CN116545018A - Self-synchronization voltage source grid-connected stability improving method based on current control loop reshaping - Google Patents

Self-synchronization voltage source grid-connected stability improving method based on current control loop reshaping Download PDF

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CN116545018A
CN116545018A CN202310574239.9A CN202310574239A CN116545018A CN 116545018 A CN116545018 A CN 116545018A CN 202310574239 A CN202310574239 A CN 202310574239A CN 116545018 A CN116545018 A CN 116545018A
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control loop
phase
voltage
current
current control
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肖华锋
吴旭
王伟
韦徵
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Southeast University
Nari Technology Co Ltd
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Southeast University
Nari Technology Co Ltd
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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
    • 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
    • H02J3/002—Flicker reduction, e.g. compensation of flicker introduced by non-linear load
    • H—ELECTRICITY
    • H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
    • H02M—APPARATUS FOR CONVERSION BETWEEN AC AND AC, BETWEEN AC AND DC, OR BETWEEN DC AND DC, AND FOR USE WITH MAINS OR SIMILAR POWER SUPPLY SYSTEMS; CONVERSION OF DC OR AC INPUT POWER INTO SURGE OUTPUT POWER; CONTROL OR REGULATION THEREOF
    • H02M7/00—Conversion of ac power input into dc power output; Conversion of dc power input into ac power output
    • H02M7/42—Conversion of dc power input into ac power output without possibility of reversal
    • H02M7/44—Conversion of dc power input into ac power output without possibility of reversal by static converters
    • H02M7/48—Conversion of dc power input into ac power output without possibility of reversal by static converters using discharge tubes with control electrode or semiconductor devices with control electrode
    • H—ELECTRICITY
    • H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
    • H02M—APPARATUS FOR CONVERSION BETWEEN AC AND AC, BETWEEN AC AND DC, OR BETWEEN DC AND DC, AND FOR USE WITH MAINS OR SIMILAR POWER SUPPLY SYSTEMS; CONVERSION OF DC OR AC INPUT POWER INTO SURGE OUTPUT POWER; CONTROL OR REGULATION THEREOF
    • H02M7/00—Conversion of ac power input into dc power output; Conversion of dc power input into ac power output
    • H02M7/42—Conversion of dc power input into ac power output without possibility of reversal
    • H02M7/44—Conversion of dc power input into ac power output without possibility of reversal by static converters
    • H02M7/48—Conversion of dc power input into ac power output without possibility of reversal by static converters using discharge tubes with control electrode or semiconductor devices with control electrode
    • H02M7/493—Conversion of dc power input into ac power output without possibility of reversal by static converters using discharge tubes with control electrode or semiconductor devices with control electrode the static converters being arranged for operation in parallel
    • 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
    • H02J2203/00—Indexing scheme relating to details of circuit arrangements for AC mains or AC distribution networks
    • H02J2203/10—Power transmission or distribution systems management focussing at grid-level, e.g. load flow analysis, node profile computation, meshed network optimisation, active network management or spinning reserve management
    • 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
    • Y02E10/50—Photovoltaic [PV] energy
    • Y02E10/56—Power conversion systems, e.g. maximum power point trackers

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  • Engineering & Computer Science (AREA)
  • Power Engineering (AREA)
  • Physics & Mathematics (AREA)
  • Nonlinear Science (AREA)
  • Inverter Devices (AREA)

Abstract

The invention discloses a self-synchronization voltage source grid-connected stability improving method based on current control loop reshaping, and belongs to the technical field of grid-connected inverter control. The method comprises the following steps: measuring the port voltage and the output current of the grid-connected inverter and calculating and outputting active power and reactive power; respectively obtaining the amplitude value and the phase angle reference of the port voltage to generate a port voltage reference value; then, taking the port voltage as a feedback value of the voltage regulator; the port voltage reference value is then subtracted from the feedback value as an input to the voltage regulator. The voltage regulator outputs a current reference value, the sum of the output current and the output value of the current control loop reshaping branch is subtracted, the current reference value is input into the current regulator, finally, the output value of the current regulator is added with the feedforward quantity of the grid voltage to obtain a modulation signal, and the modulation signal is used for generating a driving signal through SVPWM so as to control the inverter. The method of the invention improves the stable operation capability of the self-synchronous voltage source under the strong network working condition on the premise of not increasing the hardware cost.

