JP7095441B2 - Inverter controller - Google Patents

Description

The present invention relates to the configuration of an inverter control device, and more particularly to the distributed control of the frequency of carrier signals.

A DC power source is converted into an AC power source by an inverter by PWM control to drive a motor. At this time, if the frequency of the carrier signal used for PWM control is in the human audible band, it may be recognized as noise. Therefore, a method of randomly distributing the frequency of the carrier signal to make the noise white noise and making it difficult to hear is used (see, for example, Patent Documents 1 and 2).

Japanese Unexamined Patent Publication No. 2006-174645 International Publication No. 2011/148481

By the way, in recent years, a carrier signal having a low frequency may be used for reducing the loss of an inverter and for heat protection at the time of miniaturization. The frequency of the carrier signal is set to a frequency that does not resonate with the motor, case, etc., but in the low frequency range, frequencies that resonate with the motor, case, etc. are scattered near the frequency of the carrier signal. ing. Therefore, when the frequency of the carrier signal is dispersed, there is a problem that a sound different from a normal sound is generated due to resonance and is easily recognized as noise.

In this regard, in the prior art described in Patent Document 1, when the frequency of the carrier signal is set low, the width of frequency dispersion is narrowed so that resonance does not occur. However, in this method, the vibration of the frequency in the human audible range is not sufficiently converted into white noise and may be recognized as noise.

Therefore, it is an object of the inverter control device of the present invention to suppress the recognition of the sound generated by the carrier signal as noise.

The inverter control device of the present invention is an inverter control device that controls an inverter including a plurality of switching elements, and is a motor command calculation unit that generates a control command of a voltage or current supplied from the inverter to a motor, and a carrier signal. Based on the carrier signal generation unit that generates the frequency, the control command from the motor command calculation unit, and the carrier signal from the carrier signal generation unit, the plurality of switching elements of the inverter are turned on / off by PWM control. The carrier signal generation unit includes a PWM unit for off operation, sets the basic frequency of the carrier signal based on the operating point of the motor, and sets the carrier signal in a predetermined frequency range around the basic frequency. When the fundamental frequency is in the low frequency range, each frequency of the carrier signal is dispersed so that the frequency of each frequency of the carrier signal to be dispersed has a normal distribution centered on the fundamental frequency. When the fundamental frequency is in the high frequency range, each frequency of the carrier signal is dispersed so that the frequency of each frequency of the carrier signal to be dispersed has a rectangular distribution centered on the fundamental frequency. It is characterized in that it is set to a frequency that does not resonate with the motor .

The inverter control device of the present invention can suppress that the sound generated by the carrier signal is recognized as noise.

It is a system diagram which shows the structure of the motor control system using the inverter control device of embodiment. It is a functional block diagram of the inverter control device shown in FIG. FIG. 3 is a waveform diagram illustrating PWM control by the PWM unit shown in FIG. 2. It is a flowchart which shows the operation of the inverter control device of embodiment. This is a map for setting the fundamental frequency of the carrier signal from the operating point of the motor. It is a figure which shows the appearance frequency of each frequency in the case where the fundamental frequency of a carrier signal is a low frequency region, and the change of the transmission sensitivity with respect to a frequency. As shown in FIG. 6, it is a conceptual diagram which shows the appearance frequency of each frequency with respect to time when each frequency is dispersed. It is a figure which shows the appearance frequency of each frequency when the fundamental frequency of a carrier signal is a high frequency region, and the change of the transmission sensitivity with respect to a frequency. As shown in FIG. 8, it is a conceptual diagram which shows the appearance frequency of each frequency with respect to time when each frequency is dispersed.

Hereinafter, the inverter control device 60 of the embodiment will be described with reference to the drawings. First, the motor control system 100 using the inverter control device 60 will be described with reference to FIG. 1.

As shown in FIG. 1, the motor control system 100 includes a motor 50, a DC power supply 20 including a battery or a battery and a boost converter, and a plurality of switching elements 33a to 35a, 33b to 35b, and the DC power supply 20. It is composed of an inverter 30 that converts the DC power supplied from the above into AC power and supplies it to the motor 50, and an inverter control device 60 that controls the inverter 30.

