Solve the software control method that the low-yield input of single-phase photovoltaic inverter starts repeatedly
Technical field
The present invention relates to a kind of control of photovoltaic DC-to-AC converter, specifically a kind of software control method solving the low-yield input of single-phase photovoltaic inverter and repeatedly start.
Background technology
It is CN202872349U that State Intellectual Property Office discloses publication number on April 10th, 2013, and patent name is the utility model patent of the Circuits System utilizing IGBT temperature control inverter power output derate.
The grid-connected startup of traditional single phase photovoltaic combining inverter controls, and is under the N/R prerequisite of system, judges that input voltage satisfies condition and just carries out startup and net operation.And when weather such as morning, evening and wet weather, photovoltaic panel output voltage is higher, but its output energy is lower.Conventional inverter is by means of only simply judging that input voltage meets grid-connected conditions in the case, just start to carry out startup and net operation, inverter is just access grid-connected just to be dragged down input voltage, and this can cause inverter to be always in continuous start and stop state, thus have impact on the useful life of inverter.
The function of photovoltaic DC-to-AC converter is and the alternating electromotive force of public electric wire net with frequency homophase, is fed in electrical network.Because photovoltaic combining inverter is powered by direct current input side mostly, change with illumination changes by solar panel, when input energy shortage is (as most evil bad cloud, sooner or later low-light) time, and there is a larger loss in inverter work, and when the energy shortage of the storage battery of inverter, thus make power supply always be in start and stop state, this will cause inverter to occur frequent switching on and shutting down, relay frequent movement, not only reduce the useful life of inverter and relay, and can not carry out in time and net operation when inputting energy and recovering again, photovoltaic generation utilance is reduced.
Therefore, reducing inverter switching device machine number of times and actuating of relay number of times, is the problem that inverter needs to solve.
Summary of the invention
The object of the invention is to solve above-mentioned technical deficiency part, the software control method that a kind of low-yield input of solution single-phase photovoltaic inverter starts repeatedly is provided.
For achieving the above object, the technical solution adopted in the present invention is:
Solve the software control method that the low-yield input of single-phase photovoltaic inverter starts repeatedly, comprise the following steps:
A, installation switchable power supply, switchable power supply, it is the direct current exported based on solar panel, with the power supply that the alternating current of electrical network is auxiliary, when the direct current energy that solar panel exports is not enough, can electrical network be automatically switched to, power after the AC rectification of electrical network and filtering for inverter, relay and controller;
B, startup inverter, inverter is in normal also network process, and in system failure situation, relay maintains attracting state;
C, in the inverter course of work, software controlled unit keeps input voltage, busbar voltage to inverter always, and output energy is monitored, when input voltage is lower than input low pressure threshold values, or when busbar voltage is lower than bus low pressure threshold values, or power output lower than low-power threshold values time, then close inverter, relay continues to maintain attracting state, starts timer T1;
After D, startup timer T1, software controlled unit is monitored in real time to input voltage, busbar voltage, when input voltage and busbar voltage all meet grid-connected requirement, start timer T2, when the timing of T2 is greater than low-yield T_Clr recovery time of setting, software controlled unit exits low energy model, restarts and net operation; When the timing of T1 is greater than the low energy model duration T _ Pro of setting, namely when low energy model cannot reach and recover grid-connected threshold voltage within one lasting period, then think that people is for cutting off input switch or being in night, now software controlled unit disconnects relay, stops grid-connected inverters attempting.
In described step C, in the inverter course of work, software controlled unit carries out the grid-connected work of maximal power tracing (MPPT).
In described step D, restart and net operation time, software controlled unit carries out detection operation to relay, after relay test passes through, start inverter.
In described step C, when input voltage can keep minimum starting state, when only busbar voltage cannot maintain, software controlled unit control inverter carries out inversion output with impulse form.
Beneficial effect of the present invention: due to the software control method adopting the low-yield input of above-mentioned solution single-phase photovoltaic inverter repeatedly to start, the method reduce inverter switching device machine number of times and actuating of relay number of times, thus extend the useful life of inverter and relay.
Accompanying drawing explanation
Below in conjunction with the drawings and specific embodiments, the present invention is described in further detail:
Fig. 1 is the flow chart solving the software control method that the low-yield input of single-phase photovoltaic inverter starts repeatedly.
Embodiment
As shown in Figure 1, solve the software control method that the low-yield input of single-phase photovoltaic inverter starts repeatedly, comprise the following steps:
A, installation switchable power supply, switchable power supply, it is the direct current exported based on solar panel, with the power supply that the alternating current of electrical network is auxiliary, when the direct current energy that solar panel exports is not enough, can electrical network be automatically switched to, power after the AC rectification of electrical network and filtering for inverter, relay and controller;
B, startup inverter, inverter is in normal also network process, and in system failure situation, relay maintains attracting state;
C, in the inverter course of work, software controlled unit carries out the grid-connected work of maximal power tracing (MPPT), and software controlled unit keeps input voltage, busbar voltage to inverter always, and export energy monitor, when input voltage lower than input low pressure threshold values time, or busbar voltage lower than bus low pressure threshold values time, or when power output is lower than low-power threshold values, then close inverter, relay continues to maintain attracting state, starts timer T1; When input voltage can keep minimum starting state, when only busbar voltage cannot maintain, software controlled unit control inverter carries out inversion output with impulse form;
After D, startup timer T1, software controlled unit is monitored in real time to input voltage, busbar voltage, when input voltage and busbar voltage all meet grid-connected requirement, start timer T2, when the timing of T2 is greater than low-yield T_Clr recovery time of setting, software controlled unit exits low energy model, to restart and net operation, restart and net operation time, software controlled unit carries out detection operation to relay, after relay test passes through, start inverter; When the timing of T1 is greater than the low energy model duration T _ Pro of setting, namely when low energy model cannot reach and recover grid-connected threshold voltage within one lasting period, then think that people is for cutting off input switch or being in night, now software controlled unit disconnects relay, stops grid-connected inverters attempting.
The above is the preferred embodiment of the present invention; certainly the interest field of the present invention can not be limited with this; should be understood that; for those skilled in the art; technical scheme of the present invention is modified or equivalent replacement, do not depart from the protection range of technical solution of the present invention.