无功规划及其在功率管理中的运行 毕业论文外文翻译.doc

reactive power planningand operating in the deregulated power utilities. introductionthe purposes of this paper are to review the current strategy of reactive power management and search for proper reactive power strategy, which is expected to result in a more efficient and economic way in reactive power management. these goals are actually consistent with the spirit of the deregulation of power industry. reactive power affects system voltages, energy loss as well as system security. as power system deregulation has been widely accepted by power industry, the philosophy of reactive power management and power system operation is expected to be much different in order to meet the spirit of deregulation and the security requirements. in a vertically integrated utility, reactive power facilities are owned and operated by the same utility. the costs and contribution of reactive power supply are not precisely evaluated. under deregulation circumstance, the obligations and rights of the owners of reactive power facilities become an essential issue that affects not only the investment returns of power industry but also the power system security. this situation is even more complicated for the interconnection of several self-supported systems.reactive power is always required during power delivery in an ac system even there are no reactive power loads. however, unlike real power, reactive power is not consumed by any elements of a power system. reactive power is swapping twice per voltage cycle between capacitive elements and inductive elements. when capacitive elements are absorbing reactive power, inductive elements must be releasing reactive power, and vise versa. the capacities of these capacitive/inductive elements are not always constant. the amount of reactive power that is related to line charging is proportional, while that related to series reactance is proportional.reactive power compensation can be made at different levels: distribution, transmission and generation. for a vertically integrated utility, the costs of reactive power compensation might be included into distribution cost or transmission cost depending on where the compensation devices are installed. the costs of reactive power supplied by generators might not be listed separately, or even the reactive power capacities of generators are not considered as the costs of reactive power. when utilities are doing reactive power planning, different utilities might have different considerations. no matter how utilities treat the costs of reactive power compensation or how they carry out the planning, the electricity price always reflects this part of costs. in the deregulated power industry, several questions that were not seriously discussed in regulated era are raised, such as: who is responsible for the reactive power compensation, are the providers of reactive power services, do consumers need to pay for the required reactive power loads, what roles should generation companies play in reactive power compensation, etc.under deregulation circumstance, power system security faces more threats than ever. due to the potential dynamic power trading, the reactive power requirements are also dynamically changing. some generation units are inefficient in generating real power and are not competitive on power market. however, they are necessary to stay online in order to maintain system voltage. this type of must-run units causes few arguments in the regulated power industry. not all must-run units must be on-line all the time. depending load and operating conditions, some of them can be off-line but must be standby and some of them must be on-line only under certain conditions. most generators have a limitation of minimum real power output and can not simply operate as synchronous condensers. their operating costs should include real power cost.reactive power compensation atdistribution levelmain purposes of reactive power compensation at load sites are to reduce long distance transmission of reactive power and reduce the reactive power flow within distribution network, thus reduce mw loss and voltage dip. reactive power itself is sort of energy swapping between reactive element and capacitive element and is not consumed for pure reactive and capacitive elements. if most of reactive power load can be supplied at load sites, the amount of reactive power flow in either transmission network or distribution network can be reduced.fig. 1 is a 12-bus sample system which is a small piece of distribution network