Space Vector Approach Research Articles

A multi‐criteria methodology with algebraic validation for the design of space vector switching sequences over a fundamental period horizon

AbstractThis paper presents a novel methodology for the design of the Space Vector (SV) switching sequences in order to reduce the output voltage distortion and the common‐mode voltage (CMV) without increasing the number of commutations in comparison to conventional and optimised techniques presented in the literature. Three spaces can be distinguished in a converter, referring to: line‐to‐line voltages, phase voltages and switching states. Consequently, three correspondent sequences of vectors in each space can be verified. The output voltage distortion, CMV and switching count are mainly affected, respectively, by the sequences in the line‐to‐line voltage, phase voltage and switching state spaces. However, the three spaces are interdependent, and the selection of a sequence in one space affects the ones in the other spaces. As a consequence, this paper presents a novel SV approach, where the line‐to‐line voltage sequences are selected over a fundamental period horizon considering the impact in the phase voltages through an algebraic analysis, assuring minimal phase voltage transitions while using VIKOR method to choose the best trade‐off between reduction of output voltage distortion and CMV. In order to validate the proposed strategy, experimental results are given to a three‐phase five‐level Packed U‐Cell (PUC5) converter.

Performance Analysis and Evaluation of Multiphase Split-Source Inverters

Due to their many advantages over their counterparts, such as Z-source inverters (ZSIs), split-source inverters (SSIs) have recently received much attention as single-stage boost inverters. This paper discusses a multiphase version of the SSI topology for the first time. Among multiphase systems undergoing a revolution in the research area, five-phase motor drives are a relatively practical selection in industrial applications. Therefore, this paper focuses on a five-phase SSI as an example. The topology, operating principles, modulation techniques, and performance analysis of the analyzed topology are introduced. A modified space-vector modulation (MSVM) scheme is developed to eliminate low-frequency ripples in the input current. There is also a detailed analysis and graphical evaluation of the output currents ripples using the space-vector approach. It is evident that multiphase SSI is suitable for motor drives, especially when a high-output voltage gain is required. In addition to having a nearly identical ripple in output current to a conventional VSI, it has the benefit of performing the boosting action in a single stage with fewer passive components and a low ripple in input current. Finally, the simulation and experimental results have been conducted to demonstrate the viability of the multiphase SSI studied in the theoretical study and analysis.

Space-Vector Transient Analysis of Delta-Connected ThreePhase Loads

In this paper, the time-domain equivalent circuit for three-phase delta-connected loads, within the frame of the Clarke transformation and the space vector approach,is derived. The proposed theoretical derivation is a further contribution to extend the general theory of the space-vector approach for transient analysis of three-phase networks. In fact, since space vectors are defined in the time domain, the proposed methodology can be used for three-phase transient analysis, whereas the conventional steady-state analysis results as a special case. The theoretically derived equivalent circuit is validated through Matlab/Simulink simulation of a case study consisting in a specific three-phase active load. Keywords—Clarke transformation, power system analysis, space vec

Virtual Space Vector Pulse Width Modulation for Asymmetric T-Type Neutral Point Clamped 3-Level Inverter

This paper proposes a novel 3-phase asymmetric 3-level T-type NPC inverter and studies its PWM performance using a virtual space vector pulse width modulation control strategy. Firstly, the mathematical model and characteristics of this economical topology are described. Then, a virtual space vector approach is proposed to build a space vector diagram for designing SVPWM control. Similar to the conventional 3-level NPC inverter, the asymmetric inverter can also work with the neutral point voltage self-balancing in a fundamental period, which enables employment of this topology in various applications. Finally, simulation and experiment results under different load conditions have shown good output performance of the asymmetric 3-level topology. Similar tests are also performed on both conventional 2-level and 3-level inverters for comparison. For an almost similar number of different voltage vectors in the space vector diagram, the asymmetric 3-level topology can compete with conventional 3-level inverters for low-cost applications. The obvious benefit of the asymmetric 3-level inverter is a smaller number of switches devices while it can achieve output performance similar to that of the conventional 3-level. The comparative investigation also shows that the total loss given by SVPWM for the asymmetric 3-level configuration is lower than that of the traditional 3-level inverter.

