CN213637201U - Current measuring device and power grid monitoring system - Google Patents
Current measuring device and power grid monitoring system Download PDFInfo
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Abstract
The utility model relates to a flow measuring device and electric wire netting monitoring system. Wherein the current measuring device comprises a Rogowski coil and an A/D conversion circuit. The Rogowski coil is used for acquiring a first current value analog signal of the power grid wire to be measured; the A/D conversion circuit is electrically connected with the Rogowski coil and is used for converting the first current value analog signal into a first current value digital signal. It can be understood, because the luo shi coil does not use the oil-immersed formula to insulate, and no flammable explosive problem, no iron core in the insulating framework, no iron loss, the consumption is little, insulating properties is good, small light in weight, measure the frequency bandwidth, no magnetism saturation, the linearity is good, the feature of environmental protection is strong, noiselessness, the cost is low, the secondary side can open a way, can directly provide the signal for measurement system and can carry out system integration with secondary equipment lug connection, be favorable to simplifying secondary side equipment, be suitable for the big electric capacity of current electric power system, high voltage level needs.
Description
Technical Field
The utility model relates to a crystal oscillator control technical field especially relates to a current measurement device and electric wire netting monitoring system.
Background
At present, along with the increase of the transmission capacity of a power system, the improvement of the voltage class, and the proposal of a smart grid concept and the continuous maturity of the smart grid concept in recent years, higher requirements are put on equipment for collecting and detecting grid signals, and especially, the equipment has updated promises on the aspects of the accuracy, the stability, the rapidity and the like of collecting the grid signals. Therefore, the mutual inductor is more important as an intermediate link of a power grid signal and a computer control system. The accuracy and real-time of the signals collected by the mutual inductor affect the accurate analysis of the faults by the computer system and quickly respond to measures. At present, the traditional electromagnetic current transformer has been developed for decades, the mechanism and the material thereof are continuously perfected, so that the measurement precision can reach thousands of the measurement precision, but due to the influence of an iron core, the traditional measurement is limited to expose a plurality of defects, and the defects are represented as follows: 1) the electromagnetic transformer is designed according to an electromechanical relay, so that the power consumption is high, and as is well known, the corresponding volume is larger and larger as the voltage grade of the equipment is higher; 2) the dynamic change range is small, magnetic saturation can be generated, the special requirements on signals in the application occasions of measurement generally require enough precision, the special requirements on the signals in the application occasions of protection generally require a wide dynamic range, and due to the influence of iron core magnetic saturation, the two types of current sensors can be processed separately in general; 3) the output interfaces are incompatible, the output current signals can be transmitted to an upper computer after being properly processed under the general condition, however, the electromagnetic current transformer cannot be connected with control equipment due to the fact that no corresponding interface exists on the secondary side, and therefore the electromagnetic current transformer cannot adapt to the development of intellectualization and digitization of a power system at the present stage; 4) the secondary side cannot be opened, otherwise, great potential safety hazard can be caused.
SUMMERY OF THE UTILITY MODEL
The utility model provides a flow measuring device and electric wire netting monitoring system to solve the problem that traditional electromagnetic type current transformer consumption and volume are bigger, easy magnetic saturation, output interface are incompatible and the secondary side can not open a way.
An embodiment of the utility model provides a current measuring device, include:
the Rogowski coil is used for acquiring a first current value analog signal of the power grid wire to be measured; and
and the A/D conversion circuit is electrically connected with the Rogowski coil and is used for converting the first current value analog signal into a first current value digital signal.
In one embodiment, the rogowski coil comprises:
the to-be-measured power grid lead penetrates through the center of the non-magnetic annular framework;
and the insulated wire is uniformly wound on the non-magnetic annular framework.
In one embodiment, the a/D conversion circuit includes:
a circuit interface;
and the programmable gain amplifier is electrically connected with the Rogowski coil through the circuit interface, determines the maximum input range and the gain according to the current effective value of the first current value analog signal read for the first time, and amplifies the first current value analog signal according to the adjusted gain.
