Improved Space Vector Modulation Research Articles

A Novel Current Harmonic Suppression Method for HSPMSG Based on the Hybrid Rectifier

This paper presents a novel current harmonic suppression scheme for the high-speed permanent magnet synchronous generator (HSPMSG). Aiming to effectively reduce current harmonics for the HSPMSG, this paper focuses on two areas: improving the rectifier power topology and developing a current loop controller. Firstly, a hybrid rectifier based on Silicon-Carbide/Silicon (SiC/Si) is designed to equivalently increase the switching frequency of the HSPMSG to address the problem of low carrier frequency ratio. In addition, an improved space-vector-modulation (ISVM) strategy based on the hybrid rectifier is proposed. However, the harmonic distortion caused by rectifier nonlinearity will deteriorate as the switching frequency is increased. For further suppressing harmonic disturbances caused by rectifier nonlinearity, a resonant-super-twisting (R-STW) controller is designed by combining the resonant controller and the super-twisting (STW) controller in this paper. The stability of the STW is demonstrated by Lyapunov stability theory and the resonant controller is discretized. Finally, a number of simulations and experiments based on a high-speed permanent magnet synchronous generator are carried out to verify the effectiveness of the control method proposed in this paper.

Harmonic Current Control of OW-PMSM for Low-Voltage Traction by Nonlinear Disturbance Rejection With Improved Modulation Scheme

The open-winding permanent magnet synchronous motor (OW-PMSM) has been developed, mostly potential for low-voltage traction in electric vehicles. Yet, both the disturbance from vehicle system under driving and the motor with low-reactance (LR) feature expose the limits of traditional controllers that are prone to great current harmonics. Therefore, the current control for LR OW-PMSM becomes challenging. The main objective of this research is to provide a current harmonic control strategy for LR OW-PMSM by the nonlinear lumped disturbance observer (NLDO) combined with improved space vector modulation (SVM) scheme. The existence of nonlinear, unknown, unmodeled factors has been confirmed by current measurement and harmonic analysis in full operation range, and thus is considered in proposed controllers. The NLDO is designed for all the three axes under the <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">dq</i> 0 frame. The SVM algorithm is adjusted to two switching patterns in order to get widened linear voltage modulation range. In addition, in the 3-D voltage space is the possible modulation area investigated. Ultimately, the target LR OW-PMSM has been designed, prototyped, and tested. The proposed NLDO, juxtaposed with ordinary PI and deadbeat controllers, reduces current harmonics on both the motor and inverter sides, possesses high robustness, and is practical for LR motors, according to experimental results.

Design and Xilinx Virtex-field-programmable gate array for hardware in the loop of sensorless second-order sliding mode control and model reference adaptive system–sliding mode observer for direct torque control of induction motor drive

This article aims first to propose an improved space vector modulation–direct torque control in order to enhance the induction motor performance using: (1) a super-twisting controller and (2) a novel model reference adaptive system based on a sliding mode observer. Second, due to the complexity of the suggested control algorithm, this article deals also with a hardware implementation on a field-programmable gate array board. Indeed, the field-programmable gate array is mainly chosen to reduce the execution time, thanks to its parallel processing which significantly improves the quality of the control system by reducing the sampling period, and consequently the delays in the control loop. Besides, the super-twisting controller is proposed to enhance the speed regulation loop which is a second-order sliding mode control technique that uses a continuous control law to prevent the chattering phenomenon induced by the first-order sliding mode control technique. Moreover, the high performance control requires information about the rotor speed which can be obtained by a sensor. Generally, the use of the speed sensor increases the system cost and size, and reduces its system reliability. Therefore, a combination between a model reference adaptive system observer and a sliding mode observer is suggested for speed estimation and overcoming the sensitivity of the classical model reference adaptive system observer against uncertainties and stator resistance variations. The performance of the proposed space vector modulation--direct torque control--super-twisting controller with the model reference adaptive system--sliding mode observer algorithm of an induction motor is verified through simulation, hardware co-simulation and experimental validation utilizing a field-programmable gate array Virtex-5-ML507 board. The performance of the suggested sensorless control method is compared also with other recent published schemes.

