METHOD OF OUTPUT VOLTAGE CONTROL IN MULTI-CELL FREQUENCY CONVERTER Russian patent published in 2008 - IPC H02M7/493 

FIELD: electricity.

SUBSTANCE: invention refers to electric engineering and may be used in inductive heating systems with semi-conducting frequency converters when control system are designed. Method is intended for controlling output voltage of converter containing several inverters and multi-elements matching transformer with primary windings being connected to proper inverters and secondary windings being connected serially forming voltage summation circuit. Output voltage of one inverter is controlled by means of DC voltage converter connected to inverter input within the range defined by low and high thresholds. Other non-controlled inverters connected in parallel or fed from rectifiers are actuated into one of two states: "boosting voltage" or "short circuit". Output voltages of non-controlled inverters are set to be proportional to weight coefficient of bit pattern (1, 2, 4, 8, 16, ...). Different combinations of non-controlled inverters states form several levels of output voltage further creating several sub-ranges (zones) of output voltage controlling. Control is conducted by controlled inverter within those sub-ranges. Therefore, if output voltage of controlled inverter achieves proper range of controlling, states of non-controlled inverters are changed so that sum of non-controlled inverters weight coefficients being in "voltage boosting" mode could change by one. It results in control range shifting in controlled inverter by the voltage value assigned for lowest weight coefficient.

EFFECT: increase of energy indicators for conversion, creation of favourable switching conditions for converter transistors and increase of conversion power coefficient; improvement of energy indicators for conversion and provision of favourable switching modes for converter transistors.

2 dwg