CN113224797A - PI parameter configuration method for voltage and current double closed-loop control system of inverter - Google Patents

PI parameter configuration method for voltage and current double closed-loop control system of inverter Download PDF

Info

Publication number
CN113224797A
CN113224797A CN202110614906.2A CN202110614906A CN113224797A CN 113224797 A CN113224797 A CN 113224797A CN 202110614906 A CN202110614906 A CN 202110614906A CN 113224797 A CN113224797 A CN 113224797A
Authority
CN
China
Prior art keywords
loop
current
voltage
frequency
parameter
Prior art date
Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
Granted
Application number
CN202110614906.2A
Other languages
Chinese (zh)
Other versions
CN113224797B (en
Inventor
田震
傅晓锦
吕菁
Current Assignee (The listed assignees may be inaccurate. Google has not performed a legal analysis and makes no representation or warranty as to the accuracy of the list.)
Shanghai Dianji University
Original Assignee
Shanghai Dianji University
Priority date (The priority date is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the date listed.)
Filing date
Publication date
Application filed by Shanghai Dianji University filed Critical Shanghai Dianji University
Priority to CN202110614906.2A priority Critical patent/CN113224797B/en
Publication of CN113224797A publication Critical patent/CN113224797A/en
Application granted granted Critical
Publication of CN113224797B publication Critical patent/CN113224797B/en
Active legal-status Critical Current
Anticipated expiration legal-status Critical

Links

Images

Classifications

    • 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
    • H02J3/01—Arrangements for reducing harmonics or ripples
    • 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
    • H02J3/388—Islanding, i.e. disconnection of local power supply from the network
    • 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
    • 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
    • H02J2203/20—Simulating, e g planning, reliability check, modelling or computer assisted design [CAD]
    • 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
    • Y02E40/40—Arrangements for reducing harmonics

Landscapes

  • Engineering & Computer Science (AREA)
  • Power Engineering (AREA)
  • Inverter Devices (AREA)

Abstract

The invention discloses a PI parameter configuration method of a voltage and current double closed-loop control system of an inverter, which comprises the following steps: setting the cut-off frequency of a current loop within the range of 10-20% of the angular frequency corresponding to the switching frequency of the inverter so as to meet the condition of simplifying a transfer function structure in engineering, setting a PI parameter of the current loop by adopting a pole configuration method, constructing the relation between poles and zeros in the current loop closed-loop transfer function by using a reference variable n, simplifying the current loop closed-loop transfer function by an approximate factorization method, and setting the PI parameter of a voltage loop by using an oscillation index method. Therefore, the problem that the method cannot be used due to the limitation of inductance parameters and current parameters in the process of PI parameter setting by using a typical system configuration method is solved.

