Voltage control circuit, voltage control system and method

Abstract

The invention provides a voltage control circuit and a voltage control system and method, and the circuit comprises an AC-DC conversion unit which has an input end connected with a power supply side AC power supply and an output end connected with a DC bus; the input end of the DC-AC conversion unit is connected with the DC bus, and the output end outputs a stable user-side AC power supply; the first end of the bidirectional direct-current conversion unit is connected with the direct-current bus, and the second end is connected with the first battery module; the output end of the new energy module is connected with the second end of the bidirectional direct current conversion unit, and the new energy module is used for generating electric energy and adjusting power generation output power; the second battery module is connected to the direct current bus; the control unit controls the bidirectional direct current conversion unit so as to carry out charging and discharging control on the first battery module. The method compensates the loss of a long-distance power transmission line, meets the power demand of a user side, reduces the demand for the power of a power grid, makes full use of new energy, and improves the environmental protection property and economical efficiency. And the efficiency is improved.

Description

Technical Field

[0001] The present invention relates to the field of power control, and in particular, to a voltage control circuit, a voltage control system and a method. Background Art

[0002] In rural areas, there is a certain distance (for example, 2 km to 3 km) between the substation transformer and the user side. This distance needs to be achieved through long-distance transmission lines for power transmission. Since the rural power grid often uses 16-square-millimeter aluminum wires for overhead laying, the long-distance aluminum wires have a large line impedance. When the power consumption increases, the voltage drop generated on the transmission line also increases, resulting in a decrease in the actual voltage at the user side and the problem that electrical equipment cannot be used normally.

[0003] Therefore, how to avoid the low-voltage problem caused by the impedance of the transmission line has become one of the problems that need to be solved urgently by those skilled in the art.

[0004] It should be noted that the above introduction of the technical background is only for the convenience of clearly and completely explaining the technical solution of the present invention and facilitating the understanding of those skilled in the art. It cannot be considered that the above technical solutions are well known to those skilled in the art just because these solutions are described in the background art part of the present invention. Summary of the Invention

[0005] In view of the above-mentioned disadvantages of the prior art, the purpose of the present invention is to provide a voltage control circuit, a voltage control system and a method for solving the low-voltage problem caused by the impedance of the transmission line in the prior art.

[0006] To achieve the above object and other related objects, the present invention provides a voltage control circuit, which at least includes:

[0007] An AC-DC conversion unit, a DC-AC conversion unit, a bidirectional DC conversion unit, a first battery module, a new energy module, a second battery module and a control unit;

[0008] The input end of the AC-DC conversion unit is connected to the power supply side AC power supply, and the output end is connected to the DC bus;

[0009] The input end of the DC-AC conversion unit is connected to the DC bus, and the output end outputs a stable user side AC power supply;

[0010] The first end of the bidirectional DC conversion unit is connected to the DC bus, and the second end is connected to the first battery module;

[0011] The output end of the new energy module is connected to the second end of the bidirectional DC conversion unit, and is used for generating electric energy and adjusting the power generation output power;

[0012] The second battery module is connected to the DC bus;

[0013] The control unit controls the bidirectional DC conversion unit to perform charge and discharge control on the first battery module.

[0014] Optionally, the control unit includes a voltage loop and a current loop;

[0015] The voltage loop generates a reference current based on the difference between a reference voltage and the bus voltage on the DC bus. Among them, the voltage loop includes a difference calculator, a proportional-integral controller, and a limiter; the positive-phase input terminal of the difference calculator receives the reference voltage, the inverting input terminal receives the bus voltage, and outputs a voltage difference; the proportional-integral controller is connected to the output terminal of the difference calculator to perform proportional integration on the voltage difference; the limiter is connected to the output terminal of the proportional-integral controller to limit the amplitude of the current output by the proportional-integral controller;

[0016] The current loop generates a switching control signal for the bidirectional DC conversion unit based on the difference between the reference current and the inductor current in the bidirectional DC conversion unit;

[0017] Wherein, the set output voltage of the AC-DC conversion unit is less than the reference voltage; the maximum current limit value of the limiter is positive; the minimum current limit value of the limiter is positive or negative and less than the maximum current limit value.

[0018] To achieve the above and other related purposes, the present invention also provides a voltage control system, which at least includes:

[0019] A first contactor, a second contactor, and the above voltage control circuit;

[0020] The first contactor is connected in series on the input-output path of the voltage control circuit;

[0021] The first end of the second contactor is connected to the input end of the AC-DC conversion unit, and the second end is connected to the user end;

[0022] The control unit also generates control signals for the first contactor and the second contactor.

[0023] Optionally, the first contactor is a DC contactor, one end of the DC contactor is connected to the connection node of the AC-DC conversion unit, the bidirectional DC conversion unit, and the second battery module, and the other end is connected to the input end of the DC-AC conversion unit;

[0024] Alternatively, the first contactor is an AC contactor, one end of the AC contactor is connected to the output end of the DC-AC conversion unit, and the other end is connected to the second end of the second contactor.

[0025] More optionally, the AC-DC conversion unit, the DC-AC conversion unit, the bidirectional DC conversion unit, the new energy module, and the control unit are arranged in the same cabinet, the first battery module is arranged inside or outside the cabinet, and the second battery module is arranged outside the cabinet.

