# Fault Ride-Through Enhancement of Grid Supporting Inverter-Based Microgrid Using Delayed Signal Cancellation Algorithm Secondary Control

^{1}

^{2}

^{*}

## Abstract

**:**

## 1. Introduction

## 2. Grid Supporting Microgrid Modeling

#### 2.1. Output LC Filter

_{f}and shunt capacitance C

_{f}. The grid impedance or transformer leakage inductance or both serve as coupling inductor [58]. The LC filter arrangement depicted is used for the grid-connected inverter with local load in between. This work focuses on the parallel operation of inverter-based microgrid with a local load while in grid supporting mode. Consequently, the LC filter is used in inverter output considering the presence grid impedance between the microgrid and the host grid. The cut-off frequency f

_{c}of the LC filter is given by

#### 2.2. Grid Synchronization

_{q}to zero.

#### 2.3. Primary Control

#### 2.3.1. Droop-Based Power Control

_{p}and k

_{q}are the coefficients of the frequency and voltage droops of the inverter, respectively. Similarly, P* and Q* are active and reactive power references, respectively. Furthermore, the measured output of active power and reactive power are signified by P

_{m}and Q

_{m}, respectively. Also, ω* signifies the set-point frequency while E* is the rated set-point amplitude of the voltage. Hence, voltage magnitude and frequency are set by the coefficients of the voltage and frequency droops specified for the active power and reactive power. In Equation (4), droop control shares every load change among inverters by adjusting the frequency by the specified coefficient of frequency-active power droop. In a grid-supporting VSI, the measured active power and reactive power P

_{m}and Q

_{m}at any point in time are computed using the measured output three-phase current and voltage transformed to the equivalent direct-quadrature components as depicted in Equation (5) at the fundamental frequency of ω*

#### 2.3.2. Power/Voltage Loop Control

_{d}and v*

_{q}) of direct-quadrature axes based on its synchronization with the grid. Consequently, the voltage/power loop control uses the v*

_{d}and v*

_{q}to generates the references currents (i*

_{d}and i*

_{q}) for the direct-quadrature axes components using the measured active power and reactive power as given in the Equations (4) and (5) and shown in Figure 2. This control can also be realized with a PI control scheme such that the controller output is given by

_{IV}and k

_{PV}are the integral gain and proportional gain of the voltage PI control respectively. The v

_{dp}is the drop in voltage due to the grid or virtual impedance.

_{d}and i*

_{q}, generated are computed using the output of the droop power-sharing P

_{m}and Q

_{m}such that

_{d}is constant and the active power is regulated by adjusting the current i

_{d}. Similarly, the reactive power regulated through the current i

_{q}control. Therefore, the active power and reactive power transferred to the AC side is determined by making P

_{m}and Q

_{m}the subjects of the formulas in terms of stationary quantities in Equation (7) [66].

#### 2.3.3. Current Loop Control

_{d}and i*

_{q}, generated by the loop of voltage control, the loop of current control generates reference voltage (u

_{d}and u

_{q}) of direct-quadrature-axes for the PWM. This control is realized using a PI controller such that the controller output is expressed as

_{ii}and k

_{pi}denote integral and proportional gains of the current control loop respectively. The direct-quadrature axes components v

_{d}and v

_{q}of the voltage signify the feed-forward quantities while +(ωL)i*

_{q}and −(ωL)i*

_{d}signify the cross decoupled quantities. The feed-forward and cross decoupled quantities are employed to accomplish independent d–q axis current controls. Lastly, L in the cross-decoupled quantities is the output filter inductor.

## 3. Proposed LVRT/FRT Scheme

#### 3.1. Secondary Voltage Control

_{N}signifies the rated grid voltage at nominal value, reactive power Q

_{N}corresponds to the rated reactive current of the inverter and reactive power reference Q

_{ref}corresponds to the required reactive current that will be injected

_{.}of the microgrid. The reference required signal of reactive current is obtained in the same degree with the depth of voltage sag on the grid, through the proposed secondary control loop. Once this voltage falls below 0.9 of the nominal value, the secondary control scheme will instantly commence reactive current/power support as shown in the Equation (9). The injection of reactive power/current is systematically regulated to ensure the restoration of voltage above 0.9 of the nominal value, instead of exactly 0.9 V

_{N}. The immediate detection of faults in systems is crucial in enhancing the overall reliability, productivity, and safety, hence the Clarke transformation of the measured grid voltage is done using Equation (9) and shown in Figure 4. The magnitude is conditioned using a first-order low pass filter and subsequently monitored. The essence of this is to prevent and unnecessary activation of the anti-parallel IGBT-diode switching arrangement for the inductance. With this, fault occurrence and clearance are detected with 0.05 s as shown in the results.

