JPH01301183A - Detecting instrument for single phase ac signal - Google Patents

Abstract

PURPOSE:To accurately detect an AC signal at high speed by providing an observer which produces two-phase sine wave signal differing from a single phase AC signal (voltage or current) by 90 deg. in phase, and computing a square root for the sum of a square of each signals. CONSTITUTION:An AC (example : 50Hz) voltage from a single phase AC voltage source 1 is added through an auxiliary transformer 2 to an observer 8 and outputted state estimating values X1, X2. By this detecting system, without consideration on removing of a 100Hz ripple, it is able to make haste a presumed speed and to detect quickly a sudden change of the AC voltage. Also, for instance in case a high frequency of the 5th power is included, if a constant number at presumed time of the observer 8 is set up in slightly higher value than a 1/250Hz, an amplitude of a standard-wave being removed the higher frequency more than the 5th power is able to detect continuously. The state estimating values X1, X2 are added into a computing element 9 and outputted on computing an amplitude estimating value (X1<2>+X2<2>)<1/2>. Its amplitude estimating value is brought into 1/2<1/2> by a gain means 10 and outputted as a practice estimating value.

Description

[Detailed Description of the Invention] [Objective of the Invention] (Industrial Application Field) The present invention relates to a single-phase grid-connected inverter that detects signals such as single-phase AC voltage and current, and performs various types of control and protection. The present invention relates to a single-phase AC signal detection device suitable for application to devices such as single-phase output uninterruptible power supplies.

(Prior art) In single-phase AC output uninterruptible power supplies (UPS) and single-phase grid-connected inverter devices, it is necessary to detect single-phase AC voltage No. A in order to control and protect these devices. is of course necessary. There are various methods for detecting the single-phase AC signal, and some examples of voltage detection are shown in FIGS. 7, 9, and 10.

In FIG. 7, 1 is a single-phase AC voltage source, 2 is an auxiliary transformer that lowers the voltage level, 3 is a rectifier, and 4 is a filter for removing ripples contained in the output of the rectifier.

In the filter 4, 4a is a resistor, 4b is a capacitor, and 4c is a variable resistor. Output Vp of that filter 4
is entered into a comparator, sample/
It is converted into a digital signal through a hold and A/D converter, and is used for various types of control and protection.

In the detection method using the device shown in FIG. 7, for example, when the frequency of the AC power source 1 is 50 Hz, a ripple of 100 Hz occurs in the output of the rectifier 3. For this reason 1
．． It is necessary to set the cutoff frequency of the fillet 4 to a value considerably lower than 100 Hz (for example, 20 Hz). However, doing so has the first drawback that the voltage detection response becomes slow. Also, filter 4
is composed of a resistor 4a and a capacitor 4b. Therefore, when the waveform of the AC power supply 1 is distorted as shown in FIG. 8, the second drawback is that the capacitor is charged at a peak and a value far from the average value or effective value is detected.

FIG. 9 is a diagram showing an example of a conventional method for detecting single-phase alternating current. In FIG. 9, the same reference numerals as those in FIG. 7 indicate the same members as those in FIG. 7, and the explanation thereof will be omitted. In FIG. 9, 1a is a load or another power source, and 2b is a CT.

2C is a resistor for converting the current signal detected by the CT 2b into a voltage signal.

The principle of the detection method shown in FIG. 9 is similar to the voltage detection method shown in FIG. 7 described above. The detection method shown in FIG. 9 also has the first and second drawbacks described in the detection method shown in FIG. 7.

FIG. 10 is a diagram showing another example of the conventional method for detecting single-phase AC voltage. In FIG. 10, the same reference numerals as those in FIG. 7 indicate the same members as those in FIG. 7, and the explanation thereof will be omitted. In this Figure 10, 2a is an auxiliary transformer, 5 is a VCO (m-voltage controlled oscillator), and 6 is a vC
O Counter that counts the output frequency, 7 is PLL (
This is a phase-locked loop (phase-locked loop). In FIG. 10, the rectifier 3 can be replaced with an absolute value detection circuit.

