JP5558376B2 - Power supply - Google Patents

Description

  The present invention relates to a power supply device used in an ion accelerator that is a discharge device for performing ion acceleration, and more particularly to a power supply device applied to a hall thruster that is an electric propulsion device mounted on an artificial satellite or the like.

  As an ion acceleration device which is a discharge device for performing ion acceleration, particularly an electric propulsion device mounted on an artificial satellite or the like, there are an electromagnetic acceleration type Hall thruster and an electrostatic acceleration type ion thruster. For example, the Hall thruster introduces gas from one of the annular discharge spaces, ionizes the gas in the discharge space, accelerates it, and outputs the ions to the other discharge space. The thrust of the Hall thruster is obtained by the reaction of the ion output. Magnetic flux is formed in the annular discharge space in the radial direction, and due to the Hall effect by this magnetic flux, electrons drift in the circumferential direction of the annular discharge space, and axial movement is suppressed. Thereby, only ions can be accelerated efficiently.

  One of the problems in stably operating the Hall thruster is the occurrence of a discharge oscillation phenomenon. There are several types of vibration phenomena related to the discharge vibration phenomenon. Among these vibration phenomena, there is a phenomenon called discharge vibration in which the current waveform of the anode current vibrates at a frequency of about 10 kHz. This discharge vibration has a significant effect on the stability, reliability and durability of a system equipped with a Hall thruster. Therefore, a control method for suppressing the discharge vibration phenomenon is necessary, and conventionally, a control method for suppressing the discharge vibration has been proposed (for example, see Patent Document 1 below).

  As described in Patent Document 1, discharge oscillation occurs when the anode voltage Va, the magnetic flux density B, and the gas flow rate Q are in a certain relationship. For this reason, the discharge vibration becomes a problem particularly when the operating condition changes, for example, when the ignition of the Hall thruster is started. That is, when the ignition of the Hall thruster is started, as the anode voltage Va rises, it passes transiently through the region of the operating condition where the discharge vibration occurs, and as a result, for example, the protection of the power source works due to the discharge vibration. Startup may not be possible.

  In order to avoid this, a method has been proposed in which the anode voltage and the coil current are simultaneously controlled at the start of ignition to stably ignite (see, for example, Patent Document 1 and Non-Patent Document 1 below). For example, according to Non-Patent Document 1, according to this ignition start-up method, in addition to suppressing discharge oscillation, it is possible to prevent generation of pulsed current by making the magnetic flux density at the moment of ignition relatively weak. The effect is said to be obtained.

JP 2007-177639 A

T.A. Tamida, H .; Osuga, T .; Nakagawa, T .; Ozaki, I .; Suga, K .; Matsui. “Oscillation-Free Operation of Hall Through by the Synchronous Control of Power Conditioners”, Trans. JSAS Space Tech. Japan, Vol. 7, no. iss26 (2009), pp. 47-52.

  As described above, it is important to stabilize the operation of the Hall thruster by suppressing the discharge oscillation by the transient control of the coil current at the start of ignition, and the magnetic flux density necessary for the discharge space is accurately applied. Is Rukoto.

  This magnetic flux density is usually adjusted by controlling the value of the coil current that flows through the coil of the electromagnet for generating the magnetic field. However, there is an exact difference between the coil current at that time and the magnetic flux density actually formed. Has hysteresis characteristics. Therefore, in order to obtain an accurate magnetic flux density when the coil current is changed transiently at the time of ignition start-up, this hysteresis characteristic must be sufficiently grasped.

  When the electromagnet is used in a region where the current value and the magnetic flux density are sufficiently low so as not to reach the magnetic flux saturation, the hysteresis characteristic of the electromagnet does not become a big problem. However, if the electromagnet core is reduced in size and weight to reduce the size of the device, it may be used up to the saturation flux of the core. In such a case, the magnetic flux density generated due to the hysteresis characteristic is Depends on value history.

  Here, a particular problem arises when the ignition is started again after the apparatus is temporarily stopped to reduce the coil current to zero. That is, even if the coil current is set to zero, the core may have a certain magnetic flux density due to the residual magnetic field. In that case, when the ignition is started again, a magnetic flux density stronger than expected is applied, and as a result, it passes transiently through the region of the operating condition where the discharge oscillation occurs, and the stable ignition start-up is performed. There is a possibility that it cannot be raised.

