Unified power quality controller suitable for fault ride-through and control method

Abstract

The invention discloses a unified power quality controller suitable for fault ride-through and a control method. A UPQC is connected on the two sides of a photovoltaic power station exit transformer in a bridging mode, and the amplitude of an inverter exit voltage in a high voltage failure is compensated to keep the amplitude in a rated value. The harmonic component of a network voltage is compensated through a UPQC system, the exit voltage THD of a photovoltaic grid-connected inverter is close to 0, and the failure test speed and the response speed of the photovoltaic grid-connected inverter in a photovoltaic power station are improved. Reactive compensation benefits are provided by the UPQCs under the condition the volume design of meeting high voltage ride-through with a 1.3-time rated value. When a low voltage drops, the photovoltaic power station is matched to generate reactive power, the requirement of a power grid for photovoltaic power station reactive power can be met faster, and in a high voltage failure, an APF absorbs power grid reactive power to help to restore a power grid voltage.

Description

technical field [0001] The present invention relates to a novel unified power quality conditioner (unified power quality conditioner, UPQC), in particular to a unified power quality controller and a control method suitable for high / low voltage ride-through of grid-connected photovoltaic power plants. Background technique [0002] In recent years, the total installed capacity of photovoltaic power plants in China has been increasing continuously, and the impact of centralized photovoltaic power generation on the power system is increasing. The effect of off-grid and grid-connected photovoltaic power plants on the frequency and amplitude of the grid cannot be ignored. The "Technical Regulations for Connecting Photovoltaic Power Stations to Power Systems" implemented in June 2013 stipulates that large and medium-sized photovoltaic power stations should have low-voltage ride-through capabilities. The power station can operate normally when the grid voltage is 0.9pu-1.1pu, and c...

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Problems solved by technology

2. Adjust the transformation ratio of the transformer. This solution cannot adjust the voltage smoothly and is not suitable for popularization and application.

Therefore, it is very important to improve the efficiency and speed of fault detection and reduce the adjustment time of reactive power issued by photovoltaic power plants, and the voltage harmonic components in the grid will affect the impact of the phase-locked loop (PLL) of the photovoltaic inverter system on the grid. The detection speed and accuracy of high / low voltage faults will affect the overall response speed and accuracy of photovoltaic power plants

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