Direct-current solid-state circuit breaker and current detection method thereof

Abstract

The invention discloses a direct-current solid-state circuit breaker and a current detection method thereof. An introduced conduction voltage drop detection circuit comprises a differential circuit, a resistor R1 and a small switching power semiconductor device; the resistance value of the resistor R1 is far greater than the on resistance of the semiconductor device, and the small switch power semiconductor device adopts the same control signal as the power semiconductor device; the small switch power semiconductor device and the resistor R1 are connected in series and then are connected in parallel at two ends of the power semiconductor device; the two input ends of the differential circuit are connected to the two ends of the resistor R1 in parallel, and one path of voltage difference of the output ends of the differential circuit is connected to the controller through the current conditioning circuit. And one path of the output end of the differential circuit is connected to the driving circuit through the short-circuit current protection circuit. The current detection circuit can effectively detect the line current in real time, and rapidly turn off the solid-state circuit breaker when a short-circuit fault occurs; when a line overload fault occurs, an alarm is given in time, and overload delay turn-off protection is carried out; and the circuit also has the functions of overvoltage, undervoltage and over-temperature protection and the like.

Description

Technical Field

[0001] The present invention relates to the technical field of power distribution network of electric power system, and in particular to a DC solid-state circuit breaker and a current detection method thereof. Background Art

[0002] With the transformation of the global energy structure and the widespread popularity of clean energy, the development of new power systems and microgrids is becoming a focus. Faced with the increasing impact and nonlinear loads in the distribution network, the complexity of the new power system has far exceeded that of the traditional system. In particular, the integration of microgrids, especially in DC systems, due to the lack of natural zero-crossing points of the current, when a short-circuit fault occurs, the current will rise rapidly, which requires the protection equipment to cut off the fault circuit in a very short time. These changes not only put forward higher requirements on the breaking capacity of the switch protection equipment, but also require the protection system to have higher reliability, intelligence and flexibility. At the same time, as users' expectations for power supply quality continue to increase, how to quickly cut off the short-circuit current to effectively suppress the grid voltage drop and interruption during the fault has become a key issue that needs to be solved urgently. In this context, DC solid-state circuit breakers (SSCBs), as a new generation of power protection equipment, play an important role in DC distribution systems.

[0003] Compared with traditional mechanical switches, DC solid-state circuit breakers use power semiconductor devices as the core components of protection devices, which have significant advantages. First, they can quickly cut off the current in microseconds, effectively resisting the potential threats caused by overload or short circuit. Second, solid-state circuit breakers have no mechanical moving parts and no arcs, which reduces the probability of failure and improves the stability and reliability of the system. Third, solid-state circuit breakers are easy to achieve closer integration and coordination with smart grids and microgrids, supporting the intelligent and efficient operation of power systems.

[0004] However, its core devices usually use power semiconductor devices, such as thyristors (SCR), insulated gate bipolar transistors (IGBT), metal oxide semiconductor field effect transistors (MOSFET), integrated gate commutated thyristors (IGCT), etc. In practical applications, it still faces a series of challenges and limitations, which to a certain extent restrict its wide promotion and in-depth application. First, the large conduction loss is a significant problem of solid-state circuit breakers. Under normal working conditions, the semiconductor devices in solid-state circuit breakers need to be continuously turned on, and their inherent on-resistance leads to higher energy loss than mechanical switches. This loss not only reduces the overall energy efficiency of the system, but also causes the heating problem of the device itself, posing a potential threat to long-term stable operation; second, the rapid detection and response of fault current is another major challenge faced by solid-state circuit breakers. Solid-state circuit breakers can cut off short-circuit currents in a very short time. This process requires high detection accuracy, ultra-fast response speed and a wide range of measurement. To ensure that the fault can be accurately identified and measures can be taken quickly at the moment of occurrence, thereby effectively ensuring the safe and stable operation of the power system; third, solid-state circuit breakers will withstand extremely high voltage shocks during the disconnection process. Since the protection equipment is required to be able to cut off the short-circuit current in a very short time, this leads to a sharp rise in the voltage across the device, which places extremely high demands on the voltage resistance of power semiconductor devices. How to ensure that the device is not damaged by excessive voltage while ensuring a fast response is a key problem that needs to be solved in the development of solid-state circuit breaker technology. Fourth, high cost is also a major obstacle to the promotion and application of solid-state circuit breakers. Compared with traditional mechanical switches, solid-state circuit breakers use advanced power semiconductor devices and complex control technology, resulting in relatively high manufacturing costs. This has limited the widespread application of solid-state circuit breakers in large-scale power systems to a certain extent. Therefore, although DC solid-state circuit breakers have many advantages, they still face problems such as large conduction losses, challenges in fault current detection and response, high voltage shocks, and high costs in actual applications.

