基于动态下垂控制的温控负荷一次调频控制策略

利用温控负荷(thermostatically controlled load, TCL)作为调频资源参与电网调频是应对高比例可再生能源发电并网导致电力系统维持频率稳定能力下降的有效手段。文中提出一种基于动态下垂控制的TCL一次调频控制策略,考虑聚合商TCL平均温度状态(state of temperature, SOT)、调频容量和系统频率变化率,构建动态下垂控制模型,实时调整下垂控制系数,改变TCL聚合商调频参与度。当向上调频时,锁定关状态TCL;当向下调频时,锁定开状态TCL,确保频率快速恢复至额定值附近。同时,为确保用户的舒适度,利用TCL的SOT优先级排序列表派遣法,确定TCL参与调频顺序。在Matlab/Simulink平台上进行仿真分析,仿真结果验证了文中所提策略在确保用户舒适度、改善频率质量等方面的有效性。     

Experiences in modelling the performance of generating plant for frequency response studies on the British transmission grid

Significant changes to the generation mix on the British transmission system have occurred in the past 10 years, and this trend is expected to continue in the future with an increase in renewable generation. This change, in conjunction with market changes, has driven the need to establish suitable generator models for thermal plant used in dynamic response studies. These studies are presently used to quantify the dynamic requirement that secures the transmission system against large instantaneous losses of power. This paper provides an account of the experiences gained in modelling the performance of generators based in Great Britain. Established governor models to represent the behaviour of traditional coal and oil fired plant already exist and comments are made on their performance against system incidents. Models of combined cycle units using traditional open cycle gas turbine models have shown poor correspondence with monitored grid data in simulations. A gas and steam turbine governor model to represent combined cycle plant was developed, and is presented, with results from validation trials against recorded test data. Improvements in simulating grid frequency have been demonstrated using the developed models in a full network simulation of a recent generator loss event.     

Review of modeling and control strategy ofthermostatically controlled loads for virtualenergy storage system

The increasing penetration of renewable energy sources (RESs) brings more power generation fluctuations into power systems, which puts forward higher requirement on the regulation capacities for maintaining the power balance between supply and demand. In addition to traditional generators for providing regulation capacities, the progressed information and communication technologies enable an alternative method by controlling flexible loads, especially thermostatically controlled loads (TCLs) for regulation services. This paper investigates the modeling and control strategies of aggregated TCLs as the virtual energy storage system (VESS) for demand response. First, TCLs are modeled as VESSs and compared with the traditional energy storage system (ESS) to analyze their characteristic differences. Then, the control strategies of VESS are investigated in microgrid and main grid aspects, respectively. It shows that VESS control strategies can play important roles in frequency regulation and voltage regulation for power systems’ stability. Finally, future research directions of VESS are prospected, including the schedulable potential evaluation, modeling of TCLs, hierarchical control strategies of VESS considering ESSs and RESs and reliability and fast response in frequency control for VESS.     

A nonlinear control method for price-based demand response program in smart grid

This paper proposes a price-based demand response program by the nonlinear control method. The demand response program is formulated as a nonlinear power management system with price feedback. We give the conditions of the price parameters for both the global asymptotic stability of the system and the social welfare optimality of the equilibrium point. Furthermore, the system is shown to be input-to-state (ISS) stable when there are additive disturbances on the power measurements and the price, and the discrete-time implementation of the power management system is given. Simulation results demonstrate the balance between supply and demand and the stability of the system with and without disturbances.     

A novel domestic electric water heater model for a multi-objective demand side management program

This paper presents a novel domestic hot water heater model to be used in a multi-objective demand side management program. The model incorporates both the thermal losses and the water usage to determine the temperature of the water in the tank. Water heater loads are extracted from household load data and then used to determine the household water usage patterns. The benefits of the model are: (1) the on/off state of the water heater and temperature of the water in the tank can be accurately predicted, and (2) it enables the development of water usage profiles so that users can be classified based on usage behaviour. As a result, the amount of ancillary services and peak shaving that can be achieved are accurately predictable and can be maximized without adversely affecting users.     

