JP2008096081A - Refrigerating cycle device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a refrigerating cycle device for realizing highly reliable driving of an expander. <P>SOLUTION: The refrigerating cycle device is provided with the expander 2, a bypass circuit 5, and an opening and closing valve 6. It is provided with a generator controller 18 including a position speed estimating part 24 estimating a magnetic pole position and a speed of a rotor of a generator 2b provided in the expander 2, and a power converter 19 operable as a power rectifier and a power inverter. When a compressor 1 is stopped, the opening and closing valve 6 is immediately opened, and within a period from right after stopping of the compressor 1 until passage of a predetermined time, a state of controlling a rotational frequency of the generator 2b by the generator controller 18 is maintained until a direct current voltage value detected by a direct current voltage detecting part 27 exceeds a predetermined value, and the generator 2b is constrained by the generator controller 18 after the direct current voltage value exceeds the predetermined value. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a refrigeration cycle apparatus including an expander.

  In recent years, in an apparatus for driving an electric motor such as a compressor in an air conditioner, there is an increasing need to reduce power consumption from the viewpoint of protecting the global environment. As one of the technologies for reducing the power consumption, there is a refrigeration cycle apparatus that recovers power from an expander driven by expansion energy of a refrigerant and uses the recovered power as auxiliary power for driving a compressor. (For example, refer to Patent Document 1).

  FIG. 5 shows a system configuration of the refrigeration cycle apparatus of Patent Document 1. This refrigeration cycle is driven by the expansion energy of the refrigerant provided between the compressor 1 that compresses the refrigerant, the condenser 3 that condenses the refrigerant, the evaporator 4 that evaporates the refrigerant, and the condenser 3 and the evaporator 4. It is comprised from the expansion turbine 2a of the expander 2 by which the expansion turbine 2a is directly connected with the generator 2b via the power shaft 2c. AC power from the AC power supply 11 is converted into DC power by the first converter 51, and this DC power is converted into AC power by the inverter 16 to drive the compressor 1.

  On the other hand, the expansion turbine 2 a driven by the expansion energy of the refrigerant drives the generator 2 b via the power shaft 2 c, and AC power obtained from the generator 2 b is input to the second converter 52. In the second converter 52, AC power obtained from the generator 2 b is converted into DC power, and this DC power is used as auxiliary power for driving the compressor 1.

  However, in the configuration of Patent Document 1, since there is no means for controlling the rotational speed of the expansion turbine 2a (that is, the generator 2b via the power shaft 2c), the expansion turbine 2a has an optimal rotational speed in the refrigeration cycle. (In other words, there is a problem that it is impossible to operate the generator 2b through the power shaft 2c).

  Therefore, a means for controlling the number of revolutions of the generator 2b is required, but in recent years, a highly efficient synchronous generator in which a permanent magnet is arranged on the rotor is used as a generator from the viewpoint of protecting the global environment. In order to control the rotational speed of the synchronous generator, a variable speed converter (hereinafter referred to as a PWM converter) that performs PWM control based on rotor position information is required. In particular, when applied to the generator in the expander of the refrigeration cycle apparatus described in Patent Document 1, it is difficult to attach a position sensor for detecting the magnetic pole position of the rotor, so the stator winding of the synchronous generator A method has been devised for estimating the magnetic pole position of the rotor by estimating the induced voltage generated in (see, for example, Non-Patent Document 1).

FIG. 6 shows the configuration of the wind power generation system described in Non-Patent Document 1. The embedded magnet synchronous generator 62 (symbol in the drawing is IPMSG) is driven by a wind turbine 61 connected through a gear. Here, in the position / velocity estimation unit 64, the embedded magnet synchronous power generation is internally provided from the γ-δ axis current obtained by coordinate conversion of the detected currents iu and iv from the current detectors 20a and 20b at the estimated position θ and the voltage command value. Using the model of the machine 62, the position and speed of the rotor of the embedded magnet synchronous generator 62 are estimated by estimating the induced voltage of the embedded magnet synchronous generator 62. The torque command Tg * is derived by the maximum power tracking control unit 65 from the estimated speed ω of the embedded magnet synchronous generator 62, and the loss of the embedded magnet synchronous generator 62 is minimized by the maximum efficiency control unit 66 from the torque command Tg *. Such current commands id * and iq * are derived. The current flowing through the embedded magnet synchronous generator 62 is current feedback controlled by the voltage command generator 67 and driven by the PWM converter 63.
JP 61-29647 A Proceedings of the Annual Conference of the Institute of Electrical Engineers of Japan (4th volume), 209-210

