SINGLE-PHASE CONVERTER UNIT OF A COMBINED POWER SUPPLY SYSTEM WITH A THREE-LEVEL INVERTER

Abstract

Improvement of the principle of formation of the output current of the converter unit with a three-level a grid inverter, which by reducing the error contributes to improving the quality of the current at the point of connection to the grid.  Synthesis of the converter control system structure based on the analysis of processes in electrical circuits and use of computer simulation.
Findings.  The dependencies  for  determining  the  amplitude  of current  pulsations,  the  error of the formation  of  current;  is  defined  ways  to  achieve  close  to  zero,  the  current  deviation  for  the  modulation period with unipolar PWM; the dependence of the specified deviation value for a relay current regulator
with a constant key switching frequency; structure and corresponding parameters of the current control loop with a combination of PWM and of relay control of current; evaluation of the circuit capabilities taking into account energy losses in the keys, developed a computer model of the “converter, network and load” system. Originality. The method of forming a current of a single-phase three-level grids inverter based on current deviation from a reference value has been improved, providing an average current deviation over the  modulation  period  close  to  zero,  corresponding  dependencies  have  been  established  for  its
implementation  for  unipolar  PWM  and  in  combination  with  a  relay  current  controller.  The  structure  of control system of a grid inverter with a combined current formation is proposed.
Practical  value.    Solutions  that  are  obtained  are  the  basis  for  the  development  for  converters  of combined power supply systems with renewable sources of electricity.