Energy management system and energy management method for electromagnetic vibration energy harvesting device

Abstract

The application provides an energy management system and method of an electromagnetic vibration energy harvesting device. The energy management system comprises an AC / DC selection unit, a three-phase rectification circuit, a filter circuit, a charging management unit, an anti-backflow circuit and a system power supply module. The AC / DC selection unit selectively turns on an AC path or a DC path based on the time-varying characteristics of the real-time current output by the electromagnetic vibration energy harvesting device. The three-phase rectification circuit is used to rectify the AC current in the AC path into DC current. The filter circuit is used to filter the DC current passing through the DC path. The charging management unit manages the charging of the energy storage device based on the current input from the AC path or the DC path. The anti-backflow circuit is used to prevent backflow of the current. The system power supply module is used to supply power to the AC / DC selection unit and the charging management unit. The application can achieve flexible and efficient energy management according to the energy output characteristics of the electromagnetic vibration energy harvesting device.

Description

Technical Field

[0001] This application belongs to the field of vibration energy harvesting and management technology, specifically, it provides an energy management system and energy management method for an electromagnetic vibration energy harvesting device. Background Technology

[0002] Vibration energy is widely present in the natural environment. For example, the passage of trains can cause vibrations in tracks and bridges. Effectively collecting this energy can meet the power supply needs of some low-power microelectromechanical systems (MEMS) such as wireless sensor networks. Currently, environmental vibration energy recovery methods mainly include electrostatic, piezoelectric, and electromagnetic methods. Among them, electromagnetic vibration energy harvesting devices show good application prospects due to their advantages such as low system cost, high output power, and mature technology.

[0003] The energy output of electromagnetic vibration energy harvesting devices comes from randomly generated vibration sources and cannot be continuously and stably powered to the load through direct connection. Therefore, it is necessary to charge the energy storage device (such as supercapacitors, lithium batteries, etc.) through real-time output current. However, due to the extremely wide range of variations in vibration amplitude and frequency, for example, in the field of rail transportation, heavy-haul trains exert a large excitation force on the track vibration, and the output voltage of vibration energy harvesting devices can usually reach tens of volts, making it impossible to directly charge supercapacitors, lithium batteries, or directly power electrical equipment. At the same time, since heavy-haul freight cars usually have dozens of carriages, charging supercapacitors or lithium batteries with a constant voltage or constant current for a long time will not only damage the supercapacitors or lithium batteries, but also damage the vibration energy harvesting device due to the electromechanical coupling effect.

[0004] In addition, for vibration sources with large spans, such as tracks and bridges, multiple electromagnetic vibration energy harvesting devices with DC and AC output modes are often rationally deployed to convert vibration energy of different modes into electrical energy output as efficiently as possible, given the significant differences in vibration modes at different locations.

[0005] Therefore, there is an urgent need for a system that can flexibly and efficiently manage energy based on the energy output characteristics of electromagnetic vibration energy harvesting devices to meet the power supply needs of microelectromechanical systems such as wireless sensor networks. Summary of the Invention

[0006] To address the problems existing in the prior art, this application provides an energy management system for an electromagnetic vibration energy harvesting device. The energy management system is located between the electromagnetic vibration energy harvesting device and the energy storage device, and includes: an AC / DC selection unit, a three-phase rectifier circuit, a filter circuit, a charging management unit, an anti-backflow circuit, and a system power supply module.

[0007] The AC / DC selection unit is connected to the output terminal of the electromagnetic vibration energy harvesting device. Based on the time-varying characteristics of the real-time current output by the electromagnetic vibration energy harvesting device, it selectively conducts either the AC path or the DC path.

[0008] The three-phase rectifier circuit is used to rectify the AC current in the AC path into DC current.

[0009] The filtering circuit is used to filter the DC current passing through the DC path;

[0010] The charging management unit manages the charging of the energy storage device based on the current input through the AC or DC path.

[0011] The backflow prevention circuit is used to prevent current from flowing from the energy storage device to the charging management unit;

[0012] The system power supply module is used to supply power to the AC / DC selection unit and the charging management unit.

[0013] The energy management system for the electromagnetic vibration energy harvesting device provided in this application sets up an AC / DC selection unit between the real-time current output by the electromagnetic vibration energy harvesting device and the power management module. This allows for simultaneous connection of the AC and DC paths to the corresponding input ports of the power management module. Furthermore, it adaptively switches on or off the AC or DC path based on the time-varying characteristics (current waveform) of the real-time current. This ensures that the electromagnetic vibration energy harvesting device can effectively transmit the current to the energy management module without any manual adjustment, regardless of the output current, thus greatly increasing the compatibility of the electromagnetic vibration energy harvesting device.

[0014] Furthermore, the AC / DC selection unit includes a first switching device, a second switching device, and a comparison module; the input terminals of the first switching device, the second switching device, and the comparison module are all connected to the output terminal of the electromagnetic vibration energy harvesting device for inputting the real-time current; the output terminal of the comparison module simultaneously outputs a line switching signal to the first switching device and the second switching device, wherein when the real-time current is AC current, the line switching signal is a high-level signal, and when the real-time current is DC current, the line switching signal is a low-level signal; the first switching device only conducts the AC path from the electromagnetic vibration energy harvesting device to the charging management unit when the line switching signal is a high-level signal; the second switching device only conducts the DC path from the electromagnetic vibration energy harvesting device to the charging management unit when the line switching signal is a low-level signal.

[0015] Preferably, the first switching device is an N-channel MOSFET, the second switching device is a P-channel MOSFET, and the comparison module includes a first diode, a first capacitor, a second capacitor, a first resistor, a second resistor, and a first comparator. The positive terminal of the first diode is connected to the output terminal of the electromagnetic vibration energy harvesting device, and the negative terminal is connected to the first terminal of the first capacitor. The second terminal of the first capacitor is connected to the first terminal of the second capacitor, the first terminal of the first resistor, and the first terminal of the second resistor. The second terminal of the second capacitor and the second terminal of the first resistor are both grounded. The second terminal of the second resistor is connected to the non-inverting input terminal of the first comparator, and the inverting input terminal of the first comparator is used to receive a reference voltage. The drain (D) and source (S) terminals of the first switching device are connected to the output terminal of the electromagnetic vibration energy harvesting device and the input terminal of the three-phase rectifier circuit, respectively. The source (S) and drain (D) terminals of the second switching device are connected to the output terminal of the electromagnetic vibration energy harvesting device and the input terminal of the filter circuit, respectively. The output terminal of the first comparator is connected to the gate (G) terminals of the first and second switching devices, and is used to output the line switching signal to the first and second switching devices.