[0026] To achieve the above object and other related objects, the present invention further provides a voltage control method, which is implemented based on the above voltage control system. The voltage control method at least includes:

[0027] S1) Disconnect the second contactor, close the first contactor, and control the voltage control circuit to enter the working state; obtain and judge whether the user-side AC power supply output by the voltage control circuit is normal; if not, restart the voltage control circuit; if normal, the voltage control circuit generates and supplies the user-side AC power supply in the working state;

[0028] S2) If the restart times of the voltage control circuit are greater than the set times within the set time, supply power from the power supply-side AC power supply, and return to step S1) after the first preset duration;

[0029] S3) If the power of the second battery module is lower than the first set power, supply power from the power supply-side AC power supply, and the first battery module discharges to the DC bus based on the bidirectional DC conversion unit; during the new energy generation period and the electricity peak period, return to step S1) after the second preset duration or when the power of the second battery module reaches the second set power; wherein, the first set power is less than the second set power.

[0030] Optionally, in step S1), when the voltage control circuit is in the working state:

[0031] The first period, the second period, and the third period are set in sequence in a cycle; within the first period, the second period, and the third period, if the voltage of the first battery module is less than the discharge cut-off voltage of the first battery module or the SOC of the first battery module is less than the first set percentage, the minimum current limit value in the bidirectional DC conversion unit is a positive value, and the bidirectional DC conversion unit charges the first battery module; if the voltage of the first battery module is greater than the set voltage, the minimum current limit value in the bidirectional DC conversion unit is a negative value, and the bidirectional DC conversion unit discharges to the DC bus;

[0032] Among them, the first time period is the power consumption trough 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 power consumption peak period in the evening and at night; the discharge current of the bidirectional DC conversion unit in the first time period and the third time period is less than the discharge current in the second time period; the set voltage is at least 2V greater than the discharge cut-off voltage of the first battery module, and the first set percentage is set to 10%-20%.

[0033] More optionally, the voltage of the first battery module is the voltage signal sampling value on the input terminal side of the first battery module.

[0034] More optionally, a fourth time period is also set between the first time period and the second time period, and the first battery module is charged and heated during the fourth time period so that the first battery module can be normally charged.

[0035] More optionally, a fifth time period is also set between the second time period and the third time period, and the first battery module is charged to the equalizing charge voltage during the fifth time period.

[0036] More optionally, the discharge current of the first battery module during discharge does not exceed 70% of the maximum discharge current value of the battery.

[0037] More optionally, the maximum discharge power of the bidirectional DC conversion unit is limited to be between 0.5 and 1.2 times the new energy power generation power.

[0038] More optionally, in step S3), the basis for determining that the power of the second battery module is lower than the first set power is: the SOC of the second battery module is less than or equal to the second set percentage and is in the power consumption trough period at night and in the morning, where the second set percentage is set to 30%-55%; or the SOC of the second battery module is less than or equal to the third set percentage, where the third set percentage is set to 15%-30%; or the bus voltage is lower than the discharge cut-off voltage of the second battery module.

[0039] More optionally, in step S3), the basis for determining that the power of the second battery module reaches the second set power is: the SOC of the second battery module is greater than or equal to the fourth set percentage, where the fourth set percentage is set to 30%-50%; or the bus voltage is greater than the set value, where the set value is less than the set output voltage of the AC-DC conversion unit and the difference is not greater than 5V.

[0040] As described above, the voltage control circuit, voltage control system and method of the present invention have the following beneficial effects:

[0041] 1. A voltage control circuit is provided at the user side in the present invention. The voltage control circuit compensates for the losses of the long-distance transmission line, and obtains a stable AC power supply with a set voltage at the user side to meet the power consumption requirements.

[0042] 2. The voltage control circuit of the present invention uses an energy storage battery to ensure the normal operation of the AC-DC conversion unit, avoiding the situation where the AC-DC conversion unit cannot operate normally when the voltage at the input end of the power supply control circuit is too low.

[0043] 3. The voltage control circuit of the present invention connects the energy storage battery and the AC-DC conversion unit in parallel on the DC bus. By providing a part of the output power with the energy storage battery, the demand for grid power is reduced, and thus the voltage drop on the long-distance transmission line is reduced, and the power consumption pressure of other users on the transmission line is reduced.

[0044] 4. In the voltage control circuit of the present invention, the electric energy generated by new energy is compensated to the DC bus to make full use of new energy, improve environmental protection and economy; further, the losses of the AC-DC conversion and DC-AC conversion units are also compensated to improve the efficiency. BRIEF DESCRIPTION OF THE DRAWINGS

[0045] Figure 1 It shows a schematic structural diagram of the voltage control circuit of the present invention.

[0046] Figure 2 It shows a schematic principle diagram of the control unit of the present invention.

[0047] Figure 3 It shows the voltage relationship of the present invention.

[0048] Figure 4 It shows a schematic diagram of the relationship between the maximum limit value and the minimum limit value in the limiter of the present invention.

[0049] Figure 5 It shows a schematic structural diagram of the voltage control system of the present invention.

[0050] Figure 6 It shows a state diagram of the control unit of the present invention realizing voltage control.

[0051] Figure 7 It shows a schematic working principle diagram of the voltage control circuit of the present invention.

