WO2021140667A1 - Power supply device and electrical propulsion system - Google Patents

Abstract

This power supply device (100) that supplies power to a Hall thruster (40) which is an electrical propulsion device having a channel (45) that accelerates ions and generates thrust, is provided with an anode power supply (11) that generates a voltage to be applied to an anode electrode (43) provided inside the channel, and a control unit (10) that controls the anode power supply. The control unit controls the anode power supply so that the voltage to be applied to the anode electrode becomes a voltage that is obtained by superposing an alternating current voltage, at a frequency at least 10 times the discharge fluctuation of an anode current that is the current flowing through the anode electrode, on a direct current voltage.

Description

Power supply and electric propulsion system

The present invention relates to a power supply device and an electric propulsion system that supply electric power to a hall thruster, which is an electric propulsion device mounted on an artificial satellite or the like.

The Hall thruster introduces gas from one of the channels, which is an annular discharge space, ionizes the gas in the channel, accelerates it, and outputs it to the other of the channels. The thrust of the Hall thruster is obtained by the reaction of the output of this ion. A magnetic flux is formed in the channel in the radial direction, and due to the Hall effect due to this magnetic flux, electrons drift in the circumferential direction of the channel, and the movement in the axial direction is suppressed. This makes it possible to efficiently accelerate only the ions.

One of the problems in operating the Hall thruster stably is the occurrence of the vibration phenomenon of the anode current. There are several types of anode current vibration phenomena, and vibrations with frequencies of several kHz to 30 kHz are called discharge vibrations, from the viewpoint of power supply design and electromagnetic compatibility (EMC), and , It becomes a big problem because of the influence on the stability and reliability of the system equipped with the Hall thruster. Therefore, a control method for suppressing this discharge vibration phenomenon is required. For example, Patent Document 1 describes a method for suppressing discharge vibration.

Japanese Unexamined Patent Publication No. 2007-177639

As described in Patent Document 1, discharge vibration occurs when the anode voltage, the magnetic flux density, and the gas flow rate have a certain relationship. Further, the discharge vibration can be suppressed to some extent by appropriately setting the anode voltage Va, the gas flow rate Q, and the magnetic flux density B determined by the coil current Ic. That is, there is a stable region in which the discharge vibration is sufficiently reduced by the combination of Va, Q and Ic. Normally, by controlling Va, Q and Ic inside this stable region, stable operation without discharge vibration is possible. For example, when Va and Q are set to certain values, stable operation is possible by setting Ic in the stable region.

However, since this stable region strongly depends on the state of the Hall thruster channel, this stable region changes when the Hall thruster is operated for a long time. This secular change is due in part to the wear of the Hall thruster channels. For this reason, when the Hall thruster is operated for a long time and the channel changes over time, the stable operating region in which discharge vibration does not occur also changes at the same time, and there is a problem that control becomes impossible.

The present invention has been made in view of the above, and an object of the present invention is to obtain a power supply device capable of suppressing discharge vibration of the anode current and realizing stable operation regardless of the state of the Hall thruster.

In order to solve the above-mentioned problems and achieve the object, the present invention is a power supply device for supplying power to an electric propulsion device having a channel which is a discharge space for accelerating ions to generate thrust, and in the channel. It is provided with an anode power supply that generates a voltage applied to the anode electrode provided in the above, and a control unit that controls the anode power supply. The control unit controls the anode power supply so that the voltage applied to the anode electrode is an AC voltage whose frequency is 10 times or more the discharge vibration of the anode current, which is the current flowing through the anode electrode, superimposed on the DC voltage. To do.

The power supply device according to the present invention has the effect of suppressing the discharge vibration of the anode current and realizing stable operation regardless of the state of the Hall thruster.

The figure which shows the configuration example of the electric propulsion system realized by applying the power supply device which concerns on Embodiment 1. The figure which shows an example of the processing circuit which realizes the control part of the power supply device which concerns on Embodiment 1. The figure which shows an example of the discharge vibration of the anode current generated in a general Hall thruster. The figure which shows the main part of the electric propulsion system which concerns on Embodiment 1. The figure which shows an example of the anode voltage and the anode current output by the anode power source of the power supply device which concerns on Embodiment 1. The waveform of the discharge vibration of the anode current shown in FIG. 3 is shown with the horizontal axis as the frequency. FIG. 1 for explaining the operation of the power supply device according to the first embodiment suppressing the discharge vibration of the anode current. FIG. 2 for explaining the operation of the power supply device according to the first embodiment suppressing the discharge vibration of the anode current. The figure which shows the main part of the electric propulsion system which concerns on Embodiment 2. The figure which shows the main part of the electric propulsion system which concerns on Embodiment 3. The figure which shows the main part of the electric propulsion system which concerns on Embodiment 4. The figure which shows an example of the anode power source which realizes the electric propulsion system which concerns on Embodiment 4. The figure for demonstrating the electric propulsion system which concerns on Embodiment 5. The figure which shows the main part of the electric propulsion system which concerns on Embodiment 5. The figure which shows the main part of the electric propulsion system which concerns on Embodiment 7.

Hereinafter, the power supply device and the electric propulsion system according to the embodiment of the present invention will be described in detail with reference to the drawings. The present invention is not limited to this embodiment.

Embodiment 1.
FIG. 1 is a diagram showing a configuration example of an electric propulsion system realized by applying the power supply device according to the first embodiment. The electric propulsion system 300 according to the first embodiment includes a hollow cathode 30, an electric propulsion device, a Hall thruster 40, and a power supply device 100 that supplies electric power to the hollow cathode 30 and the Hall thruster 40. FIG. 1 shows a cross section of a magnetic layer type Hall thruster called an SPT (Stationary Plasma Thruster) type, which is common as a Hall thruster 40. Further, the gas supply system to the Hall thruster 40 is also shown. The electric propulsion system 300 shown in FIG. 1 shall be mounted on an artificial satellite.