of new york city. the loads and shunt compensations shown in the figure are three phase total. balanced three-phase load is assumed in the calculation. four compensation cases are presented to illustrate the effects on mw loss and voltage dip. all four cases are under same load conditions as shown in fig. 1 except that the reactive power compensations are different:case 1 : without reactive power compensation.case 2: reactive power compensations are shown in fig. 1.case 3: total reactive power compensation of case 2(1380 kvar) is made at bus # 1case4: reactive power compensation at bus #1 is increased to obtain unity power factor.similar situation can be found from bus voltages. compensation method of case 2 is most effective in voltage improvement among those cases. case 3 and case 4 have no direct effects on bus voltages of distribution network.reactive power compensation in transmission networkfor normal operation the compensation should be sufficient to keep the voltages of feeders within an acceptable range. for emergency operation the compensation should be able to keep the voltages within a wider acceptable range with the reactive power support from generation companies.fig. 2 is a small system of 110 buses, 136 branches including 71 transformers and 33 generators. system load is about 400 mw. individual bus loads are not shown in the figure. the first case is base case. in the base case power factors of generators are not necessary the same and, similarly, power factors of load buses are not necessary the same either. in the second case, load conditions are the same as base case, including 3 shunt compensations, but with the generators operating near unity power factor. the last four cases, generators are operating near unity power factor and the power factor of all load buses is assumed 1.0, 0.95, 0.9 and 0.85, respectively.reactive power resreve of generatorsthe proposed reactive power management scheme assumes that generators are not responsible for reactive power supply under normal operation conditions. the generators, however, have to have sufficient reactive power reserve for contingencies. an important issue is how much reserve is necessary for each generator since reactive power capacity directly affects generator price. properties of contingency, location of power plant and criteria of voltage quality all affect the required amount of reactive power reserve for the generators. for the interconnected system, the strength of tie lines and neighboring systems also play an essential role. it is different from the estimation of real power spinning reserve, power plant outage is not necessary severer than reactive power facility failure. therefore the reactive power reserve for contingency for each generator should be carefully defined.conclusionsthis paper suggests that the distribution companies are responsible for the compensation of reactive power loads and the transmission companies are responsible for the necessary reactive power compensation to ensure the power delivery under normal conditions. the generation companies are responsible for reactive power requirements under contingency conditions. transmission companies are entitled to charge to distribution companies for supplying reactive power load if the distribution companies are unable to keep unity power factor. generation companies are entitled to charge the transmission companies for the reactive power supplies during normal operation. the generators should keep certain amounts of reactive power reserve for contingencies. 英文文献译文无功规划及其在功率管理中的运行、绪论这篇论文的目的是评论无功管理的发展策略和寻找一个更适当的无功策略，即期望其在无功管理中更有效更经济的方法。这些目标事实上是和电力工业异常时的精神是一致的。无功功率影响系统的电压、能量损耗及系统安全。随着电力系统违规规则被广泛接受，为了会合规则的精神和安全需求，电力系统管理和电力系统运行方面的专家被寄予不同的期望。在一个垂直的、完整的效用体系中，无功设备通过相同的效用承认和运行。无功补偿的代价和贡献并不是实际的估值。在违规条件下，无功设备所有者的权利和职责成为本质的事件，不仅影响电力工业的投资回报还影响电力系统的安全。这种情形在几个自给的互相联络的系统中甚至更复杂。无功功率在一个甚至没有无功负载的交流系统的功率传输中也是必需的，不像有功，无功不被电力系统中的任何一个元件消耗。无功在容性元件和感性元件之间每一电压周期交换两次。当容性元件吸收无功，则感性元件必须发出无功，而且数值相同。这些容性/感性元件的容量并不常常是不变的。线性负荷无功的量是均衡的，相关的连续电抗也是均衡的。无功补偿可以被调整在不同的标准：分配、传输、产生。作为一个垂直的完整的设备，无功补偿器的成本或许包括在配电成本中或者在输电成本中取决于补偿设备的安装位置。发电机无功补偿的供给成本可能不被分离列出，或者甚至发电机的无功能量作为无功成本不被考虑。当设备作为无功规划，不同的设备可能有不同的考虑。不管无功补偿的成本怎样，他们怎样编制计划，电费始终反映这部分费用。在电力工业中，有几个不严重的在控制时代被讨论的问题被提出，像：谁负责无功功率的补偿？是无功补偿装置提供，消费者是否需要支付无功负载的费用？发电机应该在无功功率补偿中担当什么角色？等等。在违规情况下，电力系统安全比以前面临更多的威胁。由于电力潜在的动态交换，无功需求也是动态变化的。一些发电厂发出有功效率低下及在电力市场不具有竞争力。但是它们为了加强系统电压保持上电网是必要的。这种必须运行的电厂在被管制的电力工业引起一些争议。依据负荷和运行条件，它们中的一些可以不用上网但是必须作为后备，另一些仅在确定的条件下必须上网。大部分发电机有实际最小视在功率输出的限制，并且不能简单地作为同步电容器运转。它们的运行费用应该包含视在功率成本。ii、配电网络中的无功补偿 负载点无功补偿的主要目的是减小长距离输电的无功功率和减少配电网络的