基于有源谐波电阻控制的下垂控制变流器振荡抑制策略

The droop control converter exhibits capacitive characteristics in the frequency band below 50 Hz, which leads to the problem of RLC oscillation when it interacts with the inductive power grid, thus causing harm to the power grid. Based on this, this paper firstly establishes a sequence impedance model of droop control converter using the harmonic linearization method, which reveals the mechanism of oscillation after the interaction between the droop control converter and the power grid. Then, a control strategy for active harmonic resistance based on droop control converter is proposed, which only requires modifying the voltage loop command of the converter to shape the impedance characteristics (excluding the fundamental frequency) into resistive behavior, thereby avoiding oscillations when interacting with an inductive grid. To address the possible influence of active harmonic resistance on the stability of the system, an adaptive control strategy is proposed to adjust the parameter value, thus ensuring consistent suppression of system oscillation. Finally, simulation and hardware-in-the-loop (HIL) experiments validate the effectiveness of the active harmonic resistance control strategy.