RATIONALE FOR REALIZATION OF PHASE-SHIFTING DEVICE WITH CODE ADJUSTMENT DEPENDING ON FREQUENCY OF VOLTAGE
Analysis of control systems of semiconductor converter shows that the deviation of the network frequency negatively affects some consumers of electrical energy on ship, in particular, the phase-shifting devices that it is part of the control system of valve converter. As a result, an error appears in the formation of a given control angle, which leads to a change in the output parameters of the converter and a deterioration in its adjustment characteristics. The object of the research is a three-phase rectifier; it performed based on a semi-controlled bridge circuit. The purpose of the study is to reduce the sensitivity to changing the frequency of the input voltage and improve the control characteristics of the controlled rectifier. For this objective, simulation models of the channels of the control system of a controlled rectifier with various types of phase-shifting devices have been developed and investigated. The output mean value of rectified voltage of the converter was measured with variation of voltage frequency and variation of control angle. The processing of data obtained because of modeling a rectifier used as a source of power for the active load is presented. Comparison of simulation results showed that the presence of a memory block consisting of a digital phase-shifting system could reduce error of the mean of the rectified voltage output from the controlled rectifier. The results of research show practical possibility of realization control system based on the proposed digital phase-shifting device with resistance to frequency variations in the supply network. The realized system control is advisable to apply in the structure of a controlled rectifier in order to reduce the error of the output mid-rectified voltage when supplying from voltage sources on ship.