The power supply device 100 will be described. The power supply device 100 includes a control unit 10, an anode power supply 11, an external coil power supply 12, an internal coil power supply 13, a heater power supply 14, a keeper power supply 15, a cathode side flow rate regulator 16, and an anode side flow rate regulator. It is provided with 17.

The control unit 10 controls the operations of the anode power supply 11, the external coil power supply 12, the internal coil power supply 13, the heater power supply 14, the keeper power supply 15, the cathode side flow rate regulator 16, and the anode side flow rate regulator 17. The control unit 10 is realized by, for example, a processing circuit including the processor 201 and the memory 202 shown in FIG. When the control unit 10 is realized by the processing circuit shown in FIG. 2, a program for operating as the control unit 10 is stored in the memory 202 in advance, and the processor 201 reads the program from the memory 202 and executes the program. The control unit 10 is realized. The processor 201 is a CPU (also referred to as a Central Processing Unit, a central processing unit, a processing unit, an arithmetic unit, a microprocessor, a microcomputer, or a DSP (Digital Signal Processor)). The memory 202 is non-volatile, for example, RAM (Random Access Memory), ROM (Read Only Memory), flash memory, EEPROM (Erasable Programmable Read Only Memory), EEPROM (registered trademark) (Electrically Erasable Programmable Read Only Memory), and the like. Alternatively, it is a volatile semiconductor memory.

The anode power supply 11 applies a voltage to the anode electrode 43 included in the Hall thruster 40 described later. The external coil power supply 12 applies a voltage to the external coil 42 included in the Hall thruster 40 described later. The internal coil power supply 13 applies a voltage to the internal coil 41 included in the Hall thruster 40 described later. The heater power supply 14 supplies electric power to a heater for heating the inside of the hollow cathode 30. The keeper power supply 15 supplies electric power to a keeper electrode provided on the electron emitting side of the hollow cathode 30. The cathode side flow rate regulator 16 adjusts the amount of gas flowing into the hollow cathode 30. The anode-side flow rate regulator 17 adjusts the amount of gas flowing into the Hall thruster 40.

Next, the Hall thruster 40 will be described. The Hall thruster 40 has a channel 45 which is an annular discharge space. The Hall thruster 40 is supplied with gas from one of the channels 45, specifically from the side where the anode electrode 43 is provided, and this gas is ionized in the channel 45 to accelerate and output to the other. Get thrust with. For example, the Hall thruster 40 in FIG. 1 is supplied with Xe gas.

A voltage is applied between the hollow cathode 30 which is a cathode and the anode electrode 43 in order to accelerate the ions in the channel 45. This is the anode voltage Va. The current that flows when accelerating the ions is the anode current Ia. In order to efficiently accelerate only the ions, the electrons are confined in the channel 45 by the Hall effect of the magnetic field. This magnetic field is formed by electromagnets, namely the internal coil 41 and the external coil 42, provided inside and outside the channel 45. Further, this magnetic field is designed to be applied substantially uniformly in the radial direction of the annulus of the channel 45 by the pole piece 44 provided near the outlet of the channel 45. Further, the Hall thruster 40 is designed so that the magnetic flux density B near the outlet of the channel 45 is the highest by the magnetic circuit formed including the pole piece 44 and the like. Normally, a magnetic circuit including a pole piece 44 is constructed of electromagnetic soft iron.

The above electromagnet may be composed of permanent magnets only inside, only outside, or partly. Generally, the magnetic flux density is changed by adjusting the coil current Ic, which is the current flowing through the internal and external electromagnets. The coil current Ic is generally driven by a constant current source, and by controlling the coil current Ic, the magnetic flux density formed inside the channel 45 is controlled.

Since the Hall thruster 40 accelerates and injects only ions, an electron source for injecting electrons at the same time to maintain electrical neutrality is required. The hollow cathode 30 shown in FIG. 1 is this electron source. A positive voltage of about 200 to 300 V is applied to the anode electrode 43 of the Hall thruster 40 with respect to the hollow cathode 30. Ions are accelerated by the electric field generated inside the channel 45 of the Hall thruster 40 due to the potential difference between the hollow cathode 30 and the anode electrode 43.

Normally, a DC (Direct Current) voltage is applied to the anode electrode 43. However, even though the DC voltage is applied, the phenomenon that the current vibrates violently occurs. This is the so-called discharge vibration phenomenon. FIG. 3 shows the situation. FIG. 3 is a diagram showing an example of the discharge vibration of the anode current generated in a general Hall thruster, and shows the relationship between the anode voltage and the anode current when the discharge vibration occurs. As shown in FIG. 3, in the discharge vibration, the anode voltage is a constant value, but the anode current fluctuates greatly. If the impedance of the power supply is not large enough, the anode voltage will fluctuate slightly due to the influence of current fluctuations, but the fluctuation is usually designed to be sufficiently small.

Theoretically, this fluctuation phenomenon has been explained in detail. The cause of the vibration is the fluctuation of the plasma density inside the Hall thruster, and very simply, the discharge is turned on and off. The frequency of this vibration depends on various parameters related to the Hall thruster discharge. Therefore, the frequency of vibration can fluctuate depending on operating conditions such as coil current and gas flow rate, Hall thruster state, and aging deterioration, but it does not fluctuate so much. However, depending on the conditions, the amplitude of this vibration becomes very large, which affects the operation of the power supply, the EMC, the life of the Hall thruster, and the like.

FIG. 4 is a diagram showing a main part of the electric propulsion system 300 according to the first embodiment. In FIG. 4, among the components shown in FIG. 1, only the Hall thruster 40, the hollow cathode 30, and the anode power supply 11 are described, and the description of other components is omitted.

