CN111884268B - Optimal power flow control method of alternating current-direct current hybrid power distribution network considering reliability index - Google Patents
Optimal power flow control method of alternating current-direct current hybrid power distribution network considering reliability index Download PDFInfo
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- CN111884268B CN111884268B CN202010673114.8A CN202010673114A CN111884268B CN 111884268 B CN111884268 B CN 111884268B CN 202010673114 A CN202010673114 A CN 202010673114A CN 111884268 B CN111884268 B CN 111884268B
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- H—ELECTRICITY
- H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
- H02J—CIRCUIT ARRANGEMENTS OR SYSTEMS FOR SUPPLYING OR DISTRIBUTING ELECTRIC POWER; SYSTEMS FOR STORING ELECTRIC ENERGY
- H02J4/00—Circuit arrangements for mains or distribution networks not specified as ac or dc
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- H—ELECTRICITY
- H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
- H02J—CIRCUIT ARRANGEMENTS OR SYSTEMS FOR SUPPLYING OR DISTRIBUTING ELECTRIC POWER; SYSTEMS FOR STORING ELECTRIC ENERGY
- H02J2203/00—Indexing scheme relating to details of circuit arrangements for AC mains or AC distribution networks
- H02J2203/10—Power transmission or distribution systems management focussing at grid-level, e.g. load flow analysis, node profile computation, meshed network optimisation, active network management or spinning reserve management
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- H—ELECTRICITY
- H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
- H02J—CIRCUIT ARRANGEMENTS OR SYSTEMS FOR SUPPLYING OR DISTRIBUTING ELECTRIC POWER; SYSTEMS FOR STORING ELECTRIC ENERGY
- H02J2203/00—Indexing scheme relating to details of circuit arrangements for AC mains or AC distribution networks
- H02J2203/20—Simulating, e g planning, reliability check, modelling or computer assisted design [CAD]
Abstract
The invention relates to an optimal power flow control method of an alternating current-direct current hybrid power distribution network considering reliability indexes, which is characterized by comprising the contents of rapid power flow calculation, optimal modeling, optimal power flow control and the like, wherein the optimal power flow problem can be solved only by common control parameters.
Description
Technical Field
The invention relates to the field of alternating current and direct current hybrid power distribution networks, in particular to an optimal power flow control method of an alternating current and direct current hybrid power distribution network considering reliability indexes.
Background
With the increase of the demand of electric energy and the need of environmental protection, sustainable low-carbon energy application is gradually paid attention to and developed. The power electronic technology plays an important role in the novel energy conversion process. With the development of power electronic technology and the increase of direct-current power supply and load proportion, the traditional alternating-current power distribution network is changed into an alternating-current and direct-current hybrid power distribution network.
The optimal power flow is an important means for ensuring the safe operation of the power distribution network, is also a foundation and a premise for the optimal operation of the alternating current-direct current hybrid power distribution network, and has important theoretical value and engineering significance. Meanwhile, the reliability management of the power distribution network is always the most important of the work of the power department in China. In view of the fact that currently, the optimal power flow with reliability indexes rarely considered exists, and the problem that the algorithm oscillates and other limitations exist in the process of directly applying the existing intelligent algorithm to solve the optimal power flow problem of the alternating current-direct current hybrid power distribution network.
Disclosure of Invention
The invention aims to solve the problems in the prior art, and aims to provide an optimal power flow control method of an alternating current-direct current hybrid power distribution network, which is high in calculation speed, strong in applicability and good in application effect and considers reliability indexes.
