The active and apparent powers of two converter circuits with different spectrums of their input and output are calculated. The first circuit is a single phase bridge with pure resistive load. This circuit is linear one, with sinusoidal input and non-sinusoidal output. The main power theories allow obtaining the correct results. The second circuit is a simple series diode resistance connection. This circuit is one with nonlinear input (sinusoidal voltage and non-sinusoidal current) and linear non-sinusoidal output. The main power theories do not allow obtaining the correct results of apparent power calculation. The conclusion drawn is that the main power theories allow obtaining the correct results of active power calculations of linear and non-linear circuits. These theories can't be applied for the apparent power calculations of nonlinear circuits and systems.
Keywords-main powers; limits in application; calculation of active and apparent powers
The buck converter's operation is analyzed using difference equation method. Set of second order linear difference equations is obtained describing transient and steady state processes. The solutions of these sets are obtained in closed form. Thus, the non-linear problem of converter analysis is turned to the linear one. The solutions obtained determine the converter voltages and currents at the discrete instants of transistor ignitions. The equations allowed finding converter voltages and currents as continuous functions are appeared. The theoretical results are verified by numerical calculations, simulation, and experiments with physical model. A good accordance is observed.
This study presents a qualitative and quantitative analysis of the output current response of a three-phase buck rectifier. The DC-side of the three-phase pulse-width modulation (PWM) buck rectifier is loaded by a typical series equivalent circuit comprising a resistor, an inductor and a constant voltage. An analytical solution of transient and steady-state processes is obtained using the difference equation method in the continuous conduction mode. The proposed analytical solution exhibits two repetition intervals, which accurately predict the ripple components of the output current. Hence, the solution of the process envelopes is obtained. The derivation of the plant transfer function from the analytical solution of the output current is also presented. System simulations and experimental studies are carried out to validate the analytical approach with various output loads.
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