Dorina-Mioara Purcaru

Modelling the PWM Zeta converter in discontinuous conduction mode

A full-order dynamic model of the pulse-width modulation (PWM) DC-to-DC Zeta converter in discontinuous conduction mode (DCM) is presented in this paper. The derivation procedure is based on the small-signal PWM switch model in DCM used in conjunction with a PWM derived Zeta topology. The small-signal characteristics of the PWM Zeta converter in DCM obtained in a similar way as the small-signal properties of a linear amplifier are presented in a symbolic form. Such a model can be directly used in conjunction with a computational environment as Matlab, MathCAD and Mathematica to analyze the small-signal low-frequency dynamics of the PWM Zeta converter in DCM.

On EM disturbances over digital equipment used for monitoring and events recording in a power system

Some characteristics of a digital equipment used for parameters monitoring and events recording in a power system are presented. The PC-XX/104 PROCESS CONTROL equipment (PC/104 compatible) refers to modular structures that use a central unit for data acquisition and processing. The basic constructive variants include 8 analogue inputs (4 for voltages, 4 for currents) with (non)unified signals. The equipment can also operate in systems where several equipment are connected in a FB232 compatible network to provide communication between equipment, separated by considerable distances. Synchronization between real-time clocks is required in this case. Specific matters related to the transmission modalities of EM disturbances that might influence data acquisition and processing are presented for these equipment. A special attention is given to the capacitive couplings that allow the transmission of disturbances exceeding the limits imposed by CISPR 11 norms. According to these norms, the solutions proposed for the improvement of the EMC corresponding to the digital equipment used for parameters monitoring and events recording in a power system are correct, certifying the obtaining of measurements which are immune to external EM disturbances.

Application of fourier method in energetics, for root-mean-square value and phase shift measurement

Recorded information about transmission system faults or disturbances is essential for determining the performance of system components and to analyze the nature and cause of a disturbance in energetics. The systems for disturbance recording perform the monitoring and analysis of different events specific to energetic systems. The root-mean-square (RMS) values and phase shifts of voltages and currents are widely used in post-failure analysis and for monitoring the characteristic parameters of electric lines. This paper deals with the Fourier method adequate for measurement of RMS values and phase shifts in energetic systems. Experimental results obtained using a system for disturbance recording in power stations of energetic system are also presented.