In one embodiment, the current measuring device further comprises a signal conditioning module, wherein the signal conditioning module comprises a filter circuit and a voltage follower circuit;
the filter circuit and the voltage follower circuit are sequentially connected in series between the Rogowski coil and the A/D conversion circuit, the first current value analog signal is filtered through the filter circuit, harmonic waves in the current value analog signal are filtered, and the filtered first current value analog signal is stably output to the A/D conversion circuit through the voltage follower circuit.
In one embodiment, the A/D conversion circuit comprises an A/DE7753 chip.
In one embodiment, the current measuring device further includes:
the standard mutual inductor is electrically connected with the A/D conversion circuit and used for acquiring a second current value analog signal of the power grid wire to be measured and converting the second current value analog signal into a second current value digital signal through the A/D conversion circuit;
and the main control circuit is electrically connected with the A/D conversion circuit and is used for determining a ratio difference value and an angle difference value between the second current value digital signal and the first current value digital signal, performing ratio difference compensation on the first current value digital signal according to the ratio difference value and performing angle difference compensation on the first current value digital signal according to the angle difference value.
In one embodiment, the current measuring device further includes a wireless transmission module, and the wireless transmission module is electrically connected to the main control circuit and is configured to send the compensated first current value digital signal.
In one embodiment, the current measuring device further comprises an energy obtaining module, and the energy obtaining module comprises:
the energy taking mutual inductor is used for obtaining electric energy from the power grid wire to be measured and generating a primary voltage;
and the voltage doubling rectifying circuit is electrically connected with the energy taking mutual inductor and is used for performing voltage doubling rectifying treatment on the primary voltage to generate working voltage and supplying the working voltage to the A/D conversion circuit, the main control circuit and the signal conditioning module.
In one embodiment, the current measuring device further includes a battery, and when the energy obtaining module cannot normally provide the working voltage, the battery provides the working voltage for the a/D conversion circuit, the main control circuit, and the signal conditioning module.
In one embodiment, the current measuring device further comprises a power management module, and the power management module is electrically connected with the energy taking module and the battery respectively;
when the working voltage is increased to a first preset threshold value or reduced to a second preset threshold value, the power supply management module controls the battery to provide the working voltage; otherwise, the power management module controls the energy taking module to provide working voltage.
Based on the same inventive concept, the utility model also provides a power grid monitoring system, power grid monitoring system includes the current measurement device of any one of the above-mentioned embodiments.
To sum up, the utility model provides a flow measuring device and electric wire netting monitoring system. Wherein the current measuring device comprises a Rogowski coil and an A/D conversion circuit. The Rogowski coil is used for acquiring a first current value analog signal of the power grid wire to be measured; the A/D conversion circuit is electrically connected with the Rogowski coil and is used for converting the first current value analog signal into a first current value digital signal. It can be understood, because the luo shi coil does not use the oil-immersed formula to insulate, and no flammable explosive problem, no iron core in the insulating framework, no iron loss, the consumption is little, insulating properties is good, small light in weight, measure the frequency bandwidth, no magnetism saturation, the linearity is good, the feature of environmental protection is strong, noiselessness, the cost is low, the secondary side can open a way, can directly provide the signal for measurement system and can carry out system integration with secondary equipment lug connection, be favorable to simplifying secondary side equipment, be suitable for the big electric capacity of current electric power system, high voltage level needs.
Drawings
Fig. 1 is a schematic structural diagram of a current measuring device according to an embodiment of the present invention;
fig. 2 is a schematic structural diagram of a rogowski coil according to an embodiment of the present invention;
fig. 3 is a structural view of a signal conditioning module and an AD conversion circuit according to an embodiment of the present invention;
fig. 4 is a schematic diagram of a working flow of an AD conversion circuit provided in an embodiment of the present invention;
fig. 5 is a schematic flow chart illustrating signal compensation according to an embodiment of the present invention;
fig. 6 is a schematic structural diagram of the voltage-doubling rectifying circuit, the battery and the power management module provided by the embodiment of the present invention.
