WO2022068222A1 - 一种级联式电力电子变压器及其控制方法 - Google Patents

一种级联式电力电子变压器及其控制方法 Download PDF

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Publication number
WO2022068222A1
WO2022068222A1 PCT/CN2021/095148 CN2021095148W WO2022068222A1 WO 2022068222 A1 WO2022068222 A1 WO 2022068222A1 CN 2021095148 W CN2021095148 W CN 2021095148W WO 2022068222 A1 WO2022068222 A1 WO 2022068222A1
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transformer
voltage
output
electrical angle
converter
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PCT/CN2021/095148
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English (en)
French (fr)
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董钺
庄加才
徐君
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阳光电源股份有限公司
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Priority to US18/010,435 priority Critical patent/US20230231466A1/en
Priority to JP2022562772A priority patent/JP7389923B2/ja
Priority to EP21873884.7A priority patent/EP4224694A1/en
Publication of WO2022068222A1 publication Critical patent/WO2022068222A1/zh

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    • H—ELECTRICITY
    • H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
    • H02M—APPARATUS FOR CONVERSION BETWEEN AC AND AC, BETWEEN AC AND DC, OR BETWEEN DC AND DC, AND FOR USE WITH MAINS OR SIMILAR POWER SUPPLY SYSTEMS; CONVERSION OF DC OR AC INPUT POWER INTO SURGE OUTPUT POWER; CONTROL OR REGULATION THEREOF
    • H02M3/00—Conversion of dc power input into dc power output
    • H02M3/22—Conversion of dc power input into dc power output with intermediate conversion into ac
    • H02M3/24—Conversion of dc power input into dc power output with intermediate conversion into ac by static converters
    • H02M3/28—Conversion of dc power input into dc power output with intermediate conversion into ac by static converters using discharge tubes with control electrode or semiconductor devices with control electrode to produce the intermediate ac
    • H02M3/325—Conversion of dc power input into dc power output with intermediate conversion into ac by static converters using discharge tubes with control electrode or semiconductor devices with control electrode to produce the intermediate ac using devices of a triode or a transistor type requiring continuous application of a control signal
    • H02M3/335—Conversion of dc power input into dc power output with intermediate conversion into ac by static converters using discharge tubes with control electrode or semiconductor devices with control electrode to produce the intermediate ac using devices of a triode or a transistor type requiring continuous application of a control signal using semiconductor devices only
    • H02M3/33561—Conversion of dc power input into dc power output with intermediate conversion into ac by static converters using discharge tubes with control electrode or semiconductor devices with control electrode to produce the intermediate ac using devices of a triode or a transistor type requiring continuous application of a control signal using semiconductor devices only having more than one ouput with independent control
    • H—ELECTRICITY
    • H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
    • H02M—APPARATUS FOR CONVERSION BETWEEN AC AND AC, BETWEEN AC AND DC, OR BETWEEN DC AND DC, AND FOR USE WITH MAINS OR SIMILAR POWER SUPPLY SYSTEMS; CONVERSION OF DC OR AC INPUT POWER INTO SURGE OUTPUT POWER; CONTROL OR REGULATION THEREOF
    • H02M1/00—Details of apparatus for conversion
    • H02M1/0003—Details of control, feedback or regulation circuits
    • H02M1/0025—Arrangements for modifying reference values, feedback values or error values in the control loop of a converter
    • 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
    • H02M1/0067—Converter structures employing plural converter units, other than for parallel operation of the units on a single load
    • H02M1/0074—Plural converter units whose inputs are connected in series
    • H—ELECTRICITY
    • H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
    • H02M—APPARATUS FOR CONVERSION BETWEEN AC AND AC, BETWEEN AC AND DC, OR BETWEEN DC AND DC, AND FOR USE WITH MAINS OR SIMILAR POWER SUPPLY SYSTEMS; CONVERSION OF DC OR AC INPUT POWER INTO SURGE OUTPUT POWER; CONTROL OR REGULATION THEREOF
    • H02M1/00—Details of apparatus for conversion
    • H02M1/08—Circuits specially adapted for the generation of control voltages for semiconductor devices incorporated in static converters
    • H02M1/081—Circuits specially adapted for the generation of control voltages for semiconductor devices incorporated in static converters wherein the phase of the control voltage is adjustable with reference to the AC source
    • H—ELECTRICITY
    • H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
    • H02M—APPARATUS FOR CONVERSION BETWEEN AC AND AC, BETWEEN AC AND DC, OR BETWEEN DC AND DC, AND FOR USE WITH MAINS OR SIMILAR POWER SUPPLY SYSTEMS; CONVERSION OF DC OR AC INPUT POWER INTO SURGE OUTPUT POWER; CONTROL OR REGULATION THEREOF
    • H02M3/00—Conversion of dc power input into dc power output
    • H02M3/22—Conversion of dc power input into dc power output with intermediate conversion into ac
    • H02M3/24—Conversion of dc power input into dc power output with intermediate conversion into ac by static converters
    • H02M3/28—Conversion of dc power input into dc power output with intermediate conversion into ac by static converters using discharge tubes with control electrode or semiconductor devices with control electrode to produce the intermediate ac
    • H02M3/325—Conversion of dc power input into dc power output with intermediate conversion into ac by static converters using discharge tubes with control electrode or semiconductor devices with control electrode to produce the intermediate ac using devices of a triode or a transistor type requiring continuous application of a control signal
    • H02M3/335—Conversion of dc power input into dc power output with intermediate conversion into ac by static converters using discharge tubes with control electrode or semiconductor devices with control electrode to produce the intermediate ac using devices of a triode or a transistor type requiring continuous application of a control signal using semiconductor devices only
    • H02M3/33569—Conversion of dc power input into dc power output with intermediate conversion into ac by static converters using discharge tubes with control electrode or semiconductor devices with control electrode to produce the intermediate ac using devices of a triode or a transistor type requiring continuous application of a control signal using semiconductor devices only having several active switching elements
    • H02M3/33576—Conversion of dc power input into dc power output with intermediate conversion into ac by static converters using discharge tubes with control electrode or semiconductor devices with control electrode to produce the intermediate ac using devices of a triode or a transistor type requiring continuous application of a control signal using semiconductor devices only having several active switching elements having at least one active switching element at the secondary side of an isolation transformer
    • 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
    • H02M7/4807—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 having a high frequency intermediate AC stage
    • 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
    • H02M1/0067—Converter structures employing plural converter units, other than for parallel operation of the units on a single load
    • H02M1/007—Plural converter units in cascade
    • 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
    • H02M1/0067—Converter structures employing plural converter units, other than for parallel operation of the units on a single load
    • H02M1/0077—Plural converter units whose outputs are connected in series
    • 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
    • H02M1/0067—Converter structures employing plural converter units, other than for parallel operation of the units on a single load
    • H02M1/008—Plural converter units for generating at two or more independent and non-parallel outputs, e.g. systems with plural point of load switching regulators
    • 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
    • H02M7/02—Conversion of ac power input into dc power output without possibility of reversal
    • H02M7/04—Conversion of ac power input into dc power output without possibility of reversal by static converters
    • H02M7/12—Conversion of ac power input into dc power output without possibility of reversal by static converters using discharge tubes with control electrode or semiconductor devices with control electrode
    • H02M7/21—Conversion of ac power input into dc 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
    • H02M7/217—Conversion of ac power input into dc 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
    • 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
    • H02M7/02—Conversion of ac power input into dc power output without possibility of reversal
    • H02M7/04—Conversion of ac power input into dc power output without possibility of reversal by static converters
    • H02M7/12—Conversion of ac power input into dc power output without possibility of reversal by static converters using discharge tubes with control electrode or semiconductor devices with control electrode
    • H02M7/21—Conversion of ac power input into dc 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
    • H02M7/217—Conversion of ac power input into dc 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
    • H02M7/23—Conversion of ac power input into dc 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 arranged for operation in parallel
    • 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
    • H02M7/483—Converters with outputs that each can have more than two voltages levels
    • 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
    • H02M7/483—Converters with outputs that each can have more than two voltages levels
    • H02M7/49—Combination of the output voltage waveforms of a plurality of converters
    • 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
    • H02M7/493—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 the static converters being arranged for operation in parallel

Definitions

  • the present application relates to the technical field of power electronics, and more particularly, to a cascaded power electronic transformer and a control method thereof.
  • FIG. 1 shows a cascaded power electronic transformer, and its single-phase topology is: each phase includes n transformers, each transformer has m primary side windings and r secondary side windings, n+m ⁇ 3 , r ⁇ 1, each primary side winding is connected in series with a DC/AC converter, and each secondary side winding is connected in series with an AC/DC converter; the DC sides of the n*m DC/AC converters pass through each A front-stage converter is connected in series to obtain the input port of the cascaded power electronic transformer; the cascaded power electronic transformer has one or more output ports, and each of the output ports is passed from each transformer. Each secondary side selects at least one AC/DC converter, and then connects the DC sides of these AC/DC converters in series and parallel to obtain.
  • the present application provides a cascaded power electronic transformer and a control method thereof, so as to realize power balance control between different primary side windings in the cascaded power electronic transformer.
  • each phase of the cascaded power electronic transformer includes n transformers, each transformer has m primary side windings and r secondary side windings, n ⁇ 2, m ⁇ 2, r ⁇ 1, each primary side winding is connected in series with a DC/AC converter, and each secondary side winding is connected in series with an AC/DC converter; the direct current of n*m said DC/AC converters
  • the input ports of the cascaded power electronic transformers are formed in series after passing through a front-stage converter on each side; the cascaded power electronic transformers have one or more output ports, and each output port is Each of the secondary sides of each transformer selects at least one AC/DC converter, and then the DC sides of these AC/DC converters are connected in series and parallel to form;
  • the cascaded power electronic transformer control method includes:
  • the DC/AC converter whose ith primary side winding is connected in series is abbreviated as the ith primary side converter
  • the AC/DC converter whose kth secondary side winding is connected in series It is abbreviated as the k-th secondary-side converter
  • its first primary-side converter bridge arm voltage is used as the reference voltage
  • the reference voltages corresponding to the transformers in the same phase are equal, and the reference voltages corresponding to the transformers in the same position of the three-phase are staggered by 2 ⁇ /3 electrical angle;
  • the sum of the DC link currents of the m primary side converters of the transformer is divided by m, as the current given, and it is subtracted from the DC link current I dcij of the ith primary side converter of the s th transformer, through the th
  • a regulator calculates and outputs the electrical angle ⁇ i1 of the s-th transformer; on the premise that the power balance between different secondary windings under the same output port is realized by adjusting the electrical angles ⁇ 1ps , ⁇ 2ps , ...
