Electric power conversion device and air conditioner

Abstract

Provided is an electric power conversion device or the like that is configured to reduce an electric power supply harmonic current. An electric power conversion device (100) comprises a rectifier circuit (10) that converts an AC voltage applied from an AC electric power supply (E1) to a DC voltage, a smoothing capacitor (30) that smooths the DC voltage on the output side of the rectifier circuit (10), an inverter circuit (40) that converts the DC voltage of the smoothing capacitor (30) to an AC voltage and drives a motor (M1) using the AC voltage, an electric power supply voltage detection unit (50) that detects the electric power supply voltage of the AC electric power supply (E1), and a control unit (80) that controls the inverter circuit (40), the control unit (80) changing an amount of compensation for a command voltage or a command electric current when the inverter circuit (40) is driven, so as to reduce an electric power supply harmonic current, on the basis of the electric power supply voltage.

Description

Power conversion device and air conditioner

[0001] The present disclosure relates to a power conversion device and the like.

[0002] With regard to a power conversion device that converts AC power into DC power and further converts this DC power into a predetermined AC power, for example, the technology described in Patent Document 1 is known. That is, Patent Document 1 describes controlling the inverter unit based on the voltage across an inductance element so that the transfer characteristics of the input / output voltage of the inverter unit become attenuation characteristics due to a phase lead element and a second-order lag element connected in series.

[0003] Patent No. 4067021

[0004] In the technology described in Patent Document 1, the inverter unit is controlled so as to reduce the harmonic components of the LC resonance, but there is room for improvement in terms of reducing the power supply harmonic current.

[0005] Therefore, an object of the present disclosure is to provide a power conversion device or the like that is adapted to reduce power supply harmonic currents.

[0006] In order to solve the above-mentioned problems, the power conversion device according to the present disclosure includes a rectifier circuit that converts an AC voltage applied from an AC power supply into a DC voltage, a smoothing capacitor that smooths the DC voltage on the output side of the rectifier circuit, an inverter circuit that converts the DC voltage of the smoothing capacitor into an AC voltage and drives a motor with the AC voltage, a power supply voltage detection unit that detects the power supply voltage of the AC power supply, and a control unit that controls the inverter circuit, and the control unit changes the amount of compensation for a command voltage or a command current when driving the inverter circuit to a predetermined value based on the power supply voltage so as to reduce power supply harmonic currents.

[0007] According to the present disclosure, it is possible to provide a power conversion device or the like that is adapted to reduce power supply harmonic currents.

[0008] 1 is a configuration diagram of a power conversion device according to a first embodiment. FIG. 2 is a functional block diagram of a control unit of the power conversion device according to the first embodiment. FIG. 3 is a functional block diagram of a power supply current oscillation suppressor of the power conversion device according to the first embodiment. FIG. 4 is a waveform diagram showing the relationship between an AC voltage, a line voltage, a phase voltage, and a power supply phase in the power conversion device according to the first embodiment. FIG. 5 is a waveform diagram showing changes in a phase voltage, a commutation section flag, and an oscillation suppression compensation amount in the power conversion device according to the first embodiment. FIG. 6 is a waveform diagram showing changes in a power supply phase and a distortion suppression compensation amount in the power conversion device according to the first embodiment. FIG. 7 is a functional block diagram of a command voltage regulator of the power conversion device according to the first embodiment. FIG. 8 is a waveform diagram of a power supply current of an R phase in the power conversion device according to the first embodiment. FIG. 9 is another waveform diagram of a power supply current of an R phase in the power conversion device according to the first embodiment. FIG. 10 is a diagram showing an example of an analysis result of a power supply harmonic current in the power conversion device according to the first embodiment. FIG. 11 is a functional block diagram of a power supply abnormality detector of the power conversion device according to the first embodiment. FIG. 12 is a functional block diagram of a control unit of the power conversion device according to the second embodiment. FIG. 13 is a functional block diagram of a command voltage regulator of the power conversion device according to the second embodiment. FIG. 14 is a functional block diagram of a control unit of the power conversion device according to the third embodiment. FIG. 15 is a functional block diagram of a current regulator of the power conversion device according to the third embodiment. Fig. 10 is a configuration diagram of an air conditioner according to a fourth embodiment Fig. 11 is a waveform diagram showing changes in phase voltage, output voltage of a rectifier circuit, and power supply current of an R phase in a comparative example when current oscillation suppression control is not performed

[0009] First Embodiment FIG. 1 is a configuration diagram of a power conversion device 100 according to a first embodiment. The power conversion device 100 shown in FIG. 1 converts AC power supplied from an AC power source E1 into DC power, converts the DC power into a predetermined AC power, and outputs the converted AC power to a motor M1. The motor M1 may be, for example, a permanent magnet synchronous motor or another type of motor. As shown in FIG. 1, the power conversion device 100 includes a rectifier circuit 10, a DC reactor 20, a smoothing capacitor 30, and an inverter circuit 40. In addition to the above-described components, the power conversion device 100 also includes a power supply voltage detector 50, a DC voltage detector 60, a bus current detector 70, and a controller 80.

[0010] The rectifier circuit 10 converts AC voltage applied from a three-phase AC power source E1 into DC voltage (pulsating DC voltage). For example, a full-wave rectifying diode bridge circuit may be used as the rectifier circuit 10, but the present invention is not limited thereto. Alternatively, a switching-type rectifier circuit may be used as the rectifier circuit 10. As shown in FIG. 1 , the output side of the rectifier circuit 10 is connected to the inverter circuit 40 via a positive DC line K1 and a negative DC line K2.

[0011] The DC reactor 20 is an element for smoothing the pulsating DC voltage applied from the rectifier circuit 10 and suppressing inrush current at startup. As shown in Fig. 1, the DC reactor 20 is provided on the positive DC line K1. More specifically, the DC reactor 20 is provided on the positive DC line K1 between the rectifier circuit 10 and a connection point between the DC line K1 and the smoothing capacitor 30.

[0012] The smoothing capacitor 30 is an element that smoothes the DC voltage on the output side of the rectifier circuit 10, and is connected to the DC lines K1 and K2 on the output side of the rectifier circuit 10. Specifically, one end (one lead wire) of the smoothing capacitor 30 is connected to the positive DC line K1, and the other end (the other lead wire) is connected to the negative DC line K2. For example, a film capacitor is used as such a smoothing capacitor 30.

