Control Strategy for Distributed Generation Units through Active Power Sharing & Frequency Recovery

Due to growth in the global population, as well as the increase in the use of devices that consume electricity, demand for electrical power has grown to unprecedented levels. However, the electricity supply has become saturated due to environmental, social, and geographical factors. To address these problems, attempts have been made to meet the electrical energy demand locally via Microgrid and distributed generations (DGs).Small sized synchronous generator based distributed generators (DG) often have low start-up times and can serve as dispatch able generators in a Microgrid environment. The advantage is that it allows the power network to operate in a true smart grid environment. The disadvantage is that such DGs typically tend to have low inertia and the prime movers driving these resources need to be controlled in real time for them to operate effectively in islanded, grid-connected modes and during transition from grid connected mode to islanded mode and vice versa. When multiple DGs are present in the Microgrid, the overall control can become complicated because of the need for sharing the resources. A smart grid environment is then necessary to control all dispersed generation sources in the Microgrid. The most common control strategy adopted for multiple DGs connected to a network is droop control. Droop control ensures that the load needed to be served is shared by all the generators in the network in proportion to their generating capability. When DGs operate in a Microgrid environment, there is a need for coordinated operation between the DGs, the utility grid and the loads. This project describes a control method for distributed generation (DG) units to implement recovery simultaneously in an active power sharing and frequency islanded Microgrid. Conventional active power–frequency (P–f) droop control is used for the DG controller, and the frequency deviation is recovered by the DG itself via self-frequency recovery control, without requiring secondary frequency control. Because the electrical distance (impedance) from each DG unit to a point where the load demand changes differs among DG units, the instantaneous frequency deviations may differ between DG units. These differences are fed into the integrators of the self-frequency recovery control and may result in errors in active power sharing. To solve this problem and share active power more accurately, a compensation control method is developed for active power sharing, which considers the droop coefficients of each of the DG units. Simulation results show that the proposed control method is effective. The control method was modeled and tested using MATLAB/Simulink, and the simulation results demonstrate the effectiveness of the approach.