KR20050052348A - Control apparatus of ac electric motor - Google Patents

Abstract

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a system for driving a field-mounted synchronous motor by a power converter without using a position detection signal. The present invention relates to a control device of an AC motor that starts a power converter in a state where a rotor or a rotor of the motor is idle. It is about.

Description

Control apparatus of an AC electric motor {Control apparatus of AC electric motor}

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a control device for starting a power converter from a state in which a rotor or a mover of an electric motor is idle in a system for driving a field-mounted synchronous motor by a power converter without using a position detection signal.

(Prior art)

FIG. 15 shows a prior art, wherein the power converter 1 is composed of a switching element and a passive element, and is supplied with electric power from an alternating current or direct current power source 4, and supplies electric power to the alternating-current motor 3. Doing. The power converter 1 is controlled by the control unit 2.

The AC motor 3 has a field magnetic pole in the rotor, and generates an induced voltage when the rotor is rotated in a terminal open state. Such an electric motor is collectively referred to herein as a synchronous motor equipped with a field. In addition, although the present application mainly describes a rotating motor, it is well known that in the case of a linear motor, the same can be considered if the rotor is read as a mover and a rotation as movement.

In the configuration handled herein, the AC motor 3 does not have a position sensor and a terminal voltage sensor of the rotor. In general, in order to drive the field-mounted synchronous motor, it is necessary to supply a voltage and a current corresponding to the position of the rotor. Therefore, in the absence of the sensor, it is necessary to estimate the rotor position in some way.

The control calculator 22 estimates the rotor position in the state of supplying power to the AC motor 3, calculates the voltage and current to be supplied by the converter 1, and applies the switching element to the switching element to realize this. Outputs the on / off signal provided. The control calculator 22 performs a process of synthesizing the current value obtained from the current sensors 5A and 5B of the motor, for example, combining the three-phase current from the two-phase current and converting it into orthogonal rotational coordinates. Information about the motor current is obtained and necessary calculation is performed based on this. Such a so-called position sensorless drive technology of field-mounted synchronous motors has been proposed in the past and will not be described here since it will not be mentioned again. As literatures described in detail regarding the position sensorless driving technique, for example, there are the followings.

Reference 1: Watannabe, et a1, "DC-Brushless Servo System without Rotor Position and Speed Sensor," Proceedings of IEEE Internatonal Conference on Industrial Electronics, Control, and Instrumentation 1987, vol. 1, pp. 228-234. (1987 )

By the way, one of the big problems in the position sensorless drive of the field-mounted synchronous motor is the method of starting the transducer in the state where the rotor is idle (called free run start). That is, as shown in Fig. 15, since the control system performs control based on the electric current of the electric motor, no information of the electric motor can be obtained at all when the converter is stopped and no electric current flows.

If the rotor is stationary, for example, the output voltage of the transducer can be adjusted so that a current flows through a phase, whereby the rotor can be positioned and then operation started. However, if the converter outputs an inappropriate voltage while the rotor is idle, current control is disabled because the motor is generating a dynamic induced voltage and cannot start, or in the worst case, the switching element of the converter due to overcurrent. If there is a permanent magnet in the motor or if the motor has a permanent magnet, there is a risk of demagnetization.

As a means for solving such a problem, a method of shorting the windings of the electric motor by means of a converter and estimating the rotor position based on the current flowing at this time is disclosed in the following document.

Reference 2: Japanese Patent Application Laid-Open No. 11-75394 "Power Converter for AC Rotors"

Claim 1 of the said document discloses the content which turns on at least one of the switching elements which comprise a power converter, and estimates the position of a rotor based on the electric current which flows at that time. Since the current flowing when the winding of the motor is shorted is determined uniformly by the rotor position and speed of the motor and the circuit constant of the motor, it is possible to calculate the position and speed of the rotor by analyzing this current. It is pointed out.

In Fig. 15, the free run start calculation section 23 generates the on / off signal to the switching element for winding short circuit, calculates the rotor position at the time of rotor idle based on the current information obtained from the processing section 21, and The starting procedure is executed based on the obtained rotor information. After the startup, the process shifts to the normal operation, so that the processing is switched to the control calculating section 22 by the switch 24. This switching is undertaken by the control switching unit 25 which controls the operation of the control unit 2.

However, in the above-mentioned patent document, after the claim 2, the behavior at the time of shorting all the phase windings of an electric motor is described, and the specific method of rotor position estimation when only a part of phase is short-circuited is not described in detail. .

Furthermore, it is presupposed that the structure which detects phase current is not assumed, and the structure which does not detect phase current is not mentioned.

The present application clarifies the above items and provides a more general free run start technique.

