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The demand for highly efficient and dynamic electric vehicles (EVs) has increased dramatically. The traction inverter, a pivotal component in an EV powertrain, plays a crucial role. This study is dedicated to designing a traction inverter with focus on achieving high efficiency and elevated power density and mitigating electromagnetic interference (EMI) issues. To realize these objectives, autonomous gate drivers (AGDs) are proposed and designed using LTspice simulation software. The aim is to achieve zero voltage switching (ZVS) at both turn-on and turn-off through the utilization of triangular current mode (TCM) control on the gate driver. The AGDs implement a current modulation scheme by sensing the current and voltage and generating gate-source voltage signals with minimal delays. The implemented current modulation scheme by the AGDs results in an efficiency exceeding 99% for a 10 kW power rating. The sinusoidal output waveforms not only contribute to extending the motor lifespan by mitigating sharp-edge voltages but also bring advantages such as reduced switch stress, decreased EMI, and simplified thermal management. [ABSTRACT FROM AUTHOR]

A general platform is introduced to study the dynamics of power systems with high voltage dc (HVDC) transmission links. Small-signal stability, voltage stability, and interaction phenomena of power systems with both line-commutated-converter HVDC (LCC-HVDC) and voltage-source-converter HVDC (VSC-HVDC) are addressed using the proposed platform. In this platform, the entire power system is modeled as a multivariable feedback control system (FCS) which consists of three interconnected blocks. The contents as well as the inputs and outputs of the blocks are selected such that the conventional analysis tools for power system stability are applicable, both in the time and frequency domains. In the FCS model, the relationships between different instabilities are clear, and participant agents of each instability can be determined. The model is developed in a modular and hybrid style, to make it feasible for a large power system. The proposed model is validated against an electromagnetic transient simulation program (PSCAD) using time responses. [ABSTRACT FROM AUTHOR]

Soft-switching converters equipped with insulated gate bipolar transistors (IGBTs) in silicon (Si) have to be dimensioned with respect to additional losses due to the dynamic conduction losses originating from the conductivity modulation lag. Replacing the IGBTs with emerging silicon carbide (SiC) transistors could reduce not only the dynamic conduction losses but also other loss components of the IGBTs. In the present paper, therefore, several types of SiC transistors are compared to a state-of-the-art 1200-V Si IGBT. First, the conduction losses with sinusoidal current at a fixed amplitude (150 A) are investigated at different frequencies up to 200 kHz. It was found that the SiC transistors showed no signs of dynamic conduction losses in the studied frequency range. Second, the SiC transistors were compared to the Si IGBT in a realistic soft-switching converter test system. Using a calorimetric approach, it was found that all SiC transistors showed loss reductions of more than 50%. In some cases loss reductions of 65% were achieved even if the chip area of the SiC transistor was only 11% of that of the Si IGBT. It was concluded that by increasing the chip area to a third of the Si IGBT, the SiC vertical trench junction field-effect transistor could yield a loss reduction of approximately 90%. The reverse conduction capability of the channel of unipolar devices is also identified to be an important property for loss reductions. A majority of the new SiC devices are challenging from a gate/base driver point-of-view. This aspect must also be taken into consideration when making new designs of soft-switching converters using new SiC transistors. [ABSTRACT FROM AUTHOR]

In this paper, the stability limitations are analyzed for a voltage-source converter (VSC) based high-voltage direct-current (HVDC) link using power-synchronization control for two feasible operation modes: alternating-voltage control and reactive-power control. As a comparison, the analysis has been done by the phasor approach and the space-vector approach. While the phasor approach is straightforward to apply and gives intuitive analytical results, the space-vector approach reflects more dynamic insights of the system. This is achieved by using a unified dynamic modeling of both the ac system and the VSC by means of a new introduced modeling approach Jacobian transfer matrices. This approach shows that non-minimum-phase phenomena due to competing effects between alternating voltages and currents following phase-angle changes impose a fundamental limitation on the achievable bandwidth of the VSC-HVDC link. At moderate voltage levels, a VSC-HVDC link operating in alternating-voltage control mode is able to achieve higher bandwidth than in reactive-power control mode since the right-half plane (RHP) zero is located further from the origin in the former mode. [ABSTRACT FROM PUBLISHER]

In this paper, a method to adjust the ac winding capacitance of high-voltage high-frequency transformers by means of winding–rectifier integration is described. First, a theoretical background to the method is given. From the theory, an equivalent circuit describing the characteristics of the combination of the transformer and the rectifier is derived. The derived circuit introduces the concept of a dc capacitance. Finally, the equivalent circuit and the method itself are verified by means of experiments on a transformer–rectifier system from an industrial application with the ratings 70 kV, 30 kW, and 25 kHz. The results from the experiments show that it is possible to vary the ac component of the winding capacitance from a few percent up to 95% of the total winding capacitance. This means that it is virtually free to choose between ac and dc capacitances during the design stage. This is very important in applications such as resonant converters with transformers having secondary windings connected to rectifiers with capacitive output filters. [ABSTRACT FROM AUTHOR]

