The Rovigo plant is expected to generate enough energy to power over 16,500 homes. Image: PRNewsFoto/SunEdison http://www.pv-magazine.com/ ...
Politehnica University of Bucharest
Department of Automatics and Computer Science
Design Consideration on Algorithms and Control Structures for Photovoltaic Grids
Ciprian Lupu, Catalin Petrescu, Alina Peterscu-Nita, Mircea Lupu 19th International Conference on System Theory, Control and Computing - ICSTCC-2015 October 14 - 16, 2015, Cheile Gradistei - Fundata Resort, ROMANIA.
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OUTLINE
… Important results include tiny elements of equal importance …
19th International Conference on System Theory, Control and Computing - ICSTCC-2015 October 14 - 16, 2015, Cheile Gradistei - Fundata Resort, ROMANIA.
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OUTLINE
Introduction
Proposed idea
Experimental results
Conclusions
19th International Conference on System Theory, Control and Computing - ICSTCC-2015 October 14 - 16, 2015, Cheile Gradistei - Fundata Resort, ROMANIA.
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INTRODUCTION
The continuous decrease of the price for solar panels and of the afferent equipment (euro/KW) can lead now to an increase in the flexibility of these sources of green energy.
In general the quantity of energy provided cannot be changed on
a large front unless important investment are made or by grouping with storing systems or other sources of energy with continuous variation.
!!!
19th International Conference on System Theory, Control and Computing - ICSTCC-2015 October 14 - 16, 2015, Cheile Gradistei - Fundata Resort, ROMANIA.
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INTRODUCTION
The Rovigo plant is expected to generate enough energy to power over 16,500 homes. Image: PRNewsFoto/SunEdison http://www.pv-magazine.com/
19th International Conference on System Theory, Control and Computing - ICSTCC-2015 October 14 - 16, 2015, Cheile Gradistei - Fundata Resort, ROMANIA.
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INTRODUCTION
Virtual Power Plant solution:
The basic idea of a VPP is that a number of small scale production units of electricity can be operated as if they formed one huge power plant, like a conventional coal fuelled plant. !!! Individual units (especially solar farms) cannot guarantee a stable production level around the clock, but the combination of different sources can.
(Smart Grids and Virtual Power Plants. Point of departure. 10 March 2011) 19th International Conference on System Theory, Control and Computing - ICSTCC-2015 October 14 - 16, 2015, Cheile Gradistei - Fundata Resort, ROMANIA.
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INTRODUCTION
The typical structures :
(CHP) - Combined heat and power generators
19th International Conference on System Theory, Control and Computing - ICSTCC-2015 October 14 - 16, 2015, Cheile Gradistei - Fundata Resort, ROMANIA.
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INTRODUCTION
The typical structures:
19th International Conference on System Theory, Control and Computing - ICSTCC-2015 October 14 - 16, 2015, Cheile Gradistei - Fundata Resort, ROMANIA.
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INTRODUCTION
The typical structures:
(CHP) - Combined heat and power generators
19th International Conference on System Theory, Control and Computing - ICSTCC-2015 October 14 - 16, 2015, Cheile Gradistei - Fundata Resort, ROMANIA.
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INTRODUCTION
Other control structures (ICSTCC 2014 + CSCS 2015):
•C acts for the general (virtual) balance set point; •The requested power, represented by r is compared with the global output y and, accordingly, rc – the (re) calculated set point - is adjusted. •In particular, the controller C can be designed by using various classical algorithms, e.g. PI, PID, RST etc. 19th International Conference on System Theory, Control and Computing - ICSTCC-2015 October 14 - 16, 2015, Cheile Gradistei - Fundata Resort, ROMANIA.
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INTRODUCTION
Other control structures (ICSTCC 2014 + CSCS 2015 variant):
ESU Energy Storage Unit
•Fr and Fy are (digital/software implemented) filters for set point (reference) and for global measured load (y), respectively. •The structural combination of C, Fr and Fy suggests the use of a RST control algorithm with two degrees of freedom, featuring superior performance.
OK for real time functioning!!!
