Abstract:
The present disclosure relates to an energy management system (EMS) and a method using the same, wherein the EMS comprises, a communication module receiving a channel information of a high voltage direct current (HVDC) system via a network; a circuit realization unit obtaining a connection information among constituent elements symbolizing the constituent elements among each node in electrical symbols by sequentially following pre-set nodes of the HVDC system, and forming the HVDC system by connecting the symbolized constituent elements using electrical lines by using the channel information of HVDC system received by the communication module; a system analyzing unit analyzing an operation mode of the HVDC system through the connection information among the constituent elements of the HVDC system obtained by the circuit realization unit; and a controller managing and controlling the HVDC system by giving an energy management command in response to the operation mode analyzed by the system analyzing unit.

Description:
CROSS-REFERENCE TO RELATED APPLICATION 
       [0001]    The present application is based on, and claims priority from, Korean Application Numbers 10-2008-0011845, filed Feb. 5, 2008, the disclosure of which is incorporated by reference herein in its entirety. 
       BACKGROUND 
       [0002]    The following description relates to an energy management system (EMS) and a control method using the same, and more particularly to an energy management system (EMS) and a control method using the same, capable of determining an operation mode of a high voltage direct current (HVDC) using system information inputted from the EMS via a network. 
         [0003]    There may be two types of power channel coupling methods in which one type is to be coupled with an existing alternating current (AC) power system to one or more loads such as, but are not limited to, household appliances and other energy consuming devices without use of intermediate components, and the other is to be coupled with a power system to loads by converting an alternating current (AC) to a direct current (DC) using an AC-DC converter. Herein, the phrase “coupled with” is defined to mean directly connected to or indirectly connected with through one or more intermediate components. Such intermediate components may include both hardware and software based components. 
         [0004]    Recently, interests have increased on the method of coupling the power channel to loads using the AC-DC converter instead of the method dispensing with an intermediate component. This is because the method using the AC-DC converter has an advantage in terms of cost when the power is supposed to be transmitted to a long distance location. Furthermore, the method using the AC-DC converter is capable of transmitting a large capacity of power without affecting the AC power system, and is connectible to other systems of different frequencies. Meanwhile, a high voltage direct current (HVDC) system using an AC-DC converter has been locally set up here in Korea between a southern town known as Haenam and a southernmost Jaeju island. 
         [0005]      FIG. 1  is a schematic block diagram illustrating a high voltage direct current (HVDC) system that connects a power channel between two local areas. 
         [0006]    Referring to  FIG. 1 , the HVDC system may comprise: a first transformer  110  connected to an AC bus line  100  of a first area and a second transformer  112 ; a first converter unit  120  converting an AC inputted from the first transformer  110  and the second transformer  112  to a DC and a second converter unit  122 ; a first inverter unit  124  and a second inverter unit  126  that convert DC to AC; a third transformer  114  and a fourth transformer  116  that convert the voltage of the AC converted by the first and second inverter unit  124  and  126 , and are connected to an AC bus line  101  of a second area; a first DC line  102  connecting the first converter unit  120  to the first inverter unit  124  and a second DC line  103  connecting the second converter unit  122  to the second inverter unit  126 ; a total of  18  circuit breakers  131 ˜ 148  for protecting each constituent element comprising a system and the high voltage direct current system; and a first bypass line  104  and second bypass line  105  for transmitting the power detouring an accident section during an accident. The first converter unit  120  and the second converter unit  122  may include four converters, and the first and second inverter unit  124  and  126  may include four inverters. 
         [0007]    Meanwhile, the HVDC system needs an effective power supply that is stable in response to a system status, the function of which is performed by an energy management system (EMS). That is, the EMS is an automatic control system capable of collecting data of nation-wide power stations and major substations for production of economic electric power and provision of the power to loads, whereby a power system network can be generally controlled and loads can be effectively distributed. 
         [0008]    The EMS now analyzes a system based on actual operation information of the HVDC system. The actual operation information of the HVDC system may be obtained by an operator of a HVDC substation. To be more specific, a manager of the EMS (hereinafter referred to as EMS manager) may obtain the actual operation information of the HVDC system via communication (e.g., telephone communication) with an HVDC substation operator. 
