Neuro-fuzzy current controller for three-level cascade inverter based D-STATCOM


Distribution STATCOM (D-STATCOM) is a custom power device connected in parallel to power system. In this paper, Neuro-Fuzzy Controller (NFC) which has robust structure is proposed for control of D-STATCOM’s dq-axis currents. Designed NFC is first order Mamdani type NFC structure and has two inputs, one output and six layers. DSTATCOM is based on three-level cascaded inverter and this inverter is controlled with Sinusoidal Pulse Width Modulation (SPWM) technique. dSPACE’s DS1103 control card is used for real-time implementation of D-STATCOM’s control algorithm. The performance of D-STATCOM using NFC is evaluated by changing of reference reactive current (iqref) as on-line. Under this condition, some experimental results obtained from experimental setup are given.


  2. Neuro-Fuzzy Current Controller
  3. SPWM
  4. Three-Level Cascade Inverter



Fig.1. Three-level cascaded inverter based D-STATCOM



Fig.2. Changing of dc link voltages

 Fig.3. iqref tracking performance of iq

Fig.4. Phase-a current and voltage waveforms of D-STATCOM


Fig.5. Changing of modulation index

Fig.6. Changing of phase angle


In this paper, NFC is developed to synthesize the current control loop of D-STATCOM. NFC which is a combination of ANN and FLC gives the D-STATCOM a good dynamic response and excellent tracking ability in changing of iqref. Experimental results show that Neuro-Fuzzy current controlled D-STATCOM can provide the desired reactive power exact and fast within own rated power limits even in the worst operating condition.


[1] S. Mohagheghi, “Adaptive Critic Designs Based Neuro-Controllers for Local and Wide Area Control of a Multimachine Power System with A Static Compensator,” Phd. Thesis, Georgia Institute of Technology, 2006.

[2] C. Schauder, H. Mehta, “Vector Analysis and Control of Advanced Static VAr Compensators,” Generation, Transmission and Distribution, IEE Proceedings C, vol.140, pp. 299-360, 1993.

[3] V. Blasko, V. Kaura, “A New Mathematical Model and Control of A Three-Phase AC-DC Voltage Source Converter,” IEEE Transactions on Power Electronics, vol.12, pp. 116-123, 1997.

[4] P. W. Lehn, M. R. Iravani, “Experimental Evaluation of STATCOM Closed Loop, IEEE Transactions on Power Delivery,” vol.13, pp. 1378-1384, 1998.

[5] P. Rao, M. L. Crow, Z. Yang, “STATCOM Control for Power System Voltage Control Applications,” IEEE Transactions on Power Delivery, vol.15, pp.1311-1317, 2000.

Enhancement of Power Quality in Distribution System using D-Statcom


STATCOM (static synchronous compensator) as a shunt-link flexible AC transmission system(FACTS) controller has shown extensive feasibility in terms of cost-effectiveness in a wide range of problem solving abilities from transmission to distribution levels. Advances in power electronic technologies such as Voltage Source Converter (VSC) improves the reliability and functionality of power electronic based controllers hence resulting in increased applications of STATCOM. In this paper, design and implementation of a Distribution type, Voltage Source Converter (VSC) based static synchronous compensator (DSTATCOM) has been carried out. It presents the enhancement of power quality problems, such as voltage sag and swell using Distribution Static Compensator (D-STATCOM) in distribution system. The model is based on Sinusoidal Pulse Width Modulation (SPWM) technique. The control of the Voltage Source Converter (VSC) is done with the help of SPWM. The main focus of this paper is to compensate voltage sag and swell in a distribution system. To solve this problem custom power devices are used such as Fixed Compensators (FC, FR), Synchronous Condenser, SVC, SSSC, STATCOM etc. Among these devices Distribution STATCOM (DSTATCOM) is the most efficient and effective modern custom power device used in power distribution networks. DSTATCOM injects a current into the system to mitigate the voltage sag and swell. The work had been carried out in MATLAB environment using Simulink and SIM power system tool boxes. The proposed D-STATCOM model is very effective to enhance the power quality of an isolated distribution system feeding power to crucial equipment in remote areas. The simulations were performed and results were found to be satisfactory using MATLAB/SIMULINK.


  1. Statcom
  2. Facts Controllers
  3. D-Statcom
  4. Voltage Source Converter
  5. Total Harmonic Distortions



Fig.1 Schematic diagram of D-STATCOM



 Fig.2 Three Phase to Ground -Voltage at Load Point is 0.6600 p.u

Fig.3 Double Line to Ground- Voltage at Load Point is 0.7070 p.u

Fig.4 Line to Line- Voltage at Load Point is 0.7585

Fig.5 Single Line to Ground- Voltage at Load Point is 0.8257

Fig.6 The waveforms shows THD (41.31%) results of fixed load and variable inductive load.

Fig..7 The wave forms shows THD (21.28%) results of fixed load and variable capacitive load

Fig.8 Three Phase to Ground-Voltage at Load Point is 0.9367 p.u

Fig.9 Double Line to Ground- Voltage at Load Point is0.9800 p.u

Fig.10 Line to Line- Voltage at Load Point is 1.068

Fig.11 Single Line to Ground – Voltage at Load Point is 0.9837

Fig.12 The waveform for pure inductive,capacitive loads with statcom

Fig.13 The waveform for without filter THD results 41.31%

Fig.14 The above waveform for with filter THD results 1.11%


The simulation results show that the voltage sags can be mitigate by inserting D-STATCOM to the distribution system. By adding LCL Passive filter to D-STATCOM, the THD reduced. The power factors also increase close to unity. Thus, it can be concluded that by adding DSTATCOM with LCL filter the power quality is improved.


[1] A.E. Hammad, Comparing the Voltage source capability of Present and future Var Compensation Techniques in Transmission System, IEEE Trans, on Power Delivery. Volume 1. No.1 Jan 1995.

[2] G.Yalienkaya, M.H.J Bollen, P.A. Crossley, “Characterization of Voltage Sags in Industrial Distribution System”, IEEE transactions on industry applications, volume 34, No. 4, July/August, PP.682-688, 1999

[3] Haque, M.H., “Compensation of Distribution Systems Voltage sags by DVR and D STATCOM”, Power Tech Proceedings, 2001 IEEE Porto, Volume 1, PP.10-13, September 2001.

[4] Anaya-Lara O, Acha E., “Modeling and Analysis Of Custom Power Systems by PSCAD/EMTDC”, IEEE Transactions on Power Delivery, Volume 17, Issue: 2002, Pages: 266 272.

[5] Bollen, M.H.J.,”Voltage sags in Three Phase Systems”, Power Engineering Review, IEEE, Volume 21, Issue: 9, September 2001, PP: 11-