Here, in the circuit diagram shown in FIG. 1, some power supplies including the anode power supply 11 are shown as components, but the wiring on the primary side thereof is omitted. The electric system of an artificial satellite is connected to a DC system generally called a satellite bus, and receives power from there. It should be noted that each power source constituting the power supply device 100 is also connected to this satellite bus on the primary side and receives electric power from the satellite bus.

The anode power supply 11 according to the first embodiment shown in FIG. 4 has a configuration in which a DC power supply 111 and an AC power supply 112 are connected in series. With such a power supply configuration, when the AC power supply 112 applies an AC voltage having a frequency sufficiently higher than the frequency of discharge vibration, for example, 10 times, to the DC voltage from the DC power supply 111, the output waveform of the voltage is, for example. A waveform as shown in FIG. 5 can be obtained. That is, the anode power supply 11 outputs a voltage having a waveform similar to the anode voltage shown in FIG. FIG. 5 is a diagram showing an example of the anode voltage and the anode current output by the anode power supply 11 of the power supply device 100 according to the first embodiment.

The inventor has found that when the Hall thruster 40 is driven by a voltage waveform in which such high-frequency alternating current is superimposed, the amplitude of current fluctuation due to low-frequency discharge vibration becomes small as shown in FIG. Compared with FIG. 3 in which the high frequency alternating current is not superimposed, when the high frequency alternating current is superimposed, the amplitude of the low frequency current fluctuation due to the discharge vibration becomes smaller as shown in FIG.

The mechanism of this phenomenon is as follows. By applying a vibration having a frequency higher than the frequency of the discharge vibration (several kHz to several tens of kHz) to the DC voltage, the diffusion of electrons under the Reynolds stress is promoted, so that the viscosity of the plasma increases. As a result, the fluctuation of the plasma is suppressed, and the current fluctuation of several kHz to several tens of kHz, which is the discharge vibration peculiar to the Hall thruster 40, is suppressed.

There are several types of current vibration phenomenon of the Hall thruster 40 depending on its physical mechanism. First, there is "discharge vibration" that the power supply device 100 according to the present embodiment is trying to suppress, and the frequency is set to several kHz to several tens of kHz depending on the shape and conditions of the Hall thruster. This phenomenon is caused by fluctuations in plasma density within the Hall thruster.

Next, there is vibration of 100 kHz to 1 MHz called transient vibration. It is said that this is due to the time constant of the ions passing through the acceleration region of the Hall thruster. Further, a phenomenon called electron drift vibration occurs at 1 MHz to 10 MHz. This is due to the non-uniformity of electrons in the circumferential direction of the annulus in the acceleration region of the Hall thruster, which is due to the non-uniformity of the magnetic field and gas density in the circumferential direction.

In the higher frequency region, there are electron cyclotron vibration (around 1 GHz) and Langmuir vibration (0.1 GHz to 10 GHz). These are not the vibrations generated by the operation of the Hall thruster 40, but the vibration phenomena generated in the bulk plasma itself.

The power supply device 100 according to the present embodiment uses transient vibration and electron drift vibration, which are vibrations in the MHz region or lower, in order to suppress discharge vibration. The waveform of the discharge vibration of the anode current shown in FIG. 3 is as shown in FIG. 6 when the horizontal axis is represented as a frequency. From FIG. 6, it can be seen that peaks exist in the discharge vibration region of 3 kHz to 50 kHz, the transient vibration region of 100 kHz to 300 kHz, and the electron drift vibration region of 1 MHz to 2 MHz, and the vibration phenomenon appears in these regions. ..

In this state, the power supply device 100 applies, for example, the circuit (anode power supply 11) shown in FIG. 4 to superimpose a high frequency on the voltage waveform. For example, assuming that an alternating current of 200 kHz is superimposed, the vibration of the current increases at a frequency close to 200 kHz as shown in FIG. At the same time, the vibration component of the discharge vibration existing at 3 kHz to 50 kHz is reduced. FIG. 5 shows this in the time domain. It can be considered that this is because the discharge vibration is suppressed because the vibration is increased by applying a frequency close to the transient vibration in the vicinity of 200 kHz and the electron diffusion in the transient phenomenon is promoted. Note that FIG. 7 is a first diagram for explaining an operation in which the power supply device 100 according to the first embodiment suppresses the discharge vibration of the anode current.

Similarly, the discharge vibration can be suppressed by using the region of the electron drift vibration. FIG. 8 shows an example of a waveform when the anode power supply 11 of the power supply device 100 superimposes an AC voltage of 1.3 MHz on the anode voltage. In this case as well, as in the case of superimposing the AC voltage around 200 kHz shown in FIG. 7, the intensity of the discharge vibration is reduced instead of being promoted and increased by the electron drift vibration of 1 MHz to 2 MHz. Note that FIG. 8 is a second diagram for explaining the operation of the power supply device 100 according to the first embodiment suppressing the discharge vibration of the anode current.

In this way, by superimposing the alternating current in the frequency band where transient vibration or electron drift vibration occurs on the power supply voltage, that is, the anode voltage of direct current, it is possible to suppress the current vibration intensity of the discharge vibration in a completely different frequency region. Become.

Note that the document "Japanese Unexamined Patent Publication No. 2013-222578" describes a technique of applying a voltage obtained by superimposing an AC voltage on a DC voltage to an anode electrode of a Hall thruster.

