JP7111026B2 - Electric motor drive system and inverter control method in electric motor drive system - Google Patents

Description

The present invention relates to a motor control method in a system in which a permanent magnet synchronous motor is driven by an inverter.

The input three-phase AC voltage is converted to DC voltage by a rectifier (diode rectifier, PWM converter, 120° current converter, etc.), and the DC voltage is output as an AC voltage with a desired frequency and amplitude by an inverter, and the motor is operated. Consider a motor drive system to be controlled.

When the motor is a Permanent Magnet Synchronous Motor (hereinafter also referred to as PMSM), it is known that load fluctuations easily excite torque oscillations, and vibration suppression control is required for stable driving. has been devised.

Further, as one of the PMSM control methods, there is a sensorless V/f control which is a simple realization method that eliminates the need to consider speed sensor accuracy, sensor failure risk, and component cost at high speeds. As an example of such control, Patent Document 1 has been proposed, and in this sensorless V/f control, the detected current is fed back to the frequency command and voltage command to suppress vibration.

Further, there is a PWM (Pulse Width Modulation) method as a pulse generation method often used in power converters such as rectifiers and inverters.

PWM is widely used because it is easy to achieve a suitable output of voltage vectors and the computational load is not heavy. Patent Document 1, which is an example of the sensorless V/f control, also assumes PWM.

However, since PWM is a method of outputting a command voltage on average based on a carrier frequency (its own pulse generation frequency), it does not necessarily generate an optimum pulse for expressing the command voltage. To address this problem, a pulse generation method has been proposed in which a fixed pulse pattern that can appropriately express a command voltage based on the fundamental frequency is calculated in advance.

JP-A-2000-236694

Masahiko Tsukagoshi, Kounori Matsuse, "Derivation of Optimal Fixed Pulse Pattern Conforming to Harmonic Regulations for Large-capacity PWM Rectifier", IEEJ Vol. 131, No. 3, 2011

In the prior art, no specific control configuration is proposed for controlling the PMSM with a fixed pulse pattern, nor is there any discussion of points to note in implementation.

SUMMARY OF THE INVENTION The present invention has been made in view of the above points, and its object is to provide a motor drive system and an inverter control method in a motor drive system that can perform vibration suppression control of a permanent magnet synchronous motor using a fixed pulse pattern. to provide.

The electric motor drive system according to claim 1 for solving the above problems,
A system for driving a permanent magnet synchronous motor by an inverter controlled by a gate signal output from a pulse pattern table reference unit having a fixed pulse pattern table,
a speed control unit that outputs a second speed command based on a first speed command that is set and input to the system and a third speed command that is input to the pulse pattern table reference unit;
A second speed command output from the speed control unit, a detected current obtained by detecting the current flowing in the permanent magnet synchronous motor, and a phase output from the pulse pattern table reference unit are input, and the vibration component of the permanent magnet synchronous motor is input. a vibration suppression control unit that performs suppression control of the vibration component and outputs a modulation rate defined by a ratio of voltage and frequency corresponding to the third speed command and a third speed command; with
The pulse pattern table reference unit receives as inputs the modulation rate and the third speed command output from the vibration suppression control unit, and calculates the phase obtained by integrating the gate signal of each semiconductor element of the inverter and the third speed command. It is characterized by outputting

Further, the electric motor drive system according to claim 2 is characterized in that, in claim 1,
The pulse pattern table reference unit
A table in which the modulation rate and the phase are associated with the voltage level expressed by the fixed pulse pattern in advance, and the modulation rate output from the vibration suppression control unit and the third speed command are integrated. a fixed pulse pattern table that receives a phase as an input and outputs a voltage level corresponding to the input modulation rate and phase;
a gate generator that generates a gate signal for each semiconductor element of the inverter based on the voltage level output from the fixed pulse pattern table;
It is characterized by outputting a phase obtained by integrating the generated gate signal and the third speed command.

Further, the electric motor drive system according to claim 3 is characterized in that, in claim 1 or 2,
The modulation rate input to the pulse pattern table reference section is a modulation rate corresponding to the first speed command instead of the modulation rate from the vibration suppression control section.

