CN111740454B - Mixed micro-grid alternating-current and direct-current voltage unified control method based on bus interface converter - Google Patents

Mixed micro-grid alternating-current and direct-current voltage unified control method based on bus interface converter Download PDF

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CN111740454B
CN111740454B CN202010708707.3A CN202010708707A CN111740454B CN 111740454 B CN111740454 B CN 111740454B CN 202010708707 A CN202010708707 A CN 202010708707A CN 111740454 B CN111740454 B CN 111740454B
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voltage
grid
alternating
alternating current
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CN111740454A (en
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任春光
赵多
贾燕冰
张佰富
韩肖清
秦文萍
王弈赫
郝冠斐
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Taiyuan University of Technology
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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
    • H02J4/00—Circuit arrangements for mains or distribution networks not specified as ac or dc
    • 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
    • H02J3/18—Arrangements for adjusting, eliminating or compensating reactive power in networks
    • H02J3/1821—Arrangements for adjusting, eliminating or compensating reactive power in networks using shunt compensators
    • H02J3/1835—Arrangements for adjusting, eliminating or compensating reactive power in networks using shunt compensators with stepless control
    • H02J3/1842—Arrangements for adjusting, eliminating or compensating reactive power in networks using shunt compensators with stepless control wherein at least one reactive element is actively controlled by a bridge converter, e.g. active filters
    • 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
    • H02M7/66—Conversion of ac power input into dc power output; Conversion of dc power input into ac power output with possibility of reversal
    • H02M7/68—Conversion of ac power input into dc power output; Conversion of dc power input into ac power output with possibility of reversal by static converters
    • H02M7/72—Conversion of ac power input into dc power output; Conversion of dc power input into ac power output with possibility of reversal by static converters using discharge tubes with control electrode or semiconductor devices with control electrode
    • H02M7/79—Conversion of ac power input into dc power output; Conversion of dc power input into ac power output with 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
    • H02M7/797—Conversion of ac power input into dc power output; Conversion of dc power input into ac power output with 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
    • 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
    • Y02E40/00—Technologies for an efficient electrical power generation, transmission or distribution
    • Y02E40/30—Reactive power compensation

Abstract

The invention relates to the field of control and electric energy quality control of an alternating current/direct current hybrid micro-grid bus interface converter, in particular to a hybrid micro-grid alternating current/direct current voltage unified control method based on the bus interface converter. The invention effectively solves the problem of different voltage qualities caused by coupling of the double frequency fluctuation power between the AC and DC subnetworks under the condition of unbalanced voltage. The main circuit consists of an AC/DC sub-network and a bidirectional interface converter connected with the two sub-networks; the control circuit consists of an alternating current part and a direct current part. The alternating-current side controls the converter through bidirectional power flow and a proportional resonance algorithm, and compensates negative sequence voltage by utilizing the power margin transmitted by the converter; the direct current side is introduced with a step-down chopper circuit, and the pulsating voltage of the direct current bus is stabilized by a power compensation principle. The invention realizes the purpose of compensating AC/DC voltage simultaneously by controlling the bus interface converter, improves the utilization rate of the bidirectional interface converter and ensures the running reliability of the micro-grid.

Description

Mixed micro-grid alternating-current and direct-current voltage unified control method based on bus interface converter
Technical Field
The invention relates to the field of hybrid micro-grid AC/DC bus interface converter control and hybrid micro-grid power quality control, in particular to a hybrid micro-grid AC/DC voltage unified control method based on a bus interface converter.
Background
Along with the continuous rise of the permeability of new energy, the AC/DC hybrid micro-grid gradually becomes the trend of future development of the micro-grid due to the fact that the AC micro-grid and the DC micro-grid can be effectively combined. The actual AC/DC hybrid micro-grid is often positioned at the tail end of the power distribution network, the self capacity of the power distribution network is relatively small, when an asymmetric fault occurs in a large power grid or unbalance occurs in a load, negative sequence components can occur in the voltage, the current or the load voltage and the current of the power grid, so that the voltage at the PCC is unbalanced, and DC voltage pulsation is further caused. Meanwhile, some single-phase alternating current loads with high requirements on the electric energy quality are often connected into a direct current micro-grid through an inverter, and direct current bus voltage double frequency pulsation can be caused, so that alternating current harmonic pollution is further caused. The alternating current unbalanced voltage and the direct current double frequency pulsating voltage not only influence the normal operation of the alternating current/direct current sub-network and the bidirectional interface converter, but also cause other electric energy quality problems by being coupled to the other side through the bidirectional AC/DC converter, and influence the safe and stable operation of the whole hybrid micro-grid.
