用于消纳风电的城区用户电热水器负荷群滑模控制策略研究

居民电热水器是一种典型的热储能负荷,用电产生的热水具有热存储性,可以消纳波动性风电。提出了用于消纳风电的电热水器负荷群滑模控制策略,来实时控制电热水器负荷群。控制率与电热水器群数量、热水使用情况等相关,对于消纳风电具有较强的鲁棒性。采用某城区居民区电热水器负荷群的仿真研究表明,提出的电热水器群滑模控制策略能有效消纳风电,验证了电热水器负荷群滑模控制策略有效性。     

Heat Pump Water Heater Control

A control system is described for a heat pump water heater which uses the thermostat on an existing electric water heater to determine the need for water heating. The control system allows an installer to wire in an electric water heater with the heat pump using the same connections for supplying power to the water heater which would normally be used. This control system will also automatically turn off the heat pump when frost forms on the evaporator coil and will allow the electric elements in the tank to heat the water. The system is easy to install, provides reliable operation of a heat pump, does not create any unusual safety problems, and gives uninterrupted hot water service.     

电动车用感应电机磁场定向矢量控制研究

电动车用感应电机参数变化易引起电机振荡现象，文中以含微分运算的三相感应电机模型为基础，提出了一种具有转差频率控制的转子磁场定向矢量控制方法，给出了相关的理论推导及实验结果。该方法能够有效地抑制由于电机参数变化过大导致的电机振荡现象，能使电机可靠地运行于弱磁区域，可满足高功率密度、高转速电动车用感应电机的控制要求。实验结果验证了该方法的正确性及有效性。     

电能计量中谐波影响的研究

针对谐波条件下感应式和电子式电能表2种电能表的计量误差进行了分析和讨论,指出现有感应式电能表无法区分线性与非线性负荷,对于非线负荷其计量电能小于基波电能;而电子式电能表虽能对线性和非线性负荷加以区分,但同样存在计量误差,计量方式不合理的问题,提出一种较合理的改进计量方式.     

Flux synthesizing linear induction motor with super multiphase switching

A novel concept of structure and control of linear induction motors (LIMs) called “Flux Synthesizing Linear Induction Motors (FSLIMs),” is proposed where each slot has a conductor carrying an electric current whose amplitude and phase angle are controlled with super multiphase switching devices. It is well known that an LIM has the merits of direct drive and simple structure. However, a conventional LIM has low power factor and energy efficiency. The end effect is one of the significant reasons for the bad characteristics. Strategies against the effect have been limited by conventional three-phase winding. On the other hand, high-speed power-switching devices are available at a reasonable cost. A super multiphase drive enables more freedom for controls with the proposed structure of the FSLIM. Basic characteristics of a tubular test LIM with twelve slots have been measured and calculated to investigate an appropriate flux synthesis. As a result, an appropriate switching scheme which synthesizes sinusoidal distribution of the gap flux density, enables the end-effects to be suppressed and, consequently, improves the energy efficiency. In addition, basic conditions for the field-coordinated oriented control of a thrust force are satisfied by keeping the amplitude of the gap flux constant with the flux synthesis.     

On the variation with flux and frequency of the core loss coefficients in electrical machines

A model of core losses, in which the hysteresis coefficients are variable with the frequency and induction (flux density) and the eddy-current and excess loss coefficients are variable only with the induction, is proposed. A procedure for identifying the model coefficients from multifrequency Epstein tests is described, and examples are provided for three typical grades of non-grain-oriented laminated steel suitable for electric motor manufacturing. Over a wide range of frequencies between 20-400 Hz and inductions from 0.05 to 2 T, the new model yielded much lower errors for the specific core losses than conventional models. The applicability of the model for electric machine analysis is also discussed, and examples from an interior permanent-magnet and an induction motor are included.     

