Petr Krejci

This paper focuses on the pivotal role of Harmonic Filters (HFs) in mitigating harmonic distortion within electrical systems to enhance power quality and efficiency. Harmonic distortion, characterized by deviations from the ideal sinusoidal waveform of electrical power, can cause equipment malfunctions, overheating, and a reduced lifespan of infrastructure. HFs, known for their cost-effectiveness and simplicity, employ inductors, capacitors, and resistors to selectively reduce specific harmonic frequencies, thereby improving system reliability and performance. The document explores traditional design methodologies of harmonic filter design, emphasizing criteria and considerations critical for effective harmonic mitigation. It highlights the use of advanced simulation tools, such as MATLAB/Simulink and PF DigSilent, which enable precise analysis and optimization of filter designs to meet specific system requirements. Moreover, it discusses the significance of designing filters with adequate margins to ensure system safety and reliability, considering the variability of loads and the presence of other harmonic sources. Driven by the necessity to enhance harmonic filter design in the face of increasingly complex electrical infrastructures, this paper advocates for leveraging recent advances in simulation tools.

Load Flow Analysis in Power System Network Incorporating STATCOM: A Comparison of the Direct and Indirect Algorithm of the Newton-Raphson Method

Currently regulators are increasingly being applied to optimize power flow in connection with the installation of photovoltaic power plants in low voltage networks. These devices use the insensitivity of standard meters to rapid changes of the energy flow direction and thus affect the measured values of consumed energy and the energy supplied to the network. At the laboratory comparative measurements were made on simulated current flows so that these properties of the devices were shown in relation to the parameters of the test waveforms. Some electricity meters and some network analyzers were tested. If power regulation cycle runs during 1s aggregation interval then measured values may differ from reality. Test results have confirmed that electricity meters are not able to correctly measure the measured electrical power in the circuit with power controller. In contrast, network analyzers mostly evaluate both positive and negative energy correctly.

This study describes the impact of operation of big customers on voltage quality (VQ) parameters in medium-voltage (MV) distribution grids. The survey is based on the evaluation of 45 VQ measurements which were carried out in 15 different delivery points of other customers. These 45 measurements were made in years 2014, 2015 and 2016 (15 measurements a year) and were evaluated according to the standard EN 50160. The impact on voltage variations and other VQ parameters was analysed.

Electric power is the electrical appliances basic means for their functionality. In case that the electrical energy customer causes problems arise thereby complaints the power quality. In areas with frequent complaints of power quality measurements were made in order to resolve the reported complaints and also in order to investigate the cause of exceeding the compatibility level of power quality.

In 1997 cooperation began between the Faculty of Electrical Engineering and Computer Science and the power company CEZ on a joint project that involved monitoring selected voltage quality parameters. Over the course of several years measurements were carried out at 59 points of the distribution system at a low voltage (LV) level and their power supply nodes at medium voltage (MV) and high voltage (HV) levels, which constituted more than 100 measured points. The measurements continued until 2012 (with a one-year break in 2009) and with a total scope of five cycles of three-year measurements. The last phase of the measurements was focused, inter alia, on the evaluation of 15th and 21st voltage harmonics. From 2013, the cooperation focused again on monitoring flicker in localities with the occurrence of elevated levels of this voltage quality parameter. At these sites, the monitoring of flicker was carried out for two weeks in spring and autumn for a period of three years. The basis for evaluating the quality parameters is the standard EN 50160.

In 1997 cooperation began between the Faculty of Electrical Engineering and Computer Science and the power company CEZ on a joint project that involved monitoring selected voltage quality parameters. Over the course of several years measurements were carried out at 59 points of the distribution system at a low voltage (LV) level and their power supply nodes at medium voltage (MV) and high voltage (HV) levels, which constituted more than 100 measured points. The measurements continued until 2012 (with a one-year break in 2009) and with a total scope of five cycles of three-year measurements. The last phase of the measurements was focused, inter alia, on the evaluation of 15th and 21st voltage harmonics. From 2013, the cooperation focused again on monitoring flicker in localities with the occurrence of elevated levels of this voltage quality parameter. At these sites, the monitoring of flicker was carried out for two weeks in spring and autumn for a period of three years. The basis for evaluating the quality parameters is the standard EN 50160.

In recent years, the utilizing of intelligent technology in a classical distribution and transmitting system becomes more and more important in all energy-related topics. The development bring us to the new era of power electrical engineering, to the era of Smart-Grids. These intelligent grids allow us to operate the grid with a specific set of requirements, such as bi-directional power flows, maximal utilization of renewable energy sources using energy storage devices, grid desynchronization and re-synchronization up to individual energy object level - Autonomous systems or more precisely Off-Grid systems. In this case, Off-Grid system can be understood as a basic cell of the entire Smart-Girds. However, it should be noted that in the Off-Grid system operation can occur some disadvantages as well. Based on the author's experience, the disadvantages lies in e.g. rapid changes in power consumption or generation, changes in the short circuit power influenced the protection system as well as the power quality parameters. This paper presents a long-term evaluation of power quality parameters of the real-operated Off-Grid system in VSB - TU Ostrava campus, Czech Republic.