Double Fourier Integral Analysis Research Articles

An Improved Phase-Disposition Pulse Width Modulation Method for Hybrid Modular Multilevel Converter

The hybrid modular multilevel converter (MMC) consisting of half-bridge submodules (HBSMs) and full-bridge submodules (FBSMs) is a promising solution for overhead lines high-voltage direct current systems (HVDC) due to the advantages of direct current short circuit fault ride-through (DC-FRT) capability. This paper proposes an improved phase-disposition pulse width modulation (PDPWM) method for the hybrid modular multilevel converter. The number of carriers can be reduced from 3N (N is the number of submodules in each arm) to 6. The theoretical harmonic analysis of the improved PDPWM method for hybrid MMC is performed by using double Fourier integral analysis. The influence of three carrier displacement angles between HBSMs and FBSMs in the upper and lower arms on harmonic characteristics is investigated. The output voltage harmonics minimization PDPWM scheme and circulating current harmonics cancellation PDPWM scheme can be achieved by selecting the optimum carrier displacement angles, respectively. The proposed method for hybrid MMC is verified by the simulation and experimental results.

Double Fourier Integral Analysis Based Convolutional Neural Network Regression for High-Frequency Energy Disaggregation

Non-Intrusive Load Monitoring aims to extract the energy consumption of individual electrical appliances through disaggregation of the total power load measured by a single smart-meter. In this article we introduce Double Fourier Integral Analysis in the Non-Intrusive Load Monitoring task in order to provide more distinct feature descriptions compared to current or voltage spectrograms. Specifically, the high-frequency aggregated current and voltage signals are transformed into two-dimensional unit cells as calculated by Double Fourier Integral Analysis and used as input to a Convolutional Neural Network for regression. The performance of the proposed methodology was evaluated in the publicly available U.K.-DALE dataset. The proposed approach improves the estimation accuracy by 7.2% when compared to the baseline energy disaggregation setup using current and voltage spectrograms.

Modular Multilevel Converter Switching Frequency Harmonics Analysis and Suppression Through Cell Voltage Control

This paper investigates the impact of reference's bias on the high frequency voltage spectrum for the modular multilevel converters (MMC). Analytical solution of the voltage spectrum under carrier Phase Shifted Pulse Width Modulation (PSPWM) is derived using double Fourier integral analysis. The distribution of the switching frequency voltage harmonics is found to be directly related to the ratio between the dc-link voltage and the cell voltage. A control method utilizing this phenomenon is thereby proposed to suppress switching frequency harmonics in the Differential Mode Voltage (DMV) and Common Mode Voltage (CMV). Cell voltage control trade-offs considering different cell numbers, different ac voltages, 3rd harmonics injection, and cell voltage stress are also investigated. The analysis and control method are validated through experiments on a 1.25 megawatt MMC testbed.

Analysis and Reduction of Stator Copper Losses in Three-phase Four-switching Inverter-fed SPMSM Drives Using Space Vector Pulse-width Modulation

In consideration of cost reduction, three-phase four-switch (TPFS) converters are applied in permanent magnet synchronous motor/generator (PMSM/G) drive application. However, the reduced number of active vectors has a negative influence on the signal waveform and the stator copper losses. With respect to the stator copper loss reduction, the root-mean-square (RMS) value of the stator copper loss ripple is chosen as a performance criterion in this paper. It is proved in this paper that the stator current ripple plays a more important role than the equivalent resistance in the copper loss ripples by double Fourier integral analysis. Thus, the RMS value of the stator current ripple can be applied as an analytical approach to evaluate the stator harmonic copper losses of the two proposed space vector modulation (SVM). Consequently, the proposed SVM strategy realizes the high-frequency stator copper loss ripple reduction. The experimental results demonstrate the validation of the proposed analysis.

Analytical Voltage-Source Inverter Current and Conduction Loss Models for EV Power Train Simulations

This study introduces a novel approach to derive analytical expressions of modulated semi-conductor current waveforms, which are used to develop accurate and numerically efficient average value models of the transistor current, diode current and conduction loss in VSI-drives. The approach is based on a double Fourier integral analysis of semi-conductor switching signals. Compared to previous studies, the proposed models show improved accuracy. Furthermore, the presented framework is readily generalized to evaluate the performance of practical, carrier-based PWM strategies within detailed EV power train simulations.

System Efficiency Improvement for Electric Vehicles Adopting a Permanent Magnet Synchronous Motor Direct Drive System

To improve the endurance mileage of electric vehicles (EVs), it is important to decrease the energy consumption of the Permanent Magnet Synchronous Motor (PMSM) drive system. This paper proposes a novel loss optimization control strategy named system efficiency improvement control which can optimize both inverter and motor losses. A nonlinear power converter loss model is built to fit the nonlinear characteristics of power devices. This paper uses double Fourier integral analysis to analytically calculate the fundamental and harmonic components of motor current by which the fundamental motor loss and harmonic motor loss can be accurately analyzed. From these loss models, a whole-frequency-domain system loss model is derived and presented. Based on the system loss model, the system efficiency improvement control method applies the genetic algorithm to adjust the motor current and PWM frequency together to optimize the inverter and motor losses by which the system efficiency can be significantly improved without seriously influence on the system stability over the whole operation range of EVs. The optimal effects of system efficiency is verified by the experimental results in both Si-IGBT-based PMSM system and SiC-MOSFET-based system.

