Control of Transformerless Inverter-Based Two-Stage Grid-Connected Photovoltaic System Using Adaptive-PI and Adaptive Sliding Mode Controllers

Abstract

To enhance the move towards a sustainable society, the solar Photovoltaic (PV) industry and its applications are progressing at a rapid rate. However, the associated issues need to be addressed when connecting PV to the grid. Advanced and efficient controllers are required for the DC link to control the second harmonic ripple and current controllers to inject quality active and reactive power to the grid in the grid-connected PV system. In this paper, DC-link voltage, active power, and reactive power are successfully controlled in stationary reference using Adaptive-PI (A-PI) and Adaptive-Sliding Mode Controller (A-SMC) for a 3 kW single-phase two-stage transformerless grid-connected inverter. A Resonant Harmonic Compensator (RHC)-based Proportional Resonant (PR) controller is employed in the current-controlled loop. The magnitude, phase, and frequency information of the grid voltage are provided by Second-Order General Integral (SOGI)-based PLL that has harmonic immunity, fast-tracking accuracy, and a rapid-dynamic response. MATLAB®/Simulink®/Simscape R2017b were used for the test bench implementation. Two scenarios were considered: in the first case, the input PV power feedforward loop was avoided, while in second case, it was included. The feedforward loop of input PV power improved the overall system dynamics. The results show that the designed controller improves both the steady-state and dynamic performance as compared with a proper-regulated PI-controller. The proposed controllers are insensitive to active and reactive power variations, and are robust, stable, faster, and fault tolerant, as compared to controllers from prior studies.

Maximum power point tracker using an intelligent sliding mode controller of a photovoltaic system

“…Once the MPP is attained, the PV array operation is sustained at that point and the disturbance is stopped unless a change in dIPV is noted. In this case, the algorithm decrement or increment the VPV voltage of the PV array to track a new MPP [20], [21]. The size of the increment determines the rate at which the MPP is tracked.…”

Design and Performance Evaluation of a Step-Up DC–DC Converter with Dual Loop Controllers for Two Stages Grid Connected PV Inverter

“…The most important part in the 2nd stage is the control of the inverter that is implemented in the form of two cascaded loops, i.e., inner and outer loop. In the proposed model, the dual loop control architecture is implemented using a stationary reference frame (αβ), as presented in Figure 8 [27]. The voltages and currents are transformed from abc frame to αβ frame as: Initially, the measured DCL voltage is compared with the reference to generate an error.…”

Design of an On-Grid Microinverter Control Technique for Managing Active and Reactive Power in a Microgrid

“…The phase angle of the grid voltage must be calculated in real time to define the power ratio between the grid and the inverter [28]. In this investigation, the second-order generalized integrator (SOGI)based phase-locked loop (PLL) is implemented (Figure 13) because it presents harmonic immunity, a fast tracking accuracy, and a rapid dynamic response [6]. The phase detector is composed of an orthogonal signal generator and obtains the Park transform of the waves to detect the components q and d in the rotating reference frame.…”

“…Another study related to active and reactive power control techniques for two-stage on-grid inverters in a photovoltaic system was presented in [6]. In this case, the DC link voltage, active power, and reactive power were successfully controlled with an adaptive-PI and adaptive-sliding-mode controller.…”