研究目的
To solve the problems of serious harmonics in current and power, high sampling frequency requirement, and long execution time in traditional model predictive direct power control (MPDPC) for grid-connected inverters (GCIs) by proposing a novel dead-beat MPDPC strategy that uses three inverter voltage vectors selected based on power errors to ensure constant switching frequency, positive duration times, and improved steady-state performance without iterative calculations.
研究成果
The proposed improved three-vector based dead-beat MPDPC strategy effectively eliminates power ripples, ensures positive duration times for inverter voltage vectors, maintains a constant switching frequency, and provides fast dynamic responses. It simplifies filter design, reduces computational burden by avoiding iterative calculations, and is feasible for implementation on DSPs in industrial applications, as validated by experimental results.
研究不足
The improved strategy requires a slightly longer execution time (41.2 μs) compared to the conventional method (38.5 μs) due to additional vector selection algorithms. The experimental validation is limited to a 1 kW setup, and the method may need further testing for higher power applications or different grid conditions.
1：Experimental Design and Method Selection:
The study involves designing and implementing an improved three-vector based dead-beat model predictive direct power control (MPDPC) strategy for a three-phase grid-connected inverter (GCI). The method is based on selecting inverter voltage vectors using power errors rather than the grid voltage vector position to avoid negative duration times and ensure constant switching frequency. Delay compensation and symmetrical 3+3 pulse patterns are used.
2：Sample Selection and Data Sources:
A 1 kW GCI experimental setup is used, with grid voltages and currents sampled using voltage and current transducers. The system parameters include a grid voltage of 156 V (RMS phase-to-phase), rated power of 1 kW, frequency of 50 Hz, line inductance of 6 mH, DC link voltage of 280 V, and sampling frequency of 10 kHz.
3：List of Experimental Equipment and Materials:
Equipment includes a TMS320F2812 DSP for control execution, a DC power supply for the DC-link voltage, three line inductors (6 mH each), voltage and current transducers for sampling, a Semikron IGBT driver circuit (SKHI 61 R) for generating drive signals, IGBTs for the inverter, and a YOKOGAWA DL750 oscilloscope for waveform acquisition.
4：Experimental Procedures and Operational Workflow:
Grid voltages and currents are sampled, apparent power is calculated, and a phase-locked loop (PLL) is used to obtain the grid voltage phase angle. After delay compensation, inverter voltage vectors are selected based on power errors, and their duration times are calculated. Drive signals are generated and applied to the IGBTs in a symmetrical 3+3 pattern. Steady-state and dynamic performance tests are conducted with power step changes.
5：Data Analysis Methods:
Experimental data, including power fluctuations, execution times, and total harmonic distortion (THD) of currents, are analyzed. Fast Fourier transform (FFT) is used for harmonic analysis, and comparisons are made between conventional and improved MPDPC strategies.
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