Frequency Characteristics of Southwest Power Grid and Scheme of Over-Frequency Generator Tripping

Based on the single machine model, the key factors affecting the frequency response of the system are studied, the expressions of the initial frequency change rate and the maximum frequency deviation after large disturbance are derived, and the mechanism of improving the frequency stability of conventional units and new energy frequency response, DC frequency modulation, load frequency response, emergency control and other factors is analyzed. According to the frequency response characteristics of Southwest Power Grid, the over-frequency generator tripping scheme is designed from the aspects of high frequency generator tripping object, starting threshold, generator tripping capacity, etc., and the coordination principle of high cycle generator tripping, generator overspeed protection and low frequency load shedding is proposed. The effectiveness of the proposed scheme is verified by practical examples.

I. Introduction

The frequency stability of power system reflects the balance of active power in the system. It is the basic condition for the safe and stable operation of the system, and the abnormal frequency will bring serious consequences to the safe operation of the generating unit and the power system and the users. Therefore, in order to ensure the security, stability and economic operation of power grid, it is necessary to deeply study the frequency characteristics of power grid, master the variation law of power grid frequency, and provide scientific basis for the formulation of power grid frequency control scheme [1] –[3].