Abstract: A VSC-MTDC (multi-terminal dc) system consists of voltage-source converters (VSCs) connected to a dc network at their dc terminals. The MTDC is most vulnerable to a dc fault which paralyses all the VSCs until the dc fault is cleared. As dc circuit breakers are expensive, this paper proposes a solution based on extinguishing the dc fault current by opening all the ac-circuit breakers (ac-CBs) which the VSCs are already equipped with on the ac-sides. However, it is necessary to identify which dc line is the faulted line (in case it is a permanent fault) so that it can be isolated by fast dc switches (which are much more economical than the dc circuit breakers), prior to restoring the MTDC system by re-closing all the ac-CBs. This paper presents the handshaking method, which locates and isolates the faulted dc line and restores the MTDC without telecommunication.

Abstract: This paper describes a prototype micropower instrumentation amplifier intended for chronic sensing of neural field potentials (NFPs). NFPs represent the ensemble activity of thousands of neurons and code-useful information for both normal activity and disease states. NFPs are small - of the order of tens of muV- and reside at low bandwidths that make them susceptible to excess noise. Therefore, to ensure the highest fidelity of signal measurement for diagnostic analysis, the amplifier is chopper-stabilized to eliminate 1/f and popcorn noise. The circuit was prototyped in an 0.8 mum CMOS process and consumes under 2.0 muW from a 1.8 V supply. A noise floor of 0.98 muVrms was achieved over a bandwidth from 0.05 to 100 Hz; the noise-efficiency factor of 4.6 is one of the lowest published to date. A flexible on-chip high-pass filter is used to suppress front-end electrode offsets while maintaining relevant physiological data. The monolithic architect and micropower low-noise low-supply operation could help enable applications ranging from neuroprosthetics to seizure monitors that require a small form factor and battery operation. Although the focus of this paper is on neurophysiological sensing, the circuit architecture can be applied generally to micropower sensor interfaces that benefit from chopper stabilization.

Abstract: There is a growing demand for low-power, small-size and ambulatory biopotential acquisition systems. A crucial and important block of this acquisition system is the analog readout front-end. We have implemented a low-power and low-noise readout front-end with configurable characteristics for Electroencephalogram (EEG), Electrocardiogram (ECG), and Electromyogram (EMG) signals. Key to its performance is the new AC-coupled chopped instrumentation amplifier (ACCIA), which uses a low power current feedback instrumentation amplifier (IA). Thus, while chopping filters the 1/f noise of CMOS transistors and increases the CMRR, AC coupling is capable of rejecting differential electrode offset (DEO) up to plusmn50 mV from conventional Ag/AgCl electrodes. The ACCIA achieves 120 dB CMRR and 57 nV/radicHz input-referred voltage noise density, while consuming 11.1 muA from a 3 V supply. The chopping spike filter (CSF) stage filters the chopping spikes generated by the input chopper of ACCIA and the digitally controllable variable gain stage is used to set the gain and the bandwidth of the front-end. The front-end is implemented in a 0.5 mum CMOS process. Total current consumption is 20 muA from 3V

Abstract: This paper presents a new technique for continuously calibrating the sensitivity of a current measurement microsystem based on a Hall magnetic field sensor. An integrated reference coil generates a magnetic field for calibration. Using a variant of the chopper modulation, the spinning current technique, combined with a second modulation of the reference signal, the sensitivity of the complete system is continuously measured without interrupting normal operation. Modulation and demodulation schemes allowing the joint processing of both external and reference magnetic fields are proposed. Additional techniques for extracting the very low reference signal are presented. The implementation of the microsystem is then discussed. Finally, measurements validate the calibration principle. A thermal drift lower than 50 ppm/degC is achieved. This is 6-10 times less than in state-of-the-art implementations. Furthermore, the calibration technique also compensates drifts due to mechanical stresses and ageing

Abstract: A system and method for retrofitting a propulsion circuit of an existing Off Highway Vehicle to enable the propulsion circuit to operate as a hybrid energy Off Highway Vehicle propulsion circuit. The hybrid propulsion circuit includes a primary power source, and a traction motor for propelling an Off Highway Vehicle in response to the primary electric power. The traction motor has a motoring mode of operation and a power dissipation mode of operation. The traction motor generates dynamic braking electrical power in the power dissipation mode of operation. An electrical energy storage system includes a chopper circuit coupled to an energy storage device. The storage device is responsive to the chopper circuit to selectively store electrical energy generated in the power dissipation mode. The storage system selectively provides secondary electric power from the storage device to traction motor to assist in propelling the Off Highway Vehicle during the motoring mode.