  • the compensation electrical angle ⁇ j is superimposed to obtain the compensated electrical angle ⁇ kps of the j th transformer;
  • the bridge arm voltage square waves of the primary side and secondary side converters of the s th transformer are calculated.
  • the electrical angle ⁇ i1 and the electrical angle ⁇ kps of the s th transformer are calculated to obtain each primary of the s th transformer.
  • the bridge arm voltage square wave of the side and secondary side converters including:
  • the duty cycle D 1 of the first primary-side converter of the s-th transformer is calculated according to the electrical angle ⁇ 11 and the electrical angle ⁇ kps of the s-th transformer, and the electrical angle ⁇ of the s-th transformer is obtained i1 and the electrical angle ⁇ kps are calculated to obtain the duty cycle D i of the ith primary side converter of the s th transformer;
  • ⁇ 11 represents the difference between the bridge arm voltage of the first primary side converter of the s th transformer and itself electrical angle, that is, zero;
  • the bridge arm voltage square wave of the first primary side converter of the s th transformer is calculated, and according to the electrical angle ⁇ i1 of the s th transformer and the duty cycle
  • the square wave of the bridge arm voltage of the i-th primary side converter of the s-th transformer is calculated from the ratio D i
  • the k-th secondary voltage of the s-th transformer is calculated according to the compensated electrical angle ⁇ kps of the s-th transformer.
  • the voltage square wave of the bridge arm of the side converter is calculated.
  • the electrical angle ⁇ kps of the s-th transformer is calculated and obtained, including:
  • the DC link voltage loop corresponding to the ith primary side converter of the s th transformer specifically includes:
  • the given DC link voltage U dcref of the DC/AC converters on the primary side of all transformers is equal ; After the DC link voltage U dcis of the converter is subtracted, it is calculated and output by the third regulator as the output of the DC link voltage loop;
  • control loop designed for the h-th series branch of the g-th parallel branch under the same output port specifically includes:
  • constant current output is required: divide the output power given Poref of the output port by p*q*U o as the current given of each parallel branch of each series branch, so as to realize the current sharing of each parallel branch ; After subtracting the given current from the output current I ogh of the h th series branch of the g th parallel branch, the sixth regulator is used to calculate the output; at the same time, the voltage of the q series branches is calculated After the summation is divided by q as the voltage reference of each series branch to realize the voltage equalization of each series branch; the voltage reference is combined with the output voltage U of the hth series branch of the gth parallel branch. After the ogh is subtracted, the output is calculated by the seventh regulator, and the sum of the output of the sixth regulator is used as the output of the control loop.
  • the cascaded power electronic transformer control method further includes: performing a power frequency secondary operation on the DC link of each primary side converter of each transformer, respectively. harmonic suppression;
  • the DC link of a single primary side converter of a single transformer is subjected to power frequency second harmonic suppression, specifically: the DC current of the primary side converter passes through a 100Hz second-order band-pass filter to extract the power frequency second harmonic.
  • the second harmonic component of the power frequency is fed back and given as 0.
  • the proportional resonance controller with a resonance frequency of 100Hz is used to calculate the output, and the output result is superimposed on the compensation before the converter. electrical angle ⁇ kps .
  • a cascaded power electronic transformer includes a main circuit and a controller, each phase of the main circuit includes n transformers, each transformer has m primary side windings and r secondary side windings, n ⁇ 2, m ⁇ 2, r ⁇ 1, each primary side winding is connected in series with a DC/AC converter, and each secondary side winding is connected in series with an AC/DC converter; the DC side of n*m said DC/AC converters
  • the input ports of the cascaded power electronic transformers are formed in series after passing through a front-stage converter; the cascaded power electronic transformers have one or more output ports, and each output port is At least one AC/DC converter is selected for each secondary side of the transformer, and then the DC sides of these AC/DC converters are connected in series and parallel to form;
  • the controller includes a processor, a memory and a program stored on the memory and can run on the processor, and the processor implements the following steps when executing the program:
  • the DC/AC converter whose ith primary side winding is connected in series is abbreviated as the ith primary side converter
  • the AC/DC converter whose kth secondary side winding is connected in series It is abbreviated as the k-th secondary-side converter
  • its first primary-side converter bridge arm voltage is used as the reference voltage
  • the reference voltages corresponding to the transformers in the same phase are equal, and the reference voltages corresponding to the transformers in the same position of the three-phase are staggered by 2 ⁇ /3 electrical angle;
  • the sum of the DC link currents of the m primary side converters of the transformer is divided by m, as the current given, it is subtracted from the DC link current I dcis of the ith primary side converter of the s th transformer, and passed through the A regulator calculates and outputs the electrical angle ⁇ i1 of the s-th transformer; on the premise that the power balance between different secondary windings under the same output port is realized by adjusting the electrical angles ⁇ 1ps , ⁇ 2ps , ..., ⁇
  • the compensation electrical angle ⁇ j is superimposed to obtain the compensated electrical angle ⁇ kps of the j th transformer;
  • the bridge arm voltage square waves of the primary side and secondary side converters of the s th transformer are calculated.
  • the processor implements that after compensation, the calculation of the electrical angle ⁇ i1 of the s th transformer and the electrical angle ⁇ kps of the s th transformer obtains the electrical angle ⁇ of the s th transformer.
  • the step of the bridge arm voltage square wave of each primary side and secondary side converter includes:
  • the duty cycle D 1 of the first primary-side converter of the s-th transformer is calculated according to the electrical angle ⁇ 11 and the electrical angle ⁇ kps of the s-th transformer, and the electrical angle ⁇ of the s-th transformer is obtained i1 and the electrical angle ⁇ kps are calculated to obtain the duty cycle D i of the ith primary side converter of the s th transformer;
  • ⁇ 11 represents the difference between the bridge arm voltage of the first primary side converter of the s th transformer and itself electrical angle, that is, zero;
  • the bridge arm voltage square wave of the first primary side converter of the s th transformer is calculated, and according to the electrical angle ⁇ i1 of the s th transformer and the duty cycle
  • the square wave of the bridge arm voltage of the i-th primary side converter of the s-th transformer is calculated from the ratio D i
  • the k-th secondary voltage of the s-th transformer is calculated according to the compensated electrical angle ⁇ kps of the s-th transformer.
  • the voltage square wave of the bridge arm of the side converter is calculated.
  • the calculation performed by the processor to obtain the electrical angle ⁇ kps of the s-th transformer includes:
  • the DC link voltage loop corresponding to the ith primary side converter of the s th transformer specifically includes:
  • the given DC link voltage U dcref of the DC/AC converters on the primary side of all transformers is equal ; After the DC link voltage U dcis of the converter is subtracted, it is calculated and output by the third regulator as the output of the DC link voltage loop;
  • control loop designed for the h-th series branch of the g-th parallel branch under the same output port specifically includes:
  • constant current output is required: divide the output power given Poref of the output port by p*q*U o as the current given of each parallel branch of each series branch, so as to realize the current sharing of each parallel branch ; After subtracting the given current from the output current I ogh of the h th series branch of the g th parallel branch, the sixth regulator is used to calculate the output; at the same time, the voltage of the q series branches is calculated After the summation is divided by q as the voltage reference of each series branch to realize the voltage equalization of each series branch; the voltage reference is combined with the output voltage U of the hth series branch of the gth parallel branch. After the ogh is subtracted, the output is calculated by the seventh regulator, and the sum of the output of the sixth regulator is used as the output of the control loop.
  • the processor further implements the step of performing power frequency second harmonic suppression for each primary-side converter DC link of each transformer;
  • the power frequency second harmonic suppression is performed for the DC link of a single primary side converter of a single transformer, including:
  • the DC current of the primary side converter passes through a 100Hz second-order band-pass filter, extracts the second harmonic component of the power frequency, and feeds back the second harmonic component of the power frequency, and sets it as 0. After subtracting the two
  • the calculation output is performed by a proportional resonance controller with a resonance frequency of 100 Hz, and the output result is superimposed on the electrical angle ⁇ kps before compensation.
  • the present application adjusts the electrical angles ⁇ 21 , ⁇ 31 , . . . , ⁇ m1 to realize the power flow between different primary side windings in the same transformer, and then realize the power balance between different primary side windings in the same transformer.
  • the present application adjusts the electrical angles ⁇ 1ps , ⁇ 2ps , ⁇ 2ps , ..., ⁇ rps to realize the power flow between different secondary side windings under the same output port, and then realize the power balance between different secondary side converters under the same output port; Compensating electrical angles ⁇ 2 , ⁇ 3 , .
  • the present application achieves power balance between different primary side windings in the same transformer and between different transformers, it also achieves power balance among different primary side windings in the entire cascaded power electronic transformer.
  • 1 is a schematic structural diagram of a cascaded power electronic transformer
  • FIG. 2 is a flowchart of a method for controlling a cascaded power electronic transformer disclosed in an embodiment of the application;
  • FIG. 3 is a control block diagram of a cascaded power electronic transformer disclosed in an embodiment of the application.
  • Fig. 4 is the control block diagram of calculating duty ratio D i ;
  • FIG. 5 is a block diagram of the corresponding relationship between the electrical angle ⁇ i1 , the duty cycle D i , the electrical angle ⁇ kps and the converter;
  • Fig. 6 is the voltage timing diagram between different windings on the same transformer
  • FIG. 7 is a flowchart of a method for calculating and obtaining the electrical angle ⁇ kps of the s-th transformer disclosed in an embodiment of the present application.
  • the embodiment of the present application discloses a control method for a cascaded power electronic transformer, which is applied to the cascaded power electronic transformer shown in FIG. 1 .
  • the cascaded power electronic transformer control method includes:
  • Step S02 superimposing the compensated electrical angle ⁇ j on the basis of the electrical angle ⁇ kps of the j th transformer to obtain the compensated electrical angle ⁇ kps of the j th transformer.
  • the DC/AC converter in which the i-th primary side winding of the s-th transformer is connected in series is simply referred to as the i-th transformer of the s-th transformer.
  • a primary side converter, the AC/DC converter in which the kth secondary side winding of the sth transformer is connected in series is referred to as the kth secondary side converter of the sth transformer for short.
  • the same transformer can be realized by adjusting the electrical angle between the bridge arm voltages of different primary side converters in the same transformer.
  • the power flow between different primary windings in the same transformer is realized, and the power balance between different primary windings in the same transformer is realized.
