Space Vector Modulation Method Research Articles

An Active Hybrid Modulation Strategy for a Si/SiC Hybrid Multilevel Converter

This paper proposes a hybrid modulation strategy for a medium-voltage hybrid seven-level (7-L) converter, which consists of a three-phase silicon (Si) IGBT-based active-neutral-point-clamped (ANPC) stage and a cascaded silicon carbide (SiC) MOSFET-based H-bridge (HB) stage in each phase. Within the framework of the proposed modulation strategy, three floating HB converters are controlled using a high-frequency three-level (3-L) space-vector-modulation (SVM), while a low-frequency modulation is applied to the ANPC converter. To regulate the DC voltages across floating capacitors, a zero-sequence voltage (ZSV) injection method is adopted. The proposed method possesses three major advantages. First, it enables the simplification from a 7-L to a 3-L SVM, which significantly reduces the computational burden. Second, with all the high-frequency switching actions assigned to SiC devices in the HB stage, the power loss of the hybrid 7-L converter is reduced. Third, the hybrid modulation together with the ZSV injection enables a wider stable operating range compared to the existing 7-L SVM method. Finally, both simulation and experimental results performed on the scale-down and the full-scale 1 MVA prototype validate the effectiveness of the proposed hybrid modulation strategy.

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.

Development of a vector control system of the semiconductor converter, which will provide a polyharmonic operating mode of a polyphase electric machine

A system for vector control of current in the circuit of a polyphase electric machine has been developed. For this, on the basis of the analysis of electromagnetic processes in a multiphase semiconductor converter of electrical energy, its discrete mathematical model was created, which takes into account the redistribution of electromagnetic energy by individual spatial harmonic components depending on the number of phases. Using this mathematical model and the scheme of injection of higher current harmonics, which provides a polyharmonic mode of operation of a semiconductor converter, a method for independent control of the spatial harmonic components of the input current of the converter has been developed. The formation in each of the phases of polyharmonic currents, conjugated in shape and phase with the voltage supplying the converter, is carried out by means of control actions in the form of voltage vectors of a semiconductor switch, the implementation of which is carried out by the method of multiphase space-vector modulation. To check the developed provisions, a simulation model of a nine-phase semiconductor converter of electrical energy with a vector control system was created. The results of the study of the model confirmed the adequacy of the developed technical solutions, the use of which will ensure the most complete realization of the own advantages of a multiphase electric machine in order to generally improve the weight, size and energy indicators of the autonomous power supply system.

Generalized Space-Vector-Modulation Method for Soft-Switching Three-Phase Inverters

Three-phase inverters are usually required to output reactive power in electric machine drives, renewable energy generation, static var generators, and other power electronic systems. Therefore, the inverter may operate within wide power factor angle range. However, the traditional zero-voltage-switching space vector modulation (ZVS-SVM) method for three-phase inverters is only applicable when power factor angle is between -π/6 and +π/6. In this article, a general ZVS-SVM method for three-phase inverter with arbitrary output is proposed. The principles for vector selection and vector sequence arrangement are discussed in detail. With only one switching operation of the auxiliary switch in each switching cycle, ZVS of all switches can be achieved. Operation stage analyses and ZVS condition of the inverter with the proposed method are introduced. In addition, the resonant parameters design considerations and loss analyses are investigated. Finally, the proposed ZVS-SVM method is verified by the experiment.

Improved Direct Model Predictive Control for Grid-Connected Power Converters

This paper proposes a computationally efficient and robust direct model predictive control (DMPC) technique with enhanced steady-state performance for power converters tied to the electric utility. The discrete space vector modulation (DSVM) method is considered in the design of the suggested DMPC, where virtual voltage vectors (VVs) besides the real ones are utilized for improving the steady-state response of the proposed controller. Furthermore, for averting the high computational burden and making the proposed control technique simple, a deadbeat (DB) function is employed for calculating the reference VV based on the required reference current. Subsequently, a discrete-time integral term is combined with this DB function to enhance the robustness of the suggested DMPC technique against variations of the model parameters. Finally, the best virtual or real VV is chosen by a certain quality function, which will be applied to the power converter in the next sample. The suggested technique is verified by simulation results and its performance is compared with the classical DMPC and voltage-oriented control (VOC).

