CN112134303B - Dead-beat current control method based on hexagonal converter wind power generation system - Google Patents

Dead-beat current control method based on hexagonal converter wind power generation system Download PDF

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CN112134303B
CN112134303B CN202010957744.8A CN202010957744A CN112134303B CN 112134303 B CN112134303 B CN 112134303B CN 202010957744 A CN202010957744 A CN 202010957744A CN 112134303 B CN112134303 B CN 112134303B
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bridge arm
reference value
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phase
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CN112134303A (en
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荣飞
潘烙
徐爽
孙宗卿
刘成
陈志忠
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Hunan University
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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
    • H02J3/38—Arrangements for parallely feeding a single network by two or more generators, converters or transformers
    • H02J3/381—Dispersed generators
    • 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
    • H02J3/38—Arrangements for parallely feeding a single network by two or more generators, converters or transformers
    • H02J3/46—Controlling of the sharing of output between the generators, converters, or transformers
    • H02J3/466—Scheduling the operation of the generators, e.g. connecting or disconnecting generators to meet a given demand
    • H—ELECTRICITY
    • H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
    • H02M—APPARATUS FOR CONVERSION BETWEEN AC AND AC, BETWEEN AC AND DC, OR BETWEEN DC AND DC, AND FOR USE WITH MAINS OR SIMILAR POWER SUPPLY SYSTEMS; CONVERSION OF DC OR AC INPUT POWER INTO SURGE OUTPUT POWER; CONTROL OR REGULATION THEREOF
    • H02M5/00—Conversion of ac power input into ac power output, e.g. for change of voltage, for change of frequency, for change of number of phases
    • H02M5/02—Conversion of ac power input into ac power output, e.g. for change of voltage, for change of frequency, for change of number of phases without intermediate conversion into dc
    • H02M5/04—Conversion of ac power input into ac power output, e.g. for change of voltage, for change of frequency, for change of number of phases without intermediate conversion into dc by static converters
    • H02M5/22—Conversion of ac power input into ac power output, e.g. for change of voltage, for change of frequency, for change of number of phases without intermediate conversion into dc by static converters using discharge tubes with control electrode or semiconductor devices with control electrode
    • H02M5/275—Conversion of ac power input into ac power output, e.g. for change of voltage, for change of frequency, for change of number of phases without intermediate conversion into dc by static converters using discharge tubes with control electrode or semiconductor devices with control electrode using devices of a triode or transistor type requiring continuous application of a control signal
    • H02M5/293—Conversion of ac power input into ac power output, e.g. for change of voltage, for change of frequency, for change of number of phases without intermediate conversion into dc by static converters using discharge tubes with control electrode or semiconductor devices with control electrode using devices of a triode or transistor type requiring continuous application of a control signal using semiconductor devices only
    • H—ELECTRICITY
    • H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
    • H02P—CONTROL OR REGULATION OF ELECTRIC MOTORS, ELECTRIC GENERATORS OR DYNAMO-ELECTRIC CONVERTERS; CONTROLLING TRANSFORMERS, REACTORS OR CHOKE COILS
    • H02P9/00—Arrangements for controlling electric generators for the purpose of obtaining a desired output
    • 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
    • H02J2300/00—Systems for supplying or distributing electric power characterised by decentralized, dispersed, or local generation
    • H02J2300/20—The dispersed energy generation being of renewable origin
    • H02J2300/28—The renewable source being wind energy
    • H—ELECTRICITY
    • H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
    • H02M—APPARATUS FOR CONVERSION BETWEEN AC AND AC, BETWEEN AC AND DC, OR BETWEEN DC AND DC, AND FOR USE WITH MAINS OR SIMILAR POWER SUPPLY SYSTEMS; CONVERSION OF DC OR AC INPUT POWER INTO SURGE OUTPUT POWER; CONTROL OR REGULATION THEREOF
    • H02M5/00—Conversion of ac power input into ac power output, e.g. for change of voltage, for change of frequency, for change of number of phases
    • H02M5/02—Conversion of ac power input into ac power output, e.g. for change of voltage, for change of frequency, for change of number of phases without intermediate conversion into dc
    • H02M5/04—Conversion of ac power input into ac power output, e.g. for change of voltage, for change of frequency, for change of number of phases without intermediate conversion into dc by static converters
    • H02M5/22—Conversion of ac power input into ac power output, e.g. for change of voltage, for change of frequency, for change of number of phases without intermediate conversion into dc by static converters using discharge tubes with control electrode or semiconductor devices with control electrode
