Power conversion device

Abstract

A power conversion device for converting input AC power supplied from an AC power source into output AC power of a predetermined voltage and frequency, the power conversion device including an inverter circuit that supplies the output AC power to a motor and a compensation unit that compensates for harmonics of input power to the motor. The compensation unit detects a harmonic component that is generated in synchronization with a rotational speed of the motor in the input power, and changes a phase of AC voltage output from the inverter circuit at the same frequency as the harmonic component, thereby reducing the harmonic component.

Description

Technical Field

[0001] This disclosure relates to a power conversion device. Background Technology

[0002] The induced voltage of a motor sometimes contains harmonic components that are 5 times, 7 times, or even more than the motor's rotational speed (electric angular velocity) (see, for example, Patent Document 1).

[0003] [Cited Documents]

[0004] [Patent Documents]

[0005] [Patent Document 1] Japanese Patent Application Publication No. 2012-165634 Summary of the Invention

[0006] [Technical problem to be solved]

[0007] However, if harmonic components are included in the motor's induced voltage, then since harmonic components are also generated in the motor's input power, harmonics of the same order (order) as those generated in the motor's input power may appear on the input side of the inverter circuit that supplies power to the motor.

[0008] The purpose of this disclosure is to provide a power conversion device that can reduce harmonics generated on the input side of an inverter circuit.

[0009] [Technical Solution]

[0010] The power conversion device disclosed herein is a device for converting input AC power supplied from an AC power source into output AC power of a predetermined voltage and frequency. It includes: an inverter circuit that supplies the output AC power to a motor; and a compensation unit that compensates for harmonics in the input power to the motor. The compensation unit detects harmonic components in the input power that are generated synchronously with the motor's rotational speed, and changes the phase of the AC voltage output from the inverter circuit at the same frequency as the harmonic components, thereby reducing the harmonic components.

[0011] According to the power conversion device of this disclosure, the phase of the AC voltage output from the inverter circuit is changed at the same frequency as the harmonic components generated in the input power of the motor, thereby reducing the harmonic components generated in the input power of the motor, and thus reducing the harmonics generated on the input side of the inverter circuit.

[0012] In the power conversion device disclosed herein, the compensation unit generates a compensation amount that varies at the same frequency as the harmonic component, and changes the phase of the AC voltage at the same frequency as the harmonic component based on the compensation amount.

[0013] According to the power conversion device of this disclosure, the phase of the AC voltage is changed at the same frequency as the harmonic component according to the compensation amount, thereby reducing the harmonics generated on the input side of the inverter circuit.

[0014] In the power conversion device disclosed herein, the compensation unit adjusts the phase of the compensation amount according to the detected harmonic components, and changes the amplitude of the compensation amount according to any one of the motor's speed, torque, and power.

[0015] As with the power conversion device disclosed herein, the compensation unit adjusts the phase of the compensation amount according to the detected harmonic components, and changes the amplitude of the compensation amount according to any one of the motor's speed, torque, and power, thereby reducing the harmonics generated on the input side of the inverter circuit.

[0016] In the power conversion device disclosed herein, the compensation unit adjusts the amplitude of the compensation amount according to the detected harmonic components, and changes the phase of the compensation amount according to any one of the motor's speed, torque, and power.

[0017] As with the power conversion device disclosed herein, by means of the compensation unit adjusting the amplitude of the compensation amount according to the detected harmonic components, and by changing the phase of the compensation amount according to any one of the motor speed, torque and power, the harmonics generated on the input side of the inverter circuit can be reduced.

[0018] In the power conversion device disclosed herein, the compensation unit adjusts the phase and amplitude of the compensation amount according to the detected harmonic components.

[0019] As with the power conversion device disclosed herein, the compensation unit adjusts the phase and amplitude of the compensation amount according to the detected harmonic components, thereby reducing the harmonics generated on the input side of the inverter circuit.

[0020] The power conversion device disclosed herein includes a converter circuit that rectifies the input AC power and supplies power to the inverter circuit. Between the converter circuit and the inverter circuit, a capacitor is connected in parallel with the converter circuit, and the compensation unit detects the harmonic components from the voltage across the capacitor.

[0021] As with the power conversion device disclosed herein, even if the compensation unit detects the harmonic components from the voltage across the capacitor, it can reduce the harmonics generated on the input side of the inverter circuit.

[0022] The power conversion device disclosed herein includes a converter circuit that rectifies the input AC power and supplies power to the inverter circuit, a reactor connected between the converter circuit and the AC power source or the inverter circuit, and a compensation unit that detects the harmonic components from the voltage across the reactor.

[0023] As with the power conversion device disclosed herein, even if the compensation unit detects the harmonic components from the voltage across the reactor, it can reduce the harmonics generated on the input side of the inverter circuit.

[0024] The power conversion device disclosed herein includes a converter circuit that rectifies the input AC power and supplies power to the inverter circuit, a reactor connected between the converter circuit and the AC power source or the inverter circuit, and a compensation unit that detects the harmonic components of the current flowing from the reactor.