However, the technique described in the above document and the technique for generating the anode voltage by the power supply unit 100 according to the present embodiment are different. The technique described in the above document attempts to control the frequency of discharge vibration by superimposing an AC voltage having a frequency close to the frequency of discharge vibration on a DC voltage. In that case, it does not matter whether the intensity of the vibration becomes stronger or weaker (generally, superimposing a frequency higher than the frequency of the original discharge vibration lowers the intensity, and superimposing a lower frequency increases the intensity). On the other hand, the frequency of the AC voltage superimposed on the DC voltage when the power supply device 100 generates the anode voltage is different from the frequency of the discharge vibration as described above. That is, the power supply device 100 reduces the intensity of the discharge vibration by superimposing the frequency of the vibration region based on another physical mechanism, which is completely different from the frequency of the discharge vibration.

Although it was stated that the frequencies are completely different, as shown in FIG. 6, each vibration region is limited to some extent due to the physical phenomenon on which they are based. For example, transient vibration is generally set to 100 kHz or higher. Therefore, it can be seen that it is necessary to superimpose an AC voltage having a frequency of 5 times or more, preferably 10 times or more the frequency of the discharge vibration to be suppressed. The current waveform of discharge vibration can be easily observed by observing it on the time axis using an oscilloscope, for example, but it is difficult to observe the frequency of transient vibration or electron drift vibration in the time domain because of its high frequency. Therefore, it is practically useful to use the frequency of discharge vibration as a control index.

On the other hand, when the current waveform is observed with a spectrum analyzer, for example, the characteristics shown in FIG. 6 can be observed, and the frequencies of transient vibration or electron drift vibration can be roughly identified. If the operation as shown in FIG. 7 or 8 is intended, it is appropriate to apply the AC waveform in accordance with the frequency of the transient vibration or the electron drift vibration. Compared to discharge vibration, transient vibration and electron drift vibration do not have a clear frequency, and their spectral width is relatively wide, so they are approximately 0.5 to 2 times the center value of those frequencies. By applying a frequency in the range of, the effect desired by the present invention can be obtained. The range of approximately 0.5 to 2 times the center value of the frequency corresponds to the frequency band in which transient vibration or electron drift vibration occurs. That is, the range of about 0.5 to 2 times the center value of the frequency at which the transient vibration appears corresponds to the frequency band where the transient vibration occurs, and is approximately 0 with respect to the center value of the frequency at which the electron drift vibration appears. The range of .5 to 2 times corresponds to the frequency band in which electron drift vibration occurs.

In the electric propulsion system 300 according to the present embodiment, even if the frequency of the discharge vibration of the Hall thruster 40 fluctuates slightly due to aging or operating conditions of the Hall thruster 40, the anode power supply 11 does not have the frequency of the discharge vibration at all. Since it is driven at a different frequency, it does not affect the effect of suppressing discharge vibration. Therefore, a stable effect can be expected regardless of the state of the Hall thruster 40.

The waveform of the AC voltage that the anode power supply 11 superimposes on the DC voltage may be any AC such as a sine wave, a square wave, and a triangular wave. Further, since the amplitude of the superimposed AC waveform is generally larger and more expensive in the AC power supply than in the DC power supply, it is desirable to reduce the amplitude of the superimposed AC voltage to the extent that the effect can be obtained. It is known that the amplitude of the superimposed AC voltage is generally 1/5 to 1/100 of the voltage value of the DC power supply. If the amplitude is too large, the AC power supply becomes too large, and if the amplitude is too small, no effect is produced.

The operation of the anode power supply 11 of the power supply device 100 is controlled by the control unit 10. That is, the control unit 10 of the power supply device 100 controls the anode power supply 11 so that the AC voltage having a frequency determined based on the frequency of the transient vibration or the frequency of the electron drift vibration outputs the anode voltage superimposed on the DC voltage.

As described above, in the electric propulsion system 300 according to the present embodiment, the anode power supply 11 of the power supply device 100 generates a voltage in which an AC voltage is superimposed on a DC voltage, and the hole thruster 40 uses this voltage as an anode voltage. It is applied to the anode electrode 43 of. The frequency of the AC voltage used to generate the anode voltage shall be a frequency determined based on the frequency of transient vibration or the frequency of electron drift vibration. Specifically, the frequency of the AC voltage is a frequency included in the frequency band in which transient vibration occurs or a frequency included in the frequency band in which electron drift vibration occurs. As a result, the amplitude of the discharge vibration of the anode current flowing through the anode electrode 43 can be suppressed regardless of the state of the Hall thruster 40. That is, stable operation of the Hall thruster 40 can be realized.

Embodiment 2.
Next, the second embodiment will be described. The configuration of the electric propulsion system according to the second embodiment is the same as that of the first embodiment. In the present embodiment, the description will be focused on the parts different from those in the first embodiment. In the following description, the electric propulsion system according to the second embodiment will be referred to as an electric propulsion system 300a.

FIG. 9 is a diagram showing a main part of the electric propulsion system 300a according to the second embodiment. FIG. 9 shows that the anode power supply 11 of FIG. 4 is replaced with the anode power supply 11a, and similarly to FIG. 4, only the Hall thruster 40, the hollow cathode 30 and the anode power supply 11a are included in the components of the electric propulsion system 300a. It is described, and the description of other components is omitted. The other components are the same as those of the electric propulsion system 300 according to the first embodiment.

As shown in FIG. 9, the anode power supply 11a according to the second embodiment has a configuration in which the DC power supply 111 and the secondary side of the transformer 113 are directly connected, and the AC power supply 112 is connected to the primary side of the transformer 113. As described in the first embodiment, the frequency of the AC voltage output by the AC power supply 112 is a high frequency of 100 kHz or more. Therefore, when the transformer 113 is used for the power output, the transformer 113 can be relatively miniaturized, and at the same time, the output of the AC power supply 112 is insulated, which is advantageous in terms of the configuration of the AC power supply 112. Since the frequency is 100 kHz or higher, it is necessary to use a transformer 113 having excellent high frequency characteristics such as ferrite for the core.

