JP4140304B2 - Motor control device - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a motor control device, and more particularly to a motor control device for driving and controlling a synchronous motor having a saliency provided with a plurality of phase motor coils without using a position sensor.
[0002]
[Prior art]
Conventionally, as a so-called sensorless driving method for driving and controlling a synchronous motor including a plurality of coils such as a synchronous reluctance motor without using a rotor position sensor, for example, an estimated current value calculated from an applied voltage and a motor model A technique has been proposed in which the rotor position is estimated based on the difference from the measured current value measured by the current sensor.
[0003]
[Problems to be solved by the invention]
However, in the above-described prior art, a complicated calculation process for calculating the estimated current value sequentially from the motor model is required in the drive control process, and thus it is necessary to use a microcomputer capable of high-speed processing. Furthermore, since the rotor position is estimated using the measured current value measured by the current sensor, it is necessary to obtain an accurate measured current value, and a highly accurate current sensor is required. For this reason, there is a problem that not only the drive control processing in the motor control device becomes complicated, but also the manufacturing cost of the control device increases.
[0004]
The present invention has been made in view of the above-described problems, and an object to be solved is to provide a motor control device capable of stably performing sensorless driving of a synchronous motor with a simple and inexpensive configuration.
[0005]
[Means for Solving the Problems]
In order to achieve this object, the motor control device according to claim 1 is a motor control for driving and controlling a synchronous motor having a saliency having a plurality of phase motor coils by an inverter circuit composed of a plurality of switching elements. In the apparatus, voltage amplitude setting means for setting an amplitude of an applied voltage to be applied to the synchronous motor to a predetermined value determined in accordance with a command rotational speed and a command torque, and a motor of at least one of the plurality of phases Current detection means for detecting current; phase difference detection means for detecting a phase difference between the motor current detected by the current detection means and the applied voltage; and a phase difference between the motor current and the applied voltage is the command. Applied voltage phase setting means for setting the phase of the applied voltage so as to match a target phase difference set according to the rotation speed and the command torque Applying voltage duty creating means for creating an applied voltage duty for supplying to the inverter circuit based on the voltage amplitude set by the voltage amplitude setting means and the voltage phase set by the applied voltage phase setting means; It is characterized by having.
[0006]
Therefore, the voltage amplitude setting means sets the amplitude of the applied voltage to be applied to the synchronous motor to a predetermined value that is predetermined according to the command rotational speed and the command torque, and the current detection means is at least one of the plurality of phases. One phase of the motor current is detected, the phase difference detecting means detects the phase difference between the motor current detected by the current detecting means and the applied voltage, and the applied voltage phase setting means is configured to detect the motor current and the The phase of the applied voltage is set so that the phase difference with the applied voltage matches the target phase difference set according to the command rotational speed and the command torque, and the applied voltage duty creating means is the voltage amplitude setting means. An applied voltage duty to be supplied to the inverter circuit is created based on the voltage amplitude set by the voltage and the voltage phase set by the applied voltage phase setting means That.
[0007]
Therefore, when the phase difference between the motor current and the applied voltage does not match the target phase difference, the applied voltage phase setting means applies the phase difference between the motor current and the applied voltage so as to match the target phase difference. Since the voltage phase is set, the synchronous motor can be stably driven and controlled. Further, the voltage amplitude setting means sets the amplitude of the applied voltage to be applied to the synchronous motor to a predetermined value according to the command rotational speed and the command torque, so that the command rotational speed and the command torque are constant. The voltage amplitude is a constant value. At this time, since the torque is autonomously generated and the rotor position autonomously returns to the target control position due to the characteristics of the synchronous motor having saliency, the synchronous motor can be driven and controlled more stably.
[0008]
Further, in the motor control device according to claim 2, the phase difference detection unit samples the motor current detected by the current detection unit at a predetermined period, and from the sampling time immediately after the polarity of the sampling value is reversed. Next, the period up to the sampling time immediately after the polarity is reversed, or the same polarity is 2 or more after the polarity is next reversed from the sampling point where the same polarity is 2 or more consecutive times after the polarity of the sampling value is reversed An integral value of a sine wave basic function is calculated in a period up to a sampling time that is repeated a predetermined number of times, and a phase difference between the motor current and the applied voltage is detected based on the integral value.