#### 3.2. DSC Algorithm for Unbalance Detection and PCC Voltage

_{qp}and v

_{qn}are subsequently kept for half a period in two independent data buffers. Lastly, the positive component and negative component final samples are obtained and immediately kept in the two buffers at a time equivalent to half a period. The components and their additions are expressed in Equations (13)–(16):

_{p}injected into the grid while considering power electronic switch thresholds. Similarly, the PCC voltage negative sequence control restores quadrature component to the zero references of normal condition. This balances and buffers the further PCC voltage unbalance introduced through reactive power injection into the grid.

## 4. Power Flow and Switched Reactor

#### 4.1. Voltage Source Inverter and Grid Interactive Power Flow

_{i}signifies the VSI voltage and v

_{g}represents the grid voltage. Similarly, the inherent impedances of the inverter and its filter circuit are lumped together as Z

_{i}while the grid impedance is represented as Z

_{g}. The load current and impedance are signified by I

_{L}and Z

_{L}. These aforementioned impedances are typically inductive owing to the significant output inductance of the VSI. Nevertheless, this inverter impedance can be greatly influenced by the type of control strategy employed [70], and grid impedance is highly resistive in low-voltage distribution feeder lines [71]. Similarly, the impedance (resistance and inductive reactance) of the grid is significantly present and taken into consideration in microgrids located at a long distance away far from the host grid. Consequently, this work put into consideration the line impedance of the grid. In line with the stipulation of the grid codes, only reactive current is injected all through the period of voltage sag. Consequently, the resulting compensating voltage is relatively in phase with the grid voltage.

#### 4.2. Switched Inductance: Sizing and Switching

_{g}represents the phase voltage of the host grid, V

_{mg}represents phase voltage within the microgrid. Similarly, X

_{n}signifies needed switched inductive reactance while I

_{n}signifies current flow across X

_{n}. The inverter voltage is therefore given by

_{n}the subject of the formula in Equation (18). It is therefore given as

_{i}is in phase with the current flowing through the switched inductance X

_{n}, hence angle θ is calculated from

#### 4.3. Active Power Referencing and Fault Current Limiting

_{rated}represents the maximum tolerance in which the active reference limit triggers and S

_{max}represents the inverter maximum complex power specified by the manufacturer. The maximum complex power confines the references of active power and reactive power within its value as shown in Equation (23).

## 5. Results and Discussions

#### 5.1. Symmetrical Fault

#### 5.2. Asymmetrical Fault

_{ab}, V

_{bc}, and V

_{ca}. Applying NEMA (National Equipment Manufacturer Association in the United States of America) voltage unbalance definition which is given as the ratio of maximum deviation from the mean phase to phase voltage to mean of phase to phase voltages, the unbalance within the grid under L-G fault is calculated. Similarly, the unbalance calculated for other types of asymmetrical faults are given in Table 6. The proposed control actively compensated the unbalance in line to line voltages by reducing the unbalance to relatively negligible percentages.

