Auxiliary Thyristors Research Articles

A High-Precision Flat-Top Pulsed Power Supply Topology Based on SFPFN and Active Coupled Inductor Filter

This study presents a power supply topology capable of generating a large current pulse with a long flat-top duration and a high output voltage. The proposed topology is based on the sequentially fired pulse forming network (SFPFN) and the active coupled inductor filter. The SFPFN generates the primary inaccurate current pulse, and the filter then shapes the current to achieve accurate output. In order to achieve the required accuracy, a novel active coupled inductor filter is proposed which consists of a switched-mode compensator, an auxiliary thyristor pair, a DC bias capacitor, and a coupled inductor. It is designed to deviate most of the voltage and current stress to the coupled inductor, the auxiliary thyristor pair, and the DC bias capacitor, thus reducing the semiconductor devices requirements of the switched-mode compensator. Experimental results based on a 335 A low-power prototype verified the capability of the proposed topology to produce high-precision current pulses and the potential to be generalized to high-power scenarios.

A model predictive fault‐tolerant control strategy for non‐redundant T‐inverters with multiphysics‐circuit coupling loss analysis

SummaryThis paper presents a multiobjective optimal power prediction fault‐tolerant control (MO2PPC) approach for mitigating DC link neutral‐point voltage imbalance and current ripple problems in three‐level T‐type inverter (3LT2I). Additionally, an auxiliary thyristor is employed to isolate and reconstruct the faulty phase into an 8ST2I for ensuring uninterrupted operation during phase failure. A method called injected bias current‐MO2PPC (IBC‐MO2PPC) fault‐tolerant strategy is proposed for this structure. This approach eliminates the need for DC or AC current sensors to reconstruct the three‐phase current, thereby reducing neutral‐point oscillation caused by phase deficiency and ensuring full power output after failure. Additionally, nonfaulty phase power loss is compared and analyzed to verify the stability of this method following a phase fault. The internal losses and temperature distribution of an IGBT module in a bridge arm before and after a fault are verified through a multiphysics‐circuit model in COMSOL‐Simulink coupling simulation presented last. The model shows reduced conduction losses and overall lower temperature distribution in the IGBT module after fault reconstruction. Experiments and multiphysics simulations have demonstrated that this approach displays exceptional robustness and sustainability throughout the entire fault cycle.

Thyristor-Based DCCB With Reliable Fast Reclosing Protection Ability by Restoring Capacitor Polarity

Lots of dc circuit breakers have been proposed for protecting medium voltage dc (MVDC) systems. However, they normally have one or more following limitations: low operational reliability, lack of controllability, lack of reclosing protection ability, power supply required, and high construction cost. To overcome these problems, a novel thyristor-based dc circuit breaker (TCB) is proposed in this paper. The proposed TCB could break the bi-directional current actively and reliably. In the reclosing process, the polarity of capacitor in the counter current loop could restore automatically to the initial state, and the auxiliary thyristor could be turned <sc xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">off</small> naturally. As a result, the proposed TCB guarantees reliable fast reclosing protection ability on the premise of no additional pre-charge power supply. Moreover, all thyristors of the proposed TCB could be turned <sc xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">off</small> by voltage drop of the anti-parallel diodes, and the overvoltage problem caused by reverse recovery process of thyristors is eliminated, which further enhances the reliability of TCB. The detailed topology introduction, parameters designing guidelines, scaled-down experimental results, and comparative study of the proposed TCB are all presented.