[0009]
Therefore, since only the polarity information of the motor current is used, there is no need to consider the gain error of the current sensor, and it can be configured using an inexpensive current sensor. In addition, since the integral value of the sine wave basic function is used, even if noise is mixed in the motor current and an error occurs in the integration period, the influence on the integral value is small, and the phase difference between the motor current and the applied voltage is always accurate. Can be detected.
[0010]
According to a third aspect of the present invention, in the motor control device according to the third aspect, the current detection unit is configured to detect a current in an upper stage or a lower stage of at least one arm of the inverter circuit.
[0011]
Therefore, by using a current sensor such as a sense MOSFET for detecting the arm current, it is possible to reduce the size and cost of the motor control device.
[0012]
DETAILED DESCRIPTION OF THE INVENTION
Embodiments of a motor control apparatus embodying the present invention will be described below with reference to the drawings.
[0013]
FIG. 1 is a block diagram showing the overall configuration of the motor control device 1 of the present embodiment.
[0014]
As shown in FIG. 1, the motor control device 1 includes a synchronous reluctance motor (SynRM) (hereinafter also simply referred to as a motor) as a synchronous motor including a stator composed of a plurality of (three-phase) coils and an iron core rotor. 2 is driven by an inverter circuit 3 and a microcomputer (hereinafter referred to as a microcomputer) 4.
[0015]
As shown in the circuit diagram of FIG. 2, the inverter circuit 3 includes a power MOSFET 31uh (arm upper stage), a sense MOSFET 31ul (arm lower stage), and a V phase which are connected to a DC power supply 30 and supply power to the U phase of the motor 2. A power MOSFET 31vh (arm upper stage), a sense MOSFET 31vl (arm lower stage), a power MOSFET 31wh (arm upper stage) and a sense MOSFET 31wl (arm lower stage) for supplying power to the W phase are respectively connected. Sense MOSFETs 31ul, 31vl, and 31wl are connected to the lower arm of each phase, and an arm current signal that flows when the gate signal of the lower arm of each phase is ON is detected. The relationship between the motor current and the arm current is as shown by the graph in FIG. 3, and the current value at predetermined time intervals of the motor current is the arm current value. In addition, the sense MOSFET 31ul (31vl, 31wl) detects the current by dividing the arm current. Hereinafter, in this specification, arm current is treated as motor current. The sense MOSFETs 31ul, 31vl, 31wl constitute the current detection means of the present invention.
[0016]
The microcomputer 4 includes a CPU, ROM, and RAM (not shown), and the CPU reads and executes a program stored in the ROM, whereby the torque setting unit 41, the rotation speed setting unit 42, and the voltage phase basic value setting. A unit 43, a voltage amplitude setting unit 44, a sine wave basic function creating unit 45, an applied voltage duty creating unit 46, a target sine wave basic function integral value setting unit 47, and a sine wave basic function integrator 48 are realized. To do. The voltage amplitude setting unit 44 is the voltage amplitude setting unit of the present invention, the sine wave basic function creating unit 45 is the sine wave basic function creating unit, the applied voltage duty creating unit 46 is the applied voltage duty creating unit, and the sine wave. The basic function integrator 48 constitutes the phase difference detection means. .
[0017]
The torque setting unit 41 sets a command torque based on a command from a host device in which the motor control device 1 is incorporated.
[0018]
The rotation speed setting unit 42 sets the command rotation speed based on a command or the like from a host device in which the motor control device 1 is incorporated.
[0019]
The voltage phase basic value setting unit 43 sets the voltage phase basic value based on the command torque set in the torque setting unit 41 and the command rotational speed set in the rotational speed setting unit 42. More specifically, a data table including a data sequence of voltage phase basic values with respect to the command torque and the command rotation speed is stored in the ROM, and the voltage phase basic value is obtained from the data table based on the command torque and the command rotation speed. Read and set.
[0020]
The voltage amplitude setting unit 44 sets the voltage amplitude based on the command torque set by the torque setting unit 41 and the command rotational speed set by the rotational speed setting unit 42. More specifically, a data table including a data sequence of voltage amplitude values with respect to the command torque and the command rotation speed is stored in the ROM, and the voltage amplitude value is read from the data table based on the command torque and the command rotation speed. Settings are made.
