Research On Energy Management Strategy Of Wind-Solar Complementary DC Microgrid With Hybrid Energy Storage

The energy crisis and environmental pollution have led to the rapid development of renewable energy such as wind and solar energy,thus realizing the transformation and upgrading of energy structure.However,the renewable energy represented by wind energy and solar energy has randomness and uncertainty,which will cause the bus voltage of the microgrid to fluctuate,which has an negative impact on the stable operation of the microgrid.This paper takes the wind-solar complementary DC microgrid with Hybrid energy storage system(HESS)as the research object,deeply studies the power distribution control strategy of hybrid energy storage system,and analyzes the working mode of DC microgrid,giving various working modes under DC microgrid energy management strategy.The main work of this paper is as follows:Firstly,the photovoltaic cell and wind turbine models are established,the output characteristics of the two are analyzed,and the maximum power tracking strategy is run separately.The maximum power tracking control strategy of the joint operation is also given.Secondly,the principle of power allocation of hybrid energy storage system is studied,and the power allocation strategy of hybrid energy storage system is proposed.In the same energy storage unit,based on the mixed drooping coordinated control strategy combined with the voltage drooping method and the integral drooping method,when the battery drooping method is used to control the battery to suppress non-high frequency components,each battery in the energy storage unit battery pack is not considered.The difference in state of charge(SOC)causes the battery to be overcharged and overdischarged.By establishing a mathematical model between the battery SOC and the voltage droop coefficient,the battery SOC dynamically adjusts the voltage droop coefficient to achieve a reasonable distribution of non-high frequency components between the batteries;between different energy storage units,the dynamic adjustment of the energy storage unit SOC is proposed.The power distribution strategy of the drooping coefficient realizes the reasonable distribution of power between different energy storage units.And build a simulation model to verify the rationality of the proposed control strategy.Thirdly,the wind-solar complementary DC microgrid is divided into different working areas,and the two operating states of the DC microgrid are analyzed.The self-congestion mode in the working area and the mutual assistance mode in different working rooms are proposed,combined with the output power of the power generating unit.In the case of load power and SOC of the energy storage element,the operating state is further divided into five operating modes,and corresponding energy management strategies are given.A simulation model was built in MATLAB to verify the effectiveness of the proposed management strategy.Finally,the hardware and software design is carried out,and the DC microgrid hybrid energy storage experimental platform is built.The experiment mainly verifies the effectiveness of the hybrid drooping method.The experimental results show that the coordinated control strategy based on the hybrid droop method can effectively stabilize the DC bus voltage,and can also reasonably distribute the non-high frequency components according to the SOC of the battery,effectively preventing the battery from overcharging and over-discharging,which proves that the strategy has better practical application value.