Method of super super decoupled loadflow computation for electrical power system
First Claim
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1. A method of forming/defining and solving a model of a power network to affect control of voltages and power flows in a power system, comprising the steps of:
- obtaining on-line/simulated data of open/close status of switches and circuit breakers in a power network, and reading data of operating limits of a power network components including PV-node, a generator-node where Real-Power-P and Voltage-Magnitude-V are given/assigned/specified/set, generators maximum and minimum reactive power generation capability limits and transformers tap position limits,obtaining on-line readings of given/assigned/specified/set real and reactive power at PQ-nodes, the load-nodes where Real-Power-P and Reactive-Power-Q are given/assigned/specified/set, real power and voltage magnitude at PV-nodes, voltage magnitude and angle at the reference/slack node, and transformer turns ratios, which are the controlled variables/parameters,initiating loadflow calculation with initial approximate/guess solution of the same voltage magnitude and angle as those of the slack/reference node for all the other nodes referred to as the slack-start,forming and storing factorized gain matrices [Yθ
] and [YV] using the same indexing and addressing information for both as they are of the same dimension and sparsity structure, wherein said [Yθ
] relate vector of modified real power mismatches [RP] to angle corrections vector [Δ
θ
] in equation [RP]=[Yθ
][Δ
θ
] referred to as P-θ
sub-problem, and said [YV] relate vector of modified reactive power mismatches [RQ] to voltage magnitude corrections vector [Δ
V] in equation [RQ]=[YV][Δ
V] referred to as Q-V sub-problem,restricting transformation/rotation angle Φ
p to maximum −
48°
in determining transformed real and reactive power mismatch as,
Δ
Pp′
=Δ
Pp Cos Φ
p+Δ
Qp Sin Φ
p—
for PQ-nodes
(23)
Δ
Qp′
=Δ
Qp Cos Φ
p−
Δ
Pp Sin Φ
p—
for PQ-nodes
(24)
Wherein, Δ
Pp and Δ
Qp are real and reactive power mismatches at node-p,calculating modified real and reactive power mismatches as given in the following in the most general form of equations that take different form for different Super Super Decoupled Loadflow model;
RPp=[Δ
Pp′
+(Gpp′
/Bpp′
)Δ
Qp′
]/Vp2—
for PQ-nodes
(17)
RQp=[Δ
Qp′
−
(Gpp′
/Bpp′
)Δ
Pp′
]/Vp—
for PQ-nodes
(18)
and calculating modified real power mismatch at a PV-node as,
RPp=Δ
Pp/(KpVp2)—
for PV-nodes
(19)
Wherein, Kp=Absolute(Bpp/Yθ
pp)
(29)
and Vp is voltage magnitude at node-p, and Bpp is imaginary part of the diagonal element Ypp of the admittance matrix without network shunts, and Yθ
pp is the diagonal element of the gain matrix [Yθ
],using network shunt parameter bp′
that appears in diagonal elements of gain matrix [YV] as given in the following in the most general form of equations that take different form for different loadflow model;
bp′
=−
bp Cos Φ
p+[QSHp′
−
(Gpp′
/Bpp′
)PSHp′
]/Vs2 or
bp′
=2[QSHp′
−
(Gpp′
/Bpp′
)PSHp′
]/Vs2
(22)
wherein, Gpp′ and
Bpp′
are the real and imaginary parts of the transformed diagonal element Ypp′
of the admittance matrix without network shunts, bp is network shunt susceptance at node-p, V5 is slack-node voltage magnitude, and
PSHp′
=PSHp Cos Φ
p+QSHp Sin Φ
p—
for PQ-nodes
(25)
QSHp′
=QSHp Cos Φ
p−
PSHp Sin Φ
p—
for PQ-nodes
(26)
wherein, PSHp, and QSHp are given/specified/scheduled/set real and reactive power respectively,performing loadflow calculation by solving a Super Super Decoupled Loadflow model of the power network defined by set of equations [RP]=[Yθ
][Δ
θ
] and [RQ]=[YV][Δ
V] employing successive (1θ
, 1V) iteration scheme, wherein each iteration involves one calculation of [RP] and [Δ
θ
] to update voltage angle vector [θ
] and then one calculation of [RQ] and [Δ
V] to update voltage magnitude vector [V], to calculate values of the voltage angle and the voltage magnitude at PQ-nodes, voltage angle and reactive power generation at PV-nodes, and turns ratio of tap-changing transformers in dependence on the set of said obtained-online readings, or given/scheduled/specified/set values of controlled variables/parameters and physical limits of operation of the network components,evaluating loadflow calculation for any of the over loaded power network components and for under/over voltage at any of the network nodes,correcting one or more controlled parameters and repeating the calculating, performing, evaluating, and correcting steps until evaluating step finds no over loaded components and no under/over voltages in the power network, andaffecting a change in the power flowing through network components and voltage magnitudes and angles at the nodes of the power network by actually implementing the finally obtained values of controlled variables/parameters after evaluating step finds a good power system or alternatively a power network without any overloaded components and under/over voltages, which finally obtained controlled variables/parameters however are stored in case of simulation for acting upon fast in case the simulated event actually occurs.
