Voltage Space Vector Research Articles

Deadbeat two-vector model predictive current control for open-winding primary permanent-magnet linear motor

The structure of open-winding motor fed by the dual-inverter can increase the winding terminal voltage of the primary permanent-magnet linear motor (PPMLM). So, it is an effective method to improve the thrust performance of the PPMLM. Based on the detailed derivation of the mathematical model of the open-winding PPMLM and the in-depth analysis of the space voltage vector distribution characteristics of the dual-inverter, a deadbeat two-vector model predictive current control (MPCC) model is proposed in this paper. First, the optimal vector of the inverter 1 is determined by judging the position of the large sector. Second, two optimal vectors of the inverter 2 is determined by judging the position of the small sector. Finally, the duty cycle of the two optimal vectors of the inverter 2 is calculated to realize the proposed deadbeat two-vector MPCC algorithm. Compared with the traditional model predictive torque control (MPTC) and MPCC strategies, the proposed algorithm has the advantages of lower current harmonics (lower 34 % and 44 % under rated conditions, respectively) and better thrust performance (higher 77 % and 61 % under rated conditions, respectively) as well as lower computational complexity. Simulation and experimental results show that the proposed two-vector MPCC has good steady-state and dynamic performances, which can reduce the current harmonics and thrust ripple, and thus improve the motor drive performance compared with the traditional method.

Fault tolerance for PWM rectifiers based on basic voltage space vector model

Fault tolerance for PWM rectifiers based on basic voltage space vector model

Polar Voltage Space Vectors of the Six-Phase Two-Level VSI

The paper recommends polar voltage space vectors of the six-phase and two-level inverter as a useful mathematical tool for vector control of the inverter. The inverter model is described using three mathematical tools: analytic expressions, voltage state, and space vectors. The analytic formulas allow for the determination of elementary physical inverter quantities: current and voltage. The state voltage vectors make it easy to define phase voltage distribution in every possible state of the inverter and voltage space vectors are the most important tool used for inverters’ control. The space vectors are defined using the standard voltage space vector transformation, while the state vectors are denoted by binary numbers and determine all voltage states of the inverter. The proposed notation system and vectors’ marking seem to be extremely useful in specifying the inverter states. This system certifies a deep correlation between the space and state vectors as they are described using the same digits. The properties of the system were confirmed during the simulation tests. Some examples of the inverter vector control based on polar voltage space vectors prove that the proposed solution is a useful mathematical tool and may be in fact suitable in designing inverter control algorithms. The simulation experiment described in this paper shows that the assumed control strategy allows for a significant reduction in the amount of switching compared to PWM. At the same time, the adopted vector strategy allows for the obtaining of a very favorable value of the current THD coefficient while maintaining the RMS values of the currents.

A Novel Zero-Sequence-Voltage-Balanced SVPWM With the Analyses of Common-Mode Voltage and Differential-Mode Current

In three-phase voltage source converters (VSCs), the high-frequency leakage current can be easily suppressed by the common-mode choke, while low-frequency component would be an unfavorable factor to the inductor design. Thus, as the excitation source, the low-frequency common-mode voltage (CMV) should be properly managed. This article analyzes the low-frequency CMV impulse by constructing a 3-D voltage vector space, and a novel modulation method is proposed to eliminate the low-frequency CMV. Meanwhile, a comparative study is conducted between the proposed method and the other four typical space vector pulsewidth modulation (PWM) (SVPWM) method from the view of CMV and differential-mode current (DMC). In the analysis, a double-current-ripple-envelopes method is proposed to describe the current ripples. Besides, the influence of modulation indexes and power factors on DMC are considered and evaluated. And a guiding rule for choosing the appropriate modulation method for three-phase VSCs is provided. Finally, the theoretical analysis and proposed method are experimentally validated under a 5-kW three-phase PWM converter.

Software in-the-Loop Simulation of an Advanced SVM Technique for 2ϕ-Inverter Control Fed a TPIM as Wind Turbine Emulator

An appropriate modulation scheme selection ensures inverter performance. Thus, space vector modulation (SVM) is more efficient and has its own distinct advantages compared to other pulse width modulation (PWM) techniques. This work deals with the development of an advanced space vector pulse width modulation (SVM) technique for two-phase inverter control using an XSG library to ensure rapid prototyping of the controller FPGA implementation. The proposed architecture is applied digitally and in real time to drive a two-phase induction motor (TPIM) for small-scale wind turbine emulation (WTE) profiles in laboratories with minimum current ripple and torque oscillation. Four space voltage vectors generated for the used SVM technique do not contain a zero vector. Hence, for an adequate adjustment of these four vectors, a reference voltage vector located in the square locus is determined. Considering the asymmetry between the main and auxiliary windings, the TPIM behavior, which is fed through the advanced SVM controlled-two-phase inverter (2ϕ-inverter), is studied, allowing us to control the speed and the torque under different conditions for wind turbine emulation. Several quantities, such as electromagnetic torque, rotor fluxes, stator currents and speed, are analyzed. To validate the obtained results using both Simulink and XSG interfaces, the static and dynamic characteristics of the WTE are satisfactorily reproduced. The collected speed and torque errors between the reference and actual waveforms show low rates, proving emulator controller effectiveness.