Abstract: In this paper, an offset-stabilized operational amplifier is described. The amplifier employs a chopper amplifier in a low frequency path to cancel the offset of a wide-bandwidth amplifier. A sample-and-hold circuit is used to reduce the chopper ripple, and the low frequency path is also offset-stabilized to further reduce the residual offset. The amplifier has less than 1.5 offset at a 16-kHz chopper frequency, a unity gain frequency of 1.3 MHz with a 50-pF load, and draws 700 from a 5-V supply. The amplifier was realized in a 0.7 CMOS process, and has an effective chip area of 3.6.

Abstract: A chopper-stabilized amplifier receiving an input signal includes a first operational transconductance amplifier (2) having an input chopper and an output chopper for chopping an output signal produced by the first operational transconductance amplifier. A switched capacitor notch filter (15) will filter the chopped output signal by operating synchronously with the chopping frequency of output chopper to filter ripple voltages that otherwise would be produced by the output chopper. In one embodiment a second operational transconductance amplifier amplifies the notch filter output. The input signal is fed forward, summed with the output of the second operational transconductance amplifier, and applied to the input of a fourth operational transconductance amplifier. Ripple noise and offset are substantially reduced.

Abstract: A chopper-stabilized instrumentation amplifier is targeted for "deep-brain" human implants and consumes 2.2muW from a 1.8V supply. The integrated noise from 0.5 to 100 Hz is 0.94muV, providing a noise efficiency factor of 4.9. The use of chopper stabilization provides rail-to-rail inputs and 105dB CMRR. An integrated 0.5Hz HPF is used to suppress electrode offsets. The circuit is also used in micropower bridge interfaces for impedance measurement and pressure sensing.

Abstract: In this paper, a control strategy for reduced acoustic noise and sensorless operation of a switched reluctance (SR) motor is proposed for heating, ventilation, and air conditioning (HVAC) application, where the magnitude of the dc-bus voltage is controlled as a function of speed and the motor is operated in a single-pulse mode for all speed range. The dc-bus voltage is controlled by incorporating a dc chopper between the three-phase line rectifier and a split dc-link capacitor-type four-switch power converter. Such controller reduces the acoustic noise, provides more accurate position estimation for sensorless operation, and improves the life expectancy of the motor. The algorithm is first simulated through MATLAB/SIMULINK and then tested on a four-phase 8/6-pole 4-kW SR motor. The test results of achieved acoustic noise and improved sensorless operation are presented. Through the proposed method, the acoustic noise is reduced by almost 15 dB compared to the conventional scheme at low-speed regime. The proposed method is intended to drive a fan type of load in HVAC applications, where the dynamic performance requirement is not a stringent criterion.

Abstract: Parallel operation of synchronous and induction generators in micro hydro scheme is presented. The synchronous generator has an exciter, which provides a fixed excitation to produce normal rated terminal voltage at full resistive load. On the other hand, the induction generator has neither exciter nor speed controller. Static compensator (STATCOM) is connected to the common bus for terminal voltage and frequency control. A resistive dump load is connected across the DC link capacitor of STATCOM through a chopper to control active power. Simulink model is developed to perform transient analysis of the proposed scheme. Experimental results are presented to compare with the simulation results. It is found that connection of an induction generator in parallel with the synchronous is much simpler than connecting two synchronous generators in parallel.

