Circuit protection device and distributed energy supply system

Abstract

The present invention relates to the field of circuit protection technology, and specifically to a circuit protection device and a distributed energy supply system. The device includes a reverse power detection unit, whose input end is connected to the current of the energy supply unit to be protected, for detecting whether the power is reversed; the energy supply unit to be protected is used to run in parallel with other power supply units; a voltage disconnection detection unit, whose input end is connected to the voltage of the energy supply unit to be protected, for detecting whether the voltage is normal; a logic processing circuit having a first logic AND unit; the input end of the first logic AND unit is respectively connected to the output end of the reverse power detection unit and the voltage disconnection detection unit, and the output end of the first logic AND unit is connected to the circuit breaker unit of the energy supply unit to be protected; the circuit breaker unit is used to control the on and off of the energy supply unit to be protected. When reverse power occurs in the energy supply unit to be protected, the logic processing circuit controls the circuit breaker unit to act to ensure that the energy supply unit to be protected does not supply power to other power supply units.

Description

Technical Field

[0001] The present invention relates to the field of circuit protection technology, and in particular to a circuit protection device and a distributed energy supply system. Background Art

[0002] Distributed energy supply refers to the cascade utilization of energy through the trigeneration of cooling, heating and electricity, with a comprehensive energy utilization efficiency of more than 70%, and the realization of modern energy supply methods near the load center. Compared with the traditional centralized energy system, distributed energy has the advantages of saving power transmission and distribution investment, improving energy utilization efficiency, flexible equipment start and stop, improving the reliability and safety of system energy supply, energy saving and environmental protection. According to the relationship with the power grid, the distributed energy system mainly includes four types: independent operation, grid-connected but not connected to the Internet, grid-connected and connected to the Internet, and all power generation is connected to the Internet.

[0003] In the past, most distributed energy supply systems were off-grid systems, that is, isolated grids operated independently and used their own electricity. However, since the self-generated electricity may not be enough to provide users with use, the operation of this system is unstable. Therefore, the distributed energy supply system that is connected to the grid but not on the grid is commonly used.

[0004] Since the distributed energy supply system that is connected to the grid but not to the grid involves the connection of energy power supply to the municipal power grid, if there is a problem with the energy power supply to the municipal power grid, the instability of the energy power supply or other problems will affect the municipal power supply, thereby causing instability in the entire distributed energy supply system. Summary of the invention

[0005] In view of this, an embodiment of the present invention provides a circuit protection device and a distributed energy supply system to solve the problem of instability of the distributed energy supply system.

[0006] According to a first aspect, an embodiment of the present invention provides a circuit protection device, comprising:

[0007] A reverse power detection unit, whose input end is connected to the current of the energy supply unit to be protected, for detecting whether the power is reversed; wherein the energy supply unit to be protected is used for grid-connected operation with other power supply units;

[0008] A voltage disconnection detection unit, whose input terminal is connected to the voltage of the energy supply unit to be protected, for detecting whether the voltage is normal;

[0009] A logic processing circuit comprises a first logic AND unit; wherein the input end of the first logic AND unit is respectively connected to the output end of the reverse power detection unit and the voltage line break detection unit, and the output end of the first logic AND unit is connected to the circuit breaker unit of the energy supply unit to be protected; the circuit breaker unit is used to control the on and off of the energy supply unit to be protected.

[0010] The circuit protection device provided in an embodiment of the present invention connects the output ends of a reverse power detection unit and a voltage disconnection detection unit to a first logic AND unit, and detects whether reverse power occurs (i.e., whether the current is reversed) when the voltage of the energy supply unit to be protected is normal; when reverse power occurs in the energy supply unit to be protected, the logic processing circuit controls the circuit breaker unit to operate, so that the energy supply unit to be protected is disconnected, so as to ensure that the energy supply unit to be protected does not supply power to other power supply units, thereby enhancing the stability of the distributed energy supply system subsequently formed by the energy supply unit to be protected and the circuit protection device.

[0011] In combination with the first aspect, in a first implementation of the first aspect, the logic processing circuit further includes:

[0012] The first delay unit has an input end connected to the output end of the first logic unit, and an output end of the delay unit connected to the disconnection unit.

[0013] The circuit protection device provided in the embodiment of the present invention has a first delay unit arranged between the output end of the first logic AND unit and the circuit breaker unit, which is used to control the action of the circuit breaker unit by delaying for a period of time after the reverse power occurs. This can prevent the action of the circuit breaker unit caused by the reverse power caused by the volatility of the energy supply unit to be protected, avoid the frequent action of the circuit breaker unit, and further ensure the stability of the distributed energy supply system formed subsequently.

[0014] In combination with the first aspect, in a second implementation of the first aspect, the logic processing circuit further includes a second logic AND unit and a third logic AND unit; wherein the circuit protection device further includes:

[0015] The first frequency action element and the second frequency action element are respectively connected to the energy supply unit to be protected, and are used to output corresponding logic signals when detecting that the frequency in the energy supply unit to be protected is less than the first frequency or the second frequency;

[0016] A first logic OR unit, whose input ends are respectively connected to the frequency of the energy supply unit to be protected and the detection result of the first parameter, wherein the first parameter includes voltage or current; the output end of the first logic OR unit and the output end of the first frequency action element are respectively connected to the second logic AND unit, the output end of the first logic OR unit and the output end of the second frequency action element are respectively connected to the third logic AND unit; the second logic AND unit and the third logic AND unit are respectively connected to the circuit breaker unit.