    • H02M5/275—Conversion of ac power input into ac power output, e.g. for change of voltage, for change of frequency, for change of number of phases without intermediate conversion into dc by static converters using discharge tubes with control electrode or semiconductor devices with control electrode using devices of a triode or transistor type requiring continuous application of a control signal
    • H02M5/293—Conversion of ac power input into ac power output, e.g. for change of voltage, for change of frequency, for change of number of phases without intermediate conversion into dc by static converters using discharge tubes with control electrode or semiconductor devices with control electrode using devices of a triode or transistor type requiring continuous application of a control signal using semiconductor devices only
    • H02M5/2932—Conversion of ac power input into ac power output, e.g. for change of voltage, for change of frequency, for change of number of phases without intermediate conversion into dc by static converters using discharge tubes with control electrode or semiconductor devices with control electrode using devices of a triode or transistor type requiring continuous application of a control signal using semiconductor devices only with automatic control of output voltage, current or power
    • H—ELECTRICITY
    • H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
    • H02P—CONTROL OR REGULATION OF ELECTRIC MOTORS, ELECTRIC GENERATORS OR DYNAMO-ELECTRIC CONVERTERS; CONTROLLING TRANSFORMERS, REACTORS OR CHOKE COILS
    • H02P2101/00—Special adaptation of control arrangements for generators
    • H02P2101/15—Special adaptation of control arrangements for generators for wind-driven turbines
    • H—ELECTRICITY
    • H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
    • H02P—CONTROL OR REGULATION OF ELECTRIC MOTORS, ELECTRIC GENERATORS OR DYNAMO-ELECTRIC CONVERTERS; CONTROLLING TRANSFORMERS, REACTORS OR CHOKE COILS
    • H02P2103/00—Controlling arrangements characterised by the type of generator
    • H02P2103/20—Controlling arrangements characterised by the type of generator of the synchronous type
    • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
    • Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
    • Y02E—REDUCTION OF GREENHOUSE GAS [GHG] EMISSIONS, RELATED TO ENERGY GENERATION, TRANSMISSION OR DISTRIBUTION
    • Y02E10/00—Energy generation through renewable energy sources
    • Y02E10/70—Wind energy
    • Y02E10/76—Power conversion electric or electronic aspects

Abstract

The invention discloses a deadbeat control method based on a hexagonal converter wind power generation system. The wind power generation system includes: a direct-drive permanent magnet synchronous generator and a hexagonal converter; the direct-drive permanent magnet synchronous generator is coaxially connected with the wind turbine and is directly merged into an alternating current power grid through AC/AC conversion of a hexagonal converter; the converter is formed by connecting 6 identical bridge arms end to end, and each bridge arm is formed by connecting N full-bridge submodules and an inductor L in series; the direct-drive permanent magnet synchronous generator three-phase R, S, T and the grid three-phase U, V, W are alternately connected to six vertexes of a hexagon; the method comprises the steps of firstly, respectively calculating a machine side current reference value, a network side current reference value, a circulating current reference value and a neutral point voltage reference value by adopting maximum power tracking control and bridge arm energy balance control, thereby obtaining a bridge arm current reference value and a bridge arm voltage reference value and realizing the dead-beat prediction control of bridge arm current; the control method is not influenced by the frequency fluctuation of the machine side and the network side, is simple and can greatly reduce the pressure of a digital processor.

Description

Dead-beat current control method based on hexagonal converter wind power generation system
Technical Field
The invention belongs to the field of power electronic current transformation, and particularly relates to a deadbeat current control method based on a hexagonal current transformer wind power generation system.
Background
With the increasing global warming effect in recent years and the increasing shortage of traditional fossil energy supply, people begin to explore the development and utilization of new energy. Wind energy is a pollution-free renewable energy source, and is made to stand out in the field of new energy power generation by utilizing the characteristics of simplicity and inexhaustibility.
According to research, if 1% of the total amount of wind energy in the world is utilized, 3% of the world's energy can be saved. The utilization of wind energy may replace traditional energy sources such as fossil fuel and nuclear energy in the future. Wind power generation is taken as an effective solution to the problems of energy shortage, atmospheric pollution, energy conservation, emission reduction and the like in all countries in the world, so that the wind power generation is paid more and more attention and is applied.