Two different dynamic effects influencing the insulated gate bipolar transistor (IGBT) losses in soft-switching converters are demonstrated. The first one, the Dynamic tail-charge effect shows that the tail charge is dependent not only on the absolute value of the current at turn-off, but also on the dynamics of the current. This effect may have a significant impact on the optimization of zero-current-switching converters. The Dynamic conduction losses originate from the conductivity modulation lag of the IGBT. It is shown by experiments that the on-state losses depend on the operating frequency. Different methods to accurately determine the on-state losses are evaluated. It was found that the best method is an indirect measurement, where the stray inductance is identified by the use of an oscillating circuit. The experiments are performed under a sinusoidal current excitation at a fixed amplitude (150 A) for different frequencies (up to 104 kHz). The switching devices used are IGBT modules rated 300–400 A/1200 V in a bridge-leg configuration. From the experiments performed, it is found that IGBTs of a modern punch-though (PT) designs have the lowest losses in the series-loaded resonant converters studied in this paper. [ABSTRACT FROM PUBLISHER]

Analyzes an algorithm for estimating speed and position of alternating current machinery. Applications included in the algorithm; Verification of low parameter sensitivity in the entire speed range; Attention to examining sensorless permanent-magnet and reluctance synchronous motor drives.

Deals with the application of the internal model control (IMC) to the alternating current (ac) machine current control. Introduction of the permanent magnet synchronous machine (PMSM); How the method can be applied to PMSM and induction machines; Analysis of IMC with respect to sensitivity; Factors included in the consideration of discrete-time implementation issues; Presentation of simulations and experimental results.

Enhanced active resonant (EAR) dc circuit breakers (DCCBs) are a novel type of DCCB that use a discharge closing switch as interruption medium. A technical limitation of discharge closing switches is the minimum voltage across the main gap required for successful triggering. A novel commutation process creating the minimum voltage internally is proposed, which allows to simplify the EAR DCCB configuration and to reduce its component count. In the prototype, the discharge closing switch is implemented with a TVG. Experiments show that the TVG can be triggered reliably down to a voltage of 50  $\mathrm{V}$ and that the discharge in the TVG is highly oscillatory at low current. The originally proposed EAR DCCB configuration has to be tuned such that the commutation to the TVG succeeds at low current. Conversely, the novel commutation process decouples the minimum voltage from the current level by adjusting the triggering delay. This allows reliable commutation irrespective of the operating conditions. It is shown that the novel commutation process does not adversely affect dc interruption. Proactive commutation operation and auto-reclosing strategies are demonstrated. [ABSTRACT FROM AUTHOR]

DC grid has become an important application in power transmission. However, the exist works only have the method to obtain the droop coefficient in a radial topology. Also, this droop coefficient is for V-I droop control. There is no such like method to obtain the droop coefficient for the P-V droop control. This paper proposed a new method for a complex dc grid to obtain the droop coefficients. Firstly, based on the converter control strategies, the types of converter were classified. It will help to find out which kinds of converter can be participated into the dc-side voltage control. Secondly, a virtual node was defined, and the matrix of the dc grid was reshaped to fit the new added virtual node by using the proposed simplification method. An example was shown how this method worked. After that a new method of calculating the P-V droop coefficient was proposed. Finally, a simulation model was investigated to verify if the proposed method can operate in a real system. The results showed that the simplification method can ensure the mathematical relationships of the dc system. And simulations show good performances of the droop coefficient calculation method. [ABSTRACT FROM AUTHOR]

Direct current circuit breakers (DCCBs) have become a large research topic and are considered one of the critical components for future DC grids. Proposed DCCB concepts may be grouped into hybrid DCCBs and active resonant DCCBs. In this work, the enhanced active resonant (EAR) DCCB family is introduced. EAR DCCBs combine elements of hybrid and active resonant DCCBs. The EAR DCCB family consists of one unidirectional and six bidirectional concepts. All concepts feature proactive commutation. The main characteristic of the EAR DCCBs is that discharge closing switches are used instead of semiconductors with turn-off capability. Relevant discharge closing switch technology is reviewed, a laboratory prototype is explained, and experimental results are presented to demonstrate the feasibility of the proposed DCCB concepts. [ABSTRACT FROM AUTHOR]

An increasing share of fluctuating and intermittent renewable energy sources can cause over-currents (OCs) in the power system. The heat generated during OCs increases the junction temperature of semiconductor devices and could even lead to thermal runaway if thermal limits are reached. In order to keep the junction temperature within the thermal limit of the semiconductor, the power module structure with heat-absorbing material below the chip is investigated through COMSOL Multiphysics simulations. The upper limits of the junction temperature for Silicon (Si) and Silicon Carbide (SiC) are assumed to be 175 and 250 ∘ C, respectively. The heat-absorbing materials considered for analysis are a copper block and a copper block with phase change materials (PCMs). Two times, three times, and four times of OCs would be discussed for durations of a few hundred milliseconds and seconds. This article also discusses the thermal performance of a copper block and a copper block with PCMs. PCMs used for Si and SiC are LM108 and Lithium, respectively. It is concluded that the copper block just below the semiconductor chip would enable OC capability in Si and SiC devices and would be more convenient to manufacture as compared to the copper block with PCM. [ABSTRACT FROM AUTHOR]