  • any output port of the cascaded power electronic transformer since there is at least one secondary winding in each transformer to form an electrical connection through the AC/DC converter, it can be adjusted by adjusting different secondary windings under the same output port.
  • the electrical angle between the bridge arm voltages of the side converter is used to realize the power flow between different secondary side windings under the same output port, thereby realizing the power balance between different secondary side windings under the same output port.
  • the bridge arm voltage of the first primary side converter is used as the reference voltage (all corresponding transformers in the same phase).
  • the difference in the line parameters of different transformers will lead to power imbalance when different transformers apply the same electrical angle between the primary side converter bridge arm voltage and the secondary side converter bridge arm voltage, so by adjusting the electrical angle
  • ⁇ 1ps , ⁇ 2ps , ..., ⁇ rps are used to balance control between different secondary windings under the same output port
  • the first transformer can be used as a reference, and the electrical angles ⁇ 1ps and ⁇ of the remaining n-1 transformers can be measured.
  • the embodiment of the present application designs a primary-side winding balance control current loop (refer to the reference numeral 100 in FIG. 3 ) for m-1 primary-side windings under each transformer, and adjusts the electrical angle by adjusting the electrical angle.
  • a transformer balance control current loop is designed for n-1 transformers in each phase (see Figure 3).
  • Reference numeral 200) in the following description in conjunction with FIG. 3 its working principle is as follows:
  • the balanced control current loop corresponding to the i-th primary side winding of the s-th transformer takes the sum of the DC link currents of the m primary-side converters of the s-th transformer and divides it by m, as a given current, and compares it with the s-th transformer After the DC link current I dcis of the ith primary side converter of the transformer is subtracted, the electrical angle ⁇ i1 of the s th transformer is output through a first calculation (eg, a PI regulator).
  • a first calculation eg, a PI regulator
  • the transformer balance control current loop corresponding to the jth transformer takes the sum of the DC link currents of m*n primary-side converters in each phase and divides it by n, as the current given, and the m primary-side converter DC links of the jth transformer are divided by n.
  • the output electrical angle ⁇ j is calculated by a second regulator (eg, a PI regulator).
  • the compensated electrical angle ⁇ j is superimposed on the electrical angle ⁇ kps of the j th transformer to obtain the compensated electrical angle ⁇ kps of the j th transformer.
  • Step S03 After compensation, calculate and obtain the bridge arm voltage square waves of the primary side and secondary side converters of the s th transformer according to the electrical angle ⁇ i1 and the electrical angle ⁇ kps of the s th transformer.
  • step S03 the electrical angle ⁇ i1 of the s-th transformer, the electrical angle ⁇ kps of the first transformer, and the compensated electrical angle of the j-th transformer calculated in steps S01 to S02 ⁇ kps is put into use to complete the operation control of cascaded power electronic transformers. At this time, power balance control between different primary windings in the same transformer and between different transformers can be realized.
  • the square wave of the bridge arm voltage of each primary side and secondary side converter of the s th transformer is calculated according to the electrical angle ⁇ i1 and the electrical angle ⁇ kps of the s th transformer, specifically including:
  • the square wave of the bridge arm voltage of the The square wave of the bridge arm voltage of the k-th secondary side converter of the s-th transformer is obtained by calculating the electrical angle ⁇ kps of the s-th transformer, and the corresponding control block diagram is shown in Figure 5.
  • the voltage sequence between different windings on the same transformer is shown in Figure 6.
  • the waveforms from top to bottom are: the first primary side converter bridge arm voltage waveform, the first secondary side converter bridge arm voltage waveform, The bridge arm voltage waveform of the i-th primary side converter and the bridge arm voltage waveform of the k-th secondary side converter.
  • the embodiments of the present application adjust the electrical angle by adjusting the electrical angle. ⁇ 21 , ⁇ 31 , .
  • the embodiment of the present application also adjusts the electrical angle ⁇ 1ps , ⁇ 2ps , . Compensation electrical angles ⁇ 2 , ⁇ 3 , .
  • the way to obtain the electrical angle ⁇ kps of the s-th transformer is to realize the power between different secondary windings under the same output port by adjusting the electrical angles ⁇ 1ps , ⁇ 2ps , ..., ⁇ rps
  • the balanced method can be directly implemented by the existing calculation method.
  • Step S011 operate the DC link voltage loop corresponding to the i-th primary side converter of the s-th transformer
  • the DC link voltage given U dcref of the DC/AC converters on the primary side of all transformers is equal.
  • the DC link voltage loop of the i-th primary-side converter of the s-th transformer (refer to the reference numeral 300 in FIG. 3 for the corresponding control block diagram) connects the DC-link voltage given U dcref with the DC-link voltage of this primary-side converter After U dcis is subtracted, the output is calculated by a third regulator (for example, a PI regulator) as the output of the DC link voltage loop.
  • a third regulator for example, a PI regulator
  • Step S012 Run the control loop designed for the h-th series branch of the g-th parallel branch under the same output port.
  • constant voltage output ie voltage mode: divide the given voltage Uoref of the output port by q as the given voltage of each series branch to achieve voltage equalization of each series branch; divide each series branch After dividing the given voltage U oref of the circuit by q, it is subtracted from the actual value of the voltage U oh , and the output is calculated by the fourth regulator (such as a PI regulator), and the output result is multiplied by 1/p as the current of each parallel branch.
  • the fourth regulator such as a PI regulator
  • constant current output (ie current mode) is required: divide the output power given Poref of the output port by p*q*U o as the current given of each parallel branch of each series branch, so as to realize each parallel connection
  • the sixth regulator for example, a PI regulator
  • the voltages of the q series branches are summed and divided by q as the voltage reference of each series branch, so as to realize the voltage equalization of each series branch; the voltage reference is combined with the gth parallel branch
  • the output is calculated by a seventh regulator (eg, a PI regulator), and the sum of the output of the sixth regulator and the output of the sixth regulator is used as the output of the control loop.
  • Step S013 adding the output of the DC link voltage loop and the output of the control loop to obtain an electrical angle ⁇ kps before compensation.
  • control method further includes: performing power-frequency second harmonic suppression for each primary-side converter DC link of each transformer (for the corresponding control block diagram, see FIG. 3 ). 600).
  • the power frequency second harmonic suppression is performed for the DC link of a single primary side converter of a single transformer, specifically:
  • the DC current of the primary side converter passes through a 100Hz second-order band-pass filter, extracts the second harmonic component of the power frequency, and feeds back the second harmonic component of the power frequency, and sets it as 0. After subtracting the two
  • the proportional resonance controller with the resonance frequency of 100Hz is used to calculate the output, and the output result is superimposed on the electric angle ⁇ kps before the compensation of the converter.
  • the embodiments of the present application further disclose a cascaded power electronic transformer, which includes a main circuit and a controller.
  • Each phase of the main circuit includes n transformers, each transformer has m primary side windings and r secondary side windings, n ⁇ 2, m ⁇ 2, r ⁇ 1, each primary side winding is connected in series with a DC /AC converter, each secondary side winding is connected in series with an AC/DC converter;
  • the DC sides of the n*m DC/AC converters each pass through a front-stage converter and are connected in series to form the cascaded power Input ports of electronic transformers;
  • the cascaded power electronic transformers have one or more output ports, each of which is obtained by selecting at least one AC/DC converter from the secondary side of each transformer, and then The DC sides of these AC/DC converters are formed in series and parallel;
  • the controller includes a processor, a memory and a program stored on the memory and can run on the processor, and the processor implements the following steps when executing the program:
  • the DC/AC converter whose ith primary side winding is connected in series is abbreviated as the ith primary side converter
  • the AC/DC converter whose kth secondary side winding is connected in series It is abbreviated as the k-th secondary-side converter
  • its first primary-side converter bridge arm voltage is used as the reference voltage
  • the reference voltages corresponding to the transformers in the same phase are equal, and the reference voltages corresponding to the transformers in the same position of the three-phase are staggered by 2 ⁇ /3 electrical angle;
  • the sum of the DC link currents of the m primary side converters of the transformer is divided by m, as the current given, it is subtracted from the DC link current I dcis of the ith primary side converter of the s th transformer, and passed through the A regulator calculates and outputs the electrical angle ⁇ i1 of the s-th transformer; on the premise that the power balance between different secondary windings under the same output port is realized by adjusting the electrical angles ⁇ 1ps , ⁇ 2ps , ..., ⁇
  • the compensation electrical angle ⁇ j is superimposed to obtain the compensated electrical angle ⁇ kps of the j th transformer;
  • the bridge arm voltage square waves of the primary side and secondary side converters of the s th transformer are calculated.
  • the processor implements that after compensation, the calculation of the electrical angle ⁇ i1 of the s th transformer and the electrical angle ⁇ kps of the s th transformer obtains the electrical angle ⁇ of the s th transformer.
  • the step of the bridge arm voltage square wave of each primary side and secondary side converter includes:
  • the duty cycle D 1 of the first primary-side converter of the s-th transformer is calculated according to the electrical angle ⁇ 11 and the electrical angle ⁇ kps of the s-th transformer, and the electrical angle ⁇ of the s-th transformer is obtained i1 and the electrical angle ⁇ kps are calculated to obtain the duty cycle D i of the ith primary side converter of the s th transformer;
  • ⁇ 11 represents the difference between the bridge arm voltage of the first primary side converter of the s th transformer and itself electrical angle, that is, zero;
  • the bridge arm voltage square wave of the first primary side converter of the s th transformer is calculated, and according to the electrical angle ⁇ i1 of the s th transformer and the duty cycle
  • the square wave of the bridge arm voltage of the i-th primary side converter of the s-th transformer is calculated from the ratio D i
  • the k-th secondary voltage of the s-th transformer is calculated according to the compensated electrical angle ⁇ kps of the s-th transformer.
  • the voltage square wave of the bridge arm of the side converter is calculated.
  • the calculation performed by the processor to obtain the electrical angle ⁇ kps of the s-th transformer includes:
  • the DC link voltage loop corresponding to the ith primary side converter of the s th transformer specifically includes:
  • the given DC link voltage U dcref of the DC/AC converters on the primary side of all transformers is equal ; After the DC link voltage U dcis of the converter is subtracted, it is calculated and output by the third regulator as the output of the DC link voltage loop;
  • control loop designed for the h-th series branch of the g-th parallel branch under the same output port specifically includes:
  • constant current output is required: divide the output power given Poref of the output port by p*q*U o as the current given of each parallel branch of each series branch, so as to realize the current sharing of each parallel branch ; After subtracting the given current from the output current I ogh of the h th series branch of the g th parallel branch, the sixth regulator is used to calculate the output; at the same time, the voltage of the q series branches is calculated After the summation is divided by q as the voltage reference of each series branch to realize the voltage equalization of each series branch; the voltage reference is combined with the output voltage U of the hth series branch of the gth parallel branch. After the ogh is subtracted, the output is calculated by the seventh regulator, and the sum of the output of the sixth regulator is used as the output of the control loop.