Description

PI parameter configuration method for voltage and current double closed-loop control system of inverter
Technical Field
The invention relates to the technical field of new energy power systems and micro-grids, in particular to a PI parameter configuration method of a voltage and current double closed-loop control system of an inverter.
Background
When the new energy is connected to the grid or operates in an isolated island, relevant requirements such as harmonic content, voltage deviation, voltage fluctuation, voltage flicker and the like must be met. The harmonic content has been a hot problem in research. The new energy is filtered by an LC/LCL filter, but the LC filter or the LCL filter can generate a high resonance peak value, and the method is usually solved by adopting a passive damping method or an active damping method, wherein passive damping is to connect resistors in series in a capacitor to weaken the resonance peak value, the method can reduce the operation efficiency of the system, and the operation reliability of the system can be influenced by the heating of the resistors. Active damping is achieved by increasing the damping of the control system. Since the inverter and the filter are regarded as controlled objects, the output voltage or current is controlled to reduce the error with the reference value, and if the PI parameter of the double closed-loop control system is not designed reasonably, the system can not output ideal waveforms. However, the existing PI parameter configuration methods for the voltage and current double closed-loop control system have different conditions, so that the PI parameter configuration method for the double closed-loop control system, which can make up for the defects of the original method, is particularly important.
Through retrieval, the chinese patent application No. CN201610408203.3 discloses a method for calculating the PI parameters of a voltage-current dual closed-loop controller by using a particle swarm algorithm, which performs iterative optimization by monitoring the states of voltage, current, active power, reactive power, etc. through a particle swarm algorithm, thereby dynamically adjusting the PI parameters. The method for setting the voltage and current double closed-loop PI parameters in the patent has the following defects: the online calculation has extremely high requirements on hardware, and can be used in a large amount in the process of carrying out new energy power generation equipment grid connection and isolated island operation by applying a voltage and current double closed-loop controller, the cost and the equipment complexity can be greatly increased by adopting the method, the system operation reliability can also be reduced, and in addition, the calculation results of both the particle swarm algorithm and the genetic algorithm have randomness, so that the method is extremely easy to fall into a local optimal solution. The conventional methods all have different drawbacks, as the above methods are actually dual closed loop controller parameter design schemes using the hervez criterion and the li-reed-chiffon stability criterion. The determinants required for the herwitz stability criterion are constructed by making the eigenequations equal to zero, but the process of solving the determinant is computationally expensive. Therefore, the optimization is generally performed by a particle swarm algorithm or a genetic algorithm. In addition, a method for setting parameters by adopting a pole configuration method is also provided, because a closed-loop zero point is omitted, the parameter configuration needs to be repeatedly tested and completed, a P controller is required to be adopted in a current loop, and a PI controller cannot be adopted. Still another approach uses a typical system configuration, but is limited in application by filter parameters, resulting in an inability to meet approximate engineering simplifications.
Disclosure of Invention
The invention aims to provide a PI parameter configuration method of a voltage and current double closed-loop control system of an inverter, and aims to solve the problem that the method cannot be used due to the limitation of inductance parameters and current parameters in the process of PI parameter setting by using a typical system configuration method.
The purpose of the invention is realized as follows: a voltage and current double closed-loop control system PI parameter configuration method of an inverter comprises the following steps: setting the cut-off frequency of a current loop within the range of 10-20% of the angular frequency corresponding to the switching frequency of the inverter so as to meet the condition of simplifying a transfer function structure in engineering, setting a PI parameter of the current loop by adopting a pole configuration method, constructing the relation between poles and zeros in the current loop closed-loop transfer function by using a reference variable n, simplifying the current loop closed-loop transfer function by an approximate factorization method, and setting the PI parameter of a voltage loop by using an oscillation index method.
Further, the following relation is proposed:
Figure BDA0003096994900000031
in the formula, L1And C represents the filter inductance and filter capacitance on the inverter side, omegaccThe cutoff frequency of the current loop;
when the above relation is satisfied, the output voltage U can be considered asodOutput U relative to current loopdIs a slow disturbance, the transfer function of the LC filter and the output voltage UodThe closed loop transfer function formed by negative feedback can be approximately equivalent to an open loop transfer function.
Further, the cut-off frequency ω of the current loopccShould be selected reasonably, not onlyThe cut-off frequency of the current inner ring can be ensured to be larger than that of the voltage outer ring, the LC filter can be ensured to filter the subharmonic of the switching frequency without attenuating the harmonic of 10 times or below, namely, the cut-off frequency of the filter design can meet the following relation:
Figure BDA0003096994900000032
wherein f is0Representing the grid frequency, fcRepresenting the inverter switching frequency;
by at the cut-off frequency omega of the current loopccThe range is selected to equate the closed loop transfer function to an open loop transfer function, the equivalent open loop transfer function of the current loop being:
Figure BDA0003096994900000033
in the formula, R1Is the equivalent resistance value, K, of the filter inductorCPAnd KCIRespectively representing the proportional parameter and the integral parameter of the current loop PI controller.
Further, a pole configuration method is used for PI parameter setting on the current loop open-loop transfer function, namely, PI parameter calculation of the current loop is carried out according to the following relation:
Figure BDA0003096994900000034
in the formula, ξ represents the damping ratio, ωnRepresenting an undamped natural oscillation angular frequency;
because a zero point exists in the current loop closed loop transfer function, the overshoot of the system is not too large, and xi is selected to be larger, wherein omega isnThe selection of the frequency characteristic curve of the amplitude frequency of the current loop is to ensure that the cut-off frequency of the frequency characteristic curve of the amplitude frequency of the current loop is between 1/5 and 1/10 of the angular frequency corresponding to the switching frequency of the inverter.
Further, a variable n is set to construct the relation between the zero and the pole in the current loop closed-loop transfer function, and the order is as follows:
KCI/KCP＝n(R1/L1)；
the closed loop transfer function of the current loop is simplified into the following form by adopting an approximate factorization method:
Figure BDA0003096994900000041
further, the voltage ring PI parameter is configured by an oscillation index method, and a calculation formula is as follows:
Figure BDA0003096994900000042
in the formula, KVIAnd KVPRespectively representing the voltage loop integral constant and the proportional parameter, and h is the bandwidth.
Further, the above-mentioned value of h is in the range of 3 to 10, and the value of h is preferably 5.
The invention has the beneficial effects that:
1. by setting the cut-off frequency range of the current loop open-loop transfer function, the problem that the method is not applicable when the capacitance and inductance values do not meet the simplification conditions in the process of setting the PI parameter by the traditional typical system configuration method is effectively solved;
2. by introducing a variable n, the relation between a zero and a pole of a current loop closed-loop transfer function is constructed;
3. an approximate factorization method is adopted, which is similar to a system identification method, so that the voltage ring PI parameter can be set by adopting an oscillation index method;
4. the voltage and current of the system can be effectively controlled, and therefore the harmonic content of the system is reduced.
Drawings
FIG. 1 is a schematic flow diagram of the present invention;
FIG. 2 is a diagram of a virtual synchronous generator in a grid-connected mode;
FIG. 3 is a diagram of a virtual synchronous generator in an island mode;
FIG. 4 is a block diagram of a dual closed-loop control system in dq coordinate system;
FIG. 5 is a block diagram of a decoupled d-axis control system;
FIG. 6 is a log amplitude-frequency characteristic of an open loop transfer function for a typical type II system;
FIG. 7 is ωnBode plot of current loop open loop transfer function under variation;
FIG. 8 is ωnA current loop step response curve during variation;
FIG. 9 is a Bode plot of the current loop open loop transfer function as ξ changes;
FIG. 10 is a current loop step response curve with ξ changes;
FIG. 11 is an amplitude-frequency characteristic curve of the voltage outer loop open-loop transfer function obtained by using the "approximate factorization method" and without decomposition;
FIG. 12 is an amplitude-frequency characteristic of a voltage loop closed loop transfer function;
fig. 13 is an error curve input to the d-axis voltage loop PI controller in the grid-connected mode;
FIG. 14 is an error curve input to a d-axis voltage loop PI controller in island mode;
fig. 15 is a graph of output voltage versus load current in the grid-connected mode;
FIG. 16 is a graph of output voltage versus load current in an island mode;
FIG. 17 is a graph of output voltage harmonic spectra for a first set of parameters;
FIG. 18 is a graph of output voltage harmonic spectra for a second set of parameters;
FIG. 19 is a graph of the output voltage harmonic spectra for a third set of parameters;
FIG. 20 is a graph of the output voltage harmonic spectra for a fourth set of parameters;
FIG. 21 is a graph of the harmonic spectrum of the output voltage for the fifth set of parameters.
Detailed Description
The invention will be further described with reference to the accompanying figures 1-21 and specific examples.
The invention provides a PI parameter configuration method of a voltage and current double closed-loop control system of an inverter, which can be suitable for occasions of double closed-loop PI parameter setting during new energy grid connection or island operation.
Fig. 2 is a conceptual diagram of inverter grid-connected operation based on a virtual synchronous generator control strategy, and fig. 3 is a conceptual diagram of inverter island operation based on the virtual synchronous generator control strategy. For the inductance voltage and the capacitance current respectively listed as KVL and KCL equations, the following formula can be obtained:
Figure BDA0003096994900000061
Figure BDA0003096994900000062
in the formula, R1Is the equivalent resistance of the filter inductor; l is1Representing inverter-side filter inductance values; c is a filter capacitance value; u. ofa、ub、ucThree-phase voltages output by the inverters respectively; u. ofoa、uob、uocRespectively, capacitor terminal voltages; i.e. iLa、iLb、iLcRespectively the current on the filter inductor at the side of the inverter; i.e. ioa、iob、iocRespectively the current on the net side filter inductor.
An alternating current signal in an abc three-phase natural coordinate system is converted into a direct current signal rotating synchronously with the dq axis. And obtaining a complex frequency domain equation of the LC filter under the dq axis through constant amplitude Park transformation and Laplace transformation. As shown in the following formula:
Figure BDA0003096994900000071
in the formula, omega is angular frequency; s is the complex frequency; and the other variables are dq axis variables corresponding to the variables in the abc three-phase coordinate system. It is obvious from the above formula that the dq axes are coupled, and the influence between the voltage and the current of the dq axes can be eliminated through feedforward decoupling, so that the design of a control system becomes simple.
Using an inverter and an LC filter asThe controlled object, the voltage outer ring and the current inner ring are all regulated by adopting PI. Equivalent gain K of inverterpwmThe proportionality coefficient K reduced to the current inner ringCPIntegral coefficient KCIIn (1). And (3) carrying out feedforward decoupling control to eliminate the coupling relation between dq axes. The influence of the disturbance signal on a voltage loop and a current loop is eliminated by introducing the disturbance signal as a positive feedback signal. Synthesized voltage U of droop-controlled outputdrefAs a reference value of the voltage outer loop, the mathematical model of the controller under the dq0 coordinate axis is:
Figure BDA0003096994900000072
due to the dual nature of the dq axes, the control system is designed here with the d axis as an example: controlling droop to the d-axis component U of the output voltagedrefAs the reference value of the voltage outer ring, the actual output voltage U of the inverterodAs a feedback signal, the coupling amount is ω L1ILq. Therefore, - ω L is introduced in the feed forward compensation1ILqTo counteract the effects of coupling; d-axis component I of output currentodFor disturbance signals of voltage outer loop, I can be introducedodThe signal is used as a positive feedback signal to counteract the influence of the disturbing signal. Voltage outer loop output signal IdrefAs a reference value for the current inner loop. Actual output current I of inverterodAs a feedback signal of the current inner loop, a d-axis component U of the output voltageodIs a disturbance signal of the current inner loop. Feed forward compensation using- ω CUqBy using UodThe signal is used as a positive feedback signal to offset the influence brought by the current inner loop disturbing signal.
The setting of the double closed loop parameters is carried out according to the principle that the frequency of a control system is limited by the switching frequency of the inverter, and the cutoff frequency of the current inner loop is required to be smaller than the angular frequency corresponding to the switching frequency of the inverter during design. The current loop is composed of a current PI controller and an equivalent gain K of an inverterPWMAnd the inductance equivalent admittance on the inverter side, due to KPWMReduced to the current loop PI parameter, i.e. K PWM1. Electric inductionDirect component of flow ILdForming a feedback branch of current loop control.