One Novel Soft-Starting Control Strategy for Induction Motor Based on Space Voltage Vectors

Abstract This study presents a novel control strategy of discrete variable frequency (DVF) based on space voltage vectors for a three-phase induction motor (IM) soft-starting. The proposed strategy is developed in four steps. First, conducting states of the three-phase thyristor circuits are analysed, and the formation mechanism of space voltage vectors is also demonstrated. Then, DVF control strategy of IM based on hexagon flux linkage loci is expounded categorically, which contains frequency f/7 control, frequency f/4 control, frequency f/3 control and ramp voltage control. Next, under two-phase stationary coordinate system, stator flux equation of IM is derived, and the decrease in stator flux when zero-vector voltage working is calculated accurately. In the end, an experimental system of IM based on three-phase thyristor circuits is constructed, and the experimental results are dealt with and compared with the usual ramp voltage technique. The study results show that IM driven by the proposed strategy can steadily operate at the preset discrete frequency, and the effective value of starting current of IM can be decreased by nineteen percent. The experimental results verify the conclusions.

Control Strategy of Three-Level NPC Inverter Based on Variable Coefficient Virtual Vector Model Predictive Control

The Conventional model predictive control (C-MPC) uses only a single voltage vector in each control period, resulting in poor control performance. In addition, the computational burden in discrete space state generated by three-level inverter cannot be ignored. To improve the control performance, this paper proposes a variable coefficient virtual vector MPC (VC-VV-MPC) method, a five-level virtual space voltage vector is constructed to improve the control performance, and a scaling coefficient is used to further improve the control performance. In addition, a voltage vector pre-selection method is used to reduce the computational burden. The simulation and experiment results shown that, compare with C-MPC and adjacent vector MPC (AV-MPC), the proposed VC-VV-MPC can achieve the improvement of control performance under lower computational burden.

Обзор и классификация пространственно-временных векторов дискретных состояний семифазного преобразователя

The subject of the research is the control algorithms for a seven-phase converter that implement space-vector voltage modulation of a seven-phase motor as an alternative to a three-phase engine in modern electric traction. The study used elements of set theory, combinatorics, Fourier series expansion and vector analysis. Checking research results was implemented on a special stand for experimental studies of spatial vector voltage modulation of a seven-phase motor.

Review and classification of space-time vectors of discrete states ofa seven-phase converter

The subject of the research is the control algorithms for aseven-phase converter that implement space-vector voltage modulation of aseven-phase motor as an alternative to a three-phase engine in modernelectric traction. The study used elements of set theory, combinatorics,Fourier series expansion and vector analysis. Checking research results wasimplemented on a special stand for experimental studies of spatial vectorvoltage modulation of a seven-phase motor. Keywords: Power of the mathematical set of logical states of aseven-phase converter, vector space of generalized vectors of discretestate, combinations of generalized vectors of discrete voltage states of aseven-phase motor\

Common-Mode Voltage Reduction Algorithm for Photovoltaic Grid-Connected Inverters with Virtual-Vector Model Predictive Control

Model predictive control (MPC) has been proven to offer excellent model-based, highly dynamic control performance in grid converters. The increasingly higher power capacity of a PV inverter has led to the industrial preference of adopting higher DC voltage design at the PV array (e.g., 750–1500 V). With high array voltage, a single stage inverter offers advantages of low component count, simpler topology, and requiring less control tuning effort. However, it is typically entailed with the issue of high common-mode voltage (CMV). This work proposes a virtual-vector model predictive control method equipped with an improved common-mode reduction (CMR) space vector pulse width modulation (SVPWM). The modulation technique essentially subdivides the hexagonal voltage vector space into 18 sub-sectors, that can be split into two groups with different CMV properties. The proposal indirectly increases the DC-bus utilization and extends the overall modulation region with improved CMV. The comparison with the virtual-vector MPC scheme equipped with the conventional SVPWM suggests that the proposed technique can effectively suppress 33.33% of the CMV, and reduce the CMV toggling frequency per fundamental cycle from 6 to either 0 or 2 (depending on which sub-sector group). It is believed that the proposed control technique can help to improve the performance of photovoltaic single-stage inverters.

