Changeover method of HVDC transmission system

Abstract

A changeover method of a high voltage direct current (HVDC) transmission system is provided. A first system is set to an active state. A ready signal is transmitted from the first system to a first COL. A ready detection signal and an active signal are transmitted to the first system, in response to the ready signal. A confirm signal is transmitted to the first system in response to the active signal when the ready detection signal matches the ready signal.

Claims

1. A changeover method of a high voltage direct current (HVDC) transmission system comprising a first system, a second system, a first changeover logic (COL), and a second COL, the changeover method comprising: setting the first system to an active state and the second system to an inactive state; transmitting a ready signal from the first system to the first COL; transmitting a ready detection signal and an active signal from the first COL to the first system, in response to the ready signal; transmitting a first confirm signal from the first system to the first COL in response to the active signal when the ready detection signal matches the ready signal; transmitting a system signal from the first system to the first COL; obtaining a fault signal by the first COL after transmission of the system signal from the first system to the first COL; transmitting a fault detection signal from the first COL to the first system in response to the obtained fault signal; determining, by the first system, whether the system signal and the fault detection signal are the same, wherein the system signal includes the fault signal when the first system has a fault and the fault detection signal is equal to the fault signal; transmitting a second confirm signal from the first system to the first COL when the system signal and the fault detection signal are determined to be the same at the first system; and changing, by the first COL, the first system from the active state to the inactive state and changing the second system from the inactive state to the active state, in response to the second confirm signal.

2. The changeover method according to claim 1, further comprising changing, by the first COL, the first system to the inactive state and changing the second system to the active state, when the confirm signal is not received by the first COL for a time equal to or longer than a critical time after the fault detection signal is transmitted by the first COL.

3. The changeover method according to claim 1, wherein the obtaining of the fault signal by the first COL comprises obtaining the fault signal when the first COL fails to receive a specific signal transmitted by the first system.

4. The changeover method according to claim 1, further comprising maintaining the inactive state of the first system and the active state of the second system even when the fault signal is not obtained by the first COL after the second system is changed to the active state.

5. The changeover method of claim 1, further comprising transmitting another active signal to the second system to continue to perform an operation for the HVDC transmission system when the second system is changed from the inactive state to the active state.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

(1) FIG. 1 is a schematic diagram of a general high voltage direct current (HVDC) transmission system.

(2) FIG. 2 represents a pair of systems including HVDC transmission systems and a pair of changeover logics (COL).

(3) FIG. 3 is a flowchart of an embodiment in initial operation and in normal operation.

(4) FIGS. 4, 5 and 6 represent signal exchanges between the pair of systems and a first COL in initial operation and in normal operation according to an embodiment.

(5) FIG. 7 is a flowchart of an operating method of the first COL when a fault signal is obtained according to an embodiment.

(6) FIGS. 8, 9, 10, 11 and 12 represent signal exchanges between the pair of systems and the first COL in the flowchart of FIG. 7.

DETAILED DESCRIPTION OF THE EMBODIMENTS

(7) Reference will now be made in detail to the embodiments of the present disclosure, examples of which are illustrated in the accompanying drawings.

(8) According to an embodiment, a changeover method of a high voltage direct current (HVDC) transmission system including a first system 1, a second system 2, a first changeover logic (COL) 3, and a second COL 4 includes: setting the first system 1 to an active state; transmitting a ready signal from the first system 1 to the first COL 3; transmitting a ready detection signal and an active signal from the first COL 3 to the first system 1, in response to the ready signal; and transmitting a confirm signal from the first system 1 to the first COL 3 in response to the active signal when the ready detection signal matches the ready signal.

(9) According to another embodiment, the changeover method further includes obtaining a fault signal by the first COL 3 and transmitting a fault detection signal from the first COL 3 to the first system 1 in response to the fault signal.

(10) According to still another embodiment, the changeover method further includes transmitting a confirm signal from the first system to the first changeover in response to the fault detection signal, and changing the first system to an inactive state and changing the second system to an active state, in response to the confirm signal.

(11) According to a still another embodiment, the transmitting of the confirm signal from the first system 1 to the first COL 3 includes checking whether the fault detection signal matches the fault signal, and transmitting a confirm signal from the first system 1 to the first COL 3 when the fault detection signal matches the fault signal.

(12) According to a still another embodiment, the changeover method further includes changing the first system 1 to an inactive state and changing the second system 2 to an active state when the confirm signal is not received by the first COL for a time equal to or longer than a critical time after the fault detection signal is transmitted by the first COL 3.

(13) According to still another embodiment, the obtaining of the fault signal by the first COL 3 includes obtaining the fault signal when the first COL fails to receive a specific signal transmitted by the first system 1.

(14) According to still another embodiment, the obtaining of the fault signal by the first COL 3 includes obtaining the fault signal by the first COL 3 when the first system 1 has a fault and transmits the fault signal to the first COL 3.

