JP2002071731A - Circuit for detecting relative potential to ground of inverter control amplifier tester - Google Patents

Abstract

PROBLEM TO BE SOLVED: To detect a correct relative potential to ground from a gate signal inputted from a control amplifier in a control amplifier tester which behaves similarly to when an induction motor is driven by a VVVF inverter and which outputs equivalent electrical signals to the control amplifier of the VVVF inverter. SOLUTION: The relative potential to ground is detected from a minute time, a dead time in the minute time, an ON time of the P-side gate signal and a polarity of a current by inputting each phase gate signal of the VVVF inverter control amplifier.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a test apparatus for an inverter control amplifier, and more particularly to a main circuit portion of a VVVF inverter based on a control signal of the control amplifier of the VVVF inverter when an induction motor is connected as a load of the VVVF inverter. And an inverter control amplifier test mainly comprising an electronic circuit such as a microcomputer, which operates equivalently to the operation of the induction motor and feeds back an electric signal equivalent to that when the induction motor is operating to the control amplifier of the VVVF inverter. The present invention relates to a circuit for detecting an accurate relative potential to ground from a gate signal output from an inverter control amplifier in an apparatus.

[0002]

2. Description of the Related Art Conventionally, in order to check whether a control amplifier of a VVVF inverter is operating normally,
DC power supply, filter reactor, filter capacitor and PWM converter (hereinafter collectively referred to as VV
VF inverter main circuit section) and an induction motor were connected to perform the test. Thus, the actual PWM
When connecting the inverter main circuit and the induction motor to the control amplifier of the VVVF inverter to check and test the hardware and software of the control amplifier, PWM
It takes a lot of time to set up the inverter main circuit section, the induction motor, and the peripheral rotating body test apparatus, and also requires a lot of power.

As an improvement of this point, an inverter control amplifier test apparatus that operates equivalently in real time to the operation of a VVVF inverter control amplifier when an induction motor is connected as a load of the VVVF inverter is provided by a VVVF inverter main circuit section and an induction motor. It is possible to simulate all PWM inverter main circuit sections and induction motors without having a rotating body such as an electric motor and only by changing the software constants in the test equipment. Have been.

Hereinafter, the principle of the present invention will be described using a seven-dimensional linear simultaneous differential equation combining a PWM inverter main circuit, a three-phase induction motor, and load inertia. 3
The phase-two phase conversion matrix is represented as [C] in the following equation (1).

[0005]

(Equation 1)

The voltages of the d and q axis components of the stator (represented by the abbreviation S) of the cage type three-phase induction motor are represented by Vds, Vqs, and the currents of the d and q components of the stator and the rotor (represented by the abbreviation r). Are Ids, Iqs, Idr, Iqr, the resistance and self-inductance of the stator and the rotor are Rs, Rr, Ls, Lr, the exciting inductance is M, the number of pole pairs p of the three-phase induction motor and the rotational angular velocity ω.
Assuming that the product of m is newly called an electrical angular velocity and that it is ωr, using a differential operator P (= d / dt), an equivalent circuit of a three-phase induction motor, a quaternary first-order simultaneous differential equation, is (2) It is represented by an equation.

[0007]

(Equation 2)

If the generated torque of the three-phase induction motor is TL and the moment of inertia of the load is J, and the braking component is ignored, the torque equation is expressed by equation (3).

[0009]

[Equation 3]

Further, a filter reactor (Rd, L
d) and the DC power supply unit having the filter capacitor Cd are represented by Expressions (4) and (5) by the DC power supply voltage Vs, the filter voltage Vf, the filter reactor current I1, and the PWM converter input current I2.

[0011]

(Equation 4)

Induction motor stator d, q-axis voltages Vds, Vq
s, and the currents Ids, Iqs and P of the filter capacitor Cd.
When the loss of the PWM converter is neglected, the output Vf × I2 to the WM converter has a relationship expressed by the following equation (6). Therefore, the DC power supply unit of the VVVF inverter and the induction motor are mathematically expressed. Can connect.