Detailed Description
In order to make the above objects, features and advantages of the present invention more comprehensible, embodiments of the present invention are described in detail below with reference to the accompanying drawings. In the following description, numerous specific details are set forth in order to provide a thorough understanding of the present invention. The present invention can be embodied in many different forms other than those specifically described herein, and it will be apparent to those skilled in the art that similar modifications can be made without departing from the spirit and scope of the invention, and it is therefore not to be limited to the specific embodiments disclosed below.
Referring to fig. 1, an embodiment of the present invention provides a current measuring device, which includes a rogowski coil 100 and an a/D conversion circuit 200.
The rogowski coil 100 is used for acquiring a first current value analog signal of a power grid wire to be measured; the a/D conversion circuit 200 is electrically connected to the rogowski coil 100, and is configured to convert the first current value analog signal into a first current value digital signal.
It can be understood that because the rogowski coil 100 does not use the oil-immersed type to insulate, does not have the flammable and explosive problem, does not have the iron core in the insulating framework, and no iron loss, the consumption is little, and insulating properties is good, and small light in weight, measurement frequency bandwidth is wide, does not have the magnetism saturation, and the linearity is good, and the feature of environmental protection is strong, noiselessness, and the cost is low, and the secondary side can open a way, can directly provide the signal for measurement system and can carry out system integration with secondary equipment lug connection, is favorable to simplifying secondary side equipment, is suitable for the big electric capacity of current electric power system, high voltage level needs.
In one embodiment, the rogowski coil 100 comprises a non-magnetic toroidal former and an insulated wire. The non-magnetic annular framework is characterized in that the power grid lead to be measured penetrates through the center of the non-magnetic annular framework; and the insulated wires are uniformly wound on the non-magnetic annular framework.
It is understood that, in the present embodiment, the current measuring apparatus includes the rogowski coil 100 and the a/D conversion circuit 200. The basic structure of the rogowski coil 100 is to uniformly and densely wind an enameled wire on an insulated non-magnetic ring-shaped framework, and place a primary side wire to be measured (i.e., the power grid wire to be measured) at the center of the non-magnetic ring-shaped framework, as shown in fig. 2. The cross section of the non-magnetic annular framework is selected to be rectangular so as to be suitable for busbars with different sizes in the screen cabinet. The operating principle of the rogowski coil 100 is that when the primary side current changes, an induced electromotive force is generated on the secondary side (i.e. the rogowski coil 100), and a primary side current value to be measured can be obtained by performing certain signal calculation and processing on the electromotive force.
Assume that the rogowski coil 100 in this embodiment is circular in cross-section. a. b is the inner and outer diameters of the rogowski coil 100, and dr is the unit length of the cross-sectional diameter of the nonmagnetic annular skeleton.
When the non-magnetic loop coil has good uniformity, a measured wire passing through the central axis of the coil is electrified (assuming that the current is I), and a corresponding variable magnetic field H is generated in the surrounding space surrounded by the loop winding, according to the ampere loop law:
if the radius of the coil is r, the magnetic field strength is:
the magnetic induction B is:
magnetic flux through a single turn coil is
A mutual electromotive force of
The resistance of the coil being
The present embodiment uses a high-precision rogowski coil 100 as the sensing head of the present system, and the measurement transformation ratio is 1A: 0.2 mV. Assuming that the A/D converter circuit 200 requires a steady state voltage input of 0.5V maximum, the maximum measurable current is only 2500A; if the maximum pulse voltage acceptable by the a/D conversion circuit 200 is 6V, since the high-frequency signal can be measured by using the rogowski coil 100, a larger pulse voltage is obtained, and thus, the measurable pulse maximum current can reach 30kA, thereby increasing the measurement range of the current.
In addition, the rogowski coil 100 is insulated without oil immersion, so that the problem of flammability and explosiveness is avoided, an iron core is not arranged in an insulating framework, the iron loss is avoided, the power consumption is low, the insulating property is good, the size is small, the weight is light, the measurement frequency band is wide, no magnetic saturation is caused, the linearity is good, the environmental protection property is strong, no noise is caused, the manufacturing cost is low, and the problems that the power consumption and the size of a traditional electromagnetic current transformer are large, the magnetic saturation is easy to cause, and a secondary side cannot be opened are solved.
