JP4439869B2 - Inverter control device and air conditioner - Google Patents

Description

  The present invention relates to an inverter control device using an extremely small capacity reactor and a capacitor.

  Conventionally, a motor drive inverter control device as shown in FIG. 9 is well known as a general motor drive inverter control device used in general-purpose inverters.

  In FIG. 9, the main circuit is composed of a DC power supply device 113, an inverter 3, and a motor 4. The DC power supply device 113 is used for the AC power supply 1, the rectifier circuit 2, and the DC voltage source of the inverter 3. Are composed of a smoothing capacitor 112 for storing electrical energy and a power factor improving reactor 111 of the AC power source 1.

  On the other hand, in the control circuit, motor voltage creating means 14 for creating each phase voltage command value of the motor 4 based on the speed command of the motor 4 given from the outside, and each phase voltage command created from the motor voltage creating means 14 It is comprised from the PWM control means 18 which produces | generates the PWM signal of the inverter 3 based on a value.

  Here, when the AC power supply 1 is 220 V (AC power supply frequency 50 Hz), the input of the inverter 3 is 1.5 kW, and the smoothing capacitor 112 is 1500 μF, the harmonics of the AC power supply current when the power factor improving reactor 111 is 5 mH and 20 mH. The relationship between the wave component and the order with respect to the AC power supply frequency is shown in FIG. FIG. 10 is shown together with the IEC (International Electrotechnical Commission) standard. When the power factor improving reactor 111 is 5 mH, the third harmonic component greatly exceeds that of the IEC standard. In the case of, it is understood that the IEC standard is cleared in the harmonic components up to the 40th order (see, for example, Non-Patent Document 1).

  For this reason, it is necessary to take measures such as further increasing the inductance value of the power factor improving reactor 111 in order to clear the IEC standard even when the load is high, increasing the size and weight of the inverter device, and further increasing the cost. There was an inconvenience of inviting.

  Therefore, a DC power supply device as shown in FIG. 11 has been proposed as a DC power supply device that suppresses an increase in inductance value of the power factor improving reactor 111 and achieves a reduction in power harmonic components and a higher power factor ( For example, see Patent Document 1).

  In FIG. 11, the AC power supply voltage of the AC power supply 1 is applied to the AC input terminal of the full-wave rectifier circuit formed by bridge-connecting the diodes D1 to D4, and the output is charged to the intermediate capacitor C via the reactor Lin. The electric charge of the intermediate capacitor C is discharged to the smoothing capacitor CD, and a DC voltage is supplied to the load resistor RL. In this case, the transistor Q1 is connected to the positive and negative DC current path connecting the load side of the reactor Lin and the intermediate capacitor C, and the transistor Q1 is driven by the base drive circuit G1.

  The circuit further includes pulse generation circuits I1 and I2 for applying a pulse voltage to the base drive circuit G1, and a dummy resistor Rdm. The pulse generation circuits I1 and I2 are circuits for detecting a zero cross point of the AC power supply voltage, respectively. From the detection of the zero cross point, the pulse current circuit is configured to flow a pulse current through the dummy resistor Rdm until the instantaneous value of the AC power supply voltage becomes equal to the voltage across the intermediate capacitor C.

  Here, the pulse generation circuit I1 generates a pulse voltage in the first half of the half cycle of the AC power supply voltage, and the pulse generation I2 generates a pulse voltage in the second half of the half cycle of the AC power supply voltage.

  When the transistor Q1 is turned on and a current is forced to flow through the reactor Lin, a backflow prevention diode D5 is connected so that the charge of the intermediate capacitor C is not discharged through the transistor Q1, and further, the intermediate capacitor C A backflow prevention diode D6 and a reactor Ldc for enhancing the smoothing effect are connected in series to a path for discharging the electric charge of the current to the smoothing capacitor CD.