[0013] Generally, film capacitors are smaller in size (volume) than large-capacity electrolytic capacitors. Therefore, using a film capacitor as smoothing capacitor 30 allows for the miniaturization of the circuit board (not shown) of power conversion device 100. Furthermore, because film capacitors use an insulating plastic film as a dielectric, there is no particular need to use an electrolyte, as in electrolytic capacitors. Therefore, there is almost no risk of malfunctioning of the film capacitor, even when used in a high-temperature environment in the summer, such as in the outdoor unit of an air conditioner.

[0014] However, if a small-capacity film capacitor is used in consideration of the unit price per capacitance, power supply harmonic currents (harmonic currents on the AC power supply E1 side) are likely to occur. Furthermore, the resonant frequency between the film capacitor and the DC reactor 20 is often 10 times or more the power supply frequency (50 Hz or 60 Hz). As a result, power supply harmonic currents of high orders, such as 17th and 19th orders, tend to increase. Therefore, in the first embodiment, the control unit 80 controls the inverter circuit 40 in a predetermined manner to suppress power supply harmonic currents. The type of smoothing capacitor 30 is not limited to a film capacitor, and other types of capacitors, such as an electrolytic capacitor, may also be used.

[0015] The inverter circuit 40 is a power converter that converts the DC voltage of the smoothing capacitor 30 into a predetermined AC voltage and drives the motor M1 with this AC voltage. As shown in FIG. 1 , the inverter circuit 40 is configured such that a first leg including a series connection of switching elements S1 and S2, a second leg including a series connection of switching elements S3 and S4, and a third leg including a series connection of switching elements S5 and S6 are connected in parallel to the smoothing capacitor 30. In the example shown in FIG. 1 , IGBTs (Insulated Gate Bipolar Transistors) are used as the switching elements S1 to S6, but this is not limiting. That is, MOSFETs (Metal Oxide Semiconductor Field Effect Transistors) or bipolar transistors may also be used as the switching elements S1 to S6.

[0016] In the first leg described above, the connection point between the pair of switching elements S1 and S2 is connected to the windings of the motor M1 via wiring. The same applies to the remaining second and third legs. In the inverter circuit 40, to prevent breakdown of the switching elements S1 to S6 due to commutation, freewheeling diodes (reference numbers not shown) are connected in anti-parallel to each of the switching elements S1 to S6. If the switching elements S1 to S6 have parasitic diodes, these parasitic diodes function as freewheeling diodes, so there is no need to provide separate freewheeling diodes.

[0017] The power supply voltage detection unit 50 detects the power supply voltage of the AC power supply E1. In the example of FIG. 1, the power supply voltage detection unit 50 is connected so as to detect the voltage of the AC power supply E1 having three phases (R phase, S phase, and T phase). The power supply voltage detection unit 50 is configured to include resistance elements R1 to R6. For example, one end (the side of the resistance element R1) of the series connection of the resistance elements R1 and R2 is connected to the R-phase wiring K Ｒ and the other end (the side of the resistor element R2) is connected to the ground terminal of the control unit 80. The connection point between the resistor elements R1 and R2 is connected to the input terminal of the control unit 80 via a wire. The voltage of one resistor element R2 of the pair of resistor elements R1 and R2 is applied to the input terminal of the control unit 80 as an AC voltage signal ErN indicating the R-phase voltage.

[0018] The control unit 80 calculates the voltage between the R-phase terminal and the ground terminal of the AC power supply E1 based on the voltage of the resistance element R2 and the voltage division ratio of the resistance elements R1 and R2. The same applies to the series connection of the resistance elements R3 and R4 used to detect the S-phase voltage and the series connection of the resistance elements R5 and R6 used to detect the T-phase voltage. In this way, the AC voltage signals ErN, EsN, and EtN for three phases are input to the input terminals of the control unit 80, respectively.

[0019] The DC voltage detection unit 60 detects the DC voltage across the smoothing capacitor 30 and includes resistor elements R7 and R8. In the example of FIG. 1 , one end (the resistor element R7 side) of the series connection of the resistor elements R7 and R8 is connected to the positive DC line K1. The other end (the resistor element R8 side) of the series connection of the resistor elements R7 and R8 is connected to the negative DC line K2 and the ground terminal of the control unit 80. The connection point between the resistor elements R7 and R8 is connected to the input terminal of the control unit 80 via a wiring. The voltage of one of the pair of resistor elements R7 and R8, the resistor element R8, is applied to the input terminal of the control unit 80 as a DC voltage signal Edc. The control unit 80 calculates the DC voltage of the smoothing capacitor 30 at every moment based on the voltage of the resistor element R8 and the voltage division ratio of the resistor elements R7 and R8.

[0020] The bus current detector 70 detects the bus current flowing through the DC line K2. As shown in FIG. 1 , the bus current detector 70 includes a resistor element R9 provided on the DC line K2 and an amplifier 71 that amplifies the voltage across the resistor element R2. A bus current signal Ish is input from the amplifier 71 to an input terminal of the control unit 80. The control unit 80 calculates the bus current based on the bus current signal Ish. For example, the control unit 80 samples the bus current twice per PWM period.

[0021] In addition to the above-mentioned functions, the control unit 80 also has the function of controlling the inverter circuit 40 in a predetermined manner. That is, the control unit 80 converts the momentarily detected values ​​(analog signals) of the power supply voltage detection unit 50, the DC voltage detection unit 60, and the bus current detection unit 70 into digital signals, and controls the inverter circuit 40 in a predetermined manner based on these digital signals. Note that a sample-and-hold circuit (not shown) or an A / D converter (not shown) is appropriately used for the conversion from analog signals to digital signals. The control unit 80 then outputs predetermined PWM signals based on PWM control (Pulse Width Modulation) to the switching elements S1 to S6. For example, a microcomputer or a DSP (Digital Signal Processor) may be used as the control unit 80.

[0022] 2 is a functional block diagram of a control unit 80 of the power conversion device. As shown in Fig. 2, the control unit 80 includes a current reproduction calculator 81, a three-phase / two-axis converter 82, a speed controller 83, a d-axis command current generator 84, and a voltage controller 85. In addition to the components described above, the control unit 80 also includes a speed / phase / output estimator 86, a two-axis / three-phase converter 87, a command voltage regulator 88, a PWM controller 89, and a power supply current oscillation suppressor 90.

