Overload protection method for a solid state circuit breaker, solid state circuit breaker and power distribution system

Abstract

The present disclosure relates to an overload protection method for a solid state circuit breaker, the method comprising measuring a temperature of a power electronic switch in the solid state circuit breaker, detecting an overload current flowing through the solid state circuit breaker, determining an overload trip time of the solid state circuit breaker in dependence of the temperature and the overload current, and opening the power electronic switch after the trip time. Furthermore, the present disclosure relates to a solid state circuit breaker and a power distribution system.

Description

Technical Field

[0001] This disclosure relates to an overload protection method for a solid-state circuit breaker, a solid-state circuit breaker, and a power distribution system. Background Technology

[0002] Circuit breakers are widely used in power grid systems, especially in distribution systems. On one hand, when a load or line experiences overload, short circuit, or leakage, the circuit breaker can disconnect the line within a specified time, thus ensuring the safety of the load and the line. On the other hand, circuit breakers can also act as switches to connect and disconnect large electrical equipment, such as electric motors.

[0003] Traditional circuit breakers include thermal-magnetic circuit breakers and electronic circuit breakers. A thermal-magnetic circuit breaker is a purely mechanical type. When an overload occurs in the circuit, the current through the thermal-magnetic circuit breaker increases. The thermal element in the circuit breaker heats up, which in turn heats the bimetallic strip. The bimetallic strip is composed of different metals and therefore has different coefficients of thermal expansion. Therefore, when the temperature changes, the bimetallic strip deforms and bends. When the deformation reaches a certain degree, it triggers the free-tripping mechanism, causing the circuit breaker to trip.

[0004] Based on the purely mechanical structure of thermal-magnetic circuit breakers, their design and production require complex design and precise thermal adjustment processes. Also due to the structure of thermal-magnetic circuit breakers, their overload current operating error is relatively large; even thermal-magnetic circuit breakers of the same model are difficult to guarantee with identical tripping times. Furthermore, after a thermal-magnetic circuit breaker trips, manual reclosing is required to restore power.

[0005] Electronic circuit breakers do not use mechanical structures to control circuit breaker tripping. Instead, they use current transformers to collect the current magnitude and compare it with a set threshold. When the current exceeds the threshold, the electronic circuit breaker can send a signal to the electronic trip unit according to the set tripping delay time to execute the tripping action.

[0006] Electronic circuit breakers are designed strictly according to national standards or manufacturer-specified overload tripping curves, thus providing accurate tripping delay times for overload currents of corresponding magnitudes. However, a drawback of existing electronic circuit breakers is that they cannot account for the impact of ambient temperature on the load, wiring, and the circuit breaker itself. For example, if the tripping action continues at a predetermined threshold when the ambient temperature is too high, it may cause the load, wiring, and circuit breaker to overheat or even be damaged.

[0007] In the context of vigorously developing smart grids, intelligent circuit breaker equipment is indispensable. Intelligent circuit breaker equipment needs to meet the requirements of automatic disconnection and connection, and also needs to be able to automatically adjust to an appropriate overload tripping time based on the effects of overload current and temperature. Summary of the Invention

[0008] This disclosure provides an overload protection method for a solid-state circuit breaker, a solid-state circuit breaker, and a power distribution system incorporating the solid-state circuit breaker. According to the overload protection method and the solid-state circuit breaker of this disclosure, the overload tripping time can be adjusted not only according to the magnitude of the overload current but also according to temperature, thereby improving the protection of the load, the line, and the circuit breaker itself.

[0009] Embodiments of this disclosure provide an overload protection method for a solid-state circuit breaker, comprising: measuring the temperature of a power electronic switch in the solid-state circuit breaker, detecting an overload current flowing through the solid-state circuit breaker, determining an overload tripping time of the solid-state circuit breaker based on the temperature and the overload current, and disconnecting the power electronic switch after the tripping time has elapsed.

[0010] According to an embodiment of this disclosure, determining the overload tripping time of the solid-state circuit breaker based on the temperature and the overload current includes: adjusting a predetermined setting current value of the solid-state circuit breaker based on the temperature; determining the relationship between the overload tripping time and the overload current based on the adjusted setting current value; and determining the overload tripping time based on the overload current and the relationship between the overload tripping time and the overload current.

