DC power distribution system, controller, operation state determination method, and program

Abstract

To quickly and accurately detect an incident generated in a DC power distribution system.SOLUTION: A DC power distribution system for distributing power from a power supply device to a load device via a power distribution network comprises: a measuring instrument provided in the power distribution network, the measuring instrument comprising a nano optical modulator for converting a measured value of an electric signal to an optical signal for transmission using an optical fiber; and a controller comprising a determination unit that acquires a voltage value and current value measured by the measuring instrument using a nano optical receiver for converting the optical signal to an electric signal through the optical and determines an operation state of the DC power distribution system on the basis of predetermined information on the voltage value and the current value. The determination unit determines that any of states of inrush current, load connection, load ON / load OFF, and load fluctuation has occurred as the operation state.SELECTED DRAWING: Figure 1

Description

Technical Field

[0001] The present invention relates to a technique for detecting accidents such as ground faults and short circuits occurring in a power distribution system.

Background Art

[0002] In a power distribution system, when an accident such as a ground fault or a short circuit is detected, it is necessary to take measures such as stopping the power distribution from the power supply device.

[0003] As an example of a device for detecting accidents such as ground faults and short circuits, a distance relay (e.g., the Mori relay described in Non-Patent Document 1) is used at the power transmission end of an AC substation or the like. The distance relay uses voltage and current as input quantities and operates when a function of the ratio of voltage to current becomes equal to or less than a predetermined value. This ratio is called the impedance seen by the relay.

[0004] By the way, in communication buildings, data centers, etc., a high-voltage DC power distribution system has been introduced in order to reduce the power loss of the entire system and achieve energy savings. In the high-voltage DC power distribution system, power distribution is performed at a high voltage such as 380V.

Prior Art Documents

Non-Patent Documents

[0005]

Non-Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0006] In a high-voltage DC power distribution system, since there is no reactance component in the DC power, distance relays such as the Morley relay described in Non-Patent Document 1 cannot be used. Also, distance relays for high-voltage DC power distribution such as 380 V do not exist on the market.

[0007] There are existing prior arts for detecting accidents such as ground faults and short circuits that occur in a DC power distribution system, but the detection accuracy is not sufficient, for example, misdetection may occur where an event that is not an accident is detected as an accident.

[0008] Also, in the prior art, metal wires are used for signal transmission, and there is a possibility of misdetection due to the influence of noise. Further, in the prior art, the delay time in the monitoring and control of devices using metal wires, optical couplers, etc. is large. Therefore, for example, it has been difficult to apply an accident detection system between bases several kilometers apart.

[0009] An object of the present invention is to provide a technology that enables quick and accurate detection of accidents that occur in a DC power distribution system.

Means for Solving the Problems

[0010] According to the disclosed technology, there is provided a DC power distribution system for distributing power from a power supply device to a load device via a power distribution network, a measuring instrument provided in the power distribution network, the measuring instrument including a nanophotonic modulator that converts a measured value of an electrical signal into an optical signal for transmission via an optical fiber; a control device that acquires voltage values and current values measured by the measuring instrument via the optical fiber using a nanophotodetector that converts an optical signal into an electrical signal, and determines an operating state in the DC power distribution system based on predetermined information regarding the voltage values and current values; The determination unit determines that any one of inrush current, load connection, load ON·load OFF, and load fluctuation has occurred as the operating state A DC power distribution system is provided.

Advantages of the Invention

[0011] According to the disclosed technology, it becomes possible to quickly and accurately detect an accident occurring in a DC power distribution system.

Brief Description of the Drawings

[0012]

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Embodiments for Carrying Out the Invention

[0013] Hereinafter, embodiments of the present invention (these embodiments) will be described with reference to the drawings. The embodiments described below are merely examples, and the embodiments to which the present invention is applied are not limited to the following embodiments.

[0014] The DC power distribution system in this embodiment is assumed to be a high-voltage DC power distribution system that distributes power in DC at 380V (hereinafter referred to as the DC power distribution system). However, "380V" is an example. In addition, the present invention is applicable not only to high-voltage DC power distribution systems but also to DC power distribution systems in general.

[0015] (System Configuration Example 1) Fig. 1 shows Configuration Example 1 of the DC power distribution system in this embodiment. Configuration Example 1 is a system that distributes electric power in DC from Site A to Site B. In addition, power distribution from Site B to Site A is also possible. That is, bidirectional power distribution is possible. Sites A and B are buildings such as communication buildings, for example, but are not limited to buildings. There is no particular limitation on the distance between Site A and Site B, but in this embodiment, they may be several kilometers apart.

[0016] In Configuration Example 1, Converter A20 is provided at Site A, and Converter B30 is provided at Site B. Each converter is a DC / DC converter, which is a device that converts the magnitude of DC voltage. Converter A20 may be an AC / DC converter. As shown in the figure, each converter has a voltage conversion unit, as well as an insulation function and a gate block function.