With the above configuration, the transistor Q1 is turned on in a part or all of the phase interval in which the instantaneous value of the AC power supply voltage does not exceed the voltage across the intermediate capacitor C, thereby suppressing the increase in size of the device and the harmonics. Component reduction and higher power factor can be achieved.
JP-A-9-266684 Inverter Drive Handbook Editorial Committee, “Inverter Drive Handbook”, published by Nikkan Kogyo Shimbun, first edition in 1995

  However, the above-described conventional configuration still has the smoothing capacitor CD having a large capacity and the reactor Lin (described in the simulation result at 1500 μF and 6.2 mH in Patent Document 1), and further the intermediate capacitor. C, transistor Q1, base drive circuit G1, pulse generation circuits I1 and I2, dummy resistor Rdm, backflow prevention diodes D5 and D6, and a reactor Ldc that enhances the smoothing effect, thereby increasing the size of the device and the number of parts. There has been a problem of incurring a cost increase accompanying the increase.

  The present invention solves such a conventional problem, and an object of the present invention is to provide a motor drive inverter control device that is small, light, and low in cost.

In order to solve the above-described problems, the present invention includes a rectifier circuit that receives an AC power supply, an inverter that converts DC power into AC power, and a motor. The rectifier circuit includes a diode bridge, an AC input side of the diode bridge, or a DC current. It is composed of an extremely small capacity reactor connected to the output side, an extremely small capacity capacitor is provided between the DC buses of the inverter, and obtained from the PN voltage detection means for detecting the DC voltage value of the inverter and the PN voltage detection means. Speed determining means for outputting a command to temporarily reduce the speed command value of the motor when the detected DC voltage value of the inverter is lower than the withstand voltage of the surrounding elements and is equal to or higher than a preset threshold value; Motor voltage command generating means for generating each phase voltage command value of the motor based on the motor speed command value obtained from the speed determining means; PN voltage correction means for deriving a PN voltage correction coefficient from a comparison between the inverter DC voltage reference value and the inverter DC voltage detection value obtained from the PN voltage detection means, and each phase voltage obtained from the motor voltage command preparation means Motor voltage command correction means for correcting each phase voltage command value by multiplying the command value by a PN voltage correction coefficient that is an output value of the PN voltage correction means.

With the above configuration, a small, lightweight, and low cost motor drive inverter control device is realized by using a small capacitor and small capacitor, and the inverter DC voltage fluctuates greatly, making it difficult or impossible to drive the motor. Even in such a case, the inverter is operated so that the voltage applied to the motor is almost constant to maintain the motor drive, and further, the inverter DC voltage jumps due to regenerative energy during the high-speed rotation of the motor, and the carrier frequency component The purpose is to prevent peripheral circuit components from being damaged by ripples.

  The inverter control device of the present invention can realize a small, light, and low-cost motor drive inverter control device by using a small-capacity reactor and a small-capacitance capacitor, and it is difficult to drive the motor because the inverter DC voltage fluctuates greatly. Alternatively, even if it becomes impossible, it becomes possible to maintain the motor drive by making the voltage applied to the motor almost constant by the PN voltage correction means, and further, the DC voltage jumps due to regenerative energy during high-speed rotation of the motor In addition, even if the ripple of the carrier frequency component appearing in the inverter DC voltage increases, it is possible to avoid the destruction of the peripheral circuit components and to improve the reliability of the system.

A first invention includes a rectifier circuit having an AC power supply as an input, an inverter for converting DC power to AC power, and a motor. The rectifier circuit is connected to a diode bridge and an AC input side or a DC output side of the diode bridge. A PN voltage detecting means for detecting the DC voltage value of the inverter, and a DC voltage of the inverter obtained from the PN voltage detecting means. A speed determining means for outputting a command to temporarily reduce the speed command value of the motor when the detected value is lower than the withstand voltage of the surrounding elements and is not less than a preset threshold value; Based on the obtained motor speed command value, motor voltage command creating means for creating each phase voltage command value of the motor, and a preset inverter PN voltage correction means for deriving a PN voltage correction coefficient from a comparison between the current voltage reference value and the DC voltage detection value of the inverter obtained from the PN voltage detection means, each phase voltage command value obtained from the motor voltage command preparation means, and PN And a motor voltage command correction unit that corrects each phase voltage command value by multiplying by a PN voltage correction coefficient that is an output value of the voltage correction unit, thereby using an extremely small capacitor and reactor. This makes it possible to realize a small, lightweight, low-cost inverter control device for motor drive, and the voltage applied to the motor is almost constant even when the inverter DC voltage fluctuates and the motor drive becomes difficult or impossible. It is possible to operate the inverter so that the drive of the motor can be maintained, and the regeneration during the high-speed rotation of the motor Jumping and DC voltage by energy, it is possible to avoid the destruction of the peripheral circuit components as the ripple of the carrier frequency component appearing in the inverter DC voltage is increased.

