CN105680686A

CN105680686A - MMC-based novel topological structure for photovoltaic power generation system

Info

Publication number: CN105680686A
Application number: CN201510465286.5A
Authority: CN
Inventors: 姚致清; 赵倩; 张群; 陈朋; 李志勇; 杨慧霞; 蒋冠前; 胡晓静
Original assignee: Xuchang Kaipu Electric Institute
Current assignee: Xuchang Kaipu Electric Institute
Priority date: 2015-08-03
Filing date: 2015-08-03
Publication date: 2016-06-15

Abstract

The invention relates to a novel topological structure for a photovoltaic power generation system. The novel topological structure comprises photovoltaic arrays (PV), maximum power trackers (MPPT), DC converting circuits (DC/DC) and modular power units, wherein the maximum power trackers control the DC converting circuits to finish maximum power tracking of the photovoltaic arrays and output electric energy generated by the photovoltaic arrays as energy sources of the power units; and a system controller controls various switching devices in the power units to carry out corresponding connection and breaking to maintain the stability of capacitor voltages in the power units according to collected related data, and obtains a high-voltage DC which is formed by superposing the capacitor voltages input into the power units at an output end. The novel topological structure has the advantages that each photovoltaic array is provided with a maximum power tracking module, so that the influence caused by uneven shading or illuminating is reduced and the efficiency is improved; by the modular power units, high-voltage DC output can be achieved in a manner of superposing the power units; local direct grid connection can be carried out; long-range power transmission can also be carried out; redundancy control can be achieved; system maintenance is facilitated; a control strategy is simple and reliable; the floor area is small; and the transmission power is high.

Description

Based on the photovoltaic generating system novel topological structure of MMC

Technical field

The present invention relates to power electronics and custom power field, it is specifically related to a kind of photovoltaic generating system novel topological structure.

Background technology

(1) no matter from the world or from China, conventional energy resources is all very limited, and the primary energy source reserves of China, well below the mean level (ML) in the world, approximately only have the 10% of world's total reserves. Sun power is the inexhaustible renewable energy sources of the mankind, the advantage such as abundance and potential economy with sufficient spatter property, absolute security, relative popularity, certain long lifetime and non-maintaining property, resource, has critical role in long-term energy strategy. It is anticipated that to the year two thousand thirty, renewable energy source will account for more than 30% in total energy structure, and the accounting of solar energy power generating in world's total electricity supply also will reach more than 10%; To the year two thousand forty, renewable energy source will account for more than the 50% of total energy consumption, and solar energy power generating will account for more than the 20% of total electricity; To 21 end of the centurys, renewable energy source will account for more than 80% in energy structure, and sun power generating will account for more than 60%;

Within (2) 2013 years, Chinese photovoltaic generation adding new capacity reaches 12WG, increases by 232% on a year-on-year basis, accounts for the newly-increased capacity 31.2% of global photovoltaic generation in 2013. Compared with the European newly-increased generating of volt in 2013 time, Chinese 2013 volt in time newly-increased capacity of installed generator close Europe summations, it is meant that China surmounts Germany becomes maximum light volt market, the whole world. 2013, in the newly-increased generating capacity of China's light volt, 93.81% was photovoltaic generation, and 6.19% is distributed photovoltaic. The data display that prediction industrial research institute issues, ended for the end of the year 2013, and China has 741 large-scale projects of generating electricity by way of merging two or more grid systems, and more than 60% is distributed in the Northwest of China. The present invention by embedding utility power quality control link in control strategy, it is achieved meritorious grid-connected, harmonics restraint, reactive-load compensation multifunctional multiplexing, it is to increase based on the photovoltaic generating system utilization ratio of MMC so that electrical network clean and effective.Improve electrical network to dissolve the ratio of generation of electricity by new energy simultaneously;

(3) conventional photovoltaic power generation system capacity is little, and floor space is big, and adopts this novel topological structure, it is not necessary to DC bus-bar voltage can be maintained higher level by step-up transformer, both direct grid-connected transmission of electricity also photovoltaic electric can can be carried out long-distance transmissions.

Summary of the invention

The object of the invention provides a kind of photovoltaic generating system novel topological structure, this topological framework adopts the form of multiple power unit cascade to realize High voltage output, and each photovoltaic array has MPPT unit, improve the efficiency of photovoltaic array, in addition output volts DS can be maintained higher level by this kind of topological framework, it is possible to be applied to long distance power transmission.

For realizing above object, the present invention is achieved through the following technical solutions:

1, a kind of photovoltaic generating system novel topological structure, comprises photovoltaic array (PV), maximal power tracing controller (MPPT), DC transfer circuit (DC/DC) and modular power unit. Maximal power tracing controller control DC transfer circuit completes maximum power point of photovoltaic array and follows the tracks of, and the electric energy that photovoltaic array produces is exported, as the energy derive of power cell, central controller carries out corresponding turn-on and turn-off according to each switch device in the relevant Data Control power cell gathered, and then maintain the stable of capacitance voltage in each power cell, and obtain the high voltage direct current formed by each input power cell capacitance voltage superposition at output terminal;

2, maximal power tracing controller (MPPT) is realized by DC transfer circuit, thus reaches the object that photovoltaic array is operated in peak power point so that it is most effective, and provides energy to power cell. Maximal power tracing controller is realized in FPGA by software programming, and DC transfer circuit is realized by a diode, an IGBT and inductance;

3, power cell adopts standard power unit, and its structure is half-bridge structure, connects by IGBT and diode, then DC capacitor composition in parallel. Its energy comes from photovoltaic array power stage, and central controller control power cell carries out discharge and recharge, thus maintains capacitance voltage and stablize;

4, transverter is three-phase, is often made up of 2N standard power unit, is divided into upper and lower two groups, and the power cell number often organized is N number of, and exporting phase voltage level ladder number is N+1, to be coupled or the inductance of non-coupled connects between upper and lower two groups of power cells.

