Voltage Direct Current Circuit Breakers Research Articles

Synthetic test circuit with two‐level voltage source for HVDC circuit breakers

AbstractIn order to ensure the reliable interruption of high voltage direct current circuit breaker (HVDC CB), the breaking test of HVDC CB plays an important role in its performance verification. In this paper, the interruption process of the HVDC CB is analyzed, and the equivalent requirements for the breaking test of HVDC CB are summarized. In the breaking test of high voltage and high current, the transient interruption voltage (TIV) duration is short, which leads to insufficient voltage stress. A new synthetic test circuit for testing the interruption performance of HVDC CBs is proposed, which can solve the problem of insufficient TIV duration caused by insufficient test capacity. Subsequently, the working principle of the test circuit is introduced in detail and the design method of the circuit parameters is given. The short‐circuit current breaking test simulation of HVDC CB is carried out. The simulation results fit most well with the results of actual test cases, which verifies the universality of this test method. Finally, a test platform is built to verify the principle of the test circuit. TIV rose to 2.5 kV compared to the predetermined system voltage of 1.67 kV during the test, which means that the key stress provided by the test circuit can meet the expected requirements.

Analysis and Design of a Thomson Coil Actuator System for an HVDC Circuit Breaker

In this study, we analyze and design a Thomson coil actuator system (TCAS) that ensures stable operation of a high voltage direct current circuit breaker. High voltage direct current circuit breakers require a high-speed actuator and proper brake system that can absorb the kinetic energy of fast-moving mass to prevent damage and malfunction of the device. However, existing brake systems degrade the responsiveness of TCAS. Therefore, the proposed TCAS is designed to improve the low responsiveness of the actuator, which is caused by braking forces, by applying a series spring brake system and latch type holding system. An equivalent circuit model of TCAS that reflects its electromagnetic and kinetic properties is derived and applied to the design of the TCAS. The validity of the proposed TCAS design and analysis model is verified through prototype experiments. The experimental results show that the proposed TCAS completes a 30 mm stroke opening operation in 5.4 ms at a drive voltage of 300 V, and the analysis results reveal that the error rate for the experimental results is 4.65 %.

Coupled Inductance Model of Full-Bridge Modules in Hybrid High Voltage Direct Current Circuit Breakers

Extraction of the current commutation loop (CCL) inductance is necessary for the overvoltage analysis of power devices. In general, each transient process of a converter corresponds to a specific CCL. However, there is no such single CCL in the full-bridge module in hybrid dc circuit breakers during the turn- off transient. First, this article proposes a coupled inductance model of full-bridge modules. The model has less number of inductance compared to the traditional partial inductance model. Second, this article proposes the extraction method of inductances that can be easily obtained by both simulation and measurement. Moreover, the measured overvoltage waveforms of insulated gate bipolar translators (IGBTs) in the full-bridge module agree with the simulation results. Third, we propose an equivalent circuit of the series full-bridge modules in a 500 kV hybrid circuit breaker based on the proposed coupled inductance model. The mutual inductances among different modules are considered due to the compact structure of the series modules. The measured results show that the overvoltage of the IGBT in the series module could be well-predicted by the proposed equivalent circuit.

An IEGT Model for Analyzing the High Current Turn-off Characteristics in DC Circuit Breaker Applications

The direct current (DC) circuit breaker based on semiconductor power devices is one of the critical components in multiterminal flexible high voltage DC transmission technology. A press pack injection enhanced gate transistor (IEGT) can realize a low on-state voltage similar to a gate turn-off (GTO) thyristor while achieving better high current turn-off capability and wider safety operating area than an IGBT. Therefore, an IEGT is a promising candidate for high voltage DC circuit breaker applications. The fault current conducted by devices in DC circuit breaker applications is 4~6 times the device rated current, which brings great risks to reliable operation. Optimizing the device turn-off characteristics and then realizing reliable operation are indispensable parts of DC circuit breaker design. For analyzing the high current turn-off characteristics under the working conditions of a DC circuit breaker, an IEGT model is proposed in this paper. In the model, a simple method for predicting the static-state I-U characteristics is established. In addition, based on the differences in the gate structures of IEGTs and IGBTs and the influence of the gate structure on the nonlinear capacitances between device terminals, the nonlinear capacitances are greatly improved to better describe the turn-off transient process. Subsequently, the model is verified by experiments. The model is expected to be a convenient simulation tool for designing a high voltage DC circuit breaker with IEGTs.

A novel HVDC circuit breaker for HVDC application

Hybrid high voltage direct current circuit breakers (DCCBs) are capable of interrupting fault current within a few milliseconds, but this technology has high capital cost, especially in a meshed HVDC grid. To increase the economic competitiveness of hybrid DCCBs, this paper proposes a capacitor commutated dc circuit breaker (CCCB). The CCCB mainly comprises an auxiliary branch with a fast dis-connector in series with semiconductor devices and the main branch with the series connection of a dc capacitor and diode valves. This paper provides a detailed depiction of the CCCB. The topology and operating principles are discussed. The impact of snubber circuits and stray inductances on the commutation process is analyzed. The general sizing method for the main components in the CCCB is detailed. Reclosing to transmission lines with different operating conditions is studied. Several extended topologies are proposed to further reduce the semiconductor cost and on-state operation power loss. The power loss and cost of CCCB are assessed. Extensive simulations on PSCAD/EMTDC verified the dc fault isolation and reclosing of the CCCB.