A smoothing capacitor 31 that smoothes the voltage from the DC power supply 20 and a high voltage VH across the smoothing capacitor 31 are located between the negative side electric circuit 11 on the input side (DC power supply 20 side) of the inverter 30 and the high voltage path 13. A high voltage sensor 32 for detecting the above is provided. Further, between the negative side electric circuit 11 on the opposite side of the DC power supply 20 of the smoothing capacitor 31 and the high voltage path 13 facing the DC power supply 20, the upper arm switching elements 33a to 35a for each of the U, V, and W phases, respectively. Six switching elements of the lower arm switching elements 33b to 35b are arranged in series, two for each phase. The output lines 55, 56, 57 of each phase of U, V, and W are connected between the upper arm switching elements 33a to 35a and the lower arm switching elements 33b to 35b. The U, V, and W output lines 55, 56, and 57 are connected to the input terminals of the U, V, and W phases of the motor 50, respectively. Further, diodes 36a to 38a and 36b to 38b are connected in antiparallel to each of the upper arm switching elements 33a to 35a and the lower arm switching elements 33b to 35b of the U, V, and W phases, respectively. The inverter 30 turns on / off the six switching elements of the upper arm switching elements 33a to 35a and the lower arm switching elements 33b to 35b to convert DC power into AC power and supplies it to the motor 50.

A current sensor 53 that detects the current flowing through each of the output lines 56 and 57 and outputs them as current signals Iv and Iw on the two output lines 56 and 57 that supply V and W phase power from the inverter 30 to the motor 50. , 54 are attached. Further, the motor 50 is equipped with a resolver 52 that detects the rotation speed or the rotation angle θ of the rotor. The inverter control device 60 includes a CPU 61, a storage unit 62, a device / sensor interface 63 for connecting each device and a sensor, and the CPU 61, the storage unit 62, and the device / sensor interface 63. It is a computer connected by the data bus 64.

The switching elements 33a to 35a and 33b to 35b of the inverter 30 are connected to the inverter control device 60 via the device / sensor interface 63 and are configured to be driven by a command of the inverter control device 60. The V and W phase current sensors 53 and 54 and the resolver 52 attached to the motor 50 are connected to the device / sensor interface 63 of the inverter control device 60, respectively, and the current detected by each sensor, the rotation angle θ of the rotor, etc. The signal of is input to the inverter control device 60 via the device / sensor interface 63.

The inverter control device 60 stores a control program for controlling the inverter 30 and control data in the storage unit 62. As shown in FIG. 2, the inverter control device 60 has three functional blocks of a motor command calculation unit 65, a carrier signal generation unit 66, and a PWM unit 67 that operate by the cooperation of the CPU 61 and the storage unit 62. ing.

The motor command calculation unit 65 is a torque command Trqcom of the motor 50 input from an external control device or another control block, current signals Iv and Iw detected by the current sensors 53 and 54, and a rotor detected by the resolver 52. Based on the rotation angle θ, the U, V, and W phase voltage commands V _U , V _V , and V _W , which are control commands, are calculated and output to the PWM unit 67.

The carrier signal generation unit 66 identifies the operation point of the rotation speed and torque of the motor 50 from the rotation speed of the rotor detected by the resolver 52 and the torque command Trqcom of the motor 50, and stores the map in the storage unit 62 (described later). The basic frequency Fc of the carrier signal is set based on the operating point of the motor 50 with reference to). Further, the carrier signal generation unit 66 disperses the frequency of the carrier signal with a dispersion width which is a predetermined frequency range around the fundamental frequency Fc. Then, the carrier signal of each distributed frequency is output to the PWM unit 67. Further, the vehicle speed is input from an external control device or another control block.

The PWM unit 67 turns on / from the plurality of switching elements 33a to 35a and 33b to 35b of the inverter 30 by PWM control based on the voltage command from the motor command calculation unit 65 and the carrier signal from the carrier signal generation unit 66. Operate off.

The PWM control of the inverter control device 60 will be briefly described with reference to FIG.