The papers in this special issue cover the following topics: survey and device related topics; reliability; modeling; packaging and modules; high-temperature aspects; gate and base drivers and aspects on switching speed; cascode circuits; dc-dc converters; resonant and soft-switching converters, matrix converters; and grid-side and motor-drive applications. [ABSTRACT FROM AUTHOR]

Inverter‐based generators (IBGs) are becoming popular in modern power systems. When the penetration of IBGs is increasing in power systems, new stability, protection, and monitoring challenges are introduced in the grid. Grid‐forming (GFM) control of converters is seen as a promising solution for future power grids to overcome particular stability challenges. Here, the technical challenges of the GFM‐based IBGs are reviewed from the point of view of TSOs and academic research. The properties of different GFM methods are studied for different GFM‐based IBGs for a single grid‐tied IBG and using the IEEE 9‐bus test system. Simulation results are provided by using the PSCAD‐EMT simulation software. [ABSTRACT FROM AUTHOR]

Wireless control of modular multilevel converter (MMC) submodules can benefit from different points of view, such as lower converter cost and shorter installation time. In return for the advantages, the stochastic performance of wireless communication networks necessitates an advanced converter control system immune to the losses and delays of the wirelessly transmitted data. This article proposes an advancement to the distributed control of MMCs to be utilized in wireless submodule control. Using the proposed method, the operation of the MMC continues smoothly and uninterruptedly during wireless communication errors. The previously proposed submodule wireless control concept relies on implementing the modulation and individual submodule-capacitor-voltage control in the submodules using the insertion indices transmitted from a central controller. This article takes the concept as a basis and introduces to synthesize the indices autonomously in the submodules during the communication errors. This new approach allows the MMC continue its operation when one, some, or all submodules suffer from communication errors for a limited time. The proposal is validated experimentally on a laboratory-scale MMC. [ABSTRACT FROM AUTHOR]

Recent advancements in the silicon carbide (SiC) power semiconductor technology offer improvements for high-power converters, where today silicon (Si) devices are still dominant. Bipolar SiC devices feature particularly good conduction capability while blocking high voltages. With expected advances in SiC material quality and processing technology, resulting in higher charge carrier lifetimes, methods for tailoring will be required. In this article, three differently optimized 10-kV SiC p-i-n diodes are compared regarding their switching and conduction performance in a 50-kHz LCC converter with a high output voltage. The converter topology features capacitively assisted switching, resulting in reduced switching losses for diodes with short reverse recovery tails. One diode group was subjected to a novel carrier lifetime tailoring method, involving simultaneous annihilation and generation of carbon vacancies. Another group was tailored via proton irradiation. Tradeoffs for the optimization of the diodes are highlighted. The analysis is supported by circuit simulations, device simulations, static measurements, switching waveform measurements, and calorimetric loss measurements. The results show a total rectifier loss reduction of 37%, compared to a state-of-the-art implementation with eight 1-kV Si diodes. The switching losses account for 3%–19% of the total losses, indicating a much higher possible operation frequency. [ABSTRACT FROM AUTHOR]

Recent developments in medium-voltage (MV) silicon and silicon carbide (SiC) power semiconductor devices are challenging state-of-the-art converter and auxiliary power supply (APS) designs. The APS is an important converter component, which energizes the gate-drive units and, therefore, has an influence on the overall reliability and efficiency of the converter system. There has, however, been comparably little research on how the APS of high-power converter submodules can be realized, in particular, for high-voltage applications. New, or improved, solutions may build on state-of-the-art topologies in the near future, but utilize MV SiC technology in the APS circuit itself to enable improved efficiency, reliability, simplicity, and compactness. Externally-fed APS concepts could provide several further advantages. Their various benefits on converter and system level may enable them to be a competitive solution for future APS concepts. Especially, light-based power supply systems are considered most useful since they offer extreme voltage isolation capability and immunity to electromagnetic interference. This article presents a review of the wide range of solutions for APSs, possible implementation options, and the most important design considerations. The different solutions are evaluated in a qualitative fashion, providing an overview of available APS concepts with regard to the requirements for high-power converter applications. [ABSTRACT FROM AUTHOR]

A high-voltage tapped-inductor buck converter utilizing a novel autonomous high-voltage valve is presented in this paper. Its application as auxiliary power supply for high-power cascaded-converter submodules is discussed, followed by a presentation of the most challenging problems in designing a low-power high-voltage step-down converter. The TI-buck converter topology is analyzed, which together with the novel autonomous high-voltage valve overcomes most of the problems. Analytical expressions describing the operation as well as circuit simulations are presented. Finally, an experimental evaluation of a 3-kV 70-W prototype converter utilizing the proposed autonomous high-voltage valve with series-connected super-junction MOSFETs is presented. [ABSTRACT FROM PUBLISHER]

A circuit solution to the normally-ON property of the normally-ON silicon carbide junction field-effect transistor, namely the self-powered gate driver, has been recently proposed. This letter sheds some light on the design process of the self-powered gate driver concept as well as limitations from the system perspective. It is experimentally shown that the parameters of the self-powered gate driver must be chosen taking into account a tradeoff between a fast response and stable operation of the driver. Moreover, the influence of the shoot-through current in the fast activation of the self-powered gate driver is also presented. [ABSTRACT FROM AUTHOR]

