System and method for sts control of utility-power-priority uninterruptible power supply

Abstract

The present invention relates to an STS control system and method for a commercial power priority supply type uninterruptible power supply, and more specifically, to an STS control system and method for a commercial power priority supply type uninterruptible power supply that prevents the generation of circulating current caused by simultaneous conduction of both thyristors and prevents a delay in switching time by detecting whether the actual turn-off condition of the commercial power side thyristor is satisfied during a switching operation through a static switching switch composed of a commercial power side thyristor and an inverter side thyristor, and then turning on the inverter side thyristor.

Description

Technology Field

[0001] The present invention relates to an STS control system and method for a commercial power priority supply type uninterruptible power supply, and more specifically, to an STS control system and method for a commercial power priority supply type uninterruptible power supply that prevents the generation of circulating current caused by simultaneous conduction of both thyristors and prevents a delay in switching time by detecting whether the actual turn-off condition of the commercial power side thyristor is satisfied during a switching operation through a static switching switch composed of a commercial power side thyristor and an inverter side thyristor, and then turning on the inverter side thyristor. Background Technology

[0003] Commercial power refers to AC power supplied from an external power grid, and power outages can occur due to various causes, such as natural disasters like typhoons and lightning, overloads, and cable damage. Among UPS operating modes, the commercial power priority supply method allows commercial power to be supplied directly to the UPS load through an STS switching unit during normal operation, bypassing the inverter and significantly reducing power conversion losses. Consequently, UPS efficiency is improved, and the burden of internal heat generation and cooling is reduced, which is advantageous for reducing long-term operating costs, including electricity bills and maintenance expenses.

[0005] Figure 1 is a reference diagram of an STS control system of a conventional commercial power priority supply type uninterruptible power supply.

[0007] Referring to FIG. 1, during the process of switching the UPS load (950) from the commercial power source (910) to the inverter (920) in the event of a power outage, a circulating current path may be formed between the inverter (920) and the commercial power source (910) due to the characteristics of the UPS load (950) and the characteristics of the thyristor (930, 940) elements constituting the STS. This may cause an overcurrent to occur in the inverter (920) or a problem with cutting off the load power supply. Therefore, when switching through the STS, stable switching operation and protection of the inverter (920) must be achieved by controlling the turn-on and turn-off timing of the thyristors (930, 940) by considering the load characteristics.

[0008] As described above, a thyristor (930, 940) is generally applied to the STS device. The thyristor (930, 940) is composed of a PNPN structure in which a PNP transistor and an NPN transistor are internally combined, and the two transistors supply base current to each other through internal feedback action and maintain a turned-on state with self-holding characteristics. Therefore, once the thyristor (930, 940) is turned on, it continues to maintain a conductive state even if the gate signal is removed, and it is turned off only when the magnitude of the current of the thyristor (930, 940) decreases to a size below the holding current.

[0010] Figure 2a is a graph illustrating the phase difference between the commercial power voltage and the current flowing through the commercial power side thyristor under inductive load conditions.

[0012] Referring to FIG. 2a, depending on the configuration of the UPS load (950), a phase difference occurs between the commercial power supply (910) voltage (V) and the current (I) flowing through the commercial power supply side thyristor (930), and accordingly, a period in which the polarity of the voltage (V) and current (I) of the commercial power supply side thyristor (930) differs from each other may occur. For example, even if the voltage (V) applied to the commercial power supply side thyristor (930) switches to negative polarity (-), the current (I) may maintain positive polarity (+) for a certain period of time. Alternatively, even if the voltage (V) applied to the commercial power supply side thyristor (930) switches to positive polarity, the current (I) may maintain negative polarity for a certain period of time. This period of polarity mismatch between the voltage (V) and current (I) increases as the power factor of the load decreases. For example, when the load power factor is 0.8, the phase difference between the voltage (V) and the current (I) is approximately 36.8°, and during one cycle of the alternating current, a period in which the polarities of the voltage (V) and the current (I) are different from each other occurs repeatedly.

[0013] As described above, in the section where the polarity of the voltage (V) and the current (I) is different from each other and the magnitude of the current (I) flowing through the commercial power side thyristor (930) does not decrease below the magnitude of the maintenance current, the commercial power side thyristor (930) is not turned off and continues to maintain the turned-on state.

[0014] In particular, in a three-phase system, since these polarity mismatch sections occur at different times for each phase, the commercial power side thyristor (930) of a specific phase may turn off later than expected in the event of a power outage or an abnormality. Therefore, if the inverter side thyristor (940) is turned on without accurately determining the actual conduction state of the commercial power side thyristor (930), a circulating current may occur due to the simultaneous conduction of both thyristors (930, 940), so special caution is required when switching through the STS.

[0016] FIG. 2b is a graph showing the commercial power current during STS switching operation under inductive load conditions; FIG. 2c is a graph showing the inverter current during STS switching operation under inductive load conditions.

[0018] When an event such as a power outage occurs at a time when the polarity of the voltage (V) and current (I) of the commercial power side thyristor (930) is different, the gate signal to the commercial power side thyristor (930) is removed and the inverter side thyristor (940) is turned on at the same time, the magnitude of the current flowing through the commercial power side thyristor (930) maintains a value greater than the magnitude of the maintenance current, so that the commercial power side thyristor (930) may not be turned off. At this time, the commercial power side thyristor (930) and the inverter side thyristor (940) conduct simultaneously, and a circulating current path may be formed between the commercial power side thyristor (930) and the inverter side thyristor (940). Referring to FIGS. 2b and 2c, it can be seen that at the switching point (approx. 0.084 seconds; T1), current flows from the inverter (920) to the commercial power supply (910), causing an overcurrent in the commercial power supply current (I1) and the inverter current (I2). This may cause damage to the inverter (920) components or trigger system protection operations, which may disrupt the stable power supply to the UPS load (950).

