JP2002112588A - Freezing system controller - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a small size and low price freezing system controller which can control the capability of a compressor to realize energy saving. SOLUTION: A small size and low price inverter is provided to realize energy saving of the freezing system, by assuring the operation in the desired frequency, using a rectifying circuit 2 including, at the intermediate potential point, an induction motor 7 having the two-phase stator winding of a main winding and an auxiliary winding and an inverter 3, in which four switching element are connected by the bridge connection method.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a control device for a refrigeration system such as a refrigerator, and more particularly to a control device capable of changing a refrigerating capacity of a refrigeration system by changing a rotation speed of a compressor using an inverter. About.

[0002]

2. Description of the Related Art In a refrigerating system such as a refrigerator, an induction motor has been widely used as a compressor which is the heart of the refrigerating system. In general, an induction motor having a two-phase winding of a main winding / auxiliary winding of a running capacitor type is used in order to increase the efficiency.

[0003] However, in this method, since the rotation speed of the motor is always constant, a large amount of refrigeration is provided when the refrigeration load is small, so that there is much waste.

In recent years, with the progress of power electronics, in the field of refrigeration systems such as refrigerators, the compressor is controlled by an inverter for the purpose of energy saving and the like, and the refrigeration capacity is changed according to the load state by operating at a variable speed. This greatly contributes to energy saving of equipment.

In particular, brushless motors are characterized by high efficiency because permanent magnets are used for the rotor.
In particular, it has recently been used actively for energy saving.

A control device for such a conventional refrigeration system is disclosed, for example, in Japanese Patent Application Laid-Open No. 9-152200.

Hereinafter, a control device of a conventional refrigeration system will be described with reference to FIG. FIG. 7 shows a block diagram of a control device of a conventional refrigeration system.

In FIG. 7, reference numeral 100 denotes a commercial power supply,
For Japan, 100V50Hz or 100V60Hz
Is used. Reference numeral 101 denotes a converter, which converts an AC voltage of the commercial power supply 100 into a DC voltage. Specifically, for example, a voltage doubler rectifier circuit as shown in FIG. 8 is used.

The voltage doubler rectifier circuit used in the converter 101 converts the AC voltage (100 V) of the commercial power supply 100 into two.
Convert to a DC voltage of 80V. This voltage doubler rectifier circuit is widely used in inverters. Also, a full-wave rectifier circuit (converting an AC voltage of 100 V into a DC voltage of 140 V) or the like is used.

Reference numeral 102 denotes an inverter, which converts a DC voltage output of the converter 102 into a three-phase AC voltage by connecting six switching elements in a three-phase bridge. Reference numeral 103 denotes a brushless motor built in the compressor. The brushless motor 103 includes a stator having three-phase windings 104 and a rotor 105 on which permanent magnets are arranged.

Reference numeral 106 denotes an inverter control means for controlling the number of rotations of the brushless motor 103 by controlling six switching elements of the inverter 102.
Reference numeral 107 denotes a refrigeration system control unit that detects a temperature in the refrigerator, an outside air temperature, and the like, and instructs the inverter control unit 106 on an optimum rotation speed.

[0012]

However, in the above-described configuration, there are problems that the size of the circuit is increased, the number of steps is increased, and the cost is increased because six switching elements are required. In addition, the motor also requires a brushless motor, which requires a permanent magnet for the rotor, and the compressor itself must be newly developed. Was.

The present invention provides a capacitor run type 2 which is generally widely used for driving with a single-phase commercial power supply.
The phase induction motor can be used with an inverter, the circuit is small and low-cost, and a general compressor can be used, making it easy to save energy even in small lots without increasing the cost of the compressor. It is an object to provide a control device for a refrigeration system.

It is another object of the present invention to realize stable operation even in variable capacity operation of the compressor.

[0015]

SUMMARY OF THE INVENTION In order to solve this problem, the present invention is configured so that an inverter capable of driving a two-phase induction motor can be realized with a reduced number of switching elements.

Thus, the number of switching elements in the circuit is reduced as compared with the conventional case, and the circuit can be realized at a small size and at low cost. Also, since a compressor using a general two-phase induction motor can be used, without increasing the cost of the compressor,
Since the operation can be performed with the refrigerating capacity according to the refrigerating load, the energy of the refrigerating system can be saved.

Further, the output voltage of the rectifier circuit is switched according to the output frequency of the inverter.

Accordingly, when the output frequency of the inverter is low, the duty of the PWM control (on time / carrier cycle) is low, and the motor efficiency is reduced, the output voltage can be reduced and the duty cycle can be increased, so that the motor efficiency can be increased. And the energy of a larger refrigeration system can be saved.

Further, the output voltage of the rectifier circuit is switched, and when the voltage of the rectifier circuit changes, the change is detected to correct the duty.

Thus, the output voltage of the rectifier circuit is switched, and the output voltage of the inverter can be maintained at a constant level even when the output voltage of the rectifier circuit is gradually changing. Becomes possible.

Further, when the output voltage of the rectifier circuit is switched from the low side to the high side, a change in the output voltage of the rectifier circuit is predicted, and the duty of the output waveform of the inverter is corrected. .

As a result, even when the output voltage of the rectifier circuit is switched from a low side to a high side, the inrush current of the motor can be prevented and a stable operation can be continued.

Further, the output voltage of the rectifier circuit is detected as a ripple voltage, and the output voltage of the inverter is corrected in accordance with the change in the ripple voltage.

As a result, the motor current waveform becomes a stable waveform without being affected by the ripple voltage, eliminating unnecessary vibration of the compressor, and enabling a stable operation.

Further, the present invention is configured to detect an unstable operation of the motor and change the output voltage of the inverter.

As a result, the current pulsation can be suppressed by lowering the output voltage of the inverter when the unstable operation due to the current pulsation at a low frequency occurs.
Therefore, unnecessary vibration of the compressor is eliminated, and stable operation can be performed.

