Control device of direct-current power transmission system and optical energy storage direct-current power transmission system

Abstract

The invention relates to a control device of a direct-current power transmission system and an optical energy storage direct-current power transmission system. The control device of the direct-current power transmission system comprises a sampling circuit, a boosting unit, a first switch, a second switch, a third switch, an energy consumption unit and a control circuit, specifically, an input current of the DC power transmission system and an output current and an output voltage of a boost unit are sampled in real time through a sampling circuit and are transmitted to a control circuit, so that the controller can control the DC power transmission system when the input current and / or the output current is greater than a preset current and the output voltage is less than a preset voltage. The control unit controls the boost unit to increase the output voltage so as to suppress the short-circuit current flowing into the load, and controls the first switch to be turned off and the second switch and the third switch to be turned on, so that the electric energy of the direct-current power supply is dissipated through the energy consumption unit, the short-circuit fault of the direct-current power transmission system is clear, and the stability and safety of the direct-current digital display system are improved.

Description

Technical Field

[0001] The present application relates to the technical field of direct current transmission, and in particular to a control device for a direct current transmission system and a photovoltaic energy storage direct current transmission system. Background Art

[0002] When a DC transmission system fails, it is difficult to clear the DC short circuit fault. The traditional method is to use a DC circuit breaker to increase the resistance of the fault circuit, or to add a freewheeling energy consumption branch and a charging branch to clear the DC short circuit fault. However, this fault handling method has the risk of overvoltage, which leads to instability and unsafety of the DC transmission system. Summary of the invention

[0003] Based on this, it is necessary to provide a control device for a DC transmission system and a photovoltaic energy storage DC transmission system that can handle short-circuit faults while ensuring the stability and safety of the DC transmission system.

[0004] In a first aspect, a control device for a DC power transmission system is provided, wherein an input end of the DC power transmission system is connected to a DC power source, an output end of the DC power transmission system is connected to a load, and the control device for the DC power transmission system comprises: a sampling circuit, a boost unit, a first switch, a second switch, a third switch, an energy consumption unit, and a control circuit;

[0005] The sampling circuit is used to collect the input current of the DC transmission system and the output current and output voltage of the boost unit;

[0006] The input end of the boost unit is connected to the input end of the DC power transmission system, and the output end of the boost unit is respectively connected to the first end of the first switch and the first end of the third switch; the second end of the first switch is used to connect to the load;

[0007] The second end of the third switch is connected in series with the energy consumption unit and the second switch, and then connected to the load; the energy consumption unit is also used to be connected to the load;

[0008] The control circuit is respectively connected to the sampling circuit, the boost unit, the first switch, the second switch and the third switch; the control circuit is used to control the boost unit to increase the output voltage and control the first switch to be turned off, and the second switch and the third switch to be turned on when the input current and / or the output current is greater than the preset current and the output voltage is less than the preset voltage.

[0009] In one embodiment, the sampling circuit is further used to sample the output voltage of the DC power transmission system, and the control circuit further includes:

[0010] A driving unit, wherein an output end of the driving unit is connected to a controlled end of the boost unit;

[0011] A control unit, wherein an input end of the control unit is connected to the sampling circuit, an output end of the control unit is connected to an input end of the driving unit, and the control unit is used to increase the duty cycle of the output pulse width modulation signal according to the input voltage of the DC transmission system and the output voltage of the DC transmission system when the input current and / or the output current is greater than a preset current and the output voltage is less than a preset voltage.

[0012] In one embodiment, the control circuit is further used to control the first switch and the third switch to be turned on and the second switch to be turned off after receiving the buffer signal, and to control the third switch to be turned off after a preset time;

[0013] The buffer signal is used to indicate that the input current and / or the output current has been reduced to a level less than or equal to a preset current, or the output voltage has been increased to a level greater than or equal to a preset voltage.