Improved space vector modulation algorithm of 5-level three-phase z-source based cascaded inverter

The integration of a Z-source network with a 5-Level three-phase inverter based cascaded to provide voltage step-up function is proposed in this paper. The system is controlling by an improved space vector modulation (SVM) the implantation of algorithm and innovative virtual automated solutions can be considered, very fast and very simple. The main objective of the proposed system is to achieve an output voltage twice the applied input voltage, and to eliminate the largest amount of excess harmonic. This proposed model is characterized by the ease of boosting the output voltage twice the input voltage, depending on the characteristics of the Z-source network without the need for a DC-DC rectifier. Furthermore, the proposed algorithm for this system is characterized by improving the output voltage and eliminating a large number of harmonics while greatly simplifying the calculations compared to its conventional SVM. This makes the proposed system and its algorithm an interesting alternative to classical systems and algorithms. The simulation was processed using MATLAB/Simulink. The results obtained prove and verify the effectiveness of the proposed system. From the results, of the output current total harmonic distortion (THD), it was reduced to 1.05% which is very low compared to the other algorithms in the literature.

A Novel Overlap-Time Effect Suppression for Current Source Converter

In order to ensure the continuity of the DC-side inductor current, current source converter (CSC) needs to add overlap time between the drive signals, but the overlap time will introduce low order (mainly fifth and seventh) harmonics to the grid current, which seriously degrade the harmonic performance of grid current. At present, some research has been conducted to theoretically analyze and mitigate the overlap-time effect in CSC, including the use of positive-slope sawtooth wave or negative-slope sawtooth wave as the carrier wave, turning on the switch early or delaying turning it off, and eliminating the deviation effect by compensation algorithms, etc. However, existing overlap-time suppression schemes takes the nearest three vector synthesis reference vector scheme as the object of study, in other words, the effect of overlap time on the non-nearest three-vector synthesis reference vector scheme has not been considered. To address these issues, this paper takes the non-nearest three-vector synthesis reference vector scheme as the object of study to analyze the effect of overlap time on the driving signal and establishes the quantitative relationship between the current harmonics introduced in the grid current and overlap time through Fourier decomposition. Then, the design process of the proposed improved space vector modulation by constructing freewheeling channels to replace the overlap time is presented in detail. Finally, simulation and experimental results verify that the overlap-time suppression effect of the proposed scheme is about 100%.

An enhanced control strategy based imaginary swapping instant for induction motor drives

&lt;p&gt;The main aim of this paper is to present a novel control approach of an induction machine (IM) using an improved space vector modulation based direct torque control (SVM-DTC) on the basis of imaginary swapping instant technique. The improved control strategy is presented to surmount the drawbacks of the classical direct torque control (DTC) and to enhance the dynamic performance of the induction motor. This method requires neither angle identification nor sector determination; the imaginary swapping instant vector is used to fix the effective period in which the power is transferred to the IM. Both the classical DTC method and the suggested adaptive DTC techniques have been carried out in MATLAB/SimulinkTM. Simulation results shows the effectiveness of the enhanced control strategy and demonstrate that torque and flux ripples are massively diminished compared to the conventional DTC (CDTC) which gives a better performance. Finally, the system will also be tested for its robustness against variations in the IM parameters.&lt;/p&gt;

Direct Torque Control of Induction Motors using Speed Estimator

A new approach to Direct torque control of induction motor is presented in this paper.A ripple in torque of the induction motor is a very common problem and it is to bereduced. In conventionalDTCmethodstheinverter has constant switching frequency and is dramatically increased. In proposed DTC based induction motor drive, an improved space vector modulation technique is applied to inverter control, therefore reducingthe torque/speed ripples. As the proposed approach does not include any dead beat control or hysteresis control, it automatically reduces computational calculations. Simulation results of proposed DTC based induction motor drive technique is validated using MATLAB/SIMULINK environment

An Improved Space Vector Modulation With Capacitor Voltage Control for T-Type Five-Level Nested Neutral Point Piloted Converter

In this article, a novel control method is proposed to control capacitor voltages for the T-type five-level nested neutral point piloted (5L-NNPP) converter. Due to the diversity of switching states for NNPP topology, there is no guarantee that the redundant vectors have the opposite effect on the dc bus neutral voltage. Meanwhile, the voltage balance controls between the dc bus neutral voltage and three-phase flying capacitor voltage are coupled and interacted with each other in the 5L-NNPP converter. This has severe voltage balance problems with the conventional space vector modulation (SVM), which limits its wide applications, especially under low output frequency. To solve the voltage balance problems, an improved SVM and voltage balance control (VBC) function are proposed to balance dc bus capacitor voltages and flying capacitor voltages, which realizes decoupling of voltage control. The switching states, switching principle, and dwell time calculation are developed, and the flowchart of VBC function is also elaborated on. The performance of the proposed improved SVM is investigated and compared with conventional SVM. The effectiveness and validity of the improved SVM with a VBC function is verified by simulation and experimental results of the 5L-NNPP converter.

