High Power and Medium Voltage SiC based Power Converters and Applications Opportunities and Challenges offered by HV SiC Power Devices

Subhashish Bhattacharya 전력전자학회 2019 ICPE(ISPE)논문집 Vol.2019 No.5

Impact of Centralized and Distributed Control Structures on the Harmonic Stability of Modular Multilevel Converter Based on DQ Reference Frame Impedance Assessment

Semih Isik,Subhashish Bhattacharya 전력전자학회 2023 ICPE(ISPE)논문집 Vol.2023 No.-

The Modular Multilevel Converter (MMC) is one of the suitable converter topologies for medium to high-voltage industry applications. Despite the inherent modularity and redundant structure of the MMC topology, most MMC controllers are designed based on a centralized controller structure. Even though a centralized controller inherently limits the hardware flexibility of an MMC, it is relatively faster than distributed control algorithms due to less communication and control delays. Both control structures have pros and cons, but the design of the controller may cause instability at specific frequencies when interfaced with an AC or DC grid due to control gains, delays etc. This paper investigates the effects of the control delays of the distributed controller on system stability and compares it with the centralized controller. An MMC and its controller are modeled in a Hardware-in-Loop environment with the Real Time Digital Simulator to analyze potential DC resonant frequencies in the dq reference frame. Passivity theory isapplied to the extracted frequency response to predict possible passive and non-passive regions based on control structures.

Medium Voltage Asynchronous Micro-grid Power Conditioning System enabled by HV SiC Devices

Sanket Parashar,Subhashish Bhattacharya 전력전자학회 2019 ICPE(ISPE)논문집 Vol.2019 No.5

This research paper addresses a Medium-Voltage Asynchronous Micro-grid Power Conditioning system enabled by HV SiC devices to Asynchronously flow power from microgrids to the larger grid. The Asynchronous Microgrid Power Conditioning System is a modular MVAC (13.8kV AC) to MVAC (4,160 V AC and 13.8 kV AC) power conditioning systems blocks (PCSB) that can be used for grid interconnection of Megawatt-scale flow control microgrids (Asynchronous MVAC Microgrids), bidirectional power flow capablity and scalablity so that they can be used for a broad range of flow control microgrids of different scale (100 kW to multi MW) including microgrids which have net generation or net load flow at point of connection of larger grids. This modular approach is intended to result in highervolume, lower-cost power electronics building blocks that service many applications at standard voltages: 4,160 V AC and 13.8 kV AC. This Microgrid PCS solution should enable multi-port integration of renewable energy sources to the main grid. The Microgrid PCS solution can be implemented with 3.3 kV to 10 kV SiC MOSFET modules. The modular converters will utilize highvoltage, high frequency (10 kHz) power electronics to reduce cost, size , footprint, volume and weight and to provide the bandwidth (voltage control BW = 300 Hz and current control BW = 1 kHz) needed for both the grid-facing and microgrid facing functions required by interconnection standards plus functions required for a wide range of generator, storage and load applications.

Evaluation of Extra High Voltage (XHV) Power Module for Gen3 10 kV SiC MOSFETs in a Mobile Utility Support Equipment based Solid State Transformer (MUSE-SST)

Anup Anurag,Sayan Acharya,Subhashish Bhattacharya 전력전자학회 2019 ICPE(ISPE)논문집 Vol.2019 No.5

MV solid state transformers enabled by SiC semiconductor devices is a promising replacement to conventional low frequency transformers. However, when MV SiC devices are used in converter applications, they are exposed to a high peak stress (5 kV to 10 kV) and a very high dv / dt (10 kV/μs to 100 kV/μs). Operating these semiconductor devices at these high peak stresses require careful designing from the packaging point of view, as well as designing the auxiliary systems such as the gate drivers and busbars, to handle the peak stress conditions. Recently, an extra high voltage (XHV) power module has been developed by Wolfspeed to package the 10 kV SiC MOSFETs for continuous and reliable operation. This paper aims at testing these modules in continuous operation for qualifying their operation in a MV solid state transformer. Reliable operation of these modules require the development of reliable auxiliary parts including gate drivers, bus bars and inductors. Design and development of the auxiliary system is also carried out. Successful tests demonstrating operation at MV levels are also shown. These tests serve as a qualification method for using these devices in a MV solid state transformer. It is envisaged that successful operation of these devices would accelerate the growth and deployment of MV SiC devices for field operation.

