Protection and control system, protection and control method, merging unit, and protection and control device

Abstract

To provide a protection control system having an excellent input converter, a merging unit, and a protection control device.SOLUTION: A protection and control system comprising: an input conversion board (40) that receives an electric quantity of a power system through at least one of a shunt resistor (10) and a voltage dividing resistor (11), and converts the electric quantity of the power system into an electric signal while being electrically isolated by an isolation amplifier (12,13); an averaging process (2012,2016) that calculates an average value of an output of the input conversion board (40); a subtraction process (2013,2017) that subtracts the average value from the output of the input conversion board (40); and a protection and control operation unit that performs at least one of protection and control of the power system using an output of the subtraction process (2013,2017).SELECTED DRAWING: Figure 3

Description

[Technical Field]

[0001] The present invention relates to a protection and control system, a protection and control method, a merging unit, and a protection and control device. [Background technology]

[0002] In recent years, digital protection and control systems have begun to be applied to protection and control devices, in which the functions of conventional protection and control systems are divided into a merging unit and a protection and control device, and the two are connected by a transmission network. IEC 61850 is known as the international standard for this configuration. In a digital protection and control system based on IEC 61850, the merging unit acquires the electrical quantities (current and voltage) of the power system (hereinafter, current and voltage will be referred to as electrical quantities). The merging unit performs A / D (Analog to Digital) conversion of the acquired electrical quantity signals and transmits the A / D converted digital signals to the protection and control device via process bus transmission. Furthermore, protection or control calculations such as relay operations are performed by the protection and control device.

[0003] Patent Document 1 discloses a configuration in which a very large number of, for example, 65536 (2^16) pieces of data are sequentially added to calculate an average value, thereby calculating an offset value. Furthermore, Patent Document 2 discloses that when a transient DC component due to an accident such as a ground fault is superimposed on the current taken in by the protective relay, the two auxiliary current transformers in the input converter will experience DC bias magnetization, and in the worst case scenario, this will lead to magnetic saturation of the iron core, causing distortion of the secondary output. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Japanese Patent Application Publication No. Hei 1-198213 [Patent Document 2] Japanese Patent Application Laid-Open No. 2011-155158 Summary of the Invention [Problem to be solved by the invention]

[0005] Conventionally, input converters used in protection and control devices have been wire-wound coil input converters, but this has had the problem of output saturation when a DC component is superimposed. In addition, because electrical circuit offsets affect the accuracy of input conversion circuits, there are techniques to remove the offsets. However, these techniques do not take into account non-saturating input converters, nor do they take into account protection and control systems that comply with IEC 61850. The present invention has been made in view of these problems, and an object of the present invention is to provide a protection and control system, a protection and control method, a merging unit, and a protection and control device that have a good input converter. [Means for solving the problem]

[0006] In order to solve the above problems, the present invention provides a protection and control system comprising: input conversion means for receiving an electric quantity from a power system using at least one of a shunt resistor and a voltage dividing resistor, and converting the electric quantity from the power system into an electric signal by providing electrical isolation using an insulating IC; average value calculation means for calculating an average value of the output from the input conversion means; subtraction means for subtracting the average value from the output from the input conversion means; and protection and control calculation means for performing calculations for at least one of protection and control of the power system using the output from the subtraction means. In this case, a protection and control system having a good input converter can be provided.

[0007] The present invention also provides a protection and control system including a merging unit that transmits information on electrical quantities for performing calculations for at least one of protecting and controlling a power system via a network, and a protection and control device that performs the calculations, wherein the merging unit includes input conversion means that receives electrical quantities from the power system using at least one of shunt resistors and voltage dividing resistors and converts the electrical quantities from the power system into electrical signals by providing electrical insulation with an insulating IC, average value calculation means that calculates an average value of the output of the input conversion means, and subtraction means that subtracts the average value from the output of the input conversion means, and the protection and control device includes protection and control calculation means that performs calculations using the output of the subtraction means. In this case, a protection and control system with a good input converter can be provided.

[0008] Here, for example, the average value calculation means calculates the average value using the result of filtering the output of the input conversion means, in which case the fundamental frequency can be removed and the DC component can be extracted. Furthermore, for example, the average value calculation means calculates the average value by adding up the output of the input conversion means over a period that is an integral multiple of the fundamental cycle of the power system. In this case, the offset can be calculated with higher accuracy. Furthermore, for example, the average value calculation means calculates the average value by adding up past outputs of the input conversion means over a period that is an integral multiple of the fundamental cycle of the power system. In this case, the response when a fault occurs in the electric system is superior. Furthermore, for example, the average value calculation means calculates the average value by adding the output of the A / D converter over a period that is an integer multiple of the fundamental cycle of the power system, and the period that is an integer multiple of the fundamental cycle is equal to or longer than the fundamental cycle and equal to or shorter than 30 seconds. In this case, it is possible to follow offset drift caused by temperature changes and maintain high-precision input conversion. For example, the average value calculation means updates the average value at a cycle of 30 seconds or less. In this case, it is possible to follow offset drift caused by temperature changes and maintain highly accurate input conversion. Alternatively, for example, at least one of the shunt resistor and the voltage dividing resistor, the isolation IC, and the amplifier that multiplies the input signal by a predetermined factor are mounted on the same input conversion board, and the average value calculation board and the subtraction board are mounted on a board separate from the input conversion board. In this case, the board having the average value calculation board and the subtraction board can be used in common. Furthermore, for example, an input conversion circuit is configured from at least one of a shunt resistor and a voltage dividing resistor, an isolation IC, and an amplifier that multiplies an input signal by a predetermined factor, and the input conversion circuit is provided on an input conversion board having multiple channels, and when the maximum electrical quantity taken in by at least one of the shunt resistor and the voltage dividing resistor is called the full scale, when an electrical quantity equivalent to the full scale is input to each of the multiple channels, the output amplitude of the input conversion circuit output from the input conversion board is approximately the same among the channels. In this case, a board having an average value calculation means and a subtraction means can be used in common. Furthermore, for example, if both a shunt resistor and a voltage dividing resistor are provided, and a signal obtained by converting a current taken in by the shunt resistor is input to a first isolation amplifier, the output of the first isolation amplifier is input to a first amplifying means, a signal obtained by converting a voltage taken in by the voltage dividing resistor is input to a second isolation amplifier, and the output of the second isolation amplifier is input to a second amplifying means, and the maximum current value taken in by the shunt resistor is called the current full scale and the maximum voltage value taken in by the voltage dividing resistor is called the voltage full scale, then the output amplitude of the first amplifying means when the current full scale flows through the shunt resistor is approximately the same as the output amplitude of the second amplifying means when the voltage full scale is applied to the voltage dividing resistor. In this case, a common substrate having an average value calculating means and a subtracting means can be used. For example, the input conversion means may have an A / D converter that converts an input signal into a digital value, the isolation IC may be a digital isolation IC that outputs a digital signal after electrically isolating the input digital signal, and a signal of an electrical quantity of the power system taken in by at least one of a shunt resistor and a voltage dividing resistor (if implemented) may be input to the A / D converter, the output of the A / D converter may be input to the digital isolation IC, and the output of the digital isolation IC may be the output of the input conversion means. In this case, even with such a configuration, a protection control system with a good input converter may be realized.

