Load Frequency Control of a Microgrid Based on H_∞ Control Considering Response Speed of Generators

Abstract

In this paper, load frequency control problem of a microgrid is discussed. The control is conducted to retain power demand supply balance by controling output of generators in power system. However, it becomes harder to retain the balance because of large-volume injection of renewable energy. For the problem, two approaches are considered in this research field. One is to use dispersion type power sources like batteries, and the other is to apply new control theories. Therefore, we focus on a microgrid which holds a wind turbine generator, a diesel generator and a battery, and propose a technique based a static H_∞ control. In the beginning, we design the generalized plant considering the difference of the response speed of a diesel generator and a battery. Then, static H_∞ control is applied to the generalized plant. Moreover, an LMI condition to avoid control gains to cause too big control input are combined with static H_∞ control. In numerical simulation, we validate that the controller can suppress frequency deviation and deviation of residual capacity of the battery. Futhermore, we show that the approach can design controllers with lower dimensions, and avoid undesirable control gains. In experiment with a generator and a variable resistance, the effectiveness of the controller is also confirmed.