CN113224797B - 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 PDFInfo
- Publication number
- CN113224797B CN113224797B CN202110614906.2A CN202110614906A CN113224797B CN 113224797 B CN113224797 B CN 113224797B CN 202110614906 A CN202110614906 A CN 202110614906A CN 113224797 B CN113224797 B CN 113224797B
- Authority
- CN
- China
- Prior art keywords
- loop
- current
- voltage
- frequency
- transfer function
- 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.)
- Active
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
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 situations, 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 with the application number CN201610408203.3 discloses a method for calculating the PI parameters of a voltage-current dual closed-loop controller by using a particle swarm algorithm, and iterative optimization is performed by monitoring the states of voltage, current, active power, reactive power and the like through the particle swarm algorithm, so as to dynamically adjust 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 traditional methods all have different defects, and the methods are actually double closed-loop controller parameter design schemes utilizing a Helvelz criterion and a Li Nade-Qi Pate stabilization 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 by the following steps: 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:
in the formula, L 1 And C represents the filter inductance and filter capacitance on the inverter side, omega cc The cutoff frequency of the current loop;
when the above relation is satisfied, it can be considered that the output voltage U is od Output U relative to current loop d Is a slow disturbance, the transfer function of the LC filter and the output voltage U od The 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 loop cc The selection is reasonable, the 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:
wherein, f 0 Representing the grid frequency, f c Representing the inverter switching frequency;
by at the cut-off frequency omega of the current loop cc The 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:
in the formula, R 1 Is the equivalent resistance value, K, of the filter inductor CP And K CI Respectively 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:
in the formula, ξ represents the damping ratio, ω n Representing 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 is n The selection of the frequency characteristic curve should ensure that the cut-off frequency of the amplitude frequency characteristic curve of the current loop is between 1/5 and 1/10 of the angular frequency corresponding to the switching frequency of the inverter.
Further, setting a variable n to construct a relation between a zero and a pole in a current loop closed-loop transfer function, and enabling:
K CI /K CP ＝n(R 1 /L 1 )；
the closed loop transfer function of the current loop is simplified into the following form by adopting an approximate factorization method:
further, the voltage ring PI parameter is configured by an oscillation index method, and a calculation formula is as follows:
in the formula, K VI And K VP Respectively representing the integral constant and the proportional parameter of the voltage loop, and h is the bandwidth.
Further, the above-mentioned numerical range of h is 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 schematic 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 ω n Bode plot of current loop open loop transfer function under variation;
FIG. 8 is ω n A 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 varying ξ;
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 grid-connected operation of an inverter based on a virtual synchronous generator control strategy, and fig. 3 is a conceptual diagram of island operation of an inverter 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:
in the formula, R 1 Is the equivalent resistance of the filter inductor; l is 1 Representing inverter-side filter inductance values; c is a filter capacitance value; u. of a 、u b 、u c Three-phase voltages output by the inverters respectively; u. of oa 、u ob 、u oc Respectively, capacitor terminal voltages; i.e. i La 、i Lb 、i Lc Respectively the current on the filter inductor at the side of the inverter; i.e. i oa 、i ob 、i oc Respectively the current on the network 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:
wherein, 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.
The inverter and the LC filter are used as controlled objects, and the voltage outer loop and the current inner loop are both regulated by PI. Equivalent gain K of inverter pwm The proportionality coefficient K reduced to the current inner ring CP Integral coefficient K CI In (1). And (3) performing feed-forward decoupling control to eliminate the coupling relation between the dq axes. Eliminating disturbance signal by introducing the disturbance signal as positive feedback signalThe effect of sign on the voltage and current loops. Synthesized voltage U of droop-controlled output dref As a reference value of the voltage outer ring, a mathematical model of the controller under the dq0 coordinate axis is as follows:
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 control d-axis component U of output voltage dref As the reference value of the voltage outer ring, the actual output voltage U of the inverter od As a feedback signal, the coupling amount is ω L 1 I Lq . Therefore, - ω L is introduced in the feed forward compensation 1 I Lq To counteract the effects of coupling; d-axis component I of output current od For disturbance signals of voltage outer loop, I can be introduced od The signal is used as a positive feedback signal to counteract the influence of the disturbing signal. Voltage outer loop output signal I dref As a reference value for the current inner loop. Actual output current I of inverter od As a feedback signal of the current inner loop, a d-axis component U of the output voltage od Is a disturbance signal of the current inner loop. Feed forward compensation using- ω CU q By using U od The 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 controlled by a current PI controller, and the equivalent gain K of the inverter PWM And the inductance equivalent admittance on the inverter side, due to K PWM Reduced to the current loop PI parameter, i.e. K PWM And =1. Direct component I of the inductor current Ld Forming a feedback branch of current loop control.
