A Coupled-Reactor-Commutating Sinusoidal-Wave Inverter

A coupled-reactor-commutating sinusoidal-wave current-source inverter is described. The inverter consists of two coupled-reactor-commutating inverters. By superposing the output currents of these two inverters, output currents of a 180° conducting angle are formed, and are controlled in order to achieve a sinusoidal waveform. The operation and the control scheme of the inverter are described, and experimental results are presented. Compared with the usual PWM voltage-source inverters, the on-off frequency of each chopper may be decreased almost to one tenth of that of the PWM inverter.     

多台变频器总线网络和手持控制器设计与实现

针对TMS320LF2407为控制器的通用变频器现场总线监控需要,设计了RS485总线和以单片机AT89C58为核心的手持式控制器。给出了所使用的RS485总线的通讯协议和通讯软件的系统化设计方法,分析了软、硬件的可靠性问题和解决方案。     

A novel control scheme of a parallel current-controlled PWMinverter

A parallel technique for current-controlled pulse-width-modulated (PWM) inverters is described. Two voltage source inverters, the output terminals of which are connected in parallel through current balancers, are used as a main circuit. In this scheme, excellent characteristics both in steady states and in transient states are obtained, keeping the average values of the cross current and zero sequence current at zero level. This current control scheme is applicable to large-capacity GTO inverters because good performance is attained even if the switching frequency is only a few hundred hertz, as is shown in the experimental results     

A technique of parallel connections of pulsewidth-modulated NPC inverters by using current-sharing reactors

The neutral-point-clamped (NPC) PWM inverters have many advantages such as the ability to operate the motor with nearly sinusoidal current waveforms. For this reason, in larger-capacity inverter systems, NPC PWM inverters using the GTOs, etc., have also been put into practical use because of great advantages to large-capacity ac motor drives such as lower ripple currents and higher output voltages. With the spread of applications, still larger-capacity inverters also are expected. However, since the capacities of such switching devices are insufficient, a certain technique and controlling method are proposed for the parallel connections of NPC inverters. The output voltage waveforms of the proposed inverter have certain voltage levels, and thus it is anticipated that it will be difficult to analyze the output harmonics. For such waveforms of output voltage and current-sharing reactor, a frequency analysis approach is described whose results are verified by experiments.     

Performance Evaluation of Three-Level Z-Source Inverters Under Semiconductor-Failure Conditions

This paper evaluates and proposes various compensation methods for three-level Z-source inverters under semiconductor-failure conditions. Unlike the fault-tolerant techniques used in traditional three-level inverters, where either an extra phase-leg or collective switching states are used, the proposed methods for three-level Z-source inverters simply reconfigure their relevant gating signals so as to ride-through the failed semiconductor conditions smoothly without any significant decrease in their ac-output quality and amplitude. These features are partly attributed to the inherent boost characteristics of a Z-source inverter, in addition to its usual voltage-buck operation. By focusing on specific types of three-level Z-source inverters, it can also be shown that, for the dual Z-source inverters, a unique feature accompanying it is its extra ability to force common-mode voltage to zero even under semiconductor-failure conditions. For verifying these described performance features, PLECS simulation and experimental testing were performed with some results captured and shown in a later section for visual confirmation.      

Novel Six-Step and Twelve-Step Current-Source Inverters with DC Side Commutation and Energy Rebound

Novel six-step and twelve-step current-source inverters (CSI) with dc side commutation and energy rebound capability are presented with detailed explanation of the circuit operation. The proposed inverters can operate in a very wide range of frequency and load variation by employing dc side commutation. Also, the energy rebound makes the use of low voltage silicon controlled rectifiers (SCR's) possible and increases the inverter efficiency. Unlike the dual current-source inverter, one auxiliary inverter with a power requirement of about one-half that of the main inverter is simply added to the six-step CSI in order to obtain a twelve-step CSI. Motor operation is possible in four quadrants in both six-and twelve-step inverters. The advantages of the proposed CSI's over conventional ones are described, and experimental results are given in oscillograms.     

Textile Applications of Adjustable-Frequency Drives with Digital Ratio Control

The application of digital techniques to program and to process the input signals to adjustable-frequency inverters for the control of rugged ac motors is becoming widespread. It was perhaps inevitable that digital signal control would eventually be combined with the inherently digital adjustable-frequency power inverter to produce systems having high overall line speed accuracy, adjustable ``digital gearing' between sections, locked-in-step acceleration from creep to run speed, and in-train digital jogging. A short introduction to adjustable-frequency motor control is given, and the use of digital techniques for controlling adjustable-frequency inverters to produce digital speed systems is described. Early applications of the first solid-state inverters to synthetic fiber spinning and their continued use is described. Specific current applications of digitally controlled adjustable-frequency speed systems are discussed, and potential applications that demonstrate how the capabilities of such systems can be used to provide economic solutions to many textile industry drive problems are reviewed.     

