Inverter device, motor drive device using the same, and refrigeration equipment

Abstract

To detect a bus current and reproduce a three-phase current as well as to suppress current distortion.SOLUTION: An inverter device includes an inverter circuit 4 that converts a DC voltage into a three-phase AC voltage on the basis of a PWM signal. The inverter device reproduces a three-phase current from a DC bus current in the inverter circuit 4, calculates a voltage command value from the three-phase current and a current command value, and calculates a three-phase modulated wave command value to be output to a PWM control unit 26 on the basis of the voltage command value. In a state where downhill sections in a triangular carrier wave are defined as first and third sections, and uphill sections in the triangular carrier wave are defined as second and fourth sections, a modulated wave computing unit 25 adds an adjustment amount to a three-phase modulated wave signal in the second section, and subtracts 1 / 2 of the adjustment amount in each of the first and third sections, and in a case where a predetermined adjustment amount is added to the three-phase modulated wave signal in the fourth section, the modulated wave computing unit 25 excessively subtracts 1 / 2 of predetermined adjustment amount for the fourth section extra in the third section.SELECTED DRAWING: Figure 7

Description

[Technical Field]

[0001] The present invention relates to an inverter device, a motor drive device using the inverter device, and a refrigeration appliance. [Background technology]

[0002] Inverter devices that convert direct current into alternating current are widely used in grid-connected inverters, uninterruptible power supplies (UPS), AC motor drives, and the like.

[0003] In such inverter devices, a means for detecting the phase current of each phase on the AC side is required to control the output current.As an inexpensive current detection means, a method has been disclosed in which the DC bus current of the inverter main circuit is detected and distributed to each phase according to the on / off state of the switching of the inverter main circuit, thereby estimating the phase current of each phase.

[0004] Known current detection methods include the technology disclosed in Patent Document 1. Patent Document 1 discloses a technique for adjusting a modulated wave to ensure the duration of a DC bus current when the duration of the DC bus current is shorter than the minimum detectable interval. Patent Document 2 discloses a method for suppressing the effects of current ripples while ensuring the duration of the DC bus current. [Prior art documents] [Patent documents]

[0005] [Patent Document 1] Patent No. 3664040 [Patent Document 2] Patent No. 4866216 Summary of the Invention [Problem to be solved by the invention]

[0006] The technology disclosed in Patent Document 1 divides one cycle of a triangular wave carrier that generates a PWM signal into a first half and a second half, and detects the DC bus current in either of these periods. If the time width of the DC bus current is shorter than the minimum detectable interval, a correction voltage is added to the voltage command value of each phase in the first half of the triangular wave carrier, increasing the time width of the interphase voltage to detect the DC bus current. In addition, in the second half of the triangular wave carrier, the correction voltage added in the first half is subtracted so as not to affect the average output voltage in the first and second halves.

[0007] However, in the technology disclosed in Patent Document 1, although the average value of the output voltage of each phase before and after the correction process remains unchanged, adding the correction voltage generates unnecessary current ripple, and the average value of this current change is not zero, resulting in current distortion and torque pulsation. In particular, when the motor winding inductance is small, current distortion due to the addition / subtraction of the correction voltage is likely to occur.

[0008] On the other hand, the technology disclosed in Patent Document 2 distributes the subtraction process of the correction voltage to intervals before and after the addition interval, making it possible to suppress the average value of the current ripple to 0. However, the technology disclosed in Patent Document 2 has the problem that the current detection interval is 1.5 times longer than before, and the frequency of the current ripple is also reduced to 2 / 3 of the carrier frequency.

