基于无谐波检测的有源电力滤波器模型预测控制研究

发布时间：2018-04-23 14:45

本文选题：电容中分型APF + 无谐波检测策略　；参考：《中国矿业大学》2017年硕士论文

【摘要】：在我国低压三相四线制供电系统中,由各类非线性和不对称负载引起的谐波以及中性线电流问题日益突出。三相四线制有源电力滤波器(APF)作为一种能有效改善电网谐波和不平衡电流问题的装置备受关注。本文以三桥臂电容中分型APF为研究对象,对基于无谐波电流检测的模型预测电流跟踪控制策略展开研究。首先,为简化控制系统和降低成本,以综合补偿谐波与无功电流为目标,研究了一种基于无谐波检测的APF电网电流直接控制策略。通过分析APF交、直流侧的能量传递过程,指出直流侧电压控制输出可作为无谐波检测方案中的指令电流。推演分析传统APF谐波检测环节的等效形式,并由此讨论检测误差影响,证明在综合补偿目标下可省去谐波检测环节,再通过进一步简化推出电网电流直接控制策略。经过总结,分别从四个方面对比分析有、无谐波检测环节的两种APF控制策略。其次,因有限控制集模型预测控制(FCS-MPC)简单易行、响应快速,将其应用于电容中分型APF的电流跟踪控制策略中。建立三维坐标系下的系统数学模型,分析三相电流耦合消除和不平衡电流抑制原理。先后推导出以补偿电流、电网电流为控制对象的两种预测模型,并建立相应的单目标与多目标控制下的评价函数,对比分析两种模型下的控制流程。推导模型预测控制下由控制延时与电感失配系数决定的系统稳定性条件。采用双环PI控制以保证直流侧电容电压的稳定和均衡,并设计控制器参数。再次,针对常规模型预测控制方法存在的采样频率高、开关频率不固定等问题,给出了一种适用于所研究APF结构的定频模型预测控制方法。该方法结合SVPWM实现原理,通过空间划分和电网电压矢量定位,确定每个控制周期输出所需的基本电压矢量组合,并根据预测模型计算出各矢量的作用时间,经过脉冲调制,最终可实现开关频率的基本固定,获得更好的补偿性能。对定频控制下的系统实现流程和电流跟踪控制过程进行分析,总结其与常规模型预测控制方法之间的区别。最后,设计了APF系统主要仿真参数,并对所研究电流控制策略进行仿真分析。仿真结果表明,在综合补偿时,直流侧电压控制能自动补偿有功检测误差,验证了无谐波检测方案的可行性;并且在模型预测控制下电流动态响应迅速,与有谐波检测时相比,无谐波检测策略下系统的稳态补偿效果更好。通过仿真分析采样频率、多目标权值系数、控制延时以及电感失配系数对系统补偿性能的影响,为控制性能的进一步优化提供了参考依据。此外,仿真结果显示直流侧稳压和均压控制性能良好,验证了双环PI控制的有效性。通过与常规模型预测控制的仿真对比,表明定频模型预测控制下系统的动态响应速度相当,但稳态补偿精度更高,且受参数变化影响较小。
[Abstract]:In China's low voltage three-phase four-wire power supply system, harmonic and neutral line current problems caused by various nonlinear and asymmetric loads are becoming increasingly prominent. The three-phase four-wire active power filter (APF) has attracted much attention as a device that can effectively improve the harmonic and unbalanced current problems of power network. In this paper, the model predictive current tracking control strategy based on harmonic free current detection is studied based on the three-leg capacitor parting APF. Firstly, in order to simplify the control system and reduce the cost, a direct control strategy for APF power network based on harmonic detection is studied, aiming at synthetically compensating harmonic and reactive current. By analyzing the energy transfer process of the APF AC and DC side, it is pointed out that the DC side voltage control output can be used as the instruction current in the harmonic free detection scheme. By deducing and analyzing the equivalent form of traditional APF harmonic detection link and discussing the influence of detection error, it is proved that harmonic detection can be eliminated under the comprehensive compensation target, and then the direct control strategy of power network current is put forward through further simplification. After summing up, two kinds of APF control strategies without harmonic detection are compared and analyzed from four aspects. Secondly, because the FCS-MPC (finite Control set Model Predictive Control) is simple and fast, it is applied to the current-tracking control strategy of classified APF in capacitors. The mathematical model of the system in three dimensional coordinate system is established, and the principle of three-phase current coupling elimination and unbalanced current suppression is analyzed. Two predictive models with compensation current and power network current as the control object are derived successively, and the corresponding evaluation functions under single-objective and multi-objective control are established, and the control flow under the two models is compared and analyzed. The stability conditions of the system determined by the control delay and the inductance mismatch coefficient under the model predictive control are derived. Double loop Pi control is used to ensure the stability and equalization of DC capacitor voltage, and the controller parameters are designed. Thirdly, aiming at the problems of high sampling frequency and unstable switching frequency in the conventional model predictive control method, a fixed frequency model predictive control method suitable for the studied APF structure is presented. Combined with the principle of SVPWM, the basic voltage vector combination for each control period output is determined by space division and grid voltage vector location. The working time of each vector is calculated according to the prediction model, and the pulse modulation is carried out. Finally, the switching frequency can be basically fixed and better compensation performance can be obtained. The system implementation flow and current tracking control process under constant frequency control are analyzed, and the differences between them and conventional model predictive control methods are summarized. Finally, the main simulation parameters of APF system are designed, and the current control strategy is simulated and analyzed. The simulation results show that the DC side voltage control can automatically compensate for the active power detection error and verify the feasibility of the harmonic detection scheme, and the dynamic response of the current under the model predictive control is fast, compared with the harmonic detection, the simulation results show that the DC side voltage control can automatically compensate for the active power detection error, and verify the feasibility of the harmonic detection scheme. The steady-state compensation effect of the system is better under the strategy of harmonic detection. The effects of sampling frequency, multi-objective weight coefficient, control delay and inductor mismatch coefficient on the compensation performance of the system are analyzed by simulation, which provides a reference for the further optimization of the control performance. In addition, the simulation results show that the DC side voltage stabilization and voltage sharing control performance is good, which verifies the effectiveness of double loop Pi control. The simulation results show that the dynamic response speed of the system is equal to that of the conventional model predictive control, but the steady-state compensation accuracy is higher, and it is less affected by the change of parameters.
【学位授予单位】：中国矿业大学
【学位级别】：硕士
【学位授予年份】：2017
【分类号】：TM761

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