[0019] Generally, in UPS systems with a commercial power priority supply method, a sufficient turn-off time is secured to prevent the generation of circulating current caused by the simultaneous turn-on of the commercial power side thyristor and the inverter side thyristor during the switching process. In some systems, the switching time is set to the level of a half-cycle of the AC power.

[0020] However, if the switching time becomes excessively long, a power outage period occurs during which power is not supplied to the UPS load (950) during that time, which can degrade the power quality of the UPS. Therefore, it is very important to secure an optimized switching time that can minimize the power outage period while ensuring complete turn-off of the thyristor.

[0022] In order to solve the aforementioned problems, the inventors of the present invention propose a novel STS control system and method for a commercial power priority supply type uninterruptible power supply, and details thereof will be described below. Prior art literature

[0024] Korean Registered Patent No. 10-2105090 'Output Phase Feedback Synchronization Device and Method for Parallel Operation of Uninterruptible Power Supply' The problem to be solved

[0025] It was devised to solve the problems of the aforementioned prior art,

[0027] The present invention aims to provide an STS control system and method for a commercial power priority supply type uninterruptible power supply, which prevents the generation of circulating current caused by simultaneous conduction of both thyristors and prevents a delay in switching time by detecting whether the actual turn-off condition of the commercial power side thyristor is satisfied during a switching operation through a static switching switch composed of a commercial power side thyristor and an inverter side thyristor, and then turning on the inverter side thyristor. means of solving the problem

[0029] The present invention may be implemented by an embodiment having the following configuration to achieve the above-mentioned purpose.

[0031] According to one embodiment of the present invention, the STS control system of a commercial power priority supply type uninterruptible power supply according to the present invention comprises: a converter that converts AC power supplied from a commercial power source into DC power; a power storage unit that stores DC power converted by the converter; an inverter that converts DC power stored in the power storage unit into AC power; a commercial power side thyristor located between a first node and a UPS load in a path branched from a first node, where a power line connecting the output side of the commercial power source and the input side of the converter is a power line; an inverter side thyristor located in a power line connecting the output side of the inverter and the UPS load; a current detection unit that detects the current flowing through the commercial power side thyristor in real time; a voltage detection unit that detects the voltage of the commercial power source in real time; and a control unit that controls a gate signal applied to the commercial power side thyristor and the inverter side thyristor based on the current detected by the current detection unit and the voltage detected by the voltage detection unit.

[0032] According to another embodiment of the present invention, the control unit of the STS control system of a commercial power priority supply type uninterruptible power supply according to the present invention is characterized by comprising: an event determination module that determines whether an event occurs based on voltage information detected by the voltage detection unit; and a polarity determination module that determines whether the polarity of the voltage of the commercial power and the current flowing through the commercial power side thyristor matches when the event occurs.

[0033] According to another embodiment of the present invention, the control unit of the STS control system of the commercial power priority supply type uninterruptible power supply according to the present invention further comprises a first control module that removes the gate signal applied to the commercial power side thyristor and immediately applies the gate signal to the inverter side thyristor when it is determined that the voltage of the commercial power and the polarity of the current flowing through the commercial power side thyristor match.

[0034] According to another embodiment of the present invention, the control unit of the STS control system of the commercial power priority supply type uninterruptible power supply according to the present invention further comprises a current magnitude comparison module that compares the magnitude of the current flowing through the commercial power side thyristor with the magnitude of a reference current when it is determined that the voltage of the commercial power and the polarity of the current flowing through the commercial power side thyristor are inconsistent.

[0035] According to another embodiment of the present invention, in an STS control system of a commercial power priority supply type uninterruptible power supply according to the present invention, the comparison of the magnitude of the current flowing through the commercial power side thyristor and the magnitude of the reference current is performed by a hardware comparator.

[0036] According to another embodiment of the present invention, the control unit of the STS control system of the commercial power priority supply type uninterruptible power supply according to the present invention further comprises a second control module that immediately turns on the inverter-side thyristor when the magnitude of the current flowing through the commercial power side thyristor has a value less than or equal to the reference current magnitude.

[0037] According to another embodiment of the present invention, the second control module of the STS control system of the commercial power priority supply type uninterruptible power supply according to the present invention is characterized by not applying a gate signal to the inverter-side thyristor when the magnitude of the current flowing through the commercial power side thyristor has a value exceeding the reference current magnitude.

[0038] According to another embodiment of the present invention, the commercial power side thyristor of the STS control system of the commercial power priority supply type uninterruptible power supply according to the present invention comprises: a first commercial power side thyristor that supplies a current in the positive polarity direction from the commercial power to the UPS load; and a second commercial power side thyristor that supplies a current in the negative polarity direction from the commercial power to the UPS load.

[0039] According to another embodiment of the present invention, the inverter-side thyristor of the STS control system of a commercial power priority supply type uninterruptible power supply according to the present invention is characterized by comprising: a first inverter-side thyristor that supplies a current in a positive polarity direction from the inverter to the UPS load; and a second inverter-side thyristor that supplies a current in a negative polarity direction from the inverter to the UPS load.

