CN117674590A - Direct-current boost converter and control method thereof - Google Patents
Direct-current boost converter and control method thereof Download PDFInfo
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- CN117674590A CN117674590A CN202311685028.9A CN202311685028A CN117674590A CN 117674590 A CN117674590 A CN 117674590A CN 202311685028 A CN202311685028 A CN 202311685028A CN 117674590 A CN117674590 A CN 117674590A
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Classifications
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- H—ELECTRICITY
- H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
- H02M—APPARATUS FOR CONVERSION BETWEEN AC AND AC, BETWEEN AC AND DC, OR BETWEEN DC AND DC, AND FOR USE WITH MAINS OR SIMILAR POWER SUPPLY SYSTEMS; CONVERSION OF DC OR AC INPUT POWER INTO SURGE OUTPUT POWER; CONTROL OR REGULATION THEREOF
- H02M3/00—Conversion of dc power input into dc power output
- H02M3/02—Conversion of dc power input into dc power output without intermediate conversion into ac
- H02M3/04—Conversion of dc power input into dc power output without intermediate conversion into ac by static converters
- H02M3/06—Conversion of dc power input into dc power output without intermediate conversion into ac by static converters using resistors or capacitors, e.g. potential divider
- H02M3/07—Conversion of dc power input into dc power output without intermediate conversion into ac by static converters using resistors or capacitors, e.g. potential divider using capacitors charged and discharged alternately by semiconductor devices with control electrode, e.g. charge pumps
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- H—ELECTRICITY
- H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
- H02H—EMERGENCY PROTECTIVE CIRCUIT ARRANGEMENTS
- H02H7/00—Emergency protective circuit arrangements specially adapted for specific types of electric machines or apparatus or for sectionalised protection of cable or line systems, and effecting automatic switching in the event of an undesired change from normal working conditions
- H02H7/10—Emergency protective circuit arrangements specially adapted for specific types of electric machines or apparatus or for sectionalised protection of cable or line systems, and effecting automatic switching in the event of an undesired change from normal working conditions for converters; for rectifiers
- H02H7/12—Emergency protective circuit arrangements specially adapted for specific types of electric machines or apparatus or for sectionalised protection of cable or line systems, and effecting automatic switching in the event of an undesired change from normal working conditions for converters; for rectifiers for static converters or rectifiers
- H02H7/1213—Emergency protective circuit arrangements specially adapted for specific types of electric machines or apparatus or for sectionalised protection of cable or line systems, and effecting automatic switching in the event of an undesired change from normal working conditions for converters; for rectifiers for static converters or rectifiers for DC-DC converters
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- Dc-Dc Converters (AREA)
Abstract
The invention discloses a direct-current boost converter and a control method thereof, and relates to the technical field of boost conversion. The direct current boost converter comprises a capacitor bridge arm, a power inductor, an input side diode and an output side diode; the capacitor bridge arm comprises N submodules and a capacitor C N+1 The method comprises the steps of carrying out a first treatment on the surface of the Wherein the nth sub-module includes a first IGBTT n1 Second IGBTT n2 Third IGBTT n3 Capacitor C n The method comprises the steps of carrying out a first treatment on the surface of the N is less than or equal to N; first IGBTT n1 Collector and capacitor C of (2) n Is connected with the negative electrode of the battery; third IGBTT n3 Collector and capacitor C of (2) n Is connected with the positive electrode of the battery; first IGBTT n1 Emitter and capacitance C of (2) n+1 Is connected with the negative electrode of the battery; third IGBTT n3 Emitter and capacitance C of (2) n+1 Is connected with the positive electrode of the battery; second IGBTT n2 Emitter and capacitance C of (2) n Is connected with the negative electrode of the battery; second IGBTT n2 Collector and capacitor C of (2) n+1 Is connected to the positive electrode of the battery.The invention can effectively improve the boost conversion efficiency and the equipment capacity and reduce the voltage class of the power tube and the equipment size.
Description
Technical Field
The invention relates to the technical field of boost conversion, in particular to a direct-current boost converter and a control method thereof.
