Improving control system of output voltage in “shaft generator - frequency converter” complex

The article focuses on operation of the ship shaft generator on the joint buses of the main switchboard through a frequency converter that consists of an uncontrolled rectifier and a self-excited inverter with pulse width modulation. The most common schemes of using shaft generators on ships are given, their advantages and disad-vantages are analyzed. There has been illustrated a flowchart and given a detailed description of the operation of a ship electric power plant with power take-off from the main engine. A control system regulating the constant flow interlinkage in the “frequency converter - shaft generator” complex, which ensures stable output voltage, has been developed. It has been stated that a random change in the rotational speed or in a torque fluctuation of the shaft generator rotor have little impact on the quality of generated electricity. Simulation modeling of the complex is given in the MATLAB/Simulink software package. The developed controller of a self-excited inverter supports continuous flow interlinkage by vector control. There has been demonstrated the composition and operation principle of the control system of output voltage of a shaft generator by using vector regulation method. Modeling has proved the availability of the self-excited inverter control system. The oscillograms of modeling the input and output current and voltage values have been obtained. The modeling results justified that changing the input voltage and frequency of the generator provided the high quality output voltage indicators. Harmonic distortion coefficients and static deviations have been analyzed. The expediency of using combined filters of higher harmonics to eliminate interharmonics and higher harmonics in the ship network has been proved. Practical recommendations are given to improve the quality of operation of the ship electrical complex with a shaft generator.