Because wind energy has uncertainty, most of the electric energy generated by the fan cannot be directly utilized, and the wind energy needs to be subjected to a series of transformation, control and processing by a power electronic converter device so as to be connected to the power grid. At present, a series of topological structures of power electronic devices related to wind power grid connection have been proposed at home and abroad, a hexagonal converter is a two-port AC/AC converter which is proposed in recent years, direct voltage transformation and frequency conversion control of 2 medium and high voltage AC ports can be realized only by 6 bridge arms, and the hexagonal converter has good low-frequency performance, and is very suitable for wind power generation and motor driving because the frequency of a fan is generally low.
Therefore, the control based on the hexagonal converter wind power generation system has great significance for the research of wind power integration and the development and utilization of new energy.
The traditional wind power grid-connected converter adopts a backrest type structure, needs a plurality of switching devices when AC/AC conversion is carried out, has higher cost and larger loss during operation, and causes more and more serious power grid pollution. Therefore, there is a need to develop a new topology and a control method thereof that can reduce the cost, reduce the loss, and improve the power quality of the power grid.
Disclosure of Invention
The invention aims to provide a deadbeat current control method based on a hexagonal converter wind power generation system, aiming at the defects of the prior art, which can effectively reduce the cost of a digital processor, reduce the switching frequency, improve the tracking precision of the system and ensure the electric energy quality of the generated energy of a fan under the condition of wind speed change.
In order to achieve the purpose, the invention adopts the technical scheme that:
(1) the wind energy is captured by a system wind turbine, a direct-drive permanent magnet synchronous generator which is coaxially connected is dragged to generate power, R, S, T three phases of the wind driven generator and U, V, W three phases of a power grid are alternately connected to six hexagonal vertexes, and electric energy generated by the wind driven generator is directly connected to the grid after being converted by a hexagonal converter AC/AC.
(2) The method comprises the steps that a machine side current reference value is obtained by carrying out maximum power tracking control on a direct-drive permanent magnet synchronous generator, a network side current reference value is obtained by controlling a power grid to absorb active power and balance power sent by a fan, a direct current circulation reference value is obtained by controlling the balance of capacitor voltages of odd bridge arms and even bridge arms, an alternating current circulation reference value is obtained by controlling the balance of capacitor voltages of sub-modules of each bridge arm, the four current components are superposed to obtain a bridge arm current reference value, the value of the next control period of each parameter in the formula is predicted, the bridge arm voltage of the next control period is obtained by calculating a bridge arm voltage expression, and the modulation voltage of each bridge arm of a converter is modulated by adopting a nearest level approximation mode, so that a control signal of each sub-module of each bridge arm is obtained;
the invention has the beneficial effects that: 1) compared with the traditional back-to-back type converter, the six-bridge-arm AC/AC converter adopts a hexagonal converter topology, can directly carry out AC/AC conversion through six bridge arms, greatly reduces the number of used submodules, effectively reduces the cost and improves the working efficiency; 2) because the invention provides the dead-beat tracking control of the bridge arm current, the influence of machine side frequency and network side frequency fluctuation is not required to be considered, and the double-closed-loop control mode of the current inner ring and the voltage outer ring is adopted, the output current is ensured to meet the sine change rule, the impact on the power grid after wind power integration is effectively reduced, the switching frequency and the number of PI regulators can be greatly reduced by combining with the recent level approximation modulation mode, and the pressure of a digital processor is reduced.
Drawings
FIG. 1 is a topological structure diagram of a wind power generation system based on a hexagonal converter;
FIG. 2 is a dead-beat current control block diagram of a hexagonal converter based wind power generation system;
FIG. 3 is a net side phase current waveform under nominal operating conditions;
FIG. 4 illustrates the machine side phase current waveforms under nominal operating conditions;
FIG. 5 illustrates distortion of the grid-side phase current waveform under nominal operating conditions;
fig. 6 illustrates the distortion rate of the phase current waveform on the machine side under the rated operating condition.
Detailed Description
In order to make the technical problems, technical solutions and advantageous effects solved by the present invention more clear, the present invention is further described in detail below with reference to the accompanying drawings. It should be understood that the specific embodiments described herein are merely illustrative of the invention and are not intended to limit the invention.