[0005] As the core protection equipment of the new power system, DC solid-state circuit breakers are responsible for the detection of normal current, overload current and short-circuit current. Under normal and overload conditions, the power system has extremely high requirements for current detection, and needs to ensure the accuracy of measurement and the clarity of display. When a fault current occurs suddenly, the current change rate and amplitude increase significantly. At this time, the requirements for current detection are fast response and accurate judgment, but its accuracy does not require high accuracy under normal conditions. At present, existing research on fault current detection methods mainly focuses on detection methods based on current sensors. [1] , Small resistance detection method [6] , Detection method based on saturation voltage [2] , Detection method based on source parasitic inductance [7] and detection method based on gate voltage of power device [8]. The small resistance detection method will cause additional losses and is not suitable for current detection of solid-state circuit breakers. The detection method based on source parasitic inductance and the detection method based on the gate voltage of power devices can only detect fault current, and are not easy to detect and are easily interfered with. The current detection of the line circuit also requires additional circuits, which increases the cost. The DC current sensor method generally uses Hall sensors for current detection. When faced with the needs of large bandwidth and wide range, the design is complex and expensive, and the measurement accuracy is also limited. Based on the detection method of saturation voltage, if a drive and protection circuit composed of discrete components is used, when the circuit breaker is disconnected, the two ends of the circuit breaker are high voltage, and the problem of how to start is faced. Therefore, a high-cost dedicated control chip for oversaturation protection is usually used. The detection method based on the gate voltage of the power device is affected by the distributed parameters and voltage of the solid-state circuit breaker, and the mechanism is relatively complex. As a new type of protection equipment for power systems, DC solid-state circuit breakers have high requirements for the current detection accuracy of normal operation, so high-precision current detection methods are required.

[0006] At present, the line current detection method based on current sensor has high requirements on the bandwidth of the current sensor and high cost. Detection of on-state voltage drop is widely used in semiconductor devices. Patent CN202311128333.8 can monitor the operating status of switching devices in real time by detecting on-state voltage drop. However, the requirements for detection range and accuracy will inevitably lead to an increase in cost, which is not conducive to the commercialization of solid-state circuit breakers. Patent CN202110030399.8 uses the oversaturation protection function of the driver chip to perform fault current protection of the switching device. The oversaturation protection function integrated in the driver chip can achieve oversaturation protection while driving the switching device. However, this not only fails to achieve the purpose of detecting line current, but also because the protection voltage threshold of the driver chip is fixed, it is inconvenient to flexibly and accurately adjust the protection threshold during application. There are also related technical solutions that utilize the characteristics of different driving voltages of switching devices in the on and off states to optimize the problem of excessive voltage drop when the switching device is turned off. However, this method requires the addition of a high-voltage diode so that when the switching device is turned off, the diode is in a reverse cutoff state to protect the detection circuit, and multiple diodes need to be connected in series to reduce the influence of parasitic capacitance on the detection of the conduction voltage drop. When the switching device is turned on, the voltage drop of the diode is related to the current flowing through the diode, which will affect the accuracy of the calculation of the conduction voltage drop of the switching device, thereby affecting the accuracy of the line current detection and the fault protection of the solid-state circuit breaker. Another common current measurement method is the resistance detection method. Such a measurement method requires the measurement of resistance in series in the line, which brings additional conduction loss, and a complex compensation circuit needs to be added in the subsequent circuit to adjust the compensation gain. The detection method based on source parasitic inductance and the detection method based on the gate voltage of the power device can only detect the fault current. In practical applications, the parasitic inductance value is difficult to control, the gate voltage changes are small and not easy to detect and are easily interfered with, and the current detection of the line circuit also requires additional circuits, which increases the cost. Summary of the invention

[0007] The object of the present invention is to provide a DC solid-state circuit breaker and a current detection method thereof.

[0008] The technical solution adopted by the present invention is:

[0009] A DC solid-state circuit breaker includes a core component of a solid-state circuit breaker, a power semiconductor device, a conduction voltage drop detection circuit, a short-circuit protection circuit, a controller, and a drive circuit connected to the controller, a current conditioning circuit, a power semiconductor device surface temperature sampling and conditioning circuit, and a DC voltage sampling and conditioning circuit;

[0010] The on-state voltage drop detection circuit includes a differential circuit, a resistor R1 and a low-power semiconductor device; the resistance value of the resistor R1 is much larger than the on-state resistance of the power semiconductor device, and the control signal of the low-power semiconductor device is the same as the control signal of the power semiconductor device of the core component of the solid-state circuit breaker; one end of the low-power semiconductor device is connected to one end of the power semiconductor device, and one end of the low-power semiconductor device is connected to the other end of the power semiconductor device after being connected in series with the resistor R1; the two input ends of the differential circuit are respectively connected to the two ends of the resistor R1, and the voltage difference at the output end of the differential circuit is connected to the controller through the current conditioning circuit, and the current conditioning circuit conditions the collected voltage difference to a signal that the controller can match; the output end of the differential circuit is connected to the drive circuit through the short-circuit current protection circuit;

