JPH04161060A - Shaper for ac three-phase signal - Google Patents

Abstract

PURPOSE:To shape an AC three-phase input signal into a sine wave signal containing no higher harmonic by calculating the sum of signal level of two phases out of three phases of an AC three-phase signal fed to a zero-cross detecting means thereby detecting a zero-cross point. CONSTITUTION:In case of a sine wave signal containing no higher harmonic, a relation 1U+1V+1W=0 is satisfied for the signal levels 1U, 1V, 1W of an AC three-phase signal in U, V and W phases for a time t1. The relation is satisfied so long as three phases have identical waveforms even if higher harmonics are contained therein. Zero-cross points A, B are detected for phase W, for example, and a following zero-cross point C is predicted. An angular speed in the interval B-C is then determined and added to the angle at the zero-cross point B every predetermined time thus shaping an AC input signal into a sine wave signal.

Description

DETAILED DESCRIPTION OF THE INVENTION <Industrial Application Field> The present invention relates to a device for waveform shaping a three-phase alternating current signal using a microcomputer (hereinafter referred to as microcomputer).

<Conventional technology> Conventionally, for example, in a magnetic levitation railway as shown in Figure 2,
A transmitting antenna 2 and, for example, a superconducting magnet 3 are mounted on the vehicle 1, and current coils of U, V, and W phases (not shown) and three crossed induction wires 4u, 4V, and 4W are mounted on the ground side of the vehicle 1. are arranged in parallel along the direction of travel. Cross guide line 4u,
4v and 4w intersect each other at equal intervals so that the received signal becomes a sine wave, and the intersections Xu, Xv, and Xw are Xu
-+Xv→Xw+Xu→... They are arranged at equal intervals from each other.

In such a magnetic levitation railway, when the output signal of the transmitting antenna 2 is received by a crossing guide line, the reception level is high at the center between the intersections of the crossing guide lines, and the reception level decreases at the intersection. Then, while the vehicle 1 is running, the transmitting antenna 2
When receiving the signal from the cross guiding wires 4u, 4v, 4w
A signal with a waveform approximating a sine wave is output with a phase difference of 2o0. When a current with the same waveform as the signal output from these cross-induction wires 4u, 4v, and 4w is passed through the current coil, the magnetic field of the current coil moves sequentially from U→■→W-4U→river phase, and the magnetic field of the current coil This allows the vehicle 1 on which the superconducting magnet is mounted to travel.

In order to run such a magnetically levitated railway vehicle 1 smoothly, a sine wave signal that does not contain harmonics is required. Therefore, noise mixed into the input three-phase AC signal or signal level fluctuation A waveform shaping device for a three-phase AC signal is known that outputs a signal waveform-shaped into a sine wave by removing distortion caused by the waveform (see Japanese Patent Laid-Open Publication Nos. 62-8300).

This is the phase ratio of the signal level (U/V, V/W, W/U) if all three-phase AC signals of U phase, ■ phase, and W phase are sine waves.
is constant at any phase angle. Even if the signal level of one phase is distorted by noise or level fluctuation, the signal level of the remaining one can be calculated from the signals of the other two phases based on the phase ratio. The phase signal level is calculated and waveform shaping is performed.

<Problem to be solved by the invention> However, when a crossed induction wire is used for the receiving coil,
In order to output sinusoidal signals from the intersecting guide lines 4u, 4v, and 4W, the shapes of the intersecting guide lines 4u, 4v, and 4W must be arranged accurately, which is quite difficult. Therefore, as shown in Figure 3, the waveform of the signal output from the crossed guiding wires 4υ, 4v, and 4W does not become a sine wave as shown by the broken line, but due to the characteristics of the crossing guiding wires, harmonics are added to the sine wave. The signal will have a waveform like the solid line included. Therefore, if the sine wave contains harmonics, the phase ratio of the U phase, ■ phase, and W phase will not be constant, and based on the phase ratio, the three-phase AC signal will be mixed with noise, level fluctuations, Alternatively, it becomes difficult to remove distortion caused by phase loss in the signal.

