Summary of the invention
In order to address the above problem, the invention provides a kind of soft starting circuit of current transformer, both realized less starting current; Make heat dissipation design more or less freely; Realized the less impulse current that is incorporated into the power networks again, can be widely used in the charging process of DC load, reduced impact DC load.
The main technical schemes that the present invention adopted is:
A kind of soft starting circuit of current transformer; Comprise main circuit; Said main circuit comprises DC/DC translation circuit, DC/AC translation circuit and the switch that is incorporated into the power networks that connects successively; Said DC/DC translation circuit comprises one or more separate direct current channel; At least one said direct current channel is the copped wave direct current channel that which is provided with DC chopper circuit; The input of said direct current channel is the load link; Output is provided with the dc-link capacitance that is used to form its output end voltage; Output connects the DC end of said DC/AC translation circuit; One end of the said switch that is incorporated into the power networks connects the AC end of said DC/AC translation circuit; The power connector end that other end formation is connected with electrical network or AC power; Comprise that also one or more is provided with the soft branch road that opens that soft breakdown closes; A said soft end that opens branch road connects the power connector end of the said switch that is incorporated into the power networks; The other end connects said load link; Said many soft opening differently in the branch road are softly opened branch road the direct current channel with different are corresponding respectively; Said one or more soft opening has at least one to be provided with the soft resistance that opens in the branch road, and at least one is provided with soft open resistance said soft to open branch road corresponding with said copped wave direct current channel.
Said DC/AC translation circuit holds the AC end to be provided with inverter bridge and isolating transformer successively from DC.
Said DC chopper circuit preferably is made up of direct current channel filter circuit and electronic switch assembly; Said direct current channel filter circuit is L, CL, LC or LCL filter circuit; Said electronic switch assembly is made up of first power switch pipe and second power switch pipe; The collector electrode of said first power switch pipe connects the positive terminal of dc-link capacitance; Emitter connects the collector electrode of said second power switch pipe and the cathode output end of said direct current channel filter circuit, and the emitter of said second power switch pipe connects the negative pole end of dc-link capacitance.
The soft starting circuit of said current transformer can also be provided with and be used to regulate the output voltage amplitude of said inverter bridge and the digital control unit of phase place.
In the soft starting circuit of aforementioned any said current transformer, the output of said DC chopper circuit preferably adopts the PWM mode to regulate through said digital control unit.
Soft starting circuit for above-mentioned any one current transformer; At least one is provided with soft said soft opening of opening resistance also is parallel with one or more and softly opens bypass by what the bypass resistance of mutual series connection and by-pass switch were formed on the branch road, and the pairing soft branch road that opens of at least one said copped wave direct current channel is to be provided with the said soft soft branch road that opens that opens bypass.
Beneficial effect of the present invention:
Owing to be provided with the soft branch road that opens; Can be before be incorporated into the power networks through the soft resistance that opens the input of said direct current channel be inserted said AC network earlier; And utilize AC network that said dc-link capacitance is charged; Reduced starting current on the one hand; Correspondingly reduced the heat radiation requirement; On the other hand; Before being incorporated into the power networks, realized charging to dc-link capacitance; For further to solve reduce to be incorporated into the power networks the time the impulse current problem done necessary preparation, a plurality of soft branch roads that open are set help optimal control start-up course.
Owing to be provided with the copped wave direct current channel that is provided with DC chopper circuit; Can make full use of the size of the voltage transformation changing function dc-link capacitance voltage of DC chopper circuit; Normally the raise voltage of dc-link capacitance can reach coupling with the voltage in the switch outside of being incorporated into the power networks in size to make the switch closure moment of the being incorporated into the power networks inboard voltage of switch that is incorporated into the power networks as much as possible.
Because said DC/AC translation circuit is provided with inverter bridge; The mapping function that can make full use of inverter bridge makes and to be incorporated into the power networks the voltage in the inboard voltage of switch and the outside with width of cloth homophase or basically with width of cloth homophase; Promptly reach synchronously, to reduce even to eliminate the switch closure rush of current of moment that is incorporated into the power networks.
Owing to be provided with the soft bypass of opening; And adopt the isolating transformer that boosts; Formerly closed soft breakdown closes after the dc-link capacitance charging; The closes bypass switch dc-link capacitance voltage that further raises again; Even output voltage not through the said DC chopper circuit of digital control adjusting; As long as it is suitable that the resistance of bypass resistance is chosen; Still can realize that dc-link capacitance voltage is not less than the peak value of the inside cord voltage of the isolating transformer that boosts at least, therefore can simplied system structure, improve system reliability.