[0011] The short-circuit current protection circuit is used to quickly cut off the solid-state circuit breaker to protect the line when a short-circuit fault occurs in the line and the voltage difference detected by the on-state voltage drop detection circuit exceeds the set value; the driving circuit is used to drive the power semiconductor device and the small-power semiconductor device of the on-state voltage drop detection circuit; the power semiconductor device surface temperature sampling and conditioning circuit detects and obtains the surface temperature T of the power semiconductor device, the core component of the solid-state circuit breaker; the DC voltage sampling and conditioning circuit is used to collect the line voltage; the controller calculates and processes the collected line voltage, the voltage difference of the on-state voltage drop detection circuit and the temperature parameters of the power semiconductor device, and controls the opening and closing of the power semiconductor device.

[0012] Furthermore, the driving signal output terminal of the controller and the output terminal of the short-circuit current protection circuit are respectively connected to two input terminals of an AND gate, and the output terminal of the AND gate is connected to the driving circuit.

[0013] Furthermore, the controller is also connected to an LED display circuit and a communication circuit; the LED display circuit is used to display the state and electrical parameters of the solid-state circuit breaker; and the communication circuit is used to realize the communication function of the DC solid-state circuit breaker.

[0014] Furthermore, the core component power semiconductor device of the solid-state circuit breaker adopts thyristor (SCR), insulated gate bipolar transistor (IGBT), metal oxide semiconductor field effect transistor (MOSFET), integrated gate commutated thyristor (IGCT) or junction field effect transistor (JFET); the controller adopts single chip microcomputer, DSP or ARM.

[0015] Further, as an optional implementation, the short-circuit current protection circuit includes a comparison circuit and an RS latch circuit, the negative input terminal of the comparison circuit is connected to the output terminal of the differential circuit, and the positive input terminal of the comparison circuit is grounded through a reference voltage source; the output terminal of the comparison circuit is connected to the S input terminal of the RS latch circuit; the Q output terminal of the RS latch circuit is connected to the input terminal of a NOT gate, and the output terminal of the NOT gate serves as the output terminal of the short-circuit current protection circuit; the R input terminal of the RS latch circuit is connected to the drive signal output terminal of the controller.

[0016] Furthermore, as a preferred implementation, the Q output terminal of the RS latch circuit is connected to one input terminal of the AND gate through a NOT gate, the driving signal output terminal of the controller is connected to the other input terminal of the AND gate; and the output terminal of the AND gate is connected to the driving circuit.

[0017] A current detection method for a DC solid-state circuit breaker obtains a current model flowing through the line according to formula (1) by collecting the voltage across a resistor R1 in a conduction voltage drop detection circuit and the surface temperature of a power semiconductor device. The specific form of formula (1) can be derived through theory and experiment.

[0018] I DS =f(V R , V gs ,T) (1)

[0019] Among them, I DS is the current flowing through the solid-state circuit breaker, that is, the real-time line current value; V gs is the driving voltage of the power semiconductor device. Once the circuit breaker is designed, its value is fixed; V R is the voltage across the resistor of the solid-state circuit breaker detection circuit, that is, the voltage difference between the power semiconductor device and the small power semiconductor device of the detection branch; T is the surface temperature of the power semiconductor device.

[0020] Furthermore, the DC solid-state circuit breaker current model is obtained through the following steps.

[0021] Step 1: According to the rated current specification I of the solid-state circuit breaker d , in 0~k·I d The model is experimentally tested at N points in the range, where k is the current coefficient of the solid-state circuit breaker;

[0022] Step 2: Measure the voltage V across the resistance of the detection circuit of the solid-state circuit breaker from the initial state to the stable state. Ri 、Circuit breaker current I dsi , and the surface temperature T of the power semiconductor device i , i is 1 to N;

[0023] Step 3: According to V Ri ,I dsiand T i The experimental data is fitted to obtain the DC solid-state circuit breaker current model;

[0024] Step 4: Use the fitted current model to calculate the current in the controller.

[0025] Furthermore, the current obtained according to the current model is used for accurate calculation of the line current and protection against short-circuit faults; that is, firstly, the current is sent to the controller through the differential circuit and the conditioning circuit, and the current flowing through the circuit breaker is obtained according to the functional relationship between the voltage across the resistor R1 and the surface temperature of the power semiconductor device and the current flowing through the circuit breaker, so as to display the line current in real time, as well as the status display, alarm or delayed disconnection when the line is overloaded; secondly, when a short-circuit fault occurs in the line, according to the positive correlation between the voltage signal across the resistor R1 and the line current, the power semiconductor device is quickly disconnected through the differential circuit and the short-circuit current protection circuit to protect the safety of the line.

