JPH09130972A - Method and apparatus for calculating operational phase of specific frequency component signal and digital control system - Google Patents

Abstract

PROBLEM TO BE SOLVED: To determine the operational phase of a specific frequency component signal accurately and to control an active filter using the operational phase signal. SOLUTION: Assuming the value of a specific frequency component signal at current point of time t1 is V1, the value of that signal at a previous sampling time t0 is V0, the phase at current point of time is ϕ, and the sampling period is TS, operational phase sin(ω0 t1+ϕ) of that signal can be determined as follows; sin(ω0 t1+ϕ)=sin[tan<-1> (V1sinω0 TS)/-(V1cosω0 TS-V0)}]. Since the operational phase is calculated according to the formula in a digital control system, it can be determined accurately regardless of noise in the vicinity of zero-cross point. When the apparatus is applied to the digital control system for active filter, the operational phase of an AC power supply can be calculated accurately from a sampled voltage thereof thus realizing a highly accurate control.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION In a digital control system, when an analog signal having a single specific frequency as a component is sampled and converted into a digital signal to perform control calculation,
In some cases, it is necessary to obtain the operating phase and express this signal in the form of a mathematical expression. The present invention relates to a method and an apparatus for accurately obtaining an operating phase of a signal having the above-mentioned specific frequency component, and a digital control system for controlling an active filter using the method.

[0002]

2. Description of the Related Art Conventionally, as a method of expressing an operating phase of a signal having a component of a specific frequency, for example, a time from that point is counted with reference to a zero cross point of the signal, and a phase of the signal is represented. It has been known.

[0003]

The above method has the following problems. (1) If distortion or noise is superimposed on the waveform near the zero cross point, a large error occurs. (2) When the phase suddenly shifts, it may become unusable.

The present invention has been made in consideration of the above-mentioned problems of the prior art. The first object of the present invention is to superimpose a slight noise or the like on a signal of a specific frequency component, or to make a sudden noise. It is an object of the present invention to provide a method and a device for calculating an operating phase that can accurately obtain the operating phase of a signal even if there is a large phase shift and can express the signal by a mathematical expression. A second object of the present invention is to accurately calculate the operating phase of an AC power supply from a sampled AC power supply voltage, and to calculate the operating phase and the AC power supply based on the sampled values of the harmonics contained in the AC power supply current. An object of the present invention is to provide a digital control system for an active filter that removes harmonics contained in current.

[0005]

FIG. 1 is a diagram for explaining a method of calculating an operating phase according to the present invention. In the figure, V is a signal of a specific frequency component, t1 is the present time, t0 is a time before one sampling time Ts, V1 is the value of the signal V at the present time, V1
0 is the value of the signal V one sampling time before, φ is the current phase of the signal V, and Ts is the sampling period.

In the present invention, the operating phase of the signal of the above-mentioned specific frequency component is obtained as follows in FIG. In FIG. 1 (a), if V0 and V1 are values of a sine wave waveform having a specific frequency, V0 and V1 are expressed by the following equation (1).
It can be expressed by (2). V0 = Vm sin (ωo t1 + φ-ωTs) (1) V1 = Vm sin (ωo t1 + φ) (2) where Vm is the peak value of the signal V of the specific frequency component, and ωo
Is the angular frequency of the signal of the specific frequency component.

From the above equations (1) and (2), the following equation (3) is obtained. V0 / V1 = Vm sin ([omega] t1 + [phi]-[omega] Ts) / Vm sin ([omega] t1 + [phi]) = cos [omega] Ts- {sin [omega] Ts / tan ([omega] t1 + [phi])} (3) From the above equation (3), the following (4) ) Is obtained. tan (ωo t1 + φ) = V1sinωo Ts / (V1cosωo Ts -V0) (4)

Therefore, the following expression (5) is obtained from the expression (4). sin (ωo t1 + φ) = sin {tan ^-1 (V1sinωoTs) / (V1cosωoTs-V0)} ...... (5) That is, as shown in Fig. 1 (b), the value of the signal of the specific frequency component one sampling before. The phase of the signal of the specific frequency component can be obtained from V0 and the sampling value V1 at the present time by the above equation (5), and the signal of the specific frequency component can be expressed by a mathematical expression.

