Figure 1.
Three-phase LCL-filtered GTI with the proposed control scheme. GTI, grid-tied inverter; HCC, hysteresis current controller.
Table 1.
System parameters
| System parameter | Symbol | Value |
|---|---|---|
| DC link voltage | Vd | 600 V |
| Grid voltage | Vg | 230 V (RMS) |
| Grid frequency | fg | 50 Hz |
| Sampling rate | 0.2 μs | |
| Inverter-side inductance | L1 | 1.74 mH |
| Grid-side inductance | L2 | 0.68 mH |
| Filter capacitance | C | 10 μF |
| Inductor’s resistance | r1,2 | 0.2 Ω |
| Coefficient of NFTSMC | α, β, k1, k2 | 1.8, 1.3, 300, 1 |
| PMR gains | Kp, Kr, k5, k7 | 10, 2,000, 2,000, 2,000 |
| Bands of the hysteresis function | h | 2,000 |
Figure 2.
Steady-state waveforms of GTI (a) grid current (i2a, i2b, i2c) (b) load current (ila, ilb, ilc) (c) grid voltage (vga, vgb, vgc). GTI, grid-tied inverter.
Figure 3.
Grid current (i2a, i2b, i2c) responses to the variation of reference grid current.
Figure 4.
Fast Fourier transform of Grid-side current (i2a) for two different values of L2: (a) 20% decrease and (b) 500% increase. THD, total harmonic distortion.
Figure 5.
Simulation results under distorted grid voltage conditions: (a) grid voltage (b) grid current.
Figure 6.
Load step change at t = 0.1 s. (a) load current (ila, ilb, ilc) and (b) grid current (i2a, i2b, i2c).
Figure 7.
Comparison of the proposed NTFSMC with ordinary SMC under step change. SMC, sliding mode controller.
Figure 8.
Fast Fourier transform of grid-side current (i2a) for Non-ideal DC voltage. THD, total harmonic distortion.
Figure 9.
Fast Fourier transform switching pulses (a) h = 2,000 (b) h = 1,000,000. THD, total harmonic distortion.
Figure 10.
Non-symmetrical distortions in C phase. (a) non-symmetrical load and (b) sinusoidal grid current.
Table 2.
Comparison of the proposed system with other works
| Reference | Huang et al. (2023) | Zhang and Fei (2023) | Sozanski and Szczesniak (2023) | Proposed |
|---|---|---|---|---|
| Transient response performance | Very high | Very high | Medium | Very high |
| Robustness | High | High | High | Very high |
| PWM method | PWM | PWM | PWM | Hysteresis |
| Switching frequency | 20 Khz | Not reported | 25.6 Khz | Not fixed |
| Non-linear load performance | Very high | Very high | Very high | Very high |
| Complexity | High | High | High | Low |
| Computational burden | Very high | High | High | Low |
| Best grid THD | 0.98 | 1.56 | Not reported | 0.33 |