CN115118168A - Buck type alternating current conversion device and control method - Google Patents
Buck type alternating current conversion device and control method Download PDFInfo
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- CN115118168A CN115118168A CN202210860720.XA CN202210860720A CN115118168A CN 115118168 A CN115118168 A CN 115118168A CN 202210860720 A CN202210860720 A CN 202210860720A CN 115118168 A CN115118168 A CN 115118168A
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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
- H02M5/00—Conversion of ac power input into ac power output, e.g. for change of voltage, for change of frequency, for change of number of phases
- H02M5/02—Conversion of ac power input into ac power output, e.g. for change of voltage, for change of frequency, for change of number of phases without intermediate conversion into dc
- H02M5/04—Conversion of ac power input into ac power output, e.g. for change of voltage, for change of frequency, for change of number of phases without intermediate conversion into dc by static converters
- H02M5/22—Conversion of ac power input into ac power output, e.g. for change of voltage, for change of frequency, for change of number of phases without intermediate conversion into dc by static converters using discharge tubes with control electrode or semiconductor devices with control electrode
- H02M5/275—Conversion of ac power input into ac power output, e.g. for change of voltage, for change of frequency, for change of number of phases without intermediate conversion into dc 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
- H02M5/293—Conversion of ac power input into ac power output, e.g. for change of voltage, for change of frequency, for change of number of phases without intermediate conversion into dc 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 using semiconductor devices only
- H02M5/2932—Conversion of ac power input into ac power output, e.g. for change of voltage, for change of frequency, for change of number of phases without intermediate conversion into dc 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 using semiconductor devices only with automatic control of output voltage, current or power
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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
- Y02B—CLIMATE CHANGE MITIGATION TECHNOLOGIES RELATED TO BUILDINGS, e.g. HOUSING, HOUSE APPLIANCES OR RELATED END-USER APPLICATIONS
- Y02B70/00—Technologies for an efficient end-user side electric power management and consumption
- Y02B70/10—Technologies improving the efficiency by using switched-mode power supplies [SMPS], i.e. efficient power electronics conversion e.g. power factor correction or reduction of losses in power supplies or efficient standby modes
Abstract
The invention provides a Buck type alternating current conversion device and a control method, wherein the device comprises an alternating current power supply module and 4 alternating current switching tubes; the alternating current power supply module is sequentially connected with 4 alternating current switching tubes in series; a flying capacitor is connected between the output end of the first alternating current switching tube and the output end of the third alternating current switching tube; the output end of the second alternating current switching tube is connected to the output end of the fourth alternating current switching tube through a load; when power is supplied, the first alternating current switch tube and the fourth alternating current switch tube are conducted complementarily; the second alternating current switch tube and the third alternating current switch tube are conducted in a complementary mode. The invention further provides a control method of the Buck type three-level alternating current conversion device based on the Buck type three-level alternating current conversion device, the phase difference of control signals of the first alternating current switching tube and the second alternating current switching tube is 180 degrees, and the control method can be used for reducing the voltage stress of the switching tubes by half and greatly reducing the weight and the volume of a filter by increasing the number of the switching tubes and introducing flying capacitors to construct an intermediate level.
Description
Technical Field
The invention belongs to the technical field of multilevel conversion, and particularly relates to a Buck type alternating current conversion device and a control method.
Background
The multilevel conversion can reduce the voltage stress of the switching tube, so that the switching tube can bear higher voltage, the output result has better waveform quality, and the multilevel conversion is a research hotspot of high-power electronics at the present stage. The existing power electronic device technology level can not realize the conversion of high power and high frequency, and only a better method is sought to achieve the goal starting from the power topology. The multilevel conversion technology realizes high-voltage and high-power output by improving the circuit topology of the multilevel conversion technology, a step-up and step-down transformer and a voltage-sharing circuit are not needed, and the harmonic wave of the output voltage is small and the voltage stress born by a switch tube is low due to the increase of the level number of the output voltage.
The AC/AC converter is used for converting one form of alternating current into another form of alternating current, wherein the main functions for voltage reduction conversion are as follows: the power frequency transformer has large volume and weight, is not suitable for the requirement of miniaturization of electronic products, and has unstable voltage and lower conversion efficiency. The power input and output of the phase-controlled ac voltage regulator circuit include significant harmonic components and are generally only suitable for power regulation of thermal or mechanical inertial loads. The AC-DC-AC converter has too many conversion times, high energy loss ratio, low economical efficiency and conversion efficiency and serious harmonic pollution to a power grid. Electronic transformer, although its volume weight is little, its quantity of switchgear is very much, results in the reliability ratio low, and also does not have steady voltage and voltage regulation function. A high frequency AC/AC converter which can realize electric isolation, but the topology and control circuit are complex, the number of switch devices is very large, and the reliability is not high. Matrix converters, which have high requirements for operating environment and numerous switching devices, also face complicated control strategies.
