scholarly journals Compensation of Reactive Power and Unbalanced Power in Three-Phase Three-Wire Systems Connected to an Infinite Power Network

2019 ◽  
Vol 10 (1) ◽  
pp. 113 ◽  
Author(s):  
Pedro A. Blasco ◽  
Rafael Montoya-Mira ◽  
José M. Diez ◽  
Rafael Montoya ◽  
Miguel J. Reig
Keyword(s):  
Linear Systems ◽  
Reactive Power ◽  
Current System ◽  
Positive Sequence ◽  
Power Network ◽  
Negative Sequence ◽  
Three Phase ◽  
Network Losses ◽  
Infinite Power

The compensation of an electrical system from passive compensators mainly focuses on linear systems where the consumption of charges does not vary significantly over time. In three-phase three-wire systems, when the network voltages are unbalanced, negative-sequence voltages and currents appear, which can significantly increase the total apparent power supplied by the network. This also increases the network losses. This paper presents a method for calculating the compensation of the positive-sequence reactive power and unbalanced powers caused by the negative-sequence line currents using reactive elements (coils and/or capacitors). The compensation is applied to three-phase three-wire linear systems with unbalanced voltages and loads, which are connected to an infinite power network. The method is independent of the load characteristics, where only the line-to-line voltages and line currents, at the point where compensation is desired, need to be known in advance. The solution obtained is optimal, and the system observed from the network behaves as one that only consumes the active power required by a load with a fully balanced current system. To understand the proposed method and demonstrate its validity, a case study of a three-phase three-wire linear system connected to an infinite power network with unbalanced voltages and currents is conducted.

scholarly journals Unbalanced Voltages Impacts on the Energy Performance of Induction Motors

2018 ◽  
Vol 8 (3) ◽  
pp. 1412 ◽  
Author(s):  
Enrique C. Quispe ◽  
Iván D. López ◽  
Fernando J. T. E. Ferreira ◽  
Vladimir Sousa
Keyword(s):  
Induction Motor ◽  
Induction Motors ◽  
Energy Performance ◽  
Positive Sequence ◽  
Negative Sequence ◽  
Voltage Unbalance ◽  
Three Phase ◽  
Motor Load ◽  
Sequence Parameters

<p class="Abstract">This paper presents the results of a study about the effects of unbalanced voltages on the energy performance of three-phase induction motors. The principal contribution of this paper is that presents a detailed analysis of the influence of positive and negative sequence voltage components and the angle between them on several characteristics such as: line currents, losses, efficiency and power factor under different voltage unbalanced conditions. A three-phase induction motor of 3 HP was used as a case study. The results of the investigation show that the positive sequence voltage must be considered together with the voltage unbalance factor (VUF) or percent voltage unbalance (PVU) index to evaluate the performance of the induction motor. It is also shown that the behavior of the motor load influences on the positive sequence parameters next to the voltage, while in the case of negative sequence only influences the negative sequence voltage.</p>

scholarly journals Reactive Power Compensation and Imbalance Suppression by Star-Connected Buck-Type D-CAP

Energies ◽  
2019 ◽  
Vol 12 (10) ◽  
pp. 1914 ◽  
Author(s):  
Xiaosheng Wang ◽  
Ke Dai ◽  
Xinwen Chen ◽  
Xin Zhang ◽  
Qi Wu ◽  
...  
Keyword(s):  
Control Strategy ◽  
Reactive Power ◽  
Reactive Power Compensation ◽  
Positive Sequence ◽  
Negative Sequence ◽  
Type D ◽  
Load Imbalance ◽  
Three Phase ◽  
Unbalanced Load ◽  
Line Loss

Reactive power and negative-sequence current generated by inductive unbalanced load will not only increase line loss, but also cause the malfunction of relay protection devices triggered by a negative-sequence component in the power grid, which threatens the safe operation of the power system, so it is particularly important to compensate reactive power and suppress load imbalance. In this paper, reactive power compensation and imbalance suppression by a three-phase star-connected Buck-type dynamic capacitor (D-CAP) under an inductive unbalanced load are studied. Firstly, the relationship between power factor correction and imbalance suppression in a three-phase three-wire system is discussed, and the principle of D-CAP suppressing load imbalance is analyzed. Next, its compensation ability for negative-sequence currents is determined, which contains theoretical and actual compensation ability. Then an improved control strategy to compensate reactive power and suppress imbalance is proposed. If the load is slightly unbalanced, the D-CAP can completely compensate the reactive power and negative-sequence currents. If the load is heavily unbalanced, the D-CAP can only compensate the positive-sequence reactive power and a part of the negative-sequence currents due to the limit of compensation ability. Finally, a 33 kVar/220 V D-CAP prototype is built and experimental results verify the theoretical analysis and control strategy.

