Three-leg Voltage Source Inverter Research Articles

Three-Phase Inverter with Direct Torque Control for a Brushless DC Motor

This paper presents the implementation of a three-leg voltage source inverter fed by a brushless DC motor. The open-loop speed control with direct torque is employed in this motor. The rotation of the motor is controlled by using an optimal voltage vector which is related to the calculation of stator flux and electromechanical torque. The experimental results show that this system has greater capability to reduce spike and ripple on the voltage, current, stator flux, and electromechanical torque than the conventional speed controller which feeds the voltage vector from the hall-effect sensors.

Dynamic Voltage Restorer Integrated with Photovoltaic-Thermoelectric Generator for Voltage Disturbances Compensation and Energy Saving in Three-Phase System

The dynamic voltage restorer (DVR) combined with a photovoltaic–thermoelectric generator (PV-TEG) system is proposed for voltage disturbance compensation in the three-phase four-wire distribution system. The PV-TEG hybrid energy source is used in the DVR system to improve the system ability for deep and long-period power quality disturbance compensation. In addition, the DVR will save grid energy consumption when the hybrid PV-TEG module generates sufficient power to meet the load demand. An enhanced variable factor adaptive fuzzy logic controller (VFAFLC)-based maximum power point tracking (MPPT) control scheme is proposed to extract the maximum possible power from the PV module. Since the PV and TEG combine a hybrid energy source for generating power, the DVR can work efficiently for the voltage sag/swell, outage compensation, and energy conservation mode with minimum energy storage facilities. The in-phase compensation method and the three-leg voltage source inverter (VSI) circuit are chosen in the present system for better voltage and/or power compensation. To confirm the effectiveness of the proposed hybrid PV-TEG integrated DVR system, a simulation-based investigation is carried out with four different operational modes with MATLAB software. The study results confirm that the proposed DVR system can compensate power quality disturbances of the three-phase load with less total harmonics distortion (THD) and will also work efficiently under energy conservation mode to save grid energy consumption. Moreover, the proposed VFAFLC-based control technique performs better to achieve the maximum power point (MPP) quickly and accurately, thereby improving the efficiency of the hybrid energy module.

Non-independent speed control for dual-PMSM drives fed by a single three-leg VSI

<span>The objective of this article is to analyze the performances of Non-Independent Speed Control of Dual-PMSM (Permanent Magnet Synchronize Motor) Drives by a single Three-Leg Voltage Source Inverter (VSI) using control of Mean and Differential Torque technique. In general, there are two types of control strategies for Dual-Motor drives. One is Master-Slave technique and another one is Mean Control technique. For mean control technique, this study chooses mean and differential approach for the motors parameters and averaging the voltage space vector. The advantages of Dual-Motor drives fed by a single inverter topology are, it can reduce size and cost compared to the Dual-motor drives fed by individual inverter, either in industrial or in traction applications. However, by using a single three-phase inverter, the topology only restricted for the same operating conditions which are at the same speed, same parameters and same direction. The dual-motors are dependent (non-independent) on the other motor. It is can only be tested on different load operation. The analysis is focuses on speed and load variation for Dual-PMSM drives considering the forward and reverse operations of the motor. This simulation model is modelled using MATLAB-Simulink.</span>

Dual-Level Located Feedforward Control for Five-Leg Two-Mover Permanent-Magnet Linear Motor Traction Systems

Based on the model predictive current control (MPCC), a dual-level located feedforward control (DLFC) is proposed for the five-leg dual-mover primary permanent-magnet linear motor traction system, in which, two three-phase movers are fed by one five-leg voltage-source inverter (VSI). In the proposed DLFC, the studied traction system is divided into dual-level subsystems, including mover level and system level. In the mover level, it is assumed that one mover is fed by one three-leg VSI. The reference synchronous currents are replaced by the reference static voltages, and the model current predictions are eliminated by the discrete mover voltage vectors (MVVs). Furthermore, the global optimal MVVs are determined by the mover-level geometrical location. If the implementation conflicts between two global optimal MVVs, two local optimal MVVs will be determined by the system-level geometrical location to replace one former global optimal MVV. Compared with MPCC, the computation burden of DLFC can be significantly reduced. If both control methods use the same sampling period, they have the same performances. On the other hand, DLFC can use shorter sampling period, and it can perform better than MPCC. All the theoretical analyses are verified by simulation and experimental results.

