WO2006035540A1

WO2006035540A1 - Ac power generator and stirling refrigerator employing the same

Info

Publication number: WO2006035540A1
Application number: PCT/JP2005/013257
Authority: WO
Inventors: Takashi Komori
Original assignee: Sharp Kabushiki Kaisha
Priority date: 2004-09-29
Filing date: 2005-07-19
Publication date: 2006-04-06
Also published as: JP2006101616A

Abstract

In accordance with variation in a DC voltage, i.e. an input voltage Vdc(t) to an inverter circuit, the duty ratio D(t) of a voltage pulse in the carrier period immediately after is modified. More specifically, processing for correcting the duty ratio D(t) is carried out for every one carrier period. Consequently, the duty ratio D(t) of the voltage pulse is corrected so that the AC waveform draws an ideal sine curve even if the input voltage Vdc(t) is varied. Thus, it is possible to obtain an AC power generator capable of supplying stable AC power.

Description

Specification

AC power generation device and Stirling refrigerator using the same

TECHNICAL FIELD [0001] The present invention relates to an AC power generation device that outputs single-phase AC power and a Stirling refrigerator using the AC power generation device.

Background art

Conventionally, an AC power generation device that converts DC power into AC power has been used.

An AC power generator is a variable voltage that can change both the voltage and frequency of the output AC waveform by controlling the duty ratio of the switching element (the ratio of the ON period to one carrier cycle). A variable frequency (WVF) circuit, that is, an inverter circuit is used.

Patent Document 1: Japanese Patent Application No. 11-187654

Disclosure of the invention

Problems to be solved by the invention

[0003] The conventional AC power generation device described above is based on the assumption that the DC voltage input to the inverter circuit is always constant during one cycle of the AC waveform. The duty ratio of the pulse has been determined.

[0004] However, if the DC voltage input to the inverter circuit fluctuates during one cycle of the AC voltage, the switching elements constituting the inverter circuit are controlled using the above-described duty ratio. Inverter circuit force The output AC voltage waveform is different from the ideal AC voltage waveform.

[0005] The present invention has been made in view of the above-described problems, and an object of the present invention is to provide an inverter circuit card or the like even when the input DC voltage fluctuates during one cycle of the AC voltage. AC power generator that produces an ideal sine curve with output AC voltage waveform and

V, is to provide a Stirling refrigerator.

Means for solving the problem

[0006] The AC power generation device of the present invention is an inverter circuit that converts DC power into AC power. And a voltage measurement circuit for measuring the voltage of the DC power and a microcomputer for inputting a voltage signal for specifying the measured voltage and controlling the inverter circuit by PWM (Pulse Width Modulation) using the voltage signal. ing. The microcomputer also adjusts the duty ratio for each carrier period in PWM control so that the waveform of the AC power becomes a sine curve when the voltage signal fluctuates.

[0007] According to the above configuration, the waveform of the AC power output from the AC power generation device can be brought close to an ideal sine curve.

[0008] A Stirling refrigerator of the present invention includes a linear motor that includes the above-described AC power generation device and a coil to which AC power is supplied, and uses a magnetic force generated around the coil, and a piston that reciprocates by the linear motor. And a displacer that reciprocates due to pressure fluctuation caused by the reciprocating motion of the piston.

[0009] According to the above Stirling refrigerator, the AC power generation device outputs the AC voltage applied to the linear motor so that the waveform of the AC voltage does not become a distorted waveform different from the sine curve. Adjust the AC power voltage waveform. Therefore, the vibration of the Stirling refrigerator caused by the reciprocating motion of the piston and the displacer can be reduced.

The invention's effect

[0010] According to the present invention, the waveform of the AC voltage output from the AC power generation device draws an ideal sine curve.

[0011] The above and other objects, features, aspects and advantages of the present invention will become apparent from the following detailed description of the invention which is understood in conjunction with the accompanying drawings.

Brief Description of Drawings

FIG. 1 is a diagram for explaining a configuration of an AC power generation device used in Embodiment 1.

FIG. 2 is a block diagram of a microcomputer used in the AC power generation device according to the first embodiment.

FIG. 3 is a diagram showing the relationship between the ONZOFF operation of the U-phase transistor of Embodiment 1 and the set value of the up-Z down timer.

[Fig. 4] ONZOFF operation and up-Z down timer of V-phase transistor of Embodiment 1 It is a figure which shows the relationship with a setting value.

FIG. 5 is a diagram for explaining a U-phase voltage pulse and a V-phase voltage pulse.

