Research On The Control Of Solar Flywheel Energy Storage System

With the development of human science and technology,traditional energy has been unable to meet the needs of society,and new energy technology has developed rapidly and has already occupied a considerable proportion in modern power system.Among which,photovoltaic power generation is widely used in many countries because of its advantages of clean,large storage volume and extensive distribution and others.However,because the photovoltaic cells are susceptible to the external factors,so that its output power will fluctuate irregularly,which makes it difficult to provide the electricity stably.Flywheel energy storage is a new type of energy storage which uses motor to drive the flywheel rotating and convert electrical energy to the flywheel kinetic energy,compared with the traditional way of chemical energy storage,it has the various characteristics,such as high energy storage density,long working time,running without pollution,etc,and holds great potential applications.This paper takes independent solar energy flywheel energy storage system as the study object,aiming at the efficiency problem of solar energy flywheel energy storage system during the energy storage phase,the control method,which takes flywheel system stable photovoltaic cell array DC bus voltage as the load to provide stable voltage,and stores the residual energy after supplying the load into the flywheel system,is studied.This paper,firstly,introduces the structure and principle of flywheel system,by comparing the advantages and disadvantages of all kinds of commonly used flywheel motor and combining with the characteristics of the photovoltaic power generation,to choose the cost-effective asynchronous motor with simple structure and easy for maintaining as the flywheel drive motor.Secondly,the simulation model of photovoltaic cells is built according to the principle of photovoltaic cells and its output characteristics under different conditions;after the comparison of various commonly used maximum power tracking algorithm,perturbation and observation method is proposed to work on photovoltaic cells based on particle swarm algorithm adjusting PID parameter modification,which realizes the maximum power tracking control over the photovoltaic cells;Then,according to the characteristics of the variable photovoltaic power output,control method of wheel motor chooses direct torque control technology with quicker response and less dependence in motor parameter,to analyze its principle,and established the direct torque control simulation model of asynchronous motor in the Matlab/Simulink;The control in the phase of flywheel energy storage system is studied,taking the PV array output power,load power and DC bus voltage in real time as reference,to calculate the reference speed and reference flux linkage of direct torque control of asynchronous motor,which enable the flywheel system to track the change of the PV(photovoltaic)array output power in the process of energy storage,to maintain balance among load power,PV power and flywheel energy storage under the condition of guaranteeing the stability of DC bus voltage;When the speed of asynchronous motor reaches the rated speed,flux weakening control of the motor will happened,which realizes the motor faster rotation in constant power,and maximizes the transfer of extra energy into the flywheel system,so that the utilization efficiency of photovoltaic power generation can be improved.Last but not the least,establishing and emulating the solar energy flywheel energy storage control system model within Matlab/Simulink,and the results show that the proposed control method can rapidly response to the change of external environment,which improve the energy use ratio and has a certain practicability.