In order to solve the above-mentioned problems, the inventions of claims 1 and 2 of the present invention determine the operating phase sin (ωo t + φ) of the signal of the specific frequency component based on the above-mentioned principle as shown in equation (5). Therefore, the operating phase of the signal of the specific frequency component can be expressed by a mathematical expression by a relatively simple calculation.
Further, even if noise or the like is superposed near the zero cross point or there is a sudden phase shift, the operating phase can be accurately obtained. Therefore, in the digital control system, highly accurate control can be performed by relatively simple arithmetic processing.

According to a third aspect of the present invention, the operating phase of the AC power supply is obtained from the value V0 before one sampling of the AC power supply voltage and the current sampling value V1 by the above equation (5), and the operating phase is used. Since the harmonics of the specific frequency component contained in the AC current are removed based on the sampling value of the specific frequency component output by the bandpass filter, it is possible to perform highly accurate control with relatively simple arithmetic processing. You can

[0011]

BEST MODE FOR CARRYING OUT THE INVENTION Next, an embodiment of the present invention will be described by taking a digital control system of an active filter as an example.
In addition, although the digital control system of the active filter will be described in the following embodiments, the application target of the present invention is not limited to the digital control system.
It can be applied to various digital control systems that predict and control the variable after one sampling.

FIG. 2 is a diagram showing the overall configuration of an active filter control system according to an embodiment of the present invention. In the figure, reference numeral 1 is an AC / DC converter including switching means SC1 to SC4 and a capacitor C1. AC
The / DC converter 1 is controlled by the control device (not shown) so that the PW
The M voltage is controlled, the AC voltage supplied from the power supply 3 via the three-winding transformer Tr is converted into the DC voltage, and the DC voltage is supplied to the load L such as an electric vehicle.

During operation of the AC / DC converter 1, the AC / DC converter 1 outputs a harmonic of 1.8 kHz (angular frequency = ω) corresponding to the switching frequency of PWM control (1.8 kHz in this embodiment). ) Occurs. The harmonics cause resonance with the distributed constants of the distribution line and the like, and have an adverse effect such as an abnormal increase in voltage. 2 is an active filter main circuit for removing the above harmonics,
The active filter main circuit is S connected in a bridge
It is composed of switching means A1 to SA4 and a capacitor C2.
The harmonics are removed by M control.

Reference numeral 4 denotes a harmonic detection analog active filter for selectively passing the above 1.8 kHz harmonic, which is an AC / DC detected by the current detector CT2.
Only the harmonic component ih is extracted from the current iL flowing into the converter 1 without phase delay. Reference numeral 5 is an analog-digital converter, and the analog-digital converter 5 outputs the output ih of the harmonic active analog active filter 4 and the input voltage VS of the active filter main circuit 2 detected by the voltage detecting transformer TR1. Inflow current i into the active filter main circuit 2 detected by the current detector CT1
c and the capacitor C2 detected by the voltage detector Vdt
The voltage Vdc between both ends is sampled and converted into a digital signal.

6 is a digital signal processor (hereinafter D
SP) and calculates a digital signal output from the analog-digital converter 5 to generate a control signal for PWM controlling the switching means SA1 to SA4 of the active filter main circuit 2, and the control output is the drive circuit 7. And the switching means SA1 to SA4 are controlled.

FIG. 3 is a block diagram showing the processing in the DSP 6, FIG. 4 is a diagram showing the configuration of the phase calculating means shown in FIG. 3, and FIG. 5 is a diagram showing the configuration of the predicting means 6a shown in FIG. In FIGS. 3, 4, and 5, the same components as those shown in FIG. 2 are designated by the same reference numerals, 4 is the above-mentioned harmonic active analog active filter, and 5 is the above-mentioned analog digital. Converter, 6 is DSP, 7 is switching means SA1 to SA of the active filter main circuit 2
4 is a drive circuit. Further, 61b in FIG. 4 is a storage means for storing the value before one sampling, 62b is a calculating means for obtaining sin (ωo t1 + φ) from the above equation (5), and 61a in FIG. 5 is for storing the value before one sampling. Storage means, 6
Reference numeral 2a is a calculation means for calculating a value after one sampling from the present time.

