Sliding-mode control of dc/dc converters for photovoltaic systems

Carlos Andres Ramos Paja, Ph.D.
Associate Professor
Universidad Nacional de Colombia
Sede Medellin
Brief Description of the Tutorial:

Photovoltaic (PV) systems are, nowadays, one of the most viable option to supply electrical energy in remote locations due to its reduced maintenance requirements and high portability. Moreover, PV installations are becoming profitable even without governments incentives, however it is needed to reduce the return-of-investment time to make them attractive for consumer level urban applications. This objetive requires to overcome three main problems: reduce the time required to reach the optimal operation condition of the PV source, reject perturbations coming from the load (e.g. grid oscillations) and mitigate the environmental perturbations (e.g. fast charge of solar irradiance).

The sliding-mode control technique is one of the most promising solutions to face those problems due to the following characteristics:

  1. Sliding-mode controllers (SMC) do not require to linearize the model of the dc/dc converter, hence no operating point must be defined for the analysis.
  2. The SMC ensure the global stability of the system, hence a safe operation is ensured.
  3. The SMC generates the semiconductors control signal without PWM circuits, hence a faster response is achieved in comparison with the classical PWM-based linear controllers.
  4. The dynamic response of the PV voltage, i.e. also of the PV power, can be designed.

The tutorial will cover two cases: first, the design of the Maximum Power Point Tracking (MPPT) algorithm to detect, on-line, the optimal operation condition of the PV system; and second, the design of the SMC to follow the MPPT commands. Moreover, a unified design process for both SMC and MPPT controllers will be introduced. Finally, a unified SMC providing both the voltage regulation and MPPT function is described.

The tutorial content is based on recent state-of-the-art works published in Q1 Journal Papers. Moreover, Matlab and PSIM circuital simulations will be used to illustrate the controller performance, and those files will be provided to the tutorial audience with the associated slides.

Brief description of the intended audience:

The topics covered in this tutorial have a wide range of applications including, but not limited to, isolated PV systems (remote locations energy production), mobile applications, grid-connected applications. Moreover, apart from researchers working on photovoltaic systems, also researchers working on fuel cells, battery charger/discharger, wind energy and micro-grids will found valuable methods in this tutorial. The methodology based on practical examples will be suitable for academic researchers and industrial engineers. Finally, the audience should be familiar with the following topics: basic control theory and non-linear circuits such as the dc/dc boost converter. Senior and junior researches, and master and PhD students, will find themselves confortable in this tutorial. undergraduate students will require at least basic knowledge on non-linear mathematics and circuits to attend the course.