130 kHz 7.5 kW current source inverters using static inductiontransistors for induction heating applications

A control scheme of a high-frequency high-power current source inverters using static induction transistors is described which aims at the suppression of the surge voltage and reduction of the switching loss during the commutation of current. The inverter is operated at a leading power factor, which requires the phase angle of the output current to be adjusted to each specific load point by the controller. The stable operation is verified by the experiments under the commutation inductance 1.8 μH, i.e., 18% reactance (130 kHz, 250 V, 30 A, base). As a result, the inverter efficiency is estimated to be 97%, excluding the loss of the drive circuit and the control circuit     

Bidirectional triode thyristor applied voltage rate effect following conduction

This paper describes the bidirectional thyristor commutation effect which involves the rate at which off-state voltage can be applied following current flow. This effect is contrasted to the circuit commutated turn-off time effect associated with semiconductor controlled rectifiers. To help describe the commutation effect in bidirectional devices, two common circuit applications are discussed. A test method is introduced for characterizing the commutation behavior as a function of all operating conditions. A great deal of quantitative information about the commutation effect is presented for a typical medium current bidirectional triode thyristor.     

一种谐振复位单端正激电路的设计

基于谐振磁复位技术,设计了一种单端正激变换器,通过变压器激磁电感和谐振电容,将变压器磁芯能量转换到输入源,并防止变压器磁芯饱和。在转换过程中,激磁能量通过准正弦波的形式,先由变压器激磁电感传递到谐振电容,再由谐振电容传递到输入源。对这种电路的设计方法进行了探讨,用具体电路说明了优化设计过程。     

New two-quadrant chopper with simultaneous control

A two-quadrant chopper circuit equipped with an improved commutation scheme and capable of giving variable positive voltage and current in either direction is described. Saturable reactors are used to support the direct bus voltage during the commutation interval. This commutation scheme has the advantages of low trapped energy, self-healing capability, low cost, etc. This chopper circuit has been designed, fabricated and tested on a 2·2 kW, 220 V separately excited DC motor. Theoretical deductions and their experimental verification are presented in the normalized form.     

Three-Phase Low-Frequency Commutation Inverter for Renewable Energy Systems

The connection of distributed power sources with the utility grid generally needs an electronic power converter for processing the locally generated power and injecting current into the system. If the source provides a dc voltage, the converter must be able to produce a low-distortion high-power-factor ac current. The same aspects related with the voltage and current distortion produced by nonlinear loads can be considered for the injection of power into the grid. In the absence of a specific standard, this paper takes as a reference the limits for current harmonics given by international standards. The justification for this approach is that, from the resulting line voltage degradation, there is no difference between injected and absorbed currents. This paper presents a three-phase inverter using low-frequency commutation. An auxiliary circuit is added to the inverter topology to reduce the output voltage distortion, thus improving the current waveform. The main advantages of this approach are the minimization of the switching losses and the elimination of the electromagnetic interference, which avoids high-frequency filters necessary in high-frequency commutation inverters     

含受控源电路的改进分析方法

含受控源电路的分析是电路分析课程中的一个难点,受控源的存在增加了线性电路分析的难度。本文运用了电路的等效概念,首先对于几种特殊结构类型的含受控源支路采用线性电阻进行等效替代,从而简化了求解过程。然后在含受控源电路中运用戴维宁定理进行电路分析时,对于戴维宁定理的等效电阻的求解,本文又提出了一种有效的电路等效替代方法。最后通过举例,说明利用该方法可使复杂的计算变得简单。     

Z-Source AC–AC Converters Solving Commutation Problem

A new family of Z-source ac-ac converters with buck-boost ability are proposed, including four switches single-phase structure and six switches three-phase structure. New commutation strategies for these converters are proposed and safe commutation can be achieved without snubber circuit. The commutation strategies are easily to realize by sampling only voltage signals, and two switches are always turned on, so switching loss can be reduced. Analysis based on state-space averaging reveals the relationship between Z-source inductor current and filter inductor current as well as voltage ratio. The design considerations of voltage-fed single-phase topology are given as an example. Simulation results on the voltage-fed topologies and experimental results on voltage-fed single-phase topology verified the unique features of Z-source ac-ac converters and the proposed commutation strategies. These converters have merits such as less conduction and switching loss, less devices, therefore high efficiency and reliability can be achieved.     

Three-phase unbalanced-voltage compensators

In this paper, three-phase unbalanced-voltage compensators using ac choppers are proposed. The proposed three-phase unbalanced-voltage compensators are made up of three single-phase ac choppers and transformers for unbalanced-voltage compensation and output voltage regulation. The proposed compensators use ac choppers which solve the commutation problem, limit the switch voltage stress to the maximum line voltage, and also raise efficiency using regenerative dc snubbers. Compared with previous unbalanced-voltage compensators that use complex voltage source inverters, the proposed unbalanced-voltage compensators use ac choppers and utilize source or output line voltages in 30° phase shift with the phase voltages as the input of the ac chopper. Then, the proposed compensators give high efficiency, fast dynamics, simple power circuit, and reduced control circuit. It is also shown via some simulation and experimental results that the presented unbalanced-voltage compensators give good dynamic and steady state performances.     