[0052] DESCRIPTION OF REFERENCE NUMERALS

[0053] 1 Voltage control circuit

[0054] 11 AC-DC conversion unit

[0055] 12 DC-AC conversion unit

[0056] 13 Bidirectional DC conversion unit

[0057] 14 First battery module

[0058] 15 New energy module

[0059] 151 Photovoltaic panel

[0060] 152 Maximum power point tracking module

[0061] 16 Second battery module

[0062] 17 Control unit

[0063] 171 Voltage loop

[0064] 172 Current loop

[0065] 17a Difference operator

[0066] 17b Proportional integral controller

[0067] 17c Limiter

[0068] 17d Difference operator

[0069] 2 First contactor

[0070] 3 Second contactor Specific implementation manner

[0071] The following uses specific specific examples to illustrate the implementation manners 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 implementation manners. 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.

[0072] Please refer to Figures 1 to 7 . It should be noted that the diagrams provided in this embodiment only illustrate the basic concept of the present invention in a schematic manner. Therefore, only the components related to the present invention are shown in the diagrams, rather than being drawn according to the number, shape, and size of the components in actual implementation. The types, quantities, and proportions of the components in actual implementation can be arbitrarily changed, and the component layout type may also be more complex.

[0073] As Figure 1 shown, the present invention provides a voltage control circuit 1, and the voltage control circuit 1 includes:

[0074] AC-DC conversion unit 11, DC-AC conversion unit 12, bidirectional DC conversion unit 13, first battery module 14, new energy module 15, second battery module 16, and control unit 17.

[0075] AsFigure 1 As shown, the input end of the AC-DC conversion unit 11 is connected to the power supply side AC power source, and the output end is connected to the DC bus.

[0076] Specifically, the input end of the AC-DC conversion unit 11 is connected to the transformer through a long-distance transmission line, which is used to convert the AC power provided by the transformer into DC power to obtain the DC bus voltage; any circuit structure that can convert AC power into DC power is applicable to the present invention and will not be elaborated here one by one. The voltage control circuit 1 of the present invention is arranged at the end of the power distribution area. As an example, the length of the transmission line between the AC-DC conversion unit 11 and the transformer is not less than half of the distance between the transformer and the user, including but not limited to one-fourth, one-fifth, one-tenth; of course, the closer the voltage control circuit 1 of the present invention is to the user end, the better the effect.

[0077] As Figure 1 shown, the input end of the DC-AC conversion unit 12 is connected to the DC bus, and the output end outputs a stable user side AC power source.

[0078] Specifically, the DC-AC conversion unit 12 converts the DC power on the DC bus into AC power and supplies it to the user; any circuit structure that can achieve inversion is applicable to the present invention and will not be elaborated here one by one.

[0079] As Figure 1 shown, the first end of the bidirectional DC conversion unit 13 is connected to the DC bus, and the second end is connected to the first battery module 14.

[0080] Specifically, the bidirectional DC conversion unit 13 is used for the energy conversion between the first battery module 14 and the DC bus, and any structure that can achieve bidirectional DC conversion is applicable to the present invention.

[0081] As Figure 1 shown, the output end of the new energy module 15 is connected to the second end of the bidirectional DC conversion unit 13, which is used to generate electric energy and regulate the power generation output power.

[0082] Specifically, the new energy module 15 is connected to the connection node between the bidirectional DC conversion unit 13 and the first battery module 14. The electric energy generated by the new energy module 15 can be stored in the first battery module 14 or transmitted to the DC bus through the bidirectional DC conversion unit 13. In this embodiment, the new energy module 15 includes a photovoltaic panel 151 and a maximum power point tracking module 152 (Maximum power point tracking, MPPT); wherein, the photovoltaic panel 151 converts solar energy into electric energy; one end of the maximum power point tracking module 152 is connected to the output end of the photovoltaic panel 151, and the other end is connected to the second end of the bidirectional DC conversion unit 13. By real-time monitoring and adjusting the voltage and current of the photovoltaic panel 151, it is always maintained at the maximum power point, thereby maximizing the utilization of solar energy resources and improving the energy conversion efficiency of the system.

[0083] As Figure 1 shown, the second battery module 16 is connected to the DC bus and is used to store the electric energy on the DC bus.

[0084] As Figure 1 shown, the control unit 17 controls the bidirectional DC conversion unit 13 to achieve charge and discharge control of the first battery module 14.

