Showing papers on "Inverter published in 2000"

Variable current limit control for vehicle electric drive system

Abstract: A vehicle electric drive system includes an internal combustion engine, an electric motor/generator driven by the engine, a first inverter/rectifier coupled to motor/generator, a bus coupled to the first inverter/rectifier, a second inverter/rectifier coupled to the bus, and a traction motor/generator coupled to an output of the second inverter/rectifier, an operator speed control member, and a controller coupled to the second inverter/rectifier for controlling a current output of the second inverter/rectifier as a function of a position of the speed control member Also included is an operator controlled foot pedal and a transducer coupled to the foot pedal and generating a signal representing foot pedal position which is supplied to the controller The controller limits current supplied by the second inverter/rectifier to the traction motor/generator to a limit current as a function of the transducer signal The controller, foot pedal and transducer cooperate to vary the limit current in response to movement of the foot pedal A spring biases the foot pedal to an upper limit position The controller causes the second inverter/rectifier to supply to the traction motor/generator a maximum amount of current, (such maximum current being a function of the foot pedal position), but not more than that required to achieve the speed commanded by the speed control

Experimental fault-tolerant control of a PMSM drive

Abstract: The paper describes a study and an experimental verification of remedial strategies against failures occurring in the inverter power devices of a permanent-magnet synchronous motor drive. The basic idea of this design consists of incorporating a fourth inverter pole, with the same topology and capabilities of the other conventional three poles. This minimal redundant hardware, appropriately connected and controlled, allows the drive to face a variety of power device fault conditions while maintaining a smooth torque production. The achieved results also show the industrial feasibility of the proposed fault-tolerant control, that could fit many practical applications.

Phase-locked loop for grid-connected three-phase power conversion systems

Abstract: Analysis and design of a phase-locked loop (PLL) is presented for the power factor control of grid-connected three-phase power conversion systems. The dynamic characteristics of the closed loop PLL system with a second order are investigated in both continuous and discrete-time domains, and the optimisation method is discussed. In particular, the performance of the PLL in the three-phase system is analysed under the distorted utility conditions such as the phase unbalancing harmonics, and offset caused by nonlinear loads and measurement errors. The PLL technique for the three-phase system is implemented in software of a digital signal processor to verify the analytic results, and the experiments are carried out for various utility conditions. This technique is finally applied to the grid-connected photovoltaic power generation system with the current-controlled PWM inverter as a subpart for generating the current reference of the inverter. The experimental results demonstrate its phase tracking capability in the three-phase grid-connected operation.

Fundamentals of a new diode clamping multilevel inverter

Abstract: The conventional diode clamping inverter suffers from such problems as DC link unbalance, indirect clamping of the inner devices, turn-on snubbing of the inner DC rails as well as series association of the clamping diodes etc It is due largely to these problems that the application of the conventional diode clamping inverter in practice has been deterred, in spite of the growing discussion in the literature The paper proposes a new diode clamping inverter, which works without the series association of the clamping diodes An auxiliary resistive clamping network solving the indirect clamping problem of the inner devices is also discussed for both the new and conventional diode clamping inverter Operation principle, clamping mechanism, auxiliary clamping as well as experimentation are presented

Out of control because of harmonics-an analysis of the harmonic response of an inverter locomotive

Abstract: Presents a method to use linear analysis to capture the frequency coupling of nonlinear and time-varying components. System stability is analyzed by connecting the harmonic transfer functions of the different component models. This facilitates an object-oriented approach to modeling, which supports reuse of models. An analysis of the complete railway system is, of course, difficult. Several locomotives can be moving along the power distribution line at the same time, and depending on the distance between them, the interaction changes. The power consumption also changes, depending on operating modes. During normal operation, energy is consumed from the network, but as modern locomotives use electrical braking, the power flow changes direction during deceleration, and energy is delivered back to the grid. The inverter trains are not passive systems. The converters are controlled with only limited system knowledge (local measurements of currents and voltages), making analysis and control design an even bigger challenge.

