Fregqency And Power Balance Control Technology Of Microgrids With Hydro-Wind-Solar Energy

Power shortages still exist in remote areas of China.These areas are far away from large power grids and rely on long-distance transmission lines for power supply.The construction cost is high and the quality of power supply is difficult to guarantee.Relying on local distributed energy sources such as wind power,hydropower,and photovoltaics to form a microgrid is one of the solutions to such problems.Combining hydropower,photovoltaic and wind power to form a microgrid to form a complementarity between multiple micropower sources can not only enhance the consumption of distributed energy,but also improve the power supply reliability of the internal load of the microgrid,which is also a kind of future development.trend.This paper builds a water-wind-light microgrid model to study the coordinated control and optimized operation of small-scale hydropower,wind power and photovoltaic in the water-wind-light microgrid,which can effectively solve the operation of multiple micropower complementary microgrids.Control problems.This paper considers the influence of natural factors on distributed power in the microgrid,analyzes and establishes mathematical models of hydropower units,wind power units and photovoltaic power generation,followed by analysis of three typical distributed power inverter control methods.Compare the principles,advantages and disadvantages and operating ranges of power control,constant voltage and frequency control and droop control,and then compare the control methods of the three microgrid systems to study the frequency regulation and power balance control of the water-wind-light microgrid Good foreshadowing.Aiming at the frequency regulation strategy of the isolated grid of the water-wind-light microgrid,it is divided into two parts according to whether the small hydropower has a storage reservoir.The first part is a water-wind-light micro-grid composed of small hydropower with storage reservoirs,which is independently frequency-modulated by the hydropower system.First,the transfer function of each module is analyzed and studied with reference to the principle of operation of the hydroelectric generating unit,and the effects of the permanent slip coefficient andPID parameters on the hydropower system with load frequency modulation are simulated and analyzed.The hydropower system performs frequency modulation independently,and the frequency can be controlled within 0.1 Hz.The second part is the water-wind-light micro-grid composed of radial flow hydropower units.The output of the small hydropower unit changes with the change of the incoming water runoff and does not have the ability of frequency modulation.For this situation,a micro-grid model based on improved droop control and wind-light cooperative frequency modulation is proposed.The combination of energy storage and frequency control through the inverter.Firstly,the micro-grid model of wind-solar cooperative frequency modulation is introduced,and the model is simulated and analyzed.The simulation results show that when the micro-grid load changes suddenly,the frequency amplitude is controlled within 0.1 Hz in 0.2 seconds,which verifies the Mention the effectiveness of the control plan.Aiming at the problem of frequency deviation caused by the fluctuation of load demand power in the power system,a control model of microgrid containing electric vehicles participating in regional grid frequency modulation is proposed.By controlling the charge and discharge power of electric vehicles and energy storage power stations inside the microgrid,Adjust the frequency deviation of the regional power grid.When the stable operation of the power grid is threatened,the frequency shift exceeds the FM dead zone,and the response level is reached,the power grid dispatch center is allocated to the traditional FM unit and the microgrid according to the power deficit.The microgrid is based on the received grid control instructions and electric vehicles and The available power capacity and other information of energy storage feedback are used for power distribution,and the output power of the microgrid is changed to meet the requirements of frequency modulation.The simulation results show that the control strategy proposed in this chapter is effective.Aiming at the optimization of power balance operation under the grid-connected condition of water-wind-photomicrogrid,a model of grid-optimized operation of water-wind-photomicrogrid is proposed.According to the characteristics of unstable output of wind turbines and photovoltaic power generation,the output control ofhydropower units is used And battery charge and discharge control to achieve the purpose of power balance,the use of improved particle swarm algorithm to simulate the microgrid model.Under the premise of satisfying the safe operation of the microgrid,in order to maximize the utilization of wind energy and photovoltaics,by controlling the water diversion flow of the hydropower and the storage battery,the load fluctuation rate is minimized and the exchange power between the distribution network and the microgrid is minimized.At all times,the output power value of the hydropower unit,the battery charge and discharge power value,and the exchange power value of the distribution network and the microgrid.After the optimization,the exchange power of the microgrid and the distribution network is reduced by about41% compared with the unoptimized exchange power.The effectiveness of the grid optimization operation model also shows the feasibility of supplementing the load with the wind-photovoltaic microgrid to preferentially use wind power and photovoltaics,reuse hydropower to regulate output,and charge and discharge the battery.Aiming at the optimization of power balance operation under the isolated grid condition of water-wind-photomicrogrid,a model for optimized operation of isolated grid-water-wind-photomicrogrid is proposed.When the output of wind turbine and photovoltaic power generation is greater than the load demand,the extra battery The electrical energy is stored;when the output of the wind turbine and photovoltaic power generation does not meet the load demand,the output of the hydropower unit and the charge and discharge power output of the battery are increased;when the power output of the four still does not meet the load power demand,a certain amount of controllable load is interrupted to maintain Power balance in the microgrid.This operation optimization model aims at the minimum load fluctuation rate and the total amount of interruption load throughout the day,and uses the Q learning algorithm to optimize the isolated network operation model.The results show that the total load interruption during the whole day after optimization is reduced by about 49%compared with the non-optimization,and there are several moments when the non-optimization interruption load demand exceeds the controllable load,whichaffects the reliability of the microgrid operation;while the operation is optimized After this phenomenon did not appear,the microgrid can be operated safely,and the results show the feasibility of this optimized operation model.