[0085] Specifically, in this embodiment, the control unit 17 includes a voltage loop 171 and a current loop 172. The voltage loop 171 generates a reference current I Busref based on the difference between the reference voltage U Bus and the bus voltage U ref on the DC bus (the sampling signal of the bus voltage in this example). Among them, the voltage loop 171 includes a difference operator 17a, a proportional-integral controller 17b, and a limiter 17c; the positive-phase input terminal of the difference operator 17a receives the reference voltage U Busref , the inverting input terminal receives the bus voltage U Bus , and outputs a voltage difference; the proportional-integral controller 17b is connected to the output terminal of the difference operator 17a and performs proportional-integration on the voltage difference; the limiter 17c is connected to the output terminal of the proportional-integral controller 17b to limit the amplitude of the current output by the proportional-integral controller 17b to obtain the reference current I ref . The current loop 172 generates a switch control signal Ctl for the bidirectional DC conversion unit 13 based on the difference between the reference current I ref and the inductor current I in the bidirectional DC conversion unit 13 (the sampling signal of the inductor current in this example); in this example, the current loop 172 is implemented by a difference operator 17d. Among them, the reference voltage U Busref is greater than the set output voltage U AC / DC of the AC-DC conversion unit 11. As Figure 3 shown, as an example, UAC / DC Set to 55.2V, U Busref Set to 56.3V, with a difference within 3V; when working normally, the AC-DC conversion unit 11 controls the voltage on the DC bus at the set output voltage U AC / DC At this time, the output current of the proportional-integral controller 17b is limited by the maximum current limit value Imax of the limiter 17c. The maximum current limit value Imax of the limiter 17c is set to a positive value (as Figure 4 shown, as an example, greater than 8A); when the load on the user side is large, the AC-DC conversion unit 11 cannot control the voltage on the DC bus at the set output voltage U even when reaching the maximum output power AC / DC At this time, the bus voltage U Bus drops significantly. The output current of the proportional-integral controller 17b is limited by the minimum current limit value Imin of the limiter 17c. The minimum current limit value Imin of the limiter 17c is adjusted to a positive or negative value according to time and the battery SOC (as Figure 4 shown, as an example, the positive value is set to 8A and the negative value is set to -15A) and is less than the maximum current limit value Imax.

[0086] The voltage control circuit 1 of the present invention can compensate the voltage at the user end, overcome the problem of transmission line voltage drop, and ensure the stability of the AC voltage on the user side.

[0087] As Figure 5 shown, the present invention also provides a voltage control system, including:

[0088] The voltage control circuit 1, the first contactor 2 and the second contactor 3.

[0089] As Figure 5 shown, the first contactor 2 is connected in series on the input-output path of the voltage control circuit 1.

[0090] Specifically, as Figure 5 shown, as an example, the first contactor 2 is set as an AC contactor. One end of the AC contactor is connected to the output end of the direct-AC conversion unit 12, and the other end is connected to the second end of the second contactor 3. At this time, if the first contactor 2 is disconnected, the line between the output end of the direct-AC conversion unit 12 and the user end is disconnected, and the voltage control circuit 1 does not supply power to the user end; if the first contactor 2 is turned on, the line between the output end of the direct-AC conversion unit 12 and the user end is connected, and the voltage control circuit 1 supplies power to the user end.

[0091] Specifically, as another example, the first contactor 2 is set as a DC contactor. One end of the DC contactor is connected to the connection node of the AC-DC conversion unit 11, the bidirectional DC conversion unit 13, and the second battery module 16, and the other end is connected to the input end of the DC-AC conversion unit 12. At this time, if the first contactor 2 is disconnected, the input end of the DC-AC conversion unit 12 is open-circuited, and the DC-AC conversion unit 12 cannot work and provide the corresponding AC output power supply; if the first contactor 2 is turned on, the input end of the DC-AC conversion unit 12 obtains a DC voltage, and the DC-AC conversion unit 12 generates an AC output power supply and supplies power to the user side.

[0092] It should be noted that the first contactor 2 can be set at any position that can control the on-off of the path where the voltage control circuit 1 is located. For example, the first contactor 2 is connected in series with the voltage control circuit 1, which will not be elaborated here one by one.

[0093] As Figure 5 shown, the first end of the second contactor 3 is connected to the input end of the AC-DC conversion unit 11, and the second end is connected to the user side.

[0094] Specifically, the second contactor 3 is an AC contactor for connecting the transformer and the user side; when the second contactor 3 is disconnected, the transformer does not directly supply power to the user side; when the second contactor 3 is turned on, the transformer directly supplies power to the user side.

[0095] As Figure 5 shown, the control unit 17 also generates control signals for the first contactor 2 and the second contactor 3.

[0096] As an implementation manner of the present invention, the AC-DC conversion unit 11, the DC-AC conversion unit 12, the bidirectional DC conversion unit 13, and the control unit 17 are arranged in the same cabinet. The capacity of the first battery module 14 can be set as needed. When the capacity of the first battery module 14 is large, the volume of the first battery module 14 is also relatively large and is arranged outside the cabinet; when the capacity of the first battery module 14 is small, the volume of the first battery module 14 is also relatively small and is arranged inside the cabinet. The second battery module 16 generally has a large capacity and volume and is arranged outside the cabinet.

[0097] The present invention also provides a voltage control method, which is implemented based on the voltage control system of the present invention. The voltage control method includes:

[0098] S1) Disconnect the second contactor 3, close the first contactor 2, and control the voltage control circuit 1 to enter the working state; obtain and judge whether the AC power supply on the user side output by the voltage control circuit 1 is normal; if it is not normal, restart the voltage control circuit 1; if it is normal, the voltage control circuit 1 generates the AC power supply on the user side and supplies power in the working state.

[0099] Specifically, in this embodiment, the state machine of the control unit 17 is in an idle state at the start-up stage, and then powers on. After the power-on is completed, it enters the standard state, where the standard state includes four states. In the standard state, the control unit 17 first enters the first state, connects the voltage control circuit 1 to the access path, and performs a self-check on the voltage control circuit 1. If it is normal, the voltage control circuit 1 provides an AC power supply to the user side; if it is abnormal, it restarts.

