3MW DUAL OUTPUT HIGH VOLTAGE POWER SUPPLY … · 2018-09-27 · amit patel et al. 1 3mw dual output...
Transcript of 3MW DUAL OUTPUT HIGH VOLTAGE POWER SUPPLY … · 2018-09-27 · amit patel et al. 1 3mw dual output...
Amit Patel et al.
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3MW DUAL OUTPUT HIGH VOLTAGE POWER SUPPLY OPERATION:
RESULTS FOR ACCURACY, STABILITY AND PROTECTION
AMIT PATELa, DISHANG UPADHYAY, HITESH DHOLA, NIRANJANPURI GOSWAMI, KUSH MEHTA,
N.P.SINGH, BHAVIN RAVAL, RASESH DAVE, SANDIP GAJJAR, VIKRANT GUPTA, ARUNA
THAKAR, KUMAR RAJNISH , DIPAL SONI , SRIPRAKASH VERMA, RAGHURAJ SINGH , RAJESH
TRIVEDI, APARAJITA MUKHERJEE, UJJWAL BARUAH
ITER-India, Institute for Plasma Research, Gandhinagar, INDIA a Email : [email protected]
Abstract
In a nuclear fusion, plasma temperature is increased by external heating systems like neutral beam injectors (NBI) and
radio frequency heating. Radio Frequency (RF) heating devices generate frequency ranges from few MHz to tens of GHz viz.
ion cyclotron (IC), electron cyclotron(EC) and lower hybrid(LH) systems where high voltage power supply (HVPS) are
required preliminary. ITER requires 20 MW of ICRF for heating and driving plasma current. Seeing the availability of vacuum
tubes and stringent specifications demanded for plasma heating, a series connection of power amplifiers seems only a feasible
technical solution where RF power amplified at each stage. A required RF Amplifier must be having power capability of
1.5MW supporting matched and mismatched load (VSWR 2) over the wide frequency range of 35MHz- 65MHz. Pulse step
modulation (PSM) based HVPS are in use for similar application since last 2 decades. A unique scheme of feeding two stages
of RF Amplifier by single HVPS is endeavoured. Developed HVPS supports the operation by providing dc voltage to
intermediate stage and end stage of IC RF amplifiers, subsequently 8-13.5 kV, 250 kW and 15-27 kV, 2800 kW. Present papers
describes the consumption of dual output HVPS with IC RF Amplifiers system for different load conditions. A detailed
description of vital wire-burn test towards amplifier side, demonstrating tight synchronization among both stages is discussed
including test set up and fuse wire dimension. HVPS performance parameters of ripple, accuracy and stability over extended
duration are presented for various scenario of RF Amplifier operation taking due care of all interlock protections.
1. INTRODUCTION
For fusion research, various RF heating systems (i.e IC, EC and LH systems) are used for plasma heating using
high power vacuum tubes i.e. Tetrode, Diacrode, Gyrotron and Klystrons. HVPS are used to bias vacuum device
by providing anode/plate voltage which finally appeared as RF Voltage [1]-[2]. The HVPSs are typically with
voltage ranges of 30-100 kV and power level of 3- 8 MW [3]. Such systems demands specialise limits of ripple
voltage, voltage control accuracy and minimal short circuit energy. Besides that, HVPS also supports extreme
dynamics and superior transient response. Pulse Step Modulation (PSM) based HVPS utilizing fast semiconductor
switches (IGBT, MOSFET) being utilized from last two decades [3].
ITER requires 20 MW of ICRF sources where each unit must be having power capability of 1.5MW supporting
operation at matched and mismatched load (VSWR 2) over the wide frequency range of 35MHz- 65MHz. For
such high power, cascaded chain of RF amplifier is possible solution mainly due to available range of vacuum
tubes. The IC RF system at ITER-India test facility comprises of 3 levels RF amplifiers viz. High Power
Amplifier-1 (HPA-1), HPA-2 and HPA-3 where final RF output is 1.5MW as shown in Fig.1 [4]. A required
HVPS voltage range is mentioned in Fig.1 while voltage variation requirement at mismatched load is as shown in
Fig. 2, plotted in reference to phase of reflection coefficients [5] .
FIG. 1: 1.5 MW Cascaded RF Amplifier FIG. 2: Voltage Requirement at VSWR 2
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2. DUAL OUTPUT HVPS: TOPOLOGY & DEVELOPMENT
A Dual Output HVPS is developed to feed HPA-2 and HPA-3 with novel concept of independent voltage control
in close synchronisation with both output [6]-[7]. The specifications of HVPS are listed in Table 1. Dual output
HVPS appeared as an advantageous over conventional scheme of two individual HVPS for cascaded stages. Single
HVPS feeding two cascaded stages of amplifier proves higher power density as creepage and clearance need to
be taken for one HVPS only. It also holds an economic advantages as it eliminates a necessity of one HVPS. On
the other hand, few challenges also associated viz. voltage control of dual output for both stages by single
controller maintaining a balanced load on both feeding transformers.
