CN109905043B - Modulation method of three-phase four-wire system soft switching rectifier with voltage-sharing function - Google Patents
Modulation method of three-phase four-wire system soft switching rectifier with voltage-sharing function Download PDFInfo
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- CN109905043B CN109905043B CN201910263762.3A CN201910263762A CN109905043B CN 109905043 B CN109905043 B CN 109905043B CN 201910263762 A CN201910263762 A CN 201910263762A CN 109905043 B CN109905043 B CN 109905043B
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Abstract
The invention discloses a three-phase four-wire system soft switching rectifier with a voltage-sharing functionThe modulation method of (3) is to fix and equalize the switching frequencies of all the main switching tubes and the auxiliary switching tubes; in each switching period, the time when the current conversion from the diode to the complementary switch tube occurs in the four groups of bridge arms is synchronized, and the auxiliary switch tube S is turned off before the synchronization timeauxThe bus voltage at two ends of the four groups of bridge arms is resonated to be zero; after the process of converting all the diodes to the main pipe is finished, increasing the straight-through process of the bridge arms according to the polarity of the balanced inductive current, and when the balanced inductive current flows out of the middle points of the fourth group of bridge arms, not increasing the straight-through process of the bridge arms; when the balanced inductor current flows into the middle point of the fourth group of bridge arms, the bridge arm through process is increased, and the resonant capacitor CrauxAfter the voltage resonance on the auxiliary switch tube S is zeroauxZero voltage turn-on is performed. The invention can effectively restrain the reverse recovery current of the main switch anti-parallel diode, has small switch loss and is beneficial to improving the efficiency and the power density.
Description
Technical Field
The invention relates to the technical field of rectifiers, in particular to a modulation method of a three-phase four-wire system soft switching rectifier with a voltage-sharing function.
Background
The traditional three-phase four-wire system rectifier with the voltage-sharing function comprises four groups of half-bridge arms, wherein each group of bridge arms is composed of two series-connected full-control main switch tubes containing anti-parallel diodes. The middle points of the first group of half-bridge arms, the second group of half-bridge arms and the third group of half-bridge arms are connected with a three-phase power grid through three AC-side filter inductors, and the middle points of the three-phase power grid are directly connected with the middle point of a DC-side series capacitor group to form a three-phase four-wire system AC-DC converter; the middle point of the fourth group of half-bridge arms is connected with the middle point of the direct-current side series capacitor group through a balance inductor to form a voltage-sharing circuit. The upper and lower ends of the four groups of bridge arms are respectively connected in parallel to form a positive bus and a negative bus, and the direct current side series capacitor group is bridged between the positive bus and the negative bus. The first group of half-bridge arms, the second group of half-bridge arms and the third group of half-bridge arms of the traditional three-phase four-wire system rectifier circuit with the voltage-sharing function are controlled in a sine wave pulse width modulation mode, the fourth group of half-bridge arms are controlled in a pulse width modulation mode, the circuit works in a hard switching state, and a switching device and a diode in the circuit respectively generate large switching loss and diode reverse recovery loss in the work process, so that the improvement of working frequency is limited, and a filter in the circuit is large in size and low in power density.
Disclosure of Invention
The invention aims to provide a modulation method of a three-phase four-wire soft switching rectifier with a voltage-sharing function, which reduces switching loss, improves the working efficiency and power density of a circuit and is applied to the field of power conversion.
The technical scheme adopted by the invention is as follows:
the invention provides a modulation method of a three-phase four-wire system soft switching rectifier with a voltage-sharing function, which comprises the following steps: the switching frequencies of all the main switching tubes and the auxiliary switching tubes are fixed and the same; in each switching period, the time when the commutation from the diode to the complementary switch tube of the four groups of bridge arms is carried out is synchronized, and the auxiliary switch tube S is turned off before the synchronous timeauxThe bus voltage resonance at the two ends of the four groups of bridge arms is zero, and a condition is created for zero voltage switching-on of the main switching tubes on the bridge arms; after the process of converting all the diodes to the main pipe is finished, increasing the straight-through process of the bridge arms according to the polarity of the balanced inductive current, and when the balanced inductive current flows out of the middle points of the fourth group of bridge arms, not increasing the straight-through process of the bridge arms; when the balanced inductor current flows into the middle point of the fourth group of bridge arms, the bridge arm through process is added to magnetize the resonant inductor, and after the process is finished, the resonant capacitor CrauxWill resonate, CrauxAfter the voltage resonance on the auxiliary switch tube S is zeroauxZero voltage turn-on is performed.
