CA2792702A1 - Stabilized high-voltage power supply - Google Patents
Stabilized high-voltage power supply Download PDFInfo
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- CA2792702A1 CA2792702A1 CA2792702A CA2792702A CA2792702A1 CA 2792702 A1 CA2792702 A1 CA 2792702A1 CA 2792702 A CA2792702 A CA 2792702A CA 2792702 A CA2792702 A CA 2792702A CA 2792702 A1 CA2792702 A1 CA 2792702A1
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- voltage
- power supply
- converter
- output
- power
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Classifications
-
- H—ELECTRICITY
- H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
- H02M—APPARATUS FOR CONVERSION BETWEEN AC AND AC, BETWEEN AC AND DC, OR BETWEEN DC AND DC, AND FOR USE WITH MAINS OR SIMILAR POWER SUPPLY SYSTEMS; CONVERSION OF DC OR AC INPUT POWER INTO SURGE OUTPUT POWER; CONTROL OR REGULATION THEREOF
- H02M7/00—Conversion of ac power input into dc power output; Conversion of dc power input into ac power output
- H02M7/02—Conversion of ac power input into dc power output without possibility of reversal
- H02M7/04—Conversion of ac power input into dc power output without possibility of reversal by static converters
- H02M7/12—Conversion of ac power input into dc power output without possibility of reversal by static converters using discharge tubes with control electrode or semiconductor devices with control electrode
- H02M7/21—Conversion of ac power input into dc power output without possibility of reversal by static converters using discharge tubes with control electrode or semiconductor devices with control electrode using devices of a triode or transistor type requiring continuous application of a control signal
- H02M7/217—Conversion of ac power input into dc power output without possibility of reversal by static converters using discharge tubes with control electrode or semiconductor devices with control electrode using devices of a triode or transistor type requiring continuous application of a control signal using semiconductor devices only
- H02M7/25—Conversion of ac power input into dc power output without possibility of reversal by static converters using discharge tubes with control electrode or semiconductor devices with control electrode using devices of a triode or transistor type requiring continuous application of a control signal using semiconductor devices only arranged for operation in series, e.g. for multiplication of voltage
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- H—ELECTRICITY
- H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
- H02M—APPARATUS FOR CONVERSION BETWEEN AC AND AC, BETWEEN AC AND DC, OR BETWEEN DC AND DC, AND FOR USE WITH MAINS OR SIMILAR POWER SUPPLY SYSTEMS; CONVERSION OF DC OR AC INPUT POWER INTO SURGE OUTPUT POWER; CONTROL OR REGULATION THEREOF
- H02M1/00—Details of apparatus for conversion
- H02M1/0067—Converter structures employing plural converter units, other than for parallel operation of the units on a single load
- H02M1/007—Plural converter units in cascade
-
- H—ELECTRICITY
- H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
- H02M—APPARATUS FOR CONVERSION BETWEEN AC AND AC, BETWEEN AC AND DC, OR BETWEEN DC AND DC, AND FOR USE WITH MAINS OR SIMILAR POWER SUPPLY SYSTEMS; CONVERSION OF DC OR AC INPUT POWER INTO SURGE OUTPUT POWER; CONTROL OR REGULATION THEREOF
- H02M1/00—Details of apparatus for conversion
- H02M1/0067—Converter structures employing plural converter units, other than for parallel operation of the units on a single load
- H02M1/0077—Plural converter units whose outputs are connected in series
-
- H—ELECTRICITY
- H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
- H02M—APPARATUS FOR CONVERSION BETWEEN AC AND AC, BETWEEN AC AND DC, OR BETWEEN DC AND DC, AND FOR USE WITH MAINS OR SIMILAR POWER SUPPLY SYSTEMS; CONVERSION OF DC OR AC INPUT POWER INTO SURGE OUTPUT POWER; CONTROL OR REGULATION THEREOF
- H02M3/00—Conversion of dc power input into dc power output
- H02M3/02—Conversion of dc power input into dc power output without intermediate conversion into ac
- H02M3/04—Conversion of dc power input into dc power output without intermediate conversion into ac by static converters
- H02M3/10—Conversion of dc power input into dc power output without intermediate conversion into ac by static converters using discharge tubes with control electrode or semiconductor devices with control electrode
- H02M3/145—Conversion of dc power input into dc power output without intermediate conversion into ac by static converters using discharge tubes with control electrode or semiconductor devices with control electrode using devices of a triode or transistor type requiring continuous application of a control signal
- H02M3/155—Conversion of dc power input into dc power output without intermediate conversion into ac by static converters using discharge tubes with control electrode or semiconductor devices with control electrode using devices of a triode or transistor type requiring continuous application of a control signal using semiconductor devices only
- H02M3/156—Conversion of dc power input into dc power output without intermediate conversion into ac by static converters using discharge tubes with control electrode or semiconductor devices with control electrode using devices of a triode or transistor type requiring continuous application of a control signal using semiconductor devices only with automatic control of output voltage or current, e.g. switching regulators
- H02M3/158—Conversion of dc power input into dc power output without intermediate conversion into ac by static converters using discharge tubes with control electrode or semiconductor devices with control electrode using devices of a triode or transistor type requiring continuous application of a control signal using semiconductor devices only with automatic control of output voltage or current, e.g. switching regulators including plural semiconductor devices as final control devices for a single load
- H02M3/1584—Conversion of dc power input into dc power output without intermediate conversion into ac by static converters using discharge tubes with control electrode or semiconductor devices with control electrode using devices of a triode or transistor type requiring continuous application of a control signal using semiconductor devices only with automatic control of output voltage or current, e.g. switching regulators including plural semiconductor devices as final control devices for a single load with a plurality of power processing stages connected in parallel
- H02M3/1586—Conversion of dc power input into dc power output without intermediate conversion into ac by static converters using discharge tubes with control electrode or semiconductor devices with control electrode using devices of a triode or transistor type requiring continuous application of a control signal using semiconductor devices only with automatic control of output voltage or current, e.g. switching regulators including plural semiconductor devices as final control devices for a single load with a plurality of power processing stages connected in parallel switched with a phase shift, i.e. interleaved
Abstract
A stabilized high-voltage power supply is disclosed, having a general setup similar to a pulse-step modulator. The power supply comprises a plurality of DC power modules (40) having their outputs connected in a series configuration. Each power module comprises a DC voltage source (41), a DC-DC converter (42), and an output switching circuit (43). The total output voltage of the power supply is regulated by regulating the DC link voltage at the output of each power module. This is achieved by an appropriate feedback control circuit driving the DC-DC
converter of each power module. In this manner, low output ripple and a rapid response to changes in output current can be achieved. The power supply may be used, e.g., as the cathode power supply of a gyrotron.
converter of each power module. In this manner, low output ripple and a rapid response to changes in output current can be achieved. The power supply may be used, e.g., as the cathode power supply of a gyrotron.
Description
CA Application Blakes Ref.: 78680/00001 4 The present invention relates to a high-voltage power supply comprising a plurality of DC power modules connected in series, each module providing a DC link voltage that may be selectively 6 switched. This general setup is often called a "pulse-step modulator"
(PSM).
9 Pulse-step modulators are widely used as voltage supplies for high-power vacuum tubes in various applications, in particular, as modulation amplifiers in AM
transmitters or radar systems.
11 An early example of a pulse-step modulator is disclosed, e.g., in EP 0 066 904.
13 A typical prior-art pulse-step modulator is illustrated in Fig. 1. The modulator comprises a 14 plurality of identical DC power modules 10 connected to the secondaries of a multi-secondary transformer 14. Each module comprises a rectifier circuit 11 and a smoothing capacitance 12 16 for providing a DC link voltage, and a switching circuit 13 for selectively providing the DC link 17 voltage to the output of the module. A free-wheeling diode in each switching circuit ensures that 18 an unidirectional current may flow through each module even when the output switch of the 19 module is open.
21 The total output voltage Vtot of such a PSM-type power supply can be modulated by switching 22 the DC link voltages to the outputs of the modules 10 in an on/off fashion. This 30 provides a 23 rather coarse, step-wise modulation of the total output voltage, the steps being determined by 24 the individual output voltages of the modules ("coarse-step modulation", CSM). For more accurate control, pulse-width modulation (PWM) at the outputs of the modules is often 26 additionally employed. Intricate switching schemes have been suggested to ensure that the 27 power load is distributed equally over the modules, and to increase the effective PWM
28 frequency without increasing the actual switching frequency of each module. Since PWM occurs 29 at much higher frequencies than the mains frequency, PWM is also usually employed to remove voltage ripple at multiples of the mains frequency.
22294238.2 1 CA Application Blakes Ref.: 78680/00001 1 Whereas PWM allows for a very accurate control of the total output voltage, any PWM
2 switching scheme requires a PWM output filter to eliminate voltage ripple at the PWM
3 frequency.
One potential application of a PSM-type power supply is its use as the cathode power supply 6 (main power supply, MPS) of a gyrotron. A gyrotron is a particular type of vacuum tube, which 7 emits millimeter-wave electromagnetic radiation. Typical beam output powers range from some 8 tens of kilowatts well into the megawatt range. Gyrotrons are used, inter alia, in nuclear fusion 9 research to heat plasmas.
11 A gyrotron typically comprises an electron gun, an acceleration chamber, a resonance cavity 12 immersed in a strong magnetic field, and an electron collector. An electron beam is accelerated 13 to relativistic energies and subjected to the magnetic field. The electrons gyrate around the 14 magnetic field lines and emit electromagnetic radiation. By interaction of the relativistic electrons with the radiation field, amplification of the electromagnetic radiation occurs.
16 Gyrotrons are as such well known and are available commercially from a variety of 17 manufacturers.
19 A gyrotron, together with a typical configuration of its power supplies, is illustrated in highly schematic form in Fig. 2. A typical gyrotron comprises a filament F heating a cathode K for 21 emitting electrons. The electrons are accelerated in the acceleration chamber past an anode A
22 and past a body electrode B to reach the resonance cavity. The electrons finally hit a collector 23 C, which is typically kept at a lower potential than the body electrode to decelerate the 24 electrons ("depressed collector"). Several power supplies are employed to operate the gyrotron. A filament power supply FPS powers the filament F. A cathode power supply MPS
26 provides a negative voltage between the collector C and the cathode K, this voltage being in 27 the range of several tens of kilovolts. A body power supply BPS provides a positive voltage, 28 which is also typically in the range of a few tens of kilovolts, between the collector C and the 29 body electrode B. An anode power supply APS allows to selectively switch a voltage between the cathode K and the anode A to modulate the beam current. Other configurations of 31 electrodes and power supplies have been suggested, which however need not be discussed 32 here.
