Four-wire Circuits Research Articles

Research on Inverter Control Strategy Based on FPGA

Abstract This study adopts a composite repetitive controller strategy in a three-phase four-wire circuit, combining proportional resonance and repetitive control, which effectively suppresses harmonics and improves system performance. At higher switching frequencies, FPGA is used to achieve efficient control to ensure system stability and performance. This research provides new ideas for improving the performance of on-board inverters, especially in terms of high-speed control, nonlinear load and harmonic processing. SiC devices and composite control strategies provide more sustainable solutions for future rail transit systems.

Automatic adjustment of the parameters of the temperature measurement algorithm in a wide range

Existing methods and devices for measuring temperature are described, and it is noted that resistance thermometers are most widely used as temperature sensors in systems for collecting and monitoring environmental parameters. It is shown that the main source of temperature measurement errors when connecting sensors remotely is the resistance of the connecting lines, determined by their length. The main methods for reducing the measurement error caused by the influence of the resistance of the vehicle connection line on the temperature measurement results are considered. The advantages of two-wire circuits in comparison with three- and four-wire circuits are formulated. As an analogue, a two-wire method of measuring temperature with an integrating converter is considered in detail, implemented on the basis of a device with a built-in microcontroller, and allowing to obtain such advantages as reducing measurement time, detuning from interference and quantization noise and, as a result, reducing the temperature measurement error in comparison with similar two-wire measurement methods. An alternative two-wire method for measuring temperature with automatic adjustment of the parameters of the measurement algorithm is proposed, aimed at increasing the measurement accuracy by weakening the influence of the time constant. The search for the optimal time of the first integration step was carried out. Experimental studies and evaluation calculations were carried out to confirm the effectiveness of the proposed solution. The coefficient of variation when the resistance of the vehicle changes in the range of 1–4 kOhm lies in the range, and the range of change in the relative error of resistance measurement when using auto-tuning within the specified range has decreased by more than 4 times. The results of the experiment allow us to count on the possibility of using the method in control and regulation systems with remote connection of temperature sensors.

Description of a three-phase, four-wire system with a nonlinear receiver and an asymmetric voltage source using CPC power theory

This article mathematically describes a three-phase, four-wire circuit in the case of a nonlinear, unbalanced load, asymmetry of the power source with a periodic, non-sinusoidal waveform. This description uses Currents' Physical Components (CPC) power theory for three-phase circuits. Determining the energy flow between the source and the load is possible by decomposing the phase current into components depending on the physical nature of the phenomena in this circuit. Mathematical relationships were determined enabling decomposition into components depending on the direction of energy flow and the causes of their creation. A calculation example using the determined relationships and calculation results has been presented. The presented computational concept is important for mathematical analyzes in circuits with nonlinear three-phase receivers. Knowing the nature of physical phenomena, it is possible to perform measures that limit the value of the current supplying the load.

Разработка синхронного детектора для измерения сопротивлений наноструктур

This paper presents a circuit which is used to measure the resistances of nanostruc-tures and describes the principle of its operation. Next, stated a problem in the opera-tion of this circuit and presented a method for solving this problem. The main goal of the work was to develop a lock-in for measuring current values in a four-wire circuit for measuring the resistance of nanostructures. The text reveals the basic principles of construction of lock-in amplifiers, its nuances and functions and where they can be used. The schemes of the device itself, its components are also given. The main purpose of this paper is to convey information on how lock-in amplifiers are work how they can be made and what they require for proper functioning. At the end of the article, the characteristics of the developed lock-in are presented and graphs illustrating the operation of each part of it are given.

Prediction of Three-phase Four-wire Circuit Balance State Based on Current Sensor Data Fusion and Improved Back Propagation Neural Network

Prediction of Three-phase Four-wire Circuit Balance State Based on Current Sensor Data Fusion and Improved Back Propagation Neural Network

The method of calculating LC parameters of balancing compensators in a three-phase four-wire circuit for an unbalanced linear receiver

The article uses the Currents’ Physical Component (CPC) power theory to determine the parameters of the reactive compensator in the case of a three-phase four-wires unbalanced receiver on a non-sinusoidal periodic power supply. The basic relationships and the way of calculating the compensator reactance is presented. The compensator was built from two parts: the first working in the star-topology, and the second in the triangle-topology. The correctness of the formulas has been verified by presenting the results of calculations for an exemplary system.

Ground Fault Overvoltage With Inverter-Interfaced Distributed Energy Resources

Ground fault overvoltage can occur in situations in which a four-wire distribution circuit is energized by an ungrounded voltage source during a single-phase-to-ground fault. The phenomenon is well documented with ungrounded synchronous machines, but there is considerable discussion about whether inverters cause this phenomenon and, consequently, whether inverters require effective grounding. This paper examines the overvoltages that can be supported by inverters during single-phase-to ground faults via theory, simulation, and experiment. It identifies the relevant physical mechanisms, quantifies expected levels of overvoltage, and makes recommendations for optimal mitigation. It concludes that under many circumstances, effective grounding of inverters is not necessary to prevent ground fault overvoltage.