Disclosure of Invention
In order to solve the technical problems, the invention provides a Buck type alternating current conversion device and a control method, wherein an intermediate level is constructed by increasing the number of switching tubes and introducing flying capacitors, so that the voltage stress of the switching tubes can be reduced by half, the weight and the volume of a filter are greatly reduced, and the Buck type alternating current conversion device can be used in high-voltage output occasions.
In order to achieve the purpose, the invention adopts the following technical scheme:
a Buck type alternating current conversion device comprises an alternating current power supply module and 4 alternating current switching tubes; the alternating current power supply module is sequentially connected with 4 alternating current switching tubes in series; a flying capacitor is connected between the output end of the first alternating current switching tube and the output end of the third alternating current switching tube; the output end of the second alternating current switching tube is connected to the output end of the fourth alternating current switching tube through a load;
in the process of supplying power by the alternating current power supply module, the first alternating current switching tube and the fourth alternating current switching tube are conducted complementarily; the second alternating current switch tube and the third alternating current switch tube are conducted in a complementary mode.
Furthermore, the control signals of the first alternating current switching tube and the second alternating current switching tube have a phase difference of 180 degrees; the control signals of the third alternating current switching tube and the fourth alternating current switching tube have a 180-degree difference.
Further, the transformation system further comprises a filter circuit; and the output end of the second alternating current switching tube is connected to the output of the fourth alternating current switching tube through a filter circuit.
Further, the filter circuit adopts an LC filter circuit.
Further, the 4 alternating current switching tubes have the same structure; each alternating current off switch consists of two MOS tubes with opposite polarities, and a parasitic diode is arranged in each MOS tube.
The invention also provides a control method of the Buck type three-level alternating current conversion device, which is realized based on the Buck type alternating current conversion device and comprises the following steps:
calculating a first error signal between an output voltage reference value and a sampling value of the Buck type alternating current conversion device;
calculating a second error signal between the voltage reference value of the flying capacitor and the sampling value of the flying capacitor;
carrying out carrier modulation on the first error signal and the second error signal; and acquiring an input voltage sampling signal of the alternating current power supply module, performing logic adjustment on the input voltage sampling signal and a signal subjected to carrier modulation, and controlling the corresponding MOS (metal oxide semiconductor) tube in the alternating current switching tube to work by changing the polarity of the input voltage sampling signal.
Further, the process of calculating the first error signal between the output voltage reference value and the sampling value of the Buck ac conversion device is as follows:
obtaining output voltage reference value U of Buck type three-level alternating current conversion device 0_ref Sampling value U of Buck type AC conversion device 0_f After comparison by the comparator, a first error signal U is obtained through an output voltage PI regulator 0_e 。
Further, the process of calculating the second error signal between the voltage reference value of the flying capacitor and the sampling value of the flying capacitor is as follows:
acquiring voltage reference value U of flying capacitor c_ref Sampling value U of sum flying capacitor c_f After comparison by the comparator, a second error signal U is obtained through an output voltage PI regulator c_e 。
Further, the process of performing carrier modulation on the first error signal and the second error signal is as follows:
the first error signal U 0_e And a second error signal U c_e Are respectively multiplied by weight K 1 And K 2 And then adding to obtain a third error signal U e1 Via a carrier signal U c-1 After modulation, PWM control signal U of first AC switch tube is obtained p2 ；
The first error signal U 0_e And a second error signal U c_e Are respectively multiplied by weight K 1 And K 2 And then subtracting to obtain a fourth error signal U e2 Via a carrier signal U c-2 After modulation, PWM control signal U of second AC switch tube is obtained p3 。
Further, the process of controlling the operation of the corresponding MOS transistor in the ac switching transistor by changing the polarity of the input voltage sampling signal includes:
input voltage sampling signal U i_f Output U after passing through zero comparator p1 When the alternating current of the alternating current power supply module is in a positive half period, U p1 Is positive and is changed into U through NOT gate N1 Is negative, the U N1 And U p2 、U p3 After common logic modulation, K in 4 AC switching tubes 1b ～K 4b Go high; k 1a ～K 4a Keeping the same; wherein K 1b ～K 4b Each of the 4 alternating current switching tubes has the same polarity; k 1a ～K 4a The other of the 4 alternating current switching tubes is respectively, and the polarities are the same; the group b of switching tubes are constantly switched on, and the group a of switching tubes realize high-frequency chopping;
when the alternating current of the alternating current power supply module is in a negative half period, U p1 Is negative and becomes U through NOT gate N1 Is positive, the U is N1 And U p2 、U p3 After common logic modulation, K in 4 AC switching tubes 1a ～K 4a Changing to a high level; k 1b ～K 4b Keeping the same; namely, the switch tubes in the group a are constantly on, and the switch tubes in the group b realize high-frequency chopping.
