Modulation Inverter Research Articles

Decoupling Network of Field-Oriented Control in Variable-Frequency Drives

A synchronous current controller for field-oriented control is a popular control scheme that is used in industry to separately control the synchronous current of an induction motor in steady state. However, in some transient states such as during start-up and variation of the mechanical load, the synchronous current along the d -axis remains coupled to the q -axis current. Conventional decoupling current control considers only the model of an induction motor to compensate these coupling terms, but the motor is often powered by an inverter, which also influences the current, voltage, and torque behavior. Thus, a novel decoupling current control method is proposed to consider the coupling terms of both the motor and power converter in a synchronous current controller. Existing approaches assume that the motor is directly connected to the power supply, so a model is also suggested for a pulse width modulation (PWM) inverter. Analytical equations with simulation and experimental results prove that the coupling terms are still present when not considering the PWM inverter in the decoupling network. The proposed method shows good performance, and the d -axis current is always separated from the q -axis current during variation of the mechanical load.

Performance evaluation of a new control scheme of distributed two-stage PV conversion system using three levels voltage source inverter for stand-alone application

In this paper a distributed two-stage photovoltaic system using three levels inverter for stand-alone application is treated. The maximum power point tracking based on the “perturb & observe” (P&O) approach as a control strategy of the two boost DC-DC converters is applied. In order to get the best AC voltage waveform, the space vector pulse width modulation technique is used in this paper. To maintain the two capacitors voltages of DC bus equal, a new algorithm using the load, capacitors and boost converters currents is introduced to control loop. Without introduced any system to regulate the fluctuation of the DC bus and to get a stable output inverter voltage, authors in this paper propose a proportional regulator of inverter modulation index. A theoretical analysis with a complete simulation of the system with different profiles of irradiance for each DC/DC converter is presented to prove the excellent performance of the proposed technique.

Generic Modeling of N-Level Pulse Width Modulation Voltage Source Inverters and their Control

A generic and mathematic tool is adapted and used for pulse width modulation inverter modelling and control. The model is developed on the elementary switching cell and finally extended to some N-level topologies and three-phase inverters. Based on the generalized inverses, the solution set of pulse width modulation carrier based scheme is highlighted. The degree of freedom highlighted for the modulation control are linked to the architecture described. A specific example is illustrated and based on a H-bridge 3 level topology.

Nonlinear modulation of interacting between COMT and depression on brain function

BackgroundThe catechol-O-methyltransferase (COMT) gene is related to dopamine degradation and has been suggested to be involved in the pathogenesis of major depressive disorder (MDD). However, how this gene affects brain function properties in MDD is still unclear. MethodsFifty patients with MDD and 35 cognitively normal participants underwent a resting-state functional magnetic resonance imaging scan. A voxelwise and data-drive global functional connectivity density (gFCD) analysis was used to investigate the main effects and the interactions of disease states and COMT rs4680 gene polymorphism on brain function. ResultsWe found significant group differences of the gFCD in bilateral fusiform area (FFA), post-central and pre-central cortex, left superior temporal gyrus (STG), rectal and superior temporal gyrus and right ventrolateral prefrontal cortex (vlPFC); abnormal gFCDs in left STG were positively correlated with severity of depression in MDD group. Significant disease×COMT interaction effects were found in the bilateral calcarine gyrus, right vlPFC, hippocampus and thalamus, and left SFG and FFA. Further post-hoc tests showed a nonlinear modulation effect of COMT on gFCD in the development of MDD. Interestingly, an inverted U-shaped modulation was found in the prefrontal cortex (control system) but U-shaped modulations were found in the hippocampus, thalamus and occipital cortex (processing system). ConclusionOur study demonstrated nonlinear modulation of the interaction between COMT and depression on brain function. These findings expand our understanding of the COMT effect underlying the pathophysiology of MDD.

