Showing papers on "Three-phase published in 2001"

Design and control of an LCL-filter-based three-phase active rectifier

Abstract: This paper proposes a step-by-step procedure for designing the LCL filter of a front-end three-phase active rectifier. The primary goal is to reduce the switching frequency ripple at a reasonable cost, while at the same time achieving a high-performance front-end rectifier (as characterized by a rapid dynamic response and good stability margin). An example LCL filter design is reported and a filter has been built and tested using the values obtained from this design. The experimental results demonstrate the performance of the design procedure both for the LCL filter and for the rectifier controller. The system is stable and the grid current harmonic content is low both in the lowand high-frequency ranges. Moreover, the good agreement that was obtained between simulation and experimental results validates the proposed approach. Hence, the design procedure and the simulation model provide a powerful tool to design an LCL-filter-based active rectifier while avoiding trial-and-error procedures that can result in having to build several filter prototypes.

A new hybrid filter to dampen resonances and compensate harmonic currents in industrial power systems with power factor correction equipment

Abstract: A new hybrid power filter is presented for three phase industrial power systems which include passive power factor correction equipment (PFC). The hybrid filter damps resonances occurring between line impedances and the PFC. In addition, the hybrid filter topology can be used to compensate harmonic currents. The capacitors of the PFC, which generally cause resonant problems in harmonic distorted networks, can be used for passive filtering by connecting a transformer with a low magnetizing inductance in series hence creating a single harmonic trap. The primary side of the transformer is connected to a low VA-rated three-phase current controlled inverter which builds the active part of the hybrid topology. Simulation results and experimental results are presented verifying the damping and harmonic compensation performance of the proposed topology.

Unified constant-frequency integration control of three-phase power factor corrected rectifiers, active power filters, and grid-connected inverters

Abstract: An unified constant-frequency integration (UCI) control method based on one-cycle control employs an integrator with reset as its core component along with a few logic and linear components to control the pulse width of a three-phase recitifier, active power filter, or grid-connected inverter so that the all three phase current draw from or the current output to the utility line is sinusoidal. No multipliers and reference calculation circuitry are needed for controlling active power filters. The UCI control employs constant switching frequency and operates in continuous conduction mode (CCM). If in some cases a DSP is desired for some other purposes, the Unified Constant-frequency Control function can be realized by a low cost DSP with a high reliability, because no high speed calcutation, high speed A/D converter, and mutipliers are required.

Comparison of single-sensor current control in the DC link for three-phase voltage-source PWM converters

Abstract: This paper presents a technique for reconstructing converter line currents using the information from a single current sensor in the DC link of a converter and comparative evaluation of the performance of single sensor control techniques in the DC link for voltage-source pulsewidth modulation (V-S PWM) converters. When 3/spl phi/ input currents cannot be reconstructed, three methods to acquire the DC-link current are compared. Two of them are methods of modifying the switching state (I, II), and another is a method of using the predictive state observer. Also, compensation of sampling delay, and a simultaneous sample value of input currents in the center of a switching period are included. Suitable criteria for the comparison are identified, and the differences in the performance of these methods are investigated through experimental results for a typical V-S PWM converter rated at 10 kVA.

A novel modeling and control method for three-phase PWM converters

Abstract: The pulse-width modulated (PWM) voltage-source converter (VSC) and current-source converter (CSC) are the building blocks of most of the switch-mode power electronic systems. Irrespective of the converter type, the controller is supposed to fulfill two objectives: (1) real power flow control which leads to the regulation of the DC quantity (DC voltage in VSC and DC current in CSC), and (2) reactive power flow control on the AC-side. The major difficulty in control is caused by the nonlinearities in the converter model. The existing control techniques are based on the design of the PI-controllers without the knowledge of the converter model, linearizing the nonlinear model, or splitting the original system into linear and nonlinear parts and dealing with them separately. In this paper, a power balance equation and nonlinear input transformation are used to derive a linear model from the original nonlinear model. Then, a decoupled state-feedback control method is applied to the new model. The accuracy of the new model and the performance of the applied control method are evaluated using the simulation results obtained from the PSCAD/EMTDC simulation package. It is shown that as a result of using the new model and applying the state-feedback control technique, the dynamics of the system are considerably improved resulting in short response times. It is also shown that the approach taken in modeling and control results in excellent results even at low switching frequencies making the scheme very suitable for high-power applications.

