考虑电压动态的电力系统频率强度量化方法

Quantification Method for Power System Frequency Strength Considering Voltage Dynamics

现有电力系统频率强度量化方法通常假设各节点电压幅值恒定。然而,频率扰动过程中各节点电压幅值并非恒定,且可能通过影响负荷等途径而作用于系统频率,故电压恒定的假设可能导致量化结果不准确,甚至出现错误的结论。为此,提出了一种考虑电压动态的电力系统频率强度量化方法。首先,建立了考虑电压动态的系统频率响应模型。其中,电压动态对系统频率的影响通过一个全局耦合项表征,并揭示了电压和频率的交互作用路径。基于此,分析了多种考虑电压动态的设备及负荷对系统频率的影响,包括采用混合同步控制的构网型变流器、附加频率或电压外环的跟网型变流器,以及考虑电压特性的恒阻抗-恒电流-恒功率(ZIP)静态负荷和异步电机负荷等。然后,通过将电压耦合项分区解耦并进行统一简化建模,量化分析了系统各区域的频率支撑能力以及整个系统的频率强度。最后,通过仿真验证了所提频率强度量化方法的有效性。

The current quantification methods of power system frequency strength usually assume that the voltage magnitude at each node is constant.However,during the process of frequency disturbance,the voltage at each node is not constant and may affect the system frequency through various pathways such as influencing loads.Therefore,the assumption of constant voltage may lead to the conclusion with the inaccurate quantification results,or even erroneous conclusions.Therefore,a quantification method of power system frequency strength considering voltage dynamics is proposed.First,a frequency response model for the system that considers voltage dynamics is established,in which the influence of voltage dynamics on the system frequency is characterized by a global coupling term,revealing the interaction paths between voltage and frequency.Based on this,the specific effects of various devices and loads that consider voltage dynamics on the system frequency are analyzed,including the grid-forming converters employing hybrid synchronization control,grid-following converters with additional frequency or voltage outer loops,and constant impedance-constant current-constant power(ZIP)static loads and asynchronous motor loads with distinctive voltage characteristics.Next,by partitioning and decoupling the voltage coupling term and performing unified and simplified modeling,the frequency support capability of each zone in the system as well as the overall frequency strength is quantitatively analyzed.Finally,the effectiveness of the proposed method for quantifying frequency strength is validated through simulations.