Power supply control circuit, power district voltage control system and method

Abstract

The application provides a power supply control circuit, a transformer area voltage control system and method, comprising: an AC-DC module, an input end of which is connected with an AC power supply on a power supply side, and an output end of which is connected with a DC bus; a DC-AC module, an input end of which is connected with the DC bus, and an output end of which is connected with a stable AC power supply on a user side; a first bidirectional DC conversion module, a first end of which is connected with the DC bus, and a second end of which is connected with a first battery; a new energy power generation module, an output end of which is connected with the second end of the first bidirectional DC conversion module, and which is used for generating electric energy and adjusting power generation output power; a second bidirectional DC conversion module, a first end of which is connected with the DC bus, and a second end of which is connected with a second battery; and a control module, which controls each bidirectional DC conversion module. The application can obtain a stable AC power supply on the user side, can normally work even if the voltage on the input side is too low, has low demand for power grid power, and fully utilizes new energy to improve environmental protection, economy and efficiency.

Description

Technical Field

[0001] This invention relates to the field of power supply control, and in particular to a power supply control circuit, a transformer substation voltage control system, and a method. Background Technology

[0002] In a power system, power plants generate high-voltage alternating current (AC). This AC power is transmitted through transmission lines to various substations, which convert it into medium-voltage power (such as 10kV) suitable for urban power distribution. The medium-voltage power is then transmitted through distribution lines to various distribution transformers, which convert it into low-voltage power (such as single-phase 220V or three-phase 380V) for user use.

[0003] At the power supply end far from the transformer, the transformer transmits low-voltage AC power to users through long-distance (about 2km~3km) transmission lines. The line impedance is high, and when the user's power consumption is slightly high, the transmission line will generate a large voltage drop, resulting in low voltage on the user side (the actual power supply voltage on the user side is often less than 180V or 320V), which affects the normal operation of electrical equipment and thus affects the user's production and life.

[0004] Therefore, how to solve the problem of low voltage on the user side has become one of the urgent problems to be solved by those skilled in the art.

[0005] It should be noted that the above description of the technical background is only for the purpose of providing a clear and complete explanation of the technical solutions of the present invention and facilitating understanding by those skilled in the art. It should not be assumed that the above technical solutions are known to those skilled in the art simply because they have been described in the background section of this invention. Summary of the Invention

[0006] In view of the shortcomings of the prior art described above, the purpose of this invention is to provide a power control circuit, a transformer area voltage control system and method to solve the problem of low voltage on the user side in the prior art.

[0007] To achieve the above and other related objectives, the present invention provides a power control circuit, the power control circuit comprising at least:

[0008] AC to DC conversion module, DC to AC conversion module, first bidirectional DC conversion module, first battery, new energy power generation module, second bidirectional DC conversion module, second battery, control module and capacitor module;

[0009] The input terminal of the AC to DC converter is connected to the AC power supply on the power supply side, and the output terminal is connected to the DC bus.

[0010] The input terminal of the DC-to-AC module is connected to the DC bus, and the output terminal outputs a stable AC power supply to the user side.

[0011] The first end of the first bidirectional DC-DC converter module is connected to the DC bus, and the second end is connected to the first battery.

[0012] The output terminal of the new energy power generation module is connected to the second terminal of the first bidirectional DC-DC converter module, and is used to generate electrical energy and regulate the power output.

[0013] The first end of the second bidirectional DC-DC converter module is connected to the DC bus, and the second end is connected to the second battery;

[0014] The control module controls each bidirectional DC-DC converter module to control the charging and discharging of the corresponding battery;

[0015] The capacitor module is connected to the DC bus and is used to stabilize the bus voltage.

[0016] Optionally, the control module includes a control unit corresponding to each bidirectional DC-DC converter module, and each control unit includes a voltage loop and a current loop;

[0017] The voltage loop generates a reference current based on the difference between the reference voltage and the bus voltage on the DC bus. The voltage loop includes a difference calculator, a proportional-integral controller, and a limiter. The non-inverting input of the difference calculator receives the reference voltage, and the inverting input receives the bus voltage, outputting a voltage difference. The proportional-integral controller is connected to the output of the difference calculator and performs proportional integration on the voltage difference. The limiter is connected to the output of the proportional-integral controller and limits the amplitude of the current output by the proportional-integral controller.

[0018] The current loop generates the switching control signal for the corresponding bidirectional DC-DC converter module based on the difference between the reference current and the inductor current in the corresponding bidirectional DC-DC converter module.

[0019] Wherein, the set output voltage of the AC to DC module is greater than the reference voltage; the maximum current limit of the limiter is positive or negative; the minimum current limit of the limiter is negative and less than the maximum current limit.

[0020] To achieve the above and other related objectives, the present invention also provides a transformer substation voltage control system, which includes at least:

[0021] The first contactor, the second contactor, and the aforementioned power control circuit;

[0022] The first contactor is connected in series in the input / output path of the power control circuit;

[0023] The first end of the second contactor is connected to the input end of the AC to DC module, and the second end is connected to the output end of the DC to AC module;

[0024] The control module also generates control signals for the first contactor and the second contactor.

