Common-mode Voltage Research Articles

Research on Analysis and Suppression Methods of the Bearing Current for Electric Vehicle Motor Driven by SiC Inverter

The silicon carbide (SiC) inverter brings great advantages to the motor drive systems of new energy vehicles; however, severe challenges to the bearings also happen. The high dc bus voltage and switching frequency of SiC inverter can increase the discharge frequency and energy when the bearing grease film collapses. As a result, the bearing suffers severe electric corrosion, and the service life of the motor drive system can be shortened. In this paper, the characteristics of common-mode voltage and bearing voltage are analyzed, firstly under space vector pulse width modulation (SVPWM). After that, the common-mode equivalent circuit model of the motor drive system is established. The frequency characteristics of bearing voltage are revealed, and the safe working area is determined. Then, the frequency characteristics of bearing voltage and current are verified based on IGBT and SiC inverters in experiments. After that, by designing a common-mode filter, the bearing voltage and current are significantly attenuated. Furthermore, the active zero state PWM (AZSPWM) is adopted to reduce the common-mode voltage from the inverter. At the same time, combined with the common-mode filter, the bearing voltage and current are further reduced. The experimental results show that the switching frequency has a decisive effect on the amplitude of bearing voltage and current. The bearing voltage can be attenuated to around half of the reference bearing voltage by using the common-mode filter and AZSPWM strategy, respectively. The combination of the common-mode filter and AZSPWM strategy can reduce the bearing voltage to around one-fourth of the reference bearing voltage, which can effectively reduce the breakdown time and discharge energy of the grease oil film.

A Comprehensive Review on Space Vector Based-PWM Techniques for Common Mode Voltage Mitigation in Photovoltaic Multi-Level Inverters

Nowadays, transformer-less photovoltaic (PV) multi-level inverters (MLIs) are commonly employed in both industrial and residential settings. This structure has attracted increased attention due to its unique advantages, such as higher efficiency, lower cost and size, better waveform quality, and inherent fault tolerance. However, due to the removal of the transformer, the common mode voltage (CMV) becomes one of the crucial issues in transformer-less PV MLIs. The high-frequency variation in CMV results in a leakage current that deteriorates the line current quality, increases the PV power system losses, leads to severe electromagnetic emissions (EMI), reduces the PV array lifespan, and causes personal safety problems. In this regard, this paper presents a review of the existing and recent research on modulation techniques based on space vector pulse width modulation (SVPWMs) that overcome this issue in transformer-less three-level NPC-MLIs (3L-NPC-MLIs). The reduced CMV-SVPWM (RCMV-SVPWM) can be mainly categorized as an RCMV-SVPWM based on the vector type, based on virtual vectors, and based on the two-level SVPWM (2L-SVPWM). Their features and their limitations in terms of several main criteria are discussed. In the final section of this paper, some challenges and future trends for this research area are projected.

Analysis and assessment of electrical and thermal performance of five‐phase voltage source inverter under different modulation strategies: Comparative study under balanced and unbalanced load

SummaryThis paper compares four modulation strategies applied to five‐phase voltage source inverters (5PH‐VSI). The modulation strategies under investigation are sine wave pulse width modulation (S‐PWM), fifth‐harmonic injection PWM (FH‐PWM), space vector‐PWM using two large vectors (2V‐SVPWM), and space vector‐PWM using two medium and two large vectors (4V‐SVPWM). The study utilizes simulations to analyze the results based on four performance criteria: low‐order harmonics (LOH), maximum modulation index (MMI), common mode voltage (CMV), and total harmonic distortion (THD) under balanced and unbalanced load. To validate the simulation results for these criteria, an experimental test‐bench is employed, which includes a 5PH‐VSI feeding an R‐L load, and controlled by a low‐cost STM32F4‐DISCOVERY microcontroller board. Additionally, a mathematical approach is used to calculate the total thermal losses (TTL) then simulations are performed using Piecewise Linear Electrical Circuit Simulation (PLECS) software to assess the modulation schemes based on additional thermal performance criteria: conduction losses (CL), switching losses (SL), TTL, the efficiency, and the maximum permissible heat sink thermal resistance (MPHTR) at the steady‐state regime. The results indicate that the 4V‐SVPWM method demonstrates superior efficiency in terms of THD. Furthermore, it showcases the lowest TTL at high switching frequencies, allowing for the best efficiency and minimizing MPHRT, therefore providing the largest margin for the heat sink thermal resistance design. On the other hand, the 2V‐SVPWM offers the highest MMI, but this comes at the cost of high TTL and some LOHs appearing. In addition, it exhibits the highest CMV for unbalanced load. S‐PWM and FH‐PWM offer the advantage of simpler implementation.

