Digital signal processing for plc communications having communication frequencies

DIGITAL SIGNAL PROCESSING FOR PLC COMMUNICATIONS WHICH

HAVE COMMUNICATION FREQUENCIES | Patent application. |

No.

RELATED PATENT DOCUMENT j I give a deposit

This patent document claims priority over US patent application series no. 13 / 334,522 filed on December 22, 2011, the content of which is incorporated herein in its entirety as a reference.

BACKGROUND OF THE WORLD TECHNIQUE IN THE FIELD OF THE INVENTION

Service providers use distributed networks to provide services to customers across large geographic areas. For example, energy companies use power distribution lines to transport energy from one or more generating stations (power plants) to customer and commercial locations alike. The generating stations use alternating current (AC) to transmit electricity over long distances through the lines for the distribution of electricity. Transmission over long distances can be done using relatively high voltages. Substations positioned near the consumer sites ensure a lower voltage from high voltages to lower voltages (for example, using transformers). Electricity distribution lines carry this lower AC voltage from substations to consumer locations with end-point devices.

Communications providers may use a distributed communications network to provide communications services to their subscribers. Similarly, electricity companies use a network of electricity transmission lines, measuring devices and other network elements to provide electricity to consumers in a geographic region and to receive data from consumer locations including, but not limited to, without limitation, data regarding the measured consumption of electricity. A system can provide these reporting functions using a set of data collectors (collectors) that are designed to communicate with nearby endpoint devices. However, data communication between a command center, collectors and many thousands of endpoint devices through power transmission lines can be a very challenging issue.

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The total number of endpoint devices contributes to a multitude of issues including, endpoint processing energy, memory size, endpoint cost, AC power interference, and more. For example, processing the digital signal of communications between devices may be complicated by these and other factors.

BRIEF DESCRIPTION

Aspects of the present disclosure consider systems and methods for use with reception circuits that track AC frequency. These and other aspects of the present disclosure are exemplified by a number of illustrated implementations and applications, some of which are shown in figures and characterized in the following claims section.

Particular embodiments of the present disclosure are directed to a circuit-based apparatus having a transmitter-receiver circuit configured and arranged to communicate through lines for the distribution of electricity using AC (AC). One or more processing circuits are configured and arranged to provide an analog-to-digital converter (ADC) module configured and arranged to provide an analog signal to the digital converter (ADC) module configured to generate a digital audio signal. input from an analog signal that was received at the transmitter-receiver circuit. This digital input signal may be an over-sampled digital signal, in which the digital signal is over-sampled relative to downstream processing (for example, FFT-based processing). A decimator module is configured and arranged to produce, in response to a variable decimation rate, a decimated version of the digital input signal by decimating the over-sampled signal to reduce the sampling rate. A reference signal module is configured and arranged to generate a reference signal that responds to the decimation rate. A module for modifying decimation is configured and arranged to change, in response to an indication of a change in a phase difference between the reference signal and AC, the decimation rate to counteract the phase difference. This can be particularly useful for maintaining a close correlation between the transmitted signal frequencies (which vary according to the AC frequency) and the signal processing (which may use an FFT with a sampling rate that varies according to the AC frequency. ).

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Other embodiments contemplate methods for using one or more circuits of a receiving device. Such a method may include conversion, using an analog-to-digital converter (ADC) and a digital input signal from power distribution lines that can carry alternating current (AC) in a digital form. This digital input signal may be an over-sampled digital signal, in which the digital signal is over-sampled relative to downstream processing (for example, FFT-based processing).

A processing circuit (s) can then be used to decimate the digital input signal according to a decimation rate. A reference signal can be generated by the processing circuit which is sensitive to the decimation rate. The processing circuit may also be used to detect a change in phase difference between the AC and the reference signal and to change, in response to detecting a change in the phase difference, the decimation rate to counteract the detected change. in the phase difference.

The above description does not intend to describe each illustrated embodiment or implementation of this disclosure. The following figures and detailed description, including the description in the appended claims, describe in more detail some of these embodiments.