## 6. Conclusions

## Author Contributions

## Funding

## Conflicts of Interest

## References

- Viral, R.; Khatod, D.K. Optimal planning of distributed generation systems in distribution system: A review. Renew. Sustain. Energy Rev.
**2012**, 16, 5146–5165. [Google Scholar] [CrossRef] - Tan, X.; Li, Q.; Wang, H. Advances and trends of energy storage technology in Microgrid. Int. J. Electr. Power Energy Syst.
**2013**, 44, 179–191. [Google Scholar] [CrossRef] - Lai, J.; Lu, X.; Li, X.; Tang, R.-L. Distributed Multiagent-Oriented Average Control for Voltage Restoration and Reactive Power Sharing of Autonomous Microgrids. IEEE Access
**2018**, 6, 25551–25561. [Google Scholar] [CrossRef] - Strasser, T.; Andren, F.; Kathan, J.; Cecati, C.; Buccella, C.; Siano, P.; Leitao, P.; Zhabelova, G.; Vyatkin, V.; Vrba, P.; et al. A Review of Architectures and Concepts for Intelligence in Future Electric Energy Systems. IEEE Trans. Ind. Electron.
**2015**, 62, 2424–2438. [Google Scholar] [CrossRef] - Saleem, H.A. Microgrid Modeling and Grid Interconnection Studies. Master’s Thesis, University of Tennessee, Knoxville, TN, USA, 2014. [Google Scholar]
- Lu, X.; Wang, J.; Guerrero, J.M. Virtual Impedance Based Fault Current Limiters for Inverter Dominated AC Microgrids. IEEE Trans. Smart Grid
**2018**, 3053, 1599–1612. [Google Scholar] [CrossRef] - Khadkikar, V. Enhancing Electric Power Quality Using UPQC: A Comprehensive Overview. IEEE Trans. Power Electron.
**2012**, 27, 2284–2297. [Google Scholar] [CrossRef] - Sadeghkhani, I.; Esmail, M.; Golshan, H. A Current Limiting Strategy to Improve Fault Ride-Through of Inverter Interfaced Autonomous Microgrids. IEEE Trans. Smart Grid
**2017**, 8, 2138–2148. [Google Scholar] [CrossRef] - Pogaku, N.; Prodanović, M.; Green, T.C. Modeling, analysis and testing of autonomous operation of an inverter-based microgrid. IEEE Trans. Power Electron.
**2007**, 22, 613–625. [Google Scholar] [CrossRef] - Rocabert, J.; Luna, A.; Blaabjerg, F.; Rodriguez, P. Control of Power Converters in AC Microgrids. IEEE Trans. Power Electron.
**2012**, 27, 4734–4749. [Google Scholar] [CrossRef] - Baghaee, H.R.; Mirsalim, M.; Gharehpetian, G.B.; Talebi, H.A. A new current limiting strategy and fault model to improve fault ride-through capability of inverter interfaced DERs in autonomous microgrids. Sustain. Energy Technol. Assess.
**2017**, 24, 71–81. [Google Scholar] [CrossRef] - Guerrero, J.M.; GarciadeVicuna, L.; Matas, J.; Castilla, M.; Miret, J. A Wireless Controller to Enhance Dynamic Performance of Parallel Inverters in Distributed Generation Systems. IEEE Trans. Power Electron.
**2004**, 19, 1205–1213. [Google Scholar] [CrossRef] - Roslan, A.M.; Ahmed, K.H.; Finney, S.J.; Williams, B.W. Improved Instantaneous Average Current-Sharing Control Scheme for Parallel-Connected Inverter Considering Line Impedance Impact in Microgrid Networks. IEEE Trans. Power Electron.
**2011**, 26, 702–716. [Google Scholar] [CrossRef] - Caldognetto, T.; Tenti, P. Microgrids Operation Based on Master–Slave Cooperative Control. IEEE J. Emerg. Sel. Top. Power Electron.
**2014**, 2, 1081–1088. [Google Scholar] [CrossRef] - Wang, C.; Li, X.; Guo, L.; Li, Y. A seamless operation mode transition control strategy for a microgrid based on master-slave control. Sci. China Technol. Sci.
**2012**, 55, 1644–1654. [Google Scholar] [CrossRef] - Papadimitriou, C.N.; Zountouridou, E.I.; Hatziargyriou, N.D. Review of hierarchical control in DC microgrids. Electr. Power Syst. Res.
**2015**, 122, 159–167. [Google Scholar] [CrossRef] - Tayab, U.B.; Roslan, M.A.B.; Hwai, L.J.; Kashif, M. A review of droop control techniques for microgrid. Renew. Sustain. Energy Rev.