If a current is applied to the current coil based on such a three-phase AC signal, there is a possibility that the vehicle 1 may not be able to run smoothly.

The present invention has been made in view of such conventional problems, and an object of the present invention is to provide a waveform shaping device for a three-phase AC signal that shapes the input waveform of a three-phase AC signal into a sine wave signal containing no harmonic components. With the goal.

<Means for Solving the Problem> Therefore, as shown in FIG. 1, the present invention converts an input three-phase AC signal containing harmonic components into a sine wave signal containing no harmonic components. In a waveform shaping device for 3-phase AC signals that shapes and outputs the waveform, each phase signal of the 3-phase AC is inputted, the sum of the signal level values of the two phases is calculated, and the other signal level is calculated from the calculated value. a zero intersection detection means for detecting a zero intersection of a phase signal; a time measurement means for measuring the time from the previous zero intersection detected by the zero intersection detection means until the current zero intersection is detected; An angular velocity calculation means that predicts the next zero crossing point based on the time measured by the measuring means and calculates the angular velocity between the zero crossing points, and a sine wave signal whose waveform is shaped based on the angular velocity calculated by the angular velocity calculation means. A sine wave signal output means is provided.

<Operation> According to the above configuration, when a three-phase AC signal is input to the zero-crossing detection means, the zero-crossing detection means calculates the sum of the two-phase signal level values from each signal level value of the three-phase AC signal. and detect the zero intersection.

When a zero intersection is detected by the zero intersection detection means, the time measuring means measures the time from when the zero intersection is detected to when the next zero intersection is detected.

The angular velocity calculation means calculates the time between the measured zero intersections by
Predict the next zero crossing point and calculate the angular velocity of each phase during that time.

The sine wave signal output means outputs a sine wave signal whose waveform has been shaped based on this angular velocity.

Therefore, it becomes possible to waveform shape an input three-phase AC signal into a sine wave signal that does not contain harmonic components.

<Example> Hereinafter, an example of the present invention will be described based on FIGS. 4 to 10.

In FIG. 4 showing this embodiment, the A/D converter 11
．． 12.13 inputs the respective voltages of the U, V, and W phases, converts them into A/D, and outputs them to the microcomputer (hereinafter referred to as microcomputer) 14.

The microcomputer 14 includes an MPU, ROM, RAM, input/output interface, and an A/D converter 11.1.
2. Shape the three-phase AC signal input from 13 into a sine wave signal. The sine wave whose waveform was shaped by the microcomputer 14 is U,
(2), is output to each W-phase D/A converter 15, 16, 17, and the D/A converter 15, 16, 17 converts the digital value of the input sine wave into an analog value, and then outputs it to each amplifier 18, 19, . 20 to output a sine wave.

Next, the effect of shaping the waveform of a three-phase AC signal into a sine wave will be explained based on FIG.

In FIG. 5, the horizontal axis is the time axis and the axis of the angle of the AC signal corresponding to time, and the vertical axis shows the signal level value.

Time t for U, V, and W phases of three-phase AC.

The respective signal level values 1u, lv, 1w in
The relational expression lv+1w=0 holds true. From this relational expression, in the case of a repetitive waveform, if lu+1V=o then 1w= O1v+1w=
If O, then lu=0. If 1w+1u=0, then lv=0, and this point is the zero intersection. At this zero crossing point, even if the three-phase AC signal contains harmonic components, the above relational expression holds true if the three phases have the same waveform. Therefore, by adding the signal level values of two phases and detecting the point where the added value becomes O, it is possible to detect the zero crossing points of the remaining l phases. For example, the zero crossing point of the W-phase AC signal is detected in Figure 5 A and B, the next zero crossing point C is predicted, the angular velocity between B and C is determined, and the angle of the zero crossing point B is calculated. By adding the angular velocity to the angle at regular intervals based on the above, it is possible to shape the waveform into a sine wave signal.

Next, the operation of the microcomputer 14 will be explained based on the flowchart shown in FIG.

In step 1 (denoted as S in the figure), the initial values, that is, the intersection flags uflag and vflag Swflag are set to "o". Note that the intersection flag will be described later.