[0009] Furthermore, the present invention provides a protection and control method that includes taking in an electrical quantity from a power system using at least one of a shunt resistor and a voltage dividing resistor, providing electrical insulation using an insulating IC to convert the electrical quantity from the power system into an electrical signal, calculating an average value for the converted electrical signal, subtracting the average value from the converted electrical signal, and using the subtracted electrical signal to perform calculations for at least one of protection and control of the power system. In this case, a protection and control method with a good input converter can be provided.

[0010] Furthermore, the present invention provides a merging unit that transmits information on electrical quantities for performing at least one of protection and control calculations via a network, comprising: input conversion means that receives electrical quantities from a power system using at least one of a shunt resistor and a voltage dividing resistor, and converts the electrical quantities from the power system into electrical signals by providing electrical insulation using an insulating IC; average value calculation means that calculates an average value of the output of the input conversion means; and subtraction means that subtracts the average value from the output of the input conversion means, and the information on the electrical quantities is transmitted using the output of the subtraction means. In this case, a merging unit with a good input converter can be provided.

[0011] The present invention is a protection and control device characterized by comprising: input conversion means for receiving an electrical quantity from a power system using at least one of a shunt resistor and a voltage dividing resistor, and converting the electrical quantity from the power system into an electrical signal by providing electrical insulation using an insulating IC; average value calculation means for calculating an average value of the output from the input conversion means; subtraction means for subtracting the average value from the output from the input conversion means; and protection and control calculation means for performing calculations for at least one of protection and control of the power system using the output from the subtraction means. In this case, a protection and control device with a good input converter can be provided. [Effects of the Invention]

[0012] According to the present invention, it is possible to provide a protection and control system, a merging unit, and a protection and control device having a good input converter, and also to provide a protection and control method capable of performing good input conversion. [Brief explanation of the drawings]

[0013] [Figure 1] 1 is a diagram illustrating a protection and control system according to an embodiment of the present invention to which the international standard IEC 61850 is applied. [Figure 2] FIG. 2 is a block diagram illustrating the configuration of a merging unit in the present embodiment. [Figure 3] FIG. 10 is a diagram illustrating main processing in a merging unit, divided into hardware processing and software processing. [Figure 4] 1A, 1B, and 1C are diagrams illustrating the calculation of an average value applied in this embodiment, and FIG. 1A' is a diagram illustrating a comparative example of the calculation of an average value. [Figure 5] FIG. 10 is a block diagram illustrating the configuration of a merging unit in a second embodiment. [Figure 6] FIG. 10 is a block diagram illustrating the configuration of a protection and control device according to a third embodiment. [Figure 7] FIG. 2 is a diagram illustrating processing by a calculation processing unit. DETAILED DESCRIPTION OF THE INVENTION

[0014] Hereinafter, an embodiment of the present invention will be described with reference to the drawings. [Example]

[0015] DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS In the present specification and drawings, a communication interface is abbreviated as a communication IF. This embodiment is an embodiment in which the present invention is applied to a protection and control system to which the international standard IEC 61850 is applied.

[0016] FIG. 1 is a diagram illustrating a protection and control system S of this embodiment to which the international standard IEC 61850 is applied. The protection and control system S includes a protection and control device 100, a plurality of merging units 1, a SCADA device 5, and the protection and control device 100. The protection and control device 100 is connected to a transmission path called a station bus and a transmission path called a process bus. The station bus and the process bus are made redundant, and the protection and control device 100 and the merging unit 1 have two communication interfaces for each bus.

[0017] The protection and control device 100 is connected to the merging unit 1 via a process bus. The merging unit 1 acquires electrical quantities (current and voltage) of the power system. The merging unit 1 performs A / D (Analog to Digital) conversion on the acquired electrical quantity signals and transmits the A / D converted digital information via communication IF 31 and communication IF 32. The protection and control device 100 receives the electrical quantity information transmitted from the merging unit 1 via communication IF 1003 and communication IF 1004. At this time, a communication method called SV (Sampled Value) is used.

[0018] The protection and control device 100 performs protection relay calculations based on the information on the electrical quantity, and when the relay operation conditions are met, it transmits trip command information to the merging unit 1. At this time, a communication method called GOOSE is used. As shown in Figure 1, multiple merging units 1 may be installed within a substation.

[0019] The protection and control device 100 is also connected to the SCADA device 5, which is a higher-level device, via a station bus. The protection and control device 100 transmits its own device status and the like to the SCADA device 5, and receives command information from the SCADA device 5. The SCADA device 5 receives the information transmitted from the protection and control device 100 via the communication IF 1003 and the communication IF 1004. At this time, a communication method called MMS is used. Communication methods such as SV, GOOSE, and MMS are specified in the international standard IEC 61850.

[0020] Fig. 2 is a block diagram illustrating the configuration of the merging unit 1 in this embodiment. Fig. 3 is a diagram illustrating the main processing in the merging unit 1, divided into hardware processing and software processing. The software processing is processing in the arithmetic processing unit 200, which will be described later.

