Conventional Space Vector Modulation Research Articles

A Rapidly Reconfigurable DC Battery for Increasing Flexibility and Efficiency of Electric Vehicle Drive Trains

Traditional electric vehicle (EV) battery drive trains comprise hard-wired batteries forming a fixed high-voltage DC link, and a main inverter. This paper proposes a novel topology to break hard-wired batteries into smaller subunits interfaced by low-voltage field effect transistors (FET). The new DC link, named <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">reconfigurable DC battery</i> , can offload a great portion of the switching duty from the main inverter. Several benefits follow: <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">1)</i> The proposed topology reduces the total loss despite the added components. The net loss is reduced because the reconfigurable DC battery can generate an optimal high-frequency voltage waveform to spare up to 2/3 of the switching actions of the main inverter—i.e., delegating the modulation duty from the main inverter to the reconfigurable DC battery. The added semiconductor loss is negligible compared to that of the main inverter, thanks to small voltage steps of multilevel conversion and the latest low-voltage transistors. <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2)</i> The main inverter’s output waveform has less distortion, e.g., down to 50% compared to conventional space-vector modulation. This distortion reduction is a consequence of large segments of the overall output voltage (particularly the apex) being entirely formed by the reconfigurable DC battery with multilevel precision. <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">3)</i> The multilevel output qualities substantially reduce the voltage transients d <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">v</i> /d <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">t</i> of the inverter output, which is known to reduce insulation and bearing stress in motors. <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">4)</i> The topology eliminates the vulnerability of large hard-wired battery packs to the weakest cells. <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">5)</i> The constant presence of the high voltage in conventional hard-wired batteries and the associated issues, e.g., during manufacturing, maintenance, and crashs are avoided because of normally-off FETs. We demonstrate the proposed motor drive on a 3-kW setup with eight battery modules.

A Novel SVM Strategy to Reduce Current Stress of High-Frequency Link Matrix Converter

High-frequency link matrix converter (HFLMC) can directly realize DC/AC conversion without intermediate energy storage components, reduce the power conversion stage, and improve efficiency and power density. With the conventional space vector modulation strategy, the secondary side voltage of the high-frequency transformer presents an asymmetric trapezoidal wave, which leads to the DC magnetic bias phenomenon and increases the current stress in secondary side switches. This paper proposes a novel SVM strategy for HFLMC. It optimizes the space vector distribution, makes secondary side voltage periodic and symmetric, and reduces the switching actions. The current stress is reduced, and the converter's efficiency is improved. Simulation and experiment results verify the advantages of the proposed modulation strategy.

Total harmonic distortion analysis of inverter fed induction motor drive using neuro fuzzy type-1 and neuro fuzzy type-2 controllers

Introduction. When the working point of the indirect vector control is constant, the conventional speed and current controllers operate effectively. The operating point, however, is always shifting. In a closed-system situation, the inverter measured reference voltages show higher harmonics. As a result, the provided pulse is uneven and contains more harmonics, which enables the inverter to create an output voltage that is higher. Aim. A space vector modulation (SVM) technique is presented in this paper for type-2 neuro fuzzy systems. The inverter’s performance is compared to that of a neuro fuzzy type-1 system, a neuro fuzzy type-2 system, and classical SVM using MATLAB simulation and experimental validation. Methodology. It trains the input-output data pattern using a hybrid-learning algorithm that combines back-propagation and least squares techniques. Input and output data for the proposed technique include information on the rotation angle and change of rotation angle as input and output of produced duty ratios. A neuro fuzzy-controlled induction motor drive’s dynamic and steady-state performance is compared to that of the conventional SVM when using neuro fuzzy type-2 SVM the induction motor, performance metrics for current, torque, and speed are compared to those of neuro fuzzy type-1 and conventional SVM. Practical value. The performance of an induction motor created by simulation results are examined using the experimental validation of a dSPACE DS-1104. For various switching frequencies, the total harmonic distortion of line-line voltage using neuro fuzzy type-2, neuro fuzzy type-1, and conventional based SVMs are provided. The 3 hp induction motor in the lab is taken into consideration in the experimental validations.

