Investigation of failures in operation of heat networks of large heat supply systems

The effect of deviations in heat network parameters on operation of heating system and hot-water supply systems in buildings is examined. The consequences of a decrease in the water temperature in a heat network under extreme weather conditions in a range below the design ambient air temperature, the efficiency of disconnection of a hot water supply system (HWSS) heater in this period, and deviations in the normal heat supply in the transition period at relatively high outdoor temperatures are considered. The specific and scope of failures depend on the design-heating load to design hot water supply load ratio for the heat network. A mathematical model was developed, and numerical investigation was performed of modern schemes of heat points which are designed primarily for covering the hot water supply load and recovering the heating system heat output in case of low or no hot water consumption in HWSS. The performed calculations demonstrate that the heating system has no time to restore its heat output, thereby considerably reducing air temperature in the heated premises. The lower the ambient air temperature and the lower the ratio of the design loads for hot water supply and heating, the greater is this decrease. At the same time, in case of a sudden decrease in the outdoor temperature and an accident in the heat supply system, the heating system must be the priority consumer, since a heating failure not only decreases the thermal comfort of consumers but can cause emergency situations in local utility systems, such as a cold water supply system. Correction of failures in a heat supply system requires calculation of operating conditions of heat networks.     

Reliability and availability modelling of combined heat and power (CHP) systems

Many subsystems are involved in the reliability modeling of combined heat and power (CHP) systems, but in most studies these subsystems have not been classified and in many cases have been considered separately. Furthermore, calculating the reliability from the generation point to the consumer has not yet been studied. Herein, we classify combined heat and power subsystems and model their reliability, availability and mean-time-to-failure indices based on interactions between subsystems from the generation site to consumer delivery. The proposed CHP reliability and availability model is based on the state space and the continuous Markov method with electricity-generation, fuel-distribution and heat-generation subsystems. The effects of fuel- and water-distribution networks at the CHP site and the hot-water-distribution network on the consumer-utility reliability of CHP systems were fully assessed in an applicable case study. Additionally, we present a sensitivity analysis for island, standby and parallel operational modes of CHP systems. The results from the case study prove that improving the gas-distribution network, the network delivering hot water to the consumers and the water-delivery network to the CHP, in addition to optimizing the failure and repair rates of CHP systems, have considerable effects on the reliability improvement of the complete integrated system and have major roles in technical and economic feasibility studies of CHP systems.     

高背压双抽热电联产机组联合运行特性及负荷分配

大型汽轮机组采用高背压方式进行供热能够尽可能多利用排汽余热,节能效果显著,在热负荷允许的条件下,已成为越来越多火电厂供热改造的首选。针对某电厂2×330 MW高背压抽汽热电联产机组进行建模,分析其理论供热能力,结合热网供回水温度分析其调峰能力与经济性投运条件,研究了采用抽凝-抽背方式(EC-EHBP)、双抽凝方式(EC-EC)运行时的抽汽与负荷分配问题,确定了抽汽分配和电负荷分配原则,明确了不同环境温度下的背压运行方式。研究结果对电厂实际运行具有指导意义。     

高背压双抽热电联产机组联合运行特性及负荷分配

大型汽轮机组采用高背压方式进行供热能够尽可能多利用排汽余热,节能效果显著,在热负荷允许的条件下,已成为越来越多火电厂供热改造的首选。针对某电厂2×330 MW高背压抽汽热电联产机组进行建模,分析其理论供热能力,结合热网供回水温度分析其调峰能力与经济性投运条件,研究了采用抽凝-抽背方式(EC-EHBP)、双抽凝方式(EC-EC)运行时的抽汽与负荷分配问题,确定了抽汽分配和电负荷分配原则,明确了不同环境温度下的背压运行方式。研究结果对电厂实际运行具有指导意义。     

300MW热电联产供热系统分析与能耗计算

热电联产是能源利用的有效方式。针对目前热电联产普遍采用的抽汽供热模式,基于一般化供热系统原理,进行热电联产供热的热力学本质分析,提出循环水直供直连供热模式,以降低系统能耗。利用串联系统单耗分析方法,针对300 MW热电机组进行一般化供热系统的单耗分析计算,得到热电联产传统抽汽供热模式各子系统的能耗分布,为热电联产总能系统能耗分析的实施奠定了基础,并据此计算分析了热电联产循环水直供直连供热模式的能耗分布。对比可知,热电联产循环水直供直连供热模式单耗为32.70kg/GJ,比传统抽汽供热模式单耗(60.62kg/GJ)降低近1/2,热电联产供热系统节能降耗尚存巨大空间。     

张家口风电中心110kV智能变电站建设及应用

介绍了张家口风电中心110 kV 智能变电站工程。重点分析了该工程的技术特点和实施方案,指出智能变电站建设中的主要技术创新点：智能终端与一次设备结合,简化开关内部二次回路;过程层设备实现开关场就地安装,采用通用面向对象的变电站事件（generic object oriented substation event,GOOSE）网络化方式实现信息共享;一次设备的在线监测系统提高设备的智能化;生产辅助系统与视频系统联动实现站内照明、通风、空调、采暖、给排水的智能控制。     