As shown in FIG. 3A, the sine wave signals e _U , e _V , e _W of each phase of U, V, W having an angular frequency ω ₀ and a peak value V ₀ , and an angular frequency ω _c which is a carrier signal. , The triangular carrier wave e _c of the peak value V _c , and the switching elements 33a, 34a, 35a of the upper arm and the switching elements 33b, 34b of the lower arm of each phase of the inverter 30 shown in FIG. The 35b and 35b are alternately turned on / off. As a result, the voltages V _U , V _V , and V _W with respect to the DC midpoints (midpoints between the high voltage path 13 and the negative side electric circuit 11) of the U, V, and W output lines 55, 56, and 57 are shown in FIG. 3 ( As shown in FIG. 3 (d) from b), it becomes either VH / 2 or −VH / 2, and the one-point chain line a, the two-point chain line b, and the broken line in FIGS. 3 (b) to 3 (d). The pulse train is modulated like the sine waves d, e, and f as shown in c. Further, the line voltage V _UV , which is the potential difference between the U-phase voltage V _U and the V-phase voltage V _V , is like a sinusoidal wave h between VH and −VH as shown in FIG. 3 (e). It becomes a modulated pulse train g. Here, the output frequency can be controlled by the angular frequency ω ₀ of the sinusoidal signals e _U , e _V , e _W , and the magnitude thereof is the peak value V of the sinusoidal signals e _U , e _V , e _W. It can be controlled by the ratio of the peak value V _c of ₀ and the triangular carrier wave e _c (α = V ₀ / V _c ).

When the frequency of the triangular carrier wave _ec , which is a carrier signal, is high, the number of switchings increases, the alternating current waveform supplied to the motor 50 becomes closer to a sine wave, and smooth control can be performed. On the other hand, since the number of switchings increases, the switching loss increases and the amount of heat generated increases. On the other hand, when the frequency is low, the current waveform supplied to the motor 50 is deviated from that of the sine wave, but since the number of switchings is small, the switching loss is small and the calorific value is also small.

Therefore, when the rotation speed of the motor 50 is high, a high frequency triangular carrier wave _ec is often used, and when the rotation speed of the motor 50 is low, a low frequency triangular carrier wave _ec is often used. .. Further, even when the temperatures of the switching elements 33a to 35a and 33b to 35b rise, the frequency of the triangular carrier wave _ec may be lowered to suppress heat generation.

Next, the operation of the inverter control device 60 of the present embodiment will be described with reference to FIGS. 4 to 9. The inverter control device 60 repeatedly executes steps S101 to S112 of FIG. 4 while the motor 50 is in operation.

As shown in step S101 of FIG. 4, the carrier signal generation unit 66 identifies the operating point of the motor 50 from the rotation speed of the rotor detected by the resolver 52 and the torque command Trqcom of the motor 50. In step S102 of FIG. 4, the carrier signal generation unit 66 determines whether or not the operating point specified in step S101 is within the range of rotation speed and torque at which the frequency of the carrier signal can be dispersed. If NO is determined in step S102 of FIG. 4, the process proceeds to step S112 of FIG. 4, and the carrier signal generation unit 66 ends the process without dispersing the frequency of the carrier signal.

On the other hand, if the carrier signal generation unit 66 determines YES in step S102 of FIG. 4, the carrier signal generation unit 66 proceeds to step S103 of FIG. 4 and selects the fundamental frequency of the carrier signal with reference to the map shown in FIG. The map shown in FIG. 5 is a map in which the fundamental frequency is defined with respect to the rotation speed, output torque, and temperature of the motor 50.

In the map shown in FIG. 5, the operating regions surrounded by the maximum torque line p, the equal output line q, and the maximum speed line r are shown by solid lines, three regions A1, B1, C1, and three regions A2, which are indicated by broken lines. It is divided into B2 and C2. Region A1 is a region where the rotation speed is low and torque is large, region B1 is a region where the rotation speed is larger and torque is smaller than region A1, and region C1 is a region where the rotation speed is equal to or more than a predetermined value or the output torque is equal to or less than a predetermined value. .. The carrier signal generation unit 66 sets the low frequency Fc1 as the fundamental frequency when the operating point of the motor 50 is in the region A1, and sets the high frequency Fc3 as the fundamental frequency when the operating point is in the region C1. When the operating point is in the region B1, the medium frequency Fc2 is set as the fundamental frequency. Here, Fc1, Fc2, and Fc3 can take various values.

The three regions A2, B2, and C2 shown by the broken lines in FIG. 5 are regions in which the fundamental frequencies of the switching elements 33a to 35a, 33b to 35b, and the motor 50 are set to Fc1, Fc2, and Fc3, respectively, when the temperature rises. .. Regions A2 and B2 are regions A1 and B1 expanded to regions where the rotation speed is high and the output torque is small, respectively. The area C2 is obtained by reducing the area by the amount that the area B2 is expanded from the area C1. When the temperatures of the switching elements 33a to 35a, 33b to 35b and the motor 50 further rise, the regions A2 and B2 shown in FIG. 5 are expanded to the high-speed rotation speed region, and the region C2 is further reduced by that amount. It may be a map like this.