[0026] Furthermore, the DC solid-state circuit breakers suitable for the current detection method include unidirectional and bidirectional DC solid-state circuit breakers, or single-pole, bipolar and multi-pole solid-state circuit breakers.

[0027] The present invention adopts the above technical solution, introduces a conduction voltage drop detection circuit, and deeply studies the precise functional relationship between current and the conduction voltage drop and temperature of the solid-state circuit breaker. By measuring the conduction voltage drop and the surface temperature of the device with high precision, the present invention can indirectly but accurately calculate the current value flowing through the solid-state circuit breaker. This method does not require a current sensor, is not only compatible with overvoltage saturation technology, and realizes effective short-circuit current protection for solid-state circuit breakers, but also provides accurate current detection function under normal working conditions and overload conditions.

[0028] The present invention brings a new solution to the current detection field of solid-state circuit breakers. Its high precision and high reliability make the present invention have broad application prospects in the protection equipment of new power systems, and is expected to provide solid technical support for the safe, stable and efficient operation of power systems. BRIEF DESCRIPTION OF THE DRAWINGS

[0029] The present invention is further described in detail below with reference to the accompanying drawings and specific embodiments;

[0030] Figure 1 This is a principle block diagram of a DC solid-state circuit breaker of the present invention;

[0031] Figure 2 It is a structural schematic diagram of a specific embodiment of a DC solid-state circuit breaker of the present invention;

[0032] Figure 3 It is a structural schematic diagram of another specific embodiment of a DC solid-state circuit breaker of the present invention;

[0033] FIG4( a) is a logic timing diagram of a short-circuit fault detection response circuit in the event of a short-circuit fault;

[0034] FIG4( b ) is a logic timing diagram of a short-circuit fault detection response circuit in a normal working state;

[0035] Figure 5 When the current is 0~5A, the current in the DC solid-state circuit breaker and the voltage V across the resistor R1 R And the measured data diagram of the surface temperature T of the Sic MOSFET semiconductor device;

[0036] Figure 6 When the current is 5-20A, the current in the DC solid-state circuit breaker and the voltage V across the resistor R1 R Graph showing the measured data of the surface temperature T of SiC MOSFET semiconductor devices.

[0037] Figure numerals: core component of solid-state circuit breaker power semiconductor device-1; on-state voltage drop detection circuit-2; short-circuit protection circuit-3; drive circuit-4; current conditioning circuit-5; controller-6; power semiconductor device surface temperature sampling and conditioning circuit-7; line DC voltage sampling and conditioning circuit-8; LED display circuit-9; communication circuit-10. DETAILED DESCRIPTION

[0038] In order to make the purpose, technical solutions and advantages of the embodiments of the present application clearer, the technical solutions in the embodiments of the present application will be clearly and completely described below in conjunction with the drawings in the embodiments of the present application.

[0039] like Figures 1 to 6 As shown in one, the present invention discloses a DC solid-state circuit breaker, which includes a core component of a solid-state circuit breaker, a power semiconductor device, a conduction voltage drop detection circuit, a short-circuit protection circuit, a controller, and a drive circuit connected to the controller, a current conditioning circuit, a power semiconductor device surface temperature sampling and conditioning circuit, and a DC voltage sampling and conditioning circuit;

[0040] The on-state voltage drop detection circuit includes a differential circuit, a resistor R1 and a low-power semiconductor device; the resistance value of the resistor R1 is much larger than the on-state resistance of the power semiconductor device, and the control signal of the low-power semiconductor device is the same as the control signal of the power semiconductor device of the core component of the solid-state circuit breaker; one end of the low-power semiconductor device is connected to one end of the power semiconductor device, and one end of the low-power semiconductor device is connected to the other end of the power semiconductor device after being connected in series with the resistor R1; the two input ends of the differential circuit are respectively connected to the two ends of the resistor R1, and the voltage difference at the output end of the differential circuit is connected to the controller through the current conditioning circuit, and the current conditioning circuit conditions the collected voltage difference to a signal that the controller can match; the output end of the differential circuit is connected to the drive circuit through the short-circuit current protection circuit;

[0041] The short-circuit current protection circuit is used to quickly cut off the solid-state circuit breaker to protect the line when a short-circuit fault occurs in the line and the voltage difference detected by the on-state voltage drop detection circuit exceeds the set value; the driving circuit is used to drive the power semiconductor device and the small-power semiconductor device of the on-state voltage drop detection circuit; the power semiconductor device surface temperature sampling and conditioning circuit detects and obtains the surface temperature T of the power semiconductor device, the core component of the solid-state circuit breaker; the DC voltage sampling and conditioning circuit is used to collect the line voltage; the controller calculates and processes the collected line voltage, the voltage difference of the on-state voltage drop detection circuit and the temperature parameters of the power semiconductor device, and controls the opening and closing of the power semiconductor device.