Modified SVPWM technique for CMV reduction in asymmetrical dual three phase induction machine drive

Due to its advantages, the asymmetrical dual three-phase induction motor drive is a strong choice in high-power applications. However, the common-mode voltage produced by the voltage source inverters affects the winding insulation and damages the bearings. Common-mode voltage is also responsible for electromagnetic interference and leakage currents. This paper, therefore, analyses the common-mode voltage produced by the inverter supplying a dual three-phase induction motor drive and proposes a novel modified space vector decomposition-based Space Vector Pulse Width Modulation (SVPWM) technique for common mode reduction. The vector space decomposition-based space vector modulation technique offers excellent flexibility as it reduces the common-mode voltage (CMV) by exploiting the additional degree of freedom in a dual three-phase system. The common-mode voltage (CMV) can be reduced to one-sixth of the DC link voltage compared to the highest CMV, i.e. half of the DC-link voltage produced in conventional space vector modulation. The proposed method is also validated experimentally to demonstrate the effectiveness of the proposed scheme in terms of the amplitude of CMV, pulsations, and total harmonic distortion(THD) in current.

A Space Vector Modulation Strategy for PMSMs Operating at Low Switching-to-Fundamental Frequency Ratio

A novel space vector modulation (SVM) strategy for a permanent magnet synchronous machine drive, operating at low switching-to-fundamental frequency ratio, is presented in this paper. The proposed strategy is based on applying more than two active vectors in a switching period, aiming to consider the expected rotation and possible movement from one sector to another of the voltage reference vector within that period. The method is simple as the calculation of the duty cycles is still based on the expressions for a conventional SVM. Current distortion and efficiency calculations are also provided, comparing the proposed SVM with conventional SVM and six-step modulation. The results show that the proposed method generates a current distortion similar to the conventional SVM at high frequency ratios but much lower at low frequency ratios. Moreover, comparing with six-step modulation, the current distortion generated by the proposed SVM is always lower, independent of the frequency ratio. On the other hand, the efficiency of the inverter obtained with the proposed SVM is higher than the one obtained with conventional SVM. The effectiveness of the proposed strategy is validated via simulations and experiments.

DC-Side Soft-Switching Inverter With Modified Space-Vector Modulation Scheme

Three-phase soft-switching inverters are promising in order to reduce the losses in the switching devices and to reduce the electromagnetic interference produced by severe di/dt and dv/dt, which enables the operation of the inverter at higher switching frequency. This work proposes a DC-side three-phase zero-voltage soft-switching inverter topology that can be sub-categorized under actively clamped resonant dc-link topologies. Moreover, a modified space-vector modulation scheme is proposed, such that all the devices operate under zero-voltage switching condition. Compared to other similar dc-link soft-switching topologies, the proposed topology does not require feedback from the inverter output currents to achieve soft-switching operation. Unlike conventional space-vector modulation techniques, the proposed modified space-vector modulation does not require to turn-on the top and/or the bottom three switches of the two-level inverter at the same time to implement the zero vectors, which allows a reduction of the effective commutating time of the two-level inverter switches by one-third, during a grid voltage cycle. The auxiliary capacitor is only charged to a fraction of the dc bus voltage. Simulation and experimental results on a 10-kW and 100-kHz switching frequency lab-scale prototype are presented to demonstrate the validity and effectiveness of the proposed zero-voltage switching topology and modulation scheme on reducing the switching losses and electromagnetic interference.