[0023] The current reproduction calculator 81 reproduces the output currents (Iu, Iv, Iw) of the inverter circuit 40 based on the bus current signal Ish input from the bus current detector 70 (see FIG. 1) and the three-phase command voltages (Vu**, Vv**, Vw**).

[0024] The three-phase / two-axis converter 82 converts the three-phase output currents (Iu, Iv, Iw) reproduced by the current reproduction calculator 81 into the control axis phase θ of the rotor of the motor M1 (see FIG. 1) estimated by the speed / phase / output estimator 86. ｄｃand calculate the dc-axis current Idc and the qc-axis current Iqc based on the above. The actual direction of the magnetic flux of the magnet in the motor M1 (see FIG. 1) is the d-axis, and the axis perpendicular to this d-axis is the q-axis. The d-axis assumed by the control unit 80 is the dc-axis (similar to the qc-axis). In other words, the dc-axis current Idc and the qc-axis current Iqc are the motor currents of the dc-axis and qc-axis assumed by the control unit 80.

[0025] A speed controller 83 generates a qc-axis command current Iqc* based on an external speed command. A d-axis command current generator 84 generates a dc-axis command current Idc*. A voltage controller 85 calculates a dc-axis command voltage Vdc* and a qc-axis command voltage Vqc* based on the dc-axis command current Idc*, the qc-axis command current iqc*, the dc-axis current Idc, the qc-axis current Iqc, the speed command, the motor constants, etc.

[0026] The speed / phase / output estimator 86 estimates the phase difference between the dc-qc axes and the actual d-q axes of the motor M1 (see FIG. 1) based on the dc-axis command voltage Vdc*, the qc-axis command voltage Vqc*, the dc-axis current Idc, the qc-axis current Iqc, motor constants, etc. The speed / phase / output estimator 86 also estimates the estimated speed and control axis phase θ of the motor M1 (see FIG. 1) based on the phase difference, etc. ｄｃ Calculate.

[0027] Then, a subtractor 101 subtracts the estimated speed from a predetermined speed command, and the value after subtraction is input to the speed controller 83. Since these processes are well known, detailed explanations will be omitted. Also, the speed / phase / output estimator 86 calculates the output P ｉｎｖ Calculate.

[0028] P ｉｎｖ =Vdc*×Idc+Vqc*×Iqc...(1)

[0029] In this way, the output P calculated by the speed / phase / output estimator 86 ｉｎｖ The value of is output to the power supply current vibration suppressor 90. The two-axis / three-phase converter 87 receives the dc-axis command voltage Vdc* and the qc-axis command voltage Vqc* as well as the control axis phase θ calculated by the speed / phase / output estimator 86.ｄｃ Based on the above, three-phase command voltages (Vu*, Vv*, Vw*) are calculated.

[0030] The command voltage regulator 88 adjusts the three-phase command voltages (Vu*, Vv*, Vw*) based on the compensation amount Kc (also referred to as an adjustment gain) calculated by the power supply current oscillation suppressor 90, and generates adjusted three-phase command voltages (Vu**, Vv**, Vw**). The calculation of the compensation amount Kc and the adjustment of the three-phase command voltages (Vu*, Vv*, Vw*) will be described later.

[0031] The PWM controller 89 calculates a modulation factor for PWM control based on the three-phase command voltages (Vu**, Vv**, Vw**) as well as the DC voltage signal Edc input from the DC voltage detector 60 (see FIG. 1), and generates a PWM signal. The on / off of the switching elements S1 to S6 (see FIG. 1) of the inverter circuit 40 (see FIG. 1) is controlled based on the PWM signal thus generated.

[0032] The power supply current oscillation suppressor 90 is configured to suppress the output P ｉｎｖ In addition, a compensation amount Kc for suppressing the oscillation of the power supply current is calculated based on the AC voltage signals (ErN, EsN, EtN) input from the power supply voltage detection unit 50 (see FIG. 1). The compensation amount Kc calculated by the power supply current oscillation suppressor 90 is output to the command voltage regulator 88. The compensation amount Kc is a compensation amount for the command voltage (or command current) when driving the inverter circuit 40, and the calculation method thereof will be described later.

[0033] Fig. 3 is a functional block diagram of the power supply current vibration suppressor 90. As shown in Fig. 3, the power supply current vibration suppressor 90 includes a line voltage calculator 91, a phase voltage calculator 92, a phase calculator 93, and a rectifier circuit commutation estimator 94. In addition to the components described above, the power supply current vibration suppressor 90 also includes a vibration suppression compensation amount LUT (Look Up Table) 95, a distortion suppression compensation amount LUT (Look Up Table) 96, an adder 97, a multiplier 98, and a power supply abnormality detector 99.

[0034] The line voltage calculator 91 uses the AC voltage signals (ErN, EsN, EtN) to calculate the line voltages (Ers, Est, Etr) of the AC power supply E1 (see FIG. 1) based on the following equations (2) to (4).

[0035] Ers=ErN-EsN...(2) Est=EsN-EtN...(3) Etr=EtN-ErN...(4)

[0036] The phase voltage calculator 92 uses the line voltages (Ers, Est, Etr) to calculate the phase voltages (Er, Es, Et) of each phase of the AC power supply E1 (see FIG. 1) based on the following equations (5) to (7).

[0037] Er=(Ers-Etr) / 3...(5) Es=(Est-Ers) / 3...(6) Et=(Etr-Est) / 3...(7)

[0038] The phase calculator 93 calculates the power supply phase θs based on the line voltages (Ers, Est, Etr) according to the following equation (8): Here, the power supply phase θs means the phase of the power supply voltage in the AC power supply E1.

[0039] θs= arctan {(-√3 Ers) / (2Est+Ers)}-30°...(8)

[0040] FIG. 4 is a waveform diagram showing the relationship between AC voltage, line voltage, phase voltage, and power supply phase. The horizontal axis of each waveform diagram shown in FIG. 4 represents time. The vertical axis of each waveform diagram, from top to bottom, represents the AC voltage (i.e., AC voltage signal (ErN, EsN, EtN)), line voltage (Ers, Est, Etr), three-phase phase voltages (Er, Es, Et), and the AC voltage power supply phase θs. When the line voltages (Ers, Est, Etr) are calculated from the AC voltage signals (ErN, EsN, EtN) based on the above-described equations (2) to (4), a sinusoidal waveform such as that shown in FIG. 4 is obtained. Similarly, when the phase voltages (Er, Es, Et) are calculated based on the above-described equations (5) to (7), a sinusoidal waveform such as that shown in FIG. 4 is obtained. The power supply phase θs increases linearly from −π [rad] to +π [rad] over time, and then returns to −π [rad] and increases linearly again, repeating this change.

