CN115441715A - Constant voltage control method and circuit of converter and converter assembly - Google Patents

Constant voltage control method and circuit of converter and converter assembly Download PDF

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Publication number
CN115441715A
CN115441715A CN202211114037.8A CN202211114037A CN115441715A CN 115441715 A CN115441715 A CN 115441715A CN 202211114037 A CN202211114037 A CN 202211114037A CN 115441715 A CN115441715 A CN 115441715A
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current
voltage
transformer
inverter bridge
given
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孙运杰
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Xian Linchr New Energy Technology Co Ltd
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Xian Linchr New Energy Technology Co Ltd
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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
    • H02M1/32—Means for protecting converters other than automatic disconnection
    • 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
    • H02M7/00—Conversion of ac power input into dc power output; Conversion of dc power input into ac power output
    • H02M7/42—Conversion of dc power input into ac power output without possibility of reversal
    • H02M7/44—Conversion of dc power input into ac power output without possibility of reversal by static converters
    • H02M7/48—Conversion of dc power input into ac power output without possibility of reversal by static converters using discharge tubes with control electrode or semiconductor devices with control electrode
    • H02M7/53—Conversion of dc power input into ac power output without possibility of reversal 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
    • H02M7/537—Conversion of dc power input into ac power output without possibility of reversal 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, e.g. single switched pulse inverters
    • H02M7/5387—Conversion of dc power input into ac power output without possibility of reversal 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, e.g. single switched pulse inverters in a bridge configuration
    • H02M7/53871—Conversion of dc power input into ac power output without possibility of reversal 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, e.g. single switched pulse inverters in a bridge configuration with automatic control of output voltage or current
    • H02M7/53873—Conversion of dc power input into ac power output without possibility of reversal 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, e.g. single switched pulse inverters in a bridge configuration with automatic control of output voltage or current with digital control

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  • Engineering & Computer Science (AREA)
  • Power Engineering (AREA)
  • Inverter Devices (AREA)

Abstract

The invention provides a constant voltage control method, a constant voltage control circuit and a constant voltage control converter assembly of a converter, wherein the constant voltage control method of the converter calculates the voltage difference of positive and negative buses by acquiring the voltages of the positive and negative buses, and obtains corresponding given direct current component parameters, the change of the given direct current component parameters reflects the change of excitation inrush current, the given direct current component parameters serve as alternating current output given, the constant voltage output control is carried out on the converter, when a transformer is initially electrified to generate direct current component magnetic flux and cause excitation inrush current, the voltages of the positive and negative buses are unbalanced, at the moment, the converter cancels out the excitation inrush current according to the generated given direct current component parameters, the influence of the excitation inrush current on the buses is reduced, the voltages of the positive and negative buses are restored to be balanced, and the normal work of an inverter bridge circuit is ensured.

Description

Constant voltage control method and circuit of converter and converter assembly
Technical Field
The invention belongs to the technical field of converters, and particularly relates to a constant voltage control method and circuit of a converter and a converter assembly.
Background
The inverter is generally used for performing ac-to-dc or dc-to-ac power conversion, wherein an inverter bridge circuit is a main component in the inverter, and an output end of the inverter is further connected to a transformer for further performing power conversion or electrical isolation.
When the converter is in an alternating current constant voltage output mode, in the starting process, because the magnetic flux of the transformer cannot suddenly change, when voltage is suddenly applied, the transformer can generate direct-current component magnetic flux for preventing the magnetic flux from suddenly changing, the direct-current component magnetic flux is superposed with alternating magnetic flux generated by alternating voltage, an alternating magnetic flux peak value of 2 times can be generated at most generally, and the magnetic flux peak value exceeds the saturation magnetic flux of the transformer, so that the excitation inrush current of the transformer is caused.
Disclosure of Invention
The invention aims to provide a constant voltage control method of a converter, and aims to solve the problem that the voltages of positive and negative buses are unbalanced due to magnetizing inrush current when the traditional converter is started.
The first aspect of the embodiment of the invention provides a constant voltage control method of a converter, wherein the converter comprises an inverter bridge circuit, a filter circuit and a transformer which are sequentially connected;
the constant voltage control method of the converter comprises the following steps:
acquiring positive and negative bus voltages of the inverter bridge circuit, and calculating to obtain the voltage difference of the positive and negative buses;
and determining a given direct-current component parameter based on the voltage difference of the positive bus and the negative bus, and giving the given direct-current component parameter as the alternating-current output of the converter so as to control the voltage difference of the positive bus and the negative bus of the inverter bridge circuit within a preset range after the inverter bridge circuit is electrified.
Optionally, the given direct-current component parameter is a preset given voltage, and the preset given voltage is used as an alternating-current output given of the converter;
the preset given voltage comprises a given standard alternating current voltage and a preset direct current voltage component.
Optionally, the step of giving the given dc component parameter as the ac output of the converter to control the voltage difference between the positive bus and the negative bus of the inverter bridge circuit within a preset range after power-on specifically includes:
outputting a matched inversion regulating signal to the inverter bridge circuit according to the preset given voltage so that the filter circuit outputs the preset given voltage to the transformer to drive the transformer to generate total magnetic flux corresponding to the preset given voltage;
and the accumulated magnetic flux of the preset direct-current voltage component counteracts the initial direct-current magnetic flux in the total magnetic flux of the transformer so as to control the voltage difference of the positive bus and the negative bus of the inverter bridge circuit within a preset range after the inverter bridge circuit is electrified. Optionally, the step of the accumulated magnetic flux of the preset dc voltage component offsetting the initial dc magnetic flux in the total magnetic flux of the transformer specifically includes:
and setting the preset direct-current voltage component as the alternating-current output of the converter for a preset action time t, so that the accumulated magnetic flux of the preset direct-current voltage component counteracts the initial direct-current magnetic flux in the total magnetic flux of the transformer.