[0017] Between Converter A20 at Site A and Converter B30 at Site B, there is a power distribution network (positive-side power distribution line and negative-side power distribution line), and a 380V DC current is distributed from Converter A20 at Site A to Converter B30 at Site B. Note that Converter B30 is an example of a load device that receives the distributed power. Also, at Site B, one or more load devices (such as servers) are connected under Converter B30. "Load device" includes devices such as Converter B30 and servers powered by Converter B30. In addition, the "DC power distribution system" includes Converter A20, the power distribution network, and the load device.

[0018] Also, in the example shown in FIG. 1, a semiconductor circuit breaker 90 is provided outdoors at base A, and when an accident is detected, the semiconductor circuit breaker 90 can cut off the circuit between base A and base B. Communication is performed between the semiconductor circuit breaker 90 and the control device 100A via an optical fiber.

[0019] Converter A20 is an example of a power supply device that can supply sufficient current to the accident point when an accident (e.g., ground fault, short circuit, partial short circuit, etc.) occurs in the power distribution network (including the power network in the load device receiving power supply).

[0020] In addition, a control device 100A is provided at base A, and a control device 100B is provided at base B. The control device 100A and the control device 100B are connected by an optical network (optical fiber). The optical network used for connection between devices in this embodiment is not limited to a specific optical network, but is, for example, a power-saving, low-latency, high-speed optical network such as the photonic network of IOWN.

[0021] The control device 100A may be a device inside the converter A20 or a device outside the converter A20. Also, the control device 100A may be provided outside base A. The control device 100B may be a device inside the converter B30 or a device outside the converter B30. Also, the control device 100B may be provided outside base B. Also, instead of providing a control device for each base, it is also possible to provide one control device for multiple bases.

[0022] As shown in FIG. 1, a learning device 200 is provided. The learning device 200 can be installed anywhere. For example, a virtual machine on the cloud may be used as the learning device 200. The learning device 200 is connected to the control device 100A and the control device 100B via an optical network (optical fiber). Note that the control device 100A or the control device 100B may function as the learning device 200.

[0023] In the DC power distribution system according to this embodiment, at Site A, a neutral point grounding configuration using a high resistance is employed. Specifically, as shown in FIG. 1, between the output portion of Converter A20 and the power distribution terminal (the boundary portion between the inside and outside of Site A), Resistor 1 and Resistor 2 are provided between the positive-side power distribution line and the negative-side power distribution line, and the neutral point therebetween is grounded to the earth. Both Resistor 1 and Resistor 2 are high resistances of, for example, about several MΩ. Note that the neutral point grounding configuration using a high resistance may be provided inside Converter A20.

[0024] As shown in FIG. 1, at Site A, a voltmeter 3 is provided between the positive-side power distribution line (+) and the neutral point, a voltmeter 4 is provided between the negative-side power distribution line (-) and the neutral point, and an ammeter 5 is provided between the neutral point and the grounding point.

[0025] In addition, ammeters 6 and 7 are provided for the negative-side power distribution line and the positive-side power distribution line. Also, a zero-phase current transformer 8 (ZCT) is provided. When an imbalance occurs in the reciprocating current in the positive-side power distribution line and the negative-side power distribution line, the zero-phase current transformer 8 measures and outputs the current value generated due to the imbalance.

[0026] Also, at Site B, a voltmeter 9 is provided between the positive-side power distribution line and the negative-side power distribution line between the power receiving terminal (the boundary portion between the outside and inside of Site B) and Converter B30, and an ammeter 10 is provided for the positive-side power distribution line.

[0027] The deployment method of measuring instruments such as the ammeters and voltmeters shown in FIG. 1 is an example. More measuring instruments may be deployed than the deployment method shown in FIG. 1, or fewer measuring instruments may be deployed. For example, no measuring instruments may be deployed on the Site B side.

[0028] (Regarding the connection configuration using an optical fiber) At base A shown in FIG. 1, between the control device 100A and the voltage conversion unit 20, between the control device 100A and each voltmeter, between the control device 100A and each ammeter, and between the control device 100A and the semiconductor circuit breaker 90 are all connected by optical fibers. The same applies to other bases.

[0029] Also, in information transmission using an optical fiber, by assigning different wavelengths (frequencies) for each type of information to be transmitted, it is possible to instantaneously transmit and receive various information even with a single optical fiber. For example, it is possible to assign different frequencies for voltage and current, or different frequencies for each characteristic waveform. Based on the result determined from the information acquired via the optical fiber, the control device 100A can quickly control the gate block and the semiconductor circuit breaker 90 via the optical fiber, thereby preventing the spread of an accident.

[0030] FIG. 2 shows a more specific connection configuration example. Note that in FIG. 2, as an example of the functional units in the control device 100 described in FIG. 5 to be described later, the control unit 140 and the monitoring unit 110 are shown. FIG. 2 is an example, and for example, the monitoring unit in FIG. 2 may be replaced with a determination unit, or the control unit may be replaced with a determination unit.

[0031] FIG. 2(a) shows a configuration in which the voltage conversion unit 20 (including an insulation function, a gate block function, etc.) and the control unit 140 are connected by an optical fiber. Regarding the communication of the optical signal on the optical fiber, for example, different frequencies are assigned for the frequency for state monitoring and the frequency for the control signal.

