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The paper presents novel transformer-flux-balancing control methods for the isolated bidirectional full-bridge (FB) converter with active clamp and the bidirectional dual-active bridge (DAB) converter. Both approaches are based on the sensing and control of the transformer magnetizing current. For the isolated bidirectional FB converter the magnetizing current is obtained by sensing a single current,...
Field experiences have demonstrated that semiconductor devices are vulnerable to failures (open-& short-circuit). In many critical applications, such failures are unacceptable and high system reliability is required. In this paper, a topology modification for the T-type 3-level inverter is explored to achieve the fault-tolerant operation and enhance the system reliability in the case of device...
Considering stability, the loadability of long line ac transmission system is typically far below its thermal limitation. To partially address this problem, a hybrid ac/dc approach is investigated in this paper by superposing dc current on ac currents along existing ac lines, and no changes of insulators, towers and conductors are required. First, detailed performance comparison between line commutated...
Many industrial applications involve loads which are very sensitive to electrical disturbances in the supply. These instances involve both various types of voltage unbalance as well as more series disturbances such as symmetrical and asymmetrical faults. This paper proposes a voltage unbalance and an unsymmetrical fault correction technique for a three phase load utilizing an industry-standard current...
The new grid codes demand the wind turbine systems to ride through recurring grid faults. Many control strategies have been proposed for the Doubly Fed Induction Generator under single grid fault, but their performance under recurring grid faults have not been studied yet. In this paper, five different control strategies for DFIG to ride through single grid faults are presented, and their performance...
Lack of DC short circuit fault blocking and ride through capability is one of main issues in applications of Modular Multilevel Converter (MMC) to actual HVDC transmission system. Recently, several topologies have been proposed to provide DC short circuit fault blocking capability and/or DC fault ride through capability. In this paper, the operation principles, functionalities, and characteristics...
In the LLC resonant converter, the air gap is generally positioned in the core of the transformer for proper magnetizing inductance. Traditional transformer design methods assume infinite permeability of the core and no energy stored in the core. The improved design methodology for the gapped transformer is proposed with the optimum relative permeability and gap selection to meet the temperature rise...
Two AC-DC converter topologies for 3-phase utility grid interface using high frequency (HF) or medium frequency (MF) transformers have been proposed in this paper. The transformer primary side converter structure is similar in both the topologies (say T-I and T-II), but the secondary side converter structures as well as the modulation schemes are different. The line-frequency AC voltage from the utility...
Multi-level rectifier topologies are widely used in applications of the wide-power range. T-type topology, which is one of many three-level topologies, has an advantage in terms of an efficiency compared to a neutral-point clamped (NPC)-type. In applications using T-type rectifier topology, the interest in reliability has been increased recently. Therefore, a tolerance control for T-type rectifiers...
This paper presents an open-circuit fault detection method and its tolerant control strategy for a Parallel-Connected Single Active Bridge (PCSAB) dc-dc converter. The structural and operational characteristics of the PCSAB converter lead to several advantages especially for high power applications. By paralleling modular converters, the power and current ratings of each modular converter can be lowered...
A single-phase Dual Active Half Bridge (DAHB) DC-DC converter topology is evaluated for medium voltage (MV) application. A 15kV SiC-IGBT based three-level half-bridge is connected to the high voltage (HV) primary side of a high frequency (HF) transformer operating at 10kHz link-frequency. A 1200V SiC-MOSFET based two-level H-bridge is connected on the low voltage (LV) secondary side. This topology...
This paper describes a high-speed protection circuit for IGBTs subjected to hard-switching faults (HSF). The reverse transfer capacitance depends on a collector-emitter voltage and it produces a significant effect on a switching behavior not only under normal conditions but also under HSF conditions. A gate charge characteristic under HSF conditions differs from that under normal turn-on conditions...
The phase-shifted full-bridge (PSFB) converter topology provides a platform which enables the achievement of high power-density through low-loss operation at high frequency. However, this topology is also subject to the risk of flux imbalance in the main power transformer if precautions are not taken to prevent its occurrence. This paper evaluates the power-density implications of the several known...
New grid codes demand the wind turbine systems to ride through recurring grid faults. In this paper, the performance of the Doubly Fed Induction Generator wind turbine system under recurring grid faults is analyzed. The stator natural flux produced by the voltage recovery after the first grid fault may be superposed on the stator natural flux produced by the second grid fault, and it may result in...
With the stator directly connected to the grid, doubly-fed induction generator is very sensitive to gird disturbance. However, wind turbines are required to stay connected to the grid for a given time duration during grid fault, according to the low voltage ride-through requirement. The key point of the low voltage ride-through solution is to depress high rotor current during grid fault. This paper...
In this paper, the analysis and design of the high frequency corona generator with LCC resonant topology applied in film treatment is proposed. The designed converter works with a specified output voltage, which makes the film treatment efficient and stable. By making the converter operate in a critical mode, the analysis and design is simplified and the resonant parameters can be described by time...
This paper provides an overview of DC side fault tolerance issues of VSC based HVDC system and the need for fault tolerant converters. The working principle and DC fault ride through capability of recently introduced Alternate Arm Modular Multilevel Converter(AAMMC) has been discussed. The capacitor voltage balancing issues of AAMMC is analyzed and a novel scheme for balancing capacitor voltages of...
The increase in the number of power electronic applications has led to harmonic pollution of the power grid. Harmonic resonance that can result in severe voltage distortion is a well documented problem. Several suppression techniques have been proposed to solve this problem. This paper proposes a technique to cooperatively operate multiple Active Power Line Conditioner (APLC) installed in the same...
This paper describes a novel protection method to limit the fault currents caused by short circuit in a voltage source converter (VSC) based DC systems with capacitors connected to the DC bus. Analyzing the development of DC fault current in such DC systems shows that capacitor discharge dominates the very rapid fault current rising at the instance of faults. If this high slope fault current surge...
Transformerless Intelligent Power Substation (TIPS) is a 3-phase Solid State Transformer (SST) to interconnect 13.8 kV, 3-phase distribution grid with 480 V, 3-phase utility grid. The concept of TIPS was proposed as a solid state alternative to the conventional line frequency transformer. Various advantages of TIPS include unity power factor operation, controlled bidirectional power flow capability,...
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