CN105141135A - Control method for multi-way parallel full-bridge LLC converter in cascading power supply system - Google Patents
Control method for multi-way parallel full-bridge LLC converter in cascading power supply system Download PDFInfo
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Abstract
The invention relates to a control method for a multi-way parallel full-bridge LLC converter in a cascading power supply system. The cascading power supply system employed in the method comprises a pre-stage converter, LLCs, and a post-stage converter, wherein the pre-stage converter, the LLCs and the post-stage converter are sequentially connected to form a three-stage cascading structure. An energy storage device of the pre-stage converter is located at one side of a two-way DC-DC converter, and the other side of the two-way DC-DC converter is in parallel connection with a plurality of LLCs which are connected to one side of a three-phase inverter of the post-stage converter in a parallel manner. The other side of the three-phase inverter is connected with a filter, and the filter is connected with a power grid. In a full-load range, the invention proposes a complete voltage control and current-sharing scheme, and the method enables the LLCs to be capable of achieving the voltage control of a DC bus under the conditions of no load and heavy load.
Description
Technical field
The invention belongs to and belong to cascading power source system regions, relate to the control method of multi-channel parallel full-bridge LLC converter in a kind of cascading power source system.
Background technology
Cascading power source system, adopts the form of cascade to connect multiple power subsystem, achieves multi-stage transformation, be widely applied in recent years in the field such as distributed power generation and electric automobile.For family photovoltaic generating system, prime adopts Boost circuit to carry out MPPT control to photovoltaic, and rear class adopts high-frequency isolation type DC-DC converter to provide electrical isolation for this system, and promotes DC bus-bar voltage, realizes being incorporated into the power networks eventually through inverter.As everyone knows, LLC mode of resonance high-frequency isolation DC-DC converter has high efficiency and power density, and wider gain ranging, is used widely in recent years in the field such as distributed generation system and electric automobile.But multi-channel parallel LLC controls in DC bus-bar voltage and also there are some technical problems to be optimized in current-sharing.
One, comparatively large at equivalent output resistance, under namely unloaded operating mode, by the impact of parasitic parameter, upwarping easily appears in its gain curve, produces output voltage and raises, unmanageable phenomenon.Affect by it, if control its prime bus with LLC, when rear class busbar voltage is constant, prime busbar voltage can lower than reference value.If control its rear class bus with LLC, when prime busbar voltage is constant, rear class busbar voltage can higher than reference value.Can adopt the mode of determining FREQUENCY CONTROL under idle condition to this, but the method can cause very high idling frequency, thus cause LLC decrease in efficiency.In order to raising efficiency, switching tube also can be made in stability at lower frequencies discontinuous operation, namely adopt burst pattern to control.The method causes output voltage ripple excessive, can cause larger electromagnetic interference to direct current cascading power source system, is unfavorable for that the long-term stability of system is run.
They are two years old; be limited by narrower closed-loop bandwidth; the dynamic responding speed of LLC is relatively slow, especially in cascading power source system, when system produces disturbance; power occurs uneven; larger impact may be caused to DC bus-bar voltage, make DC bus-bar voltage exceed normal operation range, finally cause current transformer in system normally to work; by trigger protection action time serious, cause system crash.So control DC bus-bar voltage have vital effect for cascading power source system.
Its three, in order to expand power grade, when LLC converter is carried out parallel connection, being limited by the difference of each road parameter, will there is certain difference in the inductive current on each LLC converter, cause occurring circulation or the unequal problem of heat distribution in system.This is rather unfavorable to whole direct current cascading power source system.
According to the problems referred to above, controlling and the target such as current-sharing to realize DC bus-bar voltage in full-load range, needing to study performance better and be convenient to the new type multipath full-bridge LLC in parallel resonant type DC-DC converter DC bus-bar voltage control that realizes and current share scheme.
Through retrieval, find the patent document of following near field.
Power converter technical field (CN103633850A), particularly relates to a kind of half-bridge LLCPFM frequency changer circuit and control method thereof, comprises switching circuit, LLC resonant circuit and rectifying output circuit; Switching circuit is formed by two groups of half-bridge sub module cascade, and often organize half-bridge submodule and comprise 2 MOSFET pipes, the intermediate node of two groups of half-bridge submodules connects the voltage input side of LLC resonant circuit, and the voltage outlet side of LLC resonant circuit connects rectifying output circuit.Pwm signal is sent to switching circuit according to the current value of load or magnitude of voltage; Switching circuit generates drive singal according to pwm signal and is supplied to two groups of half-bridge submodules, to realize soft switch conversion.The present invention adopts LLC resonant technology to realize zero voltage switch, reduce the switching loss of circuit, realize efficient half-bridge soft switch conversion, adopt electric asymmetric topology structural design, circuit is reacted fast, improves circuit stability and reduce the volume and weight of circuit.