Further, the electric motor drive system according to claim 4 is the electric motor drive system according to claim 1 or 2,
The modulation rate input to the pulse pattern table reference section is set to the modulation rate corresponding to the second speed command instead of the modulation rate from the vibration suppression control section.

Further, the electric motor drive system according to claim 5 is the electric motor drive system according to any one of claims 1 to 4,
The vibration suppression control unit is
a three-phase/two-phase conversion unit that converts the detected current into a dq-axis current according to the phase input from the pulse pattern table reference unit; and vibration suppression that multiplies the converted d-axis current or q-axis current by a vibration suppression gain. Obtain the vibration component by the gain section and
It is characterized in that suppression control of the vibration component is performed by obtaining a deviation between the obtained vibration component and the input second speed command.

Further, the inverter control method in the electric motor drive system according to claim 6 includes:
An inverter control method in a system in which a permanent magnet synchronous motor is driven by an inverter controlled by a gate signal output from a pulse pattern table reference unit having a fixed pulse pattern table, comprising:
The pulse pattern table reference unit is a table in which the modulation rate and the phase are associated in advance with the voltage level expressed by the fixed pulse pattern, and the modulation rate output from the vibration suppression control unit and the third A fixed pulse pattern table that receives as input a phase obtained by integrating a speed command and outputs a voltage level corresponding to the input modulation rate and phase,
a step in which the speed control unit outputs a second speed command by controlling the third speed command input to the pulse pattern table reference unit to follow the first speed command set and input to the system; ,
A vibration suppression control unit receives, as inputs, a detected current obtained by detecting a current flowing through the permanent magnet synchronous motor, a phase output from the pulse pattern table reference unit, and a second speed command output from the speed control unit. A step of obtaining a vibration component of the synchronous motor, performing suppression control of the vibration component, and outputting a third speed command and a modulation factor defined by a ratio of voltage and frequency corresponding to the third speed command. When,
a step in which a gate generation unit of a pulse pattern table reference unit generates a gate signal for each semiconductor element of the inverter based on a voltage level output from the fixed pulse pattern table;
a step in which the pulse pattern table reference unit outputs a phase obtained by integrating the third speed command;
and a step of outputting the generated gate signal to the inverter by a gate generation unit of the pulse pattern table reference unit.

(1) According to the inventions described in claims 1 to 6, in a motor drive system premised on controlling a permanent magnet synchronous motor using a fixed pulse pattern, vibration suppression control of the permanent magnet synchronous motor is performed. can be done.
(2) According to the third and fourth aspects of the present invention, it is possible to avoid sudden changes in the output voltage level of the fixed pulse pattern table.
(3) According to the fifth aspect of the invention, the vibration suppression control can be performed by feeding back the obtained vibration component to the second speed command side.

1 is a system configuration diagram of Example 1 of the present invention; FIG. FIG. 2 is a configuration diagram of a vibration suppression control unit in FIG. 1; FIG. 2 is a configuration diagram of a pulse pattern table reference unit in FIG. 1; Shows simulation results of vibration suppression control according to the present invention, (a) is a characteristic diagram of speed and speed command, (b) is a characteristic diagram of motor torque, (c) is a waveform diagram of three-phase voltage around 0.4 s, (d) is a waveform diagram of three-phase voltage around 0.5 s.

INDUSTRIAL APPLICABILITY The present invention is applied to a motor drive system that drives a permanent magnet synchronous motor with an inverter controlled based on a fixed pulse pattern.

Hereinafter, embodiments of the present invention will be described with reference to the drawings, but the present invention is not limited to the following embodiment examples. In the following description, the "electrical angular frequency" may also be referred to as "speed" because the output frequency of the inverter is proportional to the number of revolutions of the motor. Considering that the control output is always electrically realized, in this specification, the electrical angular frequency obtained by multiplying the number of rotations of the motor by the pole logarithm is replaced with the speed.