Background
In recent years, the problems of exhaustion of fossil energy and climate change are becoming serious, and the development of new energy power generation technology is greatly promoted to relieve the dependence of energy consumption on fossil energy and land resources, so that the method is a necessary path for sustainable development. The offshore wind power resources in China are rich, the offshore wind power station is close to the developed provinces of coastal economy, the on-site digestion advantage is huge, and the advantages of relatively stable wind power resources, high average wind speed, more wind power utilization hours, no need of occupying land resources and the like exist in the offshore wind power station, so that the development of the offshore wind power technology and the construction of the offshore wind power station become necessary choices for the vigorous development of renewable energy sources.
The existing offshore wind farm which is built or put into production and is connected with the grid through a high-voltage direct-current transmission line mainly uses an alternating-current energy collection system. The electric energy generated by the generator needs to be transmitted by high-voltage direct current after passing through the generator side converter, the grid side converter, the step-up transformer and the rectifier in sequence and is integrated into an onshore alternating current power grid, and multiple power transformation loops carried out in the process can cause a large amount of energy loss, so that the economic cost is higher, and the reliability of an offshore wind power system is also reduced.
Compared with an alternating current energy collection system, the direct current energy collection system adopts a direct current technology to collect electric energy, and generally adopts a power electronic converter, so that the direct current energy collection system has the advantages of smaller volume and lighter weight compared with an alternating current power frequency converter, simplifies the electric energy conversion process, and has remarkable advantages in the aspects of volume, quality, system loss, construction cost and the like of equipment. The DC/DC boost converter is an important link of energy collection and electric energy delivery of the full direct current wind power plant, and the circuit topology, the control strategy and the dynamic characteristics of the DC/DC boost converter have key influences on wind power plant energy collection and delivery efficiency and quality, so that the problems of improving conversion efficiency, reducing power tube voltage level, improving equipment capacity, reducing equipment volume and weight and the like are the main contents of the current scholars.
Disclosure of Invention
The invention aims to provide a direct current boost converter and a control method thereof, which can effectively improve conversion efficiency and equipment capacity and reduce voltage class of a power tube and equipment size.
In order to achieve the above object, the present invention provides the following solutions:
a dc boost converter, comprising: the power supply comprises a capacitor bridge arm, a power inductor, an input side diode and an output side diode;
the positive electrode of the input side diode is connected with the high-voltage end of the input side; the negative electrode of the output side diode is connected with the output side high-voltage end; the negative electrode of the input side diode and the positive electrode of the output side diode are connected with one end of the power inductor; the other end of the power inductor is connected with the head end of the capacitor bridge arm; the tail end of the capacitor bridge arm is connected with the public low-voltage end;
the capacitor bridge arm comprises N sub-modules and a capacitor C arranged at the tail end of the capacitor bridge arm N+1 The method comprises the steps of carrying out a first treatment on the surface of the Wherein the nth sub-module includes a first IGBTT n1 Second IGBTT n2 Third IGBTT n3 Capacitor C n The method comprises the steps of carrying out a first treatment on the surface of the N is less than or equal to N; the first IGBTT n1 And the collector of (C) and the capacitor C n Is connected with the negative electrode of the battery; the third IGBTT n3 And the collector of (C) and the capacitor C n Is connected with the positive electrode of the battery; the first IGBTT n1 Emitter and capacitance C of (2) n+1 Is connected with the negative electrode of the battery; the third IGBTT n3 Is connected with the capacitor C n+1 Is connected with the positive electrode of the battery; the second IGBTT n2 Is connected with the capacitor C n Is connected with the negative electrode of the battery; the second IGBTT n2 And the collector of (C) and the capacitor C n+1 Is connected to the positive electrode of the battery.
Optionally, the input side and the output side of the dc boost converter are electrically non-isolated.
Optionally, the dc boost converter further comprises a dc breaker; the direct current breaker is arranged on the output side of the direct current boost converter and is used for achieving fault isolation on the high voltage side.
Optionally, the redundant design of the direct current boost converter comprises a plurality of groups of capacitor bridge arms, and each IGBT and each capacitor in the plurality of groups of capacitor bridge arms are connected in parallel node by node.
Optionally, each IGBT in the capacitor leg is driven independently.
