Method and system for controlling power output of an inverter

Abstract

According to a first aspect of the invention, there is provided a method of controlling a power output of an inverter (12). The method comprises measuring an output current (I A ) of the inverter (12), determining a difference between the output current (I A ) and a reference current (I A *), and controlling a reference input voltage (V DC *) of the inverter (12) as a function of the determined difference. In a second aspect of the invention, there is described a system (10) for controlling a power output of an inverter (12). The system comprises an inverter (12) arranged to output a current (I A ) as a function of a reference input voltage (V DC *). The system (10) further comprises a controller (14, 16) arranged to determine a difference between the output current (I A ) and a reference current (I A *). The controller (14, 16) is further arranged to control the reference input voltage (V DC *) as a function of the determined difference. The method may allow for control of a photovoltaic inverter at a power less than its maximum capability for a given solar irradiation, which may avoid the problem of the photovoltaic array voltage rising above a level where the inverter can run.

Description

technical field [0001] The invention relates to a method and a corresponding system for controlling the power output of an inverter, especially a photovoltaic inverter. In particular, the invention relates to a method and system for limiting the power output of an inverter. Background technique [0002] Traditionally, photovoltaic inverters operate at the maximum power point (MPP) to maximize revenue from solar panel factories. For example, in US2013 / 0155735, in figure 2 In B is shown a control system that controls the inverter such that the PV array voltage is kept at the optimum level required by the maximum power point. An integral controller (PI control) and a limiter are part of the inverter's internal control arrangement, which enables it to track the desired MPP voltage. [0003] However, recently, there are cases where the inverter output power must be limited below the MPP. For example, this may be because the power company has issued an order to limit the outpu...

AI Technical Summary

Problems solved by technology

[0005] (a) the cost of allowing the voltage to rise and accepting a higher voltage-rated inverter, or otherwise resizing the system to reduce the voltage, both of which result in higher costs;

[0006] (b) using an extra resistor to dissipate unnecessary power with a controller such as a "chopper" (see e.g. US2010 / 0275966) - this is expensive and requires facilities to dissipate the heat generated in the resistor, and are therefore not practical in large systems

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