Analysis and Compensation of Inverter Nonlinearity for Three-Level T-Type Inverters

This paper addresses the inverter nonlinearity of a three-level T-type inverter. The main causes of the nonlinearity are pulse shaping, pulse skipping due to narrow pulses for the dead time, and voltage drop of the switching devices. Although the same causes have existed in two-level inverters, the pulse skipping phenomenon and results are quite different in the case of the three-level T-type inverter. The effects of pulse shaping and skipping have been investigated and discussed. In addition, the voltage drop of the switching devices has been considered in conjunction with the conduction path of the T-type inverter. Compensation methods based on the pulse width modulation (PWM) of T-type inverter to alleviate the inverter nonlinearity have been proposed from research results. The proposed methods could be easily implemented by adding appropriate offset voltages to the voltage references of the inverter in PWM. Furthermore, a neutral voltage balancing method of a three-level T-type inverter has been proposed in conjunction with the proposed PWM methods using offset voltage. Through extensive experimental tests, the fifth- and seventh-harmonic components of the current are conspicuously reduced along with the even harmonics. The neutral voltage of the inverter can be balanced effectively with the proposed offset voltage adjustments as well.

A Family of Neutral-Point-Clamped Circuits of Single-Phase PV Inverters: Generalized Principle and Implementation

The common-mode leakage current should be carefully considered when designing a transformer-less photovoltaic (PV) inverter since the leakage current can cause the output current distortion and increase the operational risk. The unipolar sinusoidal pulse width modulation of the traditional H-bridge inverter can produce the superior output performance but will cause a high-frequency fluctuated common-mode voltage and consequently the nonnegligible leakage current. To attenuate the fluctuation phenomena of common-mode voltage, few neutral-point-clamped (NPC) circuits have been designed to clamp the neutral-point voltage and maintain the common-mode voltage constant. This paper analyzes the equivalent common-mode circuit of single-phase inverters and proposes a generalized design principle of multiterminal NPC circuits, whose unidirectional and bidirectional variations are fully analyzed. Subsequently, two types of single-phase PV inverters with the NPC circuits are proposed. Also, the operational losses and component counts are compared between the proposed topologies and the traditional NPC inverters. The experimental results verified the theoretical findings.

Performance Evaluation and Comparison of Two Cascaded Configurations of PV Generators-Five Levels Inverter for a Stand-Alone Application in South Algeria

In this paper two configurations of solar photovoltaic energy conversion using the NPC five levels inverter for stand-alone application in south Algeria are proposed and their performances compared. The first cascade uses four separate PV sources and the second configuration use only one PV generator. In these two cases and without DC/DC converter introduced between PV source and inverter and to get a stable AC voltage, authors in propose a proportional regulator of inverter modulation index. The SVPWM technique is used in order to get the best voltage waveform. For the second configuration proposed, we introduce in the control loops another algorithm which uses the redundant vectors of space vector diagram of inverter to stabilise the DC bus voltages. A real data of temperature and solar irradiation obtained by radiometric station in Ghardaïa city in south Algeria are used to test the performance of proposed controls. The simulation results show that the inverter output voltage is stable for the two configurations proposed despite the variation of solar irradiation, temperature and load. Also, the THD obtained is in the limits of international standards. Then, the PV cascade with separate PV sources is the best solution, seeing that we do not need to use another algorithm in the control loops.

Modified Synchronous Reference Frame Based Shunt Active Power Filter with Fuzzy Logic Control Pulse Width Modulation Inverter

Harmonic distortion in power networks has greatly reduced power quality and this affects system stability. In order to mitigate this power quality issue, the shunt active power filter (SAPF) has been widely applied and it is proven to be the best solution to current harmonics. This paper evaluates the performance of the modified synchronous reference frame extraction (MSRF) algorithm with fuzzy logic controller (FLC) based current control pulse width modulation (PWM) inverter of three-phase three-wire SAPF to mitigate current harmonics. The proposed FLC is designed with a reduced amount of membership functions (MFs) and rules, and thus significantly reduces the computational time and memory size. Modeling and simulations of SAPF are carried out using MATLAB/Simulink R2012a with the power system toolbox under steady-state condition, and this is followed with hardware implementation using a TMS320F28335 digital signal processor (DSP), Specrum Digital Inc., Stafford, TX, USA. The results obtained demonstrate a good and satisfactory response to mitigate the harmonics in the system. The total harmonic distortion (THD) for the system has been reduced from 25.60% to 0.92% and 1.41% in the simulation study with and without FLC, respectively. Similarly for the experimental study, the SAPF can compensate for the three-phase load current by reducing THD to 5.07% and 7.4% with and without FLC, respectively.