The technical scheme adopted for realizing the aim of the invention is as follows: an optimal power flow control method of an alternating current-direct current hybrid power distribution network considering reliability indexes is characterized by comprising the following steps:
1) and (3) fast load flow calculation:
establishing a power balance equation of the AC/DC hybrid power distribution network with the total node number N belonging to [3,9999] based on power balance:
in formula (1), j is 1, 2. PjsFor algebraic sum of active power injected into the source or load at node j, QjsIs the algebraic sum of the reactive power of the power supply or the load injected into the j node; pjAlgebraic sum Q for injecting active power of j node for other nodesjInjecting algebraic sum of reactive power of j nodes into other nodes;
the solving method of the formula (1) adopts a Newton Raphson method: performing Taylor series expansion on the power balance equation and omitting more than two terms to obtain a Newton Raphson method correction equation for load flow calculation of the AC/DC hybrid power distribution network, wherein the matrix form is expressed as a formula (2);
in the formula (2), J is a coefficient matrix of the correction equation, Δ P is an unbalance amount of active power of each node, Δ Q is an unbalance amount of reactive power of each node, Δ V is a correction amount of voltage amplitude of each node, and Δ θ is a voltage of each nodeThe correction amount of the angle; j matrix of (2 k)1-1) rows (2 k)1-1) column elements, 2k2Line 2k2The elements of the column are all set to the number 1, where k1＞0、k2The node numbers with the node voltage amplitude values and the node voltage phase angles being fixed values are respectively greater than 0;
2) optimizing and modeling:
distributing the power electronic converters of the same grade according to a formula (3) in a rated capacity proportion, and balancing the thermal stress of the power electronic converters to optimize the service life of the power electronic converters; calculating according to a formula (4) to balance the reliability index of the thermal stress of the power electronic converter;
firstly, considering the optimization strategy of the reliability index,
in the formulas (3) and (4),
reference value of active power, P, allocated to the i-th power electronic converterciIs the actual value of the active power, P, of the ith power electronic converteri cNormalizing value for i-th power electronic converter active power, CiRated capacity, P, of the i-th power electronic convertercIs the active power sum of the power electronic converters of the same level, NcNumber of power electronic converters of the same level, PdeFor power electronic converter reliability index value, Pmax、PminRespectively are the upper limit value and the lower limit value of the active power of the power electronic converter after normalization, Npmax、NpminThe number of the power electronic converter power upper limit and the number of the power electronic converter power lower limit exceeding the normalization are respectively;
(ii) an objective function of the image data,
considering the reliability index and the voltage margin index, adding a punishment item in the objective function, and establishing the objective function considering the reliability index:
min{Ploss+MvVde+Mp∑Pde} (5)
in the formula (5), PlossIs the total active power loss value, V, of the AC/DC hybrid power distribution networkdeAs an indication of the voltage margin, Mv＞0、MpA penalty factor is more than 0; in the formula (6), Vmax、VminRespectively an upper limit and a lower limit of the voltage margin, Nvmax、NvminThe number of the upper limit and the lower limit exceeding the voltage margin are respectively; vjIs the jth node voltage amplitude;
thirdly, the constraint condition is satisfied,
and (3) constraint of an equation: formula (1); the inequality constrains: the method comprises the steps of power supply capacity, power upper and lower limit constraints and upper and lower limit constraints of all regulation variables;
3) optimal power flow control:
aiming at the minimized objective function in the formula (5), carrying out iterative solution on decision variables according to a formula (7), wherein in the formula (7), the optimized decision variables comprise direct-current power supply node voltage, active power, direct-current-direct-current converter load active power and outlet side voltage, alternating-current power supply node power, voltage amplitude and reactive power compensation; z > 0 is the number of iterations, a > 0 is the number of decision variables in the z-th iteration, b > 0 is the number of candidate solutions in the z-th iteration; p is 1,2, …, a is the decision variable index, q is 1,2, …, b is the candidate solution index, xz,p,qThe value of the p-th decision variable in the q-th candidate solution for the z-th iteration,
new value of the p-th decision variable in the q-th candidate solution, x, for the z-th iterationz,p,bestFor the best value of the p-th decision variable in the b candidate solutions in the z-th iteration,xz,p,worstis the worst value of the p-th decision variable in the b candidate solutions in the z-th iteration, r1,z,p、r2,z,pFor the p decision variable in the z iteration at [0,1 ]]Two random numbers, x, set within a rangebestTrend toward the best solution, xworstIn order to be the trend of the worst solution,
the optimal power flow control method of the alternating current-direct current hybrid power distribution network considering the reliability index has the beneficial effects that: due to the adoption of rapid power flow calculation, optimal modeling and optimal power flow control, the optimal power flow problem can be solved only by using common control parameters, and meanwhile, in the aspect of solving the optimal power flow problem of the AC/DC hybrid power distribution network, the control method has the advantages of high stability, strong optimization capability and high calculation speed, and can well solve the optimal power flow problem of the AC/DC hybrid power distribution network with two ends, multiple ends and multiple feed-ins.
Drawings
FIG. 1 is a block diagram of an optimal power flow control method of an AC/DC hybrid power distribution network in consideration of reliability indexes;
FIG. 2 is a schematic view of the embodiment of FIG. 1;
FIG. 3 is a graphical representation of the objective function value of the algorithm of FIG. 2 as the number of iterations increases;
fig. 4 is a graph of normalized active power comparison before and after the reliability index optimization of fig. 2.
Detailed Description
The present invention will be described in further detail with reference to fig. 1-4 and the specific embodiments described herein, which are only for the purpose of explaining the present invention and are not intended to limit the present invention.