Compared with prior art, the invention has the beneficial effects as follows:

1, owing to each photovoltaic array has MPPT controller, it is to increase photovoltaic array efficiency;

2, power cell can by overlapped in series to tens even several hundred, it is possible to effectively promote converter power;

3, by the overlapped in series of power cell, direct current bus can maintain very high voltage range, makes distant-range high voltage direct current transmission become possibility, and control strategy is relatively simple;

4, adopt the power cell of standard, shorten the manufacturing cycle and save cost;

5, flexible configuration different exchange system can be adapted to, it is to increase the convenience of application.

Fig. 1 is Novel photovoltaic transmission of electricity topological framework schematic diagram

Fig. 2 is DC transfer circuit schematic diagram

Fig. 3 is power cell structure schematic diagram

Embodiment:

1, see Fig. 1, comprise exchange system, transformer, central controller, maximal power tracing controller, photovoltaic array (PV), DC transfer circuit (DC/DC) and modular power unit.The power that photovoltaic array produces, the DC transfer circuit controlled by maximal power tracing controller (MPPT) is exported, and this power is as the energy derive of power cell. In the relevant Data Control power cell that central controller is returned by gathering, IGBT turns off and conducting, makes capacitor charge and discharge, maintains its voltage and stablizes. Direct current bus can be made to maintain high voltage grade by the overlapped in series of power cell, it is possible to directly apply to long distance power transmission, for Application of Solar Energy provides a kind of possibility in high voltage direct current transmission;

2, Fig. 2 is seen, MPPT is realized by DC transfer circuit, measure photovoltaic array outward current and both end voltage thereof, maximum power point voltage reference value is obtained by disturbance observation (PerturbandObserve), the actual photovoltaic array both end voltage that records and this voltage are compared, its difference through pi regulator, export with triangle wave after as the triggering signal of IGBT in DC transfer circuit, and then control photovoltaic array is operated in peak power point place;

3, Fig. 3 is seen, power cell adopts standard power unit, its structure is 1/4 bridge structure, connect by an IGBT and diode, DC capacitor composition in parallel again, power cell corresponding output end as shown in FIG., and is connected in series the facies unit forming transverter successively with other power cells, forms transverter after three facies unit parallel connections;

4, in the relevant Data Control power cell that central controller is returned by gathering, corresponding IGBT turns off and conducting, makes capacitor charge and discharge, maintains its voltage and stablizes;

5, power cell number of connecting can be arbitrary value in theory, and upper and lower bridge arm is connected by converter reactor, therefore DC bus-bar voltage can maintain high voltage grade, it is possible to directly applies to high voltage direct current transmission.

Claims

1. the present invention relates to a kind of photovoltaic generating system novel topological structure, it is characterised in that comprise photovoltaic array (PV), maximal power tracing controller (MPPT), DC transfer circuit (DC/DC) and modular power unit; Maximal power tracing controller control DC transfer circuit completes maximum power point of photovoltaic array and follows the tracks of, and the electric energy that photovoltaic array produces is exported, as the energy derive of power cell, central controller carries out corresponding turn-on and turn-off according to each switch device in the relevant Data Control power cell gathered, and then maintain the stable of capacitance voltage in each power cell, and obtain the high voltage direct current formed by each input power cell capacitance voltage superposition at output terminal.

2. photovoltaic generating system novel topological structure according to claim 1, it is characterised in that, the size of photovoltaic array scale, the power cell quantity of novel topological structure all can adjust arbitrarily according to demand in system nominal power range.

3. photovoltaic generating system novel topological structure according to claim 1, it is characterized in that, maximal power tracing control (MPPT) is realized by DC transfer circuit, thus reaches the object that photovoltaic array is operated in peak power point, make it most effective, and provide energy to power cell; Maximal power tracing controller is realized in FPGA by software programming, and DC transfer circuit is realized by a diode, an IGBT and inductance.

4. photovoltaic generating system novel topological structure according to claim 1, it is characterised in that, power cell adopts standard power unit, and its structure is half-bridge structure, connect with a diode by an IGBT, then parallel connection DC capacitor forms;Its energy comes from photovoltaic array and exports, and central controller control power cell carries out discharge and recharge, thus maintains capacitance voltage and stablize.

5. photovoltaic generating system novel topological structure according to claim 1, it is characterized in that, transverter is three-phase, often it is made up of 2N standard power unit, it is divided into upper and lower two groups, the power cell number often organized is N number of, and exporting phase voltage level ladder number is N+1, to be coupled or the inductance of non-coupled connects between upper and lower two groups of power cells.

6. photovoltaic generating system novel topological structure according to claim 1, it is characterised in that, power unit module, redundancy height.

7. photovoltaic generating system novel topological structure according to claim 1, it is characterised in that described photovoltaic array is made up of solar panel.