In Poland, there has been a steady increase in the share of wind-generated energy in the overall energy balance of the country. However, wind power plants belong to unstable energy sources—the amount of generated power is variable in time. Variable generation may cause problems with the quality of energy transmitted in electricity networks. Therefore, this article presents the results of field tests of the impact of the Vestas V90 2 MW wind turbine on selected voltage quality parameters occurring in the grid. Due to the multifaceted influence of the power plant on the parameters of the grid to which it is connected, the article focuses only on four selected parameters: voltage value, zero and reverse asymmetry, and the value of the voltage distortion factor. The research conducted by the authors confirmed the positive influence of the operation of the wind power plant on the quality parameters of the electricity transmitted through the power grid. An increase in the power generated in the tested Vestas V90 power plant resulted in a decrease in the values of both the asymmetry factor (zero and reverse) and the total voltage distortion factor THD_U.

The article presents the possibility of using the currents’ physical components (CPC) theory to generate the reference current of the active power filter (APF). The solution proposed by the authors is based on the cooperation of minimizing balancing compensators (MBC), which, due to their use in 4-wire systems, have been divided into two structures. The first compensator, which purpose is to minimize and balance the reactive current and the unbalanced current of the zero sequence, is built in the star system (STAR-MBC). The purpose of the second compensator, which operation occurs in the delta system (DELTA-MBC), is to minimize and balance the other two components, i.e., the unbalanced current of the negative sequence and the unbalanced current of the positive sequence. The two structures cooperating with each other significantly reduce the currents associated with the reactive elements, i.e., reactive current, and the unbalanced current. As mentioned, these currents are reduced but not compensated to zero or to the reference value. In order for the compensation and balancing to bring the preferable effect, an APF system should be included, which will cooperate with MBC compensators. This solution is presented in this publication. The control of the active part of the hybrid active power filter (HAPF), which was presented in the paper, consists of the reflection of the waveform of the nonsinusoidal active current. In this approach, no current shift in relation to voltage is obtained, but the waveforms of these quantities remain distorted. The reactive current is compensated and the unbalanced currents are balanced. The second definition of generating a reference current can also be used. Through this approach, the active current with a sinusoidal waveform is achieved. The second approach allows for an additional reduction of the three-phase RMS value of the load’s current. In both of these approaches, the active currents flowing through the lines will reflect the amplitude and phase asymmetry that is present in the supply voltage. The APF system will follow the changes in power or load conditions and generate the correct value for the reference current. The calculations presented in the article, as well as the current and voltage waveforms, were created as a result of the constructed mathematical models, which were used for theoretical illustrations. Calculations and waveforms were generated based on a script written in Matlab.

The phenomenon of voltage asymmetry is common in electricity networks and is the cause of many unfavourable phenomena occurring, such as an increase in power and energy losses, as well as the abnormal operation of certain loads. Voltage asymmetry can be caused by several different factors, which include the design of the transmission line (e.g., routing of conductors in relation to each other and the earth), the parameters of consumer circuits (e.g., unequal loading of individual phases), or the design of network equipment (e.g., generators or transformers). An asymmetrical condition also occurs during system disturbances such as single-phase short circuits or lightning. One of the many factors impinging on voltage asymmetry in the electrical network is also the effect of load, but in the case of medium voltage power networks, this effect is neglected in the literature. This paper presents and evaluates the influence of the power consumed by consumers on the values of zero-voltage asymmetry factor indices in medium voltage compensated power networks with the neutral point earthed by an inductance (Petersen coil) operating with wind and photovoltaic power plants.

Over the last few years, a dynamic increase in the installed capacity of distributed energy sources has been observed, with the largest share being photovoltaic sources. The power grid is a system of connected vessels, and changing the structure of electricity production has a specific impact on the operation of this network, which makes it necessary to study the impact of the sources on the power system. The current and projected increase in the number of connected installations will make the issues of interaction and cooperation of distributed sources with the network extremely important. The article presents an analysis of the impact of a photovoltaic farm on selected parameters of the quality of electricity supply. This analysis was made on the basis of simulation results in a computer program and measurement tests carried out on a real photovoltaic farm with a capacity of 1.8 MW connected to the medium voltage power grid. The impact of the farm-generated power on the values of fundamental indicators of the quality of electricity supply, such as voltage deviations, voltage asymmetry factors, and voltage distortions factors, is presented. These relationships were determined based on the correlation and regression analysis of individual electrical quantities.

The subject of this article is to exhibit the possibility of describing three-phase circuits powered from an asymmetric sinusoidal voltage source. Determining the physical components of the current associated closely with specific physical phenomena makes it possible to distinguish the components of unbalanced from the active and reactive components. Each of these currents, excluding the active current, contributes to the power of unbalanced and reactive power, which should be minimized or completely removed from the circuit.

The article presents the results of the analysis of parameters describing electricity consumption in individual phases of the production cycle on a poultry farm. One full broiler rearing cycle on the farm was analyzed. Electrical parameters were tested during the broiler rearing process using a power quality analyzer with a measurement interval of 1 min. During the tests, the analyzer recorded the active and reactive power, phase and line voltage, power factor, and frequency. On the basis of collected data, original indicators describing electricity consumption per chicken w_kA, w_kQ, and per unit area w_iA, w_iQ were determined. The regression curves of active and reactive power consumption in particular stages of the cycle were also determined, and the minimum and maximum values of active and reactive power consumption were determined. The accomplished research can be used in planning electricity demand in energy-self-sufficient areas. The presented original indicators can be used to determine power demand on broiler farms, depending on the planned production volume or size of farm buildings.