Compared with the prior art, the invention has the following beneficial effects:
by adopting the modulation method, all main switching tubes and auxiliary switching tubes in the three-phase four-wire system soft switching rectifier circuit with the voltage-sharing function can realize the full-range zero-voltage switching in the power frequency period, the reverse recovery of diodes in the converter is restrained, and the electromagnetic interference is reduced. The switching loss of a power device and the reverse recovery loss of a diode in the circuit are reduced, and the efficiency and the power density are improved.
Drawings
Fig. 1 is a three-phase four-wire system soft switching rectifier topology diagram with voltage-sharing function.
Fig. 2 is a schematic diagram of six working intervals divided according to the input current waveform in one power frequency period.
FIG. 3 is a timing diagram of driving pulse control in interval I according to the present invention.
FIGS. 4-18 show equivalent circuits of the present invention in each phase of a switching cycle in interval I.
Fig. 19 shows the main operating voltage and current waveforms for one switching cycle in interval I according to the present invention.
Detailed Description
The present invention will be described in detail with reference to specific examples. The following examples will assist those skilled in the art in further understanding the invention, but are not intended to limit the invention in any way. It should be noted that variations and modifications can be made by persons skilled in the art without departing from the spirit of the invention. All falling within the scope of the present invention. The present invention will be described in detail with reference to the accompanying drawings.
Referring to fig. 1, the three-phase four-wire system soft switching rectifier circuit with voltage-sharing function includes an ac-side filter inductor La、Lb、Lc(ii) a Balance inductance Lbal(ii) a Four groups of half-bridge arms; DC side series capacitor group Co1And Co2(ii) a DC side series load RL1And RL2(ii) a And a group comprising a parallel diode DauxAuxiliary switch tube SauxResonant inductor LrA clamp capacitor CcFormed auxiliary resonant branch, in which the resonant inductance LrAnd a clamp capacitor CcAfter being connected in series, the auxiliary switch tube S is connected withauxParallel connection; each of the four groups of half-bridge arms consists of two series-connected fully-controlled main switch tubes containing anti-parallel diodes, and the upper and lower main switch tubes and the anti-parallel diodes of the first group of bridge arms are S1、S4And D1、D4The upper and lower main switch tubes and their anti-parallel diodes of the second set of bridge arms are S respectively3、S6And D3、D6The upper and lower main switch tubes and their anti-parallel diodes of the third set of bridge arms are S5、S2And D5、D2The upper and lower main switch tubes and their anti-parallel diodes of the fourth group of bridge arms are respectively S7、S8And D7、D8The middle points of the first group of bridge arms, the second group of bridge arms and the third group of bridge arms are respectively connected with a filter inductor La、Lb、LcOne end of, La、Lb、LcThe other ends of the three-phase capacitors are respectively connected with a three-phase power grid, and the midpoint of the three-phase power grid is directly connected to a series capacitor bank Co1And Co2The middle point of the fourth group of bridge arms is connected with a balance inductor LbalOne end of, LbalThe other end of the capacitor is connected with a direct current side in series with a capacitor group Co1And Co2DC side series load RL1And RL2Are connected to each other. Of four sets of armsThe upper end and the lower end are respectively connected in parallel to form a positive public bus and a negative public bus, and the auxiliary resonance branch is connected between the public bus and the direct current side capacitor bank. Each switching tube S in the circuit1～S8And SauxThe two ends of the collector and the emitter are respectively connected with a resonance capacitor C in parallelr1～Cr8And Craux。
For a three-phase four-wire system soft switching rectifier with voltage-sharing function, the three-phase four-wire system soft switching rectifier can be used according to a three-phase input current ia、ib、icDivides the operating region into six regions, as shown in fig. 2, while balancing the inductor current ibalThere are also two cases of greater than zero and less than zero. With three-phase currents ia、ib、icIn region I, and balancing inductor current IbalAnd for example, the working process of the circuit working in one switching period is analyzed.
Since in region I, IaGreater than zero, ib、icAnd ibalLess than zero, in one switching cycle, there are four diode processes, respectively D, converting current to the main switching tube1To S4Commutation, D6To S3Commutation, D2To S5Commutation, D7To S8And (6) converting current. In order to align the four commutation moments, different types of sawtooth waves are selected as carriers according to the directions of point currents in the bridge arms. When the bridge arm midpoint current is flowing into the bridge arm midpoint, i is shown in FIG. 3aAnd ibalSelecting descending sawtooth wave as carrier wave, and when the bridge arm midpoint current is flowing out of the bridge arm midpoint, ibAnd icSelecting rising sawtooth wave as carrier to switch the main switch tube S4、S3、S5And S8Is aligned to the switching cycle start time. At this time, in one switching cycle, the driving pulse control timing of the switching tube is as shown in fig. 3, and the inverter has 15 operating states in total. FIGS. 4-18 are equivalent circuits for one switching cycle in this region, the main voltage and current waveforms during operation are shown in FIG. 19, and the voltage and current reference directions of the circuits are shown in the figure1 is shown. The circuit works in other intervals similarly.