  However, when the system configuration described in Non-Patent Document 1 is applied to the refrigeration cycle apparatus described in Patent Document 1, an expansion turbine (that is, a generator via a power shaft) at an optimum rotation speed in the refrigeration cycle. It is possible to control the rotation speed, but the expansion energy does not disappear immediately even if the compressor in operation stops, and while the expansion energy exists, the expansion turbine (ie, via the power shaft) The generator will continue to be driven. Here, when the PWM converter is continuously operated, electric energy is extracted while the rotational speed of the generator is controlled. However, when the compressor that consumes the electric energy is stopped, the extracted electric energy is If the stored electrical energy exceeds the allowable value of an element such as a PWM converter, the element may be destroyed.

  In addition, when the operation of the PWM converter is stopped along with the stop of the compressor, the expansion turbine enters a free-run state and continues to be driven according to the expansion energy existing in the refrigeration cycle. If the allowable value of the expansion turbine is exceeded, the expansion turbine may be destroyed.

  The present invention solves the above-described conventional problems, and controls the number of revolutions of the generator by estimating the magnetic pole position of the rotor of the generator provided in the expander, and has reliability including stopping. It aims at providing the refrigerating-cycle apparatus for implement | achieving the drive of a high expander.

  In order to solve the conventional problems, a refrigeration cycle apparatus according to the present invention includes a compressor that compresses a refrigerant, a condenser that condenses the refrigerant, an evaporator that evaporates the refrigerant, and a condenser and an evaporator. The rotation speed of the generator directly connected to the expander via the power shaft is controlled, including an expander that is driven by the expansion energy of the refrigerant and a power converter that can operate as a forward converter and a reverse converter. Generator control means, DC voltage detection means for detecting the DC voltage value of the power converter, a bypass circuit for short-circuiting the high-pressure side and low-pressure side of the refrigerant, and an opening / closing means for opening and closing the bypass circuit When the compressor is stopped, the opening / closing means is immediately opened, and the DC voltage detecting means is used in a period from when the compressor stops until a predetermined time elapses. By Until the detected DC voltage value exceeds a predetermined value, the generator control means keeps the number of revolutions of the generator controlled, and after the DC voltage value exceeds the predetermined value, the generator control means controls the generator. It is to be restrained.

  As a result, when the compressor stops, the expansion energy enters the free-run state due to the expansion energy present in the refrigeration cycle, and the electric energy obtained by the regenerative operation by the generator control means is accumulated and converted into power. It is possible to prevent the elements such as the compressor from being destroyed, and to further reduce the load at the time of restarting the compressor or the expander by rapidly reducing the expansion energy.

  The refrigeration cycle apparatus of the present invention controls the rotational speed of the generator by estimating the magnetic pole position and speed of the rotor of the generator provided in the expander, and is a highly reliable expander including a stop. Driving can be realized.

  1st invention is the expansion | swelling which is provided between the compressor which compresses a refrigerant | coolant, the condenser which condenses a refrigerant | coolant, the evaporator which evaporates a refrigerant | coolant, and the condenser and an evaporator, and is driven by the expansion energy of a refrigerant | coolant And a generator control means for controlling the rotational speed of the generator directly connected to the expander via the power shaft, including a power converter operable as a forward converter and a reverse converter, and a direct current of the power converter A refrigeration cycle apparatus comprising a DC voltage detection means for detecting a side voltage value, a bypass circuit for short-circuiting the high-pressure side and the low-pressure side of the refrigerant, and an opening / closing means for opening and closing the bypass circuit, wherein the compressor is stopped In such a case, the opening / closing means is immediately opened, and until the DC voltage value detected by the DC voltage detection means exceeds the predetermined value in a period immediately after the compressor stops and until a predetermined time elapses. Generator The generator speed is controlled by the control means, and the generator is controlled by the generator control means after the DC voltage value exceeds the predetermined value. When the compressor stops, the refrigeration cycle It is possible to prevent the expander from being in a free-run state due to the expansion energy present in the battery, and the electrical energy obtained by the regenerative operation by the generator control means from being accumulated to destroy elements such as the power converter, Furthermore, the load at the time of restarting a compressor or an expander can be reduced by rapidly reducing the expansion energy.

