JP2002176767A - Control method of compressor - Google Patents

Abstract

PROBLEM TO BE SOLVED: To prevent a part from being damaged by suppressing an overshoot of the output voltage of an active filter from being overshot. SOLUTION: In this control method for compressor, a rectifying part converts AC power supply into DC voltage, the active filter turns the DC voltage into a prescribed DC voltage and supplies it to an inverter, the inverter converts the DC voltage into arbitrary AC voltage and applies it to a motor of the compressor to activate the active filter. By activating the active filter, a power supply synchronized signal synchronized with the DC power supply is obtained, an inner counter of a microcomputer is cleared (ST1), the set value of the output DC voltage is set to 228 V and the active filter is activated (ST2, ST3), and a rising edge of the power supply synchronized signal is counted by a counter (ST4, ST5). When the count value reaches 2, the set value of the output DC voltage is switched to 350 V at ordinary operation to reduce a boost range at each stage.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a control technique for inverter-controlling a motor (brushless DC motor) of a compressor such as an air conditioner, and more particularly to a control technique for controlling an output voltage of a power factor improving power supply circuit (active filter). The present invention relates to a method for controlling a compressor to be controlled.

[0002]

2. Description of the Related Art In recent air conditioners and the like, it is common to employ inverter control for a compressor motor. In this inverter control, an AC power supply is converted into a DC power supply, and the converted DC voltage is converted into an arbitrary AC voltage by an inverter and applied to the motor.

As a means for converting the AC power supply to a DC power supply, a capacitor input type power supply circuit is generally employed. However, the waveform of the AC current input from the AC power supply becomes distorted, and the harmonic current is reduced. Occurs. In order to make the input AC current waveform substantially sinusoidal (sinusoidal), for example, as shown in FIG. 4, a control device including a power supply circuit of a boost converter type active filter has been proposed.

In FIG. 4, the control device includes a rectifier 2 for full-wave rectifying an AC power supply 1 and converting the DC power into a DC voltage. The DC voltage is boosted to a predetermined voltage, and the input AC current waveform is changed into a sine wave. An active filter unit 3 for controlling, an inverter unit 5 for converting an output DC voltage (output voltage) of the active filter unit 3 into a three-phase AC voltage and applying the three-phase AC voltage to a motor 4 of the compressor, and an active filter unit 3 A control IC 6 for controlling, and a control circuit (microcomputer) 7 for outputting a control signal (ON / OFF, output voltage set value) of the control IC 6 and a control signal (including a PWM waveform) of a switching element of the inverter unit 5
And a driver unit 8 that drives a switching element of the inverter unit 5 according to the control signal.

The active filter section 3 includes a rectifying section 2
Choke coil 3a connected in series to the positive terminal side of
A reverse blocking diode 3b connected in series to the boost choke coil 3a; and a switching element (IGBT; insulated gate transistor) 3 connected to the negative terminal side of the rectifier 2 between the boost choke coil 3a and the reverse blocking diode 3b.
c, a smoothing capacitor 3d for smoothing the output voltage, an input voltage detection circuit 3e for detecting the input voltage, a current detection circuit (shunt resistor) 3f for detecting the current, and an output voltage detection circuit for detecting the output voltage 3g.

According to the above control device, the active filter unit 3 is controlled and the switching element of the inverter unit 5 is controlled so that the motor 4 has a rotation speed (target operating frequency of the compressor) required for controlling the room temperature of the air conditioner. Is turned on and off. In this case, the control circuit 7 controls the control signal (ON / O) necessary for the control IC 6 to set the current operating frequency of the compressor to the target operating frequency.
FF, set value of output DC voltage) and output motor P
Perform WM control.

The control IC 6 includes an active filter unit 3
Input the detection input voltage, current and output voltage at
The switching element 3c is switched in a predetermined manner so that the input AC current waveform has a sine wave shape and the output voltage has a set value. The active filter unit 3
Is already known, and the description thereof is omitted.

[0008] As described above, by making the input AC current waveform a sine wave shape, the distortion wave of the input AC current waveform can be reduced and the harmonic current can be reduced, so that the power factor can be improved. .

The control IC 6 activates the active filter section 3 according to a control signal (ON / OFF, set value of output DC voltage) from the control circuit 7, and
The output voltage is boosted to the set value of the output DC voltage. For example, in the case of an air conditioner, the set value of the output DC voltage is (square root 2) × input voltage × 1.2 (input voltage fluctuation) +10 V in consideration of the operation guarantee range of the input voltage fluctuation. Specifically, when AC 200 V is rated, the set value of the output DC voltage at the time of startup is 350 V.

[0010]

In the compressor control method described above, the active filter section 3 is activated to boost the output voltage to 350 V. However, since the output voltage is large, the voltage is inevitably increased as shown in FIG. Overshoot increases.

