Power supply device and power supply method

Abstract

To provide a method of extracting electricity simply, safely, and efficiently from an AC wiring connecting a power converter and an AC load by using an electrostatic induction method.SOLUTION: A power supply device includes: a shield that has a configuration surrounding an AC wiring that connects a power converter and an AC load; a rectifier circuit with an input end to which a wiring from the shield is connected; a smoothing capacitor that is connected to an output end of the rectifier circuit; and a voltage conversion circuit that uses a voltage of the smoothing capacitor that charges the power generated in the shield by electrostatic induction. The output power from the voltage conversion circuit is supplied to external equipment.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to a power supply device and a power supply method for a monitoring sensor or the like. [Background technology]

[0002] With the recent spread of IoT technology, various sensors are now used not only in the consumer sector, such as home appliances and automobiles, but also in industrial sectors, such as factory equipment, wind power generation, and railway motors.

[0003] The role of these sensors is to grasp the status of operating equipment in real time, and in the event of a malfunction or other abnormality, not only to quickly shut down the equipment but also to use the collected data to diagnose the remaining lifespan and notify the operator when it is time to replace parts.

[0004] In particular, in the industrial sector, especially for equipment such as wind power generation equipment that is located in places where people cannot frequently inspect it, or for equipment such as railway motors that are difficult to inspect because most of the day is spent in motion, there is a growing need to use sensors to remotely monitor the equipment to constantly understand its status, quickly detect abnormalities such as breakdowns, and determine the need for parts replacement, etc.

[0005] Furthermore, for safety reasons, high-voltage equipment such as power transmission facilities and railway motors are often configured to be inaccessible to humans, making remote monitoring using sensors essential.

[0006] When configuring a remote monitoring system using sensors, a challenge arises: securing a power source for the sensors. Generally, monitoring systems using sensors use general-purpose power supplies of DC 15V or DC 24V, or commercial power supplies of AC 100V. However, the aforementioned wind power generation and railway motors often do not have an appropriate power source on the equipment side, making it necessary to add a power source just for the sensors, which poses challenges such as increasing the size of the equipment and manufacturing costs.

[0007] Therefore, as a method for supplying power to a sensor without providing a new power source, a technology has been disclosed that simply extracts power from an AC power cable. There are two main types of methods for extracting power from a power cable: the first is an electromagnetic induction method, and the second is an electrostatic induction method. For example, Patent Document 1 discloses a technology relating to the first electromagnetic induction method, and Patent Documents 2 to 4 disclose technologies relating to the electrostatic induction method. [Prior art documents] [Patent documents]

[0008] [Patent Document 1] Patent Publication No. 2021-027659 [Patent Document 2] International Publication No. 2009 / 072444 [Patent Document 3] Japanese Patent Application Laid-Open No. 2003-284252 [Patent Document 4] Japanese Patent Application Laid-Open No. 2013-172584 Summary of the Invention [Problem to be solved by the invention]

[0009] Patent Document 1 discloses a method for extracting power by electromagnetic induction, which allows for easy and safe extraction of power while maintaining insulation from the power cable. However, this method has the problem that when the current flowing through the power cable is small, the induced magnetic field is also small, resulting in less power being extracted.

[0010] Patent Documents 2 to 4 disclose methods for extracting power by electrostatic induction, which do not have the above-mentioned problems associated with the method described in Patent Document 1, but which have other problems as described below.

[0011] In the method described in Patent Document 2, as shown in Figure 5(a) of the same document, one end of the wiring for extracting power must be directly connected to the power line. In this case, in the case of high-voltage equipment exceeding AC 600V, such as railway motors, the sensor must be directly connected to the high-voltage power line, which requires insulation from the perspective of ensuring safety and protecting the equipment. Therefore, it is difficult to achieve the goal of extracting power from the power cable simply and safely.

[0012] In the method described in Patent Document 3, as shown in Figure 4 of the same document, a load is connected in parallel to part of the stray capacitance generated between the power cable and the earth potential to extract power. However, with this configuration, sufficient power cannot be extracted because the impedance of the stray capacitance in parallel with the load is not high.