[0014] In one embodiment, the energy consumption unit includes a resistor and a capacitor, and the resistor and the capacitor are sequentially connected in series between the third switch and the second switch.

[0015] In one embodiment, the sampling circuit comprises:

[0016] A first Hall current sensor, which is connected in series between the input end of the DC power transmission system and the boost unit;

[0017] A second Hall current sensor, the second Hall current sensor is connected in series between the boost unit and the first switch;

[0018] A Hall voltage sensor, wherein the input end of the Hall voltage sensor is connected to the output end of the boost unit;

[0019] The sampling unit is connected to the first Hall current sensor, the second Hall current sensor and the Hall voltage sensor respectively.

[0020] In one embodiment, the control unit comprises:

[0021] A first operational amplifier, wherein the input end of the first operational amplifier is connected to the first output end of the sampling circuit; the first operational amplifier is used to proportionally reduce the input current;

[0022] A second operational amplifier, wherein the input end of the second operational amplifier is connected to the second output end of the sampling circuit; the first operational amplifier is used to proportionally reduce the output current and output voltage of the boost unit;

[0023] An analog-to-digital conversion module, the analog-to-digital conversion module is connected to the first operational amplifier and the second operational amplifier respectively;

[0024] The controller is connected to the analog-to-digital conversion module and is used to generate a pulse width modulation signal to the drive unit according to the input voltage of the DC power transmission system and the output voltage of the DC power transmission system.

[0025] In one embodiment, the first switch, the second switch and the third switch are all a combination of one or more of a fully controlled device, a half-controlled device and a mechanical switch.

[0026] In one embodiment, the boost unit is a quadratic topology converter.

[0027] In one embodiment, the pulse width modulation signal is a square wave signal.

[0028] In a second aspect, a photovoltaic energy storage direct current transmission system is provided, comprising:

[0029] Photovoltaic DC power supply, used to convert solar energy into DC voltage;

[0030] A direct current transmission system, wherein the input end of the direct current transmission system is connected to a photovoltaic direct current power source, and the output end of the direct current transmission system is used to connect a load;

[0031] A control device for a DC power transmission system as described above.

[0032] The control device of the DC power transmission system and the photovoltaic energy storage DC power transmission system include a sampling circuit, a boost unit, a first switch, a second switch, a third switch, an energy consumption unit, and a control circuit. Specifically, the sampling circuit samples the input current of the DC power transmission system and the output current and output voltage of the boost unit in real time and transmits them to the control circuit, so that when the input current and / or output current is greater than a preset current and the output voltage is less than a preset voltage, the controller controls the boost unit to increase the output voltage to suppress the short-circuit current flowing into the load, and controls the first switch to be turned off, and the second switch and the third switch to be turned on, so that the electric energy of the DC power supply is dissipated through the energy consumption unit, thereby clearing the short-circuit fault of the DC power transmission system and improving the stability and safety of the DC digital display system. BRIEF DESCRIPTION OF THE DRAWINGS

[0033] In order to more clearly illustrate the technical solutions in the embodiments of the present application or the conventional technology, the drawings required for use in the embodiments or the conventional technology descriptions are briefly introduced below. Obviously, the drawings described below are only some embodiments of the present application. For ordinary technicians in this field, other drawings can be obtained based on these drawings without creative work.

[0034] Figure 1 One of the structural block diagrams of a control device for a DC power transmission system according to an embodiment;

[0035] Figure 2 It is a schematic diagram of the on-off states of a first switch, a second switch and a third switch in a control device of a direct current power transmission system of an embodiment when the direct current power transmission system is in a normal working state;

[0036] Figure 3 It is a schematic diagram of the on-off states of a first switch, a second switch and a third switch in a control device of a direct current power transmission system of an embodiment when the direct current power transmission system is in a working state of a short circuit fault;

[0037] Figure 4 This is a second structural block diagram of a control device for a DC power transmission system according to an embodiment;

