CN113759163B - Low-power-consumption current transformer and control method - Google Patents
Low-power-consumption current transformer and control method Download PDFInfo
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- G—PHYSICS
- G01—MEASURING; TESTING
- G01R—MEASURING ELECTRIC VARIABLES; MEASURING MAGNETIC VARIABLES
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Abstract
The invention discloses a low-power consumption current transformer and a control method, wherein an energy storage capacitor and a super capacitor in the low-power consumption current transformer are connected in parallel and are respectively connected with a control unit through a DCDC (direct current to direct current) converter, the control unit is in communication connection with a temperature measurement unit and a communication unit, and an acquisition unit is used for switching between sampling and power supply states according to a control signal output by the control unit in a time-sharing manner; the energy storage capacitor is used for storing energy in the power supply stage of the current transformer and supplying power for the control unit in the sampling stage; the super capacitor is used for storing redundant electric energy and supplying power for the control unit when no current exists on the primary side; the DCDC converter is used for converting the output voltage of the energy storage capacitor or the super capacitor into a voltage which can supply power for the control unit and realize the starting of the control unit; the control unit is used for collecting sampling signals and temperature signals of the transformer. The invention integrates the functions of power control, signal acquisition and wireless transmission, and can safely and rapidly finish site construction by combining the edge gateway of the receiving end.
Description
Technical Field
The invention relates to the technical field of power grids, in particular to a low-power-consumption current transformer and a control method.
Background
At present, a power distribution network has a large number of circuits and metering points, electric quantity index monitoring is required to be completed, a single-function measuring sensor of a current transformer is generally adopted for monitoring, an acquired current signal is transmitted to a metering chip at the rear end, a traditional acquisition system relies on a rechargeable battery with a limit of charge and discharge service life or a disposable lithium battery with a limit of capacity to provide starting current and working current, and the problem that the power supply is not provided for the metering chip at the rear end while the current signal is transmitted can not be achieved, so that when the battery fails or the battery quality is problematic, the problem occurs after a period of on-site installation and operation, and the battery is replaced at the moment, so that the problem that the continuous operation is inconvenient and the high maintenance cost and the problem that the user experience is poor are brought.
In addition, in the current DCDC converter design, under the condition that the power supply power is limited, the output voltage slowly rises, the DCDC converter starts to work, the DCDC converter stops working immediately after the voltage drops due to the fact that the power supply output current becomes large, at the moment, the back-end control unit MCU is powered down because the power supply time is too short and low-power consumption processing is not completed yet, then the power supply voltage starts to rise again, and a new round of operation is started again: the DCDC converter operates-the power supply output current increases-the power supply voltage drops-the DCDC converter stops operating-the power supply voltage rises-the dead cycle.
Disclosure of Invention
In order to solve the technical problems, the invention provides a low-power-consumption current transformer and a control method.
In order to achieve the above purpose, the technical scheme of the invention is as follows:
The low-power consumption current transformer comprises an acquisition unit, an energy storage capacitor, a super capacitor, a DCDC converter, a control unit, a temperature measurement unit and a communication unit, wherein the energy storage capacitor and the super capacitor are connected in parallel and are respectively connected with the control unit through the DCDC converter, the control unit is in communication connection with the temperature measurement unit and the communication unit,
The acquisition unit is connected with the power supply circuit and is used for switching between sampling and power supply states according to the control signal output by the control unit in a time-sharing way, the sampling stage is used for acquiring a current signal of the power supply circuit and sending the current signal to the control unit, and the power supply state is used for charging the energy storage capacitor or charging the super capacitor after calculation and control by the control unit;
the energy storage capacitor is used for storing energy in the power supply stage of the current transformer and supplying power for the control unit in the sampling stage;
The super capacitor is used for switching to the three states of disconnection, charging and discharging according to the current condition of the primary side calculated by the control unit, storing redundant electric energy and supplying power to the control unit when no current exists on the primary side;
the DCDC converter is used for converting the output voltage of the energy storage capacitor or the super capacitor into a voltage which can supply power for the control unit and realize the starting of the control unit;
the control unit is used for collecting the sampling signals of the mutual inductor and the temperature signals output by the temperature measuring unit and analyzing and processing the signals;
The temperature measuring unit is used for detecting the temperature of the primary side power supply circuit and outputting the temperature to the control unit;
the communication unit is used for realizing the communication between the control unit and the collector.