Problems on loop (algorithm) design and Fr and Fy filters
19th International Conference on System Theory, Control and Computing - ICSTCC-2015 October 14 - 16, 2015, Cheile Gradistei - Fundata Resort, ROMANIA.
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PROPOSED IDEA
The operational “base” is represented by the division of a big
source in groups of panels of different sizes in an optimal way, attempting to transition to a “continuous” variation source over an as larger is possible domain.
19th International Conference on System Theory, Control and Computing - ICSTCC-2015 October 14 - 16, 2015, Cheile Gradistei - Fundata Resort, ROMANIA.
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PROPOSED IDEA
Each subgroup can be independent, connected or disconnected so
as to generate electricity. The amount of energy generated by each subgroup is measured in real time.
19th International Conference on System Theory, Control and Computing - ICSTCC-2015 October 14 - 16, 2015, Cheile Gradistei - Fundata Resort, ROMANIA.
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PROPOSED IDEA
The electrical connections of each (PV) subgroup are made using
corresponding (hysteresis) switches (sw1) – correspondent software component exists.
19th International Conference on System Theory, Control and Computing - ICSTCC-2015 October 14 - 16, 2015, Cheile Gradistei - Fundata Resort, ROMANIA.
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PROPOSED IDEA
Proposed control structure: The optimisation algorithm has the role of selecting those subgroups, which summed, will generate a quantity of energy (Y) as close as possible to the desired value (Sp – set point). The optimisation algorithm solution, is materialised by ON/OFF position of the switch elements (sw1 – swn) which will allow for the energy produced by the panels to reach the inverter group and the connecting elements to the grid (I&HPC). (I&HPC - Inverters and High Power Connectors). 19th International Conference on System Theory, Control and Computing - ICSTCC-2015 October 14 - 16, 2015, Cheile Gradistei - Fundata Resort, ROMANIA.
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PROPOSED IDEA
Proposed control structure: ( y _ opt , C ) F _ Opt (Y , Sp) C [c1, , cn ], Y [ y1, , yn ] y _ opt 1 ci * yi , where i = 1, 2, ..., N N
ci {0;1}
(I&HPC - Inverters and High Power Connectors). 19th International Conference on System Theory, Control and Computing - ICSTCC-2015 October 14 - 16, 2015, Cheile Gradistei - Fundata Resort, ROMANIA.
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PROPOSED IDEA
Proposed control structure: PV subgroup designing - all equal elements similar to numeric-anagogic converters (DAC)
y1 y2 yn
YMAX yc n
The solution is a "balance" between accuracy vs. implementation cost.
(I&HPC - Inverters and High Power Connectors).
A relative optimisation can be built by splitting of the load by powers of 2 (2, 4, 8 etc.), as similarity the case of successive-approximation ADCs.
19th International Conference on System Theory, Control and Computing - ICSTCC-2015 October 14 - 16, 2015, Cheile Gradistei - Fundata Resort, ROMANIA.
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PROPOSED IDEA
Proposed control structure: PV subgroup designing - functional solution This solution takes into account the following elements: minimal, intermediary and maximal values of energy needed to be generated; maximum value of the global perturbation (GP) which could affect the system; Local perturbation (LP) values which could affect the main elements. (I&HPC - Inverters and High Power Connectors). 19th International Conference on System Theory, Control and Computing - ICSTCC-2015 October 14 - 16, 2015, Cheile Gradistei - Fundata Resort, ROMANIA.
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PROPOSED IDEA
Proposed control structure: PV subgroup designing - functional solution Example : Minimal value=0 MW,
intermediary value=1 MW, and maximum value =1.5 MW. Global perturbation GP=0.25%. Local perturbation LP=0.1%.
(I&HPC - Inverters and High Power Connectors). 19th International Conference on System Theory, Control and Computing - ICSTCC-2015 October 14 - 16, 2015, Cheile Gradistei - Fundata Resort, ROMANIA.
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PROPOSED IDEA
Proposed control structure: PV subgroup designing - functional solution Example : Solution - two main subgroups: S1=1 MW and S2=0.5 MW Some extra subgroup that considering also the global perturbation (GP):
(I&HPC - Inverters and High Power Connectors).
