Abstract
This paper proposes a novel finite control set model predictive control (FCS-MPC) strategy with merely grid-injected current sensors for an inductance-capacitance-inductance (LCL)-filtered grid-tied inverter, which can obtain a sinusoidal grid-injected current whether three-phase grid voltages are balanced or not. Compared with the conventional FCS-MPC method, four compositions are added in the proposed FCS-MPC algorithm, where the grid voltage observer (GVO) and Luenberger observer are combined together to achieve full status estimations (including grid voltage, capacitor voltage, inverter-side current, and grid-injected current), while the sequence extractor and the reference generator are applied to eliminate the double frequency ripples of the active or reactive power, or the negative sequence component (NSC) of the grid-injected current caused by the unbalanced grid voltage. Simulation model and experimental platform are established to verify the effectiveness of the proposed FCS-MPC strategy, with full status estimations under both balanced and unbalanced grid voltage conditions.
Highlights
Grid-tied inverters have been widely utilized in distributed generation systems, since they are the interfaces between DC sources and power grids [1,2]
The digital control algorithm is implemented in dSPACE 1202 platform, where a control desk project is established to regulate control parameters and reference values, as well as display the experimental results which cannot be probed by the Yokogawa DL 1640 digital oscilloscope assembled with two current probes HIOKI 3276, including the inverter-side currents, grid-injected currents, capacitor voltages, grid voltages, active power, and reactive power in this paper
The digital control algorithm is implemented in dSPACE 1202 platform, where a control desk project is established to regulate control parameters and reference values, as well as display the experimental results which cannot be probed by the Yokogawa DL 1640 digital oscilloscope assembled with two HIOKI 3276, including the inverter-side currents, grid-injected currents, capacitor voltages, grid voltages, active power, and reactive power in this paper
Summary
Grid-tied inverters have been widely utilized in distributed generation systems, since they are the interfaces between DC sources and power grids [1,2]. Aiming at reducing the number of sensors, many sensorless control schemes, such as virtual flux [13,14], state observer [15,16], and so on, were widely adopted These control schemes are usually designed under the ideal grid voltage condition, and the negative effects caused by the negative sequence component (NSC) are not considered. The variables of methods proposed in [18,19] are all based on the full state measurements, while only one kind of sensor is reduced in [20,21] Note that it is of great challenge for the LCL-filtered grid-tied inverter to further reduce the number of sensors, especially under the unbalanced grid voltage condition. A novel FCS-MPC approach for the control of an LCL-filtered grid-tied inverter using merely grid-injected current sensors under the unbalanced grid voltage condition has been presented.
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