3C strategy for inverters in parallel operation achieving an equal current distribution

Abstract: A circular chain control (3C) strategy for inverters in parallel operation is presented in the paper. In the proposed inverter system, all the modules have the same circuit configuration, and each module includes an inner current loop and an outer voltage loop control. A proportional-integral controller is adopted as the inner current loop controller to expedite the dynamic response, while an H/sup /spl infin// robust controller is adopted to reach the robustness of the multimodule inverter system and to reduce possible interactive effects among inverters. With the 3C strategy, the modules are in circular chain connection and each module has an inner current loop control to track the inductor current of its previous module, achieving an equal current distribution. Simulation results of two-module and a three-module inverter systems with different kinds of loads and with modular discrepancy have demonstrated the feasibility of the proposed control scheme. Hardware measurements are also presented to verify the theoretical discussion.

Multilevel PWM methods at low modulation indices

Abstract: When utilized at low amplitude modulation indices, existing multilevel carrier-based PWM strategies have no special provisions for this operating region, and several levels of the inverter go unused. This paper proposes some novel multilevel PWM strategies to take advantage of the multiple levels in both a diode-clamped inverter and a cascaded H-bridges inverter by utilizing all of the levels in the inverter even at low modulation indices. Simulation results show what effects the different strategies have on the active device utilization. A prototype 6-level diode-clamped inverter and an 11-level cascaded H-bridges inverter have been built and controlled with the novel PWM strategies proposed in this paper.

Contactless electrical energy transmission system

Abstract: A high-performance contactless electrical energy transmission (CEET) technique which employs the inductive energy transmission principle is described. The proposed technique enables the implementation of high-efficiency, high-power-density, fully-regulated CEET systems suitable for applications with a wide input range and a wide load range. The CEET system in this invention consists of an input-side variable-frequency inverter and an output-side regulated rectifier. A high efficiency of the system is achieved by recovering the energy stored in the leakage inductances of the transformer by incorporating them in the operation of the circuit, and by employing high-frequency-inverter and controlled-rectifier topologies that allow a controlled bi-directional power flow through the transformer. A feed forward, variable-switching-frequency control of the inverter is used to maintain a substantially constant power transfer through the transformer when the input voltage changes. A local PWM control is used for the output-side rectifier to achieve a tight regulation of the output in the presence of load variations.

A fuzzy-logic-controlled single-stage converter for PV-powered lighting system applications

Abstract: This paper presents a fuzzy-logic-controlled single-stage power converter (SSC) for photovoltaic (PV)-powered lighting system applications. The SSC is the integration of a bidirectional buck-boost charger/discharger and a class-D series resonant parallel loaded inverter. The designed fuzzy logic controller (FLC) can control both the charging and discharging current, and can improve its dynamic and steady-state performance. Furthermore, a maximum power point tracker (MPPT) based on a perturb-and-observe method is also realized to effectively draw power from PV arrays. Both the FLC and the MPPT are implemented on a single-chip microprocessor. Simulated and experimental results obtained from the proposed circuit with an FLC have verified the adaptivity, robustness and feasibility.

A new PWM strategy for common mode voltage reduction in neutral-point clamped inverter-fed AC motor drives

Abstract: In this paper, the relationship between common-mode voltage and switching states in a neutral-point-clamped (NPC) inverter is clarified, and a new pulsewidth-modulation (PWM) strategy for reducing the common-mode voltage in an NPC inverter-fed AC motor drives is proposed. Among a total of 27 switching states in the NPC inverter, the proposed PWM uses only 19 switching states that generate common-mode voltage of which the magnitude is the same or less than one-sixth of DC-bus voltage. Moreover, the proposed PWM strategy satisfied the constraint that the output voltage vector should be changed by only one switching action. Not requiring extra hardware, the NPC inverter with the proposed PWM results in a remarkable reduction in peak-to-peak of common-mode voltage, compared to a two-level inverter and an NPC inverter controlled by conventional PWM. The proposed PWM strategy can be easily implemented in software without degradation of control performance in AC motor drives.

An induction motor drive system with improved fault tolerance

Abstract: This paper investigates the utilization of a low cost topology that permits the fault-tolerant operation of a three-phase induction motor drive system. When one of the inverter legs is lost, the machine can operate with only two stator windings by connecting the machine neutral either to the middle point of a capacitor bank or to a fourth converter leg. The structure proposed and the operation principle of the system are presented. The machine model corresponding to the asymmetric two-windings machine is developed and a suitable controller is proposed. Experimental results are presented.