[0013]

(Equation 5)

Here, in the above invention, the DC power source unit constant,
When the stator d, the q voltage Vds, and Vqs determined by the induction motor constant, the load inertia moment, the gate signal G of the PWM converter from the control amplifier, and the positive / negative of the three-phase current are determined,
The fact that d, q-axis current, electric angular velocity ωr, filter current I1, and voltage of the filter capacitor Cd, that is, the filter voltage Vf of the stator and the rotor are obtained from the equations (2) to (5) is used. Further, strictly speaking, the simultaneous differential equations of the seven-dimensional element must be calculated by simultaneously combining the equations (2) to (5). In the present invention, however, the electric angular velocity is calculated in the minute time to be calculated. ωr and filter voltage Vf
Is not greatly changed, the equations (2), (3), and (4), (5) are calculated without simultaneous equations, thereby facilitating the solution of the differential equation. That is, the equation (2) is expressed in the form of a quaternary linear simultaneous differential equation as shown in the following equations (7), (8) and (9).

[0015]

(Equation 6)

The expression (3) is changed to the following expression (10).

[0017]

(Equation 7)

Equation (4) is expressed as in equation (11).

[0019]

(Equation 8)

Equation (5) is transformed into a form as shown in equation (12) by substituting equation (6).

[0021]

(Equation 9)

Further, the equations (7) and (10) to (12) are discretized to form an algebraic equation, which is operated by a microcomputer such as a DSP (digital, signal, processor) to obtain the stator and Rotor d, q-axis current Ids, Iqs, Idr, Iqr, electrical angular velocity ωr, filter current I
1 and the filter voltage Vf can be obtained. (7),
Methods for discretizing equations (10) to (12) to form an algebraic equation include the Euler method, the Runge method, the Kutta method, and the like. Here, the Euler method will be used. Assuming that data is collected and calculated at each sampling interval ΔT,
When the Euler method with a small time ΔT is applied to the equations (7), (10) to (12), the following equations (13) to (1)
Equation 6) is obtained.

[0023]

(Equation 10)

The predicted value, which is the solution value of the Euler method, is as follows when the previous predicted value is represented by a suffix [n] and the current predicted value is represented by a suffix [n + 1]. [I [n]] t = [Ids [n], Iqs [n], Idr
[N], Iqr [n]] [V [n]] t = [Vds [n], Vqs [n]] [I [n + 1]] t = [Ids [n + 1], Iqs [n + 1], I
dr [n + 1], Iqr [n + 1]].

Therefore, the phase voltage applied to the three-phase induction motor is sampled at every minute time ΔT, and the equations (13) to (13) are obtained.
Assuming that the calculation of (16) is performed, 3
Stator d of phase induction motor, q-axis voltage [V [n]] t, electric angular velocity predicted value ωr [n] of previous calculation, stator and rotor d, q-axis current predicted value [I [n] T, the filter current predicted value I1 [n], and the filter voltage predicted value Vf [n], and the current electric angular velocity predicted value ωr [n + 1] is fixed by the equations (13) to (16). The child and rotor d, q-axis current predicted value [I [n + 1]] t, filter current predicted value I1 [n + 1], and filter voltage predicted value Vf [n + 1] can be calculated. here,
In equation (8), ωr uses the predicted electric angular velocity value ωr [n], and the stator d and the q-axis voltage [V [n]] are next to the phase voltages Vu, Vv, and Vw of the three-phase induction motor. It can be calculated by the following equation (17).

[0026]

(Equation 11)

The stator d and the q-axis currents Ids [n + 1] and Iqs [n + 1] in the calculated current predicted value [I [n + 1]] t are extracted, and are shown in the following (18). According to the formula, two-phase three-phase conversion is performed by an inverse matrix [C] -1 of the conversion matrix [C], and a three-phase current predicted value is obtained.
Iu [n + 1], Iv [n + 1], Iw [n + 1] are calculated.

[0028]

(Equation 12)

The calculated three-phase current predicted value Iu [n +
1], Iv (n + 1), Iw (n + 1), electric angular velocity predicted value ωr (n +
1] and the smoothing capacitor voltage predicted value Vf [n + 1] are fed back to the control amplifier, so that the control amplifier
The same operation as when the induction motor is driven by the VVF inverter is performed.

