Control of Single-Phase-to-Three-Phase AC/DC/AC PWM Converters for Induction Motor Drives

This paper proposes a novel control scheme of single-phase-to-three-phase pulsewidth-modulation (PWM) converters for low-power three-phase induction motor drives, where a single-phase half-bridge PWM rectifier and a two-leg inverter are used. With this converter topology, the number of switching devices is reduced to six from ten in the case of full-bridge rectifier and three-leg inverter systems. In addition, the source voltage sensor is eliminated with a state observer, which controls the deviation between the model current and the system current to be zero. A simple scalar voltage modulation method is used for a two-leg inverter, and a new technique to eliminate the effect of the dc-link voltage ripple on the inverter output current is proposed. Although the converter topology itself is of lower cost than the conventional one, it retains the same functions such as sinusoidal input current, unity power factor, dc-link voltage control, bidirectional power flow, and variable-voltage and variable-frequency output voltage. The experimental results for the V/f control of 3-hp induction motor drives controlled by a digital signal processor TMS320C31 chip have verified the effectiveness of the proposed scheme     

Four-wire dynamic voltage restorer based on a three-dimensional voltage space vector PWM algorithm

A modified voltage space vector pulse-width modulated (PWM) algorithm for a four-wire dynamic voltage restorer (DVR) is described. The switching strategy based on a three-dimensional (3-D) /spl alpha//spl beta/O voltage space is applicable to the control of three-phase four-wire inverter systems such as the split-capacitor PWM inverter and the four-leg PWM inverter. In contrast to the conventional voltage space vector PWM method, it controls positive, negative and zero sequence components of the terminal voltages instantaneously. Three 3-D modulation schemes are analyzed with respect to total harmonic distortion (THD), weighted total harmonic distortion (WTHD), neutral line ripple and switching loss over the whole range of the modulation index when the DVR experiences both balanced and unbalanced sags with phase angle jumps. Experimental results from a 9 kW DVR system using a split-capacitor PWM inverter are presented to validate the simulation results.     

Interleaved PWM with discontinuous space-vector modulation

This paper describes the effect of interleaved discontinuous space-vector modulation (SVM) in paralleled three-phase systems using three-phase pulsewidth modulation (PWM) rectifiers as an example. At the discontinuous point of the SVM, the phase shift between the switching signals of the paralleled modules generates a zero-sequence excitation to the system. Because the conventional control in a balanced three-phase system with only dq channels cannot reject this disturbance, a beat-frequency circulating current will develop on the zero axis. Based on this observation, a SVM without using zero vectors is used to eliminate the cause of pure zero-sequence current for parallel operation. Using this SVM, the circulating current is observable in dq channels. It can be suppressed dynamically by strong current loops of power-factor-correction (PFC) circuits. The concept is verified experimentally on a breadboard system     

Design of a position sensor for torque ripple minimization of a voltage source inverter fed self-synchronous machine

A study on the torque ripple minimization of a voltage source inverter fed selfsynchronous machine is presented. This study is based on a design of a position sensor which allows us to suppress undesirable voltage harmonics and hence to minimize electromagnetic torque ripple. We use the optimized pulse width modulation (PWM) method as a basis for the design of this position sensor. Thus, the obtained inverter control circuit is a very simple design and there is no need for a microprocessor or for specialized PWM integrated circuits for its implementation. The obtained simulation results are compared with practical results for a self-controlled synchronous machine, using the classical control method and the proposed method.     

单周期控制三相电压型PWM整流器

文章对基于单周期控制的三相PWM高功率因数整流器进行了研究,推导了单周期控制三相电压型PWM整流器的控制规律。它不需要乘法器更不需要对输入电压进行检测,其控制逻辑简单并且以恒定频率工作,可以在每个开关周期控制输入电流跟踪正弦参考量,从而实现低电流谐波畸变和高功率因数。基于Multisim2001软件平台,建立了基于单周期控制的三相电压型PWM整流器的仿真模型,完成了6kW三相PWM整流器的设计和实验研究,仿真和试验结果都验证了理论分析的正确性。     

High-precision current source using low-loss, single-switch,three-phase AC/DC converter

A three-phase AC/DC converter based on isolated Cuk topology feeding an inductive load is presented. The main goal is to get a compact, highly stable current source to feed an electromagnet. A high power factor is achieved, at constant duty-cycle and switching frequency, by discontinuous input current mode operation. The converter presents a linear relationship between the duty-cycle and the output current, making it easier to design the control system. Additionally the voltage stress on the power transistor is constant and does not depend on the duty-cycle. An auxiliary circuit allows zero voltage turn-off while limiting the over-voltage on the switch produced by the transformer leakage inductance. Pulse-width modulation (PWM) control is used to reduce sensitivity to line disturbances and to eliminate the 300-Hz ripple on the output current. Experimental measurements taken on a 400-W prototype confirm theoretical forecasts     

