DE19838229A1 - Electric energy transmission system from photo-voltaic cells into electric supply network, stabilizes parameters of central DC voltage and/or current circuit through conventional DC pulse converter - Google Patents

Abstract

Each photo-voltaic cell (1) or a group of cells (2) with equal load characteristic operate over an individual MPP regulator (3) on a central DC voltage circuit (4) with constant voltage and/or on a central DC circuit (5) with constant current. A stabilization of parameters of the central DC voltage and/or current circuit, as well as the energy transmission from the circuit to the input of a conventional AC converter (7 + 12) results from the use of a conventional DC pulse converter (9).

Description

The invention relates to an electrical system for energy transmission from a variety photovoltaic cells with the same and / or different load characteristics in one electrical network with constant or variable parameters.

It is known to interconnect photovoltaic cells (FC) so that their summed Voltages meet the requirements for a grid feed-in over a Grid inverter (NWR) necessary grid inverter input voltage is sufficient.

The total voltages are some 100 V, up to about 700 V when in public 400 V three-phase networks are to be fed.

The parallel interconnection of such groups of FCs prevents the optimal one Energy yield of the groups, since one takes into account the optimal energy yield Current distribution among the groups is not guaranteed. That's why every group works generally on its own NWR with its own MPP regulation with regard to the respective feeding group.

The object of the invention is to be able to optimally operate photovoltaic cells with variable energy delivery capacity even when they are to feed together into a network and have different currents and output voltages,

• - without using several NWR and  
• - Without the voltages at the output of a group of FCs touching should assume large sizes.

The object is achieved in that each cell or a group of Cells with the same load characteristics via their own MPP controller on one central DC circuit with constant voltage and / or to a central DC circuit works with constant current and that by means of a known one DC pulse controller to keep the parameters of the central DC voltage or DC circuit as well as the energy transfer from the central DC voltage or DC circuit on the input of a known Grid inverter takes place.

The invention is explained in more detail using exemplary embodiments in accordance with the attached figure:
Individual FZ 1 and / or FZ connected in groups 2 work via an MPP controller 3 on the strands of a central DC voltage circuit 4 with constant voltage and / or on the strand of a central DC circuit 5 with constant current.

The central DC voltage circuit 4 has a lower voltage than that which would be required for feeding into the grid 6 via a NWR 7 working as a voltage inverter, the voltage difference between the input 8 of the NWR 7 and the central DC voltage circuit 4 being formed by a known DC pulse generator 9 is, so that the magnitude of the voltage of the DC voltage circuit 4 remains controllably constant, ie regardless of the magnitude of the voltage at the output of FZ 1 or group 2 .

The central DC circuit 5 carries a current which is determined by the DC pulse adjuster 10 and kept constant. This stream is the one hand, the DC input lying in the circuit 5 11 impressed on the rectifiers as a current change formed NWR 12 and on the other hand, via diodes 13, to which the outputs of the MPP regulators are connected in 3 of the FZ 1 or group 2 in parallel.

If the voltages at the outputs of the MPP controllers 3 are greater than the flow voltage of the diodes 13 in question , the outputs of the MPP controllers 3 each supply a partial voltage in the DC circuit 5 , as a result of which the voltage across the DC input 11 occurs at constant current in DC circuit 5 of the NWR 12 increased.

The energy supply from the FC 1 or 2 takes place either on the DC voltage circuit 4 or on the DC circuit 5 or on both circuits 4 , 5 by appropriate control of the two DC controllers 9 and 10 depending on the operational suitability, the voltages at the outputs of the Specify MPP controller 3 constant or variable in time in order to achieve the greatest transmission efficiency of the sum of all MPP controllers.

Reference list

FZ photovoltaic cell
NWR grid inverter
MPP maximum power point

1

Single FZ

2nd

Group of FZ

3rd

MPP controller

4th

DC circuit

5

DC circuit

6

network

7

Grid inverter (NWR)

8th

Entrance to the NWR

7

9

DC pulse controller

10th

DC pulse controller

11

DC input of the NWR

12th

12th

Grid inverter (NWR)

13

Diodes

Claims (1)

Electrical system for energy transfer from a large number of photovoltaic cells with the same and / or different load characteristics into an electrical network with constant or variable parameters, characterized in that each cell ( 1 ) or a group of cells ( 2 ) with the same load characteristics has its own MPP -Controller ( 3 ) works on a central DC circuit ( 4 ) with constant voltage and / or on a central DC circuit ( 5 ) with constant current and that the parameters of the central DC voltage ( 4 ) are kept constant by means of a known DC pulse adjuster ( 9 ). or DC circuit ( 5 ) and the energy transfer from the central DC voltage ( 4 ) or DC circuit ( 5 ) to the input of a known grid inverter ( 7 ) + ( 12 ).