Preferably, the acquisition unit comprises a current transformer, a clamping circuit, a current doubler rectifying circuit and a sampling resistor switching circuit, wherein the secondary side signal output end of the current transformer is connected with the signal input end of the clamping circuit, the circuit signal output end of the clamping circuit is connected with the circuit signal input end of the current doubler rectifying circuit, the circuit signal output end of the current doubler rectifying circuit is connected with an energy storage capacitor, the sampling resistor switching circuit is connected between the clamping circuit and the current doubler rectifying circuit, the sampling signal output end of the sampling resistor switching circuit is connected to a control unit, the control unit outputs a control signal to the control signal input end of the sampling resistor switching circuit,
The current transformer is connected with the power supply circuit and is used for outputting alternating current signals through electromagnetic induction;
the clamping circuit is used for clamping the amplitude of an alternating current signal output by the current transformer to a reasonable voltage;
The current doubling rectifying circuit is used for charging the negative half-period current waveform of the alternating current signal output by the clamping circuit through a capacitor on the basis of the traditional half-wave rectification common ground, and outputting a current larger than the half-wave rectification after the positive half-period current is overlapped with the positive half-period current to charge the energy storage capacitor or the super capacitor;
The sampling resistor switching circuit is used for receiving the control signal output by the control unit to control the sampling resistor time-sharing access circuit so as to realize the switching of the transformer between the sampling state and the power supply state; for outputting the sampling signal to the control unit.
Preferably, the DCDC converter includes resistors R1, R2 and R3, the resistors R1 and R2 are connected in series between the signal input terminal of the DCDC converter and the ground, and the enable terminal is coupled between the resistors R1 and R2 and connected to the voltage output terminal of the DCDC converter via the resistor R3.
Preferably, the sampling resistor switching circuit includes a sampling resistor R6, a resistor R5, two MOS transistors Q5 and Q6, two control signal input ends sw_ir_h and sw_ir_l, and a sampling signal output end i_sig, where the control signal input ends sw_ir_h and sw_ir_l are respectively connected to gates of the MOS transistors Q5 and Q6, a drain electrode of the MOS transistor Q5 is connected to a drain electrode of the Q6, sw_ir_h is connected to a source electrode of the Q5 via the resistor R5, the sampling resistor R6 is connected to a source electrode of the Q6, R6 is connected between a signal output end of the clamping circuit and a ground line via Q5 and Q6, the sampling signal output end i_sig is coupled between R6 and Q6, and the control signal input ends sw_ir_h and sw_ir_l are both connected to a time-sharing control signal output end of the control unit.
Preferably, the communication unit comprises a Lora or RF wireless communication module.
A control method of a low-power consumption current transformer comprises the following steps:
The sampling resistor R6 is controlled to be connected into a circuit of the secondary side of the current transformer in a time sharing mode according to the control signal output by the control unit so as to realize the switching of the current transformer between sampling and power supply states, and the current transformer is used for collecting current information of the primary side power supply circuit and sending the current information to the sampling unit when the current transformer is in a sampling stage; when the current transformer is in a power supply state, the current transformer is used for charging an energy storage capacitor or a super capacitor;
when the voltage of Vct rises and Vct is larger than Venh (R1+R3|R2)/(R3|R2), the enabling end of the DCDC converter is controlled to be opened, and the output voltage of the energy storage capacitor or the super capacitor is converted into a voltage which can supply power to the control unit and realize the starting of the control unit; when the voltage of Vct is reduced and Vct < [ Venl/R2- (Vo-Venl)/R3 ]. Times.R1+ Venl ], the enable end of the DCDC converter is controlled to be closed,
Wherein Vct is output voltage of the current transformer after rectification and filtration of the current transformer, venh is the start voltage of the EN pin of the DCDC chip, venl is the stop voltage of the EN pin of the DCDC chip, R1, R2 and R3 are resistors, and Vo is the output voltage of the DCDC converter.
Preferably, the method further comprises the following steps: and in the synchronous time period, taking zero crossing points or peak values or valley values of alternating current signals as references, calculating sampling resistor access time points by combining the power grid frequency and the current of the last time, and controlling the sampling resistor to be accessed into a circuit of the secondary side of the current transformer at the corresponding access time points.
