Steel rail potential direct current energy taking device and method applied to subway sensor power supply

Abstract

The invention relates to the field of direct-current energy taking, in particular to a steel rail potential direct-current energy taking device and method applied to subway sensor power supply. In order to solve the problems of sensor power supply in a subway direct-current power supply system, for example, cable laying is difficult, battery maintenance cost is high, and environment energy collection is limited, the device utilizes steel rail potential to carry out efficient energy collection. The device comprises a main power module and a control module, wherein the main power module comprises a rectifier bridge, a double-MOSFET structure, a voltage-stabilizing filter capacitor Cbus and an energy collector; and the control module executes a maximum power point tracking strategy through the voltage measurement interface and the grid control interface. The strategy comprises a periodic open-circuit voltage acquisition stage, an optimal voltage regulation stage and a voltage holding stage, the input voltage is stabilized at 1 / 2 of the open-circuit voltage by controlling the on-off state of the double MOSFETs, and the Cbus voltage is dynamically maintained to fluctuate around the optimal reference voltage by + / -5%. Stable and efficient power supply is realized, and the maintenance cost is reduced.

Description

Technical Field

[0001] This invention relates to the field of DC power harvesting, and provides a DC power harvesting device and method for rail potential in subway sensor power supply. Background Technology

[0002] In recent years, the application of wireless sensor nodes in urban electrified rail systems has become increasingly common, especially in subways and other similar applications where their importance is increasingly prominent. However, the power supply for wireless sensors has become a significant technical challenge. Existing power supply methods, such as wired cables or batteries, have limitations in urban rail transit. Particularly in underground systems like subways, the laying and power supply of wired cables face technical challenges. The complexity of the underground environment and space constraints make cable laying more difficult, and maintenance and fault detection requirements are higher. Battery power is limited by battery life and requires regular replacement, which not only increases maintenance costs and manpower demands but may also affect normal subway operations. Environmental energy harvesting technology can utilize various energy sources, such as solar, wind, vibration, and magnetic field energy. However, in underground environments like subways, solar and wind energy are limited by the lack of sunlight and enclosed conditions. While vibration energy can be generated during subway operation, its collection efficiency is low and its structure is complex. Magnetic field energy harvesting is also difficult to achieve due to the scarcity of alternating magnetic fields caused by DC power supply systems. In subway DC power supply systems, most countries use an ungrounded mode, where the rails possess rail potential. Therefore, the need for energy harvesting using this voltage is quite urgent. Summary of the Invention

[0003] The purpose of this invention is to solve the technical problems of unstable and efficient power supply for sensors in subway DC power supply systems, which are caused by difficulties in laying wired cables, high battery maintenance costs, and limited collection of environmental energy (solar / wind / vibration / magnetic field energy).

[0004] To achieve the above objectives, the present invention employs the following technical means:

[0005] This invention provides a rail potential DC power harvesting device for powering subway sensors, comprising a main power module and a control module;

[0006] The main power module includes:

[0007] The rectifier bridge: its input end is directly connected to the steel rail and the concrete structure;

[0008] The dual MOSFET structure consists of two MOSFET transistors Q1 and Q2 connected in series, with the source of transistor Q1 connected to the negative terminal of the rectifier bridge output.

[0009] The voltage regulator capacitor (Cbus) is connected between the drain of transistor Q1 and the source of transistor Q2;

[0010] The energy harvester is connected to the drain of transistor Q2 at its input.

[0011] The control module:

[0012] The voltage measurement interface is connected to the output of the rectifier bridge to acquire the input voltage Uin.

[0013] The gate control interface is connected to the gates of transistors Q1 and Q2 respectively;

[0014] Configured to execute a maximum power point tracking control strategy, the input voltage Uin is stabilized at half the open-circuit voltage Uoc by periodically switching the operating state of the dual MOSFET structure.

[0015] In the above scheme, the maximum power point tracking control strategy includes:

[0016] Open-circuit voltage acquisition stage: Disconnect transistor Q1, measure the open-circuit voltage Uoc of the rail potential, and calculate the optimal reference voltage Vref = Uoc / 2;

[0017] Optimal voltage regulation phase: Turn on transistor Q1, and regulate the voltage of bus capacitor Cbus to Vref through switching transistor Q2;

[0018] Voltage holding phase: The switching state of transistor Q2 is dynamically controlled to make the Cbus voltage fluctuate around Vref;

[0019] The aforementioned stages are executed cyclically according to a preset time period.