[0032] FIG. 2(b) shows a configuration in which the voltmeter and the monitoring unit 110 are connected by an optical fiber. The monitoring unit 110 monitors the voltage obtained by the voltmeter. For this communication, the frequency for voltage is used.

[0033] In addition, the voltmeter is equipped with a nano optical modulator for E-O conversion, and the monitoring unit 110 side is equipped with a nano photoreceiver for O-E conversion. The measurement signal (electrical signal) of the voltage probe in the voltmeter is directly or indirectly converted into an optical signal by the nano optical modulator and transmitted to the monitoring unit 110. Note that the nano optical modulator may be used without passing through the voltage probe.

[0034] Both the nano optical modulator and the nano photoreceiver operate at high speed and high efficiency, realizing energy-saving and high-speed operation. Therefore, even if the voltmeter and the monitoring unit 110 are remote from each other, low-latency and rapid monitoring control can be realized.

[0035] Figure 2(c) shows a configuration in which the ammeter and the monitoring unit 110 are connected by an optical fiber. The monitoring unit 110 monitors the current obtained by the ammeter. A frequency for current is used for this communication.

[0036] In addition, the ammeter is equipped with a nano optical modulator for E-O conversion, and the monitoring unit 110 side is equipped with a nano photoreceiver for O-E conversion. The measurement signal (electrical signal) of the current probe in the ammeter is directly or indirectly converted into an optical signal by the nano optical modulator and transmitted to the monitoring unit 110. Note that the nano optical modulator may be used without passing through the current probe. Both the nano optical modulator and the nano photoreceiver operate at high speed and high efficiency, realizing energy-saving and high-speed operation. Therefore, even if the ammeter and the monitoring unit 110 are remote from each other, low-latency and rapid monitoring control can be realized.

[0037] Note that by multiplexing the optical signal from the voltmeter and the optical signal from the ammeter, the voltage value (using the frequency for voltage) and the current value (using the frequency for current) may be transmitted to the monitoring unit through a single optical fiber.

[0038] Also, as described above, the control device 100 and the learning device 200 are also connected by an optical fiber. For example, in information communication via an optical fiber from the control device 100 to the learning device 200, by using different frequencies for the information on state monitoring, control signal information, voltage information, and current information respectively, efficient information transmission can be realized with a single optical fiber.

[0039] (Operation Overview) Next, the overall operation overview of the DC power distribution system shown in FIG. 1 will be described. At site A, each measuring instrument performs measurements at short time intervals (for example, in units of several microseconds to several milliseconds), and the control device 100A acquires the measurement results obtained by each measuring instrument. Similarly, at site B, each measuring instrument performs measurements at short time intervals (for example, measurements in units of several microseconds to several milliseconds), and the control device 100B acquires the measurement results obtained by each measuring instrument.

[0040] Both the control device 100A and the control device 100B are capable of determining the operating state (accidents and events other than accidents such as load fluctuations) in the DC power distribution system. However, in this embodiment, it is assumed that the control device 100A performs the determination.

[0041] When the control device 100A determines the operating state, the control device 100B transmits the measurement results obtained by each measuring instrument at site B to the control device 100A via an optical network (optical fiber). Also, the control device 100B monitors the state of the load device at short time intervals (for example, measurements in units of several microseconds to several milliseconds), and transmits the information on the state of the load device (equipment information) obtained by the monitoring to the control device 100A via an optical network (optical fiber). By using an optical network, low-latency and highly reliable transmission becomes possible, and even if the distance between sites is large (for example, several kilometers), the processing such as accident detection and interruption of this system can be performed at high speed.

[0042] Based on each measurement result and device information obtained at base point A and base point B, the control device 100A determines the operating states such as ground fault (+ side), ground fault (- side), short circuit, partial short circuit, inrush current, load connection, load ON·load OFF, load fluctuation, etc. from any one, or any plurality (including all) of the voltage value, current value, waveform indicating the change in voltage value, waveform indicating the change in current value, and device information.

[0043] Note that a short circuit means that the positive-side distribution line and the negative-side distribution line are connected with a small resistance, and a partial short circuit means that the positive-side distribution line and the negative-side distribution line are connected with a large resistance.

[0044] The control device 100A displays the determination result. By the control device 100A sending the determination result to the control device 100B, the control device B can also display the determination result.

[0045] In addition, when the control device 100A detects an accident such as a ground fault or a short circuit, it can send an abnormal signal to the converter A20 via an optical fiber, operate the gate block in the converter A20, and stop the power distribution. Also, the control device 100A can cut off the circuit between base point A and base point B by sending an abnormal signal to the semiconductor circuit breaker 90 connected by an optical fiber. Further, when the control device 100A detects an accident such as a ground fault or a short circuit, by sending the determination result or an abnormal signal to the control device 100B, the control signal 100B can operate the gate block etc. at base point B.

[0046] In addition, since the control device 100A can distinguish events such as inrush current and load connection that are not accidents from the waveform indicating the change in current value or voltage value, it can prevent malfunction such as erroneously stopping the power distribution.

[0047] Also, in this embodiment, since various signals are transmitted and received via an optical network (optical fiber), false detection can be reduced without being affected by the noise generated in metal wires.