22294238.2 2 CA Application Blakes Ref.: 78680/00001 1 An extremely important parameter for the operation of the gyrotron is the so-called beam 2 voltage between the cathode K and the body electrode B. The electrons are accelerated 3 between the cathode and the body electrode by this voltage, i.e., the kinetic energy of the 4 electrons and therefore their relativistic mass increase is determined by this voltage. Through the relativistic mass increase, this voltage influences the cyclotron frequency of the electrons.
6 Since the cavity of a gyrotron typically has a high quality factor 0, already small variations in 7 the cyclotron frequency can dramatically influence the output power of the gyrotron. The beam 8 voltage should therefore be as accurate as possible and should have as little ripple as possible.
In the configuration of Fig. 2, the quality of the beam voltage is determined both by the quality 11 of the cathode power supply MPS and of the body power supply BPS.
Whereas the current 12 load on the body power supply BPS is relatively low (typically in the range of a few tens of 13 milliamperes), the current load on the cathode power supply MPS is typically in the range of 14 several tens of amperes. In addition, the cathode power supply MPS must be capable of rapidly responding to large, rapid current changes while maintaining the beam voltage at a 16 predetermined value as accurately as possible. This presents a considerable challenge to the 17 successful design of a cathode power supply.
19 In particular, if PWM is employed for regulating the MPS output voltage, the PWM output filter must be designed to ensure both a rapid response to a change in current load and a low voltage 21 ripple due to PWM. These two requirements are difficult if not impossible to satisfy 22 simultaneously. Furthermore, parasitic capacitances of the transformer may propagate the 23 PWM frequency and its harmonics back into the mains grid, which may lead to EMC problems.
If, on the other hand, only coarse-step modulation is used without employing PWM, 26 considerable ripple from the mains may result, and voltage regulation can only occur stepwise.
28 In J. Alex et al., "A new klystron modulator for XFEL based on PSM
technology", Proceedings of 29 PAC07, Albuquerque, New Mexico, USA (2007), a particular type of PSM has been suggested to drive a klystron tube. A plurality of DC power modules are connected in series. Each module 31 comprises a rectifier with a smoothing capacitance, followed by a boost converter (step-up 32 converter), acting as a constant power converter to charge a large output capacitance (20 mF).
22294238.2 3 CA Application Blakes Ref.: 78680/00001 1 The voltage across the output capacitance can be selectively connected to the output of the 2 module by an output switching circuit. The power supply acts to provide short high-voltage 3 pulses to a load (specifically, a klystron connected to the power supply via a pulse transformer).
4 During each pulse, power is drawn from the output capacitances of the modules. Consequently, the voltage at the output of each module drops significantly during each pulse. Subsequently the 6 output capacitance of each module is recharged by the boost converter.
The boost converter is 7 controlled in a manner to ensure that constant power is drawn from the mains supply to keep 8 power variations ("flicker") on the mains grid due to the pulses as low as possible.
A further development of this type of power supply is disclosed in J. Alex et al., "A new 11 prototype modulator for the European XFEL Project in pulse step modulator technology", 12 Proceedings of PAC09, Vancouver, BC, Canada, May 4-8, 2009. Again, each module employs 13 a boost converter to ensure constant power consumption on the mains supply. Pulse-width 14 modulation is employed to compensate for the voltage droop on the storage capacitance during the pulse in order to improve the flatness of the pulse.
17 A high-voltage power supply of the same general type, wherein each module comprises a 18 boost converter acting as a constant-power converter, is also disclosed in EP 2 099 127 Al.
These power supplies cannot overcome the deficiencies noted above in connection with the 21 more traditional kinds of PSM power supplies if both a rapid response to current changes and 22 low voltage ripple are needed, since stabilization of the total output voltage still either requires 23 PWM or, in the alternative, can be only carried out stepwise.
SUMMARY OF THE INVENTION
26 It is therefore an object of the present invention to provide a high-voltage power supply that is 27 capable of providing a stable total output voltage having low voltage ripple while 5 being able to 28 handle large, rapid current changes.
This object is achieved by a high-voltage power supply as specified in claim I. The invention 31 further provides a method of operation of such a power supply, as laid down in claim 11, a 32 method of use as laid down in claim 13, and a gyrotron employing such a power supply as laid 22294238.2 4 CA Application Blakes Ref.: 78680/00001 1 down in claim 14. Further embodiments of the invention are laid down in the dependent claims.
3 According to the present invention, a high-voltage power supply is provided, comprising:
4 a plurality of DC power modules having their outputs connected in a series configuration, each power module comprising a DC voltage source, a DC-DC converter receiving an 6 input voltage from said DC voltage source and providing a DC link voltage, and an output 7 switching circuit for selectively connecting said DC link voltage to the output of said power 8 module, 9 characterized in that the power supply comprises, for each DC power module, a feedback control circuit operable to provide driving signals to the DC-DC
converter of said 11 power module in a manner that regulates said DC link voltage to a predetermined reference 12 voltage.
14 Therefore, in contrast to the prior art, the DC-DC converter is not operated to ensure that constant power is drawn from the DC voltage source of the module, but it is operated as a 16 voltage regulator, ensuring that the DC link voltage takes a predetermined reference value. The 17 reference voltages of all involved modules are preferably identical, such that the total output 18 voltage of the power supply is the reference voltage, multiplied by the number of modules 19 involved.
21 Each module will therefore normally comprise a DC link voltage sensor for measuring the DC
22 link voltage, and the feedback control circuit will normally receive the measured DC link 23 voltage from the sensor, optionally process the measured voltage (e.g., by subjecting it to a 24 low-pass filter), and compare it to the (optionally also pre-processed) reference voltage. A
difference signal will be fed to a suitable controller, e.g., a PI or PID
controller. The controller 26 output will be fed to an actuator, which calculates the driving signals for the DC-DC converter.
28 Advantageously, when deriving the driving signals, the actuator may directly take into account 29 the major disturbance variables of the control loop, in particular, the actual output current of the power modules and/or the actual input voltage of the power modules. In this manner, a very 31 rapid response to changes in these disturbance variables may be achieved. In particular, the 32 power supply may comprise at least one current sensor for measuring an output current of said 22294238.2 5 CA Application Blakes Ref.: 78680/00001 1 DC power modules, and the feedback control circuit may then be adapted to derive driving 2 signals for the DC-DC converter of each power module taking into account the measured 3 output current. A single current sensor for the complete power supply may be sufficient;
4 however, it is preferred that each module comprises its own current sensor. Furthermore, each power module may comprise an input voltage sensor for determining an input voltage of its 6 DC-DC converter, and the voltage control circuit may then be adapted to derive driving signals 7 for the DC-DC converter of each power module taking into account the measured input voltage.
8 The DC-DC converter will normally be a switched converter operable at a variable duty cycle.
9 The feedback control circuit may then be adapted to calculate the duty cycle taking into account the measured disturbance variables, i.e., the measured output current and/or the 11 measured input voltage, and to operate the DC-DC converter at that duty cycle. A possible 12 formula for the duty cycle in the case of a boost converter will be given in section "Detailed 13 Description of Preferred Embodiments" below; however, other relationships taking into account 14 these disturbance variables are also conceivable.
16 Preferably, the DC-DC converter of each power module is a boost converter. However, it is 17 conceivable to employ any other type of switched DC-DC converter, such as, e.g., a buck 18 converter, a buck-boost converter, or a SEPIC. For practical reasons, it is preferred that the 19 converter is capable of delivering an output voltage that is higher than the input voltage, which would render buck converters less preferred. Since it is furthermore preferred to minimize any 21 losses, a boost converter with its simple topology is the 22 preferred converter type.
24 A boost converter comprises at least one output capacitance and at least one converter switching element cooperating with at least one choke inductance and at least one diode (or 26 any other unidirectional switching element) to charge the output capacitance to the DC link 27 voltage. The feedback control circuit is then operable to control the DC
link voltage by switching 28 the converter switching element at a variable duty cycle.
An interleaved topology of the boost converter may be chosen to reduce AC
currents in the 31 input and output capacitances, and to further reduce voltage ripple. The boost converter of each 32 power module may therefore comprise at least two interleaved boost converter circuits adapted 22294238.2 6 CA Application Blakes Ref.: 78680/00001 1 to charge a common output capacitance. The control circuit is preferably operable to operate 2 the interleaved boost converter circuits in a synchronous but phase-shifted manner.
3 In a concrete setup, such an interleaved boost converter topology may comprise at least one 4 common output capacitance, at least one first converter switching element (possibly two or more such elements connected in series) cooperating with at least one first choke inductance 6 (possibly two or more such inductances in a series configuration with the first switch elements) 7 and diode (possibly two or more diodes in a series configuration with the first choke 8 inductances) to charge said output capacitance to the DC link voltage, and at least one second 9 converter switching element (possibly two or more such elements connected in series) cooperating with at least one second choke inductance (possibly two or more such inductances 11 in a series configuration with the second switch elements) and diode (possibly two or more 12 diodes in a series configuration with the second choke inductances) to charge the same output 13 capacitance. The control circuit is then operable to control the DC link voltage by driving the 14 first and second converter switching elements at a variable duty cycle, preferably in a synchronous but phase-shifted manner.
17 In order to ensure a rapid response to current changes and to reduce switching losses, the 18 control circuit preferably operates the boost converter of each power module in discontinuous 19 mode during voltage regulation. This can be ensured by appropriately choosing the choke inductance to be lower than the so-called critical choke inductance in the intended operating 21 regime of the module. An example for the calculation of the critical choke inductance is 22 provided below in section "Detailed Description of Preferred Embodiments".
24 The control circuits of the individual modules may be commonly controlled by a main control system for the modules. In particular, the overall step-response behavior of the power supply to 26 disturbances such as current changes may be improved by driving the DC-DC converters of 27 different DC power modules in a synchronous but phase-shifted manner. In this manner, the 28 DC-DC converters of some modules in the appropriate phase within the converter cycle time 29 can react to disturbances earlier than those lagging behind in phase.
