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CN106786797B - A kind of control method for the microgrid inverter improving microgrid busbar voltage quality - Google Patents

A kind of control method for the microgrid inverter improving microgrid busbar voltage quality Download PDF

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CN106786797B
CN106786797B CN201611225599.4A CN201611225599A CN106786797B CN 106786797 B CN106786797 B CN 106786797B CN 201611225599 A CN201611225599 A CN 201611225599A CN 106786797 B CN106786797 B CN 106786797B
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voltage
harmonic
current
microgrid
inverter
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CN106786797A (en
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赖纪东
闵小宇
苏建徽
杜燕
汪海宁
施永
杨向真
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Hefei University of Technology
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Hefei University of Technology
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    • HELECTRICITY
    • H02GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
    • H02JCIRCUIT ARRANGEMENTS OR SYSTEMS FOR SUPPLYING OR DISTRIBUTING ELECTRIC POWER; SYSTEMS FOR STORING ELECTRIC ENERGY
    • H02J3/00Circuit arrangements for AC mains or AC distribution networks
    • H02J3/38Arrangements for parallely feeding a single network by two or more generators, converters or transformers
    • H02J3/46Controlling of the sharing of output between the generators, converters, or transformers

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  • Power Engineering (AREA)
  • Inverter Devices (AREA)

Abstract

本发明公开了一种改善微网母线电压质量的微网逆变器的控制方法,其特征是:所述微网逆变器是通过自身控制独立工作实现微网母线电压质量改善,以及单元之间功率分配;并能够接受上层中央管理系统调度,根据上层管理系统的调度指令调整微网逆变器输出电压,实现母线电压控制与电压质量改善。本发明利用微网逆变器参与微网母线电压质量控制,通过控制逆变器输出阻抗吸收负载谐波电流,不仅可以减少微网专门用于电能质量改善电力电子装置的投入,而且由于微网逆变器安装的分散性使得控制更加灵活。

The invention discloses a control method of a micro-grid inverter for improving the voltage quality of a micro-grid bus, which is characterized in that: the micro-grid inverter works independently through its own control to realize the improvement of the voltage quality of the micro-grid bus; It can also accept the scheduling of the upper-level central management system, and adjust the output voltage of the micro-grid inverter according to the scheduling instructions of the upper-level management system to achieve bus voltage control and voltage quality improvement. The invention uses the micro-grid inverter to participate in the voltage quality control of the micro-grid bus, and absorbs the load harmonic current by controlling the output impedance of the inverter, which can not only reduce the investment of the micro-grid dedicated to improving the power quality of power electronic devices, but also The decentralized nature of the inverter installation allows for more flexible control.