  In particular, in the inverter control device according to the first aspect of the present invention, the overvoltage protection means that operates only when the inverter is abnormally stopped is provided in parallel with a small-capacitance capacitor, so that direct current due to regenerative energy when the motor is stopped is provided. Voltage jump can be suppressed.

  According to a third aspect of the invention, in particular, in the inverter control device according to any one of the first and second aspects, the inverter operating frequency obtained from the motor speed command value obtained from the speed determining means is an even number times the AC power source frequency. By avoiding the fixed frequency within the frequency range that has the frequency width set in advance around the resonance frequency and the resonance frequency, the resonance phenomenon between the inverter frequency and the AC power supply frequency is avoided. By doing so, unstable operation of the motor can be prevented and stable driving can be realized.

  In particular, in the inverter control device according to any one of the first to third inventions, the fourth invention has a small capacity so that the resonance frequency of the small capacity reactor and the small capacity capacitor is greater than 40 times the AC power supply frequency. The combination of the reactor and the small-capacitance capacitor is determined, and the harmonic component of the AC power supply current can be suppressed and the IEC standard can be cleared.

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

(Embodiment 1)
FIG. 1 shows a system configuration diagram of a motor drive inverter control apparatus showing a first embodiment of the present invention.
In FIG. 1, the main circuit is an AC power source 1, a diode bridge 2 for converting AC power to DC power, a small capacity reactor 11 of 2 mH or less, a small capacity capacitor 12 of 100 μF or less, and converting DC power to AC power. And the motor 4 driven by AC power converted by the inverter 3.

  On the other hand, in the control circuit, the motor voltage command creating means 14 for creating each phase voltage command value of the motor 4 based on the speed command ω * of the motor 4 given by the speed determining means 19 and the DC voltage value of the inverter 3 are obtained. A PN voltage correction coefficient is derived by dividing a preset DC voltage reference value of the inverter 3 by the PN voltage detection means 15 and a DC voltage detection value of the inverter 3 obtained from the PN voltage detection means 15 to obtain a PN voltage correction coefficient. When the voltage detection value is less than or equal to zero, each phase voltage command value obtained from the PN voltage correction means 16 for setting the maximum value of the preset PN voltage correction coefficient to the PN voltage correction coefficient and the motor voltage command creation means 14 Motor voltage command correction means 17 for correcting each phase voltage command value by multiplying PN voltage correction coefficient which is an output value of PN voltage correction means 16; Motor voltage command correction value created from the command correcting means 17 and a PWM control means 18 for generating a PWM signal of inverter 3 as applied to the motor 4.

Hereinafter, a specific method will be described.
The motor voltage command creating means 14 creates each phase voltage command value v _u ^* , v _v ^* , v _w ^* by the calculation represented by the equation (1).

Here, V _m is a motor voltage value, and θ ₁ is derived by time-integrating the speed command ω * as represented by the equation (2).

FIG. 2 is a diagram showing a first embodiment of the PN voltage correction means 16 according to the present invention. In the PN voltage correction means 16, the preset DC voltage reference value _{Vpn0 of} the inverter 3 and the PN voltage detection means. deriving a PN voltage correction factor k _pn as in equation (3) using the DC voltage detection value v _pn of inverter 3 obtained from 15.

Here, since a small-capacitance capacitor is used in the present invention, the DC voltage detection value v _pn may become zero, so it is necessary to set a minute term δ ₀ for preventing zero splitting.