[0025] Optionally, the first contactor is a DC contactor, one end of which is connected to the connection node of the AC to DC module, the first bidirectional DC conversion module and the second bidirectional DC conversion module, and the other end is connected to the input terminal of the DC to AC module;

[0026] Alternatively, the first contactor is an AC contactor, with one end connected to the output terminal of the DC-to-AC module and the other end connected to the second terminal of the second contactor.

[0027] To achieve the above and other related objectives, the present invention also provides a transformer substation voltage control method, implemented based on the aforementioned transformer substation voltage control system, wherein the transformer substation voltage control method includes at least:

[0028] S1) Disconnect the second contactor, close the first contactor, and control the power control circuit to enter the working state; acquire and determine whether the user-side AC power output by the power control circuit is normal; if it is not normal, restart the power control circuit; if it is normal, the power control circuit generates user-side AC power and supplies power in the working state.

[0029] S2) If the number of restarts of the power control circuit within the set time exceeds the set number, then the power supply side AC power supply will provide power, and the second battery will be charged by the second bidirectional DC-DC conversion module for a first preset time before returning to step S1).

[0030] S3) If the charge of the second battery is lower than the first set charge, the power supply side AC power supply is used to charge the second battery based on the second bidirectional DC-DC conversion module; when the charging time reaches the second preset time, or the charge of the second battery reaches the second set charge, return to step S1); wherein, the first set charge is less than the second set charge.

[0031] Optionally, in step S1), when the power control circuit is in the operating state:

[0032] During the first time period, the first battery discharges to a third set power level; during the second time period, the first battery is charged based on the power generated by the new energy power generation module, and the excess power is supplied to the DC bus; during the third time period, the first battery discharges; wherein, the first time period, the second time period, and the third time period are set sequentially, the first time period is the off-peak electricity consumption period at night and in the morning, the second time period is the new energy power generation period, and the third time period is the peak electricity consumption period in the evening and at night;

[0033] During the fourth time period, the second battery discharges; during the fifth time period, the second battery stabilizes its charge within a set range through charging and discharging; during the sixth time period, the second battery discharges; wherein the fourth, fifth, and sixth time periods are set sequentially, the fourth time period is the off-peak electricity consumption period at night and in the morning, the fifth time period is the peak electricity consumption period during the day and the peak electricity consumption period at night, and the sixth time period is the normal electricity consumption period at night.

[0034] Alternatively, a seventh period is provided between the first period and the second period, during which the first battery is charged and heated so that the first battery can be charged normally.

[0035] And / or, an eighth period is provided between the fourth period and the fifth period, during which the second battery is charged and heated so that the second battery can be charged normally.

[0036] Alternatively, during the second time period, when there is excess electrical energy, the maximum discharge power of the first bidirectional DC-DC converter module is limited to between 0.5 and 1.2 times the power of the new energy generation.

[0037] Alternatively, a ninth period is provided between the second period and the third period, during which the first battery is fully charged.

[0038] Alternatively, during the fifth time period, when the voltage of the second battery is greater than a first preset value, the second battery is controlled to discharge; otherwise, when the SOC of the second battery is less than or equal to a first preset percentage or the voltage of the second battery is less than a second preset value, the second battery is controlled to charge; wherein, the first preset value is greater than the second preset value.

[0039] Alternatively, the voltage of the second battery is a voltage signal sample value at the input terminal side of the second battery.

[0040] Alternatively, in step S3), the basis for determining that the power of the second battery is lower than the first set power is: the SOC of the second battery is less than or equal to the second set percentage and is during the off-peak electricity consumption period at night and in the morning, wherein the second set percentage is set to 30%-55%; or the SOC of the second battery is less than or equal to the third set percentage, wherein the third set percentage is set to 15%-30%.

[0041] Alternatively, in step S3), the basis for determining that the charge of the second battery has reached the second set charge is: the SOC of the second battery is greater than or equal to a fourth set percentage, wherein the fourth set percentage is set to 60%-100%.

[0042] As described above, the power control circuit, transformer area voltage control system, and method of the present invention have the following beneficial effects:

[0043] 1. The present invention sets up a power control circuit at the end of the transformer area, and compensates for the loss of long-distance transmission lines through the power control circuit to obtain a stable AC power supply with a set voltage on the user side to meet the power demand.

[0044] 2. The power control circuit of the present invention utilizes an energy storage battery to ensure the normal operation of the DC-to-AC module, avoiding the situation where the DC-to-AC module cannot work properly when the voltage at the input terminal of the power control circuit is too low.

[0045] 3. The power control circuit of the present invention connects the energy storage battery and the AC to DC module in parallel on the DC bus. The energy storage battery provides a portion of the output power, reducing the demand on the power grid, thereby reducing the voltage drop on long-distance transmission lines and reducing the voltage pressure on other users on the transmission lines.

[0046] 4. The power control circuit of the present invention compensates the electrical energy generated by the new energy source to the DC bus to make full use of the new energy source and improve environmental protection and economy; furthermore, it compensates for the losses of the AC to DC module and the DC to AC module to improve efficiency. Attached Figure Description

[0047] Figure 1 The diagram shown is a structural schematic of the power control circuit of the present invention.

[0048] Figure 2 The diagram shown is a schematic representation of the control unit of this invention.

