Proposed Space Vector Modulation Strategy Research Articles

Space-vector modulation for three-phase indirect matrix converters to reduce common-mode voltage

This paper presents a space vector modulation strategy for a three-phase indirect matrix converter to reduce the common-mode voltage and maintain the output performance. To reduce the peak value of the common-mode voltage to 57.7% of the input phase voltage, three active voltage vectors are used to generate the desired output voltage with arbitrary amplitude and frequency, instead of using both active and zero voltage vectors as in the traditional space vector modulation strategy. Although the common-mode voltage is reduced, the output waveform quality of the three-phase indirect matrix converter deteriorates due to the absence of the zero voltage vectors. To overcome this problem, the proposed space vector modulation strategy is redesigned to control the rectifier stage of the indirect matrix converter by utilizing three active current vectors instead of two as usual. Consequently, the constant average dc-link voltage is achieved, which can improve the output performance in terms of the output voltage and current harmonic distortion. The simulation is implemented by PSIM software and experimental results are provided to verify the effectiveness of the proposed space vector modulation strategy.

A New Space Vector Modulation Strategy to Enhance AC Current Quality of Isolated DC–AC Matrix Converter

The isolated dc-ac matrix converter is a promising option to connect dc system and ac system, performing directional power conversion and providing galvanic isolation. Due to the absence of the bulky dc-link capacitor, the converter can be compact. However, when a conventional modulation method is applied to the converter, the coupling of H-bridge and matrix converter will result in numerous harmonics in ac current. This article proposes a new space vector modulation (SVM) strategy for isolated ac-dc matrix converter. It improves the duty cycle calculation to reduce the harmonics in ac current while the number of switching actions remains low. Furthermore, considering the essential commutation process of matrix converter can also impact waveform quality, two-step commutation and optimized zero vectors are adopted to reduce narrow pulsewidth modulation pulses, ensuring the gating signals are always long enough to finish commutation. Simulation and experimental results are provided to verify the performance of the proposed SVM strategy.

Generalized Space Vector Modulation for Ripple Current Reduction in Quasi-Z-Source Inverters

This article proposes a generalized space vector modulation (SVM) strategy for the three-phase quasi-Z-source inverter (qZSI), which can reduce the inductor current ripples by limiting the peaks in different sectors of the vector space. In the conventional ZSVM6 strategy, the shoot-through interval is divided into six equal parts, which is easy to implement. However, the inductor current ripples are not optimized. Generally, larger inductance is required to limit the current ripples, resulting in poor power density. By contrast, the proposed SVM strategy can minimize the current ripple, while maintaining the same total shoot-through time. Although the shoot-through intervals in the proposed SVM strategy are not identical, easy implementation still holds. The generalized strategy can ensure that the inductor current ripples are always smaller than the peak of the inductor discharging current ripple in a switching cycle. The proposed SVM strategy is derived in details and compared with the conventional ZSVM6 strategy. Simulations and experimental tests are presented to verify the effectiveness of the proposed modulation strategy for the inductor ripple current reduction.

SVM Strategy for Mitigating Low-Order Harmonics in Isolated AC–DC Matrix Converter

Isolated ac–dc matrix converter features bidirectional power conversion, galvanic isolation, and high power density. However, the conventional pulsewidth modulation methods in the literature can lead to the input ac distortions in the isolated ac–dc matrix converter with excessive low-order harmonics. To improve the current quality and maintain a low number of switching actions, an improved space vector modulation (SVM) strategy is proposed in this article. The SVM switching sequence and the distribution of zero vectors are designed to mitigate the low-order harmonics. To verify the performance, an in-depth study of the harmonics generation mechanism in the converter is conducted based on a developed mathematical converter model. The performances of the conventional SVM strategy and the proposed SVM strategy are compared, and simulation and experimental results are provided.

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.

