A Robust Dynamic Control Strategy for Standalone PV System under Variable Load and Environmental Conditions

Abstract

Dual-stage standalone photovoltaic (PV) systems suffer from stability, reliability issues, and their efficiency to deliver maximum power is greatly affected by changing environmental conditions. A hybrid back-stepping control (BSC) is a good candidate for maximum power point tracking (MPPT) however, there are eminent steady-state oscillations in the PV output due to BSC’s recursive nature. The issue can be addressed by proposing a hybrid integral back-stepping control (IBSC) algorithm where the proposed integral action significantly reduces the steady-state oscillations in the PV array output under varying temperature and solar irradiance level. Simultaneously, at the AC stage, the primary challenge is to reduce both the steady-state tracking error and total harmonic distortion (THD) at the output of VSI, resulting from the load parameter variations. Although the conventional sliding mode control (SMC) is robust to parameter variations, however, it is discontinuous in nature and inherit over-conservative gain design. In order to address this issue, a dynamic disturbance rejection strategy based on super twisting control (STC) has been proposed where a higher order sliding mode observer is designed to estimate the effect of load disturbances as a lumped parameter which is then rejected by the newly designed control law to achieve the desired VSI tracking performance. The proposed control strategy has been validated via MATLAB Simulink where the system reaches the steady-state in 0.005 s and gives a DC–DC conversion efficiency of 99.85% at the peak solar irradiation level. The AC stage steady-state error is minimized to 0 V whereas, THD is limited to 0.07% and 0.11% for linear and non-linear loads, respectively.

Maximum Power Point Tracking Algorithm of Photo-Voltaic Array through Determination of Boost Converter Conduction Mode

“…For larger systems, the use of string inverters and a central inverter is preferred [13,14]. Standalone PV systems, on the other hand, work without needing to be connected to a grid, and are capable of supplying electricity in the absence of a grid using excess energy stored in a battery [15,16]. This implies that the requirement of energy storage is imperative for such PV solutions.…”

Study and Implementation of a High-Quality True Sine Wave DC-to-AC Inverter for Solar Power Generation Systems

“…However, they are mathematically complex and computationally time consuming [ 27 , 28 , 29 ]. Recently, the improved sliding mode reaching law (ISMRL) has provided a terminable system state convergence time to reject the steady-state error (i.e., the terminable time for the system trajectory to reach the sliding mode region in the presence of uncertainty) [ 30 , 31 , 32 , 33 , 34 , 35 , 36 , 37 , 38 , 39 , 40 , 41 ]. However, it should be noted that even if ISMRL makes the solar power generation system achieve the expected control effect, it is easy for the solar array to become partially shielded by buildings, trees, dust, etc.…”

Effective dynamic disturbance rejection scheme based on higher order sliding mode control for DC-AC inverter under load variation

“…Voltage source inverter (VSI) is widely employed in power generation systems, [1][2][3] uninterruptible power supplies, 1,4 electric vehicles systems (EVS), 5 and renewable energy systems, 6,7 in order to supply power to the variety of loads. In these applications, accurate regulation of the inverter output voltage and current are of significant importance.…”

“…Some of the important factors that degrade the inverter output performance in these applications include inverter non-linear dynamics, sudden load changes, measurements errors, actuator degradation, electromagnetic interference, etc. [1][2][3][4][5][6][7] These disturbances cripple the inverter's output voltage and degrade the control performance, which results in high harmonic content and steady-state error in the output 8,9 that may cause damage to the application systems. Therefore, it is important to design an inverter control scheme that will be robust enough to withstand the disturbances resulting from load fluctuations such that the steady-state error performance can be improved, thereby minimizing the total harmonic distortion.…”