JP4591007B2 - Converter device - Google Patents

Description

  The present invention relates to a converter device that supplies DC power to an inverter device of an air conditioner, for example.

  Conventionally, for example, in an air conditioner, AC power received from an AC power source is converted into DC power by a converter device, this DC power is converted to AC power of a predetermined frequency by an inverter device, and supplied to a compressor. The rotation speed of this compressor is controlled. In the air conditioner, the value of the alternating current supplied from the alternating current power source is detected, and when the detected value exceeds a predetermined value, the inverter device is controlled to drop to the compressor having the largest power consumption. Reduce the power supply. Thereby, the alternating current value from the said alternating current power supply is reduced, and the operation | movement of the breaker of this alternating current power supply is prevented.

  In a conventional air conditioner, a current transformer (hereinafter referred to as CT) is provided between the AC power source and the converter device, and the AC current value from the AC power source is measured by the CT.

  However, when the CT is used, there is a problem that the cost of the air conditioner is increased. In addition, the circuit configuration of the air conditioner is complicated.

  Therefore, conventionally, an air conditioner in which CT is deleted and an alternating current value from an alternating current power source is estimated by a microcomputer (hereinafter referred to as a microcomputer) based on an output voltage value and an output current value of a converter device. It has been proposed (see, for example, Japanese Patent Application Laid-Open No. 2003-254591: Patent Document 1, Japanese Patent Application Laid-Open No. 2004-153889: Patent Document 2).

The microcomputer of this air conditioner calculates by substituting the value of the DC voltage and DC current output from the converter device, the value of the AC voltage of the AC power supply, the power factor and the circuit efficiency into the following equation (1). The AC current value from the AC power source is estimated.
I _ac = I _dc × (V _dc / (V _ac × cos θ × η)) (1)
Here, I _ac is an AC current value of the AC power source, Vac is an AC voltage value of the AC power source, I _dc is a DC current value from the converter device, and V _dc is a DC voltage value from the converter device. Where cos θ is the power factor and η is the circuit efficiency. Note that the AC voltage value _Vac of the AC power supply is not an actual measurement value, but an arithmetic value calculated based on the rated value of the AC power supply or the DC voltage value from the converter device.

However, since the conventional air conditioner has a relatively large error in the AC voltage value _Vac , which is a rated value or a calculated value, the estimated value _Iac of the AC current according to the equation (1) has a relatively large error. There is a problem of being big. Therefore, when the operating range of the air conditioner is set to a range in which the AC power supply breaker does not operate based on the estimated value _Iac of the above formula (1), it is set to a range of about 85% or less of the estimated value _Iac. You may need to In other words, the conventional air conditioner may be able to set the operating range only to a range of about 85% with respect to the range that can be operated without actually operating the AC power supply breaker. Therefore, the conventional air conditioner described above has a problem in that the performance actually possessed cannot be sufficiently exhibited, and an excessive performance may be given to the actually required performance.
JP 2003-254591 A JP 2004-153889 A

  Then, the subject of this invention is providing the converter apparatus which can estimate the alternating current value supplied from alternating current power supply with high precision.

In order to solve the above problems, a converter device of the present invention includes a rectifying unit that converts AC power from an AC power source into DC power;
An inductance element connected in series to one of the AC power lines connecting the AC power source and the rectifying unit;
A switching unit that short-circuits the AC power supply when turned on via the inductance element;
A switching control unit for controlling on / off of the switching unit;
An estimated value calculating unit that calculates an estimated value of the alternating current supplied from the alternating current power source based on the value of the direct current output from the rectifying unit and the duty ratio by which the switching control unit drives the switching unit; In a converter device comprising:
Estimated value of the alternating current is characterized Rukoto determined by the following formula.
_{I ac = A × I dc /} (1-C × D on) + B
Here, I _ac is an estimated value of AC current, I _dc is a DC current value output from the rectifier, D _on is a duty ratio for driving the switching unit, and A, B, and C are constants. It is.