The specific phase analysis is as follows:
stage one (t)0～t1)：
As shown in FIG. 4, a first upper tube diode D1Second leg lower tube diode D6Third bridge lower tube diode D2On the fourth bridge arm, there is a diode D7Are all conducted and are composed of resonant inductors LrA clamp capacitor CcAuxiliary switch SauxIn the auxiliary circuit formed, the clamping capacitor CcVoltage at both ends is UCcAuxiliary switch SauxConducting, and linearly increasing the resonant inductor current;
stage two (t)1～t2)：
As shown in fig. 5, at t1Time auxiliary switch SauxTurn-off, resonant inductance LrMake the main switch tube S4、S3、S5、S8Parallel capacitor Cr4、Cr3、Cr5、Cr8Discharging while making the auxiliary switch SauxParallel capacitor CrauxCharging at t2At the moment, the main switch S4、S3、S5、S8Parallel capacitor Cr4、Cr3、Cr5、Cr8The voltage of (2) resonates to zero, and this stage ends;
stage three (t)2～t3)：
As shown in fig. 6, at t2After time D4、D3、D5、D8Will be conducted to connect Cr4、Cr3、Cr5、Cr8The upper voltage is clamped to zero, which may be at t2Time on S4、S3、S5、S8Can realize S4、S3、S5、S8Zero voltage of (d) at t3Time of day, D4、D3、D5、D8The current drops to zero and the phase ends.
Stage four (t)3～t4)：
As shown in fig. 7, at D4、D3、D5、D8After the circuit is shut down, the circuit enters a current conversion stage, and the current iaBy a diode D1To the switching tube S4Current conversion, current ibBy a diode D6To the switching tube S3Current conversion, current icBy a diode D2To the switching tube S5Current conversion, current ibalBy a diode D7To the switching tube S8And (6) converting current. At this stage the resonant inductance LrThe voltage across is clamped at Udc-UCcWherein U isdcFor the rectifier output voltage, U, over the bus capacitance on the DC sidedc＝Udcp+UdcnResonant inductor current iLrLinearly decreases at t4At the moment, the commutation of the four bridge arms is finished, and the stage is finished.
Stage five (t)4～t5)：
As shown in fig. 8, at t4Switch tube S is switched on at any moment1、S6、S2、S7And increasing the direct connection process of the bridge arm, and magnetizing the resonant inductor to meet the condition of zero voltage switching-on of the main switching tube. Switch tube S1、S6、S2、S7After being switched on, the resonant inductor L is connectedrThe voltage across the terminals being clamped at Udc-UCcResonant inductor current iLrThe linear decrease continues.
Stage six (t)5～t6)：
As shown in fig. 9, at t5Time-off switch tube S1、S6、S2、S7Then, iLrContinue to descend, CrauxStarting discharge, Cr1、Cr6、Cr2、Cr7Charging begins, the circuit enters a second resonance at t6Time CrauxThe voltage on resonates to zero and the phase ends.
Stage seven (t)6～t7)：
As shown in fig. 10, t6After time, DauxWill be conducted to connect CrauxThe upper voltage is clamped to zero and is an auxiliary tube SauxThe zero voltage of (1) is turned on to provide a condition that can be at t6Give time to SauxSending a signal to turn on SauxRealize zero voltage turn-on when S4At t7At time off, this phase ends.
Stage eight (t)7～t8)：
As shown in FIG. 11, S4At t7After the bridge arm is turned off, the upper main switching tube and the lower main switching tube of the first bridge arm start to convert current, and Cr4Start of charging, Cr1Starting discharge at t8Time of day, Cr4Voltage on to Udc，Cr1The voltage above drops to zero and the phase ends.
Stage nine (t)8～t9)：
Commutation is completed in the first leg, D, as shown in FIG. 121After the follow current is conducted, S1Is turned on at this stage S1、S3、S5、S8Remains on, at t9Time S2And turning off, and finishing the phase.
Stage ten (t)9～t10)：
As shown in FIG. 13, S2At t9After the moment is cut off, the third bridge arm starts to convert current, Cr2Start of charging, Cr5Starting discharge at t10Time of day, Cr2Voltage on to Udc，Cr5The voltage above drops to zero and the phase ends.
Stage eleven (t)10～t11)：
As shown in fig. 14, at t10At the moment, after the third bridge arm finishes the commutation, D2After the follow current is conducted, S2Is turned on at this stage S1、S3、S2、S8Remains on, at t11Time S3And turning off, and finishing the phase.
