Energy management system using load following- terminal slide mode control strategy in DC microgrid with hybrid energy storage system

Smart Energy Management and Power Flow Control for Multi-Microgrids Interfacing with Utility Grid

Fuzzy logic and state machine control-based hybrid energy management system of power sharing with smart mode-transition for DC microgrid

In this paper, a nonlinear decentralized double‐integral sliding mode controller (DI‐SMC) is designed along with an energy management system (EMS) for the DC microgrid (DCMG). This DCMG includes having a hybrid energy storage system (HESS) that incorporates a battery energy storage system (BESS) and supercapacitor energy storage system (SCESS) while the load demand is met through the power generated from solar photovoltaic (SPV) units. First, dynamical models of each subsystem of DCMGs such as the SPV system, BESS, and SCESS are developed to capture highly nonlinear behaviors of DCMGs under various operating conditions. The proposed nonlinear DI‐SMC is then designed for each power unit in DCMGs to ensure the desired voltage level at the common DC‐bus and appropriate power dispatch of different components to fulfill the load requirement of the DCMG. On the other hand, an energy management system (EMS) is designed to determine the set point for the controller with an aim of ensuring the power balance within DCMGs under various operating conditions where the overall stability is assessed using the Lyapunov theory. Simulation studies along with the processor‐in‐loop validation, including a comparative study with a proportional‐integral (PI) controller, verify the applicability and effectiveness of the EMS‐based DI‐SMC under different operating conditions of the DCMG.

Research carried out in this paper proposes a reduced sensor energy management system (EMS) for a DC microgrid with a hybrid energy storage system (HESS). The proposed system ensures continuous power supply to loads in a DC microgrid. The EMS considers the renewable power variation, availability of grid, state of charge of HESS and changes in local loads. without measuring load currents / powers, this system can detect the operating mode of system. In the proposed system, current stress on a battery can be reduced by supercapacitor and better DC link voltage regulation is achieved. The EMS also addresses extreme operating conditions such as load shedding, off-MPPT operation of PV, elimination of critical oscillation of HESS powers. With the time domain simulation studies, the performance of the proposed EMS is verified.

Power demand all around the world is increasing day by day and conventional energy sources are getting depleted. In order to meet the power demand and to reduce the carbon emission caused by the conventional energy sources, alternate renewable energy sources are important. wind and solar are two reliable energy sources among the various renewable energy sources. In this proposed paper wind and photovoltaic (PV) energy-based direct current (DC) microgrid is proposed with super capacitor and battery hybrid energy storage systems. Constant DC link voltage is the replication of energy balance in DC microgrid. The main goal of the proposed microgrid energy management algorithm is to maintain the constant DC link voltage irrespective of the intermittent nature of the renewable energy sources, load variations and under fault conditions. Energy management system is designed such that battery energy storage system handles the average power requirements and super capacitor handles the transient power requirements caused by the load, renewable energy variation and also caused due to fault conditions. The proposed system improves battery life along with effective DC link voltage regulation. The proposed control algorithm of energy management is compared with conventional energy management system in MATLAB/Simulink and presented for various studies.

Nonlinear integral backstepping based control of a DC microgrid with renewable generation and energy storage systems

This paper introduces an improved decentralized control strategy for a photovoltaic (PV) hybrid energy storage (HES) system (HESS) in a DC microgrid. The power sharing method of the HES system is discussed in depth. The basic principle of virtual resistance and capacitance droop (VRCD) control, which consists of virtual resistance droop (VRD) and virtual capacitance droop (VCD) control, is analyzed in detail to achieve the decoupling of the HES system for high- and low-frequency load power distribution. For the virtual capacitance control loop, the voltage compensator is added to achieve terminal voltage restoration of the supercapacitor (SC). For the virtual resistance control loop, in order to solve the problems of the unbalanced state of charge (SOC) of battery storage, a virtual resistance droop control based on a novel adaptive function is introduced. Finally, a model of the HESS in a DC microgrid is built in a real-time emulator to verify the effectiveness of the proposed control strategy.

A direct current (DC) microgrid containing a photovoltaic (PV) system, energy storage and charging reduces the electric energy conversion link and improves the operational efficiency of the system, which has a broad development prospect. The instability and randomness of PV and charging loads pose a challenge to the safe operation of DC microgrid systems. The safety of grid operation and charging need to be taken into account. However, few studies have integrated the safety of charging devices with grid operation. In this paper, a two-level control strategy is used for the DC microgrid equipped with hybrid energy storage systems (ESSs) with the charging equipment’s safety as the entry point. The primary control strategy combines the health of the charging equipment with droop control to effectively solve the problem of common DC bus voltage deviation and power distribution. The consistency the control algorithm for multiple groups of hybrid ESSs ensures the local side DC bus voltage level and ensures reasonable power distribution among the ESSs. The simulation results in MATLAB/Simulink show that the control strategy can achieve power allocation with stable voltage levels in the case of fluctuating health of the charging equipment, which guarantees the safe operation of the microgrid and charging equipment.

Islanded DC microgrids composed of distributed generators (DGs), constant power loads (CPLs), parallel converters, batteries and supercapacitors (SCs) are typical nonlinear systems, and guaranteeing large-signal stability is a key issue. In this paper, the nonlinear model of a DC microgrid with a hybrid energy storage system (HESS) is established, and large-signal stability criteria are obtained. The HESS consists of batteries and SCs. The derived criteria reveal the influences of the filter parameters, CPL power, DG power and the proportional control parameters of the battery converter and the SC converter on the system large-signal stability. Furthermore, important large-signal stabilization methods for regulating the HESS converter’s control parameters can easily achieve the large-signal stabilization of islanded DC microgrids without extra equipment. The paper is summarized as follows: First, the topology of and control strategy for a DC microgrid with an HESS and CPLs are proposed. Then, according to the characteristics of the HESS, the DGs and the CPLs, the system is equivalently simplified. Finally, the nonlinear model and large-signal stability criteria are both derived using the mixed potential theory, and a large-signal stabilization design method for the HESS converter’s control parameters is proposed. The experimental and simulation results show the effectiveness of the proposed large-signal stabilization method.