[0040] According to another embodiment of the present invention, the STS control system of a commercial power priority supply type uninterruptible power supply according to the present invention further comprises: a first circuit breaker installed in a power line connecting the output side of the commercial power supply and the input side of the converter; a second circuit breaker installed in a power line connecting the first node and the commercial power side thyristor; and a third circuit breaker installed in a power line connecting the second node, which is the junction point of the commercial power side thyristor and the inverter side thyristor, and the input side of the UPS load.

[0041] According to one embodiment of the present invention, an STS control method for a commercial power priority supply type uninterruptible power supply according to the present invention comprises: a step of determining whether an event occurs based on voltage information detected by the voltage detection unit; a step of determining whether the polarity of the voltage of the commercial power and the current flowing through the commercial power side thyristor matches when an event occurs; and a step of removing the gate signal applied to the commercial power side thyristor and immediately turning on the inverter side thyristor when the polarity of the voltage of the commercial power and the current flowing through the commercial power side thyristor matches.

[0042] According to another embodiment of the present invention, the STS control method of a commercial power priority supply type uninterruptible power supply according to the present invention further comprises: a step of removing a gate signal applied to a commercial power side thyristor when the voltage of the commercial power and the polarity of the current flowing through the commercial power side thyristor are mismatched; a step of comparing the magnitude of the current flowing through the commercial power side thyristor with the magnitude of a reference current; and a step of immediately turning on the inverter side thyristor when the magnitude of the current flowing through the commercial power side thyristor is less than or equal to the magnitude of the reference current.

[0043] According to another embodiment of the present invention, the STS control method of a commercial power priority supply type uninterruptible power supply according to the present invention is characterized by further including the step of not applying a gate signal to the inverter-side thyristor when the magnitude of the current flowing through the commercial power side thyristor exceeds the magnitude of the reference current. Effects of the invention

[0045] The present invention has the following effects by means of the above-described configuration.

[0047] The present invention has the effect of preventing the generation of circulating current caused by the simultaneous conduction of both thyristors and preventing a delay in switching time by detecting whether the actual turn-off condition of the commercial power side thyristor is satisfied during a switching operation through a static switching switch composed of a commercial power side thyristor and an inverter side thyristor, and then turning on the inverter side thyristor.

[0049] Meanwhile, it should be added that even if an effect is not explicitly mentioned here, the effects described in the following specification and the provisional effects expected by the technical features of the present invention are treated as described in the specification of the present invention. Brief explanation of the drawing

[0051] FIG. 1 is a reference diagram of an STS control system of a conventional commercial power priority supply type uninterruptible power supply; FIG. 2a is a graph illustrating the phase difference between the commercial power voltage and the current flowing through the thyristor under inductive load conditions; FIG. 2b is a graph showing the commercial power current during switching operation through the STS under inductive load conditions; FIG. 2c is a graph showing the inverter current during switching operation through the STS under inductive load conditions; FIG. 3 is a conceptual diagram of an STS control system of a commercial power priority supply type uninterruptible power supply according to an embodiment of the present invention; FIG. 4 is a reference diagram showing the power flow when commercial power is supplied first; Figure 5 is a reference diagram showing the power flow when an event occurs; FIG. 6 is a reference diagram showing that a circulating current is generated when the inverter-side thyristor is turned on while the commercial power-side thyristor is not turned off when an event occurs; FIG. 7 is a block diagram of the control unit; FIG. 8 is a graph showing the commercial power current during STS switching operation under inductive load conditions; FIG. 9 is a graph showing the inverter current during STS switching operation under inductive load conditions; Figure 10 is a flowchart of the STS control method of a commercial power priority supply type uninterruptible power supply. Specific details for implementing the invention

[0052] Hereinafter, embodiments of the present invention will be described in more detail with reference to the accompanying drawings. Embodiments of the present invention may be modified in various forms, and the scope of the present invention should not be interpreted as being limited to the embodiments below, but should be interpreted based on the matters described in the claims. Furthermore, these embodiments are provided merely for reference to more completely explain the present invention to those with average knowledge in the art.

[0053] As used herein, the singular form may include the plural form unless the context clearly indicates otherwise. Additionally, as used herein, “comprise” and / or “comprising” specify the presence of the mentioned features, numbers, steps, actions, parts, elements, and / or groups thereof, and do not exclude the presence or addition of one or more other features, numbers, actions, parts, elements, and / or groups.

[0055] FIG. 3 is a conceptual diagram of an STS control system of an uninterruptible power supply with a commercial power priority supply method according to an embodiment of the present invention; FIG. 4 is a reference diagram showing power flow when commercial power is priority supplied; and FIG. 5 is a reference diagram showing power flow when an event occurs.

[0057] Hereinafter, with reference to the attached drawings, an STS control system (1) of a commercial power priority supply type uninterruptible power supply device according to one embodiment of the present invention will be described in detail.

[0059] Referring to FIGS. 3 to 5, the present invention relates to an STS control system (1) of an uninterruptible power supply (UPS) with a commercial power priority supply method, and more specifically, to an STS control system (1; hereinafter referred to as 'STS control system') of an uninterruptible power supply with a commercial power priority supply method that prevents the generation of circulating current caused by simultaneous conduction of both thyristors and prevents a delay in the switching time by detecting whether the actual turn-off condition of the commercial power side thyristor is satisfied during a switching operation through a static transfer switch (STS) composed of a commercial power side thyristor and an inverter side thyristor, and then turning on the inverter side thyristor.