Phase-modular buck–boost dc/ac inverters extend the voltage conversion range of conventional buck-type inverter topologies, and accordingly offer significant advantages for variable-speed motor drives powered from dc sources with wide-voltage-ranges like fuel cells or batteries. In this letter, two new modulation schemes are applied to the six-switch buck–boost Y-inverter (6YI) topology, with an analysis of the efficiency improvement for the proposed third harmonic injection pulsewidth modulation (TPWM) and discontinuous PWM (DPWM) schemes relative to conventional sinusoidal PWM (SPWM). Third harmonic injection PWM (TPWM) substantially reduces conduction losses and discontinuous PWM (DPWM) extends this gain by eliminating high-frequency switching for one-third of the fundamental period. These gains are validated on a 1 kW hardware demonstrator across a dc input voltage from 80 to 240 V, with DPWM reducing total converter losses by 31% over SPWM for a peak efficiency at nominal load of 95.6% with a power density of $62.3\ {\rm W/in^3}$. [ABSTRACT FROM AUTHOR]

This paper describes issues related to parallel connection of SiC bipolar junction transistors (BJTs) in discrete packages. The devices are applied in a high-frequency dc/dc boost converter where the switching losses significantly exceed the conduction losses. The design and construction of the converter is discussed with special emphasis on successful parallel-operation of the discrete BJTs. All considerations are experimentally illustrated by a 6-kW, 250-kHz boost converter (300 V/600 V). A special solution for the base-drive unit, based on the dual-source driver concept, is also shown in this paper. The performance of this driver and the current sharing of the BJTs are both presented. The power losses and thermal performance of the parallel-connected transistors have been determined experimentally for different powers and switching frequencies. An efficiency of 98.23% (±0.02%) was measured using a calorimetric setup, while the maximum temperature difference among the four devices is 12 °C. [ABSTRACT FROM AUTHOR]

This article presents an online health monitoring scheme for dc capacitors in modular multilevel converters (MMCs). The health monitoring algorithm is based on detecting changes in the dc capacitance value over time. The proposed algorithm only utilizes measurements that are typically available in flexible alternating current transmission systems and high-voltage direct current applications. Hence, in the proposed estimation method, no additional sensors are used. The estimation scheme considers the presence of noise in voltage and current measurements, and utilizes a recursive least square estimator in conjunction with a special low-pass filter to minimize the estimation errors. Simulation results of a hardware replica, as well as experimental results on a low-power MMC prototype show that the proposed scheme can identify the dc-link capacitance value with a maximum error of 1%. [ABSTRACT FROM AUTHOR]

The use of solid rotor and pole-plate synchronous machines has several advantages, among which is the fact that it provides a more robust rotor compared to laminated equivalents. This paper investigates the time and space harmonic losses in solid rotor synchronous machines. The work considers the use of copper coating on the pole-plates, studying the effect that this design modification has on the losses. A recommendation is given based on this study, which is considered to reduce the time harmonic losses without detrimental effects as far as the space harmonic losses are considered. [ABSTRACT FROM PUBLISHER]

The very low on-state resistance, the voltage-controlled gate, and the relative simplicity of fabrication of the normally ON silicon carbide junction field-effect transistor (JFET) make this device the most important player among all state-of-the-art silicon carbide transistors. However, the normally ON nature counts as the main factor which keeps this device far from being considered as an alternative to the silicon insulated-gate bipolar transistor. A self-powered gate driver without external power supply for normally ON silicon carbide JFETs is presented in this paper. The proposed circuit is able to handle the short-circuit currents when the devices are subjected to the dc-link voltage by utilizing the energy associated with this current. On the other hand, it supplies the necessary negative gate-source voltage during the steady-state operation. A detailed description of the operating states in conjunction with a theoretical analysis of the proposed self-powered gate driver is presented. The first part of the experimental investigation has been performed when the proposed circuit is connected to a device which is directly subjected to the dc-link voltage. The second set of measurements were recorded when the self-powered gate-driver was employed as the driver of normally ON components in a half-bridge converter. From the experimental results, it is shown that the short-circuit current is cleared within approximately 20 μs after the dc-link voltage is applied, while the power consumption when all devices are kept in the OFF state equals 0.37 W. Moreover, it is experimentally shown that the proposed gate driver can properly switch when it is employed in a half-bridge converter. Finally, limitations regarding the range of the applications where the self-powered gate drive can efficiently operate are also discussed. [ABSTRACT FROM AUTHOR]

This paper introduces a new method for the preliminary design of power controllers (PCs) in the electric power grid. The method, which is denoted the ideal phase-shifter (IPS) method, utilizes the concept of the power controller plane where the active power of the PC line is plotted versus the difference in voltage angle between the PC terminals. The power controller plane makes it possible to graphically visualize the working area of a PC in a power grid and thus determine the grid situations which are dimensioning for the PC. The IPS method offers the possibility of plotting the grid characteristics in the power controller plane which are unbiased with respect to the reactive properties of the PC. This makes the method suitable for comparison and preliminary design of PCs of different types and with different characteristics by simple geometrical considerations. In this process, the IPS method uses the power-flow control method for deriving the PC characteristics. This paper includes an application example of the method where it is used for dimensioning of two different PCs in a 26-bus test system. [ABSTRACT FROM AUTHOR]