[0049] Figure 3 The diagram shown illustrates the working principle of the power control circuit of this invention.

[0050] Figure 4 The diagram shown is a structural schematic of the transformer substation voltage control system of the present invention.

[0051] Figure 5 The diagram shows the state of the control module implementing the transformer area voltage control method of the present invention.

[0052] Component designation explanation

[0053] 1-Power control circuit; 11-AC to DC module; 12-DC to AC module; 13-First bidirectional DC conversion module; 14-First battery; 15-New energy power generation module; 151-Photovoltaic panel; 152-Maximum power point tracking unit; 16-Second bidirectional DC conversion module; 17-Second battery; 18-Control module; 180-Control unit; 18a-Voltage loop; 18b-Current loop; 181-Differential calculator; 182-Proportional-integral controller; 183-Limiter; 184-Differential calculator; 19-Capacitor module; 2-First contactor; 3-Second contactor. Detailed Implementation

[0054] The following specific examples illustrate the implementation of the present invention. Those skilled in the art can easily understand other advantages and effects of the present invention from the content disclosed in this specification. The present invention can also be implemented or applied through other different specific embodiments, and various details in this specification can also be modified or changed based on different viewpoints and applications without departing from the spirit of the present invention.

[0055] Please see Figures 1-5 It should be noted that the illustrations provided in this embodiment are only schematic representations of the basic concept of the present invention. Therefore, the drawings only show the components related to the present invention and are not drawn according to the actual number, shape and size of the components in the actual implementation. In the actual implementation, the form, quantity and proportion of each component can be arbitrarily changed, and the layout of the components may also be more complex.

[0056] like Figure 1 As shown, the present invention provides a power control circuit 1, which includes:

[0057] AC to DC conversion module 11, DC to AC conversion module 12, first bidirectional DC conversion module 13, first battery 14, new energy power generation module 15, second bidirectional DC conversion module 16, second battery 17, control module 18 and capacitor module 19.

[0058] like Figure 1 As shown, the input terminal of the AC to DC module 11 is connected to the AC power supply on the power supply side, and the output terminal is connected to the DC bus.

[0059] Specifically, the input terminal of the AC-to-DC module 11 is connected to the transformer via a long-distance transmission line to convert the AC power supplied by the transformer into DC power and output DC bus voltage. Any circuit structure that can convert AC power to DC power is applicable to this invention, and will not be described in detail here. The power control circuit 1 of this invention is located at the end of the transformer substation. As an example, the length of the transmission line between the AC-to-DC module 11 and the transformer is not less than half the distance between the transformer and the user.

[0060] like Figure 1 As shown, the input terminal of the DC-to-AC module 12 is connected to the DC bus, and the output terminal outputs a stable AC power supply to the user side.

[0061] Specifically, the DC-to-AC module 12 converts the DC power supply on the DC bus into AC power supply and provides it to the user; any circuit structure that can achieve inversion is applicable to this invention, and will not be described in detail here.

[0062] like Figure 1 As shown, the first end of the first bidirectional DC-DC converter module 13 is connected to the DC bus, and the second end is connected to the first battery 14, which is used to realize bidirectional energy conversion between the first battery 14 and the DC bus.

[0063] like Figure 1 As shown, the output terminal of the new energy power generation module 15 is connected to the second terminal of the first bidirectional DC-DC conversion module 13, which is used to generate electrical energy and regulate the power output.

[0064] Specifically, the new energy power generation module 15 is connected to the connection node between the first bidirectional DC-DC converter module 13 and the first battery 14. The electrical energy generated by the new energy power generation module 15 can be stored in the first battery 14 or transmitted to the DC bus through the first bidirectional DC-DC converter module 13. In this embodiment, the new energy power generation module 15 includes a photovoltaic panel 151 and a maximum power point tracking unit 152. The photovoltaic panel 151 converts solar energy into electrical energy. One end of the maximum power point tracking unit 152 (MPPT) is connected to the output end of the photovoltaic panel 151, and the other end is connected to the second end of the first bidirectional DC-DC converter module 13. By monitoring and adjusting the voltage and current of the photovoltaic panel 151 in real time, it keeps the panel at its maximum power point, thereby maximizing the utilization of solar energy resources and improving the energy conversion efficiency of the system.

[0065] like Figure 1 As shown, the first end of the second bidirectional DC-DC converter module 16 is connected to the DC bus, and the second end is connected to the second battery 17; it is used to realize bidirectional energy conversion between the second battery 17 and the DC bus.

[0066] like Figure 1As shown, the control module 18 provides control signals to each module in the power control circuit 1, including but not limited to controlling each bidirectional DC-DC converter module to control the charging and discharging of the corresponding battery.