Description

A kind of control method for the microgrid inverter improving microgrid busbar voltage quality
Technical field
The present invention relates to a kind of control methods of microgrid inverter for improving microgrid busbar voltage quality.
Background technique
Microgrid as one can both be incorporated into the power networks also can the independently operated compact electrical generating systems of off-grid, net internal loading form With very big randomness and diversity.And a large amount of civilian and commercial plants have power electronic devices interface in netting, and make It obtains load and is characterized primarily by nonlinear characteristic.Harmonic current caused by nonlinear load is in line impedance and inverter output impedance Upper generation harmonic wave pressure drop, will lead to the distortion of busbar voltage, influence bus load supplying quality, possibly even cause when serious be System unstability.To improve microgrid power supply quality, a kind of common method is to install power quality additional to improve device, such as active filter.So And the power load type and capacity on micro-capacitance sensor median generatrix have very big uncertainty, this gives power quality controlling device On-position selection bring difficulty.Ensure that load power quality just needs a large amount of power quality adjusting device, this Micro-grid system construction and operating cost can undoubtedly be significantly greatly increased.Increase utility power quality control function by microgrid inverter, it can The local compensation for being easily carried out harmonic wave is administered.Therefore, inverter is made to have harmonics restraint function by microgrid inverter control Can, to the investment for improving power electronic equipment in reduction microgrid dedicated for power quality, and improvement micro-capacitance sensor busbar voltage Quality advance system reliability has important theory and realistic meaning.Microgrid busbar voltage controls under the conditions of nonlinear load, The control mode of multi-resonant controller is used mainly under rest frame.It is controlled for the harmonic component of each frequency System, every control for increasing a frequency harmonic component, just needs to increase a resonant controller, and all inverters both participate in The control of quality of voltage.This control program, all inverters both participate in the control of harmonic voltage, and inverter participates in quality of voltage Control is without selectivity.However, in micro-capacitance sensor and not all inverter be suitable for participate in quality of voltage adjust, work as gird-connected inverter When itself full capacity exports, then it is difficult to participate in the control of quality of voltage.In addition, every increase first harmonic voltage control, just needs to increase Add a resonant controller, contravarianter voltage controller is complicated.
Summary of the invention
The present invention be to avoid above-mentioned deficiency of the prior art, provide a kind of control of system flexibly, control method Improve the control method of the microgrid inverter of microgrid busbar voltage quality under succinct nonlinear load.
The present invention adopts the following technical scheme that in order to solve the technical problem
The characteristics of control method of the microgrid inverter of present invention improvement microgrid busbar voltage quality, is: the microgrid inversion Device is to control to work independently by itself to realize power distribution between the improvement of microgrid busbar voltage quality and microgrid inverter; And the scheduling of upper layer center management system can be received, it is defeated to adjust microgrid inverter according to the dispatch command of upper layer center management system Voltage out realizes that busbar voltage control and quality of voltage improve.
The characteristics of control method of the microgrid inverter of present invention improvement microgrid busbar voltage quality, lies also in: inverse in microgrid The voltage control loop for becoming device increases harmonic impedance control, by simulating harmonic wave negative impedance absorbing load harmonic current, improves microgrid Busbar voltage quality.
The characteristics of control method of the microgrid inverter of present invention improvement microgrid busbar voltage quality, lies also in: real-time monitoring Microgrid inverter exports electric current, the harmonic components of microgrid inverter output electric current is extracted, according to virtual impedance and line impedance meter It calculates and obtains harmonic reference voltage, by the harmonic reference voltage superposition to fundamental wave reference voltage, and then control inverter output electricity Pressure, makes inverter have negative harmonic impedance characteristic, improves busbar voltage quality with this;Meanwhile in the microgrid inverter receiving The size of the scheduling of layer managing system, real time modifying virtual impedance and line impedance is to adapt to system difference operating condition.
The characteristics of control method of the microgrid inverter of present invention improvement microgrid busbar voltage quality, lies also in: the microgrid The control algolithm of inverter output voltage is:
It is calculated using sagging control and obtains microgrid inverter fundamental wave reference voltage ureff
By feeder current ioLow-pass filtered device LPF extracts fundamental current io1, by the fundamental current io1Multiplied by virtual Impedance ZvObtain virtual impedance voltage uv
