A distributed VSG control method for a battery energy storage system with a cascaded H-bridge in a grid-connected mode

With the high penetration of renewable energy,new challenges,such as power fluctuation suppression and inertial support capability,have arisen in the power sector.Battery energy storage systems play an essential role in renewable energy integration.In this paper,a distributed virtual synchronous generator(VSG)control method for a battery energy storage system(BESS)with a cascaded H-bridge converter in a grid-connected mode is proposed.The VSG is developed without communication dependence,and state-of-charge(SOC)balancing control is achieved using the distributed average algorithm.Owing to the low varying speed of SOC,the bandwidth of the distributed communication networks is extremely slow,which decreases the cost.Therefore,the proposed method can simultaneously provide inertial support and accurate SOC balancing.The stability is also proved using root locus analysis.Finally,simulations under different conditions are carried out to verify the effectiveness of the proposed method.

Multi-Scale Fusion Model Based on Gated Recurrent Unit for Enhancing Prediction Accuracy of State-of-Charge in Battery Energy Storage Systems

Accurate prediction of the state-of-charge(SOC)of battery energy storage system(BESS)is critical for its safety and lifespan in electric vehicles.To overcome the imbalance of existing methods between multi-scale feature fusion and global feature extraction,this paper introduces a novel multi-scale fusion(MSF)model based on gated recurrent unit(GRU),which is specifically designed for complex multi-step SOC prediction in practical BESSs.Pearson correlation analysis is first employed to identify SOC-related parameters.These parameters are then input into a multi-layer GRU for point-wise feature extraction.Concurrently,the parameters undergo patching before entering a dual-stage multi-layer GRU,thus enabling the model to capture nuanced information across varying time intervals.Ultimately,by means of adaptive weight fusion and a fully connected network,multi-step SOC predictions are rendered.Following extensive validation over multiple days,it is illustrated that the proposed model achieves an absolute error of less than 1.5%in real-time SOC prediction.

Massive energy storage system for effective usage of renewable energy

The current energy trend indicates a strong thrust toward transforming renewable energy as a major power source.To achieve this mission,battery energy storage systems(BESSs)are indispensable.Although BESSs are expensive,cost reduction can be achieved by using BESSs for multiple purposes,such as load leveling,business continuity planning,frequency control,capacity market,arbitrage,and emergency power.In this paper,various applications of BESSs are classified.The possibility of achieving conflict-free combination of different applications is demonstrated.The total required energy storage capacity in Japan is estimated to be 150–200 GWh by 2030.The present status of NaS batteries for multipurpose use and new trends in battery-based businesses are introduced.

Improved Energy Management Strategy for Prosumer Buildings with Renewable Energy Sources and Battery Energy Storage Systems

The concept of utilizing microgrids(MGs)to convert buildings into prosumers is gaining massive popularity because of its economic and environmental benefits.These pro-sumer buildings consist of renewable energy sources and usually install battery energy storage systems(BESSs)to deal with the uncertain nature of renewable energy sources.However,because of the high capital investment of BESS and the limitation of available energy,there is a need for an effective energy management strategy for prosumer buildings that maximizes the profit of building owner and increases the operating life span of BESS.In this regard,this paper proposes an improved energy management strategy(IEMS)for the prosumer building to minimize the operating cost of MG and degradation factor of BESS.Moreover,to estimate the practical operating life span of BESS,this paper utilizes a non-linear battery degradation model.In addition,a flexible load shifting(FLS)scheme is also developed and integrated into the proposed strategy to further improve its performance.The proposed strategy is tested for the real-time annual data of a grid-tied solar photovoltaic(PV)and BESS-powered AC-DC hybrid MG installed at a commercial building.Moreover,the scenario reduction technique is used to handle the uncertainty associated with generation and load demand.To validate the performance of the proposed strategy,the results of IEMS are compared with the well-established energy management strategies.The simulation results verify that the proposed strategy substantially increases the profit of the building owner and operating life span of BESS.Moreover,FLS enhances the performance of IEMS by further improving the financial profit of MG owner and the life span of BESS,thus making the operation of prosumer building more economical and efficient.

