Showing papers on "Inverter published in 2006"

High-Power Converters and AC Drives

Abstract: Preface. Part One Introduction. 1. Introduction. 1.1 Introduction. 1.2 Technical Requirements and Challenges. 1.3 Converter Configurations. 1.4 MV Industrial Drives. 1.5 Summary. References. Appendix. 2. High-Power Semiconductor Devices. 2.1 Introduction. 2.2 High-Power Switching Devices. 2.3 Operation of Series-Connected Devices. 2.4 Summary. References. Part Two Multipulse Diode and SCR Rectifiers. 3. Multipulse Diode Rectifiers. 3.1 Introduction. 3.2 Six-Pulse Diode Rectifier. 3.3 Series-Type Multipulse Diode Rectifiers. 3.4 Separate-Type Multipulse Diode Rectifiers. 3.5 Summary.(c) References. 4. Multipulse SCR Rectifiers. 4.1 Introduction. 4.2 Six-Pulse SCR Rectifier. 4.3 12-Pulse SCR Rectifier. 4.4 18- and 24-Pulse SCR Rectifiers. 4.5 Summary. References. 5. Phase-Shifting Transformers. 5.1 Introduction. 5.2 Y/Z Phase-Shifting Transformers. 5.3 /Z Transformers. 5.4 Harmonic Current Cancellation. 5.5 Summary. Part Three Multilevel Voltage Source Converters. 6. Two-Level Voltage Source Inverter. 6.1 Introduction. 6.2 Sinusoidal PWM. 6.3 Space Vector Modulation. 6.4 Summary. References. 7. Cascaded H-Bridge Multilevel Inverters. 7.1 Introduction. 7.2 H-Bridge Inverter. 7.3 Multilevel Inverter Topologies. 7.4 Carrier Based PWM Schemes. 7.5 Staircase Modulation. 7.6 Summary. References. 8. Diode-Clamped Multilevel Inverters. 8.1 Introduction. 8.2 Three-Level Inverter. 8.3 Space Vector Modulation. 8.4 Neutral-Point Voltage Control. 8.5 Other Space Vector Modulation Algorithms. 8.6 High-Level Diode-Clamped Inverters. 8.7 Summary. References. Appendix. 9. Other Multilevel Voltage Source Inverters. 9.1 Introduction. 9.2 NPC/H-Bridge Inverter. 9.3 Multilevel Flying-Capacitor Inverters. 9.4 Summary. References. Part Four PWM Current Source Converters. 10. PWM Current Source Inverters. 10.1 Introduction. 10.2 PWM Current Source Inverter. 10.3 Space Vector Modulation. 10.4 Parallel Current Source Inverters. 10.5 Load-Commutated Inverter (LCI). 10.6 Summary. References. Appendix. 11. PWM Current Source Rectifiers. 11.1 Introduction. 11.2 Single-Bridge Current Source Rectifier. 11.3 Dual-Bridge Current Source Rectifier. 11.4 Power Factor Control . 11.5 Active Damping Control. 11.6 Summary. References. Appendix. Part Five High-Power AC Drives. 12. Voltage Source Inverter-Fed Drives. 12.1 Introduction. 12.2 Two-Level VBSI-Based MV Drives. 12.3 Neutral-Point Clamped (NPC) Inverter-Fed Drives. 12.4 Multilevel Cascaded H-Bridge (CHB) Inverter-Fed Drives. 12.5 NPC/H-Bridge Inverter-Fed Drives. 12.6 Summary. References. 13. Current Source Inverter-Fed Drives. 13.1 Introduction. 13.2 CSI Drives with PWM Rectifiers. 13.3 Transformerless CSI Drive for Standard AC Motors. 13.4 CSI Drive with Multipulse SCR Rectifier. 13.5 LCI Drives for Synchronous Motors. 13.6 Summary. References. 14. Advanced Drive Control Schemes. 14.1 Introduction. 14.2 Reference Frame Transformation. 14.3 Induction Motor Dynamic Models. 14.4 Principle of Field-Oriented Control (FOC). 14.5 Direct Field-Oriented Control. 14.6 Indirect Field-Oriented Control. 14.7 FOC for CSI-Fed Drives. 14.8 Direct Torque Control. 14.9 Summary. References. Abbreviations. Appendix Projects for Graduate-Level Courses. P. 1 Introduction. P. 2 Sample Project. P. 3 Answers to Sample Project. Index. About the Author.

