Patent Publication Number: US-2017350924-A1

Title: Device for measuring loss in reactive power compensation system

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
     This application claims the priority of Korean Patent Application No. 10-2016-0070213 filed on Jun. 7, 2016, in the Korean Intellectual Property Office, the disclosure of which is hereby incorporated by reference in its entirety. 
     BACKGROUND 
     1. Technical Field 
     The present disclosure relates to a device for measuring a loss in a reactive power compensation system. 
     2. Description of the Related Art 
     When power is supplied to a receiving end connected to a load, the power is not all used by the load. In other words, the power is not all used as active power by the load and part of the power is lost as reactive power, not contributing to a real work. 
     To minimize or compensate the reactive power, a reactive power compensation system is employed. 
     The reactive power compensation system adjusts a phase of a voltage or a phase of current and thus the reactive power may be minimized. 
     Meanwhile, there may be a loss due to constituent devices of the reactive power compensation system. 
     However, it is a problem that it is difficult to identify how much loss has occurred by various devices configured in a conventional reactive power compensation system. 
     Accordingly, from the perspective of a purchaser of the reactive power compensation system, it is a problem that it is difficult to determine the economical efficiency on the purchase of the reactive power compensation system. Furthermore, it is impossible to continuously identify a loss due to the reactive power compensation system and prepare a countermeasure corresponding to the identified loss. 
     Also, from the perspective of a manufacturer of the reactive power compensation system, since the loss of the reactive power compensation system cannot be identified, it is difficult to answer purchaser&#39;s inquiries regarding the loss and furthermore it is difficult to advertise reliability of the system to the purchasers. 
     In addition, in order to reflect the amount of maintenance/repair and a loss of the reactive power compensation system to design, the loss of the reactive power compensation system should be identified. Nevertheless, it has not been possible to identify the loss of the reactive power compensation system according to the related art. 
     Accordingly, since a loss of the reactive power compensation system cannot be identified, accurate evaluation about the entire system including the reactive power compensation system is not possible and the loss cannot be reflected in the design of a next system. 
     SUMMARY 
     It is an object of the present disclosure to address the above-described problems and other problems. 
     It is another object of the present disclosure to provide a device for measuring a loss in a reactive power compensation system, by which a loss of various devices included in a reactive power compensation system may be identified. 
     Objects of the present disclosure are not limited to the above-described objects and other objects and advantages can be appreciated by those skilled in the art from the following descriptions. Further, it will be easily appreciated that the objects and advantages of the present disclosure can be practiced by means recited in the appended claims and a combination thereof. 
     In accordance with one aspect of the present disclosure, there is provided a device for measuring a loss in a reactive power compensation system to compensate reactive power, which includes at least one load, a reactive power compensation unit, at least one detection unit, a measurement unit, and a loss calculation unit. 
     The at least one load may be connected to a receiving end. 
     The reactive power compensation unit may be connected to the receiving end and may include at least one device. 
     The at least one detection unit may be provided at the at least one device and may detect a voltage, a phase of a voltage, current, and a phase of current. 
     The measurement unit may measure voltage data, current data, and a phase angle based on the voltage, the phase of a voltage, the current, and the phase of current detected by the at least one detection unit. 
     The loss calculation unit may calculate loss power of the at least one device based on the measured voltage data, current data and phase angle. 
    
    
     
       BRIEF DESCRIPTION OF DRAWINGS 
         FIG. 1  illustrates a device for measuring a loss in a reactive power compensation system according to an embodiment of the present disclosure. 
         FIG. 2  is a flowchart of a compensation method of a reactive power compensation system. 
     
    
    