Improved EEMF-Based Position Sensorless Control for Non-sinusoidal Back-EMF PMSMs

Kim Heonyoung,Lee Kibok,Bhattacharya Subhashish 대한전기학회 2022 Journal of Electrical Engineering & Technology Vol.17 No.2

A restricted number of the stator and rotor slots in PMSMs distorts the air-gap fl ux distribution and eff ective air-gap length. Such distortions result in varying machine parameters with rotor position. In particular, the rotor fl ux linkage harmonics cause a non-sinusoidal back-EMF, which introduces machine harmonic currents if PI current controllers are employed. As a result, it deteriorates the rotor position estimation performance in extended EMF (EEMF)-based sensorless control. This is because both sinusoidal machine current and back-EMF are assumed for the rotor position estimation. Such degradation of the angle estimation performance can result in controller trips due to overcurrent, especially in the case of step load changes. This paper presents a detailed modeling of the harmonic rotor fl ux linkage and voltage, and introduces virtual rotor fl ux linkage terms in the synchronous reference frame to simplify the harmonic voltage terms. From the harmonic voltage model, a harmonic voltage injection method is proposed in addition to conventional EEMF-based sensorless control. The proposed scheme can provide sinusoidal motor current control for entire operating conditions. Additionally, experimental results confi rm that the proposed control method can achieve the improved performance of the EEMF-based sensorless control

Design Optimization and Performance Analysis of a Three-Phase Three-Level MVDC Bidirectional Isolator using Series-Connected 10kV SiC MOSFETs and 10kV SiC JBS diodes

Sanket Parashar,Nithin Kolli,Raj Kumar Kokkonda,Subhashish Bhattacharya 전력전자학회 2023 ICPE(ISPE)논문집 Vol.2023 No.-

This research article presents a thorough investigation of the 3 Level - 3 Phase (3L-3P) Neutral Point Clamped (NPC) Dual Active Bridge (DAB) topology for designing Medium Voltage (MV) DC isolators. An equivalent circuit model is utilized to provide a detailed analysis of the switching transition at specific operating points, including α = 60° , 0 < φ < 90° (φ≠ 60° ) α = 60°, φ = 60°. These operating points not only ensure optimal performance but also minimize the Common Mode (CM) current injected into the operating environment. The article also employs the model to evaluate the minimum current required for Zero Voltage Switching (ZVS) operation, snubber current during turn transition, and the loss in the snubber resistor. Furthermore, the article proposes a dynamic voltage balancing algorithm that significantly reduces DC offset by 80% and switching losses by 50% through precise turn-off Vds mismatch across MOSFETs and Diodes within a specified limit of 100V. The accuracy of the model used in the proposed algorithm is validated through experimental turn-off waveforms of SiC MOSFET at 1.75kV. The article introduces experimental test benches to examine the impact of base plate capacitance (Cbs) on the voltage mismatch and snubber losses in the 3L pole, providing valuable insights into the behavior of the topology under various conditions. The experiments are conducted up to 6kV DC bus voltage, and the snubber loss and dynamic voltage mismatch across series connected MOSFETs and diodes are evaluated and validated through the theoretical model.

The Influence of the LC with Clamping Diodes dv/dt Filter on Current Control of PMSM Drives in Case of Inverter Output Current Sensing and Its Compensation

Heonyoung Kim,Byeong-Heon Kim,Subhashish Bhattacharya 전력전자학회 2019 ICPE(ISPE)논문집 Vol.2019 No.5

