JP2006101616A - Ac power generating device and stirling refrigerating apparatus using the same - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an AC power generating device that can feed more stable AC power. <P>SOLUTION: The duty ratio D(t) of a voltage pulse of a carrier cycle, immediately after the variation of a DC voltage, that is, an input voltage Vdc(t) to an inverter circuit 100 is changed, in response to the variation. In other words, processing for correcting the duty ratio D(t) is performed at each cycle of the carrier cycle. As a result of this processing, the duty ratio D(t) of the voltage pulse is corrected so that an AC waveform draws an ideal sine curve, even if the inputted DC voltage is varied. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to an AC power generation apparatus that outputs single-phase AC power and a Stirling refrigerator using the AC power generation apparatus.

Conventionally, an AC power generation device that converts DC power into AC power has been used. As an AC power generator, a variable voltage variable frequency (which can change both the voltage and frequency of an output AC waveform by controlling the duty ratio of the switching element (the ratio of the ON period to one carrier cycle) is provided. A VVVF (Variable Voltage Variable Frequency) circuit, that is, an inverter circuit is used.
Japanese Patent Application No. 11-187654

  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, and the duty ratio of each voltage pulse constituting the AC voltage waveform. Has been determined.

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

  The present invention has been made in view of the above-described problems, and its object is to reduce the AC voltage output from the inverter circuit even when the input DC voltage fluctuates during one AC voltage cycle. An AC power generation device in which a waveform draws an ideal sine curve and a Stirling refrigerator using the AC power generation device.

  The AC power generation device of the present invention uses an inverter circuit that converts DC power into AC power, a voltage measurement circuit that measures the voltage of DC power, and a voltage signal that specifies the measured voltage, and uses the voltage signal. And a microcomputer for controlling the PWM (Pulse Width Modulation) of the inverter circuit. In addition, the microcomputer 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.

  According to said structure, the waveform of the alternating current power output from an alternating current power generation apparatus can be brought close to an ideal sine curve.

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

  According to the above Stirling refrigerator, the AC power generator is configured so that the AC voltage applied to the linear motor does not have a distorted waveform different from that of the sine curve. Adjust the waveform. Therefore, the vibration of the Stirling refrigerator caused by the reciprocating motion of the piston and the displacer can be reduced.

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

(Embodiment 1)
First, the AC power generation device of the embodiment and the Stirling refrigerator using the same 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 a manner as shown in FIG. The four switching elements are transistors Gu, Gx, Gv, and Gy, each of which has a flywheel diode connected between the source electrode and the drain electrode.

  As can be seen from 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.

  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.

  Further, a capacitor CC for stabilizing the potential of the inverter circuit 100 is provided. Between the capacitor C and the capacitor CC and the inverter circuit 100, a resistor R1 and a resistor R2 are provided in parallel with the capacitors C and CC. The resistor R1 and the resistor R2 are connected in series and function as a voltage dividing circuit that divides the voltage between the two input terminals of the inverter circuit 100. A capacitor CCC is connected in parallel to the resistor R2. The capacitor CCC is for stabilizing the potential of the node between the resistor R1 and the resistor R2.

  A node between the resistor R1 and the resistor R2 is connected to the voltage sensor of the microcomputer 1000. Therefore, the potential of the node between the resistor R1 and the resistor R2 is detected by the microcomputer 1000. Using the potential value, microcomputer 1000 detects the value of the DC voltage input to 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 incorporated.

  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 an arithmetic unit, and a RAM ( Random Access Memory) and read-only ROM (Read Only Memory) are provided. The ROM stores a program for controlling the transistors as the four switching elements.

  The RAM is a storage means for temporarily storing the result of the operation performed by the CPU according to the program stored in the ROM, and may include a temporary storage means such as a register. Further, 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.

  Further, the microcomputer 1000 is provided with two registers corresponding to the two phases of the up / down timer 1, respectively. A set value to be described later is determined by this register. This set value determines the amplitude and frequency of a signal wave (sin wave) in PWM control. The setting value is set 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.

  The program in the ROM is set so that the phase angle difference between the U phase and the V phase is 180 degrees. The PWM control signal output from the U-phase control circuit is transmitted to the respective gate electrodes of the transistors Gu and Gx. The PWM control signal output from the V-phase control circuit is transmitted to the gate electrodes of the transistors Gv and Gy.