The effect provided in the summary of the invention is only the effect of the embodiment, not all the effects of the invention, and one of the above technical solutions has the following advantages or beneficial effects:
the invention provides a Buck type alternating current conversion device and a control method, wherein the device comprises an alternating current power supply module and 4 alternating current switching tubes; the alternating current power supply module is sequentially connected with 4 alternating current switching tubes in series; a flying capacitor is connected between the output end of the first alternating current switching tube and the output end of the third alternating current switching tube; the output end of the second alternating current switching tube is connected to the output end of the fourth alternating current switching tube through a load; in the process of supplying power by the alternating current power supply module, the first alternating current switching tube and the fourth alternating current switching tube are conducted complementarily; the second alternating current switch tube and the third alternating current switch tube are conducted in a complementary mode. The control signals of the first alternating current switching tube and the second alternating current switching tube have a 180-degree difference; the control signals of the third alternating current switching tube and the fourth alternating current switching tube have a 180-degree difference. Based on a Buck type alternating current conversion device, a control method of the Buck type three-level alternating current conversion device is also provided, and the method comprises the following steps: calculating a first error signal between an output voltage reference value and a sampling value of the Buck type alternating current conversion device; calculating a second error signal between the voltage reference value of the flying capacitor and the sampling value of the flying capacitor; carrying out carrier modulation on the first error signal and the second error signal; and acquiring an input voltage sampling signal of the alternating current power supply module, performing logic adjustment on the input voltage sampling signal and a signal subjected to carrier modulation, and controlling the corresponding MOS (metal oxide semiconductor) tube in the alternating current switching tube to work by changing the polarity of the input voltage sampling signal. The invention constructs the middle level by increasing the number of the switching tubes and introducing the flying capacitor, can reduce the voltage stress of the switching tubes by half, greatly reduces the weight and the volume of the filter, and can be used in high-voltage output occasions.
Drawings
Fig. 1 is a schematic circuit connection diagram of a Buck-type ac conversion device according to embodiment 1 of the present invention;
fig. 2 shows an operating state of a Buck-type ac conversion device according to embodiment 1 of the present invention during one input voltage cycle;
fig. 3 shows waveforms of a Buck-type ac conversion device D <0.5 according to embodiment 1 of the present invention;
fig. 4 is a schematic diagram of an operation mode of a Buck-type ac conversion device D <0.5 according to embodiment 1 of the present invention;
FIG. 5 shows waveforms of a Buck-type AC converting apparatus provided in embodiment 1 of the present invention when D is greater than or equal to 0.5;
FIG. 6 is a schematic diagram of an operating mode of a Buck-type AC converter device D ≧ 0.5 according to embodiment 1 of the present invention;
fig. 7 is a schematic diagram of a control method of a Buck-type three-level ac conversion device according to embodiment 2 of the present invention;
fig. 8 shows a flying capacitor charging/discharging circuit of a three-level Buck AC/AC converter in embodiment 2 of the present invention;
fig. 9 is a schematic diagram of duty cycle of flying capacitor voltage closed loop correction switching tube in embodiment 2 of the present invention;
fig. 10 is a simulation waveform of embodiment 2 of the present invention when the effective value of the output voltage is equal to 90V and the duty ratio D is less than 0.5;
FIG. 11 shows simulation waveforms when the output voltage is 130V and the duty ratio D is greater than or equal to 0.5 in embodiment 2 of the present invention.
Detailed Description
In order to clearly explain the technical features of the present invention, the following detailed description of the present invention is provided with reference to the accompanying drawings. The following disclosure provides many different embodiments, or examples, for implementing different features of the invention. To simplify the disclosure of the present invention, the components and arrangements of specific examples are described below. Furthermore, the present invention may repeat reference numerals and/or letters in the various examples. This repetition is for the purpose of simplicity and clarity and does not in itself dictate a relationship between the various embodiments and/or configurations discussed. It should be noted that the components illustrated in the figures are not necessarily drawn to scale. Descriptions of well-known components and processing techniques and procedures are omitted so as to not unnecessarily limit the invention.
Example 1
The invention also provides a Buck type alternating current conversion device, which comprises an alternating current power supply module and 4 alternating current switching tubes, wherein the alternating current power supply module is connected with the 4 alternating current switching tubes; the alternating current power supply module is sequentially connected with 4 alternating current switching tubes in series; a flying capacitor is connected between the output end of the first alternating current switching tube and the output end of the third alternating current switching tube; the output end of the second alternating current switching tube is connected to the output end of the fourth alternating current switching tube through a load; in the process of supplying power by the alternating current power supply module, the first alternating current switching tube and the fourth alternating current switching tube are conducted complementarily; the second alternating current switch tube and the third alternating current switch tube are conducted in a complementary mode.