An embodiment of the above-mentioned conventional invention will be described below with reference to a control circuit block diagram shown in FIG. In FIG.
The control amplifier test apparatus 10 for the VF inverter
The gate signal G is input from the control amplifier 1 of the inverter,
Three-phase current signals Iu ', Iv', Iw 'and filter voltage signal Vf'
And a d / q-axis voltage calculation circuit 11, a current calculation circuit 12, a two-phase / three-phase conversion circuit 13, a filter voltage calculation circuit 14, a rotation speed calculation circuit for outputting the electrical angular velocity signal ωr ′ to the control amplifier 1 of the VVVF inverter. 15 and a D / A conversion circuit 16.

The control amplifier 1 of the VVVF inverter receives the gate signal G, that is, the U-phase gate signals Gup and Gu.
The n- and V-phase gate signals Gvp and Gvn and the W-phase gate signals Gwp and Gwn are output to the d- and q-axis voltage calculation circuits 11. The gate signals Gup and Gun are P-side and N-side gate signals of the U-phase switching element. When the signal is "1", the element is ON, and when it is "0", the element is OFF. Either of these gate signals Gup and Gun is “1”, or both are “0” in order to prevent the switching element short circuit between the U-phase legs. The same applies to gate signals of other phases.

The d- and q-axis voltage calculation circuits 11 respectively provide a gate signal G for each phase, predicted three-phase currents Iu [n], Iv [n], and Iw.
[N], and a filter voltage predicted value Vf [n],
Gate signal G of each phase and predicted three-phase currents Iu [n], Iv
[N] and Iw [n] depending on the positive and negative polarities, each phase voltage V
u, v, w are calculated, and the stators d,
The q-axis voltages Vds [n] and Vqs [n] are calculated, and the calculated stator d and the q-axis voltages Vds [n] and Vqs [n] are output to the current calculation circuit 12 and the filter voltage calculation circuit 14.

That is, if the relative value (1 or 0) of the output potential of each phase of the PWM converter with respect to the negative side of the VVVF inverter main circuit DC power supply is named as ground potential Vg, for example,
In the phase, when the gate signal Gup = 1, the U relative ground potential Vgu = 1, and otherwise, the gate signal Gun =
When it is 1, the U relative ground potential Vgu = 0. However, when the P-side and N-side gate signals are both 0, the phase voltage is determined by the direction in which the phase current flows.
When p = Gun = 0 and the U-phase current Iu ≧ 0, the U relative ground potential Vgu = 0, and the gate signal Gup = Gun =
0, and when the U-phase current Iu <0, the U relative ground potential Vg
u = 1.

Since the ground potentials Vgv and Vgw of the other phases can be obtained in the same manner, the phase voltages Vu, Vv, Vv, Vv, and Vg calculated by the following equations (19) and (20) using the filter voltage Vf. Vw can be obtained, and further, the operation stator d and the q-axis voltages Vds [n] and Vqs [n] can be obtained by the equation (17).

[0035]

(Equation 13)

The current calculation circuit 12 calculates the stator d, the q-axis voltages Vds [n] and Vqs [n] at every sampling time interval ΔT,
Electric angular velocity predicted value ω output from rotation speed calculation circuit 15
Input r [n], and calculate the stator and rotor d, q-axis current predicted values Ids [n], Iqs [n], Idr
[N] and Iqr [n], based on equation (13), the current stator and rotor d, q-axis current predicted value Ids [n + 1], Iq
s [n + 1], Idr [n + 1], Iqr [n + 1] are calculated, these values are stored internally, and the two-phase / three-phase conversion circuit 13,
It outputs to the filter voltage calculation circuit 14 and the rotation speed calculation circuit 15.

The two-phase / three-phase conversion circuit 13 includes a stator d and a q-axis current predicted value Ids output from the current operation circuit 12.
[N] and Iqs [n] are input, and three-phase current predicted values Iu [n + 1], Iv [n + 1], and Iw [n + 1] are calculated based on the equation (18). The values are d, q-axis voltage calculation circuit 11 and D /
Output to the A conversion circuit 16.

The filter voltage calculating circuit 14 outputs the stator and rotor d, q-axis current predicted values Ids [n], Iqs output from the current calculating circuit 12 at every sampling time interval ΔT.
[N] and operation stator d, q-axis voltage Vds [n], Vqs
[N] is input, and the current filter input current prediction value is calculated based on equations (15) and (16) based on the filter input current prediction value I1 [n] and the filter voltage prediction value Vf [n] obtained as a result of the previous calculation. Value I1 [n + 1] and predicted filter voltage Vf
[N + 1] is calculated, these values are stored internally, and the filter voltage predicted value Vf [n + 1] is output to the d / q-axis voltage calculation circuit 11 and the D / A conversion circuit 16.