[0021]
The sine wave basic function creation unit 45 is based on the frequency determined by the command rotational speed set in the rotational speed setting unit 42 and the phase difference between the applied voltage and the motor voltage set in the voltage phase basic value setting unit 43. A sine wave basic function of the applied voltage is created based on the corrected voltage phase basic value.
[0022]
The applied voltage duty creating unit 46 applies an applied voltage duty (PWM signal) for driving the motor 2 from the voltage amplitude set by the voltage amplitude setting unit 44 and the sine wave basic function created by the sine wave basic function creating unit 45. ) And supplied to the inverter circuit 3.
[0023]
The sine wave basic function integrator 48 integrates the sine wave basic function created by the sine wave basic function creation unit 45 in an integration period determined based on the current signal output from the inverter circuit 3, thereby obtaining a sine wave basic function. Calculate the function integral value.
[0024]
Here, the processing contents in the sine wave basic function integrator 48 will be described in detail with reference to FIG.
[0025]
In FIG. 4, a graph of the motor current value (arm current value) measured by the sense MOSFET 31ul (31vl, 31wl) and a graph of the sine wave basic function of the applied voltage are shown side by side. The motor current value is sampled at a predetermined period, and each sampling value is indicated by a plurality of points plotted on the graph. Here, the polarity of the motor current value is negative at the sampling time t0, positive at t1 to t9, and negative at t10 to t18, as shown in FIG. That is, the polarity is inverted from negative to positive at t1, and the polarity is inverted again from t to positive at t10.
[0026]
Then, integration of the sine wave basic function is performed in a period from a sampling time t1 immediately after the polarity of the current sampling value is inverted and becomes positive to a sampling time t10 immediately after the polarity is inverted and becomes negative. Do. Here, the integration period (t1 to t10) is determined by the phase difference between the sine wave basic function and the motor current value, and the integration value of the sine wave basic function is determined by the integration period. The reverse is also true.
[0027]
For example, when the phase difference = 0 °, the integral value is indicated by the hatched portion in FIG. Further, when 0 ° <phase difference <90 °, the integral value is indicated by the hatched portion in FIG. 5B and is an intermediate value between the maximum value and 0. When the phase difference is 90 °, the integral value becomes 0 as shown by the hatched portion in FIG. Further, when the phase difference is greater than 90 °, the integral value becomes a negative value.
[0028]
Accordingly, by calculating the integral value of the sine wave basic function, the phase difference between the motor current value and the sine wave basic function (ie, applied voltage) can be recognized.
[0029]
The target sine wave basic function integral value setting unit 47 sets the sine wave basic function corresponding to the target phase difference based on the command torque set in the torque setting unit 41 and the command rotational speed set in the rotational speed setting unit 42. Set the integral value of the target sine wave basic function that is the integral value. More specifically, a data table including a data string of target sine wave basic function integral values with respect to the command torque and the command rotational speed is stored in the ROM, and the target sine is derived from the data table based on the command torque and the command rotational speed. The wave basic function integral value is read and set.
[0030]
Then, a deviation between the sine wave basic function integration value calculated by the sine wave basic function integrator 48 and the target sine wave basic function integration value set by the target sine wave basic function integration value setting unit 47 is obtained, A value obtained by multiplying the deviation by the gain is fed back to the output side of the voltage phase basic value setting unit 43 (the feedback unit is indicated by reference numeral 49 in FIG. 1). The feedback system gain is calculated in advance and stored in the ROM. Further, the voltage phase basic value setting unit 43 and the feedback unit 49 constitute the applied voltage phase setting means of the present invention. That is, the voltage phase basic value set by the voltage phase basic value setting unit 43 is the phase difference information between the motor current and the applied voltage expressed by the deviation between the target sine wave basic function integration value and the sine wave basic function integration value. Is then input to the sine wave basic function creation unit 45. Accordingly, since the phase difference between the motor current and the applied voltage is fed back to the applied voltage phase, the motor 2 is stably driven and controlled.
[0031]
As described above, since only the polarity information of the motor current is used, there is no need to consider the gain error of the current sensor, and an inexpensive sense MOSFET can be used as the current sensor. In addition, since the integral value of the sine wave basic function is used, even if noise is mixed in the motor current and an error occurs in the integration period, the influence on the integral value is small, and the phase difference between the motor current and the applied voltage is always accurate. Can be detected.