Preferably, the current transformer is switched between sampling and power supply states, and specifically comprises the following steps:
when Q1+Q2> Q3, the current transformer is switched to an acquisition state;
When (q1+q2) ×p4×ηq4, the current transformer is switched to a power supply state, where Q1 is the energy remaining in the previous stage, Q2 is the energy obtained by charging in the present stage, Q3 is the capacity of the energy storage capacitor, P4 is the margin of the energy storage capacitor, Q4 is the energy consumed by the system in the present stage, and η is the efficiency.
Preferably, the method further comprises the following steps:
The control unit receives the temperature information of the power supply circuit and the current information of the primary side power supply circuit of the current transformer, which are acquired by the temperature measurement unit, and wirelessly transmits the temperature information and the current information to the acquisition unit;
And the collector receives the temperature and current information and uploads the temperature and current information to the cloud, the cloud judges whether the temperature and the current exceed a preset threshold value, and if so, the cloud sends alarm information to related personnel.
Preferably, the method further comprises the following steps: the control unit starts the temperature measurement unit according to the fact that the primary side current is larger than a set value, and the set value can be distributed to the low-power-consumption current transformer through the collector after being configured through the cloud.
Based on the technical scheme, the invention has the beneficial effects that: according to the invention, the starting process is completed through hardware and software starting algorithm from complete power failure to work of the wireless transmitting system by virtue of the current obtained by the transformer from the primary side induction, the starting operation is completely independent of the stored electric energy of the energy storage capacitor or the super capacitor, the minimum starting current performance after long-term operation is consistent with that of factory delivery, the power consumption requirement of sensor intermittent can be met when the current of the primary side of the current transformer is more than or equal to 0.5A, the overall performance is stable, the battery is not required to be replaced, and the service life is long.
Drawings
The following describes the embodiments of the present invention in further detail with reference to the drawings.
FIG. 1 is a schematic diagram of a low power consumption current transformer according to an embodiment, wherein M1 is a clamping circuit; m2 is a current doubler rectifying circuit; m3 is an energy storage capacitor; m4 is a DCDC converter; m5 is a sampling resistor switching circuit; m6 is a control unit; m7 is a temperature measurement unit; m8 is a communication unit; m9 is a super capacitor;
FIG. 2 is a circuit diagram of a current doubler rectifier in a low power current transformer in one embodiment;
FIG. 3 is a circuit diagram of a DCDC converter in a low power current transformer;
FIG. 4 is a circuit diagram of a sampling resistor switching in a low power current transformer in one embodiment;
FIG. 5 is a prior art circuit diagram of a DCDC converter;
FIG. 6 is a circuit diagram of a DCDC converter in a low power current transformer in one embodiment;
fig. 7 is a schematic diagram illustrating an operating state of a low power consumption current transformer according to an embodiment.
Detailed Description
In order to more clearly illustrate the present invention, the present invention will be further described with reference to preferred embodiments. It is to be understood by persons skilled in the art that the following detailed description is illustrative and not restrictive, and that this invention is not limited to the details given herein.
In the description of the present invention, it should be noted that, unless explicitly specified and limited otherwise, the terms "mounted," "connected," and "connected" are to be construed broadly, and may be either fixedly connected, detachably connected, or integrally connected, for example; can be directly connected or indirectly connected through an intermediate medium, and can be communication between two elements. The specific meaning of the above terms in the present invention will be understood in specific cases by those of ordinary skill in the art.
As shown in figure 1, the invention provides an open-close type wireless transformer which is installed on site quickly without breaking the insulation skin or leading-out wires. The inside has mixed current signal acquisition and current signal and got the electric function, integrated power control, signal acquisition, wireless emission function, the border gateway that combines the receiving terminal can safe quick accomplish site operation, specifically include control unit M6, current transformer CT, clamp circuit M1, doubly current rectifying circuit M2, sampling resistor switching circuit M5, energy storage capacitor M3, super capacitor M9, DCDC converter M4, temperature measurement unit M7 and communication unit M8, wherein, current transformer secondary side signal output part is connected clamp circuit's signal input part, clamp circuit's circuit signal output part is connected doubly current rectifying circuit's circuit signal input part, doubly current rectifying circuit's circuit signal output part is connected energy storage capacitor, sampling resistor switching circuit inserts between clamp circuit and the doubly current rectifying circuit, sampling resistor switching circuit sampling signal output part is connected to the control unit, control unit output control signal is to sampling resistor switching circuit's control signal input part, and energy storage capacitor and super capacitor are parallelly connected, and are connected with control unit through DCDC converter respectively, control unit communication connection temperature and communication unit are described below specifically to measure the unit.