[0020] In the above scheme, during the optimal voltage regulation phase:

[0021] When the Cbus voltage is higher than Vref, the low-power microcontroller module drives the transistor to drive Q2 to draw energy from the load to reduce the Cbus voltage.

[0022] When the Cbus voltage is lower than Vref, the low-power microcontroller module drives the turn-off transistor Q2 to raise the Cbus voltage.

[0023] In the above scheme, during the optimal voltage regulation phase:

[0024] The voltage holding phase includes:

[0025] The dynamic comparison unit monitors the deviation between the bus capacitor voltage Cbus and the optimal reference voltage Vref in real time.

[0026] The switch control unit, in response to the deviation, performs the following:

[0027] When the Cbus voltage is higher than Vref, the low-power microcontroller module drives the transistor Q2 to open the load current path, and Cbus discharges to the load to reduce the voltage.

[0028] When the Cbus voltage is lower than Vref, the low-power microcontroller module drives the turn-off transistor Q2 to cut off the load current path, and Cbus stops discharging, causing the voltage to rise again.

[0029] The fluctuation suppression unit controls the Cbus voltage fluctuation within ±5%V by adjusting the switching frequency of transistor Q2.

[0030] In the above scheme, the optimal voltage holding phase is maintained for 10-50ms.

[0031] This invention also provides a method for DC power harvesting from rail potential for use in subway sensor power supply, comprising:

[0032] Periodically disconnect the power extraction circuit from the rail and measure the open-circuit voltage Uoc;

[0033] The optimal operating voltage Vref = Uoc / 2 is calculated based on Uoc.

[0034] The voltage of the bus capacitor Cbus is adjusted to Vref using a dual MOSFET structure and dynamically maintained near that voltage.

[0035] The energy stored in the Cbus is delivered to the load.

[0036] In the above scheme, the process of dynamically maintaining the voltage includes:

[0037] When the Cbus voltage deviates from Vref, the low-power microcontroller module controls the switching transistor Q2 to change the load current path, so that the Cbus voltage returns to the Vref fluctuation range.

[0038] In the above scheme, the time to dynamically maintain the voltage Vref is 10-50ms.

[0039] Because the present invention employs the above-mentioned technical means, it has the following beneficial effects:

[0040] (1) This invention can efficiently utilize the potential difference existing in subway rails and convert it into electrical energy to power sensor equipment. Compared with traditional wired cable power supply and battery power supply methods, this system significantly reduces cable laying costs and manual inspection costs. In addition, this energy harvester also solves the problem that other environmental energy harvesting technologies are difficult to apply in underground tunnel environments due to space constraints, environmental interference, or insufficient energy density. By making full use of the unique resource of rail potential, this solution provides a feasible solution for the self-powering of sensors in subway systems.

[0041] (2) The rail potential energy harvester provided by this invention employs a controller and a dual MOSFET structure to achieve the optimized goal of maximizing energy harvesting. By precisely controlling the switching timing of the MOSFETs, the harvester can switch to the open-circuit state within a preset time interval to detect the open-circuit voltage (Uoc) of the rail potential. During MOSFET conduction, the system maintains the input voltage stably at the optimal operating voltage (Uoc / 2) through real-time feedback control, thereby ensuring that the energy harvester always operates at the maximum power point. This dynamic regulation mechanism significantly improves energy harvesting efficiency, greatly increasing the energy collection rate compared to traditional methods. Attached Figure Description

[0042] Figure 1 Schematic diagram of a rail potential energy harvester;

[0043] Figure 2 Equivalent circuit diagram for rail potential energy extraction;

[0044] Figure 3 : Schematic diagram of maximum energy acquisition control strategy;

[0045] Figure 4 Schematic diagram of a two-stage MOSFET structure;

[0046] Figure 5 : The curve showing the relationship between load resistance and output power;

[0047] Figure 6 Design flowchart of rail potential energy harvesting device. Detailed Implementation

[0048] The embodiments of the present invention will be described in detail below. Although the present invention will be described and illustrated in conjunction with some specific embodiments, it should be noted that the present invention is not limited to these embodiments. On the contrary, any modifications or equivalent substitutions made to the present invention should be covered within the scope of the claims of the present invention.