Optionally, the given dc component parameter is a compensation current;
the step of determining a given direct-current component parameter based on the voltage difference between the positive bus and the negative bus, giving the given direct-current component parameter as the alternating-current output of the converter, and controlling the voltage difference between the positive bus and the negative bus of the inverter bridge circuit within a preset range after the inverter bridge circuit is powered on specifically comprises the following steps:
determining a compensation current based on the voltage difference of the positive and negative buses;
and inputting the compensation current into the transformer as a given direct current component parameter to generate a direct current with a corresponding size and direction, offsetting the direct current component current generated by the transformer, and eliminating the excitation inrush current so as to control the voltage difference of the positive bus and the negative bus of the inverter bridge circuit within a preset range.
Optionally, the constant voltage control method of the converter further includes:
the given direct-current component parameter is given as alternating-current output, and constant-voltage control is performed by adopting a voltage ring so as to control the voltage difference of positive and negative buses of the converter within a preset range after the converter is electrified;
the input parameters of the voltage ring are as follows: and the sum of the given standard alternating voltage and the product of the positive and negative bus voltage difference multiplied by the proportionality coefficient.
The second aspect of the embodiment of the invention provides a constant voltage control circuit of a converter, wherein the converter comprises an inverter bridge circuit, a filter circuit and a transformer which are sequentially connected;
the constant voltage control circuit includes:
the sampling circuit is correspondingly connected with the inverter bridge circuit and is used for sampling positive and negative bus voltage, output voltage and output current of the inverter bridge circuit;
and the control circuit is respectively connected with the inverter bridge circuit and the sampling circuit, and is used for realizing the steps of the constant voltage control method of the converter according to the sampling signal output by the sampling circuit.
Optionally, the sampling circuit comprises a current sampling circuit and a voltage sampling circuit.
A third aspect of an embodiment of the present invention provides a converter assembly, including the converter constant voltage control circuit as described above;
the converter comprises an inverter bridge circuit, a filter circuit and a transformer which are sequentially connected, and the constant voltage control circuit is correspondingly connected with the inverter bridge circuit.
Optionally, the inverter bridge circuit includes an inverter bridge and a bus capacitor connected to two ends of the inverter bridge, where the bus capacitor includes a first capacitor and a second capacitor connected in series;
a connection node of the first capacitor and the second capacitor, a neutral point of the transformer and a grounding end of the filter circuit are connected in common;
the inverter bridge is a two-level inverter bridge or a three-level inverter bridge.
Compared with the prior art, the embodiment of the invention has the following beneficial effects: the constant voltage control method of the converter calculates the voltage difference of the positive bus and the negative bus by acquiring the positive bus voltage and the negative bus voltage of the inverter bridge circuit, and acquires the corresponding given direct current component parameter, wherein the change of the given direct current component parameter reflects the change of the excitation inrush current, the given direct current component parameter is used as the alternating current output given, the constant voltage output control is carried out on the converter, when the transformer is initially electrified to generate direct current component magnetic flux and cause the excitation inrush current, the positive bus voltage and the negative bus voltage are unbalanced, at the moment, the converter and the excitation inrush current are mutually offset according to the generated given direct current component parameter, the influence of the excitation inrush current on the buses is reduced, the positive bus voltage and the negative bus voltage are restored to be balanced, and the normal work of the inverter bridge circuit is ensured.
Drawings
Fig. 1 is a schematic circuit diagram of a converter according to an embodiment of the present invention;
fig. 2 is a schematic flow chart of a constant voltage control method for a converter according to an embodiment of the present invention;
FIG. 3 is a first flowchart of step S20 in the embodiment of FIG. 2;
FIG. 4 is a second flowchart of step S20 in the embodiment of FIG. 2;
fig. 5 is a block diagram of a constant voltage control circuit of a converter according to an embodiment of the present invention;
fig. 6 is a block diagram of an equivalent control loop of the constant voltage control circuit of the inverter shown in fig. 5.
Detailed Description
In order to make the technical problems, technical solutions and advantageous effects to be solved by the present invention more clearly apparent, the present invention is further described in detail below with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are merely illustrative of the invention and do not limit the invention.
Furthermore, the terms "first", "second" and "first" are used for descriptive purposes only and are not to be construed as indicating or implying relative importance or implicitly indicating the number of technical features indicated. Thus, a feature defined as "first" or "second" may explicitly or implicitly include one or more of that feature. In the description of the present invention, "a plurality" means two or more unless specifically defined otherwise.
The first aspect of the embodiment of the present invention provides a constant voltage control method for a converter 10, which is applied to the converter 10, where as shown in fig. 1, the converter 10 includes an inverter bridge circuit 11, a filter circuit 12, and a transformer T1 that are connected in sequence, the inverter bridge circuit 11 may adopt a two-level inverter bridge or a three-level inverter bridge and other circuit structures, such as the two-level inverter bridge shown in fig. 1, each bridge arm of the two-level inverter bridge includes two power switching tubes and two inverse diodes, the two-level inverter circuit outputs two high and low levels, each bridge arm of the three-level inverter bridge includes four power switching tubes and six diodes, and the three-level inverter bridge may output high and low levels through the opening of upper and lower tubes and output zero levels through the clamping action of the middle diode, for a total of three level states.