Referring to fig. 1, the optimal power flow control method for the alternating current-direct current hybrid power distribution network considering the reliability index, provided by the invention, comprises the following steps:
1) and (3) fast load flow calculation:
establishing a power balance equation of the AC/DC hybrid power distribution network with the total node number N belonging to [3,9999] based on power balance:
in formula (1), j is 1, 2. PjsFor algebraic sum of active power injected into the source or load at node j, QjsIs the algebraic sum of the reactive power of the power supply or the load injected into the j node; pjAlgebraic sum Q for injecting active power of j node for other nodesjInjecting algebraic sum of reactive power of j nodes into other nodes;
the solving method of the formula (1) adopts a Newton Raphson method: performing Taylor series expansion on the power balance equation and omitting more than two terms to obtain a Newton Raphson method correction equation for load flow calculation of the AC/DC hybrid power distribution network, wherein the matrix form is expressed as a formula (2);
in the formula (2), J is a coefficient matrix of a correction equation, Δ P is the amount of unbalance of active power of each node, Δ Q is the amount of unbalance of reactive power of each node, Δ V is the correction amount of voltage amplitude of each node, and Δ θ is the correction amount of voltage phase angle of each node; j matrix of (2 k)1-1) rows (2 k)1-1) column elements, 2k2Line 2k2The elements of the column are all set to the number 1, where k1＞0、k2The node numbers with the node voltage amplitude values and the node voltage phase angles being fixed values are respectively greater than 0;
2) optimizing and modeling:
distributing the power electronic converters of the same grade according to a formula (3) in a rated capacity proportion, and balancing the thermal stress of the power electronic converters to optimize the service life of the power electronic converters; calculating according to a formula (4) to balance the reliability index of the thermal stress of the power electronic converter;
firstly, considering the optimization strategy of the reliability index,
in the formulas (3) and (4),
reference value of active power, P, allocated to the i-th power electronic converterciIs the actual value of the active power, P, of the ith power electronic converteri cNormalizing value for i-th power electronic converter active power, CiRated capacity, P, of the i-th power electronic convertercIs the active power sum of the power electronic converters of the same level, NcNumber of power electronic converters of the same level, PdeFor power electronic converter reliability index value, Pmax、PminRespectively are the upper limit value and the lower limit value of the active power of the power electronic converter after normalization, Npmax、NpminThe number of the power electronic converter power upper limit and the number of the power electronic converter power lower limit exceeding the normalization are respectively;
(ii) an objective function of the image data,
considering the reliability index and the voltage margin index, adding a punishment item in the objective function, and establishing the objective function considering the reliability index:
min{Ploss+MvVde+Mp∑Pde} (5)
in the formula (5), PlossIs the total active power loss value, V, of the AC/DC hybrid power distribution networkdeAs an indication of the voltage margin, Mv＞0、MpA penalty factor is more than 0; in the formula (6), Vmax、VminRespectively an upper limit and a lower limit of the voltage margin, Nvmax、NvminThe number of the upper limit and the lower limit exceeding the voltage margin are respectively; vjIs the jth node voltage amplitude;
thirdly, the constraint condition is satisfied,
and (3) constraint of an equation: formula (1); the inequality constrains: the method comprises the steps of power supply capacity, power upper and lower limit constraints and upper and lower limit constraints of all regulation variables;
3) optimal power flow control:
aiming at the minimized objective function in the formula (5), carrying out iterative solution on decision variables according to a formula (7), wherein in the formula (7), the optimized decision variables comprise direct-current power supply node voltage, active power, direct-current-direct-current converter load active power and outlet side voltage, alternating-current power supply node power, voltage amplitude and reactive power compensation; z > 0 is the number of iterations, a > 0 is the number of decision variables in the z-th iteration, b > 0 is the number of candidate solutions in the z-th iteration; p is 1,2, …, a is the decision variable index, q is 1,2, …, b is the candidate solution index, xz,p,qThe value of the p-th decision variable in the q-th candidate solution for the z-th iteration,
new value of the p-th decision variable in the q-th candidate solution, x, for the z-th iterationz,p,bestIs the best value, x, of the p-th decision variable in the b candidate solutions in the z-th iterationz,p,worstIs the worst value of the p-th decision variable in the b candidate solutions in the z-th iteration, r1,z,p、r2,z,pFor the p decision variable in the z iteration at [0,1 ]]Two random numbers, x, set within a rangebestTrend toward the best solution, xworstIn order to be the trend of the worst solution,
3. example (b):
referring to fig. 2, by using the optimal power flow control method of the alternating current-direct current hybrid power distribution network considering the reliability index, the objective function value and the active loss are calculated under the given network topology, the power generation and load parameter conditions and the optimization parameters of the power system.
Referring to fig. 3, the result and the objective function value calculated by using the optimal power flow control method of the alternating current-direct current hybrid power distribution network considering the reliability index are calculated.
Referring to fig. 4, by using the optimal power flow control method of the alternating current-direct current hybrid power distribution network considering the reliability index, the calculated result is compared before and after the power electronic converters normalize the active power value optimization after considering the reliability index.