[0048] <Example of determination result> Fig. 3 shows an example of the detected values by the measuring instruments and the determination results. In Fig. 3, V1 represents the detected value of the voltmeter 3 between the neutral point and the positive side distribution line, and V2 represents the detected value of the voltmeter 4 between the neutral point and the negative side distribution line. A is, for example, the detected value (current value) of the ammeter 7 or the ammeter 6. "peak" means the maximum value (the maximum value among the values that vary in a short time).

[0049] dV1 / dt is the derivative of V1 with respect to time t and represents the change of V1 over time. The same applies to dV2 / dt and dA / dt. ∫(dA / dt)dt represents the integral of the change amount of A.

[0050] (V1 + V2) / I, where I is, for example, the detected value (current value) of the ammeter 7 or the ammeter 6. By (V1 + V2) / I, the impedance Z (when only considering direct current, it may also be referred to as "resistance") can be obtained.

[0051] For example, when an accident such as a short circuit occurs in the power distribution network between base point A and base point B, the control device 100A can calculate the impedance of the power distribution line between base point A (specifically, the measuring instrument) and the accident point by (V1 + V2) / I, and calculate the distance between base point A and the accident point. That is, the distance can be calculated by dividing the impedance obtained by (V1 + V2) / I by the impedance per unit length of the power distribution line between base point A and the accident point.

[0052] Note that the impedance per unit length of the power distribution line is determined by the thickness (cross-sectional area) of the power distribution line. Also, generally, the thickness of the power distribution line (that is, the impedance per unit length of the power distribution line) is determined by the scale of the power distribution network (inter-base distribution, in-base distribution, etc.). Therefore, the control device 100A stores in advance the impedance per unit length of the power distribution line for each scale of the power distribution network in the storage unit, and calculates the distance using the impedance per unit length that conforms to the scale of the power distribution network to be controlled. Also, when the control device 100A captures a transient phenomenon of current or voltage, it may perform impedance derivation including the component of jX (reactance).

[0053] In FIG. 3, for example, it is shown that when measurement results corresponding to a voltage waveform in which V1 suddenly becomes 0 and V2 suddenly becomes 380V are obtained, it can be determined that a ground fault has occurred in the positive-side distribution line. The same applies to other events as shown in FIG. 3. More specific determination logic (flow) will be described later.

[0054] The control device 100A and the control device 100B each transmit the acquired measurement results and the like to the learning device 200, and the learning device 200 may learn the relationship between the waveform and the event from either or both of the voltage value waveform and the current value waveform.

[0055] The learning method is not limited to a specific method. For example, a neural network model may be used. As an example, an example of learning about inrush current will be described. First, a large number of waveforms obtained from the measurement results of an ammeter when inrush current occurs in the power distribution network are acquired as learning data.

[0056] The learning device 200 inputs the waveform of the learning data into the model and learns the parameters of the model so that the classification of the waveform becomes "inrush current". Then, the learned model is stored in the control device 100A. The control device 100A can determine whether the waveform of the measurement result corresponds to inrush current by using the model.

[0057] Similarly, each of the events such as ground fault (+ side), ground fault (- side), short circuit, partial short circuit, load connection, load ON (load connection) · load OFF, load fluctuation, etc. can be discriminated using the model.

[0058] Performing discrimination of an event (operating state) using a neural network model as described above is an example.

[0059] For example, for each event, a representative waveform observed when the event occurs is prepared as a representative waveform and stored in the storage unit of the control device 100A. The control device 100A can compare the detected waveform with the representative waveforms of each event and determine that an event with a representative waveform close to the detected waveform has occurred. In the comparison between the detected waveform and the representative waveforms of each event, for example, any one or a plurality (including all) of a plurality of feature amounts (e.g., slope, time length from the start of change to the end of change, magnitude of change (difference between the value before change and the value after change)) are compared between the observed waveform and the representative waveform, and it may be determined whether the detected waveform and the representative waveform are close based on whether the difference in each feature amount is smaller than a threshold value.

[0060] (System configuration example 2) FIG. 4 shows a configuration example 2 of the DC power distribution system in the present embodiment. Configuration example 2 is a system that distributes (feeds) power from a power supply device such as a rectifier device 60 to a load device 80 inside the base C. The base C is, for example, a building such as a communication building, but is not limited to a building.

[0061] Configuration example 2 only differs in scale from configuration example 1, and the basic configuration is the same between configuration example 1 and configuration example 2. Also, in configuration example 2 as well as in configuration example 1, the control devices, between the control device and the learning device, and between the control device and the ammeter / voltmeter are connected by optical fibers. Also, a nano optical modulator is used for the ammeter / voltmeter, and a nano photoreceiver is used on the monitoring unit side that monitors the signal of the ammeter / voltmeter.

[0062] The rectifier device 60 converts alternating current from a commercial power supply into direct current and outputs direct current power. Similar to the converter A20 in configuration example 1, the rectifier device 60 has a voltage conversion unit and also has an insulation function and a gate block function. The load device 80 is, for example, a device such as a server, and the converter 70 exists inside the load device. The converter 70 has a voltage conversion unit and also has an insulation function and a gate block function. Also, in the rectifier device 60, similar to configuration example 1, it has a high-resistance neutral point grounding configuration and is equipped with measuring instruments such as a voltmeter, an ammeter, and a zero-phase current transformer.