A high-performance ZVS full-bridge DC-DC 0-50-V/0-10-A power supplywith phase-shift control

This paper presents a high-performance DC-DC switching mode power supply designed to deliver a regulated 0-50 V/0-10 A output. The proposed power supply is based on a modified version of the zero-voltage switching (ZVS) full-bridge (FB) phase-shift DC-DC converter, which incorporates commutation auxiliary inductors to provide ZVS for the entire load range as well as a commutation aid circuit to clamp the output diode voltage. The control strategy is based on two control loops operating in cascade mode. The inner loop maintains a regulated output current, whereas the external voltage loop regulates the output voltage, independently of load and input-voltage changes. In order to obtain a high-reliability converter, the control circuit has been implemented using just two integrated circuits (ICs). The phase-shift regulator UC3875 IC generates the gate drive signal to the MOSFET's. The control loop regulators are implemented using the TL074 IC. A theoretical analysis was conducted, and experimental results were obtained for a 0-50 V/0-10 A power supply operating at 100 kHz     

Sensorless control of ultrahigh-speed PM brushless motor using PLL and third harmonic back EMF

Application-specific integrated circuit (ASIC) ML4425 is often used for sensorless control of permanent-magnet (PM) brushless direct current (BLDC) motor drives. It integrates the terminal voltage of the unenergized winding that contains the back electromotive force (EMF) information and uses a phase-locked loop (PLL) to determine the proper commutation sequence for the BLDC motor. However, even without pulsewidth modulation, the terminal voltage is distorted by voltage pulses due to the freewheel diode conduction. The pulses, which appear very wide in an ultrahigh-speed (120 kr/min) drive, are also integrated by the ASIC. Consequently, the motor commutation is significantly retarded, and the drive performance is deteriorated. In this paper, it is proposed that the ASIC should integrate the third harmonic back EMF instead of the terminal voltage, such that the commutation retarding is largely reduced and the motor performance is improved. Basic principle and implementation of the new ASIC-based sensorless controller will be presented, and experimental results will be given to verify the control strategy. On the other hand, phase delay in the motor currents arises due to the influence of winding inductance, reducing the drive performance. Therefore, a novel circuit with discrete components is proposed. It also uses the integration of third harmonic back EMF and the PLL technique and provides controllable advanced commutation to the BLDC motor.     

基于DSP组合式变频器的设计

介绍了基于DSP的三相航空变频电源的设计原理和方法。采用电压型PWM整流器、高频链逆变器和周波变流器级联组合,使整机开关最大程度地实现了软开关,可靠解决了周波变流器的换流问题。实验结果表明,该变换器设计合理,具有较高的功率因数和可靠性。     

Integrated ZVT auxiliary commutation circuit for input stage of double-conversion UPSs

This paper proposes an integrated zero voltage transition (ZVT) auxiliary commutation circuit applied to a universal input ac/dc system with a bidirectional converter for dc bus and battery bank interface. With the bidirectional converter it is possible to reduce the cost of the battery bank and virtually eliminate both low and high frequency current ripple in the batteries. An integrated ZVT auxiliary commutation circuit has been included to the system to achieve ZVT commutation at the main switches in all operation modes. In addition, this auxiliary commutation circuit controls the di/dt of the resonant process, allowing the utilization of slow diodes [intrinsic diodes of metal oxide semiconductor field effect transistors (MOSFETs)] in the bidirectional converter and, therefore, reducing the overall system cost. Integrated commutation circuit is based on a new concept in which the energy involved in one or more commutation processes is utilized to assist another commutation processes. Moreover, a control system has been developed and analyzed for the correct operation of the proposed system. Experimental results based on a 580-W prototype are presented to demonstrate the good performance of the proposed system.     

Analysis, designing, and experimentation of a transformer-assistedPWM zero-voltage switching pole inverter

This paper proposes a transformer-assisted pulsewidth modulation (PWM) zero-voltage switching pole inverter. As the auxiliary-resonant-commutated pole inverter (ARCPI), the proposal guarantees zero-voltage switching of the main switch and zero-current switching of the auxiliary switch, with a small power auxiliary circuit and full PWM capability. In particular, problems outstanding with the ARCPI such as control complexity, auxiliary switch protection, and center-tap potential variation, etc., are solved in the proposal. The commutation process is discussed step by step in the paper. A detailed analysis for the auxiliary circuit with regard to commutation duration/duty-cycle limitation, auxiliary switch peak current/RMS current, resonant capacitor RMS current, as well as pole output voltage loss are presented afterwards. A design methodology for the auxiliary circuit is recommended based on the analysis. The proposal is experimentally verified with a 4.25 kW half-bridge inverter prototype     