[0027]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention according to claim 1 of the present invention provides a motor having two-phase stator windings for driving a compression element, a main winding and an auxiliary winding, a rectifier circuit, and four switching circuits. An inverter having elements bridge-connected, a stator winding of each phase of the motor connected to an output of the inverter, a common terminal of the stator winding of the motor connected to an intermediate voltage point of the rectifier circuit, A refrigeration system control device comprising frequency setting means for changing the frequency according to the state of the system, and waveform generating means for driving the inverter at the frequency set by the frequency setting means. Inverter operation that changes the rotation speed with only four switching elements can be performed using a compressor having a generally widely used two-phase induction motor without changing It has the effect of say.

According to a third aspect of the present invention, there is provided a refrigeration system control device comprising switching means for switching the output voltage of the rectifier circuit according to the output frequency set by the frequency setting means. The output voltage of the rectifier circuit can be switched accordingly.

According to a seventh aspect of the present invention, there is provided a switching means for switching an output voltage of a rectifier circuit according to an output frequency set by a frequency setting means, a voltage detecting means for detecting an output voltage of the rectifier circuit, and the switching means. And a correction means for correcting the output voltage of the inverter by the voltage detection means at the time of the switching by the refrigeration system.The output voltage of the rectifier circuit is detected, and an optimum value is output from the inverter based on the detected value. It has an effect that an output voltage can be obtained.

According to a ninth aspect of the present invention, when the switching means switches the output voltage of the low rectifier circuit to the output voltage of the high rectifier circuit, a change in the output voltage of the rectifier circuit is predicted to correct the output voltage of the inverter. Means for controlling the refrigeration system comprising means and means for correcting the change in the output voltage of the rectifier circuit to a preset predicted value so that the output voltage of the inverter can be corrected to the predicted value. Having.

According to a tenth aspect of the present invention, there is provided a voltage detecting means for detecting an output voltage of a rectifier circuit, and a ripple correcting means for correcting an output voltage of an inverter in accordance with a change in a ripple voltage detected by the voltage detecting means. And has the effect of being able to produce the output voltage of the inverter according to the ripple voltage of the rectifier circuit.

An eleventh aspect of the present invention is a control device for a refrigeration system, comprising: a turbulence detecting means for detecting an unstable operation of a motor; and a parameter correcting means for changing an output voltage of an inverter by the turbulence detecting means. That is, when the occurrence of unstable operation of the motor at a low frequency is detected, the output voltage of the inverter can be reduced.

Hereinafter, an embodiment of the present invention will be described with reference to FIG.
This will be described with reference to FIG.

(Embodiment 1) FIG. 1 is a block diagram of a control device of a refrigeration system according to Embodiment 1 of the present invention.

In FIG. 1, reference numeral 1 denotes a commercial power supply. In a general household in Japan, a single-phase alternating current of 100 V, 50 Hz or 60 Hz is generally used.

Reference numeral 2 denotes a rectifier circuit that converts an AC voltage of the commercial power supply 1 into a DC voltage. The rectifier circuit 2 is a circuit that can switch between a voltage doubler rectifier circuit and a full-wave rectifier circuit using a relay 2h.
80 V (for double voltage rectification) or 140 V DC (for full wave rectification).

The rectifier circuit 2 includes four rectifier diodes 2a to 2a.
21d is bridge-connected. Electrolytic capacitor 2
The positive terminal of e is connected to the connection point between the bridge-connected rectifier diode 2a and the rectifier diode 2c, and the negative terminal of the electrolytic capacitor 2f is the bridge-connected rectifier diode 2a.
b and the connection point between the rectifier diode 2d. Further, the positive terminal of the electrolytic capacitor 2e and the electrolytic capacitor 2f
Further, an electrolytic capacitor 2g is connected between the negative terminals of.

The negative terminal of the electrolytic capacitor 2e and the positive terminal of the electrolytic capacitor 2f are directly connected, and the connection point between the rectifier diode 2c and the rectifier diode 2d is connected via a relay 2h.

Relay 2h is on (short circuit between contacts)
At this time, in the positive half cycle of the AC input of the commercial power supply 1, the electrolytic capacitor 2e is charged, and in the negative half cycle, the electrolytic capacitor 2f is charged.

By performing the rectification in this way, 280 V DC rectified by a double voltage is generated between the negative terminal of the electrolytic capacitor 2f and the positive terminal of the electrolytic capacitor 2e (that is, between the negative terminal and the positive terminal of the electrolytic capacitor 2g). become.
Therefore, each of the electrolytic capacitors 2e and 2f has a DC voltage of 140V.
Is charged.

When the relay 2h is off (release between contacts), the charging direction in both half cycles of the commercial power supply is the same, and in both directions, the series circuit of the electrolytic capacitor 2g and the electrolytic capacitors 2e and 2f is charged. Direction. At this time, the charging voltage is DC 140V.

Since the electrolytic capacitors 2e and 2f divide this voltage, if they have the same capacity, each of them is charged with 70V DC.

Reference numeral 3 denotes an inverter which receives a DC voltage output rectified by the rectifier circuit 2 and converts the DC voltage output into a two-phase AC having an arbitrary frequency and an arbitrary voltage.

The inverter 3 includes switching elements 3a-3
d are bridge-connected. In this embodiment, an FET is used as a switching element. Each switching element 3a-3d has a built-in high-speed diode in the reverse current direction in parallel. The built-in high-speed diode functions to flow a circulating current when the switching elements 3a to 3d are turned off.

Reference numeral 4 denotes a compressor for circulating the refrigerant in the refrigeration system. The compressor 4 has a compression element 6 and a two-phase induction motor 7 in a sealed container 5. The rotating motion generated by the two-phase induction motor 7 is transmitted to the compression element via a shaft 8 having a crank as a reciprocating motion, and the piston (not shown) reciprocates in a cylinder (not shown) to perform compression work. Converting.

The induction motor 7 has a main winding and an auxiliary winding, and a stator (not shown) having a two-phase winding 9 having one terminal serving as a common terminal, and a cage type rotor 10. Consists of The main winding terminal of the induction motor 7 is connected to one output of the inverter 3, and the auxiliary winding is connected to the other output. The common terminal is an electrolytic capacitor 2
It is connected to the intersection of e and 2f.