[0025] As with the power conversion device disclosed herein, even if the current flowing from the reactor in the compensation section detects the harmonic components, the harmonics generated on the input side of the inverter circuit can be reduced.

[0026] In the power conversion device disclosed herein, the compensation unit acquires a signal for detecting the harmonic components during a period when the voltage vector of the inverter circuit does not change.

[0027] According to the power conversion device disclosed herein, since the compensation unit acquires a signal for detecting the harmonic components during the period when the voltage vector of the inverter circuit does not change, the detection accuracy of the harmonic components can be improved compared to the case where the acquisition is performed during the period when the voltage vector changes. Attached Figure Description

[0028] [ Figure 1 An example diagram of harmonics generated on the input side of an inverter circuit.

[0029] [ Figure 2 [Illustrative diagram of the first related technology for reducing harmonic components of the input power of a motor.]

[0030] [ Figure 3 A diagram illustrating the changes in the motor's operating range caused by variations in voltage control rate.

[0031] [ Figure 4[Illustrative diagram of the second related technology for reducing harmonic components of the input power of a motor.]

[0032] [ Figure 5 [Illustrative diagram of the present disclosure of the technology for reducing harmonic components of the input power to a motor.]

[0033] [ Figure 6 An example diagram illustrating the relationship between amplitude manipulation and the electrical power of the 6th harmonic component.

[0034] [ Figure 7 An example diagram illustrating the relationship between phase manipulation and the electrical properties of the 6th harmonic component.

[0035] [ Figure 8 A schematic diagram illustrating an example of test results when driving a motor on an actual machine using the techniques disclosed herein.

[0036] [ Figure 9 A schematic diagram illustrating an example of test results when driving a motor on an actual machine using the techniques disclosed herein.

[0037] [ Figure 10 A schematic diagram of the first configuration example of the power conversion device.

[0038] [ Figure 11 A schematic diagram of the second configuration example of the power conversion device.

[0039] [ Figure 12 A schematic diagram of the first configuration example of the control unit.

[0040] [ Figure 13 A schematic diagram of the second component example of the control unit.

[0041] [ Figure 14 A schematic diagram of the third component example of the control unit. Detailed Implementation

[0042] The implementation method will be described below. First, the harmonics generated on the input side of the inverter circuit will be explained.

[0043] The magnetomotive force and gap permeance of a motor change with its rotational position. Consequently, the interlinkage magnetic flux changes synchronously with the motor's rotational speed. The induced voltage of the motor may contain harmonic components that are 5 times, 7 times, or even higher than the motor's rotational speed (electric angular velocity). If these harmonic components are present in the induced voltage, the input power to the motor may contain harmonic components that are 6 times, or even higher than, the motor's drive frequency.

[0044] For example, if an inverter circuit without internal energy storage elements (energy storage components), such as a capacitorless inverter, is used, harmonic components generated in the motor's input power may also generate harmonics of the same order in the power supply at the inverter circuit's input side. If these harmonics flow to the power supply present at the inverter circuit's input side, the current at the power supply side will contain harmonics with the frequency of the motor's input power ± the frequency of the power supply voltage (power supply harmonics). Therefore, it is necessary to reduce the harmonic components of the motor's input power so that each power supply harmonic generated by the motor's input power harmonic components falls below the power supply harmonic limit (regulation value). Figure 1 This is an example diagram of harmonics generated on the input side of a power conversion circuit. The horizontal axis represents the order of the harmonics (a multiple of the frequency of the power supply voltage). Figure 1 Examples are shown where the 30th and 32nd power supply harmonics are harmonic components generated in the motor's input power and exceed the power supply harmonic limits.

[0045] The higher the motor's rotational speed, the greater the amplitude of the various power supply harmonics generated by the harmonic components of the motor's input power, exceeding the power supply harmonic limits. Therefore, there exists a technique to reduce the harmonic components of the motor's input power by directly manipulating the voltage command value supplied to the inverter circuit.

[0046] Figure 2 This is an explanatory diagram of a first related technology (Japanese Patent Application Laid-Open No. 2010-98941) for reducing harmonic components of the input power to a motor. In this first related technology, the compensation amount for reducing harmonic components of the motor's input power is added together with the voltage control rate (also called modulation rate) of the inverter circuit. However, to reduce the harmonic components of the motor's input power, it is necessary to reduce the DC component of the voltage control rate to prevent the compensation amount from becoming saturated. Since the size of the motor's operating range (e.g., maximum speed) is proportional to the DC component of the voltage control rate, as the compensation amount increases, it is necessary to reduce the motor's operating range (see...). Figure 3 ).

[0047] Figure 4 This is an explanatory diagram of a second related technology (Japanese Patent Application Laid-Open No. 2012-165634) for reducing harmonic components of the input power to a motor. In this second related technology, compensation values ​​(d-axis compensation voltage vd_h and q-axis compensation voltage vq_h) used to distort the motor current are compared with the output of the current control unit (command values ​​for controlling the motor current, i.e., d-axis voltage command value vd_h). and q-axis voltage command value vq The superposition of these values ​​generates a new voltage command value, vd'. and vq' However, if the new voltage command value vd' and vq' The magnitude of the voltage control rate changes as the compensation values ​​(d-axis compensation voltage vd_h and q-axis compensation voltage vq_h) are superimposed, and thus the voltage control rate also changes. Therefore, similar to the first related technology, to prevent the compensation value from saturating, it is necessary to reduce the DC component of the voltage control rate (the output of the current control unit (vd_h)). vq The magnitude of the voltage vector formed by the voltage vector must be reduced, and the operating range of the motor must be lowered (see...). Figure 3 ).