Selective Lower Order Harmonic Elimination in DC-AC Converter Using Space Vector Approach

A novel space vector-based approach is introduced in this brief to selectively eliminate the lower order harmonics from the DC-AC converter output waveform by making use of double switching clamping sequences. This technique uses a volt-second balance for control of fundamental voltage while using the dwell time rearrangement of the active vector in a sub-cycle to obtain the elimination of fifth or seventh harmonics. Further, the closed-form expression of the dwell time-division coefficient (DTDC) for the active vector dwell time division rearrangement is expressed. The proposed PWM technique is compared with other space vector-based PWM techniques in terms of voltage weighted total harmonic distortion, switching power loss, and lower order harmonic magnitudes. Further, the experimental results are presented to show the effectiveness of the proposed PWM techniques in terms of harmonic elimination.

A New Approach to the PWM Modulation for the Multiphase Matrix Converters Supplying Loads with Open-End Winding

This article presents three variants of the Pulse Width Modulation (PWM) for the Double Square Multiphase type Conventional Matrix Converters (DSM-CMC) supplying loads with the open-end winding. The first variant of PWM offers the ability to obtain zero value of the common-mode voltage at the load’s terminals and applies only six switches within the modulation period. The second proposal archives for less Total Harmonic Distortion (THD) of the generated load voltage. The third variant of modulation concerns maximizing the voltage transfer ratio, minimizing the number of switching, and the common-mode voltage cancellation. The discussed modulations are based on the concept of sinusoidal voltage quadrature signals, which can be an effective alternative to the classic space-vector approach. In the proposed approach, the geometrical arrangement of basic vectors needed to synthesize output voltages is built from the less number of vectors, which is equal to the number of the matrix converter’s terminals. The PWM duty cycle computation is performed using only a second-order determinant of the voltages coordinate matrix without using trigonometric functions. A new approach to the PWM duty cycles computing and the load voltage synthesis by 5 × 5 and 12 × 12 topologies has been verified using the PSIM simulation software.

Carrier-based PWM Method for Indirect Matrix Converters based on Space Vector Analysis

In this paper, a novel approach to realize the carrier-based pulse width modulation (CBPWM) method for indirect matrix converter (IMC) is presented. The advantage of the proposed CBPWM method is that only one triangular carrier signal with constant gradient falling and rising edges is used to generate the PWM to the power switches in both the rectifier and the inverter stages of IMC. The analysis of the proposed CBPWM method is based on the space vector approach and the relationship between CBPWM and space vector pulse width modulation (SVPWM) methods is provided. In this paper, four CBPWM methods called: sinusoidal PWM, third harmonic injection PWM, symmetrical PWM and discontinuous PWM are presented. These different CBPWM schemes are established according to the distribution of zero vectors and the switching pattern of the SVPWM method. The comparison of output voltage performance with different CBPWM schemes are investigated. Compared to the conventional method the calculation time of the proposed method is reduced around 50%. Concretely, the calculation time of the SVPWM method is 45 μs, while the calculation time of the proposed method is 22 μs. The experiments have been carried out to show the effectiveness of the proposed method.

Space-Vector Based Excitation of a Bipolar Transmitter for Wireless Power Transfer Applications

A space-vector (SV) based excitation method for wireless power transfer systems with a bipolar transmitter is introduced in this article. Unlike traditional bipolar excitation techniques that rely on fixed transmitter current distributions, this SV approach provides an elegant analytical method of redistributing a greater magnitude of current to the transmitter coil, which is closer to a misaligned receiver. This method is shown to require a smaller transmitter current vector magnitude for a required output power compared to all other bipolar coil excitation schemes over a broad range of receiver misalignments, thereby reducing conduction losses within the system. Additionally, the gradual redistribution of transmitter current as a function of receiver misalignment achieved by the SV method causes it to be less influenced by errors in receiver position sensing compared to conventional methods. Experimental results shows that the proposed method in conjunction with single coil operation at extreme misalignments was able to achieve a coil efficiency profile with minimal variation due to misalignment (93.2% at perfect alignment to 92.7% at a misalignment of 20 cm, for 2 kW power transfer into a 200 V battery load.)