[0060] To this end, the STS control system (1) may include a commercial power supply (10), a converter (20), an inverter (30), a power storage unit (40), a commercial power supply side thyristor (50), an inverter side thyristor (60), a current detection unit (70), a voltage detection unit (80), and a control unit (90).

[0062] The commercial power supply (10) is an AC power supply provided from a power grid and is configured to supply power to the commercial power load (A1) and UPS load (A2) under normal conditions. The commercial power supply (10) is a grid power supply with a constant voltage and frequency, and power outages may occur due to natural disasters such as typhoons or lightning strikes, overloads, or cable damage. In the following, the occurrence of a power outage will be referred to as the occurrence of an event. Also, the above-mentioned "normal conditions" is understood to mean a time when no event has occurred. The commercial power load (A1) is connected to a power line branched from the power line connecting the commercial power supply (10) and the converter (20) described later, and may be, for example, lighting equipment, air conditioning equipment, elevators, or escalators, but the scope of the present invention is not limited by the above examples. The UPS load (A2) is connected to the output side of the commercial power side thyristor (50) and the inverter side thyristor (60), and may be, for example, critical equipment that does not allow momentary power interruption. And the UPS load (A2) may be, for example, an inductive load, but the scope of the present invention is not limited thereto.

[0063] The converter (20) is connected to the output side of the commercial power source (10) and is configured to convert the alternating current power supplied from the commercial power source (10) into direct current so that the power storage unit (40) can be charged. The converter (20) can normally convert the alternating current power supplied from the commercial power source (10) into direct current. In addition, a first circuit breaker (CB1) may be installed in the power line connecting the output side of the commercial power source (10) and the input side of the converter (20). The first circuit breaker (CB1) can normally maintain a closed (On) state to form a path for power to be supplied from the commercial power source (10) to the converter (20). In addition, it can trip when an overcurrent or short circuit occurs in the converter (20) or the power storage unit (40) to protect the system of the commercial power source (10) and the converter (20).

[0064] The inverter (30) is configured to convert the DC power stored in the power storage unit (40) into AC power and supply it to the UPS load (A2). The inverter (30) operates in a standby state during normal operation and can maintain phase synchronization with the commercial power supply (10). Additionally, when an event occurs, the inverter (30) can immediately switch from the standby state to the actual power supply state by turning on the inverter-side thyristor (60).

[0065] The power storage unit (40) is configured to store DC power supplied from the commercial power source (10) under normal conditions and converted by the converter (20). The power storage unit (40) preferably includes a secondary battery that receives electrical energy under normal conditions, stores it in the form of chemical energy, and converts the stored chemical energy back into electrical energy and releases it when an event occurs. Below, the power path leading to the power storage unit (40) via the commercial power source (10) and the converter (20) is set as the 'charging path (P1)'.

[0066] The commercial power side thyristor (50) is configured to provide a power path between the first node (N1) and the UPS load (A2) in a path branched from the first node (N1) of the power line connecting the output side of the commercial power (10) and the input side of the converter (20), thereby supplying alternating current power supplied from the commercial power (10) to the UPS load (A2). The commercial power side thyristor (50) is normally conductive to form a path through which alternating current power supplied from the commercial power (10) is supplied to the UPS load (A2), and it is preferable that it is cut off when an event occurs to prevent the formation of a circulating current path. Below, the power path supplied to the UPS load (A2) through the commercial power (10) and the commercial power side thyristor (50) is set as the 'first supply path (P2)'.

[0067] Additionally, the commercial power side thyristor (50) may include a first commercial power side thyristor (510) and a second commercial power side thyristor (530).

[0068] The first commercial power side thyristor (510) is configured to conduct a positive polarity current flowing from the commercial power source (10) toward the UPS load (A2). The first commercial power side thyristor (510) is turned on when a gate signal is applied to the commercial power side thyristor (50) and a positive polarity voltage is applied, and can be turned off when the magnitude of the current flowing from the commercial power source (10) is lowered to a first reference current magnitude or lower. Therefore, when the UPS load (A2) is an inductive load, the first commercial power side thyristor (510) does not immediately cut off the first supply path (P2) even if the gate signal to the commercial power side thyristor (50) is removed at the time of an event, but can cut off the first supply path (P2) after the magnitude of the current flowing through the first commercial power side thyristor (510) is lowered to a first reference current magnitude or lower. It is preferable that the first reference current mentioned above has positive polarity.

[0070] Figure 6 is a reference diagram showing that when an event occurs, a circulating current is generated as the inverter-side thyristor is turned on while the commercial power-side thyristor is not turned off.

[0072] The second commercial power side thyristor (530) is configured to conduct a negative polarity current flowing from the UPS load (A2) toward the commercial power source (10). The second commercial power side thyristor (530) is turned on when a gate signal is applied to the commercial power side thyristor (50) and a negative polarity voltage supplied from the commercial power source (10) is applied, and can be turned off when the magnitude of the negative polarity current flowing through the second commercial power side thyristor (530) is lowered to a magnitude less than or equal to the second reference current.