Hybrid Sliding Mode Control Technology of Electric Vehicle Based on Wireless Sensor

The purpose of this study is to solve defects of the existing control strategy long convergence time, sliding mode chattering and so on. For Sensorless Brushless DC motor control strategy, a modified extended Kalman state correction estimation scheme is proposed, and dual mode high-order non-singular terminal hybrid sliding mode control technology is put forward. TMS320F2812DSP core controller and CM200DY-12H inverter module and construction electric car core control module are established, and the program algorithm of the extended Kalman algorithm and hybrid sliding mode control is constructed. The results showed that the control system designed can suppress the system chattering, and the system has strong robustness, which has low requirement on the system model and can eliminate external disturbance input, showing outstanding performance in the convergence time and anti disturbance performance. In summary, a dual mode high-order non-singular terminal hybrid sliding mode control technology put forward is quite suitable for electric vehicle control system.

Online Dead Time Effect Compensation Algorithm of PWM Inverter for Motor Drive Using PR Controller

This paper proposes the dead time effect compensation algorithm using proportional resonant controller in pulse width modulation inverter of motor drive. To avoid a short circuit in the dc link, the dead time of the switch device is surely required. However, the dead time effect causes the phase current distortions, torque pulsations, and degradations of control performance. To solve these problems, the output current including ripple components on the synchronous reference frame and stationary reference frame are analyzed in detail. As a results, the distorted synchronous d-and q-axis currents contain the 6th, 12th, and the higher harmonic components due to the influence of dead time effect. In this paper, a new dead time effect compensation algorithm using proportional resonant controller is also proposed to reduce the output current harmonics due to the dead time and nonlinear characteristics of the switching devices. The proposed compensation algorithm does not require any additional hardware and the offline experimental measurements. The experimental results are presented to demonstrate the effectiveness of the proposed dead time effect compensation algorithm.

Photovoltaic System Based Series Active Power Filter to Enhance Power Quality through Electrical Network

This paper presents a study of proposed approach founded on series active power filter based on photovoltaic array (PV-SAPF) which is controlled by classical PI using pulse width modulation inverter (PWM). The proposed system is connected to grid system to feed linear and nonlinear loads to handle deep sags, swells voltage, voltage distortion and power factor crushing caused by any electrical perturbation. In the other hand, the excess of the energy is injected into the mains when the network is not affected and after compensation. To prove the effectiveness of the planned system, the PV-SAPF is carried out using MATLAB / Simulink environment. The results Simulations results proved the ability and the efficiency of the proposed system in mitigation the harmonic voltage distortion, correction the voltage sag and swell, power factor improvment and power quality enhancement.

Comparative Study of Fault Diagnostic Methods in Voltage Source Inverter Fed Three Phase Induction Motor Drive

Three phase Pulse Width Modulation inverter plays vital role in industrial applications. The performance of inverter demeans as several types of faults take place in it. The widely used switching devices in power electronics are Insulated Gate Bipolar Transistors (IGBTs) and Metal Oxide Field Effect Transistors (MOSFET). The IGBTs faults are broadly classified as base or collector open circuit fault, misfiring fault and short circuit fault. To develop consistency and performance of inverter, knowledge of fault mode is extremely important. This paper presents the comparative study of IGBTs fault diagnosis. Experimental set up is implemented for data acquisition under various faulty and healthy conditions. Recent methods are executed using MATLAB-Simulink and compared using key parameters like average accuracy, fault detection time, implementation efforts, threshold dependency, and detection parameter, resistivity against noise and load dependency.

Ibilgailu elektrikoen potentzia-bihurgailuen hozte-metodoak

Ibilgailu elektrikoari loturiko potentzia-bihurgailuetan, korronte-dentsitate handitan (500 A ingurukoak) lan egiten duten IGBT transistoreak eta diodoak erabiltzen dira. Korronte altuak direla eta, handitu egiten dira gailu erdieroale horietan gertatzen diren kommutazio- eta kondukzio-galerak, eta ondorioz, potentzia-erdieroaleak berotu egiten dira. Moduluen efizientzia eta fidagarritasuna ziurtatzeko, beharrezkoa da hozte-sistema eraginkor eta egoki bat aukeratzea. Artikulu honetan, potentzia-bihurgailuen moduluen hozte-metodoak berrikusi eta eztabaidatuko dira.