A discharge port 11 for discharging the compressed refrigerant gas and a suction port 12 for sucking the compressed refrigerant gas are provided at the entrance and exit of the compression element 6. From the discharge port 11 of the compression element 6 to the condensation element 13, the pressure reduction element 14, the evaporation element 1
5 and is connected to return to the compression element 6 from the suction port 12 again.

The high-temperature and high-pressure refrigerant gas compressed by the compression element 6 is radiated by the condensation element 13 to be liquefied. At this time, heat is promoted by blowing air with the condensing fan 16. The refrigerant liquefied by the condensing element 13 is decompressed by the decompression element 14. Generally, a capillary tube or an expansion valve is used as the pressure reducing element 14.

The refrigerant decompressed by the decompression element 14 is supplied to the evaporator 1
At 5, it evaporates (vaporizes) and absorbs the heat around it.
At this time, heat absorption (cooling) is promoted by blowing air with the evaporating fan 17 similarly to the condensing element 13. The evaporated refrigerant gas returns to the compression element 6 via the suction port 12 again, and the cycle is repeated to continue the cooling operation.

Reference numeral 18 denotes refrigeration system control means for controlling the entire refrigeration system described above. Reference numeral 19 denotes a temperature detecting means for detecting the temperature of each part in the refrigeration system (for example, the inside temperature, the outside air temperature, the condensation temperature, the evaporation temperature, etc.).

Reference numeral 20 denotes a manual setting means, which can manually change the cooling capacity of the refrigeration system. For example, when the cooling operation is to be performed rapidly (for example, a push button switch is turned on), a high rotation speed can be obtained. The compressor 4 can be operated continuously for a certain period of time, and rapid cooling can be performed.

The refrigeration system control means 18 receives the outputs from the temperature detection means 19 and the manual setting means 20 and determines the frequency to be applied to the compressor 4 by the frequency setting means 21. 16 and a load such as the evaporating fan 17.

For example, if the temperature in the refrigerator is high, the compressor 4 is operated at a high frequency to perform cooling at once, and if the temperature in the refrigerator is low, the compressor 4 is operated at a low frequency to perform energy saving operation. When the quick setting is instructed by the manual setting means 20, the compressor 4 is operated at a high frequency to perform cooling at a stretch.

Reference numeral 23 denotes a voltage pattern selecting means for selecting an optimal voltage pattern set in advance according to the set frequency set by the frequency setting means 21. According to the selected voltage pattern, the output voltage setting means 24 sets the voltage output from the inverter 3. Here, the voltage applied to the main winding and the voltage applied to the auxiliary winding can be set individually.

Reference numeral 25 denotes a waveform generating means, which receives the parameters set by the frequency setting means 21 and the output voltage setting means 24 as inputs and generates ON / OFF signals for the switching elements 3a to 3d of the inverter 3 corresponding thereto. Here, a signal is generated by PWM (pulse width modulation) control so as to obtain a desired output waveform.

Reference numeral 26 denotes drive means for turning on / off the switching elements 3a to 3d of the inverter 3 according to the on / off signal generated from the waveform generation means 25.

Reference numeral 27 denotes voltage detecting means, which outputs the output voltage V1 of the rectifier circuit 2 and the output voltage V1 to the electrolytic capacitor 2e,
An intermediate voltage V2 at the intermediate voltage point of the rectifier circuit 2 divided by 2f is detected.

Numeral 28 denotes a correcting means, and a voltage detecting means 27
Based on the output voltage V1 of the rectifier circuit 2 detected at step (1), an output for correcting the output voltage of the inverter 3 based on the amount of change is sent to the output voltage setting means 24.

Reference numeral 29 denotes a ripple correction means, which calculates a ripple voltage of the electrolytic capacitor 2e and a ripple voltage of the electrolytic capacitor 2f from the voltage detecting means 27, and an inverter so that a predetermined motor current can flow regardless of the ripple voltage. Output voltage setting means 24 outputs the output for correcting the output voltage of
To send to.

Reference numeral 30 denotes a current sensor which detects a current flowing between the common terminal of the two-phase winding 9 of the induction motor 7 and an intermediate voltage point of the rectifier circuit 2 (ie, a motor current). For example, a current transformer or a DC current sensor is used. Reference numeral 31 denotes a current detection unit which receives an output of the current sensor 30 as an input and detects an operation state (a load state and an operation state) of the compressor 4.

Reference numeral 32 denotes a turbulence detecting means for monitoring the flow of the motor current based on the output of the current detecting means 31 and detecting an unstable phenomenon (such as periodically changing) of the motor current. 33 is a parameter changing means, which is a turbulence detecting means 3
When the motor current instability is detected in step 2, the parameter of the output voltage is changed to eliminate the instability,
The instruction is sent to the output voltage setting means 24. Here, the parameter specifically reduces the output voltage.

Reference numeral 34 denotes switching means for changing the output voltage of the rectifier circuit 2 according to an instruction from the refrigeration system control means 18. Specifically, a signal for turning on / off the relay 2h of the rectifier circuit 2 is generated.

According to the present embodiment, when the relay 2h is on, the rectifier circuit 2 has a double voltage rectification configuration, and the output voltage is 280 V when the input voltage is 100 V AC. When the relay 2h is off, the rectifier circuit 2 has a full-wave rectification configuration, and the output voltage is 140V. Therefore, the output voltage of the rectifier circuit 2 can be switched in two stages.

The refrigeration system control means 18 is a frequency setting means 35 is a prediction correction means, and the switching means 34
When the output voltage V1 is changed from 140 V to 280 V, that is, when the relay 2h is turned on from off, the output voltage V1 changes abruptly. Absent. Therefore, the change of the output voltage V1 at this time is stored in advance, and a signal is sent to the output voltage setting means 24 so as to correct the output voltage of the inverter 3 based on the timing.