[0011] According to an embodiment of this disclosure, adjusting the predetermined setting current value of the solid-state circuit breaker based on the temperature includes: if the temperature is higher than a first threshold when the temperature rises, derating the predetermined setting current value of the solid-state circuit breaker based on the temperature.

[0012] According to an embodiment of this disclosure, adjusting the predetermined setting current value of the solid-state circuit breaker based on the temperature further includes: after the temperature exceeds the first threshold, if the temperature decreases to below the first threshold but above the second threshold, keeping the derating-adjusted setting current value unchanged; if the temperature decreases to below the second threshold, restoring the derating-adjusted setting current value to the predetermined setting current value.

[0013] According to an embodiment of this disclosure, when the temperature rises, if the temperature is higher than a first threshold, derating the predetermined setting current value of the solid-state circuit breaker based on the temperature includes: adding an increment to the temperature and derating the predetermined setting current value of the solid-state circuit breaker based on the temperature after the added increment, and / or adding a decrement to the predetermined setting current value and derating the predetermined setting current value based on the predetermined setting current value after the added decrement.

[0014] Embodiments of this disclosure provide a solid-state circuit breaker, comprising: a power electronic switch for switching on and off lines connected to the solid-state circuit breaker; a temperature measurement unit for measuring the temperature of the power electronic switch in the solid-state circuit breaker and transmitting the corresponding temperature signal to a processing unit; a current detection unit for detecting the overload current flowing through the solid-state circuit breaker and transmitting the corresponding overload current signal to the processing unit; the processing unit for determining the overload tripping time of the solid-state circuit breaker based on the temperature signal and the overload current signal, and sending a drive signal to the drive unit after the tripping time has elapsed; and a drive unit for disconnecting the power electronic switch based on the drive signal.

[0015] According to an embodiment of this disclosure, the processing unit adjusts a predetermined setting current value of the solid-state circuit breaker based on the temperature signal, and determines the relationship between the overload tripping time and the overload current based on the adjusted setting current value.

[0016] According to an embodiment of this disclosure, when the temperature rises, if the value of the temperature signal is higher than a first threshold, the processing unit derating the predetermined setting current value of the solid-state circuit breaker based on the value of the temperature signal.

[0017] According to an embodiment of this disclosure, after the value of the temperature signal exceeds the first threshold, if the temperature drops to below the first threshold but above the second threshold, the processing unit keeps the derating adjusted setting current value unchanged; if the value of the temperature signal drops to below the second threshold, the processing unit restores the derating adjusted setting current value to a predetermined setting current value.

[0018] Embodiments of this disclosure provide a power distribution system including a plurality of the aforementioned solid-state circuit breakers, wherein the adjusted setting current value of the solid-state circuit breaker closer to the power source is greater than the adjusted setting current value of the solid-state circuit breaker closer to the load.

[0019] Embodiments of this disclosure provide a multi-pole solid-state circuit breaker, comprising: a plurality of power electronic switches for switching multiple lines connected to the solid-state circuit breaker; a temperature measurement unit for measuring the temperature of the plurality of power electronic switches in the solid-state circuit breaker and transmitting the corresponding temperature signals to a processing unit; a current detection unit for detecting overload current flowing through the multiple lines of the solid-state circuit breaker and transmitting the corresponding overload current signals to the processing unit; the processing unit for determining the overload tripping time of the solid-state circuit breaker based on the temperature signal of the highest temperature and the overload current signal of the largest overload current, and sending a drive signal to the drive unit after the tripping time has elapsed; and the drive unit for disconnecting the plurality of power electronic switches based on the drive signal.

[0020] According to an embodiment of this disclosure, the processing unit adjusts a predetermined setting current value of the solid-state circuit breaker based on a temperature signal of the highest temperature among the temperatures, and determines the relationship between the overload tripping time and the maximum overload current based on the adjusted setting current value.