  According to a second aspect of the present invention, particularly in the refrigeration cycle apparatus according to the first aspect of the present invention, when the DC voltage value exceeds a predetermined value, the switching elements of the upper arm or the lower arm of the power converter are turned on all at once. The input terminal of the generator can be short-circuited regardless of the direction of the phase current flowing through the generator, and the generator can be reliably restrained.

  According to a third aspect of the invention, particularly in the refrigeration cycle apparatus of the first aspect, when the DC voltage value exceeds a predetermined value, the generator is constrained by flowing a DC current of a predetermined magnitude through the generator. In addition, the generator can be reliably restrained without flowing more current than necessary.

  In the refrigeration cycle apparatus according to the third aspect of the present invention, particularly in the refrigeration cycle apparatus according to the third aspect of the invention, the magnitude of the direct current flowing through the generator is increased stepwise or continuously with respect to the elapsed time. By moderately changing the current, it is possible to reduce physical stress applied to the mechanism of the expander that is directly connected via the power shaft when restraining the generator.

  In the fifth aspect of the invention, particularly in the refrigeration cycle apparatus of the third or fourth aspect of the invention, a preset upper limit value is set so that the magnitude of the direct current flowing through the generator is smaller than the demagnetizing current of the generator. It is provided and can prevent demagnetization of a generator reliably when restraining an expander.

  According to a sixth aspect of the invention, in particular, in the refrigeration cycle apparatus according to any one of the first to fifth aspects of the invention, the generator control means includes a current detection means for detecting a current flowing in the stator winding of the generator, and a generator. An induced voltage estimating means for estimating an induced voltage generated in the generator from a value of the applied voltage to be applied and a current value detected by the current detecting means, and a generator based on the induced voltage value estimated by the induced voltage estimating means Position and speed estimation means for estimating the rotor magnetic pole position and speed of the rotor, and it is not necessary to attach a position sensor for detecting the magnetic pole position of the rotor such as an encoder or resolver. Improvements can be made.

  In a seventh aspect of the invention, in particular, in the refrigeration cycle apparatus according to any one of the first to sixth aspects of the invention, while the compressor is in operation, the generator is regenerated by the generator control means to drive power from the expander. The recovered power is used as auxiliary power for driving the compressor, and energy can be saved by significantly reducing the power of the compressor.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings. Note that the present invention is not limited to the embodiments.

(Embodiment 1)
FIG. 1 shows a system configuration of a refrigeration cycle apparatus according to an embodiment of the present invention. This refrigeration cycle is driven by refrigerant expansion energy provided between the compressor 1 that compresses the refrigerant, the condenser 3 that condenses the refrigerant, the evaporator 4 that evaporates the refrigerant, and the condenser 3 and the evaporator 4. The expansion turbine 2a of the expander 2, the bypass circuit 5 that short-circuits the high-pressure side and the low-pressure side of the refrigerant, and the on-off valve 6 that opens and closes the bypass circuit 5 that is normally closed. The turbine 2a is directly connected to the generator 2b via the power shaft 2c.

  AC power from the AC power supply 11 is converted into DC power by the rectifier circuit 12 and then smoothed by the smoothing capacitor 13. This smoothed direct current power is an inverter 16 that converts direct current power into alternating current power, and a drive signal for driving the inverter 16 based on the rotational speed command value of the compressor 1 output from the operation command unit 14. It is converted into AC power for driving the compressor 1 by a compressor control device 15 constituted by the inverter control unit 17 to be generated.

  The expansion turbine 2a driven by the expansion energy of the refrigerant generates AC power by driving the generator 2b via the power shaft 2c. The generated AC power is converted into DC power by regenerative operation by the generator control device 18 based on the rotation speed command value of the generator 2b output from the operation command unit 14. This DC power is used as auxiliary power for driving the compressor 1, and is thus supplied to both ends of the smoothing capacitor 13.

