Discontinuous Space Vector Modulation Research Articles

Design and implementation of a discontinuous SVM applied for a quasi Z-source inverter with power loss reduction

Design and implementation of a discontinuous SVM applied for a quasi Z-source inverter with power loss reduction

New Discontinuous Space Vector Modulation Strategies for Impedance-Source Inverter With Superior Thermal and Harmonic Performance

Impedance-source inverters provide a promising single-stage power conversion with boost-buck capabilities and inverter legs short-circuit immunity. To achieve superior thermal and output harmonic performance, two novel discontinuous modulation strategies for the three-phase quasi-Z source inverter, called the maximum-boost discontinuous space vector modulation (SVM) and the simple-boost discontinuous SVM respectively, are proposed in this article. By properly arranging the shoot-through states and clamping a certain switch to the positive or negative dc-link rail during one-third of the fundamental period, reduced thermal stresses and superior total harmonic distortion performance can be achieved. The proposed modulation strategies are analyzed and compared to the conventional ones in terms of current stresses, power losses, thermal stresses, and output harmonics. Finally, simulations and experimental tests are carried out to validate the performance of the proposed modulation strategies and verify the presented analysis.

An Improved Discontinuous Space Vector Modulation for a Three-Phase Z-Source Inverter With a Modified Reference

An Improved Discontinuous Space Vector Modulation for a Three-Phase <i>Z</i>-Source Inverter With a Modified Reference

A novel impedance source inverter topology with active front-end for AC drives

A unique impedance Source Inverter with an Active Front-End is proposed in this paper, that can be used for controlling AC Drives. There are a number of modulation schemes that may be used with the three-phase impedance source inverters, ultimate reduction in the switching losses makes the discontinuous modulation schemes seem most appropriate. The discontinuous modulation schemes are differentiated into two classes based on the technique used for achieving shoot-through (ST) state: single-phase-leg ST-based and three-phase-leg ST-based (3P) discontinuous modulation schemes. In this paper, we discuss the improvements in Single Phase Maximum Boost Discontinuous Space Vector modulation (1P/MB/DSVM) scheme under similar operating conditions, by simplifying gate signal generation and improving the conversion efficiency. A simulated analysis and comparison of the conventional and the enhanced 1P/MB/DSVM schemes is also discussed using PLECS. Lastly, verification of the simulation outcomes and reported analysis is carried out by making use of a three-phase quasi-Z-source inverter (qZSI) prototype which demonstrates improvement in conversion efficiency, utilizing the refined 1P/MB/DSVM scheme.

Thermal optimized discontinuous modulation strategy for three phase impedance source inverter

A novel space vector modulation (SVM) strategy called maximum-boost discontinuous SVM (MBDSV) is proposed in this paper to reduce the thermal stress of three phase impedance source inverters (ISI). By exploiting the switch clamping mechanism and arranging the shoot-through (ST) states properly, the proposed strategy obtains the flowing merits: further optimize the thermal performance, improve the reliability, reduce the current stress and maximize the dc-link utilization of ISI. The proposed MBDSV was compared to the existing modulation strategies and the feasibility of the MBDSV had been benchmarked by simulation and experiments.

An Improved Discontinuous Space Vector Modulation for Z-Source Inverter With Reduced Power Losses

This article proposes a control strategy for a three-phase Z-source inverter (ZSI) using a modified discontinuous space vector modulation. The main advantages of the proposed control strategy are the enhanced output power quality and the compromise in the reduction between the conduction and switching losses. Furthermore, the reduced switching losses are achieved by the elimination of one switching transition in each half sector with a proper selection of the shoot-through (ST) state distribution. In addition, the reduced conduction losses are achieved by dividing all sectors equally into 30°. The MATLAB/SIMULINK simulation is carried out to verify the effectiveness of the proposed control strategy and to compare it with the existing space vector modulation techniques that utilize distributions of four and six ST vectors. PLECS software is used for the calculation of the conduction and switching losses. Compared to the other modulation techniques, the key features of the proposed control strategy are the improved boosting capability of the output voltage, the low total harmonic distortion, the reduced conduction and switching losses, and the reduced inductance current ripple. An experimental test bench that comprises a three-phase ZSI feeding an $R$ load, controlled by a dSPACE MicroLabBOX, is used to verify experimentally the effectiveness of the proposed control strategy. It is envisaged that the proposed control strategy can be very useful for electrical drive applications integrating a three-phase ZSI due to its capability to improve the output waveform and reduce the harmonic distortions, switching, and conduction losses.