[0048] As described above, in the first and second related technologies, there is a trade-off between reducing the harmonic components of the motor's input power and ensuring the motor's operating range. According to the technology of this disclosure, both reducing the harmonic components of the motor's input power and ensuring the motor's operating range can be achieved.

[0049] Figure 5 This is an illustration of a technique disclosed herein for reducing harmonic components in the input power of a motor. In this technique, harmonic components in the input power of the motor that are synchronously generated with the motor's rotational speed are detected, and the phase of the AC voltage output from the inverter circuit is changed at the same frequency as the detected harmonic component, thereby reducing the harmonic component. In this technique, as... Figure 5 As shown, the operation of pulsating the phase α of the entire voltage vector (the composite vector of the d-axis voltage and the q-axis voltage) at the same frequency as the detected harmonic components can be performed without changing the voltage control law.

[0050] Operating phase α at the same frequency as the harmonic components of the motor's input power is equivalent to causing the trajectories of the d-axis and q-axis voltages to change on the same arc at the same frequency as the harmonic components of the motor's input power. Furthermore, if phase α is operated at the same frequency as the harmonic components of the motor's input power, the harmonic components in the AC voltage output from the inverter circuit (the harmonic components of the motor's input power plus the motor's drive frequency and the harmonic components of the motor's input power minus the motor's drive frequency) will appear with the same amplitude.

[0051] For example, Equations 1, 2, and 3 below represent the u-phase AC voltage output from the inverter circuit when the phase α of the entire voltage vector is pulsated.

[0052]

[0053] v uThis represents the u-phase AC voltage (u-phase voltage of the motor) output from the inverter circuit, V. u θ represents the amplitude of the u-phase voltage. e The angle of rotation of the motor rotor (electrical angle) is represented by δ', where δ' represents the difference between the phase of the AC voltage output from the inverter circuit and the angle of rotation of the motor rotor (voltage phase). Asin(6θ) e +B) represents the compensation amount (also called compensation amount C) used to compensate for the harmonics of the input power of the motor by adjusting the voltage phase reference value δ. A represents the amplitude of compensation amount C, and B represents the reference phase of compensation amount C.

[0054] Substituting Equation 2 into Equation 1 yields Equation 3. The amplitude of the second term in Equation 3 is "-(1 / 2)AV". u "This is equivalent to the amplitude of the harmonic component after subtracting the motor's drive frequency from the frequency of the harmonic component of the motor's input power. The amplitude of the third term in Equation 3 is "-(1 / 2)AV". u "It is equivalent to adding the frequency of the harmonic component of the motor's input power to the amplitude of the harmonic component of the motor's drive frequency."

[0055] Although Equations 1, 2, and 3 illustrate the case where the entire voltage vector pulsates according to a sine wave, the entire voltage vector can also pulsate according to other periodic waveforms such as triangular waves and rectangular waves.

[0056] Next, by causing the phase of the AC voltage output from the inverter circuit to fluctuate (ripple) at the same frequency as the harmonic components generated synchronously with the motor's input power and speed, it is theoretically derived that the harmonic components generated in the motor's input power can be reduced. It should be noted that although a permanent magnet synchronous motor is used as an example here, this method can be applied to other types of motors. Furthermore, although the description illustrates the reduction of harmonic components six times the motor's drive frequency, it is also possible to reduce higher harmonic components such as 12th or 18th times the drive frequency.

[0057] The voltage equations for a permanent magnet synchronous motor are represented by Equations 4 and 5 below.

[0058]

[0059] v d Represents the d-axis voltage, v q R represents the q-axis voltage. a L represents the armature winding resistance of the motor. d L represents the d-axis inductance. q Indicates q-axis inductance, i d Represents the d-axis current, i q Represents the q-axis current, ω eThe electric angular velocity of the motor is represented by s, and the time differential operator is represented by s. d Represents the d-axis magnetic flux. q K represents the q-axis magnetic flux. q6 K represents the amplitude of the q-axis magnetic flux. d6 Λ represents the amplitude of the magnetic flux along the d-axis. a This refers to the magnetic flux of a permanent magnet.

[0060] In permanent magnet synchronous motors, the higher the rotational speed, the more significant the impact of power supply harmonics. Therefore, as the rotational speed increases, the armature winding resistance R... a The effect is negligible. Therefore, for the sake of simplicity, Equation 4 can be transformed into Equation 6 below.

[0061]

[0062] To make the phase of the AC voltage pulsate according to a sinusoidal waveform, the d-axis voltage v is... d and q-axis voltage v q Defined as shown in Equations 7 and 8 below. V a Represents the d-axis voltage v d and q-axis voltage v q The amplitude. Substituting Equation 8 into Equation 7 and rearranging, we obtain Equation 9 below.

