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  1. Security is a well-known function to any transmission operator and system planner. As the world is moving toward the decarbonization of the power industry, it is more complicated for the system operators to maintain an acceptable level of security in the power system operation. More large-scale wind farms are being incorporated into the grid, and thus, the voltage stability concern is increasing. In practice, several contingencies are imagined by the system operators to assess the reliability of the grid. Since voltage stability is one of the major menaces that can trigger voltage instability in a power system, this paper ismore »attempting to present to the transmission system planners and operators a dedicated methodology to facilitate the incorporation of large-scale wind farms into a transmission grid under high penetration of wind power. the stability of a wind-dominated power system is discussed based on Q-V and P-V methodologies and some N-1 contingencies with the Remedial Action Schemes (RAS). Furthermore, a methodology to rank the worst contingencies and to predict the voltage collapse during the highest wind penetration level is presented. Simulations have been, extensively, carried out to examine the methodology and have provided valuable information about the static security of the wind-dominated power system. The results can be used by the transmission system operator to anticipate voltage instability or voltage collapse in the power system during high wind penetration levels.« less
    Free, publicly-accessible full text available November 23, 2022
  2. Wide band gap (WBG) devices have been widely adopted in numerous industrial applications. In medium voltage applications, multi-level converters are necessary to reduce the voltage stress on power devices, which increases the system control complexity and reduces power density and reliability. High voltage silicon carbide (SiC) MOSFET enables the medium voltage applications with less voltage level, simple control strategy and high power density. Nevertheless, great challenges have been posed on the gate driver design for high voltage SiC MOSFET. Wireless power transfer (WPT) can achieve power conversion with large airgap, which can satisfy the system isolation requirement. Thus, in thismore »article, a WPT based gate driver is designed for the medium voltage SiC MOSFET. The coil is optimized by considering voltage isolation, coupling capacitance, size, and efficiency. Experimental prototype was built and tested to validate the effectiveness of the proposed WPT based gate driver.« less
    Free, publicly-accessible full text available November 16, 2022
  3. This article proposes a new framework for the substation demand reduction and power loss minimization in distribution networks by implementing conservation voltage reduction (CVR) strategy. The proposed framework coordinates Battery Energy Storage Systems (BESS), Smart PV inverters and voltage control devices -including OLTC and voltage regulators- so that the substation demand and network power loss are reduced while the service voltage range meets the IEEE 1547 standard (120-114 V). The suggested CVR strategy is applied to the IEEE 34-bus case study system consisting of two PV generations and BESS. The smart PV inverters are controlled based on the combined Volt/VArVolt/Wattmore »(VVW) characteristics scheme. Also, BESS is charged and discharged with regard to the time and peaks have control modes, respectively. The Arithmetic Optimization Algorithm (AOA) is implemented in MATLAB scripts for solving the optimization problem. Power flow studies are carried out using OpenDSS software. Results reveal that the new framework can achieve higher substation demand reduction considering the concurrent control of PVs and BESS.« less
    Free, publicly-accessible full text available November 14, 2022
  4. MMC-based back-to-back (B2B) converters are promising for hybrid AC/DC transmission systems when integrating large scale PV sources. This paper proposes a novel configuration for hybrid AC transmission systems with B2B converters and multi-terminal direct current (MTDC) operation which facilitates the integration of PV energy and enhances the system stability and reliability. This is achieved by an advanced interconnection with two operation modes: 1-A bi-directional power flow via AC connections, and 2- Direct active power injection to the MTDC from PV source. Conventional outer, inner and capacitor voltage balancing control systems are utilized in this study for regulating the currents andmore »voltages of B2B converter. Also, The Perturb and observe (P and O) technique is implemented for obtaining maximum power point tracking (MPPT) of the PV generation considering a dc-dc boost converter. The efficacy of this proposed configuration is verified through time-domain simulations carried out by MATLAB/SIMULINK.« less
    Free, publicly-accessible full text available November 8, 2022
  5. Abstract—Wide band gap (WBG) devices, like silicon carbide (SiC) MOSFET has gradually replaced the traditional silicon counterpart due to their advantages of high operating temperature and fast switching speed. Paralleling operations of SiC MOSFETs are unavoidable in high power applications in order to meet the system current requirement. However, parasitics mismatches among different paralleling devices would cause current unbalance issues, which would reduce the system reliability and maximum current capability. Thus, to achieve current balancing operation, this paper proposes a solution of using multi-level active gate driver, where the dynamic current sharing during turn-on and turn-off processes are achieved bymore »adjusting the delays, intermediate turn-on and turn-off voltages. The static current sharing is maintained by regulating the static turn-on gate voltage, where the on-state resistance mismatch between different devices can be compensated. A double pulse test setup with two different SiC MOSFETs is built to emulate the scenario of worst case application with large differences of threshold voltage and on-state resistance. The experimental results demonstrate that the proposed active gate driver can achieve both dynamic and static current sharing operations for SiC MOSFETs with paralleling operation. Moreover, the system control diagram is discussed. Simulation studies are conducted to achieve closed-loop control of the paralleled SiC MOSFETs with the aid of the active gate driver approach.« less
    Free, publicly-accessible full text available November 2, 2022
  6. This paper presents the design of a three-phase three-limb high-efficiency medium-voltage medium-frequency transformer with an integrated leakage layer using ribbon-based nanocrystalline cores for three-phase grid-connected applications. The design methodology is based on a custom-core approach developed by a series of design equations that allow the user to select a design that best fits the transformer specifications. A 150kVA 10-kHz 5-kV-to-400-V three-phase three-limb transformer is designed to validate the proposed design method. In addition, a series of experimental characterisation tests are conducted to measure the performance of the design according do the theoretical performance.
