CN105305401A - Grid connected control method for photovoltaic high voltage DC grid connected current transformer - Google Patents
Grid connected control method for photovoltaic high voltage DC grid connected current transformer Download PDFInfo
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Abstract
The invention relates to a grid connected control method for a photovoltaic high voltage DC grid connected current transformer. According to the grid connected control method, an input voltage and an input current of a photovoltaic array are sampled, an input voltage instruction of the photovoltaic high voltage DC grid connected current transformer is acquired through a largest power tracking controller; a photovoltaic array input voltage and the input voltage instruction are contrasted, and an output current instruction of the photovoltaic high voltage DC grid connected current transformer can be acquired through PI adjustment; an output current of each DC/DC power unit is contrasted with an average input current value of each DC/DC power unit, and a current sharing error adjusting signal is acquired through PI adjustment; the output current instruction of the photovoltaic high voltage DC grid connected current transformer and a voltage sharing error adjusting signal of each DC/DC power unit are summed to acquire a current closed-loop control instruction of each DC/DC power unit; a practical output current of each DC/DC power unit and the current closed-loop control instruction are contrasted to acquire a modulation wave of each DC/DC power unit; the modulation wave is contrasted with a triangular carrier wave of a fixed frequency to generate a PWM signal of each DC/DC power unit, and power devices of each DC/DC power unit are controlled.
Description
Technical field
The present invention relates to a kind of grid-connected control method of photovoltaic high voltage direct current grid-connected converter.
Background technology
China photovoltaic adding new capacity 13GW in 2014, rank first in the world, accumulative installed capacity reaches 32.9GW, is only second to Germany, occupies the second in the world, wherein based on large-scale desert power station.And these remote districts, many places, desert power station, local electricity needs is little, and photovoltaic generation is difficult to on-site elimination, grid-connected difficult problem ubiquity, and nest electrical phenomena is day by day serious.At large-scale load center, along with environmental problem is day by day serious, be badly in need of a large amount of clean electric power and supplement generating breach.Traditional High-voltage AC Network is subject to the restriction of environmental problem/system instability/power transmission distance problem, effectively cannot realize the long-distance sand transport of extensive clean electric power.Traditional thyristors high voltage dc transmission technology, is subject to the restriction of cost and technology intrinsic characteristic, cannot be applied in the flexible DC transmission system of multi-voltage grade and power grade.Photovoltaic generation is badly in need of electric power conveying technology Large Copacity clean electric power remote conveying can being delivered to load center.
Along with the fast development of power electronic device and power converter topology, Technology of HVDC based Voltage Source Converter is increasingly mature flexibly, direct-current transmission converter valve cost reduces greatly, and the flexible DC transmission system being applicable to different transmission distance and transmitted power starts to enter builds the application stage.Photovoltaic generation and Technology of HVDC based Voltage Source Converter are combined into a new technical research direction.
Photovoltaic generation is incorporated to bulk power grid by high-voltage dc transmission electric network, has following advantage:
1) adopt photovoltaic high voltage direct current interconnection technology, decrease inversion link, improve efficiency, add renewable energy power generation energy contribution rate;
2) for western part desert photovoltaic plant from far-off regions, photovoltaic high voltage direct current transmission can adopt cable laying, passes through complex-terrain and sea, reduces Transmission Cost;
3) under equivalent transmission voltage grade, direct current transportation is larger than ac transmission capacity, and power transmission is apart from farther, and cost is lower.Direct current transportation electromagnetic radiation is less, with environmental friendliness;
4) adopt high voltage direct current transmission, there is not the problem of frequency stabilization and angle stability, circuit can not produce and consume idle simultaneously, can reduce the grid-connected impact on bulk power grid of regenerative resource greatly.
External development direct current transportation project is studied widely at present, and European Project construction, based on the super grids of Technology of HVDC based Voltage Source Converter, connects the renewable energy power generation projects such as the offshore wind field/photovoltaic plant in European North Sea Spectrum.In May, 2011, China built up first flexible DC power transmission project---Shanghai Nanhui wind field flexible DC power transmission project, along with putting into operation of Dalian flexible DC power transmission project over strait and Xiamen flexible DC power transmission project, China is building the country that flexible DC power transmission project is maximum, capacity is maximum in the world by formally becoming.Offshore wind electric field access flexible DC power transmission network is the main application form of current regenerative resource access direct current network, and photovoltaic plant has the electric power transfer demand same with wind energy turbine set direct current transportation, but photovoltaic high voltage direct current interconnection technology is studied less both at home and abroad, and correlative study is still in the exploratory stage.
