Patent Application
20130176016
Claim and incorporate by reference domestic priority application and foreign priority application as follows:
This application claims the benefit under 35 U.S.C. Section 119 of Korean Patent Application Serial No. 10-2011-0121039, entitled filed Nov. 18, 2011, which is hereby incorporated by reference in its entirety into this application.
1. Field of the Invention
The present invention relates to a signal converting apparatus of a power metering system, a power metering system and a method for signal-converting in a power metering system. More particularly, the present invention relates to a signal converting apparatus of a power metering system, a power metering system and a method for signal-converting in a power metering system to process by combining into one signal by up converting current and voltage signals.
2. Description of the Related Art
In recent, the studies for a smart grid technology through the convergence of information and communication technology and energy technology have been actively realized. In order to implement the smart grid, the usage amount of power is accurately calculated, and an electronic metering technology to convert this into the digital information and a communication technology to transmit the converted digital information are required.
Generally, the electronic metering system is constituted of a signal sensing block, a signal conversion block, a calculation block and a control block; and, in a conventional method, in order to process the voltage and current signals of a single of a 3-phase power signal, each of the analog signals is converted into a digital signal respectively through signal conversion blocks (ADC) of two (voltage and current) or six (3-phase voltages and currents). Accordingly, a large system area and a high current consumption may be caused.
In the conventional method, there are problems that a large area system is required and a high current consumption is generated by being provided with analog-digital converters for each of the single or 3-phase voltage and current signals.
The present invention has been invented in order to overcome the above-described problems and it is, therefore, an object of the present invention to process a signal conversion with one analog-digital converter by processing the signal by up converting the frequencies of current and voltage signals and combining these into one signal.
And also, in the conventional method, since the input frequency bandwidth of the analog-digital converter is a low frequency bandwidth (DC˜2KHz), there are problems of the resolution deterioration of ADC due to the DC offset and the 1/f noises and the SNR reduction or the like; and, in accordance with one embodiment of the present invention, it is, therefore, another object of the present invention to process an analog-digital conversion without being affected by the DC offset and the 1/f noises during the analog-digital conversion process or by shifting a frequency into a reduced frequency bandwidth.
In accordance with one aspect of the present invention to achieve the object, there is provided a signal converting apparatus of a power metering system including: a frequency shift unit for shifting a frequency(s) of at least one signal of sensed current and voltage signals by a shift frequency(s) so that the current and voltage signals have different frequency bandwidths; a signal coupling unit for coupling the current and voltage signals having different frequency bandwidths into one signal; and an analog-digital convert unit for converting an analog signal coupled as said one signal into a digital signal(s).
In another example of the present invention, the frequency shift unit may shift each of the sensed current and voltage signals by each of different shift frequencies.
In another example, the current and voltage signals may be 3-phase signals.
And also, in one example, the frequency shift unit may consist of frequency synthesizers to generate frequency-shifted intermediate frequencies by synthesizing frequencies of both signals and each different shift frequency so that the current and voltage signals have different frequency bandwidths; and the signal coupling unit may be a power coupling unit.
And also, in one example, the analog-digital convert unit may include: a sigma-delta converter for converting the analog signal coupled as said one signal into the digital signal; and a digital filter unit for converting the converted digital signal into a desired digital data signal(s) by down-sampling.
At this time, in one example, the digital filter unit may consist of decimation filters, and the decimation filters may convert the converted digital signal into desired N-bit digital data signals by band-pass filtering in a low frequency band and down-sampling.
Also, in one example, the analog-digital convert unit further may include a band pass filter for removing a DC offset and a 1/f noise component in a low frequency band from the converted digital signal in the sigma-delta converter to output the result.
And also, in one example, the signal converting apparatus of a power metering system further may include: frequency down converters for recovering signals corresponding to the current and voltage signals from the digital signal converted in the sigma-delta converter by down-shifting by each shifted frequency, wherein the digital filter unit may convert the current and voltage signals recovered in the frequency down converters into desired digital data signals by down-sampling.
