Average Current Method Research Articles

Fault tolerant control on single phase open circuit fault for dual-three phase PMSM

The dual three-phase motor can ensure the continuous operation of the motor under the condition of single-phase open circuit. This paper will mainly focus on exploring the fault handling and operation methods of dual three-phase motor under the condition of single-phase open circuit. Based on the analysis of motor fault operation, this paper proposes an average current detection method based on threshold judgment. Through this method, the single-phase open circuit fault can be detected and processed within 2 cycles, which allow system to handle the fault rapidly and reduce the impact of the fault, thus the reliability and operation stability of the motor drive system can be improved.

Improved energy saving control of IPMSM based on the weighted average current method

Aiming at the low efficiency of vector control system caused by unreasonable current allocation, an improved energy saving control strategy based on weighted average current method is proposed in this paper, and the research is carried out on the background of interior permanent magnet synchronous motor vector control system. This method does not add new parameters, but achieves the goal of reducing motor loss and improving current utilization rate. Firstly, according to the mathematical model of permanent magnet synchronous motor considering iron loss resistance, the relationship between motor torque and d-q axis current is deduced. Then, by introducing the weighted average current factor, the minimum copper loss current and the minimum iron loss current are calculated analytically. Finally, the simulation analysis shows that the energy saving strategy proposed in this paper can further reduce the electrical loss of permanent magnet motor compared with the traditional energy saving control method, which proves the feasibility of this method in improving the energy efficiency of the vector control system of permanent magnet motor.

Weighted average current method for active damping control based on grid voltage feed-forward

In the weak current network environment, the existence of power network impedance will reduce the current control stability margin of LCL grid connected inverter, the stability margin will gradually deteriorate as the inductive component of the power network impedance increases, leading to system instability. In this paper, an improved weighted average current control strategy is proposed, which is based on the active damping control of the voltage feedforward of the charged network. In the new control strategy, with the zero-pole cancellation method, a new weighting coefficient related only to the parameters of LCL filter is obtained, which reduces the order of the system, suppresses the influence of power network impedance, and improves the stabilization of the system, getting better inverter output current quality. Then the influence of power network impedance on the control system of grid connected inverter is analyzed, and the feed-forward control of grid voltage is improved to improve the stability of inverter in weak current network. The Bode diagram analysis and MATLAB simulation results proved that the proposed control strategy is feasible.

Separate-Structure UDE-Based Current Resonant Control Strategy on $LCL$-Type Grid-Tied Inverters With Weighted Average Current Method for Improved Injected Current Quality and Robustness

Due to its effective high-frequency suppression ability, the LCL filter has been widely used between inverters and the grid. However, its resonance causes system instability. The weighted-average current (WAC) strategy has been extensively studied to suppress resonance. By selecting a proper weight factor of the inductor and injected current, the order of the LCL can be reduced to first without resonance in the control loop, which can significantly simplify the controller design. Nevertheless, disturbances and uncertainties in the system will affect the control performance of the inverter. In this article, for a WAC-form LCL grid-tied inverter, a separate-structure uncertainty and disturbance estimator (SUDE) inner-loop control strategy with a zero-phase, low-pass, time-delay FIR filter is designed in the discrete domain to eliminate the influence of disturbances and parameter uncertainties on the system, and a proportional resonant controller is adopted as an outer-loop controller. By using the proposed FIR filter, the performance in the rejection of high-frequency harmonics is improved. Moreover, the stability of the proposed two-degree-of-freedom compound controller is analyzed in detail, and the superiority and effectiveness of its robustness to grid impedance and harmonic rejection are shown. Finally, the proposed strategies are validated on a 2-kW experimental platform.

A coupled thermohydraulic/neutronic investigation of noise propagation in VVER-1000 reactor using[formula omitted] nanofluid coolant

Thermohydraulic and neutronic coupling for the VVER-1000 reactor carried out by applying Al2O3 nanofluid as coolant in this paper. The simulation took place in two sections; with the neutronic section, the discretization of the nodal (average current) method for dissociation of two-group diffusion equations accomplished and with the thermohydraulic section, the finite volume method for decomposition of conservation equations (mass, momentum and energy) in static and transient states was used.In this study, neutronic and thermohydraulic noises (Fourier transform) in the frequency domain were analyzed by applying propagation noise sources in the VVER-1000 reactor core. With the neutronic section, macroscopic cross sections were generated making use of Al2O3 nanofluid as coolant with different volume fractions by means of WIMS-D5 computation code.The ultimate goal of the paper is to perform neutronic and thermohydraulic simulations of VVER-1000 reactor using Al2O3 nanofluid as coolant in the frequency domain. Two separate noise scenarios for the inlet nanofluid coolant (coolant temperature and velocity) with different volume fractions of Al2O3 nanoparticles (0.001%, 0.1% and 1.0%) were considered in the analysis. Final results showed that the core power peaking factors will be less influenced by inlet fluctuations when applying more nanoparticles in the reactor coolant.

