CN107147317B - A kind of inverter parallel control method based on RC virtual impedance - Google Patents
A kind of inverter parallel control method based on RC virtual impedance Download PDFInfo
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- CN107147317B CN107147317B CN201710370547.4A CN201710370547A CN107147317B CN 107147317 B CN107147317 B CN 107147317B CN 201710370547 A CN201710370547 A CN 201710370547A CN 107147317 B CN107147317 B CN 107147317B
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- H—ELECTRICITY
- H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
- H02M—APPARATUS FOR CONVERSION BETWEEN AC AND AC, BETWEEN AC AND DC, OR BETWEEN DC AND DC, AND FOR USE WITH MAINS OR SIMILAR POWER SUPPLY SYSTEMS; CONVERSION OF DC OR AC INPUT POWER INTO SURGE OUTPUT POWER; CONTROL OR REGULATION THEREOF
- H02M7/00—Conversion of ac power input into dc power output; Conversion of dc power input into ac power output
- H02M7/42—Conversion of dc power input into ac power output without possibility of reversal
- H02M7/44—Conversion of dc power input into ac power output without possibility of reversal by static converters
- H02M7/48—Conversion of dc power input into ac power output without possibility of reversal by static converters using discharge tubes with control electrode or semiconductor devices with control electrode
- H02M7/493—Conversion of dc power input into ac power output without possibility of reversal by static converters using discharge tubes with control electrode or semiconductor devices with control electrode the static converters being arranged for operation in parallel
Abstract
The invention discloses a kind of inverter parallel control methods based on RC virtual impedance.The sagging control that the control method passes through addition differentiation element first carries out Parallel Control to inverter, then addition RC virtual impedance ring will export active reactive power decoupled and divide equally in the case where line impedance difference to power, then adds the secondary control based on the control of ratio resonance and improve assignment accuracy.The advantages that control method for parallel of the invention multi-inverter parallel control different for line impedance in low-voltage circuit has apparent advantage, has power distribution fast, and power distribution is more accurate, and circulation is small, has realistic meaning.
Description
Technical field
The present invention relates to inverter parallel systems in field of power electronics more particularly to a kind of based on RC virtual impedance
Inverter parallel control method.
Background technique
With getting worse for energy crisis in global range and problem of environmental pollution, point of renewable energy is combined
Cloth generation technology is increasingly becoming the important directions of modern power systems development.Distributed power generation is mainly with photovoltaic power generation, wind
Based on machine power generation, small fuel cell power generation and ocean current power generation.This generation mode is different from traditional centralized bulk power grid hair
The disadvantages of electric mode, power supply mode is flexible, and economy is good, and it is big to overcome traditional bulk power grid line loss, seriously polluted.It removes
Except this, distributed generation system can independent operating support network voltage in main electric network fault.What distributed generation resource was issued
Generally direct current need to be converted to three-phase alternating current by inverter and be electrically accessed power grid, therefore inverter technology is extremely important.In order to
The stability and scalability for improving distributed generation system, realize high-power power supply, each inverter in electricity generation system is more
It runs in parallel.The key of inverter parallel is to realize the mean allocation of power, and to make to be supported on every
It is evenly distributed between inverter, it is necessary to which the amplitude of every inverter output voltage, phase and frequency will protect at any time
It holds equal, avoids generating circulation between inverter, the overload or heavy service of single or multiple inverters.
Being divided into both at home and abroad about the research of inverter parallel control mode at present has interconnection line Parallel Control and without interconnection line
Independent control two major classes.Having interconnection line traffic control is exactly connecting line physically, main thought be from Traditional DC power supply and
Connection technology is that a kind of active load divides equally technology.From the angle of control strategy and control center of gravity, there is interconnection line parallel technology
It is broadly divided into centralized control, master & slave control, 3C control and distributed logic control.But it with the development of distributed generation system, uses
It is more and more in inverter number in parallel, so as to cause using the signal for the parallel system intermodule for having interconnection line control mode
Line becomes increasingly complex, and bring interference is also increasing.There is bad influence brought by interconnection line system to reduce and overcome,
Scientist proposes arcless breaking technology, i.e., sagging control.Core concept without interconnection control method for parallel is from same
The phenomenon that output voltage frequency declines as output power increases in step generator.This method is according to detection inverter output work
Rate come to output voltage amplitude and frequency be finely adjusted, indirectly inhibit the circulation between inverter, so that it is equal to reach load
The purpose divided.In order to obtain preferable stream effect, this control mode requires power detection speed fast, and control precision is wanted
It is high.