[0009] SUMMARY OF THE INVENTION The present invention has been made in view of the above-mentioned prior art, and an object of the present invention is to provide a device that detects bus currents, reproduces three-phase currents, and suppresses current distortion. [Means for solving the problem]

[0010] In order to achieve the above object, the present invention provides an inverter device comprising: a PWM controller that generates a PWM signal based on a three-phase modulating wave and a triangular carrier wave; an inverter circuit that converts a DC voltage into a three-phase AC voltage based on the PWM signal generated by the PWM controller; a current reproduction calculator that detects a DC bus current of the inverter circuit and reproduces the three-phase current; and a voltage command calculator that calculates a voltage command value based on the three-phase current reproduced by the current reproduction calculator, wherein the inverter device further comprises a modulating wave calculator that calculates a three-phase modulating wave command value to be output to the PWM controller based on the voltage command value calculated by the voltage command calculator, and the section where the triangular carrier wave falls is designated as a first section. a second section being a section after the first section where the triangular wave carrier wave rises, a third section being a section after the second section where the triangular wave carrier wave falls, and a fourth section being a section after the third section where the triangular wave carrier wave rises, the modulated wave calculator adds a predetermined adjustment amount to the three-phase modulated wave signal in the second section, subtracts 1 / 2 of the predetermined adjustment amount in each of the first section and the third section, and further, when adding a predetermined adjustment amount to the three-phase modulated wave signal in the fourth section, it also subtracts 1 / 2 of the predetermined adjustment amount of the fourth section in the third section. The frequency of the current ripple must match the carrier frequency. It is characterized by: [Effects of the Invention]

[0011] According to the present invention, it is possible to provide a device that detects bus currents, reproduces three-phase currents, and suppresses current distortion. [Brief explanation of the drawings]

[0012] [Figure 1] 1 is a diagram showing an overall configuration of an inverter device 100 according to a first embodiment of the present invention. [Figure 2] 2 is a diagram showing the internal configuration of a controller 11 in an inverter device 100. FIG. [Figure 3] 1 is a diagram showing the waveform of one cycle of a carrier wave 40 that generates a PWM control signal. [Figure 4]2 is a diagram showing the configuration of a modulated wave calculator 25 and a PWM controller 26. FIG. [Figure 5] FIG. 10 is a diagram showing an example of a waveform obtained by a conventional adjustment method. [Figure 6] FIG. 10 is a diagram showing another example of a waveform obtained by a conventional adjustment method. [Figure 7] FIG. 4 is a diagram showing an example of a waveform in an adjustment method according to the first embodiment of the present invention. [Figure 8] FIG. 10 is a diagram showing the verification results of three-phase current waveforms (50, 51, 52) that demonstrate the effect of the first embodiment of the present invention. [Figure 9] FIG. 10 is a diagram showing the overall configuration of a motor driving device 200 according to a second embodiment of the present invention. [Figure 10] FIG. 10 is a block diagram showing the internal configuration of a controller 208 in FIG. 9. [Figure 11] FIG. 10 is a diagram showing the configuration of a refrigeration device 300 according to a third embodiment of the present invention. DETAILED DESCRIPTION OF THE INVENTION

[0013] Hereinafter, embodiments of the present invention will be described with reference to the drawings. The embodiments of the present invention are not limited to the specific configurations described below. In the drawings, the same reference numerals indicate the same or corresponding parts. [Example]

[0014] An inverter device 100 and a control method thereof according to a first embodiment of the present invention will be described below with reference to Figures 1 to 8. The first embodiment shown in Figures 1 to 8 corresponds to a grid-connected inverter device for a photovoltaic power generation facility or a storage battery and a control method thereof.

[0015] Fig. 1 is a diagram showing the overall configuration of an inverter device 100 according to a first embodiment of the present invention. The inverter device 100 shown in Fig. 1 is connected on its AC side to an AC power source 1, and on its DC side to a DC load or a DC power source (hereinafter referred to as "DC load / DC power source 10").

[0016] The inverter device 100 includes a noise filter 2 connected in series to an AC power supply 1, a reactor 3, and an inverter circuit 4 connected to a DC load / DC power supply 10. The inverter device 100 further includes a capacitor 5 connected between the positive and negative electrodes of the DC side of the inverter circuit 4, a voltage detection circuit 6 that detects the AC voltage of the AC power supply 1, a voltage detection circuit 7 that detects the DC voltage between the positive and negative electrodes, a shunt resistor 8 and an amplifier 9 that are provided between the capacitor 5 and the inverter circuit 4, and a controller 11 that performs pulse width modulation (hereinafter referred to as PWM (Pulse Width Modulation)) control of the inverter circuit 4.