Here, as a problem of the transformer 113 to be used, there is a problem that the core is likely to be saturated by the DC current on the secondary side because the DC current on which the AC current of the transformer 113 output is superimposed flows on the secondary side. .. In the design of the transformer 113, it is necessary to design so that the core is not saturated. Alternatively, there is a method in which the transformer 113 is configured with an air core. When the transformer 113 is an air core, there is no concern that the core will be saturated, and there is no need to consider frequency characteristics. On the other hand, the coupling between the primary side and the secondary side tends to be poor, and it is necessary to consider this point in the power supply design.

As described above, according to the second embodiment, there is an effect that the device can be miniaturized.

Embodiment 3.
Next, the third embodiment will be described. The configuration of the electric propulsion system according to the third embodiment is the same as that of the first embodiment. In the present embodiment, the description will be focused on the parts different from those in the first embodiment. In the following description, the electric propulsion system according to the third embodiment will be referred to as an electric propulsion system 300b.

In FIG. 4 used in the description of the first embodiment, the anode power supply 11 having a configuration in which the DC power supply 111 and the AC power supply 112 are connected in series is shown. On the other hand, most DC power supplies in recent years use a highly efficient switching method, and it is conceivable to apply a switching power supply as an AC power supply 112.

FIG. 10 is a diagram showing a main part of the electric propulsion system 300b according to the third embodiment. FIG. 10 shows that the anode power supply 11 of FIG. 4 is replaced with the anode power supply 11b, and similarly to FIG. 4 and the like, only the Hall thruster 40, the hollow cathode 30 and the anode power supply 11b are among the components of the electric propulsion system 300b. Is described, and the description of other components is omitted. The other components are the same as those of the electric propulsion system 300 according to the first embodiment.

As shown in FIG. 10, the anode power supply 11b according to the third embodiment is realized by using a switching power supply. A switching power supply has internal switching elements such as IGBTs (Insulated Gate Bipolar Transistor) and MOSFETs (Metal Oxide Semiconductor Field Effect Transistor), and by turning the switching elements on and off at high speed, voltage can be converted and controlled. It is something to go. The anode power supply 11b shown in FIG. 10 includes a step-down chopper circuit 114 having a MOSFET as a switching element as the simplest example of a switching power supply. Generally, in a switching power supply, the voltage and current fluctuations caused by switching are smoothed so as not to affect the load, and at the same time, the load fluctuations do not adversely affect the power supply, so a filter is applied to the output side. Is provided. Therefore, the anode power supply 11b shown in FIG. 10 also includes a filter. In FIG. 10, as an example of the simplest filter, a filter circuit 115, which is an LC filter composed of a reactor (inductance value: L) and a capacitor (capacitor capacity: C), is shown.

The anode power supply 11b shown in FIG. 10 will be described in more detail. The voltage and current of the switching power supply fluctuate immediately after the switching portion. That is, the AC component is superimposed on the DC component of the voltage and current. This AC component is called ripple. A filter is required to properly smooth this ripple component and bring it closer to direct current.

Now, when the voltage on the primary side of the switching power supply is V0, consider converting this to the output voltage Va by the step-down chopper circuit 114 as shown in FIG. 10, for example. Va is the DC component of the output voltage, that is, the average value. Assuming that the switching duty ratio is d, there is a relationship of the following equation (1).

Va = d x V0 ... (1)

Here, the switching frequency is fsw. In the case of a one-parallel step-down chopper, the ripple frequency is also fsw. When the output of the power supply is provided with the filter circuit 115 as shown in FIG. 10, the amplitude Vr of the ripple appearing in the output is represented by the following equation (2).

Vr = V0 / (ω ² LC)
ω = 2 × π × fsw… (2)

From the above equations (1) and (2), the ratio of the ripple amplitude Vr to the output voltage Va, that is, the output volatility r is expressed by the following equation (3).

r = Vr / Va = 1 / (ω ² LC) / d
fsw ² × LC = 1 / (r × d × 4π ² )… (3)

For example, in a normal power supply design, performance such as an output volatility r of 1% or less, preferably 0.2% or less is required. Considering that the value of the duty ratio d is about 0.5 from the viewpoint of power supply efficiency and the like, when r> 0.2%, “fsw ² × LC> 25” is obtained. When the filter circuit 115 is designed with such a value, the output Va becomes a DC waveform with little fluctuation.

On the contrary, if the filter circuit 115 is properly designed, the AC component can be appropriately superimposed on the output voltage Va. As described in the first embodiment, it is known that the amplitude of the AC voltage to be superimposed on the DC voltage output by the anode power supply 11b is effectively about 1/5 to 1/100 of the DC voltage. According to this, when r = 0.2 to 0.01 is used, “0.25 <fsw ² × LC <5” is obtained. That is, if the filter circuit 115 is designed so as to satisfy this relationship, a ripple having a switching frequency of the switching power supply (step-down chopper circuit 114) and a desired amplitude is generated in the voltage output by the anode power supply 11b.

Further, the anode power supply capable of suppressing the amplitude of the discharge vibration of the anode current by matching the switching frequency fsw of the step-down chopper circuit 114 with the frequency of the transient vibration or the electron drift vibration described in the first embodiment. It becomes possible to realize 11b.

The configuration of the anode power supply 11b shown in FIG. 10 is not significantly different from the normal power supply configuration, but also the values of the reactor and the capacitor constituting the filter circuit 115 are considerably smaller than the values normally required as described above. Therefore, the filter circuit 115 can be miniaturized, and the merit as a power source is very large.

Embodiment 4.
Next, the fourth embodiment will be described. The configuration of the electric propulsion system according to the fourth embodiment is the same as that of the first embodiment. In the present embodiment, the description will be focused on the parts different from those in the first embodiment. In the following description, the electric propulsion system according to the fourth embodiment will be referred to as an electric propulsion system 300c.

