Design of a Novel Pulse Capacitor Charge Power System Based on Inertial Energy Storage
Zhang’ao Ren, Kexun Yu, Zhenxiu Lou, Caiyong Ye, Yuan Pan Department of Electrical Machines and Drives
Huazhong University of Science and Technology Wuhan, 430074, China
Email: renzando@smail.hust.edu.cn
Abstract—In this paper, a novel high-voltage generator- Homopolar Inductor Alternator (HIA) pulse-charge for the capacitor bank with repetitive frequency though inertial energy storage system has been designed. A diesel engine provides energy as a prime motor in this system, and then drives the HIA to the rated speed by the flywheel energy storage device, the AC pulse-charge for the capacitor bank with repetitive frequency through power electronic conversion. We have introduced the theory of the HIA and the operation mode of this system, and we have analyzed the rotor speed change according to the principle of energy conservation. Based on the main physical characteristics of IGCT, a functional model has been investigated and realized with the simulation tool of PSIM package. Finally, we have set up the main circuit topology for this system, and verified its feasibility though the analysis of the circuit simulation by Simulink package.
Keywords-Inertial Energy Storage, HIA, Pulse Capacitor Charge, IGCT, PSIM/Simulink package
I. INTRODUCTION
Recently, more than a decade, with development of the pulsed power technology, it has been applied widely in military and civilian areas. The feasibility of rotating electrical machine which was used as pulse power supply has been proved. It was used successfully in Tokmak, laser-flash lamps, electromagnetic rail gun and other devices. For example, the CPA (Compensate Pulsed Alternator) has been used in power electromagnetic railguns [1]. In this paper, we have designed a new type of pulse power supply system with HIA [2] [3] due to its high power density and efficiency. Integrated flywheel energy storage system with homopolar Inductor Motor/Generator has been researched in [4], and the control strategy of a synchronous homopolar machine was figure out in [5]. Comparative study in synchronous homopolar and permanent magnet machines was done in [6].
Fig.1 System structure diagram
This High voltage generator (HIA) completes the energy conversion between electrical and mechanical through the
inertial energy storage of the speed-decline. We have analyzed the speed change under pulse charging operation mode according to the principle of conservation of energy. A functional model of the IGCT has been established based on its main physical characteristics [7] [8] [9]. Finally, we have set up a main circuit topology for this system [10] [11], and verified its feasibility though the analysis of the circuit simulation.
II. THEORY AND SPEED CHANGE OF HIA
Firstly, we give the three-dimensional model and side view of the HIA’s rotor,
Fig.2 Three-dimensional model of rotor
Fig.3 Side view of rotor
Both ends of the rotor are homopolar, but two sides have a dislocation of 180 electrical angular degrees, the stator is also divided into two sections corresponding. The armature winding is the same as general synchronous generator. The excitation winding fixes in the middle of two stator core, around the rotor, its axis coincide with the alternator axis. There is no winding on the solid-iron-core rotor; this structure is conducive to its high-speed spin. Therefore, it is also a type of brushless excitation alternator.
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Φm
Φσ
Fig.4 Magnetic circuit of alternator
Due to the HIA has advantages of high power density and efficiency, it is suited for space and weight restricted occasion.
It is mainly applied in submarines, carrier-based power supply, aviation, electromagnetic forward of ship, as well as hybrid cars and wind power and other fields.
There are 9 pulse groups in this charging mode; 10 pulses in each group last 1 seconds, therefore, there are a total of 90 pulses. We also use 60s to drag the HIA to the original rated speed after all charge has ended.
We can get the speed change curve of the HIA under this operation mode according to the principle of conservation of energy. We approximate speed for the linear decline, and draw its change by the equation below.
( ) 0 2 2 2
2 2
0
1 1 *( )( )
2 30
1 * *( )
2 30
J pg DE b e
DE e
M W n M P t J n n
P t J n
π π
× Δ × − × = −
×
－
＝
(1)
Where M is the group number, ΔWJ is the energy required which charge the capacitor from 0 to the rated voltage,
PDE means the power of the diesel engine, the time that we drag the HIA from 0 to the rated speed needs t0, nband ne
are the speeds of the beginning and ending of capacitor charging.