[0016] Preferably, the rectifier circuit includes a second diode, a third capacitor, a fourth capacitor, and a first inductor; the second diode is used to rectify the current in the DC path; the third capacitor, the fourth capacitor, and the first inductor form a CLCπ-type filter for filtering the current in the DC path.

[0017] Furthermore, the charging management unit includes a sampling module, a BMS chip, a main control module, and a current switching module. The sampling module is used to acquire the voltage amplitude distribution of the real-time current and the voltage status of the energy storage device. The BMS chip is used to convert the current input to the three-phase rectifier circuit or filter circuit into a charging current for charging the energy storage device. Based on the voltage amplitude distribution of the real-time current output by the sampling module, the main control module acquires the voltage amplitude and rate of change information of the real-time current, and, in conjunction with the voltage status of the energy storage device, controls the current switching module to switch the charging current output by the BMS chip.

[0018] Preferably, the sampling module includes several voltage-dividing resistors and several corresponding second comparators. The several voltage-dividing resistors are connected in series between the generator operating threshold voltage output terminal and the ground terminal of the electromagnetic vibration energy harvesting device, and are used to output the corresponding comparison voltage to the non-inverting input terminal of the corresponding second comparator. The inverting input terminal of the second comparator is used to receive the voltage amplitude of the real-time current, and the output terminal is connected to the main control module. A third comparator is also included, with its non-inverting input terminal used to receive the voltage of the energy storage device, its inverting input terminal used to receive the reference voltage, and its output terminal connected to the main control module.

[0019] Preferably, the current switching module selectively connects either the first charging path or the second charging path between the BMS chip and the energy storage device based on the current switching signal output by the main control module.

[0020] Preferably, the main control module adopts a joint optimization charging strategy that considers energy output characteristics and energy storage status to regulate the charging process of the energy storage device, wherein the energy output characteristics include the voltage amplitude and rate of change information of the real-time current.

[0021] Furthermore, the joint optimization charging strategy considering energy output characteristics and energy storage state includes the following operations:

[0022] The voltage of the energy storage device and the voltage amplitude and rate of change of the real-time current output by the electromagnetic vibration energy harvesting device are acquired in real time.

[0023] When the voltage of the energy storage device is less than the slow charging threshold voltage, the charging current is controlled to not exceed the first current value;

[0024] When the voltage of the energy storage device is greater than or equal to the slow charging threshold voltage and less than the fast charging threshold voltage, it is further determined whether the real-time current output by the electromagnetic vibration energy harvesting device simultaneously satisfies that the voltage amplitude is greater than or equal to the working threshold voltage of its generator and the rate of change of the voltage amplitude is less than or equal to the rate of change threshold. If both conditions are met, the charging current is controlled to the second current value; otherwise, the charging current is controlled to not exceed the first current value, wherein the second current value is much greater than the first current value.

[0025] When the voltage of the energy storage device is greater than or equal to the fast charging threshold voltage, the charging current is controlled to not exceed the third current value, wherein the third current value is less than or equal to the second current value.

[0026] This application also provides an energy management method for an electromagnetic vibration energy harvesting device, which uses the aforementioned energy management system of the electromagnetic vibration energy harvesting device to manage the charging process of the electromagnetic vibration energy harvesting device to the energy storage device. Attached Figure Description

[0027] Figure 1 This is a schematic diagram illustrating the application of the energy management system of the electromagnetic vibration energy harvesting device provided in the embodiments of this application;

[0028] Figure 2 This is a schematic diagram of the energy management system of the electromagnetic vibration energy harvesting device provided according to an embodiment of this application;

[0029] Figure 3 This is a schematic diagram of the AC / DC selection unit provided according to an embodiment of this application;

[0030] Figure 4 This is a schematic diagram of the switching signal output by the comparison module according to an embodiment of the present application when an AC current is input;

[0031] Figure 5 This is a schematic diagram of the switching signal output by the comparison module according to an embodiment of the present application when a DC current is input;

[0032] Figure 6 The circuit schematic diagram is provided for the filter circuit according to the embodiments of this application;

[0033] Figure 7 The schematic diagram of the BMS chip and three-phase rectifier circuit provided according to the embodiments of this application is shown below.

[0034] Figure 8 This is a schematic diagram showing the voltage amplitude variation of the real-time current output by an electromagnetic vibration energy harvesting device according to some embodiments.

[0035] Figure 9 The curves showing the charging of the energy storage device and the change in the generator output torque of the vibration energy harvesting device according to the embodiments of this application are shown.

[0036] Figure 10 This is a schematic diagram illustrating the specific implementation process of the joint optimization charging strategy provided in the embodiments of this application;

[0037] Figure 11 The circuit schematic diagram is provided for the sampling module according to the embodiments of this application;

[0038] Figure 12 This is a pin diagram of the main control module provided according to an embodiment of this application;

[0039] Figure 13 This is a schematic diagram illustrating the change in generator output torque of the vibration energy harvesting device during charging according to the joint optimized charging strategy provided in the embodiments of this application;

[0040] Figure 14 This is a circuit diagram of the anti-backflow circuit provided according to an embodiment of this application;

[0041] Figure 15This is a schematic diagram of the power failure of the energy storage device when an anti-backflow circuit is added according to an embodiment of this application. Detailed Implementation

[0042] The present application will now be further described based on preferred embodiments and with reference to the accompanying drawings.

[0043] Furthermore, for ease of understanding, various components on the drawings have been enlarged or reduced, but this is not intended to limit the scope of protection of this application.

[0044] In the description of the embodiments of this application, it should be noted that if terms such as "upper," "lower," "inner," or "outer" are used to indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings, or the orientation or positional relationship commonly used when the product of this application is in use, they are only for the convenience of describing this application and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation, and therefore should not be construed as a limitation on this application. In addition, in the description of this application, in order to distinguish different units, the terms "first," "second," etc. are used in this specification, but these are not limited by the manufacturing order, nor should they be construed as indicating or implying relative importance. Their names may differ in the detailed description and claims of this application.

