JP5640865B2 - Cell multiplex inverter - Google Patents

Description

  The present invention relates to a cell multiple inverter that performs variable speed control of a PM motor (Permanent Magnet Synchronous Motor) by magnetic pole position estimation, and in particular, estimates a rotor magnetic pole position by applying a pulse voltage or a high-frequency voltage to the PM motor. The present invention relates to PM sensor position sensorless control using magnetic pole position estimation values.

(1) Cell multiplex inverter A cell multiplex inverter has a plurality of DC link portions insulated by an input transformer instead of a single inverter, such as a conventional 2-level inverter or 3-level inverter, and is called a cell unit. Patent Documents 1 and 2 disclose conventional techniques capable of outputting a multi-stage voltage in which the outputs of each cell unit are superimposed by serially connecting a single-phase inverter composed of a single-phase bridge circuit in multiple stages. There is. Further, there is Patent Document 3 as a regenerative cell multiplex inverter.

  FIG. 3 shows the overall configuration of the cell multiplex inverter, and FIG. 4 shows the main circuit configuration of the cell unit. In FIG. 3, each phase arm for applying a voltage to the U, V and W phases of the AC motor Motor connects the output terminals of the cell units U1 to U3, V1 to V3 and W1 to W3 in series (cell multiplexing). The AC power supplies of the cell units U1 to U3, V1 to V3, and W1 to W3 are taken in from the secondary windings of the common input transformer TR, and the AC motor Motor can be supplied with variable speed drive AC current.

  When each arm of each cell unit is a cell multiplex inverter that performs PWM control, a high voltage output can be obtained by making the phase of the carrier signal the same in the cell units of the same arm. Furthermore, by switching the phase of the carrier signal, uniform switching can be obtained between the units, between the phases, and within the phases (see, for example, Patent Document 1). Furthermore, a PWM inverter having an equivalently high carrier frequency can be realized by setting the carrier signals to different phases.

(2) Magnetic pole position estimation Currently, a sensorless control technology for a PM motor that detects the position of a rotor magnetic pole of a PM motor without using a position sensor and realizes motor drive control has been established. In this sensorless control, if the control is performed while the rotor magnetic pole position is unknown when the inverter is started, the PM motor may step out. Therefore, a pulse for estimating the magnetic pole position is applied to the winding of the PM motor when the inverter is started. There is a method for estimating the initial magnetic pole position from changes in the current and voltage of the PM motor when a voltage is applied (see, for example, Patent Document 4).
FIG. 5 is a pulse current path diagram of a PM motor driven by a two-level inverter, and FIG. 6 shows an example of a pulse voltage and a winding current waveform applied to the PM motor. The PM motor utilizes the fact that the impedance of the armature winding changes depending on the rotor magnetic pole position, and applies this pulse voltage to the armature winding of the PM motor while changing the electrical angle phase of the pulse voltage generated from the inverter. Thus, the inductance is measured from the change in the current flowing through the winding of the PM motor, and the electrical angle phase at which the inductance is minimized is estimated as the magnetic pole position.

(3) Sensorless control of PM motor in low speed range by harmonics The magnetic pole position estimation method by applying the pulse voltage described above can estimate the magnetic pole position when the PM motor is in a stopped state. However, if the PM motor is rotating at the time of magnetic pole position estimation, the PM motor rotates during the magnetic pole position estimation process and the winding inductance changes. is there. Moreover, since the applied pulse voltage is small, the output voltage error is large, and a static estimation mechanism such as a magnetic flux observer has a problem that the model parameter error becomes large.

  In contrast to this method, there is a method in which a harmonic current is positively passed through the PM motor winding and the magnetic pole position is estimated from the behavior even when the PM motor is rotating at a low speed (for example, see Patent Document 5). In this method, a sinusoidal high-frequency voltage is injected into the d-axis current command (field component) of the vector control inverter, and the harmonic current contained in the q-axis current obtained by rotating coordinate conversion is extracted from the detected current of the motor at this time. The magnetic pole position is estimated from the phase of the harmonic current. Alternatively, from the d and q axis currents idc and iqc obtained by rotating the motor detection current, the harmonic current components included therein are extracted, and the mapping of the harmonic current components to the positive phase axis and the negative phase axis is obtained. The asymmetry of these two mapping components is obtained as a feature value, and the magnetic pole position is estimated from this feature value.

JP 2005-278266 A JP 2006-109688 A JP 2006-230027 A JP 2001-78486 A JP 2003-153582 A

  Conventional techniques of Patent Documents 1 to 3 are inventions of a cell multiplex inverter, and there is no mention of estimation of the magnetic pole position of a PM motor.

  In the magnetic pole position estimation method described in Patent Document 4, a pulse voltage is applied to a PM motor, and impedance is measured from current characteristics. At this time, by utilizing the change in inductance due to the field direction of the permanent magnet, voltage pulses are output at various angles on fixed coordinates, thereby measuring the change in impedance. However, if a pulsed voltage is applied, the current also flows in the direction of generating torque, which may cause the motor to rotate. If the motor rotates during estimation of the magnetic pole position, This makes it impossible to accurately estimate the position of the magnetic pole.

