CN115514219A - Three-level DCDC converter with flying capacitor, system and control method - Google Patents
Three-level DCDC converter with flying capacitor, system and control method Download PDFInfo
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- CN115514219A CN115514219A CN202211165805.2A CN202211165805A CN115514219A CN 115514219 A CN115514219 A CN 115514219A CN 202211165805 A CN202211165805 A CN 202211165805A CN 115514219 A CN115514219 A CN 115514219A
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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
- H02M3/10—Conversion of dc power input into dc power output without intermediate conversion into ac by static converters using discharge tubes with control electrode or semiconductor devices with control electrode
- H02M3/145—Conversion of dc power input into dc power output without intermediate conversion into ac by static converters using discharge tubes with control electrode or semiconductor devices with control electrode using devices of a triode or transistor type requiring continuous application of a control signal
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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
- H02M1/00—Details of apparatus for conversion
- H02M1/0003—Details of control, feedback or regulation circuits
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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
- H02M1/00—Details of apparatus for conversion
- H02M1/08—Circuits specially adapted for the generation of control voltages for semiconductor devices incorporated in static converters
- H02M1/088—Circuits specially adapted for the generation of control voltages for semiconductor devices incorporated in static converters for the simultaneous control of series or parallel connected semiconductor devices
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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
- H02M3/08—Conversion of dc power input into dc power output without intermediate conversion into ac by static converters using discharge tubes without control electrode or semiconductor devices without control electrode
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- Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
- Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
- Y02E—REDUCTION OF GREENHOUSE GAS [GHG] EMISSIONS, RELATED TO ENERGY GENERATION, TRANSMISSION OR DISTRIBUTION
- Y02E10/00—Energy generation through renewable energy sources
- Y02E10/50—Photovoltaic [PV] energy
- Y02E10/56—Power conversion systems, e.g. maximum power point trackers
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Abstract
The application discloses three-level DCDC converter with flying capacitor, system and control method, including: the high-power-consumption flying capacitor comprises an inductor, a first switch tube, a second switch tube, a first diode, a second diode, a flying capacitor, a third diode, a fourth diode, a first voltage-dividing capacitor, a second voltage-dividing capacitor and a controller; and the controller is used for triggering the second switch tube and the first switch tube to act simultaneously when the voltage of the flying capacitor is less than the voltage of the second voltage-dividing capacitor, and charging the flying capacitor until the voltage of the flying capacitor is more than or equal to the voltage of the second voltage-dividing capacitor. According to the scheme, as long as the voltage of the flying capacitor is smaller than that of the second voltage division capacitor, the flying capacitor is charged all the time, and the voltage of the flying capacitor is improved. When the voltage of the flying capacitor rises, the voltage of the first voltage-dividing capacitor is adjusted, and the voltage of the second voltage-dividing capacitor is indirectly adjusted, so that the voltages of the first voltage-dividing capacitor and the second voltage-dividing capacitor are balanced, and the safety of the two voltage-dividing capacitors is protected.
Description
Technical Field
The application relates to the technical field of power electronics, in particular to a three-level DCDC converter with a flying capacitor, a system and a control method.
Background
At present, three-level DCDC converters with flying capacitors, hereinafter referred to as three-level DCDC converters, are used in many applications. For example, in a photovoltaic power generation situation, the input end of the three-level DCDC converter is connected to the photovoltaic string, the output end of the three-level DCDC converter is connected to the inverter, the three-level DCDC converter can boost the voltage of the photovoltaic string and then output the boosted voltage to the inverter, and the inverter converts the direct current into the alternating current for grid connection.
In practical applications, when the three-level DCDC converter is operated, the load at the rear stage may be directly connected to other converters, and when the output voltage at the rear stage rapidly rises for some reason, for example, the voltage of the connected inverter suddenly rises, which may cause the output voltage of the three-level DCDC converter to rise instantaneously.
However, the voltage Vcf of the flying capacitor in the three-level DCDC converter is controlled by the switching tube, and cannot rapidly rise along with the output voltage, in this case, the diode bears the reverse voltage and is cut off, if the three-level DCDC converter continues to operate, the voltage imbalance of the two voltage-dividing capacitors is caused, and even one of the voltage-dividing capacitors may be damaged due to overvoltage.
Disclosure of Invention
In order to solve the above problems, the present application provides a three-level DCDC converter with a flying capacitor, a system and a control method, which can equalize the voltages of two voltage-dividing capacitors when the output voltage increases.