[0038] Figure 5 It is a schematic diagram of the on-off states of a first switch, a second switch and a third switch in a control device of a direct current power transmission system of an embodiment when the direct current power transmission system is in a buffering working state;

[0039] Figure 6 The third structural block diagram of the control device of the DC power transmission system of one embodiment;

[0040] Figure 7 A fourth structural block diagram of a control device for a DC power transmission system according to an embodiment;

[0041] Figure 8 This is a diagram showing the selection of the first switch, the second switch and the third switch of an embodiment. DETAILED DESCRIPTION

[0042] In order to facilitate understanding of the present application, the present application will be described more fully below with reference to the relevant drawings. Embodiments of the present application are provided in the drawings. However, the present application can be implemented in many different forms and is not limited to the embodiments described herein. On the contrary, the purpose of providing these embodiments is to make the disclosure of the present application more thorough and comprehensive.

[0043] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as those commonly understood by those skilled in the art to which this application belongs. The terms used herein in the specification of this application are only for the purpose of describing specific embodiments and are not intended to limit this application.

[0044] It is understood that the terms "first", "second", etc. used in this application may be used herein to describe various elements, but these elements are not limited by these terms. These terms are only used to distinguish a first element from another element. For example, without departing from the scope of this application, a first switch may be referred to as a second switch, and similarly, a second switch may be referred to as a first switch. Both the first switch and the second switch are switches, but they are not the same switch.

[0045] It can be understood that the “connection” in the following embodiments should be understood as “electrical connection”, “communication connection”, etc. if the connected circuits, modules, units, etc. have electrical signals or data transmission between each other.

[0046] It can be understood that “at least one” means one or more, “plurality” means two or more, and “at least a portion of an element” means a part or all of an element.

[0047] When used herein, the singular forms "a", "an", and "said / the" may also include plural forms, unless the context clearly indicates otherwise. It should also be understood that the terms "include / comprise" or "have" and the like specify the presence of stated features, wholes, steps, operations, components, parts, or combinations thereof, but do not exclude the possibility of the presence or addition of one or more other features, wholes, steps, operations, components, parts, or combinations thereof. At the same time, the term "and / or" used in this specification includes any and all combinations of the relevant listed items.

[0048] In one embodiment, Figure 1 As shown, a control device 10 of a DC power transmission system is provided, wherein the input end of the DC power transmission system is connected to a DC power source 20, and the output end of the DC power transmission system is connected to a load 30. The control device 10 of the DC power transmission system includes: a sampling circuit 102, a boost unit 104, a first switch (such as Figure 1 SW1 shown), the second switch (as Figure 1 SW2 shown), the third switch (such as Figure 1 SW3 as shown), energy consumption unit 106, and control circuit 108.

[0049] The sampling circuit is used to collect the input current of the DC transmission system and the output current and output voltage of the boost unit.

[0050] The input end of the boost unit is connected to the input end of the DC power transmission system, and the output end of the boost unit is respectively connected to the first end of the first switch and the first end of the third switch; the second end of the first switch is used to connect the load.

[0051] The second end of the third switch is connected in series with the energy consumption unit and the second switch in sequence and then connected to the load; the energy consumption unit is also used to be connected to the load.

[0052] The control circuit is respectively connected to the sampling circuit, the boost unit, the first switch, the second switch and the third switch; the control circuit is used to control the boost unit to increase the output voltage, and control the first switch to be turned off, and the second switch and the third switch to be turned on when the input current and / or the output current is greater than the preset current and the output voltage is less than the preset voltage. The preset current can be a current value determined according to the short-circuit safety threshold of the DC power transmission system, and can also be a safe current value determined according to the rated current. Exemplarily, the preset current can be a current value greater than 1.1 times the rated current. Correspondingly, the preset voltage can be a voltage value determined according to the short-circuit safety threshold of the DC power transmission system, and can also be a safe voltage value corresponding to the rated voltage. Exemplarily, the preset voltage can be a voltage value lower than 0.9 times the rated voltage.