     DETAILED DESCRIPTION 
     The above objects, features and advantages will become apparent from the detailed description with reference to the accompanying drawings. Embodiments are described in sufficient detail to enable those skilled in the art in the art to easily practice the technical idea of the present disclosure. Detailed descriptions of well-known functions or configurations may be omitted in order not to unnecessarily obscure the gist of the present disclosure. Hereinafter, embodiments of the present disclosure will be described in detail with reference to the accompanying drawings. Throughout the drawings, like reference numerals refer to like elements. 
     As the inventive concept allows for various changes and numerous embodiments, particular embodiments will be illustrated in the drawings and described in detail in the written description, wherein like reference numerals in the drawings denote like elements, and thus their description will not be repeated. The suffix “module” and “unit” for components, which are used in the description below, are assigned and mixed in consideration of only the easiness in writing the specification. That is, the suffix itself does not have different meanings or roles. However, this is not intended to limit the present inventive concept to particular modes of practice, and it is to be appreciated that all changes, equivalents, and substitutes that do not depart from the spirit and technical scope of the present inventive concept are encompassed in the present inventive concept. In the description of the present inventive concept, certain detailed explanations of related art are omitted when it is deemed that they may unnecessarily obscure the essence of the inventive concept. 
       FIG. 1  illustrates a device for measuring a loss in a reactive power compensation system according to an embodiment of the present disclosure. 
     Referring to  FIG. 1 , the device for measuring a loss in a reactive power compensation system according to the present embodiment may include a reactive power compensation unit  30  and a control system  40 . 
     A plurality of loads  21   a,    21   b,    21   c,    23   a,    23   b,  and  23   c  may be connected to a receiving end  11 . In detail, a branch line  12  may be branched from the receiving end  11 , and the loads  21   a,    21   b,    21   c,    23   a,    23   b,  and  23   c  may be connected to the branch line  12   
     Although  FIG. 1  illustrates that the branch line  12  is connected to the receiving end  11 , the loads  21   a,    21   b,    21   c,    23   a,    23   b,  and  23   c  may be directly connected to the receiving end  11  without the branch line  12 . 
     The loads  21   a,    21   b,    21   c,    23   a,    23   b,  and  23   c  may be connected to a system other than the receiving end  11 . The system may be an AC system, a DC system, or a HVDC system. However, the present disclosure is not limited thereto. 
     The loads  21   a,    21   b,    21   c,    23   a,    23   h,  and  23   c  may be loads provided in ironworks, for example, are furnaces  21   a,    21   b,  and  21   c  or smelting furnaces  23   a,    23   b,  and  23   c . However, the present disclosure is not limited thereto. 
     The reactive power compensation unit  30  may be connected parallel to the loads  21   a,    21   b,    21   c,    23   a,    23   b,  and  23   c  and commonly with the loads  21   a,    21   b,    21   c,    23   a,    23   b,  and  23   c  to the branch line  12  or the receiving end  11 , but the present disclosure is not limited thereto. Accordingly, power supplied to the receiving end  11  may be supplied not only to the loads  21   a,    21   b,    21   c,    23   b,  and  23   c,  but also to the reactive power compensation unit  30 . 
     The reactive power compensation unit  30 , as illustrated in  FIG. 2 , may include a Thyristor-controlled reactor (TCR)  25 , a Thyristor-switched capacitor (TSC)  27 , and a harmonic filter unit  29 . 
     The TCR  25  may include a reactor and a thyristor switch. The number or arrangement of reactors may be implemented by various methods. 
     The TSC  27  may include a capacitor and a thyristor switch. The number or arrangement of capacitors may be implemented by various methods. 
     The harmonic filter unit  29  may include a plurality of filters. Each filter may include a resistor, a capacitor, and an inductor. Although the resistor and the inductor may be connected in parallel, but the present disclosure is not limited thereto. 
     Both the TCR  25  and the TSC  27  may not be necessarily provided. Only one of the TCR  25  and the TSC  27  may be provided, but the present disclosure is not limited thereto. 
     Although not illustrated, a fixed compensation unit may be further provided in addition to the TCR  25  or the TSC  27 . The fixed compensation unit may be a fixed capacitor. 
     The reactive power compensation unit  30  may control the Thyristor switch provided therein to compensate the reactive power. 
     The above configuration is described below in detail. 
     As illustrated in  FIG. 2 , a voltage, current, and a phase angle may be measured (S 111 ). 
     For example, a voltage, current, and a phase angle may be detected by a first detection unit  13  and then measured by a measurement unit  41  provided in the control system  40 . In detail, a voltage transformer  13   a  of the first detection unit  13  may detect a voltage and a phase of a voltage applied to the branch line  12 , and a current transformer  13   b  of the first detection unit  13  may detect current and a phase of current applied to the branch line  12 . 
     The voltage and the phase of a voltage, and the current and the phase of current, detected by the first detection unit  13  are provided to the measurement unit  41 . Accordingly, the measurement unit  41  may measure voltage data, current data, and a phase angle based on the voltage, the phase of a voltage, the current, and the phase of current. 
     The phase angle may be calculated based on the phase of a voltage and the phase of current. For example, when a phase of current is ahead of a phase of a voltage, it may be referred to as leading, and when a phase of a voltage is ahead of a phase of current, it may be referred to as lagging. 
     For example, when a phase angle in leading is expressed by a positive phase angle, a phase angle in lagging may be expressed by a negative phase angle. 
     When the loads  21   a,    21   b,    21   c,    23   a,    23   b,  and  23   c  are directly connected to the receiving end  11 , a voltage and a phase of a voltage on a line of the receiving end  11  is detected by the voltage transformer  13   a  of the first detection unit  13 , and current and a phase of current flowing in the line of the receiving end  11  may be detected by the current transformer  13   b  of the first detection unit  13 . 