Currently, a large number of documents offer many solutions to the different power quality problems in hybrid micro-grids. The compensation methods for the three-phase unbalanced voltages are roughly classified into two types: 1. the series or parallel connection of the power quality regulator has obvious defects because additional devices are needed to be added and the cost is increased; 2. the three-phase unbalanced voltage is compensated by using a distributed energy source or an energy storage converter and the like. The dc voltage ripple control strategies can also be divided into two categories: 1. the passive or active filter circuit is introduced, the method can effectively inhibit the direct current ripple voltage, but the cost problem caused by introducing additional devices is also existed; 2. and the double frequency pulsating voltage is indirectly eliminated through an impedance remodeling control method. At present, different solutions are respectively provided for alternating current unbalanced voltage and direct current pulsating voltage, but few researches relate to a method for uniformly treating the quality of the alternating current and direct current voltage of a hybrid micro-grid.
Disclosure of Invention
The invention designs a mixed micro-grid bus interface converter alternating-current and direct-current voltage unified control method based on a step-down type power compensation circuit aiming at the defects of the prior art in order to solve the problem of different voltage qualities caused by coupling of double frequency fluctuation power between alternating-current and direct-current subnets under the condition of unbalanced voltage.
The technical scheme of the invention is as follows: a mixed micro-grid AC/DC voltage unified control method based on a bus interface converter includes a mixed micro-grid, a DC micro-grid and a bidirectional interface converter connected with the AC/DC micro-grid, wherein the bidirectional interface converter includes a three-phase full-bridge circuit and a step-down chopper circuit. The direct-current capacitor of the three-phase full-bridge circuit is connected in parallel with two sides of a bridge arm of the full-bridge circuit, the alternating-current side adopts inductance L for filtering, and the step-down chopper circuit is a fluctuation power compensation circuit and comprises inductance L ac Capacitance C ac And a group of bridge arms composed of IGBTs connected in series with each other, an inductance L ac And capacitor C ac And one end of the serial branch is connected to the middle of the bridge arm, the other end of the serial branch is connected to the negative electrode of the bridge arm, and the whole fluctuation power compensation circuit is connected in parallel to the positive and negative sides of the direct current capacitor of the three-phase full-bridge circuit. The bidirectional interface converter alternating current bus is connected with the alternating current micro-grid and is connected with the large power grid through the public grid connection point PCC, and the direct current bus is connected with the direct current micro-grid. The hybrid micro-grid control circuit comprises an alternating current controller and a direct current controller, wherein the alternating current controller comprises a positive sequence controller, a negative sequence controller and a PR controller.
The alternating current side positive sequence controller obtains an alternating current positive sequence current reference value i in a unified control method + αβ_ref The negative sequence controller obtains an alternating negative sequence current reference value i - αβ_ref Ac positive sequence current reference i + αβ_ref Ac negative sequence current reference value i - αβ_ref Synthesizing an alternating current total reference value, comparing the alternating current reference value with an alternating current actual value, inputting the alternating current total reference value into a PR controller, outputting a trigger pulse through PWM modulation to control a three-phase full-bridge circuit, and obtaining alternating current and direct current side waves by a direct current controller according to the input alternating current side voltage current of an interface converter and the direct current micro-grid load side voltage currentAnd the dynamic power is subjected to capacitive reference voltage calculation link and capacitive voltage and current double closed-loop control to obtain PWM modulation waves, and finally a series of trigger pulse control fluctuation power compensation circuits with adjustable duty ratio are output through a PWM module.