BRIEF DESCRIPTION OF THE FIGURES

Various embodiments of exemplary character may be more fully understood by considering the following detailed description in connection with the accompanying drawings, wherein:

Figure 1 is a block diagram of an example of a communication system through the transmission line for electricity in which the end points communicate data with the collecting units, in accordance with the modalities of realizing the present disclosure;

Figure 2 illustrates a block diagram for a collector device, according to the modalities of making the present disclosure; and

Figure 3 illustrates another block diagram for a collector device that may be placed in a distribution substation, in accordance with the modalities of making the present disclosure.

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Even though the disclosure is prone to various modifications and alternative forms, examples thereof have been presented with exemplary character in the drawings and will be described in detail. It should be understood, however, that the intention is not to limit disclosure to particular embodiments presented and / or described. On the contrary, the intention is to cover all changes, equivalences and alternatives that fall under the spirit and field of disclosure.

DETAILED DESCRIPTION

Aspects of the present disclosure are assumed to be applicable to a variety of different devices, systems, and arrangements, including those that may be implemented for receiver circuits that communicate through power distribution lines. Even though this disclosure is not necessarily limited to such applications, various aspects of the disclosure may be considered through a discussion of the various examples using this context.

Ways of making the present disclosure envisage receiver circuits configured and arranged to process communication signals that are received through the lines for the distribution of electricity, which transports electricity using alternating current (AC). Receiver circuits can be configured to process received signals using AC as a coordinating reference. The frequency of the AC line is subjected to significant frequency fluctuations, and the receiver is designated to compensate for these fluctuations by making appropriate adjustments to the signal processing.

In accordance with certain embodiments of the present disclosure, the bandwidth requirements of a complex system communicating through power distribution lines are met by using a receiver that processes a received signal in the digital domain. In particular embodiments, signal processing includes the use of a fast Fourier transform (FFT) to allow the signal to be represented in the frequency range. The FFT algorithm can be designed to match the channel frequencies used by the transmitter. The methods for carrying out the present disclosure are thus directed to compensate for the changes in channel frequencies that result from the corresponding AC frequency changes.

For example, in certain embodiments, the transmitted signals may track the frequency of the AC line. For example, a frequency channel

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4 -12- 2012 be determined by using the AC line frequency as a reference signal or clock. In this example, the frequency channel has a central frequency that will vary as the frequency of the AC line will vary. This can be particularly useful for filtering out harmonics that can be triggered by the AC power supplier. This AC frequency and the resulting harmonics can vary around an ideal frequency of about 60 Hz in the United States and around 50 Hz in Europe. These standard frequencies, however, are relatively arbitrary (for example, defined by a standard that may be changed in the future) and do not necessarily limit the various embodiments discussed below.

The output of an FFT may vary according to a number of input parameters. One of these parameters is the sampling rate for the digital signal transformed by the FFT. The methods for carrying out this disclosure envisage adjusting the sampling rate provided by the FFT. Adjusting the sampling rate can be done by changing a decimated rate of the over-sampled signal to counteract the changes in AC frequency.

Aspects of the present disclosure envisage a receiver circuit of a data collector (collector) that is configured and arranged to link its signal processing (for example, an FFT algorithm) closely enough to the frequency of the line for the transmission of electricity for the demodulation of complex data for the data received from endpoints.

The ability to link effectively and efficiently can be particularly useful for allowing a large number of densely packaged frequency channels in a limited bandwidth, in which individual channel frequencies are maintained within extremely tight tolerances. For example, the present disclosure may be particularly useful for maintaining orthogonality between the sub-channels throughout the system bandwidth.

In the case of a particular embodiment, an upstream receiver re-sampling rate closely monitors the frequency of the line for the transmission of electricity (for example, at 1 part per 10 million) and to facilitate demodulation of end-point signals with a receiver on FFT base.

Particular embodiments of the present disclosure envisage a circuit-based apparatus, which has a transmitter-receiver circuit configured and arranged to communicate through the lines for the distribution of electricity, which transports electricity using alternating current (AC). SunU ^ co ^ x // fi ¢ -2014-00475 i-12'2012 configured and arranged one or more processing circuits to provide an analog-to-digital converter (ADC) module configured to generate a digital input signal of to an analog signal that was received at the transmitter-receiver circuit. This digital input signal may be an over-sampled digital signal, in which the digital signal is over-sampled relative to downstream processing (for example, FFT-based processing). A decimator module is configured and arranged to produce, in response to a variable decimation rate, a decimated version of the digital input signal by decimating the over-sampled signal to reduce the sampling rate. A reference signal generator module is configured and arranged to generate a reference signal having a frequency that is dependent on the decimation rate. A module for modifying decimation is configured and arranged to change, in response to a change indication in a phase difference between the reference signal and AC, the decimation rate to counteract the phase difference. This may be particularly useful for maintaining a close correlation between the transmitted signal frequencies (which vary according to the AC frequency) and the signal processing (which may use an FFT with a sampling rate that varies according to the AC frequency).