For example, the rated voltage of a component such as a smoothing capacitor may be exceeded, which may not only cause damage to the component or the like at worst, but also may require a time Ta until the output voltage reaches a constant value of 350 V. There were drawbacks.

In particular, when the input power supply voltage (AC power supply 1) fluctuates in the negative direction, the difference between the peak value of the input power supply voltage and the set value of the output DC voltage of the active filter unit 3 increases, and the active filter unit 3 , The step-up width becomes large, and the above-described problem is likely to occur.

As a specific example, when the output voltage is reduced by 20% from the rated AC 200 V, the output voltage becomes 225 V at the reduced peak value of AC 160 V. Therefore, the output voltage must be increased by 125 V until the output voltage set value becomes 350 V. However, the step-up width in the active filter section 3 increases accordingly. At the time of rating after the activation of the active filter section 3, it is necessary to increase 68V until the output voltage setting of the active filter section 3 reaches 350V at a peak value of 282V.

SUMMARY OF THE INVENTION The present invention has been made in consideration of the above problems, and has as its object to suppress overshoot of the output voltage of an active filter, prevent damage to various components, and reduce the output voltage during startup in a short time. It is an object of the present invention to provide a compressor control method that can stabilize a set value of an output DC voltage required for the control.

[0015]

SUMMARY OF THE INVENTION In order to achieve the above object, the present invention converts an AC power supply into a DC voltage by a rectifier and supplies the DC voltage as a predetermined DC voltage to an inverter by an active filter. The inverter means applies an arbitrary AC voltage to the compressor motor, and when the motor is operated at a predetermined operating frequency, the switching means of the active filter is driven in a predetermined manner so that at least the input AC current waveform is sinusoidal. In the method of controlling a compressor, a rectangular wave power supply synchronizing signal synchronized with the AC power supply is obtained, and when the output DC voltage is set at the time of starting the active filter, the set value of the output DC voltage is lower than that in the normal operation. Value and the set value of the output DC voltage every predetermined time by the power supply synchronization signal. Increase in Kaiteki, eventually switched to the normal set value of the output DC voltage during operation, it is characterized in that so as to suppress the overshoot of the output voltage of the active filter.

The predetermined time may be a time when the edge of the power supply synchronizing signal is counted and the count value reaches a predetermined value. Thus, for example, in an air conditioner or the like, the power supply synchronization signal can be easily obtained by the current sensor or the detection circuit for overcurrent protection, and the edge count can be obtained by the microcontroller of the control means. Since it can be performed by the internal counter of the computer, it is not necessary to add a new hardware circuit or the like.

According to the compressor control method of the present invention, while obtaining a rectangular wave power supply synchronization signal synchronized with the AC power supply,
When setting the output DC voltage at the start of the active filter, the set value of the output DC voltage is set to a value lower than the set value in the normal operation, and the edges of the power supply synchronization signal are counted. When the value reaches the value, the set value is switched to the value at the time of the normal operation, and the overshoot of the output voltage of the active filter is suppressed.

When the set value of the output DC voltage in the normal operation is 350 V, a value lower than the set value in the normal operation (set value of the output DC voltage) is 288 V, and the predetermined value of the counter is The time required for the output voltage of the active filter to reach at least 288 V may be obtained empirically. This ensures that the output voltage of the active filter is boosted to a value one step lower and then boosted to the set value during normal operation, so that the boost control of the active filter is appropriately performed.

[0019]

FIG. 1 is a block diagram showing an embodiment of the present invention.
This will be described in detail with reference to FIG. In FIG. 2,
The same parts as those in FIG. FIG. 3 is a graph corresponding to FIG.

In FIG. 2, the control device to which the compressor control method of the present invention is applied includes a control signal (ON / O) for starting the active filter unit 3 to the control IC 6.
FF, the set value of the output DC voltage), the set value of the output DC voltage is set at least one step lower, and after a predetermined period of the frequency of the AC power supply 1, the set value is switched to the set value for normal operation. A control circuit (microcomputer) 10 for performing control is provided.

In the predetermined period, a current waveform of the AC power supply 1 is detected by a current detection sensor (CT) 11 and a current detection circuit 12 to generate a rectangular wave signal (power supply synchronization signal). It is obtained by counting with a counter 10a inside the computer 10.

The power supply synchronizing signal is a rectangular wave signal whose polarity is inverted at the zero-cross point of the AC current waveform. In an air conditioner or the like, the current detection sensor 11 and the current detection circuit 12 are already used for overcurrent protection. If there is one, a power supply synchronizing signal can be obtained using the sensor and the detection circuit, and there is no need to add a new sensor or detection circuit. The other parts of the control device are the same as those of the control device shown in FIG.
The function of the control circuit 7 shown in FIG.

