Showing papers on "Three-phase published in 1995"

Space vector modulated three-phase to three-phase matrix converter with input power factor correction

Abstract: Analysis, design, and implementation of the space vector modulated three-phase to three-phase matrix converter with input power factor correction are presented. The majority of published research results on the matrix converter control are given an overview, and the one which employs simultaneous output-voltage and input-current space vector modulation, is systematically reviewed. The modulation algorithm is theoretically derived from the desired average transfer functions, using the indirect transfer function approach. The algorithm is verified through implementation of a 2 kVA experimental matrix converter driving a standard induction motor as a load. The switching frequency is 20 kHz. The modulator is implemented with a digital signal processor. The resultant output voltages and input currents are sinusoidal, practically without low-frequency harmonics. The input power factor is above 0.99 in the whole operating range.

A three-phase power flow method for real-time distribution system analysis

Abstract: This paper presents a three-phase power flow solution method for real-time analysis of primary distribution systems. This method is a direct extension of the compensation-based power flow method for weakly meshed distribution systems from single phase to three-phase, with the emphasis on modeling of dispersed generation (PV nodes), unbalanced and distributed loads, and voltage regulators and shunt capacitors with automatic local tap controls. The method proposed here is capable of addressing these modeling challenges while still maintaining a high execution speed required for real-time application in distribution automation systems. The paper also includes test results from the application of a computer program developed based on the proposed method to large primary electric distribution systems. >

New control algorithms for series and shunt three-phase four-wire active power filters

Abstract: This paper presents the general equations that relate the new concepts of instantaneous active and reactive power theory and the well known theory of Symmetrical Components, for the case of 3-phase 4-wire systems, where zero sequence components and harmonics may be present in both voltages and currents. Based on these equations, new control algorithms for 3-phase 4-wire shunt and series active filters for unbalanced power systems are proposed and validated through simulations. The control algorithms presented here are very important for active power filter design and also for FACTS technology reactive power compensators. >

A three-phase active power filter operating with fixed switching frequency for reactive power and current harmonic compensation

Abstract: The performance and dynamic characteristics of a three-phase active power filter operating with fixed switching frequency is presented and analyzed in this paper. The proposed scheme employs a PWM voltage-source inverter and has two important characteristics. First, it operates with fixed switching frequency, and second, it can compensate the reactive power and the current harmonic components of nonlinear loads. Reactive power compensation is achieved without sensing and computing the reactive component of the load current, thus simplifying the control system. Current harmonic compensation is done in time domain. The principles of operation of the proposed active power filter along with the design criteria of the power and control circuit components are discussed in detail. Finally, experimental results obtained from a 5 kVA prototype confirm the feasibility and the features of the proposed system. >

A delta-configured auxiliary resonant snubber inverter

Abstract: A delta (/spl Delta/) configured auxiliary resonant snubber inverter is developed to overcome the voltage floating problem in a wye (Y) configured resonant snubber inverter. The proposed inverter is used to connect auxiliary resonant branches between phase outputs to avoid a floating point voltage which may cause overvoltage failure of the auxiliary switches. Each auxiliary branch consists of a resonant inductor and a reverse blocking auxiliary switch. Instead of using an anti-paralleled diode to allow resonant current to flow in the reverse direction, as in the Y-configured version, the resonant branch in the /spl Delta/-configured version must block the negative voltage, typically done by a series diode. This paper shows single-phase and three-phase versions of /spl Delta/-configured resonant snubber inverters and describes in detail the operating principle of a single-phase version. The extended three-phase version is proposed with nonadjacent state space vector modulation. For hardware implementation, a single-phase 1 kW unit and a three-phase 100 kW unit were built to prove the concept. Experimental results show the superiority of the proposed topology.