The method for uniformly controlling the alternating-current and direct-current voltages of the hybrid micro-grid based on the bus interface converter is characterized in that a mathematical model of the bidirectional interface converter under an alpha beta coordinate system is established on an alternating side, the fundamental wave power and positive sequence current of the converter are controlled through bidirectional power flow and a Proportional Resonance (PR) algorithm, and the negative sequence voltage is compensated by utilizing the power allowance transmitted by the converter; the fluctuation power compensation circuit is introduced at the direct current side, and the fluctuation power compensation circuit absorbs the double frequency fluctuation power at the alternating current and direct current sides simultaneously by the power compensation principle, and finally, a method for eliminating the alternating current negative sequence voltage and the direct current ripple voltage is realized simultaneously, and the specific expansion is as follows:
step one: detecting output voltage u of alternating current side of three-phase full-bridge circuit abc And output current i abc Transforming the alpha-beta coordinates to obtain each quantity u in the alpha-beta coordinate system αβ 、i αβ For u αβ And i αβ Positive and negative sequence separation is carried out to obtain positive sequence voltage u αβ + Positive sequence current i αβ + And negative sequence voltage u αβ － Negative sequence current i αβ － ；
Step two: in the positive sequence controller, the positive sequence voltage u obtained in the step one is calculated αβ + Coordinate transformation is carried out, and positive sequence voltage amplitude U under abc coordinate system is extracted ac Then collecting the DC capacitor voltage U of the three-phase full bridge circuit dc And filtering the double frequency component through a wave trap to obtain a direct current average value U dc For positive sequence voltage amplitude U ac And DC voltage average value U dc Respectively carrying out normalization treatment to obtain U ac_norm And U dc_norm Then, difference is made between the two normalized scalar quantities, and the difference value delta U norm And a power reference value P ref 、Q ref Multiplying to control power bi-directional flow, and adding DeltaU norm 、P ref 、Q ref U αβ + The input reference current calculation module calculates the reference current to obtain an alternating positive sequence current reference value i + αβ_ref ；
Step three: in the negative sequence controller, first, for each axis component i of the current in the alpha-beta coordinate system α 、i β Root mean square value is obtained, and then a larger value and the rated current I of the converter are selected max (rated current I) max Representing the rated power of the converter, which can be set by the user according to the capacity of the converter), and inputting an error signal into a proportional controller to obtain a negative sequence voltage compensation coefficient; secondly, the negative sequence voltage u obtained in the step one is processed αβ － Multiplying the negative sequence voltage compensation coefficient to obtain an alternating negative sequence current reference value i - αβ_ref The method comprises the steps of carrying out a first treatment on the surface of the Finally, the reference value i of the alternating current positive sequence current obtained in the step two is compared with the reference value i of the alternating current positive sequence current obtained in the step two + αβ_ref Subtracting to obtain a total current reference value, and then the total current reference value is combined with an alternating current total actual value i αβ After comparison, the current is input into a PR controller, the PR controller is adopted to track a current reference value, and a trigger pulse is output through PWM modulation to control a three-phase full-bridge circuit;
step four: the above steps achieve the purpose of eliminating the negative sequence component of the ac voltage, but still cannot completely eliminate the double frequency fluctuation power, so that the dc side fluctuation power compensation circuit needs to be controlled. In the DC controller, the positive sequence voltage u αβ + Positive sequence current i αβ + And negative sequence voltage u αβ － Negative sequence current i αβ － Input into an alternating current fluctuation power calculation module, and calculate and obtain alternating current output frequency doubling fluctuation power p of the converter according to the instantaneous power theory 1 Simultaneously collecting direct-current load voltage and current U in direct-current micro-grid ac_L 、i ac_L Inputting into a DC power calculation module, and extracting DC side double frequency fluctuation power p by a band-pass filter 2 Ac side double frequency fluctuation power p 1 And direct-current side double frequency fluctuation power p 2 Adding to obtain the active power secondary fluctuation value
Figure BDA0002595697360000041
The active power secondary fluctuation value +.>
Figure BDA0002595697360000042
The input capacitance reference voltage calculation module further obtains an alternating current capacitance C in the compensation circuit ac Voltage reference value u * ac_c And AC capacitor C ac Actual voltage u ac_c After comparison, the alternating-current capacitor C is obtained through PIR control ac Current reference value i * ac_c ；
Step five: the alternating current capacitor C obtained in the step four ac Current reference value i * ac_c And capacitor C in compensation circuit ac Actual value i of current ac_c Compared with the prior art, the obtained error signal is compensated by a proportion adjustment link and then the duty ratio d' and the alternating current capacitance C are controlled ac Voltage reference value u * ac_c The duty ratio d ' is obtained through voltage feedforward control, the duty ratio d ' and the duty ratio d ' are synthesized to form the duty ratio d, and a series of trigger pulse is output through PWM modulation to control the fluctuation power compensation circuit.
