Multifunctional study of single-phase ups with current fed full-bridge converter

Optimal scheduling of the battery energy storage (BES) in a microgrid is presented in this paper. The microgrid model in this paper consists of a photovoltaic (PV) power plant, a wind generator (WG), battery energy storage (BES), load, and diesel generator (DG). BES is required to store the generation excess from renewable energy sources (RES). BES also can store energy from the main grid but optimization is required to decide when to charge and discharge the battery. The optimization goal is to minimize electricity costs when the main grid is available and fuel costs when it is not available. The optimization problem in this paper is a linear programming (LP) problem that is modeled and solved with Python Gurobi. Optimization results are presented for different cases. A DG is used only when the main grid is not available due to the high fuel price. Electricity cost from DG is 5.28 times higher than the cost from the grid for the first case and 4.36 times higher for the second case. There is no generation excess in the second case so the battery is not used when the main grid is not available.

This paper proposes a novel optimal configuration method of distributed generation and energy storage in microgrid. Firstly, K-means clustering method is introduced to formulate the typical days of the output power of renewable generation and load of the microgrid. Secondly, an optimal configuration model of distributed generation and energy storage in microgrid is established with the objective function of minimizing the annual total cost. Then, a hybrid solving strategy combing genetic algorithm, dynamic programming and primal-dual interior point method is proposed. Case studies are carried out on a real-world microgrid in China, and the results show the rationality of the model and the effectiveness of the solving algorithm.

Microgrids are small-scale power networks that include renewable energy sources, load, energy storage systems, and energy management systems (EMS). Lithium-ion batteries are the most used battery for energy storage in microgrids due to their advantages over other types of batteries. However, to protect the battery from the explosion and to manage to charge and discharge based on state-of-charge (SoC) value, this type of battery requires the use of an energy management system. The main objective of this paper is to propose an intelligent control strategy for energy management in the microgrid to control the charge and discharge of Li-ion batteries to stabilize the system and reduce the cost of electricity due to the high cost of grid electricity. The proposed technique is based on a fuzzy logic controller (FLC) for voltage control. The FLC is based on the measured voltage of the direct current (DC) bus and the fixed reference voltage to generate buck/boost converter signal control. The proposed technique has been simulated and tested using MATLAB/Simulink software which illustrates the tracking of desired power and DC bus voltage regulation. The simulation results confirm that the proposed systems can diminish the deviations of the system's voltage.

High electricity consumption in Sarawak’s cities is a concern, driven by residential, industrial, and commercial users. Greater demand for electrical energy requires more electrical resources, affecting grid stability. To prevent blackouts and enhance grid resilience, electric vehicles can serve as distributed energy storage in microgrids. The biggest problem facing energy storage is that not all batteries within energy storage are the same. Every battery cell in the battery pack has a different rate of self-discharge, capacity, internal resistance, and aging, even though they have the same chemical and physical characteristics. These variations lead to power imbalances in energy storage. Therefore, to address this issue, a unique voltage equalization method using a modular flyback converter is presented. Its core objective is to correct voltage imbalances among batteries. The proposed method is modelled using MATLAB, and the performance of the system has been evaluated. Furthermore, the developed model is implemented in a microgrid and tested for two different cases (with and without energy storage for electric cars). From the simulation outcomes, it has been verified that the developed cell balancing technique performs well in equalizing the voltage of cells than the conventional methods.

The increasing use of renewable energy makes balancing generation and demand in power systems more challenging. This has led to a growing focus on battery technologies and energy storage solutions. These systems are essential for the effective integration of renewable energy into sustainable power networks. However, most experimental studies of lithium-ion batteries are limited to deep charge and discharge cycles, which do not fully represent how batteries operate in stationary applications. In these applications, batteries experience not only the main charge and discharge processes but also additional stress from current fluctuations due to the variable nature of renewable energy. These smaller cycles, known as micro-cycles, have a depth of discharge of less than 2% and occur alongside the primary charge and discharge processes. This paper presents the results of an experimental study focused on battery aging, considering micro-cycles that emulate real-world conditions for batteries in microgrid storage systems. It demonstrates that the degradation in storage systems occurs differently when compared to deep charge and discharge cycles. It provides a detailed analysis of the degradation processes occurring in microgrid batteries using EIS diagnostics and post-mortem analysis and demonstrates the applicability of the findings for renewable energy systems.