The filter circuit 12 may adopt an LC filter circuit 12 with a corresponding structure, as shown in fig. 1, in order to realize filter resonance of signals of positive and negative half shafts of the inverter bridge and generate a sinusoidal alternating signal, optionally, the filter circuit 12 includes a three-phase T-type filter.
The LC filter circuit 12 and the inverter bridge circuit 11 form a high-frequency inverter circuit to output sinusoidal alternating signals, the output end of the LC filter circuit 12 is connected to the primary winding of the transformer T1, the output end of the converter 10 may be the output end of the LC filter circuit 12 or the secondary winding of the transformer T1, and the specific output position is not limited.
In order to reduce the influence of the magnetizing inrush current on the positive and negative buses, a constant voltage control method of the converter 10 is provided, and as shown in fig. 2, the constant voltage control method of the converter 10 includes:
s10, acquiring positive and negative bus voltages of the inverter bridge circuit 11, and calculating to obtain the voltage difference of the positive and negative buses;
step S20, determining a given dc component parameter based on the voltage difference between the positive and negative buses, and giving the given dc component parameter as the ac output of the converter 10, so as to control the voltage difference between the positive and negative buses of the inverter bridge circuit 11 within a preset range after power-on.
In this embodiment, the voltage sampling circuit 212 additionally provided or the voltage sampling circuit 212 in the original converter 10 may be used to obtain the voltages of the positive and negative buses of the inverter bridge circuit 11, and perform difference and amplification conversion on the voltages of the positive and negative buses, so as to calculate the voltage difference between the positive and negative buses.
Meanwhile, a given direct-current component parameter is used as an alternating-current output setting, constant-voltage output control is performed on the inverter bridge circuit 11, so that excitation inrush current generated during initial power-on is offset, and the voltage difference between a positive bus and a negative bus of the inverter bridge circuit 11 is controlled within a preset range.
Under a normal working state, when the transformer T1 receives an input sinusoidal alternating signal, alternating magnetic flux is generated, at this time, no direct-current component magnetic flux is generated by the transformer T1, the magnetic flux of the transformer T1 does not exceed the saturation magnetic flux of the transformer T1, no excitation inrush current is generated, namely no direct-current component current is input to a positive bus or a negative bus through the filter circuit 12 and the corresponding diode, the voltages of the positive bus and the negative bus are kept balanced, the voltage difference of the positive bus and the negative bus of the inverter bridge circuit 11 is within a preset range, a direct-current component parameter is given as a first preset value, the first preset value is taken as an output given value, the inverter bridge circuit 11 outputs a sinusoidal alternating signal with a corresponding size under a constant-voltage control mode, and the transformer T1 is excited normally.
When the transformer T1 is initially electrified, alternating magnetic flux is generated by receiving an input sinusoidal alternating signal, meanwhile, direct-current component magnetic flux for preventing magnetic flux change is generated, the two magnetic fluxes are superposed, when saturation magnetic flux of the transformer T1 is exceeded, magnetizing inrush current of the transformer T1 is equivalent to direct-current component current, the direct-current component magnetic flux is input to a positive bus through a diode of an upper bridge arm or input to a negative bus through a diode of a lower bridge arm, positive bus voltage or negative bus voltage is unbalanced, at the moment, a given direct-current component parameter is equal to a second preset value, the second preset value is larger than or smaller than a first preset value, constant-voltage output control is performed by taking the second preset value as an output given value, compensation magnetic flux or compensation current generated by a difference value of the second preset value and the first preset value counteracts and compensates the direct-current component magnetic flux or the direct-current component current generated by the transformer T1, magnetizing inrush current is eliminated, the positive bus voltage or the negative bus voltage is gradually restored to a balanced state, the equivalent direct-current component is changed to zero, and the transformer T1 finally generates alternating magnetic flux according to a normal working state according to the input sinusoidal alternating signal.
The method corresponds to a mode of generating direct current component magnetic flux or direct current component current during initial power-on, namely after the initial power-on, the control module controls the inverter bridge circuit 11 to generate a given direct current component parameter with a corresponding magnitude according to an input given voltage, the given direct current component parameter generates direct current component magnetic flux or direct current with a corresponding magnitude and direction after being output to the transformer T1, and the magnetic flux or the current is offset with the magnetic flux or the generated direct current component of the transformer T1, so that the magnetic flux of the transformer T1 is adjusted to exit a saturation region, and the probability of generating magnetizing inrush current is reduced.
Meanwhile, according to different modes of offset compensation, the given dc component parameter may be selected as a corresponding parameter, optionally, the given dc component parameter is a preset given voltage, and the preset given voltage is used as an ac output given voltage of the converter 10;
the preset given voltage comprises a given standard alternating current voltage and a preset direct current voltage component.
In this embodiment, in a normal operating state, when the transformer T1 receives an input sinusoidal alternating signal, an alternating magnetic flux is generated, at this time, no direct-current component magnetic flux is generated by the transformer T1, the magnetic flux of the transformer T1 does not exceed the saturation magnetic flux of the transformer T1, and no excitation inrush current is generated, that is, no direct-current component current is input to the positive bus or the negative bus through the filter circuit 12 and the corresponding diode, voltages of the positive and negative buses are kept balanced, a voltage difference between the positive and negative buses of the inverter bridge circuit 11 is within a preset range, a given direct-current component parameter is a given standard alternating-current voltage, a given standard alternating-current voltage is used as an output given, the inverter bridge circuit 11 outputs a sinusoidal alternating signal with a size corresponding to the given standard alternating-current voltage in a constant-voltage control mode, and the transformer T1 is normally excited.