FIG. 6 is a flowchart for explaining an AC power shaping process of the embodiment.

FIG. 7 is a cross-sectional view showing the structure of the Stirling refrigerator of the embodiment.

Explanation of symbols

[0013] 40 Stirling refrigerator, 100 inverter circuit, 1000 microcomputer.

BEST MODE FOR CARRYING OUT THE INVENTION

[0014] First, an AC power generation device according to an embodiment and a Stirling refrigerator using the AC power generation device will be described with reference to FIGS.

As shown in FIG. 1, the AC power generation device of the present embodiment has an inverter circuit 100. The inverter circuit 100 has four switching elements and is connected to a linear motor M housed in the Stirling refrigerator 40, for example, in the manner shown in FIG. The four switching elements are transistors Gu, Gx, Gv, and Gy, each with a flywheel diode connected between the source and drain electrodes

As shown in FIG. 1, the transistor Gu and the transistor Gx are connected in series, and the transistor Gv and the transistor Gy are connected in series. The linear motor M has one terminal connected to a node between the transistor Gu and the transistor Gx, and the other terminal connected to a node between the transistor Gv and the transistor Gy.

In addition, a smoothing capacitor C is provided in parallel with the inverter circuit 100. A rectifier D is provided in parallel to the smoothing capacitor C. Further, an AC power supply G is provided in parallel with the rectifier D.

[0018] Further, a capacitor CC for stabilizing the potential of the inverter circuit 100 is provided. Further, between the capacitor C and the capacitor CC and the inverter circuit 100, a resistor R and a resistor R are provided in parallel to the capacitors C and CC. Resistance

1 2

R and resistor R are connected in series, and the two inputs of inverter circuit 100

1 2

It functions as a voltage dividing circuit that divides the voltage between the terminals. Also, for resistor R

2 Capacitor CCC is connected in parallel. Capacitor CCC consists of resistor R and resistor R Is to stabilize the potential of the node between the two.

2

In addition, a node between the resistor R and the resistor R is a voltage sensor of the microcomputer 1000.

1 2

Connected to the sensor. Therefore, the potential of the node between resistor R and resistor R is

1 2

Detected by the mouth computer 1000. Using the potential value, the micro computer 1000 detects the value of the DC voltage input to the inverter circuit 100. In short, a voltage signal specifying the voltage of DC power input to the inverter circuit 100 is input to the voltage sensor.

FIG. 2 is a block diagram for explaining the configuration of a microcomputer 1000 for controlling a single-phase linear motor in which one PWM inverter control timer (one channel) is built.

As shown in FIG. 2, the microcomputer 1000 of the AC power generation device according to the present embodiment includes a clock circuit as an oscillator, a CPU (Central Processing Unit) as a calculation means, and a rewritable storage means. RAM (Random Access Memory) and read-only ROM (Read Only Memory). The ROM stores a program for controlling the transistors as the four switching elements.

[0022] The RAM is a storage means for temporarily storing the results of the operation performed by the CPU in accordance with the program stored in the ROM, and may include temporary storage means such as a register. Furthermore, the clock is used to form a clock pulse that is a basis for operating a timer described later using a signal transmitted from the oscillator.

[0023] In addition, the microcomputer 1000 is provided with two registers corresponding to the two phases of the up-Z down timer 1! /, Respectively. This register determines the setting value described later. This setting value determines the amplitude and frequency of the signal wave (sin wave) in PWM control. In addition, the setting value is determined by the microcomputer 1000 when the duty ratio of the peak voltage pulse constituting the target AC waveform, that is, the maximum voltage value of the AC voltage and the frequency of the target AC waveform are input. Calculated automatically.

[0024] In addition, the above-described ROM in the ROM is set so that the phase angle difference between the U phase and the V phase is 180 degrees. Is set. The PWM control signal output from the U-phase control circuit is sent to the gate electrodes of transistors Gu and Gx. The PWM control signal output from the V-phase control circuit is sent to the gate electrodes of transistors Gv and Gy.

Next, the timing of the opening / closing operation for each carrier period of the transistors Gu, Gx, Gv, and Gy in the AC power generation device of the present embodiment will be described using FIG. 3 and FIG. .

[0026] During the period in which the U-phase control outputs a PWM signal based on the U-phase set value shown in Fig. 3, the up / down timer 1 is set to the set values SI, S2, ... When the value is reached, a PWM control signal is automatically output from microcomputer 1 000 to U-phase transistors Gu and Gx, and after transistor Gx is turned off, transistor Gu is turned on. Thereafter, the transistor Gu is automatically turned OFF a predetermined time before the ON timing of the transistor Gx. When the up / down timer 1 reaches the set values SI, S2,... During the countdown, the microcomputer 1000 automatically outputs a PWM control signal to the U-phase transistor Gx. As a result, the transistor Gx is turned ON.