S3 =
S1 GP = 0.333 MW 1 - GP
S4 =
S 2 GP = 0.166 MW 1 - GP
The local perturbation is 0.1MW and will be compensated by a group with value (S5 = 0.1 MW), and if we want a complete solution, we must also consider GP (S6 = 0.133 MW).
Efficiency dispute!!!
19th International Conference on System Theory, Control and Computing - ICSTCC-2015 October 14 - 16, 2015, Cheile Gradistei - Fundata Resort, ROMANIA.
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PROPOSED IDEA
Proposed control structure (variant): PV subgroup designing - combined solution
•a fixed number of groups (of type S1 and S2 – or all equal); • and a group that can generate a variable quantity of energy (of type ADC), which can compensate global and local variations that are produced by perturbation
19th International Conference on System Theory, Control and Computing - ICSTCC-2015 October 14 - 16, 2015, Cheile Gradistei - Fundata Resort, ROMANIA.
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EXPERIMENTAL RESULTS
The comparative developed tests:
(a number of tests have been implemented in Simulink-Matlab) Scenario evolutions Sample / Element
Action
10 / SP
up
1.0
50 / GP
down
0.25
150 / SP
up
1.5
180 / LP (S2) down
0.1
200 / GP
up
0.25
240 / F (S2)
fail
0.0
300 / SP
down
1.0
Value
SP – Set Point; GD – Global Perturbation; LD – Local Perturbation; F - fail
19th International Conference on System Theory, Control and Computing - ICSTCC-2015 October 14 - 16, 2015, Cheile Gradistei - Fundata Resort, ROMANIA.
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EXPERIMENTAL RESULTS
Experimental platform (Matlab tests)
19th International Conference on System Theory, Control and Computing - ICSTCC-2015 October 14 - 16, 2015, Cheile Gradistei - Fundata Resort, ROMANIA.
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EXPERIMENTAL RESULTS
Performance criteria:
The “global error”
y 1 yi , where i = 1, 2, ..., N N
ei r i y1 i y2 i ... yn i yCV Ns
ERRs i ei , 0
Ns
ERRa i ei 0
i=0, 1, …, Ns, and Ns is the number of samples
(ERRs) - integral (with sign) global error (ERRa) - integral absolute global error 19th International Conference on System Theory, Control and Computing - ICSTCC-2015 October 14 - 16, 2015, Cheile Gradistei - Fundata Resort, ROMANIA.
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EXPERIMENTAL RESULTS
A) PV with all equal element;
ERRa is 24(!)
6 equal size elements of 0.35 MW
19th International Conference on System Theory, Control and Computing - ICSTCC-2015 October 14 - 16, 2015, Cheile Gradistei - Fundata Resort, ROMANIA.
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EXPERIMENTAL RESULTS
B) PV with “logic” designed elements;
ERRa is 2.1314
S1 = 1 MW, S2 = 0.5 MW, S3 = 0.333 MW, S4 = 0.166 MW, S5 = 0.1 MW and S6 = 0.133 MW 19th International Conference on System Theory, Control and Computing - ICSTCC-2015 October 14 - 16, 2015, Cheile Gradistei - Fundata Resort, ROMANIA.
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EXPERIMENTAL RESULTS
C) Mixture between A and B configurations;
ERRa is 9.3
S1 = 1 MW, S2 = 0.5 MW, S3 = S4 = S5 = S6 = 0.15 MW
19th International Conference on System Theory, Control and Computing - ICSTCC-2015 October 14 - 16, 2015, Cheile Gradistei - Fundata Resort, ROMANIA.
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EXPERIMENTAL RESULTS
D) PV with “variable" component;
ERRa is 2.1214 the best !!!!
S1 = 1 MW, S2 = 0.5 MW, S3 = 0.633 MW. S3 was divided in 36 elements and the designed precision error was T= S3/36 = 0.0176 MW. This value is of course affected by the GP. 19th International Conference on System Theory, Control and Computing - ICSTCC-2015 October 14 - 16, 2015, Cheile Gradistei - Fundata Resort, ROMANIA.