When the fundamental frequency selected in step S103 is the low frequency Fc1, the carrier signal generation unit 66 determines YES in step S104 of FIG. 4 (the fundamental frequency is in the low frequency range), and determines that the fundamental frequency is in the low frequency range, and the step of FIG. Proceeding to S105, it is determined whether or not the vehicle speed is in the low speed region where the generation of abnormal noise is anxious. This low-speed region can be set in various ways depending on the vehicle type, but for example, 20 to 40 km / h or less may be set as the low-speed region.

If the carrier signal generation unit 66 determines YES in step S105 of FIG. 4, the carrier signal generation unit 66 proceeds to step S106 of FIG. 4 and selects a normal distribution method. The normal distribution method is a control method in which each frequency of the carrier signal is dispersed so that each frequency of the carrier signal has a normal distribution centered on the fundamental frequency Fc1. Then, the carrier signal generation unit 66 determines the dispersion width ΔFc1 which is a predetermined frequency range from the fundamental frequency Fc1 in step S107 of FIG. 4, and determines the maximum frequency Fmax1 and the minimum frequency Fmin1 of the dispersion shown in FIG. 6A. do. Then, the process proceeds to step S108 of FIG. 4, the detailed frequency distribution is determined from the fundamental frequency Fc1 and the dispersion width ΔFc1, and the frequency distribution control is executed in step S109 of FIG.

FIG. 7 shows an example of a detailed frequency distribution. As shown in FIG. 7, the frequency of the carrier signal is randomly changed every time Δt so that the frequency of the number of times that a certain frequency is continued for the time Δt has a normal distribution between the maximum frequency Fmax1 and the minimum frequency Fmin1. Is. As a result, the noise generated by the frequency of the carrier signal is dispersed between the maximum frequency Fmax1 and the minimum frequency Fmin1, and the human hearing feels that the noise is reduced. The time Δt, each frequency of the carrier signal, and the dispersion width ΔFc1 are selected with reference to the map created in advance. In this case, the average value of each frequency of the carrier signal is the fundamental frequency Fc1.

As shown in FIG. 6B, the fundamental frequency Fc1 is set to a frequency that does not resonate with the motor 50 or the like, and the vibration transmission sensitivity is low. Since the fundamental frequency Fc1 is a low frequency, frequencies at which resonance with the motor 50 or the like occurs are scattered in the vicinity of the fundamental frequency Fc1. Therefore, as shown in FIG. 6B, the vibration transmission sensitivity is high in the region where the frequency is slightly higher than the fundamental frequency Fc1 or in the region where the frequency is slightly lower.

Since the inverter control device 60 of the present embodiment increases the frequency of appearance in the vicinity of the fundamental frequency Fc1 having low transmission sensitivity and distributes the frequency of the carrier signal so that the frequency of appearance in the region where the transmission sensitivity is high decreases. , It is possible to suppress the generation of noise due to resonance and suppress the feeling of abnormal noise. As a result, even when the frequency of the carrier signal is low, it is possible to suppress the recognition of the sound generated by the carrier signal as noise.

On the other hand, when the carrier signal generation unit 66 selects the high frequency Fc3 as the fundamental frequency in step S103 of FIG. 4, it determines NO (the fundamental frequency is not in the low frequency region but in the high frequency region) in step S104 of FIG. Then, the process proceeds to step S110 in FIG. 4 to select the rectangular distribution method. The rectangular distribution method is a control method in which each frequency of the carrier signal is dispersed so that each frequency of the carrier signal has a rectangular distribution centered on the fundamental frequency Fc3. Then, the carrier signal generation unit 66 determines the dispersion width ΔFc3 which is a predetermined frequency range from the fundamental frequency Fc3 in step S111 of FIG. 4, and determines the maximum frequency Fmax3 and the minimum frequency Fmin3 of the dispersion shown in FIG. 8A. do. Here, the dispersion width ΔFc3 may have the same frequency width as the dispersion width ΔFc1 described above, or may have a wider frequency width or a narrower frequency width.

In the frequency dispersion control in this case, as shown in FIG. 9, the frequency of the carrier signal is randomly changed every time Δt, and the frequency of the number of times that a certain frequency is continued for the time Δt is between the maximum frequency Fmax3 and the minimum frequency Fmin3. The rectangular distribution, that is, the distribution width ΔFc3 is evenly distributed. Therefore, the noise generated by the frequency of the carrier signal becomes white noise evenly distributed between the maximum frequency Fmax3 and the minimum frequency Fmin3, and it seems that the noise is reduced. The time Δt, the frequency of the carrier signal, and the dispersion width ΔFc3 are selected with reference to the map created in advance. In this case, the average frequency of the carrier signal is the fundamental frequency Fc3.