[0063] In addition, similar to the control devices 100A, 100B, and the learning device 200 in Configuration Example 1, control devices 100C-1, 100C-2, and the learning device 200 are provided. Here, the control device 100C-2 is a functional unit inside the load device 80. The operation in Configuration Example 2 is the same as the operation in Configuration Example 1.

[0064] (Configuration Example of Control Device 100) As an example, a configuration example of the control devices 100A and 100B in the DC power distribution system shown in FIG. 1 will be described. Here, as an example, it is assumed that the control device 100A performs the determination process and the control device 100B does not perform the determination process.

[0065] FIG. 5 shows a configuration example of the control device 100A. As shown in FIG. 5, the control device 100A includes a monitoring unit 110, a determination unit 120, a communication unit 130, a control unit 140, a storage unit 150, and a display unit 160. Each unit is connected as shown in the figure. The connection lines are, for example, optical fibers.

[0066] The monitoring unit 110 acquires the measurement results obtained by the measuring instruments (voltmeter, ammeter, etc.) within Site A via an optical fiber and inputs the acquired measurement results to the determination unit 120. Note that the determination unit 120 may also acquire the measurement results obtained by the measuring instruments (voltmeter, ammeter, etc.) within Site A via an optical fiber. In addition, the monitoring unit 110 can also acquire the device information (e.g., information of Converter A20) within Site A via an optical fiber.

[0067] The communication unit 130 communicates with other control devices 100 and the learning device 200 via an optical fiber. More specifically, the communication unit 130 receives the measurement results and device information from the control device 100B at Site B and inputs them to the determination unit 120.

[0068] Based on the measurement results input from the monitoring unit 110 and the information input from the communication unit 130, the determination unit 120 determines the operating states such as ground fault (+ side), ground fault (- side), short circuit, partial short circuit, inrush current, load connection, load ON·load OFF, and load fluctuation.

[0069] In the storage unit 150, for example, thresholds necessary for determination are stored. Also, when determination is performed using the above-described model, the storage unit 150 stores the model (specifically, learned parameters), and the determination unit 120 reads the model from the storage unit 150 and uses it for determination.

[0070] Further, the determination unit 120 may store in the storage unit 150 the determination results of the operating states such as ground fault (+ side), ground fault (- side), short circuit, partial short circuit, inrush current, load connection, load ON·load OFF, and load fluctuation, and the waveforms of the voltage values, the waveforms of the current values, or both the waveforms of the voltage values and the waveforms of the current values corresponding to the determination results. The stored data (data of a set of determination results and waveforms) can be used as learning data in the learning device 200. Note that, instead of providing the learning device 200, the control device 100A may be provided with a learning function.

[0071] When the determination result is an accident such as a ground fault or a short circuit, the control unit 140 transmits an abnormal signal for operating the gate block to the converter A20 via an optical fiber. Also, the abnormal signal may be transmitted to the semiconductor circuit breaker 90 via an optical fiber. The display unit 160 displays the determination result and the like.

[0072] Note that, if each of the units 110 to 160 shown in FIG. 5 is provided with a determination function and an accident or the like can be determined only by the determination function, the result of the determination may be preferentially used.

[0073] FIG. 6 is a diagram showing a configuration example of the control device 100B at the base B. As shown in FIG. 6, the control device 100B includes a monitoring unit 110, a communication unit 130, a control unit 140, and a display unit 160.

[0074] The monitoring unit 110 acquires the measurement results measured by each measuring instrument at site B via an optical fiber, and also acquires the device information of the load device at site B via an optical fiber. The communication unit 130 transmits the measurement results and device information acquired by the monitoring unit 110 to the control device 100A at site A via an optical fiber.

[0075] In the control device 100A, a determination process is executed, and the determination result is transmitted to the control device 100B at site B via an optical fiber. For example, when the determination result indicates the occurrence of an accident, the control unit 140 outputs an abnormal signal to operate the gate block at site B. Also, the display unit 160 outputs information indicating that an accident has occurred. Alternatively, an abnormal signal may be transmitted from the control device 100A to the control device 100B at site B.

[0076] Figure 7 is a diagram showing a configuration example of the learning device 200. As shown in Figure 7, the learning device 200 includes a learning unit 210, a storage unit 220, and a communication unit 230. The communication unit 230 receives learning data (e.g., data of a pair of an event and a waveform) from the control devices 100A, 100B, etc. via an optical fiber, and stores the learning data in the storage unit 220. The learning unit 210 performs learning using the learning data. For example, as described above, learning of a neural network model is performed. The communication unit 230 transmits the learned model to the control device 100A, etc.

[0077] <Hardware configuration example> Each of the control devices 100A, 100B, 100C-1, 100C-2, and the learning device 200 may be configured such that each component is an independent device and the components are connected by an optical fiber, or may be a device configured by causing a computer to execute a program. This computer may be a physical computer or a virtual machine.

