Neuro Fuzzy based controller for Power Quality Improvement

International Conference on Computational Intelligence and Communication Networks, 2015

ABSTRACT: Use of power electronic converters with nonlinear loads leads to power quality problems by producing harmonic currents and drawing reactive power. A shunt active power filter provides an elegant solution for reactive power compensation as well as harmonic mitigation leading to improvement in power quality. However, the shunt active power filter with PI type of controller is suitable only for a given load. If the load is varied, the proportional and integral gains are required to be fine tuned for each load setting. The present study deals with hybrid artificial intelligence controller, i.e. neuro fuzzy controller for shunt active power filter. The performance of neuro fuzzy controller over PI controller is examined and tabulated. The salvation of the problem is extensively verified with various loads and plotted the worst case out of them for the sustainability of the neuro fuzzy controller.



  1. Active Power Filter
  2. Neuro Fuzzy Controller
  3. Back Propagation Algorithm
  4. Soft Computing





Fig 1. Schematic Diagram of Shunt Active Power Filter




Fig 2. (a) Waveform of Load Current, Compensating Current, Source

Current and Source Voltage for Case V of Table1 (1kVA with α=60o) and

(b) Waveform of Source Voltage and in phase Source Current of Fig. (a) Reproduced



The application of hybrid artificial intelligence technique on shunt active power filter is proved to be an eminent solution for the mitigation of harmonics and the compensation of reactive power. The hybrid artificial intelligence used here is the neuro fuzzy controller. It takes the linguistic inputs as a fuzzy logic controller and it adapts any situation in between the running of the program as the neural network. The simulation results states that the active power filter controller with neuro fuzzy controllers have been seen to eminently minimize harmonics in the source current when the load demands non sinusoidal current, irrespective of whether the load is fixed or variable when compared to PI Controller. Simultaneously, the power factor at source also becomes the unity, if the load demands reactive power. The neuro fuzzy controller is far superior to the PI controller for all the loads. In the present work, a range of values of the load is considered to robustly test the controllers. It has been demonstrated that neuro fuzzy controller offers more acceptable results over the PI controller. The neuro fuzzy controller, therefore, significantly improves the performance of a shunt active power filter.



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Static synchronous compensator (STATCOM) Projects

static synchronous compensator (STATCOM), also known as a static synchronous condenser (STATCON), is a regulating device used on alternating current electricity transmission networks. It is based on a power electronics voltage-source converter and can act as either a source or sink of reactive AC power to an electricity network. If connected to a source of power it can also provide active AC power. It is a member of the FACTS family of devices. It is inherently modular and electable.

A STATCOM is a voltage source converter (VSC)-based device, with the voltage source behind a reactor. The voltage source is created from a DC capacitor and therefore a STATCOM has very little active power capability. However, its active power capability can be increased if a suitable energy storage device is connected across the DC capacitor. The reactive power at the terminals of the STATCOM depends on the amplitude of the voltage source. For example, if the terminal voltage of the VSC is higher than the AC voltage at the point of connection, the STATCOM generates reactive current; conversely, when the amplitude of the voltage source is lower than the AC voltage, it absorbs reactive power.The response time of a STATCOM is shorter than that of a static VAR compensator (SVC), mainly due to the fast switching times provided by the IGBTs of the voltage source converter. The STATCOM also provides better reactive power support at low AC voltages than an SVC, since the reactive power from a STATCOM decreases linearly with the AC voltage (as the current can be maintained at the rated value even down to low AC voltage).

STATCOM-Based Voltage Regulator for Self-Excited Induction Generator Feeding Nonlinear Loads


ABSTRACT: This paper deals with the performance analysis of a static compensator (STATCOM)-based voltage regulator for self-excited induction generators (SEIGs) supplying nonlinear loads. In practice, a number of loads are nonlinear in nature, and therefore, they inject harmonics in the generating systems. The SEIG’s performance, being a weak isolated system, is very much affected by these harmonics. The additional drawbacks of the SEIG are poor voltage regulation and that it requires an adjustable reactive power source with varying loads to maintain a constant terminal voltage. A three-phase insulated-gate-bipolar transistor- based current-controlled voltage source inverter working as STATCOM is used for harmonic elimination, and it provides the required reactive power for the SEIG, with varying loads to maintain a constant terminal voltage. A dynamic model of the SEIG–STATCOM feeding nonlinear loads using stationary d−q axes reference frame is developed for predicting the behaviour of the system under transient conditions. The simulated results show that SEIG terminal voltage is maintained constant, even with nonlinear balanced and unbalanced loads, and free from harmonics using STATCOM-based voltage regulator.


