CN107196327B - Feedforward control method for restraining power oscillation of modular voltage source type converter valve - Google Patents
Feedforward control method for restraining power oscillation of modular voltage source type converter valve Download PDFInfo
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- H—ELECTRICITY
- H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
- H02J—CIRCUIT ARRANGEMENTS OR SYSTEMS FOR SUPPLYING OR DISTRIBUTING ELECTRIC POWER; SYSTEMS FOR STORING ELECTRIC ENERGY
- H02J3/00—Circuit arrangements for ac mains or ac distribution networks
- H02J3/36—Arrangements for transfer of electric power between ac networks via a high-tension dc link
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- H—ELECTRICITY
- H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
- H02J—CIRCUIT ARRANGEMENTS OR SYSTEMS FOR SUPPLYING OR DISTRIBUTING ELECTRIC POWER; SYSTEMS FOR STORING ELECTRIC ENERGY
- H02J3/00—Circuit arrangements for ac mains or ac distribution networks
- H02J3/24—Arrangements for preventing or reducing oscillations of power in networks
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- H—ELECTRICITY
- H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
- H02J—CIRCUIT ARRANGEMENTS OR SYSTEMS FOR SUPPLYING OR DISTRIBUTING ELECTRIC POWER; SYSTEMS FOR STORING ELECTRIC ENERGY
- H02J3/00—Circuit arrangements for ac mains or ac distribution networks
- H02J3/36—Arrangements for transfer of electric power between ac networks via a high-tension dc link
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Abstract
The invention provides a feedforward control method for inhibiting power oscillation of a modular voltage source type converter valve, which comprises the following steps: collecting active and reactive three-phase voltage U at side of modular voltage source converter valve systemsabcThree-phase current IsabcUpper bridge arm current ITabcLower bridge arm current IBabcAnd a direct current voltage Udc(ii) a For the Usabc、IsabcDQ conversion is carried out to obtain a system side voltage component usdq(usd、usq) The current component i of the feedbacksDQ(IsD、IsQ) (ii) a Calculating the active reference current I of the outer looprDObtaining the outer ring reactive reference current IrQ(ii) a Said IrD、IrQAnd isDQObtaining a reference voltage U through decoupling and PI controlrefDQ(ii) a According to the DC voltage UdcAcquiring a feedforward control signal; adding the reference voltage under the DQ axis and the feedforward signal to obtain a reference voltage U of feedforward controlreffabc(ii) a Obtaining a current conversion suppression voltage U under a static abc coordinate through circulation suppressionzabc(ii) a Will be the UreffabcAnd the UzabcAnd superposing to obtain reference voltages of the upper and lower bridge arms, and obtaining a switch control signal of the modular voltage source converter valve through nearest level approximation modulation.
Description
Technical Field
The invention relates to a flexible direct current transmission technology, in particular to a feedforward control method for restraining power oscillation of a modular voltage source type converter valve.
Background
The Modular Multilevel Converter (MMC) adopts a controllable turn-off power electronic device and a Pulse Width Modulation (PWM) technology, can realize independent control of active power and reactive power, can supply power to a passive network, is a novel Multilevel Converter topological structure, and has become a research hotspot in the current international power electronic field. The HVDC system based on the modular voltage source converter valve can overcome the defects of silicon controlled rectifier direct current and has wide application prospect in the fields of connecting a new energy power generation field (such as wind power generation, solar power generation and the like) to a power grid, supplying power to remote loads, constructing urban load centers and the like. However, when the flexible dc converter valve is transported in an overhead line, a long distance, and a small power, the problem of dc voltage and power oscillation is likely to occur, which limits the application of the high-power converter valve in the small power.
