Electric Vehicle Inverter Research Articles

Analysis and Experimentation of a Three Phase Asymmetric Cascaded Multilevel Inverter for Electric Vehicles

Multilevel inverters have been gaining immense popularity in high power applications such as Electric vehicles, Flexible AC Transmission Systems etc. This paper focuses on an asymmetric cascaded multilevel inverter employing the variable frequency carrier phase shifted PWM technique. The major advantage of this strategy is that it aids in balancing the switch utilization. The proposed strategy was found to have lower THD and switching losses when compared to the conventional strategies. The simulation was performed using MATLAB/Simulink and the results were verified experimentally.

Design and Analysis of Electrical Properties of a Multilayer Ceramic Capacitor Module for DC-Link of Hybrid Electric Vehicles

Multilayer capacitors with high ripple current and high capacitance were manufactured. The electrical properties of these capacitors were characterized for potential application for DC-link capacitors in hybrid electric vehicle inverters. Internal electrode structures were designed to achieve high capacitance and reliability. A single multilayer capacitor showed 0.46 3F/cm₃ of capacitance, 0.65% of dielectric loss, and 1450 V to 1650 V of dielectric breakdown voltage depending on the design of the internal electrode. The capacitor module designed with several multilayer capacitors gave a total capacitance of 450 3F, which is enough for hybrid electric vehicles. In particular, an equivalent series resistance of 4.5 m7 or less will result in 60 A rms , thereby reaching the allowed ripple current for hybrid electric vehicles.

Self-Tuning Fuzzy PI-Type Controller in Z-Source Inverter for Hybrid Electric Vehicles

This paper presents new algorithms to control speed induction motor (SIM) and the peak dc-link voltage (PDV) across the inverter bridge in z-source inverters (ZSI) by applying self-tuning fuzzy PI controller (SFP) with robust structure and non-linear characteristic. In particular, this so-called SFP based control algorithm (SFPA) is applied to a closed loop speed control system of induction motor, which relies on direct torque control scheme combined with modified space vector modulation (DTCMSVM) control strategy with so many exceptional features (e.g. fast torque response, low steady state torque ripple, and high accurate). Additionally, SFPA is used to control SIM and PDV are more adaptive to the sudden change of parameters such as load torque, stator resistance and dc input voltage (DIV), respectively. The transient response of SIM and PDV are thus improved with less over shoot, short rise time, small steady-state error and fast settling time, with low disturbance for output voltage stabilization in the inverter bridge. As a result, we achieve higher accuracy and robustness of SIM control system. Our new SFPA is verified in both simulation and experimental implementation using MATLAB and dSPACE DS1103, respectively. DOI: http://dx.doi.org/10.11591/ijpeds.v2i4.571

Analysis and Evaluation of DC-Link Capacitors for High-Power-Density Electric Vehicle Drive Systems

In electric vehicle (EV) inverter systems, direct-current-link capacitors, which are bulky, heavy, and susceptible to degradation from self heating, can become a critical obstacle to high power density. This paper presents a comprehensive method for the analysis and comparative evaluation of dc-link capacitor applications to minimize the volume, mass, and capacitance. Models of equivalent series resistance that are valid over a range of frequency and operating temperature are derived and experimentally validated. The root-mean-square values and frequency spectra of the capacitor current are analyzed with respect to three modulation strategies and various operating conditions over practical ranges of load power factor and modulation index in EV drive systems. The modeling and analysis also consider the self-heating process and resulting core temperature of the dc-link capacitors, which impacts their lifetimes. Based on an 80-kW permanent-magnet (PM) motor drive system, the application of electrolytic capacitors and film capacitors has been evaluated by both simulation and experimental tests. The inverter power density is improved from 2.99 kW/L to 13.3 kW/L, without sacrificing the system performance in terms of power loss, core temperature, and lifetime.