Constant boost control of the Z-source inverter to minimize current ripple and voltage stress

Abstract: This paper proposes two constant boost-control methods for the Z-source inverter, which can obtain maximum voltage gain at any given modulation index without producing any low-frequency ripple that is related to the output frequency and minimize the voltage stress at the same time. Thus, the Z-network requirement will be independent of the output frequency and determined only by the switching frequency. The relationship of voltage gain to modulation index is analyzed in detail and verified by simulation and experiments.

Wireless-Control Strategy for Parallel Operation of Distributed-Generation Inverters

Abstract: In this paper, a method for the parallel operation of inverters in an ac-distributed system is proposed. This paper explores the control of active and reactive power flow through the analysis of the output impedance of the inverters and its impact on the power sharing. As a result, adaptive virtual output impedance is proposed in order to achieve a proper reactive power sharing, regardless of the line-impedance unbalances. A soft-start operation is also included, avoiding the initial current peak, which results in a seamless hot-swap operation. Active power sharing is achieved by adjusting the frequency in load transient situations only, owing to which the proposed method obtains a constant steady-state frequency and amplitude. As opposed to the conventional droop method, the transient response can be modified by acting on the main control parameters. Linear and nonlinear loads can be properly shared due to the addition of a current harmonic loop in the control strategy. Experimental results are presented from a two-6-kVA parallel-connected inverter system, showing the feasibility of the proposed approach

Digital control in power electronics

Abstract: This book presents the reader, whether an electrical engineering student in power electronics or a design engineer, a selection of power converter control problems and their basic digital solutions, based on the most widespread digital control techniques. The presentation is primarily focused on different applications of the same power converter topology, the half-bridge voltage source inverter, considered both in its single- and three-phase implementation. This is chosen as the test case because, besides being simple and well known, it allows the discussion of a significant spectrum of the most frequently encountered digital control applications in power electronics, from digital pulse width modulation (DPWM) and space vector modulation (SVM), to inverter output current and voltage control, ending with the relatively more complex VSI applications related to the so called smart-grid scenario. This book aims to serve two purposes: (1) to give a basic, introductory knowledge of the digital control techniques applied to power converters; and (2) to raise the interest for discrete time control theory, stimulating new developments in its application to switching power converters.

$Z$ -Source Inverter for Residential Photovoltaic Systems

Abstract: This paper proposes a Z-source inverter system for a split-phase grid-connected photovoltaic system. The operation principle, control method, and characteristics of the system are presented. A comparison between the new and traditional system configurations is performed. Simulation and experimental results are also shown to verify the proposed circuit and analysis

Flyback-Type Single-Phase Utility Interactive Inverter With Power Pulsation Decoupling on the DC Input for an AC Photovoltaic Module System