Summary of the invention
One kind that ended questions to be solved by this invention are the technical issues of for the above-mentioned prior art and propose is suitable
For parallelly connected reverse converter system, the asynchronous control strategy of line impedance, purpose are exactly existing in order to overcome in low-pressure system
The disadvantages of dynamic response present in technology is slow, output power couples, output power cannot be divided equally, by utilizing addition differential ring
Section enhancing dynamic property, addition RC virtual impedance decouple respectively power, and addition secondary control enhancing system becomes in load
Stability when change.
In order to achieve the goal above, the present invention is achieved by the following technical solutions:
Construct an inverter parallel simulation model.One inverter parallel circuit is built using Matlab/Simulink
System model, two inverter parameters are consistent.Every inverter output connects LCL filter, uses the voltage based on PR controller
Current double closed-loop control controls it, and makes output waveform three-phase sine-wave.
Sagging control is carried out to inverter parallel system.Every inverter output voltage and electric current are acquired, calculated
The average active power of output and reactive power of every inverter are obtained, the electricity of every inverter is calculated by sagging formula
Press reference value.
Add differentiation element.Since the sagging control parameter of tradition is definite value, dynamic response is poor, therefore this is in sagging control
The response speed that differentiation element improves sagging control is added in system, and then improves the dynamic response of voltage reference value, to improve
Power distribution speed.
Add RC virtual impedance.It will cause power coupling in low-pressure system for the sagging control of tradition, line impedance is not
Power can not be divided equally simultaneously, and the present invention uses addition RC virtual impedance that output impedance decouples power for perception, and
Make the equivalent total output impedance of two inverters identical by the difference to virtual impedance value, to divide equally to power.
Add secondary control.For the sagging control of tradition impacted problem of system stability when loading variation, addition
Voltage reference value is arrived by calculating feedback in the phase angle of ac bus and amplitude by secondary control, system when improving load variation
Stability.
Above-mentioned control method for parallel is crossed, it is fast that inverter output power in line impedance difference in low-pressure system may be implemented
It is fast accurately to divide equally, and system reliable and stable can be run.
The present invention has the following effects: the present invention can inverter and it is fashionable quickly power is divided equally, dynamic property is good.
The present invention, can be to function under inverter line impedance different condition in low-pressure system by adding RC virtual impedance to control loop
Rate is divided equally, it is ensured that every inverter work is in normal condition.The present invention passes through the amplitude and phase to ac bus voltage
Angle is acquired and adds secondary control, is loading the stability that may insure system voltage and frequency when variation, is enhancing system
Reliability.
Detailed description of the invention
A kind of inverter parallel control method structural block diagram based on RC virtual impedance of Fig. 1
Fig. 2 inverter parallel control structure block diagram of the present invention
The sagging control Dynamic Response Simulation result figure of Fig. 3 tradition
Fig. 4 Dynamic Response Simulation comparative result figure of the present invention
The sagging control power distribution simulation result diagram of Fig. 5 tradition
Fig. 6 power distribution simulation result comparison diagram of the present invention
The sagging stability of control system simulation result diagram of Fig. 7 tradition
Fig. 8 present system Simulation of stability comparative result figure
Specific embodiment
In order to be easy to understand the technical means, the creative features, the aims and the efficiencies achieved by the present invention, tie below
Conjunction is specifically illustrating, and further illustrates the present invention.
Referring to fig. 2, a kind of inverter parallel control method structure chart based on RC virtual impedance.Control method is mainly by four
Part forms: the closed-loop control of single inverter, improved sagging control, virtual impedance ring, secondary control.The present invention is mainly ground
Study carefully rear three parts, single inverter control uses conventional method.The control method working principle is as follows: first in the sagging control of tradition
The dynamic responding speed of differentiation element enhancing system is added in system；Secondly, addition RC virtual impedance to inverter output voltage into
Row compensation, divides equally power；Ac bus voltage is introduced electricity by the secondary control for then adding electric voltage frequency and amplitude
Reference value is pressed, the stability of system is increased.
Three-phase full-bridge inverter parallel circuit model, inverter direct-current power supply voltage are built using Matlab/Simulink
It for 650V, is controlled using SPWM, frequency of modulated wave 50Hz, carrier frequency 10kHz.Closed loop control is carried out to inverter
System.Inverter output end mouth connects a LCL filter, by inverter end inductance Li, capacitor C, load end inductance LgComposition.To electricity
Feel LiElectric current and capacitor C on voltage sampled, carry out calculating feedback by PR controller and be adjusted to SPWM modulating wave
System, achievees the effect that double-closed-loop control, so that inverter output waveforms are three-phase sine-wave.
