interference (EMI) by using the RPWM switching.     

Control of a three-phase PWM rectifier using estimated AC-side andDC-side voltages

A new control method of a pulsewidth modulation (PWM) rectifier without measuring AC- and DC-side voltages is proposed. As information about these voltages is necessary for the controller, all required voltage values are estimated from the measured line currents and the calculated values of the input reactor voltage during switching of the rectifier circuit. The input reactor voltage can be obtained by using a differentiator that produces the derivative of the line current or by detecting the voltage induced in a secondary winding wound on the input reactor. The secondary winding creates the electric isolation between the main circuit and the controller. The proposed method is verified by experiment. This paper describes the estimation method, gives the configuration of the controller, and discusses steady-state and transient performances of the rectifier     

电流型PWM整流器的控制器设计

电流型PWM整流器因其良好的功率因数和直流电流源特性,可望在某些场合取代产生大量谐波的二极管或晶闸管相控整流装置,但是由于其本身的强耦合非线性特性,使得变流器常采用复杂的直接电流控制策略,从而使控制器的设计非常复杂。文中提出一种改进的基于d-q坐标系的间接电流控制方法,在电网电压平衡情况下,通过解耦控制,能获得线性的动态响应。     

A vector controlled current-source PWM rectifier with a novelcurrent damping method

Three-phase current-type pulse width modulation (PWM) rectifiers are becoming increasingly popular as the front-end converter unit in power electronic systems due to tighter electromagnetic compatibility (EMC) regulations. In this paper the control of the current source PWM rectifier in the synchronously rotating reference frame is discussed. A control system is presented in which the active and reactive power are independently controlled with real and imaginary axis components of the supply current vector. A new damping method for supply current oscillations is introduced. The method operates in an open-loop manner and is very suitable for microcontroller implementation since the calculation power demand is low. Furthermore, it is shown that in the synchronously rotating coordinates, where the sinusoidal variables appear as DC quantities, the compensation of the reactive power drawn by the supply filter can be done very easily. The proposed control methods are realized using a single-chip Motorola MC68HC916Y1 microcontroller. The experimental tests show excellent performance in both steady state and transient conditions     

A 100 kW high-performance PWM rectifier with a ZCT soft-switching technique

This paper presents a 100 kW three-phase pulse-width modulated (PWM) boost rectifier that serves as the front-end power source for a DC distributed power system. A zero current transition (ZCT) soft-switching technique is applied to achieve greater performance in this high-power converter. This ZCT soft-switching technique assists the turn-on as well as the turn-off of the main and auxiliary insulated gate bipolar transistor (IGBT) switches. An issue about the implementation of the ZCT soft-switching technique in three-phase applications is discussed. A space vector modulation (SVM) scheme suitable for high power applications with high performance is identified. Experimental results demonstrate that high performance is achieved, in terms of wide control bandwidth, low total harmonic distortion (THD), unity power factor and high efficiency.     

一种新型开关表的PWM整流器直接功率控制

为了提高三相电压电压型PWM整流器的性能,改善传统开关表的直接功率控制时开关损耗大且不固定,以及有功功率和无功功率控制解耦能力不足的问题,文中通过对PWM整流器和瞬时功率理论研究的基础上,提出一种基于三电平比较器的新的开关表直接功率的方法,并通过设置扇形边界死区的控制策略细分开关表,这种新开关表通过消除两个扇区中间区域的错误控制,能较好的降低主电路开关频率,增加功率控制性能,使交流侧电流输入谐波率更小,提高整流器的功率因数。在MATLAB/Simulink环境下,对改进前后直接功率控制的稳态性能进行比较,验证了该设计方法的可行性,具有应用参考价值。     

三相双象限PWM整流分析

以三相电压型桥式PWM整流电路（VSR）为研究对象,首先建立起了三相VSR dq数学模型,然后在此模型的基础上对三相VSR采取电流直接控制的矢量控制策略并建立起相应的仿真模型,最后通过改变直流侧的负载来观察三相VSR工作状态和工作象限的变化,以此验证采取的控制策略的可行性。     