0 50 100 150
0.8 0.85 0.9 0.95 1 1.05 1.1 1.15
1.2x 104
Time t(s)
Rotor Speed n(r/min)
Fig.5 Speed change of the HIA
III. TOPOLOGY OF THE MAIN CHARGING CIRCUIT A. Functional model of IGCT
IGCT (Integrated Gate Commutated Thyristor) combines advantages of the stability of the transistor’s turn-off and the low loss of the thyristor’s on-state. Therefore, IGCT has been widely applied in high-power fields in the world.
Various models for IGCTs have been achieved presently, whose basic simulation methods are different. The IGCT model described in this paper is in functional level, which treats the device as a “black box” and detailed the externally observed behavior without any detailed consideration on its physical effects occurring inside the device.
We have set up the functional model of IGCT by PSIM package. We simulated various stages of switching action with sub-circuits, and then package them to the final model. There are four main parts in this model, which are sub-circuit for turn-on and -off delay time, steady on- and off-state, turning-on dynamic and turning-off dynamic simulation.
(a) Sub-circuit for turn-on and -off delay time
(b) Sub-circuit for on- and off-state
(c) Sub-circuit for turning-on simulation PEDS2009
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(d) Sub-circuit for turning-off simulation
(e) Complete circuit package for IGCT
(f) The IGCT testing circuit Fig.6 Functional model of IGCT B. Design of Main Capacitor Charging Circuit
There phase medium frequency AC power generated by the HIA converts to DC with little ripples by an uncontrolled AC- DC converter. To protect from the inner over-voltage, an absorb circuit composed by D1, C1 and R1, called DC-Link must be placed before the high-voltage and high-power switch- IGCT. Then the DC power pulse-charge for the capacitor bank under the control of the IGCTs. The stored energy in capacitor of each pulse released by the discharge load completely and then we charge for the capacitor bank to the specific voltage by the charging circuit.
When we use the IGCT in series, due to the differences in characteristics, it would have unbalanced distribution of static and transient voltage which would lead over-voltage to threat particular device’s safety. In this system, we have design both static and transient voltage sharing of series connected IGCTs paralleled with R- and RC-snubbers, protecting from above problem. Synchronous signal detection is also considered in Fig.7.
IV. SIMULATION AND ANALYSIS
The parameters of the IGCT’s functional model circuit are designed according to the datasheet of ABB Company’s product-5SHY35L4512 [12]. The DC voltage of the testing
circuit is 2250V, causing load current 1KA. In order to make the simulation more accurate and closer to the actual situation, snubber circuit and stray inductance should be added to this testing circuit. We focus on the turn-off characteristics of IGCT because of its direct influence to our main charging circuit. Fig.
8 and 9 shows the simulation and product’s experimental waveforms of IGCT’s turning-off.
1.5 1.55 1.6 1.65
0 500 1000 1500 2000 2500 3000
t/ms
U/V(I/A)
turning-off voltage and current
turning-off voltage
turning-off current
Fig.8 Turning-off simulation waveform of IGCT
Fig.9 Actual behavior of IGCT during switching-off Comparing simulation waveform with actual behavior of IGCT, we can get very good consistency. The main factors of the simulation error are the parameter of the circuit actual stray inductance and the precision of measure.
The parameters of the main charging circuit shows in table
Ⅰbelow.
TABLE I. PARAMETER OF THE MAIN CIRCUIT
Object Description Parameter HIA Homopolar Inductor
Alternator
1.2MW,5000V 6000- 12000r/min
C1/μF Absorb capacitor 20
R1/Ω Absorb resistance 1.5
IGCT1,2,3 Integrated Gate
Commutated Thyristor 5SHY35L4512 R2,R4,R6/Ω Static voltage sharing
resistance 4.3
R3,R5,R7/Ω Transient voltage sharing
resistance 5.4
C2,C3,C4/μF Transient voltage sharing
capacitor 1.8
C/μF Main charging capacitor 8000 PEDS2009
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IGCT1
D1
C1 R1
R2
R3 C2
Driver circuit
Control circuit
C
D2
R4
R5 D3 C3
R6
R7 D4 C4
IGCT2 IGCT3
Driver circuit
Control circuit
Driver circuit
Control circuit
Synchronous signal detection
HIA
Discharge Load
Fig.7 Main capacitor charging circuit topology
The waveforms simulated by the Simulink toolbox of the charging circuit and the current of HIA are showed in Fig.10 and Fig. 11.