Disclosure of Invention
To solve the above technical problem, it is a primary object of an embodiment of the present invention to provide a feedforward control method for suppressing power oscillation of a modular voltage source converter valve, the method further including,
collecting active and reactive three-phase voltage U at side of modular voltage source converter valve systemsabcThree-phase current IsabcUpper bridge arm current ITabcLower bridge arm current IBabcAnd a direct current voltage Udc；
For the Usabc、IsabcDQ conversion is carried out to obtain a system side voltage component u under a two-phase rotating coordinate systemsdq(usd、usq) The current component i of the feedbacksDQ(IsD、IsQ)；
Calculating the outer loop active reference current I according to the active reference and the active feedbackrdSelecting a reactive current calculation mode according to the outer ring reactive power control mode to obtain an outer ring reactive power reference current Irq；
Calculating the active reference current I obtained by the outer ringrDReactive reference current IrQAnd the feedback current isDQObtaining reference voltage U under DQ axis through decoupling and PI controlrefDQ；
According to the DC voltage UdcObtaining a feedforward control signal, and controlling the DC voltage and a reference voltage U at the DC voltage control enddc *Making a difference, carrying out low-pass filtering on the direct current voltage at a non-voltage control end to obtain a difference signal, and carrying out proportional integral or proportional control to obtain a feedforward control signal U based on a D axisfDQQ-axis feedforward control signal UfQAnd DQ Axis feedforward control Signal UfDQ；
Adding the reference voltage to the feed-forward signal on the DQ axis, i.e. UrefDQ+UfDQ、UrefDQ+UfD、UrefDQ+UfQDQ inverse transformation is carried out to obtain a reference voltage U of feedforward controlreffabc；
The upper and lower arms are subjected to current I through circulation suppressionTabc、IBabcAveraging, and performing 2 frequency-doubling DQ conversion of negative sequence to obtain conversionDQ component of current is controlled by an inner loop PI to obtain output voltage U for suppressing current conversionzDQThen obtaining the commutation suppression voltage U under the static abc coordinate through 2-frequency-multiplication DQ inverse transformationzabc；
Will be the UreffabcAnd the UzabcAnd superposing to obtain reference voltages of an upper bridge arm and a lower bridge arm, and obtaining a switch control signal of the modular voltage source converter valve through nearest level approximation modulation so as to realize suppression of power oscillation of the modular voltage source converter valve.
According to the embodiment of the invention, the direct-current voltage of the flexible direct-current power transmission system is used as the feedforward signal, so that the links of coordinate transformation and filtering for extracting the damping signal from the system current are avoided, the calculated amount is reduced, and the implementation is convenient. The method can enhance the stability and control of the direct current transmission system under the condition of low power and long-distance transmission, and the suppression of direct current voltage and power oscillation from the converter valve is realized by directly correcting the output voltage.
Drawings
In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings required to be used in the description of the embodiments will be briefly introduced below, and it is obvious that the drawings in the following description are only some embodiments of the present invention, and it is obvious for those skilled in the art that other drawings can be obtained according to the drawings without inventive labor.
Fig. 1 is a schematic structural diagram of a system for dc power transmission of a modular voltage source converter valve in a power transmission system according to an embodiment of the present invention;
FIG. 2 is a schematic diagram of a feed-forward control flow of power oscillation of a modular voltage source converter valve according to an embodiment of the present invention;
FIG. 3 is a schematic diagram of a modular voltage source converter valve phase-locked loop according to an embodiment of the invention;
FIG. 4 is a schematic diagram of outer loop reactive power control of a modular voltage source converter valve according to an embodiment of the present invention;
FIG. 5 is a schematic diagram of an outer loop active power control of a modular voltage source converter valve according to an embodiment of the present invention;
FIG. 6 is a schematic diagram illustrating the outer loop current limiting of the modular voltage source converter valve according to an embodiment of the present invention;
FIG. 7 is a schematic diagram of a D-axis proportional integral feedforward control of a voltage control terminal of a modular voltage source converter valve according to an embodiment of the invention;
FIG. 8 is a schematic diagram illustrating proportional feedforward control of the Q-axis of the voltage control terminal of the modular voltage source converter valve according to an embodiment of the present invention;
FIG. 9 is a schematic diagram of proportional-integral feedforward control of a DQ axis at a voltage control terminal of a modular voltage source converter valve according to an embodiment of the invention;
FIG. 10 is a schematic diagram of proportional feedforward control of the D-axis of the voltage control terminal of the modular voltage source converter valve according to the embodiment of the invention;
FIG. 11 is a schematic diagram illustrating proportional feedforward control of the Q-axis of the voltage control terminal of the modular voltage source converter valve according to an embodiment of the present invention;
FIG. 12 is a diagram illustrating proportional feedforward control of a DQ axis at a voltage control terminal of a modular voltage source converter valve according to an embodiment of the invention;
FIG. 13 is a schematic diagram of a proportional-integral feedforward control of the D-axis of the non-voltage control terminal of the modular voltage source converter valve in accordance with the embodiment of the present invention;
FIG. 14 is a schematic diagram of proportional-integral feedforward control of the non-voltage control end Q-axis of a modular voltage source converter valve according to an embodiment of the invention;
FIG. 15 is a schematic diagram of proportional-integral feedforward control of a DQ axis at a non-voltage control end of a modular voltage source converter valve according to an embodiment of the invention;
