A multifunctional dynamic voltage restorer for power quality improvement

Power quality is a major concern in electrical power systems. The power quality disturbances such as sags, swells, harmonic distortion and other interruptions have an impact on the electrical devices and machines and in severe cases can cause serious damages. Therefore it is necessary to recognize and compensate all types of disturbances at an earliest time to ensure normal and efficient operation of the power system. To solve these problems, many types of power devices are used. At the present time, one of those devices, Dynamic Voltage Restorer (DVR) is the most efficient and effective device used in power distribution systems. In this paper, design and modeling of a new structure and a new control method of multifunctional DVRs for voltage quality correction are presented. The new control method was built in the stationary frame by combining Proportional Resonant controllers and Sequence-Decouple Resonant controllers. The performance of the device and this method under different conditions such as voltage swell, voltage sag due to symmetrical and unsymmetrical short circuit, starting of motors, and voltage distortion are described. Simulation result show the superior capability of the proposed DVR to improve power quality under different operating conditions and the effectiveness of the proposed method. The proposed new DVR controller is able to detect the voltage disturbances and control the converter to inject appropriate voltages independently for each phase and compensate to load voltage through three single-phase transformers.Web of Science116art. no. 135

Backup alternatives for 110 kV lines

The paper describes backup alternatives for 110 kV lines. Line backup is one of input parameters used to optimise the renovation of 110 kV lines. The optimisation is based on the principle of reliability centred maintenance (RCM) which depends on the technical condition and importance of a particular element. The paper starts with illustrating the method of reliability schemes. This method enables the evaluation of failure-free operation probability. The probability of a failure-free operation can be estimated for all backup types of 110 kV lines existing in the distribution network. To compare different backup alternatives, type lines were selected and calculated with. The results of the method helped estimate the effects of a line failure for a particular distribution district

Advanced Control of the dynamic voltage restorer for mitigating voltage sags in power systems

The paper presents a vector control with two cascaded loops to improve the properties of Dynamic Voltage Restorer (DVR) to minimize Voltage Sags on the grid. Thereby, a vector controlled structure was built on the rotating dq-coordinate system with the combination of voltage control and the current control. The proposed DVR control method is modelled using MATLAB-Simulink. It is tested using balanced/ unbalanced voltage sags as well as fluctuant and distorted voltages. As a result, by using this controlling method, the dynamic characteristics of the system have been improved significantly. The system performed with higher accuracy, faster response and lower distortion in the voltage sags compensation. The paper presents real time experimental results to verify the performance of the proposed method in real environments

Use of the EMTP-ATP software to develop a dynamic model of the technological centre

This paper deals with analysis of power generating units installed within the technological centre. To be able to analyse behaviour of such a complex system with accumulation, the dynamic model of the technology was created using the EMTP-ATP software. The current configuration of the dynamic model is based on the block diagram containing all the unconventional sources of electric power. The values produced by ATPDraw are shown in graphs for reference. The dynamic model will serve the purpose of research and observation of the entire technological centre with respect to transients at individual sources of power

Modelling and optimization in microgrids

The expansion of renewable energies is progressing strongly. The influence on the power supply networks by the variability of the infeed must be met with new concepts. In this paper, we investigate the possibilities of integrating microgrids as a cooperating unit in the power supply network to support further expansion of renewable energy sources (RES) power plants. In this paper, a differentiation of microgrids from similar network structures is established, and a classification of proposed groups is made. Then, after the description of the simulation of the components in a microgrid, with practical advice, an example model is shown, which aids the dimensioning of the components within a microgrid to achieve a specified goal.Web of Science104article number: 52

Distributed generation power systems in wastewater management

The article concerns the energy security of a wastewater treatment process caused by unforeseen situations related to the risk of electrical power outages. In this case, renewable energy sources based on distributed generation power systems can solve this problem in each wastewater treatment plant. The article highlights e related challenges and proposes the direction of solutions in this regard based on Czech conditions. The first part of the paper deals with the consequences of long-term outage of wastewater treatment plants on the population and the environment. There are several solutions presented for blackout conditions, and model calculations are made based on data from a Czech wastewater treatment plant. Diesel engine-generators, biogas as a cogeneration source of heat and electricity, solar panels with storage systems and combined biogas and solar systems were considered as approaches to provide energy autonomy during a blackout in a wastewater treatment plant. Special attention was paid to a combination of CHP units with solar panels and batteries. The results were evaluated for three different locations for this combination. It was concluded that biogas combustion in the CHP unit was the most profitable option, allowing the production of electricity independently of the grid for its own consumption and possibly for other operations. The last part of the paper deals with the transition to island operation, which must occur during a blackout. This transition is more difficult for both solar panels and cogeneration units if they were to supply electricity to the grid before a blackout. The transition to energy island operation could be ensured by frequency relay and processor devices to control the circuit breaker. Then, to maintain island operation, it would be necessary to have an automatic load shedding/application system.Web of Science1517art. no. 628