The control signals of the first alternating current switching tube and the second alternating current switching tube have a 180-degree difference; the control signals of the third alternating current switching tube and the fourth alternating current switching tube have a 180-degree difference.
Fig. 1 is a schematic circuit connection diagram of a Buck-type ac conversion device according to embodiment 1 of the present invention; AC power supply module u i Four AC switch tubes S 1 、S 2 、S 3 And S 4 Each alternating current switch tube is respectively formed by connecting an a tube and a b tube in series, and the flying capacitor C fly Output filter inductance L f Output filter capacitorC f And a resistance R 0 And (4) forming. S1 and S4 are in complementary conduction, S2 and S3 are in complementary conduction, and control signals of S1 and S2 are different in phase angle of 180 degrees; the control signals of S3 and S4 differ by a phase angle of 180 deg..
Fig. 2 shows an operating state of a Buck-type ac conversion device according to embodiment 1 of the present invention during one input voltage cycle;
within a range of input voltages, the polarity differs according to the input voltage and the inductor current [9 ]]There are several different converter states, which are: u. of i >0，i Lf <0、u i >0，i Lf >0、u i <0，i Lf >0 and u i <0，i Lf <0。
When the load is resistive, only u i >0，i Lf >0 or u i <0，i Lf <0, the four cases mentioned above occur when the load is a capacitive or inductive load.
If: assume that the load is resistive and the circuit transitions to B (u) i >0，i Lf >0) A stage; the switch tube, the diode, the inductor and the capacitor are ideal components, and the internal resistance of the power supply is zero; flying capacitor C fly Voltage u across Cy Constant equal to u i /2。
When duty ratio D<0.5, since we assume the circuit transition is at B (u) i >0，i Lf >0) Stage, so in this stage, the switch tubes of the group a are chopped at high frequency (S) 1a 、S 2a 、S 3a 、S 4a ) B group of switch tubes are constantly on (S) 1b 、 S 2b 、S 3b 、S 4b ). Fig. 3 shows a Buck-type ac conversion device D according to embodiment 1 of the present invention<A waveform at 0.5;
four operation modes exist in one operation period Ts, as shown in fig. 4, which is a schematic view of an operation mode when D <0.5 of a Buck-type ac conversion device according to embodiment 1 of the present invention;
in the working mode 1[ t ] 0 ,t 1 ]At t, at 0 At any moment, switch tube S 1a And a switching tube S 3a Open, open switchPipe S 2a And a switching tube S 4a And (6) turning off. At power source u i To the inductor L f Charging with a current i Lf And linearly increases. At this time A, E the voltage drop between the two points is u AE ＝u i -u Cy ＝u i /2. Added to the switching tube S 2a And a switching tube S 4a A voltage of u across i /2. Wherein i Lf The amount of increase during this period is
In the operating mode 2[ t ] 1 ,t 2 ]At t, at 1 At any moment, switch tube S 3a And a switching tube S 4a Open and close the tube S 1a And a switching tube S 2a And (6) turning off. At this time, the inductance L f Releasing the previously stored energy, corresponding to the current i Lf The linearity decreases. The flying capacitor voltage remains constant as u i /2. A. The voltage at point E is 0. Added to the switching tube S 1a And a switching tube S 2a A voltage of u across i /2. Wherein i Lf The reduction during this period is:
in the operating mode 3[ t ] 2 ,t 3 ]At t, at 2 At any moment, switch tube S 1a And a switching tube S 3a Turn-off, switch tube S 2a And a switching tube S 4a And (4) opening. The working principle is similar to that of the working mode 1, except that the power supply acts as a flying capacitor. The flying capacitor discharges and its voltage drops, at which point the voltage drop at A, E is u AE ＝u Cy ＝u i /2. Added to the switching tube S 1a And a switching tube S 3a A voltage of u across i /2。
In the operating mode 4[ t ] 3 ,t 4 ]At t 1 At any moment, switch tube S 3a And a switching tube S 4a Turn-off, switch tube S 1a And a switching tube S 2a And (4) opening. Its mode of operation is the same as mode 3 and will not be described in detail here.