[0032]
Further, the voltage amplitude setting unit 44 sets the applied voltage to a predetermined value in accordance with the command torque and the command rotational speed, and the voltage amplitude is constant when the command torque and the command rotational speed are constant. When the integral value of the sine wave basic function does not match the integral value of the target sine wave basic function (that is, when the phase difference between the applied voltage and the motor current does not match the target phase difference), the synchronous reluctance motor Torque is autonomously generated by the characteristics of (SynRM) and acts to approach a normal phase difference. Therefore, in combination with the above-described action by the feedback control of the applied voltage phase, the motor 2 is driven and controlled more stably.
[0033]
Here, the action of autonomous torque generation will be described with reference to FIGS. FIG. 6 shows the phase difference (phase difference between the applied voltage and the motor current) when the synchronous reluctance motor (hereinafter abbreviated as “SynRM”) is controlled at the target control phase, and the deviation of the estimated coordinate from the actual coordinate. It is a graph which shows the relationship. FIG. 7 shows a case where voltage amplitude constant control is applied in SynRM (voltage phase 110 ° in which the control phase is a voltage phase and the current phase is 45 ° in the control to keep the voltage phase and voltage amplitude constant on the estimated coordinates is the target control. Current amplitude constant control (current minor loop is provided to control the current phase on the estimated coordinates, the current phase is controlled by keeping the current amplitude constant, and the current phase is 45 ° as the target control phase) 5 is a graph showing the relationship between motor torque and deviation of estimated coordinates from actual coordinates when applying. FIG. 8 shows the relationship between the motor torque and the deviation of the estimated coordinate from the actual coordinate when the constant voltage amplitude control is applied to the synchronous motor (SynRM) having a salient pole and the permanent magnet type synchronous motor (SPM). It is a graph to show.
[0034]
As apparent from the graph of FIG. 6, in SynRM, the phase difference decreases when the estimated coordinate shift is near -45 ° to 15 ° (region A), and the phase difference starts to increase above 15 ° (region). B). For this reason, there are two estimated coordinate shifts in the same phase difference, and the estimated coordinate shift cannot be uniquely estimated from the phase difference. Is the estimated coordinate shifted from the actual coordinate to the leading side? Cannot judge whether it is shifted to the delay side. However, if the estimated coordinates match the actual coordinates (the estimated coordinate deviation is 0), it is within the area A, and therefore when the estimated coordinate deviation enters the area B, it is automatically returned to the area A. Such control may be performed.
[0035]
In this embodiment, the control phase is automatically returned to the region A by applying the constant voltage amplitude control to the SynRM. Details will be described below with reference to FIG. First, problems of a method of applying constant current amplitude control to the conventional SynRM will be described. When an error occurs between the actual coordinates and the estimated coordinates due to torque disturbance, etc., and the estimated coordinates deviate from the actual coordinates to the advance side (the actual rotor is delayed) (FIG. 9), the torque decreases and the rotational speed decreases. As a result, the actual rotor is further delayed, and the deviation of the estimated coordinate is further shifted to the advance side (the estimated coordinate is further advanced compared to the actual coordinate) (FIG. 10). Therefore, when the estimated coordinates deviate from the actual coordinates to enter the area B, the estimated coordinate deviation cannot be automatically returned to the area A, and the motor cannot be driven stably. On the other hand, in the method of applying the voltage amplitude constant control to the SynRM according to this embodiment, an error occurs between the actual coordinates and the estimated coordinates, and the estimated coordinates are shifted from the actual coordinates to the advance side (the actual rotor is delayed). In this case (FIG. 11), the torque increases autonomously and the rotational speed increases, so that the actual rotor moves forward, and the estimated coordinate and the actual coordinate approach each other with a delay in the estimated coordinate (FIG. 12). In addition, when the estimated coordinates deviate from the actual coordinates toward the delay side (the actual rotor advances) (FIG. 13), the torque is autonomously decreased and the rotational speed is decreased, thereby causing a delay in the actual rotor and the estimated coordinates. The shift of the distance advances and the estimated coordinates and the actual coordinates approach (FIG. 12). Therefore, even when the estimated coordinates deviate from the actual coordinates toward the advance side and enter the area B, the deviation of the estimated coordinates returns to the area A by the action of the autonomously generated torque, so that the SynRM can be driven and controlled stably. It is.