[0021] The overload protection method for solid-state circuit breakers disclosed herein allows for consideration of not only the magnitude of the overload current but also the influence of temperature on the power electronic switches within the circuit breaker when setting the overload tripping time. For example, when the operating temperature of the power electronic switches is also high due to higher ambient temperatures, the method disclosed herein can shorten the overload tripping time, thereby enabling faster tripping and preventing damage to the load equipment, lines, and the solid-state circuit breaker itself caused by the combined effects of high temperature and heat accumulation.

[0022] Furthermore, a distribution system with multiple solid-state circuit breakers according to this disclosure can achieve graded protection of load devices. In the event of an overload, only the solid-state circuit breaker closest to the fault location will operate, thus avoiding cascading tripping and minimizing the number of load devices affected by the fault. Attached Figure Description

[0023] To more clearly illustrate the technical solutions of the embodiments of this disclosure, the accompanying drawings used in the description of the embodiments will be briefly introduced below. Obviously, the drawings described below are merely some exemplary embodiments of this disclosure. For those skilled in the art, other drawings can be obtained based on these drawings without any creative effort.

[0024] Figure 1 A modular structure diagram of a solid-state circuit breaker according to an embodiment of the present disclosure is shown.

[0025] Figure 2A flowchart of an overload protection method for a solid-state circuit breaker according to an embodiment of the present disclosure is shown.

[0026] Figure 3 A three-dimensional graph showing the relationship between overload tripping time and temperature and load current according to an embodiment of the present disclosure is provided.

[0027] Figure 4 A flowchart illustrating an example method for determining the overload tripping time of a solid-state circuit breaker according to an embodiment of this disclosure is shown.

[0028] Figure 5 A surface plot showing the adjustment of the set current value with respect to temperature according to an embodiment of the present disclosure is illustrated.

[0029] Figure 6 A flowchart illustrating an example method for adjusting a predetermined setting current value of a solid-state circuit breaker according to an embodiment of the present disclosure is shown.

[0030] Figure 7 A schematic diagram of the structure of a power distribution system according to an embodiment of the present disclosure is shown. Detailed Implementation

[0031] To make the objectives, technical solutions, and advantages of this disclosure more apparent, exemplary embodiments according to this disclosure will now be described in detail with reference to the accompanying drawings. Obviously, the described embodiments are merely some embodiments of this disclosure, and not all embodiments of this disclosure. It should be understood that this disclosure is not limited to the exemplary embodiments described herein.

[0032] In this specification and accompanying drawings, substantially the same or similar method steps and elements are indicated by the same or similar reference numerals, and repeated descriptions of these method steps and elements will be omitted. Furthermore, in the description of this disclosure, terms such as "first," "second," etc., are used only to distinguish descriptions and should not be construed as indicating or implying relative importance or order. In embodiments of this disclosure, unless otherwise expressly stated, "connection" does not necessarily mean "direct connection" or "direct contact," but only requires electrical connection.

[0033] Figure 1 A modular structure diagram of a solid-state circuit breaker 100 according to this disclosure is shown. Unlike traditional thermal-magnetic circuit breakers and electronic circuit breakers, the solid-state circuit breaker 100 has no mechanically moving parts; instead, it uses high-power power electronic switches, such as MOSFETs and IGBTs, to disconnect and connect current. Therefore, there are no contacts in the solid-state circuit breaker, and thus no electric arc. Furthermore, the power electronic switch-based structure makes it easier to control the solid-state circuit breaker, thereby facilitating its intelligent operation. Figure 1In this circuit breaker, the solid-state circuit breaker 100 includes a power electronic switch 101 for switching the circuit connected to the solid-state circuit breaker 100. Furthermore, the solid-state circuit breaker 100 also includes a temperature measurement unit 102 for measuring the temperature of the power electronic switch 101 and transmitting the corresponding temperature signal to a processing unit 104; a current detection unit 103 for detecting the overload current flowing through the solid-state circuit breaker 103, i.e., the overload current of the power electronic switch 101, and transmitting the corresponding overload current signal 110 to the processing unit 104; and a processing unit 104 for determining the overload tripping time of the solid-state circuit breaker 100 based on the temperature signal 120 and the overload current signal 110, and sending a drive signal 130 to a drive unit 105 after the tripping time has elapsed. The solid-state circuit breaker 100 also includes a drive unit 101 for disconnecting the power electronic switch based on the drive signal 130.

