三相PWM整流器的高性能控制

发布时间：2018-04-02 05:09

本文选题：PWM整流器　切入点：特定谐波消除　出处：《北方工业大学》2017年硕士论文

【摘要】：三相电压型PWM整流器具有网侧电流正弦化、可以工作在单位功率因数下且直流侧电压可调、脉动小等优点。随着科学技术的飞速发展,人们对电能质量的要求也变得越来越高,对于开关损耗小、谐波含量低的PWM整流器的控制技术的研究是很有必要的。因此低开关频率下的谐波消除技术受到了人们的重视。特定谐波消除法是一种基于低频下实现特定次谐波消除的技术。本文主要针对该技术进行细致研究。首先建立了基于三相PWM整流器的特定谐波消除数学模型,得到了一组非线性方程组,通过对非线性方程组的求解得到开关角。本文采用牛顿同伦算法对非线性方程组进行求解,该算法具有牛顿法收敛高精度和同伦算法收敛范围大的优点。其次,对基于SHE-PWM的电网电压定向控制策略进行了研究。该方法基于两相旋转坐标系进行,通过电流前馈解耦控制,使有功电流和无功电流独立控制;通过电流谐波补偿的方法,使电流反馈中只含有基波电流,从而降低了电流内环的调节难度。该方法可以实现特定次谐波消除的目的,稳态性能较SVPWM好,但动态响应速度慢。最后本文采用特定谐波消除法与模型预测控制结合的方法(SHE-MPC)对三相电压型PWM整流器进行闭环控制。目标函数由网侧电流误差和SHE参考电压跟踪误差两部分组成,可同时兼顾动态电流跟踪性能和稳态电流谐波特性。传统SHE-MPC控制方法采用无滤波参考电流法计算SHE参考电压,整流器开关过程产生的高频谐波会反馈回控制系统,使SHE参考电压波形失真,稳态网侧电流出现5、7等非理想的低次谐波。本文提出了一种通过对实际电流谐波进行补偿来计算SHE参考电压的方法,可有效滤除实际网侧电流中的开关纹波,从而稳定SHE参考电压波形。由仿真结果可知,采用实际电流谐波补偿SHE-MPC控制,稳态时,网侧电流中的非理想低次谐波基本消除,稳态电流总谐波失真(THD)和动态响应速度性能较优。
[Abstract]:Three-phase voltage source PWM rectifier has the advantages of sinusoidal current in grid side, adjustable DC voltage and low pulsation under unit power factor. With the rapid development of science and technology, the demand for power quality is becoming higher and higher. For small switching losses, It is necessary to study the control technology of PWM rectifier with low harmonic content. Therefore, the harmonic elimination technology at low switching frequency has been paid more attention to. The special harmonic elimination method is based on the realization of specific subharmonic at low frequency. This paper mainly studies the technology of wave cancellation. Firstly, the mathematical model of special harmonic elimination based on three-phase PWM rectifier is established. A set of nonlinear equations is obtained, and the switching angle is obtained by solving the nonlinear equations. In this paper, Newton homotopy algorithm is used to solve the nonlinear equations. The algorithm has the advantages of high precision convergence of Newton method and large convergence range of homotopy algorithm. Secondly, the voltage oriented control strategy based on SHE-PWM is studied. The method is based on two-phase rotating coordinate system and is controlled by current feedforward decoupling control. The active current and reactive current are controlled independently, and by the method of current harmonic compensation, there is only fundamental current in the current feedback, which reduces the difficulty of adjusting the inner loop of current. This method can realize the purpose of eliminating the special harmonic wave. The steady-state performance is better than that of SVPWM. But the dynamic response speed is slow. In the end, the closed-loop control of three-phase voltage-source PWM rectifier is carried out by using the method of special harmonic elimination and model predictive control. The objective function is derived from the error of current on the grid side and the reference voltage of SHE. The trace error is composed of two parts, Both dynamic current tracking performance and steady current harmonic characteristics can be taken into account. The traditional SHE-MPC control method uses the unfiltered reference current method to calculate the SHE reference voltage, and the high frequency harmonics generated in the switching process of the rectifier will be fed back to the control system. This paper presents a method to calculate the reference voltage of SHE by compensating the harmonic of the actual current, which causes the distortion of the SHE reference voltage waveform and the non-ideal low-order harmonics, such as 5 / 7 of the steady-state grid-side current. The switching ripple in the actual grid side current can be effectively filtered and the SHE reference voltage waveform can be stabilized. From the simulation results, it can be seen that the SHE-MPC control is compensated by the actual current harmonics. In the steady state, the non-ideal low-order harmonics in the grid-side current are basically eliminated. The steady-state total harmonic distortion (THD) and dynamic response speed are better.
【学位授予单位】：北方工业大学
【学位级别】：硕士
【学位授予年份】：2017
【分类号】：TM461

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