Inverter Leg Research Articles

Development of grid‐interactive inverter utilising induction motor driven photovoltaic water pumping system

The stand-alone solar photovoltaic water pumping system (SPVWPS) remains idle for a significant period of time, when irrigation is not required and when sun is not available. Due to this large idle period, the effective utilisation of SPVWPS assets, i.e. solar photovoltaic array, power electronics converter, and motor, is poor. This study presents an approach to increase the effective utilisation of SPVWPS under the aforementioned idle period. It is proposed to interface the grid with SPVWPS without adding extra power electronic interface. An innovative integrated photovoltaic inverter is constructed using existing SPVWPS components. The inverter enables the transfer of active power and exchange of reactive power with the grid during an idle period of SPVWPS. The three legs of the voltage source inverter (VSI) are interleaved with motor windings. The VSI switches are controlled with synchronous pulse width modulation to force a cophasal current in the motor windings. This accompanies a net motor torque to zero under grid-interactive operation. Hence, the three-phase VSI operates as a single-phase grid synchronise converter, and the motor windings are used as filter inductance. The control system is presented to establish grid-interactive functionality. A prototype is developed to verify system performance. The control system is implemented using the ARM Cortex-M4 microcontroller.

Novel switching technique for five leg inverter in dual motor control

<p><span>This work presents a novel switching technique for five leg inverter in dual motor control. As the technology advances in industry, requirements in reducing the cost plays an important role with reliable product design. In conventional method, the six legs are used in 2- three phase Voltage Source Inverters (VSI) to control 2 motors. This proposed technique will give the improved performance of speed control for dual motor control using Five Leg Inverter (FLI). New proposed method suggests to use 5-inverter legs instead of 6-inverter legs to control 2 induction motors. New Switching technique proposed in FLI system is designed in effective way that improved performance and Total Harmonic Distortion of ~23% achieved. The load sharing on common leg is called Common Mode (CM) of operation. In this new method, closed loop control designed by using space vector pulse width modulation (SVPWM) and Direct Torque Control (DTC) in FLI Technology. With this new method smooth speed regulation is achieved when load torque is changed. THD% for CM-FLI is reduced when compared with convetional FLI technique. The new Switching technique is controlled in effective way that the common leg is not overloaded and able to drive both the induction motors independently at required speeds. Proposed switching technique verified at different operating speeds with No load and rated torque. Simulation results computed using MATLAB/SIMULINK Software. </span></p>

ANFIS based Transformerless UPFC for Effective Power Flow Control

This paper focus on specially designed ANFIS based Power Quality Conditioner for Micro Grid applications. Three leg inverter coupled with solar PV with MPPT used as Compensator can be used for distinct DGs in the micro grid for power quality improvement of the entire system. Optimum control can be achieved to avoid detraction for voltage, current and Power flowing between Grid and DG. The Power Quality conditioner and DG inverter have dual use for this particular purpose. Primarily used as power converter for injecting power created from DG to Grid, secondly performed as parallel Active Power Filter for compensating harmonics, unbalanced voltage, current, active and reactive power demand for the balance and unbalance burden with in the Grid and neutral conductors. This paper is extended with ANFIS Controller for better improvement of Power Quality. The above mentioned task extensively simulated under MATLAB/Simulink platform revels that soon after compensation the THD.

A Three-Level DC-Link Quasi-Switch Boost T-Type Inverter with Voltage Stress Reduction

In recent years, the three-level T-Type inverter has been considered the best choice for many low and medium power applications. Nevertheless, this topology is known as a buck converter. Therefore, in this paper, a new topology incorporating the dc-link type quasi-switched boost network with the traditional three-level T-type inverter is proposed to overcome the limit of traditional three-level T-Type inverter. The space vector pulse width modulation scheme is considered to control this topology, which provides some benefits such as enhancing modulation index and reducing the magnitude of common-mode voltage. For this scheme, the zero, medium, and large vectors are utilized to generate the output voltage. The shoot-through state which is adopted by turning on all power switches of inverter leg is inserted into zero vector to boost the dc-link voltage. As a result, there is no distortion at the output waveform. The control signal of intermediate network power switches is also detailed to improve the boost factor and voltage gain. As a result, the voltage stress on power devices like capacitors, diodes, and switches is decreased significantly. To demonstrate the outstanding of proposed structure and its control strategy, some comparisons between the proposed method and other ones are performed. Simulation and experimental prototype results are conducted to verify the accuracy of the theory and effectiveness of the inverter.

