High Voltage Pulse Generator Using Transformer ... - IEEE Xplore

IEEE TRANSACTIONS ON PLASMA SCIENCE, VOL. 41, NO. 5, MAY 2013

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High Voltage Pulse Generator Using Transformer Parasitic Components for Pulsed Corona Discharge Generation Michał Balcerak, Member, IEEE, Marcin Hołub, Stanisław Kalisiak, and Michał Ze´nczak

Abstract— This paper proposes a new topology of a nanosecond, high voltage pulse generator devoted to pulsed corona discharge (PCD) reactor supply. The proposed topology is based on solid state, semiconductor switches and uses parasitic components of transformers. A prototype construction of the proposed generator loaded with a PCD reactor with 6.4-pF capacitance is able to generate high voltage pulses with maximum amplitude of 14 kV (using 5.4-kV supply and up to six modules of proposed topology, each equipped with a MOSFET transistor with 1-kV blocking capability) with voltage steepness of 730 V/ns. Obtained pulses are 65-ns long. The peak power delivered to the PCD reactor is > 0.3 MW while the energy consumed reaches 7 mJ/pulse. This paper also compares two different mechanical constructions of such generators and gives an overview of analytical and numerical voltage waveform analyzes. Index Terms— Glow discharges, plasma sources, pulsed power supplies, pulse generation.

I. I NTRODUCTION

R

ECENTLY, a strong emphasis of community on environmental protection is visible. This results in intensification of research focusing on finding new technologies to remove pollutants from the environment [1]. One of the very promising technology in many processes, especially for removing gaseous harmful substances from the atmosphere, is the nonequilibrium plasma technology [2], [3]. For the generation of nonequilibrium plasmas a physical phenomena of gas molecule bombardment by another molecules at a specific energy (in practice, these are usually electrons, e.g., electron beam) or through electrical discharges is most commonly used. Most widely used are three methods of exiting nonequilibrium plasma in gas: 1) dielectric barrier discharge (DBD) method [4]; 2) pulsed corona discharge (PCD) approach [5]; and 3) gliding arc discharge [6]. DBD reactor is essentially a multilayer capacitor, whereas the PCD reactor is a system of two electrodes, giving an extremely uneven distribution of the electric field such as pin-to-plate or a wire and the inner surface of the cylinder arrangement.

Manuscript received September 18, 2012; revised January 30, 2013; accepted March 30, 2013. Date of publication April 22, 2013; date of current version May 6, 2013. This work was supported by the European Union using the Baltic Sea Region Programme from 2007 to 2013, Project Acronym “PlasTEP.” The authors are with the West Pomeranian University of Technology, Szczecin 70-310 Poland (e-mail: [email protected]; [email protected]; [email protected]; [email protected]). Color versions of one or more of the figures in this paper are available online at http://ieeexplore.ieee.org. Digital Object Identifier 10.1109/TPS.2013.2256372

It is possible to use a simple high voltage, sine wave source (from several to several tens of kV) with a frequency of 50 Hz–50 kHz to generate the plasma in a DBD reactor. To generate plasma in PCD reactors it is necessary to have a high voltage pulsed source (from several to several tens of kV), with a high voltage steepness (typical in the range from several hundred to several thousand V/ns). Because the construction of PCD reactors is much simpler and it has better flow capacity than DBD reactor, a high-efficient topology of HV generator is required. Additionally, using HV pulse generator for DBD reactors it is also possible to significantly improve the energy efficiency of plasma generation [7]. Currently, to the generation of high voltage pulses systems of rotating spark gaps, gas gaps with trigger electrodes or thyratrons [8] are often used. From the point of the dynamic parameters of modern power transistors, such as MOSFETs, HV pulse generators are possible to implement, however voltage blocking parameters are definitely too low [9]. To comply with voltage requirements of HV pulse generators a semiconductor switches are serially connected [10] or the Marx topology is used [11]. This paper attempts to develop and analyze the power converter topology that will allow to increase the voltage induced by a single transistor and simultaneously increase the voltage rise steepness at the output of the inverter. II. D ESCRIPTION OF P ROPOSED G ENERATOR T OPOLOGY As in introduction, a new high voltage generator topology is proposed based on solid-state semiconductor switches. In constructed prototype MOSFET switches are used; because of their extraordinary speed IXYS DE475-102N21A are used. Generator setup, briefly shown in Fig. 1, is composed of n identical modules. A single module topology is shown in Fig. 2(a). Each module is composed of a single power switch, two capacitors C1 and C2 , and two transformers AT1 and AT2 . While the power switch remains open capacitors C1 and C2 [Fig. 2(a)] are charged from the supply unit (VDC ) to VDC /n through AT1 and AT2 transformer windings of each module and serially connected diode D S together with additional inductances L S , as shown in Fig. 1. After all switches are operated (in all modules simultaneously) voltages across capacitors C1 and C2 of all modules are summed on the generator output. After enlarging the output voltage using output transformer turns ratio the output voltage of secondary sides is added together as symbolically shown in Fig. 2(b).