  • the processor further implements the step of performing power frequency second harmonic suppression for each primary-side converter DC link of each transformer;
  • the power frequency second harmonic suppression is performed for the DC link of a single primary side converter of a single transformer, including:
  • the DC current of the primary side converter passes through a 100Hz second-order band-pass filter, extracts the second harmonic component of the power frequency, and feeds back the second harmonic component of the power frequency, and sets it as 0. After subtracting the two
  • the calculation output is performed by a proportional resonance controller with a resonance frequency of 100 Hz, and the output result is superimposed on the electrical angle ⁇ kps before compensation.

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Abstract

本申请公开了一种级联式电力电子变压器及其控制方法，实现了不同一次侧绕组间的功率均衡。该方法包括：计算第s个变压器的θi1和θkps，以及第j个变压器的θj；s＝1、2、…、n；在同一变压器中，以第一个一次侧变换器桥臂电压为基准，第i个一次侧变换器桥臂电压与该基准之间的电角度为θi1，i＝2、3、…、m，第k个二次侧变换器桥臂电压与该基准之间的电角度为θkps，k＝1、2、…、r，第j个变压器的一、二次侧变换器桥臂电压之间的补偿电角度为θj，j＝2、3、…、n；在第j个变压器的θkps的基础上叠加θj，得到补偿后的θkps；在补偿后，将第s个变压器的θi1和θkps投入使用。

Description

一种级联式电力电子变压器及其控制方法
本申请要求于2020年09月30日提交中国专利局、申请号为202011069564.2、申请名称为“一种级联式电力电子变压器及其控制方法”的中国专利申请的优先权，其全部内容通过引用结合在本申请中。
技术领域
本申请涉及电力电子技术领域，更具体地说，涉及一种级联式电力电子变压器及其控制方法。
背景技术
图1示出了一种级联式电力电子变压器，其单相拓扑结构为：每相包括n个变压器，每个变压器具有m个一次侧绕组和r个二次侧绕组，n+m≥3，r≥1，每个一次侧绕组串接一个DC/AC变换器，每个二次侧绕组串接一个AC/DC变换器；n*m个所述DC/AC变换器的直流侧各经过一个前级变换器后串联得到所述级联式电力电子变压器的输入端口；所述级联式电力电子变压器具有一个或多个输出端口，每个所述输出端口都是通过从每个变压器的二次侧各选取至少一个AC/DC变换器，然后将这些AC/DC变换器的直流侧进行串并联得到。
但是，目前还没有一种控制方式能够实现所述级联式电力电子变压器内不同一次侧绕组之间的功率均衡控制。
申请内容
有鉴于此，本申请提供一种级联式电力电子变压器及其控制方法，以实现所述级联式电力电子变压器内不同一次侧绕组之间的功率均衡控制。
一种级联式电力电子变压器控制方法，其中，所述级联式电力电子变压器的每相包括n个变压器，每个变压器具有m个一次侧绕组和r个二次侧绕组，n≥2，m≥2，r≥1，每个一次侧绕组串接一个DC/AC变换器，每个二次侧绕组串接一个AC/DC变换器；n*m个所述DC/AC变换器的直流侧各经过一个 前级变换器后串联构成所述级联式电力电子变压器的输入端口；所述级联式电力电子变压器具有一个或多个输出端口，每个所述输出端口都是通过从每个变压器的二次侧各选取至少一个AC/DC变换器，然后将这些AC/DC变换器的直流侧进行串并联构成；
所述级联式电力电子变压器控制方法包括：
计算得到第s个变压器的电角度θ i1和θ kps，以及第j个变压器的补偿电角度θ j；s＝1、2、…、n；
其中，在同一变压器中，将其第i个一次侧绕组串接的DC/AC变换器简称为第i个一次侧变换器，将其第k个二次侧绕组串接的AC/DC变换器简称为第k个二次侧变换器，以其第一个一次侧变换器桥臂电压作为基准电压，将第i个一次侧变换器桥臂电压与所述基准电压之间的电角度记为θ i1，i＝2、3、…、m，将第k个二次侧变换器桥臂电压与所述基准电压之间的电角度记为θ kps，k＝1、2、…、r；同相的各个变压器对应的所述基准电压相等，三相同一位置上的变压器对应的所述基准电压之间互错2π/3电角度；将第j个变压器的一次侧变换器桥臂电压和二次侧变换器桥臂电压之间的补偿角度记为θ j，j＝2、3、…、n；则：第s个变压器的第i个一次侧绕组对应的均衡控制电流环取第s个变压器的m个一次侧变换器的直流链电流之和除以m，作为电流给定，将其与第s个变压器的第i个一次侧变换器的直流链电流I dcij相减后，通过第一调节器计算输出第s个变压器的电角度θ i1；在通过调节电角度θ 1ps、θ 2ps、…、θ rps实现同一输出端口下不同二次侧绕组之间功率均衡的前提下，第j个变压器对应的变压器均衡控制电流环取每相m*n个一次侧变换器直流链电流之和除以n，作为电流给定，与第j个变压器的m个一次侧变换器直流链电流之和相减后，通过第二调节器计算输出补偿电角度θ j；
在第j个变压器的电角度θ kps的基础上叠加补偿电角度θ j，得到补偿后的第j个变压器的电角度θ kps；
在补偿后，根据第s个变压器的电角度θ i1以及电角度θ kps计算得到第s个变压器的各一次侧、二次侧变换器的桥臂电压方波。
可选的，在上述公开的任一级联式电力电子变压器控制方法中，所述在补偿后，根据第s个变压器的电角度θ i1以及电角度θ kps计算得到第s个变压器的 各一次侧、二次侧变换器的桥臂电压方波，包括：
在补偿后，根据第s个变压器的电角度θ 11以及电角度θ kps计算得到第s个变压器的第一个一次侧变换器的占空比D 1，以及根据第s个变压器的电角度θ i1以及电角度θ kps计算得到第s个变压器的第i个一次侧变换器的占空比D i；θ 11表示第s个变压器的第1个一次侧变换器桥臂电压与自身之间的电角度，即为零；
根据第s个变压器的电角度θ 11和占空比D 1计算得到第s个变压器的第1个一次侧变换器的桥臂电压方波，根据第s个变压器的电角度θ i1和占空比D i计算得到第s个变压器的第i个一次侧变换器的桥臂电压方波，以及根据第s个变压器的补偿后的电角度θ kps计算得到第s个变压器的第k个二次侧变换器的桥臂电压方波。
可选的，在上述公开的任一级联式电力电子变压器控制方法中，计算得到第s个变压器的电角度θ kps，包括：
运行第s个变压器的第i个一次侧变换器对应的直流链电压环；
运行针对同一输出端口下第g个并联支路的第h个串联支路设计的控制环；
将所述直流链电压环的输出与所述控制环的输出相加得到补偿前的电角度θ kps；
其中，所述运行第s个变压器的第i个一次侧变换器对应的直流链电压环，具体包括：
所有变压器一次侧的DC/AC变换器的直流链电压给定U dcref均相等；第s个变压器的第i个一次侧变换器的直流链电压环将直流链电压给定U dcref与本一次侧变换器的直流链电压U dcis相减后，通过第三调节器计算后输出，作为本直流链电压环的输出；
其中，所述运行针对同一输出端口下第g个并联支路的第h个串联支路设计的控制环，具体包括：
在同一输出端口下，判断本输出端口是要求恒压输出还是恒流输出；
若要求恒压输出：将该输出端口的电压给定Uoref除以q后作为每个串联支路的电压给定，以实现各串联支路的均压；将每个串联支路的电压给定U oref 除以q后和电压实际值U oh相减，通过第四调节器计算输出，输出结果乘以1/p作为每个并联支路的电流给定，以实现各并联支路的均流；将所述电流给定与第g个并联支路的第h个串联支路的输出电流I ogh进行比较，其偏差值经第五调节器计算输出作为所述控制环的输出，g＝1、2、…、p，h＝1、2、…、q；
若要求恒流输出：将该输出端口的输出功率给定Poref除以p*q*U o作为每个串联支路的每个并联支路的电流给定，以实现各并联支路的均流；将所述电流给定与第g个并联支路的第h个串联支路的输出电流I ogh相减后，通过第六调节器进行计算输出；与此同时，将q个串联支路电压求和后除以q作为每个串联支路的电压给定，以实现各串联支路的均压；将所述电压给定与第g个并联支路第h个串联支路的输出电压U ogh相减后，通过第七调节器计算输出，与所述第六调节器的输出之和作为所述控制环的输出。
可选的，在上述公开的任一级联式电力电子变压器控制方法中，所述级联式电力电子变压器控制方法还包括：分别针对各变压器的各一次侧变换器直流链进行工频二次谐波抑制；
其中，针对单个变压器的单个一次侧变换器直流链进行工频二次谐波抑制，具体为：一次侧变换器的直流电流通过100Hz二阶带通滤波器，提取其中的工频二次谐波分量，将此工频二次谐波分量做反馈、以0做给定，两者相减后通过谐振频率为100Hz的比例谐振控制器进行计算输出，其输出结果叠加到本变换器补偿前的电角度θ kps上。