A Carrier-Based Discontinuous PWM Method With Varying Clamped Area for Vienna Rectifier

The three-level Vienna rectifier is an attractive topology for power factor correction applications. However, for practical high-frequency applications, the nonlinearity caused by snubber circuit and parasitic capacitance of Vienna rectifier's switching device will distort input current. This paper proposes a carrier-based discontinuous space-vector modulation (CB-DSVM) method with varying clamped area for Vienna rectifier in high switching frequency applications. The equivalent circuit of Vienna rectifier considering the nonlinear factors is built and the effect of pulse shaping around current zero-crossing point is investigated. The voltage errors caused by the nonlinearity of switching device will distort terminal voltage, which mainly appears at the zero-crossing time. A DSVM method with the fixed clamped area around the zero-crossing point is proposed to reduce the voltage errors and then the simplified CB-DSVM method with varying clamped area by adding a clamped factor to the judging conditions is further studied, which will reduce low-order harmonics of the CB-DSVM method. Simulations and experiments are carried out in a 600 W Vienna rectifier platform, which demonstrates the validity of the proposed method. Compared with the CB-SVM method, the proposed CB-DSVM method with varying clamped area has comparative neutral-point voltage balancing ability and better input current quality.

A generalized switching function-based discontinuous space vector modulation technique for unbalanced two-phase three-leg inverters

This paper presents a discontinuous space vector modulation technique for unbalanced two-phase three-leg inverters. This technique is based on the shift-angle and generalized modulation algorithm obtained for generating the unbalanced two-phase output voltage. Furthermore, the discontinuous switching sequence intends to improve the commutations of power switching devices in each inverter leg that achieves a minimum number of switching state changes in one sampling cycle. Therefore, the switch commutations can be reduced by one-third in one main period. The step- by-step procedure of the modulation algorithm for easy implementation in a digital control platform is discussed. The performance of the developed modulation technique is verified through both simulation and experimental results in a nonunity power factor balanced two-phase load and asymmetrical two-phase induction motor drive.

Quasi-switched inverter using space vector pulse width modulation with triangular comparison for photovoltaic applications

This work analyzes a prototype of a quasi-switched boost inverter (qSBI) feeding an isolated resistive load from a DC source. The use of spatial vector pulse width modulation (SPWM) with triangular comparison is proposed to increase the qSBI gain factor, and its performance is contrasted with other types of spatial vector modulations, such as discontinuous modulations. To verify the validity of the method for voltage range extension in the qSBI converter, a semi-customized test platform was developed. This platform uses a DSP floating point card (Analog Devices ADSP-21369) for processing and control strategies and an interface card that includes a programmable logic array (FPGA) from Xilinx (Spartan-3), which allows to develop the synchronized modulation qSBI needs. The experimental results show improvements in the performance of the qSBI converter in terms of gain factor, voltage reduction in the capacitor, and input current profiles. Discontinuous space vector modulation strategies do not perform well when compared to continuous SVPWM or SPWM modulations, because the ripple levels in the currents taken from the PV module are approximately twice as great as in continuous modulation techniques. Finally, the usefulness of a qSBI as PV microinverter is confirmed by two practical experimental cases of a PV photovoltaic system with a maximum power point adjustment algorithm (MPPT).

