Emre Gurpinar

Single-Phase T-Type Inverter Performance Benchmark Using Si IGBTs, SiC MOSFETs, and GaN HEMTs

In this paper, benchmark of Si IGBT, SiC MOSFET, and Gallium nitride (GaN) HEMT power switches at 600-V class is conducted in single-phase T-type inverter. Gate driver requirements, switching performance, inverter efficiency performance, heat sink volume, output filter volume, and dead-time effect for each technology is evaluated. Gate driver study shows that GaN has the lowest gate driver losses above 100 kHz and below 100 kHz, SiC has lowest gate losses. GaN has the best switching performance among three technologies that allows high efficiency at high-frequency applications. GaN-based inverter operated at 160-kHz switching frequency with 97.3% efficiency at 2.5-kW output power. Performance of three device technologies at different temperature, switching frequency, and load conditions shows that heat sink volume of the converter can be reduced by 2.5 times by switching from Si to GaN solution at 60 °C case temperature, and for SiC and GaN, heat sink volume can be reduced by 2.36 and 4.92 times, respectively, by increasing heat sink temperature to 100 °C. Output filter volume can be reduced by 43% with 24, 26, and 61 W increase in device power loss for GaN-, SiC-, and Si-based converters, respectively. WBG devices allow reduction of harmonic distortion at output current from 3.5% to 1.5% at 100 kHz.

Performance Evaluation of a Three-Level ANPC Photovoltaic Grid-Connected Inverter With 650-V SiC Devices and Optimized PWM

Photovoltaic (PV) energy conversion has been on the spotlight of scientific research on renewable energy for several years. In recent years, the bulk of the research on PV has focused on transformerless grid-connected inverters, more efficient than traditional line transformer-based ones, but more critical from a power quality point of view, especially in terms of ground leakage current. Neutral-point-clamped (NPC) inverters have recently gained interest due to their intrinsically low ground leakage current and high efficiency, especially for MOSFET-based topologies. This paper presents an active NPC (ANPC) topology equipped with 650-V silicon carbide (SiC) MOSFETs, with a new modulation strategy that allows to reap the benefits of the wide-bandgap devices. An efficiency improvement is obtained due to the parallel operation of two devices during the freewheeling intervals. Simulations and experimental results confirm the effectiveness of the proposed converter.

Performance analysis of SiC MOSFET based 3-level ANPC grid-connected inverter with novel modulation scheme

Performance analysis of three-level active neutral point clamped (ANPC) inverter with 650V SiC MOSFETs by ROHM is presented with a new switching pattern that utilises the active rectification capability of SiC devices. Performance analysis of the converter with 700V DC link and 230Vrms grid voltage are presented for different switching frequency, device case temperature and load conditions. The switching frequency is varied from 10kHz to 80kHz at four different output power and four different heat sink temperature conditions. The experimental results show that the converter can maintain high efficiency under wide load, frequency and heat sink temperature conditions. Robust performance of SiC devices can lead to reduction in passive component size, by utilizing high switching frequency and heat sink weight and volume by operating SiC at higher case temperature conditions.

Reliability-Driven Assessment of GaN HEMTs and Si IGBTs in 3L-ANPC PV Inverters

In this paper, thermal loading of the state-of-the-art gallium nitride (GaN) High-electron-mobility transistors (HEMTs) and traditional Si Insulated-gate bipolar transistors (IGBTs) in three-level active neutral-point-clamped photovoltaic inverters is presented considering real-field long-term mission profiles (i.e., ambient temperature and solar irradiance). A comparison of Si IGBT against GaN HEMT with three different possibilities: 1) with thermal interface material (TIM) at 10 kHz; 2) without TIM at 10 kHz; and 3) with TIM at 300 kHz has been performed. The assessment results indicate lower thermal stress with GaN HEMT devices at 10 kHz in comparison with Si IGBT. At high switching frequencies, the results show that the significant system level cost savings can be achieved without compromise of operating efficiency with GaN HEMTs. Both simulations and experimental tests are provided to demonstrate the thermal loading analysis approach. More important, the proposed analysis and comparison approach can be used for lifetime and reliability analysis of wide bandgap devices.

