Control-Loop-Based Impedance Enhancement of Grid-Tied Inverters for Harmonic Suppression: Principle and Implementation
Abstract
:1. Introduction
1.1. Background and Significance
1.2. Literature Review
1.3. Formulation of the Problem of Interest for This Study
1.4. Scope and Contribution of This Paper
1.5. Organization of the Mauscript
2. Principle of Control-Loop-Based Impedance Enhancement
2.1. Reshaping Principle Based on Output Impedance Models
2.2. Deduction Principle Based on Output Impedance Models
3. Analysis of Impact on Output Impedance of Various Control
3.1. Impact on Output Impedance Using Voltage Feedback Control
3.2. Impact on Output Impedance Using Current Feedback Control
- (a).
- As indicated in (4), Zoi will be enhanced when Ki is negative. If (5) is satisfied, the two basic methods will have an identical ability to enhance output impedance. Bode plots are given in Figure 7 to verify the enhancement effectiveness of the output impedance. The output impedance will be enhanced when Ku is positive for voltage feedback control, while Ki is negative for current feedback control.
- (b).
- The capacity of the two basic methods to reshape the output impedance is identical and they are equivalent when (5) is satisfied except in one circumstance, that is, when Ku is equal to 1/GoZo, Ki will trend to be infinite.
3.3. Impedance Enhancement Control Loop Based on Basic Impedance Reshaped Methods
4. Implementation and Optimization of Control-Loop-Based Impedance Enhancement
5. Simulations and Experimental Verifications
6. Conclusions
Author Contributions
Funding
Conflicts of Interest
References
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Symbol | Quantity | Value |
---|---|---|
ug | Grid voltage | 220 V |
fg | Frequency | 50 Hz |
Udc | DC voltage | 400 V |
L1 | Filter inductor at inverter side | 2.4 mH |
L2 | Filter inductor at grid side | 2.4 mH |
Zg | Grid impedance | 0.2 Ω/0.08 mH |
Cf | Filter capacitor | 4 μF |
fs | Switch frequency | 16 kHz |
Gic | Capacitor current regulator | 30 |
Ginv | Gain of the inverter | 1 |
Kp | Proportional coefficient | 1 |
KR | Resonance regulator coefficient | 50 |
ωc | Band frequency | 10 rad s−1 |
TLPF | Time constant of low pass filter | 40 μs |
iref | Reference current | 10 A |
Control Strategy | THD of Grid Current/% |
---|---|
Dual-loop control strategy | 13.17 |
Grid voltage feedforward control strategy | 5.78 |
Proposed control strategy | 5.75 |
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Wang, F.; Zhang, L.; Guo, H.; Feng, X. Control-Loop-Based Impedance Enhancement of Grid-Tied Inverters for Harmonic Suppression: Principle and Implementation. Energies 2018, 11, 2874. https://doi.org/10.3390/en11112874
Wang F, Zhang L, Guo H, Feng X. Control-Loop-Based Impedance Enhancement of Grid-Tied Inverters for Harmonic Suppression: Principle and Implementation. Energies. 2018; 11(11):2874. https://doi.org/10.3390/en11112874
Chicago/Turabian StyleWang, Fei, Lijun Zhang, Hui Guo, and Xiayun Feng. 2018. "Control-Loop-Based Impedance Enhancement of Grid-Tied Inverters for Harmonic Suppression: Principle and Implementation" Energies 11, no. 11: 2874. https://doi.org/10.3390/en11112874