Improved space vector modulation algorithm of 5-level three-phase z-source based cascaded inverter

The integration of a Z-source network with a 5-Level three-phase inverter based cascaded to provide voltage step-up function is proposed in this paper. The system is controlling by an improved space vector modulation (SVM) the implantation of algorithm and innovative virtual automated solutions can be considered, very fast and very simple. The main objective of the proposed system is to achieve an output voltage twice the applied input voltage, and to eliminate the largest amount of excess harmonic. This proposed model is characterized by the ease of boosting the output voltage twice the input voltage, depending on the characteristics of the Z-source network without the need for a DC-DC rectifier. Furthermore, the proposed algorithm for this system is characterized by improving the output voltage and eliminating a large number of harmonics while greatly simplifying the calculations compared to its conventional SVM. This makes the proposed system and its algorithm an interesting alternative to classical systems and algorithms. The simulation was processed using MATLAB/Simulink. The results obtained prove and verify the effectiveness of the proposed system. From the results, of the output current total harmonic distortion (THD), it was reduced to 1.05% which is very low compared to the other algorithms in the literature.

High‐frequency common‐mode voltage mitigation for current‐source inverter in transformerless photovoltaic system using active zero‐state space vector modulation

Space vector modulation (SVM) schemes with leakage current mitigation capability for current-source inverters (CSIs) in transformerless photovoltaic (PV) systems have not been well explored yet. In this study, the advantage of a special SVM scheme, called active zero-state SVM (AZS-SVM), on suppressing high-order harmonics in the common-mode voltage (CMV) is revealed and theoretically analysed, since the high-frequency components in the CMV have decisive impacts on the generated leakage current. A five-segment sequence is proposed for AZS-SVM applied for CSIs. Both simulation and experiments are conducted on a (2.5 kW/208 V/6.94 A) grid-connected three-phase CSI, which validates the effectiveness of the designed AZS-SVM to mitigate the CMV high-order harmonics when compared to that by conventional SVM under different operating conditions.

Optimal Current Ripple PWM for Three-Level Inverter With Common Mode Voltage Reduction

Three-level inverter has been widely used in electric drives and renewable power generation system. However, the common mode voltage (CMV) and output current ripple reduction of three-level inverter should be carefully regulated for the appropriate operation. As these two targets are mutually interrelated, the conventional space vector modulation (SVM) scheme cannot cope with them decently. To overcome this drawback, this paper proposes a novel modified SVM scheme to realize CMV and current ripple reduction simultaneously. The generating mechanism of output current ripple is analyzed, and the relationship between current ripple and utilized vectors is quantitatively described. Based on the analyses, the proposed optimal current ripple and CMV reduction pulse width modulation (OCR-CMVRPWM) method adopts four voltage vectors (large, medium, small and zero vectors) to reduce root mean square (RMS) value of current ripple by allocating the sequence and dwell times of utilized vectors. Compared to the existing PWM methods, the proposed OCR-CMVRPWM scheme can reduce the peak of CMV to half of value using the conventional SVM, and obtain a significant reduction of output current total harmonic distortion (THD). The effectiveness of the proposed method is validated by both simulation and experimental results.

A novel multiport converter switching scheme to integrate multiple renewable energy sources

SummaryIn this paper, an innovative switching scheme named simultaneous space vector modulation (SSVM) is proposed for integrating various AC sources in the energy industry using a unified multiport converter. The proposed SSVM technique is applied to the multileg topology of a multiport converter, which is an encouraging option for the grid integration of renewable energy sources and multimachine drives. Considering the shared leg in the multileg converter, the proposed SSVM can utilize the utmost simultaneous switching states between different ports, resulting in lower switching loss and better DC‐link voltage utilization compared with the conventional sequential space vector modulation approach. A novel decision matrix concept is introduced to identify the simultaneous switching states. For this aim, according to the number of ports of the multileg converter, decision matrices containing valid simultaneous switching states are first calculated. Then, they are defined as look‐up tables in the proposed SSVM to be retrieved and exploited in every sampling period. The effectiveness of the proposed SSVM for a seven‐leg version of the multileg converter is assessed using the simulation analysis and real‐time validation. The capability of the proposed SSVM‐based multiport converter in grid integration of AC renewable energy sources is also verified considering two permanent magnet synchronous generator (PMSG)‐based wind turbines with real wind speed patterns. The simulation results confirm that the proposed SSVM is properly able to manage the power flow between different ports and improve the DC voltage utilization and switching loss compared with the sequential SVM.