Performance analysis of UniTL-H6 inverter with SiC MOSFETs

A transformerless single-phase PV inverter has been tested with latest generation 650V/ 20A SiC MOSFETs from ROHM. Test results show that the inverter can be operated with high efficiency at high switching frequencies due to high switching and conduction performance of the devices. Results also show that reduction in output filter size, reduced harmonic distortion and increase in power density are enabled by SiC MOSFETs for PV inverters without compromising on the efficiency of the system.

Novel multilevel hybrid inverter topology with power scalability

In this paper, a novel multilevel hybrid inverter is presented. The inverter is based on 2 floating capacitors and 16 active switches for five-level voltage waveform between the output of the inverter and neutral point of DC link. The proposed inverter structure, switching states and commutation scheme for different output voltage levels are presented. The proposed topology is simulated and verified experimentally. The simulation results show that proposed topology can achieve higher efficiency in comparison to state-of-the-art hybrid topologies due to reduced conduction and switching losses at low modulation index and light load conditions. Experimental results show that the converter is successfully operated up to 1 kV DC link voltage and 12 kW output power.

SiC and GaN based BSNPC inverter for photovoltaic systems

Recent studies show that Silicon Carbide and Gallium Nitride based power semiconductors promise better performance over conventional Silicon based devices. In this study, the performance analysis of a three level inverter based on SiC and GaN is discussed for photovoltaic applications. The converter can achieve 99.2% efficiency at 16kHz switching frequency and 1.4kW output power, and operate with good efficiency up to 160kHz. The impact of high performance of SiC and GaN devices on output filter size and cooling requirements is discussed. The study shows that with wide-bandgap devices, heat sink volume can be reduced by 72% and output filter size can be reduced by 57% while keeping very good efficiency.

Performance evaluation of a 3-level ANPC photovoltaic grid-connected inverter with 650V SiC devices and optimized PWM

Photovoltaic energy conversion has been on the spotlight of scientific research for several years. Special attention was paid to the grid-connected inverters that do not feature an insulation transformer (transformerless topologies). In this framework, Neutral Point Clamped inverters have gained interest due to the low ground leakage current. Recently, the research has been focused on high-efficiency MOSFET-based topologies. In this paper an Active-NPC topology is equipped with 650V ROHM SiC devices. A new modulation strategy that allows to exploit the characteristics of Sic MOSFETs, is proposed. It permits to obtain very high efficiency due to the parallel operation of the devices during the freewheeling phases of the inverter output current. Simulation and experimental results show the benefits of this choice.

Built-in reliability design of a high-frequency SiC MOSFET power module

A high frequency SiC MOSFET-based three-phase, 2-level power module has been designed, simulated, assembled and tested. The design followed a built-in reliability approach, involving extensive finite-element simulation based analysis of the electro-thermo-mechanical strain and stress affecting the switch during both manufacturing and operation: structural simulations were carried out to identify the materials, geometry and sizes of constituent parts which would maximize reliability. Following hardware development, functional tests were carried out, showing that the module is suitable for high switching frequency operation without impairing efficiency, thus enabling a considerable reduction of system-level size and weight.

Tradeoff Study of Heat Sink and Output Filter Volume in a GaN HEMT Based Single-Phase Inverter

This paper presents the tradeoff study of heat sink and output filter volume of a GaN HEMT based single-phase inverter. The selected topology is three-level active neutral point clamped (ANPC) inverter, and the main aim is to explore the benefits of the GaN HEMTs at 600 V blocking class on the system level efficiency, and power density under the wide range of operating conditions. The paper starts by introducing the inverter topology, selected pulse width modulation scheme and followed by the device features, static, and dynamic characterization and continues with presenting and discussing the results of extensive experimental and analytical characterization. After this, the impact of GaN HEMTs on inverter volume is discussed in terms of heat sink and output filter volume analysis under different switching frequency and heat sink temperature conditions. The calculation of heat sink volume and single stage LC output filter volume are presented with respect to experimental results of the single phase prototype. The findings from static, dynamic characterization, and single phase prototype results clearly show that GaN HEMT has excellent switching performance under wide load current and heat sink temperature conditions. The high performance of the inverter leads to reduction of the combined total volume, including output filter and heat sink volume.