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Abstract
A method of performing loadflow calculations for controlling voltages and power flow in a power network by reading on-line data of given/specified/scheduled/set network variables/parameters and using control means, so that no component of the power network is overloaded as well as there is no over/under voltage at any nodes in the network following a small or large disturbances. The invented generalized Super Super Decoupled Loadflow (SSDL) calculation method is characterized in that 1) modified real power mismatch at any PQ-node-p is calculated as RPp=[ΔPp′+(Gpp′/Bpp′)ΔQp′]/Vp2, which takes different form for different manifestation of the generalized version SSDL-X′X′ method, 2) transformed values of known/given/specified/scheduled/set quantities in the diagonal elements of the gain matrix [YV] of the Q-V sub-problem are present, and 3) transformation angles are restricted to maximum of −48° particularly for the most successful version SSDL-YY method, and these inventive loadflow calculation steps together yield some processing acceleration and consequent efficiency gains, and are each individually inventive. The other two Super Super Decoupled Loadflow methods: BGX′ version (SSDL-BGX′) and X′GpvX′ version (SSDL-X′GpvX′) are characterized in the use of simultaneous (1V, 1θ) iteration scheme thereby calculating mismatches only once in each iteration and consequent efficiency gain.
-
Citations
2 Claims
-
1. A method of forming/defining and solving a model of a power network to affect control of voltages and power flows in a power system, comprising the steps of:
-
obtaining on-line/simulated data of open/close status of switches and circuit breakers in a power network, and reading data of operating limits of a power network components including PV-node, a generator-node where Real-Power-P and Voltage-Magnitude-V are given/assigned/specified/set, generators maximum and minimum reactive power generation capability limits and transformers tap position limits, obtaining on-line readings of given/assigned/specified/set real and reactive power at PQ-nodes, the load-nodes where Real-Power-P and Reactive-Power-Q are given/assigned/specified/set, real power and voltage magnitude at PV-nodes, voltage magnitude and angle at the reference/slack node, and transformer turns ratios, which are the controlled variables/parameters, initiating loadflow calculation with initial approximate/guess solution of the same voltage magnitude and angle as those of the slack/reference node for all the other nodes referred to as the slack-start, forming and storing factorized gain matrices [Yθ
] and [YV] using the same indexing and addressing information for both as they are of the same dimension and sparsity structure, wherein said [Yθ
] relate vector of modified real power mismatches [RP] to angle corrections vector [Δ
θ
] in equation [RP]=[Yθ
][Δ
θ
] referred to as P-θ
sub-problem, and said [YV] relate vector of modified reactive power mismatches [RQ] to voltage magnitude corrections vector [Δ
V] in equation [RQ]=[YV][Δ
V] referred to as Q-V sub-problem,restricting transformation/rotation angle Φ
p to maximum −
48°
in determining transformed real and reactive power mismatch as,
Δ
Pp′
=Δ
Pp Cos Φ
p+Δ
Qp Sin Φ
p—
for PQ-nodes
(23)
Δ
Qp′
=Δ
Qp Cos Φ
p−
Δ
Pp Sin Φ
p—
for PQ-nodes
(24)
Wherein, Δ
Pp and Δ
Qp are real and reactive power mismatches at node-p,calculating modified real and reactive power mismatches as given in the following in the most general form of equations that take different form for different Super Super Decoupled Loadflow model;
RPp=[Δ
Pp′
+(Gpp′
/Bpp′
)Δ
Qp′
]/Vp2—
for PQ-nodes
