Bidirectional controllable coupled inductor Z-source solid-state DC circuit breaker and application method thereof

Abstract

The present invention discloses a bidirectional controllable coupled inductor Z-source solid-state DC circuit breaker and an application method thereof, comprising a thyristor T3, wherein the cathode of the thyristor T3 is connected in series with a capacitor C and a resistor R in sequence, the end of the resistor R away from the capacitor is grounded, the anode of the thyristor T3 is connected to one end of a main switch branch, the main switch branch is connected in parallel with an energy absorption branch, the cathode of the thyristor T3 is connected to one end of a commutation branch, the other end of the commutation branch is connected to the end of the capacitor C close to the resistor R, and the commutation branch is coupled to the main switch branch; the anode of the thyristor T3 is connected to the positive electrode of a DC power supply U0, and the other end of the main switch branch is connected to a load U s The positive pole of the thyristor T3 is connected to the load U s The other end of the main switch branch is connected to the positive electrode of the DC power supply U0, and the load U s The negative electrode of the DC power supply U0 is connected to the negative electrode of the DC power supply U0. The present invention can accurately shut down when the load suddenly changes and can actively shut down small currents.

Description

Technical Field

[0001] The present invention belongs to the technical field of DC circuit breakers, and in particular relates to a bidirectionally controllable coupled inductor Z-source solid-state DC circuit breaker, and also relates to an application method of the bidirectionally controllable coupled inductor Z-source solid-state DC circuit breaker. Background Art

[0002] As the integration of large-scale photovoltaic power generation into the grid becomes increasingly challenging, new technologies are essential. Furthermore, due to the low impedance of DC transmission lines, the fault current rises rapidly and has a high amplitude when a short-circuit fault occurs, requiring DC circuit breakers to respond quickly and break current and voltage with a large amplitude. Furthermore, DC system current has no natural zero-crossing point, resulting in a high rate of current rise during a fault, seriously impacting the continuity and reliability of power supply to sensitive loads. This makes short-circuit protection a significant challenge. Solid-state DC circuit breakers offer broad application prospects due to their rapid fault current interruption time, the absence of arcing during the interruption process compared to mechanical switches, the potential for risk to surrounding equipment, and their extended service life. Currently, solid-state DC circuit breakers are primarily used in the 270V DC aerospace sector and are rarely used in 1500V DC photovoltaic power generation and energy storage applications. Because mechanical circuit breakers commonly used in solar-powered energy storage systems generate arcs when interrupting fault currents, severely eroding the contacts and shortening their service life, the arcs also pose a risk of damage to surrounding equipment. Therefore, solid-state DC circuit breakers are an attractive option for solar-powered energy storage systems due to their inherent advantages. Z-source solid-state DC circuit breakers, as a novel DC protection method, utilize thyristors as the main switches. Compared to fully controlled devices such as insulated gate bipolar transistors and metal-oxide semiconductor field-effect transistors (MOSFETs) used in traditional solid-state DC circuit breakers, thyristors offer lower conduction losses, greater voltage and current withstand capabilities, and lower cost. Leveraging an LC oscillating impedance source network, they enable autonomous commutation during fault transients and rapidly shut down the main thyristors, effectively suppressing short-circuit current peaks and providing more effective protection. Among various solutions, Z-source solid-state DC circuit breakers are attracting significant attention for their simple structure, low cost, fast response, natural commutation, and the absence of a detection and control system. However, traditional Z-source solid-state DC breakers suffer from issues such as false operation during sudden load changes and an inability to actively shut down low currents. Summary of the Invention

[0003] The purpose of the present invention is to provide a bidirectional controllable coupled inductor Z-source solid-state DC circuit breaker to solve the problems of traditional Z-source solid-state DC circuit breakers causing malfunction when the load changes suddenly and being unable to actively shut down small currents.

[0004] Another object of the present invention is to provide an application method of a bidirectional controllable coupled inductor Z-source solid-state DC circuit breaker.

[0005] The technical solution adopted by the present invention is a bidirectional controllable coupled inductor Z-source solid-state DC circuit breaker, including a thyristor T3, wherein the cathode of the thyristor T3 is connected in series with a capacitor C and a resistor R in sequence, the end of the resistor R away from the capacitor is grounded, the anode of the thyristor T3 is connected to one end of a main switch branch, the main switch branch is connected in parallel with an energy absorption branch, the cathode of the thyristor T3 is connected to one end of a commutation branch, the other end of the commutation branch is connected to the end of the capacitor C close to the resistor R, and the commutation branch is coupled to the main switch branch;

[0006] The anode of thyristor T3 is connected to the positive electrode of DC power supply U0, and the other end of the main switch branch is connected to the load U s The positive connection of the load U s The negative electrode of is connected to the negative electrode of the DC power supply U0;

[0007] Alternatively, the anode of thyristor T3 and the load U s The other end of the main switch branch is connected to the positive electrode of the DC power supply U0, and the load U s The negative pole of is connected to the negative pole of DC power supply U0.

