Abstract:
A device for controlling a high voltage direct current (HVDC) transmission system is provided. The device includes: a communication unit communicating with a control device; a control unit obtaining a databack signal received through the communication unit, checking a data line error and a line connection error based on an obtained databack signal, and outputting a valve control signal based on the databack signal; and an output unit outputting the valve control signal to a valve control device based on control of the control unit.

Description:
CROSS-REFERENCE TO RELATED APPLICATION 
     Pursuant to 35 U.S.C. §119(a), this application claims the benefit of earlier filing date and right of priority to Korean Application No. 10-2014-0008586, filed on Jan. 23, 2014, the contents of which is incorporated by reference herein in its entirety. 
     BACKGROUND 
     The present disclosure relates to a device and method for controlling a high voltage direct current (HVDC) transmission system. 
     HVDC transmission is performed by converting alternating current (AC) power generated from a power station into DC power to transmit the DC power and then re-converting the DC power into the AC power at a power receiving point to supply power. The HVDC transmission may enable efficient and economical power transmission through a voltage increase that is the advantage of AC power transmission. Also, the HVDC transmission may overcome many limitations of the AC transmission. 
     A HVDC transmission system may be classified into current-type HVDC using a thyristor and voltage-type HVDC using IGB or GTO. The current-type HVDC is suitable for large power transmission and the voltage-type HVDC is suitable for system stabilization or small power transmission due to high loss. 
     In particular, the valve controller of the HVDC transmission system may affect the performance of the entire HVDC transmission system depending on how stably measured data may be maintained and controlled in DC transmission. There is a need for the stability and smooth data flow control of an HVDC transmission system structure. 
     In general, data state monitoring consumes a long time to check the cause of an event and to perform corresponding processing while monitoring by software. 
     That is, there is a need for a hardware design considering high data reliability and possible events for a state contact of a physical line connected to the HVDC transmission system and a state contact of data. However, since a typical HVDC transmission system is configured to analyze measurement data transmitted to the system and simply distribute analyzed data to a valve control module when the measurement data is transmitted to the system, there is a limitation in that it is not easy to analyze a cause of an event and process the event. 
     SUMMARY 
     Embodiments provide a device and method for controlling a high voltage direct current (HVDC) transmission system that enable data validity and a connection state to be checked based on data obtained from the HVDC transmission system. 
     Embodiments provide a device and method for controlling a high voltage direct current (HVDC) transmission system that enable the effectiveness of data obtained from the HVDC transmission system and a connection state to be checked so that it is possible to output control data for valve control having high reliability. 
     In one embodiment, a device for controlling a high voltage direct current (HVDC) transmission system includes: a communication unit communicating with a control device; a control unit obtaining a databack signal received through the communication unit, checking a data line error and a line connection error based on an obtained databack signal, and outputting a valve control signal based on the databack signal; and an output unit outputting the valve control signal to a valve control device based on control of the control unit. 
     In another embodiment, a method of controlling a HVDC transmission system includes: checking a data error and a line connection error depending on presence and absence of an error data output of the databack signal and on presence and absence of an input of the databack signal based on an obtained databack signal; and notifying that the data error or line connection error is sensed. 
     The details of one or more embodiments are set forth in the accompanying drawings and the description below. Other features will be apparent from the description and drawings, and from the claims. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a block diagram of a control device of a high voltage direct current (HVDC) transmission system to which an embodiment is applied. 
         FIG. 2  illustrates the form of data obtained from the control device of the HVDC transmission system according to an embodiment. 
         FIG. 3  is a flow chart for data error verification according to an embodiment. 
         FIG. 4  is a flow chart for data error verification according to an embodiment. 
     
    
    
