Four-switch Three-phase Inverters Research Articles

Fault-Tolerant Predictive Torque Control Design for Induction Motor Drives Based on Discrete Space Vector Modulation

Four-switch three-phase inverters (FSTPIs) are generally applied as fault-tolerant topologies or cost-effective topologies for induction motor (IM) drives. However, conventional predictive torque control (PTC) for FSTPI-fed IM suffers from poor steady-state performance and tedious weighting factor assignment. In this article, a PTC based on discrete space vector modulation (PTC-DSVM) for an FSTPI-fed IM drive is proposed. First, the relationship between the dc-link capacitor voltage offset (CVO) and the load current is derived, and a stator voltage compensation strategy is proposed to suppress the CVO. Meanwhile, a reference-voltage-vector-error-based cost function that combines the reference stator flux vector control, the stator voltage compensation strategy, and the deadbeat control is designed to fully eliminate the weighting factors in the cost function of the conventional PTC. In addition, a DSVM scheme is developed to increase the number of admissible voltage vectors and improve the steady-state performance of IM drives. A preselection algorithm based on the offset voltage vector and sector division is designed to reduce the number of candidate voltage vectors. Extensive simulations and experimental results with a 2.2-kW IM are demonstrated to validate the effectiveness of the proposed control strategy.

A new quasi‐Z‐source switched‐boost four‐switch three‐phase inverter with independent shoot‐through and non‐shoot‐through modulation indexes

Four-switch three-phase inverters (FSTPI) are the cost-optimised version of two-level voltage source inverters (TL-VSI), promoted for low-power/low-voltage machine drive systems. Adding impedance-based networks to the input of conventional VSIs provides both step-up and step-down features; however, the shoot-through (ST) modulation index limits the maximum attainable modulation index. Furthermore, in FSTPI, one switching leg has two series capacitors instead of power switches. Therefore, they are exposed to the voltage imbalance problem. This paper proposes a novel step-up FSTPI with independent shoot-through and non-shoot-through (NST) modulation indexes, improved boost factor, continuous input current, and high efficiency. This topology incorporates a quasi-z-source switched-boost network with independent power switches and three duty ratios that affords two active states and one shoot-through event. These features enhance the performance of this topology if compared with former FSTPI and quasi-z-source FSTPI. For evaluating the performance of this topology, simulation in MATLAB software and experiment on a prototype have been done. Simulation and experimentation results confirm the proposed topology.

Triple-Voltage-Vector Model-Free Predictive Current Control for Four-Switch Three-Phase Inverter-Fed SPMSM Based on Discrete-Space-Vector Modulation

The four-switch three-phase (FSTP) inverters are known for their cost-effective advantages and minimal switching losses. However, such inverter topology’s progress is lagging due to control constraints and requirements, including voltage vector limitations and parameter perturbations. To overcome the issue, this paper proposes a triple-voltage-vector model-free predictive current control (TVV-MFPCC) for FSTP inverter-fed surface permanent magnet synchronous motor (SPMSM) drives. The proposed TVV-MFPCC uses the principle of discrete-space-vector modulation (DSVM) to increase the voltage vector selections. Three primary voltage vectors, either the same or distinct, are linearly combined to yield the synthesized voltage vectors. A redundant voltage vector reduction scheme is also introduced to lessen calculations by optimally reducing the candidate voltage vectors to sixteen equivalent hybrid switching modes. To improve prediction accuracy, the TVV-MFPCC performs three different current readings and three current difference calculations in each sampling period. Experiments using a TMS320F28379D microcontroller are conducted to compare the performance of the proposed TVV-MFPCC against conventional MFPCC (C-MFPCC) and validate the scheme.

A new configuration for four-switch three-phase inverters based on aswitched-capacitor step-up cell for electric vehicles application

This paper proposes a new configuration for four-switch three-phase inverters based on a step-up switchedcapacitor cell, which is called switched-capacitor four-switch three-phase inverter (SCFSTPI). This converter includes eight power switches and two DC-link capacitors. Voltage step-up feature, high efficiency, integrated structure, and bidirectional power flow are the main contribution of this new configuration. A modified space vector modulation (SVM) strategy is presented to generate appropriate pulses for the converter. This modulation method also eliminates the effect of capacitors voltage imbalance problem on the inverter output voltage and current. Simulation and experimental results are presented and investigated to confirm the performance of this topology. Results validate the operation of the proposed topology and its modulation. SCFSTPI is applicable in electric vehicle (EV) drive systems and similar applications that need step-up inverters.