Single phase induction motor drives-a literature survey

Abstract: This paper deals with a literature survey of various existing power converter topologies, which have been proposed for adjustable-speed single-phase induction motor drives (SPIMD). Included in the paper are several newly proposed power converter topologies. A study of the merit and demerit of different power converter topologies have been carried out. Various converter topologies have been compared in this paper. Among these converter topologies, the adjustable frequency PWM inverter is the best choice for single-phase induction motor drives. However, adjustable-frequency drives have not been widely used with single-phase induction motors. The open-loop constant V/f control law cannot be used with the single-phase induction motor drives as it is used with three phase motors. The variation of the operating frequency at lower speed range with constant load torque causes variation in the motor's slip. A constant V/f control is suitable only over the upper speed range. However, improvements in the low frequency performance require the use of constant power dissipation in the motor. Simulation studies for some of the existing topologies as well as for the proposed ones have been carried out.

Characterization of three phase flux reversal machine as an automotive generator

Abstract: The three phase flux reversal machine (FRM) is a doubly-salient stator-permanent magnet (PM) machine with flux linkage reversal in the stator three phase concentrated windings. It can operate in both motoring and generating modes. In this paper, a prototype three phase flux reversal machine operating as a generator is studied both theoretically and experimentally. The equivalent model considering the core losses is obtained through extensive loss tests. A constant output voltage rectifier-chopper unit is then coupled with the loss model and the PSpice simulation is carried out. Hardware of the rectifier-chopper unit is then built and put into operation together with the FRM. Encouraging results are achieved indicating that the three phase FRM, with proper output control, is a viable option for the next generation automotive generator system with the merits of robustness, low cost, wide speed range and fast transient response. Whereas the studied machine in this paper is only a prototype, a new three phase FRM of improved design is being built and its projected performance in terms of the power density and the cogging torque is much better.

Three-phase PWM boost-buck rectifiers with power-regenerating capability

Abstract: Three-phase pulsewidth-modulated (PWM) boost-buck rectifiers with power-regenerating capability are investigated. The converters under consideration are capable of: (1) both voltage step-up and step-down; (2) bidirectional power processing; and (3) almost unity-power-factor operation with nearly sinusoidal AC current. Expected advantages are: (1) applicability to lower voltage applications, e.g., direct retrofit to replace diode or thyristor rectifiers; (2) switching loss reduction in the inverter load; (3) low-order harmonic control in the inverter load output voltage; (4) blanking time effect mitigation in the inverter load; and (5) a modest level of voltage sag/swell compensation. In this paper, firstly, a step-by-step power stage derivation process is described. Then, taking the Cuk-Cuk realization as an example, its operating principle and modulation scheme are described. A steady-state model and dynamic model for controller design are also described. Representative results of circuit simulations and hardware experiments are presented. Through these procedures, the feasibility of the presented three-phase PWM boost-buck rectifier with power-regenerating capability is demonstrated.

A three-phase soft-transition inverter with a novel control strategy for zero-current and near zero-voltage switching