Space Vector Transients of Three-phase Transformers

This paper is devoted to the transient analysis of three-phase transformers by means of the space vector tool. Space vector definition is based on the Clarke transformation, operating in the time domain. Thus, the space vector is better suited to transient analysis when compared with approximate approaches based on the phasor symmetrical-component transformation. Space-vector equivalent circuits are derived for three-phase transformers with Wye and Delta connections. A case study, consisting in the transient due to a capacitor bank insertion, shows that the proposed space-vector approach can clearly evidence the asymmetrical transient behavior of the phase variables in terms of different peak levels and oscillations amplitude.

Conventional and Second Order Sliding Mode Control of Permanent Magnet Synchronous Motor Fed by Direct Matrix Converter: Comparative Study

The main objective of this work revolves around the design of second order sliding mode controllers (SOSMC) based on the super twisting algorithm (STA) for asynchronous permanent magnet motor (PMSM) fed by a direct matrix converter (DMC), in order to improve the effectiveness of the considered drive system. The SOSMC was selected to minimize the chattering phenomenon caused by the conventional sliding mode controller (SMC), as well to decrease the level of total harmonic distortion (THD) produced by the drive system. In addition, the literature has taken a great interest in the STA due to its robustness to modeling errors and to external disturbances. Furthermore, due to its low conduction losses, the space vector approach was designated as a switching law to control the DMC. In addition, the topology and design method of the damped passive filter, which allows improvement of the waveform and attenuation of the harmonics of the input current, have been detailed. Finally, to discover the strengths and weaknesses of the proposed control approach based on SOSMC, a comparative study between the latter and that using the conventional SMC was executed. The results obtained confirm the effectiveness of SOSMC over the conventional SMC under different operating conditions.

Six-Leg Single-Phase AC–DC–AC Multilevel Converter With Transformers for UPS and UPQC Applications

This article investigates a single-phase ac–dc–ac multilevel converter composed of two three-leg converters series-connected throughout two transformers (one on the grid side and one on the load side), sharing the same dc-link. The proposed converter allows to feed the load with sinusoidal voltages (keeping constant amplitude and frequency) under grid voltage disturbances, as sags, swells, and harmonics. Besides, the converter can operate with a sinusoidal grid current with a high power factor and can be applied to systems with either equal or different voltage levels at the input and output. Circuit model equations, pulse width modulation (PWM) technique based on space vector approaches, and a control system are presented. The proposed topology is compared with the conventional one in terms of harmonic distortion, semiconductor losses, transformers losses, and total power losses. Simulation and experimental results are presented under the same conditions to validate PWM and control strategies.

Carrier-Based Discontinuous PWM for a Five-Level Unidirectional Rectifier

In applications, where bidirectional power flow is not required, unidirectional pulsewidth modulated (PWM) rectifiers are advantageous in terms of power density, hardware simplicity, and reliability compared to the conventional PWM rectifiers. For high-power medium-voltage applications, a discontinuous pulsewidth modulation (DPWM) strategy is useful in reducing the switching loss. This article proposes a DPWM strategy for a recently proposed five-level unidirectional rectifier. The rectifier is analyzed in the space vector (SV) domain to determine the switching sequences for DPWM. Two such DPWM sequences (i.e., DPWMA and DPWMB) are identified. Implementation of these DPWM sequences in the SV domain is known to be very computation intensive. Therefore, carrier-based implementation of both the DPWM strategies is proposed, which are derived following the SV approach. The proposed strategies are found to be very simple with very few computations. A new voltage-balancing method for the dc-link capacitors is also proposed in this article. Performances of these DPWM strategies over the entire operating range are predicted analytically and verified experimentally. This article is accompanied by MATLAB files demonstrating various performance indexes of the proposed DPWM sequences.