[0017] The circuit protection device provided in an embodiment of the present invention adopts a first frequency action element and a second frequency action element to realize two-stage low-frequency disconnection. When a low-frequency fault is detected in the energy supply system to be protected, the action of the circuit breaker unit is controlled to ensure the reliability of the distributed energy supply system formed subsequently.

[0018] In combination with the second implementation of the first aspect, in a third implementation of the first aspect, the logic processing circuit further includes:

[0019] A second delay unit is connected between the second logic unit and the circuit breaker unit;

[0020] The third delay unit is connected between the third logic AND unit and the circuit breaker unit.

[0021] The circuit protection device provided by the embodiment of the present invention,

[0022] In combination with the second implementation of the first aspect, in a fourth implementation of the first aspect, the logic processing circuit further includes a fourth logic AND unit and a fifth logic AND unit; and the circuit protection device further includes:

[0023] The first voltage action element and the second voltage action element are respectively connected to the energy supply unit to be protected, and are used to detect the magnitude and direction of the voltage in the energy supply unit to be protected and output corresponding logic signals;

[0024] A second logic OR unit, whose input end is respectively connected to the detection result of the first parameter; the output end of the second logic OR unit and the output end of the first voltage action element are respectively connected to the fourth logic AND unit, and the output end of the second logic OR unit and the output end of the second voltage action element are respectively connected to the fifth logic AND unit; wherein the fourth logic AND unit and the fifth logic AND unit are respectively connected to the circuit breaker unit.

[0025] The circuit protection device provided in an embodiment of the present invention adopts a first voltage action element and a second voltage action element to realize two-stage low-voltage disconnection. When a low-voltage fault is detected in the energy supply system to be protected, the action of the circuit breaker unit is controlled to ensure the reliability of the distributed energy supply system formed subsequently.

[0026] In combination with the fourth implementation of the first aspect, in the fifth implementation of the first aspect, the input end of the second logic AND unit is also connected to the output end of the voltage break detection unit.

[0027] The circuit protection device provided by the embodiment of the present invention eliminates low voltage faults caused by voltage disconnection in combination with the detection result of the voltage disconnection detection unit during low voltage disconnection, thereby providing a guarantee for the subsequent troubleshooting of low voltage faults.

[0028] In combination with the fourth implementation of the first aspect, in a sixth implementation of the first aspect, the logic processing circuit further includes a sixth logic AND unit and a seventh logic AND unit; wherein the circuit protection device further includes:

[0029] The third frequency action element and the fourth frequency action element are respectively connected to the energy supply unit to be protected, and are used to output corresponding logic signals when detecting that the frequency in the energy supply unit to be protected is greater than the third frequency or the fourth frequency;

[0030] A third logic OR unit, whose input end is connected to the detection result of the frequency; the output ends of the third logic OR unit and the third frequency action element are respectively connected to the sixth logic AND unit; the output ends of the third logic OR unit and the fourth frequency action element are respectively connected to the seventh logic AND unit; the sixth logic AND unit and the seventh logic AND unit are respectively connected to the circuit breaker unit.

[0031] The circuit protection device provided in an embodiment of the present invention adopts a third frequency action element and a fourth frequency action element to realize two-stage over-frequency disconnection. When an over-frequency fault is detected in the energy supply system to be protected, the action of the circuit breaker unit is controlled to ensure the reliability of the distributed energy supply system formed subsequently.

[0032] In combination with any one of the second to fifth embodiments of the first aspect, in a seventh embodiment of the first aspect, the logic processing circuit further includes an eighth logic AND unit and a ninth logic AND unit; wherein the circuit protection device further includes:

[0033] The first current action element and the second current action element are respectively connected to the energy supply unit to be protected, and are used to detect the magnitude and direction of the current in the energy supply unit to be protected and output corresponding logic signals;

[0034] The tenth logic AND unit has its input ends respectively connected to the detection results of the frequency and the voltage of the energy supply unit to be protected; the output end of the tenth logic AND unit and the output end of the first current action element are connected to the eighth logic AND unit, and the output end of the tenth logic AND unit and the output end of the second current action element are connected to the ninth logic AND unit; the eighth logic AND unit and the ninth logic AND unit are respectively connected to the circuit breaker unit.

[0035] The circuit protection device provided in an embodiment of the present invention adopts a first current operating element and a second current operating element to realize two-stage overcurrent disconnection. When an overcurrent fault is detected in the energy supply system to be protected, the action of the circuit breaker unit is controlled to ensure the reliability of the distributed energy supply system formed subsequently.

[0036] According to a second aspect, an embodiment of the present invention further provides a distributed energy supply system, the system comprising:

[0037] Mains power supply unit and energy supply unit;

[0038] The circuit protection device according to the first aspect of the present invention or any one of the embodiments of the first aspect;

[0039] A grid-connected switch, wherein the energy supply unit is connected to the mains power supply unit through the grid-connected switch; wherein the circuit protection device is connected to the power output end of the energy supply unit, and the circuit protection device is used to control the action of the grid-connected switch so that the energy supply unit is connected to the grid but not to the Internet.

[0040] In the distributed energy supply system provided by the embodiment of the present invention, when reverse power occurs in the energy supply unit to be protected, the logic processing circuit controls the action of the grid-connected switch to disconnect the energy supply unit to be protected, thereby ensuring that the energy supply unit to be protected does not supply power to other power supply units, thereby ensuring the stability of the distributed energy supply system.

[0041] In combination with the second aspect, in the first implementation of the second aspect of the present invention, the energy supply unit also includes: a power supply circuit that supplies power to the backup power supply. BRIEF DESCRIPTION OF THE DRAWINGS

[0042] In order to more clearly illustrate the specific implementation methods of the present invention or the technical solutions in the prior art, the drawings required for use in the specific implementation methods or the description of the prior art will be briefly introduced below. Obviously, the drawings described below are some implementation methods of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying creative work.