Postfault Operation of Onboard Integrated Battery Charger via a Nine-Phase EV-Drive Train

This article presents the operation of onboard integrated battery chargers tied to a nine-phase EV-drive train, shedding light on the charging performance during the postfault operation, when one or more faulty inverter legs are disconnected. The objective in that case is to ensure balanced grid currents, while maintaining minimum machine losses at zero average torque production. The proposed concept requires a minimalistic change from a control structure perspective to switch between the pre- and postfault cases. Limitations and fault cases are discussed and corroborated with experimental tests on a 1.5-kW prototype.The derived concept is parameter independent and applicable to nine-phase drives, irrespective of the type of rotor used.

Finite Element Analysis on Multiple IGBT Switch Open-Circuit Fault in PWM Inverter Fed Induction Motor

This study analyzes the single and multiple IGBT switch open circuit fault in an inverter fed induction motor (IM) using Finite Element Method. The finite element simulation is carried out in ANSYS Maxwell and Simplorer for various fault conditions such as single IGBT switch open in an inverter leg, two IGBT switch open in the inverter same leg and in different leg. A three-phase 7.5kW IM is modelled in ANSYS Maxwell which is fed through a three-phase voltage source inverter modelled in ANSYS Simplorer. Inverter switches are controlled using sinusoidal pulse width modulation technique. Several electromagnetic parameters such as torque, speed, line voltage, phase current, flux line & flux density distribution over the machine and radial air gap flux density are analysed.

An LCL-Based SS Compensated WPT Converter With Wide ZVS Range and Integrated Coil Structure

In this article, a zero-voltage switching (ZVS) series–series compensated wireless power transfer (WPT) converter with phase shift modulation is proposed, which can realize output current regulation over wide range. In the proposed WPT converter, an auxiliary LCL resonant network is connected between two midpoints of the H-bridge legs of inverter to provide the peak current for ZVS operation during the dead time, with low rms current to decrease the conduction losses. To reduce the volume of the auxiliary network, an integrated coil structure is applied and the magnetic saturation is avoided due to the orthogonal coil currents. Time-domain analysis and ZVS operation of the proposed WPT converter are performed. Design and optimization of the LCL network are performed. Experimental results of a prototype with 8−20 A adjustable output current confirm the feasibility of the proposed method.

Deadbeat Predictive Current Control-Based Fault-Tolerant Scheme for Dual Three-Phase PMSM Drives

In this article, a deadbeat predictive current control-based fault-tolerant scheme is proposed and developed for the dual three-phase permanent-magnet synchronous motor (PMSM) drives. For the open-phase fault of the dual three-phase PMSM, the current references are derived without low-order components for minimum stator copper loss. The utilization of the deadbeat predictive current control guarantees high-control bandwidth for the current references under fault-tolerant operation. Then, a fault-tolerant control scheme is proposed for the open-switch fault based on the hybrid current references, which can fully utilize the remaining one health switch in the faulty inverter leg and minimize the stator copper loss. The additional copper loss caused by the open-switch fault can be reduced by around half with the proposed fault-tolerant control compared to previous remedial strategies. Thus, the ultimate torque output under the open-switch fault can be increased by around 20%. The machine model, the space vector diagram, and the control structure of the motor systems remain unchanged with the proposed fault-tolerant control scheme. The validity of the proposed fault-tolerant control schemes is verified by experiments.