[0053] When at least one of the input current and the output current is less than or equal to the preset current, or the output voltage is greater than or equal to the preset voltage, the DC transmission system is considered to be in a normal working state. Figure 2 As shown, the control circuit controls the first switch to be closed, and the second switch and the third switch to be turned on. At this time, the electrical signal flowing out of the DC power supply flows directly to the load through the boost unit, that is, the control device of the DC power transmission system at this time controls the first switch to be closed, and the second switch and the third switch to be turned on, so that the DC power supply can normally transmit electrical energy to the load.

[0054] When the input current and / or output current is greater than the preset current and the output voltage is less than the preset voltage, it is considered that a short circuit fault occurs in the DC transmission system. Figure 3 As shown, the controller can reduce the short-circuit current flowing to the load by controlling the boost unit to increase the output voltage, thereby preventing the connected load from being impacted by an excessive short-circuit current; and the controller also controls the first switch to be turned off, and the second switch and the third switch to be turned on, so that the electrical signal flowing out of the DC power supply flows to the energy-consuming unit after passing through the boost unit to consume part of the electrical energy, thereby suppressing the sharply increased short-circuit current from damaging the connected load.

[0055] Furthermore, the sampling circuit collects the input current of the DC power transmission system and the output current and output voltage of the boost unit respectively, which can prevent the abnormal current output by the DC power supply from flowing to the boost unit, causing the boost unit to output abnormal output current and output voltage to the load, thereby damaging the load. Moreover, when the DC power transmission system is in a normal working state, the controller does not output a pulse width modulation signal to the boost unit, that is, the input current of the DC power transmission system is consistent with the output current of the boost unit, and the input voltage of the DC power transmission system is consistent with the output voltage of the boost unit. Therefore, by collecting the input current of the DC power transmission system and the output current and output voltage of the boost unit respectively through the sampling circuit, it is possible to quickly determine whether the DC power transmission system has a fault, thereby improving the reliability of the control device of the DC power transmission system.

[0056] The control device of the DC power transmission system comprises a sampling circuit, a boost unit, a first switch, a second switch, a third switch, an energy consumption unit, and a control circuit; specifically, the sampling circuit samples the input current of the DC power transmission system and the output current and output voltage of the boost unit in real time, and transmits the samples to the control circuit, so that when the input current and / or output current is greater than a preset current and the output voltage is less than a preset voltage, the controller controls the boost unit to increase the output voltage to suppress the short-circuit current flowing into the load, and controls the first switch to be turned off, and the second switch and the third switch to be turned on, so that the electric energy of the DC power supply is dissipated through the energy consumption unit, thereby clearing the short-circuit fault of the DC power transmission system and improving the stability and safety of the DC digital display system.

[0057] In one embodiment, the sampling circuit is further used to sample the output voltage of the DC power transmission system.

[0058] like Figure 4 As shown, the control circuit also includes: a driving unit 1082 and a control unit 1084.

[0059] The output end of the driving unit is connected to the controlled end of the boost unit.

[0060] The input end of the control unit is connected to the sampling circuit, and the output end of the control unit is connected to the input end of the driving unit. The control unit is used to increase the duty cycle of the output pulse width modulation signal according to the input voltage of the DC transmission system and the output voltage of the DC transmission system when the input current and / or the output current is greater than the preset current and the output voltage is less than the preset voltage.

[0061] When the DC power transmission system is in a normal working state, the input voltage of the DC power transmission system is equal to the output voltage of the DC power transmission system, that is, the duty cycle of the pulse width modulation signal output at this time is 0 or no pulse width modulation signal is output. When a short circuit fault occurs in the DC power transmission system, a duty cycle greater than 0 can be determined based on the input voltage of the DC power transmission system and the output voltage of the DC power transmission system, so that the boost unit can be controlled to increase the output voltage.