[0021] The merging unit 1 transmits information on electrical quantities for performing calculations for at least one of protection and control of the power system via a process bus, which is a network. 2, the merging unit 1 is composed of three boards: an input conversion board 40, an operation board 41, and an output board 42. The input conversion board 40 and the operation board 41 are connected by a cable 43. The operation board 41 and the output board 42 are connected by a cable 44.

[0022] The input conversion board 40 takes in the current and voltage of the power system. The input conversion circuit of this embodiment has two channels, with the circuit including the shunt resistor 10 referred to as channel 1 and the circuit including the voltage dividing resistor 11 referred to as channel 2. The input conversion board 40 is composed of the shunt resistor 10, the voltage dividing resistor 11, the isolation amplifiers 12 and 13, the amplifier circuits 101 and 102.

[0023] The shunt resistor 10 converts the current of the power system into a voltage. The voltage across the shunt resistor 10 is input to the isolation amplifier 12. The isolation amplifier 12 is an example of an isolation IC or a first isolation amplifier, and amplifies the voltage across the shunt resistor 10 while providing electrical insulation. In this case, it can also be said that the isolation amplifier 12 outputs an analog signal obtained by multiplying the input analog signal by a predetermined magnification while providing electrical insulation. The output of the isolation amplifier 12 is input to the amplifier circuit 101. The amplifier circuit 101 is an example of an amplifying means or a first amplifying means, and outputs a signal obtained by multiplying the input signal by a predetermined magnification. The shunt resistor 10, the isolation amplifier 12, and the amplifier circuit 101 form an input conversion circuit for one current channel (channel 1).

[0024] Furthermore, voltage dividing resistor 11 divides the voltage of the power system at a predetermined voltage division ratio, and the divided voltage is input to isolation amplifier 13. Isolation amplifier 13 is an example of an isolation IC or a second isolation amplifier, and amplifies the divided voltage while providing electrical insulation. In this case, it can also be said that isolation amplifier 13 outputs an analog signal obtained by multiplying the input analog signal by a predetermined magnification while providing electrical insulation. The output of isolation amplifier 13 is input to amplifier circuit 102. Amplification circuit 102 is an example of an amplifying means or a second amplifying means, and outputs a signal obtained by multiplying the input signal by a predetermined magnification. Voltage dividing resistor 11, isolation amplifier 13, and amplifier circuit 102 form an input conversion circuit for one voltage channel (channel 2).

[0025] In this case, it can be said that the signals of the electrical quantity of the power system taken in by the shunt resistor 10 and the voltage dividing resistor 11 are input to the isolation amplifiers 12 and 13, and the outputs of the isolation amplifiers 12 and 13 are input to the amplifier circuits 101 and 102. The input conversion board 40 functions as an input conversion means that takes in an electrical quantity from the power system through at least one of the shunt resistor 10 and the voltage dividing resistor 11, and converts the electrical quantity from the power system into an electrical signal by providing electrical insulation through the isolation amplifier 12, which is an isolation IC. In this case, it can be said that the shunt resistor 10, the voltage dividing resistor 11, the isolation amplifiers 12 and 13, and the amplifier circuits 101 and 102 are mounted on the same input conversion board 40. Furthermore, the input conversion board 40 can be said to have an input conversion circuit including a shunt resistor 10, a voltage dividing resistor 11, isolation amplifiers 12 and 13, and amplifier circuits 101 and 102, and has a plurality of channels.

[0026] When the maximum current value taken in by shunt resistor 10 is referred to as the full current scale and the maximum voltage value taken in by voltage dividing resistor 11 is referred to as the full voltage scale, the output amplitude of amplifier circuit 101 when the full current scale flows through shunt resistor 10 and the output amplitude of amplifier circuit 102 when the full voltage scale is applied to voltage dividing resistor 11 are assumed to be substantially equal. This can also be said to mean that when the maximum amount of electricity taken in by shunt resistor 10 or voltage dividing resistor 11 is referred to as the full scale, and an amount of electricity equivalent to the full scale is input to each of multiple channels, the output amplitudes of the input conversion circuits output from input conversion board 40 are substantially the same between channels. It can also be said that the output amplitude of amplifier circuit 101 when the full current scale flows through shunt resistor 10 and the output amplitude of amplifier circuit 102 when the full voltage scale is applied to voltage dividing resistor 11 are substantially the same.

[0027] Although the input conversion board 40 of this embodiment has been described as having an input conversion circuit with one current channel and one voltage channel, the number of current and voltage channels that the input conversion board 40 has is not limited to this.

[0028] The arithmetic board 41 is composed of an analog filter 103, an analog filter 104, an A / D converter 14, an integrated circuit unit 20, a non-volatile memory 30, a communication IF 31, and a communication IF 32. The output signal of amplifier circuit 101 is input to analog filter 103 via cable 43. The output signal of amplifier circuit 102 is input to analog filter 104 via cable 43. A / D converter 14 is a multi-channel A / D converter that receives the output signals of analog filters 103 and 104, converts the voltage values ​​of the input signals into digital information (digital values), and outputs the converted digital information. The converted digital information is input to integrated circuit unit 20. In this case, it can also be said that the outputs of the amplifier circuits 101 and 102 are input to the A / D converter 14.

[0029] The integrated circuit unit 20 is composed of an arithmetic processing unit 200, a transmission / reception circuit 201, and a multiple I / O circuit 202. The arithmetic processing unit 200, the transmission / reception circuit 201, and the multiple I / O circuit 202 are connected to one another via an internal bus, which is indicated by a thick line in Fig. 2. When the integrated circuit unit 20 is a system on chip (SoC), the arithmetic processing unit 200 is a CPU (Central Processing Unit), the transmission / reception circuit 201 is a circuit constructed in an FPGA (Field Programmable Gate Array) circuit, and the multiple I / O circuit is a circuit built into the SoC.

[0030] The arithmetic processing unit 200 performs predetermined processing on the data converted into digital form by the A / D converter 14, generates SV (Surveillance) data, and executes SV transmission processing, the details of which will be described later with reference to Fig. 3. In the SV transmission processing, the arithmetic processing unit 200 instructs the transmission / reception circuit 201 to transmit the SV data via the communication IF 31 and the communication IF 32. The arithmetic processing unit 200 also processes trip command information received via the communication IF 31 and the communication IF 32. The arithmetic processing unit 200 outputs a trip signal via the multiple I / O circuit 202 to drive the output circuit 33 for driving a relay in the output board 42. The multiple I / O circuit 202 is a circuit that interfaces with external circuits, and includes a circuit that supports communication standards such as SPI communication. In this embodiment, the non-volatile memory 30 and the output circuit 33 for driving relays in the output board 42 are connected via the multiple I / O circuit 202.