  The generator control device 18 includes a speed error between the target rotational speed (the rotational speed command value of the generator 2b) and the current speed ω (the current value of the estimated speed estimated by the position speed estimating unit 24), and a current detector. The applied voltage command value of the generator 2b from the detected phase current values (iu, iv, iw) of the generator 2b detected by the current detectors 20a, 20b and the current detection unit 21 and the magnetic pole position θ estimated by the position speed estimation unit 24. Based on the sine wave drive unit 22 for calculating (vu *, vv *, vw *) and the detected current value and the voltage command value (vu *, vv *, vw *), the stator winding of the generator 2b An induced voltage estimator 23 that estimates the induced voltage generated in each phase, and a position and speed estimator 24 that estimates the magnetic pole position and speed of the rotor in the generator 2b using the induced voltage estimated by the induced voltage estimator 23. And the voltage command value (vu * , Vv *, vw *) into a drive signal for driving the power converter 19, and a power converter 19 that can operate as a forward converter and an inverse converter. Rotate as directed.

  Here, when the rotation speed of the generator 2b is controlled by the generator control device 18, since the power running operation or the regenerative operation is performed according to the magnitude of the expansion energy, the rotor of the generator 2b in either operation mode is controlled. It must be possible to estimate the magnetic pole position. Hereinafter, after describing the specific operation of the generator control device 18 for the power running operation of the generator 2b, only the differences from the power running operation for the regenerative operation will be described.

  First, the sine wave drive unit 22 has a speed control gain (KPW: speed control proportional) so that the speed error between the rotational speed command value ω * of the generator 2b given from the operation command unit 14 and the estimated speed ω becomes zero. The current command value I * is calculated by the PI control represented by the equation (1) using the gain, KIW: speed control integral gain.

I * = KPW · (ω * −ω) + KIW · (ω * −ω) (1)
Next, the sine wave drive unit 22 uses the calculated current command value I * and the current command phase βT to calculate the dq-axis current command value (id *, iq *) by the calculation of Equation (2) and Equation (3). )

id * = − I * · sin (βT) (2)
iq * = I * · cos (βT) (3)
In addition, in the sine wave drive unit 22, the phase current command values (iu *, iv *, iw *) of the stator winding are set to the dq axis current command values (id *, iq *) and the current magnetic pole position θ (position). The current position value estimated by the speed estimation unit 24 is used to perform two-phase to three-phase conversion by the calculations of Expressions (4) to (6). Since the two-phase to three-phase conversion is publicly known, the description thereof is omitted.

iu * = {√ (2/3)} · {id * · cos θ}
−iq * · sin θ} (4)
iv * = {√ (2/3)} · {id * · cos (θ−120 °)
−iq * · sin (θ−120 °)} (5)
iw * = {√ (2/3)} · {id * · cos (θ + 120 °)
−iq * · sin (θ + 120 °)} (6)
The sine wave drive unit 22 uses the phase current command values (iu *, iv *, iw *) and the output signals of the current detectors 20a and 20b to detect the phase current detection values (iu, iv, iw) are expressed by equations (7) to (9) using current control gains (KPKn, KIKn, n = 1, 2, 3 (for three phases)) so that the current error with respect to iv, iw) becomes zero. The voltage command values (vu *, vv *, vw *) are calculated by the PI control.

vu * = KPK1 · (iu * −iu) + KIK1 · Σ (iu * −iu) (7)
vv * = KPK2 · (iv * −iv) + KIK2 · Σ (iv * −iv) (8)
vw * = KPK3 · (iw * −iw) + KIK3 · Σ (iw * −iw) (9)
The phase current detection values (iu, iv, iw) are subjected to three-phase to two-phase conversion to obtain dq-axis current detection values (id, iq), and dq-axis current command values (id *, iq *) and dq-axis After obtaining the dq axis voltage command value (vd *, vq *) by performing PI control so that the current error from the current detection value (id, iq) becomes zero, the dq axis voltage command value (vd *, vq) is obtained. *) May be subjected to two-phase to three-phase conversion to obtain phase voltage command values (vu *, vv *, vw *). Here, since the three-phase to two-phase conversion is also known in the same manner as the two-phase to three-phase conversion, description thereof is omitted.

