Performance comparison of five-level NPC and ANPC converters in medium voltage drives for hydro power application

This paper compares the performance of a five-level neutral-point clamped (NPC) converter and a five-level active neutral-point clamped converter (ANPC) for a medium voltage and variable speed pumped-storage hydropower application. It is found that the ANPC converter has a lower current total harmonic distortion (THD) compared with the NPC converter under the same switching frequency, while the losses are higher. However, the simple structure and the easiness of controlling the DC-link voltage means that the five-level ANPC converter has a high potential in the market of the aforementioned application

Thermal modelling of a mutlichip IGBT power module

Life time prediction and thermal management are among the key issues regarding the performance of today\u27s semiconductor devices. And a fast and accurate thermal model can be used to tackle those problems more efficiently. In this paper, different thermal models of an IGBT power module have been established and compared. Firstly, a 3D finite element method (FEM) model is simulated in COMSOL. And then, a lumped parameter thermal model with considering different aspects (heat spreading and thermal coupling) is derived. The simulation indicates that the proposed model can achieve a relatively accurate result within a short simulation time

In situ key aging parameter determination of a vehicle battery using only CAN signals in commercial vehicles

In this article, an on-line impedance measurement technique for a battery pack is demonstrated and proofed, using only the already existing sensors and accessible bus data in an electrified vehicle. A sufficient amount of AC harmonics in the DC-link current, for the identification purposes, is created in normal driving conditions. Fourier analysis is used to process the data and extract the impedance information. It is found that the proposed on-line method can accurately measure the battery pack impedance at a low frequency range (5 Hz to 10 mHz) with 40 Hz sampling frequency in the bus data. A key impedance value in the electrochemical impedance spectroscopy can be captured clearly in different conditions, which can be used to track the battery state of health. A recorded current waveform during an on-road test is reproduced by a state-of-art battery tester in a lab and the obtained results are compared with impedance values measured by a classic potentiostat. The results from the on-road test have an excellent agreement with lab measurements

A Study on the Lifetime of Q2L-MMC-DAB’s Switches for Wind Turbine Applications

This paper studies the lifetime of semiconductor switches of a dual-active-bridge (DAB) DC-DC converter for wind turbine applications. Quasi-two-level operating modular multilevel converters (MMC) are used as the building blocks of the DAB converter. One of the established lifetime models is used for the lifetime estimation of the switches. Measurement data of an onshore wind turbine for three hundred days is used as the mission profile. It is shown that the short-term thermal cycles (cycles with frequency in the range of switching frequency) are detrimental to the lifetime estimation of the auxiliary switches of the MMCs’ submodules. Thus, neglecting the short-term thermal cycles will overestimate the lifetime of the auxiliary switches by several orders of magnitude. On the other hand, these cycles will not affect the lifetime of the bypass switches considerably. It is also shown that the thermal stress on the secondary-side auxiliary switches is more severe than the primary-side ones. It is suggested that two parallel devices should be used for the secondary-side auxiliary switches; as a consequence, a reasonable lifetime is achieved for the secondary-side auxiliary switches

Low Frequency influence on degradation of commercial Li-ion battery

The Tesla model 3 has rapidly become one of the most popular electric vehicles (EV), being the best selling EV in 2020 and the second best selling in 2021. In this paper the ageing implications of varying time scales in usage of the battery are investigated for the 2170 cells used in the Tesla model 3. It is shown that dynamic usage in the range of approximately 0.01 to 0.1 Hz has a statistically significant impact on ageing, while dynamic usage in range 0.1 to 1 Hz does not show significant impact on ageing. Furthermore the individual electrode ageing is investigated by non-invasive electrochemical techniques, revealing the profound impact on ageing from Si addition to the negative electrode, where it is shown that substantial part of the ageing comes from loss of Si in the negative electrode

Power Loss Analysis in a SiC/IGBT Propulsion Inverter Including Blanking Time, MOSFET’s Reverse Conduction and the Effect of Thermal Feedback Using a PMSM Model

