# THD Reduction in Wind Energy System Using Type-4 Wind Turbine/PMSG Applying the Active Front-End Converter Parallel Operation

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## Abstract

**:**

^{®}(Matlab r2015b, Mathworks, Natick, MA, USA) is analyzed, and the experimental laboratory tests using the concept of rapid control prototyping (RCP) and the real-time simulator Opal-RT Technologies

^{®}(Montreal, QC, Canada) is achieved. The obtained results show a type-4 WT with a total output power of 6 MVA, generating a THD reduction up to 5.5 times of the total WES current output by Fourier series expansion.

## 1. Introduction

- (i)
- Increased the converter power capacity.
- (ii)
- Minimized size of each VSC unit, which manages a portion of the total nominal power.
- (iii)
- A reduced ripple on the injected current, which improves the voltage quality at the Point of Common Coupling (PCC).
- (iv)
- An increased equivalent switching frequency, generating a smaller passive filter on the AC-side.
- (v)
- The possibility of THD Reduction at the WES, modifying the Digital sinusoidal pulse width modulation (DSPWM) switching signals in each VSC.

^{®}is analyzed, and the experimental laboratory tests using the concept of rapid control prototyping (RCP) and the real-time simulator Opal-RT

^{®}is achieved. The obtained results show a WES prototyping that incorporates a type-4 wind turbine with a total output power of 6 MVA and a THD reduction of up to 5.5 times.

^{®}. Finally, in Section 6, the conclusions are presented.

## 2. Modeling of the Type-4 WT-PMSG

#### 2.1. Modeling of the Machine-Side VSC Control at AFE Converter

_{MSC}is the PMSG armature inductance, R

_{MSC}is the PMSG stator phase resistance, v

_{MSC}and i

_{MSC}are the MSC voltage and current, respectively, v

_{WT-PMSG}is the generated WT-PMSG voltage.

_{rPMSG}is the PMSG rotor angular velocity; λ

_{mPMSG}is the maximum flux linkage generated by the PMSG rotor magnets and transferred to the stator windings.

_{rPMSG}L

_{MSC}in (2) indicates the coupled dynamics between ${i}_{MSC}^{d}$ and ${i}_{MSC}^{q}$. To decouple these dynamics, the ${i}_{MSC}^{q}$ vector signals are changed, based in the dq reference frame, i.e.,

_{MSC}=2.2/τ

_{MSC}is the MSC bandwidth of the closed loop control and τ

_{MSC}is compensator response time.

_{MSC}, in the range from 5 to 0.5 ms is selected, in this case a τ

_{MSC}= 2.2 ms is designated.

#### 2.2. Modeling Power Transfer Control between the WT-PMSG and AFE Converter

_{WTb}= ω

_{rPMSGb}; (ii) the WES base power is determined by the WT-PMSG nominal power, P

_{WESb}= P

_{WT-PMSGb}; iii) the output base power of the AFE converter is determined by the base WES power, P

_{AFEb}= P

_{WESb}; this power is transferred from WT to PMSG through the electric torque, this is represented by:

_{ePMSG}is the PMSG electrical torque, ${L}_{MSC}^{d}$ and ${L}_{MSC}^{q}$ are the dq reference frame components of the PMSG armature inductance.

_{mWT}is the WT mechanical torque.

_{rPMSG}control. By using Laplace transformation, the WT-PMSG plant in the frequency domain is represented, i.e.,

_{mWT}≈ T

_{ePMSG}, then, in the control design it is considered that T

_{mWT}= 0; generating a single input single output system (SISO), as shown in (15).

_{rPMSG}reference commands in the closed-loop transfer function, the proportional-integral (PI) compensators are used. The feedback loop $\left[{\iota}_{rPMSG}^{q}(s)\right]$ is:

_{PMSG}is the response time by the closed loop of the WT-PMSG first-order transfer function. This is selected according to the WT-PMSG transferred power and this must be at least ten times higher than τ

_{MSC}.