         [0009]    Using the aforementioned method, the EMS can receive the operation information from the EMS operator to generate an electric circuit of HVDC system based on the inputted operation information. A channel is analyzed based on the electric circuit information (i.e., connection information among electrical elements comprising the HVDC system) thus generated to provide an energy management for power control. Furthermore, the electrical circuit of the HVDC system may be displayed on a screen for the EMS operator to view. 
         [0010]    For example, the EMS operator obtains normal operation mode information via communication with an HVDC substation operator to input the normal operation mode information to the EMS. The EMS generates the electric circuit of the HVDC system based on the inputted normal operation mode information, as depicted in  FIG. 2 , and performs the power control by analyzing the system based on the generated electric circuit information. 
         [0011]    However, the aforementioned method suffers from a drawback in that erroneous system analysis may be made by mistakes of the operator as the operation information of the HVDC system is acquiesced from the operator, making it difficult to cope with sudden happenings of accidents. 
         [0012]    For instance, in a case the HVDC substation operator makes a wrong judgment on an operation mode to send to the EMS operator operation information different from actual operation information, the wrong operation information may be inputted to an EMS application program, and a wrong interpretation of the system may be made, resulting in provision of wrong energy management. 
         [0013]    Another drawback is that the EMS manager may not obtain the operation information on the HVDC system due to interrupted communications with the HVDC substation operator, whereby the EMS may fail to perform the power control based on the actual operation mode of the HVDC system. 
       SUMMARY 
       [0014]    Accordingly, the present disclosure is intended to solve the aforementioned disadvantages and to provide an energy management system and method for monitoring HVDC system using the same, capable of determining an operation mode of a HVDC necessary for system analysis of power control using system information inputted from the EMS via a network. 
         [0015]    In one general aspect of the present disclosure, an Energy Management System (EMS) comprises: a communication module receiving a channel information of a high voltage direct current (HVDC) system via a network; a circuit realization unit obtaining a connection information among constituent elements symbolizing the constituent elements among each node in electrical symbols by sequentially following pre-set nodes of the HVDC system, and forming the HVDC system by connecting the symbolized constituent elements using electrical lines by using, the channel information of HVDC system received by the communication module; a system analyzing unit analyzing an operation mode of the HVDC system through the connection information among the constituent elements of the HVDC system obtained by the circuit realization unit; and a controller managing and controlling the HVDC system by giving an energy management command in response to the operation mode analyzed by the system analyzing unit. 
         [0016]    Implementations of this aspect may include one or more of the following features. 
         [0017]    An order of nodes is set up in such a manner that a point where electrical impedances are changed by the constituent elements included in the HVDC system is designated as a node. 
         [0018]    The constituent elements include at least one of a transformer, an inverter, a converter and a circuit breaker. 
         [0019]    The EMS of claim  3 , wherein the channel information includes at least one of a circuit breaker status information, a DC voltage information and a power information. 
         [0020]    The circuit realization unit connects or disconnects the circuit breaker via the circuit breaker status information included in the channel information to obtain the connection information among the constituent elements included in the HVDC system in a case the constituent element is the circuit breaker. 
         [0021]    In another general aspect of the present disclosure, the control method comprising: receiving channel information of a high voltage direct current (HVDC) system via a network; symbolizing the constituent elements among each node in electrical symbols by sequentially following pre-set nodes of the HVDC system by using the channel information of HVDC system, and obtaining connection information among constituent elements comprising the HVDC system by connecting the symbolized constituent elements using electric lines; and determining an operation mode of the HVDC system using the connection information among the constituent elements included in the HVDC system. 
         [0022]    Implementations of this aspect may include one or more of the following features. 
         [0023]    The constituent elements include at least one of a transformer, an inverter, a converter and a circuit breaker, and the channel information includes at least one of circuit breaker status information, DC voltage information and power information. 