Reduction of Electromagnetic Interference for Permanent Magnet Synchronous Motor Using Random PWM Switching Method Based on Four-Switch Three-Phase Inverters

The four-switch three-phase inverters have become an effective approach for fault-tolerant reconstruction and operation of the six-switch three-phase topology. However, the conventional control strategy for four-switch three-phase inverters can result in a large number of current harmonic components, high electromagnetic acoustic noise, and electromagnetic interference (EMI). Therefore, this paper proposes a random switching frequency pulse width modulation method under the centrosymmetry period with a two-state Markov chain based on four-switch three-phase inverters (RSFPWM-CPTMC). In this method, random numbers are optimized and evenly distributed on both sides of the center frequency within a specific frequency bandwidth range, which significantly reduces the current harmonics and EMI at the switching frequency and frequency multiplication. The spectral characteristics generated by the random switching frequency under the centrosymmetry period with the two-state Markov chain are evaluated and compared to that provided by the traditional fixed switching frequency pulse width modulation (FSFPWM). Simulations and experiments are carried out to illustrate the superiority of the proposal.

Comment on ‘General SVPWM strategy for three different four‐switch three‐phase inverters’

A correction to an error in the equation of a paper published by the authors in the Electronics Letters entitled ‘General SVPWM strategy for three different four-switch three-phase inverters’ is given. The errors are analysed and two modification methods are proposed.

A Current Control Scheme of Brushless DC Motors Driven by Four-Switch Three-Phase Inverters

Based on the brushless dc motor driven by a four-switch three-phase inverter (FSTPI), a current control scheme is proposed to reduce the current ripple of both the normal conduction region and the commutation region. Assuming c-phase winding is connected to the middle point of a dc-link capacitance, in the normal conduction region when a-phase and b-phase windings conduct, the current of c-phase may not be zero because of c-phase back electromotive force. The proposed strategy adds two regulating vectors into each control cycle based on the traditional PWM scheme, and controls the c-phase current to be zero by controlling the working time of the regulating vectors in each control cycle. In the commutation region, the noncommutated phase or the outgoing phase switch is modulated by comparing the change rate of the incoming and outgoing phase currents to maintain the noncommutated phase current constant. Compared with the traditional current control strategy, good control effect is kept in both the normal conduction region and the commutation region by accurately controlling the working time of the voltage vectors. The proposed strategy does not need to adjust the parameters of the controller, and it is simple and easy to implement. The experimental results prove the correctness and effectiveness of the control strategy.

Low Cost and High Performance UPQC with Four-Switch Three-Phase Inverters

This paper introduces a low cost, high efficiency, high performance three-phase unified power quality conditioner (UPQC) by using four-switch three-phase inverters (FSTPIs) and an extra capacitor in the shunt active power filter (APF) side of the UPQC. In the proposed UPQC, both shunt and series APFs are developed by using FSTPIs so that the number of switching devices is reduced from twelve to eight devices. In addition, by inserting an additional capacitor in series with the shunt APF, the DC-link voltage in the proposed UPQC can also be greatly reduced. As a result, the system cost and power loss of the proposed UPQC is significantly minimized thanks to the use of a smaller number of power switches with a lower rating voltage without degrading the compensation performance of the UPQC. Design of passive components for the proposed UPQC to achieve a good performance is presented in detail. In addition, comparisons on power loss, overall system efficiency, compensation performance between the proposed UPQC and the traditional one are also determined in this paper. Simulation and experimental studies are performed to verify the validity of the proposed topology.

General SVPWM strategy for three different four‐switch three‐phase inverters

Four-switch three-phase inverters (FSTPIs) are post-fault reconfigured topologies for a two-level inverter with failure of a power switch or a leg, and space vector pulse-width modulation (SVPWM) strategies have been used to control FSTPIs. However, different faulty legs correspond to different topologies of FSTPIs which are controlled by different SVPWM strategies; therefore, three SVPWM strategies need to be prepared for three FSTPIs, respectively, which takes up lots of memory space in the controller and increases the complexity of the control strategy. To overcome these disadvantages, a general SVPWM strategy that can be used to control three FSTPIs is proposed. Experimental results have shown the validity and feasibility of the proposed strategy.

