Design and implementation of the software phase-locked loop for cascading power conversion devices

With the development of power electronic technology, the accurate phase information is crucial for the normal operation of power conversion devices, especially high voltage and power; obtaining the accurate phase and angular frequency of grid is the premise achieving the control of voltage and current. In this, the weakness of the hardware phase lock is firstly analysed, and the software phase lock technology which has the advantages of free design, low cost and strong adaptability is further proposed. The method of the PI parameters of the control loop is obtained of software phase lock loop and its modeling. Based on the theory analysis, the hardware experiment is done the platform of power conversion device. During the experiment the PI parameters of software phase lock loop are firstly regulated; the expected phase can´t be obtained. Eventually the correction and limitation are added and the precise phase tracking of grid voltage is achieved, which validates the correctness of the proposed phase lock control strategy.