In FIG. 10, the PLL 7 outputs count start/stop pulses to the counter 6 every cycle in synchronization with the AC power supply 1. The counter 6 is controlled by one pulse from the PLL 7 and outputs a count value for each cycle. As a result, in the circuit of Fig. 10,
The average value V of the AC voltage is detected as C. With such a detection method, even if the waveform of the AC power source 1 is distorted, the average value can be accurately detected.

(Problems to be Solved by the Invention) As described above, in the conventional single-phase AC voltage detection method shown in FIGS. 7 and 9, it is necessary to use a filter with a low cutoff frequency, that is, a large time constant. . Therefore, the detection response is slow, and accurate detection of distorted waveforms cannot be performed. In addition, in the conventional detection method shown in Fig. 10, although the average value is accurately detected,
In the case of z, detection is performed only every 20 m5). Therefore, a sudden change in voltage cannot be detected.

Due to these drawbacks, the conventional voltage detection method has had the problem of difficulty in high-speed control and protection. Such problems are the same in the case of current detection.

The present invention has been made in view of the above, and an object of the present invention is to provide a single-phase AC signal capable of detecting a single-phase AC signal <tS pressure or current) at high speed and accurately in order to facilitate high-speed control and protection. The object of the present invention is to provide a detection device.

[Structure of the invention]

(Problem 2B to be Solved by the Invention) The single-phase AC signal detection device of the present invention includes an observer that generates a two-phase sine wave signal having a phase difference of 90'' from a human-powered single-phase AC signal, and the two-phase sine wave signal. and calculation means for calculating the square root of the sum of the squares of each of the squares.

That is, the single-phase AC signal detection device of the present invention includes an observer that estimates the internal state of the AC signal generation mechanism based on a model of a sine wave signal generator, and the output of the observer, that is, the estimated state value is based on the model of the sine wave signal generator. The fundamental wave amplitude is continuously detected by the square root of the sum of the squares of each sine wave signal by utilizing the fact that the two-phase sine wave signals are shifted by 90 degrees.

(Function) The observer means has a phase difference of 9 from the input single-phase AC signal.
Generate two-phase sine wave signals that differ by 0°.

Based on the two-phase sine wave signals, the calculation means calculates the square root of the sum of the squares of the respective signals. Thereby, the fundamental wave amplitude is detected continuously.

(Example) Before giving a detailed explanation of the present invention, a detailed explanation of the present invention will be given. The principle is substantially the same for voltage detection and current detection. Therefore, the principle in the case of voltage detection will be explained below.

! The 11-phase AC voltage source can be viewed as a sinusoidal voltage generator with the following state equation:

Here, ω-2πf, and f is the frequency.

For example, y=x1-42VIIlcos (ωt+φ) (3) At this time, x2-"l 2 vm sin (ω is 10φ) (4)
It is. Now, if we define , then equations (1) and (2) can be expressed as follows.

X 閤A x (
6)y-Cx
(7) Reference 1 (D.G., Luenberger,
”Observing Ll+estate ora
1inear system”, IEEEE T
rans, Nil.

Electron, MIL-8, pp, y4-go
According to the observer theory shown in (1964), for a system of a sinusoidal voltage generator (single-phase AC voltage source) whose state equation is expressed by equations (6) and (7), A full-dimensional observer can be constructed.

z-(A-LC)z+Ly (8)△ x m z
(9) Here, z−Cz z)T (T represents transpose) is the state of the observer, L−(ρ g ]T is the design parameter, and the matrix A
-If the eigenvalue of LC is stable, that is, the real part is negative, then the formula (G)
, (7) is the state estimate for the single-phase AC voltage source. Estimation error e (t) (e(t) −x(L
)−x(t)] is the equation and e(t) = (A
-LC) e(t) (10), so if A-LC is a stable matrix, Ωim e(t)-
0 or j-4o.

1 im x (t) = x (L) (
fl) i-Po.

becomes.

When x (t) approaches x (t) expressed by equations (3) and (4) at t-flash, the following equation holds, so the amplitude can be detected continuously by taking the square root.

Further, by multiplying the estimated amplitude value by 1/47, the effective value V 2 can be detected continuously.

A first embodiment of the present invention utilizes the above principle, and will be described in detail with reference to FIGS. 1 to 3.

In FIG. 1, 1 and 2 indicate an AC power source and an auxiliary transformer, respectively, as in FIG. 7. Furthermore, 8 is an arithmetic unit which inputs the AC voltage from the auxiliary transformer 2, and 10 is a gain means of 2, which calculates an effective value estimate from the amplitude estimate.