[0017] The operation modes of the inverter circuit 4 will be described below. The operation modes of the inverter circuit 4 include a rectification mode (AC / DC conversion mode) and a regeneration mode (DC / AC conversion mode). The rectification mode is a mode in which AC power is received from the AC power source 1 and supplied to the DC load / DC power source 10. The regeneration mode is a mode in which DC power from the DC load / DC power source 10 is inversely converted and output to the AC power source 1 (AC load). Switching between these two operation modes is achieved by a control signal from the controller 11. Examples of the DC power source used for the DC load / DC power source 10 include a solar power generation facility and a storage battery.

[0018] The AC power supply 1 shown in FIG. 1 is a three-phase AC power supply, and the inverter circuit 4 is configured as a three-phase bridge circuit corresponding to the three-phase AC power supply 1.

[0019] The capacitor 5 is an element for suppressing ripple voltage and surge voltage of the DC voltage on the DC side of the inverter circuit 4.

[0020] Controller 11 generates a pulse width modulation (PWM) signal for controlling the switching (on / off) of each semiconductor switching element of inverter circuit 4 based on detection signals from voltage detection circuit 6, voltage detection circuit 7, and amplifier 9. A processing unit such as a microcomputer or a DSP (Digital Signal Processor) can be used as controller 11. Controller 11 also includes a sample-and-hold circuit and an A / D (Analog / Digital) converter, which converts the input voltage and current detection signals into digital signals.

[0021] The internal configuration of the controller 11 will be described below with reference to Fig. 2. Fig. 2 is a diagram showing the internal configuration of the controller 11 in the inverter device 100. The controller 11 operates to generate a PWM signal for the inverter circuit 4 by the above-mentioned arithmetic processing device executing a predetermined program.

[0022] As shown in FIG. 2, the controller 11 includes a power supply phase calculator 21, a current reproduction calculator 22, a voltage command calculator 23, a two-axis / three-phase converter 24, a modulated wave calculator 25, a PWM controller 26, and a three-phase / two-axis converter 27.

[0023] The power supply phase calculator 21 receives the AC voltage detection signal detected by the voltage detection circuit 6 and calculates the power supply voltage phase (θ s ) and calculate the calculated power supply voltage phase (θ s ) to the two-axis / three-phase converter 24 and the three-phase / two-axis converter 27, respectively.

[0024] The three-phase / two-axis converter 27 converts the power supply voltage phase (θ s ) based on the three-phase current i of the inverter circuit 4 reproduced by a current reproduction calculator 22 described later. u , i v , i w The d-axis current detection value I d and q-axis current detection value I q Convert to.

[0025] The voltage command calculator 23 calculates the d-axis current command value Id * and the q-axis current command value I q * and the d-axis current detection value I obtained by the three-phase / two-axis converter 27. d and q-axis current detection value I q To eliminate the error, proportional-integral (PI) control is used to calculate the d-axis voltage command value V d * and q-axis voltage command value V q * A known technique can be used for this voltage command calculation, and a detailed description thereof will be omitted.

[0026] 2, the two-axis / three-phase converter 24 is connected to the d-axis voltage command value V d * and the q-axis voltage command value V q * and the power supply voltage phase (θ s ) and the three-phase voltage command value (v u * ,v v * ,v w * ) and outputs it to the modulated wave calculator 25. The processing of the modulated wave calculator 25 and the PWM controller 26 will be described in detail later with reference to FIG.

[0027] The current reproduction calculator 22 detects the bus current of the inverter circuit 4 output from the shunt resistor 8 and the amplifier 9. sh and the three-phase modulated wave command value m output by the modulated wave calculator 25. u ’ ,m v ’ ,m w ’ Using this, the three-phase current i of the inverter circuit 4 u , i v , i w The specific current reproduction process will be explained with reference to FIG.