FIG. 1 shows a system configuration diagram according to the first embodiment, in which a permanent magnet synchronous motor 50 is driven by an inverter 40. As shown in FIG. In the system of FIG. 1, a first speed command ω1 is set and input based on the operating amount of the control panel.

10 compares the input first speed command ω1 with the third speed command ω3 output from the vibration suppression control unit 20 (described later) (speed command input to the pulse pattern table reference unit 30). is a speed control unit that performs, for example, PI (proportional/integral) control so as to follow ω1 to calculate the second speed command ω2.

Reference numeral 20 denotes a three-phase (U, V, W) detected current idet obtained by detecting a current flowing through the permanent magnet synchronous motor 50 by means of a current transformer (not shown), and a phase θ and a speed output from the pulse pattern table reference unit 30. The second speed command ω2 output from the control unit 10 is input, the vibration suppression control unit obtains the vibration component of the permanent magnet synchronous motor 50 by, for example, the configuration shown in FIG.

In FIG. 2 showing an example of the vibration suppression control unit 20, 21 coordinate-transforms the three-phase detected current idet into a dq-axis current by using the phase θ input from the pulse pattern table reference unit 30, for example, the q-axis It is a three-phase/two-phase converter that outputs a current iq.

The q-axis current iq output from the three-phase/two-phase converter 21 is passed through the low-pass filter 22 to remove noise, and then multiplied by the vibration suppression gain Gv in the vibration suppression gain unit 23 .

In the circuit of FIG. 2, the vibration component of the permanent magnet synchronous motor 50 is obtained by the 3-phase/2-phase conversion section 21, the low-pass filter 22, and the vibration suppression gain section 23. FIG.

A subtractor 24 subtracts the output (vibration component) of the vibration suppression gain 23 from the second speed command ω2 input from the speed control unit 10 .

The subtraction result of the subtractor 24 is output from the vibration suppression control section 20 as the third speed command ω3.

Reference numeral 25 denotes a ratio multiplier that sets the ratio of voltage and speed (electrical angular frequency obtained by multiplying the number of rotations of the motor by the number of pole pairs), that is, the ratio Gd of voltage and frequency. By multiplying the subtraction output ω3 of the subtractor 24 by the ratio Gd of the ratio multiplier 25, the modulation factor d is output.

Reference numeral 30 in FIG. 1 inputs the modulation rate d and the third speed command ω3 output from the vibration suppression control section 20, and sets the voltage level corresponding to the modulation rate d and the speed command ω3 to the fixed voltage level shown in FIG. It is a pulse pattern table reference unit that is referred to by the pulse pattern table 32 and generates and outputs the gate signal g and the output phase θ.

In FIG. 3 showing details of the pulse pattern table reference unit 30, 31 is an integrator that integrates the third speed command ω3 input from the vibration suppression control unit 20 and outputs an output phase θ.

Reference numeral 32 denotes a fixed pulse pattern table in which the modulation factor and phase are associated with the voltage level expressed by the fixed pulse pattern in advance. The output phase .theta. is input, and the voltage level L corresponding to the modulation factor d and the output phase .theta. is output as a reference result.

A gate generator 33 generates a gate signal g for each semiconductor element (not shown) in the inverter 40 based on the voltage level L output from the fixed pulse pattern table 32 .

This gate signal g is input to the inverter 40, a voltage is applied to the PMSM 50 by switching each semiconductor element in the inverter, a current flows through the PMSM 50, and the current is detected as idet.

The fixed pulse patterns tabulated in the fixed pulse pattern table 32 are obtained by using the method of, for example, Non-Patent Document 1, "Derivation of Optimal Fixed Pulse Patterns Conforming to Harmonic Regulations for Large-Capacity PWM Rectifiers". A fixed pulse pattern is obtained. It is also assumed that the fixed pulse pattern is tabulated in advance in the fixed pulse pattern table 32 so that the voltage level L to be output can be known by referring to the output phase θ and the modulation factor d.

In the electric motor drive system configured as described above, first, the overall vibration suppression control will be described.