In one embodiment, the current measuring device further comprises a signal conditioning module 300 comprising a filter circuit 310 and a voltage follower circuit 320.
The filter circuit 310 and the voltage follower circuit 320 are sequentially connected in series between the rogowski coil 100 and the a/D conversion circuit 200, the filter circuit 310 filters the first current value analog signal, filters out harmonics in the current value analog signal, and stably outputs the filtered first current value analog signal to the a/D conversion circuit 200 through the voltage follower circuit 320.
Referring to fig. 3, in the embodiment, the first current value analog signal output by the rogowski coil 100 first passes through a filter circuit 310 (including R1-R4 and C1-C4), filters out harmonics in the first current value analog signal, so that the filtered first current value analog signal is smoother, and the filtered first current value analog signal enters a voltage follower circuit 320 (including a voltage follower OP07) to reduce the influence of the following circuits on the output first current value analog signal. The resistor R1 is 100 omega, the resistor R2 is 1k omega, the capacitors are all 0.033uF, and the resistors on other branches are all set in similar proportion.
The first current value analog signal after signal conditioning is sent to a microprocessor module to be subjected to A/D conversion. Two issues must be considered at this time: 1) the resolution of the A/D conversion is matched with the range of the analog input voltage; 2) an integrator having excellent design performance. Based on this, in one embodiment, the a/D conversion circuit 200 includes a circuit interface and a programmable gain amplifier; the programmable gain amplifier is electrically connected with the rogowski coil 100 through the circuit interface, determines a maximum input range and a gain according to the current effective value of the first current value analog signal read for the first time, and amplifies the first current value analog signal according to the adjusted gain.
In this embodiment, after the a/D conversion circuit 200 initially reads the effective value of the first current value analog signal, the magnitude of the electromotive force signal acquired for the first time is calculated according to the effective value, the gain and the maximum input range of the a/D conversion circuit 200 are determined according to the magnitude of the electromotive force signal, and the first current value analog signal is amplified according to the adjusted gain.
It will be appreciated that in order to make the transmitted data more accurate, it is often desirable that the received first current value analog signal has an amplitude very close to the upper limit of the range of the a/D input voltage. Therefore, in the present embodiment, signals with different amplitudes are amplified by changing the gain of the amplifier. In order to meet the current signals in different measurement ranges and improve the resolution of the A/D, the precision of a processing system is improved, the programmable gain amplifier can be used with the A/D to adjust the gain of an input signal, the dynamic change of an input analog signal is allowed in a larger range, and the purpose of expanding the A/D input voltage range is achieved.
As a crucial part of the processing circuit of the rogowski coil 100, the design of the integrator directly affects the measurement accuracy of the whole system. The designed integrator with excellent performance not only aims at ensuring linearity and measuring accuracy, but also has the performance of accurately and quickly reflecting transient current, and can accurately reflect real current.
According to the above description of the requirement of the programmable gain amplifier and the function of the different types of integrators, the present embodiment employs an a/DE7753 chip manufactured by a/DI company, which contains the programmable gain amplifier inside, the gain of which can be selected from 1, 2, 4, 8 and 16, and most importantly, a digital integrator, and an external interface of the rogowski coil 100, so as to accurately recover the analog signal of the first current value output by the rogowski coil 100.
