Abstract
When a fault occurring in the tie line of photovoltaic power station is cleared by the protection three-phase trip, photovoltaic power source (PVS) will form an unplanned island with the local load. However, since the voltage regulation and frequency control capability of PVS is generally poor, it is very difficult to satisfy the synchronous reclosing conditions, eventually resulting in an automatic reclosing failure. According to the islanding control strategy of PVS and the principle of phase-locked loop (PLL), a vector relationship model of PVS port actual voltage, port calculation voltage, grid-connected point voltage and so on before and after reclosing is established. Based on this, the influences of reclosing phase difference, amplitude difference and frequency difference on reclosing impulse voltage and current are analyzed, and a synchronous check reclosing strategy applicable to the tie line of PVS is proposed, which can effectively improve the success rate of the three-phase reclosing in tie line. Digital simulation results verify the correctness of the proposed reclosing strategy.
Highlights
In recent years, photovoltaic power has become an important field for global energy transformation with rapidly increased installed capacity, which is mainly attributed to its technology advancement and cost reduction [1]
It is necessary to consider the influence of the phase difference between the PVS port voltage and the grid-connected point voltage before reclosing on Ug, and the reclosing impulse voltage no longer increases monotonously as the island amplitude increases
Aiming at the adverse effects of PVS access on the threephase reclosing of tie line, this paper establishes a vector relationship model of PVS port voltage, grid-connected point voltage and so on before and after reclosing, analyzes the influencing factors of the reclosing impulse voltage and current, and proposes a synchronous check reclosing strategy applicable to the tie line of PVS
Summary
Photovoltaic power has become an important field for global energy transformation with rapidly increased installed capacity, which is mainly attributed to its technology advancement and cost reduction [1]. Compared with the traditional synchronous motor, PVS does not have strong voltage regulation capability and physical inertia for frequency maintenance, which leads to that the voltage amplitude and frequency during the island operation are changed and it is hard to satisfy quasi-synchronization reclosing conditions [6]–[8], eventually resulting in reclosing failure To solve this problem, the general practice adopted at present is to intertrip PVS or lock three-phase reclosing when a fault occurs in the tie line, but this practice will result in that plenty of PVS exit operation or the local load power supply is interrupted, affecting the safe and stable operation of the power grid and the efficient use of renewable energy. Digital simulation results verify the correctness of analysis conclusions and proposed reclosing strategy
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