Modular and scalable interleaved operating AC/DC or DC/DC power converter array for HVDC systems

For connecting HV DC grids either to AC grids or to DC sources, power electronic converters (AC/DC and DC/DC topologies) in the power range from a few hundred kilowatts up to the MW range are needed. Typical requirements are: (1) High conversion efficiencies, even on low load conditions (2) High reliability and redundancy, service under system operation (3) Low harmonic grid impact, provision of grid support and grid services (e.g. voltage control, reactive power on demand, fault ride through) (4) Accurate DC voltage control and dynamic power flow control (5) Battery and load protection features The paper will present a multi converter system, using IGBT based converter modules, which can be combined in any number and operate in an interleaved parallel control mode. Due to the phase shift between the partial output currents, the resulting current ripple becomes fairly low and the power quality is sufficient, even with low inductance values of the output chokes. For efficiency optimization it is possible to switch off individual modules during partial load conditions. Then, PWM patterns need to be reconfigured and synchronized under real time conditions. As the converter arrays are controlled by DSP based processing cards synchronous PWM pattern processing has been implemented and proven successfully. Power quality improvement functions (e.g. reactive power, harmonics control / compensation, correction of unsymmetrical grid voltages) have been integrated in the control procedure.