Other embodiments contemplate methods for using one or more circuits of a receiving device. Such a method may include the conversion, using an analog-digital converter (ADC), and an analog input signal from the lines for the distribution of electricity, which transports electricity using alternating current (AC), in a digital form.

This digital input signal may be an oversampled digital signal, in which the digital signal is over-sampled relative to downstream processing (for example, FFT-based processing). A processing circuit (s) may be used to decimate the digital input signal according to a decimation rate. A reference signal can be generated by the processing circuit, a signal that is dependent on the decimation rate. The processing circuit may also be used to detect a change in a phase difference between the AC and the reference signal and to change, in response to detecting a change in the phase difference, the decimation rate to counteract the change. detected in the phase difference.

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More particular embodiments of the present disclosure contemplate a receiver device that is configured to decode orthogonal carrier frequency channels. For example, orthogonal frequency division multiplexing (OFDM) is a method for encoding digital data on multiple orthogonal carrier frequency channels. The orthogonal nature of the frequency channels ensures that intermodulation between sub-channels does not take place. For example, an FFT may be modularized for a given set of orthogonal channels and such that each channel is made separable by the way of being able to reject components from other channels. Aspects of the present disclosure admit that a component of an appropriately modulated FFT is related to the filling time of the FFT buffer (for example, the time represented by a complete set of input samples). If this filling time is correlated with the channel frequency, the FFT can reduce or eliminate the "spectral leak", which may be caused by a mismatch in this correlation. Thus, the orthogonal properties of the channels are effectively maintained at the receiver.

Specific embodiments of the present disclosure admit that the correlation mismatch may result when channel cycles (one cycle being a full period) are not aligned with the length of the filling time. If the time recording contains a number of cycles that is not integer, spectral leakage can occur. The receiver can be configured to use a FFT of a certain size (size being the total number of samples). Sample rate (f_s) represents the number of samples per time period (for example, samples / second) and thus the filling time is the FFT size divided by the sampling rate. Channel frequency uses AC frequency as a reference point for generating carrier frequency channels. The receiver is therefore configured to adjust the filling time, using a variable sampling rate, to maintain a correlation between the filling time and the carrier frequency channels. In the case of particular embodiments, the variable sampling rate corresponds to a resampling / decimator device which reduces the sampling rate of an over-sampled signal by selecting the samples from the over-sampled signal at a variable rate. This variable rate can be considered either as the decimation / resampling rate, or the sampling rate that results from the decimation rate.

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Certain aspects and methods of carrying out the present disclosure consider receiving devices, and the corresponding methods, which may cause an adjustment of the decimator rate. For example, particular embodiments admit that the receiver can determine the amount of adjustment using a feedback circuit.

The reaction circuit is intended to produce an adjustment relative to the mismatches between the decimation rate and the AC frequency, thus compensating for the FFT mismatches that relate to the transmitted channel frequencies. For a given AC frequency, the receiver is able to determine the desired decimation / re-sampling rate. Accordingly, the reaction circuit is configured to be AC ​​frequency dependent.

In the case of particular ways of realizing the present disclosure, a reference signal from the decimation / re-sampling rate is generated. Specifically, the reference signal frequency may be set to generate a reference signal that has a frequency that corresponds to the desired AUC frequency for the decimation rate. The loop filter then determines the adjustment by comparing the reference signal with the AC signal to make an adjustment that compensates for the differences between the two signals. In the case of an embodiment, the comparison includes the detection of a phase relationship / difference between the two signals. Particular embodiments admit that an exact match between the phases (for example, deviation of zero degrees) is not required as long as the phase relationship is constant. Thus, the loop filter may use a derivative of the detected phase to calculate the adjustment based on a rate of change in the phase relationship.