Embodiment
As shown in Figure 1, a kind of soft starting circuit of current transformer comprises main circuit, and said main circuit comprises DC/DC translation circuit, DC/AC translation circuit and the switch that is incorporated into the power networks that connects successively, and promptly inner DC/DC of employing of this current transformer and DC/AC two go on foot conversion.Electric energy can two-way flow between DC load and AC network, when electric energy by DC load when AC network flows, said current transformer is in the discharge operating state, otherwise then is in the charging operating state.Said DC/DC translation circuit comprises one or more separate direct current channel; At least one said direct current channel is the copped wave direct current channel that which is provided with DC chopper circuit; The input of said direct current channel is the load link; Like storage battery, electronic load etc.; Output is provided with the dc-link capacitance that is used to form its output end voltage; Dc-link capacitance can be used for the electric energy of temporary transient storage from load or AC network side, also can be used for DC filtering.Output connects the DC end of said DC/AC translation circuit, and an end of the said switch that is incorporated into the power networks connects the AC end of said DC/AC translation circuit, the power connector end that other end formation is connected with electrical network or AC power.
The soft start of said current transformer comprises that also one or more is provided with the soft branch road that opens that soft breakdown closes; A said soft end that opens branch road connects the power connector end of the said switch that is incorporated into the power networks; The other end connects said load link; Said many soft opening differently in the branch road are softly opened branch road the direct current channel with different are corresponding respectively; Said one or more soft opening has at least one to be provided with the soft resistance that opens in the branch road, and at least one is provided with soft open resistance said soft to open branch road corresponding with said copped wave direct current channel.
Said DC/AC translation circuit holds the AC end to be provided with inverter bridge and isolating transformer successively from DC; Said inverter bridge is the core of realizing the DC/AC conversion; Said isolating transformer can be boost, step-down or 1:1 isolating transformer, whether the main circuit that the said switch that is incorporated into the power networks is used to control said current transformer inserts said AC network.
When starting said current transformer; Closed earlier said soft breakdown closes MC; The electric energy of AC network output is via soft resistance and the DC/DC translation circuit of opening; Charge to dc-link capacitance; Switch is in off-state owing to be incorporated into the power networks; And said main circuit has the ability of certain adjusting output; The inboard voltage of the feasible switch that is incorporated into the power networks is relatively independent of the outside voltage (being ac grid voltage) of the switch that is incorporated into the power networks to a certain extent; Feasible adjusting be incorporated into the power networks the inboard voltage of switch reach with ac grid voltage with width of cloth homophase or become possibility with width of cloth homophase basically, soft existence of opening resistance has obviously reduced starting current.What is called is meant that with width of cloth homophase difference between two amplitudes (or two phase place) is within the corresponding difference tolerance limit that requires based on being incorporated into the power networks basically.
Utilize the voltage transformation function of said DC/DC translation circuit; Can easily change the size of the voltage of dc-link capacitance; The voltage of dc-link capacitance of normally raising makes the be incorporated into the power networks switch closure moment inboard voltage of switch that is incorporated into the power networks to reach coupling in size with its outside voltage, preferably dc-link capacitance voltage is elevated to more than the peak value of isolating transformer inside cord voltage.
For promptly fixed said inverter bridge; In use common no-load voltage ratio of not regulating said isolating transformer; But preferably regulate the interchange output of said inverter bridge; Change the voltage magnitude and the phase place of its output; Because there is the quantitative relationship of confirming in the output voltage of said inverter bridge with the inboard voltage of the switch that is incorporated into the power networks; Therefore the output of regulating said inverter bridge is equivalent to change indirectly the amplitude and the phase place of the inboard voltage of the switch that is incorporated into the power networks, the same width of cloth homophase of outside voltage or basically with width of cloth homophase in the switch of therefore can realizing being incorporated into the power networks.
It is thus clear that; Through the soft interim path that opens branch road as start-up course is set; The gap that cooperates DC/DC conversion rising dc-link capacitance voltage to dwindle outside voltage magnitude in the switch that is incorporated into the power networks; And the output voltage amplitude and further the making of phase place of regulating inverter bridge are incorporated into the power networks the interior outside of switch voltage with width of cloth homophase or basically with width of cloth homophase; Can make the steady butt joint in switch closure its interior outside of moment of being incorporated into the power networks; Realize being incorporated into the power networks synchronously with this, thereby reduce even eliminate the switch closure rush of current of moment that is incorporated into the power networks.