(Means to solve the task)

The present invention provides a power converter for an AC motor comprising a power converter for driving a multiphase AC motor and a control unit for generating and outputting an on / off signal for the switching element constituting the power converter. The control unit sets at least one group consisting of a plurality of windings of the polyphase of the electric motor, and when the motor is idle, the switching element is operated to substantially rotate the windings of the phases belonging to the group in turn for the respective groups. A short circuit is provided, and the power converter for AC motor is started based on the electric current flowing at the time of short circuit, and estimating the position of the rotor or the mover of the electric motor.

In addition, the present invention is a power converter for driving a multi-phase AC motor, and a power converter for an AC motor comprising a control unit for generating and outputting an on / off signal for the switching element constituting the power converter, the switching The device is configured by reversely connecting diodes to a plurality of self-extinguishing switching elements, respectively, and the control unit includes whether current flows and current flows when an ON signal is applied to one of the switching elements during idle of the motor. Provided is a power converter for an AC motor, characterized in that for estimating the position of the rotor or the mover of the motor based on the information on the image.

In addition, the present invention is a power converter for driving a multi-phase AC motor, and a power converter for an AC motor comprising a control unit for generating and outputting an on / off signal for the switching element constituting the power converter, the switching The device is configured by reversely connecting diodes to a plurality of self-extinguishing switching elements, respectively, and the control unit gives an ON signal to the first switching element of the switching elements when the motor is idle. If the current does not flow by the action, the ON signal is continued or interrupted until it flows, and when the current flows, the first position of the rotor or the mover of the motor is estimated based on the information on the current flow. It provides a power converter for an AC motor, characterized in that.

Moreover, in the said structure, after recording the time when a current flow was detected, in this structure, all the switching elements of a power converter are turned off, the on-signal is continuously supplied or interrupted to a 2nd switching element newly, and a current does not flow. When the state of the current flows from the current flow to the current flow, the second position of the rotor or the motor of the electric motor is estimated based on the information on the current flow, and the time when the current flow is detected is recorded. A power converter for an AC motor is provided which derives the speed of the rotor or the mover from the time of the second current detection and the position of the rotor or the mover.

Moreover, in the said structure, after recording the time which detected current flow, in this structure, all the switching elements of a power converter are turned off, a new signal is given to a 2nd switching element, and the presence or absence of current flow immediately after that is A power converter for an AC motor is provided, characterized by specifying the rotation direction of the rotor.

In addition, the present invention provides an n-phase inverter having a direct current voltage portion having a direct current voltage component, at least two switching elements connected in series and having n arm parts connected at both ends in parallel to the direct current voltage portion; An electric motor drive system comprising a field-mounted n-phase motor in which terminals are connected to connecting portions of switching elements in the n arm portions of the n-phase inverter, wherein the arm points are larger than the connection points of the terminals of the motor. When the switching element group on the positive electrode side of the direct current voltage portion is the upper arm and the switching element group on the negative electrode side is the lower arm, current flows only in the switching element group of one phase in at least one of all the upper arm and all the lower arm. In the state, the current (direct current input current) between the DC voltage section and the switching element group is detected, and the detected value is To provide a control device, characterized in that for estimating the rotor position of the mover or the electric motor.

In addition, the present invention provides an n-phase inverter having a direct current voltage portion having a direct current voltage component, at least two switching elements connected in series and having n arm parts connected at both ends in parallel to the direct current voltage portion; In an electric motor drive system comprising a field-mounted n-phase motor in which a terminal is connected to a connection portion between switching elements in the n arm portions of the n-phase inverter, the switching element connects a diode to a self-extinguishing switching element in parallel. The rotor and the rotor of the electric motor based on the current between the DC voltage section and the switching element group, that is, the DC input current, Or it provides a control device, characterized in that for estimating the position of the mover.

In addition, in the above-described configuration, the present invention alternately repeatedly applies an ON signal and an OFF signal to one of the switching elements, detects a DC input current during a period in which each OFF signal is applied, and the detected value is from zero. When it changes to a non-zero value, it provides the control apparatus characterized by determining that the rotor or the mover of the said electric motor passed through the predetermined position.

In addition, the present invention provides a DC voltage portion having a DC voltage component, at least two switching elements connected in series, n arm portions having both ends connected in parallel to the DC voltage portion, and each of the arm portions. An n-phase inverter formed by connecting a diode with a polarity that prevents a direct-current voltage of the direct-current voltage portion between one connection portion between the switching elements and each of the positive electrode and the negative electrode of the direct-current voltage portion; An electric motor drive system comprising a field-mounted n-phase motor in which terminals are connected to a point where the diodes in n arm parts are connected, wherein each arm part is located closer to the positive electrode side of the DC voltage part than a connection point of the motor terminal. If the switching element group is called the upper arm and the switching element group on the negative electrode side is called the lower arm, When the ON signal is applied to one of the upper and lower arms, the control device is characterized by estimating the position of the rotor or the mover of the motor based on the current between the arm and the direct current voltage unit. do.

