Vibration power generation device using a single-phase permanent magnet synchronous linear generator

Abstract

To provide a vibration power generation device that uses a single-phase permanent magnet type linear power generator to achieve downsizing, capable of efficiently generating power even from slight vibration.SOLUTION: A vibration power generation device includes a vibration sensor 15 that detects an induction voltage E generated in a coil 14 of a linear power generator 1, a single-phase converter 21 that includes switching elements 21a to 21d, is connected to the input and output ends of the coil 14, and converts AC voltage to DC voltage, and control means 4 that controls the switching elements 21a to 21d on the basis of a detection value detected by the vibration sensor 15 in such a way that the value of a load current I reaches a desired value and is in phase with the induction voltage E.SELECTED DRAWING: Figure 2

Description

[Technical field]

[0001] The present invention relates to a vibration power generation device that utilizes a single-phase permanent magnet synchronous linear generator, which is particularly useful for energy harvesting applications and the like. [Background technology]

[0002] For example, as one of the mechanisms for converting the vibration energy of surplus vibrations into electrical energy for energy harvesting, a single-phase permanent magnet synchronous linear generator as shown in Patent Document 1 is known. Surplus vibrations refer to vibrations that occur even when there is no intention to vibrate. This generator is used in a manner that extracts vibrations with increased amplitude by utilizing a resonant spring.

[0003] Figure 6 shows a model of the generator 1. The coil 14 has a winding inductance L and a winding resistance r, and when an induced voltage (induced electromotive force) E is generated in the coil 14, a voltage appears between the terminals 14a and 14b of the coil 14. At this time, by connecting a load resistance R between the terminals 14a and 14b of the coil 14, an output voltage V can be taken out through the load resistance R.

[0004] In this case, since the amplitude of the surplus vibration is generally small, on the order of a few tens of mm, and the frequency is also low, on the order of a few tens of Hz, it is necessary to increase the number of turns in the armature to obtain a sufficient induced voltage E. Furthermore, the output voltage V of the generator 1 is the voltage applied to the load resistance R, and the relationship between this load voltage RI, the voltage drop rI due to the winding resistance r, and the voltage drop ωLI due to the winding inductance L is shown in a vector diagram in Figure 7. Therefore, a generator with a large number of turns (number of turns) in the armature due to the coil 14 will have a large winding inductance L, and the larger the winding inductance L, the more the output voltage V is limited by the winding inductance L.

[0005] The output power W of generator 1 is the power consumed by the load resistance R (load power: R I 2 ) and is expressed by the following formula:

[0006] W = R I 2 = R E 2 / {(R+r) 2 +(ωL) 2}≧0 …(1)

[0007] When R→0, the numerator becomes 0, and when R→∞, the denominator becomes 0. Therefore, the output power W has a maximum value in the range 0≦R≦∞. Therefore, for the load resistance R, the output power W(R·I 2 ) is differentiated to obtain the following equation:

[0008] W' = (R I 2 )'=[(E 2 )·R / {(R+r) 2 +(ωL) 2}]' =(E 2 )·{-R 2 +r 2 +(ωL) 2} / {(ωL) 2 +(R+r) 2} 2 …(2)

[0009] W' = (R I 2 When '=0, the output power W(R I 2 ) is a maximum value, so -R 2 +r 2 +(ωL) 2 = 0, the load resistance R is expressed by the following equation (3), and the maximum output power (maximum load power) Wmax is expressed by equation (4).

[0010] R = √{r 2 +(ωL) 2} …(3) Wmax = R I 2 =(E 2 ) / 「2·[√{r 2 +(ωL) 2}+r]」 …(4)

[0011] As described above, the maximum load power Wmax is limited not only by the winding resistance r but also by the winding inductance L.

[0012] This problem can be solved by connecting a capacitor C in series with the load so as to cancel the winding inductance L, as shown in Patent Document 2 (see FIG. 8). Hereinafter, this capacitor C will be referred to as the series capacitor.

[0013] As a vector diagram, as shown in Figure 9(a), the impedance ωL of the winding inductance L can be reduced by the impedance 1 / (ωC) of the series capacitor C, and therefore the effect of the winding inductance L can be completely cancelled by setting ωL = 1 / ωC ​​as shown in Figure 9(b). This makes it possible to make the phase of the load current I the same as the induced voltage E of the generator 1.