Sensorless Speed Vector Control Based on MRAS of Asymmetrical Two-Phase Induction Motor

This paper presents the sensorless speed vector control of an asymmetrical two-phase induction motor based on model reference adaptive system (MRAS). A three-leg voltage source inverter with carrier based space vector pulse width modulation (SVPWM) is used to offer unbalanced two-phase voltages for eliminating electromagnetic torque pulsaions. In order to perform rotor field orientation control the asymmetrical two-phase induction motor model is treated as a balanced model. Design of controllers for speed and current loops is fully given.The proposed flux and speed estimators can satisfactorily operate in various conditions. The dynamic and steady state performances of the proposed method are verified by both simulation and experimental results. The simltaion and experimental results are in good agreement.

Performance Evaluation of Three-Leg Voltage Source Inverter Fed Unsymmetrical Two-Phase Induction Motor Based on Genetic Algorithm for Parameter Estimation

This paper presents an evaluation method of performance characteristics in terms of loss, currents and electromagnetic torque of an unsymmetrical two-phase induction motor driven by a three-leg Voltage Source Inverter (VSI) providing unbalanced two-phase voltages. The model parameters for consideration of loss and dynamic performance of the motor are estimated by using Genetic Algorithm (GA). Also, synthesized winding current waveforms based on a~superposition method and frequency domain of known harmonic voltages are investigated. The methodology of the proposed GA applied to parameter estimation of the unsymmetrical two-phase induction motor is fully given. Carrier-based unbalanced Space Vector Pulse With Modulation (SVPWM) is employed and implemented on a~low-cost microcontroller. In order to prove the validity of the model with the parameters obtained by GA, performance comparison with the experiment and the model with the parameters obtained by conventional test in laboratory has been made. The results of simulation with the proposed parameters and experiment are in good agreement.

Efficient Two-Phase Induction Motor Driven Water Pumping System Using Modified V/F Control

In recent years, the utilization of a solar energy source has increased impressively, especially in solar water pumping applications. A single-phase induction motor (SPIM) plays an essential role in such systems. Construction simplicity, high reliable operation, low cost, and low maintenance are the main advantages of the SPIM. Nevertheless, for variable speed drives the SPIM has an inherent problem of low efficiency at low speeds. In order to improve the performance of the SPIM driven water pumping system, a modified two-phase induction motor (TPIM) from an existing SPIM driven by a three-leg voltage source inverter (VSI) is introduced. This paper aims to propose a modified V/F speed control method for improving performances of the TPIM driven water pumping system. The proposed system is supplied with two-phase orthogonal voltages generated by the three-leg VSI based on a carrier-based space vector pulse width modulation strategy (CBSVPWM). The performances of the proposed driven water pumping system are investigated under various conditions for two types of CBSVPWM, namely balanced and unbalanced two-phase voltages. The obtained results are also compared with the ones for a conventional water pumping system. The experimental results verify the validity of the proposed pump system.

Direct RFOC Strategies Aimed to Symmetrical Two-Phase IM Drives: Comparison Between B4- and B6-Inverters in the Stator

This paper deals with an investigation of the steady-state and transient performance of the direct rotor flux-oriented control (RFOC) strategies implemented in symmetrical two-phase induction motors (2PIMs). Such an investigation is structured within a comparison study considering: 1) the case of a two-leg voltage source inverter (B4-inverter), and 2) the case of a three-leg voltage source inverter (B6-inverter), in the stator of the 2PIM. Following a presentation of both drives, the principle of the RFOC is briefly recalled. Then, a special attention is paid to the implementation of the direct RFOC on current-regulated B4- and B6-inverters. The control of the power switches is achieved by two two-level hysteresis regulators in the B4-inverter rather than three in the B6-inverter. Initiated by a simulation-based analysis of the selected steady-state features of both 2PIM drives under direct RFOC strategies, the comparison study is then extended to a deep experimental investigation of the steady-state operation with emphasis on the dc-link capacitor voltages, the stator line-to-line and phase voltages, stator phase currents, the rotor flux, and the electromagnetic torque. The established results reveal three major limitations of the B4-inverter fed 2PIM drive, such as: 1) unbalanced dc-link capacitor voltages at low speeds; 2) a reduced speed range due to the low level of the phase voltages; and 3) an injection of harmonics due to the $d$ – $q$ transformation. While the B6-inverter exhibits balanced dc-link capacitor voltages in the total constant torque region with higher ripple of the stator phase currents and of the electromagnetic torque, the experiment-based comparison is achieved by an investigation of the dynamic behaviors of both drives under step- and ramp-shaped reversals of the reference speed. It highlights the poor dynamic behavior of the B4-inverter fed 2PIM drive under both shapes of speed reversal.

