| In the parallel system of microgrid inverters whose line parameters are mainly resistive,the traditional P-f/ Q-U droop control is no longer applicable.In the low-voltage microgrid,due to the inconsistent line impedance and the unequal capacity of the inverter,load sharing control is often implemented by introducing virtual impedance,but the introduction of virtual impedance leads to an increase in the total impedance of the system,resulting in further degradation of the line voltage.In addition,it is very important to realize the accurate distribution of load current and ensure the quality of the bus voltage in the island microgrid.Due to the access of a large number of nonlinear loads,the traditional droop control is difficult to meet the harmonic power sharing control and ensure system stability.Aiming at the above problems,an improved droop control strategy based on virtual complex impedance is proposed.By designing the value of the virtual complex impedance to achieve the purpose of power decoupling,and improving the droop control loop.Under the condition of realizing the fundamental frequency power sharing,a harmonic virtual impedance control strategy is proposed to ensure that the harmonic virtual impedance follows the change of the harmonic current to achieve accurate harmonic power sharing.At the same time,the voltage harmonic compensation method is introduced to further reduce the harmonic distortion of the bus voltage caused by the nonlinear load and improve the voltage quality.Through the analysis of the simulation results built in Matlab/Simulink,the adaptive droop control and voltage compensation methods are used to realize the voltage compensation and power sharing of the microgrid,improve the voltage quality,and ensure that the system frequency is in a stable range Internal fluctuation speeds up the dynamic response of the system and improves the stability of the system.The feasibility and effectiveness of the proposed method are verified. |
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