[0062] In one embodiment, Figure 5 As shown, the control circuit is also used to control the first switch and the third switch to be turned on and the second switch to be turned off after receiving the buffer signal, and to control the third switch to be turned off after a preset time.

[0063] The buffer signal is used to indicate that the input current and / or the output current has been reduced to a level less than or equal to a preset current, or the output voltage has been increased to a level greater than or equal to a preset voltage.

[0064] When the input current and / or output current has been reduced to less than or equal to the preset current, or the output voltage has been increased to greater than or equal to the preset voltage, it can be considered that the DC power transmission system has been out of the working state of the short circuit fault, so the first switch can be opened to allow the electric energy to flow to the load through the closed first switch. Furthermore, if there are elements or devices such as batteries, capacitors, phase change energy storage materials, flywheel energy storage devices, etc. that can store electric energy in the energy consumption unit, when the third switch is turned on, the electric energy stored therein can also be released to the load to achieve electric energy recovery.

[0065] After a preset time, the controller controls the third switch to turn off so that the DC power supply can normally supply power to the load. The preset time can be determined according to the capacity and discharge capacity of the element or device capable of storing electrical energy in the energy consumption unit so that the element or device capable of storing electrical energy can be completely discharged.

[0066] In one embodiment, Figure 4 As shown, the energy consumption unit includes a resistor R and a capacitor C, and the resistor and the capacitor are connected in series between the third switch and the second switch in sequence.

[0067] Among them, the resistor can consume part of the electric energy when a short circuit fault occurs in the DC transmission system; the capacitor can store part of the electric energy when a short circuit fault occurs in the DC transmission system, and release the stored electric energy when the DC transmission system is in a buffer working state.

[0068] In one embodiment, Figure 6 As shown, the sampling circuit includes: a first Hall current sensor 1022 , a second Hall current sensor 1024 , a Hall voltage sensor 1026 , and a sampling unit 1028 .

[0069] The first Hall current sensor is connected in series between the input end of the DC power transmission system and the boost unit. The first Hall current sensor is used to sample the input current of the DC power transmission system (such as Figure 6 The i shown in ).

[0070] The second Hall current sensor is connected in series between the boost unit and the first switch. The second Hall current sensor is used to sample the output current of the boost unit (such as Figure 6 The i shown out ).

[0071] The input end of the Hall voltage sensor is connected to the output end of the boost unit. The Hall voltage sensor is used to sample the output voltage of the boost unit (such as Figure 6 The V out ).

[0072] The sampling units are respectively connected to the first Hall current sensor, the second Hall current sensor and the Hall voltage sensor.

[0073] Since the Hall current sensor and the Hall voltage sensor can perform measurements without contacting the current conductor and the circuit, the use of Hall sensors to collect the input current of the DC transmission system, the output current and the output voltage of the boost unit can achieve electrical isolation, thereby improving the safety of the control device and personnel of the DC transmission system.

[0074] In one embodiment, Figure 7 As shown, the control unit 1084 includes: a first operational amplifier 1092 , a second operational amplifier 1094 , an analog-to-digital conversion module 1096 and a controller 1098 .

[0075] The input end of the first operational amplifier is connected to the first output end of the sampling circuit; the first operational amplifier is used to proportionally reduce the input current.

[0076] The input end of the second operational amplifier is connected to the second output end of the sampling circuit; the first operational amplifier is used to proportionally reduce the output current and output voltage of the boost unit.

[0077] The analog-to-digital conversion module is connected to the first operational amplifier and the second operational amplifier respectively.

[0078] The controller is connected to the analog-to-digital conversion module, and is used for generating a pulse width modulation signal to the drive unit according to an input voltage of the direct current transmission system and an output voltage of the direct current transmission system.

[0079] The controller can determine a voltage corresponding to the input current determined by the first operational amplifier, and the voltage is the input voltage of the DC power transmission system reduced in proportion to the input current. Thus, the controller can determine the output voltage of the DC power transmission system according to the reduced input voltage of the DC power transmission system and the output voltage of the DC power transmission system.

