UPS逆变器数字控制研究

UPS逆变器的数字控制是实现全数字控制UPS的关键。本文对数字PID控制进行研究。针对数字PID控制方法输出性能不够理想的问题,提出了准双环控制,并采用了死区补偿和输出电流补偿。实验结果表明死区补偿和输出电流补偿的有效性以及整个控制策略的可行性。对无差拍控制方法进行研究,针对无差拍控制对系统参数变化的鲁棒性问题,提出了一种新的控制方案——渐近收敛无差拍控制。该方案与传统无差拍控制的区别是,不是将正弦信号作为参考电压,而是采用当前的输出电压和正弦信号的加权平均作为下一控制周期的目标量。理论分析和实验结果表明,渐近收敛无差拍控制有良好的稳态性能和快速的动态响应,对系统参数的变化有较好的鲁棒性。     

非线性电感在并网逆变器中的应用

在分析了无差拍控制电压源与电流源输出的逆变器基本原理的基础上,计算了该方法在单极性调制下输出滤波电感的取值,并分析了单极性调制方案下输出电流过零点处失真形成的原因。通过仿真建模研究了电感的非线性特性对输出电流畸变的影响,提出了在模型中对非线性电感的感值进行补偿的办法,最后通过仿真和实验验证了该方法的可行性。     

基于DSP无差拍控制的逆变电源研究

随着高性能数字信号处理器的广泛应用,传统模拟控制的逆变技术被数字化电源取代已成为必然趋势.逆变电源因非线性负载等因素引起的干扰,采用常规控制难以获得理想的控制效果.提出一种基于DSP实现的PI控制和无差拍控制方法相结合的数字双闭环控制方法.逆变器控制电路的电流内环采用优化了的数字PI控制方法;电压外环采用干扰预测型无差拍控制方法.该方案将无差拍控制的瞬时响应快,精度高和PI控制简单,参数易整定,鲁棒性好等优点相结合,能够得到更优的控制效果.最后的仿真试验表明,采用数字双闭环控制方法的逆变器具有输出波形好,响应快和负载适应能力强等优点.     

基于全维状态观测器的永磁同步电机无差拍直接转矩控制

永磁同步电机传统的直接转矩控制存在磁链幅值和转矩脉动大的缺点。文中研究了基于状态观测器的无差拍直接转矩控制方案,通过构造全维状态观测器的方法来观测定子磁链幅值,消除了初始磁链误差以及电机参数对传统的观测方法影响的问题。此外针对传统控制系统产生的时滞现象,文中的研究提前一个周期计算出所需的电压矢量,实现了转矩和磁链无差拍控制。仿真结果表明,所提出的基于全维状态观测器的无差拍控制能较好地抑制磁链和转矩脉动,具有良好的控制性能。     

单相光伏并网逆变器无差拍控制的研究与仿真

光伏并网逆变器是光伏发电系统的主要部件,为了达到更好的效率输出更高质量的电能,对逆变器电流进行快速有效的控制尤为关键。该文简单介绍了当前光伏并网逆变器的几种常用控制方法及其基本思想,分析了并网逆变器的工作原理和无差拍控制方法的原理,给出了逆变器脉冲宽度的计算和参考电流的获取方法,通过MATLAB/Simulink软件仿真表明,无差拍控制在单相光伏并网逆变器控制中动态响应特性好,控制方便,电流跟踪电网电压波形好。     

电压不平衡时基于改进无差拍控制的VSC-HVDC系统

VSC-HVDC在电网电压不平衡情况下,输出功率及直流母线电压会产生二倍频波动,进而影响系统的稳定运行。文中研究了柔性直流输电系统在电压不平衡情况下的改进无差拍控制策略,该策略以瞬时有功功率波动分量为零为约束条件,推导了正负序参考电流表达式。针对传统无差拍控制算法存在的控制延时及对交流侧电感参数变化鲁棒性差的问题,提出了一种改进无差拍控制策略。该控制策略利用拉格朗日插值法预测出下一个采样时刻的参考电流;对电网电压进行了线性预测;对网侧电流进行了非线性预测。最后借助MATLAB/Simulink平台搭建相应的仿真模型,仿真结果证明了该控制策略的正确性和有效性。     