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DS L S HV Probe

M5

Mi REACTOR Fig. 3. Simulation results for step response of an ideal and nonideal transformer model [12].

All of the below mentioned analyzes and results are obtained assuming that all transformers in each module have identical parameters (AT2 = AT1 , L e2 = L e1 , L e2,2 = L e1,2 , Ciw2 = Ciw1 , and V AT 2 = V AT 1 ), and all primary side capacitors have equal capacity (C2 = C1 ). Using this simplification the voltage waveform VM on output terminals of a single module can be described as follows: ⎡ ⎛ √ ⎞ 2 + ω2 − −2π ω t 1 iw1 t⎠ VM = 2Vinit ⎣(1 + A) · e Q1 ·ω1 cos ⎝ 2 1 − k2 ⎛ √ ⎞⎤ 2 + ω2 + −2π ω t 1 iw1 t ⎠⎦ (1) −A · e Qiw ·ωiw cos ⎝ 2 1 − k2

Pearson Current Monitor

M1

VDC

Fig. 1.

Constructed prototype and the measurement setup.

Ciw2

Le2,2 AT2

AT2

VAT2

Le2

T

C2

T

C2

VC2 UM

VC1

C1 AT1

VAT1

(a)

C1

where A=

Le1

AT1

Ciw1

Le1,2

(b)

Fig. 2. Proposed high voltage generator topology. (a) Single-module of the proposed topology. (b) Generator module, including parasitic capacitances and voltage distribution, after precharging.

Proposed topology uses parasitic capacitances of transformers [as shown in Fig. 2(b)] to generate high voltage output pulses with short durations. Parasitic capacitances of transformers together with serial, parasitic inductance of transformers form a second resonant circuit with resonant frequency much higher than the main resonant frequency of the circuit C1 – AT1 and C2 – AT2 . To visualize the influence of parasitic component parameter variation on system behavior a numerical model is prepared using PLECS 3.2.3. Converter model, as shown in Fig. 2(a), is prepared with parameter set as following: C1 = C2 = 2.2 nF, inductance of transformers: L e1 = L e1,2 = L e2 = L e2,2 = 1 μH, turn ratio υ = 1, magnetic coupling k = 1. For nonideal transformer model the magnetic coupling k = 0.9 and an additional interwinding capacity Ciw1 = Ciw2 = 25 pF is added as in Fig. 2(b). Remaining parameters are kept constant. Exemplary simulation results are shown in Fig. 3 [12].

1 (1 + ω12

2ϑk) − 2

1 2 ωiw1

−

2 1 ω12

+

− 4 ω12 ω21 (1 − k 2 )

1 2 ωiw1

1

iw1

2 1 ω12

2 = ω12 + ωiw1

2

+

1 2 ωiw1

− 4 ω12 ω21 (1 − k 2 ) 1

iw1

2 1 − k2 − 4ω12 ωiw1

(2)

where VM is the single module voltage after switching on of the transistor T , Vinit is the output voltage of a single module prior transistor T operation, k is the magnetic coupling √ coefficient of transformers AT1 (and AT2 ), k = M1 / (L e1 · √ L e1,1 ) = M2 / (L e2 · L e1,1 ), ϑ is the winding ratio of the transformer secondary side to its primary, ω1 is the angular velocity of a resonant circuit combining transformer AT1 primary side and the capacitor C1 equal to the angular velocity ω2 of a resonant circuit AT2 transformer primary side and C2 , ωiw1 is the angular velocity of a resonant circuit combining transformer AT1 and the interwinding parasitic capacitance Ciw1 equal to angular velocity ωiw2 of the system AT2 –Ciw2 , Q iw is the quality factor of a resonant circuit combining transformer AT1 and the interwinding parasitic capacitance Ciw1 , and Q 1 is the quality factor of a resonant circuit combining transformer AT1 primary side and the capacitor C1 . Assuming the magnetic coupling coefficient k is higher than zero, that is 0 < k < 1, and the angular velocity of the resonant circuit of parasitic parameters is significantly higher than one of the main circuit, that is ωiw1 ω1 with additional remark

BALCERAK et al.: HIGH VOLTAGE PULSE GENERATOR USING TRANSFORMER PARASITIC COMPONENTS FOR PCD

Fig. 4.

