KR20180132856A - AC power regulator - Google Patents

Abstract

An AC power regulator having a function of controlling power supply to a load by phase control and measuring an effective value of an output voltage or an output current supplied to the load, the AC power regulator comprising: An effective value calculation unit for calculating an effective value of an output voltage or an output current on the basis of the measured instantaneous value; The correcting unit for correcting the difference based on the deviation from the sampling point to be measured is provided to more accurately measure the effective value of the output voltage or the output current value.

Description

AC power regulator

The present invention relates to an AC power regulator that performs control of power supply from an AC power source to a load by phase control.

Since the required electric power varies depending on the operation state in various electric devices (loads), while the voltage (effective value) of the commercial AC power source is a predetermined value (for example, 200 V) An AC power regulator for regulating the voltage of the AC power and supplying it to the load is used.

In such a power regulator, there are a phase control method, a time division control method, and an amplitude control method as its control methods.

Regarding this control method, a conventional technique relating to measurement of an effective value of an output voltage or an output current with respect to a load in a phase control method is disclosed in Patent Document 1. [

Patent Document 1: Japanese Patent Laid-Open Publication No. 2012-178030

The measurement of the effective value of the output voltage or the output current supplied to the load in the AC power regulator can be performed by measuring the measured value (AD conversion instantaneous value) of the voltage or current, which is an instantaneous value obtained based on the sampling period, And calculates the effective value of the output voltage or the output current based on the acquired value.

Fig. 3 is a diagram for explaining the calculation of the effective value of the output voltage. The waveforms in Fig. 3 represent one control cycle (half cycle of power supply) obtained by doubling the voltage value. Here, for the purpose of simplification, sampling is performed 10 times in one control cycle (the timing indicated by the dashed line indicates each sampling point). The rms value of the output voltage corresponds to the square root of the area of the trigger angle range of the waveform in the figure. As an actual apparatus, an approximate value of the area of the waveform in the figure is calculated based on each instantaneous value obtained at the sampling point, and the effective value is calculated by taking the square root of the approximate value. Incidentally, the trigger angle? Is a value representing the ratio of the time during which a power control element such as a thyristor is turned on to the time of one control cycle (0 <? <1). Here, the time during which the power control element is on is the time from the power control element being turned on during the control cycle to the zero point (off point) at which the control cycle ends.

Here, conventionally, the sampling point is determined based on the zero cross point. Therefore, as shown in the figure, the sampling point and the trigger point corresponding to the trigger angle do not coincide with each other. In this case, the hatched portion (difference between the trigger point and the sampling point) shown in the figure becomes an error factor.

As will be understood from the drawing, when the trigger angle is close to 1 (100%) or 0 (0%), the error factor is small. However, since the trigger angle is 0.5 (50% , The error factor becomes large.

Further, the deviation amount of the trigger point and the sampling point is between 0 and the sampling period, and when the deviation amount approaches the sampling period, the error factor is maximized.

Such an error factor has become a problem that can not be overlooked depending on the accuracy obtained as an apparatus.

In view of the above, the present invention relates to an AC power regulator that performs control of power supply from an AC power source to a load by phase control, and more accurately measures an effective value of an output voltage or an output current It is an object of the present invention to provide a possible AC power regulator.

(Configuration 1) An AC power regulator having a function of controlling power supply to a load by phase control and measuring an effective value of an output voltage or an output current supplied to the load, characterized in that, at a sampling timing, An effective value calculating unit for calculating an effective value of an output voltage or an output current on the basis of the measured instantaneous value, And a correction unit for correcting a difference (difference) based on a deviation from a sampling point for measuring the instantaneous value.

(Constitution 2) The AC power regulator according to Structure 1, wherein the correction section determines the sampling point to be synchronous with the trigger point.

(Arrangement 3) The AC power regulator according to Structure 2, characterized in that the sampling point is delayed from the trigger point by a predetermined margin value.

(Arrangement 4) The rheostat calculation unit calculates the rms value of the output voltage or the output current by executing the trapezoidal approximate calculation based on the measured instantaneous value. AC power regulator.

(Arrangement 5) The AC power regulator according to Structure 4, characterized in that the calculation of the effective value of the output voltage in accordance with the trapezoidal approximate calculation is performed based on the following formula.

