High-voltage line magnetic field energy harvesting system and maximum power output method thereof

Abstract

The present application relates to magnetic field energy collection technology, and specifically discloses a high-voltage line magnetic field energy collection system and a maximum power output method thereof, the system comprising a magnetic field energy collection device, an active rectifier, a bidirectional DC / DC converter and an energy storage device; the magnetic field energy collection device converts the alternating magnetic field around the high-voltage line into alternating current; the active rectifier is used to convert the alternating current into direct current and realize maximum power tracking; the bidirectional DC / DC converter comprises two MOSFETs and an inductor, and is connected with the energy storage device, and the output voltage of the active rectifier is controlled by controlling the duty cycle; the energy storage device is used to store the energy that cannot be consumed by the electrical equipment, and supplies energy for the electrical equipment when the magnetic field energy collection device is insufficient. The effect is that when the magnetic field energy collection device collects energy, maximum power tracking and constant voltage output can be realized; when the magnetic field energy collection device does not collect energy, constant voltage output can also be realized through the energy storage device.

Description

Technical Field

[0001] The present invention relates to a magnetic field energy collection technology, and in particular to a high-voltage line magnetic field energy collection system and a maximum power output method thereof. Background Art

[0002] High-voltage power lines are the largest component of the power system and shoulder the heavy responsibility of transmitting electrical energy. During the digital construction of high-voltage power lines, various sensors, video surveillance equipment, inspection equipment, communications equipment, and other electrical equipment must be installed at the power line locations to conduct comprehensive status monitoring of the power lines. Power lines and traction power supply lines are often located in remote and remote areas with complex geographical environments and variable weather conditions. Although solar energy combined with energy storage batteries is a commonly used DC power supply mode, it is limited by the weight and capacity of the batteries, adverse weather conditions such as nighttime, rainy weather, ice and snow, and the manual maintenance costs after long-term operation. This mode can no longer meet the needs of electrical equipment for long-term stable power supply.

[0003] Magnetic field energy harvesting technology uses the principle of mutual inductance to directly induce electrical energy from high-voltage lines, and is almost unaffected by weather and the environment. For example, Chinese patent CN113746212A discloses a high-voltage precedent and high-efficiency induction power collection system. However, as the power consumption of various types of electrical equipment continues to increase, it will reach tens of watts or more in the future. In situations where volume and weight are strictly limited, there is an urgent need to increase the power density of the power collection device. In addition, electrical equipment requires a stable voltage supply, and existing power boosting methods only focus on power boosting, and voltage stabilization control is sacrificed. Therefore, how to achieve constant voltage control while achieving maximum power tracking urgently needs to be studied. Summary of the Invention

[0004] The present invention provides a high-voltage line magnetic field energy collection system, which can stably supply power to electrical equipment under a wide current range and simultaneously achieve maximum power tracking of a magnetic field energy collection device.

[0005] To achieve the above objectives, the specific technical solutions adopted by the present invention are as follows:

[0006] A high-voltage line magnetic field energy collection system includes a magnetic field energy collection device, an active rectifier, a bidirectional DC / DC converter and an energy storage device;

[0007] The magnetic field energy harvesting device comprises an electromagnetic core and a winding for converting the alternating magnetic field around the high voltage line into alternating current;

[0008] The active rectifier includes four diodes, two MOSFETs, and a filter capacitor. The four diodes and filter capacitor cooperate to convert AC power into DC power. The two MOSFETs are controlled by the driving circuit to turn on and off, providing a new path for the current, thereby achieving maximum power tracking.

[0009] The bidirectional DC / DC converter includes two MOSFETs and an inductor, the high-voltage side of which is connected to the output end of the active rectifier device, and the low-voltage side of which is connected to the energy storage device. The output voltage of the active rectifier device is controlled by controlling the duty cycle thereof;

[0010] The energy storage device is used to store energy that cannot be consumed by the electrical equipment, and when the magnetic field energy collection device is insufficient to draw power, the energy storage device is discharged to supply energy to the electrical equipment.

