JPH02116759A - Power measurement device - Google Patents

Abstract

(57) [Abstract] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

DETAILED DESCRIPTION OF THE INVENTION (Al Industrial Application Field) This invention relates to a power measuring device for measuring power in an AC power supply circuit.

(b) Conventional technology When operating multiple alternating current generators or in parallel with a commercial power source, it becomes necessary to control the power amount of each generator to a preset input value. . When controlling the amount of electric power in this manner, it is necessary to measure the electric power value in each generator. For this reason, conventionally, a voltage waveform and a power waveform in a generator are detected, and the two are synthesized by an analog circuit to obtain a power value.

(C1 Problem to be Solved by the Invention) However, in order to synthesize the voltage waveform and the power waveform, a complicated electric circuit is required, resulting in an increase in cost.

An object of the present invention is to provide a power measuring device that can calculate a power value using a voltage value and a current value with a simple configuration, and can realize cost reduction by simplifying the structure.

(Means for Solving Problem d1) The power measuring device of the present invention includes a DC conversion means for converting the voltage and current of an AC power supply into a DC signal, and a zero-cross timing detection means for detecting the zero-cross timing of the voltage and current of the AC power supply. The present invention is characterized by further comprising: a calculation means for determining a phase difference between voltage and current based on the detection result of the zero-cross timing detection means, and calculating a power value from this phase difference and the output of the DC conversion means.

That is, as shown in the functional block diagram of FIG. 1, the voltage and current of the AC power supply device are detected by the voltage detection means and the current detection means. The detection results of the voltage detection means and current detection means are input to the power value calculation means via the DC conversion means, and are also input to the zero cross timing detection means. The zero-crossing timing detection means detects the zero-crossing timing of the voltage waveform and current waveform,
This result is input to the phase difference calculation means. The phase difference calculation means calculates the phase difference between the voltage waveform and the current waveform based on the detection result input from the zero cross timing detection means,
This result is input to the voltage value calculation means. The voltage value calculation means receives the voltage value and current value input from the DC conversion means,
The power value is calculated based on the phase difference input from the phase difference calculation means.

(e) Effect In the present invention, the period r shown in FIG. AT and phase shift S (phase difference θ) are determined. Note that FIG. 2 shows waveforms when the load is L. On the other hand, the detection results of the voltage detection means and current detection means are converted into DC signals by the DC conversion means. For this DC voltage value and the DC, the phase difference is determined based on the voltage as described above, but when the load has a large C component, the phase difference is determined based on the current.

(f) Embodiment FIG. 3 is a circuit diagram of a power measuring device which is an embodiment of the present invention. In the following embodiments, it is assumed that the load impedance is a load with a large L component.

After the voltage generated by the generator G is stepped down by the transformer 8, it is inputted from the A/D converter 2 to the CPUI via the rectifier 41 and the filter 42. The filter 42 removes unnecessary components such as noise from the signal, includes a comparator 43 and a CR filter element, and constitutes the DC conversion means 4 together with the rectifier 41. Further, the current of the generator G is transformed by a current transformer 9, and a rectifier 51 and a filter 5
The signal is input from the A/D converter 3 to the CPUI via the A/D converter 2.

The filter 52 has the same configuration as the filter 42 described above, and together with the rectifier 51 constitutes the DC conversion means 5. The voltage stepped down by the transformer 8 is input to the zero cross detection circuit 6, and the current transformed by the current transformer 9 is input to the zero cross detection circuit 7. The zero cross detection circuit 6.7 is a fourth circuit that outputs a detection pulse to the input terminals inl and in2 of the CPUI at the time of zero cross of the voltage waveform and the current waveform.
The figure shows an RA that constitutes a part of the control unit of the power measuring device.
This is a memory map of the main parts of M.

RAM memory areas MAI and M of the CPUI
Timers Tl and T2 are respectively assigned to A2.

Further, numerical values A and B used in calculations described later are stored in memory areas MA3 and MA4, and a phase difference θ between voltage and current is stored in memory area MA5. Furthermore, MA6. Each of MA7 has DC conversion means 4,
The voltage value E and current value I manually inputted from each of 5 are stored, and the power value P obtained by calculation is stored in the memory area MA8.

FIG. 5 is a flowchart showing the processing procedure of the control section of the power measuring device.

When the zero-cross detection pulse is output from the zero-cross detection circuit 6 (+1), timers Tl and T2 assigned to the memory areas MA1 and MA2 are activated (n2). Thereafter, when a zero-cross detection pulse is output from the zero-cross detection circuit 7 (n3), the contents of the timer T2 are stored as a numerical value B (n4). Furthermore, when the zero-crossing detection pulse is output again from the zero-crossing detection circuit 6 (n5), twice the contents of the timer TI is set as the value A and the memory area MA is
3 (n6).

Memory area MA3. Numerical values A and B stored in MA4 represent the phase shift (time unit) and period between the voltage waveform and current waveform, respectively. This phase shift (in hours)
and calculate the phase difference θ based on the period (n
7). Read the voltage value E and current value ■ input from the A/D converter 2.3 (n8), multiply these by cos θ to find the power value P (n9), and
8, while storing the power value P in nlO as the voltage value E
and the current value I. In the above processing, n7. n9 corresponds to the calculation means of this invention.

As described above, according to this embodiment, the voltage and current of the generator G can be converted into direct current, the phase difference θ can be determined from the voltage waveform and the current waveform, and the power value P can be easily determined from these. .

Moreover, if a commercially available CPU equipped with a zero-cross detection terminal is used as CPU 1, zero-cross detection circuits 6 and 7 can be used.
can be omitted, further simplifying the configuration.

(g1 Effects of the Invention According to this invention, the voltage value and current value of an AC power source can be determined with an extremely simple configuration, the phase difference between the voltage waveform and the current waveform can be determined, and the power value can be easily determined from these values. This has the advantage of reducing device size and cost.

[Brief explanation of the drawing]

FIG. 1 is a functional block diagram of the present invention, and FIG. 2 is a diagram showing the operation of the present invention. 3 is a circuit diagram of a power measuring device that is an embodiment of the present invention, FIG. 4 is a memory map of the main part of the RAM that constitutes a part of the control section of the same power measuring device, and FIG. 5 is a control diagram of the power measuring device. 3 is a flowchart showing the processing procedure of the section. 4.5 - DC conversion means, 6.7 - Zero cross detection circuit, G - Generator. No. 4 Figure Figure

Claims (1)

[Claims] (1) A DC converter that converts the voltage and current of the AC power supply into a DC signal, a zero-cross timing detection means that detects the zero-cross timing of the voltage and current of the AC power supply, and a voltage and current signal based on the detection results of the zero-cross timing detection means. A power measuring device comprising: calculation means for determining a phase difference with a current and calculating a power value from this phase difference and the output of a DC conversion means.