**2017**, 76, 717–727. [Google Scholar] [CrossRef] - Zhao, X.; Guerrero, J.M.; Savaghebi, M.; Vasquez, J.C.; Wu, X.; Sun, K. Low-Voltage Ride-Through Operation of Power Converters in Grid-Interactive Microgrids by Using Negative-Sequence Droop Control. IEEE Trans. Power Electron.
**2017**, 32, 3128–3142. [Google Scholar] [CrossRef] - Kroposki, B.; Pink, C.; DeBlasio, R.; Thomas, H.; Simões, M.; Sen, P.K. Benefits of Power Electronic Interfaces for Distributed Energy Systems. IEEE Trans. Energy Convers.
**2010**, 25, 901–908. [Google Scholar] [CrossRef] [Green Version] - Gkavanoudis, S.I.; Demoulias, C.S. A Control Strategy for Enhancing the Fault Ride-Through Capability of a Microgrid During Balanced and Unbalanced Grid Voltage Sags. Sustain. Energy Grids Netw.
**2015**, 3, 1–11. [Google Scholar] [CrossRef] - Glover, J.D.; Sarma, M.S.; Overbye, T.J. Power System Analysis and Design, 5th ed.; Global Engineering Publisher: Stamford, CT, USA, 2012; ISBN 9781111425777. [Google Scholar]
- Kothari, D.P.; Nagrath, I.J. Modern Power System Analysis, 3rd ed.; Tata McGraw Hill Education Private Limited: New Delhi, India, 2003; ISBN 9780070494893. [Google Scholar]
- Buraimoh, E.; Davidson, I.E. Comparative Analysis of the Fault Ride-Through Capabilities of the VSG Methods of Microgrid Inverter Control under Faults. In Proceedings of the SAUPEC/RobMech/PRASA 2019, Bloemfontein, South Africa, 28–30 January 2019; pp. 400–405. [Google Scholar]
- Ramana Reddy, K.V.; Ramesh Babu, N.; Sanjeevikumar, P. A Review on Grid Codes and Reactive Power Management in Power Grids with WECS; Springer: Singapore, 2018; pp. 525–539. [Google Scholar]
- Meegahapola, L.; Datta, M.; Nutkani, I.; Conroy, J. Role of fault ride-through strategies for power grids with 100% power electronic-interfaced distributed renewable energy resources. Wiley Interdiscip. Rev. Energy Environ.
**2018**, 7, e292. [Google Scholar] [CrossRef] - Wang, X.; Yang, Z.; Fan, B.; Xu, W. Control Strategy of Three-Phase Photovoltaic Inverter under Low-Voltage Ride-Through Condition. Math. Probl. Eng.
**2015**, 2015, 1–23. [Google Scholar] [CrossRef] - Zhao, X. Power System Support Functions Provided by Smart Inverters—A Review. CPSS Trans. Power Electron. Appl.
**2018**, 3, 25–35. [Google Scholar] [CrossRef] - Luna, A.; Rocabert, J.; Candela, J.I.; Hermoso, J.R.; Teodorescu, R.; Blaabjerg, F.; Rodriguez, P. Grid Voltage Synchronization for Distributed Generation Systems Under Grid Fault Conditions. IEEE Trans. Ind. Appl.
**2015**, 51, 3414–3425. [Google Scholar] [CrossRef] - Chen, L.; Chen, H.; Yang, J.; Zhu, L.; Tang, Y.; Koh, L.H.; Xu, Y.; Zhang, C.; Liao, Y.; Ren, L. Comparison of Superconducting Fault Current Limiter and Dynamic Voltage Restorer for LVRT Improvement of High Penetration Microgrid. IEEE Trans. Appl. Supercond.
**2017**, 27, 1–7. [Google Scholar] [CrossRef] - Rezkallah, M.; Chandra, A.; Hamadi, A.; Ibrahim, H.; Ghandour, M. Power Quality in Smart Grids. In Pathways to a Smarter Power System; Elsevier Ltd.: Amsterdam, The Netherlands, 2019; pp. 225–245. ISBN 9780081025925. [Google Scholar]
- Hagh, M.T.; Khalili, T. A Review of Fault Ride-Through of PV and Wind Renewable Energies in Grid Codes. Int. J. Energy Res.
