Improved Design of Sliding-Mode Controllers Based on the Requirements of MPPT Techniques

• Published in: IEEE transactions on power electronics Vol. 31; no. 1; pp. 235 - 247
• Main Authors: Gonzalez Montoya, Daniel, Ramos-Paja, Carlos Andres, Giral, Roberto
• Format: Journal Article
• Language: English
• Published: New York IEEE 01.01.2016; The Institute of Electrical and Electronics Engineers, Inc. (IEEE)
• Subjects: Algorithm design and analysis; Algorithms; Arrays; Capacitors; Controllers; Design engineering; Direct current; Electric currents; Electric potential; Inverters; Mathematical models; Nonlinear equations; Simulation; Switches; Switching; Voltage; Voltage control; Nonlinear control systems; maximum power point tracker; photovoltaic system; sliding mode control; DC-DC power converter
• ISSN: 0885-8993; 1941-0107
• DOI: 10.1109/TPEL.2015.2397831

In many grid-connected applications, a dc/dc switching converter is usually connected between the PV modules and the inverter. This paper presents an improved procedure to design a sliding controller for the PV system, which drives the PV voltage to follow a reference provided by an external MPPT algorithm and mitigates the perturbations caused by the irradiance changes and oscillations in the bulk voltage. By considering that the switching surface is the linear combination of the input capacitor current and the PV voltage error, the proposed design exhibits advantages in comparison with existing solutions that rely in the linearization of inner current loop dynamics. The proposed integral procedure, by taking also into account the effects in the closed-loop system dynamics of a reference filter, ensures a stable sliding regime in all the desired operation range of the system, while the settling time and overshoot of the PV voltage required by an MPPT algorithm are provided. Differently from a previous similar but less rigorous approach, the switching function and reference filter parameters are obtained by numerically solving a set of nonlinear equations. Simulations and experiments were used to demonstrate the efficiency of the proposed solution in presence of environmental and load perturbations.