Fig. 5. Construction overview and outer dimensions (mm) of the PCD reactor used for experiments.

Main components of the measurement setup.

that the quality factor Q of all converter modules is equal to infinity (1) can be simplified to the form (3) as follows: 2 ωiw1 t VM ≈ 2Vinit 1 + ϑk 1 − cos . (3) 1 − k2 Equation (3) gives a simplified description of the first part of the time domain output signal, that is the first resonant period of Ciw1 and L e1 . Several modules of proposed converter topology can be connected in series to obtain even higher output voltage values. Output voltage of the full supply system is a sum of output voltages of all used stages as in (3) Vout = n · VM

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(4)

where n is the number of stages used, Vout is the output voltage of the full converter, and VM is the output voltage of a single stage. In the following part of this paper it is assumed, that the initial voltage of the supply system VDC prior transistor operations can be described as VDC = n · Vinit . Transformer parasitic inductance, apart from taking part in resonance, limits the current rising slope of power transistor limiting the turn-on losses of the switches. Losses can be further reduced if it is possible to switch transistors off while capacitors C1 and C2 are recharged into negative values. In such a case zero current switching principle can be obtained. Several modules of such topology can be connected in series increasing the maximal output voltage value. Capacitances and parasitic inductances present at each power switch terminals construct a low pass filter limiting the maximal voltage rising slope in nonidentical transistor gate timing. Therefore, a limited precision (in the range of a couple nanoseconds) of transistor timing (jitter) is feasible without the risk of damaging power switches because of overvoltage. The energy transferred into plasma reactor is limited to the energy stored in capacitors C1 and C2 of all modules and therefore such construction is not sensitive to overloads that might occur during reactor damage or arc type discharge. Voltage at the terminals of the proposed converter has a dc bias voltage, which is advantageous from the viewpoint of efficiency of processes in plasma [13], [14]. After switching on of power transistors, the load voltage waveform is composed of voltages of the two resonant circuits. The resonant recharge of these circuits distinguishes if the energy stored in capacitors C1 and C2 is consumed by the reactor.

III. S IMULATED AND M EASURED R ESULTS To verify practical properties of proposed topology a series of barrier-less reactors are constructed. Reactors are operated in ambient air under the pressure of 0.1 MPa, in room temperature. Test stand construction is shown in Fig. 4. As can be noticed in addition to electrical parameters sensors (voltage, current, and power) an intensified-charge-coupled device (iCCD) camera is used to visually monitor a single pulse discharge. Marked, main components are described as follows: 1) DE475-102N20A power transistors with dedicated drivers; 2) air transformers on a common carcass; 3) iCCD camera lens; 4) pearson current monitor (model 6585, 250 MHz); 5) PCD reactor; and 6) Tektronix high-voltage probe (type P6015A, 20 kVDC , 75 MHz, 3.0 pF, 100 M). All the electrical waveforms are recorded using Tektronix DPO4054 (500 MHz, 2.5 GS/s). IV. C OMPARISON OF D IFFERENT M ECHANICAL C ONSTRUCTION P ROPERTIES For the purpose of verification of the influence of mechanical arrangement two types of high voltage generator are constructed. To compare both arrangements an identical load reactor is used. Reactor construction is shown in Fig. 5. The discharge, inner (high voltage) electrode is constructed using steel wire with the diameter of 0.25 mm and is connected to the positive output voltage terminal of the reactor. On both sides, symmetrically, with the spacing of 8 mm from the inner axis grounded electrodes are mounted. Outer electrodes are in the form of plates, constructed of chemically tinned PCBs with overall dimensions of 160 × 57 mm. None of electrodes are covered with a dielectric layer. Constructed reactor has an overall capacity of 3.5 pF. Initially converter topology is arranged using a staged topology, where all the power transistors are placed above one another and connected together using a vertical transformer, constructed as litz wire-based, air core element on a paper carcass. Such transformer has a turn ratio of υ = 1 and the magnetic coupling factor k = 0.8. Main parameters of such construction are shown in Table I. Capacitors C1 and C2 have the capacitance of 2.2 nF each. Generator setup prototype consists of five modules. Generator construction is shown in Fig. 6. The second arrangement is constructed using a star-like positioning of generator modules, in this case six modules are

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TABLE I M AIN S IMULATION PARAMETERS Fig. 8

Setup

n

(a) (b)

Staged Star

5 6

C1 (nF) 2.2 2.2

Ciw (pF) 52 19.5

L e1 k (μH) 4.4 0.8 2.35 0.66

Q1

Q iw

∞ ∞

50 100

Fig. 6. High voltage generator in staged arrangement: 1: transformer unit on a common carcass, 2: power transistors and dedicated drivers, and 3: module capacitors.