Photovoltaic high voltage direct current grid-connected converter is input as hundreds of to kilovolt direct current light photovoltaic array, exports the high-voltage direct current power grid being directly incorporated into tens to hundreds of kilovoltage grade.Photovoltaic high voltage direct current grid-connected converter cutting-in control scheme proposed by the invention at home and abroad still belongs to the first time proposition.Zhao Wei so equals " electric power network technique " " photovoltaic plant is through VSC-HVDC grid connection topology and control strategy thereof " that the magazine phase in November, 2012 delivers proposes a kind of photovoltaic plant high voltage direct current connect-in strategy.In the program, each photovoltaic generation unit is made up of photovoltaic array and DC/DC converter, and multiple photovoltaic generation unit exports series operation, and each generator unit carries out MPPT tracking separately.Because each photovoltaic array Difference of Output Power is large in the program, cause each generator unit Difference of Output Power very large, each power cell output voltage is seriously unbalanced, very easily causes generator unit excessive pressure damages.
Summary of the invention
The object of the invention is the shortcoming overcoming prior art, propose a kind of grid-connected control method of photovoltaic high voltage direct current grid-connected converter.
For realizing high step-up ratio, the main circuit applying the photovoltaic high voltage direct current grid-connected converter of combination method of the present invention adopts modularized circuit topology, and each module is isolated form DC/DC power cell, adopts the topological form that input is in parallel, export series connection between module.
The present invention adopts voltage and current double closed-loop and all presses flow equalizing ring combination controlling method, and step is as follows:
(1) sampled light photovoltaic array input voltage vin and input current Iin, will obtain the voltage of maximum power point as photovoltaic high voltage direct current grid-connected converter input voltage instruction Vinref by maximal power tracing controller.
(2) photovoltaic array input voltage vin is compared with photovoltaic high voltage direct current grid-connected converter input voltage instruction Vinref, draw photovoltaic high voltage direct current grid-connected converter output current instruction Ioutref by the 9th pi regulator.
(3) detect the total input voltage Iin of photovoltaic high voltage direct current grid-connected converter, ask the mean value Iin/n of n DC/DC power cell, n be more than or equal to 1 integer.
(4) output current Iin1, Iin2 of each DC/DC power cell is detected, Iinn, compare with each DC/DC power cell input current average value Iin/n respectively, each DC/DC power cell current-sharing regulating error signal Ierr1, Ierr2 is drawn by the 11 pi regulator, the first pi regulator, the second pi regulator,, Ierrn.
(5) photovoltaic high voltage direct current grid-connected converter output current instruction Ioutref is all held up poor conditioning signal Ierr1 with each DC/DC power cell respectively, Ierr2, Ierrn is added, obtain each DC/DC power cell closed-loop current control instruction Iref1, Iref2, Irefn, by each DC/DC power cell output current Iout1 of reality detected, Iout2, Ioutn and each DC/DC power cell closed-loop current control instruction Iref1, Iref2, Irefn compares, by the 3rd pi regulator, 4th pi regulator, 5th pi regulator obtains each DC/DC power cell modulating wave.
(6) modulation wave signal of generation and the triangular carrier of fixed frequency are compared by the first comparator, the second comparator, the 3rd comparator, produce each DC/DC power cell pwm signal, control turning on and off of photovoltaic high voltage direct current grid-connected converter each DC/DC power cell power device.
Grid-connected control method of the present invention, while realization input photovoltaic maximal power tracing, output direct current grid-connected current control, achieves the output Pressure and Control between each DC/DC power cell.Be the connected mode of series connection because each DC/DC power cell exports, realizing each converter, to export real-time Pressure and Control be very necessary.Accurate output voltage Balance route effectively can be avoided a certain power cell output voltage too high and cause the appearance of excessive pressure damages phenomenon, thus improves the reliability of photovoltaic high voltage direct current grid-connected converter entirety.Realize exporting Pressure and Control, in general, need to gather output voltage signal as control feedback signal.But because photovoltaic high voltage direct current grid-connected converter output voltage grade is high, voltage sampling circuit is complicated, and hardware cost is high.The present invention, by input current sharing control, realizes output voltage Pressure and Control.Its principle is in parallel in each DC/DC power cell input, and therefore input voltage is equal.Export series connection, therefore output current is equal.Principle according to power conservation can draw, the current-sharing of each DC/DC power cell input current just can realize each output voltage and all press, thus realizes utilizing low-pressure side image data to realize high-pressure side Pressure and Control.The method that the present invention adopts input current current-sharing fine setting closed loop to combine with output current closed loop, while completing the control of output direct current grid-connected current, achieves each DC/DC power cell and inputs sharing control in real time, namely achieve output Pressure and Control.By the application of control method of the present invention, reduce system cost, improve system reliability.