[0042] Further, as a feasible implementation, the driving signal output terminal of the controller and the output terminal of the short-circuit current protection circuit are respectively connected to two input terminals of an AND gate, and the output terminal of the AND gate is connected to the driving circuit.

[0043] Furthermore, the controller is also connected to an LED display circuit and a communication circuit; the LED display circuit is used to display the state and electrical parameters of the solid-state circuit breaker; and the communication circuit is used to realize the communication function of the DC solid-state circuit breaker.

[0044] Specifically, the DC solid-state circuit breaker has line overload, short circuit, over-temperature, overvoltage, undervoltage protection functions and remote control functions, as well as electrical parameter display functions such as voltage, current and power and fault status display functions.

[0045] Furthermore, the power semiconductor device of the core component of the solid-state circuit breaker can be a thyristor (SCR), an insulated gate bipolar transistor (IGBT), a metal oxide semiconductor field effect transistor (MOSFET), an integrated gate commutated thyristor (IGCT), a junction field effect transistor (JFET) and other devices.

[0046] Furthermore, the controller may be a single chip microcomputer, a DSP, an ARM, etc.

[0047] Furthermore, as a feasible implementation method, the short-circuit current protection circuit includes a comparison circuit and an RS latch circuit, the negative input terminal of the comparison circuit is connected to the output terminal of the differential circuit, and the positive input terminal of the comparison circuit is grounded through a reference voltage source; the output terminal of the comparison circuit is connected to the S input terminal of the RS latch circuit; the Q output terminal of the RS latch circuit is connected to the input terminal of a NOT gate, and the output terminal of the NOT gate serves as the output terminal of the short-circuit current protection circuit; the R input terminal of the RS latch circuit is connected to the drive signal output terminal of the controller.

[0048] Specifically, as an optional implementation, the Q output terminal of the RS latch circuit is connected to one input terminal of the AND gate through a NOT gate, the driving signal output terminal of the controller is connected to the other input terminal of the AND gate; and the output terminal of the AND gate is connected to the driving circuit.

[0049] In addition, according to the characteristics of the main switch device of the solid-state circuit breaker, the present invention proposes a current detection method based on the conduction voltage drop. The method connects a detection branch in parallel to the main switch device of the solid-state circuit breaker, collects the voltage difference between the main switch device and the detection branch switch device, and through theoretical and practical analysis, it can be known that the current of the solid-state circuit breaker has a certain functional relationship with the voltage difference, the driving voltage and temperature of the semiconductor device, as shown in formula (1). The current of the solid-state circuit breaker circuit can be obtained by collecting the voltage difference between the main switch device and the detection branch switch device and the surface temperature of the semiconductor device. The voltage difference signal is sent to the controller through the differential circuit and the conditioning circuit, and the functional relationship between the current and the voltage of the solid-state circuit breaker is calibrated. The current of the line can be accurately obtained, which is used for displaying or alarming the current when the line is operating normally or in an overload state, as well as calculating and processing other electrical parameters. When a short-circuit fault occurs in the line, the semiconductor device enters an oversaturated state, and the voltage difference passes through the differential circuit and the short-circuit protection circuit, and the line is quickly short-circuited by hardware.

[0050] I DS =f(V R , V gs ,T) (1)

[0051] Among them, I DS is the real-time line current value; V gs is the driving voltage of the power semiconductor device. Once the circuit breaker is designed, its value is fixed; V R is the voltage difference between the main switch device and the detection branch switch device; T is the surface temperature of the power semiconductor device.

[0052] like Figure 1As shown in the figure, it is a principle block diagram of a DC solid-state circuit breaker, where number 1 is the core component of the solid-state circuit breaker, the power semiconductor device VT1, and the power semiconductor device can be a thyristor (SCR), an insulated gate bipolar transistor (IGBT), a metal oxide semiconductor field effect transistor (MOSFET), an integrated gate commutated thyristor (IGCT) and a junction field effect transistor (JFET). 2 is a conduction voltage drop detection circuit, which is composed of a resistor R1 and a small power semiconductor device VT2. The control signal of the small power semiconductor device is the same as the control signal of the power semiconductor device of the core component of the solid-state circuit breaker. 3 is a short-circuit current protection circuit, which is used to compare the detected voltage difference with the set value when a short-circuit fault occurs in the line. Once the set value is exceeded, the solid-state circuit breaker is quickly cut off to protect the line. 4 is a semiconductor device drive circuit, which is used to drive the power semiconductor device and the small power semiconductor device of the detection circuit. 5 is a conditioning circuit, which adjusts the collected voltage difference to a signal that the controller can match. 6 is a solid-state circuit breaker controller, which can be a single-chip microcomputer, DSP, ARM, etc., which collects parameters such as line voltage, voltage difference of the detection circuit, and temperature of semiconductor devices, calculates and processes them, and controls the on and off of power semiconductor devices. 7 is a temperature acquisition and conditioning circuit, which is used to collect the surface temperature of power semiconductor devices and send it to the controller. 8 is a DC voltage sampling and conditioning circuit, which is used to collect the voltage of the line. 9 is an LED display module, which is used to display the status and electrical parameters of the solid-state circuit breaker. 10 is a communication module, which is used to meet the communication function.

