A Controllable Thyristor-Based Commutation Failure Inhibitor for LCC-HVDC Transmission Systems

Abstract

Commutation failure is a serious malfunction in linecommutated High Voltage Direct Current (HVDC) converters which is mainly caused by the inverter ac faults, and results in a temporary interruption of transmitted power and damage to the converter equipment. In this paper, a Controllable Commutation Failure Inhibitor (CCFI) is developed which obviates the main drawbacks of the existing power-electronic-based and faultcurrent-limiting-based strategies. Under normal circumstances, the developed CCFI improves the steady-state stability and the power transfer capability of the inverter ac lines, while it does not cause excessive voltage stress on the converter valves. In addition, it would reduce the risk of commutation failure occurrence, since it does not lead to any voltage drop in the commutation circuit. When a fault occurs at one of the inverter ac systems, its corresponding CCFI limits the fault current depending on the reduced extinction angle. This would not only inhibit the successive commutation failures on the HVDC converter, but also extend the lifetime of components in the inverter ac systems. The practical feasibility of the developed CCFI is assessed through laboratory testing, using real-time Opal-RT hardware prototyping platform. The obtained results indicate that the developed CCFI can reliably inhibit the commutation failures during various types of faults.

Analysis and Simulation Research of Cascading Faults in AC/DC Hybrid Grid

“…In this case, AC faults always lead to commutation failure, which is the direct cause of DC blocking. Various methods to reduce the probability of commutation failure have been proposed, including advancing firing angle [18], supporting the AC bus voltage [19], and current limiting technologies [20].…”

Improved Identification Method and Fault Current Limiting Strategy for Commutation Failure in LCC-HVDC

“…It is hard to completely avoid the first CF (FCF) utilizing the control optimization based methods for the reason that the interval from the fault occurrence to the FCF only sustains a few milliseconds, which consequently leads to subsequent CF (SCF). FCF can only be eliminated completely based on equipment-based methods [4], [5]. In particular, SCF will result in forced blocking of the DC system or even severe cascading failures, thus deteriorating the system operation stability [6].…”

Interaction Mechanism and Coordinated Control of Commutation Failure Prevention in Multi-Infeed Ultra-HVDC System

“…In addition to the CF mechanism analysis, various CF mitigation methods have been developed. At present, the commonly used strategies mainly fall into the following categories: (1) modifying the layout, capacity allocation, and switching control of reactive power compensation devices [21][22][23][24], (2) reforming the converter topology [25], and (3) optimizing the DC control scheme [6,10,26,27]. Reactive power compensation equipment is not only expensive but also increases short-circuit current of the AC system.…”