KR20110066006A - Electronic watt hour meter with large dynamic range - Google Patents

Abstract

PURPOSE: An electronic watt hour meter with a wide dynamic range is provided to expand the measuring range of a load current in the input range of an analog/digital converting part by turning off a part or whole of relay switches in connection with respect resistors. CONSTITUTION: A voltage converting part(110) is in parallel connection with power and detects a supplying voltage. Detected supplying voltage is converted to output a converted voltage. A current converting part(120) converts a supplying current, which is adjusted according to a controlling signal or detected according to a pre-set conversion ratio. A converted current is outputted. An analog/digital converting part(130) converts the converted voltage and the converted current into digital signals. A calculating and controlling part(140) calculates power and watt hour and controls conversion ratio by outputting a controlling signal to a current converting part.

Description

Electronic watt hour meter with large dynamic range

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an electronic wattmeter with a wide operating range capable of enlarging the range of measurable power.

 The present invention is derived from the research conducted as part of the IT New Growth Engine Technology Development Project of Korea Institute of Construction Technology [Task Management Number: B551179-09-04-00, Project Name: Development of Zero Carbon Green Home].

In general, the electronic wattmeter for measuring the amount of power supplied to the load is a voltage conversion unit to which the measured voltage is input, a current conversion unit to which the current used for the load is input, and is converted and output from the voltage conversion unit and the current conversion unit There is a power measurement unit that calculates the amount of power by receiving the magnitude of the voltage and current.

The power measuring unit converts the voltage output from the voltage converter and the current converter from analog to digital through the A / D converter, calculates power by multiplying two values, and calculates the amount of power by accumulating the value as a time function. . At this time, the effective power and reactive power can be obtained by calculating the power factor by extracting the phase difference between the output signal of the voltage converter and the output signal of the current converter.

 In order to detect a voltage in such an electronic watt-hour meter, a high voltage can be reduced to a voltage that can be accommodated by an A / D converter by using a power transformer or a voltage divider made up of a series of resistors. In addition, to detect current, a low resistance is connected in series to the power line to detect current flowing through the load through a voltage difference generated when current flows, or an induced current is generated by using a device called a CT (Current Transformer). The current across the load is measured by measuring the voltage across the parallel resistor.

 The current converting section of the electronic watt-hour meter has a fixed operating input range. Since the resistance value connected in parallel to CT is fixed, if the current flowing through the load is too large, the voltage across the parallel resistance may become too large to exceed the input range of the A / D converter in the power measurement unit, and the current flowing in the load is too small. In other words, the voltage between both ends of the parallel resistor may be so small that the A / D conversion unit may have a fine value. The structure in which resistors are connected in series with power lines also has a limited operating range. If a lot of current flows in the load, the voltage applied to the series resistor may increase, which may exceed the input range of the A / D converter.

An object of the present invention is to newly design the resistance structure of the current conversion unit in order to solve the above problems, to expand the operation range of the electronic wattmeter.

The object of the present invention is not limited to the above-mentioned object, and other objects that are not mentioned will be clearly understood by those skilled in the art from the following description.

A wattmeter according to an aspect of the present invention includes a voltage converter connected in parallel with a power source to detect a supply voltage, converting the detected supply voltage to output a converted voltage, and connected in series with the power source and provided to a load side. A current converter which detects a supply current and converts the detected supply current and outputs a converted current according to a conversion ratio adjusted and set according to a control signal, and digitally converts the converted voltage and the converted current as analog signals, respectively. A / D converter converts the signal, and calculates the power and the amount of power using the digital voltage value and the digital current value output from the A / D converter, and outputs the control signal to the current converter to the conversion ratio Operation and control unit for controlling the operation, the communication unit and the operation and control results of the operation and the control unit to enable the operation and the control unit to communicate with the outside To a display to indicate.

Here, the current conversion unit that can adjust the conversion ratio, the current transformer for converting the supply current to a small current (current transformer), and the basic resistance and the basic resistance connected in parallel to the secondary coil of the instrument current transformer It is composed of a plurality of resistors connected in parallel to the on / off by a relay switch, the conversion ratio is adjusted by adjusting the overall resistance value by receiving the control signal of the operation and control unit.

Alternatively, the current conversion unit capable of adjusting the conversion ratio includes a base resistor having a low resistance value for converting the supplied current into a voltage and a plurality of resistors connected in parallel to the base resistor and on / off by a relay switch. Thus, the conversion ratio is adjusted by adjusting the total resistance value by receiving the control signal of the operation and the control unit.

Specific details of other embodiments are included in the detailed description and the drawings.

According to the present invention, the electronic watt-hour meter with a wide operating range according to the present invention can adjust the conversion ratio of the current converter, so when the load current is large, some or all of the relay switches connected to the resistors are turned on according to the purpose. If the load current is small, the conversion ratio is reduced by lowering the overall resistance, and when the load current is small, the relay current connected to each resistor is turned off in part or all according to the purpose to increase the conversion ratio. This has the effect of enlarging the measurement range.