The use of VSD (variable speed drives) is becoming prominent in industry as it has the benefit of being more energy efficient than conventional process-control mechanisms (such as throttling). VSD usually rely on the use of inverters to produce the required frequency output, which contains time harmonics that eventually induce excess losses in the machine. These losses are the subject of analysis in this study. The results show that it is possible to influence the induced current magnitude (due to the space and time harmonics) through proper design modifications, as to reduce the consequent losses. The paper focuses specifically on DTC (direct torque control) VSD application on solid pole plate synchronous machines. One of the observed effects is that the time and space harmonics are distributed differently on the pole plates. [ABSTRACT FROM AUTHOR]

Voltage-source converters (VSC) have been widely utilized to provide instantaneous reactive power support to power systems, an application referred to as static synchronous compensator (StatCom). The integration of energy storage (ES) into a StatCom makes it possible for the StatCom to provide a certain amount of active power as well as reactive power support. The possible benefit of the additional active power of a StatCom can be power oscillation damping capability, mitigation of phase-jump-related disturbances, etc. Direct connection of an ES device to the dc link of the VSC incurs an unnecessarily high-voltage rating of the VSC due to the considerable voltage swing associated with the ES device. Dual thyristor converter topology has been proposed as the interface between the ES and the dc link of the VSC. In this paper, a cost estimation for systems with the proposed interface topology is presented regarding three types of ES: capacitors, supercapacitors, and batteries. The study shows potential cost savings with utilization of the proposed interface topology. In addition, a cost comparison between different types of ES is presented, providing a guideline for the choice of ES in these kinds of applications. [ABSTRACT FROM AUTHOR]

The recently proposed power-synchronization control for grid-connected voltage-source converters (VSCs) has been shown to be a feasible solution for high-voltage direct-current (HVDC) transmission connected to high-impedance weak ac systems. In this paper, power-synchronization control is investigated for VSC-HVDC links connected to another type of weak ac system, i.e., low-inertia or island systems. As an example, a linear model of a typical island system feeding by a VSC-HVDC link, including a synchronous generator, an induction motor, and some passive loads, is developed for tuning the control parameters of the VSC-HVDC link. Time simulations in PSCAD/EMTDC demonstrate that VSC-HVDC systems using power-synchronization control are flexible for various network conditions, such as large-ac-system connection, island systems, or passive networks. The time simulations also show that power-synchronization control can seamlessly handle transitions between operation modes, as well as ride through ac-system faults in all network conditions. [ABSTRACT FROM PUBLISHER]

In this paper, voltage-source converter (VSC) based high-voltage dc (HVDC) transmission is investigated for interconnection of two very weak ac systems. By using the recently proposed power-synchronization control, the short-circuit capacities of the ac systems are no longer the limiting factors, but rather the load angles. For the analysis of the stability, the Jacobian transfer matrix concept has been introduced. The right-half plane (RHP) transmission zero of the ac Jacobian transfer matrix moves closer to the origin with larger load angles. The paper shows that, due to the bandwidth limitation imposed by the RHP zero on the direct-voltage control of the VSC, high dc-capacitance values are needed for such applications. In addition, the paper proposes a control structure particularly designed for weak-ac-system interconnections. As an example, it is shown that the proposed control structure enables a power transmission of 0.86 p.u. from a system with the short-circuit ratio (SCR) of 1.2 to a system with an SCR of 1.0. This should be compared to previous results for VSC based HVDC using vector current control. In this case, only 0.4 p.u. power transmission can be achieved for dc link where only one of the ac systems has an SCR of 1.0. [ABSTRACT FROM AUTHOR]

This paper compares four different methods for determining the electrical damping of a power system seen from one generator as a function of frequency. This information is useful when the risk for subsynchronous resonance (SSR) in the system is evaluated. The study compares one frequency scanning method which is implemented in a time-domain digital simulation program with three methods of different complexity based on analytical calculations. The time-domain simulation method is easily implemented with a detailed model of the power system including complex load and generator models, whereas the analytical methods are based on simpler models of the power system. The computational effort is much larger for the time-domain method than for the analytical methods. In the study, all methods were used to determine the damping characteristics of a four-machine power system in different configurations. The study shows that fast analytical methods may provide results which closely agree with the detailed method of time-domain simulation. However, the study also shows that the level of accuracy in the analytical model is very important. [ABSTRACT FROM AUTHOR]

Voltage source converters (VSC) have been widely utilized to provide instantaneous reactive power support to power systems, an application referred to as static synchronous compensator (StatCom). Integration of energy storage (ES) into a StatCom makes it possible for the StatCom to provide a certain amount of active power as well as reactive power support. The possible benefit of the additional active power support of a StatCom can be power oscillation damping capability, mitigation of phase-jump related disturbances, etc. Direct connection of an ES device to the dc link of the VSC incurs unnecessarily high voltage rating of the VSC due to the considerable voltage swing associated with the ES device. In order to reduce the total cost, a dual thyristor converter topology has been proposed as the interface between the ES and the dc link of the VSC. In this paper, dynamics of the proposed system are investigated. Control strategies are proposed and verified by simulations with PSCAD/EMTDC. [ABSTRACT FROM AUTHOR]