  In the prior art described in Patent Document 1 and Non-Patent Document 1 described above, the influence of the residual magnetic field of the core of the electromagnet is not sufficiently considered. For this reason, in a case where the ignition start-up is repeated after the Hall thruster is temporarily stopped and the coil current is made zero, there is a possibility that stable ignition start-up cannot be performed. This is not limited to the Hall thruster described above, but can be similarly applied to other types of thrusters using electromagnets.

  The present invention reduces the influence of the residual magnetic field of the electromagnet as much as possible even when the ignition is started again after the thruster is temporarily stopped and the coil current is reduced to zero. An object of the present invention is to provide a power supply device that can be used.

The present invention relates to a power supply device for driving and controlling an ion accelerator having an anode electrode, a gas flow rate system, and a magnetic field generating coil, and an anode power supply for generating an electric field in a direction perpendicular to the magnetic field by applying a voltage to the anode electrode. has a coil power source configured is arranged to supply a current to the positive and negative both directions, as well as a control means for controlling the anode power supply and the coil power source to said magnetic field generating coil, the control means controls the coil power supply The direction of the current can be switched, and when starting the ignition of the ion accelerator, prior to this, the direction of the current flowing in the magnetic field generating operation is opposite to the direction of the current flowing to the magnetic field generating coil. Control for flowing a current for reducing the residual magnetic field temporarily is performed.

  According to the present invention, prior to the start-up of the thruster ignition, the residual magnetic field remaining in the electromagnet is reduced by temporarily flowing a current in the reverse direction to the magnetic field generating coil. The influence is sufficiently removed, and stable ignition start-up can always be performed.

It is a block diagram which shows the Hall thruster and its power supply device in Embodiment 1 of this invention. It is explanatory drawing which shows the hysteresis characteristic of the residual magnetic field of the core which comprises an electromagnet. FIG. 2 is a configuration diagram showing a coil power supply for reducing the influence of a residual magnetic field in the power supply device of FIG. 1. In this invention, it is explanatory drawing which shows the operation principle for reducing the influence of a residual magnetic field. It is a block diagram which shows the modification of the coil power supply of FIG. It is a block diagram which shows the coil power supply for reducing the influence of a residual magnetic field in the power supply apparatus of the Hall thruster in Embodiment 2 of this invention. It is a block diagram which shows the modification of the coil power supply of FIG. It is a block diagram which shows the coil power supply for reducing the influence of a residual magnetic field in the power supply apparatus of the Hall thruster in Embodiment 3 of this invention. FIG. 9 is a waveform diagram of an alternating current that flows through a coil in order to reduce the influence of a residual magnetic field in the configuration of FIG. 8. It is explanatory drawing which shows a mode that the residual magnetic field of a core is reduced gradually in the structure of FIG. It is explanatory drawing which shows the relationship between the coil current sent through an electromagnet, and the change of the magnetic flux density of the discharge space accompanying this in the power supply apparatus of the Hall thruster in Embodiment 4 of this invention.

Embodiment 1 FIG.
FIG. 1 is a configuration diagram showing a Hall thruster and its power supply apparatus according to Embodiment 1 of the present invention.

  The Hall thruster 1 includes an inner coil 11 and an outer coil 12 arranged concentrically as magnetic field generating coils, an annular anode electrode 14 arranged between the inner coil 11 and the outer coil 12, and an annular ion acceleration. The inner ring 15 and the outer ring 16 forming the region, the pole piece 17 for adjusting the magnetic flux density provided on the open end side of the inner ring 15 and the outer ring 16, and the gas flow rate regulator 18 for configuring the gas flow rate system Have An annular channel 19 serving as an ion acceleration region is formed in a space surrounded by the inner ring 15 and the outer ring 16, and the inner coil 11 and the outer coil 12 are wound around the core 10 so that the electromagnet It is configured. Further, the hole thruster 1 is provided with a hollow cathode 3 which is a cathode for supplying electrons to accelerate ions.