     The controller  45  may calculate reactive power based on the measured voltage, current, and phase angle (S 113 ). Next, the controller  45  may calculate a reactive power compensation amount based on the calculated reactive power (S 115 ). 
     The reactive power compensation amount may be calculated by a mathematical expression “Power Factor Compensation Target Value—Current Power Factor”. 
     The power factor may indicate a ratio of active power and apparent power. The apparent power may indicate power supplied to the receiving end  11 , and the active power may be power obtained by excluding the reactive power from the apparent power. Accordingly, as the power factor is improved by the power factor compensation, the active power may be increased and thus power loss may be reduced and the power may be efficiently used. 
     According to whether it is leading reactive power or lagging reactive power, the reactive power compensation amount may be calculated to be +Q or −Q. 
     The leading reactive power may be reactive power when the phase of current is ahead of the phase of a voltage, and the lagging reactive power may be reactive power when the phase of a voltage is ahead of the phase of current. 
     The controller  45  may control the Thyristor switch provided in the reactive power compensation unit  30  according to the reactive power compensation amount −Q or +Q (S 117 ). 
     As such, since the reactive power is compensated under the control of the Thyristor switch, the reactive power of the power supplied to the branch line  12  is minimized and thus the corresponding power may be used for the loads  21   a,    21   b,    21   c,    23   a ,  23   b,  and  23   c.    
     The reactive power compensation unit  30  may include a plurality of devices. For example, the reactive power compensation unit  30  may include the TCR  25 , the TSC  27 , and the harmonic filter unit  29 . The TCR  25 , the TSC  27 , and the harmonic filter unit  29  may be main devices. 
     in addition, the reactive power compensation unit  30  may include a battery, an emergency generator, or an air conditioner, as ancillary devices, but the present disclosure is not limited thereto. 
     Since the devices of the reactive power compensation unit  30  also operate, a loss is generated. However, conventionally, since the loss generated by the devices of the reactive power compensation unit  30  are not identified, various subsequent operations are not available. 
     According to the present disclosure, since the loss of each of the devices of the reactive power compensation unit  30  can be identified, various evaluations or subsequent actions may be taken based on the overall loss of the reactive power compensation unit  30  including the loss of the devices. 
     To measure the loss of the reactive power compensation unit  30 , a plurality of detection units may be provided. 
     For example, as the first detection unit  13  is provided between the receiving end  11  and the branch line  12 , a voltage, a phase of a voltage, current, and a phase of current on the branch line  12  may be detected. 
     For example, as a second detection unit  15  is provided at an input side of the TCR  25  of the reactive power compensation unit  30 , a voltage, a phase of a voltage, current, and a phase of current on an input side of the TCR  25  may be detected. 
     Current may flow into the TCR  25 , or may flow out from the TCR  25  during compensation. 
     For example, as a third detection unit  17  is provided at an input side of the TSC  27  of the reactive power compensation unit  30 , the voltage, the phase of a voltage, the current, and the phase of current at the input side of the TSC  27  may be detected. Current may flow into the TSC  27 , or may flow out from the TCR  25  during compensation. 
     For example, as a fourth detection unit  19  is provided at an input side of the harmonic filter unit  29  of the reactive power compensation unit  30 , the voltage, the phase of a voltage, the current, and the phase of current at the input side of the harmonic filter unit  29  may be detected. 
     For example, as a fifth detection unit  33  is provided at an input side of each ancillary device of the reactive power compensation unit  30 , the voltage, the phase of a voltage, the current, and the phase of current at the input side of each ancillary device may be detected. 
     The ancillary device may be, for example, a battery, an emergency generator, or an air conditioner, but the present disclosure is not limited thereto. 
     The first to fifth detection units  13 ,  15 ,  17 ,  19 , and  33  may respectively include the voltage transformers  13   a,    15   a,    17   a,  and  19   a  and the current transformers  13   b,    15   b,    17   b , and  19   b.    
     The control system  40  may include the measurement unit  41 , a loss calculation unit  43 , the controller  45 , and a storage unit  47 . 
     The controller  45  may manage and control the overall system including the reactive power compensation unit  30 . 
     The measurement unit  41 , the loss calculation unit  43 , and the storage unit  47  included in the control system  40  may perform specific functions under the control of the controller  45 . 
     The measurement unit  41  may receive, for example, inputs of the voltage, the phase of a voltage, the current, and the phase of current detected by the first to fifth detection units  13 ,  15 ,  17 ,  19 , and  33 , and may measure voltage data, current data, and a phase angle of a certain device based on the voltage, the phase of a voltage, the current, and the phase of current. 
     The voltage, the phase of a voltage, the current, and the phase of current detected by the first to fifth detection units  13 ,  15 .  17 ,  19 , and  33  may be analog signals. 
     The measurement unit  41  may convert the voltage, the phase of a voltage, the current, and the phase of current that are detected analog signal, to digital signals, amplify and/or modulate the converted signals, and measure the voltage data, the current data, and the phase angle. 
     The loss calculation unit  43  may calculate supply power supplied via the receiving end  11  based on the voltage data, the current data, and the phase angle detected by the first detection unit  13  and measured by the measurement unit  41 . 
     The loss calculation unit  43  may calculate loss power of each device based on the voltage data, the current data, and the phase angle measured by the measurement unit  41 . 
     The loss power of each device may be calculated by Equation 1 below. 
         P   loss   =VIt   [Equation 1]
 
