基于LCL滤波的三相电压型PWM整流器

发布时间：2018-12-12 02:46

【摘要】：可四象限运行的PWM整流器广泛应用于太阳能、风能等可再生能源的并网发电。在这些并网发电系统中PWM整流器的容量通常较大，为了降低开关损耗，同时为了降低电磁干扰，一般采用较低的开关频率。为了达到并网谐波要求，若使用传统的L滤波器则需要较大的电感值，增加了成本，降低了电流环响应速度，增大了电感压降，需要提高直流侧电压；而LCL滤波器具有三阶滤波特性，对于同样的谐波要求，所需电感较小，可以有效减少系统成本。但是LCL滤波器存在谐振问题，在某些频率作用下会产生谐振，引起系统不稳定。本文首先介绍了PWM整流器的工作原理，随后对基于L滤波器和LCL滤波的PWM整流器分别在三相ABC静止坐标系和两相dq旋转坐标系下建立了数学模型。分析了LCL滤波器的频率特性，其在谐振频率以下的频率响应与同样电感量的L滤波器基本一致，大于谐振频率后以更大的斜率衰减，但是在谐振频率处有无限大增益。随后介绍了LCL滤波器的参数设计方法，给出了设计时的限制条件，设计步骤以及验证效率的方法。在单L滤波的PWM整流器的控制策略基础上设计了电压外环，电流内环控制器。详细分析了无源阻尼法和三种有源阻尼法抑制谐振的原理，分析了数字控制过程对控制系统的影响。使用Maltab/Simulink对所设计的控制策略和阻尼策略进行了仿真验证。最后在实验台架上使用有源阻尼法进行了实验，实验结果表明LCL滤波器谐振得到了有效抑制，网侧电流谐波畸变率小，动态响应快，，输出电压稳定，抗负载扰动能力强。
[Abstract]:PWM rectifier, which can operate in four quadrants, is widely used in grid-connected power generation of renewable energy such as solar and wind energy. In these grid-connected generation systems, the capacity of PWM rectifier is usually large. In order to reduce switching loss and electromagnetic interference, a lower switching frequency is generally adopted. In order to meet the requirements of grid-connected harmonics, if the traditional L filter is used, it needs larger inductance value, increases the cost, reduces the response speed of the current loop, increases the inductance voltage drop, and raises the DC side voltage. The LCL filter has the characteristics of third-order filtering, and the inductance required for the same harmonic requirement is small, which can effectively reduce the system cost. But there is resonance problem in LCL filter, which will produce resonance under some frequency, and cause system instability. This paper first introduces the working principle of PWM rectifier, and then establishes the mathematical model of PWM rectifier based on L filter and LCL filter in three-phase ABC stationary coordinate system and two-phase dq rotation coordinate system, respectively. The frequency characteristics of LCL filter are analyzed. The frequency response below the resonant frequency is basically the same as that of the L filter with the same inductance, and the slope of the filter is larger than the resonant frequency, but there is an infinite gain at the resonant frequency. Then the parameter design method of LCL filter is introduced, and the limiting conditions, design steps and verification efficiency are given. Based on the control strategy of single L filter PWM rectifier, the voltage outer loop and current inner loop controller are designed. The principle of passive damping method and three active damping methods are analyzed in detail, and the influence of digital control process on the control system is analyzed. The designed control strategy and damping strategy are simulated by Maltab/Simulink. Finally, the active damping method is used on the experimental bench. The experimental results show that the resonance of the LCL filter is effectively suppressed, the harmonic distortion rate of the grid side current is small, the dynamic response is fast, the output voltage is stable, and the anti-load disturbance ability is strong.
【学位授予单位】：华中科技大学
【学位级别】：硕士
【学位授予年份】：2014
【分类号】：TM46;TN713

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