考虑储能变流器容量限制的电网低频振荡抑制策略

Droop control and inertia control are the typical control modes for energy storage system (ESS) suppressing low frequency oscillations. However, when the control effect is enhanced to some certain extent, ESS will limit the output power to the device maximum power (i.e., the maximum power modulation mode) and be out of the expected power control because of the limited converter capacity. This paper focuses on the evaluation indexes of the rotor speed dynamic characteristics and compares the suppression abilities of the rate of changes of the rotor speed with different ESS control modes. The study shows that the low frequency oscillations can be better suppressed with the ESS control modes than with the droop control and inertia control modes?; however, the long-term operation under the maximum power modulation mode will cause the ESS frequent charge and discharge with large currents, resulting in the sharp decrease in its service life. Therefore, a control strategy based on the maximum power modulation and the droop control is proposed to damp low frequency oscillation. The former can alternately output or absorb active power with the converter capacity to quickly make up for the system power shortage, suppressing the driving force of low frequency oscillations, i.e., the unbalanced power. When the evaluation index meets the limited requirements, under the effect of the droop control, the ESS drops out of the maximum power mode smoothly and further suppresses the rotor speed deviation to improve the frequency quality. Simulation results verify the effectiveness and advancement of the proposed control mode.