Optimized Compensation of Unwanted Current Terms by AC Power Converters Under Generic Voltage Conditions

This paper formulates an optimization-based algorithm for the compensation of unwanted current terms by means of distributed electronic power converters, such as active power filters and grid-connected inverters. The compensation goal consists in achieving suitable load conformity factors, defined at the source side and within a feasible power region in terms of the power converter capability. Based on the measured load quantities and on a certain objective function, the algorithm tracks the expected source currents, which are thereupon used to calculate proper scaling coefficients and, therefore, the compensation current references. It improves the power quality at the point of common coupling and enables full exploitation of distributed energy resources, increasing their efficiency. The compensation is based on a decoupled current decomposition and on an optimization-based algorithm. In this paper, the strategy is applied to nonlinear and unbalanced three-phase four-wire circuit, under nonsinusoidal and asymmetrical voltage conditions. The steady-state and dynamic behaviors have been analyzed by theoretical, simulation, and experimental results. Furthermore, the proposed approach is also compared to other compensation strategies showing its effectiveness.

Detecting Method for Harmonic and Fundamental Negative Sequence and Zero Sequence Currents in Unbalanced Three-Phase Four-Wire Circuits

Shunt Active Power Filter (SAPF) is a new device for compensating harmonic currents in power system [1]. For unbalanced three-phase four-wire circuits, it need detect the total of harmonic and fundamental negative sequence and zero sequence currents at the same time. Base on traditional method of ip-iq, a detecting method which is suitable for unbalanced three-phase four-wire is proposed and analyzed by mathematical reasoning. At last, correctness of the result is verified by simulation.

Decoupled Reference Generator for Shunt Active Filters Using the Conservative Power Theory

Based on the framework of the Conservative Power Theory (CPT), this paper proposes some compensation strategies for shunt current compensators. CPT current decompositions result in several current-related terms associated with specific load characteristics, such as power consumption, energy storage, unbalances and load nonlinearities. These current components are decoupled (orthogonal) from each other and are used here to define different compensation strategies, which can be selective in minimizing particular effects of disturbing loads. Compensation strategies for single- and three-phase four-wire circuits are also considered. Simulated and experimental results are described to validate the possibilities and performance of the proposed strategies.

Estimation of general energy-savings in three-phase ac power circuits by balancing phase currents using power active filter

Analyzing the ways of circuit power loss decreasing by balancing phase currents, the authors obtained analytical relations permitting to estimate power consumption decrease in a three-wire and four-wire ac circuit using a power active filter

Critical Evaluation Of Fbd, Pq And Cpt Current Decompositions For Four-wire Circuits

This paper investigates the major similarities and discrepancies of three important current decompositions proposed for the interpretation of unbalanced and/or non linear three-phase four-wire circuits. The considered approaches were the so-called FBD Theory, the pq-Theory and the CPT. Although the methods are based on different concepts, the results obtained under ideal conditions (sinusoidal and balanced signals) are very similar. The main differences appear in the presence of unbalanced and non linear load conditions. It will be demonstrated and discussed how the choice of the voltage referential and the return conductor impedance can influence in the resulting current components, as well as, the way of interpreting a power circuit with return conductor. Under linear unbalanced conditions, both FBD and pq-Theory suggest that the some current components contain a third-order harmonic. Besides, neither pq-Theory nor FBD method are able to provide accurate information for reactive current under unbalanced and distorted conditions, what seems to be done by means of the CPT.

Investigation on a New Algorithm for Instantaneous Reactive and Harmonic Currents Detection Applied to Intensive Nonlinear Loads

To pursue an improved solution to instantaneous reactive power and harmonics compensation with intensively nonlinear and quasistochastic loads, an effective algorithm is presented with comprehensive integration of the i <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">p</sub> -i <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">q</sub> and p-q methods to detect instantaneous reactive and harmonic currents. The algorithm can be applicable in three-phase circuits of any operational conditions, including three-phase four-wire circuits, asymmetric and/or harmonic voltage sources, etc. Both theoretical deduction and computer simulations demonstrate the accuracy and feasibility of the algorithm. Also, the above algorithm is expanded for further applications, which can effectively realize extraction and decomposition of the active or reactive components of either positive-sequence or negative-sequence currents with respect to any order harmonics.

