Wojciech Jarzyna

The comparison of Polish grid codes to certain European standards and resultant differences for WPP requirements

Grid Codes of Transmissions System Operators (TSO) put large demands on the currently installed Wind Power Plants (WPPs). Nowadays WPP are treated similarly as conventional power stations. They should work even if operating conditions deviate from nominal values, e.g. when during a fault the voltage at the connection bus drops nearly to zero. The paper describes grid codes distinguishing requirements of active and reactive power generation and Fault Ride Through characteristics. Among the described standards Polish, German and Danish and in some cases British and Norwegian requirements are mentioned. The differences between the standards are reviewed and are referenced to Polish grid regulations. Discussion supplements certain results of the laboratory research.

Synchronization of voltage frequency converters with the grid in the presence of notching

Purpose – In the dispersed generation system, power electronic converters allow for coupling between energy sources and the power grid. The requirements of Transmission System Operators are difficult to meet when the share of distributed energy sources of the total energy balance increases. These requirements allow to increase penetration of distributed generation sources without compromising power system stability and reliability. Therefore, in addition to control of active or reactive power, as well as voltage and frequency stabilization, the modern power electronic converters should support power grid in dynamic states or in the presence of nonlinear distortions. The paper aims to discuss these issues. Design/methodology/approach – The research methodology used in this paper is based on three steps: Mathematical modelling and simulation studies, Experiments on laboratory test stand, Analyzing obtained results, evaluating them and formulating the conclusions. Findings – The authors identified two algori...

The impact of converter's synchronization during FRT voltage recovery in two-phase short circuits

This article aims to examine the impact of synchronisation methods on transient phenomena occurring during a short-term voltage sag. The study was conducted for several synchronisation algorithms during interference from a short-term two-phase short-circuit. The research results show that in a state of transition of reduced and unbalanced voltage the best inverter results are obtained for fast-synchronisation algorithms which generate a synchronisation signal adequate to the voltage distortion. In contrast, the greatest threat turned out to be big oscillations of active power during work with advanced, time-consuming synchronisation algorithms. These oscillations adversely affect the mechanical components, particularly on the drive train system of a wind power plant if the plant uses the Fault Ride Through procedure.

COLD STORAGE-SUPPORTED AIR CONDITIONING SYSTEM IN URBAN TRANSPORT VEHICLES

A bottleneck for the development of public transport vehicles is their electricity supply. Electric buses are almost exclusively equipped with electrochemical batteries, while nearly 40% of the energy is used in the processes of air conditioning. For this reason, we developed and built a demonstration system for storing thermal energy in public transport vehicles. The most important effects are: significant reduction of financial expenses and of the total weight of all batteries with the same amount of stored energy.

Application of Model Reference Adaptive System in Natural Frequency Identification of an Active Beam Composite Structure

In many real-time systems we need to know the exact values of system parameters. Parameters identification for linear and stable systems can be done by taking special measurements. Problems can occur if the tested system is nonlinear and its parameters change due to certain variations or they depend on time. In such cases special procedures have to be applied. These procedures should operate quickly, and their computational time delay cannot affect on the entire control process. In this paper, determination of the frequency of cantilever beam with embedded piezoelectric actuator is studied. A short overview of Model Based Methods is described. A nonlinear equation of motion of the beam is rewritten as an equation with step wise changes of its natural frequency. Proposed mathematical identification methods use some input and output variables for identifying lack of information about certain parameters in a mathematical model. We take into account Decoupling Observers and Model Reference Adaptive System (MRAS). Due to the structure of the mathematical description, MRAS system found out to be more adequate option. Algorithms based on Model Identification Techniques (MIT), as well as an algorithm satisfying Lyapunov stability condition, were tested. The latter was robust on certain residual effects. Therefore, we chose it for the final test. Obtained results confirmed this choice. Presented figures show characteristics of natural frequency that have been identified. Therefore, the implemented adjusting algorithm satisfying Lyapunov stability found out to be suitable for an application in DSP. However, reducing the processing time is still a problem for future studies.

Evaluation of Suppression Methods Used for Reduction of Vibrations of the Active Composite Beam

The paper describes methods for suppressing vibrations of a cantilever beam. A piezoelectric Macro Fiber Composite (MFC) embedded on a surface of the beam is used as an actuator. The performance of P and PD controllers, resonance filters PPF and SRF, as well as Nonlinear Saturation Controllers (NSC) were evaluated. The results demonstrated that P and NSC controllers were the most effective of these algorithms. The relevant tests were carried out using a set-up controlled by a DSP board supported by a PC system.