And also, in one example, the signal converting apparatus of a power metering system further may include: frequency down converters for recovering the current and voltage signals from the converted digital data signal(s) by down-shifting by each shifted frequency.
Thereafter, in order to solve the above-described problems, in accordance with the second aspect of the present invention, there is provided a power metering system including: a current and voltage sensing block for sensing current and voltage; a signal converting apparatus of the power metering system according to any one of examples of the above-described one aspect embodiments for converting signals sensed in the sensing block into a digital signal(s); and a digital process block for calculating an amount of power from digital data values outputted in the signal converting apparatus.
And also, in one example, the analog-digital convert unit may include: a sigma-delta converter for converting the analog signal coupled as said one signal into the digital signal; and a digital filter unit for converting the converted digital signal into desired digital data signals by down-sampling, the signal converting apparatus further may include frequency down converters for recovering signals corresponding to the current and voltage signals from the digital signal converted in the sigma-delta converter by down-shifting by each shifted frequency, and the digital filter unit may convert the current and voltage signals recovered in the frequency down converters into desired digital data signals by down-sampling.
And also, in one example, the analog-digital convert unit may include: a sigma-delta converter for converting the analog signal coupled as said one signal into the digital signal; and a digital filter unit for converting the converted digital signal into a desired digital data signal by down-sampling, and the signal converting apparatus further may include frequency down converters for recovering the current and voltage signals from the converted digital data signal by down-shifting by each shifted frequency.
Thereafter, in order to solve the above-described problems, in accordance with the second aspect of the present invention, there is provided a method for signal-converting in a power metering system including: shifting a frequency(s) of at least one signal of sensed current and voltage signals by a shift frequency(s) so that the current and voltage signals have different frequency bandwidths; coupling the current and voltage signals having different frequency bandwidths into one signal; and converting an analog signal coupled as said one signal into a digital signal(s).
In another example of the present invention, in the shifting the frequency each of the sensed current and voltage signals may be shifted by each of different shift frequencies.
In another example, the current and voltage signals may be 3-phase signals.
And also, in one example, said converting an analog signal coupled as said one signal into the digital signal(s) may include: sigma-delta converting the analog signal coupled as said one signal into the digital signal with a sigma-delta modulation method; and converting the digital signal converted in the sigma-delta converting into a digital data signal(s) by down-sampling using a digital filter unit.
In accordance with another example, the digital filter unit may consist of decimation filters, and in the converting the converted digital signal into the digital data signals, a low frequency band-pass filtering and a down-sampling may be performed by using the decimation filters from the converted digital signal to be converted into desired N bit digital data signals.
And also, in accordance with one example, the converting the converted digital signal into the digital data signal(s) further may include removing a DC offset and a 1/f noise component in a low frequency band by using a band pass filter from the converted digital signal in the sigma-delta converting to output the result.
In addition, in accordance with one example, the method for signal-converting in a power metering system further may include: frequency down-converting for recovering signals corresponding to the current and voltage signals from the digital signal converted in the sigma-delta converting by down-shifting by each shifted frequency, wherein the digital filter unit may convert the current and voltage signals recovered in the frequency down-converting into desired digital data signals by down-sampling.
And also, in one example, the method for signal-converting in a power metering system further may include: frequency down-converting for recovering the current and voltage signals from the converted digital data signal by down-shifting by each shifted frequency.
These and/or other aspects and advantages of the present general inventive concept will become apparent and more readily appreciated from the following description of the embodiments, taken in conjunction with the accompanying drawings of which:
Hereinafter, embodiments of the present invention to achieve the above-described objects will be described with reference to the accompanying drawings. In the present description, like numerals refer to like elements throughout the description of the drawings and parts not relating to the description may be omitted to clearly describe the present invention.