Inverter parallel droop control method is as follows:
Two inverter capacitance voltage V are acquired respectivelyCInductive current i is surveyed with netg, inverter instantaneous output power is calculated,
Instantaneous output power obtains the mean power of inverter by a low-pass filter.Differential ring is added in the sagging method of tradition
Section improves the dynamic property of system so that the sagging factor becomes a underrange.Add RC virtual impedanceIts
Middle RvIt is virtual resistance, CvIt is simulated capacitance.Voltage compensation value after adding virtual impedance, the electricity that feedback is generated to sagging control
In pressure.The stability of system, proposes a kind of voltage magnitude based on PR controller when in order to improve load variation, frequency it is secondary
Control methods: the departure of ac bus voltage magnitude and frequency is added in the sagging control of tradition, is counted by PR controller
Feedforward after calculation as sagging control is added with the voltage that the sagging control of tradition calculates and obtains new voltage reference value.Wherein Epcc
It is voltage magnitude at PCC,It is the phase angle at PCC,andBeing divided into is their reference value.Kpc,Kic,KqcAnd Kqa
It is the adjustment parameter of PR controller.Voltage magnitude by measurement point of common coupling and the E at frequency, that is, PCC firstpccWith
Again with the rated voltage amplitude of ac busFrequencyIt is compared, obtained difference carries out PR adjusting, then feeds back every
The voltage reference value of a inverter compensates the voltage reference value generated with sagging control and is added to obtain new reference value, raw
The sagging curve of Cheng Xin.
The superiority verification step of control method is as follows:
Step 1: not considering line impedance, inverter 1 works and accesses load when emulating beginning, and inverter 2 does not connect negative
It carries.2 access system of inverter at 0.6 second, two inverters are powered to the load by inverter simultaneously at this time.Simulation result ginseng
See Fig. 3, as can be seen from Fig. traditional sagging method may be implemented to power divide equally but dynamic response it is slower.Simulated environment is not
Become, using the mentioned method of the present invention, simulation result referring to fig. 4, from used method of the invention known to figure power distribution have compared with
Good dynamic response.Comparison diagram 3 and 4 is it is found that the mentioned method of the present invention has preferable dynamic response in power-sharing, compared to tradition
Sagging control can faster divide equally power.
Step 2: causing active output power and idle defeated for inverter output impedance and line impedance characteristic mismatch
The problem of difference of line impedance will cause output voltage deviation between the coupling of power, inverter out, this step is in resistance circuit
The control method after traditional droop control method and addition RC virtual impedance is imitated respectively under the conditions of impedance is different
True comparison.Inverter 1 starts to work and accesses load in l-G simulation test, and inverter 2 does not connect load.The inverter 2 at 0.6 second
Access system, two inverters are powered to the load by inverter simultaneously at this time.Two inverter line impedances are not identical, respectively
Are as follows: Z1=0.96+j0.1245, Z2=0.64+j0.083.Conventional method simulation result is referring to Fig. 5, it is known that hinders in inverter route
When anti-and output impedance mismatches, line impedance is not identical between inverter, traditional droop method can not be active and idle to exporting
Power is divided equally, and inverter 1 is different from 2 output power of inverter.Simulated environment is constant, and it is virtual that RC is added in sagging control
Impedance, simulation result is referring to Fig. 6, and the mentioned method of the present invention can divide equally inverter output power as seen from the figure.By Fig. 5 and figure
6 simulation result compares and analyzes, it is known that after addition RC virtual impedance, two inverter active power of output and idle
Power can be divided equally.
Step 3: when system load increases or decreases, parallel system keeps the output work of each inverter equal by sagging control
Weighing apparatus distribution.But sagging control can cause to disturb to ac bus voltage and frequency in the process, influence the stabilization of bus.For
Problem above, this step secondary tune based on PR controller to the control method of step 2 and addition under conditions of load variations
Section method has carried out emulation experiment and comparative analysis.Inverter 1 starts to work and accesses load in simulations, and inverter 2 does not connect
Load.2 access system of inverter at 0.6 second, two inverters are powered to the load by inverter simultaneously at this time.At 1 second
Load mutates, and power increasing is twice.The sagging method simulation result of tradition is referring to 7, as seen from the figure, when parallel system load becomes
When change, the voltage magnitude and frequency of ac bus can generate deviation, influence the stability of system.Simulated environment is constant, is controlling
Middle addition amplitude, phase angle secondary control ring, simulation result is referring to Fig. 8.It knows when load changes, the mentioned side of the present invention
Method voltage magnitude deviation is small, and frequency variation is smaller.Fig. 7 and Fig. 8 are compared, it can be seen that compared to the sagging control of tradition, originally
Proposed method is invented when load changes, the deviation of ac bus voltage magnitude and frequency is smaller, and it is shorter to eliminate the time.