In step 2, the device is started up and the reception level of the data input from the A/D converter is the specified value V. Wait until it reaches the specified value V. When this happens, proceed to step 3.

In step 3, the cross flags uflag Svflag and wflag of each phase of USV and W are set to "
1”.

In step 4, the time measurement counter values tuStv, tw for each phase of U, V, and W are reset to O.

In step 5, the digital values of the AC signals of each phase are read from the A/D converters 11 to 13.

The reference value of the signal level of the digital value of this A/D converted AC signal is offset to the position a in Figure 5, so if the read digital value is subtracted by this offset, the reference value of the signal level is b, and the signal level value has a positive or negative sign.

In step 6, the signal levels lu, 1■ of the U, V, and W phases are
, 1w, the summed data of the two-phase signal levels inu,i
Create nv and inw.

inu =lv+1w 1nv =1w+1u inW =1u+lv In step 7, the created addition data is stored in the storage area of the RAM. The purpose of storing the addition data is to compare the sign of the next input addition data, and the stored addition data is updated every time addition data is created.

Step 8 is the addition data inu of the two-phase signal levels.
, inv, inw, or 0. To investigate this, the signs of the previous addition data stored in the RAM storage area and the current addition data are compared, and when the sign changes, it is assumed that the addition data has become 0. For example, when adding data is created from the U and ■ phases as shown in Figure 8, the previous adding data is inw' (=
lu' + 1v') as inw' = lu' +
If lv'< Oinw = lu + lv ≧0, the added data is regarded as zero. This is because the added data may not always be zero depending on the sampling timing of the signal level value.

If the sign has not changed, there is no zero crossing, so the process goes to step 10, and if the sign has changed, the process goes to step 9.

In step 9, if the added data becomes zero in step 8, it is checked whether the pattern of the previous data (lv, 1■, 1w) and the pattern of the current data are the same. For example, if the signal level changes near a zero intersection due to noise, etc., it may be detected as the next zero intersection even though it is the same zero intersection, so the same zero intersection may be detected many times. This is to prevent it from happening. To check this, for example, set flags uxflag, vxflag, and wxflag for each phase, and set U phase uxflag=1 (lv<O)=O(
lv>O) V phase vxflag= 1 (1w<O)=O(1
w>O) W phase wxflag=1 (lu<0)=0(
lu>O). Then, the stored previous flag value and the current flag value are compared. Here, if the data patterns are the same, the signal level has fluctuated due to the influence of noise, etc., and it is determined that it is not a zero crossing point, and the process proceeds to step 10. If the data patterns are not the same, it is a zero crossing point. It is determined that there is, and the process proceeds to step 16.

In step 10, as shown in FIG. 9, 1 is added to the value of the three-phase time counter to update the value of the time counter.

tu=tu+1 tv=tv+1 tw=tw+1 In step 11, it is checked whether the updated value of the time measurement counter exceeds a predetermined value (overflow). If the interval between zero intersections becomes longer and the value of the time counter exceeds a predetermined value, the value of the time counter cannot be used, so the process proceeds to step 12; if the interval does not exceed the predetermined value, the process returns to step 5.

In step 12, when the value of the time measurement counter exceeds a predetermined value, the crossing flag of the relevant phase is set to "0" so that the value of the time measurement counter cannot be used.

In step 13, it is checked whether the reception level is less than a specified value. If it is less than the specified value, the process proceeds to step 14, and if it is greater than the specified value, the process returns to step 5.

In step 14, the crossing flag of the corresponding phase whose reception level has become less than the specified value is set to "0".

In step 15, it is checked whether the crossing flag of two or more phases is set to "0". This is because it is only possible to create addition data when two or more phases are open.
In that case, the execution of this flowchart will be stopped, and for example, the crossing flag for only one phase will be set to "
0'', the zero crossing point can be detected from other phases, so the process returns to step 5. For example, if a train stops, the values of the time measurement counters for all phases exceed a predetermined value, and the metal phase crossing flag is
0", and the execution of this flowchart stops.

In step 16, the angular velocity for calculating the pressure sinusoidal wave signal up to the next zero crossing point is calculated. The formula for calculation is as shown in the table in Figure 10.