In the system configuration diagram of FIG. 1, the vibration suppression control unit 20 mainly performs vibration suppression. In the vibration suppression control, a vibration suppression effect is obtained by adding a compensation term to the speed command, so there arises a problem that the speed of the plant (PMSM 50) cannot converge to the speed command input to the system.

In order to solve this problem, the speed control unit 10 is provided to perform PI control for following the system input by comparing the speed command ω3 after vibration suppression compensation by the vibration suppression control unit 20 and the speed command ω1 of the system input. . The response of the speed control unit 10 is set to be lower than that of the vibration suppression control unit 20, and only the I control may be used when the response is not required.

As described above, the speed command is corrected twice in the entire vibration suppression control. In consideration of this, the speed command of the system input is the first speed command ω1, the speed command after the speed control is the second speed command ω2, and the speed command after the vibration suppression control is the third speed command ω3.

Next, vibration suppression control and the cycle of the pulse pattern table reference unit 30 will be described.

The cycle of vibration suppression control may be any control cycle that allows observation of current vibration. Further, the pulse pattern table reference unit 30 may have a control cycle that can appropriately express the pre-generated pulse pattern. The pulse pattern is usually set with a phase considering frequency components several times to several tens of times the fundamental wave for harmonic suppression. In other words, a control cycle capable of appropriately representing a pulse pattern is a control cycle capable of representing a frequency that is several times to several tens of times the highest frequency within the speed command range. It is assumed that the pulse pattern table reference unit 30 needs to have a shorter control period than the vibration suppression control unit 20 this time, although it depends on the speed command range and harmonic suppression accuracy requirements.

In order to obtain the output phase .theta. more accurately, the frequency integration operation is performed by the pulse pattern table reference unit 30 having a short control cycle as shown by the integrator 31 in FIG. θ is also used in the vibration suppression control section 20 as an accurate phase. However, the delay before the output phase θ, the detected current idet, or both of them are used for vibration suppression control may affect the control performance. In such a case, the amount of phase rotation during the delay may be compensated for θ by adding the delay time ta·ω3.

That is, θ+ta·ω3 obtained by adding ta·ω3 to the output phase θ (the output phase of the integrator 31) output from the pulse pattern table reference unit 30 is supplied to the three-phase/two-phase conversion unit 21 of the vibration suppression control unit 20. It may be configured to input

Next, the vibration suppression control section 20 shown in FIG. 2 will be described.

A current on the dq axis is obtained by coordinate-converting the detected current idet in the three-phase/two-phase converter 21 . In FIG. 2, only iq out of id and iq is used for control. Regarding this point, since the main purpose is to feed back the vibration component, it is possible to feed back the id, or, if there is a detection torque means, another detection amount that causes the vibration component, such as the detection torque.

In FIG. 2, vibration is suppressed by feeding back iq to ω2, but the purpose here is to feed back the vibration component to the input value of the fixed pulse pattern table 32 in FIG. Therefore, a form of feedback to another target within the range reflected in the input value of the fixed pulse pattern table 32, such as feedback to the modulation factor d and feedback to the output phase θ, is also allowed.

That is, for example, when the vibration component detection amount is fed back to the modulation rate d, the subtractor 24 in FIG. The output is multiplied by a ratio (Gd), which is the same voltage-to-frequency ratio set as in the gain multiplier 25, to obtain a modulation rate corresponding to the vibration component, and the modulation rate corresponding to the vibration component and the second The deviation from the modulation rate d (modulation rate corresponding to the second speed command) obtained by multiplying the speed command ω2 by the ratio Gd of the gain multiplier 25 is obtained by a subtractor, and the deviation output is used as the modulation rate for vibration suppression. It is output from the control unit 20 . In this case, ω3 in FIGS. 1 to 3 is treated as ω2.

Further, for example, when the vibration component detection amount is fed back to the output phase θ, the subtractor 24 in FIG. The output is integrated by an integrator similar to the integrator 31 to obtain the phase corresponding to the vibration component. The deviation from the phase θ input to the pattern table 32 is taken by a subtractor, and the deviation output is input to the fixed pulse pattern table 32 as the output phase θ, and is output from the pulse pattern table reference unit 30. . In this case, ω3 in FIGS. 1 to 3 is treated as ω2.

