一种用于提高无线并联逆变器均流性能的控制方法

本文基于传统的无互线逆变器并联下垂法,提出一种用于提高逆变器均流性能的控制方法。同时本文考虑了连线阻抗和逆变器输出阻抗,分析了逆变器并联系统的有功环流和无功环流,本文提出的控制方法可以减小下垂法的频率和幅值的波动幅度,增加系统输出的稳定性,并提高系统的动态和静态环流抑制能力。仿真和实验结果均验证了该方案的良好性能。     

两种双环控制方式对并联逆变器的影响

电压电流双环控制策略对单相逆变电源有一定的优越性,不同的采样电流方式对逆变电源输出电压外特性有着不同的影响。在控制参数一致的情况下进行对比分析,电感电流反馈方式对其输出电压外特性的影响较大,对并联逆变电源的环流影响较小;电容电流反馈对输出电压外特性的影响较小,对并联逆变电源的环流影响较小,所以文中并联系统采用电容电流反馈方式作为内环调节;通过MATLAB软件中的simulink工具验证了理论的正确性。     

并联逆变器输出滤波器的分析和改进

简述了输出滤波器在逆变器并联中的作用,对传统LC输出滤波器在逆变器并联中存在的问题进行了分析,并提出了改进的非对称T型滤波器。改进的滤波器在逆变器并联的环流抑制和控制量的选择等方面优于LC输出滤波器。理论分析和仿真结果证明提出的输出滤波器改进方法简单而有效,并将其应用到并联电路试验中,起到了较好的效果。     

逆变器无线并联控制方案的设计与实现

首先对逆变器无线并联的原理作了简单的介绍。其次依据逆变器技术指标设计了一种以dsPIC30F3011芯片为核心控制器的无线并联控制方案,结合系统主电路和相关控制原理,给出了该系统的硬件设计和软件设计。最后以两台逆变器并联为研究对象进行实验验证,实验结果表明该控制方案能够达到技术指标的要求并且能够有效地抑制并联系统产生的环流,使输出功率和负载电流得到均分。     

基于无主从式和数字均流的逆变器并联研究

逆变电源的并联对于扩大系统供电容量，提高供电系统的可靠性等具有重要的意义。本文详细分析了逆变器并联的原理，提出了一种采用无主从式方法消除逆变器并联有功环流和采用CAN现场总线消除逆变器并联无功环流的数字均流方案，这种方案可以有效的减少并联系统中逆变器之间的相互影响，提高了并联系统的工作可靠性能。该方案在3kVA逆变器并联系统中得到了成功的运用。     

DSP控制单相UPS并联直流环流分析与解决

在单相UPS的并联运行中,为了系统的稳定运行,必须对逆变输出进行均流控制。而逆变输出并联间的环流分为交流环流和直流环流。文中详细地分析了直流环流对系统的影响并对直流环流的改善提供了一种有效的解决方法。     

变压器并联运行在旁路带电作业中的应用

本文介绍了变压器并联运行在旁路带电作业中的应用实例,结合变压器并联运行的技术条件对变压器并联运行在旁路带电作业中的应用实例进行分析,并对变压器并联后的环流进行了理论计算分析和MATLAB建模仿真分析,分析结果验证试验时产生环流是两台变压器的变比和变压器阻抗的差异造成的。     

现场总线在并联逆变电源系统中的应用

提出将现场CAN总线引用到并联逆变电源系统中的设计理念,对逆变器并联技术进行分析,由此提出一种利用CAN总线实现各逆变单元的通信,最终实现消除各逆变器之间环流的方案。介绍CAN总线的特点,并利用DSP2407A实现逆变器的控制和CAN总线的通信,同时给出CAN总线的软件设计。最后在Matlab平台上对系统进行仿真,仿真实验结果证明:利用CAN总线可以更好地实现该电源系统的稳定性和抗干扰性。     