[0067] Specifically, in this embodiment, the control module 18 includes control units 180 corresponding to each bidirectional DC-DC converter module, namely, a first control unit and a second control unit. The first control unit controls the first bidirectional DC-DC converter module 13, and the second control unit controls the second bidirectional DC-DC converter module 16. For example... Figure 2 As shown, each control unit 180 includes a voltage loop 18a and a current loop 18b. The voltage loop 18a is based on a reference voltage U. Busref Bus voltage U on the DC bus Bus The difference between the sampled signal of the bus voltage (in this example) and the reference current I is generated. ref The voltage loop 18a includes a difference arithmetic unit 181, a proportional-integral controller 182, and a limiter 183; the non-inverting input of the difference arithmetic unit 181 receives a reference voltage U. Busref The inverting input terminal receives the bus voltage U. Bus The output voltage difference is calculated; the proportional-integral controller 182 is connected to the output of the difference arithmetic unit 181 and performs proportional integration on the voltage difference; the limiter 183 is connected to the output of the proportional-integral controller 182 and limits the amplitude of the current output by the proportional-integral controller 182 to obtain the reference current I. ref The current loop 18b is based on the reference current I. ref The difference between the current I in the corresponding bidirectional DC-DC converter module and the sampled signal of the inductor current in this example generates the switching control signal Ctl for the corresponding bidirectional DC-DC converter module; in this example, the current loop 18b is implemented using a difference arithmetic unit 184. The reference voltage U... Busref The output voltage U of the AC to DC module 11 is less than the set output voltage U. AC / DC As an example, U AC / DC Set to 54V, U Busref The voltage is set to 53V, with a difference within 3V. During normal operation, the AC-to-DC module 11 controls the voltage on the DC bus to the set output voltage U. AC / DCAt this point, the output current of the proportional-integral controller 182 is limited by the maximum current limit Imax of the limiter 183. The maximum current limit Imax of the limiter 183 is adjusted to a positive or negative value according to time and battery SOC (for example, a positive value is 2A and a negative value is -2A). When set to a positive value, the current flows from the DC bus to the battery (battery charging). When set to a negative value, the current flows from the battery or the new energy power generation module 15 to the DC bus (battery discharging or new energy power supply). When the user-side load is large, even if the AC to DC module 11 reaches its maximum output power, it cannot control the voltage on the DC bus to the set output voltage U. AC / DC At this time, the bus voltage U Bus The output current of the proportional-integral controller 182 is significantly reduced, and the minimum current limit value Imin of the limiter 183 is limited. The minimum current limit value Imin of the limiter 183 is negative (for example, set to -60A) and less than the maximum current limit value Imax.

[0068] It should be noted that the control unit 180 may be set in the corresponding bidirectional DC-DC conversion module, and other control circuits may be retained in the control module 18, which is not limited to this embodiment.

[0069] like Figure 1 As shown, capacitor module 19 is connected to the DC bus to stabilize the bus voltage.

[0070] Specifically, as one example, capacitor module 19 is configured as a capacitor and its control and protection circuit; as another example, capacitor module 19 is configured as a supercapacitor module. In practical use, any capacitor capable of stabilizing the bus voltage is suitable for this invention.

[0071] The power control circuit of this invention is connected in series between the transformer and the user, which can effectively overcome the voltage drop problem of the transmission line and ensure the stability of the AC voltage on the user side.

[0072] like Figure 3 As shown, the power control circuit 1 of the present invention controls the charging and discharging of the first battery 14 and the second battery 17 based on the first bidirectional DC-DC converter module 13 and the second bidirectional DC-DC converter module 16, respectively. The working principle is as follows:

[0073] like Figure 3 As shown, for the first battery 14: during the first time period, the first battery 14 discharges to a third set charge level; during the second time period, the first battery 14 is charged by the electrical energy generated by the new energy power generation module 15, and the excess electrical energy is provided to the DC bus; during the third time period, the first battery 14 discharges; wherein, the first time period, the second time period and the third time period constitute a day, and are set sequentially.

[0074] Specifically, the first time period is the off-peak electricity consumption period at night and in the morning, the second time period is the renewable energy generation period, and the third time period is the peak electricity consumption period in the evening and at night. For example, the first time period is set from 0:00 to 6:00 (during which user-side electricity consumption is relatively low), the second time period is set from 8:00 to 15:00 (during which solar energy is converted into electricity through photovoltaic panels), and the third time period is set from 17:00 to 24:00 (during which user-side electricity consumption is relatively high). In actual use, each time period needs to be sequentially connected, and the specific timing can be adjusted according to the application environment, which will not be elaborated here. During the first time period, the first battery 14 discharges to the third set charge level to ensure that the electricity generated by the photovoltaic system during the day can be stored. The third set charge level can be a fixed value (e.g., a SOC of 60%, meaning the current remaining charge of the first battery 14 accounts for 60% of its total capacity), or it can be set based on the predicted electricity generated by the photovoltaic system during the day, which will not be elaborated here. During the second time period, the electrical energy converted by the photovoltaic panel is stored in the first battery 14 to ensure maximum utilization of solar energy. As an example, when there is excess electrical energy, the maximum discharge power of the first bidirectional DC-DC converter 13 is limited to between 0.5 and 1.2 times the power generated by the new energy source (e.g., the maximum current limit Imax of the first bidirectional DC-DC converter 13 is -1A to -0.5Ppv / set output voltage U). AC / DC In practical use, the discharge power of the first bidirectional DC-DC converter module 13 can be set as needed. During the third time period, the power consumption on the user side increases, and the electrical energy stored in the first battery 14 is supplied to the user side; in this example, the first battery 14 discharges with a small current, such as -1A. In practical use, the discharge current can be set as needed.