In this paper, a novel control method of grid-connected voltage-source converters (VSCs) is proposed. The method can be generally applied for all grid-connected VSCs but may be of most importance in high-voltage dc (HVDC) applications. Different from the previous control methods, the proposed method utilizes the internal synchronization mechanism in ac systems, in principle, similar to the operation of a synchronous machine. By using this type of power-synchronization control, the VSC avoids the instability caused by a standard phase-locked loop in a weak ac-system connection. Moreover, a VSC terminal can give the weak ac system strong voltage support, just like a normal synchronous machine does. The control method is verified by both analytical models and time simulations. [ABSTRACT FROM AUTHOR]

In this paper, a controller for a thyristor switched series capacitor (TSSC) is presented. The controller aims to stabilize the power system by damping interarea power oscillations and by improving the transient stability of the system. In addition to this, a power flow control feature is included in the controller. The power oscillation damping controller is designed based on a nonlinear control law, while the transient stability improvement feature works in open loop. The damping controller is adaptive and estimates the power system parameters according to a simplified generic model of a two-area power system. It is designed for systems where one poorly damped dominant mode of power oscillation exists. In the paper, a verification of the controller by means of digital simulations of one two-area, four-machine power system, and one 23-machine power system is presented. The results show that the controller improves the stability of both test systems significantly in a number of fault cases at different levels of interarea power flow. [ABSTRACT FROM AUTHOR]

The voltage at the point of common coupling (PCC) in a weak network is very sensitive to load changes. A sudden change in active load will cause both a phase jump and a magnitude fluctuation in the bus voltage (voltage at the PCC), whereas reactive load changes mainly affect the voltage magnitude. With the addition of energy storage to a static synchronous compensator (StatCom), it is possible to compensate for the active power change as well as providing reactive power support. In this paper effective active power compensation schemes are proposed. Simulation and experimental results verify the compensation schemes by showing that a StatCom with energy storage can significantly reduce phase jumps and magnitude deviations of the bus voltage under load disturbances. [ABSTRACT FROM AUTHOR]

A transformer might be driven into saturation by faults in the connected system. In a transmission system with a Static synchronous Compensator and transformers connected at the point of common coupling, different modulation schemes utilized by the voltage source converter influence the transformer saturation in different ways. This paper compares the saturation effect during fault recovery when two alternative modulation schemes are utilized: voltage modulation and flux modulation. The comparison shows that utilization of flux modulation scheme tends to soften the saturation problem during fault recovery. However, this is achieved at a higher converter transient peak current. [ABSTRACT FROM AUTHOR]

Recent advancements in silicon carbide (SiC) power semiconductor technology enable developments in the high-power sector, e.g., high-voltage-direct-current (HVdc) converters for transmission, where today silicon (Si) devices are state-of-the-art. New submodule (SM) topologies for modular multilevel converters offer benefits in combination with these new SiC semiconductors. This article reviews developments in both fields, SiC power semiconductor devices and SM topologies, and evaluates their combined performance in relation to core requirements for HVdc converters: grid code compliance, reliability, and cost. A detailed comparison of SM topologies regarding their structural properties, design and control complexity, voltage capability, losses, and fault handling is given. Alternatives to state-of-the-art SMs with Si insulated-gate bipolar transistors (IGBTs) are proposed, and several promising design approaches are discussed. Most advantages can be gained from three technology features. First, SM bipolar capability enables dc fault handling and reduced the energy storage requirements. Second, SM topologies with parallel conduction paths in combination with SiC metal–oxide–semiconductor field-effect transistors offer reduced losses. Third, a higher SM voltage enabled by a higher blocking voltage of SiC devices results in a reduced converter complexity. For the latter, ultrahigh-voltage bipolar devices, such as SiC IGBTs and SiC gate turn-off thyristors, are envisioned. [ABSTRACT FROM AUTHOR]

Wireless control of modular multilevel converter (MMC) submodules offers several potential benefits to exploit, such as decreased converter costs and ease in converter installation. However, wireless control comes with several challenging engineering requirements. The control methods used with wired communication networks are not directly applicable to the wireless control due to the latency and reliability differences of wired and wireless networks. This article reviews the existing control architectures of MMCs and proposes a control and communication method for wireless submodule control. Also, a synchronization method for pulsewidth modulation carriers is proposed suitable for wireless control. The imperfections of wireless communication, such as higher latency and packet losses compared to wired communication, are analyzed for the operation of MMCs. The latency is fixed with a proper controller and wireless network design. The converter is rendered immune to the packet losses by decreasing the closed-loop control bandwidth. The functionality of the proposal is verified, for the first time, experimentally on a laboratory-scale MMC using a simple wireless network. It is shown that wireless control of MMC submodules with the proposed approach can perform comparably to the wired control. [ABSTRACT FROM AUTHOR]

The performance of theoretical ultrahigh-voltage power semiconductor devices has been predicted by means of numerical simulations using the Sentaurus technology computer-aided design tool. A general silicon carbide punch-through insulated-gate bipolar transistor (IGBT) structure has been implemented with suitable physics-based models and parameters to reflect the device characteristics in a wide range of device blocking voltages from 20 to 50 kV. The models for 20 kV class IGBTs have been implicitly validated by means of published experimental results. Mixed-mode simulations were performed that predicted total switching energy loss densities of 335, 629, 906, and 999 mJ/cm2 for 20, 30, 40, and 50 kV class devices, respectively, at 25 °C, JC = 20 A/cm2, and an ambipolar carrier lifetime of 20 μs. While the IGBT on-state forward voltage drop reduces, the switching losses increase with higher charge-carrier lifetime for a given current density (e.g., 20 A/cm2). The large span of simulation results will be used as an input support to the design of future high-power converters. [ABSTRACT FROM AUTHOR]