[0045] The vocabulary used in this specification is for illustrative purposes and is not intended to limit the scope of this application. It should also be noted that, unless otherwise expressly specified and limited, the terms "set," "connected," and "linked" should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral connection; they can refer to a mechanical connection, an electrical connection, or a connection within two components. Those skilled in the art will understand the specific meaning of these terms in this application.

[0046] <System Framework>

[0047] Embodiments of this application provide an energy management system for an electromagnetic vibration energy harvesting device. Figure 1 The schematic diagram of the electromagnetic vibration energy harvesting device provided in this application is as follows: Figure 1 As shown, the energy management system is connected between at least one electromagnetic vibration energy harvesting device and an energy storage device. It is used to convert the real-time current output by the electromagnetic vibration energy harvesting device into a charging current for charging the energy storage device, and to control the charging process based on the feedback signal of the energy storage device.

[0048] In the embodiments of this application, electromagnetic vibration energy harvesting devices with different output current characteristics can be installed at different locations of the vibration source. For example, located at... Figure 1The electromagnetic vibration energy harvesting device at the top center uses an AC generator to output current. When vibration occurs at its designated location, the real-time output current is an AC current; correspondingly, the device located at... Figure 1 The electromagnetic vibration energy harvesting device at the lower center uses a DC generator to generate electricity. When vibration occurs at its designated location, the real-time output current is a DC current. In some other embodiments, depending on the specific application scenario, the AC or DC current output by the electromagnetic vibration energy harvesting device may be converted into a charging current for the energy storage device through the energy management system of this application.

[0049] The reason for using different types of generators for vibration energy conversion is that vibration sources, such as bridges and tracks, generally have long dimensions and complex structures. Even the same factor causing vibration, such as vehicles or locomotives, may cause different vibration amplitudes and modes at different locations on the bridge or track. Therefore, during the installation, commissioning, and actual operation of electromagnetic vibration energy harvesting devices, it is often necessary to obtain the best energy output effect by changing the model of the electromagnetic vibration energy harvesting device or changing its working mode, based on the measured analysis of the vibration modes and conditions at the installation location. In this process, it may be necessary to convert the output real-time current from AC current to DC current, or vice versa. Although the real-time current output from a single current path can be directed to different input ports by manual adjustment, this inevitably increases the system compatibility and application difficulty. If a splitter method is used to directly direct the real-time current to both the AC and DC input terminals simultaneously, since the AC and DC currents require different rectification or filtering circuits, half of the output current will be unprocessed at any given time, resulting in a decrease in energy utilization.

[0050] To address the aforementioned issues, the energy management system of the electromagnetic vibration-type energy harvesting device provided in this application incorporates an AC / DC selection unit to achieve adaptive switching between DC and AC current paths. Figure 2 A schematic diagram of the energy management system of the electromagnetic vibration energy harvesting device is shown in some embodiments, such as... Figure 2 As shown, the energy management system includes an AC / DC selection unit, a three-phase rectifier circuit, a filter circuit, a charging management unit, an anti-backflow circuit, and a system power supply module.

[0051] The AC / DC selection unit is connected to the current output terminal of the electromagnetic vibration energy harvesting device. Based on the time-varying characteristics of the real-time current output by the electromagnetic vibration energy harvesting device, it selectively conducts either the AC path or the DC path. The three-phase rectifier circuit is used to rectify the AC current in the AC path into DC current. The filter circuit is used to filter the DC current passing through the DC path. The charging management unit manages the charging of the energy storage device based on the current input from the AC path or the DC path. The backflow prevention circuit is used to prevent current from flowing from the energy storage device to the charging management unit. The system power supply module is used to supply power to the AC / DC selection unit and the charging management unit.

[0052] The following detailed description of each of the above functional units and modules is provided in conjunction with the accompanying drawings.

[0053] <AC / DC Selection Unit>

[0054] like Figure 2 As shown, the input side of the AC / DC selection unit is connected to the current output terminal of the electromagnetic vibration energy harvesting device. It is used to receive the real-time current output by the electromagnetic vibration energy harvesting device and, according to the time-varying characteristics of the real-time current, selectively conduct either the AC path (the red current path at the top of the figure) or the DC path (the blue current path at the bottom of the figure).

[0055] Obviously, Figure 2 The number of AC / DC selection units shown can be matched with the number of electromagnetic vibration energy harvesting devices that output energy. For example, when two or more electromagnetic vibration energy harvesting devices are set at different positions of the vibration source and each outputs current converted from vibration energy, corresponding AC / DC selection units can be provided for each of them. The AC and DC paths of these AC / DC selection units are connected to the power management module described later, and the power management module performs the conversion and control of the charging current.

[0056] By setting an AC / DC selection unit between the real-time current and the charging management unit (described later), the AC or DC path can be adaptively switched according to the time-varying characteristics (current waveform) of the real-time current. This ensures that the electromagnetic vibration energy harvesting device can effectively transmit the current to the input terminal of the charging management unit without any manual adjustment, regardless of the output current. This greatly increases the compatibility of the electromagnetic vibration energy harvesting device.

[0057] In some preferred embodiments, such as Figure 2 As shown, the AC / DC selection unit includes a first switching device, a second switching device, and a comparison module. The input terminals of the first switching device, the second switching device, and the comparison module are all connected to the output terminal of the electromagnetic vibration energy harvesting device for inputting real-time current. The output terminal of the comparison module simultaneously outputs a line switching signal to the first switching device and the second switching device.

[0058] Furthermore, the comparison module outputs a high-level signal for the line switching signal when the real-time current is AC, and a low-level signal when the real-time current is DC. When the first switching device receives a high-level signal, it connects the AC path from the output terminal of the electromagnetic vibration energy harvesting device to the charging management unit, and disconnects it otherwise. When the second switching device receives a low-level signal, it connects the DC path from the output terminal of the electromagnetic vibration energy harvesting device to the charging management unit, and disconnects it otherwise.

[0059] Figure 3 The diagram shows a specific circuit schematic of the AC / DC selection unit in one particular embodiment, such as... Figure 3 As shown, the first switching device is an N-channel MOSFET Q located in the upper AC path. S1 The first MOSFET is a high-level on-type switching device; the second switching device is a P-channel MOSFET Q located in the lower DC path. S2 The MOSFET is a low-level conduction type switching device; the comparator module includes a first diode D1, a first capacitor C1, a second capacitor C2, a first resistor R1, a second resistor R2, and a first comparator U1.