Pulse Width Modulation of Three Phase Inverters Based on Linear Programming

Traditional three-phase voltage-source inverters supplied by constant dc-link voltage usually utilize the space vector PWM to achieve maximum output voltage. This paper deals with optimization of inverter leg voltages using linear programming method. System definition is based on the relationship between the known voltage vector, which is demanded by an upper control loop and the unknown leg voltages which enter the carrier-based PWM block as modulation signals. A slack variable is introduced to the system as minimization objective, defining border for all leg voltages. Optimization procedure minimizes leg voltage maxima, and thus, the maximum utilization of the dc-link voltage is ensured. The theoretical assumptions have been verified by simulations as well as by experiments on laboratory prototype.

Real-time monitoring of an electronic wind turbine emulator based on the dynamic PMSG model using a graphical interface

This paper proposes an electronic wind turbine emulator (EWTEm) platform involving the dynamic models of the wind turbine (WT), permanent magnet synchronous generator (PMSG), and turbine-generator mechanical coupling, such that a real WT can be emulated for distinct kinds of loads and wind profiles. Low implementation cost represents an advantage for the proposed EWTEm, followed by its versatility on the commercial WT emulation with different characteristics, enabling the development of both theoretical and practical laboratory researches. Besides the 3-Phase 3-Leg inverter, the system is composed of a controlled rectifier with a high power factor and a graphical interface. Thus, it is possible to perform the following tasks: 1) vary the wind speed or wind profile; 2) visualize and assess the dynamic and static performances of the EWTEm by measuring the inverter quantities, such as voltages, currents, electric power, and frequency of the PMSG; and 3) visualize the quantities that are calculated into the digital signal controller, such as WT mechanical power, electromagnetic torque and rotation speed at the PMSG shaft. Simulation results are presented, as well as experimental tests are carried out and visualized by a graphical interface considering the system subjected to several transients of load and wind speed.

Phase Reconfiguring Technique for Enhancing the Modulation Index of Multilevel Inverter Fed Nine-Phase IM Drive

In this article, a multilevel inverter (MLI) scheme is proposed for four-pole (4-pole), nine-phase (9-phase) induction motor (IM) drives with improved dc bus utilization as well as reduced device count. The proposed MLI is realized with nine three-switch inverter legs (3-SIL) and a single dc source. In the proposed MLI, each 3-SIL is utilized for exciting the two identical voltage profile coils/phase of the four-pole (4-pole) stator winding, which means each leg has to be modulated with two references. These two independent references/leg will limit the modulation index (M.I) of 3-SIL-based proposed MLI. This lower M.I will result in a requirement of the higher magnitude of dc-link voltage to achieve the rated load voltage requirement. In this article, an effective phase reconfiguring concept is proposed for reducing the dc-link voltage requirement of the proposed MLI. In addition, all the possibilities of phase reconfiguring details for proposed MLI-fed 9-phase IM drive are also presented. A three-phase carrier-based space vector pulsewidth modulation is implemented for improving the linear modulation range of proposed MLI configuration further. In contrast with existing 9-phase three-level inverters, like NPC and FC, the proposed MLI configuration requires only one dc link (with half of the magnitude) and lesser number of semiconductor devices. The proposed MLI-fed, 5 hp, 9-phase, 4-pole IM drive is validated by using Ansys Maxwell FEM simulation and experimental prototype for entire modulation range.

A Single DC Source-Based Three-Level Inverter Topology for a Four-Pole Open-End Winding Nine-Phase PPMIM Drives

