CN111900708A - A Soft-Switching Solid-State Power Controller with Current-Limiting Function - Google Patents

Abstract

The invention discloses a soft switch solid-state power controller with a current-limiting function, which comprises an alternating-current input power supply, first to fourth power switch tubes, first to fourth power diodes, a power resistor and an induction resistor, wherein the first power switch tube, the second power switch tube, the third power switch tube, the fourth power switch tube, the first power diode, the second power diode, the third power diode, the fourth power diode, the power; the first power switch tube and the second power switch tube are connected in series to form a main branch circuit, and the third power switch tube and the fourth power switch tube are connected in series to form a current-limiting branch circuit; off state when both branches are off; the open state when both branches are open; when the main branch is closed and the current-limiting branch is opened, the current-limiting branch is in a current-limiting state. When the absolute value of the peak current exceeds a threshold value, the SSPC enters a current limiting state; when the alternating current SSPC enters a current limiting state, judging whether a short-circuit fault occurs by using the voltage absolute value at the node power-off position, and if so, entering a closing state; after the current limiting process, when the absolute value of the current is lower than the threshold value, the SSPC recovers the conducting state. The invention improves the capability of SSPC to start large-capacity capacitance load and the safety of short-circuit protection in high-power application.

Description

A soft-switching solid-state power controller with current-limiting function

technical field

The invention relates to the technical field of solid-state power controllers, in particular to a soft-switch solid-state power controller with a current limiting function.

Background technique

Solid-State Power Controller (SSPC for short) is an intelligent switchgear that integrates the conversion function of relays and the circuit protection function of circuit breakers. It has no contact, no arc, no noise, fast response, electromagnetic It has the advantages of small interference, long life, high reliability and convenient computer remote control, etc., and is widely used in the power distribution system of aircraft, ships and tanks.

In the DC power distribution system, the limitation of instantaneous inrush current caused by capacitive load connection has always been the focus and difficulty of SSPC. For AC systems, due to the ZVS-on function of the AC SSPC, the instantaneous inrush current can be significantly reduced or even eliminated. However, as power capability increases, an AC SSPC can control not only one load, but also one bus line to power several loads at the same time. Therefore, each capacitive load can be connected to the bus with its own switch at any time, such as the peak of a sinusoidal voltage, creating a huge overcurrent. At the same time, as the AC SSPC expands from the aircraft power distribution system to other power distribution systems, some serious nonlinear loads may appear, such as uncontrolled rectification with large capacitance filters, and the connection of such loads will cause more serious problems. Inrush current. In addition, short-circuit faults cause continuous inrush currents.

In order to prevent overcurrent and surge current from damaging the power system, the AC SSPC must have a current limiting function, and the AC SSPC should have the ability to distinguish short-circuit faults and surge loads as soon as possible. Traditional AC SSPCs use switching devices, usually MOSFETs, to limit the inrush current. However, in this process, the MOSFET must withstand large power losses and high temperatures, so this current limiting method cannot operate for a long time, otherwise it will cause the load capacitor to be undercharged or even turned off.

The principle of current limiting is to introduce impedance. The commonly used methods are 1. Introduce a saturated iron core current limiter, but the volume of the iron core and winding is too large for SSPC, and the nonlinear change of the magnetic permeability of the iron core makes the impedance control hard to accomplish. 2. A whole cabinet control based on AC chopper is introduced, but the control is too complicated, and it is difficult for AC SSPC to ensure its reliability. In addition, the volume of the transformer cannot be ignored. Therefore, in order to improve the ability of AC solid-state power controllers (SSPCs) to start large-capacity capacitive loads and improve their short-circuit protection safety in high-power applications, it is urgent to develop new soft-switching topologies and control strategies.

SUMMARY OF THE INVENTION

The purpose of the present invention is to provide a soft-switching solid-state power controller with a current-limiting function, which is capable of starting a large-capacity capacitive load and has a high safety.