Design and implementation of a loss optimization control for electric vehicle in-wheel permanent-magnet synchronous motor direct drive system

As a main driving force of electric vehicles (EVs), the losses of in-wheel permanent-magnet synchronous motor (PMSM) direct drive system can seriously affect the energy consumption of EVs. This paper proposes a loss optimization control strategy for in-wheel PMSM direct drive system of EVs which optimizes the losses of both the PMSM and the inverter. The proposed method adjusts the copper losses and iron losses by identifying the optimal flux-weakening current, which results in the PMSM achieving the lower losses in the whole operational range. Moreover there are strongly nonlinear characteristics for the power devices, this paper creates a nonlinear loss model for three-phase half-bridge inverters to obtain accurate inverter losses under space vector pulse width modulation (SVPWM). Based on the inverter loss model and double Fourier integral analysis theory, the PWM frequency is optimized by the control strategy in order to maximize the inverter efficiency without affecting the operational stability of the drive. The proposed loss optimization control strategy can quickly find the optimum flux-weakening current and PWM frequency, and as a result, significantly broaden the high efficiency area of the PMSM direct drive system. The effects of the aforementioned strategy are verified by both theoretical analysis and experimental results.

Maximum Efficiency Control of Permanent-Magnet Synchronous Machines for Electric Vehicles

Abstract Electric vehicles (EVs) are considered as a new generation of transport to solve the energy crisis. The efficiency of permanent-magnet synchronous machine (PMSM) is an important performance for the energy loss of EVs. Considering the harmonic current caused by the PWM output voltage of inverter, this paper proposes a novel global loss model of PMSM, which can calculate both fundamental loss and harmonic loss. This model precisely estimates the harmonic loss of PMSM by double Fourier integral analysis. Based on the proposed loss model, a maximum efficiency control strategy is presented which can achieve the minimum energy loss in the whole operation range of EVs. The optimum flux-weakening current can be quickly found by the maximum efficiency control, and optimization of energy loss in PMSM direct drive system is verified by theoretical analysis and experimental results.

Double-Carrier Phase-Disposition Pulse Width Modulation Method for Modular Multilevel Converters

Modular multilevel converters (MMCs) have become one of the most attractive topologies for high-voltage and high-power applications. A double-carrier phase disposition pulse width modulation (DCPDPWM) method for MMCs is proposed in this paper. Only double triangular carriers with displacement angle are needed for DCPDPWM, one carrier for the upper arm and the other for the lower arm. Then, the theoretical analysis of DCPDPWM for MMCs is presented by using a double Fourier integral analysis method, and the Fourier series expression of phase voltage, line-to-line voltage and circulating current are deduced. Moreover, the impact of carrier displacement angle between the upper and lower arm on harmonic characteristics is revealed, and further the optimum displacement angles are specified for the circulating current harmonics cancellation scheme and output voltage harmonics minimization scheme. Finally, the proposed method and theoretical analysis are verified by simulation and experimental results.

Maximum Efficiency per Torque Control of Permanent-Magnet Synchronous Machines

High-efficiency permanent-magnet synchronous machine (PMSM) drive systems need not only optimally designed motors but also efficiency-oriented control strategies. However, the existing control strategies only focus on partial loss optimization. This paper proposes a novel analytic loss model of PMSM in either sine-wave pulse-width modulation (SPWM) or space vector pulse width modulation (SVPWM) which can take into account both the fundamental loss and harmonic loss. The fundamental loss is divided into fundamental copper loss and fundamental iron loss which is estimated by the average flux density in the stator tooth and yoke. In addition, the harmonic loss is obtained from the Bertotti iron loss formula by the harmonic voltages of the three-phase inverter in either SPWM or SVPWM which are calculated by double Fourier integral analysis. Based on the analytic loss model, this paper proposes a maximum efficiency per torque (MEPT) control strategy which can minimize the electromagnetic loss of PMSM in the whole operation range. As the loss model of PMSM is too complicated to obtain the analytical solution of optimal loss, a golden section method is applied to achieve the optimal operation point accurately, which can make PMSM work at maximum efficiency. The optimized results between SPWM and SVPWM show that the MEPT in SVPWM has a better effect on the optimization performance. Both the theory analysis and experiment results show that the MEPT control can significantly improve the efficiency performance of the PMSM in each operation condition with a satisfied dynamic performance.

A Comprehensive Investigation of Four-Switch Three-Phase Voltage Source Inverter Based on Double Fourier Integral Analysis

This paper presents a comprehensive analytical investigation of the four-switch three-phase (B4) voltage source inverter. The double Fourier integral analysis is used as an analytical approach to determine the phase-leg switched voltage spectrum under condition of natural sampling. The performance of two proposed switching sequences are subsequently evaluated when the harmonic copper losses are chosen as performance criterion. For a clear identification of dc-link voltage, the spectrum of dc-link current is characterized by convolution of switching function spectrum and corresponding phase current spectrum, in which fundamental component appears causing offset and fluctuation in dc-link two-capacitor voltages. The offset can be suppressed by certain switching states, whereas the effect of fluctuation must be neutralized through analytical compensation for modulating waveforms. Otherwise, symmetry of three-phase output currents and reliable operation of the system will not be retained. Finally, the analytically calculated spectrum of output voltage and dc-link current are demonstrated by comparing with those obtained by fast Fourier transform (FFT) analysis of simulated waveforms in MATLAB/SIMULINK. The capacitor voltage offset suppression and fluctuation effect neutralization are carried out by simulations and experiments, in which the results confirm the validity of the analytical investigation.