Space vector modulation strategy for neutral‐point voltage balancing in three‐level inverter systems

This study proposes a space vector modulation (SVM) strategy to balance the neutral-point voltage of three-level inverter systems. The proposed method is implemented by combining conventional symmetric SVM with nearest three-vector (NTV) modulation. The conventional SVM is converted to NTV modulation by properly adding or subtracting a minimum gate-on time. In addition, using this method, the switching frequency is reduced and a decrease of switching loss would be yielded. The neutral-point voltage is balanced by the proposed SVM strategy without additional hardware or complex calculations. Simulation and experimental results are shown to verify the validity and feasibility of the proposed SVM strategy.

A Novel DC-Side Zero-Voltage Switching (ZVS) Three-Phase Boost PWM Rectifier Controlled by an Improved SVM Method

A novel active clamping zero-voltage switching three-phase boost pulsewidth modulation (PWM) rectifier is analyzed and a modified minimum-loss space vector modulation (SVM) strategy suitable for the novel zero-voltage switching (ZVS) rectifier is proposed in this paper. The topology of the novel ZVS rectifier only adds one auxiliary active switch, one resonant inductor, and one clamping capacitor to the traditional hard-switched three-phase boost PWM rectifier. With the proposed SVM strategy, the novel ZVS rectifier can achieve ZVS for all the main and auxiliary switches. In addition, the antiparallel diodes can be turned OFF softly, so the reverse recovery current is eliminated. Besides, the voltage stress of all the switches is equal to the dc-link voltage. The operation principle and soft-switching condition of the novel ZVS rectifier are analyzed. The design guidelines of the soft switched circuit parameters are described in detail. A DSP controlled 30 kW prototype is implemented to verify the theory.

Capacitor Voltage Balancing of Flying Capacitor Multilevel Converters by Space Vector PWM

Proper operation of a multilevel flying capacitor converter (FCC) necessitates a closed-loop voltage balancing strategy. This paper proposes a space vector modulation (SVM)-based approach that benefits from the switching state redundancy of an n-level FCC to implicitly carry out the voltage balancing task within the switching strategy. Based on the voltage deviations of the capacitor voltages, a cost function is defined and minimized to choose the proper redundant switching states among the available switching states. The performance of a grid-connected four-level FCC under the proposed SVM strategy for various operating conditions is studied and evaluated based on time-domain simulations in the PSCAD/EMTDC environment, and experimentally verified. The studies demonstrate the capability of the proposed SVM strategy to regulate the capacitor voltages at their nominal reference values.

Operation and Control of a Hybrid Seven-Level Converter

This paper introduces a novel hybrid seven-level converter that is based on the upgrade of the five-level active neutral-point-clamped converter concept and is suitable for high-power applications. The paper provides a comprehensive analysis for the operation of the converter. Based on the analysis, a space vector modulation (SVM)-based switching strategy that takes advantage of redundant switching vectors of the SVM strategy to counteract the voltage drift phenomenon of the proposed converter is proposed. The limit to the range of operation of the seven-level converter based on the proposed SVM strategy is also presented. It is shown that the ability to stabilize the dc-link capacitor voltages and the per-phase flying capacitors is a function of the converter operating indices, i.e., the load power factor and modulation index. The salient feature of the proposed SVM-based control strategy is that it enables proper operation of the converter with no requirements for additional controls or auxiliary power circuitry, within the specified range of operation. Performance of a converter under various operating conditions, based on the proposed SVM strategy, in the MATLAB/Simulink environment, is evaluated and experimentally demonstrated.

Space Vector Modulation strategy to reduce the Common Mode perturbations in Matrix Converters

An alternative Space Vector Modulation (SVM) strategy which reduces the Common Mode (CM) perturbations when using Matrix Converters (MC) is presented in this work. The proposed method maintains the conventional SVM pattern but the zero vectors, which have been shown to introduce not only high CM voltage values but also high CM voltage time derivative. Hence the three zero vectors are replaced by three rotating ones, in such a way that the fundamental output voltage vector and the input current direction remains both unchanged. Results of the proposed SVM strategy driving a Permanent Magnet Synchronous Machine (PMSM) are provided to confirm the effectiveness of the method.

