CN207382186U - Direct-current dual power starts and switching current-limiting circuit - Google Patents

Abstract

It is started the utility model is related to a kind of direct-current dual power and switches current-limiting circuit; two-way DC power supply is connected respectively by respective contactor with starting/switching current limiting unit; starting/switch unit is made of IGBT Q1 and peak voltage absorbing circuit; absorbing circuit absorbs the due to voltage spikes that stray inductance generates on DC power supply power transmission line, and protection IGBT Q1 are unlikely to excessive pressure damages.Dash current in two-way DC power supply handoff procedure can inhibit using the utility model, while taken into account operating mode when inverter starts, inhibit inrush current, additional soft starting circuit can be saved.The utility model control strategy is simple, it can be achieved that contactor is without circuit closed and disengagement, and reliable operation has a good application prospect.

Description

DC dual power supply starting and switching current limiting circuit

technical field

The utility model relates to a power electronic technology, in particular to a DC dual power supply starting and switching current-limiting circuit suitable for an inverter power supply.

Background technique

The inverter power supply converts DC power into AC power to supply power to the load of the small grid. In order to ensure reliability, the DC input often uses two DC power sources, one for main use and one for backup. When the main power supply is cut off, it will automatically switch to the backup power supply, and the conversion of the two power supplies will not affect the normal operation of the inverter power supply. In the case of electrical isolation between the input power supply and the inverter power supply in the power-off state, a contactor is usually used as a switch, and the action time of the contactor is usually longer. If there is no large-scale power failure, the bus capacitor needs to have a large enough capacity, then the bus capacitor will be recharged when the input DC power supply is switched from low voltage to high voltage, resulting in a large inrush current and prone to tripping.

Contents of the invention

The utility model aims at the problems existing in the commonly used DC conversion switch, and proposes a DC dual power supply starting and switching current limiting circuit to suppress the impact current during the switching process of the two DC power supplies.

The technical scheme of the utility model is: a DC dual power supply starting and switching current limiting circuit, two DC input power supplies I and II supply power to the inverter, the output of the DC power supply I is connected to the contactor I, and the output of the DC power supply II is connected to the Contactor II,

The outputs of contactor I and contactor II are connected in parallel to the same point and then connected to the starting and switching current limiting unit, and the output of the starting and switching current limiting unit is connected to the DC bus capacitor of the inverter power supply;

Collect the output voltage signals of DC power supply I and DC power supply II, and send the contact feedback signals of contactor I and contactor II to the control algorithm circuit, and the control algorithm circuit generates a contactor control signal and sends it to the current limiting realization circuit and contactor control circuit The starting and switching current-limiting unit includes a parallel connection of IGBT Q1 and a voltage peak absorption circuit. The input current signal of the inverter power supply is sent to the current-limiting realization circuit as a feedback value, and the current-limiting realization circuit generates a control signal of IGBT Q1 to the starting and switching current-limiting unit.

The voltage spike absorbing circuit is composed of a first capacitor C1, a second capacitor C2, a first resistor R1, and a first diode D1; the first capacitor C1 is connected in parallel to both ends of the collector and emitter of the IGBT Q1; the first resistor R1 One end is connected to the collector of IGBT Q1, the other end is connected to one end of the second capacitor C2, and the other end of the second capacitor C2 is connected to the emitter of IGBT Q1; the first diode D1 is connected in parallel to both ends of the first resistor R1, and The anode of D1 is connected to the collector of IGBT Q1.

The current limiting implementation circuit includes a comparator N1, a D flip-flop N2, a second resistor R2, a third resistor R3, a second diode D2, a third diode D3 and an IGBT drive circuit;

The input current feedback value is sent to the positive terminal of the comparator N1, the current limit reference value is sent to the negative terminal of the comparator, and the output terminal of the comparator N1 is pulled up to the power supply Vcc through the third resistor R3; the anode of the third diode D3 is connected to the comparator Connected to the output terminal of N1, the cathode of D3 is connected to the setting terminal S of D flip-flop N2; the anode of the second diode D2 is connected to the enable and block signal of the D flip-flop generated by the control algorithm circuit, and the cathode of D2 is connected to the third diode D3 The cathode is connected; one end of the second resistor R2 is connected to the setting terminal S of the D flip-flop N2, and the other end is grounded; the clock terminal CK of the D flip-flop N2 is connected to a square wave signal of a fixed frequency, the reset terminal R is grounded, and the data input terminal D is grounded, and the reverse The phase output terminal Qn is sent to the IGBT drive circuit.