When the duty ratio D is greater than or equal to 0.5, as shown in fig. 5, the waveform of the Buck-type ac conversion device D provided in embodiment 1 of the present invention is greater than or equal to 0.5; the circuit topology also has four operating modes within one switching cycle. FIG. 6 is a schematic diagram of an operating mode of a Buck-type AC converter device D ≧ 0.5 according to embodiment 1 of the present invention;
in the working mode 1[ t ] 0 ,t 1 ]At t, at 0 At any moment, switch tube S 1a And a switching tube S 2a Open and close the tube S 3a And a switching tube S 4a And (6) turning off. At power source u i To the inductor L f Charging with a current i Lf And linearly increases. The flying capacitor maintains the voltage value of the previous operating mode, at which time the voltage drop between the two points A, E is u AB ＝u i . Added to the switching tube S 3a And a switching tube S 4a A voltage of u across i /2. Wherein i Lf The amount of increase during this period is
In the operating mode 2[ t ] 1 ,t 2 ]At t, at 1 At any moment, switch tube S 3a And a switching tube S 1a Open and close the tube S 4a And a switching tube S 2a And (6) turning off. At this time, the inductor f releases the energy stored previously, and the corresponding current i Lf The linearity decreases. The flying capacitor is in a charging state, and the final voltage is u i /2. A. The voltage of the two points B is U AB ＝U i -U Cy ＝U i /2. Added to the switching tube S 2a And a switching tube S 4a A voltage of u across i /2. Wherein i Lf The reduction during this period is:
in the operating mode 3[ t ] 2 ,t 3 ]In the working mode, the switching condition of the switching tube is the same as that of the working mode 1, so that the working process is the same as that of the working mode 1.
In the operating mode 4[ t ] 3 ,t 4 ]At t 3 At any moment, switch tube S 3a And a switching tube S 1a Turn-off, switch tube S 4a And a switching tube S 2a And (4) opening. The operation is similar to mode 2. But with the difference that in this case the flying capacitor acts as the power supply, u Cy And (4) descending. A. The voltage at two points B is u AB ＝u Cy ＝u i /2。
In steady state operation of the converter, i is in one cycle Lf The amount of increase and decrease are equal, which otherwise causes the difference between the amount of release and the amount of absorption, resulting in malfunction.
When the duty ratio D is more than or equal to 0.5, the duty ratio is larger than or equal to Δ i Lf Are equal; therefore:
finishing to obtain: u shape o ＝DU i
Therefore, the relation between the input and the output of the three-level Buck type AC/AC converter is not different from that between the two levels, namely u o ＝Du i . And because the flying capacitor is introduced into the three-level converter, the intermediate level is constructed, and the voltage stress of the switching tube is reduced by half.
In the Buck-type ac conversion device provided in embodiment 1 of the present invention, the intermediate level is constructed by increasing the number of switching tubes and introducing flying capacitors, so that the voltage stress of the switching tubes can be reduced by half, the weight and volume of the filter can be greatly reduced, and the Buck-type ac conversion device can be used in high-voltage output occasions.
Example 2:
based on the Buck-type ac conversion device provided in embodiment 1 of the present invention, embodiment 2 of the present invention further provides a control method for the Buck-type ac conversion device, and as shown in fig. 7, a schematic diagram of the control method for the Buck-type three-level ac conversion device provided in embodiment 2 of the present invention is provided, and the specific process includes:
calculating a first error signal between an output voltage reference value and a sampling value of the Buck type alternating current conversion device;
calculating a second error signal between the voltage reference value of the flying capacitor and the sampling value of the flying capacitor;
carrying out carrier modulation on the first error signal and the second error signal; and acquiring an input voltage sampling signal of the alternating current power supply module, performing logic adjustment on the input voltage sampling signal and a signal subjected to carrier modulation, and controlling the corresponding MOS (metal oxide semiconductor) tube in the alternating current switching tube to work by changing the polarity of the input voltage sampling signal.