Abstract: This paper proposes a new soft-transition control strategy for a three-phase zero-current-transition (ZCT) inverter circuit. Each phase leg of the inverter circuit consists of an LC resonant tank, two main switches, and two auxiliary switches. The proposed strategy is realized by planning the switching patterns and timings of these four switches based on the load current information. It enables all the main switches and auxiliary switches to be turned on and turned off under zero-current conditions, and achieves a near zero-voltage turn-on for the main switches. Compared with existing ZCT strategies, the diode reverse recovery current and switching turn-on loss are substantially reduced, the current and thermal stresses in the auxiliary devices are evenly distributed over every switching cycle, and the resonant capacitor voltage stress is reduced from twice the DC bus voltage to 1.3-1.4 times the DC bus voltage. The proposed strategy is also suitable for three-phase power-factor-correction (PFC) rectifier applications. The operation principles, including a detailed analyst based on the state-plane technique, and a design rule are described in this paper. The circuit operation is first verified by a computer simulation, and is then tested with a 50-kW three-phase inverter to the full power level together with a three-phase induction motor in a closed-loop speed/torque control. Significant reductions in switching losses and voltage/current stresses over existing techniques have been experimentally demonstrated.

Three-dimensional pulse-width modulation technique in three-level power inverters for three-phase four-wired system

Abstract: Shunt-connected trilevel power inverter in three-phase four-wired system as an active filter or individual current supply (peak-load supply) is studied by a novel technique: three-dimensional (3-D) voltage vectors pulse width modulation (PWM). In past decades, almost all the study for PWM is limited to the two-dimensional (2-D) domain, /spl alpha/ and /spl beta/ frames, in a three-phase three-wired system. However, in practical operation, there are many three-phase four-wired systems in distribution sites. The generalized study of 3-D two-level and three-level inverters is achieved in this paper so as to perform the basic theory of 3-D multilevel space vector switching PWM technique. The sign cubical hysteresis control strategy is proposed and studied with simulation results in 3-D aspect. The 3-D PWM technique in three-level inverters is accomplished.

Stator and rotor resistance identifier using high frequency injection

Abstract: A method and apparatus for generating stator and rotor resistance estimate, the method including the steps of providing high frequency injection voltage signals to a three phase motor, rotating three phase feedback current therefrom, converting the feedback currents to two phase currents that represent the high frequency component of the current vector wherein the d and q axis components are within a two phase voltage coordinate system and driving a regulator via one of the current components to generate a lag angle estimate, the lag angle estimate used to solve any of several different equations to calculate the stator and rotor resistance estimates.

Losses in three-phase induction machines fed by PWM converter

Abstract: The paper deals with the analysis and evaluation of test results of PWM converter-fed induction motors. The test results presented point out the dependency of the harmonic losses on the pulse frequency. The measured values were obtained by means of a novel high precision power-analyzer capable of measuring the harmonics of voltage, current and power. Following a detailed investigation regarding the sources of the harmonic losses the paper describes new methods for determining the harmonic losses by both calculation and measurement. The calculation is based on a new equivalent circuit comprising specific impedances for imaging the eddy-current circuits within the iron core derived from the fundamental equations of the three-phase asynchronous machine. These impedances permit the calculation of the harmonic iron losses under the influence of the eddy-currents in all sections of the magnetic circuit caused by the harmonics. Measured and calculated losses were found to correspond satisfactorily for the various voltage harmonics.

Method for multi-phase data communications and control over an esp power cable

Abstract: A three phase power cable is employed to transmit data encoded in a phase-to-phase manner within a high frequency carrier signal transmitted simultaneously with power transmitted from surface equipment to downhole components. The high frequency carrier signal is transmitted on all conductors of the power cable, with the signal carried on at least two phases or conductors modulated between the two conductors to encode data between the two phases. Any modulation technique may be employed. Multiple phase-to-phase signals may be encoded and transmitted between different pairs of the power cable conductors, or the same data may be encoded and transmitted in multiple phase-to-phase signals in either a single-ended or differential manner. The high frequency carrier may be employed to transmit data from sensors downhole to the surface equipment, control signals from the surface equipment to the downhole components, or both.

A FIRANN as a differential relay for three phase power transformer protection

Abstract: This paper presents an application of a finite impulse response artificial neural network (FIRANN) as differential protection for a real three phase power transformer. Three FIRANNs are designed, trained and tested. The first one has an output which identifies internal faults from any other cases like inrush current and external faults. The two others FIRANNs, each have two outputs that classify between internal and external faults, so that a backup protection is included. These FIRANNs have six inputs, one for each sampled current signal from both transformer sides. The sample rate selected is 2 kHz for a 50 Hz power frequency. All FIRANNs were trained to have a 3.5 ms fault detection time, which is considered as a very fast protection. The test results show very good behavior of the FIRANN as a differential protection and it is planned to build a prototype.

