Capacitor current-limiting power taking device based on dynamic reactive power regulation and control method thereof

Abstract

The application discloses a capacitor current-limiting power taking device based on dynamic reactive power regulation and a control method thereof. The device comprises a high-voltage arm capacitor, one end of the high-voltage arm capacitor is connected to a high-voltage power taking point, and the other end is connected to ground after being connected in series with a low-voltage arm capacitor. The low-voltage arm capacitor is connected in parallel with a first winding of a transformer. A second winding of the transformer is connected to an input end of an AC / DC unit through an alternating current (AC) load. An output end of the AC / DC unit is connected to a direct current (DC) load and a power supply end of a single-chip microcomputer respectively. The single-chip microcomputer is connected to the second winding of the transformer, a third winding of the transformer, the AC load and the DC load respectively. Surplus power taking current except for that required by a load is not dissipated in active power, thereby greatly reducing heat generation of the power taking device.

Description

Technical Field

[0001] This invention belongs to the field of power supply technology, specifically relating to a capacitor current-limiting power extraction device based on dynamic reactive power regulation and its control method. Background Technology

[0002] Currently, existing capacitor current-limiting power extraction devices in the power grid, as emerging electrical equipment, can be applied to various occasions with local power supply needs, such as pole-mounted switches and their FTUs, pole online monitoring, surge arrester online monitoring, especially in various high-potential local power supply occasions. In addition, power grid companies provide power towers with a wide coverage area for shared construction of communication base stations, avoiding the waste of resources in rebuilding towers for new communication base stations. However, communication base stations usually require large power, with 5G base stations reaching 5-10kW. Conventional power extraction schemes cannot meet this power requirement. Therefore, local power supply for communication base stations on power towers has become a major problem for shared towers.

[0003] Capacitor-based current-limited energy harvesting, as a local power system energy harvesting solution with small size, large power output, and stable energy harvesting mode, offers advantages such as convenient installation, flexible installation potential, and wide power coverage. It is the preferred solution for addressing most local power supply needs in the energy internet and solving the problem of local power supply for power poles. However, due to the special nature of the capacitor-based current-limited energy harvesting principle, its power supply mode is constant current. To ensure stable output of the energy harvesting device under various load conditions and grid fluctuations, a dynamic load must be introduced to address the problem of excess power. The conventional solution is to set up multiple sets of bleeder resistors, which are actively activated under excess power conditions to divert excess current. However, this solution converts energy into heat loss. To ensure the normal operation of the energy harvesting device under no-load conditions, the device's heat dissipation capacity must be able to meet the full discharge under the highest energy harvesting state. This solution is feasible for small energy harvesting devices of a few watts to tens of watts; however, for kilowatt-level energy harvesting devices, this heat dissipation requirement is extremely demanding and not practically feasible. Summary of the Invention

[0004] The technical problem to be solved by the present invention is to provide a capacitor current-limiting power extraction device and its control method based on dynamic reactive power regulation, which addresses the shortcomings of the prior art and solves the technical problem of excess power dissipation in capacitor current-limiting power extraction.

[0005] The present invention adopts the following technical solution:

[0006] A capacitor current-limiting power extraction device based on dynamic reactive power regulation includes a high-voltage arm capacitor, one end of which is connected to a high-voltage power extraction point, and the other end is connected to a low-voltage arm capacitor in series and then grounded; the low-voltage arm capacitor is connected in parallel with the first winding of a transformer; the second winding of the transformer is connected to the input terminal of an AC / DC unit via an AC load, and the output terminal of the AC / DC unit is connected to a DC load and the power supply terminal of a microcontroller, respectively; the microcontroller is connected to the second winding of the transformer, the third winding of the transformer, the AC load, and the DC load, respectively.

[0007] Specifically, a filter unit is installed between the second winding of the transformer and the AC load.

[0008] Specifically, the third winding of the transformer is connected to the microcontroller via a buffer unit, and the power supply terminal of the buffer unit is connected to the output terminal of the AC / DC unit.

[0009] Furthermore, an inverter unit is installed between the third winding of the transformer and the buffer unit, and the inverter unit is connected to the output terminal of the AC / DC unit and the microcontroller respectively.

