Single-phase Circuits Research Articles

Park’s Transformation for Electric Power Quality Recognition and Classification in Distribution Networks

This paper presents a novel algorithm for recognizing and classifying the power quality events based on Park’s transformation, where the three rotating abc phases are transferred to three equivalent stationary dq0 phases (d-q reference frame). This transformation is implemented, either for three-phase or single phase circuits. The proposed algorithm transferred the utility signal to a complex phasor (transformation from time domain to frequency domain). The magnitude of this phasor depends on the magnitude of the signal either a three-phase or a single phase signal. The proposed technique produces the complex phasor loci that depend on the type of power quality event; voltage sags, voltage flickers, voltage swell, and harmonics. The time of starting the disturbance is chosen randomly and the length of disturbance is arbitrary. Implementation of this technique is succeeded in recognizing and classifying the power quality events. Simulated results are presented within the text, for three-phase and single phase events.

Synthesis of loss-free resistors based on sliding-mode control and its applications in power processing

A systematic procedure to synthesize loss-free resistors (LFRs) based on sliding-mode control (SMC) of DC–DC switching converters is presented. Candidates for LFR operation are determined from the topological constraints imposed in a power converter by inducing sliding-mode motions. Two examples illustrate the use of the synthesized LFRs in power processing. The first one shows the application of the LFR as a pre-regulator stage for power factor correction (PFC) in single-phase circuits, while the second one describes its use for DC impedance matching in photovoltaic (PV) systems.

Detection for Rective Current Based on the Instantaneous Reactive Power Theory

Three-phase circuit instantaneous reactive power theory has received a successful application in detecting harmonic and reactive current timely, the ip-iq and d-q method of first proposed require the phase-locked loop and low-pass filter. The paper make corresponding improvement on the basis of the method based on amplitude integration which only can detect fundamental current , propose a method which can detect the active and reactive current, and the method based on amplitude integration can detect fundamental current of single-phase circuit directly, and simulation. The simulation results show that the method can detect the harmonic and reactive current accurately and timely, and is suitable for various circumstances that three-phase power supply distortion and asymmetry and so on, and when only detecting the harmonic current, it does not require the phase-locked loop and low-pass filter, while detecting the harmonic and reactive current, increases the phase-locked loop; when the method based on amplitude integration is directly used to detect single-phase fundamental current, the phase-locked loop and low-pass filter are not required. The paper deduces the theory of the method and researches on simulation analysis.

Исследование влияния переходного сопротивления на характеристики защиты от однофазных замыканий, основанной на контроле пульсирующей мощности

Исследование влияния переходного сопротивления на характеристики защиты от однофазных замыканий, основанной на контроле пульсирующей мощности

Comparison and Analysis on Two Improved Detecting Methods for Harmonics without PLL in Single-Phase Circuit

In order to reduce the error of the phase lock-loop (PLL) and compensate the delay of the low pass filter on harmonics detection, In the paper, a detecting-method without PLL in single-phase circuit is researched. In this method, the PLL and LPF are omitted, the feedback and average theory are used, so that the problem of detecting accuracy induced by PLL and real-time induced by LPF is solved. It is testified through comparison, analysis and simulation, that both methods can reduce the latency, improve dynamic response speed, the feedback method can reduce the delay in a dynamic, continuous process, while the average theoretical method can reduce the delay quantitatively.

Apparent Power, Power Factor, and Current Factor in Single-phase Circuits with Non-negligible Line Impedances

The first part of this article reviews the concepts of apparent power and power factor in single-phase circuits with non-negligible line impedances. The study is based on the well-known definition that the apparent power is the maximum load power subject to constant line losses and constant load voltage. In reality, however, all transmission/distribution lines have some finite impedance, and thus, the constant voltage condition cannot be maintained at the load terminals. In this article, the constant load voltage condition is relaxed and allowed to change, as long as it remains within acceptable range of application. This is a scenario that better reflects the realistic situations. Modified expressions for the apparent power and power factor are derived and discussed. The second part of the article presents a new concept called the current factor as the ratio of the minimal current to the actual current while keeping the load power constant. The current factor coincides with the power factor when the line impedances are neglected. The article explains how the current factor can be superior to the power factor when the line impedances are not negligible. The current factor is then extended to non-sinusoidal current factor for a non-linear load and is examined.