可选的，在上述公开的任一级联式电力电子变压器控制方法中，当n≥2且m＝1时，舍去上述对θ i1的计算。
或者，在上述公开的任一级联式电力电子变压器控制方法中，当n＝1且m≥2时，舍去上述对θ j的计算。
一种级联式电力电子变压器，包括主电路和控制器，所述主电路的每相包括n个变压器，每个变压器具有m个一次侧绕组和r个二次侧绕组，n≥2，m≥2，r≥1，每个一次侧绕组串接一个DC/AC变换器，每个二次侧绕组串接一个AC/DC变换器；n*m个所述DC/AC变换器的直流侧各经过一个前级变换器后串联构成所述级联式电力电子变压器的输入端口；所述级联式电力电子变压器具有一个或多个输出端口，每个所述输出端口都是通过从每个变压器的二 次侧各选取至少一个AC/DC变换器，然后将这些AC/DC变换器的直流侧进行串并联构成；
所述控制器包括处理器、存储器及存储在存储器上并能在处理器上运行的程序，处理器执行程序时实现以下步骤：
计算得到第s个变压器的电角度θ i1和θ kps，以及第j个变压器的补偿电角度θ j；s＝1、2、…、n；
其中，在同一变压器中，将其第i个一次侧绕组串接的DC/AC变换器简称为第i个一次侧变换器，将其第k个二次侧绕组串接的AC/DC变换器简称为第k个二次侧变换器，以其第一个一次侧变换器桥臂电压作为基准电压，将第i个一次侧变换器桥臂电压与所述基准电压之间的电角度记为θ i1，i＝2、3、…、m，将第k个二次侧变换器桥臂电压与所述基准电压之间的电角度记为θ kps，k＝1、2、…、r；同相的各个变压器对应的所述基准电压相等，三相同一位置上的变压器对应的所述基准电压之间互错2π/3电角度；将第j个变压器的一次侧变换器桥臂电压和二次侧变换器桥臂电压之间的补偿角度记为θ j，j＝2、3、…、n；则：第s个变压器的第i个一次侧绕组对应的均衡控制电流环取第s个变压器的m个一次侧变换器的直流链电流之和除以m，作为电流给定，将其与第s个变压器的第i个一次侧变换器的直流链电流I dcis相减后，通过第一调节器计算输出第s个变压器的电角度θ i1；在通过调节电角度θ 1ps、θ 2ps、…、θ rps实现同一输出端口下不同二次侧绕组之间功率均衡的前提下，第j个变压器对应的变压器均衡控制电流环取每相m*n个一次侧变换器直流链电流之和除以n，作为电流给定，与第j个变压器的m个一次侧变换器直流链电流之和相减后，通过第二调节器计算输出补偿电角度θ j；
在第j个变压器的电角度θ kps的基础上叠加补偿电角度θ j，得到补偿后的第j个变压器的电角度θ kps；
在补偿后，根据第s个变压器的电角度θ i1以及电角度θ kps计算得到第s个变压器的各一次侧、二次侧变换器的桥臂电压方波。
可选的，在上述公开的任一级联式电力电子变压器中，所述处理器实现的在补偿后，根据第s个变压器的电角度θ i1以及电角度θ kps计算得到第s个变压器的各一次侧、二次侧变换器的桥臂电压方波这一步骤，包括：
在补偿后，根据第s个变压器的电角度θ 11以及电角度θ kps计算得到第s个变压器的第一个一次侧变换器的占空比D 1，以及根据第s个变压器的电角度θ i1以及电角度θ kps计算得到第s个变压器的第i个一次侧变换器的占空比D i；θ 11表示第s个变压器的第1个一次侧变换器桥臂电压与自身之间的电角度，即为零；
根据第s个变压器的电角度θ 11和占空比D 1计算得到第s个变压器的第1个一次侧变换器的桥臂电压方波，根据第s个变压器的电角度θ i1和占空比D i计算得到第s个变压器的第i个一次侧变换器的桥臂电压方波，以及根据第s个变压器的补偿后的电角度θ kps计算得到第s个变压器的第k个二次侧变换器的桥臂电压方波。
可选的，在上述公开的任一级联式电力电子变压器中，所述处理器实现的计算得到第s个变压器的电角度θ kps这一步骤，包括：
运行第s个变压器的第i个一次侧变换器对应的直流链电压环；
运行针对同一输出端口下第g个并联支路的第h个串联支路设计的控制环；
将所述直流链电压环的输出与所述控制环的输出相加得到补偿前的电角度θ kps；
其中，所述运行第s个变压器的第i个一次侧变换器对应的直流链电压环，具体包括：
所有变压器一次侧的DC/AC变换器的直流链电压给定U dcref均相等；第s个变压器的第i个一次侧变换器的直流链电压环将直流链电压给定U dcref与本一次侧变换器的直流链电压U dcis相减后，通过第三调节器计算后输出，作为本直流链电压环的输出；
其中，所述运行针对同一输出端口下第g个并联支路的第h个串联支路设计的控制环，具体包括：
在同一输出端口下，判断本输出端口是要求恒压输出还是恒流输出；
若要求恒压输出：将该输出端口的电压给定Uoref除以q后作为每个串联支路的电压给定，以实现各串联支路的均压；将每个串联支路的电压给定U oref除以q后和电压实际值U oh相减，通过第四调节器计算输出，输出结果乘以1/p 作为每个并联支路的电流给定，以实现各并联支路的均流；将所述电流给定与第g个并联支路的第h个串联支路的输出电流I ogh进行比较，其偏差值经第五调节器计算输出作为所述控制环的输出，g＝1、2、…、p，h＝1、2、…、q；
若要求恒流输出：将该输出端口的输出功率给定Poref除以p*q*U o作为每个串联支路的每个并联支路的电流给定，以实现各并联支路的均流；将所述电流给定与第g个并联支路的第h个串联支路的输出电流I ogh相减后，通过第六调节器进行计算输出；与此同时，将q个串联支路电压求和后除以q作为每个串联支路的电压给定，以实现各串联支路的均压；将所述电压给定与第g个并联支路第h个串联支路的输出电压U ogh相减后，通过第七调节器计算输出，与所述第六调节器的输出之和作为所述控制环的输出。
可选的，在上述公开的任一级联式电力电子变压器中，所述处理器还实现分别针对各变压器的各一次侧变换器直流链进行工频二次谐波抑制的步骤；
其中，针对单个变压器的单个一次侧变换器直流链进行工频二次谐波抑制，具体包括：
一次侧变换器的直流电流通过100Hz二阶带通滤波器，提取其中的工频二次谐波分量，将此工频二次谐波分量做反馈、以0做给定，两者相减后通过谐振频率为100Hz的比例谐振控制器进行计算输出，其输出结果叠加到补偿前的电角度θ kps上。
可选的，在上述公开的任一级联式电力电子变压器中，当n≥2且m＝1时，所述处理器执行的程序中舍去上述对θ i1的计算。
可选的，在上述公开的任一级联式电力电子变压器中，当n＝1且m≥2时，所述处理器执行的程序中舍去上述对θ j的计算。
从上述的技术方案可以看出，由于同一变压器内各一次侧绕组之间经过DC/AC变换器和前级变换器形成了电气连接，所以本申请通过调节电角度θ 21、θ 31、…、θ m1来实现同一变压器内不同一次侧绕组之间的功率流动，进而实现同一变压器内不同一次侧绕组之间的功率均衡。对于级联式电力电子变压器的任意一个输出端口，由于每个变压器内都有至少一个二次侧绕组经过AC/DC变换器形成了电气连接，所以本申请通过调节电角度θ 1ps、θ 2ps、…、θ rps来实现同一输出端口下不同二次侧绕组之间的功率流动，进而实现同一输出端口下不同 二次侧变换器之间的功率均衡；然后，本申请通过在不同变压器的一次侧变换器桥臂电压和二次侧变换器桥臂电压之间的电角度上叠加补偿电角度θ 2、θ 3、…、θ n，实现不同变压器之间的均衡控制。当本申请实现了同一变压器内不同一次侧绕组之间、不同变压器之间的功率均衡时，也就实现了整个级联式电力电子变压器内不同一次侧绕组之间的功率均衡。
附图说明
为了更清楚地说明本申请实施例或现有技术中的技术方案，下面将对实施例或现有技术描述中所需要使用的附图作简单地介绍，显而易见地，下面描述中的附图仅仅是本申请的一些实施例，对于本领域普通技术人员来讲，在不付出创造性劳动的前提下，还可以根据这些附图获得其他的附图。
图1为一种级联式电力电子变压器结构示意图；
图2为本申请实施例公开的一种级联式电力电子变压器控制方法流程图；
图3为本申请实施例公开的一种级联式电力电子变压器控制框图；
图4为计算占空比D i的控制框图；
图5为电角度θ i1、占空比D i、电角度θ kps与变换器的对应关系框图；
图6为同一变压器上各不同绕组之间的电压时序图；
图7为本申请实施例公开的一种计算得到第s个变压器的电角度θ kps的方法流程图。
具体实施方式
下面将结合本申请实施例中的附图，对本申请实施例中的技术方案进行清楚、完整地描述，显然，所描述的实施例仅仅是本申请一部分实施例，而不是全部的实施例。基于本申请中的实施例，本领域普通技术人员在没有做出创造性劳动前提下所获得的所有其他实施例，都属于本申请保护的范围。
本申请实施例公开了一种级联式电力电子变压器控制方法，应用于图1所示级联式电力电子变压器。当n≥2且m≥2时，参见图2，所述级联式电力 电子变压器控制方法包括：
步骤S01：计算得到第s个变压器的电角度θ i1和θ kps，以及第j个变压器的补偿电角度θ j；s＝1、2、…、n；
步骤S02：在第j个变压器的电角度θ kps的基础上叠加补偿电角度θ j，得到补偿后的第j个变压器的电角度θ kps。
具体的，为便于描述，在级联式电力电子变压器的单相拓扑结构中，将第s个变压器的第i个一次侧绕组串接的DC/AC变换器简称为第s个变压器的第i个一次侧变换器，将第s个变压器的第k个二次侧绕组串接的AC/DC变换器简称为第s个变压器的第k个二次侧变换器。
由于同一变压器内各一次侧绕组之间经过DC/AC变换器和前级变换器形成了电气连接，所以可以通过调节同一变压器内不同一次侧变换器桥臂电压之间的电角度来实现同一变压器内不同一次侧绕组之间的功率流动，进而实现同一变压器内不同一次侧绕组之间的功率均衡。
另外，对于级联式电力电子变压器的任意一个输出端口，由于每个变压器内都有至少一个二次侧绕组经过AC/DC变换器形成了电气连接，所以可以通过调节同一输出端口下不同二次侧变换器桥臂电压之间的电角度来实现同一输出端口下不同二次侧绕组之间的功率流动，进而实现同一输出端口下不同二次侧绕组之间的功率均衡。