Abstract: In recent years, interest in natural energy has grown in response to increased concern for the environment. Many kinds of inverter circuits and their control schemes for photovoltaic (PV) power generation systems have been studied. A conventional system employs a PV array in which many PV modules are connected in series to obtain sufficient dc input voltage for generating ac utility line voltage from an inverter circuit. However, the total power generated from the PV array is sometimes decreased remarkably when only a few modules are partially covered by shadows, thereby decreasing inherent current generation, and preventing the generation current from attaining its maximum value on the array. To overcome this drawback, an ac module strategy has been proposed. In this system, a low-power dc-ac utility interactive inverter is individually mounted on each PV module and operates so as to generate the maximum power from its corresponding PV module. Especially in the case of a single-phase utility interactive inverter, an electrolytic capacitor of large capacitance has been connected on the dc input bus in order to decouple the power pulsation caused by single-phase power generation to the utility line. However, especially during the summer season, the ac module inverters have to operate under a very high atmospheric temperature, and hence the lifetime of the inverter is shortened, because the electrolytic capacitor has a drastically shortened life when used in a high-temperature environment. Of course, we may be able to use film capacitors instead of the electrolytic capacitors if we can pay for the extreme large volume of the inverter. However, this is not a realistic solution for ac module systems. This paper proposes a novel flyback-type utility interactive inverter circuit topology suitable for ac module systems when its lifetime under high atmospheric temperature is taken into account. A most distinctive feature of the proposed system is that the decoupling of power pulsation is executed by an additional circuit that enables employment of film capacitors with small capacitance not only for the dc input line but also for the decoupling circuit, and hence the additional circuit is expected to extend the lifetime of the inverter. The proposed inverter circuit also enables realization of small volume, lightweight, and stable ac current injection into the utility line. A control method suitable for the proposed inverter is also proposed. The effectiveness of the proposed inverter is verified thorough P-SIM simulation and experiments on a 100-W prototype

A Space Vector PWM Scheme for Multilevel Inverters Based on Two-Level Space Vector PWM

Abstract: Multilevel inverters are increasingly being used in high-power medium voltage applications due to their superior performance compared to two-level inverters. Among various modulation techniques for a multilevel inverter, the space vector pulsewidth modulation (SVPWM) is widely used. However, the implementation of the SVPWM for a multilevel inverter is complicated. The complexity is due to the difficulty in determining the location of the reference vector, the calculation of on-times, and the determination and selection of switching states. This paper proposes a general SVPWM algorithm for multilevel inverters based on standard two-level SVPWM. Since the proposed multilevel SVPWM method uses two-level modulation to calculate the on-times, the computation of on-times for an n-level inverter becomes easier. The proposed method uses a simple mapping to achieve the SVPWM for a multilevel inverter. A general n-level implementation is explained, and experimental results are given for three-level and five-level inverters

Interfacing Renewable Energy Sources to the Utility Grid Using a Three-Level Inverter

Abstract: This paper presents a novel approach for the connection of renewable energy sources to the utility grid. Due to the increasing power capability of the available generation systems, a three-level three-phase neutral-point-clamped voltage-source inverter is selected as the heart of the interfacing system. A multivariable control law is used for the regulator because of the intrinsic multivariable structure of the system. A current source (playing the role of a generic renewable energy source) is connected to the grid using a three-level inverter in order to verify the good performance of the proposed approach. Large- and small-signal d-q state-space averaged models of the system are obtained and used to calculate the multivariable controller based on the linear quadratic regulator technique. This controller simultaneously regulates the dc-link voltage (to operate at the maximum power point of the renewable energy source), the mains power factor (the power is delivered to the grid at unity power factor), and the dc-link neutral-point voltage balance. With the model and regulator presented, a specific switching strategy to control the dc-link neutral-point voltage is not required. The proposed controller can be used for any application, since its nature makes possible the control of any system variable. The good performance of the presented interfacing solution in both steady-state and transient operation is verified through simulation and experimentation using a 1-kW neutral-point-clamped voltage-source-inverter prototype, where a PC-embedded digital signal processor board is used for the controller implementation

1.3 V 20 ps time-to-digital converter for frequency synthesis in 90-nm CMOS

Abstract: We propose and demonstrate a 20-ps time-to-digital converter (TDC) realized in 90-nm digital CMOS. It is used as a phase/frequency detector and charge pump replacement in an all-digital phase-locked loop for a fully-compliant Global System for Mobile Communications (GSM) transceiver. The TDC core is based on a pseudodifferential digital architecture that makes it insensitive to nMOS and pMOS transistor mismatches. The time conversion resolution is equal to an inverter propagation delay, which is the finest logic-level regenerative timing in CMOS. The TDC is self calibrating with the estimation accuracy better than 1%. It additionally serves as a CMOS process strength estimator for analog circuits in this large system-on-chip. Measured integral nonlinearity is 0.7 least significant bits. The TDC consumes 5.3 mA raw and 1.3 mA with power management from a 1.3-V supply.