In the present invention, in the above configuration, the on-signal is continuously or intermittently applied to one of the upper and lower arms, and the current between the arm and the direct-current voltage portion during application of the on-signal is zero to zero. When it is changed to a value other than, a control device characterized in that it is determined that the rotor or mover of the electric motor has passed a predetermined position.

In addition, in the above structures, the speed of the rotor is a predetermined value when the current flow is not detected even if the on-state of the switching element is continued or interrupted or the on / off repetition is repeated for a predetermined period. The control apparatus characterized by the following is provided.

In order to perform free run, the phase, frequency, and phase sequence of the induced voltage of the field-mounted synchronous motor at the time of inverter startup are estimated or detected, and predetermined voltages derived from the voltages substantially equal to these or these are determined. It is necessary to output the voltage for passing current through the inverter at the start. In addition, in the field-mounted synchronous motor, the phase, frequency, and phase of the induced voltage correspond one-to-one with the position (electric angle), speed, and direction of rotation of the rotor. Therefore, unless misunderstanding occurs in the present application, Use terms without distinction.

(Example)

A first embodiment will be described with reference to FIG. 1.

Fig. 1 shows an equivalent circuit of a field-mounted synchronous motor and a power converter when winding short-circuit operation is performed. The motor is multiphase, and each phase consists of an induced voltage component e and an impedance Z by the field.

The induced voltage of each phase is determined uniformly by the position and speed of the rotor, and the phase difference of the induced voltage between the phases is already known. On the other hand, when the influence of magnetic saturation is small, the impedance of each phase is uniformly determined by the position of the rotor even if the polarity is constant and the polarity is constant.

Therefore, the electric current which flows when the winding of several phases of a polyphase is short-circuited is also determined uniformly by the position and speed of a rotor. Therefore, by analyzing this current, it becomes possible to estimate the position and speed of the rotor.

Specifically, a method of estimating the rotor position and speed from the information of the amplitude and phase of a current flowing through only one short circuit operation, and performing a plurality of short circuit operations to perform the phase and current of each short circuit operation There may be a method of estimating the rotor position and the rotation direction from the amount of change in phase.

Next, a description will be given of the natural law and the technical idea that constitute the principle of a free run start technique using a conventional voltage inverter, which generates an AC voltage having an arbitrary frequency and amplitude from a DC voltage.

2 shows a typical form of a conventional three-phase voltage inverter. In addition, there are also multi-level inverters (showing one arm) as shown in Fig. 3, but the natural law and the technical idea shown here can be similarly applied. In addition, although a constant is arbitrary, the case of three phase is demonstrated here.

In the three-phase voltage inverter of Fig. 2, in which a diode is anti-parallel connected to a self-lowering switching element such as an IGBT, two or more are connected in series to form an arm of one phase. Both ends are connected to a DC voltage part. In each phase arm, a field-mounted synchronous motor serving as a load is connected to the connection between the switching elements.

Here, the state where all the switches of the inverter are off and the field-mounted synchronous motor is idle is considered. At this time, the field-mounted motor generates an induced voltage as shown in FIG. 4 or FIG. 5. Although the case where an induced voltage is a sine wave is shown here, there exist some which contain a harmonic component. 4 and 5 show the case of forward rotation and reverse rotation, respectively, and the upper order is different in both.

First, the case of forward rotation, that is, the case where an induced voltage is as FIG. 4 is considered. Now, when the phase of an induced voltage is between 30 degrees and 15 degrees, the organic voltage of U phase is the lowest among three phases. In this state, as shown in FIG. 3, if only the switch Qx of the arm below the U phase is turned on, the equivalent circuit is as shown in FIG. 6, and the current is applied to any phase by the action of the diodes Dy and Dz. Does not flow.

In addition, when the phase of the induced voltage is 15 ° to 210 °, or 33 ° to 30 ° (390 °), since the U-phase induced voltage is in the middle of the V and W phases, the diode ( Under the action of Dv or Dz), no current flows, and a current flows between the U phase and another one phase.

When the phase of the induced voltage is between 210 ° and 330 °, since the U-phase voltage is maximum, both Dy and Dz are positively biased, and current flows in three phases.

That is, by turning on Qx, it is possible to specify the region where the phase of the induced voltage exists by observing whether the current does not flow, flows in two phases, or flows in three phases.

The same holds true in the case of reverse rotation, and the same phenomenon occurs when other switching elements are operated.

In addition, when electric current flows in three phases, it is also possible to estimate a rotor position using the method shown by the document 2.

Therefore, for example, if Qx is initially turned on and no current flows, it is recognized that a phase exists in the region where the U phase voltage is minimum, and if Qx is turned on and current flows in two phases, either V phase or W phase The operation is to determine the position or speed of the rotor by calculation using the method shown in Document 2 when the current flows through three phases by specifying whether the current flows through the current sequence. By this, it is possible to obtain information necessary for starting the inverter.