When the following equation is satisfied, the output voltage U can be consideredodOutput U relative to current loopdIt is a slower perturbation. Transfer function and output voltage U of LC filterodThe closed loop transfer function formed by negative feedback can be approximately equivalent to an open loop transfer function:
Figure BDA0003096994900000081
because the LC filter should filter out the switching frequency subharmonics without attenuating harmonics 10 and below, the cut-off frequency of the filter design should satisfy the following equation:
Figure BDA0003096994900000082
in the formula: f. of0Is the grid frequency; f. ofcIs the inverter switching frequency.
The cut-off frequency of the current inner ring is greater than that of the voltage outer ring, so that the response speed of the current inner ring is higher than that of the voltage outer ring, and the output reference current of the voltage outer ring can be tracked. Furthermore, since the speed of the control system is limited by the switching frequency, the cut-off frequency of the current loop should be less than the angular frequency corresponding to the switching frequency of the inverter. Thus, the cutoff frequency ω of the current loopccThe range of 10% to 20% of the angular frequency corresponding to the inverter switching frequency should be selected to satisfy the equivalent condition described above. By at the cut-off frequency omega of the current loopccReasonable selection in range can equate the closed loop transfer function described above to an open loop transfer function. Thus, the open loop transfer function of the equivalent current loop can be written as follows:
Figure BDA0003096994900000091
the characteristic equation and the expected characteristic equation of the current loop closed loop system are as follows:
Figure BDA0003096994900000092
in the formula, xi is a damping ratio; omeganIs an undamped natural oscillation angular frequency.
The PI parameter calculation formula of the current loop can be easily obtained by the following formula:
Figure BDA0003096994900000093
because a zero point exists in the current loop closed loop transfer function, the overshoot of the system is not too large, and xi is selected to be larger, omegaccThe selection of the frequency characteristic curve should ensure that the cut-off frequency of the current loop amplitude frequency characteristic curve is between 10% and 20% of the angular frequency corresponding to the inverter switching frequency.
Order:
Figure BDA0003096994900000094
when n is less than 1, a section of horizontal line parallel to the horizontal axis appears in the current open-loop amplitude-frequency characteristic curve, and the cut-off frequency of the system is always greater than the angular frequency corresponding to the switch; when n >1, attenuation of the line segment acceleration amplitude of-40 dB/dec is generated. The variable n constructs the relationship between the poles-zero of the current loop closed loop transfer function. Thus, the closed loop transfer function of the current loop can be written as follows:
Figure BDA0003096994900000101
although the approximate factorization of the second-order oscillation element into the two first-order inertia elements has certain mathematical errors, the amplitude-frequency characteristic curves of the voltage loop open-loop transfer function obtained by adopting the approximate factorization and the non-factorization are basically consistent in the overall trend in experiments. When the current loop overshoot is largerIn the middle frequency band, the two curves have obvious deviation, but the turning frequency is hardly influenced. When the current loop overshoot is small, the two curves are nearly coincident. And when the PI parameter of the voltage outer ring is researched to be set, the voltage outer ring proportionality coefficient K is determined through the turning frequency and the intermediate frequency width h of the amplitude-frequency characteristic curve of the open-loop transfer function of the voltage outer ringVPIntegral coefficient KVI. In summary, this approximate decomposition is feasible for studying voltage outer loop PI parameters.
The voltage outer ring is composed of a voltage PI controller, a current inner ring and a capacitance impedance, and the voltage U of the LC filter terminalodA feedback branch of the current outer loop is formed. The open loop transfer function of the voltage outer loop is:
Figure BDA0003096994900000102
from the above equation, the voltage outer loop is a typical type ii system.
Let τ bevFor hT, the open-loop transfer function and the closed-loop transfer function of a typical type ii system are:
Figure BDA0003096994900000103
Figure BDA0003096994900000104
and (3) solving partial derivatives of angular frequency omega and gain K on the closed-loop amplitude-frequency characteristic by adopting an oscillation index method.
The open loop gain that minimizes the resonance peak can be found as:
Figure BDA0003096994900000111
will KminSubstituting into the open-loop transfer function and the closed-loop transfer function of a typical II-type system to obtain a calculation formula of the voltage loop PI parameter without difficulty：
Figure BDA0003096994900000112
In the formula, KVIAnd KVPRespectively, the voltage loop integral constant and the proportional parameter, h ═ tauv/T＝ωT/ωVThe frequency bandwidth can be selected from 3 to 10, and the engineering h is generally 5.
The following description is given by way of example of practical application.
Fig. 2 and fig. 3 are a conceptual diagram of inverter grid-connected operation based on a virtual synchronous generator control strategy and a conceptual diagram of inverter island operation based on the virtual synchronous generator control strategy, respectively. The control method comprises a phase-locked loop PLL, abc/dq (Park coordinate transformation) and dq/abc (Park inverse transformation), active-frequency droop control, reactive-voltage droop control, a virtual synchronous generator control strategy core part (a rotor motion equation), virtual impedance control, voltage and current double closed-loop control, an SPWM (sinusoidal pulse width modulation) pulse modulator, an inverter part, an LC/LCL (inductance-capacitance/capacitance) filter and a virtual power calculation part. The specific control flow is as follows: calculating the active power P of the acquired capacitor voltage and the acquired inductor current after Park conversioneAnd reactive power Qe. On one hand, the collected frequency information is compared with the rated frequency and is input into a mechanical power signal P generated by an active frequency droop controllermThe unbalanced power signal is generated by comparing with the electromagnetic power signal, the process is equivalent to a primary speed regulating system of a centrifugal flyover speed regulating system, and the generated uneven power is directly sent to a core part (a rotor motion equation) of a virtual synchronous generator control strategy to finally generate an electrical angle theta. On the other hand, reactive power QeAnd reference reactive power QrefComparing to finally generate a voltage amplitude signal UmAnd generating a direct current signal for generating a modulation wave through virtual impedance control and double closed-loop control. The DC modulation signal and the electrical angle are input into Park inverse transformation together, the generated DC modulation signal under the dq coordinate system is inversely transformed into an SPWM modulation signal under the abc three-phase natural coordinate system, and therefore the inverter is controlled to output voltage and current meeting the national standard requirementA signal.
The two simulation models are built in Matlab/Simulnk, and the simulation parameters are shown in the following table:
Figure BDA0003096994900000121