The process of calculating the first error signal between the output voltage reference value and the sampling value of the Buck type alternating current conversion device comprises the following steps:
obtaining output voltage reference value U of Buck type three-level alternating current conversion device 0_ref Sampling value U of Buck type AC conversion device 0_f After comparison by the comparator, a first error signal U is obtained through an output voltage PI regulator 0_e 。
The process of calculating the second error signal between the flying capacitor's voltage reference value and the flying capacitor's sample value is:
acquiring voltage reference value U of flying capacitor c_ref Sampling value U of flying capacitor c_f After comparison by the comparator, a second error signal U is obtained through an output voltage PI regulator c_e 。
The process of carrying out carrier modulation on the first error signal and the second error signal comprises the following steps:
the first error signal U 0_e And a second error signal U c_e Are multiplied by weight K respectively 1 And K 2 And then adding to obtain a third error signal U e1 Via a carrier signal U c-1 After modulation, PWM control signal U of first AC switch tube is obtained p2 ；
The first error signal U 0_e And a second error signal U c_e Are respectively multiplied by weight K 1 And K 2 And then subtracting to obtain a fourth error signal U e2 Via a carrier signal U c-2 After modulation, PWM control signal U of second AC switch tube is obtained p3 。
The process of controlling the work of the corresponding MOS tube in the alternating current switching tube by changing the polarity of the input voltage sampling signal comprises the following steps:
input voltage sampling signal U i_f Output U after passing through zero comparator p1 When the alternating current of the alternating current power supply module is in a positive half period, U p1 Is positive and is changed into U through NOT gate N1 Is negative, the U N1 And U p2 、U p3 After common logic modulation, K in 4 AC switching tubes 1b ～K 4b Changing to a high level; k 1a ～K 4a Keeping the same; wherein K 1b ～K 4b Each of the 4 alternating current switching tubes is provided with the same polarity; k 1a ～K 4a The other of the 4 alternating current switching tubes is respectively, and the polarities are the same; the group b of switching tubes are constantly switched on, and the group a of switching tubes realize high-frequency chopping;
when the alternating current of the alternating current power supply module is in a negative half period, U p1 Is negative and becomes U through NOT gate N1 Is positive, the U is N1 And U p2 、U p3 After common logic modulation, K in 4 AC switching tubes 1a ～K 4a Changing to a high level; k 1b ～K 4b Keeping the same; namely, the switch tubes in the group a are constantly on, and the switch tubes in the group b realize high-frequency chopping.
When switching tube S 1 And S 3 Conducting, switching tube S 2 And S 4 Fig. 8 shows a flying capacitor charging and discharging circuit of a three-level Buck AC/AC converter in embodiment 2 of the present invention. The power supply charges the capacitor, and the voltage of the capacitor gradually rises; when switching tube S 1 And S 3 Turn-off, switch tube S 2 And S 4 When the capacitor is conducted and voltage control is carried out, the capacitor serves as a power supply and discharges to a load, and the voltage of the capacitor is gradually reduced.
In an actual circuit, since the charging and discharging time, that is, the duty ratio, is not completely equal, a certain degree of charging and discharging energy imbalance is certainly caused, so that the capacitor is overcharged or overdischarged. The reasons for this effect are two reasons: firstly, the two clusters of triangular carrier signals used in the modulation of the control waveform of the high-frequency PWM cannot be equal in amplitude completely, and the phase difference is 180 degrees; secondly, the instantaneous switching characteristics of the switching tubes cannot be completely consistent, so that the switching tubes are delayed when being switched on and switched off, and the delays are possibly different. Therefore, the duty ratio of the switching tube is different, and the charging and discharging of the capacitor are unbalanced.
Therefore, the voltage of the capacitor needs to be tracked, adjusted and controlled, and the charge and discharge of the capacitor are ensured to be balanced. The control strategy provided in the past is that flying capacitor voltage instantaneous value closed loop feedback control is adopted, and in a flying capacitor voltage control part, feedback coefficient K is adopted f Flying capacitor voltage u fed back in negative feedback manner Cy And an input voltage U i Sampling, comparing, and obtaining U after the comparison result passes through a flying capacitor PI regulator c_e 。
Fig. 9 is a schematic diagram of duty ratio of flying capacitor voltage closed loop correction switching tube in embodiment 2 of the present invention, in which two triangular carriers U with unequal voltage amplitudes and the same phase of other parameters are provided c_1 Voltage amplitude of greater than U c_2 If there is no flying capacitor voltage feedback regulation, switch tube S 1 Duty ratio S of 2 Small so that the flying capacitor voltage is greater than u i /2. (due to C) fly Is greater than the discharge time). Then the error amplified signal U c_e To be positive, it makes U c_1 The voltage rises to make the switch tube S 1 The duty ratio of (d) becomes large; at the same time, U c_2 The voltage is reduced to make the switch tube S 2 Becomes smaller. By adjusting the duty ratio, the flying capacitor voltage is returned to u i /2。。[4]Similarly, if the flying capacitor voltage is less than u i /2. Similar to the regulation method described above, the flying capacitor voltage is increased to u by closed loop regulation i /2。
Since PI closed loop negative feedback regulation is applied in the control of the fly-over voltage, the weight K 1 And K 2 Respectively influences the control precision of the output voltage and the flying capacitor voltage, and the larger the weight is, the larger the weight isThe higher the manufacturing accuracy, the smaller the weight, the lower the control accuracy. Since the purpose of this three-level topology is to reduce the voltage stress experienced by the switching tube, even small differences in voltage distribution sometimes do not affect the final purpose. The flying capacitor voltage need not completely follow half of the input voltage. Therefore, K is calculated at the time of simulation 1 And K 2 When the parameters are in the above range, the weight K is first ensured 1 Sufficiently large to be selected with a moderate weight K 2 The flying capacitor voltage may have a waveform approximately equal to half the output voltage waveform.