Based on ultra-wide output voltage range charger and the control method (CN104467443A) of LLC topology, comprise LLC resonant converter and control circuit, LLC resonant converter comprises the switching network be made up of MOSFET full-bridge circuit, the input of switching network is connected with power input, output is connected with the input of resonant network, the output of resonant network is connected with the leakage inductance of transformer, and the secondary coil of transformer is connected with rectifying and wave-filtering network; Control circuit comprises control unit, control unit is according to the switch of metal-oxide-semiconductor of the input of LLC resonant converter received and the signal controlling MOSFET full-bridge circuit of output, make LLC resonant converter can realize the no-voltage conducting of former limit switching tube in full voltage range, the zero-current switching of secondary rectifier diode.Output voltage of the present invention is wide, not by the restriction of charging object input voltage range, can be the charging of various New-energy electric vehicle.
Through contrast, there is relatively big difference in technical scheme and the present patent application of above open file.
Summary of the invention
The object of the invention is to overcome the deficiencies in the prior art part, there is provided and provide a kind of novel voltage control strategy and equal Flow Policy, for the full-bridge LLC resonant type DC-DC converter DC bus-bar voltage of stability contorting parallel connection in full-load range, ensure parallel branch current-sharing, do not change circuit hardware structure, do not produce voltage ripple yet.
The present invention solves its technical problem and takes following technical scheme to realize:
A control method for multi-channel parallel full-bridge LLC converter in cascading power source system, is characterized in that: the cascading power source system that this method adopts, and comprises front stage converter, LLC, rear class converter connect and compose three-stage cascade structure successively;
The energy storage device of front stage converter is positioned at the front side of bidirectional DC-DC converter, bidirectional DC-DC converter opposite side is parallel with multiple LLC, multiple LLC is connected in parallel on the three-phase inverter side of rear class converter, and three-phase inverter opposite side connects filter, and filter connects electrical network.
And LLC circuit comprises the switching network, resonant network and the commutated network that connect successively,
Be parallel with two brachium pontis in the circuit of switching network, wherein a brachium pontis is made up of the switching tube Q1 connected and switching tube Q2, and another brachium pontis is made up of switching tube Q3 and switching tube Q4;
Resonant network adopts LLC type resonant cavity, comprise resonant capacitance Cr, resonant inductance Lr and static exciter inductance L m, this resonant capacitance Cr, resonant inductance Lr and static exciter inductance L m connects successively, this resonant network one end is connected on the brachium pontis between switching tube Q1 and switching tube Q2, and this resonant network other end is connected on the brachium pontis between switching tube Q3 and switching tube Q4;
Rectification circuit adopts switching tube device or rectifier diode, realizes the transmission of electric energy.
And, the half-bridge full-bridge mode changing method of LLC:
When LLC is in heavy condition, switching tube Q1, Q2, Q3 and Q4 adopt pulse frequency modulated control strategy, form LLC full-bridge mode;
When LLC is in light condition, the control mode of switching tube Q1 and Q2 is constant, switching tube Q3 control signal reset and by the set of switching tube Q4 control signal, the upper switch pipe of this brachium pontis is disconnected, and lower switch pipe closes, and forms LLC half-bridge mode.
And concrete steps are:
(1) DC bus-bar voltage controls; In full-load range, it is U that two-way LLC controls prime DC bus-bar voltage
front;
1. first, generate prime DC bus-bar voltage and control half-bridge full-bridge switching mark symbol SIGNAL_FH_Front;
2. the state of determination flag position SIGNAL_FH_Front, decides to enter unloaded adjustment program or band year adjustment program;
3. prime DC bus sharing control, while the state of determination flag position SIGNAL_FH_Front, carries out prime DC bus sharing control;
(2) rear class DC bus controls; Two-way LLC controls rear class DC bus-bar voltage U
back;
1. first, full-bridge half-bridge switching controls flag bit SIGNAL_FH_Back is introduced;
2. the state of determination flag position SIGNAL_FH_Back, determines to enter unloaded adjustment program or band year adjustment program;
3. rear class DC bus sharing control, while the state of determination flag position SIGNAL_FH_Back, carries out rear class DC bus sharing control.