[0034] In the event of an overload, the solid-state circuit breaker according to this disclosure can consider not only the magnitude of the overload current when setting the overload tripping time, but also the effect of temperature on the power electronic switches in the solid-state circuit breaker. For example, when the operating temperature of the power electronic switches is high, the overload tripping time can be shortened, thereby enabling faster tripping and avoiding damage to the load equipment, lines, and the solid-state circuit breaker itself caused by the combined effects of high temperature and heat accumulation.

[0035] Figure 2 A flowchart of an overload protection method for a solid-state circuit breaker according to an embodiment of the present disclosure is shown. The method includes method step S201: measuring the temperature of the power electronic switch 101 in the solid-state circuit breaker 100; method step S202: detecting the overload current flowing through the solid-state circuit breaker 100; method step S203: determining the overload tripping time of the solid-state circuit breaker 100 based on the temperature and the overload current; and method step S204: disconnecting the power electronic switch 101 after the tripping time has elapsed.

[0036] Figure 3 An exemplary three-dimensional graph showing the relationship between overload tripping time and temperature and load current according to an embodiment of the present disclosure is provided. When performing method step S203: determining the overload tripping time of the solid-state circuit breaker 100 based on the temperature and overload current of the power electronic switch 101, the overload tripping time of the solid-state circuit breaker 100 can be determined based on this three-dimensional graph, according to the measured temperature and overload current of the power electronic switch 101.

[0037] In this three-dimensional diagram, the X-axis represents the load current flowing through the solid-state circuit breaker 100, where I n The rated current value of the solid-state circuit breaker 100 is given, and the X-axis scale is a multiple of the rated current value. When the load current exceeds the set current value I... r(The setting current value will be explained below; it is typically 0.4-1I.) n The overload current is represented by the value 101. The Y-axis represents the temperature of the power electronic switch 101 in degrees Celsius (°C), and the Z-axis represents the tripping time of the solid-state circuit breaker 100 in seconds (s). This three-dimensional diagram can be derived theoretically or experimentally based on the characteristics of the solid-state circuit breaker.

[0038] from Figure 3 As can be seen, when the temperature of the electronic switch 101 remains constant, the tripping time gradually decreases as the overload current increases; this is known as inverse-time protection. When a large overload current or short circuit exists, the inverse-time characteristic allows the solid-state circuit breaker to trip quickly, thus preventing damage to the load equipment, lines, and the solid-state circuit breaker itself from the large current. Conversely, when a small overload current exists, the solid-state circuit breaker can have a longer tripping time. On the one hand, a small overload current will not quickly cause the equipment, lines, and the solid-state circuit breaker itself to heat up and cause damage; on the other hand, if the overload current disappears within the longer tripping time, the solid-state circuit breaker may not trip, thus avoiding the adverse effects of power outages.

[0039] With a constant overload current, the tripping time gradually decreases as the temperature of the power electronic switch 101 increases. Before the solid-state circuit breaker trips, the overload current causes the load equipment, lines, and the solid-state circuit breaker itself to heat up, resulting in heat accumulation. For the load equipment and lines, heat accumulation leads to overheating and thus increases losses; in more severe cases, it can cause the load equipment and lines to malfunction or even burn out. For the solid-state circuit breaker, due to the different coefficients of thermal expansion between the different layers of materials in its power electronic switch, thermal stress is generated between the layers at high temperatures, leading to solder fatigue and bond wire breakage. Therefore, by reducing the tripping time with increasing temperature, heat accumulation can be effectively reduced, thus preventing overheating of the power electronic switch and avoiding damage to the power electronic switch and the solid-state circuit breaker.

[0040] In some embodiments of this disclosure, such as Figure 4 As shown, method step S203 may include the following method steps: method step S401: adjusting the predetermined setting current value of the solid-state circuit breaker 100 according to the temperature; method step S402: determining the relationship between the overload tripping time and the overload current according to the adjusted setting current value; and method step S403: determining the overload tripping time according to the overload current and the relationship between the overload tripping time and the overload current.

