JP4154886B2 - Residual voltage detection device for permanent magnet synchronous motor - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a device for detecting a residual voltage absolute value when a permanent magnet synchronous motor with a braking winding is driven using a PWM inverter device.
[0002]
[Prior art]
When a permanent magnet synchronous motor with a braking winding (hereinafter referred to as PM motor) is driven using a voltage-type PWM inverter device, V / f constant control may be performed without using a rotor position detector.
[0003]
FIG. 9 shows an example of a system configuration diagram for performing V / f constant control. Reference numeral 1 denotes an inverter circuit. The inverter circuit includes a forward conversion circuit COV and an inverse conversion circuit INV. After the full-wave rectification of the alternating current from the AC power source 5 by the forward conversion circuit CON, the inverter circuit converts it to a desired frequency by the reverse conversion circuit INV. And output to the PM motor 3. Reference numeral 2 denotes a control unit which is composed of a digital circuit using a microcomputer or a logic IC. That is, the frequency setting signal is applied to the V / f setting device 21 and the phase integrator 22, and the phase setting signal from the phase integrator 22 is converted into a sine wave corresponding to the phase signal in the three-phase sine wave generator 23, The sine wave signal is output to the comparator 24 after corresponding to the voltage setting from the V / f setting device 21. The comparator 24 receives the triangular wave from the triangular wave generator 25, and the triangular wave and the sine wave are compared in the comparator 24, and a PWM signal is generated via the dead time generator 26 based on the error signal. Then, this signal is applied to the gates Gu, Gx, Gv, Gy, Gw, Gz of each switching element of the inverse conversion circuit to control the output voltage of the inverter circuit. Tu, Tv, Tw, Tx, Ty, and Tz are switching elements that constitute the inverse conversion circuit INV.
[0004]
When a power failure occurs while driving the PM motor 3 using the inverter apparatus configured as described above, the PM motor 3 enters a free-run state. When power is restored during this free run, the PM motor 3 is restarted. As the restarting method, the following is considered.
(1) Assuming that the output current capacity of the inverter circuit 1 has a sufficient margin with respect to the PM motor direct input starting current, the inverter circuit 1 is restarted in anticipation of synchronous pull-in by the brake winding.
(2) The residual voltage (amplitude, frequency, magnetic pole position) of the PM motor during free running is detected by some method, the output voltages of the inverter circuits are matched, and the current is restarted from the zero state.
[0005]
In a system in which a plurality of small-capacity motors are driven by a single inverter device, the method (1) has no problem, but when the inverter device and the PM motor become a one-to-one (~ 3) system ( If the method of 2) is not adopted, not only is it uneconomical, but also the fault voltage exceeds the overcurrent capacity of the inverter circuit due to the difference between the residual voltage at the time of restart and the output voltage of the inverter circuit. It is common. Therefore, an apparatus that drives a PM motor without using a rotor position detector may include an absolute value detection circuit and a zero-point passage detection circuit for residual voltage (here, line voltage) during free run. In the case of detecting the residual voltage in the prior art, a transformer is used because of the ease of insulation, and a residual voltage detection circuit 4 is provided as shown in FIG. It is known that the output terminals (U, V, W) are divided by a resistor, and half-wave rectified before being taken into a control unit.
In the residual voltage detection circuit 4, R41 to R46 are voltage dividing resistors, D41 to D43 are diodes constituting a half-wave rectifier circuit, and AMP is an insulation amplifier.
[0006]
[Problems to be solved by the invention]
When the former transformer is used, it is easy to insulate, but has a problem that it is difficult to reduce the size because saturation at a low frequency is taken into consideration.
The latter half-wave rectification method is inexpensive and enables downsizing. However, a plurality of inverter circuits are connected to the same DC link, or a connection cable to the PM motor is closely connected. As a result of examination, it was found that the detected value is larger than the actual residual voltage value due to the influence of the neutral point potential fluctuation due to switching of the inverter circuit in operation and the stray capacitance of each part of the circuit.