As shown in FIG. 8B, since the fundamental frequency Fc3 has a high frequency that does not resonate with the motor 50 or the like, there is no frequency region in the vicinity of the fundamental frequency Fc3 where resonance with the motor 50 or the like occurs. The frequency region in the vicinity of the fundamental frequency Fc3 is a region where high-order fine membrane vibrations and the like of each device are generated. Therefore, as shown in FIG. 8B, there is no significant change in the vibration transmission sensitivity in the vicinity of the fundamental frequency Fc3, and even if the carrier signal frequency is dispersed by the dispersion width ΔFc3, abnormal noise due to resonance at a specific frequency is observed. Will not occur.

As described above, in the inverter control device 60 of the present embodiment, when the fundamental frequency Fc3 in the frequency domain where the transmission sensitivity does not change significantly is selected, the frequency of the carrier signal is evenly distributed in the range of the dispersion width ΔFc3. The noise can be reduced as white noise. As a result, it is possible to suppress the recognition of the sound generated by the carrier signal as noise.

Further, when the carrier signal generation unit 66 selects the low frequency Fc1 or the intermediate frequency Fc2 as the fundamental frequency in step S103 of FIG. 4, the carrier signal generation unit 66 determines YES in step S104 of FIG. Then, the process proceeds to step S105 in FIG. 4, and it is determined whether or not the vehicle speed is a vehicle speed at which abnormal noise is annoying. If YES is determined in step S105 of FIG. 4, the carrier signal generation unit 66 proceeds from step S106 of FIG. 4 to S109 to disperse the frequency of the carrier signal by a normal distribution method. On the other hand, if NO is determined in step S105 of FIG. 4, the carrier signal generation unit 66 proceeds to step S110 of FIG. 4 to disperse the carrier signal by the rectangular distribution method.

In this way, when the vehicle speed is high and it is difficult to hear abnormal noise due to background noise, the carrier signal is dispersed by the rectangular distribution method, and the sound generated by the carrier signal that is difficult to be mixed with background noise is converted into white noise and recognized as noise. Can be suppressed.

In the above embodiment, it is determined whether or not the abnormal noise is hard to hear due to the background noise, but the present invention is not limited to this, and the abnormal noise is heard due to the background noise depending on the on / off of the engine or the engine speed. You may try to judge whether it is difficult.

As described above, the inverter control device 60 of the present embodiment can suppress the sound generated by the carrier signal from being recognized as noise.

11 Negative side electric circuit, 13 High piezoelectric path, 20 DC power supply, 30 Inverter, 31 Smoothing capacitor, 32 High voltage sensor, 33a-35a upper arm switching element, 33b-35b lower arm switching element, 36a-38a, 36b-38b diode, 50 motor, 52 resolver, 53,54 current sensor, 55,56,57 output line, 60 inverter control device, 61 CPU, 62 storage unit, 63 equipment / sensor interface, 64 data bus, 65 motor command calculation unit, 66 carrier Signal generator, 67 PWM section, 100 motor control system.

Claims (1)

An inverter control device that controls an inverter that includes multiple switching elements.
A motor command calculation unit that generates a voltage or current control command supplied from the inverter to the motor,
A carrier signal generator that generates a carrier signal, and a carrier signal generator
A PWM unit that turns on / off the plurality of switching elements of the inverter by PWM control based on the control command from the motor command calculation unit and the carrier signal from the carrier signal generation unit is included. ,
The carrier signal generator is
The fundamental frequency of the carrier signal is set based on the operating point of the motor, and the frequency of the carrier signal is dispersed in a predetermined frequency range around the fundamental frequency.
When the fundamental frequency is in the low frequency range, each frequency of the carrier signal is dispersed so that the frequency of each frequency of the carrier signal to be dispersed has a normal distribution centered on the fundamental frequency.
When the fundamental frequency is in the high frequency range, each frequency of the carrier signal is dispersed so that the frequency of each frequency of the carrier signal to be dispersed has a rectangular distribution centered on the fundamental frequency .
The fundamental frequency shall be set to a frequency that does not resonate with the motor .
Inverter control device featuring.

Images