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多电压等级交直流配电系统潮流分析
Power Flow Analysis of AC/DC Distribution System with Multiple Voltage Levels
随着分布式电源及直流负荷的发展,兼具安全、可靠、高效的交直流混合配电网将成为未来配电网发展的一种重要形式。基于电压源型换流器的直流配电网具有可控性强、电能质量问题少、经济性好等优点,但同时也引入了有别于交流配电网的潮流计算问题。为此,文章首先建立了考虑换流器损耗以及直流变换器损耗的潮流计算模型,并给出损耗参数计算方法。其次介绍了直流系统潮流模型的求解方法,重点考虑了电压源型换流器和DC/DC变换器控制方式对潮流计算的影响,针对不同的控制策略给出不同的潮流求解方法,并给出了当潮流越限时几种有效的解决措施。最后利用IEEE 33节点直流配电网算例验证了提出的损耗模型的正确性和潮流求解方法的有效性。
With the development of distributed generation and DC loads, a safe, reliable, and efficient AC-DC hybrid distribution network will become an important form for future development of distribution network. The DC distribution network based on the voltage source converter has the advantages of strong controllability, few power quality problems, and good economy. At the same time, it also introduces a problem of power flow calculation that is different from the AC distribution network. This paper firstly establishes a model for power flow calculation that takes into account inverter losses and DC converter losses, and gives calculation method for loss parameters. Secondly, the method for solving the DC power flow model is introduced. When analyzing the power flow of the DC system, the influence of control method of the voltage source converter and the DC / DC converter on the power flow calculation is mainly considered. Different power flow solving methods are given for different control strategies. Several effective solutions are given when the flow exceeds the limit. Finally, an IEEE 33-node DC distribution network example is used to verify the correctness of the loss model proposed in this paper and the effectiveness of the power flow solution method.
交直流系统 / 电压源换流器 / DC/DC变换器 / 潮流计算
AC/DC system / voltage source converter / DC/DC converter / power flow calculation
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随着电力电子技术的发展,相比交流配电网,直流配电网在很多领域取得了技术和经济优势,具有巨大的发展前景。首先对直流配电的发展历程、优势及运行特点等进行了论述和分析；在此基础上,介绍了直流配电网在一些发达国家的研究现状与发展情况。其次,对直流配电网研究中的系统架构、控制技术、保护技术等关键问题和相关研究现状进行了全面的阐述。最后,对直流配电网在中国的发展进行了介绍和展望。
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相较交流配电网，直流配电网具有供电容量大、线路损耗小、电能质量好、无需无功补偿，以及适于各类电源和负载接入等优点。较为详细地论述了直流配电（相对交流配电）的特点、优势及其网络的整体概念，提出了直流配电网的拓扑结构，总结了直流配电网在规划设计、调度控制、继电保护及关键设备等方面的研究情况，最后指出了直流配电网优化调度、故障诊断与定位、直流断路器等尚需深入研究的问题。
In contrast to the AC distribution network， the DC distribution network has higher power supply capability， lower line losses， better power quality， freedom from reactive compensation， and is suitable for all kinds of power supply（including renewable energy power） and load access， etc. This paper deals with the DC distribution（relative to the AC distribution） characteristics， its advantages and overall concept in detail; puts forward its network topology structure; and summarizes the network planning design， dispatching control， relay protection， key equipment， and other aspects of the research. Finally， it is pointed out that the DC distribution network optimization dispatching， fault diagnosis and location， DC breaker， etc， are problems for further study.
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刘耀华, 裴玮, 杨艳红 , 等. 多端直流的交直流配电网潮流计算[J]. 电力建设, 2016,37(5):83-90.
传统的交直流潮流计算方法主要用于输电网计算，而交直流配电网需要考虑交流网侧三相不平衡和直流网侧分布式电源低压多端直流接入等问题。针对这一问题，提出了一种考虑三相不平衡的含多端直流的交直流配电网交替求解算法。（1）对交流系统和换流站三相不平衡建模；（2）计及换流站不同控制方式，推导了直流潮流方程，在其基础上，推导了含DC/DC变换器的直流潮流计算修正方程式，根据DC/DC变换器和换流站控制方式的不同，在交直流潮流计算中提出不同的等效处理方式；（3）通过改进的IEEE 34节点算例进行了仿真验证。仿真结果表明，在多端直流不同控制模式下，所述交直流配电网潮流计算方法处理三相不平衡、分布式电源直流接入等问题具有较好的收敛性能。
The traditional AC/DC power flow calculation method is mainly used for transmission network, but the AC /DC distribution network needs to consider many problems, such as three-phase unbalance on the AC side, low voltage multi-terminal DC (MTDC) access in to distributed generation on the DC side, and so on. To solve those problems, this paper proposes the MTDC power flow calculation sequential method for AC/DC hybriddistribution networkwith considering three-phase unbalance.Firstly, we construct the unbalanced three-phase model for AC system and converter station. Then,we derive DC power flow equation with considering different control modes of converter station. On this basis, we derive the modified equation for DC power flow calculation with DC/DC converter. According to different control modes for DC/DC converter and converter station, we propose the different equivalent solution ways for AC/DC power flow calculation. At last, an improved IEEE 34 node example is presented to verify the proposed algorithm. The simulation results show that the proposed power flowcalculation method of AC/DC distribution network for processing three-phase unbalance, distributed generation for DC and other problems has better convergence performance, under different control modes of MTDC.
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In this paper, a steady-state multi-terminal voltage source converter high voltage direct current (VSC MTDC) model is introduced. The proposed approach is extended to include multiple AC and DC grids with arbitrary topologies. The DC grids can thereby interconnect arbitrary buses in one or more non-synchronized AC systems. The converter equations are derived in their most general format and correctly define all set-points with respect to the system bus instead of the converter or filter bus, which is often done to simplify calculations. The paper introduces a mathematical model to include the converter limits and discusses how the equations change when a transformerless operation is considered or when the converter filter is omitted. An AC/VSC MTDC power flow is implemented using MATPOWER to show the validity of the generalized power flow model.
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文中提出了增广直角坐标下的交直流潮流模型,并采用牛顿法进行统一求解。该模型可以解决任意拓扑形式的交直流网络潮流问题,适应直流配电网的潮流计算。给出了VSC损耗模型及其具体参数计算方法,考虑了电压下垂控制的先进控制策略。采用了增广直角坐标模型,使得雅克比矩阵非常稀疏,且绝大多数非零元素在迭代过程中保持常数,极大地提高了计算效率。含多个VSC的直流配电网的仿真结果证明了所提出方法的正确性、灵活性和高效性。
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通常计算含电压源换流器(voltage source converter,VSC)的并联型直流电网与交流电网共同组成的交直流混合电力系统的潮流,按照VSC换流站的控制方式列写对应的电网潮流方程,将有多种表达形式,不便于控制方式切换时潮流的统一求解.该文建立任意控制方式下VSC换流站交,直流两侧变量关系的3个统一表达式,控制方式切换仅改变表达式中的某些系数值,使得混合电网的统一潮流表达模型不变,仅其对应的雅克比元素值改变.提出了基于牛拉法的潮流求解算法,发生电源,负荷方式变化后,首先通过调度计划切换换流站控制方式自动获得可行解.若切换后仍无可行解,则采用约束潮流方法修正指令值,最终自动求取可行解.在交直流混合电网进行诸如N - 1安全校验潮流计算,连续潮流计算需要控制方式切换时,该文表达和方法将大大提升计算效率.以含7端VSC直流电网的交直流混合电网为算例,验证了表达与求解的高效性和有效性.
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