The technical solution to achieve the purpose of the present invention is: a soft-switching solid-state power controller with a current limiting function, comprising an AC input power supply, a first power switch tube, a first power diode, a second power switch tube, and a second power diode , the third power switch tube, the third power diode, the fourth power switch tube, the fourth power diode, the power resistor and the sense resistor;

The drain of the first power switch is connected to the drain of the third power switch, and is connected to the positive terminal of the input AC power supply; the source of the first power switch is connected to the source of the second power switch, and the third power switch The source of the tube is connected to the source of the fourth power switch tube, the drain of the fourth power switch tube is connected to one end of the power resistor, the other end of the power resistor is connected to the drain of the second power switch tube, and is connected to one end of the induction resistor, The other end of the induction resistor is connected to one end of the load, and the other end of the load is connected to the negative end of the input AC power supply; the cathode of the first power diode is connected to the drain of the first power switch tube, and the anode of the first power diode is connected to the first power diode. The source of the power switch tube is connected; the cathode of the second power diode is connected to the drain of the second power switch tube, the anode of the second power diode is connected to the source of the second power switch tube; the cathode of the third power diode is connected to the The drains of the three power switches are connected to the drains, the anodes of the third power diodes are connected to the sources of the third power switches; the cathodes of the fourth power diodes are connected to the drains of the fourth power switches, and the anodes of the fourth power diodes are connected to The sources of the fourth power switch tubes are connected to each other.

Further, the first power switch tube and the second power switch tube are connected in series to form a main branch, and the third power switch tube and the fourth power switch tube are connected in series to form a current limiting branch;

When both branches are closed, it is in the closed state; when both branches are open, it is in the open state; when the main branch is closed and the current-limiting branch is open, it is in the current-limiting state.

Further, the control strategy for triggering the current limit is as follows:

The peak current detection is used to judge when the AC SSPC is converted into the current-limiting state. When the absolute value of the current exceeds the threshold U _th1 , the effective current-limiting signal is locked, the main branch of the SSPC is closed, and the current-limiting state is entered; Then, when the absolute value of the current is lower than the threshold value U _th1 , the SSPC returns to the conducting state.

Further, the strategies for distinguishing short-circuit faults or surge loads are as follows:

When the AC SSPC enters the current-limiting state, the absolute value of the voltage at the node "power-off" |u _POWEROUT |, that is, the load voltage, is used to judge whether a short-circuit fault occurs. If the absolute value of the voltage |u _{POWEROUT |} is lower than The threshold value U _th3 is determined as a short-circuit fault or a polar capacitive load that cannot be turned on by the system, and it enters the shutdown state.

Compared with the prior art, the present invention has significant advantages as follows: (1) peak current detection is used to determine when the AC SSPC is converted into a current-limiting state, the method is fast and effective, and the ability of the SSPC to start a large-capacity capacitive load is improved; (2) ) Use the load voltage to judge whether a short-circuit fault occurs. Once a short-circuit fault is found, the power supply will be cut off immediately, which improves the safety of short-circuit protection of SSPC in high-power applications.

Description of drawings

FIG. 1 is a schematic structural diagram of a soft-switching solid-state power controller with a current-limiting function of the present invention.

2 is a schematic diagram of a drive signal, an input voltage, and an output current waveform when the soft-switching solid-state power controller with a current-limiting function works according to an embodiment of the present invention.

FIG. 3 is a schematic diagram of switching mode 1 in an embodiment of the present invention.

FIG. 4 is a schematic diagram of switching mode 2 in an embodiment of the present invention.

FIG. 5 is a schematic diagram of switching mode 3 in an embodiment of the present invention.

FIG. 6 is a schematic diagram of switching mode 4 in an embodiment of the present invention.

FIG. 7 is a schematic diagram of a switch mode 5 in an embodiment of the present invention.

FIG. 8 is a block diagram of a control circuit for triggering current limit in an embodiment of the present invention.

FIG. 9 is a schematic diagram of a modal change of a current limiting process in an embodiment of the present invention.

FIG. 10 is a schematic diagram of a control circuit in which a short circuit and a surge load are separated in an embodiment of the present invention.

In the figure: u _in is the AC input; S ₁ , S ₂ , S ₃ , and S ₄ are the first, second, third, and fourth power switch tubes, respectively; D1, D2, D3, and D4 are S ₁ , S respectively _{2. The} diodes connected in parallel between the drain and source of _S3 and _{S4, ugs1, ugs2 , ugs3 and ugs4} are the driving signals _of S1, S2, _S3 and S4 respectively, and _{R limit} is the current limiting resistor , R _sense is the sense resistance, LOAD is the load resistance.

