Method for reducing output current harmonics of single-phase photovoltaic grid-connected inverter

Abstract

The invention relates to a method for reducing output current harmonics of a single-phase photovoltaic grid-connected inverter. To ensure the stable control precision of a BUS, the capacitance of the BUS is generally and greatly increased to buffer the pulsation of energy, the voltage of the BUS is smooth as much as possible, but due to the fact that the overlarge capacitance can cause the response speed of a system to be low, and cost is increased. The method for reducing the output current harmonics of the single-phase photovoltaic grid-connected inverter is characterized by comprising the step of preparing, the step of solving an error, the step of updating an old value, the step of digitalizing, the step of outputting, the step of multiplying the peak value with the standard unit sinusoidal signal sin (wt) to obtain a current set signal, and the step of carrying out deduction on the current set signal and an inductive current sampling signal IL, comparing with a cycle counter after calculating an error integral and connecting a driving signal to a main circuit switch tube. Three-time harmonic contents in an output current can be reduced in the same BUS capacitance under the condition that the gain of a BUS control loop is not reduced.

Description

technical field [0001] The invention relates to a method for reducing output current harmonics of a single-phase photovoltaic grid-connected inverter. Background technique [0002] In the grid-connected standards of many countries, there are requirements for the total harmonic distortion rate (THD for short) of the grid-connected current of the photovoltaic grid-connected inverter, so it is very important to reduce the THD of the output current of the photovoltaic grid-connected inverter. important. In a single-phase photovoltaic grid-connected inverter system, see figure 1 , the DC / DC circuit of the previous stage tracks the maximum power of the photovoltaic panel through the maximum power, and transmits the energy to the intermediate energy storage capacitor BUS, and the DC / AC circuit (that is, the inverter) in the back converts the DC The alternating current with the same frequency and phase as the grid voltage is injected into the grid. Therefore, the intermediate ene...

AI Technical Summary

Problems solved by technology

can usually be reduced by reducing the voltage regulator The 100Hz signal is filtered out by the cut-off frequency of the filter, but in order to ensure the steady-state control accuracy of the BUS, the voltage regulator of the BUS The gain cannot be reduced too much

Under normal circumstances, the capacitance of the BUS will be greatly increased to buffer the energy pulsation and make the voltage of the BUS as smooth as possible, but the response speed of the system will be slowed down due to an excessively large capacitance, and the cost will also increase.

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