A control method of a direct current boost converter is applied to the direct current boost converter, and comprises the following steps:
by controlling the switching mode of each IGBT in the capacitor bridge arm, each capacitor in the capacitor bridge arm is switched back and forth between a series connection state and a parallel connection state, electric energy is absorbed from an input side in the parallel connection state, electric energy is sent out to an output side in the series connection state, and the charging and discharging currents of the capacitor bank are controlled by the power inductor, so that a direct current boosting effect is achieved;
the control of the output voltage is realized by adjusting the duty ratio of the modulation signal of each IGBT.
Optionally, by controlling a switching mode of each IGBT in the capacitor bridge arm, each capacitor in the capacitor bridge arm is switched back and forth between a series state and a parallel state, including:
when the first IGBT and the third IGBT in each sub-module are turned on and the second IGBT is turned off, each capacitor in the capacitor bridge arm is in a parallel state, and the output voltage of the capacitor bridge arm is a single capacitor voltage;
when the first IGBT and the third IGBT in each sub-module are turned off and the second IGBT is turned on, each capacitor in the capacitor bridge arm is in a series connection state, and the output voltage of the capacitor bridge arm is the sum of the voltages of each capacitor.
Optionally, the controlling the output voltage by adjusting the duty ratio of the modulation signal of each IGBT specifically includes:
determining a duty cycle interval in which the duty cycle of the direct current boost converter monotonically increases as a working interval through simulation or theoretical calculation;
in the working interval, the difference between the given value of the output voltage and the feedback value of the output voltage is used as the input of a PI controller, and the PI controller outputs the duty ratio with interval amplitude limiting to realize the control of the output voltage.
Optionally, the control method further includes:
when a short circuit fault occurs on the input side of the direct current boost converter, a self-isolation function is realized;
when a short circuit fault occurs on the output side of the direct current boost converter, the direct current breaker is additionally arranged on the output side, so that fault isolation of the high voltage side is realized.
Optionally, the control method further includes:
when one IGBT in the capacitor bridge arm fails and cannot be disconnected, the switching task of the IGBT is borne by other IGBTs connected in parallel, and the current which should flow in the normal on state of the failed IGBT flows through the other IGBTs after the failure; the anti-parallel diode freewheeling current of the normal turn-off state of the fault IGBT flows through the anti-parallel diodes of the rest IGBTs.
According to the specific embodiment provided by the invention, the invention discloses the following technical effects:
the invention provides a direct current boost converter and a control method thereof. The invention provides a novel submodule, a non-isolated direct-current boost converter is built based on series-parallel connection of capacitors in a plurality of submodules, and IGBT of the submodule has two switching modes, so that the capacitors of the submodule can be switched back and forth between series connection and parallel connection states. The direct current boost converter has the advantages of small volume, light weight and simple modulation strategy, can effectively improve conversion efficiency and equipment capacity, and reduces the voltage level of a power tube and the size of equipment.
In addition, the invention can expand the transformation ratio of the converter by increasing the number of the sub-modules connected in series and parallel, and simultaneously, the topological structure of the capacitor bridge arm can reduce the voltage class of the IGBT, thereby realizing the self-balancing of the capacitor voltage of the sub-modules without adding additional control strategies. The direct current boost converter can independently isolate the direct current short circuit fault at the input side, and realizes redundant design in a mode of connecting multiple groups of capacitor bridge arms in parallel node by node, thereby improving the fault-tolerant operation capability and the working reliability of the direct current boost converter. The invention can realize direct-current high-power high-transformation-ratio conversion and has wide prospect in the fields of direct-current collection and direct-current delivery of new energy power plants.
Drawings
In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings that are needed in the embodiments will be briefly described below, and it is obvious that the drawings in the following description are only some embodiments of the present invention, and other drawings may be obtained according to these drawings without inventive effort for a person skilled in the art.
Fig. 1 is a circuit topology diagram of a dc boost converter provided by the present invention;
fig. 2 is a schematic structural diagram of a sub-module according to the present invention;
FIG. 3 is a schematic diagram of a redundant design topology of a DC boost converter according to the present invention;
fig. 4 is a schematic diagram showing the change of output voltage along with the duty ratio of an IGBT modulation signal under the condition of different output side load resistances of the dc boost converter provided by the present invention;
FIG. 5 is a schematic diagram of the small capacitance operation dynamics of the DC boost converter of the present invention;
FIG. 6 is a schematic diagram of the large capacitance operating dynamics of the DC boost converter provided by the present invention;
FIG. 7 is a schematic diagram of a short circuit fault at the input side of a DC boost converter according to the present invention;
fig. 8 is a schematic diagram of a short-circuit fault at the output side of the dc boost converter provided by the present invention.
