Leg Voltage Source Inverter Research Articles

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.

Resonant and a new disturbance-observer combined control for off-grid voltage source inverter

&lt;span lang="EN-US"&gt;This paper presents a new control strategy based on the combination between the resonant controller and the disturbance-observer (RSCDO) for stand-alone four-leg Voltage Source Inverter (VSI). The aim of the new controller is to regulate the inverter output voltage, reducing as much as possible the voltage Total Harmonic Distortion (THDv) in every load condition. The resonant controller allows to adjust the output voltage fundamental harmonic, whereas the disturbance observer is designed for compensating output voltage harmonics when non-linear loads have to be fed. The proposed control strategy has been tested using a 40 kVA three-phase 4-leg VSI and a dedicated control board, which uses the National Instruments System-on-Module sbRIO-9651. Experimental results demonstrate good behavior of the RSCDO controller to reject the disturbance in the output voltage, as well as a good dynamic response.&lt;/span&gt;

Thermal monitoring of the stator winding insulating part by a reliable thermal model for failure mitigation

Electrical motors fed by a voltage inverter always supply voltages in non-sinusoidal waveforms such that the current flowing through the machine is rich in harmonics. This not only increases losses in the machine but also leads to more severe thermal stress which affects the stator winding. Therefore, accurate and continuous monitoring of the coil temperature with reliable thermal models is essential, improving, the reliability of the motors. This paper focuses on the thermal reliability model study of a stator winding of Three Star Induction Machine TSIM shifted by 30° and fed by a nine leg voltage source inverter (VSI). A new application of the diffusive approach on the TSIM thermal reliability solution is also investigated. Moreover, the nodal method based on the thermal equivalent circuit is examined. The reliability, as well as the effectiveness of the proposed diffusive approach, are validated by experimental results. These results, together with the obtained simulations, show clearly the validity and the great reliability of the proposed diffusive approach.

Application of D-STATCOM for Harmonic Reduction using Power Balance Theory

In modern power systems due to prolific use of non-linear devices harmonics are present in the distribution system. To reduce the harmonics and source neutral current D-FACT along with a star-delta transformer and Power Filter is proposed in shunt. In this article, the three phase load has been taken from NTS Industries, which deals with FMCG products. This system includes 3 phase 3 wire system having industrial load such as mixer grinder, pulverizer, packaging machine, etc. A star-delta transformer along with three leg voltage source inverter and a capacitor used to filter out harmonics present in supply current. Power balance theory is used to control the D-FACT. A MATLAB Simulink model was created and the results were discussed.

Analysis of Five Leg Voltage Source Inverter Fed Dual Motor Drive System

With the advent of electric vehicle multi-machine drives are attaining overwhelming responses from the researchers and industries in recent years, as compared to their counterpart of single machine drive. In this regard, the industries are looking for multi motor control with single inverter system with precise speed control. The solution of aforesaid problem lies with multi-leg inverter fed dual induction motor drives that are capable for high power ratings and other specific applications. Any faults in the system leads to the failure of the operation of the entire drive system. Hence condition monitoring of the entire drive system becomes of paramount significance. Considering the aforementioned points, this paper focuses on the fault analysis of five leg voltage source inverter feeding dual induction motors. The drive system is simulated using MATLAB/ SIMULINK for different pulse width modulation techniques like SPWM, SVPWM and Two Arm Modulation (TAM) Techniques. The effect on fault in the inverter like opening of the switch and shorting the switch, on the performance of the induction motors are analysed. Total Harmonic Distortion (THD) of the stator current for different modulation techniques are compared for the analysis purpose. From the results it is observed that the THD is less for SVPWM techniques as compared with SPWM and TAM method. But independent control of both the machine cannot be attained by SPWM and SVPWM method. For independent speed control TAM method is used. So a trade-off has to be done considering the requirement and THD. It is finally concluded that independent speed control is achieved at the cost of higher THD.

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.

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 Active Power Filter Performance for Grid Integrated Hybrid Renewable Power Generation Systems

An active power filter implemented with a four leg voltage-source inverter using a predictive control scheme is presented. The use of a four leg voltage-source inverter allows the compensation of current harmonic components, as well as unbalanced current generated by single-phase nonlinear loads. A detailed yet simple mathematical model of the active power filter, including the effect of the equivalent power system impedance, is derived and used to design the predictive control algorithm. The compensation performance of the proposed active power filter and the associated control scheme under steady state and transient operating conditions is demonstrated through simulations and experimental results.

