A control and protection system for a flexible DC transmission system adapted to the flexible access of converter stations

Abstract

The present invention discloses a control and protection system for a flexible direct current transmission system that is adapted to the flexible access of converter stations. The present invention includes a system layer, a bus layer, and a converter layer; the system layer is a direct current coordination control device, the bus layer is a direct current station control device and a direct current bus protection device, and the converter layer is a direct current pole control device and a pole protection device; the direct current coordination control device, the direct current station control device, and the direct current pole control device constitute a flexible direct current transmission system control architecture; the direct current bus protection device and the pole protection device constitute a flexible direct current transmission system protection architecture, and the direct current bus protection device communicates with the pole protection device in the same direct current bus area, and also communicates with the direct current bus protection devices in different direct current bus areas. While reducing communications, the present invention meets the requirements of converter station standardization and plug-and-play, realizes coordinated control of multi-terminal flexible direct current systems, and realizes the independence of bus, converter, and line protection.

Description

Technical Field

[0001] The present invention belongs to the technical field of flexible direct current transmission systems, and in particular is a flexible direct current transmission system control and protection system adapted to the flexible access of converter stations. Background Art

[0002] There is communication between the converter stations under the existing multi-terminal flexible direct current transmission system architecture. If a new converter station is connected to the multi-terminal flexible direct current transmission system, in addition to designing the control and protection architecture of the new converter station, it is also necessary to upgrade and transform the communication, control and protection architecture, and procedures of the already built multi-terminal flexible direct current transmission system. In addition, the access of the converter station also affects the DC fault isolation and sound system restart strategy of the multi-terminal flexible direct current transmission system, which needs to be redesigned and the control and protection procedures modified. This brings great inconvenience to the access of the converter station.

[0003] At present, the control equipment of the multi-terminal flexible direct current transmission system is only the DC pole control device, and the protection equipment is only the pole protection device. A multi-level control and protection architecture has not been formed. In addition, there is communication between the DC pole control devices and pole protection devices of each converter station, and the communication information volume is large. The coordinated control of the overall system depends on communication. Under this architecture, if a new converter station is connected, the control and protection programs of each converter station of the original multi-terminal flexible direct current transmission system need to be upgraded, which requires a large amount of changes and a high probability of error. Summary of the invention

[0004] The technical problem to be solved by the present invention is to overcome the defects of the above-mentioned prior art and provide a flexible direct current transmission system control and protection system that is adapted to the flexible access of the converter station, so that there is no communication between devices on the same layer and no communication between devices across layers. While reducing communication, it can meet the "standardization" and "plug and play" requirements of the converter station, so as to realize the coordinated control of the multi-terminal flexible direct current system and realize the independence of bus, converter and line protection.

[0005] To this end, the present invention adopts the following technical solution: a flexible direct current transmission system control and protection system adapted for flexible access of converter stations, which includes a system layer, a bus layer and a converter layer;

[0006] The system layer is a DC coordinated control device SCC, the bus layer is a DC station control device DCC and a DC bus protection device DBP, and the converter layer is a DC pole control device PCP and a pole protection device PPR;

[0007] The DC coordinated control device SCC, the DC station control device DCC and the DC pole control device PCP form a flexible DC transmission system control architecture;

[0008] The DC coordinated control device controls the formation of the network topology operation mode, and realizes the coordinated control of the voltage control right in the DC supply area; the DC station control device realizes the distribution and transfer of the voltage control right in the area, the bus switch knife switch sequential control and the line fault recovery; the DC pole control device realizes the DC voltage control, active and reactive power control and the converter switch knife switch sequential control; the designated DC voltage control signal is sent from the DC coordinated control device to the DC station control device, and then transmitted to the DC pole control device; the DC pole control device feeds back the control mode and unlocking signal of the converter station where it is located to the DC station control device, and the DC station control device feeds back the bus switch position, the regional fixed DC voltage capability and the regional fixed DC voltage station status to the DC coordinated control device;

[0009] The DC bus protection device DBP and the pole protection device PPR form a flexible DC power transmission system protection architecture. The DC bus protection device is used for linear bus protection, and the pole protection device is used for converter station area protection. The DC bus protection device communicates with the pole protection devices in the same DC bus area, and also communicates with the DC bus protection devices in different DC bus areas.