The basic operation of the control device of the refrigeration system configured as shown in FIG. 1 will be described with reference to FIG.
FIG. 2 is a timing chart of the control device of the refrigeration system according to Embodiment 1 of the present invention. In FIG. 2, the upper four timing diagrams show the switching elements 3a to 3d of the inverter 3.
Shows the on / off timing of the.

However, the switching elements 3a, 3b
Is connected to the main winding and the switching element 3
It is assumed that the windings connected to c and 3d are auxiliary windings. The lower two timing charts in FIG. 2 are the main winding current Im and the auxiliary winding current Ia, respectively. The horizontal axis indicates the phase when one cycle of the output waveform is 360 degrees.

The switching elements 3a and 3b perform chopping of the inversion operation in all periods, and control the pulse width so that the pulse width (that is, area) of the PWM control approaches a sine wave. Looking at the switching element 3a, when the phase is near 0 degree, the pulse width is narrow,
It is turned on / off so that it becomes maximum near the degree. The output voltage can be controlled by adjusting the pulse width.

The switching element 3b performs an inversion operation of the switching element 3a (off when one is on, and on when conversely one is off). The pulse width is large in the vicinity and turned on / off so as to be minimum at around 180 degrees. Since the switching elements 3a and 3b are chopped alternately, a dead time (a period in which both are off) is provided to prevent simultaneous upper and lower ON due to operation delay of the switching elements.

The switching element 3c performs switching advanced from the switching element 3a by a phase difference Φ (90 degrees in FIG. 2), and performs PWM control in all sections. The switching element 3d is the switching element 3
The inversion operation of c is performed.

The ratio of the pulse width (ON period) of the PWM control in the carrier cycle (repetition cycle of chopping) (that is, pulse width / carrier cycle) is called a duty, and the duty is 50% at 0V output.

The current I of the main winding of the induction motor 7
m is a sine wave waveform that crosses zero at 90 degrees and 270 degrees, but is actually a waveform that includes harmonics of the carrier frequency component of the PWM control. On the other hand, the current Ia of the auxiliary winding has a waveform whose phase is advanced by Φ (90 degrees in this embodiment) from the current Im of the main winding.

By changing the duty of the PWM control of the switching element, it is possible to change the output frequency, adjust the output voltage (possible for the main winding and the auxiliary winding), adjust the main auxiliary winding voltage phase difference, and the like. Become. Therefore, drastic energy savings can be achieved by adjusting and driving these parameters so as to be optimal in terms of efficiency and the like. Next, the efficiency when the induction motor 7 is driven by the inverter 3 will be described. FIG. 3 is a characteristic diagram of frequency = motor efficiency according to the first embodiment of the present invention.

In FIG. 3, the horizontal axis represents the output frequency of the inverter 3 and the vertical axis represents the motor efficiency of the induction motor 7. FIG. 3A shows the case where the output voltage of the rectifier circuit 2 is on the high side (that is, double voltage rectification, 280 V).
B shows the case where the output voltage of the rectifier circuit 2 is on the low side (that is, full-wave rectification, 140 V).

As shown in FIG. 3A, in the case of voltage doubler rectification, the efficiency peak point is around 60 Hz, and the lower the frequency is, the lower the motor efficiency is.
In particular, when the frequency is around 30 Hz, a significant decrease in efficiency is observed.

On the other hand, when the output voltage of the rectifier circuit 2 is reduced to 140 V by performing full-wave rectification, the motor efficiency has characteristics as shown in FIG. As a result, the motor efficiency at 30 Hz can be greatly increased, and in addition to the improvement of the efficiency of the refrigeration system due to the low frequency operation, a large energy saving can be realized by increasing the motor efficiency.

Actually, by turning on / off the relay 2h shown in FIG. 1, the rectification method of the rectification circuit 2 is switched between voltage doubler rectification and full-wave rectification. This switching is performed, for example, with a threshold of 40 Hz, and when the frequency set by the frequency setting means 21 is 40 Hz or less, the relay 2h
Is turned off (full-wave rectification), and when the frequency set by the frequency setting means 21 is 41 Hz or more, the relay 2h can be turned on (double-voltage rectification).

Next, the operation of switching between voltage doubler rectification and full-wave rectification will be specifically described with reference to FIG. FIG. 4 is a timing chart showing the operation of the refrigeration system according to Embodiment 1 of the present invention.

FIG. 4A shows the output voltage of the rectifier circuit 2,
(B) shows the output frequency of the inverter 3, (C) shows the output voltage of the inverter 3, (D) shows the duty of the PWM control of the inverter 3, and (E) shows the operation of the relay 2h. The horizontal axis indicates time, and (A) to (E) are all coaxial.

In FIG. 4, during the period from time t0 to time t1, the temperature of the refrigeration system detected by the temperature detecting means 19 is sufficiently low. Machine 5 is stopped. At this time, the relay 2h is off, and the output voltage of the rectifier circuit 2 becomes 140V. Further, the output of the inverter 3 is completely stopped.

Next, since the temperature of the refrigeration system detected by the temperature detecting means 19 at time t1 has risen, the frequency setting means 21 sets an output frequency of 60 Hz. First, since 60 Hz is the frequency range in which voltage is output by voltage doubler rectification, the relay 2h is turned on, and the output voltage of the rectifier circuit 2 is set to 280V.

Next, at time t2, the output of the inverter 3 is started. The output of the inverter 3 uses a method called soft-start in which the frequency and voltage are sequentially increased from a low frequency and a low voltage.
When the voltage reaches 0 V, the change is stopped.

The change in the output voltage of the rectifier circuit 2 when the relay 2h is turned on is instantaneous and changes in one cycle of the frequency of the commercial power supply 1 (16.7 ms for 60 Hz). Therefore, here, a time difference between times t1 and t2 is provided in order to wait for the output voltage of the rectifier circuit 2 to stabilize. Needless to say, this time difference may be short.