[0060] Specifically, the anode of the first diode D1 is connected to the output terminal of the electromagnetic vibration energy harvesting device, and the cathode is connected to the first terminal of the first capacitor C1. The second terminal of the first capacitor C1 is connected to the first terminals of the second capacitor C2, the first terminals of the first resistor R1, and the second terminals of the second resistor R2. The second terminals of the second capacitor C2 and the first resistor R1 are both grounded. The second terminal of the second resistor R2 is connected to the non-inverting input terminal of the first comparator U1. The inverting input terminal of the first comparator is used to receive the reference voltage ref (e.g., 3V). The N-channel MOSFET Q... S1 As the first switching device, its drain (D) and source (S) terminals are connected to the output terminal of the electromagnetic vibration energy harvesting device and the input terminal of the three-phase rectifier circuit, respectively; the P-channel MOSFET Q... S2 As the second switching device, its source (S) and drain (D) terminals are connected to the output terminal of the electromagnetic vibration energy harvesting device and the input terminal of the filter circuit, respectively; the output terminal of the first comparator U1 is connected to the N-channel MOSFET Q. S1 The gate and P-channel MOSFET Q S2 The gate (G) terminal is connected to switch the output signal to the two MOSFETs.

[0061] The working principle of this AC / DC selection unit is as follows:

[0062] When the electromagnetic vibration energy harvesting device outputs alternating current, after passing through the first diode D1, the zero-crossing portion of the electrical energy is cut off. The alternating component can then pass through the first capacitor C1. Based on the characteristic that the voltage across a capacitor cannot change abruptly, the current is converted to direct current after passing through the second capacitor C2. This direct current is then input to the non-inverting input of the first comparator U1 through the voltage divider of the first resistor R1 and the second resistor R2. At this time, the voltage at the non-inverting input is greater than the reference voltage ref at the inverting input, causing the first comparator U1 to output a high level. The N-channel MOSFET Q... S1 Turn on, P-channel MOSFET Q S2 At this point, the alternating current output by the electromagnetic vibration energy harvesting device will enter the charging management unit through the upper alternating current path.

[0063] When the electromagnetic vibration energy harvesting device outputs DC current, according to the characteristic of a capacitor blocking DC and passing AC, the DC current is cut off after passing through the first capacitor C1. Even if a small amount of electrical energy passes through the capacitor due to current fluctuations, after the voltage division by the first resistor R1 and the second resistor R2, the voltage input to the non-inverting input terminal of the first comparator U1 is approximately 0. At this time, the voltage at the non-inverting input terminal is less than the reference voltage ref at the inverting input terminal, and the comparator outputs a low level. The N-channel MOSFET Q... S1 As of now, the P-channel MOSFET Q S2 When the circuit is open, the DC current output by the electromagnetic vibration energy harvesting device will enter the charging management unit through the DC path below.

[0064] Figure 4 This diagram illustrates the line switching signal output by the comparison module in a specific embodiment when the real-time current is an alternating current. Correspondingly, Figure 5 This diagram illustrates the line switching signal output by the comparison module when the real-time current is DC. Figure 4 , Figure 5 As can be seen, after the AC current passes through the AC / DC selection unit, it will cause the first comparator U1 to output a high level, which in turn can control the N-channel MOSFET Q. S1 To enable the AC path and control the P-channel MOSFET Q S2 The DC path is closed; after the DC current passes through the AC / DC selection unit, it will cause the first comparator U1 to output a low level, which in turn can control the P-channel MOSFET Q. S2 To enable the DC path and control the N-channel MOSFET Q S1 With the AC path closed, the current output path can be adaptively adjusted according to the energy output form of the electromagnetic vibration energy harvesting device by using the above settings, thereby greatly improving the adaptability to electromagnetic vibration energy harvesting devices with different characteristics.

[0065] It should be noted that those skilled in the art can flexibly select components to build circuits without departing from the technical concept of this application, so as to realize the function of adaptively switching AC and DC paths that the AC / DC selection unit can achieve.

[0066] Three-phase rectifier circuit and filter circuit

[0067] In the embodiments of this application, the charging management unit uses the BMS management chip described later to perform DC-DC charging operation on the energy storage device. Therefore, it is necessary to convert the AC current into DC current through a three-phase rectifier circuit in the AC path to meet the charging requirements. Figure 7 The upper right portion shows a schematic diagram of a three-phase rectifier circuit disposed on the AC path between the AC / DC selection unit and the charging management unit in some preferred embodiments.

[0068] like Figure 7 As shown, the three-phase rectifier module consists of a three-phase rectifier bridge composed of six Schottky diodes and filter and voltage stabilizing capacitors. It can rectify three-phase AC voltage from low frequency to high frequency (less than or equal to 1MHz) into DC voltage, which is then used by the subsequent circuit to synchronously step down the voltage and charge energy storage devices such as supercapacitors or lithium batteries.

[0069] Because the excitation frequency of the electromagnetic vibration energy harvesting device is relatively low in some cases, the spindle speed of the DC generator is also relatively low. That is, the DC generator operates at a low speed to generate electricity in some cases. According to the output characteristics of the DC generator, the output at low speed is not stable DC power, but relatively fluctuating electrical energy containing a small amount of AC component. At the same time, due to installation errors and other factors, the vibration energy harvesting device may experience uneven transmission during operation, which will also cause fluctuations in the output electrical energy. In addition, there are electromagnetic interferences inside the generator, noise interference from the environment and mechanical vibrations, etc. Therefore, it is necessary to further rectify and filter the electrical energy output by the DC generator. For this reason, preferably, a filter module is installed on the DC path.

