DC Microgrid Energy Storage Interface Converter Adaptive Virtual DC Motor Control

The rapid consumption of primary energy has promoted the development of new energy.Photovoltaic with power generation is an important part of new energy,and DC microgrid is the best way to absorb photovoltaic power generation at present.DC microgrid with energy storage and PV is a local power distribution system composed of solar power units,energy storage devices and loads.It can be operated as part of the power distribution system or in isolated island mode when needed.In these two ways,the energy storage device plays a key role,which improves the security and stability of the microgrid,and also ensures the power quality of the microgrid.In DC microgrid,each device is connected to DC bus through power electronic converter,so the research of bus voltage control is far-reaching significance.In this paper,by improving the control of energy storage interface converter,the energy storage can give full play to the role of absorbing photovoltaic power generation unit and inhibiting the voltage fluctuation of the bus.The details are as follows:In the traditional Virtual DC Machine(VDCM)control,the fixed moment of inertia cannot adapt to various working conditions of DC microgrid,so the adaptive control of moment of inertia is considered.After the virtual DC motor control model is equivalent simplified,small signal analysis is carried out to clarify the influence of moment of inertia on the bus voltage.After comparing the influence of temperature and light intensity on the output power of photovoltaic cells,it is found that the light intensity has a greater influence on the output power of photovoltaic unit.Based on the above two points,fuzzy control is introduced to form the Adaptive Virtual DC Machine(AVDCM)control.The fuzzy control module takes the change rate of light intensity and the change rate of bus voltage as the input and the moment of inertia as the output,so that the moment of inertia changes with the change of light intensity and bus voltage.Simulation and experiment show that the control method not only suppresses the fluctuation amplitude of bus voltage,but also accelerates the recovery time after bus voltage fluctuation,significantly reduces the influence of light intensity change,and further improves the stability of DC microgrid.In the multi-energy storage DC microgrid system,the traditional P-U droop with double closed-loop control does not have inertia characteristics and poor dynamic characteristics.This paper first improves the droop control and introduces a first-order differential link in the droop equation to improve its dynamic stability.Secondly,the adaptive virtual DC motor control is combined with the improved droop control to form an AVDCM control based on improved P-U droop coordination.The fuzzy control part takes the bus voltage change rate as input and the moment of inertia J as output.This method can take into account both power distribution and bus voltage dynamic stability.Simulation and experiment show that the output power of the energy storage device can reach the given target of droop control under this control method,and the stabilized bus voltage is closer to the rated value,and the voltage fluctuation amplitude and recovery time are improved.