In addition, the maximum differential input voltage at the V1P/V1N end of the a/DE7753 chip is ± 0.5V, the gain of the programmable gain amplifier can be selected to be 1, 2, 4, 8 and 16, and the maximum input range of the a/D can be set to be 0.5V, 0.25V, 0.125V, 0.0625V, 0.0313V0.0156V and 0.00781V respectively by setting 3 bits and 4 bits in the register of the programmable gain amplifier, namely, adaptive adjustment of the input voltage range of the channel 1 is realized by adjusting the parameter of an Analog-to-digital converter (ADC). Referring to fig. 4, the specific steps are: firstly, after an output signal of the Rogowski coil 100 is collected into an A/DE7753 chip through a channel 1 (comprising V1P and VIN), a gain is selected, the gain is designed by a programmable gain amplifier, because the size of a signal received for the first time is not known, in order to avoid the influence on the A/DE7753 chip caused by the fact that the signal exceeds a range set by the programmable gain amplifier, the gain is set to be 1 when sampling is carried out for the first time, and the maximum input range of an ADC is set to be 0.5V. Therefore, the influence on the chip caused by the fact that the external signal is too large and exceeds the range is avoided. And secondly, after the first amplification, the signals are converted into digital signals through the ADC, effective value calculation is carried out, and the magnitude of the electromotive force signals collected by the channel 1 for the first time is reversely deduced according to the effective values calculated for the first time and an effective value calculation formula. Then, the input range corresponding to the ADC is selected according to the size of the electromotive force signal acquired for the first time, and the selection of the input range (also called gear selection) is completed. And finally, according to the selection, the programmable gain amplifier register is reinitialized again, proper gain and ADC maximum range are selected for the signal, then effective value calculation is carried out, and the calculation result of the time is output and displayed.
In addition, in order to further improve the measurement accuracy, it is also necessary to perform adjustment of the offset amount of the channel by writing to the offset correction register of the a/D chip. The offset correction register can correct the offset of +/-20 mV to +/-50 mV, and the adjustment of the offset can be set by gain.
In one embodiment, the current measuring device further comprises a standard transformer (not shown) and a master control circuit 400.
The standard transformer is electrically connected with the a/D conversion circuit 200, and is configured to obtain a second current value analog signal of the power grid wire to be measured, and convert the second current value analog signal into a second current value digital signal through the a/D conversion circuit 200.
The main control circuit 400 is electrically connected to the a/D conversion circuit 200, and configured to determine a ratio difference and an angular difference between the second current value digital signal and the first current value digital signal, perform ratio difference compensation on the first current value digital signal according to the ratio difference, and perform angular difference compensation on the first current value digital signal according to the angular difference.
It is understood that the main control circuit 400 may include an intelligent chip such as an MCU (micro controller Unit), a CPU (Central Processing Unit), a DSP (Digital Signal Processing), or an FPGA (Field Programmable Gate Array). In this embodiment, the main control circuit 400 includes an MCU chip, and the MCU chip controls other modules or circuit machines to operate.
In this embodiment, the step of calculating the ratio difference value and the angle difference value by using the main control circuit 400 includes:
discretizing the first current value analog signal and the second current value analog signal to respectively obtain a current sampling value obtained by sampling the rogowski coil 100 and a current sampling value obtained by sampling the standard transformer;
and calculating the ratio difference value and the angle difference value according to the current sampling value of the Rogowski coil 100 and the current sampling value of the standard transformer by using a preset angle difference calculation formula and a ratio difference calculation formula.
In one embodiment, the current measuring apparatus further includes a wireless transmission module 800, which is electrically connected to the main control circuit and configured to transmit the compensated first current value digital signal.
In this embodiment, the wireless transmission module includes a bluetooth communication module. After A/D conversion, the generated first current value signal is transmitted to a microprocessor, and the microprocessor controls a Bluetooth communication module to output the first current value signal. The microprocessor adopts nRF52840 of Nordic SemiconductorTMBluetooth Low energy System-on-chip, the nRF52840TMThe low power consumption Bluetooth system level chip adopts 64MHz and 32 bits
CortexTMThe M4F processor has sufficient general processing capability, floating point operation and DSP performance, has a built-in PA, has a transmitting power of +8dBm, a built-in 1MB Flash memory and a 256kB RAM memory, fully supports Bluetooth 5, 802.15.4 (including ThreA/D), ANT and private 2.4GHz wireless technologies, is provided with a full-speed USB 2.0 controller and a series of peripheral devices (a plurality of devices can be supported by easy DMA), comprises a four-channel SPI interface, and meets the requirements of reading, correcting, gain amplification and adjustment of sampling value data of the A/D conversion circuit 200. In addition, the ANT technology using the microprocessor realizes bluetooth communication.