[0041] When the magnitude relationship between the three-phase voltages (Er, Es, Et) changes, the current path of the rectifier circuit 10 (see FIG. 1) switches, causing the output voltage of the rectifier circuit 10 to fluctuate suddenly. Such a sudden change in the output voltage of the rectifier circuit 10 makes it more likely that LC oscillation will occur in the power supply current. The "LC oscillation" mentioned above refers to resonance between the DC reactor 20 (see FIG. 1) and the smoothing capacitor 30 (see FIG. 1). In order to suppress the power supply harmonic current associated with such LC oscillation, in the first embodiment, the control unit 80 (see FIG. 1) performs predetermined current oscillation suppression control using a power supply current oscillation suppressor 90 (see FIG. 3). The current oscillation suppression control will be described later.

[0042] 16 is a waveform diagram showing changes in the phase voltages, the output voltage of the rectifier circuit, and the R-phase power supply current in a comparative example when current oscillation suppression control is not performed. The horizontal axis of each waveform diagram in FIG. 16 represents time. The vertical axis of each waveform diagram represents, from top to bottom, the phase voltages (Er, Es, Et), the output voltage of the rectifier circuit 10 (see FIG. 1), and the R-phase power supply current.

[0043] As described above, the current path of the rectifier circuit 10 (see FIG. 1) switches when the magnitude relationship of the phase voltages changes, causing the output voltage of the rectifier circuit 10 to fluctuate suddenly. As a result, the R-phase power supply current fluctuates slightly at the point indicated by symbol F1 in FIG. 16, generating a power supply harmonic current. Note that a sinusoidal power supply harmonic current that changes at a frequency that is n times (n is an integer) the sinusoidal fundamental wave that changes at the power supply frequency (50 Hz or 60 Hz) is called an "nth-order power supply harmonic current."

[0044] Returning to FIG. 3 , the explanation will be continued. The rectifier circuit commutation estimator 94 estimates the commutation timing from the magnitude relationship of the phase voltages based on the calculation results of the phase voltage calculator 92. Here, "commutation timing" refers to the timing when the current path in the rectifier circuit 10 (see FIG. 1 ) switches. In other words, the "commutation timing" is the timing when the magnitude relationship of the phase voltages switches. The rectifier circuit commutation estimator 94 determines a section where the voltage difference between any two of the three phase voltages is equal to or less than a predetermined value (e.g., 1 V) as a commutation section. The rectifier circuit commutation estimator 94 then outputs a predetermined commutation section flag Ft (see also FIG. 5 ) for the commutation section to the vibration suppression compensation amount LUT 95.

[0045] The vibration suppression compensation amount LUT 95 is a lookup table for generating the vibration suppression compensation amount Kc1 when the commutation section flag Ft is input from the rectifier circuit commutation estimator 94. Here, the term "lookup table" refers to a table for assigning a predetermined output value that changes from moment to moment to an input value, and is set in advance based on simulation results and actual measurement data.

[0046] Fig. 5 is a waveform diagram showing changes in phase voltage, commutation section flag, and vibration suppression compensation amount. The horizontal axis of each waveform diagram in Fig. 5 represents time. The vertical axis of each waveform diagram represents, from top to bottom, the phase voltage (Er, Es, Et), the commutation section flag Ft generated by the rectifier circuit commutation estimator 94 (see Fig. 3), and the vibration suppression compensation amount Kc1 generated by the vibration suppression compensation amount LUT 95 (see Fig. 3).

[0047] 5, when the commutation section flag Ft is input, the vibration suppression compensation amount Kc1 is generated with a waveform in which the value steeply decreases from zero to a predetermined value and then steeply increases. In this way, the control unit 80 (see FIG. 1) generates a predetermined vibration suppression compensation amount Kc1 in a commutation section (section) in which the magnitude relationship between the instantaneous values ​​of the phase voltages of the phases of the AC power supply E1 (see FIG. 1) changes. This vibration suppression compensation amount Kc1 is used to suppress high-order power supply harmonic currents, such as the 17th, 19th, and 23rd orders.

[0048] 3 is a lookup table for generating the distortion suppression compensation amount Kc2 based on the power supply phase θs, which is the calculation result of the phase calculator 93. The distortion suppression compensation amount Kc2 will be described with reference to FIG.

[0049] FIG. 6 is a waveform diagram showing changes in the power supply phase and the distortion suppression compensation amount. The horizontal axis of each waveform diagram in FIG. 6 represents time. The vertical axis of each waveform diagram, from top to bottom, represents the power supply phase θs and the distortion suppression compensation amount Kc2 generated by the distortion suppression compensation amount LUT 96 (see FIG. 3 ). In the example of FIG. 6 , the distortion suppression compensation amount Kc2 is set to change in a sawtooth waveform over time. The distortion suppression compensation amount Kc2 is also set in advance to zero when the power supply phase θs switches from π [rad] to −π [rad].

[0050] Then, over time, the distortion suppression compensation amount Kc2 increases linearly from zero to a predetermined value, then suddenly decreases, and then starts to increase again, repeating this change. In this way, the control unit 80 (see FIG. 1) generates the distortion suppression compensation amount Kc2 that changes in a sawtooth waveform based on the phase of the power supply voltage of the AC power supply E1 (i.e., the power supply phase θs). In the example of FIG. 6, the distortion suppression compensation amount Kc2 increases and decreases a total of six times while the power supply phase changes from -π [rad] to π [rad]. This distortion suppression compensation amount Kc2 is used to suppress low-order power supply harmonic currents, such as fifth-order. Note that control that suppresses power supply harmonic currents based on the vibration suppression compensation amount Kc1 and the distortion suppression compensation amount Kc2 is called "current vibration suppression control."

