CN209264817U - Passive wireless current sensor based on double-winding current transformer - Google Patents

Abstract

A passive wireless current sensor based on a double-winding current transformer, including a double-winding current transformer, a mutual inductance energy acquisition module, an energy storage module, a current sensing module, a signal processing module, and a wireless transmission module. The double-winding current transformer includes One primary side winding connected with the tested line and two secondary side windings, the two secondary side windings are respectively connected with the mutual inductance energy picking module and the current sensing module. The utility model can be applied to an electric energy monitoring system of a smart grid, without an external power supply system to provide energy, and only uses one transformer for energy collection and current sensing, which reduces the volume of the system and facilitates installation. The utility model can carry out maximum power tracking according to the current measured by the sensing module, greatly improves the power output of the energy harvesting module, reduces the starting current of the system, thereby improving the reliability of the sensor and expanding the application range.

Description

Passive wireless current sensor based on double-winding current transformer

technical field

The utility model relates to the technical field of electric power facilities, in particular to a passive wireless current sensor based on a double-winding current transformer.

Background technique

In the power monitoring and management system, due to the measurement failure of the meter itself, the illegal modification and detour of the meter by the user end, the aging line loss of the power supply equipment, etc., the line loss will occur. At present, the means of identifying the cause of the line loss mainly rely on manual on-site investigation and analysis. , low work efficiency and high labor costs. The smart grid implements online real-time monitoring of the transmission circuit, which has high monitoring efficiency, saves time and effort, and is of great significance to the safety and stability of the power system. In the prior art, the current sensors on the smart grid mostly use passive wireless current sensor products based on current transformers, and their input terminals are connected with energy harvesting transformer L1 and current harvesting transformer L2, which are used for AC energy collection and Current intensity collection. In the energy collection part, the energy collected by the transformer will charge the battery or supercapacitor through the level conversion power management unit, and output a stable DC working voltage through the DC-DC conversion module. In the signal acquisition part, a precision voltage signal amplification circuit is usually used to amplify the weak current signal, and connected to the ADC module of the single-chip microcomputer to obtain digital quantities, and finally the collected digital signals are sent to the remote monitoring system through the wireless module in the system ( Please refer to Figure 1). This passive wireless current sensor product based on current transformers has the following problems: 1. Using two transformers to collect current signals and energy respectively increases the volume of the transformer, which is not conducive to the miniaturization of monitoring equipment ;2. As the voltage of the charging capacitor/battery changes, there will be a maximum power point in the output power of the current transformer, and this power point will change with the current on one side. This product cannot achieve maximum power tracking. Thus, the maximum energy harvesting efficiency cannot be realized.

Contents of the invention

The technical problem solved by the utility model is to provide a passive wireless current sensor based on a double-winding current transformer. The sensor can be applied to the smart grid power monitoring system, used as a calibration device and an inspection table for the power grid line metering device, to analyze the line loss of the distribution line, find the cause of the line loss, and realize more intelligent power management; The sensor does not need an external power supply system to provide energy, and only uses one transformer for energy harvesting and current sensing, which reduces the size of the system and facilitates installation; the sensor energy acquisition module can perform maximum power tracking according to the current measured by the sensing module , which greatly improves the power output of the energy harvesting module and reduces the system starting current, thereby improving the reliability of the sensor and expanding the scope of use.

In order to solve the above technical problems, the utility model adopts the following technical solutions:

A passive wireless current sensor based on a double-winding current transformer, characterized in that it includes a double-winding current transformer, a mutual inductance energy acquisition module, an energy storage module, a current sensing module, a signal processing module, a wireless transmission module, and a double-winding The current transformer includes a primary side winding connected to the line under test and two secondary side windings, and the two secondary side windings are respectively connected to the mutual inductance energy harvesting module and the current sensing module; the current sensing module is connected to the signal processing module, The wireless transmitting modules are connected sequentially, and the current sensing module converts the current signal into a voltage signal and then transmits it to the signal processing module; the signal processing module performs analog-to-digital conversion on the signal and calculates the effective value of the current and then transmits it to the wireless transmitting module, and the wireless transmitting module converts the current The effective value is output to the cloud, the mutual inductance energy harvesting module is connected with the energy storage module and provides electric energy input for the energy storage module, and the energy storage module is respectively connected with the mutual inductance energy harvesting module, the current sensing module, the signal processing module, and the wireless transmission module to provide To provide electric energy, the current sensing module is connected with the mutual inductance energy acquisition module and provides a reference voltage for it.