A PI+R Control Scheme Based on Multi-Agent Systems for Economic Dispatch in Isolated BESSs

Battery energy storage systems(BESSs)are widely used in smart grids.However,power consumed by inner impedance and the capacity degradation of each battery unit become particularly severe,which has resulted in an increase in operating costs.The general economic dispatch(ED)algorithm based on marginal cost(MC)consensus is usually a proportional(P)controller,which encounters the defects of slow convergence speed and low control accuracy.In order to solve the distributed ED problem of the isolated BESS network with excellent dynamic and steady-state performance,we attempt to design a proportional integral(PI)controller with a reset mechanism(PI+R)to asymptotically promote MC consensus and total power mismatch towards 0 in this paper.To be frank,the integral term in the PI controller is reset to 0 at an appropriate time when the proportional term undergoes a zero crossing,which accelerates convergence,improves control accuracy,and avoids overshoot.The eigenvalues of the system under a PI+R controller is well analyzed,ensuring the regularity of the system and enabling the reset mechanism.To ensure supply and demand balance within the isolated BESSs,a centralized reset mechanism is introduced,so that the controller is distributed in a flow set and centralized in a jump set.To cope with Zeno behavior and input delay,a dwell time that the system resides in a flow set is given.Based on this,the system with input delays can be reduced to a time-delay free system.Considering the capacity limitation of the battery,a modified MC scheme with PI+R controller is designed.The correctness of the designed scheme is verified through relevant simulations.

Virtual Transmission Solution Based on Battery Energy Storage Systems to Boost Transmission Capacity

The increasing penetration of variable renewable energy(VRE)generation along with the decommissioning of conventional power plants in Chile,has raised several operational challenges in the Chilean National Power Grid(NPG),including transmission congestion and VRE curtailment.To mitigate these limitations,an innovative virtual transmission solution based on battery energy storage systems(BESSs),known as grid booster(GB),has been proposed to increase the capacity of the main 500 kV corridor of the NPG.This paper analyzes the dynamic performance of the GB using a wide-area electromagnetic transient(EMT)model of the NPG.The GB project,composed of two 500 MVA BESS units at each extreme of the 500 kV corridor,allows increasing the transmission capacity for 15 min during N-1 contingencies,overcoming transmission limitations under normal operation conditions while maintaining system stability during faults.The dynamic behavior of the GB is also analyzed to control power flow as well as voltage stability.The results show that the GB is an effective solution to allow greater penetration of VRE generation while maintaining system stability in the NPG.

An Analytical Method for Delineating Feasible Region for PV Integration Capacities in Net-zero Distribution Systems Considering Battery Energy Storage System Flexibility

To provide guidance for photovoltaic(PV)system integration in net-zero distribution systems(DSs),this paper proposes an analytical method for delineating the feasible region for PV integration capacities(PVICs),where the impact of battery energy storage system(BESS)flexibility is considered.First,we introduce distributionally robust chance constraints on network security and energy/carbon net-zero requirements,which form the upper and lower bounds of the feasible region.Then,the formulation and solution of the feasible region is proposed.The resulting analytical expression is a set of linear inequalities,illustrating that the feasible region is a polyhedron in a high-dimensional space.A procedure is designed to verify and adjust the feasible region,ensuring that it satisfies network loss constraints under alternating current(AC)power flow.Case studies on the 4-bus system,the IEEE 33-bus system,and the IEEE 123-bus system verify the effectiveness of the proposed method.It is demonstrated that the proposed method fully captures the spatio-temporal coupling relationship among PVs,loads,and BESSs,while also quantifying the impact of this relationship on the boundaries of the feasible region.