电网谐波与无功功率有源补偿技术的进展

从电网谐波与无功功率补偿的工程实际问题出发，结合国内外有源补偿技术的最新发展，介绍了无源电力滤波器以及低频电压源逆变器等分别与并联有源电力滤波器混合构成的补偿系统，并对其特性进行了分析和比较。     

光伏并网逆变器检测平台的研制

为保证光伏并网逆变器的性能及安全,研制了检测平台,分析了并网逆变器的测试方法和步骤,介绍了光伏并网逆变器检测平台的开发。整个检测平台由控制计算机、数据采集系统、RS 485和通用接口总线(general-purpose interface bus,GPIB)系统组成。检测平台由可编程的直流电源、交流电源和RLC负载分别模拟太阳能电池板、电网特性以及负荷特性。整个系统通过LabVIEW软件界面控制,由GPIB和RS 485总线实现仪器间的通信控制,提高了系统的自动化程度。该检测平台可用于光伏并网逆变器电气性能测试、保护功能测试、电磁兼容测试等。实践证明该系统结构配置合理、设备可靠、精度高。     

多逆变器环境微网环流控制新方法

提出一种基于虚拟同步发电机运行的逆变器并联控制方法,在与传统下垂控制方法相比较基础上,具体分析了该方法在等效输出阻抗与无功功率输出的解耦和提升负荷功率分配精度方面的优势和原理,同时对下垂控制器进行小的修正,减小并联运行逆变器空载运行电压和频率差值,以使其满足不同额定功率逆变器并联功率分配和空载环流抑制的需求,并添加微分...     

Resonant snubbers with auxiliary switches

A resonant snubber is described for voltage-source inverters, current-source inverters, and self-commutated frequency changers. The main self-turnoff devices have shunt capacitors directly across them. A temporary parallel path through a small ordinary thyristor and inductance takes over high-stress turn-on duty from the main device in a manner that leaves no energy trapped after switching     

一种新颖的多电平逆变器无源无损吸收电路

重点研究了多电平逆变器无源软开关技术,即无源无损吸收技术,提出了一种多电平变换器无源无损吸收基本单元,针对其不足,进行适当的改进,获得了一种低电压应力的多电平无源无损吸收单元,文中详细地讨论了其工作过程和设计要点。该吸收单元理论上可以应用到三相系统和任意n电平。最后建立了一台二极管箝位型三相三电平无源软开关逆变器,进行了仿真和实验研究。结果表明,所提出的多电平无源无损吸收电路,不仅能使多电平逆变器以低电压应力实现功率器件的软开关,而且电路拓扑和控制简单,具有工程实用性。     

A novel PWM scheme for a three-level voltage source inverter withGTO thyristors

This paper presents a new PWM method for the three-level GTO inverters based on the space voltage vectors. With the proposed PWM method, we can minimize the harmonic components of the output voltage by avoiding the minimum pulse width limitation problem of the GTO thyristors and keeping the voltage balancing of the DC-link capacitors. The principle of the proposed PWM method and the voltage vector output sequences are described in detail. Computer simulation and experimental results verify that the proposed PWM method is suitable for high voltage and large capacity three-level GTO inverters applied to induction motor drives     

Microgrid control based on a grid-forming inverter operating as virtual synchronous generator with enhanced dynamic response capability

This paper focuses on improving the dynamic response of autonomous microgrids (MGs) by proposing a grid-forming inverter controlled as a virtual synchronous generator (VSG), in combination with a supercapacitor (SC)-based energy storage system (ESS). By this arrangement, the MG-forming VSG is designed to react only in transitory regimes, the steady-state load being distributed to other MG-supporting inverters spread within the MG. In this way, the MG-forming VSG can maintain its full power reserve capacity for dynamic response. The paper details the control solution for the MG-forming inverter, including the VSG and SC-ESS control. The control method for the MG-supporting inverters that allow achieving the proposed control approach is also described. To prove the concept, the paper includes simulation results and experiments accomplished on a complex laboratory MG system based on three parallel inverters, one being controlled as MG-forming VSG, while the others operating as MG-supporting inverters.     