This paper presents effect of LC with clamping diodes dv/dt filter on current-controlled PMSM drives in case where 3-phase inverter output currents are measured and used in the digital control loop. In particular, this case can be reported in some cases. Firstly, power devices are equipped with integrated pilot current sensors. Secondly, PCB technology based Rogowski coils are installed in inverter leg with analog circuit to feed a signal to microcontroller. Thirdly, hall type current sensors are packaged in inverter output terminal through a bus bar. In those cases, it is inevitable to measure inverter currents because it is hard to move the location of current sensor. In this manner, the effect of filter resonance should be considered properly to control the motor current accurately because the measured inverter output current includes both motor and filter resonant current. If the resonant current of the filter is not compensated properly, it causes the DC offset of motor current which bring about the torque ripples. In order to compensate the offset, inserting a two stage Discrete Fourier Transform (DFT) is used and the calculated offset is subtracted from the sampled current. Judging by simulation and experimental results, it is confirmed that the compensation method eliminates the offset of the motor current effectively, and thereby reducing the torque ripple as well.

Modeling and Stability Assessment of Single-Phase Droop Controlled Solid State Transformer

Yos Prabowo,Vishnu Mahadeva Iyer,Byeongheon Kim,Subhashish Bhattacharya 전력전자학회 2019 ICPE(ISPE)논문집 Vol.2019 No.5

This paper addresses the modeling aspects and small-signal stability considerations for a single-phase droop controlled Solid State Transformer (SST). A state-space based modeling approach is utilized to assess the stability of the SST. It is demonstrated that physical parameter (e.g. grid impedance) variations, the choice of control parameters (e.g. droop control parameters) and the steady state operating point play a crucial role in determining the stability of the SST system that needs to handle wide load variations. Simulation results from a 1kVA droop-controlled SST system are presented to validate the analytical models.

Design and Performance Evaluation of 1.2 kV, 325 A SiC-MOSFET High Performance Module based 100 kVA Three-phase Two-level Power Block

Sayan Acharya,Anup Anurag,Nithin Kolli,Subhashish Bhattacharya 전력전자학회 2019 ICPE(ISPE)논문집 Vol.2019 No.5

To ramp up the adaptation of the highly optimized high current 1.2 kV Sillicon Carbide (SiC) based Metal Oxide Semiconductor Field Effect Transistor (MOSFET) power modules, a high power three-phase two-level power block is designed which is rated at 100 kVA and operates with 800 V DC bus. The power modules combined with low inductance busbar and optimized loop thermo-syphon based heatsink extracts the full performance of the power electronic switches. In this paper, the design details of the power block is presented. Furthermore, the performance of the power block is qualified by a back-to-back pump back test set up where two power blocks are interconnected via inductors. Furthermore, closed loop voltage and current control are implemented to circulate the desired amount of AC current between the power blocks. Moreover, heat run tests are carried out to quantify the thermal performance of the thermal management system. The experimental results demonstrate the performance benefits of the power block.

A Study on the Evolution of Solid State Transformer Technologies and Applications

Nithin Kolli,Sanket Parashar,Raj Kumar Kokkonda,Apoorv Agarwal,Anup Anurag,Subhashish Bhattacharya 전력전자학회 2023 ICPE(ISPE)논문집 Vol.2023 No.-

The advancements in power electronics have enabled the building of solid-state transformers (SSTs) to meet the demands of smart grids. An SST is an AC/AC solid-state power conversion system. Typically these SSTs can be classified based on various parameters like series/parallel interconnection, number of power conversion stages, degree of phase modularity, etc. This paper presents a survey of the work carried out to date on SSTs with multi-stage power conversion. Furthermore, the paper highlights the SSTs that enable medium voltage grid interconnection, which is enabled by high voltage (HV) SiC power devices. The design, control, development, and testing of SST with HV SiC 10 kV MOSFETs and 15 kV SiC IGBTs are presented, and a pilot demonstration for the Navy of a medium voltage (MV) 4160 V, 100 kVA SST for “Mobile Utility Support Equipment (MUSE)” based applications enabled by SiC 10 kV MOSFETs will be discussed. A Medium-Voltage Asynchronous Microgrid Power Conditioning System (Microgrid PCS), or MV-MV SST, enabled by HV SiC series-connected power devices to connect, disconnect, and enable power flow between asynchronously connected microgrids and grids is presented. The paper addresses the developed SST prototypes and provides analysis based on the related applications. The analysis also discusses the challenges and future trends regarding the implementation of SST.