Next, the control of the active filter in this embodiment will be described with reference to FIGS. 3, 4 and 5. The voltage Vdc across the capacitor C2 detected by the voltage detector Vdt, the harmonic current ih output by the harmonic detecting analog active filter 4, the voltage VS detected by the voltage detecting transformer TR1, and the detector CT1 are detected. The electric current ic is sampled by the anachronous digital converter 5, converted into a digital signal, and input to the DSP 6.

The voltage Vdc across the capacitor C2 and the reference voltage Vdc ^* input to the DSP 6 are given to the subtractor 6f,
The deviation is given to the proportional-plus-integral calculation means 6c. The proportional-plus-integral calculation means 6c performs proportional-integral calculation on the above deviation, and the peak value I of the current that should flow into the active filter main circuit 2
cor (the peak value of the fundamental wave component current of the alternating current: eg 50
Hz, angular frequency = ωo).

On the other hand, the phase calculating means 6b calculates the voltage phase φ of the AC power supply 3 (angular frequency = ωo) by the above-mentioned method from the voltage VS sampled by the anachronous digital converter 5 and converted into a digital signal, sin (ωo t1 +
φ) is output. That is, as shown in FIG. 4, the phase calculating means 6b stores the sampling value V0 of the voltage VS one sampling before by the storage means 61b, and the sampling value V1 at the present time and the sampling value one sampling before stored in the storage means 61b. Calculation means 62b based on the value V0
Then, sin (ωo t1 + φ) is obtained by the above equation (5).

The peak value Icor output by the proportional-plus-integral calculating means 6c and sin (ωo t1 + by the phase calculating means 6b)
φ) is multiplied by the multiplier 6g to generate the command value icor ^* of the alternating current flowing into the active filter main circuit 2. That is, the fundamental wave component of the alternating current flowing into the active filter main circuit 2 is controlled so that the phase φ coincides with the phase of the power supply voltage VS, and its peak value Icor
Is controlled so that voltage Vdc = reference voltage Vdc ^* .
On the other hand, the prediction means 6a predicts the value ih ^* of the harmonic component ih after one sampling.

The predicted value ih ^* after one sampling is calculated as follows. Assuming that the harmonic component is a sine wave, time t1 is the start time of the current sampling period, t0 is the time one sampling time Ts before, t2 is the time one sampling time Ts later, and the sampling value at time t0 is i0, the time The sampling value at t1 is i1,
Assuming that the sampling value ih ^{* at} time t2 is i0
, I1, ih ^* are expressed by the following equations (6a) to (6c).

Im sin (ωt1−ωTs−θ) = i0 (6a) Im sin (ωt1−θ) = i1 (6b) Im sin (ωt1 + ωTs−θ) = ih ^* (6c) where Im Is the peak value of the specific frequency component i, Ts is one sampling period, and θ is the phase of the specific frequency component.

From the above equations (6a) and (6b), the following equation (6d) is obtained. i1 sin (ωt1 −ωTs −θ) = i0 sin (ωt1 −θ) (6d) From the equation (6d), the following equation (6e) is obtained. cos (ωt1−θ) = {(i1 cos ωTs−i0) / (i1 sin ωTs)} sin (ωt1−θ) (6e) The following equation (6f) is obtained from the equation (6c). ih ^* = Im sin (ωt1 −θ) cos ωTs + Im cos (ω
t1 −θ) sin ωTs (6f) From the equations (6c), (6e), and (6f), the following equation (6) is obtained. ih ^* = 2i1 cos ωTs −i0 (6)

That is, as shown in FIG. 5, the phase calculating means 6a stores the value i0 one sampling before by the storing means 61a.
For storing the current sampling value i1 and the storage means 6
Sampling value i of one sampling before stored in 1b
Based on 0, the calculation means 62b calculates the predicted value ih ^* after one sampling by the above equation (6).

