Research on the power electronic load based on repetitive controller

The paper present a new test equipment for single-phase ac power source tests named PEL(power electronic load), the proposed architecture consists of two power stages such as input AC-DC imitation converter to imitate various loads and the output grid-connection converter to send back the recycling energy to the utility grid. In PEL, the controllable imitation converter enlarges the load bound that can be imitated, make the system more flexible, it even can simulate the nonlinear load to verify the stability of the tested ac power; and the grid-connection transformer ensures the system operate in security. A simple control scheme based on P(proportion) and PI(proportion and integral) control is proposed to ensure the system operate normally. But the phase delays in the digital control system and the controlled plant, the change of the parameter in the PEL, the unpredictable disturbances in the system will degrade the effectiveness of the simple control scheme. The repetitive control is proposed to solve the problem, it can ensure the system with excellent steady characteristics, to remedy the shortage of the repetitive controller in dynamic characteristics, the traditional P controller is connected with it in parallel connection, the compound controller acts well both in steady state and dynamic state, it even can hold a perfect effect in simulating the nonlinear load. The paper analyzes the repetitive controller in details. At last, the simulation and experimental results are provided to testify the effectiveness of the proposed control scheme.