Accompanying drawing explanation
Fig. 1 is photovoltaic high voltage direct current grid-connected converter structured flowchart of the present invention;
Fig. 2 is the flow chart of photovoltaic high voltage direct current grid-connected converter control method of the present invention.
Embodiment
The photovoltaic high voltage direct current grid-connected converter structured flowchart that the present invention applies as shown in Figure 1.Photovoltaic high voltage direct current grid-connected system 1 is made up of photovoltaic array 10, photovoltaic high voltage direct current grid-connected converter 11 and high-voltage direct current power grid 12.Photovoltaic high voltage direct current grid-connected converter 11 applies photovoltaic high voltage direct current grid-connected converter control method 13, realizes the control of generating electricity by way of merging two or more grid systems of photovoltaic array 10 pairs of high-voltage direct current power grids 11.Photovoltaic array 10 is as the input power of photovoltaic high voltage direct current grid-connected converter 11, and the output of photovoltaic high voltage direct current grid-connected converter 11 connects high-voltage direct current power grid 12.
Photovoltaic high voltage direct current grid-connected converter control method of the present invention adopts voltage and current double closed-loop and all presses flow equalizing ring combination controlling method.As shown in Figure 2, control method concrete steps of the present invention are:
(1) sampled light photovoltaic array input voltage vin and input current Iin, will obtain the voltage of maximum power point as photovoltaic high voltage direct current grid-connected converter input voltage instruction Vinref by maximal power tracing controller 210.
(2) photovoltaic array input voltage vin is compared with photovoltaic high voltage direct current grid-connected converter input voltage instruction Vinref, draw photovoltaic high voltage direct current grid-connected converter output current instruction Ioutref by the 9th pi regulator 29.
(3) detect the total input voltage Iin of photovoltaic high voltage direct current grid-connected converter 11, ask the mean value Iin/n of n DC/DC power cell, n be more than or equal to 1 integer.
(4) output current Iin1, Iin2 of each DC/DC power cell is detected, Iinn, compare with each DC/DC power cell input current average value Iin/n respectively, each DC/DC power cell current-sharing regulating error signal Ierr1, Ierr2 is drawn by the 11 pi regulator 211, first pi regulator 21, second pi regulator 22,, Ierrn.
(5) photovoltaic high voltage direct current grid-connected converter output current instruction Ioutref is all held up poor conditioning signal Ierr1 with each DC/DC power cell respectively, Ierr2, Ierrn is added, obtain each DC/DC power cell closed-loop current control instruction Iref1, Iref2, Irefn, by each DC/DC power cell output current Iout1 of reality detected, Iout2, Ioutn and each DC/DC power cell closed-loop current control instruction Iref1, Iref2, Irefn compares, by the 3rd pi regulator 23, 4th pi regulator 24, 5th pi regulator 25 obtains each DC/DC power cell modulating wave.
(6) modulation wave signal of generation and the triangular carrier of fixed frequency are compared by the first comparator 26, second comparator 27, the 3rd comparator 28, produce each DC/DC power cell pwm signal, control turning on and off of photovoltaic high voltage direct current grid-connected converter each DC/DC power cell power device.