基于模型预测的光伏并网逆变器并联控制研究

由于并联逆变器硬件参数差异和控制信号无法完全同步,使光伏并网逆变器之间存在零序环流,从而影响光伏发电厂的电能质量及系统可靠性。本研究提出一种模型预测算法来抑制零序环流,在同步旋转d-q-z坐标系下建立逆变器并联系统的状态空间模型,在此基础上构建模型预测控制模型,以调节注入电网的电流为控制目标,在成本函数中引入Z轴分量使流经逆变器的环流最小。通过与PI控制器仿真比较,所提出的基于模型预测的逆变器并联控制系统能够提高电能质量,在抑制零序环流方面具有良好的性能。     

变压器并联运行在旁路带电作业中的应用

本文介绍了变压器并联运行在旁路带电作业中的应用实例，结合变压器并联运行的技术条件对变压器并联运行在旁路带电作业中的应用实例进行分析，并对变压器并联后的环流进行了理论计算分析和MATLAB建模仿真分析，分析结果验证试验时产生环流是两台变压器的变比和变压器阻抗的差异造成的。     

Decoupling Control Strategy for Single Phase SPWM Parallel Inverters

A deconpling control strategy of inverter parallel system is proposed based on the equivalent output impedance of single phase voltage source SPWM （sinusoidal pulse width modulation） inverter. The active power and reactive power are calculated in terms of output voltage and current of the inverter, and sent to the other inverters in the parallel system via controller area network （CAN） bus. By calculating and decoupling the circumfluence of the active power and reactive power, the inverters can share load current via the regulation of the reference-signal phase and amplitude. Experimental results of an 110V/2kVA inverter parallel system show the feasibility of the decoupling control strategy.     

Suppression of line voltage related distortion in current controlled grid connected inverters

The influence of selected control strategies on the level of low-order current harmonic distortion generated by an inverter connected to a distorted grid is investigated through a combination of theoretical and experimental studies. A detailed theoretical analysis, based on the concept of harmonic impedance, establishes the suitability of inductor current feedback versus output current feedback with respect to inverter power quality. Experimental results, obtained from a purpose-built 500-W, three-level, half-bridge inverter with an L-C-L output filter, verify the efficacy of inductor current as the feedback variable, yielding an output current total harmonic distortion (THD) some 29% lower than that achieved using output current feedback. A feed-forward grid voltage disturbance rejection scheme is proposed as a means to further reduce the level of low-order current harmonic distortion. Results obtained from an inverter with inductor current feedback and optimized feed-forward disturbance rejection show a THD of just 3% at full-load, representing an improvement of some 53% on the same inverter with output current feedback and no feed-forward compensation. Significant improvements in THD were also achieved across the entire load range. It is concluded that the use of inductor current feedback and feed-forward voltage disturbance rejection represent cost-effect mechanisms for achieving improved output current quality.     

Output Impedance Design of Parallel-Connected UPS Inverters With Wireless Load-Sharing Control

This paper deals with the design of the output impedance of uninterruptible power system (UPS) inverters with parallel-connection capability. In order to avoid the need for any communication among modules, the power-sharing control loops are based on the$P/Q$droop method. Since in these systems the power-sharing accuracy is highly sensitive to the inverters output impedance, novel control loops to achieve both stable output impedance and proper power balance are proposed. In this sense, a novel wireless controller is designed by using three nested loops: 1) the inner loop is performed by using feedback linearization control techniques, providing a good quality output voltage waveform; 2) the intermediate loop enforces the output impedance of the inverter, achieving good harmonic power sharing while maintaining low output voltage total harmonic distortion; and 3) the outer loop calculates the output active and reactive powers and adjusts the output impedance value and the output voltage frequency during the load transients, obtaining excellent power sharing without deviations in either the frequency or the amplitude of the output voltage. Simulation and experimental results are reported from a parallel-connected UPS system sharing linear and nonlinear loads.     