31 Preferably, the total output voltage of the power supply during each time period in which the 32 power supply is supposed to deliver a certain predetermined, non-zero voltage value ("voltage =
22294238.2 7 CA Application Blakes Ref.: 78680/00001 1 pulse") is regulated by only controlling the DC-DC converters of the individual power modules, 2 without applying coarse-step modulation, and without applying pulse-width modulation. In other 3 words, the modules are preferably operated in a manner in which the output switching circuits 4 of all power modules remain in the same (active or passive) state over prolonged times, in particular, as long as the desired total output voltage remains unchanged, unless a fault 6 condition occurs. Such time periods will normally cover at least 10, often at least 50 switching 7 cycles of the DC-DC converter. They can last, e.g., from less than 1 ms to several seconds or 8 even longer.
In order to enable a rapid discharge of the output capacitance in cases such as a missing load, 11 each DC power module may comprise a discharge resistor and a discharge switch for 12 selectively discharging the output capacitance.
14 In preferred embodiments, the power source may comprise at least one multi-secondary transformer having a plurality of sets of secondary windings, and each DC
power module may 16 then comprise a rectifier circuit connected to one set of secondary windings. The DC voltage 17 source of each module may thus be considered to comprise this set of secondary windings and 18 the corresponding rectifier circuit. Alternatively, a separate transformer may be used for each 19 module. Depending on the field of application, it is even conceivable to use other kinds of DC
voltage sources, even batteries.
22 To improve power ratio, the high-voltage power supply may comprise a first and a second 23 multi-secondary transformer, the first transformer and the second transformer being configured 24 to provide secondary voltages that are phase-shifted between the transformers. In the case of a three-phase mains grid, this may be accomplished, e.g., by using a star-star configuration for 26 the first transformer and a delta-star configuration for the second transformer, resulting in 27 twelve-pulse rectification. Other suitable schemes for achieving a phase shift are well known in 28 the art.
The present invention also provides a method of operating a high-voltage power supply as 31 described above. The method comprises, for each power module:
32 setting the reference voltage;
22294238.2 8 CA Application Blakes Ref.: 78680/00001 1 measuring and processing the actual DC link voltage;
2 comparing the DC link voltage and the reference voltage to derive a difference signal;
3 from the difference signal, deriving an actuating signal;
4 measuring an actual output current and/or the actual input voltage;
from the actuating signal, deriving driving signals for the DC-DC converter, taking into 6 account the measured output current andlor input voltage; and 7 driving each DC-DC converter by said driving signals to actively control said output 8 voltage.
In particular, as outlined above, the driving signals may implement a duty cycle determined, 11 inter alia, by the actuating signal, the output current and the input voltage.
13 The high-voltage power supply described above may advantageously be used as a power 14 supply for a gyrotron, in particular, as its cathode power supply.
Accordingly, the present invention also relates to a gyrotron. Generally, a gyrotron has at least a cathode, a body 16 electrode, and a collector electrode, and advantageously the power supply is connected 17 between the cathode and the collector electrode.
19 While a particular application for a gyrotron has been described, there are also other fields of applications where a highly stable high-voltage power supply capable of handling rapid current 21 changes is needed, and the power supply of the present invention may be employed in such 22 other fields as well.
Preferred embodiments of the invention are described in the following with reference to the 26 drawings, which are for the purpose of illustrating the present preferred embodiments of the 27 invention and not for the purpose of limiting the same. In the drawings, 29 Fig. 1 shows a schematic block diagram of a PSM power supply according to the prior art;
32 Fig. 2 shows a highly schematic sketch of a typical gyrotron together with its 22294238.2 9 CA Application Blakes Ref.: 78680/00001 1 associated power supplies;
3 Fig. 3 shows, in a highly schematic fashion and not to scale, a typical sequence of 4 voltages, currents and rf power in a gyrotron;
6 Fig. 4 shows a schematic block diagram of a power supply according to the present 7 invention;
9 Fig. 5 shows a simplified circuit diagram of a single module of the power supply of Fig.
4; and 12 Fig. 6 shows a diagram illustrating the control loop for controlling the output voltage of 13 a module as shown in Fig. 5.
DESCRIPTION OF PREFERRED EMBODIMENTS
16 Figure 3 illustrates, in a highly schematic fashion and not to scale, a typical sequence of the 17 various voltages and currents involved in the operation of a gyrotron.
At the beginning of the 18 sequence, the cathode power supply MPS and the body power supply BPS are switched to their 19 nominal output voltages to provide a predetermined beam voltage VBK.
Both voltages are actively controlled to ensure stability of these voltages. The anode-cathode voltage vAK provided 21 by the anode power supply APS is initially kept at a value which avoids any significant beam 22 current between the cathode K and the collector C. Only when the gyrotron is to generate 23 electromagnetic radiation, the anode-cathode voltage vAK is switched to a positive value, leading 24 to a rapid rise of the beam current IK and to the emission of electromagnetic radiation with power P .
27 From this diagram it is apparent that the cathode power supply MPS must be capable of rapidly 28 reacting to large variations in beam current IK while providing a stable output 5 voltage with low 29 voltage ripple.
31 Figure 4 shows a simplified block diagram of a high-voltage power supply according to the 32 present invention, which is adapted to satisfy these requirements. The general setup is similar 22294238.2 10 CA Application Blakes Ref.: 78680/00001 1 to the setup of Fig. 1. However, instead of one single multi-secondary transformer, in the 2 present example two multi-secondary transformers 44, 45 in different configurations (YY vs.
3 DY) are used to improve overall power factor. Both transformers 44, 45 are fed by a 4 three-phase mains voltage Vm. The three primary windings of the first transformer 44 are connected in a star ("Y") configuration, while the three primary windings of the second 6 transformer 45 are connected in a delta ("D") configuration. Each transformer comprises a 7 plurality of sets of three secondaries (typically 20-30 such sets), each set being connected in a 8 star configuration. Overall, the first transformer 44 thus has a star-star ("YY") configuration, 9 while the second transformer has a delta-star ("DY") configuration. By this overall configuration of the two transformers 14, 15, the secondary voltages of the two transformers are 11 appropriately phase-shifted with respect to each other to achieve twelve-pulse rectification, 12 which leads to a high power factor of typically more than 0.95.
14 The power supply comprises a plurality of identical DC power modules 40 connected to the secondaries of the transformers 44, 45. Each DC power module comprises a rectifier circuit 41, 16 a boost converter 42, and an output switching circuit 43. The outputs of the modules 40 are 17 connected in a series configuration.
19 Fig. 5 shows a simplified circuit diagram for a single module 40, which will now be described in more detail.
22 Input terminals X10, XI 1, X12 are connected to a set of three secondaries of one of the 23 transformers 44, 45. The rectifier circuit 41 in the form of a full-bridge rectifier, consisting of six 24 diodes D1, rectifies the three-phase secondary voltage.
26 The boost converter 42 comprises two interleaved boost converter circuits having a common 27 input capacitance and charging a common output capacitance, each of the interleaved 28 converter circuits being in turn designed with two switching elements in series to reduce the 29 required voltage rating of each switching element. In more detail, the common input capacitance of the boost converter is formed by a network of capacitors C10, C11, connected in series to 31 enable the use of capacitors having a reduced voltage rating, and symmetrizing resistors R10, 32 R11 in parallel to the two capacitors. The voltage across this input capacitance is called the 22294238.2 11 CA Application Blakes Ref.: 78680/00001 1 input voltage V. The common output capacitance of the boost converter is formed by two 2 series-connected capacitors C20, C21.Each of the upper and lower terminals of the output 3 capacitance is connected to the input capacitance via two groups of elements consisting of a 4 series-connected choke inductance and diode each, the two groups being connected in parallel.
The diodes are forward-biased to allow energy to flow from the input capacitance through the 6 choke inductances into the output capacitance, but not in the reverse direction from the output 7 capacitance back into the input capacitance. Two pairs of series-connected actively controlled 8 converter switches V10, V11 and V20, V21, respectively, here in the form of IGBTs, connect the 9 connection node between an upper choke inductance and upper diode with the connection node between a lower choke inductance and lower diode. By closing these switches, current can flow 11 through these choke inductances while the output capacitance is bypassed. As a result, the 12 upper and lower choke inductance together are subjected to the input voltage, and inductive 13 energy builds up in the choke inductances due to this voltage. When the switches are opened 14 again, the stored energy in the choke inductances is transferred to the output capacitance through the diodes. The resulting output voltage (DC link voltage) Vout across the output 16 capacitance can be much larger than the input voltage. This principle of operation of a boost 17 converter is as such well known in the art.
19 A discharge resistor R40 and a switch K20 enable a rapid discharge of the output capacitance if needed. Output switches V30, V31 in the form of IGBTs selectively provide the DC link voltage 21 Vo to the output terminals X20, X21 of the module. Two reverse-biased, series-connected 22 freewheeling diodes D30, D31 enable a unidirectional current to flow between the output 23 terminals even when the output switches V30, V31 are open. The common node between the 24 two diodes D30, D31 is connected to the common node between the converter switches VIO, V11 and V20, V21, respectively, of each pair of these switches as well as to the common node 26 between the capacitors C20, C21 to provide improved symmetrization.
Additional 27 symmetrization resistors (not shown in Fig. 5) may optionally be provided in parallel to the 28 capacitors C20, C21.
A module controller 51 is fed from input terminals X10, X11 via a small transformer T10.
31 Control signals and diagnostic signals are exchanged between the module controller 51 and an 32 external main control system 53 via a fiber-optic link 52 ensuring galvanic isolation. The module 22294238.2 12 CA Application Blakes Ref.: 78680/00001 1 controller 51 controls the booster switches V10, V11, V20, V21, the discharge switch K20, and 2 the output switches V30, V31 via leads that have been omitted in Fig. 5 for the sake of clarity.
3 In the present example, all switches are implemented as semiconductor switches, in particular, 4 as IGBTs, which will usually be equipped with additional reverse-biased freewheeling diodes in parallel to the collector-emitter path (not shown). However, other types of actively controlled 6 semiconductor switches may be employed, depending on the actual load requirements, such 7 as power MOSFETs etc.