Design and performance of a passive EMI filter for use with a voltage-source PWM inverter having sinusoidal output voltage and zero common-mode voltage

This paper deals with integrating a small-sized passive electromagnetic interference (EMI) filter with a voltage-source pulse-width modulated (PWM) inverter. The purpose of the filter is to eliminate both high-frequency common-mode and normal-mode voltages from the three-phase output voltages of the inverter. A laboratory system consisting of a 5-kVA inverter, a 3.7-kW induction motor, and a specially-designed passive EMI filter was constructed to verify the viability and effectiveness of the filter. As a result, both line-to-line and line-to-neutral output voltages look purely sinusoidal as if the inverter were an ideal three-phase variable-voltage, variable-frequency power supply when viewed from the motor terminals. This results in a complete solution to serious EMI issues related to high-frequency common-mode and normal-mode voltages produced by the PWM inverter.     

死区对PWM逆变器共模电压的影响及其抑制方法

变频器采用的空间矢量脉宽调制(SVPWM)会产生共模电压,后者对变频器和电机产生危害。改进的空间矢量脉宽调制法有利于降低共模电压,但由于没有考虑死区的影响,实际效果受到较大影响。文章详细研究了死区对PWM逆变器共模电压的影响,并提出了一种消除死区的方法来抑制死区影响并对共模电压起到一定的抑制作用,使改进的空间矢量脉宽调制法能够真正达到预想的效果。最后通过Matlab仿真实验,验证了该方法的有效性。     

Parallel Connection of Two Three-Phase Three-Switch Buck-Type Unity-Power-Factor Rectifier Systems With DC-Link Current Balancing

Connecting three-phase rectifier systems in parallel shows many advantages as compared to a single rectifier system with higher output power, such as higher reliability, smaller current and voltage ripple components, lower filtering effort, or higher system bandwidth. However, current unbalance or circulating currents can occur for modular design. In this paper, the parallel connection of two three-phase three-switch buck-type unity-power-factor pulsewidth-modulation rectifier systems is experimentally investigated for a 10-kW digital-signal-processor-controlled prototype. A space vector modulation scheme is employed showing all the advantages of an interleaved operation. Three control schemes for active dc-link current balancing are described employing an additional free-wheeling state that allows to influence the rate of change of the dc-link currents and can therefore be used for dc-link current balancing. The control schemes differ concerning control action and additional switching losses. Simulation and experimental results confirm the theoretical considerations: The dc-link current-balancing capability of the different control methods is compared, and the influence of the additional free-wheeling state on switching losses and operation behavior is investigated. The most advantageous control method, which employs a hysteresis controller and shows limited switching losses, is selected. The analysis of the mains behavior shows an improvement as compared to a single rectifier operation.     

Analysis and Design of a Novel Three-Phase AC–DC Buck-Boost Converter

This paper proposes a novel three-phase ac-dc buck-boost converter. The proposed converter uses four active switches, which are driven by only one control signal. This converter is operated in discontinuous conduction mode (DCM) by using the pulsewidth modulation (PWM) technique, and the control scheme very easily and simply achieves purely sinusoidal input current, high power factor, low total harmonic distortion of the input current and step-up/down output voltage. Also, the proposed converter provides a constant average current to the output capacitor and load in each switching period. Thus, the ripple component of sixth times line frequency will not appear in the output voltage. Therefore, a smaller output capacitor can be used in the proposed converter. Moreover, the steady-state analysis of voltage gain and boundary operating condition are presented. Also, the selections of inductor, output capacitor and input filter are depicted. Finally, a prototype circuit with simple control logic is implemented to illustrate the theoretical analysis.     

Elimination of common-mode voltage in three-phase sinusoidal powerconverters

This paper presents an active solution to a common-mode voltage created by typical three-phase inverters. It is shown that the addition of a fourth leg to the bridge of a three-phase inverter eliminates the common-mode voltage to ground created by the modulation of the inverter. An appropriate four-phase LC filter is inserted between the inverter and the load in order to create sinusoidal output line-to-line voltage. A simple modification of the modulation strategy is implemented for the four-phase inverter to achieve a three-phase wye-output neutral-to-ground voltage which is equal to zero at all times for an ideal inverter. The modulation strategy thereby completely eliminates the common-mode potential produced by traditional modulation techniques with traditional three-phase inverter topologies     

