Patent Description:
The environment of the power line communication (hereinafter, also referred to as PLC) varies depending on the location, time, etc., and there are places where noise and impedance are inferior. This is because, unlike wireless communication using a communication channel whose output level is strictly limited by laws or standards, there are many noises generated from various devices connected to a power line in power line communication. For example, in power line communication systems for solar photovoltaic power generation, a DC/AC inverter (hereinafter, also referred to as an inverter) is used to convert DC power into AC power, and periodic noise (hereinafter, also referred to as inverter noise) generated by the DC/AC inverter exists. Even in a power line environment that is strongly affected by this type of periodic noise, it is necessary to perform power line communication with high quality and high efficiency.

In <CIT> (hereinafter, also referred as to Patent Document <NUM>), there is disclosed a power line communication system and a noise component remove control method for modulating and receiving data between PLC modems via a power line by an OFDM method. The PLC modem detects a noise component superimposed on a received signal transmitted and received through a power line by a sub-operational amplifier, an A/D converter, and a fast Fourier transform unit. The carrier spectrum detection circuit, the continuous signal conversion circuit, the fast inverse Fourier transform unit, and the D/A converter generate a cancel signal having the same frequency and opposite phase as the noise component detected in the transmission pause period of a predetermined cycle. An operational amplifier adds the cancel signal and an input received signal to cancel the noise component. An example of prior art can be found in <CIT>.

The present invention is defined by the attached independent claims. Other preferred embodiments may be found in the dependent claims. The present application discloses a power line communication device comprising:a transmission processing unit (<NUM>) for generating a transmission signal from transmission data to be output to a power line;an inverter noise detection processing unit (<NUM>) for detecting inverter noise by a DC/AC inverter (<NUM>) of the power line,a transmission position determination unit (<NUM>) for determining a transmission period of the transmission signal; andan output unit (<NUM>) for outputting the transmission signal in the transmission period,wherein the transmission position determination unit (<NUM>) is configured to determine the transmission period based on an amplitude of the transmission signal and a noise voltage amplitude of the power line, the noise voltage amplitude being a voltage amplitude of the inverter noise.

Hereinafter, a power line communication device according to the present embodiment will be described in detail by referring to the drawings. In the specification and the drawings, the same or corresponding elements are denoted by the same reference numerals, and a repetitive description thereof is omitted. In the drawings, for convenience of description, the configuration may be omitted or simplified. Also, at least some of the embodiments and the modified examples may be arbitrarily combined with each other. In addition, the terms in parentheses attached to each term are abbreviations used in the drawings.

The power line communication device according to present embodiment may be utilized in systems for solar photovoltaic power generation, wind power generation, hydroelectric power generation, or nuclear power generation. For example, <FIG> illustrates a configuration of a solar photovoltaic power generation system according to first embodiment. The solar photovoltaic power generation system <NUM> includes solar panels 1A, a junction box (JB) 2A, a power converter (PC) <NUM>, a grid interconnection device (GI) <NUM>, a transformer <NUM>, a monitoring device of solar photovoltaic power generation system (MD) <NUM> (hereinafter monitoring device (MD) <NUM>), an electric meter <NUM>, home appliances (HM) <NUM>, and gateways <NUM>. The system is connected to power lines 6A, <NUM>, <NUM>, and <NUM>, and a power grid <NUM>. A house load (HL) <NUM> is connected to the power line <NUM>.

In the solar panel 1A, many solar cells are arranged in a panel shape. The junction box (JB) 2A is a device for collecting DC power generated by the solar panels 1A. The power converter (PC) <NUM> is a device for converting DC power into AC power. The grid interconnection device (GI) <NUM> is a device for opening and closing the built-in interconnection relays <NUM> shown in <FIG> in accordance with the status of the solar photovoltaic power generation system <NUM> and the grid. The transformer <NUM> is a device for converting a voltage of an AC voltage. The monitoring device (MD) <NUM> is a device for monitoring and controlling the operation of the power converter (PC) <NUM> and the grid interconnection device (GI) <NUM>. The electric meter <NUM> is a device for measuring and metering electric power flowing bidirectionally between the power transmission network and the electric power line <NUM>. The home appliances (HM) <NUM> are various electrical home appliances connected to networks by IoT (Internet of Things) such as air conditioners and refrigerators. The gateways <NUM> are relay devices for connecting to other networks other than the power line communication, such as Ethernet (not shown in figures). The house load (HL) <NUM> is a home appliance other than the home appliances (HM) <NUM> connected to the power line <NUM>.

The solar panels 1A are connected to the junction box (JB) 2A via power lines 6A. The junction box (JB) 2A is connected to the power converter (PC) <NUM> via a power line <NUM>. The power converter (PC) <NUM> is connected to the grid interconnection device (GI) <NUM> via a power line <NUM>. The grid interconnection device (GI) <NUM> is connected to a transformer <NUM>, a monitoring device (MD) <NUM>, an electric meter <NUM>, home appliances (HM) <NUM>, gateways <NUM> and house loads (HL) <NUM> via a power line <NUM>. The transformer <NUM> is connected to a power grid <NUM>.

The power converter (PC) <NUM> and power interconnection device (GI) <NUM> are monitored and controlled by the monitoring device (MD) <NUM> and the transformer <NUM> converts the AC voltage to an appropriate voltage for transmission to the power grid <NUM>. In the solar photovoltaic power generation system <NUM>, the power converter (PC) <NUM>, the grid interconnection device (GI) <NUM>, the monitoring device (MD) <NUM>, the electric meter <NUM>, the home appliance (HM) <NUM> having a power line communication function, and the gateways <NUM> mutually perform power line communication via the power lines <NUM> and <NUM>.