FIG. 16 is a schematic diagram illustrating proportional feedforward control of the D-axis of the non-voltage control terminal of the modular voltage source converter valve according to the embodiment of the invention;
FIG. 17 is a schematic diagram illustrating proportional feedforward control of the non-voltage control end Q-axis of a modular voltage source converter valve according to an embodiment of the invention;
FIG. 18 is a schematic diagram illustrating proportional feedforward control of a DQ axis at a non-voltage control terminal of a modular voltage source converter valve according to an embodiment of the invention;
FIG. 19 is a schematic diagram of an inner loop and feed forward control for power oscillation suppression of a modular voltage source converter valve according to an embodiment of the present invention;
FIG. 20 is a schematic diagram of a modular voltage source converter valve circulating current suppression calculation according to an embodiment of the invention;
FIG. 21 is a schematic diagram of a modular voltage source converter valve ringing suppression control loop according to an embodiment of the present invention;
FIG. 22 is a schematic diagram illustrating generation of upper and lower bridge arm reference voltages for a modular voltage source converter valve according to an embodiment of the invention;
FIG. 23 is a schematic diagram of sending-end and receiving-end DC voltages of a modular voltage source converter valve without feedforward control according to an embodiment of the invention;
FIG. 24 is a schematic diagram of the real and reactive power at the sending end of the modular voltage source converter valve without using the feedforward control according to the embodiment of the present invention;
FIG. 25 is a schematic diagram of receiving end active and reactive power of a modular voltage source converter valve without feed-forward control according to an embodiment of the present invention;
FIG. 26 is a schematic diagram of sending-end and receiving-end DC voltages of a modular voltage source converter valve using feedforward control according to an embodiment of the present invention;
FIG. 27 is a schematic diagram of the feed end active and reactive power of the modular voltage source converter valve using feed forward control according to the embodiment of the present invention;
fig. 28 is a schematic diagram of receiving-end active and reactive powers of a modular voltage source converter valve using feed-forward control according to an embodiment of the present invention.
Detailed Description
The technical solutions in the embodiments of the present invention will be clearly and completely described below with reference to the drawings in the embodiments of the present invention, and it is obvious that the described embodiments are only a part of the embodiments of the present invention, and not all of the embodiments. All other embodiments, which can be derived by a person skilled in the art from the embodiments given herein without making any creative effort, shall fall within the protection scope of the present invention.
The embodiment of the invention provides a method for inhibiting direct-current voltage and power oscillation of a modular voltage source converter valve under the conditions of long-distance and low-power transmission, wherein a schematic diagram of long-distance power transmission of the modular voltage source converter valves at two ends is shown in figure 1, a flow schematic diagram of the inhibiting method is shown in figure 2, and the method mainly comprises the following steps:
step (ii) ofS1, collecting the side active and reactive and three-phase voltages U of the modular voltage source converter valve systemsabcThree-phase current IsabcUpper bridge arm current ITabcLower bridge arm current IBabcAnd a direct current voltage UdcWherein the phase locked loop is as shown in fig. 3;
step S2, for the Usabc、IsabcDQ conversion is carried out to obtain a system side voltage component u under a two-phase rotating coordinate systemsdq(usd、usq) The current component i of the feedbacksDQ(IsD、IsQ)；
Step S3, calculating the outer loop active reference current I according to the active reference and the active feedbackrDSelecting a reactive current calculation mode according to the outer ring reactive power control mode to obtain an outer ring reactive power reference current IrQThe outer loop reactive power control schematic diagram is shown in fig. 4, the outer loop active power control schematic diagram is shown in fig. 5, and the outer loop current amplitude limiting schematic diagram is shown in fig. 6;
step S4, calculating the active reference current I obtained by the outer looprDReactive reference current IrQAnd the feedback current isDQObtaining reference voltage U under DQ axis through decoupling and PI controlrefDQ；
Step S5, according to the DC voltage UdcObtaining a feedforward control signal, and controlling the DC voltage and a reference voltage U at the DC voltage control enddc *Making a difference, carrying out low-pass filtering on the direct current voltage at a non-voltage control end to obtain a difference signal, and carrying out proportional integral or proportional control to obtain a feedforward control signal U based on a D axisfDQQ-axis feedforward control signal UfQAnd DQ Axis feedforward control Signal UfDQThe control block diagrams are shown in fig. 7-18;
step S6, adding the reference voltage and the feedforward signal under DQ axis, namely UrefDQ+UfDQ、UrefDQ+UfD、UrefDQ+UfQDQ inverse transformation is carried out to obtain a reference voltage U of feedforward controlreffabcAs shown in fig. 19;
step S7, circulating current restraining, wherein the specific adopted method is as aboveLower two-arm current ITabc、IBabcAveraging, performing 2-frequency-multiplication DQ conversion of negative sequence to obtain DQ component of current conversion, and performing inner loop PI control to obtain output current-suppressing voltage UzDQThen obtaining the commutation suppression voltage U under the static abc coordinate through 2-frequency-multiplication DQ inverse transformationzabcAs shown in fig. 19-21;
step S8, converting the UreffabcAnd the UzabcAnd superposing to obtain reference voltages of an upper bridge arm and a lower bridge arm, and then performing nearest level approximation modulation to obtain a switch control signal of the modular voltage source converter valve so as to realize suppression of power oscillation of the modular voltage source converter valve, as shown in fig. 22.
