Smooth Integration of Rectifier-Battery Banks Operation in Real-Life Isolated Microgrids Based on Renewable Sources: Theory and Application

Isolated microgrids need dispatchable energy sources to ensure continuity of service during lack of the renewable energy sources. One common source is the diesel generator which is used as a backup and for battery charges. Practical experiences have shown that microgrids have operation problems when diesel generators and rectifiers work together to charge battery banks. This is because of resulting diesel generator voltage distortions caused by the interaction of line currents harmonics with equivalent series reactance of the AC source and the notches introduced during the current commutation between 2 SCRs of the bridge rectifier. These distortions eventually inhibit the rectifier operation, causing malfunctioning of the system. One solution is to use generators with rated power greater than the rectifiers, which results in oversized installation and high operating costs. This work proposes a solution to avoid generator oversizing by using resonant filters, notch filter and a capacitive reactive compensation circuit to avoid self-excitation of the generator. Soft-start operation of the rectifier, and disturbance decoupling in the generator are also proposed. The design allows the use of generators and rectifiers of similar power, reducing the installation and operation costs of microgrids. It has been used successfully in two real-life microgrids.

Automated summary

The study proposes a solution to avoid generator oversizing by using resonant filters, notch filter and a capacitive reactive compensation circuit, which has been successfully used in two real-life microgrids, reducing the installation and operation costs.