A zero-voltage switched, three-phase isolated PWM buck rectifier

Abstract: A novel three-phase, single-stage, isolated PWM rectifier is proposed, which is capable of achieving unity power factor, and low harmonic distortion of input currents, and at the same time realizing zero-voltage switching for all power semiconductor devices. Operation of the proposed circuit is thoroughly analyzed. Design equations and trade-offs are provided. The performance of the proposed circuit is demonstrated through a 2 kW, 100 kHz, digital signal processor controlled prototype. The conversion efficiency is around 93%. >

High Efficiency Quasi-Resonant DC Link Three-phase Power Inverter for Full-Range PWM

Abstract: A quasi-resonant dc link soft switching inverter is presented, capable of PWM operation. It requires only two additional switches, and allows loss limitation in the resonant circuit. The modulation method adopted is able to perform true PWM operation at any modulation index. Simulated and experimental results are reported, confirming the effectiveness of the proposed solution.

Performance evaluation of a 250 kW switched reluctance starter generator

Abstract: This paper describes the system integration and performance evaluation testing of a high speed, 250 kW starter/generator [S/G] system used for starting and secondary electrical power extraction from an aircraft propulsion gas turbine. The effort described here is part a contract sponsored by the USAF, Wright Laboratories, WPAFB. The paper describes a switched reluctance [SR] machine which is operating both as a motor and generator in a speed range of 0 to 22,224 r.p.m. Additionally it is one of the highest rated motor/generator systems in the SR technology. The system employs two independent channels consisting of two groups of three phase windings, two three phase inverters, and two controllers and can provide two different power output buses for independent loading. The system hardware is described briefly followed by a detail description of the test results. These show some surprises with regards to single channel operating mode. A brief derivation and explanation of the findings is provided. The motor/generator system is planned to be part of a more electric aircraft power system.

15 kV medium voltage static transfer switch

Abstract: This paper presents the development and application of a three phase medium voltage static transfer switch system (MVSTS). The MVSTS is a 15 kV class switch system rated at a continuous current of 600 A. The function of a static transfer switch is to maintain AC electrical power to a critical load by switching between two independent power sources at speeds up to 4 ms. This switching time is sufficiently fast to preserve the operation of even the most sensitive customer equipment loads during distribution system disturbances such as voltage sags or voltage swells.

Brushless three-phase DC motor

Abstract: A three-phase brushless dc motor includes a permanent-magnet rotor magnet arrangement having at least four poles and a Y-connected, or star-connected, three-phase stator winding. The winding's phases are arranged non-overlapping in slots of a slotted stator, the currents flowing in the three phases being controlled via at least three semiconductor elements by at least three magnetic-field-sensitive rotor position sensors. Each sensor is associated with a respective two of the winding's three phases and triggers a commutation which switches off the current in one of the associated two phases and switches on the current in the other of the associated two phases. The sensors are located to sense the permanent-magnet flux emanating from the rotor poles themselves. The rotor position sensors are provided at special angular locations on the stator. Each sensor is provided at an angular location at which there is not to be found, neither prior to nor subsequent to the commutation associated with that sensor, any energized stator pole; this may mean that the sensor location is (i) an angular location at which no energizable stator pole whatever is present, and it may mean that the sensor location is (ii) an angular location at which an energizable stator pole is in fact present, but during motor operation this energizable stator pole is in an unenergized state prior to a commutation associated with the particular sensor in question and likewise is in unenergized state subsequent to that commutation.

Novel DC-rail soft-switched three-phase voltage-source inverters

Abstract: A family of DC-rail soft-switched three-phase voltage-source inverters (VSIs) adopting the zero-voltage-transition (ZVT) or zero-current-transition (ZCT) techniques are proposed in this paper. Adding an active switch on the DC-rail makes the implementation of the ZVT and ZCT as easy as in a single-ended DC/DC power converter, while true pulse-width-modulation (PWM) operation is achieved by a modified space-vector modulation. As a result, these inverters can run at much higher switching frequencies than conventional hard-switched VSIs, and with higher power density and efficiency. The operation and control strategy are analyzed. Implementation and experimental results of a prototype DC-rail ZVT VSI, which is rated at 15 kVA and run at a switching frequency of 62.5 kHz, are presented. The measured efficiency with static loads reaches 93% under the input voltage of 400 V.

