Inverter Current Control in Weak Distribu3on Grids. Christoph Kammer, Alireza Karimi Automa3c Control Laboratory EPFL

Transcription

1 Inverter Current Control in Weak Distribu3on Grids Christoph Kammer, Alireza Karimi Automa3c Control Laboratory EPFL 1

2 Mo3va3onal Example 400 V rural distribu3on grid, resis3ve lines (R/X = 10) 1 50 m 300 m Grid ~ 2 3 : 4 2

3 Outline 1. Current Control Design Why is it relevant? 2. Present versus Proposed Approach 3. Plug&Play Func3onality 4. Experimental Results 3

4 Mo3va3onal Example 400 V rural distribu3on grid, resis3ve lines (R/X = 10) 1 50 m 300 m Grid ~ 2 3 : 4 4

5 Preven3ng Overvoltage Voltage Regulator (LVR) prevents overvoltage, but changes impedance 1 50 m LVR 300 m Grid ~ 2 3 : 4 5

6 Case Study of Real Grid Measurements from real grid show impact of inadequate controller 6

7 Current Controller State of the Art Tuning based on model of single inverter with PI controller 1 A ~ Grid V PLL PI - + 7

8 Current Controller State of the Art Voltage feedback increases performance, but decreases robustness 1 A ~ Grid PLL V PI - + 8

9 Current Controller State of the Art Addi3onal filters to dampen resonance peaks parameters tuned itera3vely, 3me- consuming Model neglects coupling effects, no guarantees for grid with mul3ple inverters 1 A ~ Grid V PLL Notch PI - + 9

10 Proposed Controller Simplified controller structure 1 A ~ Grid V PLL K

11 + + + Proposed Controller Simplified controller structure Design based on complete model guarantees stability and performance Grid V SI 1 ~ PLL K - V SI 2 V SI 3 PLL PLL K - K - 11

12 Novel Control Design Method Design mul3variable, fixed- structure, discrete- 3me controllers Example: PI with lowpass filter PI K Controller is op3mal and a result of a convex op3miza3on problem Performance specifica3ons on sensi3vity func3ons allows intui3ve design Easy to formulate common specifica3ons (rise 3me, overshoot, decoupling) 12

13 Novel Control Design Method Only the frequency response of the plant is required, parametric model is NOT necessary Many ways to obtain frequency response (small- signal model, dynamic phasor model, data- driven, grid impedance, mixed) Controller structure and order are independent of model complexity Guaranteed robustness towards modeling uncertain3es (e.g. changes in grid parameters) 13

14 Control Design Example 400 V rural distribu3on grid, resis3ve lines (R/X = 10) 1 50 m LVR 300 m Grid ~ 2 3 : 4 14

15 Frequency Response of System Standard single- inverter model 15

16 Frequency Response of System Complete grid model for four inverters without LVR Coupling Resonance 16

17 Frequency Response of System Complete grid model for four inverters with LVR 17

18 Current Step Response Specifica3ons: 0-70% rise- 3me <2 ms, maximum overshoot of 10%, decoupling Step response without LVR: Rise- 3me: 1.4 ms Rise- 3me: 1.8 ms Overshoot: 3 % Overshoot: 2 % 18

19 Current Step Response Specifica3ons: 0-70% rise- 3me <2 ms, maximum overshoot of 10%, decoupling Step response with LVR: Rise- 3me: 1.5 ms Overshoot: 2 % Rise- 3me: 1.9 ms Overshoot: 1 % 19

20 Plug&Play Capability Adding new inverter to exis3ng grid without redesigning controllers Decentralized design, stability and performance maintained 1 50 m 300 m Grid ~

21 Plug&Play Results Exis3ng controllers are included in the plant model, only new inverter is tuned Step response without LVR: Rise- 3me: 1.4 ms Rise- 3me: 1.3 ms Overshoot: 10 % Overshoot: 1.5 % 21

22 Plug&Play Results Exis3ng controllers are included in the plant model, only new inverter is tuned Step response with LVR: Rise- 3me: 1.4 ms Rise- 3me: 1.3 ms Overshoot: 10 % Overshoot: 1.5 % 22

23 Power Hardware- in- the- Loop Setup Experimental results obtained at SINTEF, NTNU Trondheim 1 LVR Hardware Simula3on 50 m 300 m Grid ~

24 PHIL Results Experimental results of Plug&Play controller 6 th harmonic oscilla3ons due to switching dead- 3me Solu3ons well known and compa3ble with design, but no 3me 24

25 PHIL Results Low distor3on on three- phase voltage and current 25

26 Conclusions Novel, prac3cal and powerful control design method applied to relevant problem in power grids Methodical approach guarantees stability and op3mal performance, reduces commissioning 3me Intui3ve problem formula3on well suited for prac33oners Plug&Play capability enables flexibility and compa3bility with exis3ng systems Wide range of applica3ons such as: Distribu3on grids with large amounts of distributed genera3on Large- scale windfarms Combined AC/DC grids 26

27 Thank You! Ques3ons? 27