[0010] Another technical solution of the present invention is a capacitor current-limiting power extraction control method based on dynamic reactive power regulation, which utilizes the aforementioned capacitor current-limiting power extraction device based on dynamic reactive power regulation, and includes the following steps:

[0011] The microcontroller detects the current at the second and third windings of the transformer, the voltage and current of the AC load, and the current of the DC load, respectively, and obtains the zero-crossing phase signal based on the combined current of the second and third windings.

[0012] Calculate the active component of the transformer's third winding based on the current and voltage of the third winding;

[0013] The inverter voltage phase correction amount is determined by the zero-crossing phase signal and the active component of the third winding of the transformer. Based on the inverter voltage phase correction amount, an SPWM control signal is generated to generate a corresponding equivalent sinusoidal voltage at the third winding of the transformer, thereby controlling the active component of the third winding of the transformer to be 0.

[0014] Specifically, the inverter voltage phase correction amount is determined as follows:

[0015] The third winding of the transformer is connected to the buffer unit through the inverter unit. If the active component of the third winding of the transformer is greater than 0, the phase angle difference between the inverter voltage of the inverter unit and the combined current of the second and third windings of the transformer is increased until the active component is equal to 0. If the active component of the third winding of the transformer is less than 0, the phase angle difference between the inverter voltage of the inverter unit and the combined current of the second and third windings of the transformer is decreased until the active component is equal to 0.

[0016] Specifically, the third winding of the transformer is connected to the buffer unit through the inverter unit. The microcontroller detects the voltage of the AC load or DC load respectively, compares the obtained load voltage with the reference voltage, generates an error signal, and controls the capacitor voltage in the buffer unit through the error signal to modulate the AC load or DC load voltage to the target value.

[0017] Specifically, when the load voltage is lower than the rated voltage, the capacitor voltage in the buffer unit is increased until the load voltage equals the rated voltage, thereby adjusting the effective value of the AC voltage on the inverter unit.

[0018] Specifically, when the load voltage is higher than the rated voltage, the capacitor voltage in the buffer unit is reduced until the load voltage equals the rated voltage, thereby regulating the effective value of the AC voltage on the inverter unit.

[0019] Specifically, the voltage effective value of the second winding of the transformer is affected by the transformer coupling.

[0020] Compared with the prior art, the present invention has at least the following beneficial effects:

[0021] This invention discloses a capacitor current-limiting power extraction device based on dynamic reactive power regulation. The high-voltage arm capacitor, the low-voltage arm capacitor, and the transformer are connected in series and parallel between the high-voltage power extraction point and ground. The first winding of the transformer generates current. Part of the generated current powers the AC load through the second winding, and after passing through the AD / DC unit, powers the DC load and the power extraction device itself. The other part passes through the third winding, whose power is represented as reactive power. This ensures that the excess power extraction current other than that required by the load is not dissipated in a positive manner, greatly reducing the heat generation of the power extraction device.

[0022] Furthermore, to ensure power supply to each unit of the device, high-frequency interference generated by the SPWM inverter of the third winding can be further filtered out, providing a pure 50Hz sinusoidal AC power to the load; and through the AC / DC unit, multi-level DC power supply voltage can be generated to meet the needs of various DC voltage loads and provide reliable self-power for the energy harvesting device.

[0023] Furthermore, by adjusting the voltage of the buffer unit through a microcontroller, the peak value of the SPWM voltage can be controlled, thereby achieving effective control of the inverter AC voltage.

[0024] Furthermore, an inverter unit is installed in the third winding of the transformer to regulate the transformer voltage waveform. The AC side of the inverter is connected to the third winding of the transformer, and an equivalent SPWM voltage is generated on the third winding of the transformer through high-frequency inversion. This causes the first and second windings of the transformer to generate sinusoidal voltages corresponding to the equivalent SPWM voltage, thereby realizing the control of the AC voltage waveform of the transformer. The steady-state phase angle difference between the voltage and current of the third winding of the transformer can be controlled to be 90°, so that reactive power is generated on the third winding, avoiding excessive current from generating a large amount of active power that would cause the device to overheat.