[0008] The present invention is also characterized in that:

[0009] The main switch branch includes thyristors T1 and T2. The cathode of thyristor T1 is connected to the same-name end of inductor L1, and the anode of thyristor T2 is connected to the non-same-name end of inductor L2. The cathode of thyristor T2 is connected to the anode of thyristor T1 and then to the anode of thyristor T3. The non-same-name end of inductor L1 is connected to the same-name end of inductor L2 and then to the load U. s Alternatively, the non-identical end of the inductor L1 is connected to the identical end of the inductor L2 and then connected to the positive electrode of the DC power supply U0.

[0010] The commutation branch includes a thyristor T4. The cathode of the thyristor T4 is connected to the same-name end of the inductor L3. The anode of the thyristor T4 is connected to the cathode of the thyristor T3 and the cathode of the diode D respectively. The non-same-name end of the inductor L3 is connected to the anode of the diode D and the end of the capacitor C close to the resistor R respectively. The inductor L3 is coupled with the inductor L1 and the inductor L2 respectively.

[0011] The coupling coefficients of the inductor L3 with the inductor L1 and the inductor L2 are both 0.98.

[0012] The coupling coefficient between the inductor L1 and the inductor L2 is 0.

[0013] The energy absorption branch is composed of a lightning arrester MOV, which is connected in parallel to both ends of the main switch branch.

[0014] Another technical solution adopted by the present invention is an application method of a bidirectionally controllable coupled inductor Z-source solid-state DC circuit breaker, which uses the above-mentioned bidirectionally controllable coupled inductor Z-source solid-state DC circuit breaker, and the specific steps are as follows:

[0015] Normal flow state: Current flows through the main switch branch, triggering thyristor T3 and capacitor C Perform pre-charging;

[0016] Short circuit fault occurs: When the current rises and reaches the detection current threshold, the thyristor T4 is turned on and the capacitor C Discharge, current flows through the inductor L3, and under the action of magnetic induction, the coupled inductor in the main switch branch will induce an induced current in the opposite direction to the short-circuit current. When the induced current is equal to the short-circuit current, the thyristor is turned off. When the voltage across the main switch branch is greater than the clamping voltage of the lightning arrester MOV, the lightning arrester MOV is turned on, and the short-circuit current energy is dissipated by the lightning arrester MOV, thereby realizing the interruption of the short-circuit fault current.

[0017] The present invention is also characterized in that:

[0018] When the anode of the thyristor T3 is connected to the positive electrode of the DC power supply U0, when a short circuit fault occurs, the inductor L1 senses the induced current in the opposite direction to the short circuit current, and the thyristor that is turned off is the thyristor T1;

[0019] When the anode of thyristor T3 is connected to the load U s When the positive electrode of is connected, when a short circuit fault occurs, the inductor L2 senses the induced current in the opposite direction to the short circuit current, and the thyristor that is turned off is the thyristor T2.

[0020] Active shut-off rated current: Controls thyristor T4 to conduct, pre-charges the capacitor C Discharge is carried out, and the current flows through the inductor that forms the coupling L 3. Under the action of magnetic induction, an induced current in the opposite direction to the rated current will be induced in the coupled inductor of the main switch branch. When the induced current is equal to the rated current, the thyristor of the main switch branch is turned off. When the voltage across the main switch branch is greater than the clamping voltage of the arrester MOV, the arrester MOV is turned on, and the current energy is dissipated by the arrester MOV, realizing the interruption of small current.

[0021] When the anode of the thyristor T3 is connected to the positive electrode of the DC power supply U0, the inductor L1 senses the current in the opposite direction to the short-circuit current, and the thyristor that is turned off is the thyristor T1.

[0022] When the anode of thyristor T3 is connected to the load U s When the positive electrode is connected, the inductor L2 senses the induced current in the opposite direction to the short-circuit current, and the thyristor that is turned off is the thyristor T2.

