A simple scheme for unity power-factor rectification for highfrequency AC buses

A simple scheme is proposed for offline unity power factor rectification for high-frequency AC buses (20 kHz). A bandpass filter of the series-resonant type, centered at the line frequency, is inserted between the line and the full-wave rectified load. The Q=Z ₀/R_L formed by the load and the characteristic impedance of the tank circuit determines the power factor, the boundary between continuous and discontinuous conduction modes, the peak stresses, and the transient response of the rectifier. It is shown that for Q>2/π the rectifier operates in continuous conduction mode and the output voltage is independent of the load. Also, it is shown that for Q>2 the line current is nearly sinusoidal with less than 5% third-harmonic distortion and the power factor is essentially unity. An increase in Q causes an increase in the peak voltages of the tank circuit and a slower transient response of the rectifier circuit. The DC, small-signal, and transient analyses of the rectifier circuit are carried out, and the results are in good agreement with simulation and experimental results     

Improvement of Predictive Current Control Performance Using Online Parameter Estimation in Phase Controlled Rectifier

In a phase controlled rectifier, the fastest response can be achieved by predictive current control without any overshoot. However, any error in the load parameters can cause steady state errors between a reference current and the feedback current because this current control scheme depends on the mathematical relationships between the output current, the firing angle, and the power source voltage. Thus, in the predictive current control, an accurate parameter is necessary for attaining a zero steady-state error. In this paper, the load resistance and inductance are estimated using the least square method of an online parameter calculation based on digitally sampled instantaneous voltage and currents. For the careful sampling of data and the reduction of the calculation time, a new timer-based gating algorithm is proposed and explained in detail. Using the proposed algorithm, the fastest current control performance in the transient state is obtained by the online correction of load parameters in various simulations and experimental results.     

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 single-phase capacitor clamped converter operated simultaneously as a PWM rectifier and an active power filter

A control scheme is proposed that employs an active rectifier to work simultaneously as an active power filter to decrease current harmonics. The adopted capacitor clamped rectifier is controlled to draw a sine wave line current with low current harmonics. A voltage controller, three capacitor voltage compensators and one current controller are used in the proposed control algorithm to achieve a constant DC bus voltage, balanced capacitor voltages and line current tracking. The validity of the proposed system is proved by the results of computer simulations and experimental tests.     

Single-phase high power factor pre-regulator with three-level modulation scheme

A control scheme for the single-phase three-level pulse-width modulation active rectifier is proposed. A hysteresis current control scheme is used to draw the sinusoidal line current in phase with the mains voltage. The line current command is derived from a voltage controller and a phase-locked loop circuit. The blocking voltage of each power device is clamped to half of the DC-link voltage in the proposed active rectifier. In order to generate the three-level voltage pattern on the DC side of the active rectifier, the region detector of the line voltage, capacitor voltage compensator and hysteresis current comparator are employed in the adopted control algorithm to achieve high input power factor and low current distortion. To investigate the proposed control algorithm, the adopted rectifier is simulated and experimental tests from a laboratory prototype undertaken.     

直接电流控制的三相桥式PWM整流电路的设计与分析

文章对直接电流控制的PWM整流电路开展研究,主要内容如下：（1）设计BOOST型三相桥式PWM整流器的主电路。（2）设计基于直接电流控制的PWM整流电路的控制系统。（3）建立直接电流控制系统Simulink仿真模型,进行仿真分析。仿真结果证明直接电流控制方案使得PWM整流器功率因数接近于1,流入电网的电流基本接近正弦波,对电网的谐波污染小。     

A space vector-based rectifier regulator for AC/DC/AC converters

A voltage-sourced rectifier control scheme for use with AC/DC/AC variable speed drives is presented. A control scheme is derived that directly calculates the duration of time spent on the zero state and on each switching state adjacent to the reference vector, over a constant switching interval, in order to drive the line current vector to the reference vector. In addition, under transient conditions, when deadbeat control is not possible, a control scheme is presented that ensures that the line current vector is driven in the direction of the reference current vector. The current reference for the rectifier controller is derived from the bus voltage error and a feedforward term based on the estimated converter output power. The proposed space vector-based rectifier regulator is shown to exhibit improved harmonic and transient performance over existing per-phase duty cycle prediction methods, especially at modulation indices near unity. The deadbeat control of the rectifier input current is accomplished every half-cycle with constant switching frequency while still symmetrically distributing the zero state within the half-cycle period     

