Unidirectional Voltage Research Articles

A Unidirectional Voltage Vector Preselection Strategy for Optimizing Model Predictive Torque Control With Discrete Space Vector Modulation of IPMSM

Discrete space vector modulation (DSVM) is employed to synthesize large number of voltage vectors (VVs) to improve the steady-state performance of predictive torque control (PTC). However, enumerating all the VVs in the prediction process increases the computation load of the motor drive. To address this issue, this article proposes a unidirectional VV preselection (UVVP) method for optimizing the performance of DSVM-based PTC of ac motors. The proposed UVVP method divides both voltage space vector diagram (VSVD) and flux space trajectory into twelve 30° based sectors to reduce the impact of candidate VVs with negative effects. At each flux position, the UVVP strategy can restrict the nearest candidate VVs in the 30° based VSVD region within the circular flux trajectory. This is achieved by using the speed direction to avoid the candidate VVs, which are in the same flux sector for reverse flux rotation, hence resulting in significant flux and torque ripple reduction. The main benefit of the proposed method is its simplicity since it only requires the flux sector and speed information as well as it can generate the VV enumerations online while ensuring the reduction of computation burden.

Study of Parameters Identification Method of Li-Ion Battery Model for EV Power Profile Based on Transient Characteristics Data

Power simulation of lithium ion battery through battery model is of great significance for dynamic response simulation, heat generation calculation and charge-discharge strategy development. The accuracy and applicability of the model become crucial. In order to demonstrate the battery transient characteristics more effectively, a novel identification method for parameters of the 2 <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">nd</sup> order RC equivalent circuit model was proposed. Based on the derived evolution law of battery transient characteristics under the continuous pulse excitation, four feature points are extracted for parameter identification in each cycle. The proposed method reduced the time cost of identification from 11796.88s to 0.06s while ensuring that the error of voltage doesn't exceed 2.2mV. In order to verify the power profiles applicability of the proposed method, applicability analysis of power profile for different identification methods was carried out including the methods using different amount of data (4N points, 200 points, 6000 points) under unidirectional current pulse excitation (UCPE), bidirectional current pulse excitation (BCPE) and unidirectional voltage pulse excitation (UVPE). It was illustrated that the identification process using data of multiple cycles could significantly reduce errors, including maximum error and average error. What's more, the proposed method under UCPE had the lowest maximum error of 0.420% in voltage simulation and -0.421% in the current simulation of power profiles. Compared with the conventional method (using 200 points of single pulse data for parameter identification), the proposed method can reduce the average voltage error and the maximum error by 62.5% and 11.8% respectively under the DST power profile.

Fuzzy Logic Based Controller For Buck Converter

This research aims to make buck converter prototype for PLTS system by using fuzzy logic controller. Buck converter is required in the PLTS system if the required unidirectional voltage is smaller than the output voltage of the solar cell. Buck converter used to convert 24 Volt dc voltage to 12 Volt dc with 60 watt capability. While fuzzy logic controller is used to improve buck converter performance based on pulse generation technique for switching. The application of fuzzy logic method is expected to improve the performance of the system by maintaining the stability of buck converter output voltage of 12 volts and reduce the output ripple value. Atmega8535 microcontroller is used to generate PWM pulses for switching on power circuits. The results obtained from the test using a 100 Ohm 5 Watt load obtained the buck converter output voltage of 12.4 Volt.

Chiral Voltage Propagation and Calibration in a Topolectrical Chern Circuit.

We propose an electric circuit array with topologically protected unidirectional voltage modes at its boundary. Instead of external bias fields or Floquet engineering, we employ negative impedance converters with current inversion (INICs) to accomplish a nonreciprocal, time-reversal symmetry-broken electronic network we call a topolectrical Chern circuit (TCC). The TCC features an admittance bulk gap fully tunable via the resistors used in the INICs, along with a chiral voltage boundary mode reminiscent of the Berry flux monopole present in the admittance band structure. The active circuit elements in the TCC can be calibrated to compensate for dissipative loss.