[0010] Furthermore, the control mode of the converter station includes an active control mode and a reactive control mode of the converter station.

[0011] Furthermore, the active power control mode includes constant DC voltage control, constant active power control and constant frequency control.

[0012] Furthermore, the reactive power control mode includes constant reactive power control and constant AC voltage control.

[0013] Furthermore, the DC station control device not only feeds back the bus switch position to the DC coordination control device, but also feeds back the on / off status of the converter station side switch and the on / off status of the line side switch.

[0014] Furthermore, each converter station is equipped with a DC pole control device, and each DC bus area is equipped with a DC station control device; in a power supply area at the same voltage level, more than two DC station control devices share one DC coordination control device.

[0015] Furthermore, each converter station is equipped with a set of pole protection devices, and each DC bus area is equipped with a set of DC bus protection devices.

[0016] Furthermore, the DC bus protection device is used for DC bus overvoltage and undervoltage protection, DC bus voltage unbalance protection and fault line selection when a DC line fails.

[0017] Furthermore, the converter station area protection includes AC protection, converter protection and DC line protection inside the converter station, and the DC line protection includes DC line longitudinal differential protection, DC line overload protection and DC line undervoltage and overcurrent protection.

[0018] Furthermore, the DC bus protection device communicates with the pole protection device in the same DC bus area, and also communicates with the DC bus protection devices in different DC bus areas. The communication content includes: the current value of the current in the DC line, the direction of the sudden change in current during a line fault, and the start-up failure signal of the DC bus switch.

[0019] The beneficial effects of the present invention are as follows: the present invention prevents communication between devices on the same layer and between devices across layers. While reducing communication, it meets the "standardization" and "plug and play" requirements of converter stations, realizes coordinated control of multi-terminal flexible direct current systems, and realizes independence of bus, converter, and line protection. BRIEF DESCRIPTION OF THE DRAWINGS

[0020] 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 prior art descriptions are briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention, and for ordinary technicians in this field, other drawings can be obtained based on these drawings without creative work.

[0021] Figure 1 A schematic diagram of a control and protection system for a flexible direct current transmission system adapted for flexible access to a converter station according to the present invention;

[0022] Figure 2 A schematic diagram of the communication between various control devices in the control framework of the flexible direct current transmission system of the present invention;

[0023] Figure 3 Schematic diagram of a control architecture of a five-terminal flexible direct current transmission system according to an embodiment of the present invention;

[0024] Figure 4 Schematic diagram of a five-terminal flexible direct current transmission system protection framework in an embodiment of the present invention;

[0025] In the figure, SCC represents the DC coordinated control device, DCC represents the DC station control device at the bus layer, DBP represents the DC bus protection device, PCP represents the DC pole control device, and PPR represents the pole protection device;

[0026] Figure 3 and Figure 4 In the figure, S1, S2, S3, S4, S5, and S6 represent the original converter stations, S6 represents the newly connected converter station, and A and B represent DC buses. DETAILED DESCRIPTION

[0027] In order to make the purpose, technical solution and advantages of the embodiments of the present invention clearer, the technical solution in the embodiments of the present invention will be clearly and completely described below in conjunction with the drawings in the embodiments of the present invention. Obviously, the described embodiments are part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0028] The present invention is a flexible DC transmission system control and protection system adapted to the flexible access of converter stations, which is composed of three layers, namely, a system layer, a bus layer and a converter layer. Figure 1 shown.

[0029] The system layer is the DC coordinated control device SCC, the bus layer is the DC station control device DCC and the DC bus protection device DBP, and the converter layer is the DC pole control device PCP and the pole protection device PPR; the devices on the same layer do not communicate with each other, such as PCP and PPR do not communicate, DCC and DBP do not communicate; the devices across layers do not communicate with each other, such as SCC and PCP do not communicate.