Description

Self-synchronization voltage source grid-connected stability improving method based on current control loop reshaping
Technical Field
The invention relates to the technical field of grid-connected inverter control, in particular to a self-synchronization voltage source grid-connected stability improving method based on current control loop remodeling.
Background
The current source grid-connected inverter has the advantages of high power regulation speed and high renewable energy source utilization rate, but generally takes maximized active power output as a main operation target, and cannot support grid voltage and stable frequency like a traditional synchronous generator. With the continuous improvement of the new energy power generation permeability, a strong power grid is gradually changed into a weak power grid state, and the grid-connected inverter is generated in order to enhance the adaptability of the grid-connected inverter under complex working conditions.
The self-synchronizing voltage source belongs to the potential of simulating damping and inertia of a traditional synchronous generator, although the self-synchronizing voltage source can provide frequency and voltage support for a power grid, the self-synchronizing voltage source generally adopts a control structure of a voltage and current double inner rings, oscillation risks exist under the condition of strong network, the existing virtual impedance method depends on differential operation, a low-pass filtering link is required to be introduced in order to avoid the influence of high-frequency noise, and the dynamic characteristics of the self-synchronizing voltage source are deteriorated due to the hysteresis characteristic of the low-pass filtering link.
Disclosure of Invention
Aiming at the defects of the prior art, the invention provides a self-synchronization voltage source grid-connected stability improving method based on current control loop remodeling, which aims to inhibit grid-connected current oscillation and improve the operation stability of the self-synchronization voltage source grid-connected stability under the strong-grid working condition without additionally increasing hardware cost.
The aim of the invention can be achieved by the following technical scheme:
a self-synchronizing voltage source grid-connected stability improving method based on current control loop reshaping, wherein the topological structure of the self-synchronizing voltage source comprises the following steps: a direct-current side power supply, a three-phase inverter, three-phase power grid impedance and a three-phase power grid;
the method for improving the grid-connected stability of the self-synchronous voltage source comprises the following steps of:
collecting the port voltage and the port current of an inverter;
calculating the output active power and reactive power of the inverter according to the port voltage and port current of the inverter;
the phase of the bridge arm internal potential reference value and the amplitude of the bridge arm internal potential reference value are obtained through calculation according to the active power loop and the reactive power loop respectively, and then the internal potential reference value is obtained through an internal potential calculation formula;
the voltage control loop generates a reference value of the current control loop;
reshaping a current control loop and adding grid voltage feedforward control to generate a modulation wave;
and carrying out space vector modulation on the modulated wave to generate a driving signal.
Optionally, the calculating the active power and the reactive power output by the inverter includes the following steps:
converting the inverter port voltage and port current from a three-phase stationary coordinate system to a two-phase stationary coordinate system;
the conversion formula for converting the three-phase static coordinate system voltage into the two-phase static coordinate system voltage is as follows:
the transformation formula for converting the three-phase stationary coordinate system current into the two-phase stationary coordinate system current is as follows:
the inverter outputs active power p and reactive power q through an instantaneous power calculation formula; the instantaneous power calculation formula is:
p＝1.5×(v α i α +v β i β )
q＝1.5×(v β i α -v α i β )
optionally, the phase of the internal potential reference value, the amplitude of the bridge arm internal potential reference value and the internal potential calculating method comprise the following steps:
according to an active power loop calculation formula, calculating to obtain the phase theta of the potential reference value in the bridge arm, wherein the active power loop calculation formula is as follows:
wherein P is set Outputting an active power reference value omega for a three-phase inverter n Rated angular frequency of three-phase network, D p J is virtual moment of inertia, s is Laplacian operator;
the amplitude U of the potential reference value in the bridge arm is calculated according to a reactive power loop calculation formula, wherein the reactive power loop calculation formula is as follows:
in which Q set Output reactive power reference value for three-phase inverter, V n For rated voltage amplitude of three-phase power grid, D q K is a reactive damping coefficient, S is a Laplacian operator;
obtaining an internal potential reference value U through an internal potential calculation formula according to an internal potential phase angle reference theta and an internal potential amplitude reference U φ-ref The internal potential calculation formula is as follows:
optionally, the step of generating the reference value of the current control loop by the voltage control loop includes the steps of:
taking the internal potential reference value as a reference value of a voltage control loop;
taking the port voltage as a feedback quantity of a voltage control loop;
the reference value of the voltage control loop minus the feedback quantity of the voltage control loop is used as the input of the voltage control loop, the voltage control loop outputs the reference value of the current control loop, and the transfer function of the voltage control loop is H v (s)。
Optionally, the step of reshaping the current control loop and adding the feedforward control of the grid voltage to generate a modulation wave comprises the following steps:
output current i from synchronous voltage source abc The feedback quantity 1 of the current control loop is denoted as i fb1 ；
Designing a remolding branch of the current control loop, wherein the input of the remolding branch of the current control loop is the output value of the current control loop, and the output is the feedback quantity 2 of the current control loop, which is recorded as i fb2 The method comprises the steps of carrying out a first treatment on the surface of the The transfer function of the remodelling branch of the current control loop is H ires ＝H v (s)；
Calculating feedback quantity i of current control loop fb The calculation formula is i fb ＝i fb1 +i fb2 ；
The input of the current control loop is the reference value i of the current control loop ref Subtracting the feedback quantity i of the current control loop fb ；
The output modulated wave component 1 of the current control loop is denoted v mabc1 ；
Grid voltage feedforward component v ff For the modulated wave component 2, denoted v mabc2 Calculating the modulation wave, wherein the calculation formula is v mabc ＝v mabc1 +v mabc2 。
Optionally, the step of generating a driving signal by performing space vector modulation on the modulated wave includes the following steps:
the modulation wave is sent into a PWM module to generate a driving signal to control an inverter; the modulated wave is compared with a three-phase triangular carrier wave, and a driving signal is generated by a space vector modulation method.
Optionally, the three-phase inverter includes a three-phase inverter circuit, a three-phase LC filter, a three-phase voltage sensor, a three-phase current sensor, and a three-phase inverter controller.
The three-phase inverter circuit is connected with the three-phase LC filter, and the three-phase voltage sensor and the three-phase current sensor respectively sample three-phase voltage of a filter capacitor and three-phase current of a filter inductor in the three-phase LC filter and transmit sampling signals to the three-phase inverter controller; after the three-phase inverter controller is calculated, a driving signal is output to control the three-phase inverter circuit.
The invention has the beneficial effects that:
1. according to the method, the impedance of the remodelling self-synchronous voltage source is realized through remodelling the current control loop, and compared with the current voltage-current double-closed-loop control self-synchronous voltage source, the output current oscillation can be avoided, and the stable operation under the strong network working condition is realized.
2. According to the method, the control loop is optimized, the impedance of the self-synchronous voltage source is remodeled, and compared with a scheme of adding actual impedance, the hardware cost can be saved.
3. The method of the invention realizes the remodelling of the impedance of the self-synchronous voltage source through remodelling the current control loop, can avoid low-pass filtering and differential operation compared with the traditional virtual impedance method, does not need known filtering inductance value, and is simple to realize.
Drawings
The invention is further described below with reference to the accompanying drawings.
Fig. 1 is a circuit topology diagram of a three-phase grid-connected inverter according to an embodiment of the present invention;
FIG. 2 is a schematic diagram of a form 1 of a self-synchronizing voltage source grid-connected stability improvement method based on current control loop remodeling;
FIG. 3 is a schematic diagram of a form 2 of a self-synchronizing voltage source grid-connected stability improvement method based on current control loop remodeling;
FIG. 4 is a graph of the voltage at the phase A port and the output current of the inverter before and after the method of the present invention is applied;
fig. 5 is a graph of the waveforms of the active power and the reactive power output by the inverter before and after the method of the present invention is applied.