According to the embodiment of the invention, the direct-current voltage of the flexible direct-current power transmission system is used as the feedforward signal, so that the links of coordinate transformation and filtering for extracting the damping signal from the system current are avoided, the calculated amount is reduced, and the implementation is convenient. The method can enhance the stability and control of the direct current transmission system under the condition of low power and long-distance transmission, and the suppression of direct current voltage and power oscillation from the converter valve is realized by directly correcting the output voltage.
According to an embodiment of the present invention, the following methods are implemented by using the proportional integral or proportional control and the feedforward control applied to the D axis, the Q axis and the DQ axis according to whether the converter valve controls the voltage in step S5.
When the feed-forward signal is applied to the D-axis at the voltage control end by PI control, as shown in fig. 7, the reference value U of the dc voltage is setdc *And the direct current voltage UdcMaking difference to obtain DC voltage deviation delta Udc(ii) a Performing proportional integral processing on the direct-current voltage deviation delta Udc according to the following formula to obtain the control signal:
UfD＝ΔUdc×(kp+1/sTi) (1)
wherein, UfDIs a feedforward control signal; k is a radical ofpIs a proportional control coefficient; t isiIs the rotor side integration time constant.
At the voltage control end, a feedforward signal is applied to the Q axis and PI control is adoptedThen, as shown in FIG. 8, for the DC voltage reference value Udc *And the direct current voltage UdcMaking difference to obtain DC voltage deviation delta Udc(ii) a Performing proportional integral processing on the direct-current voltage deviation delta Udc according to the following formula to obtain the control signal:
UfQ＝ΔUdc×(kp+1/sTi) (2)
wherein, UfQIs a feedforward control signal; k is a radical ofpIs a proportional control coefficient; t isiIs the rotor side integration time constant.
When the feed-forward signal is applied to the DQ axis at the voltage control terminal and PI control is adopted, as shown in fig. 9, the reference value U is set for the dc voltagedc *And the direct current voltage UdcMaking difference to obtain DC voltage deviation delta Udc(ii) a Performing proportional integral processing on the direct-current voltage deviation delta Udc according to the following formula to obtain the control signal:
UfDQ＝ΔUdc×(kp+1/sTi) (3)
wherein, UfDQIs a feedforward control signal; k is a radical ofpIs a proportional control coefficient; t isiIs the rotor side integration time constant.
When the feedforward signal is applied to the D axis at the voltage control end and proportional control is adopted, as shown in FIG. 10, the reference value U of the DC voltage is obtaineddc *And the direct current voltage UdcMaking difference to obtain DC voltage deviation delta Udc(ii) a And carrying out proportional processing on the direct-current voltage deviation delta Udc according to the following formula to obtain the control signal:
UfD＝ΔUdc×kp(4)
wherein, UfDIs a feedforward control signal; k is a radical ofpIs a proportional control coefficient.
When the feedforward signal is applied to the Q-axis at the voltage control end and proportional control is adopted, as shown in fig. 11, the reference value U of the dc voltage is obtaineddc *And the direct current voltage UdcMaking difference to obtain DC voltage deviation delta Udc(ii) a For the direct current voltage deviation delta Udc according to the following formulaAnd (3) carrying out proportional processing to obtain the control signal:
UfQ＝ΔUdc×kp(5)
wherein, UfQIs a feedforward control signal; k is a radical ofpIs a proportional control coefficient.
When the feedforward signal is applied to the DQ axis at the voltage control terminal by proportional control, as shown in fig. 12, the reference value U is set to the dc voltagedc *And the direct current voltage UdcMaking difference to obtain DC voltage deviation delta Udc(ii) a And carrying out proportional processing on the direct-current voltage deviation delta Udc according to the following formula to obtain the control signal:
UfDQ＝ΔUdc×kp(6)
wherein, UfDQIs a feedforward control signal; k is a radical ofpIs a proportional control coefficient.
