IGCT Research Articles

Power Loss Research on IGCT-applied NPC Three-level Converter

IGCT has a broad application prospects in high power conversion such as flexible DC transmission due to its characteristics of high voltage and large capacity. Compared with IGBT it has a voltage and current level of 4.5kV/4kA and its slope resistance is less than IGBT’s. In addition, due to the di/dt snubber circuit, IGCT’s opening loss will be reduced. Because of improvement of IGCT performance, the loss of IGCT-applied three-level converter will have some new characteristics, so it is necessary to model the IGCT-type three-level converter. Based on piecewise linear curve fitting method, the IGCT switching loss mathematical model is established firstly. With its use in IGCT-type three-level converter loss model, a IGCT-type three-level converter mathematical model is established. If the model is applied in the ±200kV flexible DC transmission’s calculation example, it can be concluded that the loss rate is 0.31%-0.78% when the power factor angle changes between 0 and π, while the loss rate of IGBT-type converter under same voltage level is 2%-3.5% ,so it can be concluded that IGCT is more suitable than IGBT for use in high voltage and large capacity situation such as frequency control of motor speed and flexible DC transmission.

PSPICE Simulation of IGCT and its Inverter Circuit

In order to observe the state of Integrated Gate Commutated Thyristor(IGCT) in inverter circuit and analyze the reason of its breakdown, a single 2T-3R subcircuit model of IGCT is used in Personal Simulation Program with IC Emphasis(PSPICE) environment to simulate an IGCT inverter unit of a 6kV/2MVA frequency converter. Simulation results show that when the stray inductance in inverter circuit is large, high forward blocking peak voltage will cause the breakdown of IGCT. This problem is solved by installing an absorption capacitor.

Switching Loss Analysis of 4.5-kV–5.5-kA IGCTs Within a 3L-ANPC Phase Leg Prototype

Three-level active neutral-point-clamped (NPC) (3L-ANPC) voltage-source converters (3L-ANPC-VSCs) enable additional switch states and commutations compared to the three-level NPC voltage-source converters (3L-NPC-VSCs). They are used to overcome one important disadvantage of the 3L-NPC-VSC, the unequal semiconductor loss distribution. With an accurate switching model (obtained directly from the measurements), it is possible to improve the junction temperature distribution among the power devices, increasing the 3L-ANPC-VSC output power and/or increasing the frequency and/or decreasing the derating of the converter. This paper presents the characterization of a 4.5-kV-5.5-kA integrated gate-commutated thyristor (IGCT) within a 3L-ANPC phase leg. A quantitative analysis of the switching losses using 5SHY55L4500 IGCTs and D1961SH45T press-pack diodes for a current range from 1 to 4.5 kA and junction temperatures between 25 ° C and 125 ° C is presented. The 3L-ANPC phase leg performs 32 different commutations. Each commutation exhibits different switching losses, as a result of the different commutation paths and their stray inductances. This switching energy range is presented and quantified. Finally, a simplified switching loss model considering the maximal switching losses in terms of the commutation current and the junction temperature is presented.

Fault Tolerant Operation of Power Converter with Cascaded Cells

SummaryIn the field of high power electronics for transmission applications there is currently a strong tendency towards using modular converter topologies employing cascaded cells.These multilevel converters are well suited for high power applications, due to good control performance, extensive modularity and excellent harmonic distortion. This paper concerns fault tolerance of such a cascaded converter on cell level, and a method is proposed to exclude a cell from the chain of cells in case a semiconductor switching device fails. The described method concerns a semiconductor device in presspack encapsulation that normally fails into a permanent short circuit. In particular, it is applicable to converters that use Integrated Gate Commutated Thyristors (IGCT). The application of the converter considered here is STATCOM, where several tens or even hundreds of these cells are involved. Hence, a failure in one of the applied semiconductor switching devices should not lead to a malfunction of the whole converter. A feasible method for shorting out a failed cell is proposed and experimentally validated by two consecutive tests. The principle is to initiate a shoot-through in a cell hence discharging the DC cell capacitance completely where the circuitry for di/dt-reduction during turn-on limits the surge current. Hereby the used semiconductor switching devices are put into a permanently shorted state without using additional hardware. From the observations it can be concluded that the surge leads to a stable SCFM process (Short Circuit Failure Mode) which can conduct the converter current in both directions. The test is not fully conclusive as to how long the SCFM can be sustained. However, experiences from thyristors used in HVDC applications indicate that the SCFM state can be relied on to last for several years.