[0023] The beneficial effects of the present invention are as follows: the bidirectional controllable coupled inductor Z-source solid-state DC circuit breaker of the present invention charges the capacitor through its own power supply, without the need for an external auxiliary power supply, realizes the bidirectional flow of energy in the circuit through two uncoupled branches in the main switch branch, and the coupled inductor in each branch is connected to the thyristor and then connected in parallel, and combined with the three-winding inductive coupling, the coupled inductor access is controlled, and small currents can be actively shut down during stable operation, and when the load changes, it can be accurately shut down; and when a short-circuit fault occurs, the voltage oscillation of the lower-level load can be avoided by controlling the coupled inductor access time, thereby ensuring the safety of the lower-level load; at the same time, the circuit breaker of the present invention realizes the common grounding of the source and load, and further improves the shutdown speed. When shutting down a small current, it takes about 0.25μs, and when shutting down a short-circuit fault current, it takes about 0.8ms. BRIEF DESCRIPTION OF THE DRAWINGS

[0024] Figure 1 Schematic diagram of the topological structure of the bidirectional controllable coupled inductor Z-source solid-state DC circuit breaker of the present invention during forward conduction;

[0025] Figure 2 This is a working principle diagram of the bidirectional controllable coupled inductor Z-source solid-state DC circuit breaker of the present invention for interrupting short-circuit current when conducting in the forward direction;

[0026] Figure 3 This is the simulated waveform of the thyristor T1 current when the load side of the bidirectional controllable coupled inductor Z-source solid-state DC circuit breaker of the present invention is short-circuited during forward conduction;

[0027] Figure 4 The load current simulation waveform of the bidirectional controllable coupled inductor Z-source solid-state DC circuit breaker of the present invention when it is in forward conduction and short-circuit fault occurs on the load side;

[0028] Figure 5 The current simulation waveform of the thyristor T1 when the bidirectional controllable coupled inductor Z-source solid-state DC circuit breaker of the present invention actively shuts off a small current of 2A during forward conduction;

[0029] Figure 6 The load current simulation waveform is shown when the bidirectional controllable coupled inductor Z-source solid-state DC circuit breaker of the present invention actively shuts off a small current of 2A during forward conduction;

[0030] Figure 7 Schematic diagram of the topological structure of the bidirectional controllable coupled inductor Z-source solid-state DC circuit breaker of the present invention during reverse conduction;

[0031] Figure 8 This is a simulated waveform of the thyristor T2 current when the load side of the bidirectional controllable coupled inductor Z-source solid-state DC circuit breaker of the present invention is short-circuited during reverse conduction;

[0032] Figure 9 The load current simulation waveform of the bidirectional controllable coupled inductor Z-source solid-state DC circuit breaker of the present invention when the load side is short-circuited during reverse conduction;

[0033] Figure 10 The current simulation waveform of the thyristor T2 when the bidirectional controllable coupled inductor Z-source solid-state DC circuit breaker of the present invention actively shuts off a small current of 2A during reverse conduction;

[0034] Figure 11 This is the load current simulation waveform when the bidirectional controllable coupled inductor Z-source solid-state DC circuit breaker of the present invention actively shuts off a small current of 2A during reverse conduction;

[0035] Figure 12 This is a schematic diagram of the topology of the old structure circuit breaker during forward conduction;

[0036] Figure 13 It is a comparison of the breaking time of the circuit breaker of the present invention and the circuit breaker of the old structure under the same fault current;

[0037] Figure 14 This is a comparison of the voltage that the thyristor needs to withstand when breaking the same fault current between the circuit breaker of the present invention and the circuit breaker of the old structure.

[0038] In the figure, 1. Main switch branch, 2. Commutation branch, 3. Energy absorption branch, 4. Pre-charging branch. DETAILED DESCRIPTION

[0039] The present invention will be described in detail below with reference to the accompanying drawings and specific embodiments.

[0040] Example 1

[0041] The bidirectional controllable coupled inductor Z-source solid-state DC circuit breaker of the present invention is as follows: Figure 1 As shown, it consists of a main switch branch 1, a commutation branch 2, an energy absorption branch 3 and a pre-charging branch 4. Specifically, the pre-charging branch 4 consists of a thyristor T3, a capacitor C and a resistor R. The cathode of the thyristor T3 is connected in series with the capacitor C and the resistor R in sequence. The end of the resistor R away from the capacitor is grounded. The anode of the thyristor T3 is connected to one end of the main switch branch 1. The energy absorption branch 3 is connected in parallel to the main switch branch 1. The cathode of the thyristor T3 is connected to one end of the commutation branch 2. The other end of the commutation branch 2 is connected to the end of the capacitor C close to the resistor R. The commutation branch 2 is coupled to the main switch branch 1. The anode of the thyristor T3 is connected to the positive electrode of the DC power supply U0. The other end of the main switch branch 1 is connected to the load U s The positive connection of the load U s The negative electrode of is connected to the negative electrode of the DC power supply U0, and it is forward conducting at this time.