基于重复控制和无差拍控制的逆变电源数字控制技术研究

随着DSP技术的发展，数字控制在逆变电源控制领域的应用受到人们的关注。逆变电源中因非线性负载等因素引起的干扰具有周期性，而这些干扰导致输出波形的畸变具有重复性，采用重复控制策略可以消除输出电压谐波，但该控制方法的动态响应慢。无差拍控制具有瞬时响应快，精度高等特点。文中将重复控制和无差拍控制相结合用于逆变电源数字控制系统中，得到更为完善的逆变电源控制策略。仿真结果表明，由该方法设计的控制器用于逆变电源系统具有输出波形好，动态响应快，适应负载的能力强等优点。     

有源箝位逆变器中点电压平衡控制研究

针对有源箝位三电平逆变器的特点,提出无差拍控制和新型载波调制方法,实现其电流快速跟踪控制和中点电位振荡抑制,而且,为了解决有源箝位三电平逆变器的开关损耗不均问题,提出一种载波输出方法,实现开关管损耗均衡控制,仿真和实验结果验证了提出新型无差拍控制和调制方法能够很好的跟踪给定电流、中点电位振荡和开关损耗均衡控制。     

基于电流无差拍和PI复合控制的新能源并网技术

为了提高新能源整个并网系统的性能,在分析无差拍控制和PI控制的工作原理基础上,提出了基于电流无差拍和PI复合控制的PWM逆变的控制策略。通过Matlab/Simulink建模仿真三相并网系统,采用LCL滤波器滤波。当系统接三相对称纯阻性负载和整流性负载时,将系统逆变电压与电网电压、逆变电流与电网电压进行比较,以及对三相逆变电流进行谐波分析。仿真结果表明,该并网控制策略能较好地跟踪电网电压,波形畸变较小、动态响应快。     

基于无差拍SVPWM的有源滤波器研究

采用无差拍电压空间矢量控制法来分析有源滤波器的滤波性能,给出该方法的控制策略,包括空间矢量脉宽调制（SVPWM）算法以及无差拍原理。该方法可以用来抑制和消除采样与计算方法的延时对控制精度的影响。Matlab仿真结果表明：SVPWM调制与无差拍控制结合用于有源滤波控制可以明显改进补偿的动态性能,提高滤波效果。实验结果证明该方法可行,且具有较好的实时性。     

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.     

Digital Control of Three-Phase Series-Parallel Uninterruptible Power Supply Systems

In this paper, a new digital deadbeat controller is designed, implemented, and applied to a three-phase series-parallel line-interactive uninterruptible power supply (UPS). This kind of UPS system provides input power factor correction, output voltage conditioning, and high efficiency. The objective of the controller is to achieve deadbeat dynamic response for the parallel and series converters. The proposed controller adjusts the current of the parallel converter and voltage of the series converter with two and four sampling periods, respectively. A reduced-parts topology is also introduced that has less number of power electronics components as well as switching functions. The power flow of the system in the presence of current and voltage harmonics is discussed. Simulation and experimental results are presented, which show the viability of the proposed controller for this topology.     

Analysis and design of a multiple feedback loop control strategyfor single-phase voltage-source UPS inverters

This paper presents the analysis and design of a multiple feedback loop control scheme for single-phase voltage-source uninterruptible power supply (UPS) inverters with an L-C filter. The control scheme is based on sensing the current in the capacitor of the load filter and using it in an inner feedback loop. An outer voltage feedback loop is also incorporated to ensure that the load voltage is sinusoidal and well regulated. A general state-space averaged model of the UPS system is first derived and used to establish the steady-steady quiescent point. A linearized small signal dynamic model is then developed from the system general model using perturbation and small-signal approximation. The linearized system model is employed to examine the incremental dynamics of the power circuit and select appropriate feedback variables for stable operation of the closed-loop UPS system. Experimental verification of a laboratory model of the UPS system under the proposed closed-loop operation is provided for both linear and nonlinear loads. It is shown that the control scheme offers improved performance measures over existing schemes, It is simple to implement and capable of producing nearly perfect sinusoidal load voltage waveform at moderate switching frequency and reasonable size of filter parameters. Furthermore, the scheme has excellent dynamic response and high voltage utilization of the DC source     