An Application of Neural Network-based Sliding Mode Control for Multilevel Inverters

Multi-level 3-phase inverters using cascaded H-bridges are becoming prominent in the electric drive and renewable energy sectors due to their high capacity and ability to withstand high voltage shocks. Therefore, the modulation and control techniques used in these multilevel inverters have a crucial influence on the quality of the output voltage they produce. The significantly high common-mode voltage amplitude they generate is one of their disadvantages, causing leakage currents and harmonics. This article proposes a new technique using sliding mode control combined with neural networks to manage a three-phase multi-level inverter. The research objective of this innovative technique is to eliminate the need for current controllers and conventional modulation that relies on carrier signals, reducing hardware calculations and enhancing dynamic response. In addition, it demonstrates the ability to minimize harmonics, common mode voltage, and the number of switching counts, thereby limiting the inverter switching losses and increasing device performance. Simulation results performed on a 5-level 3-phase inverter using cascaded H-bridges have confirmed the effectiveness of the proposed method.

A Novel Common-Mode Voltage Suppression Strategy for Current Source Converter

The problem of common-mode voltage (CMV) in current source converter (CSC) has been concerned with the development and application of CSC, such as in the transformerless motor drive system. Using a common-mode choke is a popular solution to suppressing CMV. The high-frequency harmonics of the CMV can be eliminated by the common-mode filter. However, the low-order harmonics cannot be eliminated effectively, especially at low modulation index, which may cause common-mode resonance and increase the size of the choke. In this paper, a novel virtual space vector modulation (VSVM) method is proposed, which constructs virtual space vectors by the original vectors. The average value of the CMV produced by each virtual vector is zero. The proposed method can reduce the amplitude and third-order harmonic component of the CMV. In addition, the number of switching transitions in a switching sequence of the proposed method is the same as the conventional 5-segment SVM. The suppression effects of different methods on the low-order harmonics of CMV are compared through simulation and experiments, and the effectiveness of the proposed methods is verified.

An Optimized Model Predictive Control Method With Fixed Switching Frequency for Eliminating Common-Mode Voltage of Five-Level Converters

In this paper, an optimized model predictive control (MPC) method with fixed switching frequency (FSF) is proposed to eliminate the common-mode voltage (CMV) and balance the capacitor voltage. Firstly, the zero CMV vector diagram is divided by finite control set MPC (FCS-MPC) to obtain the candidate vectors effectively. Then, in order to control the capacitor voltage and avoid the great computational burden originated from the redundant switching combinations, a piecewise control scheme is proposed to determine the required ones directly. The sequence generated by the selected vectors is further optimized for the purpose of saving switching transitions according to the internal and external parts of the vector diagram. Finally, the duty ratios are evaluated based on the results of the FCS-MPC in dividing sectors so as to avoid any extra complex calculation. The experimental evaluation has been carried out to validate the feasibility and effectiveness of the proposed method.

A Reduced Common-Mode Voltage Control Scheme for Three-Level H10 Converter Considering Dead-Time Effect

A Reduced Common-Mode Voltage Control Scheme for Three-Level H10 Converter Considering Dead-Time Effect

Integrated Voltage Vector–Based SVPWM for Reliability and Performance Enhancement of Five-Level HANPC Inverters

Power converters are designed to operate over a wide range of voltages to meet various industrial demands. Recently, multilevel inverters have been receiving considerable attention owing to their ability to reduce the current ripple and its associated harmonic distortion. However, for applications requiring high voltage/power ratings, large electrolytic capacitors are essential, which are significantly affected by the ripple in the DC-link current. This causes a significant reduction in the lifespan and reliability of the power converter and necessitates expensive diagnosis and maintenance procedures. Therefore, an effective method of integrated voltage vector-based space vector pulse-width modulation is proposed in this study for minimizing the ripple in the DC-link and common-mode voltage of five-level hybrid active neutral-point-clamped (5L-HANPC) inverters. The proposed method uses a unique control algorithm that can smoothly select the required voltage vectors without a noticeable distortion in the output current waveforms. Moreover, the proposed method can be applied without modifying the original topology of the 5L-HANPC inverter or adding complex compensations to the control algorithm. Extensive simulation and experimental results are provided to demonstrate the capability of the proposed approach to reduce the DC-link current ripple over a wide range of modulation indices.