When the transformer T1 is initially electrified, alternating magnetic flux is generated by receiving an input sinusoidal alternating signal, meanwhile, direct-current component magnetic flux for preventing magnetic flux change is generated, the magnetic flux of the transformer T1 is superposed, when the saturated magnetic flux of the transformer T1 is exceeded, magnetizing inrush current of the transformer T1 is equivalent to direct-current component current, the direct-current component current is input to a positive bus through a diode of an upper bridge arm or is input to a negative bus through a diode of a lower bridge arm, and therefore positive bus voltage or negative bus voltage is unbalanced, at the moment, given direct-current component parameters comprise given standard alternating-current voltage and preset direct-current voltage components, constant-voltage output control is performed by taking the given standard alternating-current voltage and the preset direct-current voltage components as output given, the preset direct-current voltage components are larger than zero or smaller than zero, wherein the preset direct-current voltage components in the given direct-current component parameters generate direct current or magnetic flux with corresponding magnitudes and directions, so that the direct-current component current or direct-current component magnetic flux generated by the transformer T1 is offset, the positive bus voltage or the negative voltage gradually recovers to a balanced state, and the preset direct-current component magnetic flux is changed to zero, and the transformer T1 finally generates the sinusoidal alternating magnetic flux according to the input sinusoidal alternating magnetic flux to a normal alternating-current working state.
Optionally, as shown in fig. 3, the step S20 specifically includes, in response to the preset parameter of the given voltage:
s21, outputting a matched inversion regulating signal to the inverter bridge circuit 11 according to the preset given voltage so that the filter circuit 12 outputs the preset given voltage to the transformer T1, and driving the transformer T1 to generate total magnetic flux corresponding to the preset given voltage in an excitation mode;
and S22, offsetting initial direct current magnetic flux in the total magnetic flux of the transformer T1 by the accumulated magnetic flux of the preset direct current voltage component so as to control the voltage difference of positive and negative buses of the inverter bridge circuit 11 within a preset range after power-on.
In this embodiment, the inversion adjustment signal is equivalent to a pulse width modulation signal, multiple paths of pulse width modulation signals are respectively output to each power switching tube in the inverter bridge circuit 11, the duty ratio of each pulse width modulation signal forms a mapping relation with a preset given voltage, and correspondingly changes along with the change of the preset given voltage, and drives the inverter bridge circuit 11 to generate the preset given voltage, and the preset given voltage is output to the transformer T1 through the filter circuit 12, and the transformer T1 is excited.
The total magnetic flux generated by the transformer T1 includes the alternating magnetic flux corresponding to the given standard alternating voltage, the initial direct current magnetic flux for counteracting the abrupt change of the magnetic flux and the magnetic flux corresponding to the preset direct current voltage component, the magnetic flux corresponding to the preset direct current voltage component is accumulated within the preset time period, the initial direct current magnetic flux is counteracted step by step, finally, the total magnetic flux of the transformer T1 only includes the alternating magnetic flux corresponding to the given standard alternating voltage, correspondingly, the final positive and negative bus voltages of the inverter bridge circuit 11 are restored to be balanced and work normally.
The magnetic flux cancellation is specifically realized by that a preset direct-current voltage component generates a direct current through the transformer T1, and a direct-current component equivalent to the magnetizing inrush current of the transformer T1 is cancelled, so that the voltage difference between the positive bus and the negative bus of the inverter bridge circuit 11 is controlled within a preset range after the inverter bridge circuit is powered on.
Corresponding to the way of magnetic flux cancellation, optionally, the step of accumulating the accumulated magnetic flux of the preset dc voltage component to cancel the initial dc magnetic flux in the total magnetic flux of the transformer T1 specifically includes:
the predetermined dc voltage component is given as an ac output of the converter 10 and lasts for a predetermined action time T, so that the accumulated magnetic flux of the predetermined dc voltage component cancels the initial dc magnetic flux in the total magnetic flux of the transformer T1.
In this embodiment, the magnitude of the pulse width modulation signal is adjusted according to the value of the preset dc voltage component, the inverter bridge circuit 11 outputs a given ac signal based on the corresponding pulse width modulation signal, the preset dc voltage component in the ac signal is continuously output, after the preset action time T is continued, magnetic flux of a preset magnitude is accumulated and formed, and initial dc magnetic flux in the total magnetic flux of the transformer T1 is offset, so that the final magnetic flux of the transformer T1 is an alternating magnetic flux generated under a standard ac voltage, and the positive and negative bus voltages of the inverter bridge circuit 11 are restored to balance.
Specifically, the relationship between the electromotive force of the transformer T1 and the total magnetic flux generated by excitation is:
Figure BDA0003844777950000091
um is an output voltage peak value of the inverter bridge circuit 11, N1 is a number of turns of a primary winding of the transformer T1, i1 is an alternating current between the inverter bridge circuit 11 and the transformer T1, R1 is a line resistance between the inverter bridge circuit 11 and the transformer T1, udc is a preset direct current voltage component output by the inverter bridge circuit 11, and α is an initial conduction angle.