Fractional Phase Lead Compensation RC for an Inverter: Analysis, Design, and Verification

Repetitive control (RC) can offer a promising accurate voltage control scheme for constant-voltage constant-frequency (CVCF) pulse width modulation (PWM) inverters to compensate the harmonic distortion caused by nonlinear loads. However, limited by digital sampling, conventional RC with integer phase lead compensation cannot exactly compensate the system phase lag, which may result in instability in the case of low sampling frequency. In this paper, a fractional phase lead compensation RC (FPLC-RC) scheme is proposed to enable the phase lead step to be fractional, which can enlarge the stability region and improve the tracking accuracy. A newly devised finite-impulse response fractional lead filter based on Lagrange interpolation is applied to approximate the fractional lead items. Meanwhile, the synthesis and analysis of fractional phase lead RC for a single PWM inverter are given. Furthermore, simulations and experiments are provided to demonstrate the validity of the proposed FPLC-RC scheme.

Reliability comparison of different power electronic converters for grid-connected PMSG wind turbines

Reliability is becoming more important as the size and number of worldwide installed wind turbines (WTs) increase. In offshore WTs, reliability evaluation is vital due to their hard and expensive repair and maintenance. Wind turbine producers, if consider reliability, can warrant that their productions will ensure high availability. Power electronic converters play an important role in reliability evaluation of grid connected variable speed WTs. This paper presents a reliability comparison between 3 types of power electronic converters that are conventionally used in the grid-connected permanent magnet synchronous generator–based wind turbines. Type 1 is back to back converter, type 2 is a pulse width modulation inverter with a conventional boost DC/DC converter and a simple diode rectifier, and type 3 is a pulse width modulation inverter with an interleaved boost DC/DC converter and a simple diode rectifier. The failure rate is calculated for each type of the converters, and then, reliability is calculated and compared. Results show that the type 3 is the most reliable and has the lowest failure rate between the above mentioned types of converters.

Design of Speed Control System for PMSM Based on Three-Level Structure

三相永磁同步电机在节约电能方面具有非常广阔的前景，它具有结构简单、体积小、效率高、易于散热和维护简单等优点。相比传统的两电平逆变器，三电平逆变器具有很多优点：单管耐压低、开关损耗降低、谐波含量小等，因此将三电平技术应用到永磁同步电机调速系统中，具有重要的理论意义和实用价值。本文主要研究了基于三电平中点箝位型(NPC)逆变器的永磁同步电机(PMSM)调速系统。电机采用转子磁场定向的矢量控制。为了达到控制目的，在三电平逆变器控制系统中引入了零序电压注入法。这种方法很好地控制了中点电压的平衡，以期降低逆变器输出电压谐波含量，改善电机定子电流波形，这将减小电机转矩脉动，改善电机控制性能。本文介绍了永磁同步电机的数学模型和矢量控制方法，阐述了中点箝位型三电平逆变器的拓扑结构和换流模式，分析了中点电位平衡算法和调制策略，最后通过实验验证了系统的可靠性和稳定性。 The three-phase PMSM has a very broad prospect in saving electrical energy. It has the characte-ristics of simple structure, small volume, high efficiency and good heat radiation. Compared with conventional two-level inverters, three-level inverter has a series of advantages such as low vol-tage-proof for single transistor, low switching loss and low harmonic content, etc. Therefore, it is of great theoretical significance and practical value to apply the three-level inverter to the speed regulating system of permanent magnet synchronous motor (PMSM). In this paper, the speed regulating system of permanent magnet synchronous motor on the basis of three level neutral point clamped (NPC) inverter is studied. Rotor flux oriented vector control method is applied on the motor. In order to implement the control process, zero sequence voltage injection method is introduced in the proposed three-level inverter control system. With this method, the balance of the neutral point voltage can be well achieved to reduce the harmonic content of the output voltage of the inverter and improve the stator current waveform, which will further minimize the motor torque ripple, and improve motor control performance. The mathematical model and vector control method of PMSM are introduced in this paper, both the topology and commutation mode of three-level inverter with neutral point clamping mode are described, and the neutral point potential balance algorithm and modulation strategy are also analyzed. Finally, the experiment verified the reliability and stability of the system.