[0063]

[0064] Solving for the current in the combined equations consisting of Equations 6 and 9 yields Equation 10.

[0065]

[0066] By solving the input power P of the motor in Equation 11 can be obtained.

[0067]

[0068] Equation 11 represents the input power P in In the middle, the electric power P of the 6th harmonic component in6 It can be transformed into the following equation 12 (the power of the 12th harmonic component is very small, so it is ignored).

[0069]

[0070] Figure 6 In Equation 12, the reference phase B is fixed, and the electric power P is the amplitude A and the 6th harmonic component. in6 An example diagram illustrating the relationship between them. Figure 7In Equation 12, the electric field P is calculated with the amplitude A fixed, the reference phase B, and the 6th harmonic component. in6 An example diagram illustrating the relationship between them. (From...) Figure 6 and Figure 7 It can be seen that, for each of the amplitude A and the reference phase B in the compensation quantity C, there exists an electric current P that can make the 6th harmonic component... in6 The optimal value is close to zero. Therefore, by adjusting the amplitude A and the reference phase B in the compensation amount C, the electrical P of the 6th harmonic component can be reduced. in6 The optimal value, close to zero, can reduce the power P of the 6th harmonic component. in6 .

[0071] For the electric power P of the 6th harmonic component in Equation 12 in6 When calculating the condition for making it zero, as shown in Equation 13, the amplitude of the cosine component of the first term of Equation 12 is made zero, and the amplitude of the sine component of the second term of Equation 12 is also made zero. Solving the combined equations expressed by Equations 13 and 14 for amplitude A and reference phase B yields the following Equation 15.

[0072]

[0073] As described above, in the technology of this disclosure, the electrical power P of the 6th harmonic component can also be adjusted by each of the amplitude A and the reference phase B to an appropriate value represented by Equation 15. in6 The value is zero. However, the technology disclosed herein can also detect harmonic components in the input power of the motor that are generated synchronously with the motor's rotational speed, and then adjust at least one of the amplitude A and the reference phase B based on the detected harmonic components using methods such as hill climbing, thereby reducing the harmonic.

[0074] The operation that makes the sixth harmonic component of the motor's input power zero does not result in the sixth harmonic component of the motor current in the rotating coordinate system being zero. The sixth harmonic component of the motor's input power can be made zero by changing at least one of the amplitude and phase of the sixth harmonic component of the motor current in the rotating coordinate system, and by adjusting the sixth harmonic component of the input power related to the d-axis and the input power related to the q-axis to be in opposite phase.

[0075] Next, an example of the configuration of a power conversion device applying the technology disclosed herein will be described.

[0076] Figure 10 This is a schematic diagram of a first configuration example of a power conversion device applying the technology disclosed herein. Figure 10The power conversion device 1A shown includes a converter circuit 2, a DC link section 3, an inverter circuit 4, and a control section 5. The power conversion device 1A is used to convert the input AC power supplied from the three-phase AC power source 6 into output AC power with a predetermined voltage and a predetermined frequency, and supply it to the motor 7.

[0077] Motor 7 is, for example, a three-phase AC motor used to drive a compressor installed in the refrigerant circuit of an air conditioner. Specifically, motor 7 is a 4-pole 6-slot or 6-pole 9-slot wound motor, etc. This motor 7 tends to contain a large amount of the 5th and 7th harmonic components of the fundamental wave, which are harmonic components of the induced voltage. The higher-order (e.g., 6th) harmonic components caused by the voltage distortion of this motor (the 5th and 7th harmonic components of the fundamental wave) are reflected in the power supply current of the AC power supply 6 and the DC link voltage v of the DC link section 3. dc They will also appear in the middle.

[0078] Converter circuit 2 is connected to AC power supply 6 and is used to convert the AC output from AC power supply 6 into DC. Converter circuit 2 is, for example, a diode bridge circuit in which multiple (in this example, six) diodes are connected in a bridge configuration. These diodes perform full-wave rectification of the AC voltage from AC power supply 6 and then convert it into DC voltage. Converter circuit 2 can be any circuit that can supply the converted DC power to inverter circuit 4 via DC link section 3, or it can be a voltage conversion circuit of other circuit form than the diode bridge circuit.

[0079] The DC link section 3 includes a capacitor 3a connected between the converter circuit 2 and the inverter circuit 4. The capacitor 3a is connected in parallel with the output of the converter circuit 2, and the DC voltage generated across the capacitor 3a (DC link voltage V) dc It is input to the input node of inverter circuit 4. A more detailed explanation of capacitor 3a will be given later.

[0080] The DC link section 3 includes a reactor 8 connected between the converter circuit 2 and the inverter circuit 4. The reactor 8 is connected in series with the DC bus located between the output section of the converter circuit 2 and the input section of the inverter circuit 4.