In place of the minute term δ ₀ in equation (3), when the detected DC voltage value v _pn is zero or less, the maximum value of the preset PN voltage correction coefficient is set as the PN voltage correction coefficient k _pn. Zero percent can be prevented.

That is, the PN voltage correction coefficient k _pn may be derived as shown in Equation (4).

Here, k _{pn # max} is a maximum value of a preset PN voltage correction coefficient.

Further, the motor voltage command correction means 17 uses the respective phase voltage command values v _u ^* , v _v ^* , v _w ^* and the PN voltage correction coefficient k _pn as shown in the equation (5) to obtain a motor voltage command correction value v _uh ^*. , V _vh ^* , v _wh ^* are derived.

As described above, by using a small capacity reactor and a small capacity capacitor, it is possible to realize a motor drive inverter control apparatus that is small, light, and low in cost, and the inverter DC voltage fluctuates greatly, making it difficult or impossible to drive the motor. Even in this case, the inverter can be operated so that the voltage applied to the motor is substantially constant, and the motor can be maintained.
Further, the operation of the speed determining means 19 will be described.

FIG. 3 shows a first operation result of the motor drive inverter control apparatus of the present invention.
Since the capacitor 12 according to the present invention uses a capacitor having a very small capacity, the regenerative energy of the motor 4 cannot be absorbed in the vicinity of the zero cross of the AC power supply voltage (arrow portion in the figure), and a phenomenon occurs in which the DC voltage jumps.

  FIG. 4 shows a second operation result of the motor drive inverter control device according to the present invention. Since the electrical energy stored in the capacitor 12 is small, charging / discharging is repeated at the carrier frequency of the inverter, and the inverter DC voltage is changed. It can be seen that a ripple of the carrier frequency component appears.

  The DC voltage jump as shown in FIG. 3 and the ripple as shown in FIG. 4 are likely to occur in the high speed rotation region (high load region) of the motor 4 and may exceed the withstand voltage of the inverter 3 and other peripheral circuits in some cases. There was sex.

  However, the speed determination means 19 outputs such that the speed command ω * is temporarily lowered when the DC voltage detection value of the inverter 3 obtained from the PN voltage detection means 15 is equal to or higher than a preset threshold value. As a result, the inverter DC voltage can be suppressed within a normal range without causing a jump of the inverter DC voltage and a ripple of the carrier frequency component exceeding the withstand voltage of the inverter 3 and other peripheral circuits.

FIG. 5 shows a specific calculation flow in the speed determining means 19.
After inputting the DC voltage detection value v _pn of the inverter 3 obtained from the PN voltage detection means 15 (201), it is compared with the threshold value (202), and when the threshold value is exceeded, the time counter is cleared. After (206), the speed command ω * is lowered (207).
Even when the DC voltage detection value v _{pn of the} inverter 3 is lower than the threshold value, the speed command ω * is kept as it is if the time counter has not passed the specified time to prevent the speed hunting operation. Yes.

  The PN voltage detection means 15 is preferably provided with a low-pass filter for the purpose of noise removal. Further, if the low-pass filter is a digital filter realized by an arithmetic unit such as a microcomputer or DSP, the cost is low. Is also advantageous.

(Embodiment 2)
FIG. 6 shows a system configuration diagram of an inverter control device for driving a motor showing a second embodiment of the present invention. An overvoltage protection means 13 is added to the main circuit in the first embodiment.

  The overvoltage protection means 13 may be any voltage absorption type element such as a surge absorber, voltage discharge type element such as a gas arrester, or any other means that can suppress voltage rise.

  In the present embodiment, the DC voltage is suppressed to a voltage at which the overvoltage protection unit 13 does not operate during normal operation, and the overvoltage protection unit 13 operates only during an emergency stop where the inverter 3 needs to be protected. And the parts used for the overvoltage protection means 13 can be used for a long time.

