A kind of variable-frequency power transmission and distribution system
Technical field
The present invention relates to the energy transmission technology of electrical field, relate to a kind of transmission and disttrbution technology that is used for electric power system or rather.
Background technology
There are two kinds of basic power transmission and distribution technology in the current power system, and promptly power frequency (50 hertz or 60 hertz) exchanges power transmission and distribution and direct current transmission and distribution, and wherein industrial frequency AC power transmission and distribution technology is most widely used.Although direct current transportation has many good qualities, because the high-voltage large-capacity dc switch is made difficulty, be difficult to realize the multiterminal transmission of electricity, so direct current transportation mainly also just is used for the occasion of point-to-point transmission of electricity at present, be the important supplement of industrial frequency AC power transmission and distribution.
Since nineteen nineties, there is the scholar to propose the thought of low-frequency ac transmission of electricity (or frequency division transmission of electricity), promptly, finally reach the purpose that improves the circuit conveying capacity by reducing the reactance that transmission frequency reduces transmission line.
No matter being industrial frequency AC transmission of electricity or low-frequency ac transmission of electricity, all is the constant frequency transmission of electricity in essence.For guarantee the scope of broad can normal trouble free service (as prevent that voltage from crossing the border etc.), the constant frequency transmission of electricity often needs to be equipped with multiple attachment device, as shunt reactor.Even like this, when the line load level changed, the efficient of constant frequency electrical power trans mission/distribution system and runnability still can worsen.
Summary of the invention
The objective of the invention is to overcome above-mentioned weak point, a kind of variable-frequency power transmission and distribution system is provided, this system improves the operational efficiency of system and improves system performance by the real time altering transmission frequency.
A kind of variable-frequency power transmission and distribution system provided by the invention, it is characterized in that, this system comprises sending end variable-frequency transformer and the receiving end variable-frequency transformer that connects by transmission line, and the sending end variable-frequency transformer connects with sending, and the receiving end variable-frequency transformer connects with receiving-end system.
The frequency of the electric energy that the sending end variable-frequency transformer comes sending when the transmission line load variations time and frequency and voltage after voltage transitions becomes optimization are delivered to the receiving end variable-frequency transformer via transmission line;
The receiving end variable-frequency transformer is required frequency of receiving-end system and voltage with the frequency and the voltage transitions of the electric energy of reception, sends into receiving-end system again.
The present invention has following technical characterstic:
(1) can realize conventional power transmission and distribution operational mode, as industrial frequency AC power transmission and distribution, direct current transmission and distribution etc.
(2) frequency of the electric energy of joining sending (f1) can change with it, as: if connect solar photovoltaic generation system, the electric energy frequency is 0 hertz (direct current); If connect common frequency power network, the electric energy frequency is 50 hertz or 60 hertz.
(3) if sending is pumped storage unit or wind-powered electricity generation unit, to change to electric energy for realizing the most efficient water energy/wind energy, generating set can change according to head and wind-force, sends the frequency conversion electric energy.
(4) operating frequency of joining receiving-end system (f3) also can change with it, as 50 hertz of direct currents, power frequency or 60 hertz, or the like.
(5) transmission frequency (f2) changes, and to improve transfer efficiency or runnability, for example, the watt level difference of Shu Songing by changing frequency, can realize the minimum line losses operation as required, and guarantees that voltage along the line distributes.
(6) in running, transmission frequency (f2) both may be lower than the frequency of two end systems (sending and receiving-end system), also may be higher than the frequency of two end systems.
Description of drawings
Fig. 1 is the schematic diagram of variable-frequency power transmission and distribution system.
Fig. 2 is a kind of embodiment schematic diagram of variable-frequency transformer.
Embodiment
Below in conjunction with accompanying drawing and example the present invention is described in further detail.
As shown in Figure 1, variable-frequency power transmission and distribution system is made up of sending end variable-frequency transformer 1, transmission line 2, receiving end variable-frequency transformer 3, is used to connect sending 4 and receiving-end system 5.
When the transmission line load variations, it is that f2, voltage are the electric energy of U2 that sending end variable-frequency transformer 1 converts the frequency f 1 of the electric energy of sending 4 and voltage U 1 to frequency according to the computation optimization result, be delivered to receiving end variable-frequency transformer 3 via transmission line 2, needs according to receiving-end system 5, receiving end variable-frequency transformer 3 is converted to receiving-end system 5 needed frequency f 3 and voltage U 3 with the electric energy that receives again, enters receiving-end system 5.Vice versa.
Sending end variable-frequency transformer 1 is adjusted computation optimization result's (comprising frequency f 2, voltage U 2) of institute's foundation, and the target difference according to system is pursued can obtain from following method usually: (1) is the optimization trend calculating of target with the network loss minimum; (2) distributing the most even with node voltage is the optimization trend calculating of target; (3) drop into the optimization trend calculating that minimum is a target with optional equipment (as the shunt compensation reactance); (4) to improve the optimization trend calculating that system stability nargin is target; Or the like.
The frequency of the electric energy of sending 4 can be constant, also can change.The operating frequency of receiving-end system 5 can be constant, also can change.When the frequency of sending 4 be change the time, sending end variable-frequency transformer 1 should change the frequency of transmission line 2 according to the computation optimization result, also wants the frequency of real-time tracking sending 4.When the frequency of receiving-end system 5 be change the time, receiving end variable-frequency transformer 3 needs the frequency of real-time tracing receiving-end system 5, thereby the correspondent frequency conversion is provided.
The variable-frequency transformer of sending end and receiving end has multiple implementation method, and wherein most typical is to adopt the electronic power transformer (also claiming electric power electric transformer or solid-state transformer) that develops rapidly for over ten years recently to realize.
As shown in Figure 2, sending end variable-frequency transformer 1 and receiving end variable-frequency transformer 3 can adopt electronic power transformer to realize, it is made up of the former side's converter 6, high-frequency isolation link 7 and the secondary side's converter 8 that are connected in series successively, can realize electric pressure and frequency translation neatly.
The above is preferred embodiment of the present invention, but the present invention should not be confined to the disclosed content of this embodiment and accompanying drawing.So everyly do not break away from the equivalence of finishing under the spirit disclosed in this invention or revise, all fall into the scope of protection of the invention.