Note that in the period shown in FIG. 3 in which the U-phase PWM control signal of this embodiment is output, the transistor Gv is always OFF and the transistor Gy is always ON.

[0028] Based on the V-phase setting value shown in Fig. 4, during the period when the V-phase control outputs the PWM signal, the up / down timer 1 is set to the set value during the count-up ... Sn-1, Sn respectively When the value becomes, the PWM control signal is automatically output from the microcomputer 1000 to the V-phase transistors Gv and Gy, and after the transistor Gy is turned off, the transistor Gv is turned on. Thereafter, the transistor Gv is automatically turned OFF a predetermined time before the ON timing of the transistor Gy. When the up Z down timer 1 reaches the set values Sn-1 and Sn during the countdown, the microcomputer 1000 automatically outputs a PWM control signal to the V-phase transistor Gy. As a result, the transistor Gy is turned ON.

[0029] Note that during the period shown in FIG. 4 during which the V-phase PWM control signal of the present embodiment is output. The transistor Gu is always off and the transistor Gx is always on.

In the present embodiment, the set value of each register of up Z down timer 1 is changed for each carrier period. In other words, the set values SI, S2, 1 and Sn for each carrier period of up Z down timer 1 in Figs. 3 and 4 are the width of the voltage pulse W

1, W2 to Wn-l, Wn changes sequentially as a graph showing the relationship between time and Wn draws a sine wave.

[0031] The voltage pulses flowing through the linear motor M are reversed between positive and negative, as shown in FIG. 3 and FIG. Except for these, the U-phase control and V-phase control are exactly the same. As described above, the U-phase PWM control signal and the V-phase PWM control signal are alternately output every half cycle of the AC waveform.

Therefore, in the present embodiment, at the timing when the positive voltage is applied to the linear motor M and the V-phase voltage pulse is output at the timing when the U-phase voltage pulse is output, Thus, a negative voltage is applied to the linear motor M.

[0033] Further, in the first half of one cycle, as shown in FIG. 5 (a), a waveform is formed only by the transistors Gu and Gy. In the second half of one cycle, as shown in Fig. 5 (b), a waveform is formed only by transistors Gv and Gx, and in the entire cycle, as shown in Fig. 5 (c), the waveform of the U phase described above is formed. The V and V phase waveforms are output alternately with a 180 ° phase shift.

Next, an AC power shaping process performed by microcomputer 10000 of the AC power generation device according to the present embodiment will be described with reference to FIG.

[0035] In the AC power shaping process of the present embodiment, first, in S1, the value of t is set to 0. This t is a value indicating the order from the zero cross phase of the voltage pulse. Next, in S2, 1 is added to the previous value of t. In short, the voltage pulse sequence is incremented one by one. Thereafter, in S3, the value of the input voltage Vdc (t) input to the inverter circuit 100 when the t-th voltage pulse is output is read from the RAM. The value of the input voltage Vdc (t) indicates the potential between resistors R and R

1 2

Voltage signal power that specifies the voltage of the signal, that is, the DC power input to the inverter circuit 100. After being acquired by the voltage sensor shown in FIG. It is stored in RAM.

Next, in S4, the voltage command value V (t) of the next voltage pulse that has been previously determined and stored in the RAM, and the value of the frequency f of the AC waveform are read out from the RAM force. The voltage command value V (t) of the next voltage pulse is a value determined based on the maximum effective voltage of the AC waveform input to the microcomputer 1000 by the user. This value indicates the magnitude of the voltage applied to the linear motor by the voltage pulse. The frequency f of the AC waveform is the frequency of the signal wave (sine force curve) in PWM control. If the maximum voltage of the AC waveform is Vmax, the relational expression of voltage command value V (t) = (Vmax / ^ 2) X sin (2 X π X f X t) is established. After that, in S5, the duty ratio D (t) = V (t) ZVdc (t) in the PWM control that is changed according to the input voltage Vdc (t) is calculated. Next, in S6, the next set value S (t) is calculated using the duty ratio D (t) and the maximum value Sp of the set value, that is, the maximum value of the up / down timer 1 shown in FIGS. decide. Here, the maximum value Sp of the set value is the peak value of the PWM control carrier wave, and is a predetermined value.