[0075] More specifically, as another implementation, the battery's charging performance is poor at low temperatures. Therefore, the battery has a heating mechanism, with a heating film inside. For example, the rated heating power is 120W. When the cell temperature is below 5°C and the battery is detected to be charging, the heating film relay is activated, and heating begins. When the cell temperature is above 12°C or when the battery is detected to be discharging, the heating film relay is deactivated, and heating stops. For the cell charging MOSFET, when the cell temperature is below 0°C, the charging MOSFET is deactivated, and charging stops; otherwise, when the cell temperature is above 1°C, the charging MOSFET is activated, and charging begins. To accommodate the battery's heating mechanism, when the power control circuit 1 of this invention is applied to cold regions, a seventh period is provided between the first and second periods. During the seventh period, the first battery 14 is charged to ensure that it has sufficient electrical energy for heating, thus ensuring that the first battery 14 can be charged normally. In this embodiment, the seventh period is set from 6:00 to 8:00. During this period, the first battery 14 is forcibly charged at 2.5A. The charging current and charging duration can meet the rated power of the battery heating, ensuring that the cell temperature of the first battery 14 reaches the charging requirements. This embodiment is not the only limitation.

[0076] More specifically, as another implementation, when the light intensity in the second time period is insufficient, a ninth time period can be set between the second and third time periods. During the ninth time period, the first battery 14 is fully charged by the power supplied by the DC bus, so as to store more power during peak electricity consumption periods. In this embodiment, the ninth time period is set from 15:00 to 17:00. During this period, the first battery 14 is charged with a current of 10A. The goal is to fully charge the first battery 14 within the ninth time period, but this embodiment is not the only option.

[0077] like Figure 3 As shown, for the second battery 17: during the fourth period, the second battery 17 discharges; during the fifth period, the second battery 17 stabilizes its charge within a set range through charging and discharging; during the sixth period, the second battery 17 discharges; wherein the fourth, fifth, and sixth periods constitute a day, and are set sequentially.

[0078] Specifically, the fourth time period is the off-peak electricity consumption period at night and in the morning; the fifth time period is the peak and off-peak electricity consumption periods during the day and at night; and the sixth time period is the normal electricity consumption period at night. The fourth time period is set from 0:00 to 6:00 (during which user-side electricity consumption is relatively low), the fifth time period is set from 8:00 to 21:00, and the sixth time period is set from 21:00 to 24:00 (during which user-side electricity consumption is relatively reduced). In actual use, the time periods need to be sequentially connected, and the specific timing can be adjusted according to the application environment, which will not be elaborated here. During the fourth time period, the second battery 17 discharges; in this example, the second battery 17 discharges with a small current, such as -1A. In actual use, the discharge current can be set as needed. During the fifth time period, when the voltage of the second battery 17 (in this example, the voltage of the second battery 17 is the voltage signal sample value at the input terminal side of the second battery 17) is greater than a first preset value, the second battery 17 is controlled to discharge. As an example, the first preset value is slightly higher than (e.g., 1V, 2V, or 3V higher) the set output voltage U of the AC to DC module 11. AC / DC The discharge current is set to -1A; otherwise, when the SOC of the second battery 17 is less than or equal to the first preset percentage (for example, the first preset percentage is 95%, that is, the current remaining charge of the battery accounts for 95% of its total capacity; in actual use, the first preset percentage can be set as needed, including but not limited to 80%, 85%, and 90%, which will not be elaborated here) or the voltage of the second battery 17 is less than the second preset value, the second battery 17 is controlled to charge. The first preset value is greater than the second preset value. For example, the second preset value is set to be slightly lower than (e.g., 1V, 2V, or 3V lower) the reference voltage U. Busref The charging current is set to 10A; the specific charging and discharging current and judgment threshold are set according to actual needs and are not limited to this embodiment. During the sixth time period, the power consumption on the user side increases, and the electrical energy stored in the second battery 17 is provided to the user side; in this example, the second battery 17 discharges with a small current, such as -1A. In actual use, the discharge current can be set as needed.

[0079] More specifically, as another implementation, also to accommodate the battery's heating mechanism, when the power control circuit 1 of this invention is applied to cold regions, an eighth period is provided between the fourth and fifth periods. During the eighth period, the second battery 17 is charged and heated to ensure that the second battery 17 can be charged normally. In this embodiment, the eighth period is the same as the seventh period, and during this period, the charging current of the second battery 17 is configured to be equal to the charging current of the first battery 14. In actual use, the corresponding time point and corresponding charging current can be configured as needed.

[0080] like Figure 4 As shown, the present invention also provides a transformer substation voltage control system, which includes:

[0081] The present invention includes a power control circuit 1, a first contactor 2, and a second contactor 3.

[0082] like Figure 4 As shown, the first contactor 2 is connected in series in the input / output path of the power control circuit 1 to control the on / off state of the power control circuit 1.

[0083] Specifically, as an example, the first contactor 2 is configured as a DC contactor. One end of the DC contactor is connected to the connection node of the AC-to-DC module 11, the first bidirectional DC-DC conversion module 13, and the second bidirectional DC-DC conversion module 16, and the other end is connected to the input terminal of the DC-to-AC module 12. When the DC contactor is open, the DC-to-AC module 12 has no input voltage and does not generate AC power on the user side. As another example, the first contactor 2 is an AC contactor. One end of the AC contactor is connected to the output terminal of the DC-to-AC module 12, and the other end is connected to the second terminal of the second contactor 3. That is, when the AC contactor is open, the output of the power control circuit 1 is disconnected from the user side. The first contactor 2 can be set in any other location that can control the on / off state of the power control circuit 1, which will not be described in detail here.

