Grid-connected power generation overvoltage adjustment method for distributed-type photovoltaic power supply

Abstract

The invention discloses a grid-connected power generation overvoltage adjustment method for a distributed-type photovoltaic power supply. The method directly cooperates with an MPPT module for use according to the magnitude of the voltage of a grid-connected point. When the voltage of the grid-connected point is in different sections, whether the MPPT module is locked or not is selected and the power is limited at the same time. The overvoltage adjustment is achieved based on a P-U sagging method, and a function of overvoltage adjustment is implanted into a conventional photovoltaic inverter, thereby enabling the conventional photovoltaic inverter to have a function of grid-connected inversion under the condition that a power grid is normal. The output can be automatically adjusted according to the condition of the voltage of the grid-connected point so as to achieve overvoltage adjustment, thereby guaranteeing that the grid-connected point voltage is within a normal range, further preventing the distributed-type photovoltaic power supply from being split with the power grid after being connected with the distribution network because of overvoltage, improving the permeability of the distributed-type photovoltaic power supply to some extent, further guaranteeing the safe and stable operation of the power grid, increasing the amount of photovoltaic power generation, and providing theoretical basis for the building of a large-scale distributed-type photovoltaic power supply.

Description

technical field [0001] The invention belongs to the technical field of smart grids, and relates to an overvoltage regulation method for grid-connected power generation of distributed photovoltaic power sources. Background technique [0002] With the increasingly prominent energy crisis, renewable energy power generation has become a development trend. Distributed photovoltaic power generation is an important form of renewable energy power generation. The large-scale access of distributed photovoltaic power sources under high penetration rates makes traditional power distribution The operation control method of the power grid has been unable to cope with it, and has changed the distribution and direction of the power flow of the traditional distribution network. These changes in the power flow have some impact on the steady-state voltage distribution of the power grid, and may even cause some nodes of the distribution network to generate excessive voltage. Voltage, so that th...

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Problems solved by technology

This method mainly has the following disadvantages: (1) Since the line impedance ratio R / X in the low-voltage distribution network is very large, the voltage at the grid-connected point is mainly related to the active power, and the reactive power has little influence on the grid voltage , in addition, distributed photovoltaic inverters generally require high power factor operation, and the above method of reactive power regulation is not very reasonable; (2) The three working modes in this method not only involve the inverter to control the DC bus voltage and Grid-connected current control, the third party mode also needs to increase the PI control regulator of the grid voltage given value Uref and the grid voltage effective value Urms, and then adjust the power output

It can be seen that this method not only involves DC bus voltage control and grid-connected current control, but also adds a closed-loop algorithm for AC side voltage, which is more complicated and troublesome to implement; According to the voltage on the grid side, the difference between the DC bus side voltage of the boost circuit and the given voltage Uref is detected in real time for closed-loop adjustment to adjust the grid-connected current; for single-stage inverters, there is no so-called DC side bus stability Therefore, it is not clear how this method is applicable to single-stage inverters, so the application scenarios of this method are relatively narrow; (4) The judgment interval of the grid voltage range is narrow, which limits the power output to a certain extent; (5) This method The maximum power tracking is always performed, and the power adjustment is only to deviate from the MPP point, instead of choosing to block the MPPT module

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