Since i1 and R1 are relatively small, they can be ignored during the transient phase of the initial power-on analysis, as well asIn the meantime, the magnetic flux accumulation effect generated by Udc is not shown, so that simplification can be realized, when the initial t =0, the bridge arm of the inverter bridge circuit 11 is switched on, and the magnetic flux is generated
Figure BDA0003844777950000092
The total flux of the transformer T1 can be solved by integration as:
Figure BDA0003844777950000093
wherein, the first and the second end of the pipe are connected with each other,
Figure BDA0003844777950000094
for the alternating flux generated by the transformer T1 at the standard alternating voltage Udc T is the accumulated flux of the predetermined direct voltage component, i 1R 1T is the current damping flux,
Figure BDA0003844777950000095
the initial direct current flux of the transformer T1 is represented by Um, which is the peak value of the output voltage of the inverter bridge circuit 11, N1 is the number of turns of the primary winding of the transformer T1, i1 is the alternating current between the inverter bridge circuit 11 and the transformer T1, R1 is the line resistance between the inverter bridge circuit 11 and the transformer T1, udc is the preset direct current voltage component, and α is the initial conduction angle.
In this embodiment, a preset dc voltage component is given as an ac output of the converter 10 and lasts for a preset action time T, an accumulated magnetic flux of the generated dc voltage component cancels an initial dc magnetic flux in a total magnetic flux of the transformer T1, and a final magnetic flux of the transformer T1 is an alternating magnetic flux through magnetic flux cancellation for a corresponding duration, so that the transformer T1 is out of magnetic saturation, the occurrence probability of an excitation inrush current is reduced, and finally, the positive and negative bus voltages of the inverter bridge circuit 11 are in a balanced state.
Optionally, the given dc component parameter may also be designed as a compensation current with a corresponding magnitude, as shown in fig. 4, the given dc component parameter is a compensation current;
step S20 specifically includes:
s23, determining a compensation current based on the voltage difference of the positive bus and the negative bus;
and step S24, inputting the compensation current into the transformer T1 as a given direct current component parameter to generate a direct current with a corresponding size and direction, offsetting the direct current component generated by the transformer T1, and eliminating excitation inrush current so as to control the voltage difference of the positive bus and the negative bus of the inverter bridge circuit 11 within a preset range.
In this embodiment, the compensation current is determined based on the positive and negative bus voltages, the compensation current corresponds to the change of the voltage difference between the positive and negative buses, the changed compensation current is input into the transformer T1 as a given dc component parameter to generate a dc current corresponding to the magnitude and direction, so as to cancel the dc component current generated by the transformer T1, eliminate the magnetizing inrush current, gradually restore the positive bus voltage or the negative bus voltage to a balanced state, further change the equivalent dc voltage component to zero, and finally the transformer T1 generates an alternating magnetic flux according to the input sinusoidal alternating signal and switches to a normal working state.
Optionally, the constant voltage control method of the converter 10 further includes:
setting a direct current component parameter as an alternating current output, and performing constant voltage control by adopting a voltage ring so as to control the voltage difference of a positive bus and a negative bus of the converter to be within a preset range after the converter is electrified;
wherein, the input parameter of voltage ring is: and the sum of the given standard alternating voltage and the product of the positive and negative bus voltage difference multiplied by the proportionality coefficient.
The preset given voltage is equal to the given standard alternating voltage and the preset direct current voltage component, namely the preset direct current voltage component is equal to the product of the voltage difference of the positive bus and the negative bus multiplied by the proportionality coefficient, namely the size of the preset direct current voltage component is as follows:
udc1= (VP 1-VP 2) × K, where VP1 represents the positive bus voltage, VP2 represents the negative bus voltage, and K is a scaling factor.
Meanwhile, the inverter bridge circuit 11 is output-controlled in a voltage loop control mode, and the sum of the given standard alternating-current voltage and the preset direct-current voltage component is used as the output given voltage of the current loop to control the inverter bridge circuit 11 to output the given standard alternating-current voltage at a constant voltage.
Wherein, in order to further stabilize the output, optionally, the constant voltage control method further comprises:
meanwhile, the inverter bridge circuit 11 is driven to output a constant voltage by adopting a control mode of a current loop and a voltage loop, wherein the voltage loop is in an outer loop control mode, and the current loop is in an inner loop control mode.
In this embodiment, double loop control is adopted, the output state of the inverter bridge circuit 11 is sampled by the voltage sampling circuit 212 and the current sampling circuit 211, and the output of the inverter bridge circuit 11 is feedback-regulated, so that negative feedback regulation of current and voltage is realized, and constant voltage output control of the converter 10 is realized.
Compared with the prior art, the embodiment of the invention has the following beneficial effects: according to the constant voltage control method of the converter 10, the voltage difference between the positive bus and the negative bus is calculated by obtaining the positive bus voltage and the negative bus voltage of the inverter bridge circuit 11, corresponding given direct current component parameters are obtained, the change of the given direct current component parameters reflects the change of excitation inrush current, the given direct current component parameters serve as alternating current output given, constant voltage output control is performed on the converter 10, when the transformer T1 is initially electrified to generate direct current component magnetic flux and cause excitation inrush current, the positive bus voltage and the negative bus voltage are unbalanced, at the moment, the converter 10 cancels out the excitation inrush current according to the generated given direct current component parameters, the influence of the excitation inrush current on the buses is reduced, the positive bus voltage and the negative bus voltage are restored to be balanced, and the inverter bridge circuit 11 is ensured to normally work.