[0025] A capacitor current-limiting power supply control method based on dynamic reactive power regulation is proposed. This method uses a microcontroller to detect the current in the second and third windings, as well as the AC load voltage and current, and the DC load current. It obtains a zero-crossing phase signal based on the combined current of the second and third windings. Based on the active power component of the transformer's third winding calculated from the current and voltage of the third winding, it calculates the inverter voltage phase correction. Using the reference phase signal and the inverter voltage phase correction as a basis, it further calculates and generates a phase control signal, causing the inverter unit to generate a corresponding inverter voltage in the third winding, ultimately making the active power component of the transformer's third winding zero.

[0026] Furthermore, the inverter voltage phase can be dynamically adjusted so that the inverter voltage phase is 90° out of phase with the third winding current phase, keeping the active component of the third winding at 0.

[0027] Furthermore, the microcontroller detects the AC or DC load voltage, compares the load voltage with the reference voltage to generate an error signal, and controls the capacitor voltage in the buffer unit through the error signal. When the load voltage is too low, the capacitor voltage in the buffer unit is increased; when the load voltage is too high, the capacitor voltage in the buffer unit is decreased. This can adjust the effective value of the AC side voltage of the inverter unit, and then affect the effective value of the second winding voltage through transformer coupling, so that the AC or DC load voltage is modulated to the target value.

[0028] Furthermore, when the load voltage is low, increasing the capacitor voltage in the buffer unit and adjusting the effective value of the AC side voltage of the inverter unit can automatically correct the load voltage when it is lower than the rated voltage.

[0029] Furthermore, when the load voltage is too high, reducing the capacitor voltage in the buffer unit and adjusting the effective value of the AC voltage on the inverter unit can automatically correct the load voltage when it is higher than the rated voltage.

[0030] In summary, this invention can calculate the SPWM control signal by measuring the current of the second and third windings of the transformer in the energy harvesting device, as well as the load voltage. This enables the microcontroller to control the buffer unit and the inverter unit, ultimately stabilizing the AC and DC load voltages. Furthermore, the active component of the third winding of the transformer is zero, allowing the excess current of the energy harvesting device to be discharged in a reactive form through the third winding, thus preventing the device from overheating. This invention possesses an engineering-featured kilowatt-level energy harvesting capability.

[0031] The technical solution of the present invention will be further described in detail below with reference to the accompanying drawings and embodiments. Attached Figure Description

[0032] Figure 1 This is a schematic diagram of the circuit principle of the power supply device of the present invention;

[0033] Figure 2 This is a schematic diagram of the reactive power control method of the present invention;

[0034] Figure 3 This is a schematic diagram of the load voltage control method of the present invention.

[0035] The components include: 1. High-voltage arm capacitor; 2. Low-voltage arm capacitor; 3. Transformer; 4. Filter unit; 5. AC / DC unit; 6. Microcontroller; 7. Inverter unit; 8. Buffer unit. Detailed Implementation

[0036] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some, not all, of the embodiments of the present invention. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0037] In the description of this invention, it should be understood that the terms "center," "longitudinal," "lateral," "upper," "lower," "front," "rear," "left," "right," "vertical," "horizontal," "top," "bottom," "inner," "outer," "one side," "one end," and "one side," etc., indicating the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings, are only for the convenience of describing the invention 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 of the invention. Furthermore, the terms "first" and "second" are used for descriptive purposes only and should not be construed as indicating or implying relative importance or implicitly specifying the number of indicated technical features. Thus, a feature defined with "first" or "second" may explicitly or implicitly include one or more of that feature. In the description of this invention, unless otherwise stated, "a plurality of" means two or more.

[0038] In the description of this invention, it should be noted that, unless otherwise explicitly specified and limited, the terms "installation," "connection," and "linking" 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 or an electrical connection; they can refer to a direct connection or an indirect connection through an intermediate medium; and they can refer to the internal connection of two components. Those skilled in the art can understand the specific meaning of the above terms in this invention based on the specific circumstances.