考虑用户响应度模糊控制的需求响应双层博弈模型

配电网中分布式新能源、可控负荷等柔性资源参与电网需求响应已成为新型电力系统削峰填谷的重要手段,而如何考虑用户响应度和平衡多主体利益十分关键。为此,文中首先建立用户响应度的模糊控制模型,并给出考虑用户响应度模糊性的供电方、负荷聚合商、用户等多主体需求响应参与方效益函数模型;进而以日负荷曲线偏差最小和系统成本最小为优化目标,上层优化采用供电方最优需求响应方案,下层优化在供电方及负荷聚合商之间求得最优任务分配,从而建立供电方、负荷聚合商、用户等多主体协同需求响应双层模型,并提出基于Stackelberg博弈理论和k-means聚类算法的求解方法;最后以某地区历史数据进行模拟仿真。结果表明文中模型在考虑用户响应度和协同多主体利益下能有效筛选优质需求响应资源,平抑负荷波动。     

Stochastic frequency-security constrained energy and reserve management of an inverter interfaced islanded microgrid considering demand response programs

This paper addresses a novel security constrained energy management system of a microgrid which considers the steady-state frequency. Microgrid frequency as a key control variable, continuously exposes to be excursed of its nominal value due to unpredictable intermittencies arise from renewable sources and/or load consumptions. Moreover, great utilization of inertia-less inverter-interfaced distributed energy resources intensifies potential frequency excursions. As a result, energy and reserve resources of a microgrid should be managed such that the microgrid frequency lies within secure margins. To that end, a new objective function on the basis of the frequency dependent behavior of droop-controlled distributed generations is formulated using a mixed integer linear programming. It is aimed to optimize the microgrid frequency according to the economic and environmental policies. Besides, to seek the active participation of the consumers into proposed frequency management approach, a linearized ancillary service demand response program is also proposed. In addition, to properly model the impacts of microgrid various uncertainties in the frequency management approach, a two-stage stochastic optimization algorithm is employed. Simulations are performed in a typical microgrid which operates in the islanded mode during a 24 h scheduling time horizon. The numerical results show the impressiveness of the proposed frequency aware energy management system while concurrently managing the microgrid security and economical aspects. Furthermore, it is demonstrated that utilization of demand response programs economizes the microgrid frequency management approach.     

Stochastic modeling for scheduling the charging demand of EV in distribution systems using copulas

Charging demand of electric vehicles (EV) has potentially a significant influence on the power grid. If this charging demand coincides mainly with the peak demand of the power grid, then additional active power has to be supplied to fulfill load management purposes. Thus, it is necessary to estimate and schedule the charging demand of the EV in order to lower the peak demand. Various estimation techniques are available such as Gaussian mixture model and copula. This paper uses copula for data estimation because copula imposes no restriction on the marginal distributions of the available data. Meanwhile, uncertain estimated data requires error elimination. Clayton copula is selected for flexile part of load profile, and Gaussian copula for non-controllable part of the load profile based on the two consecutive days (TCD) classification. Hence, the created scenarios were applied to an optimization problem that flattens the load profile as much as possible using general algebraic modeling system (GAMS). Then, this research concentrates on two new semi-automatically proposals concerned with the day-ahead charging demand response (DR) strategies. These strategies contribute to removing the estimation errors created due to the uncertainties. In order to examine the efficiency of the proposed strategies, the day-ahead pricing (DAP) with inclining block rates (IBR) model is assumed for retail electricity markets.     

Evolution of primary frequency control requirements in Great Britain with increasing wind generation

With the increase of renewable generating capacity following the ambitious targets set by many governments for the next decades, there will be major changes in power generation and challenges for balancing transmission grids. In particular, primary frequency control requirements will be increased following a potential reduction of system inertia.An assessment of the frequency response reserve needed is made through use of a simple model of the Great Britain transmission grid for different loads and wind power penetration. This model analyses the effect of changing the system inertia and the effectiveness of standard frequency response as well as dynamic frequency control support.It is observed that an increased wind power generation requires substantial additional reserves for primary frequency control if the wind turbines do not contribute to the overall system inertia. However, it is also shown that these reserves can be dramatically reduced if the system is provided with fast acting response by dynamic frequency control support.     