Detailed Description
The following description of the embodiments of the present invention will be made clearly and completely with reference to the accompanying drawings, in which it is apparent that the embodiments described are only some embodiments of the present invention, but not all embodiments. All other embodiments, which can be made by those skilled in the art based on the embodiments of the invention without making any inventive effort, are intended to be within the scope of the invention.
The invention aims to provide a direct current boost converter and a control method thereof, which can effectively improve conversion efficiency and equipment capacity and reduce voltage class of a power tube and equipment size.
In order that the above-recited objects, features and advantages of the present invention will become more readily apparent, a more particular description of the invention will be rendered by reference to the appended drawings and appended detailed description.
As shown in fig. 1, the dc boost converter of the present disclosure includes: capacitor bridge arm and power inductor L 1 Input side twoPolar tube D 1 Output side diode D 2 . Input side diode D 1 Is connected with the high-voltage end of the input side. Output side diode D 2 The negative electrode of the capacitor is connected with the high-voltage end of the output side. Input side diode D 1 Cathode of (D) and output side diode D 2 Positive electrode of (a) and power inductance L 1 Is connected to one end of the connecting rod. Power inductance L 1 The other end of the capacitor bridge arm is connected with the head end of the capacitor bridge arm. The tail end of the capacitor bridge arm is connected with the common low-voltage end. Power inductance L 1 Controlling the charge and discharge efficiency of the capacitor bridge arm, and enabling the charge current at the input side and the discharge current at the output side to pass through the power inductor L 1 Into or out of the capacitive leg. The input side and the output side of the direct current boost converter are electrically not isolated, and a common low voltage end exists.
Specifically, the capacitor bridge arm includes N sub-modules and a capacitor C disposed at an end of the capacitor bridge arm N+1 . As shown in FIG. 2, the nth (n.ltoreq.N) sub-module of the N sub-modules includes a first IGBTT n1 Second IGBTT n2 Third IGBTT n3 Capacitor C n . As shown in fig. 1 and 2, in the nth sub-module, the first IGBTT n1 Collector and capacitor C of (2) n Is connected to the negative electrode of the battery. Third IGBTT n3 Collector and capacitor C of (2) n Is connected to the positive electrode of the battery. First IGBTT n1 Capacitance C of emitter and n+1th sub-module n+1 When n=n, a first IGBTT N1 The emitter of (C) is a capacitor C arranged separately from the tail end of the capacitor bridge arm N+1 Is connected to the negative electrode of the battery. Third IGBTT n3 Emitter and capacitance C of (2) n+1 When n=n, a third IGBTT N3 The emitter of (C) is a capacitor C arranged separately from the tail end of the capacitor bridge arm N+1 Is connected to the positive electrode of the battery. Second IGBTT n2 Emitter and capacitance C of (2) n Is connected to the negative electrode of the battery. Second IGBTT n2 Collector and capacitor C of (2) n+1 Is connected to the positive electrode of the battery. From the connection relationship of the sub-modules, the first IGBTT in the nth sub-module n1 And a third IGBTT n3 In parallel relationship, a second IGBTT n2 With the first IGBTT n1 And a third IGBTT n3 In a series relationship. In the present invention,the head end of the capacitor bridge arm is the capacitor C in the first sub-module 1 Positive electrode of (a) and third IGBTT 13 Is connected to the common connection terminal of the collector electrode of (a); the tail end of the capacitor bridge arm is a capacitor C N+1 First IGBTT in the negative electrode and nth sub-module N1 Is connected to the common connection of the emitters of (a). Because the emitter potentials of the IGBTs are different, the IGBTs in the capacitor bridge arm are required to be driven independently.
In some embodiments, the invention further provides a redundancy design structure of the direct-current boost converter, wherein the redundancy design structure comprises a plurality of groups of capacitor bridge arms, and each IGBT and each capacitor in the plurality of groups of capacitor bridge arms are connected in parallel node by node.