Power Distribution Network Based on Digital 3D Twin Panoramic Modeling

Digital twins refer to virtual digital expressions constructed in virtual space that can characterize characteristics, the formation process and behavior of natural entities, and it has the characteristics of multi-physics, multi-scale and probability. This article mainly introduces the application research of digital 3D twin panorama modeling in power distribution network. This paper proposes the average current method to calculate the line loss of the power distribution network, so that the accuracy is guaranteed. In addition, the digital three-dimensional panoramic modeling method is used to optimize the grid system, and the data structure is used to calculate the power distribution network. Analyze the topological structure of the power grid, and then obtain the calculation method of the distribution network line loss. The experimental results in this paper show that the rendering efficiency of power grid results has increased by 17% based on the digital 3D twin panorama modeling, and the method and algorithm for matching video and panorama image are proposed, which solves the problem of video rotation angle on the panorama connection, so that The smoothness of panoramic roaming is improved by 23%.

PWM-VSI Fault Diagnosis for a PMSM Drive Based on the Fuzzy Logic Approach

For the purpose of increasing the reliability in a hostile environment, techniques of fault diagnosis have been reported for a three-phase voltage-source inverter (VSI). Based on the average current Park's vector method, this paper proposes a fuzzy-based fault diagnosis method for the VSI in the three-phase permanent-magnet synchronous motor drive. By utilizing the phase current information, the fault symptom variables are calculated by using the average current Park's vector method. The fuzzy logic approach is applied to process the fault symptom variables and obtain the faulty information of power switches. Compared with other fuzzy logic methods, the fuzzy logic design, fuzzy inputs, and fuzzy rules are different. The proposed fault diagnosis method can detect and locate not only the single or multiple open-circuit faults, but also the intermittent faults in power switches, which can improve the reliability of the motor drive system. The effectiveness of the proposed method is validated by both simulation and experiments.

An interleaved step-up/step-down converter for fuel cell vehicle applications

Fuel cells have received considerable attention as one of the most promising candidates for green power sources in vehicles. The voltages of fuel cells vary widely depending on the operating conditions. Furthermore, the output power of the fuel cell in a vehicular powertrain should be controlled in accordance with some energy management strategies. For these reasons, the fuel cell must be interfaced with other components by means of a DC/DC converter in fuel cell vehicle applications. A step-up/step-down converter for fuel cell vehicle applications, which effectively operates in step-up or step-down mode when the fuel cell voltage is lower or higher than the output voltage of high-voltage direct current bus, is proposed in this paper. To reduce the current ripple, the interleaved circuit structure is used for the proposed converter. The proportional-integral regulator for the fuel cell current control is achieved by a digital signal processor to improve the reliability and flexibility of the converter. Smooth transition between step-up and step-down modes is realized using average current method for the converter. The principle of operation and theoretical analysis of the converter are given. Experimental results of a prototype are provided to evaluate the performance of the proposed scheme.

An Average Current Modulation Method for Single-Stage LED Drivers With High Power Factor and Zero Low-Frequency Current Ripple

Conventional single-stage light-emitting diode (LED) drivers with a high power factor (PF) contain a significant LED current ripple at twice the ac line frequency, and would require large energy storage capacitors to limit the effect on LED light. Conventional designs and novel control techniques aim to power LED loads with a dc voltage to ensure a limited low-frequency LED current ripple. This paper proposes an average current modulation method that is designed to operate in conjunction with single-stage PF correction (PFC) circuits that contain significant ac voltage ripple, while maintaining zero low-frequency current ripple. This allows the energy storage capacitance of the PFC stage to be reduced, avoiding the need for electrolytic-type capacitors and prolonging the life of the LED driver. The average current modulation circuit requires a single low-voltage MOSFET, a current sense resistor, and a simple control circuit. By requiring no additional magnetic components, the cost of the current modulation circuit is very low and has minimal impact on the efficiency of the overall LED driver. Two experimental prototypes, an 8.75-W system with a buck–boost PFC converter and a 25-W system with a flyback PFC converter, have been built to verify the capability and excellent performance of the proposed driving technique.

