Research On Plug-and-play Control Strategy For Active Power Decoupling Circuits

The energy crisis and environmental pollution and the rapid development of distributed renewable energy sources in recent years have led to the rise of DC power grids,and hybrid AC-DC grids will become the mainstream form of future grid.Single-phase converter is one of the commonly used power electronics in hybrid AC-DC grid.The inherent double-line frequency ripple power on the AC side causes low-frequency pulsation of DC bus voltage,which brings various problems to the system,and active power decoupling technology is developed on this basis.However,most of the existing active power decoupling methods are aimed at the individual single-phase converter,and the decoupling circuit has a limited decoupling capacity,which makes it difficult to adapt to the complex pulsation power variation in the hybrid AC-DC grid,resulting in problems such as incomplete decoupling or low utilization of the decoupling circuit.The decoupling circuit with plug-and-play function can be flexibly connected to or cut out of main circuit to adapt to the power variation,and it also facilitates the modular design of the decoupling circuit.In this paper,the plug-and-play control strategy of active power decoupling circuits is studied,and the main research contents include:(1)For the single decoupling circuit,a plug-and-play control strategy based on an emulated LC resonant circuit is proposed.The same power decoupling effect is achieved by shaping the decoupling circuit with the same impedance characteristics as the passive LC resonant circuit.The decoupling principle of passive LC resonant circuit is analyzed,the construction process of impedance characteristics of active power decoupling circuit is elaborated,a specific decoupling circuit is selected for mathematical modeling and control block diagram derivation,and the parameter design and small signal stability of the system is analyzed.The control strategy uses only the information of the DC bus voltage and thus achieves plug-and-play control.(2)For multiple decoupling circuits,a cooperative control strategy based on virtual power distribution resistors is proposed,so as to realize the cooperative operation between multiple decoupling circuits in high-power situations.The capacity of a single decoupling circuit is analyzed,the virtual power distribution resistor is constructed based on the passive LCR circuit distribution principle,the mathematical modeling and control design of the specific decoupling circuit are carried out,and the power distribution principles and related parameters design process are also described.The control strategy coordinates the power distribution among circuits without communication,ensures the independence of each decoupling circuit and guarantees the plug-and-play function.Both proposed control strategies are validated by simulations and experiments,and confirmed to be effective and feasible.The paper concludes with a summary of the full work and a research outlook on the issues to be improved and refined.