Cascade protection device and method

Abstract

The invention discloses a cascade protection device and method. The cascade protection device collects current signals of an energy storage PCS loop, an upper-level connection loop and a lower-level connection loop respectively, vector sum calculation is carried out, when the vector sum is not zero, it is indicated that a short-circuit fault occurs in the cascade ring main unit, and the protection device instantaneously acts, and an outlet trips out; the lower-level integrated protection control collects a current signal of the upper-level contact loop and transmits the current signal to the upper-level integrated protection control through the communication link; a superior integrated protection control collects a current signal of a subordinate contact loop; vector sum calculation is carried out on the two current signals in an upper-level integrated protection control, when the vector sum is not zero, it is indicated that a short-circuit fault happens to a tie line, and a protection device instantaneously acts and trips out of an outlet. The all-level integrated protection control in the invention finally realizes differential protection of the whole loop by adopting a cascade scheme, and when a short-circuit fault occurs in the loop, a 0s action outlet trips, so that the operation safety of the system is improved.

Description

Technical Field

[0001] The present invention relates to the field of power transmission and distribution, and more specifically to a cascade protection device and method. Background Art

[0002] Energy storage power stations are generally composed of batteries, power conversion systems (PCS), step-up transformers, high-voltage ring network cabinets and related monitoring and management systems.

[0003] For large-capacity energy storage power stations, the high-voltage sides of multiple step-up transformers are generally cascaded through cables to form a group, and then each group is connected to the power system separately to ultimately achieve full-capacity grid connection.

[0004] The working states of the energy storage power station include charging and discharging, and the direction of power on the interconnection line is different in the two working states.

[0005] At present, the conventional protection configuration scheme is to configure differential protection only on the interconnection line between each energy storage system and the power system, and each interconnection circuit in each energy storage system only relies on delayed quick-break protection or overcurrent protection.

[0006] Since each level of the cascade circuit in each energy storage system relies only on delayed quick-break protection or overcurrent protection, the protection needs to avoid the transformer's excitation surge current and cooperate with the lower-level quick-break protection. Therefore, the function of quickly disconnecting the circuit in 0s cannot be achieved.

[0007] Therefore, there is still a lack of a device and method for quickly cutting off a circuit when a short circuit occurs in the circuit in the art. Summary of the invention

[0008] The purpose of the present invention is to provide a cascade protection device and method. The present invention realizes a cascade protection configuration scheme by adopting an integrated protection control, and in addition, communication between protections, thereby realizing the differential protection function of the entire circuit, and quickly cutting off the circuit when a short circuit occurs in the circuit, thereby improving the safety of system operation, and is not subject to geographical restrictions, and the system has strong scalability, providing a better solution for engineering applications.

[0009] In a first aspect of the present invention, a cascade protection device is provided, the device comprising:

[0010] A cascade circuit, the cascade circuit comprising:

[0011] A main line, the main line is connected to the power grid, the main line is connected to a main transformer, the main line is connected to a grid-connected busbar, and a grid-connected circuit breaker is provided on the main line;

[0012] Multiple PCS bays; and

[0013] A plurality of cascade ring network cabinets, each of which is connected to a PCS cabin, wherein the first cascade ring network cabinet is also connected to the main line, and adjacent cascade ring network cabinets are connected via a cascade line; and

[0014] Multiple integrated protection controls, each of which includes a current sensor and a judgment controller, and multiple integrated protection controls are signal-connected, and the multiple integrated protection controls include:

[0015] A mother integrated protection control, wherein the mother current sensor of the mother integrated protection control is arranged on the main line between the grid-connected bus and the first cascade ring network cabinet and is close to the grid-connected bus; and

[0016] Multiple sub-integrated protection controls, each of which includes a first current sensor, a second current sensor, and a third current sensor arranged near a cascade ring network cabinet, wherein the first current sensor is arranged on the main line or the upper cascade line, the second current sensor is arranged on the connecting line between the cascade ring network cabinet and the PCS cabin, and the third current sensor is arranged on the current level connecting line.