[0007]
FIG. 10 shows a simulation circuit implemented to confirm the neutral point potential fluctuation. As a simulation condition, the 400 V inverter device is used, and the PM motor is free-runned at a line voltage equivalent to 200 V / 50 Hz. It is assumed that a stray capacitance of 1000 pF exists between the N pole of the inverter circuit and the ground. The neutral point potential is assumed to fluctuate at 3 kHz in a square wave shape.
[0008]
FIG. 11 shows a case where there is no neutral point potential fluctuation. A point where the output of the half-wave rectifier circuit in the residual voltage detection circuit 4 is amplified by the amplifier AMP-1 is defined as a measurement point Vdet0, and the signal is further expressed by the amplifier AMP. The signal filtered at -2 is the measurement point Vdet1.
[0009]
FIG. 12 shows a case where the neutral point voltage is varied by 200V.
As is clear from a comparison between FIG. 11 and FIG. 12, the detected value of the residual voltage differs due to the fluctuation of the neutral point potential, and the rate of change is 152% (= 4.23 V / 2.78 V). Yes.
[0010]
An object of the present invention is to provide a residual voltage detecting device that is not affected by neutral point potential fluctuations due to switching of an operating inverter circuit and stray capacitance of each part of the circuit.
[0011]
[Means for Solving the Problems]
In the present invention, a permanent magnet synchronous motor is connected to the output side of the three-phase inverter circuit, and the residual voltage during free run of the synchronous motor is detected.
A full-wave rectifier circuit is connected between each phase on the output side of the three-phase inverter circuit and the negative electrode through a voltage divider circuit consisting of a resistor, and a resistor and a capacitor are formed between the voltage divider circuit and the full-wave rectifier circuit. A spike voltage prevention circuit is connected , and a residual voltage is obtained by differentially amplifying a signal between each phase output side and the negative electrode of the inverter circuit.
[0013]
DETAILED DESCRIPTION OF THE INVENTION
FIG. 1 shows an embodiment of the present invention, which is the same as the conventional one shown in FIG. 9 except that the residual voltage detection circuit 10 is different. Therefore, the duplicate description of the same part is omitted.
Residual voltage detection circuit 10 has a voltage dividing circuit 11 composed of resistors R11 to R16 provided to divide each phase voltage of inverter circuit 1, and each voltage divided by diodes D11 to D16 is full-waved. A full-wave rectifier circuit 12 for rectifying and a differential amplifier 13 for differentially amplifying the full-wave rectified signal. R and C are filter resistors and capacitors.
That is, in the present invention, the rectifier circuit is a full-wave rectifier circuit in order to extract the difference between the maximum value and the minimum value of the resistance voltage dividing value, and the difference between the P side (positive side) output and the N side (negative side) output. Dynamically amplified.
[0014]
FIG. 2 shows a simulation circuit configured as shown in FIG. 1. 3 ′ is a PM motor circuit during free running, 11 ′ is a resistance of a voltage dividing circuit, 12 ′ is a full-wave rectifier circuit, 13 'Indicates the differential amplifier portion.
[0015]
FIG. 3 shows a case where there is no fluctuation of the neutral point potential using the simulation circuit of FIG. 2, and FIG. 4 shows a simulation result when the neutral point potential is changed by 200V. . The black portion of the output Vdet0 of the differential amplifier 13 'in FIG. 4 is a neutral point potential fluctuation component that cannot be canceled even by the differential amplification method, and is filtered as shown by the signal Vdet1 by the amplifier AMP-2. Has been removed.
[0016]
According to the simulation results of FIG. 3 and FIG. 4, even if a neutral voltage fluctuation of 200 V occurs, it can be confirmed that the influence on the filtered detector is suppressed to be small, and the change in the detection signal Is 103% (= 3.36V / 3.25V).
[0017]
FIG. 5 shows a simulation result when the neutral point potential is changed by 200 V on the assumption that there is a small stray capacitance Co (stray capacitance Co shown in FIG. 2) between the full-wave rectifier circuit 12 and the differential amplifier 13. It is.