9 The power supply is operated as follows: Depending on the desired total output voltage Vtot and on the status of the modules, the main control system selects whether all or only a part of the 11 modules shall be involved in providing the desired total output voltage Vtot. The main control 12 system accordingly provides control signals to the module controllers 51 of the individual 13 modules via the fiber-optic link 52. Each module controller drives the converter switches 14 V10-V21 of its associated module to charge the output capacitance C20, C21 to a reference DC link voltage Vref determined by the main control system. This reference voltage is set to the 16 same value in all modules. It corresponds to the desired total output voltage Vtot, divided by the 17 number of involved modules. The output switches of the involved modules are then closed to 18 provide the DC link voltages of the modules to their outputs, so as to provide the sum of the DC
19 link voltages at the output of the power supply. During normal operation, and in particular during individual current pulses delivered by the power supply, the output switches remain 21 closed and are not operated, in contrast to prior-art devices, where PWM
is implemented at the 22 output. switches to provide voltage regulation. Instead, regulation of the total output voltage is 23 carried out by regulating the DC link voltages Vow supplied by the boost converters in a 24 feedback control circuit implemented in module controller 51.
26 The feedback control circuit 60 is illustrated schematically in Fig. 6.
The actual DC link voltage 27 Võt (in terms of control theory, the controlled variable of the control loop) is determined by a 28 suitable voltage sensor 65. The measured DC link voltage is subjected to a low-pass filter 64 to 29 filter out the switching frequency of the boost converter and its harmonics, and the filtered DC
link voltage is compared to the reference voltage Vref in a comparator 61. The difference Vdiff of 31 these two voltages is fed to a PI controller 62, whose controller output signal Vctri (in terms of 32 control theory, the actuating variable of the control loop) is fed to a calculating unit 63 (the 22294238.2 13 CA Application Blakes Ref.: 78680/00001 1 actuator of the control loop). An input voltage sensor 64 measures the input voltage Vin, and 2 an output current sensor measures the output current lout. These signals (corresponding to the 3 main disturbance variables of the control loop) are also fed to the calculating unit 63. From the 4 controller signal V et rt, from the input voltage V1, and from the output current km, the calculating unit 63 calculates a duty cycle (i.e., the ratio of the time during which the switches of 6 the converter are closed and the cycle time of the converter) and drives the converter switches 7 V 1 0- V 2 1 according to this duty cycle.
9 The controlled variable Võt is a quadratic function of the duty cycle. In order to achieve a linear control path, the duty cycle should therefore be a square root function of the actuating variable 11 Vcid. In this manner, a linear dependence between controller signal Vctrl (actuating variable) and 12 DC link voltage Vnut (controlled variable) results. As will be detailed further below, the boost 13 converter is preferably operated in discontinuous mode (i.e., the current in the booster choke 14 inductances substantially decreases to zero before the next booster cycle starts). The duty cycle in discontinuous mode may be calculated according to the following formula:
2 = iota = Livoster (Vcrri ¨
D
Tbooster = V2 in 17 (Equation 1).
19 Here, Tbooster is the booster cycle time (the inverse of the boost converter operating frequency, which is kept constant during operation), and Lbooster is the total choke inductance of the boost 21 converter (in the specific arrangement illustrated here, Lbooster = L10 =L11=L20=L21). Both 22 pairs of converter switches in the interleaved converter circuits are operated at the same duty 23 cycle, but phase-shifted by 1800 relative to each other.
An important property of the calculating unit is that the most important disturbance variables, 26 lnut and V,n, directly act on the actuator of the control loop. For example, in the case of a sudden 27 rise of the output load, the output current will also rise rapidly, while the DC link voltage will 28 drop slowly due to the presence of the large output capacitance. Since the increased output 29 current directly acts on the actuator, the duty cycle will be increased almost instantaneously, and the voltage drop will stop within a single booster cycle time Tbooster.
The PI controller can 31 now correct the (relatively small) voltage drop that has already occurred.
22294238.2 14 CA Application Blakes Ref.: 78680/00001 1 In order to ensure a rapid response to load changes, the boost converter should be operated in 2 discontinuous mode during normal operation. This measure also improves stability of the 3 regulation of the DC link voltage, and minimizes switching losses on the converter switches, 4 since these are always switched on at zero current. This poses certain restrictions on the booster choke inductances. In particular, the total choke inductance should not exceed a 6 certain critical value, which is well known in the art and depends on the desired operating point 7 as follows:
i14,1 = (Vour ¨ Vin) = Tbooster Latt = _______________ 2 9 2 = /out Voia (Equation2).
11 On the other hand, the choke inductance should not be too small in order to keep the input 12 current to low figures. This calls for a choice of choke inductance below but close to the critical 13 choke inductance Lcrit=
The PI controller 62 can be disabled selectively in certain situations where feedback control 16 would be inappropriate. One such situation is the case of a missing output load (no-load case), 17 if at the same time the DC link voltage V01 is higher than the reference voltage Vref . While the 18 controller is disabled, the output capacitance may be discharged down to the reference voltage 19 by closing the discharge switch K20. Once the reference voltage Vref is reached again, the controller is enabled again.
22 In order to enable controlled ramp-up of the output voltage in the no-load case, e.g., after a 23 positive change of the reference voltage Vref, particular measures are required, since Equation 24 (1) implies that the duty cycle will be zero as long as the output current is zero. In order to overcome this problem, it is possible to set the current in Equation (1) to some predetermined 26 minimum value (e.g., 1-2% of the maximum output current) if the actual measured output 27 current is smaller than this minimum value.
29 Particular measures are required for power-up. A possible power-up sequence may be implemented as follows: The input capacitance CIO, 011 and the output capacitance C20, C21 31 are initially charged to the nominal voltage of Vin via step-start switches and a charging resistor 22294238.2 15 CA Application Blakes Ref.: 78680/00001 1 (not shown in Fig. 5), as they are well known in the art. The boost converter switches remain 2 disabled until all capacitances are charged to approximately the nominal voltage of Võ, . Only 3 then the boost converter starts to operate. The boost converter is initially operated at constant 4 duty cycle, until the reference voltage is reached across the output capacitance. Only then closed-loop control starts.
7 Operating conditions of the modules are continuously supervised, and any module is switched 8 off and possibly replaced by another (so far idle) module if a fault condition is detected. In 9 particular, a fault condition is assumed if the booster input voltage or the booster output voltage is outside a predetermined range, or if the output current exceeds a predetermined maximum 11 value. In addition, temperature, desaturation etc. may also be supervised.
13 The output of each module may be provided with a small output snubber (not shown in Fig. 5) in 14 order to limit the current surge in the module in the case of a short circuit. This snubber should, however, be kept as small as possible in order not to compromise the step response under load 16 changes.
18 Actual values of capacitances, inductances, resistors etc. will largely depend on the concrete 19 application and on the desired operating point.
21 The above description is only for illustrative purposes, and a number of modifications can be 22 made without departing from the scope of the present invention. In particular, the boost 23 converter design can be different from the design as described above. In the simplest case, a 24 single converter switch may be used in conjunction with a single choke inductance, a single diode and a single output capacitor, as it is well known in the art and illustrated schematically in 26 the box symbolizing module 40 in Fig. 6. Different controller types than PI controllers may be 27 employed, such as PID controllers. All diodes (acting as passive switches) may be replaced by 28 active switching elements such as transistors if desired. The rectifier circuit may be designed 29 differently, e.g., as an actively controlled thyristor rectifier circuit. Instead of single-quadrant output switching circuits, as in the above-described embodiment, which allow only for unipolar 31 voltage and unidirectional current, also two-quadrant output switching circuits allowing for 32 bipolar voltages at unidirectional current or for unipolar voltage at bidirectional currents or even 22294238.2 16 CA Application Blakes Ref.: 78680/00001 1 four-quadrant output switching circuits allowing for arbitrary sign of both output voltage and 2 output current may be employed. Two-quadrant switching may be useful, e.g., for inverse 3 voltage operation to reduce currents after a short circuit has occurred, or for driving capacitive 4 loads such as a control electrode of a vacuum tube. Suitable output switching circuits for two-quadrant or four-quadrant operation are disclosed, e.g., in EP 2 099 127 Al, in particular in 6 its Figures 5-7, and the disclosure of that document is incorporated herein by reference in its 7 entirety for teaching suitable output switching circuits for two- and four-quadrant operation.
8 Suitable output switching circuits and modes of operation of two- and four-quadrant output 9 switching circuits are also disclosed in WO 95/10881 Al and EP 1 553 686 Al.
11 In other embodiments, depending on the intended field of use, the boost converter may be 12 replaced by any other form of switched DC-DC converter. This might be a buck converter, a 13 buck-boost converter, a SEPIC etc. Such switched-mode DC-DC converters are well known in 14 the art. The operating principles as outlined above remain the same with such DC-DC
converters. In particular, also with other types of DC-DC converters it is possible to regulate the 16 DC link voltage of each module by controlling the DC-DC converter, instead of employing PWM
17 and/or CSM schemes to regulate the total output voltage of the complete power supply.
19 The proposed power supply may not only be employed as the main power supply of a gyrotron, but may be used in any application which require a stabilized high voltage which is stable even 21 under rapid load changes. Examples include the cathode or anode power supply of any other 22 type of vacuum tube having a control electrode which may rapidly change the current in the 23 tube.
22294238.2 17 CA Application Blakes Ref.: 78680/00001 1 List of references 3 10 : power module 4 11 : rectifier circuit 12 : smoothing capacitance 6 13 : output switching circuit 7 14 : transformer 8 2 : gyrotron 9 FPS : filament power supply MPS : cathode power supply 11 BPS : body power supply 12 APS : anode power supply 13 F : filament 14 K : cathode A : anode 16 B : body electrode 17 C : collector 18 VK : cathode voltage 19 VBK : beam voltage VAK : anode-cathode voltage 21 IK : beam current 22 RI : radiated power 23 40 : power module 24 41: rectifier circuit 42 : boost converter 26 43 : output switching circuit 27 X10, X11, X12 : input terminals 28 X20, X21 : output terminals 29 Dl: rectifier diode C10, C11 : input capacitors 31 R10, R11 : divider resistors 32 L10, L11, L20, L21 :choke inductances 22294238.2 18 CA Application Blakes Ref.: 78680/00001 1 V10, V11, V20, V21 : converter switches 2 D10, D11, D20, D21 : converter diodes 3 020, 021 : output capacitors 4 R20 : dissipating resistor K40 : dissipating switch 6 V30, V31 : output switches 7 D30, D31 : freewheeling diodes 8 51 : module controller 9 52 : fiber optic link V,n : input voltage 11 Vont : DC link voltage 12 Vtot : total output voltage 13 Vref : reference voltage 14 Vdiff : voltage difference Vctri : controller output signal 16 lout : output current 17 60 : control circuit 18 61 : comparator 19 62: PI controller 63 : calculating unit 21 64 : input voltage sensor 22 65 : output voltage sensor 23 66 : output current sensor 22294238.2 19
(PSM).