Comparison of 4.5-kV Press-Pack IGBTs and IGCTs for Medium-Voltage Converters

Recently developed insulated-gate bipolar transistor (IGBT) press-pack (PP) devices with a blocking voltage of 4.5 kV are being used in medium-voltage converters as an alternative to integrated gate-commutated thyristors (IGCTs). This paper presents an overview of PP packaging and both semiconductor technologies. A quantitative comparison of these devices is achieved through measurements for a 4.5-kV 1.2-kA IGBT and a 4.5-kV 4-kA IGCT. The laboratory test bench for the switching transient characterization at a dc-link voltage of 2.5 kV and currents up to 3 kA is described. Conduction, blocking, and switching behavior for junction temperatures up to 125 °C are investigated. The IGCT and the IGBT are tested using a di/dt-limiting clamp circuit. In addition, the IGBT is tested in hard switching mode.

The Study on New Solid-State Breaker and Its Over-voltage Suppression Technique

A design scheme of the intelligent SSB (Solid State Breaker) based on the IGCT (Integrated Gate Commutated Thyris- tor) is presented. The topology of switch module and the structure of the SSB are proposed. Firstly, to the IGCT’s over-voltage sensitivity problem, a new technique of reducing the over-voltage is introduced, which releases the elect romantics energy of faulty line by a capacitive current branch to reduce the amplitude of over-voltage. Secondly, the principle of over-voltage suppression with current release branch is analyzed, and the overall control scheme of solid- state breaker is put forward. Finally, the simulation results also demonstrate its obvious effectiveness in over-voltage suppression after adding a current release branch into the SSB.

A Major Design Step in IETO Concept Realization That Allows Overcurrent Protection and Pushes Limits of Switching Performance

This paper presents the latest prototype of the integrated emitter turn-off thyristor concept, which potentially ranks among thyristor high-power devices like the gate turn-off thyristor and the integrated gate-commutated thyristor (IGCT). Due to modifications of the external driver stage and mechanical press-pack design optimization, this prototype allows for full device characterization. The turn-off capability was increased to 1600 A with an active silicon area of 823 mm2. This leads to a transient peak power of 672.1 kW/cm2. Within this paper, measurements and concept assessment are presented and a comparison to state-of-the-art IGCT devices is provided.

Loss Comparison of Different Sub-Module Implementations for Modular Multilevel Converters in HVDC Applications

SummaryThis paper presents a loss calculation and comparison between different submodule topologies and semiconductor choices for a Modular Multilevel Converter in a 1.1 GW, ± 320 kV HVDC application. Accordingly, a detailed analysis of the losses for three different M2C implementations using both insulated gate bipolar transistors (IGBTs) and integrated gate-commutated thyristors (IGCTs) is presented. The losses for six different submodule realizations are shown in a loss breakdown in Fig. 7. It shows that the very low conduction loss of the IGCT is to some degree offset by higher switching losses and extra turn-on snubber losses but that the IGCT implementations provide significantly lower losses than their IGBT counterparts. The loss break-down also shows that clamp-double submodules and full-bridge submodules suffer from approximately 25 % and 50 % additional losses respectively as compared to the half-bridge case. An experimental verification of the loss calculations has been performed using a down-scaled M2C prototype. The results show a very good agreement between calculations and measured losses.

Alternating Current Drives in the Steel Industry

In this article, a review of the state-of-the-art high-power devices, such as silicon-controlled rectifiers (SCRs), gate turn-off thyristors (GTOs), insulated-gate bipolar transistors (IGBTs), integrated gate-commutated thyristors (IGCTs), and injection-enhanced gate transistors (IEGTs), converters, such as cycloconverters and three-level inverters, and control technologies adopted for such drives, such as the vector control (VC) and the direct torque control (DTC), is presented with brief features of the industrial ac drives developed for the steel industry by the leading drive manufacturers worldwide.

Design and Implementation of a Current-Source Converter for Use in Industry Applications of D-STATCOM

<para xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> This paper deals with the design and implementation of the power stage of a forced-commutated current-source converter (CSC) for use in industry applications of distribution type static synchronous compensator (D-STATCOM). The power semiconductors are switched at 500 Hz according to the switching patterns generated by selective harmonic elimination method for the elimination of the most significant four low-order harmonics. The possibility of using various power semiconductors in CSC is examined both theoretically and experimentally. The requirement of bipolar voltage-blocking capability is achieved by the use of an asymmetric integrated gate commutated thyristor (IGCT) and a fast-recovery diode instead of a single symmetrical device, which maximizes the converter power rating and makes natural-air cooling realizable. Determination of optimum dc-link reactor in view of the power quality standards and design of optimum turn-<emphasis emphasistype="smcaps">on</emphasis> and turn-<emphasis emphasistype="smcaps">off </emphasis> snubbers in view of the chosen power semiconductor characteristics are shown to be critical design issues in the paper. Design principles are verified by both laboratory tests and field tests conducted on two different industrial D-STATCOM prototypes. It has been shown that an IGCT-based CSC can be successfully used in industry applications of D-STATCOM systems by designing the power stage according to the proposed principles. </para>