FIG. 1 is a topological structure diagram of a wind power generation system based on a hexagonal converter, wherein the wind power generation system is composed of a direct-drive permanent magnet synchronous generator and the hexagonal converter; the rotor of the direct-drive permanent magnet synchronous generator is coaxially connected with a wind turbine, and the stator is provided with three windings, namely R, S, T; u, V, W for three phases of the power grid respectively; the hexagonal converter is formed by connecting 6 identical bridge arms end to end into a hexagon; each bridge arm is formed by connecting N identical full-bridge submodules and an inductor L in series; each submodule consists of 4 IGBT tubes T1, T2, T3, T4 and 1 capacitor C; the emitter of the T1 is connected with the collector of the T2 and forms the positive terminal of the submodule, and the emitter of the T3 is connected with the collector of the T4 and forms the negative terminal of the submodule; the collector of T1 is connected with the collector of T3 and forms the anode of the submodule, the emitter of T2 is connected with the emitter of T4 and forms the cathode of the submodule; the positive electrode and the negative electrode of the capacitor C are respectively connected with the positive electrode and the negative electrode of the submodule; the R, S, T three phases of the direct-drive permanent magnet synchronous generator and the U, V, W three phases of the power grid are alternately connected to six vertexes of the hexagon; recording a bridge arm directly connected with an R phase and a W phase as a bridge arm 1, recording a bridge arm directly connected with the W phase and the S phase as a bridge arm 2, recording a bridge arm directly connected with the S phase and the U phase as a bridge arm 3, recording a bridge arm directly connected with the U phase and the T phase as a bridge arm 4, recording a bridge arm directly connected with the T phase and the V phase as a bridge arm 5, and recording a bridge arm directly connected with the V phase and the R phase as a bridge arm 6; the submodules on each bridge arm are sequentially marked as SMx_1，SMx_2，…，SMx_NX is 1, 2, … 6;
in the example, the number N of the sub-modules in each bridge arm is 6, and the side line voltage rated value U of the fan ism3.3kV, and the rated voltage value of the side line of the power grid UgIs 10kV, the number of fan pole pairs Np54, the blade radius R is 74.4m, the size of the sub-module capacitor C is 20mF, and the sub-module capacitor voltage reference value UC_refThe voltage is 2500V, the size of the bridge arm inductance L is 10mH, and the control period T is 0.0002 s.
FIG. 2 is a dead-beat current control block diagram of a hexagonal converter-based wind power generation system, comprising the following steps:
step 1: computer side phase current reference value:
reference value i of side d-axis current of pickup machinemd_ref(K) Detecting the angular speed omega (K) of the fan rotor and comparing the angular speed omega (K) with the optimal angular speed omega (0)ref(K) Making a difference, ωref(K) Provided by a manufacturer, and regulated by a first PI regulator, wherein the output of the first PI regulator is a machine side q-axis current reference value imq_ref(K) And K represents the current time:
imq_ref(K)＝(KP1+KI1×(1/s))×[ωref(K)-ω(K)]
wherein 1/s is an integration factor, KP1、KI1Proportional coefficient and integral coefficient of the first PI regulator are respectively; machine side three-phase current reference value imr_ref(K)、ims_ref(K)、imt_ref(K) Can be formed bymd_ref(K)、imq_ref(K) Carrying out dq/abc transformation to obtain the product;
step 2: calculating a network side phase current reference value:
taking a q-axis current reference value i of a network sidegq_ref(K) Measuring the capacitance voltage of all the sub-modules by a voltage transformer to obtain the average value UC_av(K) And will UC_av(K) And submodule capacitor voltage reference value UC_ref(K) Make a difference, UC_ref(K) Taking the rated value of the direct-current voltage of the submodule, regulating the rated value through a second PI regulator, wherein the output of the second PI regulator isGrid side d-axis current reference value igd_ref(K)：
