Background technology
Solid state switch is a kind of novel electric power automation equipment for fast shut-off fault, because of its have switch off time short, without arc, unglazed, silent, life-span long and functional reliability advantages of higher, there is high application prospect.
But solid state switch is compared with exchanging in the application in direct current field, has feature and the difficult point of himself: direct current is constant, unlike there being natural zero-crossing point in AC system.In high-voltage great-current occasion, the off state voltage climbing du/dt in current-rising-rate di/dt and turn off process in solid state switch opening process is very large, may cause and damages or puncture power device.Therefore, no matter which kind of power device DC solid electronic switch takes as main switch, be faced with the excessive problem of di/dt, du/dt, this is that direct current field is peculiar.In addition, even if completing, solid state switch turn-offs action, on circuit, the stored energy of inductance will produce excessive voltage at device two ends, if do not adopt an effective measure, in DC solid electronic switch when action, will be hard shutoff under large electric current, high voltage, and this will make it even damaged by enormous impact.
This problem is not all well solved at present, and the application of solid state switch in direct current field is just restricted.Also there is the DC solid electronic switch of research based on thyristor in direct current field, for example Chinese invention patent (the patent No.: a kind of resonance type DC solid electronic switch 200910026473.8) providing, its core is the mode that adopts resonant type soft-switch, manufacture the zero crossing in direct current field, realize soft the opening (shutoff) of power device, avoid firmly opening (shutoff) power device is caused to damage, but this scheme complex structure, the design difficulty of control system is larger, the reliability of solid state switch is poor, and the solid state switch quick-action being made up of thyristor is poor, be difficult to meet in DC micro-electric net quick, the requirement of reliable excision fault, therefore have some limitations.The patent of invention that the patent No. is 201110154838.2 provides a kind of DC solid circuit breaker, comprise main switch unit and auxiliary switching element, by the cooperation control of these two unit, the energy storage pulsed capacitance lower voltage of having avoided causing because of the intrinsic leakage current of device turn-offs the unreliable and fault problem that power supply has very large resonance current to flow through while turn-offing, but this DC solid circuit breaker is the solid state switch based on thyristor, same quick-action is poor, if and be applied in DC micro-electric net, can not realize the two-way flow of energy, therefore, be not suitable for DC micro-electric net.
Summary of the invention
The deficiency existing for above-mentioned prior art; the object of this invention is to provide a kind of short-circuit protection circuit and guard method of solid state switch of direct current microgrid; to avoid voltage (stream) stress that switch motion moment bears excessive; realize the soft shutoff of solid state switch; thereby while ensureing that DC micro-electric net transmission line is short-circuited; solid state switch can fast, reliably excise short trouble part, improves DC micro-electric net Supply Security and reliability.
The technical scheme that protective circuit of the present invention adopts is: a kind of short-circuit protection circuit of solid state switch of direct current microgrid; be applied to DC micro-electric net transmission line; described solid state switch is insulated gate bipolar transistor IGBT power electronic device, by anti-paralleled diode VD
1iGBT single tube V
1with anti-paralleled diode VD
2iGBT single tube V
2anti-series forms; It is characterized in that: described short-circuit protection circuit comprises RC buffering branch road and RD afterflow branch road; Described RC buffering branch circuit parallel connection is on described solid state switch, and one end of buffer capacitor Cs and one end of resistance R s of RC buffering branch road are connected in series, and the other end of buffer capacitor Cs is connected on V
1collector electrode on, the other end of resistance R s is connected on V
1emitter on; Route diode D is propped up in described RD afterflow
1, resistance R
1, diode D
2and resistance R
2be connected in series successively diode D
1negative electrode be connected on positive bus-bar, resistance R
2the other end be connected in negative busbar, diode D
2negative electrode connect signal ground.
The technical scheme that guard method of the present invention adopts is: a kind of short-circuit protection method of solid state switch of direct current microgrid, is characterized in that: be divided into two stages; First stage, while being solid state switch shutoff, DC micro-electric net transmission line short circuit current was transferred on RC buffering branch road and RD afterflow branch road by solid state switch simultaneously, occurred larger instantaneous overvoltage while preventing solid state switch shutoff; Second stage all changes of current that are short circuit current from RC buffering branch road are to RD afterflow branch road, power end is isolated, and the upper energy storing of DC micro-electric net transmission line stray inductance L mainly falls by resistance and the DC micro-electric net transmission line resistance consumption of RD afterflow branch road.