         [0024]    The obtaining step of connection information among the constituent elements comprising the HVDC system includes connecting or disconnecting the circuit breaker via the circuit breaker status information included in the channel information, and obtaining connection information among the constituent elements comprising the HVDC system in a case the constituent element is a circuit breaker. 
         [0025]    The present disclosure may provide that an electrical circuit of a HVDC system can be generated by channel information inputted from a network without any human intervention, and an operation mode of the HVDC system can be judged by the generated electric circuit information (connection information among constituent elements of the HVDC system), whereby a sudden occurrence of accident can be overcome, and an accurate channel analysis can be realized. 
         [0026]    The present disclosure may provide that the constituent elements included in the electrical circuit of the HVDC system can be expressed by electrical codes corresponding thereto, and voltages or direct current information included in the channel information inputted via the network can be included to obtain detailed information necessary for channel analysis. 
         [0027]    The present disclosure may provide that power control can be effectively performed using the EMS in the long run. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0028]      FIG. 1  is a schematic view illustrating an HVDC system coupling power channels among areas. 
           [0029]      FIG. 2  is a schematic view illustrating an exemplary implementation of a circuit of HVDC in a, system of EMS according to prior art. 
           [0030]      FIG. 3  is a schematic view illustrating an entire configuration of a power control system according to the present disclosure. 
           [0031]      FIG. 4  is a schematic view illustrating an exemplary implementation in which nodes and electrical symbols of each constituent element for embodying a circuit of the HVDC in a system of EMS. 
           [0032]      FIG. 5 ,  FIG. 6  and  FIG. 7 , are a schematic view illustrating an exemplary implementation of a circuit of the HVDC in a system of EMS according to the present disclosure. 
       
    
    
     DETAILED DESCRIPTION 
       [0033]    The EMS and the method using the same according to the present disclosure will be described in detail with reference to the accompanying drawings. Detailed descriptions of well-known functions, configurations or constructions are omitted for brevity and clarity so as not to obscure the description of the present disclosure with unnecessary detail. 
         [0034]      FIG. 3  is a schematic view illustrating an entire configuration of a power control system according to the present disclosure. 
         [0035]    Referring to  FIG. 3 , the power control system may include a remote terminal unit (RTU,  320 ), a supervisory control and data acquisition (SCADA,  310 ) system, and an energy management system (EMS,  300 ). 
         [0036]    The RTU  320  is a field device installed at a remote area power consumption (W), reactive power consumption (VAR. Volt-Ampere Reactive), transformer temperature data, information on theft, fire and circuit breaker status and sends the collected information to the SCADA  310  via wired/wireless communication devices and communication lines. The RTU  320  may acquire the circuit breaker status information, DC voltage information and power information from an HVDC power distribution system. 
         [0037]    The RTU  320  is also a device that receives a control command from the SCADA  310  and performs a controlling function by online in in real time response to the received control command. 
         [0038]    The SCADA  310  is a device for monitoring or controlling at least one RTU  320  in a centralized control method. The SCADA  310  may transmit the data collected by the RTU  320  to the EMS  300  via wired/wireless communication lines. 
         [0039]    The EMS  300  is a large-sized power channel control system that collects information on an entire power supply system from the SCADA  310  controls the operation of power generating facility connected to the channels in an optimum condition by monitoring and performs an economic energy management by using an effective management of power system. One EMS  300  is installed at an entire channel, and there is locally a central EMS that controls a whole power system of the Korean peninsula, except that there is also a Jaeju island EMS that controls Jaeju area channels. The EMS  300  according to the present disclosure corresponds to the central EMS. 
         [0040]    The EMS  300  according to the present disclosure may include a circuit generating algorithm capable of creating an electrical circuit of HVDC system. Therefore, the EMS  300  according to the present disclosure may include a communication module  302  for communication, a circuit realization unit  304 , a system analyzing unit  306  and a controller  308 . 
         [0041]    The circuit realization unit  304  receives channel information including circuit breaker status information of the HVDC system from the SCADA  310  via the communication module  302  to generate an electric circuit of the HVDC system. The system information may further include DC voltage information and power information. 