Compensate Voltage Sags in Series Transformers of Dynamic Voltage Restorers for Preventing Saturation

This paper proposes a procedure for preventing saturation in series transformers from Dynamic Voltage Restorer (DVR) systems. Power quality has been an issue that is becoming increasingly pivotal in modern industrial and commercial applications. Voltage disturbances especially the voltage sag and swell are the most common power quality problems due to increased use of a large numbers of sophisticated and sensitive electronic equipment in industrial systems. The method consists in correcting the voltage which is injected through the transformers into the power system to compensate voltage sags. To overcome this problem, custom power devices are used. One of the devices is the Dynamic Voltage Restorer (DVR), which is the most efficient and effective modern custom power device used in power distribution networks. It is a series connected power electronic based device that can quickly mitigate the voltage sags in the system and restore the load voltage to the pre-fault value. Moreover, the technique allows a certain level of sag compensation even when the estimated flux is expected to exceed the saturation limit. The voltage sag level and phase are computed through an adaptive Recursive Least Squares (RLS). In RLS Method we have to use 4-leg voltage source inverter and it can be slow process to compensate the voltage sag occur in the power system. In extension method, the Adaptive Network based Fuzzy Inference System (ANFIS) is used to reduces the voltage sag in the power system network. In these method, the 3-leg voltage source inverter as comparing to the RLS algorithm. The ANFIS system is faster and accurate to compensate voltage sags in power system. Total harmonics distortions is half of the deduced in the system.Keywords: Adaptive System Based Fuzzy Interface System (ANFIS), Dynamic Voltage Restorer (DVR), Recursive Least Squares (RLS), Saturation, Series Transformers, Voltage Sag

Power Quality Improvement in Three Phase Four Wire Distribution System with Implementation of Fuzzy Logic Controller Based Adaptive Shunt Active Filter

Non-linear loads and applications of power electronics in 3P4W (three phase four wire) distribution system are the major sources of harmonics. The power quality compensator which mitigates the problem related to Current harmonics is Shunt active filter (SAPF) or passive filter. Active filtering is the most efficient mitigating method adopted for reactive power compensation and mitigation of harmonics. The power quality compensator proposed in this paper is a SAPF which reduces the %THD, compensates reactive power and mitigates neutral current under unbalanced non-linear load condition. A 3-fi MOSFET based 3 leg VSI (Voltage Source Inverter) with DC bus capacitor as energy buffer is employed to realize the SAPF. Fuzzy logic based Direct control method is the propounded control strategy implemented for the estimation of reference current and to keep the voltage of DC capacitor to its reference value. Switching signals for the VSI is generated using Hysteresis current controller. T-connected and Zig-Zag transformers are implemented to reduce the neutral current to about 1/10th of its original value in unbalanced Non-linear load conditions. The propounded control strategy performance is validated and analyzed using MATLAB software

A New Control Algorithm for Three-Phase, Four-Wire Unified Power Quality Conditioner (UPQC) in Distributing Systems

This paper presents the new control algorithm for three-phase, four-wire distributing system using unified power quality conditioner (UPQC). The UPQC, a combination of series and shunt active filter (AF) with common dc link, is one of the best solution towards the compensation of voltage sag, swell problems and also compensate voltage flicker/imbalance, reactive power, negative sequence current and maintain zero voltage regulation (ZVR) at the point of common coupling (PCC) on distribution system. The series AF is seen by using a three-phase, three leg voltage source inverter (VSI) and the shunt AF is of a three-phase, four leg voltage source inverter (VSI). The proposed model of the UPQC is developed in the MATLAB/SIMULINK environment and the simulation results prove the power quality improvement in the system.

A control strategy based on UTT and I Cos&amp;#920 theory of three-phase, fourwire UPQC for power quality improvement

This paper presents a control strategy for a three-phase four-wire Unified Power Quality (UPQC) for an improvement of different power quality (PQ) problems. The UPQC is realized by integration of series and shunt active power filters (APFs) sharing a common dc bus capacitor. The shunt APF is realized using a thee-phase, four leg voltage source inverter (VSI) and the series APF is realized using a three-phase, three legs VSI. A control technique based on unit vector template technique (UTT) is used to get the reference signals for series APF, while ICosO theory is used for the control of Shunt APF. The performance of the implemented control algorithm is evaluated in terms of power-factor correction; load balancing, neutral source current mitigation and mitigation of voltage and current harmonics, voltage sag and swell and voltage dips in a three-phase four-wire distribution system for different combination of linear and non-linear loads. In this control scheme, the current/voltage control is applied over the fundamental supply currents/voltages instead of fast changing APFs currents/voltages, thereby reducing the computational delay and the required sensors. MATLAB/Simulink based simulations results are obtained, which support the functionality of the UPQC.