Performance of PM Motor Driven by PWM Inverter with Voltage Booster Using Both Flux Weakening Control and DC Link Voltage Control

SUMMARYIn this paper, a driving method for an interior permanent magnet (IPM) motor is proposed; this method increases the system efficiency in the constant power region. In the driving method, the pulse width modulation inverter with a voltage booster system allows the use of both flux weakening control (FWC) and dc link voltage control (DVC) to drive an IPM motor at high speed. The authors investigate how a combination of FWC and DVC is suitable for the system. First, a simulation model is introduced. This model allows the calculation of the system efficiency and each part of the system losses in the voltage booster, inverter, and IPM motor. Furthermore, the system efficiency is calculated using the simulation model, and the simulation results are discussed when the ratio between the FWC and the DVC is changed. The IPM motor drive method is expected to help achievement of high efficiency by adjusting the ratio between the two control methods in the constant power region.

DC-Link RMS Current Reduction by Increasing Paralleled Three-Phase Inverter Module Number for Segmented Traction Drive

This paper presents a three-phase inverter dc-link capacitor root-mean-square (RMS) current reduction method. The proposed method is especially suitable for high current electric drive applications while multiple switching devices have to be connected in parallel at the package level, such as Toyota Camry or Tesla Model S. This paper analyzed the proposed method theoretically using double Fourier analysis, and derived the optimal operating point. Furthermore, the effectiveness of the proposed method is also verified by simulation under different PWM strategies (SPWM, SVPWM, and DPWM1), carrier shapes (triangle and sawtooth), and power factors. The proposed dc-link capacitor current cancellation method could lead to smaller dc-link capacitor design; the system volume reduction and cost are also estimated with different number of device packages in parallel. The experimental results are also provided using a 6 kW SiC-based inverter prototype assuming three paralleled devices in each phase leg, which are consistent with the theoretical analysis and simulation results.

Generalized Average Method for Time-Invariant Modeling of Inverters

Models of inverters and other converters based on averaging have been widely used in numerous simulation applications. Generalized averaging can be applied to model both average and switching behavior of converters while retaining the faster run times associated with average-value models. Herein, generalized average models for single- and three-phase pulse width modulation inverters are proposed. These models are based on a quasi-Fourier series representation of the switching functions that includes fundamental and switching frequency components as well as sideband components of the switching frequency. The proposed models are demonstrated both in simulation and experimentally and are found to accurately portray both the fundamental and the switching behavior of the inverter. In particular, the use of sideband components allows accurate representation of the variation in switching ripple magnitude that occurs in the steady state. The generalized average models are found to have simulation run times that are significantly faster than those associated with detailed models. Therefore, the proposed generalized average models are suitable for simulation applications in which both accuracy (including the switching behavior) and fast run times are required (e.g., long simulation times, systems with multiple converters, and repeated simulations).

Cascaded Common Nodal Point Multi-level Inverter Topology

Recent trends in the multi-level inverter (MLI) technology demand reduced number of switches, driver circuits, isolated DC sources, peak inverse voltage (PIV), appreciable number of voltage level, and lower total harmonic distortion. This paper presents an improved cascaded MLI configuration. Each module comprises ten switches, two isolated DC sources, and two capacitors; it can generate a maximum of 9-level output voltage waveform. Optimized switching sequence is developed that ensures minimum switching transitions and is implemented through single-carrier pulse width modulation for the control of the proposed topology. The classical cascaded H-bridge inverter and some recently developed MLI configurations were compared with the proposed inverter circuit. Results show that the proposed inverter configuration generates high number of output voltage levels with reduced number of power switches and PIV. It also has a lower per-unit power loss profile. Unit capacitor voltage balancing scheme is developed, which ensures proper control of the unit step voltage level in each of the cascaded modules, at extreme loading condition. For two cascaded inverter modules, simulation and experimental verifications are carried out on the proposed inverter for an R–L load. Simulation results of the output voltage waveforms and its harmonic spectrum are in conformity with experimental results.