Operation of an induction motor supplied by voltage containing subharmonics

2017 ◽  
Vol 1 (1) ◽  
pp. 27-34 ◽  
Author(s):  
Tomasz Drabek
Keyword(s):  
Induction Motor ◽  
Power Supply ◽  
Induction Machine ◽  
Induction Machines ◽  
Positive Sequence ◽  
Rotor Speed ◽  
Phase Voltage ◽  
Negative Sequence ◽  
Three Phase

The paper discusses the effects of the presence of subharmonics (i.e. frequencies lower than the basic 50 Hz) in the voltage supplying the induction machine. Subharmonics in a three-phase grid are the result of the oscillations of peak values of the voltages. In induction machines, this results in the subharmonic and interharmonic currents, the generation of alternating moments, the increase in the rms value of the current of the fundamental harmonic and the oscillations of the rotor speed. In the paper is derived expression on the thermally acceptable load of the motor (by torque and power), in the case of supplying it by three-phase voltage containing a positive sequence of subharmonics. It presented the obstacles to derive the analogical expression for power supply containing a negative sequence of subharmonics.

Operation of an induction motor supplied by voltage with interharmonics

2018 ◽  
Vol 2 (1) ◽  
pp. 47-53 ◽  
Author(s):  
Tomasz Drabek
Keyword(s):  
Induction Motor ◽  
Fundamental Frequency ◽  
Skin Effect ◽  
Induction Machines ◽  
Positive Sequence ◽  
Rotor Speed ◽  
Negative Sequence ◽  
Three Phase ◽  
Total Multiplicity ◽  
Rotor Cage

The paper discusses the effects of interharmonics, i.e. frequencies higher than the fundamental frequency, not being its total multiplicity, in the voltage supplying the induction motor. The emergence of interharmonics in a three-phase grid is mainly the result of the swinging of peak mains voltages. In induction machines, this results in the occurrence of currents with interharmonic and subharmonic frequencies, the generation of alternating moments, the swinging of the rotor speed and the change in the RMS value of the current of the fundamental frequency. The paper explores these phenomena simulation, taking into account the skin effect of currents in the rotor cage. The research was carried out both for interharmonics with a positive sequence of phases as well as for the negative sequence. The paper is a continuation of work [1].

Reactive Power Limits of Single-Phase and Three-Phase DC-Link VSC STATCOMs under Negative-Sequence Voltage and Current

2021 ◽  
Author(s):  
Iosu Marzo ◽  
Jon Andoni Barrena ◽  
Alain Sanchez-Ruiz ◽  
Gonzalo Abad ◽  
Ignacio Muguruza
Keyword(s):  
Single Phase ◽  
Reactive Power ◽  
Negative Sequence ◽  
Three Phase ◽  
Power Limits

Study on a Novel Three-Phase Two-Leg Active Inverter for Electrified Railway

2015 ◽  
Vol 734 ◽  
pp. 868-872
Author(s):  
Yan Ping Sun ◽  
Mo Zhou ◽  
Guo Wang
Keyword(s):  
Simulation Model ◽  
Reactive Power ◽  
Control Method ◽  
Electric Energy ◽  
Negative Sequence ◽  
Active Elements ◽  
Three Phase ◽  
Electrified Railway ◽  
The Cost ◽  
And Control

A novel topology circuit of active compensation was discussed to be used to manage negative sequence caused by locomotive load in electrified railway. The main circuit used a three-phase two-leg compensator as active elements of shunt hybrid active compensator topology. The number of switch device in this topology was reduced by comparing with three-phase full-bridge active inverter and the cost was lower. The simulation model was developed with SIMULINK. The simulating results indicates that the shunt hybrid active compensator can restrain the problem of negative sequence which generated by locomotive load, and reduces the effect of reactive power, negative sequence, improves electric energy quality and verifies the correctness of the proposed structure and control method.

scholarly journals A rapid harmonic detection method for grid-connected photovoltaic when three-phase voltage is unbalanced

2021 ◽  
Author(s):  
Tiezhou Wu ◽  
An Wang ◽  
Yawen Xu
Keyword(s):  
Phase Angle ◽  
Detection Method ◽  
Positive Sequence ◽  
Harmonic Detection ◽  
Phase Voltage ◽  
Pass Filter ◽  
Low Pass Filter ◽  
Negative Sequence ◽  
Three Phase ◽  
Low Pass