(15) According to still another embodiment, the changeover method further includes maintaining the inactive state of the first system 1 and the active state of the second system 2 even if the fault signal is not obtained by the first COL 3 after the second system 2 is changed to the active state.

(16) FIG. 1 is a block diagram of a general HVDC transmission system.

(17) Referring to FIG. 1, a control and protection (C & P) unit plays a role in controlling an AC yard, a conversion transformer (CT.r), a converter (valve), and a DC yard that are the entire components of the HVDC transmission system.

(18) The pair of systems includes the same two systems, i.e., a first system and a second system in order to continuously perform an operation so that when the currently operating system has a trouble, such as system malfunction while providing a system, a standby spare system may continue to provide the service.

(19) In this case, the pair of systems has an active mode and a standby mode, respectively and two systems are logically combined and operate, monitoring each other. The currently operating system is called an active system and a system being in a standby state is called a standby system.

(20) The active system is actually operating and in an active state in a system, performs the input and output of all connected devices and the logic of all connected devices, and provides all operation information to the standby system that is in a standby state.

(21) The standby system awaits in a ready state to become the active system, i.e., in the inactive state, and is ready to immediately change to the active state through synchronization of all data and stage information in the active system.

(22) FIG. 2 represents a pair of systems including a pair of HVDC transmission systems and a pair of COLs.

(23) In the following, two systems are represented by two C&P units, for example.

(24) The pair of HVDC transmission systems includes two C&P units (a first C&P unit, and a second C&P unit) and two COLs (a first COL and a second COL). Which C&P unit is used in the HVDC transmission system is determined by the two COLs.

(25) The two COLs respectively check whether to activate the first COL or the second COL and whether to activate the first C&P unit or the second C&P unit so that one COL is in an active state and the other COL is in the inactive state.

(26) In this case, an active COL checks the activation of the two C&P units and a COL receiving an activation confirm signal has the right to change over.

(27) In the following, the changeover method of a pair of HVDC transmission systems according to an embodiment is described in detail with reference to FIGS. 3 to 7.

(28) In the embodiment to be described below, a system may include a C&P unit (not shown) which may perform the operations of controlling and protecting the entire HVDC transmission system.

(29) Signals transmitted between systems and COLs may be transmitted through lines connected between COLs, between a COL and a system (e.g., C&P unit) and between systems. The line may be e.g., a field bus.

(30) With reference to FIGS. 3 to 6, a method of setting an active system and an inactive system by a COL according to an embodiment in initial operation and in normal operation in a pair of systems is described.

(31) FIG. 3 is a flowchart of an embodiment in initial operation and in normal operation.

(32) In initial operation, a master COL among the two COLs is defined as a first COL 3 and the local system of the master COL is defined as a first system 1 in step S301.

(33) The master COL indicates one having a higher priority among the two COLs and the priority between COLs is set by an operator.

(34) The local system indicates one installed closer to the master COL among the two systems.

(35) The first COL 3 is a COL having the right to determine whether to operate which system among the first system 1 and the second system 2. That is, the first COL 3 is an active COL having an active state currently and is one that actually performs a changeover operation.

(36) On the contrary, the second COL 4 is an inactive COL having an inactive state currently and is one being in a standby state actually.

(37) The second COL 4 becomes an active COL instead of the first COL 3 when the first COL 3 has a fault or malfunctions, and the second COL 4 being the active COL is a COL that actually performs a changeover operation after having the active state. In the case of systems, the local system of the first COL 3 being the master COL in initial operation is defined as the first system 1. On the contrary, the remote system of the first COL 3 in consideration of a relationship with the first COL 3 is defied as the second system 2.

(38) The remote system is a system corresponding to the local system, and a system installed farther than the first system 1 from the first COL 3 is defined ad the remote system.

(39) Referring back to FIG. 3, each of the first system 1 and the second system 2 transmits ready signals to the first COL 3 in step S302.

(40) When the first COL 3 receives the ready signal, the first COL 3 determines that the first system 1 and the second system 2 may perform necessary operations.

(41) The ready signals transmitted to the first COL 3 by each of the first system 1 and the second system 2 may include pulse waves having a cycle of about 200 μs. When the first system 1 or second system 2 does not generate the ready signal for about 300 μs, the first COL 3 may determine that a system having no change for about 300 μs among the first system 1 and the second system 2 is a system that is not ready to operate.

(42) Referring to FIG. 4, the first system 1 transmits a ready signal {circle around (1)} Ready to the first COL 3 through a line to which the first system 1 and the first COL 3 are connected, and the second system 2 transmits a ready signal {circle around (1)}′ Ready to the first COL 3 through a line to which the second system 2 and the first COL 3 are connected.