A novel high-performance CMOS 1-bit full-adder cell

Abstract: A novel 16-transistor CMOS 1-bit full-adder cell is proposed. It uses the low-power designs of the XOR and XNOR gates, pass transistors, and transmission gates. The cell offers higher speed and lower power consumption than standard implementations of the 1-bit full-adder cell. Eliminating an inverter from the critical path accounts for its high speed, while reducing the number and magnitude of the cell capacitances, in addition to eliminating the short circuit power component, account for its low power consumption. Simulation results comparing the proposed cell to the standard implementations show its superiority. Different circuit structures and input patterns are used for simulation. Energy savings up to 30% are achieved.

Predicting islanding operation of grid connected PV inverters

Abstract: Increasing numbers of photovoltaic arrays are being connected to the power utility through power electronic inverters. This has raised potential problems of network protection. If, due to the action of the inverter or inverters, the local network voltage and frequency remain within regulatory limits when the utility is disconnected, then islanding is said to occur. Many methods to prevent this have been proposed and a SPICE-based model and analysis of the system are presented. Specifically aimed at predicting the effectiveness of two of these. These are: active frequency drift, which causes the inverter current to be generated slightly lower or higher in frequency than the frequency of the terminal voltage; and slip mode frequency shift, which controls the phase angle of the inverter current as a function of the frequency deviation of the terminal voltage from that of the normal network frequency. Experimental verification of the model is provided. Active frequency drift using frequency speed-up rather than speed-down is shown to be preferable for inductive loads, but conditions that resulted in islanding could be predicted. Slip mode frequency shift proved to be a more robust anti-islanding protection technique.

Predictive control of inverter supplied electrical drives

Abstract: Several proposals exist to use predictive control algorithms for inverter control Besides their common basic idea to use the extremely nonlinear but well-known behaviour of inverters to precalculate the best switching times there are many differences in detail This is the time for an attempt to design a "family tree" of predictive control algorithms by pointing out similarities and differences of the algorithms published so far

Modeling and control of a synchronous generator with an active DC load

Abstract: The design and analysis of a system consisting of a variable-speed synchronous generator that supplies an active DC load (inverter) through a three-phase diode rectifier requires adequate modeling in both time- and frequency-domains. As an example, the system's control-loops are difficult to design without an accurate small-signal model; at the same time, the system protection design requires large-signal transient modeling. A particularity of the described system is strong nonideal operation of the diode rectifier, a consequence of the large value of the generator's synchronous impedance. This nonideal behavior influences both steady-state and transient performance. This paper presents an average model of the system that accounts, in a detailed manner for the dynamics of the power source and the load, and for the effects of the nonideal operation of the diode rectifier. The model is nonlinear, but time-continuous, and can be used for large- and small-signal analysis. The developed model was verified on a 105 kW generator-set with inverter output, whose DC-link voltage control-loop design was successfully carried out based on the average model. It is shown that a high bandwidth is needed for this control-loop in order to achieve the proper impedance matching between the power source and the active electronic load.

Inverter circuit and method of operation

Abstract: An inverter includes a first switch to disconnect an output of the inverter from any device connected thereto; a second switch to disconnect and connect an input of the inverter from direct current fed to the inverter; a discharge device to discharge any residual charge on a large capacitor; a voltage sensor to measure input DC voltage to the inverter; a current sensor to measure input DC current to the inverter; and a data recorder to provide a current voltage trace to provide a current-voltage curve tracer to provide current-voltage curve data that may then be used to calibrate a maximum power point tracker or alternatively sense array shading.

Induction-generator-based system providing regulated voltage with constant frequency

Abstract: The electrical characteristics of an isolated induction-generator-based system are improved through the association with a voltage-source pulsewidth modulation (PWM) inverter The electronic converter allows the achievement of a better system behavior in many aspects: voltage regulation, frequency stabilization, and reactive power compensation The system operation strategy consists of maintaining constant synchronous frequency at the induction generator via an association with a PWM inverter The system power balance and the generator voltage regulation may be accomplished by two different means: through the rotor speed regulation, or by sending part of the energy stored in the inverter DC side to the grid through a single-phase line, in case the rotor speed is not regulated and a single-phase grid connection is available The obtained results demonstrated the system is stable, robust, and an effective source of regulated three-phase voltages

Analysis of common mode voltage-"neutral shift" in medium voltage PWM adjustable speed drive (MV-ASD) systems

