A Review of Modern Virtual Inertia Control Strategies for Microgrid Implementation

The use of inverter-based microgrids (MGs) with renewable energy sources (RESs) at the generation end is gaining popularity, with better control and environmental benefits of RES powered distributed generators (DGs) over the traditional synchronous generation units, the DGs are forming what is called the modern power system network. The generation, distribution, and transmission of power now requires more communication and control monitoring in order to realize an efficient grid network. However, the push for renewables are degrading the reliability of the overall electric grid. With the increasing use of renewable sourced, inverter based DG units the problem of frequency instability is faced during any disturbance in the system as the value of inertia/kinetic energy of inverters is zero or very less. Various studies have been taken place on the key approach of establishing inertia virtually in the low inertia generation units/inverters to imitate the synchronous generators in the grid to maintain and improving system stability. This paper presents a thorough review of state of the art frequency deviation control strategies for transient stability of MGs by the means of virtually added inertia. Major emulating virtual inertia methodologies as coefficient diagram method (CDM), H-infinity, adaptive learning etc. are discussed and compared through their schematic model, characteristics, and algorithmic flow chart.