Space vector based analysis of the variation and control of the neutral point potential of hysteresis current controlled three-phase/switch/level PWM rectifier systems

Abstract: This paper treats the control of the the capacitive output voltage center point of a unidirectional three-phase three-level PWM rectifier system. It is shown that, for hysteresis control of the input phase currents and resistive fundamental mains behavior, the center point potential can be controlled by an offset of the phase current reference values. Based on the results of a digital simulation, the transfer function is determined which describes the dynamic behavior of the system part to be controlled. Furthermore, the dimensioning of the center point voltage control is discussed. There, the considerations are related to an application of the PWM rectifier system for supplying the DC link of an uninterruptible power supply (8 kW rated power). Finally, the control behavior for stationary operation and for a step change of the load of the output voltage center point is examined for verifying the controller dimensioning. >

Three-phase step-down reversible AC-DC power converter

Abstract: Bidirectional DC current flow is not a natural feature of the buck (step-down) switch-mode rectifier, which leaves it at a disadvantage to boost (step-up) designs. A circuit topology is presented that allows bidirectional flow and which, by dual use of components, uses fewer devices than anti-parallel bridges. Sinusoidal current, controlled displacement factor, and variable voltage transfer ratio are demonstrated in a 1.5 kVA prototype. Dynamic performance is investigated through simulation and experiment. A PI plus velocity controller is shown to be adequate provided care is taken over changing between rectification and inversion.

Average current control of three-phase PWM boost rectifier

Abstract: Average current control of three-phase PWM boost rectifiers with three linear current compensators and six-step PWM is a very attractive solution for its simplicity. The performance of the closed-loop control depends on the compensator design. This paper presents a modeling, analysis and design procedure for the average current control scheme. The current compensator design is verified experimentally on a high-frequency 6 kW boost rectifier, through current waveforms. >

Phase monitor and protection apparatus

Abstract: A phase monitor and protection circuit is shown in which an impedance network (21, 23, 25) in a respective branch (20, 22, 24) connected to a neutral (26) is coupled to each phase of a three phase power supply (L1, L2, L3) to create a known voltage profile across the respective networks. A relay network (36) is coupled to one branch (20) and a control network (30) is coupled to a second branch (24) to monitor the voltage levels and deenergize the relay (R1) upon the occurrence of the reversal of any two phases or the loss of a phase. The control circuit can also be used to detect low voltage conditions and in a second embodiment provides a time delay network (44) to avoid nuisance tripping due to transient low voltage or brown out condition.

Third-Harmonic Modulated Power Electronics Interface with Three-phase Utility to Provide a Regulated DC Output and to Minimize

Abstract: A novel approach to achieve nearly sinusoidal line current rectification of three-phase utility voltages is presented. The scheme incorporates two step-up dc-dc converters to mod- ulate the dc-link currents at the third-harmonic frequency. The modulated currents are then circulated through the ac-side of the diode-bridge rectifier, using a zigzag autotransformer. Simulation results for a three-phase, 208-V (line-to-line), 1-kW system are presented. Results from experimental investigations on a labora- tory model are included, supporting the concept.

3-phase PWM boost rectifier circuit topologies using 2-level and 3-level asymmetrical half-bridges

Abstract: A 3-phase PWM boost rectifier is described that uses DC link inductors and an asymmetrical half bridge to obtain a unity fundamental power factor supply current with a low total harmonic distortion. The paper describes how the rectifier circuit structure can be broken down to form a fundamental circuit topology that contains two mutually decoupled boost power converter circuits. These boost circuits contain two near-triangular voltage sources, phase shifted from one another by 60/spl deg/ in the AC supply cycle, two DC link inductors and two semiconductor switches per circuit. The 3-phase bi-directional switches used in the bridge have very low electrical stresses with a low switching frequency, zero-voltage switching and a 0.2 p.u. current rating. Extensive analysis of the circuit switching states is presented and comparisons are made with 3-phase rectifiers using AC inductors. The operation of the rectifiers are illustrated with reference to simulation and experimental results. >

Design of a three-phase self-excited induction generator

Abstract: The main goals in the design of a self-excited induction generator (SEIG) are minimizing the rotor resistance and increasing the flux density until the magnetic circuit of the generator saturates. In this paper, a computer design package was developed in order to investigate the best way to obtain these goals. By reducing the stator core length by 40%, the frequency regulation and the voltage drop were reduced. The frequency regulation decreased from 10% to 4% and the voltage drop decreased from 30% to 6%. In addition, voltage and frequency regulations in the standard ranges were obtained in the present design without any regulation devices. >