The beneficial effect of the utility model is that: the DC dual power supply starting and switching current limiting circuit of the utility model can suppress the inrush current during the switching process of the two DC power supplies, and at the same time take into account the working conditions of the inverter power supply when starting, and suppress the inrush current at startup , can save additional soft-start circuit. The utility model has a simple control strategy, can realize the closing and disengaging of the contactor without current, is reliable in operation, and has good application prospects.

Description of drawings

Fig. 1 is a schematic structural diagram of a DC dual power supply starting and switching current limiting circuit of the present invention;

Fig. 2 is a schematic diagram of the utility model DC dual power starting and switching current limiting circuit control;

Fig. 3 is the schematic diagram of the current limiting realization circuit of the utility model;

Fig. 4 is the waveform diagram of the starting current limiting circuit of the utility model DC dual power supply;

Fig. 5 is a waveform diagram of the DC dual power supply switching current limiting circuit of the present invention.

Detailed ways

As shown in Figure 1 and Figure 2, the DC dual power supply starting and switching current limiting circuit structure and control schematic diagram, the circuit includes two DC input power supplies I and II, the two power supplies supply power to the inverter, and the output of DC power supply I is connected to the contactor I, the output of the DC power supply II is connected to the contactor II, the outputs of the contactor I and the contactor II are connected in parallel to the same point and then connected to the starting and switching current limiting unit 101, and the output of the starting and switching current limiting unit 101 is connected to the inverter power supply DC bus capacitance. Collect the output voltage signals of DC power supply I and DC power supply II, and send the contact feedback signals of contactor I and contactor II to the control algorithm circuit, and the control algorithm circuit generates a contactor control signal and sends it to the current limiting realization circuit and contactor control circuit , the input current signal of the inverter power supply is sent to the current-limiting realization circuit, and the current-limiting realization circuit generates the IGBT control signal to the starting and switching current-limiting unit 101, and finally controls the switching action of the IGBT and the contactor to coordinate and suppress the generation of starting and power switching electric shock.

In the DC dual power supply starting and switching current limiting circuit, the parasitic inductance on the output cables of DC power supply I and DC power supply II cannot be ignored, which are equivalent to the first inductance L1 and the second inductance L2 respectively.

The starting and switching current limiting unit 101 includes an IGBT Q1 and a voltage spike absorbing circuit 102 connected in parallel. The voltage spike absorption circuit 102 is composed of a first capacitor C1, a second capacitor C2, a first resistor R1, and a first diode D1. The first capacitor C1 is connected in parallel to both ends of the collector and emitter of the IGBT Q1; one end of the first resistor R1 is connected to the collector of the IGBT Q1, and the other end is connected to one end of the second capacitor C2, and the other end of the second capacitor C2 is connected to the IGBT Q1 The emitter of the first diode D1 is connected in parallel with both ends of the first resistor R1, and the anode of D1 is connected with the collector of the IGBT Q1.

As shown in FIG. 3, the schematic diagram of the current limiting realization circuit 103, the current limiting realization circuit 103 includes a comparator N1, a D flip-flop N2, a second resistor R2, a third resistor R3, a second diode D2, and a third diode D3 and IGBT drive circuit. The input current feedback value is sent to the positive terminal of the comparator N1, the current limit reference value is sent to the negative terminal of the comparator, and the output terminal of the comparator N1 is pulled up to the power supply Vcc through the third resistor R3; the anode of the third diode D3 is connected to the comparator Connected to the output terminal of N1, the cathode of D3 is connected to the setting terminal S of D flip-flop N2; the anode of the second diode D2 is connected to the enable and block signal of the D flip-flop generated by the control algorithm circuit, and the cathode of D2 is connected to the third diode D3 The cathode is connected; one end of the second resistor R2 is connected to the setting terminal S of the D flip-flop N2, and the other end is grounded; the clock terminal CK of the D flip-flop N2 is connected to a square wave signal of a fixed frequency, the reset terminal R is grounded, and the data input terminal D is grounded, and the reverse The phase output terminal Qn is sent to the IGBT drive circuit.