0 0.01 0.02 0.03 0.04 0.05 0.06 0.07
-200 0 200 400 600 800 1000
t/s
I/A
charging voltage and current
0 0.01 0.02 0.03 0.04 0.05 0.06 0.07-1000
0 1000 2000 3000 4000 5000
U/V
Fig.10 Charging voltage and current
0 0.005 0.01 0.015 0.02 0.025
-3 -2 -1 0 1 2
3 current of a phase
t/s
I/A
Fig.11 A phase current of HIA V. CONCLUSION AND FUTURE WORK
We have introduced a novel HIA pulse-charge for the capacitor bank though inertial energy storage system. The HIA will be applied widely in both military and civilian. We have designed this system, highlighted the principle of HIA and the
main charging circuit topology. This system has a very high charging efficiency, approximately as the constant-current charging. Due to its simple control and stability, this charging system has already met the requirement of new laser-weapons on bus and ship-board. But because of the restrictions of the weight and volume, the optimization of HIA and the control strategy of the main circuit need high request.
At present, a prototype of HIA is under development, which will be used to experiment this pulse-charging system for capacitor bank.
REFERENCES
[1] McCorkle, W.C., “Compensated pulsed alternators to power electromagnetic railguns,” in 12th IEEE International Pulsed Power Conference, 1999, pp. 364–368.
[2] P. Tsao, “An integrated flywheel energy storage system with homopolar inductor motor/generator and high-frequency drive,” Ph.D. dissertation, Univ. California, Berkeley, CA, 2003.
[3] P. Tsao, M. Senesky, and S. R. Sanders, “A synchronous homopolar machine for high-speed applications,” in Conf. Rec. IEEE-IAS Annu.Meeting, 2002, pp. 406–416.
[4] P. Tsao, M. Senesky, and S. R. Sanders, “An integrated flywheel energy storage system with homopolar inductor motor/generator and high- frequency drive,” IEEE Trans. on Industry Application, Vol. 39, No. 6, November/December 2003, pp. 1710-1725.
[5] M. K. Senesky, “Control of a synchronous homopolar machine for flywheel applications,” M.S. thesis, Univ. California, Berkeley, CA, 2003.
[6] M. Hippner and R. G. Harley, “High speed synchronous homopolar and permanent magnet machines comparative study,” in Conf. Rec. IEEE- IAS Annu. Meeting, 1992, pp. 74–78.
[7] Kraus R, Mattausch H J. “Status and trends of power semiconductor device models for circuit simulation,” IEEE Trans. on Power Electronics, May 1998, 13: pp. 452-465.
[8] Kuhn, H., Schroder, D., A new validated physically based IGCT model for circuit simulation of snubberless and series operation. IEEE Trans.
on IA, 2002, 38(6): pp. 1606-1612.
[9] Liqiang Yuan. “IGCT-based multilevel converters for medium voltage drive systems,” Ph.D. dissertation, Univ. Tsinghua, 2004.
[10] Y.Suh, P.Steimer, et al, "Application of IGCT in high power rectifiers,"
IEEE Industry-Applications-Society Annual Meeting, Alberta, CANADA, 2008, pp. 1672-1679.
[11] B.E.Strikland, M.Garbi, F.Cathell, S.Eckhouse and M.Nelms, “2 kJ/sec 25-kV high-frequency capacitor-charging power supply using MOSFET switches,” Proc. of the 1990 19th Power Modulator Symp., 1990, pp.531-534.
[12] ABB Semiconductors AG. ABB IGCT 5SHY35L4510 Data Sheet [M].
Switzerland, ABB, 2002.
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