Comparative Study on Different Analysis Methods of LCL Grid-connected Inverters

With the progress of science and technology, digital control has been widely used in medium and high power inverters because of its strong anti-interference ability and flexible control strategy. But at the same time, digital control will introduce control delay, which is a transcendental function and is not conducive to the stability analysis of inverter system. When analyzing in continuous s-domain, the control delay is always approximated by the rational transfer functions, such as Taylor and Pade approximation, but which approximation method is more accurate and practical remains to be studied. This paper uses first-order, second-order Taylor and Pade approximation to analyze the stability of the system, and the results are compared with those of the discretization method. The work contributes to choosing an appropriate approximation method when analyzing in continuous s-domain.