  To prevent this, the current that generates torque can be suppressed by narrowing the width of the pulse voltage, but the voltage detection time is also shortened by shortening the flow time to the PM motor, and the width of the pulse voltage. Narrowing causes a problem of voltage accuracy.

  On the other hand, in the method described in Patent Document 5, since the high frequency component is injected into the d-axis current (field component) command while the PM motor is rotating at a low speed, the generation of the torque component due to this high frequency component injection is suppressed. However, as with the magnetic pole position estimation method by applying a pulse voltage, the inverter output flowing through the PM motor winding can output only a DC voltage with the amplitude of the pulse voltage containing high frequency components. There is a problem of heat generation due to generation or excessive high frequency.

  An object of the present invention is to provide a cell multiplex inverter capable of estimating the magnetic pole position by suppressing the generation of rotational torque in the motor by applying a pulse voltage, and further estimating the magnetic pole position by suppressing noise from the motor and heat generation of the motor. It is to provide.

  In order to solve the above problems, the present invention outputs a pulse voltage or a high-frequency voltage for magnetic pole position estimation only to some of the cell units of the cell multiplex inverter, and the PM motor current and voltage at this time The magnetic pole position is estimated from the change of the above, and has the following configuration.

(1) Each phase arm that applies a voltage to the U, V, and W phases of the PM motor is connected in series with the output terminals of the cell unit that is composed of a single-phase inverter composed of a single-phase bridge circuit. In the cell multiplex inverter that outputs a multi-stage voltage in which the output of each cell unit is superimposed,
At the time of starting the inverter, a pulse voltage for magnetic pole position estimation is output only from some of the cell units, and applied to the armature winding of the PM motor while changing the electrical angle phase of the pulse voltage, Magnetic pole position estimation means for estimating the magnetic pole position from the inductance obtained from the change in current flowing in the winding of the PM motor by this pulse voltage is provided.

(2) Each phase arm that applies a voltage to the U, V, and W phases of the PM motor is connected in series with the output terminals of the cell unit that is composed of a single-phase inverter composed of a single-phase bridge circuit. In the cell multiplex inverter that outputs a multi-stage voltage in which the output of each cell unit is superimposed,
During rotation of the PM motor, a high frequency voltage for magnetic pole position estimation is injected into the voltage command of some of the cell units, and the magnetic pole position is determined from the high frequency current component included in the detected current of the PM motor at this time. It is characterized by comprising magnetic pole position estimating means for estimating.

  As described above, according to the present invention, only a part of the cell units of the cell multiplex inverter outputs a pulse voltage for magnetic pole position estimation or injects a high frequency voltage as a d-axis current command. Since the magnetic pole position is estimated from changes in the PM motor current and voltage, the following effects are obtained.

  (1) By reducing the amplitude of the pulse voltage, it is difficult to apply excessive torque to the motor, and it is possible to estimate the magnetic pole position while suppressing the rotational force of the rotor.

  (2) By estimating the magnetic pole position using the high-frequency current during motor rotation, noise from the motor and heat generation from the motor can be suppressed.

1 is a main circuit configuration diagram of a cell multiple inverter in Embodiment 1. FIG. FIG. 3 shows an example of a pulse voltage and a winding current waveform applied to the PM motor in Embodiment 1. FIG. The whole block diagram of a cell multiplex inverter. The main circuit block diagram of a cell unit. The pulse current path figure of PM motor. The example of the pulse voltage and winding current waveform which are applied to the conventional PM motor.

(Embodiment 1)
FIG. 1 is a main circuit configuration diagram of the cell multiplex inverter of the present embodiment. This figure shows a configuration in which a pulse voltage for estimating the magnetic pole position is applied between the U phase and the V phase as a configuration for estimating the magnetic pole position of the PM motor by the cell multiplex inverter.

  1 shows cell units in U phase and V phase (a DC voltage is obtained by a rectifier that rectifies an AC voltage, and this DC voltage is constituted by a single-phase inverter by a single-phase bridge circuit) U1 Although the case of a cell multiple inverter in which U3, V1 to V3 are connected in series in three stages is shown, the number of cells connected in series is not limited to three stages, and the rated voltage of the driving PM motor and the switching used for the inverter It is determined appropriately according to the rated voltage of the element. Moreover, the AC voltage of the cell unit is obtained by an input transformer (not shown).

  Since the cell multiplex inverter can output a voltage for each of the multi-stage cell units, in this embodiment, only one cell unit U3 among the cell units between U and V before starting the PM motor has various fixed coordinates. A pulse voltage is output for a certain angle, and the position of the magnetic pole is estimated.