Open-Current Vector Based SVM Strategy of Sparse Matrix Converter for Common-Mode Voltage Reduction

The concept of open-current vector for sparse matrix converter is put forward along with its application constraints in this article. Based on the open-current vector, an improved space vector modulation (SVM) strategy is proposed to reduce the peak magnitude of common-mode voltage (CMV) by 42.3% without sacrificing the performance of input and output waveforms and the voltage transfer ratio (VTR). First, the application constraints and common-mode equivalent circuit of the open-current vector in the rectifier stage of the sparse matrix converter are analyzed. After that, in accordance with the principle of minimum switching action and two adjacent active vector synthesis, the improved SVM strategy used a suitable open-current vector instead of the active-current vector in the rectifier stage when the zero-voltage vector is used in the inverter stage, which contributes to CMV reduction. The improved SVM strategy not only reduces the peak magnitude of the CMV, but also ensures that the performance of input and output waveforms and the VTR are the same with those of traditional SVM. Finally, the effectiveness of the improved SVM strategy is verified by simulation and experiments.

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.

Optimal Overlap-Time Distribution of Space Vector Modulation for Current-Source Rectifier

This article proposes an improved space vector modulation (SVM) for the current-source rectifier (CSR). Due to the overlap time during commutations of power switches, the pulsewidth-modulation (PWM) currents of CSR may suffer from a number of low-order (mainly fifth and seventh) harmonics, which seriously degrade the harmonic performance of currents and voltages on the grid side. Especially, the overlap-time effect becomes an important issue when the increased switching frequency is applied to CSR. To mitigate these low-order harmonics of the PWM converter currents resulted from the overlap-time effect, the relationship between the overlap time and the low-order harmonics in PWM currents and grid currents are analyzed at first. Then, the design process of the LC filter and the proposed SVM with optimal overlap-time distribution is presented in details. Finally, experimental results are conducted on a low power laboratory prototype to verify the effectiveness of the proposed method.

Improved Space Vector Modulation for Neutral-Point Balancing Control in Hybrid-Switch-Based T-Type Neutral-Point-Clamped Inverters With Loss and Common-Mode Voltage Reduction

Improved Space Vector Modulation for Neutral-Point Balancing Control in Hybrid-Switch-Based T-Type Neutral-Point-Clamped Inverters With Loss and Common-Mode Voltage Reduction

Improved Space Vector Modulation Technique for Neutral-Point Voltage Oscillation and Common-Mode Voltage Reduction in Three-Level Inverter

Three-level inverter has an outstanding performance and is more advantageous in the switching vector selection than two-level inverter. In particular, the neutral-point voltage unbalance and common-mode voltage (CMV) reduction of three-level inverter should be carefully regulated for the appropriate operation, both of which, however, are mutually coupled resulting that the conventional space vector modulation (SVM) scheme cannot deal with them properly. To overcome this limitation, this paper proposes an improved space vector modulation (ISVM) technique to reduce the CMV and neutral-point voltage imbalance simultaneously. The generating mechanism of neutral-point voltage oscillation is derived. Based on the analysis, the proposed ISVM method adopts four voltage vectors (large, medium, small, and zero vectors) with adjusted dwell times to eliminate the ac unbalance of the neutral-point voltage. Considering the occurrence of neutral-point voltage disturbances, the dc neutral-point unbalance voltage is controlled by selecting the P-type or N-type small vector and adjusting the dwell times of small vectors for neutral-point voltage recovery. In addition, a novel switching sequence arrangement method with the minimal number of switches transition in one switching cycles and between switching cycles is proposed to reduce the total switching loss. Theoretical analysis and verification results show that the proposed ISVM scheme can reduce the magnitude of CMV to half of value using the conventional SVM, and an accurate control of ac and dc unbalanced neutral-point voltage can be obtained.

A Three-Phase Transformerless T-Type- NPC-MLI for Grid Connected PV Systems with Common-Mode Leakage Current Mitigation