A unity-power-factor three-phase PWM SCR rectifier for high-power applications in the metal industry

Abstract: A new thyristor current-source rectifier that achieves unity power factor, low-current total harmonic distortion (THD), and DC-bus current and voltage control is presented. The rectifier is suitable for high-power applications such as induction heating and DC arc furnaces. It combines a traditional six-pulse thyristor bridge and a DC chopper that together solve power quality problems such as poor power factor and flicker generation. This topology achieves low input current THD and DC power control without additional power-factor-correction equipment, harmonic trap filters, use of multiple pulse rectifiers or high-K-factor transformers.

A new hybrid filter to dampen resonances and compensate harmonic currents in industrial power systems with power factor correction equipment

Abstract: A new hybrid power filter is presented for three phase industrial power systems which include passive power factor correction equipment (PFC). The hybrid filter damps resonances occurring between line impedances and the PFC. In addition, the hybrid filter topology cam be used to compensate harmonic currents. The capacitors of the PFC, which generally cause resonant problems in harmonic distorted networks, can be used for passive filtering by connecting the magnetizing inductance of a transformer in series. The primary side of the transformer is connected to a low VA-rated three-phase inverter which builds the active part of the hybrid topology. Simulation results and experimental results are presented verifying the damping and harmonic compensation performance of the proposed topology.

Three-level neutral point clamping pwm inverter and neutral point voltage controller

Abstract: According to a first calculated value ic that is the product of the calculated value of time of the three-phase output voltage at which the positive, negative, and neutral lines are connected to respective three phase output terminals and the neutral point predicted current value in this connection state, a second calculated value icx that is the product of the calculated value of time of the three-phase output voltage at which the lines can be in a first state in which two terminals of the three-phase output terminals are connected to the positive or neutral line and the other one of the terminals is connected to the neutral or negative line and the neutral predicted current value in the first state, and a third calculated value icy that is the product of the calculated value of time of the three-phase output voltage at which the lines can be in a second state in which two terminals of the three-phase output terminals are connected to the neutral or negative line and the other one of the terminals is connected to the positive or neutral line and the neutral predicted current value in the second state, the time ratio of the first and second states for a PWM period is so determined that the current flowing through the neutral line is made to approach zero or the potential of the neutral line of the three-phase output voltages is made to approach the mid point between the voltages of the positive and negative lines.

Comparative theoretical and experimental evaluation of bridge leg topologies of a three-phase three-level unity power factor rectifier

Abstract: In this paper a theoretical and experimental analysis of the voltage stress on the power semiconductors employed in a bridge leg of a unidirectional three-phase three-level PWM (VIENNA) rectifier is given. Furthermore, a new turn-on snubber is proposed which does improve the rectifier efficiency by 0.3% as verified by an experimental analysis and a detailed loss breakdown.

A Novel Single-Phase Self-Regulated Self-Excited Induction Generator Using a Three-Phase Machine

Abstract: This paper presents a steady-state analysis of a novel single-phase self-regulated self-excited induction generator which employs a three-phase machine. Performance equations are derived using the method of symmetrical components, while the pattern search method of Hooke and Jeeves is used for the determination of the machine variables. The advantages of the generator include simple circuit configuration, small voltage regulation, good phase balance, and large power output. With an appropriate choice of the series and shunt capacitances, a nearly balanced operating condition can be obtained for a certain load. The theoretical analysis is validated by experiments performed on a small induction machine.