  In the configuration of FIG. 1, when a three-stage cell unit system for each phase outputs a pulse voltage of + Vdc for all three stages, a pulse voltage of 3 × Vdc is output per phase. The switching element is turned on to output a 1 × Vdc pulse voltage.

  Considering the line between U and V, there are six cell units, and if the switching element is turned on so as to output the pulse voltage to only one cell unit U3 (the switching element in FIG. 1). As shown in the example of the pulse voltage for estimating the magnetic pole position and the winding current waveform applied to the PM motor in FIG. 2, the amplitude of the pulse voltage is the pulse voltage when all the cell units output. Compared to the above, the voltage becomes “1 / (number of stages × 2)”, and the amplitude of the pulse voltage can be reduced, so that the current flowing through the winding can also be reduced.

  As a result, the pulse voltage amplitude can be suppressed and the torque applied to the PM motor by the pulse voltage can be reduced in the magnetic pole position estimation at the start of the inverter, so the PM motor rotor can be fixed using a brake mechanism or the like. Therefore, an accurate magnetic pole position can be estimated.

  Note that the number of cell units that output a pulse voltage is not limited to one unit, and the pulse voltage can be output only to some of the cell units of the cell units of the cell multiple inverter.

(Embodiment 2)
In this embodiment, the main circuit configuration of the cell multiplex inverter is the same as that shown in FIG. 1, and the control circuit configuration for magnetic pole position estimation is the same as in Patent Document 5, except that the cell unit has a three-stage configuration. A sinusoidal single vibration high-frequency voltage is injected into the d-axis current command of the vector control inverter, and the magnetic pole position is estimated from the high-frequency detection current of the PM motor.

  The magnetic pole position estimation according to this embodiment will be described. The cell multiplex inverter can output a voltage with different voltage commands for each of the cell units connected in series, and the PM motor is driven and controlled by the cell multiplex inverter when the PM motor rotates. Note that a method for driving and controlling the PM motor by the cell multiplex inverter is performed by a known technique such as a PWM control method disclosed in Patent Documents 1 to 3, for example.

  Furthermore, in this embodiment, only a high-frequency current is extracted from the detected current of the motor by superimposing a high-frequency voltage on the voltage output of the fundamental wave component of the motor drive control in only some units of the cell multiplex inverter (only the high-frequency component is extracted) The high frequency component may be separated by a known technique such as separation of the fundamental wave component using a filter such as HPF), and the impedance is obtained from the high frequency voltage and the extracted high frequency voltage. Based on this, the magnetic pole position when the PM motor rotates can be estimated.

  For example, in a system with three cell units per phase, if a switching element is controlled so that an arbitrary cell unit that outputs a voltage of a basic component for motor drive control outputs a high-frequency voltage alternately one by one Compared with the case where all three cell units synchronously output a high-frequency voltage, the amplitude of the high-frequency voltage becomes 1/3. Considering the line between U and V, there are six cell units. If only one cell unit is superposed on the fundamental wave, the switching unit is controlled so that the cell unit alternately outputs a high-frequency voltage. The amplitude of the high-frequency voltage becomes “1 / (number of stages × 2)” compared to the voltage amplitude when all the cell units output the high-frequency voltage synchronously, and the amplitude of the high-frequency voltage can be reduced. For this reason, since the amplitude of the high frequency voltage can be reduced, the high frequency voltage width can be expanded, voltage errors due to dead time can be reduced, useless high frequency can be suppressed, and noise and heat generation from the motor can be suppressed.

  The unit that outputs the high-frequency voltage is not limited to one unit, and the high-frequency voltage can be output only to some of the cell units of the cell multiplex inverter.

U1 to U3, V1 to V3, W1 to W3 Cell unit Motor AC motor TR3 Input transformer

Claims (2)

Each phase arm that applies a voltage to the U, V, and W phases of the PM motor is connected in series to the output terminals of the cell units that are each composed of a single-phase inverter that is composed of a single-phase bridge circuit. In a cell multiple inverter that outputs a multi-stage voltage in which the output of a cell unit is superimposed,
At the time of starting the inverter, a pulse voltage for magnetic pole position estimation is output only from some of the cell units, and applied to the armature winding of the PM motor while changing the electrical angle phase of the pulse voltage, A cell multiplex inverter comprising a magnetic pole position estimating means for estimating a magnetic pole position from an inductance obtained by a change in current flowing in a winding of a PM motor by the pulse voltage. Each phase arm that applies a voltage to the U, V, and W phases of the PM motor is connected in series to the output terminals of the cell units that are each composed of a single-phase inverter that is composed of a single-phase bridge circuit. In a cell multiple inverter that outputs a multi-stage voltage in which the output of a cell unit is superimposed,
During rotation of the PM motor, a high frequency voltage for magnetic pole position estimation is injected into the voltage command of some of the cell units, and the magnetic pole position is determined from the high frequency current component included in the detected current of the PM motor at this time. A cell multiplex inverter comprising magnetic pole position estimating means for estimating.

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