Advantages and features of the present invention and methods for achieving them will be apparent with reference to the embodiments described below in detail with the accompanying drawings. However, the present invention is not limited to the embodiments disclosed below, but will be implemented in various forms, and only the present embodiments are intended to complete the disclosure of the present invention, and the general knowledge in the art to which the present invention pertains. It is provided to fully convey the scope of the invention to those skilled in the art, and the present invention is defined only by the scope of the claims. It is to be understood that the terminology used herein is for the purpose of describing particular embodiments only and is not intended to be limiting of the invention. Also, in this specification, reference to one element as "connected to" with another device includes both direct connection or coupling with another device or intervening another device in between. . In the present specification, the singular form includes plural forms unless otherwise specified in the specification. As used herein, the words "comprises" and / or "comprising" do not exclude the presence or addition of one or more other elements.

Hereinafter, embodiments of the present invention will be described with reference to the accompanying drawings.

An electronic power meter according to an embodiment will be described with reference to FIGS. 1 and 2. 1 is a block diagram illustrating a power meter according to an embodiment, and FIG. 2 is an exemplary circuit diagram illustrating a current converter of FIG. 1.

As shown in FIG. 1, the electronic power meter 100 includes a voltage converter 110, a current converter 120, an A / D converter 130, an operation and control unit 140, and a communication unit 150. And a display unit 160.

The voltage converting unit 110 is connected in parallel with a conventional commercial AC power supply (AC) to detect a supply voltage, and converts the detected supply voltage into a conversion voltage suitable for the A / D conversion unit 130 to recognize and calculate. To print.

The current converter 120 is connected in series with the AC power source (AC) to detect the supply current supplied to the load 200 side, the A / D conversion unit 130 to recognize and calculate the Output by converting to proper conversion current. Here, the current converter 120 converts the supply current into the conversion current according to a predetermined conversion ratio. The current converter 120 receives an external, for example, operation and a control signal of the controller 140 to be described later. According to the magnitude | size, the conversion ratio which converts a detected supply current into conversion current can be adjusted.

The A / D converter 130 converts the converted voltage output from the voltage converter 110 and the converted current output from the current converter 120 capable of adjusting the conversion ratio from an analog signal to a digital signal.

The calculation and control unit 140 calculates power and amount of power using the digital voltage value and the digital current value output from the A / D converter 130. For example, the calculation and control unit 140 calculates power by multiplying a voltage value and a current value output from the A / D converter 130, and calculates active power and reactive power using the phase difference between the two values. It also controls other functional blocks such as the current converter 120, the communicator 150, and the display 160.

And the calculation and control unit 140, the load 200 is very large (the current used by the load 200 is too large, so that the converted current which is the output of the current converter 120 is input to the A / D converter 130). When it is out of the range, it detects this and sends a control signal to the current converter 120 to lower the conversion ratio from the detected current to the converted current so that the magnitude of the converted current is in the input range of the A / D converter 130. In addition, the calculation and control unit 140, the current used by the load 200 is so small that the conversion current output of the current converter 120 is compared with the input range of the A / D converter 130. If the value is too small, it is difficult to measure the change in the minute current value. Therefore, the control current is sent to the current converting part 120 to increase the conversion ratio, so that the converted current is also converted to the A / D converting part even for the minute load 200 current. For low load 200 current by allowing input to be large enough to Also it makes it possible to accurately measure.

When the conversion ratio of the current converter 120 is adjusted according to the magnitude of the current of the load 200, even if the input range of the A / D converter 130 is limited to a certain range, It is possible to provide an electronic new energy meter 100 that can be used over a wider operating range. At this time, when the conversion ratio is adjusted, the correction coefficient is reflected in the calculation and the calculation process of the controller 140 so that the actual power value can be calculated. As the conversion ratio is changed, the calculation and the control unit 140 consider the same ratio to calculate the power value so that even if the conversion ratio is changed.

Meanwhile, the communication unit 150 is in charge of a communication function so that the operation and control unit 140 can communicate with the outside, and the display unit 160 displays the results of the operation and control unit 140.

In FIG. 1, a power supply unit is required to operate each functional block. However, since a DC power supply is required in a normal digital circuit, those skilled in the art will clearly understand the necessity, and thus are not illustrated separately.

Hereinafter, referring to FIG. 2, the current converter 120 of FIG. 1 will be described in detail.

As shown in FIG. 2, the current converter 120 senses the load 200 current using, for example, a current transformer CT. When a load current flows through the primary coil of the CT, it is converted (induced) into a microcurrent that can be measured by the secondary coil, and returned to a measurable voltage through a parallel resistor (R0) connected to the secondary coil.

Since the A / D converter 130 converts the voltage across both ends of R0 into a digital signal, the conversion ratio of the CT and the resistor R0 correspond to the input range of the A / D converter 130 that converts the voltage from analog to digital. It is chosen and used to fit. However, if the current converter 120 is connected to both ends of the CT only when the resistor R0 is connected in the state in which the plurality of resistors R1 to Rk are not connected in FIG. 2, that is, the relay switch is turned off. When the range varies widely, the voltage across R0 may be large enough to exceed the input range of the A / D converter 130 or may be too small to be difficult to measure. Also, the voltage between R0's both ends may change according to the size of R0. For example, when R0 is large, the voltage across R0 increases for the same current, and conversely, when R0 resistance is small, the voltage also decreases.