Coordinated voltage regulation strategy of OLTC and BESS considering switching delay

When large-scale distributed renewable energy power generation systems are connected to the power grid,the risk of grid voltage fluctuations and exceeding the limit increases greatly.Fortunately,the on-load tap changer(OLTC)can adjust the transformer winding tap to maintain the secondary side voltage within the normal range.However,the inevitable delay in switching transformer taps makes it difficult to respond quickly to voltage fluctuations.Moreover,switching the transformer taps frequently will decrease the service life of OLTC.In order to solve this critical issue,a cooperative voltage regulation strategy applied between the battery energy storage systems(BESSs)and OLTSs.is proposed By adjusting the charge and discharge power of BESSs,the OLTC can frequently switch the transformer taps to achieve rapid voltage regulation.The effectiveness of the proposed coordinated regulation strategy is verified in the IEEE 33 node distribution systems.The simulation results show that the proposed coordinated regulation strategy can stabilize the voltage of the distribution network within a normal range and reduce the frequency of tap switching,as such elongating the service life of the equipment.

Deep reinforcement learning for online scheduling of photovoltaic systems with battery energy storage systems

A new online scheduling algorithm is proposed for photovoltaic(PV)systems with battery-assisted energy storage systems(BESS).The stochastic nature of renewable energy sources necessitates the employment of BESS to balance energy supplies and demands under uncertain weather conditions.The proposed online scheduling algorithm aims at minimizing the overall energy cost by performing actions such as load shifting and peak shaving through carefully scheduled BESS charging/discharging activities.The scheduling algorithm is developed by using deep deterministic policy gradient(DDPG),a deep reinforcement learning(DRL)algorithm that can deal with continuous state and action spaces.One of the main contributions of this work is a new DDPG reward function,which is designed based on the unique behaviors of energy systems.The new reward function can guide the scheduler to learn the appropriate behaviors of load shifting and peak shaving through a balanced process of exploration and exploitation.The new scheduling algorithm is tested through case studies using real world data,and the results indicate that it outperforms existing algorithms such as Deep Q-learning.The online algorithm can efficiently learn the behaviors of optimum non-casual off-line algorithms.

考虑储能单元健康状态与荷电状态一致性的BESS功率分配策略

针对由多个储能单元组成的大型电池储能系统(BESS)不规则充放电导致的储能单元健康状态(SOH)和荷电状态(SOC)不一致性问题,研究储能单元内SOH差异与SOC一致性的关系。结合充放电优先级排序和自适应变异粒子群优化(AMPSO)算法,提出考虑储能单元SOH和SOC一致性的BESS功率分配策略。基于包含BESS、风/光发电、电动汽车和常规负荷的共直流母线型集中式微电网并网示范平台的实测数据,对所提功率分配控制策略与传统功率分配控制策略进行了对比仿真分析。仿真结果表明,所提控制策略可有效提高储能单元SOC的一致性,延长储能单元使用寿命,降低储能单元运行损耗,增强BESS双向调节能力。

Contingency Reserve Evaluation for Fast Frequency Response of Multiple Battery Energy Storage Systems in a Large-scale Power Grid

Recently,the fast frequency response(FFR)service by large-scale battery energy storage systems(BESSs)has been successfully proved to arrest the frequency excursion during an unexpected power outage.However,adequate frequency response relies on proper evaluation of the contingency reserve of BESSs.The BESS FFR reserve is commonly managed under fixed contracts,ignoring various response characteristics of different BESSs and their coexisting interactions.This paper proposes a new methodology based on dynamic grid response and various BESS response characteristics to optimise the FFR reserves and prevent the frequency from breaching the under-frequency load shedding(UFLS)thresholds.The superiority of the proposed method is demonstrated to manage three large-scale BESSs operating simultaneously in an Australian power grid under high renewable penetration scenarios.Further,the proposed method can identify remaining battery power and energy reserve to be safely utilised for other grid services(e.g.,energy arbitrage).The results can provide valuable insights for integrating FFR into conventional ancillary services and techno-effective management of multiple BESSs.