The application provides a take three level DCDC converter of flying capacitor, includes: the high-voltage power supply comprises an inductor, a first switch tube, a second switch tube, a first diode, a second diode, a flying capacitor, a third diode, a fourth diode, a first voltage-dividing capacitor, a second voltage-dividing capacitor and a controller;
the first end and the second end of the inductor are respectively connected with the positive input end of the converter and the anode of the first diode, and the anode and the cathode of the second diode are respectively connected with the cathode of the first diode and the positive output end of the converter;
the first end and the second end of the second switch tube are respectively connected with the anode of the first diode and the first end of the first switch tube, and the second end of the first switch tube is connected with the negative input end of the converter;
two ends of the flying capacitor are respectively connected with the cathode of the first diode and the second end of the second switch tube, the cathode and the anode of the third diode are respectively connected with the cathode of the first diode and the cathode of the fourth diode, and the anode of the fourth diode is connected with the second end of the second switch tube;
two ends of the first voltage-dividing capacitor are respectively connected with the positive output end of the converter and the anode of the third diode, and two ends of the second voltage-dividing capacitor are respectively connected with the anode of the third diode and the negative input end of the converter;
and the controller is used for triggering the second switch tube and the first switch tube to act simultaneously when the voltage of the flying capacitor is less than the voltage of the second voltage-dividing capacitor, and charging the flying capacitor until the voltage of the flying capacitor is more than or equal to the voltage of the second voltage-dividing capacitor.
Preferably, the controller is specifically configured to control the first switching tube and the second switching tube to sequentially operate according to the following three modes:
in the first mode: controlling the first switch tube and the second switch tube to be closed;
in a second mode: the second switch tube is controlled to be disconnected, and the first switch tube is controlled to be closed;
in a third mode: and controlling the first switch tube and the second switch tube to be disconnected.
Preferably, the controller is specifically configured to obtain a duty cycle of the first switching tube and a duty cycle of the second switching tube according to the voltage of the flying capacitor, the voltage of the first voltage-dividing capacitor, and the input voltage of the converter, trigger the first switching tube according to the duty cycle of the first switching tube, and trigger the second switching tube to operate according to the duty cycle of the second switching tube.
Preferably, the controller is further configured to obtain a duty ratio adjustment amount according to the voltage of the flying capacitor and the voltage of the second voltage-dividing capacitor;
the duty ratio after the first switching tube is adjusted is the difference between the duty ratio before the adjustment and the duty ratio adjustment amount, and the duty ratio after the second switching tube is adjusted is the sum of the duty ratio before the adjustment and the duty ratio adjustment amount.
Preferably, the duty cycle adjustment amount is proportional to an absolute value of a difference between the voltage of the flying capacitor and the voltage of the second voltage-dividing capacitor.
Preferably, the duty cycle is proportional to a first voltage, which is a sum of a voltage of the first voltage-dividing capacitor and a voltage of the flying capacitor, and inversely proportional to a second voltage, which is a difference between the second voltage and an input voltage of the converter.
Preferably, the controller is further configured to control the second switching tube and the first switching tube to operate in an interleaved manner when the voltage of the flying capacitor is greater than or equal to the voltage of the second voltage-dividing capacitor.
The present application provides a power supply system comprising: an inverter and at least one of the above-described three-level DCDC converters with flying capacitors;
the output end of the three-level DCDC converter with the flying capacitor is connected with the input end of the inverter.
The application also provides a control method of a three-level DCDC converter with a flying capacitor, wherein the converter comprises the following steps: the high-voltage power supply comprises an inductor, a first switch tube, a second switch tube, a first diode, a second diode, a flying capacitor, a third diode, a fourth diode, a first voltage-dividing capacitor and a second voltage-dividing capacitor;
the method comprises the following steps:
obtaining the voltage of the flying capacitor and the voltage of the second voltage-dividing capacitor;
when the voltage of the flying capacitor is smaller than that of the second voltage-dividing capacitor, the second switch tube and the first switch tube are triggered to act simultaneously to charge the flying capacitor until the voltage of the flying capacitor is larger than or equal to that of the second voltage-dividing capacitor.
Preferably, triggering the second switch tube and the first switch tube to act simultaneously specifically includes:
the first switch tube and the second switch tube are controlled to work in the following three modes in sequence:
in the first mode: controlling the first switch tube and the second switch tube to be closed;
in the second mode: the second switch tube is controlled to be disconnected, and the first switch tube is controlled to be closed;
in the third mode: and controlling the first switch tube and the second switch tube to be disconnected.
Preferably, triggering the second switch tube and the first switch tube to act simultaneously specifically includes:
the duty ratio of the first switching tube and the duty ratio of the second switching tube are obtained according to the voltage of the flying capacitor, the voltage of the first voltage division capacitor and the input voltage of the converter, the first switching tube is triggered according to the duty ratio of the first switching tube, and the second switching tube is triggered to act according to the duty ratio of the second switching tube.
Preferably, the method further comprises the following steps:
obtaining a duty ratio regulating quantity according to the voltage of the flying capacitor and the voltage of the second voltage division capacitor;
the duty ratio after the first switching tube is adjusted is the difference between the duty ratio before the adjustment and the duty ratio adjustment amount, and the duty ratio after the second switching tube is adjusted is the sum of the duty ratio before the adjustment and the duty ratio adjustment amount;
the duty ratio adjustment amount is proportional to the absolute value of the difference between the voltage of the flying capacitor and the voltage of the second voltage-dividing capacitor.
Preferably, the duty cycle is proportional to a first voltage, which is a sum of a voltage of the first voltage-dividing capacitor and a voltage of the flying capacitor, and inversely proportional to a second voltage, which is a difference between the second voltage and an input voltage of the converter.