[0013] As shown in Figure 3 of Patent Document 4, the method described in Patent Document 4 addresses the above-mentioned issues of Patent Document 3 by connecting an inductance in parallel to the stray capacitance for extracting power, thereby increasing the equivalent impedance of the stray capacitance by causing parallel resonance, thereby extracting sufficient power to the load. However, this configuration has the following problems.

[0014] (1) Adding inductance increases the size and cost of the device. (2) The inductance value required to establish the conditions for parallel resonance is limited and cannot be freely selected. Depending on the conditions, a large inductance value may be required, which increases the size and cost of the device. (3) If the value of the stray capacitance changes due to long-term operation of the device, the resonance condition will be lost and the efficiency of power extraction will decrease.

[0015] SUMMARY OF THE INVENTION An object of the present invention is to provide a means for extracting low voltage power from a high voltage, high current power line without causing the above-mentioned problems. [Means for solving the problem]

[0016] In order to solve the above-mentioned problems, one of the representative power supply devices according to the present invention is a power supply device that connects a power converter and an AC load. Any 2-phase or 3-phase Around the AC wiring Each individually a shield having an enclosing shape; The two-phase or three-phase From the shield each The wire is connected to its own input end Consists of a two-phase or three-phase diode full-bridge circuit It comprises a rectifier circuit, a smoothing capacitor connected to the output terminal of the rectifier circuit, and a voltage conversion circuit that uses the voltage of the smoothing capacitor, which is charged with power generated in the shield by electrostatic induction, as its input voltage, and supplies the output power from the voltage conversion circuit to an external device. [Effects of the Invention]

[0017] According to the present invention, power is extracted by electrostatic induction while being isolated from the power cable, so that a power source for the sensor can be secured safely and simply. Also, since the floating capacitance and the load are connected in series, the efficiency of power extraction can be improved. Furthermore, because it is an electrostatic induction system, it is possible to extract power efficiently even with a small current. Problems, configurations, and effects other than those described above will become apparent from the following description of the preferred embodiments. [Brief explanation of the drawings]

[0018] [Figure 1] 1 is a diagram illustrating a configuration of a power supply device according to a first embodiment of the present invention. [Figure 2] FIG. 10 is a diagram illustrating a configuration of a power supply device according to a second embodiment of the present invention. [Figure 3] FIG. 10 is a diagram illustrating an example of the configuration of a power supply device according to a third embodiment of the present invention. [Figure 4] FIG. 10 is a diagram illustrating a configuration of a power supply device according to a fourth embodiment of the present invention. [Figure 5] FIG. 10 is a diagram illustrating an example of the configuration of a power supply device according to a fifth embodiment of the present invention. [Figure 6] FIG. 10 is a diagram illustrating an example of the configuration of a power supply device according to a sixth embodiment of the present invention. [Figure 7]FIG. 1 is a diagram showing an equivalent circuit of the prior art. [Figure 8] FIG. 2 is a diagram showing an equivalent circuit of the power supply device according to the first embodiment. [Figure 9] FIG. 10 is a diagram illustrating an example of the configuration of a power supply device according to a seventh embodiment of the present invention. [Figure 10] FIG. 10 is a diagram illustrating another example of the configuration of a power supply device according to the seventh embodiment of the present invention. DETAILED DESCRIPTION OF THE INVENTION

[0019] Hereinafter, as modes for carrying out the present invention, Examples 1 to 7 will be described with reference to the drawings. Note that the present invention is not limited to these Examples. In addition, in the drawings, the same parts are denoted by the same reference numerals. [Example]

[0020] FIG. 1 is a diagram showing the configuration of a power supply device according to a first embodiment of the present invention. 1, power is supplied to an AC motor 101 from a motor drive inverter (power converter) 100 via a power cable 107, which is the motor wiring. A shield 106 provided on any one phase of the power cable 107 is connected to the anode of a rectifier diode 104 for power supply to extract power.