Analytical calculation of the RMS current stress on the DC-link capacitor of voltage-PWM converter systems

Abstract: A simple analytical expression for the current stress on the DC-link capacitor caused by the load-side inverter of a voltage DC-link-converter system is derived. The DC-link capacitor-current RMS value is determined from the modulation depth and by the amplitude and the phase angle of the inverter output current assuming a sinusoidal inverter output current and a constant DC-link voltage. Despite neglecting the output-current ripple, the results of the analytical calculation are within 8% of measurements made from digital simulation and an experimental system, even if the output-current ripple is relatively high as in the case of low-frequency IGBT inverter systems. The simple analytical expression provides significant advantages over simulation methods for designing the DC-link capacitor of PWM converter systems.

High-Quality Power Generation Through Distributed Control of a Power Park Microgrid

Abstract: Inverters are a necessary interface for several forms of distributed generation (DG) and where they form a microgrid they have the potential to offer high power quality. The challenge is to coordinate the actions of a group of inverters so that they offer the level of power quality known to be possible from fast local control of a single inverter. The case examined here is a power park of several inverter-based DG in relatively close proximity. A basic requirement is that the inverters regulate the grid voltage and share the real and reactive power demands according to their ratings. In small girds with high proportions of nonlinear and unbalanced loads it is also important to actively control the waveform quality in terms of harmonics, transient disturbances, and balance. Further, it is important that these duties are shared equally between the units rather than having one master unit taking the lead in the voltage control function. A constraint faced in designing a sharing system is the limited bandwidth of signal communication even over distances of a few meters. A control method is proposed that separates the control tasks in the frequency domain. Power sharing and voltage regulation are controlled centrally and commands are distributed through a low-bandwidth communication link. Waveform quality functions are controlled in high bandwidth controllers distributed to each local inverter. Experimental tests on a grid of three 10-kVA inverters are used to show that the method fully exploits the inherent fast response of the inverters while also ensuring voltage balance even with extreme load imbalance. It is shown that circulating currents are avoided during steady state and transients

Combined operation of unified power-quality conditioner with distributed generation

Abstract: This paper describes analysis results of a combined operation of the unified power quality conditioner with the distributed generation. The proposed system consists of a series inverter, a shunt inverter, and a distributed generator connected in the dc link through a rectifier. The proposed system can compensate voltage sag and swell, voltage interruption, harmonics, and reactive power in both interconnected mode and islanding mode. The performance of proposed system was analyzed using simulations with power system computer aided design/electromagnetic transients dc analysis program, and experimental results with the hardware prototype. The proposed system can improve the power quality at the point of installation on power distribution systems or industrial power systems.

Optimal Design of a Hybrid Winding Structure for Planar Contactless Battery Charging Platform

Abstract: Planar contactless battery charging platform is an emerging technology that has the potential of unifying the charging protocols of portable consumer electronic products. In this paper, a new hybrid structure which consists of a coil and a spiral winding is proposed for improving the uniform magnetic field distribution over the charging surface. An analysis into an optimal design of the number of turns and the dimension of the spiral winding is presented for a given concentrated coil. The uniform magnetic field distribution of the designed prototype is measured by an electromagnetic compatibility scanner and by an energy-receiving coil. Based on circuit modeling and analysis, the inverter circuit topology and particularly the resonant compensation tank is designed for maximizing power transfer for multiload applications. A design procedure is proposed and verified by the experiments. An efficiency of about 80% has been achieved for the coupled structures when four loads are charged on the platform simultaneously.