[0042] The commutation branch 2 includes a thyristor T4, the cathode of the thyristor T4 is connected to the same-name end of the coupled inductor L3, the anode of the thyristor T4 is connected to the cathode of the thyristor T3 and the cathode of the diode D respectively, and the non-same-name end of the coupled inductor L3 is connected to the anode of the diode D and the end of the capacitor C close to the resistor R respectively.

[0043] The main switch branch 1 includes a thyristor T1, a thyristor T2, an inductor L1, and an inductor L2. The inductor L1 and the inductor L2 are coupled with the inductor L3 respectively, and the coupling coefficient K is 0.98. There is no coupling between the inductor L1 and the inductor L2, that is, the coupling coefficient K is 0. The cathode of the thyristor T1 is connected to the same-name end of the coupled inductor L1, and the anode of the thyristor T2 is connected to the non-same-name end of the coupled inductor L2. The cathode of the thyristor T2 is connected to the anode of the thyristor T1 and then to the anode of the thyristor T3. The non-same-name end of the coupled inductor L1 is connected to the same-name end of the coupled inductor L2 and then to the load U. s positive connection.

[0044] Energy absorption branch 3 consists of a lightning arrester MOV, which is connected in parallel to both ends of the main switch branch 1. When the voltage across the lightning arrester MOV reaches its clamping voltage, the lightning arrester MOV is turned on and can quickly dissipate system energy. The clamping voltage of the lightning arrester MOV is 1.2 to 2 times the system voltage value.

[0045] Example 2

[0046] The application method of the bidirectional controllable coupled inductor Z-source solid-state DC circuit breaker of the present invention adopts the bidirectional controllable coupled inductor Z-source solid-state DC circuit breaker of Example 1, which is forward-conducting, such as Figure 2 As shown, the specific steps are:

[0047] In the normal flow state, current flows through the main switch branch 1, triggering thyristor T3 to pre-charge capacitor C. The polarity of capacitor C is positive on the left and negative on the right. The system's conduction loss is the current loss in a single semiconductor device, which has lower conduction loss than the current Z-source DC circuit breaker. At this time, no current flows through the commutation branch, and the voltage across the MOV in the energy absorption branch is very low, so the MOV will not conduct.

[0048] When a short circuit occurs:

[0049] Phase 1: The current in the main switch branch rises to a short-circuit current, and the short-circuit current reaches the detection current threshold. i th Before, the load current i dc for:

[0050] (1)

[0051] In formula (1), i 0 is the load current i dc The initial value of U s is the voltage across the load, t For time;

[0052] Phase 2: When the short-circuit current reaches the detection current threshold, which is set to 10 times the system rated current, thyristor T4 is turned on, discharging the pre-charged capacitor C. Current is injected into the same-name terminal of the coupled inductor L3 through thyristor T4. Under the action of magnetic induction, the coupled inductor L1 in the main switch branch 1 induces an induced current in the opposite direction to the short-circuit current. When the induced current is equal to the short-circuit current, thyristor T1 is turned off.

[0053] According to Kirchhoff's voltage law (KVL):

[0054] (2)

[0055] In formula (2), u 1 is the voltage across the coupled inductor L1, u T1 is the voltage across thyristor T1, u C is the voltage across capacitor C, u 2 is the voltage across the coupled inductor L3, n is the turns ratio, k is the mutual inductance coefficient of the coupled inductors, u MOV is the voltage across the MOV;

[0056] The voltage across the MOV u MOV Smaller than the clamping voltage of MOV u clamp When , we can get:

[0057] (3)

[0058] In formula (3), α is U s and u clamp In order to turn off the thyristor T1, the thyristor T1 voltage u T1 Should be less than 0;

[0059] Phase 3: When the voltage across main switch branch 1 exceeds the clamping voltage of the arrester MOV, the arrester MOV is turned on, and the current in main switch branch 1 begins to transfer to the arrester MOV. The arrester MOV absorbs the short-circuit current energy and dissipates it as heat, thus interrupting the short-circuit fault current.

[0060] After thyristor T1 is turned off, capacitor C continues to discharge. Ignoring the voltage drop and loss of thyristor T4, capacitor C and coupled inductor L3 still form an LC oscillation circuit. According to Kirchhoff's voltage law (KVL), it can be deduced that:

[0061] (4)

[0062] From the structure, we can see that the voltage across the capacitor C is u C and the current of capacitor C i C The initial values are U S and- nki th , therefore, the solution of formula (5) is:

[0063] (5)

[0064] when u MOV achieve u clamp The value of u MOV = u clamp =α U S ; To ensure that the thyristor T1 is turned off, during the turn-off period of the thyristor T1 t q , u T1 should always be negative. Therefore, we have:

[0065] (6)

[0066] According to formula (6), the value of the capacitor C can be obtained i th 、 n 、 k 、 L The relationship between 3 and α;

[0067] Thyristor selection: The maximum current and voltage that the thyristor can withstand during the short-circuit fault interruption process are the most important factors to prevent damage. In the main switch branch, the maximum current flowing through thyristor T1 and thyristor T2 should be greater than the set detection current threshold. i th, In addition, the voltage to be withstood should be greater than the voltage of the MOV u clamp The maximum voltage and current that thyristor T3 can withstand should be greater than U S and , thyristor T3 is used to charge capacitor C, the maximum charging current i Dmax Should be:

[0068] (7)

[0069] The maximum current flowing through thyristor T3 must be greater than i Dmax .