[0031] The processing of the arithmetic processing unit 200 in this embodiment is roughly divided into a process of acquiring the amount of electricity in the power system and transmitting it as SV data, and a process of processing a trip command by GOOSE. Of these, the program processing content of the former will be explained using Figure 3. In Figure 3, explanation of the hardware parts common to Figure 2 will be omitted. That is, in the explanation of Figure 3, the software processing performed by the arithmetic processing unit 200 will be explained. The software processing includes gain processing 2010 and 2014, filter processing 2011 and 2015, averaging processing 2012 and 2016, subtraction processing 2013 and 2017, SV generation processing 2018, and SV data transmission processing 2019.

[0032] The gain 2010 multiplies the A / D converted value of the electrical quantity taken in by the shunt resistor 10 by a predetermined coefficient. The gain 2014 also multiplies the A / D converted value of the electrical quantity taken in by the voltage dividing resistor 11 by a predetermined coefficient. The predetermined coefficient is, for example, a coefficient stored in the nonvolatile memory 30. This coefficient is adjusted for each channel before shipping, for example, and absorbs amplitude errors in the input conversion circuit. The output signal of the gain 2010 is referred to as V1, and the output signal of the gain 2014 is referred to as V2.

[0033] The filter processing 2011 is a software process that executes a digital filter operation having low-pass filter characteristics, and removes the fundamental frequency from the output signal V1 of the gain 2010 and extracts the DC component. The averaging process 2012 performs averaging based on the data of the DC component extracted by the filtering process 2011, and outputs an average value Vavg1. The subtraction processing 2013 subtracts the average value Vavg1, which is the output value of the averaging processing 2012, from the output signal V1 of the gain 2010. As a result, the output signal of the subtraction processing 2013 becomes a value in which the DC component (offset) of the V1 signal has been cancelled. In other words, the output value of the subtraction processing 2013 becomes a value in which only the AC component of the V1 signal has been extracted.

[0034] The filtering process 2015, averaging process 2016, and subtraction process 2017 are all similar processes except that the input is V2 instead of V1. The output value of the subtraction process 2017 is a value obtained by canceling the offset of the V2 signal.

[0035] In this case, the averaging processes 2012 and 2016 function as an average value calculation means that calculates an average value for the output of the input conversion board 40. At this time, the averaging processes 2012 and 2016 calculate the average value using the results of the filter processes 2011 and 2015 applied to the output of the input conversion board 40. The subtraction processes 2013 and 2017 function as subtraction means for subtracting an average value from the output of the input conversion board 40, which is an average value calculation means. Furthermore, the protection and control device 100 has a protection and control calculation means that performs calculations for at least one of protection and control of the power system using the outputs of the subtraction processes 2013 and 2017 that are subtraction means. It can be said that the averaging processes 2012 and 2016 and the subtraction processes 2013 and 2017 are implemented on a board separate from the input conversion board 40. It can also be said that the outputs of the amplifier circuits 101 and 102 are input to the A / D converter 14, and that the output of the input conversion board 40 used by the averaging processes 2012 and 2016 and the subtraction processes 2013 and 2017 is the output signal of the A / D converter 14.

[0036] The SV generation process 2018 obtains values ​​obtained by canceling the offset of the V1 and V2 signals from the subtraction processes 2013 and 2017, and generates frame data for transmitting the SV data. The SV data transmission process 2019 transmits the frame data generated in the SV generation process 2018 to the transmission / reception circuit 201, and instructs it to transmit the SV data via the communication IF 31 and the communication IF 32. As a result, the offsets of the V1 and V2 signals are cancelled and the SV data is transmitted.

[0037] Next, the calculation of the average value performed by the averaging process 2012 will be described. 4(a), (b), and (c) are diagrams illustrating the calculation process of the average value applied in this embodiment, and FIG. 4(a') is a diagram illustrating a comparative example of the calculation process of the average value. 4, the horizontal axis represents time. The sampling period of the A / D converter 14 is Ts. Furthermore, since the averaging process is common to each channel, V1 is generally represented as V and Vavg1 as Vavg. The same applies to the averaging process 2016.

[0038] In the averaging process 2012 in this embodiment, an average value Vavg is calculated for N consecutive A / D converted data. As shown in Figure 4(a), the average value calculated using N pieces of data over a period of Ts × N is maintained for the next period of Ts × N. This allows the average value to be updated every Ts × N. Another feature of this method is that the calculated average value does not use the most recent value at that time, but rather past data.

[0039] In addition, the data period Ts×N used to calculate the average value in the averaging process 2012 in this embodiment is an integer multiple of the period of the fundamental wave (fundamental period). For example, if the fundamental wave is 50 Hz, the value of N is a number that establishes a relationship such that Ts×N is an integer multiple of 20 ms. Furthermore, the data period Ts×N used to calculate the average value is set to a value between one period of the fundamental wave and 30 seconds. This can also be said to mean that the data period Ts×N used to calculate the average value is a value that is equal to or greater than the fundamental period and equal to or less than 30 seconds.

[0040] Next, the effects of this embodiment will be described. First, according to this embodiment, the shunt resistor 10 and the voltage dividing resistor 11 are used to receive the current and voltage of the power system through resistance, and the isolation amplifiers 12 and 13 provide electrical insulation. The input converters used in conventional protection and control devices are input converters compatible with wound coils, but they have the problem of output saturation when DC components are superimposed. IEC 61869, a related standard to the international standard IEC 61850, recommends non-saturating input converters, and a configuration using the shunt resistor 10 and the voltage dividing resistor 11 as in this embodiment can achieve a non-saturating input converter.

[0041] However, the inventors have found that when a configuration in which the current and voltage of the power system are received by resistors and electrical isolation is achieved by isolation amplifiers 12 and 13 is put into practical use in a protection and control system, the effect of offset in the electrical circuit cannot be ignored.