Corporate social responsibility of water and sanitation company in the Czech Republic - Case study

The issue discussed in this article concerns corporate social responsibility (CSR), which is playing an increasingly important role in the context of sustainable development of enterprises. The purpose of the current work was to assess the practices applied in the area of corporate social responsibility in water and sanitation companies, based on the opinions of employees and managers. The motivation for undertaking research on this topic resulted from the scarcity of scientific studies on the measurement of the corporate social responsibility concept in water and sanitization companies using a multidimensional approach based on the ISO 26000 standard. The study used methodological triangulation based on the use of qualitative and quantitative research methods to verify information from different sources. This approach allowed the authors to obtain the data more effectively and analyze the problem from numerous different perspectives. The study used an interview method that targeted water and sanitization utility staff. In-depth research was based on the case study method, which is particularly important when researching complex phenomena. For this purpose, surveys were carried out, the results of which indicate that corporate social responsibility of the surveyed enterprise is at a high level, and that there are statistically significant differences between individual dimensions of CSR. The results indicate that the surveyed company is oriented towards supporting activities in the area of corporate social responsibility, in accordance with the in the concept of sustainable development.Web of Science1413art. no. 398

Renewable energy sources as backup for a water treatment plant

The article is focused on the issue of blackouts in a water industry and the selection of a renewable energy source for a water treatment plant. In the case of power outage, it is necessary to constantly ensure the supply of a drinking water, if this requirement would not be met, it could cause of deterioration of hygiene and health of the population. To be able to convey drinking water during a blackout, it is mandatory to have a backup power supply. The state of the current water treatment plants in the Czech Republic is that they are using diesel generators as backup power supply, which causes air pollution. There are other options of power supply that can be used, such as renewable energy sources. By using a multi-criteria analysis method, renewable energy sources were analyzed for a water treatment plant in the selected region. Based on the results, it seems that the most suitable choice is a small hydro power plant at the entry points of water treatment plant. Other possibilities of renewable energy sources that may be suitable for a water treatment plant and the usage of a multi-criteria analysis method for a water treatment plant in other countries are also discussed.Web of Science1517art. no. 628

IOT-enabled model for weed seedling classification: An application for smart agriculture

Smart agriculture is a concept that refers to a revolution in the agriculture industry that promotes the monitoring of activities necessary to transform agricultural methods to ensure food security in an ever-changing environment. These days, the role of technology is increasing rapidly in every sector. Smart agriculture is one of these sectors, where technology is playing a significant role. The key aim of smart farming is to use the technologies to increase the quality and quantity of agricultural products. IOT and digital image processing are two commonly utilized technologies, which have a wide range of applications in agriculture. IOT is an abbreviation for the Internet of things, i.e., devices to execute different functions. Image processing offers various types of imaging sensors and processing that could lead to numerous kinds of IOT-ready applications. In this work, an integrated application of IOT and digital image processing for weed plant detection is explored using the Weed-ConvNet model to provide a detailed architecture of these technologies in the agriculture domain. Additionally, the regularized Weed-ConvNet is designed for classification with grayscale and color segmented weed images. The accuracy of the Weed-ConvNet model with color segmented weed images is 0.978, which is better than 0.942 of the Weed-ConvNet model with grayscale segmented weed images.Web of Science5127225

Analysis of the power supply restoration time after failures in power transmission lines

This paper presents the analysis of power supply restoration time after failures occurring in power lines. It found that the power supply restoration time depends on several constituents, such as the time for obtaining information on failures, the time for information recognition, the time to repair failures, and the time for connection harmonization. All these constituents have been considered more specifically. The main constituents' results values of the power supply restoration time were analyzed for the electrical networks of regional power supply company "Oreolenergo", a branch of Interregional Distribution Grid Company (IDGC) of Center. The Delphi method was used for determining the time for obtaining information on failures as well as the time for information recognition. The method of mathematical statistics was used to determine the repair time. The determined power supply restoration time (5.28 h) is similar to statistical values of the examined power supply company (the deviation was equal to 9.9%). The technical means of electrical network automation capable of the reduction of the power supply restoration time have also been found. These means were classified according to the time intervals they shorten.Web of Science1311art. no. 273