(Embodiment 3)
A specific method for setting the inverter operating frequency according to the present invention will be described below. Since the motor drive inverter control apparatus of the present invention uses a small-capacitance capacitor, the inverter DC voltage greatly pulsates at a frequency twice the AC power supply frequency f _S as shown in FIG.

Therefore, at the frequency at which the inverter operating frequency f ₁ obtained from the motor speed command ω * obtained from the speed determining means 19 is an even multiple of the AC power source frequency f _S , the frequency at which the inverter DC voltage pulsates (AC power source frequency). a resonance phenomenon occurs in synchronism with a frequency twice as high as f _S.

FIG. 8 shows an operation result when the inverter operating frequency f ₁ is twice the AC power supply frequency f _S. A resonance phenomenon occurs in synchronization with the frequency at which the inverter DC voltage pulsates, and a negative DC component is present in the motor current. It can be seen that they are superimposed.

  Therefore, the brake torque is generated in the motor, and adverse effects such as a decrease in output torque and an increase in motor loss occur.

The specifications at this time are as follows: the inductance value of the small capacity reactor is 0.5 mH, the capacity of the small capacity capacitor is 10 μF, the AC power source is 220 V (50 Hz), the inverter operating frequency is 100 Hz (here, the number of poles of the motor is Because of the two poles, the inverter operating frequency is equal to the motor speed command value), and the inverter carrier frequency is 5 kHz.
Therefore, in the setting of the inverter operation frequency f _1, the inverter operating frequency f ₁ is required to avoid being constantly fixed case such that Equation (6).

Here, n is an integer, Δf is a preset frequency width, and the frequency width Δf is basically set so that the influence of the resonance phenomenon described above is reduced.

Further, when the inverter operating frequency f ₁ exceeds the resonance frequency obtained by the equation (6), it is avoided that the inverter operating frequency f ₁ is changed at a stretch in a transient state such as acceleration or deceleration and fixed at the resonance frequency.

  Note that the frequency width Δf does not necessarily need to be set, and may not be set depending on the driving condition (such as during light load) (in this case, Δf = 0 may be set).

  As described above, by avoiding the resonance phenomenon between the inverter frequency and the AC power supply frequency, unstable operation of the motor can be prevented and stable driving can be realized.

(Embodiment 4)
A specific method for determining the specifications of the small-capacity capacitor and small-capacity reactor according to the present invention will be described below.

In the motor drive inverter control device of the present invention, the resonance frequency f _LC (LC resonance frequency) of the small capacitor and the small reactor is changed to AC in order to suppress the harmonic component of the AC power supply current and clear the IEC standard. The combination of the small capacitor and the small reactor is determined so as to be larger than 40 times the power supply frequency f _S.

Here, when the capacitance of the small capacitor is C [F] and the inductance value of the small capacitor is L [H], the LC resonance frequency f _LC is expressed as shown in Equation (7).

That is, the combination of the small-capacitance capacitor and the small-capacity reactor is determined so as to satisfy f _LC > 40 f _S (because the IEC standard specifies the 40th harmonic in the harmonic component of the AC power supply current). .

  As described above, by determining the combination of the small-capacitance capacitor and the small-capacity reactor, the harmonic component of the AC power supply current can be suppressed and the IEC standard can be cleared.

  Note that the present invention described in the first to fourth embodiments can be applied to a motor drive inverter control device that drives a motor using an inverter circuit. For example, an air conditioner equipped with an inverter circuit, a refrigerator, an electric washing machine, an electric dryer, an electric vacuum cleaner, a blower, a heat pump water heater and the like. For any product, by reducing the size and weight of the motor drive inverter device, the degree of freedom in product design is improved, and an inexpensive product can be provided.

  As described above, the motor drive inverter control device according to the present invention can realize a small, light and low cost motor drive inverter control device by using a small-capacity reactor and a small-capacitance capacitor, and the inverter DC voltage is greatly increased. Even if it becomes difficult or impossible to drive the motor due to fluctuations, it is possible to maintain the motor driving by making the voltage applied to the motor almost constant by the PN voltage correction means, and to further rotate the motor at high speed Even if the DC voltage jumps due to regenerative energy at the time or the ripple of the carrier frequency component that appears in the inverter DC voltage increases, it is possible to avoid the destruction of peripheral circuit components and improve the system reliability. Speed sensors such as pulse generators such as compressor drive motors Not only in the case it can not be used, but the present invention when, which may comprise a speed sensor, such as servo drive can be applied.

