Microscale combined heat and power (CHP) unit based on solid oxide fuel cells (SOFC) for distributed generation was analyzed. Operation principle is provided, and the technology development in recent years is briefly discussed. System baseline for numerical analysis under steady-state operation is given. Grid-connected unit, fuelled by biogas corresponds to potential market demand in Europe, therefore has been selected for analysis. Fuel processing method for particular application is described. Results of modeling performed in ASPEN Plus engineering software with certain assumptions are presented and discussed. Due to high system electrical efficiency exceeding 40%, and overall efficiency over 80%, technology is an example of highly competitive and sustainable energy generation unit.

In this paper, a novel bacterial foraging algorithm (BFA) based approach for robust and optimal design of PID controller connected to power system stabilizer (PSS) is proposed for damping low frequency power oscillations of a single machine infinite bus bar (SMIB) power system. This paper attempts to optimize three parameters (Kp, Ki, Kd) of PID-PSS based on foraging behaviour of Escherichia coli bacteria in human intestine. The problem of robustly selecting the parameters of the power system stabilizer is converted to an optimization problem which is solved by a bacterial foraging algorithm with a carefully selected objective function. The eigenvalue analysis and the simulation results obtained for internal and external disturbances for a wide range of operating conditions show the effectiveness and robustness of the proposed BFAPSS. Further, the time domain simulation results when compared with those obtained using conventional PSS and Genetic Algorithm (GA) based PSS show the superiority of the proposed design.

Intensive modernization and reconstruction of the energy sector takes place throughout the

world. The EU climate and energy policy will have a huge impact on the development of the energy

sector in the coming years. The European Union has adopted ambitious goals of transforming

towards a low-carbon economy and the integration of the energy market. In June 2015, the G7 countries

announced that they will move away from coal fired energy generation. Germany, which

has adopted one of the most ambitious energy transformation programs among all industrialized

countries, is leading these transformations. The long-term strategy, which has been implemented

for many years, allowed for planning the fundamental transformation of the energy sector; after the

Fukushima Daiichi nuclear disaster, Germany opted for a total withdrawal from nuclear energy and

coal in favor of renewable energy. The German energy transformation is mainly based on wind and

solar energy. Germany is the fifth economic power in the world and the largest economy in Europe.

Therefore, the German energy policy affects the energy policy of the neighboring countries. The

article presents the main assumptions of the German energy policy (referred to as Energiewende).

It also presents the impact of changes in the German energy sector on the development of energy

systems in selected European countries.

This paper addresses the state-variable stabilising control of the power system using such series FACTS devices as TCPAR installed in the tie-line connecting control areas in an interconnected power system. This stabilising control is activated in the transient state and is supplementary with respect to the main steady-state control designed for power flow regulation. Stabilising control laws, proposed in this paper, have been derived for a linear multi-machine system model using direct Lyapunov method with the aim to maximise the rate of energy dissipation during power swings and therefore maximisation their damping. The proposed control strategy is executed by a multi-loop controller with frequency deviations in all control areas used as the input signals. Validity of the proposed state-variable control has been confirmed by modal analysis and by computer simulation for a multi-machine test system.

The paper presents analysis of optimisation results of power system stabilizer (PSS) parameters when taking into account the uncertainty of mathematical model parameters of the power system (PS) elements. The Pareto optimisation was used for optimisation of the system stabilizer parameters. Parameters of five stabilizers of PSS3B type were determined in optimisation process with use of a genetic algorithm with tournament selection. The results obtained were assessed from the point of view of selecting the criterion function. The analysis of influence of the parameter uncertainty on the quality of the results obtained was performed.

This paper deals with a three-phase power system with hybrid transformer (HT) installed between two AC sources. The main aim of this paper is analyze the basic properties of HT with active load and ability to bidirectional energy flow. The HT contains two main units – a conventional transformer with electromagnetic coupling and PWM AC line chopper connected with secondary windings with electric coupling. The HT is located between the distribution system and a Local Balancing Area (LBA) with low power local energy sources. After describing the HT circuit and three-phase, twosources power system, the mathematical and circuit models of the AC source with HT are presented. These models are verified by means of the simulation and experimental test results obtained for a three-phase HT of about 3 kVA rated power.