This article proposes a three-level inverter topology for nine-phase pole phase-modulated induction motor (PPMIM) drives by using the two identical voltage profile coils (IVPC) of a four-pole stator winding. In general, the two IVPCs of each phase winding are connected in series, but in this article, these two IVPCs are separated and excited with conventional two-switch inverter legs without disturbing the flux per pole and other machine parameters. The 18 IVPCs of four-pole nine-phase induction motor (IM) are excited with 18 two-switch inverter legs and fed by the same dc source. Each two-switch inverter leg generates the two-level voltage across each IVPC winding, i.e., the resultant voltage seen by the phase winding is a three-level voltage waveform. As compared to conventional nine-phase neutral point and flying capacitor multilevel inverters (MLIs), the requirement of the dc-link magnitude for the proposed topology is reduced by 50%. The nine-phase PPMIM drive is modulated with the carrier-based three-phase space vector pulsewidth modulation in order to enhance the linear modulation range (LMR). The inverter legs associated with two IVPCs per phase in 9-phase 4-pole (9PH-4PO) mode and six IVPCs per phase in 3-phase 12-pole (3PH-12PO) mode are modulated with the same reference wave and phase-displaced triangular waves. This results in the generation of multilevel voltage with improved harmonic voltage profile, i.e., minimizes the torque pulsations of nine-phase PPMIM drive. The validation of the proposed MLI-fed 5 hp nine-phase PPMIM drive is carried out by using the Ansys Maxwell FEM tool as well as with an experimental prototype.

Fault Diagnosis of Open-Switch Failure in a Grid-Connected Three-Level Si/SiC Hybrid ANPC Inverter

A diagnostic method for an open-circuit switch failure in a hybrid active neutral-point clamped (HANPC) inverter is proposed in this paper. The switching leg of the HANPC inverter consists of four silicon insulated gate bipolar transistors and two silicon carbide metal-oxide-semiconductor field-effect transistors to achieve higher efficiency and power density compared to conventional neutral-point clamped inverters. When an open-circuit failure occurs in a switching device, the output current is severely distorted, causing damage to the inverter and the connected loads. The proposed diagnostic method aims to detect the open-switch failure and protect the related devices without additional sensors or circuits. The faulty conditions of six different switches are investigated based on the current distortion in the stationary reference frame. By analyzing the individual characteristic of each switch failure, it is possible to detect the exact location of the failed switch in a short period. The effectiveness and feasibility of the proposed fault-diagnostic method are verified using simulation and experimental results.

Dual Motor Control using Double Zero Sequence Injection Method in Five Leg Voltage Source Inverter

This paper presents in to Dual Motor Control using double zero sequence injection method in 5- leg voltage source inverter. As industry looking for reducing the semiconductor switching devices, like IGBT/MOSFET’s in dual induction motor control. The main reason behind reducing the switching elements to reduce the weight, cost and size of the components. As conventional inverter require six inverter legs to control two induction motors. In this proposed work five inverter legs used instead of six legs in dual motor control. With this reduced one leg, two switching devices will be reduced and one phase of the inverter leg is common between the two motors, so called five leg inverter (FLI). The main switching methodology used for inverter control is Carrier based Double Zero Sequence Injection Method (DZSM). This Double Zero Sequence Injection Method applied to FLI system is having the one common leg. One of the C Phase modulation signal added to other modulating signals of all phases of other motor respectively. A subsequent each phase degree of freedom is represented by the zero-sequence signal. This paper investigates the independent speed control of dual induction motors at different speeds connected to five leg voltage source inverter system, using MATLAB/SIMULINK Software.

Nonlinear Effect of Dead Time in Small-Signal Modeling of Power-Electronic System Under Low-Load Conditions

Dead time is required to ensure that the switches of a synchronous switching inverter leg never conduct at the same time. During dead time, the current commutates to an antiparallel diode that can cause a voltage error depending on the instantaneous current direction. To measure a frequency response from a system, external injections are commonly required to perturb the system. The perturbation can change the current direction at the frequency of the injection, causing a voltage error at the injection frequency due to the dead time. The error depends on the perturbation amplitude, inductor current ripple, and fundamental current amplitude. This article proposes a describing-function method to model the dead-time effect under low-load conditions. It is shown that a nonlinear damping effect from the dead time can occur under low-load conditions and cannot be modeled with a resistor-like element. Real-time hardware-in-the-loop-simulation results are presented and used to demonstrate the effectiveness of the proposed method. Experimental measurements are used to verify the nonlinear dead-time effect.

