Transmission and distribution coordination for distributed energy resources integration to electricity markets
One or more systems and methods according to the present disclosure may apply a model for integrating distribution systems having proliferated distributed energy resources into the independent system operator energy market, particularly when one or more distribution systems are connected to a transmission system via multiple interconnection buses. Additionally, systems and methods for applying a compact multi-port model for power exchanges and associated bidding strategies are described. A the multi-port power exchange model may be constructed based on the operational feasible region of a distribution system; describing physical operation characteristics of distributed energy resources, flexible loads, and the distribution network; and the bidding strategy model may describe total operating cost of the distribution system, while recognizing electrically coupled injections of multiple interconnection buses.
1. A method of operating an electrical power grid, comprising:
collecting bids describing one or more electricity characteristics, by an operator, in an energy market from one or more electricity transmitters and one or more distributors, wherein at least one of the distributors includes interconnected distributed energy resources, the distributed energy resources intermittently providing electricity to their interconnected distributor; and
clearing in an operator day-ahead energy market model, by the operator, the energy market with consideration of a transfer limit on the electrical power grid to determine commitments of electrical power;
providing one or more electricity characteristics to the one or more distributors and to the distributed energy resources; and
causing a controlling of dispatch of the electrical power through the electrical power grid based on the commitments to capture impacts of the interconnected distributed energy resources while respecting the transfer limit on the electrical power grid;
wherein, in the collecting step, the one or more distributors prepares a projected feasible operation region of a corresponding distribution system and submits it to the operator, together with bids of distributed energy resources, the projected feasible operation region including one or more desired variables; and
wherein, in the clearing step, solutions to the one or more desired variables are sent to the one or more distributors.
2. The method of claim 1 , wherein the projected feasible operation region is based on a feasible operation region represented by the following:
p ii′,t =G ii′ ·( v i,t −v i,t )− B ii′ ·(θ i,t −θ i′,t ); ii′∈ d D ,t∈ (12)
q ii′,t =−B ii′ ·( v i,t −v i′,t )− G ii′ ·(θ i,t −θ i′,t ); ii′∈ d D ,t∈ (13)
+ = + ; i∈ d D / d B ,t∈ (14)
+ = + ; i∈ d D / d B ,t∈ (15)
= P i,t ; i∈ d B ,t∈ (16)
= q i,t ; i∈ d B ,t∈ (17)
v i,t =1; i∈ d B ,t∈ (18)
− P ii′ UB ≤p ii′,t ≤P ii′ UB ; ii′∈ d D ,t∈ (19)
V i LB ≤v i,t ≤V i UB ; i∈ d D / t∈ (20)
− P i UB ≤p i,t ≤P i UB ; i∈ d B ,t∈ (21)
− Q i UB ≤q i,t ≤Q i UB ; i∈ d B ,t∈ (22)
P g LB ≤p g,t ≤p g UB ; g∈ d D ,t∈ (23)
Q g LB ≤q g,t ≤Q g UB ; g∈ d D ,t∈ (24)
wherein p ii′,t represents active power flow along line ii′ at time t; q ii′,t represents reactive power flow along line ii′ at time t; G ii′ and B ii′ represent conductance and susceptance of line ii′; v i,t represents voltage magnitude of bus i at time t; θ i,t represents a voltage phase angle of bus i at time t; p g,t represents active power dispatch of unit g at time t; q g,t represents reactive power dispatch of unit g at time t; notations , , , and denote sets of buses, lines, DERs, flexible loads, and fixed loads in a distribution system; denotes a set of time intervals in a scheduling horizon, indexed by time t; Q f,t represents reactive power demand of fixed load f at time t; P ii′ UB represents an active power limit of line ii′; V i LB /V i UB represents a lower/upper voltage limit of bus i; and P g LB /P g UB and Q g LB /Q g UB represent active and reactive power bounds limiting dispatch ranges of DERs.
3. The method of claim 1 , wherein the projected feasible operation region is realized through a process of eliminating one or more variables by applying a Gaussian elimination and a Fourier-Motzkin elimination sequentially.
4. The method of claim 3 , wherein applying the Fourier-Motzkin elimination includes executing one or more filtering techniques to eliminate redundant constraints.
5. The method of claim 2 , wherein the projected feasible operation region is realized through a process of eliminating one or more variables by applying a Gaussian elimination and a Fourier-Motzkin elimination sequentially.
6. The method of claim 5 , wherein applying the Fourier-Motzkin elimination includes executing one or more filtering techniques to eliminate redundant constraints.
7. The method of claim 4 , wherein the projected feasible operation region is represented by the following:
·θ i,t + ·p i,t + ·p g,t ≤B h,t ; h∈ d,t ,t∈ (27)
wherein θ i,t represents a voltage phase angle of bus i at time t; A h,i,t θ , A h,i,t P , and A h,g,t G are generated coefficients to desired variables θ i,t (i∈ d B ), P i,t , and P g,t ; B h,t is a generated constant term; d,t , indexed by h, represents all generated constraints at time t of distribution system d; and denotes a set of time intervals in a scheduling horizon, indexed by time t.