The predicted value ih ^* of the harmonic component after one sampling obtained by the predicting means 6a is given to the subtractor 6h and subtracted from the above-mentioned AC current command value icor ^* ,
A current command value icr (including compensation for harmonic components) is generated. That is, the predicted value ih ^* of the harmonic component (angular frequency = ω) is added to the command value of the AC current icor ^* (angular frequency = ωo) ^.
(Corresponding to the compensation value of the harmonic component) is superimposed to generate the current command value icr that should flow into the active filter main circuit 2. The switching time calculating means 6d calculates the switching time as follows based on the current command value icr.

FIG. 6 is an equivalent circuit of the active filter main circuit shown in FIG. 2. As shown in FIG.
The value of AF is L, the voltage on the input side of the active filter main circuit 2 is VS, the voltage on the AC side of the bridge circuit composed of the switching means SA1 to SA4 is Vi, and the capacitor C
1 is Vdc, the input current of the active filter main circuit 2 is ic, and the sampling cycle is Ts,
The following expressions (7), (8) and (9) are established.

VS = Vi + L (di / dt) (7) di / dt = (1 / L) (VS-Vi) (8) Δic = (1 / L) (VS-Vi) ΔT ... (9) Where Δic = icr−ic, icr = icor ^* −ih ^* ,
ΔT = Ts = t1 + t2, Vi = Vdc.

From the above relationship, the switching means SA1.about.
The switching period t1 and t2 of SA4 is (10)
It is calculated by the equation (11). t1 = {VS Ts-L (icr-ic)} / Vdc (10) t2 = Ts-t1 (11) Switching period t1, t calculated as described above
2 is given to the drive circuit 7 via the PWM signal generation means 6e, and the switching means SA1 to SA4 of the active filter main circuit 2 are controlled.

That is, as shown in FIG. 7, the period t
During the time tcal (for example, 10 μs) for calculating 1 and t2, the switch means SA1 and SA3 are turned on. When this period elapses, if the period t1 is positive, the switch means SA1 and SA4 are turned on during the period t1, and
When the period t1 is negative, the switch means SA2, SA3 are turned on during the period | t1 |. Then, when the period t1 has elapsed, the switch means SA1 and SA3 are turned on for the period t2 (= t2 '+ tcal).

As described above, the switching means SA1 to S
By driving A4, the harmonic of a specific frequency (1.8 kHz in this embodiment) superimposed on the power supply side is absorbed by the active filter, and the above harmonic can be removed. In the present embodiment, as described above, the prediction method of the present invention is applied to the digital control system of the active filter, and the active filter is controlled using the predicted value ih ^* of the predicted harmonic component after one sampling. Therefore, it is possible to perform highly accurate control using an accurate predicted value.

[0031]

As described above, the following effects can be obtained in the present invention. (1) Since the operating phase of the signal of the specific frequency component is obtained by the equation (5), the operating phase of the signal of the specific frequency component can be obtained by a relatively simple calculation and can be expressed by an equation. Further, the operating phase can be accurately obtained even if noise or the like is superposed near the zero cross point or there is a sudden phase shift. Therefore, in the digital control system, the operating phase of the specific frequency can be obtained by a relatively simple arithmetic process, and highly accurate control can be performed.

(2) From the value V0 of the AC power supply voltage before one sampling and the current sampling value V1 from the above (5)
The operating phase of the AC power supply is obtained from the formula and expressed by a mathematical formula, and based on the sampling value of the specific frequency component output by the bandpass filter using the mathematical formula, the harmonic of the specific frequency component contained in the alternating current is removed. Since this is done, the active filter can be controlled with high precision by simple arithmetic processing.

[Brief description of the drawings]

FIG. 1 is a diagram illustrating a method of calculating an operating phase according to the present invention.

FIG. 2 is a diagram showing a configuration of an active filter control system according to an embodiment of the present invention.

FIG. 3 is a block diagram showing processing in the DSP 6 in FIG.

FIG. 4 is a diagram showing a configuration of a phase calculation means 6b shown in FIG.

5 is a diagram showing a configuration of a prediction means 6a shown in FIG.

FIG. 6 is an equivalent circuit of the active filter main circuit shown in FIG.

FIG. 7 is a diagram showing the operation of the switching means of the active filter.