igd_ref(K)＝(KP2+KI2×(1/s))×[UC_ref(K)-UC_av(K)]
Wherein KP2、KI2Proportional coefficient and integral coefficient of the second PI regulator respectively; grid side three-phase current reference value igu_ref(K)、igv_ref(K)、igw_ref(K) Can be formed bygd_ref(K)、igq_ref(K) Carrying out dq/abc transformation to obtain the product;
and step 3: calculating a circulation reference value:
(1) according to the capacitance voltages of all the sub-modules measured in the step 2, calculating the average value U of the capacitance voltages of the sub-modules on the odd bridge arm and the even bridge arm respectivelyC1,3,5_av(K)、UC2,4,6_av(K) The difference between the two is processed by a third PI regulator, and the output of the third PI regulator is a bridge arm circulating current direct current component reference value icir1_ref(K)：
icir1_ref(K)＝(KP3+KI3×(1/s))×[UC1,3,5_av(K)-UC2,4,6_av(K)]
Wherein KP3、KI3Proportional coefficient and integral coefficient of the third PI regulator are respectively;
(2) detecting output voltage v of bridge arm xbx(K) Respectively calculating the average value U of the capacitor voltages of the submodules of the bridge arm x according to the capacitor voltages of all the submodules measured in the step 2Cx_av(K) Will U isCx_av(K) And UC_ref(K) Comparing, by the fourth P regulator, the output of the fourth P regulator with vbx(K) Multiplying, summing the results of 6 bridge arms to obtain a reference value i of the circulating current component of the bridge armcir2_ref(K)：
icir2_ref(K)＝∑KP4×vbx(K)×[UC_ref(K)-UCx_av(K)]
Wherein KP4The proportionality coefficients of the fourth P regulator are respectively;
(3) will icir1_ref(K) And icir2_ref(K) Adding to obtain total circulationReference value icir_ref(K)：
icir_ref(K)＝icir1_ref(K)+icir2_ref(K)
And 4, step 4: substituting the machine side current reference value, the network side current reference value and the circulation reference value obtained by calculation in the steps into the following formula to obtain the current reference value i of each bridge armx_ref(K)：
i1_ref(K)＝(1/3)×[imr_ref(K)-ims_ref(K)+igv_ref(K)-igw_ref(K)]+icir_ref(K)
i2_ref(K)＝(1/3)×[imr_ref(K)-ims_ref(K)+igw_ref(K)-igu_ref(K)]+icir_ref(K)
i3_ref(K)＝(1/3)×[ims_ref(K)-imt_ref(K)+igw_ref(K)-igu_ref(K)]+icir_ref(K)
i4_ref(K)＝(1/3)×[ims_ref(K)-imt_ref(K)+igu_ref(K)-igv_ref(K)]+icir_ref(K)
i5_ref(K)＝(1/3)×[imt_ref(K)-imr_ref(K)+igu_ref(K)-igv_ref(K)]+icir_ref(K)
i6_ref(K)＝(1/3)×[imt_ref(K)-imr_ref(K)+igv_ref(K)-igw_ref(K)]+icir_ref(K)
And 5: the U obtained by the calculation in the step 3C1,3,5_av(K)、UC2,4,6_av(K) Taking difference, the output of the fifth PI regulator is the neutral point voltage reference value vst_ref(K)：
vst_ref(K)＝(KP5+KI5×(1/s))×[UC1,3,5_av(K)-UC2,4,6_av(K)]
Wherein KP5、KI5Proportional coefficient and integral coefficient of the fifth PI regulator respectively;
step 6: predicting a bridge arm current reference value:
ix_ref(K+1)＝2×ix_ref(K)-ix_ref(K-1)
wherein ix_ref(K +1) is the predicted value of the bridge arm current reference value in the next control period, ix_ref(K-1) the reference value of the bridge arm current obtained by calculation in the previous control period from the step 1 to the step 4;
and 7: and (3) predicting the actual measured value of the bridge arm current:
ix(K+1)＝2×ix(K)-ix(K-1)
wherein ix(K +1) is the predicted value of the bridge arm current measured value in the next control period, ix(K) Is the actual measured value of the bridge arm current in the current control period, ix(K-1) is an actual measurement value of the bridge arm current in the previous control period;
and 8: acquiring a machine side voltage:
detecting line voltage between the phases of machine side T, R by vmtr(K) Represents; detecting line voltage between the phases of machine side R, S by vmrs(K) Represents; detecting line voltage between the phases of machine side S, T by vmst(K) Represents; three phase voltage v on machine sidemr(K)、vms(K)、vmt(K) Obtained by the following calculation:
vmr(K)＝(1/3)×[vmrs(K)-vmtr(K)]