[0070] Figure 6 The schematic diagram of the filter circuit is shown in some preferred embodiments, such as... Figure 6 As shown, the filter circuit includes a second diode D. r Third capacitor C f1 Fourth capacitor C f2 and the first inductor L f ,like Figure 6 As shown, through the second diode D r Due to its unidirectional conductivity, the AC component in the output current of the DC generator is cut off, achieving a rectification effect. The third capacitor C... f1 Fourth capacitor C f2 and the first inductor Lf This forms a CLCπ-type filter. Preferably, the third capacitor C f1 A relatively small value can be used to filter high-frequency signals in the output power. The first inductor L f The value of the capacitor needs to be selected based on the desired filtering effect and the capacitor value. It is used to further filter out high-frequency interference signals in the output power and to suppress pulsating signals in the power. The fourth capacitor, C... f2 A relatively large value can be selected to smooth out fluctuations in the electrical energy and maintain the stability of the output voltage. Through the rectifier and filter module, the electrical energy output by the DC generator is converted into stable DC power for use by the subsequent power management module.

[0071] In some preferred embodiments, the second diode D r Schottky diodes can be used to reduce voltage drop and improve power conversion efficiency. Furthermore, the number of capacitors in a CLC π-type filter is not limited to two. Multiple capacitors can be placed to achieve better filtering effect, depending on the output characteristics of different generators and actual application scenarios.

[0072] <Charging Management Unit>

[0073] The charging management unit is connected between the AC / DC selection unit and the energy storage device, and is used to optimize the energy output from the electromagnetic vibration energy harvesting device to the energy storage device. In some preferred embodiments, such as Figure 2 As shown, the charging management unit includes a BMS chip, a main control module, a sampling module, and a current switching module.

[0074] Figure 7 The schematic diagram of the BMS chip D1 and its peripheral circuitry in a specific embodiment is shown. The BMS chip is model BQ24650RVAR, and its input port VDC supports input DC current of 5V-30V and adjusts the charging current according to the charging status of the energy storage device (such as the voltage VBAT of the energy storage device).

[0075] Generally, such as Figure 7 The BMS chip shown has a built-in charging current adjustment function, which can adjust the charging current according to the comparison between the collected voltage VBAT of the energy storage device and the preset voltage.

[0076] For example, when the load is a wireless network device with an operating voltage of around 5V, a supercapacitor with a full-charge voltage of 5.5V or slightly higher can be selected, and an appropriate capacity (e.g., 100F or higher) can be chosen according to the load conditions of the function. Under this condition, the BMS chip D1 can set a slow-charge threshold voltage (e.g., 3V) and a fast-charge threshold voltage (4.1V), and control the energy storage device to be charged with a smaller slow-charge current or a larger fast-charge current according to the comparison result between the feedback input VBAT and the above two threshold voltages.

[0077] Specifically, under this setting, when the DC current input to the BMS chip's input terminal VDC+ exceeds 5V (but does not exceed 30V), D1 enters the charging working state. When the terminal voltage VBAT of the energy storage device does not exceed 3V, the BMS charges the energy storage device with a slow charging current of, for example, about 0.8A. When VBAT is between 3V and 4.1V, it charges the energy storage device with a fast charging current much greater than 0.8A, for example, about 10*0.8A=8A. When VBAT exceeds 4.1V, and the supercapacitor is close to full charge, it continues to charge on one hand and discharges to the load on the other. At this time, the energy storage device can be charged with a small micro-charging current.

[0078] The aforementioned BMS chip charging management strategies, which are known to those skilled in the art, are generally applicable to scenarios with relatively stable current input sources. For example, when photovoltaic equipment is used as the current input, the voltage at the VDC terminal remains basically constant for a period of time, thus enabling stable charging of the energy storage device over a longer period of time.

[0079] However, for electromagnetic vibration energy harvesting devices, the energy source is highly random, resulting in significant fluctuations in the voltage amplitude and duration of VDC.

[0080] Figure 8 This illustration shows, in a specific embodiment, the variation of the voltage amplitude (i.e., VDC terminal voltage) of the real-time current output by the electromagnetic vibration energy harvesting device over a period of time, as follows: Figure 8 As shown, the duration of the first segment of real-time current on the left is short, and its maximum voltage amplitude is low, indicating that the size of the object causing the vibration may be short (such as the locomotive head), and the generator has not yet entered the ideal working state after starting (i.e., its output voltage has not yet reached the working threshold voltage value U). out The vibration stops when it disappears; the second segment of real-time current represents the possibility of an object passing through the vibration source at high speed. Although its voltage peak is high, its duration is shorter, making it unable to stably output energy; the third segment of current on the right represents a longer object (such as a complete locomotive) passing through the vibration source at a constant speed. Its real-time current waveform has a stable segment that exceeds the generator's optimal operating threshold voltage U. outThe time period.

[0081] Figure 9 This diagram illustrates, in some embodiments, the variation curves of the charging current of the energy storage device and the output torque of the generator of the vibration energy harvesting device. Figure 9 It can be seen that when the vibration energy harvesting device starts to output energy due to vibration, if it is charged with a large current, the excessive current will cause the generator main shaft torque to increase rapidly due to the effect of electromechanical coupling. This will have a braking effect on the rotation of the generator main shaft, which will in turn cause the vibration energy harvesting device to vibrate significantly, damage the device, and affect its service life. Only when the vibration energy harvesting device is in a stable operating state is it suitable to output a larger current in a more stable state.

[0082] It is evident that for electromagnetic vibration energy harvesting devices with a high degree of randomness in output energy, since they cannot continuously and stably output electrical energy like voltage or current stabilizers, when controlling their charging, in addition to considering the charging state on the energy storage side, it is also necessary to take into account the output characteristics such as energy amplitude and stability (or rate of change) on the output side.

[0083] Therefore, in some preferred embodiments of this application, such as Figure 2 As shown, by setting a main control module, a sampling module, and a current switching module in the charging management unit, the conventional method of charging management solely through a BMS chip is improved, thereby enabling the use of a joint optimization charging strategy that considers energy output characteristics and energy storage status to regulate the charging process of the energy storage device.

[0084] Specifically, Figure 10 The following flowchart illustrates a joint optimization charging strategy considering energy output characteristics and energy storage state in some preferred embodiments of this application. Figure 2 and Figure 10 This paper explains the joint optimization charging strategy.

[0085] As in 2 and Figure 10 As shown, the acquisition module monitors the voltage value of the VDC+ port in real time to obtain the effective voltage amplitude and rate of change of the real-time current output by the electromagnetic vibration energy harvesting device; at the same time, it monitors the voltage VBAT of the energy storage device in real time.