8. The method of claim 6 , wherein the projected feasible operation region is represented by the following
·θ i,t + ·p i,t + ·p g,t ≤B h,t ; h∈ d,t ,t∈ (27)
wherein θ i,t represents a voltage phase angle of bus i at time t; where A h,i,t θ , A h,i,t P , and A h,g,t G are generated coefficients to desired variables θ i,t (i∈ d B ), P i,t , and P g,t ; B h,t is a generated constant term; d,t , indexed by h, represents all generated constraints at time t of distribution system d; and denotes a set of time intervals in a scheduling horizon, indexed by time t.
9. The method of claim 7 , wherein one or more distribution-side variables is set to equal one or more transmission-side counterparts as follows:
{circumflex over (p)} i′,d,t =p i,t ; i′∈ i,d T ,i∈ d B ,t∈ (28)
θ i′t =θ i,t ; i′∈ i,d T ,i∈ d B ,t∈ (29)
wherein {circumflex over (p)} i′,d,t and {circumflex over (θ)} i′,t represent transmission system counterparts of p i,t and θ i,t ; d B represents a set of duplicated interconnection buses in distribution system d; i,d T represents a transmission system counterpart of d B ; and denotes a set of time intervals in a scheduling horizon, indexed by time t.
10. The method of claim 4 , wherein the operator includes the projected feasible operation region in the day-ahead energy market model.
11. The method of claim 6 , wherein the operator includes the projected feasible operation region in the day-ahead energy market model.
12. A method of operating an electrical power grid, comprising:
collecting bids describing one or more electricity characteristics, by an operator, in an energy market from an electricity transmitter and one or more distributors, wherein the one or more distributors include interconnected distributed energy resources, each distributed energy resource intermittently providing electricity to its interconnected distributor;
calculating, by the operator, a distribution-to-distribution sub-matrix of an energy market clearing model for each distributor and releasing the calculated distribution-to-distribution sub-matrix to each distributor;
preparing, by each distributor, a multi-port power-exchange model from the calculated distribution-to-distribution sub-matrix and submitting the prepared multi-port power-exchange model to the operator; and
clearing, in the energy market clearing model, by the operator, the energy market with consideration of a transfer limit on the electrical power grid to determine commitments of electrical power;
providing one or more electricity characteristics to the one or more distributors and to the distributed energy resources; and
causing a controlling of dispatch of the electrical power through the electrical power grid based on the commitments to capture impacts of the interconnected distributed energy resources while respecting the transfer limit on the electrical power grid;
wherein the energy market clearing model additionally includes one or more elements of a distribution-to-transmission sub-matrix to account for impacts of the distributors on one or more transmission line constraints.
13. The method of claim 12 , wherein the multi-port power-exchange model accounts for one or more physical operation features of a corresponding distributor.
14. The method of claim 13 , wherein the multi-port power-exchange model is represented by the following:
· p n ≤B h ; h∈ (40)
wherein represents a set of ports indexed by n; A h,n represents a generated coefficient to p n ; p n denotes power flow injected into a distribution system through port n; B h represents a generated constant term; and represents a set of generated constraints indexed by h.
15. The method of claim 12 , wherein the preparing step includes formulating an operation feasible region.
16. The method of claim 15 , wherein the operation feasible region is represented by the following:
− F l UB ≤ ·( − − )≤ F l UB ; l∈ (41)
p n = ·( − − ); n∈ (42)
− F n UB ≤p n ≤F n UB ; n∈ (43)
P g LB ≤p g ≤P g UB ; g∈ (44)
P d LB ≤p d ≤P d UB ; d∈ (45)
wherein F l UB and F n UB represent capacity limits of distribution line l and port n; SF l,i and SF n,i represents shift factors of bus i to line l and port n, respectively; P f represents demand level of fixed load f; [P g LB , P g UB ] and [P d LB , P d UB ] represent dispatch ranges of DER g and flexible load d; and represents a set of ports is indexed by n.
17. The method of claim 16 , wherein the multi-port power-exchange model is constructed from (41)-(45) by applying Gaussian elimination and Fourier-Motzkin elimination.
18. The method of claim 17 , wherein the application of Fourier-Motzkin elimination includes a step of removing redundant constraints through the sequential application of Imbert's acceleration theorems, boundary filtering, and linear programming filtering.
19. The method of claim 16 , further comprising optimizing a total operating cost of each distribution system by solving the following or an approximation thereof:
min C ( {circumflex over (p)} n )= · p g − ·p d (46)
Constraints (41) and (44)-(45); (47)
{circumflex over (p)} n = ·( − − ); n∈ (48)
wherein p n represents power flow injected into a distribution system through port n; {circumflex over (·)} indicates a known solution of a variable; C({circumflex over (p)} n ) represents an operating cost as a function of p n over a feasible region; C g and C d represents price of DER g and flexible load d; p g and p d denote dispatches of DER g and flexible load d; P f represents demand level of fixed load f; SF n,i is shift factor of bus i to port n; i , i , and i denote sub-sets of DERs, flexible loads, and fixed loads at bus i, indexed by g, d, and f, and represents a set of ports is indexed by n.