基于模型预测的三电平APF控制策略研究

发布时间：2018-03-15 05:35

本文选题：三电平有源电力滤波器　切入点：谐波检测　出处：《中国矿业大学》2017年硕士论文　论文类型：学位论文

【摘要】：近年来电力系统谐波污染问题日益严重,而有源电力滤器(APF)因其补偿方式灵活、响应性能好且受电网参数的影响小等优势备受关注。本文以三相三线NPC结构的三电平并联型APF为研究对象,分别就其谐波电流检测方法、电流跟踪控制策略展开研究。首先,研究出一种基于双同步坐标系解耦的柔性锁相环(DDSRF-SPLL)锁相与DFT滤波相结合的改进FBD检测方法。在算法中,一方面采用了基于DDSRF-SPLL锁相的方法,该方法通过把电网电压分解到坐标系dq+与dq-中,交叉解耦后得到基频正序分量,将其作为锁相环节输入信号,实现准确锁相,提高了对复杂电网情况下的适应性;同时在另一方面采用DFT滤波的方式取代传统方法中LPF的功能,通过修改角频率的方式来实现谐波的检测,该方法可以降低检测延时,提高检测精度。仿真结果验证了所研究方法的正确性。其次,针对传统模型电流预测中滚动次数过多的问题,研究出一种简化的三电平APF多目标模型预测电流控制策略。建立三电平NPC结构APF数学模型,分析各个矢量对中点电位的影响,利用扇区的分解减少最优开关矢量输出的滚动次数,并与传统MPCC策略做对比仿真分析。针对控制延时问题,给出该策略控制延时的补偿措施。然后在评估函数中引入开关频率约束,实现多目标的优化控制,对比分析有无开关约束条件下的补偿效果,最后通过突增负载来验证其动态响应性能及对负载波动的适应性。仿真结果表明,简化的多目标模型预测电流控制策略在动态响应及控制流程简化等方面优势突出。再次,提出一种基于扇区分级判断的模型预测电压控制策略。针对模型预测电流控制方法中多次滚动的问题,借鉴基于αβ坐标系下空间矢量脉宽调制(SVPWM)的思想,利用扇区的两次判断,即可从27个矢量中确定出最优开关矢量,省去了滚动寻优的环节,大幅度提高了寻优效率,同时针对中点电位平衡问题引入一种基于小矢量的定性控制方法;然后讨论延时与电感偏差系数对该策略的控制系统稳定性的影响,仿真结果证实了该改进的模型预测电压控制策略在稳态、动态和电感参数变化条件下的有效性,且中点电位平衡可以得到很好控制。最后,设计三相三线制NPC结构的三电平并联型APF实验平台整体结构框架及选取主电路关键参数,对本文的研究的改进FBD谐波电流检测法、简化的多目标模型预测电流控制策略及基于扇区分级判断的模型预测电压控制策略进行实验验证,并同时测得不同控制算法的运算时长且做对比分析,实验结果证明了所研究内容的正确性与可行性。
[Abstract]:In recent years, the problem of harmonic pollution in power system is becoming more and more serious, but the active power filter (APF) is flexible because of its compensation method. In this paper, the three-level parallel APF with three-phase three-wire NPC structure is taken as the research object, and the harmonic current detection method and current tracking control strategy are studied respectively. In this paper, an improved FBD detection method based on dual synchronous coordinate system decoupling is proposed, which combines the phase lock of flexible PLL DDSRF-SPLL with DFT filter. In the algorithm, on the one hand, the method based on DDSRF-SPLL is used. By decomposing the grid voltage into the coordinate system dq and dq-, the positive sequence component of the fundamental frequency is obtained by cross-decoupling, which is used as the input signal of the phase-locked loop to realize the accurate phase-locked and improve the adaptability of the complex power network. On the other hand, the DFT filter is used to replace the function of LPF in the traditional method, and the harmonic detection is realized by modifying the angular frequency. The method can reduce the detection delay. The simulation results verify the correctness of the proposed method. Secondly, aiming at the problem of excessive rolling times in the traditional model current prediction, the simulation results verify the correctness of the proposed method. A simplified three-level APF multi-objective model predictive current control strategy is developed. A three-level NPC structure APF mathematical model is established to analyze the effect of each vector on the neutral point potential. The sector decomposition is used to reduce the rolling times of the optimal switching vector output, and the simulation results are compared with the traditional MPCC strategy. Then the switching frequency constraint is introduced into the evaluation function to realize the multi-objective optimal control, and the compensation effect under the condition of switching constraints is compared and analyzed. The simulation results show that the simplified multi-objective model predictive current control strategy has outstanding advantages in dynamic response and control process simplification. A model predictive voltage control strategy based on sector classification judgment is proposed. Aiming at the problem of multiple rolling in the model predictive current control method, the idea of SVPWM based on space vector pulse width modulation (SVPWM) in 伪尾 coordinate system is used for reference, and the second judgment of sector is used. The optimal switching vector is determined from 27 vectors, and the rolling optimization is eliminated, and the optimization efficiency is greatly improved. At the same time, a qualitative control method based on small vector is introduced to solve the midpoint potential balance problem. Then, the effects of delay and inductance deviation coefficient on the stability of the control system are discussed. The simulation results show that the improved model predictive voltage control strategy is effective under the conditions of steady, dynamic and inductance parameters. The neutral-point potential balance can be well controlled. Finally, a three-level parallel APF experimental platform with three-phase three-wire NPC structure is designed and the key parameters of the main circuit are selected. The improved FBD harmonic current detection method is studied in this paper. The simplified multi-objective model predictive current control strategy and the model predictive voltage control strategy based on sector grading judgment are verified experimentally. At the same time, the operation time of different control algorithms is measured and compared. The experimental results show the correctness and feasibility of the research.
【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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