Rectifier for minimum line-current harmonics and maximum powerfactor

Rectifier line current harmonics interfere with proper power system operation, reduce rectifier power factor, and limit the power available from a given service. The rectifier's output filter inductance determines the rectifier line current waveform, the line current harmonics, and the power factor. Classical rectifier analysis usually assumes a near-infinite output filter inductance, which introduces significant error in the estimation of line current harmonics and power factor. A quantitative analysis of single and three-phase rectifier line current harmonics and power factor as a function of the output filter inductance is presented. For the single phase rectifier, one value of finite output filter inductance produces maximum power factor and a different value of finite output filter inductance produces minimum line current harmonics. For the three phase rectifier, a near-infinite output filter inductance produces minimum line current harmonics and maximum power factor, and the smallest inductance that approximates a near-infinite inductance is determined     

A unity power factor PWM rectifier with DC ripple compensation

This paper presents a new topology for a pulsewidth modulation (PWM) rectifier which achieves unity power factor on the AC supply side and ripple reduction on the DC output side. The main circuit of this rectifier consists of a conventional PWM rectifier and a pair of additional switches. The switches and PWM rectifier are controlled such that the ripple current on the DC line is reduced, and unity power factor is achieved on the AC line. As a result, this circuit does not require a large DC capacitor or a passive LC resonant circuit. Furthermore, control of the additional switches and PWM rectifier requires only a simple control circuit. The effectiveness of this circuit was confirmed by experiments and analysis. The rectifier is useful for uninterruptible power systems (UPSs) and DC power supplies, especially for cases in which batteries are connected to the DC line     

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。     

Implementation of a three-level rectifier for power factorcorrection

In this paper, a new single-phase switching mode rectifier (SMR) for three-level pulse width modulation (PWM) is proposed to achieve high input power factor, low current harmonics, low total harmonic distortion (THD) and simple control scheme. The mains circuit of the proposed SMR consists of six power switches, one boost inductor, and two DC capacitors. The control algorithm is based on a look-up table. There are five control signals in the input of the look-up table. These control signals are used to control the power flow of the adopted rectifier, compensate the capacitor voltages for the balance problem, draw a sinusoidal line current with nearly unity power factor, and generate a three-level PWM pattern on the AC side of adopted rectifier. The advantages of using three-level PWM scheme compared with two-level PWM scheme are using low voltage stress of power switches, decreasing input current harmonics, and reducing the conduction losses. The performances of the proposed multilevel SMR are measured and shown in this paper. The high power factor and low harmonic currents at the input of the rectifier are verified by software simulations and experimental results from a laboratory prototype     

A hybrid structure using phase-controlled rectifiers andhigh-frequency converters for magnet-load power supplies

Thyristor rectifiers are still the preferred choice for large magnet power supplies. However, large harmonic voltages, resulting in large current ripple, and slow dynamic response are major drawbacks of these converters. This paper presents a topology and a control technique for hybrid large-power high-precision magnet power supplies. The system consists of a phase controlled rectifier connected in series with a high-frequency PWM converter. The rectifier is designed to handle the main output power and the PWM converter is used only for harmonics cancellation and error compensation. A feedforward control scheme is proposed to ensure that the desired power sharing is maintained during both the steady state and transient operations. The operating principles of the proposed structure are discussed in the paper, and the results from a 1 kVA experimental setup are provided to validate the proposed topology     

Single-phase integrated power quality compensator based oncapacitor-clamped configuration

A control scheme of an integrated power quality compensator, which employs an active rectifier to work simultaneously as an active power filter (APF) to decrease current harmonics, is proposed. The employed rectifier is based on a capacitor-clamped configuration to produce multilevel pulsewidth modulation waveforms which result in low voltage stress and low conduction loss on the power switches. The proposed active rectifier is controlled to track the supply current to be a sinusoidal wave with low current harmonics. The advantages of the proposed control scheme are high power factor, low current harmonics, no complicated calculations for current harmonics elimination, and no dedicated APF needed for harmonic elimination. The experimental results are used to verify the validity and effectiveness of the proposed control scheme     

