Voltage drop generator and its control method for low voltage ride through test

Abstract

The invention provides a voltage drop generator and a control method thereof for low voltage ride through test, the voltage drop generator is connected with a photovoltaic grid-connected power generation unit through a step-up transformer; the voltage drop generator includes a bypass switch S 1 , short circuit switch S 2 , Ground combination switch S 3 , Ground combined reactance X p and current limiting combined reactance X S ; The high-voltage side of the step-up transformer is Y connection, and the step-up transformer passes through the current-limiting combined reactance X S Connected to grid, bypass switch S 1 Combined with current limiting reactance X S Parallel connection; step-up transformer, short-circuit switch S 2 , Ground combined reactance X p and ground combination switch S 3 In series, the neutral point and grounding combination switch S on the high voltage side of the step-up transformer 3 Connect the other end to ground. The invention can simulate various power grid voltage fault types such as three-phase symmetrical drop, single-phase grounding, two-phase grounding, two-phase short circuit, etc., and realizes that the step size is 5% of the rated voltage of the power grid, and the depth of the drop is from 0% to 100% of the power grid Full range of rated voltage 20 grid voltages with uniform drop depths to simulate fault drops.

Description

technical field [0001] The invention relates to a detection device in the detection field of photovoltaic grid-connected inverters, in particular to a voltage drop generator for low voltage ride-through test and a control method thereof. Background technique [0002] With the rapid development of the photovoltaic industry, the proportion of photovoltaic power generation in the grid continues to increase. If the large-capacity photovoltaic grid-connected power generation unit cannot maintain the voltage and frequency of the grid when the grid fails and the voltage drops, it will have a major impact on the stability of the power system. Photovoltaic grid-connected inverters, as the core components of large and medium-sized photovoltaic power plants, must have low-voltage ride-through capabilities. Therefore, as a photovoltaic grid-connected inverter testing laboratory must have a testing device for testing whether the photovoltaic grid-connected inverter has low voltage ride-...

AI Technical Summary

Problems solved by technology

[0016] In addition, the current voltage drop generator used for the low voltage ride-through test of the photovoltaic grid-connected inverter generally needs to design the topology structure and the reactance of each three-phase reactor according to the specific three-phase grid voltage level U and the internal impedance a of the grid. Value calculation, such as designing a topology for a 10kV three-phase power grid, and correspondingly calculating the reactance value of the three-phase reactor; if designing a topology for a 35kV power grid, and correspondingly calculating the three-phase reactance In addition, even if the voltage level of the power grid is the same, if the internal impedance of the power grid differs greatly, the topology structure and the calculation of the reactance value of the three-phase reactor must be recalculated, and the control logic of each internal switch must be recalculated accordingly. Change

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