In this embodiment, the current transformer CT is connected to the power supply circuit, and is switched between a sampling state and a power supply state according to a control signal output by the control unit in a time-sharing manner, where the sampling stage is used to collect a current signal of the power supply circuit and send the current signal to the control unit, and the power supply state is used to charge the energy storage capacitor or the super capacitor.
In this embodiment, the front end clamping circuit M1 clamps the amplitude of the output signal of the transformer to a reasonable voltage, so as to prevent the voltage from exceeding the withstand voltage value of the rear end device too high. And clamping to the optimal voltage between contradictions of large volume capacity and low withstand voltage of the same volume capacity of the rear-end energy storage capacitor.
In this embodiment, the double-current rectifying circuit M2 is a double-current rectifying circuit, and three-voltage and multiple-current rectifying circuits can be selected according to actual requirements. As shown in fig. 2, in the case of ensuring that the transformer output signal and the back-end sampling circuit are grounded together, the charge of the negative half cycle of the transformer signal is stored by using a capacitor and a diode, and is superimposed into the current of the positive half cycle after being conducted through a triode in the positive half cycle. The defect that the conventional full-bridge rectification does not commonly use the ground and half-wave rectification wastes negative half-cycle current is overcome.
In this embodiment, the energy storage capacitor M3 is used for storing energy in the power supply stage of the current transformer and supplying power to the control unit in the sampling stage, the capacity of the energy storage capacitor M3 is constrained by the calculation of the eight stages of the current transformer, and the withstand voltage is selected according to the Vct voltage, so that the power supply of the rear load can be ensured, and the problems of long sensor starting time and large required primary side starting current caused by large capacity of the capacitor are avoided. Meanwhile, the structural member is small in size, and the requirement of wiring intensive sites on small size of the installed sensor is met.
As shown in fig. 3, the DCDC converter M4 with ultra-low static power consumption in the present embodiment includes resistors R1, R2 and R3, the resistors R1 and R2 are connected in series between the signal input terminal and the ground of the DCDC converter, and the enable terminal is coupled between the resistors R1 and R2 and connected to the signal output terminal of the DCDC converter through the resistor R3. The ultra-low quiescent current reduces losses to the limited output current of the transformer and improves energy conversion efficiency at the uA level of output current. The power supply requirement of the whole circuit at a primary side current of 0.5A can be achieved.
The energy conversion efficiency equation of the DCDC converter is:
Vct*Ict*η＝Vo*Io，
the ratio of output to input current is obtained after deformation:
Io/Ict＝(Vct/Vo)*η，
Wherein Ict is the output current of the transformer after M2 rectification and filtration; vct is the output voltage of the transformer after M2 rectification and filtration; η is the overall conversion efficiency of M4; vo is the output voltage of M4; io is the output current of M4, it can be seen that when the back-end circuit operating voltage is met, a Vo voltage as small as possible is selected, and a larger output current can be obtained than the conventional 3.3V output voltage. The ratio of the Io/Ict current can reach about 2 by matching with high enough efficiency eta. That means that a current of about 2mA at a low voltage can be outputted through M4 when 1mA is obtained from the transformer side.
Initially the DCDC converter is turned off, the Vo output is 0V, and resistor R3 corresponds to a pull-down resistor r3|r2 in parallel with R2. Let Venh be the DCDC chip EN pin on voltage and Venl be the DCDC chip EN pin off voltage.