Angular velocity dθ. The predicted zero intersection θ is calculated by dividing the angle 1800 between the previous zero intersection and the current zero intersection by the value of the time counter between zero intersections. This is the value obtained by adding a correction value due to the deviation between the zero crossing point and the detected zero crossing point. If there is no deviation, the vehicle is running at a constant speed.

For example, if it is a zero intersection, a detected phase, or a U phase, the calculation formula is determined by first checking the intersection pattern of the ■ phase, and then checking the forward and backward movement of the vehicle. The angle θ here is 5°. is multiplied by 1000 to improve accuracy.

In step 17, the next zero crossing point is predicted based on the angular velocity calculated in step 16.

In step 18, a sine wave signal up to the next zero crossing point is calculated, and the calculated sine wave signal is output to the D/A converter of the corresponding phase. The sine wave signal is calculated based on the angular velocity calculated in step 16. After performing this process, the process returns to step 4, and the zero-crossing phase time measurement counter value is reset to "0".

In addition, steps 5 to 9 or zero intersection detection means, step 4
．． 10 corresponds to time measuring means, steps 16 to 17 correspond to angular velocity calculation means, and step 18 corresponds to sine wave signal output means.

This configuration is based on the principle that the point where the sum of the two-phase signals of the three-phase AC signal becomes zero is the zero crossing point of the remaining one phase. By detecting a zero crossing point, predicting the next zero crossing point, and outputting a sine wave signal up to the next zero crossing point based on this prediction, the input three-phase AC signal can be converted to a sine wave signal that does not include harmonics. The waveform can be shaped and output, and the performance of the waveform shaping device for three-phase AC signals can be improved.

<Effects of the Invention> As explained above, according to the present invention, two of the three-phase AC signals
The input three-phase AC signal is detected by detecting the zero crossing point of the remaining one phase from the sum of the phase signals, predicting the next zero crossing point, and calculating and outputting a sine wave signal based on this prediction. Since the waveform can be shaped and a sine wave signal containing no harmonics can be output, the performance of the waveform shaping device for three-phase AC signals can be improved.

[Brief explanation of drawings]

Fig. 1 is a functional block diagram showing the configuration of the present invention, Fig. 2 is a diagram showing the relationship between the vehicle and the crossing guidance line, Fig. 3 is a signal waveform diagram of Fig. 2, and Fig. 4 is a diagram related to the present invention. A block diagram in one embodiment, FIG. 5 is an explanatory diagram showing the operating principle of FIG. 4,
6 is a flowchart showing the operation of the microcomputer in FIG. 4, FIG. 7 is an explanatory diagram of the reception level in FIG. 6, and FIG.
FIG. 9 is an explanatory diagram of the time measurement counter of FIG. 6, and FIG. 10 is a chart showing the calculation formula for the angular velocity of FIG. 6. 1...Vehicle 2...Transmission antenna 3...Superconducting magnet 4u, 4v, 4w-...Cross guiding wire 1
1-13...A/D converter 14...Microcomputer 15-17...D/A converter 18-2
0...Amplifier patent applicant Fujio Sasashima Representative, Japan Signal Co., Ltd., Railway Technology Research Institute, Patent attorney Figure 7 Figure 8 Figure 9

Claims (1)

[Claims] The input three-phase AC signal containing harmonic components is
In a waveform shaping device for three-phase AC signals that shapes and outputs the waveform into a sine wave signal that does not contain harmonic components, the signals of each phase of the three-phase AC are input individually, and the sum of the signal level values of the two phases is calculated. and a zero intersection detection means for detecting the zero intersection of the signal of the other phase from the calculated value, and a time from the previous zero intersection detected by the zero intersection detection means until the current zero intersection is detected. A time measuring means for measuring the time; An angular velocity calculating means for predicting the next zero intersection based on the time measured by the time measuring means and calculating an angular velocity between the zero crossings; and an angular velocity calculated by the angular velocity calculating means. A waveform shaping device for a three-phase alternating current signal, comprising: a sine wave signal output means for outputting a sine wave signal whose waveform has been shaped based on .