Photovoltaic Based DC Microgrid Research Articles

Voltage Stability in a Photovoltaic-based DC Microgrid with GaN-Based Bidirectional Converter using Fuzzy Controller for EV Charging Applications

Electric vehicles are growing in importance owing to their desirable characteristics leading to utilization. It is a significant challenge to maintain voltage for DC microgrids when integrating with EVs. The work aims to enhance voltage stability in a DC microgrid and the electric vehicle charging using GaN devices in the converter. This is done by developing a DC microgrid with better voltage regulation, loss reduction, and increased efficiency and these are analyzed using PLECS software. Under different operating conditions, the proposed converter can respond to load fluctuations and maintain its voltage profile stable. The approach meets the increasing demand for vehicle charging by upgrading DC microgrid technology. The use of GaN-based converters improves voltage stability while allowing for efficient integration of EVs into the grid thereby giving more options for transportation.

A Photovoltaic-Based DC Microgrid System: Analysis, Design and Experimental Results

Due to the exhaustion of fossil energy, the utilization of renewable energy resources is developing quickly. Due to the intermittent nature of the renewable energy resources, the energy storage devices are usually adopted in renewable power generation system to enhance the system reliability. In this paper, the photovoltaic-based DC microgrid (PVDCM) system is designed, which is composed of a solar power system and a battery connected to the common bus via a boost converter and a bidirectional buck/boost converter, respectively. As the photovoltaic (PV) panels might operate in a maximum power point tracking (MPPT) mode or constant voltage mode, meanwhile, the power can flow between the battery and the load bidirectionally. Therefore, for the sake of optimizing power utilization in the PVDCM system, a control strategy making the system able to switch from one operating mode to another smoothly and automatically is proposed in this paper. Moreover, the small-signal modeling method based on averaged state-space is no more applicable in this study, thus the nonlinear analysis method with discrete-time mapping model is adopted for stability analysis. Based on the stability analysis, the closed-loop parameters are designed to make sure the whole system can operate properly in all operating modes. The control strategy and stability analysis based on the nonlinear analysis method in the closed-loop design are verified by experiment results.

Evaluation of a Communication-Assisted Overcurrent Protection Scheme for Photovoltaic-Based DC Microgrid

Integration of distributed generations units in distribution systems affects the amplitude and the direction of fault currents. On the other hand, dc fault currents have large amplitude and fast transients. Thus, the setting and coordination of overcurrent relays in dc microgrids will be a challenging issue. This paper proposes a new communication-assisted overcurrent protection scheme for photovoltaic (PV)-based dc microgrids. The proposed scheme has lower cost than the schemes based on the differential protection and also provides the backup protection for the relays. First, possibility of using the overcurrent-based protection is evaluated using a comprehensive strategy for every line section of the system. The strategy determines which relays have to be set for protection of the microgrid in the grid-connected and islanded operation modes. Then, the selectivity and coordination problems of the overcurrent relays in the presence of the PV units are solved by implementing blocking and intertripping schemes using communication infrastructures of the smart grids. Finally, the proposed protection scheme is validated by simulation results on a dc microgrid test system.

Photovoltaic-based DC microgrid with partial shading and fault tolerance

Partial shading is a common problem that affects bus regulation in DC microgrids with several photovoltaic (PV) modules as energy sources, as a result of reduced solar irradiance reaching the modules. The problem can be mitigated by incorporating batteries, but if they are not included, appropriate control strategies must be used. This paper presents a new approach in a PV-based DC microgrid, which provides a high quality bus voltage regulation in islanding mode, without being affected by partial shading or problems associated with PV module connection and disconnection. The solution proposed herein ensures a proper voltage regulation without being affected by problems such as failures in PV modules or mismatch between them. Besides, it can help to prevent PV partial shade stress by disconnecting the modules affected. A further advantage of the approach is the flexibility to connect more PV modules. The advantages of this approach were verified in a 200 W prototype.

Fault Detection and Location of Photovoltaic Based DC Microgrid Using Differential Protection Strategy

A new differential current-based fast fault detection and location scheme for multiple Photovoltaic-based dc microgrid is proposed in this paper. A multiterminal dc (MTDC) distribution network is an effective solution for present grid scenario, where local distribution is incorporated primarily by power electronics based dc loads. PV systems with auxiliary power sources and local loads are used for MTDC connection, especially when ac utility grid is integrated with it by voltage source converters. Pole to pole and pole to ground faults are basically considered as dc distribution network hazards. As PV is connected through dc cable, high resistive dc arc fault is also studied in present literature. The proposed PV system is considered with arc-fault circuit interrupters as backup protection and is used to detect arcing series fault. Fast acting dc switching is considered for proposed differential current-based unit protection. A discrete frame differential current solution is considered to classify the fault type by modified cumulative sum average approach. By calculating unknown dc cable resistance accurately by non-iterative Moore-Penrose pseudo inverse technique, the fault distance is calculated. TMS320C6713 DSP based test-bench is used for verification of the scheme.

Energy management in DC microgrid with energy storage and model predictive controlled AC–DC converter

Renewable energy-based direct current microgrids are becoming popular due to their higher energy efficiency than AC microgrids. Energy storage system (ESS) helps to stabilise the system against the instability caused by stochastic nature of the renewable sources as well as demand variation within a microgrid. This work proposes effective energy management and control techniques for a photovoltaic-based DC microgrid. In order to regulate power exchange with the main grid, model predictive controller (MPC) is proposed to control bidirectional voltage source converter. The performance of MPC is compared with classical PI controller. Frequency approach control of hybrid ESS comprising of battery and supercapacitor is used to suppress both low- and high-frequency power variation in the microgrid by exchanging power with DC bus. To confirm the efficacy of proposed control strategy, real-time simulations of the system are carried out considering both grid-connected and islanded modes of the microgrid operation. The results show the effectiveness of the proposed control strategy for energy management in the microgrid. Further, real-time controller hardware-in-the-loop experiment validates the simulation results.