By feeder current ioIt is extracted through harmonic wave and obtains harmonic current components iom, m=6n ± 1, n=1,2,3 ..., it will be described humorous Wave current component iomWith m subharmonic reactance XmIt is multiplied and obtains m subharmonic voltage reference value urefm, m=6n ± 1;
By feeder current ioFundametal compoment, which is filtered out, through high-pass filter HPF obtains harmonic current ih, by the harmonic current ih Multiplied by harmonic wave resistance RhObtain harmonic wave resistive reference voltage value urefR
Then, harmonic impedance voltage reference value urefhAre as follows:
Wherein, virtual impedance Zv, harmonic compensation number m, harmonic wave reactance XmAnd harmonic wave resistance RhReceive upper layer central management The scheduling of system, being capable of online modification.
The characteristics of control method of the microgrid inverter of present invention improvement microgrid busbar voltage quality, lies also in:
It is calculated by formula (1) and obtains microgrid inverter with reference to given voltage uref:
uref=ureff+uv+urefh (1)
The microgrid inverter is referred into given voltage urefReference voltage ac-dc axis point under rotation transformation to rotating coordinate system AmountBy microgrid inverter output voltage uoRotation transformation is voltage ac-dc axis component u under rotating coordinate systemodq, then voltage error ΔudqAre as follows:
By the voltage error Δ udqFundamental current reference value is obtained using the fundamental wave controller characterized by formula (2) (ifdq)k:
(ifdq)k=a0(Δudq)k+a1(Δudq)k-1-b1(ifdq)k-1 (2)
In formula (2), k is kth time sampling instant, and k-1 is -1 sampling instant of kth, b1=-1, kvPFor fundamental wave controller proportionality coefficient, kvIFor fundamental wave controller integral coefficient, TsFor the sampling period.
The voltage error Δ udqM subharmonic current reference value is obtained via the m subharmonic controller that formula (3) characterize (imdq)k:
(imdq)k=c1(Δudq)k+c2(Δudq)k-2-d1(imdq)k-1-d2(imdq)k-2 (3)
In formula (3):
Wherein, m is corresponding each overtone order, kRhFor harmonic controller proportionality coefficient, ωcFor harmonic controller cutoff frequency Rate, ω0For fundamental voltage frequency;
Based on individual harmonic current reference value (imdq)kIt calculates and obtains harmonic current reference value (ihdq)kAre as follows:
Then have: current reference valueAre as follows:
By microgrid inverter electric current iLElectric current ac-dc axis electric current i under rotation transformation to rotating coordinate systemLdq, by current reference ValueWith electric current ac-dc axis electric current i under rotating coordinate systemLdqIt is poor to make, then through current controller output voltage reference value Udq, by institute State voltage reference value UdqThrough u under rotation transformation to rest frameabc, with the uabcSPWM modulation is participated in, microgrid inversion is controlled The on-off of device power switch tube.
Microgrid busbar voltage controls under the conditions of the present invention is directed to nonlinear load, gives whether inverter participates in voltage matter Amount control is controllable, participates in harmonic voltage number improves optional system control method, and harmonic controling is calculated under single coordinate transform Method;Its microgrid inverter can not only receive the control of tension management system call, but also can be detached from top level control independent operating.Based on list The control of coordinate transform resonance, the control to two order harmonic components may be implemented in a resonant controller, and can receive upper layer Scheduling participates in specified subharmonic voltage control;Compared with the prior art, the invention has the advantages that:
1, present system can reduce the investment of dedicated microgrid electric energy governing device;
2, present system is more flexible in terms of busbar voltage quality control;
3, the micro-grid inverter voltage control algolithm of present system is more succinct.
Detailed description of the invention
Fig. 1 is micro-grid system structural block diagram according to the present invention
Fig. 2 is busbar voltage System control structures schematic diagram of the present invention;
Fig. 3 is control method flow chart of the present invention;
Specific embodiment
Referring to Fig. 1, in the present embodiment micro-grid system include several distributed generation units, it is linear and non-linear negative Load, driving circuit, over-sampling modulate circuit and protection circuit, are connected in parallel between several distributed generation units, including Main circuit, local controller are connected to common bus by feeder line;Main circuit includes that sequentially connected micro- source, three phase full bridge are inverse Become device, filter inductance L, filter capacitor C, feeder line, three-phase full-bridge inverter circuit includes six power switch tubes, and common bus is also Connect linear and nonlinear load;Several distributed generation units, linear and nonlinear load form independent micro-capacitance sensor, system It further include the communication system for connecting local controller and microgrid central controller.
The control method for improving the microgrid inverter of microgrid busbar voltage quality in the present embodiment is: microgrid inverter is logical It crosses itself control autonomous working and realizes power distribution between the improvement of microgrid busbar voltage quality and microgrid inverter;And it can Receive the scheduling of upper layer center management system, microgrid inverter output electricity is adjusted according to the dispatch command of upper layer center management system Pressure realizes that busbar voltage control and quality of voltage improve.