Open-End Multilevel Six-Phase Machine Drive System With Five Three-Leg Converters

This paper proposes and investigates a multilevel ac six-phase motor drive. The system is composed of five isolated three-leg voltage source inverters feeding the open-end windings of an asymmetrical six-phase induction motor (SPIM), which is adequate to generate multilevel voltages for high-power systems with voltage rating restrictions. A simple space vector pulse-width modulation (PWM) based on three similar individual planes and its implementation by means of equivalent level-shifted PWM are presented. A space vector pattern with a high number of voltage vectors redundancies is obtained. These redundancies and the application sequence of the voltage vectors are selected to minimize the amount of changes in the switching states and to decrease the harmonic distortion of the generated voltages. The vector pattern of this optimal modulation is obtained by analyzing only one plane and applied in the same way to the three planes as if they were independent. The developed PWM techniques have low computational complexity and are suitable for low-cost hardware implementations. Simulation results are used to compare the proposed topology with a conventional configuration in terms of harmonic distortion and semiconductor losses. Experimental results demonstrate the feasibility of the proposed drive system.

Simplified Model Predictive Control Method for Three-Phase Four-Leg Voltage Source Inverters

A simplified model predictive control method is presented in this paper. This method is based on a future reference voltage vector for a three-phase four-leg voltage source inverter (VSI). Compared with the three-leg VSIs, the four-leg VSI increases the possible switching states from 8 to 16 owing to a fourth leg. Among the possible states, this should be considered in the model predictive control method for selecting an optimal state. The increased number of candidate switching states and the corresponding voltage vectors increase the calculation burden. The proposed technique can preselect 5 among the 16 possible voltage vectors produced by the three-phase four-leg voltage source inverters, based on the position of the future reference voltage vector. The discrete-time model of the future reference voltage vector is built to predict the future movement of the load currents, and its position is used to choose five preselected vectors at every sampling period. As a result, the proposed method can reduce calculation load by decreasing the candidate voltage vectors used in the cost function for the four-leg VSIs, while exhibiting the same performance as the conventional method. The effectiveness of the proposed method is demonstrated with simulation and experiment results.

Dual distribution static compensator for three‐phase four‐wire distribution system

This study proposes a dual three-leg voltage source inverter (VSI)-based distribution static compensator to compensate unbalanced and non-linear loads in three-phase four-wire distribution systems. The proposed topology uses two three-leg inverters having common dc link with single dc capacitor and an additional small rating ac capacitor connected from the negative terminal of VSI to the system neutral. The proposed scheme with associated control algorithm has capability to compensate unbalanced non-linear load and hence makes source current as balanced sinusoidal and at desired power factor. The control algorithm also ensures the proper sharing of reactive, harmonics and unbalanced powers between two VSIs and controls the grid current total harmonic distortion level even in the presence of unbalanced and distorted voltages. The performance of the proposed scheme has been verified using simulation and experimental studies under different voltage conditions and detailed results are presented.

Three‐leg inverter‐based distribution static compensator topology for compensating unbalanced and non‐linear loads

This study proposes a new three-leg voltage source inverter (VSI)-based distribution static compensator (DSTATCOM) topology to compensate unbalanced and non-linear loads in low-voltage three-phase four-wire distribution systems. The proposed topology uses a three-leg VSI with a single DC storage capacitor. This scheme has an additional small AC capacitor which is connected between negative DC bus to the system neutral. As the proposed topology uses a single DC-link capacitor, the DC voltage balancing issues associated with the popular split capacitor neutral clamped VSI topology is avoided. Moreover, the topology is able to compensate neutral current without using four-leg inverter topology. Analysis and modelling of the proposed topology is explained in detail. Simulation studies are carried out to verify the performance of the proposed scheme and results are presented. The performance of the new topology has been compared with conventional three-leg two level split capacitor VSI-based DSTATCOM topology. Results are also experimentally verified on a laboratory prototype of DSTATCOM.