Preferably, the method further comprises the following steps:
when the voltage of the flying capacitor is larger than or equal to the voltage of the second voltage-dividing capacitor, the second switch tube and the first switch tube are controlled to act in a staggered mode.
Therefore, the application has the following beneficial effects:
the converter provided by the application can control the working modes of the first switch tube and the second switch tube of the converter according to the magnitude relation between the voltage of the flying capacitor and the voltage of the second voltage-dividing capacitor, and the flying capacitor is always charged as long as the voltage of the flying capacitor is smaller than the voltage of the second voltage-dividing capacitor, so that the voltage of the flying capacitor is increased until the voltage of the flying capacitor is larger than or equal to the voltage of the second voltage-dividing capacitor. When the voltage of the flying capacitor rises, the voltage of the first voltage-dividing capacitor can be adjusted, so that the voltage of the second voltage-dividing capacitor is indirectly adjusted, the voltages of the first voltage-dividing capacitor and the second voltage-dividing capacitor are balanced, and the safety of the two voltage-dividing capacitors is protected.
Drawings
FIG. 1 is a circuit diagram of a three-level DCDC converter with flying capacitors;
FIG. 2 is a current path diagram of a three-level DCDC converter with flying capacitors;
fig. 3 is a schematic diagram of a three-level DCDC converter with a flying capacitor according to an embodiment of the present disclosure;
fig. 4 is a path diagram corresponding to a first mode provided in the embodiment of the present application;
fig. 5 is a path diagram corresponding to a second mode provided in the embodiment of the present application;
fig. 6 is a path diagram corresponding to a third mode provided in the embodiment of the present application;
FIG. 7 is a graph illustrating timing and parameter variations provided by an embodiment of the present application;
fig. 8 is a schematic diagram of a power supply system according to an embodiment of the present application;
fig. 9 is a flowchart of a control method of a three-level DCDC converter with a flying capacitor according to an embodiment of the present disclosure.
Detailed Description
In order to make those skilled in the art better understand and implement the technical solutions provided by the embodiments of the present application, the circuit topology of the three-level DCDC converter with flying capacitor is described first.
Referring to fig. 1, a circuit diagram of a three-level DCDC converter with flying capacitors is shown.
As can be seen from fig. 1, the three-level DCDC converter with flying capacitor includes: the high-voltage switch comprises an inductor L, a first switch tube S1, a second switch tube S2, a first diode D1, a second diode D2, a flying capacitor Cf, a third diode Dh, a fourth diode Df, a first voltage division capacitor Co1 and a second voltage division capacitor Co2.
For convenience of description, the following embodiments refer to a three-level DCDC converter with a flying capacitor as a converter.
The first end and the second end of the inductor L are respectively connected with the positive input end of the converter and the anode of the first diode D1, and the anode and the cathode of the second diode D2 are respectively connected with the cathode of the first diode D1 and the positive output end of the converter.
The first end and the second end of the second switch tube D2 are respectively connected to the anode of the first diode D1 and the first end of the first switch tube, and the second end of the first switch tube D1 is connected to the negative input terminal of the converter.
Two ends of the flying capacitor Cf are respectively connected with the cathode of the first diode D1 and the second end of the second switch tube S2, the cathode and the anode of the third diode Dh are respectively connected with the cathode of the first diode D1 and the cathode of the fourth diode Df, and the anode of the fourth diode Df is connected with the second end of the second switch tube S2.
Two ends of the first voltage-dividing capacitor Co1 are respectively connected with the positive output end of the converter and the anode of the third diode Dh, and two ends of the second voltage-dividing capacitor Co2 are respectively connected with the anode of the third diode Dh and the negative input end of the converter.
In addition, the converter further comprises an input capacitor Cin, and two ends of the input capacitor Cin are respectively connected with the positive input end and the negative input end of the converter.
The input voltage of the converter is Vin, and the output voltage is Vout, where VL is the positive input terminal of the converter, VH is the positive output terminal of the converter, and Vcom is the common terminal of the negative input terminal and the negative output terminal of the converter.
In order to avoid voltage imbalance between Co1 and Co2 during operation of the converter, the minimum value Vcf (min) of the voltage Vcf of Cf needs to be controlled to be greater than the maximum value Vco2 (max) of the voltage Vco2 of Co2, i.e. Vcf (min) > Vco2 (max).
When the output voltage of the subsequent stage rises rapidly for some reason, namely Vout, vco1, vco2 rise instantaneously, but the voltage Vcf of Cf is controlled by the switching tube and cannot rise rapidly following the output voltage, and the condition of Vcf (min) > Vco2 (max) cannot be satisfied. In this case, D2 is subjected to reverse voltage cut-off, and if the converter continues to operate, the current commutation path is no longer Cin-L-S2-Cf-D2-Co2-Co1. Instead, a new commutation path (Cin-L-S2-Df-Co 1) is created, in which an analysis is made as to whether the boost ratio N of the converter is greater than 2, as shown in fig. 2. Wherein the step-up ratio is the ratio of the output voltage to the input voltage of the converter.