Increase harmonic impedance control in the voltage control loop of microgrid inverter, it is humorous by simulation harmonic wave negative impedance absorbing load Wave electric current improves microgrid busbar voltage quality.By extracting harmonic current on feeder line, line impedance and virtual impedance, meter are considered Corresponding subharmonic voltage reference value is sought in calculation, and control microgrid inverter output voltage realizes changing for microgrid busbar voltage quality indirectly It is kind.
Specific implementation by real-time monitoring microgrid inverter export electric current, extract microgrid inverter output electric current harmonic wave at Point, it is calculated according to virtual impedance and line impedance and obtains harmonic reference voltage, by harmonic reference voltage superposition to fundamental wave with reference to electricity Pressure, and then inverter output voltage is controlled, so that inverter is had negative harmonic impedance characteristic, busbar voltage quality is improved with this;Together When, microgrid inverter can receive the manage and dispatch of upper layer central controller, real time modifying virtual impedance and line impedance it is big It is small to adapt to system difference operating condition.Upper layer central controller can be online to determine modification according to system busbar voltage condition Microgrid inverter participates in the variables such as harmonic voltage coefficient, each frequency harmonic impedance size, virtual impedance size, this makes system control System is more flexible, is suitable for the micro-grid system of different networking structures and does not have to operating condition.The control flow of microgrid inverter As shown in Figure 3.
It for the control of harmonic current, is generally realized under rest frame, uses a controller for every subharmonic. By will be realized under harmonic conversion to rotating coordinate system in the present invention, since adjacent subharmonic is characterized as together under rotating coordinate system One frequency AC amount, a controller can realize the control to two frequency harmonic components.Compared with being controlled under rest frame, The use of half harmonic controller can be reduced, controller is more succinct, operand is small.
The control algolithm of microgrid inverter output voltage is:
It is calculated using sagging control and obtains inverter fundamental wave reference voltage ureff
By feeder current ioLow-pass filtered device LPF extracts fundamental current io1, by fundamental current io1Multiplied by virtual impedance ZvObtain virtual impedance voltage uv
By feeder current ioIt is extracted through harmonic wave and obtains harmonic current components iom, m=6n ± 1, n=1,2,3 ..., it will be described humorous Wave current component iomWith m subharmonic reactance XmIt is multiplied and obtains m subharmonic voltage reference value urefm, m=6n ± 1;
By feeder current ioFundametal compoment, which is filtered out, through high-pass filter obtains harmonic current ih, by harmonic current ihMultiplied by humorous Wave resistance RhObtain harmonic wave resistive reference voltage value urefR
Then, harmonic impedance voltage reference value urefhAre as follows:
Wherein, virtual impedance Zv, harmonic compensation number m, harmonic wave reactance XmAnd harmonic wave resistance RhReceive upper layer central management The scheduling of system, being capable of online modification.
It is to carry out in specific implementation as follows:
It is calculated by formula (1) and obtains microgrid inverter with reference to given voltage uref:
uref=ureff+uv+urefh (1)
Microgrid inverter is referred into given voltage urefReference voltage ac-dc axis component under rotation transformation to rotating coordinate systemBy microgrid inverter output voltage uoRotation transformation is voltage ac-dc axis component u under rotating coordinate systemodq, then voltage error Δ udqAre as follows:
By the voltage error Δ udqFundamental current reference value is obtained using the fundamental wave controller characterized by formula (2) (ifdq)k:
(ifdq)k=a0(Δudq)k+a1(Δudq)k-1-b1(ifdq)k-1 (2)
In formula (2), k is kth time sampling instant, and k-1 is -1 sampling instant of kth, b1=-1, kvPFor fundamental wave controller proportionality coefficient, kvIFor fundamental wave controller integral coefficient, TsFor the sampling period.
Voltage error Δ udqM subharmonic current reference value (i is obtained via the m subharmonic controller that formula (3) characterizemdq)k:
(imdq)k=c1(Δudq)k+c2(Δudq)k-2-d1(imdq)k-1-d2(imdq)k-2 (3)
In formula (3):
Wherein, m is corresponding each overtone order, kRhFor harmonic controller proportionality coefficient, ωcFor harmonic controller cutoff frequency Rate, ω0For fundamental voltage frequency;
Based on individual harmonic current reference value (imdq)kIt calculates and obtains harmonic current reference value (ihdq)kAre as follows:
Then have: current reference valueAre as follows:
By microgrid inverter electric current iLElectric current ac-dc axis electric current i under rotation transformation to rotating coordinate systemLdq, by current reference ValueWith electric current ac-dc axis electric current i under rotating coordinate systemLdqIt is poor to make, then through current controller output voltage reference value Udq, will be electric Press reference value UdqThrough u under rotation transformation to rest frameabc, with uabcSPWM modulation is participated in, control microgrid inverter power is opened Close the on-off of pipe.