[0030] The DC coordinated control device SCC, DC station control device DCC and DC pole control device PCP constitute a flexible DC transmission system control architecture. In the flexible DC transmission system control architecture, each converter station is equipped with a set of DC pole control device PCP, and each DC bus area is equipped with a set of DC station control device DCC; in a power supply area under the same voltage level, all DC station control devices DCC share a set of DC coordinated control device SCC.

[0031] The DC coordinated control device controls the formation of network topology operation mode, and realizes the coordinated control of voltage control rights in the DC supply area; the DC station control device realizes the distribution and transfer of voltage control rights in the area, bus switch knife switch sequential control and line fault recovery; the DC pole control device realizes DC voltage control, active and reactive power control and converter switch knife switch sequential control; Figure 2 As shown, the designated DC voltage control signal is sent from the DC coordination control device to the DC station control device, and then transmitted to the DC pole control device; the DC pole control device feeds back the control mode of the converter station where it is located and the unlocking signal to the DC station control device, and the DC station control device feeds back the bus switch position, regional fixed DC voltage capability and regional fixed DC voltage station status to the DC coordination control device.

[0032] Taking the five-terminal flexible DC transmission system as an example, converter station S2 is equipped with one SCC, converter stations S1, S2 and S3 share DC bus A, converter stations S4, S5 and S6 share DC bus B, converter stations S2 and S4 are each equipped with one DCC, and the five converter stations S1 to S5 are each equipped with one PCP, and the PCPs do not communicate with each other. The SCC on converter station S2 communicates with the DCC on converter station S2 and the DCC on converter station S4, but not with any PCP; the DCC on converter station S2 communicates with the PCPs on converter stations S1, S2 and S3 respectively; the DCC on converter station S4 communicates with the PCPs on converter stations S4 and S5 respectively. The newly connected converter station S6 (or new energy station) is connected to the DC bus B, is equipped with one PCP, and communicates with the DCC of converter station S4, achieving the purpose of plug-and-play. The overall control architecture is as follows: Figure 3 shown.

[0033] The DC bus protection device DBP and the pole protection device PPR form a flexible DC power transmission system protection architecture. The DC bus protection device is used for linear bus protection, and the pole protection device is used for converter station area protection. The DC bus protection device communicates with the pole protection device in the same DC bus area, and also communicates with the DC bus protection devices in different DC bus areas. The communication content includes: the current value of the DC line, the direction of the current sudden change during line fault (for fault line selection), and the DC bus switch start failure signal. In the flexible DC power transmission system protection architecture, each converter station is equipped with a set of pole protection devices PPR, and each DC bus area is equipped with a set of DC bus protection devices DBP.

[0034] Specifically, the control mode of the converter station includes an active control mode and a reactive control mode of the converter station. The active control mode includes a constant DC voltage control, a constant active power control and a constant frequency control. The reactive control mode includes a constant reactive power control and a constant AC voltage control.

[0035] Specifically, the DC station control device not only feeds back the bus switch position to the DC coordination control device, but also feeds back the on / off state of the converter station side switch and the on / off state of the line side switch.

[0036] The DC bus protection device is used for DC bus overvoltage and undervoltage protection, DC bus voltage unbalance protection and fault line selection when the DC line fails. The DC bus protection device communicates with the pole protection devices in the same DC bus area and also communicates with the DC bus protection devices in different DC bus areas.

[0037] The converter station area protection includes AC protection, converter protection and DC line protection inside the converter station, and the DC line protection includes DC line longitudinal differential protection, DC line overload protection and DC line undervoltage and overcurrent protection.

[0038] Taking the five-terminal flexible DC system as an example, converter stations S1, S2 and S3 share the DC bus A, converter stations S4, S5 and S6 share the DC bus B, converter stations S2 and S4 are each equipped with a set of DBP, and the five converter stations are each equipped with a set of PPR, and the PCPs do not communicate with each other. The DBP on converter station S2 communicates with the PPR on converter stations S1, S2 and S3, and also communicates with the DBP on converter station S4; the DBP on converter station S4 communicates with the PPR on converter stations S4 and S5. The newly connected converter station S6 (or new energy station) is connected to the DC bus B, equipped with a set of PPR, and communicates with the DBP of converter station S4. The overall protection architecture is as follows. Figure 4 shown.