Note that the relational expression D (t) = (Wt / T) = (1−St / Sp) is established. Here, the pulse width Wt is the width of the t-th voltage pulse, that is, the ON time of the switching element, and T is the period of the carrier in the PWM control, that is, the carrier period. Therefore, the following set value St = Sp X [l-D (t)] is established. Therefore, the next set value St is easily calculated using the duty ratio D (t) of the next voltage pulse and the maximum set value Sp.

[0038] After that, in S7, the set value S (t) is used to output a PWM control signal to each transistor as described with reference to FIGS.

[0039] As described above, according to the AC power generation device of the present embodiment, the voltage pulse of the immediately following carrier cycle corresponding to the fluctuation of the DC voltage, that is, the input voltage Vdc (t) to the inverter circuit 100. Change the duty ratio D (t). In other words, the process of correcting the duty ratio D (t) is executed every carrier period. Through this process, the duty ratio D (t) of the voltage pulse is corrected so that the AC waveform draws an ideal sine curve. Therefore, according to the AC power generation device of the present embodiment as described above, an ideal sine curve is obtained. AC power to draw is generated.

[0040] Next, in S8, it is determined whether or not the force has ended one carrier cycle. In S8, if one carrier cycle is not completed, the power carrier that repeats the process in S8 is repeated. If one carrier cycle completes, the process in S9 is executed. In S9, it is determined whether or not t = n, that is, whether or not it is the last carrier period in one AC waveform period. In S9, if t = n, the force for executing the process of S1 is not t = n.In S2, t is incremented by 1 and the process of adjusting the duty ratio of the next carrier cycle is executed. .

[0041] A Stirling refrigerator that can be used more effectively if the AC power generation device of the present embodiment is used will be described below.

In the Stirling refrigerator, as will be described later, the piston reciprocates by the linear motor, and thereby the displacer reciprocates. In addition, one end of each of the piston and the displacer is fixed to the panel. Therefore, if the waveform of the AC voltage applied to the linear motor M deviates from the ideal sine curve, the Stirling refrigerator vibration due to the reciprocating motion of the piston and the displacer may increase. If the AC power generation device described above is used, the waveform of the AC voltage applied to the linear motor is likely to be an ideal sine curve. Therefore, the AC power generation device described above is very suitable for controlling the Stirling refrigerator 40.

[0043] Hereinafter, the Stirling refrigerator of the present embodiment will be described with reference to the drawings.

FIG. 7 is a cross-sectional view showing the Stirling refrigerator 40 of the embodiment. In the Stirling refrigerator 40, a cylindrical piston 1 and a displacer 2 are fitted in a cylindrical cylinder 3 composed of two parts. The piston 1 and the displacer 2 are provided via a compression space 9 and have an axis Y as a common drive shaft.

An expansion space 10 is formed on the distal end side of the displacer 2. The compression space 9 and the expansion space 10 communicate with each other via a medium flow passage 11 through which a working medium such as helium flows. A regenerator 12 is provided in the medium flow passage 11. The regenerator 12 accumulates the heat of the working medium and supplies the accumulated heat to the working medium. In the middle of the cylinder 3, a flange 3a is provided. A dome-shaped pressure vessel 4 must be attached to the collar 3a A bounce space (rear space) 8 sealed by is formed.

The piston 1 is integrated with the support panel 5 on the rear end side. The displacer 2 is integrated with the support panel 6 through a rod 2a passing through the center hole la of the piston 1. The support panel 5 and the support panel 6 are connected by bolts and nuts 22. As will be described later, when the piston 1 reciprocates, the displacer 2 reciprocates in a state having a predetermined phase difference with respect to the piston 1 due to the inertial force generated between the piston 1 and the displacer 2.

An inner yoke 18 is fitted on the outer side of the cylinder 3 in the bounce space 8. The outer yoke 17 is opposed to the inner yoke 18 through the gap 19. A drive coil 16 is fitted inside the outer yoke 17. An annular permanent magnet 15 is movably provided in the gap 19. The permanent magnet 15 is integrated with the piston 1 through a cup-shaped sleeve 14. The inner yoke 18, the outer yoke 17, the drive coil 16, and the permanent magnet 15 constitute a linear motor 13 (M) that moves the piston 1 along the axis Y.

[0047] Lead wires 20 and 21 are connected to the drive coil 16. The lead wires 20 and 21 pass through the wall surface of the pressure vessel 4 and are connected to the inverter circuit 100 of the AC power generation device. Drive power is supplied to the linear motor 13 (M) by the IPM 200 of the AC power generator.