[0028] 3 is a diagram showing the waveform of one cycle of the carrier wave 40 that generates the PWM control signal. u ’ ,mv ’ ,m w ’ By comparing the PWM control signals Pup, Pvp, and Pwp (these are control signals for the upper arm elements. The control signals for the lower arm elements are omitted here because they are the inverses of the control signals for the upper arm elements) corresponding to each phase, the bus current detection signal i shown in FIG. sh In the section where the PWM control signal Pup=0, Pvp=1, and Pwp=1, sh =i u In the interval Pup=0, Pvp=0, Pwp=1, i sh =i w Therefore, as shown in Figure 3, the bus current detection signal i sh If sampling is performed at the circled points, the phase currents of two phases i u , i w However, if the time width of the above section is narrower than the time available for sampling, the corresponding phase current cannot be detected. A solution to this problem will be described later with reference to FIGS. 5 to 7.

[0029] The three-phase current reproduced by the current reproduction calculator 22 is input to a three-phase / two-axis converter 27, and is converted into the power supply voltage phase (θ s ) and the d-axis current I d and q-axis current I q Calculate the following.

[0030] Next, the processing of the modulated wave calculator 25 and the PWM controller 26 will be described with reference to Fig. 4. Fig. 4 is a diagram showing the configurations of the modulated wave calculator 25 and the PWM controller 26.

[0031] The modulated wave calculator 25 includes a modulated wave converter 30 and a modulated wave regulator 31. The modulated wave converter 30 converts the three-phase voltage command value (v u * ,v v * ,v w * ) to the DC voltage detection signal E dc The three-phase modulated wave signal (m u ,m v ,mw )

[0032] m u =v u * / (Edc / 2) m v =v v * / (Edc / 2) m w =v w * / (Edc / 2) The modulation wave regulator 31 receives the bus current detection signal i sh The modulated wave of each phase is adjusted so as to secure the time width of the section corresponding to each phase current. Specific adjustment processing will be described with reference to FIGS.

[0033] 5 is a diagram showing an example of a waveform obtained by a conventional adjustment method. In this example, the bus current detection signal i sh In order to secure the time width of the three-phase modulated wave signal m u Adjustment amount Δm u1 and Δm u2 In order to maintain the average value of the modulated wave during one period of the carrier wave 40, an adjustment amount Δm u1 and Δm u2 Although not shown in FIG. 5, the modulated wave m v and m w A similar adjustment process is performed on

[0034] The addition / subtraction of such modulation waves causes an extra current ripple component Δi u In the example shown in FIG. 5, the current ripple component Δi u rises in the positive direction, and in the half-cycle section of the downslope of the carrier wave 40, the current ripple component Δi u Therefore, the current ripple component Δi u The average value of is not 0, and a positive bias component appears in the U-phase current.

[0035] Similarly, in the ascending half-cycle section of the carrier wave 40, the adjustment amount Δm u is subtracted, and the adjustment amount Δm u When adding, a negative bias component appears in the U-phase current. When the three-phase modulated wave is a periodic waveform, the adjustment amount Δm u Since the modulated wave also periodically changes, the bias component of the U-phase current fluctuates periodically due to the addition / subtraction of the modulated wave, resulting in current distortion.

[0036] 6 is a diagram showing another example of a waveform obtained by a conventional adjustment method. In this example, the bus current detection signal i sh In order to secure the time width of the three-phase modulated wave signal m u Adjustment amount Δm u1 and Δm u2 In order to maintain the average value of the modulated wave, the adjustment amount Δm is added in two half-cycle sections (I and III, and IV and VI) of the carrier wave 40 before and after the adjustment section. u1 / 2 and Δm u2 Subtract / 2 from each.

[0037] The addition / subtraction of such modulation waves causes an extra current ripple component Δi u However, as shown in Figure 6, the subtraction process is performed before and after the addition process, so the current ripple component Δi u The average value of is 0. Therefore, there is little current distortion in the U-phase current. However, as shown in Figure 6, the interval between current detections at which the current detection value is updated is 1.5 times the triangular wave carrier wave period, and the frequency of the current ripple is also reduced to 2 / 3 of the carrier frequency. This phenomenon may result in increased noise from inverters and motor drives.

[0038] Means for solving this problem will be described below. Fig. 7 is a diagram showing an example of waveforms in the adjustment method according to the first embodiment of the present invention.