    Free, publicly-accessible full text available October 10, 2022
  7. Wide band gap (WBG) devices have been widely applied in industrial applications owning to their advantages of low switching loss, low on-stage voltage drop, and high operating temperature. Paralleling operation of power devices/modules is attractive due to its cost-effective and high power characteristics. In applications require very high current capability, paralleling operation of off-the-shelf power devices/modules becomes the only choice. However, current balancing operation of individual power device/module becomes difficult due to the differences of circuit parasitics. To investigate the device/module and circuit parasitics influences on the current sharing performance, in this article, a subcircuit model was built in MATLAB.more »Comprehensive comparisons and analysis are performed, which can provide guidance for engineers when designing the system with paralleling devices/modules. Moreover, the solutions to achieve current balancing operating are proposed with the aid of active gate driver. Experiment results are presented and analyzed to validate the effectiveness of current sharing solutions.« less
    Free, publicly-accessible full text available August 25, 2022
  8. The CLLC converter is widely used in the power electronic applications as a DC transformer, which can provide galvanic isolation, bidirectional power flow and an adjustable output voltage with the use of proper controls. As the most critical component in the CLLC converter, the high frequency (HF) transformer should be optimized according to the design targets, such as efficiency and power density. Starting with the analysis of the CLLC operating characteristics, this paper proposes a formal approach to design the HF transformer of a 100kW CLLC converter for a grid-tied application. The optimization method for the HF transformer is presentedmore »and the effect of the resonant inductor is analyzed. The optimized transformer is simulated with the finite element analysis (FEA) and Matlab/Simulink.« less
  9. Silicon carbide (SiC) MOSFET features low switching loss and it is advantageous in high switching frequency application, but the manufacture per Ampere cost is approximately five times higher than the silicon (Si) IGBT. Therefore, by paralleling Si IGBT and SiC MOSFET together, a trade-off between cost and loss is achieved. In this paper, a four control freedoms active gate driver (AGD) including turn-on delay, turn-off delay, and two independent gate voltages, is proposed to optimize the performance of the paralleled device. By adjusting these four control freedoms, optimal operation for paralleled device can be obtained. Moreover, the proposed AGD canmore »dynamically adjust the current ratio between two paralleled devices, which can help achieve thermal balance between two devices and improve system reliability. Double pulse test (DPT) experimental results are presented and analyzed to validate the effectiveness of the proposed AGD for paralleled Si IGBT and SiC MOSFET application.« less
  10. In this work, a 25 kW all silicon carbide (SiC) series-resonant converter (SRC) design is proposed to enable a single stage dc to dc conversion from 3kV to 540V (±270V) for future electric aircraft applications. The proposed SRC consists of a 3-level neutral-point-clamped (NPC) converter using 3.3kV discrete SiC MOSFETs on the primary side, a H-bridge converter using 900V SiC MOSFET modules on the secondary side and a high frequency (HF) transformer. The detailed design methods for the SRC power stage and the HF transformer are presented. Especially, a tradeoff between the complexity for the cooling system and the needmore »for power density is addressed in the transformer design, leading to a novel multi-layer winding layout. To validate the effectiveness of the proposed SRC design, a converter prototype has been developed and comprehensive experimental studies are performed.« less