the simulation time is set to be 0.15 second under an island mode, the inverter is provided with a 20kW resistive load at the beginning, a 2kW load is put in at 0.05 second, and a 4kW load is cut off at 0.1 second.
In the grid-connected mode, the output current has larger inductive components, so that the current change is slower than that in the island mode. In order to better observe the change condition of the current, the simulation time is set to be 0.9 second, the inverter emits 15kW of active power at 0s, 5kW of active power is increased due to environmental change or the requirement of a power system at 0.35 s, and 3kW of active power is reduced at 0.65 s.
Keeping xi 0.8 constant, omeganFrom 2 pi fcA gradual decrease of/5 to 2 pi fc/15 and is taken into the current loop PI parameter formula to obtain KCPAnd KCIAnd obtaining a corresponding current loop open-loop transfer function. And (3) drawing a bode curve of the current loop open-loop transfer function and the step response of the current loop closed-loop system by using Matlab. As shown in fig. 7 and 8, respectively.
Maintenance of omegan＝2πfcAnd the voltage loop is not changed, xi is gradually increased from 0.8 to 2, and a bode curve of the voltage loop open-loop transfer function and the step response of the voltage loop closed-loop system are drawn by Matlab. As shown in fig. 9 and 10, respectively.
The following conclusions can be drawn by comparing several figures: when xi remains unchanged, ωnWhen the phase angle margin is gradually reduced, curves in the Bode graph are closer to the ordinate axis, the cut-off frequency of the current loop is continuously reduced, and the phase angle margin is unchanged. From the step response curve, ω can be seennDoes not affect the overshoot of the system, σ%, but follows ωnThe time until the steady state is reached is gradually longer.
When ω isnWhen xi is gradually increased and keeps unchanged, the curve in the Bode graph is gradually far awayFrom the axis of ordinate, current loop cutoff frequency ωccAnd the phase angle characteristic curve is gradually close to a-90-degree horizontal line, and the phase angle margin is gradually increased. In addition, as can be seen from the step response curve, the larger ξ is, the smaller the overshoot σ% of the system is.
The cut-off frequency of the current loop open loop transfer function should be chosen in the range of 2-4 kHz, where the cut-off frequency is chosen to be around 3 kHz. By selecting different xi and omeganAnd obtaining five groups of parameters with different overshoot sigma% for testing, thereby obtaining the selection rule of the PI parameters. Five sets of parameters are shown in the following table:
Figure BDA0003096994900000131
and obtaining five groups of current loop PI parameters according to the five groups of data. And h is set to 5, and five sets of PI parameters are substituted into a voltage ring PI parameter calculation formula to obtain respective voltage outer ring PI parameters. The first group with larger sigma% and the fifth group with smaller sigma% are selected to draw the amplitude-frequency characteristic curve of the voltage outer ring open-loop transfer function obtained by adopting an approximate factorization method and a non-factorization method. As shown in fig. 8.
The left side and the right side of fig. 11 are amplitude-frequency characteristic curves of the first group of data and the fifth group of data, respectively, the dotted line is the amplitude-frequency characteristic curve of the "approximate decomposition method", and the solid line is the unprocessed amplitude-frequency characteristic curve. The approximate values of the intersection points of the two curves (dotted lines) and the horizontal axis are respectively 1.5kHz and 1.74kHz which are lower than the cut-off frequency of the current loop, so that the current loop can track the output current reference value of the voltage loop. In addition, the two curves of the left image are obviously separated in the middle frequency band, but the influence on the turning frequency is not large, and the two curves on the right side are approximately overlapped. Therefore, the approximate factorization can satisfy PI parameter setting of the outer ring of the voltage on engineering.
And respectively substituting the calculated PI parameters into a Simulink simulation model. The simulated THD values in island mode and grid mode are the same. The following table is the PI parameters and corresponding THD values calculated using the above table.
Figure BDA0003096994900000141
When the first set of parameters is selected in the double closed-loop control system, the amplitude-frequency characteristic curve of the closed-loop transfer function of the voltage loop of the system is as shown in fig. 12, and has a wide bandwidth in a low frequency band, so that the amplitude of the output voltage can meet the requirements of the system when the inverter operates at an allowable frequency offset. The error of the output voltage at 50Hz is about 0.293%, which is far less than the voltage of a 220V power supply system specified by the national standard, not lower than 10% of the rated voltage and not higher than 7% of the rated voltage.
In an island operation mode, a three-phase voltage value synthesized by the output voltage value of the reactive-voltage droop controller and the electrical angle output by the virtual synchronous generator module is subjected to Park conversion and then is used as a reference value of d-axis and q-axis components of the voltage-current double closed-loop controller. D-axis component U of voltage reference value at the beginning of simulationdref311V and outputs a d-axis component U of the voltageodThe error signal of the initial input of the d-axis voltage PI controller is 311.1 because of 0V. Because the initial error of the double closed-loop controller is large, if the value before being input into the integrator and the value output by the integrator cannot reach a value close to 0 as soon as possible, the integrator will be saturated, which means that normal voltage and current waveforms cannot be generated. If the current loop integral constant of the first two sets of data is large, the above phenomenon will occur if it is not limited. An amplitude limiter can be added in front of the voltage loop PI controller for amplitude limiting, and the integral constant of the voltage loop can also be reduced at the same time.
The phenomenon only occurs in island operation and is related to the topological structure of the system. Fig. 13 and 14 are error signals input to the d-axis voltage loop PI controller in the grid-connected mode and the island mode, respectively. It can be seen that the initial value of the error signal in the island mode is 311.1, the time for reaching the stable state is long, while the initial value of the error signal in the grid-connected mode is high, the process for reaching the stable state is very short, and the stability can be reached within 1 millisecond. When configuring the dual closed loop PI parameters in the island operation mode, care should be taken to select the PI parameters with the minimum overshoot.
Fig. 15 and 16 are waveform diagrams of output voltage and output current in the grid-connected mode and the island mode, respectively, when the first set of data is used. It can be seen from the figure that the system can respond quickly when the load changes, allowing the current to increase or decrease rapidly while maintaining the stability of the voltage.
The simulation results prove the correctness and the effectiveness of the voltage and current double-closed-loop parameter configuration method.
While the preferred embodiments of the present invention have been described, those skilled in the art will appreciate that various changes and modifications can be made therein without departing from the spirit and scope of the invention as defined by the appended claims.

