Review of Small-Signal Converter-Driven Stability Issues in Power Systems

Abstract

New grid devices based on power electronics technologies are increasingly emerging and introduce two new types of stability issues into power systems, which are different from traditional power system stability phenomena and not well understood from a system perspective. This paper intends to provide the state of the art on this topic with a thorough and detailed review of the converter-driven stability issues in partial or all power electronics-based grids. The underlying and fundamental mechanisms of the converter-driven stability issues are uncovered through different types of root causes, including converter controls, grid strength, loads, and converter operating points. Furthermore, a six-inverter two-area meshed system is constructed as a representative test case to demonstrate these unstable phenomena. Finally, the challenges to cope with the converter-driven stability issues in future power electronics-based grids are identified to elucidate new research trends.

Online-Harmonic-Detection-Based System Stabilization Function for Grid-Forming Inverters Under Various Grid Conditions

“…Additionally, Z o is the full-order transfer function matrix considering the inner voltage and current loops as shown in (9), and G VVr is the transfer function matrix from the reference voltage to the output voltage as given in (10).…”

“…With the four transfer function matrices in (1), ( 2), (9), and (10), the full impedance model of GFM (Z o_GFM_1 ) can be derived as a 2×2 multi-input-multi-output transfer function as shown in (13). (13) Note that this model can be extended to other outer power control methods, such as dVOC or VSM, by replacing the P-θ relationship in ( 5) and the Q-V relationship in (6).…”

“…6 can be obtained as shown in Fig. 8, where Z o_ff and G VVr_ff consider the impact of H v compared with Z o in (9) and G vvr in (10), respectively; and Z veq depicts the impact of Z v blocks on both power loops and inner voltage loops. Therefore, the full-order model Z o_GFM_2 (s) can be obtained as (18).…”

“…Typical outer power loop control methods of GFMs include the frequency droop control [3], [4], the virtual synchronous machine control (VSM) [5], and the dispatchable virtual oscillator control (dVOC) [6], [7], etc. These control loops in GFMs may interact with different impedances of the rest of the system and introduce small-signal stability issues into the grids [8], [9], [10]. The small-signal stability issues could be further categorized into two types according to the frequency range.…”

A Potential Issue of Using the MIMO Nyquist Criterion in Impedance-Based Stability Analysis

“…With the increasing penetration of renewables in power systems, the small-signal stability issue across a wide frequency range becomes a concern [1,2]. The impedance-based stability criterion offers an effective way to analyze the small-signal stability of such systems since no detailed internal information about system components is required [3].…”