vms(K)＝(1/3)×[vmst(K)-vmrs(K)]
vmt(K)＝(1/3)×[vmtr(K)-vmst(K)]
and step 9: acquiring a network side phase voltage:
sensing line voltage between net side U, V phases by vguv(K) Represents; sensing line voltage between net side V, W phases by vgvw(K) Represents; sensing line voltage between net side W, U phases by vgwu(K) Represents; the three-phase voltage at the network side can be obtained according to the measured three-phase line voltage v at the network sidegu(K)、vgv(K)、vgw(K) Calculated by the following formula:
vgu(K)＝(1/3)×[vguv(K)-vgwu(K)]
vgv(K)＝(1/3)×[vgvw(K)-vguv(K)]
vgw(K)＝(1/3)×[vgwu(K)-vgvw(K)]
step 10, calculating a bridge arm voltage reference value:
v1(K)＝vgw(K)-vmr(K)-(L/T)×[i1_ref(K+1)-i1(K+1)]-vst_ref(K)
v2(K)＝vms(K)-vgw(K)-(L/T)×[i2_ref(K+1)-i2(K+1)]+vst_ref(K)
v3(K)＝vgu(K)-vms(K)-(L/T)×[i3_ref(K+1)-i3(K+1)]-vst_ref(K)
v4(K)＝vmt(K)-vgu(K)-(L/T)×[i4_ref(K+1)-i4(K+1)]+vst_ref(K)
v5(K)＝vgv(K)-vmt(K)-(L/T)×[i5_ref(K+1)-i5(K+1)]-vst_ref(K)
v6(K)＝vmr(K)-vgv(K)-(L/T)×[i6_ref(K+1)-i6(K+1)]+vst_ref(K)
wherein v isx(K) Representing a bridge arm voltage reference value of the x-th bridge arm in the current control period, wherein T is the control period;
step 11: calculating control signals of each submodule of each bridge arm:
according to the calculated vxAnd (K +1) obtaining a switching signal of a single submodule of each bridge arm by adopting a modulation mode of nearest level approximation.
In the above step, KP1＝160，KI1＝15000，KP2＝50000，KI2＝500000，KP3＝1，KI3＝12，KP4＝0.0000046，KP5＝100，KI5＝300。
Fig. 3 shows the waveform of the network side phase current under the rated working condition, the output waveform is smooth, and the sine change rule is satisfied.
Fig. 4 is a side phase current waveform under a rated working condition, and an output waveform is relatively smooth, which indicates that the dead-beat tracking performance of the bridge arm current is good.
Fig. 5 shows the distortion rate of the grid-side current under the rated working condition, the total distortion rate is 3.87%, the harmonic content of the output current is low, and the grid-connected requirement is met.
Fig. 6 shows the distortion rate of the current on the machine side under the rated working condition, and the total distortion rate is 1.53%, which shows the effectiveness of the control method provided by the invention and can track the current of the bridge arm in a dead beat manner.

Claims (3)

1. A deadbeat current control method based on a hexagonal converter wind power generation system is characterized in that the wind power generation system consists of a direct-drive permanent magnet synchronous generator and a hexagonal converter;
the rotor of the direct-drive permanent magnet synchronous generator is coaxially connected with a wind turbine, and the stator is provided with three windings which are R, S, T three phases respectively;
the hexagonal converter is formed by connecting 6 identical bridge arms end to end into a hexagon; each bridge arm is formed by connecting N identical full-bridge submodules and an inductor L in series; each submodule consists of 4 IGBT tubes T1, T2, T3, T4 and 1 capacitor C; the emitter of the T1 is connected with the collector of the T2 and forms the positive terminal of the submodule, and the emitter of the T3 is connected with the collector of the T4 and forms the negative terminal of the submodule; the collector of T1 is connected with the collector of T3 and forms the anode of the submodule, the emitter of T2 is connected with the emitter of T4 and forms the cathode of the submodule; the positive electrode and the negative electrode of the capacitor C are respectively connected with the positive electrode and the negative electrode of the submodule; the R, S, T three phases of the direct-drive permanent magnet synchronous generator and the U, V, W three phases of the power grid are alternately connected to six vertexes of the hexagon; recording a bridge arm directly connected with an R phase and a W phase as a bridge arm 1, recording a bridge arm directly connected with the W phase and the S phase as a bridge arm 2, recording a bridge arm directly connected with the S phase and the U phase as a bridge arm 3, recording a bridge arm directly connected with the U phase and the T phase as a bridge arm 4, recording a bridge arm directly connected with the T phase and the V phase as a bridge arm 5, and recording a bridge arm directly connected with the V phase and the R phase as a bridge arm 6; each bridge armThe upper sub-modules are sequentially marked as SMx_1，SMx_2，…，SMx_NX is 1, 2, … 6;
