JPWO2018047290A1 - AC power regulator - Google Patents

Abstract

An AC power regulator having a function of performing control of power supply to a load by phase control and measuring an effective value of an output voltage or output current supplied to the load, an output supplied to the load at a predetermined sampling timing. A measurement unit that measures an instantaneous value of the voltage or the output current, an effective value calculation unit that calculates an effective value of the output voltage or the output current based on the measured instantaneous value, a trigger point in phase control, and the instantaneous value And a correction unit that corrects the difference based on the deviation from the sampling point to be measured, thereby more accurately measuring the effective value of the output voltage or the output current value.

Description

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

While the voltage (effective value) of a commercial AC power supply is a predetermined value (for example, 200 V), various electric devices (loads) may change the necessary power depending on the operating state, so that commercial AC An AC power regulator that regulates the voltage of an AC power supply and supplies it to a load is used.
In such a power regulator, there are a phase control method, a time division control method, an amplitude control method and the like as a control method thereof.
With respect to these control methods, Patent Document 1 discloses a prior art related to measurement of an effective value of an output voltage or an output current to a load in a phase control method.

JP, 2012-178030, A

In the AC power regulator, the measurement of the effective value of the output voltage or output current supplied to the load can be performed by using one measurement value (instant value for AD conversion) of the voltage or current which is an instantaneous value obtained based on the sampling period. The control voltage is acquired over the control cycle, and the effective value of the output voltage or output current is calculated based on this.
FIG. 3 is a diagram for explaining the calculation of the effective value of the output voltage. The waveform in the figure shows one control cycle (half cycle of the power supply) although the voltage value is squared. Here, for the sake of simplicity, an example in which sampling is performed ten times in one control cycle is taken as an example (the timing indicated by the alternate long and short dash line indicates each sampling point). The effective value of the output voltage corresponds to the square root of the area of the range of the trigger angle of the waveform in the figure. As an actual device, 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 square root of this is calculated to calculate the effective value. The trigger angle (φ) is a value indicating the ratio of the time during which the power control element such as the thyristor is on to the time of one control cycle (0 <φ <1). Here, the time during which the power control element is on refers to the time from the power control element being on during the control cycle to the zero point (off point) at which the control cycle ends.
Here, conventionally, the sampling point is determined on the basis of the zero crossing point. Therefore, as shown in the figure, the sampling point may not coincide with the trigger point corresponding to the trigger angle. In this case, the hatched portion (the difference between the trigger point and the sampling point) shown in the figure becomes an error factor.
As understood from the figure, since the area at both ends of the waveform is small, this error factor is small when the trigger angle is close to 1 (100%) or 0 (0%), but the trigger angle is small. Is larger than 0.5 (50%).
Further, the shift amount between the trigger point and the sampling point is between 0 and the sampling period, and the above error factor is maximized when the shift amount becomes close to the sampling period.
Such an error factor is a problem that can not be overlooked depending on the accuracy required for the device.

  The present invention relates to an AC power regulator which performs control of power supply from an AC power supply to a load by phase control in view of the above-mentioned point, and is an AC capable of more accurately measuring an effective value of an output voltage or an output current. The purpose is to provide a power regulator.

(Configuration 1)
An AC power regulator having a function of performing control of power supply to a load by phase control and measuring an effective value of an output voltage or output current supplied to the load, which is supplied to the load at sampling timing. A measurement unit that measures an instantaneous value of the output voltage or the output current, an effective value calculation unit that calculates an effective value of the output voltage or the output current based on the measured instantaneous value, a trigger point in phase control, And a correction unit configured to correct a difference based on a deviation from a sampling point at which the instantaneous value is measured.

(Configuration 2)
The AC power regulator according to Configuration 1, wherein the correction unit determines the sampling point to be synchronized with the trigger point.

(Configuration 3)
The AC power regulator according to Configuration 2, wherein the sampling point is delayed from the trigger point by a preset margin value.

(Configuration 4)
In any one of configurations 1 to 3, the effective value calculating unit calculates an effective value of the output voltage or the output current by performing trapezoidal approximation calculation based on the measured instantaneous value. AC power regulator as described.

(Configuration 5)
The alternating current power regulator according to Configuration 4, wherein the calculation of the effective value of the output voltage by the trapezoidal approximation calculation is performed based on the following equation.