Discontinuous SVPWM Techniques of Three-Leg VSI-Fed Balanced Two-Phase Loads for Reduced Switching Losses and Current Ripple

In this paper, various types of discontinuous space vector pulse-width modulation techniques for a three-leg voltage source inverter supplying balanced two-phase loads are proposed. The main objectives of the paper are to analyze switching loss characteristics associated with semiconductor devices and to reduce output current ripple by dealing with various types of zero space vector time in each switching sequence. Capabilities of reductions in switching losses and current ripple for both balanced and unbalanced output phase voltages at high modulation index and load power factor angle of 30° lagging are focused. The validity of the proposed techniques is verified by simulation and experimental results in terms of voltage spectrum, current waveforms, reductions in switching losses, and output current ripple at high modulation index when compared to a continuous space vector pulse-width modulation technique.

THREE-PHASE FOUR-WIRE PV-BASED SERIES HYBRID ACTIVE POWER FILTER FOR POWER QUALITY IMPROVEMENT

This paper proposes a photovoltaic (PV)-based three-phase four-wire (3P4W) series hybrid active power filter (SHAPF) it comprises of a series active power filter (SAPF) and an LC shunt passive filter. The proposed system eliminates both the current and voltage harmonics and compensates reactive power, neutral current and voltage interruption. A SAPF demands a source of energy for compensating the voltage sag/swell. This system introduces a new topology for SHAPF utilizes the PV with DC–DC boost converter as a source of DC power for SAPF. The compensation current reference evaluation is based on the twin formulation of the vectorial theory of electrical power theorem with fuzzy logic controller (FLC). The PV array/battery managed DC–DC boost converter is employed to step up the voltage to meet the DC bus voltage requirement of the three-leg voltage source inverter (VSI). The foremost benefit of the proposed system is that, it will provide uninterrupted compensation for the whole day. This system utilizes the renewable energy accordingly saves the energy and shares the load during the solar irradiation available. The simulation and experimental studies are carried out to validate the effectiveness of the proposed PV-SHAPF.

Performance of a Self-Excited Induction Generator With DSTATCOM-DTC Drive-Based Voltage and Frequency Controller

This paper presents the performance of a self-excited induction generator (SEIG) with a voltage and frequency controller (VFC) in a standalone microhydro power generating system. The VFC consists of a distribution static compensator (DSTATCOM) and a direct torque controlled variable frequency induction motor drive (VFIMD) operating as an electronic load controller (ELC). The DSTATCOM is an insulated-gate bipolar transistor-based three-leg voltage source inverter with a self-sustaining dc bus. The main objective of DSTATCOM is to regulate the system voltage through reactive power compensation. In addition to voltage regulation, the DSTATCOM compensates the harmonics generated by nonlinear loads as well as ELC. The ELC controls the system frequency through the active power balance. The VFIMD of the ELC drives a pump and it consumes the power in excess of consumer load power to maintain constant power generation at the SEIG terminals, which in turn regulates the system frequency. A prototype-proposed VFC is developed and tested with a variety of loads. Experimental results demonstrate that the proposed VFC can effectively control the system voltage and frequency.

Design and implementation of PV-based three-phase four-wire series hybrid active power filter for power quality improvement

This paper proposes a Photovoltaic (PV)-based three-phase four-wire Series Hybrid Active Power Filter (SHAPF), it comprises of a Series Active Power Filter (SAPF) and an LC shunt passive filter. The proposed system eliminates both the current and voltage harmonics and compensates reactive power, neutral current and voltage interruption. A SAPF demands a source of energy for compensating the voltage sag/swell. This system found a new topology for SHAPF which utilizes the PV with DC–DC boost converter as a source of DC power for the series active filter. The compensation current reference evaluation is based on the twin formulation of the vectorial theory of electrical power theorem with Fuzzy Logic Controller (FLC). The PV array/battery managed DC–DC boost converter is employed to step up the voltage to meet the DC bus voltage requirement of the three-leg Voltage Source Inverter (VSI). The foremost benefit of the proposed system is that, it will provide uninterrupted compensation for the whole day. This system utilizes the renewable energy; accordingly saves the energy and provides the uninterruptable power supply to critical/sensitive load, through the PV array/battery bank during both day time and night time. An experimental model was established and results were obtained, which indicated the capability of the proposed control scheme.

