JP2005304248A - Motor drive inverter control device and electrical equipment - Google Patents

Abstract

An object of the present invention is to provide a motor drive inverter control device that is small, light, and low in cost.
An inverter for driving a motor having a very small capacity reactor and a capacitor having a very small capacity between DC buses of the inverter. In a PN voltage predicting means, the inverter actually outputs a voltage. By calculating the predicted DC voltage value at the timing from the time-series data of the detected DC voltage value and applying an appropriate current to the motor 4 so that an excessive motor voltage is not applied while the inverter DC voltage is rising, a small size can be obtained.・ Even in a lightweight and low-cost motor drive inverter control device, it is possible to construct a system that does not easily cause an overcurrent protection stop operation.
[Selection] Figure 1

Description

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

  As a general motor drive inverter control device used in a general-purpose inverter or the like, a motor drive inverter control device as shown in FIG. 8 is well known.

  In FIG. 8, 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. FIG. 9 shows the relationship between the wave component and the order with respect to the AC power supply frequency.

  FIG. 9 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.

  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 direct current power supply device described as shown in FIG. 10 is proposed as a direct current 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, refer to Patent Document 1).

  In FIG. 10, 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 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. Component reduction and higher power factor can be achieved.
JP-A-9-266684

  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 provides an AC power source as an input, a rectifier circuit including a diode bridge, a small-capacity reactor connected to an AC input side or a DC output side of the diode bridge, and DC power to AC An inverter that converts power, a motor that is driven by AC power converted by the inverter, a small-capacitance capacitor provided between the DC buses of the inverter, and a PN voltage detection means that detects a DC voltage value of the inverter PN voltage prediction means for calculating a DC voltage prediction value at a timing at which the inverter actually outputs a voltage from time series data of the DC voltage detection value of the inverter obtained from the PN voltage detection means; Based on the speed command value of the motor, the motor voltage command value that creates the voltage command value for each phase of the motor is generated. PN voltage correction means for deriving a PN voltage correction coefficient from a comparison between a preset DC voltage reference value of the inverter and a DC voltage prediction value of the inverter obtained from the PN voltage prediction means, and the motor voltage Motor voltage command correction means for correcting each phase voltage command value by multiplying each phase voltage command value obtained from the command creation means by a PN voltage correction coefficient that is an output value of the PN voltage correction means. This is an inverter controller for driving a motor.

  With this 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 this case, it is possible to maintain the motor drive by operating the inverter so that the voltage applied to the motor is substantially constant.

  According to the present invention, it is possible to provide a motor drive inverter control device that is small, light, and low in cost.

  A first invention is a rectifier circuit comprising an AC power supply as an input, a diode bridge, a small capacity reactor connected to the AC input side or DC output side of the diode bridge, and an inverter for converting DC power to AC power A motor driven by AC power converted by the inverter, a small-capacitance capacitor provided between the DC buses of the inverter, PN voltage detection means for detecting a DC voltage value of the inverter, and the PN voltage detection PN voltage prediction means for calculating a DC voltage prediction value at a timing at which the inverter actually outputs a voltage from time series data of the DC voltage detection value of the inverter obtained from the means, and a speed command value of the motor given from the outside Motor voltage command generating means for generating each phase voltage command value of the motor based on PN voltage correction means for deriving a PN voltage correction coefficient from a comparison between the DC voltage reference value of the inverter and the DC voltage prediction value of the inverter obtained from the PN voltage prediction means, and obtained from the motor voltage command preparation means. Motor voltage command correction means for correcting each phase voltage command value by multiplying each phase voltage command value by a PN voltage correction coefficient that is an output value of the PN voltage correction means.

  Thus, by providing a motor voltage command correction means for correcting each phase voltage command value, a small, lightweight and low cost motor drive inverter control device can be realized by a small capacitor and a small reactor, and an inverter DC Even when the voltage fluctuates greatly and it becomes difficult or impossible to drive the motor, it is possible to operate the inverter so that the voltage applied to the motor becomes substantially constant and to keep the motor driven.

  Further, by suppressing the peak of the motor current, it is possible to expand the operation region where the overcurrent protection stop operation does not occur, and it is possible to construct a cheaper system if the current capacity of the inverter can be reduced. The motor drive 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. Even when the driving is difficult or impossible, the driving of the motor can be maintained by making the voltage applied to the motor almost constant by the PN voltage correcting means.