Next, a more accurate position detection method is shown below.

Consider the case where the phase of the induced voltage is in the range of 30 ° to 15 ° in the forward rotation state and only the Qx is in the on state. In this case, when the phase of the induced voltage exceeds 150 ° by the rotation of the rotor, the magnitude relationship between the induced voltage of the U phase and the V phase is reversed as shown in FIG. 4, so that the diode Dy in FIG. ) Is forward biased, and current flow begins in the U and V phases.

On the other hand, even in the case of reverse rotation, when the phase is between 330 ° and 210 ° in FIG. 5, no current flows even when only Qx is turned on. In this case, however, when the phase is less than 210 °, as shown in Fig. 5, the induced voltages of the U and W phases are replaced, the diode Dz is forward biased, and the current flow in the U and W phases. To start.

From the above, the position of the rotor is determined by continuing the on state of the arm Qx below the U phase, detecting that current flow has started from the current non-flow state, and determining which of the V phase and the W phase has flowed. The direction of rotation can be determined as follows.

If current flowed on V, it is forward rotation and phase is 150 °

If current flowed on W, reverse rotation, phase is 210 °

When the current flows immediately when the first Qx is turned on, if the Qx is turned off once, and the Qx is turned on again to check for the presence of current flow, the Qx may be rotated one day by rotating the rotor. Since the current does not flow immediately even when turned on, the above operation may be started therefrom.

In addition, it is clear that the above-described phenomenon and determination can be similarly realized by operating any switch as well as the operation of the U-bottom lower arm.

As described above, when the rotation direction and the phase are discriminated, it is possible to specify the "switching element in which current does not flow even if it is turned on immediately after". In other words, if the phase is 150 ° in forward rotation, even if Qy or Qw is turned on quickly after turning off Qx in FIG. 2, the current does not flow immediately. On the other hand, if it is reverse rotation and the phase is 210 °, even if Qz or Qv is turned on quickly after turning off Qx, current does not flow immediately.

Therefore, when current flow is detected by continuing the on state of Qx, when Qx is turned off and the specified switching element is turned on as described above, current flow starts in a phase in which the magnitude relationship of the induced voltage is replaced as before. do.

By this operation, the phases of different induced voltages (called θ ₁ and θ ₂ ) at two time points (called t ₁ and t ₂ ) can be obtained. ) Can be obtained.

ω = (θ ₂ -θ ₁ ) / (t ₂ -t ₁ )

As mentioned above, since the phase, phase order (rotation direction), and frequency of the induced voltage were known, the inverter can be started based on these values.

In addition, the calculation accuracy of the speed can be improved by operating the switching element as described above three times or more and detecting the change of phase in a longer time interval. This is particularly effective when the time measurement can only be performed for each control period in discrete time control using a CPU or the like.

The operation shown above is shown in a flowchart, as shown in FIG.

 In addition, although the said means assumes the case where the phase current of an inverter can be detected, it is similarly applicable also in the structure which detects the electric current of the lower arm (it may be an upper arm) of an inverter as shown in FIG.

That is, in operation of the switching element shown in this application, by limiting the switching element to operate to the element which belongs to a lower arm (or upper arm), the current which flows through the lower arm (or upper arm) while turning on an element, This is because the phase current of the motor coincides in principle.

If the switch is turned off after the current flow is detected, the current on the switch cannot be detected, but the current on the other phase continues to flow through the diode of the lower arm (or upper arm) of the phase, so that it can continue to be detected. With the current being zero, it can be regarded that the current of the phase in which the switch is turned off is also zero.

As described above, only a slight change is necessary for the method of determining that the current has become zero after the switch-off. However, for other procedures and determinations, the method of current detection can be used in the same manner as in the method shown in FIG. Can be.

 However, as shown in Fig. 9, the current detection method uses a configuration in which a diode is bypassed to detect a current of the self-extinguishing type switch by bypassing the diode in the switching element in which the diodes are connected in anti-parallel to the self-extinguishing type switch. In this case, it is necessary to change some of the above methods.

First, the current when Qx is turned on can be detected using the current detector Rsu. However, at this time, current flows through either the V phase or the W phase, and the current flows through the diode Dy or Dz, and thus cannot be detected by the current detectors Rsv and Rsw. Therefore, at the start of current flow through here, the direction of rotation cannot be specified.

This problem can be solved as follows. That is, after detecting the start of current flow by Qx on, Qx is turned off, and then Qy or Qz is quickly turned on and the current of the arm of the on-phase is monitored. At this time, for example, when Qy is turned on and no current flows immediately thereafter, since it means that the induced voltage of the V phase is the minimum among the three phases, it can be determined as "forward rotation". Conversely, if the current flows immediately by turning on Qy, the induced voltage of the W phase becomes minimum, and therefore, it can be determined as "reverse rotation". The same determination can be made when Qz is turned on instead of Qy.

