摘要
【目的】随着大规模分布式光伏接入,潮流反送所引起的电压越限问题给电力系统的安全稳定运行带来了严峻挑战。为解决该问题,国内外均规定光伏需具有电压-无功等支撑功能,即依据电压偏差进行主动无功/有功调节。然而,该类规定通常仅考虑平衡电压场景,如何保证不平衡电压下的调压性能鲜有研究。【方法】文章以电压-无功功率控制(volt-var control,VVC)为例,分析了电压不平衡度对光伏逆变器无功功率调节性能的影响,并提出了一种以三相电压偏差最小为目标的改进型电压支撑控制方法。首先,基于瞬时功率理论分析了电压不平衡度与有功、无功功率间的数学关系,证明了无功功率的电压调节作用及电压偏差最小值点的存在;然后,以三相电压总偏差为指标,计算了电压偏差最小时对应的正序电压及无功功率,进而利用该点、电压偏差限值及光伏无功容量对电压支撑控制曲线进行了动态调节。【结果】Matlab/Simulink仿真结果表明,所提改进型电压支撑控制方法在保证三相电压不越限的同时实现了最小无功输出下的三相电压与标称电压偏差最低,完成不平衡场景下三相电压的经济、高效调节。【结论】所提控制策略为传统VVC控制与负序电流/功率控制的有效协同,在辐照度、温度等变化引起光伏出力改变或电压不平衡度变化时仍可维持三相电压运行在并网标准限值范围内,显著提升了传统VVC控制功能的适应性。
[Objective]With the integration of large-scale distributed photovoltaics,issues such as reverse power flow and overvoltage arise,posing challenges to the safe and stable operation of power systems.To address this issue,both domestically and internationally,regulations mandate that PV systems must have grid support capabilities,such as voltagereactive control,which actively regulates reactive power based on voltage deviations.However,such regulations are typically designed for balanced voltage scenarios and unbalanced voltage conditions are rarely considered.[Methods]Therefore,using voltage-reactive power control(volt-var control,VVC)as an example,this study analyzes the influence of voltage imbalance on the reactive power output and proposes an improved voltage-support control method aimed at minimizing three-phase voltage deviation.Based on instantaneous power theory,the mathematical relationship between voltage imbalance and active/reactive power is derived,demonstrating the voltage regulation effect of reactive power and the existence of the minimum voltage point.Then,with the three-phase voltage deviation as an index,the positive sequence voltage and reactive power corresponding to such point are calculated,and dynamic adjustments to the voltage-support control curve are made using this point,voltage limits,and reactive power capacity of PV inverters.[Results]Matlab/Simulink simulation results demonstrate that the proposed improved voltage-support control method ensures that three-phase voltages remain within limits while achieving minimal deviation from the nominal voltage under the lowest reactive power output.This ensures economical and efficient regulation of the three-phase voltage in unbalanced scenarios.[Conclusions]The proposed control strategy effectively coordinates the traditional VVC control with negative-sequence current/power control.It maintains three-phase voltages within grid-connected standard limits despite changes in irradiance,temperature,or other factors causing photovoltaic power fluctuations or voltage-unbalance variations,significantly enhancing the adaptability of conventional VVC control functions.
作者
曹晓庆
李特
李林
陈迪
周正旭
时晓洁
CAO Xiaoqing;LI Te;LI Lin;CHEN Di;ZHOU Zhengxu;SHI Xiaojie(Wuhan Huayuan Electric Power Design Institute Co.,Ltd.,Wuhan 430074,China;School of Electrical and Electronic Engineering,Huazhong University of Science and Technology,Wuhan 430074,China)
出处
《电力建设》
北大核心
2025年第8期34-44,共11页
Electric Power Construction
基金
国家自然科学基金青年科学基金项目(52307202)。
关键词
不平衡电网电压
光伏并网变换器
电压支撑
功率控制
瞬时功率理论
unbalanced grid voltage
grid integration of PV
voltage support
voltage-reactive power control
instantaneous power theory