A New Simplified Multilevel Inverter Topology for DC–AC Conversion

Abstract: Multilevel converters offer high power capability, associated with lower output harmonics and lower commutation losses. Their main disadvantage is their complexity, requiring a great number of power devices and passive components, and a rather complex control circuitry. This work reports a new multilevel inverter topology using an H-bridge output stage with a bidirectional auxiliary switch. The new topology produces a significant reduction in the number of power devices and capacitors required to implement a multilevel output. The new topology is used in the design of a five-level inverter; only five controlled switches, eight diodes, and two capacitors are required to implement the five-level inverter using the proposed topology. The new topology achieves a 37.5% reduction in the number of main power switches required (five in the new against eight in any of the other three configurations) and uses no more diodes or capacitors that the second best topology in the literature, the Asymmetric Cascade configuration. Additionally, the dedicated modulator circuit required for multilevel inverter operation is implemented using a FPGA circuit, reducing overall system cost and complexity. Theoretical predictions are validated using simulation in SPICE, and satisfactory circuit operation is proved with experimental tests performed on a laboratory prototype

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

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

An improved control strategy for grid-connected voltage source inverters with a LCL filter

Abstract: This paper proposes a novel control strategy for grid-connected voltage source inverters (VSI) with an LCL-filter. The strategy "split" the capacitor of LCL-filter into two parts, and the current flowing between these two parts is measured and used as the feedback of a current regulator to stabilize and improve the system performances. By this way, the inverter control system is simplified from third-order to first-order, and the close loop control system can easily be optimized for minimum steady-state error and current harmonic distortion. The characteristics of the inverter system with the proposed controller are investigated and compared with the traditional strategy. Simulations results are provided, and the new current control strategy has been experimentally tested on a 5kW fuel cell inverter.

Extended operation of flying capacitor multilevel inverters

Abstract: Recent research in flying capacitor multilevel inverters (FCMIs) has shown that the number of voltage levels can be extended by changing the ratio of the capacitor voltages. For the three-cell FCMI, four levels of operation are expected if the traditional ratio of the capacitor voltages is 1:2:3. However, by altering the ratio, the inverter can operate as a five-, six-, seven-, or eight-level inverter. According to previous research, the eight-level case is referred to as maximally distended (or full binary combination schema) since it utilizes all possible transistor switching states. However, this case does not have enough per-phase redundancy to ensure capacitor voltage balancing under all modes of operation. In this paper, redundancy involving all phases is used along with per-phase redundancy to improve capacitor voltage balancing. It is shown that the four- and five-level cases are suitable for motor drive operation and can maintain capacitor voltage balance under a wide range of power factors and modulation indices. The six-, seven-, and eight-level cases are suitable for reactive power transfer in applications such as static var compensation. Simulation and laboratory measurements verify the proposed joint-phase redundancy control.

System and method for powering a load

Abstract: A power supply (6) for inductively powering a remote device (8) has an inverter (10) operating at an operating frequency and a primary coil (24). A phase comparator (35) compares the phase of the voltage or current delivered by the power supply (6). If the phase relationship detected by the comparator (35) is unacceptable, the inverter (10) is disabled. After a period of time, the inverter (10) is re-enabled, and the phase relationship is again determined.

A grid-interfacing power quality compensator for three-phase three-wire microgrid applications

Abstract: This paper proposes a grid-interfacing power quality compensator for three-phase three-wire microgrid applications with consideration of both the power quality of the microgrid and the quality of currents flowing between the microgrid and utility system. It is proposed that two inverters connected in shunt and series are used for each distributed generation (DG) system in the microgrid. In each inverter, both positive- and negative-sequence components are controlled to compensate for the effects caused by the unbalanced utility grid voltages. Specifically, the shunt inverter is controlled to ensure balanced voltages within the microgrid and to regulate power dispatches among parallel-connected DG systems, while the series inverter balances the line currents by injecting appropriate voltage components. A current-limiting algorithm is also proposed and integrated within the inverter control schemes to protect the microgrid from large fault currents during utility voltage sags. The proposed compensator has been tested in simulations and experimentally using a laboratory hardware prototype.

