Research On Grid-connected Control Strategy Of Photovoltaic Power Generation System Based On Hybrid Energy Storage

Today,in order to solve faced the energy shortage and environmental problems by mankind,it is necessary to vigorously promote and develop green,clean and renewable energy such as solar energy.However,new solar energy has the characteristics of random,intermittent,and unpredictable power generation.In large-scale development and utilization,its low controllability and low predictability threaten the control and coordination capabilities of the power grid.Therefore,this paper uses hybrid energy storage to compensate the fluctuating power of photovoltaic power system,so that photovoltaic power system is controllable and adjustable.This article focuses on the hybrid energy storage-based photovoltaic power system,and mainly studies the hybrid energy storage fuzzy control,the LCL three-phase grid-connected inverter control and the hybrid energy storage-based photovoltaic power system grid-connected control.1.In response to the requirements of decoupling the input variables of the hybrid energy storage system and improving the control accuracy,a multi-input fuzzy coordinated control strategy for the hybrid energy storage system is proposed.A multi-input fuzzy controller is established based on the estimated fluctuating power of the photovoltaic power system and the current energy state of batteries and super capacitors.The fuzzy relationship matrix is used to introduce the mutually influencing input into the multi-input fuzzy controller,and the weights are multiplied.Fuzzy rules are established according to the hybrid energy storage system’s state of charge.Secondly,the fuzzy controllers of energy storage devices are established respectively according to the state of charge of the hybrid energy storage system.Energy status,real-time adjustment of the time constant of the low-pass filter,to achieve the purpose of coordinated distribution of fluctuating power by different energy storage media.2.Aiming at the resonance problem of the LCL three-phase grid-connected inverter,it is used to suppress by the capacitive current feedback active damping method.The current inner loop is controlled by a PR regulator.The topology and working principle of the LCL type three-phase grid-connected inverter are analyzed,and its state space mathematical model is established,and the LCL filter is taken as the cut-in Point to study the control scheme of the three-phase grid-connected inverter.In order to prevent the LCL filter from becoming a design factor of the restraint current controller due to the too small resonance frequency,a design method of capacitive current feedback active damping PR regulator is proposed.Through appropriate simplification,the design is simple,reasonable and applicable.The parameters of the relatively strong current inner loop PR regulator.3.Designed and analyzed the grid-connected control strategy of photovoltaic power system based on hybrid energy storage.On the DC side,the output power fluctuations of the photovoltaic power system are extracted through the feedback of the energy storage components in the hybrid energy storage module,and the hybrid energy storage is used to coordinate and control the grid-connected power fluctuations.The hybrid energy storage is coordinated and controlled by the set DC bus the actual value of the voltage is the input value for control.Secondly,the front stage of the two-stage LCL inverter mainly controls the photovoltaic power system to operate at the maximum power point and stabilizes the DC bus voltage;on the AC side,the latter stage of the two-stage LCL inverter converts the DC power into high-quality AC power Then feed into the grid.The fourth part of this article is the overall simulation and experiment,which verifies the validity and correctness of the control strategy proposed in the article.