Claims (1)
1. a grid-connected control method for photovoltaic high voltage direct current grid-connected converter, is characterized in that: described control method concrete steps are:
(1) sampled light photovoltaic array input voltage vin and input current Iin, will calculate the voltage of maximum power point as photovoltaic high voltage direct current grid-connected converter input voltage instruction Vinref by maximal power tracing controller (210);
(2) photovoltaic array input voltage vin is compared with photovoltaic high voltage direct current grid-connected converter input voltage instruction Vinref, draw photovoltaic high voltage direct current grid-connected converter output current instruction Ioutref by the 9th pi regulator (29);
(3) detect photovoltaic high voltage direct current grid-connected converter (11) total input voltage Iin, ask the mean value Iin/n of n DC/DC power cell, n be more than or equal to 1 integer;
(4) output current Iin1, Iin2 of each DC/DC power cell is detected, Iinn, the output current of each DC/DC power cell is compared with each DC/DC power cell input current average value Iin/n respectively, each DC/DC power cell current-sharing regulating error signal Ierr1, Ierr2 is drawn by the 11 pi regulator (211), the first pi regulator (21), the second pi regulator (22),, Ierrn;
(5) photovoltaic high voltage direct current grid-connected converter output current instruction Ioutref is all held up poor conditioning signal Ierr1 with each DC/DC power cell respectively, Ierr2, Ierrn is added, obtain each DC/DC power cell closed-loop current control instruction Iref1, Iref2 ... Irefn, by each DC/DC power cell output current Iout1 of reality detected, Iout2, Ioutn and each DC/DC power cell closed-loop current control instruction Iref1, Iref2, Irefn compares, by the 3rd pi regulator (23), 4th pi regulator (24), 5th pi regulator (25) obtains each DC/DC power cell modulating wave,
(6) triangular carrier of the modulation wave signal generated and fixed frequency is compared by the first comparator (26), the second comparator (27), the 3rd comparator (28), produce each DC/DC power cell pwm signal, control turning on and off of photovoltaic high voltage direct current grid-connected converter each DC/DC power cell power device.
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Cited By (6)
| Publication number | Priority date | Publication date | Assignee | Title |
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| CN109921662A (en) * | 2019-03-25 | 2019-06-21 | 哈工大（张家口）工业技术研究院 | The control method of high-frequency isolation type variable topology AC-DC converter |
| CN110352554A (en) * | 2017-01-05 | 2019-10-18 | 通用电气公司 | Power converter for energy system |
| CN111509998A (en) * | 2020-05-24 | 2020-08-07 | 哈尔滨理工大学 | Current equalizing device and method based on sliding current equalizing |
| CN111969581A (en) * | 2020-08-17 | 2020-11-20 | 博阳能源科技有限公司 | Power supply system with single-power input interface compatible with photovoltaic and wind power |
| CN111969582A (en) * | 2020-08-17 | 2020-11-20 | 博阳能源科技有限公司 | Power supply system based on compatible photovoltaic of droop parallel operation single power input interface and wind-powered electricity generation |
| CN112054682A (en) * | 2020-09-22 | 2020-12-08 | 曲阜师范大学 | Current sharing control method for flexible direct-current transmission direct-current converter of offshore wind farm |
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Cited By (10)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN110352554A (en) * | 2017-01-05 | 2019-10-18 | 通用电气公司 | Power converter for energy system |
| CN109921662A (en) * | 2019-03-25 | 2019-06-21 | 哈工大（张家口）工业技术研究院 | The control method of high-frequency isolation type variable topology AC-DC converter |
| CN111509998A (en) * | 2020-05-24 | 2020-08-07 | 哈尔滨理工大学 | Current equalizing device and method based on sliding current equalizing |
| CN111509998B (en) * | 2020-05-24 | 2023-10-31 | 哈尔滨理工大学 | Flow equalization device and flow equalization method based on sliding flow equalization |
| CN111969581A (en) * | 2020-08-17 | 2020-11-20 | 博阳能源科技有限公司 | Power supply system with single-power input interface compatible with photovoltaic and wind power |
| CN111969582A (en) * | 2020-08-17 | 2020-11-20 | 博阳能源科技有限公司 | Power supply system based on compatible photovoltaic of droop parallel operation single power input interface and wind-powered electricity generation |
| CN111969582B (en) * | 2020-08-17 | 2021-09-24 | 博阳能源科技有限公司 | Power supply system based on compatible photovoltaic of droop parallel operation single power input interface and wind-powered electricity generation |
| CN111969581B (en) * | 2020-08-17 | 2021-09-24 | 博阳能源科技有限公司 | Power supply system with single-power input interface compatible with photovoltaic and wind power |
| CN112054682A (en) * | 2020-09-22 | 2020-12-08 | 曲阜师范大学 | Current sharing control method for flexible direct-current transmission direct-current converter of offshore wind farm |
| CN112054682B (en) * | 2020-09-22 | 2022-06-14 | 曲阜师范大学 | Current sharing control method for flexible direct-current transmission direct-current converter of offshore wind farm |
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