Discontinuous Space Vector Modulation Strategy for Three-Level Neutral Point Clamped Inverter

This paper presents a discontinuous space vector modulation (SVM) strategy for a three-level neutral point clamped (3L-NPC) inverter. The proposed scheme, calculation switching time of the 3L-NPC inverter is fully described. A mathematical analysis of the duty cycle is determined by utilizing the calculated switching time method. The main advantages of the proposed method are minimization of the number of commutations of switches and reduction of the switching losses. Simulated and calculation results are presented to verify the validity and effectiveness of the proposed modulation scheme.

Implementation of Three Phase-Discontinuous Space Vector Modulation Using Single DSC-PWM Module

The paper presents an implementation of a discontinuous space vector modulation of three phase inverter. The modulation is implemented in a DSC (Digital Signal Controller) using only one PWM module. Phases of the inverter work in a complementary mode. This implementation gives an assumption to use one DSC for simultaneous controlling of several three phase inverters. Furthermore, a simulation comparison of discontinuous and continuous space vector modulation is made.

Research on Parallel Interleaved Inverters with Discontinuous Space-Vector Modulation

Parallel converter can significantly increase the capacity of the converter and improve the power quality of AC side, but the circulation which can lead to high switching loss and even damage the devices will easily exist in the direct parallel converters. In this paper, the average model of parallel interleaved inverters system to analyze the circulation current is shown, and the cross current is relevant to DC-bus voltage and the overlap time of zero vectors in the switching period. Based on this observation, a discontinuous space vector modulation without using zero vectors (000) is eliminate and suppress the zero-sequence current to entire system. Finally, the effectiveness of modulation strategy is verified by the simulations in this paper.

Discontinuous Random Space Vector Modulation for Electric Drives: A Digital Approach

Space vector modulation (SVM), with its many advantages over classical pulsewidth modulation technique (PWM), is gaining in popularity. However, only deterministic SVM exists. Randomized PWM (RPWM) with its cleaner harmonic spectrum is gaining interest for industrial applications required to meet electromagnetic compatibility standards. Inverter switching losses are optimized and life expectancy can be increased using a suitable discontinuous modulation technique. Here, we present, a discontinuous and randomized-modulation technique based on space vector calculation, intended for electric-drive oriented hybrid electric vehicle, which has the advantages of SVM and clean harmonic-spectrum and the efficiency of RPWM and DPWM, respectively.

Total Flux Minimization Control for Integrated Inter-Phase Inductors in Paralleled, Interleaved Three-Phase Two-Level Voltage-Source Converters With Discontinuous Space-Vector Modulation

This paper presents a control method to minimize the total flux in the integrated interphase inductors of paralleled, interleaved three-phase two-level voltage-source converters (VSCs) using discontinuous space vector modulation (DPWM). Specifically, different inductor structures used to limit circulating currents are introduced and compared, and the structure and flux distribution of two types of integrated interphase inductors are analyzed in detail. Based on that, a control method to minimize the total flux in such integrated interphase inductor is proposed for a parallel converter system using interleaved DPWM. The method eliminates the circulating currents during the peak range of the converter output currents; hence the total flux is minimized and only determined by the system load requirements. This control method introduces very limited additional switching actions, which do not significantly affect the converter electrothermal design. Experimental results verify the analysis and the feasibility of the proposed control method.

Control of Parallel Multiple Converters for Direct-Drive Permanent-Magnet Wind Power Generation Systems

This paper proposes control strategies for megawatt-level direct-drive wind generation systems based on permanent magnet synchronous generators. In the paper, a circulating current model is derived and analyzed. The parallel-operation controllers are designed to restrain reactive power circulation and beat-frequency circulation currents caused by discontinuous space-vector modulation. The control schemes do not change the configurations of the system consisting of parallel multiple converters. They are easy to implement for modular designs and large impedance required to equalize the current sharing is not needed. To increase the system reliability, a robust adaptive sliding observer is designed to sense the rotor position of the wind power generator. The experimental results proved the effectiveness of the control strategies.