[0073] Referring to FIG. 6, when the UPS load (A2) is an inductive load, when an event occurs, the second commercial power side thyristor (530) does not immediately block the first supply path (P2) even if the gate signal to the commercial power side thyristor (50) is removed, but can block the first supply path (P2) after the magnitude of the current flowing through the second commercial power side thyristor (530) is reduced to a magnitude less than or equal to the second reference current. Therefore, when the inverter side thyristor (60) is turned on while the commercial power side thyristor (50), for example, the second commercial power side thyristor (530), is not turned off simultaneously with the occurrence of an event, the current supplied from the power storage unit (40) can be supplied to the commercial power load (A1) through the second commercial power side thyristor (530). Therefore, an overcurrent may occur in the inverter (30), causing the inverter (30) to automatically trip or the internal components of the inverter (30) to burn out, resulting in a power outage. Additionally, disturbances to the commercial power supply (10) system may occur. Even when the inverter-side thyristor (60) is turned on while the first commercial power supply-side thyristor (510) is not turned off, a problem with circulating current may occur.

[0074] Referring to FIGS. 3 to 5, the first commercial power side thyristor (510) and the second commercial power side thyristor (530) are connected in reverse parallel to each other and conduct alternately, thereby supplying power supplied from the commercial power source (10) to the UPS load (A2) over the entire AC cycle.

[0075] Additionally, a second circuit breaker (CB2) may be installed in the power line connecting the first node (N1) and the commercial power side thyristor (50). The second circuit breaker (CB2) remains closed under normal conditions, thereby forming a path through which AC power supplied from the commercial power source (10) is supplied to the UPS load (A2) via the commercial power side thyristor (50). Furthermore, it may trip when an overcurrent or short circuit occurs in the commercial power side thyristor (50) or the UPS load (A2), thereby protecting the system of the commercial power source (10) and the commercial power side thyristor (50).

[0076] The inverter-side thyristor (60) is located on the power line connecting the output side of the inverter (30) and the UPS load (A2) and is configured to provide a power path so that power stored in the power storage unit (40) is supplied to the UPS load (A2) when an event occurs. The inverter-side thyristor (60) is normally shut off, but when an event occurs, it becomes conductive to form a path through which AC power supplied from the power storage unit (40) and converted by the inverter (30) is supplied to the UPS load (A2). Below, the power path supplied to the UPS load (A2) through the power storage unit (40), the inverter (30), and the inverter-side thyristor (60) is set as the 'second supply path (P3)'. The first supply path (P2) and the second supply path (P3) can be selectively activated. More specifically, the first supply path (P2) is activated during normal operation, and the second supply path (P3) can be activated when an event occurs.

[0077] Additionally, the inverter-side thyristor (60) may include a first inverter-side thyristor (610) and a second inverter-side thyristor (630).

[0078] The first inverter-side thyristor (610) is configured to conduct a positive polarity current flowing from the inverter (30) toward the UPS load (A2). The first inverter-side thyristor (610) is turned on when a gate signal is applied to the inverter-side thyristor (60) and a positive polarity voltage is applied, and can be turned off when the magnitude of the current flowing from the inverter (30) is lowered to below the third reference current. The third reference current may have the same value as the first reference current or may have a different value. The aforementioned third reference current is positive polarity.

[0079] The second inverter-side thyristor (630) is configured to conduct a negative polarity current flowing from the UPS load (A2) toward the inverter (30). The second inverter-side thyristor (630) receives a negative polarity voltage supplied from the inverter (30), and turns on when the inverter-side thyristor (60) receives a gate signal from the control unit (90). It can be turned off when the magnitude of the current flowing from the inverter (30) drops below the magnitude of the fourth reference current. The fourth reference current may have the same value as the second reference current or may have a different value. The aforementioned fourth reference current is negative polarity.

[0080] The power line of the commercial power side thyristor (50) and the power line of the inverter side thyristor (60) can be joined at the second node (N2) in front of the UPS load (A2) input terminal to form a single path. In some cases, the inverter side thyristor (60) is characterized by not turning on immediately by receiving a gate signal from the control unit (90) when an event occurs, and details regarding this will be explained in the control unit (90).

[0081] In addition, a third circuit breaker (CB3) may be installed in the power line connecting the second node (N2) and the UPS load (A2). The third circuit breaker (CB3) can normally remain closed to form a path for power to be supplied to the UPS load (A2). Additionally, it can trip to protect the UPS load (A2) in the event of an overcurrent or short circuit accident.

[0082] The current detection unit (70) is configured to detect the magnitude and polarity information of the current flowing through the commercial power supply side thyristor (50). In the case of a three-phase system, the current detection unit (70) can detect the magnitude and polarity information of the current of each phase in real time. The information detected by the current detection unit (70) can be transmitted to the control unit (90). The current detection unit (70) may be any configuration among various known current detection means, such as a shunt resistor, a current converter, or a Hall sensor.

[0083] The voltage detection unit (80) is configured to detect a power outage or abnormal state of the commercial power supply (10) and to detect the voltage magnitude and polarity information of the commercial power supply (10). In the case of a three-phase system, the voltage detection unit (80) can detect the voltage magnitude and polarity information of each phase in real time. The information detected by the voltage detection unit (80) can be transmitted to the control unit (90). The voltage detection unit (80) may be any configuration among various known voltage detection means, such as a resistor voltage divider or a voltage converter, for example.

[0085] Figure 7 is a block diagram of the control unit.