Claims (2)

1. a kind of control method for the microgrid inverter for improving microgrid busbar voltage quality, it is characterized in that: the microgrid inverter It is to control to work independently by itself to realize power distribution between the improvement of microgrid busbar voltage quality and microgrid inverter;And It can receive the scheduling of upper layer center management system, microgrid inverter output is adjusted according to the dispatch command of upper layer center management system Voltage realizes that busbar voltage control and quality of voltage improve;Increase harmonic impedance control in the voltage control loop of microgrid inverter, By simulating harmonic wave negative impedance absorbing load harmonic current, improve microgrid busbar voltage quality;
The control algolithm of the microgrid inverter output voltage is:
It is calculated using sagging control and obtains microgrid inverter fundamental wave reference voltage ureff
By feeder current ioLow-pass filtered device LPF extracts fundamental current io1, by the fundamental current io1Multiplied by virtual impedance ZvObtain virtual impedance voltage uv
By feeder current ioIt is extracted through harmonic wave and obtains harmonic current components iom, m=6n ± 1, n=1,2,3..., by the harmonic wave Current component iomWith m subharmonic reactance XmIt is multiplied and obtains m subharmonic voltage reference value urefm, m=6n ± 1;
By feeder current ioFundametal compoment, which is filtered out, through high-pass filter HPF obtains harmonic current ih, by the harmonic current ihMultiplied by Harmonic wave resistance RhObtain harmonic wave resistive reference voltage value urefR
Then, harmonic impedance voltage reference value urefhAre as follows:
Wherein, virtual impedance Zv, harmonic compensation number m, harmonic wave reactance XmAnd harmonic wave resistance RhReceive upper layer center management system Scheduling, being capable of online modification.
2. the control method of the microgrid inverter according to claim 1 for improving microgrid busbar voltage quality, it is characterized in that:
It is calculated by formula (1) and obtains microgrid inverter with reference to given voltage uref:
uref=ureff+uv+urefh (1)
The microgrid inverter is referred into given voltage urefReference voltage ac-dc axis component under rotation transformation to rotating coordinate systemBy microgrid inverter output voltage uoRotation transformation is voltage ac-dc axis component u under rotating coordinate systemodq, then voltage error Δ udqAre as follows:
By the voltage error Δ udqFundamental current reference value (i is obtained using the fundamental wave controller characterized by formula (2)fdq)k:
(ifdq)k=a0(Δudq)k+a1(Δudq)k-1-b1(ifdq)k-1 (2)
In formula (2), k is kth time sampling instant, and k-1 is -1 sampling instant of kth, b1=-1, kvPFor fundamental wave controller proportionality coefficient, kvIFor fundamental wave controller integral coefficient, TsFor the sampling period;
The voltage error Δ udqM subharmonic current reference value (i is obtained via the m subharmonic controller that formula (3) characterizemdq)k:
(imdq)k=c1(Δudq)k+c2(Δudq)k-2-d1(imdq)k-1-d2(imdq)k-2 (3)
In formula (3):
Wherein, m is corresponding each overtone order, kRhFor harmonic controller proportionality coefficient, ωcFor harmonic controller cutoff frequency, ω0For fundamental voltage frequency;
Based on individual harmonic current reference value (imdq)kIt calculates and obtains harmonic current reference value (ihdq)kAre as follows:
Then have: current reference valueAre as follows:
By microgrid inverter electric current iLElectric current ac-dc axis electric current i under rotation transformation to rotating coordinate systemLdq, by current reference value With electric current ac-dc axis electric current i under rotating coordinate systemLdqIt is poor to make, then through current controller output voltage reference value Udq, by the voltage Reference value UdqThrough u under rotation transformation to rest frameabc, with the uabcSPWM modulation is participated in, microgrid inverter power is controlled The on-off of switching tube.
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CN108414838B (en) * 2018-02-06 2020-03-17 西安交通大学 Method for measuring line impedance of inverter parallel system
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CN110323783B (en) * 2019-07-24 2021-01-08 阳光电源股份有限公司 Photovoltaic grid-connected inverter and control method thereof
CN112701720B (en) * 2020-12-17 2022-11-01 电子科技大学 Hybrid control method for constant power load of alternating-current micro-mesh belt
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