**2018**, 43, 1342–1356. [Google Scholar] [CrossRef] - Kou, W.; Wei, D. Fault ride through strategy of inverter-interfaced microgrids embedded in distributed network considering fault current management. Sustain. Energy Grids Netw.
**2018**, 15, 43–52. [Google Scholar] [CrossRef] - Zamani, M.A.; Yazdani, A.; Sidhu, T.S. A Control Strategy for Enhanced Operation of Inverter-Based Microgrids Under Transient Disturbances and Network Faults. IEEE Trans. Power Deliv.
**2012**, 27, 1737–1747. [Google Scholar] [CrossRef] - Buraimoh, E.; Davidson, I.E. Development of an IGBT-Diode based Fault Current Limiter for Fault Ride-Through Enhancement in Microgrid Application. In Proceedings of the IEEE PES/IAS PowerAfrica, Abuja, Nigeria, 20–23 August 2019; pp. 190–195. [Google Scholar]
- He, H.; Chen, L.; Yin, T.; Cao, Z.; Yang, J.; Tu, X.; Ren, L. Application of a SFCL for Fault Ride-Through Capability Enhancement of DG in a Microgrid System and Relay Protection Coordination. IEEE Trans. Appl. Supercond.
**2016**, 26, 1–8. [Google Scholar] [CrossRef] - Choi, D.H.; Yoo, J.I.; Kim, D.; Lee, S.H.; Park, J.W. Analysis on Effect of SFCL Applied to an Isolated Microgrid with a Dynamic Load Model. IEEE Trans. Appl. Supercond.
**2017**, 27, 1–4. [Google Scholar] [CrossRef] - Naderi, S.B.; Negnevitsky, M.; Jalilian, A.; Tarafdar Hagh, M.; Muttaqi, K.M. Optimum Resistive Type Fault Current Limiter: An Efficient Solution to Achieve Maximum Fault Ride-Through Capability of Fixed-Speed Wind Turbines During Symmetrical and Asymmetrical Grid Faults. IEEE Trans. Ind. Appl.
**2017**, 53, 538–548. [Google Scholar] [CrossRef] - Rashid, G.; Ali, M.H. Fault ride through capability improvement of DFIG based wind farm by fuzzy logic controlled parallel resonance fault current limiter. Electr. Power Syst. Res.
**2017**, 146, 1–8. [Google Scholar] [CrossRef] - Ghanbari, T.; Farjah, E. Unidirectional Fault Current Limiter: An Efficient Interface Between the Microgrid and Main Network. IEEE Trans. Power Syst.
**2013**, 28, 1591–1598. [Google Scholar] [CrossRef] - Piya, P.; Ebrahimi, M.; Karimi-Ghartemani, M.; Khajehoddin, S.A. Fault Ride-Through Capability of Voltage-Controlled Inverters. IEEE Trans. Ind. Electron.
**2018**, 65, 7933–7943. [Google Scholar] [CrossRef] - Palizban, O.; Kauhaniemi, K.; Guerrero, J.M. Microgrids in active network management—Part I: Hierarchical control, energy storage, virtual power plants, and market participation. Renew. Sustain. Energy Rev.
**2014**, 36, 428–439. [Google Scholar] [CrossRef] - Palizban, O.; Kauhaniemi, K.; Guerrero, J.M. Microgrids in active network management—Part II: System operation, power quality and protection. Renew. Sustain. Energy Rev.
**2014**, 36, 440–451. [Google Scholar] [CrossRef] - Li, X.; Zhang, H.; Shadmand, M.B.; Balog, R.S. Model Predictive Control of a Voltage-Source Inverter with Seamless Transition between Islanded and Grid-Connected Operations. IEEE Trans. Ind. Electron.
**2017**, 64, 7906–7918. [Google Scholar] [CrossRef] - Kleftakis, V.; Lagos, D.; Papadimitriou, C.; Hatziargyriou, N.D. Seamless Transition between Interconnected and Islanded Operation of DC Microgrids. IEEE Trans. Smart Grid
**2019**, 10, 248–256. [Google Scholar] [CrossRef] - Ochs, D.S.; Mirafzal, B.; Sotoodeh, P. A method of seamless transitions between grid-tied and stand-alone modes of operation for utility-interactive three-phase inverters. IEEE Trans. Ind. Appl.
**2014**, 50, 1934–1941. [Google Scholar] [CrossRef] - Micallef, A.; Apap, M.; Spiteri-Staines, C.; Guerrero, J.M. Single-Phase Microgrid with Seamless Transition Capabilities between Modes of Operation. IEEE Trans. Smart Grid
**2015**, 6, 2736–2745. [Google Scholar] [CrossRef] - Rasheduzzaman, M.; Kimball, J.W. Modeling and Tuning of an Improved Delayed-Signal-Cancellation PLL for Microgrid Application. IEEE Trans. Energy Convers.
**2019**, 34, 712–721. [Google Scholar] [CrossRef] - Gude, S.; Chu, C.C. Three-Phase PLLs by Using Frequency Adaptive Multiple Delayed Signal Cancellation Prefilters under Adverse Grid Conditions. IEEE Trans. Ind. Appl.