A Space Vector Modulation Strategy for a Back-to-Back Five-Level HVDC Converter System

The DC-capacitor voltage drift is the main technical drawback of a multilevel diode-clamped converter (DCC) system. This paper proposes a space vector modulation (SVM)-based switching strategy that takes advantage of the redundant switching states of the SVM to counteract the voltage drift phenomenon of a five-level DCC-based back-to-back high-voltage direct-current (HVDC) converter system. The proposed strategy is based on online minimization of a quadratic cost function, associated with the voltage deviations of the dc capacitors. The salient feature of the proposed strategy is that it enables voltage balancing of the DC capacitors with no requirements for offline calculations, additional controls, or auxiliary power circuitry. Performance of the proposed SVM-based balancing strategy for a back-to-back HVDC converter system, based on time-domain simulation studies in the PSCAD/EMTDC environment, is evaluated and experimentally verified. The studies demonstrate capability of the proposed SVM strategy to control and maintain voltage balance of DC capacitors.

Analysis and Control of DC-Capacitor-Voltage-Drift Phenomenon of a Passive Front-End Five-Level Converter

The phenomenon of dc-capacitor-voltage drift is the main technical drawback of a passive front-end multilevel diode-clamped converter (DCC). This paper formulates and analyzes the dc-capacitor-voltage-drift phenomenon of a passive front-end five-level DCC, which operates based on a sinusoidal pulsewidth-modulation (SPWM) switching strategy. The analysis shows dependence of the voltage drift on the modulation index and the ac-side power factor of the DCC. The analysis concludes that an SPWM strategy, without the use of auxiliary power circuitry, is not able to prevent the voltage-drift phenomenon of a five-level DCC. This paper also proposes a space-vector-modulation (SVM)-based switching strategy that takes advantage of redundant switching vectors of the SVM method to counteract the voltage-drift phenomenon. The limit to the range of operation of a five-level DCC, which is based on the proposed SVM strategy, is also presented. The salient feature of the proposed strategy is that it enables voltage balancing of the dc capacitors with no requirements for additional controls or auxiliary-power circuitry, within the specified range of operation. The performance of a DCC under various operating conditions, based on time-domain simulation studies in the MATLAB/SIMULINK environment, is evaluated. This paper demonstrates capability of the proposed SVM strategy to control and maintain voltage balance of dc capacitors.

A Space Vector Modulation Approach for a Multimodule HVDC Converter System

This paper presents the application of a space vector modulation (SVM) strategy for a multimodule converter system that 1) enables low switching frequency, 2) eliminates/minimizes ac-side voltage harmonics, particularly low-order harmonics, and 3) provides maximum ac-side fundamental voltage component. The SVM strategy is based on a sequential sampling technique. The SVM provides harmonic cancellation/minimization by introducing appropriate phase shift for the corresponding voltage harmonics of the converter modules, while maintaining the fundamental voltage components of modules in-phase to obtain maximum ac-side voltage. The SVM eliminates the need for complicated transformer arrangement for harmonic reduction, and thus provides high degree of modularity by utilization of identical transformers for converter modules. The proposed SVM strategy is developed for a back-to-back HVDC converter station in which each converter system is composed of four identical modules. Based on a dynamic model of the system, converter controls are designed and performance of the SVM strategy in terms of converter harmonics and dynamic performance are presented. The studies are performed in time-domain, using the PSCAD/EMTDC software tool.

A Space Vector Modulated STATCOM Based on a Three-Level Neutral Point Clamped Converter

This paper presents a space vector modulation (SVM)-based switching strategy for a three-level neutral point clamped (NPC) converter that is adapted as a STATCOM. The main feature of the proposed SVM switching strategy is that it enables balancing voltages of the dc capacitors, with no requirement of additional controls or auxiliary devices. The proposed SVM strategy also improves the STATCOM ac-side harmonic spectrum and reduces voltage variations of the converter neutral point. Based on a dynamic model of the NPC-based STATCOM, two controllers to regulate the dc-side voltage and control the injected reactive power are designed. Performance of the STATCOM and the corresponding controllers are evaluated based on digital time-domain simulation studies in the PSCAD/EMTDC environment. The studies demonstrate the capabilities of the proposed SVM technique to maintain voltage balance of the dc capacitors and control the STATCOM reactive power exchange for various operating conditions