[0084] like Figure 4 As shown, the first end of the second contactor 3 is connected to the input end of the AC to DC module 11, and the second end is connected to the output end of the DC to AC module 12.

[0085] Specifically, the second contactor 3 is an AC contactor used to directly transmit the AC power supplied by the transformer to the user side.

[0086] like Figure 4 As shown, in this embodiment, the control module 18 also generates control signals for the first contactor 2 and the second contactor 3.

[0087] The present invention also provides a transformer substation voltage control method, implemented based on the transformer substation voltage control system of the present invention, the transformer substation voltage control method comprising:

[0088] S1) Disconnect the second contactor 3, close the first contactor 2, and control the power control circuit 1 to enter the working state; obtain and determine whether the user-side AC power output of the power control circuit 1 is normal; if it is not normal, restart the power control circuit 1; if it is normal, the power control circuit 1 generates user-side AC power and supplies power in the working state.

[0089] Specifically, in this embodiment, the state machine of the control module 18 is initially in an idle state, then powered on, and enters a standard state after power-on. The standard state includes four states. In the standard state, the control module 18 first enters the first state, controls the power control circuit 1 to connect to the path, performs a self-test on the power control circuit 1, and if it is normal, the power control circuit 1 provides AC power to the user side; if it is abnormal, it restarts.

[0090] More specifically, such as Figure 5 As shown, as an example, the first state performs the following operations step by step: First, disconnect the second contactor 3 to power off the first bidirectional DC-DC converter module 13 and the second bidirectional DC-DC converter module 16. Then, close the first contactor 2 to connect the power supply circuit 1 to the power supply path. Next, power on the first bidirectional DC-DC converter module 13 and the second bidirectional DC-DC converter module 16. Subsequently, power on the DC-to-AC converter module 12, and the power control circuit 1 begins to operate.

[0091] More specifically, in this embodiment, if the DC-to-AC module 12 has no output or its output voltage exceeds the normal range, the power control circuit 1 is determined to be malfunctioning; if the output voltage of the DC-to-AC module 12 is within the normal range, the power control circuit 1 is determined to be functioning normally. Other methods for determining whether the DC-to-AC module 12 is functioning normally are also applicable to this invention and are not limited to this embodiment.

[0092] More specifically, if the power control circuit 1 malfunctions, it enters the second state to restart. In the first state, the first contactor 2 and the second contactor 3 are disconnected, and the first bidirectional DC-DC converter module 13 and the second bidirectional DC-DC converter module 16 are turned off. After the shutdown state is maintained for 10 seconds, it returns to the first state, and the power control circuit 1 is re-evaluated for normal operation.

[0093] More specifically, when the power control circuit 1 is functioning normally, its operating status is as described above. Figure 3 I will not go into detail here.

[0094] S2) If the number of restarts of the power control circuit 1 within the set time exceeds the set number, then the power supply side AC power supply will supply power, and the second battery 17 will be charged by the second bidirectional DC-DC conversion module 16 for a first preset time before returning to step S1).

[0095] Specifically, such as Figure 5 As shown in this example, if the number of times the device switches from the first state to the second state reaches 3 times within 30 minutes, it will enter the third state and return to the first state after running in the third state for 1 hour. The set time, set number of times, and first preset duration can be adjusted according to actual needs and are not limited to this embodiment.

[0096] More specifically, such as Figure 5As shown, in the third state, the first contactor 2 is disconnected and the second contactor 3 is closed. At this time, the transformer supplies power to the user side through the transmission line, and the power control circuit 1 does not supply power. Furthermore, the second bidirectional DC-DC converter module 16 is turned on, and the second battery 17 is charged with a high current of 10A. The charging current can be set according to actual needs. In addition, in this embodiment, the first bidirectional DC-DC converter module 13 is in the off state. In actual use, the first bidirectional DC-DC converter module 13 can also be in the on state.

[0097] S3) If the power of the second battery 17 is lower than the first set power, the power supply side AC power supply is used to charge the second battery 17 based on the second bidirectional DC-DC conversion module 16; when the charging time reaches the second preset time, or the power of the second battery 17 reaches the second set power, return to step S1); wherein, the first set power is less than the second set power.

[0098] Specifically, such as Figure 5 As shown, in this embodiment, the basis for determining that the power level of the second battery 17 is lower than the first preset power level is as follows: the SOC of the second battery 17 is less than or equal to 50% of the second preset percentage and it is during the off-peak electricity consumption period at night and in the morning (e.g., 0:00~5:00). The second preset percentage is set to 30%-55%, including but not limited to 35%, 40%, 45%, and 50%, which will not be elaborated here; or the SOC of the second battery 17 is less than or equal to a third preset percentage, which is set to 15%-30%, including but not limited to 20% and 25%, which will not be elaborated here. When the power level in the second battery 17 is (too low) lower than the first preset power level, there may be a risk that the power control circuit 1 of the present invention cannot operate normally. The specific judgment criteria can be set according to actual needs and are not limited to this embodiment.