When the feed-forward signal is applied to the D-axis at the non-voltage control end and PI control is adopted, as shown in fig. 13, the reference value U of the dc voltage is setdc *And the direct current voltage UdcMaking difference to obtain DC voltage deviation delta Udc(ii) a Performing proportional integral processing on the direct-current voltage deviation delta Udc according to the following formula to obtain the control signal:
UfD＝ΔUdc×(kp+1/sTi) (7)
wherein, UfDIs a feedforward control signal; k is a radical ofpIs a proportional control coefficient; t isiIs the rotor side integration time constant.
When the feed-forward signal is applied to the Q-axis at the non-voltage control end and PI control is adopted, as shown in fig. 14, the reference value U of the dc voltage is setdc *And the direct current voltage UdcMaking difference to obtain DC voltage deviation delta Udc(ii) a Performing proportional integral processing on the direct-current voltage deviation delta Udc according to the following formula to obtain the control signal:
UfQ＝ΔUdc×(kp+1/sTi) (8)
wherein, UfQIs a feedforward control signal; k is a radical ofpIs a proportional control coefficient；TiIs the rotor side integration time constant.
When the feed-forward signal is applied to the DQ axis at the non-voltage control terminal and PI control is adopted, as shown in fig. 15, the reference value U is set for the dc voltagedc *And the direct current voltage UdcMaking difference to obtain DC voltage deviation delta Udc(ii) a Performing proportional integral processing on the direct-current voltage deviation delta Udc according to the following formula to obtain the control signal:
UfDQ＝ΔUdc×(kp+1/sTi) (9)
wherein, UfDQIs a feedforward control signal; k is a radical ofpIs a proportional control coefficient; t isiIs the rotor side integration time constant.
When the feed-forward signal is applied to the D-axis at the non-voltage control end and proportional control is adopted, as shown in FIG. 16, the reference value U of the DC voltage is obtaineddc *And the direct current voltage UdcMaking difference to obtain DC voltage deviation delta Udc(ii) a And carrying out proportional processing on the direct-current voltage deviation delta Udc according to the following formula to obtain the control signal:
UfD＝ΔUdc×kp(10)
wherein, UfDIs a feedforward control signal; k is a radical ofpIs a proportional control coefficient.
When the feedforward signal is applied to the Q axis at the non-voltage control end and proportional control is adopted, as shown in fig. 17, the reference value U of the dc voltage is obtaineddc *And the direct current voltage UdcMaking difference to obtain DC voltage deviation delta Udc(ii) a And carrying out proportional processing on the direct-current voltage deviation delta Udc according to the following formula to obtain the control signal:
UfQ＝ΔUdc×kp(11)
wherein, UfQIs a feedforward control signal; k is a radical ofpIs a proportional control coefficient.
When the feedforward signal is applied to the DQ axis at the non-voltage control end by proportional control, as shown in fig. 18, the reference value U is set to the dc voltagedc *And the direct current voltage UdcMaking difference to obtain DC voltage deviation delta Udc(ii) a And carrying out proportional processing on the direct-current voltage deviation delta Udc according to the following formula to obtain the control signal:
UfDQ＝ΔUdc×kp(12)
wherein, UfDQIs a feedforward control signal; k is a radical ofpIs a proportional control coefficient.
Step S1-S7 calculates a calculated reference voltage after feedforward control is applied, step S8 adds and subtracts the calculated circulating current suppression control signal and the calculated reference voltage to respectively obtain reference voltages of an upper bridge arm and a lower bridge arm, and the reference voltages are modulated to realize power and voltage oscillation of the voltage source converter valve under long distance and low power.
In order to more clearly illustrate the technical solution of the present invention, a detailed embodiment is described below.
The embodiment of the invention performs transient time domain simulation on a researched system. The simulation is carried out by adopting two ends of long-distance power transmission adopting a metal return wire with 3000MVA direct-current voltage +/-500 kV, a power transmitting end adopts constant power control, a power receiving end adopts constant voltage control, both the transmitting end and the receiving end adopt unit power factors, direct-current voltage simulation waveforms of the transmitting end and the receiving end obtained without taking inhibiting measures are shown in fig. 23, active and reactive waveforms of the transmitting end are shown in fig. 24, and active and reactive waveforms of the receiving end are shown in fig. 25. As seen from the time domain waveform, the DC voltage and power contain 1Hz fluctuation component.
