Lyapunov Function and Sliding Mode Control Approach for the Solar-PV Grid Interface System

Abstract

Abstract-This paper deals with control of a solar photovoltaic (PV) power generating system interfaced with the grid. A sliding mode control approach (SMC) is used for achieving maximum power tracking (MPT) control of solar-PV array. The Lyapunov function-based control approach is designed and modeled for the DC-AC inverter to serve the functions of an active power injection to the grid, balanced grid currents at unity power factor and load currents harmonics compensation. Proposed approaches eliminate the need of adjustment of system parameters under changing loads and generation scenario. The effectiveness of proposed control strategies is established using its stability analyses. The performance of solar-PV power generating system with proposed control algorithms is demonstrated using simulation and experimental studies under various operating conditions. Index Terms-Lyapunov-based function, MPT, PV array, power quality improvement sliding mode control approach, stability analysis. I. INTRODUCTIONENEWABLE energy programs are receiving reasonable attention worldwide to cater the needs of electricity. According to U.S. Energy Information Administration (EIA) reports, the growth rate of such programs is 2.5% per/year [1]. In fact, there is tremendous potential available to produce electricity using the solar energy. The recent trends are indicating increase in capital investments of solar based power projects. Solar photovoltaic (PV) panel generates DC power and hence additional components, such as power converters are instrumental to tie it with the AC grid. Further, solar based power generation is intermittent in nature which varies very rapidly changes in solar irradiation. Therefore, solar based power penetration into grid adversely affects the stability of the network and quality of supply. For the secure and reliable integrations of such solar-PV systems with the grid, different standards are in practice in various countries such as in [2]. To control the operation under these guidelines, solutions have also been reported in the literature using a single-stage inverter [3-4] and two-stage inverter [5][6][7][8].To know which topology is preferred for a typical application, a comparative study has been made in [9]. The single stage topology is considered more efficient due to less number of components. However, two-stage power conversion provides more flexibility in design, operation and control. The DC-DC converter is employed in between solar-PV array and DC link of an inverter and controlled to achieve maximum power tracking (MPT) from a solar PV array.Various control approaches have been reported in the literature to improve the efficiency of solar PV array [10]. Each MPT method has its own advantages and disadvantages. Compared to the existing MPT methods, perturbation and observation is widely used in industry due to its simplicity, but it suffers during rapid solar irradiation change [10][11]. In addition, at steady state, the operating point oscillates around the maximum power point (MPP), which lead...

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