A new regenerative snubber circuit for large-capacity three-level GTO inverter systems

Increase in the capacity of GTOs has made remarkable progress in recent years. At present, 4.5-kV, 4.0-kA GTOs are commercially available, and 6.0-kV, 6.0-kA GTOs made from 6-inch silicon wafers are appearing. The 6-inch GTOs will be applied to our three-level GTO inverter system. In order to apply GTOs to voltage-source inverters, snubber circuits are necessary for limiting on the turn-on di/dt and turn-off dv/dt. To realize high efficiency of the system, regenerative snubber circuits are often applied. A conventional circuit applied to three-level GTO inverters had the problem of long paths created for snubber circuits of the inner GTOs. Another circuit using a current transformer for recovering the energy trapped in the snubber circuits of the inner GTOs has been presented. In this paper, a new regenerative snubber circuit is proposed, which is more suitable for three-level GTO inverter systems with many phase-legs. By applying the snubber circuit, all snubber energy generated by each GTO switching can be regenerated to the dc link. In addition, high current turn-off performance of both the inner and the outer GTOs is verified by several successful experimental results using 6-inch 6.0-kV, 6.0-kA GTOs. © 1997 Scripta Technica, Inc. Electr Eng Jpn, 120(2): 41–48, 1997     

A regenerative centrifuge drive using a current-fed inverter withvector control

The authors describe the development of a centrifuge drive based on a current-fed inverter. The power circuit circuit is briefly described and a block diagram of the vector control is presented. Experience in tuning the speed regulator and modifying the torque pulsations in order to prevent coupling chatter is discussed. A specially shaped enclosure was designed to accommodate the end user's space requirement and also to provide space for the electronics that control the sequence of operation. A number of these drives have been in operation for more than two years, and operating experience concerning cycle time, power consumption, and reliability is presented     

一种新型移相级联式高压变频器

采用HV-IGBT元件、作桥级联式的电平逆变技术多重化输出和模块化设计的移相级联式高压变频器．具有结构简洁．安全可靠、无谐波污染等特点．详细介绍了其结构和特点。经试验和实际应用证明．这种高压变频器所用功率器件少．负荷均衡．输入输出线性度好．具有良好的控制特性。     

一种新型移相级联式高压变频器

介绍Diamond-HV移相级联式高压变频器的原理、结构、控制策略、技术性能及现场应用结果。这种高压变频器设计新颖、独特，功率器件少、结构简洁，可靠性高，负荷均衡、线性度好，具有良好的控制特性。移相变压器副边绕组少、制作简单。多电平逆变器能产生多阶梯、低失真电压波形，特别适合于大功率高电压场合。Diamond-HV系列高压变频器输入输出谐波含量低、du／dt小，可直接驱动普通异步电动机．     

A new medium-voltage PWM inverter topology for adjustable-speeddrives

In this paper, a new pulsewidth modulation (PWM) inverter topology suitable for medium-voltage (2300/4160 V) adjustable-speed drive systems is proposed. The modular inverter topology is derived by combining three standard three-phase inverter modules and a 0.33-pu output transformer. The output voltage is high-quality multistep PWM with low dv/dt. Further, the approach also guarantees balanced operation and 100% utilization of each three-phase inverter module over the entire speed range. These features enable the proposed topology to be suitable for powering constant-torque, as well as variable-torque type loads. Clean power utility interface of the proposed inverter system can be achieved via an 18-pulse input transformer. Analysis, simulation and experimental results are shown to validate the concepts     

A two-switch high-performance current regulated DC/AC convertermodule

A high-performance current regulated single-phase DC/AC converter module is proposed in this paper. Its novel features include: a two-switch topology with no “shoot-through” paths, high input to-output voltage gain, low and constant switching frequencies, and practically instantaneous recovery from input or output transients. Moreover, by utilizing an inner filter capacitor current control loop the proposed module can maintain nearly perfect sinusoidal output voltages even with highly nonlinear loads. Furthermore, three-phase operation can be obtained easily by using three of these modules. Finally, the paper includes the analysis and design of the converter power and control circuits and the experimental evaluation of key predicted results     

A current regulated switched capacitor static volt ampere reactivecompensator

This paper introduces a current regulated switched capacitor static VAr compensator (SVC). The physical mechanisms governing the performance of the switched capacitor SVC are explained in detail. A relevant equivalent circuit is presented which helps prove that the oscillation of reactive power takes place in two different loops; between the main 60 Hz source and the AC input of the converter bridge; and between the energy storing device (in this case, a capacitor) and a set of fictitious voltage sources used for modeling the solid-state switches. The paper discusses the performance of such a device and presents the basic analytical expressions     

A new modular motor-modular inverter concept for medium-voltageadjustable-speed-drive systems

In this paper, a new modular motor-modular inverter concept for medium-voltage adjustable-speed drive (MV-ASD) systems is introduced. It is shown that standard MV motor winding connections can be reconnected into several three-phase groups, each powered by a separate three-phase pulsewidth modulation inverter, resulting in a high-performance MV-ASD system. The proposed approach is fault tolerant and can continue to operate at reduced power levels, under inverter and/or motor faults. An example 250 hp four-pole 60 Hz 2300 V/4160 V motor winding connection diagram along with the associated inverter configurations is analyzed. Results from analysis are presented on the aspects of faults and motor operation under partial winding excitation. Experimental results on a low-voltage (460 V) 10 hp ASD are demonstrated     