In the present specification, if there is no limitation of “direct” in relations that one element is connected, coupled or arranged to the other elements; they may exist in shapes of “direct connection, couple or arrangement” as well as connection, couple or arrangement by inserting another element therebetween. And also, the terms representing “contact” such as “on”, “above”, “bottom”, “below” or the like are also similar. In case when the element being a reference is inverted or the direction thereof is changed, it will be interpreted that the relative direction concepts corresponding thereto are implicated.
In this specification, the singular form includes the plural form unless the context clearly indicates otherwise. Further, terms “comprises” and/or “comprising” used herein specify the existence of described components, steps, operations, and/or elements, but do not preclude the existence of addition of one or more other components, steps, operations, and/or elements.
Hereinafter, the reference numerals which are not shown in the drawings referred to the detailed description respectively may be the reference numerals shown in the other drawings including the same constructions.
At first, a signal converting apparatus of a power metering system in accordance with a first embodiment of the present invention will be described in detail with reference to the accompanying drawings.
Referring to
The frequency shift unit 10 shifts the frequency(s) of at least one signal of sensed current and voltage signals by a shift frequency(s) so that the current and voltage signals have different frequency bandwidths. In the frequency shift unit 10, an intermediate frequency(s) is generated by shifting the frequency(s) of at least one signal of sensed current and voltage signals by the shift frequency(s) so that the current and voltage signals have different frequency bandwidths, thereby coupling into one signal without the collision of frequency bandwidths. For example, in case of a single phase system, the current and voltage signals can have different frequency bandwidths by shifting a frequency of any one signal among the current and voltage signals by the shift frequency or the frequencies of both of the current and voltage signals by each of different shift frequencies. At this time, a fundamental frequency signal (˜60 Hz) of the sensed voltage and current signals is deteriorated due to a DC offset and a 1/f noise of signal convert blocks such as a voltage reference block, an ADC or the like to supply a required reference voltage during the signal conversion, whereby the frequency needs to be shifted. At this time, the shift frequency may be a frequency capable of shifting to a frequency bandwidth without being affected by the DC offset and the 1/f noise at a low frequency bandwidth in the analog-digital convert process.
And also, referring to
Generally, the signal of power line has the characteristics of intensity of 110V or 220V or a fundamental frequency of 60 Hz; and, at this time, the frequency components generate harmonic components due to the nonlinear characteristics on the paths of a power supply source and power supply line. Generally, since a power meter analyzes until 20th harmonic components, the intermediate frequency between the frequency shifted voltage and current signals can have a shift period, e.g., above 1.2 KHz.
Referring to
Referring to
Referring to
Herein, fm1 is fo1+fc1 and fm2 is fo2+fc2. That is, for example, the voltage and current signal having the fundamental frequency fo is up-converted to the shift frequency of fc1 and fc2 by the frequency mixer, as shown in
Since the analog-digital conversions are performed in each of the frequency bandwidths through the frequency conversion in accordance with the embodiments of the present invention, the interference between different frequencies or different phases can be minimized.
In one example, the current and voltage signals may be a single phase, or as shown in
In case of the 3-phase signal, since the frequency mixer 10 is required for each phase, for example, 6 numbers of frequency mixers 10, or 7 numbers of frequency mixers 10 for 3-phase 4 wire system are needed. Or except any one of the 3-phase voltage and current signals, in case when the remaining signals are shifted by each of different shift frequencies, only 5 numbers of frequency mixers 10 may be included. Referring to
In
And also, referring to
Subsequently, in
In general, the signal of the power line has the intensity of 110V or 220V and the frequency characteristics of 60 Hz; and, at this time, the frequency components generate the harmonic components due to the non-linear characteristics on the paths of the power supply source and the power supply lines. In general, since the power meter analyzes to the 20th harmonic components, the analog-digital convert unit 50 outputs as the digital signal of N-bits having a specific sampling frequency fSampling in order to convert the analog signal constituted of the fundamental frequencies and the harmonic components of the frequency shifted current and voltage signals included into the one signal combined in the signal coupling unit 30 into the digital signal. At this time, in order to obtain the high accuracy and high sensitivity, the sigma-delta Σ−Δ method can be employed. The sigma-delta method is formed of a sigma-delta converter 51 for the modulation and a decimation filter(s) 53 for the demodulation.