  Specifically, the dq-axis current command value (id, iq) is obtained by the calculations of Expressions (10) and (11).

id = {√ (2)} · {iu · sin (θ + 60 °) + iv · sinθ}
(10)
iq = {√ (2)} · {iu · cos (θ + 60 °) + iv · cos θ)}
(11)
The dq-axis voltage command values (vd *, vq *) are current control gains (KPD: d-axis current proportional gain, KID: d-axis current integral gain, KPQ: q-axis current proportional gain, KIQ: q-axis current integral. (Gain) is used to calculate by Expressions (12) and (13).

vd * = KPD · (id * −id) + KID · Σ (id * −id) (12)
vq * = KPQ · (iq * −iq) + KIQ · Σ (iq * −iq) (13)
Here, the phase voltage command values (vu *, vv *, vw *) are expressed by Equations (14) to (16) by performing two-phase to three-phase conversion on the dq-axis voltage command values (vd *, vq *). It is obtained by calculation.

vu * = {√ (2/3)} · {vd * · cos θ
−vq * · sin θ} (14)
vv * = {√ (2/3)} · {vd * · cos (θ−120 °)
−vq * · sin (θ−120 °)} (15)
vw * = {√ (2/3)} · {vd * · cos (θ + 120 °)
−vq * · sin (θ + 120 °)} (16)
Next, a method for estimating the induced voltage of the generator 2b in the first embodiment of the present invention will be described. As the induced voltage values (eu, ev, ew) induced in the windings of the respective phases, the phase current detection values (iu, iv, iw) and the phase voltage command values (vu *, vv *, vw *) are used. Is obtained by the calculations of equations (17) to (19).

eu = vu * -R.iu-L.d (iu) / dt (17)
ev = vv * −R · iv−L · d (iv) / dt (18)
ew = vw * −R · iw−L · d (iw) / dt (19)
Here, R is the resistance per phase of the winding of the generator 2b, and L is its inductance. Further, d (iu) / dt, d (iv) / dt, d (iw) / dt are time derivatives of iu, iv, and iw, respectively, and the following equations are obtained by expanding the equations (17) to (19). obtain.

eu = vu *-R · iu
− (La + La) · d (iu) / dt
-Las · cos (2θ) · d (iu) / dt
-Las · iu · d {cos (2θ)} / dt
+ 0.5 · La · d (iv) / dt
−Las · cos (2θ−120 °) · d (iv) / dt
−Las · iv · d {cos (2θ−120 °)} / dt
+ 0.5 · La · d (iw) / dt
-Las · cos (2θ + 120 °) · d (iw) / dt
-Las · iw · d {cos (2θ + 120 °)} / dt (20)
ev = vv * −R · iv
− (La + La) · d (iv) / dt
−Las · cos (2θ + 120 °) · d (iv) / dt
-Las · iv · d {cos (2θ + 120 °)} / dt
+ 0.5 · La · d (iw) / dt
−Las · cos (2θ) · d (iw) / dt
-Las · iw · d {cos (2θ)} / dt
+ 0.5 · La · d (iu) / dt
−Las · cos (2θ−120 °) · d (iu) / dt
-Las · iu · d {cos (2θ−120 °)} / dt (21)
ew = vw * -R · iw
− (La + La) · d (iw) / dt
-Las · cos (2θ−120 °) · d (iw) / dt
-Las · iw · d {cos (2θ−120 °)} / dt
+ 0.5 · La · d (iu) / dt
−Las · cos (2θ + 120 °) · d (iu) / dt
-Las · iu · d {cos (2θ + 120 °)} / dt
+ 0.5 · La · d (iv) / dt
−Las · cos (2θ) · d (iv) / dt
-Las · iv · d {cos (2θ)} / dt (22)
Where R is the resistance per winding phase, la is the leakage inductance per winding phase, La is the average effective inductance per winding phase, and Las is the effective inductance amplitude per winding phase. It is. Further, d (iu) / dt, d (iv) / dt, and d (iw) / dt are obtained by first order Euler approximation. Note that the u-phase current iu is obtained by changing the sign of the sum of the v-phase current iv and the w-phase current iw. Furthermore, when Expressions (20) to (22) are simplified, Expressions (23) to (25) shown below are obtained. Here, assuming that the phase current detection value (iu, iv, iw) is a sine wave, the phase current detection value (iu, iv, iw) is created from the current command amplitude I * and the current command phase βT. Simplified. In the present embodiment, the induced voltage estimation unit 23 obtains the estimated voltage estimated values (eu, ev, ew) from the equations (23) to (25).