When the voltage of the Vct rises, starting the output of the DCDC converter when Vct is (R3|R2)/(R1+R3|R2) > Venh, and converting to obtain the voltage Vct > Venh (R1+R3|R2)/(R3|R2) when the DCDC chip is started;
After the DCDC converter outputs the voltage, resistor R3 becomes a resistor that is pulled up to Vo. Calculated according to kirchhoff's current law:
(Vct-Venl)/R1+(Vo-Venl)/R3＝Venl/R2
Converting to obtain the voltage Vct < [ Venl/R2- (Vo-Venl)/R3 ]. Times.R1+ Venl when the DCDC chip is closed; the voltage at which the DCDC is turned off after Vct decreases can be made much smaller than the voltage at which the DCDC is turned on when Vct increases by selecting an appropriate resistance value. The larger voltage hysteresis interval enables the back-end control unit MCU to have enough time to finish low-power consumption processing so that the output current is reduced to a plurality of uA, the Ict current is correspondingly reduced after the output current is reduced, and the Vct voltage starts to rise. This prevents the occurrence of a constant restart.
Venh was set to 1V and Venl was set to 0.6V. When R3 is not added, the DCDC converter is started only by setting the starting voltage to 4.4V according to R1 and R2, such as the following resistor values:
as shown in fig. 5, the voltage dividing resistor connection of the conventional EN pin:
The DCDC is enabled when Vct is calculated to rise to 4.38V, and is disabled when Vct voltage drops to 2.63V after the enablement.
Instead, the voltage dividing resistor connection method of the present invention is as shown in fig. 6:
The DCDC is started when Vct is calculated to rise to 4.4V, and is turned off when Vct voltage drops to 1.9V after start.
This can be achieved by: the invention can obtain smaller Vct falling closing value when the same Vct rising starting value.
As shown in fig. 4, the sampling resistor switching circuit M5 in this embodiment includes a sampling resistor R6, a resistor R5, two MOS transistors Q5 and Q6, two control signal input ends sw_ir_h and sw_ir_l, and a sampling signal output end i_sig, where the control signal input ends sw_ir_h and sw_ir_l are respectively connected to gates of the MOS transistors Q5 and Q6, a drain electrode of the MOS transistor Q5 is connected to a drain electrode of the Q6, sw_ir_h is connected to a source electrode of the Q5 through the resistor R5, R6 is connected to a source electrode of the Q6, R6 is connected between a signal output end of the clamping circuit and a ground line through the Q5 and Q6, the sampling signal output end i_sig is coupled between the R6 and Q6, and the control signal input ends sw_ir_h and sw_ir_l are both connected to time-sharing control signal output ends of the control unit. The control signal output by the MCU in a time-sharing way controls the time-sharing multiplexing function of sampling and supplying power of the same transformer.
When the sampling resistor switching circuit M5 is used for sampling, the MOS transistors Q5 and Q6 are conducted, and the sampling resistor R6 is connected to the output end of the transformer. Voltage signal output by i_sig=primary side current/turns ratio R6.
When the sampling resistor switching circuit M5 is used for supplying power, the MOS transistors Q5 and Q6 are closed, and the mutual inductor signal directly enters the M2 to supply power to the back-end circuit.
According to the invention, the sampling resistor R6 is disconnected by default, the transformer outputs a signal to supply power to the control unit MCU, and when the control unit MCU completes low-power consumption processing, sampling and power supply are controlled by dynamically dividing a plurality of time periods, as shown in FIG. 7, the primary side current is I1, the turns ratio n of the transformer, the capacity of the energy storage capacitor M3 is at most 0.8 and is used for power supply (remaining margin), and the control unit MCU is powered on for low-power consumption initialization time Tmi. After the initialization is completed, the control unit MCU current is reduced to I LP. The main operation of the current transformer is divided into eight stages:
1. Power-on low-power consumption initialization phase T0:
(I1/n)*T0*0.8*Vct*η>(Vo*Io*Tmi+Vo*ILP*(T0-Tmi))；
2. The 1 st energy storage stage T1: the energy charged in the time of +T1 except the energy consumed by the control unit MCU in the power-on initialization stage is larger than the capacity Q3 of the energy storage capacitor M3 (at most Q3 is actually reached, the design of the formula larger than Q3 ensures that M3 can be fully charged, the redundant electric energy can be consumed through M1 clamping,
(I1/n)*T0*Vct*η-(Vo*Io*Tmi+Vo*ILP*(T0-Tmi))+(I1/n)*T1-Vo*ILP*T1/η>Q3；
3. Zero crossing synchronization and current temperature acquisition processing stage T2: the control unit MCU + peripheral accumulated consumption current I2,
(Q3+(I1/n)*T2)*0.8*Vct*η>Vo*I2*T2；
4. The 2 nd energy storage stage T3 is that the redundant electric energy in the last stage and the charging capacitor in the stage are larger than the capacity Q3 of the energy storage capacitor M3,