针对级联式电力电子变压器的单相拓扑结构中的每一个变压器，本申请实施例在同一变压器中，以其第一个一次侧变换器桥臂电压作为基准电压(同相的各个变压器对应的所述基准电压相等，三相同一位置上的变压器对应的所述基准电压之间互错2π/3电角度)，将第i个一次侧变换器桥臂电压与所述基准电压之间的电角度记为θ i1，i＝2、3、…、m，将第k个二次侧变换器桥臂电压与所述基准电压之间的电角度记为θ kps，k＝1、2、…、r，则：上述调节同一变压器内不同一次侧变换器桥臂电压之间的电角度的过程，也就是通过调节电角度θ 21、θ 31、…、θ m1来进行同一变压器内不同一次侧绕组之间的均衡控制；上述调节同一输出端口下不同二次侧变换器桥臂电压之间的电角度的过程，也就是通过调节电角度θ 1ps、θ 2ps、…、θ rps来进行同一输出端口下不同二次侧绕组之间的 均衡控制。
不同变压器线路参数上的差异，会导致不同变压器在一次侧变换器桥臂电压和二次侧变换器桥臂电压之间施加同一个电角度时也可能产生功率不均衡，所以在通过调节电角度θ 1ps、θ 2ps、…、θ rps来进行同一输出端口下不同二次侧绕组之间的均衡控制时，可以以第一个变压器为基准，对其余n-1变压器的电角度θ 1ps、θ 2ps、…、θ rps叠加一个补偿电角度(同一变压器下对应的电角度θ 1ps、θ 2ps、…、θ rps所叠加的补偿电角度相等，不同变压器下对应的电角度θ 1ps、θ 2ps、…、θ rps所叠加的补偿电角度根据本变压器本身的功率偏移程度确定)，从而实现不同变压器之间的功率均衡。为便于描述，以下将第j个变压器的一次侧变换器桥臂电压和二次侧变换器桥臂电压之间的补偿电角度记为θ j，j＝2、3、…、n。
当实现了同一变压器内不同一次侧绕组之间、不同变压器之间的功率均衡时，也就实现了整个级联式电力电子变压器内不同一次侧绕组之间的功率均衡。
基于以上描述，本申请实施例针对每个变压器下的m-1个一次侧绕组分别设计了一个一次侧绕组均衡控制电流环(参见图3中的附图标记100)，以及在通过调节电角度θ 1ps、θ 2ps、…、θ rps实现同一输出端口下不同二次侧绕组之间功率均衡的前提下，针对每相中n-1个变压器分别设计了一个变压器均衡控制电流环(参见图3中的附图标记200)，下面结合图3描述其工作原理如下：
第s个变压器的第i个一次侧绕组对应的均衡控制电流环取第s个变压器的m个一次侧变换器的直流链电流之和除以m，作为电流给定，将其与第s个变压器的第i个一次侧变换器的直流链电流I dcis相减后，通过第一(例如PI调节器)计算输出第s个变压器的电角度θ i1。
第j个变压器对应的变压器均衡控制电流环取每相m*n个一次侧变换器直流链电流之和除以n，作为电流给定，与第j个变压器的m个一次侧变换器直流链电流之和相减后，通过第二调节器(例如PI调节器)计算输出电角度θ j。然后，在第j个变压器的电角度θ kps的基础上叠加补偿电角度θ j，即可得到补偿后的第j个变压器的电角度θ kps。
步骤S03：在补偿后，根据第s个变压器的电角度θ i1以及电角度θ kps计算 得到第s个变压器的各一次侧、二次侧变换器的桥臂电压方波。
具体的，按照步骤S03给出的方式，将步骤S01～步骤S02中计算出的第s个变压器的电角度θ i1、第1个变压器的电角度θ kps以及第j个变压器补偿后的电角度θ kps投入使用，完成对级联式电力电子变压器的运行控制，此时即可实现同一变压器内不同一次侧绕组之间、不同变压器之间的功率均衡控制。
其中，所述在补偿后，根据第s个变压器的电角度θ i1以及电角度θ kps计算第s个变压器的各一次侧、二次侧变换器的桥臂电压方波，具体包括：
在补偿后，根据第s个变压器的电角度θ 11(θ 11表示第s个变压器的第1个一次侧变换器桥臂电压与自身之间的电角度，即为零)以及电角度θ kps计算得到第s个变压器的第一个一次侧变换器的占空比D 1，以及根据第s个变压器的电角度θ i1以及电角度θ kps计算得到第s个变压器的第i个一次侧变换器的占空比D i，对应的控制框图如图4所示；然后，根据第s个变压器的电角度θ 11和占空比D 1计算得到第s个变压器的第1个一次侧变换器的桥臂电压方波，根据第s个变压器的电角度θ i1和占空比D i计算得到第s个变压器的第i个一次侧变换器的桥臂电压方波，以及根据第s个变压器的电角度θ kps计算得到第s个变压器的第k个二次侧变换器的桥臂电压方波，对应的控制框图如图5所示。
同一变压器上各不同绕组之间的电压时序如图6所示，从上到下波形依次是：第1个一次侧变换器桥臂电压波形、第1个二次侧变换器桥臂电压波形、第i个一次侧变换器桥臂电压波形、第k个二次侧变换器桥臂电压波形。
由以上对本申请实施例技术方案的全部描述可以看出，由于同一变压器内各一次侧绕组之间经过DC/AC变换器和前级变换器形成了电气连接，所以本申请实施例通过调节电角度θ 21、θ 31、…、θ m1来实现同一变压器内不同一次侧绕组之间的功率流动，进而实现同一变压器内不同一次侧绕组之间的功率均衡。对于级联式电力电子变压器的任意一个输出端口，由于每个变压器内都有至少一个二次侧绕组经过AC/DC变换器形成了电气连接，所以本申请实施例还通过调节电角度θ 1ps、θ 2ps、…、θ rps来实现同一输出端口下不同二次侧绕组之间的功率流动，进而实现同一输出端口下不同二次侧变换器之间的功率均衡；然后， 本申请实施例通过在不同变压器的一次侧变换器桥臂电压和二次侧变换器桥臂电压之间的电角度上叠加补偿电角度θ 2、θ 3、…、θ n，实现不同变压器之间的均衡控制。当本申请实施例实现了同一变压器内不同一次侧绕组之间、不同变压器之间的功率均衡时，也就实现了整个级联式电力电子变压器内不同一次侧绕组之间的功率均衡。
其中，需要说明的是，计算得到第s个变压器的电角度θ kps的方式，也即通过调节电角度θ 1ps、θ 2ps、…、θ rps实现同一输出端口下不同二次侧绕组之间功率均衡的方式，可以直接采用现有的计算方式实现。
假设同一输出端口下所有AC/DC变换器通过串并联组合得到了p个并联支路和q个串联支路，p≥1，q≥1，则在需要实现同一输出端口下p个并联支路均流和q个串联支路均压的场合下，可采用如下计算方式来计算得到第j个变压器的电角度θ kps，如图7所示，包括：
步骤S011：运行第s个变压器的第i个一次侧变换器对应的直流链电压环；
具体的，所有变压器一次侧的DC/AC变换器的直流链电压给定U dcref均相等。第s个变压器的第i个一次侧变换器的直流链电压环(对应的控制框图参见图3中的附图标记300)将直流链电压给定U dcref与本一次侧变换器的直流链电压U dcis相减后，通过第三调节器(例如PI调节器)计算后输出，作为本直流链电压环的输出。
步骤S012：运行针对同一输出端口下第g个并联支路的第h个串联支路设计的控制环。
具体的，在同一输出端口下，判断本输出端口是要求恒压输出还是恒流输出；恒压输出下对应的所述控制环的控制框图参见图3中的附图标记400，恒流输出下对应的所述控制环的控制框图参见图3中的附图标记500。
若要求恒压输出(即电压模式)：将该输出端口的电压给定Uoref除以q后作为每个串联支路的电压给定，以实现各串联支路的均压；将每个串联支路的电压给定U oref除以q后和电压实际值U oh相减，通过第四调节器(例如PI调节器)计算输出，输出结果乘以1/p作为每个并联支路的电流给定，以实现各 并联支路的均流；将所述电流给定与第g个并联支路的第h个串联支路的输出电流I ogh进行比较，其偏差值经第五调节器(例如PI调节器)计算输出作为所述控制环的输出，g＝1、2、…、p，h＝1、2、…、q。
若要求恒流输出(即电流模式)：将该输出端口的输出功率给定Poref除以p*q*U o作为每个串联支路的每个并联支路的电流给定，以实现各并联支路的均流；将所述电流给定与第g个并联支路的第h个串联支路的输出电流I ogh相减后，通过第六调节器(例如PI调节器)进行计算输出；与此同时，将q个串联支路电压求和后除以q作为每个串联支路的电压给定，以实现各串联支路的均压；将所述电压给定与第g个并联支路第h个串联支路的输出电压U ogh相减后，通过第七调节器(例如PI调节器)计算输出，与所述第六调节器的输出之和作为所述控制环的输出。
步骤S013：将所述直流链电压环的输出与所述控制环的输出相加得到补偿前的电角度θ kps。
可选的，在上述公开的任一实施例中，所述控制方法还包括：分别针对各变压器的各一次侧变换器直流链进行工频二次谐波抑制(对应的控制框图参见图3中的附图标记600)。其中，针对单个变压器的单个一次侧变换器直流链进行工频二次谐波抑制，具体为：
一次侧变换器的直流电流通过100Hz二阶带通滤波器，提取其中的工频二次谐波分量，将此工频二次谐波分量做反馈、以0做给定，两者相减后通过谐振频率为100Hz的比例谐振控制器进行计算输出其输出结果叠加到本变换器补偿前的电角度θ kps上。
上述任一实施例均是针对n≥2且m≥2的情况提出的。当n≥2且m＝1时，直接舍去上述对θ i1的计算即可。当n＝1且m≥2时，直接舍去上述对θ j的计算即可。
与上述方法实施例相对应的，本申请实施例还公开了一种级联式电力电子 变压器，包括主电路和控制器。所述主电路的每相包括n个变压器，每个变压器具有m个一次侧绕组和r个二次侧绕组，n≥2，m≥2，r≥1，每个一次侧绕组串接一个DC/AC变换器，每个二次侧绕组串接一个AC/DC变换器；n*m个所述DC/AC变换器的直流侧各经过一个前级变换器后串联构成所述级联式电力电子变压器的输入端口；所述级联式电力电子变压器具有一个或多个输出端口，每个所述输出端口都是通过从每个变压器的二次侧各选取至少一个AC/DC变换器，然后将这些AC/DC变换器的直流侧进行串并联构成；
所述控制器包括处理器、存储器及存储在存储器上并能在处理器上运行的程序，处理器执行程序时实现以下步骤：