有源箝位软开关充电机的设计与仿真研究

传统硬开关电路影响效率和可靠性的同时,对其他设备的电磁干扰也较大,软开关则可解决上述问题。本文提出了一种基于辅助谐振换流的新型ZVT-PWM变换器,即通过采用简单的有源辅助谐振网络实现了主、辅开关管的软开关,主开关管实现了零电压开通,开关管电流电压应力小。利用这种软开关技术研制了一台用于为风力发电蓄电池充电的充电机,给出了充电机的控制系统框图,简单介绍了充电机的工作原理。最后利用Pspice给出了运行波形和仿真结果。     

Phase-controlled DC-AC converter with high-frequency switching

An analysis of the phase-controlled DC-AC converter is presented. This converter has a pair of switches in each side of the primary and the secondary of the isolation transformer. The voltage conversion ratio is controlled by the phase difference between the two pairs of switches. The averaged equivalent circuit for low frequency operation is derived. The switching surge during commutation is much reduced by dividing the reactor into two parts. As a result, the transformer is miniaturized by increasing the switching frequency and the reactive energy can be easily recovered to the DC source. This DC-AC converter is especially suitable for small uninterruptible power supply systems     

矩阵变换器的换流研究

本文讨论了矩阵变换器的换流特点，详细分析了矩阵变换器基于负载电流、基于电源电压以及改进型的基于电源电压三种换流策略的换流方法，对这三种换流方法进行比较，最后对改进型基于电源电压的换流策略采用MATLAB／SIMULINK进行仿真，给出具体的仿真电路和波形，证明了改进型基于电源电压换流策略的正确性。     

State-plane analysis of a constant-frequency clamped-modeparallel-resonant converter

A novel clamped-mode parallel-resonant converter which operates at a constant frequency and provides a wide output voltage regulation range is proposed and analyzed. Employing graphical state-plane techniques, five circuit operating modes are identified and their mode boundaries defined. Regions for natural and forced commutation of power devices are specified. The DC control-to-output characteristics are derived to facilitate converter design. The predicted operating modes are experimentally verified using a 105 kHz prototype circuit     

A comparison of load commutated inverter systems for inductionheating and melting applications

A comparative analysis of a current source inverter and a voltage source inverter suitable for induction heating and melting applications is presented. Both power supplies considered operate on the principle of load commutation. The comparison is based on criteria such as input power factor, component ratings, maximum and minimum operating frequencies, operation under varying load conditions, inverter starting capability, and system and control simplicity. The voltage source series resonant inverter is found to offer the best overall performance with respect to converter utilization     

Switching technique for current-controlled AC-to-AC converters

The AC-to-AC converter called the matrix converter is very simple in structure and has powerful controllability. However, there are few practical applications, particularly in power electronics fields. The major reasons largely lie in the commutation problem and complexity of the control circuit. This paper proposes a novel commutation technique which is very simple to implement. This commutation scheme allows the deadtime to avoid current spikes of nonideal switches and, at the same time, establishes a current path of the inductive load to avoid voltage spikes. A switching technique of the matrix converter using a space-vector-modulation (SVM) based hysteresis current controller (HCC) is also proposed. The switching technique is implemented without any computational burden and is controlled with a simple control circuit. This technique utilizes advantages of the HCC and SVM technique. Simulation and experimental results obtained on a 5 kW single-phase AC chopper and an 11 kW three-phase to three-phase matrix converter are discussed     

A novel ZCS-PWM power-factor preregulator with reduced conduction losses

This paper proposes a new single-phase high-power-factor rectifier, which features regulation by conventional pulsewidth modulation (PWM), soft commutation, and instantaneous average line current control. A new zero-current-switching PWM (ZCS-PWM) auxiliary circuit is configured in the presented ZCS-PWM rectifier to perform ZCS in the active switches and zero-voltage switching in the passive switches. Furthermore, soft commutation of the main switch is achieved without additional current stress by the presented ZCS-PWM auxiliary circuit. A significant reduction in the conduction losses is achieved, since the circulating current for the soft switching flows only through the auxiliary circuit and a minimum number of switching devices are involved in the circulating current path and the proposed rectifier uses a single converter instead of the conventional configuration composed of a four-diode front-end rectifier followed by a boost converter. Nine transition states for describing the behavior of the ZCS-PWM rectifier in one switching period are described. The PWM switch model is used to predict the system performance. A prototype rated at 1 kW, operating 50 kHz, with an input ac voltage of 220 V/sub rms/ and an output voltage 400 V/sub dc/ has been implemented in laboratory. An efficiency of 97.3% and power factor over 0.99 has been measured. Analysis, design, and the control circuitry are also presented in this paper.