[0080] Specifically, the pulse width modulation signal can be determined according to the following formula:

[0081] Verr=Vin-Vo;

[0082] Wherein, Verr is the error voltage, Vo is the input voltage of the DC transmission system after being scaled down, and Vin is the output voltage of the DC transmission system after being scaled down.

[0083]

[0084] Where M is the gain, P is the proportional control coefficient, I is the integral control coefficient, and k is the total number of calculations of the historical error voltage. j is the jth Verr.

[0085] again:

[0086]

[0087] Where D is the duty cycle of the pulse width modulation signal.

[0088] Therefore, the duty cycle of the pulse width modulation signal at any short circuit fault moment can be determined according to the above formula.

[0089] In one embodiment, the first switch, the second switch and the third switch are all a combination of one or more of a fully controlled device, a half-controlled device and a mechanical switch. Figure 8 As shown, any of the first switch, the second switch and the third switch can be Figure 8 Any switch or multiple switches shown in the figure are connected in series or in parallel.

[0090] In one embodiment, Figure 7 As shown, the boost unit is a quadratic topology converter. Based on the quadratic topology converter of this structure, the gain can be determined The determination formula of .

[0091] Among them, U fault It is the fault point. It can be seen that in the event of a fault in the DC transmission system, electrical isolation can be achieved through capacitors, thereby improving the safety of the DC transmission system.

[0092] In one embodiment, the pulse width modulation signal is a square wave signal.

[0093] According to the duty cycle of the pulse width modulation signal determined above, a square wave signal can be uniquely determined. The square wave signal has a high anti-interference ability, thereby improving the reliability of the control device of the direct current transmission system.

[0094] The duty cycle of the square wave signal can be any value between 0 and 1.

[0095] In one embodiment, a photovoltaic energy storage DC power transmission system includes: a photovoltaic DC power source, a DC power transmission system, and a control device of the DC power transmission system as described above.

[0096] Photovoltaic DC power supplies are used to convert solar energy into DC voltage.

[0097] The input end of the DC transmission system is connected to the photovoltaic DC power source, and the output end of the DC transmission system is used to connect the load.

[0098] The photovoltaic energy storage DC transmission system equipped with the control device of the DC transmission system can realize self-detection and self-processing of DC faults, thereby improving the reliability, safety and automation of the photovoltaic energy storage DC transmission system.

[0099] In the description of this specification, the description with reference to the terms "some embodiments", "other embodiments", etc. means that the specific features, structures, materials or characteristics described in conjunction with the embodiment or example are included in at least one embodiment or example of the present application. In this specification, the schematic description of the above terms does not necessarily refer to the same embodiment or example.

[0100] The technical features of the above-described embodiments may be arbitrarily combined. To make the description concise, not all possible combinations of the technical features in the above-described embodiments are described. However, as long as there is no contradiction in the combination of these technical features, they should be considered to be within the scope of this specification.

[0101] The above-described embodiments only express several implementation methods of the present application, and the descriptions thereof are relatively specific and detailed, but they cannot be understood as limiting the scope of the present application. It should be pointed out that, for a person of ordinary skill in the art, several variations and improvements can be made without departing from the concept of the present application, and these all belong to the protection scope of the present application. Therefore, the protection scope of the present application shall be subject to the attached claims.