     DETAILED DESCRIPTION OF THE EMBODIMENTS 
     The terms or words used in the detailed description and claims should not be limitatively construed as typical meanings or meanings indicated in dictionaries but should be construed as meanings and concepts matching the technical spirit of the present invention based on the principle that the inventor may properly define the concepts of terms in order to describe his or her invention in the best mode. 
     Thus, since embodiments described in the detailed description and configurations shown in the drawings are only examples and do not cover all the technical spirits of an embodiment, it should be understood that there may be various equivalents and variations that may replace them upon filing the present application. 
       FIG. 1  is a block diagram of a control device of a high voltage direct current (HVDC) transmission system to which an embodiment is applied, and  FIG. 2  illustrates the form of data obtained from the control device of the HVDC transmission system according to an embodiment. 
     Referring to  FIGS. 1 and 2 , a control device  100  of the HVDC transmission system according to an embodiment may include a communication unit  110 , a data processing unit  120 , a storage unit  130 , an output unit  140 , and a control unit  150 . 
     The communication unit  110  may receive data on each device connected to the HVDC transmission system. 
     The data processing unit  120  may decode data received through the communication unit  110  to output decoded data to the control unit  150 . Also, it may encode data analyzed and processed by the control unit  150  after the decoding to output encoded data to a higher application block. 
     The storage unit  130  may store data received from the communication unit  110  or store information on how the data has been processed. Also, the storage unit  130  may store data checked by the control unit  150 , reference information for checking a line error, and check result information. 
     The output unit  140  may data calculated and processed by the data processing unit  120  and the control unit  150  to a valve control unit (not shown) as a valve control value. 
     The control unit  150  may monitor the state of data obtained from each controller module connected to the HVDC transmission system obtained through the communication unit  110  and generate valve control data accordingly. 
     In particular, the control unit  150  according to an embodiment may include a data monitoring unit  151  and a line monitoring unit  152 . 
     The data monitoring unit  151  may detect errors of data measured and applied from controllers and check the states of data. The data monitoring unit  151  may check the presence and absence of the errors of data based on pulse data including M groups including N signals as shown in  FIG. 2 . 
     The line monitoring unit  152  may check the reception (receiving rate) of data preset based on the same data as that monitored by the data monitoring unit  151  to check the presence and absence of a line connection. 
     The type of data obtained in an embodiment may be M databack groups DMn signals including N pulse signals for a certain period T as shown in  FIG. 2 . The data obtained from the control device  100  of the HVDC transmission system according to an embodiment may be a pulse signal received for 4 ms (P H ms) at an interval of 4 ms (P L ms) for a period T of 16.67 ms. The data input period, section and interval may vary depending on an embodiment. 
     Each of the databack signals includes thyristor conduction information, gamma operation information, and break-over diode (BOD) information. 
     The control unit  150  may monitor a data error and line connection according to various pieces of information included in the databack signal and depending on the presence and absence of an input of a signal. 
     In the following, data and line error monitoring operations according to an embodiment are described in detail with reference to  FIGS. 3 and 4 . 
       FIG. 3  is a flow chart for data error verification according to an embodiment. 
     Although it is described as an example that the control unit  150  for the data error verification according to an embodiment is performed at the monitoring unit  151  included in the control unit, the function may be a portion of the overall operations of the control unit  150 . The data monitoring unit  151  may be configured in the control unit  150  to be integrated into the control unit  150  or configured in a separate external device. 
     Referring to  FIG. 3 , the control unit  150  according to an embodiment may obtain data from control devices connected to the HVDC transmission system and operate in an error monitoring mode in which obtained data is monitored, in step S 310 . 
     The control unit  150  may receive the databack signals DB 1  to DBN as shown in  FIG. 2  according to the error monitoring mode in step S 320 . 
     The control unit  150  may determine whether a check period for checking the presence and absence of an error and state information on the databack signal has arrived in step S 330 . 
     The check period may correspond to a pulse input period included in the databack signal and is described with e.g., 4 ms in an embodiment. 
     The control unit  150  may check the state of data and the presence and absence of error data based on pulse signal data included in the databack signal when the check period of the databack signal has arrived. 
     The control unit  150  may check whether error data included in each data in the pulse signal data is output to be high in step S 350 . 
     When there is no error in data obtained from a control device, error data may be included and output as a low signal in the pulse signal, and when there is an error in the data, the error data may be included and output as a high signal in a pulse signal of corresponding data. 
     Thus, the control unit  150  may determine whether pulse signal data has error data having a high signal, and when there is error data, it is possible to count the number of error data. 
     The control unit  150  may determine whether the number of counted error data or the number of pulse signals of error data represented by high is equal to or larger than a reference number in step S 360 . The reference number may be a level at which error data affects system and valve control. Thus, the reference number is not limited and may vary according to a system or user setting. 
     When the number of the counted error data is smaller than the reference number, the control unit  150  may determine that obtained data is in a normal state and output the data to a valve control device (not shown). 
     On the contrary, when the number of the counted error data is equal to or larger than the reference number, the control unit  150  may determine that the obtained data is error data and output a corresponding result in various forms, in step S 380 . 
       FIG. 4  is a flow chart for line connection error verification according to an embodiment. 
     Although it is described as an example that the control unit  150  for the line connection error verification is performed at the line monitoring unit  152  included in the control unit  150 , the function may be a portion of the overall operations of the control unit  150 . The line monitoring unit  152  may be configured in the control unit  150  to be integrated into the control unit  150  or configured in a separate external device. 
     Referring to  FIG. 4 , the control unit  150  according to an embodiment may obtain data from control devices connected to the HVDC transmission system by using physical lines and operate in an error monitoring mode in which obtained data is monitored, in step S 410 . 
     The control unit  150  may receive the databack signals DB 1  to DBN as shown in  FIG. 2  according to the error monitoring mode, in step S 420 . 
     The control unit  150  may determine whether a check period for checking the presence and absence of an error and state information on the databack signal has arrived in step S 430 . The check period may correspond to a pulse input period included in the databack signal and is described with e.g., 4 ms to be the same as the data check period of the data error verification in an embodiment. 
     The control unit  150  may check the presence and absence of no input data based on pulse signal data included in the databack signal when the check period of the databack signal has arrived, in step S 440 . 
     Simultaneously with or separately from the data error verification, the control unit  150  check at the line monitoring unit  152  based on obtained data whether there is a databack signal not received among preset N (22 in an embodiment) databack signals. 
     The control unit  150  may check based on the databack signal whether a line signal is input to a line connected physically to control devices and check whether there is on input databack signal, in step S 450 . 
     The control unit  150  may check information on a physical line receiving a signal not input when no input signal among databack signals is checked in step S 460 . 
     The control unit  150  may define that the no input databack signal is an event generated by the error of a physical line connected to a control device, and check information on a line transmitting and receiving the no input signal. 
     The control unit  150  may check information on a checked line and the no input signal and output a corresponding error notification in step S 470 . 
     Although an embodiment describes that the error of a signal line to which a databack signal is not input is checked and a notification is output, it may be processed that a corresponding signal line has an error event when the databack signal is not input a certain number of times or more. 
     Although an embodiment describes check and output operations of a data error and a line error separately based on the databack signal input from control devices, it is possible to perform data error verification and line verification simultaneously at the data monitoring unit  151  and the line monitoring unit  152  of the control unit  150  based on the databack signal. 
     Embodiments are mainly described above. However, they are only examples and do not limit the present invention. A person skilled in the art may appreciate that many variations and applications not presented above may be implemented without departing from the essential characteristic of embodiments. For example, each component specifically represented in embodiments may vary. 
     In addition, it should be construed that differences related to such a variation and such an application are included in the scope of the present invention defined in the following claims.