This paper presents a comparison of power losses for two silicon carbide (SiC) and one silicon insulated gate bipolar transistor (Si IGBT) power modules in a three-phase inverter, when considering the effect of blanking time and the MOSFET\u27s reverse conduction. The total power losses versus different switching frequencies are also compared for the three inverters. The focus of this paper is to determine the influence of junction temperature and thermal feedback on the power loss calculation. The analysis shows that, without accounting for the thermal feedback, the loss levels are substantially underestimated, 11-15% on the conduction losses of the SiC inverters and up to 18% on the switching losses of the IGBT inverter. The data is derived at a chosen high torque, low speed operating point of a permanent magnet synchronous machine (PMSM). The operating point is considered as a worse operating condition from the power loss perspective

Hybrid Output Voltage Modulation (PWM-FSHE) for a Modular Battery System Based on a Cascaded H-Bridge Inverter for Electric Vehicles Reducing Drivetrain Losses and Current Ripple

This paper shows a preliminary study about the output voltage modulation of a modular battery system based on a seven-level cascaded H-bridge inverter used for vehicle propulsion. Two generally known modulation techniques, pulse width modulation (PWM) and fundamental selective harmonic elimination (FSHE), are extensively compared for such an innovative modular battery system inverter considering EVs\u27 broad torque-speed range. The inverter and the battery losses, as well as the inverter-induced current THD, are modeled and quantified using simulations. At low speeds, if the modulation index M is below 0.3, FSHE induces a high current THD (>>5%) and, thus, cannot be used. At medium speeds, FSHE reduces the drivetrain losses (including the battery losses), while operating at higher speeds, it even reduces the current THD. Thus, an individual boundary between multilevel PWM and FSHE can be determined using weightings for efficiency and current quality. Based on this, a simple hybrid modulation technique is suggested for modular battery system inverters, improving the simulated drive cycle efficiency by a maximum of 0.29% to 0.42% for a modeled small passenger vehicle. Furthermore, FSHE\u27s high speed dominance is demonstrated using a simple experimental setup with an inductive load

An accurate method for leakage inductance calculation of shell-type multi core-segment transformers with circular windings

The leakage field in shell-type transformers is strongly affected by the boundary conditions introduced by the core walls and thus the effect of the core should be considered properly in the leakage inductance calculation. In this paper, a new method for accurate calculation of the leakage inductance of shell-type multi core-segment transformers with circular windings is presented. For this purpose, first, the expressions for self and mutual inductances are derived in cylindrical coordinates considering the core walls as the flux-normal boundary condition. Then, a new approach is proposed for calculating the leakage inductance considering the number and dimensions of the used core segments. The method is developed at first for single and double core-segment transformers (known also as E-core and U-core transformers) and then adopted for shell-type segmented-core transformers. The method is verified by 3-D FEM simulations. The comparisons with the previous analytical methods demonstrate the superiority of the proposed method. A transformer prototype has been built and verification tests have been conducted. The comparisons show that the leakage inductance can be estimated with an error less than 1%, demonstrating a very high accuracy with the proposed method

Efficiency of Active Three-Level and Five-Level NPC Inverters Compared to a Two-Level Inverter in a Vehicle

This paper deals with a comparison of a standard two-level inverter, with a three-level and a five-level active neutral point clamped (ANPC) inverter for vehicle traction applications. The inverter efficiencies during different drive cycles are assessed and an efficiency enhancement of the multilevel inverters for partial loading and different drive cycle scenarios is found

An Accurate Analytical Method for Leakage Inductance Calculation of Shell-Type Transformers With Rectangular Windings

This paper presents an accurate analytical method for calculating the leakage inductance of shell-type E-core transformers with rectangular windings. For this purpose, first, an expression for calculating the leakage inductance per unit length inside the core window considering the core walls as the flux-normal boundary condition is derived. Then, a new accurate method for determining the Mean Length of Turns (MLT) based on the total stored energy is presented. The MLT is needed for the leakage inductance calculation using 2-D methods. By dividing the MLT into three partial lengths and calculating the corresponding leakage inductances using three different core window arrangements, the effect of core structure on the total leakage inductance is considered. The method is verified by 3-D FEM simulations as well as the leakage inductance measurements on two different fabricated transformer prototypes. The superiority of the method is also confirmed by comparisons with the previous analytical approaches. The proposed method enables the leakage inductance calculation with an error less than 1%, compared to the 3-D FEM results. Using the presented method, the leakage inductance calculations can be performed rapidly and accurately in the design stage without the need for time-consuming 3-D FEM simulations