An improved deadbeat control for UPS using disturbance observers

A digital control technique for the inverter stage of uninterruptible power supplies is proposed, which is based on a predictive regulator on both output voltage and inductor current. Its aim is to achieve a deadbeat dynamic response for the controlled variables (output voltage and inverter current). Besides the linear state feedback which allocates system poles at the origin so as to achieve deadbeat response for all state variables, the use of a disturbance observer for the estimation of the load current and of any other source of errors (such as dead-times, parameter, and model mismatches) is investigated. The proposed solution is able to guarantee a fast dynamic response and also a precise compensation of any source of unpredictable disturbance. Moreover, with a proper design of observer parameters, it is possible to reduce control sensitivity to model uncertainties, parameter mismatches, and noise on sensed variables, which usually characterizes existing deadbeat control techniques. Finally, the control algorithm is quite simple and requires only the measurements of the output voltage and inductor current. Experimental results on a single-phase 2 kVA prototype show the effectiveness of the proposed approach.     

H∞ loop-shaping controller designs for thesingle-phase UPS inverters

This paper proposes the H_∞ loop-shaping approach to the designs of sinusoidal output voltage tracking controllers for single-phase UPS inverters. Selection of weighting functions is introduced, which is quite different from the case of step tracking. By modeling the uncertainty in load as plant output multiplicative perturbation, two H_∞ loop-shaping control schemes that use only a capacitor voltage sensor are presented. The first design adopts a single-loop control scheme which has the advantage of simple control structure and easy implementation. But its transient performance and robustness are not satisfactory. The second controller with a dual-loop structure, additionally employing output of a capacitor current estimator as feedback, provides improved performance over the single-loop scheme and has the feature of low distortion, good regulating performance and insensitivity to the variation in load. Simulation and hardware experimental results, with comparison to the PI-based multiple feedback loop design, are given to validate the robustness property and regulating performance of the proposed controllers     

Deadbeat control of PWM inverter with modified pulse patterns foruninterruptible power supply

A modified algorithm of pulse-width-modulation (PWM) inverter deadbeat control suitable for uninterruptible-power-supply (UPS) systems is presented. Two state variables are measured at each sampling interval, then, using the data, the pulse width is computed in real time in order to force the output voltage equal to the reference at each sampling instant which is called the deadbeat control. Two kinds of PWM pulse patterns are used to increase the fundamental component of the output voltage, considering the microprocessor computation time. Experimentation and simulation has verified that the proposed control scheme increased the output-voltage amplitude, providing an excellent transient response and accurate phase positioning for various load conditions. This algorithm is suitable for applications of high-power UPS systems, in which the switching frequency is in the range of a few kHz and the precise control of power flow is required     

基于Buck-Boost逆变器的离散滑模控制仿真研究

为了获得比较理想的正弦输出电压，优化逆变器的动态性能，文中基于Buck—Boost逆变器．采用了离散滑模变结构的控制策略。Buck—Boost逆变器可以获得比直流输入电源高或低的交流输出电压，文中阐述了其工作原理．并结合状态方程，推导出滑模面的存在条件、到达条件和稳定条件，然后对电路参数、控制系数以及控制算法进行了设计。仿真结果表明采用离散滑模控制的Buck—Boost逆变器对系统扰动和负载变化具有很强的鲁棒性，系统具有良好的动态响应。     

Robust Model-Following Control of Parallel UPS Single-Phase Inverters

This paper presents a robust control technique applied to modular uninterruptible power-supply (UPS) inverters operating in parallel. When compared to conventional proportional–integral (PI) control, the proposed technique improves the response of the output voltage to load steps and to high distorted output currents, reducing the distortion of the output voltage. Furthermore, an excellent distribution of currents between modules is achieved, resulting in fine power equalization between the inverters on stream. The crossover frequency of the different loop gains involved is moderate, so that robustness to variations of the operation point and to modeling uncertainties is achieved. A comparative study with a two-loop conventional PI control scheme is presented. Experimental results on a 1-kVA modular online UPS system confirm the viability of the proposed scheme.