Operational Transresistance Amplifier-Based Multiphase Sinusoidal Oscillators

Multiphase sinusoidal oscillator circuits are presented which utilize Operational Transresistance Amplifier (OTRA) as the active element. The first circuit producesnodd-phase oscillations of equal amplitudes and equally spaced in phase. The second circuit is capable of producingnodd- or even- phase oscillations equally spaced in phase. An alternative approach is discussed in the third circuit, which utilizes a single-phase tunable oscillator circuit which is used to inject signals into a phase shifter circuits. An automatic gain control (AGC) circuit has been implemented for the second and third circuit. The circuits are simple to realize and have a low component count. PSPICE simulations have been given to verify the theoretical analysis. The experimental outcome corroborates the theoretical propositions and simulated results.

Research on Soft Switching Power Supply with High Power Factor Based on Boost Converter

With the development of power electronics，the technology of Switching Mode Power Supply(SMPS) is gradually perfected. However，there is no end to the demand for a high power and high performance power supply. Nowadays, Power Factor Correction (PFC) technique is widely researched. This paper mainly analyzes the fundamental configuration of the switching power supply. And we study the basic structure and the operating principles of ZVT-boost soft-switching PFC circuit and the implementing principle of soft switch. For the power requirements, the two-stage PFC circuit is used. The forward stage is a single-phase Boost Power Factor Correction circuit and the backward stage main circuit is a full-bridge converter with the phase-shifting control soft-switching technique. Finally the simulating analysis is performed to the designed system.

Didactic Videos about Basic Concepts on Alternating Current Circuits

This work emphasizes the importance of the formulation and application of didactic videos mainly in subjects where the classes are exclusively theoretical, as in the case of the subject ET016 â?? Electrotechnics, taught at the School of Electrical and Computer Engineering â?? UNICAMP. It is mandatory and it is offered to the students of the following Colleges: Food Engineering, Agricultural Engineering, Control and Automation Engineering, Mechanical Engineering and Chemical Engineering. In this subject, basic concepts of electricity are taught: single-phase and three-phase circuits; electrical energy production, transmission and application; physical principles and main application of transformers; electrical machinery of induction, asynchronous and direct current; and basic concepts of electric installations and protection devices. Upon elaborating and making these videos available, we aim at arousing a larger interest on the students, causing them to complement and reinforce the content taught at the attended theoretical classes.

Small-signal modelling and linear control of a high efficiency dual boost single-phase power factor correction circuit

In this study, a small-signal model-based linear control design of a single-phase AC-DC dual boost power factor correction (PFC) pre-regulator is presented. The converter consists of two interleaved boost converters. A high rated main boost, used for current wave-shaping and energy control, operates at low frequency; whereas an auxiliary boost uses a low rated device operating at high frequency and is controlled to compensate the low-frequency ripple generated by the main boost. The control scheme proposed for the dual PFC is based on a small-signal averaged model of the converter, which is developed using the state-space average modelling technique along with the small-signal linearisation process. The linear controllers are designed in the frequency domain, and are adjusted in order to ensure the required performance of the PFC, namely a close-to-unity input power factor and a regulated DC voltage. Experimental results based on a laboratory 1 kW prototype validate the proposed theoretical approach.