Detailed Description
The following description of the embodiments of the present invention will be made clearly and completely with reference to the accompanying drawings, in which it is apparent that the embodiments described are only some embodiments of the present invention, but not all embodiments. All other embodiments, which can be made by those skilled in the art based on the embodiments of the invention without making any inventive effort, are intended to be within the scope of the invention.
In some embodiments of the invention, a method for improving grid-connected stability of a self-synchronous voltage source based on current control loop remodeling is disclosed, and a grid-connected inverter topology structure applying the control method comprises the following steps: a direct-current side power supply, a three-phase inverter, three-phase power grid impedance and a three-phase power grid; the three-phase inverter comprises a three-phase inverter circuit, a three-phase LC filter, a three-phase voltage sensor, a three-phase current sensor and a three-phase inverter controller;
in a three-phase inverter: the three-phase inverter circuit is connected with the three-phase LC filter, and the three-phase voltage sensor and the three-phase current sensor respectively sample three-phase voltage of a filter capacitor and three-phase current of a filter inductor in the three-phase LC filter and transmit sampling signals to the three-phase inverter controller; after the three-phase inverter controller is calculated, a driving signal is output to control a three-phase inverter circuit;
the method for improving the grid-connected stability of the self-synchronous voltage source of the embodiment comprises the following steps:
s1, collecting port voltage v of an inverter abc And output current i abc The specific process comprises the following steps:
s11, collecting three-phase voltage of a filter capacitor of a three-phase LC filter by using a three-phase voltage sensor as the port voltage v of an inverter abc Three-phase current sensor is used for collecting three-phase LC filter filtering inductance three-phase current as inverter output current i abc ；
S12, the port voltage v of the inverter abc And output current i abc The analog quantity is converted into digital quantity and is transmitted to a three-phase inverter controller.
S2, calculating the active power and the reactive power output by the inverter, wherein the specific process comprises the following steps:
s21, the port voltage v of the inverter abc And port current i abc Converting from a three-phase stationary coordinate system to a two-phase stationary coordinate system;
the conversion formula for converting the three-phase static coordinate system voltage into the two-phase static coordinate system voltage is as follows:
the transformation formula for converting the three-phase stationary coordinate system current into the two-phase stationary coordinate system current is as follows:
s22, obtaining the active power p and the reactive power q output by the inverter through an instantaneous power calculation formula; the instantaneous power calculation formula is:
p＝1.5×(v α i α +v β i β )
q＝1.5×(v β i α -v α i β )
s3, calculating an internal potential amplitude U and a phase theta reference value and calculating an internal potential reference value;
s31, calculating the phase theta of the potential reference value in the bridge arm according to an active power loop calculation formula, wherein the active power loop calculation formula is as follows:
wherein P is set Outputting an active power reference value omega for a three-phase inverter n Rated angular frequency of three-phase network, D p J is virtual moment of inertia, s is Laplacian operator;
s32, calculating the amplitude U of the potential reference value in the bridge arm according to a reactive power loop calculation formula, wherein the reactive power loop calculation formula is as follows:
in which Q set Output reactive power reference value for three-phase inverter, V n For rated voltage amplitude of three-phase power grid, D q K is a reactive damping coefficient, and s is a Laplacian operator.
S33, obtaining an internal potential reference value U through an internal potential calculation formula according to the internal potential phase angle reference theta and the internal potential amplitude reference U φ-ref The internal potential calculation formula is as follows:
the step of generating a current reference value by the S4 voltage control loop comprises:
s41, the internal potential reference value u obtained in step S33 φ-ref Reference value u as voltage control loop ref ；
S42, the port voltage v abc As a voltage control loop feedback quantity u fb ；
S43, reference value u of voltage control loop φ-ref Subtracting the feedback quantity u of the voltage control loop fb As input to the voltage control loop, the voltage control loop outputs a reference value i of the current control loop ref The transfer function of the voltage control loop is H v (s)。
S5, reshaping the current control loop and generating a modulation wave by applying grid voltage feedforward control, wherein the step of reshaping the current control loop comprises the following steps of:
s51, outputting current i from the synchronous voltage source abc The feedback quantity 1 of the current control loop is denoted as i fb1 ；
S52, designing a remolding branch of the current control loop, wherein the input of the remolding branch of the current control loop is the output value of the current control loop, the output is the feedback quantity 2 of the current control loop, and the feedback quantity is recorded as i fb2 The method comprises the steps of carrying out a first treatment on the surface of the The transfer function of the remodelling branch of the current control loop is H ires ＝H v (s) corresponds to FIG. 2The self-synchronous voltage source grid-connected stability improvement method form 1 based on current control loop reshaping is shown.