Between time t2 and t3, the compressor 5
Is operating, the refrigeration system has a high refrigeration capacity, and cools the inside of the refrigerator at a stretch. In this way, the inside of the refrigerator is sufficiently cooled, and at time t3, the temperature detecting means 19
Since the temperature of the refrigeration system detected by the above has decreased, the frequency setting means 21 sets the output frequency to 30 Hz.

At this time, the output frequency and the output voltage of the inverter 3 are soft-down in the same manner as at the time of starting, and the output frequency and the output voltage are gradually changed so as to reach the target of 30 Hz and 50 V. At this time, since the relay 2h remains ON, the output voltage of the rectifier circuit 2 remains at 280V.

Next, at time t4, the relay 2h is turned off. At this time, the output voltage of the rectifier circuit 2 changes slowly, unlike when the relay 2h is turned on. This time varies depending on the capacity of the electrolytic capacitors 2e, 2f, 2g of the rectifier circuit 2 and the load condition of the compressor 5, but it takes about 140 seconds for about 1 second.
Reach V.

At this time, the output voltage V1 of the rectifier circuit 2 is detected by the voltage detecting means 27, and the output voltage of the inverter 3, that is, the duty of the PWM control output from the inverter 3 is changed by the correcting means. As shown between t4 and t5 in FIG. 4, the duty of the PWM control of the inverter 3 is increased in accordance with the fall of the output voltage of the rectifier circuit 2.

By doing so, the inverter 3
Can maintain a constant voltage. This can prevent the actual rotation speed from changing,
Stable operation is obtained.

During the period from time t5 to time t6, the operation at 30 Hz is continued, and the operation for energy saving is continued. Then, at time t6
In this case, it is assumed that the manual setting means 20 issues an instruction for quick freezing. It is assumed that the compressor 5 is operated at a high speed of 60 Hz for rapid cooling.

At time t6, relay 2h is turned on. At this time, the output voltage of the rectifier circuit 2 changes from 140V to 280V almost instantaneously as described at the time t1.
Therefore, in this portion, it is difficult to change the duty while watching the voltage as described above, and there is a possibility that the motor current may flow too much.

Therefore, here, the switching means 34 receives a signal that turns the relay 2h from off to on, and the prediction correcting means 35 determines that the output voltage of the rectifier circuit 2 changes in a preset pattern, and assumes that the PWM of the inverter 3 Change the control duty. Specifically, after generating a delay of several ms in consideration of the operation delay of the relay, 100% to 75% every half cycle of the power supply frequency (8.3 ms at 60 Hz).
% And 50%. Such a change can prevent a rush current of the motor.

Thereafter, the soft-up is performed in the same manner as in the other cases, and the state becomes 60 Hz and 100 V at time t7. This operation is continued to realize rapid freezing.

At time t8, it is determined that the temperature of the refrigeration system detected by the temperature detecting means 19 is sufficiently low, the output frequency is set to 0 Hz by the frequency setting means 21, and all the outputs of the inverter 3 are stopped. , Relay 2
h is also turned off, and the compressor 5 stops.

Next, the effect of the ripple voltage on the electrolytic capacitors 2e, 2f and 2g will be described with reference to FIG. FIG. 5 is a timing chart of the output voltage and the correction duty of the rectifier circuit 2 according to the first embodiment of the present invention.

FIG. 5A is a timing chart of the output voltage of the rectifier circuit 2, and reference numeral 51 denotes the output voltage V 1 of the rectifier circuit 2.
52 indicates an intermediate voltage V2 of the rectifier circuit 2. Here, the voltage across the electrolytic capacitor 2e is V1-
It can be calculated by V2, and changes as shown by the broken line 53.

Output voltage V1 of rectifier circuit 2 and intermediate voltage V2
Is detected by the voltage detecting means 27 shown in FIG. At the same time, V1-V2 is calculated to find the voltage across the electrolytic capacitor 2e. The ripple correction means 29 calculates the output correction duty of these data.

FIG. 5B shows the result of calculating the correction duty. Reference numeral 54 denotes a correction duty based on the intermediate voltage V2 (a voltage across the electrolytic capacitor 2f), and reference numeral 55 denotes a correction duty relative to the voltage across the electrolytic capacitor 2e.

The duty of the output of the inverter 3 is corrected by the correction duty. The correction duty used for the correction varies depending on the state of the PWM control, and the duty is corrected based on the following concept. Here, the concept of the main winding will be described.

The duty of the switching element 3a is 50
% Or more, power is supplied mainly to the electrolytic capacitor 2e, so that the duty of the PWM control output from the inverter 3 is corrected by the correction duty indicated by 55 in FIG. 5B. For example, at time t10, the supplied voltage is high, so that the duty is corrected to be smaller than the originally generated duty. At time t13, the supplied voltage is low, so that the duty is corrected to be larger than the originally generated duty.

If the duty of the switching element 3a is 50% or less, power is supplied mainly to the electrolytic capacitor 2f. Therefore, the PWM control output from the inverter 3 with the correction duty indicated by 54 in FIG. Is corrected. For example, at time t12, since the supplied voltage is high, the correction is made so as to be smaller than the originally generated duty, and at time t11, the supplied voltage is conversely corrected so as to be larger than the originally generated duty.

Since the duty of the PWM control output from the inverter 3 can be changed by the voltage supplied in this manner, the output voltage level can be kept constant, and the pulsation of the current due to the influence of the ripple voltage of the rectifier circuit 2 can be achieved. And stable operation can be obtained.

Next, the current instability phenomenon will be described with reference to FIG. FIG. 6 is a waveform diagram of the motor current when the current instability occurs according to the first embodiment of the present invention. The horizontal axis in FIG. 6 is the time axis, and the vertical axis is the motor current.

Although a normal current waveform has a substantially sinusoidal current, the motor current is generated excessively when the PWM control duty is high and the input voltage is high at low frequency operation, and the motor current suddenly becomes unstable. May occur. At that time, the phenomenon that the motor current changes from a large current to a small current as shown in FIG. 6 is repeated. At this time, there arises a problem that the compressor 5 itself vibrates greatly, and the input greatly increases.