After a feedforward control module is added in a control system, direct-current voltage simulation waveforms of a transmitting end and a receiving end are shown in fig. 26, an active and reactive waveform of the transmitting end is shown in fig. 27, and an active and reactive waveform of the receiving end is shown in fig. 28. Comparing fig. 23 and 26, fig. 24 and 27, fig. 25 and 28, from the waveform, by adding the feedforward control module, the modular voltage source converter valve can avoid the direct current voltage and the power oscillation under the low power, which is consistent with the theoretical analysis.
The direct current voltage and power oscillation problem of the modular voltage source converter valve under long distance and low power of the embodiment of the invention provides a feedforward control method based on the direct current voltage, which specifically comprises proportional feedforward control and proportional integral feedforward control of a voltage control end, and proportional feedforward control and proportional integral feedforward control of a non-voltage control end, wherein the additional control is respectively added to a D axis, a Q axis and a DQ axis, corresponding parameters of a controller are designed, real-time simulation is carried out, the effectiveness of a control strategy provided by the embodiment of the invention is verified, and the direct current voltage and power oscillation of the modular voltage source converter valve under long distance and low power can be effectively inhibited. The embodiment of the invention avoids the coordinate transformation and the number of the resonance controllers under the DQ coordinate, reduces the calculated amount and is convenient to realize.
It will be understood by those skilled in the art that all or part of the steps in the method for implementing the above embodiments may be implemented by relevant hardware instructed by a program, and the program may be stored in a computer readable storage medium, such as ROM/RAM, magnetic disk, optical disk, etc.
The above-mentioned embodiments are intended to illustrate the objects, technical solutions and advantages of the present invention in further detail, and it should be understood that the above-mentioned embodiments are only exemplary embodiments of the present invention, and are not intended to limit the scope of the present invention, and any modifications, equivalent substitutions, improvements and the like made within the spirit and principle of the present invention should be included in the scope of the present invention.
Claims (16)
1. A feed-forward control method for suppressing power oscillation of a modular voltage source type converter valve is characterized by comprising the following steps,
collecting active and reactive three-phase voltage U at side of modular voltage source converter valve systemsabcThree-phase current IsabcUpper bridge arm current ITabcAnd lower bridge arm current IBabcAnd a direct current voltage Udc；
For the three-phase voltage UsabcThree-phase current IsabcDQ conversion is carried out to obtain a system side voltage component u under a two-phase rotating coordinate systemsdqI.e. usd、usqAnd a feedback current component isDQI.e. IsD、IsQ；
According to active reference andwork feedback calculation outer loop active reference current IrDSelecting a reactive current calculation mode according to the outer ring reactive power control mode to obtain an outer ring reactive power reference current IrQ；
Calculating the obtained outer ring active reference current IrDOuter ring reactive reference current IrQWith said feedback current component isDQObtaining reference voltage U under DQ axis through decoupling and PI controlrefDQ；
According to the DC voltage UdcObtaining a feedforward control signal, and controlling the DC voltage U at a DC voltage control enddcAnd a DC voltage reference value Udc *Taking a difference, and applying the DC voltage U to a non-voltage control enddcLow-pass filtering to obtain difference signal, proportional-integral or proportional-control to obtain D-axis feedforward control signal UfDQ-axis feedforward control signal UfQAnd DQ Axis feedforward control Signal UfDQ；
The reference voltage U under DQ axisrefDQAre added separately to each feedforward control signal, i.e. UrefDQ+UfDQ、UrefDQ+UfD、UrefDQ+UfQCarrying out DQ inverse transformation to obtain a reference voltage U of feedforward controlreffabc；
The current I of the upper bridge arm and the lower bridge arm is restrained by circulation currentTabc、IBabcAveraging, performing 2-frequency-multiplication DQ conversion of negative sequence to obtain DQ component of circulating current, and performing inner loop PI control to obtain output circulating current suppression voltage UzDQAnd then obtaining the circulating current suppression voltage U under the static abc coordinate through 2-frequency-multiplication DQ inverse transformationzabc；
Reference voltage U to be feedforward controlledreffabcWith said circulating current suppression voltage UzabcAnd superposing to obtain reference voltages of an upper bridge arm and a lower bridge arm, and then obtaining a switch control signal of the modular voltage source converter valve through nearest level approximation modulation.
2. The method of claim 1, wherein the calculated outer loop active reference current I is calculatedrDOuter ring reactive reference currentIrQWith said feedback current component isDQI.e. IsD、IsQObtaining reference voltage U under D axis through decoupling and PI controlrefDAnd reference voltage U under Q-axisrefQComprises the steps of (a) preparing a mixture of a plurality of raw materials,
UrefD＝μsd-(kp2+1/sTi2)(IrD-IsD)+LsωsIsQ
UrefQ＝μsq-(kp2+1/sTi2)(IrQ-IsQ)+LsωsIsD；
wherein Ls is bridge arm reactance, ω s synchronous electrical angular velocity, kp2And Ti2 is an integral time constant of the inner loop proportional integral PI control.