[0099] Specifically, such as Figure 5 As shown, in this embodiment, the criterion for determining that the charge level of the second battery 17 has reached the second preset charge level is that the SOC of the second battery is greater than or equal to a fourth preset percentage. The fourth preset percentage is set to 60%-100%, including but not limited to 65%, 70%, 80%, and 90%, which will not be elaborated here. When the charge level in the second battery 17 is higher than the second preset charge level, the power control circuit 1 of the present invention can operate normally. The specific judgment criteria can be set according to actual needs and are not limited to this embodiment.

[0100] More specifically, such as Figure 5As shown, in the fourth state, the first contactor 2 is disconnected and the second contactor 3 is closed. At this time, the transformer supplies power to the user side through the transmission line, and the power control circuit 1 does not supply power. Furthermore, the second bidirectional DC-DC converter module 16 is turned on, and the second battery 17 is charged with a high current of 10A. The charging current can be set according to actual needs. In addition, in this embodiment, the first bidirectional DC-DC converter module 13 is in the off state. In actual use, the first bidirectional DC-DC converter module 13 can also be in the on state.

[0101] In summary, this invention provides a power control circuit, a transformer substation voltage control system, and a method, comprising: an AC-to-DC module, a DC-to-AC module, a first bidirectional DC-DC conversion module, a first battery, a new energy power generation module, a second bidirectional DC-DC conversion module, a second battery, and a control module; the input terminal of the AC-to-DC module is connected to the AC power supply on the power supply side, and the output terminal is connected to the DC bus; the input terminal of the DC-to-AC module is connected to the DC bus, and the output terminal outputs a stable user-side AC power supply; the first terminal of the first bidirectional DC-DC conversion module is connected to the DC bus, and the second terminal is connected to the first battery; the output terminal of the new energy power generation module is connected to the second terminal of the first bidirectional DC-DC conversion module, used to generate electrical energy and regulate the power output; the first terminal of the second bidirectional DC-DC conversion module is connected to the DC bus, and the second terminal is connected to the second battery; the control module controls each bidirectional DC-DC conversion module to control the charging and discharging of the corresponding battery. The power control circuit, transformer area voltage control system, and method of this invention compensate for losses in long-distance transmission lines, obtaining a stable AC power supply with a set voltage on the user side to meet electricity demand; utilize energy storage batteries to ensure the normal operation of the DC-to-AC module; reduce the demand on grid power, decrease voltage drop on long-distance transmission lines, and reduce the voltage pressure on other users on the transmission lines; fully utilize new energy sources, improving environmental protection and economy; furthermore, it compensates for losses in the AC-to-DC and DC-to-AC modules, resulting in high efficiency. Therefore, this invention effectively overcomes the various shortcomings of the prior art and has high industrial application value.

[0102] The above embodiments are merely illustrative of the principles and effects of the present invention and are not intended to limit the invention. Any person skilled in the art can modify or alter the above embodiments without departing from the spirit and scope of the present invention. Therefore, all equivalent modifications or alterations made by those skilled in the art without departing from the spirit and technical concept disclosed in the present invention should still be covered by the claims of the present invention.

Claims

1. A power control circuit, disposed at the end of a transformer substation, characterized in that, The power control circuit includes at least: AC to DC conversion module, DC to AC conversion module, first bidirectional DC conversion module, first battery, new energy power generation module, second bidirectional DC conversion module, second battery, control module and capacitor module; The input terminal of the AC to DC converter is connected to the AC power supply on the power supply side, and the output terminal is connected to the DC bus. The input terminal of the DC-to-AC module is connected to the DC bus, and the output terminal outputs a stable AC power supply to the user side. The first end of the first bidirectional DC-DC converter module is connected to the DC bus, and the second end is connected to the first battery. During the off-peak electricity consumption periods at night and in the morning, the first bidirectional DC-DC converter module controls the first battery to discharge to a third set charge level. During the renewable energy generation period, the first bidirectional DC-DC converter module charges the first battery based on the electrical energy generated by the renewable energy generation module and provides the excess electrical energy to the DC bus. The output terminal of the new energy power generation module is connected to the second terminal of the first bidirectional DC-DC converter module, and is used to generate electrical energy and regulate the power output. The first end of the second bidirectional DC-DC converter module is connected to the DC bus, and the second end is connected to the second battery; wherein, during the daytime peak electricity consumption period and the nighttime peak electricity consumption period, the second bidirectional DC-DC converter module controls the second battery to stabilize the power of the battery within a set range through charging and discharging; The control module controls each bidirectional DC-DC converter module to control the charging and discharging of the corresponding battery; The capacitor module is connected to the DC bus and is used to stabilize the bus voltage.