Digital implementation of a line current shaping algorithm for three phase high power factor boost rectifier without input voltage sensing

Abstract: In this paper the implementation of a simple yet high performance digital current mode controller that achieves high power factor operation for a three phase boost rectifier is explained. This objective is achieved without input voltage sensing and without transformation of the control variables into rotating reference frame. The controller uses a resistor emulator concept for shaping of input current like input voltage in discrete domain. In implementation, Texas Instruments's DSP based unit TMS320F240F EVM is used as the digital hardware platform. The algorithm is tested on a 4 kW, 670 V DC output, boost rectifier. The execution time of the control algorithm is found to be less than 40 /spl mu/sec.

Analysis of the neutral conductor current in a three phase supplied network with nonlinear single phase loads

Abstract: This paper describes which factors (i.e. load and supply) have an important effect on the neutral conductor current. It is shown that an asymmetry up to 10/spl deg/ or an unbalance of 10% in the power supply has only a minor effect on the RMS-value of the neutral conductor current. An unbalance in load conditions increases the neutral conductor current. Harmonics in the power supply voltage highly affects the RMS-value of the neutral conductor current.

Sensorless vector control system of induction motor and method thereof

Abstract: A sensorless vector control system of an induction motor includes: a magnetic flux and speed controlling unit for receiving a predetermined command value and generating two phase voltages of DC component; a first reference frame converting unit for converting the two phase voltages of DC component into three phase voltages of AC component; an inverter for receiving the three phase voltages of AC component and driving an induction motor; a current detecting unit for receiving the three phase power of AC component flowing between the inverter and the induction motor, and detecting and outputting three phase currents of AC component; a second reference frame converting unit for receiving the three phase currents of AC component, and converting and outputting two phase currents of DC component; a magnetic flux and speed estimating unit for receiving the two phase voltage of DC component and the two phase currents of DC component, estimating a magnetic flux and speed required for a vector control; and a primary resistance estimating unit for receiving the two phase voltages of DC component, the two phase currents of DC component and the magnetic flux and speed estimated values, estimating a primary resistance and outputting it. Since the speed and the torque of the induction motor can be controlled, the vector control system can be adopted even to the application sector which requires a tension control such as paper, metal film or fiber which allows only a vector control as well as the variable speed.

Improved transient and steady state voltage regulation for single and three phase uninterruptible power supplies

Abstract: Most of the many reported control algorithms for uninterruptible power supplies use either filter inductor or filter capacitor currents as feedback variables to regulate the output voltage. This paper explores the fundamental performance issues associated with the use of these quantities as feedback variables, with a view to determining their contribution to the transient system response in any particular situation. Then a proportional plus resonant (P+resonant) compensator is added into the outer voltage regulation loop to achieve zero steady error, to develop a high performance UPS control algorithm which is applicable to both single and three phase systems. Theory, simulation and experimental results are presented in the paper.

A novel concept for mains voltage proportional input current shaping of a VIENNA rectifier eliminating controller multipliers. I. Basic theoretical considerations and experimental verification

Abstract: Part I of this paper proposes a novel mains voltage proportional input current control concept eliminating the multiplication of the output voltage controller output and the mains AC phase voltages for the derivation of mains phase current reference values of a three phase/level/switch PWM (VIENNA) rectifier system. Furthermore, the concept features a low input current ripple amplitude as, e.g., achieved for space vector modulation, a low amplitude of the 3rd harmonic of the current flowing into the output voltage center point and a wide range of modulation. The practical realization of the analog control concept as well as experimental results for application with a 5 kW prototype of the PWM rectifier are presented. Furthermore, a control scheme which relies only on the absolute values of the input phase currents and a modified control scheme which does not require information about the mains phase voltages and therefore is ideally suited as a basis for the development of an integrated control circuit for three phase power factor correction is presented.