9 Pulse-step modulators are widely used as voltage supplies for high-power vacuum tubes in various applications, in particular, as modulation amplifiers in AM
transmitters or radar systems.
11 An early example of a pulse-step modulator is disclosed, e.g., in EP 0 066 904.
13 A typical prior-art pulse-step modulator is illustrated in Fig. 1. The modulator comprises a 14 plurality of identical DC power modules 10 connected to the secondaries of a multi-secondary transformer 14. Each module comprises a rectifier circuit 11 and a smoothing capacitance 12 16 for providing a DC link voltage, and a switching circuit 13 for selectively providing the DC link 17 voltage to the output of the module. A free-wheeling diode in each switching circuit ensures that 18 an unidirectional current may flow through each module even when the output switch of the 19 module is open.
21 The total output voltage Vtot of such a PSM-type power supply can be modulated by switching 22 the DC link voltages to the outputs of the modules 10 in an on/off fashion. This 30 provides a 23 rather coarse, step-wise modulation of the total output voltage, the steps being determined by 24 the individual output voltages of the modules ("coarse-step modulation", CSM). For more accurate control, pulse-width modulation (PWM) at the outputs of the modules is often 26 additionally employed. Intricate switching schemes have been suggested to ensure that the 27 power load is distributed equally over the modules, and to increase the effective PWM
28 frequency without increasing the actual switching frequency of each module. Since PWM occurs 29 at much higher frequencies than the mains frequency, PWM is also usually employed to remove voltage ripple at multiples of the mains frequency.
22294238.2 1 CA Application Blakes Ref.: 78680/00001 1 Whereas PWM allows for a very accurate control of the total output voltage, any PWM
2 switching scheme requires a PWM output filter to eliminate voltage ripple at the PWM
3 frequency.
One potential application of a PSM-type power supply is its use as the cathode power supply 6 (main power supply, MPS) of a gyrotron. A gyrotron is a particular type of vacuum tube, which 7 emits millimeter-wave electromagnetic radiation. Typical beam output powers range from some 8 tens of kilowatts well into the megawatt range. Gyrotrons are used, inter alia, in nuclear fusion 9 research to heat plasmas.
11 A gyrotron typically comprises an electron gun, an acceleration chamber, a resonance cavity 12 immersed in a strong magnetic field, and an electron collector. An electron beam is accelerated 13 to relativistic energies and subjected to the magnetic field. The electrons gyrate around the 14 magnetic field lines and emit electromagnetic radiation. By interaction of the relativistic electrons with the radiation field, amplification of the electromagnetic radiation occurs.
16 Gyrotrons are as such well known and are available commercially from a variety of 17 manufacturers.
19 A gyrotron, together with a typical configuration of its power supplies, is illustrated in highly schematic form in Fig. 2. A typical gyrotron comprises a filament F heating a cathode K for 21 emitting electrons. The electrons are accelerated in the acceleration chamber past an anode A
22 and past a body electrode B to reach the resonance cavity. The electrons finally hit a collector 23 C, which is typically kept at a lower potential than the body electrode to decelerate the 24 electrons ("depressed collector"). Several power supplies are employed to operate the gyrotron. A filament power supply FPS powers the filament F. A cathode power supply MPS
26 provides a negative voltage between the collector C and the cathode K, this voltage being in 27 the range of several tens of kilovolts. A body power supply BPS provides a positive voltage, 28 which is also typically in the range of a few tens of kilovolts, between the collector C and the 29 body electrode B. An anode power supply APS allows to selectively switch a voltage between the cathode K and the anode A to modulate the beam current. Other configurations of 31 electrodes and power supplies have been suggested, which however need not be discussed 32 here.
22294238.2 2 CA Application Blakes Ref.: 78680/00001 1 An extremely important parameter for the operation of the gyrotron is the so-called beam 2 voltage between the cathode K and the body electrode B. The electrons are accelerated 3 between the cathode and the body electrode by this voltage, i.e., the kinetic energy of the 4 electrons and therefore their relativistic mass increase is determined by this voltage. Through the relativistic mass increase, this voltage influences the cyclotron frequency of the electrons.
6 Since the cavity of a gyrotron typically has a high quality factor 0, already small variations in 7 the cyclotron frequency can dramatically influence the output power of the gyrotron. The beam 8 voltage should therefore be as accurate as possible and should have as little ripple as possible.
In the configuration of Fig. 2, the quality of the beam voltage is determined both by the quality 11 of the cathode power supply MPS and of the body power supply BPS.
Whereas the current 12 load on the body power supply BPS is relatively low (typically in the range of a few tens of 13 milliamperes), the current load on the cathode power supply MPS is typically in the range of 14 several tens of amperes. In addition, the cathode power supply MPS must be capable of rapidly responding to large, rapid current changes while maintaining the beam voltage at a 16 predetermined value as accurately as possible. This presents a considerable challenge to the 17 successful design of a cathode power supply.
19 In particular, if PWM is employed for regulating the MPS output voltage, the PWM output filter must be designed to ensure both a rapid response to a change in current load and a low voltage 21 ripple due to PWM. These two requirements are difficult if not impossible to satisfy 22 simultaneously. Furthermore, parasitic capacitances of the transformer may propagate the 23 PWM frequency and its harmonics back into the mains grid, which may lead to EMC problems.
If, on the other hand, only coarse-step modulation is used without employing PWM, 26 considerable ripple from the mains may result, and voltage regulation can only occur stepwise.
28 In J. Alex et al., "A new klystron modulator for XFEL based on PSM
technology", Proceedings of 29 PAC07, Albuquerque, New Mexico, USA (2007), a particular type of PSM has been suggested to drive a klystron tube. A plurality of DC power modules are connected in series. Each module 31 comprises a rectifier with a smoothing capacitance, followed by a boost converter (step-up 32 converter), acting as a constant power converter to charge a large output capacitance (20 mF).
22294238.2 3 CA Application Blakes Ref.: 78680/00001 1 The voltage across the output capacitance can be selectively connected to the output of the 2 module by an output switching circuit. The power supply acts to provide short high-voltage 3 pulses to a load (specifically, a klystron connected to the power supply via a pulse transformer).
4 During each pulse, power is drawn from the output capacitances of the modules. Consequently, the voltage at the output of each module drops significantly during each pulse. Subsequently the 6 output capacitance of each module is recharged by the boost converter.
The boost converter is 7 controlled in a manner to ensure that constant power is drawn from the mains supply to keep 8 power variations ("flicker") on the mains grid due to the pulses as low as possible.
A further development of this type of power supply is disclosed in J. Alex et al., "A new 11 prototype modulator for the European XFEL Project in pulse step modulator technology", 12 Proceedings of PAC09, Vancouver, BC, Canada, May 4-8, 2009. Again, each module employs 13 a boost converter to ensure constant power consumption on the mains supply. Pulse-width 14 modulation is employed to compensate for the voltage droop on the storage capacitance during the pulse in order to improve the flatness of the pulse.
17 A high-voltage power supply of the same general type, wherein each module comprises a 18 boost converter acting as a constant-power converter, is also disclosed in EP 2 099 127 Al.
These power supplies cannot overcome the deficiencies noted above in connection with the 21 more traditional kinds of PSM power supplies if both a rapid response to current changes and 22 low voltage ripple are needed, since stabilization of the total output voltage still either requires 23 PWM or, in the alternative, can be only carried out stepwise.
SUMMARY OF THE INVENTION
26 It is therefore an object of the present invention to provide a high-voltage power supply that is 27 capable of providing a stable total output voltage having low voltage ripple while 5 being able to 28 handle large, rapid current changes.
This object is achieved by a high-voltage power supply as specified in claim I. The invention 31 further provides a method of operation of such a power supply, as laid down in claim 11, a 32 method of use as laid down in claim 13, and a gyrotron employing such a power supply as laid 22294238.2 4 CA Application Blakes Ref.: 78680/00001 1 down in claim 14. Further embodiments of the invention are laid down in the dependent claims.
3 According to the present invention, a high-voltage power supply is provided, comprising:
4 a plurality of DC power modules having their outputs connected in a series configuration, each power module comprising a DC voltage source, a DC-DC converter receiving an 6 input voltage from said DC voltage source and providing a DC link voltage, and an output 7 switching circuit for selectively connecting said DC link voltage to the output of said power 8 module, 9 characterized in that the power supply comprises, for each DC power module, a feedback control circuit operable to provide driving signals to the DC-DC
converter of said 11 power module in a manner that regulates said DC link voltage to a predetermined reference 12 voltage.
14 Therefore, in contrast to the prior art, the DC-DC converter is not operated to ensure that constant power is drawn from the DC voltage source of the module, but it is operated as a 16 voltage regulator, ensuring that the DC link voltage takes a predetermined reference value. The 17 reference voltages of all involved modules are preferably identical, such that the total output 18 voltage of the power supply is the reference voltage, multiplied by the number of modules 19 involved.
21 Each module will therefore normally comprise a DC link voltage sensor for measuring the DC
22 link voltage, and the feedback control circuit will normally receive the measured DC link 23 voltage from the sensor, optionally process the measured voltage (e.g., by subjecting it to a 24 low-pass filter), and compare it to the (optionally also pre-processed) reference voltage. A
difference signal will be fed to a suitable controller, e.g., a PI or PID
controller. The controller 26 output will be fed to an actuator, which calculates the driving signals for the DC-DC converter.
28 Advantageously, when deriving the driving signals, the actuator may directly take into account 29 the major disturbance variables of the control loop, in particular, the actual output current of the power modules and/or the actual input voltage of the power modules. In this manner, a very 31 rapid response to changes in these disturbance variables may be achieved. In particular, the 32 power supply may comprise at least one current sensor for measuring an output current of said 22294238.2 5 CA Application Blakes Ref.: 78680/00001 1 DC power modules, and the feedback control circuit may then be adapted to derive driving 2 signals for the DC-DC converter of each power module taking into account the measured 3 output current. A single current sensor for the complete power supply may be sufficient;
4 however, it is preferred that each module comprises its own current sensor. Furthermore, each power module may comprise an input voltage sensor for determining an input voltage of its 6 DC-DC converter, and the voltage control circuit may then be adapted to derive driving signals 7 for the DC-DC converter of each power module taking into account the measured input voltage.