DESIGN AND DEVELOPMENT OF INTERLEAVED BOOST CONVERTER AS A POWER QUALITY IMPROVEMENT IN ONE PHASE ROTARY WITH INDUCTIVE AND RESISTIVE LOADS

The unidirectional voltage source is obtained through an uncontrolled 220 Volt single phase full wave rectifier circuit. Installation of large amount capacitors as a filter affect input waveform. Due to the harmonics distort sinusoidal input voltage from the PLN grid. The difference in voltage waveforms and input currents that occur can affect the value of the resulting factor. Based on this problem, a study was made on theimprovement of power factors using a series of Interleaved Boost Converter which functioned as a series of Power Factor Correction (PFC) and voltage regulators with a setting method using Fuzzy logic. This Interleaved Boost Converter circuit is made to work in the condition of the Discontinues Conduction Mode (DCM) so that any load that is supplied to the circuit will make the system resistive. So, it is expected that thevoltage and input current waveforms will produce a factor value close to the unity value. The results of this study are the Interleaved Boost Converter series that can be used as a Power Factor Correction circuit and also as a voltage regulator. It improves power factor from 0.9 to 0.93.

Design, Operation, and Control of S3 Inverter for Single-Phase Microgrid Applications

A single-phase voltage source inverter with a front-end dc–dc conversion stage followed by a synchronized push–pull configuration operating at a desired fundamental frequency (FF) is presented. The duty cycle of the dc–dc conversion stage is varied in the form of a unidirectional sine wave to produce a similar output voltage across the dc-link capacitor. The unidirectional voltage is made into an alternating voltage by the synchronized push–pull configuration. This inverter employs three semiconductor switches, in which one is operating at a high frequency and the rest are operating at an FF. Hence, it is named as the S3 inverter. Furthermore, simple and cost-effective analog circuits are presented for the generation of switching pulses and the control of the amount of power fed to the grid. The hardware prototype of the S3 inverter has been built in a laboratory, and its performance during the stand-alone and grid-connected modes of operation is validated.

Simplified embedded control scheme for two‐stage multistring off‐grid inverter

This study proposes an embedded control for an off-grid single-phase multistring inverter with front-end DC–DC conversion stage followed by a synchronised H-bridge. In this inverter, the duty cycle of DC–DC converter is varied in the form of fully rectified sinusoidal fashion to produce a similar output voltage across the DC-link capacitor. This unidirectional voltage is converted into an AC voltage by the synchronised H-bridge. An application of this inverter topology with the proposed control scheme in micro-grid is investigated in the present study. The proposed control scheme not only possesses better steady-state performance with both linear and non-linear loads but also provides fast dynamic response during a step change in load. A digital controller based on field programmable gate array is utilised for the simultaneous generation of high-frequency switching pulses for DC–DC converter and synchronised fundamental frequency switching pulses for H-bridge. The entire system is simulated in MATLAB/Simulink® environment and its functioning is verified with linear and non-linear loads. The hardware prototype of inverter is also built in the laboratory and its performance is validated. Further, the better performance of the proposed system for supplying household appliances is ascertained in the laboratory.

A Study of Unidirectional Driving Circuit of Piezoelectric Device Considering Energy Recovery

Common R or R-L load do not need special inverter circuits, however piezoelectric load can be considered as R-C load and its voltage does not become 0 even though the applied voltage is 0. Therefore it needs some special inverter with circuit that can discharge the capacitive energy. Especially for unidirectional square-wave voltage driving, it becomes more serious problem. In this paper, an energy recovery circuit for unidirectional square-wave voltage driving for piezoelectric load is proposed. With the circuit, the peak load current and the power supply capacity can be reduced because the energy in the load capacitor is saved to a capacitor for energy recovery and recharged from the capacitor. The appropriateness is proved from the simulation of the proposed circuit.

Hysteretic Current-Voltage Characteristics and Memristive Behaviors in AgI Nano-Particles Assembly

This paper reports obvious hysteretic current-voltage (I–V) characteristics and memristive behaviors of bulk silver iodide (AgI) nano-particles assembly, obtained using a chemical reaction method. According to the as-obtained stable bipolar I–V plots, resistance ratio between high resistance state and low resistance state was measured to be over 100 on a sandwich structure of Ag/AgI/Ag. Dependences of I–V loops on voltage scan rate (0.1, 1, 10 and 100 V/s), voltage range (0.9, 1.2, 1.8 and 3.25 V) and testing temperature (−50, −25, 0, 25, 50°C) were investigated. An electrochemical redox reaction of I2 on the interface between Ag electrode and AgI electrolyte was suggested for explanation. This model was further confirmed by applying unidirectional voltage scan, asymmetric voltage and results from sandwich structure using Pt electrodes.