In certain embodiments of the present disclosure, the frequency of the reference signal may be set to a value that correlates to the frequencies carrying the virtual channel. The frequencies that carry the virtual channel represent the frequencies that match the decimation rate. These virtual channel carrier frequencies will therefore correspond equally in the FFT using a decimated signal at the decimation rate. The frequency of the reference signals can, therefore, be set to a reference frequency that would result in the frequencies carrying virtual channels if the reference frequency was the current AC frequency. In this way, a frequency mismatch between the reference frequency and the AC frequency corresponds to a mismatch between the decimation rate and the current AC frequency.

In accordance with various ways of realizing the present disclosure, the lines for the distribution of electricity may

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2014'00475 ί &lt;»'ai2 provided from one or more generating stations (power stations) to residential and commercial consumers alike. The generating stations use AC to transmit electricity over long distances through the lines for the distribution of electricity. Transmission over long distances can be achieved using a relatively high voltage. Substations located near consumer positions ensure a drop from high voltage to lower voltage (for example, using transformers). Electricity distribution lines carry this lower AC voltage from substations to consumer locations. Depending on the distribution network, exact voltages and Ac frequencies may vary. For example, voltages can generally be in the range 100-240 V (expressed as mean square root voltage) with two frequencies commonly used at 50 Hz and 60 Hz. In the United States, for example, a distribution network can supply consumer locations at 120 and / or 240 V at 60 Hz.

Figure 1 is a block diagram of a system, with an exemplary character, of communication through a line for the transport of electricity in which the end points communicate data with collecting units, in accordance with the modalities of realizing the present disclosure. The communication system 100 through the line for the transmission of electricity includes a service network in which several end points 114 are coupled (for example, communicatively coupled) to the collecting units 108 through the lines for the distribution of electricity 116. according to the means of In making this disclosure, the final points 114 may provide data from utility meters. For example, data may be provided from meters for measuring electricity, from gas meters and from water meters, which are installed in the respective gas and water networks. Further, while the present disclosure generally refers to endpoints 114 as providers of utility data measurement (eg, electricity) through a network for electricity distribution, other data may also be communicated.

Endpoints 114 may be implemented to monitor and report various service network operation characteristics. For example, within a grid for the distribution of electricity, measuring devices can monitor the characteristics related to the electricity consumption in the network. Examples

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4 -12- 20J2 average electricity, overloads, power outages and load changes, among other features. In the case of gas and water distribution networks, measuring devices can measure similar characteristics related to gas and water consumption (for example, total flow and pressure).

The final points 114 report the operating characteristics of the network through the communication channels. Communication channels are portions of the spectrum through which data is transmitted. The central frequency and bandwidth of each communication channel may depend on the communication system in which they are implemented. in the case of some implementations, the communication channels for the utility measuring devices (for example, the electrical measuring devices, gas and / or water) may be transmitted using line communication networks for the transmission of electricity that allocates available bandwidth between endpoints in accordance with a multi-access spectrum allocation technique through orthogonal frequency distribution (OFDMA) or with another technique for channel allocation.

When the endpoints 114 are implemented in connection with the devices for measuring electricity in a network for electricity distribution, the endpoints transmit reporting data specifying up-to-date information of the measuring device which may include measurements of total electricity consumption, electricity consumption for a period of time, peaks of electricity consumption, instantaneous voltage, peak voltage, minimum voltage and other measurements related to electricity consumption and electricity management (for example, load information). Each of the endpoints may also transmit other data, such as status data (for example, operating in a normal operating mode, emergency power mode, or other status such as a power return status. after a power outage).

In the case of some implementations, the symbols (representing one or more bits representing reporting and / or status data) are transmitted through lines for the distribution of electricity 116 for a specified symbol period. A symbol period is a period of time in which each symbol is communicated. Some specific embodiments envisage the use of multi-tone transmitted phase symbols (MTPSK), although other types of schemes may be used.

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4 -β- 20C multi-tone relative phase (MTFSK w / θ) can also be used. For additional previous details about such symbols, reference will be made to the publication of US Patent no. 20100164615, System And Method For Relative Phase

Shift Keying, application no. 12 / 347,052, filed on December 31, 2008, which is fully incorporated herein by reference.

