Marek Gołębiowski

Inverters operation in rigid and autonomous grid

Purpose – The aim of this paper is to develop the method of optimal control of the three‐phase inverter system for autonomous and power grid operation. The presented method will also allow the cooperation of several inverters creating an autonomous network. This system should also be able to reduce demanded higher harmonics in power voltage according to the list of numbers of these harmonics. In this article the authors describe a system that is used to create a symmetrical three‐phase voltage. The supply power is taken from the renewal source. The inverter system as well as cooperation of several such systems to create an autonomous network is under consideration. The generated three‐phase voltage should be symmetrical even when the RL load is not symmetrical or else it changes in impulse. Cooperation of the system with the autonomous network is also under consideration. The task is to supply the set current of the basic harmonic to the power grid and possibly to reduce voltage higher harmonics on output...

Voltages in the Shaft of the Induction Motor in 3D FEM Formulation

A 3D model reflecting entire internal structure of the asynchronous machine using finite elements method, has been presented here. Nodal finite elements have been used to approximate scalar potential and edge finite elements to approximate vector magnetic potential. This model includes both the skew of the rotor bars as well cross current flowing through the rotor iron laminates. The three-phase stator winding is supplied with four-lead mains voltage. The axial flux was calculated by integration of the vector potential around the shaft of the machine. Making isolation between I a mine worse in the area of tooth stator, was leading to the voltage in the rotor shaft, this voltage was used for diagnostics. Plots were calculated following the switching on the machine at various speeds. Bar as well as ring fractures were simulated. The simulation results have been confirmed by the theoretical anticipations.

Effectiveness Analysis of Small Hybrid Power Plant with Energy Storage

The objective of this paper is to investigate and compare the expected yield of small renewable energy power plants. The method of determining configuration of photovoltaic system, able to work autonomously under the given load conditions, has been presented. The impact of support such systems by a wind turbine has been investigated in case of minimal demanded battery capacity and the total energy yield. The simulation study has been performed using data describing the typical climatic conditions in 61 locations on Polish territory. The results showed that minimal demand battery capacity depends mostly on daily character of system load and cannot be noticeable decrease owing to wind turbine support.

Calculation of eddy current and hysteresis losses during transient states in laminated magnetic circuits

Purpose The purpose of this paper is to develop the method of taking the eddy current losses in the laminated magnetic circuits into account during implicit transient calculations. The nonlinear magnetization characteristic of iron and the hysteresis losses can also be considered in the simulations done with the developed method. Design/methodology/approach The paper presents complex equivalent magnetic permeability derived from the presumed angular frequency in a laminated magnetic circuit. On this basis, the synthesis of a magnetic permeability as a function of the Laplace variable “s” is presented. After transformation of the variable “s” to a variable “z” of the Z transformation, it is possible to conduct discrete time calculation of transient states of magnetic circuits including the eddy current losses. An iterative process is developed to take the saturation of the magnetic circuit in these calculations into account. As regards hysteresis losses, the scalar model of magnetic hysteresis by Juhani Tellinen was implemented. The new method is validated by calculations of a two-coil transformer. Findings It is important to take into account the losses in sheet metal directly in the implicit transient calculations. This possibility is provided by the presented method based on the synthesis of the equivalent magnetic permeability μ^(s). The presented method was proved to be correct and efficient. The calculated sheet metal losses were compared with the results presented in literature. Good conformance of results was attained. Practical implications The method enables calculation of eddy current and hysteresis losses in laminated magnetic circuits during calculations of transient states. It does not need, unlike the previous methods, previously provided information (“a priori”) about the content of higher harmonics in waveforms. The method takes into account mutual dependence of transient waveforms of currents in the analysed system and losses of laminated magnetic circuit, expressed by eddy currents and hysteresis losses. Its implementation comes down to using in calculations a filter of the IIR type and corresponds to its calculation complexity. The author plans to use the presented method in the finite elements method transient calculations. Originality/value A new approach is a synthesis of the equivalent magnetic permeability in Laplace domain, which creates an equivalent RC circuit for permeability. Analytic equations for parameters of this equivalent circuit are original. A method for considering nonlinear magnetization characteristic and hysteresis losses was presented. In calculations of transient states of systems with magnetic circuits, one can use the developed equivalent circuit of magnetic permeability in a form of the IIR filter. Operator magnetic permeability includes fractional derivative of Laplace’s variable “vs”. Therefore, the equivalent IIR filter includes “history” of the processes that take place in the laminated magnetic circuit to the current, calculated time moment. This “history” in terms of its content is limited only by the degree of the applied IIR filter. It enables to calculate “step by step”, without previous (“a priori”) knowledge about harmonic components of the whole waveforms. It was necessary in the previously used methods, when determining parameters of magnetic permeability. The method proposed in the paper allows for calculations with taking into account direct dependence of an electric part of the system on its magnetic part.

Autotransformer rectifier circuits with parallel connection without the use of IPT chokes - review

When using many rectifying devices, higher harmonic components of currents absorbed by them from the grid become significantly important. They can cause very harmful phenomena connected with grid voltage drop, glimmering of lights or significant power losses. The presented 18 pulse rectifier circuits enable to lower the content of higher harmonics of the grid currents. When considering leakage inductance of autotransformers and supplying grid these rectifier circuits may be classified to the ‘clean power’ circuit type. Due to instability of ITP type chokes and their vulnerability to magnetic circuits saturation it was decided to resign from their application. Different 18 pulse rectifier circuits were analyzed and diode currents waveforms were calculated and their characteristic parameters were presented. These results may simplify the process of designing such circuits.

Rectifier circuits with magnetically non-coupled chokes

When using many rectifying devices, higher harmonic components of currents absorbed by them from the grid become significantly important. They can cause very harmful phenomena connected with grid power outages, glimmering of lights or significant heat losses. The 18 pulse rectifier circuits presented in the article enable to lower the content of higher harmonics of the current absorbed from a grid. When considering appropriate values of leakage inductance of chokes and the supplying grid these rectifier circuits may be classified to the ‘clean power’ circuit type. Due to instability of ITP type chokes and their vulnerability to magnetic circuits saturation it was decided to resign from their application. Autotransformer or ZSBT chokes were replaced with magnetically non-coupled chokes. These presented results may simplify the process of designing such circuits.

Thermal Coupling Analysis of the Permanent Magnet Synchronous Generator

The construction and thermal analysis of the 2 KW generator designed for a small wind power station with vertical axis of rotation was presented in this article. The analysis is required in order to determine temperature distribution inside the machine to avoid magnets demagnetization and insulation damage. The presented thermal analysis of synchronous generator prototype was made using Computational Fluid Dynamics (CFD) Ansys Fluent analysis. In order to determine losses at the machine components Ansys Maxwell system was used. The analysis was made for three variants of the air flow speed around the generator frame. The lowest speed corresponds to the conditions of air flow during the study at the test stand, while higher speeds simulate the normal generator operation.