[0017] The judgment controller includes a comparator, which is used to judge whether the upper current and the lower current are equal or whether the current flowing into the cascade ring network cabinet of this level and the current flowing out of the cascade ring network cabinet of this level are equal, and cut off the short circuit fault when it is judged that the currents are not equal.

[0018] In another preferred example, each of the cascaded ring main unit forms a level.

[0019] In another preferred example, the PCS compartment is connected to the battery compartment.

[0020] In another preferred example, the cascade circuit is grounded.

[0021] In another preferred example, the grid-connected busbar is connected to the main line section between the main transformer and the cascade ring main unit.

[0022] In another preferred embodiment, on the main line, grid-connected circuit breakers are provided on both sides of the connection with the grid-connected busbar.

[0023] In another preferred embodiment, the grid-connected bus is a 6-35 kV grid-connected bus.

[0024] In a second aspect of the present invention, a cascade protection method is provided, the method comprising:

[0025] (a) providing a cascade protection device as claimed in claim 1;

[0026] (b) The cascade protection device collects current signals of the energy storage PCS circuit, the upper interconnection circuit, and the lower interconnection circuit respectively, and performs vector sum calculation. When the vector sum is not 0, it indicates that a short circuit fault has occurred in the cascade ring network cabinet, and the protection device trips at the outlet instantaneously;

[0027] (c) The integrated protection control of the lower level collects the current signal of the upper level interconnection circuit and transmits it to the integrated protection control of the upper level through the communication link; the integrated protection control of the upper level collects the current signal of the lower level interconnection circuit; the two current signals are vector-sum calculated in the integrated protection control of the upper level. When the vector sum is not 0, it indicates that a short circuit fault has occurred in the interconnection line, and the protection device trips at the output instantaneously.

[0028] In another preferred example, the cascade ring network cabinet has an isolating switch. In response to a circuit fault, the action information is fed back to the integrated protection control where the circuit breaker is located through a communication link, and the circuit breaker is finally tripped to eliminate the short circuit fault; at the same time, the integrated protection control at each level is actuated to cause the PCS compartment at the same level to exit operation.

[0029] In another preferred example, the cascade ring network cabinet contains a circuit breaker. In response to the integrated protection control unit judging that it is a (b) fault, the upper and lower level connecting circuit breakers are actuated locally to exit the operation of the current level and the following PCS; in response to the integrated protection control unit judging that it is a (c) fault, the lower level connecting circuit breaker is tripped and the lower level PCS operation is exited at the same time.

[0030] In another preferred example, for a meshed PCS, the integrated protection control sends an instruction to stop the PCS operation while the action circuit breaker trips, which can effectively reduce the impact of the short circuit on the PCS equipment.

[0031] It should be understood that within the scope of the present invention, the above-mentioned technical features of the present invention and the technical features specifically described below (such as embodiments) can be combined with each other to form a new or preferred technical solution. Due to space limitations, they will not be described one by one here. BRIEF DESCRIPTION OF THE DRAWINGS

[0032] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings required for use in the embodiments or the description of the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying creative work.

[0033] Figure 1 It is a circuit diagram of a cascade protection device in one embodiment of the present invention.

[0034] In each of the accompanying drawings, the symbols are as follows:

[0035] 1- Main transformer;

[0036] 2-Grid-connected circuit breaker;

[0037] 3- Cascade ring main unit;

[0038] 4-PCS cabin;

[0039] 5-Battery compartment;

[0040] 61-mother integrated protection control;

[0041] 62-sub integrated protection control;

[0042] 7- Main line;

[0043] 8-Grid-connected busbar;

[0044] 9- Cascade circuit;

[0045] 10-mother current sensor;

[0046] 101- a first current sensor;

[0047] 102- a second current sensor;

[0048] 103 - a third current sensor. DETAILED DESCRIPTION

[0049] After extensive and in-depth research and a large number of screenings, the inventor has developed a cascade protection device and method for the first time. The present invention uses an "integrated protection control" to achieve the differential protection function of each level of grid-connected cabinets and upper and lower level interconnection circuits, meeting the action requirements of 0s tripping during short circuits; by adopting a cascade protection configuration scheme, segmented management of interconnection circuits at all levels is achieved, and the system has strong scalability; through the cascade of communication links, reliable protection action is achieved. The present invention was completed on this basis.