A novel 7-level reduced-switch MLI topology fed PMSM drive for electric vehicle system

The compact and efficient design motivates the renewable energy-powered permanent magnet synchronous motor drive for electric vehicle applications. The available renewable energy is interfaced with a power drive by employing an electronic commutator such as a conventional 3-level inverter. But, the multilevel inverter produces favorable merits by producing staircase output voltage from several input direct current (DC) sources. The cascaded H-bridge multilevel inverter plays a significant role in many applications, but it was developed only for limited voltage levels. The major problem in cascaded h-bridge multilevel inverter (CHBMLI) requires more switching devices for higher voltage levels, which increases the size, cost and space of the electric vehicle (EV). To overcome above-mentioned problems, a new objective has been developed by employing the novel Reduced-switch multilevel inverter topology for higher voltage levels. This improves the voltage quality and reducing the harmonic level, and common-mode voltage issues. The main contribution of this work is, developing the novel 5-level, 7-level reduced-switch multilevel inverter (RSMLI) topologies with reduced switching devices with favourable merits over CHBMLI topology. Finally, the performance of proposed novel 5-level and 7-level RSMLI topologies fed PMSM drive for EV system has been verified, by using MATLAB/Simulink computing tool, and simulation results are presented with comparisons.

Multi-objective based Hybrid Artificial Intelligence Controlled Parallel Inverter in Islanded and Grid Connected Operations

Background: The Integration of non-conventional energy systems (NCES), like solar, wind, etc., into the grid with power electronic devices is adapted to meet the demand. Parallel connection of inverters (PCI) is an efficient method to boost power handling capacity, reliability, and system efficiency. However, the main drawback is the unequal power sharing among the inverters while using the conventional droop control technique (CDC). In addition, the circulating currents (CC) flow between these PCI, leading to common mode voltage (CMV), current waveform distortion, and reduction in the system's overall performance. Objectives: This work consists of a photovoltaic system (PVS) and battery energy storage system (BES) as the distributed generation (DG) unit to voltage source inverter (VSI) 1 and 2. The multi- objectives of the suggested work are (a) the equal power/load sharing among two inverters, (b) effective minimization of CC and the CMV, (c) maintaining constant DC-link (DCL) voltage during different solar irradiation and constant temperature, and (d) the reduction in total harmonic distortion (THD) of load current. Methods: A novel approach related to the enhanced droop control (EDC) method with an adaptive neuro-fuzzy hybrid controller (ANFHC) was suggested here to overcome the above issues. The performance analysis of the suggested technique was done in the Matlab/ Simulink platform with islanded and grid-connected modes for different loads. Results: A comparative analysis with the available methods like the proportional integral controller (PIC) and sliding mode controller (SMC) was carried out to exhibit the viability of the developed control technique. Conclusion: This study focused on the operation and control of a PCI with ANFHC in islanded and grid-connected modes to address issues such as uniform power sharing and reduction of CC and CMV.

Analysis, Calculation and Reduction of Shaft Voltage in Induction Generators

This paper presents analysis of shaft voltage in different configurations of a Doubly Fed Induction Generator (DFIG) and an Induction Generator (IG) with a back-to-back inverter in wind turbine applications. Detailed high frequency model of the proposed systems have been developed based on existing capacitive couplings in IG & DFIG structures and common mode voltage sources. In this research work, several arrangements of DFIG based wind energy conversion systems are investigated on shaft voltage calculation and its mitigation techniques. Placements of an LC line filter in different locations and its effects on shaft voltage elimination are studied with mathematical analysis and simulations.