Hybridization of Energy Storages (ESs) with different characteristics is an effective and economic solution to enhance system performance. Hybrid Energy Storage System (HESS) in centralized coordination is normally implemented. To maintain system operation in case of communication failure, a novel algorithm is proposed for HESS distributed control in this paper. DC bus voltage is regarded as the global information carrier for indication of system power balance. All ESs are configured as slack terminals with droop control for obtainment of the reference bus voltages. Localized Low Pass Filters (LPFs) are added to ESs with low ramp rates to realize system net power decomposition and ESs power scheduling in distributed manner. To overcome the disadvantages of distributed control including voltage deviation and power sharing errors, multi-level Energy Management System (EMS) is applied. HESS distributed control is scheduled as the primary control. Bus voltage restoration and power sharing compensation are implemented in secondary control. Autonomous SoC recovery for ESs with high ramp rates is applied in tertiary control. Load shedding and generation curtailment are used to limit system net power range. MATLAB Simulink model is developed for the verification of the proposed method.

Ship propulsion shafts experience large power and torque fluctuations due to hydrodynamic interactions and wave excitation. The hybrid energy storage system (HESS) is an effective solution to address the impact of these fluctuations for all-electric ships. The new HESS introduced to combat the problem, however, will interact with the power generation and motor control systems, affecting both system efficiency and reliability. In our previous work [1], we proposed an energy management system (EMS) for HESS to incorporate information from other shipboard power units to manage the energy storage components and avoid undesirable interactions, especially those interactions between the batteries and ultra-capacitors. In this work, we pursue a more proactive approach to dealing with the interactions by designing an integrated EMS that encompasses the controls of power generators, electric propulsion motor, and HESS. Through model predictive control (MPC), such an integrated approach takes advantages of the predictive nature of MPC and allows us to judiciously coordinate the different entities of the shipboard power microgrid under constraints, thereby providing benefits in system performance. Results presented in this paper compare the proposed integrated EMS with non-integrated EMS to demonstrate its benefits.

An integrated energy storage framework with significant energy management and absorption mechanism for machine learning assisted electric vehicle application

In recent years, the interest in using DC microgrids has greatly increased due to their higher efficiency, less complexity, and greater transmission power compared to AC microgrids. To address challenges in DC microgrids in the presence of electrical vehicles (EVs) and the uncertainty of charging EVs, researchers have used PV/EV combination systems with energy storage systems (ESS). Controlling DC microgrids, including PV/EV/ESS, is crucial to cope with the existing challenges. On the other hand, the research on DC microgrids' protection systems is in the early stages, and there are still many challenges in this field. In addition, differences in control systems can pose different challenges for the protection system. The simulation results in this paper demonstrate that considering the best case (use of unipolar resistance grounding system) the DC bus voltage is improved by 22.3% (based on MAPE% data comparison). In the protection part, the empirical‐mode decomposition (EMD) method and selecting a suitable intrinsic mode functions (IMF) have been used to protect the DC microgrid. The proposed protection method has been tested under pole‐to‐pole and pole‐to‐ground fault conditions. The results show that the proposed method is capable of detecting various fault types in the studied microgrid.

The direct current (DC) systems have outstanding advantages compared to the alternating current (AC), especially when it comes to renewable energy resources (RER) and microgrids (MGs). Therefore, the DC microgrid (DCMG) has become popular and drawn the attention of researchers. Due to the integration of different power sources in the single DC bus, including solar photovoltaics (PV), wind farms, diesel generators, and energy storage systems, maintaining stable bus voltage requires a complicated control system to ensure a fast-decision-making procedure. This paper presents an energy management strategy for the DCMG using a fuzzy logic-based controller. The proposed DCMG uses a hybrid energy storage system (HESS) for energy balancing and a diesel generator as a backup. The proposed strategy uses generation and loads demand and battery state of charge (SoC) to control the power flow within the MG. The energy management system keeps the SoC in a suitable range to increase the battery life. By controlling the charging and discharging of the HESS, the proposed method has a fast response to the load variation and RER intermittency to prevent the fluctuation of the voltage level of the DC bus and keep it constant. The obtained results validate the efficacy of the proposed fuzzy logic controller.

In this work, a control strategy is developed for different components in DC microgrids where set points for all controllers are determined from an energy management system (EMS). The proposed EMS-based control scheme is developed for DC microgrids with solar photovoltaic (PV) systems as the primary generation units along with energy storage systems. In this work, the concept of dual energy storage systems (DESSs) is used, which includes a battery energy storage system (BESS) and supercapacitor (SC). The main feature of this DESS is to improve the dynamic performance of DC microgrids during severe transients appearing from changes in load demands as well as in the output power from solar PV units. Furthermore, the proposed EMS-based control scheme aims to enhance the lifetime of the BESS in DC microgrids with DESSs and voltage stability as compared to the same without SCs. The proposed EMS-based control strategy uses proportional-integral (PI) controllers to regulate the switching control actions for different converters within the DC microgrid based on the decision obtained from the EMS in order to achieve the desired control objectives. The performance of the proposed scheme was analyzed through simulation results in terms of improving the voltage stability, maintaining the power balance, and enhancing the lifetime of BESSs within a DC microgrid framework incorporated with the DESS. The simulations are carried out in the MATLAB/SIMULINK simulation platform and compared with a similar approach having only a single energy storage system, i.e., the BESS.