JPH08110359A - Method for measuring momentary value of polyphase voltage - Google Patents

Abstract

PURPOSE: To establish a method for accurately measuring the momentary value of the maximum value of a fundamental wave voltage in a polyphase voltage containing high harmonic voltages and at the same time obtain the momentary value of the polyphase fundamental wave voltage by utilizing the value for applying to the control of an AC electrical equipment. CONSTITUTION: By converting a polyphase voltage 1 onto α-βplane by α βconversion 2, a rotary vector whose amplitude is equal to that of the polyphase voltage can be obtained. By converting the rotary vector onto α'-β' plane of rotary coordinates 3 which rotate at the same angular velocity as the polyphase voltage 1 and averaging the components of α' axis and β' axis on the rotary coordinates independently on time axis by time averaging 4, the influence of high harmonic voltage can be eliminated. By performing amplitude calculation 5 using two components of α' axis and β' axis which are averaged on time axis, a momentary value 8 of the maximum value of the fundamental wave voltage in the polyphase voltage can be obtained. Further, the momentary value of a polyphase fundamental wave voltage 9 is obtained by a rotary coordinate inverse conversion 6 and αβ inverse conversion 7.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to the control of multi-phase voltages including harmonic voltages, for example power active filters, and the maximum value of the fundamental wave voltage in the multi-phase voltages required for controlling the amplitude of alternating voltage. The present invention relates to a method for detecting the instantaneous value of and the instantaneous value of the polyphase fundamental wave voltage.

[0002]

2. Description of the Related Art As disclosed in Japanese Patent Laid-Open No. 1-311286, a method of measuring an instantaneous value of a maximum value of a sine wave AC voltage is converted into a DC voltage by a rectifier, and a value after an arbitrary time from a point of zero crossing A method of calculating the instantaneous value of the maximum value by measuring, and further, JP-A-3-39659 and JP-A-3-2525.
No. 60, JP-A-3-39661, etc., a method of calculating the instantaneous value of the maximum value from the data of three points of the measured AC voltage at arbitrary fixed intervals has been adopted. However, in the power active filter and the amplitude control of the AC voltage, control using the maximum value of the AC voltage and the instantaneous value of the fundamental wave voltage is required, and most of the AC voltage handled includes harmonic voltage. Therefore, the above-mentioned measurement method assuming that the measured AC voltage is a sine wave causes an error due to the harmonic voltage.

[0003]

SUMMARY OF THE INVENTION Therefore, an object of the present invention is to develop a method of measuring the instantaneous value of the maximum value of the fundamental wave voltage in the polyphase voltage including the harmonic voltage, and to determine the instantaneous value of the polyphase fundamental wave voltage. An object of the present invention is to improve a control method of an AC electric device by providing a system capable of outputting a value.

[0004]

As shown in FIG. 1, the method for measuring the instantaneous value of the maximum value of the fundamental wave voltage in the polyphase voltage and the instantaneous value of the polyphase fundamental wave voltage according to the present invention is as follows. Conversion 2 and rotation coordinate conversion 3 convert to a static vector, time average 4 removes the harmonic voltage, and the maximum instantaneous value 8 which is the maximum instantaneous value of the fundamental wave voltage in the multi-phase voltage Calculated by amplitude calculation 5. Further, the value obtained by removing the harmonic voltage by the time average 4 is converted by the rotational coordinate reverse conversion 6 and the αβ reverse conversion 7 to obtain the instantaneous value of the multiphase fundamental wave voltage 9. Hereinafter, this will be described using a three-phase voltage. Now, assuming that the fundamental wave voltage of the three-phase voltage is Va (t), Vb (t), Vc (t), the harmonic voltage Vha (t), Vhb (t), V
If hc (t) is included, α of these voltages
β conversion is

[Equation 1] Can be expressed as From this, the instantaneous value Vem (t) of the maximum value of the three-phase voltage is

[Equation 2] Can be obtained by However, the first on the right side of the equation (1)
The term is the fundamental wave voltage of the three-phase voltage, and the harmonic voltage included in the second term is

(Equation 3) Can be expressed as Here, the expression (1) is α shown in FIG.
Corresponding to β conversion 2, the instantaneous value of the maximum value of the multiphase voltage is obtained by the equation (2). However, since the polyphase voltage includes the harmonic voltage, the calculated value of the equation (2) can be obtained by including the harmonic voltage. Therefore, the instantaneous value of the maximum value of the fundamental wave voltage in the polyphase voltage is calculated. Will not match. To compensate for this,
The following method shown in FIG. 1 corrects the error generated by the harmonic voltage.