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EXPERIMENTAL RESULTS
Experimental platform
panels (3) with a capacity of 215W 19th International Conference on System Theory, Control and Computing - ICSTCC-2015 October 14 - 16, 2015, Cheile Gradistei - Fundata Resort, ROMANIA.
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EXPERIMENTAL RESULTS
Experimental platform
7 panels, NI data acquisition system, relay, NI CVI software
19th International Conference on System Theory, Control and Computing - ICSTCC-2015 October 14 - 16, 2015, Cheile Gradistei - Fundata Resort, ROMANIA.
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CONCLUSIONS
The main idea of this approach was the increase of the predictability and flexibility of the PV grid. The operational “base” is represented by the division of a big source in groups of panels of different sizes in an optimal way, attempting to transition to a “continuous”variation source over an as larger is possible domain.
Four control structures has been proposed: PV with all equal element, PV with “logic” designed elements, Mixture between previously two configurations, PV with “variable" component. 19th International Conference on System Theory, Control and Computing - ICSTCC-2015 October 14 - 16, 2015, Cheile Gradistei - Fundata Resort, ROMANIA.
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References
1. David Beauvais, Alexandre Prieur, François Bouffard, Smart grid to balance renewable energies – Contributing distributed energy resources (2012‐177 (RP‐TEC) 411‐Flexin, March 2012) 2. M. Liserre, T. Sauter, and J. Y. Hung, “Future energy systems, integrating renewable energy sources into the smart power grid through industrial electronics,” IEEE Ind. Electron. Mag., vol. 4, no. 1, pp. 18–37, Mar. 2010. 3. Ahmadi, H.; Marti, J.R.; Dommel, H.W., "A Framework for Volt-VAR Optimization in Distribution Systems," Smart Grid, IEEE Transactions on , vol.6, no.3, pp.1473,1483, May 2015 4. Natsheh, E.M.; Albarbar, A.; Yazdani, J., "Modeling and control for smart grid integration of solar/wind energy conversion system," Innovative Smart Grid Technologies (ISGT Europe), 2011 2nd IEEE PES International Conference and Exhibition on , vol., no., pp.1,8, 5-7 Dec. 2011 5. T. Zhou and B. François, “Modelling and control design of hydrogen production process for an active wind hybrid power system,” Int. J. Hydrogen Energy, vol. 34, no. 1, pp. 21–30, Jan. 2009. 6. M. Varlam, M. Culcer, A. Enache, M. Raceanu, Mariana Iliescu, A. Badea, I. Stefanescu , A hydrogen-based peak power management unit (U.P.B. Sci. Bull., Series C, Vol. 74, Iss. 1, 2012) pp. 33-38 7. Ciprian Lupu, Catalin Petrescu, Mircea Lupu, An Approach for Stabilized Control Structure on Photovoltaic Grids, The 20th International Conference on Control Systems and Computer, Bucharest, Romania, from May 27 to May 29, pp. 18-24, 2015. 8. Romică Trandafir, Modele si Algoritmi de Optimizare (ro) - Models and Optimised Algorithms, Editura AGIR, Bucuresti 2004 9. http://www.itg.ge/solar-energy.html 10. Ciprian Lupu, Dumitru Oancea, Balancing Structure for Multiple Generator, Journal of Electrical and Electronics Engineering, Volume 7, Issue 1, May 2014, ISSN: 1844-6035 11. I. Bucur, N. Cupcea, C. Ştefǎnescu, A. Surpǎţeanu, “Power-Driven Mapping K-LUT-based FPGA Circuits,” IEEE CAS 2009 Proceedings, pp. 435-438, (2009).
MCPL 2007 4th IFAC Conference, September 27-30, Sibiu, Romania
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Thank you! An Approach for Stabilized Control Structure on Photovoltaic Grids
19th International Conference on System Theory, Control and Computing - ICSTCC-2015 October 14 - 16, 2015, Cheile Gradistei - Fundata Resort, ROMANIA.
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