[0043] Figure 1 is a structural block diagram of a circuit protection device according to an embodiment of the present invention;

[0044] Figure 2 is a structural block diagram of a circuit protection device according to an embodiment of the present invention;

[0045] Figure 3 is a structural block diagram of a circuit protection device according to an embodiment of the present invention;

[0046] Figure 4 is a specific schematic structural block diagram of a circuit protection device according to an embodiment of the present invention;

[0047] Figure 5 is a structural block diagram of a circuit protection device according to an embodiment of the present invention;

[0048] Figure 6 is a specific schematic structural block diagram of a circuit protection device according to an embodiment of the present invention;

[0049] Figure 7 is a structural block diagram of a circuit protection device according to an embodiment of the present invention;

[0050] Figure 8 is a specific schematic structural block diagram of a circuit protection device according to an embodiment of the present invention;

[0051] Fig. 9 is a structural block diagram of a circuit protection device according to an embodiment of the present invention;

[0052] Fig.10 is a specific schematic structural block diagram of a circuit protection device according to an embodiment of the present invention;

[0053] Fig.11 is a structural block diagram of a distributed energy supply system according to an embodiment of the present invention;

[0054] Fig.12 It is a specific schematic structural block diagram of a distributed energy supply system according to an embodiment of the present invention. DETAILED DESCRIPTION

[0055] In order to make the purpose, technical solution and advantages of the embodiments of the present invention clearer, the technical solution in the embodiments of the present invention will be clearly and completely described below in conjunction with the drawings in the embodiments of the present invention. Obviously, the described embodiments are part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative work are within the scope of protection of the present invention.

[0056] It should be noted that the energy supply unit to be protected described in the embodiment of the present invention is used to connect to the grid with other energy supply units to supply power to the load. The energy supply unit to be protected is connected to the grid but not connected to the grid. Therefore, the operating state of the energy supply unit to be protected needs to be detected during operation. When an abnormality occurs, corresponding actions need to be taken in time to ensure the stability and reliability of the entire power supply system.

[0057] The detection of the operating status of the energy supply unit to be protected is realized by a circuit protection device, the input of which is taken from the secondary three-phase current of the connecting line TA of the energy supply unit to be protected and the secondary three-phase voltage of the bus TV on the device side. The circuit protection device collects the voltage and current signals at the output end of the energy supply unit to be protected and performs corresponding detection on it to determine whether the energy supply unit to be protected is normal. For example, when the frequency, voltage, etc. drop due to a power grid fault, or other faults occur, it is necessary to disconnect the energy supply unit to be protected to prevent the expansion of the accident.

[0058] An embodiment of the present invention provides a circuit protection device, such as Figure 1 As shown, the circuit protection device includes a reverse power detection unit 110, a voltage disconnection detection unit 120, and a logic processing circuit 130. The output end of the reverse power detection unit 110 and the output end of the voltage disconnection detection unit 120 are connected to the input end of the logic processing circuit; that is, the output signals of the reverse power detection unit 110 and the voltage disconnection detection unit 120 are processed by the logic processing circuit and then output to the disconnection unit 140 to control the disconnection unit 140.

[0059] Specifically, the voltage disconnection detection unit 120 is connected to the voltage of the energy supply unit to be protected to detect whether the voltage is normal. The voltage disconnection detection unit 120 can be a voltage transformer or other voltage detection unit. The specific structure of the voltage disconnection detection unit 120 is not limited in any way, and it only needs to ensure that it can detect whether the voltage of the energy supply unit to be protected is abnormal.

[0060] For example, when the voltage disconnection detection unit 120 detects that the output voltage of the energy supply unit to be protected is normal, it outputs a logic signal "1"; when the voltage disconnection detection unit 120 detects that the output voltage of the energy supply unit to be protected is abnormal, it outputs a logic signal "0".

[0061] If the voltage disconnection detection unit 120 detects that the output voltage of the energy supply unit to be protected is normal, it outputs a logic signal "0"; when the voltage disconnection detection unit 120 detects that the output voltage of the energy supply unit to be protected is abnormal, it outputs a logic signal "1"; then, a logic NOT gate needs to be connected between the output end of the voltage disconnection detection unit 120 and the logic processing circuit 130.

[0062] The input end of the reverse power detection unit 110 is connected to the current of the energy supply unit to be protected, so as to detect whether the power is reversed. Since the power depends on the voltage and current output by the energy supply unit to be protected, whether the power is reversed is not only related to the voltage, but also to the current. Therefore, a first logic and unit 131 is also provided in the logic processing circuit 130, and the input end distribution of the first logic and unit 131 is connected to the output end of the reverse power detection unit 110 and the voltage disconnection detection unit 120. When one of the two is abnormal, the first logic and unit 131 controls the circuit breaker unit 140 to operate and disconnect the energy supply unit to be protected from the power grid system. It can be seen that when the voltage disconnection detection unit 120 detects that the voltage at the output end of the energy supply unit to be protected is normal, the reverse power detection unit 110 only needs to detect whether the current at the output end of the energy supply unit to be protected is reversed to determine whether the power is reversed. When the circuit is reversed, the reverse power detection unit 110 can output a logic signal "0".

[0063] The reverse power detection unit 110 may be a reverse power relay or other detection units. For example, when it is necessary to detect whether the current of the energy supply unit to be protected is reversed, a current detection element may be used. In this embodiment, there is no restriction on the specific structure of the reverse power detection unit 110, and it is only necessary to ensure that it can detect whether the power at the output end of the energy supply unit to be protected is reversed.