The motor current detected by the current sensor 30 and the current detecting means 31 is sent to the turbulence detecting means 32. The turbulence detecting means 32 detects this change in the current, and when the change in the current exceeds a certain amount, determines that a current pulsation, that is, turbulence has occurred, and sends a command to the parameter changing means 33. In the parameter changing means 33, one of the parameters, PW
The duty of M control is changed to suppress the turbulence. The disturbance detection means 32 determines that the disturbance has been suppressed.

At this time, if the turbulence detecting means 32 determines that the turbulence cannot be suppressed, the duty of the output voltage is further corrected by the parameter changing means 33. This operation is continued until the tune stops.

By doing so, a stable motor current without current pulsation can be obtained, and a refrigeration system with less compressor vibration can be provided.

As described above, the first embodiment of the present invention
The control device of the refrigeration system has the following effects.

A motor 7 having two-phase stator windings 9 for driving a compression element and a main winding and an auxiliary winding, a rectifier circuit 2 and an inverter 3 having four switching elements bridge-connected.
And the stator winding of each phase of the motor 7 is connected to the output of the inverter 3, the common terminal of the stator winding of the motor 7 is connected to the intermediate voltage point of the rectifier circuit 2, and the frequency is changed according to the state of the refrigeration system. By using a control device for a refrigeration system comprising a frequency setting means 21 for changing the frequency and a waveform generating means 25 for driving the inverter 3 at the frequency set by the frequency setting means 21, the motor can be generally used without changing the motor. A two-phase induction motor, which is widely used as a capacitor run motor, can be used for inverter operation in which the number of revolutions is changed using only four switching elements. Can be realized. In addition, since a compressor using a general two-phase induction motor can be used, it is possible to operate the compressor with a refrigerating capacity according to a refrigerating load without increasing the cost of the compressor. it can.

The intermediate voltage point of the rectifier circuit 2 can be easily obtained by setting the connection point of the capacitors 2e and 2f connected in series between the positive output and the negative output of the rectifier circuit 2. No new loss occurs due to the use of split capacitors. The frequency setting means 21
Since the control device of the refrigeration system includes the switching unit 34 that switches the output voltage of the rectifier circuit 2 according to the output frequency set in the step 3, the output voltage of the rectifier circuit can be switched according to the output frequency of the inverter 3.
Since the output voltage of the rectifier circuit can be selected in accordance with the output frequency of the inverter 3, the efficiency of the motor can be maintained high, and a larger refrigeration system can be saved.

The switching means 34 comprises the frequency setting means 21
The output voltage of the inverter 3 is lowered by lowering the output voltage of the rectifier circuit 2 when the output frequency set in the above is low, and increasing the output voltage of the rectifier circuit 2 when the output frequency is high. Duty (on time /
When the carrier efficiency is low and the motor efficiency is low, the output voltage of the rectifier circuit 2 can be lowered and the duty can be widened, so that the efficiency of the motor can be increased and the energy saving of a larger refrigeration system can be achieved. Become.

The output of the inverter 3 is PWM-controlled, so that a low duty is output when the output voltage of the rectifier circuit 2 is high, and a high duty is output when the output voltage of the rectifier circuit 2 is low. Even if the output voltage of the rectifier circuit 2 changes, the output voltage of the inverter 3 can be kept constant, so that the motor 7 can operate stably.

Further, by configuring the rectifier circuit 2 to be able to switch between voltage doubler rectification and full-wave rectification by turning on / off the relay 2h, the output of the rectifier circuit 2 can be easily obtained only by turning on / off the relay 2h. Voltage 280V / 140
V. In addition, since only switching by the relay 2h is performed, no extra loss occurs, which contributes to energy saving of the refrigeration system.

Switching means 3 for switching the output voltage of rectifier circuit 2 according to the output frequency set by frequency setting means 21
4 and a voltage detecting means 2 for detecting an output voltage of the rectifier circuit 2
7 and a correcting means 2 for correcting the output voltage of the inverter 3 by the voltage detecting means 27 at the time of switching by the switching means 34.
The control device for the refrigeration system comprising the rectifier circuit 8 detects the output voltage of the rectifier circuit and can output the optimum output voltage from the inverter based on the detected value. Even when the output voltage of the circuit is gradually changing, the output voltage of the inverter can be maintained at a constant level, so that stable operation of the compressor can be achieved.

In particular, in the circuit according to the first embodiment of the present invention, the output voltage of rectifier circuit 2 is set to the higher side (voltage doubler rectifier:
When the voltage is switched from 280 V) to the lower side (full-wave rectification: 140 V), the voltage changes slowly due to the charged electric charges of the electrolytic capacitors 2 e, 2 f, and 2 g. Therefore, in accordance with the voltage drop detected by the voltage detecting means 27, the inverter 3
By performing the correction so as to increase the output voltage (i.e., the duty of the PWM control), a stable operation of the compressor with a small fluctuation in the rotation speed becomes possible.

When the switching means 34 switches from the low output voltage of the rectifier circuit 2 to the output voltage of the high rectifier circuit, the prediction correction means 35 predicts a change in the output voltage of the rectifier circuit 2 and corrects the output voltage of the inverter. By controlling the change in the output voltage of the rectifier circuit 2 to a preset predicted value, it is possible to correct the output voltage of the inverter to be suitable for the predicted value by using the control device of the refrigeration system including the rectifier circuit. Thus, even when the output voltage is rapidly changed from a low side to a high side, the inrush current of the motor can be prevented, and continuous stable operation can be performed.

Further, the refrigerating circuit comprises voltage detecting means 27 for detecting the output voltage of the rectifier circuit 2 and ripple correcting means 29 for correcting the output voltage of the inverter according to the change in the ripple voltage detected by the voltage detecting means 27. By using the control device of the system, the output voltage of the inverter according to the ripple voltage of the rectifier circuit 2 can be obtained, so that the motor current waveform becomes a stable waveform without being affected by the ripple voltage, and an extra compressor Vibration is eliminated, and stable operation can be performed.