In correspondence to the constant voltage control method of the inverter 10, as shown in fig. 3, a second aspect of the embodiment of the present invention provides a constant voltage control circuit 20 of the inverter 10, including:
the sampling circuit 21 is correspondingly connected with the inverter bridge circuit 11, and the sampling circuit 21 is used for sampling positive and negative bus voltages, output voltages and output currents of the inverter bridge circuit 11;
the control circuit 22 and the control circuit 22 are respectively connected with the inverter bridge circuit 11 and the sampling circuit 21, and the control circuit 22 is used for realizing the steps of the constant voltage control method of the converter 10 according to the sampling signals output by the sampling circuit 21.
In this embodiment, the sampling circuit 21 is configured to sample the positive and negative bus voltages and the output voltage of the inverter bridge circuit 11, and the control circuit 22 performs difference and amplification conversion on the positive and negative bus voltage calculations, so as to calculate the voltage difference between the positive and negative buses.
Meanwhile, the control circuit 22 takes the given direct-current component parameter as an alternating-current output setting, and performs constant-voltage output control on the inverter bridge circuit 11 to offset the magnetizing inrush current generated during initial power-on, so as to control the voltage difference between the positive bus and the negative bus of the converter 10 within a preset range.
Under a normal working state, when the transformer T1 receives an input sinusoidal alternating signal, an alternating magnetic flux is generated, at this time, no direct-current component magnetic flux is generated by the transformer T1, the magnetic flux of the transformer T1 does not exceed the saturation magnetic flux of the transformer T1, no excitation inrush current is generated, that is, no direct-current component current is input to the positive bus or the negative bus through the filter circuit 12 and the corresponding diode, voltages of the positive bus and the negative bus are kept balanced, a voltage difference between the positive bus and the negative bus of the converter is within a preset range, the control circuit 22 determines a given direct-current component parameter as a first preset value, the first preset value is used as an output given value, the inverter bridge circuit 11 outputs a sinusoidal alternating signal of a corresponding magnitude under a constant voltage control mode of the control circuit 22, and the transformer T1 is normally excited.
When the transformer T1 is initially electrified, alternating magnetic flux is generated by receiving an input sinusoidal alternating signal, meanwhile, direct-current component magnetic flux for preventing magnetic flux change is generated, the two magnetic fluxes are superposed, when saturation magnetic flux of the transformer T1 is exceeded, magnetizing inrush current of the transformer T1 is equivalent to direct-current component current, the direct-current component current is input to a positive bus through a diode of an upper bridge arm or is input to a negative bus through a diode of a lower bridge arm, positive bus voltage or negative bus voltage is unbalanced, at the moment, a given direct-current component parameter is equal to a second preset value, the second preset value is larger than or smaller than a first preset value, a control circuit 22 performs constant-voltage output control by taking the second preset value as an output given value, compensation magnetic flux or compensation current generated by the difference value of the second preset value and the first preset value counteracts and compensates the direct-current component magnetic flux or the direct-current component current generated by the transformer, magnetizing inrush current is eliminated, the positive bus voltage or the negative bus voltage is gradually restored to a balanced state, the equivalent direct-current component current is changed to zero, and the transformer T1 finally generates alternating magnetic flux according to be switched to a normal working state according to the input sinusoidal alternating signal.
Meanwhile, according to different modes of offset compensation, the given direct-current component parameter can be correspondingly selected as a corresponding parameter, optionally, the given direct-current component parameter is preset given voltage, and the preset given voltage is used as alternating-current output given voltage of the converter;
the preset given voltage comprises a given standard alternating current voltage and a preset direct current voltage component.
In this embodiment, in a normal operating state, when the transformer T1 receives an input sinusoidal alternating signal, an alternating magnetic flux is generated, at this time, no direct-current component magnetic flux is generated by the transformer T1, the magnetic flux of the transformer T1 does not exceed the saturation magnetic flux of the transformer T1, and no excitation inrush current is generated, that is, no direct-current component current is input to the positive bus or the negative bus through the filter circuit 12 and the corresponding diode, voltages of the positive bus and the negative bus are kept balanced, a voltage difference between the positive bus and the negative bus of the inverter bridge circuit 11 is within a preset range, a given direct-current component parameter is a given standard alternating-current voltage, a given standard alternating-current voltage is used as an output given, the inverter bridge circuit 11 outputs a sinusoidal alternating signal with a size corresponding to the given standard alternating-current voltage in a constant voltage control mode, and the transformer T1 is excited normally.
When the transformer T1 is initially electrified, alternating magnetic flux is generated by receiving an input sinusoidal alternating signal, meanwhile, direct-current component magnetic flux for preventing magnetic flux change is generated, the magnetic flux of the two magnetic fluxes are superposed, when the saturated magnetic flux of the transformer T1 is exceeded, the transformer T1 is excited to surge current, the equivalent direct-current component current is input to a positive bus through a diode of an upper bridge arm or input to a negative bus through a diode of a lower bridge arm, and therefore the positive bus voltage or the negative bus voltage is unbalanced, at the moment, a given direct-current component parameter comprises a given standard alternating-current voltage and a preset direct-current voltage component, constant-voltage output control is performed by taking the given standard alternating-current voltage and the preset direct-current voltage component as output given, the preset direct-current voltage component is larger than zero or smaller than zero, wherein the preset direct-current voltage component in the given direct-current component parameter generates direct current or magnetic flux with the corresponding magnitude and direction, so as to offset the direct-current component current or direct-current component magnetic flux generated by the transformer T1, the positive-current or direct-current bus voltage is gradually restored to a balanced state, the preset direct-current voltage component is changed to zero, and the transformer T1 finally generates sinusoidal alternating flux according to the input sinusoidal alternating signal, and is switched to a normal working state.