[0014] FIG. 10 shows the generator output power W when series capacitor C is not connected to generator 1, and FIG. 11 shows the generator output power W when series capacitor C is connected to generator 1.

[0015] When the series capacitor C is not connected, the above-mentioned equations (2) to (4) hold, whereas the equations corresponding to equations (2) to (4) when the series capacitor C is connected are the following equations (5) to (7).

[0016] W' = (R I 2 )'=[(E 2 )·R / {(R+r) 2 +(ωL-1 / ωC) 2}]' =(E 2 )*{-R 2 +r 2 +(ωL-1 / ωC) 2} / {(ωL-1 / ωC) 2 +(R+r) 2} 2 …(5) R = √{r 2 +(ωL-1 / ωC) 2} =r …(6) Wmax = R I 2 =(E 2 ) / 「2·[√{r 2+(ωL-1 / ωC) 2}+r]" =E 2 / 4r …(7)

[0017] In this way, regarding the power (voltage, current) output by the generator 1, by changing the state in FIG. 10 where the load current I is not in phase with the induced voltage E of the generator 1 to the state in FIG. 11 where the load current I is in phase with the induced voltage E of the generator 1 by setting ωL-1 / ωC=0, it is possible to eliminate the reactive component of the output power W of the generator 1, reduce the power consumption in the winding resistance r of the generator 1, and increase efficiency. In addition, since the power limit caused by the winding inductance L can be eliminated, the upper limit (E 2 ) / (4·r)

[0018] In the example of Figure 10, under the conditions of E = AC100V, 50Hz, L = 50mH, r = 10Ω, the maximum output power (maximum load power) Wmax of Generator 1 was 175W, whereas in the example of Figure 11, under the conditions of E = AC100V, 50Hz, L = 50mH, r = 10Ω, C = 200μF, the maximum output power (maximum load power) Wmax of Generator 1 is 250W, a significant improvement in efficiency.

[0019] Furthermore, even when a power conversion section 100 consisting of a rectifier circuit 100a using a diode D and a smoothing capacitor Cdc is provided between the generator 1 and the load resistor R as shown in FIG. 12, the maximum output power (maximum load power) Wmax of the generator 1 becomes 250 W, and the effect of connecting the series capacitor C remains unchanged. [Prior art documents] [Patent documents]

[0020] [Patent Document 1] Patent Publication No. 2017-229118 [Patent Document 2] Patent Publication No. 10-80197 Summary of the Invention [Problem to be solved by the invention]

[0021] However, series capacitor C needs to be compatible with AC, and so a film capacitor is usually selected, but in the power supply equivalent to 250 W shown in Fig. 11, a film capacitor with a rated voltage of 100 VAC and a capacitance of 200 μF will have larger external dimensions than the diode D and smoothing capacitor Cdc (usually a DC capacitor that uses a polarized aluminum electrolytic capacitor) shown in Fig. 12 used in power conversion unit 100. This increase in dimensions reduces the value of a product intended for energy harvesting.

[0022] To give a specific example of dimensions, diode D has a withstand voltage of 200V and a rated current of 3A, and is approximately 30mm wide, 5mm deep, and 20mm high.

[0023] Furthermore, a smoothing capacitor Cdc having a capacitance of 1000 μF has a withstand voltage of 200 V and is approximately 35 mm in diameter and 30 mm in height.

[0024] In contrast, if a series capacitor C with a capacitance of 100 μF is used in parallel with a voltage rating of AC 200V and a capacitance of 50 μF, two AC-compatible capacitors with a width of about 50 mm, depth of about 35 mm, and height of about 50 mm are required, which requires dimensions about three times the installation area and about 1.5 times the height compared to diode D and smoothing capacitor Cdc. As such, even simply adding a series capacitor C places significant dimensional constraints.

[0025] The present invention has been made in light of these problems, and aims to realize a vibration-powered generator of a new configuration that utilizes a single-phase permanent magnet synchronous linear generator, is small in size, and is capable of generating electricity efficiently even from slight vibrations. [Means for solving the problem]

[0026] Therefore, in the present invention, a single-phase converter using a switching element is used to offset the winding inductance, rather than using a large series capacitor.