[0011] Optionally, one of the MOSFETs is connected in parallel to each of the two diodes opposite to each other in the two bridge arms of the active rectifier. When the two MOSFETs are turned on at the same time, the two MOSFETs provide a short-circuit branch for the magnetic field energy collection device, and the induced current is 0 at this time; when the two MOSFETs are turned off at the same time, the four diodes in the active rectifier form a bridge rectifier circuit, and the induced current in the magnetic field energy collection device flows to the electrical equipment.

[0012] Optionally, the driving circuit implements maximum power point tracking by controlling the continuous on time and off time of two MOSFETs in the active rectifier, wherein:

[0013] On-time t 0opt According to t 0opt =T / 4-Δt / 2 setting;

[0014] The disconnection time Δt is set according to Δt = 2BsatAcoreN / (Uo+2Ud);

[0015] T is the working period of the magnetic field energy harvesting device, B sat is the saturation magnetic induction intensity of the core, A core is the cross-sectional area of ​​the core, N is the number of winding turns, U o is the output voltage, U d is the diode conduction voltage drop.

[0016] Optionally, a constant voltage output is achieved for the electrical device through the bidirectional DC / DC converter.

[0017] Optionally, the two MOSFETs in the bidirectional DC / DC converter are connected in series between the output ends of the active rectifier, and their common end is connected to the energy storage device through the inductor; the drive circuit of the two MOSFETs is provided with a voltage acquisition module, a PI controller, and a PWM waveform generator, the voltage acquisition module is used to acquire the output voltage of the active rectifier, compare the output voltage of the active rectifier with a reference voltage, input the error value into the PI controller and generate a control signal, and the control signal generates a PWM wave through the PWM waveform generator, which is used to control the conduction and shutdown of the two MOSFETs in the bidirectional DC / DC converter.

[0018] Optionally, the driving circuit is configured with supply voltages of different voltage levels according to the type of the electrical equipment, and a corresponding reference voltage is set according to the supply voltage.

[0019] Optionally, power balance is achieved by charging and discharging the energy storage device;

[0020] When the high-voltage line current is large, so that the energy collected by the magnetic field energy collection device is greater than or equal to the energy consumed by the electrical equipment, the energy storage device absorbs and stores the excess energy, and the magnetic field energy collection device simultaneously supplies power to the electrical equipment and the energy storage device;

[0021] When the high-voltage line current is small, so that the energy collected by the magnetic field energy collection device is less than the energy consumed by the electrical equipment, the energy storage device releases energy to provide part of the energy for the electrical equipment, and the magnetic field energy collection device and the energy storage device simultaneously supply power to the electrical equipment;

[0022] When the high-voltage line current is 0, the energy storage device independently supplies power to the electrical equipment.

[0023] Optionally, the energy storage device is a supercapacitor or an energy storage battery.

[0024] Based on the above system, the present invention also provides a maximum power output method of a high-voltage line magnetic field energy collection system, comprising the following steps:

[0025] S1: Initial state: The two MOSFETs in the active rectifier and the two MOSFETs in the bidirectional DC / DC converter are both in the off state. The energy collected by the magnetic field energy harvesting device is directly used to power the electrical equipment through the active rectifier. The output voltage and saturation of the energy storage device are detected.

[0026] S2: Perform the following operations based on the output voltage:

[0027] A: If there is an output voltage, the first control strategy controls the two MOSFETs in the active rectifier to achieve maximum power tracking. At the same time, the second control strategy controls the two MOSFETs in the bidirectional DC / DC converter to charge or discharge the energy storage device and ensure constant voltage power supply to the power device.

[0028] B: If there is no output voltage, the second control strategy is used to directly control the two MOSFETs in the bidirectional DC / DC converter to discharge the energy storage device to ensure constant voltage power supply to the electrical equipment;

[0029] Optionally, the first control strategy is that the driving circuit implements maximum power tracking by controlling the continuous on time and off time of two MOSFETs in the active rectifier, wherein:

[0030] On-time t 0opt According to t 0opt =T / 4-Δt / 2 setting;

[0031] The disconnection time Δt is set according to Δt = 2BsatAcoreN / (Uo+2Ud);

[0032] T is the working period of the magnetic field energy harvesting device, B sat is the saturation magnetic induction intensity of the core, A core is the cross-sectional area of ​​the core, N is the number of winding turns, U o is the output voltage, U d is the magnitude of the diode conduction voltage drop, and the working cycle of the magnetic field energy harvesting device is obtained by performing zero-crossing detection on the output voltage signal of the magnetic field energy harvesting device;

[0033] The second control strategy is to collect the output voltage and the reference voltage level of the electrical equipment through the PI controller, and then control the two MOSFETs in the bidirectional DC / DC converter through PWM to realize the charging or discharging of the energy storage device to ensure constant voltage power supply to the electrical equipment.