[0039] In Figure 7, section I, where the triangular wave carrier wave 40 slopes downward, is set as section 1, section II, which occurs after section 1 and where the triangular wave carrier wave 40 slopes upward, is set as section 2, section III, which occurs after section 2 and where the triangular wave carrier wave 40 slopes downward, is set as section 3, section IV, which occurs after section 3 and where the triangular wave carrier wave 40 slopes upward, is set as section 4, and section V, which occurs after section 4 and where the triangular wave carrier wave 40 slopes downward, is set as section 5.

[0040] In this example, the modulated wave calculator 25 calculates the bus current detection signal i in the ascending half-cycle sections (second section II and fourth section IV) of the carrier wave 40, which is a triangular wave. sh In order to secure the time width of the three-phase modulated wave signal m u For this, the predetermined adjustment amount Δm u1 and Δm u2 In order to maintain the average value of the modulated wave, the adjustment amount Δm is added in two half-cycle sections (first section I, third section III, fifth section V) of the carrier wave 40 on the downslope before and after the second section II and the fourth section IV. u1 / 2 and Δm u2 In addition, in the downhill sections sandwiched before and after the uphill section (third section III), the adjustment amount Δm u1 and Δm u2 When performing the addition process, half of each adjustment amount is overlapped and subtracted (adjustment amount Δm u1 / 2 + adjustment amount Δm of the fourth section IV u2 / 2).

[0041] The addition / subtraction of such modulation waves causes an extra current ripple component Δi u However, as shown in Figure 7, the subtraction process is performed before and after the addition process, so the current ripple component Δi u The average value of is 0. Therefore, there is little current distortion in the U-phase current. In addition, because the subtraction process of the adjustment amount is performed in the downhill section, the frequency of the current ripple is the same as the carrier frequency. In other words, this adjustment method can suppress noise caused by frequency components other than the existing carrier frequency.

[0042] Furthermore, similar modulation wave adjustment can be performed by interchanging the ascending and descending slopes of the triangular carrier wave shown in Figures 5 to 7. A detailed description will be omitted here.

[0043] Finally, the configuration and operation of the PWM controller 26 in FIG. 4 will be briefly described.

[0044] The PWM control method in the PWM controller 26 is not particularly limited, but for example, a so-called triangular wave comparison method can be adopted, in which a triangular wave or sawtooth wave carrier wave signal is generated using the built-in functions of a microcomputer, and the output signal level is controlled by comparing it with the output of each register. Below, a more specific explanation will be given using the triangular wave comparison method using a triangular wave carrier wave signal.

[0045] However, the triangular wave comparison method using a triangular wave carrier signal is merely one example, and a sawtooth wave carrier signal may also be used. Furthermore, from the viewpoint of ease of implementation and reduction of hardware costs, it is preferable to adopt the triangular wave comparison method, but the present invention is not limited to this.

[0046] The PWM controller 26 uses a timer function to generate a triangular wave carrier wave signal in the carrier wave generator 35, and also generates peak-trough signals that indicate the timing of the peaks (the apexes of the upward convex portions) and troughs (the apexes of the downward convex portions).

[0047] The three-phase modulated wave command value m output by the modulated wave calculator 25 u ’ ,m v ’ ,m w ’ is input to a buffer register 32 and transferred to a comparison register 33 at the time of the peak or valley of the carrier wave in accordance with the peak / valley signal. A comparator 34 compares the output (modulated wave signal) of the comparison register 33 with the carrier wave signal generated by a carrier wave generator 35, and generates a PWM signal. FIG. 8 is a diagram showing the verification results of three-phase current waveforms (50, 51, 52) demonstrating the effect of the first embodiment of the present invention. The waveforms in FIG. 8(a) are verification results using the conventional method shown in FIG. 5. The waveforms in FIG. 8(b) are verification results using the adjustment method according to the first embodiment of the present invention shown in FIG. 7. Comparing the two verification results, it can be seen that the distortion of the three-phase currents has been improved. In particular, since the magnitude relationship of the three-phase modulated waves changes around the time when the relationship in magnitude of the three-phase currents changes, when the method shown in FIG. 5 is used, the bias components of the phase currents change suddenly, resulting in a current discontinuity phenomenon. On the other hand, when the method shown in FIG. 7 is used, the current discontinuity is eliminated and current distortion is reduced.