2. The power control circuit according to claim 1, characterized in that: The control module includes control units corresponding to each bidirectional DC-DC converter module, and each control unit includes a voltage loop and a current loop; The voltage loop generates a reference current based on the difference between the reference voltage and the bus voltage on the DC bus. The voltage loop includes a difference calculator, a proportional-integral controller, and a limiter. The non-inverting input of the difference calculator receives the reference voltage, and the inverting input receives the bus voltage, outputting a voltage difference. The proportional-integral controller is connected to the output of the difference calculator and performs proportional integration on the voltage difference. The limiter is connected to the output of the proportional-integral controller and limits the amplitude of the current output by the proportional-integral controller. The current loop generates the switching control signal for the corresponding bidirectional DC-DC converter module based on the difference between the reference current and the inductor current in the corresponding bidirectional DC-DC converter module. Wherein, the set output voltage of the AC to DC module is greater than the reference voltage; the maximum current limit of the limiter is positive or negative; the minimum current limit of the limiter is negative and less than the maximum current limit.

3. A transformer substation voltage control system, characterized in that, The transformer area voltage control system includes at least: The first contactor, the second contactor, and the power control circuit as described in any one of claims 1-2; The first contactor is connected in series in the input / output path of the power control circuit; The first end of the second contactor is connected to the input end of the AC to DC module, and the second end is connected to the output end of the DC to AC module; The control module also generates control signals for the first contactor and the second contactor.

4. The transformer substation voltage control system according to claim 3, characterized in that: The first contactor is a DC contactor. One end of the DC contactor is connected to the connection node of the AC to DC module, the first bidirectional DC conversion module and the second bidirectional DC conversion module, and the other end is connected to the input terminal of the DC to AC module. Alternatively, the first contactor is an AC contactor, with one end connected to the output terminal of the DC-to-AC module and the other end connected to the second terminal of the second contactor.

5. A transformer substation voltage control method, implemented based on the transformer substation voltage control system as described in claim 3 or 4, characterized in that, The transformer area voltage control method includes at least the following: S1) Disconnect the second contactor, close the first contactor, and control the power control circuit to enter the working state; acquire and determine whether the user-side AC power output by the power control circuit is normal; if it is not normal, restart the power control circuit; if it is normal, the power control circuit generates user-side AC power and supplies power in the working state. S2) If the number of restarts of the power control circuit within the set time exceeds the set number, then the power supply side AC power supply will provide power, and the second battery will be charged by the second bidirectional DC-DC conversion module for a first preset time before returning to step S1). S3) If the charge of the second battery is lower than the first set charge, the power supply side AC power supply is used to charge the second battery based on the second bidirectional DC-DC conversion module; when the charging time reaches the second preset time, or the charge of the second battery reaches the second set charge, return to step S1); wherein, the first set charge is less than the second set charge.

6. The transformer substation voltage control method according to claim 5, characterized in that: In step S1), when the power control circuit is in the working state: During the first time period, the first battery discharges to a third set power level; during the second time period, the first battery is charged based on the power generated by the new energy power generation module, and the excess power is supplied to the DC bus; during the third time period, the first battery discharges; wherein, the first time period, the second time period, and the third time period are set sequentially, the first time period is the off-peak electricity consumption period at night and in the morning, the second time period is the new energy power generation period, and the third time period is the peak electricity consumption period in the evening and at night; During the fourth time period, the second battery discharges; during the fifth time period, the second battery stabilizes its charge within a set range through charging and discharging; during the sixth time period, the second battery discharges; wherein the fourth, fifth, and sixth time periods are set sequentially, the fourth time period is the off-peak period of electricity consumption at night and in the morning, the fifth time period is the peak and off-peak period of electricity consumption during the day and at night, and the sixth time period is the normal period of electricity consumption at night.

7. The transformer substation voltage control method according to claim 6, characterized in that: A seventh period is provided between the first period and the second period, during which the first battery is charged and heated so that the first battery can be charged normally. And / or, an eighth period is provided between the fourth period and the fifth period, during which the second battery is charged and heated so that the second battery can be charged normally.

8. The transformer substation voltage control method according to claim 6, characterized in that: During the second time period, the maximum discharge power of the first bidirectional DC-DC converter module is limited to between 0.5 and 1.2 times the power of new energy generation.

9. The transformer substation voltage control method according to claim 6, characterized in that: A ninth period is provided between the second period and the third period, during which the first battery is fully charged.

10. The transformer substation voltage control method according to claim 6, characterized in that: During the fifth time period, when the voltage of the second battery is greater than the first preset value, the second battery is controlled to discharge; otherwise, when the SOC of the second battery is less than or equal to the first preset percentage or the voltage of the second battery is less than the second preset value, the second battery is controlled to charge; wherein, the first preset value is greater than the second preset value.

11. The transformer substation voltage control method according to claim 10, characterized in that: The voltage of the second battery is the voltage signal sample value at the input terminal side of the second battery.

12. The transformer substation voltage control method according to any one of claims 5-11, characterized in that: In step S3), the basis for determining that the power of the second battery is lower than the first set power is: the SOC of the second battery is less than or equal to the second set percentage and is during the off-peak electricity consumption period at night and in the morning, wherein the second set percentage is set to 30%-55%; or the SOC of the second battery is less than or equal to the third set percentage, wherein the third set percentage is set to 15%-30%.

13. The transformer substation voltage control method according to any one of claims 5-11, characterized in that: In step S3), the basis for determining that the charge of the second battery has reached the second set charge is that the SOC of the second battery is greater than or equal to the fourth set percentage, wherein the fourth set percentage is set to 60%-100%.

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