(43) When the first COL 3 receives the ready signals {circle around (1)} Ready and {circle around (1)}′ Ready respectively from the first system 1 and the second system 2, the first COL 3 transmits ready detection signals {circle around (2)} Ready Detection and {circle around (2)}′ Ready Detection respectively to the first system 1 and the second system 2 in step S303.

(44) In the present embodiment, the ready detection signals {circle around (2)} Ready Detection, {circle around (2)}′ Ready Detection are signals responsive to the read signals {circle around (1)} Ready and {circle around (1)}′ Ready transmitted from each system to the COL, and the ready detection signals may include that the COL has detected that each system having transmitted the ready signal has been ready to operate.

(45) The ready detection signal transmitted by the COL may include the same content as the ready signal transmitted from each system to the COL.

(46) For example, when the ready signal is a sine wave having a cycle of about 200 μs and a maximum value of A, the ready detection signal may equally be a sine wave having the cycle of about 200 μs and the maximum value of A.

(47) Then, as shown in FIGS. 4 to 12, the first system 1 and the second system 2 continues to transmit the ready signals to the first COL 3, and the first COL 3 continues to transmit the ready detection signals to the first system 1 and the second system 2, respectively.

(48) Referring back to FIG. 3, when the first COL 3 transmits the ready signals to the first system 1 and the second system 2 respectively, the first COL 3 transmits an active signal to the first system 1 in step S304.

(49) Referring to FIG. 4, the first COL 3 determines that the first system 1 being the local system of the first COL 3 needs to be activated, and transmits an active signal to the first system 1 in order to set the first system 1 to an active system.

(50) Referring back to FIG. 3, when the first system 1 receives the active signal transmitted by the first COL 3, the first system 1 determines whether the ready signal transmitted by the first system 1 matches the ready detection signal received by the first system 1 in step S305.

(51) As an example of methods of determining whether the ready signal matches the ready detection signal, the ready signal and the ready detection signal are sampled in units of about 10 μs within a range of about 200 μs to determine every 10 μs whether the output value of the ready signal is equal to the output value of the ready detection signal.

(52) Until it is determined that the ready signal matches the ready detection signal, the first system 1 continues to determine whether the ready signal matches the ready detection signal.

(53) When it is determined that the ready signal transmitted by the first system 1 matches the ready detection signal transmitted to the first system 1, the first system 1 transmits a confirm signal to the first COL 3 in step S306.

(54) As shown in FIG. 5, the first system 1 receiving the active signal from the COL 3 transmits the confirm signal to the first COL 3.

(55) The confirm signal represented in FIG. 5 is described below in detail.

(56) The confirm signal according to the present embodiment includes that the ready detection signal transmitted to the first COL 3 matches the ready signal transmitted to the first system 1.

(57) In the present embodiment, a system receiving the active signal transmits the confirm signal to a COL for a cycle of e.g., about 200 μs) and may not transmit the confirm signal after one cycle.

(58) Referring back to FIG. 3, when the first COL 3 receives the confirm signal from the first system 1, the COL 3 sets the first system 1 having transmitted the confirm signal to an active system in step S307.

(59) Referring to FIG. 6, the first COL 3 sets the first system 1 to the active system after receiving the confirm signal from the first system 1, and sets the second system 2 to an inactive system.

(60) After setting the first system 1 to the active system, the first COL 3 continues to transmit the confirm signal to the first system 1.

(61) After the first system 1 continues to receive the confirm signal from the first COL 3, the first system 1 performs an operation necessary for the entire HVDC transmission system as the active system until the first system 1 has a fault.

(62) In the following, how an active COL obtains a fault signal and changes over a system is described with reference to FIGS. 7 to 12.

(63) The first system 1 is a system set as an active system by the first COL 3 in initial operation and the first COL 3 is a COL set to an active C&P unit in step S701.

(64) The first system 1 is a system actually operating in the entire HVDC transmission system, the first system 1 may include a first C&P unit (not shown), the second system 2 may include a second C&P unit (not shown), and the first and second C&P units perform the operations of controlling and protecting the entire HVDC transmission system.

(65) The second system 2 is a system set to an inactive system in initial operation and is a system being in a standby state. When it is found that the first system 1 has a fault or malfunctions, the second system 2 is set to an active system by the first COL 3, and after the second system 2 is set to the active system, it performs an operation necessary for the entire HVDC transmission system (e.g., control and protection of the entire HVDC transmission system).

(66) While the first system 1 operates as the active system, the first system 1 transmits a system signal to the first COL 3 and the first COL 3 obtains a fault signal from the first system 1 in step S702.

(67) Referring to FIG. 8, the first system 1 transmits the system signal to the first COL 3, and the first COL 3 obtains the fault signal.

(68) As discussed earlier, when the first system 1 has a fault, there is a case where the first system 1 transmits the fault signal to the first COL 3, but irrespective of whether the first system 1 has the fault, the first COL 3 may obtain the fault signal because there is noise due to a physical damage or defect on the line between the first system 1 and the first COL 3 even though the first system 1 has transmitted a normal signal system signal.