The rotation speed calculation circuit 15 outputs the stator and rotor d, q-axis current predicted values Ids [n], Iqs [n], Id output from the current calculation circuit 12 at each sampling time interval ΔT.
r [n] and Iqr [n] are input, and the current electrical angular velocity predicted value ωr [n + 1] is calculated based on equation (14) using the electric angular velocity predicted value ωr [n] of the previous calculation result. This value is stored internally and output to the current calculation circuit 12 and the D / A conversion circuit 16.

The D / A conversion circuit 16 obtains three-phase current predicted values Iu [n], Iv [n], Iw [n] from the two-phase / 3-phase conversion circuit 13.
From the filter voltage calculation circuit 14
Vf [n] and an electrical angular velocity prediction value ωr [n] from the rotation speed calculation circuit 15 are further converted into digital / analog signals to convert the three-phase current signals Iu ′, Iv ′, Iw ′ and the filter voltage signal Vf. And the electrical angular velocity signal ωr ′
Output to the control amplifier 1 of the inverter.

[0041]

However, in the d- and q-axis voltage calculation circuits 11 configured as described above, for example, during the short time ΔT, for example, the U-phase gate signal Gup or Gu
When a gate signal in which one or both (time different in time) of n are “1” and both are “0” is inputted, an accurate relative potential to ground cannot be detected.
Consequently, there is a problem that accurate d and q axis voltage calculations cannot be performed. In particular, when the switching frequency of the VVVF inverter is high and the pulse width is narrow, there is a problem that a d and q axis voltage calculation error increases.

The present invention has been made in view of the above circumstances, and is not limited to a VVVF inverter, and is an inverter control amplifier constituted only by an electronic circuit such as a microcomputer, which operates equivalently in real time to the operation of the inverter control amplifier. Input from the inverter control amplifier
An object of the present invention is to provide a method for detecting an accurate relative potential to ground for a very short time ΔT from the side gate signal and the N side gate signal to calculate an accurate d, q axis voltage.

That is, the means for achieving the object are as follows: 1) In claim 1, connected to the gate output terminal of the inverter control amplifier, which is the device under test, and equivalently controlling the operation of the inverter main circuit section and the load. Means for detecting a dead time Td from the P-side and N-side gate signals within a short time, means for detecting an ON time Tp of the P-side gate signal within a short time, Means for calculating a relative potential with respect to ground based on the polarity of the current of the equivalent load, the ON time Tp of the P-side gate signal, the dead time Td, and the minute time. This is a relative potential detection circuit.

The principle of the present invention will be described with reference to FIGS. In the U-phase dead time time interval explanatory diagram of FIG.
The U-phase P-side and N-side gate signals of the PWM converter are Gup and Gun, respectively, and the sampling time interval is Δ
Assuming that the time interval of T and Gup = 1 is Tup and the time interval of Gun = 1 is Tu, the gate signals Gu on the P side and the N side are Gu.
The dead time interval Tud in which both p and Gun are 0 is illustrated in FIG. Therefore, the dead time interval T
ud is obtained by equation (21). Tud = ΔT− (Tup + Tun) (21) Here, for example, when the gate signal Gup or Gun is 1 during the sampling time interval ΔT, the dead time time interval Tud = 0, and according to the equation (21) The dead time interval Td in all cases can be obtained. V, W
Similarly, for the dead time time intervals Tvd and Twd of the phase, the time intervals Tvp and T
wp, time intervals Tvn and Twn in which the N-side gate signal is 1
Can be obtained by using.

Next, in the U relative ground relative potential deriving flowchart of FIG. 3, the U phase ground relative potential Vgu is calculated using the dead time time interval Tud and the direction in which the U phase current predicted value Iu [n] flows. It is required as follows. That is, when the U-phase current predicted value Iu [n] is negative, it is obtained by the equation (22), and when it is positive, it is obtained by the equation (23). Vgu = (Tud + Tup) / ΔT (22) Vgu = Tup / ΔT (23) Similarly, the dead time intervals Tvd and Twd and the current for the relative ground potentials Vgv and Vgw of the other phases. It can be obtained by using the flowing directions of the predicted values Iv [n] and Iw [n].