[0049] Furthermore, to better illustrate the present invention, numerous specific details are set forth in the following detailed embodiments. Those skilled in the art will understand that the present invention can be practiced without these specific details.

[0050] To address the shortcomings of the aforementioned background technologies, this invention proposes an innovative rail potential energy harvester for DC subway systems. This harvester can utilize the rail potential to collect energy and thus provide power to sensors. During subway train operation, a certain potential difference is generated in the track; this invention effectively harvests this energy through voltage division. This ensures a continuous and stable power supply to the sensors, even in complex underground environments. Compared to traditional battery-powered, wired-powered, and environmentally dependent energy harvesting methods, this invention provides a more stable, lower-cost, and significantly improved safety energy supply.

[0051] Specifically, this invention discloses a rail potential DC power harvesting device for powering subway sensors. This belongs to the field of DC power harvesting and solves the problems of unstable, complex, and costly power supply for subway system sensors located on underground tracks. This invention consists of a collector main power module and a low-power microcontroller module.

[0052] In this invention, the described collector main power module includes a rectifier bridge, a dual MOSFET structure, a voltage-regulating filter capacitor Cbus, and an energy harvester. The dual MOSFET structure is composed of two MOSFET transistors Q1 and Q2, while the rectifier bridge consists of four diodes D1, D2, D3, and D4. The specific connections of these components are as follows: the rectifier bridge is directly connected to the steel rail and the concrete structure; the voltage-regulating filter capacitor Cbus is connected between the dual MOSFET structures; and the energy harvester is connected to the second MOSFET of the dual MOSFET structure. The low-power microcontroller module consists of low-power micro-peripheral circuitry and is connected to the rectifier bridge voltage measurement interface and the gate of the dual MOSFET structure.

[0053] Maximum energy harvesting control strategy design

[0054] A complete hardware architecture is built around a low-power microcontroller. The low-power microcontroller is responsible for high-precision sampling of the input voltage and real-time monitoring of voltage changes via its built-in analog-to-digital converter (ADC). The subsequent circuitry employs a dual-MOSFET structure, whose switching states are precisely controlled by the low-power microcontroller. By controlling the on / off state of the dual MOSFETs, the system can achieve an open-circuit state when needed to measure the open-circuit voltage (Uoc), and dynamically correct the input voltage during normal operation to maintain it stably at the optimal operating voltage (Uoc / 2), thereby maximizing energy harvesting.

[0055] Example 1

[0056] The technical solution and specific implementation methods of the invention will be further described in detail below with reference to the accompanying drawings and implementation examples.

[0057] Figure 1 This invention relates to a rail potential energy harvester, a method for harvesting environmental energy based on rail potential. This falls under the field of DC energy harvesting and solves the problems of unstable, complex, and costly power supply for sensors in subway systems located on underground tracks. The invention consists of a main power module for the harvester and a low-power microcontroller module. The main power module includes a rectifier bridge, a dual MOSFET structure, a voltage-stabilizing filter capacitor Cbus, and the energy harvester. The dual MOSFET structure is composed of two MOSFET transistors Q1 and Q2, while the rectifier bridge consists of four diodes D1, D2, D3, and D4. The specific connections of these components are as follows: the rectifier bridge is directly connected to the rail and concrete structure; the voltage-stabilizing filter capacitor Cbus is connected between the dual MOSFET structures; and the energy harvester is connected to the second MOSFET in the dual MOSFET structure. The low-power microcontroller module consists of low-power micro-peripheral circuitry and is connected to the rectifier bridge voltage measurement interface and the gate of the dual MOSFET structure.