DC voltage control and stability analysis of PWM-voltage-type reversible rectifiers

A PWM voltage rectifier has useful characteristics on its DC and AC sides. On its DC side, a DC-link unidirectional voltage is obtained and bidirectional power transfer capability is possible by reversing the flow direction of the DC-link current. On its AC side, near sinusoidal current waveforms and AC four-quadrant operation can be obtained, leading to high-quality power being exchanged between the power converter and the mains. The use of AC filters becomes unnecessary. The rectifier DC voltage must be regulated to a constant value. In this paper, three solutions for the DC voltage control are presented. In the first solution, the DC voltage is controlled by acting upon the quadrature component of the power converter fundamental Park's voltages with relation to the mains voltages. Slow responses are necessary because of stability reasons. Also, load power variations produce both active and reactive power variations in the power converter AC side. To improve the DC voltage response, a second control solution is presented. The power converter currents in Park's coordinates must be controlled. The DC voltage is controlled by controlling the direct Park's current component and, thus, acting only on the active power of the converter AC side. Faster responses are achieved. In this case, load power variations do not produce reactive power variations in the converter AC side. The third control solution is a simplified version of this last one. Experimental results from a 2 kVA IGBT-based prototype showing good system dynamic performance are presented.

Kinetics of electroluminescence of zinc sulfide

Time changes in the intensity of luminescence of zinc sulfide electroluminophores induced by rectangular unidirectional voltage pulses are considered. The origin of luminescence spikes that are observed under application and removal of voltage is discussed. Results of studies of these spikes and microscopic observations show that the light spikes observed under application of voltage can be ascribed to migration of holes that appear in barriers during the previous voltage pulse into the crystal interior.

The temperature dependence of ferroelectric imprint

Abstract Unidirectional voltage pulse stressing can induce a significant amount of asymmetry in the retention characteristics in certain LSCO/PLZT/LSCO thin films. A large asymmetry was developed within 1000 s of unidirectional pulsing with a 100-Hz (50% duty cycle) square wave at 125°C while no significant retention asymmetry was developed at 25°C in the same time frame. The change in respective switched and non-switched polarizations after voltage pulse stressing follow an Arrhenius behavior. The thermal activation energies (Ea) derived from the Arrhenius plots are Ea = 0.21 eV for the change in switched polarization and an Ea = 0.56 eV for the change in non-switched polarization.

Mechanism of prebreakdown spacer charging in non-uniform fields under unidirectional voltages

Charge densities on cylindrical spacers placed in a rod-plane gap geometry were measured using a capacitive probe in an SF/sub 6/ environment. The corona discharge occurring at the tip of the rod electrode was found to be a main source of charge accumulation for DC and lightning impulse voltages. Further, microdischarges occurring at asperities or other locations with high electric fields on the plane electrode may explain the nature of spacer charge accumulation under positive polarity voltage application. For DC voltages that are lower than the corona inception, the charge accumulation may be explained by the drift of charge carriers present in the gas; this mechanism is not effective under impulse voltages. >

Effective Utilization of Surge Protection Devices

A systematic method is described for selecting the energy rating for surge protection devices when coordinated with a known impedance and subjected to typical low-voltage ac transients. A review of line transient generation characteristics, source impedance determination, and load surge protection device characteristics is given. From this study, an analytical model of the source, line, and load protection device is presented with closed-form mathematical expressions for suppressor current and energy. Results are obtained and compared for a unidirectional voltage impulse, a decaying oscillatory voltage wave, and a unidirectional current wave. From the analysis, the effect that line impedance has on each of these waveforms is shown graphically. In addition, the validity of the analytical model is confirmed experimentally.

The production of pulsed E.H.T. voltages for electrostatic coalescence

The use of an electric field, applied between immersed electrodes, is known to promote the separation of water-in-oil type dispersions or emulsions. Recent work has established that pulsed unidirectional voltages applied to electrodes insulated from the liquids is an efficient means of promoting phase disengagement particularly for dispersions with a high conducting phase content. The range of applications is thus extended to include chemical engineering operations such as solvent extraction and crude oil dehydration. It has been shown that the rate of coalescence is not only a function of pulse amplitude but also its shape, mark space ratio and frequency; all of these parameters having physical optimum values. There is, at present, no commercially available package capable of generating a pulsed EHT output of any form in the required frequency range (0.1 – 50 Hz). This paper therefore describes an existing arrangement for laboratory use and a more compact solid state version. The implementation of monitoring and external control facilities is also briefly mentioned.