[0050] The present invention provides a cascade protection device and method.

[0051] A) An "integrated protection control" is set in each cascaded ring network cabinet. The protection device collects the current signals of the energy storage PCS loop, the upper interconnection loop, and the lower interconnection loop respectively, and performs vector sum calculation through the "integrated protection control". When the vector sum is not 0, it means that a short circuit fault has occurred in the ring network cabinet, and the protection device instantly operates the outlet;

[0052] B) The lower-level "integrated protection control" collects the current signal of the upper-level interconnection loop and transmits it to the upper-level "integrated protection control" through the communication link; the upper-level "integrated protection control" collects the current signal of the lower-level interconnection loop; the two current signals are vector-sum calculated in the upper-level "integrated protection control". When the vector sum is not 0, it means that a short-circuit fault has occurred in the interconnection line, and the protection device instantly operates the outlet;

[0053] C) When the cascade ring network cabinet is an isolating switch, it does not have the ability to break short-circuit current. Therefore, when the "integrated protection control" detects a fault in the circuit, it must feed back the action information to the "integrated protection control" where the circuit breaker is located through the communication link and finally trip the circuit breaker to remove the short-circuit fault. At the same time, the "integrated protection control" at each level will actuate the PCS at this level to exit operation;

[0054] D) When there is a circuit breaker in the cascade ring network cabinet, if the "integrated protection control" determines that it is A) fault, the upper and lower level contact circuit breakers will be operated locally, and the PCS operation of this level and the following levels will be exited; if the "integrated protection control" determines that it is B) fault, the lower level contact circuit breaker will be tripped, and the lower level PCS operation will be exited at the same time;

[0055] E) For "grid-type PCS", the "integrated protection control" can issue an instruction to stop PCS operation at the same time as the circuit breaker trips, which can effectively reduce the impact of short circuit on PCS equipment.

[0056] It should be noted that the present invention can also be applied to the cascade solution between the "box-inverter-in-one machines" of each photovoltaic sub-array in a photovoltaic project.

[0057] The main advantages of the present invention include:

[0058] (a) By adopting the "integrated protection control", the differential protection function of each level of interconnected power cabinets and upper and lower level interconnection circuits is realized, meeting the action requirements of 0s tripping in case of short circuit, thus improving the safety of system operation;

[0059] (b) By adopting the cascade protection configuration scheme, segmented management of interconnection circuits at all levels is achieved, which is not restricted by geographical location and has strong system scalability;

[0060] (c) Reliable protection action is achieved through cascading of communication links.

[0061] The present invention will be further described below in conjunction with specific embodiments. It should be understood that these embodiments are only used to illustrate the present invention and are not intended to limit the scope of the present invention. In addition, the accompanying drawings are schematic diagrams, so the device and apparatus of the present invention are not limited by the size or ratio of the schematic diagrams.

[0062] It should be noted that, in the claims and description of the present invention, relational terms such as first and second, etc., are only used to distinguish one entity or operation from another entity or operation, and do not necessarily require or imply any such actual relationship or order between these entities or operations. Moreover, the terms "include", "comprise" or any other variants thereof are intended to cover non-exclusive inclusion, so that a process, method, article or device including a series of elements includes not only those elements, but also other elements not explicitly listed, or also includes elements inherent to such process, method, article or device. In the absence of further restrictions, the elements defined by the sentence "comprise one" do not exclude the existence of other identical elements in the process, method, article or device including the elements.

[0063] Example

[0064] The cascade protection device of this embodiment is as follows Figure 1 The device includes a cascade circuit and multiple integrated protection controls.