Next, the operation of the control device having the above configuration will be described with reference to the flowchart of FIG. 1 and the graph of FIG. First, the control circuit 10 controls the motor 4 of the compressor.
Is started and controlled, at least the set value of the start-up and start-up output DC voltage is output to the control IC 6, and the rotation of the motor 4 is controlled by a control signal (including PWM) for controlling the inverter unit 5.

At the time of the start, the control section 10 executes the flowchart of FIG. 1, clears and initializes the value n of the counter 10a (step ST1), and sets the set value of the start output DC voltage to the set value of 350 V in the normal operation. 288 value one step lower
V (step ST2). Then, a control signal (ON / OFF, set value of output DC voltage; 288 V) for starting the compressor is output to the control IC 6 (step S).
T3), a rising edge of the power supply synchronizing signal is detected from the start time t1 (see FIG. 3A) (step ST4).

Subsequently, when the rising edge of the power supply synchronizing signal is detected (see time t2 in FIG. 3A), the process proceeds from step ST4 to ST5, where the counter 10a is incremented and the count value n is set to n + 1. Until the count value n reaches a predetermined value, the above steps ST4 and S
T5 and ST6 are repeated. During this time, the control IC 6 activates the active filter section 3 and controls the switching of the switching element 3c so that the output voltage becomes 288V.

The predetermined value of the count value n is empirically obtained and, for example, as shown in FIG. 3, such that the output voltage of the active filter section 3 reaches the set value of 288 V in two periods of the power supply synchronizing signal. Then, it is sufficient to set “2”.

Subsequently, when the value n of the count 10a becomes 2 (see the time point t3 in FIG. 3A), the process proceeds from step ST6 to ST7, in which the set value of the output DC voltage is set to 350 V which is the set value in normal operation. Switch. Thereby, the control IC
Reference numeral 6 controls the switching of the switching element 3c so that the output voltage of the active filter unit 3 becomes 350V.

As described above, the set value of the output DC voltage is 288 V for a predetermined time after the activation of the active filter unit 3.
Thereafter, the set value of the output DC voltage is switched to the set value of 350 V in the normal operation, so that the step-up width at each stage can be smaller than in the conventional case. Therefore, at least the overshoot at the final stage can be suppressed, and damage to components such as the smoothing capacitor can be prevented.

As shown in FIG. 3, the period from the start to the predetermined time, that is, the time from t1 to t3 in FIG. 3 is slightly different depending on the start timing, but the time is within the fluctuation range of the start timing (maximum synchronization). (１ ／ cycle of signal)
It is a good idea to empirically take this into account. Specifically, the output voltage of the active filter unit 3 is set to fall, for example, in the vicinity of 288 V during a period from the start to the predetermined time.

As described above, since the output voltage overshoot is suppressed particularly in the final stage,
The time Tb (<Ta; see FIG. 5) until the output voltage of the active filter unit 3 stabilizes to the normal output voltage set value can be shortened. Further, since the output voltage of the active filter unit 3 is boosted to the normal output voltage set value in two stages, the software of the control circuit 10 can be simple and the load on the microcomputer can be reduced. According to the above-described effects, when the motor 4 is applied to a compressor of an air conditioner, stable control can be performed without causing a problem in room temperature control.

In the above embodiment, the set value of the output DC voltage is switched to the set value for the normal operation in two steps, but the same processing can be applied to two or more steps. In this case, the set value of the output DC voltage at each stage is switched at intervals (empirical periods of the power supply synchronization signal) empirically obtained in advance.

Thus, the more the number of stages, the smaller the boosting width in each stage. That is, the overshoot of the output voltage is reduced, which is particularly effective against fluctuations in the input AC power supply. On the other hand, the time required for the output voltage to stabilize to the normal output voltage set value may be long.However, the magnitude of the overshoot of the output voltage and the output voltage may be reduced to the normal output voltage set value. The number of stages may be obtained in consideration of the time until stabilization.

[0033]

According to the present invention described above, the following effects can be obtained. According to the present invention, an AC power supply is converted into a DC voltage by a rectifier, and this DC voltage is supplied to an inverter as a predetermined DC voltage by an active filter, and is applied to the compressor motor as an arbitrary AC voltage by the inverter. When the motor is operated at a predetermined operating frequency, in a compressor control method for driving the switching means of the active filter in a predetermined manner so that at least the input AC current waveform is sinusoidal, a rectangular wave power supply synchronized with the AC power supply is provided. While getting the synchronization signal,
When setting the output DC voltage when the active filter is started, the set value of the output DC voltage is set to a value lower than that in the normal operation, and the set value of the output DC voltage is set at predetermined intervals by the power supply synchronization signal. The output voltage is gradually increased when the active filter is started, since the output DC voltage is finally switched to the set value of the output DC voltage in the normal operation. At this time, since the boost width is small, despite the fluctuation of the input AC power supply,
Overshoot of the output voltage of the active filter can be suppressed, and as a result, damage to components such as the smoothing capacitor can be prevented. Further, there is an effect that the time until the output voltage of the active filter stabilizes to the output voltage set value in the normal state can be shortened.