In Figure 1, the end points 114 transmit symbols through the communication channels to the respective collecting units 108. in the case of certain embodiments, the final points 114 may be allocated to the locations of the consumers (for example, buildings). Often, but not always, 112 transformers can be located near consumer locations. These transformers 112 provide a voltage drop before AC power is supplied to a consumer. Collecting units 108 may include circuits (for example, including one or more processors) that are configured and arranged to communicate with endpoints 114 through power distribution lines 116. Collecting units 108 may also include circuits for interfacing with a command center 104. The interface with the command center 104 can be implemented using various different communication networks including, but not limited to, a wide area network (WAN) that uses ethernet.

In accordance with certain embodiments of the present disclosure, the manifolds are installed in distribution substations 106 and are used to control two-way communication with both the command center 104 (for example, located in the utility company's offices) and endpoints 114. (for example, located in the spaces for measuring devices at consumer premises). In accordance with certain embodiments, the manifolds 108 are constructed in accordance with an industrial level computer specification to withstand the aggressive environment of a substation.

In the case of certain embodiments of the present disclosure, collectors 108 are configured to receive data from several different endpoints 114 while storing data in a local database. A collector 108 may also act on the basis of data received from end points 114 and data transmitted from end points 114 to a control center 104. For example, in the case of a PLC network, command center 104 may receive data indicating that electricity consumption is significantly higher in a particular portion of the electricity grid than in other portions of the ENPORA T power grid. )

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- ^ Λ3ί · ^SRL· 'Τ' / ^ “2014-00475 * '12' 2012 electric. Based on this data, the command center 104 may allocate additional resources to that particular part of the network (eg load balancing) or provide data to a power plant operator 102 (ie, specify that there is increased electricity consumption in the particular part of the electricity grid).

In accordance with certain embodiments, command center 104 provides an interface that allows other devices to access the data that was received from endpoints 114. For example, user devices may be owned by the utility provider, by maintenance personnel and / or utility utility customers. The data identifying the increased electricity consumption described above may be provided to a user device accessible to the system operator 100, which may, in turn, cause appropriate action regarding the increased consumption. In addition, data that identifies a usage time measurement and / or a peak demand measurement can also be provided to user devices. Similarly, in the event of a power failure, the control center 104 may provide the user devices with data that is accessible to consumers to provide information on the power outage and provide information on how long this power is to be consumed. stops.

The collectors 108 can communicate with the command center 104 through a wide area network (WAN), a local area network (l_AN), the internet, or other communications networks. These data networks can be implemented as a cable or wireless network. Wired networks may include any networks with information support restrictions including, but not limited to, networks implemented using wire conductor, fiber optic material, or waveguides. Wireless networks include all propagation networks in free space including, but not limited to, networks implemented using radio waves and optical networks in the open air.

Symbols from a certain endpoint can be transmitted through any of the thousands of communication channels in the system. For example, a specific channel may be assigned to each endpoint using the OFDMA technique or another channel allocation technique. The allocation of channels for endpoints 114 may be stored, for example, in a communications database that is accessible to collectors 108.

In accordance with the methods of carrying out the present disclosure, each manifold 108 may be configured to be in communication with thousands of

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4 -12- 2012 final 114 and there may be thousands of collectors 108 in communication with the command center 104. For example, a single collector can be configured to communicate with over 100,000 endpoint devices and a command center can either configured to communicate with over 1,000 collectors.

There can be millions of endpoints and many thousands of them can communicate with the same collector through a shared electricity distribution line. Accordingly, ways of achieving the present disclosure take into account coordinated communications with the use of carefully designed time-based protocols and associated considerations.

For example, collectors 108 may be designed to demodulate transmissions from endpoint devices 114 in the digital domain using one or more digital signal processors (DSPs). The DSP may include (or receive an input from) an analog-to-digital converter (ADC) that produces a digital input signal that includes modulated signals to carry data, in which modulation uses corresponding carrier frequencies.

The DSP can demodulate the digital input signal to retrieve the data. Certain ways of realizing the present disclosure envisage the transformation of the digital input signal in the frequency domain as part of the demodulation. More specific embodiments ensure this transformation with the use of an FFT. The FFT can be performed on a decimated version of the digital input signal, in which the decimation rate is dependent on a frequency of AC energy transported on the power line. Assuming that other FFT parameters, such as the total number of samples, are retained, a change in the decimation rate would result in a change in the time between the samples. By changing the time between samples, the sampling rate of the FFT input is effectively offset to monitor changes in carrier frequencies, which may be caused by changes in the AC frequency.