S53, calculating the feedback quantity i of the current control loop fb The calculation formula is i fb ＝i fb1 +i fb2 ；
S54, the input of the current control loop is the current control loop reference value i obtained in the step S43 ref Subtracting the feedback quantity i of the current control loop fb 。
In other examples of the present invention, according to the principle of equivalent transformation of the transfer function block diagram, the comparison point of the current control loop remodelling branch in the step S53 may be further advanced to obtain the form 2 of the self-synchronous voltage source grid-connected stability improving method based on current control loop remodelling shown in fig. 3, where the transfer function of the corresponding current control loop remodelling branch is H ires ＝H v (s)/H v (s)＝1。
Correspondingly, step S42 port voltage v abc The feedback quantity 1 of the voltage control loop is denoted as u fb1 The output value of the current control loop remodelling branch is voltage control loop feedback quantity 2, which is marked as u fb2 Feedback quantity u of voltage control loop fb ＝u fb1 +u fb2 。
Accordingly, the feedback amount i of the current control loop in step S53 fb ＝i fb1 ＝i abc 。
S55, output modulation wave component 1 of current control loop is marked as v mabc1 ；
S56, grid voltage feedforward component v ff For the modulated wave component 2, denoted v mabc2 Calculating the modulation wave, wherein the calculation formula is v mabc ＝v mabc1 +v mabc2 ；
S6, generating a driving signal by space vector modulation. The specific process is as follows: modulating wave v obtained in S5 mabc Sending the signals into a PWM module to generate driving signals and control an inverter; modulated wave v mabc The drive signal is generated by space vector modulation (SVPWM) method compared with the three-phase triangular carrier.
Application examples:
embodiments of the method of the above embodiments in a specific application scenario are further disclosed below. Specifically, a main circuit and an inverter control method of a typical grid-connected system are shown in fig. 1. The direct current side of the main circuit part can be regarded as a direct current source with constant voltage, the direct current-alternating current conversion part is realized by a three-phase full-bridge inverter circuit consisting of 6 IGBTs, and the current output by the bridge arm is connected into a power grid after LC filtering. And the sampling part is used for obtaining the port voltage and the output current of the inverter through a sampling device. And the inverter control part inputs the port voltage and the output current of the inverter to the power calculation module to obtain the instantaneous output active power and reactive power of the inverter, the instantaneous output active power of the inverter is input to the active power/frequency (P/f) regulating module to obtain the reference internal potential phase, and the instantaneous output reactive power of the inverter is input to the reactive power/voltage (Q/u) regulating module to obtain the reference internal potential amplitude. And calculating a reference value of the voltage control loop according to the internal potential phase and the amplitude, wherein the port voltage is used as a feedback value of the voltage control loop. The reference value and the feedback value of the voltage control loop are subjected to difference and input into a voltage regulating module, and the voltage regulating module outputs a current reference value. Further, calculating a feedback value of the current control loop according to the output current and the current control loop remolding branch, and inputting a difference between a reference value and the feedback value of the current control loop into the current control module. And then, the output value of the current control module is added with the power grid voltage feed-forward to obtain a modulation wave. And finally, generating a driving signal by modulating the modulated wave through space vector modulation SVPWM, and driving the IGBT.
