Decentralized Circulating Currents Suppression for Paralleled Inverters in Microgrids Using Adaptive Virtual Inductances
Abstract
:1. Introduction
2. Paralleled Inverters with Conventional Droop Control
2.1. Conventional Droop Control
2.2. Generating of Circulating Current
3. Adaptive Virtual Inductance Control Method
3.1. Operational Principle of the Virtual Inductance Control Method
3.2. Realization of the Adaptive Virtual Inductance
3.3. Stability Analysis
- Case 1:
- n1 = 5 × 10−3 V/Var, Lvt1 = 2 mH, ωf1 = 30 rad/s, m1 is varying from 1 × 10−5 to 1 × 10−3 rad/(s·W);
- Case 2:
- m1 = 2.5 × 10−4 rad/(s·W), Lvt1 = 2 mH, ωf1 = 30, n1 is varying from 1 × 10−4 to 5 × 10−2 V/Var;
- Case 3:
- m1 = 2.5 × 10−4 rad/(s·W), n1 = 5 × 10−3 V/Var, Lvt1 = 2 mH, ωf1 is varying from 0 to 150 rad/s;
- Case 4:
- m1 = 2.5 × 10−4 rad/(s·W), n1 = 5 × 10−3 V/Var, ωf1 = 30, Lvt1 is varying from 100 μH to 10 mH.
3.4. Design of the Key Parameters
4. Simulation and Experimental Verification
5. Conclusions
Author Contributions
Funding
Acknowledgments
Conflicts of Interest
Nomenclature
DGs | distributed generators |
PCC | the point of common coupling |
LPF | low-pass filter |
PLL | phase-locked loop |
Voi, V*o, Vg | output voltage, nominal output voltage, voltage at PCC |
δi, θi | power angle, impedance angle |
Pi, Qi, Qcc | output active power, output reactive power, circulating reactive power flow |
ωi, ω*, ωfi | system frequency, nominal frequency, corner frequency of the LPF |
mi, ni | droop coefficients of active and reactive power |
ki | capacity ratio of each inverter |
Xvi, XLi | initially added constant virtual output inductance, line inductance |
Xi, ΔXvi | equivalent output inductance, adaptive virtual inductance |
Xset, Qset | pre-set inductance and reactive power for the reference DG inverter |
kv | adaptive coefficient |
Vvα, Vvβ | the α and β components of the voltage across virtual inductance |
iα, iβ | the α and β components of output current |
QN | the rated power of the whole system |
Xvtimin, Xvtimax | the minimum and maximum total virtual inductance |
a | constant within (5)–(10) |
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System Parameter | Inverter 1 | Inverter 2 |
---|---|---|
DC link voltage | 720 V DC | 720 V DC |
Nominal AC bus voltage | 380 V | 380 V |
Nominal frequency | 50 Hz | 50 Hz |
Nominal output power | 5 kW, 1.5 kVar | 10 kW, 3 kVar |
Filter inductance | 1 mH | 1.5 mH |
Filter capacitance | 30 μF | 50 μF |
Line impedance | 0.22 Ω, 100 μH | 0.235 Ω, 110 μH |
Initial constant virtual inductance | 2.1 mH | 2.3 mH |
P-ω droop coefficient | 2.5 × 10−4 rad/(s·W) | 1.25 × 10−4 rad/s·W |
Q-V droop coefficient | 2 × 10−3 V/Var | 1 × 10−3 V/Var |
Voltage regulator | kpvd1 = 0.1, kivd1 = 50 kpvq1 = 0.1, kivq1 = 50 | kpvd2 = 0.15, kivd2 = 50 kpvq2 = 0.15, kivq2 = 50 |
Current regulator | kpid1 = 10, kiid1 = 1000 kpiq1 = 10, kiiq1 = 1000 | kpid2 = 10, kiid2 = 1500 kpiq2 = 10, kiiq2 = 1500 |
Corner frequency of the LPF ωf | 30 rad/s | 30 rad/s |
Set value of the adaptive virtual inductance Xset | 2 mH | 2 mH |
Coefficient kv | 4 × 10−6 | 4 × 10−6 |
Set value of the reactive power Qset | 1.5 kVar | 1.5 kVar |
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Chen, J.; Hou, S.; Li, X. Decentralized Circulating Currents Suppression for Paralleled Inverters in Microgrids Using Adaptive Virtual Inductances. Energies 2018, 11, 1725. https://doi.org/10.3390/en11071725
Chen J, Hou S, Li X. Decentralized Circulating Currents Suppression for Paralleled Inverters in Microgrids Using Adaptive Virtual Inductances. Energies. 2018; 11(7):1725. https://doi.org/10.3390/en11071725
Chicago/Turabian StyleChen, Jiawei, Shuaicheng Hou, and Xiang Li. 2018. "Decentralized Circulating Currents Suppression for Paralleled Inverters in Microgrids Using Adaptive Virtual Inductances" Energies 11, no. 7: 1725. https://doi.org/10.3390/en11071725