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 of the control cycle during the effective value measurement) The instantaneous voltage value at the measurement point, E _i is the instantaneous voltage value at any measurement point between E _m and E _n ), n is the number of samplings in a half cycle of the power supply, and m and Δθ are The value calculated by the equation (Equation 2, Equation 3). In the following equation, φ is a trigger angle, and here, it is assumed that the on ratio (the ratio of the time during which the power control element such as the thyristor is on to the time of one control cycle), 0 ≦ φ ≦ 1.

  According to the AC power regulator of the present invention, it is possible to correct the difference based on the shift between the trigger point in phase control and the sampling point at which the instantaneous value is measured. It becomes possible to measure accurately.

Schematic block diagram showing the configuration of an AC power regulator according to an embodiment of the present invention The flowchart which shows the outline of processing operation concerning the present invention of the exchange power regulator of an embodiment Figure showing the square of the voltage value Explanatory drawing for comparing the error in this invention and a conventional system Diagram to explain trapezoidal approximation and rectangular approximation

  Hereinafter, embodiments of the present invention will be specifically described with reference to the drawings. In addition, the following embodiment is one form at the time of embodying this invention, Comprising: This invention is not limited within the range.

FIG. 1 is a block diagram schematically showing the configuration of an AC power regulator according to an embodiment of the present invention. The AC power regulator 100 according to this embodiment is an AC power regulator that performs control of power supply to a load by phase control, and a target load factor (0) input from a temperature regulator (not shown) that is an external device. Control of power supply from the AC power supply 3 to the heater which is the load 2 is performed based on 1 to 1 (0% to 100%).
The AC power regulator 100 of this embodiment is
A control target input processing unit 110 that calculates a trigger angle φ for phase control based on a target load factor given by a temperature controller (not shown);
A thyristor phase control unit 120 that controls the thyristor 130 based on the trigger angle φ;
A thyristor 130 that switches power supply from the AC power supply 3 to the load 2 by a trigger signal output from the thyristor phase control unit 120;
Current transformer 140,
A / D conversion timing interrupt processing unit 150,
And a zero point interrupt processing unit 160.
Note that the trigger angle is the ratio to the half cycle of the AC voltage in the section from the trigger point that is the timing to turn on the semiconductor element that controls AC power such as a thyristor to the 0V point of the AC voltage that the element turns off. It is

The A / D conversion timing interrupt processing unit 150
An A / D conversion timing control unit 151 that performs processing such as control of sampling timing;
An output voltage A / D conversion 1521 that A / D converts an output voltage value for the load 2 and an output current A / D that A / D converts an output (voltage value) from the current transformer 140 that detects an output current for the load 2 An A / D conversion unit 152 comprising a conversion 1522;
And a square value integrating unit 153 for performing a process of squaring and integrating the instantaneous values of the voltage (or current) obtained from the A / D conversion unit 152.
The A / D conversion timing control unit 151 functions as a correction unit that corrects the difference based on the difference between the trigger point in phase control and the sampling point at which the instantaneous value is measured by controlling the sampling timing.
Also, the output voltage A / D conversion 1521 (or the output current A / D conversion 1522) is the output voltage (or the output current) supplied to the load 2 at the sampling timing instructed from the A / D conversion timing control unit 151. Functions as a measurement unit that measures the instantaneous value of

The zero point interrupt processing unit 160
A zero point detection unit 161 that detects a zero cross point of the AC power supply 3;
A squared integrated value storage unit 162 that stores the value calculated by the squared value integration unit 153;
The output voltage (or output current) supplied to the load 2 based on the value stored in the squared integration value storage unit 162, that is, the value obtained by squaring the instantaneous value of the output voltage (or output current) and integrating it. And an effective value calculating unit that calculates an effective value for each control cycle (for each zero point).