[0100] More specifically, as Figure 6 shown, as an example, the first state gradually performs the following operations: disconnect the second contactor 3, close the first contactor 2, connect the voltage control circuit 1 to the power supply path, turn on the AC / DC conversion unit 12, and the voltage control circuit 1 starts to work. If the AC / DC conversion unit 12 has no output or the output voltage exceeds the normal range, it is determined that the voltage control circuit 1 is abnormal; if the output voltage of the AC / DC conversion unit 12 is within the normal range, it is determined that the voltage control circuit 1 is normal. Other methods for determining whether the AC / DC conversion unit 12 is normal are also applicable to the present invention and are not limited to this embodiment.

[0101] Further, when the voltage control circuit 1 is abnormal, it enters the second state to restart. In the second state, disconnect the first contactor 2 and the second contactor 3, and turn off the bidirectional DC conversion unit 13. After maintaining the off state for 10 s, it returns to the first state to re-determine whether the voltage control circuit 1 is normal.

[0102] As Figure 7 shown, when the voltage control circuit 1 is normal, in the first time period, the second time period, and the third time period set in sequence, if the voltage of the first battery module 14 (in this embodiment, the voltage of the first battery module 14 within each time period is the voltage signal sampling value at the input terminal side of the first battery module 14) is less than the discharge cut-off voltage of the first battery module 14, or the SOC of the first battery module 14 is less than the first set percentage, the minimum current limit value Imin in the bidirectional DC conversion unit 13 is set to a positive value, and the bidirectional DC conversion unit 13 charges the first battery module 14; if the voltage of the first battery module 14 is greater than the set voltage, the minimum current limit value Imin in the bidirectional DC conversion unit 13 is set to a negative value, and the bidirectional DC conversion unit 13 discharges to the DC bus. Among them, the discharge current of the bidirectional DC conversion unit 13 in the first time period and the third time period is less than the discharge current in the second time period.

[0103] Specifically, the first period, the second period, and the third period are set in sequence to constitute a natural day. Among them, the first period is the power consumption trough period at night and in the morning, the second period is the new energy power generation period, and the third period is the power consumption peak period in the evening and at night. As an example, the first period is set to 0:00 to 8:00, the second period is set to 8:00 to 17:00, and the third period is set to 17:00 to 24:00. In actual use, the specific time of each period needs to be adjusted in combination with local weather, power consumption demand and other conditions, and is not limited to this embodiment. The discharge cut-off voltage is the lowest voltage that the battery is allowed to reach during discharge and is determined according to the performance requirements of the first battery module 14. In this embodiment, the discharge cut-off voltage of the first battery module 14 is set to 46V (less than the set output voltage U of the AC-DC conversion unit 11 AC / DC ). The first set percentage (i.e., the percentage of the current remaining battery power to its total capacity) is used to indicate that the battery power is low (if the battery power is lower than the first set percentage, the battery will be damaged), and is also determined according to the performance requirements of the first battery module 14. In this embodiment, the first set percentage is set to 10% - 20%, including but not limited to 15%. When the voltage of the first battery module 14 is greater than the set voltage, it indicates that a certain amount of electric energy is stored in the first battery module 14. The excess power generated by the new energy module 15 can be transmitted to the DC bus through the bidirectional DC conversion unit 13. In this embodiment, the set voltage is at least 2V greater than the discharge cut-off voltage of the first battery module 14 but needs to be less than the set output voltage U of the AC-DC conversion unit 11 AC / DC , as an example, 3V, 4V, 5V greater, which can be set according to actual needs and is not limited to this embodiment.

[0104] More specifically, during the first period, the new energy module 14 does not work, and the power consumption of the user side is relatively small. If the voltage of the first battery module 14 is less than 46V, or the SOC of the first battery module 14 is less than 15%, the minimum current limit value Imin in the bidirectional DC conversion unit 13 is set to 2A (generally a positive value less than 5A). At this time, since the new energy module 15 cannot generate electric energy, the bidirectional DC conversion unit 13 obtains electric energy from the DC bus and charges the first battery module 14. If the voltage of the first battery module 14 is greater than 50V, the minimum current limit value Imin in the bidirectional DC conversion unit 13 is set to -1A (generally a negative value greater than -3A). At this time, the first battery module 14 has excess electric energy that can be provided to the DC bus through the bidirectional DC conversion unit 13. In the initial stage, if the above conditions are not met, the bidirectional DC conversion unit 13 supplies power to the DC bus with a small current (generally a negative value greater than -3A, such as -2A, -1A).