[0027] Specifically, the present invention is a vibration power generation device that uses a single-phase permanent magnet synchronous linear generator to generate power from external vibrations, and is characterized by comprising: a vibration sensor that detects induced voltage generated in the coil of the linear generator; a single-phase converter that has a switching element and is connected to the input / output terminals of the coil to convert AC voltage to DC voltage; and control means that controls the switching element based on the detection value detected by the vibration sensor so that the load current has a desired value and is in phase with the induced voltage.

[0028] In this way, the induced voltage that is generated in the single-phase permanent magnet synchronous linear generator and cannot be seen directly can be accurately detected, and the reactive component of the generator's output power (reactive power caused by winding inductance) can be eliminated through the control means, thereby increasing power generation efficiency. Moreover, since a single-phase converter rather than a series capacitor is used as a means for canceling the winding inductance and controlled by the control means, the vibration power generator can be made compact and can be easily attached to the location where excess vibration is generated.

[0029] The control means preferably controls the output voltage of the single-phase converter to a voltage higher than the induced voltage through a switching operation.

[0030] In this way, even when a higher voltage is required on the load side than the generator, boosting can be achieved only by switching control of the single-phase converter without using a boost chopper.

[0031] A specific embodiment of the control means includes an induced voltage calculation unit that calculates the amplitude of the induced voltage from the detection value of the vibration sensor, a coil voltage calculation unit that calculates the voltage drop in the coil for a desired load current, a converter command generation unit that calculates the amplitude and phase of the output voltage of a single-phase converter so that the desired load current is in phase with the induced voltage, and a switching control unit that controls the switching element based on the converter command.

[0032] In this way, the reactive power caused by the winding inductance can be cancelled reliably.

[0033] A specific embodiment of the control means includes a current command generating unit that generates a current command from the detection value of the vibration sensor such that the load current value is in phase with the induced voltage and becomes a desired value, a current detection unit that detects the load current, a converter command generating unit that generates a command to a single-phase converter based on the deviation between the load current detected by the current detection unit and the current command, and a switching control unit that controls a switching element based on the converter command.

[0034] In this way, a part of the converter command can be formed by a feedback system, so that the algorithm for generating the converter command can be simplified. Effect of the Invention

[0035] According to the present invention as described above, by canceling the winding inductance of a single-phase permanent magnet synchronous linear generator using a single-phase converter, it is possible to avoid the use of a series capacitor, thereby realizing a compact size, and to provide an environmentally friendly vibration-based power generation device that can generate power efficiently even from slight vibrations. [Brief description of the drawings]

[0036] [Figure 1] FIG. 1 is a diagram showing a schematic configuration of a single-phase permanent magnet type synchronous linear generator that constitutes a vibration power generation device according to an embodiment of the present invention. [Diagram 2] FIG. 2 is a configuration diagram of the vibration power generation device according to the embodiment. [Diagram 3] 4 is a vector diagram showing voltage control of the vibration power generation device. [Figure 4] FIG. 3 is a diagram showing a comparative example to FIG. 2. [Diagram 5] FIG. 3 is a configuration diagram corresponding to FIG. 2 and showing a modified example of the present invention. [Figure 6] A diagram showing a typical generator model. [Figure 7] A vector diagram showing the voltage-current relationship in the generator. [Figure 8] Circuit diagram of a vibration power generation device with an added series capacitor. [Figure 9] FIG. 9 is a vector diagram showing the voltage-current relationship in the configuration of FIG. 8. [Figure 10] 7 is a graph showing the relationship between the load resistance and the output power of the generator in the case of FIG. 6. [Figure 11] 9 is a graph showing the relationship between the load resistance and the output power of the generator in the case of FIG. 8. [Figure 12] 9 is a graph showing the relationship between the load resistance and the output power of the generator, corresponding to FIG. 8, when a power conversion unit or the like is added. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0037] Hereinafter, an embodiment of the present invention will be described with reference to the drawings.

[0038] The vibration power generation device of this embodiment uses a single-phase permanent magnet synchronous linear generator to generate electricity from the vibrations of floors or stairs when people walk, the vibrations of cars or trains, and the vibrations of the exhaust pipes of thermoacoustic power generation devices.

[0039] 1 shows a schematic diagram of a vibration power generation device A that uses a single-phase permanent magnet type synchronous linear generator 1. The actual structure of the single-phase permanent magnet type synchronous linear generator 1 can be realized in various specific embodiments.

