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

Abstract

A protection control system includes: an input conversion substrate 40 that takes in an electric quantity from a power system via at least one of a shunt resistor 10 and a voltage dividing resistor 11, and converts the electric quantity from the power system to an electric signal by achieving electrical insulation by using insulation amplifiers 12 and 13; and a protection control arithmetic means that performs averaging processing 2012 and 2016 for calculating an average value on the outputs of the input conversion substrate 40, subtraction processing 2013 and 2017 for subtracting the average value from each of the outputs of the input conversion substrate 40, and an arithmetic operation for at least one of protection and control of the power system by using the outputs of the subtraction processing 2013 and 2017. This provides a protection control system, a merging unit, and a protection control device each having an excellent input converter.

Description

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

[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.

[0002] In recent years, digital protection and control systems have begun to be adopted for 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 via a transmission network. IEC 61850 is known as an international standard for this configuration. In a digital protection and control system based on IEC 61850, the merging unit acquires electrical quantities (current and voltage) from 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 and control calculations, such as relay calculations, are performed by the protection and control device.

[0003] Patent Document 1 discloses a configuration in which an offset value is calculated by sequentially adding a very large number of data, for example, 65,536 (2^16) pieces of data, and calculating an average value. Patent Document 2 also discloses that when a transient DC component due to an accident such as a ground fault is superimposed on the current taken in by a protective relay, the two auxiliary current transformers in the input converter will experience DC bias magnetization, and in the worst case, the iron core will reach magnetic saturation, causing distortion of the secondary output.

[0004] Japanese Patent Laid-Open No. 1-198213 Japanese Patent Laid-Open No. 2011-155158

[0005] Conventionally, input converters used in protection and control devices have employed wire-wound coil input converters, but these converters have the problem of output saturation when DC components are superimposed. Furthermore, because electrical circuit offsets affect the accuracy of input conversion circuits, techniques exist for eliminating the offsets. However, these techniques do not take into account non-saturating input converters. Furthermore, they do not take into account protection and control systems that comply with IEC 61850. The present invention was invented in light of these problems. It is an object of the present invention to provide a protection and control system, a protection and control method, a merging unit, and a protection and control device that have good input converters.

[0006] In order to solve the above problems, the present invention provides a protection and control system 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 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 has input conversion means that receives electrical quantities from the 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 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 has 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 this case, the fundamental frequency can be removed and the DC component can be extracted. Also, for example, the average value calculation means calculates the average value by adding the output of the input conversion means over a period that is an integer multiple of the fundamental period 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 past outputs of the input conversion means over a period that is an integer multiple of the fundamental period of the power system. In this case, the response to an accident in the electrical 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 period of the power system, and the period that is an integer multiple of the fundamental period is equal to or longer than the fundamental period and equal to or shorter than 30 seconds. In this case, offset drift due to temperature changes can be tracked and high-precision input conversion can be maintained. Furthermore, for example, the period at which the average value calculation means updates the average value is equal to or shorter than 30 seconds. In this case, offset drift due to temperature changes can be tracked and high-precision input conversion can be maintained. Alternatively, for example, 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 are mounted on the same input conversion board, while the average value calculation means and the subtraction means are mounted on a separate board from the input conversion board. In this case, a common board having the average value calculation means and the subtraction means can be used. Furthermore, for example, an input conversion circuit is formed 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 with an input conversion board having multiple 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 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 across the channels. In this case, a common board having the average value calculation means and the subtraction means can be used.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, 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 that are implemented is input to the A / D converter, the output of the A / D converter is input to the digital isolation IC, and the output of the digital isolation IC is the output of the input conversion means. In this case, even with such a configuration, a protection and control system with a good input converter can 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, the merging unit 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 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 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 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 having a good input converter can be provided.

[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.

[0013] FIG. 1 is a diagram illustrating a protection and control system of this embodiment to which the international standard IEC 61850 is applied. FIG. 2 is a block diagram illustrating the configuration of a merging unit in this embodiment. FIG. 3 is a diagram illustrating the main processing in the merging unit, divided into hardware processing and software processing. (a), (b), and (c) are diagrams illustrating the calculation processing of an average value applied in this embodiment. Also, (a') is a diagram illustrating a comparative example of the calculation processing of an average value. FIG. 4 is a block diagram illustrating the configuration of a merging unit in embodiment 2. FIG. 5 is a block diagram illustrating the configuration of a protection and control device in embodiment 3. FIG. 6 is a diagram illustrating the processing of an arithmetic processing unit.

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

[0015] An embodiment of the present invention will be described with reference to the accompanying drawings. In this 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 that conforms to the international standard IEC 61850.