Figure 2 illustrates a block diagram for a collector device, in accordance with the modalities of making the present disclosure. The collector 202 includes a receiver circuit 204 coupled to power distribution lines 206. In certain embodiments, the receiver circuit 204 may also include transmitter components, that is, it may also be a transmitter-receiver. ADC 208 converts the signal from the receiving circuit 204 into a digital form.

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Aspects of the present disclosure admit that, while ADCs can provide high sampling rates at relatively low costs, performing signal processing at high sampling rates can be particularly complicated. Furthermore, decimating from a high (over-sampled) sampling rate to a lower sampling rate may result in processing gains, improving receiver sensitivity. Accordingly, a decimator module 212 may reduce the sampling rate of the signal according to a decimation rate. The decimated signal can then be provided to a module for signal processing 220. In cases of specific embodiments, the module for signal processing 220 uses an FFT as part of the signal processing and demodulation. For example, data communications may use orotgonal frequency channels to reduce or eliminate interference between channels. The FFT may be designated to preserve the orthogonal nature of the channels during the transformation when the frequency of the channels is known. For example, the FFT can be designed with an FFT size that ensures that the FFT filling time is an integer multiple of the channel periods. If the channel frequency changes, the FFT fill time may no longer be an integer multiple of the channel periods. Accordingly, various embodiments of the present disclosure contemplate adjusting the filling time including, for example, adjusting the sampling rate of the samples used to fill the FFT buffer.

In accordance with the embodiments of the present disclosure, the decimator module 212 is configured to operate at a variable decimation rate. In this way, a digital signal from an ADC operating at a sampling rate of N samples / second that is decimated with a variable decimation rate of M produces a signal that has a sampling rate of N / M. In specific embodiments, the N / M sampling rate is varied such that a number of samples, at the N / M sampling rate, corresponds to an integer multiple of the channel periods. For example, a symbol period used for orthogonal channel protocols may be selected such that it is an integer multiple of the channel periods. Thus, the N / M sampling rate is varied to provide a number of sample sets for a symbolic period.

Aspects of the present disclosure admit that due to the fact that channel periods are related to the frequency of the AC, the decimation rate M may also be related to the frequency of the AC. ADC 208 provides the digital signal _ wT pnVJ

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the phase difference detector 216. A reference signal generator 214 produces a reference signal which is also provided to the phase difference detector 216. In accordance with the embodiments of the present disclosure, the reference signal generator 214 produces a reference signal generator 214. reference signal that has a frequency that is dependent on the decimation rate of the decimator module 212. In more specific embodiments, the frequency of the reference signal corresponds to an AC frequency that would result in channel frequencies that match the decimator rate. For example, the transmitter device may generate the channel carrier frequencies based on the current AC Fac frequency. The desired decimation rate can therefore be determined as a function of the current Fac. The reference signal generator 214 can reverse this process and determine a desired Fac from the current decimation rate. When the desired Fac (represented by the reference signal) matches the current Fac, the decimator rate may be assumed to be correct; however, a mismatch between these frequencies would indicate that the current decimation rate must be adjusted.

Aspects of the present disclosure acknowledge that the current Fac does not have to be calculated using a frequency calculation module. Certain embodiments may compare the reference signal with the AC signal to determine a frequency mismatch. In particular, a phase difference detector module 216 may be used to detect the phase difference between the two signals. This difference is then provided to a module 218 for modifying decimation (decimation rate).

Module 218 for modifying decimation determines an adjustment that must be made to the decimation rate. This adjustment is provided to both the reference signal generator module 214 and the decimator module 212. In accordance with certain embodiments, the module for modifying the decimation 218 is configured to respond to a change in the phase difference (for example, the derivative of the phase difference). phase). This can be particularly useful for simplifying the adjustment process by allowing the two signals to be at any phase angle from one another, as long as the frequencies match and the difference in the phase difference does not change.

Figure 3 shows another block diagram for a collector device that can be located in a distribution substation, according to modalities d

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Î 4 'β- 2012 realization of the present disclosure. Although aspects of the present disclosure are not limited to a specific standard of electricity supply (for example, they may apply to standards in different countries that are susceptible to change in the future), substations for electricity distribution lower electricity AC transmitted using three phases. Accordingly, Figure 3 shows ADCs 302 which are connected to a respective phase.