  Each of the above-described configurations may be configured as hardware with a dedicated circuit or the like, or may be implemented as software on 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 difference between the trigger point in phase control and the sampling point at which the instantaneous value is measured, thereby reducing the output voltage (or output current). The actual value is to be measured more accurately.
As described above, conventionally, the sampling point is determined based on the sampling cycle based on the zero cross point regardless of the timing of the trigger point (if there is no change in the power supply cycle and the sampling cycle) , Sampling points will be fixed). Therefore, as shown in FIG. 3, a shift occurs between basically fixed sampling points and a variable trigger point, and the hatched portion shown in the figure causes an error. Since the sampling period is basically a short period (about 100 μs or less), conventionally, there has been no problem awareness even with the above error factors. However, as understood from the figure, when the trigger point is immediately after the sampling point, the amount of deviation between the trigger point and the sampling point is maximized and the vicinity of the center of the waveform (the trigger angle is 0. 0). In the case of about 5), the area of the hatched portion, that is, the amount of error is maximized. Such an error may be a non-negligible value in order to perform more accurate control in the AC power regulator 100.
The AC power regulator 100 according to the present embodiment reduces the influence of such an error factor, and makes it possible to measure the effective value of the output voltage (or output current) more accurately. Specifically, by controlling the sampling point to be at the same time as the trigger point (the sampling point is immediately after the trigger point), an error factor based on the deviation between the trigger point and the sampling point is minimized. is there.

The approximate calculation method of the effective value calculation in the present invention will be described.
First, as a precondition, the trigger angle φ is 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) with the trigger point turned on as the trigger point. . Here, the trigger angle φ is a numerical value representing a ratio to the cycle T of a half cycle. Therefore, 0 ≦ φ ≦ 1. As described above, the sampling point, which is the measurement timing of the instantaneous voltage, shall be synchronized with the trigger point, and the measurement of the instantaneous voltage thereafter (or earlier) shall be performed every nth of the cycle T of a half cycle. . That is, the sampling period is T / n.
As a result, the number of measurement points (sampling points) of the phase-controlled half cycle instantaneous voltage is _n from θ ₁ to θ _n . The initial zero point of the phase-controlled half cycle is θ ₀ , and the zero point at the end of the half cycle is θ _{n + 1} . The instantaneous voltages of θ ₀ and θ _{n + 1} are 0 V because they are zero points, and there is no need to measure the instantaneous voltage. Also, let the trigger point be θ _m and the instantaneous voltage at that point be E _m .
At this time, the phase angle φ of the trigger point is the measurement interval T / n, a value obtained by dividing φ · T by the measurement interval T / n, and a value obtained by rounding off the decimal part of n · φ It can be expressed by the number 4 using the gaussian meaning.

  Here, if there is a trigger point between (m-1) times and m times of the measurement interval T / n from the first zero point, then the equation 5 is given.

Further, when the general expression (θ _i ) of the sampling point is written using Δθ defined by the equation 6, the equation 7 is obtained.

Here, i is an integer in the range of 1 ≦ i ≦ n

Here, when a function of the voltage and f (theta), the voltage E _i of each instantaneous voltage measurement point is several 8.

i is an integer in the range of 1 ≦ i ≦ n, but since the thyristor is off when 1 ≦ i ≦ m−1, the voltage at the measurement point is 0, so it was omitted in the following power calculation and effective value calculation.

  From the above instantaneous voltage measurement values, the approximate expression for calculating the average power of a half cycle when phase control is performed at the trigger angle φ based on the trapezoidal approximation calculation is given by Equation 9, and can be summarized by Equation 10.

Here, E _{n + 1} is the instantaneous voltage at the end of the half cycle, so E _{n + 1} = 0. Further, since P _R = E _e ² / R, from these, the general formula of E _e is represented by Formula 11.

  Equation 11 is a general equation for calculating the effective value of the output voltage by performing trapezoidal approximation calculation based on the instantaneous value of the measured voltage. By controlling the sampling point to be synchronized with the trigger point and performing calculation based on the trapezoidal approximation calculation, it is possible to measure the effective value of the output voltage more accurately.

Also, if n is a large value, _En ² will be a very small value compared to E _e. good.

Next, an outline of calculation processing of the effective value of the output voltage in the AC power regulator 100 of the present embodiment will be described based on FIG.
FIG. 2 is a flowchart showing an outline of the process of calculating the effective value of the output voltage, and calculates the effective value of the output voltage in a half cycle (half cycle of the power supply) by the processes of steps 201 to 210. .

  First, the trigger point is acquired from the thyristor phase control unit 120 in the A / D conversion timing control unit 151 (step 201), and the sampling point is determined to be the same timing as the trigger point (step 202). The sampling timing is determined so that the trigger point and the sampling point in FIG. 3 coincide with each other (the sampling point immediately after the trigger point), and this is used as a reference point. As arranged, each sampling point is to be determined. Since there is basically no need for sampling before the trigger point, a sampling point may be set immediately after the trigger point, and thereafter, may be used as a sampling point for each sampling cycle.

