Parameter Matching and Optimization of a Hybrid Type DC SFCL Considering the Transient Characteristics of VSC-Based DC Systems

Abstract

Voltage source converter-based (VSC-based) DC systems play an important role in connecting large-scale renewable energy and distributed energy, but they are vulnerable to DC short-circuit fault and lacks mature protection devices and appropriate protection strategies. Therefore, a hybrid type DC superconducting fault current limiter (H-SFCL) is proposed and the current limiting mechanism of the SFCL is analyzed. According to the requirements and strategies for protection, several different effective parameter matching and optimization methods of the H-SFCL are proposed by combining optimization algorithms and two short-circuit transient calculation models of VSC-based DC systems. The optimization methods proposed in this paper are compared and analyzed in terms of convergence, running time, calculation range and stability of optimization results, revealing their respective calculation characteristics. Finally, the effectiveness of parameter matching and optimization methods are well validated by comparison and analysis of simulation. The proposed methods can select a good parameter matching scheme of the H-SFCL to deal with different requirements.Keywords: hybrid type DC SFCL (H-SFCL); DC circuit breaker (DCCB); voltage source converter (VSC); parameter matching; optimization IntroductionVoltage source converter (VSC)-based DC transmission technology can realize active and reactive power controlling [1] and bus voltage supporting [2], which can restrain the fluctuation and randomness of renewable energy in a large range and has potential advantages in renewable energy paralleling in the power grid [3,4]. Meanwhile with a common DC voltage and easy parallel connections, VSC-based DC transmission technology is the most appropriate for multi-terminal DC systems (MTDC) [5]. As a promising research hotspot, several VSC-based demonstration projects have been built including the conventional two or three level converter and modular multi-level converter [6][7][8][9][10]. Nevertheless, the safe, reliable and continuous operation of VSC-based DC system is the premise of exerting its own advantages. Due to the low damping of the DC system, DC short-circuit fault with high current rising rate and fast fault propagation speed is a great threat to the VSC-based DC system [11], which requires the sensitivity of fault identification and the rapidity of protective action. According to [12,13], DC short-circuit current must be interrupted within 5 ms to ensure the safety of VSC components.At present, there are three main methods to deal with DC short-circuit fault, including blocking trigger pulse of converter, opening all AC circuit breakers (ACCBs) on AC sides of the VSC system then opening DC circuit breakers (DCCBs) [13]. DC short-circuit current is difficult to be cleared because

Directional Correction of Over-Current Relay Using Voltage Slope in Multi Terminal DC System With SFCL

“…On the other hand, an appropriate protection method is required to operate DCCB. Established protection schemes for DC system include traveling wave, overcurrent, voltage level and current differential protection [9][10][11][12]. According to a collaborative research conducted in the TEWNTIES project in 2010, the best method for DC system protection is the current differential method using backup by overcurrent protection [13].…”

Interactions between a half‐bridge MMC and a hybrid DC breaker during fault current interruption compared to a full‐bridge MMC

“…There are some projects and publications regarding the fault detection, clearing, fault currents and the block of the HVDC converters during DC faults in, e.g. multi‐terminal systems [7, 17–22]. However, to the best knowledge of the authors, there are almost no publications treating the physical interactions between the DCCB and the corresponding VSC HVDC converters regarding the MMC internal values and especially the submodule voltage during the interruption of the DC current.…”

High‐voltage DC circuit breaker with gradual fault‐current limitation mechanism for VSC‐HVDC applications

“…To overcome the capacity issues of DCCB's, the DCCBs with FCLs of both types are used these days. Some examples of DCCBs with fault‐current limiting characteristics are reported in studies 26‐33 …”