When the rotation direction, i.e., the upper order, is determined in this manner, the necessary information can be obtained after that by the procedure already described, and the inverter can be started. For example, if the current does not flow immediately by turning on Qy, the ON state of Qy may be continued as it is. On the contrary, if the current flows immediately by turning on Qy, Qy may be turned off quickly and on Qz.

The technical idea shown above was related with the structure which detects phase current or the current of each phase arm in an inverter. However, there is also a configuration in which the current between the DC voltage portion of the inverter and the switch group, i.e., the DC input current of the inverter (hereinafter referred to simply as DC input current) is detected without detecting the phase current. In this case, since the information of the phase current is not obtained directly, another devise is necessary.

Fig. 10 shows a configuration for detecting a DC input current in a three-phase voltage inverter. The load of the inverter is a field-mounted synchronous motor. In normal operation, the control system drives the motor based on the detection value of the DC input current. As the specific method, it is disclosed by following Document 3, for example.

Reference 3: Sato Miscellaneous: 「The Stabilization V / f Control Method of PMSM by Detection of Inverter DC Current」, The Korean Institute of Electrical Engineers 2004, No.1 to 56

In addition, the general principle in the case of performing a free run in such a structure is demonstrated using FIG. 11 conceptually illustrates a drive system by an inverter of an n-phase field-mounted motor. The motor is represented by an equivalent circuit, and displays the first to third phases, and describes the induced voltage (e) and the impedance (Z) for each phase, with the phase numbers as subscripts. Current detection of the inverter is performed only with respect to the DC input current idc.

In FIG. 11, the example of the case where the switch SIP, S2P, and S3N of an inverter is turned on and all other switches are turned off is shown. In other words, only one of the lower arms of the inverter is turned on. In this state, since idc coincides with the current of the third phase of the motor, the phase current of the third phase of the motor can be known by detecting idc.

Here, when the rotation speed can be considered to be substantially constant, the induced voltage fundamental wave ex of the x-phase of the n-phase field-mounted motor can be generally expressed as follows.

ex = ωΨsin {ωt + θx + θo}

Where ω; Electrical angle frequency, Ψ; Winding flux chains by field, t; Time, θx; x phase phase angle (but θ1 = 0), θo; Initial phase angle

Usually, 0x is an integer different for each phase, and the value of 0x of each phase is already known because it is a design matter. In addition, since the phase angle θ ₁ = 0 of the _first phase is set as described above, the initial phase angle θ o is the phase angle of the induced voltage e ₁ of the first phase at time t = 0. Further, the electric angle frequency ω is proportional to the rotational speed of the rotor, specifically, if the number of poles is P

ω = (P / 2) × 2π × N / 60 (N is the rotational speed of the rotor every minute)

Relationship is always established. In addition, since the case where the rotational speed N is almost constant is discussed, ω is unknown here, but it is called an integer.

Is also a known integer.

From the above, it is understood that the unknown in Equation 2 is two of? And? O. In addition, if these two values are known, the induced voltage ex of each phase is found out, and the system can be started by applying the voltage corresponding to this from the inverter.

On the other hand, it is known that the impedance Zx of each phase becomes a function of only the magnetic pole position, that is, a value specified by ω and θo.

Therefore, in a state where the rotor is idle and ω and θo are unknown, it can be seen that the current flowing when the switch is turned on, as shown in FIG. 1, becomes different from ω and θo.

Therefore, the DC input current idc at this time, and the current of the third phase of the motor in the example of FIG. 11 include information of ω and θo, and it is possible to specify ω and θo using the detection value of idc. .

Specifically, since the unknown number is two types of ω and θo and only the information obtained is idc, it becomes one type, and ω and θo cannot be specified by this alone, but two or more times after turning on the corresponding switch in FIG. 11. Detects idc or detects idc every time the switch is turned on two or more times, or after the first switch-on operation, idc is detected and all switches are turned off and another switch group is By detecting idc by turning it on, two or more values can be obtained as idc, and different circuit equations can be obtained each time. Therefore, since two or more equations exist for two unknowns, in principle, ω and θo Can be obtained.

In the above description, the operation in the case where the specific switches (SIP, S2P, and S3N) are turned on is taken as an example, but the above principle is established regardless of the constant and the operating switch. However, if the upper and lower arms of the same phase are turned on at the same time, the DC voltage section of the inverter is short-circuited. Therefore, it is necessary to turn on only one phase to at least one of the upper and lower arms and turn on the other phase to the other.

In the above description, the case where one phase switch is turned on for at least one of the upper and lower arms has been described. However, by using idc when only one switch is turned on for both the upper and lower arms, an operation that eliminates ambiguity can be performed. Can be. That is, in the state of FIG. 11, only the sum of the electric currents of a 1st phase and a 2nd phase is known, and each value is unknown. On the other hand, for example, in FIG. 11, when only the upper arm S1P of the first phase and the lower arm S3N of the third phase are turned on, the currents of the first and third phases coincide, that is, both values are known. . Therefore, since the circuit equation in the case of obtaining ω and Qo as described above is simplified and the calculation load of the CPU is reduced, the apparatus can be configured at low cost.