[0039] It should be understood that, when used in this specification and the appended claims, the terms "comprising" and "including" indicate the presence of the described features, integrals, steps, operations, elements and / or components, but do not exclude the presence or addition of one or more other features, integrals, steps, operations, elements, components and / or collections thereof.

[0040] It should also be understood that the terminology used in this specification is for the purpose of describing particular embodiments only and is not intended to limit the invention. As used in this specification and the appended claims, the singular forms “a,” “an,” and “the” are intended to include the plural forms unless the context clearly indicates otherwise.

[0041] It should also be further understood that the term "and / or" as used in this specification and the appended claims refers to any combination of one or more of the associated listed items and all possible combinations, and includes such combinations.

[0042] The accompanying drawings illustrate various structural schematic diagrams according to embodiments disclosed in this invention. These drawings are not to scale, and some details have been enlarged for clarity, and some details may have been omitted. The shapes of the various regions and layers shown in the drawings, as well as their relative sizes and positional relationships, are merely exemplary and may deviate from reality due to manufacturing tolerances or technical limitations. Furthermore, those skilled in the art can design regions / layers with different shapes, sizes, and relative positions as needed.

[0043] This invention provides a capacitor current-limiting power extraction device and its control method based on dynamic reactive power regulation. The device generates current in the first winding of the transformer through the series and parallel connection of the high-voltage arm capacitor, the low-voltage arm capacitor, and the transformer, thereby providing a certain current to the second and third windings. The second winding is connected to an AC load via a filter unit, which filters out high-frequency noise and improves power quality. An AC / DC unit is connected in parallel to the AC load to provide DC power to the DC load and also to power the energy extraction device. The third winding is connected to the AC side of an inverter unit, allowing control of the voltage of each winding of the transformer by adjusting the inverter voltage. A buffer unit is connected to the DC side of the inverter unit to provide the energy required for inverter operation, stabilize the inverter output voltage, and stop the inverter unit from working when no inverter control is needed.

[0044] Please see Figure 1 The present invention discloses a capacitor current limiting power extraction device based on dynamic reactive power regulation, comprising a high-voltage arm capacitor 1, a low-voltage arm capacitor 2, a transformer 3, a filter unit 4, an AC / DC unit 5, a microcontroller 6, an inverter unit 7, and a buffer unit 8.

[0045] One end of the high-voltage arm capacitor 1 is connected to the high-voltage power take-off point, and the other end is connected to the ground after being connected in series with the low-voltage arm capacitor 2; the low-voltage arm capacitor 2 is connected in parallel with the first winding of the transformer 3; the second winding of the transformer 3 is connected to the input terminal of the filter unit 4; the output terminal of the filter unit 4 is connected in sequence to the AC load and the input terminal of the AC / DC unit 5; the output terminal of the AC / DC unit 5 is connected to the DC load, as well as the power supply terminals of the microcontroller 6, inverter unit 7 and buffer unit 8 set in the device; the third winding of the transformer 3 is connected to the AC terminal of the inverter unit 7; the DC terminal of the inverter unit 7 is connected to the buffer unit 8.

[0046] The high-voltage arm capacitor 1 and the low-voltage arm capacitor 2 are connected in series between the high-voltage power take-off point and ground, generating a small current in the main circuit.

[0047] Transformer 3 converts the small current in high-voltage arm capacitor 1 and low-voltage arm capacitor 2 into a large current, and achieves electrical isolation between the AC / DC unit 5 connected by the second winding and the AC terminal of the inverter unit 7 connected by the third winding.

[0048] The filter unit 4 is used to filter out the high-frequency components of the second winding of transformer 3, thereby improving the power supply quality of AC and DC loads.

[0049] AC / DC unit 5 is used to convert alternating current into stable direct current to power DC loads, microcontroller 6, inverter unit 7, and buffer unit 8.

[0050] The microcontroller 6 is used to measure the current of the second winding and the third winding of the transformer 3, the AC load voltage and current and the DC load current, and to calculate the inverter voltage phase correction amount, and generate an SPWM signal to control the inverter unit 7.