[0040] In the single-phase permanent magnet synchronous linear generator 1, a mover 11 having a permanent magnet 10 is arranged reciprocally within a casing 12, and the permanent magnet 10 connects magnetic flux through a yoke 13. This magnetic flux becomes a magnetic flux linkage for a coil 14 fixed to the casing 12. The mover 11 is supported by a resonant spring (leaf spring) 12a forming part of the casing 12, and when an external vibration Vib is applied to the resonant spring 12a, the mover 11 vibrates. As a result, the magnetic flux linkage moves together with the vibration Vib, generating an induced voltage E in the coil 14. This induced voltage E is input to the power conversion unit 2, converted into direct current, and provided to the load 3 as an output voltage V. The power conversion unit 2 is controlled by a control means 4.

[0041] On the other hand, a vibration sensor 15 such as a position sensor, a speed sensor, an acceleration sensor or the like is attached at a position for detecting the vibration displacement of the mover 11 , and the detection value of this vibration sensor 15 is inputted to the control means 4 .

[0042] 2, the power conversion unit 2 of the present embodiment is configured by connecting a single-phase converter 21 to the coil terminals 14a, 14a. A load 3 (load resistor R) is connected to the output side of the single-phase converter 21 via a smoothing capacitor Cdc.

[0043] The single-phase converter 21 has switching elements 21a-21d on each of a pair of upper and lower arms, and is PWM-controlled by a switching command S from the control means 4 to convert AC to DC. In the figure, the switching elements 21a-21d are illustrated as IGBTs, but it goes without saying that other elements can be used for the switching elements 21a-21d. Note that it is necessary to synchronize with the frequency of the induced voltage E, and PFM control that controls the voltage by changing the frequency is not used.

[0044] The control means 4 is composed of an induced voltage calculation unit 41, a coil voltage calculation unit 42, a converter command generation unit 43, and a switching control unit 44.

[0045] The induced voltage calculation unit 41 calculates the amplitude of the induced voltage E of the generator 1 from the detection value of the vibration of the mover 11 obtained from the vibration sensor 15. For example, as the vibration displacement, A sin(ω t) [m] … (8) If we detect the vibration velocity, A·ω·cos(ω·t)[m / sec] …(9) The induced voltage is expressed as follows, where K is the induced voltage constant [V sec / m]: K·A·ω·cos(ω·t)[V] …(10) It becomes.

[0046] The coil voltage calculation unit 42 calculates the voltage drop rI due to the winding resistance r and the voltage drop ωLI due to the winding inductance L in the vector diagram of FIG.

[0047] The converter command generating unit 43 calculates the amplitude |Vconverter| and phase α of the output voltage Vconverter of the single-phase converter 21 based on the following equations so that the load current I is in phase with the induced voltage E of the generator 1 and the value of the load current I becomes a desired value. |Vconverter|=√{(|E|-|rI|) 2 +(|ωLI|) 2} …(11) α=tan -1 {|ωLI| / (|E|-|rI|)} …(12)

[0048] Upon receiving the above converter command, the switching control unit 44 controls the on / off times and the switching timings of the switching elements 21a to 21d in the single-phase converter 21 so as to satisfy the formulas (11) and (12).

[0049] As a result, in the power (current) output by generator 1, the load current I can be made in phase with the induced voltage E of generator 1, eliminating the reactive component of the output power W of generator 1 (reactive power caused by the winding inductance), reducing the power consumption in the winding resistance r of generator 1, and enabling efficient power generation.

[0050] In particular, when attempting to pick up linear vibrations from surplus vibrations as part of energy harvesting, the amplitude is small and the frequency is low, and increasing the number of turns in coil 14 increases the winding resistance r, so that the losses in the generator 1 itself make it impossible to generate power.

[0051] In this embodiment, in order to efficiently extract power even from such a weak vibration source, it is possible to eliminate the reactive power (power limit) caused by the winding inductance L without using a series capacitor C with a large DC-compatible size, so that in principle there is no upper limit (E 2 ) / (4·r) power output.

[0052] Also, in terms of dimensions, because single-phase converter 21 is used in place of diode D shown in FIG. 12, the height remains the same and the installation area is about twice as large (including the driver section of the switching element). However, compared with using AC-compatible series capacitor C, which has larger dimensions, the overall size can be made smaller, and there are sufficient advantages such as an improved space factor and easier installation on the target from which surplus vibrations are to be extracted.