The main parameter values of this embodiment are as follows: main circuit parameter, DC side voltage V dc =700v, inverter side filter inductance l=150uh, filter inductance subcircuit 0.01Ω, filter capacitance c=600uf, damping resistance R d Ac bus line voltage effective value 315V, ac bus voltage frequency f =0.2Ω 0 =50hz, a line resistance of 0Ω, a line inductance of 0Ω, an inverter rated capacity of 500kW, and an inverter switching frequency of 3.2kHz. Controller parameters, active power given P set =500 kW, reactive power given Q set =0kvar, virtual moment of inertia j=0.3, reactive inertia coefficient k=318, active damping coefficient D p = 252.87, reactive damping coefficient D q =2000, the virtual resistance is 0.01Ω, the virtual inductance is150uH, scaling factor of voltage controller K pv =50, integral coefficient K of voltage controller iv =0, current controller scaling factor K pi =0.64, integral coefficient of current controller K ii ＝100。
In order to verify the effectiveness of the self-synchronous voltage source grid-connected stability improving method based on current control loop reshaping, a simulation model is built in MATLAB/Simulink to verify the effectiveness of the control method. The inverter runs off the network in a time period of 0-0.1 s, is connected with the network at a moment of 0.1s, and the active power is given by P set =500 kW, the reactive power given as 0kvar,0.4s moment using the method of the invention.
Fig. 4 shows waveforms of the a-phase port voltage and the output current of the self-synchronizing voltage source before and after the present method is adopted. The method is not adopted in the time period of 0-0.1 s, the grid is connected at the moment of 0.1s and the time period of 0.1-0.4 s, and the port voltage does not generate fluctuation and the output current oscillates because the line impedance is 0. At the moment of 0.4s, the output current oscillation is fast attenuated by adopting the method of the invention, and the output current oscillation is completely restrained at the moment of 0.8 s.
Fig. 5 shows the output of active and reactive power waveforms from a synchronous voltage source before and after the present method. The method is not adopted in the invention, and the output active power and the reactive power are oscillated. At the moment of 0.4s, the output active power and the reactive power are fast attenuated by adopting the method of the invention, the oscillation of the output active power and the reactive power at the moment of 0.8s is completely inhibited, the active power reaches a given value of 500kW, and the reactive power reaches a given value of 0kVar.
In the description of the present specification, the descriptions of the terms "one embodiment," "example," "specific example," and the like, mean that a particular feature, structure, material, or characteristic described in connection with the embodiment or example is included in at least one embodiment or example of the present invention. In this specification, schematic representations of the above terms do not necessarily refer to the same embodiments or examples. Furthermore, the particular features, structures, materials, or characteristics described may be combined in any suitable manner in any one or more embodiments or examples.
The foregoing has shown and described the basic principles, principal features and advantages of the invention. It will be understood by those skilled in the art that the present invention is not limited to the embodiments described above, and that the above embodiments and descriptions are merely illustrative of the principles of the present invention, and various changes and modifications may be made without departing from the spirit and scope of the invention, which is defined in the appended claims.

Claims (7)

1. A self-synchronizing voltage source grid-connected stability improving method based on current control loop reshaping is characterized in that the topological structure of the self-synchronizing voltage source comprises the following steps: a direct-current side power supply, a three-phase inverter, three-phase power grid impedance and a three-phase power grid;
the method for improving the grid-connected stability of the self-synchronous voltage source comprises the following steps of:
collecting the port voltage and the port current of an inverter;
calculating the output active power and reactive power of the inverter according to the port voltage and port current of the inverter;
the phase of the bridge arm internal potential reference value and the amplitude of the bridge arm internal potential reference value are obtained through calculation according to the active power loop and the reactive power loop respectively, and then the internal potential reference value is obtained through an internal potential calculation formula;
the voltage control loop generates a reference value of the current control loop;
reshaping a current control loop and adding grid voltage feedforward control to generate a modulation wave;
and carrying out space vector modulation on the modulated wave to generate a driving signal.
