Dual-Mode Power Operation for Grid-Connected PV Systems with Adaptive DC-link Controller

Abstract

Photovoltaic (PV) power systems are integrated with high penetration levels into the grid. This in turn encourages several modifications for grid codes to sustain grid stability and resilience. Recently, constant power management and regulation is a very common approach, which is used to limit the PV power production. Thus, this article proposes dual-mode power generation algorithm for grid-connected PV systems. The developed system considers the two-stage PV configuration for implementation, where the dual-mode power generation technique is executed within the DC–DC conversion (boost) stage. Most of the techniques adopted for dual-mode power operation employ the conventional perturb and observe method, which is known with unsatisfactory performance at fast-changing atmospheric conditions. Considering this issue, this study suggests a modified maximum power point tracker for power extraction. Furthermore, a new adaptive DC-link controller is developed to improve the DC-link voltage profile at different operating conditions. The adaptive DC-link controller is compared with the traditional PI controller for voltage regulation. The inverter control is accomplished using finite-set model predictive control with two control objectives, namely reference current tracking and switching frequency minimization. The overall control methodology is evaluated at different atmospheric and operating conditions using MATLAB/Simulink software.

Predictive Fixed Switching Maximum Power Point Tracking Algorithm with Dual Adaptive Step-Size for PV Systems

“…To this end, Table 4 gives the values of the THD for the currents. It should be stated that the tuning procedure of the weighting factor is accomplished as discussed in [11]. The two methods are further evaluated according to the required computational load and average switching frequency ( f s ).…”

“…Thus, the modes of the boost converter are clarified in Figure 3. Simply put, the state-space behavior of the boost is characterized by [11].…”

“…It is worth mentioning that the selection of the weighting factor is crucial in the design of the cost function. It should not affect the primary objective of the controller [11]. Figure 7 shows the overall control strategy for the two-stage PV system, where the predictive fixed switching MPPT technique is implemented in the DC-DC conversion stage.…”

“…However, the implementation is very simple without any tuning efforts. Recently, model predictive control has gotten a significant attention, especially the finite-set model predictive control (FS-MPC), in which the optimal switching state of the converter is applied directly according to a predefined cost function [11].…”

Model-Based Maximum Power Point Tracking Algorithm With Constant Power Generation Capability and Fast DC-Link Dynamics for Two-Stage PV Systems

“…Furthermore, the DC-link voltage suffers from undesirable DC offsets due to the gradual or dynamic change of the power at the PV-side. To the best of authors' knowledge, this observation is not addressed before in the two-stage PV system except for [29] (previous publication of the authors). However, only simulation results are provided there.…”