Harish Suryanarayana Doctoral Student Energy Sources and Systems Purdue University

 Custom Power  The Distribution Static Compensator  Symmetrical Component Theory  Fuzzy Logic  Fuzzy Logic Based Supervision  Simulation Results

 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

 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.

Courtesy : PSERC 2003 Seminar

 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.

 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

 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.

 Reference Compensator Currents.  Reference Compensator Currents with loss.

 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.

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

 Inputs:  Outputs:  Calculation of P loss

 Inputs to the Fuzzy controller: Error and change in error of the capacitor voltage.

 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 )

Capacitor Voltage Waveform during a load change derr err NLNMNSZPSPMPL NLLLLMSSZ NMLLMSSZS NSLMSSZZZ ZMZZZZZM PSZZZSSML PMSZSSMLL PLZSSMLLL derr err NLNMNSZPSPMPL NLSK i­ SK i SK i­ ZZZZ NMSK i­ SK i ZZZZ NSLK i ZZZZ Z Z PSZZZZLK i PMZZZZSK i PLZZZZSK i Rule base for K p Rule base for K i

 Inputs:  Outputs:  Calculation of P loss

System ParametersValues Supply voltage220V (phase-rms), 50 Hz Unbalanced load R la = 50 , L la = 20 mH R lb = 35 , L lb = 40 mH R la = 70 , L la = 20 mH Non-linear loadThree-phase full wave rectifier drawing a dc current of 5 A DC capacitor 2200 µF Interface inductor L f = 20 mH, R f = 5  Reference dc link voltage 500 V Hysteresis band 0.6 A Gains tuned using the Energy concept K p = 110, K i = 55

Filter Current - Reference and Actual

Source Currents – Balanced and Sinusoidal

Normally tuned PI and Fuzzy Supervised waveforms

 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.