  According to the said structure, the alternating current power from alternating current power supply is rectified by a rectification part, and is converted into direct-current power. The converted DC power is supplied to, for example, an inverter device and the like, converted into AC power having a predetermined frequency by the inverter device, and a compressor of, for example, an air conditioner supplied with the AC power is driven. At this time, the power factor is controlled by turning on the switching unit and short-circuiting the AC power source via the inductance element when the switching unit is turned on. Based on the value of the direct current from the rectifying unit and the duty ratio when the switching control unit performs on / off control of the switching unit, an estimated value of the alternating current supplied from the alternating current power source is calculated by the estimated value calculation unit Is done. Since this estimated value is calculated based on the DC current and the duty ratio, the error is relatively smaller than the estimated value calculated based on the AC voltage value including a relatively large error as in the prior art. Therefore, for example, when an air conditioner is configured using this converter device, the operating range of the air conditioner can be set to the maximum range as long as the AC power supply breaker does not actually operate.

  Further, since the estimated value is calculated based on the two parameters of the direct current and the duty ratio, the direct current voltage value, direct current value output from the converter device, and the alternating current voltage of the alternating current power supply as in the conventional case. The processing load of the estimated value calculation unit can be reduced compared to calculating the estimated value based on the three parameters. Therefore, it is possible to reduce the cost of a program such as a microcomputer that constitutes the estimated value calculation unit, or by using an inexpensive microcomputer having a low processing capability. Further, even when the estimated value is calculated using a table, the table stored in advance in the storage unit such as a memory can be reduced in scale, so that the occupation ratio in the storage unit of this table can be reduced, and the storage unit Can be small.

Furthermore , according to the above formula, the value of the alternating current can be estimated from the direct current value output from the rectifying unit and the duty ratio at which the switching unit is driven.

As described above, the converter device according to the present invention includes an inductance connected in series to one of a rectifying unit that converts AC power from an AC power source into DC power, and an AC power line that connects the AC power source and the rectifying unit. A switching unit that short-circuits the AC power supply when turned on via the inductance element, a switching control unit that controls on / off of the switching unit, a value of the direct current output from the rectifying unit, and the switching Since the control unit includes an estimated value calculation unit that calculates an estimated value of the alternating current supplied from the alternating current power source according to the following formula based on the duty ratio for driving the switching unit, it is relatively large as in the past. The error of the estimated value of the alternating current can be made smaller than the estimated value calculated based on the alternating voltage value including the error. Therefore, for example, when an air conditioner is configured using this converter device, the operating range of the air conditioner can be set to the maximum range as long as the AC power supply breaker does not actually operate.
_{I ac = A × I dc /} (1-C × D on) + B
Here, I _ac is an estimated value of AC current, I _dc is a DC current value output from the rectifier, D _on is a duty ratio for driving the switching unit, and A, B, and C are constants. It is.

  Hereinafter, the present invention will be described in detail with reference to the illustrated embodiments.

  FIG. 1 is a schematic view showing an outdoor unit of an air conditioner using a converter device according to an embodiment of the present invention.

  The outdoor unit of the air conditioner includes a converter unit 1 connected via a relay switch 4 to an AC power source 3 that supplies single-phase AC power, and an inverter unit 7 that is supplied with DC power from the converter unit 1. And a compressor 9 to which three-phase AC power is supplied from the inverter unit 7. The converter unit 1 and the inverter unit 7 are connected to a control unit 8 so that their operations are controlled.

  The converter unit 1 has a reactor 5 as an inductance element connected to one output line of the AC power supply 3. One end of the AC input terminal of the diode bridge DB1 is connected to the other end of the reactor 5, and the other AC input terminal of the diode bridge DB1 is connected to the other output line of the AC power source 3. The positive side DC output terminal of the diode bridge DB1 is connected to the positive side input terminal of the inverter unit 7, and the negative side DC output terminal of the diode bridge DB1 is connected to the negative side input terminal of the inverter unit 7. Further, a smoothing capacitor C1 is connected between the positive side DC output terminal and the negative side DC output terminal of the diode bridge DB1. Further, two voltage doubler capacitors C2 and C3 are connected in series between the positive DC output terminal and the negative DC output terminal of the diode bridge DB1. The diode bridge DB1, the smoothing capacitor C1, and the voltage doubler capacitors C2 and C3 constitute a rectifier circuit.