eu = vu * + R · I * · sin (θ + βT)
+1.5 ・ (la + La) ・ cos (θ + βT)
-1.5 · Las · cos (θ-βT) (23)
ev = vv * + R · I * · sin (θ + βT−120 °)
+1.5 ・ (la + La) ・ cos (θ + βT-120 °)
-1.5 · Las · cos (θ-βT-120 °) (24)
ew = vw * + R · I * · sin (θ + βT + 120 °)
+1.5 ・ (la + La) ・ cos (θ + βT + 120 °)
-1.5 · Las · cos (θ-βT + 120 °) (25)
Next, the position / speed estimation unit 24 estimates the magnetic pole position and speed of the rotor in the generator 2b using the induced voltage estimated values (eu, ev, ew). In the position / speed estimation unit 24, the estimated position θ recognized by the generator control device 18 is corrected by using the error of the induced voltage, so that the estimated position θ is converged to a true value. Also, an estimated speed ω is generated therefrom. Therefore, the induced voltage reference value (eum, evm, ewm) of each phase is obtained by the following equation. However, the induced voltage amplitude value em is obtained by matching the amplitude values of eu, ev, and ew.

eum = em · sin (θ + βT) (26)
evm = em · sin (θ + βT−120 °) (27)
ewm = em · sin (θ + βT + 120 °) (28)
A deviation ε between the induced voltage reference value esm (s = u, v, w (s represents a phase)) thus obtained and the induced voltage estimated value es is obtained, and if this deviation ε becomes zero, Since the estimated position θ becomes a true value, the estimated position θ is obtained by performing PI calculation using the deviation ε so that the deviation ε is converged to zero. Further, the estimated speed ω is obtained by calculating the fluctuation value of the estimated position θ.

ε = es-esm (s = u, v, w) (29)
Finally, the PWM signal generation unit 25 outputs a drive signal for driving the power converter 19 based on the phase voltage command values (vu *, vv *, vw *) derived by the sine wave driving unit 22. . The power converter 19 is operated by this drive signal.

  Note that by changing the phase of the voltage command values (vu *, vv *, vw *) applied to the generator 2b, it is possible to switch from power running to regenerative operation. By using (−βT) instead of the current command phase βT, the magnetic pole position and speed in the generator 2b can be estimated even during regenerative operation. However, when the compressor 1 is driven by the compressor control device 15 and the expansion turbine 2a starts to be driven by the expansion energy, the estimated speed ω increases, so the current command value I * decreases and its sign Since the switching from the power running operation to the regenerative operation is performed at the time of reverse rotation, it is necessary to change the sign of the current command phase βT according to the timing.

  With the above configuration, the generator control device 18 generates the estimated position θ using the deviation ε between the induced voltage estimated value derived from the model based on the phase voltage equation and the induced voltage reference value, and generates a sinusoidal phase. Position sensorless sine wave drive that enables power running and regenerative operation by passing current, and it is not necessary to install a position sensor that detects the magnetic pole position of the rotor such as an encoder or resolver, thus reducing cost and reliability Can be improved.

  Further, the refrigeration cycle apparatus according to the embodiment of the present invention includes a compressor rotation speed command to the compressor control device 15, an open / close valve open / close command to the open / close valve 6, and generator control from the operation command unit 14 in FIG. 1. A generator rotation speed command and a generator restraint command are output to the device 18, respectively.

  FIG. 2 is an operation explanatory diagram when the compressor is stopped in the refrigeration cycle apparatus according to the embodiment of the present invention. As shown in FIG. 2, when the compressor 1 stops at time T0 (see (a) of FIG. 2), the on-off valve 6 is immediately opened and the refrigerant expansion energy is reduced by the bypass circuit 5 (see FIG. 2). 2 (see (b) of FIG. 2) and within a period (time T0 to T2) immediately after the compressor 1 stops and until a predetermined time Ts elapses (time T0 to T2), detected by the resistors 26a and 26b and the DC voltage detector 27. Until the time T1 when the DC voltage value exceeds the predetermined value Vs, the rotation speed of the generator 2b is controlled by the generator control device 18, and after the DC voltage value exceeds the predetermined value (time T1 to T2). The generator 2b is restrained by the generator control device 18 (see (c) to (e) of FIG. 2). As a result, when the compressor stops, the expansion energy enters the free-run state due to the expansion energy present in the refrigeration cycle, and the electric energy obtained by the regenerative operation by the generator control means is accumulated and converted into power. It is possible to prevent the elements such as the compressor from being destroyed, and to further reduce the load at the time of restarting the compressor or the expander by rapidly reducing the expansion energy.