[0086] Next, the main control module determines whether VBAT is greater than or equal to the slow charging threshold voltage. If VBAT is less than the slow charging threshold voltage at this time, the charging current will be limited to a level that does not exceed the first current value, regardless of whether the electromagnetic vibration energy harvesting device outputs real-time current.

[0087] If the main control module determines that VBAT is greater than or equal to the slow-charge threshold voltage, it further checks whether it is less than the fast-charge threshold voltage. As mentioned earlier, the fast-charge threshold voltage represents the voltage at which the energy storage device is close to full charge. For example, when the full charge voltage of the energy storage device is 5V, the fast-charge threshold voltage can be set to around 4.1V. When the voltage of the energy storage device exceeds the fast-charge threshold voltage, regardless of whether the vibration energy harvesting device outputs real-time current, the charging current will be set to a level that does not exceed the third current value.

[0088] Since the fast charging threshold voltage represents that the energy storage device is close to full charge, the third current value can be set to a micro-current state, such as 0.1A to 0.2A. That is, when the energy storage device is close to full charge, it is charged in real time with a micro-current to ensure that it can be safely fully charged and maintained at the optimal charge and discharge level.

[0089] When the voltage of the energy storage device is between the slow-charge threshold voltage and the fast-charge threshold voltage, it indicates that the energy storage device is ready for high-current fast charging. At this time, if... Figure 10 As shown, the real-time current characteristics of the vibration energy harvesting device are further judged. Specifically, it is judged in turn whether the voltage amplitude of the real-time current output by the electromagnetic vibration energy harvesting device exceeds the operating threshold voltage of its generator, and whether the rate of change of the voltage amplitude is lower than the preset rate of change threshold. If either of these conditions is not met, it means that the vibration energy harvesting device is either in the start-up / end-up stage or its output has not reached a steady state. In this case, the charging current is still limited to not exceed the first current value to protect the mechanical structure of the vibration energy harvesting device. When both conditions are met, the charging current is set to a second current value that is much greater than the first current value (e.g., when the first current value is 0.8A, the second current value is set to about 8A) to make full use of the relatively stable output energy of the vibration energy harvesting device to charge the energy storage device.

[0090] Figure 11 , Figure 12 The circuit diagrams of the sampling module and the main control module are shown in some preferred embodiments, while the specific circuit of the current switching module is shown in [the diagram]. Figure 7 .

[0091] As shown in the figure, the sampling module may include several voltage divider resistors (R). re1 To R re5 The voltage divider circuit formed by the generator has one end grounded and the other end used to input the generator's operating threshold voltage U. out The operating threshold voltage of the generator can be determined based on the specific generator model used in the electromagnetic vibration energy harvesting device. For example, if it can enter the ideal working state when its output is 10V, then the operating threshold voltage U can be set accordingly. out Set to 10V.

[0092] Furthermore, when using dry cell batteries or button batteries as the system power supply module, it is generally impossible to directly provide a 10V operating threshold voltage. Therefore, it is possible to use... Figure 11 As shown, a boost converter chip U2 is used to boost the voltage to obtain a 10V U. out .

[0093] Furthermore, such as Figure 11 As shown, several comparison voltages are drawn from the voltage divider resistors and connected to the non-inverting input of the corresponding second comparators (U3 to U7). The VDC+ terminal is connected to the inverting input of each second comparator, and the output of each second comparator is connected to the IO1 to IO5 ports of the main control module. By adjusting the resistance value of each voltage divider resistor, the comparison voltage values ​​can be set according to preset step sizes. For example, the comparison voltages input to the non-inverting inputs of U3 to U7 are 10V, 9V, 8V, 7V, and 6V, respectively.

[0094] like Figure 12 As shown, the main control module M1 can determine whether the effective voltage amplitude of the real-time current output by the electromagnetic vibration energy harvesting device exceeds the operating threshold voltage U by combining the high and low level signals output by the various second comparators. out， And by measuring the difference in amplitude between two time intervals, information about the rate of change can be obtained.

[0095] Furthermore, such as Figure 11 As shown, the sampling module also includes a third comparator U8, which is used to compare the voltage VBAT of the energy storage device with the reference voltage ref (e.g., 3V). The comparison result is also input to the IO9 port of the main control module M1 to determine whether the energy storage device has entered the fast charging stage.

[0096] like Figure 7 As shown, the current switching module is located between the BMS chip's charging output port and the energy storage device's BAT charging terminal VBAT, and includes a resistor R. SR1 R SR2 And a third switching device (NMOS transistor) and a fourth switching device (PMOS transistor), the third and fourth switching devices are respectively connected to resistor R. SR1 R SR2 The main control module simultaneously outputs current switching signals to the gates of two switching devices via IO6 port to control the charging current to selectively pass through either the NMOS or PMOS transistor. When IO6 outputs a high level, the NMOS transistor turns on and the PMOS transistor turns off, thereby causing R... SR1 The first charging path is activated, R SR2The second charging path is turned off; when IO6 outputs a low level, the NMOS transistor is turned off and the PMOS transistor is turned on, thereby turning off the first charging path and turning on the second charging path.

[0097] The working principles of the acquisition module, main control module, BMS chip, and current switching module are as follows:

[0098] 1) When the voltage value VBAT of the energy storage module is less than or equal to the 3V slow-charge threshold voltage, this voltage value is fed back to the BMS chip, and the BMS chip outputs its preset slow-charge current. At this time, since the voltage value VBAT of the energy storage module is also collected by the sampling module and input to the main control module, when the main control module determines that the voltage value of the energy storage module has not exceeded the slow-charge threshold voltage, regardless of the state of the VDC+ value collected on the vibration energy harvesting device side, it sets IO6 to a high level, thereby turning on R... SR1 The current is output through the current-carrying circuit.

[0099] 2) When VBAT is in the 3V~4.1V range, the BMS chip outputs its preset fast charging current based on the feedback VBAT voltage value. This fast charging current is generally 10 times the slow charging current. At this time, the main control module further determines whether fast charging can be performed with the second charging current. If the determination result is no, IO6 is set to low level. At this time, R SR2 When the circuit is open, although the BMS chip outputs a much larger fast charging current than its slow charging current, by setting R... SR1 R SR2 The ratio of the resistance value, for example, the resistance value R. SR2 Set to approximately R SR1 10 times that, enabling the use of R SR2 The output current remains the first charging current; if the judgment result is yes, then R is turned on by setting IO6 to a high level. SR1 In the current path, charging with the second charging current can be achieved.