[0016] 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, multiple 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 IFs 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 converts the acquired electrical quantity signals into analog to digital (A / D) 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 in 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 information transmitted from the protection and control device 100 via communication IF 1003 and 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 used to perform calculations for at least one of protecting and controlling the power system via a process bus, which is a network. As shown in Figure 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 also 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 an input analog signal by a predetermined multiplication factor 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 multiplication factor. The shunt resistor 10, the isolation amplifier 12, and the amplifier circuit 101 constitute a one-channel current input conversion circuit (channel 1).

[0024] Furthermore, the voltage divider resistor 11 divides the voltage of the power system at a predetermined voltage division ratio, and the divided voltage is input to the isolation amplifier 13. The 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 the 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 the isolation amplifier 13 is input to the amplifier circuit 102. The amplifier 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. The voltage divider resistor 11, the isolation amplifier 13, and the amplifier circuit 102 constitute an input conversion circuit for one voltage channel (channel 2).

[0025] In this case, it can be said that the signals of the electrical quantities 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 the electrical quantities of the power system using at least one of the shunt resistor 10 and the voltage dividing resistor 11, and converts the electrical quantities of the power system into electrical signals by providing electrical isolation using the isolation amplifier 12, which is an isolation IC. It can also 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 comprises an input conversion circuit, and the input conversion circuit can be said to have multiple 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 is approximately equal to the output amplitude of amplifier circuit 102 when the full voltage scale is applied to voltage dividing resistor 11. 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 amplitude of the input conversion circuit output from input conversion board 40 is approximately equal 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 is approximately equal to the output amplitude of amplifier circuit 102 when the full voltage scale is applied to voltage dividing resistor 11.

[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 operation 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 the amplifier circuit 101 is input to the analog filter 103 via a cable 43. The output signal of the amplifier circuit 102 is input to the analog filter 104 via a cable 43. The A / D converter 14 is a multi-channel A / D converter that receives the output signals of the analog filters 103 and 104, converts the voltage values ​​of the input signals into digital information (digital values), and outputs the converted digital information. 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 central processing unit (CPU), 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 data by the A / D converter 14, generates SV (Surveillance) data, and executes SV transmission processing. This will be described in detail 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 IFs 31 and 32. The arithmetic processing unit 200 also processes trip command information received via the communication IFs 31 and 32. The arithmetic processing unit 200 outputs a trip signal via the multiple I / O circuit 202 to drive the relay-driving output circuit 33 in the output board 42. The multiple I / O circuit 202 is a circuit that interfaces with external circuits and includes circuits compatible with communication standards such as SPI communication. In this embodiment, the non-volatile memory 30 and the relay-driving output circuit 33 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 processing for acquiring the amount of electricity in the power system and transmitting it as SV data, and processing for processing a trip command using GOOSE. Of these, the program processing content of the former will be explained using FIG. 3. In FIG. 3, explanation of the hardware parts common to FIG. 2 will be omitted. That is, in the explanation of FIG. 3, the software processing performed by the arithmetic processing unit 200 will be explained. The software processing includes gains 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 non-volatile memory 30. This coefficient is adjusted for each channel before shipping, for example, and absorbs amplitude errors of 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 to extract a DC component. The averaging processing 2012 performs averaging based on the data of the DC component extracted by the filter processing 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, the averaging process 2016, and the 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 average value calculation means that calculate an average value for the output of the input conversion board 40, which is an average value calculation means. At this time, the averaging processes 2012 and 2016 calculate an average value using the results of the filter processes 2011 and 2015 applied to the output of the input conversion board 40. Furthermore, the subtraction processes 2013 and 2017 function as subtraction means that subtract 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 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, which 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 offsets 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 by 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 SV data is transmitted with the offsets of the V1 and V2 signals canceled.

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

[0038] In the averaging process 2012 of this embodiment, an average value Vavg is calculated for N consecutive A / D converted data. As shown in FIG. 4A, the average value calculated for N 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 the calculated average value is that it does not use the most recent value at that time, but rather uses 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 assumed to be 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 satisfies the relationship 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, 13 is put into practical use in a protection and control system, the influence 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 up to 200 A are required to be input, whereas rated currents are typically 1 A or 5 A. To design the converter to accept a maximum of 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 a rated value of 1 A becomes small. Furthermore, to protect a power system using a protective relay, accurate measurement of electrical quantities even at electrical quantities 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, offsets generated in each IC remain, 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 period of the fundamental wave. Because the above-mentioned 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 period of the fundamental wave. However, it is difficult to completely remove the fundamental wave component using digital filter calculations. Because the fundamental wave component is attenuated at a constant rate, it remains, albeit with a small amplitude. Therefore, by using data over a period that is an integer multiple of the period of the fundamental wave and adding the data over this period to calculate the average value, the offset can be calculated with higher accuracy.

[0047] Furthermore, in a configuration in which the current and voltage of a 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 follow offset drift caused by temperature changes and maintain high-precision input conversion.