**2018**, 54, 3832–3844. [Google Scholar] [CrossRef] - Huang, Q.; Rajashekara, K. An Improved Delayed Signal Cancellation PLL for Fast Grid Synchronization under Distorted and Unbalanced Grid Condition. IEEE Trans. Ind. Appl.
**2017**, 53, 4985–4997. [Google Scholar] [CrossRef] - Karimi, M.; Mokhtari, H.; Iravani, M.R. Wavelet based on-line disturbance detection for power quality applications. IEEE Trans. Power Deliv.
**2000**, 15, 1212–1220. [Google Scholar] [CrossRef] - Mokhtari, H.; Karimi-Ghartemani, M.; Iravani, M.R. Experimental performance evaluation of a wavelet-based on-line voltage detection method for power quality applications. IEEE Trans. Power Deliv.
**2002**, 17, 161–172. [Google Scholar] [CrossRef] - Cardenas, R.; Diaz, M.; Rojas, F.; Clare, J. Fast Convergence Delayed Signal Cancellation Method for Sequence Component Separation. IEEE Trans. Power Deliv.
**2015**, 30, 2055–2057. [Google Scholar] [CrossRef] - Golestan, S.; Freijedo, F.D.; Vidal, A.; Yepes, A.G.; Guerrero, J.M.; Doval-Gandoy, J. An Efficient Implementation of Generalized Delayed Signal Cancellation PLL. IEEE Trans. Power Electron.
**2016**, 31, 1085–1094. [Google Scholar] [CrossRef] - Contreras, C.; Guajardo, D.; Diaz, M.; Rojas, F.; Espinoza, M.; Cardenas, R. Fast Delayed Signal Cancellation based PLL for unbalanced grid conditions. In Proceedings of the 2018 IEEE International Conference on Automation/Congress of the Chilean Association of Automatic Control, Concepción, Chile, 17–19 October 2018; pp. 1–6. [Google Scholar]
- Wang, Y.F.; Li, Y.W. Analysis and digital implementation of cascaded delayed-signal-cancellation PLL. IEEE Trans. Power Electron.
**2011**, 26, 1067–1080. [Google Scholar] [CrossRef] - Mahlooji, M.H.; Mohammadi, H.R.; Rahimi, M. A review on modeling and control of grid-connected photovoltaic inverters with LCL filter. Renew. Sustain. Energy Rev.
**2018**, 81, 563–578. [Google Scholar] [CrossRef] - Ahmad, A.A.; Abrishamifar, A.; Farzi, M. A New Design Procedure for Output LC Filter of Single Phase Inverters. In Proceedings of the 3rd International Conference on Power Electronics and Intelligent Transportation System, Shenzhen, China, 13–14 November 2010; pp. 86–91. [Google Scholar]
- Gomes, C.C.; Cupertino, A.F.; Pereira, H.A. Damping techniques for grid-connected voltage source converters based on LCL filter: An overview. Renew. Sustain. Energy Rev.
**2018**, 81, 116–135. [Google Scholar] [CrossRef] - Che, L.; Shahidehpour, M.; Alabdulwahab, A.; Al-Turki, Y. Hierarchical Coordination of a Community Microgrid With AC and DC Microgrids. IEEE Trans. Smart Grid
**2015**, 6, 3042–3051. [Google Scholar] [CrossRef] - Dissanayake, A.M.; Ekneligoda, N.C. Transient Optimization of Parallel Connected Inverters in Islanded AC Microgrids. IEEE Trans. Smart Grid
**2018**, 10, 1–12. [Google Scholar] [CrossRef] - Guo, Y.; Lu, X.; Chen, L.; Zheng, T.; Wang, J.; Mei, S. Functional-Rotation—Based Active Dampers in AC Microgrids with Multiple Parallel Interface. IEEE Trans. Ind. Appl.
**2018**, 9994, 1–9. [Google Scholar] [CrossRef] - Wei, B.; Guerrero, J.M.; Vásquez, J.C.; Guo, X. A Circulating-Current Suppression Method for Parallel Connected Voltage Source Inverters (VSI) with Common DC and AC Buses Xiaoqiang Guo. IEEE Trans. Ind. Appl.
**2017**, 9994, 1–11. [Google Scholar] - Sun, Y.; Hou, X.; Yang, J.; Han, H.; Su, M.; Guerrero, J.M. New Perspectives on Droop Control in AC Microgrid. IEEE Trans. Ind. Electron.
**2017**, 64, 5741–5745. [Google Scholar] [CrossRef] [Green Version] - Mehrasa, M.; Pouresmaeil, E.; Sepehr, A.; Pournazarian, B.; Marzband, M.; Catalão, J.P.S. Control technique for the operation of grid-tied converters with high penetration of renewable energy resources. Electr. Power Syst. Res.