一种新型的多电平逆变器空间矢量控制方法

基于传统的两电平逆变器空间电压矢量方法,提出了一种新型的多电平逆变器空间电压矢量实现方法,该方法将一相的逆变单元分为基本单元和调制单元两部分,相应地对参考电压也要进行分解处理。在一个脉宽调制(PWM)周期中,只对调制单元进行PWM控制,基本单元输出的电平不变。仿真研究表明该方法输出电压波形总畸变率较小,可用于单元串联多电平逆变器的控制。     

A multilevel inverter based on cascade connection of submultilevel units with reduced switch count

In this paper, a multilevel inverter based on cascade connection of new submultilevel inverters is presented. The suggested submultilevel inverter is constructed using series connection of basic switching units. The proposed multilevel inverter uses fewer power switches in comparison with some similar topologies which results in reduction of switch gate drivers and also converter size and cost. The proposed multilevel inverter can be implemented in both symmetric and asymmetric configurations. The multilevel inverter configuration and operation principle are described in detail, and then, design methods of symmetric and asymmetric configurations are given. Determination of the optimal number of basic units and cascaded submultilevel inverters regarding criteria such as number of switches and total blocking voltage (TBV) of switches is studied. Power losses of the proposed multilevel inverter are calculated, and then, its symmetric and asymmetric configurations are compared with each other and also with similar cascaded multilevel inverters in various items. The validity of the suggested cascaded multilevel inverter is verified using both computer simulations and laboratory prototype implementation.     

A new five-level inverter with reduced leakage current for photovoltaic system applications

A general growth is being seen in the use of renewable energy resources, and photovoltaic cells are becoming increasingly popular for converting green renewable solar energy into electricity. Since the voltage produced by photovoltaic cells is DC, an inverter is required to connect them to the grid with or without transformers. Transformerless inverters are often used for their low cost and low power loss, and light weight. However, these inverters suffer from leakage current in the system, a challenge that needs to be addressed. In this paper, a topology with two alternative connection models is presented to stabilize the common mode voltage and reduce the leakage current. The output voltage characteristic of the proposed inverter is five-level, which reduces the harmonic distortion in the output current compared to the two- and three-level inverters. The operation modes and output of the proposed topology are described and analyzed. The structures of the proposed inverter are simulated in MATLAB/Simulink and are compared with some well-known structures. Results show that the proposed structure with both connection models effectively reduces leakage current and improves grid current THD.     

基于预警单元的逆变器并联系统分层故障诊断系统

随着逆变器并联系统规模的增大,电源系统对故障诊断提出了新的要求.结合逆变器并联系统故障诊断的特点,对所存在的问题进行了分析,并通过新的应用思路,将神经网络和专家系统应用到逆变器并联系统的故障诊断中.提出并定义了故障预警的一系列相关概念,设计了预警单元的工作结构.在此基础上提出了一种新的基于故障预警单元的分层故障诊断专家系统,详细阐述了故障预警单元的实现以及诊断系统的工作原理.通过原理分析及仿真结果可以看出,提出的方法对神经网络和专家系统在故障诊断中的有效应用具有很好的推动作用和一定的指导意义.     

New Approach to a High-Power GTO PWM Inverter for AC Motor Drives

A control method for GTO PWM inverter parallel-set operation and a new protection system for prevention of short-circuit faults caused by turn-off failure, both to realize a high-power drive system are described. Timing control of GTO gate pulse command provided by a feedback loop, and a reactor at the output of the inverter can minimize the cross current flowing between inverters and can balance the output current of each inverter in inverter parallel-set operation. This method eliminates the necessity of selecting GTO's of equal characteristics, and can apply to parallel-set operation of three or more inverters. The new protection system judges the on and off states of the GTO from the GTO gate-cathode voltage and detects turn-off failure of the GTO. This method positively stops the inverter system safely and reliably upon turn-off failure of the GTO. Experiments are carried out on a 30-kVA inverter and two sets of 450-kVA GTO inverters.     

A new five-level inverter with reduced leakage current for photovoltaic system applications

A general growth is being seen in the use of renewable energy resources, and photovoltaic cells are becoming increasingly popular for converting green renewable solar energy into electricity. Since the voltage produced by photovoltaic cells is DC, an inverter is required to connect them to the grid with or without transformers. Transformerless inverters are often used for their low cost and low power loss, and light weight. However, these inverters suffer from leakage current in the system, a challenge that needs to be addressed. In this paper, a topology with two alternative connection models is presented to stabilize the common mode voltage and reduce the leakage current. The output voltage characteristic of the proposed inverter is five-level, which reduces the harmonic distortion in the output current compared to the two- and three-level inverters. The operation modes and output of the proposed topology are described and analyzed. The structures of the proposed inverter are simulated in MATLAB/Simulink and are compared with some well-known structures. Results show that the proposed structure with both connection models effectively reduces leakage current and improves grid current THD.