Fail-safe control apparatus for electric vehicle driving motor

Abstract: A PWM generation block implements two-phase/three phase conversion of torque current and exciting current and, on the basis of the converted three-phase torque and exciting currents and a three-phase current for driving and controlling the drive motor, outputs a PWM signal. A torque current estimator receives the same three-phase current as that of the three-phase current input to the PWM generation block, and implement three-phase/two-phase conversion of a three-phase current, by using a phase angle output from the microcomputer to calculate and output estimation values of the torque and exciting currents. A first comparator compares the absolute value of amplitude and the phase angle of the motor primary current and the motor primary frequency which are respectively output from the microcomputer with those which are respectively output from a fail-safe control block. The first comparator outputs a fail-safe signal when it detects differences between the compared values. A second comparator compares the estimation values of the torque and exciting currents which are output from the torque estimator with the torque and exciting currents which are output from the fail-safe control block, respectively. The second comparator outputs a fail-safe signal when it detects differences between the signals compared thereby.

Three-phase sinusoidal current rectifier with zero-current switching

Abstract: This paper presents the application of zero-current switching in a three-phase rectification scheme with nearly sinusoidal line currents. The principle of third harmonic current circulation is used to reduce the distortion in the line currents. Zero-current switching is accomplished with the use of only two switches. The operation of the circuit is verified experimentally. Comparisons with a PWM based rectifier and a six-switch rectifier in terms of component stresses and EMI filter considerations are presented. >

High phase order cycloconverting generator and drive means

Abstract: An electrical generator, consisting of a high phase order generator and a high phase order cycloconverter. Output from said cycloconverter may be high phase order, three phase, single phase, or direct current. Output from said cycloconverter may be of arbitrary frequency, voltage, and phase. Power electronic components are smaller and more efficiently used. Slower and therefor less expensive devices may be beneficially used. Variable speed resources may be used without the use of a DC to DC converter, enhancing power production efficiency. In a beneficial embodiment of the present invention, said cycloconverter is used to provide power directly to a high phase order motor, whereby diesel electric drive means may be constructed to higher specific power and higher efficiency.

Design of a versatile three-phase AC line conditioner

Abstract: This paper describes the design of a line conditioner for three phase AC-AC power conditioning. It is based on a three phase PWM AC-AC buck-boost power converter. It has several advantages in terms of size, weight, efficiency and performance over state-of-the-art line conditioners. Design specifications and relationships are presented. Analytical formulae for determining the efficiency of the line conditioner are presented. A controller design which features fast transient response is developed. Operation of the line conditioner in the presence of voltage sags and surges, load addition and rejection is illustrated by means of simulation. Experimental results verifying the operation of the power circuit are also presented.

A novel three-phase three-switch three-level unity power factor boost-type pwm rectifier

Abstract: Based on the combination of a three-phase diode bridge and a DC/DC boost converter a new three-phase three-switch three-level PWM rectifier system is developed. It can be characterized by sinusoidal mains current consumption, controlled output voltage and low blocking voltage stress on the power transistors. The application could be, e.g., for feeding the DC link of a telecommunications power supply module. The stationary operational behavior, the control of the mains currents and of the output voltage are analyzed. Finally, the stresses on the system components are determined by digital simulation and compared to the stresses in a conventional PWM rectifier system.

Delta connected resonant snubber circuit

Abstract: A delta connected, resonant snubber-based, soft switching, inverter circuit achieves lossless switching during dc-to-ac power conversion and power conditioning with minimum component count and size. Current is supplied to the resonant snubber branches solely by the dc supply voltage through the main inverter switches and the auxiliary switches. Component count and size are reduced by use of a single semiconductor switch in the resonant snubber branches. Component count is also reduced by maximizing the use of stray capacitances of the main switches as parallel resonant capacitors. Resonance charging and discharging of the parallel capacitances allows lossless, zero voltage switching. In one embodiment, circuit component size and count are minimized while achieving lossless, zero voltage switching within a three-phase inverter.