Protection on DC micro-electric net transmission line is mainly current comparison pilot protection, mainly comprises DC solid electronic switch, RC buffering branch road, RD afterflow branch road, current Hall transducer H etc.In the time of circuit generation one pole shorted to earth fault, under the effect of current comparison pilot protection, the solid state switch at that being short-circuited circuit two ends is accepted to control simultaneously and is disconnected, now line short circuit current is transferred on RC buffering branch road and RD afterflow branch road by solid state switch simultaneously, while preventing solid state switch shutoff, there is larger instantaneous overvoltage, then, short circuit current from RC buffering branch road all the changes of current to RD afterflow branch road, the upper energy storing of circuit stray inductance L is by by the resistance of afterflow branch road, line resistance and earth resistance Rg consume, therefore, solid state switch is able to smooth shutoff, make this circuit depart from micro-electrical network, reach the object of excision fault, in the time of circuit generation intereelectrode short-circuit fault, the solid state switch at two-wire line two ends will receive to control simultaneously and disconnect, now line short circuit current is transferred on RC buffering branch road and RD afterflow branch road by solid state switch simultaneously, while preventing solid state switch shutoff, there is larger instantaneous overvoltage, then, short circuit current from RC buffering branch road all the changes of current to RD afterflow branch road, power end is isolated, the upper energy storing of circuit stray inductance L consumes the resistance by afterflow branch road and line resistance, therefore, solid state switch is able to smooth shutoff equally, make this circuit depart from micro-electrical network, reach the object of excision fault.
Technical advantage of the present invention is as follows:
1, short-circuit protection circuit comprises RC buffering branch road and RD afterflow branch road, when guard method based on this circuit topological structure effectively prevents solid state switch shutoff there is larger peak voltage in two ends, reduce the impact of short circuit current to solid state switch, on protection circuit, other power electronic device are without prejudice;
2, when IGBT type solid state switch needn't be waited until electric current natural zero-crossing, could turn-off, compared with thyristor-type solid state switch, IGBT type solid state switch action control is flexible, speed is fast, there is the ability that realizes switching within the time of Microsecond grade, can meet the requirement of fast, reliably excising fault in DC micro-electric net.
Embodiment
Understand and enforcement the present invention for the ease of those of ordinary skill in the art, below in conjunction with drawings and Examples, the present invention is described in further detail, should be appreciated that exemplifying embodiment described herein, only for description and interpretation the present invention, is not intended to limit the present invention.
Ask for an interview Fig. 1; the technical scheme that protective circuit of the present invention adopts is: a kind of short-circuit protection circuit of solid state switch of direct current microgrid; be applied to DC micro-electric net transmission line, described solid state switch is insulated gate bipolar transistor IGBT power electronic device, by anti-paralleled diode VD
1iGBT single tube V
1with anti-paralleled diode VD
2iGBT single tube V
2anti-series forms; It is characterized in that: described short-circuit protection circuit comprises RC buffering branch road and RD afterflow branch road; Described RC buffering branch circuit parallel connection is on described solid state switch, and one end of buffer capacitor Cs and one end of resistance R s of RC buffering branch road are connected in series, and the other end of buffer capacitor Cs is connected on V
1collector electrode on, the other end of resistance R s is connected on V
1emitter on; Route diode D is propped up in described RD afterflow
1, resistance R
1, diode D
2and resistance R
2be connected in series successively diode D
1negative electrode be connected on positive bus-bar, resistance R
2the other end be connected in negative busbar, diode D
2negative electrode connect signal ground.
The transmission line of the DC micro-electric net of the present embodiment is bipolarity transmission line, and circuit equivalent model adopts two π pattern piece series connection forms of omitting electricity and lead parameter, carrys out simulation distribution parameter with segmented lumped parameter resistance R, inductance L, capacitor C.Line simulation fault point is set up in centre, is used for simulating two kinds of short trouble types of one pole shorted to earth and intereelectrode short-circuit.
In the time that micro-electrical network is normally worked, DC solid electronic switch V
1, V
2, V
3, V
4, V
5, V
6, V
7, V
8all, in opening state, can realize the two-way flow of energy.If energy flows to bus two from bus one, the switching tube of actual real conducting is V
1, V
3, V
5, V
7, antiparallel diode VD
2, VD
4, VD
6, VD
8forward conduction; If energy flows to bus one from bus two, the switching tube of real conducting is V
2, V
4, V
6, V
8, antiparallel diode VD
1, VD
3, VD
5, VD
7forward conduction.Now, the diode D of afterflow branch road
1, D
2, D
3, D
4oppositely cut-off, afterflow branch road does not have electric current to pass through.
The situation that flows to bus two taking energy from bus one is below as embodiment, and during to short circuit, on solid state switch turn off process and circuit, two stages of afterflow passage of short circuit current are carried out labor.