[0064] The circuit protection device provided in this embodiment connects the output ends of the reverse power detection unit and the voltage line break detection unit to the first logic AND unit, and detects whether reverse power occurs (i.e., whether the current is reversed) when the voltage of the energy supply unit to be protected is normal; when reverse power occurs in the energy supply unit to be protected, the logic processing circuit controls the circuit breaker unit to operate, so that the energy supply unit to be protected is disconnected, so as to ensure that the energy supply unit to be protected does not supply power to other power supply units, thereby enhancing the stability of the distributed energy supply system subsequently formed by the energy supply unit to be protected and the circuit protection device.

[0065] As an optional implementation of this embodiment, Figure 2 As shown, the logic processing circuit 130 includes a first delay unit. The input end of the first delay unit is connected to the output end of the first logic unit 131, and the output end of the first delay unit is connected to the circuit breaker unit 140. The first delay unit can be a time relay, or other timing units, etc. When the first logic unit 131 confirms that the circuit breaker unit 140 needs to be controlled to act, its output signal is delayed for a period of time by the first delay unit before being output to the circuit breaker unit 140 to avoid misoperation.

[0066] A first delay unit is set between the output end of the first logic unit 131 and the circuit breaker unit 140, which is used to control the action of the circuit breaker unit 140 by delaying for a period of time after the reverse power occurs. This can prevent the action of the circuit breaker unit caused by the reverse power caused by the volatility of the energy supply unit to be protected, avoid the frequent action of the circuit breaker unit, and further ensure the stability of the distributed energy supply system formed subsequently.

[0067] In some optional implementations of this embodiment, the circuit protection device is also used to detect whether a low-frequency fault occurs in the energy supply unit to be protected. In this embodiment, two-stage low-frequency separation is taken as an example. Figure 3 As shown, the logic processing circuit 130 further includes a second logic AND unit 132 and a third logic AND unit 133. The circuit protection device includes a first frequency action element 150, a second frequency action element 160 and a first logic OR unit 170.

[0068] Specifically, the first frequency action element 150 and the second frequency action element 160 are respectively connected to the energy supply unit to be protected, and are used to output corresponding logic signals when it is detected that the frequency in the energy supply unit to be protected is less than the first frequency or the second frequency.

[0069] The first frequency action element 150 and the second frequency action element 160 are respectively arranged at different positions of the energy supply unit to be protected, and are used to detect the frequency of the electrical signal at different positions and output corresponding logic signals. That is, the first frequency action element 150 and the second frequency action element 160 can also be called a low-frequency first-stage element and a low-frequency second-stage element. Among them, the working principles of the first frequency action element 150 and the second frequency action element 160 are similar, and the working principle is described below only by taking the first frequency action element 150 as an example.

[0070] The first frequency action element 150 can detect whether the frequency in the electrical signal is lower than the first frequency through a hardware circuit, and output a logic signal to the logic processing circuit 130 when the frequency is lower than the first frequency, so as to control the operation of the circuit breaker unit 140; wherein the hardware circuit can be a signal analysis circuit (analyzing the frequency in the electrical signal) and a comparison circuit connected in series. The first frequency action element 150 can also be a processing chip. After the electrical signal is input into the processing chip, the processing chip analyzes and processes it to extract the frequency in the electrical signal, and compares the extracted frequency with the first frequency, and outputs a corresponding logic signal.

[0071] like Figure 3As shown, the circuit protection device further includes a first logic or unit 170, the input signal of the first logic or unit 170 is the frequency of the energy supply unit to be protected and the detection result of the first parameter, wherein the first parameter includes voltage or current. As described above, the input signal of the circuit protection device is the voltage or current at the output end of the energy supply unit to be protected, then after the voltage or current is input to the circuit protection device, the processing chip can be used to analyze the voltage or current signal to determine whether it is abnormal.

[0072] The purpose of using the second logic AND unit 132 and the third logic AND unit 133 is to facilitate subsequent troubleshooting. Specifically, if the first frequency action element 150 does not detect an abnormality, and the second logic AND unit 132 outputs a signal to control the disconnection unit 140 to disconnect, it can be determined that the fault is caused by the first logic OR unit 170.

[0073] The first frequency action element and the second frequency action element are used to realize two-stage low-frequency disconnection. When a low-frequency fault is detected in the energy supply system to be protected, the action of the circuit breaker unit is controlled to ensure the reliability of the distributed energy supply system formed subsequently.

[0074] As an optional implementation of this embodiment, Figure 4 As shown, the logic processing circuit 130 also includes a second delay unit and a third delay unit. The second delay unit is arranged between the second logic AND unit 132 and the circuit breaker unit 140, and the third delay unit is arranged between the third logic AND unit 133 and the circuit breaker unit 140. The working principle of the second delay unit and the third delay unit is the same as that of the first delay unit. For details, please refer to the relevant description of the first delay unit above, which will not be repeated here. It should be noted that the specific delay time of the second delay unit and the third delay unit can be specifically set according to the actual situation, and no limitation is made here.

[0075] For example, Figure 4 As shown, the input signal of the first logic OR unit 170 outputs a corresponding action signal when one of the following conditions is met. That is:

[0076] (1) f<45Hz or f>55Hz;

[0077] (2) Low voltage Umax≤U l ;

[0078] (3) Low current Imax≤I l ;

[0079] (4) If the frequency slip -df / dt≥HC, the low-frequency decoupling is locked and self-maintained until the frequency returns to above the operating frequency, then the lock is released;

[0080] (5) Negative sequence voltage U2 ≥ 8V, indicating a short circuit fault.