2. The method for improving grid-connected stability of a self-synchronous voltage source based on current control loop remodeling according to claim 1, wherein the step of calculating the active power and the reactive power output by the inverter comprises the steps of:
converting the inverter port voltage and port current from a three-phase stationary coordinate system to a two-phase stationary coordinate system;
the conversion formula for converting the three-phase static coordinate system voltage into the two-phase static coordinate system voltage is as follows:
the transformation formula for converting the three-phase stationary coordinate system current into the two-phase stationary coordinate system current is as follows:
the inverter outputs active power p and reactive power q through an instantaneous power calculation formula; the instantaneous power calculation formula is:
3. the method for improving grid-connected stability of the self-synchronous voltage source based on current control loop remodeling according to claim 1, wherein the phase of the internal potential reference value, the amplitude of the bridge arm internal potential reference value and the internal potential calculation method comprise the following steps:
according to an active power loop calculation formula, calculating to obtain the phase theta of the potential reference value in the bridge arm, wherein the active power loop calculation formula is as follows:
wherein P is set Outputting an active power reference value omega for a three-phase inverter n Rated angular frequency of three-phase network, D p J is virtual moment of inertia, s is Laplacian operator;
the amplitude U of the potential reference value in the bridge arm is calculated according to a reactive power loop calculation formula, wherein the reactive power loop calculation formula is as follows:
in which Q set Output reactive power reference value for three-phase inverter, V n For rated voltage amplitude of three-phase power grid, D q K is a reactive damping coefficient, S is a Laplacian operator;
obtaining an internal potential reference value U through an internal potential calculation formula according to an internal potential phase angle reference theta and an internal potential amplitude reference U φ-ref The internal potential calculation formula is as follows:
4. the method for improving grid-connected stability of a self-synchronous voltage source based on current control loop remodeling according to claim 1, wherein the step of generating a reference value of the current control loop by the voltage control loop comprises the steps of:
taking the internal potential reference value as a reference value of a voltage control loop;
taking the port voltage as a feedback quantity of a voltage control loop;
the reference value of the voltage control loop minus the feedback quantity of the voltage control loop is used as the input of the voltage control loop, the voltage control loop outputs the reference value of the current control loop, and the transfer function of the voltage control loop is H v (s)。
5. The method for improving grid-connected stability of a self-synchronous voltage source based on current control loop remodeling according to claim 1, wherein the method for remodeling the current control loop and adding grid voltage feedforward control to generate a modulation wave comprises the following steps:
output current i from synchronous voltage source abc The feedback quantity 1 of the current control loop is denoted as i fb1 ；
Designing a remolding branch of the current control loop, wherein the input of the remolding branch of the current control loop is the output value of the current control loop, and the output is the feedback quantity 2 of the current control loop, which is recorded as i fb2 The method comprises the steps of carrying out a first treatment on the surface of the The transfer function of the remodelling branch of the current control loop is H ires ＝H v (s)；
Calculating feedback quantity i of current control loop fb The calculation formula is i fb ＝i fb1 +i fb2 ；
The input of the current control loop is the reference value i of the current control loop ref Subtracting the feedback quantity i of the current control loop fb ；
The output modulated wave component 1 of the current control loop is denoted v mabc1 ；
Grid voltage feedforward component v ff For the modulated wave component 2, denoted v mabc2 Calculating the modulation wave, wherein the calculation formula is v mabc ＝v mabc1 +v mabc2 。
6. The method for improving grid-connected stability of a self-synchronous voltage source based on current control loop remodeling according to claim 1, wherein the step of spatially vector modulating the modulated wave to generate a driving signal comprises the steps of:
the modulation wave is sent into a PWM module to generate a driving signal to control an inverter; the modulated wave is compared with a three-phase triangular carrier wave, and a driving signal is generated by a space vector modulation method.
7. The method for improving grid-connected stability of a self-synchronous voltage source based on current control loop remodeling according to claim 1, wherein the three-phase inverter comprises a three-phase inverter circuit, a three-phase LC filter, a three-phase voltage sensor, a three-phase current sensor and a three-phase inverter controller;
the three-phase inverter circuit is connected with the three-phase LC filter, and the three-phase voltage sensor and the three-phase current sensor respectively sample three-phase voltage of a filter capacitor and three-phase current of a filter inductor in the three-phase LC filter and transmit sampling signals to the three-phase inverter controller; after the three-phase inverter controller is calculated, a driving signal is output to control the three-phase inverter circuit.
CN202310574239.9A 2023-05-19 2023-05-19 Self-synchronization voltage source grid-connected stability improving method based on current control loop reshaping Pending CN116545018A (en)

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