And, described step (1) in 1. half-bridge full-bridge switching mark symbol SIGNAL_FH_Front product process be:
When LLC is transformed into Light Condition by heavy duty, SIGNAL_FH_Front is become " 0 " from " 1 ", and switching tube Q3 disconnects, and switching tube Q4 closes, and LLC is transformed into half-bridge by full-bridge;
When LLC is transformed into heavy condition by zero load, SIGNAL_FH_Front is become " 1 " from " 0 ", and switching tube Q3, Q4 normally work, and LLC is transformed into full-bridge by half-bridge.
And, described step (1) in 2. flag bit SIGNAL_FH_Front determine that the flow process of half-bridge full-bridge operating state is specially:
If SIGNAL_FH_Front is " 0 ", then enter unloaded adjustment program, the original frequency of setting two-way LLC is f
h_Front, utilize the operating frequency to LLC such as Dead band controller and accumulator to regulate, this frequency is at f
h_Frontinitial value on, with Δ f
1step change, until output voltage is controlled in the absolute value of reference value error at Δ U
1scope in;
If SIGNAL_FH_Front is " 1 ", then enters band and carry adjustment program, the original frequency of setting two-way LLC is f
f_Front, the full-bridge LLC converter that band carries under operating mode is controlled.This frequency is at f
f_Frontinitial value on, with Δ f
2step change, until output voltage is controlled in the absolute value of reference value error at Δ U
2scope in;
If in the course of the work, detect that SIGNAL_FH_Front signal is transformed into " 1 " by " 0 ", then regulate programming jump to carry adjustment program to band by zero load and run;
When detecting that SIGNAL_FH_Front signal is transformed into " 0 " by " 1 ", then carried by band and regulate programming jump to run to unloaded adjustment program.
And, step (1) in 3. prime DC bus current-sharing control method be:
Detect each road LLC resonant inductance current effective value, it is sorted from small to large successively;
The frequency of the road LLC that current effective value is minimum remains unchanged;
When the absolute difference of the current effective value of current effective value immediate Liang Ge road LLC is greater than Δ I
fronttime, current effective value to rise maximum Δ f compared with the operating frequency of great mono-road LLC
3, and current effective value is constant compared with the operating frequency of little mono-road LLC.When this absolute difference is less than or equal to Δ I
fronttime, two-way LLC operating frequency remains unchanged;
From the two-way LLC that current effective value is minimum, the like, except the two-way LLC that effective value is minimum and maximum, in each control cycle, all the other LLC carry out frequency adjustment respectively with effective value and its immediate two-way LLC, until the inductive current effective value of all LLC is consistent, the inductive current effective value Error Absolute Value of the immediate two-way LLC of all sizes is less than Δ I
front.
And, step (2) in 1. half-bridge full-bridge switching mark symbol SIGNAL_FH_Back product process be:
As rear class converter power output P
backbe less than P
ltime, now SIGNAL_FH_Back is become " 0 " from " 1 ", indicates that LLC is transformed into Light Condition by heavy duty, and now, switching tube Q3 disconnects, and switching tube Q4 closes, and LLC is transformed into half-bridge by full-bridge;
As rear class converter power output P
backbe greater than P
utime, now SIGNAL_FH_Back is become " 1 " from " 0 ", indicates that LLC is transformed into heavy condition by zero load, and now, switching tube Q3, Q4 normally work, and LLC is transformed into full-bridge by half-bridge.
And, step (1) in 2. flag bit SIGNAL_FH_Back determine that the flow process of half-bridge full-bridge operating state is specially:
If SIGNAL_FH_Back is 0, then enters unloaded adjustment program, utilize Dead band controller etc. to regulate the operating frequency of LLC;
If SIGNAL_FH_Back is 1, then enters band and carry adjustment program, the full-bridge LLC converter that band carries under operating mode is controlled;
If in the course of the work, detect that SIGNAL_FH_Back signal is transformed into " 1 " by " 0 ", then regulate programming jump to carry adjustment program to band by zero load, LLC is converted into full-bridge by half-bridge and runs;
When detecting that SIGNAL_FH_Back signal is transformed into " 0 " by " 1 ", then carried by band and regulate programming jump to unloaded adjustment program, LLC is converted into half-bridge by full-bridge and runs.