Les decharges frappant les surfaces isolantes et l'electrostatique

When an unidirectional voltage is applied to a point-to-plane (point I, plane B) electrode system with an insulating plate inserted between them, a corona effect takes place at the point I when the voltage increases, and another one of the opposite polarity occurs when the voltage decreases. The ions released by these corona effects are trapped at the air—insulating plate interface, where they form a circular layer. In order to know the characteristics of this layer, two methods are used: (i) an induction probe, which must contact the insulating surface F, measures the charge density at different distances from the layer centre; (ii) the dust patterns method is used also in order to materialize the regions of each polarity. When the plane electrode B remains attached to the back side of the insulating plate during the detection, the two methods notably contradict each other. These contradictions are explained by the fact that the probe contacting F detects only the charge trapped on F; however, the powder detects the algebraic sum of the trapped charge on F and of the induced charge on B. Finally, it may be shown that the powder materializes the edge effect of the pseudo-condenser formed by the plane electrode B and the circular charged region on F. The study of the characteristics of the charged layer trapped on F shows that as long as the electric field near I tends to exceed the critical value ± g, the ions in the air distribute on F in such a manner that an electrostatic equilibrium is obtained as with conductors; because g is not zero, such an equilibrium cannot be realized completely. The contradictions observed between the two detection methods disappear if the charges are detected after B has been removed far from the insulating plate. The phenomena are disturbed, however, by ionisation of the air space that forms between the plate and B during their separation. This ionisation causes the rather imperfect transfer of the charge layer, previously induced on B, to the back side of the plate where it is trapped. The study performed here shows that gas discharge phenomena on striking insulating walls allow many experimental demonstrations of the classical Laws of Electrostatics. Before the availability of films and plates of highly polymeric materials, simple, practical applications of these Laws were very scarce.

Linear induction accelerators made from pulse-line cavities with external pulse injection

Two types of linear induction accelerator have been reported previously. In one, unidirectional voltage pulses are generated outside the accelerator and injected into the accelerator cavity modules, which contain ferromagnetic material to reduce energy losses in the form of currents induced, in parallel with the beam, in the cavity structure. In the other type, the accelerator cavity modules are themselves pulse-forming lines with energy storage and switches; parallel current losses are made zero by the use of circuits that generate bidirectional acceleration waveforms with a zero voltage-time integral. In a third type of design described here, the cavities are externally driven, and 100% efficient coupling of energy to the beam is obtained by designing the external pulse generators to produce bidirectional voltage waveforms with zero voltage-time integral. A design for such a pulse generator is described that is itself one hundred percent efficient and which is well suited to existing pulse power techniques. Two accelerator cavity designs are described that can couple the pulse from such a generator to the beam; one of these designs provides voltage doubling. Comparison is made between the accelerating gradients that can be obtained with this and the preceding types of induction accelerator.

The Development of Electrical Discharges in Simulated "Tree" Channels

The development of spark discharges in 5 x 10-3 cm diameter cylindrical tubules of 0.5 cm length bounded by solid dielectric has been studied by making the conventional electric strength measurements and by using a self-triggered high speed camera which possesses a temporal resolution of 5 ns and a spatial resolution of about 50 line-pairs per mm to obtain sequential photographs of the prebreakdown luminescence accompanying voltage collapse. The photographs verify the deductions made from the information obtained from the electric strength measurements: the walls of the tubules interfere with the breakdown processes in the confined gas and collect considerable charge. This results in an electrostatic field which appreciably distorts the applied field. It is evident that the electric strength of tree channels under unidirectional voltage waveforms can be very high, approaching that of the solid insulation. It is concluded that the mechanisms of trapping and decay of charge in a solid insulation are important factors in assessing its resistance to tree penetration, and that the channels of electrical trees cannot be an effective extension of the electrodes into the insulation as is almost universally assumed.

A canthi-skin electrode electroretinogram, independent of eye movements (author's transl)

In order to avoid misinterpretation of ERG recordings taken with canthiskin electrodes, the potential deriving from the two electrodes was fed into a balancing amplifier that eliminated opposing voltages and amplified unidirectional voltages. During voluntary as well as nystagmus caused eye movements as well as those caused by nystagmus clearly distinguishable averaged ERG's were recorded.

Negative resistance in Al-CdS-Al structures under unidirectional voltage pulse excitation

Vacuum condensed Al-CdS-Al structures have been studied under unidirectional voltage pulse excitation. The current-voltage characteristics show negative resistance in the low-voltage region. The results are explained in terms of the build-up process of barrier field at the cathode owing to reapplication of the time increasing voltage, superposed on the decay of space charge in the barrier region accumulated during application of the previous voltage pulse. The voltage corresponding to the minimum in the current-voltage characteristics has been used to evaluate the lifetime of positive space charge trapped in the surface states at the metal semiconductor contact interface. This is in the range of a few milliseconds. The results depend upon the contact characteristics and are affected by the external dc biasing of the cathode barrier.