Control for the Three-Phase Four-Wire Four-Leg APF Based on SVPWM and Average Current Method

A novel control method is proposed for the three-phase four-wire four-leg active power filter (APF) to realize the accurate and real-time compensation of harmonic of power system, which combines space vector pulse width modulation (SVPWM) with triangle modulation strategy. Firstly, the basic principle of the APF is briefly described. Then the harmonic and reactive currents are derived by the instantaneous reactive power theory. Finally simulation and experiment are built to verify the validity and effectiveness of the proposed method. The simulation results show that the response time for compensation is about 0.025 sec and the total harmonic distortion (THD) of the source current of phaseAis reduced from 33.38% before compensation to 3.05% with APF.

Calculation Method Research about Theoretical Line Loss' Boundary of Distribution Network

Based on mastering the supply power and the maximum load of the 10kV distribution transformers, this paper calculated the maximum and minimum load shape coefficient of the transformers and segmented lines, and obtained the upper and lower limitation of the theoretical line loss with average current method. In the largest variable loss calculating process, this paper put forward an effective iterative fitting algorithm. Firstly, it fitted out the ultimate load curve of the transformer high voltage side, then it fitted through iteration out the ultimate load curve of the superior branch lines and calculated the maximum shape coefficient, considering the influence of transformers loss on the line load curve in the calculation process. The calculation method provided theory evidence for enterprise line loss management level evaluation and vulnerable spot location in the line loss management and enterprise future line loss rate indicator setting.

Modeling, analysis, and control of a rectifier with power factor correction in half-bridge configuration

This paper presents the detailed analysis of a single-phase rectifier with high power factor correction in half-bridge boost configuration (RPFCU-HBB). The purpose of this work was to achieve a unity power factor and regulated output voltage. Modeling and linearization around the RPFCU-HBB point of operation are exposed in detail. The analysis and design considerations of the current controller and the output voltage using the average current method are given. The control scheme to eliminate the voltage unbalance of the two output condensers is discussed in detail. The theoretical results are checked through the simulation of the RPFCU-HBB switch model, as well as through experimental work. By using the following parameters in the experimental prototype: input voltage of 120 Vrms, output power of 80 W, and output voltage of 450 V, we obtain a power factor of 0.99 and a total harmonic distortion of 2.5%.

Current Sharing Control Strategy Based on Phase Link

A simple current sharing control technique for the switching power supply is presented herein, whose basic concept is that the control effort created from the voltage loop is finely tuned by the control effort created from the current sharing loop based on the proposed phase link so as not only to obtain the desired output voltage but also to make the load current distributed among phases as evenly as possible. Such a control method is not only without any current sharing bus as compared with the traditional current sharing methods, but also suitable for multiple phases under the condition that any one phase among multiple phases fails. Moreover, based on phase link, there is no divider used, as compared with the traditional average current method, and hence, the number of logic elements in the field-programmable gate array (FPGA) can be reduced. In this paper, the detailed basic operating principles, together with new mathematical deductions based on the superposition concept, are firstly described, and secondly some experimental results, based on the FPGA to realize the fully digitalized control of the overall system using one-comparator counter-based sampling without any analog-to-digital converter (ADC), are provided to verify the effectiveness of proposed control strategy.

The Average Capacitor Current Method for Delay Calculation in MOS Circuits

The transient response of metal-oxide-semiconductor (MOS) gates is a topic covered in most textbooks on digital integrated circuits and very-large-scale-integration (VLSI) design. One method often used to calculate first-order estimates of gate delays is the average capacitor current method. Using this method, the delay is calculated assuming that the capacitor current is constant and equal to the average of the capacitor current values at the limits of the time interval of interest. In this paper, this method is discussed and compared with other methods of delay calculation using integration and curve-fitting techniques familiar to electrical and computer engineering students. Since the computation of the capacitor current is relatively complicated because it requires the calculation of the MOS transistor currents, for propagation delay calculation there is no benefit in calculating the capacitor current twice. A single current calculation, corresponding to the familiar midpoint integration method, is sufficient to get the same or better accuracy as that of the average capacitor current method. The two-point Gauss quadrature formula is shown to provide excellent results with two capacitor current evaluations.

통신위성 배터리 충,방전기 설계 및 해석

In this study, a battery charge and discharge regulator of modular type is designed as paralleled bi-directional converter that is possible to provide the power without failure not only in the steady state but also in the transient period by the step load variation or the unexpected faults among the converter modules. Each converter module is designed to get stability, performance, reliability, and maintainability and the average current mode method used for controller has the advantages such as noise immunity, fast response, and the real average current signal acquisition. The equivalent model and small signal model for the paralleled battery chargerIdischarger are presented, and also the transfer functions are analyzed for the CCM(Continuous Charge Mode), CDM(Continuous Discharge Mode) and DDM(Discontinuous Discharge Mode). The experiments of the paralleled bi-directional converter are carried out in the step load variation, and in faults of one converter module respectively. And the performance of paralleled bi-directional converter is verified via the experimental results.