#### 2.3. Modeling of the Grid-Side VSC Control of the AFE Converter

_{GSC}and R

_{GSC}are the RL filter parameters through which the AFE converter is connected to the grid, v

_{GSC}and i

_{GSC}are the GSC voltage and current, respectively; v

_{WES}is the generated WES voltage.

_{0}is the WES angular frequency; the generated GSC voltages are given by:

_{0}L

_{GSC}in (19) indicates the coupled dynamics between ${i}_{GSC}^{d}$ and ${i}_{GSC}^{q}$. Decoupling these dynamics changes ${m}_{GSC}^{d}$ and ${m}_{GSC}^{q}$, based in the dq reference frame, i.e.,

_{GSC}=2.2/τ

_{GSC}is the GSC bandwidth of the closed-loop control.

_{GSC}is selected from 5 to 0.5 ms based on the transferred power.

#### 2.4. The DC-Side Control of the AFE Converter

_{DC}is the stored energy in the capacitor and C

_{DC}is the DC-link capacitance.

_{DC}(s) ≈ P

_{GSCref}(s), and using the d reference frame component of grid-side VSC plant described in (22) the DC-link control is made, generating the active power control, that is:

_{WES}is the presented reactive power at the WES.

_{WES}presented in (32) must be at least ten times higher than τ

_{GSC}.

#### 2.5. System Parameters Design of the AFE Converter

_{WT-PMSG}, that is: the current is i

_{MSC}= (2/3)(P

_{WT-PMSG}/v

_{MSC}); the machine-side impedance is Z

_{MSCt}= v

_{MSC}/i

_{MSC}, thus, the MSC works with 15% of the total WT-PMSG impedance, i.e., Z

_{MSC}= (0.15)Z

_{MSCt}; from the WT-PMSG characteristics the following parameters are taken: L

_{MSC}, R

_{MSG}, D, H. The element’s values of the GSC are obtained from the WES nominal power, but to achieve P

_{WES}= P

_{WT-PMSG}i

_{GSC}is generated using i

_{MSC}= (2/3)(P

_{WES}/v

_{GSC}); the grid-side impedance is Z

_{GSCt}=v

_{GSC}/i

_{GSC}the GSC works with 15% of the total WES impedance, i.e.,: Z

_{GSC}= (0.15)Z

_{GSCt}; therefore, L

_{GSC}is calculated with L

_{GSC}= Z

_{GSC}/ω

_{0}, the R

_{GSC}value varies according to the transferred power, in a range from 0.1 Ω to 0.5 Ω; the base WES capacitance C

_{WES}is calculated with C

_{WES}= 1/(Z

_{GSC}ω

_{0}). Then, a better time response in the WES feedback is achieved, since the L

_{MSC}and R

_{MSC}values are used in (10), H and D values are used in (17), L

_{GSC}and R

_{GSC}values are used in (26), to obtain the system feedback gains. It is important to establish that from the generated active power by the GSC, v

_{WES}is kept constant in the presence of any perturbation; for which, it is essential to calculate the correct capacitance value that maintains the DC-link compensation. This is determined from the base DC-link capacitance, i.e., C

_{DC}= (3/8)C

_{WES}, determining the store energy in Equation (30).

## 3. Modeling of the DSPWM Technique Applied in the THD Reduction

_{p}is the carrier signal phase shift angle of each VSC.

_{WT-PMSG}represents the WT-PMSG voltage, v

_{WES}exemplifies the WES voltage, v

_{MSC}

_{,GSC}is the VSC AC-side output voltage of MSC or/and GSC, and ${Z}_{MSC,GSC}^{h,l}$ is the AC-side filter of MSC or/and GSC.

_{MSC}

_{,GSC}value depends on ${M}_{MSC,GSC}^{h,l}$ signal modulation. The modulated and carrier signals implement the DSPWM technique of Figure 3; these have modulation frequencies of 60Hz (ω

_{0}) and 7kHz (fω), respectively.