Claims (8)

1. A voltage and current double closed-loop control system PI parameter configuration method of an inverter is characterized by comprising the following steps: setting the cut-off frequency of a current loop within the range of 10-20% of the angular frequency corresponding to the switching frequency of the inverter so as to meet the condition of simplifying a transfer function structure in engineering, setting a PI parameter of the current loop by adopting a pole configuration method, constructing the relation between poles and zeros in the current loop closed-loop transfer function by using a reference variable n, simplifying the current loop closed-loop transfer function by an approximate factorization method, and setting the PI parameter of a voltage loop by using an oscillation index method.
2. The method for configuring the PI parameter of the voltage-current double closed-loop control system of the inverter according to claim 1, wherein the following relation is provided:
Figure FDA0003096994890000011
in the formula, L1And C represents the filter inductance and filter capacitance on the inverter side, omegaccThe cutoff frequency of the current loop.
3. The method of claim 2, wherein the cut-off frequency of the filter design satisfies the following relationship:
Figure FDA0003096994890000012
wherein f is0Representing the grid frequency, fcRepresenting the inverter switching frequency;
by at the cut-off frequency omega of the current loopccThe range is selected to equate the closed loop transfer function to an open loop transfer function, the open loop transfer function being:
Figure FDA0003096994890000013
in the formula, R1Is the equivalent resistance value, K, of the filter inductorCPAnd KCIRespectively representing the proportional parameter and the integral parameter of the current loop PI controller.
4. The method for configuring the PI parameter of the voltage-current double closed-loop control system of the inverter according to claim 3, wherein the PI parameter calculation of the current loop is performed according to the following relation:
Figure FDA0003096994890000021
in the formula, ξ represents the damping ratio, ωnRepresenting an undamped natural oscillation angular frequency;
omega mentioned abovenThe selection of the frequency characteristic curve of the amplitude frequency of the current loop is to ensure that the cut-off frequency of the frequency characteristic curve of the amplitude frequency of the current loop is between 1/5 and 1/10 of the angular frequency corresponding to the switching frequency of the inverter.
5. The PI parameter configuration method of the voltage and current double closed-loop control system of the inverter according to claim 4, wherein a variable n is set to construct a relation between a zero and a pole in a current loop closed-loop transfer function, so that:
KCI/KCP＝n(R1/L1)；
the closed loop transfer function of the current loop is simplified into the following form by adopting an approximate factorization method:
Figure FDA0003096994890000022
6. the method for configuring the PI parameter of the voltage and current double closed-loop control system of the inverter according to claim 5, wherein the PI parameter of the voltage ring is configured by an oscillation index method, and the calculation formula is as follows:
Figure FDA0003096994890000023
in the formula, KVIAnd KVPRespectively representing the voltage loop integral constant and the proportional parameter, and h is the bandwidth.
7. The PI parameter configuration method of the voltage-current double closed-loop control system of the inverter as claimed in claim 6, wherein the value of h is in a range of 3-10.
8. The PI parameter configuration method of the voltage-current double closed-loop control system of the inverter as claimed in claim 7, wherein the value of h is 5.
CN202110614906.2A 2021-06-02 2021-06-02 PI parameter configuration method for voltage and current double closed-loop control system of inverter Active CN113224797B (en)