(Q3+(I1/n)*T2)*Vct*η-Vo*I2*T2+(I1/n)*T3*Vct*η>Q3；
5. RF communication phase T4: the control unit MCU in the RF communication stage and the peripheral accumulated consumption current I4,
(Q3+(I1/n)*T4)*0.8*Vct*η>Vo*I4*T4；
6. 3 Rd energy storage phase T5:
(Q3+(I1/n)*T4)*Vct*η-Vo*I4*T4+(I1/n)*T5*Vct*η>Q3；
7. super capacitor charging phase T6: m3 is already fully charged, at which time excess power is dissipated to the supercapacitor M9 (capacity Q9) rather than clamped by M1,
(I1/n)*Vct*T6＝Q9*T6；
8. The super capacitor power supply stage TL is utilized when the primary side is not provided with current: the super capacitor is used for supplying power when no current exists at the primary side, at the moment, Q9 provides current for the control unit MCU in low-power-consumption operation,
Q9*TL*0.8*η-Vo*ILP*TL>0。
In summary, when q1+q2> Q3, the current transformer is switched to the collection state;
when (Q1 +Q 2) P4 eta > Q4, the current transformer is switched to a power supply state,
Wherein, Q1 is the energy remained in the previous stage, Q2 is the energy obtained by charging in the present stage, Q3 is the capacity of the energy storage capacitor, P4 is the allowance of the energy storage capacitor, Q4 is the energy consumed by the system in the present stage, and eta is the efficiency.
The invention can flexibly combine each stage according to the primary side current. After one of the operating mode oscilloscope tests is started, the latter process loops between T1 and T4. The circulation flow is as follows:
T0->T1->T2->T3->T4->T1->T2->T1->T2->T1->T2->T3->T4->T5->T6->T1->T2->T1->T2->T1->T2->T3->T4->T5->T6……->T1->T2->T3->T4->T1->T2->T3->T4……
When the primary side has no current and later has current, the flow is as follows:
TL->T4->TL->T4……->T0->T1->T2->T3->T4……
The invention can increase the number of times of adoption according to the magnitude of the primary side current, shorten the energy storage time to achieve the purpose of increasing the current temperature sampling times in one RF emission period so as to improve the measurement accuracy. For example, when the collected current is relatively large (for example, when the primary side current is more than 20A), 3 times of data can be collected in one RF emission period, and 1 time of super capacitor charging is started. And after a period of acquisition, the current becomes small, the sampling times in the period are reduced, and the super capacitor is stopped from being charged.
The system can complete data acquisition and wireless transmission functions when the primary side input current is lower through designing different energy storage and discharge time periods, the length of each time period can be dynamically adjusted according to the size of the primary side input current, the wireless transmission period, the data sampling frequency and the accuracy can be balanced, and the system can be normally started to acquire transmission data when the primary side current is extremely low (less than 0.5A) by adopting a multi-section working algorithm.
The invention designs a sampling resistor access time point algorithm which is calculated by judging the zero crossing point of an alternating current signal as a reference in a synchronous time period and combining the power grid frequency and the current of the last time. A suitable access point can avoid the problem of waveform imbalance after access. The algorithm reduces the distortion degree of the alternating current signal when the sampling resistor is connected, and improves the sampling precision of the current signal when the sampling resistor is dynamically switched on and off.
The control unit M6 in this embodiment employs a high energy efficiency ratio control unit MCU supporting a low operating voltage. The control unit MCU is combined to flexibly switch the high-frequency clock and the low-frequency clock, and the low-power consumption wake-up and the rapid switching working state characteristics obtain good low-power consumption effects.
In this example, the temperature measuring unit M7 is started and closed by controlling the power supply to the temperature sensor, and when the power supply of the temperature measuring unit is turned off, the current consumption of the measuring unit is saved, so that the system power consumption is reduced. When the primary side wire heats due to large contact resistance or overload, the system can give an alarm in time, so that the loss is reduced.
In this embodiment, the communication unit M8 adopts a Lora wireless communication module with high sensitivity, adjustable transmitting power and adjustable air communication baud rate. The equivalent working power consumption of M8 is: working power data volume/communication rate. Under the condition of a certain amount of transmitted data, the transmitting power is high, the consumption current is high, the communication distance is long, the communication speed is high, the communication time is short, the power is saved, and the communication distance is short.