[0081] In inverter circuit 4, the input node is connected in parallel with capacitor 3a of DC link section 3. The output of DC link section 3 is switched to convert to three-phase AC and supplied to the connected motor 7. In this embodiment, inverter circuit 4 is constructed by bridging multiple switching elements. Since this inverter circuit 4 outputs three-phase AC to motor 7, it has six switching elements. Specifically, inverter circuit 4 has three switching legs connected in parallel, and each switching leg has two switching elements connected in series. In each switching leg, the midpoints of the upper and lower switching elements are connected to the coils of each phase of motor 7, respectively. Furthermore, a freewheeling diode is connected in anti-parallel to each switching element. Inverter circuit 4 controls the DC link voltage v input from DC link section 3 by switching these switching elements on / off. dc The voltage is switched to a three-phase AC voltage and supplied to the motor 7. It should be noted that the control unit 5 controls the on / off operation.

[0082] The control unit 5 detects the harmonic components in the input power of the motor 7 that are synchronized with the rotational speed of the motor 7, and changes the phase of the AC voltage output from the inverter circuit 4 at the same frequency as the detected harmonic components to reduce the harmonic components. The control unit 5 controls the switching (on / off) in the inverter circuit 4 by changing the phase of the AC voltage in this way.

[0083] Figure 11 This is a schematic diagram of a second configuration example of a power conversion device applying the technology disclosed herein. Descriptions of configurations (structures) identical to those in the first configuration example have been omitted by reference to the foregoing description. Figure 11 The power conversion device 1B shown includes a converter circuit 2, a DC link section 3, an inverter circuit 4, and a control section 5. The power conversion device 1B is used to convert the input AC power supplied from the single-phase AC power source 6 into output AC power with a predetermined voltage and a predetermined frequency, and supply it to the motor 7.

[0084] Converter circuit 2 is connected to AC power supply 6 via reactor 8 and is used to rectify (convert) the AC output from AC power supply 6 into DC. Converter circuit 2 is, for example, a diode bridge circuit that connects multiple (four in this example) diodes in a bridge configuration. These diodes perform full-wave rectification of the AC voltage from AC power supply 6, thereby converting it into DC voltage. Converter circuit 2 can be any voltage conversion circuit, different from the diode bridge circuit, as long as it can supply the converted DC power to inverter circuit 4 via DC link section 3.

[0085] The reactor 8 is connected between the AC power supply 6 and the converter circuit 2. Specifically, it is inserted in series between the AC output side of the AC power supply 6 and the AC input side of the converter circuit 2.

[0086] Figure 10 and Figure 11 In this context, the capacitance value of capacitor 3a is essentially insufficient to smooth the output of converter circuit 2, but it is configured to suppress ripple voltage caused by the switching operation of inverter circuit 4 (responding to the switching frequency f). c (Voltage fluctuations). Specifically, capacitor 3a is composed of a small-capacity capacitor (e.g., a film capacitor) having a capacitance value approximately 0.01 times that of a smoothing capacitor (e.g., an electrolytic capacitor) used in a general power conversion device to smooth the output of converter circuit 2 (e.g., around tens to hundreds of μF).

[0087] As described above, since the capacitance of capacitor 3a is small, the output of converter circuit 2 in DC link section 3 cannot be smoothed. Therefore, in response to the power supply voltage v of AC power supply 6... in The frequency pulsation component will remain in the DC voltage (DC link voltage V). dc For example, regarding the DC link voltage v dc In terms of Figure 10 In the case of a three-phase AC power supply of 6, the power supply voltage is v in A pulsating component at a frequency six times that of the frequency, in Figure 11 In the case of a single-phase AC power supply 6, the power supply voltage is v in A pulsating component with a frequency twice that of the frequency of the pulsating component.

[0088] Furthermore, in the case where the power conversion device uses not only capacitor 3a but also reactor 8, an LC filter is constructed from reactor 8 and capacitor 3a. The resonant frequency f of this LC filter is... r It is the commercial frequency (power frequency) f of the N-phase AC power supply 6. in The frequency is N times or more, and the inductance of reactor 8 and the capacitance of capacitor 3a are set to attenuate the ripple voltage caused by the switching operation of inverter circuit 4.

[0089] N×f in ≤f r ≤f c / 4

[0090] f r =1(2π√LC)

[0091] L represents the inductance of reactor 8, and C represents the capacitance of capacitor 3a.

[0092] As described above, in the case of a capacitorless inverter (specifically, an electrolytic capacitorless inverter) where the capacitance of capacitor 3a in the DC link section 3 is small, harmonics caused by the distortion components (harmonic components) generated in the input power of the motor 7 may flow to the power supply side. Even when the power conversion device is a matrix converter, harmonics caused by the distortion components generated in the input power of the motor may also flow to the power supply side.

[0093] The control unit 5 has the function of changing the phase of the AC voltage output from the inverter circuit 4 according to the same frequency as the harmonic component generated synchronously with the input power of the motor 7 and the rotational speed of the motor 7, thereby reducing the harmonic component (harmonic component reduction function). By means of the harmonic component reduction function, the harmonics generated on the input side of the inverter circuit 4 (e.g., power supply harmonics flowing to the power supply side) can be reduced.

[0094] Next, an example of the configuration of the control unit 5 with harmonic component reduction function will be described.