(17)
RQp=[Δ
Qp′
−
(Gpp′
/Bpp′
)Δ
Pp′
]/Vp—
for PQ-nodes
(18)
and calculating modified real power mismatch at a PV-node as,
RPp=Δ
Pp/(KpVp2)—
for PV-nodes
(19)
Wherein, Kp=Absolute(Bpp/Yθ
pp)
(29)
and Vp is voltage magnitude at node-p, and Bpp is imaginary part of the diagonal element Ypp of the admittance matrix without network shunts, and Yθ
pp is the diagonal element of the gain matrix [Yθ
],using network shunt parameter bp′
that appears in diagonal elements of gain matrix [YV] as given in the following in the most general form of equations that take different form for different loadflow model;
bp′
=−
bp Cos Φ
p+[QSHp′
−
(Gpp′
/Bpp′
)PSHp′
]/Vs2 or
bp′
=2[QSHp′
−
(Gpp′
/Bpp′
)PSHp′
]/Vs2
(22)
wherein, Gpp′ and
Bpp′
are the real and imaginary parts of the transformed diagonal element Ypp′
of the admittance matrix without network shunts, bp is network shunt susceptance at node-p, V5 is slack-node voltage magnitude, and
PSHp′
=PSHp Cos Φ
p+QSHp Sin Φ
p—
for PQ-nodes
(25)
QSHp′
=QSHp Cos Φ
p−
PSHp Sin Φ
p—
for PQ-nodes
(26)
wherein, PSHp, and QSHp are given/specified/scheduled/set real and reactive power respectively,performing loadflow calculation by solving a Super Super Decoupled Loadflow model of the power network defined by set of equations [RP]=[Yθ
][Δ
θ
] and [RQ]=[YV][Δ
V] employing successive (1θ
, 1V) iteration scheme, wherein each iteration involves one calculation of [RP] and [Δ
θ
] to update voltage angle vector [θ
] and then one calculation of [RQ] and [Δ
V] to update voltage magnitude vector [V], to calculate values of the voltage angle and the voltage magnitude at PQ-nodes, voltage angle and reactive power generation at PV-nodes, and turns ratio of tap-changing transformers in dependence on the set of said obtained-online readings, or given/scheduled/specified/set values of controlled variables/parameters and physical limits of operation of the network components,evaluating loadflow calculation for any of the over loaded power network components and for under/over voltage at any of the network nodes, correcting one or more controlled parameters and repeating the calculating, performing, evaluating, and correcting steps until evaluating step finds no over loaded components and no under/over voltages in the power network, and affecting a change in the power flowing through network components and voltage magnitudes and angles at the nodes of the power network by actually implementing the finally obtained values of controlled variables/parameters after evaluating step finds a good power system or alternatively a power network without any overloaded components and under/over voltages, which finally obtained controlled variables/parameters however are stored in case of simulation for acting upon fast in case the simulated event actually occurs. - View Dependent Claims (2)
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Current AssigneeSureshchandra B. Patel
-
Original AssigneeSureshchandra B. Patel
-
InventorsPatel, Sureshchandra B.
-
Primary Examiner(s)BARNES-BULLOCK, CRYSTAL JOY
-
Application NumberUS10/570,023Publication NumberTime in Patent Office2,531 DaysField of Search700292-295, 700/297, 700/298, 702 57- 59, 702/64, 702/65, 702/182, 307/20, 307/68, 323/205, 323/318, 323/268, 324/76.77, 324/76.79, 324/76.81, 324/98, 324/500, 324/512, 324/521, 324/522, 324/537, 340/500, 340/540, 340/635, 340/657, 340/658, 340600-664, 361/1, 361/18, 361/52, 361/54, 361/57, 361 62- 64, 361/67, 361/88, 361/90, 361/91.1, 361/92, 363/74US Class Current700/298CPC Class CodesH02J 2203/20 Simulating, e g planning, r...H02J 3/06 Controlling transfer of pow...Y02E 60/00 Enabling technologies; Tech...Y04S 40/20 Information technology spec...