Designing of SPVWM Inverter Controlled System By Using Suitable Architecture Of Power Quality Enhancement Device For Driving Mixed Loads

The stability of a power system is the ability of a power system to restore an operating state of equilibrium for a given initial operating condition after it has been subjected to a physical disturbance, most of the variables of the system being limited so that almost the entire system remains intact. Designing of a SPVWM controlled inverter that has to be made available for efficient power supply to the load of different types. The control of inverter has to be designed in order to enhance the system power supply. To achieve this a space vector pulse width modulation technique has been designed which is then used to provide pulses to the three leg inverter. To design a power quality enhancement device with a simplified architecture such that it will accommodate for the reactive power supply along with an improvement in the active power available at the load terminals. Thus it can be drawn from this work that while designing an inverter with SPVWM control strategy the proposed power quality enhancement device can serve the purpose with better results in terms of power and efficiency. This architecture can also be used in hybrid systems thus making it more reliable controlling method. The system designed is also fitted to feed different types of load like nonlinear load, balanced load and unbalanced load.

A review on developments of polyphase machines

Despite machines were acquainted more than hundred, a considerable length of time ago, the innovative research work in this zone seems to be never completion. For machine drive applications, multiphase induction motor might conceivably meet the interest for high power electric drive frameworks which would both rough & vitality productive. Polyphase drives have many advantages such as reduction in the torque pulsation and increase in its frequency, reduction in power per leg of inverter, reduced volume for same output power, lower dc link current harmonic and reduced rotor copper losses. Due to these advantages the multi-phase systems are used in electric ship propulsion, locomotive traction, electric and hybrid electric vehicles, “more-electric” aircraft, and high-power industrial applications. To look into the an assortment of issues identified with the utilization of multi-phase machine as compared to the conventional three-phase machine, the research has been in progress from last few decades. Therefore this paper reviews the advance committed to multi-phase machine drive innovative work since its origin. Apart from this, Modelling, PWM schemes and its areas of applications are also discussed.

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.

Control Strategy for a Five-Leg Inverter Supplying Dual Three-Phase PMSM

This study presents a novel control strategy for a five-leg inverter-fed dual three-phase permanent-magnet synchronous motor (DT-PMSM)system. Three different five-leg inverter topologies (operating modes) can be reconfigured by choosing a pair of phases for sharing the common leg. The five-leg inverter operation mode with 150° phase difference can achieve full torque output, but the utilization of DC bus voltage is low. The operation mode with 30° phase difference has higher DC bus voltage utilization but lower output torque. The modified double zero-sequence injection (DZI) PWM strategy based on carrier-based PWM (CBPWM) for five-leg inverter operating modes is proposed. This strategy can achieve the maximum DC bus voltage utilization. The five-leg inverter operating modes can be used as a fault-tolerant solution for the occurrence of a fault in one leg of the six-leg inverter. Compared with the commonly used open phases fault-tolerant control (FTC) strategies, this strategy has the advantages of without increasing the stator copper, reducing the torque ripples, and implementing easily. Experimental results verify the effectiveness and feasibility of the proposed strategy.

Common Mode Voltage Elimination for Quasi-Switch Boost T-Type Inverter Based on SVM Technique

In this paper, the effect of common-mode voltage generated in the three-level quasi-switched boost T-type inverter is minimized by applying the proposed space-vector modulation technique, which uses only medium vectors and zero vector to synthesize the reference vector. The switching sequence is selected smoothly for inserting the shoot-through state for the inverter branch. The shoot-through vector is added within the zero vector in order to not affect the active vectors as well as the output voltage. In addition, the shoot-through control signal of active switches of the impedance network is generated to ensure that its phase is shifted 90 degrees compared to shoot through the signal of the inverter leg, which provides an improvement in reducing the inductor current ripple and enhancing the voltage gain. The effectiveness of the proposed method is verified through simulation and experimental results. In addition, the superiority of the proposed scheme is demonstrated by comparing it to the conventional pulse-width modulation technique.