A control method for a three-level grid-connected system with combined optical storage
A control method and three-level technology, applied in the field of power grid, can solve problems such as complex control methods, achieve the effects of reducing costs, improving operating efficiency, and increasing flexibility
Active Publication Date: 2019-05-24
GUANGZHOU INST OF ENERGY CONVERSION - CHINESE ACAD OF SCI
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[0002] For the photovoltaic grid-connected inverter structure, it is usually divided into two types: 1. Bipolar inverter, the front stage is a DC / DC step-up converter, which is responsible for maximum power tracking control while increasing the photovoltaic output voltage. The first stage is the DC / AC inverter link. This kind of inverter is generally connected to the grid as a current source or supplied to the local independent load in the form of a voltage source; 2. Single-stage inverters do not have an intermediate DC / DC link. One-stage converter is used to perform the function of two-stage inverter, so the system will reduce cost and improve efficiency, but the control method will be more complicated
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[0032] A three-level grid-connected system based on combined optical storage, such as figure 1 As shown, it is a device that integrates solar photovoltaic power generation and energy storage system, and sends new energy power generation to the grid through a unipolar three-level inverter. This reduces system cost and improves overall system efficiency, especially for medium and high power applications.
[0033] In the proposed system, the renewable energy generates maximum power to be delivered to the grid, while allowing the system to control the charging and discharging of the energy storage system according to the requirements. The proposed system realizes photovoltaic MPPT by controlling the capacitor voltage on the DC side, and at the same time can maintain the midpoint voltage (referring to the midpoint potential voltage of the three-level inverter, that is, the voltage at the connection between the first capacitor and the second capacitor). Stablize. In addition, in t...
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The invention discloses an energy-storage combined tri-level grid-connected system control method. A grid-connected system comprises a photovoltaic plate, an energy storage system, a first capacitor, a second capacitor and a tri-level inverter. The control method includes the steps that when the grid-connected systems runs in a grid connection manner, drive signals are generated through an electric potential compensation control method and loaded to the tri-level converter, and accordingly, symmetric output of neutral-point voltage of the tri-level inverter under the unbalanced condition and restraining on influences on the neutral-point electric potential stability of the tri-level inverter and the grid-connected electric energy quality from the fluctuation of the output power of the photovoltaic plate are achieved; meanwhile, photovoltaic running is conducted in the maximum power tracking mode through control over the voltage of the first capacitor, an energy storage system generates instruction characters to control a storage battery to charge or discharge according to the second capacitor voltage reference value, and accordingly stability of the neutral point electric potential is maintained. According to the energy-storage combined tri-level grid-connected system control method, the grid-connected current can still be symmetrically output under the conditions of output power fluctuation caused by illumination changes and the unbalanced neutral-point voltage.
Description
technical field [0001] The invention relates to the technical field of power grids, in particular to a control method for a three-level grid-connected system combining optical storage. Background technique [0002] For the photovoltaic grid-connected inverter structure, it is usually divided into two types: 1. Bipolar inverter, the front stage is a DC / DC step-up converter, which is responsible for maximum power tracking control while increasing the photovoltaic output voltage. The first stage is the DC / AC inverter link. This kind of inverter is generally connected to the grid as a current source or supplied to the local independent load in the form of a voltage source; 2. Single-stage inverters do not have an intermediate DC / DC link. One-stage converter is used to perform the function of two-stage inverter, thus the system will reduce cost and improve efficiency, but the control method will be more complicated. The current industry standard for high-power applications is us...
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IPC IPC(8): H02J3/38H02S40/32
CPCH02J3/385H02S40/32Y02E10/56
Inventor 张继元舒杰王浩吴昌宏黄磊吴志锋崔琼张伟
Owner GUANGZHOU INST OF ENERGY CONVERSION - CHINESE ACAD OF SCI