Further, a controller for a refrigeration system comprising a turbulence detecting means 32 for detecting an unstable operation of the motor 7 and a parameter correcting means 33 for changing the output voltage of the inverter 3 by the turbulence detecting means 32 is provided. When it is detected that an unstable operation of the motor at a low frequency has occurred, the output voltage of the inverter can be reduced, so that the current pulsation of the motor current can be suppressed, and unnecessary vibration of the compressor is eliminated, thus ensuring stable operation. You will be able to drive in a different way.

In the description of the first embodiment, the compression element 6 is of a reciprocating type (reciprocating type), but any type of compression type such as a rotary type (rotary type) or a spiral type (scroll type) may be used. .

The motor 7 used in the compressor 5
Has been described as an induction motor, but any other motor (for example, a synchronous motor, etc.) may be used as long as it has a two-phase winding having one side as a common terminal.

Although the voltage of the rectifier circuit 2 is switched by using the relay 2h, it goes without saying that other switching elements (for example, a triac) can be used.

Although the voltage of the rectifier circuit 2 is switched between voltage doubler rectification and full-wave rectification, another method (for example, a method of providing an intermediate tap or an active method such as a step-up chopper) is used. Needless to say, the same effect can be obtained.

Although the switching elements of the upper and lower arms of the inverter 3 are chopped alternately, it is apparent that there is no problem in turning off the other while switching only one side.

Although the DC voltage and the motor current are input to the state detecting means 3, it is obvious that other methods (for example, the outside air temperature or the inside temperature) may be used as long as the state of the load torque can be known. It is.

[0123]

As described above, the compressor control device of the present invention comprises a motor having two-phase stator windings of a main winding and an auxiliary winding for moving a compression element, a rectifier circuit 2, An inverter 3 in which two switching elements are bridge-connected, and a stator winding of each phase of the motor connected to an output of the inverter;
A common terminal of a stator winding of the motor is connected to an intermediate voltage point of the rectifier circuit, and frequency setting means for changing a frequency according to a state of a refrigeration system; and the inverter is driven at a frequency set by the frequency setting means. By using a two-phase induction motor generally used as a motor for a condenser run without changing the motor, only four switching elements can be used without changing the motor. As a result, the inverter operation for changing the rotation speed can be performed, so that the number of switching elements in the circuit is reduced as compared with the conventional case, and it is possible to realize a small size and low cost. In addition, since a compressor using a general two-phase induction motor can be used, it is possible to operate the compressor with a refrigerating capacity according to a refrigerating load without increasing the cost of the compressor. it can.

Further, by providing a control device for the refrigeration system comprising switching means for switching the output voltage of the rectifier circuit according to the output frequency set by the frequency setting means, the output voltage of the rectifier circuit can be changed according to the output frequency of the inverter. Can be switched, so that the output voltage of the rectifier circuit can be selected according to the output frequency of the inverter, so that the efficiency of the motor can be maintained at a high level, and larger refrigeration system energy can be saved.

Further, switching means for switching the output voltage of the rectifier circuit according to the output frequency set by the frequency setting means, voltage detecting means for detecting the output voltage of the rectifier circuit, and output voltage of the inverter at the time of switching by the switching means. Is controlled by the refrigeration system including the correction means for correcting the output voltage by the voltage detection means, the output voltage of the rectifier circuit can be detected, and the output value can be obtained from the inverter based on the detected value. Therefore, the output voltage of the rectifier circuit is switched, and the output voltage of the inverter can be maintained at a constant level even when the output voltage of the rectifier circuit is gradually changing. It becomes possible.

Further, when the switching means switches from the low output voltage of the rectifier circuit to the output voltage of the high rectifier circuit, the refrigeration system comprises prediction correction means for predicting a change in the output voltage of the rectifier circuit and correcting the output voltage of the inverter. By using the control device of the system, the change in the output voltage of the rectifier circuit can be corrected to the output voltage of the inverter appropriate to the predicted value by setting the change in the output voltage of the rectifier circuit to a preset predicted value. Even when the voltage is suddenly changed when the voltage is switched from the low side to the high side, the rush current of the motor can be prevented and the continuous stable operation can be performed.

Further, the control of the refrigeration system includes voltage detecting means for detecting the output voltage of the rectifier circuit, and ripple correcting means for correcting the output voltage of the inverter in accordance with the change in the ripple voltage detected by the voltage detecting means. By using the device, the output voltage of the inverter according to the ripple voltage of the rectifier circuit can be obtained, so that the motor current waveform becomes a stable waveform without being affected by the ripple voltage, and the extra compressor vibration is reduced. And stable operation can be performed.

Further, by providing a controller for a refrigeration system comprising a turbulence detecting means for detecting an unstable operation of the motor and a parameter correcting means for changing the output voltage of the inverter by the turbulence detecting means, the motor at a low frequency can be obtained. When it is detected that unstable operation has occurred, the output voltage of the inverter can be reduced,
The current pulsation of the motor current can be suppressed, unnecessary vibration of the compressor is eliminated, and stable operation can be performed.

[Brief description of the drawings]

FIG. 1 is a block diagram of a control device of a refrigeration system according to a first embodiment of the present invention.

FIG. 2 is a timing chart of the control device of the refrigeration system according to the first embodiment of the present invention.

FIG. 3 is a characteristic diagram of frequency = motor efficiency according to the first embodiment of the present invention.

FIG. 4 is a timing chart showing the operation of the refrigeration system according to Embodiment 1 of the present invention.

FIG. 5 is a timing chart of an output voltage and a correction duty of the rectifier circuit 2 according to the first embodiment of the present invention.

FIG. 6 is a waveform diagram of a motor current when a current instability occurs according to the first embodiment of the present invention;

FIG. 7 is a block diagram of a control device of a conventional refrigeration system.