[0034] The remarkable effects of the present invention are:

[0035] The present invention is configured with an active rectifier, a bidirectional DC / DC converter, and an energy storage device. When the magnetic field energy collection device collects energy, the maximum power tracking is achieved by controlling the continuous on-time and off-time of the switch tube in the active rectifier. The bidirectional DC / DC converter and the energy storage device cooperate to achieve constant voltage output to the electrical equipment. When the magnetic field energy collection device does not collect energy, the bidirectional DC / DC converter and the energy storage device can also directly achieve constant voltage output to the electrical equipment, thereby effectively ensuring that the system can provide stable power supply to the electrical equipment over a wide current range. BRIEF DESCRIPTION OF THE DRAWINGS

[0036] Figure 1 is a schematic diagram of the magnetic field energy collection system provided by the present invention;

[0037] Figure 2 This is a block diagram of the control circuit principle of the magnetic field energy harvesting system in a specific embodiment of the present invention;

[0038] Figure 3 1 is a waveform diagram of a magnetic field energy collection system in a specific embodiment of the present invention;

[0039] Figure 4 It is a timing waveform diagram of a voltage regulation circuit based on an active rectifier bridge in a specific embodiment of the present invention. DETAILED DESCRIPTION

[0040] The following describes the embodiments of the present invention in detail with reference to the accompanying drawings. The embodiments are provided for illustrative purposes only and are not to be construed as limiting the present invention. The accompanying drawings are provided for reference and illustration only and do not constitute a limitation on the scope of protection of the present invention. Many changes may be made to the present invention without departing from the spirit and scope of the present invention.

[0041] like Figure 1 、 Figure 2 As shown, this embodiment provides a high-voltage line magnetic field energy harvesting system, including a magnetic field energy harvesting device, an active rectifier, a bidirectional DC / DC converter and an energy storage device;

[0042] The magnetic field energy harvesting device comprises an electromagnetic core and a winding for converting the alternating magnetic field around the high voltage line into alternating current;

[0043] The active rectifier includes four diodes, two MOSFETs, and a filter capacitor. The four diodes and filter capacitor cooperate to convert AC power into DC power. The two MOSFETs are controlled by the driving circuit to turn on and off, providing a new path for the current, thereby achieving maximum power tracking.

[0044] The bidirectional DC / DC converter includes two MOSFETs and an inductor, the high-voltage side of which is connected to the output end of the active rectifier device, and the low-voltage side of which is connected to the energy storage device. The output voltage of the active rectifier device is controlled by controlling the duty cycle thereof;

[0045] The energy storage device is used to store energy that cannot be consumed by the electrical equipment, and when the magnetic field energy collection device is insufficient to draw power, the energy storage device is discharged to supply energy to the electrical equipment.

[0046] pass Figure 2It can be seen that a MOSFET is connected in parallel to each of the two diodes in the two opposite arms of the active rectifier. When the two MOSFETs are turned on at the same time, the two MOSFETs provide a short-circuit branch for the magnetic field energy harvesting device, and the induced current is zero at this time. When the two MOSFETs are turned off at the same time, the four diodes in the active rectifier form a bridge rectifier circuit, and the induced current in the magnetic field energy harvesting device flows to the electrical device. By configuring two MOSFETs in the active rectifier, when the two MOSFETs are turned on at the same time, it can be considered that the MOSFET provides a short-circuit branch for the magnetic field energy harvesting device, and the induced current flows through the MOSFET instead of flowing to the load. Therefore, the induced current is zero at this time. When the two MOSFETs are turned off at the same time, it can be considered that the induced current flows to the load. By controlling the continuous on-time and off-time of the MOSFET, maximum power tracking of the magnetic field energy harvesting system can be achieved.