A spike-like voltage (black part superimposed on the detection value Vdet0) is generated due to the neutral point potential fluctuation that cannot be canceled even by the differential amplification method due to the slight stray capacitance Co in the detection circuit. Is getting bigger. When the stray capacitance Co is present, the neutral point potential fluctuation and the change in the detection signal due to the stray capacitance Co are 121% (= 3.92 V / 3.25 V).
A spike voltage prevention circuit 14 indicated by a dotted line in FIG. 1 is inserted to suppress the spike voltage. The spike voltage prevention circuit 14 is connected to the full-wave rectifier circuit 12, and specifically, is inserted between the voltage divider circuit 11 and the full-wave rectifier circuit 12.
[0018]
FIG. 6 shows the simulation circuit. The spike voltage prevention circuit is inserted in each of the three phases and resistors R21 to R23 inserted on the N side, capacitors C12, 14, and 16, respectively, and inserted on each phase and the P side. And capacitors C11, 13 and 15.
[0019]
FIG. 7 shows a simulation result when there is no neutral point potential variation using FIG. 6, and FIG. 8 shows a simulation result when the neutral point potential is varied by 200V. As is clear from these, spikes appearing at the output of the differential amplifier are reduced by connecting a spike prevention circuit to the full-wave rectifier circuit to reduce the current flowing through the stray capacitance present at the input of the differential amplifier. The change in the detection signal due to the neutral point potential fluctuation is 103% (1.64 V / 1.59 V).
[0020]
【The invention's effect】
As described above, according to the present invention configured using the full-wave rectifier circuit as the residual voltage detection device, it is possible to detect the absolute value of the residual voltage of the PM motor during free run without using a transformer. Thus, the PM motor drive inverter device can be reduced in size.
Even when multiple inverter devices are connected to the same DC link, or when the connection cable to the PM motor is closely connected, it is affected by fluctuations in the neutral point potential due to switching of the operating inverter circuit. Without this, it is possible to stably detect the absolute value of the residual voltage.
[Brief description of the drawings]
FIG. 1 is a configuration diagram showing an embodiment of the present invention.
FIG. 2 is a simulation circuit according to the present invention.
FIG. 3 is a simulation output waveform diagram in the case of no neutral point potential fluctuation.
FIG. 4 is a simulation output waveform diagram with neutral point potential fluctuation.
FIG. 5 is an output waveform diagram of simulation in the presence of stray capacitance, in the case of neutral point potential fluctuation.
FIG. 6 is a simulation circuit according to the present invention.
FIG. 7 is a simulation output waveform diagram when there is no neutral point potential fluctuation.
FIG. 8 is a simulation output waveform diagram with neutral point potential fluctuation.
FIG. 9 is a configuration diagram of a conventional inverter device.
FIG. 10 is a simulation circuit of a conventional residual voltage detection device. FIG. 11 is an output waveform diagram of a conventional simulation in the case of no neutral point potential fluctuation.
FIG. 12 is an output waveform diagram of a conventional simulation in the case of neutral point potential fluctuation.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 1 ... Inverter circuit 2 ... Control part 3 ... Permanent magnet synchronous motor 4,10 ... Residual voltage detection apparatus 5 ... AC power supply 11 ... Voltage divider circuit 12 ... Full wave rectifier circuit 13 ... Differential amplifier 14 ... Spike voltage prevention circuit

Claims (1)

In connecting a permanent magnet synchronous motor to the output side of the three-phase inverter circuit and detecting the residual voltage during free run of this synchronous motor,
A full-wave rectifier circuit is connected between each phase on the output side of the three-phase inverter circuit and the negative electrode through a voltage divider circuit consisting of a resistor, and a resistor and a capacitor are formed between the voltage divider circuit and the full-wave rectifier circuit. A residual voltage detection device for a permanent magnet synchronous motor, wherein a residual voltage is obtained by connecting a spike voltage prevention circuit and differentially amplifying a signal between each phase output side and the negative electrode of the inverter circuit.

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