Flexible, Highly Dynamic, and Precise 30-kA Arbitrary Current Source

High-power current sources with high dynamic performance, ultralow current ripple, and absolute reference tracking accuracy are the key elements for magnets (bumper and septum) that are used in accelerators. Similar requirements are also encountered in plasma research applications in fusion reactors, as well as plasma research for the future high voltage direct current circuit breakers. Therefore, the current source must be able to drive resistive/inductive and highly fluctuating loads without any compromise in its performance. In this paper, such a flexible, dynamic, and accurate current source is introduced, which able to provide amplitudes up to 30 kA and bipolar voltages up to 10 kV. The system’s operating concept is presented and its design procedure in order to fulfill a list of demanding specifications is demonstrated. In addition, a detailed description of its near-optimal, advanced control system is presented. Finally, the theoretical considerations are verified by extensive simulation results for various operating scenarios, including driving chaotic arc loads.

A new topology for current limiting HVDC circuit breaker

With the high voltage direct current Transmission (HVDC) booming, HVDC grid has received wide attention. As an essential component in HVDC grid, high voltage direct current circuit breakers (DCCB) requires urgent and intensive study. A novel topology for current limiting DCCB (CL-DCCB) is proposed in this paper. The topology consists of several units which are divided into two classes: main circuit breaker (MCB) and branch circuit breakers (BCBs). The number of inductor branches can be flexibly selected to enhance the current limiting effect. The CL-DCCB can start current limiting operation when a suspected fault occurs. When the detection circuit reveals what has happened, it can be determined whether to implement breaking operation or recover to normal state. This mode allows longer fault detection time and circuit breaker operation delay while guaranteeing the fault current within the maximum limit of the system. Finally, Simulation model and experiment prototype are built to study the design criteria for CL-DCCB. It is observed that the maximum detection delay can be extended to 12 ms. Moreover, the current limiting effect can be enhanced when the number of inductor branches or the inductance of each branch is increased.

Design and Experimental Tests of a Superconducting Hybrid DC Circuit Breaker

Direct current (DC) circuit breakers are a key enabling technology for fault management in multiterminal high-voltage DC (HVDC) systems. DC fault isolation is challenging due to the high rate of rise of the fault current and the lack of natural current zero-crossings found in ac systems. In this paper, we present a novel superconducting hybrid dc circuit breaker that utilizes the intrinsic characteristics of the superconductor material. The automatic quench of the superconductor coil as a result of a high fault current transfers the current from the mechanical switch to the semiconductor switch. The isolating mechanical switch is able therefore to open at low current and recover its dielectric capability rapidly. A low voltage DC circuit breaker prototype has been built using a multistrand magnesium diboride (MgB2) coil, a vacuum interrupter, and an insulated-gate bipolar transistor module. This prototype successfully demonstrated interruption of 500 A DC within 4.4 ms. This paper presents the design of the superconducting hybrid breaker prototype and a detailed analysis of the experimental results. This superconducting hybrid dc circuit breaker has significant potential for scaling up the high-voltage and high-current applications.

Test Circuits for HVDC Circuit Breakers

High voltage direct current circuit breakers (HVDC CBs) are necessary for reliable and safe operation of future multi-terminal meshed HVDC grids. So far no commercially mature products of such equipment exist. A few industrial concepts as a result of advances in power electronics have been proposed and prototypes have been built. However, performances of these concepts have never been demonstrated under realistic operation conditions. Since these tests require construction of high power DC sources incurring significant investment costs, alternative test circuits providing equivalent stresses must be considered. In this paper various test methods and circuits used for testing HVDC CBs are investigated and their performance is evaluated against the stresses in a conceptual future HVDC grid. A novel method of testing an HVDC CB using existing installations in a high power ac test laboratory is proposed and its prospective fault current and voltage is experimentally demonstrated. It is concluded that adequate test circuits need to maintain the supply voltage not only up to the current zero in the main interrupter unit of the HVDC CB, but also during the entire energy dissipation phase of the interruption process.

A Compact Design for High Voltage Direct Current Circuit Breaker

The absence of current-zero points in the direct current (DC) waveform of high voltage DC (HVDC) circuit breakers makes the interruption process more severe than the case of conventional AC networks with sinusoidal currents. In this way, in the current HVDC networks, a parallel precharged capacitor is inserted to inject the reverse current into the interruption chamber of the vacuum circuit breaker and create the artificial current-zero points. In this paper, a novel method for reverse current injection has been proposed. In this method, two separate helical flux compression generators (HFCGs) have been applied to generate the reverse current and an intense axial magnetic field (AMF), respectively. Numerical simulation of high-current vacuum arc (VA) in the presence of very strong AMF has been presented. For this purpose, the magnetohydrodynamic equations describing the behavior of the VA are coupled to a simple circuit analysis and the previously developed multiphysics model of HFCG. The results indicate that the explosively driven current injection set can make current-zero points properly in a typical HVDC network and lead to successful interruption of fault current. This method needs much less volume and cost in comparison to the parallel precharged capacitor sets.

HVDC Circuit Breaker Development and Field Tests

With the growth of direct current transmission, the need and scope of application for a high voltage direct current circuit breaker have increased. This paper reports on the development of two different dc breaker prototypes and full scale field tests of these breakers on the ±400-kV, 1360-km long Pacific DC Intertie.