Two channels are arranged in the A/DE7753 chip, the A/DE7753 chip also comprises a channel 2 (namely V2P and V2N), so that a second current value analog signal measured by a standard transformer is obtained by the channel 2, and a channel 1 is compensated systematically according to the second current value analog signal, and the channel 1 is compensated systematically mainly from two aspects of a specific difference and an angular difference.
Discretizing the first current value analog signal and the second current value analog signal to respectively obtain a current sampling value obtained by sampling the rogowski coil 100 and a current sampling value obtained by sampling the standard transformer;
the channel 2 is used for carrying out the ratio difference calculation on the channel 1, and the ratio difference formula is
Wherein e isFIs the angular difference, i1(k) Current sample values for sampling the rogowski coil 100, i2(k) In order to sample the current sample values obtained by the standard transformer, n represents the number of the current sample values, and k is 0, 1, 2 …, n-1.
The angular difference, i.e. the phase difference, is directed to the correlation function, which is based on the principle that two sinusoidal signals of the same frequency have a cross-correlation function whose value at zero time is proportional to the cosine of their phase difference. The derivation of the angular difference equation is as follows, assuming that both channel 1 and channel 2 contain noiseOf a common frequency signal i1(t) and i2(t) a specific expression of
For common frequency signal i1(t) and i2The cross-correlation operation of (t) includes:
from the analysis of expression (9), the last three terms of expression (9) are not related, so they have an integral of zero in the period [0, T ], leaving only the first term. Then, when τ is 0, expression (9) may be changed to
As can be seen from expression (10): the values of the cross-correlation function of two sinusoidal signals of the same frequency at zero time are proportional to the cosine of their phase difference.
For common frequency signal i1(t) and i2(t) performing an autocorrelation operation to obtain
Substituting the expression (12) into the expression (11), discretizing, and obtaining the angular difference
Because the ratio difference compensation is easy, the compensation can be realized only by converting to obtain an effective value and then carrying out corresponding ratio calculation. For angular difference compensation, because the signals acquired by data acquisition are discrete waveforms, and the sampling frequency and the sampling point are different, in order to calculate the angular difference value of the system, the two signals need to be sampled at the same time, and the angular difference value can be calculated through an angular difference calculation function.
In one embodiment, the first current value digital signal is subjected to angular difference compensation by a spline interpolation method according to the angular difference value.
It is understood that classical newton interpolation, FIR digital filters, etc. are currently used when compensating for angular differences. However, since the voltage and current waveforms in the power system are all sine waves and the waveforms are generally smooth, the angular difference compensation is completed by using the spline interpolation method in the embodiment. Compared with other algebraic interpolation methods, spline interpolation has the characteristics of good smoothness, strong approximability and easiness in calculation, and is more suitable for being adopted in the embodiment.
Referring to fig. 5, the main process of compensating channel 1 by using channel 2 includes: the method comprises the steps of firstly restoring a discrete waveform of an original signal (namely the first current value digital signal formed after A/D conversion) into a corresponding analog signal through a spline interpolation method, then sampling the analog signal at the same time point according to a sampling point of a measured signal, calculating the current value and the current difference value at the same time point through an expression (7) and an expression (13) in sequence to obtain the size of a ratio difference and an angle difference, multiplying the measured signal by the ratio difference value, and subtracting the angle difference value, so that the compensation of the ratio difference and the angle difference can be realized.
In addition, an interface directly connected with the rogowski coil 100 sensor is arranged in an a/DE7753 chip in the a/D conversion circuit 200, so that a plurality of external analog circuits are omitted, external interference is reduced, for the specific difference and the angular difference of the gain amplifier, a compensation register specially containing the angular difference and the specific difference is also arranged in the a/DE7753 chip, and a current effective value calculation circuit is arranged at the same time, so that the a/D conversion circuit 200 can directly obtain a current effective value without data calculation in a microprocessor, and the processing speed of the microprocessor is improved.