[0053] Figure 2 This is an application example of the present invention. The main switch device of the VT1 DC solid-state circuit breaker in the figure can usually adopt power semiconductor devices such as SiC MOSFET and SiC IGBT in consideration of the conduction loss. The current detection circuit is composed of the switch device VT2, the detection resistor R1, etc. Among them, VT1 and VT2 use a synchronous driving voltage, that is, the switch devices VT1 and VT2 are turned on and off at the same time. The detection resistor R1 is slightly larger in value, which can make the current value on the current detection branch very small. According to the positive correlation between the conduction voltage drop of the switch device and the current of the switch device, the conduction voltage drop on VT2 is very small and the main circuit current I DS Therefore, when the main switch device is turned on, the voltage V across the detection resistor R1 It can be roughly considered as the conduction voltage drop of the main switch device. When the main switch device is turned off, the switch devices on the current detection branch remain turned off synchronously, so the voltage difference across the detection resistor is 0. The voltage V across the detection resistor R1 The real-time temperature is obtained by differential circuit acquisition and combined with VT1 temperature sampling and conditioning circuit. The data is processed in the main controller to obtain a more accurate line current value I. DS .

[0054] Figure 3 This is an application case of the present invention. In the figure, VT1 and VT3 are the main switch devices of the bidirectional DC solid-state circuit breaker. Considering the conduction loss, power semiconductor devices such as SiC MOSFET and SiC IGBT can usually be used. In order to meet the flow conditions of bidirectional DC, the main switch device adopts a pair of power semiconductor devices in reverse series. In the case of bidirectional current, the entire circuit maintains a symmetrical structure. The current detection circuit is composed of switch devices VT2, VT4, detection resistors R1, R2, etc. Among them, VT1 and VT2 use a synchronous driving voltage, and VT3 and VT4 use a synchronous driving voltage, that is, the switch devices VT1 and VT2, VT3 and VT4 are turned on and off at the same time. The detection resistors R1 and R2 are slightly larger in value, which can make the current value on the current detection branch very small. According to the positive correlation between the conduction voltage drop of the switch device and the current of the switch device, the conduction voltage drop on VT2 and VT4 is very small and the main circuit current I DS Therefore, when the main switch device is turned on, the voltage V across the detection resistor R1 and V R2 It can be roughly considered as the conduction voltage drop of the main switch device. When the main switch device is turned off, the switch devices on the current detection branch remain turned off synchronously, so the voltage difference across the detection resistor is 0. The voltage V across the detection resistor R1 and V R2 The real-time temperature is obtained by differential circuit acquisition and combined with VT1 and VT3 temperature sampling and conditioning circuits. The data is processed in the main controller to obtain a more accurate line current value I. DS .

[0055] When the solid-state circuit breaker is turned on and the line current is normal, the voltage sampling value across the detection resistor is connected to the inverting input terminal of the voltage comparison circuit, and the detection threshold reference voltage V ref Connect to the positive input terminal. When a short circuit fault occurs, the detection voltage V R As the line current I DS When the detection threshold voltage V refAfter that, the output of the voltage comparison circuit changes from the high level in the normal state to the low level, and the RS latch output Q of the logic circuit changes to the high level and maintains it, and then the logic is inverted, and the high level signal is driven to output the low level through the AND gate to shut down a pair of switch devices in the main circuit and the current detection branch. When the drive signal becomes low again, the S and R terminals of the latch input high level and low level respectively. If the switch device is driven to open again by the drive signal at this time, the DC solid-state circuit breaker will be opened again. Figure 4 (a) is a logic timing diagram of the short-circuit fault detection response circuit after a short-circuit fault occurs. Figure 4 (b) is a logic timing diagram of the short-circuit fault detection response circuit under normal operation. Where V GS It is the control signal of the switch device after the logic AND gate. By setting the threshold voltage, different levels of short-circuit protection can be met. If overcurrent occurs and the bidirectional DC solid-state circuit breaker needs to be shut down with delay, the main controller can obtain the real-time current value through the current detection branch and realize control and delayed shutdown as needed.