And under the condition that the primary side current is judged to have redundant electric energy after meeting the requirements of each working stage of the system, the redundant electric energy is stored in the super capacitor M9. When there is no current at all at the primary side, the current transformer CT is already unable to supply any current. At this time, the super capacitor provides the MCU sleep current and RF transmitting heartbeat signal to inform the edge acquisition terminal. And the wireless transformer starts a new round of energy storage acquisition and emission process when the current exists on the primary side. Compared with the traditional disposable lithium battery and rechargeable battery, the super capacitor has the advantages of long service life and small volume.
The foregoing is merely a preferred embodiment of a low-power consumption current transformer disclosed in the present invention, and is not intended to limit the protection scope of the embodiments of the present disclosure. Any modification, equivalent replacement, improvement, or the like made within the spirit and principles of the embodiments of the present specification should be included in the protection scope of the embodiments of the present specification.
It should also be noted that the terms "comprises," "comprising," or any other variation thereof, are intended to cover a non-exclusive inclusion, such that a process, method, article, or apparatus that comprises a list of elements does not include only those elements but may include other elements not expressly listed or inherent to such process, method, article, or apparatus. Without further limitation, an element defined by the phrase "comprising one … …" does not exclude the presence of other like elements in a process, method, article or apparatus that comprises the element.
In this specification, each embodiment is described in a progressive manner, and identical and similar parts of each embodiment are all referred to each other, and each embodiment mainly describes differences from other embodiments. In particular, for system embodiments, since they are substantially similar to method embodiments, the description is relatively simple, as relevant to see a section of the description of method embodiments.
Claims (7)
1. The low-power consumption current transformer is characterized by comprising an acquisition unit, an energy storage capacitor, a super capacitor, a DCDC converter, a control unit, a temperature measurement unit and a communication unit, wherein the energy storage capacitor and the super capacitor are connected in parallel and are respectively connected with the control unit through the DCDC converter, the control unit is in communication connection with the temperature measurement unit and the communication unit,
The acquisition unit comprises a current transformer, a clamping circuit, a current doubler rectifying circuit and a sampling resistor switching circuit, wherein a secondary side signal output end of the current transformer is connected with a signal input end of the clamping circuit, a circuit signal output end of the clamping circuit is connected with a circuit signal input end of the current doubler rectifying circuit, a circuit signal output end of the current doubler rectifying circuit is connected with an energy storage capacitor, the sampling resistor switching circuit is connected between the clamping circuit and the current doubler rectifying circuit, a sampling signal output end of the sampling resistor switching circuit is connected to a control unit, and the control unit outputs a control signal to a control signal input end of the sampling resistor switching circuit, wherein the current transformer is connected with a power supply circuit and is used for outputting alternating current signals through electromagnetic induction; the clamping circuit is used for clamping the amplitude of an alternating current signal output by the current transformer to a reasonable voltage; the current doubling rectifying circuit is used for charging the negative half-period current waveform of the alternating current signal output by the clamping circuit through a capacitor on the basis of the traditional half-wave rectification common ground, and outputting a current larger than the half-wave rectification after the positive half-period current is overlapped with the positive half-period current to charge the energy storage capacitor or the super capacitor; the sampling resistor switching circuit comprises a sampling resistor R6, a resistor R5, two MOS tubes Q5 and Q6, two control signal input ends SW_IR_H and SW_IR_L and a sampling signal output end I_SIG, wherein the control signal input ends SW_IR_H and SW_IR_L are respectively connected with grids of the MOS tubes Q5 and Q6, a drain electrode of the MOS tube Q5 is connected with a drain electrode of the Q6, the SW_IR_H is connected with a source electrode of the Q5 through the resistor R5, the sampling resistor R6 is connected with a source electrode of the Q6, R6 is connected between a signal output end of a clamping circuit and a ground wire through the Q5 and Q6, the sampling signal output ends I_SIG are coupled between the R6 and the Q6, and the control signal input ends SW_IR_H and SW_IR_L are both connected with a time-sharing control signal output end of a control unit and are used for receiving control signals output by the control unit to control the sampling resistor time-sharing access circuit so as to realize the switching of the transformer between sampling states and power supply states; for outputting the sampling signal to the control unit;
the energy storage capacitor is used for storing energy in the power supply stage of the current transformer and supplying power for the control unit in the sampling stage;
The super capacitor is used for switching to the three states of disconnection, charging and discharging according to the current condition of the primary side calculated by the control unit, storing redundant electric energy and supplying power to the control unit when no current exists on the primary side;
The DCDC converter comprises resistors R1, R2 and R3, wherein the resistors R1 and R2 are connected in series between a signal input end and a ground wire of the DCDC converter, an enabling end is coupled between the resistors R1 and R2 and is connected to a voltage output end of the DCDC converter through the resistor R3, and the voltage output end is used for converting an energy storage capacitor or super capacitor output voltage into a voltage which can supply power for a control unit and realize starting of the control unit;
the control unit is used for collecting the sampling signals of the mutual inductor and the temperature signals output by the temperature measuring unit and analyzing and processing the signals;
The temperature measuring unit is used for detecting the temperature of the primary side power supply circuit and outputting the temperature to the control unit;
the communication unit is used for realizing the communication between the control unit and the collector.