[0048] In the first embodiment described above, the bus current detection signal i sh In order to secure the time width of , the three-phase modulation wave m u Adjustment amount Δm u In addition, in two half-cycle sections of the carrier wave falling before and after the addition section, the adjustment amount Δm u Furthermore, when adding the adjustment amounts on an uphill slope before and after a downhill slope, half of each adjustment amount is subtracted in an overlapping manner.

[0049] According to the first embodiment, by adjusting the modulated wave as described above, the average value of the current ripple due to the addition / subtraction of the modulated wave can be suppressed to approximately 0, thereby reducing current distortion and matching the frequency of the current ripple with the carrier frequency. [Example]

[0050] A second embodiment of the present invention will be described below with reference to Figures 9 and 10. In the second embodiment, a motor control device including the inverter device described above will be described.

[0051] 9 is a diagram showing the overall configuration of a motor drive device 200 according to Example 2 of the present invention. As shown in Fig. 9, motor drive device 200 is connected to an AC power supply 201 and a motor 210, and mainly includes a rectifier circuit 202, a smoothing capacitor 203, an inverter circuit 204, a current detection circuit 206, a DC voltage detection circuit 207, and a controller 208.

[0052] 1 includes the smoothing capacitor 203, the inverter circuit 204, the current detection circuit 206, the DC voltage detection circuit 207, and the controller 208. The noise filter 2 and the reactor 3 are omitted from the inverter device 100 shown in FIG. 9. The inverter device 100 converts the DC voltage converted by the rectifier circuit 202 into an AC voltage and supplies it to the motor 210.

[0053] Rectifier circuit 202 is connected to AC power supply 201 and converts the AC voltage from AC power supply 201 into a DC voltage. Smoothing capacitor 203 is connected to a DC output terminal of rectifier circuit 202 and smoothes the DC voltage output from rectifier circuit 202. Inverter circuit 204 turns semiconductor switching elements such as IGBTs and power MOSs on and off in accordance with a PWM signal input from controller 208, converts the DC voltage output from smoothing capacitor 203 into an AC voltage, and outputs the AC voltage to drive motor 210.

[0054] When power is supplied from a DC power supply such as a storage battery instead of the AC power supply 201, the rectifier circuit 202 may be omitted and the output of the DC power supply may be input to the inverter circuit 204.

[0055] Further, the current detection circuit 206 detects the DC current (bus current) of the inverter circuit 204 by a shunt resistor provided between the smoothing capacitor 203 and the inverter circuit 204. The DC voltage detection circuit 207 detects the DC voltage across the smoothing capacitor 203.

[0056] The controller 208 generates a PWM signal for controlling the inverter circuit 204 based on the outputs of the current detection circuit 206 and the DC voltage detection circuit 207. The controller 208 can be implemented using a semiconductor computing element such as a microcomputer or a DSP (Digital Signal Processor).

[0057] Fig. 10 is a block diagram showing the internal configuration of the controller 208 shown in Fig. 9. The controller 208 calculates a voltage command signal to be applied to the motor 210 and generates a PWM control signal to control the inverter circuit 204. More specifically, the controller 208 includes a speed controller 220, a d-axis current command generator 221, a voltage controller 222, a two-axis / three-phase converter 223, a modulated wave calculator 224, a speed & phase estimator 225, a three-phase / two-axis converter 226, a current reproduction calculator 227, and a PWM controller 228.

[0058] The speed controller 220 receives the difference between the speed command and the estimated speed output by the speed and phase estimator 225, and calculates the q-axis current command value I q * The d-axis current command generator 221 outputs the d-axis current command value I d * Output.

[0059] The voltage controller 222 calculates the d-axis current command value I d * and the q-axis current command value I q * , and the dc-axis current detection value Idc and the qc-axis current detection value Iqc output by the three-phase / two-axis converter 226, and calculates and outputs a dc-axis voltage command value Vdc and a qc-axis voltage command value Vqc. Note that the dc-qc axes are the estimated axes of the control system.