[Number 1]

E _e is the effective value of the output voltage, E _m , E _n , E _i is the instantaneous value of the output voltage (E _m is the measured voltage value immediately after the trigger and E _n is the last voltage measuring point (E _i is an instantaneous voltage value of an arbitrary measurement point between E _m and E _n ), n is the number of times of sampling in half cycle of the power source, and m and ?? 2, the number 3). In the following expression,? Is a trigger angle, assuming an On ratio (a ratio of the time during which a power control element such as a thyristor is turned on to the time of one control cycle), and 0??? .

[Number 2]

[Number 3]

According to the AC power regulator of the present invention, since the difference based on the deviation between the trigger point in the phase control and the sampling point for measuring the instantaneous value can be corrected, the effective value of the output voltage or the output current value can be measured more accurately .

1 is a schematic block diagram showing a configuration of an AC power regulator according to an embodiment of the present invention;
2 is a flowchart showing an outline of a processing operation of the AC power regulator according to the embodiment of the present invention;
[Fig. 3] Diagram showing a waveform obtained by doubling the voltage value
4 is an explanatory diagram for comparing an error in the present invention with a conventional method
5 is a view for explaining a trapezoid approximation and a rectangle approximation;

Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings. Incidentally, the following embodiments are only examples for embodying the present invention, and the present invention is not limited thereto.

1 is a block diagram schematically showing a configuration of an alternating-current power regulator of an embodiment according to the present invention. The AC power regulator 100 of the present embodiment is an AC power regulator that performs control of power supply to a load by phase control. The AC power regulator 100 includes a target load ratio (0 to 1 (0% to 100%)), the power supply from the AC power source 3 to the heater which is the load 2 is controlled.

The AC power regulator 100 of the present embodiment includes a control target input processing section 110 for calculating a trigger angle for phase control based on a target load ratio given from a body temperature regulator A thyristor 130 for switching the power supply from the AC power supply 3 to the load 2 by a trigger signal output from the thyristor phase control unit 120, A current transformer 140, an A / D conversion timing interruption processing unit 150, and a zero-point interruption processing unit 160. [

Incidentally, the trigger angle is a ratio of a half-cycle of an AC voltage to a point of a 0 V point of an AC voltage at which the element is turned off from a trigger point at which a semiconductor element for controlling AC power such as a thyristor is turned on .

The A / D conversion timing interruption processing section 150 includes an A / D conversion timing control section 151 for performing processing such as sampling timing control, an A / D conversion timing control section 151 for outputting an output D conversion 1522 for A / D-converting the output (voltage value) from the current transformer 140 that detects the output current to the load 2, / D conversion unit 152 and a square value for performing a process of squaring and integrating the instantaneous value of the voltage (or current) obtained from the A / D conversion unit 152 ) Integrating section 153. [0035]

The A / D conversion timing control unit 151 functions as a correction unit for correcting the difference based on the deviation between the trigger point in the phase control and the sampling point for measuring the instantaneous value, by controlling the sampling timing.

The output voltage A / D conversion 1521 (or the output current A / D conversion 1522) is an output voltage of the A / D converter 1522 at the sampling timing instructed from the A / D conversion timing control unit 151 And functions as a measuring section for measuring the instantaneous value of the voltage (or the output current).

The zero point interruption processing section 160 includes a zero point detection section 161 for detecting a zero cross point of the AC power source 3 and a square sum value storage section The output voltage (or output current) supplied to the load 2 based on the value obtained by squaring the instantaneous value of the value stored in the square sum accumulated value storage unit 162, that is, the output voltage And an effective value calculating unit 163 for calculating the effective value of the output current (or output current) for each control cycle (every zero point).

Incidentally, each of the above-described configurations may be configured by hardware in a dedicated circuit or the like, and may be realized by software in a general-purpose circuit such as a microcomputer.

The AC power regulator 100 of the present embodiment having the above configuration corrects the difference based on the deviation between the trigger point in the phase control and the sampling point for measuring the instantaneous value so that the rms value of the output voltage It is to measure the value more accurately.

As described above, conventionally, the sampling point is determined based on the sampling period on the basis of the zero cross point regardless of the timing of the trigger point (if there is no change in the power supply period and the sampling period, the sampling point is fixed do). Therefore, as shown in Fig. 3, there is a deviation between each fixed sampling point and the fluctuating trigger point, and the hatched portion shown in the figure becomes an error factor. Since the sampling period is basically a short period (about 100 占 퐏 ec or less), there has been no problem with the above-mentioned error factors. However, as can be seen from the figure, when the trigger point is immediately after the sampling point, when the deviation between the trigger point and the sampling point is maximized and the vicinity of the center of the waveform (trigger angle is about 0.5) I.e., the error, is maximized. Such an error can be a value that can not be ignored in order to perform more accurate control in the AC power regulator 100. [

The AC power regulator 100 of the present embodiment makes it possible to more accurately measure the effective value of the output voltage (or the output current) by reducing the influence of such an error factor. Specifically, the error factor based on the deviation between the trigger point and the sampling point is minimized by controlling the sampling point to be synchronous with the trigger point (immediately after the sampling point).