A Load-Independent Controllable Z-Source Circuit Breaker With an Intrinsic Fault Detection Method

The Z-source circuit breaker using thyristor as the main switch benefits from its low cost, low conduction loss, and high ruggedness. However, the fault protection of the conventional Z-source circuit breakers only relies on the change of the load. In this paper, a load-independent controllable Z-source circuit breaker (CZCB) with an intrinsic fault detection circuit is proposed. It will not be protected by mistake during any load step change, and an accurate fault current detection can be achieved with a specific threshold. Meanwhile, the fault current is monitored by the on-state voltage of the main thyristor, so no additional sensor is needed. An auxiliary thyristor is used to turn off the main thyristor reliably when an overcurrent is detected. In addition, only one inductor is needed in the CZCB, and the <i>L-C</i> parameter is much smaller than the conventional Z-source breakers, leading to lower size and cost. The performance of the proposed CZCB is verified by simulation and experiment. The results show that the fault current can be cleared within a few microseconds, and the total fault isolation time is only about 38 <i>&#x03BC;</i>s.

Fault Current Bypass-Based DC SSCB Using TIM-Pack Switch

This letter proposes a new bypass-based solid-state circuit breaker (SSCB) using thyristor-IGBT-MOV (TIM)-Pack switch for DC applications. The presented SSCB features three key advantages. First, the stored inductive energy of dc systems is prevented to flow through faulty sections, and the response speed is within microseconds, which enhances safety. Second, MOVs are disconnected from the power line during OFF-state, which improves reliability. Third, the proposed topology takes full use of the benefits of high-power rating thyristors in a TIM-Pack. To validate the proposed SSCB, experiments of a 600 V/145 A scale-down prototype are conducted. Results show that the fault current reduces to zero in 6 s; peak voltage on the main and auxiliary thyristors reaches 826 V and 600 V, respectively; while, overshoot voltage on the main and auxiliary IGBTs reaches 185 V and 245 V, respectively.

Fast Y-Type Thyristor-Based DC SSCB Using Complementary Commutation in a Capacitor–Capacitor Pair Structure

This article proposes a new thyristor-based dc solid-state circuit breaker (SSCB) named Y-type. Main contributions focus on a new complementary commutation circuit including a capacitor–capacitor pair, which features three remarkable advantages. First, a fast commutation is achieved using a countercurrent pulse injection by the capacitor–capacitor pair structure. Second, metal-oxide varistors (MOVs) are disconnected from the power line when SSCB is <sc xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">off</small> , which solves the reliability issue due to the MOV degradation and enhances the voltage utilization rate of the main switch. Third, benefiting from the capacitor–capacitor pair structure, reliable reclosing and rebreaking are obtained for practical applications. Experiments are conducted on a 400 V/120 A prototype to validate the proposed Y-SSCB. The peak voltage on the main and auxiliary thyristors reaches 773 and 400 V, respectively. Also, the peak voltage on the auxiliary capacitors pair reaches 740 and 400 V. The Y-SSCB achieves a fast reaction time of 80 μs in interrupting 120 A short-circuit fault current.

The switching principle of thyristor assistant arc extinguishing hybrid on-load tap-changer

Thyristor assistant arc extinguishing hybrid on-load tap-changer uses thyristor auxiliary mechanical switch which combines the advantages of mechanical switch and thyristor switch. The hybrid OLTC has high reliability, a relatively small amount of work needs to be maintained. It is a kind of very promising transformer OLTC. This project focus on the application of the hybrid OLTC in 110, 220kV transformer, introduces the auxiliary thyristor arc hybrid on-load tap-changer principle of passive trigger with odd block switch to even block as an example, describes the hybrid on-load tap-changer switching process, and the switching principle of simulation verification, on the basis of summarizing the characteristics of hybrid on-load tap-changer.

Novel Bidirectional DC Solid-State Circuit Breaker With Operating Duty Capability

DC microgrids have received remarkable interest in both the academia and the industry for over a decade, yet the protection of dc microgrids remains as a major challenge. This challenge is rooted in the nonexistence of natural zero-crossing point in dc microgrids which rapidly increase the fault current. In this article, a novel bidirectional dc solid-state circuit breaker (dc SSCB) to reinforce the bidirectional flow of energy which significantly boosts the overall efficiency of the power supply of dc microgrids is presented. The proposed topology can perform the operating duty of reclosing and rebreaking, and the commutation capacitor is charged and recharged naturally without any complex control of the main or auxiliary thyristors, which is considered atypical of existing topologies. A clear and detailed analysis of the operation of the proposed topology is presented. Finally, the experimental results are presented to confirm the effectiveness of the proposed novel bidirectional dc SSCB.

