跟网型逆变器同步稳定性分析及增强控制方法

doi:10.19595/j.cnki.1000-6753.tces.250588

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摘要

新能源并网逆变器接入弱电网时易在大扰动下同步失稳,易致新能源系统脱网,影响电力系统的安全稳定运行。本文针对跟网型并网逆变器在大扰动下的同步稳定性问题,构建了考虑锁相环动态和电网阻抗的跟网逆变器降阶模型,在所建模型基础上结合相平面法研究了电网电压暂降时跟网逆变器的同步失稳问题,发现锁相环在暂态过程中具有负阻尼效应,是导致逆变器同步失稳的主导因素。基于此,提出了一种改进锁相方法,通过在传统锁相环结构中引入频率偏差反馈,提升了锁相环的等效转动惯量和阻尼系数,增强了逆变器在大扰动下的同步稳定性。搭建了2MW并网逆变器仿真模型和硬件在环实验平台,结果验证了所提方法的有效性。

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关键词 ：新能源发电, 跟网型并网逆变器, 锁相环, 同步稳定性, 稳定控制

Abstract：

Renewable energy resources (RESs) such as wind power and photovoltaic power have been developed rapidly and applicated in large scale in recent years. The phase-locked loop (PLL) based grid-following inverters (GFLIs) are widely used to connect RESs to the power system due to their advantages of high efficiency, flexibility and controllability. However, with the continuous increase in penetration of power electronic devices and RESs within the power system, GFLIs are prone to loss synchronous stability under transient events like grid voltage sage, grid short circuit and so on, resulting in disconnection of RESs and threatening the safe and stable operation of the power system. Therefore, it is crucial to study the stability issues of GFLIs under transient events. The analysis results reveal that the PLL poses a negative damping effect, which will decrease GFLI’s synchronous stability during transient events, especially under weak grid condition. To address this issue, a stability control method is proposed in this work to enhance GFLI’s synchronous stability during transient events in weak grid condition.
The basic idea of the proposed stability control method is to reduce the negative damping effect introduced by the PLL. Base on this, a feedback loop that uses the deviation of the angular speed between the PLL and the grid as feedback signal is added to the conventional PLL, thereby reducing the negative damping effect of the PLL. Theoretical analysis shows that the stability control method improves the small-signal stability margin of GFLI, increases the equivalent inertia and damping coefficient of GFLI, and thus enhances system’s synchronous stability. The parameter design principle of the stability control method is given with consideration of different grid conditions.
Simulation and hardware-in-the-loop (HIL) experiment results validate that the proposed stability control method can enhance the stability of GFLI under the conditions of grid voltage sag, sudden changes in grid impedance and grid phase. With the traditional PLL that doesn’t adopt the stability control method, the system losses synchronous stability when grid voltage drops from 1pu to 0.63pu, grid impedance steps from 1p.u. to 1.58p.u. and grid phase steps 190°. On the contrary, with the stability control method, the GFLI grid-connected system can maintain stability when grid voltage drops to 0.58pu, grid impedance steps to 1.68p.u. and grid phase steps 200°.
The following conclusions can be drawn through the research presented in this paper: (1) The necessary condition for GFLI grid-connected system to maintain stability during transient events lies in the existence of a post-fault steady-state equilibrium point (SEP), which must satisfy the small-signal stability criterion. (2) The smaller the voltage sage, grid inductance, PLL’s integral coefficient, and the system active current, the greater the system stability. PLL’s proportional coefficient poses dual effects on GFLI’s stability. Within a certain range, increased proportional coefficient can enhance system’s synchronous stability. However, excessive proportional coefficient will induce overspeed angular velocity in the GFLI, even make the system fail to meet the small-signal stability condition, thereby deteriorating system’s stability. (3) The proposed stability control method can not only enhance the small-signal stability margin of GFLI, but also strengthen synchronous stability.

Key words： Renewable energy power generation grid-following inverter phase-locked loop synchronous stability stability control

收稿日期: 2025-04-11

PACS:

TM464

基金资助:

直流输电技术国家重点实验室开放基金资助项目（SKLHVDC-2023-KF-04）

通讯作者: 陈家伟男,1986年生,教授,博士生导师,研究方向为新能源发电与微电网、分布式发电系统功率控制与能量管理策略等。E-mail：echenjw@cqu.edu.cn

作者简介: 王鹏飞男,1997年生,博士研究生,研究方向为新能源并网系统稳定性分析与控制。E-mail：20231301012@stu.cqu.edu.cn

引用本文:

王鹏飞, 陈家伟, 罗超, 顾浩瀚, 蔡海青. 跟网型逆变器同步稳定性分析及增强控制方法[J]. 电工技术学报, 0, (): 20250588-20250588. Wang Pengfei, Chen Jiawei, Luo Chao, Gu Haohan, Cai Haiqin. Synchronous Stability Analysis and Enhancement Control Method for Grid-following Inverters. Transactions of China Electrotechnical Society, 0, (): 20250588-20250588.

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