地铁牵引供电PWM整流器智能维护技术

面向应用于地铁牵引供电系统中的PWM整流器的智能诊断技术开展了研究。文中首先围绕影响PWM整流器可靠性最大的直流支撑电容器提出了基于参数拟合以及Miner累积损伤原则的电解电容器损伤预测方法;其次,文中基于PWM整流器直流中近端非金属性短路时短路电流受其交流电抗器抑制,从而无法可靠实现保护的特点,研究了PWM整流器的非金属性短路电流辨识方法;最后,结合PWM整流器对高性能故障诊断以及虚拟仪器技术的支持,基于分层分布思想以及虚拟仪器技术设计了地铁牵引变电所内PWM整流器的综合监控系统,介绍了系统的组成原理并给出了现场故障录波结果。     

Active damping control of a high-power PWM current-source rectifier for line-current THD reduction

The use of active damping to reduce the total harmonic distortion (THD) of the line current for medium-voltage (2.3-7.2 kV) high-power pulsewidth-modulation (PWM) current-source rectifiers is investigated. The rectifier requires an LC filter connected at its input terminals, which constitutes an LC resonant mode. The lightly damped LC filter is prone to series and parallel resonances when tuned to a system harmonic either from the utility or from the PWM rectifier. These issues are traditionally addressed at the design stage by properly choosing the filter resonant frequency. This approach may result in a limited performance since the LC resonant frequency is a function of the power system impedance, which usually varies with power system operating conditions. In this paper, an active damping control method is proposed for the reduction in line current THD of high-power current-source rectifiers operating at a switching frequency of only 540 Hz. Two types of LC resonances are investigated: the parallel resonance excited by harmonic currents drawn by the rectifier and the series resonance caused by harmonic pollution in the source voltage. It is demonstrated through simulation and experiments that the proposed active damping control can effectively reduce the line-current THD caused by both parallel and series resonances.     

On the DSP-based switch-mode rectifier with robust varying-band hysteresis PWM scheme

This paper presents the development of digital signal processor (DSP) based switch-mode rectifier (SMR) with robust varying-band hysteresis current-controlled (HCC) pulse width modulated (PWM) schemes. First, a robust fixed-frequency HCC PWM control scheme is developed. Through robust harmonic spectrum shaping, the constant frequency control performance is insensitive to the changes of system parameters and operating condition, and the low frequency harmonics possess smaller magnitudes. Next, the robust HCC PWM schemes of SMR with linearly and randomly varying hysteresis bands are proposed. The harmonic spectra of the SMR are shaped to be uniformly distributed. As to the output voltage regulation control, the dynamic plant model is first estimated. Then accordingly, the controller is quantitatively designed to meet the prescribed control requirements. Significant power quality improvement in line drawn current for the SMR is achieved by using the developed HCC PWM schemes.     

Computations of the passive electrical parameters of neurons usinga system model

Time-domain analysis of voltage responses to current pulse stimulation has been used to estimate the electrotonic parameters of neurons using the signal model. Errors are likely to accumulate from various steps of the analysis due to noise and electrode artifacts. A system model, which has inherent noise immunity and filtering properties, is presented here. This model employs frequency-domain analysis of the input impedance of a neuronal model (an RC cable). The resistances and capacitances of the system model are estimated from the cell-input impedance using an optimization strategy. Using the expression for the input impedance, any specified number of equalizing time constants can be computed exactly. The accessibility to these equalizing time constants 1) provides greater insight into the charge equalization along the length and circumference of the cable, and 2) improves the estimation of all other passive parameters including the electrotonic length. Thus, the system model approach allows information to be extracted more directly and accurately than the signal model approach.     

Real-time multi-DSP control of three-phase current-source unitypower factor PWM rectifier

The design of a real-time multi-DSP controller for a high-quality six-valve, three-phase current-source unity power factor pulse-width-modulated (PWM) rectifier is discussed. With the decoupler preprocessor and the dynamic trilogic PWM trigger scheme, each of the three input currents can be controlled independently. The pole-placement control method implemented, which is based on the a-b- c frame system model and fast parallel computer control, achieves fast AC current response. The low-frequency resonance in the AC filter L-C networks is damped effectively. The experimental results were obtained for a 1 kVA bipolar transistor current-source PWM rectifier with a real-time controller using three TMS320C25 DSPs     