Effects of space vector modulation strategy on hybrid (Si-SiC) inverter losses

Effects of space vector modulation strategy on hybrid (Si-SiC) inverter lossesThis work summarizes efficiency measurement results of a full bridge, 3 phase inverter composed of state-of-the-art Si IGBT transistors and Si or SiC diodes. Different (symmetrical and discontinuous) space vector modulation strategies were chosen in order to examine their influence (together with modulation frequency) on inverter losses. Induction machine was used as load, different load points were examined. Results clearly show, that proper modulation strategy, minimizing the switching losses of semiconductor switches, can increase the overall output efficiency at about 1% in case of both silicon and hybrid constructions. The drawback of DPWM approach is connected with the decreased quality of inverter output current. Hybrid technology can also improve the output efficiency at about 1% when compared to traditional constructions, but only in case of elevated switching frequencies. At low frequencies (below 10 kHz) modern semi-conductors offer comparable results at much lower device costs.

Common-Mode Circulating Current Control of Paralleled Interleaved Three-Phase Two-Level Voltage-Source Converters With Discontinuous Space-Vector Modulation

This paper presents a control method to limit the common-mode (CM) circulating current between paralleled three-phase two-level voltage-source converters (VSCs) with discontinuous space-vector pulsewidth modulation (DPWM) and interleaved switching cycles. This CM circulating current can be separated into two separate components based on their frequency; the high-frequency component, close to the switching frequency, can be effectively limited by means of passive components; the low-frequency component, close to the fundamental frequency, embodies the jumping CM circulating current observed in parallel VSCs. This is the main reason why it is usually recommended not to implement discontinuous and interleaving PWM together. The origin of this low-frequency circulating current is analyzed in detail, and based on this, a method to eliminate its presence is proposed by impeding the simultaneous use of different zero vectors between the converters. This control method only requires six additional switching actions per line cycle, presenting a minimum impact on the converter thermal design. The analysis and the feasibility of the control method are verified by simulation and experimental results.

Evaluation of a Multilevel Cascaded-Type Dynamic Voltage Restorer Employing Discontinuous Space Vector Modulation

In this paper, the application of a cascaded multilevel inverter as a dynamic voltage restorer (DVR) is investigated. Two discontinuous multilevel space vector modulation (SVM) techniques are implemented for DVR control and are shown to reduce inverter switching losses while maintaining virtually the same harmonic performance as the conventional multilevel SVM at a high number of levels. This paper also presents a mathematical relationship for computing the distortion at the point of common coupling (PCC) as a function of the distortion of the DVR. This enables the selection of the number of levels required for a certain application. An extended sag duration support compared to the two-level DVR is another advantage of the DVR with a cascaded multilevel inverter. The common-mode voltage (CMV) at the PCC has been evaluated for the three SVM techniques (the conventional multilevel SVM and the two discontinuous SVM), presenting a lower CMV for the second discontinuous SVM. A design example is presented for an 11-kV 5-MVA DVR multilevel cascaded inverter for up to 17 levels, employing the conventional multilevel SVM and the two discontinuous SVM techniques.

Interleaved PWM with discontinuous space-vector modulation

This paper describes the effect of interleaved discontinuous space-vector modulation (SVM) in paralleled three-phase systems using three-phase pulsewidth modulation (PWM) rectifiers as an example. At the discontinuous point of the SVM, the phase shift between the switching signals of the paralleled modules generates a zero-sequence excitation to the system. Because the conventional control in a balanced three-phase system with only dq channels cannot reject this disturbance, a beat-frequency circulating current will develop on the zero axis. Based on this observation, a SVM without using zero vectors is used to eliminate the cause of pure zero-sequence current for parallel operation. Using this SVM, the circulating current is observable in dq channels. It can be suppressed dynamically by strong current loops of power-factor-correction (PFC) circuits. The concept is verified experimentally on a breadboard system.