A modified type-2 neuro-fuzzy SVM-based inverter fed IM drive

In indirect vector control, the conventional speed and current controllers operate satisfactorily when the operating point is constant. But the operating point is always dynamic; the reference voltages obtained in a closed-loop system feeding to the inverter contains more harmonics. Due to this, the pulses which are going to produce are uneven and in turn, understudy creates the inverter output voltages produced with more harmonics. In order to produce a better output voltage from the inverter, this paper presents the neuro-fuzzy type-2 (NFT2) space vector modulation technique. Performance comparison of the inverter is done with conventional space vector modulation (SVM) and neuro-fuzzy type-1 (NFT1) system using MATLAB simulation and experimental validation. The performance parameters of the induction motor based on current, torque, and speed with neuro-fuzzy type-2 space vector modulation is compared with conventional and type-1 neuro-fuzzy SVM. The % THD of inverter output voltages are also compared. The experimental validation of a DSpace-1104 is used to analyse the performance of the induction motor which is obtained by the simulation. The experimental validations are carried out considering 2HP induction motor in the lab.

A Modified Type-2 Neuro-fuzzy SVM based inverter fed IM drive

In indirect vector control, the conventional speed and current controllers operate satisfactorily when the operating point is constant. But the operating point is always dynamic; the reference voltages obtained in a closed-loop system feeding to the inverter contains more harmonics. Due to this, the pulses which are going to produce are uneven and in turn, understudy creates the inverter output voltages produced with more harmonics. In order to produce a better output voltage from the inverter, this paper presents the neuro-fuzzy type-2 (NFT2) space vector modulation technique. Performance comparison of the inverter is done with conventional space vector modulation (SVM) and neuro-fuzzy type-1 (NFT1) system using MATLAB simulation and experimental validation. The performance parameters of the induction motor based on current, torque, and speed with neuro-fuzzy type-2 space vector modulation is compared with conventional and type-1 neuro-fuzzy SVM. The % THD of inverter output voltages are also compared. The experimental validation of a DSpace-1104 is used to analyse the performance of the induction motor which is obtained by the simulation. The experimental validations are carried out considering 2HP induction motor in the lab.

Grid integration of multiple wind turbines using a multi-port converter—A novel simultaneous space vector modulation

In this paper, an innovative approach of integrating multiple doubly-fed induction generator (DFIG)-based wind turbines using a single multi-port converter unit, named as a unified expandable power converter (UEPC) is presented. A novel partial simultaneous space vector modulation (PSSVM) scheme, adopted to the unified structure, is proposed to enhance the operational efficiency and DC-link utilization. The unified configuration can integrate two or more DFIGs through a multi-port converter in a cost-effective and efficient way. The unified structure enjoys compactness, plug & play capability, fewer switches, and a lower installation cost. Comparing with the conventional sequential space vector modulation (SSVM), which only uses the individual active vectors, the proposed PSSVM can utilize common active vectors between different ports, which is the main salient feature of this method. The performance of PSSVM is also validated via an OPAL-RT real-time simulator. The real-time outcomes prove that the proposed PSSVM can improve the DC-link voltage utilization and switching loss compared with the SSVM. The effectiveness of the proposed PSSVM based unified configuration in both normal and faulty conditions are evaluated and compared with the conventional structure using MATLAB/Simulink. The simulation results endorse the finding that regardless of the shared switches in the unified expandable power converter, the independent control and maximum power extraction from the wind are guaranteed using the proposed PSSVM.