Abstract: In this paper, an analysis of common mode voltage or "neutral lift" in the new emerging voltage source inverter type medium voltage adjustable speed drive (MV-ASD) systems is presented. Both cascaded multilevel (CML) inverter and 3-level NPC inverter topologies are analyzed. An equivalent circuit model to determine the common mode voltage stress is presented. Analysis and simulation results are discussed and worst case common mode voltage excursion is computed for an example 800 hp, 4160 V MV-ASD. It is shown that certain system components are excessively stressed and in the MV-ASD system these data are particularly useful in specifying system components and for proper design of the system. Possible effects of common mode voltage and its dv/dt on medium voltage motor bearings are discussed. A new multilevel PWM strategy is introduced which results in zero common-mode voltage. Simulation results are shown to illustrate the effectiveness of these schemes. Finally, experimental results from a 800 hp, 4160 V, MV-ASD system are presented.

Energy management uninterruptible power supply system

Abstract: A power system is provided in which a grid supplies electrical power to a load and in which backup power is provided from one of a generator and a dc storage device. The power system includes a standalone inverter having an input and an output. The output of the standalone inverter is connected to the load. The power system includes a grid parallel inverter having an input and an output. The output of the grid parallel inverter is connected to the grid. A dc bus is electrically connected to the input of the standalone inverter and to the input of the grid parallel inverter.

Interconnection power converter and power generation apparatus using the same

Abstract: In a solar power generation apparatus using a solar battery having a relatively large ground capacitor and a power conditioner having a non-insulated input and output, a customer's ground fault interrupter may perform unwanted interruption due to a ground fault outside the customer's premises. To prevent this, when a ground fault is detected by a detector capable of detecting a ground fault within a shorter time than the customer's ground fault interrupter, the gate of inverter of the power conditioner is blocked, a switch is changed to an open state, and the input voltage of inverter is held at a voltage value higher than the peak value of the alternate current voltage of a power system until at least the switch changes to the open state.

Rotor-flux-oriented control of a single-phase induction motor drive

Abstract: This paper investigates the vector control of a single-phase induction motor drive to implement low-cost systems for low-power applications. The static power converter side is implemented using a single-phase rectifier cascaded with a four-switch inverter. The vector control is based upon field orientation concepts that have been adapted for this type of machine. Simulation and experimental results are provided to illustrate the system operation.

Analysis, designing, and experimentation of a transformer-assisted PWM zero-voltage switching pole inverter

Abstract: This paper proposes a transformer-assisted pulsewidth modulation (PWM) zero-voltage switching pole inverter. As the auxiliary-resonant-commutated pole inverter (ARCPI), the proposal guarantees zero-voltage switching of the main switch and zero-current switching of the auxiliary switch, with a small power auxiliary circuit and full PWM capability. In particular, problems outstanding with the ARCPI such as control complexity, auxiliary switch protection, and center-tap potential variation, etc., are solved in the proposal. The commutation process is discussed step by step in the paper. A detailed analysis for the auxiliary circuit with regard to commutation duration/duty-cycle limitation, auxiliary switch peak current/RMS current, resonant capacitor RMS current, as well as pole output voltage loss are presented afterwards. A design methodology for the auxiliary circuit is recommended based on the analysis. The proposal is experimentally verified with a 4.25 kW half-bridge inverter prototype.

Implementation of three level hysteresis current control for a single phase voltage source inverter

Abstract: Single phase hysteresis current controllers have traditionally been implemented using two level modulation which is known to be inferior to three level modulation. This paper presents a simple, low cost, and effective technique to allow single phase hysteresis current regulation to be implemented as three level modulation process. This achieves a substantial reduction in the magnitude and variation of the switching frequency, thus improving efficiency, while retaining all of the advantages identified with hysteresis current control. The operation and control of the inverter are described, together with simulation and experimental results.

Analytical Single-Electron Transistor(SET)Model for Design and Analysis of Realistic SET Circuits

Abstract: In this work, we propose a compact, physically based, analytical single-electron transistor (SET) model suitable for the design and analysis of realistic SET circuits. The model is derived on the basis of the "orthodox" theory of correlated single-electron tunneling and the steady-state master equation method. The SET inverter characteristics are successfully calculated using the model implemented in the simulation program with integrated circuit emphasis (SPICE). The hybrid circuit of SETs with metal-oxide-semiconductor field-effect transistors (MOSFETs) is also successfully simulated. By utilizing the model, it is clarified that the drain-voltage-induced shift of the gate voltage dependence of SET current reaches one-half of the drain voltage in the case of a completely symmetric SET.