the deadbeat current control method based on the hexagonal converter wind power generation system is characterized by comprising the following steps of:
step 1: computer side phase current reference value:
reference value i of side d-axis current of pickup machinemd_ref(K) Detecting the angular speed omega (K) of the fan rotor and comparing the angular speed omega (K) with the optimal angular speed omega (0)ref(K) Making a difference, ωref(K) Provided by a manufacturer, and regulated by a first PI regulator, wherein the output of the first PI regulator is a machine side q-axis current reference value imq_ref(K) And K represents the current time:
imq_ref(K)＝(KP1+KI1×(1/s))×[ωref(K)-ω(K)]
wherein 1/s is an integration factor, KP1、KI1Proportional coefficient and integral coefficient of the first PI regulator are respectively; machine side three-phase current reference value imr_ref(K)、ims_ref(K)、imt_ref(K) Can be formed bymd_ref(K)、imq_ref(K) Carrying out dq/abc transformation to obtain the product;
step 2: calculating a network side phase current reference value:
taking a q-axis current reference value i of a network sidegq_ref(K) Measuring the capacitance voltage of all the sub-modules by a voltage transformer to obtain the average value UC_av(K) And will UC_av(K) And submodule capacitor voltage reference value UC_ref(K) Make a difference, UC_ref(K) Taking the rated value of the direct-current voltage of the submodule, and regulating the rated value through a second PI regulator, wherein the output of the second PI regulator is a grid-side d-axis current reference value igd_ref(K)：
igd_ref(K)＝(KP2+KI2×(1/s))×[UC_ref(K)-UC_av(K)]
Wherein KP2、KI2Proportional coefficient and integral coefficient of the second PI regulator respectively; grid side three-phase current reference value igu_ref(K)、igv_ref(K)、igw_ref(K) Can be formed bygd_ref(K)、igq_ref(K) Carrying out dq/abc transformation to obtain the product;
and step 3: calculating a circulation reference value:
(1) according to the capacitance voltages of all the sub-modules measured in the step 2, calculating the average value U of the capacitance voltages of the sub-modules on the odd bridge arm and the even bridge arm respectivelyC1,3,5_av(K)、UC2,4,6_av(K) The difference between the two is processed by a third PI regulator, and the output of the third PI regulator is a bridge arm circulating current direct current component reference value icir1_ref(K)：
icir1_ref(K)＝(KP3+KI3×(1/s))×[UC1,3,5_av(K)-UC2,4,6_av(K)]
Wherein KP3、KI3Proportional coefficient and integral coefficient of the third PI regulator are respectively;
(2) detecting output voltage v of bridge arm xbx(K) Respectively calculating the average value U of the capacitor voltages of the submodules of the bridge arm x according to the capacitor voltages of all the submodules measured in the step 2Cx_av(K) Will U isCx_av(K) And UC_ref(K) Comparing, by the fourth P regulator, the output of the fourth P regulator with vbx(K) Multiplying, summing the results of 6 bridge arms to obtain a reference value i of the circulating current component of the bridge armcir2_ref(K)：
icir2_ref(K)＝∑KP4×vbx(K)×[UC_ref(K)-UCx_av(K)]
Wherein KP4The proportionality coefficients of the fourth P regulator are respectively;
(3) will icir1_ref(K) And icir2_ref(K) Adding to obtain a total circulating current reference value icir_ref(K)：
icir_ref(K)＝icir1_ref(K)+icir2_ref(K)
And 4, step 4: substituting the machine side current reference value, the network side current reference value and the circulation reference value obtained by calculation in the steps into the following formula to obtain the current reference value i of each bridge armx_ref(K)：