[0041] The setting current value I of solid circuit breaker 100 r Also known as the long-delay setting current value. When the load current exceeds I...r At that time, the solid-state circuit breaker 100 tripped after a delay, I r Therefore, it also indicates the maximum current that the solid-state circuit breaker 100 can withstand without tripping. The setting current value I of the solid-state circuit breaker 100. r It must be greater than the load current I b However, it must be less than the maximum allowable current I of the load device or line. z In practical applications, it can be based on the aforementioned I. b and I z The size of the preset setting current value I is appropriately set. r It is usually in the range of 0.4-1I. n Adjustment is performed within the range of I, where I n This refers to the rated current value of the solid-state circuit breaker. For example, the rated current value I of solid-state circuit breaker 100... n It is 100A, while the load current I b If the setting current value I is 60A, r Set to 1x I n If the current setting is too low, the protection sensitivity will be insufficient. Therefore, the setting current value I can be adjusted. r Preset to 0.7 times I n That is, 70A. Therefore, the solid-state circuit breaker 100 sets a preset (i.e., predetermined) current value I. r Installed in the wiring.

[0042] During subsequent operation, the solid-state circuit breaker 100 can adjust the predetermined setting current value I according to the temperature of the solid-state circuit breaker 100. r Dynamic adjustment is performed, i.e., method step S401 is executed. The temperature of the solid-state circuit breaker 100 can be, for example, the surface temperature or junction temperature of the power electronic switch, which is affected by the ambient temperature of the circuit breaker, the magnitude of the load current, and time. For example, method step S401 can refer to... Figure 5 The set current value I shown in the figure r The temperature adjustment surface plot is used. Figure 5 In the diagram, the X-axis represents the predetermined setting current value I. r , where I n This is the rated current value, which is 100A in this case. The X-axis scale is the rated current value I. n The Y-axis represents the temperature of the power electronic switch 101, in degrees Celsius (°C), and the Z-axis represents the adjusted setting current value I. r The unit is ampere-ampere (A). Here, it is assumed that the temperature of the solid-state circuit breaker 100 under normal operating conditions is 50°C, meaning that the predetermined setting current value I is not applied at this temperature. rAdjustments can be made. When the temperature is above 50°C, the setting current value can be gradually decreased as the temperature increases. Conversely, when the temperature is below 50°C, the setting current value can be gradually increased as the temperature decreases. For example, the adjusted setting current value I... r 'With temperature T and predetermined set current value I r The relationship can be described by the following formula.

[0043] I' r =I r (a·T+b) (1)

[0044] In this context, coefficient a is negative and b is positive.

[0045] According to the adjusted setting current value I r The relationship between the overload tripping time and the overload current can be determined, for example, by the following formula.

[0046] I 2 T1=(cI′ r ) 2 T r (2)

[0047] Where I represents the overload current, T1 represents the overload tripping time, and I r ' represents the adjusted setting current value, c is a constant, which is usually taken in the range of 6 to 12, and T r This represents the tripping time setting value. Trip time setting value T r It is a value preset according to the characteristics of the trip unit. Under the same conditions, the trip time setting value T is... r The larger the value, the longer the overload tripping time.

[0048] Based on the adjusted setting current value I r After determining the relationship between the overload tripping time T1 and the overload current I, the corresponding overload tripping time T1 can be determined according to the magnitude of the detected overload current I. The solid-state circuit breaker 100 will then disconnect after the overload tripping time has elapsed.

[0049] Combining formulas (1) and (2) will establish the following... Figure 3 The diagram shows the three-dimensional relationship between the overload tripping time T1 and the temperature T and the load current I. Equations (1) and (2), and the parameters therein, can be derived theoretically or experimentally based on the characteristics of the solid-state circuit breaker.

[0050] According to embodiments of this disclosure, method step S401: adjusting the predetermined setting current value of the solid-state circuit breaker 100 based on temperature may further include the following method step: if the temperature rises above a first threshold, derating the predetermined current setting value of the solid-state circuit breaker 100 based on the temperature. By executing this method step, derating of the current setting value can be avoided when the temperature rise is not significant, thereby preventing the solid-state circuit breaker from being overly sensitive to temperature changes.