[0047] In a specific implementation, the driving circuit realizes maximum power tracking by controlling the continuous on time and off time of the two MOSFETs in the active rectifier, wherein:

[0048] The continuous conduction time t0opt is based on t 0opt =T / 4-Δt / 2 setting;

[0049] The disconnection time Δt is based on Δt=2B sat A core N / (U o +2U d )set up;

[0050] T is the working period of the magnetic field energy harvesting device, B sat is the saturation magnetic induction intensity of the core, A core is the cross-sectional area of ​​the core, N is the number of winding turns, U o is the output voltage, U d is the diode conduction voltage drop.

[0051] In addition, the system can also achieve constant voltage output to the electrical equipment through the bidirectional DC / DC converter. Figure 2It can be seen that the two MOSFETs in the bidirectional DC / DC converter are connected in series between the output terminals of the active rectifier, and their common terminal is connected to the energy storage device through the inductor; the drive circuit of the two MOSFETs is provided with a voltage acquisition module, a PI controller, and a PWM waveform generator. The voltage acquisition module is used to acquire the output voltage of the active rectifier, compare the output voltage of the active rectifier with the reference voltage, input the error value into the PI controller and generate a control signal. The control signal generates a PWM wave through the PWM waveform generator, which is used to control the conduction and shutdown of the two MOSFETs in the bidirectional DC / DC converter.

[0052] In specific implementation, the output voltage of the active rectifier can be collected and compared with the reference voltage. The error value can be input into the PI controller to generate a control signal. The control signal is passed through a pulse width modulation (PWM) waveform generator to generate a PWM wave. The PWM wave is used to control the on and off of the MOSFET. The system can control the output voltage of the rectifier to maintain different voltage levels by setting different reference voltage values, thereby providing power supply voltages of different voltage levels to the load.

[0053] The energy storage device in the system can be a supercapacitor or an energy storage battery, and power balance is achieved through charging and discharging of the energy storage device;

[0054] When the high-voltage line current is large, so that the energy collected by the magnetic field energy collection device is greater than or equal to the energy consumed by the electrical equipment, the energy storage device absorbs and stores the excess energy, and the magnetic field energy collection device simultaneously supplies power to the electrical equipment and the energy storage device;

[0055] When the high-voltage line current is small, so that the energy collected by the magnetic field energy collection device is less than the energy consumed by the electrical equipment, the energy storage device releases energy to provide part of the energy for the electrical equipment, and the magnetic field energy collection device and the energy storage device simultaneously supply power to the electrical equipment;

[0056] When the high-voltage line current is 0, the energy storage device independently supplies power to the electrical equipment.

[0057] Based on the above system, this embodiment further provides a maximum power output method of the high-voltage line magnetic field energy harvesting system as described above, comprising the following steps:

[0058] S1: Initial state: The two MOSFETs in the active rectifier and the two MOSFETs in the bidirectional DC / DC converter are both in the off state. The energy collected by the magnetic field energy harvesting device is directly used to power the electrical equipment through the active rectifier. The output voltage and saturation of the energy storage device are detected.

[0059] S2: Perform the following operations based on the output voltage:

[0060] A: If there is an output voltage, the first control strategy controls the two MOSFETs in the active rectifier to achieve maximum power tracking. At the same time, the second control strategy controls the two MOSFETs in the bidirectional DC / DC converter to charge or discharge the energy storage device and ensure constant voltage power supply to the power device. At this time, the waveform is as follows Figure 3 As shown, u gs1 (t) and u gs2 (t) are the control signals of switches S1 and S2 respectively. When the two MOSFETs in the active rectifier are turned on at the same time, the core voltage u2(t) can be reduced, thereby slowing down the accumulation of magnetic flux in the core. When the two MOSFETs in the active rectifier are turned off at the same time, the core voltage is equal to the load voltage, the magnetic flux begins to accumulate, the magnetic field energy harvester begins to collect energy, and the secondary current flows to the load. When 2t0+Δt=T / 2, the system output power is maximum.