In accordance with the embodiments of the present disclosure, the input of the line transformer may be used as an input for the line voltage, as opposed to the inputs of Phase A, Phase B, Phase C, which are the current transformer inputs used for the currents. phase. AB phase inputs may include communication signals from endpoints. as a result, each phase is monitored and used when receiving communication signals from the endpoints. The energy supply component of these three phases, however, is dependent on the charge of the substation, which can vary significantly. The line voltage, on the other hand, generally has a more stable and predictable AC signal component. Accordingly, certain embodiments use the AC frequency from the line voltage for the control reaction circuit.

The ADCs 302 each produce a digital output at a high overburden rate. V ariable decimators (for re-sampling) 304 decimates these digital signals at a reduced sampling rate. Decimated signals are used by the processing modules 308. In certain embodiments, a fixed decimation module 306 may be implemented in addition to the variable decimals 304.

The phase detector 310 produces a signal that represents the phase difference between the digital signals from the power distribution line and a reference signal produced by the generator 316. In the case of a particular embodiment, the reference generator 316 is a direct digital synthesizer ( DDS). Accordingly, the phase detector module 310 detects any phase shift between the digitized line voltage and the reference signal. In the case of a particular embodiment, the phase shift is detected by multiplying the two input signals together. The result can then be filtered with a 312 filter (for example, to remove noise and frequencies above the basic AC frequency). Filter 312 can be any of a number of different filter types, including, but not necessarily limited to, different filter types going down, passing through »» »^of_ss^{&gt; e} J

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στ2 Ο 1 4-Ο Ο 475 t * - «- gold up, filter stops the band, or filter passes the band. Filter 312 may be configured and arranged to filter line harmonics and / or frequency components that are caused by the signal processing element. For example, the output of the phase detector contains the sum of the difference of the two inputs, so for component inputs that are close to 60 Hz, the output will be a signal that varies slightly in the vicinity of the superimposed DC with an image close to 120 Hz. Other phase detector circuits are also possible and the filter 312 can be configured and arranged accordingly.

The derivative block 314 determines the rate of change for the output of the phase detector 310. In the case of a particular embodiment, the derivative block 314 can be modulated using a proportional-integral-derivative (PID) controller module. The embodiment of figure 3 uses the derivative portion of this controller as an input to module 320 for adjusting the decimation rate. The decimation rate adjustment is then used by module 318 to determine the sampling rate to determine the desired sampling rate. The derived signal represents a phase change, and if the AC signal and the reference signal have different frequencies they may have a phase relationship that changes over time. Once the frequencies are adjusted, the phase difference / angle may remain relatively constant. Accordingly, module 320 for the decimation rate may be configured to provide an adjustment of the decimation rate which causes an adjustment of the frequency of the reference signal which counteracts the changing phase. For example, an increasing phase angle (positive derivative value) may be counteracted by a reduction in the decimation rate. A decreasing phase angle (negative derivative value) can be counteracted by increasing the decimation rate. This is just one example, and the particular relationship between the phase angle and the decimation rate can be set based on how the phase angle is determined.

According to the embodiments of the present disclosure, the derivative module 314 operates on a portion of the output signal of the reaction circuit 312 which is near DC. Accordingly, the reaction circuit 312 may be used to remove harmonics and interference (for example, portions of the image near 120 Hz). In the case of a non-limiting example, the reaction circuit 312 may be implemented as a low-pass filter, such as a low-pass filter.

Butterworth with 6 poles.

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An argument for filter selection is to reduce the group delay while increasing harmonic attenuation (120 Hz). For example, a corner frequency (for example, 27.5 Hz) can be selected to optimize group delay to attenuation. The particular values, including the corner frequency, are easily adjustable depending on the specific application.

In accordance with certain embodiments of the present disclosure, the amplitude of the line voltage input is pre-scaled (such as the reference signal) to produce an output of the loop filter 312 which is between -1.0 and +1.0. Such normalization can be particularly useful in applications that use a PID controller module, for example, by simplifying the loop amplification process.