[0051] According to embodiments of this disclosure, when the temperature of the power electronic switch 101 in the solid-state circuit breaker 100 fluctuates, the method for derating the predetermined current setting value of the solid-state circuit breaker 100 based on the temperature if the temperature exceeds a first threshold may further include the following steps: after the temperature exceeds the first threshold, if the temperature decreases to below the first threshold but above a second threshold, the drated setting current value remains unchanged; if the temperature decreases to below the second threshold, the drated setting current value is restored to the predetermined setting current value. The first threshold and the second threshold can be set according to application requirements.

[0052] Figure 6 The following describes the method steps of an example method for adjusting a predetermined setting current value of a solid-state circuit breaker according to an embodiment of the present disclosure. Starting from method step S601, the solid-state circuit breaker operates at a predetermined current setting value. In the event of a temperature increase, in step S602, the temperature is compared with a first threshold. If the temperature does not exceed the first threshold, the predetermined current setting value remains unchanged. If the temperature exceeds the first threshold, step S603 is executed: the predetermined current setting value is derating based on the temperature. The solid-state circuit breaker operates with the derating-adjusted current setting value. If the temperature continues to rise, derating can be performed again based on the temperature. If the temperature decreases, in step S605, the temperature is compared with a second threshold. If the temperature does not fall below the second threshold, the derating-adjusted current setting value remains unchanged. If the temperature falls below the second threshold, the derating-adjusted current setting value is restored to the predetermined current setting value.

[0053] When ambient temperature fluctuates drastically, causing continuous fluctuations in the operating temperature of solid-state circuit breakers, setting a second threshold can avoid frequent adjustments to the current setting value, thereby preventing the solid-state circuit breaker from frequently opening and closing. This allows for more stable power supply to the load equipment, and by reducing the number of switching operations, it can also extend the lifespan of the solid-state circuit breaker.

[0054] According to embodiments of this disclosure, when the temperature of the power electronic switch 101 in the solid-state circuit breaker 100 rises, if the temperature is higher than a first threshold, derating the predetermined current setting value of the solid-state circuit breaker based on the temperature may include: adding an increment to the temperature and derating the predetermined current setting value of the solid-state circuit breaker based on the temperature after the added increment, and / or adding a decrement to the predetermined current setting value and derating the predetermined current setting value based on the predetermined current setting value after the added decrement.

[0055] Under harsh operating conditions, the temperature of the power electronic switch in a solid-state circuit breaker will continuously rise due to environmental influences. In this case, to protect the power electronic switch, the solid-state circuit breaker needs to stop operating quickly, i.e., disconnect. According to the relationship between the overload tripping time T1 and the overload current I given by formula (2), the predetermined current setting value can be significantly dated to reduce the tripping time T1. Thus, the predetermined current setting value can be dated by adding an increment to the measured temperature of the power electronic switch 101 and / or adding a decrement to the predetermined current setting value.

[0056] Reference Figure 5 The adjustment surface plot of the set current value with respect to temperature is shown, for example, at a predetermined current set value of 1I. n At a temperature of 65℃, the derating current setting at this coordinate location corresponds to 90A. If a significant derating adjustment is needed for this predetermined current setting, the adjusted current setting can be selected at a larger temperature coordinate and / or a smaller current setting coordinate. For example, a predetermined current setting of 0.4I can be selected. n At a temperature of 70℃, the adjusted current setting value corresponding to this coordinate is approximately 50A.

[0057] Based on the significantly derating current setting, solid-state circuit breakers can have shorter overload tripping times. Therefore, solid-state circuit breakers can stop operating more quickly, thus preventing damage to the solid-state circuit breaker and its power electronic switches from high temperatures, even when ambient temperatures are continuously rising.

[0058] Figure 7 A power distribution system according to the present disclosure is shown. The power distribution system includes a plurality of solid-state circuit breakers Q1-Q4 according to embodiments of the present disclosure, wherein the adjusted current setting of the solid-state circuit breaker closer to the power source is greater than the adjusted current setting of the solid-state circuit breaker closer to the load, i.e., I′ r，Q1 >I′ r，Q3 , and I′ r，Q1 >I′ r，Q2 >I′ r，Q4 .