And, step (1) in 3. rear class DC bus current-sharing control method be:
Detect each road LLC resonant inductance current effective value, it is sorted from small to large successively;
The frequency of the road LLC that current effective value is minimum remains unchanged;
When the absolute difference of the current effective value of current effective value immediate Liang Ge road LLC is greater than Δ I
backtime, current effective value to rise maximum Δ f compared with the operating frequency of great mono-road LLC
3, and current effective value is constant compared with the operating frequency of little mono-road LLC; When this absolute difference is less than or equal to Δ I
backtime, two-way LLC operating frequency remains unchanged;
From the two-way LLC that current effective value is minimum, the like; Except the two-way LLC that effective value is minimum and maximum, in each control cycle, all the other LLC need to carry out frequency adjustment respectively with effective value and its immediate two-way LLC, until the inductive current effective value of all LLC is consistent, the inductive current effective value Error Absolute Value of the immediate two-way LLC of size is less than Δ I
back, this measure can reach the object that multichannel LLC reaches parallel current-sharing.
Advantage of the present invention and good effect are:
1, the present invention is by changing the operating state of switching tube, under the operating mode of LLC underloading, full-bridge LLC is changed into half-bridge LLC, achieve suppression LLC voltage gain curve being upwarped to phenomenon, neither promote the unloaded operation frequency of LLC, also can not produce excessive voltage ripple.
2, in full-load range, the present invention proposes a whole set of complete voltage control and current share scheme, adopt this method that LLC can all can be realized controlling DC bus-bar voltage under unloaded and heavily loaded operating mode.
3, adopt this method, the setting of controlling dead error, can ensure that circuit is when disturbance occurs, LLC can not frequently switch under half-bridge and full-bridge two states.And when LLC switches under two kinds of operating modes, by rationally arranging frequency initial value, the voltage and current that can reduce to cause in the transfer impacts.And based on this, two-way LLC driving frequency is adjusted by the mean value of introducing two-way LLC inductive current absolute value, LLC parallel current-sharing can be realized, reduce intrasystem circulation.
Accompanying drawing explanation
Fig. 1 is cascading power source system configuration schematic diagram;
Fig. 2 is that full-bridge LLC resonance DC-DC converter half-bridge/full-bridge mode switches schematic diagram;
Fig. 2 (a) is LLC full-bridge mode schematic diagram;
Fig. 2 (b) is LLC half-bridge mode schematic diagram;
To be LLC control and sharing control flow chart based on the prime DC bus-bar voltage of Dead band controller Fig. 3;
Fig. 4 is that LLC prime DC bus-bar voltage controls half-bridge full-bridge (unloaded heavy duty) switching mark symbol product process figure;
To be LLC control and sharing control flow chart based on the rear class DC bus-bar voltage of Dead band controller Fig. 5;
LLC full-bridge half-bridge mode when Fig. 6 is the control of rear class DC bus-bar voltage switches schematic diagram.
Embodiment
Below in conjunction with accompanying drawing, also by specific embodiment, the invention will be further described, and following examples are descriptive, are not determinate, can not limit protection scope of the present invention with this.
The control method of multi-channel parallel full-bridge LLC converter in a kind of cascading power source system, the structure of cascading power source system involved in the present embodiment as shown in Figure 1, comprise front stage converter, LLC, rear class converter connect and compose three-stage cascade structure successively, prime DC bus-bar voltage is transformed into rear class DC bus-bar voltage.
The concrete structure of front stage converter is bidirectional DC-DC converter side series connection accumulation device, and bidirectional DC-DC converter opposite side is parallel with multiple LLC circuit; Two LLC circuit are parallel with in cascading power source system shown in the present embodiment.
LLC circuit comprises switching network, resonant network and commutated network,
Switching network is specially: be parallel with two brachium pontis in the circuit of switching network, wherein a brachium pontis is made up of the switching tube Q1 connected and switching tube Q2, another brachium pontis is made up of switching tube Q3 and switching tube Q4, switching network utilizes switching tube Q1, Q2, Q3 and Q4, the structure of the controlled inverter of composition single-phase full bridge;
Resonant network adopts LLC type resonant cavity, comprise resonant capacitance Cr, resonant inductance Lr and static exciter inductance L m, this resonant capacitance Cr, resonant inductance Lr and static exciter inductance L m connects successively, this resonant network one end is connected on the brachium pontis between switching tube Q1 and switching tube Q2, and this resonant network other end is connected on the brachium pontis between switching tube Q3 and switching tube Q4;
Rectification circuit adopts switching tube device or rectifier diode, realizes the transmission of electric energy.