According to the compressor control method of the present invention, a rectangular wave power supply synchronizing signal synchronized with the AC power supply is obtained.
When setting the output DC voltage at the start of the active filter, the set value of the output DC voltage is set to a value lower than the set value in the normal operation, and the edges of the power supply synchronization signal are counted. When the set value is reached, the set value is switched to the value in the normal operation, so that the same effect as described above can be obtained, and in the case of an air conditioner or the like, the current sensor and the detection circuit are excessive. Since they are already provided for current protection, they can also be used to obtain a power supply synchronization signal. If the internal counter of the microcomputer of the control means is used, it is not necessary to add hardware. Therefore, there is an effect that the setting control of the output voltage setting value is simple and the load on the microcomputer of the control means is light.

[Brief description of the drawings]

FIG. 1 is a schematic flowchart illustrating a method of controlling a compressor according to an embodiment of the present invention.

FIG. 2 is a schematic block diagram for explaining a control device to which the control method of the compressor shown in FIG. 1 is applied.

FIG. 3 is a schematic graph showing the embodiment of the present invention and illustrating a method of controlling a compressor.

FIG. 4 is a schematic block diagram for explaining a conventional motor control device.

FIG. 5 is a schematic graph for explaining the operation of the control device shown in FIG. 4;

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 AC power supply 2 Rectification part 3 Active filter part 3c Switching element 3d Smoothing capacitor 4 Motor (of a compressor) 5 Inverter part 6 Control IC 7,10 Control circuit (microcomputer) 10a Counter 11 Current sensor (CT) 12 Current detection circuit

──────────────────────────────────────────────────の Continued on the front page (51) Int.Cl. ⁷ Identification code FI Theme coat ゛ (Reference) H02M 7/48 H02M 7/48 Y F-term (Reference) 5H006 AA02 BB05 CA01 CA07 CB01 CC02 CC08 DA02 DA04 DB02 DC02 DC05 GA02 5H007 BB06 CA01 CB02 CB05 CC12 CC23 DB01 DB03 DC02 DC05 EA02 5H730 AA17 AA18 AS13 BB14 BB57 CC04 DD03 EE02 EE07 FD01 FD11 FD41 FF09 FG05 XC14

Claims (4)

[Claims] 1. An AC power supply is converted into a DC voltage by a rectifier, the DC voltage is supplied to an inverter as a predetermined DC voltage by an active filter, and the inverter supplies an arbitrary AC voltage to a motor of a compressor. When the motor is operated at a predetermined operating frequency, in a compressor control method for driving the switching means of the active filter in a predetermined manner so that at least the input AC current waveform becomes a sine wave, a rectangular wave synchronized with the AC power supply is used. While obtaining the power supply synchronization signal, when setting the output DC voltage at the time of activation of the active filter, the set value of the output DC voltage is set to a lower value than in the normal operation, and the output is set at a predetermined time by the power supply synchronization signal. Increase the DC voltage setting step by step, and finally set the output DC voltage during normal operation A control value of the output voltage of the active filter to suppress overshoot of the output voltage of the active filter. 2. The compressor control method according to claim 1, wherein the predetermined time is a time when the edge of the power supply synchronization signal is counted and the count value reaches a predetermined value. 3. An AC power source is converted into a DC voltage by a rectifier, the DC voltage is supplied to an inverter as a predetermined DC voltage by an active filter, and the inverter applies an arbitrary AC voltage to a motor of a compressor. When the motor is operated at a predetermined operation frequency, in a compressor control method for driving the switching means of the active filter in a predetermined manner so that at least the input AC current waveform is sinusoidal, a rectangular wave synchronized with the AC power supply is used. While obtaining the power supply synchronization signal, when setting the output DC voltage at the time of starting the active filter, the output DC voltage set value is set to a value lower than the set value in normal operation, and the edge of the power supply synchronization signal is counted. And
When the count value reaches a predetermined value, the set value is switched to a value at the time of normal operation to suppress an overshoot of the output voltage of the active filter. 4. When the set value of the output DC voltage in the normal operation is 350 V, a value lower than the set value in the normal operation (set value of the output DC voltage) is set to 288 V, and the predetermined value of the counter is set. 4. A method according to claim 3, wherein the value is obtained by empirically determining the time for the output voltage of the active filter to reach at least 288V.