         [0042]    To this end, when a point is where electrical impedances are changed by electrical elements (hereinafter referred to as constituent elements) such as a transformer, an inverter, a converter and a circuit breaker that form the HVDC system, the point is designated as a node in the circuit realization unit  304 , and the designated node information is stored. The circuit realization unit  304  may also store information on constituent elements to be connected to each designated node, and electrical code shapes relative to each constituent element. 
         [0043]    Now, referring to  FIG. 4 , the constituent elements including the transformer, the inverter, the converter and the circuit breaker are symbolized in electrical symbols. Furthermore,  FIG. 4  illustrates that a point connected by each constituent element, i.e., a point where electrical impedances are changed, is designated as a node. 
         [0044]    A point for connecting a first converter unit  120  to a first DC line  102 , a point for connecting a second converter unit  122  to a second DC line  103 , a point for connecting a first inverter unit  124  to the first DC line  102 , and a point for connecting a second inverter unit  126  to the second DC line  103  are respectively set up as a DC node DCN 1 R, a DC node DCN 2 R, a DC node NCN 1 I and a DC node DCN  21 . 
         [0045]    Each tab of a first transformer  110  is set up as CT 1 P (AC node), CT 1 S (secondary node) and CT 1 T (tertiary node), each tab of a second transformer  112  is set up as CT 2 P, CT 2 S and CT 2 T, each tab of a third transformer  114  is set up as CT 3 P, CT 3 S and CT 3 T, and each tab of a fourth transformer  116  is set up as CT 4 P, CT 4 S and CT 4 T. 
         [0046]    Furthermore, four converters in the first converter unit  120  and the second converter unit  122  are bound into two groups, each having two converters, and symbolized in two groups of converters  120 - 1 ,  120 - 2 ,  122 - 1  and  122 - 2 , where connecting points of the symbolized converters  120 - 1 ,  120 - 2 ,  122 - 1  and  122 - 2  are designated as nodes  6  and  11 . At the same time, four converters in the first inverter unit  124  and the second inverter unit  126  are bound into two groups, each having two inverters, and symbolized in two groups of inverters  124 - 1 ,  124 - 2 ,  126 - 1  and  126 - 2 , where connecting points of the symbolized converters  124 - 1 ,  124 - 2 ,  126 - 1  and  126 - 2  are designated as nodes  17  and  22 . 
         [0047]    Now, the circuit of the HVDC system is divided into a converter unit side  155  and an inverter unit side  156  based on a median line of the first DC line  102  and the DC line  103 . A node by a circuit breaker CB 1  which is a central point of the first DC line  102  of the converter unit side  155  is designated as No. 1, and node numbers are sequentially designated up to a central point of the second DC line  103  along a first bypass line  104 . Successively, node numbers are designated up to the second converter unit  122  from the first converter unit  120  connected to the first DC line  102 . Node numbers are also designated in the inverter unit side  156  in the same manner as that of the converter unit. 
         [0048]    To be more specific, a node by a circuit breaker CB 10  which is a central point of the first DC line  102  is designated as  12 , and node numbers are designated up to a central point of the second DC line  103  along with a second bypass line  105 . Node numbers are designated up to the second inverter unit  126  from the first inverter unit  124  connected to the first DC line  102 . It should be apparent that points may be numbered by using methods other than the designation of node numbers as used above. 
         [0049]    The circuit realization unit  304  may symbolize each constituent element starting from the node number  1  based on the system information and pre-stored information, and connect each constituent element using electrical lines. If the constituent element is a circuit breaker, the circuit breaker may be connected or disconnected using circuit breaker status information included in the system information to generate an electric circuit of the HVDC system. 
         [0050]    Now, the circuit of the HVDC system will be described in detail with reference to  FIGS. 5 to 7 . 