[0059] By designing the adjusted current setting of the solid-state circuit breaker in this way, it is possible to ensure that only the solid-state circuit breaker closest to the fault location will operate in the event of an overload, thus avoiding cascading tripping and minimizing the number of load devices affected by the fault.

[0060] Embodiments of this disclosure provide a multi-pole solid-state circuit breaker, comprising: a plurality of power electronic switches for switching multiple lines connected to the solid-state circuit breaker; a temperature measurement unit for measuring the temperature of the plurality of power electronic switches in the solid-state circuit breaker and transmitting the corresponding temperature signals to a processing unit; a current detection unit for detecting overload current flowing through the multiple lines of the solid-state circuit breaker and transmitting the corresponding overload current signals to the processing unit; the processing unit for determining the overload tripping time of the solid-state circuit breaker based on the temperature signal of the highest temperature and the overload current signal of the largest overload current, and sending a drive signal to the drive unit after the tripping time has elapsed; and the drive unit for disconnecting the plurality of power electronic switches based on the drive signal.

[0061] According to an embodiment of this disclosure, the processing unit adjusts a predetermined setting current value of the solid-state circuit breaker based on a temperature signal of the highest temperature among the temperatures, and determines the relationship between the overload tripping time and the maximum overload current based on the adjusted setting current value.

[0062] Multi-pole solid-state circuit breakers can be, for example, three-pole or four-pole circuit breakers. A three-pole circuit breaker is connected to the three phase lines of the power supply line and has three power electronic switches to disconnect the three phase lines in the event of an overload current. A four-pole circuit breaker is connected to the three phase lines and the neutral line of the power supply line and has four power electronic switches to disconnect the three phase lines and the neutral line in the event of an overload current.

[0063] The block diagrams of circuits, units, devices, apparatuses, devices, and systems disclosed herein are merely illustrative examples and are not intended to require or imply that connections, arrangements, or configurations must be made in the manner shown in the block diagrams. As those skilled in the art will recognize, these circuits, units, devices, apparatuses, devices, and systems can be connected, arranged, and configured in any manner that achieves the desired purpose. The circuits, units, devices, and apparatuses disclosed herein can be implemented in any suitable manner, such as using application-specific integrated circuits (ASICs), field-programmable gate arrays (FPGAs), or using general-purpose processors in conjunction with programs.

[0064] Those skilled in the art should understand that the specific embodiments described above are merely examples and not limitations. Various modifications, combinations, partial combinations, and substitutions can be made to the embodiments of this disclosure according to design requirements and other factors, as long as they are within the scope of the appended claims or their equivalents, and thus fall within the scope of the rights to be protected by this disclosure.

Claims

1. An overload protection method for a solid-state circuit breaker, comprising: Measure the temperature of the power electronic switches in the solid-state circuit breaker. The overload current flowing through the solid-state circuit breaker is detected, wherein the overload current is a current greater than a predetermined setting current value of the solid-state circuit breaker. The overload tripping time of the solid-state circuit breaker is determined based on the temperature and the overload current. The power electronic switch is disconnected after the tripping time has elapsed. The determination of the overload tripping time of the solid-state circuit breaker based on the temperature and the overload current includes: The predetermined setting current value is adjusted according to the temperature to obtain the adjusted setting current value. Based on the adjusted setting current value, the inverse-time tripping relationship between the overload tripping time and the overload current is determined, and The overload tripping time is determined based on the overload current and the inverse time tripping relationship; The inverse time-limited tripping relationship satisfies the following formula: in, I The overload current, T 1 represents the overload tripping time. I r ' represents the adjusted setting current value, and c is a constant. T r The preset tripping time setting value.

2. The overload protection method according to claim 1, wherein, The adjustment of the predetermined setting current value of the solid-state circuit breaker based on the temperature includes: If the temperature rises above a first threshold, the predetermined setting current value of the solid-state circuit breaker is derating adjusted based on the temperature.