The basic principles, main features and advantages of the present invention have been shown and described above.The technology of the industry
Personnel are it should be appreciated that the present invention is not limited to the above embodiments, and the above embodiments and description only describe this
The principle of invention, various changes and improvements may be made to the invention without departing from the spirit and scope of the present invention, these changes
Change and improvement all fall within the protetion scope of the claimed invention.The claimed scope of the invention by appended claims and its
Equivalent defines.
Claims (1)
1. a kind of inverter parallel control method based on RC virtual impedance, it is characterised in that in low-voltage circuit, for inversion
Quickly accurately power can be divided equally when device line impedance difference, successively contain following steps:
Step 1: one inverter simulation model of construction
One three-phase full-bridge inverter circuit model, inverter direct-current power supply voltage V are built using Matlab/SimulinkdcFor
650V is controlled using SPWM, frequency of modulated wave 50Hz, carrier frequency 10kHz；
Step 2: the Double closed-loop of voltage and current based on PR control
Step 1 builds a three-phase full-bridge inverter, and step 2 is based on step 1 and carries out closed-loop control to inverter；Inverter output
Port connects a LCL filter, by inverter end inductance Li, capacitor C, load end inductance LgComposition；To inductance LiElectric current and electricity
The voltage held on C is sampled, and is carried out calculating feedback by PR controller and is modulated to SPWM modulating wave, reaches two close cycles control
The effect of system, so that inverter output waveforms are three-phase sine-wave；
Step 3: sagging control
(1) the consistent inverter of two parameters in step 2 is carried out in parallel；Two inverter capacitance voltage V are acquired respectivelyCWith
Inductance LgElectric current ig, inverter instantaneous output power is calculated by equation:
(2) instantaneous output power obtains the mean power of inverter by a low-pass filter:
Wherein ω0It is the cutoff frequency of filter；
According to droop control method:
Wherein m, n are the sagging factor, and value is customized by the user；P*And Q*For value and power reference, it is generally set to 0；
(3) Parallel Control can be carried out to inverter by sagging control；
Step 4: improved sagging control
(1) the sagging formula after improveing is as follows:
(2) in order to modify equivalent inverter output impedance, divide equally to power, need to add virtual impedance Zv, it includes electricity
Resistance and capacity cell are introduced into output current feedback path, Zv(s) it is defined as
Wherein RvIt is virtual resistance, CvIt is simulated capacitance；The expression formula of virtual impedance ring is as follows:
Wherein VcαAnd VcβFor the voltage compensation value after addition damped impedance, feed back in the voltage generated to sagging control；
(3) in order to improve load variation the stability of system, proposes a kind of voltage magnitude based on PR controller when, the two of frequency
Secondary control preparation method: being added the departure of point of common coupling voltage magnitude and frequency in the sagging control of tradition, by PR controller into
Feedforward after row calculating as sagging control is added with the voltage that the sagging control of tradition calculates and obtains new voltage reference value, table
Up to formula are as follows:
Wherein EpccIt is voltage magnitude at PCC,It is the phase angle at PCC,andBeing divided into is their reference value；Kpc,
Kic,KqcAnd KqaIt is the adjustment parameter of PR controller；At voltage magnitude and frequency, that is, PCC first by measurement point of common coupling
EpccWithAgain with the rated voltage amplitude of point of common couplingFrequencyIt is compared, obtained difference carries out PR
Adjust, then feed back each inverter voltage reference value compensate with it is sagging control generate voltage reference value be added
To new reference value, generate new sagging.
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| CN109995073B (en) * | 2018-01-03 | 2023-03-21 | 东莞市钜大电子有限公司 | Photovoltaic off-grid inverter parallel connection method based on droop method |
| CN108054747B (en) * | 2018-01-11 | 2021-12-07 | 上海电力设计院有限公司 | Parallel control method of direct current converter and direct current micro-grid |
| CN108683208B (en) * | 2018-04-04 | 2019-09-27 | 西安理工大学 | A method of improving photovoltaic energy storage inverter parallel stability |
| CN110086370B (en) * | 2019-05-16 | 2020-11-06 | 上海海事大学 | Fault-tolerant control method for three-phase bridge inverter, electronic device and storage medium |
| CN112242719B (en) * | 2019-07-17 | 2022-04-15 | 华北电力大学 | Inverter improved droop control method based on virtual synchronous machine technology |
| CN113489062B (en) * | 2021-08-10 | 2023-03-21 | 上海弘正新能源科技有限公司 | Droop control method for improving vector parallel operation of three-phase machine based on virtual resistance-capacitance algorithm |
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| CN105305410A (en) * | 2015-10-16 | 2016-02-03 | 国网上海市电力公司 | DC distribution system energy storage device adaptive virtual impedance droop control method |
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