<FIG> illustrates a configuration of a power converter (PC) <NUM> according to first embodiment. The power converter (PC) <NUM> includes a DC/DC converter (DC/DC CON) <NUM>, a DC/AC inverter (DC/AC INV) <NUM>, a power converting control unit (PCC) <NUM>, and a power line communication device (PLC) <NUM>. The DC power generated by the solar panels 1A and collected in the junction box (JB) 2A is inputted to the power converter (PC) <NUM> via the power line <NUM>.

The DC/DC converter (DC/DC CON) <NUM> is a circuit for stabilizing DC voltages of DC power. The DC/AC inverters (DC/AC INV) <NUM> is a circuit for converting AC power into DC power. The power converting control unit (PCC) <NUM> is a circuit for controlling the DC/DC converter (DC/DC CON) <NUM> and the DC/AC inverter (DC/AC INV) <NUM>. The power line communication device (PLC) <NUM> is a device for transmitting information acquired by the power line communication from the monitoring device (MD) <NUM> via the power lines <NUM> and <NUM> to the power converting control unit (PCC) <NUM>.

The DC/DC converter (DC/DC CON) <NUM> is connected to the power line <NUM>, the DC/AC inverter (DC/AC INV) <NUM>, and the power converting control unit (PCC) <NUM>. The DC/AC inverter (DC/AC INV) <NUM> is connected to the DC/DC converter (DC/DC CON) <NUM>, the power converting control unit (PCC) <NUM>, and the power line <NUM>. The power converter control unit (PCC) <NUM> is connected to the DC/DC converter (DC/DC CON) <NUM>, the DC/AC inverter (DC/AC INV) <NUM>, and the power line communication device (PLC) <NUM>. The power line communication device (PLC) <NUM> is connected to the power line <NUM> and the power converting control unit (PCC) <NUM>.

The DC power inputted from the power line <NUM> is stabilized by the DC/DC converter (DC/DC CON) <NUM>, converted from DC power to AC power by the DC/AC inverter (DC/AC INV) <NUM>, and outputted to the power line <NUM>. The operations of the DC/DC converter (DC/DC CON) <NUM> and the DC/AC inverter (DC/AC INV) <NUM> are controlled by a power converter control unit (PCC) <NUM>. In order to increase efficiency the operation of the power converter (PC) <NUM>, the power line communication device (PLC) <NUM> acquires information of the status of the solar photovoltaic power generation and grid from the monitoring device (MD) <NUM> by the power line communication, and transmits the information to the power converting control unit (PCC) <NUM>.

<FIG> illustrates the configuration of the grid interconnection device (GI) <NUM> according to first embodiment. The grid interconnection device (GI) <NUM> includes interconnection relay <NUM>, a grid interconnection control unit (GIC) <NUM>, and a power line communication device (PLC) <NUM>. The interconnection relay <NUM> is a switch circuit that determines whether the power line <NUM> and the power line <NUM> are short-circuited. The grid interconnection control unit (GIC) <NUM> is a circuit for controlling the interconnection relay <NUM>. The power line communication device (PLC) <NUM> is a device for transmission information acquired from the monitoring device (MD) <NUM> through power line communication to the grid interconnection control unit (GIC) <NUM>.

The interconnection relay <NUM> is connected to the power line <NUM>, the grid interconnection control unit (GIC) <NUM>, and the power line <NUM>. The grid interconnection control unit (GIC) <NUM> is connected to the interconnection relay <NUM> and the power line communication device (PLC) <NUM>. The power line communication device (PLC) <NUM> is connected to the grid interconnection control unit (GIC) <NUM> and the power line <NUM>.

The AC power outputted from the power converter (PC) <NUM> is inputted to the grid interconnection device (GI) <NUM> via the power line <NUM>. The grid interconnection device (GI) <NUM> opens and closes the interconnection relay <NUM> according to the status of the power generation of the solar photovoltaic power generation system and the grid. The operation of the interconnection relay <NUM> is controlled by the grid interconnection control unit (GIC) <NUM>. In order to make the operation of the grid interconnection device (GI) <NUM> more efficient, the power line communication device (PLC) <NUM> acquires information on the status of the power generation of the solar power generation system and the grid from the monitoring device (MD) <NUM> by the power line communication, and transmits the information to the grid interconnection control unit (GIC) <NUM>.

<FIG> shows a configuration example of a power line communication device (PLC) <NUM> according to first embodiment. The power line communication device (PLC) <NUM> is connected to another power line communication device (PLC) <NUM> via a power line <NUM> or <NUM>. Each power line communication device (PLC) <NUM> includes filter <NUM> and <NUM>, a reception processing unit (RP) <NUM>, an inverter noise detection processing unit (INDP) <NUM>, a synchronization processing unit (SP) <NUM>, a transmission position determination unit (TPD) <NUM>, an output unit (OU) <NUM>, a transmission processing unit (TP) <NUM>, a storage device (SD) <NUM>, and a CPU <NUM>.

The filter <NUM> and <NUM> are circuits for removing excessive wave components from signals inputted from the power line <NUM> or <NUM>. The reception processing unit (RP) <NUM> is a processing circuit for acquiring reception data from a PLC reception signal. The inverter noise detection processing unit (INDP) <NUM> is a circuit for detecting inverter noise from an input signal. The synchronous processing unit (SP) <NUM> is a processing unit for synchronizing the waveforms of the detected inverter noises with the system clocks of the power line communication device (PLC) <NUM>. The transmission position determination unit (TPD) <NUM> is a determination circuit for determining a PLC transmission period. The output unit (OU) <NUM> is a circuit for outputting the PLC transmission signal to the power line <NUM> or <NUM>. The transmission processing unit (TP) <NUM> is a processing unit for generating PLC transmission signals based on transmission data read from the storage device (SD) <NUM>. The storage device (SD) <NUM> is a device for holding transmission/reception data. A CPU (Central Processing Unit) <NUM> is a central processing device for controlling the power line communication device (PLC) <NUM>. The bus <NUM> is an internal bus connecting the storage device (SD) <NUM> and the CPU <NUM>, and the signal line (SL) <NUM> is an internal signal line connecting the CPU <NUM> and the internal circuits.

