传统的基于最小二乘法的谐波状态估计受到量测装置少、精确的谐波阻抗获取难、网络拓扑结构复杂以及电网运行方式变化等因素的限制,造成量测方程欠定、系统非全局可观以及节点间耦合关系难以准确提取等问题.文中提出了一种基于改进生成对抗网络的谐波状态估计方法.该方法基于pix2pix谐波状态估计网络拟合监测节点与目标节点间的耦合关系,利用采集的历史谐波数据,对模型进行批量训练,通过训练之后的生成网络估算目标节点谐波电流、谐波电压幅值,实现基于数据驱动的谐波状态估计.在加噪环境下对模型进行测试,仿真结果验证了所提方法的有效性.

随着接入电网的半导体器件开关频率的提高,换流器注入电网的谐波向着高频化方向延伸.超高次谐波是配电网电力电子化必然带来的电能质量新问题之一.本文针对非故意发射超高次谐波,从PWM脉宽调制的原理出发,分析了非故意发射超高次谐波产生原因及频率分布特征,并给出了一种能够反映超高次谐波典型特征的优选聚合频带方法,进一步分析了不同因素对超高次谐波发射的影响,为超高次谐波的检测与识别、相关标准的制定以及治理方法提供理论依据.

For households, water supply, power supply, pipeline gas and centralized heating are necessaries to maintain the normal life of a family. For Chinese urban families, water, electricity, gas, warm services are often provided by different government utility companies. Aimed at the shortage of the manual measurement of the above mentioned services‘ consumptions, a new mechanism using network metering devices is proposed in this paper. Based on the general network measurement mechanism and through analysis, this paper proposes using meter communication network as the public communication network of various metering devices, forming wireless mesh network by metering devices, constituting a virtual private network by the power company's network, and accessing to metering network based on SCEP protocol and certificates of devices. Under this new network measurement mechanism, a network routing optimization strategy, a data acquisition protocol based on IPv6 and a mesh network management system are designed, and preliminary experiments have been carried on. Experimental results show that the proposed mechanism can realize functions through the network, including the control of multi-measuring devices, topology discovery, data acquisition, fulfilling the multi-meter data acquisition system via network.

The impact of large-scale electric vehicle (EV) charging load on grids has become a hot issue all over the world, which is a strong random process with a variety of factors intertwined, and raises a major problem in research. Therefore, the article presents a decoupling analysis method which studies charging load and normal load independently and then carries out an integrated analysis with the power grid. Firstly, we calculate the average, maximum, minimum, fluctuating power of charging load and their parameters by Monte Carlo method, and get the function laws of vehicle scale and charging power on them. After that, in a scene of large penetration rate, it analyzes the influence of EV on the grid at all levels, and determines the possibility of main problems. By using this method, some conclusions are obtained. The method and the basic laws gained in this paper are universal, and can provide support for the future research of EV’s charging load.

风电的次同步谐振具有时变特性,但尚未有文献对其开展量化评估研究.为此,基于建立的考虑励磁的双馈风机的输入阻抗频域模型,引入风速的概率分布,结合Monte Carlo模拟和核心平滑密度估计技术,提出了双馈风电的频率时变次同步谐振的概率评估方法.应用所提方法,通过算例研究了风速和串补度对次同步谐振频率和系统总电阻的概率密度及累计概率分布的影响,较为全貌地刻画了双馈风电SSR的时变特性,揭示了其带宽变化特点.结果表明:双馈风机串补输电系统的发散型次同步谐振频率具有一定的带宽,且其概率密度呈现出频率区间边界小中间大的分布;串补度决定次同步谐振的频率和阻尼所处区间位置,而风速则影响区间内的频率和阻尼的概率分布.

最近电平-脉宽调制(NL-PWM)适用于中压模块化多电平换流器(MMC),较最近电平调制(NLM)可大幅减少谐波电流.NL-PWM通过电压排序实现桥臂子模块均压,均压切换设置在阶梯波跳变点,可减少额外的开关切换,但也限制了均压频率,影响了均压效果.PWM开关频率较高,在其开关点进行均压切换可大幅提高均压频率.现有NL-PWM方法基于三角载波,其开关点随参考电压变化,不便于均压控制的实施.该文提出非倍频和倍频的基于锯齿载波的NL-PWM方法,锯齿载波具有固定的跳变点便于均压控制.分析了所提调制的谐波特性,研究表明,采用倍频锯齿载波NL-PWM方法可在降低开关频率的同时保证良好的均压效果与输出电能质量.此外,所提调制亦可避免功率开关的窄脉冲.仿真与实验研究验证了理论分析的正确性.

中压多电平换流器常采用模块化结构,可应用于交/直流配电网.配电网电压较低,换流器子模块数较少,因此常采用载波移相脉宽调制(CPS-PWM)提升等效开关频率.建立CPS-PWM模型是换流器系统级建模的基础之一.调制环节非线性,因此常分析其基波.现有CPS-PWM基波近似模型以桥臂等效开关频率为准,在不对称规则采样下模型延时偏低、误差较大.以子模块为基础,通过子模块输出叠加建立了零阶保持器(ZOH)经纯延时近似、不近似以及纯延时环节经Padé近似的3种形式CPS-PWM基波近似模型,更准确地反映了CPS-PWM的频率特性.仿真研究验证了理论分析的正确性.