Optionally, the preset dc voltage component cancels the initial dc flux of the total flux of the transformer T1.
Specifically, the relationship between the electromotive force and the magnetic flux of the transformer T1 is:
Figure BDA0003844777950000131
um is the peak value of the output voltage of the inverter bridge circuit 11, N1 is the number of turns of the primary winding of the transformer T1, i1 is the alternating current between the inverter bridge circuit 11 and the transformer T1, R1 is the line resistance between the inverter bridge circuit 11 and the transformer T1, udc is the direct current voltage component output by the inverter bridge circuit 11, and α is the initial conduction angle.
Because i1 and R1 are relatively small, they can be ignored in analyzing the transient stage of initial power-on, and at the same time, the magnetic flux accumulation effect generated by Udc is not shown, so that it can be simplified, when initial t =0, the bridge arm of inverter bridge circuit 11 is switched on, and the magnetic flux is turned on
Figure BDA0003844777950000141
The total flux of the transformer T1 can be solved by integration as:
Figure BDA0003844777950000142
wherein the content of the first and second substances,
Figure BDA0003844777950000143
is the alternating flux of the transformer T1, udc T is the accumulated flux of the DC voltage component, i1 × r1 × t is the current decay flux,
Figure BDA0003844777950000144
the initial direct current flux of the transformer T1 is provided, um is the output voltage peak value of the inverter bridge circuit 11, N1 is the number of turns of the primary winding of the transformer T1, i1 is the alternating current between the inverter bridge circuit 11 and the transformer T1, R1 is the line resistance between the inverter bridge circuit 11 and the transformer T1, udc is the direct current voltage component, and alpha is the initial conduction angle.
The preset direct-current voltage component is used as alternating-current output of the converter 10 to be given and continuously preset for the action time T, the generated accumulated magnetic flux of the direct-current voltage component counteracts the initial direct-current magnetic flux in the total magnetic flux of the transformer T1, and then the magnetic flux is counteracted for a corresponding duration, and the final magnetic flux of the transformer T1 is the alternating magnetic flux, so that the transformer T1 is out of magnetic saturation, the probability of excitation inrush current is reduced, and the fact that the positive bus voltage and the negative bus voltage of the inverter bridge circuit 11 are in a balanced state is finally achieved.
Optionally, the given dc component parameter may also be designed as a compensation current of a corresponding magnitude, the compensation current is determined based on the positive and negative bus voltages, the compensation current is input to the transformer T1 as the given dc component parameter to generate a dc current of a corresponding magnitude and direction, so as to cancel the dc component current generated by the transformer T1, eliminate an inrush current, gradually restore the positive bus voltage or the negative bus voltage to a balanced state, further change the equivalent dc voltage component to zero, and finally generate an alternating magnetic flux according to the input sinusoidal alternating signal by the transformer T1, and switch to a normal operating state.
Meanwhile, the control circuit 22 performs output control on the inverter bridge circuit 11 by using a voltage ring control mode, as shown in fig. 4, the control circuit is a dual-loop control model for controlling voltage and current by using an ac constant voltage of a typical converter, where REF0 is a given standard ac voltage, REF1 is a preset given voltage, 222 is a voltage controller, 223 is a current controller, and the controller generally has a proportional controller, a proportional-integral controller, or a proportional resonant controller; 211 is a current sampling circuit, 212 is a voltage sampling circuit, and Vout is an inversion output voltage; in the embodiment, in the voltage setting control loop, the voltage difference (increased by (VP 1-VP 2) × K) between the positive bus and the negative bus is added to the REF0 to obtain the final output given voltage REF1, and the accumulated magnetic flux of the preset direct current voltage component udc lasting the preset action time T actively adjusts the magnetic flux of the transformer T1 to exit the saturation region, so that the occurrence probability of the magnetizing inrush current is reduced, and the stable operation of the equipment is ensured.
The present invention further provides a converter 10 assembly, where the converter 10 assembly includes a constant voltage control circuit 20 of the converter 10, and the specific structure of the constant voltage control circuit 20 of the converter 10 refers to the above embodiments, and since the converter 10 assembly adopts all technical solutions of all the above embodiments, the converter at least has all beneficial effects brought by the technical solutions of the above embodiments, and details are not repeated herein. The converter 10 includes an inverter bridge circuit 11, a filter circuit 12 and a transformer T1 connected in sequence, and the constant voltage control circuit 20 is correspondingly connected to the inverter bridge circuit 11.
In this embodiment, the inverter bridge circuit 11 includes an inverter bridge and a corresponding bus capacitor, optionally, as shown in fig. 1, the inverter bridge circuit 11 includes an inverter bridge and a bus capacitor connected to two ends of the inverter bridge, and the bus capacitor includes a first capacitor and a second capacitor connected in series;
the connection node of the first capacitor and the second capacitor, the neutral point of the transformer T1, and the ground terminal of the filter circuit 12 are connected in common, the connection node of the bus capacitor serves as the neutral point of the voltage of the inverter output as a direct output, and the connection node is connected to the neutral point of the transformer T1 and the ground terminal of the filter circuit 12.
The inverter bridge can select an inverter bridge with a corresponding structure, and optionally, the inverter bridge is a two-level inverter bridge or a three-level inverter bridge.
For example, as shown in fig. 1, each arm of the two-level inverter bridge includes two power switching tubes and two inverse diodes, the two-level inverter circuit outputs two high and low levels, each arm of the three-level inverter bridge includes four power switching tubes and six diodes, and the three-level inverter bridge can output high and low levels through the turn-on of the upper and lower tubes and output a zero level through the clamping action of the middle diode, so that the total three level states are three.