In the time there is one pole shorted to earth fault on circuit, taking positive bus-bar generation shorted to earth as example, under the effect of current comparison pilot protection, DC solid electronic switch V
1, V
2, V
3, V
4disconnect simultaneously.
Ask for an interview Fig. 2, during for the one pole ground short circuit of the embodiment of the present invention solid state switch turn-off before short circuit current figure, short circuit current is poured into short circuit trouble point from bus bar side respectively, solid state switch V flows through respectively
1, VD
2and V
4, VD
3.Stage one: in the time that solid state switch turn-offs, line short circuit current is transferred on RC buffering branch road and RD afterflow branch road by solid state switch simultaneously, and line short circuit current to buffer capacitor Cs shunting, has alleviated solid state switch V by resistance R s
1, V
4burden, suppressed du/dt and overvoltage, and solid state switch V
2originally just there is no real conducting, therefore there is not the buffer problem while shutoff, solid state switch V
3in the time of short circuit by the rated current change of current to antiparallel diode VD
3upper, there is no the impact of short circuit current, thus there is not the buffer problem while shutoff yet, meanwhile, the diode D in afterflow branch road
1, D
3forward bias, for short circuit current provides afterflow passage; Stage two: all the change of current is to RD afterflow branch road rapidly from RC buffering branch road for short circuit current, and mains side is isolated, and the upper energy storing of circuit stray inductance L consumes by resistance, line resistance and the earth resistance Rg of afterflow branch road.
Ask for an interview Fig. 3, during for the one pole ground short circuit of the embodiment of the present invention, solid state switch closes the short circuit current afterflow passage figure that has no progeny, and short circuit current is punished into two branch roads from signal ground, and branch road one power supply of flowing through, by buffering branch road Cs and Rs, antiparallel diode VD
2flow to fault point, branch road two flows to the resistance R of afterflow branch road from signal ground
1with diode D
1, via line resistance R, inductance L form afterflow passage, the energy of releasing, opposite side symmetry.
In the time there is intereelectrode short-circuit fault on circuit, under the effect of current comparison pilot protection, solid state switch V
1, V
2, V
3, V
4, V
5, V
6, V
7, V
8accept to control to disconnect simultaneously.
Ask for an interview Fig. 4, during for the intereelectrode short-circuit of the embodiment of the present invention solid state switch turn-off before short circuit current figure, positive bus-bar short circuit current is poured into short circuit trouble point from bus bar side respectively, negative busbar short circuit current flows to respectively bus both sides from fault point.Stage one: in the time that solid state switch turn-offs, line short circuit current is transferred on RC buffering branch road and RD afterflow branch road by solid state switch simultaneously, and line short circuit current is shunted to buffer capacitor Cs by resistance R s, respectively by V
1, V
4, V
6, V
7the change of current, to buffering branch road separately, has alleviated solid state switch V
1, V
4, V
6, V
7burden, suppressed du/dt and overvoltage, and solid state switch V
2and V
8originally just there is no real conducting, therefore there is not the buffer problem while shutoff, solid state switch V
3and V
5in the time of short circuit by the rated current change of current to antiparallel diode VD separately
3and VD
5upper, there is no the impact of short circuit current, thus there is not the buffer problem while shutoff yet, meanwhile, the diode D in afterflow branch road
1, D
2, D
3, D
4forward bias, for short circuit current provides afterflow passage; Stage two: all the change of current is to RD afterflow branch road rapidly from RC buffering branch road for short circuit current, and mains side is isolated, and the upper energy storing of circuit stray inductance L consumes by resistance and the line resistance of afterflow branch road.
Ask for an interview Fig. 5, during for the intereelectrode short-circuit of the embodiment of the present invention, solid state switch closes the short circuit current afterflow passage figure that has no progeny, and short circuit current is divided into two branch roads from circuit, and branch road one passes through V
7buffering branch road Cs and Rs, antiparallel diode VD
8, power supply, V
1buffering branch road Cs and Rs, antiparallel diode VD
2via line resistance R, inductance L flow to fault point, and branch road two is by the resistance R of afterflow branch road
2, diode D
2, resistance R
1, diode D
1, line resistance R, inductance L get back to fault point, forms afterflow passage, the energy of releasing, opposite side symmetry.
Should be understood that; the above-mentioned description for preferred embodiment is comparatively detailed; can not therefore think the restriction to scope of patent protection of the present invention; those of ordinary skill in the art is under enlightenment of the present invention; do not departing from the scope situation that the claims in the present invention protect; can also make and replacing or distortion, within all falling into protection scope of the present invention, request protection range of the present invention should be as the criterion with claims.