计算得到第s个变压器的电角度θ i1和θ kps，以及第j个变压器的补偿电角度θ j；s＝1、2、…、n；
其中，在同一变压器中，将其第i个一次侧绕组串接的DC/AC变换器简称为第i个一次侧变换器，将其第k个二次侧绕组串接的AC/DC变换器简称为第k个二次侧变换器，以其第一个一次侧变换器桥臂电压作为基准电压，将第i个一次侧变换器桥臂电压与所述基准电压之间的电角度记为θ i1，i＝2、3、…、m，将第k个二次侧变换器桥臂电压与所述基准电压之间的电角度记为θ kps，k＝1、2、…、r；同相的各个变压器对应的所述基准电压相等，三相同一位置上的变压器对应的所述基准电压之间互错2π/3电角度；将第j个变压器的一次侧变换器桥臂电压和二次侧变换器桥臂电压之间的补偿角度记为θ j，j＝2、3、…、n；则：第s个变压器的第i个一次侧绕组对应的均衡控制电流环取第s个变压器的m个一次侧变换器的直流链电流之和除以m，作为电流给定，将其与第s个变压器的第i个一次侧变换器的直流链电流I dcis相减后，通过第一调节器计算输出第s个变压器的电角度θ i1；在通过调节电角度θ 1ps、θ 2ps、…、θ rps实现同一输出端口下不同二次侧绕组之间功率均衡的前提下，第j个变压器对应的变压器均衡控制电流环取每相m*n个一次侧变换器直流链电流之和除以n，作为电流给定，与第j个变压器的m个一次侧变换器直流链电流之和相减后，通过第二调节器计算输出补偿电角度θ j；
在第j个变压器的电角度θ kps的基础上叠加补偿电角度θ j，得到补偿后的 第j个变压器的电角度θ kps；
在补偿后，根据第s个变压器的电角度θ i1以及电角度θ kps计算得到第s个变压器的各一次侧、二次侧变换器的桥臂电压方波。
可选的，在上述公开的任一级联式电力电子变压器中，所述处理器实现的在补偿后，根据第s个变压器的电角度θ i1以及电角度θ kps计算得到第s个变压器的各一次侧、二次侧变换器的桥臂电压方波这一步骤，包括：
在补偿后，根据第s个变压器的电角度θ 11以及电角度θ kps计算得到第s个变压器的第一个一次侧变换器的占空比D 1，以及根据第s个变压器的电角度θ i1以及电角度θ kps计算得到第s个变压器的第i个一次侧变换器的占空比D i；θ 11表示第s个变压器的第1个一次侧变换器桥臂电压与自身之间的电角度，即为零；
根据第s个变压器的电角度θ 11和占空比D 1计算得到第s个变压器的第1个一次侧变换器的桥臂电压方波，根据第s个变压器的电角度θ i1和占空比D i计算得到第s个变压器的第i个一次侧变换器的桥臂电压方波，以及根据第s个变压器的补偿后的电角度θ kps计算得到第s个变压器的第k个二次侧变换器的桥臂电压方波。
可选的，在上述公开的任一级联式电力电子变压器中，所述处理器实现的计算得到第s个变压器的电角度θ kps这一步骤，包括：
运行第s个变压器的第i个一次侧变换器对应的直流链电压环；
运行针对同一输出端口下第g个并联支路的第h个串联支路设计的控制环；
将所述直流链电压环的输出与所述控制环的输出相加得到补偿前的电角度θ kps；
其中，所述运行第s个变压器的第i个一次侧变换器对应的直流链电压环，具体包括：
所有变压器一次侧的DC/AC变换器的直流链电压给定U dcref均相等；第s个变压器的第i个一次侧变换器的直流链电压环将直流链电压给定U dcref与本一次侧变换器的直流链电压U dcis相减后，通过第三调节器计算后输出，作为 本直流链电压环的输出；
其中，所述运行针对同一输出端口下第g个并联支路的第h个串联支路设计的控制环，具体包括：
在同一输出端口下，判断本输出端口是要求恒压输出还是恒流输出；
若要求恒压输出：将该输出端口的电压给定Uoref除以q后作为每个串联支路的电压给定，以实现各串联支路的均压；将每个串联支路的电压给定U oref除以q后和电压实际值U oh相减，通过第四调节器计算输出，输出结果乘以1/p作为每个并联支路的电流给定，以实现各并联支路的均流；将所述电流给定与第g个并联支路的第h个串联支路的输出电流I ogh进行比较，其偏差值经第五调节器计算输出作为所述控制环的输出，g＝1、2、…、p，h＝1、2、…、q；
若要求恒流输出：将该输出端口的输出功率给定Poref除以p*q*U o作为每个串联支路的每个并联支路的电流给定，以实现各并联支路的均流；将所述电流给定与第g个并联支路的第h个串联支路的输出电流I ogh相减后，通过第六调节器进行计算输出；与此同时，将q个串联支路电压求和后除以q作为每个串联支路的电压给定，以实现各串联支路的均压；将所述电压给定与第g个并联支路第h个串联支路的输出电压U ogh相减后，通过第七调节器计算输出，与所述第六调节器的输出之和作为所述控制环的输出。
可选的，在上述公开的任一级联式电力电子变压器中，所述处理器还实现分别针对各变压器的各一次侧变换器直流链进行工频二次谐波抑制的步骤；
其中，针对单个变压器的单个一次侧变换器直流链进行工频二次谐波抑制，具体包括：
一次侧变换器的直流电流通过100Hz二阶带通滤波器，提取其中的工频二次谐波分量，将此工频二次谐波分量做反馈、以0做给定，两者相减后通过谐振频率为100Hz的比例谐振控制器进行计算输出，其输出结果叠加到补偿前的电角度θ kps上。
可选的，在上述公开的任一级联式电力电子变压器中，当n≥2且m＝1时，所述处理器执行的程序中舍去上述对θ i1的计算。
可选的，在上述公开的任一级联式电力电子变压器中，当n＝1且m≥2时， 所述处理器执行的程序中舍去上述对θ j的计算。
本说明书中各个实施例采用递进的方式描述，每个实施例重点说明的都是与其他实施例的不同之处，各个实施例之间相同相似部分互相参见即可。对于实施例公开的级联式电力电子变压器实施例而言，由于其与实施例公开的方法相对应，所以描述的比较简单，相关之处参见方法部分说明即可。
本申请的说明书和权利要求书及上述附图中的术语“第一”、“第二”等是用于区别类似的不同对象，而不必用于描述特定的顺序或先后次序。而且，术语“包括”、“包含”或者其任何其他变体意在涵盖非排他性的包含，从而使得包括一系列要素的过程、方法、商品或者设备不仅包括那些要素，而且还包括没有明确列出的其他要素，或者是还包括为这种过程、方法、商品或者设备所固有的要素。在没有更多限制的情况下，由语句“包括一个”限定的要素，并不排除在包括要素的过程、方法、商品或者设备中还存在另外的相同要素。
对所公开的实施例的上述说明，使本领域专业技术人员能够实现或使用本申请。对这些实施例的多种修改对本领域的专业技术人员来说将是显而易见的，本文中所定义的一般原理可以在不脱离本申请实施例的精神或范围的情况下，在其它实施例中实现。因此，本申请实施例将不会被限制于本文所示的这些实施例，而是要符合与本文所公开的原理和新颖特点相一致的最宽的范围。

Claims (12)

  1. 一种级联式电力电子变压器控制方法，其特征在于，所述级联式电力电子变压器的每相包括n个变压器，每个变压器具有m个一次侧绕组和r个二次侧绕组，n≥2，m≥2，r≥1，每个一次侧绕组串接一个DC/AC变换器，每个二次侧绕组串接一个AC/DC变换器；n*m个所述DC/AC变换器的直流侧各经过一个前级变换器后串联构成所述级联式电力电子变压器的输入端口；所述级联式电力电子变压器具有一个或多个输出端口，每个所述输出端口都是通过从每个变压器的二次侧各选取至少一个AC/DC变换器，然后将这些AC/DC变换器的直流侧进行串并联构成；
    所述级联式电力电子变压器控制方法包括：
    计算得到第s个变压器的电角度θ i1和θ kps，以及第j个变压器的补偿电角度θ j；s＝1、2、…、n；
    其中，在同一变压器中，将其第i个一次侧绕组串接的DC/AC变换器简称为第i个一次侧变换器，将其第k个二次侧绕组串接的AC/DC变换器简称为第k个二次侧变换器，以其第一个一次侧变换器桥臂电压作为基准电压，将第i个一次侧变换器桥臂电压与所述基准电压之间的电角度记为θ i1，i＝2、3、…、m，将第k个二次侧变换器桥臂电压与所述基准电压之间的电角度记为θ kps，k＝1、2、…、r；同相的各个变压器对应的所述基准电压相等，三相同一位置上的变压器对应的所述基准电压之间互错2π/3电角度；将第j个变压器的一次侧变换器桥臂电压和二次侧变换器桥臂电压之间的补偿角度记为θ j，j＝2、3、…、n；则：第s个变压器的第i个一次侧绕组对应的均衡控制电流环取第s个变压器的m个一次侧变换器的直流链电流之和除以m，作为电流给定，将其与第s个变压器的第i个一次侧变换器的直流链电流I dcis相减后，通过第一调节器计算输出第s个变压器的电角度θ i1；在通过调节电角度θ 1ps、θ 2ps、…、θ rps实现同一输出端口下不同二次侧绕组之间功率均衡的前提下，第j个变压器对应的变压器均衡控制电流环取每相m*n个一次侧变换器直流链电流之和除以n，作为电流给定，与第j个变压器的m个一次侧变换器直流链电流之和相减后，通过第二调节器计算输出补偿电角度θ j；
    在第j个变压器的电角度θ kps的基础上叠加补偿电角度θ j，得到补偿后的 第j个变压器的电角度θ kps；
    在补偿后，根据第s个变压器的电角度θ i1以及电角度θ kps计算得到第s个变压器的各一次侧、二次侧变换器的桥臂电压方波。
  2. 根据权利要求1所述的级联式电力电子变压器控制方法，其特征在于，所述在补偿后，根据第s个变压器的电角度θ i1以及电角度θ kps计算得到第s个变压器的各一次侧、二次侧变换器的桥臂电压方波，包括：
    在补偿后，根据第s个变压器的电角度θ 11以及电角度θ kps计算得到第s个变压器的第一个一次侧变换器的占空比D 1，以及根据第s个变压器的电角度θ i1以及电角度θ kps计算得到第s个变压器的第i个一次侧变换器的占空比D i；θ 11表示第s个变压器的第1个一次侧变换器桥臂电压与自身之间的电角度，即为零；