_{t1,t2p}is the composed carrier signal, θ

_{p}is phase shift angle of each VSC, fω is switching frequency of the carrier signal, t

_{1}is the time for the up-slope, t

_{2}is the time for the down-slope.

_{1}for up-slope is:

_{2}for down-slope is:

_{WES}is the corresponding angle of each phase in the three-phase WES grid.

^{tth}harmonic magnitude.

## 4. Simulation Results: Study Case for WES

^{®}(Matlab r2015b, Mathworks, Natick, MA, USA) and Opal-RT Technologies

^{®}module (OP-5600) (Montreal, QC, Canada) are the main elements in the WES real-time simulation, since the OP-5600 module uses the rapid control prototyping (RCP) concept, which allows testing of the control law without the need for any programming code.

^{®}by a rotor wind model developed by RISOE National Laboratory based on Kaimal spectra. Figure 6b shows the behavior of the WT mechanical torque and the PMSG electric torque in the presence of wind fluctuations. It is possible to observe that the electric torque follows the mechanical torque behavior, due to the effective structure of the MSC closed-loop control.

## 5. Real Time Simulation Results: Study Case for WES using Opal-RT Technologies^{®}

^{®}is simulated; generating an RCP concept that tests the WES dynamics without the need for any programming code. Specifically, the VSC of the AFE converter is composed by the insulated gate bipolar transistor (IGBTs), these use a switching frequency of 7 kHz. Figure 14a shows the wind fluctuations generated by a rotor wind model developed by RISOE National Laboratory based on Kaimal spectra. Figure 14b contains the mechanical torque behavior generated by the wind turbine, and in response to the applied control at the MSC, the PMSG electric torque is able to follow the same behavior.

^{®}. Figure 15a contains the current portion that handles the first VSC connected in parallel; as can be seen, as only three VSCs are connected in parallel, each one handles only a third of the total current generated by the MSC. The total current is presented in Figure 15b, and this is transferred by the WT-PMSG to the AC grid through the AFE converter. In Figure 15c, the generated voltage by the MSC is observed. It is important to mention that the main objective of the GSC is to support the constant DC-link in the presence of any disturbance (such as voltage/current variations due to wind fluctuations or reactive power exchanges by the behavior of the WT). This is evidenced in Figure 15d and is possible due to the applied control robustness. Figure 15e shows the GSC ability to exchange reactive power, that is, the ability of the injection/absorption of 6 MVA into the AC grid. Figure 15f contains the handled current portion by the first VSC connected in parallel at the GSC; similarly, as only three VSCs are connected in parallel, each one handles only a third of the total current generated by the GSC; the total current is presented in Figure 15g. Finally, in Figure 15h, the handled voltage by the GSC is observed, this is taken from the PCC attached to the AC grid. The THD of the handled total current by the GSC is generated through the OPAL-RT

^{®}. The generated THD without phase shift between the carriers of each VSC connected in parallel corresponds to 8.85%. The produced THD once the phase shift between the carriers of each VSC is made corresponds to 2.18%, and the phase shift from equation (33) is calculated; therefore, it is demonstrated that making the WES real-time simulation and applying the phase shift between the carriers of each VSC, the THD can be reduced up to four times.

## 6. Conclusions

^{®}, generating an RCP concept, which tests the WES dynamics without the need for any programming code.