[0070] Selection of coupling inductors and capacitors: When designing coupling inductors, the maximum current and the inductance of the coil should be considered. According to formula (1), the coupling inductor limits the rate of rise of the fault current. The larger the inductance, the slower the rate of rise of the fault current. The weight and volume of the coupling inductor are larger. According to formula (3), the turns ratio of the coupling inductor is n Should be greater than α / k; C, L3 and n The relationship between them is shown in formula (6).

[0071] As the voltage and current ratings increase, the size and cost of the coupled inductor also increase, and the mutual inductance of the coupled inductor k The value of will decrease; According to formula (3), as k The decrease, n It must be increased to ensure the normal operation of the arrester MOV; according to formula (6), k The change of the value of will affect the value of C. k As the value of C decreases, the required value of C gradually increases. Therefore, a larger value of C can be used to compensate for k of the reduction.

[0072] The same letters used in formula (1) to formula (7) of the method of the present invention represent the same definitions.

[0073] Figure 3 The current simulation waveform of thyristor T1 in the case of load side short circuit fault when it is forward-conducting at a DC voltage level of 1500V. t =0.3s when a short circuit fault occurs on the load side and the current rises rapidly. When the fault current detection threshold is reached, the thyristor T4 is triggered and the current of the thyristor T1 begins to decrease. t =0.30047s, the current of thyristor T1 drops to 0.

[0074] Figure 4This is the load current simulation waveform when the load side is short-circuited at a DC voltage level of 1500V. When a short-circuit fault occurs on the load side, the current rises rapidly. When it reaches the detection current threshold i th , triggering thyristor T4, and the current of thyristor T1 begins to decrease. At this time, the energy absorption branch starts to work, and the load side current gradually drops to zero. The turn-off time is 0.8ms, ensuring the safety of the load side.

[0075] Example 3

[0076] The application method of the bidirectional controllable coupled inductor Z-source solid-state DC circuit breaker of the present invention adopts the bidirectional controllable coupled inductor Z-source solid-state DC circuit breaker of Example 1, which is forward-conducting, and specifically comprises the following steps:

[0077] In the normal flow state: current flows through the main switch branch 1, triggering the thyristor T3 to pre-charge the capacitor C;

[0078] When the rated current is actively shut down: the thyristor T4 is controlled to be turned on, the pre-charged capacitor C is discharged, and the current flows through the coupled inductor L3. Under the action of magnetic induction, an induced current in the opposite direction to the rated current will be induced in the coupled inductor L1 of the main switch branch 1. When the induced current is equal to the rated current, the thyristor T1 of the main switch branch 1 is turned off. When the voltage across the main switch branch 1 is greater than the clamping voltage of the lightning arrester MOV, the lightning arrester MOV is turned on, and the current energy is dissipated by the lightning arrester MOV, completing the rated current shutdown and realizing the interruption of small current.

[0079] like Figure 5 and Figure 6 As shown, it actively shuts off the 2A small current. t =0.3s, the thyristor T4 is triggered and the current of thyristor T1 begins to decrease. t =0.30000025s, the current of thyristor T1 drops to zero, and at the same time the energy absorption branch starts to work, the load side current gradually drops to zero, and the turn-off time is 0.25μs.

[0080] Example 4

[0081] The bidirectional controllable coupled inductor Z-source solid-state DC circuit breaker of the present invention is as follows: Figure 7As shown, it consists of a main switch branch 1, a commutation branch 2, an energy absorption branch 3 and a pre-charging branch 4. Specifically, the pre-charging branch 4 consists of a thyristor T3, a capacitor C and a resistor R. The cathode of the thyristor T3 is connected in series with the capacitor C and the resistor R in sequence. The end of the resistor R away from the capacitor is grounded. The anode of the thyristor T3 is connected to one end of the main switch branch 1. The energy absorption branch 3 is connected in parallel to the main switch branch 1. The cathode of the thyristor T3 is connected to one end of the commutation branch 2. The other end of the commutation branch 2 is connected to the end of the capacitor C close to the resistor R. The commutation branch 2 is coupled to the main switch branch 1. The anode of the thyristor T3 is connected to the load U s The other end of the main switch branch 1 is connected to the positive electrode of the DC power supply U0, and the load U s The negative electrode of the DC power supply U0 is connected to the negative electrode of the load U s The negative electrode of is connected to the negative electrode of the DC power supply U0, and it is reverse conducting at this time.