[0021] A voltage generated in the shield 106 by electrostatic induction causes a current to flow through the rectifier diode 104 to charge the smoothing capacitor 105. The rectifier diode 104 and the smoothing capacitor 105 are connected in such a manner that the cathode of the rectifier diode 104 is connected to one terminal of the smoothing capacitor 105, and the other terminal of the smoothing capacitor 105 is connected to earth.

[0022] The power stored in the smoothing capacitor 105 is input to a voltage conversion circuit 102 such as a DC-DC converter, converted to a desired voltage value, and supplied to the sensor 103, causing the sensor 103 to operate.

[0023] The power supply device shown as the first embodiment is characterized in that the wiring connected to the shield 106 for extracting power is connected to the voltage conversion circuit 102 and the smoothing capacitor 105 via the rectifier diode 104 .

[0024] Here, the difference from the prior art will be explained using Figures 7 and 8. Figure 7 is a diagram showing an equivalent circuit of the prior art. In the prior art, a load 109 is connected in parallel to one stray capacitance 701 from a series circuit of stray capacitances 108, 701, and 702 formed between a power cable 107 and a shield 106 or between a shield 106 and earth, and power is extracted from there.

[0025] In this configuration, when the potential of power cable 107 increases toward the positive side, a charging current flows to stray capacitance 701, and part of this current also flows to load 109, supplying power. Next, when the polarity of power cable 107 reverses and the potential of power cable 107 decreases toward the negative side, all of the charge stored in stray capacitance 701 is discharged. As a result, only a portion of the power supplied from power cable 107 can be extracted by load 109, resulting in poor efficiency.

[0026] FIG. 8 is a diagram illustrating an equivalent circuit of the power supply device according to the first embodiment. In the configuration of Example 1, rectifier diode 104 is inserted in series with smoothing capacitor 105, so even when the polarity of power cable 107 becomes negative and the potential decreases, the charge stored in smoothing capacitor 105 is not discharged and the extracted power can be maintained. Next, the maintained power is used to supply power to load 109 until the potential of power cable 107 becomes positive again. This configuration makes it possible to continuously and efficiently supply power from the power cable.

[0027] Furthermore, in the configuration of Example 1, the wiring for extracting power is connected to the shield 106 insulated from the power cable 107, so that a high voltage is not applied to the load, as in Patent Document 2, for example, which is a desirable configuration from a safety standpoint.

[0028] Furthermore, in the configuration of Example 1, since power is extracted by electrostatic induction, it is possible to extract the required power even when the current flowing through power cable 107 is small, unlike, for example, Patent Document 1. As mentioned above, in the electromagnetic induction system, when the current flowing through power cable 107 is small, the magnetic field generated around the cable is also small, making it impossible to extract sufficient power. On the other hand, in the electrostatic induction system, power is extracted by the potential fluctuation of power cable 107, so sufficient power can be extracted even when the current is small.

[0029] In addition, since the parallel resonance phenomenon is not used, as in Patent Document 4, there are no restrictions on the main circuit constants required to establish the resonance conditions, and there is no concern about a decrease in power supply efficiency due to fluctuations in the resonance point caused by deterioration over time, thereby improving long-term reliability. [Example]

[0030] FIG. 2 is a diagram showing the configuration of a power supply device according to a second embodiment of the present invention. The feature of the second embodiment is that the power supply device of the first embodiment is installed on all three-phase power cables 107. That is, a shield 106 and a rectifier diode 104 are provided for all three-phase power cables 107, and the rectifier diodes 104 are commonly connected to a smoothing capacitor 105.

[0031] In the configuration of Example 1 shown in FIG. 1, power is extracted only from single-phase power cable 107, so power can be charged into smoothing capacitor 105 only when the potential of power cable 107 is on the positive side, and power cannot be extracted when the potential of power cable 107 is on the negative side.

[0032] 2, the configuration of Example 2 eliminates periods during which charging is not possible by extracting power from three phases simultaneously. Three-phase power cables 107 generally have a phase shift of 120 degrees each, so by combining these, for example, even when one phase of power cable 107 is at a negative potential, the remaining phases will have a positive potential, making charging possible.