  Furthermore, since the predicted DC voltage at the timing when the inverter actually outputs voltage is derived from the time series data of the detected DC voltage in the PN voltage predicting means, an unnecessarily high motor voltage can be obtained while the inverter DC voltage is rising. Since an appropriate current can be supplied to the motor without applying it, the effect of expanding the operating range that does not lead to overcurrent protection stop operation can be achieved, and a more inexpensive system can be constructed by lowering the current capacity of the inverter. There is an effect.

  According to a second aspect of the present invention, an inverter operating frequency obtained from an externally provided motor speed command value is a resonance frequency that is an even multiple of an AC power supply frequency, and a frequency width that is set in advance around the resonance frequency. It is characterized by avoiding being fixed steadily within the given frequency range, preventing the unstable phenomenon of the motor by avoiding the resonance phenomenon between the inverter frequency and the AC power supply frequency, Stable driving can be realized.

  3rd invention determines the combination of the said small capacity reactor and the said small capacity capacitor so that the resonant frequency of a small capacity reactor and a small capacity capacitor may become larger than 40 times the alternating current power supply frequency, Therefore, 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, motor voltage generating means 14 for generating each phase voltage command value of the motor 4 based on the speed command ω * of the motor 4 given from the outside, and PN voltage detection for detecting the DC voltage value of the inverter 3 Means 15; a PN voltage predicting means 19 for calculating a DC voltage predicted value at a timing at which the inverter 3 actually outputs a voltage; and an inverter for obtaining a preset DC voltage reference value of the inverter 3 from the PN voltage predicting means 19 The PN voltage correction coefficient is derived by dividing by the predicted DC voltage value of 3, and when the detected DC voltage value is less than or equal to zero, the maximum value of the preset PN voltage correction coefficient is set as the PN voltage correction coefficient. The voltage correction means 16 is multiplied by each phase voltage command value obtained from the motor voltage command creation means 14 and the PN voltage correction coefficient which is the output value of the PN voltage correction means 16. Thus, the motor voltage command correction means 17 for correcting each phase voltage command value, and the PWM signal of the inverter 3 such that the motor voltage command correction value created from the motor voltage command correction means 17 is applied to the motor 4 are obtained. It is comprised from the PWM control means 18 to produce | generate.

  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.

  Specific operations and calculation methods will be described below.

  The motor voltage command creating means 14 creates each phase voltage command value by the calculation represented by the equation (1).

  Here, Vm is a motor voltage value, and is derived by time-integrating the speed command ω * as represented by Expression (2).

  FIG. 2 is a diagram showing a first embodiment of the PN voltage correcting means 16 according to the present invention. In the PN voltage correcting means 16, the preset DC voltage reference value Vpno of the inverter 3 and the PN voltage predicting means 19 are shown. Is used to derive a PN voltage correction coefficient Kpn as shown in Equation (3).

  Here, since a small-capacitance capacitor is used in the present invention, there is a case where the predicted DC voltage value becomes zero, so it is necessary to set a minute term for preventing zero splitting. It should be noted that, instead of the minute term in equation (3), when the predicted DC voltage value is less than or equal to zero, the maximum value of the preset PN voltage correction coefficient is set as the PN voltage correction coefficient to prevent zero splitting. Can do.

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

  Here, Kpn_max is a maximum value of a preset PN voltage correction coefficient.

  Further, the motor voltage command correction means 17 derives a motor voltage command correction value as shown in Equation (5) using each phase voltage command value and the PN voltage correction coefficient.

  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 PN voltage predicting means 19 will be described.

  FIG. 3 shows the operation of the motor-control PWM timer of the microcomputer used in the motor drive inverter control apparatus of the present invention.

  The count value of the PWM timer repeats the up / down operation, and the duty value of the PWM output is reflected at the timing of shifting from the down count to the up count, that is, the timing at which the PWM timer underflows.

  First, the operation when the PN voltage predicting means 19 is not provided will be described.

  At the timing of 1 in FIG. 3, the PN voltage detection means 15 detects the DC voltage value of the inverter 3. Thereafter, calculation is performed by the PN voltage correction means 16 and the motor voltage command correction means 17 by the timing of 3, and the PWM signal of the inverter 3 finally generated by the PWM control means 18 is output at the timing of 3. Will be. As described above, the PWM signal corrected and calculated based on the DC voltage value of the inverter 3 detected at the timing 1 is output at the timing 3, and a control delay corresponding to one carrier cycle occurs.

