A Single-End Protection Scheme for Hybrid MMC HVDC Grids Considering the Impacts of the Active Fault Current-Limiting Control

Abstract

In the hybrid modular multilevel converter (MMC) based high voltage direct current (HVDC) systems, the fault current can be actively suppressed by the converter itself, which endows a smaller requirement for current-limiting reactors (CLR) and a larger time margin for fault detection algorithms, comparing with the half-bridge MMC. But the robustness to fault resistance and noise disturbance of existing boundary protection schemes will be deteriorated with small CLRs. Moreover, the fast response of the fault current-limiting control will change the output DC voltage of hybrid MMC, which affects the fault characteristics and may cause mal-operation of existing protection algorithms. Thus, a single-end protection scheme considering the impacts of the active current-limiting control is proposed for the hybrid MMC based DC grids. The travelingwave characteristics under different fault stages are analyzed to evaluate the impacts of the fault current-limiting control. In addition, a coordination protection strategy versus different fault conditions is adopted to improve reliability. Various cases in PSCAD/EMTDC are simulated to verify that the proposed method is robust to fault resistance, fault distance, power reversal, AC faults, and immune to noise.

Multi‐vendor interoperability in HVDC grid protection: State‐of‐the‐art and challenges ahead

“…In HVDC grids allowing for a complete collapse of the DC voltage, the DC fault current can be controlled to zero by using FBCs [56,57]. By contrast, in HVDC grids requiring to maintain a certain level of DC voltage, DC fault current can be limited to various levels by reducing the inserted submodules or inserting negative voltages depending on the converter technologies [54,55].…”

“…High‐speed DCCBs are likely to require smaller limiting inductances while ensure continuous operation of the HVDC grid during DC faults [96, 98]. Recent work focuses on (i) optimizing DCCB parameters coordinating with converter DC fault‐ride‐through requirements (DC‐FRT) [97, 98], (ii) coordinating fault clearing with pole voltage rebalancing in symmetrical monopolar systems [26, 27], (iii) novel DCCB technology, such as unidirectional DCCBs [100] and (vi) using the current control capability of hybrid MMCs to reduce the required speed, breaking capability and/or energy dissipation capability [55, 101, 102].…”

An Improved DC Line Fault Detection Scheme Using Zone Partition for MTDC Wind Power Integration Systems

“…As pointed out in [20], for boundary protection schemes, large CLRs (more than 100mH) are required to guarantee high reliability and selectivity. Various simulation results demonstrate that 200mH CLRs are required to guarantee robustness to high fault resistances and noise disturbance [21]. However, the cost and weight of CLRs should also be considered, which means the sizes of CLR may not be sufficient for selective and reliable protection design.…”

“…Pilot protection schemes can guarantee high reliability to identify external and internal faults under weak boundary conditions [25][26]. However, they are highly dependent on the communication between stations, which is sensitive to data code error and synchronization error [21]. Hence, single-end non-boundary fault detection schemes independent of CLRs are required.…”

Research on Multi-Port DC-DC Converter Based on Modular Multilevel Converter and Cascaded H Bridges for MVDC Applications

“…In high-voltage and high-power DC conversion occasions, MMC also has greater advantages. However, in the case of medium-voltage and low-voltage power distribution levels, the structural characteristics of MMC will lead to a great increase in cost and losses [14][15][16][17][18], [20][21][22][23].…”