Firstly, if the boosting ratio N is greater than 2, vin is less than Vco2, the inductor L bears a forward voltage drop, the current of the inductor L continuously rises, and meanwhile, the current of the inductor L directly passes through Co2 to form a loop until the current rises to Vin and then oscillates to a steady state. In this case, the voltage imbalance between Co1 and Co2 will be caused, and it is likely that Co1 will be damaged by overvoltage.
Secondly, if the step-up ratio is less than 2, vin > Vco2, the inductor L suffers a reverse voltage drop, the current of the inductor L decreases, meanwhile, the current of the inductor L directly passes through Co2 to form a loop, and the energy on the inductor L is completely transferred to Co2, which also causes the voltage Vco2 at two ends of Co2 to rapidly increase, in this case, the voltage imbalance between Co1 and Co2 will be caused, and even Co1 may be damaged due to overvoltage.
In addition, df is turned on only when Cf is charged before operation, and is turned off during normal operation, and a model with a small current carrying capacity is generally selected during model selection. When S1 alone is turned on, the current path is shown as a dashed line in fig. 2: cin-L-S2-Df-Co1, the input current directly flows through Df, and when the boost ratio is less than 2, the inductor L bears forward voltage drop, the input current iL flowing through Df continuously increases, and if the input current iL is serious, the current carrying capacity of the inductor L may be exceeded, so that the Df is damaged.
In such a case, if the converter stops operating, it may cause protection of the entire system or more serious damage. For example, in a photovoltaic system, the inverter is connected to the rear stage of the converter, and when the inverter enters a high voltage ride through or other conditions, the output voltage may rise instantaneously, but there is a delay in the voltage control of Cf, in which case the converter continues to operate, which may cause a voltage imbalance between Co1 and Co2, further affecting the safe and stable operation of the whole inverter.
Therefore, in order to solve the problem of voltage unbalance between Co1 and Co2 when the output voltage rises, a new control mode is adopted.
In order to make the aforementioned objects, features and advantages of the present application more comprehensible, embodiments accompanying figures and detailed description thereof are described in further detail below.
Referring to fig. 3, the figure is a schematic diagram of a three-level DCDC converter with a flying capacitor according to an embodiment of the present disclosure.
The structure of the converter provided in this embodiment can be referred to the description of fig. 1, and is not described herein again.
In order to equalize the voltages of the two voltage-dividing capacitors, the controller 100 in the converter according to the embodiment of the present application is configured to trigger the second switching tube S1 and the first switching tube S2 to simultaneously operate when the voltage of the flying capacitor Cf is less than the voltage of the second voltage-dividing capacitor Co2, so as to charge the flying capacitor Cf until the voltage of the flying capacitor Cf is greater than or equal to the voltage of the second voltage-dividing capacitor Co2.
The simultaneous triggering action of the first switch tube S1 and the second switch tube S2 means that the actions of the two switch tubes are not staggered, but are simultaneous, for example, when S1 is conducted, S2 is also conducted, that is, the simultaneous conduction is controlled to belong to one of simultaneous triggering; in addition, when the trigger S2 is turned off, the trigger S1 is turned on, which belongs to one of simultaneous triggers; in addition, when the trigger S1 is turned off, the trigger S2 is turned off at the same time, which is also one of simultaneous triggers.
Since the voltage of the flying capacitor Cf is smaller than the voltage of the second voltage-dividing capacitor Co2, the second diode D2 is always turned off in the reverse direction. The flying capacitor Cf and the first voltage division capacitor Co1 can be regarded as loads, and the voltage of the first voltage division capacitor Co1 can be controlled, so that the voltage unbalance of the two voltage division capacitors is restrained. Meanwhile, the voltage Vcf of the flying capacitor Cf is controlled, the Vcf is rapidly increased, and the control mode is not exited until the voltage Vcf (min) > Vco2 (max) is met.
The converter provided by the embodiment of the application can control the working mode of the converter according to the magnitude relation between the voltage of the flying capacitor and the voltage of the second voltage-dividing capacitor, and the flying capacitor is charged all the time as long as the voltage of the flying capacitor is smaller than the voltage of the second voltage-dividing capacitor, so that the voltage of the flying capacitor is increased until the voltage of the flying capacitor is larger than or equal to the voltage of the second voltage-dividing capacitor. When the voltage of the flying capacitor rises, the voltage of the first voltage-dividing capacitor can be adjusted, so that the voltage of the second voltage-dividing capacitor is indirectly adjusted, the voltages of the first voltage-dividing capacitor and the second voltage-dividing capacitor are balanced, and the safety of the two voltage-dividing capacitors is protected.
And the controller is specifically used for obtaining the duty ratio of the first switching tube and the duty ratio of the second switching tube according to the voltage of the flying capacitor, the voltage of the first voltage division capacitor and the input voltage of the converter, triggering the first switching tube according to the duty ratio of the first switching tube, and triggering the second switching tube to act according to the duty ratio of the second switching tube.