The filter <NUM> is connected to the power line <NUM> or <NUM> and the reception processing unit (RP) <NUM>. The reception processing unit (RP) <NUM> is connected to a storage device (SD) <NUM>, and the storage device (SD) <NUM> is connected to the CPU32 via a bus <NUM>. Further, the CPU <NUM> is connected to an inner signal line (SL) <NUM>. The filter <NUM> is connected to the power line <NUM> or <NUM> and the inverter noise detection processing unit (INDP) <NUM>. The inverter noise detection processing unit (INDP) <NUM> is connected to the synchronization processing unit (SP) <NUM>, and the synchronization processing unit (SP) <NUM> is connected to the transmission position determination unit (TPD) <NUM>. The transmission position determination unit (TPD) <NUM> is connected to the output unit (OU) <NUM>. Further, the output unit (OU) <NUM> is connected to the power line <NUM> or <NUM> and the transmission processing unit (TP) <NUM>. The transmission processing unit (TP) <NUM> is connected to the storage device (SD) <NUM>.

The operation of transmission device (TD) will be described with reference to <FIG>. By filter <NUM>, in voltage waveforms on the power lines <NUM> or <NUM> , frequency components other than the inverter noise frequency determined by the operating frequency of the DC/AC inverter (DC/AC INV) <NUM> are removed. The inverter noise detection processing unit (INDP) <NUM> determines the presence or absence of inverter noise. For example, the presence or absence of inverter noise corresponding to the operating frequency <NUM> of the DC/AC inverter (DC/AC INV) <NUM> is determined. When it is determined that the inverter noise is present, the synchronization processing unit (SP) <NUM> synchronizes the inverter noise waveforms with the system clock of the power line communication device (PLC) <NUM>. Based on the synchronized inverter noise waveform, the transmission position determination unit (TPD) <NUM> determines that the PLC transmission period is a period in which the transmission signal amplitude of the transmission processing unit (TP) <NUM> exceeds a predetermined value from the inverter noise voltage amplitude. The output unit (OU) <NUM> outputs the PLC transmission signal output from the transmission processing unit (TP) <NUM> to the power line <NUM> or <NUM> only during the PLC transmission period based on the determination result of the transmission position determination unit (TPD) <NUM>. The transmission processing unit (TP) <NUM> generates a PLC transmission signal of the PLC transmission data read from the storage device (SD) <NUM>, and outputs the PLC transmission signal to the output unit (OU) <NUM>.

In the same way, the operation of the reception device (RD) will be described with reference to <FIG>. The reception device (RD) removes frequency components other than the PLC transmission signal in the filter <NUM> from the PLC reception signal inputted from the power line <NUM> or <NUM>. The reception processing unit (RP) <NUM> acquires the PLC reception data from the PLC reception signal, and writes the PLC reception data to the storage device (SD) <NUM>.

<FIG> shows an example of an operation waveform of the power line communication device according to first embodiment. The A of <FIG> shows waveforms of outputs of the DC/AC inverters (DC/AC INV) <NUM>. The B of <FIG> shows an inverter noise waveform superimposed on the waveform of the A of <FIG> by the operation of the DC/AC inverter (DC/AC INV) <NUM>. The C of <FIG> shows a logical output result of the transmission position determination unit (TPD) <NUM>. The D of <FIG> shows the waveforms of the PLC transmitted on power line <NUM> or <NUM> from the transmission device (TD). As shown in the A of <FIG>, the DC/AC inverter (DC/AC INV) <NUM> output AC voltages in rectangular waves by PWM (Pulse Width Modulation). The inverter noise is generated in synchronization with the rectangular wave, and the voltage amplitude of the inverter noise shown in the B of <FIG> is proportional to the magnitude of the temporal change rate of the AC voltage value to be output. Since the temporal change rate becomes maximum when the absolute value of the AC voltage value to be output is smallest, the voltage amplitude of the inverter noise becomes maximum, and conversely, when the absolute value of the AC voltage value is maximum, the voltage amplitude of the inverter noise becomes minimum. As shown in the C of <FIG>, the transmission position determination unit (TPD) <NUM> determines a period in which the amplitude of the PLC transmission signal shown in the D of <FIG> exceeds a predetermined value from the voltage amplitude of the inverter noise shown in the B of <FIG> as a PLC transmission period, and determines other periods as a PLC transmission impossible period. (○ means output enable and × means output disable in the C of <FIG>) As shown in the D of <FIG>, the PLC transmission signal is output from the output unit (OU) <NUM> to the power line <NUM> or <NUM> only during the PLC transmission period.

The amplitude of the PLC transmission signal output to the power line <NUM> or <NUM> during the PLC transmission is always larger than the predetermined amplitude of the inverter noise signal voltage generated in the power line <NUM> or <NUM>. Since the PLC transmission signal is not logically inverted even when the inverter noise is superimposed on the PLC transmission signal, the influence of the inverter noise is reduced and the communication characteristics are improved.

<FIG> shows an exemplary configuration of the power line communication device (PLC) <NUM> according to the modified example of first embodiment. In this modified example, in addition to the configuration of <FIG>, the reception device (RD) further includes an inverter noise detection processing unit (INDP) <NUM>, a synchronization processing unit (SP) <NUM>, a reception position determination unit (RPD) <NUM>, and an input unit (IU) <NUM>.

The inverter noise detection processing unit (INDP) <NUM> is a circuit for detecting inverter noise. The synchronization processing unit (SP) <NUM> is a processing circuit for synchronizing with the waveform of the inverter noise detected by the inverter noise detection processing unit (INDP) <NUM>. The reception position determination unit (RPD) <NUM> is a determination circuit for determining a PLC reception period. The input unit (IU) <NUM> is a circuit for inputting a PLC reception signal from the power line <NUM> or <NUM>. The operation of each circuit will be described later.

