【作者】 周娟；

【导师】 伍小杰；

【作者基本信息】 中国矿业大学 ， 电力电子与电力传动， 2011， 博士

【摘要】 科技和经济的发展使得电能需求更加广泛,在三相四线制低压供电系统中,更多的非线性负荷投入使用,这给电能质量带来了更大的挑战,三相四线制系统谐波和不平衡的问题日益突出。并联型四桥臂有源电力滤波器是解决这些问题的有效措施之一,本文针对四桥臂有源电力滤波器的关键技术展开了研究。准确、快速的谐波电流检测是保证有源电力滤波器良好补偿性能的前提。本文在分析传统FBD算法以及基于广义积分器谐波检测方法的基础上,提出了采用广义积分器和FBD法相结合的检测方案。利用广义积分器的选频特性提取基波电压正序分量,结合FBD功率理论实现谐波电流的检测,该方法可以降低由于广义积分器本身所造成的输出信号幅值衰减的影响,提高原FBD检测算法的执行速度。仿真和实验验证了所提方法的合理性及可行性。四桥臂变流器开关状态多,电压调制复杂,为了简化调制算法,本文提出新型三维空间矢量脉宽调制(3D-SVPWM)策略。基于分类算法,对参考电压矢量所在区域进行了判断,并根据中间变量的线性组合直接获取基矢量的作用时间。针对参考电压对称无畸变及含有谐波两种情况进行了仿真和实验验证,结果表明所提算法均能调制得到与参考电压吻合的输出电压,证实了新型3D-SVPWM算法的正确性和可行性。同时,分析了四桥臂APF的过调制策略以及死区效应的影响,并给出了适用于四桥臂逆变器死区补偿的脉冲调整法,通过仿真对该死区补偿方法进行了验证。有源滤波器电流环控制要求补偿电流无误差地跟踪给定信号,传统的dq坐标系下PI控制很难消除稳态误差,本文提出了两种补偿电流跟踪控制方案：针对电网频率波动和三相不平衡问题,在αβγ静止坐标系下采用并联的改进PR控制器实现零稳态误差跟踪,详细总结了PR控制器各参数对性能指标的影响和设计方法；提出内置重复控制的无差拍控制策略实现四桥臂有源滤波器电流环控制,消除周期性稳态误差,给出了用于改善系统稳定性的低通滤波及补偿环节的的具体设计方法。对所提的两种电流环控制策略进行了仿真和实验验证,结果表明,所提方法均能有效地抑制谐波,较好地解决三相不平衡问题。主电路参数及直流侧电压控制同样影响APF的补偿性能。本文分析了各参数之间的关系,借助矢量轨迹分析方法确定四桥臂APF的主电路参数。分析了三相四线制APF交、直流侧能量交换特点,采用补偿瞬时有功电流的方法实现直流侧电压的控制,设计了控制器参数。通过仿真和实验验证了主电路参数选取的合理性以及直流侧电压控制方案的可行性。更多还原

【Abstract】 Technological and economic development has stimulated the demand in electrical energy. In the three-phase four-wire low-voltage power supply system, further application of non-linear loads has brought greater challenges to power quality, coupled with the increasingly prominent problems of harmonic current and unbalanced issue in three-phase four-wire system. Four-leg active power filters (APF) has become one of the effective measures to solve the problem of harmonic in three-phase four-wire system. This paper studied the key technologies of four-leg active power filters.Accurate and rapid detection of harmonic currents is the premise to ensure the good compensation performance of active power filter. Based on the analysis of the traditional FBD algorithm and the harmonic detection method of the generalized integrator, this paper proposed the detection scheme combining the generalized integrator and FBD. The frequency-selective characteristics of the generalized integrator were utilized to extract the components of positive sequence fundamental voltage, combined with the FBD power theory to realize harmonic current detection, The method can reduce the impact of the attenuation of output signal amplitude caused by the generalized integrator itself, and improve the execution speed of the original FBD detection algorithm. Simulations and experiments verified the rationality and feasibility of the method.Four-leg converter has so many switch states and the modulation voltage is also complex, so in order to simplify the modulation algorithm, this paper presented a new strategy, that is, three-dimensional space vector pulse width modulation (3D-SVPWM). Based on the classification algorithm, the region judgment of the reference vector was realized and the duty ratios of the switching vectors were given by the linear operation of the inner products. Simulations and experiments were carried out for two situations on reference voltages without distortion and reference voltages including harmonics. The results show that the proposed modulation algorithm can obtain the output voltage in agreement with reference voltage which verify the correctness and validity of this proposed scheme. The adaptability of different over-modulation strategies for the four-leg APF was studied and the influence of dead-time effect on the output voltage of four-leg active filter was analyzed. In addition, a pulse adjustment method applicable to the dead-time compensation of four-leg inverter was proposed and the simulation results show that this method can effectively compensate for dead-time effect of four-leg converter.The current loop control of active power filter (APF) requires the compensation current to track the given signal without any error, while it is difficult to eliminate steady-state error by using the traditional PI controller in synchronous d-q frame. In this paper, two tracking control schemes were proposed. As to the grid frequency fluctuation and the unbalanced problem of three-phase system, the parallel improved controller in theαβγcoordinate was proposed to obtain zero steady-state error. The paper concluded the effect of PR controller parameters on the performance index and the debugging methods of the parameters. The deadbeat control strategy with plug-in repetitive controller was proposed to realize the current loop control of the four-leg APF and eliminate periodic steady-state error. The design method of the low-pass filter and the compensator were given which were used to improve the system stability. The simulation and experiment were carried out to verify the proposed control strategies. The results suggest that the two proposed methods can both effectively restrain harmonics and solve the unbalanced problem excellently.The parameters selection of power circuit and stability of DC-link voltage are inflence factors to the performance of APF also. The relationship of parameters was analized and the power circuit parameters were determined by using the vector locus analysis method. According to the analysis of energy transfer between the source and DC-link capacitor, control scheme of DC-link voltage were presented by compensating instantaneous active current. Parameters of the controller were designed. Simulation and experimental results show that the method of the power circuit parameters selection is resonable and the DC-link voltage control scheme is effective.更多还原