Current Ripple Analysis of Three-Phase Vienna Rectifier Considering Inductance Variation of Powder Core Inductor

Three-phase three-level Vienna rectifier using powder core inductors has been widely used for power conversion. Inductor current ripple analysis of rectifier is essential for pulsewidth modulation method optimization, loss estimation, filter inductor design, etc. However, it is hard to analyze the current ripple of Vienna rectifier. Moreover, the inductance of powder core inductor varies with sinusoidal input current, which makes it even more complicated. In this article, a current ripple analysis method for three-phase Vienna rectifier considering the inductance variation of the powder core inductor is presented. The current ripple distribution of Vienna rectifier with constant inductance is studied based on the space vector approach. To determine the current ripple of Vienna rectifier with powder core inductors, an inductor voltage calculation method considering inductance variation is proposed. The compensation voltage is introduced to compensate for the effect of inductance variation on current ripple. Then, the analytical expression of the peak-to-peak current ripple with powder core inductor is derived. In addition, a design method of powder core inductor is proposed based on the analytical expression. At last, the correctness of the analytical result is verified by both simulation and experiment.

CMV reduction in a three‐to‐seven phase direct matrix converter using SVPWM

The pulse-width modulation (PWM)-controlled modern electric drives causes some serious problems such as the generation of common-mode voltage (CMV) and high dv/dt. The CMV might cause high-frequency leakage currents that flow through the possible path that is bearing of the motor. Thus, the flow of current through the motor bearing leads to its premature failure. One of the main challenges in developing PWM methods for control of motor drives is the problem of CMV and its reduction/elimination. In this study, a modulation technique based on space-vector approach is developed to reduce the CMV in a three-to-seven-phase direct matrix converter. CMV reduction becomes possible by selecting suitable zero-voltage vectors for a specific duration and the use of a selected set of active vectors for the output voltage synthesis. The proposed space-vector PWM (SVPWM) for the reduction of CMV is performed with a seven-phase R–L load to show the viability of the proposed technique. The proposed SVPWM technique is implemented experimentally in dSPACE working in conjunction with field-programmable gate array processor board using a system generator. Hardware results that validate the proposed control algorithm are discussed.

Single‐phase universal active power filter based on ac–dc–ac converter with eight controlled switches

This study presents an ac–dc–ac converter with eight controlled switches. The proposed topology is applied as a universal active power filter, compensating for disturbances in the grid voltage, voltage sags/swells, and harmonics generated by non-linear loads. The difference between the proposed and conventional solution is the addition of an uncontrolled leg (composed only of diodes) to increase the number of voltage levels, reducing harmonics and the average switching frequency. For performance comparisons, current total harmonic distortion (THD), voltage weighted THD, switching and conduction losses of the semiconductors, and average switching frequency were used as parameters. Control and pulse-width modulation techniques based on space vector approaches were developed to eliminate zero-crossing distortions caused by the use of the uncontrolled leg. Simulation and experimental results were presented for validation of the mathematical model.

An Alternative Carrier-Based Implementation of Space Vector Modulation to Eliminate Common Mode Voltage in a Multilevel Matrix Converter

The main aim of the paper is to find a control method for a multilevel matrix converter (MMC) that enables the elimination of common mode voltage (CMV). The method discussed in the paper is based on a selection of converter configurations and the instantaneous output voltages of MMC represented by rotating space vectors. The choice of appropriate configurations is realized by the use of space vector modulation (SVM), with the application of Venturini modulation functions. A multilevel matrix converter, which utilizes a multilevel structure in a traditional matrix converter (MC), can achieve an improved output voltage waveform quality, compared with the output voltage of MC. The carrier-based implementation of SVM is presented in this paper. The carrier-based implementation of SVM avoids any trigonometric and division operations, which could be required in a general space vector approach to the SVM method. With use of the proposed control method, a part of the high-frequency output voltage distortion components is eliminated. The application of the presented modulation method eliminates the CMV in MMC what is presented in the paper. Additionally, the possibility to control the phase shift between the appropriate input and output phase voltages is obtained by the presented control strategy. The results of the simulation and experiment confirm the utility of the proposed modulation method.