Calculated values Vαx (t) and Vβx of the equation (1)
(T) are components of the α axis and the β axis on the α-β plane, respectively. Considering this component as a vector component on the α axis and the β axis, and combining these components, a rotation vector is obtained. Furthermore, considering a rotation coordinate α′-β ′ plane that rotates at the same speed as the angular frequency of the fundamental wave voltage in the multiphase voltage 1, and converting the above rotation vector onto this plane,

[Equation 4] become. However, the vector converted by the equation (4) draws a vector locus on the rotation coordinate α′-β ′ plane as shown in FIG. This vector locus becomes an error generated by the harmonic voltage. Therefore, in order to remove this error, α '
Axis component Vαx '(t) and β'axis component Vβx' (t)
Is time-averaged as

(Equation 5) Becomes This is the average value Vα according to the time average 4 in FIG.
m ′ (t) and Vβm ′ (t) will be obtained. By using these two time-averaged values, the vector magnitude Vo
When p (t) is calculated,

(Equation 6) This value gives the instantaneous value 8 of the maximum value of the fundamental wave voltage in the multiphase voltage. The vector display of this is a time-averaged multi-phase voltage vector 12 indicated by Vop (t) in FIG.

As described above, the average values Vαm '(t) and Vβm' (t) obtained by the time average 4 are components of the α'axis and the β'axis from which the harmonic voltage is removed. This component is equal to the fundamental wave voltage in the remaining three-phase voltage after removing the harmonic voltage of the second term on the right side of the equation (1). Therefore, the above average value Vα
By converting m ′ (t) and Vβm ′ (t) from the rotating coordinates into the α-β plane and further into the polyphase coordinates, the three-phase fundamental voltage can be obtained. Of these transformations, the transformation from rotational coordinates to the α-β plane is

(Equation 7) Can be done by Expression (7) is a calculation for obtaining the inverse rotation coordinate transformation 6 of FIG. Furthermore, the conversion from α-β plane to polyphase coordinates is

(Equation 8) Can be expressed as Formula (8) is the three-phase fundamental wave voltage Va1.
(T), Vb1 (t), and Vc1 (t) are represented and can be obtained by calculation of the αβ inverse transform 7 of FIG.

[0007]

According to the present invention, the method for measuring the instantaneous value of the maximum value of the fundamental wave voltage and the instantaneous value of the polyphase fundamental wave voltage in the multiphase voltage including the harmonic voltage is as follows. The vector obtained by converting into the rotation vector by the αβ conversion 2 and converted into the rotation coordinate that rotates at the same angular frequency as the fundamental wave voltage in the multiphase voltage by the rotation coordinate conversion 4 is time averaged by the time average 4. As a result, a vector with the harmonic voltage removed can be obtained. The magnitude of this vector is obtained as the maximum instantaneous value 8 by the amplitude calculation 5. On the other hand, when the vector component obtained by the time average 4 is converted into αβ coordinates by the rotating coordinate inverse transform 6 and then converted into polyphase coordinates by the αβ inverse transform 7, the harmonic voltage is removed to obtain the polyphase fundamental wave voltage. Get 9. Furthermore, an effective control system can be configured by applying the above-described method of measuring the maximum value of the fundamental wave voltage in the polyphase voltage and the instantaneous value of the polyphase fundamental wave voltage to the control of the AC electric equipment.

[0008]

FIG. 1 is a schematic diagram of a method for measuring an instantaneous value of a polyphase fundamental voltage according to the present invention. A method for obtaining an instantaneous value of the maximum value of the fundamental wave voltage in the polyphase voltage and an instantaneous value of the polyphase fundamental wave voltage. It shows how to find the value. First, in the method of obtaining the instantaneous value of the maximum value of the fundamental wave voltage in the multiphase voltage, the multiphase voltage 1 is calculated by the αβ conversion 2 to obtain the rotation vector. The magnitude of this rotation vector is equal to the amplitude of the multi-phase voltage, and by measuring the magnitude of this vector, the instantaneous value of the maximum value of the multi-phase voltage including the harmonic voltage can be obtained. However, in many cases, the maximum instantaneous value excluding the harmonic voltage is required. Here, in order to remove the harmonic voltage, a method of converting the rotation vector onto the rotation coordinate and making it stand still, and then performing time averaging is used. This operation is performed by the rotational coordinate conversion 3 and the time average 4 in FIG. When the obtained result is calculated by the amplitude calculation 5, the maximum instantaneous value that does not include the harmonic voltage can be obtained.

Next, how to obtain the instantaneous value of the polyphase fundamental wave voltage will be described. In FIG. 1, the output of time average 4 does not include the harmonic voltage, so if this output is converted to the α-β plane and returned to the polyphase coordinates, the instantaneous value of the polyphase fundamental wave voltage is obtained. You can In this operation, the inverse rotation coordinate transformation 6 in FIG. 1 takes charge of the transformation into the α-β plane, and the αβ inverse transformation 7 obtains the polyphase fundamental wave voltage 9 transformed into the polyphase coordinates.