Because of the intermittence and randomness of renewable energy and the continuous variability of load. By configuring a certain capacity of energy storage in microgrid, the active and reactive power throughput can be flexibly and quickly adjusted to smooth load fluctuations and reliability of power supply improvement. It can improve the power quality and keep the system stable. Therefore, the application potential of distributed energy storage system in microgrid and distribution system is huge. In terms of give full play to the performance advantages of energy storage through distribution system, it is necessary to study the core technologies of modular integration, topology, capacity design and control of energy storage through distribution system. The feasibility and value of energy storage through distribution system in power system engineering are demonstrated. Based on the analysis of relevant requirements, a energy storage through distribution system based on micro energy storage unit is proposed in this paper. This structure is very suitable for energy storage components to be connected to the micro-grid to achieve plug and play, high efficiency, high reliability and high flexibility of energy storage system applications.

In western China, photovoltaic and energy storage microgrid systems are often used to solve local clean energy supply problems. This paper studies the energy management strategy of a typical photovoltaic energy storage microgrid in western China. Propose a novel optimization method of operation strategy based on particle swarm optimization, get the optimal setting scheme of important parameters of the energy management strategy. The historical data of the actual demonstration system is used to simulate and verify the optimized energy management strategy. The simulation results prove that the proposed method can improve the operating effect of the photovoltaic and energy storage microgrid, we can better results in many aspects such as photovoltaic power generation utilization rate, load loss rate, and economy.

In this paper, a two-switch high frequency flyback type zero voltage soft switching PWM DC-DC converter using IGBTs is proposed. Effective applications for this power converter can be found in auxiliary power supplies of rolling stock transportation and electric vehicles. This power converter is basically composed of two active power switches and a flyback high frequency transformer. In addition to these, two passive lossless snubbers with power regeneration loops for energy recovery, consisting of a three winding auxiliary high frequency transformer, auxiliary capacitors and diodes are introduced to achieve zero voltage soft switching from light to full load conditions. Furthermore, this power converter has some advantages such as low cost circuit configuration, simple control scheme and high efficiency. Its operating principle is described and to determine circuit parameters, some practical design considerations are discussed. The effectiveness of the proposed power converter is evaluated and compared with the hard switching PWM DC-DC converter from an experimental point of view.

The design and implementation of an energy-management system (EMS) applied to a residential direct current microgrid (DC-µG) is presented in this work. The proposed residential DC-µG is designed to provide a maximum power of one kilowatt by using two photovoltaic arrays (PAs) of 500 W, a battery bank (BB) of 120 V–115 Ah, a supercapacitor module of 0.230 F and a bidirectional DC–AC converter linked to the AC main grid (MG). The EMS works as a centralized manager and it defines the working operation mode for each section of the DC-µG. The operation modes are based on: (1) the DC-link bus voltage, (2) the generated or demanded power to each section of the DC-µG and (3) the BB’s state of charge. The proposed EMS—during the several working operation modes and at the same time—can obtain the maximum energy from the PAs, reduce the energy consumption from the main grid and keep the DC-link bus voltage inside a range of 190 V ± 5%. The EMS and local controllers are implemented by using LabVIEW and NI myRIO-1900 platforms. Moreover, experimental results during connection and disconnection of each DC-µG sections and different on-the-fly transitions are reported, these results focus on the behavior of the DC bus, which shows the DC bus robustness and stability. The robustness of the DC-µG is demonstrated by maintaining a balance of energy between the sources and loads connected to the DC bus under different scenarios.

South Africa first implemented rolling blackouts known as load shedding to protect the integrity and maintain stability of their ailing electrical grid over a decade ago. Since then, load shedding has become a daily occurrence, which South Africa plans to alleviate through the addition of grid-connected renewable generation. Significant renewable energy (RE) additions can however negatively affect a grid, prompting South Africa to develop RE-specific grid code requirements as mitigation. Given this strategy to address the country’s supply challenges using RE, and the still unknown effects of the country’s aggressive RE integration planned, South Africa must perform the necessary simulations tailored to the country’s unique grid conditions, and local RE-specific grid code requirements to ensure a RE-driven solution are indeed viable. Prompted by the lack of a suitably tailorable simulation platform, this paper proceeds to discuss the development of a tailorable grid code-guided renewable power plant (RPP) behavioral studies testbed. The testing methodology involves feeding grid disturbance event data to an RPP modeled after Eskom’s Sere wind farm in South Africa, which is operated in line with local RPP-specific grid code voltage and frequency requirements to assess the testbed’s grid code-guided RPP operating approach. Results show the testbed to effectively distinguish between grid code-specified no-fault, fault ride-through, and trip conditions, operating the simulated RPP accordingly. Consequently, as compared to comparable RE integration simulation platforms, the reviewed testbed has the potential of producing individualized results, owing to its tailorable grid, RPP, and incorporated grid code guiding specifications.