Switching frequency reduction technique for DSVM‐based predictive torque control of induction motor

This study proposes a new strategy to decrease the switching frequency of the predictive torque control–discrete space vector modulation (PTC–DSVM) method, which is a combination of the PTC scheme and the DSVM. The principle of the PTC–DSVM method is based on selecting a sequence of voltage vectors, called virtual voltage vectors, instead of a single voltage vector and applying it to the power converter in prefixed time intervals. The proposed switching frequency reduction method operates based on appropriately arranging the voltage vectors forming the virtual voltage vector so that, on average, a maximum of one commutation per inverter switching state change is achieved. As a result of the suggested method, the average switching frequency is reduced in all operating conditions, while the performance of the proposed method remains as satisfactory as the conventional approach. The reduction of switching frequency also results in a decrease in the switching losses. The proposed method is an offline approach and selects the appropriate application order for the real voltage vectors based on the described rules, which do not impose any further computational load to the control algorithm. In order to validate the proposed method performance, the control algorithm has been implemented on a laboratory prototype.

Dc‐link capacitor voltage control for the NPC three‐level inverter with a newly MPC‐based virtual vector modulation

Dc-link capacitor voltage unbalance would affect the performance of the neutral-point clamped (NPC) three-level inverter. With the traditional virtual space vector modulation (VSVPWM) method, the dc-link capacitor voltage could be kept balance under the different modulation indexes or power factors. With the virtual medium vector being set as an adjustable one, the voltage balance could be better guaranteed no matter there might have some non-linear factors However, whether the traditional or improved VSVPWM method has a complicated trigonometric calculation, thus, a newly MPC-based virtual vector modulation has been proposed in this paper. With the 19 virtual space vectors being in roll optimisation, a nice current trajectory, dc-link capacitor voltage balance, even a relative low switch losses have been implemented. Considering that the optimised virtual space vector could not be taken as a direct output, the distribution of the basic vectors has been generated to make it being favourable for modulation. The effectiveness of this MPC-based virtual vector modulation is verified in comparisons with other methods, which can save over 67.3% execution time of the traditional SVPWM method, and over 46.6% of the improved VSVPWM way while provide a better dc-link capacitor voltage balance and output current quality.

Modulation Method for Nine-Switch Converter Based on Equivalent Mechanism Between Nine-Switch Converter and Dual Six-Switch Converters

In this article, the equivalent mechanism between nine-switch converter (NSC) and the two six-switch converters (SSCs) is explained in detail. In order to achieve the decoupling of the upper and lower ac terminals, the concept of virtual leg is proposed and the decoupling model of NSC is established based on virtual legs. In this model, the NSC is equivalent to dual constrained SSCs. Continually, the space vector modulation method of NSC is proposed based on dual constrained SSCs modulation for both common frequency and different frequency modes. In the proposed modulation method, the concept of space vector distance function (SVDF) is proposed. SVDF represents the actual switching times between any two actual working states of NSC. The closer distance between the two actual states is, the smaller the actual switching loss will be. Using the modulation method, the NSC can realize the independent control of two sets of three-phase ac voltage and achieve the same control performance as the dual SSCs. The validity of the proposed converter is verified through simulations and experiments.

Sliding mode and predictive current control strategy of the three-phase Vienna rectifier

This study involves the design and implementation of a novel double closed-loop control of the three-phase Vienna rectifier. To achieve the unit power factor operation of the rectifier and reduce the harmonic content of the grid side, the double closed-loop control strategy is proposed on the basis of the voltage control of the outer loop and the current control of the inner loop. The voltage outer loop adopts the sliding-mode variable structure control strategy based on the improved reaching law; this strategy can effectively suppress switching jitter. The current inner loop adopts an improved predictive current control strategy that combines the traditional finite control set model predictive control (FCS-MPC) with the space vector modulation method (SVPWM), such that the optimal switching state obtained by the predictive controller is modulated to generate a switching signal. Moreover, the switching frequency can be controlled by adjusting the frequency of the carrier, and the switching frequency is fixed while preserving the advantages of model prediction control. The primary advantages of the proposed double closed-loop control strategy are as follows: (1) it does not require proportional–integral controllers in the current control loops, and (2) it keeps the output voltage stable. The Vienna rectifier simulation is performed on MATLAB. Then an experimental prototype based on SiC devices is developed to verify the excellent performance of the proposed strategy in steady and transient states.

A Simple Space Vector Modulation of High-Frequency AC Linked Three-Phase-to-Single-Phase/DC Converter

High frequency (HF) ac linked converter functions well to interface between buses with different voltage types. Using a three-phase-to-single-phase matrix converter, a single-phase cyclo converter, and a HF transformer, we can compose a HF ac linked converter to interface between three-phase ac grids and single-phase ac or dc distributed generations (DGs). In this paper, a novel space vector modulation (SVM) method is proposed for such kind of converter. The proposed SVM method converts the mains three-phase ac voltage to a HF ac voltage at the primary side of transformer, and then unfolds the HF ac voltage to a single-phase ac or dc voltage at the secondary side of transformer. Without need to compute separate switching signals for the primary and secondary converters and then coordinate their operations elaborately, the proposed SVM method can be easily implemented by incorporating the HF chopping into the SVM of traditional indirect matrix converter. Therefore, no complicated duty cycle computation or elaborate switching states combination is required. Simulation and hardware-in-loop implementation demonstrate the validity of the proposed method.

