IGBT Switching Frequency Research Articles

Measurement method of the IGBT chip temperature fluctuation based on electrothermal model derivation

The IGBT chip temperature is an important index affecting device reliability. Due to the existence of packaging, the temperature data of the IGBT chip is difficult to obtain directly. Because the large IGBT switching frequency, the temperature changes quickly. The chip junction temperature fluctuation is too difficult to measure. Based on the Cauer electrothermal coupling model, this paper deduces the calculation formula of the IGBT chip temperature fluctuation. Through the on-stage voltage, collector current, thermal resistance, thermal capacitance, on time and off time that can be directly monitored, the chip temperature fluctuation inside the package can be calculated. Then the accuracy of the calculation formula of temperature fluctuation is verified by experimental method, and the experimental results confirm the feasibility of this method. The chip temperature fluctuation monitored by this method is the premise for the lifetime prediction and reliability research of the IGBT, which plays a great role in the engineering field.

Investigation on the method of battery self-heating using motor pulse current

The charging and discharging performance of lithium-ion battery at low temperature will decline greatly, which seriously affects the adaptability of electric vehicles at low temperature. This paper proposes to use the inductance characteristic of the motor stator and the switching control characteristic of the motor controller to form pulse current in the battery, and realize the self-heating of the power battery at low temperature. Using this method the heating of the battery can be achieved without any additional hardware or cost. The experimental result shows the average temperature rise rate of the power battery reaches 2.88°C/min. And the influence of different parameters on the heating effect is analyzed through the experiments, including IGBT switching frequency, d-axis voltage, motor-rotor position, and battery internal resistance.

Modeling of high frequency high voltage of waveforms on life of enamel insulation

<p>In recent years it has been observed that insulation failure in electrical motors is caused by adjustable speed drives fed by power electronic converters. These converters produce impulse waveforms having a high slew rate generated by the high switching frequency of IGBTs. This paper focuses on high switching frequency stress in low voltage electrical motors for adjustable speeds. To examine the motor winding insulation under such stress twisted-pair samples were developed from enameled wires. A single-coated polyester of enamel with a thickness of 40 microns is used for this work. High-frequencies, high voltages of Square, and Square-rising, Square-spike waveforms of 10-30 kHz are used here. The test results show that the insulation fails earlier for the Square waveform compared to the Square-spike and Square-rising waveforms. In a nutshell, there is an analysis of PD formation in the insulation system at a higher switching frequency is analyzed. Electric field distributions between twisted pairs with various air gaps of the insulation system stressed by the Square and Square-rising waveforms up to 30 kHz are modeled using COMSOL software.</p>

Improved voltage equalization control strategy in modular multilevel converter

In order to solve the problem of traditional carrier phase-shift modulation with multiple ratios or PI controllers and cumbersome tuning parameters, this paper proposes an improved carrier phase-shift method. The control signal is no longer generated by a large number of proportional or PI controllers, but rather by the number of turn-on sub-modules and sorting principles. However, because the method uses a sorting method, the IGBT switching frequency is too high. Therefore, a sorting trigger condition that can effectively reduce the switching frequency is proposed, and the lower switching frequency is realized by reducing the times of sorting. At the same time, the method has better modulation wave following characteristics, and it is easy to achieve the suppression of the circulation. For the circulation problem, the second-frequency negative sequence component is extracted by rotating coordinate transformation, and it is suppressed by PI control. A 21-level MMC model was built in MATLAB / simulink to analyze the sub-module capacitor voltage fluctuation, output current, voltage distortion rate and bridge-arm circulation. It is verified that the modulation method can combine sorting algorithm and circulation suppression method at the same time, and has better voltage equalization and circulation suppression effects.

A Simplified Space Vector Pulsewidth Modulation Scheme for Three-Phase Cascaded H-Bridge Inverters

A simplified space vector pulsewidth modulation (SVPWM) for three-phase cascaded H-bridge (CHB) inverters is presented in this article. Treating each unit as a three-level inverter and adopting serial calculation mode, a CHB inverter is modulated unit by unit using three-level SVPWM. Duty cycles of real sector are obtained by mapping duty cycles of sector 1, in which the calculation of three-level SVPWM is done. The process of implementing multilevel SVPWM is simplified to the process of implementing three-level SVPWM. By reusing field-programmable gate array (FPGA) chip resource that is used for the calculation of three-level SVPWM, the presented SVPWM can be easily adopted for a CHB inverter with different number of units, while the FPGA chip resource utilization is reduced significantly. In addition, the presented SVPWM provides an effective switching frequency higher than the switching frequency of IGBTs. Simulation and experimental results are provided to verify the feasibility of the presented SVPWM.