H桥级联型PWM整流器的原理与控制算法的研究

级联型H桥整流器随着级联H桥的增多,总电压被开关管分压,降低了每个开关管上的耐压要求,同时该拓扑可以实现能量双向流动,对功率因数进行校正,因此适用于无输入变压器的高压大容量场合。研究了级联型H桥的工作原理,针对直流母线电压不平衡问题,研究了一种基于比例-积分（PI）调节器的控制算法,保证空载和满载条件下都能够实现电压平衡控制。搭建三模块级联型H桥整流器的实验样机,实验结果表明了控制算法的有效性。     

A novel load current control method for a leading power factorvoltage source PWM rectifier

A novel PWM voltage source rectifier, controlled by the load DC current instead of the DC voltage, has been developed. Its main characteristics are: (a) there is neither input current sensors nor DC voltage sensor; (b) it works with an unchangeable and predefined PWM pattern; (c) it presents a very strong stability; (d) its stability does not depend on the size of the DC capacitor; (e) it can work at leading power factor for all load conditions; and (f) it can also work with zero regulation for all load conditions. Digital simulations, analyses, and experiments confirm all these characteristics of the control method     

Simple and effective open switch fault diagnosis of single-phase PWM rectifier

In order to obtain lower harmonics distortion and higher power factors, single-phase pulse-width modulation (PWM) rectifiers are adopted in AC railway drive systems. Therefore, its reliability is of most importance with regard to the safe operation of the train. In this paper, a fault diagnosis method for open switch fault in single-phase PWM rectifier is proposed based on the switching system theory. It requires no additional sensor, nor extra operation states need to be set. Four observers which correspond to four kinds of open switch faults are utilized to detect and locate the faults. Real-time simulations are carried out to validate the effectiveness of this method.     

ESR and capacitance monitoring of a dc-link capacitor used in a three-phase PWM inverter with a front-end diode rectifier

Condition monitoring plays an important role in estimating health condition of capacitors because the ageing of the capacitors is usually accompanied by an increase in equivalent series resistance (ESR) and a decrease in capacitance. Either capacitance or ESR cannot be a unique indicator of the lifetime of capacitors in some cases. This paper presents a condition monitoring method of a dc-link capacitor used in a three-phase PWM inverter with a front-end diode rectifier intended for motor drives. The monitoring method extracts both the ESR and capacitance of a capacitor under test from the actual ripple current and voltage without disconnecting the capacitor nor injecting an additional current. The monitoring method, therefore, can be implemented online. Experimental results verify that the monitoring method independently obtains the ESR and capacitance changes of the capacitor under test. This contributes to accurate lifetime estimation of dc-link capacitors.     

A Voltage-sensorless control method to balance the input currents of a three-wire boost rectifier under unbalanced input Voltages condition

This paper proposes a control method that can balance the input currents of the three-phase three-wire boost rectifier under unbalanced input voltage condition. The control objective is to operate the rectifier in the high-power-factor mode under balanced input voltage condition but to give overriding priority to the current balance function in case of unbalance in the input voltage. The control structure has been divided into two major functional blocks. The inner loop current-mode controller implements resistor emulation to achieve high-power-factor operation on each of the two orthogonal axes of the stationary reference frame. The outer control loop performs magnitude scaling and phase-shifting operations on current of one of the axes to make it balanced with the current on the other axis. The coefficients of scaling and shifting functions are determined by two closed-loop proportional-integral (PI) controllers that impose the conditions of input current balance as PI references. The control algorithm is simple and high performing. It does not require input voltage sensing and transformation of the control variables into a rotating reference frame. The simulation results on a MATLAB-SIMULINK platform validate the proposed control strategy. In implementation Texas Instrument's digital signal processor TMS320F240F is used as the digital controller. The control algorithm for high-power-factor operation is tested on a prototype boost rectifier under nominal and unbalanced input voltage conditions.     

Dynamic and steady state analysis of a three phase buck rectifier

Current source rectifiers among other alternatives, offer several advantages over line commutated rectifiers. Advantages include displacement power factor control and reduced line current harmonic distortion. This paper analyzes the current source rectifier (CSR) in transient and steady state, the models are developed in a synchronous reference frame. The load behavior is characterized for two load conditions, resistive load or, in general, increasing current for increasing voltage, and constant output power, decreasing output current for increasing voltage. Constant power operation can occur for a converter system supplying a pulse width modulation (PWM) inverter with high dynamics. Several static converter characteristics such as power factor, real and reactive power are analyzed for both types of load. Transient characteristics are analyzed for both types of load by exact small-signal model with full set of equations