[0061] B: If there is no output voltage, the second control strategy is used to directly control the two MOSFETs in the bidirectional DC / DC converter to discharge the energy storage device to ensure constant voltage power supply to the electrical equipment;

[0062] In a specific implementation, the first control strategy is that the driving circuit realizes maximum power tracking by controlling the continuous on-time and off-time of the two MOSFETs in the active rectifier, wherein:

[0063] On-time t 0opt According to t 0opt =T / 4-Δt / 2 setting;

[0064] The disconnection time Δt is set according to Δt = 2BsatAcoreN / (Uo+2Ud);

[0065] T is the working period of the magnetic field energy harvesting device, B sat is the saturation magnetic induction intensity of the core, A core is the cross-sectional area of ​​the core, N is the number of winding turns, U o is the output voltage, U d is the magnitude of the diode conduction voltage drop, and the working cycle of the magnetic field energy harvesting device is obtained by performing zero-crossing detection on the output voltage signal of the magnetic field energy harvesting device;

[0066] The second control strategy is to collect the output voltage and the reference voltage level of the electrical equipment through the PI controller, and then control the two MOSFETs in the bidirectional DC / DC converter through PWM to realize the charging or discharging of the energy storage device to ensure constant voltage power supply to the electrical equipment.

[0067] Based on the above system, this embodiment further provides a constant voltage output method as described above, comprising the following steps:

[0068] When the capacitor is fully charged, the following operations are performed according to the output voltage to maintain a constant output voltage. The waveform is as shown in the figure below. Figure 4 As shown, u gs3 (t) and u gs4 (t) are the control signals of switches S3 and S4 respectively. Constant voltage control is achieved by controlling the simultaneous on and off of S3 and S4:

[0069] A: If the output voltage exceeds the reference value, the third control strategy controls the two MOSFETs in the bidirectional DC / DC converter to be turned on simultaneously so that the current of the magnetic field energy harvester does not flow to the load and supercapacitor, thereby reducing the voltage.

[0070] B: If the output voltage is lower than the reference value, the third control strategy is used to directly control the two MOSFETs in the bidirectional DC / DC converter to be turned off simultaneously, so that the current of the magnetic field energy harvester flows to the load, thereby increasing the voltage;

[0071] The above embodiments are preferred implementation modes of the present invention, but the implementation modes of the present invention are not limited to the above embodiments. Any other changes, modifications, substitutions, combinations, and simplifications that do not deviate from the spirit and principles of the present invention should be considered as equivalent replacement methods and are included in the scope of protection of the present invention.

Claims

1. A high-voltage line magnetic field energy collection system, characterized in that: It includes a magnetic field energy harvesting device, an active rectifier, a bidirectional DC / DC converter and an energy storage device; The magnetic field energy harvesting device comprises an electromagnetic core and a winding for converting the alternating magnetic field around the high voltage line into alternating current; The active rectifier includes four diodes, two MOSFETs, and a filter capacitor. The four diodes and the filter capacitor cooperate to convert AC power into DC power. The two MOSFETs are controlled by the driving circuit to turn on and off, providing a new path for the current, thereby achieving maximum power tracking. The bidirectional DC / DC converter includes two MOSFETs and an inductor, the high-voltage side of which is connected to the output end of the active rectifier, and the low-voltage side of which is connected to the energy storage device. The output voltage of the active rectifier is controlled by controlling the duty cycle of the inductor; The energy storage device is used to store energy that cannot be consumed by the electrical equipment, and when the magnetic field energy collection device is insufficient to draw power, the energy storage device is discharged to supply energy to the electrical equipment; The driving circuit implements maximum power tracking by controlling the continuous on-time and off-time of the two MOSFETs in the active rectifier, wherein: On-time t 0opt According to t 0opt =T / 4-Δt / 2 setting; The disconnection time Δt is based on Δt=2B sat A core N / (U o +2U d )set up; T is the working period of the magnetic field energy harvesting device, B sat is the saturation magnetic induction intensity of the core, A core is the cross-sectional area of ​​the core, N is the number of winding turns, U o is the output voltage, U d Is the diode conduction voltage drop; The driving circuit is configured with supply voltages of different voltage levels according to the type of electrical equipment, and is provided with corresponding reference voltages according to the supply voltages, and achieves constant voltage output to the electrical equipment through the bidirectional DC / DC converter.