i1_ref(K)＝(1/3)×[imr_ref(K)-ims_ref(K)+igv_ref(K)-igw_ref(K)]+icir_ref(K)
i2_ref(K)＝(1/3)×[imr_ref(K)-ims_ref(K)+igw_ref(K)-igu_ref(K)]+icir_ref(K)
i3_ref(K)＝(1/3)×[ims_ref(K)-imt_ref(K)+igw_ref(K)-igu_ref(K)]+icir_ref(K)
i4_ref(K)＝(1/3)×[ims_ref(K)-imt_ref(K)+igu_ref(K)-igv_ref(K)]+icir_ref(K)
i5_ref(K)＝(1/3)×[imt_ref(K)-imr_ref(K)+igu_ref(K)-igv_ref(K)]+icir_ref(K)
i6_ref(K)＝(1/3)×[imt_ref(K)-imr_ref(K)+igv_ref(K)-igw_ref(K)]+icir_ref(K)
And 5: the U obtained by the calculation in the step 3C1,3,5_av(K)、UC2,4,6_av(K) Taking difference, the output of the fifth PI regulator is the neutral point voltage reference value vst_ref(K)：
vst_ref(K)＝(KP5+KI5×(1/s))×[UC1,3,5_av(K)-UC2,4,6_av(K)]
Wherein KP5、KI5Proportional coefficient and integral coefficient of the fifth PI regulator respectively;
step 6: predicting a bridge arm current reference value:
ix_ref(K+1)＝2×ix_ref(K)-ix_ref(K-1)
wherein ix_ref(K +1) is the predicted value of the bridge arm current reference value in the next control period, ix_ref(K-1) the reference value of the bridge arm current obtained by calculation in the previous control period from the step 1 to the step 4;
and 7: and (3) predicting the actual measured value of the bridge arm current:
ix(K+1)＝2×ix(K)-ix(K-1)
wherein ix(K +1) is the predicted value of the bridge arm current measured value in the next control period, ix(K) Is the actual measured value of the bridge arm current in the current control period, ix(K-1) is an actual measurement value of the bridge arm current in the previous control period;
and 8: acquiring a machine side voltage:
detecting line voltage between the phases of machine side T, R by vmtr(K) Represents; detecting line voltage between the phases of machine side R, S by vmrs(K) Represents; detecting line voltage between the phases of machine side S, T by vmst(K) Represents; three phase voltage v on machine sidemr(K)、vms(K)、vmt(K) Obtained by the following calculation:
vmr(K)＝(1/3)×[vmrs(K)-vmtr(K)]
vms(K)＝(1/3)×[vmst(K)-vmrs(K)]
vmt(K)＝(1/3)×[vmtr(K)-vmst(K)]
and step 9: acquiring a network side phase voltage:
sensing line voltage between net side U, V phases by vguv(K) Represents; sensing line voltage between net side V, W phases by vgvw(K) Represents; sensing line voltage between net side W, U phases by vgwu(K) Represents; the three-phase voltage at the network side can be obtained according to the measured three-phase line voltage v at the network sidegu(K)、vgv(K)、vgw(K) Calculated by the following formula:
vgu(K)＝(1/3)×[vguv(K)-vgwu(K)]
vgv(K)＝(1/3)×[vgvw(K)-vguv(K)]
vgw(K)＝(1/3)×[vgwu(K)-vgvw(K)]
step 10, calculating a bridge arm voltage reference value:
v1(K)＝vgw(K)-vmr(K)-(L/T)×[i1_ref(K+1)-i1(K+1)]-vst_ref(K)
v2(K)＝vms(K)-vgw(K)-(L/T)×[i2_ref(K+1)-i2(K+1)]+vst_ref(K)
v3(K)＝vgu(K)-vms(K)-(L/T)×[i3_ref(K+1)-i3(K+1)]-vst_ref(K)
v4(K)＝vmt(K)-vgu(K)-(L/T)×[i4_ref(K+1)-i4(K+1)]+vst_ref(K)
v5(K)＝vgv(K)-vmt(K)-(L/T)×[i5_ref(K+1)-i5(K+1)]-vst_ref(K)
v6(K)＝vmr(K)-vgv(K)-(L/T)×[i6_ref(K+1)-i6(K+1)]+vst_ref(K)
wherein v isx(K) Representing a bridge arm voltage reference value of the x-th bridge arm in the current control period, wherein T is the control period;
step 11: calculating control signals of each submodule of each bridge arm:
according to the calculated vx(K) And obtaining the switching signal of a single submodule of each bridge arm by adopting a modulation mode of nearest level approximation.
2. The deadbeat current control method based on hexagonal converter wind power generation system according to claim 1, wherein the number of submodules N in each bridge arm is 6, and a fan side line voltage rated value U is setm3.3kV, and the rated voltage value of the side line of the power grid UgIs 10kV, the sub-module capacitor C is 20mF, and the sub-module capacitor voltage reference value UC_refThe voltage is 2500V, the size of the bridge arm inductance L is 10mH, and the control period T is 0.0002 s.
3. The method for deadbeat current control for a hexagonal current transformer based wind power system as claimed in claim 1 wherein K isP1＝160，KI1＝15000，KP2＝50000，KI2＝500000，KP3＝1，KI3＝12，KP4＝0.0000046，KP5＝100，KI5＝300。
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