直流配电网光伏变流器柔性出力自适应分段下垂控制

doi:10.12204/j.issn.1000-7229.2021.10.007

摘要/Abstract

摘要：

在含光伏的直流配电网系统中,传统的下垂控制在光伏出力变化的情况下,存在功率分配不均衡及母线电压偏差大等问题。针对光伏出力受环境因素影响较为严重,引起传统下垂控制效果变差这一问题,根据光伏出力变化情况自适应调节下垂特性曲线,使其在重载条件下实现功率的精确分配,在轻载条件下,实现母线电压的稳定控制。通过建立下垂控制输出阻抗模型,分析了下垂系数自适应变化对系统环流抑制能力及均流度的影响。在MATLAB/Simulink中搭建光伏直流配电网进行仿真验证。理论分析和仿真验证表明所提光伏变流器柔性出力自适应分段下垂控制能够按照光伏电源出力动态调节功率分配任务,在重载时可以提高系统功率分配精度,轻载情况下可以减小直流母线电压偏差。

关键词: 直流配电网, 下垂控制, 光伏出力, 功率分配

Abstract:

In a DC distribution system with photovoltaic power, according to traditional droop control, when photovoltaic power output changes, there will be problems such as unbalanced power distribution and large deviation of bus voltage. Photovoltaic power output is seriously affected by environmental factors, which causes the effect of traditional droop control to deteriorate. In response to this problem, the droop characteristic curve can be adaptively adjusted according to the changes in the photovoltaic output, so that it can achieve accurate power distribution under heavy load conditions. At the same time, this solution can also achieve stable control of the bus voltage under light load conditions. Through the establishment of the output impedance model of droop control, the influence of the adaptive change of droop coefficient on the system's circulation suppression and current sharing is analyzed. In addition, a DC distribution network with photovoltaic power is built in MATLAB/Simulink for simulation verification. A combination of theoretical analysis and simulation verification shows that the proposed adaptive segmented droop control for flexible output of photovoltaic converter can dynamically adjust the power distribution task according to the photovoltaic power output. Specifically, the system power distribution accuracy can be improved when the load is heavy, and the DC bus voltage deviation can be reduced when the load is light.

Key words: DC distribution network, droop control, PV output, power distribution

中图分类号:

TM402

刘青, 张彤钰, 田艳军. 直流配电网光伏变流器柔性出力自适应分段下垂控制[J]. 电力建设, 2021, 42(10): 60-70.

LIU Qing, ZHANG Tongyu, TIAN Yanjun. Adaptive Segmented Droop Control for Flexible Output of Photovoltaic Converter in DC Distribution Network[J]. ELECTRIC POWER CONSTRUCTION, 2021, 42(10): 60-70.

图/表 18

图1 光伏接入直流配电网系统拓扑结构

Fig.1 Topology of photovoltaic power's parallel connection to DC distribution network

图2 直流配电网协调运行控制

Fig.2 Coordinated operation control of DC distribution network

图3 分段下垂特性曲线

Fig.3 Characteristic curve of segmented droop

图4 直流配电网简化电路模型

Fig.4 Simplified circuit model of DC distribution network

图5 优化前光伏变流器柔性出力自适应分段下垂控制特性曲线随δi变化情况

Fig.5 Characteristic curve of adaptive segmented droop control based on flexible output of PV converter before optimization δichanges

图6 出力不同的光伏电源的优化前光伏变流器柔性出力自适应分段下垂控制曲线

Fig.6 Adaptive segmented droop control curve for flexible output of photovoltaic converter before optimization for photovoltaic power supply with different output

图7 优化后光伏变流器柔性出力自适应分段下垂控制曲线

Fig.7 Optimized adaptive segmented droop control curve for flexible output of photovoltaic converter

图8 光伏变流器柔性出力自适应分段下垂控制系统的控制框图

Fig.8 Control block diagram of adaptive segmented droop control for flexible output of photovoltaic converter

图9 储能装置控制框图

Fig.9 Control block diagram of energy storage device

图10 PQ控制模式下G-VSC控制框图

Fig.10 G-VSC control block diagram in PQ control mode

表1 系统主要参数

Table 1 Main parameters of the system

表2 各下垂控制方法的k'droopi值

Table 2 Value of each droop control method

图11 随 k ' d r o o p i变化的输出阻抗特性波特图

Fig.11 Bode diagram of the output impedance characteristics with k ' d r o o p i

图12 光伏电源辐照度变化图

Fig.12 Radiation variation diagram of photovoltaic power supply

图13 各光伏电源出力系数

Fig.13 Radiation variation diagram of photovoltaic power supply

图14 不同下垂控制方法电压对比

Fig.14 Voltage comparison chart of different droop control method

图15 4种下垂控制方法下各变流器输出功率图

Fig.15 Output power diagram of each converter under four droop control methods

图16 各光伏侧变流器输出功率对比图

Fig.16 Comparison of output power of each PV-side converter

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