Research On Power Coordinated Control Strategy Of Combined Three Phase Microgrid System

In recent years,the microgrid system with energy storage equipment has shown great advantages in distributed generation access.It can be used as a controllable generator/supplied unit to operate in parallel and in the event of a power grid failure or anomaly.Disconnecting from the external distribution network and autonomous operation of islands are seen as the best way to use distributed energy.However,the actual microgrid system is usually a single-phase/three-phase hybrid system.The single-phase power supply and load during islanding operation easily lead to unbalanced three-phase voltage,which leads to the power coordination control strategy of the combined three-phase microgrid system.Research mainly includes the following aspects:(1)The power coordination control of the in-phase parallel unit is analyzed in detail.The mathematical model of the single-phase full-bridge converter in the three-phase stationary coordinate system is established.The commonly used double closed-loop control strategy is given.The loop current phenomenon between the same phase and the traditional power calculation method in the droop control of the virtual combined three-phase converters is limited,and the sags and virtual impedance control based on the virtual three-phase instantaneous power are described to realize the power between the in-phase parallel units.distribution.(2)Phase-locked loop based on the phase synchronization control and voltage compensation control were analyzed,through the mathematical model analysis pointed out that each phase is independent of each other,no coupling relationship,and then for the combined three-phase converter phase synchronization control difficulties,A novel 120° phase detector and phase-locked loop-based phase-to-phase synchronous control are proposed to achieve 120° phase-locking of the non-reference relative reference phase lead or lag signal,thereby achieving a phase difference of 120° between the non-reference phase and the reference phase.Based on this,voltage compensation control is given to further improve the quality of power supply.(3)The power coordination control of the virtual combined three-phase converter and the traditional three-phase converter is analyzed,and the mathematical model of the traditional three-phase converter in the ?? coordinate system is deduced,and the unbalanced load is pointed out.The limitation of traditional droop control,given the traditional three-phase converter control method for power distribution strategy,using the positive sequence voltage separated by the load voltage to track the command voltage obtained by sagging the positive sequence power can realize the traditional three.The phase converter only contains the positive sequence current,and the negative sequence current and the zero sequence current are all shared by the virtual combined three-phase converter.(4)On the basis of theoretical research,a semi-physical experiment platform based on dSPACE was built,and the effectiveness of the control strategy was validated experimentally.The experimental results show that the proposed control strategy can realize the power distribution between the in-phase parallel units under the dynamic steady-state conditions according to the set ratio,the phase and amplitude of different phases can be synchronously controlled,and the voltage nubalance at 100%unbalanced load is 0.1.%,with higher power quality and virtual combined three-phase converters and traditional three-phase converters can achieve power coordination control according to the power distribution strategy...