Fig. 7. High voltage generator unit in star arrangement: 1: transformer unit on a common carcass, 2: power transistors and C1 , C2 capacitors.

used for prototype construction. The central part is composed out of a common, air cored transformer unit. litz wire transformer windings are in addition commonly wired. Because of the mechanical properties of such arrangement each fourth inductor winding is incomplete and in result the maximum output voltage value is limited with the factor of (4n − 1)/4n, where in this case n = 6. Such a transformer has an inductance of 0.35 μH and the coupling factor of k = 0.66. Capacitors C1 and C2 have capacitances of 2.2 nF each. Constructed prototype is shown in Fig. 7. In test stand measurement results the output voltage is slightly smaller when compared with (1), (3), and (4). This can be partly explained by energy transfer from initially charged capacitors (C1 and C2 in each module) to a summarized load capacitance of 6.5 pF (3.5 pF of reactor capacitance and 3.0 pF of high voltage sensor). The ratio of maximal output voltage of loaded and unloaded (idle operation) pulse generator are given in (5) and (6) as follows: Q converter + Q Load , (Cconverter + CLoad ) C1 2 (1 + ϑ) VDC + CLoad VDC 2n(1+ϑ)2 = C1 · 2 (1 + ϑ) VDC + C Load 2 2n(1+ϑ)

Vloaded = Vloaded Vunloaded

(5) (6)

where C1 · (2n(1 + ϑ)2 )−1 is the summarized pulse generator capacitance on converter output after transistor operation; 2(1 + ϑ)VDC is the summarized capacitor voltage multiplied by transformer ratio. Based on analytical system description summarized in (1), (3), (4), and (6) a simulation model is constructed in

Fig. 8. Comparison of simulation results according to (1), (6) and (3), (6) with measured output voltage waveforms. (a) Staged. (b) Star arrangements.

M ATLAB. System parameters were identified using the Agilent U1733C LCR-meter and are summarized in Table I. Q 1 , Q iw , and parasitic L e1 inductance values are experimentally chosen. Measured self-inductances of transformer windings are 0.94 and 0.36 μH in staged and star arrangement, respectively. Pulse generators are loaded with the capacity 6.5pF that led to output voltage maximum value reduction of 8.0% and 9.0% for staged and star arrangement, respectively. In both cases the dc supply voltage value for initial charging is VDC = 1000 V. This voltage is insufficient for plasma generation, therefore load can be assumed to have a purely capacitive character. Simulation results are shown in Fig. 8. A comparison of output voltage waveforms for VDC = 1 kV is shown in Fig. 9. As can be noticed the star arrangement is characterized by a slightly smaller maximum voltage value but shorter pulse length, simultaneously voltage steepness is similar for both constructions. To compare main properties of both constructions both generators are supplied with a voltage value of VDC = 4 kV and loaded with a PCD reactor as shown in Fig. 5. Figs. 10 and 11 show an overview of obtained voltage and current waveforms for both generator constructions. In star arrangement, as mentioned, the output pulse is ∼10% shorter, which has a major impact on shape and value of the reactor current. As can be noticed in presented waveforms star arrangement can be characterized by shorter pulse duration because of a smaller value of transformer parasitic capacity and inductance product. Further voltage oscillations in both cases result


Fig. 9. Comparison of output voltage waveforms for different generator mechanical arrangements.

Fig. 10. Output voltage (blue: 4 kV/div), current (cyan: 5 A/div), and energy (red: 1 mJ/div) delivered to PCD reactor when supplied with a staged generator construction; 40 ns/div.

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Fig. 12. PCD reactor voltage and current waveforms for different VDC : I: displacement current, II: streamer discharge current, and III: glow-like discharge current.

Fig. 13. iCCD camera image of a single, positive pulse supply for a single electrode reactor construction.