Results are reported from a successful field test with a silicon carbide (SiC) metal‐oxide‐semiconductor field‐effect transistor (MOSFET) traction inverter. The train has been operated over a 3‐month period in the Stockholm metro system. Increased traction inverter power density has been achieved, with volume and weight reductions of 51% and 25%, respectively. Lower power losses permit the use of car motion cooling. A sound pressure level reduction of 9 dB(A) was measured in the field with the higher inverter switching frequency permitted by using SiC. Complementing tests have been performed in the laboratory to compare thermal performance of silicon and SiC in the same power semiconductor housing. Propulsion system power losses are reduced by 19% with SiC. Acoustic noise reductions while increasing switching frequency are also reported. [ABSTRACT FROM AUTHOR]

The temperature evolution during a short-circuit (SC) fault in the dies of three different silicon carbide (SiC) 1200-V power devices is presented in this article. Transient electrothermal simulations are performed based on the reconstructed structure of commercially available devices. The simulations reveal the location of the hottest point in each device. The nonisothermal electrical analysis supports the necessity to turn-off SC events rapidly to protect the immunity of the device after a fault. The analysis also reveal differences in delay required to turn-off devices depending on their type. A thorough analysis of the temperature rise in the die of the SiC metal-oxide semiconductor field-effect transistors (MOSFET) device is also presented, where the maximum temperature with regards to different fault cases and circuit characteristics is presented. The impact of the gate resistance, circuit inductance, detection time, drain-source voltage, and gate-source voltage are considered. [ABSTRACT FROM AUTHOR]

This article studies a new hybrid converter that utilizes thyristors and full-bridge (FB) arms for achieving high-power capability with reduced semiconductor power rating compared to the FB modular multilevel converter. The study covers the theoretical analysis of the energy balancing, the dimensioning principles, the maximum power capability, and the limitations imposed by the discontinuous operation of the converter. Based on the analysis of these aspects, the theoretical analysis is concluded by identifying the operational constraints that need to be fulfilled for maximizing the power capability of the converter. It is concluded that the maximum power capability can be achieved for a certain range of modulation indices and is limited by both the commutation time of the thyristors and the power angle. Moreover, the P–Q capability of the hybrid converter is presented and discussed. Finally, simulation and experimental results that confirm the theoretical analysis and the feasibility of the studied converter are presented and discussed. [ABSTRACT FROM AUTHOR]

Future meshed high-voltage direct current grids require modular multilevel converters with extended functionality. One of the most interesting new submodule topologies is the semi-full-bridge because it enables efficient handling of dc-side short circuits while having reduced power losses compared to an implementation with full-bridge submodules. However, the semi-full-bridge submodule requires the parallel connection of capacitors during normal operation, which can cause a high redistribution current in case the voltages of the two submodule capacitors are not equal. The maximum voltage difference and resulting redistribution current have been studied analytically by means of simulations and in a full-scale standalone submodule laboratory setup. The most critical parameter is the capacitance mismatch between the two capacitors. The experimental results from the full-scale prototype show that the redistribution current peaks at 500 A if the voltage difference is 10 V before paralleling and increases to 2500 A if the difference is 40 V. However, neglecting very unlikely cases, the maximum voltage difference predicted by simulations is not higher than 20–30 V for the considered case. Among other measures, a balancing controller is proposed, which reduces the voltage difference safely if a certain maximum value is surpassed. The operating principle of the controller is described in detail and verified experimentally on a down-scaled submodule within a modular multilevel converter prototype. It can be concluded that excessively high redistribution currents can be prevented. Consequently, they are no obstacle for using the semi-full-bridge submodule in future HVdc converters. [ABSTRACT FROM AUTHOR]

Converter-grid interaction is of great interest in a weak-grid condition. This paper presents a single-input–single-output (SISO) open-loop transfer function for the stability analysis of grid-connected voltage-source converters. Differing from the conventional input impedance method and the eigenvalue analysis, an alternative multi-input–multi-output closed-loop system is developed in the paper and it eventually yields an SISO open-loop transfer function. This enables the application of a single Nyquist curve for analyzing the overall system stability. The model is validated against time-domain simulations as well as experimental results showing excellent accuracy for predicting the system stability. [ABSTRACT FROM AUTHOR]