The above-described method for measuring the instantaneous value of the maximum value of the fundamental wave voltage in the polyphase voltage and the instantaneous value of the polyphase fundamental wave voltage is
The experimental results used for measuring the commercial three-phase voltage are shown below. The measured three-phase voltage is a commercial voltage of three-phase 200V, and the harmonic voltage contained in this is a fifth harmonic voltage of about 1.9.
%, The 7th harmonic voltage is about 1.2%, and other high-order harmonic voltages are included, but they are omitted because they are within the measurement error range. The content of the 3rd harmonic voltage was in the order that can be ignored for the 5th harmonic voltage and the 7th harmonic voltage, because the transformer for the instrument was Δ-connected. Furthermore, the unbalanced component of the fundamental wave voltage was of a magnitude that did not affect the maximum measured value.
The commercial three-phase voltage 14 in FIG. 3 indicates the voltage waveform of each phase of the measured commercial three-phase voltage. The result of calculating the instantaneous value of the maximum value of this voltage by the equations (1) and (2) is the curve of the instantaneous value 15 of the maximum value in the second stage of FIG. As shown in the figure, the measured value contains the sixth harmonic component most, and is about ±
There is an error of 2.6%. Similarly, the curve shown in the third row of FIG. 3 is the characteristic of the instantaneous value 16 of the maximum value of the fundamental wave voltage in the commercial three-phase voltage obtained by using the equation (6). Since the harmonic voltage is removed from this curve, the error is ± 0.28%, which is a highly accurate result compared with the result obtained by using the equation (2). The measurement example of the maximum instantaneous value is shown above, but the waveform at the bottom of FIG. 3 shows the basic three-phase voltage obtained from the commercial three-phase voltage shown at the top of FIG. The waveform of the wave voltage 17 is shown.
This waveform is within a distortion rate of ± 0.8% and is a highly accurate three-phase fundamental wave voltage waveform.

[0011]

As described above, according to the present invention, it is possible to remove the harmonic voltage by averaging the multiphase voltage including the harmonic voltage on the rotating coordinates after αβ conversion. The instantaneous value of the maximum value of the fundamental wave voltage in the voltage can be accurately obtained. Further, it is also possible to obtain the instantaneous value of the multiphase fundamental wave voltage by utilizing the above method of removing the harmonic voltage. Therefore, a high-quality control system can be constructed by using this method for controlling AC electric equipment.

[Brief description of drawings]

FIG. 1 is a diagram showing an embodiment of a method for measuring an instantaneous value of a maximum value of a fundamental wave voltage in a polyphase voltage and an instantaneous value of a polyphase fundamental wave voltage of the present invention.

FIG. 2 is a diagram showing a method of removing an error caused by a harmonic voltage and an error by time averaging according to the present invention.

FIG. 3 is an example in which the instantaneous value of the maximum value of the fundamental wave voltage in a commercial three-phase voltage and the instantaneous value of the three-phase fundamental wave voltage are measured using the method of the present invention.

[Explanation of symbols]

1 Measured multi-phase voltage 2 Calculation of αβ conversion using formula (1) 3 Calculation of rotational coordinate conversion using formula (4) 4 Calculation of α'axis and β'axis using formula (5) Calculation of time average of components 5 Calculation of instantaneous value of maximum value using formula (6) 6 Calculation of inverse rotation coordinate conversion using formula (7) 7 Calculation from αβ coordinates using formula (8) Calculation of conversion to phase coordinates 8 Instantaneous value of maximum value of fundamental wave voltage in polyphase voltage 9 Instantaneous value of polyphase fundamental wave voltage 10 Vector locus drawn by harmonic voltage 11 Vector of polyphase voltage at t 12 hours Averaged vector of multi-phase voltage 13 Vector of multi-phase voltage at time ti 14 Waveform of commercial three-phase voltage 15 Instantaneous value Vem (t) 16 No. (6) of the maximum value of commercial three-phase voltage obtained by the equation (2) The instantaneous value Vop (t) 17 of the maximum value of the fundamental wave voltage in the commercial three-phase voltage obtained by the equation) was obtained by the equation (8). Phase fundamental voltage

Claims (1)

[Claims] 1. A method for obtaining an instantaneous value of a maximum value of a fundamental wave voltage in a polyphase voltage including a harmonic wave voltage and an instantaneous value of the polyphase fundamental wave voltage by using αβ conversion, wherein By converting the multi-phase voltage containing to the rotation vector that rotates on the α-β plane by αβ conversion, the rotation frequency of the rotation frequency that rotates at the same angular velocity as the angular frequency of the fundamental wave voltage in the multi-phase voltage including the above harmonic voltage After converting to the α'-β 'plane, the value obtained by eliminating the harmonic voltage by the time average of the two components of the α'axis and β'axis is obtained, and from that value, the maximum value of the fundamental wave voltage in the multiphase voltage In addition to finding the instantaneous value of, using the two components averaged over time,
A method for measuring the instantaneous value of the maximum value of the fundamental wave voltage in the polyphase voltage and the instantaneous value of the polyphase fundamental wave voltage, wherein the instantaneous value of the polyphase fundamental wave voltage is obtained by inverse conversion.