[0053] Generally, in order to improve usability, the output voltage of the rectifier circuit 100a using a diode D is boosted in a boost chopper circuit (DC / DC conversion circuit) 5 in the output section on the load side as shown in FIG. 4. However, the single-phase converter 21 used in FIG. 2 has a boost function, and the control means 4 can control the output voltage V of the single-phase converter 21 to a voltage higher than the induced voltage E through a switching operation, making the boost chopper unnecessary.

[0054] In addition, the control means 4 calculates the voltage drop rI due to the winding resistance r and the voltage drop ωLI due to the winding inductance L for the desired load current I, and calculates the amplitude |Vconverter| and phase α of the single-phase converter 2 so that the load current I is in phase with the induced voltage E of the generator 1. Based on this, the control means 4 controls the switching elements 21a to 21d, thereby reliably eliminating the reactive component of the output power W of the generator 1 (reactive power caused by the winding inductance), reducing the power consumption at the winding resistance r of the generator 1, and enabling efficient power generation.

[0055] Although one embodiment of the present invention has been described above, the specific configuration of each part is not limited to the above-described embodiment.

[0056] For example, the control means 104 shown in FIG. 5 can be composed of a current command generating unit 141 that generates a current command Iref from the detection value of the vibration sensor 15 so that the load current has a desired value in phase (θ) with the induced voltage, a current detection unit 142 that detects the load current I, a converter command generating unit 143 that generates a command to the single-phase converter 21 based on the deviation between the load current I detected by the current detection unit 142 and the current command Iref, and a switching control unit 144 that controls the switching elements 21a to 21d based on the converter command.

[0057] In this case, a hysteresis comparator is used in the converter command generating unit 143, and the switching timing of the switching elements 21a to 21d of the single-phase converter 21 is determined according to the magnitudes of the current command Iref and the actual current I. As a result, the current I becomes approximately in phase with the induced voltage E of the generator 1, making it possible to increase the generator efficiency.

[0058] In this way, a part of the converter command can be formed by a feedback system, so that the algorithm for generating the converter command can be simplified.

[0059] In addition, various modifications are possible without departing from the spirit of the present invention, such as using a battery as the load to store electricity. [Explanation of symbols]

[0060] A…Vibration power generation device E…Induced voltage (induced electromotive force) V: Output voltage 1...Single-phase permanent magnet synchronous linear generator 4. Control means 10...Permanent magnet 14…Coil 15...Vibration sensor 21...Single-phase converter 21a to 21d: Switching elements 41...Induced voltage calculation section 42... Coil voltage calculation section 43... Converter command generator 44...Switching control section 141...Current command generation section 142...Current detection unit 143... Converter command generation unit 144...Switching control unit

Claims

1. A vibration power generation device that uses a single-phase permanent magnet synchronous linear generator to generate power from external vibrations, A vibration power generation device comprising: a vibration sensor that detects an induced voltage generated in a coil of the linear generator; a single-phase converter having a switching element and connected to an input / output terminal of the coil for converting AC voltage into DC voltage; and control means that controls the switching element based on a detection value detected by the vibration sensor so that a load current has a desired value and is in phase with the induced voltage.

2. 2. The vibration power generating device according to claim 1, wherein the control means controls the output voltage of the single-phase converter to a voltage higher than the induced voltage through the switching operation.

3. 3. The vibration-powered energy generator according to claim 1 or 2, wherein the control means comprises: an induced voltage calculation unit that calculates an amplitude of an induced voltage from a detection value of the vibration sensor; an induced voltage calculation unit that calculates a voltage drop in the coil for a desired load current; a converter command generation unit that calculates an amplitude and a phase of an output voltage of the single-phase converter so that the desired load current is in phase with the induced voltage; and a switching control unit that controls the switching element based on the converter command.

4. 3. The vibration-to-energy generator according to claim 1 or 2, wherein the control means comprises: a current command generation unit that generates a current command from a detection value of the vibration sensor such that a load current in phase with an induced voltage becomes a desired value; a current detection unit that detects the load current; a converter command generation unit that generates a command to the single-phase converter based on a deviation between the load current detected by the current detection unit and the current command; and a switching control unit that controls the switching element based on the converter command.

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