Abstract: PROBLEM TO BE SOLVED: To construct a chopper circuit C for compensating voltage unbalance that occurs between two series smoothing capacitors 12, 13 constructing a direct-current circuit of a high-speed control system, in a power conversion device in which a half-bridge power converter is used for a rectifier circuit A and an inverter circuit B. SOLUTION: The copper circuit C is provided with a voltage controller 35 and a pulse width modulator 39. The voltage controller computes the current command value for the chopper circuit C so that voltage unbalance between the two series smoothing capacitors 12, 13 is reduced. The current command value for the chopper circuit C and a current detection value of the chopper circuit C are compared to each other at constant sampling intervals. Then, a PWM signal is so generated as to invert the polarity of an error current, based on its positive/negative polarity. Turn-on/off of IGBTs 23, 24 is thereby determined so that the current command value for the chopper circuit C and the current detection value of the chopper circuit C agree with each other, at all times. COPYRIGHT: (C)2007,JPO&INPIT

Abstract: A PFC controller controls switching of switch elements of booster chopper circuits arranged in parallel. The PFC controller is provided with a circuit (SLOG) for generating another switch signal (GD_S) having a shifted phase to a switch signal of one switch element. The circuit is provided with a first counter (COUNTM) which counts clock signals by a cycle unit of one switch signal; a second counter (COUNTS) which counts the clock signals by a cycle unit having a prescribed phase difference to the one switch signal; and a first register (REG1) which holds the first counter count value that corresponds to a high-level period of the one switch signal. Other switch signals turn on other switch elements upon count start of the second counter, and turn off such switch elements in timing when a count value of the second counter accords with a value held by the first register. A circuit scale is small and operation accuracy is not easily greatly affected by process fluctuation.

Abstract: A Superconducting Magnetic Energy Storage System (SMES) consists of a high inductance coil emulating a constant current source. Such a SMES system, when connected to a power system, is able to inject/absorb active and reactive power into or from a system. The active power injected into the system is controlled by varying the duty cycle of the switches in the dc-dc chopper while the SMES coil is discharging into the system. The reactive power is controlled by the magnitude of the converter output voltage. The storage setup is tested on a WSCC 3 machine 9 bus system. The behavior of the system is tested for a three phase fault on the network at different locations. The transient behavior of the system is observed with and without the SMES unit. The SMES unit is able to damp out the post-fault oscillations within a short time.

Abstract: In this paper, seven candidate ride-through methods for wind farms connected to the main grid via VSC-HVDC transmission are evaluated. The most critical fault case is considered: a severe three-phase dip in the main-grid voltage. It is found that, unless very high demands regarding the speed of output-power reduction are placed on the wind turbine generators, a small braking resistor (with limited energy dissipation capability, controlled by a chopper) should be installed in the HVDC transmission. This also has the advantage that the mechanical stress on the wind turbine generators will be reduced. Furthermore, it is shown that a large braking resistor, which is able to dissipate the rated power of the wind farm for the duration of the fault event, is not needed for good performance. (au)

Abstract: Welding systems are presented, in which a single power source provides a first DC output to a plurality of digital waveform controlled chopper modules. Welding modules are also disclosed for converting an input DC signal to a welding signal, which are comprised of a down-chopper for providing a welding signal waveform according to a pulse width modulated switching signal, along with a digital waveform controller providing the switching signal according to a desired waveform.

Abstract: An over-sampling analog-to-digital converter (ADC) uses a chopper stabilized voltage reference with improved reference voltage offset cancellation and reduced source induced 1/f noise. The chopper stabilized voltage reference receives chopper clocks that have been correlated with the serial bitstream produced by the sigma-delta modulator of the ADC. The chopper clocks are generated so that the reference voltage produces for each distinct bitstream level an independent sequence of voltages that comprise alternatively positive and negative voltage reference offset contributions. After integration (averaging) is performed within the sigma-delta modulator, these equal and opposite reference offset contributions cancel out regardless of the bit pattern comprising the bitstream.