High-frequency power transmission and selective distribution among loads by using distributed constant lines

A widely used high-frequency induction heating system usually consists of a high-frequency power source and a load circuit to be heated. Since such a system can heat only one load circuit, heating two or more loads requires that other sytems be devised. Several problems result, including the need for many power sources, switches, and high-frequency power transmission lines. To solve these problems, the authors propose a new system that can selectively supply two induction heating circuits with high-frequency power. This system is composed of a high-frequency voltage-type inverter, a parallel resonant load circuit, and a series resonant load circuit, which are connected in series by distributed constant lines of specific length. Analysis of the operating characteristics of the system confirms that the system can supply the loads with high-frequency power selectively and efficiently, with minimum interference between loads. The authors have compared theoretical simulation waveforms with actual waveforms observed on experimental equipment with output ratings of 1 to 2 MHz and 1 kW. As a result, experimental data agree well with theoretical data. This paper describes an operating principle and operating conditions of the system, and verifies that the theory we discuss is reasonable.     

考虑热负荷二维可控性的微网热电协调调度

考虑到区域内用户的热、电需求,近年来以微型燃气轮机为核心的热电联供系统在微网中得到广泛应用。如何协调调度微网的供热、供电,是提高可再生能源吸纳率、降低微网热电联供成本的关键。文中从用户供热舒适度的模糊性、微网供热系统的热惯性角度考虑,提出采用室内热舒适度指标将热负荷需求由传统的曲线转换为区间,从而使热负荷在各时间点上具有弹性;同时以自回归滑动平均(ARMA)模型描述供热系统多时段间的耦合关系,使供热量在时间轴上具有一定的可调节性。文中将上述两个特性统称为热负荷的二维可控性。算例分析了考虑热负荷二维可控性后,微网在孤网/并网运行时微型燃气轮机运行平稳性、弃风/光、购/售电量等方面,结果显示所述方法可有效减少热—电刚性耦合,为实现微网中热—电的时间平移和优化匹配提供了一种新思路。     

感应加热电源中频率跟踪控制电路的设计与分析

为使感应加热电源中的逆变器始终工作在功率因数接近或等于1的准谐振或谐振状态,设计出一种适合中频感应加热电源的频率跟踪控制电路。控制电路通过压控振荡器和逻辑电路实现了频率跟踪,经过示波器的测试,电路稳定性得到了提高,捕捉速度明显改善。     

热力实时定价机制下热电联产机组多能源市场协同决策研究

随着能源市场化改革逐步深入,市场机制下热电联产(CHP)机组的运行与决策受到广泛关注,而以热定电限制了CHP机组的灵活性,影响其独立参与市场的收益.基于此,采用实时定价的热力市场机制挖掘需求灵活性,提出热力实时定价机制下CHP机组在多能源市场中的协同决策双层模型,即CHP机组参与电力市场的同时,在热力市场制定实时热价进行负荷管理释放灵活性,以最大化参与能源市场的利润.其中上层模型为CHP机组最优电力报价与热力定价模型,下层模型为电力批发市场出清模型与热用户决策模型.利用KKT条件等将双层模型转化为混合整数线性规划模型以进行求解.通过算例验证所提模型的可行性与有效性,算例结果表明热力实时定价在有效提高CHP机组电力侧灵活性与机组利润的同时,改善了用户与社会福利.最后,探究了热力实时定价机制下CHP机组在电力市场的策略报价行为.     

利用建筑物与热网热动态特性提高热电联产机组调峰能力

提出了综合考虑建筑物与集中供热管网热动态特性的热电联合运行模式,解决了因传统"以热定电"运行模式而导致的热电联产机组调峰能力不足的问题。详细介绍了基于建筑物与热网热动态特性的热电联合系统的构成方案;着重对比分析了考虑建筑物与热网热动态特性前后的热电联产机组运行点的变化情况,在此基础上明确了其能够提高机组调峰能力的机理;给出了综合考虑建筑物与热网热动态特性的热电联合调度模型。算例结果表明,所述综合模型可以显著提高机组的上调节和下调节容量,其效果优于仅考虑建筑物或者热网单一环节热动态特性的模型。进一步,将系统源侧"热电耦合"特性扩展到荷侧,利用系统"源荷协调控制"实现了机组"热电解耦"。     

交流牵引供电系统仿真通用数学模型及其应用

对交流牵引供电系统进行统一的数学建模,是实现数字化仿真的关键。以多导体传输线模型为基础,构建了适用于不同供电方式的牵引网统一数学模型;基于牵引变电所端口电气量通用变换关系,推导了适用于不同变压器接线形式和不同相序接入的牵引变电所通用等值电路;在链式网络结构的基础上,建立了交流牵引供电系统仿真通用数学模型,并改进潮流计算方法。以此为基础,开发交流牵引供电仿真软件。实例计算表明,该模型具有良好的通用性和较高的精确度,适用于高速、重载电气化铁道牵引供电系统仿真。     