[0051] 3 is a calculator for adding the vibration suppression compensation amount Kc1 and the distortion suppression compensation amount Kc2. The multiplier 98 multiplies the calculation result of the adder 97 by the output P of the inverter circuit 40 (see FIG. 1). ｉｎｖ That is, the adder 97 and the multiplier 98 perform the calculation of the following equation (9). ｉｎｖ The value of is calculated based on the above formula (1).

[0052] Kc=(Kc1+Kc2)×P ｉｎｖ ...(9)

[0053] That is, the control unit 80 (see FIG. 1) generates a vibration suppression compensation amount Kc1 and also generates a distortion suppression compensation amount Kc2, and calculates the compensation amount Kc for the command voltage Vu** based on the sum of the vibration suppression compensation amount Kc1 and the distortion suppression compensation amount Kc2. As described above, in the first embodiment, the power supply current vibration suppressor 90 calculates the compensation amount Kc from time to time based on feedforward control. This shortens the delay time associated with the calculation process compared to when feedback control is performed, thereby stabilizing the control from the calculation of the compensation amount Kc to its reflection in the three-phase command voltages (Vu**, Vv**, Vw**).

[0054] In addition, the output P of the inverter circuit 40 ｉｎｖ It can be seen from equation (9) that the smaller the output power (P), the smaller the compensation amount Kc. ｉｎｖ The smaller the output power (P) of the inverter circuit 40, the smaller the compensation amount Kc for the command voltage. ｉｎｖ This is because when the output P of the inverter circuit 40 is small, the ripple component of the power supply current is also small. ｉｎｖ In response to this, the power supply current oscillation suppressor 90 adjusts the compensation amount Kc from moment to moment.

[0055] Furthermore, the timing and order in which each data item in the vibration suppression compensation amount LUT 95 and the distortion suppression compensation amount LUT 96 is read are set in advance so as to correct the delay time from when the AC voltage signals (ErN, EsN, EtN) are input to the control unit 80 until they are reflected in the PWM control. A power supply abnormality detector 99 shown in Fig. 3 detects an abnormality in the AC power supply E1 (see Fig. 1) based on the phase voltages (Er, Es, Et). Details of the power supply abnormality detector 99 will be described later.

[0056] As described above, the command voltage regulator 88 shown in Fig. 2 adjusts the three-phase command voltages (Vu*, Vv*, Vw*) based on the compensation amount Kc to generate adjusted three-phase command voltages (Vu**, Vv**, Vw**). Such adjustment of the three-phase command voltages will be described with reference to Fig. 7.

[0057] 7 is a functional block diagram of the command voltage regulator 88. As shown in FIG. 7, the command voltage regulator 88 includes an adder 88a and multipliers 88b, 88c, and 88d. The adder 88a adds a value of "1" to the compensation amount Kc calculated by the power supply current oscillation suppressor 90 (see FIG. 3). The multiplier 88b multiplies the calculation result of the adder 88a by the U-phase command voltage Vu* to generate a new command voltage Vu**.

[0058] Similarly, a multiplier 88c calculates a V-phase command voltage Vv**, and another multiplier 88d calculates a W-phase command voltage Vw**. A PWM signal is generated based on the adjusted three-phase command voltages (Vu**, Vv**, Vw**). The control unit 80 (see FIG. 1) then changes a compensation amount Kc for the three-phase command voltages (command voltages) used to drive the inverter circuit 40, based on the power supply voltage, to a predetermined value so as to reduce power supply harmonic currents. The specific manner in which the compensation amount Kc is changed to reduce power supply harmonic currents is preset as a vibration suppression compensation amount LUT 95 (see FIG. 3) and a distortion suppression compensation amount LUT 96 (see FIG. 3).

[0059] Fig. 8A is a waveform diagram of the power supply current of the R phase. Note that the horizontal axis of Fig. 8A represents time, and the vertical axis represents the power supply current of the R phase. In the example of Fig. 8A, the vibration suppression compensation amount Kc1 and the distortion suppression compensation amount Kc2 are not reflected in the PWM control until time t1. Furthermore, after time t1, the vibration suppression compensation amount Kc1 is reflected in the PWM control, but the distortion suppression compensation amount Kc2 is not reflected in the PWM control. In other words, after time t1, current vibration suppression control is performed based only on the vibration suppression compensation amount Kc1.

[0060] As indicated by symbol G1 in Fig. 8A, the power supply current oscillates finely and periodically until time t1. Furthermore, as indicated by symbol H1, the fine oscillations of the power supply current are suppressed after time t1. This is because the three-phase command voltages (Vu**, Vv**, Vw**) are generated based on the vibration suppression compensation amount Kc1, thereby suppressing high-order power supply harmonic currents such as the 17th, 19th, and 23rd orders.

[0061] Figure 8B is another waveform diagram of the R-phase power supply current. Note that the vertical and horizontal axes in Figure 8B are the same as those in Figure 8A. In the example of Figure 8B, until time t2, the vibration suppression compensation amount Kc1 is reflected in the PWM control, while the distortion suppression compensation amount Kc2 is not reflected in the PWM control. Furthermore, after time t2, both the vibration suppression compensation amount Kc1 and the distortion suppression compensation amount Kc2 are reflected in the PWM control. In other words, after time t2, current vibration suppression control is performed based on the vibration suppression compensation amount Kc1 and the distortion suppression compensation amount Kc2.

[0062] The waveform indicated by symbol H1 in the period up to time t2 in Fig. 8B and the waveform indicated by symbol H1 in the period after time t1 in Fig. 8A are similar in that only the vibration suppression compensation amount Kc1 is reflected in the PWM control. Furthermore, as indicated by symbol Q1 in Fig. 8B, fine oscillations in the power supply current are further suppressed after time t2. This is because low-order power supply harmonic currents, such as the fifth order, are suppressed by generating three-phase command voltages (Vu**, Vv**, Vw**) based on the distortion suppression compensation amount Kc2.

[0063] FIG. 9 is a diagram showing an example of the analysis results of power supply harmonic current. The horizontal axis of FIG. 9 represents the order of the power supply harmonic current, and the vertical axis represents the harmonic content. The "power supply harmonic regulation" shown in the legend specifically refers to the power supply harmonic regulation IEC 61000-3-12. "No compensation" is a comparative example in which neither the vibration suppression compensation amount Kc1 nor the distortion suppression compensation amount Kc2 is reflected in PWM control. "Compensation" represents a case in which both the vibration suppression compensation amount Kc1 and the distortion suppression compensation amount Kc2 are reflected in PWM control (i.e., the first embodiment).