A novel instantaneous power control strategy and analytic model for integrated rectifier/inverter systems

Abstract: This paper is concerned with the design and implementation of an integrated pulse width modulation (PWM) rectifier/inverter for three-phase induction motor drives. Two identical PWM converters are used to serve as power regulator with unity power factor and servo motor drive using field-oriented control, respectively. A new input-output instantaneous power balancing approach is proposed to improve the dynamic response of input power regulation during output load change in order to minimize the DC-link capacitance. By using the synchronous rotating-frame current regulators, both the input and output currents of the integrated system are characterized with fast current response and low harmonic distortion. The effects of the dynamic response using different input power control methods are compared and the systematic design and analysis of the proposed method are also presented. Theoretical results of the analysis are verified experimentally.

Power supplies having protection circuits

Abstract: A power supply including an inverter receiving a DC input signal from a DC input source ( 11 ). The inverter is comprised of two half bridges (S 1 A, S 2 A and S 1 B, S 2 B). Each inverter is driven by a signal source ( 13 A, 13 B), which outputs an AC signal. The output from each inverter is input to a first stage harmonic filter. The power supply includes an output circuit that includes first and second rectifiers (D 1, D 2 ) arranged about a point so that if the inverter attempts to drive the point beyond a predetermined first and second voltage, the respective rectifier conducts in order to return at least one of power and current to the DC input source. The output from the first harmonic filter (L 1 A, C 1; L 1 B, C 1 ) is output to a second harmonic filter (L 2, C 2 ) and is then output from the power supply.

A Four-Level Inverter Based Drive with a Passive

Abstract: Multilevel inverters are suited for high power drive applications due to their increased voltage capability. Specifically, as compared to three level inverters, for a given dc bus voltage, a four-level inverter is able to synthesize better waveforms with re- duced device ratings. In a medium voltage drive, a conventional diode bridge rectifier is a low cost multilevel solution if the dc bus voltages can be balanced from the inverter side alone. In this paper, operation of four-level drive with a passive rectifier is investigated, and modulation constraints of the inverter, arising from the capac- itor voltage balancing requirements are examined. Simulation and experimental results are presented to demonstrate the link voltage balancing strategy and the performance of the four-level drive. Index Terms—Diode clamped inverters, four level inverters, high power drives, multilevel converters.

Strategies for handling UPFC constraints in steady-state power flow and voltage control

Abstract: The unified power flow controller (UPFC), with its unique combination of fast shunt and series compensation, is a powerful device which can control three power system parameters. In planning and designing such devices in power systems, power engineers must consider the impact of device internal limits on its performance. This paper develops a power injection model (PIM) based UPFC control approach to consider a number of internal limits imposed on the UPFC, including series injection voltage magnitude, line current through the series inverter, real power transfer between the shunt inverter and series inverter, shunt side current and shunt injection voltage magnitude. Constrained control strategies are proposed and tested on a 28-node test system. The numerical results illustrate the effectiveness of the proposed method.

Application of parallel connected NPC-PWM inverters with multilevel modulation for AC motor drive

Abstract: The neutral point clamped (NPC)-PWM inverters have been put into practical use for large capacity AC motor drives, because of their many advantages. With the increase in use, still larger capacity inverters are also expected. In this paper, a parallel connected NPC-PWM inverter is applied for AC motor drive. The conventional modulation techniques are extended to improve the inverter characteristics. To determine an optimum modulation for controlling the parallel connected NPC-PWM inverter, various modulation techniques are devised and discussed, whose results are verified by experiment.

Si complementary single-electron inverter with voltage gain

Abstract: A Si complementary single-electron inverter in which two identical single-electron transistors (SETs) are packed is fabricated on a silicon-on-insulator substrate. For the fabrication, the vertical pattern-dependent oxidation method, which enables the formation of two tiny SETs aligned in parallel, is modified so that the two SETs can be connected in series to realize an inverter configuration. The resultant circuit occupies a very small area: 100×100 nm for each SET. For complementary operation, the electrical characteristics of one of the SETs are shifted using a side gate situated near the SET. Input–output transfer with a voltage gain larger than unity is demonstrated at 27 K.