Small-Signal Stability Analysis of Inverter-Fed Power Systems Using Component Connection Method

The small time constants of power electronics devices lead to dynamic couplings with the electromagnetic transients of power networks, and thus complicate the modeling and stability analysis of power-electronics-based power systems. This paper presents a computationally efficient approach to assess the small-signal stability of inverter-fed power systems. The power system is partitioned into individual components, including the power inverters, network impedances, and power loads. The state-space model of individual inverter is first built, where the frequency response and eigenvalue analysis collectively characterize the contributions of different controller parameters to the terminal behavior in a wide frequency range. These component models, together with the network equations, are then algebraically assembled based on the interconnection relations at their terminals. As a consequence, the state matrix of the whole system, which is essential to the system stability analysis, can be reformulated in a computationally efficient way. The experimental results are finally given to validate the effectiveness of the modeling method and system stability analysis.

I. Introduction

The growing penetration of the power electronics-interfaced renewable energy sources has led to the emergence of power-electronic-based power systems into electrical grids, such as wind farms [1], photovoltaic power plants [2], and micro-grids [3]. Those systems are featured with the high efficiency and flexibility in electric power generation and distribution, but are also more susceptible to the network disturbances in a wide frequency range [4]. In inverter-fed power systems, a number of oscillation phenomena have been reported, which includes the low-frequency oscillations caused by the droop-enabled power control [5], and grid synchronization control [6]. In addition, the harmonic-frequency oscillations from hundreds of hertz to several kilohertz may happen, which is caused by the interaction of the inner control loops as well as the inductive or capacitive behavior of inverters [7]. It is undoubtable that these oscillation phenomena will weaken the power quality and cause the instability of power system.