Other embodiments contemplate the use of one, or both, proportional and integral outputs of the PID controller module as part of the control reaction circuit. The additional output (s) may be particularly useful for acquiring a fast AC frequency link and / or ensuring long-term accuracy. Aspects of the present disclosure admit, however, that using the proportional and integral parts of the PID reaction may complicate the tuning of the loop and may sometimes increase instability.

In the case of an embodiment, the output of module 320 for adjusting the decimation rate can be determined by multiplying the output of the derivative module 314 by an amplification factor. More involved algorithms can also be used if desired.

In the case of a particular exemplary and exemplary embodiment, the reference signal frequency may be controlled by varying its sampling rate, but, regardless of the output frequency, the reference signal generator 316 always produces the same set number of cycles in one. set number of samples. This results in the same number of input samples for FFTs in the set number of cycles. Specifically, the same decimation rate that commands the sampling rate for the reference generator 316 also directs the sampling rate for decimating (re-sampling) phase A, phase B and phase C through variable decimator modules 304. For example, the AC frequency that follows the re-sampling rate may be represented by the algorithm A / ((A * G * H) / (D * E * current AC frequency)), where: A = the sampling rate (per crystal base) of the digital input signal; D = a fixed decimator rate; E = number of samples ^ Tco ^

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0 / FFT input; G = symbol period; and H = nominal frequency of AC. A number of different values ​​can be selected as being suitable for applications (for example, regarding processor efficiency, available memory and / or communication bandwidth). An optimal solution for a given application can also be based on the transmitter power, channel noise, and desired bit error rate. These factors may be particularly relevant for the selection of a symbol period and the corresponding reference DDS output number per symbol period.

These signals and the associated logic and functionality described in connection with the figures can be implemented in a number of different ways. unless otherwise indicated, various general purpose systems and / or logic circuits may be used with programs in accordance with the present knowledge, or may prove useful in constructing an even more specialized apparatus that can execute the required method. For example, according to the present disclosure, one or more of the methods may be implemented within an unmodifiable circuit by programming a general-purpose processor, another complete or semi-programmable logic circuit and / or by combining such hardware and a general purpose processor configured with software. Accordingly, the various components and processes shown in the figures may be implemented in a variety of circuit-based forms, such as those using data processing modules.

It is known that aspects of the disclosure can be implemented with computer / processor based system configurations, other than those expressly described herein. The structure required for many of these systems and circuits will be evident from the application envisaged and from the description above.

The various terms and techniques are used by those skilled in the art to describe issues that relate to one or more communications, protocols, applications, implementations and mechanisms. Such a technique is the description of an implementation of a technique expressed in terms of an algorithm or a mathematical expression. While such techniques can be implemented, for example, by executing code on a computer, the expression of that technique can be transformed and communicated as a formula, algorithm, or mathematical expression.

For example, a block that designates "C = A + B" as an additive function implemented in hardware and / or software would

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summed output (C) as in combinatorial logic circuits. Thus, the use of the formula, algorithm, or mathematical expression as descriptions must be understood as having at least a physical embodiment in the hardware (such as a processor in which the techniques of the present disclosure can be applied and also implemented as a means of embodiment).

In certain embodiments, the instructions executable by the computer are stored for execution in a manner consistent with one or more of the methods of this disclosure. The instructions can be used to make a general-purpose or special-purpose processor that is programmed with the instructions to perform the steps of the method. The steps can be performed by specific hardware components that have logically unmodifiable component for performing the steps, or by any combination of programmed computer components and common hardware components.

In some embodiments, aspects of the present disclosure may be provided as a computer program product, which may include a computer readable environment, which has inside instructions stored, which may be used to program a computer. computer (or other electronic devices) to perform a process according to this disclosure. Accordingly, the computer readable medium includes any type of media / medium readable by the appropriate computer for storing electronic instructions.

The various embodiments described above are provided as a means of illustration and should not be considered as limiting disclosure. Based on the above discussion and illustrations, those skilled in the art will readily acknowledge that the embodiments may be applicable to a number of applications involving data transmission through power distribution lines. Various modifications and changes can be made without following strictly the exemplary embodiments illustrated and described herein.

For example, such changes may include variants of mechanisms for synchronizing (and / or tracking) the frequency of the AC line. Such changes and changes do not depart from the spirit and scope of the present disclosure, including the issues set forth in the following claims.