Energy Storage System State Of Charge Research Articles

Energy Management System of Microgrid using Optimization Approach

Microgrid technology can efficiently integrate a new practical way for large-scale application of grid-connected generation of renewable energy. An Energy Management System (EMS) in microgrid, is important for optimum use of the distributed energy resources in smart, protected, consistent, and synchronized ways. This paper discusses the management of Energy Storage System (ESS) connected in a microgrid with a solar array and control the battery discharge and charge operations with converter based on the necessity of the demand. Problem for one-day energy management of microgrid is discussed. This paper focuses on analyzing of heuristic and optimization approach for minimizing total variable electricity prize for clear and cloudy day. The output variables like power of PV, grid, ESS, and loads, grid voltage, ESS state of charge and price graphs are analyzed for each case. The MATLAB software is used for simulating this case study.

Research on Control Strategy of Isolated DC Microgrid Based on SOC of Energy Storage System

With the rapid development of renewable energy technologies, islanded DC microgrids have received extensive attention in the field of distributed power generation due to their plug-and-play, flexible operation modes and convenient power conversion, and are likely to be one of the mainstream structures of microgrids in the future. The islanded DC microgrid contains multiple distributed power generation units. The battery energy storage system (BESS) is the main controlled unit used to smooth power fluctuations. The main parameter of concern is the state of charge (SOC). In order to maintain the stability of the microgrid, this paper takes the islanded DC microgrid as the research object and designs a control strategy based on the SOC of the BESS. Additionally, in the control strategy, the BESS’s energy balance control strategy and the microgrid’s operation control strategy are emphatically designed. The designed BESS control strategy adjusts the droop coefficient in real time according to the SOC of the battery energy storage unit (BESU), and controls the charge and discharge power of the BESU to achieve the SOC balance among the BESUs. The microgrid operation control strategy takes the energy storage system (ESS) as the main controlled unit to suppress power fluctuations, and distributes the power of distributed power sources according to the SOC of the BESS to achieve power balance in the microgrid, and control the DC bus voltage fluctuation deviation within 4.5%.

Coordinated LVRT Control for a Permanent Magnet Synchronous Generator Wind Turbine with Energy Storage System

This study introduces a coordinated low-voltage ride through (LVRT) control method for permanent magnet synchronous generator (PMSG) wind turbines (WT) interconnected with an energy storage system (ESS). In the proposed method, both the WT pitch and power converters are controlled to enhance the LVRT response. Moreover, the ESS helps in regulating the dc link voltage during a grid fault. Previous LVRT methods can be categorized into strategies with or without an additional device for the LVRT. The latter scheme is advantageous from the perspective of no additional installation cost; in this case, pitch and converter controllers are used. Meanwhile, the former method uses an additional device for LVRT operation and hence, involves additional expense. However, it can effectively enhance the LVRT response by reducing the LVRT burden on the WT. Moreover, the additional device can be used for various WT power control applications and it is common that the ESS is interconnected to the WT for multiple objectives. Previous studies focused on these two aspects separately; hence, a method of coordinated control for an ESS and a WT is needed as more ESSs are required to connect to WTs for flexible wind power operation. The proposed method introduces a control method with different LVRT modes considering the ESS state of charge (SoC). When the WT does not have a sufficient inertial response operation range, the ESS reserve energy capacity is required for LVRT operation. This coordinated LVRT method employs both the WT and ESS controls when it is hard to handle the LVRT using the WT control alone at high wind speeds. In this case, power curve analysis is used to obtain the appropriate power reference during the fault period. In addition, a power reference is also used to ensure a safe operation. Using the proposed method, an ESS can be operated in a manner that is appropriate for WT operation, especially at high wind speeds. To validate the effectiveness of the proposed method, we considered two case studies. One study compares the LVRT response between the WT itself and the proposed method. The other research work compares the response of the conventional LVRT method that uses a WT and an ESS and with that of the proposed method. From these case studies, we concluded that the proposed method achieved a better performance while operating within the constraints of the WT rotor speed and ESS SoC limits.