A Generalized Modulation Method for Common-Mode Voltage Reduction of Dual-Input Three-Level Inverter

The dual-input three-level inverter should have the ability to operate in certain areas where the dc-links are unbalanced. This paper proposes a generalized large-medium-zero space vector modulation (GLMZ-SVM) method to obtain high-quality output currents and suppress common-mode voltage (CMV) amplitude simultaneously when the dc-links are unbalanced. In this method, a modified space voltage vector diagram (MSVVD) based on the unbalancing factor is obtained, which is highly asymmetrical compared to the space vector diagram when the dc-links are balanced. Then, a novel sector division method of MSVVD is presented by six medium vectors and six large vectors. In each sector, the large, medium, and zero vectors are used to synthesize the reference voltage vector to reduce the CMV amplitude. The duty cycles of large, medium and zero vectors are calculated based on the modified volt-second balance principle with the unbalancing factor. To further reduce harmonics and avoid switching losses between switching cycles, a symmetrical five-segment switching sequence is designed. Comparisons with conventional methods show that the CMV amplitude of the proposed method is reduced by half and the high-quality output currents are obtained. Both simulation and experimental results validate the correctness of the theoretical analyses and the effectiveness of the proposed scheme.

MULTI-LEVEL SVM FOR SIX-PHASE MULTI-LEVEL INVERTERS TO DRIVE DUAL STATOR INDUCTION MACHINE

This article proposes a new six-phase multi-level space vector modulation (SVM) method to control a six-phase induction machine (SPIM) driven by a multi-level separate direct current (DC) source (SDCS) inverter.

Input Power Factor Compensation Strategy for Zero CMV-SVM Method in Matrix Converters

The space vector modulation (SVM) method using only rotating vectors is very effective to suppress the common-mode voltage (CMV) for matrix converters (MCs). However, the effect of the input filter on the input power factor (IPF) has not been fully investigated when using this method. This study investigated the effect of the input filter on the displacement angle and proposes an IPF compensation strategy for the zero CMV-SVM method in MCs. The proposed strategy analyzes the duty cycles of rotating vectors under the IPF-compensation condition. Through this analysis, the proposed strategy adjusts the zero vector by using a set of three counterclockwise-rotating vectors or three clockwise-rotating vectors to make all the duty cycles non-negative, ensuring that the zero CMV-SVM method can be applied to compensate the IPF for the MCs. This study also determines the condition to achieve unity IPF for the main power source and the maximum allowable IPF if the above condition is not met. Finally, experimental results are provided to validate the theoretical study.

Model Predictive Torque Control With SVM for Five-Phase PMSM Under Open-Circuit Fault Condition

This article proposes a novel model predictive torque control combined with space vector modulation (SVM) to enhance the fault-tolerant performance of a five-phase permanent magnet synchronous motor under open circuit fault. Inherited the merits of MPC and SVM, a joint control of different subspaces and enhancement of steady-state performance can be achieved by the proposed strategy. For the harmonic regulation, the <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">x–y</i> currents are predicted and restricted together with the torque and the stator flux-linkage. The SVM method is implemented in terms of the voltage vector selection and synthesis. The nonzero switching states, which generate a larger voltage vector in the <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">α–β</i> subspace, are selected as the candidate states to suppress the harmonic voltage. During the vector synthesis process, two arbitrary voltage vectors in the quadrant where the desired voltage vector locates are considered as the active voltages. Consequently, the best vector synthesis and dwell time are obtained by optimizing the cost function. The effectiveness of the proposed method has been validated by comparative experiments.

