Transient performance comparison of grid-forming converters with different FRT control strategies

doi:10.1007/s11708-022-0856-2

Front. Energy

2023, Vol. 17

Issue (2) : 239-250 https://doi.org/10.1007/s11708-022-0856-2

RESEARCH ARTICLE

Transient performance comparison of grid-forming converters with different FRT control strategies

Chao SHEN¹(

), Wei GU¹, Enbo LUO²

¹. School of Electrical Engineering, Southeast University, Nanjing 214135, China
². Electric Power Test and Research Institute, Yunnan Power Grid, Kunming 650032, China

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Abstract

Grid-forming converters (GFMs) are faced with the threat of transient inrush current and synchronization instability issues when subjected to grid faults. Instead of disconnecting from the grid unintentionally, GFMs are required to have fault ride through (FRT) capability to maintain safe and stable operation in grid-connected mode during grid fault periods. In recent studies, different FRT control strategies with distinguishing features and that are feasible for different operation conditions have been proposed for GFMs. To determine their application scope, an intuitive comparison of the transient performance of different FRT control strategies is presented in this paper. First, three typical FRT control strategies (virtual impedance, current limiters, and mode-switching control) are introduced and transient mathematical models are established. A detailed comparison analysis on transient inrush current and transient synchronization stability is then presented. The results will be useful for guiding the selection and design of FRT control strategies. Finally, simulation results based on PSCAD/EMTDC are considered to verify the correctness of the theoretical analysis.

Keywords grid-forming converters (GFMs) fault ride through (FRT) transient stability transient inrush current transient modeling

Corresponding Author(s): Chao SHEN

Online First Date: 04 January 2023 Issue Date: 29 May 2023

Cite this article:

Chao SHEN,Wei GU,Enbo LUO. Transient performance comparison of grid-forming converters with different FRT control strategies[J]. Front. Energy, 2023, 17(2): 239-250.

URL:

https://academic.hep.com.cn/fie/EN/10.1007/s11708-022-0856-2
https://academic.hep.com.cn/fie/EN/Y2023/V17/I2/239

Fig.1 Different stages of GFMs throughout the whole transient period.

Fig.2 Control block diagram of a GFM connected to a grid with three typical FRT control strategies.

Tab.1 The corresponding relationship between the switcher and FRT control

Tab.2 Transient current elimination of GFMs with different FRT control strategies

Fig.3 Equivalent model of a GFM when different FRT control strategies are adopted.

Parameter	Value	Parameter	Value	Parameter	Value
V_dc/V	1000	P₀ + jQ₀/kVA	20 + j5	K_p	20
E₀/V_g/V	311/311	ω₀/(rad·s^–1)	314.15	K_i	400
J	5.0224	K	32	I_max/A	100
D	8	R₂ + jX₂/Ω	0.314 + j0.785	I_ref/A	30
D_q	166.7	R₁ + jX₁/Ω	0.314 + j0.314	$I d ref ∗$ and $I q ref ∗$ /A	80
L_f/C_f	3 mH/40 μF	Z_v/Ω	0.157 + j1.57	$I q r e f ∗ / A$	60

Tab.3 Detailed parameters of the grid-connected GFM

Fig.4 Time-domain simulation results of a GFM with different time delays.

Fig.5 Control topology of different synchronization control strategies.

Fig.6 Transient stability mechanism of a GFM under different FRT control modes.

Fig.7 Design-oriented transient stability analysis of the GFM.

Fig.8 Transient instability phenomenon of a GFM with different FRT control strategies when the grounded fault is cleared at 1.9 s.

Fig.9 Simulation results of a GFM with different FRT control strategies when detailed control parameters are re-designed.

Fig.10 Simulation results of a GFM with phase portrait in the ω-δ domain when different FRT control strategies are considered.

Tab.4 Transient stability comparison throughout FRT process

Fig.11 Relationship between the CCT and SCR. (The bold solid line is the CCT under VIC, the dashed line is the CCT under MSC, and the solid line is the CCT under CLC.)

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