A Single-Phase Utility-Interface Circuit Without Any AC Inductor nor EMI Filter

This paper proposes a single-phase utility-interface circuit without any ac inductor nor electromagnetic-interference filter to eliminate switching voltage/current ripples and electromagnetic noise. The main circuit of the proposed circuit consists of a diode-clamped linear amplifier (DCLA) and a voltage balancing circuit. The circuit configuration of the DCLA is similar to a diode-clamped multilevel inverter, except for using complimentary MOSFETs as a power device. As a result, the DCLA makes it possible to generate a sinusoidal output voltage without any ac filter. This paper presents new control methods of the output voltage and current to connect the DCLA with the utility grid. The experimental results show a power conversion efficiency as high as 93% and a current total harmonic distortion of less than 2%.

A Novel Detection Method of Active and Reactive Currents in Single-Phase Circuits Using the Correlation and Cross-Correlation Coefficients and Its Applications

This paper proposes a novel method of detecting the active and reactive currents in single-phase circuits using the correlation and cross-correlation coefficients in the time domain. The active current is detected using the correlation coefficient between the source voltage and load current waveforms, and the reactive current is detected using the cross-correlation coefficient. The basic principle of the proposed detection method is discussed, and the proposed method is applied to a previously proposed single-phase shunt active filter for consumer electronic equipment. Simulation and experimental results demonstrate the excellent practicability of the proposed detection method.

Compact high-voltage vacuum circuit breaker, a feasibility study

This study focuses on a compact vacuum circuit breaker (CB) for nominal voltage of 72.5 kV, nominal current of 2000 A and short circuit current of 31.5 kA. The dielectric conception of the vacuum interrupter (VI) is based on a multiple floating shield configuration which reduces the risk of total breakdown due to partial breakdown between the contacts and shield. An optimised electrical field distribution on the contact surface with the maximum field pointing towards the floating shield is arranged and hence reducing the breakdown effective area of the contacts facing each. All tests have been performed on a specially designed single-phase circuit breaker pole-unit equipped with a low energy spring type mechanism. Interruption performance was confirmed in direct tests. The circuit-breaker pole was proved to be restrike-free with respect to cable charging class C2. Dielectric tests in new condition and after interruption tests confirmed the announced ratings. These tests confirm the feasibility of this HV-CB with 25% more compact VTs based on the outlined dielectric conception.

Quantitative comparison of power decompositions

This paper presents a comparison on power decompositions in a simple single phase circuit with nonsinusoidal waveforms of voltage and/or currents by giving particular emphasis to Reactive Power compensation. The experimental circuit is analysed by using exact analytical expressions for current and voltages determined via considering source impedance and nonlinearity, which is introduced due to supply side harmonics. Results demonstrate that; power decompositions proposed by Kusters and Moore, Fryze, Shepherd and Zakikhani, Sharon, and Czarnecki provide correct information regarding Power Factor improvement with passive compensation in nonsinusoidal voltage source–linear load, nonsinusoidal voltage source–nonlinear load and sinusoidal voltage source–nonlinear load cases. In these cases, Reactive component of Kusters and Moore's power decomposition can completely be compensated when Power Factor is maximum if there is no resonance or significant changes on load voltages in the case of compensation capacitance is inserted. The Reactive components of Fryze, Shepherd and Zakikhani, Sharon, Czarnecki's power decompositions attain minimum value when power factor is maximum. Furthermore, Kusters and Moore's Reactive Power could directly be related to the power of optimum compensation capacitance. On the other hand, power decompositions proposed by Budeanu, Kimbark and Depenbrock do not provide any useful information about optimum Reactive Power compensation with a basic capacitance in the cases nonsinusoidal voltage source–linear load and nonsinusoidal voltage source–nonlinear load although they can completely be compensated in these cases. An important observation is that; Distortion Powers of Budeanu and Kimbark, and Depenbrock's Residual Power have compensable parts; on the other hand, Kusters and Moore's Residual Reactive Power, Sharon's Complementary Power, Depenbrock's In Phase Power and Czarnecki's Scattered Power are almost constant when the power of compensation capacitor is varied.