Above-mentioned multiple LLC circuit in parallel is in the three-phase inverter side of rear class converter, and three-phase inverter opposite side connects filter, and filter connects electrical network.
The present embodiment adopts the LLC converter of multi-channel parallel, realizes from prime DC bus-bar voltage to the conversion of rear class DC bus-bar voltage and electrical isolation, utilizes LLC to control prime DC bus-bar voltage and rear class DC bus-bar voltage.
LLC half-bridge full-bridge mode switches schematic diagram as shown in Figure 2.LLC full-bridge mode is as shown in Fig. 2 (a), and when LLC is in heavy condition, switching tube Q1, Q2, Q3 and Q4 adopt pulse frequency modulated control strategy; LLC half-bridge mode is as shown in Fig. 2 (b), and when LLC is in light condition, the control mode of switching tube Q1 and Q2 is constant, by switching tube Q3 control signal reset and by the set of switching tube Q4 control signal, the upper switch pipe of this brachium pontis is disconnected, and lower switch pipe closes.Therefore when zero load, can full-bridge LLC be converted to half-bridge LLC, effectively control the effect of output voltage under reaching idle condition.
The concrete control method of the present embodiment is:
(1) DC bus-bar voltage controls; In full-load range, when two-way LLC controls prime DC bus-bar voltage U
fronttime, for ensureing the Tracing Control to LLC input voltage, concrete control flow chart is as shown in Figure 3;
1. first, generate prime DC bus-bar voltage and control half-bridge full-bridge switching mark symbol, as shown in Figure 4; When two-way LLC controls prime DC bus-bar voltage, for ensureing the Tracing Control to LLC input voltage, introduce full-bridge half-bridge switching controls flag bit SIGNAL_FH_Front.
As front stage converter power output P
frontbe less than P
ltime, now SIGNAL_FH_Front is become " 0 " from " 1 ", indicates that LLC is transformed into Light Condition by heavy duty.Switching tube Q3 disconnects, and switching tube Q4 closes, and LLC is transformed into half-bridge by full-bridge.
As front stage converter power output P
frontbe greater than P
utime, now SIGNAL_FH_Front is become " 1 " from " 0 ", indicates that LLC is transformed into heavy condition by zero load.Switching tube Q3, Q4 normally work, and LLC is transformed into full-bridge by half-bridge.
2. the state of determination flag position SIGNAL_FH_Front, decides to enter unloaded adjustment program or band year adjustment program, is specially:
If SIGNAL_FH_Front is " 0 ", then enter unloaded adjustment program, the original frequency of setting two-way LLC is f
h_Front, utilize the operating frequency (duty ratio is constant) to LLC such as Dead band controller and accumulator to regulate, this frequency is at f
h_Frontinitial value on, with Δ f
1step change, until output voltage is controlled in the absolute value of reference value error at Δ U
1scope in;
If SIGNAL_FH_Front is " 1 ", then enters band and carry adjustment program, the original frequency of setting two-way LLC is f
f_Front, the full-bridge LLC converter that band carries under operating mode is controlled.This frequency is at f
f_Frontinitial value on, with Δ f
2step change, until output voltage is controlled in the absolute value of reference value error at Δ U
2scope in;
If in the course of the work, detect that SIGNAL_FH_Front signal is transformed into " 1 " by " 0 ", then regulate programming jump to carry adjustment program to band by zero load and run;
When detecting that SIGNAL_FH_Front signal is transformed into " 0 " by " 1 ", then carried by band and regulate programming jump to run to unloaded adjustment program;
While the state of 3. determination flag position SIGNAL_FH_Front, carry out prime DC bus sharing control;
Detect each road LLC resonant inductance current effective value, it is sorted from small to large successively;
The frequency of the road LLC that current effective value is minimum remains unchanged;
When the absolute difference of the current effective value of current effective value immediate Liang Ge road LLC is greater than Δ I
fronttime, current effective value to rise maximum Δ f compared with the operating frequency of great mono-road LLC
3, and current effective value is constant compared with the operating frequency of little mono-road LLC.When this absolute difference is less than or equal to Δ I
fronttime, two-way LLC operating frequency remains unchanged;
From the two-way LLC that current effective value is minimum, the like, except the two-way LLC that effective value is minimum and maximum, all the other LLC in each control cycle need to carry out twice frequency adjustment (carrying out frequency adjustment respectively with effective value and its immediate two-way LLC), until the inductive current effective value of all LLC is consistent, the inductive current effective value Error Absolute Value of the immediate two-way LLC of size is less than Δ I
front.
