A low-voltage ride-through detection device for grid-connected photovoltaic inverters

Abstract

The invention relates to a low-voltage ride-through detection device for a grid-connected photovoltaic inverter. The device includes a current-limiting reactor, a short-circuit reactor and a combined grounding switch; the current-limiting reactor, an intermediate reactor-circuit breaker unit, a short-circuit reactor and a combined grounding switch are connected in series; the current-limiting reactor is connected to 10 / 35kV power grid; the intermediate reactor-circuit breaker unit and the grounding combination switch are respectively connected to the neutral point of the high voltage side of the step-down transformer; the step-down transformer is connected to the grid-connected photovoltaic inverter. Under the condition that the short-circuit capacity is kept constant, the detection device changes the ratio of current limiting and short-circuit reactors through different switching modes of several circuit breakers, so as to meet the low-voltage ride-through detection of different drop ranges by using less reactors. requirements, so as to detect the low voltage ride-through capability of photovoltaic inverters.

Description

technical field [0001] The invention relates to a detection device, in particular to a low-voltage ride-through detection device for a grid-connected photovoltaic inverter. Background technique [0002] With the rapid development of my country's photovoltaic industry, the proportion of photovoltaic power generation in the grid continues to increase. If the power grid fails and the voltage drops, the photovoltaic power generation system will be disconnected and tripped, which will affect the stability of the power system and even cause a complete paralysis of the power grid. As the core component of the photovoltaic power station, the photovoltaic inverter can maintain grid connection when the grid fails, and even provide a certain amount of reactive power to the grid to support the recovery of the grid until the grid returns to normal, thereby "crossing" this low-voltage area. Therefore, as a photovoltaic inverter testing laboratory, it is necessary to have a testing device...

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Problems solved by technology

[0004] use figure 1 There are several characteristics in the form of passive reactors: first, high-power reactors must be selected, so the volume of the device is relatively large

Second, the number of drop points of the device is limited by the number of reactors, and it is impossible to satisfy many drop amplitudes at the same time

Third, it is cumbersome to replace the reactor configuration or change the main circuit structure during the test, which is not conducive to the rapid realization of voltage drops of various amplitudes and forms

[0012] Fourth: During low-voltage ride-through detection, the voltage amplitude error before, during and after the device falls shall not exceed ±5%, and the device's fall time and recovery time shall not exceed 20ms

This allows the device to match the Z 1 ,Z 2 When the reactance value is high, it is difficult to meet the requirements of the above four conditions at the same time

In addition, even if the configured reactor Z 1 ,Z 2 It can meet the requirements, but the device has cumbersome steps when replacing the reactor, which is not conducive to quickly realize the low voltage ride-through test of various drop amplitudes and multiple types of drop methods

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