[0051] Inverter unit 7 is used to generate an SPWM equivalent sinusoidal voltage in the third winding of transformer 3, so that the voltages of the first and second windings of transformer 3 are corresponding sinusoidal waveforms.

[0052] The buffer unit 8 is used to provide a stable DC voltage and instantaneous inverter energy to the inverter unit 7, and to stop supplying energy when the inverter unit 7 does not need to work.

[0053] Please see Figure 2 The present invention provides a capacitor current limiting power extraction control method based on dynamic reactive power regulation, which is as follows:

[0054] The microcontroller detects the current in the second and third windings, the AC load voltage and current, and the DC load current, and obtains a zero-crossing phase signal based on the combined current of the second and third windings.

[0055] The active component of the transformer's third winding is calculated based on the current and voltage of the third winding. If the active component is greater than 0, the phase angle difference between the inverter voltage and the current formed by the second and third windings increases; if the active component is less than 0, the phase angle difference between the inverter voltage and the current formed by the second and third windings decreases. This results in an inverter voltage phase correction.

[0056] Based on the reference phase signal and the inverter voltage phase correction, an SPWM control signal is calculated and generated, which causes the inverter unit to generate the corresponding inverter voltage in the third winding, ultimately making the active component of the transformer's third winding zero.

[0057] Please see Figure 3 Regarding the load voltage, the specific control is as follows:

[0058] The microcontroller detects the AC or DC load voltage, compares the load voltage with the reference voltage, and generates an error signal.

[0059] The voltage of the capacitor in the buffer unit is controlled by the error signal. When the load voltage is too low, the voltage of the capacitor in the buffer unit is increased, and when the load voltage is too high, the voltage of the capacitor in the buffer unit is decreased, thereby regulating the effective value of the AC side voltage of the inverter unit.

[0060] By influencing the effective value of the second winding voltage through transformer coupling, the AC or DC load voltage is modulated to the target value.

[0061] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some, not all, of the embodiments of the present invention. The components of the embodiments of the present invention described and shown in the accompanying drawings can generally be arranged and designed in various different configurations. Therefore, the following detailed description of the embodiments of the present invention provided in the accompanying drawings is not intended to limit the scope of the claimed invention, but merely to illustrate selected embodiments of the invention. All other embodiments obtained by those skilled in the art based on the embodiments of the present invention without inventive effort are within the scope of protection of the present invention.

[0062] Example 1

[0063] A capacitor current-limiting power supply device with dynamic reactive power modulation is used for local power supply of a 10kV pole-mounted switch.

[0064] The high-voltage arm capacitor is a high-voltage ceramic capacitor with a capacitance of 5nF;

[0065] The low-voltage arm capacitor is a high-voltage film capacitor with a capacitance of 1nF;

[0066] The transformer is a three-winding transformer, with rated voltages of 1500V, 220V, and 27V for the first, second, and third windings, respectively.

[0067] The filter unit is a thin-film capacitor with a capacitance of 47uF;

[0068] The AC / DC unit consists of a rectifier bridge and an electrolytic capacitor;

[0069] The microcontroller is an STM32.

[0070] The inverter unit consists of an inverter bridge and its drive circuit.

[0071] The buffer unit is an electrolytic capacitor with a capacitance of 5mF.

[0072] This device can be used for local power extraction from 10kV pole-mounted switches. Through a microcontroller, inverter unit, and buffer unit, reactive power modulation can be achieved to replace traditional active power modulation. This allows a portion of the extracted power to be converted into reactive power when the load is less than the rated load, which can significantly reduce the heat dissipation of the device.

[0073] In summary, the present invention provides a capacitor current-limiting power harvesting device and its control method based on dynamic reactive power regulation. By measuring the current of the second and third windings of the transformer in the power harvesting device and the load voltage, an SPWM control signal is calculated. This enables the microcontroller to control the buffer unit and the inverter unit, ultimately stabilizing the AC and DC load voltages. Furthermore, the active component of the third winding of the transformer is zero, allowing the excess current of the power harvesting device to be discharged in a reactive form through the third winding, thus preventing the device from overheating. This invention possesses an engineering-feasible kilowatt-level power harvesting capability.