A Fault-Tolerant Permanent-Magnet Traction Module for Subway Applications

A fault-tolerant permanent-magnet traction module is proposed for subway application, which has three different operation modes: normal, isolation, and fault-tolerant mode. In normal mode, 2 three-phase permanent-magnet synchronous machines (PMSMs) are controlled by 2 three-leg voltage-source inverters (VSIs), respectively. The proposed module can output maximum torque and reach the maximum velocity. When one leg fails, the corresponding PMSM is isolated from the fault VSI and the fault subway train operates in isolation mode, in which the traction effort is reduced but the maximum velocity can be maintained under light load. However, the fault subway train will stop if the load is heavy. To avoid the stop, the fault subway train is switched into fault-tolerant mode, in which the healthy VSI and fault VSI are reconfigured to 1 five-leg VSI by a fault-tolerant bridge. Due to lower phase-phase voltage apportionment ratio, the fault-tolerant mode is not used until the velocity is decreased to half of the maximum velocity. In fault-tolerant mode, the nonadjacent selection principle is proposed to prevent the common leg from overcurrent damage. The subway train equipped with the proposed module can maintain basic operation performances if any leg fails. The performances are analyzed and the effectiveness is verified by experimental results.

A Simplified Modulation Strategy for Three-leg Voltage Source Inverter Fed Unsymmetrical Two-winding Induction Motor

This paper presents a simplified modulation strategy for the three-leg VSI fed twowinding induction motor. The strategy provides independent unbalanced voltage control for the main and auxiliary windings. This make the motor can be reversed rotation through the range of motor speed operation without limitation of voltage boost of the auxiliary winding. To study the advantages of the proposed drive, the experimental results such as voltage stresses, hysteresis band of the currents in locus, and also acoustic noise levels of the three-leg VSI are compared with those of the conventional two-leg topology. The results obviously show that the proposed technique achieves superior performance compared with the traditional scheme in case of dramatic increase of DC bus utilization, effective reduction of harmonic voltages content, and also significant enhancement of motor efficiency.

Development and Application of the Two-Phase Orthogonal Power Supply for Electromagnetic Stirring

This paper presents a three-leg voltage-source inverter topology for two-phase orthogonal power supply used for driving electromagnetic stirring. Compared with the conventional two two-leg inverter, the three-leg structure reduced the loss of power module and switching. The improved structure has an inductor in series between two-phase orthogonal power supply and the common phase of electromagnetic stirring, which make it possible to apply deadbeat current control method to two-phase orthogonal power supply, thus the controller design is simplified, the current adjustment speed is enhanced, and the current waveform is improved. A control strategy with reactive power compensation is proposed for enhancing the utilization rate of a three-phase pulsewidth modulation (PWM) rectifier in two-phase power supply, which makes it possible that the three-phase PWM rectifier not only operating rectification status but also operating reactive power compensation status. Hence, the reactive compensation cost of enterprises will be decreased. At last, simulation and industrial application results are provided to verify the effectiveness of the proposed topology and control strategy.

Composite observer‐based control algorithm for distribution static compensator in four‐wire supply system

This study presents an implementation of composite observer-based control algorithm in three-leg voltage source inverter (VSI)-based distribution static compensator (DSTATCOM) in four-wire power distribution network. This control algorithm is used for extraction of load fundamental current components of polluted load currents. These components of load currents are used for estimation of reference source currents to generate the gating pulses of insulated gate bipolar transistors used in VSI of DSTATCOM. This control algorithm is implemented for mitigation of power quality problems such as reactive power compensation, harmonic elimination and load balancing under linear/non-linear loads. The performance of DSTATCOM is found quite satisfactory for these unbalanced loads.