[0095] Figure 12 This is a schematic diagram (block diagram) of the first configuration example of the control unit. Figure 12 The control unit 5A shown is an example of control unit 5. Control unit 5A outputs a gate signal G, a control signal used to turn on / off the switching elements within the inverter circuit 4, to the inverter circuit 4. Control unit 5A includes a motor control unit 11, a compensation unit 20, an adder 13, and a PWM calculation unit 12. The functions of these components in control unit 5A are achieved by having a processor (e.g., a CPU (Central Processing Unit) operate the program, which is readablely stored in memory.

[0096] Motor control unit 11 generates and outputs a voltage phase reference value δ for controlling the phase of the AC voltage output from inverter circuit 4 and a voltage control rate K of inverter circuit 4. s Voltage control rate is also known as modulation rate.

[0097] The compensation unit 20 compensates for harmonics in the input power of the motor 7. The compensation unit 20 detects harmonic components in the input power of the motor 7 that are synchronized with the motor 7's rotational speed, and changes the phase of the AC voltage output from the inverter circuit 4 at the same frequency as the detected harmonic component to reduce the harmonic component. The compensation unit 20 generates a compensation amount C(=Asin(6θ)) that varies at the same frequency as the detected harmonic component. e +B)), and according to the compensation amount C, the phase δ' of the AC voltage output from the inverter circuit 4 changes at the same frequency as the detected harmonic component.

[0098] In this example, the compensation unit 20 adjusts the reference phase B of the compensation amount C based on the amplitude a of the detected harmonic components, and adjusts the reference phase B based on the rotational speed (electric angular velocity ω) of the motor 7. e ), output torque T of motor 7 e and the input power P of motor 7 in0 The amplitude A of the compensation amount C can be changed by any one of the following. The compensation unit 20 includes a harmonic component detection unit 21, a reference phase calculation unit 22, an integrator 23, an adder 24, a waveform generation unit 25, an amplitude calculation unit 26, and a multiplier 27.

[0099] The harmonic component detection unit 21 detects the amplitude 'a' of the harmonic component generated synchronously with the rotational speed of the motor 7 in the input power of the motor 7 using Fourier transform and other methods. Since the power input to the inverter circuit also generates harmonics of the same order as the 6th harmonic component generated in the motor's input power, the harmonic component detection unit 21 can detect the amplitude 'a' of the harmonic component by, for example, from the DC link voltage 'v' across the capacitor 3a. dc The amplitude 'a' of the harmonic components generated in the input power of the motor 7 is detected. Alternatively, the harmonic component detection unit 21 can detect the amplitude 'a' of the harmonic components generated in the input power of the reactor 8. L The amplitude 'a' of the harmonic components generated in the input power of the motor 7 is detected. Alternatively, the harmonic component detection unit 21 can detect the reactor current i flowing in the reactor 8. L The amplitude 'a' of the harmonic components generated in the input power of the motor 7 is detected. Alternatively, the harmonic component detection unit 21 may also actually monitor the input power of the motor 7 and detect the amplitude 'a' of the harmonic components generated in the input power of the motor 7 based on the monitored value.

[0100] The harmonic component detection unit 21 acquires a signal for detecting the amplitude 'a' of the harmonic component during a period when the voltage vector of the inverter circuit 4 does not change (e.g., during a period when the output voltage vector is zero). Accordingly, the detection accuracy of amplitude 'a' can be improved compared to the case where the signal for detecting amplitude 'a' is acquired during a period when the voltage vector changes.

[0101] The reference phase calculation unit 22 adjusts the reference phase B of the compensation amount C based on the amplitude 'a' of the harmonic components detected by the harmonic component detection unit 21. For example, the reference phase calculation unit 22 can adjust the reference phase B of the compensation amount C using a hill-climbing method, by reducing the detected amplitude 'a' based on the amplitude detected by the harmonic component detection unit 21. Accordingly, an optimal reference phase B (an example of a target value for reference phase B) for reducing the amplitude of the harmonic components generated in the input power of the motor 7 can be obtained.

[0102] On the other hand, the compensation unit 20 uses the integrator 23 to measure the rotational speed (electric angular velocity ω) of the motor 7. e Integrating at 6 times the frequency of ) generates 6θ. e The reference phase B calculated by the reference phase calculation unit 22 and the 6θ obtained by the integrator 23. e Added by adder 24, we can obtain (6θ) e +B). Waveform generation unit 25 generates a waveform synchronized with the rotational speed of motor 7, with a phase of (6θ). e +B) sine wave sin(6θ) e +B). Although this example illustrates a pulsation according to a sine wave, a phase of (6θ) can also be used. e Other periodic waveforms such as triangular waves and rectangular waves (+B)

[0103] The amplitude calculation unit 26 calculates the amplitude based on the rotational speed (electric angular velocity ω) of the motor 7. e ), output torque T of motor 7 e and the input power P of motor 7 in0 Any one of the components changes the amplitude A of the compensation amount C. The amplitude calculation unit 26, for example, adjusts the electrical angular velocity ω based on the power supply harmonics being below the harmonic limit. e The correlation between amplitude A and electric angular velocity ω is based on the relationship between the amplitude A and electric angular velocity ω. e The detected or commanded value generates the optimal amplitude A (an example of the target value of amplitude A). The relationship between power supply harmonics and harmonic limits is, for example, a predetermined rule determined through experiments (tests), and can be defined using lookup tables, calculation formulas, etc. Similarly, even when the electric angular velocity ω... e Replaced with output torque T e Or input power P in0 In such cases, this correlation can also be used to obtain the optimal amplitude A.