As a configuration for detecting the DC input current, in addition to the configuration shown in FIG. 10, as shown in FIG. 12, a current that bypasses the diodes of the upper and lower arms (may be the upper arm) may be detected. The characteristic of the scheme of FIG. 12 is that only the current in one direction is detected, and the reflux current flowing between the lower arms, for the case of FIG. However, in the above-described method, the detected current is the same in both the configuration of FIG. 10 and the configuration of FIG. 12. Therefore, the above-described derivation method of ω and θo can also be used in the configuration of FIG. 12.

Further, by applying the technical idea already described with reference to Figs. 2 to 6, it is possible to realize simpler free run starting based on the detection value of the DC input current, which will be described below.

FIG. 13 shows an example of a method of operating a switch at the time of performing a free run in the configuration of FIG. 10. First, as shown in Fig. 13A, the case where only Qx is turned on is considered. At this time, if a current flows, the current circulates between at least one of Qx, Dy, or Dz and the electric motor, and does not appear as idch, so current detection is not possible.

Next, Qx is turned off, and all the switches are in the off state. In this case, since the impedance of the motor has an inductance component, the current does not immediately become zero, and the U-phase current flows through the diode Du of the upper arm and flows to the power supply side. In this way, an electric current flows in the path | route of the DC power supply part, Dy or Dz, an electric motor, and Du, and idc appears. When the U-phase current is attenuated to zero, the current is cut off by the action of the diode, and the current is in a non-current state.

Therefore, by turning off Qx after turning on Qx and ideally detecting idc immediately after turning it off, it is possible to determine whether current flows by turning on Qx.

That is, by the above operation, by idc detection, it is possible to determine whether the phase of the induced voltage is within a range where the U phase voltage is minimum or not.

Further, if the on / off signal is repeatedly applied to Qx, idc is detected while the respective off signals are applied, and idc becomes zero while the operation continues, the phase of the induced voltage is the minimum of the U phase induced voltage. It can be considered that it entered the range (30 degrees-150 degrees in the case of forward rotation, 210 degrees-330 degrees in the case of reverse rotation). After that, if the on / off operation of Qx is continued again and idc disappears again to zero, it can be considered that the rotor position has passed 150 ° (210 ° in the case of reverse rotation) at an electric angle. That is, although there is a delay from the start of the U-phase current flow to the detection of idc ≠ 0, the rotor position can be specified by the pin point. When the on / off operation of Qx is performed at a high frequency, the delay can be shortened, or the time delay can be predicted and corrected in advance.

Further, if it is determined that the specific phase angle has passed as described above by the on / off operation of Qx, immediately after that, even if one of Qy or Qz (which may be Qv or Qw) is turned on or off, idc = becomes o. As described above, immediately after the passage of the phase angle, as shown in FIGS. 4 and 5, the induced voltage of either phase of the V phase or the W phase is minimized, and the lower arm of the phase is turned on. Even if the current does not flow.

Therefore, immediately after the passage of the phase angle, for example, Qy is turned on and off, and idc immediately after turning off is detected, and if the detected value is zero, it can be determined that the forward rotation is performed, and if the detected value is not zero, the reverse rotation. Subsequently, the on / off operation of Qy and the detection of idc are continued if the forward rotation is performed, and it can be determined that the phase of the induced voltage has passed 270 ° by idc disappearing to zero, and if the reverse rotation, Qz instead of Qy. The on / off operation of can be performed, and it can be judged similarly that the phase of the induced voltage passed 90 degrees.

In this way, since the time when the phase of the induced voltage passes through two specific points is found out, the frequency can be calculated by the equation (1).

As described above, also in the method of detecting the DC input current, the phase, phase, and frequency of the induced voltage can be obtained by applying the above-described technical ideas using Figs. Can be done.

On the other hand, when the configuration of FIG. 12 described above is used as the configuration of the detection unit of the DC input current, the current flowing back to the lower arm can be detected. Therefore, whether the current flows by turning on one of the switches of the lower arm. Can be determined directly.

Fig. 14 shows an example of a path of current when the Qx which is an arm switch below the U phase is turned on. As can be seen from this figure, when current flows to the motor by turning on Qx, the current can be detected as a direct current input current.

Therefore, as explained above, for example, if current does not flow immediately after turning on Qx, the phase of the induced voltage is within the range where the U-phase voltage becomes the minimum among the three phases (30 ° to the forward rotation). 150 ° and in the case of reverse rotation, 210 ° to 330 °), and if the current flows in reverse, it is found to be in another range.