**2019**, 166, 18–28. [Google Scholar] [CrossRef] - Liu, J.; Miura, Y.; Bevrani, H.; Ise, T. Enhanced Virtual Synchronous Generator Control for Parallel Inverters in Microgrids. IEEE Trans. Smart Grid
**2017**, 8, 2268–2277. [Google Scholar] [CrossRef] - Ramirez, D.; Martinez-Rodrigo, F.; de Pablo, S.; Carlos Herrero-de Lucas, L. Assessment of a non linear current control technique applied to MMC-HVDC during grid disturbances. Renew. Energy
**2017**, 101, 945–963. [Google Scholar] [CrossRef] - Morales, A.; Robe, X.; Sala, M.; Prats, P.; Aguerri, C.; Torres, E. Advanced grid requirements for the integration of wind farms into the Spanish transmission system. IET Renew. Power Gener.
**2008**, 2, 47–59. [Google Scholar] [CrossRef] [Green Version] - Jiménez, F.; Gómez-Lázaro, E.; Fuentes, J.A.; Molina-García, A.; Vigueras-Rodríguez, A. Validation of a double fed induction generator wind turbine model and wind farm verification following the Spanish grid code. Wind Energy
**2012**, 15, 645–659. [Google Scholar] [CrossRef] - Bakkar, M.; Bogarra, S.; Córcoles, F.; Saura, J.; Moreno, M. Power Control Strategies During Voltage Sags According to Spanish Grid Code. Renew. Energy Power Qual. J.
**2018**, 1, 493–498. [Google Scholar] [CrossRef] - Chen, X.; Zhang, Y.; Wang, S.; Chen, J.; Gong, C. Impedance-Phased Dynamic Control Method for Grid-Connected Inverters in a Weak Grid. IEEE Trans. Power Electron.
**2017**, 32, 274–283. [Google Scholar] [CrossRef] - Davari, M.; Mohamed, Y.A.-R.I. Robust Vector Control of a Very Weak-Grid-Connected Voltage-Source Converter Considering the Phase-Locked Loop Dynamics. IEEE Trans. Power Electron.
**2017**, 32, 977–994. [Google Scholar] [CrossRef] - Sadeghkhani, I.; Esmail, M.; Golshan, H.; Mehrizi-sani, A.; Guerrero, J.M. Low-Voltage Ride-Through of A Droop-Based Three-Phase Four-Wire Grid-Connected Microgrid. IET Gener. Transm. Distrib.
**2018**, 12, 1906–1914. [Google Scholar] [CrossRef] - Camacho, A.; Castilla, M.; Miret, J.; Vasquez, J.C.; Alarcon-Gallo, E. Flexible Voltage Support Control for Three-Phase Distributed Generation Inverters Under Grid Fault. IEEE Trans. Ind. Electron.
**2013**, 60, 1429–1441. [Google Scholar] [CrossRef] - Camacho, A.; Castilla, M.; Miret, J.; Borrell, A.; de Vicuna, L.G. Active and Reactive Power Strategies With Peak Current Limitation for Distributed Generation Inverters During Unbalanced Grid Faults. IIEEE Trans. Ind. Electron.
**2015**, 62, 1515–1525. [Google Scholar] [CrossRef] - Haque, M.M.; Wolfs, P. A review of high PV penetrations in LV distribution networks: Present status, impacts and mitigation measures. Renew. Sustain. Energy Rev.
**2016**, 62, 1195–1208. [Google Scholar] [CrossRef] - Standard EN 50160. Voltage Characteristics of Electricity Supploed by Public Distribution Systems; European Committee on Electro-Technical Standardization: Brussels, Belgium, 2001. [Google Scholar]
- International Electrotechnical Commission. Limits for Harmonic Current Emissions; International Electrotechnical Commission: Geneva, Switzerland, 2000. [Google Scholar]
- Sadeghkhani, I.; Golshan, M.E.H.; Mehrizi-Sani, A.; Guerrero, J.M.; Ketabi, A. Transient Monitoring Function-Based Fault Detection for Inverter-Interfaced Microgrids. IEEE Trans. Smart Grid
**2018**, 9, 2097–2107. [Google Scholar] [CrossRef] - Dhar, S.; Patnaik, R.K.; Dash, P.K. Fault Detection and Location of Photovoltaic Based DC Microgrid Using Differential Protection Strategy. IEEE Trans. Smart Grid
**2018**, 9, 4303–4312. [Google Scholar] [CrossRef]