3. The overload protection method according to claim 2, wherein, The adjustment of the predetermined setting current value of the solid-state circuit breaker based on the temperature also includes: After the temperature exceeds the first threshold, if the temperature drops to below the first threshold but above the second threshold, the derating adjusted setting current value remains unchanged. If the temperature drops to below the second threshold, the derating adjusted setting current value is restored to the predetermined setting current value.

4. The overload protection method according to claim 2, wherein, In the event of an increase in temperature, if the temperature exceeds a first threshold, derating the predetermined setting current value of the solid-state circuit breaker based on the temperature includes: An increment is added to the temperature, and the predetermined setting current value of the solid-state circuit breaker is derating adjusted based on the temperature after the increment, and / or The predetermined setting current value is reduced by an additional amount, and a derating adjustment is performed based on the predetermined setting current value after the additional reduction.

5. A solid-state circuit breaker, comprising: A power electronic switch is used to switch the circuit connected to the solid-state circuit breaker on and off. The temperature measurement unit is used to measure the temperature of the power electronic switches in the solid-state circuit breaker and transmit the corresponding temperature signal to the processing unit. A current detection unit is used to detect the overload current flowing through the solid-state circuit breaker and transmit the corresponding overload current signal to the processing unit, wherein the overload current is a current greater than the predetermined setting current value of the solid-state circuit breaker. The processing unit is configured to determine the overload tripping time of the solid-state circuit breaker based on the temperature signal and the overload current signal, and after the tripping time has elapsed, send a drive signal to the drive unit. The drive unit is used to disconnect the power electronic switch according to the drive signal. The processing unit is configured as follows: The predetermined setting current value is adjusted according to the temperature signal to obtain the adjusted setting current value. The inverse-time tripping relationship between the overload tripping time and the overload current is determined based on the adjusted setting current value; and The overload tripping time is determined based on the overload current signal and the inverse time tripping relationship; The inverse time-limited tripping relationship satisfies the following formula: in, I The overload current, T 1 represents the overload tripping time. I r ' represents the adjusted setting current value, and c is a constant. T r The preset tripping time setting value.

6. The solid-state circuit breaker according to claim 5, wherein, If the temperature rises and the value of the temperature signal is higher than a first threshold, the processing unit will derating the predetermined setting current value of the solid-state circuit breaker based on the value of the temperature signal.

7. The solid-state circuit breaker according to claim 6, wherein, After the temperature signal value exceeds the first threshold, if the temperature drops to below the first threshold but above the second threshold, the processing unit keeps the derating adjusted setting current value unchanged. If the temperature signal value drops to below the second threshold, the processing unit restores the derating adjusted setting current value to the predetermined setting current value.

8. A power distribution system comprising a plurality of solid-state circuit breakers according to any one of claims 5 to 7, wherein The adjusted setting current value of a solid-state circuit breaker that is closer to the power source is greater than that of a solid-state circuit breaker that is closer to the load.

9. A multi-pole solid-state circuit breaker, comprising: Multiple power electronic switches are used to switch multiple lines connected to the solid-state circuit breaker on and off. The temperature measurement unit is used to measure the temperature of multiple power electronic switches in the solid-state circuit breaker and transmit the corresponding temperature signals to the processing unit. A current detection unit is used to detect the overload current flowing through multiple lines of the solid-state circuit breaker and transmit the corresponding overload current signal to the processing unit, wherein the overload current is a current greater than the predetermined setting current value of the solid-state circuit breaker. The processing unit is configured to determine the overload tripping time of the solid-state circuit breaker based on the temperature signal of the highest temperature and the overload current signal of the maximum overload current, and after the tripping time has elapsed, send a drive signal to the drive unit. The drive unit is used to disconnect the plurality of power electronic switches according to the drive signal. The processing unit is configured as follows: The predetermined setting current value is adjusted based on the temperature signal of the highest temperature to obtain the adjusted setting current value. The inverse-time tripping relationship between the overload tripping time and the maximum overload current is determined based on the adjusted setting current value; and The overload tripping time is determined based on the overload current signal of the maximum overload current and the inverse time tripping relationship; The inverse time-limited tripping relationship satisfies the following formula: in, I max ' is the maximum overload current, T 1 represents the overload tripping time. I r ' represents the adjusted setting current value, and c is a constant. T r The preset tripping time setting value.

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