A simplified time-domain design and implementation of cascaded PI-sliding mode controller for dc-dc converters used in off-grid photovoltaic applications with field test results

A time-domain design methodology for voltage regulation control of dc-dc boost and buck-boost converters based on a multi-loop controller with PI regulator for the outer loop and an inner loop with sliding mode current controller has been developed for renewable energy applications such as photovoltaic (PV)-fed dc-dc converters. This paper proposes a new method for the design of PI regulators in such multi-loop control scheme. The proposed design presents a simple analytical method for selecting controller gains and has been validated by simulation as well as hardware implementation. Also, this paper presents an illustrative example based on the proposed design for the voltage regulation control of PV-fed boost converters for off-grid applications. The simulation results for varying irradiation, temperature and load along with stability analysis have been presented in this paper. The proposed controller is implemented in hardware for a 1.1 kW PV-array-fed boost converter. Performance analysis based on field test results using real-time weather data validates the proposed design. Therefore the proposed controller could be considered as an attractive solution for off-grid renewable energy applications like PV- or fuel-cell-fed dc-dc converter, where the variations are stochastic in nature.