3. Method according to claim 1, characterized in that the direct voltage U is dependent ondcAnd the DC voltage reference value Udc *The step of obtaining the feedforward control signal, namely applying the feedforward control signal to the D axis, comprises the following steps:
when the converter valve at the DC voltage control end is subjected to feedforward control, a DC voltage reference value U is subjected to feedforward controldc *And the direct current voltage UdcMaking difference to obtain DC voltage deviation delta Udc；
For the DC voltage deviation Delta UdcCarrying out proportional integral processing according to the following formula to obtain a D-axis feedforward control signal:
UfD＝ΔUdc×(kp+1/sTi)
wherein, UfDA D-axis feedforward control signal; k is a radical ofpIs a proportional control coefficient; t isiIs the rotor side integration time constant.
4. Method according to claim 1, characterized in that said direct voltage U is dependent on said direct voltagedcAnd a DC voltage reference value Udc *The step of obtaining the feedforward control signal, namely applying the feedforward control signal to the Q axis, comprises the following steps:
when the converter valve at the DC voltage control end is subjected to feedforward control, a DC voltage reference value U is subjected to feedforward controldc *And the direct current voltage UdcMaking difference to obtain DC voltage deviation delta Udc；
Carrying out proportional integral processing on the direct current voltage deviation delta Udc according to the following formula to obtain a Q-axis feedforward control signal,
UfQ＝ΔUdc×(kp+1/sTi)
wherein, UfQFeeding forward a control signal for the Q axis; k is a radical ofpIs a proportional control coefficient; t isiIs the rotor side integration time constant.
5. Method according to claim 1, characterized in that the direct voltage U is dependent ondcAnd a DC voltage reference value Udc *To obtain the feed-forward control signal based on the DQ axis, that is, the feed-forward control signal can be applied to the D and Q axes simultaneously includes:
when the converter valve at the direct current voltage control end is subjected to feedforward control, the direct current voltage reference value U is subjected to feedforward controldc *And the direct current voltage UdcMaking difference to obtain DC voltage deviation delta Udc；
Performing proportional integral processing on the direct current voltage deviation delta Udc according to the following formula to obtain a DQ axis feedforward control signal:
UfDQ＝ΔUdc×(kp+1/sTi)
wherein, UfDQA D-axis feedforward control signal; k is a radical ofpIs a proportional control coefficient; t isiIs the rotor side integration time constant.
6. Method according to claim 1, characterized in that the direct voltage U is dependent ondcAnd a DC voltage reference value Udc *To obtain a feedforward control signal, i.e., the application of the feedforward control signal to the D-axis includes,
when the converter valve at the direct current voltage control end is subjected to feedforward control, the direct current voltage reference value U is subjected to feedforward controldc *And the direct current voltage UdcMaking difference to obtain DC voltage deviation delta Udc；
For the DC voltage deviation Delta UdcCarrying out proportion processing according to the following formula to obtain a D-axis feedforward control signal,
UfD＝ΔUdc×kp
wherein, UfDA D-axis feedforward control signal; k is a radical ofpIs a proportional control coefficient.
7. Method according to claim 1, characterized in that the direct voltage U is dependent ondcAnd a DC voltage reference value Udc *The step of obtaining the feedforward control signal, namely applying the feedforward control signal to the Q axis, comprises the following steps:
when the converter valve at the direct current voltage control end is subjected to feedforward control, the direct current voltage reference value U is subjected to feedforward controldc *And the direct current voltage UdcMaking difference to obtain DC voltage deviation delta Udc；
For the DC voltage deviation Delta UdcCarrying out proportion processing according to the following formula to obtain a Q-axis feedforward control signal,
UfQ＝ΔUdc×kp
wherein, UfQFeeding forward a control signal for the Q axis; k is a radical ofpIs a proportional control coefficient.
8. Method according to claim 1, characterized in that the direct voltage U is dependent ondcAnd a DC voltage reference value Udc *To obtain a feed-forward control signal based on the DQ axis, i.e. the feed-forward control signal may be applied to the DQ axis simultaneously comprises,
when the converter valve at the direct current voltage control end is subjected to feedforward control, the direct current voltage reference value U is subjected to feedforward controldc *And the direct current voltage UdcMaking difference to obtain DC voltage deviation delta Udc；
For the DC voltage deviation Delta UdcPerforming proportional processing according to the following formula to obtain a DQ axis feedforward control signal,
UfDQ＝ΔUdc×kp
wherein, UfDQFeeding forward a control signal for a DQ axis; k is a radical ofpIs a proportional control coefficient.