In accordance with the embodiments of the present invention, for example, since 2 or 6 voltage and current signals can be converted through one analog-digital converter 50 in the single and 3-phase power system, the power consumption and the size of system can be reduced.
And also, one example, the analog-digital convert unit 50 can include the sigma-delta converter 51 and the digital filter unit 53. At this time, the sigma-delta converter 51 converts the analog signal combined as one signal into the digital signal by performing the modulation with the sigma-delta method. The digital filter unit 53 converts the converted digital signal into a desired digital data signal(s) by down-sampling. Referring to
At this time, referring to
Herein, the decimation filter 53 may be formed by including a CIC and Sinc, Half-Band or the like. The decimation filter 53 can remove the noise of the high frequency bandwidth due to a noise transfer function (NTF) of the sigma-delta converter 51 as shown in
Explaining in detail, the analog signal constituted of the fundamental signals and harmonic components of the frequency shifted current and voltage included in the one signal combined in the signal coupling unit 30 is inputted into the sigma-delta converter 51. At this time, the sigma-delta converter 51 can convert into the digital signal of 1 bit by performing the sampling and modulation with the period of the over sampling frequency Fm. The modulation signal of 1 bit over sampled than a practical signal frequency is recovered to the desired sampling frequency fSampling by being demodulated in the decimation filters 53. At this time, the over sampling frequency is several MHz bandwidths and the sampling frequency may have approximately 2 KHZ˜10 KHz bandwidths. Generally, the sampling frequency may have a frequency above 2.4 KHz as two times of the signals of the frequency bandwidth fBW including the fundamental frequency components of 60 Hz and the harmonic frequency components 120 Hz˜1.2 KHz, in the embodiments of the present invention, since the frequency shifted current and voltage signals are included in the one signal in the signal coupling unit, the sampling frequency can be determined considering on the shift frequency.
Referring to
In accordance with another embodiment, it is available for sampling the signal having the higher SNR, without being affected by the DC offset and the 1/F noises due to the sigma-delta converter 51.
And also, reviewing one example with reference to
Referring to
At this time, referring to
The frequency down converters 60 down-shift the frequencies of the voltage signals and the current signals passing, for example, the high pas filter by each of the shift frequencies fc1 and fc2 to generate the signals by dividing the voltage signal of the frequency fo1 and the current signal of the frequency fo2, respectively. The signal combined as one signal in the power combiner 30 is recovered to the voltage and current signals by each of the frequency down converters 60, respectively. At this time, for example, the decimation filter(s) 53 can convert into the desired N-bit digital data signal(s) with the low frequency band-pass filtering and the down-sampling.
And also, referring to
Referring to
The present embodiments, as shown in
Since 2 or 6 voltage and current signals are converted through one analog-digital converter 50 in the one-phase and 3-phase power systems, the power consumption and the size of the system can be reduced.
The signal converting apparatus of the power metering system in accordance with the present embodiments may be implemented with an integrated circuit or a system-on-chip.
Thereafter, the power metering system in accordance with the second embodiment of the present invention will be explained in detail with reference to the following drawings. In explain the embodiments of the present invention, the signal converting apparatus of the power metering system in accordance with the above-described first embodiment and
Referring to
The current and voltage sensing blocks 5 and 6 sense the current and voltage signals. That is, the voltage and the current of the power lines can output the voltage signals corresponding to the sizes thereof by being sensed through each of the sensors. For example, the current and voltage sensing blocks 5 and 6 may be constituted of a current transformer for sensing the part of the current signal and a voltage divider for sensing the part of the voltage signal. The current transformer and the voltage divider attenuate the voltage and the current of the sensed power lines in thousands of 1 and output as the voltage signals of the attenuated sizes.
