On the modelling, analysis, and design of a suboptimal controller for a class of wind/PV/battery based DC microgrid

Abstract

This study deals with the comprehensive modelling, analysis, and control of a DC microgrid (MG) in islanded mode. The proposed DC MG comprises a wind turbine, a photovoltaic (PV) source, battery storage, DC/DC source, and load side converters with DC loads. To this aim, a circuit‐oriented modelling of the whole system is developed. The PV source is modelled with a single‐diode electrical circuit. Afterward, a mathematical model of the system with state‐space representation was derived. A detailed analysis of PV system design is performed because the parameters of PV are appearing in the dynamic model of DC MG. For the purpose of controller development, the dynamic model of the DC MG, which is modelled by a non‐linear‐non‐affine eight‐order system, is linearized around an equilibrium point using the Jacobian matrix framework, while stability using eigenvalue is carried out showing that the stability is guaranteed under operating condition. Finally, for the first time, the state‐dependent Riccati equation (SDRE) technique is proposed to find the optimal regulation problem for the DC MG with non‐linear‐non‐affine dynamics. The numerical simulation studies first confirm the validity of the performed mathematical, then the effectiveness of the proposed non‐linear controller is evaluated under illumination and load change.

Accurate voltage regulation for a DC microgrid using nonlinear state feedback controller

“…In recent years, a growing trend toward renewable energy sources (RESs) has emerged, driven by factors such as the continuous depletion of fossil fuels, cost-related barriers, and increasing electricity demand [1][2][3]. Wind and solar power, in particular, have gained significant attention due to their rapid cost reductions over the past decade.…”

Research on fast frequency response to AC grid of a battery‐free MVDC system incorporating a high proportion of distributed photovoltaic generation units with reserve capacity

“…In summary, it can be seen that although distributed PV power systems with energy storage systems can utilize the charging and discharging process of energy storage systems to quickly output the stored power to provide support capability for AC grid, the high cost of energy storage equipment and maintenance costs can increase the total investment in the system. Therefore, it is necessary to let a DPVGU operate in a way of power reduction [15], not functioning at MPP, which is capable of adjusting its output power within a narrow range [16], so as to respond the power needs of the system. Literature [17] proposed a constant voltage control (CVC) strategy of the PV power generation system, when the output power of PV panels is greater than that required by the loads and the battery is fully charged.…”

“…If AC grid does not provide the DC voltage reference value, it is necessary for DPVGUs to maintain the MVDC bus voltage stabilisation while retaining the reserved power required by the system. When the frequency deviation of AC power grid exceeds the frequency regulation action threshold, the MVDC system can actively transmit some or all of the reserved power to AC grid through MMC to provide fast frequency support [21]. Thus, it is necessary to investigate how DPVGUs leave the reserved power according to the system requirements through coordinated control strategies and how to utilize the reserved power to provide support for AC grid.…”

Modular DC‐DC converter with reduced current ripple and low voltage stress suitable for high voltage applications

“…Moreover, connecting power supplies with lower dc voltages to the distribution networks with higher voltages (1.1 kV, 2.2 kV, etc.) through these converters can be considered as other applications of such converters 6 …”

“…through these converters can be considered as other applications of such converters. 6 A key factor in classifying high step-up dc-dc topologies is electrical connections between their components, which can be categorized into two stages: non-isolated and isolated converters. However, the existence of complicated highfrequency transformers in the structure of the isolated converters causes employing the non-isolated techniques are considered more efficient: on condition that the isolation is unnecessary.…”