9. The method of claim 1, wherein the obtaining a feedforward control signal, the method further comprises,
when the converter valve at the non-DC voltage control end carries out feedforward, the DC voltage U is converted into the DC voltage UdcLow-pass filtering to obtain DC voltage deviation delta Udc；
For the DC voltage deviation Delta UdcProportional integral processing is carried out according to the following formula to obtain a feedforward control signal of the D axis,
UfD＝ΔUdc×(kp+1/sTi)
wherein, UfDA D-axis feedforward control signal; k is a radical ofpIs a proportional control coefficient; t isiIs the rotor side integration time constant.
10. The method of claim 1, wherein the obtaining a feedforward control signal, the method further comprises,
when the converter valve at the non-DC voltage control end carries out feedforward, the DC voltage U is converted into the DC voltage UdcLow-pass filtering to obtain DC voltage deviation delta Udc；
For the DC voltage deviation Delta UdcProportional integral processing is carried out according to the following formula to obtain a feedforward control signal of the Q axis,
UfQ＝ΔUdc×(kp+1/sTi)
wherein, UfQFeeding forward a control signal for the Q axis; k is a radical ofpIs a proportional control coefficient; t isiIs the rotor side integration time constant.
11. The method of claim 1, wherein the obtaining a feedforward control signal, the method further comprises,
when the converter valve at the non-DC voltage control end carries out feedforward, the DC voltage U is converted into the DC voltage UdcLow-pass filtering to obtain DC voltage deviation delta Udc；
For the DC voltage deviation Delta UdcPerforming proportional integral processing according to the following formula to obtain a feedforward control signal of the DQ axis:
UfDQ＝ΔUdc×(kp+1/sTi)
wherein, UfDQFeeding a control signal for a front DQ axis; k is a radical ofpIs a proportional control coefficient; t isiIs the rotor side integration time constant.
12. The method of claim 1, wherein the obtaining a feedforward control signal, the method further comprises,
when the converter valve at the non-DC voltage control end carries out feedforward, the DC voltage U is converted into the DC voltage UdcLow-pass filtering to obtain DC voltage deviation delta Udc；
For the DC voltage deviation Delta UdcCarrying out proportion processing according to the following formula to obtain a feedforward control signal of the D axis:
UfD＝ΔUdc×kp
wherein, UfDA D-axis feedforward control signal; k is a radical ofpIs a proportional control coefficient.
13. The method of claim 1, wherein the obtaining a feedforward control signal, the method further comprises,
when the converter valve at the non-DC voltage control end carries out feedforward, the DC voltage U is converted into the DC voltage UdcLow-pass filtering to obtain DC voltage deviation delta Udc；
For the DC voltage deviation Delta UdcCarrying out proportion processing according to the following formula to obtain a feedforward control signal of the Q axis,
UfQ＝ΔUdc×kp
wherein, UfQFeeding forward a control signal for the Q axis; k is a radical ofpFor proportional controlAnd (4) the coefficient.
14. The method of claim 1, wherein the obtaining a feedforward control signal, the method further comprises,
when the converter valve at the non-DC voltage control end carries out feedforward, the DC voltage U is converted into the DC voltage UdcLow-pass filtering to obtain DC voltage deviation delta Udc；
For the DC voltage deviation Delta UdcPerforming proportional processing according to the following formula to obtain a feedforward control signal of the DQ axis,
UfDQ＝ΔUdc×kp
wherein, UfDQFeeding forward a control signal for a DQ axis; k is a radical ofpIs a proportional control coefficient.
15. The method of claim 1, wherein the method comprises averaging upper and lower bridge arm currents, performing 2-frequency-multiplication DQ conversion of negative sequence to obtain zero-sequence currents of the upper and lower arms, wherein the zero-sequence currents of the upper and lower bridge arms are DQ components of circulating current, and performing inner loop PI control to obtain circulating current suppression voltage U under output stationary abc coordinates for suppressing circulating currentzabc。
16. The method of claim 1, wherein the U isreffabcAnd UzabcSuperposing to obtain the reference voltage U of the upper and lower bridge armsTreffabcAnd UBreffabcObtaining the switch control signal of the modular voltage source converter valve through the recent level approximation modulation,
UTreffabc＝Ureffabc+Uzabc
UBreffabc＝Ureffabc-Uzabc。
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