三相并网DC/AC变换器控制策略研究

Research on Control Strategy of Three⁃phase Grid⁃connected DC/AC Converter

并网变换器拓扑结构和控制方法的选择和设计对并网效率、谐波含量、并网质量等产生重要影响,直接影响并网系统的安全性和可靠性。提出基于前馈解耦的电压电流双闭环三相并网变换器控制策略,使输出电压能够快速跟踪额定输出电压,达到所需要输出电压的标准,提高输出电压响应速度,并实现无静差。通过建立三相并网变换器在dq轴坐标系下的数学模型,引入前馈解耦控制,建立电压控制器和电流控制器的输出解耦数学模型,并分析前馈解耦控制的原理,采用电压、电流双闭环实现系统的控制。电压调节器的输出作为有功电流的给定值,电流调节器用来独立调节系统的有功、无功电流,使系统的有功、无功电流实时跟踪指令电流值。利用MATLAB/Simulink搭建三相并网变换器控制模型,分析开关的脉冲信号、LC滤波前后电压、电流和谐波等,验证了所提控制方式的正确性和有效性。

The selection and design of topology and control method of grid connected converter have an important impact on grid connected efficiency,harmonic content,grid connected quality and other factors,which directly affect the safety and reliability of grid connected system.The control strategy of voltage current double closed⁃loop three⁃phase grid connected converter based on feedforward decoupling was proposed,which makes the output voltage quickly track the rated output voltage,reach the required output voltage standard,improve the output voltage response speed,and realize no static error.The mathematical model of three⁃phase grid connected converter in dq axis coordinate system was established.The feedforward decoupling control was introduced.The output decoupling mathematical model of voltage controller and current controller was established.The principle of feedforward decoupling control was analyzed.Moreover,the voltage and current double closed loops were eventually used to realize the control of the system.The output of voltage regulator was used as the given value of active current,and the current regulator was used to adjust the active and reactive current of the system independently,so that the active and reactive current of the system can track the command current value in real time.A three⁃phase grid⁃connected converter control model was built using MATLAB/Simulink,and the pulse signal of switch,voltage,current and harmonic before and after LC filtering were analyzed to verify the correctness and effectiveness of the proposed control method.