If the absolute value of two-way LLC inductive current effective value error is less than Δ I
front, two-way LLC frequency does not all change.This measure can reach the object of parallel current-sharing.
(2) rear class DC bus controls;
When two-way LLC controls rear class DC bus-bar voltage U
backtime, ensure the Tracing Control to LLC input voltage, concrete control flow chart is as shown in Figure 5.
1. first, full-bridge half-bridge switching controls flag bit SIGNAL_FH_Back is introduced, as shown in Figure 6;
As rear class converter power output P
backbe less than P
ltime, now SIGNAL_FH_Back is become " 0 " from " 1 ", indicates that LLC is transformed into Light Condition by heavy duty, and now, switching tube Q3 disconnects, and switching tube Q4 closes, and LLC is transformed into half-bridge by full-bridge;
As rear class converter power output P
backbe greater than P
utime, now SIGNAL_FH_Back is become " 1 " from " 0 ", indicates that LLC is transformed into heavy condition by zero load, and now, switching tube Q3, Q4 normally work, and LLC is transformed into full-bridge by half-bridge;
2. the state of determination flag position SIGNAL_FH_Back, determines to enter unloaded adjustment program or band year adjustment program;
If SIGNAL_FH_Back is 0, then enters unloaded adjustment program, utilize Dead band controller etc. to regulate the operating frequency (duty ratio is constant) of LLC;
If SIGNAL_FH_Back is 1, then enters band and carry adjustment program, the full-bridge LLC converter that band carries under operating mode is controlled;
If in the course of the work, detect that SIGNAL_FH_Back signal is transformed into " 1 " by " 0 ", then regulate programming jump to carry adjustment program to band by zero load, LLC is converted into full-bridge by half-bridge and runs;
When detecting that SIGNAL_FH_Back signal is transformed into " 0 " by " 1 ", then carried by band and regulate programming jump to unloaded adjustment program, LLC is converted into half-bridge by full-bridge and runs;
3. rear class DC bus sharing control;
The inductive current effective value I of LC
lr1be greater than the mean value I on the second tunnel
lr2, and error exceedes Δ I
backtime, the operating frequency rising Δ f of first via LLC
3, the operating frequency of the second road LLC remains unchanged;
As the inductive current effective value I of the second road LLC
lr2be greater than the mean value I of the first via
lr1, and error exceedes Δ I
backtime, the operating frequency rising Δ f of the second road LLC
3, the operating frequency of first via LLC remains unchanged;
If the absolute value of two-way LLC inductive current effective value error is less than Δ I
back, frequency does not change.
Detect each road LLC resonant inductance current effective value, it is sorted from small to large successively;
The frequency of the road LLC that current effective value is minimum remains unchanged;
When the absolute difference of the current effective value of current effective value immediate Liang Ge road LLC is greater than Δ I
backtime, current effective value to rise maximum Δ f compared with the operating frequency of great mono-road LLC
3, and current effective value is constant compared with the operating frequency of little mono-road LLC; When this absolute difference is less than or equal to Δ I
backtime, two-way LLC operating frequency remains unchanged.
From the two-way LLC that current effective value is minimum, the like; Except the two-way LLC that effective value is minimum and maximum, in each control cycle, all the other LLC need to carry out twice frequency adjustment (carrying out frequency adjustment respectively with effective value and its immediate two-way LLC), until the inductive current effective value of all LLC is consistent, the inductive current effective value Error Absolute Value of the immediate two-way LLC of size is less than Δ I
back, this measure can reach the object that multichannel LLC reaches parallel current-sharing.
Although disclose embodiments of the invention and accompanying drawing for the purpose of illustration, but it will be appreciated by those skilled in the art that: in the spirit and scope not departing from the present invention and claims, various replacement, change and amendment are all possible, therefore, scope of the present invention is not limited to the content disclosed in embodiment and accompanying drawing.