[0105] More specifically, during the second time period, the new energy module 14 starts to operate and generate electrical energy. If the voltage of the first battery module 14 is less than 46V, or the SOC of the first battery module 14 is less than 15%, the minimum current limit value Imin in the bidirectional DC conversion unit 13 is set to 3A (generally a positive value less than 5A, preferably greater than the charging currents in the first and third time periods). At this time, the electrical energy generated by the new energy module 15 is preferentially supplied to the first battery module 14 to maintain the minimum voltage for the normal operation of the first battery module 14. If the electrical energy provided by the new energy module 15 is insufficient, the bidirectional DC conversion unit 13 obtains electrical energy from the DC bus and charges the first battery module 14. If the voltage of the first battery module 14 is greater than 50V, the minimum current limit value Imin in the bidirectional DC conversion unit 13 is set to -15A (generally a negative value less than -10A, greater than the discharge currents in the first and third time periods). At this time, the excess electrical energy generated by the new energy module 15 can be supplied to the DC bus through the bidirectional DC conversion unit 13. In the initial stage, if the above conditions are not met, the bidirectional DC conversion unit 13 supplies power to the DC bus with the maximum set current (generally a negative value less than -10A, such as -15V).

[0106] More specifically, during the third time period, the new energy module 14 does not operate, and the power consumption at the user side is relatively large. If the voltage of the first battery module 14 is less than 46V, or the SOC of the first battery module 14 is less than 15%, the minimum current limit value Imin in the bidirectional DC conversion unit 13 is set to 2A (generally a positive value less than 5A). At this time, since the new energy module 15 cannot generate electrical energy, the bidirectional DC conversion unit 13 obtains electrical energy from the DC bus and charges the first battery module 14. If the voltage of the first battery module 14 is greater than 50V, the minimum current limit value Imin in the bidirectional DC conversion unit 13 is set to -1A (generally a negative value greater than -3A). At this time, the excess electrical energy in the first battery module 14 can be supplied to the DC bus through the bidirectional DC conversion unit 13. In the initial stage, the voltage of the first battery module 14 is generally greater than 50V.

[0107] More specifically, as another implementation, the battery has poor charging performance at low temperatures. Therefore, the battery has a heating mechanism, and a heating film is provided inside the battery. As an example, the rated heating power is 120W. When the temperature of the battery cell is lower than 5°C and it is detected that the battery is in the charging state, the heating film relay closes and the heating starts; when the temperature of the battery cell is higher than 12°C or it is detected that the battery is in the discharging state, the heating film relay opens and the heating stops; for the charging MOS transistor of the battery cell, when the temperature of the battery cell is lower than 0°C, the charging MOS transistor opens and the charging stops; otherwise, when the temperature of the battery cell is higher than 1°C, the charging MOS transistor closes and the charging starts. To adapt to the heating mechanism of the battery, when the voltage control circuit 1 of the present invention is applied in cold regions, a fourth time period is also set between the first time period and the second time period. During the fourth time period, the first battery module 14 is charged so that the first battery module 14 has enough electrical energy for heating to ensure that the first battery module 14 can be charged normally; in this embodiment, the fourth time period is set to 6:00 - 8:00, and during this time period, a forced charge of 3A is applied to the first battery module 14. The charging current and charging duration can meet the rated heating power of the battery to ensure that the temperature of the battery cell of the first battery module 14 reaches the charging requirement. This is not limited to this embodiment. It should be noted that at this time, the first time period is adjusted to 0:00 - 6:00.

[0108] More specifically, as yet another implementation, when the light intensity in the second time period is insufficient, a fifth time period can also be set between the second time period and the third time period. During the fifth time period, the first battery module 14 is fully charged with the electrical energy provided by the DC bus to store more electrical energy for the peak power consumption period. In this embodiment, the fifth time period is set to 15:00 - 17:00. During this time period, the first battery module 14 is charged with a current of 8A (greater than the charging currents in other time periods, including but not limited to 6A, 10A, 12A, which is set according to actual needs); if the voltage of the first battery module 14 is greater than the equalizing charge voltage, the minimum current limit value Imin in the bidirectional DC conversion unit 13 is set to -1A (generally a negative value greater than -3A), and the bidirectional DC conversion unit 13 discharges. Among them, the equalizing charge voltage is an important parameter for balancing the voltages of individual battery cells in the battery pack during the charging process, ensuring that the battery pack can be charged evenly and avoiding overcharging or undercharging. Therefore, the equalizing charge voltage can be determined according to the performance requirements of the first battery module 14. In this embodiment, the equalizing charge voltage is set to 53.5V (in this example, less than the set output voltage U of the AC-DC conversion unit 11 AC / DC ). In this embodiment, the fifth time period is set to 15:00 - 17:00. At this time, the second time period is adjusted to 8:00 - 15:00.

[0109] In this embodiment, the discharge current of the first battery module 14 during each time period does not exceed 70% of the maximum discharge current value of the battery; further, the maximum discharge power of the bidirectional DC conversion unit 13 is limited to be between 0.5 and 1.2 times the new energy power generation power.

[0110] S2) If the restart times of the voltage control circuit 1 are greater than the set times within the set time, it is powered by the power supply side AC power supply, and returns to step S1) after the first preset duration.

[0111] Specifically, in this example, if the number of times of switching from the first state to the second state reaches 3 times within 30 minutes, it enters the third state and returns to the first state after operating in the third state for 1 hour; among them, the set time, the set times, and the first preset duration can be adjusted according to actual needs, and are not limited to this embodiment.

[0112] More specifically, as Figure 6 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 voltage control circuit 1 is not powered. In this embodiment, the bidirectional DC conversion unit 13 is in the shutdown state, and can also be in the startup state during actual use.