Common-Mode Voltage Suppression of a Five-Level Converter Based on Multimode Characteristics of Selective Harmonic Elimination PWM

The combination of five-level converters with selective harmonic elimination pulse-width modulation (SHEPWM) is a practical need in medium-voltage, high-power applications. However, how to suppress the common-mode voltage (CMV) in this case becomes a difficult problem. Although CMV suppression under high switching frequency (SF) modulations and three-level SHEPWM has been discussed in many studies, these methods are not applicable to five-level SHEPWM. This is partly because the zero-sequence voltage under SHEPWM is difficult to adjust and partly because the solution spaces of three- and five-level SHEPWM are completely different. Moreover, conventional CMV suppression in three-level SHEPWM must sacrifice the switching angles to control the zero-sequence voltage, which makes the equivalent SF increase. Therefore, in this article, we propose a novel CMV suppression method that effectively utilizes the multimode characteristics of five-level SHEPWM. Multimode characteristics refers to the output waveform containing different levels of jump patterns. Therefore, there are a large number of switching angle trajectories in five-level SHEPWM, which outputs the same fundamental voltage with different CMVs. The proposed method uses the special multimode characteristics to reduce the CMV without sacrificing the switching angles. Its effectiveness and feasibility are verified by experiments.

Improved Topology and Control Strategies for DC Converters in Wind Power Full DC Systems

This study presents an enhanced composite modular DC/DC converter topology designed to address critical technical requirements in wind power full DC systems, including high capacity, high conversion ratio, and fault isolation. The proposed topology combines MMC circuits and module combination circuits, allowing for exceptional modularity and configurability. Through the serial and parallel connection of multiple modules, the voltage or current levels can be further enhanced. Regarding the control strategy, the paper adopts SOGI phase-locked and coordinate transformation technology to precisely measure and control the differential and common-mode voltages within the MMC modules. A mathematical model is established, providing a theoretical foundation for experimental analysis. The research emphasizes the implementation of key strategies such as circulating current suppression, nearest level approximation, and capacitor voltage sorting. To validate the practicality and effectiveness of the proposed converter topology and control strategy, an experiment is conducted using a ±30 kV/±300 kV, 300 MW model constructed within the MATLAB/Simulink simulation environment.

Optimal Design of a Submodule Capacitor in a Modular Multilevel Converter for Medium Voltage Motor Drives

This paper proposes an algorithm for determining the optimal capacitance by utilizing a mathematical model of a submodule (SM) capacitor in a modular multilevel converter (MMC) specifically for medium voltage motor drives (MVDs). By approximating the voltage fluctuation of the SM capacitor during low-frequency operation, it is feasible to ascertain the minimum capacitance required for the SM capacitor, ensuring that its voltage fluctuations remain within an acceptable limit that is predefined as a specified value. Moreover, the study considered the injection of both a high-frequency common-mode voltage (CMV) and a circulating current to alleviate the SM voltage fluctuation during the acceleration of motor drives. The effectiveness of the proposed method is validated through verification using time-domain simulation results obtained using the MATLAB/SIMULINK software and real-time simulation results acquired using the OPAL-RT simulator platform.

Comparison of control techniques for three-phase distributed generation based on VOC and DPC

This paper presents a comparison among control strategies of active rectifiers used for grid connected distributed generation systems from renewable sources. The considered techniques are: Voltage Oriented Control (VOC), Direct Power Control (DPC), two DPC based techniques to minimize the Common Mode (CM) emissions called DPC-EMC1 and DPC-EMC2 set up by the authors and their versions based on virtual flux. All the described techniques have been implemented using Matlab-Simulink® environment and PLECS®. In the results the current injected into the grid, the THD of the injected current vs. generated power and vs. DC link voltage and the CM voltage are shown.

A novel programmed hybrid modulation for electromagnetic interference mitigation and current ripple control in miniaturised synchronous machine drives

AbstractA novel programmed hybrid spreading spectrum modulation method to mitigate electromagnetic interference (EMI) emission and bearing current in the context of miniaturised and lightweight synchronous machine drives is proposed. The proposed method adopts the combination of conventional pulsewidth modulation (PWM) and low common mode voltage PWM. The offline look‐up table for switching frequency is acquired by analysing the root mean square voltage values at different modulation indices and angles. By adjusting the switching frequency according to this table, the spectrum can be spread into the sidebands of the switching frequency, and the harmonic spike can be suppressed. To address the challenge of increased current ripple and harmonic distortion in high torque density motors under overload conditions, a motor model that considers the cross‐saturation and slotting effect is presented. This motor model is used to derive the switching frequency correction factors, aiming to mitigate the influence of saturation and slotting effect on harmonic amplification. The proposed method is well‐suited for controlling synchronous motors using three‐phase two‐level voltage source inverters. The simulation and experimental results validate the effectiveness of the proposed method, showcasing its advantages in terms of computational complexity reduction and significant attenuation of peak EMI currents.

