Abstract
With the increasing demand of users for power sources and quality, how to provide high-quality renewable clean energy has become a key issue of power electronics. The main idea of this paper is to develop a composite control including a PI control and repetitive control for a single-phase grid-connected inverter to eliminate the effects of harmonics, which can obtain better steady-state and dynamic responses of the single-phase inverter system and reduce the net current harmonics. The modelling of a single-phase inverter is first introduced; then a first-order repetitive control is developed for the proposed grid-connected inverter. Moreover, a high-order repetitive controller is adopted to further improve the robustness against the uncertainties in the period of signals. The stability and performance analysis are given for the first-order repetitive control and high-order repetitive control. Finally, comparative simulations are conducted in a circuit-level inverter model, which show the effectiveness of the proposed method.
Highlights
There are some critical issues to be addressed in the renewable energy powered grid-connected systems
We validate the effectiveness of the proposed control algorithms by using Simpower systems Toolbox in Matlab/Simulink. e simulation model of a single-phase grid-connected inverter is built to compare the current harmonic suppression of First-Order Repetitive Control (FORC) and High-Order Repetitive Control (HORC). e FFT analysis tool in Simulink is used to get the total harmonic distortion (THD). rough the block diagram of current loop control system in Figure 6 and the topology structure in Figure 5 of the single-phase grid-connected inverter, the simulation diagram of the single-phase inverter can be obtained as Figure 9
E main circuit simulation module is composed of a DC power supply, an IGBT inverter bridge, a filter inductor, an AC source of public power grid, and an output current detection module. e control part consists of a control circuit, a PWM generator module, and a PLL module. e current loop is used in the control loop. e control module includes a PI control, a first-order repetitive control, or a high-order repetitive control, respectively
Summary
Full-bridge inverter circuit is simple in terms of structure and easy to control; it has been widely used in the high-power occasions. E main circuit of the single-phase grid-connected inverter is shown, which is a voltage type full-bridge circuit composed of four IGBTs and continuous current diodes in reverse parallel. En, we know that the single-phase grid-connected inverter adopts the double loop control strategy of voltage and current loop, and the outer loop is the DC side voltage loop, whose function is to keep the DC side voltage stable. Is paper only studies the inverter function of the later stage of the grid-connected system; the front end of the inverter bridge can be regarded as a constant voltage DC power supply, while the voltage loop is not considered E inner loop is a current loop, the output current of the inverter is in the same phase as the grid voltage, and the current amplitude is determined by the output of the voltage loop regulator. is paper only studies the inverter function of the later stage of the grid-connected system; the front end of the inverter bridge can be regarded as a constant voltage DC power supply, while the voltage loop is not considered
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