Battery energy storage system for frequency support in microgrids and with enhanced control features for uninterruptible supply of local loads

This paper proposes a battery energy storage system (BESS) to support the frequency control process within microgrids (MG) with high penetration of renewable energy sources (RES). The solution includes features that enhance the system’s stability and security of supply. The BESS can operate connected to MG or islanded and the transition between the two states is seamlessly coordinated by an original method. The BESS active power response is governed by an improved frequency controller on two layers, namely primary and secondary. It responds to frequency deviations by combining a conventional droop control method with a virtual inertia function to improve the system’s stability. The proposed BESS may also compensate the power of the local loads, so that the MG frequency transients can be reduced and, depending on the remaining inverter capacity, voltage support in the point of common coupling with the MG may be provided. If the MG power quality degrades in terms of the voltage and frequency, the BESS and the local load are disconnected from the MG and continue operating islanded. The BESS is reconnected to the MG after a smoothly resynchronization of the local voltage with the MG, without disturbing the local loads supply. Simulation and experimental results assesses the proposed control solutions.     

Impact of demand response resources on unit commitment and dispatch in a day-ahead electricity market

Demand response (DR) has recently become an important resource in both system operation and market operation. The focus of this paper is to investigate and quantify the cost impact of various demand response modelings on unit commitment and dispatch in a day-ahead market regime. We have used mixed integer programming unit commitment model, in the market operation framework. Day-ahead market is modeled with a typical test system. Our research results show that DR can exert downward pressure on electricity prices, causing significant implications on social welfare. Results from this work will help policy makers, resource planners, and market designers to make more informed decisions with the goal of better accommodating more demand response resources in the future.     

Analysis of the demand charge in DC railway systems and reduction of its economic impact with Energy Storage Systems

In addition to energy consumption, DC railway operators must also pay for the demand charge. This term of the electricity bill has not been studied in detail in the literature and penalizes power peaks. The big fluctuations on the power demand which characterize railway systems make the demand charge important for railway operators. This paper studies the impact of the demand charge on DC railway systems and proposes a solution based on Energy Storage Systems (ESSs) to reduce it. An analysis of the main parameters of the ESS regarding the reduction of the demand charge is provided, as well as an explanation of the effects of different control strategies on the system performance. Most of the savings obtained with the installation of ESSs come from the reduction in the energy consumption; nevertheless, the savings coming from the reduction in the demand charge are significant and contribute to the economic viability of the investment.     

提升火电机组一次调频性能的火电-储能一体化系统研究

提出了一种火电-储能一体化系统的构造方法,并设计了协同调频控制策略以改善火电机组一次调频性能。在严重有功扰动场景下,利用储能装置的快速响应能力提升了火电机组的一次调频响应速率,改善系统频率跌落深度。在负荷日常波动场景下,利用储能装置响应一次调频指令的高频分量,抑制了火电机组一次调频功能的频繁动作。此外,提出了储能能量恢复控制策略,采用火电充裕的能量恢复储能荷电状态,避免储能的过度充放。算例分析表明,所提方法可有效提升火电机组的一次调频性能,并能够有效维持运行过程中储能的荷电状态。     

冲击负荷接入电网的电能质量分析与治理方案研究

随着冲击性负荷的日益增多,迫切需要对大量冲击性负荷接入电网时所引发的电能质量问题进行有效的分析。结合重庆电网,提出了分析大量冲击性负荷接入系统时的电能质量评估方法并给出了综合的治理方案。首先基于电流的实测数据建立了冲击负荷的新型拟合模型,并结合ward等值理论和戴维南定理多电势转化方法搭建了重庆地区的等值电网,将冲击负荷模型接入等值电网中,以此为平台研究了多个冲击性负荷接入对重庆电网电能质量的综合影响。针对电能质量超标的情况,分析了提高冲击负荷接入的电压等级、加装滤波器或SVC等治理措施,并结合重庆电网冲击负荷实测电能质量数据提出了治理方案。在PSCAD中搭建了仿真模型,验证了分析结果的有效性和准确度,为冲击负荷接入重庆电网的综合治理提供了理论参考。     