**Figure 1.**FRT/LVRT curves defined by Spanish grid code [26].

**Figure 2.**Grid-connected inverter interfaced DER primary control consisting droop, voltage, and current control loops.

**Figure 4.**Reactive currents injection/absorbed during faults, according to Spanish network code P.O. 12.2 Spanish grid code requirements [45].

Parameters | Descriptions | Values |
---|---|---|

kVA_{1} | DER 1 rated power | 12 kVA |

kVA_{2} | DER 2 rated power | 6 kVA |

V _{abc} | Voltage (phase-phase) | 400 V |

V _{dc} | DC bus voltage | 1100 V |

f | Frequency | 50 Hz |

C | LC filter capacitance | 2.31 μF |

L | LC filter inductance | 11 mH |

Parameters | Descriptions | Values |
---|---|---|

ω_{cut} | Cut-off angular frequency | 100π |

E | Single-phase voltage reference | 330 V |

K_{p I} | Direct-quadrature current loop P gain | 100 |

K_{i I} | Direct-quadrature current loop I gain | 1000 |

K_{p PCC+-} | Positive sequence and negative sequence P gain | 0.0125 |

K_{i PCC+-} | Positive sequence and negative sequence I gain | 2 |

Parameters | Descriptions | Values |
---|---|---|

f _{min} | PLL minimum frequency | 45 Hz |

K_{p PLL} | Regulator P gain | 180 |

K_{i PLL} | Regulator I gain | 3200 |

K_{d PLL} | Regulator D gain | 1 |

Parameters | Descriptions | Values |
---|---|---|

L_{r} | Reactor inductance | 0.005 |

R_{on} | Switch internal resistance | 0.001 |

R_{s} | Switch snubber resistance | 0.00001 |

Voltage Sag | DER | Signal | Total Harmonic Distortion (%) | ||
---|---|---|---|---|---|

Pre-Fault | Fault | Post-Fault | |||

70% | 1 | Voltage | 0.33 | 1.17 | 0.33 |

Current | 2.01 | 2.15 | 1.99 | ||

2 | Voltage | 0.33 | 1.17 | 0.33 | |

Current | 3.94 | 1.50 | 3.67 | ||

60% | 1 | Voltage | 0.32 | 1.20 | 0.33 |

Current | 2.06 | 2.06 | 2.09 | ||

2 | Voltage | 0.32 | 1.20 | 0.33 | |

Current | 3.78 | 3.64 | 3.74 | ||

50% | 1 | Voltage | 0.32 | 1..25 | 0.33 |

Current | 2.06 | 2.05 | 2.01 | ||

2 | Voltage | 0.32 | 1.25 | 0.33 | |

Current | 3.78 | 3.37 | 3.84 |

Fault Type | Voltage Unbalance | |
---|---|---|

Grid | Microgrid | |

L-G | 24.14% | 4.44% |

L-L-G | 24.31% | 7.13% |

L-L | 35.36% | 12.20% |

© 2019 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**

Buraimoh, E.; Davidson, I.E.; Martinez-Rodrigo, F.
Fault Ride-Through Enhancement of Grid Supporting Inverter-Based Microgrid Using Delayed Signal Cancellation Algorithm Secondary Control. *Energies* **2019**, *12*, 3994.
https://doi.org/10.3390/en12203994

**AMA Style**

Buraimoh E, Davidson IE, Martinez-Rodrigo F.
Fault Ride-Through Enhancement of Grid Supporting Inverter-Based Microgrid Using Delayed Signal Cancellation Algorithm Secondary Control. *Energies*. 2019; 12(20):3994.
https://doi.org/10.3390/en12203994

**Chicago/Turabian Style**

Buraimoh, Elutunji, Innocent E. Davidson, and Fernando Martinez-Rodrigo.
2019. "Fault Ride-Through Enhancement of Grid Supporting Inverter-Based Microgrid Using Delayed Signal Cancellation Algorithm Secondary Control" *Energies* 12, no. 20: 3994.
https://doi.org/10.3390/en12203994