Coordinated Fuzzy-Based Low-Voltage Ride-Through Control for PMSG Wind Turbines and Energy Storage Systems

Coordinated control methods involving a wind turbine (WT) and an energy storage system (ESS) have been proposed to meet several objectives, such as smoothing wind power (WP) fluctuations, shaving peaks, enabling power scheduling, and allowing low-voltage ride-through (LVRT). LVRT requirement is defined by grid operators, and it should be satisfied whenever grid faults occur. Several methodologies have been proposed for the LVRT both with or without the use of an ESS. Furthermore, using an ESS is more advantageous for several WP applications. By using an ESS, WTs can be operated in a more economic and reliable way. However, the installation cost of an ESS is high and it has operation range constraints for charging and discharging. Moreover, the WT operation condition and ESS state-of-charge (SoC) can be different when a grid fault occurs. Therefore, it is necessary to coordinate both units, WT and ESS, for reliable and economic operation during a grid fault. Thus, we propose a coordinated fuzzy-based LVRT method that considers the different operation conditions of a WT and an ESS. From the proposed method, the effective reference powers of a WT and an ESS are evaluated by considering the rotor speed and SoC in the fuzzy control algorithm. The effectiveness of the proposed method is validated by considering two case studies on ESS SoC and WT rotor speed violations.

Quantifying cumulative effects of stochastic forecast errors of renewable energy generation on energy storage SOC and application of Hybrid-MPC approach to microgrid

Energy storage system (ESS) is crucial for microgrid to mitigate adverse impacts of renewable energy generation by participating in primary frequency regulation. In previous studies, research on evaluating the cumulative impacts of stochastic forecast errors (SFE) of renewable energy generation on the variance of SOC (state of charge) of ESS is lacking. This paper presents quantification models of the impacts of SFE on the variance of SOC of ESS. Novel SFE propagation and accumulation models are introduced. The effects of dispatch control and droop control on ESS at different time scales are comprehensively considered. The mechanism of ESS working from a stable state to an unstable state owing to SOC deviation is demonstrated. Then aiming at solving the problem that ESS is forced to quit operation owing to SOC deviation, an online hybrid model predictive control (Hybrid-MPC) based strategy is proposed. Hybrid-MPC consists of two hierarchies: one is decreasing horizon rolling optimization which is specially for handling small SFE and the other is heuristic cooperative control which is designed to tackle large SFE. Besides, feedback correction is applied to change the real-time operation status of microgrid in time. Finally, the strategy is tested in a self-developed program named microgrid real operation simulation (MG-ROS).

Adaptive Coordination for Power and SoC Limiting Control of Energy Storage in an Islanded AC Microgrid With Impact Load

Isochronous controlled battery energy storage system (ESS) can maintain constant frequency in an islanded ac microgrid, but its power and state of charge (SoC) may go beyond limit due to intermittent renewable energy resources and impact load change. This paper introduces a control strategy integrated with bang-bang and backlash mechanism to coordinate distributed energy resources (DERs). When overloading will take place, ESS will change from isochronous control to droop control, with droop gain varying based on bang-bang control, by which the overloaded power will be spontaneously transferred from ESS to other DERs. Moreover, frequency will be automatically restored when impact load disappears, which eliminates the effort of secondary frequency control. When SoC of ESS comes to limit, the diesel generator will change from droop control to isochronous control, whereas ESS will adopt virtual inertia and grid-supporting droop control to help stabilize frequency. A backlash mechanism is also employed to latch the control mode near SoC limit. Comprehensive tests on real-time simulator demonstrated the effectiveness of the proposed control strategy.

Decentralized Fuzzy Logic Control of Microgrid for Electric Vehicle Charging Station

As already happens with the electric vehicles (EVs) expansion, technology associated with their charge also must be improved. This paper presents a novel decentralized control method (DCM) for charging stations (CSs) based on a medium-voltage direct current (MVDC) bus. This kind of CSs is integrated in a microgrid with a photovoltaic system, a battery energy storage system (ESS), a local grid connection, and two units of fast charge. The main contribution of this paper resides in the cited DCM based on fuzzy logic that includes the state of charge (SOC) of the battery ESS as a control variable. This control contains two independent fuzzy logic systems (one for the battery ESS and other for the grid), whose function is to maintain the MVDC voltage and the battery ESS SOC within proper thresholds and to keep the power balance stable among the units of fast charge and the rest of the CS components. The new control method was tested in a considerable number of operating situations (two hundred cases studied) under different conditions of sun irradiance, initial SOC of battery ESS, and number of EVs connected to the CS with the objective of showing its correct performance in all the considered scenarios.

New Power Management Strategies for a Microgrid with Energy Storage Systems

The combination of cascade control and local control is proposed as a method to compensate power fluctuations caused by load and renewable energy sources in a microgrid with distributed power generation systems- (DGs).The use of energy storage system(ESS) such as EDLC facilitates power ompensation. However, since the energy capacities of these components are limited, the contol of their state of charge(SoC) is necessary. This paper addresses real and reactive power management strategies of electronically interfaced distributed generation(DG)units in the context of a multiple-DG microgrid system,and a new method to control ESS's SoC which would enable power compensation with less energy capacity and with less effect to the compensation result is proposed.