[0033] As a result, the configuration of Example 2 can extract up to three times as much power as the configuration of Example 1. Other effects are the same as those of Example 1.

[0034] Furthermore, although Example 1 is configured to extract power only from single-phase power cable 107, and Example 2 is configured to extract power from all three-phase power cables 107, this does not exclude a configuration in which power is extracted from any two of the three power cables 107. In this case, although not shown, a shield 106 and a rectifier diode 104 are provided for each of the power cables 107 for any two of the three phases, and the rectifier diodes 104 are commonly connected to the smoothing capacitor 105. [Example]

[0035] FIG. 3 is a diagram illustrating an example of the configuration of a power supply device according to a third embodiment of the present invention. The third embodiment is characterized in that the power extraction wiring is connected between any two phases, rather than between the shield 106 and the earth.

[0036] In the configuration of the third embodiment, as shown in FIG. 3, a shield 106 is provided for each of two different phases, and the shields 106 are input to a two-phase diode bridge rectifier circuit formed of rectifier diodes 104 to extract power.

[0037] This configuration eliminates the need to connect one end of the wiring that extracts power to earth, increasing the degree of freedom in installation. For example, when attaching a sensor to a motor on a railway vehicle, the wiring cannot be directly connected to earth because the vehicle is in motion.

[0038] One possible solution is to connect the wiring to a pseudo-earth such as the vehicle body. However, this method causes the current from the power extraction circuit to flow into the vehicle body, resulting in leakage current. This can cause radiated noise from the vehicle body, which can cause various signaling devices to malfunction.

[0039] In the configuration of Example 3, there is no need to connect wiring to the ground, so the above problems do not occur and it is possible to extract power more easily than when there is a ground. Other functions and effects are the same as in Examples 1 and 2. [Example]

[0040] FIG. 4 is a diagram showing the configuration of a power supply device according to a fourth embodiment of the present invention. The feature of the fourth embodiment is that the power take-off wiring in the configuration of the third embodiment is expanded to include power cables 107 of any two phases to all three phases.

[0041] That is, in the configuration of Example 3, power is extracted from potential changes in two-phase power cables, but in the configuration of Example 4, power is extracted from potential changes in all three phases, making it possible to extract 1.5 times more power than in Example 3. Other effects are the same as in Examples 1 to 3. [Example]

[0042] FIG. 5 is a diagram illustrating an example of the configuration of a power supply device according to a fifth embodiment of the present invention. The fifth embodiment is characterized in that a transformer 200 is interposed between the rectifier diode 104 and the shield 106 .

[0043] The potential of shield 106 is induced by potential fluctuations in power cable 107, and if this voltage is lower than the voltage required by the load, it must be boosted by some means. Therefore, while it is possible to boost the voltage to some extent by providing voltage conversion circuit 102 with a boost function, a switching regulator such as a DC-DC converter is generally used as this voltage conversion circuit 102. Therefore, if the boost ratio becomes too high, losses in voltage conversion circuit 102 increase, reducing the efficiency of the entire circuit, or there is a possibility that problems such as an inability to boost the voltage at all may occur.

[0044] In the configuration of the fifth embodiment, by employing the transformer 200, when a large step-up ratio is required, it is possible to minimize losses and boost the voltage by using a step-up transformer. This makes it possible to improve the efficiency of the entire system. Other functions and effects are the same as those of the first to fourth embodiments.

[0045] Here, if the voltage generated in the shield 106 is higher than the voltage required by the load, the voltage conversion circuit 102 can use the transformer 200 as a step-down transformer to easily obtain an appropriate voltage.

[0046] Conversely, when the generated voltage is low and the voltage applied to the load is insufficient, the transformer 200 functions as a step-up transformer to step up the generated voltage and supply it to the load, as described above.