  1. Harmonic elimination
  2. Load balancing
  3. Nonlinear loads
  4. Self-excited induction generator (SEIG)
  5. Static compensator (STATCOM)



Fig. 1. Schematic diagram of proposed scheme of SEIG–STATCOM system


Fig.2 Control scheme of SEIG–STATCOM system


 Fig. 3. Voltage buildup of SEIG and switching in STATCOM.

Fig. 4. Waveform of three-phase SEIG–STATCOM system supplying diode rectifier with resistive load change from no load, to three-phase (22 kW), to one-phase (15 kW), to three-phase (22 kW) loads, and to no load.

Fig. 5. Waveform of three-phase SEIG–STATCOM system supplying diode rectifier with capacitive filter and resistive load change from no load, to three-phase (15 kW), to one-phase (24 kW), to three-phase (15 kW) loads, and to no load.

Fig. 6. Waveforms of three-phase SEIG–STATCOM system supplying diode rectifier with capacitive filter and resistive load change from no load, to three-phase (15 kW), to three-phase (22 kW), to three-phase (15 kW) loads, and to no load.

Fig. 7. Waveforms of three-phase SEIG–STATCOM system supplying thyristorized rectifier with resistive load change from no load, to three-phase (18 kW) at 60firing angle, to no load.


It has been observed that the developed mathematical model of a three-phase SEIG–STATCOM is capable of simulating its performance while feeding nonlinear loads under transient conditions. From the simulated results, it has been found that the SEIG terminal voltage remains constant, with the sinusoidal feeding of the three-phase or single-phase rectifiers with resistive and with dc capacitive filter and resistive loads. When a single-phase rectifier load is connected, the STATCOM balances the unbalanced load currents, and the generator currents and voltage remain balanced and sinusoidal; therefore, the STATCOM acts as a load balancer. The rectifier-based nonlinear load generates the harmonics, which are also eliminated by STATCOM. Therefore, it is concluded that STATCOM acts as voltage regulator, load balancer, and harmonic eliminator, resulting in an SEIG system that is an ideal ac power-generating system.


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[4] L. Wang and R. Y. Deng, “Transient performance of an isolated induction generator under unbalanced excitation capacitors,” IEEE Trans. Energy Convers., vol. 14, no. 4, pp. 887–893, Dec. 1999.

Simulation of Power Active Filter using Instantaneous Reactive Power Theory


 The paper presents the structure of an active parallel filter for reducing harmonic pollution and reactive power. The active power filter control is based on instantaneous reactive power theory. The authors present the modelling of parallel active filter based on this theory and the simulation results in MATLAB-SIMULINK. The method is based on instantaneous reactive power (TPRI_P).


  1. Distorting regime
  2. Harmonic pollution
  3. Power active filter
  4. Reactive power
  5. Simulation



Figure 1. Parallel active filter


Figure 2. The unfiltered current and the current filtered on phase “a”

Figure 3. The active and reactive powers

Figure 4. Current harmonics with three-phase load

Figure 5. Current harmonics with both loads


We considered three-phase system with the balanced voltages and presented the conventional method for determining the current value based on the instantaneous active power which was called TPRI_P. The control is made in the system of axes α – β, which use direct and inverse transformation to obtain the equations from one system to another coordinate axes. The currents obtained in the α-β are related to the alternating current power on the network to obtain the compensation current based on current knowledge of the load, in contrast to the conventional method (TPRI_Q) to obtain the controlled values of currents directly. As can be seen in calculations involved only active powers, perfectly measurable.

Also is observed that:

  • It produces an increase of the current THD network in the case of the system constant

instantaneous power of the energy source.

  • Is observed a small fluctuation by active power and reactive power of network in the system

constant instantaneous power of the energy source.

  • Regarding the homopolar power, network evolution is similar in both cases.


 * * Software Matlab 6.5.

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