The duty ratio is in direct proportion to a first voltage and in inverse proportion to a second voltage, the second voltage is the sum of the voltage of the first voltage-dividing capacitor and the voltage of the flying capacitor, and the first voltage is the difference between the second voltage and the input voltage of the converter.
The initial duty ratio D of the first switching tube and the second switching tube can be obtained by the following formula:
D＝(Vco1+Vcf–Vin)/(Vco1+Vcf)
wherein Vco1 is the voltage of the first voltage-dividing capacitor, vcf is the voltage of the flying capacitor, and Vin is the input voltage of the converter.
As the adjustment progresses, the voltage Vco2 of the second voltage-dividing capacitor rises, and the duty adjustment amount Dcf needs to be calculated in real time in order to control the voltage Vcf of the flying capacitor to reach the new voltage threshold.
The controller is also used for obtaining a duty ratio regulating quantity according to the voltage of the flying capacitor and the voltage of the second voltage division capacitor;
the duty ratio after the first switching tube is adjusted is the difference between the duty ratio before the adjustment and the duty ratio adjustment amount, and the duty ratio after the second switching tube is adjusted is the sum of the duty ratio before the adjustment and the duty ratio adjustment amount.
The duty ratio adjustment amount is proportional to the absolute value of the difference between the voltage of the flying capacitor and the voltage of the second voltage-dividing capacitor. That is, the larger the difference between the voltages of the second voltage-dividing capacitors in the voltage domain of the flying capacitor is, the larger the duty ratio adjustment amount is.
And superposing the duty ratio regulating quantity on the initial duty ratio, wherein the duty ratio regulating quantity is specifically as follows:
finally, the duty ratios of the first switching tube S1 and the second switching tube S2 are respectively:
Ds1＝D-Dcf；
Ds2＝D+Dcf。
wherein, dcf is the duty ratio regulating quantity, ds1 is the duty ratio regulated by the first switching tube, and Ds2 is the duty ratio regulated by the second switching tube.
The operation mode of the converter provided by the embodiment of the present application is specifically described below with reference to the accompanying drawings.
The converter and the controller provided by this embodiment are specifically configured to control the first switching tube and the second switching tube to sequentially operate according to the following three modes:
in the first mode: controlling the first switch tube and the second switch tube to be closed;
in the second mode: controlling the second switch tube to be disconnected and the first switch tube to be closed;
in the third mode: and controlling the first switch tube and the second switch tube to be disconnected.
Referring to fig. 4, this figure is a path diagram corresponding to the first mode provided in the embodiment of the present application.
The first switch tube S1 and the second switch tube S2 are both in a conducting state, the flying capacitor Cf has no charge-discharge loop, and the voltage Vcf at two ends of the flying capacitor Cf is basically unchanged. The input power supply charges for inductance L, and the voltage drop VL at inductance L both ends is input voltage Vin, and inductance's electric current iL rises, promptly:
VL＝Vin＝L*diL/dt。
referring to fig. 5, this figure is a path diagram corresponding to the second mode provided in the embodiment of the present application.
First, the first switching tube S1 is turned on, and the second switching tube S2 is turned off, and first, the boosting ratio N is smaller than 2 times, and the input voltage Vin is greater than the voltage Vcf of the flying capacitor. The voltage VL of the inductor continues to bear the forward voltage, the current iL of the inductor continues to rise, the inductor L continues to store energy, and at the same time, the current flows through the flying capacitor Cf, the flying capacitor Cf charges, and the voltage Vcf of the flying capacitor rises.
If the boosting ratio N is greater than 2, the input voltage Vin is less than the voltage Vcf of the flying capacitor. The voltage VL of the inductor L continues to bear the reverse voltage, the current iL of the inductor will start to drop, but still flow through the flying capacitor Cf, the energy on the inductor L is transferred to the flying capacitor Cf, and the voltage Vcf of the flying capacitor rises.
VL＝Vin–Vcf＝L*diL/dt；
iL/Cf＝dVcf/dt。
Referring to fig. 6, this figure is a path diagram corresponding to the third mode provided in the embodiment of the present application.
The first switch tube S1 and the second switch tube S2 are both turned off, the inductor L bears a reverse voltage drop, the inductor current iL decreases, and at the same time, the current charges the capacitor through the flying capacitor Cf and the first voltage dividing capacitor Co1, the energy on the inductor L is transferred to the capacitor, the current flowing through the inductor L and the diode Df decreases, and the voltage Vcf of the flying capacitor Cf and the voltage Vco1 of the first voltage dividing capacitor Co1 increase.
VL＝Vin–Vcf–Vco1＝L*diL/dt；
iL＝Cf*dVcf/dt＝Co1*dVco1/dt。
The first mode can charge the inductor L, the flying capacitor Cf has no charge-discharge loop, the voltage Vcf of the flying capacitor Cf is basically unchanged, and the voltage Vcf of the first voltage division capacitor Co1 connected with the load is reduced. In the second mode, flying capacitor Cf charges alone to control its voltage Vcf across to rise rapidly. In the third mode, the inductor L charges the flying capacitor Cf and the first voltage-dividing capacitor Co1 at the same time, and the charging currents are the same.