The filter <NUM> is connected to an inverter noise detection processing unit (INDP) <NUM> and an input unit (IU) <NUM>. The inverter noise detection processing unit (INDP) <NUM> is connected to the synchronization processing unit (SP) <NUM>. The synchronization processing unit (SP) <NUM> is connected to the reception position determination unit (RPD) <NUM>. The reception position determination unit (RPD) <NUM> is connected to the input unit (IU) <NUM>. The input unit (IU) <NUM> is connected to the reception processing unit (RP) <NUM>.

Since the operation of transmission device (TD) is the same of first embodiment, the explanation is omitted.

The operation of the reception device (RD) will be described with reference to <FIG>. The filter <NUM> removes frequency components other than the inverter noise frequency determined from the operating frequency of the DC/AC inverter (DC/AC INV) <NUM> from the PLC reception signal inputted from the power line <NUM> or <NUM>. The inverter noise detection processing unit (INDP) <NUM> detects the inverter noise in the PLC received signal passing through the filter <NUM>, and determines whether or not the PLC received signal has inverter noise. For example, the presence or absence of inverter noise corresponding to the operating frequency <NUM> of the inverter (DC/AC INV) <NUM> is determined. The synchronization processing unit (SP) <NUM> synchronizes the waveforms of the inverter noise with the system clock of the power line communication device (PLC) <NUM> when it is determined that the inverter noise is present. The reception position determination unit (RPD) <NUM> determines the PLC reception period based on the determination criterion of the transmission position determination unit (TPD) <NUM>. For example, similarly to the transmission position determination unit (TPD) <NUM>, a period in which the reception signal amplitude exceeds a predetermined value from the inverter noise voltage amplitude is determined as the PLC reception period. Based on the result of the reception position determination unit (RPD) <NUM>, the input unit (IU) <NUM> of the transmission position determination unit (TPD) <NUM> inputs the PLC reception signal that has passed through the filter <NUM> to the reception processing unit (RP) <NUM> only during the PLC reception period. The reception processing unit (RP) <NUM> writes the PLC reception data acquired from the PLC reception signals to the storage device (SD) <NUM>.

In the modified example of first embodiment, the PLC reception signal is inputted to the reception processing unit (RP) <NUM> only during the PLC reception period based on the determination result of the reception position determination unit (RPD) <NUM>. Since the PLC reception signal is not input in a period other than the PLC reception period, the reception processing unit (RP) <NUM> can stop the operation. As a result, the power consumption of the reception processing unit (RP) <NUM> can be reduced.

<FIG> shows an exemplary configuration of a power line communication device (PLC) <NUM> according to second embodiment. In the configuration of second embodiment, the transmission position determination unit of the transmission device (TD) is replaced with the transmission position determination unit (TPD) <NUM> as compared with the modified example of first embodiment. The reception device (RD) further includes a half-wavelength shift processing unit (HSP) <NUM> and an addition unit (AU) <NUM>. Since the configurations other than the transmission position determination unit (TPD) <NUM> of the transmission device (TD), the half-wavelength shift processing unit (HSP) <NUM> of the reception device (RD), and the addition unit (AU) <NUM> are substantially the same as those of the modified example of first embodiment, their explanations are omitted.

The transmission position determination unit (TPD) <NUM> is a determination circuit for determining the PLC transmission period, similarly to the transmission position determination unit (TPD) <NUM> of the modified example of embodiment. However, unlike the transmission position determination unit (TPD) <NUM>, the transmission position determination unit (TPD) <NUM> is a circuit that determines a period corresponding to the half-wavelength of the inverter noise as a PLC communication execution period, and determines a period immediately after that corresponding to the half-wavelength of the inverter noise as a PLC communication standby period. The half-wavelength shift processing unit (HSP) <NUM> is a circuit for generating a half-wavelength shift signal in which the phase corresponding to the half-wavelength of the inverter noise is shifted. The addition unit <NUM> adds the half-wavelength shifted signal and the PLC-received signal that has passed through the filter <NUM>.

In the present embodiment, the synchronization processing unit (SP) <NUM> connected to the inverter noise detection processing unit (INDP) <NUM> of the reception device (RD) is connected to the half-wavelength shift processing unit (HSP) <NUM>. The half-wavelength shift processing unit (HSP) <NUM> is further connected to the addition unit (AU) <NUM>. The addition unit (AU) <NUM> is connected to the filter <NUM> and the reception processing unit (RP) <NUM>.

The operation of the transmission device (TD) is explained with reference to <FIG>. By filter <NUM>, voltage waveforms on the power lines <NUM> or <NUM> are removed frequency components other than the inverter noise frequency determined by the operating frequency of the DC/AC inverter (DC/AC INV) <NUM>. The inverter noise detection processing unit (INDP) <NUM> determines the presence or absence of inverter noise. For example, the presence or absence of inverter noise corresponding to the operating frequency <NUM> of the DC/AC inverter (DC/AC INV) <NUM> is determined. When it is determined that the inverter noise is present, the synchronization processing unit (SP) <NUM> synchronizes the inverter noise waveforms with the system clock of the power line communication device (PLC) <NUM>. Based on the synchronized inverter noise waveform, the transmission position determination unit (TPD) <NUM> determines that the period corresponding to the half-wavelength of the inverter noise is the PLC communication execution period, and determines that the period corresponding to the half-wavelength of the inverter noise immediately following the PLC communication execution period is the PLC communication standby period. The output unit (OU) <NUM> outputs the PLC transmission signal output from the transmission processing unit (TP) <NUM> to the power line <NUM> or <NUM> during the PLC communication execution period based on the determination result of the transmission position determination unit (TPD) <NUM>.