During a blackout, after the post-disaster collapse of an electric power system (EPS), units of thermal power plants should switch-over to the house load operation mode (PPW). However, regarding the dynamics of a post-disaster blackout process, many units can be in forced outage Therefore, restart of these units from the start-up sources with a self-start capability is necessary. The Transmission Network Code in force imposes periodic tests and system tests for such sources. Any system test must be preceded and followed by simulation investigations in which the possibilities: (1) to bring voltage to the started-up power plant by a starting path and (2) to activate the highest-power auxiliaries (PW) of the unit being started-up are evaluated. In the paper, chosen results of simulative investigations of the transient phenomena in the starting path from the hydroelectric power plant of Włocławek (HPP Włocławek) to the thermal power plant of P˛atnów (TPP P˛atnów), related to the system test conducted in September 2017 have been presented.

The paper presents a new method for simultaneous tracking of varying grid impedance and its uncertainty bounds. Impedance tracking consists of two stages. In the first stage, the actual noise estimate is obtained from least squares (LS) residua. In the second stage, the noise covariance matrix is approximated with the use of residual information. Then weighted least squares (WLS) method is applied in order to estimate impedance and background voltage. Finally uncertainty bounds for impedance estimation are computed. The robustness of the method has been verified using simulated signals. The proposed method has been compared to sliding LS. The results have shown, that the method performs much better than the LS for all considered cases, even in the presence of significant background voltage variations.

Finding the most critical contingencies in a power system is a difficult task as multiple evaluations of load and generation scenarios are needed. This paper presents a mathematical formulation for selecting, ranking, and grouping the most critical N-1 network contingencies, based on the calculation of a Power Constraint Index (PCI) obtained from the Outage Transfer Distribution Factors (OTDF). The results show that the PCI is only affected by the impedance parameter of the transmission network, the topology, and the location of all generators. Other methods, such as the Performance Index (PI) and the Overload Index (OL) are affected by the power generation and demand variations. The proposed mathematical formulation can be useful to accelerate the calculation of other methods that evaluate contingencies in power system planning and operation. Furthermore, the fast calculation of indices makes it suitable for online evaluation and classification of multiple events considering the current topology. The results showed that the proposed al- gorithm easily selected and ranked the expected contingencies, with the highest values of the index corresponding to the most critical events. In the filtering process, the computa- tional calculation time improved without losing the robustness of the results.

In this paper, the results of correlations between air temperature and electricity demand by linear regression and Wavelet Coherence (WTC) approach for three different European countries are presented. The results show a very close relationship between air temperature and electricity demand for the selected power systems, however, the WTC approach presents interesting dynamics of correlations between air temperature and electricity demand at different time-frequency space and provide useful information for a more complete understanding of the related consumption.

This paper presents a study on ferroresonance occurring in a high voltage 400 kV transmission grid due to energization of power transformer under no-load conditions. The system scenarios analyzed in the present paper are considered as critical for development and modernization plans as currently announced by the national grid operator in Poland. The PSCADsimulation modelwas developed and applied for several study cases of a system with double-circuit arrangement of a transmission line. It is shown that the ferroresonant oscillations can be initiated by two-phase switching operation of a line circuit breaker. The impact of the double-circuit length on the ferroresonance mode and severity is demonstrated with the use of the Poincaré map analysis and Short Time Fourier Transform. It is demon- strated that the length of the transmission line that is mutually coupled in the double-circuit arrangement has a significant impact on the ferroresonance occurrence and on its mode. As the ferroresonance can pose severe threat to the power system components due to the severe overvoltage and overcurrent oscillations, the analysis presented in this paper demonstrates the necessity of the ferroresonance analyses for any re-designed transmission system.

This paper considers electric shock hazard due to induced sheath voltages in 110 kV power cables. The purpose of this paper is to find an optimal configuration of the power cable system, taking into account electric shock hazard and ability of the system to transfer maximal power. A computer simulations on a computer model of the local power system, comprising high voltage power cables, were carried out. This model enables to analyse various configurations of the metallic cable sheaths bonding and earthing (singlepoint bonding, both-ends bonding, cross-bonding) and their impact on induced voltages in the cable sheaths. The analysis presented in the paper shows, that it is possible to find an optimal configuration of the complicated power cable system, in terms of electric shock hazard, maximal power transfer as well as economic aspects.