[0039] It is obvious that those skilled in the art can easily make various modifications to the above embodiments and apply the general principles described herein to other embodiments without creative work. Therefore, the present invention is not limited to the above embodiments, and improvements and modifications made by those skilled in the art to the present invention based on the disclosure of the present invention should be within the protection scope of the present invention.

Claims

1. A control and protection system for a flexible direct current transmission system with flexible access to a converter station, characterized in that: Including system layer, bus layer and converter layer; The system layer is a DC coordination control device, the bus layer is a DC station control device and a DC bus protection device, and the converter layer is a DC pole control device and a pole protection device; The DC coordination control device, DC station control device and DC pole control device constitute a flexible DC power transmission system control architecture; The DC coordinated control device controls the formation of the network topology operation mode, and realizes the coordinated control of the voltage control right in the DC supply area; the DC station control device realizes the distribution and transfer of the voltage control right in the area, the bus switch knife switch sequential control and the line fault recovery; the DC pole control device realizes the DC voltage control, active and reactive power control and the converter switch knife switch sequential control; the designated DC voltage control signal is sent from the DC coordinated control device to the DC station control device, and then transmitted to the DC pole control device; the DC pole control device feeds back the control mode and unlocking signal of the converter station where it is located to the DC station control device, and the DC station control device feeds back the bus switch position, the regional fixed DC voltage capability and the regional fixed DC voltage station status to the DC coordinated control device; The DC bus protection device and the pole protection device constitute a flexible DC power transmission system protection architecture. The DC bus protection device is used for linear bus protection, and the pole protection device is used for converter station area protection. The DC bus protection device communicates with the pole protection device in the same DC bus area, and also communicates with the DC bus protection devices in different DC bus areas.

2. The control and protection system of the flexible direct current transmission system according to claim 1 is characterized in that: The control modes of the converter station include active power control mode and reactive power control mode.

3. The control and protection system of the flexible direct current transmission system according to claim 2 is characterized in that: The active power control modes include constant DC voltage control, constant active power control and constant frequency control.

4. The control and protection system of the flexible direct current transmission system according to claim 2 is characterized in that: The reactive power control mode includes constant reactive power control and constant AC voltage control.

5. The control and protection system of the flexible direct current transmission system according to claim 1 is characterized in that: The DC station control device not only feeds back the bus switch position to the DC coordination control device, but also feeds back the on / off state of the converter station side switch and the on / off state of the line side switch.

6. The control and protection system of the flexible direct current transmission system according to claim 1, characterized in that: Each converter station is equipped with a DC pole control device, and each DC bus area is equipped with a DC station control device; in a power supply area at the same voltage level, more than two DC station control devices share one DC coordination control device.

7. The control and protection system of the flexible direct current transmission system according to claim 1, characterized in that: Each converter station is equipped with a pole protection device, and each DC bus area is equipped with a DC bus protection device.

8. The control and protection system of the flexible direct current transmission system according to claim 1, characterized in that: The DC bus protection The device is used for DC bus overvoltage, undervoltage protection, DC bus voltage imbalance protection and DC line fault protection. Select line.

9. The control and protection system of the flexible direct current transmission system according to claim 1, characterized in that: The converter station area protection includes AC protection, converter protection and DC line protection inside the converter station, and the DC line protection includes DC line longitudinal differential protection, DC line overload protection and DC line undervoltage and overcurrent protection.

10. The control and protection system of the flexible direct current transmission system according to claim 1, characterized in that: The DC bus protection device communicates with the pole protection devices in the same DC bus area and also communicates with the DC bus protection devices in different DC bus areas. The communication content includes: the current value of the current in the DC line, the direction of the current sudden change when the line fails, and the DC bus switch knife start failure signal.

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