It can be understood that an operating voltage needs to be provided for the current detection device to enable the current detection device to operate normally, and therefore, in one embodiment, the current measurement device further includes a battery 500, and the a/D conversion circuit 200, the main control circuit 400 and the signal conditioning module can be powered by the battery 500.
It can be understood that, because the whole current measuring device has a small volume, the electric quantity of the battery 500 used is limited, and in order to avoid repeatedly replacing the battery, the energy obtaining module is further utilized in this embodiment to obtain electric energy from the power grid wire to be measured so as to generate working voltage for supplying power. Based on this, as shown in fig. 6, the current measuring apparatus further includes an energy obtaining module 600, and the energy obtaining module 600 includes an energy obtaining transformer 610 and a voltage doubling rectifying circuit 620.
The energy-taking mutual inductor 610 obtains electric energy from the power grid wire to be measured through the energy-taking mutual inductor 610 and generates primary voltage.
The voltage doubling rectifying circuit 620 is electrically connected to the energy-taking transformer 610, and is configured to perform voltage doubling rectifying processing on the primary voltage to generate a working voltage, and provide the working voltage to the a/D conversion circuit 200, the main control circuit 400, and the signal conditioning module.
In this embodiment, the energy obtaining module 600 uses permalloy with high magnetic permeability in a weak magnetic field as a magnetic core, the winding is about 2000 turns, the initial starting current is designed to be 2A, and the output voltage is 3V after voltage doubling rectification and power management. The voltage-doubling rectifying module uses the storage effect of a capacitor on charges to enable the output voltage to be twice of the input voltage, namely, the voltage-doubling rectifying scheme is obtained, IN the embodiment, a rectifying diode adopts IN4148WS, and the capacitor adopts 680 uF. In addition, the coefficient of the voltage-multiplying rectifying module can be adjusted according to actual needs, so that the adjusted output voltage meets the working needs of other modules/circuits.
In one embodiment, the current measuring apparatus further includes a power management module 700, where the power management module 700 is electrically connected to the energy obtaining module 600 and the battery 500 respectively; when the operating voltage increases to a first preset threshold or decreases to a second preset threshold, the power management module 700 controls the battery 500 to provide the operating voltage; otherwise, the power management module 700 controls the energy obtaining module 600 to provide the working voltage.
It is understood that, in order to avoid frequent switching of the power supply mode at a certain voltage, the battery 500 is controlled to provide the operating voltage by the power management module 700 when the operating voltage increases to the high voltage threshold or when the operating voltage decreases to the low voltage threshold. If not, the energy-taking module 600 is used to provide working voltage under other conditions, so as to avoid burning out the circuit due to too large or too small current, prolong the service time of the battery 500 and avoid frequent battery replacement.
In this embodiment, the power management module 700 uses the comparator chip MIC833 with reference potential to design the voltage threshold, i.e. the high voltage threshold VHthIs composed of
Low voltage threshold VLthIs composed of
V in the present exampleHthAnd VLth3.56V and 2.49V, respectively. For example, the voltage output by the current power taking module is 3.5V and is always in a boosting state; when the voltage output by the power-taking module rises to 3.56V, in order to avoid the power-taking module being burned out, the output of the power-taking module is turned off by the power management module 700, and the battery 500 is started to supply power. Similarly, the voltage output by the current power taking module is 2.5V and is always in a voltage reduction state; when the voltage output by the power-taking module rises to 3.56V, in order to avoid the power-taking module being burned out, the output of the power-taking module is turned off by the power management module 700, and the battery 500 is started to supply power.
In this embodiment, the comparator chip MIC833 is used to determine whether to generate an enable signal according to the high voltage threshold and the low voltage threshold, and then control the analog switch TPS2105 to select whether the battery 500 supplies power or the CT power, and then the voltage regulator chip AMS1117 is used to stabilize the output operating voltage at 3V, and the output operating voltage is provided to the microprocessor, the signal conditioning module 300, the a/D conversion circuit 200, and the like.