[0081] Please combine Figure 4 , the setting instructions for the fixed value in the above judgment conditions:

[0082] (1) The frequency setting value should avoid the minimum frequency value during normal operation, which can generally be set to 48-49 Hz, and the action time is generally set to 0.2-0.5S.

[0083] (2) The low voltage lockout value can be 0.65 to 0.7 times the rated voltage.

[0084] (3) The frequency slip value shall not be less than 3Hz / S.

[0085] (4) The low current lockout value can be 0.1 to 0.15 times the rated current.

[0086] As Figure 4 In a specific application example of the illustrated embodiment, when any condition of the input signal is satisfied, the first logic OR unit 170 outputs a logic signal "0"; when the first frequency action element 150 or the second frequency action element 160 detects a frequency abnormality, it outputs a logic signal "0"; the first logic OR unit 170 and the first frequency action element 150 output logic signals to the logic processing circuit 130, and the logic processing circuit 130 performs a logic AND operation on the two input logic signals, and outputs the logic operation result to the circuit breaker unit 140 to control the operation of the circuit breaker unit 140.

[0087] As an optional implementation of this embodiment, the circuit protection device is also used to detect whether a low-voltage fault occurs in the energy supply unit to be protected. In this embodiment, two-stage low-voltage disconnection is taken as an example. Figure 5 As shown, the logic processing circuit 130 further includes a fourth logic AND unit 134 and a fifth logic AND unit 135. The circuit protection device includes a first voltage action element 180, a second voltage action element 190 and a second logic OR unit 200.

[0088] in, Figure 5 The working principle of the two-stage low-voltage splitter is similar to Figure 3 The working principle of the two-stage low-frequency stripping shown is similar, except that Figure 3 In the embodiment, the first frequency action element 150 and the second frequency action element 160 are connected to the logic processing circuit 130, and Figure 5The first voltage action element 180 and the second voltage action element 190 are connected to the logic processing circuit 130 ; and the input signal of the second logic OR unit 200 is different from the input signal of the first logic OR unit 170 .

[0089] Specifically, the working principles of the first voltage action element 180 and the second voltage action element 190 are similar to the working principles of the first frequency action element 150 and the second frequency action element 160. The difference is that the frequency action element detects the frequency in the electrical signal, while the voltage action element detects the magnitude and direction of the voltage in the electrical signal. Since the voltage action element also needs to detect the direction of the voltage in the electrical signal, a voltage direction element is also required in the voltage action element. The voltage direction element can be a voltage detection unit for detecting the direction of the voltage; it can also be other direction elements (for example, a unidirectional conductive device, when the device is turned on, it indicates that the voltage is in the first direction; when the device is turned off, it indicates that the voltage is in the second direction). For other details, please refer to Figure 3 The relevant description about the frequency action element in the illustrated embodiment will not be repeated here.

[0090] like Figure 5 As shown, the input signal of the second logic OR unit 200 is the detection result of the first parameter, that is, the detection result of the voltage or current. Specifically, the output end of the second logic OR unit 200 and the output end of the first voltage action element 180 are respectively connected to the fourth logic AND unit 134, and the output end of the second logic OR unit 200 and the output end of the second voltage action element 190 are respectively connected to the fifth logic AND unit 135; wherein the fourth logic AND unit 134 and the fifth logic AND unit 135 are respectively connected to the disconnection unit.

[0091] Optionally, the input terminal of the second logical OR unit 200 is also connected to the output terminal of the voltage break detection unit 120 .

[0092] For example, Figure 6 As shown, Figure 6 Shows Figure 5A specific application example of low-voltage parallel separation is shown. The input signal of the second logic OR unit 200 includes: the output signal of the voltage disconnection detection unit 120, the voltage action unit, the voltage slip action unit, the negative sequence voltage action unit and the low current action unit. Among them, the action basis of the voltage action unit is: the maximum voltage in the circuit is less than the preset voltage value; the action basis of the voltage slip action unit is: the voltage slip in the circuit is greater than the preset slip value; the action basis of the negative sequence voltage action unit is: the negative sequence voltage in the circuit is greater than the preset negative sequence voltage value; the action basis of the low current action unit is: the current in the circuit is less than the preset current value. The judgment of the maximum voltage, voltage slip, negative voltage and current in the circuit can be realized by a processing chip. After the processing chip processes the electrical signal, it obtains the corresponding judgment result, and inputs the judgment result into the second logic OR unit 200 for logical AND operation.

[0093] When the energy supply unit to be protected has both active power and reactive power shortages, if the voltage drops quickly, resulting in a reduction in active load, the frequency will drop very little or increase instead of drop, so low-voltage disconnection is required. That is, PT disconnection, low voltage, voltage slip, negative sequence voltage, and low current blocking elements are set in the input signal of the second logic OR unit 200 to ensure the reliability of low-voltage disconnection, and two-stage directional elements are set to ensure the selectivity of low-voltage disconnection.

[0094] The low-voltage decoupling is composed of two-stage low-voltage operating elements and locking elements. The power connection method is assumed to be 90° connection and started by phase. The directional element in the first voltage operating element has a voltage memory function to eliminate the dead zone of three-phase short-circuit faults in the vicinity.

[0095] Among them, the action equation of the voltage-actuated element is:

[0096] U ab ≤U dn and

[0097] or,

[0098] U bc ≤U dn and

[0099] or,

[0100] U ca ≤U dn and

[0101] t≥T n ;

[0102] Where: I a ,I b ,I c——Calculated value of three-phase current;

[0103] U ab , U bc , U ca ——Calculated value of three-phase phase-to-phase voltage;

[0104] ——U bc with I a , U ca with I b , U ab with I c The angle between

[0105] α——Power internal angle, which can be set to 0°, 30° or 60°.