The mixed micro-grid bus interface converter alternating-current and direct-current voltage unified control method based on the step-down power compensation circuit has the advantages compared with the prior art that: (1) When the AC/DC hybrid micro-grid is in an unbalanced working condition, the purpose of compensating the AC negative sequence voltage and the DC pulsating voltage can be achieved, the efficiency of distributed energy sources is improved, the utilization rate of the bidirectional AC/DC converter is improved, and the micro-grid can be ensured to operate optimally and stably. (2) The step-down type fluctuation power compensation circuit is introduced to the direct current side, so that double frequency fluctuation power on the two sides of alternating current and direct current can be absorbed simultaneously without adding an additional device, the capacity of a direct current bus capacitor can be greatly reduced, and the investment and the operation cost of a micro-grid are reduced.
Drawings
Fig. 1 is a diagram of a hybrid micro-grid ac/dc bus interface converter based on a step-down power compensation circuit according to the present invention;
fig. 2 is a schematic diagram of unified control of ac/dc voltage of a hybrid micro-grid bus interface converter based on a step-down power compensation circuit according to the present invention.
Detailed Description
A mixed micro-grid AC/DC voltage unified control method based on a bus interface converter includes a mixed micro-grid, a DC micro-grid and a bidirectional interface converter connected with the AC/DC micro-grid, wherein the bidirectional interface converter includes a three-phase full-bridge circuit and a step-down chopper circuit. The three-phase full-bridge circuit comprises three groups of bridge arms which are mutually connected in parallel, each group of bridge arms comprises two IGBTs which are mutually connected in series, each IGBT consists of a power tube and an anti-parallel diode, a direct-current capacitor of the three-phase full-bridge circuit is connected in parallel with two sides of the bridge arm of the full-bridge circuit, an alternating-current side adopts inductance L for filtering, and a step-down chopper circuit is a fluctuation power compensation circuit and comprises inductance L ac Capacitance C ac And a group of bridge arms composed of IGBTs connected in series with each other, an inductance L ac And capacitor C ac And one end of the serial branch is connected to the middle of the bridge arm, the other end of the serial branch is connected to the negative electrode of the bridge arm, and the whole fluctuation power compensation circuit is connected in parallel to the positive and negative sides of the direct current capacitor of the three-phase full-bridge circuit. The bidirectional interface converter alternating current bus is connected with the alternating current micro-grid and is connected with the large power grid through the public grid connection point PCC, and the direct current bus is connected with the direct current micro-grid. The hybrid micro-grid control circuit comprises an alternating current controller and a direct current controller, wherein the alternating current controller comprises a positive sequence controller, a negative sequence controller and a PR controller.
The method for uniformly controlling the alternating-current and direct-current voltages of the hybrid micro-grid based on the bus interface converter comprises the following specific implementation steps:
step one: detecting output voltage u of alternating current side of three-phase full-bridge circuit abc And output current i abc Transforming the alpha-beta coordinates to obtain each quantity u in the alpha-beta coordinate system αβ 、i αβ For u αβ And i αβ Positive and negative sequence separation is carried out to obtain positive sequence voltage u αβ + Positive sequence current i αβ + And negative sequence voltage u αβ － Negative sequence current i αβ － ；
Step two: in the positive sequence controller, the positive sequence voltage u obtained in the step one is calculated αβ + Coordinate transformation is carried out, and positive sequence voltage amplitude U under abc coordinate system is extracted ac Then collecting the DC capacitor voltage U of the three-phase full bridge circuit dc And filtering the double frequency component through a wave trap to obtain a direct current average value U dc For positive sequence voltage amplitude U ac And DC voltage average value U dc Respectively carrying out normalization treatment to obtain U ac_norm And U dc_norm Then, difference is made between the two normalized scalar quantities, and the difference value delta U norm And a power reference value P ref 、Q ref Multiplying to control power bi-directional flow, and adding DeltaU norm 、P ref 、Q ref U αβ + The input reference current calculation module calculates the reference current to obtain an alternating positive sequence current reference value i + αβ_ref ；