[0100] 3) When VBAT exceeds 4.1V, the BMS chip will output a relatively small regulating current. Therefore, regardless of the level of IO06, the current will be transmitted through R... SR1 Or R SR2 The charging current in the circuit is extremely weak, meaning that a third charging current, which is less than the second charging current, can be used for charging.

[0101] Figure 13 The figure shows the motor torque of the vibration energy harvesting device in a specific embodiment using the above-described joint optimized charging strategy. For comparison, the figure also shows the motor torque in the unoptimized state. Figure 13It can be seen that, according to the joint optimized charging strategy, the energy storage element can be fully charged quickly, and the torque of the generator main shaft is at a safe level, which will not cause severe vibration of the structure. However, if an unoptimized charging strategy is used, it will cause a sharp increase and drastic change in torque, which will lead to severe vibration of the structure and a shortened service life.

[0102] <Anti-backflow circuit>

[0103] Unlike a stable power supply, electromagnetic vibration energy harvesting devices do not continuously output electrical energy because environmental vibrations are not constant. To prevent the electrical energy stored in the energy storage device from flowing back into the charging management unit when the vibration energy harvesting device stops working, thereby damaging the module, in some preferred embodiments of this application, an anti-backflow circuit is also provided between the charging management unit and the energy storage device to achieve unidirectional control of the charging direction and prevent current from flowing from the energy storage device to the charging management unit.

[0104] Figure 14 The schematic diagram of the anti-backflow circuit is shown in some specific embodiments, such as... Figure 14 As shown, the backflow prevention circuit includes a first transistor Q1, a second transistor Q2, a first switching transistor Q3, and a first current-limiting resistor R. cl1 Second current-limiting resistor R cl2 Among them, the first transistor Q1 and the second transistor Q2 are both PNP transistors, and the first switching transistor Q3 is a P-type MOSFET.

[0105] Specifically, the emitter of the first transistor Q1 is connected to the positive output terminal of the BMS chip and the drain (D) of the first switching transistor Q3, and the base is connected to the first current-limiting resistor R. cl1 The first terminal is connected to the base of the second transistor Q2, and the collector is connected to the first current-limiting resistor R. cl1 The first terminal is connected; the emitter of the second transistor Q2 is connected to the source of the first switching transistor Q3 and the positive terminal of the energy storage device input, and the collector is connected to the gate (G) of the first switching transistor Q3 and the second current-limiting resistor R. cl2 The first terminal is connected; the negative terminal of the BMS chip output is connected to the first current-limiting resistor R. cl1 Second terminal, second current-limiting resistor R cl2 The second end and the negative terminal of the energy storage device input are both connected to the ground.

[0106] The working principle of this anti-backflow circuit is as follows:

[0107] When the vibration energy harvesting device is working normally, the charging management unit outputs electrical energy. On the one hand, this causes the voltage difference between the emitter and base of the first transistor Q1 to be greater than the transistor's forward voltage drop, turning on the first transistor Q1. The bases of both the first transistor Q1 and the second transistor Q2 follow the output voltage of the charging management unit. On the other hand, the energy flows into the subsequent stage through the body diode of the first switching transistor Q3, causing the source of the first switching transistor Q3 and the emitter of the second transistor Q2 to also follow the output voltage of the charging management unit. The voltage difference between the gate and source of the first switching transistor Q3 reaches the conduction condition, turning on the first switching transistor Q3. There is no voltage difference between the emitter and base of the second transistor Q2, so the second transistor Q2 is turned off. Therefore, when the vibration energy harvesting device is working normally, the electrical energy output by the charging management unit will continuously flow into the energy storage device.

[0108] When the vibration energy harvesting device stops working, the charging management unit stops outputting electrical energy. There is no voltage difference between the emitter and base of the first transistor Q1, so the first transistor Q1 is turned off. The energy storage device starts outputting electrical energy forward, causing the voltage difference between the emitter and base of the second transistor Q2 to be greater than the transistor's on-state voltage drop. The second transistor Q2 then turns on. The base of the second transistor Q2 and the source of the first switching transistor Q3 both follow the output voltage of the energy storage device. There is no voltage difference between the gate and source of the first switching transistor Q3, so the first switching transistor Q3 is turned off. Therefore, when the vibration energy harvesting device stops working, the electrical energy in the energy storage device will not flow back to the charging management unit.

[0109] The introduction of the anti-backflow circuit ensures that when the vibration energy harvesting device is working normally, the electrical energy output by the charging management unit can flow into the energy storage device with extremely low loss. When the vibration energy harvesting device stops working, the electrical energy stored in the energy storage device will not flow back into the charging management unit and cause circuit damage. Figure 15 The illustration shows a comparison of the power loss of the supercapacitor, which serves as an energy storage device, with and without an anti-backflow circuit in a specific embodiment. The experimental comparison demonstrates that with the anti-backflow circuit added, the power loss rate of the supercapacitor is significantly reduced compared to without it. Aside from the minimal power consumption of the anti-backflow circuit itself, no electrical energy flows back from the energy storage module to the charging management unit. This verifies the effectiveness of applying the anti-backflow circuit to the energy management circuit of the vibration energy harvesting system.

[0110] To ensure the stable operation of each functional module in the system, the system power supply module can select appropriate dry cell batteries, button batteries, lithium batteries, etc., based on the specifications of multiple comparators and the main control module in the system. For example, Figure 12The main control module M1 shown can use a 3.3V operating voltage, and its power consumption in the working state is no more than 2.7mW. It can be used as the core, and the power consumption of other power-consuming modules can be taken into account to select a suitable power supply module.

[0111] The specific embodiments of this application have been described in detail above. For those skilled in the art, several improvements and modifications can be made to this application without departing from the principle of this application, and these improvements and modifications also fall within the protection scope of the claims of this application.