  Further, one of the AC input terminals of the diode bridge DB2 is connected to a connection point (neutral point) between the two voltage doubler capacitors C2 and C3, and the other of the AC input terminals of the diode bridge DB2 is connected to It is connected to the other output line of the AC power source 3. The collector of the NPN transistor Tr is connected to the positive DC output terminal of the diode bridge DB2, and the emitter of the transistor Tr is connected to the negative DC output terminal of the diode bridge DB2. The output terminal of the control unit 8 is connected to the base of the transistor Tr. The diode bridge DB2 and the transistor Tr constitute a switching unit.

  The inverter unit 7 includes an inverter circuit composed of a plurality of switching elements, and this inverter circuit is connected to the output terminal of the control unit 8.

  The control unit 8 outputs a drive signal for driving the transistor Tr of the converter unit 1 and also outputs a drive signal for driving the inverter circuit of the inverter unit 7. The power factor is optimized by generating a drive signal for the converter unit 1 based on the drive signal for the inverter circuit.

Further, the control unit 8 functions as an estimated value calculation unit that estimates the value of the alternating current supplied from the AC power supply 3 to the converter unit 1. That is, the control unit 8 includes a microcomputer including a processor and a memory, and stores a program for calculating the following expression (2) and a constant in the memory of the microcomputer.
_Iac = A * _Idc / (1-C * _Don ) + B ... (2)
Here, I _ac is an estimated value of the AC current supplied from the AC power supply 3, I _dc is a DC current value output from the converter unit 1, and D _on is a transistor Tr of the converter unit 1 driven. The duty ratio, and A, B, and C are constants.

Further, the control unit 8 includes a current detection circuit that detects a DC current output from the converter unit 1, and detects a DC current value I _dc by the current detection circuit. Further, based on the drive signal output to the transistor Tr of the converter unit 1, the duty ratio D _on of this drive signal is calculated. The microcomputer of this control unit calculates the alternating current value I _ac from the alternating current power source by substituting the direct current value I _dc and the duty ratio D _on into the equation (2) for calculation. The control unit 8 and the converter unit 1 constitute a converter device of the present invention.

  An air conditioner including the converter device having the above configuration operates as follows.

  First, when the air conditioner is activated, the relay switch 4 is turned on, and AC power having a predetermined rated voltage and frequency is supplied from the AC power source 3 to the converter unit 1. The control unit 8 calculates the frequency and voltage value of the AC power to be supplied from the inverter unit 7 to the compressor 9 in response to the load such as the room temperature, and based on this frequency, the drive signal is sent to the inverter circuit. Is output. Further, a voltage value or the like of DC power to be supplied from the converter unit 1 to the inverter unit 7 is calculated, and a driving signal for the transistor Tr of the converter unit 1 is output based on the calculated value.

  In the converter unit 1, the transistor Tr is turned on for a short period every half cycle of the AC power source based on the drive signal from the control unit 8, and the connection point (intermediate point) between the two voltage doubler capacitors C2 and C3. ) And the other output line of the AC power supply 3 are short-circuited. Thereby, a closed circuit is formed via the AC power supply 3 and the reactor 5 to control the power factor. Thus, the control unit 8 functions as a switching control unit.

  In the inverter unit 7, on the basis of the drive signal from the control unit 8, the switching element of the inverter circuit is turned on / off to output three-phase AC power having a predetermined frequency.