In FIG. 2, the q-axis current iq is passed through a low-pass filter (LPF) 22 to reduce noise. The low-pass filter 22 is not essential for vibration suppression control, and iq may be used without providing a filter. However, in the fixed pulse pattern, since switching is performed in synchronization with the output frequency, there is no appropriate constant sampling period, and switching noise may affect vibration suppression control. Therefore, stable control can be performed by providing the low-pass filter 22 with a time constant that can remove switching noise.

The strength of vibration suppression is adjusted by the vibration suppression gain Gv. The vibration suppression gain Gv is a value equal to or greater than 0. If Gv is small, control is high in responsiveness and vibration suppression performance is low, and if Gv is large, control is low in response and high vibration suppression performance.

Next, the modulation factor setting will be explained.

In the configuration of FIG. 2, the modulation factor d is obtained by multiplying the third speed command ω3 by the ratio Gd. Therefore, ω1 and ω2 may be used instead of ω3.

That is, when the modulation factor is obtained using the first speed command ω1, the ratio multiplier 25 in FIG. 2 is removed, and the first speed command ω1 in FIG. is multiplied by the frequency ratio Gd to generate the modulation factor d, and the generated modulation factor d is directly input to the fixed pulse pattern table 32 of the pulse pattern table reference unit 30 .

When the modulation factor is obtained using the second speed command ω2, the ratio multiplier 25 of FIG. 2 is arranged on the input side of the subtractor 24, and the ratio Gd is multiplied to generate a modulation factor d, and the generated modulation factor d is input to the fixed pulse pattern table 32 of the pulse pattern table reference unit 30 .

However, when the modulation factor d is generated from the first speed command ω1 and the second speed command ω2, the ratio between the speed command ω3 and the modulation factor d used to generate the output phase θ is not always constant. In other words, since the correspondence between the modulation factor d and the switching frequency becomes unknown, it is desirable to create the fixed pulse pattern table 32 with a sufficient margin for the number of switching times.

FIG. 4 shows the result of a simulation for confirming the effect of the vibration suppression control in the first embodiment. 4, (a) is a characteristic diagram of speed and speed commands ω1 to ω3, (b) is a characteristic diagram of motor torque, (c) is a waveform diagram of three-phase voltage around 0.4 s, and (d) is a diagram of 0.4 s. The waveform diagram of the three-phase voltage around 5s is shown.

In this simulation, a constant load of about 150 Nm was applied until 0.4 seconds, and the load was changed stepwise up to about 720 Nm after 0.4 seconds. A first speed command ω1, which is a system input, is set to 860 Hz. As for the time domain, only the domain related to vibration suppression control is taken out.

As can be seen from the speed graph in FIG. 4(a), load fluctuations are dealt with by lowering the third speed command ω3. The plant speed is the number of revolutions converted into an electrical frequency, and is always approximately the same as ω3. Since the third speed command ω3 has decreased, the speed control unit 10 operates to increase the second speed command ω2.

In the graph of the motor torque in FIG. 4(b), it can be seen that the load fluctuation can be followed without overshooting, although some vibration components can be seen during the rise. When the torque is steady, there is a period in which the torque ripple intermittently increases, which is an impact due to pulse pattern switching.

The three-phase voltage graphs of FIGS. 4(c) and (d) show that this simulation is performed with a fixed pulse pattern. The reason why the dotted level lines in FIGS. 4(c) and 4(d) do not always match the output voltage value is that the DC voltage fluctuates and the presence of the output filter. It can be seen that the pulse pattern changes before the load change of 0.4 s shown in FIG. 4(c) and after the load change of 0.5 s shown in FIG. 4(d).

That is, when the constant load changes to load fluctuation at 0.4 s and the third speed command ω3 decreases, the modulation factor d is changed, and the output voltage level L of the fixed pulse pattern table 32 decreases. has changed from FIG. 4(c) to FIG. 4(d).