A power electronic simulation software saber is used for carrying out simulation experiments on the three-level Buck type AC/AC converter. The simulation model is shown in the appendix, wherein the simulation parameters are as follows: input voltage effective value U i 220V; the switch adopts an ideal device; the input voltage frequency fs is 25 kHz; flying capacitor C fly 3.3 muF, filter inductance L f 0.6mH, filter capacitance C f 4.4 μ F; the load is a resistive load, and Po is 500W.
Fig. 10 shows a simulation waveform of embodiment 2 of the present invention when the effective value of the output voltage is equal to 90V and the duty ratio D is less than 0.5.
As shown in fig. 10 (a), the duty ratio is adjusted to make the output voltage U 0 130V, the purpose of the Buck circuit, namely, reducing the voltage, was successfully achieved. The effect of the three levels we studied is shown in fig. 10 (b), which uses the flying capacitor to reduce the switching stress of the switching tube to half of the input voltage, the capacitor voltage u in the figure Cy The voltage is exactly half of the input voltage, which shows that the requirement of reducing the switching stress of the switching tube is achieved in the simulation.
In fig. 10 (c), filter inductor front end voltage u AE It is apparent that the waveform has been high frequency chopped, with values of 0 and u i The high frequency change between/2, if filtered by the filter, will become a continuous output voltage. In FIG. 10 (d), it is evident that at the input voltage u i When the switching tubes of the group a are chopped at high frequency, the switching tubes of the group b are constantly switched on; when the input voltage u i When the voltage is negative, the b groups of switching tubes chop at high frequency, and the a groups of switching tubes are constantly switched on. This indicates polarity in the simulation modelThe decision circuit is not problematic.
As can be seen in fig. 10 (f) and 10 (e), when the switching tube S is opened and closed 1a Or a switching tube S 2a When only one of them is conducted, it will make the inductive current i Lf Will increase; when switching tube S 1a And a switching tube S 2a Turn off at the same time to make the inductive current i Lf Will be reduced.
FIG. 11 is a schematic diagram showing simulation waveforms when the output voltage is 130V and the duty ratio D is greater than or equal to 0.5, and the sum D of the simulation results of D is greater than or equal to 0.5 in embodiment 2 of the present invention<0.5 is similar in principle, and the only difference is that when D is more than or equal to 0.5, the voltage u at the front end of the filter inductor AE Is always at u i A combination of u and 2 i To change in time.
In the control method of the Buck-type ac conversion device provided in embodiment 2 of the present invention, by increasing the number of switching tubes and introducing flying capacitors, an intermediate level is constructed, so that the voltage stress of the switching tubes can be reduced by half, the weight and volume of the filter can be greatly reduced, and the Buck-type ac conversion device can be used in high-voltage output occasions.
It is noted that, herein, relational terms such as first and second, and the like may be used solely to distinguish one entity or action from another entity or action without necessarily requiring or implying any actual such relationship or order between such entities or actions. Furthermore, the terms "comprises," "comprising," or any other variation thereof, are intended to cover a non-exclusive inclusion, such that a process, method, article, or apparatus that comprises a list of elements does not include the inherent elements. Without further limitation, an element defined by the phrase "comprising an … …" does not exclude the presence of other identical elements in the process, method, article, or apparatus that comprises the element. In addition, parts of the above technical solutions provided in the embodiments of the present application, which are consistent with the implementation principles of corresponding technical solutions in the prior art, are not described in detail so as to avoid redundant description.
Although the embodiments of the present invention have been described with reference to the accompanying drawings, the scope of the present invention is not limited thereto. Various modifications and alterations will occur to those skilled in the art based on the foregoing description. And are neither required nor exhaustive of all embodiments. On the basis of the technical scheme of the invention, various modifications or changes which can be made by a person skilled in the art without creative efforts are still within the protection scope of the invention.
Claims (10)
1. A Buck type alternating current conversion device is characterized by comprising an alternating current power supply module and 4 alternating current switch tubes; the alternating current power supply module is sequentially connected with 4 alternating current switching tubes in series; a flying capacitor is connected between the output end of the first alternating current switching tube and the output end of the third alternating current switching tube; the output end of the second alternating current switching tube is connected to the output end of the fourth alternating current switching tube through a load;
in the process of supplying power by the alternating current power supply module, the first alternating current switching tube and the fourth alternating current switching tube are conducted complementarily; the second alternating current switch tube and the third alternating current switch tube are conducted in a complementary mode.