[0106] U dn , T n (n=1,2)——respectively the first and second stage low voltage constants and their time constants.

[0107] Since the voltage disconnection detection unit (eg, voltage transformer) may cause malfunction of low voltage disconnection when detecting voltage abnormality, in low voltage fault disconnection, the input end of the second logic OR unit 200 is also connected to the output end of the voltage disconnection detection unit.

[0108] If the calculation shows that negative sequence voltage (3U2>8V) but no negative sequence current (3I2<0.1I e ) and each phase has current (0.06I e <I<1I e ), it is judged that the voltage transformer is disconnected. At this time, the voltage transformer disconnection alarm signal can be delayed for 10 seconds and automatically restored after the voltage returns to normal.

[0109] After the voltage slip element is actuated, the output is instantly locked and self-maintained until the voltage returns to above the set action voltage value.

[0110] In case of short circuit fault, the output is locked by negative sequence voltage; in addition, the output can be locked when the voltage is too low (the maximum phase-to-phase voltage is less than 20V) or the line load current is very small.

[0111] Among them, the setting instructions for low-voltage decoupling are as follows:

[0112] (1) The low voltage disconnection voltage setting value should avoid the minimum voltage value during normal operation. It can be set to ensure that the disconnection range has sufficient sensitivity coefficient. It is generally set to 0.6 to 0.8 times the rated operating voltage. The action time is generally set to 0.2 to 0.5S. When necessary, a directional element can be installed on the interconnection line to limit the low voltage disconnection range.

[0113] (2) The voltage slip can generally be 30~50V / S.

[0114] (3) The low current lockout value can be 0.1 to 0.15 times the rated current.

[0115] In some optional implementations of this embodiment, the circuit protection device is also used to detect whether an over-frequency fault occurs in the energy supply unit to be protected. In this embodiment, two-stage over-frequency disconnection is taken as an example. Figure 7 As shown, the logic processing circuit 130 further includes a sixth logic AND unit 136 and a seventh logic AND unit 137. The circuit protection device further includes a third frequency operating element 210 and a fourth frequency operating element 220.

[0116] Specifically, the third frequency action element 210 and the fourth frequency action element 220 are used to output corresponding logic signals when detecting that the frequency in the energy supply unit to be protected is greater than the third frequency or the fourth frequency. That is, when the frequency in the energy supply unit to be protected is greater than the third frequency, the third frequency action element 210 is actuated; when the frequency in the energy supply unit to be protected is greater than the fourth frequency, the fourth frequency action element 220 is actuated. The working principles of the third frequency action element 210 and the fourth frequency action element 220 are the same as those of the first frequency action element 150 and the second frequency action element 160, except for the basis of action. Among them, the basis for the action of the third frequency action element 210 and the fourth frequency action element 220 is that the frequency in the energy supply unit to be protected is greater than a certain frequency; and the basis for the action of the first frequency action element 150 and the second frequency action element 160 is that the frequency in the energy supply unit to be protected is less than a certain frequency. Therefore, for the remaining structural details of the third frequency action element 210 and the fourth frequency action element 220, please refer to Figure 3 The description of the first frequency operating element 150 and the second frequency operating element 160 in the illustrated embodiment will not be repeated here.

[0117] The input end of the third logic OR unit 230 is connected to the detection result of the frequency (for example, frequency slip, frequency size, etc.), wherein the output ends of the third logic OR unit 230 and the third frequency action element 210 are respectively connected to the sixth logic AND unit 136; the output ends of the third logic OR unit 230 and the fourth frequency action element 220 are respectively connected to the seventh logic AND unit 137; the sixth logic AND unit 136 and the seventh logic AND unit 137 are respectively connected to the circuit breaker unit.

[0118] The working principle of the two-stage over-frequency decoupling is similar to that of the above-mentioned two-stage under-frequency decoupling. The difference is that the input signal of the third logic OR unit 230 is different from the input signal of the first logic OR unit 170; the above-mentioned third frequency action element 210 and fourth frequency action element 220 are different from each other. Figure 3 The first and second frequency action elements in the embodiment have different action bases.

[0119] The input signal of the third logic OR unit 230 is as follows: Figure 8 As shown, it includes frequency magnitude and frequency slip. When the energy supply unit to be protected is disconnected from the main interconnection line of the distributed energy supply system, the frequency of the regional power grid may increase due to the inability to deliver power. For this reason, an over-frequency disconnection function is set in the circuit protection device. The circuit protection device is provided with a two-stage two-time limit over-frequency element. In order to prevent over-cutting of the unit, it can be locked through the frequency slip element. Among them, the locking is realized by the third logic or unit 230.

[0120] Optionally, a delay unit is provided between the sixth logic AND unit 136 and the disconnecting unit 140 , and between the seventh logic AND unit 137 and the disconnecting unit 140 , respectively.

[0121] Instructions for setting the over-frequency decoupling setting value:

[0122] The frequency setting value should avoid the highest frequency value during normal operation, and the delay time can be (0.2~5)S.

[0123] In some other optional implementations of this embodiment, the circuit protection device is also used to detect whether an overcurrent fault occurs in the energy supply unit to be protected. In this embodiment, a two-stage overcurrent disconnection is taken as an example. Fig. 9 As shown, the logic processing circuit 130 further includes an eighth logic AND unit 138 and a ninth logic AND unit 139. The circuit protection device further includes a first current action element 240, a second current action element 250 and a tenth logic AND unit 260.