Detailed ways

The soft-switching solid-state power controller with current limiting function of the present invention includes an AC input power supply u _in , a first power switch S ₁ , a first power diode D ₁ , a second power switch S ₂ , and a second power diode D ₂ , a third power switch tube S ₃ , a third power diode D ₃ , a fourth power switch tube S ₄ , a fourth power diode D ₄ , a power resistor R _limit and a sense resistor R _sense ;

The drain of the _first power switch S1 is connected to the drain of the _third power switch S3, and is connected to the positive terminal of the input AC power supply u _in ; the source of the _first power switch S1 is connected to the second power switch S3. _The source of S2 is connected to the source, the source of the _third power switch S3 is connected to the source of the _fourth power switch S4, and the drain of the _fourth power switch _{S4 is connected to one end of the power resistor R limit .} The other end is connected to the drain of the _second power switch tube S2, and is connected to one end of the sense resistor R _sense , the other end of the sense resistor R _sense is connected to one end of the load LOAD, and the other end of the load LOAD is connected to the input AC power supply u _in . The cathode of the _first power diode D1 is connected to the drain of the _first power switch tube S1, and the anode of the _first power diode D1 is connected to the source of the _first power switch tube S1; the second power diode _The cathode of D2 is connected to the drain of the _second power switch S2, the anode of the _second power diode D2 is connected to the source of the _second power switch S2; the cathode of the _third power diode D3 is connected to the third power The drain of the switch S3 is connected to the drain, the anode of the _third power diode _D3 is connected to the source of the _third power switch S3; the cathode of the _fourth power diode D4 is connected to the drain of the _fourth power switch S4 , the anode of the _fourth power diode D4 is connected to the source of the _fourth power switch tube S4.

As a specific example, the _first power switch S1 and the _second power switch S2 are connected in series to form a main branch, and the _third power switch S3 and the _fourth power switch S4 are connected in series to form a current-limiting branch ;

When both branches are closed, it is in the closed state; when both branches are open, it is in the open state; when the main branch is closed and the current-limiting branch is open, it is in the current-limiting state.

Further, the control strategy for triggering the current limit is as follows:

The peak current detection is used to judge when the AC SSPC is converted into the current-limiting state. When the absolute value of the current exceeds the threshold U _th1 , the effective current-limiting signal is locked, the main branch of the SSPC is closed, and the current-limiting state is entered; Then, when the absolute value of the current is lower than the threshold value U _th1 , the SSPC returns to the conducting state.

Further, the strategies for distinguishing short-circuit faults or surge loads are as follows:

When the AC SSPC enters the current-limiting state, the absolute value of the voltage at the node "power-off" |u _POWEROUT |, that is, the load voltage, is used to judge whether a short-circuit fault occurs. If the absolute value of the voltage |u _{POWEROUT |} is lower than The threshold value U _th3 is determined as a short-circuit fault or a polar capacitive load that cannot be turned on by the system, and it enters the shutdown state.

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

Example

Referring to FIG. 1 , a soft-switching solid-state power controller with current limiting function of the present invention is characterized in that it includes an AC input power supply u _in , a first power switch tube S ₁ , a first power diode D ₁ , and a second power switch tube S ₂ , second power diode D ₂ , third power switch tube S ₃ , third power diode D ₃ , fourth power switch tube S ₄ , fourth power diode D ₄ , power resistor R _limit and sense resistor R _sense ;

The drain of the _first power switch S1 is connected to the drain of the _third power switch S3, and is connected to the positive terminal of the input AC power supply u _in ; the source of the _first power switch S1 is connected to the second power switch S3. _The source of S2 is connected to the source, the source of the _third power switch S3 is connected to the source of the _fourth power switch S4, and the drain of the _fourth power switch _{S4 is connected to one end of the power resistor R limit .} The other end is connected to the drain of the _second power switch tube S2, and is connected to one end of the sense resistor R _sense , the other end of the sense resistor R _sense is connected to one end of the load LOAD, and the other end of the load LOAD is connected to the input AC power supply u _in . The cathode of the _first power diode D1 is connected to the drain of the _first power switch tube S1, and the anode of the _first power diode D1 is connected to the source of the _first power switch tube S1; the second power diode _The cathode of D2 is connected to the drain of the _second power switch S2, the anode of the _second power diode D2 is connected to the source of the _second power switch S2; the cathode of the _third power diode D3 is connected to the third power _The drain of the switch S3 is connected, the anode of the _third power diode D3 is connected to the source of the _third power switch S3; the cathode of the _fourth power diode D4 is connected to the drain of the _fourth power switch S4 , the anode of the _fourth power diode D4 is connected to the source of the _fourth power switch tube S4.

Further, the first power switch tube S ₁ and the second power switch tube S ₂ are connected in series to form a main branch, and the third power switch tube S ₃ and the fourth power switch tube S ₄ are connected in series to form a current-limiting branch;

When both branches are closed, it is in the closed state; when both branches are open, it is in the open state; when the main branch is closed and the current-limiting branch is open, it is in the current-limiting state.