At this time, the single phase of current and voltage signals can be sensed; and, as shown in
Subsequently, the signal converting apparatus of the power metering system converts the signals sensed in the current and voltage sensing blocks 5 and 6 into the digital signal. At this time, the signal converting apparatus of the power metering system may be a signal converting apparatus in accordance with any one of the above-described examples of the first embodiments.
Referring to
Further, at this time, referring to
And also, referring to
The additional explanations will be referred to the above-described first embodiment.
Thereafter, the digital signal process block 200 calculates an amount of power from the digital data values outputted in the signal converting apparatus. The digital signal process block 200 calculates an active power, a reactive power, a power factor or the like required in the power metering system, and may be constituted of an integrator, a multiplexer, a filter or the like by the digital circuits.
The power metering system in accordance with the present embodiments can be implemented with an integrated circuit or a system-on-chip.
Thereafter, a method for signal-converting in a power metering system in accordance with the third embodiment of the present invention will be described in detail with reference to the drawings. In explain the present embodiments, the signal converting apparatus of the power metering system in accordance with the above-described first embodiment and
Referring to
In the step S100 of shifting the frequency of
At this time, on one example, in the step S100 of shifting the frequencies, the sensed current and voltage signals can be shifted by each of different shift frequencies. In accordance with the present embodiments, by shifting all of the sensed current and voltage signals by the shift frequencies, respectively, the resolution deterioration of the analog-digital converting and the SNR reduction or the like due to the DC offset and the 1/f noises in the low frequency bandwidth can be prevented. Also, in one example, the current and voltage signals may be a single phase or may be a 3-phase signal as shown in
And then, in the step S200 of combining as one signal, the current and voltage signals having different frequency bandwidths are combined into one signal.
Sequentially, in the analog-digital conversion step S300, the analog signal combined into one signal is converted into the digital signal.
And also, in one example, the analog-digital conversion step S300 can include sigma-delta conversion steps S310 and S2310 and steps S330, S1330 and S2330 of converting into the digital data signals. At this time, in the sigma-delta conversion steps S310 and S2310, the analog signal combined into one signal is converted into the digital signal with the sigma-delta conversion method. And also, in the steps S330, S1330 and S2330 of converting into the digital data signals, the signals can be converted into the desired digital data signals by down-sampling from the digital signals converted in the sigma-delta conversion steps S310 and S2310 using the digital filter unit 53.
And also, referring to
And also, referring to
In addition, reviewing one example with reference to
And also, referring to
In accordance with the embodiments of the present invention, by being processed by combining into one signal by up converting the frequencies of the current and voltage signals, two or six voltage and current signals can be processed through one analog-digital converter in the single or 3-phase power system; and, accordingly, the power consumption and the size of the system can be reduced.
And also, in accordance with one embodiment, by processing the analog-digital conversion by shifting the frequencies of the sensed current and voltage signals into different frequency bandwidths, the interference between frequencies different from each other or phases different from each other can be minimized. In addition, in accordance with one embodiment, by processing the analog-digital conversion by shifting the sensed current and voltage signals into the different frequency bandwidths, the sampling of signals having high SNR can be available since the analog-digital conversion process is not affected by the DC offset and the 1/f noises or is reduced to a minimum.
This invention may be embodied in different forms and should not be construed as limited to the embodiments set forth herein. Rather, these embodiments are provided so that this disclosure will be thorough and complete, and will fully convey the scope of the invention to those skilled in the art. As described above, although the preferable embodiments of the present invention have been shown and described, it will be appreciated by those skilled in the art that substitutions, modifications and variations may be made in these embodiments without departing from the principles and spirit of the general inventive concept, the scope of which is defined in the appended claims and their equivalents.
| Number | Date | Country | Kind |
|---|---|---|---|
| 10-2011-0121039 | Nov 2011 | KR | national |