As shown in fig. 3, in a specific embodiment, the redundancy design structure of the dc boost converter of the present invention is formed by connecting two groups of identical capacitor bridge arms node by node, and after the two groups of identical capacitor bridge arms are connected in parallel, the two groups of identical capacitor bridge arms can be equivalently a single group of capacitor bridge arms with capacitance value enlarged by two times. In the running process, when one IGBT in the multi-group capacitor bridge arm fails to be turned off due to the fact that the IGBT cannot be turned on, the switching task is borne by other IGBTs connected in parallel, and the current which should be circulated in the normal on state of the failed IGBT is circulated through the other IGBTs after the failure; the anti-parallel diode freewheeling current of the normal turn-off state of the fault IGBT flows through the anti-parallel diodes of the rest IGBTs.
Based on the direct current boost converter, the invention also provides a control method of the direct current boost converter, which comprises the following steps: by controlling the switching mode of each IGBT in the capacitor bridge arm, each capacitor in the capacitor bridge arm is switched back and forth between a series connection state and a parallel connection state, electric energy is absorbed from an input side in the parallel connection state, electric energy is sent out to an output side in the series connection state, and the charging and discharging currents of the capacitor bank are controlled by the power inductor, so that a direct current boosting effect is achieved.
Specifically, when the first IGBT and the third IGBT in each sub-module are turned on and the second IGBT is turned off, each capacitor in the capacitor bridge arm is in a parallel state, and the output voltage of the capacitor bridge arm is a single capacitor voltage. When the first IGBT and the third IGBT in each sub-module are turned off and the second IGBT is turned on, each capacitor in the capacitor bridge arm is in a series connection state, and the output voltage of the capacitor bridge arm is the sum of the voltages of each capacitor. Power ofInductance L 1 An input/output node connected to the head end of the capacitor bridge arm, and a power inductor L when each capacitor of the capacitor bridge arm is switched between a series state and a parallel state 1 The voltage is periodically changed, so that the current direction of the capacitor bridge arm is periodically changed, and electric energy conversion is realized.
In the running process, the direct current boost converter can independently isolate the short circuit fault of the input side, but a direct current breaker is required to be additionally arranged on the output side. As shown in fig. 7, when the input voltage of the dc boost converter is suddenly dropped due to a short-circuit fault, the parallel capacitance of the capacitor arm cannot absorb energy from the input side in the charging period [0, dt ], and the input side diode D is used for the parallel capacitance 1 The existence of the capacitor bridge arm avoids the discharge of the capacitor in the capacitor bridge arm through the short circuit point at the input side, so that the current at the input side is zero. When the capacitor bridge arm is connected in series with the capacitor to discharge the high-voltage side, and the voltage balance is achieved, the current of the output side is automatically disconnected, and the self-isolation function is realized.
When a short circuit fault occurs on the output side of the direct current boost converter, the direct current breaker is additionally arranged on the output side, so that fault isolation of the high voltage side is realized. As shown in fig. 8, when a short-circuit fault occurs on the output side, the IGBT in the circuit cannot block the input side and the capacitor arm via the output side diode D 2 And the capacitor bridge arm IGBT anti-parallel diode discharges to a high-voltage side short-circuit point, which leads to the output current surge, the IGBT and the output side diode D 2 And the overcurrent is damaged, so that a direct current breaker is additionally arranged on the output side, and the fault isolation of the high voltage side is realized.
The working principle of the direct current boost converter is verified through simulation software Simulink, the simulation result is shown in fig. 4, the abscissa of fig. 4 is the duty ratio of IGBT modulation signals, the ordinate is the ratio of the output voltage to the input voltage of a capacitor bridge arm, and R represents the load resistance of the output side. As can be seen from the simulation results shown in fig. 4, the output voltage can be controlled by changing the duty ratio of the power tube modulation signal, but the output voltage does not show a linearly increasing result with the increase of the duty ratio. When the duty ratio is too high, the discharging time is reduced to limit the power sent to the high-voltage side by the capacitor bank, and in application, the duty ratio is limited in a section in which the variable ratio monotonically increases along with the duty ratio, so that the effectiveness of a control strategy is ensured.