## Author Contributions

## Funding

## Acknowledgments

## Conflicts of Interest

## Nomenclature

α_{GSC} | GSC bandwidth of the closed-loop control |

α_{MSC} | MSC bandwidth of the closed-loop control |

φ | Modulated signal angle |

ϕ | WT-PMSG three-phase angle |

ϕ_{WES} | WES three-phase angle |

λ_{mPMSG} | PMSG maximum flux linkage |

θ_{p} | Phase shift angle of each VSC |

τ_{GSC} | GSC compensator response time |

τ_{MSC} | MSC compensator response time |

τ_{PMSG} | PMSG compensator response time |

ω_{rPMSG} | PMSG rotor angular velocity |

ω_{rPMSGb} | PMSG base rotor angular velocity |

ω_{WTb} | WT base angular velocity |

ω_{o} | WES angular frequency |

AFE | Active Front-End |

C_{t1,t2p} | Composed carrier signal |

C_{DC} | DC-link capacitance |

C_{WES} | WES capacitance |

D | PMSG viscous damping |

DFIG | Double-fed induction generator |

DSPWM | Digital sinusoidal pulse width modulation |

DSPWM_{GSC} | Modulated index vector at GSC |

DSPWM_{MSC} | Modulated index vector at MSC |

E_{GSC} | GSC control input |

E_{MSC} | PMSC control input |

fω | Switching frequency |

GSC | Grid-side VSC |

H | Inertia constant |

i_{GSC} | GSC current |

i_{MSC} | MSC current |

i_{rPMSG} | PMSG rotor current |

I_{DC} | DC-link current |

ki_{GSC} | GSC integral compensator gain |

ki_{MSC} | MSC integral compensator gain |

ki_{rPMSG} | PMSG integral compensator gain |

kp_{GSC} | GSC proportional compensator gain |

kp_{MSC} | MSC proportional compensator gain |

kp_{rPMSG} | PMSG proportional compensator gain |

L_{GSC} | GSC inductance |

L_{MSC} | WT-PMSG armature inductance |

MSC | Machine-side VSC |

p | Number of VSC in parallel |

PCC | Point of Common Coupling |

P_{GSCref} | GSC active power reference |

PMSG | Permanent magnet synchronous generator |

P_{WESb} | WES base power |

P_{WT-PMSGb} | WT-PMSG base power |

P_{AFEb} | AFE converter base power |

Q_{GSCref} | GSC reactive power reference |

Q_{WESref} | WES reactive power reference |

Q_{WES} | WES reactive power |

RCP | Rapid control prototyping |

R_{DC} | DC-link resistance |

R_{GSC} | GSC resistance |

R_{MSC} | MSC resistance |

s | Laplace operator |

SCIG | squirrel-cage induction generator |

Superscript d | d axis of dq reference frame |

Superscript g | MSC dq components vector |

Superscript h | MSC three-phase vector |

Superscript k | VSC dq components vector |

Superscript l | VSC three-phase vector |

Superscript n | Harmonic number |

Superscript q | q axis of dq reference frame |

Superscript ref | Corresponding Reference value |

t_{1} | up-slope time |

t_{2} | down-slope time |

T_{ePMSG} | PMSG electrical torque |

THD | Total Harmonic Distortion |

T_{mWT} | WT mechanical torque |

U_{DC} | Energy capacitor |

v_{GSC} | GSC voltage |

v_{WES} | WES voltage |

v_{WESL-L} | WES line to line voltage |

v_{MSC} | WT-PMSG voltage |

v_{WT} | Wind turbine voltage |

v_{WT-PMSG} | Generated WT-PMSG voltage |

V_{DC} | DC-link voltage |

V_{DCref} | DC-link voltage reference |

VSC | voltage source converter |

WES | Wind Energy System |

WT | Wind Turbine |

Z_{GSCt} | GSC impedance |

Z_{GSC} | Total WES impedance |

Z_{MSC} | Total WT-PMSG impedance |

Z_{MSCt} | MSC impedance |

## References

- Wang, S.; Wang, S. Impacts of wind energy on environment: A review. Renew. Sustain. Energy Rev.
**2015**, 49, 437–443. [Google Scholar] [CrossRef] - Salgado-Herrera, N.M.; Medina-Rios, A.; Tapia-Sánchez, R. Reactive Power Compensation in Wind Energy Systems through Resonant Corrector in Distributed Static Compensator. J. Electr. Power Compon. Syst.
**2017**, 45, 1859–1869. [Google Scholar] [CrossRef] - Yaramasu, V.; Dekka, A.; Durán, M.J.; Kouro, S.; Wu, B. PMSG-based wind energy conversion systems: survey on power converters and controls. IET Electr. Power Appl.
**2017**, 11, 956–968. [Google Scholar] [CrossRef] - Renewable Energy (REN21): Global Status Report, Renewables 2017. Available online: http://www.ren21.net/status-of-renewables/global-status-report/ (accessed on 17 November 2017).
- Global Wind Energy Council (GWEC): Global Wind Report: Annual Market Update. April 2017. Available online: http://www.gwec.net (accessed on 14 January 2018).