Further, the control strategy for triggering the current limit is as follows:

The peak current detection is used to judge when the AC SSPC is converted into the current-limiting state. When the absolute value of the current exceeds the threshold U _th1 , the effective current-limiting signal is locked, the main branch of the SSPC is closed, and the current-limiting state is entered; Then, when the absolute value of the current is lower than the threshold value U _th1 , the SSPC returns to the conducting state.

Further, the strategies for distinguishing short-circuit faults or surge loads are as follows:

When the AC SSPC enters the current-limiting state, the absolute value of the voltage at the node "power-off" |u _POWEROUT |, that is, the load voltage, is used to judge whether a short-circuit fault occurs. If the absolute value of the voltage |u _{POWEROUT |} is lower than The threshold value U _th3 is determined as a short-circuit fault or a polar capacitive load that cannot be turned on by the system, and it enters the shutdown state.

₁ , the first power switch S1 and the _second power switch S2 are connected in series to form a main branch, and the _third power switch S3 and the _fourth power switch S4 are connected in series to form a current limiting branch.

The different functions of the soft-switching solid-state power controller with the current-limiting function in this embodiment are realized by switching between the following three states.

(1) Closed state: Both branches are closed.

(2) Open state: Both branches are open.

(3) Current-limiting state: the main branch is closed, and the current-limiting branch is open.

Combined with the waveforms of the sspc starting and stopping work in Figure 2, the following working modes can be obtained:

Switch mode 1 [t ₀ ˜t ₁ ] is shown in FIG. 3 : in this mode, the first power switch S ₁ , the third power switch S ₃ , and the fourth power switch S ₄ are turned off, and the first power switch S 1 , the third power switch S 3 , and the fourth power switch S 4 The _second power switch tube S2 is closed; because the input voltage is in the positive half cycle, the _first power diode D1 acts as a clamp, so the circuit does not form a loop.

Switch mode 2 [t ₁ ˜t ₂ ] is shown in FIG. 4 : in this mode, the first power switch tube S ₁ , the third power switch tube S ₃ , and the fourth power switch tube S ₄ are turned off, and the first power switch tube S 1 , the third power switch tube S 3 , and the fourth power switch tube S 4 The _two power switch tube S2 is closed; while the input voltage is commutated to the negative half cycle, the diode D1 is conducting forward, and the circuit forms a loop

Switch mode 3 [t ₂ ˜t ₃ ] is shown in FIG. 5 : in this mode, the first power switch S ₁ , the second power switch S ₂ , the third power switch S ₃ , and the fourth power switch S 1 _The switch tube S4 is closed; since the first power diode D1 _conducts in the forward direction, the voltage across the two ends is zero, and at this time, the _first power switch tube S1 is turned on at zero voltage. At this time, the solid-state power controller realizes soft turn-on, the circuit works normally, and the current limiting circuit works.

Switch mode 4 [t ₃ ˜t ₄ ] is shown in FIG. 6 : in this mode, the first power switch S ₁ , the third power switch S ₃ , and the fourth power switch S ₄ are closed, and the second power switch S 1 is closed. _The power switch tube S2 is disconnected; the circuit loop continues to work, and the loop current is switched from the _second power switch tube S2 to the _second power diode D2 being turned on.

Switching mode 5 [t ₄ ˜t ₅ ] is shown in FIG. 7 : in this mode, the first power switch S ₁ , the third power switch S ₃ , and the fourth power switch S ₄ are closed, and the second power switch S 1 is closed. _The power switch S2 is turned off; at time t5, since the input voltage is converted from positive to negative and the input current is zero at this time, the _first power switch S1 realizes zero-current turn-off, and at this time the solid-state power The controller implements a soft shutdown, the circuit stops working and the current limiting circuit also stops working.

The above working modes are the modal analysis of the working process of the solid-state power controller during turn-on and turn-off.

The control strategy for triggering the current limit is as follows:

The peak current detection is used to judge when the AC SSPC transitions to the current-limiting state, which proves that the method is fast and effective. The block diagram of the control circuit is shown in Figure 8. When the absolute value of the current exceeds the threshold U _th1 , the effective current-limiting signal is locked, and the main branch of the SSPC is turned off. Therefore, the inrush current is limited by R _limit . The modal changes of this process are shown in Figure 9.