[0042] A wide dynamic range is required for input converters used in protection and control systems. For example, currents of up to 200 A are required to be input, whereas rated currents are typically 1 A or 5 A. To design a converter capable of inputting up to 200 A, the full scale of the input section of the A / D converter 14 must be adjusted to several hundred A. As a result, the voltage level at the rated voltage of 1 A becomes small. Furthermore, to protect the power system using a protective relay, accurate measurement of electrical quantities even lower than the rated value is required.

[0043] While the explanation here is based on the input section of the A / D converter 14, the same applies to the shunt resistor 10. Furthermore, considering the heat generated by a large current of 200 A flowing through the shunt resistor 10, the resistance value of the shunt resistor 10 is on the order of milliohms. As a result of these constraints, it is difficult to design a large voltage across the shunt resistor 10, and signal amplification is required using the isolation amplifier 12 and the amplifier circuit 101. However, the larger the amplification factor, the greater the offset generated in each IC. As mentioned above, input converters used in protection and control systems require a wide dynamic range. Therefore, in order to ensure accuracy when an electrical quantity lower than the rated value is input, the amplified offset becomes non-negligible. In other words, a technology that can cancel offsets with higher accuracy than the technology disclosed in the prior art is needed. As mentioned above, this issue is particularly pronounced in circuits that input current, which involves heat generation problems.

[0044] To solve this problem, in this embodiment, the offset is removed by an averaging process 2012. Furthermore, in this embodiment, the following process is executed to cancel the offset with higher precision.

[0045] First, filtering 2011 is performed to extract the DC component, and then averaging 2012 is performed. Because the input waveform is a sine wave, filtering is not necessarily required. However, if filtering 2011 is not performed, and there is a frequency deviation in the frequency of the electrical system, the addition period will not be an integer multiple of the frequency, resulting in an offset calculation error. As a result, the offset generated in each IC remains, which ultimately manifests as a lack of precision as an input converter.

[0046] Furthermore, the data period Ts×N used to calculate the average value in the averaging process 2012 is an integer multiple of the fundamental wave period. Because the aforementioned filter process 2015 is performed, ideally the data period used to calculate the average value does not need to be an integer multiple of the fundamental wave period. However, it is difficult to completely remove the fundamental wave component using digital filter calculations. Because it is attenuated at a certain rate, the fundamental wave component remains, even though its amplitude is small. For this reason, the offset can be calculated with higher accuracy by using data over a period that is an integer multiple of the fundamental wave period and adding the data over this period to calculate the average value.

[0047] Furthermore, in a configuration where the current and voltage of the power system are received through resistance and electrical isolation is achieved using an isolation amplifier, it is necessary to consider the need to cancel a larger electrical circuit offset than in the past. The electrical circuit offset drifts with temperature. Because the amount of offset generated is larger than in the past, it is necessary to consider the time constant of temperature drift and update the average value at an appropriate interval. In this embodiment, the data period Ts × N used to calculate the average value is set to a value between one fundamental wave cycle and 30 seconds. This also makes it possible to update the average value at an interval of 30 seconds or less between one fundamental wave cycle and 30 seconds. This makes it possible to track offset drift due to temperature changes and maintain high-precision input conversion.

[0048] In order to track offset drift caused by temperature changes, the average value must be updated at a frequency that can track the time constant of the temperature drift. If the average value is simply being updated, there is no problem if the period Ts × N of the data used to calculate the average value exceeds 30 seconds. However, since the calculated average value must match the result of temperature drift and the offset must be canceled out, it is preferable that the period Ts × N of the data used to calculate the average value be a value between one fundamental wave period and 30 seconds.

[0049] In addition, as shown in Fig. 4(a), the averaging process in this embodiment is configured to maintain the average value calculated from N pieces of data over a period of Ts x N for the next period of Ts x N. At this time, the N pieces of data used in the averaging process are data from one sample before to N samples before. In other words, data from past samples is used.

[0050] On the other hand, in this averaging process, it is also possible to calculate the average value using the most recent value at that time, as shown in Figure 4(a'), for example. In other words, it is also possible to use data from (N-1) samples ago from the current sample data (data 0 samples ago). However, in this case, there is a problem with the response when an accident occurs in the electrical system. When an accident occurs, the waveforms of the voltage and current input to the input converter are disturbed. Although protection and control systems have mechanisms for detecting such waveform disturbances when an accident occurs, the offset cancellation function may have the effect of making such changes appear smaller. Therefore, it is desirable to calculate the average value using data from past samples, as in this embodiment.

[0051] For example, consider a case where an accident occurs in an electrical system at the timing of V[0]. In the implementation of FIG. 4(a) used in this embodiment, Vavg is calculated without including the value of V[0] at that time. As a result, the voltage and current waveforms due to the accident in the electrical system are correctly propagated to subsequent stages, and the mechanism for detecting waveform disturbances can correctly detect the occurrence of the accident. However, in the implementation of FIG. 4(a'), Vavg is calculated including the value of V[0] at that time, which is an abnormal value. As a result, if the potential direction of the abnormal value V[0] matches the potential direction of the offset of the electrical circuit, the voltage and current waveforms due to the accident in the electrical system will be erroneously propagated as small to subsequent stages, and the mechanism for detecting waveform disturbances may not correctly detect the occurrence of the accident.

[0052] Furthermore, in this embodiment, signal amplification is performed within input conversion board 40 by amplifier circuits 101 and 102, and operation board 41 is mounted as a separate board. By providing amplifier circuits 101 and 102, if the gain of each amplifier circuit is appropriately designed, it is possible to design the output amplitude of input conversion board 40 when a full-scale current is input to channel 1, which receives a current as an input, to be approximately equal to the output amplitude of input conversion board 40 when a full-scale voltage is input to channel 2, which receives a voltage as an input. As a result, when a lineup of multiple types of input conversion boards with different channel configurations is available, it is possible to share operation board 41. As described above, according to the present invention, the shunt resistor 10 or the voltage dividing resistor 11 takes in the electrical quantity from the power system, and the isolation amplifiers 12 and 13 provide electrical isolation to realize input conversion.