2. The low power consumption current transformer of claim 1, wherein the communication unit comprises a Lora or RF wireless communication module.
3. The control method for the low-power consumption current transformer according to claim 1 or 2, comprising the following steps:
The sampling resistor R6 is controlled to be connected into a circuit of the secondary side of the current transformer in a time sharing mode according to the control signal output by the control unit so as to realize the switching of the current transformer between sampling and power supply states, and the current transformer is used for collecting current information of the primary side power supply circuit and sending the current information to the sampling unit when the current transformer is in a sampling stage; when the current transformer is in a power supply state, the current transformer is used for charging an energy storage capacitor or a super capacitor;
when the voltage of Vct rises and Vct is larger than Venh (R1+R3|R2)/(R3|R2), the enabling end of the DCDC converter is controlled to be opened, and the output voltage of the energy storage capacitor or the super capacitor is converted into a voltage which can supply power to the control unit and realize the starting of the control unit; when the voltage of Vct is reduced and Vct < [ Venl/R2- (Vo-Venl)/R3 ]. Times.R1+ Venl ], the enable end of the DCDC converter is controlled to be closed,
Wherein Vct is output voltage of the current transformer after rectification and filtration of the current transformer, venh is the start voltage of the EN pin of the DCDC chip, venl is the stop voltage of the EN pin of the DCDC chip, R1, R2 and R3 are resistors, and Vo is the output voltage of the DCDC converter.
4. A control method of a low power consumption current transformer according to claim 3, further comprising the steps of:
And in the synchronous time period, taking zero crossing points or peak values or valley values of alternating current signals as references, calculating sampling resistor access time points by combining the power grid frequency and the current of the last time, and controlling the sampling resistor to be accessed into a circuit of the secondary side of the current transformer at the corresponding access time points.
5. A method of controlling a low power current transformer according to claim 3, wherein the current transformer is switched between a sampling and a power supply state, comprising the steps of:
when Q1+Q2> Q3, the current transformer is switched to an acquisition state;
When (Q1 +Q 2) P4 eta > Q4, the current transformer is switched to a power supply state,
Wherein, Q1 is the energy remained in the previous stage, Q2 is the energy obtained by charging in the present stage, Q3 is the capacity of the energy storage capacitor, P4 is the allowance of the energy storage capacitor, Q4 is the energy consumed by the system in the present stage, and eta is the efficiency.
6. A control method of a low power consumption current transformer according to claim 3, further comprising the steps of:
The control unit receives the temperature information of the power supply circuit and the current information of the primary side power supply circuit of the current transformer, which are acquired by the temperature measurement unit, and wirelessly transmits the temperature information and the current information to the acquisition unit;
And the collector receives the temperature and current information and uploads the temperature and current information to the cloud, the cloud judges whether the temperature and the current exceed a preset threshold value, and if so, the cloud sends alarm information to related personnel.
7. The method for controlling a low power consumption current transformer according to claim 6, further comprising the steps of:
the control unit starts the temperature measurement unit according to the fact that the primary side current is larger than a set value, and the set value can be distributed to the low-power-consumption current transformer through the collector after being configured through the cloud.
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