- Salgado-Herrera, N.M.; Medina-Ríos, A.; Tapia-Sánchez, R.; Anaya-Lara, O. Reactive power compensation through active back to back converter in type-4 wind turbine. In Proceedings of the 2016 IEEE International Autumn Meeting on Power, Electronics and Computing (ROPEC), Ixtapa, Mexico, 9–11 November 2016; pp. 1–6. [Google Scholar]
- Jlassi, I.; Estima, J.O.; Khil, S.K.E.; Bellaaj, N.M.; Cardoso, A.J.M. Multiple Open-Circuit Faults Diagnosis in Back-to-Back Converters of PMSG Drives for Wind Turbine Systems. IEEE Trans. Power Electron.
**2015**, 30, 2689–2702. [Google Scholar] [CrossRef] - Hu, W.; Chen, Z.; Wang, Y.; Wang, Z. Flicker Mitigation by Active Power Control of Variable-Speed Wind Turbines with Full-Scale Back-to-Back Power Converters. IEEE Trans. Energy Convers.
**2009**, 24, 640–649. [Google Scholar] - Lee, J.S.; Lee, K.B.; Blaabjerg, F. Open-Switch Fault Detection Method of a Back-to-Back Converter Using NPC Topology for Wind Turbine Systems. IEEE Trans. Ind. Appl.
**2015**, 51, 325–335. [Google Scholar] [CrossRef] - Nasiri, M.; Mohammadi, R. Peak Current Limitation for Grid Side Inverter by Limited Active Power in PMSG-Based Wind Turbines During Different Grid Faults. IEEE Trans. Sustain. Energy
**2017**, 8, 3–12. [Google Scholar] [CrossRef] - Juan, Y.L. Single switch three-phase ac to dc converter with reduced voltage stress and current total harmonic distortion. IET Power Electron.
**2014**, 7, 1121–1126. [Google Scholar] [CrossRef] - Ackermann, T. Wind Power in Power Systems, 2nd ed.; John Wiley & Sons Ltd.: Hoboken, NJ, USA, 2012; pp. 203–204. [Google Scholar]
- Salgado-Herrera, N.M.; Mancilla-David, F.; Medina-Ríos, A.; Tapia-Sánchez, R. THD mitigation in type-4 Wind Turbine through AFE Back to back converter. In Proceedings of the 2015 North American Power Symposium (NAPS), Charlotte, NC, USA, 4–6 October 2015; pp. 1–6. [Google Scholar]
- Hou, C.C.; Cheng, P.T. Experimental Verification of the Active Front-End Converters Dynamic Model and Control Designs. IEEE Trans. Power Electron.
**2011**, 26, 1112–1118. [Google Scholar] [CrossRef] - Fioretto, M.; Raimondo, G.; Rubino, L.; Serbia, N.; Marino, P. Evaluation of current harmonic distortion in wind farm application based on Synchronous Active Front End converters. In Proceedings of the IEEE Africon’11, Livingstone, Zambia, 13–15 September 2011; pp. 1–6. [Google Scholar]
- Shen, L.; Bozhko, S.; Asher, G.; Patel, C.; Wheeler, P. Active DC-Link Capacitor Harmonic Current Reduction in Two-Level Back-to-Back Converter. IEEE Trans. Power Electron.
**2016**, 31, 6947–6954. [Google Scholar] [CrossRef] - Cai, X.; Zhang, Z.; Cai, L.; Kennel, R. Current balancing control of high power parallel-connected AFE with small current ripples. In Proceedings of the 2015 9th International Conference on Power Electronics and ECCE Asia (ICPE-ECCE Asia), Seoul, Korea, 1–5 June 2015; pp. 624–630. [Google Scholar]
- Liu, C.; Sun, P.; Lai, J.S.; Ji, Y.; Wang, M.; Chen, C.L.; Cai, G. Cascade dual-boost/buck active-front-end converter for intelligent universal transformer. IEEE Trans. Ind. Electron.
**2012**, 59, 4671–4680. [Google Scholar] [CrossRef] - Hiskens, I.A. Dynamics of Type-3 Wind Turbine Generator Models. IEEE Trans. Power Syst.
**2012**, 27, 465–474. [Google Scholar] [CrossRef] [Green Version] - Yazdani, A.; Iravani, R. Voltage-Sourced Converters in Power Systems: Modeling, Control and Applications; John Wiley & Sons, Inc.: Hoboken, NJ, USA, 2010; pp. 385–412. [Google Scholar]
- Orlando, N.A.; Liserre, M.; Mastromauro, R.A.; Dell’ Aquila, A. A Survey of Control Issues in PMSG-Based Small Wind-Turbine Systems. IEEE Trans. Ind. Inform.
**2013**, 9, 1211–1221. [Google Scholar] [CrossRef] - Salgado-Herrera, N.M.; Medina-Ríos, J.A.; Tapia-Sánchez, R.; Anaya-Lara, O.; Rodríguez-Rodríguez, J.R. DSPWM multilevel technique of 27-levels based on FPGA for the cascaded DC/AC power converter operation. Int. Trans. Electr. Energy Syst.
**2018**, 28. [Google Scholar] [CrossRef]