As shown in Figure 6; Realize that above-mentioned DC/DC conversion mainly is to realize through the output of regulating said DC chopper circuit; Said DC chopper circuit preferably is made up of direct current channel filter circuit FLT and electronic switch assembly (i.e. brachium pontis shown in the figure) BR; Said direct current channel filter circuit can be L, CL, LC or LCL filter circuit; Be preferably LCL-T type filter circuit; The single-termination load; Under the accumulator charging/discharging circuit normal operating conditions, can reduce the ripple level of load one side direct current preferably.Said electronic switch assembly is made up of first power switch pipe (like the S1 among Fig. 6) and second power switch pipe (like the S2 among Fig. 6); The collector electrode of said first power switch pipe connects the positive terminal of dc-link capacitance; Emitter connects the collector electrode of said second power switch pipe and the cathode output end of said direct current channel filter circuit (being the output of energy storage inductor), and the emitter of said second power switch pipe connects the negative pole end of dc-link capacitance.Said power switch pipe can be controllable type device for power switching such as metal-oxide-semiconductor, IGBT pipe, carborundum SiC power device or IGCT, and the said DC chopper circuit that is constituted is the boost type DC chopper circuit.The control end of said first, second power switch pipe (being the gate pole end) connects the corresponding control circuit of control unit; Thus can be through the operating state and the mode of mode power controlling switching tubes such as pulse-width modulation; Regulate the chopper circuit parameter, on dc-link capacitance, form needed output.
Be equipped with said electronic switch assembly on other direct current channels except said copped wave direct current channel; Wherein the point that is connected with second power switch tube S 2 of first power switch tube S 1 constitutes the load link of its place direct current channel; The output of said electronic switch assembly constitutes the output of its place direct current channel; For the ease of expressing, this direct current channel is called basic direct current channel (referring to the second direct current channel of Fig. 4).
The soft starting circuit of said current transformer also preferably is provided with and is used to regulate the output voltage amplitude of said inverter bridge (being generally three phase inverter bridge) and the digital control unit of phase place; Through digital control technology said inverter bridge is controlled, improved the synchronous precision that is incorporated into the power networks.
For the soft starting circuit of aforementioned any described current transformer, the output of said boost type DC chopper circuit preferably adopts the PWM mode to regulate through said digital control unit.Through changing the ON time of the power switch pipe in the said electronic switch assembly; Change said boost type DC chopper circuit average value of output voltage; Thereby change the value of said dc-link capacitance voltage, be not less than the peak value of isolating transformer inside cord voltage in the practical application at least.
In the DC/DC conversion, be fully independently between each direct current channel, so each direct current channel can work independently separately, promptly allow part direct current channel work in the practical application and the part direct current channel stops.
Preferably, said direct current channel is one, two or three, and as previously mentioned, when a direct current channel, it is said copped wave direct current channel, and its circuit constitutes single-phase semi-bridge boost booster circuit (referring to Fig. 6); When being provided with two direct current channels; It all is said copped wave direct current channel; Perhaps one is said copped wave direct current channel; Another is said basic direct current channel; Be preferably the former; Constitute single-phase full bridge (or claiming the H bridge) boost booster circuit (referring to Fig. 7),, should be provided with the soft branch road that opens that opens resistance with soft at least one direct current channel for the situation that is provided with two direct current channels; When being provided with three direct current channels; It all is said copped wave direct current channel; Perhaps wherein two be said copped wave direct current channel; Article one, be said basic direct current channel, be preferably the former, constitute three-phase half-bridge boost booster circuit (referring to Fig. 8); Compare circuit shown in Figure 7; Its rate of pressure rise is faster, for the situation that is provided with three direct current channels, wherein should be provided with the soft branch road that opens that opens resistance with soft at least two direct current channels.
When being provided with more direct current channels, only need in the practical application to select 1-3 bar direct current channel wherein and form above-mentioned any boost booster circuit to get final product.
The soft starting circuit of said current transformer can have multiple concrete way of realization; With the situation that is provided with two direct current channels is example; The soft relative position that opens resistance and soft breakdown pass can be changed each other can not be provided with filter (referring to Fig. 4) on (referring to Fig. 2 and 3), the part direct current channel, soft the opening of part can not be provided with the soft resistance (referring to Fig. 5) that opens on the branch road; As long as for current transformer generally speaking, the voltage of dc-link capacitance can be elevated to setting and get final product.
The primary side of said isolating transformer or secondary end can also be connected with the communication channel filter circuit, are used for the filtering of said DC/AC translation circuit AC side.