[Explanation of symbols]

 2 Rectifier circuit 3 Inverter 6 Compression element 7 Induction motor 13 Condensing element 14 Decompression element 15 Evaporation element

 ──────────────────────────────────────────────────続 き Continued on the front page F term (reference) 3L045 AA02 BA01 CA02 DA02 LA06 NA01 5H576 AA03 BB02 BB03 BB04 CC05 DD01 DD04 EE11 EE25 FF02 FF03 FF04 FF07 FF08 GG04 GG10 HA03 HB01 JJ03 KK05 LL22 LL24LL43LL

Claims (11)

[Claims] 1. A compression element, a condensation element, a decompression element,
A refrigeration system including an evaporating element, a motor having two-phase stator windings of a main winding and an auxiliary winding for moving the compression element, a rectifier circuit, an inverter in which four switching elements are bridge-connected, The stator windings of each phase of the motor are connected to the output of the inverter, the common terminal of the stator windings of the motor is connected to the intermediate voltage point of the rectifier circuit, and the frequency is changed according to the state of the refrigeration system. A control device for a refrigeration system, comprising: a setting unit; and a waveform generating unit configured to drive the inverter at a frequency set by the frequency setting unit. 2. The refrigeration system controller according to claim 1, wherein the intermediate voltage point of the rectifier circuit is a connection point of a capacitor connected in series between a positive output and a negative output of the rectifier circuit. 3. A compression element, a condensation element, a decompression element,
A refrigeration system including an evaporating element, a motor having two-phase stator windings of a main winding and an auxiliary winding for moving the compression element, a rectifier circuit, an inverter in which four switching elements are bridge-connected, The stator windings of each phase of the motor are connected to the output of the inverter, the common terminal of the stator windings of the motor is connected to the intermediate voltage point of the rectifier circuit, and the frequency is changed according to the state of the refrigeration system. Setting means; a waveform generating means for driving the inverter at the frequency set by the frequency setting means; and switching means for switching the output voltage of the rectifier circuit according to the output frequency set by the frequency setting means. Control device for refrigeration system. 4. The refrigeration system according to claim 3, wherein the switching means reduces the output voltage of the rectifier circuit when the output frequency set by the frequency setting means is low, and increases the output voltage of the rectifier circuit when the output frequency is high. Control device. 5. The refrigeration system according to claim 3, wherein the output of the inverter is PWM-controlled, and outputs a low duty when the output voltage of the rectifier circuit is high, and outputs a high duty when the output voltage of the rectifier circuit is low. System control unit. 6. The rectifier circuit comprises a bridge connection of four diodes, two capacitors connected in series at the output thereof, and a connection between the midpoint of the bridge-connected one-side diode and the midpoint of the series-connected capacitors. 4. The control device for a refrigeration system according to claim 3, wherein a relay is connected to the refrigeration system when the relay is on, and is switched to full-wave rectification when the relay is off. 7. A compression element, a condensation element, a decompression element,
A refrigeration system including an evaporating element, a motor having two-phase stator windings of a main winding and an auxiliary winding for moving the compression element, a rectifier circuit, an inverter in which four switching elements are bridge-connected, The stator windings of each phase of the motor are connected to the output of the inverter, the common terminal of the stator windings of the motor is connected to the intermediate voltage point of the rectifier circuit, and the frequency is changed according to the state of the refrigeration system. Setting means, a waveform generating means for driving the inverter at a frequency set by the frequency setting means, and a switching means for switching the output voltage of the rectifier circuit according to the output frequency set by the frequency setting means, Voltage detection means for detecting the output voltage of the rectifier circuit, and the output voltage of the inverter to the voltage detection means at the time of switching by the switching means Control apparatus for a refrigeration system including a correcting means for correcting Ri. 8. The output voltage of the rectifier circuit is switched from a high side to a low side, and when the voltage detected by the voltage detection means is falling, the output voltage of the inverter is raised in accordance with the fall of the output voltage of the rectification circuit. The control device for a refrigeration system according to claim 7, wherein the correction is performed so as to perform the correction. 9. A compression element, a condensation element, a decompression element,
A refrigeration system including an evaporating element, a motor having two-phase stator windings of a main winding and an auxiliary winding for moving the compression element, a rectifier circuit, an inverter in which four switching elements are bridge-connected, The stator windings of each phase of the motor are connected to the output of the inverter, the common terminal of the stator windings of the motor is connected to the intermediate voltage point of the rectifier circuit, and the frequency is changed according to the state of the refrigeration system. Setting means, a waveform generating means for driving the inverter at a frequency set by the frequency setting means, and a switching means for switching the output voltage of the rectifier circuit according to the output frequency set by the frequency setting means, The switching means predicts a change in the output voltage of the rectifier circuit when switching from the output voltage of the lower rectifier circuit to the output voltage of the higher rectifier circuit. Control apparatus for a refrigeration system including a prediction correction means for correcting the output voltage. 10. A refrigeration system comprising a compression element, a condensation element, a decompression element, and an evaporation element, wherein a motor having two-phase stator windings for driving the compression element is provided. A rectifier circuit, an inverter in which four switching elements are bridge-connected, and a stator winding of each phase of the motor connected to an output of the inverter, and a common terminal of the stator winding of the motor connected to the rectifier circuit. Frequency setting means connected to the intermediate voltage point and changing the frequency according to the state of the refrigeration system, waveform generating means for driving the inverter at the frequency set by the frequency setting means, and output voltage of the rectifier circuit And a ripple correction means for correcting the output voltage of the inverter in accordance with a change in the ripple voltage detected by the voltage detection means. System control unit. 11. A refrigeration system comprising a compression element, a condensation element, a decompression element, and an evaporation element, wherein a motor having a two-phase stator winding, a main winding and an auxiliary winding, for moving the compression element. A rectifier circuit, an inverter in which four switching elements are bridge-connected, and a stator winding of each phase of the motor connected to an output of the inverter, and a common terminal of the stator winding of the motor connected to the rectifier circuit. Frequency setting means connected to the intermediate voltage point and changing the frequency according to the state of the refrigeration system, waveform generating means for driving the inverter at the frequency set by the frequency setting means, and unstable operation of the motor A controller for a refrigeration system, comprising: a turbulence detecting means for detecting an output of the inverter;