Influence of square waveform on life of twisted pairs due to power electronic converters

Issues in the life of stator winding of electrical motors fed by inverter drives have been concerned about researchers over the last two decades for obtaining adjustable speeds.The Power Electronic Converters produces a square waveform (duty cycle, 50%) with fast rising pulses due to the high switching frequency of IGBT’s, causes premature failure of motor winding insulation. The Life of such motor insulation is tested using twisted pair samples which are prepared using enamel wires.The enamel coating is of Modified Polyester (Class-F insulation) with different makes have the same thickness of 40 microns and Polyester-imide (Class-H insulation) thickness of 40 microns are the two primary insulation tested in this work and the results are compared. The breakdown test was performed with high voltage power frequency sinusoidal waveform and high frequency square waveform of different frequency levels of 5 kHz to 30 kHz. The test results show that breakdown strength of Class F insulation is more than that of Class H insulation.

Improved Nearest-Level Modulation for a Modular Multilevel Converter With a Lower Submodule Number

This letter proposes an improved nearest-level modulation (NLM) method to enhance the quality of output voltage of a modular multilevel converter (MMC) with the low amount of submodules, as well as restrain the voltage fluctuation of the submodules. By adding a small offset, which is alternating at the double fundamental frequency to the reference signals, a small phase shift of the step-changing moment between upper and lower arms’ voltage emerges. As a result, an odd-level difference between the output voltage of lower arm and that of upper arm occurs, which can increase the level number of output voltage from $N + 1$ to $2N + 1$ , where N is the number of submodules per arm. With the proposed method, the total harmonic distortion (THD) of the output voltage is mitigated without increasing the switching frequency of IGBTs or changing the average voltage of submodules’ capacitor. In addition, within a special range of power factor angle, the circulating current can be reduced by choosing the proper phase between the fundamental and the double fundamental frequency. Simulation and experimental results verify the effectiveness and validity of the proposed NLM scheme.

Voltage Balancing Method on Expert System for 51-Level MMC in High Voltage Direct Current Transmission

The Modular Multilevel Converters (MMC) have been a spotlight for the high voltage and high power transmission systems. In the VSC-HVDC (High Voltage Direct Current based on Voltage Source Converter) transmission system, the energy of DC link is stored in the distributed capacitors, and the difference of capacitors in parameters and charge rates causes capacitor voltage balance which affects the safety and stability of HVDC system. A method of MMC based on the expert system for reducing the frequency of the submodules (SMs) of the IGBT switching frequency is proposed. Firstly, MMC with 51 levels for HVDC is designed. Secondly, the nearest level control (NLC) for 51-level MMC is introduced. Thirdly, a modified capacitor voltage balancing method based on expert system for MMC-based HVDC transmission system is proposed. Finally, a simulation platform for 51-level Modular Multilevel Converter is constructed by using MATLAB/SIMULINK. The results indicate that the strategy proposed reduces the switching frequency on the premise of keeping submodule voltage basically identical, which greatly reduces the power losses for MMC-HVDC system.

Determination of the maximum value of the switching frequency IGBT module

An algorithm for the calculation of the maximum switching frequency of IGBT modules in the two-level voltage inverter mode, constant or cyclic loads, is proposed. The junction temperature of the IGBT does not exceed the maximumallowable value. The factors influencing the maximum allowed switching frequency of IGBT is considered.

Unity power factor boost converter with phase shifted parallel IGBT operation for medium power applications

Phase-shifted parallel (PSP) operation of IGBTs is proposed for unity pf boost converters, to increase both the converter power rating and operating frequency. This technique allows unity pf operation of medium power AC and DC motor drives, and switch mode power supplies from a single-phase, unregulated AC supply, with minimum line current harmonic distortion. Since operating frequency is increased by integer multiples of IGBT switching frequency, the same core size for the boost inductor can be used to transfer larger amounts of power at the expense of additional power switching elements and a simple pulse separation circuit. Equal average current sharing is inherent in PSP operation strategy without any external circuits for equalisation. The design and implementation of a 28 kW, 40 kHz unity pf boost converter with two phase-shifted parallel IGBTs are presented. Advantages and disadvantages of PSP IGBT operation in increasing the power rating of boost converters are also given in comparison with other converter and power semiconductor parallel operation techniques.