含光伏的油田综合能源系统的热电厂和需求响应协同调峰能力分析

大规模发展可再生能源是构建低碳可持续能源系统的重要保障,源-荷协同调峰是消纳可再生能源的有效途径。为此,研究含光伏的油田综合能源系统的热电厂和需求响应协同调峰,分析冬季典型场景下的热电厂热电耦合机理,建立热电耦合调峰约束;针对油田综合负荷的用能特性和分布式光伏发电的特点,建立负荷集群的用电数学模型和用热数学模型,考虑热电机组、负荷响应及源-荷系统运行技术约束,以油田全局能耗成本最小为目标建立自备热电厂和需求响应协同调峰优化模型,制定油田电网源-荷协同调峰策略,通过循环寻优求解源-荷协同最大调峰能力。算例分析表明,源-荷协同光伏发电调峰能有效地提高油田电网对光伏发电的消纳能力,供暖负荷的需求响应使冬季热电厂“以热定电”的刚性约束弹性化,调峰贡献度在需求响应中占比最大。     

300MW机组一次调频功能的应用与分析

介绍了纳雍发电厂一厂4×300MW机组一次调频控制逻辑和参数设置,通过3种不同投入方式的试验和分析,表明“CCS＋DEH”方式的调节性能较好,一次调频响应速度快,机组主汽压较稳定,是目前投入一次调频功能的最优方式。     

计及用户综合用能行为和政策导向的广域综合能源系统联合规划方法

针对日益加深的能源环境问题,从更大范围的宏观角度来研究综合能源系统规划具有重要意义。提出一种计及用户综合用能行为和政策导向的广域综合能源系统规划方法。首先,建立用户用能决策的效用模型。然后,分别构建综合能源系统中各类市场主体的规划收益模型。同时考虑供能改造的环境效益,建立政府对供需双侧污染排放的评估模型。在此基础上,基于不同主体间的博弈机理分析,构建面向广域综合能源系统的双层动态博弈规划模型。最后,利用迭代搜索法对模型进行求解。仿真结果验证了该方法的正确性和有效性。     

需求响应参与大规模风电接入下的电力系统频率调节研究

针对大规模风电接入下的电力系统频率稳定控制问题,研究了需求响应对系统频率的调节作用。为了反映风电的特点,建立了大规模风电接入下的电力系统频率响应模型,模型中对风电和火电机组分别进行了建模。风电机组可以通过暂时释放转子动能参与调频,然而在扰动过大时会导致系统失稳。通过采取一种类似于低压低频减载的需求响应控制方法,即在频率跌落时关闭部分用电设备,待频率恢复后将这些设备重新打开,可以为电力系统调频提供支持。仿真结果表明,需求响应与风电机组同时参与电力系统调频,能够克服风电机组的失稳问题,大大提高风电系统的频率稳定性。     

Application of a simplified Grey Wolf optimization technique for adaptive fuzzy PID controller design for frequency regulation of a distributed power generation system

A Simplified Grey Wolf Optimizer (SGWO) is suggested for resolving optimization tasks. The simplification in the original Grey Wolf Optimizer (GWO) method is introduced by ignoring the worst category wolves while giving priority to the better wolves during the search process. The advantage of the presented SGWO over GWO is a better solution taking less execution time and is demonstrated by taking unimodal, multimodal, and fixed dimension test functions. The results are also contrasted to the Gravitational Search Algorithm, the Particle Swarm Optimization, and the Sine Cosine Algorithm and this shows the superiority of the proposed SGWO technique. Practical application in a Distributed Power Generation System (DPGS) with energy storage is then considered by designing an Adaptive Fuzzy PID (AFPID) controller using the suggested SGWO method for frequency control. The DPGS contains renewable generation such as photovoltaic, wind, and storage elements such as battery and flywheel, in addition to plug-in electric vehicles. It is demonstrated that the SGWO method is superior to the GWO method in the optimal controller design task. It is also seen that SGWO based AFPID controller is highly efficacious in regulating the frequency compared to the standard PID controller. A sensitivity study is also performed to examine the impact of the unpredictability in the parameters of the investigated system on system performance. Finally, the novelty of the paper is demonstrated by comparing with the existing publications in an extensively used two-area test system.