3. Mitigation of Destabilizing Effects of CPL in a Boost Converter Feeding Total CPL

In dc microgrids, a dc/dc boost converter is usually required to interface renewable energy sources (solar PV, fuel cells etc.) to the dc bus or to meet the high voltage requirement of certain loads. In such situations, due to tight regulation of downstream power converter and the presence of other electronic loads, the equivalent load to the boost converter may exhibit CPL behaviour. In this chapter, the mitigation of CPL induced instabilities in a boost converter is addressed using a robust SMC designed using novel nonlinear switching functions. A PWM based SMC is presented to mitigate the destabilizing effects of CPL in a boost converter supplying a CPL. The existence of sliding mode and large-signal stability of the system are proved. The effectiveness of the controller is validated through simulation studies and experimental results under different operating conditions. Furthermore, a modified nonlinear switching function is proposed which incorporates tight voltage regulation capability. The modified nonlinear switching function, having inherent characteristics to ensure supply of constant power to CPL and output voltage regulation, is then used to design a discontinuous sliding mode controller. The existence of sliding mode and stability of the switching function are proved. A limit on the CPL power is established to ensure system stability under different operating conditions. The performance of the proposed controller is validated through real-time simulation results under sufficiently wide variations in the input voltage and the load.