  Next, a specific method for restraining the generator 2b will be described. In the generator control device 18 of the refrigeration cycle apparatus according to the embodiment of the present invention, when the DC voltage value exceeds the predetermined value Vs in FIG. 2, the switching elements of the upper arm or the lower arm of the power converter 19 are collectively connected. The generator 2b is restrained by turning it on.

  FIG. 3 is a configuration diagram of the power converter 19. As illustrated in FIG. 3, the power converter 19 includes switching elements 31 a to 31 f and diodes 32 a to 32 f. In FIG. 3, the direction of each phase current flowing through the input terminal of the generator 2b is indicated by an arrow. When the switching elements 31a, 31c, 31e of the upper arm are collectively turned on, the switching elements 31a, 31c and the diode 32e A short circuit is comprised and the generator 2b can be reliably restrained by a short circuit current flowing through the generator 2b. Note that even if the switching elements 31b, 31d, 31f of the lower arm are turned on all at once, a short circuit is formed, and the same effect can be obtained.

  Furthermore, in the generator control device 18 of the refrigeration cycle apparatus according to the embodiment of the present invention, as another method, as shown in FIGS. 4A to 4C, a DC current having a predetermined magnitude is supplied to the generator 2b. The generator 2b may be restrained by flowing. In this case, the generator can be surely restrained without flowing a current more than necessary to the generator 2b.

  Here, FIG. 4 is an explanatory diagram of the operation of the refrigeration cycle apparatus when the generator is restrained in the embodiment of the present invention. In FIG. 4A, the DC voltage value exceeds a predetermined value Vs from a predetermined time T1. In the period until the time Ts elapses (time T1 to T2), the generator 2b is constrained by continuously supplying a constant DC current Is0 to the generator 2b. For example, a phase current command for a stator winding The values (iu *, iv *, iw *) are set as iu * = Is, iv * = iw * = − Is / 2, and a direct current is applied using equations (7) to (9). Necessary voltage command values (vu *, vv *, vw *) are derived.

Further, as shown in FIG. 4B, when the direct current is increased stepwise with respect to the time elapsed from the time T1 when the direct current voltage value exceeds the predetermined value Vs, the direct current passed through the generator 2b. Therefore, the physical stress applied to the mechanism of the expander 2 when the generator 2b is restrained can be reduced. FIG. 4B shows the DC current value Is1 (time T1 to T
a) → Is2 (time Ta to Tb) → Is3 (time Tb to T2). The number of stages may be further increased.

  Further, as shown in FIG. 4C, when the DC current is continuously increased with respect to the time elapsed from the time T1 when the DC voltage value exceeds the predetermined value Vs, the DC current that flows through the generator 2b. Therefore, the physical stress applied to the mechanism of the expander 2 when restraining the generator 2b can be further reduced than in the case of FIG. 4B. In FIG. 4C, the DC current value is changed in a linear function from Is4 (time T1) to Is5 (time Tc), but is not particularly limited and takes a form other than the linear function. Needless to say.

  In addition, as shown to Fig.4 (a)-(c), the magnitude | size of the direct current sent through the generator 2b is provided with the preset upper limit so that it may become smaller than the demagnetizing current of the generator 2b. Thus, demagnetization of the generator 2b can be reliably prevented when the generator 2b is restrained.

  Further, while the compressor 1 is being operated by the compressor control device 15, power is recovered from the expander 2 by regenerating the generator 2 b by the generator control device 18, and the recovered power is used as the compressor. By using it as auxiliary power for driving 1, the power of the compressor 1 can be greatly reduced and energy saving can be achieved.

  In FIG. 1, two current detectors 20a and 20b for detecting the current of the generator 2b are provided and used for estimating the magnetic pole position and speed of the rotor. However, the direct current (power conversion) of the power converter 19 is used. For example, the current of the generator 2b may be detected from the current flowing in the wiring between the capacitor 19 and the smoothing capacitor 13).

  In FIG. 1, the rotational speed control is performed so that the rotational speed of the generator 2 b follows the rotational speed command value of the generator 2 b given from the operation command unit 14. For example, the torque may be controlled.