Ultrafast integrable and reconfigurable XNOR, AND, NOR, and NOT photonic logic gate

Abstract: A novel, simple, compact, and integrable scheme of reconfigurable and ultrafast photonic logic gate is demonstrated, based on a single semiconductor optical amplifier (SOA) and able to process ultrafast signals. XNOR function has been optically implemented exploiting four-wave mixing and cross-gain modulation in an SOA. The same scheme can be easily reconfigured to obtain AND, NOR, and NOT logic gates. Performances in terms of bit error rate for 20-ps return-to-zero signals at 10 Gb/s show a power penalty limited to 0.5 dB for all logic gates but the AND, which experiences regeneration (-2-dB power penalty) due to nonlinear SOA noise compression.

High performance torque and flux control for multilevel inverter fed induction motors

Abstract: This paper presents a high-performance torque and flux control strategy for high-power induction motor drives. The control method uses the torque error to control the load angle, obtaining the appropriate flux vector trajectory from which the voltage vector is directly derived based on direct torque control principles. The voltage vector is then generated by an asymmetric cascaded multilevel inverter without need of modulation and filter. Due to the high output quality of the inverter, the torque response presents nearly no ripple. In addition, switching losses are greatly reduced since 80% of the power is delivered by the high-power cell of the asymmetric inverter, which commutates at fundamental frequency. Simulation and experimental results for 81-level inverter are presented.

Boost current multilevel inverter and its application on single-phase grid-connected photovoltaic systems

Abstract: This work presents a novel current multilevel (CML) inverter topology, named boost CML inverter, and its application on energy processing of single-phase grid-connected photovoltaic (PV) systems. The structure allows a high power factor operation of a PV system, injecting a quasi-sinusoidal current into the grid, with virtually no displacement in relation to the line voltage at the point of common coupling among the PV system and the loads. The major appeals of using the CML technique are the balanced current sharing among semiconductor switches and the decrease of the current slope in the circuit devices, with a consequent reduction of conducted and radiated electromagnetic interference (EMI). The CML technique also allows adapting or minimizing current waveforms harmonic content. System description, mathematical approach, and design guidelines are presented, providing an overview of the new topology. In order to validate the proposed concepts, experimental measurements, made in a small-scale laboratory prototype, are also presented. The obtained results evidence the feasibility of the application of this new topology on singlephase grid-connected PV systems.

Modeling and design of a neutral-point voltage regulator for a three-level diode-clamped inverter using multiple-carrier modulation

Abstract: The three-level diode-clamped multilevel converter commonly called the neutral-point-clamped converter has become established to be a preferred topology for high-power motor drive applications operating at several kilovolts. Although solutions to the problem of maintaining a stable neutral-point voltage in the converter continue to be the topic of research, a simple solution based on a design-oriented dynamic model of the system is not widely known. This paper presents the design, analysis, and implementation of a simple neutral-point voltage regulator for a three-level diode-clamped multilevel inverter, which uses a multiple-carrier sine-triangle modulator in conjunction with a closed-loop controller for neutral-point regulation. Redundant state choices are controlled via a continuous offset voltage that regulates the dc injection into the midpoint of the dc bus. A small-signal transfer function is developed in closed form, for neutral-point regulation, with the voltage offset as the control variable. Besides maintaining dc-bus voltage balance, the use of the approach leads to a significant reduction in the voltage distortion at the neutral point, allowing a definitive reduction in the required dc bus capacitance. Analytical, computer simulation, and experimental results verifying the approach are presented in this paper.