基于解耦策略的直线感应牵引电机法向力自适应最优控制

中低速磁悬浮列车和部分地铁车辆均采用直线感应牵引电机作为驱动机构,该电机特有的边缘效应和法向力对直线感应牵引电机的效率以及性能均产生很大的负面影响,因此直线感应牵引电机采用常规的电传动控制策略并不能取得良好的控制效果。该文充分考虑边缘效应的影响,建立了直线感应牵引电机的数学模型。将推力与磁通进行解耦,并分析磁通、推力与电流控制环节的非线性与时变性,提出了神经自适应控制的设计方法。分析了法向力的组成与特性,得出其数学表达式,以推力与磁通解耦为基础,结合最优化理论,考虑多个优化目标建立损耗最小函数,实现直线感应牵引电机的损耗最优控制。计算机仿真与实验对所提控制策略与传统控制策略进行对比,验证了该方法在典型工况下的有效性。     

Disturbance-free operation of a multiphase current-regulated motordrive with an opened phase

Although design of induction motor drives employing field oriented control has reached a relatively mature state, relatively little effort has been directed toward improving the reliability of these drives. In this paper, a new, improved induction motor control strategy is proposed incorporating a multiphase machine that allows for continuous, disturbance-free operation of the drive even with complete loss of one (or more) legs of the inverter or motor phase. A complete analysis of both an even phase and an odd phase machine utilizing this new control and circuit concept is included     

An Energy-Efficient Electric Plant for Hot Steam and Water Supply of Agricultural Enterprises

The efficiency of electric energy use in the thermal technological processes of agricultural production can be significantly increased by using it during a period of reduced rate. The design features of an energy-efficient electric storage unit for steam and hot water supply of the agricultural facilities are considered. The electric plant includes a storage water heater, steam generator, section of steam superheating to a temperature of 140°C, control cabinet, and stop and safety valves. When heating the heat medium in all units of the plant, an indirect electric heating method was applied. A method of calculation of the electrical, thermal energy, and structural parameters is proposed. The results of physical modeling of the processes of heat transfer between the electric heater and heat medium are presented, and they are described mathematically. The dependence of the heat transfer coefficient on the specific surface power of the heaters when water boils in a large volume for the installed structure of the electric steam generator is obtained. The dynamics of the convective heat transfer between the electric heater and steal flow is studied. The economic efficiency of use of the storage electric plant is demonstrated, and it is shown in practical use.     

基于改进DBSCAN-RNN的电力负荷建模及可调特征提取

针对面向能源消纳的电力负荷实时调控需求,以电热水器为例建立调控模型,提出一种改进DBSCAN-RNN算法的电力负荷可调特征提取与可调潜力挖掘方法。以改进DBSCAN聚类结果作为RNN输入获得一种深度学习新策略,基于改进DBSCAN-RNN进行电器群设定温度与天气温度、电器负荷功率的建模,考虑用户电器使用习惯,输出输入量对电器实际功率的影响因子以及电器可调功率与真实功率对应的状态方程参数。某市电热水器群实际数据结果表明所提方法可正确有效地获取海量电热水器群聚合负荷模型及其可调功率。     

Development of a Monte Carlo based aggregate model for residential electric water heater loads

A model for a residential electric water heater load is developed using an energy flow analysis of the water heater tank. An aggregate model for residential electric water heater loads is then developed using a rejection type Monte Carlo simulation technique. The resultant aggregate model is then used to assess the effectiveness of several demand-side management strategies using the water heater load profile presented in a previous analysis.     

Research and development of conversion of direct current voltage to the quasi-sinusoidal voltage with pulse-width modulation