A new generalized inverter based on the active hybrid

The building block for the new generalized immittance inverter is a 3-port known as the active hybrid network. One of its ports is bidirectional, and matches a design admittance y₀. The second port operates in the send, while the third port operates in the receive direction. The hybrid is constructed from an op-amp and a 5-port network composed of a few resistors and the design admittance y₀. There are two versions of the hybrid: the voltage-inverting (i.h.) and the noninverting hybrid (n.i.h.). The inverter consists of an i.h. and an n.i.h. connected at their unidirectional ports in a loop. The gyration admittances are actual driving-point admittances in the circuit, namely the design admittances y₀, y'₀ of the two hybrids. Such an inverter, when terminated at its output port by a load admittance y, will give at its input port an input admittance y_in = y₀y'₀/y. Expressions are derived for the y parameters of the inverter at higher frequencies, thus accounting for the finite bandwidth of the op-amp. Two special cases are particularly treated, and experimental results are obtained for them. The first is the case of the resistive gyrator, for which y₀ and y'₀ are pure conductances. The second is the case of the capacitive gyrator, for which y₀ and y'₀ are pure capacitive susceptances. The capacitive gyrator is used to produce the supercapacitor, or f.d.n.r., and the results of measurements on a number of f.d.n.r. networks are given.     

变流器型分布式电源的短路电流响应特性

分布式电源的短路电流计算是含分布式电源配电网的故障分析的基础。针对变流器并网型分布式电源,在分析电压源变流器控制系统结构的基础上,仿真研究了幅相控制、矢量解耦控制和电流瞬时值跟踪控制策略下变流器的短路电流变化特征,给出了配电网最严重短路情况下变流器型分布式电源输出电流的统一表达式。最后通过示例说明了分布式电源出力对短路电流的影响。     

A multicarrier modular photovoltaic grid-connected inverter with a new phase-shift rule

Photovoltaic grid-connected inverters are distributed power generation devices that convert the dc power from solar panels to high-quality ac power at the utility grid interface. Adopting modular design in these systems improves expandability, serviceability, reliability and efficiency. In this paper, the phase-shifted carrier technique, which is normally used in high-power multiconverter schemes, is applied to a modular residential photovoltaic grid-connected inverter to improve the output power quality. First, it is shown, through analysis and simulation, that in the commonly-used grid-connected inverter topology based on the phase-shift modulated full-bridge converter, the well-known rule for the phase-shift between the carrier signals of the adjacent modules is not effective for both odd and even number of modules. Then, a new general rule for the phase-shift is systematically derived and its effectiveness in improving the output power quality for odd and even numbers of modules is verified through simulation.     

A circulating current control scheme for multiple three‐level NPC inverter systems

In recent years, motor drive systems for steel rolling mills have been steadily increasing in capacity. In particular, the development of three‐level NPC (Neutral Point Clamped) inverters is now focusing on the replacement of cycloconverters. In order to satisfy such a requirement, in this paper a multiple three‐level NPC inverter system is proposed. The configuration consists of two three‐level NPC inverters with the same configuration connected in parallel by current limiting reactors. In this case, the circulating current flowing between the two three‐level NPC inverters must be controlled to prevent a decrease in the maximum output capacity. In particular, a new method for control of the circulating current is a major topic of discussion. The method is based on space voltage vector‐based PWM (Pulse Width Modulation) control for the three‐level NPC inverters and the circulating current is controlled by adjusting the output durations of the respective space voltage vectors. In this method the circulating current controller can be decoupled from the motor current controller. Therefore, it is possible to design the different controllers independently. In addition, the experimental results obtained using an induction motor show that the circulating current can be reduced to within 2% of the rated motor current when the motor current response exceeds 1000 rad/s. © 2001 Scripta Technica, Electr Eng Jpn, 136(2): 38–48, 2001     

一种新型的双极性脉冲电流源

在瞬变电磁探测领域中,发射电流波形的质量将会直接影响到地质体感应信号的检测。瞬变电磁法理论基于阶跃波电流源激励,为了探测浅层部地质信息,要求脉冲电流关断延时短、上升下降沿线性度高,探测系统动态性能好,但由于发射线圈呈感性,在大电感负载下实现理想的阶跃脉冲是非常困难的。研究改善发射电流脉冲波形前、后沿波形质量的电路拓扑、控制方法,并研究了电磁发射机整流方案。分析了电路的工作原理,讨论了电路参数优化计算,从负载电流上升、下降沿波形的线性度和稳压电容电压波动范围出发,给出了恒流电路中电感值和钳位电容值的最优值选取方法,并通过仿真实验,验证了理论分析的正确性。与已报道电路相比,该电路结构简单,上升、下降沿线性度好,动态性能好。     

变频驱动异步电机再生制动及馈电技术

针对通用变频器不能直接用于快速启动、制动和频繁正反转调速场合问题,探讨了变频调速系统中的再生能量产生机理,尤其是对再生能量回馈状态下惯性体的运动能量、有源逆变回馈能量、制动转矩进行了定量分析,揭示了各物理量之间的关系,设计了一种通用变频器能量回馈控制系统。实验表明,该系统馈送电流谐渡小,功率因数高,能够有效地实现能量回收和精确制动;该系统使得变频器可以实现四象限运行,节能效果明显。     

新型零电流开关高频谐振逆变器的设计

针对目前全桥负载感应加热电源工作过程中存在的开关损耗较大问题,设计了一种应用于高频感应加热电源中的新型零电流开关谐振逆变器.分析了开关模式的7种状态,利用四阶Runge-Kutt方法对逆变器的实际功率、视在功率、开关电流、开关电压、输出功率进行了理论分析.通过抑制开关电流/电压提高了功率因数,并利用实验结果验证了理论分析的正确性.