Based on the switching characteristics of the sub-modules provided by the invention, the modulation strategy of the whole direct current boost converter is designed. Firstly, a duty cycle section in which the duty cycle of the direct current boost converter monotonically increases is obtained as a working section through simulation or theoretical calculation. In the working interval, the difference between the given value of the output voltage and the feedback value of the output voltage is used as the input of a PI controller, and the PI controller outputs the duty ratio with interval amplitude limitation as the control quantity, so as to realize the control of the output voltage. The switching signals of the first IGBT and the third IGBT are complementary to the switching signals of the second IGBT, and dead zone protection exists.
The DC boost converter of the invention presents different internal dynamics according to different parameters of the capacitance and inductance elements.
(1) Small capacitance operating dynamics
When the capacitance C is enoughUnder the condition, the direct current boost converter is in a small capacitance working dynamic state. Capacitor group is through power inductance L 1 The voltage curve of charge and discharge accords with the dynamic characteristic of the second-order circuit, and qualitative analysis of the output voltage characteristic can be given by the simulation analysis result shown in fig. 4: with the increase of the duty ratio, the output voltage tends to increase and decrease first under the condition that the input voltage and the load condition are unchanged. In the monotonically increasing interval, the duty cycle increase allows the capacitor to absorb more input side power during charging, release to the high side, and the pump increases the voltage on the high side. Further increases in duty cycle result in the duration of the discharge cycle being limited, and even if the capacitor voltage is kept at a high level, its energy cannot be sufficiently discharged to the high-voltage side, resulting in the high-voltage side voltage reaching a peak value and then beginning to drop.
As shown in FIG. 5, the internal dynamics of the small-capacitance simulation circuit is consistent with the theoretical analysis, when the capacitance is switched between the series connection state and the parallel connection state, the charge-discharge voltage curve of the capacitance accords with the transient second-order circuit response, and the voltage fluctuation amplitude is larger due to smaller capacitance, so the capacitance is moved in the analysis circuitIn the state, the converter is not considered as a constant value, so that the analysis process is complex, and the explicit relation between the converter transformation ratio and the duty ratio is difficult to obtain. The abscissa in fig. 5 is time; the inductive voltage u is sequentially from top to bottom L Inductor current i L Capacitance voltage u C First IGBTT n1 And a third IGBTT n3 A switching status signal (status) of the switching tube.
According to the dynamic characteristics, the control method of the direct current boost converter circuit can be designed, and a duty ratio interval in which the circuit variable ratio monotonically increases along with the duty ratio is obtained through simulation calculation. Taking the interval as a working interval, taking the difference between the high-voltage side voltage command value and the high-voltage side voltage sampling value, sending the difference into a PI control loop with output limit, and outputting the current duty ratio command value, thereby realizing the no-static-difference control of the high-voltage side voltage in the theoretical transformation ratio interval.
(2) Large capacitance operating dynamics
When the capacitance C is enoughThe DC boost converter is a large capacitance operating dynamics. When the capacitance value is larger, the capacitance voltage will fluctuate near the steady-state voltage, when the capacitance is large enough and the fluctuation amplitude is small enough, the capacitance voltage can be used as a direct current during analysis, and errors caused by ignoring capacitance voltage dynamics can be ignored. The fluctuation amplitude of the capacitor generated by the charge and discharge of the capacitor is smaller than 10% of the steady-state value, and the error caused by ignoring the dynamic state of the capacitor voltage is negligible.
As shown in fig. 6, by power inductance L 1 The principle of volt-second balance in the period can obtain the input side voltage u through dynamic analysis L Capacitance-voltage steady-state value u C Output voltage u H The following relationship is approximately satisfied:
wherein P is transmission power, T is IGBT switching period, L is power inductance L 1 Is a value of inductance of (a); t is t 1 、t 2 When the transformation ratio is large enough, the reversing process is short and can be approximately 0; n is the number of bridge arm capacitors. The abscissa in fig. 6 is time; the inductive voltage u is sequentially from top to bottom L Inductor current i L Capacitance voltage u C First IGBTT n1 And a third IGBTT n3 A switching status signal (status) of the switching tube.
According to the dynamic characteristic, the converter under the condition of large capacitance also has a section in which the circuit transformation ratio monotonically increases along with the duty ratio, and the output side voltage control can be realized by adopting a PI controller with amplitude limitation in the section.