Similarly, the operation of the reception device (RD) will be described with reference to <FIG>. When the inverter noise detection processing unit (INDP) <NUM> determines that there is inverter noise in the PLC reception signal, the half-wavelength shift processing unit (HSP) <NUM> generates a half-wavelength shift signal in which the phase corresponding to the half-wavelength of the inverter noise is shifted with respect to the PLC reception signal. The addition unit (AU) <NUM> performs a process of adding the half-wavelength shifted signal and the original PLC-received signal that has passed through the filter <NUM>. In the reception device (RD), the reception processing unit (RP) <NUM> acquires the PLC-received data from the output signal of the addition unit (AU) <NUM>, and writes the PLC-received data to the storage device (SD) <NUM>.

<FIG> shows an example of a waveform of a power line communication operation according to second embodiment. The A of <FIG> shows an output waveform of the DC/AC inverter (DC/AC INV) <NUM>. The B of <FIG> shows an inverter noise waveform generated by the operation of the DC/AC inverter (DC/AC INV) <NUM> in the power line <NUM> or <NUM>. The C of <FIG> shows a logical output result of the transmission position determination unit (TPD) <NUM>. The D of <FIG> shows an output waveform of the transmission processing unit (TP) <NUM>. The E of <FIG> shows the waveforms of the PLC reception signals inputted to the reception device (RD) via power line <NUM> or <NUM>. The F of <FIG> shows an output waveform of the half-wavelength shift processing unit (HSP) <NUM>. The G of <FIG> shows an output waveform of the addition unit (AU) <NUM>. As shown in the C of <FIG>, the transmission position determination unit (TPD) <NUM> sequentially and alternately determines the period corresponding to the half-wavelength of the inverter noise as the PLC communication execution period PLC and communication standby period. As shown in the D of <FIG>, the PLC transmission signal is outputted from the transmission processing unit (TP) <NUM> during the PLC communication execution period. As shown in the E of <FIG>, the PLC reception signal waveform inputted to the reception device (RD) via the power line <NUM> or <NUM> is a waveform in which the inverter noise shown in the B of <FIG> is superimposed on the output waveform of the transmission processing unit (TP) <NUM> shown in the D of <FIG>. As shown in the F of <FIG>, the output waveform of the half-wavelength shift processing unit (HSP) <NUM> is a waveform obtained by shifting the phase of the PLC reception signal waveform shown in the E of <FIG> corresponding to the half-wavelength of the inverter noise. In the output waveform of the addition unit (AU) <NUM>, as shown in the G of <FIG>, the inverter noise waveform shown in the E of <FIG> and the inverter noise waveform shown in the F of <FIG> are cancelled.

The inverter noise component included in the output wavelength of the half-wavelength shift processing unit (HSP) <NUM> of the PLC reception signal is inversely related to the inverted noise component that is superimposed on the original PLC reception signal. Since the inverter noise component is canceled by adding the output waveform of the half-wavelength shift processing unit (HSP) <NUM> and the original PLC reception signal waveform, the influence of the inverter noise can be reduced.

Further, since the cycle of the inverter noise is the same as the cycle of the commercial power supply, it is possible to reduce the influence of periodic noise other than the inverter noise generated in the cycle of the commercial power supply.

<FIG> shows the configuration of the first modified example of second embodiment. Compared to second embodiment, the reception device (RD) has a configuration in which a noise waveform storage device (NWS) <NUM> is added. The transmission device (TD) includes only the transmission processing unit (TP) <NUM>. Since the circuits other than the noise waveform storage device (NWS) <NUM> are the same as those of second embodiment, their explanations are omitted.

The noise waveform storage device (NWS) <NUM> of the reception device (RD) is a device for holding and storing a waveform having only an inverter noise frequency component from which the PLC-signal frequency component is removed, out of the inverter noise detected by the inverter noise detection processing unit (INDP) <NUM>.

The inverter noise detection processing unit (INDP) <NUM> of the reception device (RD) is connected to the synchronization processing unit (SP) <NUM> and the noise waveform storage device (NWS) <NUM>. A noise waveform storage device (NWS) <NUM> is connected to the half-wavelength shift processing unit (HSP) <NUM>. The half-wavelength shift processing unit (HSP) <NUM> is connected to the addition unit (AU) <NUM>.

In the first modified example of second embodiment, the noise waveform storage device (NWS) <NUM> of the reception device (RD) extracts and stores a waveform containing a large amount of inverter noise obtained by removing PLC-signal frequency components from the inverter noise waveform detected by the inverter noise detection processing unit (INDP) <NUM>. Alternatively, the noise waveform storage device (NWS) <NUM> stores a waveform including a large amount of inverter noise of the power line <NUM> or <NUM> acquired when the PLC communication is not performed. The half-wavelength shift processing unit (HSP) <NUM> generates a half-wavelength shift signal having a phase shift corresponding to the half-wavelength of the inverter noise with respect to the waveform including a large amount of inverter noise stored in the noise waveform storage device (NWS) <NUM>. The addition unit (AU) <NUM> adds the half-wavelength shift signal and the original PLC reception signal inputted through the filter <NUM>. Since the output waveform of the half-wavelength shift processing unit (HSP) <NUM> is a waveform including a large amount of inverter noise and does not include any PLC reception data, the addition processing of the addition unit (AU) <NUM> does not interfere with the PLC communication data included in the original PLC transmission signal. The reception processing unit (RP) <NUM> acquires the PLC reception data from the output signal of the addition unit (AU) <NUM> from which the inverter noise has been cancelled, and writes the PLC reception data to the storage device (SD) <NUM>.

In the operation of the transmission device (TD), the transmission processing unit (TP) <NUM> outputs the PLC transmission signal to the power line <NUM> or <NUM> at any time. The first modified example does not require PLC standby periods based on synchronized inverter noise waveforms, as second embodiment. This is because the reception device (RD) of the first modified example can cancel the inverter noise generated in the power line <NUM> or <NUM> over the entire cycle as described above, and can execute the PLC communication operation at any time since the inverter noise does not interfere with the PLC transmit signals.