[Explanation of symbols]

1 AC / DC converter 2 Active filter main circuit 3 Power supply 4 Harmonic detection analog active filter 5 Analog-digital converter 6 Digital signal processor (DS
P) 7 drive circuit SC1 to SC4 switching means SA1 to SA4 switching means C1 capacitor C2 capacitor Tr transformer L load CT1 current detector CT2 current detector TR1 voltage detection transformer Vdt voltage detector LAF, Lcon reactor 6a predicting means 6b phase calculation Means 6c Proportional-integral calculation means 6d Switching time calculation means 6e PWM signal generation means 6f, 6h Subtraction means 6g Multiplier

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor, Miss Abdara 338, Kamisakuyanagi, Yamato City, Kanagawa Prefecture, Toyo Denki Seizo Co., Ltd. (72) Inventor, Katsuji Iida, 338, Kamisakuyanagi, Yamato City, Kanagawa Prefecture Toyo Denki Manufacturing Co., Ltd.

Claims (3)

[Claims] 1. A method of calculating an operating phase of a specific frequency component signal, wherein an analog signal of a single specific frequency component is sampled and converted into a digital signal, and an operating phase of the signal of the specific frequency component at the present time is obtained from the digital signal. Where V0 is the value of the signal of the specific frequency component one sampling time before, V1 is the sampling value of the signal of the specific frequency component at the present time, and ω is the angular frequency of the specific frequency f.
o (= 2πf) and the sampling period is Ts,
A specific frequency component signal characterized in that the operating phase sin (ωo t1 + φ) of the specific frequency component signal is obtained from the following formula: sin (ωo t1 + φ) = sin [tan ⁻¹ {V1sinωo Ts / (V1cosωo Ts −V0)}] Operating phase calculation method. 2. A specific frequency component signal for obtaining an operating phase at the present time of the signal of the specific frequency component based on an output of an analog-digital converter which samples an analog signal of a single specific frequency component and converts it into a digital signal. An operating phase calculation device, comprising: storage means for storing a value of the specific frequency component signal before one sampling; value V0 of the signal for the specific frequency component one sampling time before stored in the storage means; Based on the sampling value V1 of the signal of the specific frequency component, the angular frequency ωo of the specific frequency, and the sampling period Ts, the operating phase sin (ωo t1
+ Φ) is calculated from the following formula: sin (ωo t1 + φ) = sin [tan ⁻¹ {V1sinωo Ts / (V1cosωo Ts −V0)}] The operating phase of the signal of the specific frequency component is calculated. apparatus. 3. A bridge circuit comprising switching means connected in a bridge shape, and a capacitor connected to the DC side of the bridge circuit, controlling the switching means, and being supplied from an AC power supply. A digital control system of an active filter for removing a harmonic component of a specific frequency contained in an alternating current, wherein a band pass filter for passing a harmonic component of a specific frequency contained in an alternating current iL, and the band pass filter output Specific frequency component i
An analog-digital converter that samples and converts the instantaneous value of h, the instantaneous value of the AC power supply voltage VS, and the instantaneous value of the current ic flowing into the bridge circuit into a digital signal, and the output of the analog-digital converter. And a digital control means for controlling the switching means of the bridge circuit based on the sampling value V1 of the AC power supply voltage VS sampled at the present time, the previous sampling value V0 of the AC power supply voltage VS, and the above-mentioned sampling value V0. Based on the angular frequency ωo of the specific frequency and the sampling period Ts, the operating phase sin (ωo t1 + φ) of the power supply voltage is calculated by the following formula, and sin (ωo t1 + φ) = sin [tan ⁻¹ {V1sinωo Ts / (V1cosωo Ts -V0)}] generates a fundamental wave component of the AC current based on operating phase calculated by the phase calculating means Icor ^*, also sampled Based on the sampling values of the components of the specific frequencies, 1 obtains the predicted value ih ^* of the signal of the specific frequency component after the sampling time, the output ih ^* of the prediction means is subtracted from the fundamental wave component of the AC current Icor ^* An active filter digital control system for calculating an opening / closing time of the switching means based on the subtraction result, the power supply voltage VS and the current ic.