When the following equation is satisfied, the output voltage U can be considered od Output U relative to current loop d It is a slower perturbation. Transfer function and output voltage U of LC filter od Closed loop transmission with negative feedbackThe transfer function can be approximately equivalent to an open loop transfer function:
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:
in the formula: f. of 0 Is the grid frequency; f. of c 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 cut-off frequency ω of the current loop cc The 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 loop cc Reasonable 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:
the characteristic equation and the expected characteristic equation of the current loop closed loop system are as follows:
in the formula, xi is a damping ratio; omega n Is an undamped natural oscillation angular frequency.
The PI parameter calculation formula of the current loop can be easily obtained by the following formula:
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, omega cc The 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:
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:
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 large, the two curves in the middle frequency band 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 fixed, the voltage outer ring ratio 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 ringExample coefficient K VP Integral coefficient K VI . In summary, this approximate decomposition is feasible for the study of 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 terminal od A feedback branch of the current outer loop is formed. The open loop transfer function of the voltage outer loop is:
from the above equation, the voltage outer loop is typical of type ii systems.
Let τ be v = hT, the open-loop transfer function and the closed-loop transfer function of a typical type ii system are:
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:
will K min Substituting the closed loop transfer function and the open loop transfer function of a typical II-type system, and then obtaining a calculation formula of the voltage loop PI parameter without difficulty:
in the formula, K VI And K VP Respectively representing voltage loop integral constant and proportional parameter，h＝τ v /T＝ω T /ω V The frequency bandwidth can be selected from 3 to 10, and the engineering h is generally 5.
The following is an 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-current double closed-loop control, an SPWM (sinusoidal pulse width modulation) pulse modulator, an inverter part, an LC/LCL (liquid crystal/liquid crystal) 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 conversion e And reactive power Q e . 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 controller m The 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 Q e And reference reactive power Q ref Comparing to finally generate a voltage amplitude signal U m And generating a direct current signal for generating a modulation wave through virtual impedance control and double closed-loop control. The direct current modulation signal and the electrical angle are input into Park inverse transformation together, the generated direct current modulation signal under the dq coordinate system is inversely transformed into an SPWM modulation signal under an abc three-phase natural coordinate system, and therefore the inverter is controlled to output voltage and current signals meeting the national standard requirements.
The two simulation models are built in Matlab/Simulnk, and the simulation parameters are shown in the following table:
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 required to be increased due to environmental changes or power system at 0.35 s, and 3kW of active power is reduced at 0.65 s.
Keep xi =0.8 constant, ω n From 2 pi f c A gradual decrease of/5 to 2 pi f c /15 and substituting into the current loop PI parameter formula to find K CP And K CI And 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 omega n ＝2πf c And 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, ω n When 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 seen n Does not affect the overshoot of the system, σ%, but follows ω n The time to reach the steady state is gradually increased.
When ω is n Keeping unchanged, when xi is gradually increased, the curve in the Bode diagram is gradually far away from the ordinate axis, and the cutoff frequency omega of the current loop is cc And 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.
Cut-off frequency of current loop open loop transfer functionShould be chosen in the range of 2 to 4kHz, where the cut-off frequency is chosen to be around 3 kHz. By selecting different xi and omega n And 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:
and obtaining five groups of current loop PI parameters according to the five groups of data. And h =5, substituting five sets of PI parameters 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.
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 very wide bandwidth in a low frequency band, so that the amplitude of the output voltage can be ensured to meet the requirements of the system when the inverter operates at an allowable frequency deviation. The error of the output voltage at 50Hz is about 0.293%, which is far less than the voltage of 220V power supply system specified by the national standard and is not lower than the rated voltage by 10% 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 serves 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 simulation dref =311V, and the d-axis component U of the output voltage od =0V, the error signal of the initial input of the d-axis voltage PI controller is 311.1. 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 (3)
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 cutoff 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;
the following relation is also proposed:
in the formula, L 1 And C represents the filter inductance and filter capacitance on the inverter side, omega cc The cutoff frequency of the current loop;
the cut-off frequency of the filter design should satisfy the following relationship:
wherein f is 0 Representing the grid frequency, f c Representing the inverter switching frequency;
by at the cut-off frequency omega of the current loop cc The range is selected to equate the closed loop transfer function to an open loop transfer function, the open loop transfer function being:
in the formula, R 1 Is the equivalent resistance value, K, of the filter inductor CP And K CI Respectively representing a proportional parameter and an integral parameter of the current loop PI controller;
the current loop PI parameter calculation is performed with the following relation:
in the formula, ξ represents the damping ratio, ω n Representing an undamped natural oscillation angular frequency;
omega mentioned above n The selection of the frequency characteristic curve is to ensure that the cut-off frequency of the current loop amplitude frequency characteristic curve is between 1/5 and 1/10 of the angular frequency corresponding to the inverter switching frequency;
setting a variable n to construct the relation between the zero and the pole in the current loop closed-loop transfer function, and enabling:
K CI /K CP ＝n(R 1 /L 1 )；
the closed loop transfer function of the current loop is simplified into the following form by adopting an approximate factorization method:
the voltage ring PI parameter is configured by adopting an oscillation index method, and the calculation formula is as follows:
in the formula, K VI And K VP Respectively representing the voltage loop integral constant and the proportional parameter, and h is the bandwidth.