Claims (10)
1. the control method of multi-channel parallel full-bridge LLC converter in cascading power source system, is characterized in that: the cascading power source system that this method adopts, and comprises front stage converter, LLC, rear class converter connect and compose three-stage cascade structure successively;
The energy storage device of front stage converter is positioned at the front side of bidirectional DC-DC converter, bidirectional DC-DC converter opposite side is parallel with multiple LLC, multiple LLC is connected in parallel on the three-phase inverter side of rear class converter, and three-phase inverter opposite side connects filter, and filter connects electrical network.
2. the control method of multi-channel parallel full-bridge LLC converter in cascading power source system according to claim 1, is characterized in that: LLC circuit comprises the switching network, resonant network and the commutated network that connect successively,
Be parallel with two brachium pontis in the circuit of switching network, wherein a brachium pontis is made up of the switching tube Q1 connected and switching tube Q2, and another brachium pontis is made up of switching tube Q3 and switching tube Q4;
Resonant network adopts LLC type resonant cavity, comprise resonant capacitance Cr, resonant inductance Lr and static exciter inductance L m, this resonant capacitance Cr, resonant inductance Lr and static exciter inductance L m connects successively, this resonant network one end is connected on the brachium pontis between switching tube Q1 and switching tube Q2, and this resonant network other end is connected on the brachium pontis between switching tube Q3 and switching tube Q4;
Rectification circuit adopts switching tube device or rectifier diode, realizes the transmission of electric energy.
3. the control method of multi-channel parallel full-bridge LLC converter in cascading power source system according to claim 2, is characterized in that: the half-bridge full-bridge mode changing method of LLC:
When LLC is in heavy condition, switching tube Q1, Q2, Q3 and Q4 adopt pulse frequency modulated control strategy, form LLC full-bridge mode;
When LLC is in light condition, the control mode of switching tube Q1 and Q2 is constant, switching tube Q3 control signal reset and by the set of switching tube Q4 control signal, the upper switch pipe of this brachium pontis is disconnected, and lower switch pipe closes, and forms LLC half-bridge mode.
4. the control method of multi-channel parallel full-bridge LLC converter in cascading power source system according to claim 1, is characterized in that: concrete steps are:
(1) DC bus-bar voltage controls; In full-load range, it is U that two-way LLC controls prime DC bus-bar voltage
front;
1. first, generate prime DC bus-bar voltage and control half-bridge full-bridge switching mark symbol SIGNAL_FH_Front;
2. the state of determination flag position SIGNAL_FH_Front, decides to enter unloaded adjustment program or band year adjustment program;
3. prime DC bus sharing control, while the state of determination flag position SIGNAL_FH_Front, carries out prime DC bus sharing control;
(2) rear class DC bus controls; Two-way LLC controls rear class DC bus-bar voltage U
back;
1. first, full-bridge half-bridge switching controls flag bit SIGNAL_FH_Back is introduced;
2. the state of determination flag position SIGNAL_FH_Back, determines to enter unloaded adjustment program or band year adjustment program;
3. rear class DC bus sharing control, while the state of determination flag position SIGNAL_FH_Back, carries out rear class DC bus sharing control.
5. the control method of multi-channel parallel full-bridge LLC converter in cascading power source system according to claim 4, is characterized in that: described step (1) in the product process of 1. half-bridge full-bridge switching mark symbol SIGNAL_FH_Front be:
When LLC is transformed into Light Condition by heavy duty, SIGNAL_FH_Front is become " 0 " from " 1 ", and switching tube Q3 disconnects, and switching tube Q4 closes, and LLC is transformed into half-bridge by full-bridge;
When LLC is transformed into heavy condition by zero load, SIGNAL_FH_Front is become " 1 " from " 0 ", and switching tube Q3, Q4 normally work, and LLC is transformed into full-bridge by half-bridge.
6. the control method of multi-channel parallel full-bridge LLC converter in cascading power source system according to claim 4, is characterized in that: described step (1) in 2. flag bit SIGNAL_FH_Front determine that the flow process of half-bridge full-bridge operating state is specially:
If SIGNAL_FH_Front is " 0 ", then enter unloaded adjustment program, the original frequency of setting two-way LLC is f
h_Front, utilize the operating frequency to LLC such as Dead band controller and accumulator to regulate, this frequency is at f
h_Frontinitial value on, with Δ f
1step change, until output voltage is controlled in the absolute value of reference value error at Δ U
1scope in;
If SIGNAL_FH_Front is " 1 ", then enters band and carry adjustment program, the original frequency of setting two-way LLC is f
f_Front, the full-bridge LLC converter that band carries under operating mode is controlled.This frequency is at f
f_Frontinitial value on, with Δ f
2step change, until output voltage is controlled in the absolute value of reference value error at Δ U
2scope in;
If in the course of the work, detect that SIGNAL_FH_Front signal is transformed into " 1 " by " 0 ", then regulate programming jump to carry adjustment program to band by zero load and run;
When detecting that SIGNAL_FH_Front signal is transformed into " 0 " by " 1 ", then carried by band and regulate programming jump to run to unloaded adjustment program.