[0036]
Furthermore, the present invention has a stronger action of the torque generated autonomously than the method of applying the constant voltage amplitude control to the conventional permanent magnet type synchronous motor (SPM), and the motor can be driven and controlled more stably as shown in FIG. The description will be given with reference. In the method of applying constant voltage amplitude control to a permanent magnet type synchronous motor (SPM) (the control phase is the voltage phase and the voltage phase 25 ° where the current phase is 0 ° is the target control phase), the estimated coordinates are the actual coordinates. When proceeding from, the increase in torque generated autonomously is very small compared to SynRM. Further, when the estimated coordinates are delayed from the actual coordinates, the torque that decreases autonomously is very small compared to SynRM. Therefore, the torque for autonomously stabilizing the motor is very small compared to the method of applying the constant voltage amplitude control to the SynRM of the present embodiment. On the other hand, in the method of applying the voltage amplitude constant control to the SynRM of the present embodiment, the torque that increases and decreases autonomously when the estimated coordinate advances from the real coordinate or when the estimated coordinate is delayed is a permanent magnet type synchronous motor ( Very much compared to SPM). As a result, the torque for autonomously stabilizing the motor is significantly increased as compared with the prior art, and the motor can be driven more stably.
[0037]
In addition, this invention is not limited to each embodiment mentioned above, A various change is possible in the range which does not deviate from the main point of this invention.
[0038]
For example, in the above-described embodiment, the phase difference detection unit samples the motor current detected by the sense MOSFET 31ul or the like at a predetermined period, and immediately after the polarity is reversed next from the sampling time immediately after the polarity of the sampling value is reversed. The integration value of the sine wave basic function determined by the command speed and the applied voltage phase is calculated in the period up to the sampling time, and the phase difference between the motor current and the applied voltage is detected based on the integrated value. However, it is not limited to this. For example, the integration period may be a period from a sampling time when the polarity of the sampling value is inverted after a predetermined number of consecutive times with the same polarity of 2 or more to a sampling time when the polarity of the next polarity is inverted and then the same polarity is 2 or more times. Good. FIG. 14 shows the second sampling time t2 when the polarity of the sampling value is inverted and changed from negative to positive and then becomes positive, and the period starts, and then the polarity is inverted and changed from positive to negative. In this example, the second sampling time point t11 that has continuously become negative polarity after the time is reached ends. According to this modification, since the period when the same polarity continues for a predetermined number of times after reversing the polarity of the motor current is the start or end of the period, even when the current polarity changes in small increments due to motor current chattering, It is possible to prevent erroneous detection at the start / end time more reliably.
[0039]
In the above-described embodiment, an example in which the present invention is a control device for a synchronous reluctance motor has been described. However, the control device may be configured as a control device for another type of synchronous motor having saliency. For example, the present invention may be applied to a control device for an internal magnet type permanent magnet synchronous motor (IPM motor) in which a permanent magnet is housed in a rotor core.
[0040]
In the above-described embodiment, the arm current signal of the lower arm of each phase is detected. However, the arm current signal of the upper arm may be detected.
[0041]
【The invention's effect】
As described above, according to the motor control device of the present invention, when the phase difference between the motor current and the applied voltage does not match the target phase difference, the motor current and the applied voltage are set by the applied voltage phase setting means. Since the phase of the applied voltage is controlled so that the phase difference between the two coincides with the target phase difference, the synchronous motor can be driven and controlled stably. Further, the voltage amplitude setting means sets the amplitude of the applied voltage to be applied to the synchronous motor to a predetermined value according to the command rotational speed and the command torque, so that the command rotational speed and the command torque are constant. The voltage amplitude is a constant value. At this time, due to the characteristics of the synchronous motor having saliency, the torque is autonomously generated and the rotor position autonomously returns to the target control position, so that the synchronous motor can be driven and controlled more stably. Play. Furthermore, since complicated calculation processing is not required and current detection does not have to be highly accurate, the motor control device can be configured to be small and inexpensive using an inexpensive microcomputer, current sensor, or the like. Also play.