Abstract: A chopper regulator circuit has: a power output portion for a first and a second load; a first output detection portion detecting the output to the first load; a second output detection portion detecting the output to the second load; a first and a second reference voltage generation portion; an output control portion controlling the amount of outputted electric power based on a result of comparison between two input voltages; and a switching control portion switching which of the first and second loads to supply electric power to and switching what voltages to handle as the input voltages. The input voltages are so switched that, when electric power is supplied to the first load, the detected voltage detected by the first output detection portion and the reference voltage generated by the first reference voltage generation portion are handled as the input voltages and, when electric power is supplied to the second load, the detected voltage detected by the second output detection portion and the reference voltage generated by the second reference voltage generation portion are handled as the input voltages. Thus, a chopper regulator circuit is realized that can easily supply two loads with adequate electric power with minimum disadvantages such as an increase in the total number of components needed.

Abstract: Recently, a simulation method for power electronic devices has emerged, which has high accuracy and short run times based on a Fourier model of the device physics. This paper describes the use of the Fourier models for diodes and insulated gate bipolar transistors (IGBTs) and implementation in MATLAB and Simulink in a formal optimization strategy. In particular, this paper investigates coupled circuit, diode, and IGBT behavior. Conclusions are drawn concerning device loading and circuit design, particularly the role of stray inductance.

Abstract: This paper proposes a system, based on a self- excited induction generator with a shunt electronic converter, to feed isolated three-phase and single-phase linear or nonlinear loads. The electronic converter is composed by a three-phase four-wire voltage source inverter (VSI) and, connected to its dc side, two dc/dc converters. The VSI compensates the current harmonics, the reactive power and the load unbalances. The first of the dc/dc converters is a battery charger/discharger and the other converter dissipates the active power excess, through a chopper, so these dc/dc converters keep the active power balance of the complete system. The designed control architecture assures that, in steady state, the rms values of the voltages and the frequency remain at the their reference values. The simulated results show a good performance of the system under different loading conditions.

Abstract: A comprehensive treatment of the limitations and possibilities for single-pulse selection in synchrotron operating modes with approximately 150 ns bunch separation, as occurs in the standard operating mode at the Advanced Photon Source, is presented. It is shown that the strength of available materials and allowable kinetic energy build-up limit single-bunch selection for this separation to sample sizes of approximately 100 microm, and that for minimization of kinetic energy build-up it is preferable to increase the r.p.m. within physically acceptable limits rather than increase the disc radius to obtain a desirable peripheral speed. A slight modification of the equal-bunch spacing standard fill patterns is proposed that allows use of samples as large as 500 microm. The corresponding peripheral speed of the chopper wheel is approximately 600 m s(-1), which is within the limits of high-strength titanium alloys. For smaller samples, peripheral speeds are proportionally lower. Versatility can be achieved with interchangeable chopper wheels and the use of different orientations of the rotation axis relative to the X-ray beam, which opens the possibility of larger, rather than one-of-a-kind, production runs.

Abstract: Electronic ballasts usually present two stages, one for feeding the high pressure sodium (HPS) lamp and the other for power factor correction (PFC). This paper presents electronic ballasts using ac-ac converters without a PFC stage. The use of an indirect ac-ac converter, or an indirect frequency changer, to feed the HPS lamp is investigated. Modulation strategies are proposed to improve the input and output characteristics of the converter. Further studies lead to a novel HPS electronic ballast which uses an ac chopper capable of achieving PFC and supplying high frequency to the lamp. Different converter topologies, bidirectional switches, and a modulation strategy for the ac chopper are presented. Due to the output characteristic of both topologies, the lamp current is modulated at the frequency of the voltage source and the consequences of this operation are discussed. The experimental results for both electronic ballasts supplying 250-W HPS lamps are presented

Abstract: This disclosure describes a chopper mixer telemetry circuit for use in a wireless receiver. The receiver may be located in an implantable medical device (IMD) or external programmer. The chopper mixer telemetry circuit may include a mixer amplifier that operates as a synchronous demodulator to provide selective extraction of wireless signals received from a transmitter while suppressing out-of-band noise that can undermine the reliability of the telemetry link between an IMD or programmer and another device. The mixer amplifier may utilize parallel signal paths to convert the received telemetry signal into an in-phase (I) signal component and a quadrature (Q) signal component and recombine the I and Q signal components to reconstruct the total signal independently of the phase mismatch between the transmitter and receiver. Each signal path may include a chopper-stabilized mixer amplifier that amplifies telemetry signals within a desired band while suppressing out-of-band noise.