The modulation strategy of each IGBT is designed according to the method:
t epsilon [0, dT), the first IGBT and the third IGBT which are connected in parallel with each submodule of the whole capacitor bridge arm are all turned on, the second IGBT which is connected in series is all turned off, and all capacitors are connected in parallel at the low-voltage side for charging. Where d is the duty cycle, T is the switching period, and dT is the switching time. When all the capacitors are connected in parallel, the output voltage value u of the capacitor bridge arm c For a single capacitance voltage value U C U is namely c ＝U C Lower than the input side DC voltage u L Power inductance L 1 The voltage is the input side DC voltage u L The discharge current is reduced due to the difference between the discharge current and the capacitor voltage, and the current flows through anti-parallel diodes of the IGBTs; when the bridge arm current finishes reversing, the input side passes through the power inductor L 1 Charging the parallel capacitor string.
And when T epsilon [ dT, T), the second IGBT of each sub-module of the capacitor bridge arm is turned on, the first IGBT and the third IGBT are turned off, and the capacitor is connected in series to the high-voltage side for discharging. When all the capacitors are connected in series, the output voltage of the capacitor bridge arm is u c ＝(N+1)*U C The power inductance voltage is the difference between the input side voltage and the capacitor string voltage, the charging current is rapidly reduced, the current flows through the IGBT anti-parallel diode, and the bridge arm current finishes reversingThe capacitor bridge arm discharges to the output side through the power inductor.
In summary, the dc boost converter and the control method thereof provided by the present invention have the following advantages: (1) The direct-current boost converter provided by the invention can be expanded to a high-voltage large-transformation-ratio working scene; (2) The invention can change the duty ratio of the power tube modulation signal, thereby controlling the output voltage; in the effective working interval of the duty ratio, the output voltage monotonically increases along with the increase of the duty ratio, and in the application, the duty ratio is limited in the working interval that the change ratio monotonically increases along with the duty ratio, so that the effectiveness of a control strategy is ensured; (3) The number of the submodules can be expanded, and as the number of the series-parallel capacitors is increased, the output voltage can be increased, and the transformation ratio of the direct-current boost converter can be increased; (4) Similar to the modularized multi-level technology, the direct current boost converter can reduce the back pressure born by each IGBT, and the back pressure born by each IGBT is at most input side voltage, so that the voltage class of the power tube is reduced; (5) The point-by-point parallel connection method used by the redundancy design structure of the direct-current boost converter can balance the problem of inconsistent parameters caused by aging of multiple capacitors, and after the circuit operates for a certain time, the parameter difference among multiple groups of parallel capacitors is smaller than the aging difference among multiple isolated capacitors, so that the circuit can operate for a long time; and the redundancy strategy can carry out hot redundancy backup on all IGBTs, after a fault occurs, the fault IGBT is disconnected, and other IGBTs connected in parallel with the fault IGBT automatically bear the switching tasks of the original IGBTs, so that the fault-tolerant operation capability and the working reliability of the direct-current boost converter are improved.
In the present specification, each embodiment is described in a progressive manner, and each embodiment is mainly described in a different point from other embodiments, and identical and similar parts between the embodiments are all enough to refer to each other.
The principles and embodiments of the present invention have been described herein with reference to specific examples, the description of which is intended only to assist in understanding the methods of the present invention and the core ideas thereof; also, it is within the scope of the present invention to be modified by those of ordinary skill in the art in light of the present teachings. In view of the foregoing, this description should not be construed as limiting the invention.
Claims (10)
1. A dc boost converter, comprising: the power supply comprises a capacitor bridge arm, a power inductor, an input side diode and an output side diode;
the positive electrode of the input side diode is connected with the high-voltage end of the input side; the negative electrode of the output side diode is connected with the output side high-voltage end; the negative electrode of the input side diode and the positive electrode of the output side diode are connected with one end of the power inductor; the other end of the power inductor is connected with the head end of the capacitor bridge arm; the tail end of the capacitor bridge arm is connected with the public low-voltage end;
the capacitor bridge arm comprises N sub-modules and a capacitor C arranged at the tail end of the capacitor bridge arm N+1 The method comprises the steps of carrying out a first treatment on the surface of the Wherein the nth sub-module includes a first IGBTT n1 Second IGBTT n2 Third IGBTT n3 Capacitor C n The method comprises the steps of carrying out a first treatment on the surface of the N is less than or equal to N; the first IGBTT n1 And the collector of (C) and the capacitor C n Is connected with the negative electrode of the battery; the third IGBTT n3 And the collector of (C) and the capacitor C n Is connected with the positive electrode of the battery; the first IGBTT n1 Emitter and capacitance C of (2) n+1 Is connected with the negative electrode of the battery; the third IGBTT n3 Is connected with the capacitor C n+1 Is connected with the positive electrode of the battery; the second IGBTT n2 Is connected with the capacitor C n Is connected with the negative electrode of the battery; the second IGBTT n2 And the collector of (C) and the capacitor C n+1 Is connected to the positive electrode of the battery.