Therefore, the apparatus of FIG. 1 operates as follows.

That is, the AC voltage of single-phase AC voltage source 1 is transferred to auxiliary transformer 2.
is added to the observer 8 via. Auxiliary calculations are performed to calculate and output the estimated amplitude value. The estimated amplitude value is reduced to 1/42 by the gain means 10 and output as an effective estimated value.

FIG. 2 is a detailed diagram showing the inside of the arithmetic unit 9 in FIG. 1. In FIG. 2, 11a and 11Δ 2 Δ 2 are multipliers whose output is their square Xt+X2, 11c is an adder, and 12 is a square root calculator.

Therefore, the circuit of FIG. 2 operates as follows.

It is added to the adder Δ2 11c as X t and X 2 by Δ2 Δ2 11a and llb. The adder 11c adds (xr to 2 +x2) to the square root calculator 12. Square Root Operation FIG. 3 is a detailed diagram showing the inside of the observer 8 in FIG. 1. In FIG. 3, 13a.

13b is an integrator, 14a to 14e are gain means, 15a
, 15b is an adder. FIG. 3, which is represented by such circuit elements, represents equations (8) and (9) in a block diagram.

According to the detection method using an observer as described above, 1
Without considering ripple removal at 00Hz,
The eigenvalues of the matrix A-LC can be arbitrarily selected. Therefore, the estimation speed can be increased by making the real part of the eigenvalue of the matrix A-LC a sufficiently large negative value.
Sudden changes in AC voltage can be detected immediately.

Further, assume that the AC voltage waveform is distorted due to the influence of other loads connected to the AC power supply, and includes, for example, fifth-order harmonics. In this case, the estimated time constant of the observer may be set to a threshold value slightly lower than 1/250 Hz. Thereby, it is possible to continuously detect the amplitude of the fundamental wave from which high frequencies of the fifth order or higher are removed.

Although FIGS. 1 to 3 described above show an embodiment using a full-dimensional observer, in addition to the above-mentioned document 1, document 2
(D.G. Luenberger, “An InL
ro-ducLlon to observers'',
IEEE Trans, AuLoa+aLIcCo
ntro1. AC-16, pp, 59[1-602,
1971) and Reference 3 (T., E., Forewann.
and D.Wllllamson,”
Designo1' low-order observer
vers f'or 1inear feedback
control laws', IEEE Trans
, Automatic Control.

Ac-1'7. pp, 301-308. t972
) can also be used.

The minimum dimension observer for a system of a sinusoidal voltage generator (single-phase AC voltage source) whose state equation is expressed by equations (8) and (7) is as follows.

2-1αω・2+ω(1+α)y (14)△ 0) is a parameter that determines the estimated speed of the observer.As is clear from equation (15), the minimum dimension observer utilizes the fact that the value of xl has already been obtained as y, and by estimating only X2. It has the characteristics of reducing the order of the observer and simplifying the structure.

A second embodiment of the present invention using a minimum dimension observer will be described with reference to FIGS. 4 and 5.

FIG. 4 is the same as FIG. 1 except that the full-dimensional observer 8 in FIG. 1 is replaced with a minimum-dimensional observer 8a. FIG. 5 is a diagram showing details of the observer 8a in FIG. 4, in which 16 is an integrator, 17a, 17b, and 17c are gain means, and 18a.

18b is an adder. Figure 5 shows formulas (14> to (18))
is expressed in a block diagram.

In the embodiments shown in FIGS. 4 and 5, the alternating current voltage can be detected continuously, as in the first embodiment described above.

In the above explanation, the model expressed by equations (1) and (2) was considered as a model of a sine wave voltage generator.

However, many other models of sinusoidal voltage generators are possible. In reality, the equation of state expression is different each time the basis of the state space is taken differently, and so
Exists in H number. For example, the following expressions are also possible.

When expressed like this, Xl(t) −11' 2V, ・cos (ωt+φ
) (27), then x2 ” ”-” ” J-wovm 4 sin
(ωt +φ). When a full-dimensional observer is configured for equations (25) and (26), the amplitude can be detected as follows. In short, no matter how it is expressed, it is sufficient to prepare an observer and a detection formula corresponding to it.

