三相不平衡条件下微电网光伏逆变器控制策略研究

发布时间：2018-01-19 01:29

本文关键词： 交流微电网光伏逆变器负序电压二阶广义积分器比例谐振调节器　出处：《广西大学》2017年硕士论文　论文类型：学位论文

【摘要】：微电网作为有效整合分布式能源的小型发配电系统,具有运行灵活、绿色环保、能量转化率高的优点。光伏发电作为微电网的重要电源,光伏逆变器是将光伏阵列发出来的直流电能逆变成交流电能的关键器件,在微电网三相不平衡条件下,逆变器采用常规比例积分(Proportional-Integral,PI)控制策略,输出三相电流不平衡、有功功率、无功功率产生二倍频波动,不符合并网的要求。因此,研究微电网三相不平衡条件下光伏逆变器的不平衡控制策略具有重要意义。本文分析了光伏逆变器在微电网理想电压条件下采用基于dq旋转坐标系的PI控制策略,通过仿真和实验验证了在理想电压条件下逆变器采用PI控制策略能达到并网的要求。微电网三相不平衡时,电压成分中含有负序分量。本文分别通过理论推导、仿真和实验验证了常规的PI控制策略缺乏对负序分量的控制能力。本文采用基于双二阶广义积分器锁频环(DSOGI-FLL)的正、负序分离系统对电压进行正、负序分离。对微电网三相不平衡条件下光伏逆变器的功率进行分析,结合分离出来的正、负序电压分量和直流电压外环输出的有功功率,无功功率给定值,分别计算出实现逆变器三个不同控制目标的参考电流指令值。采用改进的比例谐振(Proportional-Resonant,PR)调节器对三相不平衡下逆变器的电流进行控制。本文对微电网光伏支路进行设计与实现,对光伏支路的断路器、多功能电表、电流互感器进行选型,并设计与研制了测量及计量回路、分合闸操作回路、状态指示回路;对逆变器直流侧的支撑电容、交流侧的滤波电感电容进行设计计算,依据逆变器的功率、输入输出电压电流选取电压、电流传感器和IPM功率模块等元器件,并制作出三相光伏逆变器样机。通过仿真验证了本文所提的不平衡控制策略可以分别实现逆变器输出有功功率稳定、无功功率稳定、三相电流平衡等不同的控制目标;通过实验验证了本文所提的不平衡控制策略可以实现逆变器输出三相电流平衡的控制目标。
[Abstract]:As a small power generation and distribution system which integrates distributed energy effectively, microgrid has the advantages of flexible operation, green environment protection and high energy conversion. Photovoltaic power generation is an important power source for microgrid. Photovoltaic inverter is the key device that inverts the DC energy from the photovoltaic array into AC electric energy, under the condition of three-phase imbalance of microgrid. The inverter adopts the conventional proportional integral integral-integral (Pi) control strategy to output three-phase current imbalance, active power, reactive power to produce double frequency fluctuation. Does not meet the requirements of grid connection. It is of great significance to study the unbalanced control strategy of photovoltaic inverter under the condition of three-phase unbalance of microgrid. In this paper, the Pi control of photovoltaic inverter based on dq-rotating coordinate system under ideal voltage condition of microgrid is analyzed. Strategy. The simulation and experiments show that the Pi control strategy can meet the requirements of grid connection under ideal voltage conditions. There are negative sequence components in the voltage component. The simulation and experiments show that the conventional Pi control strategy lacks the control ability of negative sequence components. In this paper, the positivity of DSOGI-FLLL-based frequency locking loop based on double second order generalized integrator is adopted. The negative sequence separation system carries on the positive and the negative sequence separation to the voltage. The power of the photovoltaic inverter under the microgrid three-phase unbalance condition is analyzed, and the separation is combined with the positive. A given value of the active and reactive power output from the negative sequence voltage component and the DC voltage outer loop. The reference current instruction values for realizing three different control objectives of the inverter are calculated respectively, and the improved proportional resonance is adopted. This paper designs and implements the photovoltaic branch circuit of the microgrid, and selects the circuit breaker, multi-function meter and current transformer of the photovoltaic branch circuit. The measuring and measuring circuit, the closing and closing circuit and the state indicating loop are designed and developed. The supporting capacitance of DC side of inverter and filter inductor capacitance of AC side are designed and calculated. According to the power of inverter, input and output voltage and current, current sensor and IPM power module and other components are selected. A prototype of the three-phase photovoltaic inverter is made. The simulation results show that the unbalanced control strategy proposed in this paper can achieve the stability of the output active power and reactive power of the inverter respectively. Three phase current balance and other different control objectives; Experimental results show that the unbalanced control strategy proposed in this paper can achieve the control goal of output three-phase current balance of the inverter.
【学位授予单位】：广西大学
【学位级别】：硕士
【学位授予年份】：2017
【分类号】：TM464;TM615

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