[0087] Referring to FIGS. 3 to 5 and FIG. 7, the control unit (90) is configured to control gate signals applied to the commercial power side thyristor (50) and the inverter side thyristor (60) based on information received from the current detection unit (70) and / or the voltage detection unit (80). To this end, the control unit (90) may include an event judgment module (910), a polarity judgment module (920), a first control module (930), a current magnitude comparison module (940), and a second control module (950).

[0088] The event determination module (910) is configured to determine whether an event has occurred based on current information and / or voltage information received from the current detection unit (70) and / or the voltage detection unit (80). For example, the event determination module (910) may determine that a power outage has occurred if the voltage magnitude of the commercial power supply (10) detected by the voltage detection unit (80) drops below a preset reference value. Alternatively, the event determination module (910) may determine that a power outage has occurred if the frequency of the voltage supplied from the commercial power supply (10) deviates from a preset normal range.

[0089] The polarity determination module (920) is configured to determine whether the polarity of the voltage of the commercial power supply (10) and the current flowing through the commercial power supply side thyristor (50) matches when an event occurs. For example, the polarity determination module (920) can determine whether the polarity of the voltage of the commercial power supply (10) and the current flowing through the commercial power supply side thyristor (50) matches when the event is determined by the event determination module (910), and in the case of a three-phase system, it can determine whether the polarity of the voltage and current of each phase matches.

[0090] The first control module (930) is configured such that when the polarity determination module (920) determines that the voltage of the commercial power supply (10) and the polarity of the current flowing through the commercial power supply side thyristor (50) match, it immediately removes the gate signal applied to the commercial power supply side thyristor (50) and applies the gate signal to the inverter side thyristor (60). When an event occurs in the section where the polarity of the voltage and current of the commercial power supply side thyristor (50) match, the current rapidly decreases to a level lower than the first reference current or the second reference current, so even if the inverter side thyristor (60) is immediately turned on, no problem with circulating current occurs.

[0091] The current magnitude comparison module (940) is configured to compare the magnitude of the current flowing through the commercial power side thyristor (50) with the magnitude of the corresponding reference current among the first reference current and the second reference current when it is determined by the polarity determination module (920) that the voltage of the commercial power supply (10) and the polarity of the current flowing through the commercial power side thyristor (50) are inconsistent. The comparison of current magnitudes can be performed by a comparator, and as an example, by a hardware comparator (CMPSS). A hardware comparator is a subsystem embedded as hardware in a digital control processor that compares two input values ​​in real time and outputs the result, and has the advantage of operating at a significantly faster response speed compared to a software processing method. In the case of a software processing method, values ​​are sampled and compared every preset control cycle (e.g., tens to hundreds of μs), so there is a limitation in that it cannot immediately respond to current changes occurring within the control cycle. In contrast, the hardware comparator (CMPSS) operates with a hardware clock cycle (e.g., several nanoseconds) that is significantly shorter than the software control cycle and directly compares input values, so it has the advantage of being able to detect changes in current with a significantly faster response speed compared to the software processing method.

[0092] The second control module (950) is configured to immediately turn on the inverter-side thyristor (60) when the current magnitude flowing through the commercial power side thyristor (50) is determined by the current magnitude comparison module (940) to have a value less than or equal to the corresponding reference current magnitude between the first reference current and the second reference current. Therefore, the present invention is characterized by immediately turning on the inverter-side thyristor (60) when an event occurs in a specific section where the polarity of the voltage and current of the commercial power side thyristor (50) is mismatched, thereby preventing the generation of a circulating current, and turning on the inverter-side thyristor (60) after confirming that the turn-off condition of the commercial power side thyristor (50) is satisfied. Accordingly, by setting the switching time to the level of a half-cycle of the AC power source as in the prior art, it is possible to prevent in advance the occurrence of a power outage section in which power is not supplied to the UPS load (A2) during the switching time due to the switching time being excessively long. The second control module (950) does not apply a gate signal to the inverter-side thyristor (60) when the magnitude of the current flowing through the commercial power-side thyristor (50) has a value exceeding the magnitude of the reference current (first reference current or second reference current).

[0094] FIG. 8 is a graph showing the commercial power current during STS switching operation under inductive load conditions; FIG. 9 is a graph showing the inverter current during STS switching operation under inductive load conditions.

[0096] As described above, when the UPS load (A2) is an inductive load, a phase difference between the voltage of the commercial power supply (10) and the current of the UPS load (A2) may cause a section in which the polarity of the voltage and the current differs (see FIG. 2a). In the case of the STS control system (1) according to one embodiment of the present invention, since the inverter-side thyristor (60) is turned on after the turn-off of the commercial power supply-side thyristor (50) is completed, the commercial power supply-side thyristor (50) and the inverter-side thyristor (60) do not conduct at the same time during the switching process. Referring to FIGS. 8 and 9, it can be seen that at the time of completion of the turn-off of the commercial power supply-side thyristor (50) (Ta; approximately 0.0854 seconds), the commercial power supply-side current (I3) and the inverter-side current (I4) exhibit normal current transition characteristics, and no overcurrent is generated due to circulating current.

[0098] Figure 10 is a flowchart of the STS control method of a commercial power priority supply type uninterruptible power supply.

[0100] Hereinafter, with reference to the attached drawings, an STS control method (S1; hereinafter referred to as the 'STS control method') of a commercial power priority supply type uninterruptible power supply device according to one embodiment of the present invention will be described in detail. The following STS control method (S1) will be described from the perspective of a control unit (90).