Open-Circuit Fault Diagnosis and Fault-Tolerant Control of IPMSM System

The integrated mathematical model of an interior permanent magnet synchronous machine (IPMSM) system is set up suitable for healthy state, open-circuit fault state and fault-tolerant state in this paper. An on-line open-circuit fault diagnosis method is proposed, the fault-tolerant structure is set to connect the fault phase to the middle of DC link, considering that DC link voltage is not balanced, therefore, an optimized adaptive space vector pulse width SVPWM of four-switch three-phase inverters (FSTPI) under DC-link voltage ripple condition is presented to achieve the maximum torque per ampere (MTPA) control and flux weakening control of the IPMSM system under the fault-tolerant state. Based on the abovementioned research, system simulations are implemented and simulation results are given.

Scalar PWM algorithms for four-switch three-phase inverters

Four-switch three-phase inverters (FSTPIs) have been proposed to be used in low-cost applications because of the reduced number of semiconductor devices, and space vector pulse width modulation (SVPWM) techniques have also been introduced to control FSTPIs. However, high-performance controllers are needed to implement complicated SVPWM algorithms, which limits their low-cost applications. To simplify algorithms and reduce the cost of implementation, an equivalent scalar method for SVPWM of FSTPIs is proposed. SVPWM for FSTPIs is actually a sine PWM by modulating two sine waves of 60° phase difference with a triangle wave, so such a special sine PWM can be used to control FSTPIs. The simulation and experimental results demonstrate the validity of the proposed method.

On the comparison between different space vector PWM strategies implemented in FSTPI‐fed induction motor drives

PurposeThe paper aims to discuss the comparison of the performance of four space‐vector pulse‐width modulation (SVPWM) strategies dedicated to four‐switch three‐phase inverters (FSTPI).Design/methodology/approachThe comparison is based on three comparison criteria: the total harmonic distortion, the switching loss factor, and the quality factor. The comparison is extended to the FFT of the phase currents and to the analysis of the ripples of the electromagnetic torque of the induction motor.FindingsIt has been clearly shown that the basic SVPWM strategy of the conventional six‐switch three‐phase inverter (SSTPI) offers better performance than those of the four FSTPI‐SVPWM strategies. This said, it has been found that the performance of two among the four FSTPI‐SVPWM strategies tend to those of the SSTPI‐SVPWM basic strategy, especially in high switching frequencies.Research limitations/implicationsThe work should be extended by an experimental validation of the simulation results.Practical implicationsThe established results open up crucial benefits from the point of view of cost‐effectiveness and volume‐compactness improvements of induction motor drives especially in large‐scale industries such as the automotive one where electric and hybrid propulsion systems are currently regarded as an interesting alternative to substitute or to assist the thermal propulsion systems.Originality/valueThe implementation in the FSTPI feeding an induction motor of SVPWM strategies exhibiting acceptable performance, which tend to those yielded by the SSTPI‐SVPWM basic strategy especially in high switching frequencies, is extended here.

A General PWM Strategy for Four-Switch Three-Phase Inverters

A general pulsewidth modulation (PWM) method for control of four-switch three-phase inverters is presented. The proposed vector PWM offers a simple method to select three or four vectors that effectively synthesize the desired output voltage, even in presence of voltage oscillations across the two dc-link capacitors. The method utilizes the so called space vector modulation, and includes its scalar version. Different vector combinations are compared. The effect of Wye and delta motor winding connections over the pulse width modulator is also considered. The common mode voltage generated by the four-switch three-phase converter is evaluated and compared to that provided by the standard six-switch three-phase inverter. Simulation and experimental results are presented to demonstrate the feasibility of the proposed approach

Adaptive SVM to compensate DC-link voltage ripple for four-switch three-phase voltage-source inverters

An adaptive space vector modulation (SVM) approach to compensate the DC-link voltage ripple in a B4 inverter is proposed and examined in detail. The theory, design, and performance of this pulsewidth modulation (PWM) method are presented, and the method effectiveness is demonstrated by extensive simulations and experiments. High-quality output currents are guaranteed by this approach even with substantial DC-voltage variations that might be caused by an unbalanced AC supply system, the diode rectification of the line voltages, and circulation of one output phase current through the split capacitor bank. The application of this approach to induction machine drives is also discussed. It is concluded that the DC-voltage ripple effect on the B4 inverter output can be minimized by an adaptive SVM algorithm with the advantage of improving the response of the DC-link filter and the output quality of the inverter becoming high.