  Next, the timing of the opening / closing operation for each carrier cycle of the transistors Gu, Gx, Gv, and Gy in the AC power generation device of the present embodiment will be described with reference to FIGS.

  In the period in which the U-phase control outputs the PWM signal based on the U-phase set value shown in FIG. 3, when the up / down timer 1 reaches the set values S1, S2,. A PWM control signal is automatically output from the microcomputer 1000 to the U-phase transistors Gu and Gx. After the transistor Gx is turned off, the 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 S1, S2,... During the countdown, the microcomputer 1000 automatically outputs a PWM control signal to the U-phase transistor Gx. Thereby, 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.

  In the period in which the V-phase control is outputting the PWM signal based on the V-phase set value shown in FIG. 4, the up / down timer 1 is set to each of the set values Sn-1, Sn during the count-up. Then, 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 / down timer 1 reaches the set values Sn-1 and Sn during countdown, the microcomputer 1000 automatically outputs a PWM control signal to the V-phase transistor Gy. Thereby, the transistor Gy is turned on.

  Note that in the period shown in FIG. 4 in which the V-phase PWM control signal of this 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 / down timer 1 is changed for each carrier period. That is, the set values S1, S2,... Sn-1 and Sn for each carrier period of the up / down timer 1 in FIGS. 3 and 4 are the values and times of the voltage pulse widths W1, W2,. The graph showing the relationship changes sequentially so as to draw a sine wave.

  As can be seen by comparing FIG. 3 and FIG. 4, the voltage pulses flowing through the linear motor M are positive and negative and reversed. Except for these, the U-phase control and V-phase control are exactly the same. Note that the U-phase PWM control signal and the V-phase PWM control signal are alternately output every half cycle of the AC waveform, as described above.

  Therefore, in the present embodiment, a positive voltage is applied to the linear motor M at the timing of outputting the U-phase voltage pulse, and a negative voltage is applied to the linear motor M at the timing of outputting the V-phase voltage pulse. A voltage shall be applied.

  In the first half of one cycle, as shown in FIG. 5A, a waveform is formed only by the transistors Gu and Gy. In the second half of one cycle, as shown in FIG. 5B, a waveform is formed only by the transistors Gv and Gx, and in the entire one cycle, the waveform of the U phase described above as shown in FIG. 5C. And the V-phase waveform are alternately output with the phase shifted by 180 °.

  Next, an AC power shaping process performed by the microcomputer 1000 of the AC power generation apparatus according to the present embodiment will be described with reference to FIG.

  In the AC power shaping process of the present embodiment, first, in S1, the value of t is set to 0 setting. 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, a process of incrementing the order of voltage pulses one by one is performed. 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) is a signal indicating the potential between the resistor R1 and the resistor R2, that is, a voltage signal specifying the voltage of the DC power input to the inverter circuit 100 is the voltage shown in FIG. After being acquired by the sensor, it is stored in the RAM corresponding to the order t of the voltage pulses.

  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 from the RAM. 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, and is the t-th voltage from the zero cross constituting the AC waveform. It is a value indicating the magnitude of the voltage applied to the linear motor by the pulse. The frequency f of the AC waveform is the frequency of a signal wave (sine curve) in PWM control. When the maximum voltage of the AC waveform is Vmax, a relational expression of voltage command value V (t) = (Vmax / √2) × sin (2 × π × f × t) is established. Thereafter, in S5, a duty ratio D (t) = V (t) / Vdc (t) in PWM control changed according to the input voltage Vdc (t) is calculated. Next, in S6, the next set value S (t) is set 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 a peak value of a carrier wave for PWM control, and is a predetermined value.

  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 wave in the PWM control, that is, the carrier period. Therefore, a relational expression of the next set value St = Sp × [1-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 value Sp of the set value.

  Thereafter, in S7, using the set value S (t), a PWM control signal is output to each transistor as described with reference to FIGS.

  As described above, according to the AC power generation device of the present embodiment, the duty ratio of 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. D (t) is changed. That is, a process for correcting the duty ratio D (t) is executed for each carrier period. By this processing, 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, AC power that draws an ideal sine curve is generated.

  Next, in S8, it is determined whether or not one carrier cycle has been completed. In S8, if one carrier cycle is not completed, the process in S8 is repeated. If one carrier cycle is completed, 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 process of S1 is executed. If not t = n, t is incremented by 1 in S2, and the process of adjusting the duty ratio of the next carrier cycle is executed. .