**Figure 1.**Type-4 wind turbine (WT) connected at wind energy system (WES) through the active front-end (AFE) converter parallel topology.

**Figure 3.**Digital sinusoidal pulse width modulation (DSPWM) signal applied to each voltage source converter (VSC) connected in parallel (phase a).

**Figure 6.**The behavior of the WT mechanical torque and the permanent magnet synchronous generator (PMSG) electric torque in the presence of wind fluctuations. (

**a**) Wind fluctuations; (

**b**) mechanical and electric torque.

**Figure 7.**Current present in machine-side VSC (MSC) of Active Front-End (AFE) parallel converter. (

**a**) (1) VSC; (

**b**) (2) VSC; (

**c**) (3) VSC; (

**d**) total current.

**Figure 8.**DC-Link and Reactive Power controlled by the grid-side VSC (GSC). (

**a**) DC-link voltage; (

**b**) exchange of reactive power in WES.

**Figure 9.**DSPWM signal applied to the control of the first VSC connected in parallel in GSC. (

**a**) Carrier signal; (

**b**) modulated signal; (

**c**) DSPWM.

**Figure 10.**DSPWM signal applied to the control of the second VSC connected in parallel in GSC. (

**a**) Carrier signal; (

**b**) modulated signal; (

**c**) DSPWM.

**Figure 11.**DSPWM signal applied to the control of the third VSC connected in parallel in GSC. (

**a**) Carrier signal; (

**b**) modulated signal; (

**c**) DSPWM.

**Figure 12.**Electrical variables generated by the GSC. (

**a**) Zoom of the handled current at the (1) VSC; (

**b**) the handled current at the (2) VSC; (

**c**) the handled current at the (3) VSC; (

**d**) total current; (

**e**) zoom at the magnitude voltage.

**Figure 13.**THD present at the WES. (

**a**) Without phase shift between carriers of each VSC; (

**b**) with phase shift between carriers of each VSC.

**Figure 14.**Behavior of the WT mechanical torque and the PMSG electric torque in the presence of wind fluctuations simulated in the Opal-RT Technologies