         [0051]    For exemplary purpose, in a case that a circuit breaker status information included in the system information is given as circuit breakers CB 3  ( 133 ), CB 4  ( 134 ), CB 9  ( 139 ) and CB 10  ( 140 ) being opened and that remaining circuit breakers being closed, the circuit realization unit  304  symbolizes a circuit breaker CB 2  ( 131 ) connected from a pre-set node  1  to node  1 . In circuit breakers CB 2  ( 132 ) and CB 3  ( 133 ) connected to a node  2  of the circuit breaker CB 1  ( 131 ), the circuit breaker CB 2  ( 132 ) is symbolized as being closed, while the circuit breaker CB 3  ( 133 ) is symbolized as being opened, where the two circuit breakers are connected by electric lines. Furthermore, searching of constituent elements connected to DCNIR of the circuit breaker CB 2  ( 132 ) is terminated 
         [0052]    A circuit breaker CB 4  ( 134 ) connected to node  3  of circuit breaker DB 3  ( 133 ) is symbolized as being opened, and circuit breakers CB 5  ( 135 ) and CB 6  ( 136 ) connected to node  4  is symbolized as being closed. Searching is terminated as constituent elements connected to node  5  of circuit breaker CB 5  ( 135 ) can be no longer possible. Searching of constituent elements on node DCN 2 R of circuit breaker CB 6  ( 136 ) is also stopped. As described above, the circuit breakers which are constituent elements on the DC lines on the converter side  156  and circuit breakers which are constituent elements on the bypass lines are symbolized, but the circuit breakers are connected or disconnected based on the system information including the circuit breaker status information, and connected by circuit lines. At this time, in a case the circuit breakers CB 3 , CB 4 , CB 9  and CB 10  connected to the first and second bypass lines  104  and  105  are all opened, the first and second bypass lines may be omitted. 
         [0053]    Furthermore, a converter  1  ( 120 - 1 ) connected by starting from DCNI 4  node is symbolized, and a secondary tab of the first transformer ( 110 ) connected to a node CT 1 S of the converter  1  ( 120 - 1 ) is symbolized. Furthermore, a converter  2  ( 120 - 2 ) connected to node  6  of the converter  1  ( 120 - 1 ) is symbolized, a tertiary tab of the first transformer  110  connected to a node CT 1 T of the second converter  2  ( 120 - 2 ) is symbolized, and an AC side tab connected to node CT 1 P is symbolized. 
         [0054]    A circuit breaker CB 13  ( 143 ) connected to node  7  of the converter  2  ( 120 - 2 ) is symbolized as being closed, and circuit breakers CB 14  ( 144 ) and CB 15  ( 145 ) connected to node  8  of circuit breaker CB 13  ( 143 ) is symbolized as being closed. An earth symbol connected to node  9  of a circuit breaker CB 14  ( 144 ) is symbolized, and a converter  3  ( 122 - 1 ) connected to node  10  of circuit breaker CB 15  ( 155 ) is also symbolized. A secondary tab of the second transformer  112  connected to node CT 2 S of converter  3  ( 122 - 1 ) is symbolized, and a converter  4  ( 122 - 2 ) connected to node  11  of the converter  3  ( 122 - 1 ) is symbolized. At last, converter side  156  is finalized by symbolizing a tertiary tab of the second transformer  112  connected to node CT 2 T of converter  4  ( 122 - 2 ), and symbolizing an AC side tab connected to node CT 2 P to allow finishing at node DCN 2 R of converter  4  ( 122 - 2 ). 
         [0055]    Furthermore, a circuit breaker CB 7  ( 137 ) connected to node  12  starting from node  12  is symbolized as being closed, a circuit breaker CB 8  ( 138 ) connected to node  13  of circuit breaker CB 7  ( 137 ) is symbolized as being closed, and circuit breaker CB 9  ( 139 ) is symbolized as being opened, where the electric lines are connected accordingly. A circuit connection is terminated at node DCN 1 I of circuit breaker CB 8  ( 138 ). Furthermore, a circuit breaker CB 10  ( 140 ) connected to node  14  of circuit breaker CB 9  ( 139 ) is symbolized as being opened, and CB 11  ( 141 ) and CB 12  ( 142 ) connected to node  15  are symbolized as being closed. The circuit connection is terminated, because the constituent elements connected to node  16  of circuit breaker CB 11  ( 141 ) can no longer be found. At the same time, circuit connection is also stopped at DCN 21  node of circuit breaker CB 12  ( 142 ). Thus, constituent elements on DC lines at the inverter side and bypass lines are symbolized, where the circuit lines are connected accordingly. 
