Cascaded Control of Multilevel Converter based STATCOM for Power System Compensation of Load Variation


The static synchronous compensator (STATCOM) is used in power system network for improving the voltage of a particular bus and compensate the reactive power.It can be connected to particular bus as compensating device to improve the voltage profile and reactive power compensation. In this paper, a multi function controller is proposed and discussed. The control concept is based on a linearization of the d-q components with cascaded controller methods. The fundamental parameters are controlled with using of proportional and integral controller. In closed loop method seven level cascaded multilevel converter (CMC) is proposed to ensure the stable operation for damping of power system oscillations and load variation.


  1. FACTS
  2. PWM
  3. CMC



 Figure 1.STATCOM network connection.


Figure 2. Load terminal dq0 Currents with Load variation

Figure 3. Source terminal dq0 Currents with Load variation.

Figure 4. Iqref output for load rejection.

Figure 5. Source Voltage for load rejection with AGC.

Figure 6. THD of output Voltage of Cascaded Multilevel converter.

Figure 7. THD of output Current of Cascaded Multilevel Converter

Figure 8.Source Active and Reactive power.

Figure 9. Power factor in Load and Source Bus

Figure 10.Three phase Supply Voltage of multilevel converter.


The cascaded controller is designed for seven level CMC based STATCOM. This control scheme regulates the capacitor voltage of the STATCOM and maintain rated supply voltage for any load variation with in the rated value. It has been shown that the CMC is able to reduce the THD values of output voltage and current effectively. The CMC based STATCOM ensures that compensate the reactive power and reduce the harmonics in output of STATCOM.


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[2] P. Lehn and M. Iravani, Oct.1998, “Experimental evaluation of STATCOM closed loop dynamics”, IEEE Trans. Power Delivery, vol.13, pp.1378-1384.

[3] Mahesh K.Mishra and Arindam Ghosh, Jan 2003, ”Operation of a D-STATCOM in Voltage Control Mode”, IEEE Trans. Power Delivery, vol.18, pp.258-264.

[4] Arindam Ghosh, Avinash Joshi, Jan 2000, ”A New Approach to Load Balancing and Power Factor Correction in Power Distribution System”, IEEE Trans. Power Delivery, vol.15, No.1, pp. 417-422.

[5] Arindam Ghosh, Gerard Ledwich, Oct 2003,”Load Compensating DSTATCOM in Weak AC Systems”, IEEE Trans. Power Delivery, vol.18, No.4, pp.1302-1309.


Verification of New Family for Cascade Multilevel Inverters with Reduction of Components


This paper now a new group for multilevel converter that do. as symmetric and asymmetric state. The planned multilevel converter produce DC voltage levels similar to other geography with less number of semiconductor exchange.


It results in the decline of the number of trade, losses, installation area, and converter cost. To verify the voltage injection capacity of the planned inverter, the planned topology is used in dynamic voltage restorer (DVR) to restore load voltage.


The operation and work of the planned multilevel converters are confirmed by simulation using SIMULINK/MATLAB and experimental results.


  1. Cascaded multilevel converter,
  2. New topology
  3. Reduction of components
  4. DVR




Fig. 1. Proposed cascade topology

 Fig. 2. Proposed topology with four DC voltage sources.





Fig. 3. (a) Supply voltage, (b) DVR injection voltage, and (c) load voltage for the three-phase balanced voltage sag.


Fig. 4. Output phase voltage in fault (sag) time




Fig. 5. (a) Supply voltage, (b) DVR injection voltage, and (c) load voltage for the three-phase balanced voltage swell.


Fig. 6. Output phase voltage in fault (swell) time.


 In this paper, a novel topology was given for multilevel converter, which has decreased number of exchange. The suggested topology needs fewer switches for achieving voltages for the same levels of output voltages.


This point decrease the installation area and the number of gate driver circuits. Therefore, the cost of the proposed topology is less than the conventional topology. Based on the given switching algorithm, the multilevel inverter produce near sinusoidal output voltage, causing very low harmonic distortion.


The proposed inverter used in DVR does not require any coupling series transformer and has lower cost, smaller size, and higher work and ability. Simulation results verified the validity of the given concept.


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[3] S. Mariethoz, A. Rufer, “New configurations for the three-phase asymmetrical multilevel inverter,” in Proceeding of the IEEE 39th Annual Industry Applications Conference, pp. 828-835, Oct. 2004.

[4] J.Rodriguez, J.S. Lai, F.Z. Peng, “Multilevel Inverter: A Survey of Topologies, Controls, and applications”, IEEE Trans. on Industrial Electronics, Vol. 49, No. 4, August. 2002.

[5] J.S. Lai, F.Z. Peng, “Multilevel Converters-A New Breed of power Converters”, IEEE Trans. Industry Application, Vol. 32, No. 3, pp. 509-517, MAY/JUNE.1996