18‐Sided polygon voltage space vector fed nine‐phase induction machine drive for high power applications

The advantages such as better fault-tolerant capability, less space harmonic content, and requirement of power semiconductor devices with reduced voltage ratings etc., made the multi-phase induction machines drives (IMD) best desirable for the high power applications. However, as the number of phase increases, the improvement in the LMR of the multi-phase IMDs is not significant using the conventional SVPWM techniques provided in the literature. To address the above-mentioned limitation, 18-sided polygon (octadecagon) based voltage space vector generation for a nine-phase IMD is proposed in this article without compromising in the torque harmonic profile. Using the proposed octadecagonal voltage space vector generation technique, the LMR of nine-phase IMD is significantly improved by 26.03%, 24.28%, and 9.15% in comparison to the nine-phase sinusoidal pulse width modulation, nine-phase SVPWM and individual hexagonal SVPWM techniques, respectively. Efficacy of the proposed control technique is substantiated using the results obtained from ANSYS Maxwell simulation and experimentation on 5-hp nine-phase IMD prototype in the laboratory.

A Generalized Space Vector Modulation for Cascaded H-Bridge Inverters under Faulty Conditions

In this research, a new space vector modulation control algorithm is proposed to increase the reliability and the accuracy of the cascaded H-bridge multilevel inverters in case of faulty situations where one or several power cells do not function. When one or more switches of a cell are opened or shorted, that cell is considered faulty. By giving a detailed analysis on the impact of the faulty power cells on the voltage space vectors, the inapplicable voltage vectors are removed precisely. Consequently, the optimal redundant switching states are chosen such that the highest possible output voltage can be achieved. In addition, the balance of the three phases line-to-line voltage and current are maintained. The proposed algorithm is also generalized so that it can be applied to any level of H-bridge inverters. The validity of the method is verified by numerical simulations using MATLAB Simulink with an 11-level cascaded H-bridge inverter.

Enhanced Direct Torque Control for a Three-Level T-Type Inverter

Direct torque control (DTC) is a widely used approach for motor drives due to its distinctive advantages, e.g., fast dynamic response and highly robust against motor parameters uncertainties and external disturbances. To achieve a lower torque ripple, a higher switching frequency is usually required, which, however, can reduce the drive efficiency. Using the emerging silicon carbide (SiC) devices, which can operate efficiently at a much higher switching frequency than their silicon counterparts, thus, it could be feasible to achieve high efficiency and low torque ripple simultaneously. In this work, a novel multilevel DTC for a SiC T-type inverter is proposed to significantly reduce the torque and flux ripples while retaining the fast-dynamic response. The unbalanced dc-link is a common issue of the T-type inverter, which may also lead to a higher torque ripple. To address this issue, the proposed DTC algorithm only uses the real voltage space vectors and virtual space vectors (VSVs) that do not contribute to the neutral point current such that an inherent dc-link capacitor voltage balancing can be achieved without using any active dc-link voltage controls or additional dc-link voltage and/or current sensors. The feasibility and effectiveness of proposed methods are verified by using both simulation and experimental studies.

Fault-tolerant deadbeat model predictive current control for a five-phase PMSM with improved SVPWM

The main drawbacks of traditional finite set model predictive control are high computational load, large torque ripple, and variable switching frequency. A less complex deadbeat (DB) model predictive current control (MPCC) with improved space vector pulse-width modulation (SVPWM) under a single-phase open-circuit fault is proposed. The proposed method predicts the reference voltage vector in the α-β subspace by employing the deadbeat control principle on the machine predictive model; thus, the exhaustive exploration procedure is avoided to relieve the computational load. To perform the constant switching frequency operation and achieve better steady-state performance, a modified SVPWM strategy is developed with the same conventional structure, which modulates the reference voltage vector. This new approach is based on a redesigned and adjusted post-fault virtual voltage vector space distribution that eliminates the y-axis harmonic components in the x-y subspace and ensures the generation of symmetrical PWM pulses. Meanwhile, the combined merits of the DB, MPCC, and SVPWM methods are realized. To verify the effectiveness of the proposed control scheme, comparative experiments are performed on a five-phase permanent magnet synchronous motor (PMSM) drive system.

Direct Torque Control for a Bearingless Induction Motor Based on Model prediction

Purpose The purpose of this paper is to address the large stator flux linkage ripple and electromagnetic torque ripple caused by the hysteresis comparator in traditional direct torque control for a bearingless induction motor (BIM). Design/methodology/approach Model predictive direct torque control (MPDTC) strategy is adopted. On the basis of the mathematical model of BIM, the stator current and stator flux observational values are obtained, and the electromagnetic torque and stator flux at the next moment are predicted. Then, based on the relationship between the stator flux and the electromagnetic torque, the predicted stator flux can be transformed into an equivalent flux linkage vector, which eliminates the weighting coefficients problem among multiple variables in traditional objective functions. The objective function and torque PI controller will output the optimal stator flux linkage and the increments of the torque phase angle. Through the phase angle increments, the space voltage vector can be obtained by the reference flux linkage controller instead of the stator flux linkage and the torque hysteresis controller. Findings The proposed MPDTC method can effectively improve the stator flux linkage and the torque ripple. It can implement the stable suspension of the rotor and improve the dynamic performance and steady-state accuracy of the BIM system. Originality/value A MPDTC strategy is proposed to reduce the ripple of stator flux and electromagnetic torque. The phase angle increment angle of stator flux linkage and electromagnetic torque is optimized by model prediction, and the optimal space voltage vector is obtained by designing the reference flux controller.