The approximate calculation method of the effective value calculation in the present invention will be described.

First, as a precondition, a point at which the thyristor is turned on (On) is defined as a trigger point, and the phase difference between the trigger point and the zero point at the end of the phase-controlled half cycle (half cycle of the power supply) . However, the trigger angle &amp;phiv; is a numerical value indicative of the ratio with respect to the period T of the half cycle. Therefore, 0??? 1. As described above, it is assumed that the sampling point, which is the measurement timing of the instantaneous voltage, is synchronized with the trigger point, and the instantaneous voltage thereafter (or before) is measured every nth of the cycle T of the half cycle. That is, the sampling period becomes T / n.

As a result, the measurement point (sampling point) of the half-cycle instantaneous voltage subjected to phase control is _n from? ₁ to? _N. In addition, the first zero point of the phase controlled half cycle is defined as? ₀ , and the zero point at the end of the half cycle is defined as? _{N + 1} . Since the instantaneous voltage of? ₀ and? _{n + 1} is zero, it is not necessary to measure the instantaneous voltage. Let the trigger point be θ _m and the instantaneous voltage at that point be E _m .

At this time, the phase angle? Of the trigger point is a value obtained by dividing the measurement interval T / n by the measurement interval T / n by? · T and the value obtained by subtracting the decimal point of n ·? Symbol) is used.

[Number 4]

Assuming that there is a trigger point between (m-1) times and m times of the measurement interval T / n from the first zero point, the number is five.

[Number 5]

Further, by using the general formula (? _I ) of the sampling point using ?? defined by the equation 6, it becomes the number 7.

[Number 6]

[Numeral 7]

Here, i is an integer in the range of 1? I? N

Here, letting f (?) Be a function of the voltage, the voltage E _i of each instantaneous voltage measurement point becomes 8.

[Numeral 8]

i is an integer in the range of 1 ≤ i ≤ n, but since the thyristor is off at 1 ≤ i ≤ m-1, the voltage at the measuring point becomes 0, so the following power calculation and calculation of the effective value are omitted.

From the instantaneous voltage measurement value above, the approximate expression that calculates the average power of half-cycle when the phase is controlled by the trigger angle? Based on the trapezoidal approximation calculation becomes the number 9,

[Number 9]

[Number 10]

Here, E _{n + 1} is the instantaneous voltage of the zero point at the end of the half cycle, and thus E _{n + 1} = 0. Also, since P _R = E _e ² / R, the general formula of E _e is 11 from these.

[Number 11]

Numeral 11 is a general formula for calculating the effective value of the output voltage by performing the trapezoid approximate calculation based on the instantaneous value of the measured voltage. By controlling the sampling point to be synchronous with the trigger point and calculating based on the trapezoidal approximation, the rms value of the output voltage can be measured more accurately.

If n is a large value, E _n ² is a very small value compared to E _e . Therefore, if _n is a sufficiently small value with respect to required measurement accuracy, it may be omitted to be 12.

[Number 12]

Next, an outline of the calculation process of the effective value of the output voltage in the AC power regulator 100 of the present embodiment will be described with reference to Fig. 2. Fig.

2 is a flowchart showing the outline of the process of calculating the effective value of the output voltage. By the processings of steps 201 to 210, the effective value of the output voltage in half cycle (half cycle of the power supply) .

First, in the A / D conversion timing control unit 151, a trigger point is acquired from the thyristor phase control unit 120 (step 201), and the sampling point is set to be synchronous with the trigger point (step 202) . The sampling timing is determined so that the trigger point and the sampling point are at the same time (the sampling point is immediately after the trigger point) in Fig. 3, and the sampling points are arranged for each sampling period before and after the sampling point, Determine each sampling point. In addition, since there is no need to perform sampling basically before the trigger point, it is also possible to set the sampling point immediately after the trigger point, and then set the sampling point for each sampling period thereafter.

In the following step 203, it is determined whether or not the sampling point immediately after the trigger point (the sampling point synchronized with the trigger point in step 201) has reached. If the sampling point immediately after the trigger point has been reached, The routine proceeds to step 204, in which the instantaneous output voltage instantaneous value obtained from the output voltage A / D converter 1521 is substituted into the variable E ₁ at that point in time, and the process of substituting 0 to the variable S (initializing S) . Incidentally, the initialization process of S may be performed at any timing before this.