[0056] An application example of the present invention is a DC solid-state circuit breaker prototype using a SiC MOSFET semiconductor device as a main switching device. Figure 5 When the current is 0~5A, the current in the DC solid-state circuit breaker and the voltage V across the resistor R1 R And the measured data diagram of the surface temperature T of the Sic MOSFET semiconductor device. The current model obtained from the measured data diagram is:

[0057]

[0058] In the formula, I DS is the current flowing through the solid-state circuit breaker, V R is the voltage across the sampling resistor R1, that is, the voltage difference of the MOSFET tube in the on-state voltage drop detection circuit of the main switch device SiC MOSFET of the circuit breaker, T is the surface temperature of the main switch device SiC MOSFET, a1, b1, c1 are the current model coefficients, and the present invention adopts a high-precision current sampling instrument for collection, and calibrates the current model with the accurate current value, so as to obtain the coefficient that meets the accuracy requirement in a certain current range.

[0059] Figure 6 When the current is 5-20A, the current in the DC solid-state circuit breaker and the voltage V across the resistor R1 R The measured data of the surface temperature T of the SiC MOSFET semiconductor device is shown in Figure 2. The current model obtained from the measured data is:

[0060]

[0061] In the formula, I CS is the current flowing through the solid-state circuit breaker, VR is the voltage across the sampling resistor R1, that is, the voltage difference of the MOSFET tube in the on-state voltage drop detection circuit of the main switch device Sic MOSFET of the circuit breaker, T is the surface temperature of the main switch device Sic MOSFET, a2, b2, c2, d2 are the current model coefficients, and the present invention adopts a high-precision current sampling instrument for collection, and calibrates the current model with the accurate current value, so as to obtain the coefficient that meets the accuracy requirement in a certain current range.

[0062] The model was verified using a 5.5-digit current measuring instrument, KEYSIGHT 34450A, and the error was within 5‰.

[0063] The present invention utilizes the fact that the current flowing through the power semiconductor device has a certain functional relationship with the on-voltage and the junction temperature of the semiconductor device, and indirectly obtains the line current by collecting the resistance voltage of the detection circuit, without the need for a current sensor, thereby reducing costs. It also avoids the additional loss caused by using a shunt to collect current. The present invention solves the voltage detection and logic judgment problems caused by the excessive voltage at both ends of the switch device when the solid-state circuit breaker is turned off. The current detection method of the present invention can simultaneously meet the detection accuracy and control requirements under the three states of normal operation of the line, overload and current short-circuit fault. Specifically, the method can not only effectively protect the short-circuit current fault of the solid-state circuit breaker by hardware means and realize the rapid disconnection of the line, but also ensure the accurate measurement of the line current under normal operation and overload conditions. This not only helps to accurately calculate the electrical parameters of the line and intuitively display the current, but also can provide warning and display functions in time when an overload state occurs, thereby comprehensively improving the safety and reliability of the circuit.

[0064] The solid-state circuit breaker current model of the present invention is suitable for various applications of solid-state circuit breakers. Therefore, the current detection circuit of the present invention can effectively detect the line current in real time, and by setting the protection threshold, when a short circuit fault occurs, the solid-state circuit breaker is quickly and effectively shut down by hardware protection. In the case of overcurrent, the solid-state circuit breaker can be shut down with a delay. It has the characteristics of simple circuit structure, accurate, effective and flexible functions.

[0065] Obviously, the described embodiments are part of the embodiments of the present application, rather than all of the embodiments. In the absence of conflict, the embodiments in the present application and the features in the embodiments can be combined with each other. The components of the embodiments of the present application generally described and shown in the drawings here can be arranged and designed in various different configurations. Therefore, the detailed description of the embodiments of the present application is not intended to limit the scope of the application claimed for protection, but merely represents the selected embodiments of the present application. Based on the embodiments in the present application, all other embodiments obtained by ordinary technicians of the art without making creative work are within the scope of protection of the present application.

Claims

1. A DC solid-state circuit breaker and a current detection method thereof, characterized in that: It includes a core component of a solid-state circuit breaker, a power semiconductor device, a conduction voltage drop detection circuit, a short-circuit protection circuit, a controller, and a drive circuit connected to the controller, a current conditioning circuit, a power semiconductor device surface temperature sampling and conditioning circuit, and a DC voltage sampling and conditioning circuit; The on-state voltage drop detection circuit includes a differential circuit, a resistor R1 and a low-power semiconductor device; the resistance value of the resistor R1 is much larger than the on-state resistance of the power semiconductor device, and the control signal of the low-power semiconductor device is the same as the control signal of the power semiconductor device of the core component of the solid-state circuit breaker; one end of the low-power semiconductor device is connected to one end of the power semiconductor device, and one end of the low-power semiconductor device is connected to the other end of the power semiconductor device after being connected in series with the resistor R1; the two input ends of the differential circuit are respectively connected to the two ends of the resistor R1, and the voltage difference at the output end of the differential circuit is connected to the controller through the current conditioning circuit, and the current conditioning circuit conditions the collected voltage difference to a signal that the controller can match; the output end of the differential circuit is connected to the drive circuit through the short-circuit current protection circuit; The short-circuit current protection circuit is used to quickly cut off the solid-state circuit breaker to protect the line when a short-circuit fault occurs in the line and the voltage difference detected by the on-state voltage drop detection circuit exceeds the set value; The driving circuit is used to drive the power semiconductor device and the power semiconductor device of the conduction voltage drop detection circuit; the power semiconductor device surface temperature sampling and conditioning circuit detects and obtains the surface temperature T of the power semiconductor device, the core component of the solid-state circuit breaker; the DC voltage sampling and conditioning circuit is used to collect the line voltage; the controller calculates and processes the collected line voltage, the voltage difference of the conduction voltage drop detection circuit and the temperature parameters of the power semiconductor device, and controls the opening and closing of the power semiconductor device.