Common mode far field radiation mechanisms and prediction of a buck converter with cables based on common mode voltage mutation method

AbstractIn the field of electromagnetic compatibility (EMC) research, the knowledge of the formation mechanism of the far field electromagnetic radiation and its prediction is essential for the electromagnetic noise suppression design of a switched mode power supply. This paper investigates the equivalent driving sources of the common mode (CM) current of a Buck converter with cables. Based on the concept of CM voltage mutation, this paper proposes two mechanism models of the same‐direction CM voltage driving mode and the opposite‐direction CM voltage driving mode and derives the approximate analytical formulas for the far field intensity estimation of the horizontal cables. To evaluate the predictive effectiveness of the CM far field radiation model, a 30 MHz very high frequency (VHF) Buck prototype with shielded cables is built and tested, and a shielding shell and low impedance ground conductor suppression designs are then verified. The CM electromagnetic radiation mechanisms of a non‐isolated power converter are demonstrated here. The proposed electromagnetic radiation models, approximate analytical formulas, and improvement design can help to advance the CM radiation analysis and optimization design.

Phase modulation of carriers for cascaded multilevel three-phase inverters

Cascaded multilevel three-phase inverters are commonly used in industrial applications and the quality of these inverters is highly dependent on the modulation techniques. The common mode voltage is one of the factors affecting the quality of the three-phase inverter output voltage. This paper proposes a carrier phase modulation method for cascade multilevel inverters to reduce the magnitude of common-mode voltage magnitude and harmonics. In the proposed method, the carrier phase modulator is considered as an adaptive controller and the phase of carrier is completely controlled by the magnitude of control signal. The phase modulation has a high immunity to the noises compared with the modulations of frequency and amplitude because it is difficult for noises to intrude into the phase of carrier. In addition, the algorithm of carrier phase modulation is simple and requires little memory. Moreover, the number of switching commutations of the proposed method also reduces significantly. Simulation and experiment results based on a cascaded five-level three-phase inverter system have confirmed the effectiveness of the proposed method compared with that of the popular methods using unmodulated carriers such as phase disposition (PD) and phase opposite disposition (POD).

Far field radiated emissions prediction of a flyback adapter with curved cables utilizing electromagnetic simulation method

AbstractRadiated emissions (RE) testing has long been a challenge in the development of a switched mode power supply (SMPS) with respect to electromagnetic compatibility performance. Accurate far‐field RE prediction can effectively help SMPS designers reveal and understand the mechanisms of radiation generation, and reasonably suppress it. In this paper, a model for predicting the radiation from a single excitation source and a parasitic radiator for a flyback adapter are proposed after analysing the common mode voltage and current paths. Then, novel methods are proposed to predict the far‐field RE of the flyback adapter based on measurements and electromagnetic simulations. Using these methods, the 10‐m far‐field radiation of the flyback adapter under the curved cables layout is accurately predicted and verified by experiments. Then, the characteristics and influencing factors of the radiation are analysed, including the far‐field patterns, the load volume, and the sag degree of the output cable. Finally, a suppression design of the capacitor‐inductor (CL) notch filter is designed for the frequency points that are above the standard limits, and the RE are reduced to less than 30 dBµV/m from 30 to 300 MHz. The research methods proposed in this paper have good reference significance for radiation analysis and prediction of power electronic devices.

Comparative Analysis of PWM Techniques for Interleaved Full Bridge Converter in an AC Battery Application

The AC battery utilizing second-life time batteries has gained great interest currently with the advantages of both power solutions and economic benefits. In this system, the power converters play a crucial role in the stable and effective operation of the system. This paper focused on the AC/DC stage with the chosen topology being the interleaved full bridge (IFB) converter due to its flexibility and the ability to increase the power rate of the system. For the sake of high-performance operation, various pulse width modulation (PWM) methods for this converter are analyzed. First, based on the theory of the traditional PWM methods for a full bridge inverter in combination with the interleaved technique, this paper proposed three interleaved PWM methods for the IFB converter. Secondly, the proposed methods are theoretically compared in terms of the output current, common-mode voltage, and power losses. Finally, the evaluation is carried out by both the simulation and the experimental prototype, in which the results are in good agreement with the theoretical analysis.