Pulse width modulation method for driving three phase power inverter/converter switches with balanced discontinuous phase commands

Abstract: A method and/or apparatus for converting voltage using a pulse width modulator and an inverter/converter, the inverter/converter including three legs and a triangle signal generator providing a triangle signal having a peak magnitude. A plurality of sinusoidal reference signals are provided which are displaced from one another by a phase angle. The absolute values of the maximum and minimum values of the reference signals are detected, if the absolute value of the maximum signal is greater than or equal to the absolute value of the minimum signal, the maximum signal is subtracted from the peak magnitude to produce a modifier signal. If the absolute value of the maximum signal is less than the absolute value of the minimum signal, the inverted minimum signal is added to the negative of the peak magnitude of the carrier to produce the modifier signal. The modifier signal is added to each of the sinusoidal reference signals for providing a plurality of modified reference signals to the inverter/converter, one modified reference signal provided to each leg.

Method and apparatus for detecting current delay angle from motor terminal voltage

Abstract: A method and apparatus to be used with an inverter based motor controller for determining current phase angles for the current on a single phase of a three phase AC motor from an inverter generated high frequency phase voltage sequence. The invention detects turn on delay periods and compares phase voltages during consecutive turn on delay periods to determine phase current zero crossing times which can be used along with phase voltage zero crossing times to derive current phase angle information.

A symmetrical 3 phase - 2 switch PFC-power supply for variable output voltage

Abstract: Power Factor Corrected rectifiers are a new tendency in development of power supplies. In the last few years, a lot of RD activities have led to a new category of products for one phase applications. In this comtribuction, a new simplified topology is proposed for three-phase applications, using only two active switches, and able to generate symmetrical currents in the line. Power circuits are presented. Complete simulator results with closed loop operation are given, results of an experimental verification.

Three-phase brushless self-excited synchronous generator with no rotor excitation windings

Abstract: On a stator core, there are wound T-connection primary generating windings such that the second and third single-phase windings are respectively arranged at positions electrically orthogonal to the first single-phase winding. The winding number of the first single-phase winding is 31/2 times that of the second single-phase winding or the third single-phase winding. The stator excitation windings are also wound on the stator core, which are connected to the center taps of the primary generating windings through a control rectifier. A plurality of field windings are wound on a rotor core. The field windings are arranged at positions where they are magnetically coupled with both the odd-order spatial higher harmonic components of armature reaction magnetic fields produced by currents flowing in the primary generating windings and the static magnetic fields produced by current flowing in the stator excitation windings. Due to the T-connection primary generating windings, the generator is capable of simultaneously generating not only the three-phase outputs but also the single-phase three-line outputs.

Method and system for controlling the output of an engine driven welder

Abstract: A method and system of controlling the output current/voltage characteristic curve of an engine driven alternator welder with a maximum open circuit output voltage, including a rotary engine, a three phase alternator, a rectifier bridge having a number of electronic switching devices for directing current to the output at an operating point determined by the firing angle of the switching devices, a sensor for sensing output current, a sensor for sensing output voltage, and a microprocessor output control device for controlling the firing angles of said switching devices in response to the sensed current and sensed voltage. The method and system comprise a device for creating a desired fixed slope operating current/voltage characteristic curve; an arrangement for sensing the present operating current/voltage point of the welder; and, a control for changing the firing angles of the switching devices to shift the current operating point to a new operating point on the desired, fixed slope current/voltage curve of the welder. Preferably, the switching devices include an SCR for each phase of the alternator.

A soft switching active snubber optimized for IGBT's in single switch unity power factor three-phase diode rectifiers

Abstract: This paper describes a soft switching active snubber for an IGBT operating in a single switch unity power factor three-phase diode rectifier. The soft switching snubber circuit provides zero-voltage turn-off for the main switch. The high turn-off losses of the IGBT due to current tailing are reduced by zero-voltage switching. This allows the circuit to be operated at very high switching frequencies with regulated DC output voltage, high quality input current and unity input power factor. Simulation and experimental results are included. >