The utility model adopts the start-up and current-limiting switching unit 101 to suppress the inrush current, and the realization method is: IGBT Q1 works in the switching state of a fixed frequency, and when the inrush current reaches the set value, the IGBT Q1 is turned off to reduce the input current , and then turn on IGBT Q1 when the next cycle comes.

Considering the parasitic inductance effect of the DC power transmission line, the starting and current limiting switching unit 101 also includes a peak voltage absorbing circuit 102, and the first capacitor C1 is connected in parallel to both ends of the IGBT Q1 to absorb switching noise; after the IGBT Q1 is turned off, The first inductance L1 or the second inductance L2 freewheels through the first diode D1 and charges the second capacitor C2. The second capacitor C2 makes the voltage of the IGBT Q1 turn off slowly rise, protecting the IGBT Q1 from overvoltage When the IGBT Q1 is turned on in the next cycle, the energy stored in the second capacitor C2 will be consumed by the first resistor R1.

The control algorithm circuit outputs the enable and block signals of the D flip-flop, which are connected to the set terminal S of the D flip-flop N2 through the second diode D2, the block signal is high level, the enable signal is low level, shutdown or fault protection When the control algorithm circuit gives a high-level blocking signal, the second diode D2 is turned on, and the setting terminal S of the D flip-flop N2 is pulled up to a high level. From the working principle of the D flip-flop, it can be known that Qn outputs a low-level signal, and the The IGBTs are turned off. When starting up or switching work, the control algorithm circuit gives a low-level enable signal, and the working state of the D flip-flop is determined by the output state of the comparator N1. The working process in one switching cycle is as follows: the input current feedback value obtained by sampling is sent to to the positive input terminal of the comparator N1, the set current limit reference value is sent to the negative input terminal of the comparator N1, and the output terminal of the comparator N1 is connected to the set terminal S of the D flip-flop N2 through the third diode D3, when When the current feedback value is greater than the current limit set value, the comparator N1 outputs a high level, the third diode D3 is turned on, and the setting terminal S of the D flip-flop N2 is pulled up to a high level. From the working principle of the D flip-flop, it can be known that Qn Output a low level signal to turn off the IGBT Q1. After the IGBT Q1 is turned off, the input current starts to drop. When the current feedback value is less than the current limit setting value, the comparator N1 outputs a low level, and the third diode D3 is cut off , D flip-flop N2 setting terminal S is pulled down to low level, and when the next high level of clock terminal CK of D flip-flop N2 arrives, Qn is turned from a low-level signal to a high-level signal, and IGBT Q1 is turned on again. After several switching cycles, the inverter power supply bus capacitor is charged, the input current feedback value is always less than the current limit reference value, Qn is always a high level signal, and IGBT Q1 is always in the on state.

Assuming that the voltage value of the DC power supply II is greater than the voltage value of the DC power supply I, starting from the DC power supply I, and switching to the DC power supply II, the entire starting and switching process can be described as follows:

After the control algorithm circuit detects that the state of the DC power supply I is normal, it gives the closing command of the contactor I to make it close, and at the same time enables the D flip-flop N2, the IGBT Q1 is turned on, and the capacitor of the inverter power bus begins to charge, generating an inrush current. When it is detected that the current is greater than the current limiting reference value, the IGBT Q1 is turned off, and the input current drops below the current limiting reference value. The voltage peak induced by the first inductor L1 is suppressed by the peak voltage absorbing circuit 102, and the clock terminal CK of the D flip-flop N2 When the next high level arrives, the IGBT is turned on again. After several cycles, the inverter power supply bus capacitor is charged, the input current feedback value is always less than the current limit reference value, Qn is always a high level signal, and IGBT Q1 is always in the on state.