[0082] The commutation branch 2 includes a thyristor T4, the cathode of the thyristor T4 is connected to the same-name end of the coupled inductor L3, the anode of the thyristor T4 is connected to the cathode of the thyristor T3 and the cathode of the diode D respectively, and the non-same-name end of the coupled inductor L3 is connected to the anode of the diode D and the end of the capacitor C close to the resistor R respectively.

[0083] The main switch branch 1 includes a thyristor T1, a thyristor T2, an inductor L1, and an inductor L2. The inductor L1 and the inductor L2 are coupled with the inductor L3 respectively, and the coupling coefficient K is 0.98. There is no coupling between the inductor L1 and the inductor L2, that is, the coupling coefficient K is 0. The cathode of the thyristor T1 is connected to the same-name end of the coupled inductor L1, and the anode of the thyristor T2 is connected to the non-same-name end of the coupled inductor L2. The cathode of the thyristor T2 is connected to the anode of the thyristor T1 and then to the anode of the thyristor T3. The non-same-name end of the coupled inductor L1 is connected to the same-name end of the coupled inductor L2 and then to the load U. s positive connection.

[0084] Energy absorption branch 3 consists of a lightning arrester MOV, which is connected in parallel to both ends of the main switch branch 1. When the voltage across the lightning arrester MOV reaches its clamping voltage, the lightning arrester MOV is turned on and can quickly dissipate system energy. The clamping voltage of the lightning arrester MOV is 1.2 to 2 times the system voltage value.

[0085] Example 5

[0086] The application method of the bidirectional controllable coupled inductor Z-source solid-state DC circuit breaker of the present invention adopts the bidirectional controllable coupled inductor Z-source solid-state DC circuit breaker of Example 4, which is reverse conducting, and the specific steps are as follows:

[0087] In the normal flow state, current flows through the main switch branch 1, triggering thyristor T3 to pre-charge capacitor C. The polarity of capacitor C is positive on the left and negative on the right. The system's conduction loss is the current loss in a single semiconductor device, which has lower conduction loss than the current Z-source DC circuit breaker. At this time, no current flows through the commutation branch, and the voltage across the MOV in the energy absorption branch is very low, so the MOV will not conduct.

[0088] When a short circuit occurs:

[0089] Phase 1: The current in the main switch branch rises to a short-circuit current;

[0090] Phase 2: When the short-circuit current reaches the detection current threshold, which is set to 10 times the system rated current, thyristor T4 is controlled to conduct, discharging the pre-charged capacitor C. Current is injected into the same-name terminal of the coupled inductor L3 through thyristor T4. Under the action of magnetic induction, the coupled inductor L2 in the main switch branch 1 induces an induced current in the opposite direction to the short-circuit current. When the induced current is equal to the short-circuit current, thyristor T2 is turned off.

[0091] Phase 3: When the voltage across the main switch branch 1 is greater than the clamping voltage of the arrester MOV, the arrester MOV is turned on, and the current in the main switch branch 1 begins to transfer to the arrester MOV. The arrester MOV absorbs the short-circuit current energy and converts it into heat energy for dissipation, thereby interrupting the short-circuit fault current.

[0092] The principle of the short-circuit fault current switch in this embodiment is the same as that of the second embodiment.

[0093] Figure 8 The current simulation waveform of thyristor T2 in reverse conduction under load side short circuit fault at DC 1500V voltage level is shown in Figure 2. t =0.3s when a short circuit occurs on the load side and the current rises rapidly. When the detection current threshold is reached, the thyristor T4 is triggered and the current of the thyristor T2 begins to decrease. t =0.30047s, the current of thyristor T2 drops to zero.

[0094] Figure 9 This is the load current simulation waveform when the load side is short-circuited at a DC voltage level of 1500V during reverse conduction. When a short-circuit fault occurs on the load side, the current rises rapidly. When the detection current threshold is reached, thyristor T4 is triggered, and the current of thyristor T2 begins to decrease. At this time, the energy absorption branch starts to work, and the load side current gradually drops to zero. The shutdown time is 0.8ms, ensuring the safety of the load side.