[0078] That is, the devices (control devices 100A, 100B, 100C-1, 100C-2, learning device 200) can be realized by executing a program corresponding to the processing performed by the device using hardware resources such as a CPU and a memory built into a computer. The above program can be recorded on a computer-readable recording medium (such as a portable memory), saved, or distributed. Also, it is possible to provide the above program through a network such as the Internet or e-mail.

[0079] FIG. 8 is a diagram showing an example of the hardware configuration of the above computer. The computers in FIG. 8 include a drive device 1000, an auxiliary storage device 1002, a memory device 1003, a CPU 1004, an interface device 1005, a display device 1006, an input device 1007, an output device 1008, etc., which are mutually connected by a bus BS.

[0080] A program for realizing the processing on the computer is provided, for example, by a recording medium 1001 such as a CD-ROM or a memory card. When the recording medium 1001 storing the program is set in the drive device 1000, the program is installed from the recording medium 1001 via the drive device 1000 into the auxiliary storage device 1002. However, the installation of the program does not necessarily have to be performed from the recording medium 1001, and it may be downloaded from another computer via a network. The auxiliary storage device 1002 stores the installed program and also stores necessary files, data, etc.

[0081] When there is an instruction to start a program, the memory device 1003 reads and stores the program from the auxiliary storage device 1002. The CPU 1004 realizes the functions related to the device according to the program stored in the memory device 1003. The interface device 1005 is used as an interface for connecting to the network and functions as a transmitting unit and a receiving unit. The display device 1006 displays a GUI (Graphical User Interface) etc. according to the program. The input device 1007 is composed of a keyboard, a mouse, buttons, a touch panel, etc. and is used to input various operation instructions. The output device 1008 outputs the calculation result.

[0082] (Operation Flow) Next, with reference to the flowcharts of FIGS. 9 and 10, a detailed operation example of the control device 100A will be described. The operations shown in the flowcharts of FIGS. 9 and 10 are operations executed by the determination unit 120 of the control device 100A. Also, the monitoring targets assumed in the flowcharts of FIGS. 9 and 10 are the voltage V1 between the positive-side distribution line and the neutral point (ground), the voltage V2 between the negative-side distribution line and the neutral point (ground), the voltage V1 + V2 = V between the positive-side distribution line and the negative-side distribution line, and the current flowing through the distribution line (for example, the current measured by the ammeter 7 shown in FIG. 1).

[0083] In S101, since the determination unit 120 has not detected any change in V1, V2, V, or the current, the DC power distribution system is in a normal state.

[0084] In S102, the determination unit 120 determines whether a change in voltage (V1, V2, or V) has been detected. If detected, it proceeds to S103, and if not detected, it proceeds to S112. Note that "detecting a change in voltage" means, for example, detecting that the value of the voltage at time t + Δt has changed by a threshold value or more compared to the value of the voltage at time t. The same applies to "detecting a change in current".

[0085] When a voltage fluctuation is detected (Yes in S102), in S103, the determination unit 120 determines whether the control voltage is being changed based on the information on the state of the converter A20. When a floating-charged storage battery is connected to the target DC power distribution system, in the determination in S103, it is determined whether "(the control voltage is being changed) and (the storage battery is not discharging)". If the determination in S103 is Yes, the process returns to S101; if No, the process proceeds to S104.

[0086] In S104, if the detected voltage fluctuation is a fluctuation of V (= V1 + V2), the process proceeds to S110; if the detected voltage fluctuation is not a fluctuation of V (= V1 + V2), the process proceeds to S105.

[0087] In S105, the determination unit 120 determines whether "V1 < V2". If "V1 < V2", the process proceeds to S106; if not "V1 < V2", the process proceeds to S108.

[0088] In S106 when "V1 < V2", the detection unit 120 determines that a ground fault has occurred in the positive-side distribution line. When a ground fault occurs in the positive-side distribution line, since the positive-side distribution line is grounded via a ground fault resistance (low resistance), the voltage across both ends of the positive-side resistor 1 decreases, the voltage across both ends of the negative-side resistor 2 increases, and "V1 < V2" results. In S107, the control unit 140 that has received a ground fault detection notification from the determination unit 120 sends out an abnormal signal.

[0089] If the determination in S105 is No, that is, if "V1 < V2" does not hold, in S108, the detection unit 120 determines that a ground fault has occurred in the negative-side distribution line. When a ground fault occurs in the negative-side distribution line, since the negative-side distribution line is grounded via a ground fault resistance (low resistance), the voltage across both ends of the negative-side resistor 2 decreases, the voltage across both ends of the positive-side resistor 1 increases, and "V1 > V2" results. In S109, the control unit 140 that has received a ground fault detection notification from the determination unit 120 sends out an abnormal signal.

[0090] If the determination at S104 is Yes, that is, if the fluctuation of V is detected, at S110, the determination unit 120 determines that a short circuit has occurred. At S111, the control unit 140 that has received the ground fault detection notification from the determination unit 120 sends out an abnormal signal.