The loop processing of the subsequent steps (205) to (206) is processing for determining whether or not each sampling point or zero cross point has been reached.

When reaching the sampling point has, on one assigns the value of variable E ₁ to the variable E ₂ Then, the processing to be filled with the output voltage instantaneous value obtained from the output voltage A / D conversion unit 1521 at that point in the variable E ₁ (Step 206: Yes → Step 207). Accordingly, the numerical values serving as the basis of the values of both sides of the trapezoid required for the trapezoid approximation calculation are substituted into the variables E ₁ and E ₂ .

In step 208, the squared value integration section 153 calculates the area of one measurement section in the squared waveform (Fig. 3) of the instantaneous value of the voltage in the trapezoid approximate calculation, do. That is, E ₁ ² and E ₂ ² are added, and the sampling period (T / n) is multiplied and divided by 2 (the area of one measurement section is calculated by a trapezoidal approximate calculation) S to be accumulated. In addition, the variable S is stored in the square sum accumulated value storage unit 162. [

The processing of steps 207 to 208 is executed every time each sampling point arrives based on the loop processing of the steps 205 to 206 so that the area of the squared waveform of the instantaneous value of the voltage (I.e., the integral value) is substituted into the variable S.

When the zero cross point determined by the zero point detecting unit 161 arrives, the area of the last measurement period of the square wave of the square of the instantaneous value of the voltage is accumulated in the variable S, and the square sum accumulated value storage unit 162 stores (Step 205: Yes → Step 209).

As described above, since the sampling point in this embodiment is synchronized with the trigger point and is not based on zero cross, the last measurement interval is not equal to the sampling period (there may be the same case). The last measurement period is represented by ?? / n (?? depends on the number 6), and since the voltage value (instantaneous value) of the zero cross point naturally also becomes zero, E ₁ ² and 0 ² are added, / n and multiply by 2 to sum to the variable S.

Finally, the effective value calculating unit 163 calculates the effective value E _e of the output voltage by calculating the square root of S based on S stored in the square sum accumulated value storage unit 162 (Step 210).

The effective value of the output voltage in the half cycle (half cycle of the power supply) is calculated by the above process (steps 201 to 210), and the process (steps 201 to 210) By repeating every cycle, the effective value of the output voltage of each half cycle is calculated.

In addition, in the explanation based on the flowchart of Fig. 2, the effective value E _e is not calculated using the equation 11 as it is, but it is calculated based on the equation 11 substantially as shown in the processing contents It is also possible to log the measured value (instantaneous value) and calculate the effective value E _e directly by using the number 11).

Fig. 4 is an explanatory diagram for comparing errors of the rms values calculated respectively in the present invention and the conventional system with the theoretical values.

The graph on the left side of the drawing shows an example when the present invention is applied, and X ' _{1 to} X' ₉ show respective sampling points. That is, the sampling period τ, and with one-tenth of the half cycle of the power source (Incidentally, in FIG. 4 X _'1 ~X' ₉ and X ₁ ~X ₉ is, E ² (each at the sampling timing The square of the instantaneous value of the voltage). In this example, X ' ₆ is set to be synchronous with the trigger point, and each sampling point is defined by the sampling period τ with the reference point as X' ₆ . If the width Δφ of the last section is denoted by Δθ, Δθ / n.

On the other hand, in this situation, the graph of the right side shows a case where the conventional technique is applied. In the conventional technique, the sampled points is synchronized with the zero-cross point, and as a result, between the trigger point and the sampling point X _6, produces the variation of Δφ. That is, it is possible to detect the first output voltage from the delayed sampling points X ₆ from a trigger point as Δφ, the interval between the X ₆ from the trigger point is the error factor as a non-detection period.

The graph on the upper center of the drawing is a graph showing the error with respect to the theoretical value with respect to the present invention and the conventional method, and the graph on the lower center shows a graph of the error ratio with respect to the theoretical value.

As understood from the figure, in the conventional system, the error becomes larger as the deviation ?? of the trigger point and the sampling point becomes larger, and is maximized as the deviation ?? becomes closer to the sampling period?.

On the other hand, in the present invention, as can be seen from the figure, the error is suppressed to a very small value (only an error due to the approximation of the trapezoidal approximation), and it can be seen that the error generated in the conventional method is greatly improved.