In the next step 203, it is determined whether or not the sampling point immediately after the trigger point (the sampling point made coincident with the trigger point in step 201) is reached, and if the sampling point immediately after the trigger point is reached, The process proceeds to step 204, at which time the processing of substituting the output voltage instantaneous value obtained from the output voltage A / D conversion unit 1521 into the variable E ₁ and the processing of substituting 0 into the variable S (initialization of S) Do. The initialization process of S may be performed at any timing before this.

The subsequent loop processing of step 205 to step 206 is processing to determine whether or not each sampling point or zero crossing point has been reached.
When that led to the sampling point, after substituting the value of variable E ₁ to the variable E _2, to assign the output voltage instantaneous value obtained from the output voltage A / D conversion unit 1521 at that point in the variable E ₁ treatment (Step 206: Yes → step 207). As a result, numerical values that are the sources of the values of both sides of the trapezoid necessary for the trapezoidal approximation calculation are substituted into the variables E ₁ and E ₂ .
In step 208, the square value integrating unit 153 calculates the area of one measurement section in the square waveform (FIG. 3) of the instantaneous value of voltage by trapezoidal approximation and integrates the area. That adds E ₁ ² and E ₂ ^2, this divided by 2 by multiplying the sampling period (T / n) to (1 which the area of the measurement zone was calculated by the trapezoidal approximation), variable It is integrated to S. The variable S is stored in the integrated square value storage unit 162.
Based on the loop processing of step 205 to step 206, the processing of step 207 to step 208 is executed each time each sampling point arrives, so that the area (the integral value) of the square of the instantaneous value of the voltage The approximate value of is substituted into the variable S.

When the zero crossing point determined by the zero point detection unit 161 arrives, the area of the last measurement section of the square waveform of the voltage instantaneous value is integrated into the variable S, and stored in the square integration value storage unit 162 The process is performed (step 205: Yes → step 209).
As described above, since the sampling point in the present embodiment is synchronized with the trigger point and is not based on the zero crossing, the final measurement interval is not the same as the sampling period (may be the same). Since the final measurement interval is represented by Δθ / n (Δθ is according to Equation 6) and the voltage value (instantaneous value) is naturally zero at the zero crossing point, E ₁ ² and 0 ² are added, and this is added Is multiplied by .DELTA..theta. / N and divided by two to be integrated into the variable S. FIG.
Finally, based on the S stored in the squared integrated value storage unit 162, by calculating this square root, the process of calculating the effective value E _e of the output voltage is performed by an effective value calculating section 163 ( Step 210).
By the above processing (steps 201 to 210), the effective value of the output voltage in a half cycle (half cycle of the power supply) is calculated, and each half cycle is repeated by repeating the processing (steps 201 to 210). The effective value of the output voltage of the cycle is calculated.

In the description based on the flowchart of FIG. 2, although the effective value E _e is not calculated using the above-described number 11 as it is, as is apparent from the processing content, It is calculated based on 11. (Processing may be such that each measured value (instantaneous value) is logged, and Equation 11 is directly used to calculate the effective value E _e .)

FIG. 4 is an explanatory view for comparing the errors of theoretical values calculated with the present invention and the conventional method.
Left graph of figure shows one example of applying the present invention, _X'1 ~X' ₉ is shows each sampling point. That is, the sampling period tau, those that are one-tenth of the half cycle of the power supply (Note, _X'1 ~X' ₉ and _X 1 to X ₉ in FIG. 4, in ^{E 2} (each sampling timing Indicates the square of the instantaneous value of the voltage). In this example, X ′ ₆ is determined to be at the same time as the trigger point, and each sampling point is determined at the sampling period τ with this as a reference point. The width Δφ of the last section is Δθ / n.
On the other hand, the graph on the right shows the case where the conventional method is applied in the same situation as this. In the conventional method, the sampling points are synchronized to the zero crossing point, so that the deviation of Δφ occurs between the trigger point and the sampling point X _6. That, which can be detected for the first time the output voltage at the sampling point X ₆ delayed from the trigger point only [Delta] [phi, section between X ₆ from the trigger point is made in the error factor as undetectable period.