8 The DC-DC converter will normally be a switched converter operable at a variable duty cycle.
9 The feedback control circuit may then be adapted to calculate the duty cycle taking into account the measured disturbance variables, i.e., the measured output current and/or the 11 measured input voltage, and to operate the DC-DC converter at that duty cycle. A possible 12 formula for the duty cycle in the case of a boost converter will be given in section "Detailed 13 Description of Preferred Embodiments" below; however, other relationships taking into account 14 these disturbance variables are also conceivable.
16 Preferably, the DC-DC converter of each power module is a boost converter. However, it is 17 conceivable to employ any other type of switched DC-DC converter, such as, e.g., a buck 18 converter, a buck-boost converter, or a SEPIC. For practical reasons, it is preferred that the 19 converter is capable of delivering an output voltage that is higher than the input voltage, which would render buck converters less preferred. Since it is furthermore preferred to minimize any 21 losses, a boost converter with its simple topology is the 22 preferred converter type.
24 A boost converter comprises at least one output capacitance and at least one converter switching element cooperating with at least one choke inductance and at least one diode (or 26 any other unidirectional switching element) to charge the output capacitance to the DC link 27 voltage. The feedback control circuit is then operable to control the DC
link voltage by switching 28 the converter switching element at a variable duty cycle.
An interleaved topology of the boost converter may be chosen to reduce AC
currents in the 31 input and output capacitances, and to further reduce voltage ripple. The boost converter of each 32 power module may therefore comprise at least two interleaved boost converter circuits adapted 22294238.2 6 CA Application Blakes Ref.: 78680/00001 1 to charge a common output capacitance. The control circuit is preferably operable to operate 2 the interleaved boost converter circuits in a synchronous but phase-shifted manner.
3 In a concrete setup, such an interleaved boost converter topology may comprise at least one 4 common output capacitance, at least one first converter switching element (possibly two or more such elements connected in series) cooperating with at least one first choke inductance 6 (possibly two or more such inductances in a series configuration with the first switch elements) 7 and diode (possibly two or more diodes in a series configuration with the first choke 8 inductances) to charge said output capacitance to the DC link voltage, and at least one second 9 converter switching element (possibly two or more such elements connected in series) cooperating with at least one second choke inductance (possibly two or more such inductances 11 in a series configuration with the second switch elements) and diode (possibly two or more 12 diodes in a series configuration with the second choke inductances) to charge the same output 13 capacitance. The control circuit is then operable to control the DC link voltage by driving the 14 first and second converter switching elements at a variable duty cycle, preferably in a synchronous but phase-shifted manner.
17 In order to ensure a rapid response to current changes and to reduce switching losses, the 18 control circuit preferably operates the boost converter of each power module in discontinuous 19 mode during voltage regulation. This can be ensured by appropriately choosing the choke inductance to be lower than the so-called critical choke inductance in the intended operating 21 regime of the module. An example for the calculation of the critical choke inductance is 22 provided below in section "Detailed Description of Preferred Embodiments".
24 The control circuits of the individual modules may be commonly controlled by a main control system for the modules. In particular, the overall step-response behavior of the power supply to 26 disturbances such as current changes may be improved by driving the DC-DC converters of 27 different DC power modules in a synchronous but phase-shifted manner. In this manner, the 28 DC-DC converters of some modules in the appropriate phase within the converter cycle time 29 can react to disturbances earlier than those lagging behind in phase.
31 Preferably, the total output voltage of the power supply during each time period in which the 32 power supply is supposed to deliver a certain predetermined, non-zero voltage value ("voltage =
22294238.2 7 CA Application Blakes Ref.: 78680/00001 1 pulse") is regulated by only controlling the DC-DC converters of the individual power modules, 2 without applying coarse-step modulation, and without applying pulse-width modulation. In other 3 words, the modules are preferably operated in a manner in which the output switching circuits 4 of all power modules remain in the same (active or passive) state over prolonged times, in particular, as long as the desired total output voltage remains unchanged, unless a fault 6 condition occurs. Such time periods will normally cover at least 10, often at least 50 switching 7 cycles of the DC-DC converter. They can last, e.g., from less than 1 ms to several seconds or 8 even longer.
In order to enable a rapid discharge of the output capacitance in cases such as a missing load, 11 each DC power module may comprise a discharge resistor and a discharge switch for 12 selectively discharging the output capacitance.
14 In preferred embodiments, the power source may comprise at least one multi-secondary transformer having a plurality of sets of secondary windings, and each DC
power module may 16 then comprise a rectifier circuit connected to one set of secondary windings. The DC voltage 17 source of each module may thus be considered to comprise this set of secondary windings and 18 the corresponding rectifier circuit. Alternatively, a separate transformer may be used for each 19 module. Depending on the field of application, it is even conceivable to use other kinds of DC
voltage sources, even batteries.
22 To improve power ratio, the high-voltage power supply may comprise a first and a second 23 multi-secondary transformer, the first transformer and the second transformer being configured 24 to provide secondary voltages that are phase-shifted between the transformers. In the case of a three-phase mains grid, this may be accomplished, e.g., by using a star-star configuration for 26 the first transformer and a delta-star configuration for the second transformer, resulting in 27 twelve-pulse rectification. Other suitable schemes for achieving a phase shift are well known in 28 the art.
The present invention also provides a method of operating a high-voltage power supply as 31 described above. The method comprises, for each power module:
32 setting the reference voltage;
22294238.2 8 CA Application Blakes Ref.: 78680/00001 1 measuring and processing the actual DC link voltage;
2 comparing the DC link voltage and the reference voltage to derive a difference signal;
3 from the difference signal, deriving an actuating signal;
4 measuring an actual output current and/or the actual input voltage;
from the actuating signal, deriving driving signals for the DC-DC converter, taking into 6 account the measured output current andlor input voltage; and 7 driving each DC-DC converter by said driving signals to actively control said output 8 voltage.
In particular, as outlined above, the driving signals may implement a duty cycle determined, 11 inter alia, by the actuating signal, the output current and the input voltage.
13 The high-voltage power supply described above may advantageously be used as a power 14 supply for a gyrotron, in particular, as its cathode power supply.
Accordingly, the present invention also relates to a gyrotron. Generally, a gyrotron has at least a cathode, a body 16 electrode, and a collector electrode, and advantageously the power supply is connected 17 between the cathode and the collector electrode.
19 While a particular application for a gyrotron has been described, there are also other fields of applications where a highly stable high-voltage power supply capable of handling rapid current 21 changes is needed, and the power supply of the present invention may be employed in such 22 other fields as well.
Preferred embodiments of the invention are described in the following with reference to the 26 drawings, which are for the purpose of illustrating the present preferred embodiments of the 27 invention and not for the purpose of limiting the same. In the drawings, 29 Fig. 1 shows a schematic block diagram of a PSM power supply according to the prior art;
32 Fig. 2 shows a highly schematic sketch of a typical gyrotron together with its 22294238.2 9 CA Application Blakes Ref.: 78680/00001 1 associated power supplies;
3 Fig. 3 shows, in a highly schematic fashion and not to scale, a typical sequence of 4 voltages, currents and rf power in a gyrotron;
6 Fig. 4 shows a schematic block diagram of a power supply according to the present 7 invention;
9 Fig. 5 shows a simplified circuit diagram of a single module of the power supply of Fig.
4; and 12 Fig. 6 shows a diagram illustrating the control loop for controlling the output voltage of 13 a module as shown in Fig. 5.
DESCRIPTION OF PREFERRED EMBODIMENTS
16 Figure 3 illustrates, in a highly schematic fashion and not to scale, a typical sequence of the 17 various voltages and currents involved in the operation of a gyrotron.
At the beginning of the 18 sequence, the cathode power supply MPS and the body power supply BPS are switched to their 19 nominal output voltages to provide a predetermined beam voltage VBK.
Both voltages are actively controlled to ensure stability of these voltages. The anode-cathode voltage vAK provided 21 by the anode power supply APS is initially kept at a value which avoids any significant beam 22 current between the cathode K and the collector C. Only when the gyrotron is to generate 23 electromagnetic radiation, the anode-cathode voltage vAK is switched to a positive value, leading 24 to a rapid rise of the beam current IK and to the emission of electromagnetic radiation with power P .
27 From this diagram it is apparent that the cathode power supply MPS must be capable of rapidly 28 reacting to large variations in beam current IK while providing a stable output 5 voltage with low 29 voltage ripple.
31 Figure 4 shows a simplified block diagram of a high-voltage power supply according to the 32 present invention, which is adapted to satisfy these requirements. The general setup is similar 22294238.2 10 CA Application Blakes Ref.: 78680/00001 1 to the setup of Fig. 1. However, instead of one single multi-secondary transformer, in the 2 present example two multi-secondary transformers 44, 45 in different configurations (YY vs.
3 DY) are used to improve overall power factor. Both transformers 44, 45 are fed by a 4 three-phase mains voltage Vm. The three primary windings of the first transformer 44 are connected in a star ("Y") configuration, while the three primary windings of the second 6 transformer 45 are connected in a delta ("D") configuration. Each transformer comprises a 7 plurality of sets of three secondaries (typically 20-30 such sets), each set being connected in a 8 star configuration. Overall, the first transformer 44 thus has a star-star ("YY") configuration, 9 while the second transformer has a delta-star ("DY") configuration. By this overall configuration of the two transformers 14, 15, the secondary voltages of the two transformers are 11 appropriately phase-shifted with respect to each other to achieve twelve-pulse rectification, 12 which leads to a high power factor of typically more than 0.95.
14 The power supply comprises a plurality of identical DC power modules 40 connected to the secondaries of the transformers 44, 45. Each DC power module comprises a rectifier circuit 41, 16 a boost converter 42, and an output switching circuit 43. The outputs of the modules 40 are 17 connected in a series configuration.
19 Fig. 5 shows a simplified circuit diagram for a single module 40, which will now be described in more detail.
22 Input terminals X10, XI 1, X12 are connected to a set of three secondaries of one of the 23 transformers 44, 45. The rectifier circuit 41 in the form of a full-bridge rectifier, consisting of six 24 diodes D1, rectifies the three-phase secondary voltage.