[0053] Furthermore, in a configuration that applies IEC 61850, complex calculations such as protective relay calculations are performed by the protection and control device, and the merging unit 1 is positioned as a measurement unit that A / D converts the acquired electrical quantity signals and transmits the data. However, in order to achieve non-saturated input conversion in the merging unit 1, if the electrical quantity of the power system is taken in by the shunt resistor 10 or voltage dividing resistor 11 and input conversion is performed with electrical isolation provided by the isolation amplifiers 12 and 13, it is desirable to cancel the offset of the electrical circuit in the merging unit 1.

[0054] Technically, it is possible to achieve a similar effect by removing the offset from the SV data received by the protection and control device. However, IEC 61850 is an international standard, and a system may be configured with merging units and protection and control devices from different manufacturers. IEC 61850 does not mention removing offsets, so it is not appropriate for MUs to transmit data containing offsets as SV data. In addition, because the amount of offset present in the electrical circuit depends on the design of the input conversion circuit, it is desirable to perform processing within the merging unit to remove offsets generated in the electrical circuits within the device itself before transmitting the data as SV data.

[0055] As a result, the merging unit 1 transmits SV data from which offsets occurring in the electric circuit have been removed, and the protection and control device 100 can then perform protection or control calculations. Thus, according to the configuration of this embodiment, a merging unit 1 equipped with a non-saturating input converter and capable of transmitting appropriate SV data can be realized.

[0056] Next, modifications of this embodiment will be described. In a first modification, as shown in FIG. 4(b) above, the average value is updated after a number of sampling periods (two sampling periods in the figure). This allows the average value Vavg to be a value that is not affected by an accident for the period required for detection, when the function for detecting waveform disturbances at the time of an accident described above makes a determination based on data for one or more sample periods. In other words, even when the function for detecting waveform disturbances at the time of an accident makes a determination based on data for one or more sample periods, the occurrence of an accident can be correctly detected.

[0057] In this modification, it is desirable to set the sum of the delay time Tdly and the data period Ts × N used to calculate the average value to a value between one period of the fundamental wave and 30 seconds, thereby tracking offset drift caused by temperature changes and maintaining high-precision input conversion. In the second modification, the average value Vavg is updated for each sample, as shown in Fig. 4(c), which makes it possible to more accurately follow offset drift caused by temperature changes and maintain highly accurate input conversion. Thus, according to this embodiment, a merging unit 1 having a good input converter can be realized. [Example]

[0058] The isolation IC in the first embodiment is described as the isolation amplifiers 12 and 13 that amplify the input differential voltage and provide electrical isolation. This embodiment is configured to use another type of isolation IC.

[0059] FIG. 5 is a block diagram illustrating the configuration of the merging unit 2 in the second embodiment. 2, which is the block diagram of Example 1, are assigned the same numbers and their explanations will be omitted. The merging unit 2 is composed of three boards: an input conversion board 45, an operation board 46, and an output board 42. The input conversion board 45 and the operation board 46 are connected by a cable 47.

[0060] The input conversion board 45 of this embodiment is composed of a shunt resistor 10, a voltage dividing resistor 11, amplifier circuits 105 and 106, analog filters 107 and 108, A / D converters 15 and 16, a digital isolation IC 17, and a digital isolation IC 18. The A / D converters 15 and 16 convert the input voltage value into digital information and output it as a digital signal via SPI communication. The voltage across the shunt resistor 10 is input to an amplifier circuit 105. The amplifier circuit 105 amplifies the voltage across the shunt resistor 10, and the output of the amplifier circuit 105 is input to an analog filter 107. The A / D converter 15 receives the output signal of the analog filter 107 and converts the voltage value into digital information. The converted digital information is input to a digital isolation IC 17. The digital isolation IC 17 electrically isolates the input digital signal and then transmits it to the subsequent stage.

[0061] The same applies to the circuits (amplifier circuit 106, analog filter 108, A / D converter 16, digital isolation IC 18) downstream of the voltage dividing resistor 11, which receive a voltage as input. As a result, the input conversion board 45 outputs an SPI communication signal. In the second embodiment, the isolation ICs are digital isolation ICs 17 and 18 that electrically isolate input digital signals and output the digital signals. Signals representing electrical quantities of the power system captured by the shunt resistor 10 and the voltage dividing resistor 11 are input to the A / D converters 15 and 16, and the outputs of the A / D converters 15 and 16 are input to the digital isolation ICs 17 and 18. The outputs of the digital isolation ICs 17 and 18 are the outputs of the input conversion board 40.

[0062] The operation board 46 of this embodiment connects a group of SPI communication signals from the input conversion board 45 to the multiple I / O circuit 202. Normally, SPI signals are communicated using four signal lines: CLK, SI, SO, and CS, and in 1-to-N (N: an integer of 2 or more) communication, signals other than CS are common signals. That is, in this embodiment, the number of SPI communication signal lines connected to the multiple I / O circuit 202 is five.

[0063] With this configuration, similarly to the first embodiment, the arithmetic processing unit 200 can acquire the data of the electric quantity that has been digitally converted by the A / D converter 15 and the A / D converter 16. Therefore, it is possible to obtain the same effect as in the first embodiment.

[0064] In the case of the second embodiment, since it is necessary to ensure insulation between channels, it is not possible to use a multi-channel A / D converter. In addition, it becomes necessary to mount an analog filter and an A / D converter for each channel in the input conversion board 45. Furthermore, the number of signal lines in the cable 47 is increased compared to the first embodiment, since it is the number of channels plus three lines (CLK, SI, and SO). As a result, the configuration of the first embodiment has the advantage of being able to efficiently mount an input conversion board for multiple channels. However, the present invention is similarly applicable to the configuration of embodiment 2. As described above, according to this embodiment, a merging unit 2 having a good input converter can be realized. [Example]

[0065] The above first and second embodiments have been described with reference to a configuration in which the present invention is applied to a merging unit in a protection and control system that applies IEC 61850. This embodiment is an embodiment for a protection and control device that does not apply IEC 61850. The merging unit itself does not perform protection relay calculations, but the protection and control device of this embodiment does not transmit SV and performs protection relay calculations within its own device.

[0066] FIG. 6 is a block diagram illustrating the configuration of the protection and control device 3 in the third embodiment. 2, which is the block diagram of the first embodiment, are given the same numbers and their explanations are omitted. The protection and control device 3 is composed of three boards: an input conversion board 40, an operation board 48, and an output board 42. The structural differences between this embodiment and the first and second embodiments are that the communication IF 31 and the communication IF 32 are eliminated from the operation board 48, and that the transmission / reception circuit 201 is eliminated from the integrated circuit unit 21 in the operation board 48.