Multidimensional dU/dT Effect in High-Power Thyristors

The procedure making it possible to take into account the influence of high-power thyristor design elements on its dU/dt parameter is described. A simple model is proposed, using which, it is possible to find the parameters of the auxiliary thyristor structure of a regenerative control gate that provides a specified value of the dU/dt effect in a thyristor. The minimal possible thyristor turn-on current limited by the specified limiting voltage increment rate is found.

Неодномерный эффект dU/dt в мощных тиристорах

The method allowing to take into account the influence of the design peculiarities of a power thyristor on its dU/dt parameter is described. A simple model is proposed, that makes it possible to find the parameters of the auxiliary thyristor structure that belongs to the regenera-tive control gate and provides the given value of the thyristor dU/dt parameter. The minimum possible value of turn-on current of the thyristor, limited by a given value of the maximum rate of voltage rise, is found.

A Wide-Range TCR With Low-Current THD by Optimized Combination of Coupled Reactors and Thyristor Switching and Control

A 3-phase 3-wire thyristor controlled reactor topology is presented comprising of two banks, involving thyristor switched and controlled coupled reactors (TSCCR), one bank of which is “Δ” connected and the other being “Y” connected. Each TSCCR comprises of a reactor with two well coupled identical sections, two main thyristor back-to-back switches and an auxiliary thyristor switch such that the two sections can be either connected in parallel or in series. The ratio of the effective reactor values between the “Δ” bank phase and that of the “Y” bank, as well as the condition when and which switch shall be used for phase control, are selected from an optimization process. Such an arrangement prevents the triplen harmonics from entering into the supply system and some major characteristic harmonics are also eliminated from the source current. Thus, without using any additional filters or phase shifting transformer or oversized reactors, this scheme enables reactive power control with a low current total harmonic distortion over a wide range of kVAr control. Simplicity in construction and operational requirements of the proposed topology makes it a viable and cost effective solution. Its modeling, analysis, and performance assessment are presented, supported by simulation and experimental results.

보조 사이리스터의 턴-오프 회로를 간소화한 HVDC 사이리스터 밸브 시험용 합성시험회로

This study proposes a new synthetic test circuit (STC) for HVDC thyristor valve tests. The conventional STC with a 2-phase chopper requires a 3-phase transformer, a 3-phase diode rectifier, and an IGBT to facilitate the off state of an auxiliary thyristor. In the proposed STC, these three components are replaced with one diode and one resistor, which result in the simplified implementation of the hardware of the STC. Simulation and experimental results demonstrate the validity of the proposed scheme.

Thyristor-Based HVDC With Forced Commutation

This paper presents a novel converter configuration, based solely on conventional thyristors and aimed for the use with high voltage dc (HVDC) transmission. The converter utilizes resonant turn off and forced commutation with auxiliary thyristors to aid commutation in the converter switches. The PSCAD/EMTDC simulation confirms that the HVDC inverter is capable of operating with a wide range of firing angles, including operation with reactive power export. Further simulation proves that the system is immune to commutation failure even in the case of most severe close single-phase faults. The harmonic generation is comparable to the conventional converter and also the thyristor voltage stress is not significantly increased. The auxiliary thyristors do increase costs, but this is offset by the elimination of reactive power support and the improvements in performance

Study on resonant fly-back converter for DC distribution system

This paper describes a resonant fly-back converter with thyristor switches, which can be used for the DC distribution with a PWM voltage-source inverter. The proposed converter operates to change high-voltage DC into low-voltage DC with isolation and large converting ratio. The converter has a main thyristor switch and an LC resonant circuit with an auxiliary thyristor switch for commutation in the primary side of the gap transformer. The operation of the proposed converter was verified through computer simulations with EMTP and experiments with a hardware scaled-model. The proposed converter could be implemented with commercially available components and proven technologies for supplying electricity to the rural or remote customer.