Further, the mutual inductance energy harvesting module includes a full-bridge rectifier circuit, a buffer capacitor, a comparator, a DC/DC converter, and a switch, and the full-bridge rectifier circuit is connected to the secondary side winding to rectify the current flowing out of the secondary side winding, One input port of the comparator is connected to the current sensing module and the reference voltage is provided by the current sensing module, the other input port is connected to the buffer capacitor, the output port of the comparator is connected to the switch to control the closing of the switch, and the switch is installed in the DC/DC conversion In the circuit between the converter and the full-bridge rectifier circuit, it is used to connect or disconnect the connection between the DC/DC converter and the full-bridge rectifier circuit. One end of the buffer capacitor is connected to the full-bridge rectifier circuit and the other end is connected to the comparator. DC/DC The converter is connected with the energy storage module circuit, and the power supply circuit of the comparator is connected with the energy storage module.

Further, the current sensing module includes a sampling resistor, a low-pass filter circuit and a current sensing amplifier.

Further, the energy storage module includes a supercapacitor and a lithium battery.

The passive wireless current sensor based on the double-winding current transformer of the utility model uses the double-winding current transformer to convert the large current of the primary side winding into the small current of the secondary side winding according to the principle of electromagnetic induction. The double-winding current transformer shares a primary winding and a closed iron core, and two secondary windings are used to collect electric energy and measure current respectively.

The mutual inductance energy harvesting module rectifies the current flowing out of the secondary side winding through the full bridge rectifier circuit, and then charges the buffer capacitor. Under the condition that the primary side winding current is constant, the charging power is directly related to the buffer capacitor voltage, and there is a voltage that maximizes the charging power, that is, the maximum power point voltage. The maximum power point voltage is approximately proportional to the primary side winding current, so the maximum power point voltage can be obtained by the current sensing module. The buffer capacitor voltage is connected to one input terminal of the comparator, and the reference voltage of the other input terminal of the comparator is provided by the current sensing module. When the voltage of the buffer capacitor is too large, the comparator controls the switch to close, and the DC/DC converter starts to work, and the energy is input to the energy storage module, so that the voltage of the buffer capacitor drops. When the voltage of the snubber capacitor is too small, the comparator controls the switch to be turned off, and all the current only charges the snubber capacitor, so that the voltage of the snubber capacitor rises. The capacitor voltage is maintained near the maximum power point voltage through the control of the switch and the comparator, so as to maintain the maximum charging power when the primary winding current changes.

The utility model adopts a maximum power control circuit, and performs feedback control of the output power point according to the collected current signal strength, so that the voltage of the buffer capacitor is stabilized near the maximum output power point, thereby increasing the energy collection efficiency to the maximum and reducing the system The minimum start-up current extends the applicable current range of passive wireless current sensors.

The utility model adopts a double-winding current transformer, which further reduces the volume of the transformer. At the same time, the mutual inductance energy acquisition and current collection are realized on a single transformer, the proportional relationship control of the transformer is more accurate, and the deviation of the maximum power control is reduced.

The current signal collected by the current sensing module is buffered by the signal processing module, and then periodically transmitted by the wireless transmitting module, which reduces the power consumption of the system without losing current data.

Description of drawings

Fig. 1 is a schematic structural diagram of a passive wireless current transformer in the prior art;

Fig. 2 is the structure schematic diagram of the passive wireless current sensor based on the double-winding current transformer described in the utility model;

Fig. 3 is a structural schematic diagram of the mutual inductance energy harvesting module described in the utility model;

Figure 4 is a schematic diagram of the current sensing module;

Detailed ways

The technical solution in this embodiment will be clearly and completely described below in conjunction with the accompanying drawings, and the embodiment is only a part of the embodiments of the present utility model, rather than all embodiments. All other embodiments obtained by persons of ordinary skill in the art without creative efforts fall within the protection scope of the present utility model.

Please refer to Figure 2, the utility model provides a passive wireless current sensor based on a double-winding current transformer, including a double-winding current transformer, a mutual inductance energy harvesting module, an energy storage module, a current sensing module, and a signal processing Module, wireless transmission module, double-winding current transformer includes a primary side winding connected to the line under test and two secondary side windings, and the two secondary side windings are respectively connected to the mutual inductance energy-taking module and the current sensing module; the current The sensing module is connected with the signal processing module and the wireless transmitting module in turn. The current sensing module converts the current signal into a voltage signal and then transmits it to the signal processing module; The transmitter module, the wireless transmitter module outputs the effective value of the current to the cloud, the mutual induction energy acquisition module is connected with the energy storage module and provides electric energy input for the energy storage module, and the energy storage module is respectively connected with the mutual induction energy acquisition module, the current sensing module, and the signal processing module , The wireless transmitting module is connected and provides electric energy for it. The current sensing module provides a corresponding reference voltage for the mutual inductance energy harvesting module according to the magnitude of the primary side winding current to realize the maximum power tracking of the mutual inductance energy harvesting module. The current transformer uses the principle of electromagnetic induction to convert a large current on the primary side into a small current on the secondary side. The double-winding current transformer shares a primary winding and a closed iron core, and two secondary windings are used to collect electric energy and measure current respectively.

