Five-leg Voltage Source Inverter Research Articles

Analysis, simulation and experimental strategies of 5-phase permanent magnet motor control

This paper presents a study of control strategies for 5-phase permanent magnet synchronous motors (PMSMs) supplied by a five-leg voltage source inverter. Based on the vectorial decomposition of the multi-phase machine, fictitious machines, magnetically decoupled, allow a more adequate control. In this paper, our study focuses on the vector control of a multi-phase machine using a linear proportional-integral-derivative (PID) current regulator in the cases of sinusoidal and trapezoidal back-electromotive force (EMF) waveforms. In order to determine currents' references, two strategies are adopted. First one aims to minimize copper losses under constant torque, while the second one targets to increase torque for a given copper losses. These techniques are tested under a variable speed control strategy based on a proportional-integral (PI) regulator and experimentally validated.

Sensorless Control Method for Dual Permanent Magnet Synchronous Motors Driven by Five-Leg Voltage Source Inverter with Single Current Sensor

Sensorless Control Method for Dual Permanent Magnet Synchronous Motors Driven by Five-Leg Voltage Source Inverter with Single Current Sensor

Predictive Control Scheme With Adaptive Overmodulation for a Five-Leg VSI Driving Dual PMSMs

A dual permanent magnet synchronous motors (PMSMs) system, driven by a five-leg voltage source inverter (VSI), is considered as a feasible option for low-cost and fault tolerance application. The traditional finite-control-set model predictive control (FCS-MPC) schemes without modulator generate heavy computational burden and larger current ripple. In this article, an improved predictive control method with space vector modulation (SVM) scheme is proposed for independent control of dual-motor system. Firstly, the expected voltage vectors (VVs) of dual motors are obtained with deadbeat (DB) solution, which yields a faster dynamic response. Then, in order to reduce current ripple and eliminate candidate voltage vector traversal process, an improved modulator with adaptive overmodulation is adopted to synthesize the expected VVs. The presented SVM method solves the problem caused by the conflicting switching-states demands of common leg from dual PMSMs. Moreover, an extensive comparison is performed among the proposed control method, the existing model-based control methods, and the field-oriented control (FOC) method with proportional-integral (PI) controller. All methods are experimentally carried out in steady state and transient state. The test results indicate that the proposed control scheme with adaptive overmodulation can effectively reduce current ripple, improve voltage utilization, and preserve good dynamic performance.

Optimization-Based Duty Cycle Allocation for a Five-Leg Inverter to Drive Two Electric Motors

Driving two electric motors with a five-leg voltage source inverter (FL-VSI) by connecting one phase of each motor to a common leg possesses the advantage of reducing the number of power switches. This article proposes a duty cycle allocation method to make FL-VSI use the DC bus voltage more efficiently. In this method, the motor with a smaller common leg duty cycle requirement is set as the first priority. An additional period of duty cycle is added simultaneously to the first-priority motor's three phases to compensate for the difference of the common leg duty cycle requirement between the two motors. Thereby, the duty cycles of the three legs connecting to the first-priority motor, including the common leg, are confirmed. Then, the duty cycles of the remaining two legs connecting to the second-priority motor are allocated by solving a nonlinear optimization problem. The objective of the optimization is to make the inverter output voltage close to the voltage requirement of the second-priority motor. Experiments have been implemented, and the results verify the improvement of the proposed method.

Design and Analysis of FLC based Speed Control for a Five-Leg Inverter Fed a Dual-Induction Motor System

This paper proposes progressed speed control for a five-leg voltage source inverter (FLVSI) that drives the double three-phase induction motor framework utilized in mechanical assembling measures. The serious speed control technique comprises of two regulators: 1) the first is a slip regulator that fulfills the application necessity, i.e., to control the mechanical speed of two engines similarly paying little mind to the heap condition. 2) The second is a point regulator that fulfills the FLVSI necessity, i.e., to control the stage point distinction between the two engines for limiting the regular leg current on the grounds that the basic leg current can be twice higher than other leg's current relying upon the activity state of the double motor. Dependability investigation of the two regulators under current speed control is actualized, and the entire presentation of the serious speed control for the FLVSI-took care of double engine drive framework is appeared to recognize its attainability through the simulation results.

