Decomposing Apparent Power and Losses in Distribution Systems with Nonlinear Loads

The definition of reactive power for non-sinusoidal conditions is a controversial issue.The mathematical treatment of nonlinear loads in power systems is also unsettled.This paper starts with the decomposing of apparent power in the cases of linear and nonlinear loads.When harmonics are present,apparent power is composed of active power,reactive power,and disturbed reactive power.Linear element can be defined as the element without disturbed reactive power.This definition is based on a practical engineering concept which can separate the contribution from the apparent power into utility-duty part and custom-duty part.The field investigation of home-used facilities was conducted.Also the data acquisition in the 0.4 kV distribution systems was completed.Moreover,the loss increase due to the nonlinear loads was estimated.Nonlinear loads can be a dominant effect with respect to reactive power and power factor.Field data from a number of nonlinear load types indicate that the disturbed reactive power can cause significant losses in utility supply systems.

Economic Improvement of Power Factor Correction: A Case Study

Power factor (PF) is simply an expression of energy efficiency, which is always expressed in terms of percentage. Technically, PF is a ratio of real power in Kilowatts to the apparent power, which is always expressed in kilovolts amperes. In AC power analysis, power is always expressed in three ways, the real power (P), reactive power (Q), and the apparent power (S). The real power is the work useful power, while the reactive power is the wasted power in the 3-phase AC system, and the apparent power is the vectorial sum of the two powers. The increase of reactive power will reduce the presence of real power, thus making the power to be more expensive. In this paper, we will analyze the importance of improving the power factor by applying a bank of capacitors to a case study in Lebanon. Analysis of the economic improvement in the application of power factor correction is carried out. The result shows a reduction of 12 percent in the total cost.

Different Options Regarding Power Components in Electric Circuits

This paper describes two methods of representation of voltages and currents in electric circuits： in the vector form and in the shape of oscillations, represented as diagrams in the plane. The appropriate power components are discussed depending on the representation of voltages and currents. Special attention is paid to the instantaneous power peculiarities for diverse loads and non-sinusoidal conditions. A case study of power calculations in an electric circuit with a pluggable capacitor is presented. For these types of transient modes, the instantaneous power is represented in the form of active and reactive components. Calculation of active, reactive, and exchange powers for steady-state processes is presented.

SMOGN,MFO,and XGBoost Based Excitation Current Prediction Model for Synchronous Machine

The power factor is the ratio between the active and apparent power,and it is available to determine the operational capability of the intended circuit or the parts.The excitation current of the synchronous motor is an essential parameter required for adjusting the power factor because it determines whether the motor is under the optimal operating status.Although the excitation current should predict with the experimental devices,such a method is unsuitable for online real-time prediction.The artificial intelligence algorithm can compensate for the defect of conventional measurement methods requiring the measuring devices and the model optimization is compared during the research process.In this article,the load current,power factor,and power factor errors available in the existing dataset are used as the input parameters for training the proposed artificial intelligence algorithms to select the optimal algorithm according to the training result,for this algorithm to have higher accuracy.The SMOGN(Synthetic Minority Over-Sampling Technique for Regression with Gaussian Noise)is selected for the research by which the data and the MFO(Moth-flame optimization algorithm)are created for the model to adjust and optimize the parameters automatically.In addition to enhancing the prediction accuracy for the excitation current,the automatic parameter adjusting method also allows the researchers not specializing in the professional algorithm to apply such application method more efficiently.The final result indicated that the prediction accuracy has reached“Mean Absolute Error(MAE)=0.0057,Root Mean Square Error(RMSE)=0.0093 andR2 score=0.9973”.Applying this method to themotor control would be much easier for the power factor adjustment in the future because it allows the motor to operate under the optimal power status to reduce energy consumption while enhancing working efficiency.

Research on the Characteristics of Anomalies in ELF Electromagnetic Observations in Yunnan Province

Located in an earthquake-prone region,the geological structures in Yunnan Province are complex. Taking into account that Tonghai county is located in the intersection of Xiaojiang fault and Honghe fault, an ACF-4M ELF electromagnetic instrument was installed at the Tonghai seismic station,which has produced continuous reliable data. The author collected the data and information for the year 2009 and 2010,and performed analysis on the variation characteristics of both geomagnetic fields and electrical resistivity. The result shows that the 1Hz and 39Hz electromagnetic power spectra are 0. 2 to 1. 4 orders of magnitude higher than the normal values immediately before many earthquakes. The anomalies are represented by the abrupt changes of the electric and magnetic field power spectra in earthquake and aftershock sequences,and the amplitude of change is related to the size of earthquake magnitude and epicentral distance. The electrical resistivity also obviously changes. Therefore, further research on the anomalous characteristics of ELF electromagnetic data will be meaningful to the future use of this instrument in earthquake prediction.