Parallel Connection of Integrated Gate Commutated Thyristors (IGCTs) and Diodes

This paper describes the parallel connection of 4.5 kV integrated gate commutated thyristors (IGCTs) and diodes. The impact of varying device characteristics on the stationary current distribution of parallel connected semiconductors is investigated. Possible solutions to improve the current sharing at steady state are presented. A thermal stabilization effect of parallel connected IGCTs is discussed. Furthermore, the behavior of parallel connected devices during switching transients is investigated experimentally in a 1.5-kV, 5-kA buck converter. Especially, the impact of asymmetrical circuit layouts, magnetic couplings, different turn-on and turn-off delays, and junction temperatures are considered. It is shown that a substantial current derating is necessary to enable a reliable operation of parallel IGCTs and diodes.

Reliability Enhancement of the Fast Switch in a Hybrid Superconducting Fault Current Limiter by Using Power Electronic Switches

We have investigated reliability enhancement of the fast switch (FS) by using power electronic switches such as integrated gate commutated thyristors (IGCT) in the line commutation type hybrid superconducting fault current limiter (SFCL). The FS utilizes a vacuum interrupter (VI) to open and close the primary power line. The operation of the FS highly relies upon the complete line breaking by the VI. Since the primary line resistance including the arc resistance may not be extremely high after the VI opens, there may be non-zero arc current in the VI, causing a failure in the line communication. The IGCTs are to completely remove the remanent current in the VI, guaranteeing the arc extinction and enhancing reliability in operation. We fabricated and successfully tested the SFCL which was equipped with the IGCT-assisted FS.

Feasibility Study of a Hybrid Mechanical-Static DC Circuit Breaker for Superconducting Magnet Protection

This paper describes the feasibility studies of a hybrid DC circuit breaker (CB) for quench protection of superconducting magnets rated for current up to some tens of kiloamperes (kA) and voltage of several kilovolts (kV). The proposed scheme is based on a mechanical switch paralleled to a fully controlled static CB; integrated gate commutated thyristors (IGCTs) were selected. In normal operation, the mechanical switch handles the continuous flow of DC current minimizing the on-state losses. When protection against quench is requested, the current is diverted into the static breaker that quickly interrupts the current, withstanding the reapplied voltage of several kV. The reliable turn-ON of several IGCTs in parallel with low voltage applied between anode and cathode is an issue to be assessed to confirm the feasibility of this design solution. The paper highlights that the components commonly used as snubber or protection circuit can guarantee the turn-ON of all the devices in parallel and that the IGCTs can be turned-ON with few volts applied; this latter aspect was proved by means of specific tests. Finally, a comparison between a static only and a hybrid CB is performed, highlighting the benefits introduced by the hybrid solution.

Space Vector Modulation for Low Switching Frequency Current Source Converters With Reduced Low-Order Noncharacteristic Harmonics

High-power current source converters (CSCs) are usually implemented with gate turn off thyristors (GTOs) or integrated gate commutated thyristors (IGCTs) that present a maximum switching frequency of a few kilohertz. Space vector modulation (SVM) offers a very elegant way of generating CSC gating signals online with increased gain and reduced switching frequency. However, for very low switching frequency, SVM results in low-order (5th and 7th) noncharacteristic harmonics complicating the design of the input filter. The reduction of the magnitude of these harmonics has been sought mostly through new sequences of space vectors (states) that present better performance for different ranges of modulation index and power factor. Moderate improvement can be obtained by calculating the statespsila on times for the reference vector in the middle of an SVM cycle. This paper proposes calculating the statespsila on times as the reference vector rotates. Simulation results show that this approach results in a significant reduction in the harmonic distortion of these two components, which, for a selected sequence of states, can be limited to 0.3% of the fundamental component as the modulation index varies from 0.05 to 1.0. Experimental results obtained with a digital signal processor development kit are also provided to show the superior performance of the proposed techniques.

Conceptual design of the quench protection circuits for the JT-60SA superconducting magnets

In JT-60SA, the new satellite tokamak to be built in Naka, Japan, the magnetic field for plasma generation and confinement is produced by a number of superconducting coils whose rated current ranges from 20 kA to 25.7 kA, with a nominal voltage up to 5 kV. This paper deals with the conceptual design of the Quench Protection Circuits (QPC) of JT-60SA, which must provide a fast removal of the energy stored in the superconducting coils in case of quench. The core of the QPC units is based on a dc current breaker, which diverts the coil current into a discharge resistor. Different concepts of dc circuit breaker for QPC were considered, including vacuum and static circuit breakers; then, a hybrid solution, composed of a mechanical bypass switch paralleled to a static switch based on Integrated Gate Commutated Thyristor (IGCT) technology, has been worked out. A pyrobreaker is added in series to the hybrid switch as a backup protection. The resulting design allows benefiting from the fast breaking and very low maintenance requirement of the static switches, besides maintaining the advantage of the much lower power losses of the mechanical bypass in normal operation. After a brief presentation of the preliminary studies, the selected design solution for JT-60SA is presented in detail.