FIG. 11 is a diagram showing a main part of the electric propulsion system 300c according to the fourth embodiment. FIG. 11 shows that the anode power supply 11 of FIG. 4 is replaced with the anode power supply 11c, and similarly to FIG. 4 and the like, only the Hall thruster 40, the hollow cathode 30 and the anode power supply 11c are among the components of the electric propulsion system 300c. Is described, and the description of other components is omitted. The other components are the same as those of the electric propulsion system 300 according to the first embodiment. Further, in the present embodiment, the anode power supply 11c is realized by the switching power supply as in the third embodiment.

As described in the third embodiment, the frequency of the alternating current that realizes the anode power supply 11c capable of suppressing the discharge vibration of the anode current is 100 kHz or more. In recent years, the performance of semiconductor elements has improved, and the switching frequency of switching power supplies has tended to increase, but it is still generally several tens of kHz. Therefore, in the present embodiment, the anode power supply 11c is realized by applying the switching power supply having the configuration shown in FIG. 11, and the discharge vibration of the anode current is suppressed.

The anode power supply 11c shown in FIG. 11 includes a switching power supply 116 having a circuit configuration capable of effectively doubling the switching frequency. The switching power supply 116 shown in FIG. 11 has a configuration in which two step-down chopper circuits are connected in parallel. In FIG. 11, the drive circuit 117 of the switching power supply 116 and the drive signal generated by the drive circuit 117 are shown together. The two MOSFETs 116A and 116B of the switching power supply 116 are driven with the same duty ratio, but the phases of the drive signals are shifted by 180 degrees as shown in the figure. Then, for example, even if the switching frequencies of the MOSFETs 116A and 116B are 50 kHz, the ripple of the power supply at the portion input to the filter circuit 115 at the output of the switching power supply 116 becomes 100 kHz, which is twice that. By utilizing such a circuit configuration, the switching frequency of the power supply can be set to the frequency of the AC voltage required for suppressing the discharge vibration.

Here, in each equation shown in the third embodiment, in the case of the circuit configuration of the anode power supply 11c shown in FIG. 11, it can be seen that a value twice the switching frequency of the MOSFETs 116A and 116B should be used as fsw.

Although FIGS. 10 and 11 show an example of using a step-down chopper circuit as a switching power source for realizing the anode power supplies 11b and 11c, the switching power supply is not limited to the step-down chopper circuit. Needless to say, as long as the power supply circuit performs switching internally, other methods can be applied to the anode power supply according to the present invention in the same way.

For example, the anode power supply 11d having the configuration shown in FIG. 12 can be used. The anode power supply 11d shown in FIG. 12 has a configuration in which the voltage output by the full-bridge type inverter 18 is rectified on the secondary side via the transformer 19. This is a circuit configuration widely used as a DC power supply system using a transformer. The output is generally provided with a smoothing circuit (LC filter) consisting of a reactor and a capacitor. Even in such a circuit configuration, as described in the third embodiment, the ripple of the output voltage can be controlled by appropriately setting the constant of the smoothing circuit. In particular, in the case of this circuit configuration, the output ripple frequency is twice the frequency of the inverter, so that the effect of doubling the ripple frequency as shown in FIG. 11 can also be obtained. Further, in this circuit configuration, the anode power supply 11d is an insulated type, and there are many merits in the design of the power supply.

Embodiment 5.
Next, the fifth embodiment will be described. The configuration of the electric propulsion system according to the fifth embodiment is the same as that of the first embodiment. In the following description, the electric propulsion system according to the fifth embodiment will be referred to as an electric propulsion system 300e. In this embodiment, a specific example of the power supply configuration shown in FIG. 4 described in the first embodiment or the power supply configuration shown in FIG. 9 described in the second embodiment will be described.

Specifically describing the AC power supply, for example, an anode power supply 11x having a configuration as shown in FIG. 13 in which AC is generated by a full-bridge inverter can be considered. FIG. 13 shows a DC power generation unit 20 that supplies DC power to an inverter that generates AC power. When the inverter is connected to the main circuit via a transformer as shown in FIG. 13, the DC power generation unit 20 can be configured with the same potential as the DC power generation unit 21 of the DC power supply because it can be insulated by the transformer. is there.

However, the anode power supply 11x shown in FIG. 13 requires a transformer. It is possible to configure the configuration as shown in FIG. 4 which does not require a transformer, but in this case, the potential of the power supply corresponding to the DC power generator 20 shown in FIG. 13 that supplies power to the inverter floats. It is necessary to use an insulated power supply for this part, which complicates the circuit. A configuration for solving this problem is shown in FIG.

FIG. 14 is a diagram showing a main part of the electric propulsion system 300e according to the fifth embodiment. FIG. 14 shows that the anode power supply 11 of FIG. 4 is replaced with the anode power supply 11e, and similarly to FIG. 4 and the like, only the Hall thruster 40, the hollow cathode 30 and the anode power supply 11e are among the components of the electric propulsion system 300e. Is described, and the description of other components is omitted. The other components are the same as those of the electric propulsion system 300 according to the first embodiment.

The AC power supply 23 of the anode power supply 11e shown in FIG. 14 is composed of a full-bridge inverter and is connected to the main circuit without a transformer. Although a capacitor 231 is provided at the input of the inverter, a DC power supply for supplying DC power to the inverter is not provided. That is, power is not supplied to the AC power supply 23 from other than the control power supply for operating the control circuit 233 and the drive circuit 234. However, it is assumed that some means for charging the capacitor 231 is provided as an initial state. Note that in FIG. 14, the description of the control power supply is omitted.