A Simple Multilevel Space Vector Modulation Technique and MATLAB System Generator Built FPGA Implementation for Three-Level Neutral-Point Clamped Inverter

The pulse width modulation (PWM) is an important segment in power electronic inverters and multilevel inverters (MLIs) design. The space vector modulation (SVM) methods own distinct advantages over other PWM methods. However, MLI SVM has involved more mathematics in their executions. Hence, the digital signal processors (DSPs) or field programmable gate arrays (FPGAs) based digital implementations are highly preferred for MLI SVM realizations, which require exceptional properties. The conventional MLI SVMs use complex mathematical functions to solve their internal functions to identify the space vector diagram (SVD) sub-triangle and over modulation boundary switching on-times. Particularly these are the changes in the position of reference vector with respect to their sub-triangle positions involving higher mathematical functions. This paper proposes a simplified three-level MLI SVM that reduces the sub-triangle and over modulation switching on-time calculations with reduced mathematical functions. The proposed MLI SVM is derived based on two-level SVM without changing the reference vector position, unlike the traditional approaches. This helps in extending the SVM for any n-level inverter with additional LUTs. The detailed theoretical study, MATLAB-Simulink system generator simulations and Xilinx FPGA family SPARTAN-III-3A based experimental implementations are done with three-level neutral point MLI fed induction motor drive. The theoretical design, analysis, and experimentation results validate the advantages of the proposed PWM design and its implementation. In addition, the proposed implementation is executed from the MATLAB Xilinx system generator directly into target FPGA, which makes it faithful, efficient and minimizes the time spent.

A Hybrid Space-Vector Modulation Method for Harmonics and Current Ripple Reduction of Interleaved Vienna Rectifier

Input current around zero-crossing point is distorted and the reduction of current ripple is limited when applying space-vector modulation (SVM) to the interleaved Vienna rectifier. In this article, a hybrid SVM method for two- channel interleaved Vienna rectifier is developed to reduce the harmonics distortion and current ripple. The topology of two-channel interleaved Vienna rectifier is introduced. The current distortion around the zero-crossing point and the ripple characteristics around the peak of the current with SVM are analyzed. Then, a zero-crossing clamped method is used to eliminate the current distortion in the sectors around the zero-crossing point. To reduce the current ripple, the phase-shifted angle of the carriers between two channels is modified in the sectors around the peak of the current. Furthermore, the realization of the proposed hybrid SVM method is presented in details. With the proposed hybrid SVM method, the current distortion is attenuated and the current ripple amplitude is reduced obviously without increasing the switching frequency. Finally, the performance of the proposed method is compared with the classical SVM methods in a two-channel interleaved Vienna rectifier prototype.

Two-Layer Pulsewidth Modulation Strategy for Common-Mode Voltage and Current Harmonic Distortion Reduction in Vienna Rectifier

Vienna rectifier, which is a nongenerative-boost-type rectifier, is widely used in industrial applications, such as wind turbine systems. However, the Vienna rectifier will face the challenge of reducing common-mode voltage (CMV), maintaining the sinusoidal input currents, and balancing neutral-point (NP) voltage in practice. As these issues are mutually coupled, the conventional space vector modulation (SVM) and various types of enhanced schemes cannot solve these problems properly, especially under nonunity power factor operation. To overcome these limitations, a two-layer pulsewidth modulation scheme through vector selection is developed. In the first layer of the proposed strategy, the NP voltage oscillations are mitigated by adjusting the switching sequence and dwell time of large, medium, small, and zero vectors with reduced CMV as the same in large, medium, and zero vector modulation. In the second layer of the proposed strategy, the switching states are reselected, and the dwell times are real time adjusted to eliminate the distortions in input currents. Through the aforementioned two-layer control method, CMV reduction, input current distortion elimination, and NP voltage balancing in Vienna rectifier can be realized simultaneously. The correctness and effectiveness of the proposed SVM method are verified by the experiment.

Novel space vector-based control scheme with dc-link voltage balancing capability for 10 switch converter in bipolar hybrid microgrid

Abstract Bipolar hybrid microgrid application is enhancing in power systems since this type of microgrid owns a DC and AC bus simultaneously, feeds local loads with local resources, and presents two dc voltage levels to users and resources. Interlinking converter (ILC) is the most important part of the microgrid structure due to its essential responsibilities in various applications. In this paper, a 10 switch converter is presented as an ILC for bipolar hybrid microgrid that advantages from both two and three-level converters’ benefits simultaneously, plus it is applicable to a wide variety of power ranges. This paper presents a novel space vector modulation (SVM) for 10 switch converter in order to reduce total harmonic distortion (THD) and increase the dc-link voltage utilization in comparison to prior carrier-based modulation methods. Also, a simplified, full-scale dc-link voltage balancing strategy is proposed for this converter. The performance of existing dc-link voltage balancing strategies for carrier-based modulation method which are an extension to the general control structure of a grid-tied ILC is compared to the method presented in this paper that shows the superiority of the proposed robust full-scale balancing strategy and the proposed SVM method. Moreover, the structure of grid-tied ILCs is upgraded to eliminate low order harmonics.

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.