Claims

1. A control device for a direct current transmission system, characterized in that: The input end of the DC power transmission system is connected to a DC power source, the output end of the DC power transmission system is connected to a load, and the control device of the DC power transmission system includes: a sampling circuit, a boost unit, a first switch, a second switch, a third switch, an energy consumption unit, and a control circuit; The sampling circuit is used to collect the input current of the DC power transmission system and the output current and output voltage of the boost unit; The input end of the boost unit is connected to the input end of the DC power transmission system, and the output end of the boost unit is respectively connected to the first end of the first switch and the first end of the third switch; the second end of the first switch is used to connect to a load; The second end of the third switch is connected to the load after being connected in series with the energy consumption unit and the second switch; the energy consumption unit is also used to be connected to the load; The control circuit is respectively connected to the sampling circuit, the boost unit, the first switch, the second switch and the third switch; the control circuit is used to control the boost unit to increase the output voltage, and control the first switch to be turned off, and the second switch and the third switch to be turned on when the input current and / or output current is greater than a preset current and the output voltage is less than a preset voltage.

2. The control device of the DC power transmission system according to claim 1, characterized in that: The sampling circuit is also used to sample the output voltage of the DC power transmission system. The control circuit also includes: A driving unit, wherein an output end of the driving unit is connected to a controlled end of the boost unit; A control unit, wherein an input end of the control unit is connected to the sampling circuit, an output end of the control unit is connected to an input end of the driving unit, and the control unit is used to increase the duty cycle of the output pulse width modulation signal according to the input voltage of the DC power transmission system and the output voltage of the DC power transmission system when the input current and / or the output current is greater than a preset current and the output voltage is less than a preset voltage.

3. The control device of the DC power transmission system according to claim 1, characterized in that: The control circuit is further used to control the first switch and the third switch to be turned on and the second switch to be turned off after receiving the buffer signal, and control the third switch to be turned off after a preset time; The buffer signal is used to indicate that the input current and / or the output current has been reduced to a level less than or equal to the preset current, or the output voltage has been increased to a level greater than or equal to the preset voltage.

4. The control device of the DC power transmission system according to claim 1, characterized in that: The energy consumption unit includes a resistor and a capacitor, and the resistor and the capacitor are sequentially connected in series between the third switch and the second switch.

5. The control device of the DC power transmission system according to claim 1, characterized in that: The sampling circuit comprises: A first Hall current sensor, which is connected in series between the input end of the DC power transmission system and the boost unit; a second Hall current sensor, wherein the second Hall current sensor is connected in series between the boost unit and the first switch; A Hall voltage sensor, wherein the input end of the Hall voltage sensor is connected to the output end of the boost unit; A sampling unit, wherein the sampling unit is respectively connected to the first Hall current sensor, the second Hall current sensor and the Hall voltage sensor.

6. The control device of the DC power transmission system according to claim 2, characterized in that: The control unit comprises: A first operational amplifier, wherein an input end of the first operational amplifier is connected to a first output end of the sampling circuit; the first operational amplifier is used to proportionally reduce the input current; a second operational amplifier, wherein the input end of the second operational amplifier is connected to the second output end of the sampling circuit; the first operational amplifier is used to proportionally reduce the output current and output voltage of the boost unit; an analog-to-digital conversion module, wherein the analog-to-digital conversion module is connected to the first operational amplifier and the second operational amplifier respectively; A controller is connected to the analog-to-digital conversion module, and is used to generate a pulse width modulation signal to the drive unit according to an input voltage of the DC power transmission system and an output voltage of the DC power transmission system.

7. The control device of the DC power transmission system according to claim 1, characterized in that: The first switch, the second switch and the third switch are all combinations of one or more of a fully controlled device, a half-controlled device and a mechanical switch.

8. The control device of the DC power transmission system according to claim 1, characterized in that: The boost unit is a quadratic topology converter.

9. The control device of the DC power transmission system according to claim 2, characterized in that: The pulse width modulation signal is a square wave signal.

10. A solar energy storage DC transmission system, characterized in that: include: Photovoltaic DC power supply, used to convert solar energy into DC voltage; A direct current power transmission system, wherein the input end of the direct current power transmission system is connected to the photovoltaic direct current power source, and the output end of the direct current power transmission system is used to connect to a load; A control device for a DC power transmission system as claimed in any one of claims 1 to 9.

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