  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 a spring. Therefore, if the waveform of the AC voltage applied to the linear motor M deviates from an 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.

  Hereinafter, the Stirling refrigerator according to 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 tip 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 path 11. The regenerator 12 accumulates the heat of the working medium and supplies the accumulated heat to the working medium. A flange (flange) 3 a is provided in the middle of the cylinder 3. A bounce space (back space) 8 is formed in the flange portion 3a by being sealed with a dome-shaped pressure vessel 4 attached thereto.

The piston 1 is integrated with the support spring 5 on the rear end side. The displacer 2 is integrated with the support spring 6 through a rod 2a that passes through the center hole 1a of the piston 1. The support spring 5 and the support spring 6 are connected by a bolt and a nut 22. As will be described later, when the piston 1 reciprocates, the displacer 2 reciprocates with a predetermined phase difference with respect to the piston 1 due to 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 a gap 19. A driving 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 driving coil 16, and the permanent magnet 15 constitute a linear motor 13 (M) that moves the piston 1 along the axis Y.

  Lead wires 20 and 21 are connected to the driving coil 16. Lead wires 20 and 21 penetrate the wall surface of pressure vessel 4 and are connected to inverter circuit 100 of the AC power generation device. Driving power is supplied to the linear motor 13 (M) by the IPM 200 of the AC power generation device.

  In the Stirling refrigerator 40 having the above configuration, when the piston 1 reciprocates by the linear motor 13 (M), the displacer 2 reciprocates 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.

  In the Stirling refrigerator 40 of the above-described 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 has the predetermined AC waveform. The reciprocating motion is performed at a cycle and stroke corresponding to the driving voltage. 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.

  Next, the operation principle of the free piston type Stirling refrigerator of the present embodiment will be described in more detail.

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

  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 the 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 with respect to the sine wave indicating the relationship between the pressure of the working gas in the compression space 9 and time. There is a waveform that changes with the same period. That is, the displacer 2 reciprocates with a predetermined phase difference with respect to the piston 1.

  The refrigeration capacity in the expansion space 10 is determined by the degree of fluctuation of the pressure of the working gas in the expansion space 10 caused by the reciprocating motion of the displacer 2. The pressure in the expansion space 10 is a relative position between the displacer 2 and the piston 1 caused by a 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 due to changes in

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

  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 the piston 1 of the Stirling refrigerator 40.

  Note that when converting a digital signal to an analog signal, PWM is used as described above. That is, the plurality of pulses sequentially output from the microcomputer 100 gradually change in width from a small one to a large one, and after returning to a peak width, gradually return to a small one. It is configured. Thereby, an AC waveform is generated.

  The embodiment disclosed this time should be considered as illustrative in all points and not restrictive. The scope of the present invention is defined by the terms of the claims, rather than the description above, and is intended to include any modifications within the scope and meaning equivalent to the terms of the claims.

3 is a diagram for describing a configuration of an AC power generation device used in Embodiment 1. FIG. 3 is a block diagram of a microcomputer used in the AC power generation device according to Embodiment 1. FIG. 6 is a diagram illustrating a relationship between an ON / OFF operation of a U-phase transistor and a set value of an up / down timer according to the first embodiment. FIG. 6 is a diagram illustrating a relationship between ON / OFF operation of a V-phase transistor of Embodiment 1 and a set value of an up / down timer. It is a figure for demonstrating the voltage pulse of a U phase and the voltage pulse of a V phase. It is a flowchart for demonstrating the alternating current power shaping process of embodiment. It is sectional drawing which shows the structure of the Stirling refrigerator of embodiment.

Explanation of symbols

  40 Stirling refrigerator, 100 inverter circuit, 1000 microcomputer.

Claims (2)

An inverter circuit for converting DC power to AC power;
A voltage measuring circuit for measuring the voltage of the DC power;
A voltage signal specifying the measured voltage is input, and a microcomputer for controlling the inverter circuit by PWM (Pulse Width Modulation) using the voltage signal,
In the PWM control, the microcomputer adjusts the duty ratio for each carrier period so that the waveform of the AC power becomes a sine curve even when the voltage signal fluctuates. A linear motor having the AC power generation device according to claim 1 and a coil to which the AC power is supplied, and using a magnetic force generated around the coil,
A piston that reciprocates by the linear motor;
A Stirling refrigerator comprising: a displacer that reciprocates due to pressure fluctuation caused by the reciprocating motion of the piston.

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