Multi Open-/Short-Circuit Fault-Tolerance Using Modified SVM Technique for Three-Level HANPC Converters

Open- and short-circuit faults are the most severe issues that affect the stability and reliability of power conversion systems. The space vector modulation (SVM) technique is widely used to control power converters. However, conventional SVM is incapable of controlling the system effectively when such faults occur. Considering these, this article proposes a modified SVM that is capable of tolerating the extreme cases of faults (including multi open-/short-circuit faults) simultaneously. An innovative fault tolerance method is proposed to tolerate multifaults in hybrid active neutral point converters (HANPCs). Furthermore, new voltage reference signals are created in addition to calculating voltage offset and inserting modified switching sequences. A descriptive performance analysis of the modified SVM technique is applied under healthy and faulty conditions. Correspondingly, the effects of the total harmonic distortion of the system performance are also highlighted and explained. The results reveal that the proposed control strategy can effectively maintain healthy and safe operation under faulty conditions without the need for additional parts or alteration of the topology configuration. In addition, the proposed method can be applied to HANPCs without special requirements to withstand high voltage levels. The effectiveness of the proposed method is verified by simulation and experimental results.

Endüstriyel Amaçlı Yarım H-Köprü Modüllü Üç Fazlı Çok Seviyeli Evirici Yapısı

In this paper, a new three phase multi-level inverter topology has been developed for industrial purposes. Half H-bridge level modules exist in the inverter structure. In order to change the number of levels in the output voltage, the number of level modules is changed. With the increase in the number of levels, the output voltage approaches the sinusoidal form and the total harmonic distortion (THD) values in the voltage and current decrease. The proposed inverter structure is very flexible and switching signals can be found by the generated equations. The switching strategy is not complicated. Proposed inverter was simulated for different levels and voltage and current waveforms were obtained. THD values of these waveforms were calculated. Compared with the classical Space Vector Modulation (SVM) and Pulse Width Modulation (PWM) inverters, it is seen that both current and voltage harmonics are low together. However, current harmonics are low in conventional SVM and PWM inverters, but voltage harmonics are high. The improved inverter also closes this gap by reducing the voltage harmonics. In addition, another disadvantage of conventional SVM and PWM inverters is the high voltage stresses (dv/dt) on the switching elements. Since the proposed inverter has levels on the output voltage, the dv/dt stresses on the switches are also low. Additionally, the developed inverter structure has the switch number advantage compared to its counterparts.

Advanced Switching Sequences Based Model-Predictive Control for Single-Phase NPC Converters

This article presents a continuous control set model-predictive control (MPC) technique based on advanced switching sequences (SSs) for a grid-connected single-phase three-level neutral-point-clamped converter. The SSs are developed considering the tracking performance of the current feed to the utility grid, the dc-bus capacitor voltage balancing, and the switching loss of the semiconductor devices. In the proposed strategy, with the same sampling frequency, the number of pole state changes (SCs) per control cycle is only two, while in the optimal SS and the modulated MPC (pulse pattern similar to the conventional space vector modulation technique) schemes, the number of pole SCs is four. The reduction in the number switching SCs per control cycle considerably reduces the switching loss of semiconductor devices. Moreover, to avoid the challenges of utilizing the weighting factor, a single-objective cost function is adopted to track the reference current, and the dc-bus capacitor voltages are balanced using the redundancy nature of the voltage vectors. Furthermore, the proposed scheme can ensure a fixed-switching-frequency operation, which is advantageous for selecting filter parameters during real-life implementation. The effectiveness of the proposed strategy is validated by the results obtained from both the simulation in MATLAB/Simulink and the experiment carried out using a downscaled laboratory test rig.

Improved Harmonic Profile for High-Power PWM Current-Source Converters With Modified Space-Vector Modulation Schemes

Pulsewidth-modulated (PWM) current-source converters (CSCs) have the features of simple configuration, reliable short-circuit protection, and sinusoidal ac output voltages. The conventional space-vector modulation (SVM) scheme usually generates high-magnitude low-order harmonics in CSCs with low switching frequency. In this article, two modified SVM schemes, namely MSVM1 and MSVM2, are proposed to improve the harmonic performance for PWM CSCs in the high-power applications with low switching frequencies. The MSVM1 scheme focuses on eliminating the average dwell-time error of current vectors within each sampling period, while the MSVM2 scheme is targeted to achieve the accurate dwell time of current vectors as that of the natural sampling-based SVM scheme. The theoretical analysis and the calculation equations of dwell time are derived for both MSVM1 and MSVM2. The experiments are given to verify the effectiveness of the two modified SVM schemes in improving the harmonic performance of high-power CSCs with low switching frequencies.