  In the present invention, since the main circuit is constituted by the reactor 11 and the capacitor 12 having an extremely small capacity, the inverter DC voltage fluctuates greatly, and the inverter DC voltage generated by the control delay for one carrier period described above. This change is not negligible.

  FIG. 4 is a plot of the DC voltage value of the inverter 3 detected for each carrier cycle when the voltage of the AC power supply 1 is 200 V, the frequency is 50 Hz, and the carrier frequency of the PWM signal of the inverter 3 is 5 kHz. According to the above conditions, it can be seen from FIG. 4 that a change in DC voltage value of about 18 V at the maximum occurs during the period of one carrier cycle.

For example, if the preset DC voltage reference value of the inverter 3 is 280 V, the DC voltage value at the timing 1 in FIG. 3 is 18 V, and the DC voltage value at the timing 3 is 36 V, the equation ( The PN voltage correction coefficient obtained from 4) must originally be 7.78 (= 280/36). However, since it is calculated by the DC voltage value obtained at the timing of 1 before one carrier cycle, 15.56 (= 280/18), and the PN voltage correction coefficient is twice different.

  The fact that the PN voltage correction coefficient is two times different means that the motor voltage command correction value calculated by the motor voltage command correction means 17 is multiplied by each phase voltage command value and the PN voltage correction coefficient as shown in Equation (5). As a result, the final output voltage to the motor 4 is doubled.

  In particular, when the DC voltage value of the inverter 3 is increasing, the PN voltage correction coefficient is calculated to be large, so that a voltage higher than necessary is applied to the motor 4 and the motor current jumps. It becomes. In order to eliminate the above-described problems, in the first embodiment of the present invention, a PN voltage predicting means 19 for calculating a DC voltage predicted value at a timing at which the inverter 3 actually outputs a voltage is provided. Eliminating the output voltage.

  Further, in the PN voltage predicting means 19, the result of adding the difference from the DC voltage value one carrier cycle before to the DC voltage value detected by the PN voltage detecting means 15 is set as the DC voltage predicted value.

  Specifically, if the preset DC voltage reference value of the inverter 3 is 280 V, the DC voltage value at the timing 1 in FIG. 3 is 18 V, and the DC voltage value at the timing 3 is 36 V, the timing 5 The predicted DC voltage at 54 is 54V (= 36 + (36-18)), and the PN voltage correction coefficient at timing 6 is derived as 5.19 = (280/54).

  FIG. 5 shows an operation result of the motor drive inverter control device when the PN voltage predicting means 19 is not provided in the motor drive inverter control device of the present invention, and FIG. 6 shows the motor drive inverter control device of the present invention. It is an operation result when the PN voltage prediction means 19 is provided.

  Since the capacitor 12 according to the present invention uses a capacitor having a very small capacity, the DC voltage value of the inverter 3 drops greatly in the vicinity of the zero cross of the AC power supply voltage, and a ripple having a frequency twice as long as the AC power supply cycle is generated.

  Since the DC voltage value is not predicted in the motor current waveform of FIG. 5, a sharp current flows particularly in a circled part where the DC voltage value of the inverter 3 is increasing. 6A and 6B, the DC voltage value is predicted, and since an appropriate voltage is applied to the motor 4, it can be seen that the peak of the motor current waveform is suppressed.

(Embodiment 2)
A specific method for setting the inverter operating frequency according to the present invention will be described below.

  Since the inverter controller for driving the motor of the present invention uses a small-capacitance capacitor, the inverter DC voltage greatly pulsates at twice the frequency of the AC power supply frequency as shown in FIGS. Therefore, when the inverter operating frequency f1 obtained from the motor speed command ω * given from the outside is an even multiple of the AC power supply frequency fs, it is synchronized with the frequency at which the inverter DC voltage pulsates (a frequency twice the AC power supply frequency). Then, a resonance phenomenon occurs.