  Then, gas is supplied from the bottom surface side of the channel 19, and the gas is ionized in the channel 19, and the ions are accelerated by the voltage applied between the hollow cathode 3 and the anode electrode 14, and the channel 19 is moved to the open end side. Thrust is obtained by being ejected as an ion beam. In this case, the applied voltage is the anode voltage Va, and the current flowing at that time is the anode current Ia.

  At that time, in order to efficiently accelerate only ions, electrons are confined in the annular channel 19 by the Hall effect due to the magnetic field formed by the electromagnet including the internal coil 11 and the external coil 12. Further, the magnetic flux density B in the vicinity of the exit end of the channel 19 is maximized so that the magnetic field is applied almost uniformly in the radial direction of the ring by the pole piece 17 and the magnetic circuit such as the pole piece 17 is designed. Each is designed as such. Further, the magnetic flux density is changed by adjusting the current flowing through the internal coil 11 and the external coil 12.

  The power supply device 2 drives and controls the Hall thruster 1 and the hollow cathode 3, and includes an anode power source 21 for applying a predetermined voltage to the anode electrode 14, and an internal coil power source for flowing a predetermined current through the internal coil 11. 22, an external coil power source 23 for supplying a predetermined current to the external coil 12, a gas flow rate control device 25 for controlling the gas flow rate by the gas flow rate regulator 18, and a gas flow rate control device for controlling the gas flow rate supplied to the hollow cathode 3 31, a heater power supply 26 for heating the hollow cathode 3, a keeper power supply 27 for stabilizing a flow of electrons by applying a predetermined voltage to the hollow cathode 3, and a control circuit 28 as a control means for controlling these operations It has.

  Next, the hysteresis characteristics of the core 10 around which the internal coil 11 and the external coil 12 are wound to constitute an electromagnet will be described with reference to FIG.

  First, (1) is a state in which no current flows through the internal coil 11 and the external coil 12 and there is no residual magnetic field of the core 10. When a small amount of current is passed through the coils 11 and 12 from this state, a magnetic flux density is formed as shown in (2). Between (1) and (2), the magnetic flux density increases with respect to the current approximately linearly. Usually, it is used in such a linear region.

  However, when the core 10 is reduced in size and weight and current is passed through such a linear region to obtain as strong a magnetic flux density as possible (state (3) in the figure), the core 10 begins to saturate. The magnetic flux density does not increase linearly even when a current is passed. Then, assume that the apparatus is temporarily stopped in the state of (3) and the coil current becomes zero. In that case, the magnetic flux density does not return to zero, that is, the state of (1) due to the hysteresis characteristic of the core 10, and is in a state of (5) in which a certain amount of magnetic flux remains even though no current is passed. This is the residual magnetic field. The value of the residual magnetic field depends on the past history and the type of the core 10, such as how far the current has flowed. When a current is passed through the coils 11 and 12 in order to restart the ignition of the Hall thruster 1 from the state (5), the state does not pass through the region (2), as in the state (4). The magnetic flux increases with the residual magnetic field of (5) offset. As a result, the operating condition region where the discharge oscillation occurs is passed transiently, and stable ignition startup cannot be performed.

  FIG. 3 shows a configuration of a coil power supply for eliminating such a residual magnetic field from being offset and performing stable ignition startup. In the first embodiment, the internal coil power supply 22 is provided for the internal coil 11 and the external coil power supply 23 is provided for the external coil 12, respectively. Since the basic configurations of 22 and 23 are the same, here, for convenience of explanation, the coils 11 and 12 for magnetic field generation are not distinguished, and the coil 5 and the coil power supplies 22 and 23 are not distinguished. Are simply referred to as a coil power source 6.

  In FIG. 3, the coil power source 6 includes a first current source 61 that passes a direct current Ic in one direction (forward direction) with respect to the coil 5, and a direction opposite to the first current source 61 with respect to the coil 5. And a second current source 62 for flowing a direct current Ic in the negative direction. Both current sources 61 and 62 are connected in parallel to each other, and selection switches 71 and 72 for selecting each current source 61 and 62 are individually connected to each current source 61 and 62. . Then, the control circuit 28 switches on / off the selection switches 71 and 72 of the coil power source 6 to switch the direction of the current Ic flowing through the coil 5.