[0047] 5 shows a three-phase transformer because the transformer 200 is interposed in the configuration of the fourth embodiment shown in FIG. 4, i.e., when the shields 106 are provided on all three phases, but the configuration is not limited to this. If the transformer 200 is interposed in the configuration of the third embodiment shown in FIG. 3, i.e., when the shields 106 are provided on any two phases, the transformer becomes a single-phase transformer. [Example]

[0048] FIG. 6 is a diagram illustrating an example of the configuration of a power supply device according to a sixth embodiment of the present invention. The sixth embodiment is characterized in that the shield 106 is attached in the closest position to the AC motor 101 .

[0049] Generally, voltage-type inverters are known as the most widely used power converters today, and the voltage output to each phase is a rectangular wave consisting of a low level and a high level. The width of this rectangular wave is controlled to output the desired effective voltage.

[0050] When this voltage square wave reaches the terminals of AC motor 101, which is the load, a reflection phenomenon occurs due to the difference between the impedance of power cable 107 and that of AC motor 101, and the voltage to ground at the terminals of AC motor 101 can become doubled. Therefore, if a shield 106 is provided in this area, the power that can be extracted increases, making it possible to extract a large amount of power efficiently. Other effects are the same as in the first embodiment.

[0051] The waveform caused by the reflection described above has the highest peak value at the terminals of AC motor 101 and attenuates as it returns to the inverter (power converter) 100 side. For this reason, in order to extract power efficiently, it is preferable to provide shield 106 closer to the motor than between inverter (power converter) 100 and AC motor 101. It is particularly preferable to place shield 106 close to the terminals of AC motor 101.

[0052] FIG. 6 shows a configuration in which the feature points of Example 6 are applied to the configuration of Example 1 shown in FIG. 1 , but the configurations in which the feature points of Example 6 are applied can also be adopted for the other Examples 2 to 5. [Example]

[0053] 9 and 10 are diagrams showing an example of the configuration of a power supply device according to a seventh embodiment of the present invention. In the seventh embodiment, as shown in Fig. 9 and 10, a diode bridge circuit 901 and a toroidal core 902 with a winding for extracting power are added.

[0054] The seventh embodiment is characterized in that an electromagnetic induction type power supply device is provided in parallel with the electrostatic induction type power supply device described in the first to sixth embodiments.

[0055] In an example of the configuration of the seventh embodiment shown in FIG. 9, an electromagnetic induction type power supply device including a toroidal core 902 and a single-phase diode bridge circuit 901 provided in a phase having a shield 106 is provided in parallel to the electrostatic induction type power supply device of the first embodiment shown in FIG.

[0056] In another example of the configuration of the seventh embodiment shown in FIG. 10, an electromagnetic induction type power supply device, which is made up of a toroidal core 902 and a three-phase diode bridge circuit 901 provided on each of the three-phase power cables 107, is provided in parallel with the electrostatic induction type power supply device of the fourth embodiment shown in FIG.

[0057] The electrostatic induction type power supply device using the shield 106 has the advantage of being able to stably extract power from small to large currents, since it can supply power determined by the applied voltage regardless of the current value of the power cable 107. However, there is a problem in that the absolute value of the power that can be extracted is smaller than that of the electromagnetic induction type.

[0058] On the other hand, the electromagnetic induction type has the advantage that the power that can be extracted varies depending on the current value, and while only small amounts of power can be extracted in the small current range, large amounts of power can be extracted in the large current range.

[0059] Therefore, in the seventh embodiment, by combining the electrostatic induction type and the electromagnetic induction type and utilizing the advantages of each type described above, a means is provided that can efficiently supply power over the entire range from small currents to large currents.

[0060] The configurations shown in Example 7 are the single-phase embodiment shown in FIG. 9 and the three-phase embodiment shown in FIG. 10, but it will be clear to those skilled in the art that similar effects can be obtained in each of the configurations of Examples 2, 3, and 5 by combining the electrostatic induction method and the electromagnetic induction method.