In the explanation so far, embodiments using analog circuits have been described. However, it goes without saying that the present invention can also be implemented using digital circuits.

When implementing the present invention in a digital circuit, equations (+) and (2) are used as a sine wave voltage generation mechanism.

Instead of (3), However, T - sampling time Just think about it.

and x (kT)−=x (k), Y (kT)
→ Rewriting as y (k), x (k+1) = F−x (k) (20)
y (k) = C−x (k) (21) Formula (
The full-dimensional observer for the system represented by (20), (21) becomes:

ξ(k+1)−(F−LC)ξ(k)+L−y(k) (22)x
(k)−ξ(k) (23)L−
(NR)'' is designed so that the eigenvalues of the matrix F-LC fall within the unit circle of two planes.

is the estimate of x (k). In this example, the estimated value of the amplitude is also obtained by:

An embodiment of the present invention using a digital circuit is shown in FIG.

In FIG. 6, 19 is a sample hold circuit, 20 is an A/D converter, and 21 is an arithmetic circuit, and the arithmetic circuit 21 is constituted by a microprocessor or a digital signal processor.

In the embodiment of FIG. 6, the observer calculations expressed by equations (22) and (23) and the calculation of equation (24) are realized by software. This eliminates the need for expensive multipliers, square root calculators, etc. that were necessary in the case of the analog method described above. This not only makes the hardware cheaper, but also has the advantage of eliminating the effects of temperature drift and changes over time.

Although an example in which a discrete-time all-dimensional observer is used has been described above, it goes without saying that a discrete-time minimum-dimensional observer can also be used, and embodiments using such an observer can also be realized.

As explained above, according to the embodiments of the present invention, the amplitude and effective value of single-phase AC voltage and current can be detected accurately and continuously, and sudden changes in voltage and current can also be detected quickly. Therefore, it is possible to control and protect single-phase uninterruptible power supplies, single-phase grid-connected inverters, etc. at high speed.

〔Effect of the invention〕

According to the present invention, the amplitude of a single-phase AC signal can be detected with good responsiveness, and therefore various types of control and protection can be performed at high speed.

[BRIEF DESCRIPTION OF THE DRAWINGS] FIG. 1 is a diagram showing an embodiment of the present invention using a full-dimensional observer, FIG. 2 is a diagram showing the arithmetic unit shown in FIG. 1, and FIG. FIG. 4 is a diagram showing details of the minimum dimension observer, FIG. 4 is a diagram showing another embodiment of the present invention using the minimum dimension observer, FIG. 5 is a diagram showing details of the minimum dimension observer in FIG. 4, and FIG. Figure 7 showing still another embodiment of the present invention
Figure 8 shows an example of a conventional voltage detection method, Figure 8 shows an example of a voltage waveform including distortion, Figure 9 shows an example of a conventional current detection method, and Figure 10 shows an example of a conventional voltage detection method. It is a figure which shows another example of a detection method. DESCRIPTION OF SYMBOLS 1... Single phase AC voltage source, 1a... Negative 6I or power supply, 2... Auxiliary transformer, 2a... Auxiliary voltage generator, 2b.
...CT, 2c...resistance, 3...rectifier, 4...
Filter, 4a...Resistor, 4b...Capacitor, 4
C...Variable resistance, 5...VCO56...Counter, 7...PLL, 8...All dimensions, observer, 8a
...Minimum dimension observer, 9...Arithmetic unit, 10...
・Gain, lla, llb...multiplier, 11C...
Adder, 12...Square root calculator, 13a. 13b... Integrator, 14a-14e... Gain, 1
5a, 15b... Adder, 16... Integrator, 17a
~17 c--gain, 18a, 18b-adder, 1
1...Sample hold, 20...AD converter, 2
1... Arithmetic device. Applicant's agent: Sato - Male figure 5 figure 6 figure porridge 7 figure tail 8 figure

Claims (1)

[Claims] It is characterized by comprising an observer that generates a two-phase sine wave signal whose phase differs by 90 degrees from an input single-phase AC signal, and a calculation means that calculates the square root of the sum of the squares of each of the two-phase sine wave signals. Single-phase AC signal detection device.