[0095] Example 6

[0096] The application method of the bidirectional controllable coupled inductor Z-source solid-state DC circuit breaker of the present invention adopts the bidirectional controllable coupled inductor Z-source solid-state DC circuit breaker of Example 4, which is reverse conducting, and the specific steps are as follows:

[0097] In the normal flow state: current flows through the main switch branch 1, triggering the thyristor T3 to pre-charge the capacitor C;

[0098] When the rated current is actively shut down: the thyristor T4 is controlled to be turned on, the pre-charged capacitor C is discharged, and the current flows through the coupled inductor L3. Under the action of magnetic induction, an induced current in the opposite direction to the rated current will be induced in the coupled inductor L2 of the main switch branch 1. When the induced current is equal to the rated current, the thyristor T2 of the main switch branch 1 is turned off. When the voltage across the main switch branch 1 is greater than the clamping voltage of the lightning arrester MOV, the lightning arrester MOV is turned on, and the current energy is dissipated by the lightning arrester MOV, completing the rated current shutdown and realizing the interruption of small current.

[0099] like Figure 10 and Figure 11 As shown, it actively shuts off the 2A small current. t =0.3s, the thyristor T4 is triggered and the current of thyristor T1 begins to decrease. t =0.30000025s, the current of thyristor T2 drops to zero. At the same time, the energy absorption branch starts to work, and the load current gradually drops to zero. The turn-off time is 0.25μs.

[0100] The structure of the old structure circuit breaker is as follows Figure 12 As shown, it includes a thyristor SCR1, the anode of the thyristor SCR1 is connected to the positive electrode of the DC power supply U0 and the cathode of the diode D2, the anode of the diode D2 is connected to the anode of the diode D1, and the cathode of the diode D1 is connected to the anode of the thyristor SCR2 and the load U S The positive electrode of the thyristor SCR1 is connected to the cathode of the thyristor SCR1 and the coupling inductor L is coupled to form a coupling 11 The same-name terminal, the cathode of the diode D3, and the cathode of the thyristor SCR2 are connected to form a coupled coupling inductor L 11 The non-identical terminals form a coupled inductor L 12 The same-name ends are connected to form a coupled inductor L 12 The non-identical ends are connected to the anode of diode D2 and resistor R d Connect one end of the resistor R d The other end is connected to the anode of the diode D4, and the cathode of the diode D4 is connected to the coupling inductor L 12 The anode of the diode D3 is connected to one end of the resistor R, and the other end of the resistor R is connected to the coupling inductor L. 11The non-identical end of the capacitor C is connected to the negative electrode of the DC power supply U0 and the load U S negative connection.

[0101] like Figure 13 As shown, when the circuit breaker of the present invention and the old structure circuit breaker interrupt the same magnitude of fault current, the time required for the old structure circuit breaker to interrupt the fault current is 1.25ms, while the time required for the circuit breaker of the present invention to interrupt the fault current is 0.87ms, which is 30.4% shorter than the breaking time of the old structure circuit breaker.

[0102] like Figure 14 As shown, when the circuit breaker of the present invention and the circuit breaker of the old structure interrupt the fault current of the same magnitude, the maximum surge voltage borne by the thyristor of the old structure circuit breaker when interrupting the fault current is 67V, while the maximum surge voltage borne by the thyristor of the circuit breaker of the present invention when interrupting the fault current is 57V, which is 15.9% lower than the maximum surge voltage borne by the thyristor of the old structure circuit breaker.

[0103] In the bidirectional controllable coupled inductor Z-source solid-state DC circuit breaker of the present invention, due to the presence of diode D, the current initially flowing through capacitor C in the commutation branch 2 begins to flow through diode D. Due to the forward bias voltage of diode D, the voltage of capacitor C becomes zero. Since the voltage of capacitor C does not become negative, DC capacitors can be used. Compared with AC capacitors at the same voltage, they are smaller and more economical. The main switch branch 1 is connected to the thyristor T1 and inductor L1 to form one branch, and the thyristor T2 and inductor L2 to form another branch. The coupled inductor and thyristor in each branch are connected in parallel to achieve bidirectional flow in the circuit.