[0061] In addition, in the above-mentioned Examples 1 to 7, a configuration using a shield has been described as an example of a method for extracting power using the electrostatic induction method. However, similar effects can be obtained if the configuration is such that power can be extracted via a capacitor insulated from the power cable, other than a shield. For example, the same effects can be obtained with a plate-like shield plate or a wiring-like electrode arranged along the power cable.

[0062] Although the embodiments of the present invention have been described above, the present invention is not limited to the above-described embodiments, and various modifications are possible within the scope of the gist of the present invention.

[0063] Furthermore, in cases where the power converter is an inverter for driving a motor and the AC load is an AC motor, the present invention can be used in railway vehicles, steel rolling processes, and even wind power generation, but is not limited to these. The present invention is suitable for use in fields that handle large amounts of power, where it is desired to extract power to monitor sensors and the like in a simple, safe, and highly efficient manner. [Explanation of symbols]

[0064] 100: inverter (power converter), 101: AC motor, 102: voltage conversion circuit, 103: sensor, 104: rectifier diode, 105: smoothing capacitor, 106: Shield, 107: Power cable, 109: Load, 200: Transformer, 108, 701, 702: stray capacitance, 901: diode bridge circuit, 902: Toroidal core

Claims

1. a shield having a shape that individually surrounds any two-phase or three-phase AC wiring that connects the power converter and the AC load; a rectifier circuit including a two-phase or three-phase diode full bridge circuit, each of which has wiring from the two-phase or three-phase shields connected to its own input end; a smoothing capacitor connected to the output terminal of the rectifier circuit; a voltage conversion circuit that uses the voltage of the smoothing capacitor, which is charged with power generated in the shield by electrostatic induction, as an input voltage; Equipped with The output power from the voltage conversion circuit is supplied to an external device. A power supply device characterized by:

2. A shield having a shape that individually surrounds any two-phase or three-phase AC wiring that connects a power converter and an AC load; a single-phase transformer or a three-phase transformer, each of which has wiring from the shield of the two or three phases connected to its primary side; a rectifier circuit configured as a two-phase or three-phase diode full bridge circuit that receives the output of the secondary side of the single-phase transformer or the three-phase transformer as its input; a smoothing capacitor connected to the output terminal of the rectifier circuit; a voltage conversion circuit that uses the voltage of the smoothing capacitor, which is charged with power generated in the shield by electrostatic induction, as an input voltage; Equipped with The output power from the voltage conversion circuit is supplied to an external device. A power supply device characterized by:

3. 3. The power supply device according to claim 1 or 2, The shield is attached in the immediate vicinity of the AC load. A power supply device characterized by:

4. A shield having a shape that surrounds AC wiring that connects a power converter and an AC load; a rectifier circuit having a wiring from the shield connected to its input terminal; a smoothing capacitor connected to the output terminal of the rectifier circuit; at least one toroidal core through which at least one phase of the AC wiring passes; a winding wound around the toroidal core one or more times and having two output ends; at least one two-phase diode full bridge circuit having the two output terminals connected to its input terminal and an output terminal connected to both ends of the smoothing capacitor; a voltage conversion circuit that uses as input voltage the voltage of the smoothing capacitor that is charged with power generated in the shield by electrostatic induction and power generated in the toroidal core by electromagnetic induction; Equipped with The output power from the voltage conversion circuit is supplied to an external device. A power supply device characterized by:

5. Electric power generated by electrostatic induction from a shield having a shape that individually surrounds any two-phase or three-phase AC wiring that connects a power converter and an AC load is rectified via a two-phase or three-phase diode full bridge circuit that connects each wiring from the shield of the two or three phases to its own input terminal, and charged into a smoothing capacitor; The charging voltage of the smoothing capacitor is converted and supplied to an external device. A power supply method comprising:

6. A method for charging a smoothing capacitor by rectifying electric power generated by electrostatic induction from a shield having a shape surrounding the periphery of AC wiring connecting a power converter and an AC load, and electric power generated by electromagnetic induction from a toroidal core through which the AC wiring passes, The charging voltage of the smoothing capacitor is converted and supplied to an external device. A power supply method comprising:

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