Compensation in Nonsinusoidal, Unbalanced Three-Phase Four-Wire Systems With Active Power-Line Conditioner

For three-phase four-wire circuits, two compensation criteria have been established: one based on the instantaneous value concept and the other on the average value concept. Thus, according to the instantaneous value concept the non instantaneous power current is reduced, without altering the instantaneous active power. According to the average value concept, the nonactive average-current is reduced, without altering the average power. When the zero-sequence voltage component exists, both compensation types would not enable the zero-sequence (neutral) source current elimination. Then, two approaches are marked in this paper. The first one is for eliminating the non instantaneous power current or the nonactive average-current but the neutral current can still flow. The second one for eliminating the modified non instantaneous power current or the modified nonactive average-current, thus the neutral current component is compensated. According to recent recommendations in this work three-phase systems are considered as four-conductor systems. Experimental results are obtained to confirm the theoretical properties and to show the compensator performance.

Correction to "Strategies of instantaneous compensation for three-phase four-wire circuits"

Correction to "Strategies of instantaneous compensation for three-phase four-wire circuits"

Strategies of instantaneous compensation for three-phase four-wire circuits

When the voltage source is not balanced for three-phase four-wire circuits, instantaneous compensation for the instantaneous reactive power does not eliminate the neutral current on the source side. In facti when the zero-phase voltage of the source exists, none of the present compensation strategies can guarantee the instantaneous elimination of the neutral current in three-phase four-wire systems. Two approaches are distinguished in this paper for instantaneous compensation. The first eliminates the instantaneous reactive current, thus neutral current can still flow. The second eliminates the instantaneous pseudo-reactive current, so that the neutral current component is compensated. In the latter case, a new control strategy is designed to avoid instantaneous power flowing through the compensator. It provides flexibility in compensating for the neutral current in a three-phase four-wire system including the zero-sequence voltage. Finally, simulated and experimental results are obtained to confirm the theoretical properties and show the compensator performance.

Strategies of Instantaneous Compensation for Three-Phase Four-Wire Circuits

For three-phase four-wire circuits, when the voltage source is not balanced, instantaneous compensation for the instantaneous reactive power does not eliminate the neutral current on the source side. In fact, when the zero-phase voltage of the source exists, none of the present compensation strategies can guarantee the instantaneous elimination of the neutral current in three-phase four-wire systems. Two approaches are distinguished in this paper for instantaneous compensation. The first eliminates the instantaneous reactive current, thus neutral current can still flow. The second eliminates the instantaneous pseudo-reactive current, so that the neutral current component is compensated. In the latter case, a new control strategy is designed to avoid instantaneous power flowing through the compensator. It provides flexibility in compensating for the neutral current in a three-phase four-wire system including the zero-sequence voltage. Simulated and experimental results are obtained to confirm the theoretical properties and show the compensator performance.

5486810 Infrared detector for detecting motion and fire and an alarm system including the same

A integrated IR detector for detecting both motion and fire/smoke includes in one embodiment a single source of IR radiation and separate IR sensors for sensing motion and smoke. The separate sensors are coupled by their outputs to separate amplifier circuits and provide separate outputs indicating motion (intrusion) detection and smoke detection. The entire arrangement of IR source and dual sensors are mounted in a single housing and powered by a common power supply. In a second embodiment, a single passive IR motion detector having a pair of phase opposed series connected sensors is coupled to a circuit for detecting motion (intrusion) while one of the pair of sensors is coupled to a circuit for sensing changes in ambient temperature. The circuit for detecting ambient temperature changes includes logic analysis and time constant filtering to produce an alarm signal only when ambient temperature changes exceed a preset threshold rate of degrees per second. Common power supplies and control units are disclosed which allow coupling alarm signals on a single two-wire or four-wire circuit.

A new configuration for echo canceller adaptable during double talk periods

A three-port echo canceler (EC) configuration is proposed which observes the signal of the near-end side on a two-wire circuit in addition to the four-wire circuit signals. Embedding these signals on hybrid ports into a three-dimensional autoregressive process, echo path and innovations of near- and far-end speeches can be estimated through a three-channel lattice filter. The new configuration is then able to track echo path time variance, even during double talk (DT), and requires no changeover at either the beginning or end of DT, thus eliminating the need for DT detection. Two echo synthesizers utilizing inverse lattice and the echo path estimate possess guaranteed stability without the need for testing. >

Simultaneous Two-Way Data Transmission Over a Two-Wire Circuit

Simultaneous two-way (full-duplex) data transmission in the same bandwidth normally requires separate channels, and in the telephone network is realized by using a four-wire circuit. This paper reports on investigations directed toward full-duplex operation on a two-wire circuit using a hybrid coupler and a passband automatic transversal filter at each end of the circuit to separate the two signals. Full-duplex binary transmission at a rate of 2000 Bd in each direction has been experimentally demonstrated on a limited number of twowire circuits. Photographs of eye patterns are provided to illustrate the substantial improvement over operation with hybrids alone. Limitations on performance due to unstable distant echoes are described.