From the formula iL = Cf × dVcf/dt = Co1 × dVco1/dt, the amplitude of the rise of Vcf and Vco1 is mainly related to the capacitance values of Cf and Co1. In a general application scenario, the capacitance value of Cf is much smaller than that of Co1, so the rising amplitude of Vcf is much larger than that of Vco1, on one hand, vcf is rapidly raised, the rise of Vco1 is suppressed, and on the other hand, the current flowing through diode Df is reduced.
Referring to fig. 7, a graph of timing and parameter variation provided by the embodiments of the present application is shown.
As can be seen from fig. 7, the voltage Vcf across the flying capacitor is rising all the time.
The inductor current iL decreases in the third mode and the second mode and increases in the first mode.
Moreover, the curves of iL are different for the cases where the boost ratio N of the converter is greater than 2 and less than 2.
The voltage of the flying capacitor can be rapidly increased while the voltage unbalance of the two voltage division capacitors is restrained.
The converter provided by the embodiment of the application has no mode that the second switching tube S2 is independently conducted, that is, no current path (Cin-L-S2-Df-Co 1) exists, that is, under the condition that Vcf (min) < Vco2 (max), on one hand, the voltage unbalance between the first voltage-dividing capacitor Co1 and the second voltage-dividing capacitor Co2 is suppressed, and on the other hand, the flying capacitor can be rapidly charged, and on the other hand, the situation that the current flowing through the diode Df continuously rises to cause the diode Df to be damaged due to overcurrent is avoided. After the flying capacitor is charged or the output voltage of the rear stage is reduced and meets the condition of Vcf (min) > Vco2 (max), the control mode provided by the embodiment of the application is exited.
In the converter provided by the embodiment of the application, the controller is further configured to control the second switching tube and the first switching tube to operate in a staggered manner when the voltage of the flying capacitor is greater than or equal to the voltage of the second voltage-dividing capacitor.
Based on the three-level DCDC converter with the flying capacitor provided in the above embodiments, the embodiments of the present application further provide a power supply system, which is described in detail below with reference to the accompanying drawings.
Referring to fig. 8, the figure is a schematic diagram of a power supply system according to an embodiment of the present application.
The power supply system provided by the embodiment comprises: an inverter 801 and at least one of the three-level DCDC converters 802 with flying capacitors described in the above embodiments;
the output terminal of the three-level DCDC converter 802 with the flying capacitor is connected to the input terminal of the inverter 801.
The embodiment of the present application does not specifically limit the dc power source connected to the input terminal of the three-level DCDC converter 802 with a flying capacitor, and the dc power source may be, for example, a photovoltaic string or a battery.
The power supply system provided by the embodiment of the application can balance the voltages of the two voltage division capacitors especially when the output voltage of the three-level DCDC converter 802 with the flying capacitor is increased due to the voltage increase of the inverter side, so that the safety of the voltage division capacitors and the diodes is protected, and the power supply system cannot be turned off.
Based on the three-level DCDC converter with the flying capacitor and the power supply system provided by the above embodiments, the embodiments of the present application further provide a control method of the three-level DCDC converter with the flying capacitor, which is described in detail below with reference to the accompanying drawings.
Referring to fig. 9, the figure is a flowchart of a control method of a three-level DCDC converter with a flying capacitor according to an embodiment of the present application.
In the method for controlling a three-level DCDC converter with a flying capacitor according to this embodiment, the converter includes: the high-voltage power supply comprises an inductor, a first switch tube, a second switch tube, a first diode, a second diode, a flying capacitor, a third diode, a fourth diode, a first voltage-dividing capacitor and a second voltage-dividing capacitor;
the method comprises the following steps:
s901: obtaining the voltage of the flying capacitor and the voltage of the second voltage-dividing capacitor;
s902: when the voltage of the flying capacitor is smaller than that of the second voltage-dividing capacitor, the second switch tube and the first switch tube are triggered to act simultaneously to charge the flying capacitor until the voltage of the flying capacitor is larger than or equal to that of the second voltage-dividing capacitor.
According to the control method, the working modes of the first switching tube and the second switching tube of the converter can be controlled according to the magnitude relation between the voltage of the flying capacitor and the voltage of the second voltage-dividing capacitor, and the flying capacitor is charged all the time as long as the voltage of the flying capacitor is smaller than the voltage of the second voltage-dividing capacitor, so that the voltage of the flying capacitor is increased until the voltage of the flying capacitor is larger than or equal to the voltage of the second voltage-dividing capacitor. When the voltage of the flying capacitor rises, the voltage of the first voltage-dividing capacitor can be adjusted, so that the voltage of the second voltage-dividing capacitor is indirectly adjusted, the voltages of the first voltage-dividing capacitor and the second voltage-dividing capacitor are balanced, and the safety of the two voltage-dividing capacitors is protected.
Trigger second switch tube and first switch tube simultaneous action, specifically include:
the first switching tube and the second switching tube are controlled to work in the following three modes in sequence:
in a first mode: controlling the first switch tube and the second switch tube to be closed;
in a second mode: controlling the second switch tube to be disconnected and the first switch tube to be closed;
in the third mode: and controlling the first switching tube and the second switching tube to be disconnected.