26 The boost converter 42 comprises two interleaved boost converter circuits having a common 27 input capacitance and charging a common output capacitance, each of the interleaved 28 converter circuits being in turn designed with two switching elements in series to reduce the 29 required voltage rating of each switching element. In more detail, the common input capacitance of the boost converter is formed by a network of capacitors C10, C11, connected in series to 31 enable the use of capacitors having a reduced voltage rating, and symmetrizing resistors R10, 32 R11 in parallel to the two capacitors. The voltage across this input capacitance is called the 22294238.2 11 CA Application Blakes Ref.: 78680/00001 1 input voltage V. The common output capacitance of the boost converter is formed by two 2 series-connected capacitors C20, C21.Each of the upper and lower terminals of the output 3 capacitance is connected to the input capacitance via two groups of elements consisting of a 4 series-connected choke inductance and diode each, the two groups being connected in parallel.
The diodes are forward-biased to allow energy to flow from the input capacitance through the 6 choke inductances into the output capacitance, but not in the reverse direction from the output 7 capacitance back into the input capacitance. Two pairs of series-connected actively controlled 8 converter switches V10, V11 and V20, V21, respectively, here in the form of IGBTs, connect the 9 connection node between an upper choke inductance and upper diode with the connection node between a lower choke inductance and lower diode. By closing these switches, current can flow 11 through these choke inductances while the output capacitance is bypassed. As a result, the 12 upper and lower choke inductance together are subjected to the input voltage, and inductive 13 energy builds up in the choke inductances due to this voltage. When the switches are opened 14 again, the stored energy in the choke inductances is transferred to the output capacitance through the diodes. The resulting output voltage (DC link voltage) Vout across the output 16 capacitance can be much larger than the input voltage. This principle of operation of a boost 17 converter is as such well known in the art.
19 A discharge resistor R40 and a switch K20 enable a rapid discharge of the output capacitance if needed. Output switches V30, V31 in the form of IGBTs selectively provide the DC link voltage 21 Vo to the output terminals X20, X21 of the module. Two reverse-biased, series-connected 22 freewheeling diodes D30, D31 enable a unidirectional current to flow between the output 23 terminals even when the output switches V30, V31 are open. The common node between the 24 two diodes D30, D31 is connected to the common node between the converter switches VIO, V11 and V20, V21, respectively, of each pair of these switches as well as to the common node 26 between the capacitors C20, C21 to provide improved symmetrization.
Additional 27 symmetrization resistors (not shown in Fig. 5) may optionally be provided in parallel to the 28 capacitors C20, C21.
A module controller 51 is fed from input terminals X10, X11 via a small transformer T10.
31 Control signals and diagnostic signals are exchanged between the module controller 51 and an 32 external main control system 53 via a fiber-optic link 52 ensuring galvanic isolation. The module 22294238.2 12 CA Application Blakes Ref.: 78680/00001 1 controller 51 controls the booster switches V10, V11, V20, V21, the discharge switch K20, and 2 the output switches V30, V31 via leads that have been omitted in Fig. 5 for the sake of clarity.
3 In the present example, all switches are implemented as semiconductor switches, in particular, 4 as IGBTs, which will usually be equipped with additional reverse-biased freewheeling diodes in parallel to the collector-emitter path (not shown). However, other types of actively controlled 6 semiconductor switches may be employed, depending on the actual load requirements, such 7 as power MOSFETs etc.
9 The power supply is operated as follows: Depending on the desired total output voltage Vtot and on the status of the modules, the main control system selects whether all or only a part of the 11 modules shall be involved in providing the desired total output voltage Vtot. The main control 12 system accordingly provides control signals to the module controllers 51 of the individual 13 modules via the fiber-optic link 52. Each module controller drives the converter switches 14 V10-V21 of its associated module to charge the output capacitance C20, C21 to a reference DC link voltage Vref determined by the main control system. This reference voltage is set to the 16 same value in all modules. It corresponds to the desired total output voltage Vtot, divided by the 17 number of involved modules. The output switches of the involved modules are then closed to 18 provide the DC link voltages of the modules to their outputs, so as to provide the sum of the DC
19 link voltages at the output of the power supply. During normal operation, and in particular during individual current pulses delivered by the power supply, the output switches remain 21 closed and are not operated, in contrast to prior-art devices, where PWM
is implemented at the 22 output. switches to provide voltage regulation. Instead, regulation of the total output voltage is 23 carried out by regulating the DC link voltages Vow supplied by the boost converters in a 24 feedback control circuit implemented in module controller 51.
26 The feedback control circuit 60 is illustrated schematically in Fig. 6.
The actual DC link voltage 27 Võt (in terms of control theory, the controlled variable of the control loop) is determined by a 28 suitable voltage sensor 65. The measured DC link voltage is subjected to a low-pass filter 64 to 29 filter out the switching frequency of the boost converter and its harmonics, and the filtered DC
link voltage is compared to the reference voltage Vref in a comparator 61. The difference Vdiff of 31 these two voltages is fed to a PI controller 62, whose controller output signal Vctri (in terms of 32 control theory, the actuating variable of the control loop) is fed to a calculating unit 63 (the 22294238.2 13 CA Application Blakes Ref.: 78680/00001 1 actuator of the control loop). An input voltage sensor 64 measures the input voltage Vin, and 2 an output current sensor measures the output current lout. These signals (corresponding to the 3 main disturbance variables of the control loop) are also fed to the calculating unit 63. From the 4 controller signal V et rt, from the input voltage V1, and from the output current km, the calculating unit 63 calculates a duty cycle (i.e., the ratio of the time during which the switches of 6 the converter are closed and the cycle time of the converter) and drives the converter switches 7 V 1 0- V 2 1 according to this duty cycle.
9 The controlled variable Võt is a quadratic function of the duty cycle. In order to achieve a linear control path, the duty cycle should therefore be a square root function of the actuating variable 11 Vcid. In this manner, a linear dependence between controller signal Vctrl (actuating variable) and 12 DC link voltage Vnut (controlled variable) results. As will be detailed further below, the boost 13 converter is preferably operated in discontinuous mode (i.e., the current in the booster choke 14 inductances substantially decreases to zero before the next booster cycle starts). The duty cycle in discontinuous mode may be calculated according to the following formula:
2 = iota = Livoster (Vcrri ¨
D
Tbooster = V2 in 17 (Equation 1).
19 Here, Tbooster is the booster cycle time (the inverse of the boost converter operating frequency, which is kept constant during operation), and Lbooster is the total choke inductance of the boost 21 converter (in the specific arrangement illustrated here, Lbooster = L10 =L11=L20=L21). Both 22 pairs of converter switches in the interleaved converter circuits are operated at the same duty 23 cycle, but phase-shifted by 1800 relative to each other.
An important property of the calculating unit is that the most important disturbance variables, 26 lnut and V,n, directly act on the actuator of the control loop. For example, in the case of a sudden 27 rise of the output load, the output current will also rise rapidly, while the DC link voltage will 28 drop slowly due to the presence of the large output capacitance. Since the increased output 29 current directly acts on the actuator, the duty cycle will be increased almost instantaneously, and the voltage drop will stop within a single booster cycle time Tbooster.
The PI controller can 31 now correct the (relatively small) voltage drop that has already occurred.
22294238.2 14 CA Application Blakes Ref.: 78680/00001 1 In order to ensure a rapid response to load changes, the boost converter should be operated in 2 discontinuous mode during normal operation. This measure also improves stability of the 3 regulation of the DC link voltage, and minimizes switching losses on the converter switches, 4 since these are always switched on at zero current. This poses certain restrictions on the booster choke inductances. In particular, the total choke inductance should not exceed a 6 certain critical value, which is well known in the art and depends on the desired operating point 7 as follows:
i14,1 = (Vour ¨ Vin) = Tbooster Latt = _______________ 2 9 2 = /out Voia (Equation2).
11 On the other hand, the choke inductance should not be too small in order to keep the input 12 current to low figures. This calls for a choice of choke inductance below but close to the critical 13 choke inductance Lcrit=
The PI controller 62 can be disabled selectively in certain situations where feedback control 16 would be inappropriate. One such situation is the case of a missing output load (no-load case), 17 if at the same time the DC link voltage V01 is higher than the reference voltage Vref . While the 18 controller is disabled, the output capacitance may be discharged down to the reference voltage 19 by closing the discharge switch K20. Once the reference voltage Vref is reached again, the controller is enabled again.
22 In order to enable controlled ramp-up of the output voltage in the no-load case, e.g., after a 23 positive change of the reference voltage Vref, particular measures are required, since Equation 24 (1) implies that the duty cycle will be zero as long as the output current is zero. In order to overcome this problem, it is possible to set the current in Equation (1) to some predetermined 26 minimum value (e.g., 1-2% of the maximum output current) if the actual measured output 27 current is smaller than this minimum value.
29 Particular measures are required for power-up. A possible power-up sequence may be implemented as follows: The input capacitance CIO, 011 and the output capacitance C20, C21 31 are initially charged to the nominal voltage of Vin via step-start switches and a charging resistor 22294238.2 15 CA Application Blakes Ref.: 78680/00001 1 (not shown in Fig. 5), as they are well known in the art. The boost converter switches remain 2 disabled until all capacitances are charged to approximately the nominal voltage of Võ, . Only 3 then the boost converter starts to operate. The boost converter is initially operated at constant 4 duty cycle, until the reference voltage is reached across the output capacitance. Only then closed-loop control starts.
7 Operating conditions of the modules are continuously supervised, and any module is switched 8 off and possibly replaced by another (so far idle) module if a fault condition is detected. In 9 particular, a fault condition is assumed if the booster input voltage or the booster output voltage is outside a predetermined range, or if the output current exceeds a predetermined maximum 11 value. In addition, temperature, desaturation etc. may also be supervised.
13 The output of each module may be provided with a small output snubber (not shown in Fig. 5) in 14 order to limit the current surge in the module in the case of a short circuit. This snubber should, however, be kept as small as possible in order not to compromise the step response under load 16 changes.
18 Actual values of capacitances, inductances, resistors etc. will largely depend on the concrete 19 application and on the desired operating point.