  That is, when driving the Hall thruster 1, it is necessary to energize the coil 5 to generate a magnetic field, so that the control circuit 28 turns on one selection switch 71 and turns off the other selection switch 72 during this magnetic field generation operation. Thus, the current Ic in one direction (positive direction) flows from the first current source 61 to the coil 5.

  Next, when the drive of the Hall thruster 1 is stopped and the current Ic is set to zero, the magnetic flux density does not return to the zero state due to the hysteresis characteristic of the core 10, and the current Ic flows as shown in FIG. Despite the absence, some magnetic flux remains (5) and there is a residual magnetic field.

  Therefore, the control circuit 28 temporarily turns off one of the selection switches 71 and turns on the other selection switch 72 before the ignition of the Hall thruster 1 again, so that the second current source A direct current Ic is temporarily supplied from 62 to the coil 5 in the opposite direction (negative direction) to the magnetic field generating operation. In FIG. 4, the state (6) is temporarily set by flowing the current Ic in the negative direction from the state (5). From this point, when the current Ic is decreased, the state (7) is obtained. The state (7) is not the same as the state (1) in which the residual magnetic field is completely zero, but the residual magnetic field of the core 10 is sufficiently small as compared with the state (5).

  In order to ignite the Hall thruster 1, one selection switch 71 is turned on again, the other selection switch 72 is turned off again, and one direction (positive direction) from the first current source 61 to the coil 5 is established. When a DC current Ic is passed through the state, the state (8) elapses, and a weak magnetic field suitable for ignition start-up can be realized.

  In the configuration shown in FIG. 3, both the first current source 61 and the second current source 62 are set to have a current capacity so that the same current Ic flows through the coil 5, but the residual current As long as the purpose of sufficiently reducing the magnetic field is achieved, the present invention is not limited to this configuration. For example, the current capacity of the second current source 62 is larger than the current capacity of the first current source 61 as shown in FIG. And a small current Ic may flow in the reverse direction (negative direction) with respect to the coil 5 when the residual magnetic field is reduced.

  As described above, in the first embodiment, when the ignition is started again after the Hall thruster 1 is temporarily stopped and the current flowing through the magnetic field generating coil is made zero, the magnetic field generating prior to that is performed. The residual magnetic field remaining in the core of the electromagnet can be sufficiently reduced by flowing a current in the reverse direction temporarily to the coil. As a result, it is possible to always perform stable ignition startup without the influence of the residual magnetic field.

Embodiment 2. FIG.
FIG. 6 is a block diagram showing a coil power supply portion of the Hall thruster power supply device according to the second embodiment of the present invention. Components corresponding to those in the first embodiment shown in FIG. 3 and FIG. Is attached.

  In the first embodiment, the coil power source 6 is provided with the first and second current sources 61 and 62 in which the directions of the currents flowing to the coil 5 are opposite to each other, It was made to choose. On the other hand, in the second embodiment, the single current source 61 that supplies current to the coil 5 and the direction of the current that flows through the coil 5 during the magnetic field generation operation and when the residual magnetic field is reduced are opposite to each other. And a selector switch 73 for switching the current direction. When the ignition circuit of the hall thruster 1 is ignited again, the control circuit 28 switches the connection of the changeover switch 73 and reverses the magnetic field generation operation from the current source 61 to the coil 5 prior to this. The residual magnetic field is reduced by passing a direct current Ic temporarily.

  Instead of providing the changeover switch 73 as shown in FIG. 6, for example, as shown in FIG. 7, a full bridge inverter 74 is provided between the single current source 61 and the coil 5, and the control circuit 28. Thus, even if the direction of the current flowing through the coil 5 is switched, the same effect can be obtained.

  In the second embodiment, since it is assumed that the current flowing through the coil 5 is once reduced to zero and then the direction of the current is switched, the regenerative path is not particularly described. Since there is a possibility of switching while the current is flowing, it is preferable to provide a regenerative reflux diode or the like.