  FIG. 7 shows an operation result when the inverter operating frequency is twice the AC power supply frequency. A resonance phenomenon occurs in synchronization with the frequency at which the inverter DC voltage pulsates, and a negative DC component is superimposed on the motor current. I understand that. 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 setting the inverter operating frequency f1, it is necessary to avoid being fixed constantly in the case where the inverter operating frequency is represented by the equation (6).

  Here, n is an integer, Δf is a preset frequency width, and the frequency width is basically set so that the influence of the resonance phenomenon described above is reduced. Further, when the inverter operating frequency exceeds the resonance frequency obtained by the equation (6), it is avoided that the inverter operating frequency is changed at a stroke in a transient state such as acceleration or deceleration and fixed at the resonance frequency. Note that the frequency width does not necessarily need to be set, and may not be set depending on the operation status (light load, etc.) (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 3)
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 (LC resonance frequency) of the small capacitor and the small reactor is set to the AC power frequency in order to suppress the harmonic component of the AC power source current and clear the IEC standard. The combination of the small-capacity capacitor and the small-capacity reactor is determined so as to be larger than 40 times. Here, when the capacitance of the small-capacitance capacitor is C [F] and the inductance value of the small-capacity reactor is L [H], the LC resonance frequency is expressed as shown in Expression (7).

That is, the combination of the small-capacitance capacitor and the small-capacity reactor is determined so that the LC resonance frequency is larger than 40 times the AC power supply frequency. (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 third embodiments can be applied to a motor driving inverter control device that drives a motor using an inverter circuit. For example, it is an electric device such as an air conditioner equipped with an inverter circuit, a refrigerator, an electric washing machine, an electric dryer, an electric vacuum cleaner, a blower, and a heat pump water heater. In any of the electrical devices, the motor drive inverter device can be reduced in size and weight, so that the degree of freedom in product design can be improved and an inexpensive product can be provided.

  As described above, the motor drive inverter control apparatus according to the present invention can construct a small, light, and low cost system by using a small capacity reactor and a small capacity capacitor. Thus, the present invention can be applied not only to a case where a speed sensor such as a pulse generator cannot be used but also to a case where a speed sensor can be provided such as a servo drive.

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 method of the PN voltage correction coefficient The figure which shows the operation of the same PWM timer for motor control The figure which shows the DC voltage value which is detected every the same carrier period The figure which shows the 1st operation result The figure which shows the 2nd operation result The figure which shows the 1st operation result of the inverter control apparatus for motor drive in the 2nd Embodiment of this invention. System configuration diagram of conventional motor drive inverter control device The diagram which showed the relationship between the harmonic component of alternating current power supply current in the motor drive inverter apparatus of FIG. 8, and the order with respect to alternating current power supply frequency System configuration diagram of a DC power supply that can reduce harmonic components and increase the power factor while suppressing the increase in size of conventional devices

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 PN Voltage prediction means

Claims (4)

A rectifier circuit composed of a diode bridge, a small-capacity reactor connected to the AC input side or DC output side of the diode bridge, an inverter for converting DC power into AC power, and conversion by the inverter A motor driven by the AC power generated, a small-capacitance capacitor provided between the DC buses of the inverter, PN voltage detection means for detecting a DC voltage value of the inverter, and the inverter obtained from the PN voltage detection means PN voltage predicting means for calculating a DC voltage predicted value at a timing at which the inverter actually outputs a voltage from time series data of DC voltage detected values of the motor, and based on the motor speed command value given from the outside, Motor voltage command generating means for generating each phase voltage command value, and the inverter PN voltage correction means for deriving a PN voltage correction coefficient from the comparison between the DC voltage reference value of the inverter and the DC voltage prediction value of the inverter obtained from the PN voltage prediction means, and each phase obtained from the motor voltage command preparation means A motor drive inverter control device comprising motor voltage command correction means for correcting each phase voltage command value by multiplying a voltage command value by a PN voltage correction coefficient that is an output value of the PN voltage correction means. The inverter operating frequency obtained from the motor speed command value given from the outside is within a frequency range that has a resonance frequency that is an even multiple of the AC power supply frequency and a frequency width that is set in advance around the resonance frequency. 2. The inverter control device for driving a motor according to claim 1, wherein the fixed fixing is avoided. 3. 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 greater than 40 times the AC power supply frequency. The inverter control apparatus for motor drive of description. The electric equipment carrying the motor drive inverter control apparatus of any one of the said Claims 1-3.

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