Harmonics Issues that Limit Solar Photovoltaic Generation on Distribution Circuits

Transcription

1 WREF 01 Paper # 048 Harmonics Issues that Limit Solar Photovoltaic Generation on Distribution Circuits Ketut Dartawan Ricardo Austria, Le Hui and Mark Suehiro* Pterra Consulting Maui Electric Company* May 17 th, 01 Denver, CO

2 Voltage Magnitude Voltage Magnitude I. Harmonic is Distortion of Ideal Waveform.0 Ideal Fundamental.0 Fundamental + Harmonic Voltages Versus Angles Distorted Angle (degree) Angle (degree)

3 Voltage Magnitude 3 Distortion Caused by Harmonic Source Ideal Waveform 60 Hz + 3 rd Harmonic Source 180 Hz 3 x 60 Hz Fundamental + Harmonic Voltages Versus Angles -1.0 Distorted Waveform Angle (degree)

4 Voltage Magnitude 4 Distortion Caused by Harmonic Sources Ideal Waveform 60 Hz + Multiple Harmonic Sources 3 rd,5 th,7 th,9th Fundamental + Harmonic Voltages Versus Angles -1.0 Distorted Waveform Angle (degree)

5 5 Harmonics from renewable resources Power Plant Transmission Lines Photovoltaic Panels DC AC Power Inverters Distribution Substation Harmonics

6 6 Harmonics are risky/hazardous to power systems overheating equipment over-voltages interferences with communication systems mis-operation of sensitive loads etc

7 7 IEEE standards IEEE standard 519: IEEE Recommended Practices and Requirements for Harmonic Control in Electrical Power Systems, 199 IEEE standard 1547: IEEE Standard for Interconnecting Distributed Resources with Electric Power Systems, 003

8 8 Total harmonics distortion (THD) I THD I I 3 I I 4 1 I n V THD V V 3 V V 1 4 V n

9 9 Criteria - IEEE Std Harmonic Voltage Distortion in % at PCC.3-69 kv kv > 161 kv Maximum for Individual Harmonic Total Harmonic Distortion (THD) *: only portions are shown here IEEE Std 1547 ID* Maximum Harmonic Current Distortion in % of Load Demand Current Voltages kV I SC /I L Harmonic Order (Odd Harmonics) <11 11<h<17 17<h<3 3<h<35 35<h A1 <0* A 0< THD

10 10 Even Harmonic Was not a controlling factor back when the standard was created IEEE Std 519 & 1547 Even harmonics = 5% Odd harmonics Authors recommendation (Even = Odd) Even harmonics = 100% Odd harmonics PV has even harmonics that comparable to the odd harmonic

11 11 II. Modeling and simulation Circuit model: Mile 1.47 kv CKT 10 MVA substation transformer 4 MVAR Cap Bank 500 kw PV units (total: ~ 5 MW) Harmonic source PV unit#1 Sunlight DC AC PV unit# PV unit#3 Background Harmonics Load 480 V Bus PV unit#4 Utility mile 500 MCM Cable 69 kv Bus Substation Transformer 69/1.47 kv 1.47 kv Bus Additional PV units... 4 MVAR Cap Bank 10 mile 336 Al Overhead Line Lumped Load: 3 MVA, 0.9 p.f. Filter

12 1 Harmonics from renewable Energies - below 9 th harmonic order - both even and odd harmonics TYPE-I, THD = 3% TYPE-II, THD = 6% Background harmonics: - from TV, computer, fluorescent lamps, etc - harmonic orders: 1, 3, 5, 7, 9

13 13 Study Cases Case Case 1 Case 3 Heavy load Capacitor on PV on/off Case 4 Case 1 Light Load and Capacitors off Photovoltaic Power Heavy Load and Capacitors on Light Load AM PM AM System Loading Time Profile

14 14 III. Analysis, results and discussions Research approach: Resonance Point THD Compare Harmonic Limit Decide standards PV Penetration level Harmonic order

15 15 Capacitor and Resonance Point Bus Scan Impedance Magnitude (pu) MVAR MVAR 1 MVAR 0 MVAR Harmonic Order Impedance Scan at the 1.47 kv Bus

16 Voltage Distortion (%) 16 Voltage Distortion Percentage Voltage Distortion at the 1.47 kv Bus 4 MVAR Capacitor at 1.47 kv Bus with 4 MVAR Capacitor in Service 5 Limit: 5 MW TYPE I IEEE criteria Limit: 1. MW TYPE II TYPE-I THD TYPE-II THD PV (MW)

17 Current Dis IEEE-1547 modified Violations.0 Current 0.0 Distortion Percentage (Type-II harmonics) Harmonics at 480 V Cable with 4 MVAR Capacitor in Service Current Distortion (%) 8.0 IEEE MW MW IEEE-519 modified.0 MW 4.0 IEEE-1547 modified Violations Harmonics

18 18 PV penetration limit summary Type-I Harmonics w/o background harmonics w/ background harmonics Type-II Harmonics w/o background harmonics w/ background harmonics 1.47 kv Bus 5.0 MW 3.0 MW 1. MW 0.8 MW IEEE-519 > 5.0 MW > 5.0 MW 0.6 MW 0.6 MW 480 V Cable IEEE-519 modified > 5.0 MW > 5.0 MW 1.6 MW >.0 MW IEEE-1547 modified > 5.0 MW > 5.0 MW 1.0 MW 1.0 MW

19 19 Mitigation: Harmonic filters Bus Scan Impedance Magnitude (pu) without filters With filters Substation Transformer Notch Filter Tune at the 5 th Order Harmonics High-Pass Filter Tune at the 7 th Order Harmonics Utility 69 kv Bus 1.47 kv Bus 4 MVAR Capacitor bank. Operation mode: 1,, and 4 MVAR To Distribution Circuit Harmonic Order Dirty Water Dirty power FILTER Clean Water Clean power

20 0 IV. Conclusions The maximum PV penetration can be significantly influenced by: criteria adopted capacitor operating modes harmonics injected from PV units Harmonic filters could be used to increase PV penetration