风火打捆系统中,风电机组的并网使得火电机组的次同步振荡情况变得更为复杂.基于IEEE第一标准模型搭建了风火打捆经串补外送系统,推导了直驱风机输出功率与火电机组次同步阻尼的关系,分析了其对火电机组次同步振荡的影响机理,并通过PSCAD平台结合复转矩系数法和时域仿真分析进行验证.基于此机理,提出了一种在直驱风机的网侧变流器控制系统无功外环处附加阻尼控制的抑制方法,并对其关键参数的优化设计方法进行了分析,时域仿真结果表明所提出的附加阻尼控制可以有效抑制火电机组的次同步振荡.

为定量分析间歇式分布式电源、随机性负荷等不确定因素对交直流配电网电压不确定水平的影响,该文提出一种交直流混合配电网区间潮流等效算法.首先,分别针对交流配电网与直流配电网在拓扑与运行方面的特殊性,给出了交、直流配电网区间潮流确定性等效的充分条件及其数学证明.然后,针对交直流混合配电网,进一步将交、直流区间潮流转化为非线性规划问题,并结合确定性等效与交替迭代法,设计了适用于交直流混合配电网等效区间潮流的算法流程.最后,基于IEEE 33节点系统扩展的交直流混合配电网,检验了区间潮流确定性等效及其充分条件的正确性与准确性,并通过换流站多种控制模式下的蒙特卡罗随机潮流验证了交直流混合配电网区间潮流等效算法的准确性与优越性.

统一电能质量控制器(UPQC)装置投入现场运行之前,开展基于实时数字仿真器(RTDS)的实验是非常重要的一步,不仅能够使UPQC控制器的功能和性能得到较为充分的验证,还可以积累经验为后续的物理实验提供重要的指导和借鉴.基于模块化多电平换流器(MMC)结构的UPQC由于模块数较多,需要触发的IGBT很多,为了合理利用RTDS宝贵的资源,在开展RTDS实验的时候,必须要对资源分配进行优化设计,其中脉冲的输入方案就是其中的一个重要环节.文章在分析MMC-UPQC的拓扑结构的基础之上,首先对RTDS及UPQC的物理控制器的结构和需求进行了梳理和分析,然后给出了两种脉冲输入方案并进行了对比分析,最后在RTDS平台上开展了数字-物理闭环仿真实验,实验结果验证了所给脉冲编码方案的可行性.

In this study, an interval arithmetic-based method has been proposed for contingency analysis of line outage in DC distribution networks. This method incorporates the uncertainties in source/load which become considerable in the system with increasing renewable generations and time-varying loads. Two-stage contingency analysis approach is adopted in this method. For the first stage of contingency screening, a contingency filter has been developed based on interval matrix norm to quickly estimate the bounds of operating state in the post-outage period. For the second stage of detailed analysis to the selected contingencies, the interval analytical model is first transformed into a non-linear programming-based equivalent model. To solve this model accurately and efficiently, successive linear programming and reformulation-linearisation techniques are employed. The proposed method is benchmarked against Monte Carlo simulations and line outage distribution factor-based method.

Intermittent distributed generation and stochastic loads cause uncertainty in power flow in distribution networks. To construct the relationship between power injections and node voltages over a long time scale and a wide operational region, an interval mapping model is proposed in this paper, which is composed of multiple affine power flow calculations and interval regression via quadratic programming. An acceleration mechanism using parallel processing and iterative acceleration is designed to improve modeling efficiency. The application of the interval model in overvoltage prevention coordinated control is further discussed. Numerical results tested by a modified IEEE 33-bus system demonstrate that the interval mapping model has good performance in assessing the impact boundaries of power injections on uncertain voltage responses. The acceleration mechanism for the modeling process gives the interval mapping model the potential for online application; the effect of overvoltage prevention control in simulation further shows its practical value.

The three-stage modular solid-state transformer (SST) is a typical SST with a non-trivial start-up process. Specifically, special controls must be used to reduce the inrush current in the DC/DC stage during the start-up process of these SSTs. For the DC/DC stage based on the widely studied single-phase-shift dual active bridge (DAB), no inner-phase-shift control is required in its normal operations. In this case, using the existing inner-phase-shift control to reduce the inrush current increases the PWM channel requirements of microprocessors and the complexity of the control system. To address this problem, this paper proposes a long-dead-time control with easy implementation to reduce the inrush current without introducing additional PWM channel requirements. Fixed-dead-time and varied-dead-time controls are also proposed to reduce the inrush current when restarting three-stage modular SSTs with small cell capacitors without increasing the PWM channel requirements. The varied-dead-time control is faster than the fixed-dead-time one. The magnitude of the DAB current under these controls is calculated, and the overall time for fulfilling the proposed controls is estimated. The simulation and experiment on a 510 V/380 V 500 kW cascaded-full-bridge SST reveal that the proposed controls can effectively reduce the inrush currents during the start-up and restart processes of SSTs.