变频器逆变单元死区效应分析及其补偿

在SPWM控制的变频器中,死区的加入会使输出电压和电流波形发生畸变,使谐波分量增加。文中详细分析了死区对逆变器输出电压基波的影响,并在尽量不增加通用变频器硬件基础上,提出一种具有自适应零点调整的电流反馈型补偿方法。并通过TMS320F2808 DSP芯片实现补偿算法,在5.5 kW异步电机上验证了该补偿算法的有效性。     

两种逆变器双环反馈控制技术分析与比较

为了提高逆变器的稳定性和供电质量,文中介绍了一种基于极点配置的逆变器瞬时电压电流PI控制器的设计方法,建立了系统模型,比较分析了基于电感电流反馈控制和基于电容电流反馈控制技术。仿真结果表明,基于电感电流电压双环控制技术具有较好的输出特性。     

一种基于空间矢量PWM的死区效应补偿策略研究

该论文详细分析了电压型PWM逆变器死区对输出电压和输出电流的影响,并基于预测电流控制算法,提出了一种新的补偿算法,对电压损失进行补偿.以达到使最终的输出电流跟踪于期望电流的目标。最后把该算法应用在SVPWM逆变电路中,进行了仿真和实验板的调试,仿真分析和实验结果都表明该算法对死区补偿具有良好的有效性和可行性,并且补偿算法完全由DSP完成,不需要增加硬件电路。     

A series-resonant DC/AC inverter for impedance-load drives

A DC/AC inverter without cycloconversion configured by a half-bridge series-resonant inversion (HB-SRI) circuit is presented. The inverter is a series resonator with two auxiliary switches in shunt with the resonant capacitor so as to configure adaptively the output current suitable for impedance load. The output sinusoidal voltage is synthesized by a series of equal-amplitude quasisinusoidal pulses (QSPs) and the corresponding current is formed by unequal QSPs and adaptively phase-shifts to the impedance load. The presented HB-SRI is operated by frequency modulation with a constant-on time control. System modeling and waveform syntheses for the output sinusoidal voltage and its current are clearly derived, A typical design example of a 500 W HB-SRI inverter is examined to assess the system performance. The power efficiency is over 90% when the inverter output is above 200 W. The total harmonic distortions (THDs) for various impedance loads are all within 6%     

Design method of single-phase inverters for UPS systems

This article presents the complete design of a low power voltage source inverter (VSI) dedicated for a UPS system. The analysis of the rectangular PWM-AC voltage spectrum allows for a choice of the basic architecture of the inverter. Output filter parameters were calculated to reduce the maximum amplitude of the output VSI voltage harmonics for the steady-state inverter mode. The choice of the feedback loop type was based on a discussion of the inverter output impedance using a continuous model of the inverter. The parameters of the inner loop digital control for the discrete inverter model were calculated using the Coefficient Diagram Method. The influence of the step load was modelled. The time constant of the inverter closed loop system was selected to ensure sufficient system robustness. An outer feedback loop with a plug-in repetitive controller, simplified owing to the properties of the PID/CDM inner loop control, was introduced to eliminate the periodic disturbances generated by the non-linear rectifier load and the deadtime influence. The experimental verification of the design method is presented.     

An accurate approach of nonlinearity compensation for VSI inverter output voltage

An accurate nonlinearity compensation technique for voltage source inverter (VSI) inverters is presented in this paper. Because of the nonlinearity introduced by the dead time, turn-on/off delay, snubber circuit and voltage drop across power devices, the output voltage of VSI inverters is distorted seriously in the low output voltage region. This distortion influences the output torque of IM motors for constant V/f drives. The nonlinearity of the inverter also causes 5th and 7th harmonic distortion in the line current when the distributed energy system operates in the grid-connected mode, i.e., when the distributed energy system is parallel to a large power system through the VSI inverter. Therefore, the exact compensation of this nonlinearity in the VSI inverter over the entire range of output voltage is desirable. In this paper, the nonlinearity of VSI inverter output voltage and the harmonic distortion in the line current are analyzed based on an open-loop system and a L-R load. By minimizing the harmonic component of the current in a d-axis and q-axis synchronous rotating reference frame, the exact compensation factor was obtained. Simulations and experimental results in the low frequency and low output voltage region are presented.