  Moreover, it can utilize also as a driver of actuators, such as an air conditioner, a refrigerator, an electric washing machine, an electric dryer, an air blower, an electric cleaner, and a heat pump water heater.

1 is a system configuration diagram of an inverter control device for driving a motor showing a first embodiment of the present invention. The figure which shows the derivation | leading-out method of the PN voltage correction coefficient in the 1st Embodiment of this invention The figure which shows the 1st operation result in the 1st Embodiment of this invention. The figure which shows the 2nd operation result in the 1st Embodiment of this invention. Calculation flow chart in speed determining means in the first embodiment of the present invention The system block diagram of the inverter control apparatus for motor drive which shows the 2nd Embodiment of this invention The figure which shows the 1st operation result of the inverter control apparatus for motor drive in the 3rd Embodiment of this invention. The figure which shows the 2nd operation result of the inverter control apparatus for motor drive in the 3rd Embodiment of this invention. System configuration diagram of a general motor drive inverter control device The figure which showed the relationship between the harmonic component of alternating current power supply current in the motor drive inverter apparatus of FIG. 9, and the order with respect to alternating current power supply frequency Circuit configuration diagram of a conventional DC power supply that can reduce harmonic components and increase the power factor while suppressing the increase in size of the device

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 AC power supply 2 Rectifier circuit 3 Inverter 4 Motor 11 Small capacity reactor 12 Small capacity capacitor 13 Overvoltage protection means 14 Motor voltage command preparation means 15 PN voltage detection means 16 PN voltage correction means 17 Motor voltage command correction means 18 PWM control means 19 Speed Decision means 111 Reactor 112 Smoothing capacitor 113 DC power supply device Lin, Ldc reactor D1-D6 Diode Q1 Transistor G1 Base drive circuit I1, I2 Pulse generation circuit C Intermediate capacitor CD Smoothing capacitor RL Load resistance Rdm Dummy resistance

Claims (5)

A rectifier circuit having an AC power supply as input, an inverter for converting DC power into AC power, and a motor, wherein the rectifier circuit is connected to a diode bridge and an AC input side or a DC output side of the diode bridge. A PN voltage detecting means for detecting a DC voltage value of the inverter, and a DC voltage of the inverter obtained from the PN voltage detecting means. A speed determining means for outputting a command to temporarily reduce the speed command value of the motor when the detected value is lower than the withstand voltage of the surrounding elements and is equal to or greater than a preset threshold; and the speed determining means Motor voltage command generating means for generating each phase voltage command value of the motor based on the motor speed command value obtained from the motor, and presetting PN voltage correction means for deriving a PN voltage correction coefficient from a comparison between the inverter DC voltage reference value obtained from the inverter and the inverter DC voltage detection value obtained from the PN voltage detection means; An inverter control device comprising motor voltage command correction means for correcting each phase voltage command value by multiplying each phase voltage command value to be multiplied by a PN voltage correction coefficient that is an output value of the PN voltage correction means. 2. The inverter control device according to claim 1, further comprising overvoltage protection means in parallel with a small-capacitance capacitor, wherein the overvoltage protection means operates when the inverter stops abnormally. A frequency range in which the inverter operating frequency obtained from the speed command value of the motor obtained from the speed determining means is an even multiple of the AC power supply frequency, and a frequency range set in advance around the resonance frequency. The inverter control device according to claim 1, wherein the inverter control device is prevented from being fixed in a constant manner. The combination of the small-capacity reactor and the small-capacitance capacitor is determined so that the resonance frequency of the small-capacity reactor and the small-capacitance capacitor is larger than 40 times the AC power supply frequency. The inverter control apparatus in any one. The air conditioner which has an inverter control apparatus in any one of Claims 1-4.

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