FIG. 2 is a diagram showing AC power supplied from the AC power source 3 to the converter unit 1 and drive signals received by the converter unit 1. As shown in FIG. 2, the AC voltage V _ac varies in a half cycle T ₂ , and the AC current I _ac varies in accordance with the operation of the transistor Tr in the converter unit 1. The value of the alternating current I _ac is estimated by the control unit 8. That is, the microcomputer processor of the control unit 8 executes a program for calculating the above equation (2), and substitutes constants A, B, and C stored in advance in the memory for this equation (2). At the same time, the direct current value I _dc detected by the current detection circuit of the control unit 8 and the duty ratio D _on of the drive signal output to the transistor Tr of the converter unit 1 are substituted into the equation (2) for calculation. The value of the alternating current _Iac is calculated. Incidentally, FIG. 2, an AC power source 3 shows a variation of the alternating current _{I ac} when the rated 100 V, as half the period of this case, the duty ratio _{D on} the alternating _{T 1} current _{I ac, T on} It is calculated by / _{T 1.} Incidentally, _{T 1} is a half cycle of the AC voltage _{V ac.}

Since the control unit 8 estimates the value of the alternating current I _ac from the alternating current power source 3 based on the direct current value I _dc output from the converter unit 1 and the duty ratio D _on of the drive signal of the converter unit 1, This estimated value has a relatively small error compared to the estimated value based on the AC voltage value including a relatively large error as in the prior art. FIG. 3 shows the input AC current value I _dc (mA) as the vertical axis and the variable I _dc / (1−C × D _on ) obtained from the DC current value I _dc and the duty ratio D _on as the horizontal axis. It is the figure which described the straight line F showing Formula (2) in the coordinate to do. In these coordinates, the actual measurement values A ₁ , A ₂ , A ₃ ... Of the alternating current value to the converter unit 1 are overlaid. As can be seen from FIG. 3, the equation (2) can estimate the AC current value _Iac with a small error based _on the DC current value _Idc and the duty ratio _Don . Thus, the inventor of the present application indicates that the variable I _dc / (1−C × D _on ) obtained from the DC current value I _dc and the duty ratio D _on has a proportional relationship with respect to the AC current value I _ac . The present invention was made based on this discovery.

According to FIG. 3, it was found that the error of the estimated value _Iac according to the equation (2) is within 2.5% of the actual current value. Therefore, the converter unit 1 controlled by the control unit 8 can receive power from the AC power source 3 up to a range of 97.5% of the current value at which the breaker of the AC power source 3 operates. Therefore, since the operating range of this air conditioner can be brought close to 97.5% with respect to the actual range where the breaker of the AC power supply 3 does not operate, the waste of performance as in the past and excessive performance can be achieved. Inconvenience such as giving can be prevented.

Further, the estimated value I _ac is calculated based on two parameters, ie, the DC current value I _dc and the duty ratio D _on of the drive signal of the converter unit 1. The processing load on the microcomputer can be reduced as compared with the calculation based on the three parameters of the voltage value, the DC current value, and the AC voltage of the AC power supply. Therefore, it is possible to reduce the cost of the microcomputer by reducing the program of the microcomputer and using a microcomputer with low processing capability.

  FIG. 4 is a diagram showing an outdoor unit of another air conditioner configured using the converter device of the present invention. This outdoor unit of the air conditioner is different from the outdoor unit of the air conditioner of FIG. 1 only in the circuit configuration of the converter unit 1. In FIG. 4, the same components as those of the outdoor unit of the air conditioner of FIG. 1 are denoted by the same reference numerals, and detailed description thereof is omitted.

  The converter unit 1 of the outdoor unit in FIG. 4 connects one end of the AC input terminal of the diode bridge DB2 to the other end of the reactor 5, and connects the other AC input terminal of the diode bridge DB2 to the other end of the AC power source 3. Connected to the output line. The collector and emitter of an NPN transistor Tr are connected to the positive DC output terminal and the negative DC output terminal of the diode bridge DB2, respectively, and the output terminal of the controller 8 is connected to the base of the transistor Tr. . The diode bridge DB2 and the transistor Tr constitute a switching unit. In addition, one of the AC input terminals of the diode bridge DB1 is connected to the reactor 5, and the other AC input terminal of the diode bridge DB1 is connected to a connection point (neutral point) between the two voltage doubler capacitors C2 and C3. Connected.