DC to AC inverters are the well-known and improved in various kinds photovoltaic (PV) and gird tied systems. However, these inverters are require interfacing transformers to be synchronized with the grid-connected system. Therefore, the system is bulky and not economy. The transformerless inverter (TLI) topologies and its grid interface techniques are increasingly engrossed for the benefit of high efficiency, reliability, and low cost. The main concern in the TL inverters is common mode voltage (CMV), which causes the switching-frequency leakage current, grid interface concerns and exaggerates the EMI problems. The single-phase inverter two-level topologies are well developed with additional switches and components for eliminating the CMV. Multilevel inverters (MLIs) based grid connected transformerless inverter topology is being researched to avail additional benefits from MLI, even through that are trust topologies presented in the literature. With the above aim, this paper has proposed three -phase three-level T type NP-MLI (TNP-MLI) topology with transformerless PV grid connected proficiency. The CM leakage current should handle over mitigating CMV through removing unwanted switching events in the inverter pulse width modulation (PWM). This paper is proposes PV connected T type NP-MLI interface with three-phase grid connected system with the help of improved space vector modulation (SVM) technique to mitigate the CM leakage current to overcome the above said requests on the PV tied TL grid connected system. This proposed the SVM technique to mitigate the CM leakage current by selecting only mediums, and zero vectors with suitable current control method in order to maintain the inverter current and grid interface requirements. The proposed PV tied TNP-MLI offering higher efficiency, lower breakdown voltage on the devices, smaller THD of output voltage, good reliability, and long life span. The paper also investigated the CM leakage currents envisage and behavior for the three-phase MLI through the inverter switching function, which is not discussed before. The proposed SVM on TL-TNP-MLI offers the reliable PV grid interface with very low switching-frequency leakage current (200mA) for all the PV and inverter operation conditions. The feasibility and effectiveness of the TLI and its control strategy is confirmed through the MATLAB/Simulink simulation model directly as compared with 2kW roof top PV plant connected TL-TNP-MLI experimentation, showing good accordance with theoretical investigation. The simulation and experimental results are demonstrated and presented in the good stability of steady state and dynamics performances. The proposed inverter reduces the cost of grid interface transformer, harmonics filter, and CMV suppressions choke.

An improved space vector modulation strategy for common-mode voltage reduction in matrix rectifier

Abstract The matrix rectifier modulated by the classical space vector modulation (SVM) strategy generates common-mode voltage (CMV). The high magnitude and high du/dt of the CMV causes serious problems such as motor damage, electromagnetic noise and many others. In this paper, an improved SVM strategy is proposed by replacing the zero vectors with suitable couple of active ones that substantially eliminate the CMV. Theoretical analysis proves that the proposed strategy can reduce the amplitude of the CMV to half of the original value. In addition, the quality of the input and output waveforms is not affected by extra active vectors. Simulation and experimental results demonstrate the feasibility and effectiveness of the proposed strategy are shown

Improved Space Vector Modulation for Three-to-Seven Phase Matrix Converter with Reduced Number of Switching Vectors

This paper proposes a space vector modulation (SVM) scheme for a three-to-seven-phase matrix converter (MC), feeding a variable-voltage variable-frequency multiphase drive. The main feature of the proposed technique is that it utilizes only 129 out of 2187 possible active space vectors for a successful ac-ac power conversion. Since the number of vectors is significantly reduced, the switching patterns are simplified, and the execution time of the algorithm is shortened. Despite the drastic reduction in the number of active vectors, it is found that there is no significant degradation in the performance of the MC. Furthermore, the SVM also produces balanced sinusoidal input currents with a unity power factor over a wide operational frequency range (1-110 Hz). In this paper, the theoretical analysis is supported by simulation and validated using a hardware prototype. The output voltage can reach up to 76.93% of the input voltage, which is the maximum physical limit of a three-to-seven-phase MC. In addition, it exhibits a better harmonic profile than the carrier-based modulation scheme; the total harmonic distortion for the output voltage waveform is measured to be below 5% over the entire operating frequency range.

Improved Space Vector Modulation Strategy for AC-DC Matrix Converters

In this paper, an approach to reduce the common-mode voltage and to eliminate narrow pulse for implemented AC-DC matrix converters is presented. An improved space vector modulation (SVM) strategy is developed by replacing the zero space vectors with suitable pairs of active ones. Further, while considering the commutation time, the probability of narrow pulse in the conventional and proposed SVM methods are derived and compared. The advantages of the proposed scheme include: a 50% reduction in the peak value of the common-mode voltage; improved input and output performances; a reduction in the switching loss by a reduced number of switching commutations and a simplified implementation via software. Experimental results are presented to demonstrate the correctness of the theoretical analysis, as well as the feasibility of the proposed strategy.

Research on the Amplitude Coefficient for Multilevel Matrix Converter Space Vector Modulation

This paper presents an improved space vector modulation (SVM) using amplitude coefficient on a capacitor-clamped multilevel matrix converter (MMC). The MMC utilizes a multilevel structure on a conventional matrix converter, which allows direct ac-ac power conversion without large energy store elements. This structure features, in high-voltage application, staircase out- put voltage with less voltage step, better harmonic issue, and compact design. In this paper, the MMC structure and the relative SVM is first introduced. Furthermore, the improved modulation strategy based on amplitude coefficient is employed to improve the MMC performance in terms of modulation precision. The theoretical analysis of the amplitude coefficient is discussed in detail. A comparison between the traditional SVM and the improved SVM is given to demonstrate the theoretical findings. Results from SABER simulation and experimental prototype are presented to validate the method.