Claims

1. Bidirectional controllable coupled inductor Z source solid-state DC circuit breaker, characterized in that: The invention comprises a thyristor T3, wherein the cathode of the thyristor T3 is connected in series with a capacitor C and a resistor R in sequence, the end of the resistor R away from the capacitor is grounded, the anode of the thyristor T3 is connected to one end of a main switch branch (1), the main switch branch (1) is connected in parallel with an energy absorption branch (3), the cathode of the thyristor T3 is connected to one end of a commutation branch (2), the other end of the commutation branch (2) is connected to one end of the capacitor C close to the resistor R, and the commutation branch (2) is coupled with the main switch branch (1); The anode of thyristor T3 is connected to the positive electrode of DC power supply U0, and the other end of main switch branch (1) is connected to the load U s The positive connection of the load U s The negative electrode of is connected to the negative electrode of the DC power supply U0; Alternatively, the anode of thyristor T3 and the load U s The other end of the main switch branch (1) is connected to the positive electrode of the DC power supply U0, and the load U s The negative electrode of is connected to the negative electrode of the DC power supply U0; The main switch branch (1) includes a thyristor T1 and a thyristor T2, wherein the cathode of the thyristor T1 is connected to the same-name end of the inductor L1, the anode of the thyristor T2 is connected to the non-same-name end of the inductor L2, the cathode of the thyristor T2 is connected to the anode of the thyristor T1 and then to the anode of the thyristor T3, the non-same-name end of the inductor L1 is connected to the same-name end of the inductor L2 and then to the load U s Alternatively, the non-identical end of the inductor L1 is connected to the identical end of the inductor L2 and then connected to the positive electrode of the DC power supply U0; The commutation branch (2) includes a thyristor T4, the cathode of the thyristor T4 is connected to the same-name end of the inductor L3, the anode of the thyristor T4 is connected to the cathode of the thyristor T3 and the cathode of the diode D respectively, the non-same-name end of the inductor L3 is connected to the anode of the diode D and the end of the capacitor C close to the resistor R respectively, and the inductor L3 is coupled with the inductor L1 and the inductor L2 respectively.

2. The bidirectional controllable coupled inductor Z-source solid-state DC circuit breaker according to claim 1, characterized in that: The coupling coefficients of the inductor L3 with the inductor L1 and the inductor L2 are both 0.

98.

3. The bidirectional controllable coupled inductor Z-source solid-state DC circuit breaker according to claim 2, characterized in that: The coupling coefficient between the inductor L1 and the inductor L2 is 0.

4. The bidirectional controllable coupled inductor Z-source solid-state DC circuit breaker according to claim 3, characterized in that: The energy absorption branch (3) is composed of a lightning arrester MOV, and the lightning arrester MOV is connected in parallel to both ends of the main switch branch (1).

5. The application method of the bidirectional controllable coupled inductor Z source solid-state DC circuit breaker is characterized in that: The bidirectional controllable coupled inductor Z-source solid-state DC circuit breaker according to claim 4 is used, and the specific steps are as follows: Normal flow state: Current flows from the main switch branch (1), triggering thyristor T3 and capacitor C Perform pre-charging; Short circuit fault occurs: When the current rises and reaches the detection current threshold, the thyristor T4 is turned on and the capacitor C Discharge, current flows through the inductor L3, and under the action of magnetic induction, the inductor coupled in the main switch branch (1) will induce an induced current in the opposite direction to the short-circuit current. When the induced current is equal to the short-circuit current, the thyristor is turned off. When the voltage across the main switch branch (1) is greater than the arrester MOV clamping voltage, the arrester MOV is turned on, and the short-circuit current energy is dissipated by the arrester MOV, thereby realizing the interruption of the short-circuit fault current. When the anode of the thyristor T3 is connected to the positive electrode of the DC power supply U0, when a short circuit fault occurs, the inductor L1 senses the induced current in the opposite direction to the short circuit current, and the thyristor that is turned off is the thyristor T1; When the anode of thyristor T3 is connected to the load U s When the positive electrode of is connected, when a short circuit fault occurs, the inductor L2 senses the induced current in the opposite direction to the short circuit current, and the thyristor that is turned off is the thyristor T2.

6. The application method of the bidirectional controllable coupled inductor Z-source solid-state DC circuit breaker according to claim 5, characterized in that: Active shut-off rated current: Controls thyristor T4 to conduct, pre-charges the capacitor C Discharge is carried out, and the current flows through the inductor that forms the coupling L 3. Under the action of magnetic induction, an induced current opposite to the rated current will be induced in the coupled inductor of the main switch branch (1). When the induced current is equal to the rated current, the thyristor of the main switch branch (1) is turned off. When the voltage across the main switch branch (1) is greater than the arrester MOV clamping voltage, the arrester MOV is turned on, and the current energy is dissipated by the arrester MOV, thereby realizing the interruption of small current.

7. The application method of the bidirectional controllable coupled inductor Z-source solid-state DC circuit breaker according to claim 6, characterized in that: When the anode of the thyristor T3 is connected to the positive electrode of the DC power supply U0, the inductor L1 senses the current in the opposite direction to the short-circuit current, and the thyristor that is turned off is the thyristor T1. When the anode of thyristor T3 is connected to the load U s When the positive electrode is connected, the inductor L2 senses the induced current in the opposite direction to the short-circuit current, and the thyristor that is turned off is the thyristor T2.

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