Application of IGCT in High-Power Rectifiers

This paper investigates the possibility of applying an integrated gate commutated thyristor (IGCT) into high-current high-power rectifier systems. The optimal power converter topology that fully utilizes the functionality of the IGCT is proposed. The proposed power converter consists of a front-end diode rectifier and three-level step-down dc/dc converter. As compared to two-level operation, half the input dc voltage and twice the effective switching frequency of three-level operation can provide a wider operation range of continuous conduction mode resulting in a higher average output current of less ripple size than two-level case. A laboratory prototype of a 5-kA 3.1-MW rectifier has been simulated and tested to confirm the feasibility of the IGCT in the proposed power converter topology. The proposed solution generates a relatively smooth output dc current with less contents of high-frequency harmonics, thereby avoiding the high-frequency harmonic-related problems found in insulated-gate-bipolar-transistors-based high-current rectifiers. The IGCT would play a significant role to improve the cost-effective performance and reliability in low- and medium-ranged high-current high-power rectifier systems.

IGCT Electro-Thermo-Fluidic Modelling

In high power applications, thermal considerations are fundamental. The voltage and current capabilities of today’s semiconductors increase steadily and so, too, do their power dissipations, reaching several kW per package. Generally, thermal modelling is used to design the cooling system of a power converter and to obtain an accurate prediction of the cooling system’s performance. In so doing, it is important to consider the coupling between cooling water, junction temperature and dissipated power. This paper presents a comprehensive modelling method, based on a 3D thermal model, which takes into account the electric and fluidic interactions with the temperature field in a press-pack device. The modelling method is applied to an IGCT (Integrated Gate-Commutated Thyristor) working in a high power chopper. Internal temperature measurements in switching, transient and steady-state modes are performed. Measurement results are used to fit the 3D model by adjusting the value of the thermal contact resistances between the different parts of the IGCT device. Thus, the differences between measurement and modelling result are less than 10% both in transient and steady-state modes. Finally, the model is used to determine the influence of water-flow direction on the IGCT junction temperature. Furthermore, the model is used to estimate IGCT losses and junction temperature fluctuations in the case of a DC arc furnace power supply.

Modeling of Busbars in High Power Neutral Point Clamped Three-Level Inverters

The busbars in high power neutral point clamped three-level inverters are modeled using the Maxwell Q3D Extractor software, which is based on the partial element equivalent circuits method. The equivalent circuits of the busbars and devices model are simulated in the electric simulator PSIM to analyze the effects of the parasitic inductance on the switching characteristics of the integrated gate commutated thyristor (IGCT) in different topology positions. The simulation results agree well with the measured impedance analyzer results and the IGCT test results, which proves the effectiveness of the modeling method for the large, complex busbars.

Optimization Design of High-Voltage-Balancing Circuit Based on the Functional Model of IGCT

Integrated gate commutated thyristors (IGCTs) are commonly used for high-voltage three-level pulsewidth-modulation-controlled voltage-source inverters. IGCTs are utilized in series connection when the output voltage is greater than the maximum rated voltage. Special measure must be taken to ensure the safety and reliable operation of the inverters, and to equalize the voltages across the IGCT modules, such as the dynamic voltage-balancing circuit using an snubber circuit. Based on the IGCT functional model, this paper presents an optimization design procedure of a high-voltage-balancing circuit for a 6-kV/1250-kW inverter. A tradeoff is made between the voltage imbalance, maximum turn-on current, endurance, and losses. Simulation and experiments validate the feasibility of this procedure. In addition, the specific transient processes in the three-level topology with voltage-balancing circuit are simulated, and their inner mechanisms are analyzed.

Performance Evaluation of Switch Devices Equipped in High-Power Three-Level Inverters

The feature of the integrated gate-commutated thyristors (IGCTs) makes them have excellent performance in high-voltage high-current field. The high integration of drives and devices makes it very convenient to use them. In order to examine the dynamic characters of switch devices in high-power three-level inverter, an experimental test for IGCTs and diodes equipped in inverter is proposed and described in detail. The characteristics of switch devices are compared and evaluated experimentally. The relation between the devices' switching behavior and the other elements in the inverter, such as the inverter's structure, the topology position of devices, the stray inductances in commutating loops, etc., are analyzed. Moreover, the busbar structure is improved, and the key pulsewidth-modulation parameter of the inverter is determined. Finally, the advantages of the experiment are summarized in the conclusion.