Improving the Frequency Response of High Renewable Penetrated Islanded Microgrids

The integration of renewable energy sources (RESs) into microgrid weakens the inertia of the microgrid and negatively affects its frequency stability. Recently, this problem is rectified using the derivative virtual inertia (VI) control strategy in the form of an energy storage system (ESS) to improve the inertia and frequency stability of the microgrid. The derivative VI controller calculates the rate of change of the frequency deviation (RoCoF) for injecting active power into the microgrid during periods of contingencies. However, the main problem of the derivative VI controller is that the damping effect is neglected in its design. As such, it might give an unsatisfactory performance in a microgrid with low damping. Therefore, this paper proposes an improved derivative VI controller that can emulate both inertia and damping concurrently. A differential evolution (DE) algorithm has been utilized to optimize the virtual inertia and damping coefficients. The performance of the proposed VI controller is validated through simulation studies under different RESs and loads. Moreover, performance comparison between the proposed VI controller and the existing VI control techniques shows that the frequency response is more robust and accurate under the action of the proposed VI controller.