Kazimierz Mikolajuk

Time-dependent power systems impedance-interpretation and measuring problems

Problems of interpretation and measurement of the time-local impedance of a single phase power system loaded with switched and nonlinear loads are discussed. Simulations and measurements are presented for an active method of system identification for which narrow current spikes serve as system testing signals. Two practical realizations of harmonic generating devices are discussed and compared. The fact that even a highly harmonics polluting user cannot disturb too much the system voltage waveforms, makes the time-local linear system model useful if switched or even nonlinear loads are installed in the system. The problem of linear model approximation of a real power system is considered.

A New Algorithm of PWM Converter Control for Current Harmonics Generation

This paper proposes new fixed switching frequency control techniques for power active filters. New circuit models are proposed for voltage source inverters. These models are very convenient for computing the capacitor voltage of such inverters. Analyzing such models the new method of capacitor voltage control can be deduced. Also a new method of voltage source inverter control can be deduced from this analysis. The method is based on auxiliary capacitance function. This function is equivalent to time-varying capacitance. Such capacitance function can be computed when reference signal is known. The fixed switching frequency control techniques for PWM voltage source inverter can be easy obtained when auxiliary capacitance function is known. The example of the capacitance function for the voltage waveform improvement is presented in the paper.

Transformerless synthesis of transistor and thyristor switching RLC 1-ports

As an extension of the synthesis method developed in a previous paper, the transformerless synthesis of reciprocal switched 1-ports is presented in this paper. the transformerless structures of resistance switching n-ports described by impedance, admittance or hybrid matrices have been proposed. These structures enable the synthesis of dynamical switching RC, RL and RLC 1-ports. Using the state variables method, the realizability conditions and identification formulae for constant and sinusoidal input functions have been derived. Three numerical examples illustrate the developed methods. the present theory can be applied to create new thyristor and transistor arrangements, particularly compensators and auxiliary switching LC circuits facilitating the commutation of thyristors and transistors.

Reference signal detection for voltage harmonic damping in three-phase systems

Two cases are considered: harmonic reduction and unbalanced load correction. The paper presents the method of reference signal detection for shunt active power filter control. The parallel filter used for the voltage shape improving in three-phase four wire systems is considered. The signal is detected from voltage harmonics. The method uses the state observer acting in frequency domain. The process needs a few steps of iteration to obtain a compensator current reducing voltage harmonics. The numerical observer acting simultaneously with the system has learning features.

Multiobjective optimization approach to the active power filter control

The optimisation approach to voltage harmonic elimination and voltage symmetry improving is presented. The parallel filter used for the voltage shape improving in three-phase four wire systems is considered. The nonlinear inductor is applied as a source of current and voltage harmonics. Two cases are considered: harmonic reduction and unbalanced load correction. The multiobjective optimization functions are applied to acquire the reference signal for active power filter control.

Optimization method for harmonic identification in three-phase four-wire systems

The optimization approach to voltage harmonic elimination is presented. The parallel filter used for the voltage shape improving in three-phase four wire systems is considered. The nonlinear inductor is applied as a source of current and voltage harmonics. Two cases are considered-harmonic reduction and unbalanced load correction.