2. The Buck-type ac conversion device according to claim 1, wherein the control signals of the first ac switching tube and the second ac switching tube are 180 degrees apart; the control signals of the third alternating current switching tube and the fourth alternating current switching tube have a 180-degree difference.
3. The Buck-type ac converter according to claim 1, wherein the conversion system further comprises a filter circuit;
and the output end of the second alternating current switching tube is connected to the output of the fourth alternating current switching tube through a filter circuit.
4. The Buck-type AC conversion device according to claim 3, wherein said filter circuit is an LC filter circuit.
5. The Buck-type ac converter according to claim 1, wherein the 4 ac switching tubes are identical in structure; each alternating current switch consists of two MOS tubes with opposite polarities, and a parasitic diode is arranged in each MOS tube.
6. A method for controlling a Buck-type three-level ac conversion device, which is implemented based on the Buck-type ac conversion device according to any one of claims 1 to 5, and which includes the steps of:
calculating a first error signal between an output voltage reference value and a sampling value of the Buck type alternating current conversion device;
calculating a second error signal between the voltage reference value of the flying capacitor and the sampling value of the flying capacitor;
carrying out carrier modulation on the first error signal and the second error signal; and acquiring an input voltage sampling signal of the alternating current power supply module, performing logic adjustment on the input voltage sampling signal and a signal subjected to carrier modulation, and controlling the corresponding MOS (metal oxide semiconductor) tube in the alternating current switching tube to work by changing the polarity of the input voltage sampling signal.
7. The method according to claim 6, wherein the step of calculating the first error signal between the reference value and the sampled value of the output voltage of the Buck-type AC conversion device comprises:
obtaining output voltage reference value U of Buck type three-level alternating current conversion device 0_ref Sampling value U of Buck type AC conversion device 0_f After comparison by the comparator, a first error signal U is obtained through an output voltage PI regulator 0_e 。
8. The method according to claim 7, wherein the step of calculating the second error signal between the flying capacitor voltage reference value and the flying capacitor sampling value is:
obtaining voltage reference value U of flying capacitor c_ref Sampling value U of sum flying capacitor c_f After comparison by the comparator, a second error signal U is obtained through an output voltage PI regulator c_e 。
9. The method according to claim 8, wherein the step of modulating the first error signal and the second error signal by carriers comprises:
the first error signal U 0_e And a second error signal U c_e Are respectively multiplied by weight K 1 And K 2 And then adding to obtain a third error signal U e1 Via a carrier signal U c-1 After modulation, PWM control signal U of first AC switch tube is obtained p2 ；
The first error signal U 0_e And a second error signal U c_e Are respectively multiplied by weight K 1 And K 2 And then subtracting to obtain a fourth error signal U e2 Via a carrier signal U c-2 After modulation, PWM control signal U of second AC switch tube is obtained p3 。
10. The method according to claim 9, wherein the step of controlling the operation of the corresponding MOS transistor in the ac switching transistor by changing the polarity of the input voltage sampling signal comprises:
input voltage sampling signal U i_f Output U after passing through zero comparator p1 When the alternating current of the alternating current power supply module is in a positive half period, U p1 Is positive and is changed into U through NOT gate N1 Is negative, the U N1 And U p2 、U p3 After common logic modulation, K in 4 AC switching tubes 1b ～K 4b Changing to a high level; k 1a ～K 4a Keeping the same; wherein K 1b ～K 4b Each of the 4 alternating current switching tubes is provided with the same polarity; k 1a ～K 4a The other of the 4 alternating current switching tubes is respectively, and the polarities are the same; the group b of switching tubes are constantly switched on, and the group a of switching tubes realize high-frequency chopping;
when the alternating current of the alternating current power supply module is in a negative half period, U p1 Is negative and becomes U through NOT gate N1 Is positive, the U is N1 And U p2 、U p3 After common logic modulation, K in 4 AC switching tubes 1a ～K 4a Changing to a high level; k is 1b ～K 4b Keeping the same; namely, the group a of switching tubes are constantly turned on, and the group b of switching tubes realize high-frequency chopping.
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Cited By (1)
| Publication number | Priority date | Publication date | Assignee | Title |
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| CN117277793A (en) * | 2023-11-22 | 2023-12-22 | 通号（长沙）轨道交通控制技术有限公司 | Power supply system, DC/DC converter control method and control device |
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Cited By (2)
| Publication number | Priority date | Publication date | Assignee | Title |
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| CN117277793A (en) * | 2023-11-22 | 2023-12-22 | 通号（长沙）轨道交通控制技术有限公司 | Power supply system, DC/DC converter control method and control device |
| CN117277793B (en) * | 2023-11-22 | 2024-02-13 | 通号（长沙）轨道交通控制技术有限公司 | Power supply system, DC/DC converter control method and control device |
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