Fig. 11. Output voltage (blue: 4 kV/div) and current (green: 4 A/div) waveform for star generator arrangement; 40 ns/div. Fig. 14. Voltage and current waveforms for modified reactor construction and different VDC: I: displacement current, II: streamer discharge current, and III: glow-like discharge current.

from energy remaining after discharge. After proper reactorgenerator matching, remaining energy is small and oscillating voltage can be neglected. Furthermore, additional semiconductors can be used as an arrangement of ultrafast diodes in series and in parallel to power switches that allows for remaining energy recovery into C1 and C2 . This improvement would further increase the overall supply system efficiency. V. O BTAINED D ISCHARGE A NALYSIS As discussed the star arrangement allows for shorter output pulse duration in comparison with staged construction. Therefore further results will be based on star generator construction. In accordance to experiment results discussed in [15], [16] it is possible to divide the discharge current into three basic components: 1) displacement current (reactor capacity charging current); 2) streamer discharge current; and 3) glow-like discharge current. A clear division of those three groups is shown in Fig. 11, for short output pulses. After elevating the

supply voltage to 5 kV glow-like discharge current doubled, as is shown in Fig. 12. Fig. 13 shows an overview of iCCD camera recorded view of a single, positive pulse supply for single electrode reactor construction. To increase the amount of energy consumed by reactor the single, inner discharge electrode is replaced by double, parallel electrodes made out of steel wire with the diameter of 0.35 mm separated with the distance of 18 mm. Reactor construction is shown in Fig. 16(a). Modified reactor construction has the capacity of 6.4 pF. Waveforms shown in Figs. 14 and 15 are recorded using the modifier reactor construction. Fig. 14 shows an overview of obtained voltage and current waveforms (with marked discharge current components). The current component division is not based on discharger time-resolved spectroscopy but only on characteristic current forms denoted from [15], [16]. In addition, a strong peak voltage value influence on discharge current value is observed, as in [15].

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R EFERENCES

Fig. 15. voltages.

Power and energy delivered to PCD reactor for different supply

(a)

(b) Fig. 16. Constructed PCD reactor with two wire electrodes. (a) Reactor electrode arrangement. (b) Operation with positive pulsed supply. TABLE II L OADED AND N ONLOADED G ENERATOR O UTPUT V OLTAGE R ISE R ATE (S TEEPNESS ) VDC (kV) 1 3.3 4 5 5.4

Voltage Steepness Loaded (Vs−9 ) Nonloaded (Vs−9 ) 150 180 510 490 570 620 640 710 730 740

Momentary power and energy values recorded during experiments are shown in Fig. 15. Fig. 16(a) shows reactor construction with double electrodes and Fig. 16(b) shows typical plasma production while supplying with VDC = 4 kV and pulse repetition rate of 500 pps. A summary of voltage steepness (measured from 10% to 90% of the output pulse) recorded for loaded (PCD reactor with 6.4-pF capacitance) and nonloaded generator is shown in Table II.