[0113] S3) If the power of the second battery module 16 is lower than the first set power, it is powered by the power supply side AC power supply, and the first battery module 14 discharges to the DC bus based on the bidirectional DC conversion unit 13; during the new energy power generation period and the power consumption peak period (in this embodiment, it is 5:00 - 24:00), after the second preset duration, or when the power of the second battery module 16 reaches the second set power, it returns to step S1); among them, the first set power is less than the second set power.

[0114] Specifically, as Figure 6 shown, the basis for determining that the power of the second battery module 16 is lower than the first set power is: the SOC of the second battery module 16 is less than or equal to the second set percentage and is in the power consumption trough period at night and in the morning (in this example, it is 0:00 - 5:00), where the second set percentage is set to 30% - 55%, including but not limited to 35%, 40%, 45%, 50%, and will not be elaborated one by one here. Or the SOC of the second battery module 16 is less than or equal to the third set percentage, where the third set percentage is set to 15% - 30%, including but not limited to 20%, 25%, and will not be elaborated one by one here. Or the bus voltage is lower than the discharge cut-off voltage of the second battery module 16 (set according to the actual battery performance requirements). When the power in the second battery module 16 is lower (too low) than the first set power, there may be a risk of being unable to ensure the normal operation of the voltage control circuit 1 of the present invention. The specific value and determination basis of the first set power can be set according to actual needs and are not limited to this embodiment.

[0115] Specifically, as Figure 6 shown, the basis for determining that the power of the second battery module 16 reaches the second set power is: the SOC of the second battery module 16 is greater than or equal to the fourth set percentage, where the fourth set percentage is set to 30%-50%, including but not limited to 35%, 40%, 45%. Or the bus voltage is greater than the set value, where the set value is less than the set output voltage U of the AC-DC conversion unit AC / DC , and the difference is not greater than 5V; in this example, the set value is 53V. When the power of the second battery module 16 is higher than the second set power, the voltage control circuit 1 of the present invention can operate normally, and the specific judgment basis can be set according to actual needs, not limited to this embodiment.

[0116] More specifically, as Figure 6 shown, when the power of the second battery module 16 is lower than the first set power, it enters the fourth state, disconnects the first contactor 2 and closes the second contactor 3. At this time, the transformer supplies power to the user side through the transmission line, and the voltage control circuit 1 is not powered; further, the bidirectional DC conversion unit 13 is turned on to supply the electric energy on the new energy module 15 or the first battery module 14 to the second battery module 16, and the discharge current magnitude of the bidirectional DC conversion unit 13 can be set according to actual needs. After the second preset time, or when the power of the second battery module 16 reaches the second set power, it returns from the fourth state to the first state. In this example, the second preset time is set to 1 hour.

[0117] In summary, the present invention provides a voltage control circuit, a voltage control system and a method, including: an AC-DC conversion unit, a DC-AC conversion unit, a bidirectional DC conversion unit, a first battery module, a new energy module, a second battery module and a control unit; the input end of the AC-DC conversion unit is connected to the power supply side AC power supply, and the output end is connected to the DC bus; the input end of the DC-AC conversion unit is connected to the DC bus, and the output end outputs a stable user side AC power supply; the first end of the bidirectional DC conversion unit is connected to the DC bus, and the second end is connected to the first battery module; the output end of the new energy module is connected to the second end of the bidirectional DC conversion unit for generating electric energy and adjusting the power generation output power; the second battery module is connected to the DC bus; the control unit controls the bidirectional DC conversion unit to perform charge and discharge control on the first battery module. The present invention compensates for the loss of long-distance transmission lines, meets the power consumption requirements of the user side, reduces the demand for grid power, makes full use of new energy, improves environmental protection and economy; at the same time improves efficiency. Therefore, the present invention effectively overcomes various disadvantages in the prior art and has high industrial utilization value.

[0118] The above embodiments are only illustrative of the principles and effects of the present invention and are not intended to limit the present invention. Any person familiar with this technology can modify or change the above embodiments without departing from the spirit and scope of the present invention. Therefore, all equivalent modifications or changes made by those with ordinary knowledge in the technical field without departing from the spirit and technical idea disclosed by the present invention should still be covered by the claims of the present invention.

Claims

1. A voltage control circuit, characterized in that, The voltage control circuit at least includes: an AC-DC conversion unit, a DC-AC conversion unit, a bidirectional DC conversion unit, a first battery module, a new energy module, a second battery module, and a control unit; The input end of the AC-DC conversion unit is connected to the power supply side AC power supply, and the output end is connected to the DC bus; The input end of the DC-AC conversion unit is connected to the DC bus, and the output end outputs a stable user side AC power supply; The first end of the bidirectional DC conversion unit is connected to the DC bus, and the second end is connected to the first battery module; The output end of the new energy module is connected to the second end of the bidirectional DC conversion unit, and is used to generate electric energy and adjust the power generation output power; The second battery module is connected to the DC bus; The control unit controls the bidirectional DC conversion unit to perform charge and discharge control on the first battery module.