(69) That is, the system signal in FIG. 8 may also be obtained as the fault signal by the first COL 3.

(70) However, since the system signal itself in FIG. 8 is a normal signal having no fault but the noise due to a physical damage or defect on the line through the system signal is transmitted is added to the system signal, the first COL 3 may fail to obtain the system signal and may obtain the fault signal which has noise added to the system signal.

(71) Referring back to FIG. 7, when the first COL 3 receives the fault signal from the first system 1, the COL 3 transmits a fault detection signal to the first system 1 in step S703.

(72) The first COL 3 transmits the fault detection signal including the same content as the fault signal.

(73) For example, when the fault signal is a sine wave having a cycle of about 200 μs and a maximum value of A, the fault detection signal is a sine wave having the cycle of about 200 μs and the maximum value of A as well.

(74) Referring to FIG. 9, after the first COL 3 obtains the fault signal in FIG. 8, the first COL 3 transmits the fault detection signal in FIG. 9 obtained by the first COL 3 and equal to the fault signal in FIG. 8 to the first system 1.

(75) Referring back to FIG. 7, when the first system 1 receives the fault detection signal, the first system 1 determines whether the fault detection signal transmitted by the first COL 3 is the same as the system signal transmitted by the first system 1 before the obtaining of the fault signal by the first COL 3 in step S704.

(76) Referring to FIG. 9, after the first system 1 receives the fault detection signal, the first system 1 determines whether the fault detection signal and the system signal transmitted by the first system 1 in FIG. 8 are the same each other.

(77) In FIG. 9, it is assumed that the fault signal obtained by the first COL 3 and the fault detection signal transmitted by the first COL 3 are the same.

(78) Referring to FIG. 7, when it is determined that the fault detection signal and the system signal are the same, the first system 1 transmits the confirm signal to the first COL 3 in step S705.

(79) As shown in FIG. 9, when it is determined that the fault detection signal and the system signal are the same, the first system 1 transmits to the first COL 3 the confirm signal representing that the fault detection signal and the system signal are the same.

(80) Referring back to FIG. 7, when the first COL 3 receives the confirm signal or fails to receive the confirm signal for a certain time, the first COL 3 determines that the first system 1 needs to be set to an inactive state in step S706 and the second system 2 needs to be an active system in step S707.

(81) The certain time may be, for example, 1.5 times a cycle of the confirm signal and, for another example, about 300 μs when a cycle is about 200 μs.

(82) The reason why the first COL 3 sets the first system 1 to an inactive state not only when the first COL 3 receives the confirm signal but also when the first COL 3 fails to receive the confirm signal for a certain time, is because the first system 1 may actually have a fault and thus fail to transmit the confirm signal.

(83) When the first system 1 has a fault but fails to transmit a confirm signal to the first COL 3, it is possible to increase the reliability of the entire system through the operation of forcibly changing over the system.

(84) Referring to FIG. 10, the first COL 3 receiving the confirm signal in FIG. 9 determines that the first system 1 needs to be set to an inactive system and the second system 2 needs to be an active system, and transmits the confirm signal to the second system 2.

(85) When the second system 2 receiving an active signal determines that the ready signal transmitted by the second system 2 matches the ready detection signal transmitted to the second system 2, the second system 2 transmits the confirm signal to the first COL 3.

(86) As shown in FIG. 11, the first COL 3 receiving the confirm signal transmitted by the second system 2 sets the second system 2 to an active state and continues to transmit the active signal to the second system 2.

(87) Then, the second system 2 set to the active system continues to perform operations needed as the active system in the entire HVDC transmission system, as shown in FIG. 12.

(88) As shown in FIG. 12, although a fault signal transmitted from the first system 1 to the first COL 3 is not obtained, the first COL 3 continues to maintain the state of the second system 2 in an active state and the state of the first system 1 in an inactive state. That is, the first system 1 and the second system 2 are not changed over and the second system 2 continues to perform operations as the active system.

(89) The embodiments allow the COLs to be stably maintained and although undesired fault signals are instantly input by a system to the COLs, the COLs may stably handle these signals without significantly affecting the entire changeover time, and it is possible to enhance the stability and reliability of the system by preventing undesired changeover operations.

(90) The above descriptions are only examples of the technical spirit of embodiments, so a person skilled in the art may implement various modifications and variations without departing from the spirit and scope of the embodiments.

(91) Thus, embodiments disclosed herein are intended not to limit but to describe the technical spirit of the present invention and the scope of the technical spirit of the present invention is not limited to such embodiments.

(92) The protective scope of embodiments is defined by the appended claims, and all technical spirits within the equivalent scope are construed as being included in the scope of the right of the embodiments.