     In Equation 1, “P loss ” may denote loss power, “V” may denote a voltage measured at a specific device, “I” may denote current measured at the specific device, and “t” may denote time, 
     The loss power may be cumulatively calculated in units of time. For example, when the loss power is cumulatively calculated by one hour, the loss power may be cumulatively calculated twenty-four (24) times per day and thus an average amount of the 24-times cumulatively calculated loss power may be calculated. The 24-times cumulatively calculated loss power and the daily average amount may be stored in the storage unit  47 . 
     Accordingly, the loss of the reactive power compensation unit  30  may be easily identified through the loss power calculated for each hour or the daily average amount calculated per day. Accordingly, since the identification of a loss is not a one-time performance, the loss may be identified continuously and in real time as long as the reactive power compensation unit  30  operates. 
     Accordingly, from the perspective of a purchaser or an operator of the reactive power compensation unit  30 , it is possible to determine the economical efficiency according to the loss. 
     For example, the loss calculation unit  43  may determine the economical efficiency of the reactive power compensation unit  30  by comparing the loss power consumed by the reactive power compensation unit  30  and compensation power for compensating the reactive power. Accordingly, a periodical electricity rate reduction effect of the reactive power compensation unit  30  may be obtained. 
     The economical efficiency may be determined by the controller  45  instead of the loss calculation unit  43 . 
     When a product production amount increases according to a load operation amount, an effect of reactive power compensation occurs in proportion thereto. The economical effect of the reactive power compensation may be increased particularly in the summer time when the electricity rate is high. 
     Furthermore, from the perspective of a purchaser or an operator of the reactive power compensation unit  30 , a degree of deterioration of the reactive power compensation unit  30  and a replacement cycle thereof may be identified by recognizing an increase in the loss of the reactive power compensation unit  30 . Furthermore, information about the loss obtained with respect to the reactive power compensation unit  30  may be reflected to the overall system or in the design of a next new system. 
     From the perspective of a manufacturer who sold the reactive power compensation unit  30 , the reactive power compensation unit  30  may be sold more by advertising that not only the reactive power compensation of the reactive power compensation unit  30  may be possible, but also the loss of the reactive power compensation unit  30  may be identified. 
     In addition, as the number of loads in use among the loads  21   a,    21   b ,  21   c ,  23   a,    23   b , and  23   c  may vary according to time, and as the number of the loads  21   a,    21   b,    21   c,    23   a ,  23   b,  and  23   c  vary, the loss generated in the reactive power compensation unit  30  may vary. However, since the loss of the reactive power compensation unit  30  that varies according to the number of the loads  21   a,    21   b,    21   c,    23   a,    23   b,  and  23   c  in use may be measured by the device for measuring a loss of the reactive power compensation unit  30  according to the present disclosure, an evaluation or a countermeasure thereto may be easily found. 
     As described above, the effects of the device for measuring a loss in a reactive power compensation system according to the present disclosure are as follows. 
     According to at least one of the embodiments of the present disclosure, the loss of the reactive power compensation system may be easily identified and the loss may be identified continuously and in real time. 
     According to at least one of the embodiments of the present disclosure, from the perspective of a purchaser or an operator of the reactive power compensation unit, the is economical efficiency according to the loss may be determined, and a degree of deterioration of the reactive power compensation unit and a replacement cycle thereof may be identified by recognizing an increase in the loss of the reactive power compensation unit  30 . 
     According to at least one of the embodiments of the present disclosure, from the perspective of a manufacturer who sold the reactive power compensation unit, the reactive power compensation unit may be sold more by advertising that not only the reactive power compensation of the reactive power compensation unit  30  may be possible, but also the loss of the reactive power compensation unit  30  may be identified. 
     According to at least one of the embodiments of the present disclosure, since the loss of the reactive power compensation unit that varies according to the number of the loads in use may be measured by the device for measuring a loss of the reactive power compensation unit according to the present disclosure, an evaluation or a countermeasure thereto may be easily found. 
     The present disclosure described above may be variously substituted, altered, and modified by those skilled in the art to which the present inventive concept pertains without departing from the scope and sprit of the present disclosure. Therefore, the present disclosure is not limited to the above-mentioned exemplary embodiments and the accompanying drawings.