In the anode power supply 11e, when the inverter is operated while the capacitor 231 is charged, the inverter moves by power running or regenerates depending on the output current. When moving by power running, the voltage of the capacitor 231 decreases, and when moving by regeneration, the voltage of the capacitor 231 increases. The voltage of the capacitor 231 can be kept constant by switching between power running and regeneration by the operation of the inverter. Specifically, as shown in FIG. 14, the voltage of the capacitor 231 is monitored by the voltage sensor 232 and input to the control circuit 233. Then, if the control circuit 233 controls the drive circuit 234 according to the voltage of the capacitor 231 and changes the duty ratio for switching each switching element of the inverter, the voltage of the capacitor 231 can be stabilized and the power from the outside can be stabilized. The AC power supply 23 can be operated without supply.

Embodiment 6.
Next, the sixth embodiment will be described. The configuration of the electric propulsion system according to the sixth embodiment is the same as that of the first embodiment.

As already mentioned, it is desirable to match the frequency of the AC voltage superimposed on the anode voltage to the vicinity of the frequency of transient vibration or electron drift vibration. However, when operating in an actual device, it is difficult to grasp the frequencies of those vibration phenomena. Therefore, it is desirable to have a mechanism for adjusting to the optimum frequency.

FIG. 13 shows an example thereof. The AC power supply of the anode power supply 11x shown in FIG. 13 is composed of, for example, a full-bridge inverter. Further, the AC power supply of the anode power supply 11x is coupled to the output by a transformer, and is connected in series with the output of the DC power supply. The inverter is driven by a drive circuit, and the drive signal is sent from the control circuit. That is, the control circuit generates a drive signal for driving each switching element constituting the inverter, and the drive circuit converts the drive signal generated by the control circuit into a signal at a level suitable for on / off control of the switching element for switching. Apply to the element.

The output of the anode power supply 11x is provided with a current sensor 24 which is a current detection unit for detecting the output current (anode current), and a signal indicating the detection result of the anode current is sent to the control circuit. The control circuit analyzes the waveform of the anode current detected by the current sensor 24 and evaluates the amplitude of the discharge vibration. Then, the control circuit controls the switching frequency of the switching element, that is, the frequency of the AC voltage superimposed on the DC voltage output by the DC power supply so that the amplitude of the discharge vibration is suppressed. In this way, by detecting the waveform of the anode current and controlling the frequency of the AC power supply by feedback control, it is possible to drive at an optimum frequency in which the amplitude of the discharge vibration becomes sufficiently small.

Embodiment 7.
Next, the seventh embodiment will be described. The configuration of the electric propulsion system according to the seventh embodiment is the same as that of the first embodiment. In the following description, the electric propulsion system according to the seventh embodiment will be referred to as an electric propulsion system 300f.

In the present embodiment, a Hall thruster control method including an anode power supply capable of suppressing the amplitude of discharge vibration of the anode current will be described in a form including a gas flow rate regulator and a coil power supply.

FIG. 15 is a diagram showing a main part of the electric propulsion system 300f according to the seventh embodiment. FIG. 15 is an extraction of only the components necessary for the description of the present embodiment from the components of the electric propulsion system 300 shown in FIG. 1, and the description of, for example, the power supply of the hollow cathode 30 is omitted. doing. In FIG. 15, for convenience, the external coil power supply 12 and the internal coil power supply 13 are collectively referred to as the coil power supply 29. That is, the coil power supply 29 has functions as the external coil power supply 12 and the internal coil power supply 13 shown in FIG.

FIG. 15 shows that the control unit 10 controls the DC power supply 111f and the AC power supply 112f of the anode power supply 11f, the anode side flow rate regulator 17, and the coil power supply 29. Further, it is shown that the voltage sensor and the current sensor each detect the anode voltage Va and the anode current Ia output by the anode power supply 11f, and these detected values are input to the control unit 10.

Next, the operation of the electric propulsion system 300f according to the present embodiment will be described. First, the control unit 10 sets the gas flow rate Q to the Hall thruster 40 and the output voltage Vdc of the DC power supply 111f which is the average value of the anode voltage Va according to the command value from the outside. Normally, the control unit 10 grasps how to set the coil current Ic for these operating conditions, that is, how to set the strength of the magnetic field applied to the Hall thruster 40. doing. The control unit 10 sets the coil current Ic to a value corresponding to the operating conditions. The method may be, for example, the method shown in Patent Document 1 described above. The average value of the anode voltage Va output by the anode power supply 11f is the output value Vdc of the DC power supply 111f, but the control unit 10 first determines the amplitude Vac of the output voltage of the AC power supply 112f and its frequency f. Set a typical value and start driving the AC power supply 112f.

In that state, the control unit 10 observes the waveform of the anode current Ia flowing through the Hall thruster 40. Then, the control unit 10 calculates the input power to the Hall thruster 40 by obtaining the time integral value of Va × Ia, and controls Vdc or Q so that the input power matches the command value. Alternatively, more simply, the control unit 10 obtains the product of the average value of Va and the average value of Ia, and controls Vdc or Q so that this matches the command value.

Next, the control unit 10 evaluates the amplitude of the discharge vibration of Ia. There are several possible ways to suppress this vibration. What is proposed in the sixth embodiment is to control the frequency f of the AC power supply 112f. If the control is sufficient, that is, the amplitude of the vibration of Ia cannot be suppressed below the level allowed for the performance of the power supply, it is conceivable to adjust the amplitude Vac of the output voltage of the AC power supply 112f, for example. Alternatively, there is a method in which the frequency f of the AC power supply 112f is significantly changed to change from the frequency domain of transient vibration to the frequency domain of electron drift vibration, and an attempt is made to suppress the vibration amplitude of Ia. If it is still difficult to suppress the current vibration, it is conceivable to adjust the coil current Ic.