Dissipativity-based adaptive and robust control of UPS in unbalanced operation

Abstract: In this paper we investigate the output voltage control for three phase uninterruptible power supply (UPS) using controllers based on ideas of dissipativity. To provide balanced sinusoidal output voltages even in the presence of nonlinear and unbalanced loads, we first derive a dissipativity-based controller using a conventional /spl alpha//spl beta/ (fixed frame) representation of system dynamics and a frequency-domain representation of system disturbances. Adaptive refinements have been added to the controller to cope with parametric uncertainties. Second, based on the structure of the first adaptive controller and avoiding estimation of one of the parameters, we propose a controller, which leads to an LTI closed loop system and which is directly connected to synchronous frame harmonic voltage control. For the proposed solution, a sufficient condition in terms of the design parameters is presented to guarantee stability of the desired equilibrium and robustness against some parameter uncertainties. Finally, simulation and experimental results on a three-phase prototype show the effectiveness and advantages of the proposed approach.

Torque control of brushless DC motors applied to electric vehicles

Abstract: This paper presents a high-performance torque control system for brushless DC motors applied to electric scooters, with the aim of achieving similar output characteristics to that of continuously variable transmissions. Due to the fact that brushless DC motors applied to electric vehicles requires a wide range of operating speeds, phase advance control and field weakening control techniques are adopted in this paper. For the practical application of electric scooters, the control scheme uses only one current sensor to measure the DC bus current to achieve torque control, instead of two current sensors for three phase currents. Also three position Hall sensors are used to perform phase advance control and field weakening control, instead of an expensive encoder. Both the theoretical derivation and experimental verification for the proposed control scheme are presented in this paper, where the hardware implementation is carried out based on a three phase permanent magnet motor and a TI TMS320F240 digital signal processor.

A new three-phase low THD power supply with high-frequency isolation and 60V/200A regulated DC output

Abstract: This work proposes a new isolated high power factor 12 kW power supply based on an 18-pulse transformer arrangement. Three full-bridge converters are used for isolation and to balance the DC-link currents, without current sensing or a current controller. The topology provides a regulated DC output with a very simple control strategy. Simulation and experimental results are presented in this paper.

Design of a novel multi-chip power module for a three-phase buck+boost unity power factor utility interface supplying the variable voltage DC link of a square-wave inverter drive

Abstract: The power semiconductors of one bridge leg of the buck-type input stage of a three phase buck+boost PWM rectifier are integrated into a novel power module. The basic function of the rectifier system is described, and the current stresses on the power semiconductors are calculated analytically. By an experimental analysis of the module, the switching losses of the power transistors are determined, and the system efficiency and the loss contributions of the different components are calculated. This gives a basis for the selection of advantageous operating parameters of the module in an industrial application.

Adaptive directive neural network control for three-phase AC/DC PWM converter

Abstract: A novel control strategy is proposed: adaptive B-spline neural network for three-phase AC/DC voltage source converters, which realises a sinusoidal AC input current and unity power factor. Compared with other PWM techniques, neural network control provides an excellent component of a nonlinear system and is adaptive enough to fit the environment change. An on-line B-spline neural network is used because of its local weight updating characteristic, which has the advantages of fast convergence speed and low computation complexity. This is very important for real-time control applications. Both simulation and experimental results are presented to verify the effectiveness of the proposed control strategy.

Energy control of multi-switch power supplies; an application to the three-phase buck type rectifier with input filter

Abstract: The first part of the paper presents a systematic method for the modeling of power electronic networks with multiple switches using the classical Lagrangian framework. The main advantage of this method is its structured and general character compared to other methods. The power of working with Lagrangian dynamics, especially when very large networks have to be analyzed, is that Kirchhoff's voltage law is given in advance, while the interconnection structure is based on Kirchhoff's current laws only. The physical nonlinear structure of these systems is revealed and can be used for feedback controller design and stability analysis. The second part concentrates on the proposed passivity-based controller design technique based on the Lagrangian structure. Besides its physical significance, this approach appears to be an interesting alternative when dealing with the problem of input filter influences in power electronic systems. With this technique, artificial damping is injected such that the impedances of the in- and output filters can be matched. In this way power is not reflected and resonance problems, especially during the start-up and transient conditions, are minimized. A unity power factor passivity-based control algorithm for the three-phase buck type rectifier with an input filter is proposed that does not require current sensors but only measurements of the capacitor voltages.