7. the control method of multi-channel parallel full-bridge LLC converter in cascading power source system according to claim 4, is characterized in that: step (1) in 3. prime DC bus current-sharing control method be:
Detect each road LLC resonant inductance current effective value, it is sorted from small to large successively;
The frequency of the road LLC that current effective value is minimum remains unchanged;
When the absolute difference of the current effective value of current effective value immediate Liang Ge road LLC is greater than Δ I
fronttime, current effective value to rise maximum Δ f compared with the operating frequency of great mono-road LLC
3, and current effective value is constant compared with the operating frequency of little mono-road LLC.When this absolute difference is less than or equal to Δ I
fronttime, two-way LLC operating frequency remains unchanged;
From the two-way LLC that current effective value is minimum, the like, except the two-way LLC that effective value is minimum and maximum, in each control cycle, all the other LLC carry out frequency adjustment respectively with effective value and its immediate two-way LLC, until the inductive current effective value of all LLC is consistent, the inductive current effective value Error Absolute Value of the immediate two-way LLC of all sizes is less than Δ I
front.
8. the control method of multi-channel parallel full-bridge LLC converter in cascading power source system according to claim 4, is characterized in that: step (2) in the product process of 1. half-bridge full-bridge switching mark symbol SIGNAL_FH_Back be:
As rear class converter power output P
backbe less than P
ltime, now SIGNAL_FH_Back is become " 0 " from " 1 ", indicates that LLC is transformed into Light Condition by heavy duty, and now, switching tube Q3 disconnects, and switching tube Q4 closes, and LLC is transformed into half-bridge by full-bridge;
As rear class converter power output P
backbe greater than P
utime, now SIGNAL_FH_Back is become " 1 " from " 0 ", indicates that LLC is transformed into heavy condition by zero load, and now, switching tube Q3, Q4 normally work, and LLC is transformed into full-bridge by half-bridge.
9. the control method of multi-channel parallel full-bridge LLC converter in cascading power source system according to claim 4, is characterized in that: step (1) in 2. flag bit SIGNAL_FH_Back determine that the flow process of half-bridge full-bridge operating state is specially:
If SIGNAL_FH_Back is 0, then enters unloaded adjustment program, utilize Dead band controller etc. to regulate the operating frequency of LLC;
If SIGNAL_FH_Back is 1, then enters band and carry adjustment program, the full-bridge LLC converter that band carries under operating mode is controlled;
If in the course of the work, detect that SIGNAL_FH_Back signal is transformed into " 1 " by " 0 ", then regulate programming jump to carry adjustment program to band by zero load, LLC is converted into full-bridge by half-bridge and runs;
When detecting that SIGNAL_FH_Back signal is transformed into " 0 " by " 1 ", then carried by band and regulate programming jump to unloaded adjustment program, LLC is converted into half-bridge by full-bridge and runs.
10. the control method of multi-channel parallel full-bridge LLC converter in cascading power source system according to claim 4, is characterized in that: step (1) in 3. rear class DC bus current-sharing control method be:
Detect each road LLC resonant inductance current effective value, it is sorted from small to large successively;
The frequency of the road LLC that current effective value is minimum remains unchanged;
When the absolute difference of the current effective value of current effective value immediate Liang Ge road LLC is greater than Δ I
backtime, current effective value to rise maximum Δ f compared with the operating frequency of great mono-road LLC
3, and current effective value is constant compared with the operating frequency of little mono-road LLC; When this absolute difference is less than or equal to Δ I
backtime, two-way LLC operating frequency remains unchanged;
From the two-way LLC that current effective value is minimum, the like; Except the two-way LLC that effective value is minimum and maximum, in each control cycle, all the other LLC need to carry out frequency adjustment respectively with effective value and its immediate two-way LLC, until the inductive current effective value of all LLC is consistent, the inductive current effective value Error Absolute Value of the immediate two-way LLC of size is less than Δ I
back, this measure can reach the object that multichannel LLC reaches parallel current-sharing.
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