[0067] FIG. 7 is a diagram illustrating the processing of the arithmetic processing unit 200. In FIG. The processing of the calculation processing unit 200 in this embodiment is a protective relay calculation processing using the acquired electrical quantities of the power system. Note that the same processes as those in the processing block diagram of FIG. 1 in the first embodiment are assigned the same numbers, and descriptions thereof will be omitted. The processing preceding the subtraction processing 2013 for channel 1 and the processing preceding the subtraction processing 2017 for channel 2 are common to the first embodiment. That is, as in the first embodiment, the output signal of the subtraction processing 2013 has a value obtained by canceling the DC component (offset) of the V1 signal.

[0068] The relay calculation processing 2020 obtains values ​​obtained by canceling the offset of the V1 and V2 signals from the subtraction processing 2013 and subtraction processing 2017, and performs protective relay calculation. The result of the protective relay calculation is passed to the sequence processing 2021, which performs a protection logic calculation and outputs a trip signal via the multiple I / O circuit 202 as necessary to drive the output circuit 33 for driving the relay in the output board 42.

[0069] It is clear that the present embodiment also has the same effect as the first embodiment, that is, the shunt resistor 10 or the voltage dividing resistor 11 takes in the electrical quantity from the power system, and the isolation IC provides electrical isolation to realize input conversion. As described above, according to this embodiment, it is possible to realize a protection and control device 3 having a good input converter.

[0070] In the above-described first to third embodiments, if a device that performs protective relay calculations is defined as a protection and control device, then in the first and second embodiments, the device to which the present invention is applied is a merging unit, not a protection and control device, but in the third embodiment, it is a protection and control device. Regardless of the form of the protection and control system, the device to which the present invention is applied is preferably a device having an input converter in the protection and control system. Therefore, in general, the present invention can be considered to be applicable to any protection and control system.

[0071] Furthermore, regardless of the type of protection and control system to which it is applied, a common feature is that a signal with the offset removed from the output of the input converter is generated, and that this signal is used to perform at least one of protection and control calculations.

[0072] In the first and second embodiments described above, the first embodiment uses isolation amplifiers 12 and 13, and the second embodiment uses digital isolation ICs 17 and 18. The isolation amplifiers 12 and 13 and the digital isolation ICs 17 and 18 can be generally referred to as isolation ICs. As can be seen from FIG. 2, which is a block diagram of the first embodiment, and FIG. 5, which is a block diagram of the second embodiment, which of the isolation IC and the A / D converter is located in the upstream stage depends on the type of isolation IC. In other words, the present invention is not limited to which of the isolation IC and the A / D converter is located in the upstream stage. As described in the first and second embodiments, the present invention can be applied regardless of whether the isolation IC or the A / D converter is located in the upstream stage. The present invention can also be applied when an A / D converter is not used and electrical quantities are not converted to digital.

[0073] Furthermore, the electrical circuitry may be realized by consolidating the functions of the multiple blocks described in the above embodiments into a single circuit element. For example, in the first embodiment, the amplifier circuit 101 and analog filter 103 may be realized by a single amplifier IC. Furthermore, the amplifier circuit 101 and analog filter 103 may be built-in functions of the A / D converter 14. In addition, for example, in the case of the first embodiment, the filtering process 2011, the averaging process 2012, and the subtraction process 2013 are configured to be realized by software as described in Fig. 1, but they may be implemented as hardware. Operations similar to these processes can be realized by, for example, an FPGA circuit.

[0074] The protection and control system S, merging units 1 and 2, and protection and control device 3 described above in detail can perform good input conversion.

[0075] <Explanation of protection control method> Therefore, the processing performed by the above-mentioned protection and control system S can be considered to be a protection and control method characterized by taking in the electrical quantity of the power system through at least one of the shunt resistor 10 and the voltage dividing resistor 11, providing electrical insulation using an insulating IC to convert the electrical quantity of the power system into an electrical signal, calculating an average value for the converted electrical signal, subtracting the average value from the converted electrical signal, and using the subtracted electrical signal to perform calculations for at least one of protection and control of the power system. This makes it possible to provide a protection and control method that can perform good input conversion.

[0076] The present invention is not limited to the above-described embodiments, and includes various modifications in addition to the above-described modifications. For example, the above-described embodiments have been described in detail to clearly explain the present invention, and the present invention is not necessarily limited to those including all of the described configurations. Furthermore, it is possible to replace part of the configuration of one embodiment with the configuration of another embodiment, or to add the configuration of another embodiment to the configuration of one embodiment. Furthermore, it is possible to add, delete, or replace part of the configuration of each embodiment with other configurations.

[0077] Furthermore, the above-described configurations, functions, processing units, processing means, etc. may be partially or entirely implemented in hardware, for example, by designing them as integrated circuits. The above-described configurations, functions, etc. may also be implemented in software, with a processor interpreting and executing a program that implements each function. Information such as the programs, tables, and files that implement each function can be stored in a memory, a recording device such as a hard disk or SSD (Solid State Drive), or a recording medium such as an IC card, SD card, or DVD. In addition, the control lines and information lines shown are those that are considered necessary for the explanation, and do not necessarily show all the control lines and information lines in the product. In reality, it can be assumed that almost all components are interconnected. [Explanation of symbols]

[0078] S...protection and control system, 1,2...merging unit, 3,100...protection and control device, 5...SCADA device, 10...shunt resistor, 11...voltage dividing resistor, 12,13...isolation amplifier, 14,15,16...A / D converter, 17,18...digital isolation IC, 20,21...integrated circuit section, 40...input conversion board, 101,102...amplifier circuit, 103,104...analog filter, 105,106...amplifier circuit, 107,108...analog filter, 200...arithmetic processing section, 201...transmission and receiving circuit, 202...multiple I / O circuit, 2010,2014...gain, 2011,2015...filter processing, 2012,2016...averaging processing, 2013,2017...subtraction processing, 2018...SV generation processing, 2019...SV data transmission processing