[1] R. Brandenburg, H. Barankova, L. Bardos, A. G. Chmielewski, M. Dors, H. Grosch, M. Holub, I. Jõgi, M. Laan, J. Mizeraczyk, A. Pawelec, E. Stamate, “Plasma-based depollution of exhausts: Principles, state of the art and future prospects,” in Monitoring, Control and Effects of Air Pollution. Rijeka, Croatia: InTech, 2011, pp. 229–254. [2] H.-H. Kim, “Nonthermal plasma processing for air-pollution control: A historical review, current issues, and future prospects,” Plasma Process. Polymers, vol. 1, no. 2, pp. 91–110, 2004. [3] H. Akiyama, T. Sakugawa, T. Namihira, K. Takaki, Y. Minamitani, and N. Shimomura, “Industrial applications of pulsed power technology,” IEEE Trans. Dielectr. Electr. Insul., vol. 14, no. 5, pp. 1051–1064, Oct. 2007. [4] M. Holub, S. Kalisiak, T. Jakubowski, and M. Balcerak, “Power electronic supply systems for non-thermal plasma sources,” in Proc. 18th Int. Conf. Gas Discharge Appl., Sep. 2010, pp. 1–4. [5] H. Conrads and M. Schmidt, “Plasma generation and plasma sources,” Plasma Sour. Sci. Technol., vol. 9, no. 4, pp. 441–454, 2000. [6] J. Pawlat, J. Diatczyk, and H. D. Stryczewska, “Low-temperature plasma for exhaust gas purification from paint shop—A case study,” Przeglad Elektrotechniczny (Electr. Rev.), vol. 87, no. 1, pp. 245–248, 2011. [7] K. Okazaki and T. Nozaki, “Ultrashort pulsed barrier discharges and applications,” Pure Appl. Chem., vol. 74, no. 3, pp. 447–452, 2002. [8] J. M. Williamson, D. D. Trump, P. Bletzinger, and B. N. Ganguly, “Comparison of high-voltage ac and pulsed operation of a surface dielectric barrier discharge,” J. Phys. D, Appl. Phys., vol. 39, no. 23, pp. 4400–4406, 2006. [9] Data Sheet of DE475-102N20A Transistor, Doc #9200-0238 Rev 6, IXYS, Thief River Falls, MN, USA, 2009. [10] W. D. Keith, D. Pringle, P. Rice, and P. V. Birke, “Distributed magnetic coupling synchronizes a stacked 25-kV MOSFET switch,” IEEE Trans. Power Electron., vol. 15, no. 1, pp. 58–61, Jan. 2000. [11] J.-H. Kim, B.-D. Min, S. Shenderey, and G.-H. Rim, “High voltage marx generator implementation using IGBT stacks,” IEEE Trans. Dielectr. Electr. Insul., vol. 14, no. 4, pp. 931–936, Apr. 2007. [12] M. Balcerak, M. Holub, S. Kalisiak, and M. Zenczak, “Topology of a high voltage pulse generator using parasitic parameters of autotransformers for non-thermal plasma generation,” in Proc. 15th Int. Power Electron. Motion Control Conf., 2012, pp. DS1b16-1–DS1b16-63. [13] M. Rea and K. Yan, “Evaluation of pulse voltage generators,” IEEE Trans. Ind. Appl., vol. 31, no. 3, pp. 507–511, Mar.–Jun. 1995. [14] S. Masuda and S. Hosokawa, “Pulse energization system of electrostatic precipitator for retrofitting application,” IEEE Trans. Ind. Appl., vol. 24, no. 4, pp. 708–716, Jul.–Aug. 1988. [15] D. Wang, M. Jikuya, S. Yoshida, T. Namihira, S. Katsuki, and H. Akiyama, “Pulsed streamer discharges generated by sub-microsecond pulsed power in air,” in Proc. Pulsed Power Conf., 2005, pp. 997–1000. [16] D. Wang, T. Namihira, and H. Akiyama, “Pulsed discharge plasma for pollution control,” in Air Pollution. Rijeka, Croatia: InTech, 2010, pp. 265–287.

Michał Balcerak (M’12) was born in Szczecin, Poland, in 1983. He graduated from the Electrical Department, Szczecin University of Technology, Szczecin, Poland, in 2008, where he is currently pursuing the Ph.D. degree. He is a member of a Plasma Research Team, Faculty of Electrical Power Engineering and Electrical Drives and the executive board of the BalticNetPlasmaTek network.

VI. C ONCLUSION This paper outlined the following properties: 1) proposed, new high voltage generator topology can significantly limit the necessary number of semiconductor switches; 2) obtained output voltage rising slope was steep enough to generate atmospheric pressure pulsed corona discharges in air; 3) star arrangement allowed for output voltage pulse duration reduction while limiting the maximal voltage value.

Marcin Hołub was born in Szczecin, Poland, in 1976. He graduated from the Electrical Department in 2000, and the Ph.D. degree from the Szczecin University of Technology, Szczecin, Poland, in 2005. He was with the Braunschweig University of Technology, Braunschweig, Germany. His current research interests include control systems, power electronics and plasma supply systems. Dr. Hołub is currently a member of the Plasma Research Team, Chair of Electrical Engineering, the executive board of the BalticNet-PlasmaTec network.


Stanisław Kalisiak was born in 1948 in Pełczyce, Poland. He graduated from the Electrical Department in 1975, and the Ph.D. degree from the Szczecin University of Technology, Szczecin, Poland, in 1983. He is currently a Manager of the Power Electronic Plasma Supply Laboratory, Chair of Electrical Engineering. His work includes over 50 articles and 20 granted patents concerning power electronics, control systems, and plasma technology.

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Michał Ze´nczak received the M.Sc.Eng. and Ph.D. degrees from the Technical University of Szczecin, Szczecin, Poland, in 1981 and 1989, respectively. He had an examination on a thesis presented to qualify as an Assistant Professor at the Technical University of Warsaw in 2000. From 1981 to 1984, he was with Polish Railways. Since 1984, he has been with the Technical University of Szczecin. He deals mainly with power lines and their influence on a natural environment.