Switch Fault Tolerant Model-Based Predictive Control of a VSC Connected to the Grid

During IGBT breakdowns, the grid side converter (GSC) of a renewable power plant must be disconnected from the grid. In the recent past, topological modifications propose the faulty phase to be connected to the midpoint of the dc bus as a solution. In this configuration, the converter can generate only four vectors. Moreover, since the capacitor voltages carry a voltage ripple at the grid frequency, the magnitude and angle of the vectors become variable during post-fault scenarios. The recent model predictive control (MPC) approaches select the vectors to be used in the cost function based on the location of the reference vector in a post-fault unsymmetrical vector diagram or by checking the effect of all of them, which is time consuming. This article proposes a simplified approach, which reduces the computing time by avoiding successive iterations to obtain the correct vector pairs. Furthermore, an approach to rebuild a regular hexagon from the four post-fault vectors is proposed. Hence, the proposed controller retains the advantages of the conventional space vector modulation (SVM) approach with minimal additions to handle post-fault scenarios. Finally, this article studies the limitations in the VSC output voltage and power magnitudes during post-fault scenarios. The approaches presented in this article have been verified using simulation and experimental results.

Common-Mode Voltage Reduction Method for Three-Level Inverter With Unbalanced Neutral-Point Voltage Conditions

The three-level inverter has been widely researched and adopted in industry. This article further proposes a carrier-based modulation method to reduce the common-mode voltage (CMV) and obtain high-quality output currents for three-level inverter with unbalanced neutral-point voltage conditions. In this method, the zero-sequence voltage is calculated by three-phase modulation waves, three-phase output currents, and voltages across the dc-link capacitors. The limitations of the zero-sequence component are carefully considered in order not to generate the basic voltage vector with high CMV magnitudes. In addition, a deadbeat control scheme for controlling the dc-link voltages asymmetrically with the proposed pulsewidth modulation method is presented, and asymmetrical control of dc-link voltages can be realized with fast response. Compared with the conventional space vector modulation (SVM) and the virtual SVM methods, the proposed scheme can reduce the CMV by half. Simulated and experimental results validate the effectiveness of the proposed method.

Inductor Current Ripple Analysis and Reduction for Quasi-Z-Source Inverters With an Improved ZSVM6 Strategy

The quasi-Z-source inverter (qZSI) has been widely explored for renewable energy applications due to its superiority, e.g., higher boosting ratio and operational reliability, which is attained by inserting shoot-through (ST) states. As a conventional space vector modulation (SVM) method for the three-phase qZSI, the ZSVM6 method is easy to implement by dividing the ST time into six identical intervals. However, the instantaneous inductor current ripples of the qZSI with the ZSVM6 strategy are affected by the operating conditions, e.g., modulation index m and ST duty ratio dsh. In this article, the instantaneous inductor current ripples and the maximum current ripple in the qZSI with the ZSVM6 strategy under all operational conditions are explored in detail. The operational conditions are categorized into several cases according to the relationship among the duty ratios of the active states, null states, and ST states. More importantly, an improved ZSVM6 strategy is proposed to reduce the inductor current ripple for the qZSI, in which the maximum inductor current ripple is limited by making full use of the operational states. The proposed ZSVM6 strategy keeps the total ST time in a switching cycle while maintaining the axis-symmetry feature of the inductor current, but reduces the current ripple. Simulations and experimental results confirm effectiveness of the proposal when compared with the conventional ZSVM6 strategy for ripple current reduction.