[0091] If the determination at S102 is No (that is, if the voltage fluctuation is not detected), the determination unit 120 determines the presence or absence of current fluctuation at S112, and if there is current fluctuation, proceeds to S113.

[0092] At S113, the determination unit 120 determines whether the current value has returned to the value before the fluctuation after a predetermined time has elapsed since the current fluctuation occurred. If the determination result is No, it proceeds to S116. If the determination result is Yes, it proceeds to S114, and the determination unit 120 determines that an inrush current has occurred. At S115, the control unit 140 that has received the inrush current detection notification from the determination unit 120 sends out an abnormal signal. Note that the inrush current may be regarded as the normal state and the abnormal signal may not be sent.

[0093] If the determination at S113 is No, that is, if the current has not returned to the original value after a certain time has elapsed, it proceeds to S116 in FIG. 10.

[0094] At S116, the determination unit 120 determines whether the current rise time is less than or equal to the threshold value. If the determination unit 120 determines that the current rise time is less than or equal to the threshold value, it proceeds to S117.

[0095] At S117, the determination unit 120 determines whether the load is being connected or the load is being turned on at the time of current rise based on the device information received from the base B.

[0096] If the determination result at S117 is No, at S118, the determination unit 120 determines that a partial short circuit has occurred. At S119, the control unit 140 that has received the partial short circuit detection notification from the determination unit 120 sends out an abnormal signal.

[0097] If the determination at S117 is Yes, that is, if the load is being connected or the load is being turned on, the process proceeds to S120, where the determination unit 120 determines that a load connection or load turn-on has occurred, and returns to S101.

[0098] If the determination at S116 is No, that is, if the current rise time is not less than the threshold value, the process proceeds to S121, where the determination unit 120 determines that there has been a load fluctuation, and returns to S101.

[0099] (Regarding determination by waveform) In the determination of each event shown in FIGS. 9 and 10, more specifically, the determination unit 120 makes a determination based on the waveform corresponding to the event. Note that the "waveform" used in the determination may be the waveform itself (that is, the value at each time), or feature quantities such as the slope (differential) and change time length may be used as the "waveform".

[0100] FIG. 11 is a diagram showing an image of waveforms corresponding to each of a positive ground (+), a negative ground (-), and a short circuit in the case where the determination at S102 in the flow of FIG. 9 is Yes (when there is a voltage fluctuation).

[0101] As shown in FIG. 11, when a waveform in which the potential of the positive power distribution line suddenly decreases and approaches 0V is detected between the positive power distribution line and the ground, it can be determined that a positive ground (+) has occurred. Also, when a waveform in which the potential of the negative power distribution line suddenly increases and approaches 0V is detected between the negative power distribution line and the ground, it can be determined that a negative ground (-) has occurred. The determination in S105 of FIG. 9 may be to determine whether the voltage change corresponds to a waveform having such characteristics.

[0102] Also, when a waveform in which the voltage between the positive power distribution line and the negative power distribution line suddenly decreases is detected, it can be determined that a short circuit has occurred.

[0103] FIG. 11 shows signals from the load device when each event occurs. In the case of "ground fault (+)" and "ground fault (-)", if it is found that the load device is operating normally, it is possible to more accurately determine that the voltage fluctuation is caused by the ground fault.

[0104] FIG. 12 is a diagram showing an image of waveforms corresponding to inrush current, load fluctuation, partial short circuit, load connection / load energization when there is a current fluctuation in the case of No at S102 (when there is no voltage fluctuation) in the flow of FIG. 9.

[0105] As shown in FIG. 12, the waveform of the current when inrush current occurs is such that the value of the current rises and immediately returns to the original value. S113 in FIG. 9 corresponds to determining whether the change in the measured current value corresponds to a waveform having such characteristics.

[0106] The waveform of the current when load fluctuation occurs is such that the value of the current gradually rises and does not immediately return to the original value. S116 in FIG. 10 corresponds to determining whether the change in the measured current value corresponds to a waveform having such characteristics.

[0107] The waveforms in partial short circuit and load connection / energization are similar and are waveforms in which the current suddenly increases. However, in the case of partial short circuit, no special signal (such as switch ON) is obtained from the load device, and in the case of load connection / energization, a signal such as switch ON is obtained from the load device. That is, partial short circuit and load connection / energization can be identified by the waveform and device information. S116 and S117 in FIG. 10 correspond to the determination based on the waveform and device information.

[0108] (Effect of the Embodiment) As described above, according to the technology according to this embodiment, it is possible to avoid erroneously determining events such as load fluctuations as accidents, and accurately detect accidents occurring in the DC power distribution system.

[0109] In addition, since signals are transmitted and received via an optical fiber, it is not affected by noise generated in metal wires, and false detection can be reduced. Also, a nanophotonic modulator is used for E-O conversion in the voltmeter / ammeter, and a nanophotodetector is used for O-E conversion on the information acquisition side, so high-speed operation (low-latency operation), power saving, and low-loss monitoring and control can be achieved. Also, low-latency monitoring and control can be achieved even between remote bases several kilometers or more apart.