Dielectric properties and spectroscopy of large-aspect-ratio ferroelectric thin-film heterostructures

High energy density and breakdown/operating voltages with lower dielectric film thickness and manufacturing cost are the necessary traits in futuristic capacitors for a variety of applications. Prior studies have reported the successful fabrication of high-k, thin-film ferroelectrics with aspect ratios (diameter/thickness) <1000; however, devices with aspect ratios >104–105 are necessary to meet the large-capacitive requirements in pulsed-power applications such as the inverters in hybrid electric vehicles (HEVs). It is also widely accepted that the breakdown field of thin films decreases logarithmically with an increase in the aspect ratio (area) due to the increased probability of producing a defect spot. These observations raise an important question: can we fabricate ferroelectric high-k film capacitors that have large aspect ratio and can sustain high fields? Here we report the fabrication and characterization of Pb0.92La0.08Zr0.52Ti0.48O3 thin-film capacitors with aspect ratios >104 that can be operated at ∼1 MV cm−1 and are suitable for embedded passives in HEVs. Dielectric spectroscopy showed a low-frequency anomalous relaxation behaviour in large-aspect-ratio heterostructure, which was analysed and interpreted using an equivalent circuit model. The measured anomalous relaxation behaviour was de-convoluted using the model to obtain the actual material response. High capacitances (1–5 µF) and energy densities of (∼9 J cm−3) were routinely measured in these high-aspect-ratio films.

A Comparison between Buck-Boost Inverter with and without Buffer Inductor

The electric vehicle inverter requires an induction motor drive with a high output of voltage and current to reduce the number of batteries used and in turn reduce the vehicle’s weight. In this paper compared two single Phase BuckBoost Inverter (SPBBI), that is between the SPBBI conventional topology with SPBBI new topology uses a buffer inductor. The results of comparison are expected that the new inverter topology can strengthen the voltage greater than the conventional inverter topology. The inverter’s components of capacitor and inductor were reconfigured. The circuit was simulated for various carrier and signal frequencies with various load. The simulation results of the proposed topology compared with the simulation results of conventional topologies commonly used in a variety of frequency and load values. It is shown that the output voltage and current can be strengthened significantly, with a value of more than five times of the output voltage compared to the conventional inverter. The new inverter topology is useful to be implemented for the electric vehicle.

Progress in the Development of a High-Performance Heat Sink for Hybrid Electric Vehicle Inverters

Progress in the Development of a High-Performance Heat Sink for Hybrid Electric Vehicle Inverters

23-Level Inverter for Electric Vehicles Using a Single Battery Pack and Series Active Filters

Cascaded H-bridge (CHB) multilevel inverters have been conceived as an alternative to reduce total harmonic distortion (THD) in medium-voltage drives. The reduced THD makes them useful for electric vehicle (EV) applications, but the main problem with the CHB is the large amount of isolated power sources required to feed each of the H-bridges. An improved variant known as the asymmetrical CHB (ACHB) inverter uses H-bridges of different sizes and then needs fewer isolated power sources than the CHB. However, in battery-powered EVs, only one power supply (fuel cell or battery pack) is desirable. This work presents a solution to solve the problem, operating some of the small H-bridges (Aux-bridges) as series active filters and using a small high-frequency link (HFL). With this solution, only one dc source is required to feed the inverter, and if the control is adjusted to work at particular switching points, more than 98% of power is transferred through the larger H-bridges (MAIN bridges). The proposed ACHB topology can produce any number of levels, and the M AIN bridges always commutate at fundamental frequency. As the number of levels must remain constant for all output voltages, a variable dc source is required to control the amplitude of the motor voltage. This work shows some simulations and experiments on a 2-kW 27-level ACHB working with only 23 levels. The concept is being implemented in a small EV with an ACHB drive of 18 kW.

Analysis and minimisation of DC bus surge voltage for electric vehicle applications

In electrical vehicle driving systems, the DC bus usually shows large surge voltages because of the presence of loop parasitic inductance and hard-switching operations of voltage source inverters. The unexpected transient overvoltage mostly accounts for switching devices failures. To guarantee system reliability, high-voltage-rating insulated-gate-bipolar-transistors (IGBTs) are commonly used in practical systems to accommodate potential surge voltages. This eventually results in the increase of power loss and system cost. A comprehensive study is presented in this study to minimise the surge voltage across the DC bus. It starts with a surge voltage model indicating that the commutation loop inductances and the switching dynamics are two critical contributors to voltage spikes. An optimal design approach to lower the stray inductance of the connecting busbar is presented. Considering the characteristics of electric vehicle (EV) inverters controlled by space vector modulation, a slew-rate limiter strategy is proposed to minimise the surge voltage. The low inductance busbar design and control strategy are validated by simulation and experimental test.