Therefore, relative potential Vg with respect to ground taking into account the dead time time intervals Tud, Tvd, Twd of each phase.
u, Vgv, Vgw and the filter voltage Vf,
Equations (19) and (20) are used for accurate calculation of each phase voltage Vu,
Vv and Vw can be obtained, and the operation stator d and the q-axis voltages Vds [n] and Vqs [n] can be obtained by the equation (17).
Can be requested. Hereinafter, an embodiment of the present invention will be described in detail with reference to the drawings.

[0047]

FIG. 1 is a block diagram of a control circuit of a circuit for detecting relative electric potential to ground of an inverter control amplifier test apparatus to which claim 1 of the present invention is applied. In FIG.
Is a dead time detection circuit, 22 is a P-side gate ON time detection circuit, 23 is a relative electric potential calculation circuit to ground, and the same reference numerals in FIG. 4 denote the same components.

The dead time detecting circuit 21 receives the gate signals Gp and Gn on the P side and the N side of an arbitrary phase from the control amplifier 1 of the inverter, and outputs a sampling time interval Δ
Dead time interval Td where Gp and Gn between T are both 0
Is derived by equation (21), and the relative electric potential to ground calculation circuit 2
Output to 3. The P-side gate ON time detection circuit 22 receives a P-side gate signal Gp of an arbitrary phase from the control amplifier 1 of the inverter, detects a time interval Tp of the gate signal Gp = 1 during the sampling time interval ΔT, The signal is output to the relative electric potential calculation circuit 23.

The relative electric potential calculation circuit 23 has a dead time time interval Td, a time interval Tp for the gate signal Gp = 1,
And the load current I [n] of an arbitrary phase is input. When the load current I is negative, the equation (22) is used.
The relative potential Vg to the ground is calculated by the equation 3),
Output to the d and q axis voltage calculation circuit 11. The d- and q-axis voltage calculation circuits 11 calculate relative potentials Vgu, Vgv, V
gw and the filter voltage predicted value Vf [n] are input, and the operation stator d, the q-axis voltages Vds [n] and Vqs [n] are calculated.

[0050]

As described above in detail, in the inverter main circuit and the relative ground potential detection circuit of the inverter control amplifier test apparatus for simulating the load of the present invention, the gate output terminal of the inverter control amplifier as the device under test is connected to the gate output terminal. connection,
It is possible to accurately detect the relative potential with respect to the ground every minute time ΔT of the terminal of the inverter main circuit portion to be simulated. As a result, accurate calculation stators d and q-axis voltages Vds and Vqs can be calculated.
Accurate inverter main circuit and load can be simulated. Therefore, the circuit for detecting relative electric potential to ground of the inverter control amplifier test apparatus of the present invention has extremely high practical utility.

[Brief description of the drawings]

FIG. 1 is a control circuit block diagram of a relative electric potential detection circuit to ground of an inverter control amplifier test apparatus according to one embodiment of the present invention.

FIG. 2 is an explanatory diagram of a U-phase dead time time interval according to the present invention.

FIG. 3 is a flowchart of deriving a U relative ground relative potential according to the present invention.

FIG. 4 is a control circuit block diagram of a conventional control amplifier test apparatus for a VVVF inverter.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Control amplifier of VVVF inverter 10 Control amplifier test device of VVVF inverter 11 d, q-axis voltage calculation circuit 12 Current calculation circuit 13 2-phase / 3-phase conversion circuit 14 Filter voltage calculation circuit 15 Rotation speed calculation circuit 16 D / A conversion circuit Reference Signs List 20 relative ground potential detection circuit 21 dead time detection circuit 22 P side gate ON time detection circuit 23 relative ground potential calculation circuit

Claims (1)

[Claims] 1. An inverter control amplifier test device connected to a gate output terminal of an inverter control amplifier as a device under test and equivalently operating an inverter main circuit section and a load, wherein the inverter control amplifier within a short time is Means for detecting the dead time Td from the P side and N side gate signals of the
Means for detecting the N time Tp, and means for calculating the relative potential with respect to the ground from the positive / negative of the current of the equivalent load, the ON time Tp of the P-side gate signal, the dead time Td, and the minute time. A relative potential detection circuit for an inverter control amplifier test apparatus, characterized in that a relative potential is output to d and q axis voltage calculation circuits.