    根据第s个变压器的电角度θ 11和占空比D 1计算得到第s个变压器的第1个一次侧变换器的桥臂电压方波，根据第s个变压器的电角度θ i1和占空比D i计算得到第s个变压器的第i个一次侧变换器的桥臂电压方波，以及根据第s个变压器的补偿后的电角度θ kps计算得到第s个变压器的第k个二次侧变换器的桥臂电压方波。
  3. 根据权利要求1所述的级联式电力电子变压器控制方法，其特征在于，计算得到第s个变压器的电角度θ kps，包括：
    运行第s个变压器的第i个一次侧变换器对应的直流链电压环；
    运行针对同一输出端口下第g个并联支路的第h个串联支路设计的控制环；
    将所述直流链电压环的输出与所述控制环的输出相加得到补偿前的电角度θ kps；
    其中，所述运行第s个变压器的第i个一次侧变换器对应的直流链电压环，具体包括：
    所有变压器一次侧的DC/AC变换器的直流链电压给定U dcref均相等；第s个变压器的第i个一次侧变换器的直流链电压环将直流链电压给定U dcref与本一次侧变换器的直流链电压U dcis相减后，通过第三调节器计算后输出，作为本直流链电压环的输出；
    其中，所述运行针对同一输出端口下第g个并联支路的第h个串联支路设计的控制环，具体包括：
    在同一输出端口下，判断本输出端口是要求恒压输出还是恒流输出；
    若要求恒压输出：将该输出端口的电压给定Uoref除以q后作为每个串联支路的电压给定，以实现各串联支路的均压；将每个串联支路的电压给定U oref除以q后和电压实际值U oh相减，通过第四调节器计算输出，输出结果乘以1/p作为每个并联支路的电流给定，以实现各并联支路的均流；将所述电流给定与第g个并联支路的第h个串联支路的输出电流I ogh进行比较，其偏差值经第五调节器计算输出作为所述控制环的输出，g＝1、2、…、p，h＝1、2、…、q；
    若要求恒流输出：将该输出端口的输出功率给定Poref除以p*q*U o作为每个串联支路的每个并联支路的电流给定，以实现各并联支路的均流；将所述电流给定与第g个并联支路的第h个串联支路的输出电流I ogh相减后，通过第六调节器进行计算输出；与此同时，将q个串联支路电压求和后除以q作为每个串联支路的电压给定，以实现各串联支路的均压；将所述电压给定与第g个并联支路第h个串联支路的输出电压U ogh相减后，通过第七调节器计算输出，与所述第六调节器的输出之和作为所述控制环的输出。
  4. 根据权利要求1所述的级联式电力电子变压器控制方法，其特征在于，所述级联式电力电子变压器控制方法还包括：分别针对各变压器的各一次侧变换器直流链进行工频二次谐波抑制；
    其中，针对单个变压器的单个一次侧变换器直流链进行工频二次谐波抑制，具体为：一次侧变换器的直流电流通过100Hz二阶带通滤波器，提取其中的工频二次谐波分量，将此工频二次谐波分量做反馈、以0做给定，两者相减后通过谐振频率为100Hz的比例谐振控制器进行计算输出，其输出结果叠加到本变换器补偿前的电角度θ kps上。
  5. 根据权利要求1～4中任一项所述的级联式电力电子变压器控制方法，其特征在于，当n≥2且m＝1时，舍去上述对θ i1的计算。
  6. 根据权利要求1～4中任一项所述的级联式电力电子变压器控制方法，其特征在于，当n＝1且m≥2时，舍去上述对θ j的计算。
  7. 一种级联式电力电子变压器，包括主电路和控制器，其特征在于，所 述主电路的每相包括n个变压器，每个变压器具有m个一次侧绕组和r个二次侧绕组，n≥2，m≥2，r≥1，每个一次侧绕组串接一个DC/AC变换器，每个二次侧绕组串接一个AC/DC变换器；n*m个所述DC/AC变换器的直流侧各经过一个前级变换器后串联构成所述级联式电力电子变压器的输入端口；所述级联式电力电子变压器具有一个或多个输出端口，每个所述输出端口都是通过从每个变压器的二次侧各选取至少一个AC/DC变换器，然后将这些AC/DC变换器的直流侧进行串并联构成；
    所述控制器包括处理器、存储器及存储在存储器上并能在处理器上运行的程序，处理器执行程序时实现以下步骤：
    计算得到第s个变压器的电角度θ i1和θ kps，以及第j个变压器的补偿电角度θ j；s＝1、2、…、n；
    其中，在同一变压器中，将其第i个一次侧绕组串接的DC/AC变换器简称为第i个一次侧变换器，将其第k个二次侧绕组串接的AC/DC变换器简称为第k个二次侧变换器，以其第一个一次侧变换器桥臂电压作为基准电压，将第i个一次侧变换器桥臂电压与所述基准电压之间的电角度记为θ i1，i＝2、3、…、m，将第k个二次侧变换器桥臂电压与所述基准电压之间的电角度记为θ kps，k＝1、2、…、r；同相的各个变压器对应的所述基准电压相等，三相同一位置上的变压器对应的所述基准电压之间互错2π/3电角度；将第j个变压器的一次侧变换器桥臂电压和二次侧变换器桥臂电压之间的补偿角度记为θj，j＝2、3、…、n；则：第s个变压器的第i个一次侧绕组对应的均衡控制电流环取第s个变压器的m个一次侧变换器的直流链电流之和除以m，作为电流给定，将其与第s个变压器的第i个一次侧变换器的直流链电流I dcis相减后，通过第一调节器计算输出第s个变压器的电角度θ i1；在通过调节电角度θ 1ps、θ 2ps、…、θ rps实现同一输出端口下不同二次侧绕组之间功率均衡的前提下，第j个变压器对应的变压器均衡控制电流环取每相m*n个一次侧变换器直流链电流之和除以n，作为电流给定，与第j个变压器的m个一次侧变换器直流链电流之和相减后，通过第二调节器计算输出补偿电角度θ j；
    在第j个变压器的电角度θ kps的基础上叠加补偿电角度θ j，得到补偿后的第j个变压器的电角度θ kps；
    在补偿后，根据第s个变压器的电角度θ i1以及电角度θ kps计算得到第s个变压器的各一次侧、二次侧变换器的桥臂电压方波。
  8. 根据权利要求7所述的级联式电力电子变压器，其特征在于，所述处理器实现的在补偿后，根据第s个变压器的电角度θ i1以及电角度θ kps计算得到第s个变压器的各一次侧、二次侧变换器的桥臂电压方波这一步骤，包括：
    在补偿后，根据第s个变压器的电角度θ 11以及电角度θ kps计算得到第s个变压器的第一个一次侧变换器的占空比D 1，以及根据第s个变压器的电角度θ i1以及电角度θ kps计算得到第s个变压器的第i个一次侧变换器的占空比D i；θ 11表示第s个变压器的第1个一次侧变换器桥臂电压与自身之间的电角度，即为零；
    根据第s个变压器的电角度θ 11和占空比D 1计算得到第s个变压器的第1个一次侧变换器的桥臂电压方波，根据第s个变压器的电角度θ i1和占空比D i计算得到第s个变压器的第i个一次侧变换器的桥臂电压方波，以及根据第s个变压器的补偿后的电角度θ kps计算得到第s个变压器的第k个二次侧变换器的桥臂电压方波。
  9. 根据权利要求7所述的级联式电力电子变压器，其特征在于，所述处理器实现的计算得到第s个变压器的电角度θ kps这一步骤，包括：
    运行第s个变压器的第i个一次侧变换器对应的直流链电压环；
    运行针对同一输出端口下第g个并联支路的第h个串联支路设计的控制环；
    将所述直流链电压环的输出与所述控制环的输出相加得到补偿前的电角度θ kps；
    其中，所述运行第s个变压器的第i个一次侧变换器对应的直流链电压环，具体包括：
    所有变压器一次侧的DC/AC变换器的直流链电压给定U dcref均相等；第s个变压器的第i个一次侧变换器的直流链电压环将直流链电压给定U dcref与本一次侧变换器的直流链电压U dcis相减后，通过第三调节器计算后输出，作为本直流链电压环的输出；
    其中，所述运行针对同一输出端口下第g个并联支路的第h个串联支路设 计的控制环，具体包括：
    在同一输出端口下，判断本输出端口是要求恒压输出还是恒流输出；
    若要求恒压输出：将该输出端口的电压给定Uoref除以q后作为每个串联支路的电压给定，以实现各串联支路的均压；将每个串联支路的电压给定U oref除以q后和电压实际值U oh相减，通过第四调节器计算输出，输出结果乘以1/p作为每个并联支路的电流给定，以实现各并联支路的均流；将所述电流给定与第g个并联支路的第h个串联支路的输出电流I ogh进行比较，其偏差值经第五调节器计算输出作为所述控制环的输出，g＝1、2、…、p，h＝1、2、…、q；
    若要求恒流输出：将该输出端口的输出功率给定Poref除以p*q*U o作为每个串联支路的每个并联支路的电流给定，以实现各并联支路的均流；将所述电流给定与第g个并联支路的第h个串联支路的输出电流I ogh相减后，通过第六调节器进行计算输出；与此同时，将q个串联支路电压求和后除以q作为每个串联支路的电压给定，以实现各串联支路的均压；将所述电压给定与第g个并联支路第h个串联支路的输出电压U ogh相减后，通过第七调节器计算输出，与所述第六调节器的输出之和作为所述控制环的输出。
  10. 根据权利要求7所述的级联式电力电子变压器法，其特征在于，所述处理器还实现分别针对各变压器的各一次侧变换器直流链进行工频二次谐波抑制的步骤；
    其中，针对单个变压器的单个一次侧变换器直流链进行工频二次谐波抑制，具体包括：
    一次侧变换器的直流电流通过100Hz二阶带通滤波器，提取其中的工频二次谐波分量，将此工频二次谐波分量做反馈、以0做给定，两者相减后通过谐振频率为100Hz的比例谐振控制器进行计算输出，其输出结果叠加到补偿前的电角度θ kps上。
  11. 根据权利要求7～10中任一项所述的级联式电力电子变压器，其特征在于，当n≥2且m＝1时，所述处理器执行的程序中舍去上述对θ i1的计算。
  12. 根据权利要求7～10中任一项所述的级联式电力电子变压器，其特征在于，当n＝1且m≥2时，所述处理器执行的程序中舍去上述对θ j的计算。
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