Trigger second switch tube and first switch tube simultaneous action, specifically include:
the duty ratio of the first switching tube and the duty ratio of the second switching tube are obtained according to the voltage of the flying capacitor, the voltage of the first voltage division capacitor and the input voltage of the converter, the first switching tube is triggered according to the duty ratio of the first switching tube, and the second switching tube is triggered to act according to the duty ratio of the second switching tube.
The control method provided by this embodiment further includes:
obtaining a duty ratio regulating quantity according to the voltage of the flying capacitor and the voltage of the second voltage division capacitor;
the duty ratio after the first switching tube is adjusted is the difference between the duty ratio before the adjustment and the duty ratio adjustment amount, and the duty ratio after the second switching tube is adjusted is the sum of the duty ratio before the adjustment and the duty ratio adjustment amount;
the duty ratio adjustment amount is proportional to the absolute value of the difference between the voltage of the flying capacitor and the voltage of the second voltage-dividing capacitor.
The duty ratio is proportional to a first voltage and inversely proportional to a second voltage, the second voltage is the sum of the voltage of the first voltage-dividing capacitor and the voltage of the flying capacitor, and the first voltage is the difference between the second voltage and the input voltage of the converter.
The control method provided by this embodiment further includes:
when the voltage of the flying capacitor is larger than or equal to the voltage of the second voltage-dividing capacitor, the second switch tube and the first switch tube are controlled to act in a staggered mode.
It should be noted that, in the present specification, each embodiment is described in a progressive manner, and each embodiment focuses on differences from other embodiments, and the same and similar parts among the embodiments may be referred to each other. For the system or the device disclosed by the embodiment, the description is simple because the system or the device corresponds to the method disclosed by the embodiment, and the relevant points can be referred to the method part for description.
The previous description of the disclosed embodiments is provided to enable any person skilled in the art to make or use the present application. Various modifications to these embodiments will be readily apparent to those skilled in the art, and the generic principles defined herein may be applied to other embodiments without departing from the spirit or scope of the application. Thus, the present application is not intended to be limited to the embodiments shown herein but is to be accorded the widest scope consistent with the principles and novel features disclosed herein.
Claims (14)
1. A three-level DCDC converter with a flying capacitor is characterized by comprising: the high-power-consumption flying capacitor comprises an inductor, a first switch tube, a second switch tube, a first diode, a second diode, a flying capacitor, a third diode, a fourth diode, a first voltage-dividing capacitor, a second voltage-dividing capacitor and a controller;
the first end and the second end of the inductor are respectively connected with the positive input end of the converter and the anode of the first diode, and the anode and the cathode of the second diode are respectively connected with the cathode of the first diode and the positive output end of the converter;
a first end and a second end of the second switch tube are respectively connected with an anode of the first diode and a first end of the first switch tube, and a second end of the first switch tube is connected with a negative input end of the converter;
two ends of the flying capacitor are respectively connected with the cathode of the first diode and the second end of the second switching tube, the cathode and the anode of the third diode are respectively connected with the cathode of the first diode and the cathode of the fourth diode, and the anode of the fourth diode is connected with the second end of the second switching tube;
two ends of the first voltage-dividing capacitor are respectively connected with the positive output end of the converter and the anode of the third diode, and two ends of the second voltage-dividing capacitor are respectively connected with the anode of the third diode and the negative input end of the converter;
the controller is configured to trigger the second switch tube and the first switch tube to simultaneously operate when the voltage of the flying capacitor is less than the voltage of the second voltage-dividing capacitor, so as to charge the flying capacitor until the voltage of the flying capacitor is greater than or equal to the voltage of the second voltage-dividing capacitor.
2. The converter according to claim 1, wherein the controller is specifically configured to control the first switching tube and the second switching tube to sequentially operate according to the following three modes:
in a first mode: controlling the first switch tube and the second switch tube to be closed;
in a second mode: controlling the second switch tube to be switched off, and controlling the first switch tube to be switched on;
in a third mode: and controlling the first switch tube and the second switch tube to be disconnected.
3. The converter according to claim 1 or 2, wherein the controller is specifically configured to obtain a duty cycle of the first switching tube and a duty cycle of the second switching tube according to the voltage of the flying capacitor, the voltage of the first voltage-dividing capacitor, and the input voltage of the converter, trigger the first switching tube according to the duty cycle of the first switching tube, and trigger the second switching tube to operate according to the duty cycle of the second switching tube.
4. The converter of claim 3, wherein the controller is further configured to obtain a duty cycle adjustment amount from the voltage of the flying capacitor and the voltage of the second divider capacitor;
the duty ratio after the first switch tube is adjusted is the difference between the duty ratio before adjustment and the duty ratio adjustment amount, and the duty ratio after the second switch tube is adjusted is the sum of the duty ratio before adjustment and the duty ratio adjustment amount.