A microgrid (MG) is a discrete energy system consisting of an interconnection of distributed energy sources and loads capable of operating in parallel with or independently from the main power grid. The microgrid concept integrated with renewable energy generation and energy storage systems has gained significant interest recently, triggered by increasing demand for clean, efficient, secure, reliable and sustainable heat and electricity. However, the concept of efficient integration of energy storage systems faces many challenges (e.g., charging, discharging, safety, size, cost, reliability and overall management). Additionally, proper implementation and justification of these technologies in MGs cannot be done without energy management systems, which control various aspects of power management and operation of energy storage systems in microgrids. This review discusses different energy storage technologies that can have high penetration and integration in microgrids. Moreover, their working operations and characteristics are discussed. An overview of the controls of energy management systems for microgrids with distributed energy storage systems is also included in the scope of this review.

The development of high-penetration photovoltaic power generation is an important measure to realize the energy revolution. With the continuous increase of photovoltaic capacity, the electricity generated by distributed photovoltaic can’t be absolutely integrated to power grid in the future. It is necessary to improve the scheduling requirements for photovoltaic equipment so that the system can be in safe operation. First of all, four scheduling requirements are set for the grid integration of photovoltaic equipment from the perspective of grid scheduling, which is characterized by differentiated scheduling of power and electricity between the micro-grid composed by photovoltaic equipment, energy storage and utility. Then, the capacity optimization planning model of the photovoltaic and energy storage system is established with the minimum power supply cost of the microgrid as the objective function. Finally, through the case study, it is found that industrial and commercial enterprises have the economic motivation to invest in the construction of the photovoltaic and energy storage microgrid, which will strengthen confidence in promoting the rapid development of photovoltaic power generation.

Morocco is one of the pioneering developing countries in the field of energy efficiency policy initiated over the years. Indeed, energy efficiency has become one of the main pillars of the country's energy strategy, especially with the increase in energy prices, the use of renewable energies and preserving the environment. The main objective of this work is to give an idea on the implementation of renewable energies with an energy management system by studying their efficiencies and the impact that certain choices made in a building can have on its energy balance. The historical data of the current system is used to simulate and verify the optimized energy management strategy. The obtained results prove that the proposed system can improve the operating effect of the photovoltaic and energy storage microgrid, we can better results in many aspects such as photovoltaic power generation utilization rate, and economy.

Due to the energy crisis, environmental contamination and other problems related with conventional generations, it is essential to consider the integration of renewable energy, especially wind power. This paper, therefore, outlines the design and study of an interval optimization model to determine optimal wind capacity in an existing power grid. Interval wind capacity factor is proposed to analyze and propagate the uncertainty of wind resources. This model aims at minimizing the overall cost including the variable cost of coal-fired generation, start-up/shutdown cost of generation units, capital investment of wind farm, reserve cost, penalty cost of wind curtailment and fixed operational cost of wind power. The effectiveness of the proposed model is validated by its application in a real-life power grid. Compared with previous research, this method can aid power system planners to make decisions about wind capacity considering the possibilistic uncertainty of wind resource.

An alternative control design for dc-links used to connect distributed energy resources (DERs) with the main power grid, is proposed and studied for its stability. As DERs are considered to be weak, unpredictable power sources, ac voltage regulation is applied at the side of DER connection while at the grid side, dc voltage and reactive power control is implemented. The challenging issue of achieving these tasks effectively through the design of a rather simple control scheme is examined in this paper. While the traditionally proposed techniques involve parameter-dependent controllers in order to make possible simple linear designs, in this paper, the proposed controllers are clearly simpler ones, parameter-free of proportional-integral (PI) type, but require a more complicated and advanced nonlinear analysis. To that end, incorporating the controllers into the nonlinear dc-link model, the closed-loop system is analyzed by applying advanced Lyapunov techniques combined with input to state stability notions. As shown in the paper, stability and convergence to the equilibrium is guaranteed while the extended simulations presented, fully verify the theoretical analysis.