The above-mentioned embodiments are only used for illustrating the technical solutions of the present invention, and not for limiting the same; although the present invention has been described in detail with reference to the foregoing embodiments, it will be understood by those of ordinary skill in the art that: the technical solutions described in the foregoing embodiments may still be modified, or some technical features may be equivalently replaced; such modifications and substitutions do not substantially depart from the spirit and scope of the embodiments of the present invention, and are intended to be included within the scope of the present invention.

Claims (10)

1. The constant voltage control method of the converter is characterized in that the converter comprises an inverter bridge circuit, a filter circuit and a transformer which are connected in sequence;
the constant voltage control method of the converter comprises the following steps:
acquiring positive and negative bus voltages of the inverter bridge circuit, and calculating to obtain the voltage difference of the positive and negative buses;
and determining a given direct-current component parameter based on the voltage difference of the positive bus and the negative bus, and giving the given direct-current component parameter as the alternating-current output of the converter so as to control the voltage difference of the positive bus and the negative bus of the inverter bridge circuit within a preset range after the inverter bridge circuit is electrified.
2. The constant voltage control method of the current transformer according to claim 1, wherein the given dc component parameter is a preset given voltage, and the preset given voltage is given as an ac output of the current transformer;
the preset given voltage comprises a given standard alternating current voltage and a preset direct current voltage component.
3. The method for constant voltage control of a current transformer according to claim 2, wherein the step of setting the given dc component parameter as the ac output of the current transformer to control the voltage difference between the positive and negative buses of the inverter bridge circuit within a predetermined range after power-up comprises:
outputting a matched inversion regulating signal to the inverter bridge circuit according to the preset given voltage so that the filter circuit outputs the preset given voltage to the transformer to drive the transformer to generate total magnetic flux corresponding to the preset given voltage;
the accumulated magnetic flux of the preset direct-current voltage component counteracts the initial direct-current magnetic flux in the total magnetic flux of the transformer, so that the voltage difference of positive and negative buses of the inverter bridge circuit is controlled within a preset range after the inverter bridge circuit is electrified.
4. The constant voltage control method of the inverter as claimed in claim 3, wherein the step of the accumulated magnetic flux of the predetermined dc voltage component canceling the initial dc magnetic flux of the total magnetic flux of the transformer comprises:
and setting the preset direct-current voltage component as the alternating-current output of the converter for a preset action time t, so that the accumulated magnetic flux of the preset direct-current voltage component counteracts the initial direct-current magnetic flux in the total magnetic flux of the transformer.
5. The constant voltage control method of the current transformer as claimed in claim 1, wherein the given dc component parameter is a compensation current;
the step of determining a given direct-current component parameter based on the voltage difference between the positive bus and the negative bus, giving the given direct-current component parameter as the alternating-current output of the converter, and controlling the voltage difference between the positive bus and the negative bus of the inverter bridge circuit within a preset range after the inverter bridge circuit is powered on specifically comprises the following steps:
determining a compensation current based on the voltage difference of the positive bus and the negative bus;
and inputting the compensation current into the transformer as a given direct current component parameter to generate a direct current with a corresponding size and direction, offsetting the direct current component current generated by the transformer, and eliminating the excitation inrush current so as to control the voltage difference of the positive bus and the negative bus of the inverter bridge circuit within a preset range.
6. The constant voltage control method of the current transformer of claim 2, further comprising:
the given direct-current component parameter is given as alternating-current output, and constant-voltage control is performed by adopting a voltage ring so as to control the voltage difference of positive and negative buses of the converter within a preset range after the converter is electrified;
the input parameters of the voltage ring are as follows: and the sum of the product of the positive and negative bus voltage difference multiplied by the proportionality coefficient and the given standard alternating voltage.
7. The constant-voltage control circuit of the converter is characterized in that the converter comprises an inverter bridge circuit, a filter circuit and a transformer which are sequentially connected;
the constant voltage control circuit includes:
the sampling circuit is correspondingly connected with the inverter bridge circuit and is used for sampling positive and negative bus voltage, output voltage and output current of the inverter bridge circuit;
the control circuit is respectively connected with the inverter bridge circuit and the sampling circuit, and the control circuit is used for realizing the steps of the constant voltage control method of the converter according to any one of claims 1 to 6 according to the sampling signal output by the sampling circuit.
8. The constant voltage control circuit of the current transformer as claimed in claim 7, wherein the sampling circuit comprises a current sampling circuit and a voltage sampling circuit.
9. A converter assembly, characterized by comprising a constant voltage control circuit of a converter according to claim 7 or 8;
the converter comprises an inverter bridge circuit, a filter circuit and a transformer which are connected in sequence, and the constant voltage control circuit is correspondingly connected with the inverter bridge circuit.
10. The converter assembly of claim 9, wherein the inverter bridge circuit comprises an inverter bridge and a bus capacitor coupled across the inverter bridge, the bus capacitor comprising a first capacitor and a second capacitor connected in series;
a connection node of the first capacitor and the second capacitor, a neutral point of the transformer and a grounding end of the filter circuit are connected in common;
the inverter bridge is a two-level inverter bridge or a three-level inverter bridge.
CN202211114037.8A 2022-09-14 2022-09-14 Constant voltage control method and circuit of converter and converter assembly Pending CN115441715A (en)

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Applications Claiming Priority (1)

Application Number Priority Date Filing Date Title
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