SYSTEMS OF PARALLEL OPERATING POWER ELECTRONIC CONVERTERS

The control means of each converter unit produces an output voltage based on reference signals (u* d , u* q ) that are generated from the active and reactive components (P, Q) of each converters output power. A first reference signal for a reactive component of the output voltage (u* q ) is set to zero, thus regulating the reactive component of the output voltage to zero. Therefore, only the active component is contributing to the actual output voltage. The reference signal for the active component of the output voltage (u* d ) is produced based on the active power component (P) with an active power vs. active voltage droop. To synchronize the frequencies of all converter units a reactive power vs. frequency droop is introduced for each converter unit, regulating the frequency based on changes in the reactive power component (Q) of each converter unit. Since the control means of each converter unit produces its reference signals based on the converter units own reactive and active power output, no communication is necessary between the various converter units operating in parallel. Converter units can therefore be placed anywhere without communication.