Stage twelve (t)11～t12)：
As shown in FIG. 15, S3At t11After the moment is cut off, the second bridge arm starts to convert current, Cr3Start of charging, Cr6Starting discharge at t12Time of day, Cr3Voltage on to Udc，Cr6The voltage above drops to zero and the phase ends.
Stage thirteen (t)12～t13)：
As shown in fig. 16, at t12At the moment, the second bridge arm completes commutation, D6After the follow current is conducted, S6Is turned on at this stage S1、S6、S2、S8Remains on, at t13Time S8And turning off, and finishing the phase.
Stage fourteen (t)13～t14)：
As shown in FIG. 17, S8At t13After the moment is cut off, the fourth bridge arm starts to convert current, Cr8Start of charging, Cr7Starting discharge at t14Time of day, Cr8Voltage on to Udc，Cr7The voltage above drops to zero and the phase ends.
Stage fifteen (t)14～t0')：
As shown in fig. 18, at t14At the moment, D is obtained after the fourth bridge arm finishes converting current7Conduction, S7Is turned on at this stage S1、S6、S2、S7The on state is maintained, and the stage is the same as the stage one.
Claims (1)
1. A modulation method for three-phase four-wire soft switch rectifier with voltage-sharing function is characterized in that the rectifier comprises an alternating current side filter inductor and an alternating current side filter inductorL a 、L b 、L c (ii) a Balance inductanceL bal (ii) a Four groups of half-bridge arms; DC side series capacitor bankC o1AndC o2(ii) a DC side series loadR L1AndR L2(ii) a And a group comprising a parallel diodeD aux Auxiliary switch tubeS aux Resonant inductorL r Clamping capacitorC c Formed auxiliary resonant branch, in which the resonant inductanceL r And a clamp capacitorC c After being connected in series, the auxiliary switch tube is then connected with the power supplyS aux Parallel connection; each of the four groups of half-bridge arms consists of two series-connected fully-controlled main switch tubes containing anti-parallel diodes, wherein the upper and lower main switch tubes and the anti-parallel diodes of the first group of bridge arms are respectivelyS 1、S 4AndD 1、D 4the upper and lower main switch tubes and their anti-parallel diodes of the second set of bridge arms are respectivelyS 3、S 6AndD 3、D 6the upper and lower main switch tubes and their anti-parallel diodes of the third set of bridge arms are respectivelyS 5、S 2AndD 5、D 2the upper and lower main switch tubes and their anti-parallel diodes of the fourth group of bridge arms are respectivelyS 7、S 8AndD 7、D 8the middle points of the first group of bridge arms, the second group of bridge arms and the third group of bridge arms are respectively connected with a filter inductorL a 、L b 、L c At one end of the first and second arms,L a 、L b 、L c the other ends of the three-phase capacitors are respectively connected with a three-phase power grid, and the middle points of the three-phase power grid are directly connected to a series capacitor bankC o1AndC o2the middle point of the fourth group of bridge arms is connected with a balance inductorL bal At one end of the first and second arms,L bal the other end of the capacitor is connected with the direct current side in series with a capacitor bankC o1AndC o2DC side series loadR L1AndR L2the upper and lower ends of four groups of bridge arms are respectively connected in parallel to form a positive and negative common bus, the auxiliary resonance branch is connected between the common bus and the DC side capacitor group, and each switching tube in the circuitS 1~S 8AndS aux the two ends of the collector and the emitter are respectively connected with a resonance capacitor in parallelC r1~C r8AndC raux ；
the modulation method is characterized by comprising the following steps: controlling all main switching tubes in the rectifierS 1~S 8And an auxiliary switching tubeS aux Operating at the same and fixed switching frequency; in each switching period, the time when the commutation from the diode to the complementary switch tube of the four groups of bridge arms is carried out is synchronized, and the auxiliary switch tube S is turned off before the synchronous time aux The bus voltage resonance at the two ends of the four groups of bridge arms is zero, and a condition is created for zero voltage switching-on of the main switching tubes on the bridge arms; after the process of converting all the diodes to the main pipe is finished, increasing the straight-through process of the bridge arms according to the polarity of the balanced inductive current, and when the balanced inductive current flows out of the middle points of the fourth group of bridge arms, not increasing the straight-through process of the bridge arms; when the balanced inductor current flows into the middle point of the fourth group of bridge arms, the bridge arm through process is added to charge the resonant inductor, and after the process is finished, the resonant capacitorC raux The voltage on the capacitor will resonate,C raux after the voltage resonance is zero, the auxiliary switch tubeS aux Zero voltage turn-on is performed.
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| CN103001484B (en) * | 2012-10-31 | 2015-10-14 | 上海交通大学 | The modulator approach of low auxiliary voltage zero voltage switch Bridgeless Power Factor Corrector |
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