Table 1. Specifications of Dual Output HVPS
Rated output voltage
For HPA-2 8 – 13. 5 kV
For HPA-3 15- 27 kV
Rated Current & Power
For HPA-2 15-20 A , 250 kW
For HPA-3 105- 155 A , 2800 kW
Type of duty Continuous/1 Hour ON -3 Hours OFF
Voltage control accuracy ± 1% of the max. value
Output voltage stability ± 1% of the max. value
Ripple of the output voltage ± 270 V
Resolution 100 V
Voltage rise/fall time 100 µs - 1.5 ms (Programmable)
Transient Response from 27 kV to 18 kV 100 µs
Fault energy in the Load ≤ 10 J
Let-through Energy dumped into Load < 250 A2s
Time to be ready for restart after Fault ≈ 20 ms
A configuration of Dual output HVPS is shown in Fig.3 while as built system at ITER-India premises is as shown
in Fig.4 [6].
FIG. 3.Dual Output HVPS Block Diagram FIG. 4 .Developed Dual Output HVPS
SPS Module - 1
Transformer -2
(16 Secondary)
Transformer- 1
(32 Secondary)
22 kV
SPS Module-33
SPS Module - 48
HPA-2
HPA-3
1 mH Choke
2.5 mH Choke
MODULE 1-32 MODULE 32-48
DUAL CONTROLLER
SPS Module-32
CT
CT
V
ΔV
V+ΔV
Amit Patel et al.
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Likewise the normal PSM based HVPS, it consist of Mutli-secondary transformers [8]-[10], switched power
supply (SPS) modules and controller. A controller is developed with single processor controlling two voltage
control loops with taking care of all protection devices [11]-[12]. A developed HVPS and all subcomponents
conform its traceability to various international standards viz. IEC 60146-1, UL940. Besides same, it also
conforms the requirements imposed by European Conformity (CE) for Electro-Magnetic Compatibility (EMC)
and Safety Directives.
3. TETSING & VALIDATION
Developed HVPS was validated by 3 MW, 9 MJ pulsed resistive load bank units for performance parameters
followed by integration with 1.5 MW IC RH system. As both (HVPS and IC RH) systems are located in single
lab building but on different floor levels, dc power is carried over a ~ 70m HVDC Cable. Besides same, 16 nos.
of fiber optic cables were used for synchronised operation of HVPS with IC RH system. Prior to power tests,
series of interlock tests were carried out to make surety of system investment protection in case of fault in any
system [13].
As used dc cable length is approximately 70 m, cable stored energy accumulates with HVPS stored energy so
short circuit test (wire-burn) was performed at end of cable on both output stages. Test setup is shown in Fig.5
where developed short circuit switch is used [14]. Regarding fuse wire dimensions, vacuum tube manufacturers
owns theirs recommendation viz. (1) 30 AWG, 150 mm copper wire (2) 30 AWG copper wire, length 20 mm /
kV [15]-[16]. As developed HVPS was utilised for two different type of IC RH systems, wire-burn test was
performed with both types of fuse wire lengths. On short circuiting the output of any stage of HVPS, both stage
output switches off in less than 10 µS as shown in Fig (6) qualifying a let through energy limits[6]-[7].
On completion of validation checks, HVPS was operated with IC RF system in integrated mode. RF Output power
was raised in steps from 100 kW to 1.5 MW where maximum power drawn form HVPS was approximately 2.8
MW. Under the condition of mismatched load (VSWR 2) with various degree of reflection coefficients, HVPS
output foresee high voltage – low current mode and low voltage-high current mode. At matched load conditions,
HVPS was operated up to 23 kV, 130 A while 16 kV, 164 A at one of the reflection angle at mismatched load.
[17] - [18]. A high bandwidth acquisition (5 KS/s) of both HVPS output voltage and end stage current is presented
in Fig. 7 for 4000 seconds where voltage build-up with abrupt RF power fluctuation is captured. In spite of
significant power variation, HVPS output proves its stability and accuracy as specified over the said period of
4000 seconds.
FIG. 5. Wire-burn test setup FIG. 6. Short Circuit Test at HPA-3
Ch. 3: HPA-2 Voltage (x 10000)
Ch. 4: HPA-2 voltages.
1 mH
2.5 mH
Driver Stage HVPS
Delta- V HVPS
HVPS Safety Ground
Tri-Axial Cable
Tri-Axial Cable
Motorised Switch
0.5 Ω
0.5 Ω
Fuse Wire
FIG. 7 HVPS extended duration operation
Ch. 1: Current, Ch. 2. : HPA-3 voltages (x 10000) Ch. 3. : HPA-2 voltages (x 1)
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4. FUTURE PLANS
Increasing a power density should be taken up as future work which include relocation of controller to near vicinity
of power cubicles. An online removal of faulty SPS module without generating any significant voltage glitch is
on second level of future activity.
ACKNOWLEDGEMENTS
Authors are thankful to M/s. Electronic Corporation of India Ltd. for manufacturing and supply of dual output
HVPS. Authors are also thankful to M/s. AMTECH Electronics India Ltd and M/s. Ames Impex Electricals Pvt.
Ltd for manufacturing SPS Module and Cast Resin Transformers. Authors are exceedingly thankful to IC RF team
at ITER-India for integrated campaigns.
REFERENCES
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