Geometric Algebra: A Powerful Tool for Representing Power Under Nonsinusoidal Conditions

Geometric algebra is used in this paper for a rigorous mathematical treatment of power in single-phase circuits under nonsinusoidal conditions, as complex algebra for sinusoidal conditions. This framework clearly displays the multidimensional nature of power, which is represented by a multivector. The power multivector with its three attributes (magnitude, direction and sense) provides the means to encode all the necessary information in a single entity. This property, in conjunction with the fact that there is a one-to-one correspondence between the terms of this multivector, the instantaneous and the apparent power equation, distinguishes it as a highly efficient mathematical tool. In this way one can successfully describe power phenomena and handle practical problems (e.g., power factor improvement). Two simple examples show some of these features. In short, the power multivector under nonsinusoidal situations can be perceived as the generalization of the complex power under sinusoidal situations

A Novel Detection Method of Active and Reactive Currents in Single-Phase Circuits Using PLL Circuit

A Novel Detection Method of Active and Reactive Currents in Single-Phase Circuits Using PLL Circuit

A novel method of suppressing the inrush current of transformers by using a series-connected voltage-source PWM converter

This paper proposes a novel method of suppressing the inrush current of transformers. A small-rated voltage-source PWM converter is connected in series to the transformers through a matching transformer. As the connected PWM converter serves as a resistor for the source current, no inrush phenomena occurs. The required rating of the PWM converter, which serves as the damping resistor for the inrush phenomena, is 1/400 that of the main transformers in single-phase circuits. In three-phase circuits, it is 1/900. The basic principle of the proposed method is discussed. Digital computer simulation is implemented to confirm the validity and excellent practicability of the proposed method using the PSCAD/EMTDC. A prototype experimental model is constructed and tested. The experimental results demonstrate that the proposed method can perfectly suppress the inrush phenomena. © 2006 Wiley Periodicals, Inc. Electr Eng Jpn, 157(4): 56–65, 2006; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/eej.20174

Voltage Fluctuation Compensator for Shinkansen

In AC electric Railway, three-phase voltage is changed into the single-phase circuit of two circuits with the Scott-connected transformer. If it becomes large unbalancing of the load between single-phase circuits, voltage fluctuation becomes large on three-phase side. Then, Railway Static Power Conditioner (RPC) was developed for the purpose of controlling voltage fluctuation on three-phase side. An RPC is comprised of a pair of self-commutated PWM inverters. These inverters connect the main phase and teaser feeding buses, coupled with a DC side capacitor such as a Back-To-Back (BTB) converter. In this way, the two self-commutated inverters can act as a static var compensator (SVC) to compensate for the reactive power and as an active power accommodator from one feeding bus to another.20MVA/60kV RPCs started commercial operation in 2002 at each two substations on the newly extended Tohoku Shinkansen for compensating voltage fluctuation on three-phase side caused by traction loads, absorbing harmonic current. The results of operational testing indicate that an RPC can accommodate single-phase loads such as those of PWM-controlled Shinkansen and thyristor phase-controlled Shinkansen, and handle the exciting rush current of transformers, as well as compensate for harmonics successfully.

EXPERIMENTAL VERIFICATION OF ACTIVE POWER CALCULATION IN NONSINUSOIDAL SINGLE PHASE CIRCUITS

The active power in nonlinear single-phase circuit is measured by a new specially-developed experimental model. The experiments are carried out for sinusoidal and nonsinusoidal voltage and current waveforms. The results of the experiments show that the total active power is a sum of the active powers produced by the voltage and current harmonics with the same serial number.

相関係数と相互相関係数を用いた単相回路における 有効·無効電流検出法

This paper proposes a novel method of detecting the active and reactive currents in single-phase circuits using the correlation and cross-correlation coefficients in the time domain. The active current is detected using the correlation coefficient between the source voltage waveform and load current waveform, and the reactive current is detected using the cross-correlation coefficient. The basic principle of the proposed detection method is discussed in detail, and then confirmed by digital computer simulation. Digital computer simulation results demonstrate that the proposed method can detect the active-reactive current in single-phase circuits in the time domain.