Priority Applications (1)

Application Number Priority Date Filing Date Title
CN202110614906.2A CN113224797B (en) 2021-06-02 2021-06-02 PI parameter configuration method for voltage and current double closed-loop control system of inverter

Applications Claiming Priority (1)

Application Number Priority Date Filing Date Title
CN202110614906.2A CN113224797B (en) 2021-06-02 2021-06-02 PI parameter configuration method for voltage and current double closed-loop control system of inverter

Publications (2)

Publication Number Publication Date
CN113224797A true CN113224797A (en) 2021-08-06
CN113224797B CN113224797B (en) 2023-02-21

Family

ID=77082369

Family Applications (1)

Application Number Title Priority Date Filing Date
CN202110614906.2A Active CN113224797B (en) 2021-06-02 2021-06-02 PI parameter configuration method for voltage and current double closed-loop control system of inverter

Country Status (1)

Country Link
CN (1) CN113224797B (en)

Cited By (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
CN113872229A (en) * 2021-09-15 2021-12-31 华北电力科学研究院有限责任公司 Flexible direct current transmission operation simulation method and device
CN114006387A (en) * 2021-11-19 2022-02-01 华北电力大学 Adaptive frequency subsynchronous oscillation suppression method and system based on multi-branch impedance

Citations (5)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
CN105006825A (en) * 2015-06-04 2015-10-28 广西电网有限责任公司电力科学研究院 Power electronic transformer enabling high quality of electric energy output, and control method thereof
CN108696210A (en) * 2018-05-21 2018-10-23 东南大学 Direct current generator current loop controller methods of self-tuning based on parameter identification
CN109756166A (en) * 2019-03-22 2019-05-14 大连海事大学 Permanent magnet synchronous motor two close cycles vector controlled pi regulator parameter tuning method
US20190288611A1 (en) * 2018-03-13 2019-09-19 Shanghai Jiao Tong University Nonlinear control method for micro-grid inverter with anti-disturbance
CN111245329A (en) * 2020-02-21 2020-06-05 山东省科学院自动化研究所 Parameter self-tuning method and system for current loop PI regulator of permanent magnet synchronous motor