[0074] The above content is only for illustrating the technical concept of the present invention and should not be construed as limiting the scope of protection of the present invention. Any modifications made to the technical solution based on the technical concept proposed in this invention shall fall within the scope of protection of the claims of this invention.

Claims

1. A capacitor current-limiting power extraction device based on dynamic reactive power regulation, characterized in that, The system includes a high-voltage arm capacitor (1), one end of which is connected to the high-voltage power take-off point, and the other end is connected to the low-voltage arm capacitor (2) in series and then grounded; the low-voltage arm capacitor (2) is connected in parallel with the first winding of the transformer (3); the second winding of the transformer (3) is connected to the input terminal of the AC / DC unit (5) via the AC load, and the output terminal of the AC / DC unit (5) is connected to the DC load and the power supply terminal of the microcontroller (6) respectively; the third winding of the transformer (3) is connected to the microcontroller (6) via the buffer unit (8), and the power supply terminal of the buffer unit (8) is connected to the output terminal of the AC / DC unit (5); an inverter unit (7) is provided between the third winding of the transformer (3) and the buffer unit (8), and the inverter unit (7) is connected to the output terminal of the AC / DC unit (5) and the microcontroller (6) respectively; the microcontroller (6) is connected to the second winding of the transformer (3), the third winding of the transformer (3), the AC load and the DC load respectively.

2. The capacitor current-limiting power extraction device based on dynamic reactive power regulation according to claim 1, characterized in that, A filter unit (4) is provided between the second winding of the transformer (3) and the AC load.

3. A capacitor current-limiting power extraction control method based on dynamic reactive power regulation, characterized in that, The capacitor current-limiting power extraction device based on dynamic reactive power regulation as described in claim 1 or 2 includes the following steps: The microcontroller detects the current at the second and third windings of the transformer, the voltage and current of the AC load, and the current of the DC load, respectively, and obtains the zero-crossing phase signal based on the combined current of the second and third windings. Calculate the active component of the transformer's third winding based on the current and voltage of the third winding; The inverter voltage phase correction amount is determined by the zero-crossing phase signal and the active component of the third winding of the transformer. Based on the inverter voltage phase correction amount, an SPWM control signal is generated to generate a corresponding equivalent sinusoidal voltage at the third winding of the transformer, thereby controlling the active component of the third winding of the transformer to be 0.

4. The capacitor current limiting power extraction control method based on dynamic reactive power regulation according to claim 3, characterized in that, The specific determination of the inverter voltage phase correction amount is as follows: The third winding of the transformer is connected to the buffer unit through the inverter unit. If the active component of the third winding of the transformer is greater than 0, the phase angle difference between the inverter voltage of the inverter unit and the combined current of the second and third windings of the transformer is increased until the active component is equal to 0. If the active component of the third winding of the transformer is less than 0, the phase angle difference between the inverter voltage of the inverter unit and the combined current of the second and third windings of the transformer is decreased until the active component is equal to 0.

5. The capacitor current limiting power extraction control method based on dynamic reactive power regulation according to claim 3, characterized in that, The third winding of the transformer is connected to the buffer unit through the inverter unit. The microcontroller detects the voltage of the AC load or DC load respectively, compares the obtained load voltage with the reference voltage and generates an error signal. The error signal controls the capacitor voltage in the buffer unit to modulate the AC load or DC load voltage to the target value.

6. The capacitor current limiting power extraction control method based on dynamic reactive power regulation according to claim 5, characterized in that, When the load voltage is lower than the rated voltage, increase the capacitor voltage in the buffer unit until the load voltage equals the rated voltage, thereby adjusting the effective value of the AC voltage on the inverter unit.

7. The capacitor current limiting power extraction control method based on dynamic reactive power regulation according to claim 5, characterized in that, When the load voltage is higher than the rated voltage, the capacitor voltage in the buffer unit is reduced until the load voltage equals the rated voltage, thereby regulating the effective value of the AC voltage on the inverter unit.

8. The capacitor current limiting power extraction control method based on dynamic reactive power regulation according to claim 5, characterized in that, The voltage effective value of the second winding of the transformer is affected by the transformer coupling.

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