部分接入电池储能系统的模块化多电平换流器控制方法

部分接入电池储能系统的模块化多电平换流器(MMC with partly integrated BESS,MMCPBESS)可以在接入储能的同时节约建造成本,但其控制更加复杂。针对下桥臂接入储能电池的MMC-PBESS拓扑,建立数学模型及等效电路。在此基础上给出电容电压均衡策略,提出了上/下桥臂分控的控制策略,并分析了其运行边界。在MATLAB/Simulink平台搭建仿真模型,仿真了不同交直流功率比例的运行工况,所提控制策略可以在维持电容电压平衡的同时实现对电池充电的功能。该策略无需额外的环流计算,上下桥臂控制解耦,简单灵活。

面向中压直流配电网的模块化多电平电池储能系统电荷吞吐量抑制策略

模块化多电平电池储能系统(modular multilevel converter-battery energy storage system,MMC-BESS)中各子模块功率周期性波动,与其相连的电池组充放电状态频繁切换,产生额外的电荷吞吐量,危害电池储能系统寿命。当MMC-BESS用于中压直流配电网时,其交直流侧功率传输情况复杂多变,增大电荷吞吐量的抑制难度。因此,文中针对中压直流配电网中的MMC-BESS,提出一种基于二倍频环流注入的电荷吞吐量抑制策略。首先,构建中压直流配电网中MMC-BESS的数学模型;其次,剖析MMC-BESS电荷吞吐量的产生机理,分析不同运行方式下电荷吞吐量的影响因素;再次,提出基于二倍频环流注入的电荷吞吐量抑制策略,以系统总电荷吞吐量最小为目标,选取不同工况下需注入的最优二倍频环流分量;最后,多种工况下的仿真及实验结果表明,所提方法可有效抑制中压直流配电网中MMC-BESS的电荷吞吐量。

基于动态可重构电池网络的大规模退役动力电池梯次利用储能系统运行性能评估

退役动力电池因其一致性差、安全性薄弱等缺陷在梯次利用时面临巨大挑战。动态可重构电池网络(dynamic reconfigurable battery network,DRBN)能够有效提高退役动力电池梯次利用储能系统的一致性和安全性。目前DRBN储能系统已经进入工程应用阶段,然而现有的研究缺少对大规模DRBN储能系统的运行性能评估。为此,以实际运行的大规模退役动力电池梯次利用储能系统作为分析对象,选取储能系统中80个DRBN的1个月运行数据进行分析。从运行工况、均衡效果、薄弱辨识三个方面验证了DRBN储能系统对电池模组一致性的提升效果。数据分析表明,90%的DRBN一致性良好,且其他一致性较差的DRBN都能够被准确辨识。

适用于直流链式储能的电池簇荷电状态自均衡控制策略

电池储能系统凭借其可提高可再生能源消纳能力的优势逐渐成为电网关键环节,其中的生产、使用环节导致的电池不一致性是影响储能系统容量和寿命的重要因素。在直流型高压级联链式储能的拓扑结构基础上采取分级控制策略,基于电压模式和功率模式的一级控制,针对链式电池储能系统电池荷电状态(SOC)不均衡的问题,提出了一种控制参数自适应的SOC自均衡控制策略。该策略综合考虑电池SOC偏差、各模块电容电压水平、直流系统电压控制裕度以及输出调制比上下限,实时计算均衡系数。实验结果验证了所提策略能够在SOC偏差较大以及满功率充放电切换的极端工况下,实现SOC自均衡,均衡效率较高。

含储能有源配网的经济调度与协同优化

为了提升电池储能系统的有源配网运行效益,提出面向电池储能有源配网,包含经济调度与协同优化方法的分层递阶系统架构。首先,概述模型中不同层级间的逻辑运算关系;其次,针对不同层的优化目标,建立含光-储-充有源配网的经济调度与优化的2阶段模型。第1阶段以系统成本最小化为优化目标,第2阶段以系统网损最小为目标进行建模与仿真。最后,基于不同运行场景下的仿真结果,分析光、储、充的变化规律,并给出储能系统在不同节点的优化配置方案。