[0060] The speed and phase estimator 225 receives the dc-axis current detection value Idc, the qc-axis current detection value Iqc, the dc-axis voltage command value Vdc, and the qc-axis voltage command value Vqc, and calculates and outputs an estimated speed and phase information θdc of the control system.

[0061] The two-axis / three-phase converter 223 receives the dc-axis voltage command value Vdc and the qc-axis voltage command value Vqc, and outputs the three-phase voltage command value (v u * ,v v * ,v w * ) and outputs it to the modulated wave calculator 224.

[0062] The modulated wave calculator 224 calculates the three-phase voltage command value (v u * ,v v * ,v w * ) and the DC voltage detection signal output by the DC voltage detection circuit 20 are input, and a three-phase modulated wave m u * , m v * , m w * and outputs it to the PWM controller 228 and the current reproduction calculator 227.

[0063] The current reproduction calculator 227 reproduces the bus current detection signal output by the current detection circuit 206 and the three-phase modulated wave m output by the modulated wave calculator 224. u * , m v * , m w * Using this, the output current i of the inverter circuit 204 is u , i v , i w Recreate the following.

[0064] The PWM controller 228 has the same configuration as the PWM controller 26 described in the first embodiment, and generates a PWM signal for the inverter circuit 204 .

[0065] As explained in the first embodiment, the modulated wave calculator 224 has an internal configuration similar to that of the modulated wave calculator 25 in FIG. 4, and adjusts the modulated wave using the adjustment method in FIG. 7 so that the bus current can be detected using the modulated wave adjuster 31.

[0066] As described above, according to the second embodiment, it is possible to provide motor drive device 200 that can accurately detect the bus current while suppressing the average value of the current ripple due to modulation wave adjustment to approximately zero, thereby reducing motor current distortion and making the frequency of the current ripple match the carrier frequency. Furthermore, by improving current distortion, motor drive device 200 has reduced torque pulsation, making it possible to reduce vibration, noise, and power consumption of the device. [Example]

[0067] A third embodiment of the present invention will be described below with reference to Fig. 11. In the second embodiment, a refrigeration equipment 300 including the above-described inverter circuit will be described. Here, refrigeration equipment is a general term for equipment that uses a refrigerant and a refrigeration cycle, such as an air conditioner, a refrigerator, or a freezer. More specifically, examples of refrigeration equipment include air conditioners such as room air conditioners and gas engine heat pump air conditioners, heat source equipment such as freezers and chilling units, commercial freezers such as showcases, refrigerator-freezers, unit coolers, and ice makers, transportation refrigeration equipment such as car air conditioners, and heat pump water heaters.

[0068] 11 is a diagram showing the configuration of a refrigeration equipment 300 according to a third embodiment of the present invention. The refrigeration equipment 300 is a device that adjusts the temperature of air, water, etc., and includes heat exchangers 301 and 302 that exchange heat between a refrigerant and a fluid (air, water, etc.), fans 303 and 304 that blow air to the heat exchangers 301 and 302, respectively, and a compressor 305 that compresses and circulates the refrigerant.

[0069] Furthermore, compressor 305 has compressor motor 308 equipped with a permanent magnet synchronous motor inside. Motor drive device 307 drives compressor motor 308, and compressor 305 is driven by compressor motor 308. Motor drive device 307 converts AC voltage of an AC power supply into DC voltage, and provides the DC voltage to a motor drive inverter to drive compressor motor 308.

[0070] Various types of compressors, such as a rotary compressor or a scroll compressor, can be used as the compressor 305. The compressor 305 has an internal compression mechanism that is driven by a compressor motor 308. If the compression mechanism is a scroll compressor, it is composed of a fixed scroll and an orbiting scroll. A compression chamber is formed between the scrolls as the orbiting scroll orbits relative to the fixed scroll.

[0071] By using the motor drive device 200 of Example 2 as the motor drive device 307, it is possible to reliably detect the bus current while reducing motor current distortion and making the frequency of the current ripple match the carrier frequency, thereby realizing a refrigeration device with lower vibration and higher efficiency.