2. The PI parameter configuration method of the voltage-current double closed-loop control system of the inverter as claimed in claim 1, wherein the value of h is in a range of 3-10.
3. The PI parameter configuration method of the voltage-current double closed-loop control system of the inverter as claimed in claim 2, wherein the value of h is 5.
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 CN113224797A (en) | 2021-08-06 |
| CN113224797B true 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) |
Families Citing this family (2)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| 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 |
| 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 |
Citations (3)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| 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 |
Family Cites Families (2)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN105006825B (en) * | 2015-06-04 | 2017-04-05 | 广西电网有限责任公司电力科学研究院 | A kind of electric power electric transformer and its control method of high quality of power supply output |
| CN108616141B (en) * | 2018-03-13 | 2021-07-06 | 上海交通大学 | Control method for LCL grid-connected inverter power nonlinearity in microgrid |
-
2021
- 2021-06-02 CN CN202110614906.2A patent/CN113224797B/en active Active
Patent Citations (3)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| 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)
| Title |
|---|
| Design of a high performance deadbeat-type current controller for LCL-filtered grid-parallel inverters;J. Wang等;《2015 IEEE 6th International Symposium on Power Electronics for Distributed Generation Systems (PEDG)》;20150827;全文 * |
| 并网LCL滤波的PWM整流器输入阻抗分析;李芬等;《电工技术学报》;20100126(第01期);全文 * |
| 户用型光伏并网逆变器的研究与设计;何军等;《电源技术》;20151020(第10期);全文 * |
| 电压型PWM整流器比例-积分控制器的参数设计;明战起等;《电力科学与工程》;20081128(第09期);全文 * |
| 计及RSC控制的DFIG短路电流直流分量解析表达;李生虎等;《太阳能学报》;20200228(第02期);全文 * |
Also Published As
| Publication number | Publication date |
|---|---|
| CN113224797A (en) | 2021-08-06 |
Similar Documents
| Publication | Publication Date | Title |
|---|---|---|
| CN111541274B (en) | Island micro-grid control method based on virtual synchronous generator characteristics | |
| CN106208159A (en) | Bavin based on virtual synchronous electromotor storage mixing independent micro-grid dynamic power compensation method | |
| 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 | |
| CN106849186A (en) | A kind of energy storage inverter master-slave control method based on virtual synchronous generator | |
| CN113131521A (en) | Virtual synchronous machine multi-machine parallel stable control and inertia matching method thereof | |
| CN104135003B (en) | APF control method based on active disturbance rejection and repetitive control | |
| CN104022631A (en) | Grid-connected inverter electric network harmonic wave effect inhibiting method based on LCL filtering | |
| CN113991755B (en) | New energy power generation unit self-synchronizing voltage source control method | |
| CN106159999A (en) | Bavin based on virtual synchronous electromotor storage mixing independent micro-grid dynamic frequency stable strategy | |
| Zhou et al. | Fuzzy linear active disturbance rejection control of injection hybrid active power filter for medium and high voltage distribution network | |
| 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 | |
| Soliman et al. | Experimental validation for artificial data-driven tracking control for enhanced three-phase grid-connected boost rectifier in DC microgrids | |
| CN115954899A (en) | Virtual synchronous machine grid-connected active optimization method based on frequency feedforward compensation | |
| CN115051404A (en) | Alternating voltage control method of high-voltage network-building type current converter | |
| CN113328440A (en) | Active filtering control method for PLC circuit of electric vehicle charging station | |
| CN108512227A (en) | A kind of adjusting method of single-phase LCL gird-connected inverters improved electric throttle regulator | |
| CN108736517B (en) | VSG-based inverter type distributed power supply adaptive damping control method | |
| CN114285081B (en) | Wide area power system stabilizing method based on self-adaptive virtual resistor | |
| CN114069697B (en) | Method for controlling inverter grid connection based on virtual synchronous generator principle | |
| CN115173487A (en) | Inverter stability optimization control method based on PLL link parameter adjustment | |
| CN115207988A (en) | Control method and system for new energy power generation converter | |
| CN112217378B (en) | Three-phase LCL type networking converter compound control system and method based on instruction feedforward | |
| CN114244173A (en) | Grid voltage feedforward method for weak grid AC device, electronic equipment and medium |
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 |