A Resonant Drive Circuitfor Switched ReluctanceMotor

A resonant pulse soft-switched drivecircuit for a switchedreluctancemotor is proposed. There are nines witching devicesin the circuit with three phase motor windings, three devices for main circuit, three devices for auxiliary circuit, and three devices for charging circuit. Auxiliary thyristor is used so resonance currentpulse tail-length is fast cut off. Transformeris used so that the excessive energy is restored to the source and voltage of capacit or is limited. By the simulation and experimental, it is clarified that the output torque is increased. The system yields less EMI, because of soft switching.

HVDC converter using self-commutated devices

A three-phase bridge for a high-voltage direct-current (HVDC) converter which uses auxiliary (bypass) thyristor valves connected to tapping points on the transformer secondary windings has been previously described. The performance is enhanced by using self- or force-commutated devices for these valves, and three different schemes are examined. Experimental tests on a laboratory model validate the theoretical results. Fast and continuous control of the DC voltage is possible with a typical reduction of 20%-30% of the reactive volt-ampere (VAr) absorption compared with a conventional scheme. An additional feature of the scheme is that the transformer tap changer could have a reduced range with fewer taps or even be eliminated.

Electric drive for flywheel energy storage

This paper presents the results of experimental work on flywheel energy storage systems for city buses. An efficient electronic hardware scheme is used to start the flywheel and traction machines. This scheme has been designed, fabricated and tested in our laboratory. A low frequency a.c. has been derived from an inverter fed from a three-phase uncontrolled rectifier to start the commutatorless d.c. motors. Commutation is achieved by using a capacitor and two auxiliary thyristors, whose ratings could be a fraction of full machine ratings, as they are needed during starting only. The frequency of the inverter output is controlled by a function generator. For successful commutation in all modes of operation, a capacitor voltage sensor circuit has been employed.

Simulation of flywheel energy storage system for city buses

This paper reports on computer simulation of flywheel energy storage systems for city buses. In digital simulation of the flywheel energy storage system, the objective is to assess the economic advantage obtainable from using such a system. Actual data pertaining to a particular Delhi bus route have been collected and used in this simulation study. In the second part, an efficient electronic hardware scheme to start the flywheel and traction machines, which has been designed, fabricated and tested in our laboratory, is described. In this scheme, a low frequency current has been derived from an inverter fed from a three-phase uncontrolled rectifier to start the commutatorless d.c. motors. Commutation is achieved by using a capacitor and two auxiliary thyristors, whose ratings could be a fraction of the full machine ratings, as they are needed during starting only. The frequency of the inverter output is controlled by a function generator. For successful commutation in all modes of operation, a capacitor voltage sensor circuit has been employed.

An overvoltage, self-protected thyristor with high breakover power endurance

A high-resistance region was built in between the pilot thyristor and auxiliary thyristor. The built-in resistance had the ability to transfer the breakover power to the resistance region. Power dissipation in the device could be controlled by varying the built-in resistance. Using the built-in resistance, the breakover power endurance of a thyristor with a 5.5-kV breakover voltage could be increased by more than twice that of a device with no built-in resistance. The built-in resistance also functioned as a ballast resistor to make current spreading uniform. The voltage of the resistance region did not change for the two junction temperatures studied, 23 degrees C and 100 degrees C. >

DC chopper with coupled-inductor commutation

A novel coupled-inductor commutation circuit is described. The circuit may also be used for inverters. It uses only two auxiliary thyristors, each operating in alternate cycles and eliminating the need for reversal of the commutating capacitor voltage. Trapped energy is fed back to the source. The output voltage is controllable from zero to the full input voltage. The commutation circuit can be connected to a voltage source other than that feeding the load. A DC chopper using this commutation scheme has been analysed and experimentally verified.