Practically all widely used variable-frequency alternating-current electric drives with autonomous voltage inverters (AVIs) use pulse-width modulation (PWM) according to one of the following techniques: sinusoidal, space-vector, and relay. Fulfilling the relay PWM requires an analog–digital converter (ADC) with high resolution and sample rate. Vector PWM has a nonsinusoidal output voltage that causes additional losses in the motor. The main problem of a symmetrical (centered) sinusoidal PWM is underuse of a dc link. For a long time, the vector PWM method was taken to be most promising one due to the absence of this defect. In practice, this technique is applied in areas without a strong voltage criterion, for which reason it has limited use. Moreover, due to another significant problem, which is the “dead” time on the sector borders at the vector PWM, different modified methods for constructing the sinusoidal PWM have become widespread, especially in modern asynchronous motor control systems, with the development of digital microprocessor systems. To determine the quality of different types of PWMs, a complex model of an electric drive, incorporating an inverter control system that implements different algorithms of constructing the discrete PWM signals is developed. The model and the electric circuit are constructed in LabVIEW and NI Multisim, respectively. The obtained simulation data can be used to select the optimal method of controlling the AVI. The analysis that has been conducted allows one to select an optimal PFWM control strategy in terms of research results concerning electric power quality and mechanical properties.     

Real-time Energy Control Approach for Smart Home Energy Management System

Abstract

This article investigates a real-time energy control approach for a home energy management system, including the electric water heater, air conditioner, clothes dryer, electric vehicle, photovoltaic cell, critical loads, and battery system. A demand response mechanism is proposed to enable households to participate in demand response services. Half-hour-ahead rolling optimization and a real-time control strategy are combined to achieve household economic benefits and ability to deal with complex operating environments. A fuzzy logic controller is utilized to determine battery charging/ discharging power; proper rules are proposed to ensure benefits from operating the battery under the real-time electricity price. The simulation test results indicate that the proposed control approach can optimize the schedule for home appliances and battery charging/ discharging behavior, even if the forecasted information is not accurate. A physical test platform has also been established and tested in the lab to support the operation of the whole system.     

满足电动汽车充电需求的台区柔性资源分布式协调控制

随着电动汽车行业的快速发展,交直流混合微电网经济稳定运行成为重要研究目标,需研究满足孤岛运行的电动汽车充电需求控制技术.围绕多辆电动汽车的充电需求问题,文中提出了一种基于需求的台区柔性资源分布式协调策略(DDRCS),基于电压下垂控制结构提出了一种改进的互联变换器(IC),根据分散和分布工作方式提出一种协调控制的电动汽车存储控制器,建立了基于区域电动汽车充电需求的交直流混合微电网模型,测试了两种控制器在可变光伏、商业负荷和各种故障下的性能.算例表明所提出的分布式控制器在时间延迟和故障条件优于已有分布式控制器,可提高发电可变情况下的交直流混合微电网安全经济运行能力,同时可满足多辆电动汽车充电需求.     

基于预切换状态的电热水器负荷群调控策略

风电消纳问题已成为我国风电进一步发展的瓶颈,以需求侧资源逆向匹配生产端的风电能源,是促进风电消纳的有效途径。本文以家用电热水器为研究对象,提出了一种新的需求响应调控策略:首先建立电热水器的热力学模型和动态调控模型;将电热水器在自然运行状态下1min之内将要开启或关闭的状态定义为预切换状态(pre-switching state,PSST);采取考虑PSST的分群策略,并基于T_se和C_se联合指标分别对开启群和关闭群中的电热水器进行优先级排序,生成负荷群优先序列;最后建立负荷群功率调整量优化模型。将调控策略应用于风电消纳场景并与其它策略进行对比,仿真结果表明,基于PSST的负荷群调控策略能够较好地跟踪风电响应目标,在有效减小响应误差的同时,能够均衡负荷群加热效果,具有良好的应用前景。     

A centralized demand response control strategy for domestic electric water heater group based on appliance cloud platform

Motivated by the potential ability of the domestic electric water heater (EWH) in demand response (DR), this paper proposes a centralized DR control strategy to dispatch the EWH loads considering a domestic EWH group based on the appliance cloud platform. The objective is to solve the problem of water heater load control when the appliance cloud platform participates in DR of load curtailment. To solve the problem, first, a DR system model of the appliance cloud platform is presented. Second, a model of single EWH thermal dynamics in static mode of operation is built based on energy flow analysis. Third, based on the system model and the model of EWH thermal dynamics, a DR control strategy in the timescale of minutes is proposed to implement DR control of an EWH load group in a centralized way by the appliance cloud platform. Finally, simulation results confirm the viability and efficiency of the proposed control strategy.     