After the control algorithm circuit detects that the state of the DC power supply I is abnormal and the state of the DC power supply II is normal, it first blocks the D flip-flop N2 to turn off the IGBT Q1, and then gives the disconnection command of the contactor I, so that the contactor I realizes zero-current disconnection. Open, after the control algorithm circuit receives the contactor I contact opening feedback signal, it will give the contactor II closing command. When the contactor II is closed, the control algorithm circuit enables the D flip-flop N2, and the IGBT Q1 is turned on. Since the voltage value of the DC power supply II is greater than the voltage value of the DC power supply I, the inverter power bus capacitor starts to charge, generating an inrush current. When the current is greater than the current limiting reference value, the IGBT Q1 is turned off, and the input current drops below the current limiting reference value, and the voltage peak induced by the second inductor L2 is suppressed by the peak voltage absorbing circuit 102, under the clock terminal CK of the D flip-flop N2 When a high level comes, the IGBT is turned on again. After several cycles, the inverter power supply bus capacitor is charged, the input current feedback value is always less than the current limit reference value, Qn is always a high level signal, and IGBT Q1 is always in the on state.

Figure 4 and Figure 5 show the current-limiting waveforms in the starting and switching processes respectively, and the inrush current can be effectively suppressed.

Claims (3)

1. a kind of direct-current dual power starts and switching current-limiting circuit, two-way direct-current input power supplying I and II is to inverter power supply, direct current Power supply I outputs are connected to contactor I, and DC power supply II outputs are connected to contactor II, which is characterized in that

The output-parallel of contactor I and contactor II to same point are followed by starting and switching current limiting unit, start and switching limits The output of stream unit is connected to inverter dc-link capacitance；

The contact feedback signal for gathering the output voltage signal of DC power supply I and DC power supply II, contactor I and contactor II is sent To control algolithm circuit, control algolithm circuit generates contactor control signal and send to current limliting realization circuit and contactor control electricity Road, starts and switching current limiting unit includes IGBT Q1 and voltage peak absorbing circuit in parallel, inverter input current signal As value of feedback current limliting is sent to realize circuit, current limliting realizes that circuit generates IGBT Q1 control signals to starting and switching current limiting unit.

2. direct-current dual power starts and switches current-limiting circuit according to claim 1, which is characterized in that the due to voltage spikes is inhaled Circuit is received to be made of the first capacitance C1, the second capacitance C2, first resistor R1, the first diode D1；First capacitance C1 is parallel to IGBT Q1 collector and emitters both ends；Mono- ends of first resistor R1 are connected to IGBT Q1 collectors, the other end and the second capacitance C2 One end be connected, another emitter for being terminated at IGBT Q1 of the second capacitance C2；First diode D1 is parallel to first resistor R1 Both ends, and the anode of D1 is connected with the collector of IGBT Q1.

3. direct-current dual power according to claim 1 or claim 2 starts and switching current-limiting circuit, which is characterized in that the current limliting is real Existing circuit includes comparator N1, d type flip flop N2, second resistance R2,3rd resistor R3, the second diode D2, the 3rd diode D3 And IGBT drive circuit；

Input current value of feedback is sent into comparator N1 forward ends, and current limliting reference value is sent into comparator negative end, comparator N1 outputs End is pulled to power Vcc by 3rd resistor R3；3rd diode D3 anodes are connected with comparator N1 output terminals, D3 cathodes and D Trigger N2 set ends S-phase connects；The d type flip flop that second diode D2 anodes connect the generation of control algolithm circuit enables and blocks letter Number, D2 cathodes are connected with the 3rd diode D3 cathodes；Second resistance R2 mono- terminates d type flip flop N2 set end S, other end ground connection；D Trigger N2 clock ends CK connects the square-wave signal of a fixed frequency, reset terminal R ground connection, data input pin D ground connection, reversed-phase output Qn is sent to IGBT drive circuit.