Zilong Pan’s research while affiliated with National University of Defense Technology and other places

A high voltage pulse power supply based on a Blumlein type pulse forming line (PFL) with a Periodic Slotted Insulation Structure (PSIS) is designed and constructed in this paper. The Blumlein type PFL with PSIS, which inserts PSIS both in the inner line and outer line of the conventional Blumlein type PFL, is able to obtain output waveforms with higher quality and higher energy efficiency compared with the conventional Blumlein type PFL. Meanwhile, the combined insulation structure formed by the media of PSIS and the glycerin filled with the PFL can be used to optimize the electric field strength of the PFL, thereby improving the stability and reliability of the PFL in the repetitive-operation mode. The experimental results show that the high voltage pulse power supply designed in this paper had an output power of about 5 GW at a 50 Ω load, a pulse width longer than 80 ns, a repetition rate of 20 Hz, and supported 100 pulses in one run.

A solid-state high voltage pulse power supply with three synchronous output voltages is designed and constructed in this paper. The pulse power supply consists of a fractional-turn ratio saturable pulse transformer and three six-stage Marx generators. The FRSPT not only works as step-up pulse transformers but also as magnetic switches of the Marx generators. All magnetic switches are developed based on two communal cores to achieve a perfect multiple-pulse synchronization effect. The experimental results show that the three output voltages have an amplitude of about 168 kV and a rising time of about 102.6 ns with a 2 MΩ dummy load. The pulse power supply can operate stably at frequencies of 1, 5, 10, and 15 Hz with the synchronization jitters less than 1.5 ns.

Pulse forming lines (PFL) are widely applied in high-power pulsed power generators due to their high energy density and great ability with square waveform modulation. However, the three-cylinder coaxial Blumlein line (tPFL), a commonly used PFL structure, has low energy efficiency due to the difference in impedance of the outer and inner lines. In order to increase the outer line impedance and improve the output waveform of the PFL, a racetrack Blumlein pulse forming line (r-B PFL), formed by two inner cylinders, two middle cylinders, and one outer cylinder that resembles a runway shape, is proposed in this paper. The glycerin energy storage technology and the spiral line technology were applied in the PFL. Moreover, the r-B PFL was tested experimentally after its construction, yielding a satisfactory result. The PFL structure in which multiple middle cylinders share the same outer cylinder achieves a higher outer line impedance, leading to a high energy efficiency of the PFL, which contributes to the PFL development trend toward compactness and miniaturization.

Pulsed power generators utilizing magnetic switch technology within the 100 ns scale have become widespread for surface treatment, high power microwave generation, and food processing, in which the dynamic characteristics of the magnetic switch perform an important function. The saturation process, electric field between layers, and energy loss are closely associated with the applied time scale of the magnetic core, which affects the dynamic characteristics of the switch. However, compared with the study within the microsecond scale, the dynamic characteristics of magnetic switches within the 100 ns scale have not been studied in depth. In this paper, the dynamic characteristics of a coaxial magnetic switch modulating pulse forming networks (PFNs) are studied via both field-loop co-simulation and scaled experimental test. It is found that increasing PFN section number (Ns) leads to an acceleration in the saturation process of the core, which helps understand the switch performance of the magnetic core more clearly. With respect to a specific magnetic switch based on a ferromagnetic core, it is quantitatively analyzed that increasing Ns from 1 to 10 leads to a 16.1% reduction in core saturation time (tsat), a 13.4% increase in eddy loss (EET), and a 5.7% rise in maximum interlamination field strength (Emax) under the 100 ns scale; however, tsat is reduced by 19.3%, EET increases by 5.2%, and Emax rises by 2.3% under the microsecond scale. The results could provide a design reference for magnetic switches in pulsed power generators.

A modularized generator with three long pulse modules is designed and constructed in this work. The long pulse module consists of a three-section anti-resonance network and a three-stage transmission line transformer. A single module can output a pulse with an amplitude of 33 kV and a full width at half maximum (FWHM) of 400 ns, when the primary energy storage system provides a voltage of 24 kV. After the three modules are connected in series in experiment, the modularized long pulse generator delivers a high-voltage pulse to the matched load resistor with a maximum voltage of 96 kV and an FWHM of 400 ns. Repetitive experiments at a repetition frequency of 10 Hz are also carried out.