本文从保证向电力用户连续供给一定数量和质量电能的供电能力的角度,论证了考虑电压暂降对供电可靠影响,建立计及暂降的供电可靠性评估指标体系的必要性.基于现有供电可靠性指标,相应提出了暂降等效供电可靠性指标体系,包括缺供电量等效停电时间、暂降等效平均供电可靠率和暂降等效用户平均缺供电量指标,该指标体系可以作为暂降补充指标独立计算或者纳入现有指标计算考虑暂降影响的修正指标.同时针对系统平均停电频率指标提出可以引入SARFI指标,作为暂降补充指标.最后,通过标准算例和实际试点案例说明了所提指标的合理性.

双馈风电场的次同步谐振频率具有宽频时变特性,为其抑制带来了难题.对此,基于并联型电压源换流器(VSC)技术,设计了双馈风电场群宽频带次同步谐振的抑制装置,并将其安装于风电场群的汇集线上,将抑制装置等效为受控源,给出了分析该装置抑制双馈风电场次同步谐振作用的等值电路的一般形式和简化形式,通过次同步电流的响应方程揭示了其抑制次同步谐振的作用.该装置测取汇集线的次同步电流作为馈入信号,采用宽频滤波器并进行相位补偿的方案提取振荡模态,调整其幅值和相位后,向系统中注入次同步阻尼电流,通过增强系统阻尼实现抑制.不同工况下的数字-物理闭环仿真实验结果表明,通过参数优化设计,该装置能快速、准确地动态检测出宽频带次同步谐振信号并实现有效的抑制,可集中解决大型风电场群的时变次同步谐振.

配电网的高阻抗比特点使得传统的输电网快速解耦状态估计无法使用,且快速解耦状态估计无法处理配电网中大量存在的电流幅值量测,因而往往不满足可观性要求.为此,提出一种适应于配电网的交叉逼近状态估计方法,通过交叉迭代求解所有节点电压幅值的平方和所有支路两端的相角差,待收敛后再求解电压复相量.算例分析表明所提方法对高阻抗比的配电网具有很好的适应性,在满足计算精度要求的同时具有较高的计算效率.

随着现代电力系统的不断发展,电源特性、电网络结构和负荷类型及其构成正在发生着巨大变化,电流引发的电能质量问题越来越突出,而已有方法难以对电流扰动量进行全面评估。为此,该文提出了一种改进的电流物理分量理论,包括工作电流、基波主导无功电流、基波主导负序电流、基波主导零序电流以及谐波电流分量。该方法适用于各种系统条件,并能够全面地针对电流做功效率、不平衡及谐波等物理现象进行量化。在分析电流质量评估关键问题与指标的基础上,研究了改进电流物理分量理论在电力扰动源支路或其集总支路上的电流质量评估中的应用,最后通过对物理实验与工程实测数据的评估验证了所提出方法的可行性与实用性。

随着配电系统电力电子化程度的加深和电力线通信的快速发展,配电网侧2～150 kHz的高次谐波含量不断增加,由此引发的电能质量事件及其潜在风险逐渐受到工业界的广泛关注.为研究超高次谐波在低压配电网中的传播规律,本文首先分析了低压配电网超高次谐波的典型成因,并建立了适用于描述高频特性低压配电网模型.最后,通过在Matlab/Simulink中建立的典型低压配电网测试系统,仿真研究了不同功率及线路长度对超高次谐波的影响,并着重分析了多逆变器之间、逆变器与整流型负载及变频型负载之间的相互作用及其对超高次谐波传递的影响.验证结果表明:所建立的模型充分考虑线路和变压器的高频特性,可为超高次谐波的传播特性、影响和治理提供参考.

Subsynchronous Resonance (SSR) is a potential threat for long distance power transmission from doubly fed induction generator (DFIG) based wind farms with fixed series compensation (FSC). In this paper, subsynchronous resonance damping control (SSRDC) strategy based on shunt voltage source converter is proposed. Taking account of different series compensation levels and wind speeds, several potential inputs to the SSRDC are investigated. SSRDC control parameters are determined via root locus techniques to ensure the system stability of subsynchronous modes. Considering implementation feasibility in practical project and stability of supersynchronous modes, an enhanced SSRDC is proposed. Impact of transmission line and DFIG parameters and the reactive power compensation to the mitigation effect is investigated. Time domain simulation using PSCAD/EMTDC are carried out to validate the effectiveness of the SSRDC.

为解决前推回代复仿射潮流算法在弱环及多分布式电源(DG)接口类型配电网中的适用性问题,在详细分析前推回代复仿射潮流计算特点的基础上,引入基于道路矩阵的回路分析法来解决该适应性问题.随后,针对仿射算术无法在区间不确定性条件下准确描述DG无功控制特性的不足,采用无功灵敏度矩阵与电压灵敏度矩阵两步修正的方式,提出了可计及DG无功控制特性的复仿射潮流改进算法.最后,基于IEEE 33节点系统、PG&E 69节点系统以及实际113节点系统扩展的含多DG接口类型的不同规模配电网验证了所提算法的有效性与准确性.