Claims

1. An energy management system for an electromagnetic vibration energy harvesting device, disposed between the electromagnetic vibration energy harvesting device and an energy storage device, characterized in that: It includes an AC / DC selection unit, a three-phase rectifier circuit, a filter circuit, a charging management unit, an anti-backflow circuit, and a system power supply module; The AC / DC selection unit is connected to the output terminal of the electromagnetic vibration energy harvesting device. Based on the time-varying characteristics of the real-time current output by the electromagnetic vibration energy harvesting device, it selectively conducts either the AC path or the DC path. The three-phase rectifier circuit is used to rectify the AC current in the AC path into DC current. The filtering circuit is used to filter the DC current passing through the DC path; The charging management unit manages the charging of the energy storage device based on the current input through the AC or DC path. The backflow prevention circuit is used to prevent current from flowing from the energy storage device to the charging management unit; The system power supply module is used to supply power to the AC / DC selection unit and the charging management unit; The AC / DC selection unit includes a first switching device, a second switching device, and a comparison module; The input terminals of the first switching device, the second switching device, and the comparison module are all connected to the output terminal of the electromagnetic vibration energy harvesting device for inputting the real-time current. The output of the comparison module simultaneously outputs a line switching signal to the first switching device and the second switching device. When the real-time current is an AC current, the line switching signal is a high-level signal, and when the real-time current is a DC current, the line switching signal is a low-level signal. The first switching device only conducts the AC path between the electromagnetic vibration energy harvesting device and the charging management unit when the line switching signal is a high-level signal; The second switching device conducts the DC path from the electromagnetic vibration energy harvesting device to the charging management unit only when the line switching signal is a low-level signal.

2. The energy management system of the electromagnetic vibration energy harvesting device according to claim 1, characterized in that, The first switching device is an N-channel MOSFET, the second switching device is a P-channel MOSFET, and the comparison module includes a first diode, a first capacitor, a second capacitor, a first resistor, a second resistor, and a first comparator. The positive terminal of the first diode is connected to the output terminal of the electromagnetic vibration energy harvesting device, and the negative terminal is connected to the first terminal of the first capacitor. The second terminal of the first capacitor is connected to the first terminal of the second capacitor, the first terminal of the first resistor, and the first terminal of the second resistor. The second terminal of the second capacitor and the second terminal of the first resistor are both grounded. The second terminal of the second resistor is connected to the non-inverting input terminal of the first comparator. The inverting input terminal of the first comparator is used to receive the reference voltage. The drain (D) and source (S) terminals of the first switching device are connected to the output terminal of the electromagnetic vibration energy harvesting device and the input terminal of the three-phase rectifier circuit, respectively. The source (S) and drain (D) terminals of the second switching device are connected to the output terminal of the electromagnetic vibration energy harvesting device and the input terminal of the filter circuit, respectively. The output terminal of the first comparator is connected to the gate (G) of the first switching device and the gate (G) of the second switching device, and is used to output the line switching signal to the first switching device and the second switching device.

3. The energy management system of the electromagnetic vibration energy harvesting device according to claim 1, characterized in that, The filter circuit includes a second diode, a third capacitor, a fourth capacitor, and a first inductor; The second diode is used to rectify the current in the DC path; The third capacitor, the fourth capacitor, and the first inductor form a CLCπ-type filter, which is used to filter the current in the DC path.

4. The energy management system of the electromagnetic vibration energy harvesting device according to claim 1, characterized in that, The charging management unit includes a sampling module, a BMS chip, a main control module, and a current switching module; The sampling module is used to obtain the voltage amplitude distribution of the real-time current and the voltage status of the energy storage device; The BMS chip is used to convert the current input to the three-phase rectifier circuit or filter circuit into a charging current for charging the energy storage device. The main control module obtains the voltage amplitude and rate of change information of the real-time current based on the voltage amplitude distribution of the real-time current output by the sampling module, and controls the current switching module to switch the charging current output by the BMS chip in combination with the voltage status of the energy storage device.

5. The energy management system of the electromagnetic vibration energy harvesting device according to claim 4, characterized in that, The sampling module includes: A plurality of voltage dividing resistors and a plurality of corresponding second comparators are provided. The plurality of voltage dividing resistors are connected in series between the generator operating threshold voltage output terminal and the ground terminal of the electromagnetic vibration energy harvesting device, and are used to output the corresponding comparison voltage to the non-inverting input terminal of the corresponding second comparator. The inverting input terminal of the second comparator is used to receive the voltage amplitude of the real-time current, and the output terminal is connected to the main control module. The third comparator has a non-inverting input terminal for receiving the voltage of the energy storage device, an inverting input terminal for receiving a reference voltage, and an output terminal connected to the main control module.

6. The energy management system of the electromagnetic vibration energy harvesting device according to claim 4, characterized in that, The current switching module selectively connects either the first charging path or the second charging path between the BMS chip and the energy storage device based on the current switching signal output by the main control module.

7. The energy management system of the electromagnetic vibration energy harvesting device according to claim 4, characterized in that, The main control module adopts a joint optimization charging strategy that considers energy output characteristics and energy storage status to regulate the charging process of the energy storage device. The energy output characteristics include the voltage amplitude and rate of change of the real-time current.

8. The energy management system of the electromagnetic vibration energy harvesting device according to claim 5, characterized in that, The joint optimization charging strategy, which considers energy output characteristics and energy storage state, includes the following operations: The voltage of the energy storage device and the voltage amplitude and rate of change of the real-time current output by the electromagnetic vibration energy harvesting device are acquired in real time. When the voltage of the energy storage device is less than the slow charging threshold voltage, the charging current is controlled to not exceed the first current value; When the voltage of the energy storage device is greater than or equal to the slow charging threshold voltage and less than the fast charging threshold voltage, it is further determined whether the real-time current output by the electromagnetic vibration energy harvesting device simultaneously satisfies that the voltage amplitude is greater than or equal to the working threshold voltage of its generator and the rate of change of the voltage amplitude is less than or equal to the rate of change threshold. If both conditions are met, the charging current is controlled to the second current value; otherwise, the charging current is controlled to not exceed the first current value, wherein the second current value is much greater than the first current value. When the voltage of the energy storage device is greater than or equal to the fast charging threshold voltage, the charging current is controlled to not exceed the third current value, wherein the third current value is less than or equal to the second current value.

9. An energy management method for an electromagnetic vibration energy harvesting device, characterized in that, The energy management system of the electromagnetic vibration energy harvesting device according to claim 1 is used to manage the charging process of the electromagnetic vibration energy harvesting device to the energy storage device.

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