A sub-microsecond-range pulse generator based on an antiresonance network and transmission line transformer (TLT) is presented in this paper. The three-section antiresonance network (TSAN) and three-stage TLT take the roles of the pulse forming module and pulse voltage boosting module of this generator, respectively. The TSAN is applied to obtain a high quality and fixed flat top quasisquare pulse with fewer sections, and the three-stage TLT is used to obtain a higher voltage gain. Experimental results show that if the charging voltage of the TSAN is about 15.0 kV, the amplitude and pulse duration of the output voltage of the TSAN are about 7.2 kV and 400 ns, respectively, which correspond to the theoretical calculation results. Meanwhile, the amplitude of the output voltage of TLT is about 22.0 kV, so the voltage step-up ratio of the three-stage TLT is about 3.05. This generator displayed in the publication can transmit voltage pulses with low loss.

The design, construction, and operational characteristics of a low-impedance and low pulse drop transmission line transformer (TLT) are described in this paper. The multicore coaxial transmission line used for this transformer is different from traditional coaxial transmission line since its inner conductor consists of several high-voltage cables that are connected in parallel by using two metal disks placed at both ends of them. Simultaneously, the impedance of the coaxial transmission lines with ten cables designed in this paper is perfectly reduced from 60 to $13.5~\Omega$ . Moreover, the transmission lines can withstand a high voltage of several tens of kilovolts with 13.9 mm in diameter. The transmission lines were then used to construct TLTs. The transformers are wound inductively in separated cylinders made of polypropylene to enhance the isolation from the input to the output of the transformers. Consequently, the pulse drop is substantially reduced, minimizing pulse distortion in the transformer. A three-stage TLT, whose input and output impedances are 4.5 and $40.5~\Omega$ , respectively, was developed with the transmission lines. The experimental results show that the three-stage transformer based on the low-impedance and low pulse drop design transmission lines can achieve a voltage gain factor of almost 3.0.

As a combination device for a step-up pulse transformer and a magnetic switch, the saturable pulse transformer is widely used in pulsed-power and plasma technology. A fractional-turn ratio saturable pulse transformer is constructed and analyzed in this paper. Preliminary experimental results show that if the primary energy storage capacitors are charged to 300 V, an output voltage of about 19 kV can be obtained across the capacitor connected to the secondary windings of a fractional-turn ratio saturable pulse transformer. Theoretical and experimental results reveal that this kind of pulse transformer is not only able to integrate a step-up transformer and a magnetic switch into one device, but can also lower the saturable inductance of its secondary windings, thus leading to the relatively high step-up ratio of the pulse transformer. Meanwhile, the application of the fractional-turn ratio saturable pulse transformer in a μs range pulse modulator as a voltage step-up device and main switch is also included in this paper. The demonstrated experiments display that an output voltage with an amplitude of about 29 kV, and a 1.6 μs pulse width can be obtained across a 3500 Ω resistive load, based on a pulse modulator, if the primary energy storage capacitors are charged to 300 V. This compact fractional-turn ratio saturable pulse transformer can be applied in many other fields such as surface treatment, corona plasma generation and dielectric barrier discharge.

High voltagepulse generators are widely applied in a number of fields. Defense and industrial applications stimulated intense interests in the area of pulsed power technology towards the system with high power, high repetition rate, solid state characteristics, and compact structure. An all-solid-state microsecond-range quasi-square pulse generator based on a fractional-turn ratio saturable pulse transformer and anti-resonance network is proposed in this paper. This generator consists of a charging system, a step-up system, and a modulating system. In this generator, the fractional-turn ratio saturable pulse transformer is the key component since it acts as a step-up transformer and a main switch during the working process. Demonstrative experiments show that if the primary storage capacitors are charged to 400 V, a quasi-square pulse with amplitude of about 29 kV can be achieved on a 3500 Ω resistive load, as well as the pulse duration (full width at half maximum) of about 1.3 μs. Preliminary repetition rate experiments are also carried out, which indicate that this pulse generator could work stably with the repetition rates of 30 Hz and 50 Hz. It can be concluded that this kind of all-solid-state microsecond-range quasi-square pulse generator can not only lower both the operating voltage of the primary windings and the saturable inductance of the secondary windings, thus ideally realizing the magnetic switch function of the fractional-turn ratio saturable pulse transformer, but also achieve a quasi-square pulse with high quality and fixed flat top after the modulation of a two-section anti-resonance network. This generator can be applied in areas of large power microwave sources, sterilization, disinfection, and wastewater treatment.