[0102] Referring to FIG. 10, current information and / or voltage information of the commercial power side thyristor (50) can be received first (S10). More specifically, after the current detection unit (70) obtains current information flowing through the commercial power side thyristor (50) and the voltage detection unit (80) obtains voltage information of the commercial power (10), the current information and the voltage information can be transmitted to the control unit (90). For example, the current information may include current magnitude and polarity information, and the voltage information may include voltage magnitude and polarity information. In addition, in the case of a three-phase system, current information and / or voltage information for each phase can be received in step S10.

[0103] Subsequently, it can be determined whether an event has occurred based on the current information and / or voltage information obtained in step S10 (S20). For example, if the voltage magnitude of the commercial power supply (10) obtained in step S10 drops below a preset reference value or the voltage frequency deviates from a preset normal range, it may be determined that an event has occurred, but there are no separate limitations on the method of determination. If it is determined in step S20 that no event has occurred, the process returns to step S10, and if it is determined that an event has occurred, the process proceeds to step S30.

[0104] If an event is determined to occur in step S20, it can be determined whether the polarity of the voltage of the commercial power supply (10) and the current flowing through the commercial power supply side thyristor (50) matches (S30). In the case of a three-phase system, it can be determined whether the polarity of the voltage and current of each phase matches.

[0105] In step S30, if it is determined that the voltage of the commercial power supply (10) and the polarity of the current flowing through the commercial power supply side thyristor (50) match, the gate signal applied to the commercial power supply side thyristor (50) can be removed, and the inverter side thyristor (60) can be turned on immediately (S40). In the case of a three-phase system, the gate signal of the commercial power supply side thyristor (50) of the phase in which the voltage and current polarity of the commercial power supply side thyristor (50) match is removed, and the inverter side thyristor (60) can be turned on immediately.

[0106] In step S30, if it is determined that the voltage of the commercial power supply (10) and the polarity of the current flowing through the commercial power supply side thyristor (50) are mismatched, the gate signal applied to the commercial power supply side thyristor (50) can be removed (S50). For example, if the UPS load (A2) is an inductive load, it should be noted that even if the gate signal applied to the commercial power supply side thyristor (50) is removed in step S50, the commercial power supply side thyristor (50) is not immediately turned off in the section where the polarity of the voltage and current of the commercial power supply side thyristor (50) is mismatched. Therefore, in step S50, the inverter side thyristor (60) is not immediately turned on. In the case of a three-phase system, step S50 can be performed for each phase.

[0107] After step S50, the magnitude of the current flowing through the commercial power side thyristor (50) can be compared with the magnitude of the corresponding reference current among the first reference current or the second reference current by a comparator (S60). Through step S60, it can be confirmed whether the commercial power side thyristor (50) satisfies the turn-off condition. In the case of a three-phase system, step S60 can be performed for each phase. If, in step S60, the current flowing through the commercial power side thyristor (50) has a value greater than the corresponding reference current, step S60 is repeated until the current flowing through the commercial power side thyristor (50) has a magnitude less than or equal to the corresponding reference current.

[0108] In step S60, if the current flowing through the commercial power side thyristor (50) has a magnitude less than or equal to the corresponding reference current, the inverter side thyristor (60) can be turned on (S70). That is, by turning on the inverter side thyristor (60) after it is confirmed that the commercial power side thyristor (50) has been turned off through step S70, it is possible to prevent the occurrence of circulating current and the switching time from becoming excessively long. In the case of a three-phase system, step S70 can be performed for each phase.

[0110] The above detailed description is illustrative of the present invention. Furthermore, the foregoing describes preferred embodiments of the present invention, and the present invention may be used in various other combinations, modifications, and environments. That is, modifications or alterations are possible within the scope of the concept of the invention disclosed herein, the scope equivalent to the foregoing disclosure, and / or the scope of the art or knowledge. The foregoing embodiments describe the best state for implementing the technical concept of the present invention, and various modifications required in specific fields of application and uses of the present invention are also possible. Therefore, the above detailed description of the invention is not intended to limit the present invention to the disclosed embodiments. Explanation of the symbols

[0112] 1: STS control system for commercial power priority uninterruptible power supply 10 : Commercial power 20 : Converter 30 : Inverter 40 : Power storage unit 50: Commercial power side thyristor 510: First commercial power side thyristor 530: Second commercial power side thyristor 60: Inverter-side thyristor 610: 1st inverter-side thyristor 630: Second inverter-side thyristor 70: Current detector 80: Voltage detector 90 : Control unit 910: Event determination module 920: Polarity determination module 930: 1st control module 940: Current magnitude comparison module 950 : 2nd control module A1: Commercial power load A2: UPS load CB1: 1st circuit breaker CB2: 2nd circuit breaker CB3: Third circuit breaker P1: Charging path P2: First supply path P3: Second supply route N1: 1st node N2: 2nd node S1: STS control method for commercial power priority supply type uninterruptible power supply