In addition, it can be determined that the phase of the induced voltage has passed 150 ° or 210 ° by continuing the on state of Qx and shifting the current from zero to a non-zero state.

However, as in the case of the configuration of Fig. 10, since it is not clear which current flows through either the V phase or the W phase, the direction of rotation cannot be immediately determined. As for the problem, as in the case of the configuration in Fig. 10, the direction of rotation can be determined by turning on either Qy or Qz and observing whether or not current flows through it. The principle is the same as the method in the structure of FIG.

After that, if the forward rotation is continued, the on state of Qy is continued. If the reverse rotation is continued, the ON state of Qz is continued instead of Qy, and the DC input current shifts from zero to nonzero again, thereby providing a phase of the induced voltage. If it is this forward rotation, it can be judged that it passed 270 degrees, and if it is reverse rotation, 90 degrees, and it becomes possible to calculate a frequency by Formula (1).

By the way, in the above description, in the method in which the current flow used for detecting the phase of the induced voltage is caused by the induced voltage of the electric motor, when the rotation speed of the rotor is low, that is, the amplitude of the induced voltage is small, The current may also be small and not detected. By using this, if a current is not detected for a predetermined time after starting operation of the switch, it can be determined that the rotational speed of the rotor is equal to or less than a predetermined value. Then, for example, countermeasures such as shifting to processing when the rotational speed is low can be performed.

In the free run starting method shown in Document 2, while the information of the induced voltage or the rotor is obtained by calculation using the amplitude or phase of the current, the means shown in the present application can obtain necessary information by determining only the presence or absence of the current. Therefore, there is a characteristic advantage that the algorithm is simple and more difficult to be affected by the current detection error.

In the above description, the case where a rotating machine is mainly used has been described, but the technique disclosed herein can be similarly applied to the case where a linear motor is used instead of the rotating machine. This can be made clear in view of the electrical similarity between the rotor and the linear motor.

In addition, although the three-phase case was mainly described, the technique disclosed in the present application can be similarly applied to any multi-phase AC electric power converter.

In addition, although the organic voltage waveform was explained as being a three-phase balanced sine wave, even if some harmonics are contained or there is a phase shift substantially present in the three-phase organic voltage, the essence in the present application is not affected. Technology can be applied.

It goes without saying that the above-described technique is similarly applicable to the case where the electric motor is used as a power source or when the motor is used as a generator.

Moreover, also in the apparatus in which a rotor or a mover has a position sensor or a sensor of a terminal voltage of an electric motor, it is naturally possible to apply the technique disclosed herein without using the information obtained from them. Such a thing is considered to be implemented as a technique for backup in the case of a sensor failure, for example.

In addition, in the above description, the winding is short-circuited, but in reality, there is a voltage drop in the switching element and the cable connecting the converter and the motor. However, the voltage drop is small compared to the electric constant of the motor, and can be regarded as a short circuit state substantially. In addition, considering the analysis of such small voltage drop circuit behavior, more accurate rotor position estimation becomes possible.

In addition, even when a passive element such as a filter is inserted between the inverter and the motor, in view of the impedance, the above-described method can be used without changing the gist.

1 is a diagram showing an equivalent circuit of a field-mounted synchronous motor and a power converter when winding short-circuit operation is performed.

2 shows a representative form of a conventional three-phase voltage inverter.

3 illustrates a multilevel inverter.

4 is a graph showing a change direction of an electric angle during forward rotation of a field-mounted motor.

Fig. 5 is a graph showing the direction of change in electric angle during reverse rotation of the field-mounted motor.

Fig. 6 is an equivalent circuit diagram when only the switch Qx of the arm below the U phase is turned on.

7 is an operation flow chart for determining the phase and frequency of induced voltage.

8 is a configuration circuit diagram for current detection of upper and lower arms of an inverter.

9 is another configuration circuit diagram of current detection of upper and lower arms of the inverter.

10 is a configuration circuit diagram illustrating a configuration of detecting a DC input current.

11 is a conceptual diagram of a drive system by an inver of an electric motor.

Fig. 12 is a circuit diagram of still another configuration showing the configuration of detecting a DC input current.

FIG. 13 is a diagram showing an example of switch operation when the free-run start of FIG. 10 is performed;

14 is a diagram showing a current path when the arm switch below the U phase is turned on.

15 shows a conventional example.