^{®}. (

**a**) Wind fluctuations; (

**b**) Mechanical and Electric torque.

**Figure 15.**Electrical variables generated at the WES simulated in the Opal-RT Technologies

^{®}. (

**a**) The handled current by the (1) VSC of MSC; (

**b**) total current handled by the MSC; (

**c**) voltage present at the MSC; (

**d**) DC-Link voltage controlled by the GSC; (

**e**) reactive Power controlled by the GSC; (

**f**) the handled current by the (1) VSC of GSC; (

**g**) total current handled by the GSC; (

**h**) voltage present at the GSC.

Total Phase Shift (θ_{p}) | Carrier Phase Shift in Each VSC | % Total Harmonic Distortion (THD) | ||
---|---|---|---|---|

θ_{1} | θ_{2} | θ_{3} | ||

0 | 0 | 0 | 0 | 6.8% |

π/6 | 0 | π/18 | π/9 | 4.33% |

π/3 | 0 | π/9 | 2π/9 | 1.99% |

π/2 | 0 | π/6 | π/3 | 2.054% |

2π/3 | 0 | 2π/9 | 4π/9 | 1.271% |

5π/6 | 0 | 5π/18 | 5π/9 | 1.608% |

π | 0 | π/3 | 2π/3 | 4.616% |

7π/6 | 0 | 7π/18 | 7π/9 | 5.635% |

4π/3 | 0 | 4π/9 | 8π/9 | 2.864% |

3π/2 | 0 | π/2 | π | 1.239% |

5π/3 | 0 | 5π/9 | 10π/9 | 1.36% |

11π/6 | 0 | 11π/18 | 11π/9 | 1.867% |

2π | 0 | 2π/3 | 4π/3 | 2.756% |

Wind Turbine (WT) | |||

Nominal output power | 2 MW | Base wind speed | 12 m/s |

Pitch angle | 45 deg | base generator speed | 1.2 pu |

Permanent Magnet Synchronous Generator (PMSG) | |||

Mechanical input | −8.49 × 10^{5} N.m. | Stator resistance | 8.2 × 10^{−4} Ω |

Armature inductance | 1.6 × 10^{−3} H | Flux linkage | 5.82 |

Viscous damping | 4.04 × 10^{3} N.m.s | Inertia | 2.7 × 10^{6} kg.m^{2} |

Pole pairs | 4 | Rotor type | Round |

© 2018 by the authors. Licensee MDPI, Basel, Switzerland. This article is an open access article distributed under the terms and conditions of the Creative Commons Attribution (CC BY) license (http://creativecommons.org/licenses/by/4.0/).

## Share and Cite

**MDPI and ACS Style**

Salgado-Herrera, N.M.; Campos-Gaona, D.; Anaya-Lara, O.; Medina-Rios, A.; Tapia-Sánchez, R.; Rodríguez-Rodríguez, J.R.
THD Reduction in Wind Energy System Using Type-4 Wind Turbine/PMSG Applying the Active Front-End Converter Parallel Operation. *Energies* **2018**, *11*, 2458.
https://doi.org/10.3390/en11092458

**AMA Style**

Salgado-Herrera NM, Campos-Gaona D, Anaya-Lara O, Medina-Rios A, Tapia-Sánchez R, Rodríguez-Rodríguez JR.
THD Reduction in Wind Energy System Using Type-4 Wind Turbine/PMSG Applying the Active Front-End Converter Parallel Operation. *Energies*. 2018; 11(9):2458.
https://doi.org/10.3390/en11092458

**Chicago/Turabian Style**

Salgado-Herrera, Nadia Maria, David Campos-Gaona, Olimpo Anaya-Lara, Aurelio Medina-Rios, Roberto Tapia-Sánchez, and Juan Ramon Rodríguez-Rodríguez.
2018. "THD Reduction in Wind Energy System Using Type-4 Wind Turbine/PMSG Applying the Active Front-End Converter Parallel Operation" *Energies* 11, no. 9: 2458.
https://doi.org/10.3390/en11092458