In the Stirling refrigerator 40 configured as described above, when the piston 1 moves back and forth by the linear motor 13 (M), the displacer 2 moves back and forth with a predetermined phase difference with respect to the piston 1. As a result, the working medium moves between the compression space 9 and the expansion space 10. As a result, a reverse Stirling cycle is formed.

[0049] In the above-described Stirling refrigerator 40 of the present embodiment, when a drive voltage having a predetermined AC waveform is applied to the linear motor 13 (M) by the inverter circuit 100 of the AC power generation device, the piston 1 is set to the predetermined Back and forth movement is performed with a period and stroke corresponding to the drive voltage of the AC waveform. Therefore, it is possible to control the cycle and stroke of the reciprocating motion of the piston 1 by controlling the drive voltage applied to the linear motor 13.

[0050] Next, the operating principle of the free piston type Stirling refrigerator of the present embodiment will be described in more detail. Explain in detail.

The piston 1 is driven by the linear motor 13. The piston 1 is supported on the support panel 5 by inertia. Therefore, piston 1 moves so that the relationship between its position and time draws a sine wave.

[0052] Further, due to the movement of the piston 1, the working gas in the compression space 9 moves so that the relationship between the pressure and time draws a sine wave. The working gas compressed in the compression space 9 first releases heat from the compression space 9 as a heat exchange part for heat dissipation. Next, the compressed working gas is cooled by a regenerator 12 provided around the displacer 2. Thereafter, the compressed working gas flows from the regenerator 12 into the expansion space 10 as a heat exchange part for heat absorption.

The working gas in the expansion space 10 is expanded by the movement of the displacer 2. The temperature of the expanded working gas decreases. The working gas in the expansion space 10 moves so that the relationship between its pressure and time draws a sine wave. The sine wave indicating the relationship between the pressure of the working gas in the expansion space 10 and time is a waveform having a predetermined phase difference from the sine wave indicating the relationship between the pressure of the working gas in the compression space 9 and time. However, the waveform changes with the same period. In other words, the displacer 2 reciprocates with a predetermined phase difference with respect to the piston 1.

[0054] The refrigeration capacity in the expansion space 10 is determined by the degree of fluctuation in the pressure of the working gas in the expansion space 10 caused by the reciprocating motion of the displacer 2. Further, the pressure in the expansion space 10 is a relative change between the displacer 2 and the piston 1 caused by the change between the phase of the piston 1 and the phase of the displacer 2, that is, the difference between the pressure in the expansion space 10 and the pressure in the compression space 9. Fluctuates depending on the position

[0055] The relative positional relationship between the displacer 2 and the piston 1 is determined by the mass of the displacer 2, the panel constant of the support panel 6, and the frequency of the piston 1. The mass of the displacer 2 and the panel constant of the support panel 6 are determined at the time of design.

[0056] The PWM control signal output from the microcomputer 1000 to the inverter circuit 100 is a digital signal, that is, a pulse waveform. This pulse waveform is converted into an analog signal, that is, a sine wave in the inverter circuit 100. The frequency of this sine wave becomes the frequency of piston 1 of Stirling refrigerator 40. [0057] Note that PWM is used as described above when converting a digital signal into an analog signal. In other words, multiple pulses that are sequentially output from the microcomputer 100 gradually change from a small force to a large force, and after reaching the peak width, gradually return to a smaller one. Has been. Thereby, an AC waveform is generated.

[0058] The power that has been described and illustrated in detail This invention is for purposes of illustration only and is not limiting, and the spirit and scope of the invention is limited only by the appended claims. Will be clearly understood.

Claims

The scope of the claims

[1] An inverter circuit (100) that converts DC power into AC power;

Voltage measurement circuit (R, R) for measuring the voltage of the DC power

1 2 and

A voltage signal specifying the measured voltage, and a microcomputer (1000) for controlling the inverter circuit (100) using the voltage signal by PWM (Pulse Width Modulation).

The microcomputer (1000) adjusts the duty ratio for each carrier period in the PWM control so that the waveform of the AC power becomes a sine curve even when the voltage signal fluctuates. Generator.

[2] A linear motor (100) having the AC power generation device (100, 1000) according to claim 1 and a coil (16) to which the AC power is supplied, and using a magnetic force generated around the coil (16) 13) and a piston (1) reciprocated by the linear motor (13);

A Stirling refrigerator comprising a displacer (2) that reciprocates due to pressure fluctuations caused by reciprocation of the piston (1).