Advanced techniques for integration of energy storage and photovoltaic generator in renewable energy systems

In renewable energy systems, the highly intermittent nature of energy sources with the unpredicted nature of load and grid availability make it a great challenge to operate and transition a system seamlessly under large number of modes while still being able to follow the command of the supervisory control. In this work, an advanced control technique is proposed to integrate energy storage elements with intermittent renewable sources that can achieve seamless transitions while implementing the key protections and ability to follow external commands. The proposed control technique is based on instantaneous power balance theory and dynamic power limiter of the energy source, which is implemented in fast local controller and it does not require any exclusive determination of modes. Therefore, under rapid change of source, load, and grid conditions, the proposed system can respond more quickly and make transitions with increased reliability. Furthermore, the conventional techniques for Maximum Power Point Tracking (MPPT) fail to perform efficiently under low insolation level condition and they do not offer accurate yet oscillation free operation at MPP. In this work, an adaptive tolerance band is proposed to achieve highly accurate fluctuation free MPPT under all the operating conditions, and hence, to improve the performance of the integrated system. Simulation and experimental results are presented to validate the proposed techniques.