Patent Citations (5)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
CN105006825A (en) * 2015-06-04 2015-10-28 广西电网有限责任公司电力科学研究院 Power electronic transformer enabling high quality of electric energy output, and control method thereof
US20190288611A1 (en) * 2018-03-13 2019-09-19 Shanghai Jiao Tong University Nonlinear control method for micro-grid inverter with anti-disturbance
CN108696210A (en) * 2018-05-21 2018-10-23 东南大学 Direct current generator current loop controller methods of self-tuning based on parameter identification
CN109756166A (en) * 2019-03-22 2019-05-14 大连海事大学 Permanent magnet synchronous motor two close cycles vector controlled pi regulator parameter tuning method
CN111245329A (en) * 2020-02-21 2020-06-05 山东省科学院自动化研究所 Parameter self-tuning method and system for current loop PI regulator of permanent magnet synchronous motor

Non-Patent Citations (5)

* Cited by examiner, † Cited by third party
Title
J. WANG等: "Design of a high performance deadbeat-type current controller for LCL-filtered grid-parallel inverters", 《2015 IEEE 6TH INTERNATIONAL SYMPOSIUM ON POWER ELECTRONICS FOR DISTRIBUTED GENERATION SYSTEMS (PEDG)》 *
何军等: "户用型光伏并网逆变器的研究与设计", 《电源技术》 *
明战起等: "电压型PWM整流器比例-积分控制器的参数设计", 《电力科学与工程》 *
李生虎等: "计及RSC控制的DFIG短路电流直流分量解析表达", 《太阳能学报》 *
李芬等: "并网LCL滤波的PWM整流器输入阻抗分析", 《电工技术学报》 *

Cited By (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
CN113872229A (en) * 2021-09-15 2021-12-31 华北电力科学研究院有限责任公司 Flexible direct current transmission operation simulation method and device
CN113872229B (en) * 2021-09-15 2024-02-09 国网冀北电力有限公司电力科学研究院 Flexible direct current transmission operation simulation method and device
CN114006387A (en) * 2021-11-19 2022-02-01 华北电力大学 Adaptive frequency subsynchronous oscillation suppression method and system based on multi-branch impedance
CN114006387B (en) * 2021-11-19 2024-02-02 华北电力大学 Self-adaptive frequency subsynchronous oscillation suppression method and system based on multi-branch impedance

Also Published As

Publication number Publication date
CN113224797B (en) 2023-02-21

Similar Documents

Publication Publication Date Title
CN111541274B (en) Island micro-grid control method based on virtual synchronous generator characteristics
CN106410849A (en) Virtual synchronous generator-based microgrid inverter balance control method
CN113224797B (en) PI parameter configuration method for voltage and current double closed-loop control system of inverter
CN113131521A (en) Virtual synchronous machine multi-machine parallel stable control and inertia matching method thereof
CN108429281A (en) A kind of LCL type gird-connected inverter parallel virtual impedance adjustment
CN111130142B (en) Virtual capacitance control method for double-fed wind power generation grid-connected system
Zhou et al. Fuzzy linear active disturbance rejection control of injection hybrid active power filter for medium and high voltage distribution network
CN108306332B (en) LCL type grid-connected inverter system and current tracking control method
CN107134936A (en) A kind of inverter active damping control method based on overall-finished housing
CN113991755B (en) New energy power generation unit self-synchronizing voltage source control method
Soliman et al. Experimental validation for artificial data-driven tracking control for enhanced three-phase grid-connected boost rectifier in DC microgrids
CN113964879B (en) New energy grid-connected inverter self-synchronizing voltage source control method
Babu et al. Investigation of damping effect of PLL on low-frequency harmonic stability of grid-tied inverter with αβ and dq current control schemes
CN114069697B (en) Method for controlling inverter grid connection based on virtual synchronous generator principle
CN108736517B (en) VSG-based inverter type distributed power supply adaptive damping control method
Zhou et al. DQ impedance reshaping of three-phase power-controlled grid-connected inverter for low-frequency stability improvement under weak grid condition
CN114285081B (en) Wide area power system stabilizing method based on self-adaptive virtual resistor
CN105978018A (en) LC grid-connected inverter control method
CN112217378B (en) Three-phase LCL type networking converter compound control system and method based on instruction feedforward
Kim et al. Feedback linearization control of grid-interactive PWM converters with LCL filters
CN115173487A (en) Inverter stability optimization control method based on PLL link parameter adjustment
CN114244173A (en) Grid voltage feedforward method for weak grid AC device, electronic equipment and medium
Harasis et al. Enhanced dynamic performance of grid feeding distributed generation under variable grid inductance.
CN110896226B (en) Improved direct power control method of flexible direct current transmission system
Garikapati et al. ANFIS Controlled MMC-UPQC to Mitigate Power Quality Problems in Solar PV Integrated Power System

Legal Events

Date Code Title Description
PB01 Publication
PB01 Publication
SE01 Entry into force of request for substantive examination
SE01 Entry into force of request for substantive examination
GR01 Patent grant
GR01 Patent grant