[0058] Figure 2 This is the equivalent circuit diagram of the energy extraction system designed in this invention. The distributed resistance of the rail is a trapezoidal resistance network, so the equivalent resistance of the trapezoidal resistance network can be solved, that is, the equivalent resistance network on the left is R. n1 :

[0059]

[0060] Where R m R represents the underground transverse resistance. z R represents the lateral resistance of the rail. g Indicates the resistance to ground;

[0061] The equivalent resistance network on the right is R n2 :

[0062]

[0063] The equivalent resistance network can be simplified to:

[0064] R eq =R AB +R BC +R n1 / / R n2 (3)

[0065] If, under transient conditions, the rail potential voltage is known to be U... a When the energy harvesting device is open-circuited, the open-circuit voltage of the energy harvesting device is also U. a ,Right now

[0066] U cq =U a (4)

[0067] According to Thevenin's theorem, a Thevenin equivalent circuit can be constructed. According to the maximum power transfer theorem, if the energy-collecting equivalent load achieves maximum efficiency, then the energy-collecting equivalent load and the Thevenin equivalent resistance Req have the same value.

[0068] R f =R eq (5)

[0069] That is, when the energy-harvesting load achieves maximum efficiency, the voltage across the energy-harvesting load is

[0070]

[0071] Combine (5) and (6)

[0072]

[0073] That is, when the voltage across the energy harvesting device is the open-circuit voltage U eq When the power is half of the rated power, the energy harvesting device can obtain the maximum power P. max :

[0074]

[0075] Figure 3 This invention proposes a maximum energy harvesting control strategy based on the open-circuit voltage method. The core principle of the open-circuit voltage method is that the system can achieve maximum power output when the input voltage is maintained at half of the maximum open-circuit voltage UocV. Based on this principle, this research designs a novel control method: during system operation, the system switches to the open-circuit state at fixed time intervals, accurately measuring the open-circuit voltage Uoc at this time. In the non-open-circuit state, the input voltage is adjusted in real time to half of its corresponding open-circuit voltage, Uoc / 2, thereby ensuring that the system always operates at its maximum power point.

[0076] Figure 4 This invention presents a dual-stage MOSFET structure. The first-stage MOSFET (transistor Q1) acts as a sampling-off MOSFET, switching in opposite phase with the two MOSFETs at the front end of the sample-and-hold circuit. These three MOSFETs together form a circuit that holds the sampled rail voltage. The second-stage MOSFET (transistor Q2) acts as an optimized voltage holding MOSFET. It processes the rail voltage sampled by the first-stage MOSFET to obtain the optimal voltage value, compares it with the current input voltage, and then controls the switching state of the second-stage MOSFET to keep the input voltage near the optimal value, thereby maximizing energy harvesting.

[0077] Figure 5The graph shows the output power as a function of load resistance. As the load resistance gradually increases from zero to the equivalent energy harvesting resistance Req, the output power increases. The output power reaches its peak when the load resistance equals Req, indicating that the system achieves maximum power point tracking (MPPT). Further analysis shows that the output power begins to decrease when the load resistance exceeds Req. This phenomenon indicates that the system achieves maximum energy harvesting efficiency when the load resistance is maintained near Req, corresponding to the optimal load voltage (Uoc / 2). Therefore, by precisely controlling the load voltage and stabilizing it near the optimal load voltage (Uoc / 2Uoc), the performance of the energy harvesting system can be effectively improved, ensuring its operation under optimal conditions.

[0078] In summary, the design process for a DC power harvesting device utilizing rail potential, applied to subway sensors, is as follows: Figure 6 As shown, the specific implementation method is as follows:

[0079] Step 1: The collector is in the open-circuit voltage acquisition stage, acquiring the optimal voltage Vref. During the operation of the rail potential energy collector, the first MOSFET Q1 is disconnected to make the input voltage Uin equal to the equivalent open-circuit voltage Uoc, i.e., Uin = Uoc = Ueq. At this time, the system enters the open-circuit state and can accurately measure the open-circuit voltage Uoc of the rail potential.

[0080] According to Thevenin's theorem, a Thevenin equivalent circuit can be constructed. According to the maximum power transfer theorem, if the energy-collecting equivalent load achieves maximum efficiency, then the energy-collecting equivalent load and the Thevenin equivalent resistance Req have the same value.