[0048] In order to track offset drift caused by temperature changes, it is necessary to update the average value at a frequency that can track the time constant of the temperature drift. If the average value is simply 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. 4A, 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. That is, 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. While 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 in an electrical system occurs at the timing of V[0]. In the implementation of FIG. 4(a) employed in this embodiment, Vavg is calculated without including the value of V[0] at that time. As a result, the voltage and current waveforms caused by 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 caused by the accident in the electrical system will be erroneously propagated as small values ​​to subsequent stages, and the mechanism for detecting waveform disturbances may not correctly detect the occurrence of the accident.

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

[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 while providing electrical isolation 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 a merging unit and protection and control devices from different manufacturers. IEC 61850 does not mention removing offsets, so it is not appropriate for the merging unit 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 circuitry within the device before transmitting the data as SV data.

[0055] As a result, the merging unit 1 transmits SV data from which offsets occurring in the electrical 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 plurality 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 x N used to calculate the average value to a value between one fundamental wave period and 30 seconds. This makes it possible to follow offset drift due to temperature changes and maintain highly accurate input conversion. Also, in the second modification, as shown in FIG. 4(c), the average value Vavg is updated every sample. In this way, it is possible to follow offset drift due to temperature changes with higher accuracy and maintain highly accurate input conversion. As such, according to this embodiment, a merging unit 1 having a good input converter can be realized.

[0058] The isolation ICs in the first embodiment are described as 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] 5 is a block diagram illustrating the configuration of the merging unit 2 in Example 2. Note that components common to those in Example 1, such as those in Example 1 shown in FIG. 2, are assigned the same numbers and will not be described again. The merging unit 2 is composed of three boards: an input conversion board 45, an operation board 46, and an output board 42, and 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 input voltage values ​​into digital information and output them as digital signals via SPI communication. The voltage across the shunt resistor 10 is input to the 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 the 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 the digital isolation IC 17. The digital isolation IC 17 electrically isolates the input digital signal and transmits it to subsequent stages.

[0061] The same is true for the circuits downstream of the voltage-dividing resistor 11 (amplifier circuit 106, analog filter 108, A / D converter 16, and digital isolation IC 18), which receive a voltage as an 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, which electrically isolate the input digital signal and output the digital signal. Signals representing electrical quantities in the power system captured by the shunt resistor 10 and voltage-dividing resistor 11 are input to the A / D converters 15 and 16, the outputs of the A / D converters 15 and 16 are input to the digital isolation ICs 17 and 18, and 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 one-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, similar 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, the same effect as in the first embodiment can be obtained.

[0064] In the case of the second embodiment, since it is necessary to ensure channel-to-channel insulation, it is not possible to use a multi-channel A / D converter. In addition, it is necessary to mount an analog filter and an A / D converter for each channel within the input conversion board 45. The number of signal lines on 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 a multi-channel input conversion board. However, the present invention can also be applied to the configuration of the second embodiment. As described above, according to this embodiment, a merging unit 2 having a good input converter can be realized.

[0065] In the above first and second embodiments, the present invention has been described as being applied to a merging unit in a protection and control system that conforms to IEC 61850. This embodiment is an embodiment for a protection and control device that does not conform to IEC 61850. The merging unit itself does not perform protective relay calculations, but the protection and control device of this embodiment does not transmit SVs and instead performs protective relay calculations within its own device.

[0066] 6 is a block diagram illustrating the configuration of the protection control device 3 in Example 3. Note that components common to those in Example 1, block diagram FIG. 2, are assigned the same numbers and will not be described again. The protection control device 3 is composed of three boards: an input conversion board 40, an operation board 48, and an output board 42. The differences in configuration between this example and Examples 1 and 2 are that the communication IF 31 and 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. The processing of the arithmetic processing unit 200 in this embodiment is a protective relay calculation process using the acquired electrical quantities of the power system. Note that the same processes as those in FIG. 1, which is the processing block diagram of embodiment 1, are assigned the same numbers and will not be described again. The process preceding the subtraction process 2013 for channel 1 and the process preceding the subtraction process 2017 for channel 2 are the same as in embodiment 1. That is, as in embodiment 1, the output signal of the subtraction process 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 offsets 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 provides the same effect as in the first embodiment, that is, input conversion can be achieved by taking in the electrical quantity from the power system using the shunt resistor 10 or the voltage dividing resistor 11 and providing electrical insulation using the insulating IC. In this way, according to the present embodiment, a protection and control device 3 having a good input converter can be achieved.

[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 that has an input converter in the protection and control system. Therefore, in general, the present invention can also be considered applicable to protection and control systems.