         [0056]    Still furthermore, an inverter  1  ( 124 - 1 ) connected by starting from DCN 1 I is symbolized, and a secondary tab of the third transformer  124  connected to node CT 3 S of the inverter  1  ( 124 - 1 ) is symbolized. An inverter  2  ( 124 - 2 ) connected to node  17  of inverter  1  ( 124 - 1 ) is symbolized, a tertiary tab of the third transformer  124  connected to node CT 3 T of inverter  2  ( 124 - 2 ) is symbolized, and an AC side tab connected to node CT 3 P is symbolized. Furthermore, a circuit breaker CB 16  ( 146 ) connected to node  18  of the inverter  2  ( 124 - 2 ) is symbolized as being closed, and circuit breakers CB 17  ( 146 ) and CB  18  ( 148 ) connected to node  19  of circuit breaker CB 16  ( 146 ) are symbolized as being closed. An earth symbol connected to node  20  of circuit breaker CB 17  ( 147 ) is symbolized and an inverter  3  ( 126 - 1 ) connected to node  21  of circuit breaker CB 18  ( 148 ) is symbolized, and a secondary tab of a fourth transformer  116  connected to node CT 4 S of inverter  3  ( 126 - 1 ) is symbolized. An inverter  4  ( 126 - 2 ) connected to node  22  of inverter  3  ( 126 - 1 ) is symbolized, and a tertiary tab of the fourth transformer  116  connected to node CT 4 T of inverter  4  ( 126 - 2 ) is symbolized. Furthermore, an AC side tab connected to node CT 4 P is symbolized to allow terminating at node DCN 21  of the inverter  4  ( 126 - 2 ). As a result, an electric circuit of an HVDC system is generated as shown in  FIG. 5 . 
         [0057]    In a case the circuit breakers CB 6  ( 136 ), CB 12  ( 142 ), CB 15  ( 145 ) and CB 18  ( 148 ) are opened and remaining circuit breakers receive system information of closed status, the circuit realization unit  304  may form an electric circuit as shown in  FIG. 6 . Furthermore, in a case the circuit breakers CB 3  ( 133 ), CB 4  ( 134 ), CB 5  ( 135 ), CB 9  ( 139 ), CB 10  ( 140 ) and CB 12  ( 142 ) are in an opened and remaining circuit breakers receive system information of closed status, an electric circuit may be formed as illustrated in  FIG. 7 . 
         [0058]    The realization unit  304  may transmit thus-generated electric circuit information (connection information among constituent elements of the HVDC system) to a system analyzing unit  306 . Successively, the system analyzing unit  306  may determine a current operation mode of the HVDC system via the electric circuit information inputted from the circuit realization unit  304  to analyze the system. 
         [0059]    For exemplary purpose, the current operation mode is determined as a normal operation mode by the electric circuit formed as shown in  FIG. 5 , the current operation mode is determined as a bypass operation mode by the electric circuit formed as shown in  FIG. 6 , and the current operation mode is determined as a blocking operation mode by the electric circuit as shown in  FIG. 7 . It can be known that power transmission is performed to a flow direction shown in  FIG. 6  in case of bypass operation mode, and power transmission is conducted to a flow direction shown in  FIG. 7  in case of blocking operation mode. 
         [0060]    The controller  308  may manage and control the power system by giving an energy management command via system information analyzed by the system analyzing unit  306 . 
         [0061]    Still other exemplary implementations will become readily apparent to those skilled in this art from reading the above-recited detailed description and drawings of certain exemplary implementations. It should be understood that numerous variations, modifications, and additional implementations are possible, and accordingly, all such variations, modifications, and implementations are to be regarded as being within the spirit and scope of the appended claims.