[0081] R f =R eq (5)

[0082] That is, when the energy-harvesting load achieves maximum efficiency, the voltage across the energy-harvesting load is

[0083]

[0084] Combine (5) and (6)

[0085]

[0086] That is, when the voltage across the energy harvesting device is half of the open-circuit voltage Ueq, the energy harvesting device can obtain the maximum power Pmax.

[0087]

[0088] The voltage processing circuit processes Uoc, converting it into the optimal operating voltage Uref = Uoc / 2. The system updates and maintains the acquired optimal voltage Vref, providing a stable reference voltage for subsequent power regulation and energy harvesting.

[0089] Step 2: After a few milliseconds of acquisition, the collector prepares to enter the optimal voltage holding phase. The first MOSFET Q1 is turned on, marking the end of the acquisition phase. At this point, the Cbus voltage needs to be lowered or raised to the latest updated Vref. When the bus capacitor voltage Cbus is higher than the set updated reference voltage Vref, the system will take measures to adjust the input voltage to the optimal operating voltage Vref, i.e., the second MOSFET Q2. At this time, the load begins to continuously draw energy from the Cbus capacitor, causing the capacitor voltage to gradually decrease. As the load continues to operate, the capacitor voltage continues to decrease until it drops to near the reference voltage Vref. The same applies if the bus capacitor voltage Cbus is lower than the set updated reference voltage Vref. This process continues until Vref is reached, ending this step.

[0090] Step 3: During the optimal voltage holding phase, the collector stabilizes the bus capacitor voltage Cbus at the reference voltage Vref through precise regulation. Similar to Step 2, when the Cbus voltage is higher than Vref, the system turns on MOSFET Q2, causing the Cbus voltage to decrease; conversely, when the Cbus voltage is lower than Vref, the system turns off Q2, causing the Cbus voltage to increase. During this phase, Q2 frequently switches on and off, causing the Cbus voltage to fluctuate by a certain amplitude (±0.5V) around Vref. This amplitude is related to the capacitance value of Cbus and the overall energy harvested.

[0091] Step 4: Optimal Voltage Holding Phase. This phase lasts for tens of milliseconds, after which the collector exits the optimal voltage holding phase. The system then re-enters Step 1, and this process repeats. The optimal rail potential is updated in real-time, and the system's input voltage is kept near this optimal voltage.

[0092] Step 5: Performance evaluation of the designed circuit topology was performed. In practical application tests of the sample case, when the rail voltage fluctuated within the range of -50V to 50V, the system input voltage could respond quickly and stabilize at the optimal operating voltage (Uoc / 2). This solution adopts a design combining a dual MOSFET structure with a low-power microcontroller, achieving maximum energy harvesting under different operating conditions through precise switching control and voltage regulation.

[0093] Through the above steps, the scheme successfully designed and implemented a collector capable of harvesting energy using the rail potential to power the sensor. This system effectively collects energy through voltage division, ensuring a continuous and stable power supply to the sensor even in complex underground environments. Compared to traditional battery-powered, wired-powered, and environmentally dependent energy harvesting methods, the energy supply method provided by this invention is more stable, lower in cost, and significantly improves safety.

[0094] To help those skilled in the art better understand the innovative aspects of this invention and its advantages over existing technologies, the following further analysis is provided:

[0095] 1. This invention employs a maximum power point tracking control strategy, which solves the technical problem of low energy harvesting efficiency caused by rail potential fluctuations in subway sensors by periodically switching the operating states of the dual MOSFET structure (including open-circuit voltage acquisition stage, optimal voltage adjustment stage, and voltage holding stage), thereby maximizing energy conversion efficiency.

[0096] The detailed principles are explained below:

[0097] During the open-circuit voltage acquisition phase, transistor Q1 is disconnected to put the system into an open-circuit state, accurately measuring the open-circuit voltage Uoc of the rail potential and calculating the optimal reference voltage Vref (Vref = Uoc / 2) based on this. In the optimal voltage regulation phase, transistor Q1 is turned on, and transistor Q2 is switched to regulate the voltage of the bus capacitor Cbus to Vref. Subsequently, in the voltage holding phase, the switching state of transistor Q2 is dynamically controlled to stabilize the Cbus voltage near Vref. This periodic cyclic strategy ensures that the system always operates at the maximum power point (i.e., the input voltage Uin is stable at 1 / 2 of the open-circuit voltage Uoc), because according to the maximum power transfer theorem, the system output power reaches its peak when the load voltage equals half the open-circuit voltage. Compared to the traditional fixed voltage regulation method, this dynamic tracking mechanism avoids energy loss caused by random changes in rail potential, significantly improving energy harvesting efficiency and thus providing a more stable power supply to the sensor.

