基于Takagi-Sugeno模糊模型的电流跟踪型光伏并网逆变器

Photovoltaic grid-connected inverter with current tracking control based on Takagi-Sugeno fuzzy model

逆变器是光伏并网发电中的关键设备,如何调整PWM控制信号的波形,输出与电网电压同频率同相位的电流,是并网逆变器设计中最重要的问题。在分析比较了光伏并网发电系统逆变器各种控制算法的基础上,推导出了单相全桥逆变电路功率开关管占空比关于并网电压和电流误差等可测量物理量的函数关系式,提出了一套基于Takagi-Sugeno模糊模型的PWM波形产生方法。该方法采用四输入双输出的结构,将并网电压和电流误差等可测物理量作为模糊控制器的输入量,经T-S模型模糊处理之后分别得到两组功率开关管的控制信号的占空比。该文最后以单相全桥逆变电路为例,给出了详细的仿真分析,结果显示由该方法生成的PWM控制信号较之传统滞环比较控制等,有开关频率低、硬件电路简单、谐波畸变率小等优势,可实现并网发电要求的单位功率因数。

Inverter which is essential in the photovoltaic grid-connected generation system faces an important problem that is how to adjust PWM（pulse width modulation）control signals to output current keeping sinusoidal and in phase with grid voltage.This paper proposes a new kind of method to solve the problem effectively.Firstly various kinds of control algirithms used in photovoltaic grid-connected inverter are compared,and then the function between duty cycle and several measurable variables such as grid voltage and current error is generated.Based on this function a complete method to produce PWM control signals under Takagi-Sugeno fuzzy controller is proposed.This method adopts 4-input and 2-output structure.Four variables of grid voltage,current error,reference current and its differential are taken as input.After processed under Takagi-Sugeno fuzzy controller,control signals of the four switches are obtained as output.Via anti-fuzzy interface duty cycles of the two groups of control signals are achieved.At the end of this paper the principle of a single phase full-bridge inverter is illustrated.Through simulation analysis it can be seen that compared with traditional hysteresis control the proposed method has advantages in terms of low switch frequency,simple hardware structure,small THD and so on.It feeds power to the utility with unity power factor.