[0064] 9, in the case of "without compensation," the 17th, 19th, and 23rd power supply harmonic currents, in addition to the 5th, exceed the values ​​specified in the power supply harmonic regulation. In contrast, in the case of "with compensation" where current oscillation suppression control is performed (i.e., the first embodiment), it was confirmed that the power supply harmonic currents of all orders are lower than the values ​​specified in the power supply harmonic regulation.

[0065] 10 is a functional block diagram of the power supply abnormality detector 99. As shown in FIG. 10, the power supply abnormality detector 99 includes an amplitude calculator 99a, an imbalance calculator 99b, and an abnormality determiner 99c. The amplitude calculator 99a determines whether there is an instantaneous power outage or a sudden rise in the power supply voltage based on the width and rate of change in the amplitude of the AC voltage. If it determines that there is an instantaneous power outage or a sudden rise in the power supply voltage, the amplitude calculator 99a outputs a predetermined abnormality flag to the abnormality determiner 99c.

[0066] The unbalance calculator 99b determines whether there is an unbalance or an open phase in the power supply voltage based on the unevenness ratio of the three phase voltages. If it determines that there is an unbalance or an open phase in the power supply voltage, the unbalance calculator 99b outputs a predetermined abnormality flag to the abnormality determiner 99c.

[0067] The abnormality determiner 99c outputs a predetermined power supply abnormality signal when an abnormality flag is input from at least one of the amplitude calculator 99a and the imbalance calculator 99b. In this case, the control unit 80 (see FIG. 1) stops the drive of the motor M1, for example, by stopping the output of the PWM signal to the inverter circuit 40 (see FIG. 1).

[0068] That is, when the control unit 80 determines that there is an instantaneous power outage or a sudden rise in the power supply voltage based on the amplitude and rate of change of the power supply voltage of the AC power supply E1, it stops the switching operation of the inverter circuit 40. Furthermore, when the control unit 80 determines that there is an imbalance in the phase voltages or a missing phase based on the unevenness ratio of the phase voltages of the AC power supply E1, it stops the switching operation of the inverter circuit 40. This allows appropriate protective operation to be performed when a power supply abnormality occurs. Note that when a power supply abnormality signal is input, the control unit 80 may decelerate the motor M1 as a protective operation.

[0069] According to the first embodiment, the control unit 80 controls the inverter circuit 40 based on the vibration suppression compensation amount Kc1 and the distortion suppression compensation amount Kc2, thereby suppressing LC oscillation of the power supply current. Furthermore, even when a small-capacity film capacitor is used as the smoothing capacitor 30, the power supply harmonic current can be reduced, thereby enabling operation in compliance with power supply harmonic regulations.

[0070] Furthermore, according to the first embodiment, the compensation amount Kc is reflected in the switching operation of the inverter circuit 40 based on feedforward control. Therefore, compared to when feedback control is performed, the delay time associated with the calculation process can be shortened and control can be stabilized. Furthermore, because the power supply voltage detection unit 50 can detect instantaneous changes in the AC voltage, protection operation for the inverter circuit 40 in the event of a power supply abnormality can be performed more quickly than when an abnormality is detected based on the detected value of the voltage of the DC reactor 20.

[0071] Second Embodiment The second embodiment differs from the first embodiment (see FIG. 2 ) in that the dc-axis command voltage Vdc* and the qc-axis command voltage Vqc* are adjusted instead of the three-phase command voltages (Vu*, Vv*, Vw*). The remaining features are the same as those of the first embodiment. Therefore, only the differences from the first embodiment will be described, and a description of the overlapping features will be omitted.

[0072] Fig. 11 is a functional block diagram of a control unit 80A of a power conversion device according to the second embodiment. A command voltage regulator 88A shown in Fig. 11 adjusts a dc-axis command voltage Vdc* and a qc-axis command voltage Vqc* based on a compensation amount Kc input from a power supply current vibration suppressor 90. The command voltage regulator 88A then outputs the adjusted dc-axis command voltage Vdc** and qc-axis command voltage Vqc** to a two-axis / three-phase converter 87.

[0073] Fig. 12 is a functional block diagram of the command voltage regulator 88A. As shown in Fig. 12, the command voltage regulator 88A includes an adder 88e and multipliers 88f and 88g. The adder 88e adds a value of "1" to the compensation amount Kc calculated by the power supply current vibration suppressor 90 (see Fig. 11). The multiplier 88f multiplies the dc-axis command voltage Vdc* by the calculation result of the adder 88a to calculate a new dc-axis command voltage Vdc**. Similarly, the multiplier 88g calculates the qc-axis command voltage Vqc**.

[0074] The adjusted dc-axis command voltage Vdc** and qc-axis command voltage Vqc** are then output from command voltage regulator 88A to two-axis / three-phase converter 87 (see FIG. 11). In this way, control unit 80A (see FIG. 11) changes the compensation amount Kc for the dc-axis command voltage Vdc* (command voltage) and qc-axis command voltage Vqc* (command voltage) when driving inverter circuit 40 (see FIG. 1) to a predetermined value based on the power supply voltage so as to reduce power supply harmonic currents.

[0075] <Effects> According to the second embodiment, the dc-axis command voltage Vdc* and the qc-axis command voltage Vqc* are adjusted based on the compensation amount Kc input from the power supply current vibration suppressor 90. Even with this configuration, it is possible to reduce power supply harmonic currents, similar to the first embodiment.

[0076] Third Embodiment The third embodiment differs from the first embodiment (see FIG. 2 ) in that the qc-axis command current Iqc* is adjusted instead of the three-phase command voltages (Vu*, Vv*, Vw*). The remaining features are the same as those of the first embodiment. Therefore, only the differences from the first embodiment will be described, and a description of the overlapping features will be omitted.

[0077] 13 is a functional block diagram of a control unit 80B of a power conversion device according to the third embodiment. The control unit 80B shown in FIG. 13 is configured to include a current regulator 102 instead of the command voltage regulator 88 (see FIG. 2) of the first embodiment. The current regulator 102 adjusts the qc-axis command current Iqc* based on the compensation amount Kc input from the power supply current vibration suppressor 90. The current regulator 102 then outputs the adjusted qc-axis command current Iqc** to the voltage controller 85.