Strategies for distinguishing short-circuit faults from surge loads are as follows:

As shown in Figure 10, when the AC SSPC enters the current-limiting state, the absolute value of the voltage at the node "power-off" |u _POWEROUT |, that is, the load voltage, is used to determine whether a short-circuit fault occurs. If |u _POWEROUT | is lower than the threshold value U _th3 within the judgment time T _SC , it is judged as a short-circuit fault or a polar capacitive load that the system cannot turn on. Using u _ave , u _POWEROUT passes an RC filter to estimate whether the surge load is loaded into a stable state, confirming good compatibility with different surge loads. Once a short circuit fault is found, it enters the shutdown state. For surge loads, after the current limiting process, when the absolute value of the current exceeds the threshold U _th1 , the SSPC enters the open state.

The invention adopts peak current detection to judge when the AC SSPC is converted into a current-limiting state, the method is fast and effective, and the ability of the SSPC to start a large-capacity capacitive load is improved; the load voltage is used to judge whether a short-circuit fault occurs, and once a short-circuit fault is found, it will immediately Cut off the power supply and improve the safety of short circuit protection of SSPC in high power applications.

Claims (4)

1. A soft-switching solid-state power controller with current-limiting function, comprising an AC input power source (u)_in) A first power switch tube (S)₁) A first power diode (D)₁) A second power switch tube (S)₂) A second power diode (D)₂) And the third power switch tube (S)₃) A third power diode (D)₃) And the fourth power switch tube (S)₄) And a fourth power diode (D)₄) Power resistance (R)_limit) And an induction resistance (R)_sense)；

The first power switch tube (S)₁) Drain and third power switch tube (S)₃) Drain connected to input AC power source (u)_in) A positive terminal of; first power switch tube (S)₁) Source and second power switch tube (S)₂) Source electrode connected, third power switch tube (S)₃) Source and fourth power switch tube (S)₄) Source electrode connected, fourth power switch tube (S)₄) Drain and power resistor (R)_limit) Is connected to one terminal of a power resistor (R)_limit) And the other end of the first power switch tube (S) and a second power switch tube (S)₂) The drain electrode is connected with the first electrode,and connected to the sense resistor (R)_sense) One end of (2), sense resistor (R)_sense) Is connected to one end of a LOAD (LOAD) whose other end is connected to an input ac power source (u)_in) Is connected with the negative end of the water tank; a first power diode (D)₁) And a first power switch tube (S)₁) Is connected to the drain of the first power diode (D)₁) And the first power switch tube (S)₁) The source electrodes of the two-way transistor are connected; a second power diode (D)₂) And a second power switch tube (S)₂) Is connected to the drain of the first power diode (D)₂) And a second power switch tube (S)₂) The source electrodes of the two-way transistor are connected; third power diode (D)₃) And a third power switch tube (S)₃) Is connected to the drain of the third power diode (D)₃) And the third power switch tube (S)₃) The source electrodes of the two-way transistor are connected; fourth power diode (D)₄) And a fourth power switch tube (S)₄) Is connected to the drain of the fourth power diode (D)₄) Anode of (2) and a fourth power switch tube (S)₄) Are connected.

2. Soft-switched solid-state power controller with current limiting function according to claim 1, characterized in that the first power switch tube (S)₁) And a second power switch tube (S)₂) A third power switch tube (S) connected in series to form a main branch₃) And a fourth power switch tube (S)₄) The current limiting branches are formed by connecting in series;

off state when both branches are off; the open state when both branches are open; when the main branch is closed and the current-limiting branch is opened, the current-limiting branch is in a current-limiting state.

3. The soft-switched solid-state power controller with current limiting function according to claim 1, wherein the control strategy for triggering the current limit is as follows:

peak current detection is used to determine when an AC SSPC is switched to a current limiting state when the absolute value of the current exceeds a threshold U_th1While the active current limit signal is locked, the main branch of the SSPCClosing and entering a current limiting state; when the current is limited, the absolute value of the current is lower than a threshold value U_th1When so, the SSPC resumes the on state.

4. A soft-switched solid-state power controller with current limiting capability according to claim 1, wherein the strategy to distinguish short-circuit faults or surge loads is specifically as follows:

when the AC SSPC enters the current limiting state, the absolute value of the voltage | u at the node "power off" is used_POWEROUTI.e. the load voltage, and if the voltage absolute value | u_POWEROUTL at judgment time T_SCInternal lower than threshold value U_th3And if the system is in a short-circuit fault state, judging that the system cannot be opened, and entering a closed state.

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