An approach to power system state estimation using a particle filter has been proposed in the paper. Two problems have been taken into account during research, namely bad measurements data and a network structure modification with rapid changes of the state variables. For each case the modification of the algorithm has been proposed. It has also been observed that anti-zero bias modification has a very positive influence on the obtained results (few orders of magnitude, in comparison to the standard particle filter), and additional calculations are quite symbolic. In the second problem, used modification also improved estimation quality of the state variables. The obtained results have been compared to the extended Kalman filter method.

Power systems that are highly loaded, especially by a stochastic supply of renewables and the presence of storages, require dynamic measurements for their optimal control. Phasor measurement units (PMUs) can be used to capture electrical parameters of a power system. Standards on the PMU dynamic performance have been modified to incorporate their new dynamic mode of operation. This paper examines the PMU dynamic performance and proposes essential algorithms for measurement accuracy verification. Measurements of dynamic input signals, which vary in amplitude or frequency, were taken during automated tests of two PMUs. The test results are presented and expounded with further recommendation for the performance requirements. This paper also presents and examines applied testing procedures with relevance to the specifications of the IEEE Standard for Synchrophasor C37.118.1™-2011 and its amendment C37.118.1a™-2014.

In this paper voltage stability is analysed based not only on the voltage deviations from the nominal values but also on the number of limit violating buses and severity of voltage limit violations. The expression of the actual state of the system as a numerical index like severity, aids the system operator in taking better security related decisions at control centres both during a period of contingency and also at a highly stressed operating condition. In contrary to conventional N – 1 contingency analysis, Northern Electric Reliability Council (NERC) recommends N – 2 line contingency analysis. The decision of the system operator to overcome the present contingency state of the system must blend harmoniously with the stability of the system. Hence the work presents a novel N – 2 contingency analysis based on the continuous severity function of the system. The study is performed on 4005 possible combinations of N – 2 contingency states for the practical Indian Utility 62 bus system. Static VAr Compensator is used to improve voltage profile during line contingencies. A multi- objective optimization with the objective of minimizing the voltage deviation and also the number of limit violating bus with optimal location and optimal sizing of SVC is achieved by Particle Swarm Optimization algorithm.

This paper describes a three phase shunt active power filter with selective harmonics elimination. The control algorithm is based on a digital filter bank. The moving Discrete Fourier Transformation is used as an analysis filter bank. The correctness of the algorithm has been verified by simulation and experimental research. The paper includes exemplary results of current waveforms and their spectra from a three phase active power filter.

The paper contains selected results of research on the Domestic Power System (DPS) as an unmanned factory. Models of the DPS system of the MISO type, obtained as a result of identification for 14 inputs and 4 outputs were presented. Particular attention was given to the identification and the assessment of the DPS development based on the systems and control theory. The obtained models of the DPS development were analyzed and discussed. The studies were obtained model of the development of the DPS, and on the basis of is knowledge of the structural and parametrical changes of system development. The model can be used to analyze the design and development of the system from the point of view of the growth of internal organization system and the transition to higher levels of control.

Fast and accurate grid signal frequency estimation is a very important issue in the control of renewable energy systems. Important factors that influence the estimation accuracy include the A/D converter parameters in the inverter control system. This paper presents the influence of the number of A/D converter bits b, the phase shift of the grid signal relative to the time window, the width of the time window relative to the grid signal period (expressed as a cycle in range (CiR) parameter) and the number of N samples obtained in this window with the A/D converter on the developed estimation method results. An increase in the number b by 8 decreases the estimation error by approximately 256 times. The largest estimation error occurs when the signal module maximum is in the time window center (for small values of CiR) or when the signal value is zero in the time window center (for large values of CiR). In practical applications, the dominant component of the frequency estimation error is the error caused by the quantization noise, and its range is from approximately 8×10-10 to 6×10-4.