基于DSP的异步电机变频调速系统研究

交流调速技术发展后,阀门调节速度、挡板调节速度方式都逐渐被取代,变频调速成为最有发展潜力的技术。本文在现有技术基础上,以DSP芯片TMS320F2812为核心研究了变频调速的系统组成,采用电压空间矢量控制方案将复杂的异步电机转换成简单的等效直流模型。经过结果分析后,认为此研究系统对于应用广泛的变频调速来说有重要的意义和价值。     

LCC design criteria in electrical plants oriented to energy saving

In this paper, a life-cycle cost (LCC) approach is proposed to design electric installations suitable to industrial and civil applications. The structure of the electric system under study is supposed radial, as in most cases, and composed by transformers and lines, while users are simply represented by means of their load diagrams. The LCC procedure allows us to evaluate the main characteristics of transformers (rated power) and lines (rated current) and it can be adapted to also choose particular loads like induction motors. The paper shows an improvement of the standard procedures to design electric lines constituted by cables also including the case of their parallel connections and the most convenient types of busbars. A similar concept is also applied to transformers taking into account their thermal behavior to establish their limit performance, starting from the supplied system load characteristics. In the case of induction motors, the mechanical load is considered in the evaluation of the most convenient solution. The procedure has been applied to the case of a real industrial plant and the results reported in the paper are related to it.     

Analysis of the dynamic performance of a variable-frequency induction motor drive using various control structures and algorithms

A comparative analysis of the dynamic characteristics of field-oriented induction motor drive control systems relying on the main magnetic flux linkage vector reference, space-vector pulse width modulation (SVPWM) of the voltage inverter output, and direct torque control (DTC) is carried out using the Matlab/Simulink program package, with the parameters of the induction motor model used being the same. A changeover from stepless vector control systems to systems using microprocessors and modern controllable frequency converters operating on the principle of relay control entails possible changes in the properties of the electric drives being controlled. In this connection, there is a need to compare the dynamic performance characteristics of an electric drive with a slave vector control system (with an idealized frequency converter), referred to as electric drive 1 (ED1), an electric drive with a DTC system (ED2), and an electric drive using direct torque control and SVPWM (ED3). Modeling has shown that the response time of the torque control loop in all the control systems considered is the same, the time delay being no more than 0.01 s. On the whole, speed control transients in all of the above systems take their course in one and the same way. The differences in flux linkage control transients between ED2 and ED3, on the one hand, and ED1, on the other hand, are due to the differences between the methods used to form the electromagnetic torque. No provision is made in the above control systems for the stabilization of the magnitude of the flux linkage vector. At low loads, the flux linkage automatically follows the load. In an ED3 with direct torque control, the calculation of the necessary instant magnitudes of the voltage vector projections and the SVPWM based formation of the voltages applied to the motor allows implementation of a fast-response control system with minimal harmonic distortions and torque pulsations. The control system coefficients are calculated beforehand. The speed controller is adjusted to the technical optimum. In the main flux linkage oriented control system, it is also desirable to use an SVPWM-based formation of the motor voltage.     

A harmonic model for the nonlinearities of single-phase transformer with describing functions

In a transformer, the harmonic model is essential for the filter design and analysis of harmonic power flow. Among all of the harmonic analyses of nonlinear devices, the core nonlinearity caused by the transformer hysteresis has received the most interest. Although many harmonic models have been proposed to interpret the nonlinearity of the transformer core, most of them require complex calculations. In this study, we derive the mathematical formulas of the exciting current for a single-phase transformer by the describing function methods. The mathematical expression allows us to obtain the Fourier series for the exciting current; and, then, it provides the various order harmonic magnitudes and phase angles of the exciting current. This work also presents a mathematical model characterized by simple calculation and with high precision for the harmonics of exciting current. The transformer is under no load condition. Actual measuring verifies the effectiveness of the proposed model.