Improved Model Predictive Control for Multimotor System Using Reduced-Switch-Count VSI With Current Minimization

A multi-motor system supplied from the reduced-switch-count voltage source inverter (VSI) is considered in this paper. Firstly, an improved multiple vectors model predictive control (MV-MPC) scheme is proposed for driving <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">n</i> three-phase permanent magnet synchronous motors (PMSMs) by (2 <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">n</i> +1)-leg VSI. To realize independent control of multi-motor, a control period is partitioned into multi-interval, one per motor. In the proposed MV-MPC scheme, the quasi-optimal voltage vectors (VVs) are selected to replace zero VVs under the restriction of identical common leg switching states. Thus, a whole control period can be fully utilized to generate multiple active VVs for a motor. Moreover, the overcurrent in the common leg is discussed and addressed. Take the five-leg VSI as an example, the expression of overcurrent in the common leg is first derived. Next, a general overcurrent elimination method based on current phase regulation is designed for the multi-motor system operating at an identical speed. Finally, the proposed MV-MPC scheme combined with the overcurrent elimination strategy is experimentally carried out. The test results indicate that the MV-MPC method can effectively reduce current ripple and achieve a faster dynamic response. The overcurrent elimination method can minimize the overcurrent regardless of the load conditions of the motors.

Current Reconstruction for Dual PMSMs Fed by a Five-Leg Voltage Source Inverter With a Single Current Sensor

The dual-motor system driven by five-leg voltage source inverter (FL-VSI) has been widely studied as a better fault-tolerant scheme. In this paper, a phase current reconstruction strategy based on a single current sensor is proposed to realize the phase currents reconstruction of the dual permanent magnet synchronous motors (PMSM). Firstly, the FL-VSI adopts a centralization modulation strategy to realize independent control of the two motors while expanding the speed range of the motors. Then, a pulse shift strategy applied for the dual-PMSMs system driven by FL-VSI is proposed. The phase currents can be reconstructed when two motors are running in the low modulation region, sector boundary region, or the new phase current reconstruction dead zone by the proposed method. The experimental results show that the reconstructed phase currents can always be consistent with the actual phase currents, which proves the feasibility and effectiveness of the proposed method.

Priority-Based Model Predictive Control Method for Driving Dual Induction Motors Fed by Five-Leg Inverter

This article proposes a priority-based model predictive control (PMPC) method for a five-leg voltage source inverter (FLVSI) that independently drives dual three-phase induction motors (IMs). In a FLVSI operated by a MPC method, selecting an optimal future voltage vector among all 32 candidate switching states causes a high computational burden. However, by using the PMPC, low computation and current ripples can be achieved at the same time. In the PMPC method, two IMs are prioritized, and the priority of both IMs alternates every control period. For this property, the future voltage vector for the high-priority motor (HM) is selected first; that for the low-priority motor (LM) is selected next. In other words, whereas future switching states of both IMs are optimized by one cost function in the conventional MPCs, those of the HM and LM are optimized by their cost functions in PMPC. Therefore, HM and LM have eight and four candidate voltage vectors for cost minimization, respectively, which results in low computation complexity. Furthermore, current ripples are small because the HM is optimized based on all possible candidate voltage vectors, and both IMs are selected as the HM equally. The PMPC method is demonstrated by simulation and experiment results.

An Improved PWM Method of Five-Leg VSI Fed Dual-PMSM System With Duty Cycles Regulation

The five-leg voltage source inverter dual motors system has been widely studied in recent years for its advantage of fewer power switching devices. The traditional modulation method generates the voltage vectors needed by the two motors alternately in one control period, in which active voltage vectors of one motor can operate for a short time thus limit the speed ranges of the two motors. Regarding the deficiency, the relationship between the basic active voltage vectors of the two motors is futher analyzed and an improved pulsewidth modulation (PWM) method is proposed in this article, by which the duty cycles of five-phase PWM signals are modified as a whole. Under the premise that the common leg pulse width meets the requirements of the two motors in one control period, the effective time of the active voltage vectors of the two motors is tremendously expanded with no hardware added, and the speed ranges of the two motors are thus greatly expanded. When one motor runs at a relatively low speed, the speed range of the other motor can be effectively expanded with this method, compared with the traditional one. Simulations and experiments also verify the accuracy of the theoretical analysis and the feasibility of the proposed method.