5. A converter as claimed in claim 3 or 4 wherein said duty cycle adjustment is proportional to the absolute value of the difference between the voltage of said flying capacitor and the voltage of said second divider capacitor.
6. The converter of claim 4 or 5, wherein the duty cycle is proportional to a first voltage and inversely proportional to a second voltage, the second voltage being a sum of a voltage of the first voltage-dividing capacitor and a voltage of the flying capacitor, and the first voltage being a difference between the second voltage and an input voltage of the converter.
7. The converter according to any one of claims 1-6, wherein the controller is further configured to stagger the operations of the second switch tube and the first switch tube when the voltage of the flying capacitor is greater than or equal to the voltage of the second voltage-dividing capacitor.
8. A power supply system, comprising: an inverter and at least one three-level DCDC converter with flying capacitor of any one of claims 1-7;
and the output end of the three-level DCDC converter with the flying capacitor is connected with the input end of the inverter.
9. A method of controlling a three-level DCDC converter with a flying capacitor, the converter comprising: the high-voltage power supply comprises an inductor, a first switch tube, a second switch tube, a first diode, a second diode, a flying capacitor, a third diode, a fourth diode, a first voltage-dividing capacitor and a second voltage-dividing capacitor;
the method comprises the following steps:
obtaining the voltage of the flying capacitor and the voltage of the second voltage-dividing capacitor;
when the voltage of the flying capacitor is smaller than the voltage of the second voltage-dividing capacitor, the second switch tube and the first switch tube are triggered to act simultaneously to charge the flying capacitor until the voltage of the flying capacitor is larger than or equal to the voltage of the second voltage-dividing capacitor.
10. The control method according to claim 9, wherein the triggering the second switching tube and the first switching tube to simultaneously operate specifically includes:
controlling the first switching tube and the second switching tube to work in the following three modes in sequence:
in a first mode: controlling the first switch tube and the second switch tube to be closed;
in a second mode: the second switch tube is controlled to be opened, and the first switch tube is controlled to be closed;
in the third mode: and controlling the first switch tube and the second switch tube to be disconnected.
11. The control method according to claim 9, wherein the triggering the second switching tube and the first switching tube to act simultaneously specifically includes:
and acquiring the duty ratio of the first switching tube and the duty ratio of the second switching tube according to the voltage of the flying capacitor, the voltage of the first voltage division capacitor and the input voltage of the converter, triggering the first switching tube according to the duty ratio of the first switching tube, and triggering the second switching tube to act according to the duty ratio of the second switching tube.
12. The control method according to claim 9, characterized by further comprising:
obtaining a duty ratio regulating quantity according to the voltage of the flying capacitor and the voltage of the second voltage division capacitor;
the duty ratio after the first switching tube is adjusted is the difference between the duty ratio before the adjustment and the duty ratio adjustment amount, and the duty ratio after the second switching tube is adjusted is the sum of the duty ratio before the adjustment and the duty ratio adjustment amount;
the duty ratio adjustment amount is proportional to an absolute value of a difference between the voltage of the flying capacitor and the voltage of the second voltage-dividing capacitor.
13. The control method according to claim 11 or 12, wherein the duty ratio is proportional to a first voltage that is a sum of a voltage of the first voltage-dividing capacitor and a voltage of the flying capacitor, and is inversely proportional to a second voltage that is a difference between the second voltage and an input voltage of the converter.
14. The control method according to any one of claims 9 to 12, characterized by further comprising:
and when the voltage of the flying capacitor is greater than or equal to the voltage of the second voltage division capacitor, the second switch tube and the first switch tube are controlled to act in a staggered mode.
Priority Applications (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CN202211165805.2A CN115514219A (en) | 2022-09-23 | 2022-09-23 | Three-level DCDC converter with flying capacitor, system and control method |
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| Application Number | Priority Date | Filing Date | Title |
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| CN202211165805.2A CN115514219A (en) | 2022-09-23 | 2022-09-23 | Three-level DCDC converter with flying capacitor, system and control method |
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Cited By (2)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN116247917A (en) * | 2023-05-10 | 2023-06-09 | 深圳市首航新能源股份有限公司 | Flying capacitor three-level Boost balance circuit and control method |
| CN116683744A (en) * | 2023-08-03 | 2023-09-01 | 深圳市首航新能源股份有限公司 | Control method and equipment thereof |
-
2022
- 2022-09-23 CN CN202211165805.2A patent/CN115514219A/en active Pending
Cited By (4)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN116247917A (en) * | 2023-05-10 | 2023-06-09 | 深圳市首航新能源股份有限公司 | Flying capacitor three-level Boost balance circuit and control method |
| CN116247917B (en) * | 2023-05-10 | 2023-08-29 | 深圳市首航新能源股份有限公司 | Flying capacitor three-level Boost balance circuit and control method |
| CN116683744A (en) * | 2023-08-03 | 2023-09-01 | 深圳市首航新能源股份有限公司 | Control method and equipment thereof |
| CN116683744B (en) * | 2023-08-03 | 2024-02-06 | 深圳市首航新能源股份有限公司 | Control method and equipment thereof |
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