[0124] The first current-operated element 240 and the second current-operated element 250 are respectively connected to the energy supply unit to be protected, and are used to detect the magnitude and direction of the current in the energy supply unit to be protected and output corresponding logic signals.

[0125] The working principle of the current action element (including the first current action element and the second current action element) is the same as Figure 5 The working principle of the voltage-operated element (including the first voltage-operated element and the second voltage-operated element) in the embodiment shown is similar. For details, please refer to Figure 5 The relevant description of the illustrated embodiment will not be repeated here.

[0126] Specifically, the input end of the tenth logic AND unit 260 is connected to the detection results of the frequency and the voltage of the energy supply unit to be protected. The output end of the tenth logic AND unit 260 and the output end of the first current action element 240 are connected to the eighth logic AND unit 138, the output end of the tenth logic AND unit 260 and the output end of the second current action element 250 are connected to the ninth logic AND unit 139, and the eighth logic AND unit 138 and the ninth logic AND unit 139 are connected to the disconnection unit 140 respectively.

[0127] Two-stage independent over-current disconnection is set to prevent overload of some small system interconnection lines after load transfer when the main system interconnection line is disconnected.

[0128] The protection is composed of three-phase overcurrent elements and phase-to-phase power directional elements, and can be started by low voltage and low frequency elements, with two-stage fixed values ​​and two-stage time limits. The directional elements, starting elements and overcurrent elements are all controlled by the processing chip.

[0129] There are three power direction elements, the power wiring method is 90° wiring and phase starting. The direction element has a voltage memory function to eliminate the dead zone of the three-phase short circuit fault in the vicinity.

[0130] The action equation of the current-operated element (including the first current-operated element and the second current-operated element) is:

[0131] I a ≥I gn and

[0132] or

[0133] I b ≥I gn and

[0134] or

[0135] I c ≥I gn and

[0136] t≥T n ;

[0137] Where: I a ,I b ,I c ——Calculated value of three-phase current;

[0138] U ab , U bc , U ca ——Calculated value of three-phase phase-to-phase voltage;

[0139] ——Ubc with I a , U ca with I b , U ab with I c The angle between

[0140] α——Power internal angle, which can be set to 0°, 15°, 30°, 45° or 60°.

[0141] I gn , T n (n=1,2)——respectively the first and second current constants and their time constants.

[0142] in, Fig.10 A logic block diagram of two-stage overcurrent decoupling is shown. Optionally, a delay unit is provided between the eighth logic AND unit 138 and the circuit breaker unit 140, and between the ninth logic AND unit 139 and the circuit breaker unit 140, respectively. The delay time of the delay unit can be specifically set according to actual conditions, and no limitation is made here.

[0143] Fig.10 The following are the instructions for setting the overcurrent release setting value:

[0144] The current setting value should be greater than the maximum load current of the line during normal operation and less than the stable allowable limit current. The disconnection time should be greater than the line backup protection action time.

[0145] In some optional implementations of this embodiment, the circuit protection device may also be provided with overvoltage disconnection and / or low current disconnection, etc., which will not be described in detail here.

[0146] The embodiment of the present invention also provides a distributed energy supply system, such as Fig.11 The system includes an energy supply unit 280 to be protected, other power supply units, a circuit protection device 290 and a grid-connected switch 270 .

[0147] Among them, the energy supply unit 280 to be protected is connected to other power supply units through the grid-connected switch 270, and is connected to the grid with other power supply units for operation. The circuit protection device 290 is connected to the power output end of the energy supply unit 280 to be protected, and is used to control the action of the grid-connected switch 270, so that the energy supply unit 280 to be protected is connected to the grid with other power supply units but not connected to the grid. The grid-connected but not connected to the grid: when the power load of the project is large and the amount of electricity generated by the distributed energy station supply system cannot meet the total demand of the factory power and other users within the project, it is necessary to download electricity from the grid to supplement the insufficient amount of electricity. At this time, it can be considered to adopt the form of grid-connected but not connected to the grid, giving priority to the use of electricity generated by the energy supply system, and supplementing the insufficient part from the Internet, that is, power access.

[0148] The energy supply unit 280 to be protected may be a gas supply unit, and other power supply units may be a municipal power grid, but the protection scope of the present invention is not limited thereto, and the energy supply unit to be protected and other power supply units may also be other types of power supply units.

[0149] Specifically, when the energy supply unit 280 to be protected is normal, the distributed energy supply system uses the energy supply unit 280 to be protected to supply power to the load; when the circuit protection device 290 detects that the energy supply unit 280 to be protected has an abnormality (for example, reverse power), the circuit protection device 290 controls the grid-connected switch to disconnect the energy supply unit 280 to be protected from the system.

[0150] In the distributed energy supply system provided in this embodiment, when reverse power occurs in the energy supply unit to be protected, the logic processing circuit controls the grid-connected switch to disconnect the energy supply unit to be protected, thereby ensuring that the energy supply unit to be protected does not supply power to other power supply units, thereby ensuring the stability of the distributed energy supply system.

[0151] As a specific application example of this embodiment, Fig.12 The following figure shows the application diagram of distributed energy supply system in hotel power supply system. Fig.12 The power generated by the energy supply unit to be protected is divided into two paths, one of which is provided to the load, and the other is connected to the backup power supply incoming switch, which is used for the backup power of the distributed energy supply system and the generator starting power supply to meet the requirements of daily inspection and maintenance and unit startup.

