Multistage Marx with parallel active droop compensation for long pulses

Research and development of a parallel boost network providing droop compensation for long pulse applications has reached a milestone at Stangenes Industries. The demonstration unit is capable of producing a 3.2 kV / 3.2 A pulse that persists for 3.6 ms with a stability of better than 1%. The pulse is generated by two modular stages oriented in a Marx topology with a parallel droop compensator stage. The system is meant as an integration option for an existing 30-stage, 3.8 MW Marx-modulator. The option allows for longer pulse lengths that require the reliability and flexibility inherent in solid-state switching modulators. The parallel boost stages float at the voltage of the existing Marx stages and utilize the same charging and auxiliary power networks. In this arrangement, two 30 μF boost capacitors charge in series and discharge in parallel through a 3 mH boost inductor to deliver energy to two parallel 30 μF discharge capacitors during the pulse. The maximum repetition-rate of the system is governed by the charging power available. The demonstration unit is capable of 0.25 Hz operation with the 30W charging power available; however its parent system operates reliably at up to 400 HZ with 100 μs maximum pulse lengths at 90 kV / 50 A delivering 130 kW of average power. The parent system utilizes 30 modular stages [1]. Generating voltage stability of less than 1% requires significant tuning of the feedback network located on each boost stage. Evidence suggests that the droop percentage improves with an increasing number of Marx stages if certain ripple interference strategies are implemented. Improvements to the logic on the next generation boost control card will lead to greater control over the droop parameters.