[0104] The sin(6θ) generated by the waveform generation unit 25 e +B) and the amplitude A derived from the amplitude calculation unit 26 are multiplied by the multiplier 27, thereby obtaining the compensation amount C(=Asin(6θ)). eThe voltage phase reference value δ generated by the motor control unit 11 and the compensation amount C generated by the multiplier 27 are added by the adder 13 to generate the voltage phase δ'.

[0105] PWM arithmetic unit 12 according to voltage control law K s The three-phase voltage command values ​​for phase u, phase v, and phase w are generated using polar coordinate transformation, inverse Park transformation, and space vector transformation, along with the voltage phase δ'. These three-phase voltage command values ​​are PWM (Pulse Width Modulation) signals. The PWM calculation unit 12 uses voltage control law K... s The amplitude of the three-phase voltage command value is adjusted to control the magnitude of the AC voltage output from the inverter circuit 4. The PWM calculation unit 12 converts the three-phase voltage command value into a strobe signal G and outputs it to the inverter circuit 4.

[0106] As described above, the control unit 5A detects the distorted harmonic components generated in the input power of the motor 7, and then changes the phase of the AC voltage output from the inverter circuit 4 according to the amplitude 'a' of the detected harmonic component and at the same frequency as the harmonic component, thereby reducing the harmonic component. Accordingly, the voltage control rate K can be maintained without reducing the harmonic component. s This ensures the operating range of motor 7, and because the harmonic components of the input power of motor 7 are reduced, it also reduces power supply harmonics to below the power supply harmonic limit.

[0107] Figure 13 This is a schematic diagram (block diagram) of the second configuration example of the control unit. The description of the same configuration (structure) as the first configuration example has been omitted by referring to the above description. Figure 13 The control unit 5B shown is an example of control unit 5. Control unit 5B includes a compensation unit 30.

[0108] In this example, the compensation unit 30 adjusts the amplitude A of the compensation amount C according to the amplitude a of the detected harmonic component, and adjusts it according to the rotational speed (electric angular velocity ω) of the motor 7. e ), output torque T of motor 7 e and the input power P of motor 7 in0 The compensation unit 30 includes a harmonic component detection unit 21, a reference phase calculation unit 22, an integrator 23, an adder 24, a waveform generation unit 25, an amplitude calculation unit 26, and a multiplier 27.

[0109] The reference phase calculation unit 22 calculates the rotational speed (electric angular velocity ω) of the motor 7. e ), output torque T of motor 7 e and the input power P of motor 7 in0Any one of the components modifies the reference phase B of the compensation amount C. The reference phase calculation unit 22, for example, modifies the electric angular velocity ω based on the power supply harmonics being below the harmonic regulation value. e The correlation between amplitude A and electric angular velocity ω is based on the relationship between the amplitude A and electric angular velocity ω. e The optimal reference phase B (an example of the target value of reference phase B) is generated from the detected or commanded value. The relationship between power supply harmonics and harmonic regulation values ​​is, for example, a predetermined relationship rule determined through experiments, and can be defined using lookup tables, calculation formulas, etc. Similarly, even when the electric angular velocity ω... e Replaced with output torque T e Or input power P in0 In such cases, this correlation can also be used to obtain the optimal reference phase B.

[0110] The amplitude calculation unit 26 adjusts the amplitude A of the compensation amount C based on the amplitude 'a' of the harmonic component detected by the harmonic component detection unit 21. For example, the amplitude calculation unit 26 can adjust the amplitude A of the compensation amount C using a hill-climbing method based on the amplitude 'a' detected by the harmonic component detection unit 21, so that the detected amplitude 'a' is reduced. Accordingly, an optimal amplitude A (an example of a target value for amplitude A) for reducing the amplitude of the harmonic component generated in the input power of the motor 7 can be obtained.

[0111] The sin(6θ) generated by the waveform generation unit 25 e +B) and the amplitude A derived from the amplitude calculation unit 26 are multiplied by the multiplier 27, thereby obtaining the compensation amount C(=Asin(6θ)). e +B)). The voltage phase reference value δ generated by the motor control unit 11 and the compensation amount C generated by the multiplier 27 are added by the adder 13, thereby generating the voltage phase δ'.

[0112] As described above, the control unit 5B detects harmonic components caused by distortion generated in the input power of the motor 7, and then, based on the amplitude 'a' of the detected harmonic component, fluctuates the phase of the AC voltage output from the inverter circuit 4 at the same frequency as the harmonic component, thereby reducing the harmonic component. Accordingly, the voltage control rate K can be maintained without reducing it. s This ensures the operating range of motor 7, and because the harmonic components of the input power of motor 7 are reduced, it also reduces power supply harmonics to below the power supply harmonic limit.