Claims

1. an input conversion means for taking in an electrical quantity from the power system using at least one of a shunt resistor and a voltage dividing resistor, and converting the electrical quantity from the power system into an electrical signal by providing electrical insulation using an insulating IC; an average value calculation means for calculating an average value of the output of the input conversion means; subtraction means for subtracting the average value from the output of the input conversion means; protection and control calculation means for performing calculations for at least one of protection and control of the power system using the output of the subtraction means; A protection and control system comprising:

2. A protection and control system including a merging unit that transmits information on an electrical quantity for performing at least one of protection and control calculations for a power system via a network, and a protection and control device that performs the calculations, The merging unit comprises: an input conversion means for taking in an electrical quantity from the power system using at least one of a shunt resistor and a voltage dividing resistor, and converting the electrical quantity from the power system into an electrical signal by providing electrical insulation using an insulating IC; an average value calculation means for calculating an average value of the output of the input conversion means; subtraction means for subtracting the average value from the output of the input conversion means; and The protection control device has a protection control calculation means that performs the calculation using the output of the subtraction means. A protection and control system characterized by:

3. The protection and control system according to claim 1 or 2, The protection and control system is characterized in that the average value calculation means calculates the average value using the result of filtering the output of the input conversion means.

4. The protection and control system according to claim 1 or 2, The protection and control system is characterized in that the average value calculation means calculates an average value by adding up the output of the input conversion means over a period that is an integer multiple of the fundamental period of the power system.

5. The protection and control system according to claim 1 or 2, The protection and control system is characterized in that the average value calculation means calculates an average value by adding past outputs of the input conversion means over a period that is an integer multiple of the fundamental cycle of the power system.

6. The protection and control system according to claim 1 or 2, the average value calculation means calculates an average value by adding up the output of the A / D converter over a period that is an integer multiple of the fundamental cycle of the power system; A protection and control system characterized in that the period that is an integer multiple of the fundamental cycle is greater than the fundamental cycle and less than 30 seconds.

7. The protection and control system according to claim 1 or 2, A protection and control system characterized in that the period during which the average value calculation means updates the average value is 30 seconds or less.

8. The protection and control system according to claim 1 or 2, at least one of the shunt resistor and the voltage dividing resistor, the isolation IC, and an amplifier that multiplies an input signal by a predetermined magnification are mounted on the same input conversion board; A protection and control system characterized in that the average value calculation means and the subtraction means are mounted on a board separate from the input conversion board.

9. The protection and control system according to claim 1 or 2, an input conversion circuit is configured by at least one of the shunt resistor and the voltage dividing resistor, the isolation IC, and an amplifier that multiplies an input signal by a predetermined magnification, and the input conversion circuit is provided on an input conversion board having a plurality of channels; When the maximum electrical quantity taken in by at least one of the shunt resistor and the voltage dividing resistor is referred to as a full scale, A protection and control system characterized in that when an electrical quantity equivalent to the full scale is input to each of the multiple channels, the output amplitude of the input conversion circuit output from the input conversion board is approximately the same between channels.

10. The protection and control system according to claim 1 or 2, an amplifying means for multiplying an input signal by a predetermined factor; an A / D converter for converting the output signal of the input conversion means into a digital value; The isolation IC is an isolation amplifier that electrically isolates an input analog signal and outputs an analog signal multiplied by a predetermined factor, a signal of an electrical quantity of the power system taken in by at least one of the shunt resistor and the voltage dividing resistor, which are implemented, is input to the isolation amplifier; an output of the isolation amplifier is input to the amplifying means; an output of the amplifying means is input to the A / D converter; and the output of the input conversion means used by the average value calculation means and the subtraction means is an output signal of the A / D converter.

11. The protection and control system according to claim 10, a shunt resistor and a voltage dividing resistor; a signal obtained by converting the current taken in by the shunt resistor is input to a first isolation amplifier, and an output of the first isolation amplifier is input to a first amplifying means; a signal obtained by converting the voltage taken in by the voltage dividing resistor is input to a second isolation amplifier, and an output of the second isolation amplifier is input to a second amplifying means; When the maximum current value taken in by the shunt resistor is called the current full scale and the maximum voltage value taken in by the voltage dividing resistor is called the voltage full scale, A protection and control system characterized in that the output amplitude of the first amplifier means when the full scale of the current flows through the shunt resistor is approximately the same as the output amplitude of the second amplifier means when the full scale of the voltage is applied to the voltage dividing resistor.

12. The protection and control system according to claim 1 or 2, the input conversion means has an A / D converter that converts the input signal into a digital value; the isolation IC is a digital isolation IC that outputs an input digital signal while electrically isolating the digital signal, a signal of an electrical quantity of the power system taken in by at least one of the shunt resistor and the voltage dividing resistor, which are implemented, is input to the A / D converter, an output of the A / D converter is input to the digital isolation IC, and an output of the digital isolation IC is the output of the input conversion means.

13. The electrical quantity of the power system is taken in by at least one of the shunt resistor and the voltage dividing resistor, and the electrical quantity of the power system is converted into an electrical signal by providing electrical insulation by the insulating IC; Calculate the average value of the converted electrical signal, subtracting the average value from the converted electrical signal; performing at least one of protection and control calculations for the power system using the electrical signal after the subtraction; A protection and control method.

14. A merging unit that transmits information on electrical quantities for performing at least one of protection and control calculations via a network, an input conversion means for taking in an electrical quantity from the power system using at least one of a shunt resistor and a voltage dividing resistor, and converting the electrical quantity from the power system into an electrical signal by providing electrical insulation using an insulating IC; an average value calculation means for calculating an average value of the output of the input conversion means; a subtraction means for subtracting the average value from the output of the input conversion means; A merging unit characterized in that the output of the subtraction means is used to transmit information on the electrical quantity.

15. A protection and control device, an input conversion means for taking in an electrical quantity from the power system using at least one of a shunt resistor and a voltage dividing resistor, and converting the electrical quantity from the power system into an electrical signal by providing electrical insulation using an insulating IC; an average value calculation means for calculating an average value of the output of the input conversion means; subtraction means for subtracting the average value from the output of the input conversion means; protection and control calculation means for performing calculations for at least one of protection and control of the power system using the output of the subtraction means; A protection control device comprising:

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