(Explanation of symbols for the main parts of the drawing)

1: converter 2: control unit

3: AC motor 4: power

21 processing unit 22 control operation unit

Claims (11)

In the power converter for an AC motor having a power converter for driving a multi-phase AC motor, and a control unit for generating and outputting an on / off signal for the switching element constituting the power converter, The control unit, At least one group consisting of windings of a plurality of phases of the polyphase of the motor is set, and when the motor is idle, the switching element is operated to substantially short-circuit the windings of the phases belonging to the group in sequence for the respective groups, and short-circuited. And a power converter for starting the power converter by estimating the position of the rotor or the mover of the motor on the basis of a current flowing in the city. In the power converter for AC motor having a power converter for driving a multi-phase AC motor, and a control unit for generating and outputting an on / off signal for the switching element constituting the power converter, The switching element is configured by inversely connecting diodes to a plurality of self-extinguishing switching elements, respectively, The control unit, Characterized in that the position of the rotor or the mover of the electric motor is estimated based on the presence or absence of current flow in the case where an ON signal is applied to one of the switching elements when the motor is idle, Power inverter. In the power converter for AC motor having a power converter for driving a multi-phase AC motor, and a control unit for generating and outputting an on / off signal for the switching element constituting the power converter, The switching element is configured by inversely connecting diodes to a plurality of self-extinguishing switching elements, respectively, The control unit, When the motor is idle, an ON signal is given to the first switching element of the switching elements, and if the current does not flow by the action of the diode, the ON signal is continued or interrupted until it flows. And flows, the first position of the rotor or the mover of the electric motor is estimated on the basis of the information on the current flowed. The method of claim 3, wherein After recording the time when the current flow is detected, if all switching elements of the power converter are turned off, and the ON signal is continuously supplied or interrupted to the second switching element, and the current transitions from the non-flow state to the flow state, Estimate the second position of the rotor or mover of the motor based on the information of the current flowed phase and record the time when the current flow was detected; A power converter for an AC motor, characterized in that the speed of the rotor or the mover is derived from the obtained time of the first and second current detection and the position of the rotor or the mover. The method of claim 3, wherein After recording the time when the current flow was detected, turning off all the switching elements of the power converter, giving a new signal to the second switching element, and specifying the direction of rotation of the rotor by the presence or absence of current flow immediately thereafter. Power inverter for AC motor characterized in that. An n-phase inverter having a direct current voltage portion having a direct current voltage component and at least two switching elements connected in series and having n arm portions connected at both ends in parallel to the direct current voltage portion; In an electric motor drive system comprising a field-mounted n-phase motor in which a terminal is connected to a connection portion between switching elements in the n arm portions of the n-phase inverter, In the arm parts, when the switching element group on the positive electrode side of the DC voltage portion is the upper arm and the switching element group on the negative electrode side is lower arm than the connection point of the terminal of the motor, all of the upper arm and all lower arm In a state in which a current flows in only one phase of the switching element group in at least one side, a current (direct current input current) between the DC voltage section and the switching element group is detected, and the rotor or the movable of the motor is based on the detected value. A control device for estimating the position of the ruler. An n-phase inverter having a direct current voltage portion having a direct current voltage component and at least two switching elements connected in series and having n arm portions connected at both ends in parallel to the direct current voltage portion; In an electric motor drive system comprising a field-mounted n-phase motor in which a terminal is connected to a connection portion between switching elements in the n arm portions of the n-phase inverter, The switching element is configured by connecting a diode to a self-extinguishing switching element in parallel, When at least one on signal and one off signal are applied to one of the switching elements in the inverter, the position of the rotor or the mover of the motor is set based on the current between the DC voltage portion and the switching element group, that is, the DC input current. A control device, characterized in that for estimating. The method of claim 7, wherein When an on signal and an off signal are alternately repeatedly given to one of the switching elements, and a direct current input current is detected during the period in which each off signal is applied, the detected value is changed from zero to a non-zero value. And determining that the rotor or mover of the electric motor has passed through the predetermined position. A DC voltage portion having a DC voltage component, at least two switching elements connected in series, and n arm portions whose both ends are connected in parallel to the DC voltage portion, and switching elements in the arm portions An n-phase inverter formed by connecting a diode between one connection portion and each of the positive electrode and the negative electrode of the DC voltage portion, with a polarity preventing the DC voltage of the DC voltage portion; In an electric motor drive system comprising a field-mounted n-phase motor in which a terminal is connected to a point where the diodes in the n arm portions of the n-phase inverter are connected. In each arm part, when the switching element group in the positive electrode side of the said DC voltage part rather than the connection point of the said electric motor terminal is made into the upper arm, and the switching element group in the negative electrode side is a lower arm, When the ON signal is applied to one of the upper arm and the lower arm in the inverter, the position of the rotor or the mover of the electric motor is estimated based on the current between the arm and the DC voltage unit. Device. The method of claim 9, When the ON signal is continuously or intermittently applied to one of the upper arm and the lower arm, and the current between the corresponding arm and the DC voltage portion while applying the ON signal is changed from zero to a non-zero value, the electric motor And determining that the rotor or the mover has passed the predetermined position. The method according to any one of claims 3, 7, and 9, The control apparatus characterized in that it determines that the speed of a rotor is below a predetermined value, when current flow is not detected, even if repeating a continuous period or interruption | interval of a switching element, or repeating ON / OFF for a predetermined period.