[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 the isolation amplifiers 12 and 13, and the second embodiment uses the 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, the isolation IC or the A / D converter that is located in the upstream stage depends on the type of isolation IC. In other words, the present invention is not limited to whether the isolation IC or 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 circuit unit may be realized by consolidating the functions described as multiple blocks in the above embodiments into a single circuit element. For example, in the first embodiment, the amplifier circuit 101 and the analog filter 103 may be realized by a single amplifier IC. Furthermore, the amplifier circuit 101 and the analog filter 103 may be built-in functions of the A / D converter 14. Furthermore, in the first embodiment, for example, the filter processing 2011, the averaging processing 2012, and the subtraction processing 2013 are described as being realized by software as illustrated in FIG. 1, but they may also be implemented as hardware. Calculations similar to these processes can be realized, for example, by 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] <Description of Protection and Control Method> Therefore, the processing performed by the above-described protection and control system S can be considered to be a protection and control method characterized by taking in an electrical quantity from the power system via 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 from the power system to 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. Furthermore, the above-described configurations, functions, etc. may be implemented in software by a processor interpreting and executing a program that implements each function. Information such as programs, tables, and files that implement each function can be stored in 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. Furthermore, the control lines and information lines shown are those considered necessary for explanation, and do not necessarily represent all control lines and information lines in the product. In reality, it can be assumed that almost all components are interconnected.

[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...amplification circuit, 103, 104...analog filter, 105, 106...amplification circuit, 107, 108...analog filter, 200...arithmetic processing section, 201...transmission and reception 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. A protection and control system comprising: input conversion means that takes in 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 for the output of said input conversion means; subtraction means that subtracts said average value from the output of said input conversion means; and protection and control calculation means that uses the output of said subtraction means to perform calculations for at least one of protection and control of the power system.

2. 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 said calculations, wherein the merging unit has: input conversion means that takes in the electrical quantities of the power system using at least one of a shunt resistor and a voltage dividing resistor, and converts the electrical quantities of the power system into electrical signals by providing electrical insulation using an insulating IC; average value calculation means that calculates an average value for 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 system has protection and control calculation means that performs the calculations using the output of the subtraction means.

3. A protection and control system according to claim 1 or 2, 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. A protection and control system as claimed in claim 1 or 2, 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 cycle of the power system.

5. A protection and control system as claimed in claim 1 or 2, 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. A protection and control system as claimed in claim 1 or 2, characterized in that 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, and the period that is an integer multiple of the fundamental cycle is a value that is equal to or greater than the fundamental cycle and equal to or less than 30 seconds.

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

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

9. A protection and control system as claimed in claim 1 or 2, wherein an input conversion circuit is formed from at least one of the shunt resistor and the voltage dividing resistor that are implemented, the isolation IC, and amplification means that multiplies the input signal by a predetermined magnification, and the input conversion circuit is provided with an input conversion board having multiple channels, and when the maximum amount of electricity taken in by at least one of the shunt resistor and the voltage dividing resistor that are implemented is called full scale, when an amount of electricity 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. A protection and control system as claimed in claim 1 or 2, comprising: amplification means for multiplying an input signal by a predetermined magnification; and an A / D converter for converting the output signal of said input conversion means into a digital value; said isolation IC is an isolation amplifier that electrically isolates the input analog signal and outputs an analog signal multiplied by a predetermined magnification; a signal of an electrical quantity of a power system taken in by at least one of said shunt resistor and said voltage dividing resistor, when implemented, is input to said isolation amplifier; the output of said isolation amplifier is input to said amplification means; the output of said amplification means is input to said A / D converter; and said output of said input conversion means used by said average value calculation means and said subtraction means is an output signal of said A / D converter.

11. A protection and control system according to claim 10, comprising both the shunt resistor and the voltage dividing resistor, wherein a signal obtained by converting the 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 amplification means, a signal obtained by converting the 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 amplification means, and wherein, when the maximum current value taken in by the shunt resistor is referred to as the current full scale and the maximum voltage value taken in by the voltage dividing resistor is referred to as the voltage full scale, the output amplitude of the first amplification means when the current full scale flows through the shunt resistor is approximately the same as the output amplitude of the second amplification means when the voltage full scale is applied to the voltage dividing resistor.

12. A protection and control system as claimed in claim 1 or 2, wherein the input conversion means has an A / D converter that converts an input signal into a digital value, the isolation IC is 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 the shunt resistor and the voltage dividing resistor that are implemented is input to the A / D converter, the output of the A / D converter is input to the digital isolation IC, and the output of the digital isolation IC is the output of the input conversion means.

13. A protection and control method comprising: 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 electrical signal after subtraction to perform calculations for at least one of protection and control of the power system.

14. 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 takes in 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 for the output of said input conversion means; and subtraction means that subtracts said average value from the output of said input conversion means, wherein the information on the electrical quantities is transmitted using the output of said subtraction means.

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

Images