Step three: in the negative sequence controller, first, for each axis component i of the current in the alpha-beta coordinate system α 、i β Root mean square value is obtained, and then a larger value and the rated current I of the converter are selected max Comparing, namely inputting the error signal into a proportional controller to obtain a negative sequence voltage compensation coefficient; secondly, the negative sequence voltage u obtained in the step one is processed αβ － Multiplying the negative sequence voltage compensation coefficient to obtain an alternating negative sequence current reference value i - αβ_ref The method comprises the steps of carrying out a first treatment on the surface of the Finally, the reference value i of the alternating current positive sequence current obtained in the step two is compared with the reference value i of the alternating current positive sequence current obtained in the step two + αβ_ref Subtracting to obtain a total current reference value, and then the total current reference value is combined with an alternating current total actual value i αβ After comparison, the current is input into a PR controller, the PR controller is adopted to track a current reference value, and a trigger pulse is output through PWM modulation to control a three-phase full-bridge circuit;
step four: the above steps achieve the purpose of eliminating the negative sequence component of the ac voltage, but still cannot completely eliminate the double frequency fluctuation power, so that the dc side fluctuation power compensation circuit needs to be controlled. In the DC controller, the positive sequence voltage u αβ + Positive sequence current i αβ + And negative sequence voltage u αβ － Negative sequence current i αβ － Input into an alternating current fluctuation power calculation module, and calculate and obtain alternating current output frequency doubling fluctuation power p of the converter according to the instantaneous power theory 1 Simultaneously collecting direct-current load voltage and current U in direct-current micro-grid ac_L 、i ac_L Inputting into a DC power calculation module, and extracting DC side double frequency fluctuation power p by a band-pass filter 2 Ac side double frequency fluctuation power p 1 And direct-current side double frequency fluctuation power p 2 Adding to obtain the active power secondary fluctuation value
Figure BDA0002595697360000061
The active power secondary fluctuation value +.>
Figure BDA0002595697360000062
The input capacitance reference voltage calculation module further obtains an alternating current capacitance C in the compensation circuit ac Voltage reference value u * ac_c And AC capacitor C ac Actual voltage u ac_c After comparison, the alternating-current capacitor C is obtained through PIR control ac Current reference value i * ac_c ；
Step five: the alternating current capacitor C obtained in the step four ac Current reference value i * ac_c And capacitor C in compensation circuit ac Actual value i of current ac_c Compared with the prior art, the obtained error signal is compensated by a proportion adjustment link and then the duty ratio d' and the alternating current capacitance C are controlled ac Voltage reference value u * ac_c The duty ratio d ' is obtained through voltage feedforward control, the duty ratio d ' and the duty ratio d ' are synthesized to form the duty ratio d, and a series of trigger pulse is output through PWM modulation to control the fluctuation power compensation circuit.

Claims (1)

1. A mixed micro-grid AC/DC voltage unified control method based on bus interface converter is characterized in that a mixed micro-grid main circuit comprises an AC micro-grid, a DC micro-grid and a bidirectional interface converter connected with the AC/DC micro-grid, wherein the bidirectional interface converter comprises a three-phase full-bridge circuit and a step-down chopper circuit; DC capacitance of three-phase full bridge circuit is connected in parallel with full bridgeThe two sides of a bridge arm of the circuit, the alternating current side adopts inductance L for filtering, and the step-down chopper circuit is a fluctuation power compensation circuit and comprises inductance L ac Capacitance C ac And a group of bridge arms composed of IGBTs connected in series with each other, an inductance L ac And capacitor C ac A serial branch is formed, one end of the serial branch is connected to the middle of the bridge arm, the other end of the serial branch is connected to the negative electrode of the bridge arm, and the whole fluctuation power compensation circuit is connected in parallel to the positive and negative sides of the direct current capacitor of the three-phase full-bridge circuit; the bidirectional interface converter alternating current bus is connected with the alternating current micro-grid and is connected with the large power grid through the public grid connection point PCC, and the direct current bus is connected with the direct current micro-grid; the hybrid micro-grid control circuit comprises an alternating current controller and a direct current controller, wherein the alternating current controller comprises a positive sequence controller, a negative sequence controller and a PR controller; the alternating current side positive sequence controller obtains an alternating current positive sequence current reference value i in a unified control method + αβ_ref The negative sequence controller obtains an alternating negative sequence current reference value i - αβ_ref Ac positive sequence current reference i + αβ_ref Ac negative sequence current reference value i - αβ_ref Synthesizing an alternating current total reference value, comparing the alternating current reference value with an alternating current actual value, inputting the alternating current total reference value into a PR controller, outputting a trigger pulse through PWM modulation to control a three-phase full-bridge circuit, obtaining alternating current and direct current two-side fluctuation power by a direct current controller according to the input alternating current side voltage and current of an interface converter and the direct current micro-grid load side voltage and current, obtaining PWM modulation waves through a capacitance reference voltage calculation link and capacitive voltage and current double closed-loop control, and finally outputting a series of trigger pulse with adjustable duty ratio through a PWM module to control a fluctuation power compensation circuit;