The upper graph at the center of the figure is a graph showing the error with respect to the theoretical value for the present invention and the conventional system, and the lower graph at the center is a graph showing the ratio of the error to the theoretical value.
As understood from the figure, in the conventional method, the error increases as the shift amount Δφ between the trigger point and the sampling point increases, and the shift amount Δφ maximizes as it approaches the sampling period τ.
On the other hand, in the present invention, as is apparent from the figure, the error is kept to a very small value (only the error due to the approximation of the trapezoidal approximation), and the error caused in the conventional method is greatly improved. I understand that

  As described above, according to the AC power regulator 100 of the present embodiment, the difference based on the difference between the trigger point in phase control and the sampling point at which the instantaneous value is measured can be corrected. 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.
In the case of using the rectangular approximation when obtaining the integral value of the square of the instantaneous value, as shown in FIG. 5A, the error with respect to the integral value (area) of the waveform becomes large. As shown in FIG. 5 (a), when integrating all half cycles (that is, when the trigger angle is 1), the errors are canceled before and after the peak, and the overall error is almost eliminated. If the trigger angle is less than 1, an uncancelled error occurs, and this error becomes maximum when the trigger angle is about 0.5.
On the other hand, as shown in FIG. 5B, the error can be reduced by using the trapezoidal approximation.

  In the present embodiment, the case of measuring the effective value of the output voltage has been described as an example, but the same concept can be applied to the case of measuring the effective value of the output current (however, the current) When measuring the current instantaneous value using the transformer 140, it is necessary to consider the phase delay and the lead based on the circuit characteristics).

  In this embodiment, the correction of the difference (hatched portion in FIG. 3) based on the deviation between the trigger point in phase control and the sampling point for measuring the instantaneous value is determined so that the sampling point coincides with the trigger point. Although what has been described is described as an example, it may be corrected by other methods. For example, the measurement itself is performed according to the conventional method (right side of FIG. 4), and a difference (hatched portion in FIG. 3) based on the deviation from the sampling point for measuring the instantaneous value It may be corrected to be subtracted.

  In the present embodiment, an example is described in which the more accurate value is obtained by integrating also for the last measurement interval (interval of Δφ in the graph on the left of FIG. 4), but from the graph on the left of FIG. As will be understood, the area of the section of Δφ is relatively small, so if the required accuracy can be obtained without integrating this part, integration of the section of Δφ is omitted (step 209 of FIG. 2 It may be omitted to reduce the amount of calculation.

In the present invention, “determining the sampling point to be at the same time as the trigger point” does not strictly limit the sampling point to one immediately after the trigger point, but the sampling point substantially corresponds to the trigger point. Indicates what is synchronized to
For example, if the rise of the voltage at the load is slightly delayed or deviates from the trigger point due to the circuit characteristics etc., the sampling point should come immediately after the rise of the voltage instead of making the sampling point simultaneous with the trigger point. There is a need to. This is to ensure measurement of voltage. In such a case, for example, the worst value of the delay or rise of voltage rise is set in advance as a margin value, and the sampling point is delayed from the trigger point by the margin value. Also, the sampling point is synchronized with the trigger point as a reference, and the concept of the present invention is that such a thing corresponds to “determine the sampling point to be at the same time as the trigger point”. It is.

100. . . AC power regulator 130. . . Thyristor 150. . . A / D conversion timing interrupt processing unit 151. . . A / D conversion timing control unit 152. . . A / D conversion unit 153. . . Square value integration unit 160. . . Zero point interrupt processing unit 161. . . Zero point detection unit 162. . . Squared integrated value storage unit 163. . . Effective value calculation unit 2. . . Load 3. . . AC source

Claims (5)

An AC power regulator having a function of performing control of power supply to a load by phase control and measuring an effective value of an output voltage or output current supplied to the load,
A measurement unit that measures an instantaneous value of an output voltage or an output current supplied to the load at a sampling timing;
An effective value calculating unit that calculates an effective value of an output voltage or an output current based on the measured instantaneous value;
A correction unit that corrects a difference based on a shift between a trigger point in phase control and a sampling point at which the instantaneous value is measured;
An AC power regulator comprising:   The AC power regulator according to claim 1, wherein the correction unit determines the sampling point to be synchronized with the trigger point.   The AC power regulator according to claim 2, wherein the sampling point is delayed from the trigger point by a preset margin value.   The effective value of the output voltage or the output current is calculated by performing the trapezoidal approximation calculation based on the measured instantaneous value to calculate the effective value of the output voltage or the output current. AC power regulator as described in. The AC power regulator according to claim 4, wherein the calculation of the effective value of the output voltage by the trapezoidal approximation calculation is performed based on the following equation.