基于功率变换器的梯次利用电池系统均衡控制策略

梯次利用是一种处理退役锂电池的经济高效的方法。但是在电池梯次利用过程中,存在不同新旧状态电池混用而导致的不均衡问题,会影响电池系统的安全稳定运行。本工作分析了梯次利用电池直接并联时,由于不均衡导致的电流环流以及系统容量利用率低的问题。为解决这一问题,本工作提出一种基于功率变换器的梯级电池并联系统结构及均衡控制算法。所提方法将每个电池模组和功率变换器相连组成一个功率模组,通过调节电压环路、电流环路、荷电环路的输出,分别控制每个电池模组的充放电电流,最终实现梯次利用电池均衡优化控制策略。本工作给出了系统控制策略的详细分析和实验结果讨论,以评估和验证所提均衡方法的有效性。实验测试表明,在使用相同健康程度电池、不同健康程度电池以及变负载等测试情况下,本工作所提梯次利用电池均衡控制策略都能够稳定、有效控制不同电池电流,保证电池之间的荷电参数均衡,提高了电池系统整体效率。本研究可以促进废旧电池的有效梯次利用,并为电池系统均衡控制提供新思路。通过实现电池的均衡利用,可以延长电池的使用寿命,降低系统故障风险,提高系统的可靠性和稳定性。

基于SVPWM控制的STATCOM-BESS特性分析与仿真

针对传统静止无功补偿器(static synchronous compensator-STATCOM)只能补充无功功率的不足,对直流侧并联蓄电池储能系统(battery energy storage system-BESS)的改进装置进行了研究,从而实现有功无功功率的双重控制。首先对STATCOM-BESS工作原理和数学模型进行简要介绍,之后对四象限模式的运行特性进行重点分析,并研究了基于电压空间矢量(SVPWM)有功功率无功功率独立控制的电流解耦控制技术。最后在MATLAB/Simulink中搭建STATCOM-BESS模型进行仿真分析,仿真结果显示装置在快速实现无功功率补偿的同时也可以实现有功功率的控制,并具有良好的动稳态特性,因此验证了理论分析的正确性和控制方法的有效性。

计及电池储能和抽水蓄能灵活性的电力系统优化调度方法

充分利用灵活性资源的调节能力可有效平抑新能源出力的波动,保证系统经济安全运行。提出一种计及电池储能和抽水蓄能灵活性的电力系统优化调度方法。在建立向上/向下灵活性需求模型的基础上,以调度能量成本、备用成本和灵活调节服务调用成本的总成本最小为目标,建立基于日前安全约束机组组合和实时经济再调度的混合整数线性规划模型,采用CPLEX进行求解。以IEEE-RTS-24节点系统为算例,考虑4种不同典型方案场景,对比验证了所提方法能有效提升系统运行灵活性,降低运行成本。

计及多点电池储能系统的电网二次调频协同控制

在“碳达峰•碳中和”国家能源战略变革背景下,大规模可再生能源的加速并网加剧了电力系统对于快速调频资源需求的迫切性,如何充分发挥以电池储能系统(battery energy storage systems,BESS)为代表的新型快速资源在电网调频中的作用是解决该问题的关键。首先,为满足电网各类型调频资源在自动发电控制(automatic generation control,AGC)系统中的接入监视与分类决策需求,提出“域-群-机”三级控制模型架构;然后,从BESS的荷电状态(state of charge,SOC)主动管理出发,提出基于改进的动态调频容量(dynamic available AGC,DAA)的多元集群协同控制策略,以及引入SOC影响因子的多点BESS功率分配策略;最后,结合实际电网的持续扰动工况及模拟跳机扰动工况进行仿真分析,验证了文中所提控制策略的有效性。文中所提策略不但可以显著改善各单点BESS的SOC一致性,而且能够提升电网调频品质。