Optimized one-cycle control in photovoltaic grid connected applications

Abstract: The use of one-cycle control (OCC) for maximum power point tracking (MPPT) and power factor correction (PFC) in grid connected photovoltaic (PV) applications is discussed. Circuit and operating parameters of the one cycle-based controller of a cost-effective single-stage inverter are optimized in order to obtain the best performances of the system under different irradiance levels. Firstly, design constraints are formulated which allow to get a very efficient OCC operation in terms of power extracted from the PV array, stability, and PFC. Afterwards, such constraints are used to perform the parametric optimization of the one cycle controller by means of suitable heuristic approaches. Various selection criteria of the best parameters set under different conditions are discussed and applied. Finally, a customized perturb and observe (P&O) control is applied to the optimized one cycle controlled single-stage inverter in order to perform a real MPPT in presence of varying irradiance conditions. Subjects described here are covered by the Italian Patent Application SA2005A000014-13.07.2005 and PCT Application PCT/IT2005/000747-20.12.2005

High-performance solar photovoltaic ( PV) energy conversion system

Abstract: The present invention focuses on the development of a high-performance solar photovoltaic (PV) energy conversion system. The power circuit of the invention is made of a two-stage circuit, connecting a step-up DC-DC converter and a full-bridge inverter in serial. The present invention uses an adaptive perturbation and observation method to increase tracking speed of maximum power position and at the same time reduces energy loss. In addition, the full-bridge inverter's output has to have the same phase with the utility power in order to achieve unit power factor and increase the system efficiency. The present invention uses voltage type current control full-bridge inverter to achieve the goal of merging into utility grid. The present invention provides an active Sun tracking system, by utilizing the character of changing in open circuit output voltage with Sun radiation strength to follow the Sun, and decreases the system cost and increases system effectiveness.

Fault-Tolerant Operating Strategies Applied to Three-Phase Induction-Motor Drives

Abstract: This paper presents a comparative analysis involving several fault-tolerant operating strategies, applied to three-phase induction-motor drives, that intend to compensate for inverter faults. The results presented show the advantages and the inconveniences of several fault-tolerant drive structures, under different control techniques, such as the field-oriented control and the direct torque control. Experimental results concerning the performance of the three-phase induction motor, based on the analysis of some key parameters, like induction-motor efficiency, motor power factor, and harmonic distortion of both motor line currents and phase voltages, will be presented

High-level multistep inverter optimization using a minimum number of power transistors

Abstract: Multilevel inverters with a large number of steps (more than 50 levels) can generate high quality voltage waveforms, good enough to be considered as suitable voltage template generators. Many levels or steps can follow a voltage reference with accuracy, and with the advantage that the generated voltage can be modulated in amplitude instead of pulse-width modulation. The main disadvantage of this type of topology is the large number of power supplies and semiconductors required to obtain these multistep voltage waveforms. This paper is focussed on minimizing the number of power supplies and semiconductors for a given number of levels. Different combinations of topologies are presented, and the corresponding mathematical relations have been derived. This paper shows optimized curves to obtain the relation between a minimum number of power semiconductors required for a given number of levels. Experimental results obtained from an optimized prototype, capable of generatng 81 levels of voltage with only four power supplies and 16 transistors per phase, are shown.

Model-based fault diagnosis in electric drives using machine learning

Abstract: Electric motor and power electronics-based inverter are the major components in industrial and automotive electric drives. In this paper, we present a model-based fault diagnostics system developed using a machine learning technology for detecting and locating multiple classes of faults in an electric drive. Power electronics inverter can be considered to be the weakest link in such a system from hardware failure point of view; hence, this work is focused on detecting faults and finding which switches in the inverter cause the faults. A simulation model has been developed based on the theoretical foundations of electric drives to simulate the normal condition, all single-switch and post-short-circuit faults. A machine learning algorithm has been developed to automatically select a set of representative operating points in the (torque, speed) domain, which in turn is sent to the simulated electric drive model to generate signals for the training of a diagnostic neural network, fault diagnostic neural network (FDNN). We validated the capability of the FDNN on data generated by an experimental bench setup. Our research demonstrates that with a robust machine learning approach, a diagnostic system can be trained based on a simulated electric drive model, which can lead to a correct classification of faults over a wide operating domain.