<FIG> shows an example of a waveform of a power line communication operation according to first modified example of second embodiment. The A of <FIG> shows an output waveform of the DC/AC inverter (DC/AC INV) <NUM>. The B of <FIG> shows an inverter noise waveform generated in the power line <NUM> or <NUM> by the operation of the DC/AC inverter (DC/AC INV) <NUM>. The C of <FIG> shows an output waveform of the transmission processing unit (TP) <NUM>. The D of <FIG> shows the waveforms of the PLC reception signals inputted to the reception device (RD). The E of <FIG> shows an output waveform of the half-wavelength shift processing unit (HSP) <NUM>. The F of <FIG> shows an output waveform of the addition unit (AU) <NUM>. As shown in the C of <FIG>, the PLC transmission signals <NUM> to <NUM> are output from the transmission processing unit (TP) <NUM> at arbitrary times over the entire cycle of the inverter noise. As shown in the D of <FIG>, the PLC reception signal waveform inputted to the reception device (RD) via the power line <NUM> or <NUM> is a waveform in which the inverter noise shown in the B of <FIG> is superimposed on the output waveform of the transmission processing unit (TP) <NUM> shown in the C of <FIG>. As shown in the E of <FIG>, the signal added to the PLC reception signal is a waveform including a large amount of inverter noise. As shown in the F of <FIG>, the output signal of the addition unit (AU) <NUM> has a waveform of only the PLC transmission signals <NUM> to <NUM> in which only the inverter noise is canceled.

The first modified example can eliminate second embodiment PLC communication standby time. This is because the inverter noise generated in the power line <NUM> or <NUM> is canceled over the entire cycle, and further, since the half-wavelength shift signal does not interfere with the PLC transmission signal, the PLC communication operation can be performed at an arbitrary time. As a result, second embodiment PLC communication standby period can be eliminated, and the PLC communication can be performed in both the PLC communication executing time and the PLC communication standby period, so that the communication efficiencies can be doubled. Since the transmission device (TD) does not need to include the filter <NUM>, the inverter noise detection processing unit (INDP) <NUM>, the synchronization processing unit (SP) <NUM>, and the transmission position determination unit (TPD) <NUM> as compared with second embodiment, there are effects of reducing the circuit area and power consumption. Furthermore, since the noise waveform storage device (NWS) <NUM> stores and retains a waveform containing a large amount of inverter noise, the half-wavelength shift processing unit (HSP) <NUM> can read the waveform again after acquiring and storing the waveform by an initialization operation or the like, so that it is unnecessary to acquire a waveform containing a large amount of inverter noise each time, and the operation of the reception device (RD) can be made high-speed and highly efficient.

<FIG> shows a configuration of a power line communication device (PLC) <NUM> according to the second modified example of second embodiment. In the second modified example of second embodiment, the transmission device (TD) includes a transmission processing unit (TP) <NUM> instead of the transmission processing unit (TP) <NUM>, as compared with second embodiment. Since configurations other than the transmission processing unit (TP) <NUM> are the same as those of second embodiment, their explanations are omitted.

The transmission processing unit (TP) <NUM> of the transmission device (TD), like the transmission processing unit (TP) <NUM>, is a processing circuit for generating the PLC transmission signal based on the transmission data, unlike second embodiment, is a processing circuit for outputting the same PLC transmission signal once every two times in a continuous PLC communication implementation period and PLC communication standby period.

The operation of the device is controlled so that, when it is determined that inverter noise is present in the power line <NUM> or <NUM>, the transmission processing unit (TP) <NUM> outputs the same PLC transmission signal from the output unit (OU) <NUM> one by one in the consecutive PLC communication executing period and PLC communication standby period based on the determination result obtained in the transmission position determination unit (TPD) <NUM>.

<FIG> shows exemplary waveforms of the power line communication operation according to the second modified example of second embodiment. The A of <FIG> shows an output waveform of the DC/AC inverter (DC/AC INV) <NUM>, the B of <FIG> shows an inverter noise waveform generated in the power line <NUM> or <NUM> by the operation of the DC/AC inverter (DC/AC INV) <NUM>, the C of <FIG> shows an output waveform of the transmission processing unit (TP) <NUM>, the D of <FIG> shows a PLC reception signal waveform inputted to the reception device (RD), the E of <FIG> shows an output waveform of the half-wavelength shifting processing unit (HSP) <NUM>, and the F of <FIG> shows an output waveform of the addition unit (AU) <NUM>.

In addition to the effects of second embodiment, the PLC communication implementation period and PLC communication standby period, which are consecutive in sync with the cycle of inverters noise, produce the same PLC signal wave. As a result, the PLC reception signal, which is added to the same PLC reception signal at the PLC reception device (RD), is approximately double the magnitude of the amplitude because the PLC reception signal, which is output from the addition (AU) <NUM>, is stronger. Therefore, compared with second embodiment, the effect of inverter noise can be further reduced.

As an effect of improving the noise tolerance, in addition to the effect of canceling the periodic noise including the inverter noise by the DC/AC inverter (DC/AC INV) <NUM> in second embodiment, the PLC communication signal is emphasized by the function of outputting the same PLC transmission signal as the PLC communication period also in the PLC communication standby period of the transmission processing unit (TP) <NUM>, and therefore, there is a further effect of improving the communication quality.

<FIG> shows the configuration of the third modified example of second embodiment. The reception device (RD) according to the third modified example further includes a reception position determination unit (RPD) <NUM> and an input unit (IU) <NUM> in addition to the second modified example of second embodiment. Since configurations other than the reception position determination unit (RPD) <NUM> and the input unit (IU) <NUM> are the same as those of the second modified example of second embodiment, their explanations are omitted.