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     

A fuzzy-controlled active front-end rectifier with current harmonicfiltering characteristics and minimum sensing variables

A control strategy which allows conventional voltage-source current-controlled (VSCC) pulsewidth modulation (PWM) rectifiers to work simultaneously as active power filters is presented. The proposed control strategy also allows compensating the system power factor and compensating unbalanced loads. The measurement and/or calculation of the harmonics and reactive power are not required, making the proposed control scheme very simple. The active front-end rectifier acts directly on the mains line currents, forcing them to be sinusoidal and in phase with the mains voltage supply. To improve the dynamic of the system, the amplitude of the current is controlled by a fuzzy system, which adjusts the DC-link voltage of the PWM rectifier. The strategy is based on connecting all the polluting loads between the PWM rectifier and their input current sensors. The main advantages of this approach are the following: (1) there is no need to install a specially dedicated active power filter; (2) it also works simultaneously as a power factor compensator; and (3) no special and complicated calculations are required for harmonic elimination. The viability of the proposed active front-end rectifier is proved by simulation and with experimental results obtained from a 2 kVA PWM prototype     

A fully software-controlled PWM rectifier with current link

A fully-software-controlled pulse-width-modulated (PWM) rectifier with a current link is presented. The rectifier uses six switches to connect the three-phase source of the load directly. Line power factor is controlled while maintaining DC current. The input filter of the rectifier is analyzed, showing that unity power factor is achieved by the lagging of the input current of the rectifier with respect to the source voltage. The PWM technique is developed using a space vector modulation, and its implementation is carried out with a minimal control hardware structure based on a 16 b single-chip microcomputer. It is shown experimentally that the scheme gives good performance     

Digitally controlled high power switch-mode rectifier

High power switch-mode rectifiers offer advantages over conventionally used line-commutated thyristor rectifiers in terms of size and cost. This paper describes operation of the high power switch-mode rectifier based on an original control strategy which is digitally implemented. The rectifier is operated in a constant output current mode. The control strategy provides a fast transient response to disturbances and achieves equal current sharing between the buck converter modules which are paralleled within the switch-mode rectifier. Equal current sharing is maintained in steady-state as well as in transient operation. The paper demonstrates that the transient response to load disturbances achievable with the proposed control strategy is superior to the response obtained with the conventional control strategy in terms of the output current overshoot and the settling time. The control algorithm is digitally implemented on a DSP/FPGA based digital control platform and its performance is verified on a 2 kW scaled-down experimental setup of the switch-mode rectifier.     

A complete DC and AC analysis of three-phase controlled-current PWMrectifier using circuit D-Q transformation

A recently proposed circuit P-Q transformation is used to analyze a three-phase controlled-current PWM rectifier. The DC operating point and AC transfer functions are completely determined. Most features of the power converter are clearly interpreted. They are: (1) the output voltage can be controlled from zero to maximum; (2) the system is equivalently an ideal current source in the steady state; (3) the system can be described as linear circuits; and (4) the input power factor can be arbitrarily controlled within a certain control range     

无电压传感器的三电平PWM整流器定频直接功率控制

给出了三电平PWM整流器的数学模型,在传统的直接功率控制和电压定向控制的基础上,结合虚拟磁链控制的优点,提出了一种新的三电平PWM整流器定频直接功率控制方法。该控制方法省略了电网电压传感器,实现了有功功率和无功功率的动态解耦,调制环节采用空间电压矢量调制,开关频率固定。仿真结果表明,该控制方法实现了单位功率因数运行,网侧电流谐波小,具有良好的动静态性能,保证了中点电位的平衡。     

双三电平交-直-交变频系统研究

双PWM变频调速系统采用交一直一交拓扑结构,通过可控整流,实现网侧电流接近正弦波,网侧功率因数近似为1,具有较快的动态响应,双向传输电能等诸多优点,实现了节能调速。针对NPC型三电平拓扑给出了一种参考电压分解的三电平SVPWM算法,简化为两电平SVPWM算法,比传统的三电平SVPWM算法易于实现,仿真验证7该算法的有效...