2. The high-voltage line magnetic field energy collection system according to claim 1, characterized in that: One MOSFET is connected in parallel to each of the two diodes opposite to each other in the two bridge arms of the active rectifier. When the two MOSFETs are turned on at the same time, the two MOSFETs provide a short-circuit branch for the magnetic field energy collection device, and the induced current is 0 at this time; when the two MOSFETs are turned off at the same time, the four diodes in the active rectifier form a bridge rectifier circuit, and the induced current in the magnetic field energy collection device flows to the electrical equipment.

3. The high-voltage line magnetic field energy collection system according to claim 1 or 2, characterized in that: The two MOSFETs in the bidirectional DC / DC converter are connected in series between the output terminals of the active rectifier, with their common terminal connected to the energy storage device via the inductor. The drive circuit of the two MOSFETs is provided with a voltage acquisition module, a PI controller, and a PWM waveform generator. The voltage acquisition module is used to acquire the output voltage of the active rectifier, compare the output voltage of the active rectifier with a reference voltage, input the error value into the PI controller and generate a control signal. The control signal is passed through the PWM waveform generator to generate a PWM wave for controlling the conduction and shutdown of the two MOSFETs in the bidirectional DC / DC converter.

4. The high-voltage line magnetic field energy collection system according to claim 3, characterized in that: Power balance is achieved by charging and discharging the energy storage device; When the high-voltage line current is large, so that the energy collected by the magnetic field energy collection device is greater than or equal to the energy consumed by the electrical equipment, the energy storage device absorbs and stores the excess energy, and the magnetic field energy collection device simultaneously supplies power to the electrical equipment and the energy storage device; When the high-voltage line current is small, so that the energy collected by the magnetic field energy collection device is less than the energy consumed by the electrical equipment, the energy storage device releases energy to provide part of the energy for the electrical equipment, and the magnetic field energy collection device and the energy storage device simultaneously supply power to the electrical equipment; When the high-voltage line current is 0, the energy storage device independently supplies power to the electrical equipment.

5. The high-voltage line magnetic field energy collection system according to claim 1 or 4, characterized in that: The energy storage device adopts a super capacitor or an energy storage battery.

6. A maximum power output method for a high-voltage line magnetic field energy harvesting system according to any one of claims 1 to 5, characterized in that: The following steps are involved: S1: Initial state: The two MOSFETs in the active rectifier and the two MOSFETs in the bidirectional DC / DC converter are both in the off state. The energy collected by the magnetic field energy harvesting device is directly used to power the electrical equipment through the active rectifier. The output voltage and saturation of the energy storage device are detected. S2: Perform the following operations based on the output voltage: A: If there is an output voltage, the first control strategy controls the two MOSFETs in the active rectifier to achieve maximum power tracking. At the same time, the second control strategy controls the two MOSFETs in the bidirectional DC / DC converter to charge or discharge the energy storage device and ensure constant voltage power supply to the power device. B: If there is no output voltage, the two MOSFETs in the bidirectional DC / DC converter are directly controlled by the second control strategy to discharge the energy storage device to ensure constant voltage power supply to the electrical equipment.

7. The maximum power output method of the high-voltage line magnetic field energy collection system according to claim 6, characterized in that: The first control strategy is that the driving circuit realizes maximum power tracking by controlling the continuous on-time and off-time of the two MOSFETs in the active rectifier, wherein: On-time t 0opt According to t 0opt =T / 4-Δt / 2 setting; The disconnection time Δt is based on Δt=2B sat A core N / (U o +2U d )set up; T is the working period of the magnetic field energy harvesting device, B sat is the saturation magnetic induction intensity of the core, A core is the cross-sectional area of ​​the core, N is the number of winding turns, U o is the output voltage, U d is the magnitude of the diode conduction voltage drop, and the working cycle of the magnetic field energy harvesting device is obtained by performing zero-crossing detection on the output voltage signal of the magnetic field energy harvesting device; The second control strategy is to collect the output voltage and the reference voltage level of the electrical equipment through the PI controller, and then control the two MOSFETs in the bidirectional DC / DC converter through PWM to realize the charging or discharging of the energy storage device to ensure constant voltage power supply to the electrical equipment.

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