Sensorless Control Method for Dual Permanent Magnet Synchronous Motors Driven by Five-Leg Voltage Source Inverter

The five-leg voltage source inverter (FL-VSI) is a fault-tolerant control scheme, which has the advantages of small size and low cost. Sensorless control has the advantages of increasing the reliability of permanent magnet synchronous motor (PMSM), reducing system cost and saving system space. Combining characteristics of the traditional modulation strategy of FL-VSI, a sensorless control method for the dual-PMSM system is proposed. The contributions of the proposed method are as follows. First, based on the traditional modulation strategy of the FL-VSI, the high-frequency (HF) square-wave voltages are injected in the half period of zero vectors action, which realizes the separation of the vector control period and the HF signals&#x2019; injection period and eliminates the filters for position information demodulation. Besides, a novel duty cycle modification strategy of FL-VSI is adopted to meet the switching constraints of the common leg. The proposed method can independently control two motors and is easy to implement in engineering with no additional external circuit. The experimental results show that the proposed method can accurately estimate the positions of the two motors and has good dynamic and steady-state performance.

Behavior of a Pentacle Connected Five-Phase IM Supplied by a Rectangular Voltage

The presented article deals with the steady-state analysis of five-phase Induction Motor (IM), which is supplied by rectangular voltage from a five-leg Voltage Source Inverter (VSI). The new proposed approach is derived from complex Fourier-series using to express inverter terminal voltages. Based on mathematically described inverter output voltages, a formula for VSI output space phasor was derived. Assuming sinusoidal motor winding distribution and on the basis of motor parameters, stator and rotor current space phasors for defined motor load were determined. Finally, the electromagnetic torque ripple waveforms for different IM operation states were investigated.

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.

Modulating functions of space vector PWM for five-leg inverter fed two single-phase induction motors

This paper proposes modulating functions of a space vector pulse width modulation (SVPWM) technique based on modified sectors for a five-leg voltage source inverter (VSI) fed dual single-phase induction motor system. The modified sectors are used to simplify the modulating functions in a general form. The modulating functions are fully derived, described and implemented on a DS1104 dSPACE controller. The obtained SVPWM signals are applied to a five-leg VSI for driving the two single-phase induction motors to demonstrate its feasibility in motor drive applications. The calculated and measured modulating signal waveforms of the proposed SVPWM are in good agreement. Experimental waveforms of the motor voltages and currents at different operating frequencies are demonstrated and found to be satisfactory.

Speed Control of Dual Induction Motor Using Five Leg Inverter

Over the past decade, research efforts have been made to decrease the number of power electronic devices needed in multi-motor drive systems in order to condense the overall complication and cost of the drive. This paper proposes speed control for a dual three-phase induction motor system driven by five-leg voltage source inverter (FL-VSI) which is used in industrial manufacturing processes. Industrial applications frequently need a number of variable speed electric drives. This technique uses five-leg inverter instead of using conventional two three phase inverters. In the majority of cases, these multi-motor drive systems need independent control of individual motors. It is shown recently that it is possible to separately control two three-phase induction machines supplied through a five-leg voltage source inverter, with one inverter leg being common to both machines. The entire performance of the speed control for the five leg voltage source inverter fed dual-motor drive system is investigated using MATLAB/SIMULINK software.

Advanced Speed Control for a Five-Leg Inverter Driving a Dual-Induction Motor System

This paper proposes advanced speed control for a five-leg voltage source inverter (FLVSI) that drives the dual three-phase induction motor system used in industrial manufacturing processes. The advanced speed control method consists of two controllers: 1) The first is a slip controller that satisfies the application requirement, i.e., to control the mechanical speed of two motors equally regardless of the load condition. 2) The second is an angle controller that satisfies the FLVSI requirement, i.e., to control the phase angle difference between the two motors for minimizing the common leg current because the common leg current can be twice higher than other leg's current depending on the operation condition of the dual motor. Stability analysis of the two controllers under advanced speed control is implemented, and the whole performance of the advanced speed control for the FLVSI-fed dual-motor drive system is shown to identify its feasibility through the experimental results.