Claims

Claim 1 A converter that converts AC power supplied from a commercial power source into DC power; a power storage unit that stores DC power converted by the converter; an inverter that converts DC power stored in the power storage unit into AC power; a commercial power-side thyristor located between a first node and a UPS load in a path branched from a first node where a power line connecting the output side of the commercial power source and the input side of the converter is located; an inverter-side thyristor located in a power line connecting the output side of the inverter and the UPS load; a current detection unit that detects the current flowing through the commercial power-side thyristor in real time; a voltage detection unit that detects the voltage of the commercial power source in real time; and a control unit that controls a gate signal applied to the commercial power-side thyristor and the inverter-side thyristor based on the current detected by the current detection unit and the voltage detected by the voltage detection unit; wherein the control unit includes an event determination module that determines whether an event occurs based on the voltage information detected by the voltage detection unit. An STS control system for a commercial power priority supply type uninterruptible power supply, characterized by comprising: a polarity determination module that determines whether the polarity of the voltage of the commercial power supply and the current flowing through the commercial power side thyristor matches when the above event occurs; and a first control module that, when it is determined that the polarity of the voltage of the commercial power supply and the current flowing through the commercial power side thyristor matches, removes the gate signal applied to the commercial power side thyristor and immediately applies a gate signal to the inverter side thyristor. Claim 2 delete Claim 3 delete Claim 4 A converter that converts AC power supplied from a commercial power source into DC power; a power storage unit that stores DC power converted by the converter; an inverter that converts DC power stored in the power storage unit into AC power; a commercial power-side thyristor located between a first node and a UPS load in a path branched from a first node where a power line connecting the output side of the commercial power source and the input side of the converter is located; an inverter-side thyristor located in a power line connecting the output side of the inverter and the UPS load; a current detection unit that detects the current flowing through the commercial power-side thyristor in real time; a voltage detection unit that detects the voltage of the commercial power source in real time; and a control unit that controls a gate signal applied to the commercial power-side thyristor and the inverter-side thyristor based on the current detected by the current detection unit and the voltage detected by the voltage detection unit; wherein the control unit includes an event determination module that determines whether an event occurs based on the voltage information detected by the voltage detection unit. An STS control system for a commercial power priority supply type uninterruptible power supply, further comprising: a polarity determination module that determines whether the polarity of the voltage of the commercial power supply and the current flowing through the commercial power side thyristor matches when the above event occurs; and a current magnitude comparison module that compares the magnitude of the current flowing through the commercial power side thyristor with the magnitude of a reference current when it is determined that the polarity of the voltage of the commercial power supply and the current flowing through the commercial power side thyristor do not match. Claim 5 An STS control system for a commercial power priority supply type uninterruptible power supply, characterized in that, in paragraph 4, the comparison of the magnitude of the current flowing through the commercial power side thyristor and the magnitude of the reference current is performed by a hardware comparator. Claim 6 In claim 4, the control unit further comprises a second control module that immediately turns on the inverter-side thyristor when the magnitude of the current flowing through the commercial power-side thyristor has a value less than or equal to the reference current magnitude; characterized in that it is an STS control system of a commercial power priority supply type uninterruptible power supply. Claim 7 In claim 6, the STS control system of a commercial power priority supply type uninterruptible power supply is characterized in that the second control module does not apply a gate signal to the inverter-side thyristor when the magnitude of the current flowing through the commercial power side thyristor has a value exceeding the reference current magnitude. Claim 8 An STS control system for a commercial power priority supply type uninterruptible power supply, characterized in that, in any one of claims 1 and 4 to 7, the commercial power side thyristor comprises: a first commercial power side thyristor that supplies a current in the positive polarity direction from the commercial power source to the UPS load; and a second commercial power side thyristor that supplies a current in the negative polarity direction from the commercial power source to the UPS load. Claim 9 In claim 8, the STS control system of a commercial power priority supply type uninterruptible power supply is characterized by comprising: a first inverter-side thyristor that supplies current in the positive polarity direction from the inverter to the UPS load; and a second inverter-side thyristor that supplies current in the negative polarity direction from the inverter to the UPS load. Claim 10 An STS control system for a commercial power priority supply type uninterruptible power supply, characterized by further comprising: a first circuit breaker installed in a power line connecting the output side of the commercial power supply and the input side of the converter in any one of claims 1 and 4 to 7; a second circuit breaker installed in a power line connecting the first node and the commercial power side thyristor; and a third circuit breaker installed in a power line connecting the second node, which is the junction point of the commercial power side thyristor and the inverter side thyristor, and the input side of the UPS load. Claim 11 A method for controlling an STS of a commercial power priority supply type uninterruptible power supply by an STS control system of a commercial power priority supply type uninterruptible power supply according to claim 7, comprising: a step of determining whether an event occurs based on voltage information detected by a voltage detection unit; a step of determining whether the polarity of the voltage of the commercial power and the current flowing through the commercial power side thyristor matches when an event occurs; and a step of removing the gate signal applied to the commercial power side thyristor and immediately turning on the inverter side thyristor when the polarity of the voltage of the commercial power and the current flowing through the commercial power side thyristor matches. Claim 12 A method for controlling an STS of a commercial power priority supply type uninterruptible power supply, further comprising: a step of removing a gate signal applied to the commercial power side thyristor when the voltage of the commercial power supply and the polarity of the current flowing through the commercial power side thyristor are mismatched in claim 11; a step of comparing the magnitude of the current flowing through the commercial power side thyristor with the magnitude of a reference current; and a step of immediately turning on the inverter side thyristor when the magnitude of the current flowing through the commercial power side thyristor is less than or equal to the magnitude of the reference current. Claim 13 STS control method of a commercial power priority supply type uninterruptible power supply, characterized by further including the step of not applying a gate signal to the inverter-side thyristor when the magnitude of the current flowing through the commercial power side thyristor exceeds the magnitude of the reference current in claim 12.

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