[0065] The cascade circuit includes a main line 7, a plurality of PCS cabins 4 and a plurality of cascade ring main units 3. The main line 7 is connected to the power grid, the main line 7 is connected to the main transformer 1, the main line 7 is connected to the grid bus 8, and the grid bus 8 is connected to the main line section between the main transformer 1 and the cascade ring main unit 3. On the main line 7, grid circuit breakers 2 are provided on both sides of the connection with the grid bus 8. The grid bus 8 is a 6-35kV grid bus.

[0066] Each cascade ring main unit 3 is connected to a PCS compartment 4. Each PCS compartment 4 is connected to a battery compartment 5. Each cascade ring main unit 3 forms a stage. The first cascade ring main unit 3 is also connected to the main line 7, and adjacent cascade ring main units 3 are connected via a cascade line 9. The cascade line 9 is optionally grounded.

[0067] Each integrated protection component includes a current sensor and a judgment controller. Multiple integrated protection controls are signal-connected, and the multiple integrated protection controls include a mother integrated protection control 61 and multiple sub-integrated protection controls 62. The mother current sensor 10 of the mother integrated protection control 61 is arranged on the main line 7 between the grid-connected bus 8 and the first cascade ring network cabinet 3 and is close to the grid-connected bus 8. Each sub-integrated protection control 62 includes a first current sensor 101, a second current sensor 102, and a third current sensor 103 arranged close to a first cascade ring network cabinet 3, wherein the first current sensor 101 is arranged on the main line 7 or the upper cascade line 9, the second current sensor 102 is arranged on the connecting line between the cascade ring network cabinet 3 and the PCS cabin 4, and the third current sensor 103 is arranged on the cascade line 9 of the current level. Figure 1 The double-dotted lines in the figure are communication lines.

[0068] The judgment controller includes a comparator, which is used to judge whether the upper current and the lower current are equal or whether the current flowing into the cascade ring network cabinet 3 of this level and the current flowing out of the cascade ring network cabinet 3 of this level are equal. If it is judged that the currents are not equal, the short circuit fault is cut off.

[0069] When in use, the cascade protection device collects the current signals of the energy storage PCS circuit, the upper interconnection circuit, and the lower interconnection circuit respectively, and performs vector sum calculation. When the vector sum is not 0, it indicates that a short circuit fault has occurred in the cascade ring network cabinet 3, and the protection device instantaneously trips the outlet; the lower-level integrated protection control collects the current signal of the upper interconnection circuit, and transmits it to the upper-level integrated protection control through the communication link; the upper-level integrated protection control collects the current signal of the lower-level interconnection circuit; the two current signals are vector-sum calculated in the upper-level integrated protection control. When the vector sum is not 0, it indicates that a short circuit fault has occurred in the interconnection line, and the protection device instantaneously trips the outlet.

[0070] There is an isolating switch in the cascade ring main unit 3. In response to a fault in the circuit, the action information is fed back to the integrated protection control where the circuit breaker is located through the communication link, and the circuit breaker is finally tripped to eliminate the short-circuit fault. At the same time, the integrated protection controls at each level are actuated to cause the PCS compartment 4 at this level to exit operation.

[0071] There is a circuit breaker in the cascade ring main unit 3. In response to the integrated protection control judging that a short circuit fault has occurred in the cascade ring main unit 3, the upper and lower level connecting circuit breakers are actuated locally, and the PCS operation of this level and the following levels is exited; in response to the integrated protection control judging that a short circuit fault has occurred in the connecting line, the lower level connecting circuit breaker is tripped, and the lower level PCS operation is exited at the same time.

[0072] For the grid-type PCS, the integrated protection control sends an instruction to stop the PCS operation at the same time as the circuit breaker trips, which can effectively reduce the impact of short circuit on PCS equipment.

[0073] All documents mentioned in the present invention are cited as references in this application, just as each document is cited as reference individually. In addition, it should be understood that after reading the above teachings of the present invention, those skilled in the art can make various changes or modifications to the present invention, and these equivalent forms also fall within the scope defined by the claims attached to this application.

