Research On Microgrid Inverter Control Strategy Based On Improved Droop Control Algorithm

With the development of the economy,the problems of energy shortage and environmental pollution have become increasingly seriously,the utilization of clean energy which including wind energy and solar energy has received much attention.Among them,microgrid as the most effective way to make use of distributed energy has gradually become a research hotspot for researchers.However,due to the intermittent nature of distributed energy,which brings a great challenge to the safe operation of the microgrid system.In order to ensure the people’s requirement for power quality and improve the reliability and economy of microgrid operation,proper control strategy is needed.Inverter as the core part of the microgrid system,the effective control technology of the inverter is the key to ensure the microgrid which runs safety and reliability,especially when the microgrid running in the off-grid mode,in addition to keep each parallel output a stable voltage and current,also need the inverter performs load power distribution according to its own capacity In addition to ensuring the stability of the voltage and frequency of the system,each inverter is required to carry out load power distribution according to its own capacity.Therefore,for the inverter of microgrid,a reasonable and effective control strategy is particularly important.In this paper,analyzed and discussed the traditional droop control strategy,studied the effects of different impedance transmission lines on droop control strategy.Combined with the characteristics of various inverters,and select a voltage type three phase inverter as the main topology of the circuit,and a mathematical model of the inverter is established.The inverter voltage and current double loop controller is designed.Verify the dynamic characteristics of the inverter double loop controller through simulation.Compared with the traditional quasi-static model analysis method,when analyses the droop control strategy which used in inverter,the dynamic phasor model can get a more accurate stability margin.Secondly,by studying the control method of the microgrid inverter,and analysis the main control technology of the inverter,the traditional droop control is improved.In this paper,the droop coefficient which is adaptively changed with power is proposed,and the active power and reactive power are respectively introduced in the droop coefficient.When the load power changes,the droop coefficient is dynamically adjusted according to the actual output power of the inverter.Under the premise of realizing the power distribution of each inverter according to its own capacity ratio,the inverter output voltage and the deviation of the system frequency are reduced.By analyzing the voltage drop caused by line impedance and virtual impedance,a bus voltage compensation strategy based on droop control is proposed.The strategy calculates the bus voltage deviation by the active power and reactive power of the inverter,and the voltage deviation is used as the input signal to pass through the P controller,the output obtains the voltage compensation amount.By constantly adjusting the reference voltage.the proposed compensation strategy can effectively improve the voltage drop caused by the line impedance and the virtual impedance of the system voltage.Finally,the inverter simulation model is built in Matlab/Simulink environment,and the improved droop control strategy and bus voltage compensation strategy are simulated and verified.The experimental results show that the improved strategy achieves the expected results.