[0098] 2. The dual MOSFET structure and dynamic control unit technology used in this invention solves the technical problem of unstable power supply caused by voltage fluctuations in complex underground environments by real-time monitoring and adjustment of the deviation of the bus capacitor voltage Cbus, thus achieving the effect of maintaining a highly stable output voltage.

[0099] The detailed principles are explained below:

[0100] A dual-MOSFET structure (composed of transistors Q1 and Q2 connected in series) works in conjunction with a control module (such as a low-power microcontroller) to monitor the deviation between the Cbus voltage and Vref in real time during the voltage holding phase via a dynamic comparison unit. When the Cbus voltage is higher than Vref, the control module drives transistor Q2 to turn on, opening the load current path and allowing Cbus to discharge to the load to reduce the voltage. When the Cbus voltage is lower than Vref, the control module drives transistor Q2 to turn off, cutting off the load current path and stopping Cbus from discharging, allowing the voltage to rise again. Simultaneously, a fluctuation suppression unit controls the voltage fluctuation amplitude within a preset range by adjusting the switching frequency of transistor Q2. This closed-loop control mechanism ensures that the Cbus voltage always fluctuates slightly near the optimal reference voltage, avoiding voltage drops or overshoots caused by sudden load changes or environmental interference in traditional power harvesting devices. Logically, this approach achieves adaptive adjustment of the system in dynamic environments by quickly responding to voltage deviations and adjusting the switching state, thereby ensuring the continuity and reliability of the sensor power supply.

[0101] 3. The overall device architecture and periodic energy harvesting method adopted in this invention solve the technical problems of high cost and complex maintenance of traditional power supply methods (such as wired cables or batteries) in subway systems by integrating the main power module (including rectifier bridge, dual MOSFET structure, voltage stabilizing filter capacitor Cbus and energy harvester) with the control module, and achieves the effect of significantly reducing deployment and operation and maintenance costs.

[0102] The detailed principles are explained below:

[0103] The rectifier bridge directly connects the rail to the concrete structure, converting the rail potential difference into direct current. A dual-MOSFET structure serves as the core switching element, working in conjunction with the Cbus capacitor to achieve voltage regulation and energy buffering. The energy harvester is responsible for delivering the energy stored in Cbus to the load. The control module achieves fully automatic energy harvesting by periodically executing an energy harvesting method (including measuring the open-circuit voltage Uoc, calculating Vref, adjusting the Cbus voltage, and maintaining stability). In principle, this design eliminates reliance on wired cables, avoiding the wiring challenges in underground environments. Simultaneously, the self-powered mechanism reduces the need for battery replacements, lowering the frequency of manual inspections and maintenance. Compared to environmental energy harvesting technologies relying on solar or wind power (which fail in underground tunnels due to space constraints and insufficient energy density), this invention fully utilizes the unique resource of rail potential, providing an efficient and low-cost alternative, thereby improving the system's economy and practicality.

[0104] 4. The voltage holding stage and dynamic maintenance strategy adopted in this invention solve the technical problem of power loss caused by response delay in the energy harvesting system by cyclically executing the control stage within a preset time period, thereby achieving the effect of optimizing energy transmission timing.

[0105] The detailed principles are explained below:

[0106] The control strategy executes three phases in a fixed-cycle cycle: open-circuit voltage acquisition, optimal voltage regulation, and voltage hold-up. During the voltage hold-up phase, the system dynamically maintains the Cbus voltage near Vref and adjusts the state of transistor Q2 in real time via the switching control unit. This timing design ensures that the system can quickly update the reference voltage Vref and immediately enter the regulation state when the rail potential changes, avoiding power point offset caused by sampling delays or control lags in traditional methods. The periodic cycle allows the system to periodically calibrate the open-circuit voltage while maintaining voltage stability, thus adapting to the dynamic characteristics of the rail potential (such as fluctuations caused by train operation). This not only improves the real-time performance of energy harvesting but also ensures the system's robustness during long-term operation, providing efficient and sustained energy support for the sensors.

