风电水电协同运行计划的优化（英文）

风电的随机波动和反调峰特性影响电网的运行,经常造成弃风。由于各方利益难以平衡,大规模全局优化调度难以实现。但是,可以利用水电机组的调节能力直接补偿风电的功率变化,充分利用风电能量和水电机组的容量;用相量测量单元(phasor measurement unit,PMU)建立风电和水电之间的直接联系,使风电水电协同运行(coordinated hydro and wind power generation,CHWG)可以将随机的风电转化成可以参与电力系统运行计划的电源。以风电水电协同运行理论为基础,建立风电场和水电厂协同运行的优化调度模型,在水电满足网络需求的条件下保证协同运行的发电机组共同按计划向电力系统提供有功功率。该模型考虑了风电预测置信度和电价,不但保持输出功率的平稳,而且可以根据电价变化优化确定输出功率。改进了粒子群优化算法,使其能够有效地求解优化调度模型。以华北地区某风电场不同季节的数据为例,验证了该方法的有效性。

导前微分控制在风电水电协同运行中的应用

风电的随机性导致大规模风电的接纳成为当前电力系统面临的重要问题。考虑到风电和水电的互补性,提出用水电厂来平抑由于风速的波动性和间歇性导致的风电场输出功率波动,通过控制水轮机实现风水协同运行的控制,使水电厂和风电场向电力系统提供的有功功率按调度计划输出。针对水轮机的特点,提出导前微分控制方案。仿真结果表明,在PID控制基础上并联导前微分控制比常规PID控制方案具有更好的控制效果。风电与水电的协同运行可平抑风电输出功率的波动性,减少对电网的冲击,有利于电网的长期稳定运行。

风电机组脱网的风险评估(英文)

随着风电机组大规模并网,风电对电力系统的影响逐渐显现。我国多次发生风电机组连锁脱网事故,影响了电力系统的运行。为了预警风电机组脱网,保证电力系统的安全运行,提出风电机组脱网的风险评估模型。由于故障组合数量爆炸,不可能在线分析所有的可能故障。因此,建立风电机组脱网指标,来衡量发生故障时风电机组的脱网概率。该指标不但考虑电力系统故障,同时也考虑了风电场内部故障。根据脱网指标和风电场到故障点的电气距离,对预想故障进行排序和筛选,生成有效预想故障子集;仅对有效故障集内的可能故障进行在线风险评估和风电机组脱网预警。该模型可以给出风电机组脱网容量。对某省电网在线数据仿真分析,验证了理论方法的正确性和预警模型有效性。

大规模电动汽车智能充电站对电力系统小干扰稳定性的影响(英文)

大规模智能充电站可以很好地满足和调节电动汽车的充电需求,但同时也不可避免地给电网的稳定性运行带来新的影响和挑战。基于阻尼转矩分析法(damping torque analysis,DTA),着重探讨智能充电站的接入对于输电网动态稳定性的影响。为了简化分析,单机无穷大系统将用于模拟配电网与外部输电网。配电网中的智能充电站群被视为一个接入输电网的等值智能充电站。分析得出,在大规模智能充电站的设计中,充电容量对于小干扰稳定性中的阻尼比有很大的影响。在其最佳充电容量下充电,将会最有利于保持系统的动态稳定,系统阻尼比也保持最大。根据所建立的Phillips-Heffron模型可知,在智能充电站的有功和无功控制通道上设计并加装稳定器,能够有效地提高系统阻尼,更快地抑制联络线上的功率振荡。算例分析验证了所得结论。

Connections Between Induction Generator Effect and Open-loop Modal Proximity to Cause Sub-synchronous Oscillations in Series-compensated Power System

The induction generator effect(IGE)and the openloop modal proximity(OLMP)are two different reasons why subsynchronous oscillations(SSOs)in a series-compensated power system(SCPS)may occur.The IGE attributes the growing SSOs to negative resistance,while the OLMP explains the SSO mechanism from the standpoint of modal conditions.In this paper,we investigate the connections between the IGE and the OLMP through equivalent RLC circuit and open-loop modal analysis.Our investigation is conducted for two types of seriescompensated power systems where either a synchronous generator or a DFIG is connected at the sending end.The investigation reveals the conditions,in which the IGE and the OLMP may jointly cause the growing SSOs,i.e.,both the IGE and the OLMP can explain why the growing SSOs occur.Furthermore,the investigation indicates that the IGE and the OLMP may be totally irrelevant and lead to growing SSOs separately.This implies that it is possible that in a SCPS,the growing SSOs are only due to the IGE,and the OLMP is non-existent,and vice versa.Hence,when the growing SSOs occurs in a SCPS,examination based on both the IGE and the OLMP should be carefully conducted in order to find if the oscillatory instability is due to the IGE,or the OLMP,or both of them.

Sub-synchronous Oscillations in Power Systems Caused by Grid-connected Wind Farms--A Survey of Mechanism Studies

Sub-synchronous oscillation(SSO)incidents caused by dynamic interaction between wind farms and power system grids can threaten safe and reliable operations.This paper investigates mechanism studies of SSOs in power systems induced by grid-connected wind farms.First,characteristics of several severe SSO incidents encountered by real power systems caused by grid-connected wind farms are introduced.Second,in terms of principles and responses,this paper illustrates the most commonly adopted mechanism investigation methods for SSOs,which include impedance-based analysis(IMA)and the openloop modal analysis(OMA)methods.Systematic reviews that summarize existing studies using the IMA and OMA methods are discussed in this paper.Furthermore,a discussion of the current research gaps in the investigation of SSOs in power systems caused by grid-connected wind farms is presented.