Embodiment 3 FIG.
FIG. 8 is a configuration diagram showing a coil power supply portion of the Hall thruster power supply device according to the third embodiment of the present invention. Components corresponding to those in the first embodiment shown in FIG. 3 and FIG. Is attached.

  In the first embodiment, the first and second current sources 61 and 62 in which the directions of the currents flowing through the coil 5 are opposite to each other are provided, and the current sources 61 and 62 are selected. On the other hand, in the third embodiment, demagnetization is reliably performed by applying an alternating current to the coil 5 when the residual magnetic field is reduced and gradually reducing the value of the current.

  That is, the coil power supply 6 according to the third embodiment includes a third current source 63 that sends a direct current to the coil 5 in one direction, and a fourth current that passes a positive and negative direction to the coil 5, that is, an alternating current. A current source 64. Both current sources 63 and 64 are connected in parallel to each other, and selection switches 73 and 74 for selecting each current source 63 and 64 are individually connected to each current source 63 and 64. .

  The control circuit 28 needs to generate a magnetic field by energizing the coil 5 in order to drive the Hall thruster 1. Therefore, during this magnetic field generation operation, one selection switch 73 is turned on and the other selection switch 74 is turned off so that the current Ic in one direction (positive direction) flows from the third current source 63 to the coil 5. .

  On the other hand, when the Hall thruster 1 is ignited again, prior to this, one selection switch 73 is turned off and the other selection switch 74 is turned on so that the fourth current source 64 applies to the coil 5. The residual magnetic field is surely demagnetized by applying an alternating current and gradually reducing the current value.

FIG. 9 is a waveform diagram showing an alternating current that flows from the fourth current source 64 to the coil 5 in order to reduce the residual magnetic field. As shown in FIG. 9, when the alternating current is made to gradually decrease in amplitude, as shown in FIG. 10, the residual magnetic field in the state of (5) becomes smaller every cycle of the alternating current, and finally, The magnet is almost completely demagnetized and returns to the state (1).
Such an operation is possible with the circuit configuration shown in FIG. 8, but is not limited to this, and for example, a circuit provided with the inverter 74 shown in FIG. 7 is also possible.

Embodiment 4 FIG.
In the above first to third embodiments, when the Hall thruster 1 is ignited, the residual magnetic field is reduced prior to this. On the other hand, in the fourth embodiment, the residual component of the magnetic field is predicted to some extent, and the direction of the magnetic flux of the Hall thruster 1 is alternately switched every time the ignition start-up of the Hall thruster 1 is performed or every certain operation period. Thus, the influence of the residual magnetic field is reduced.

  As described above, the direction of the magnetic flux only affects the direction of rotation of the electrons, and does not affect the performance of the Hall thruster 1. That is, even if the magnetic flux is applied from the inside to the outside of the channel 19 of the Hall thruster 1 or the magnetic flux is applied from the outside to the inside, the performance is not affected. For example, the Hall thruster 1 is stopped and ignition is started again. Each time, the direction of the magnetic flux is switched. In this case, when the current Ic is passed through the coil 5 until it is close to saturation (state (3) in FIG. 2), a hysteresis characteristic as shown in FIG. 11 appears. This characteristic is predicted, and control is performed so that a magnetic flux density having a required size and direction is applied.

  For example, in FIG. 11, when the Hall thruster 1 is ignited last time, the current flowing through the coil 5 starts from Ic1 and flows to a state close to saturation in (3). Apply current. At the next ignition start-up of the Hall thruster 1, the current flowing through the coil 5 starts from Ic2 and flows to a state close to the saturation of (6), and when the Hall thruster 1 is stopped, the current flows to Ic1.

  In order to implement this, the magnitude of the current Ic flowing through the coil 5 is controlled, and the direction of the current may be switched according to the magnitude of the current Ic. Accordingly, the specific coil power supply 6 employs any of the configurations shown in FIGS. 3 and 5 to 7 described above, and the magnitude of the current Ic supplied from the current sources 61 and 62 by the control circuit 28 is set. In addition to the control, control is performed to switch the direction of the current according to the magnitude of the current Ic.