Comparing Power Transformer Turn-to-Turn Faults Protection Methods: Negative Sequence Component Versus Space-Vector Algorithms

This paper presents a comparison of two of the most sensitive methods to detect low-level turn-to-turn faults in the windings of three-phase transformers. The performance of the negative sequence component and of the space-vector protection algorithms is tested under several internal and/or external fault conditions. The results indicate that the space-vector approach is slightly more sensitive for detecting low-level turn-to-turn winding faults. For more severe defects, the fault detection sensitivity of both methods is similar.

Design and Performance Prediction of Space Vector-Based PMU Algorithms

Phasor measurement units (PMUs) are expected to be the basis of modern power networks monitoring systems. They are conceived to allow measuring the phasor, frequency, and rate of change of frequency (ROCOF) of electrical signals in a synchronized way and with unprecedented accuracy. PMUs are intended to apply to three-phase systems and to track signal parameters evolution during network dynamics. For these reasons, the design of the algorithms and, in particular, of the filters that allow rejecting the disturbances while preserving the passband signal content is a paramount concern. In this paper, a novel space vector approach is proposed. It exploits the three-phase nature of the monitored signals together with proper lowpass and differentiation filters. Analytical formulas for performance prediction under almost all the test conditions prescribed by the synchrophasor standard C37.118.1 for PMUs, are introduced. The given expressions are extremely accurate, thus allowing to derive the filter design criteria for phasor, frequency, and ROCOF computation, so that the requirements in terms of estimation errors can be easily translated into filter specifications. The implications of the proposed approach in practical PMU design are illustrated by means of two simple design examples matching P and M compliance classes, respectively, for all the test cases of the standard. The reported performance proves the validity of the proposal.

Experimental Efficiency Comparison Between a Direct Matrix Converter and an Indirect Matrix Converter Using Both Si IGBTs and SiC <sc>mosfet</sc>s

This paper presents an experimental efficiency comparison study between two different direct ac–ac converter topologies; a direct matrix converter and an indirect matrix converter. The evaluation is performed under variable load conditions using both discrete silicon isolated gate bipolar transistor and silicon carbide MOSFETs working at power levels up to 9 kW. Each loss measurement is carried out using two power analyzers; one placed at the input and one at the output of the converter under study. To facilitate this measurement, an output filter was necessary in addition to the normal input filter. Both converters are modulated using the same traditional symmetrical space vector approach and feature an identical input/output filter design.

Development of a Three-to-Five-Phase Indirect Matrix Converter With Carrier-Based PWM Based on Space-Vector Modulation Analysis

This paper proposes an indirect matrix converter (IMC) topology to supply a five-phase load directly from three-phase ac power sources without bulky electrolytic capacitors and explains its operating principle. Using the emerging topology, which combines the five-leg inverter into the rectifier stage of the conventional IMC, the three-to-five-phase IMC topology reduces the number of power switches and results in a simpler commutation compared with the conventional three-to-five-phase direct matrix converter. In addition, a simple approach to realize the carrier-based pulsewidth modulation (CBPWM) method for a three-to-five-phase IMC is presented, and the proposed CBPWM method is analyzed based on the space-vector approach. As a result, the IMC with the proposed CBPWM method can be more easily implemented compared with IMCs with the space-vector PWM method. A three-to-five-phase IMC control platform is realized by coordinating a TMS320F28335 DSP (Texas Instruments) with an EPM7128SLC84-15 field-programmable gate array (Altera). The simulation and experimental results are provided to verify the effectiveness of the CBPWM strategy.