[0113] Figure 14 This is a schematic diagram (block diagram) of the third configuration example of the control unit. Explanations of configurations (structures) identical to those described above are omitted by referencing the above description. Figure 14 The control unit 5C shown is an example of control unit 5. Control unit 5C includes a compensation unit 40.

[0114] In this example, the compensation unit 40 adjusts the amplitude A of the compensation amount C and the reference phase B based on the amplitude a of the detected harmonic component. The compensation unit 30 includes a harmonic component detection unit 21, a reference phase calculation unit 22, an integrator 23, an adder 24, a waveform generation unit 25, an amplitude calculation unit 26, and a multiplier 27. The reference phase calculation unit 22 has the same characteristics as the first configuration example (…). Figure 12 The amplitude calculation unit 26 has the same function as the second configuration example ( Figure 13 Same function.

[0115] The control unit 5C detects the harmonic components that cause distortion in the input power of the motor 7. Then, based on the amplitude 'a' of the detected harmonic component, it causes the phase of the AC voltage output from the inverter circuit 4 to fluctuate (wave) at the same frequency as the harmonic component, thereby reducing the harmonic component. Based on this, the voltage control rate K can be maintained without reducing it. s This ensures the operating range of motor 7, and because the harmonic components of the input power of motor 7 are reduced, the power supply harmonics can also be reduced to below the power supply harmonic limit.

[0116] Figure 8 and Figure 9 This is a schematic diagram illustrating an example of test results when driving a motor on an actual machine using the technology disclosed herein, showing a motor equipped with... Figure 10 and Figure 12 The diagram shows the actual operation of the power conversion device when it drives the motor. The vertical axis represents the power P due to the 6th harmonic component of the input power to motor 7. in6 The power supply harmonics generated on the AC power supply side 6 can be varied by changing the amplitude A or the reference phase B. Since there exists an amplitude A and a reference phase B that can make the amplitude of each of the 30th and 32nd power supply harmonics approximately zero, the amplitude of each of the 30th and 32nd power supply harmonics can meet the power supply harmonic limits.

[0117] Although the embodiments have been described above, the present invention is not limited to the above embodiments. Various modifications and alterations can be made to it within the scope of the spirit of the present invention as set forth in the claims.

[0118] This international application claims priority based on Japanese Patent Application No. 2019-192870, filed on October 23, 2019, the contents of which are incorporated herein by reference in their entirety.

[0119] [Explanation of reference numerals in the attached figures]

[0120] 1A, 1B Power Conversion Devices

[0121] 4. Inverter Circuit

[0122] 5. 5A, 5B, 5C Control Units

[0123] 6. AC power supply

[0124] 7 motors

[0125] 8 Reactors

[0126] Compensation Department (numbers 20, 30, and 40)

Claims

1. A power conversion device for converting input AC power supplied from an AC power source into output AC power of a predetermined voltage and frequency, the power conversion device comprising: The inverter circuit supplies the output AC power to the motor; and The compensation unit compensates for the harmonics in the input power of the motor. in, The compensation unit detects the harmonic components in the input power that are synchronized with the speed of the motor, and changes the phase of the AC voltage output from the inverter circuit at the same frequency as the harmonic components to reduce the harmonic components.

2. The power conversion device as claimed in claim 1, wherein, The compensation unit generates a compensation amount that varies at the same frequency as the harmonic component, and causes the phase of the AC voltage to change at the same frequency as the harmonic component based on the compensation amount.

3. The power conversion device as described in claim 2, wherein, The compensation unit adjusts the phase of the compensation amount according to the detected harmonic components, and changes the amplitude of the compensation amount according to any one of the motor's speed, torque, and power.

4. The power conversion device as described in claim 2, wherein, The compensation unit adjusts the amplitude of the compensation amount according to the detected harmonic components, and changes the phase of the compensation amount according to any one of the motor's speed, torque, and power.

5. The power conversion device as claimed in claim 2, wherein, The compensation unit adjusts the phase and amplitude of the compensation amount based on the detected harmonic components.

6. The power conversion device according to any one of claims 1 to 5, further comprising: The converter circuit rectifies the input AC power and supplies power to the inverter circuit. in, A capacitor is connected in parallel with the converter circuit between the converter circuit and the inverter circuit. The compensation unit detects the harmonic components based on the voltage across the capacitor.

7. The power conversion device according to any one of claims 1 to 5, further comprising: The converter circuit rectifies the input AC power and supplies power to the inverter circuit. in, The reactor is connected between the converter circuit and the AC power supply or the inverter circuit. The compensation unit detects the harmonic components based on the voltage across the reactor.

8. The power conversion device according to any one of claims 1 to 5, further comprising: The converter circuit rectifies the input AC power and supplies power to the inverter circuit. in, The reactor is connected between the converter circuit and the AC power supply or the inverter circuit. The compensation unit detects the harmonic components based on the current flowing in the reactor.

9. The power conversion device according to any one of claims 1 to 5, wherein, The compensation unit acquires a signal for detecting the harmonic components during the period when the voltage vector of the inverter circuit does not change.

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