the method specifically comprises the following steps:
step one: detecting output voltage u of alternating current side of three-phase full-bridge circuit abc And output current i abc Transforming the alpha-beta coordinates to obtain each quantity u in the alpha-beta coordinate system αβ 、i αβ For u αβ And i αβ Positive and negative sequence separation is carried out to obtain positive sequence voltage u αβ + Positive sequence current i αβ + And negative sequence voltage u αβ － Negative sequence current i αβ － ；
Step two: in the positive sequence controller, the positive sequence voltage u obtained in the step one is calculated αβ + Coordinate transformation is carried out, and positive sequence voltage amplitude U under abc coordinate system is extracted ac Then collecting the DC capacitor voltage of the three-phase full bridge circuit
Figure FDA0004225844430000011
And filtering the double frequency component through a wave trap to obtain a direct current average value U dc For positive sequence voltage amplitude U ac And DC voltage average value U dc Respectively carrying out normalization treatment to obtain U ac_norm And U dc_norm Then, difference is made between the two normalized scalar quantities, and the difference value delta U norm And a power reference value P ref 、Q ref Multiplying to control power bi-directional flow, and adding DeltaU norm 、P ref 、Q ref U αβ + The input reference current calculation module calculates the reference current to obtain an alternating positive sequence current reference value i + αβ_ref ；
Step three: in the negative sequence controller, first, for each axis component i of the current in the alpha-beta coordinate system α 、i β Root mean square value is obtained, and then a larger value and the rated current I of the converter are selected max Comparing, namely inputting the error signal into a proportional controller to obtain a negative sequence voltage compensation coefficient; secondly, the negative sequence voltage u obtained in the step one is processed αβ － Multiplying the negative sequence voltage compensation coefficient to obtain an alternating negative sequence current reference value i - αβ_ref The method comprises the steps of carrying out a first treatment on the surface of the Finally, the reference value i of the alternating current positive sequence current obtained in the step two is compared with the reference value i of the alternating current positive sequence current obtained in the step two + αβ_ref Subtracting to obtain total reference value of AC current, and mixing the total reference value of AC current with total actual value i of AC current αβ After comparison, the current is input into a PR controller, the PR controller is adopted to track a current reference value, and a trigger pulse is output through PWM modulation to control a three-phase full-bridge circuit;
step four: the above steps achieve the purpose of eliminating the negative sequence component of the alternating voltage, but still cannot completely eliminate the double frequency fluctuation power, so that the direct current side fluctuation power compensation circuit is required to be carried outRow control; in the DC controller, the positive sequence voltage u αβ + Positive sequence current i αβ + And negative sequence voltage u αβ － Negative sequence current i αβ － Input into an alternating current fluctuation power calculation module, and calculate and obtain alternating current output frequency doubling fluctuation power p of the converter according to the instantaneous power theory 1 Simultaneously collecting direct-current load voltage and current U in direct-current micro-grid ac_L 、i ac_L Inputting into a DC power calculation module, and extracting DC side double frequency fluctuation power p by a band-pass filter 2 Ac side double frequency fluctuation power p 1 And direct-current side double frequency fluctuation power p 2 Adding to obtain the active power secondary fluctuation value
Figure FDA0004225844430000021
The active power secondary fluctuation value +.>
Figure FDA0004225844430000022
The input capacitance reference voltage calculation module further obtains an alternating current capacitance C in the compensation circuit ac Voltage reference value u * ac_c And AC capacitor C ac Actual voltage u ac_c After comparison, the alternating-current capacitor C is obtained through PIR control ac Current reference value i * ac_c ；
Step five: the alternating current capacitor C obtained in the step four ac Current reference value i * ac_c And capacitor C in compensation circuit ac Actual value i of current ac_c Compared with the prior art, the obtained error signal is compensated by a proportion adjustment link and then the duty ratio d' and the alternating current capacitance C are controlled ac Voltage reference value u * ac_c The duty ratio d ' is obtained through voltage feedforward control, the duty ratio d ' and the duty ratio d ' are synthesized to form the duty ratio d, and a series of trigger pulse is output through PWM modulation to control the fluctuation power compensation circuit.
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