[Brief description of the drawings]
FIG. 1 is a block diagram showing an overall configuration of a motor control device according to an embodiment of the present invention.
FIG. 2 is a circuit diagram of an inverter circuit.
FIG. 3 is a graph showing the relationship between motor current and arm current.
FIG. 4 is an explanatory diagram showing an example of calculating an integral value of a motor current waveform and a sine wave basic function.
FIG. 5 is an explanatory diagram showing a relationship between a phase difference between a motor current and an applied voltage and an integral value of a sine wave basic function.
FIG. 6 is a graph showing a relationship between a phase difference between an applied voltage and a motor current and a deviation of an estimated coordinate from an actual coordinate when control is performed with a target control phase in SynRM.
FIG. 7 is a graph showing the relationship between motor torque and deviation of estimated coordinates from actual coordinates when applying constant voltage amplitude control and applying constant current amplitude control in SynRM.
FIG. 8 is a graph showing a relationship between motor torque and deviation of estimated coordinates from actual coordinates when voltage amplitude constant control is applied to a motor having a salient pole (SynRM) and a permanent magnet synchronous motor (SPM), respectively. It is.
FIG. 9 is a vector diagram when the estimated coordinates are shifted from the actual coordinates to the advance side in the conventional method in which constant current amplitude control is applied to SynRM.
FIG. 10 is a vector diagram when the torque is reduced and the estimated coordinates are shifted further from the actual coordinates in the conventional method.
FIG. 11 is a vector diagram when the estimated coordinates are shifted from the actual coordinates to the advance side in the present embodiment in which voltage amplitude constant control is applied to SynRM.
FIG. 12 is a vector diagram in the case where the actual rotor advances due to the autonomous increase of torque in the present embodiment, and the estimated coordinates and the actual coordinates approach each other.
FIG. 13 is a vector diagram when the estimated coordinates are shifted from the actual coordinates to the delay side in the present embodiment.
FIG. 14 is an explanatory diagram showing an example of calculating an integral value of a motor current waveform and a sine wave basic function in a modified example.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 1 ... Motor control apparatus, 2 ... Synchronous reluctance motor (SynRM) (synchronous motor), 3 ... Inverter circuit, 4 ... Microcomputer, 31ul, 31vl, 31wl ... Sense MOSFET (current detection means), 43 ... Voltage phase basic value Setting unit 44 ... Voltage amplitude setting unit (voltage amplitude setting unit) 45 ... Sine wave basic function creating unit 45 ... Applied voltage duty creating unit (applied voltage duty creating unit) 48 ... Sine wave basic function integrator Phase difference detecting means), 49... Feedback section, 43, 49... (Applied voltage phase setting means).

Claims (3)

In a motor control device that drives and controls a synchronous motor having saliency with a plurality of phase motor coils by an inverter circuit composed of a plurality of switching elements,
Voltage amplitude setting means for setting the amplitude of the applied voltage applied to the synchronous motor to a predetermined value determined in advance according to the command rotational speed and the command torque;
Current detecting means for detecting a motor current of at least one of the plurality of phases;
A phase difference detecting means for detecting a phase difference between the motor current detected by the current detecting means and the applied voltage;
Applied voltage phase setting means for setting the phase of the applied voltage so that the phase difference between the motor current and the applied voltage matches a target phase difference set according to the command rotational speed and the command torque;
Applied voltage duty creating means for creating an applied voltage duty to be supplied to the inverter circuit based on the voltage amplitude set by the voltage amplitude setting means and the voltage phase set by the applied voltage phase setting means;
A motor control device comprising: The phase difference detection means samples the motor current detected by the current detection means at a predetermined period, and a period from the sampling time immediately after the polarity of the sampling value is inverted to the next sampling time immediately after the polarity is inverted. Or a sine wave in a period from a sampling time point where the same polarity is two or more consecutive times after the polarity of the sampling value is reversed to a sampling time point where the same polarity is two or more times after the polarity is next reversed The motor control device according to claim 1, wherein an integral value of a basic function is calculated, and a phase difference between the motor current and the applied voltage is detected based on the integral value. The motor control device according to claim 1, wherein the current detection unit is configured to detect a current in an upper stage or a lower stage of at least one arm of the inverter circuit.

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