In this way, by looking at the entire power supply device 100 that supplies power to the Hall thruster 40 and using a combination of several methods, it is possible to suppress the current vibration of the anode current and optimally control the drive conditions. Becomes possible.

In the first to seventh embodiments, the electric propulsion system including the hollow cathode 30 has been described. However, instead of the hollow cathode 30, the RF (Radio Frequency) cathode described in Documents "Japanese Patent Laid-Open No. 2015-145650" and the like is described. May be applied. The RF cathode has many merits such as low electrode wear and high reliability. The RF cathode uses an RF power supply that outputs a high-frequency AC voltage having a frequency of 1 MHz to 100 MHz, generates plasma by inductive coupling or capacitive coupling inside the cathode, and uses this as an electron source. When an RF cathode is used, a high-frequency AC voltage is applied to the cathode from an RF power source, and it is known that the voltage is not a little coupled to the anode. Therefore, if the RF cathode is used, even if a normal DC power supply is used as the anode power supply, the effect of substantially superimposing a high frequency on the anode voltage can be obtained. If the frequency is close to the frequency of the transient vibration or the electron drift vibration, the effect of suppressing the discharge vibration of the anode current can be expected as in the first to seventh embodiments. Specifically, if the frequency of the high-frequency AC voltage output by the RF power supply is within the range of the frequency at which transient vibration occurs or the frequency at which electron drift vibration appears, the discharge vibration of the anode current Can be expected to have a suppressive effect.

Further, in the first to seventh embodiments, the case where the hall thruster 40 is an SPT type hall thruster has been described, but even if it is an anode layer type hall thruster called a TAL (Thruster with Anode Layer) type, a power supply is used. There is no particular difference as the device 100. As already mentioned, the TAL type Hall thruster has high performance, but has a problem that the discharge vibration is strong and unstable. However, if each anode power supply such as the anode power supply 11 described in the first to seventh embodiments is used, the discharge vibration of the TAL type Hall thruster can be appropriately suppressed and stably driven.

The configuration shown in the above-described embodiment shows an example of the content of the present invention, can be combined with another known technique, and is one of the configurations without departing from the gist of the present invention. It is also possible to omit or change the part.

10 Control unit, 11, 11a, 11b, 11c, 11d, 11e, 11f, 11x anode power supply, 12 external coil power supply, 13 internal coil power supply, 14 heater power supply, 15 keeper power supply, 16 cathode side flow regulator, 17 anode side Flow regulator, 18 inverter, 19,113 transformer, 20,21 DC power generator, 23,112,112f AC power supply, 24 current sensor, 29 coil power supply, 30 hollow cathode, 40 hole thruster, 41 internal coil, 42 external Coil, 43 anode electrode, 44 pole piece, 45 channel, 100 power supply, 111,111f DC power supply, 114 step-down chopper circuit, 115 filter circuit, 116 switching power supply, 116A, 116B MOSFET, 117,234 drive circuit, 231 condenser, 232 voltage sensor, 233 control circuit, 300 electric propulsion system.

Claims (8)

1. A power supply that supplies electric power to an electric propulsion device that has a channel that is a discharge space that accelerates ions to generate thrust.
   An anode power supply that generates a voltage applied to the anode electrode provided in the channel, and an anode power supply.
   A control unit that controls the anode power supply and
   With
   The control unit said that the voltage applied to the anode electrode is a voltage obtained by superimposing an AC voltage having a frequency of 10 times or more the discharge vibration of the anode current, which is a current flowing through the anode electrode, on the DC voltage. Control the anode power supply,
   A power supply that is characterized by that.
2. A power supply that supplies electric power to an electric propulsion device that has a channel that is a discharge space that accelerates ions to generate thrust.
   An anode power supply that generates a voltage applied to the anode electrode provided in the channel, and an anode power supply.
   A control unit that controls the anode power supply and
   With
   The control unit sets the voltage applied to the anode electrode to be a voltage obtained by superimposing an AC voltage having a frequency in the range in which transient vibration occurs in the anode current on the DC voltage, or an electron in the anode current. The anode power supply is controlled so that the AC voltage having a frequency in the range where drift vibration occurs is superimposed.
   A power supply that is characterized by that.
3. The anode power supply includes a DC power supply and an AC power supply, and the output of the DC power supply and the output of the AC power supply are connected in series via a transformer.
   The power supply device according to claim 1 or 2.
4. The anode power supply is
   A switching power supply that converts power by turning the switching element on and off,
   A filter circuit composed of a reactor and a capacitor provided on the output side of the AC power of the switching power supply, and
   With
   When the switching frequency for turning the switching element on and off is fsw, the inductance of the reactor is L, and the capacitance of the capacitor is C.
   The fsw is 10 times or more the frequency of the discharge vibration and satisfies "fsw × fsw × L × C <5".
   The power supply device according to claim 1 or 2.
5. The anode power supply is
   A current detector that detects the anode current and
   A switching power supply that converts power by turning the switching element on and off,
   With
   The switching power supply controls the switching frequency for turning the switching element on and off based on the amplitude of the discharge vibration of the anode current.
   The power supply device according to claim 1 or 2.
6. The electric propulsion device is an anode layer type Hall thruster.
   The power supply device according to any one of claims 1 to 5, wherein the power supply device is characterized by the above.
7. The power supply device according to any one of claims 1 to 6.
   An electric propulsion device that receives power from the power supply and generates thrust,
   An electric propulsion system characterized by being equipped with.
8. An RF cathode to which a high-frequency AC voltage is applied is provided as an electron source for injecting electrons toward the anode electrode.
   The frequency of the high-frequency AC voltage is defined as a frequency in a range in which transient vibration is generated in the anode current or a frequency in a range in which electron drift vibration is generated in the anode current.
   The electric propulsion system according to claim 7.

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