[0078] FIG. 14 is a functional block diagram of the current regulator 102. As shown in FIG. 14, the current regulator 102 includes an adder 102a and a multiplier 102b. The adder 102a adds a value of "1" to the compensation amount Kc calculated by the power supply current vibration suppressor 90 (see FIG. 13). The multiplier 102b multiplies the qc-axis command current Iqc* by the calculation result of the adder 102a to calculate a new qc-axis command current Iqc**. The qc-axis command current Iqc** is then output from the current regulator 102 to the voltage controller 85 (see FIG. 13).

[0079] In this way, the control unit 80B (see FIG. 13) changes the compensation amount Kc for the qc-axis command current Iqc* (command current) when driving the inverter circuit 40 (see FIG. 1) to a predetermined value based on the power supply voltage so as to reduce the power supply harmonic current.

[0080] As in the first embodiment, the control unit 80B generates a predetermined vibration suppression compensation amount Kc1 in a commutation interval (interval) where the magnitude relationship between the instantaneous values ​​of the phase voltages of the phases of the AC power supply E1 changes, and also generates a distortion suppression compensation amount Kc2 that changes in a sawtooth waveform based on the phase of the power supply voltage of the AC power supply E1. The control unit 80B then calculates the compensation amount Kc for the qc-axis command current Iqc* (command current) based on the sum of the vibration suppression compensation amount Kc1 and the distortion suppression compensation amount Kc2.

[0081] In addition, the control unit 80B controls the output P ｉｎｖ The smaller the output power, the smaller the compensation amount Kc for the command current. ｉｎｖ The compensation amount Kc can be appropriately adjusted from moment to moment in accordance with the change in the value of the compensation amount Kc.

[0082] <Effects> According to the third embodiment, the qc-axis command current Iqc* is adjusted based on the compensation amount Kc input from the power supply current vibration suppressor 90. Even with this configuration, it is possible to reduce power supply harmonic currents, similar to the first embodiment.

[0083] Fourth Embodiment In the fourth embodiment, an air conditioner W1 (see FIG. 15) including the power conversion device 100 (see FIG. 1) configured as described in the first embodiment will be described. Note that the configuration and processing content of the power conversion device 100 are the same as those in the first embodiment, and therefore description thereof will be omitted.

[0084] Fig. 15 is a configuration diagram of an air conditioner W1 according to a fourth embodiment. The air conditioner W1 is a device that performs air conditioning such as cooling operation. As shown in Fig. 15, the air conditioner W1 includes an outdoor unit U1 that is provided with a compressor 1, an outdoor heat exchanger 2, an outdoor fan 3, and an expansion valve 4, as well as a power conversion device 100. The air conditioner W1 also includes an indoor unit U2 that is provided with an indoor heat exchanger 5 and an indoor fan 6.

[0085] The compressor 1 is a device that compresses a low-temperature, low-pressure gas refrigerant and discharges it as a high-temperature, high-pressure gas refrigerant. For example, a scroll compressor or a rotary compressor is used as this compressor 1. Although not shown in Fig. 15 , an accumulator for separating the refrigerant into gas and liquid is connected to the suction side of the compressor 1. Furthermore, a motor M1, which is a drive source for the compressor 1, is connected to the output side of the inverter circuit 40 (see Fig. 1 ) of the power conversion device 100.

[0086] The outdoor heat exchanger 2 is a heat exchanger in which heat is exchanged between the refrigerant flowing through its heat transfer tubes and the outside air sent in by the outdoor fan 3. The outdoor fan 3 is a fan that sends outside air to the outdoor heat exchanger 2 and is installed near the outdoor heat exchanger 2.

[0087] The expansion valve 4 is a valve that reduces the pressure of the refrigerant condensed in the "condenser" (one of the outdoor heat exchanger 2 and the indoor heat exchanger 5). The refrigerant reduced in pressure by the expansion valve 4 is introduced to the "evaporator" (the other of the outdoor heat exchanger 2 and the indoor heat exchanger 5). The indoor heat exchanger 5 is a heat exchanger in which heat exchange occurs between the refrigerant flowing through its heat transfer tube (not shown) and indoor air (air in the air-conditioned room) sent in by the indoor fan 6. The indoor fan 6 is a fan that sends indoor air to the indoor heat exchanger 5 and is installed near the indoor heat exchanger 5.

[0088] As shown in Fig. 15, a compressor 1, an outdoor heat exchanger 2, an expansion valve 4, and an indoor heat exchanger 5 are connected in sequence via piping 7. For example, when the air conditioner 100 is set to perform cooling operation, the refrigerant circulates sequentially through the compressor 1, the outdoor heat exchanger 2 (condenser), the expansion valve 4, and the indoor heat exchanger 5 (evaporator). Then, air cooled by heat exchange with the refrigerant flowing through the indoor heat exchanger 5 is blown out from the indoor unit U2 into the air-conditioned room.

[0089] <Effects> According to the fourth embodiment, the air conditioner W1 is provided with the power conversion device 100 having the same configuration as in the first embodiment, thereby improving the reliability of the air conditioner W1.

[0090] <<Modifications>> The power conversion devices 100, 100A, 100B and the air conditioner W1 according to the present disclosure have been described above in various embodiments. However, the present disclosure is not limited to these embodiments and various modifications can be made. For example, in the first embodiment, the power supply current vibration suppressor 90 (see FIG. 3 ) generates the vibration suppression compensation amount Kc1 and the distortion suppression compensation amount Kc2. However, the present disclosure is not limited to this. That is, the power supply current vibration suppressor 90 may calculate the vibration suppression compensation amount Kc1 using the vibration suppression compensation amount LUT 95 and calculate the compensation amount Kc for the three-phase command voltages (command voltages) based on the vibration suppression compensation amount Kc1. Alternatively, the power supply current vibration suppressor 90 may calculate the distortion suppression compensation amount Kc2 using the distortion suppression compensation amount LUT 96 and calculate the compensation amount Kc for the three-phase command voltages (command voltages) based on the distortion suppression compensation amount Kc2. In other words, at least one of the vibration suppression compensation amount and the distortion suppression compensation amount may be generated.

