Marcin Jaraczewski

The paper presents the relation between the three types of noncausal digital filters: unitary, Hermitian and antihermitian filters. A decomposition has been made of a causal filter into a Hermitian and unitary filter cascade, and the use of this decomposition to calculate the electric power quality of receivers has been highlighted. Reference has also been made to the analogy between the set of unitary filters and the unit circle in the Gaussian plane.

This paper presents a new method for passive current compensation of a real multiharmonic power source with the use of a four-terminal network. In contrast to a two-terminal compensator, a four-terminal-network compensator can fully separate the supply circuit from the load. This ensures optimal operating conditions for the source while keeping the voltage and load current unchanged. The source’s optimal working conditions mean that the source current reaches its minimal RMS value (becoming the so-called “active current”) while it transmits the desired active power to the load.

The article is about a range of issues concerning the possible use of track circuits, consisting of rail lines and impedance bonds for continuously monitoring traffic parameters of a rail vehicle moving within a separated track section. The solution to this problem may be useful in many applications and various types of rail traffic control systems that use track circuits as a source of information about the track block occupancy. One possible application may be in automatic railway crossing signalling systems (ARCS) for approach sections. In that application, the carried out measurement of the position and speed of a rail vehicle allows to determine a pre-warning time for the railway crossing.

This article presents the implementation of the low-frequency measuring method of current and voltage RMS values as well as active and reactive power of a two-terminal network, which is supplied by a sinusoidal voltage of 50 Hz. The implementation was made on a typical compact PLC-FX3G Mitsubishi Electric controller. This controller has a relatively low computing power, and when control tasks and measurements are performed simultaneously, the measurement method must be simple in order to match the limited computing power of the controller. This article describes how to implement the low-frequency measuring method onto the controller. It also presents the laboratory set for testing the controller and application. The paper also presents the results of measurements and calculations, in particular the impact of measurement time delays on errors of the RMS voltage and current values as well as active and reactive power values.

In dynamic linear systems described by differential equations with constant parameters, the poles of the rational function (transfer function of the system) play an important role. This article attempts to expand the poles concept in a situation where the system is described by the N-th order linear system with time-varying parameters. It then introduces the concept of characteristic equations and time-dependent poles.

In dynamic linear systems described by differential equations with constant parameters, the poles of the rational function (transfer function of the system) play an important role. This article attempts to expand the poles concept in a situation where the system is described by the second-order linear system with timevarying parameters. It then introduces the concept of characteristic equations and time-dependent poles.