Abstract By using power electronic devices, photovoltaic grid-connected power generation may inject harmonics into the power system. As the photovoltaic grid-connected inverter has the same basic structure as the active power filter, so the unified control of the photovoltaic grid and active filtering can be achieved. When the current unified control system compensates harmonics of the grid side, it mainly uses ip-iq harmonic detection method, which is based on instantaneous reactive power theory. When the three-phase voltage is unbalanced, the method has a large voltage phase angle detection error and the signal of the low-pass filter tracking system is long, detection time delay and even failure occur. This paper proposes an improved fast harmonic detection method. When phase deviation or amplitude change occurs to the three-phase voltage, the positive and negative-sequence voltages are simultaneously park transformed. The negative-sequence component is filtered by the current average module to obtain the fundamental amount of the voltage, then the phase angle of the positive-sequence voltage is accurately calculated to improve the harmonic current detection accuracy. Through the study of the integral method, it is found that the least common multiple of each harmonic period can be used as the integral interval, and the integral value is also zero, so the detection delay time is reduced by replacing the low-pass filter with an integration module. The simulation results show that the proposed harmonic detection algorithm can accurately detect harmonics when the three-phase voltage is unbalanced, and about 0.057 s improve the harmonic detection speed compared with the commonly used ip-iq method.

scholarly journals Features of autonomous and parallel operation of an asynchronous generator with a network of endless power in the current stage of EPS development

2021 ◽  
Vol 289 ◽  
pp. 07019
Author(s):  
Yunus Bobojonov ◽  
Tolqin Alibekova ◽  
Asror N Sultonov ◽  
Polat Quwatbaev ◽  
Atabek Ismandiyarov
Keyword(s):  
Reactive Power ◽  
Active Power ◽  
Electric Power System ◽  
Power Network ◽  
Parallel Operation ◽  
Asynchronous Machines ◽  
Reliable Source ◽  
Asynchronous Generator ◽  
Infinite Power ◽  
Current Stage

The article describes the use of asynchronous machines in generator mode to provide power to threephase consumers, as well as the features of autonomous and parallel operation of an asynchronous generator with an infinite power network. The use of static sources of reactive power allows widespread introduction of an asynchronous generator in the electric power system as a reliable source of active power.

Modified Power Compensation Control Strategy of Three-Phase Grid-Connected Inverter under Unbalanced Grid Voltage Conditions

2015 ◽  
Vol 740 ◽  
pp. 335-338 ◽  
Author(s):  
Shao Hua Sun ◽  
Hong Qi Ben
Keyword(s):  
Control Strategy ◽  
Reactive Power ◽  
Positive Sequence ◽  
Grid Voltage ◽  
Compensation Control ◽  
Active And Reactive Power ◽  
Three Phase ◽  
Grid Connected Inverter ◽  
Three Phase Inverter ◽  
Unbalanced Grid

Control strategy under unbalanced grid voltage conditions is one of the most important issues for grid-connected inverter. Under unbalanced grid voltage conditions, the 2nd active and reactive power ripples generate, they pollute the grid. To meet the demands of IEEE Std.929-2000, this paper proposed a modified power compensation control strategy; the proposed solution is based on direct power control. To provide accurate compensating power, the power model of three-phase inverter under unbalanced grid voltage conditions is given, using the positive sequence current component and the negative sequence voltage component, the compensating powers are calculated in details. Theoretical analysis and comparative simulation verification are presented to demonstrate the effectiveness of the proposed control strategy.

scholarly journals Induction Motor Stator Interturn Short Circuit Fault Detection in Accordance with Line Current Sequence Components Using Artificial Neural Network

2019 ◽  
Vol 2019 ◽  
pp. 1-11
Author(s):  
Gayatridevi Rajamany ◽  
Sekar Srinivasan ◽  
Krishnan Rajamany ◽  
Ramesh K. Natarajan
Keyword(s):  
Neural Network ◽  
Fault Detection ◽  
Induction Motor ◽  
Short Circuit ◽  
Positive Sequence ◽  
Negative Sequence ◽  
Three Phase ◽  
Sequence Components ◽  
Negative Sequence Current ◽  
Short Circuit Fault

The intention of fault detection is to detect the fault at the beginning stage and shut off the machine immediately to avoid motor failure due to the large fault current. In this work, an online fault diagnosis of stator interturn fault of a three-phase induction motor based on the concept of symmetrical components is presented. A mathematical model of an induction motor with turn fault is developed to interpret machine performance under fault. A Simulink model of a three-phase induction motor with stator interturn fault is created for extraction of sequence components of current and voltage. The negative sequence current can provide a decisive and rapid monitoring technique to detect stator interturn short circuit fault of the induction motor. The per unit change in negative sequence current with positive sequence current is the main fault indicator which is imported to neural network architecture. The output of the feedforward backpropagation neural network classifies the short circuit fault level of stator winding.

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