Claims

1. A cascade protection device, characterized in that: The device comprises: A cascade circuit, the cascade circuit comprising: A main line, the main line is connected to the power grid, the main line is connected to a main transformer, the main line is connected to a grid-connected busbar, and a grid-connected circuit breaker is provided on the main line; Multiple PCS bays; and A plurality of cascade ring network cabinets, each of which is connected to a PCS cabin, wherein the first cascade ring network cabinet is also connected to the main line, and adjacent cascade ring network cabinets are connected via a cascade line; and Multiple integrated protection controls, each of which includes a current sensor and a judgment controller, and multiple integrated protection controls are signal-connected, and the multiple integrated protection controls include: A mother integrated protection control, wherein the mother current sensor of the mother integrated protection control is arranged on the main line between the grid-connected bus and the first cascade ring network cabinet and is close to the grid-connected bus; and Multiple sub-integrated protection controls, each of which includes a first current sensor, a second current sensor, and a third current sensor arranged near a cascade ring network cabinet, wherein the first current sensor is arranged on the main line or the upper cascade line, the second current sensor is arranged on the connecting line between the cascade ring network cabinet and the PCS cabin, and the third current sensor is arranged on the current level connecting line. The judgment controller includes a comparator, which is used to judge whether the upper current and the lower current are equal or whether the current flowing into the cascade ring network cabinet of this level and the current flowing out of the cascade ring network cabinet of this level are equal, and cut off the short circuit fault when it is judged that the currents are not equal.

2. The cascade protection device according to claim 1, characterized in that: The PCS compartment is connected to the battery compartment.

3. The cascade protection device according to claim 1, characterized in that: The cascade line is grounded.

4. The cascade protection device according to claim 1, characterized in that: The grid-connected busbar is connected to the main line section between the main transformer and the cascade ring main unit.

5. The cascade protection device according to claim 1, characterized in that: On the main line, grid-connected circuit breakers are provided on both sides of the connection with the grid-connected busbar.

6. The cascade protection device according to claim 1, characterized in that: The grid-connected busbar is a 6-35kV grid-connected busbar.

7. A cascade protection method, characterized in that: The method comprises: (a) providing a cascade protection device as claimed in claim 1; (b) The cascade protection device collects current signals of the energy storage PCS circuit, the upper interconnection circuit, and the lower interconnection circuit respectively, and performs vector sum calculation. When the vector sum is not 0, it indicates that a short circuit fault has occurred in the cascade ring network cabinet, and the protection device trips at the outlet instantaneously; (c) The integrated protection control of the lower level collects the current signal of the upper level interconnection circuit and transmits it to the integrated protection control of the upper level through the communication link; the integrated protection control of the upper level collects the current signal of the lower level interconnection circuit; the two current signals are vector-sum calculated in the integrated protection control of the upper level. When the vector sum is not 0, it indicates that a short circuit fault has occurred in the interconnection line, and the protection device trips at the output instantaneously.

8. The method according to claim 7, characterized in that The cascade ring network cabinet contains an isolating switch. In response to a fault in the circuit, the action information is fed back to the integrated protection control where the circuit breaker is located through a communication link, and the circuit breaker is finally tripped to eliminate the short-circuit fault. At the same time, the integrated protection control at each level is actuated to cause the PCS compartment at the same level to exit operation.

9. The method according to claim 7, characterized in that There is a circuit breaker in the cascade ring network cabinet. In response to the integrated protection control unit judging that it is a (b) fault, the upper and lower level connecting circuit breakers are actuated locally to exit the operation of the current level and the following PCS; in response to the integrated protection control unit judging that it is a (c) fault, the lower level connecting circuit breaker is tripped and the lower level PCS operation is exited at the same time.

10. The method according to claim 9, characterized in that For a meshed PCS, the integrated protection control unit issues an instruction to stop the PCS operation at the same time as the action circuit breaker trips.

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