2. A DC solid-state circuit breaker according to claim 1, characterized in that: The driving signal output terminal of the controller and the output terminal of the short-circuit current protection circuit are respectively connected to two input terminals of an AND gate, and the output terminal of the AND gate is connected to the driving circuit.

3. A DC solid-state circuit breaker according to claim 1, characterized in that: The controller is also connected with an LED display circuit and a communication circuit; the LED display circuit is used to display the state and electrical parameters of the solid-state circuit breaker; and the communication circuit is used to realize the communication function of the DC solid-state circuit breaker.

4. A DC solid-state circuit breaker according to claim 1, characterized in that: The core components of the solid-state circuit breaker include power semiconductor devices such as thyristors, insulated gate bipolar transistors, metal oxide semiconductor field effect transistors, integrated gate commutated thyristor devices or junction field effect transistors; the controller includes a single chip microcomputer, DSP or ARM.

5. A DC solid-state circuit breaker according to claim 1, characterized in that: The short-circuit current protection circuit includes a comparison circuit and an RS latch circuit, wherein the negative input terminal of the comparison circuit is connected to the output terminal of the differential circuit, and the positive input terminal of the comparison circuit is grounded through a reference voltage source; the output terminal of the comparison circuit is connected to the S input terminal of the RS latch circuit; the Q output terminal of the RS latch circuit is connected to the input terminal of a NOT gate, and the output terminal of the NOT gate serves as the output terminal of the short-circuit current protection circuit; and the R input terminal of the RS latch circuit is connected to the drive signal output terminal of the controller.

6. A current detection method for a DC solid-state circuit breaker, applied to a DC solid-state circuit breaker according to any one of claims 1 to 5, characterized in that: The current detection method is: by collecting the voltage across the resistor R1 in the on-state voltage drop detection circuit and the surface temperature of the power semiconductor device, the current model flowing through the line is obtained. The calculation formula of the current model is as follows: I DS =f(V R ,V gs ,T) (1) Among them, I DS is the current flowing through the solid-state circuit breaker, that is, the real-time line current value; V gs is the driving voltage of the power semiconductor device; V R is the voltage across the resistor of the solid-state circuit breaker detection circuit, that is, the voltage difference between the power semiconductor device and the small power semiconductor device of the detection branch; T is the surface temperature of the power semiconductor device.

7. The current detection method of a DC solid-state circuit breaker according to claim 6, characterized in that: The DC solid-state circuit breaker current model is obtained by the following steps: Step 1: According to the rated current specification I of the solid-state circuit breaker d , in 0~k·I d The model is experimentally tested at N points in the range, where k is the current coefficient of the solid-state circuit breaker; Step 2: Measure the voltage V across the resistance of the detection circuit of the solid-state circuit breaker from the initial state to the stable state. Ri 、Circuit breaker current I dsi , and the surface temperature T of the power semiconductor device i , i is 1 to N; Step 3: According to V Ri ,I dsi and T i The experimental data is fitted to obtain the DC solid-state circuit breaker current model; Step 4: Use the fitted current model to calculate the current in the controller.

8. The current detection method of a DC solid-state circuit breaker according to claim 6, characterized in that: The current obtained according to the current model is used for accurate calculation of line current and protection against short-circuit faults; that is, firstly, it is sent to the controller through the differential circuit and the conditioning circuit, and the current flowing through the circuit breaker is obtained according to the functional relationship between the voltage across the resistor R1 and the surface temperature of the power semiconductor device and the current flowing through the circuit breaker, so as to display the line current in real time, as well as the status display, alarm or delayed disconnection when the line is overloaded; Secondly, when a short circuit fault occurs in the line, according to the positive correlation between the voltage signal across the resistor R1 and the line current, the power semiconductor device is quickly disconnected through the differential circuit and the short-circuit current protection circuit to protect the safety of the line.

9. The current detection method of a DC solid-state circuit breaker according to claim 6, characterized in that: The DC solid-state circuit breakers to which the current detection method is suitable include unidirectional and bidirectional DC solid-state circuit breakers, or single-pole, bipolar and multi-pole solid-state circuit breakers.

Images