以电厂循环水为热泵低温热源的联产供热系统的冷端优化

以电厂循环水为热泵低温热源的热电联产供热系统是利用以电为动力的压缩式热泵或者以抽汽驱动的吸收式热泵从电厂循环水中吸热,供热热量主要来自于循环水,其冷端调节同时影响发电收益和供热收益。以采用压缩式热泵的供热系统获得最大经济净收益为目标,对这种联产供热方式的冷端系统进行了研究,分析了冷端调节对系统收益的影响,建立了各个环节的数学模型并提出了求解算法。最后以某600MW机组和热泵组成的联产供热系统为研究对象,应用建立的数学模型对200万到800万m2之间的4个供热面积分别进行了计算,得出最佳入口温度持续增大,最佳循环倍率随着供热面积的增加先增大后减小直到调节范围的最小值,且冷端系统参数取最优时,系统的总收益总是小于热泵收益,实际运行时要在保证凝汽器真空不小于最低值的前提下,尽量选择接近理论最优值的循环倍率和入口温度。     

基于需求侧综合响应的热电联供型微网运行优化

热电联供型微网具有能源利用率高、灵活可靠的特点,成为实现能源生产和消费转型、解决环境问题的重要手段。热电联供型微网热、电紧密耦合,给其运行的灵活性和经济性带来了不利影响,为此提出基于需求侧综合响应的热电联供型微网运行优化方法。需求侧综合响应包含热负荷响应和电负荷响应,可为热电联供型微网的热、电生产提供优化空间。热负荷响应建模根据建筑物热工模型,建立供暖功率与室内温度的关系方程。电负荷响应考虑可转移负荷。在此基础上建立热电联供型微网运行优化混合整数线性规划模型,采用CPLEX软件进行求解。算例分析结果表明,需求侧综合响应的应用提高了热电联供型微网热、电生产的灵活性,同时给系统运行带来了可观的经济效益。     

基于信息间隙决策理论的含光热电站及热泵的综合能源系统低碳调度优化

为解决电–热综合能源系统（integrated energy system,IES）中热电供需矛盾导致的弃风及环境污染问题,提出了含光热电站及热泵的IES低碳调度优化模型。首先,在能源侧利用热泵的供热灵活性,打破热电联产（combined heat and power, CHP）机组“以热定电”的运行限制;考虑光热电站与CHP机组联合运行,进一步提升CHP机组运行的灵活性。其次,对IES中各设备容量进行优化配置,针对风电、光伏及光热出力的不确定性,采用信息间隙决策理论进行处理,提出风险规避鲁棒模型。最后,通过9节点测试系统验证所提模型的有效性,并划分不同场景验证光热电站及热泵对IES的优化效用。     

严寒地区发电厂冷却水余热回收系统的效益分析

搭建了电厂冷却水余热回收与利用实验台,通过实验对电厂冷却水余热回收与利用系统的供热效果进行分析。通过实验数据并结合长春热电一厂的实际运行情况对该系统进行了环保效益分析。利用费用年值法将此种供热方式与其他几种供热方式进行比较,提出了供热方式的选择原则,为严寒地区今后实际工程应用提供了参照数据。     

Cascade Equivalent A - H Circuit of an Induction Heating System with a Superconducting Inductor

Induction heating is used to heat metals before hot treatment. It provides a high quality of the process and is rather efficient in many cases. However, when heating nonmagnetic materials with low specific resistance, the efficiency of an induction heating setup becomes low. To increase the efficiency of induction heating systems, a heating method has been used in which a heated item is rotated in s transverse magnetic field created by superconducting coils. In this paper, an analytical method to calculate an electromagnetic field in a similar heating setup has been considered. The method is based on a cascade equivalent circuit obtained on the basis of the fundamentals of electromagnetic theory and the theory of electric circuits.     

分布式能源热网储能量化计算分析

研究分布式能源供热系统中热网储能特性是制定能源高效利用控制策略的必要前提。该文通过对分布式能源热网储能特性的研究,建立热网储能量化计算模型。该模型描述热网储能特性的重要参数-储能供能持续时间。引入影响因子θ对模型进行改进,提高热网换热段温度与实际工况的吻合度。针对3个换热站的试验数据,对改进后模型进行滞后时间计算,从而验证其正确性。通过对实际案例的计算,得到并分析热网储能供能的持续时间,得出循环水泵存在最佳流量的结论。此外,应用上述模型对分时分段供暖工况进行分析计算,得出24h内与室外温度正相关的热网供水温度随时间的分布。     

客户自备电源接入方式对其与电网并网的影响

对客户自备电源的接入方式按其与电网并网以及不并网运行分别进行分析。探讨了不并网自备电源接入方式中几种典型方案的合理性,分析了自备电源并网运行对客户及电网的影响,针对其中对电网的不利影响,提出了电网应采取的措施。     

The comparative effectiveness of serving peak loads in the variants of providing nuclear power plants with a base load

The present paper reports the results of an investigation into the effectiveness of serving peak loads in the variants of providing nuclear power plants with a base load through unloading condensing power plants, combined heat and power (CHP) plants, combined-cycle thermal power plants during night-time off-peak hours, the use of the off-peak electric power for power and heat supply, and water electrolysis with the use of hydrogen and oxygen for production of the peak electric power, as compared with the variant of the development of pumped storage hydropower plants.