High power harmonic-free AC to DC rectification

The Sequential Discharge Rectification (SDR) system is a regulated high power AC to DC converter, producing a DC output with no VAr and harmonics generation. The technology is based on the property of resonance circuits, thereby permitting the use of soft switching and self commutating low dI/dt solid states devices. The switching characteristics permit the utilization of less expensive thyristors available in high voltage, high current and high power ratings. The new circuit topology allows the energy extraction from any phase to be proportional to the square of the instantaneous line voltage. The energy extraction, performed at constant intervals, will load the AC line to the desired power level over the entire AC cycle. Since the load which the SDR technique imposes on the multiple phase inputs is equivalent to a resistive load, it produces no VAr and harmonic distortions that must be filtered out. The rectification approach of this invention includes about the same number of components as a conventional bridge rectification approach. The low dI/dt permits the utilization of high voltage high power thyristors for megawatt power applications. Test data are presented for a 144 kW AC to DC demonstration system producing a dual low ripple DC output of /spl plusmn/260 VDC. The output can be regulated, its fault current protected, with a turn-on and turnoff of about 2-3 msec and complies with the harmonic requirements imposed by the IEEE 519-1992 and IEC 555-2 specifications.