Abstract: A low-cost fuzzy controller for closed loop control of DC drive fed by four-quadrant chopper is designed and presented in this article. The fuzzy controller is implemented in a low-cost 8051 micro-controller based embedded system. The controller is used to change the duty cycle of the converter; thereby, the voltage fed to the armature of the separately excited motor to regulate the speed. The simulated closed loop performance of the fuzzy controller in respect of load variation and reference speed change has been reported. Further, the dynamic response of DC motor with fuzzy controller is tested and found to be satisfactory. As the design of proposed controller does not depend on any of the motor parameters, it can be used to control DC drive of any rating by very minor modification in the hardware. This advantage of the proposed system is tested for two different motor parameters.

Abstract: A compact pulsed high-voltage generator has been developed for applications in pulsed gas discharges. Its operation principle is based on inductive energy storage and it uses a static induction thyristor as the opening switch. It is capable of generating pulsed high voltage of ~15 kV with pulse width of ~200 ns for load resistance of 1 kOmega. This generator can be operated at repetition rate as high as 50 kHz if it is driven directly by 200 V power supply and is cooled by transformer oil. It can also be driven by a 12 V car battery through a chopper circuit, while operating at repetition rate of 2 kHz. In this case, an overall energy efficiency of ~40 % has been obtained.

Abstract: Operational settings on chopper harvesters are extremely important in green-cane harvesting since one is relying solely on the harvester to remove extraneous matter instead of the traditional pre-harvest burn method The objective of this research was to determine the combined effect of selected ground and fan speeds on sugar yield, cane quality, and field losses using a commercial chopper harvester In both 2003 and 2004, a split-plot experiment was performed at harvest with the main plots having ground speeds of 40, 48, and 56 km h-1 and subplots having primary extractor fan speeds of 650, 850, and 1050 rpm of the 15-m diameter fan Under the optimal conditions (low leaf and soil moisture), the 1050 rpm fan speed increased theoretical recoverable sugar (TRS) by 10% but decreased cane yield by 15% compared to the two lower fan speeds resulting in similar sugar yields for all fan settings Under poor conditions (high leaf and soil moisture), the 1050-rpm fan speed decreased cane yield by 13% without an increase in TRS, resulting in lower sugar yields than the low or medium fan settings Ground speed, under both conditions, did not affect cane yield or quality The chopper harvester performed well under ideal conditions with a primary fan speed of 1050 rpm but had decreasing performance under poor conditions regardless of fan speed

Abstract: Increases of switching levels and frequency make the compliance with radiated EMC standards more and more difficult. A modeling method based on the partial equivalent element circuit (PEEC) formulations, permitting to know the field emitted by the layout of complex power electronic structures, is presented in this paper. The near magnetic field of a buck chopper has been measured and calculated. The comparison of the simulated results with measurements shows the effectiveness of the modeling methods and of the near field acquisition bench.

Abstract: This paper discusses the iron loss characteristics of magnetic materials used in the chopper circuits of pulse width modulation (PWM) inverter circuits. A distinctive feature of this method, previously reported by the authors, is that the iron loss map is created by measuring the dynamic minor loop traced on the B-H plane, and it can be a useful method for calculation of the inductor iron loss in a dc chopper circuit as well as a PWM inverter circuit. In order to encourage the wide use of this method in the design of the power converters, this paper provides the characterization of loss map data in several magnetic materials, such as an iron-powder core, an amorphous core and a silicon-steel core. In addition to the loss caused by the hysteresis phenomenon, the loss caused by eddy current phenomena is discussed. Influenced by the eddy current loss, the shape of the dynamic minor loop tends to be rhombic when the inductors are magnetized using a pulse voltage, whereas the shape is oval when they are magnetized using a sinusoidal voltage. The increase in the amount of loss caused by the eddy current in each of these magnetic materials is also discussed.