As described above, according to the AC power regulator 100 of the present embodiment, since the difference based on the deviation between the trigger point in the phase control and the sampling point for measuring the instantaneous value can be corrected, the effective value Can be measured more accurately.

Further, according to the AC power regulator 100 of the present embodiment, since the trapezoidal approximation calculation is used, the error can be further reduced.

When the rectangular approximation is used to obtain the integrated value of the squared waveform of the instantaneous value, the error with respect to the integral value (area) of the waveform becomes large as shown in Fig. 5 (a). As shown in Fig. 5 (a), when all the half cycles are integrated (that is, when the trigger angle is 1), the error is canceled before and after the peak and the error as a whole is almost eliminated. However, if the trigger angle is less than 1 An error that is not canceled occurs, and when the trigger angle is about 0.5, this error becomes maximum.

On the other hand, as shown in Fig. 5 (b), by using the trapezoid approximation, the error can be reduced.

In this embodiment, the case where the rms value of the output voltage is measured is described as an example. However, the same concept can be applied to the case of measuring the rms value of the output current (however, In the case of measuring the instantaneous value, it is necessary to consider the phase delay and the leading edge based on the circuit characteristic).

In the present embodiment, the correction of the difference (hatched portion in FIG. 3) based on the deviation between the trigger point in the phase control and the sampling point for measuring the instantaneous value is performed by setting the sampling point to be synchronous with the trigger point However, it is also possible to correct it by other methods. For example, the measurement itself is performed by a conventional method (the right diagram in Fig. 4), and a difference (a hatched portion in Fig. 3) based on the deviation from the sampling point at which the instantaneous value is measured is subtracted Or the like.

In this embodiment, a more accurate value is obtained by integrating the last measurement period (Δφ section in the graph on the left side of FIG. 4). However, as can be seen from the graph on the left side of FIG. 4, (Step 209 in FIG. 2 is omitted), it is possible to reduce the amount of calculation when the necessary precision is obtained without integrating this part.

Incidentally, in the present invention, "determining the sampling point to be synchronous with the trigger point" does not strictly limit the sampling point to be immediately after the trigger point, but substantially indicates that the sampling point is synchronized with the trigger point.

For example, in the case where the rising edge of the voltage at the load is slightly later than the trigger point or is irregular due to circuit characteristics or the like, the sampling point is not made to be concurrent with the trigger point but the sampling point You need to come. This is to ensure the measurement of the voltage. In such a case, for example, the worst value (the worst value) in which the granularity of the voltage is delayed (minute) or irregular (minute) is set in advance as the margin value so that the sampling point is delayed from the trigger point by the margin value However, this also does not depend on the fact that the sampling point is synchronized with the trigger point as a reference, and the concept of the present invention corresponds to &quot; such that the sampling point is determined to be synchronous with the trigger point &quot;.

100: AC power regulator
130: Thyristor
150: A / D conversion timing interrupt processor
151: A / D conversion timing control section
152: A / D conversion section
153: a square value integrating unit
160: Zero point interrupt processor
161: Zero point detection unit
162: Square sum accumulation value storage unit
163: RMS value calculation unit
2: Load
3: AC power source

Claims (5)

An AC power regulator having a function of controlling power supply to a load by phase control and measuring an effective value of an output voltage or an output current supplied to the load,
A measuring unit for measuring an instantaneous value of an output voltage or an output current supplied to the load at a sampling timing,
An effective value calculation unit for calculating an effective value of an output voltage or an output current based on the measured instantaneous value,
A correction unit for correcting a difference based on a deviation between a trigger point in the phase control and a sampling point for measuring the instantaneous value,
And an AC power regulator. The method according to claim 1,
And the correction unit sets the sampling point to be synchronous with the trigger point. 3. The method of claim 2,
And the sampling point is delayed from the trigger point by a predetermined margin value. 4. The method according to any one of claims 1 to 3,
And the rms value calculating unit calculates a rms value of the output voltage or the output current by executing a trapezoid approximate calculation based on the measured instantaneous value. 5. The method of claim 4,
Wherein the calculation of the effective value of the output voltage according to the trapezoid approximate calculation is performed based on the following equation.
[Number 1]

E _e is the effective value of the output voltage, E _m , E _n , E _i is the instantaneous value of the output voltage (E _m is the measured voltage value immediately after the trigger and E _n is the last voltage measuring point E _i is an instantaneous voltage value of an arbitrary measurement point between E _m and E _n ), n is the number of times of sampling in half cycle of the power source, and m and ?? are respectively represented by the following equations The value to be calculated. In the following expression,? Is a trigger angle.

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