Therefore, in order to adjust the voltage input to the A / D converter 130 to match the operating range even if the load current varies widely, the resistance value connected to the secondary coil may be implemented. In some cases, as shown in FIG. 2, in order to change the total resistance value of both ends of the CT, connected to both ends of the CT (or electrically coupled in parallel with the AC power supply) according to the on / off of the relay switch and the relay switch. Connect multiple resistors (R1 to Rk). The relay switches on and off according to the magnitude of the load current to regulate the voltage across the entire parallel resistor. At this time, the on / off of the relay switch is determined according to the operation and the control signal of the controller 140. Those skilled in the art can know about the operation circuit of the relay switch and because it is a known concept, the detailed connection relationship is not shown in FIG.

 For example, to adjust the conversion ratio, R1 = R0, R2 = R0 / 2, R3 = R0 / 4, ..., Rk = R0 / (2k-1), only R0 is used and the remaining R1, ..., Rk is the voltage when the relay switch is off and not used is V0. If the relay switch is turned on to use only R1 in the presence of R0, the value of the total parallel resistance becomes R0 / 2. Therefore, the voltage between both ends of the parallel resistor becomes V0 / 2. By adjusting the relay switch of the parallel resistor in this way, it is possible to have a wide operating range depending on the load current.

A circuit for reducing noise in the current converter 120 of FIG. 2 may be further provided, but parts related to such a conventional technology are not illustrated. This is because the core of the present invention is the configuration of a circuit that can adjust the conversion ratio, not an additional area such as noise reduction.

On the other hand, according to the above, the calculation and the control unit 140 is a case of outputting a control signal by detecting a case in which the load 200 becomes very large or small, but is not limited to this, it is not limited to this, periodically convert without periodic The control signal may be output to adjust the ratio, and the subsequent conversion ratio may be determined based on power values calculated according to different conversion ratios. For example, the calculation and control unit 140 may lower the conversion ratio and lower the conversion ratio if the result of calculating the power value using the correction coefficient corresponding to the lower conversion ratio is larger than the power value before lowering the conversion ratio. have. The previous state (before the conversion ratio is lowered) is a case where the load 200 becomes very large so that the conversion current which is the output of the current conversion unit 120 exceeds the input range of the A / D conversion unit 130, and in reality, power Although the value should have been calculated larger, the power value was not calculated correctly due to the limitation of the input range of the A / D converter 130.

Hereinafter, a power meter according to another embodiment of the present invention will be described with reference to FIG. 3. 3 is an exemplary circuit diagram illustrating a current converter 121 of a wattmeter according to another embodiment.

FIG. 3 shows a current converter having the same function as the above-described current converter of FIG. 2 but somewhat different in configuration. In FIG. 2, resistors R1 to Rk connected in parallel with CT are used. However, in the present embodiment, the load current is increased by simply connecting resistors R1 to Rk having low resistance values in a current flow path. The load current is converted by changing the voltage across R0 accordingly. That is, the load current flowing through R0 is converted into a fine voltage measurable by R0 of low resistance value. At this time, as in FIG. 2, the conversion ratio is adjusted by adjusting the overall resistance value by connecting a plurality of resistors R1 to Rk to which a relay switch is added so as to be parallel to the resistor R0. The control signal for turning the relay switch on and off is transmitted from the operation and control unit 140. Using the structure as shown in FIG. 3, the electronic power meter having a wide range of operation range is converted into a signal in a measurable range suitable for the A / D converter 130 by adjusting the relay switch according to the magnitude of the load current as described above. Can be configured.

Those skilled in the art will appreciate that the present invention can be embodied in other specific forms without changing the technical spirit or essential features of the present invention. For example, a program for realizing the control method of the present invention may be implemented in various forms such as a recording medium in which a program is recorded. It is therefore to be understood that the above-described embodiments are illustrative in all aspects and not restrictive. The scope of the present invention is indicated by the scope of the following claims rather than the detailed description, and all changes or modifications derived from the meaning and scope of the claims and the equivalent concept are included in the scope of the present invention. Should be interpreted.

1 is a block diagram illustrating a power meter in an embodiment.

FIG. 2 is a circuit diagram illustrating the current converter of FIG. 1.

3 is a circuit diagram illustrating a current converter of a power amount shop according to another embodiment.

Claims (1)

A voltage conversion unit connected in parallel with a power supply to detect a supply voltage, and convert the detected supply voltage to output a converted voltage; A current converting unit connected to the power supply in series to detect a supply current provided to a load side, and converting the detected supply current and outputting a converted current according to a conversion ratio adjusted and set according to a control signal; An A / D converter converting the converted voltage and the converted current, which are analog signals, into digital signals, respectively; An arithmetic and control unit configured to calculate power and amount of power using the digital voltage value and the digital current value output from the A / D converter, and to output the control signal to the current converter to control the conversion ratio; A communication unit for allowing the operation and control unit to communicate with the outside; And Display unit indicating the operation and control results of the operation and control unit Electronic electricity meter having a wide operating range including a.

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