Advances in Fault Diagnostics and Post‐Fault Operation of Electrical Drives

Advances in Fault Diagnostics and Post‐Fault Operation of Electrical Drives

DTC Switching Strategy for Open-end Winding of Induction Machines Fed by a Dual-output Indirect Matrix Converter

This paper deals with the Direct Torque Control (DTC) of Dual Indirect Matrix Converter (DIMC) feeding an open-end winding three-phase Induction Motor (IM). Indeed, the open-end winding topology allows overcoming the main problem of Common-Mode Voltage (CMV) which is responsible of presence of stresses in the motor winding in classical topologies, controlling separately the winding of the three-phases, reducing the voltage stress of the power electronics switches and to decreasing the voltage and current harmonics in each phase. The proposed Dual-output Indirect Matrix Converter generates 18 active voltage space vectors. Whereas, in the proposed algorithm presented in this paper to ensure the control of the proposed topology it is implemented only with two null vectors and six active voltage vectors for each output. It is based on same idea of the space vector pulse width modulation that is applied separately for both converters to ensure the control of their output voltages. Indeed, to ensure the required voltage at each winding the output voltage of the first matrix converter are generated normally and output voltage of the second matrix converter are generated with 180° phase shift. The obtained simulation results prove clearly the overall performance of the control of the studied drive system based on the proposed topology and its control algorithm which may be extended to other drive system application, especially in industrial application where more improved performances are required.

Novel fuzzy direct torque control based on constructed functional transformed grey model

To reduce the ripple of the magnetic flux and torque of motors and the reduce the hysteresis in motor speed control, an improved grey model predictive fuzzy direct torque control (DTC) method based on function transformation is proposed. First, a function transformation is used to transform the sampled sequences to nonnegative values. This overcomes the disadvantages caused by fluctuant and random sampling of the motor torque and stator flux linkage. Second, an equal dimensional new information model is used to keep the dimensions unchanged, which reduces the time to predict the motor parameters through the model. Moreover, the voltage space vector plane is divided into six sectors, which simplifies the fuzzy control system rules. Simulation results show that the proposed fuzzy direct torque control based on the improved grey model method reduces the influence of hysteresis on the control system, decreases the motor flux chain and torque ripple, improves the response speed of the torque and rotational speed, reduces overshoot, achieves good effects in terms of anti-interference capability and dynamic response, and improves the real-time performance and accuracy of the fuzzy control system.

Open‐phase fault tolerant driving operation of dual‐inverter‐based traction drive

A method for achieving open-phase fault tolerant operation of a dual-inverter-based traction drive with charging capability is presented. This method utilises a contactor to connect the switching nodes of the two half bridges which are normally used for AC charging in this dual inverter configuration. These half bridges are then modulated to provide a path for zero-sequence current and enhance the available voltage vector space of the drive by injecting a controllable common-mode voltage between the two inverters. A control method and five-level modulator based on zero-sequence voltage control and phase shifted carriers are introduced to accommodate this novel remedial method. Using this approach, the open-phase faulted dual inverter drive is able to operate with twice the speed range of the conventional open-phase fault tolerant approach, which is to provide a path for zero-sequence current by connecting the negative DC rails of the two inverters with a contactor. Simulation and experimental results with a prototype dual inverter drive are presented to validate the theory of the new control and modulation method. The experimental results showcase the proposed algorithms performance by dynamically responding to an open-phase fault and starting from standstill, thereby proving its validity for an electric vehicle application.

A novel fast SVPWM method based on two-stage transformation for three-level inverter

Compared with the two-level inverter, the three-level inverter has excellent performance in pressure voltage switching loss and harmonic applied to the fields of the speed regulation and new energy generation. However, the computational complexity of the space vector pulse width modulation (SVPWM) method for multilevel inverter restricts the implementation on low cost microprocessor. This paper proposes a novel fast SVPWM method for three-level inverter to convert the space voltage vector in the three-level space to the two-level by vector subtraction with the central vector. The conduction time of each switch can be computed quickly so that the runtime is reduced significantly. Finally, the experimental results verify the effectiveness and practicability of the new space vector modulation algorithm based on two-stage transformation.