Based on the same inventive concept, the utility model also provides a power grid monitoring system, power grid monitoring system includes the current measurement device of any one of the above-mentioned embodiments.
The technical features of the embodiments described above may be arbitrarily combined, and for the sake of brevity, all possible combinations of the technical features in the embodiments described above are not described, but should be considered as being within the scope of the present specification as long as there is no contradiction between the combinations of the technical features.
The above-mentioned embodiments only represent some embodiments of the present invention, and the description thereof is specific and detailed, but not to be construed as limiting the scope of the present invention. It should be noted that, for those skilled in the art, without departing from the spirit of the present invention, several variations and modifications can be made, which are within the scope of the present invention. Therefore, the protection scope of the present invention should be subject to the appended claims.
Claims (10)
1. A current measuring device, comprising:
the Rogowski coil is used for acquiring a first current value analog signal of the power grid wire to be measured; and
the A/D conversion circuit is electrically connected with the Rogowski coil and is used for converting the first current value analog signal into a first current value digital signal;
the A/D conversion circuit includes:
a circuit interface;
and the programmable gain amplifier is electrically connected with the Rogowski coil through the circuit interface, determines the maximum input range and the gain according to the current effective value of the first current value analog signal read for the first time, and amplifies the first current value analog signal according to the adjusted gain.
2. The current measurement device of claim 1, wherein the rogowski coil comprises:
the to-be-measured power grid lead penetrates through the center of the non-magnetic annular framework;
and the insulated wire is uniformly wound on the non-magnetic annular framework.
3. The current measurement device of claim 1, further comprising a signal conditioning module comprising a filter circuit and a voltage follower circuit;
the filter circuit and the voltage follower circuit are sequentially connected in series between the Rogowski coil and the A/D conversion circuit, the first current value analog signal is filtered through the filter circuit, harmonic waves in the current value analog signal are filtered, and the filtered first current value analog signal is stably output to the A/D conversion circuit through the voltage follower circuit.
4. The current measurement device of claim 1, wherein the a/D conversion circuit comprises an a/DE7753 chip.
5. The current measurement device of claim 1, further comprising:
the standard mutual inductor is electrically connected with the A/D conversion circuit and used for acquiring a second current value analog signal of the power grid wire to be measured and converting the second current value analog signal into a second current value digital signal through the A/D conversion circuit;
and the main control circuit is electrically connected with the A/D conversion circuit and is used for determining a ratio difference value and an angle difference value between the second current value digital signal and the first current value digital signal, performing ratio difference compensation on the first current value digital signal according to the ratio difference value and performing angle difference compensation on the first current value digital signal according to the angle difference value.
6. The current measuring device of claim 5, further comprising a wireless transmission module electrically connected to the main control circuit for transmitting the compensated first current value digital signal.
7. The current measurement device of claim 5, further comprising an energy-harvesting module, the energy-harvesting module comprising:
the energy taking mutual inductor is used for obtaining electric energy from the power grid wire to be measured and generating a primary voltage;
and the voltage doubling rectifying circuit is electrically connected with the energy taking mutual inductor and is used for performing voltage doubling rectifying treatment on the primary voltage to generate working voltage and supplying the working voltage to the A/D conversion circuit, the main control circuit and the signal conditioning module.
8. The current measuring device of claim 7, further comprising a battery to provide operating voltages to the A/D conversion circuit, the master control circuit, and the signal conditioning module when the energy-harvesting module is unable to provide operating voltages properly.
9. The current measuring device of claim 8, further comprising a power management module electrically connected to the energy-harvesting module and the battery, respectively;
when the working voltage is increased to a first preset threshold value or reduced to a second preset threshold value, the power supply management module controls the battery to provide the working voltage; otherwise, the power management module controls the energy taking module to provide working voltage.
10. A grid monitoring system comprising a current measuring device according to any one of claims 1 to 9.
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| CN114325060A (en) * | 2022-01-11 | 2022-04-12 | 平高集团智能电力科技有限公司 | Current sensor system |
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