As shown in Figure 3, the mutual inductance energy harvesting module includes a full bridge rectifier circuit, a buffer capacitor, a comparator, a DC/DC converter, and a switch. The current entering the energy harvesting secondary winding is firstly rectified by the full bridge rectifier circuit, and then The buffer capacitor is charged. Under the condition that the primary side winding current is constant, the charging power is directly related to the buffer capacitor voltage, and there is a voltage that maximizes the charging power, that is, the maximum power point voltage. The maximum power point voltage is approximately proportional to the primary side winding current, so the maximum power point voltage can be obtained by the current sensing module. The voltage of the buffer capacitor is connected to one input terminal of the comparator, and the reference voltage of the other input terminal of the comparator is provided by the current sensing module. When the voltage of the buffer capacitor is too large, the comparator controls the switch to close, and the DC/DC converter starts to work, and the energy is input to the energy storage module, so that the voltage of the buffer capacitor drops. When the voltage of the snubber capacitor is too small, the comparator controls the switch to be turned off, and all the current only charges the snubber capacitor, so that the voltage of the snubber capacitor rises. The buffer capacitor voltage is maintained near the maximum power point voltage through the control of the switch and the comparator, so as to maintain the maximum charging power under the condition that the primary side winding current changes.

As shown in Figure 4, the current sensing module uses R ₀ as the sampling resistor, R ₁ , R ₂ and C ₃ form a low-pass filter circuit, which can filter out high-order harmonic components, and the common terminal of C ₁ and C ₂ is grounded. Make the signal input to the current sense amplifier INA199 positive. By changing the size of R ₀ , the range of the current sensing module can be adjusted.

The energy storage module includes a supercapacitor and a lithium battery. The supercapacitor can undertake a large instantaneous charging and discharging power to improve the stability and working life of the system. Lithium batteries have a higher energy density and can store more electrical energy.

The signal processing module converts the analog voltage signal into a digital signal and buffers it.

The wireless transmitting module periodically obtains buffered data from the signal processing module and transmits it to the cloud through GPRS, which can greatly reduce the energy consumption of the system.

The above descriptions are only illustrative specific implementations of the present utility model, and are not intended to limit the scope of the present utility model. Any equivalent changes and modifications made by those skilled in the art without departing from the concept and principle of the present utility model shall fall within the protection scope of the present utility model.

Claims (4)

1. a kind of passive and wireless current sensor based on double-winding current mutual inductor, it is characterised in that: including double-winding current Mutual inductor, mutual inductance take energy module, energy storage module, current sense module, signal processing module, wireless transmitter module, double wrap Group current transformer includes the first side winding connecting with test line and two secondary side windings, two secondary side windings Energy module and current sense module is taken to connect with mutual inductance respectively；Current sense module and signal processing module, wireless transmitter module It is sequentially connected, current sense module converts voltage signal for current signal and then passes to signal processing module；Signal processing Module carries out analog-to-digital conversion to signal and calculating current virtual value then passes to wireless transmitter module, and wireless transmitter module will be electric Stream virtual value is output to cloud, mutual inductance take can module connect with energy storage module and to provide electric energy for energy storage module defeated Enter, energy storage module takes energy module, current sense module, signal processing module, wireless transmitter module to connect with mutual inductance respectively And electric energy is provided for it, current sense module takes energy module to connect and provides reference voltage for it with mutual inductance.

2. a kind of passive and wireless current sensor based on double-winding current mutual inductor according to claim 1, feature Be: it includes full bridge rectifier, buffering capacitor, comparator, DC/DC converter, switch that the mutual inductance, which takes energy module, and full-bridge is whole Current circuit is connect with secondary side winding rectifies the electric current of secondary side winding outflow, one input port of comparator and electric current Sensing module connection simultaneously provides reference voltage, another input terminal and buffering capacitance connection, comparator output by current sense module End is connected with switch to be closed for control switch, and switch is mounted in the circuit between DC/DC converter and full bridge rectifier, Connection for being connected to or disconnecting between DC/DC converter and full bridge rectifier, buffering capacitor one end connection full-bridge rectification electricity The road other end connects comparator, DC/DC converter and energy storage module circuit connection, and power supply circuit and the energy of comparator are deposited Store up module connection.

3. a kind of passive and wireless current sensor based on double-winding current mutual inductor according to claim 1, feature Be: the current sense module includes sampling resistor, low-pass filter circuit and current sense amplifier.

4. a kind of passive and wireless current sensor based on double-winding current mutual inductor according to claim 1, feature Be: the energy storage module includes super capacitor and lithium battery.