Experimental Investigation of Inverter Open-Circuit Fault Diagnosis for Biharmonic Five-Phase Permanent Magnet Drive

This paper proposes a procedure that is suitable for experimental investigation of real-time open-switch and open-phase faults diagnosis of a five-leg voltage source inverter feeding a five-phase biharmonic permanent magnet synchronous machine (PMSM). The algorithm is based on the specific characteristics of multiphase machines, which allows inverter fault detection with sufficient robustness of the algorithm in the presence of fundamental and third harmonic components. First, the inverter fault effects analysis is achieved in the characteristic subspaces of the five-phase PMSM. Specificities that are interesting for the elaboration of a real-time fault detection and identification (FDI) process are highlighted. Original and particular algorithms are used for an accurate 2-D normalized fault vector extraction in a defined fault reference frame. This frame is dedicated only for FDI. To ensure the high immunity of the FDI process against transient states, a particular normalization procedure is applied. The normalized diagnostic signals are formulated from the defined frame and other variables derived from the reference and measured currents. Simulation and experimental results of open-switch and open-phase faults are provided to validate the proposed algorithm.

A Dual-Level Hysteresis Current Control for One Five-Leg VSI to Control Two PMSMs

A dual-level hysteresis current control (DHCC) is proposed for the five-leg drive system, in which two same three-phase permanent-magnet synchronous machines (PMSMs) are controlled by one five-leg voltage-source inverter. To overcome the coupling of the two PMSMs, the master–slave selection principle is introduced. The coupling phase with the larger absolute value of the phase current error is determined as the master coupling phase and the leg-switch-state of the common leg is set as the phase-switch-state of the master coupling phase. On the other hand, the phase-switch-states of four individual phases are directly assigned to the four individual legs, respectively. The executing process of DHCC does not require any machine parameters, which enhances the system robustness. The effectiveness of DHCC is verified by experimental results.

Real-Time Switches Fault Diagnosis Based on Typical Operating Characteristics of Five-Phase Permanent Magnetic Synchronous Machines

A novel centroid-based diagnostic method of the power switches in five-leg voltage source inverter is proposed in this paper. Using a vectorial multimachine description, a five-phase drive presenting an opened switch or an opened phase faults has typical operating characteristics in comparison to classical three-phase drives. Based on such characteristics, this paper aims to provide a simple and robust diagnostic process for switches fault regardless of the shape of the back electromotive forces (harmonic components) and the transient states due to the load variation. Original theoretical developments are presented. Experimental results are shown to validate the proposed strategy.

An efficient control of a series connected two-synchronous motor 5-phase with non sinusoidal EMF supplied by a single 5-leg VSI: Experimental and theoretical investigations

This paper proposes the control scheme of an original drive which is made up of two 5-phase permanent magnet synchronous machines (PMSM) connected in series. Even if the Electro-Motive Forces (EMF) are trapezoidal, it is possible, by using a special series connection between the two machines and by implementing a special vector control, to impose independent torques and speeds with a single five-leg Voltage Source Inverter (VSI). If special series-connection with classical vector control is sufficient to achieve flux/torque decoupling when the EMFs are sinusoidal, it is necessary to modify the control scheme when the EMFs are not sinusoidal.Simulations and experimental results demonstrate the efficiency of the independent control of the two 5-phase synchronous machines connected in series, and the efficiency of the proposed improved control for different loads.

Five-leg inverter PWM technique for reduced switch count two-motor constant power applications

Industrial applications often require a number of variable speed electric drives. In the majority of cases, these multi-motor drive systems require independent control of individual motors. Over the past decade, research efforts have been made to reduce the number of power electronic devices required in multi-motor drive systems in order to reduce the overall complexity and hence cost of the drive. It has been shown recently that it is possible to independently control two three-phase induction machines using a five-leg voltage source inverter (VSI) as the supply, with one inverter leg being common to both machines. The existing pulse-width modulation (PWM) methods for this supply topology either limit the amount of DC bus voltage available to each machine or lead to uneven and increased switching frequency across five legs of the VSI. A new PWM method that effectively utilises the standard three-phase modulators in conjunction with appropriate modifications to generate modulation signals for all five legs of the VSI is presented. It enables an arbitrary distribution of the available DC bus voltage between the two machines. The considered supply topology, when utilised in conjunction with the developed PWM technique, is well suited to constant power applications such as centre-driven winders. Verification of the developed modulation method and its applicability to winder systems are demonstrated by experimental testing that includes both steady state and transient operation.