The reception position determination unit (RPD) <NUM> is a determination circuit for determining a PLC reception period, similarly to the reception position determination unit (RPD) <NUM>, and is a circuit for determining a PLC communication standby period as a PLC reception period out of consecutive PLC communication executing periods and PLC communication standby periods, unlike the modified example of first embodiment. The input unit (IU) <NUM> is a circuit for inputting the output signal of the addition unit (AU) <NUM> to the reception processing unit (RP) <NUM> during the PLC reception period.

Reception position determination unit (RPD) <NUM>, based on the result of the sync processing unit (SP) <NUM>, determines the PLC receiving period to operate the receipt processing unit (RP) <NUM>. The input unit (IU) <NUM> controls whether or not to input the PLC reception signal that has passed through the filter <NUM> and the addition unit (AU) <NUM> based on the result of the reception position determination unit (RPD) <NUM>, and the reception processing unit (RP) <NUM> operates only during the PLC reception period during which the PLC reception signal that has been intensified is input, and the reception processing unit (RP) <NUM> writes the acquired PLC reception data to the storage device (SD) <NUM>.

In the reception device (RD) of the third modified example, the receiving position determination unit (RPD) <NUM> determines the period in which the receiving processing unit (RP) <NUM> operates, the input unit (IU) <NUM>, the receiving processing unit (RP) <NUM> operates only for the PLC receiving period in which the strengthened PLC reception signal is input, and other periods can stop operation, so power consumption can be reduced.

<FIG> shows an exemplary configuration of a power line communication device (PLC) <NUM> according to third embodiment. Since the reception device (RD) according to third embodiment includes only the filter <NUM> and the reception processing unit (RP) <NUM>, and is the same as first embodiment, their explanation is omitted. Compared to second embodiment, the transmission device (TD) according to present embodiment further comprises a half-wavelength shifting unit (HSP) <NUM> and an addition unit (AU) <NUM>. Since the configuration of the transmission device (TD) except for the half-wavelength shifting unit (HSP) <NUM> and the adding unit (AU) <NUM> is the same as that of second embodiment, their explanations are omitted.

Similar to the half-wavelength shift processing unit (HSP) <NUM> of the reception device (RD), the half-wavelength shift processing unit (HSP) <NUM> is a circuit for generating a half-wavelength shift signal in which the phase corresponding to the half-wavelength of the inverter noise is shifted, and the addition unit (AU) <NUM> is a circuit for adding the half-wavelength shift signal and the PLC transmission signal that has passed through the output unit (OU) <NUM>, similarly to the addition unit (AU) <NUM> of the reception device (RD).

The operation of the transmission device (TD) of the configuration of <FIG>, in the same way as second embodiment, when the transmission position determination unit (TPD) <NUM> determines the period corresponding to the half-wavelength of the inverse noise as the PLC communication execution period, and determines the period corresponding to the half-wavelength of the inverter noise immediately following the period as the PLC communication standby period, when it is determined that the inverse noise exists in the power line <NUM> or <NUM> by the filter <NUM>, the inverted noise detecting processing unit (INDP) <NUM>, and the synchronization processing unit (SP) <NUM>. The output unit (OU) <NUM> outputs the PLC transmission signal from the output unit (OU) <NUM> to the addition unit (AU) <NUM> during the PLC communication execution period based on the determination result of the transmission position determination unit (TPD) <NUM>.

The half-wavelength shift processing unit (HSP) <NUM> generates a half-wavelength shift signal in which the phase corresponding to the half-wavelength of the inverter noise is shifted with respect to the inverter noise detected by the inverter noise detection processing unit (INDP) <NUM>. The addition unit (AU) <NUM> generates an addition signal of the half-wavelength shift signal and the PLC transmission signal output from the output unit (OU) <NUM>. The added signal is transmitted to the power line <NUM> or <NUM>.

<FIG> shows an example of a waveform of a power line communication operation according to third embodiment. The A of <FIG> shows an output waveform of the DC/AC inverter (DC/AC INV) <NUM>, the B of <FIG> shows an inverter noise waveform generated in the power line <NUM> or <NUM> by the operation of the DC/AC inverter (DC/AC INV) <NUM>, the C of <FIG> shows an output waveform of the transmission processing unit (TP) <NUM> (output unit (OU) <NUM>), the D of <FIG> shows an output waveform of the half-wavelength shift processing unit (HSP) <NUM>, the E of <FIG> shows an output waveform of the addition unit (AU) <NUM>, and the F of <FIG> shows a reception signal waveform in the PLC reception device (RD).

As a result of offsetting the noise components of the inverters that have been overlapped prior to the signals sent from the addition unit (AU) <NUM> of the transmission device (TD) and the noise of the inverters that occur on the power line <NUM> or <NUM>, the effects of the noise of the inverters that occur on the power line <NUM> or <NUM> can be minimized, as shown in the F of <FIG>. In addition, since the cycle of the inverter noise is the same as the cycle of the commercial power supply, it is possible to improve the noise tolerance against the periodic noise generated in the cycle of the commercial power supply.

Further, as compared with second embodiment, since the reception device (RD) does not need to include the inverter noise detection processing unit (INDP) <NUM> and the synchronization processing unit (SP) <NUM>, there are effects of reducing the circuit area and power consumption.

<FIG> shows the configuration of the first modified example of third embodiment. In first modified example of third embodiment, the transmission device (TD) does not include the transmission position determination unit (TPD) <NUM> and the output unit (OU) <NUM> in third embodiment, and a noise waveform storage device (NWS) <NUM> is added. Since configurations other than the noise waveform storage device (NWS) <NUM> are the same as those of third embodiment, their explanations are omitted.

Similar to the noise waveform storage device (NWS) <NUM> in the first modified example of second embodiment, the noise waveform storage device (NWS) <NUM> of the transmission device (TD) is a device for holding and storing a waveform having only the inverter noise frequency component from which the PLC signal frequency component is removed from the inverter noise detected by the inverter noise detection processing unit (INDP) <NUM>.