[0072] It should be noted that the embodiments of the present invention are not limited to the above-described embodiments and may include various modifications. For example, the above-described embodiments have been described in detail for ease of understanding, and are not necessarily limited to those including all of the described configurations. Furthermore, it is possible to replace part of the configuration of one embodiment with the configuration of another embodiment, or to add the configuration of another embodiment to the configuration of one embodiment. Furthermore, it is possible to add, delete, or replace part of the configuration of each embodiment with other configurations. [Explanation of symbols]

[0073] 100... inverter device, 1... AC power supply, 2... noise filter, 3... reactor, 4... inverter circuit, 5... capacitor, 6... voltage detection circuit, 7... voltage detection circuit, 8... shunt resistor, 9... amplifier, 10... DC load / DC power supply, 11... controller, 21...power supply phase calculator, 22...current reproduction calculator, 23...voltage command calculator, 24...two-axis / three-phase converter, 25...modulation wave calculator, 26...PWM controller, 27...three-phase / two-axis converter, 30...modulation wave converter, 31...modulation wave adjuster, 32...buffer register, 33...comparison register, 34...comparator, 35...carrier wave generator, 40...Carrier wave, 41...Modulation wave adjustment amount, 42...Current ripple, 43...Average current ripple value, 50...U-phase current waveform, 51...V-phase current waveform, 52...W-phase current waveform, 200...motor drive device, 201...AC power supply, 202...rectifier circuit, 203...smoothing capacitor, 204...inverter circuit, 206...current detection circuit, 207...DC voltage detection circuit, 208...controller, 210...motor, 220...speed controller, 221...d-axis current command generator, 222...voltage controller, 223...two-axis / three-phase converter, 224...modulated wave calculator, 225...speed & phase estimator, 226...three-phase / two-axis converter, 227...current reproduction calculator, 228...PWM controller, 300... refrigeration equipment, 301, 302... heat exchangers, 303, 304... fans, 305... compressor, 306... refrigerant piping, 307... motor drive device, 308... compressor motor

Claims

1. An inverter device comprising: a PWM controller that generates a PWM signal based on a three-phase modulated wave and a triangular carrier wave; an inverter circuit that converts a DC voltage into a three-phase AC voltage based on the PWM signal generated by the PWM controller; a current reproduction calculator that detects a DC bus current of the inverter circuit and reproduces a three-phase current; and a voltage command calculator that calculates a voltage command value based on the three-phase current reproduced by the current reproduction calculator, a modulated wave calculator that calculates a three-phase modulated wave command value to be output to the PWM controller based on the voltage command value calculated by the voltage command calculator, In a state in which a section where the triangular wave carrier wave is downward slope is defined as a first section, a section after the first section where the triangular wave carrier wave is upward slope is defined as a second section, a section after the second section where the triangular wave carrier wave is downward slope is defined as a third section, and a section after the third section where the triangular wave carrier wave is upward slope is defined as a fourth section, the modulated wave calculator an inverter device comprising: an inverter circuit for adjusting a frequency of a current ripple to a carrier frequency by adding a predetermined adjustment amount to the three-phase modulated wave signal in the second section; subtracting half of the predetermined adjustment amount in each of the first and third sections; and, when adding a predetermined adjustment amount to the three-phase modulated wave signal in the fourth section, subtracting half of the predetermined adjustment amount of the fourth section in the third section.

2. In claim 1, The inverter device is characterized in that the modulated wave calculator comprises: a modulated wave converter that converts the voltage command value and a DC voltage detection signal of the inverter circuit into the three-phase modulated wave signal; and a modulated wave adjuster that calculates a three-phase modulated wave command value based on the three-phase modulated wave signal output by the modulated wave converter.

3. A motor drive device including an inverter that converts DC voltage into AC voltage and supplies the AC voltage to a motor, A motor drive device comprising the inverter device according to claim 1 or 2.

4. A refrigeration appliance comprising: a compressor having a motor for compressing and circulating a refrigerant; and a heat exchanger for exchanging heat between the refrigerant compressed by the compressor and a fluid, 4. A refrigeration appliance, wherein the motor is driven by the motor drive device according to claim 3.

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