[0107] In summary, this invention, through the comprehensive application of the aforementioned technical means, not only efficiently utilizes the underutilized energy source of rail potential but also solves the power supply challenges in underground environments through intelligent control strategies. Compared to traditional methods in the background art, this invention achieves significant improvements in energy efficiency, stability, cost, and applicability, providing a reliable and sustainable solution for sensor self-powering in subway systems.

Claims

1. A DC power harvesting device for rail potential used in subway sensor power supply, characterized in that, Includes the main power module and the control module; The main power module includes: The rectifier bridge: its input end is directly connected to the steel rail and the concrete structure; The dual MOSFET structure consists of two MOSFET transistors Q1 and Q2 connected in series, with the source of transistor Q1 connected to the negative terminal of the rectifier bridge output. The voltage regulator capacitor Cbus is connected between the drain of transistor Q1 and the source of transistor Q2; The energy harvester is connected to the drain of transistor Q2 at its input. The control module: The voltage measurement interface is connected to the output of the rectifier bridge to acquire the input voltage Uin. The gate control interface is connected to the gates of transistors Q1 and Q2 respectively; Configured to execute a maximum power point tracking control strategy, the input voltage Uin is stabilized at half the open-circuit voltage Uoc by periodically switching the operating state of the dual MOSFET structure.

2. The apparatus according to claim 1, characterized in that, The maximum power point tracking control strategy includes: Open-circuit voltage acquisition stage: Disconnect transistor Q1, measure the open-circuit voltage Uoc of the rail potential, and calculate the optimal reference voltage Vref = Uoc / 2; Optimal voltage regulation phase: Turn on transistor Q1, and regulate the voltage of bus capacitor Cbus to Vref through switching transistor Q2; Voltage holding phase: The switching state of transistor Q2 is dynamically controlled to make the Cbus voltage fluctuate around Vref; The aforementioned stages are executed cyclically according to a preset time period.

3. The apparatus according to claim 2, characterized in that, During the optimal voltage regulation phase: When the Cbus voltage is higher than Vref, the low-power microcontroller module drives the transistor to drive Q2 to draw energy from the load to reduce the Cbus voltage. When the Cbus voltage is lower than Vref, the low-power microcontroller module drives the turn-off transistor Q2 to raise the Cbus voltage.

4. The apparatus according to claim 2, characterized in that, During the optimal voltage regulation phase: The voltage holding phase includes: The dynamic comparison unit monitors the deviation between the bus capacitor voltage Cbus and the optimal reference voltage Vref in real time. The switch control unit, in response to the deviation, performs the following: When the Cbus voltage is higher than Vref, the low-power microcontroller module drives the transistor Q2 to open the load current path, and Cbus discharges to the load to reduce the voltage. When the Cbus voltage is lower than Vref, the low-power microcontroller module drives the turn-off transistor Q2 to cut off the load current path, and Cbus stops discharging, causing the voltage to rise again. The fluctuation suppression unit controls the Cbus voltage fluctuation within ±5% Vref range by adjusting the switching frequency of transistor Q2.

5. The apparatus according to claim 2, characterized in that, The optimal voltage holding phase lasts for 10-50ms.

6. A method for harvesting DC power from rail potential for power supply of subway sensors, characterized in that, include: Periodically disconnect the power extraction circuit from the rail and measure the open-circuit voltage Uoc; The optimal operating voltage Vref = Uoc / 2 is calculated based on Uoc. The voltage of the bus capacitor Cbus is adjusted to Vref using a dual MOSFET structure and dynamically maintained near that voltage. The energy stored in the Cbus is delivered to the load.

7. The method according to claim 6, characterized in that, The process of dynamically maintaining the voltage includes: When the Cbus voltage deviates from Vref, the low-power microcontroller module controls the switching transistor Q2 to change the load current path, so that the Cbus voltage returns to the Vref fluctuation range.

8. The method according to claim 6, characterized in that, The time to dynamically maintain the voltage Vref is 10-50 ms.

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