In this paper, a novel $dv/dt$ filter is presented targeted for 100-kW to 1-MW voltage source converters using silicon carbide (SiC) power devices. This concept uses the stray inductance between the power device and the converter output as a filter component in combination with an additional small RC-link. Hence, a lossy, bulky, and costly filter inductor is avoided and the resulting output $dv/dt$ is limited to 5–10 kV/$\mu$s independent of the output current and switching speed of the SiC devices. As a consequence, loads with $dv/dt$ constraints, e.g., motor drives can be fed from SiC devices enabling full utilization of their high switching speed. Moreover, a filter-model is proposed for the selection of filter component values for a certain $dv/dt$ requirement. Finally, results are shown using a 300-A 1700-V SiC metal–oxide–semiconductor field-effect transistor (mosfet). These results show that the converter output $dv/dt$ can be limited to 7.5 kV/ $\mu$s even though values up to 47 kV/ $\mu$s were measured across the SiC mosfet module. Hence, the total switching losses, including the filter losses, are verified to be three times lower compared to when the mosfet $dv/dt$ was slowed down by adjusting the gate driver. [ABSTRACT FROM AUTHOR]

In this paper, a new low-loss turn-on concept for the silicon insulated-gate bipolar transistor (Si-IGBT) in combination with silicon p-i-n diode is presented. The concept is tailored for two-level motor converters in the 100 kW to 1 MW range under the constraint that the output voltages slopes are limited in order to protect the motor windings. Moreover, analyses of the IGBT turn-on and diode reverse recovery voltage slopes are presented concluding that the diode reverse recovery is the worst case. The concept includes a low-cost measurement of the free-wheeling diode current and temperature by the gate driver without necessity of acquiring this information from the converter control board. By using this concept, the output dv/dt at the diode turn-off can be kept approximately constant regardless of the commutated current and junction temperature. Hence, the switching losses could be decreased for the currents and temperatures where the voltage slopes are lower when using a conventional gate driver optimized for the worst case. Moreover, results are shown for one such power semiconductor, showing a total switching loss reduction of up to 28% in comparison with a gate driver without current and temperature measurement. Finally, this concept is particularly suitable for high power semiconductor modules in half-bridge configuration which are recently proposed by several suppliers. [ABSTRACT FROM AUTHOR]

This paper presents an experimental methodology for the characterization of thermomechanical displacement and friction properties in a free-floating press-pack structure, and evaluation of the tensile stress on the semiconductor die through simulation of different mechanical and thermal loading conditions. The press-pack structure consists of a single silver-metallized (1 \mu \textm ) silicon carbide die ( 400~\mu \textm ) in contact with rhodium-coated (0.4 \mu \textm ) molybdenum square plates. The thermomechanical displacements in the press-pack structure have been obtained using the digital image correlation technique, and the mean random error has been ±0.1 \mu \textm , which is approximately 10 ppm of the measured length (10.5 mm). The developed experimental method has led to an analytical estimation of friction coefficients on the interfaces’ silicon carbide-molybdenum and molybdenum-copper. The results demonstrate that the thin silver layer behaves as a solid film lubricant. A 2-D finite-element model representing the experimental setup has been implemented. The difference in displacement between measurement and simulation is less than 8%. Furthermore, the coinfluence of the design parameters on the thermomechanical performance of the stacked structure has been analyzed through simulations. Finally, design guidelines to reduce the tensile stress on the silicon carbide die have been proposed regarding free-floating press-pack power electronics packaging. [ABSTRACT FROM PUBLISHER]

This work investigates sources of measurement errors that result for common mode/differential mode (CM/DM) separators in a practical measurement environment, with a particular focus on the recently presented input impedance criterion for CM/DM separators, derives the respective analytical expressions, and employs a detailed analytical model to verify the obtained findings. Furthermore, a method is derived, which determines the worst-case measurement error by reason of cross coupling for given measured DM and CM output voltage components. Based on an example, this work illustrates how the obtained expressions can be advantageously used in a computer program to automatically decide whether a particular spectral measurement component represents a useful measurement result or if it is strongly affected by cross coupling (CM to DM and DM to CM). Finally, the paper presents the realization and accompanying experimental results of an active CM/DM separator, which allows for low realization effort and features competitive separation capabilities (DMTR/CMRR > 50\; \textdB and CMTR/DMRR > 42\; \textdB for frequencies up to 10\; \textMHz ). [ABSTRACT FROM AUTHOR]

The stacked polyphase bridges (SPB) converter consists of several submodules that all are connected in series to a voltage source. The total dc-link voltage should split in a balanced way among the submodules. This does not always occur inherently. This paper presents an analysis of the capacitor voltage stability for the SPB converter. From the analysis, criteria for stability are derived and three alternatives of a suitable balancing controller are designed. The proposed controller alternatives and their associated stability properties are verified on an experimental setup and by simulation. [ABSTRACT FROM PUBLISHER]

An experimental analysis of the behavior under short-circuit conditions of three different silicon-carbide (SiC) 1200-V power devices is presented. It is found that all devices take up a substantial voltage, which is favorable for detection of short circuits. A transient thermal device simulation was performed to determine the temperature stress on the die during a short-circuit event, for the SiC MOSFET. It was found that, for reliability reasons, the short-circuit time should be limited to values well below Si IGBT tolerances. Guidelines toward a rugged design for short-circuit protection (SCP) are presented with an emphasis on improving the reliability and availability of the overall system. A SiC device driver with an integrated SCP is presented for each device-type, respectively, where a short-circuit detection is added to a conventional driver design in a simple way. The SCP driver was experimentally evaluated with a detection time of 180 ns. For all devices, short-circuit times well below 1 \upmu\texts were achieved. [ABSTRACT FROM AUTHOR]