DESCRIPTION OF SYMBOLS 10... Speed control part 20... Vibration suppression control part 21... 3 phase/2 phase conversion part 22... Low-pass filter 23... Vibration suppression gain part 24... Subtractor 25... Ratio multiplication part 30... Pulse pattern table reference part 31... Integrator 32... Fixed pulse pattern table 33... Gate generator 40... Inverter 50... Permanent magnet synchronous motor

Claims (6)

A system for driving a permanent magnet synchronous motor by an inverter controlled by a gate signal output from a pulse pattern table reference unit having a fixed pulse pattern table,
a speed control unit that outputs a second speed command based on a first speed command that is set and input to the system and a third speed command that is input to the pulse pattern table reference unit;
A second speed command output from the speed control unit, a detected current obtained by detecting the current flowing in the permanent magnet synchronous motor, and a phase output from the pulse pattern table reference unit are input, and the vibration component of the permanent magnet synchronous motor is input. a vibration suppression control unit that performs suppression control of the vibration component and outputs a modulation rate defined by a ratio of voltage and frequency corresponding to the third speed command and a third speed command; with
The pulse pattern table reference unit receives as inputs the modulation rate and the third speed command output from the vibration suppression control unit, and calculates the phase obtained by integrating the gate signal of each semiconductor element of the inverter and the third speed command. An electric motor drive system characterized by outputting. The pulse pattern table reference unit
A table in which the modulation rate and the phase are associated with the voltage level expressed by the fixed pulse pattern in advance, and the modulation rate output from the vibration suppression control unit and the third speed command are integrated. a fixed pulse pattern table that receives a phase as an input and outputs a voltage level corresponding to the input modulation rate and phase;
a gate generator that generates a gate signal for each semiconductor element of the inverter based on the voltage level output from the fixed pulse pattern table;
2. The motor drive system according to claim 1, wherein a phase obtained by integrating said generated gate signal and said third speed command is output. 3. The modulation rate input to the pulse pattern table reference unit is a modulation rate corresponding to the first speed command instead of the modulation rate from the vibration suppression control unit. The motor drive system according to . 3. The modulation rate input to the pulse pattern table reference unit is a modulation rate corresponding to the second speed command instead of the modulation rate from the vibration suppression control unit. The motor drive system according to . The vibration suppression control unit is
a three-phase/two-phase conversion unit that converts the detected current into a dq-axis current according to the phase input from the pulse pattern table reference unit; and vibration suppression that multiplies the converted d-axis current or q-axis current by a vibration suppression gain. Obtain the vibration component by the gain section and
5. The electric motor drive system according to any one of claims 1 to 4, wherein suppression control of the vibration component is performed by obtaining a deviation between the obtained vibration component and the input second speed command. . An inverter control method in a system in which a permanent magnet synchronous motor is driven by an inverter controlled by a gate signal output from a pulse pattern table reference unit having a fixed pulse pattern table, comprising:
The pulse pattern table reference unit is a table in which the modulation rate and the phase are associated in advance with the voltage level expressed by the fixed pulse pattern, and the modulation rate output from the vibration suppression control unit and the third A fixed pulse pattern table that receives as input a phase obtained by integrating a speed command and outputs a voltage level corresponding to the input modulation rate and phase,
a step in which the speed control unit outputs a second speed command by controlling the third speed command input to the pulse pattern table reference unit to follow the first speed command set and input to the system; ,
A vibration suppression control unit receives, as inputs, a detected current obtained by detecting a current flowing through the permanent magnet synchronous motor, a phase output from the pulse pattern table reference unit, and a second speed command output from the speed control unit. A step of obtaining a vibration component of the synchronous motor, performing suppression control of the vibration component, and outputting a third speed command and a modulation factor defined by a ratio of voltage and frequency corresponding to the third speed command. When,
a step in which a gate generation unit of a pulse pattern table reference unit generates a gate signal for each semiconductor element of the inverter based on a voltage level output from the fixed pulse pattern table;
a step in which the pulse pattern table reference unit outputs a phase obtained by integrating the third speed command;
and a step of outputting the generated gate signal to the inverter by a gate generation unit of a pulse pattern table reference unit.

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