2. The dc boost converter of claim 1, wherein the input side and the output side of the dc boost converter are electrically non-isolated.
3. The dc boost converter of claim 1, further comprising a dc breaker; the direct current breaker is arranged on the output side of the direct current boost converter and is used for achieving fault isolation on the high voltage side.
4. The dc boost converter of claim 1, wherein the redundant design of the dc boost converter includes multiple groups of capacitor legs, each IGBT and each capacitor in the multiple groups of capacitor legs being connected in parallel node by node.
5. The dc boost converter of claim 1, wherein each IGBT in the capacitor leg is driven independently.
6. A control method of a dc boost converter, applied to the dc boost converter of claim 1, comprising:
by controlling the switching mode of each IGBT in the capacitor bridge arm, each capacitor in the capacitor bridge arm is switched back and forth between a series connection state and a parallel connection state, electric energy is absorbed from an input side in the parallel connection state, electric energy is sent out to an output side in the series connection state, and the charging and discharging currents of the capacitor bank are controlled by the power inductor, so that a direct current boosting effect is achieved;
the control of the output voltage is realized by adjusting the duty ratio of the modulation signal of each IGBT.
7. The control method according to claim 6, wherein the switching mode of each IGBT in the capacitor bridge arm is controlled to switch each capacitor in the capacitor bridge arm back and forth between a series state and a parallel state, specifically including:
when the first IGBT and the third IGBT in each sub-module are turned on and the second IGBT is turned off, each capacitor in the capacitor bridge arm is in a parallel state, and the output voltage of the capacitor bridge arm is a single capacitor voltage;
when the first IGBT and the third IGBT in each sub-module are turned off and the second IGBT is turned on, each capacitor in the capacitor bridge arm is in a series connection state, and the output voltage of the capacitor bridge arm is the sum of the voltages of each capacitor.
8. The control method according to claim 6, wherein the control of the output voltage is achieved by adjusting the duty ratio of the modulation signal of each IGBT, specifically comprising:
determining a duty cycle interval in which the duty cycle of the direct current boost converter monotonically increases as a working interval through simulation or theoretical calculation;
in the working interval, the difference between the given value of the output voltage and the feedback value of the output voltage is used as the input of a PI controller, and the PI controller outputs the duty ratio with interval amplitude limiting to realize the control of the output voltage.
9. The control method according to claim 6, characterized by further comprising:
when a short circuit fault occurs on the input side of the direct current boost converter, a self-isolation function is realized;
when a short circuit fault occurs on the output side of the direct current boost converter, the direct current breaker is additionally arranged on the output side, so that fault isolation of the high voltage side is realized.
10. The control method according to claim 6, characterized by further comprising:
when one IGBT in the capacitor bridge arm fails and cannot be disconnected, the switching task of the IGBT is borne by other IGBTs connected in parallel, and the current which should flow in the normal on state of the failed IGBT flows through the other IGBTs after the failure; the anti-parallel diode freewheeling current of the normal turn-off state of the fault IGBT flows through the anti-parallel diodes of the rest IGBTs.
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| CN202311685028.9A CN117674590A (en) | 2023-12-08 | 2023-12-08 | Direct-current boost converter and control method thereof |
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Cited By (1)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN117955336A (en) * | 2024-03-27 | 2024-04-30 | 成都市易冲半导体有限公司 | Power converter, power conversion method, charging chip and charger |
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Cited By (1)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN117955336A (en) * | 2024-03-27 | 2024-04-30 | 成都市易冲半导体有限公司 | Power converter, power conversion method, charging chip and charger |
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