Cascaded H-bridge inverter motor drives for hybrid electric vehicle applications

This paper presents the asymmetric cascaded H-bridge multilevel inverter for electric vehicles (EV) and hybrid electric vehicles (HEV) applications. Currently available power inverter systems for HEVs use a DC-DC boost converter to boost the battery voltage for a traditional three-phase inverter. The present HEV drive inverters have low power density, are expensive, and have low efficiency because they need a bulky inductor. Asymmetric cascaded H-bridge multilevel inverter design for EV and HEV applications without the use of inductors to output a boosted AC voltage is proposed in this paper. Traditionally, each H-bridge needs a DC power supply having equal values of DC power sources. The proposed design uses the asymmetric cascaded multilevel inverter using non-equal DC power sources based on specified ratios. A fundamental switching scheme is used to do modulation control and to produce a seven-level phase voltage.

Application of Z-source Inverter for Permanent-magnet Synchronous Motor Drive System for Electric Vehicles

This paper presents a novel permanent-magnet synchronous motor (PMSM) drive system with bidirectional Z-Source inverter (ZSI) for electric vehicles, and a modified vector controlled scheme of the PMSM drive is developed by considering DC-link voltage boosting. Characteristics of ZSI are used for DC-link voltage control in a single stage to obtain wide speed range of PMSM instead of field weakening control. Several simulation results obtained in Saber verify the feasibility and effectiveness of the proposed system.

DC–AC Cascaded H-Bridge Multilevel Boost Inverter With No Inductors for Electric/Hybrid Electric Vehicle Applications

This paper presents a cascaded H-bridge multilevel boost inverter for electric vehicle (EV) and hybrid EV (HEV) applications implemented without the use of inductors. Currently available power inverter systems for HEVs use a dc-dc boost converter to boost the battery voltage for a traditional three-phase inverter. The present HEV traction drive inverters have low power density, are expensive, and have low efficiency because they need a bulky inductor. A cascaded H-bridge multilevel boost inverter design for EV and HEV applications implemented without the use of inductors is proposed in this paper. Traditionally, each H-bridge needs a dc power supply. The proposed design uses a standard three-leg inverter (one leg for each phase) and an H-bridge in series with each inverter leg which uses a capacitor as the dc power source. A fundamental switching scheme is used to do modulation control and to produce a five-level phase voltage. Experiments show that the proposed dc-ac cascaded H-bridge multilevel boost inverter can output a boosted ac voltage without the use of inductors.

A Scheme of EDTC Control using an Induction Motor Three-Level Voltage Source Inverter for Electric Vehicles

The object of this paper is to study a new control structure for sensorless induction machines dedicated to electrical drives using a three-level voltage source inverter VSI-NPC. The amplitude and the rotating speed of the flux vector can be controlled freely. The scheme investigated is an Enhanced direct torque control "EDTC" for electric vehicle propulsion. The considered application imposes some constraints which are achieved in EDTC control (fast torque response, optimal switching logic, torque control at zero speed, and large speed control. The results obtained for an induction motor indicate superior performance over the FOC type without need for any mechanical sensor.

A New Switched-capacitor Inverter for Electric Vehicles

This paper presents a new switched-capacitor inverter circuit based on partial charging. A number of switched-capacitor inverter circuits have been developed, but most of them are based on switching of fully charged capacitors in specific sequence to generate staircase ac voltage. In order to reduce the output distortion, the numbers of capacitors and switches should be increased. However, complexity of the circuits will also be increased dramatically. Moreover, the number of capacitors of conventional switched-capacitor inverters should be limited, otherwise, the peak output voltage could exceed stipulated limit. The new switched-capacitor circuit operates in such a manner that the capacitors will be switched to generate an ac output while they are partially charged. Each capacitor can provide multilevel voltages because the state of charge is varied. Theoretically, ac voltage with unlimited steps can be created with a few of capacitors. Experiments and simulations of a thirteen-level inverter that consists of only two capacitors are included in this paper.