2. The voltage control circuit according to claim 1, characterized in that: The 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. Among them, the voltage loop includes a difference operator, a proportional-integral controller, and a limiter; the positive-phase input end of the difference operator receives the reference voltage, the anti-phase input end receives the bus voltage, and outputs a voltage difference; the proportional-integral controller is connected to the output end of the difference operator to perform proportional integration on the voltage difference; the limiter is connected to the output end of the proportional-integral controller to limit the amplitude of the current output by the proportional-integral controller; The current loop generates a switching control signal of the bidirectional DC conversion unit based on the difference between the reference current and the inductor current in the bidirectional DC conversion unit; Among them, the set output voltage of the AC-DC conversion unit is less than the reference voltage; the maximum current limit value of the limiter is a positive value; the minimum current limit value of the limiter is a positive value or a negative value and is less than the maximum current limit value.

3. A voltage control system, characterized in that, The voltage control system at least includes: a first contactor, a second contactor, and the voltage control circuit according to any one of claims 1-2; The first contactor is connected in series on the input-output path of the voltage control circuit; The first end of the second contactor is connected to the input end of the AC-DC conversion unit, and the second end is connected to the user end; The control unit also generates control signals for the first contactor and the second contactor.

4. The voltage control system according to claim 3, wherein: The first contactor is a DC contactor, one end of the DC contactor is connected to the connection node of the AC-DC conversion unit, the bidirectional DC conversion unit, and the second battery module, and the other end is connected to the input end of the DC-AC conversion unit; Alternatively, the first contactor is an AC contactor, one end of the AC contactor is connected to the output end of the DC-AC conversion unit, and the other end is connected to the second end of the second contactor.

5. The voltage control system according to claim 3 or 4, characterized in that: The AC-DC conversion unit, the DC-AC conversion unit, the bidirectional DC conversion unit, the new energy module, and the control unit are arranged in the same cabinet, the first battery module is arranged inside or outside the cabinet, and the second battery module is arranged outside the cabinet.

6. A voltage control method, implemented based on the voltage control system described in any one of claims 3-5, characterized in that, The voltage control method at least includes: S1) Disconnect the second contactor, close the first contactor, and control the voltage control circuit to enter the working state; obtain and judge whether the user-side AC power supply output by the voltage control circuit is normal; if not, restart the voltage control circuit; if normal, the voltage control circuit generates and supplies the user-side AC power supply in the working state; S2) If the restart times of the voltage control circuit are greater than the set times within the set time, supply power from the power supply-side AC power supply, and return to step S1) after the first preset duration; S3) If the power of the second battery module is lower than the first set power, supply power from the power supply-side AC power supply, and the first battery module discharges to the DC bus based on the bidirectional DC conversion unit; in the new energy generation period and the electricity consumption peak period, after the second preset duration, or when the power of the second battery module reaches the second set power, return to step S1); wherein, the first set power is less than the second set power.

7. The voltage control method according to claim 6, wherein: In step S1), when the voltage control circuit is in the working state: The first period, the second period and the third period are set in sequence in a cycle; in the first period, the second period and the third period, if the voltage of the first battery module is less than the discharge cut-off voltage of the first battery module or the SOC of the first battery module is less than the first set percentage, the minimum current limit value in the bidirectional DC conversion unit is positive, and the bidirectional DC conversion unit charges the first battery module; if the voltage of the first battery module is greater than the set voltage, the minimum current limit value in the bidirectional DC conversion unit is negative, and the bidirectional DC conversion unit discharges to the DC bus; Wherein, the first period is the electricity consumption trough period at night and in the morning, the second period is the new energy generation period, and the third period is the electricity consumption peak period in the evening and at night; the discharge current of the bidirectional DC conversion unit in the first period and the third period is less than the discharge current in the second period; the set voltage is at least 2V greater than the discharge cut-off voltage of the first battery module, and the first set percentage is set to 10%-20%.

8. The voltage control method according to claim 7, characterized in that: The voltage of the first battery module is the voltage signal sampling value on the input terminal side of the first battery module.

9. The voltage control method according to claim 7, characterized in that: A fourth period is also set between the first period and the second period, and the first battery module is charged and heated in the fourth period so that the first battery module can be charged normally.

10. The voltage control method according to claim 7, characterized in that: A fifth period is also set between the second period and the third period, and the first battery module is charged to the equalizing charge voltage in the fifth period.

11. The voltage control method according to claim 7, wherein: The discharge current of the first battery module during discharge does not exceed 70% of the maximum discharge current value of the battery.

12. The voltage control method according to claim 11, characterized in that: The maximum discharge power of the bidirectional DC conversion unit is limited to be between 0.5 and 1.2 times the new energy generation power.

13. The voltage control method according to any one of claims 6-12, characterized in that: In step S3), the basis for determining that the power of the second battery module is lower than the first set power is as follows: the SOC of the second battery module is less than or equal to the second set percentage and it is in the power consumption trough period at night and in the morning, where the second set percentage is set to 30%-55%; or the SOC of the second battery module is less than or equal to the third set percentage, where the third set percentage is set to 15%-30%; or the bus voltage is lower than the discharge cut-off voltage of the second battery module.

14. The voltage control method according to any one of claims 6-12, characterized in that: In step S3), the basis for determining that the power of the second battery module reaches the second set power is as follows: the SOC of the second battery module is greater than or equal to the fourth set percentage, where the fourth set percentage is set to 30%-50%; or the bus voltage is greater than the set value, where the set value is less than the set output voltage of the AC-DC conversion unit and the difference is not greater than 5V.

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