A Control Strategy Based on UTT and ISCT for 3P4W UPQC

This paper presents a novel control strategy of a three- phase four-wire Unified Power Quality (UPQC) for an improvement in power quality. The UPQC is realized by integration of series and shunt active power filters (APFs) sharing a common dc bus capacitor. The shunt APF is realized using a thee-phase, four leg voltage source inverter (VSI) and the series APF is realized using a three-phase, three leg VSI. A control technique based on unit vector template technique (UTT) is used to get the reference signals for series APF, while instantaneous sequence component theory (ISCT) is used for the control of Shunt APF. The performance of the implemented control algorithm is evaluated in terms of power-factor correction, load balancing, neutral source current mitigation and mitigation of voltage and current harmonics, voltage sag and swell in a three-phase four-wire distribution system for different combination of linear and non-linear loads. In this proposed control scheme of UPQC, the current/voltage control is applied over the fundamental supply currents/voltages instead of fast changing APFs currents/voltages, there by reducing the computational delay and the required sensors. MATLAB/Simulink based simulations are obtained, which support the functionality of the UPQC. MATLAB/Simulink based simulations are obtained, which support the functionality of the UPQC.

A Simplified Control Algorithm for Three-Phase, Four-Wire Unified Power Quality Conditioner

In this paper, a simplified control algorithm for a three-phase, four-wire unified power quality conditioner (UPQC) is presented to compensate for supply voltage distortions/unbalance, supply current harmonics, the supply neutral current, the reactive power and the load unbalance as well as to maintain zero voltage regulation (ZVR) at the point of common coupling (PCC). The UPQC is realized by the integration of series and shunt active filters (AFs) sharing a common dc bus capacitor. The shunt AF is realized using a three-phase, four leg voltage source inverter (VSI) and the series AF is realized using a three-phase, three leg VSI. A dynamic model of the UPQC is developed in the MATLAB/SIMULINK environment and the simulation results demonstrating the power quality improvement in the system are presented for different supply and load conditions.

A General PWM Method for a $(2n + 1)$ -Leg Inverter Supplying $n$ Three-Phase Machines

Control of an ac machine requires only two currents. It is, therefore, possible to achieve independent control of a number of three-phase machines using various inverter topologies with a reduced switch count. One such drive system comprises <i xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">n</i> three-phase induction machines supplied by a (2 <i xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">n</i> + 1)-leg voltage source inverter (VSI). In such a configuration, one inverter leg is common for all machines. This paper presents a general pulsewidth modulation (PWM) method that is applicable for any number of machines <i xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">n</i> in the group. It is based on utilization of the standard three-phase modulators in conjunction with additional logic to generate modulation signals for all (2 <i xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">n</i> + 1) legs of the inverter, and it enables an arbitrary distribution of the available dc bus voltage between the <i xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">n</i> machines. A developed PWM method has been implemented and tested in two-machine, three-machine, and four-machine drives, supplied from five-leg, seven-leg, and nine-leg VSIs, respectively. Experimental results are reported for open-loop <i xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">V</i> / <i xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">f</i> control, closed-loop current-controlled <i xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">V</i> / <i xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">f</i> mode of operation, and full vector control. It is shown that the nonideal nature of the VSI causes unsatisfactory operation of the drive system in the open-loop <i xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">V</i> / <i xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">f</i> mode, and that closed-loop current control is, therefore, preferred in this type of a drive system. It is believed that the four-machine drive has a good potential for industrial applications since, in certain cases, it enables a considerable saving in the required number of switches and installed inverter power.

Control of a 3-phase 4-leg active power filter under non-ideal mains voltage condition

In this paper, instantaneous reactive power theory (IRP), also known as p– q theory based a new control algorithm is proposed for 3-phase 4-wire and 4-leg shunt active power filter (APF) to suppress harmonic currents, compensate reactive power and neutral line current and balance the load currents under unbalanced non-linear load and non-ideal mains voltage conditions. The APF is composed from 4-leg voltage source inverter (VSI) with a common DC-link capacitor and hysteresis–band PWM current controller. In order to show validity of the proposed control algorithm, compared conventional p– q and p– q– r theory, four different cases such as ideal and unbalanced and balanced-distorted and unbalanced-distorted mains voltage conditions are considered and then simulated. All simulations are performed by using Matlab-Simulink Power System Blockset. The performance of the 4-leg APF with the proposed control algorithm is found considerably effective and adequate to compensate harmonics, reactive power and neutral current and balance load currents under all non-ideal mains voltage scenarios.