[0110] (Summary of the Embodiment) This specification discloses at least a DC power distribution system, a control device, an operation state determination method, and a program according to the following items. (Item 1) A DC power distribution system that distributes power from a power supply device to a load device via a power distribution network, a measuring instrument provided in the power distribution network, a control device including a determination unit that acquires voltage values and current values measured by the measuring instrument through an optical fiber and determines an operation state in the DC power distribution system based on a waveform indicating a change in the voltage value and a waveform indicating a change in the current value, A DC power distribution system comprising: (Item 2) The control device, when it is determined by the determination unit that an accident has occurred in the power distribution network, includes a control unit that stops power distribution from the power supply device by operating a gate block or a circuit breaker through an optical fiber. The DC power distribution system according to Item 1. (Item 3) The measuring instrument includes a nanophotonic modulator that converts a measured value of an electrical signal into an optical signal for transmission through an optical fiber. The DC power distribution system according to Item 1 or Item 2. (Item 4) Use different frequencies for each type of information transmitted through the optical fiber. The DC power distribution system according to any one of Items 1 to 3. (Item 5) An operation state determination method in a DC power distribution system for distributing power from a power supply device to a load device via a power distribution network, comprising: a step of measuring a voltage value and a current value by a measuring instrument provided in the power distribution network; acquiring the voltage value and the current value measured by the measuring instrument through an optical fiber, and determining an operation state in the DC power distribution system based on a waveform indicating a change in the voltage value and a waveform indicating a change in the current value; An operation state determination method comprising the above steps. (Item 6) A control device used in a DC power distribution system for distributing power from a power supply device to a load device via a power distribution network, comprising: a determination unit that acquires a voltage value and a current value measured by a measuring instrument provided in the power distribution network through an optical fiber, and determines an operation state in the DC power distribution system based on a waveform indicating a change in the voltage value and a waveform indicating a change in the current value; A control device. (Item 7) A program for causing a computer to function as the control device according to Item 6.

[0111] Although the above embodiment has been described, the present invention is not limited to such a specific embodiment, and various modifications and changes are possible within the scope of the gist of the present invention described in the claims.

Explanation of Reference Numerals

[0112] 1, 2, 1, 42 Resistors 3, 4, 9, 43, 44, 49 Voltmeters 6, 7, 8, 10, 46, 47, 48, 50 Ammeters 20, 30, 70 Converters 80 Load Device 90 Semiconductor Circuit Breaker 100 Control Device 110 Monitoring Unit 120 Determination Unit 130 Communication Unit 140 Control Unit 150 Storage Unit 160 Display unit 200 Learning device 210 Learning section 220 Memory section 230 Communication section 80 Loading device 1000 Drive device 1001 Recording medium 1002 Auxiliary storage device 1003 Memory device 1004 CPU 1005 Interface device 1006 Display device 1007 Input device

Claims

1. A DC power distribution system for distributing power from a power supply device to a load device via a power distribution network, a measuring instrument provided in the power distribution network, the measuring instrument including a nano-optical modulator that converts a measured value of an electrical signal into an optical signal for transmission via an optical fiber; a control device that obtains a voltage value and a current value measured by the measuring instrument via the optical fiber using a nano-photodetector that converts an optical signal into an electrical signal, and includes a determination unit that determines an operating state in the DC power distribution system based on predetermined information regarding the voltage value and the current value; wherein the determination unit determines that any one of an inrush current, a load connection, a load ON / load OFF, and a load fluctuation is occurring as the operating state DC power distribution system.

2. The control device, when it is determined by the determination unit that an accident has occurred in the power distribution network, includes a control unit that stops power distribution from the power supply device by operating a gate block or a circuit breaker via an optical fiber The DC power distribution system according to claim 1.

3. Using different frequencies for each type of information transmitted via the optical fiber The DC power distribution system according to claim 1 or 2.

4. An operating state determination method in a DC power distribution system for distributing power from a power supply device to a load device via a power distribution network, a step of measuring a voltage value and a current value by a measuring instrument provided in the power distribution network, the measuring instrument including a nano-optical modulator that converts a measured value of an electrical signal into an optical signal for transmission via an optical fiber; a determination step of obtaining the voltage value and the current value measured by the measuring instrument via the optical fiber using a nano-photodetector that converts an optical signal into an electrical signal, and determining an operating state in the DC power distribution system based on predetermined information regarding the voltage value and the current value; wherein in the determination step, it is determined that any one of an inrush current, a load connection, a load ON / load OFF, and a load fluctuation is occurring as the operating state Operating state determination method.

5. A control device used in a DC power distribution system for distributing power from a power supply device to a load device via a power distribution network, A voltage value and a current value measured by a measuring instrument provided in the power distribution network, the measuring instrument including a nano optical modulator that converts a measured value of an electrical signal into an optical signal for transmission via an optical fiber, are obtained via the optical fiber using a nano photoreceiver that converts the optical signal into an electrical signal, and a determination unit is provided that determines an operating state in the DC power distribution system based on predetermined information regarding the voltage value and the current value. The determination unit determines that any one of inrush current, load connection, load ON / load OFF, and load fluctuation is occurring as the operating state. Control device.

6. A program for causing a computer to function as the control device according to Claim 5.

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