  In the converter unit 1 of the outdoor unit of the air conditioner in FIG. 4, the transistor Tr is turned on for a short period for each cycle of the AC power supply based on the drive signal from the control unit 8. Thereby, the output line of AC power supply 3 is short-circuited via the reactor 5, and a power factor is controlled.

In the converter device of FIG. 4 as well, as in the converter device of FIG. 1, the microcomputer of the control unit 8 calculates the equation (2), the DC current value I _dc output from the converter unit 1, and the drive of the converter unit 1 Based _on the duty ratio D _{on of the} signal, the value of the alternating current I _ac is estimated. Therefore, since the alternating current value I _dc can be estimated with higher accuracy than before, the operating range of the air conditioner can be brought close to the range where the breaker of the alternating current power supply 3 does not operate. As a result, it is possible to prevent inconveniences such as waste of performance as in the past and excessive performance.

In the above embodiment, by calculating the equation (2) by the control unit 8, the alternating current I is the value of the _ac estimated, AC current I _ac to correspond to the DC current value I _dc and the duty ratio D _on A table in which the values are described may be stored in advance in a memory such as a microcomputer. With reference to this table based on the DC current value I _dc detected by the current detection circuit and the duty ratio D _on of the drive signal output to the converter unit 1, the AC current value I _ac is read and estimated. May be. Even in this case, since the DC current value I _dc and the duty ratio D _on are smaller than the conventional parameters, the table stored in advance in the memory can be made small, so that the occupation ratio of the memory of this table can be reduced. The memory can be made small.

  Moreover, in the said embodiment, although the outdoor unit of the air conditioner was comprised using the converter apparatus of this invention, other apparatuses, such as a refrigeration apparatus, an illuminating device, an image display apparatus, or a transport apparatus, are comprised, for example. May be. Further, the converter device of the present invention is not limited to supplying DC power to the inverter, but can supply DC current to other loads.

It is the schematic which shows the outdoor unit of the air conditioner using the converter apparatus of embodiment of this invention. It is a figure which shows the alternating current power which a converter part supplies from alternating current power supply, and the drive signal which a converter part receives. It is the figure which described the estimation formula and measured value of alternating current on the coordinate. It is the schematic which shows the outdoor unit of the other air conditioner using the converter apparatus of this invention.

DESCRIPTION OF SYMBOLS 1 Converter part 3 AC power supply 4 Switch 5 Reactor 7 Inverter part 8 Control part 9 Compressor DB1, DB2 Diode bridge C1 Smoothing capacitor C2, C3 Voltage doubler capacitor Tr Transistor

Claims (1)

A rectifying unit (DB1, C1, C2, C3) for converting AC power from the AC power source (3) into DC power;
An inductance element (5) connected in series to one of the AC power lines connecting the AC power supply (3) and the rectifier (DB1, C1, C2, C3);
A switching unit (DB2, Tr) for short-circuiting the AC power supply (3) when turned on via the inductance element (5);
A switching control unit (8) for controlling on / off of the switching unit (DB2, Tr);
The direct current value (I _dc ) output from the rectifiers (DB1, C1, C2, C3) and the duty ratio (D _on ) by which the switching controller (8) drives the switching units (DB2, Tr). ) Based on the above-mentioned AC power supply (3), an estimated value calculation unit (8) for calculating an estimated value (I _ac ) of the alternating current supplied ,
The estimated value (I _ac ) of the alternating current is obtained by the following equation .
_{I ac = A × I dc /} (1-C × D on) + B
Here, I _ac is an estimated value of AC current, I _dc is a DC current value output from the rectifier, D _on is a duty ratio for driving the switching unit, and A, B, and C are constants. It is.

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