This paper presents the optimal sizing of PV/Wind/Fuel Cell/Battery Hybrid Energy System for energizing a Small Scale Industrial Application or a village domestic load of 200 kW. HOMER software is used for simulation of the complete system. The solar radiation data and wind speed data used in this paper are for the place of Coimbatore, Tamil Nadu, India which is located 11.0183° N longitude and 76.9725° E latitude. The optimized sizes of components of Hybrid Power System (HPS) are found based on Levelised Cost of Energy (LCE) and total Net Present Cost (NPC). The results are presented and compared for five different combinations of HPS components. Suggestions are also presented to choose the low cost system which produces energy at low LCE.

Many parts of remote locations in the world are not electrified even in this Advanced Technology Era. To provide electricity in such remote places renewable hybrid energy systems are very much suitable. In this paper PV/Wind/Battery Hybrid Power System (HPS) is considered to provide an economical and sustainable power to a remote load. HPS can supply the maximum power to the load at a particular operating point which is generally called as Maximum Power Point (MPP). Fuzzy Logic based MPPT (FLMPPT) control method has been implemented for both Solar and Wind Power Systems. FLMPPT control technique is implemented to generate the optimal reference voltage for the first stage of DC-DC Boost converter in both the PV and Wind energy system. The HPS is tested with variable solar irradiation, temperature, and wind speed. The FLMPPT method is compared with P&O MPPT method. The proposed method provides a good maximum power operation of the hybrid system at all operating conditions. In order to combine both sources, the DC bus voltage is made constant by employing PI Controllers for the second stage of DC-DC Buck-Boost converter in both Solar and Wind Power Systems. Battery Bank is used to store excess power from Renewable Energy Sources (RES) and to provide continuous power to load when the RES power is less than load power. A SPWM inverter is designed to convert DC power into AC to supply three phase load. An LC filter is also used at the output of inverter to get sinusoidal current from the PWM inverter. The entire system was modeled and simulated in Matlab/Simulink Environment. The results presented show the validation of the HPS design.

The aim of the paper was to analyse relations between power in professional work and in close sexual relationships. Power in professional work was analysed with respect to the managerial position, the number of subordinates and salary. Power in close sexual relationships was determined on the basis of a sense of reinforcement of power as a sexual motivation, a propensity for sexual domination, the sense of power in relations with a partner in a close relationship, sexual assertiveness, realization of one’s own sexual phantasies and inclination to initiate sexual activity. The research was carried out on a group of 205 participants in which 100 of respondents occupied managerial positions at work and 105 were subordinates. The following tools were used: the Sense of Power Scale (Anderson, John, & Keltner, 2012), the Multidimensional Sexuality Questionnaire (Snell, Fisher, & Walters, 1993), the AMORE scale (Hill & Preston, 1996), the Need for Power and Influence Questionnaire (Bennett, 1988) and a data sheet. The results showed that power in the workplace was correlated a more frequent initiation of sexual activity, greater assertiveness in sexual matters, more frequent realisation of one’s own phantasies and an increased propensity for sexual domination.

The paper is the second part of the work, devoted to a DC power supply with a power factor correction function. The power supply is equipped additionally with a shunt active power filter function, which enables the compensation of reactive and distortion power, generated by loads, connected to the same power grid node. A tunable inductive filter, included at the input of the power electronics current source – the main block of the power supply – allows for an improvement of the quality of the system control, compared to the device with a fixed inductive filter. This improvement was possible by extending the current source “frequency response”, which facilitated increasing the dynamics of current changes at the power supply input. The second part of the work briefly reminds the reader of the principle of operation and the structures of both the power supply control system and its power stage. The main purpose of this paper is to present the selected test results of the laboratory model of the electric system with the power supply.

The work presents a DC power supply with power factor correction (PFC). This device is also equipped with a parallel active filter function, which enables the possibility of compensation (minimization) of reactive and distortion power, generated by a group of loads, connected to the same power grid node. A passive filter with variable inductance applied at the input of the power supply allows for a significant improvement in quality of the system control (given specific criteria), as compared to the solution with a filter with fixed parameters. This is possible by increasing the dynamics of current changes at the power supply input (extending its “frequency response”). The paper presents the principle of operation as well as structures and models of the power supply control system and its power stage. Selected test results of the simulation model of the electric system with the power supply, in various operating conditions, are also presented.