FuZZY LOGIC BASED SUPERViSION OF DC LINK PI CONTROL IN A DSTATCOM

1. Harish Suryanarayana Doctoral Student Energy Sources and Systems Purdue University FuZZY LOGIC BASED SUPERViSIONOF DC LINK PI CONTROL IN A DSTATCOM

2. Custom Power • The Distribution Static Compensator • Symmetrical Component Theory • Fuzzy Logic • Fuzzy Logic Based Supervision • Simulation Results OverVIEW OF THE PRESENTATION

3. It is a concept based on the use of Power Electronic controllers in the distribution system to supply value- added, reliable, high-quality power to its customers. • Power Electronic Controller – DSTATCOM, DVR • Distribution level : 1kV to 38kV • High Quality Power: No sags/swells/harmonics CUSTOM POWER

4. An SSG or a Static Synchronous Generator is defined by the IEEE as a self-commutated switching power converter supplied from an appropriate electric energy source and operated to produce a set of adjustable multiphase voltages, which may be coupled to an AC power system for the purpose of exchanging independently controllable real and reactive Power. • STATCOM : An SSG with a capacitor as the energy source is known as a STATCOM or a Static Compensator. • DSTATCOM : When a STATCOM is used at the distribution level or the load end, it is known as a DSTATCOM or Distribution Static Compensator. THE DISTRIBUTION STATIC COMPENSATOR

5. DSTATCOM Courtesy : PSERC 2003 Seminar

6. DSTATCOM – Main Goals • To cancel the effect of harmonics due to load so that the current drawn from the source is nearly sinusoidal . • To help maintain near unity power factor by canceling the effect of poor load power factor • To help offset the effect of unbalanced loads, such that the current drawn from the source is balanced.

7. DSTATCOM SCHEMATIC

8. SYMMETRICAL COMPONENT THEORY • Any set of ‘n’ unbalanced polyphase quantities could be expressed as the sum of ‘n’ symmetrical sets of balanced phasors. • Three Phase: Positive Sequence, Negative Sequence and Zero Sequence

9. SYMMETRICAL COMPONENT THEORY • Source Currents are balanced. • Only the average load power is supplied by the source. • Relation between Source Currents and Source Voltages. • All equations in matrix form.

10. SYMMETRICAL COMPONENT THEORY • Reference Compensator Currents. • Reference Compensator Currents with loss.

11. FUZZY LOGIC • Concept introduced in 1965 by Lotfi. A. Zadeh • Crisp set and Fuzzy set. Ex. Set of tall people. Diagram of a crisp set and a fuzzy set.

12. FUZZY LOGIC CONTROLLER The four main components of a Fuzzy Controller. 1) The Fuzzification Interface 2) The Inference Mechanism 3) The Rule Base 4) The Defuzzification Interface

13. Inputs: • Outputs: • Calculation of Ploss FUZZY CONTROLLER

14. Fuzzification • Inputs to the Fuzzy controller: Error and change in error of the capacitor voltage.

15. INFERENCE MECHANISM • The two main functions of the inference mechanism are: a) Based on the active membership functions in error and the change in error inputs, the rules which apply for the current situation are determined. b) Once the rules which are on are determined, the certainty of the control action is ascertained from the membership values. This is known as premise quantification. ( Minimum Operation used )

16. RULE BASE Capacitor Voltage Waveform during a load change Rule base for Kp Rule base for Ki

17. Inputs: • Outputs: • Calculation of Ploss FUZZY CONTROLLER

18. DSTATCOM SCHEMATIC

19. Simulation Values

20. Simulation Results

21. Filter Current - Reference and Actual Simulation Results

22. Source Currents – Balanced and Sinusoidal Simulation Results

23. Normally tuned PI and Fuzzy Supervised waveforms Simulation Results

24. The DSTATCOM can be used to ensure balanced and sinusoidal source currents even if the load is unbalanced and non-linear. • Fuzzy supervision of the DC link PI controller can be used to reduce the error in DC Capacitor voltage during load change. Summary – Take home points