A photovoltaic grid-connected inverter derating control system and method

Abstract

The invention discloses a photovoltaic grid-connected inverter derating control system and method. The system comprises a photovoltaic grid-connected inverter, wherein the photovoltaic grid-connected inverter comprises a DC / DC module and a DC / AC module that are connected with a photovoltaic polar plate; the photovoltaic grid-connected inverter also comprises a DC / AC control unit; the DC / AC control unit comprises a first PID controller, a first limiter, a first power limiter and a second PID controller that are connected in sequence; the reference value of the first PID controller is connected with a bus voltage set value Ubusref; the feedback value of the first PID controller is connected with a bus voltage value Ubus; the first current instruction value Iref1 output by the first PID controller is limited by the first limiter to obtain a second current instruction value Iref2; the second current instruction value Iref2 passes through the first power limiter to obtain a third current instruction value Iref3; the third current instruction value Iref3 is taken as the reference value of the second PID controller; and the current value Iinv output by the DC / AC module is taken as the feedback value of the second PID controller. According to the photovoltaic grid-connected inverter derating control system and method, the system loss is lowered and the system reliability is improved.

Description

technical field [0001] The invention relates to the field of photovoltaic power generation, in particular to a photovoltaic grid-connected inverter derating control system and method. Background technique [0002] attached figure 1 The traditional grid-connected inverter is shown, and the Boost circuit performs MPPT tracking control on the PV, and transmits the PV power to the bus capacitor. The grid-connected inverter feeds the power delivered by the Boost circuit back to the grid by stabilizing the bus voltage, maintains the energy balance of the system bus, and automatically realizes grid-connected power feeding. When the grid-connected inverter needs to reduce the grid-connected feed power (reason: the inverter is overheated, the grid feed dispatch needs to reduce the grid-connected power), in order to realize the limited power processing of the photovoltaic grid-connected system, as realized in the prior art There are two main ways: [0003] First, attached figure ...

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Problems solved by technology

[0003] First, attached figure 2 As shown, adjust the inverter control loop to limit the power of the system, where the Boost continues to input power to the bus capacitor, and the grid-connected inverter suddenly reduces the load, resulting in input power > output power, and energy is accumulated in the DC bus, which will cause DC Bus capacitor overvoltage protection, if the system protection is not timely, it will cause system failure and damage

When the grid-connected inverter needs to reduce the grid-connected feed power (cause: the inverter is overheated, the grid feed scheduling needs to reduce the grid-connected power), the Boost circuit will continue to deliver power to the bus capacitor, which will cause the bus capacitor to overvoltage , causing system failure

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