[0152] The energy supply unit 280 to be protected in the distributed energy supply system described in this embodiment is connected to the grid but not connected to the Internet. On the one hand, it can not only improve the stability and reliability of the operation of the energy supply unit to be protected in the distributed energy supply system; on the other hand, since it is not connected to the Internet, the power generation of the energy supply unit to be protected is all used by the hotel, which improves the economy of the hotel's electricity use and avoids the disturbance of the local power system caused by the online operation, thereby ensuring the safe and reliable operation of the power system.

[0153] Although the embodiments of the present invention have been described in conjunction with the accompanying drawings, those skilled in the art may make various modifications and variations without departing from the spirit and scope of the present invention, and such modifications and variations are all within the scope defined by the appended claims.

Claims

1. A circuit protection device, characterized in that: include: A reverse power detection unit, whose input end is connected to the current of the energy supply unit to be protected, for detecting whether the power is reversed; wherein the energy supply unit to be protected is used for grid-connected operation with other power supply units; A voltage disconnection detection unit, whose input terminal is connected to the voltage of the energy supply unit to be protected, for detecting whether the voltage is normal; A logic processing circuit, comprising a first logic AND unit; wherein the input end of the first logic AND unit is respectively connected to the output end of the reverse power detection unit and the voltage disconnection detection unit, and the output end of the first logic AND unit is connected to the circuit breaker unit of the energy supply unit to be protected; the circuit breaker unit is used to control the on and off of the energy supply unit to be protected; The logic processing circuit further includes a second logic AND unit and a third logic AND unit; wherein the circuit protection device further includes: The first frequency action element and the second frequency action element are respectively connected to the energy supply unit to be protected, and are used to output a corresponding logic signal when it is detected that the frequency in the energy supply unit to be protected is less than the first frequency or the second frequency. The first frequency action element and the second frequency action element are respectively arranged at different positions of the energy supply unit to be protected, and are used to detect the frequency of the electrical signal at different positions and output a corresponding logic signal; A first logic OR unit, whose input ends are respectively connected to the frequency of the energy supply unit to be protected and the detection result of the first parameter, wherein the first parameter includes voltage or current; the output end of the first logic OR unit and the output end of the first frequency action element are respectively connected to the second logic AND unit, the output end of the first logic OR unit and the output end of the second frequency action element are respectively connected to the third logic AND unit; the second logic AND unit and the third logic AND unit are respectively connected to the circuit breaker unit.

2. The device according to claim 1, characterized in that The logic processing circuit further includes: The first delay unit has an input end connected to the output end of the first logic unit, and an output end of the first delay unit connected to the disconnection unit.

3. The device according to claim 1, characterized in that The logic processing circuit further includes: A second delay unit is connected between the second logic unit and the circuit breaker unit; The third delay unit is connected between the third logic AND unit and the circuit breaker unit.

4. The device according to claim 1, characterized in that The logic processing circuit further includes a fourth logic AND unit and a fifth logic AND unit; the circuit protection device further includes: The first voltage action element and the second voltage action element are respectively connected to the energy supply unit to be protected, and are used to detect the magnitude and direction of the voltage in the energy supply unit to be protected and output corresponding logic signals; A second logic OR unit, whose input end is respectively connected to the detection result of the first parameter; the output end of the second logic OR unit and the output end of the first voltage action element are respectively connected to the fourth logic AND unit, and the output end of the second logic OR unit and the output end of the second voltage action element are respectively connected to the fifth logic AND unit; wherein the fourth logic AND unit and the fifth logic AND unit are respectively connected to the circuit breaker unit.

5. The device according to claim 4, characterized in that The input terminal of the second logic OR unit is also connected to the output terminal of the voltage disconnection detection unit.

6. The device according to claim 4, characterized in that The logic processing circuit further includes a sixth logic AND unit and a seventh logic AND unit; wherein the circuit protection device further includes: The third frequency action element and the fourth frequency action element are respectively connected to the energy supply unit to be protected, and are used to output corresponding logic signals when detecting that the frequency in the energy supply unit to be protected is greater than the third frequency or the fourth frequency; A third logic OR unit, whose input end is connected to the detection result of the frequency; the output ends of the third logic OR unit and the third frequency action element are respectively connected to the sixth logic AND unit; the output ends of the third logic OR unit and the fourth frequency action element are respectively connected to the seventh logic AND unit; the sixth logic AND unit and the seventh logic AND unit are respectively connected to the circuit breaker unit.

7. The device according to any one of claims 1 to 5, characterized in that The logic processing circuit further includes an eighth logic AND unit and a ninth logic AND unit; wherein the circuit protection device further includes: The first current action element and the second current action element are respectively connected to the energy supply unit to be protected, and are used to detect the magnitude and direction of the current in the energy supply unit to be protected and output corresponding logic signals; The tenth logic AND unit has its input ends respectively connected to the detection results of the frequency and the voltage of the energy supply unit to be protected; the output end of the tenth logic AND unit and the output end of the first current action element are connected to the eighth logic AND unit, and the output end of the tenth logic AND unit and the output end of the second current action element are connected to the ninth logic AND unit; the eighth logic AND unit and the ninth logic AND unit are respectively connected to the circuit breaker unit.

8. A distributed energy supply system, characterized in that: The system comprises: Energy supply units to be protected and other power supply units; The circuit protection device according to any one of claims 1 to 7; A grid-connected switch, wherein the energy supply unit to be protected is connected to the other power supply unit through the grid-connected switch; wherein the circuit protection device is connected to the power output end of the energy supply unit to be protected, and the circuit protection device is used to control the action of the grid-connected switch so that the energy supply unit to be protected is connected to the other power supply unit and does not operate on the grid.

9. The system according to claim 8, characterized in that The energy supply unit also includes: a power supply circuit for supplying power to the backup power supply.

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