  Furthermore, although the bypass circuit 5 is provided in FIG. 1 so as to short-circuit the refrigerant on the input / output side of the expander turbine 2a, it is not particularly limited as long as the high-pressure side and the low-pressure side of the refrigerant can be short-circuited. For this reason, the refrigerant on the input / output side of the compressor 1 may be short-circuited.

  As described above, the refrigeration cycle apparatus according to the present invention controls the number of revolutions of the generator by estimating the magnetic pole position of the rotor of the generator provided in the expander, and has reliability including stopping. Since the drive of a high expander is realizable, it can apply also to products, such as a heat pump type water heater of a carbon dioxide refrigerant.

The system block diagram of the refrigerating-cycle apparatus in embodiment of this invention Operation explanatory drawing at the time of compressor stop of a refrigerating cycle device in an embodiment of the invention The block diagram of the power converter of the refrigerating-cycle apparatus in embodiment of this invention Operation explanatory diagram at the time of generator restraint of the refrigeration cycle apparatus in the embodiment of the present invention System configuration diagram of conventional refrigeration cycle equipment System configuration diagram of conventional wind power generation system

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Compressor 2 Expander 2a Expansion turbine 2b Generator 2c Power shaft 2d Generator 3 Condenser 4 Evaporator 5 Bypass circuit 6 On-off valve 11 AC power supply 12 Rectifier circuit 13 Smoothing capacitor 14 Operation command part 15 Compressor controller 16 Inverter DESCRIPTION OF SYMBOLS 17 Inverter control part 18 Generator control apparatus 19 Power converter 20a, 20b Current detector 21 Current detection part 22 Sine wave drive part 23 Induced voltage estimation part 24 Position speed estimation part 25 PWM signal generation part 26a, 26b Resistor 27 DC Voltage detector 31a to 31f Switching element 32a to 32f Diode 51 First converter 52 Second converter 61 Windmill 62 Implanted magnet synchronous generator (IPMSG)
63 PWM converter 64 Position / speed estimator 65 Maximum power tracking controller 66 Maximum efficiency controller 67 Voltage command generator

Claims (7)

A compressor that compresses the refrigerant; a condenser that condenses the refrigerant; an evaporator that evaporates the refrigerant; an expander that is provided between the condenser and the evaporator and is driven by the expansion energy of the refrigerant; Including a power converter operable as a converter and an inverse converter, a generator control means for controlling the rotational speed of a generator directly connected to the expander via a power shaft, and a DC side of the power converter A refrigeration cycle apparatus comprising: a DC voltage detection means for detecting a voltage value; a bypass circuit for short-circuiting the high-pressure side and the low-pressure side of the refrigerant; and an opening / closing means for opening and closing the bypass circuit, wherein the compressor is stopped In this case, the open / close means is opened, and the generator control means is operated until the DC voltage value detected by the DC voltage detection means exceeds a predetermined value in a predetermined period after the compressor is stopped. Wherein maintaining the state where the control was the rotational speed of the generator, after the DC voltage value exceeds the predetermined value refrigeration cycle apparatus characterized by to restrain the generator by the generator control unit by. 2. The refrigeration according to claim 1, wherein when the DC voltage value exceeds a predetermined value, the generator is constrained by turning on a switching element of an upper arm or a lower arm of the power converter. Cycle equipment. 2. The refrigeration cycle apparatus according to claim 1, wherein when the DC voltage value exceeds a predetermined value, the generator is restrained by flowing a DC current having a predetermined magnitude through the generator. The refrigeration cycle apparatus according to claim 3, wherein the DC current flowing through the generator is increased as time passes. 5. The refrigeration cycle apparatus according to claim 3, wherein the refrigeration cycle apparatus has a preset upper limit value such that a magnitude of a direct current flowing through the generator is smaller than a demagnetizing current of the generator. The generator control means includes a current detection means for detecting a current flowing in a stator winding of the generator, a value of an applied voltage applied to the generator, and a current value detected by the current detection means. Induced voltage estimating means for estimating the induced voltage generated in the generator; and position speed estimating means for estimating the magnetic pole position and speed of the rotor of the generator based on the induced voltage value estimated by the induced voltage estimating means; The refrigeration cycle apparatus according to any one of claims 1 to 5, further comprising: While the compressor is in operation, auxiliary power for driving the compressor by collecting power from the expander by regenerating the generator by the generator control means. The refrigeration cycle apparatus according to any one of claims 1 to 6, wherein the refrigeration cycle apparatus is used.

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