[0091] The same can be said for the second and third embodiments. That is, the power supply current vibration suppressor 90 may adjust the dc-axis command voltage Vdc* (command voltage) and the qc-axis command voltage Vqc* (command voltage) based on at least one of the vibration suppression compensation amount Kc1 and the distortion suppression compensation amount Kc2 (second embodiment). Also, the power supply current vibration suppressor 90 may adjust the qc-axis command current Iqc* (command current) based on at least one of the vibration suppression compensation amount Kc1 and the distortion suppression compensation amount Kc2 (third embodiment).

[0092] In the first embodiment, the output P ｉｎｖ In the above description, the compensation amount Kc is calculated by multiplying the output P ｉｎｖ In this case, the power supply current oscillation suppressor 90 may be configured to generate a monotonically increasing function (or a look-up table) in advance, such that the value of the monotonically increasing function increases and gradually approaches a predetermined saturation value as the power supply current increases. ｉｎｖ The compensation amount Kc is calculated by multiplying the value of the function for the output P ｉｎｖIn this case, the compensation amount Kc can be prevented from becoming too large in a region where the value of Kc is large. The same can be said for the second and third embodiments.

[0093] In each embodiment, the power supply voltage detection unit 50 (see FIG. 1 ) and the bus current detection unit 70 (see FIG. 1 ) are configured with a predetermined resistance element, but this is not limiting. That is, a current sensor can also be used as the power supply voltage detection unit 50 and the bus current detection unit 70. In each embodiment, the DC voltage detection unit 60 (see FIG. 1 ) is configured with a plurality of resistance elements, but this is not limiting. That is, a voltage sensor can also be used as the DC voltage detection unit 60.

[0094] In the fourth embodiment (see FIG. 15 ), the power conversion device 100 is connected to the motor M1 of the compressor 1, but the present invention is not limited to this. For example, the power conversion device 100 may be connected to an outdoor fan motor (not shown). Furthermore, the power conversion device 100 may be connected to the motor M1 of the compressor 1, and the power conversion device 100 may also be connected to the outdoor fan motor (not shown).

[0095] In the fourth embodiment (see FIG. 15 ), a configuration in which the air conditioner W1 does not include a four-way valve (not shown) has been described, but this is not limiting. That is, a four-way valve that switches the refrigerant flow path between the cooling cycle and the heating cycle may be provided. In the fourth embodiment (see FIG. 15 ), a case in which the air conditioner W1 includes the expansion valve 4 has been described, but this is not limiting. For example, a pressure reducing means such as a capillary tube may be provided instead of the expansion valve 4.

[0096] The fourth embodiment (see FIG. 15) can be applied to various types of air conditioners, such as commercial air conditioners and multi-air conditioners for buildings, in addition to room air conditioners. Each embodiment can also be applied to other devices, such as water heaters, refrigerators, freezers, and chillers.

[0097] Furthermore, the respective embodiments can be combined as appropriate. For example, a power conversion device including the control unit 80A (see FIG. 11) of the second embodiment may be used to drive the motor M1 of the compressor 1 (see FIG. 15) of the fourth embodiment. Also, a power conversion device including the control unit 80B (see FIG. 13) of the third embodiment may be used to drive the motor M1 of the compressor 1 (see FIG. 15) of the fourth embodiment.

[0098] Furthermore, each embodiment has been described in detail to clearly explain the present disclosure, and is not necessarily limited to having all of the described configurations. Furthermore, it is possible to add, delete, or replace part of the configuration of each embodiment with other configurations. Furthermore, the above-described mechanisms and configurations are those considered necessary for explanation, and do not necessarily represent all mechanisms and configurations of the product.

[0099] REFERENCE SIGNS LIST 1 Compressor 2 Outdoor heat exchanger 3 Outdoor fan 4 Expansion valve 5 Indoor heat exchanger 6 Indoor fan 10 Rectifier circuit 20 DC reactor 30 Smoothing capacitor 40 Inverter circuit 50 Power supply voltage detection unit 60 DC voltage detection unit 70 Bus current detection unit 80, 80A, 80B Control unit 90 Power supply current oscillation suppressor 100, 100A, 100B Power conversion device E1 AC power supply M1 Motor W1 Air conditioner

Claims

1. A power conversion device comprising: a rectifier circuit that converts an AC voltage applied from an AC power supply into a DC voltage; a smoothing capacitor that smoothes the DC voltage on the output side of the rectifier circuit; an inverter circuit that converts the DC voltage of the smoothing capacitor into an AC voltage and drives a motor with the AC voltage; a power supply voltage detection unit that detects the power supply voltage of the AC power supply; and a control unit that controls the inverter circuit, wherein the control unit changes a compensation amount for a command voltage or command current when driving the inverter circuit in a predetermined manner based on the power supply voltage so as to reduce power supply harmonic current.

2. The power conversion device according to claim 1, wherein the control unit generates a predetermined vibration suppression compensation amount in a section where the magnitude relationship of the instantaneous values of the phase voltages of each phase of the AC power supply changes, and calculates the compensation amount based on the vibration suppression compensation amount.

3. The power conversion device according to claim 1, wherein the control unit generates a sawtooth-shaped distortion suppression compensation amount based on the phase of the power supply voltage of the AC power supply, and calculates the compensation amount based on the distortion suppression compensation amount.

4. The power conversion device according to claim 1, wherein the control unit generates a predetermined vibration suppression compensation amount in a section where the magnitude relationship of the instantaneous values of the phase voltages of each phase of the AC power supply changes, generates a sawtooth-shaped distortion suppression compensation amount based on the phase of the power supply voltage of the AC power supply, and calculates the compensation amount based on the sum of the vibration suppression compensation amount and the distortion suppression compensation amount.

5. The power conversion device according to claim 1, wherein the control unit makes the compensation amount smaller as the output power of the inverter circuit is smaller.

6. The power conversion device according to claim 1, wherein the control unit stops the switching operation of the inverter circuit when it is determined that there is an instantaneous power outage or a sudden increase in the power supply voltage based on the change width and change speed of the amplitude of the power supply voltage of the AC power supply.

7. The power conversion device according to claim 1, wherein the control unit stops the switching operation of the inverter circuit when it is determined that there is an imbalance or a missing phase of the phase voltage based on the unbalance efficiency of the phase voltage of the AC power supply.

8. An air conditioner comprising the power conversion device according to any one of claims 1 to 7, and further comprising a compressor, an outdoor heat exchanger, an expansion valve, and an indoor heat exchanger, wherein the motor is connected to the output side of the inverter circuit as a drive source for the compressor.