21 The above description is only for illustrative purposes, and a number of modifications can be 22 made without departing from the scope of the present invention. In particular, the boost 23 converter design can be different from the design as described above. In the simplest case, a 24 single converter switch may be used in conjunction with a single choke inductance, a single diode and a single output capacitor, as it is well known in the art and illustrated schematically in 26 the box symbolizing module 40 in Fig. 6. Different controller types than PI controllers may be 27 employed, such as PID controllers. All diodes (acting as passive switches) may be replaced by 28 active switching elements such as transistors if desired. The rectifier circuit may be designed 29 differently, e.g., as an actively controlled thyristor rectifier circuit. Instead of single-quadrant output switching circuits, as in the above-described embodiment, which allow only for unipolar 31 voltage and unidirectional current, also two-quadrant output switching circuits allowing for 32 bipolar voltages at unidirectional current or for unipolar voltage at bidirectional currents or even 22294238.2 16 CA Application Blakes Ref.: 78680/00001 1 four-quadrant output switching circuits allowing for arbitrary sign of both output voltage and 2 output current may be employed. Two-quadrant switching may be useful, e.g., for inverse 3 voltage operation to reduce currents after a short circuit has occurred, or for driving capacitive 4 loads such as a control electrode of a vacuum tube. Suitable output switching circuits for two-quadrant or four-quadrant operation are disclosed, e.g., in EP 2 099 127 Al, in particular in 6 its Figures 5-7, and the disclosure of that document is incorporated herein by reference in its 7 entirety for teaching suitable output switching circuits for two- and four-quadrant operation.
8 Suitable output switching circuits and modes of operation of two- and four-quadrant output 9 switching circuits are also disclosed in WO 95/10881 Al and EP 1 553 686 Al.
11 In other embodiments, depending on the intended field of use, the boost converter may be 12 replaced by any other form of switched DC-DC converter. This might be a buck converter, a 13 buck-boost converter, a SEPIC etc. Such switched-mode DC-DC converters are well known in 14 the art. The operating principles as outlined above remain the same with such DC-DC
converters. In particular, also with other types of DC-DC converters it is possible to regulate the 16 DC link voltage of each module by controlling the DC-DC converter, instead of employing PWM
17 and/or CSM schemes to regulate the total output voltage of the complete power supply.
19 The proposed power supply may not only be employed as the main power supply of a gyrotron, but may be used in any application which require a stabilized high voltage which is stable even 21 under rapid load changes. Examples include the cathode or anode power supply of any other 22 type of vacuum tube having a control electrode which may rapidly change the current in the 23 tube.
22294238.2 17 CA Application Blakes Ref.: 78680/00001 1 List of references 3 10 : power module 4 11 : rectifier circuit 12 : smoothing capacitance 6 13 : output switching circuit 7 14 : transformer 8 2 : gyrotron 9 FPS : filament power supply MPS : cathode power supply 11 BPS : body power supply 12 APS : anode power supply 13 F : filament 14 K : cathode A : anode 16 B : body electrode 17 C : collector 18 VK : cathode voltage 19 VBK : beam voltage VAK : anode-cathode voltage 21 IK : beam current 22 RI : radiated power 23 40 : power module 24 41: rectifier circuit 42 : boost converter 26 43 : output switching circuit 27 X10, X11, X12 : input terminals 28 X20, X21 : output terminals 29 Dl: rectifier diode C10, C11 : input capacitors 31 R10, R11 : divider resistors 32 L10, L11, L20, L21 :choke inductances 22294238.2 18 CA Application Blakes Ref.: 78680/00001 1 V10, V11, V20, V21 : converter switches 2 D10, D11, D20, D21 : converter diodes 3 020, 021 : output capacitors 4 R20 : dissipating resistor K40 : dissipating switch 6 V30, V31 : output switches 7 D30, D31 : freewheeling diodes 8 51 : module controller 9 52 : fiber optic link V,n : input voltage 11 Vont : DC link voltage 12 Vtot : total output voltage 13 Vref : reference voltage 14 Vdiff : voltage difference Vctri : controller output signal 16 lout : output current 17 60 : control circuit 18 61 : comparator 19 62: PI controller 63 : calculating unit 21 64 : input voltage sensor 22 65 : output voltage sensor 23 66 : output current sensor 22294238.2 19
Claims (15)
1 A high-voltage power supply, comprising:
a plurality of DC power modules (40) having their outputs connected in a series configuration, each power module (40) comprising a DC voltage source (41), a DC-DC
converter (42) receiving an input voltage (V in) from said DC voltage source and providing a DC link voltage (V out), and an output switching circuit (43) for selectively connecting said DC link voltage (V out) to the output of said power module, characterized in that the power supply comprises, for each DC power module, a feedback control circuit (60) adapted to provide driving signals to the DC-DC
converter (42) of said power module (40) in a manner that regulates said DC link voltage (Vout) to a predetermined reference voltage (V ref).
a plurality of DC power modules (40) having their outputs connected in a series configuration, each power module (40) comprising a DC voltage source (41), a DC-DC
converter (42) receiving an input voltage (V in) from said DC voltage source and providing a DC link voltage (V out), and an output switching circuit (43) for selectively connecting said DC link voltage (V out) to the output of said power module, characterized in that the power supply comprises, for each DC power module, a feedback control circuit (60) adapted to provide driving signals to the DC-DC
converter (42) of said power module (40) in a manner that regulates said DC link voltage (Vout) to a predetermined reference voltage (V ref).
2. The high-voltage power supply according to claim 1, comprising at least one current sensor for measuring an output current (I out) of said DC power modules, wherein the feedback control circuit is adapted to derive driving signals for the DC-DC converter (42) of each power module taking into account the measured output current (I out).
3. The high-voltage power supply according to claim 1 or 2, wherein each power module comprises an input voltage sensor for determining an input voltage (V in) of the DC-DC converter of said power module, and wherein the voltage control circuit is adapted to derive driving signals for the DC-DC converter (42) of each power module taking into account the measured input voltage (V in).
4. The high-voltage power supply according to claims 2 and 3, wherein the DC-DC
converter is operable at a variable duty cycle, and wherein the feedback control circuit is adapted to calculate the duty cycle taking into account said measured output current and said measured input voltage.
converter is operable at a variable duty cycle, and wherein the feedback control circuit is adapted to calculate the duty cycle taking into account said measured output current and said measured input voltage.
5. The high-voltage power supply according to any of the preceding claims, wherein the DC-DC converter of each power module is a boost converter.
6. The high-voltage power supply according to claim 5, wherein the boost converter (42) of each power module (40) comprises at least two interleaved boost converter circuits adapted to charge a common output capacitance (C20, C21), and wherein the control circuit is operable to operate the boost converter circuits in a synchronous but phase-shifted manner.
7. The high-voltage power supply according to claim 5 or 6, wherein the control circuit (51) is operable to operate the boost converter (42) of each power module (40) in discontinuous mode during voltage regulation.
8. The high-voltage power supply according to any of the preceding claims, comprising a main control system (53) operable to drive the DC-DC converters of different DC power modules in a synchronous but phase-shifted manner.
9. The high-voltage power supply according to any of the preceding claims, comprising a main control system (53) operable to regulate a total output voltage of the power supply during a voltage pulse by only controlling the DC-DC converters of the individual power modules, without applying coarse-step modulation and without applying pulse-width modulation.
10. The high-voltage power supply according to any of the preceding claims, comprising a first and a second multi-secondary transformer (44, 45), the first transformer (44) and the second transformer (45) being configured to provide secondary voltages that are phase-shifted between the transformers so as to improve power ratio.
11. A method of operating a high-voltage power supply according to any of the preceding claims, the method comprising, for each power module (40):
setting the reference voltage (V ref);
measuring and processing the actual DC link voltage (V out);
comparing the DC link voltage (V low) and the reference voltage (V ref) to derive a difference signal (V diff);
from the difference signal, deriving an actuating signal (V ctrl), measuring an actual output current (I out) and/or the actual input voltage (V in);
from the actuating signal (V ctrl), deriving driving signals for the DC-DC
converter (42), taking into account the measured output current (l out) and/or input voltage (V in); and driving each DC-DC converter (42) by said driving signals to actively control said output voltage.
setting the reference voltage (V ref);
measuring and processing the actual DC link voltage (V out);
comparing the DC link voltage (V low) and the reference voltage (V ref) to derive a difference signal (V diff);
from the difference signal, deriving an actuating signal (V ctrl), measuring an actual output current (I out) and/or the actual input voltage (V in);
from the actuating signal (V ctrl), deriving driving signals for the DC-DC
converter (42), taking into account the measured output current (l out) and/or input voltage (V in); and driving each DC-DC converter (42) by said driving signals to actively control said output voltage.
12. The method of claim 11, wherein a total output voltage of the power supply is regulated by only controlling the DC-DC converters of the individual power modules, without applying pulse-step modulation or pulse-width modulation.
13. Use of the high-voltage power supply according to any of claims 1-10 in a gyrotron.
14. A gyrotron comprising a high-power voltage supply of any of claims 1-10.
15. The gyrotron of claim 14, having at least a cathode (K), a body electrode (B), and a collector electrode (C), wherein the high-voltage power supply is connected between the cathode (K) and the collector electrode (C).
Priority Applications (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CA2792702A CA2792702A1 (en) | 2012-10-17 | 2012-10-17 | Stabilized high-voltage power supply |
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CA2792702A CA2792702A1 (en) | 2012-10-17 | 2012-10-17 | Stabilized high-voltage power supply |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| CA2792702A1 true CA2792702A1 (en) | 2014-04-17 |
Family
ID=50483763
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CA2792702A Abandoned CA2792702A1 (en) | 2012-10-17 | 2012-10-17 | Stabilized high-voltage power supply |
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| CA (1) | CA2792702A1 (en) |
Cited By (2)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| WO2018108779A1 (en) * | 2016-12-12 | 2018-06-21 | Avl List Gmbh | Apparatus for testing electrical energy storage systems |
| CN115220511A (en) * | 2022-07-14 | 2022-10-21 | 无锡卓海科技股份有限公司 | High-voltage power supply device of electron gun capable of detecting heating current and emission current of filament |
-
2012
- 2012-10-17 CA CA2792702A patent/CA2792702A1/en not_active Abandoned
Cited By (4)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| WO2018108779A1 (en) * | 2016-12-12 | 2018-06-21 | Avl List Gmbh | Apparatus for testing electrical energy storage systems |
| CN110168897A (en) * | 2016-12-12 | 2019-08-23 | 李斯特内燃机及测试设备公司 | For testing the device of electrical energy storage system |
| CN115220511A (en) * | 2022-07-14 | 2022-10-21 | 无锡卓海科技股份有限公司 | High-voltage power supply device of electron gun capable of detecting heating current and emission current of filament |
| CN115220511B (en) * | 2022-07-14 | 2023-10-31 | 无锡卓海科技股份有限公司 | High-voltage power supply device of electron gun for detecting filament heating current and emission current |
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