  Thus, if the direction of the magnetic flux is switched, the torque can be controlled simultaneously. That is, the direction of the magnetic field determines which direction the electrons rotate in the circumferential direction, but this affects the circumferential torque of the Hall thruster 1. In this case, if a magnetic field is applied only in a certain direction, torque in the circumferential direction is accumulated. On the other hand, if an operation for switching the direction of the magnetic field is performed every certain operation period, such torque can be canceled or torque can be positively applied. Torque control is a very important issue in outer space and is extremely useful because torque control can be performed by switching the direction of the magnetic field as in the present invention.

  The present invention is particularly intended to solve the unstable phenomenon at the start of the Hall thruster and the magnetic field control method, and is effective when applied to the Hall thruster. Accordingly, in all of the above-described first to fourth embodiments, an artificial satellite propulsion device called a Hall thruster is described as the ion accelerator.

  However, the present invention may be applied to a case where a device similar to a Hall thruster is used as an ion source device. The present invention is not limited to an annular ion source device, but is a general electric propulsion device or ion acceleration device that accelerates ions by a voltage and restricts the movement of electrons by a magnetic field, such as an ion thruster. It can also be applied to.

1 Hall thruster, 11 internal coil, 12 external coil, 14 anode electrode,
2 power supply devices, 21 anode power supply, 22 internal coil power supply (magnetic field generating coil),
23 external coil power supply (magnetic field generating coil), 28 control circuit (control means),
5 coil for generating magnetic field, 6 coil power supply, 61 first current source, 62 second current source,
63 third current source, 64 fourth current source, 71, 72 selection switch,
73 changeover switch, 74 inverter.

Claims (7)

A power supply device for driving and controlling an ion accelerator having an anode electrode, a gas flow rate system, and a magnetic field generating coil,
An anode power source that generates an electric field in a direction perpendicular to a magnetic field by applying a voltage to the anode electrode, a coil power source configured to allow current to flow in both positive and negative directions with respect to the magnetic field generating coil, and the anode power source and the above Having control means for controlling the coil power supply;
The control means is capable of switching the direction of current by controlling the coil power supply, and when performing ignition start-up of the ion accelerator, prior to this, magnetic field generation is performed for the magnetic field generation coil. A power supply device that performs control to temporarily flow a current for reducing a residual magnetic field in a direction opposite to a direction of a current flowing during operation. The coil power source includes a first current source that causes a current to flow in one direction to the magnetic field generating coil, and a second current that causes a current to flow in the opposite direction to the first current source to the magnetic field generating coil. a current source, said first current source when the magnetic field generation operation, the power supply device according to claim 1, at the time of residual magnetic field reduction is constituted the second current source from a selection switch for selecting respectively, . The power supply device according to claim 2, wherein a current capacity of the second current source is set smaller than a current capacity of the first current source. The coil power supply has a single current source for supplying a current to the magnetic field generating coil and the directions of the currents flowing in the magnetic field generating coil during the magnetic field generating operation and when the residual magnetic field is reduced. The power supply device according to claim 1, comprising a changeover switch for switching a current direction or an inverter. The coil power supply includes a third current source that allows a current to flow in one direction with respect to the magnetic field generating coil;
A fourth current source supplying a current to both positive and negative directions with respect to the magnetic field generating coils, selected when the magnetic field generation operation of the third current source, at the time of residual magnetic field reduces to select the fourth current source, respectively The power supply device according to claim 1, comprising a switch. A power supply device for driving and controlling an ion accelerator having an anode electrode, a gas flow rate system, and a magnetic field generating coil,
An anode power source that generates an electric field in a direction perpendicular to a magnetic field by applying a voltage to the anode electrode, a coil power source configured to allow current to flow in both positive and negative directions with respect to the magnetic field generating coil, and the anode power source and the above Having control means for controlling the coil power supply;
The control means is capable of switching the direction of current by controlling the coil power supply, and is applied to the magnetic field generating coil each time the ion accelerator is ignited or at a certain operation period. A power supply device that controls the direction of the flowing current to be alternately reversed. The ion accelerating device includes a power supply device according to any one of claims 1 to 6 which is an ion accelerator using a Hall effect.

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