The foregoing is only a preferred embodiment of the present invention, and it should be noted that, for those skilled in the art, various modifications and improvements can be made without departing from the principle of the present invention, and these should be considered as the protection scope of the present invention.
Claims (1)
1. An optimal power flow control method of an alternating current-direct current hybrid power distribution network considering reliability indexes is characterized by comprising the following steps:
1) and (3) fast load flow calculation:
establishing a power balance equation of the AC/DC hybrid power distribution network with the total node number N belonging to [3,9999] based on power balance:
in formula (1), j is 1, 2. PjsFor algebraic sum of active power injected into the source or load at node j, QjsIs the algebraic sum of the reactive power of the power supply or the load injected into the j node; pjAlgebraic sum Q for injecting active power of j node for other nodesjInjecting algebraic sum of reactive power of j nodes into other nodes;
the solving method of the formula (1) adopts a Newton Raphson method: performing Taylor series expansion on the power balance equation and omitting more than two terms to obtain a Newton Raphson method correction equation for load flow calculation of the AC/DC hybrid power distribution network, wherein the matrix form is expressed as a formula (2);
in the formula (2), J is a coefficient matrix of a correction equation, Δ P is the amount of unbalance of active power of each node, Δ Q is the amount of unbalance of reactive power of each node, Δ V is the correction amount of voltage amplitude of each node, and Δ θ is the correction amount of voltage phase angle of each node; j matrix of (2 k)1-1) rows (2 k)1-1) column elements, 2k2Line 2k2The elements of the column are all set to the number 1, where k1＞0、k2The node numbers with the node voltage amplitude values and the node voltage phase angles being fixed values are respectively greater than 0;
2) optimizing and modeling:
distributing the power electronic converters of the same grade according to a formula (3) in a rated capacity proportion, and balancing the thermal stress of the power electronic converters to optimize the service life of the power electronic converters; calculating according to a formula (4) to balance the reliability index of the thermal stress of the power electronic converter;
firstly, considering the optimization strategy of the reliability index,
in the formulas (3) and (4),
reference value of active power, P, allocated to the i-th power electronic converterciIs the actual value of the active power, P, of the ith power electronic converteri cNormalizing value for i-th power electronic converter active power, CiRated capacity, P, of the i-th power electronic convertercIs the active power sum of the power electronic converters of the same level, NcNumber of power electronic converters of the same level, PdeFor power electronic converter reliability index value, Pmax、PminRespectively are the upper limit value and the lower limit value of the active power of the power electronic converter after normalization, Npmax、NpminThe number of the power electronic converter power upper limit and the number of the power electronic converter power lower limit exceeding the normalization are respectively;
(ii) an objective function of the image data,
considering the reliability index and the voltage margin index, adding a punishment item in the objective function, and establishing the objective function considering the reliability index:
min{Ploss+MvVde+Mp∑Pde} (5)
in the formula (5), PlossIs the total active power loss value, V, of the AC/DC hybrid power distribution networkdeAs an indication of the voltage margin, Mv＞0、MpA penalty factor is more than 0; in the formula (6), Vmax、VminRespectively an upper limit and a lower limit of the voltage margin, Nvmax、NvminThe number of the upper limit and the lower limit exceeding the voltage margin are respectively; vjIs the jth node voltage amplitude;
thirdly, the constraint condition is satisfied,
and (3) constraint of an equation: formula (1); the inequality constrains: the method comprises the steps of power supply capacity, power upper and lower limit constraints and upper and lower limit constraints of all regulation variables;
3) optimal power flow control:
aiming at the minimized objective function in the formula (5), iterative solution of decision variables is carried out according to the formula (7), and in the formula (7), the optimized decision variables comprise direct-current power supply node voltage, active power, direct-current-direct-current converter load active power and outlet side voltage, alternating-current power supply node power, voltage amplitude and reactive power compensationPaying; z > 0 is the number of iterations, a > 0 is the number of decision variables in the z-th iteration, b > 0 is the number of candidate solutions in the z-th iteration; p is 1,2, …, a is the decision variable index, q is 1,2, …, b is the candidate solution index, xz,p,qThe value of the p-th decision variable in the q-th candidate solution for the z-th iteration,
new value of the p-th decision variable in the q-th candidate solution, x, for the z-th iterationz,p,bestIs the best value, x, of the p-th decision variable in the b candidate solutions in the z-th iterationz,p,worstIs the worst value of the p-th decision variable in the b candidate solutions in the z-th iteration, r1,z,p、r2,z,pFor the p decision variable in the z iteration at [0,1 ]]Two random numbers, x, set within a rangebestTrend toward the best solution, xworstIn order to be the trend of the worst solution,
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