In the configuration of <FIG>, the noise waveform storage device (NWS) <NUM> of the transmission device (TD) holds and stores a waveform including a lot of inverted noise in which the PLC communication signal is eliminated from the inverted noise waveform detected in the inverter noise detection processing unit (INDP) <NUM>, or a lot of waveforms including the inverter noise of the power line <NUM> or <NUM> acquired when the PLC communication is not performed. The half-wavelength shift processing unit (HSP) <NUM> generates a half-wavelength shift signal in which the phase corresponding to the half-wavelength of the inverter noise is shifted, and the adding unit (AU) <NUM> adds the half-wavelength shift signal and the PLC transmission signal output from the transmission processing unit (TP) <NUM>, and then transmits the resultant signal to the power line <NUM> or <NUM>.

<FIG> shows an example of a waveform of a power line communication operation according to first modified example of third embodiment. The A in <FIG> shows an output waveform of the DC/AC inverter (DC/AC INV) <NUM>, the B in <FIG> shows an inverter noise waveform generated in the power line <NUM> or <NUM> by the operation of the DC/AC inverter (DC/AC INV) <NUM>, the C in <FIG> shows an output waveform of the transmission processing unit (TP) <NUM>, the D in <FIG> shows an output waveform of the half-wavelength shift processing unit (HSP) <NUM>, the E in <FIG> shows an output waveform of the addition unit (AU) <NUM>, and the F in <FIG> shows a PLC reception signal waveform in the reception device (RD).

In the first modified example of third embodiment, as shown in the D in <FIG>, since the output waveform of the half-wavelength shift processing unit (HSP) <NUM> includes a large amount of inverter noise, the addition processing of the addition unit (AU) <NUM> does not interfere with the PLC communication data included in the original PLC transmission signal. As a result, as shown in the F of <FIG>, the inverter noise waveform components superimposed on the power line <NUM> or <NUM> in the PLC reception signal inputted to the reception device (RD) are cancelled. Further, the power line communication device can execute the PLC communication operation in the entire period without providing a PLC communication standby period or the like.

In the first modified example of third embodiment, since the PLC communication standby period by third embodiment transmission position determination unit (TPD) <NUM> can be eliminated, the communication efficiency can be doubled as compared with the PLC communication standby period third embodiment. Since the transmission device (TD) does not need to include the transmission position determination unit (TPD) <NUM> and the output unit (OU) <NUM> as compared with third embodiment, there are effects of reducing the circuit area and the power consumption. Further, since the noise waveform storage device (NWS) <NUM> stores and holds a waveform containing a large amount of inverter noise, the waveform is acquired by an initialization operation or the like, and after the storage, the half-wavelength shift processing unit (HSP) <NUM> can read the waveform again, so that it is unnecessary to acquire a waveform containing a large amount of inverter noise each time, and the operation of the transmission device (TD) can be performed at high speed and efficiently.

<FIG> shows the configuration of second modified example of third embodiment. In second modified example of third embodiment, in addition to third embodiment configuration, the reception device (RD) further includes an inverter noise detection processing unit (INDP) <NUM>, a synchronization processing unit (SP) <NUM>, a reception position determination unit (RPD) <NUM>, and an input unit (IU) <NUM>. Since the configuration of the transmission device (TD) is the same as that of third embodiment, their explanations are omitted.

In the inverter noise detection processing unit (INDP) <NUM> of the reception device (RD), the synchronization processing unit (SP) <NUM>, the reception position determination unit (RPD) <NUM>, and the input unit (IU) <NUM> are the same as the modified example of first embodiment.

(Operations of second modified example of third embodiment) The operation of the reception device (RD) in the configuration of <FIG>, the inverter noise detection processing unit (INDP) <NUM> performs the inspection of the inverter noise from the PLC reception signal passed through filter <NUM>, to determine whether there is any inverted noise. When the inverter noise detection processing unit (INDP) <NUM> determines that there is inverter noise, the synchronization processing unit (SP) <NUM> synchronizes with the waveform of the inverter noise. The reception position determination unit (RPD) <NUM> determines the PLC reception period based on the result of the synchronization processing unit (SP) <NUM>, and the reception processing unit (RP) <NUM> operates during the PLC reception period.

In the second modified example of third embodiment, as shown in the F of <FIG>, since the same signal outputted from the transmission processing unit (TP) <NUM> is received twice in the period in which the period corresponding to the half cycle of the inverter noise is two consecutive times, the input unit (IU) <NUM> can operate only in the period corresponding to the half cycle of the second inverter noise, for example.

In the reception device (RD) of the second modified example of third embodiment, the reception position determination unit (RPD) <NUM> determines the PLC reception period, the input unit (IU) <NUM> operates only in a period corresponding to a half cycle of the inverter noise, and the reception processing unit (RP) <NUM> stops the operation in another period, therefore the power consumption can be reduced.

Any of the configurations of the present system can be implemented in either hardware or software. In addition, even when a specific numerical value example is described, it may be a numerical value exceeding the specific numerical value, or may be a numerical value less than the specific numerical value, except when it is theoretically obviously limited to the numerical value.

Although the embodiment has been described above, the power line communication device described above can be described as follows.

Claim 1:
A power line communication device comprising:
a transmission processing unit (<NUM>) for generating a transmission signal from transmission data to be output to a power line;
an inverter noise detection processing unit (<NUM>) for detecting inverter noise by a DC/AC inverter (<NUM>) of the power line,
a transmission position determination unit (<NUM>) for determining a transmission period of the transmission signal; and
an output unit (<NUM>) for outputting the transmission signal in the transmission period,
wherein the transmission position determination unit (<NUM>) is configured to determine the transmission period based on an amplitude of the transmission signal and a noise voltage amplitude of the power line, the noise voltage amplitude being a voltage amplitude of the inverter noise.