As one of circuit start condition; The AC end of said DC/AC translation circuit can be any two phase line voltages in three-phase three-wire system or the three-phase four-wire system, any phase phase voltage or the independent mains input voltage in the three-phase four-wire system from the mode that said AC network exchanges power taking, and power taking is comparatively convenient.
The soft course of work that opens circuit of above-mentioned various said current transformer is:
(1) closed soft breakdown closes, and alternating current charges to dc-link capacitance through the soft resistance that opens.
(2) through digital control technology the boost booster circuit is controlled, dc-link capacitance voltage is further raise, dc-link capacitance voltage should be not less than isolating transformer inside cord voltage peak at least.
(3) three phase inverter bridge carries out the DC/AC conversion to direct voltage, and the ac grid voltage in the voltage that the feasible switch that is incorporated into the power networks is inboard and the switch outside of being incorporated into the power networks is with width of cloth homophase or basically with width of cloth homophase.
(4) the closure switch that is incorporated into the power networks breaks off soft breakdown and closes, and accomplishes whole soft start-up process.
For the soft circuit that opens of aforesaid any one current transformer; At least one is provided with soft said soft opening of opening resistance also is parallel with one or more and softly opens bypass by what the bypass resistance of mutual series connection and by-pass switch were formed on the branch road, and the pairing soft branch road that opens of at least one said copped wave direct current channel is to be provided with the said soft soft branch road that opens that opens bypass.When being provided with two said direct current channels; The soft circuit structure that opens bypass is set can be referring to Figure 10; In this case; Can adopt digital control technology to control the output of said DC chopper circuit; Also can the output of said DC chopper circuit not regulated, prerequisite is can make bus capacitor voltage be elevated to setting through other means.
Being provided with the said soft soft course of work that opens circuit of said current transformer that opens bypass is:
(1) closed soft breakdown closes, and alternating current charges to dc-link capacitance through the soft resistance that opens.
(2) closes bypass switch, dc-link capacitance voltage further raises, and makes dc-link capacitance voltage be not less than at least to boost isolating transformer inside cord voltage peak.
(3) three phase inverter bridge carries out the DC/AC conversion to direct voltage, and the ac grid voltage in the voltage that the feasible switch that is incorporated into the power networks is inboard and the switch outside of being incorporated into the power networks is with width of cloth homophase or basically with width of cloth homophase.
(4) the closure switch that is incorporated into the power networks breaks off soft breakdown and closes, and accomplishes whole soft start-up process.
Wherein, Said isolating transformer is preferably the isolating transformer that boosts; The said soft resistance that opens resistance of corresponding same said direct current channel is preferably greater than the resistance of said bypass resistance; The said soft resistance that opens resistance is bigger; It is less to make dc-link capacitance when charging soft open electric current (electric current that flows through direct current channel in the soft start-up process is the soft electric current that opens of respective straight circulation road); The resistance of said bypass resistance is less; Make the voltage of dc-link capacitance further improve, make DC bus-bar voltage be not less than at least to boost isolating transformer inside cord voltage peak.Select for use the bypass resistance of suitable resistance can realize that dc-link capacitance voltage is not less than the peak value of the isolating transformer inside cord voltage that boosts at least; Simultaneously because isolating transformer is a step-up transformer; Dc-link capacitance voltage can be realized further raising through the bypass resistance that increases parallel connection; Need not to carry out digital control, can make that do not have impacting soft start implements more or less freelyly, has improved the reliability of system.
Said soft breakdown closes and/or by-pass switch can be all kinds of gate-controlled switches under the prior art, the preferred A.C. contactor that adopts among the present invention.Because generally load end and AC network side pressure difference are bigger; Conventional A.C. contactor is difficult to bear; Therefore select the many A.C. contactors that are provided with mutual series connection for use to main contacts; The said main contactss of two of being in distal-most end are inserted softly to be opened branch road or softly opens bypass and (referring to the S type A.C. contactor that three pairs of main contactss are connected each other and formed that contains shown in Figure 9, be equivalent to improve the voltage endurance capability of A.C. contactor accordingly.
This paper to the main circuit of said current transformer, softly open branch road and soft to open bypass alleged " input ", " output " be to be directed against said current transformer to be in the flow of electrical power direction in the said current transformer main circuit when discharging operating state; And in fact electric energy can two-way flow in current transformer, and therefore above-mentioned expression does not constitute the qualification to electric energy actual flow direction.Alleged " inboard " is the side near load, and " outside " is the side near AC network.