A new quasi-parallel resonant DC link for soft-switching PWMinverters

A new quasi-parallel resonant DC-link inverter with the more flexible pulse-width-modulation (PWM) capability and easier control is proposed in this paper. With the addition of one coupling core and one diode, the circuit can be directly applied to the single/three-phase inverter to achieve the soft-switching action. For the proposed topology, it needs neither the help of the inverter switch devices nor the requirement of voltage/current sensors. Random duration of the zero DC-link voltage can be obtained, and the voltage stresses of the inverter switches can be maintained to the minimum. The relative analysis of the presented circuit has been performed and verified by the experiment     

SVPWM电压源逆变器供电异步电动机的动态仿真

建立了三相异步电动机在d-q坐标系下的动态数学模型,并介绍了控制异步电动机运行的两种控制技术:正弦波脉宽调制(SPWM)技术和空间电压矢量脉宽调制(SVPWM)技术。在Matlab/Simulink环境下,分别建立SPWM和SVPWM电压源型逆变器供电的三相异步电动机的动态仿真模型,比较分析了在这两种控制方式下的仿真结果。结果表明,较之SPWM控制方式,SVPWM的异步电动机变频调速系统启动快,转矩脉动小,定子电流谐波小,具有较好的动态性能和稳态性能。     

An active circuit for cancellation of common-mode voltage generatedby a PWM inverter

This paper proposes an active common-noise canceler (ACC) that is capable of eliminating the common-mode voltage produced by a pulsewidth modulation (PWM) inverter. An emitter follower using complementary transistors and a common-mode transformer are incorporated into the ACC, the design method of which is also presented in detail. Experiments using a prototype ACC, whose design and construction are discussed in this paper, verify its viability and effectiveness in eliminating common-mode voltage in a 3.7 kW induction motor drive using an insulated gate bipolar transistor (IGBT) inverter. Some experimental results show that the ACC makes significant contributions to reducing a ground current and a conducted electromagnetic interference (EMI). In addition, the ACC can prevent an electric shock on a nongrounded motor frame and can suppress motor shaft voltage     

Parallel resonant DC link circuit-a novel zero switching losstopology with minimum voltage stresses

A parallel resonant DC link (PRDCL) circuit topology is proposed as an approach to realizing zero switching loss DC-AC high switching frequency power conversion. The proposed circuit is used as an interface between the DC voltage supply and a voltage source pulse width modulated (PWM) inverter to provide a short zero voltage period in the DC link of the inverter to allow zero voltage switchings to take place in the PWM inverter. The peak voltage stress on the PWM inverter switches is limited to the DC supply voltage. Another significant advantage of the circuit is that the inverter can be controlled by the conventional PWM strategy. The proposed circuit is systematically analyzed and its operation principle is explained. Design considerations and design formulas are presented. A complete zero voltage switching DC-AC system consisting of the proposed circuit and a PWM inverter was simulated on a computer     

Power Injection System for Grid-Connected Photovoltaic Generation Systems Based on Two Collaborative Voltage Source Inverters

This paper presents a new topology for the power injection system that is based on the parallel association of two voltage source inverters. One operates using a quasi-square voltage waveform strategy, and the other operates with a pulsewidth-modulation (PWM)-based strategy. The aims of this topology are to inject the power from the photovoltaic generation system using the quasi-square inverter and to control the current quality using the PWM inverter. The proposal optimizes the system design, permitting the reduction of system losses and an increase of the energy injected into the grid.     

基于DSP的SVPWM与载波PWM的统一性研究

 针对脉宽调制(PWM)逆变器,在研究逆变电源电压矢量的基础上,将空间矢量脉宽调制(SVPWM)技术应用于三相和单相PWM逆变电源,分别给出了三相和单相SVPWM的数字信号处理(DSP)算法,给出了一种开关模式优化的单相SVPWM算法,导出了三相和单相SVPWM基于载波调制的调制波形式以及零序信号形式,指出载波零序信号在本质上对应着逆变器零电压矢量作用时间分配与分布,论证了SVPWM与载波PWM的统一,实验结果验证了SVPWM算法的有效性.     

Parallel processing inverter system

A novel method of instantaneous voltage and power balance control of a parallel processing inverter system is proposed. It consists of a high-speed switching PWM (pulsewidth modulated) inverter with an instantaneous current minor loop controller, a voltage major loop controller, and a power balance controller. This system realizes the following functions with only one inverter: constant AC output voltage control with reactive power control, active filtering to absorb load current harmonics, DC voltage and current control as AC-to-DC converter, and uninterruptible power supply (UPS) for stand-alone operation. This system covers a wide application range, including UPS systems, new energy systems, and active filters with voltage control functions