CN110611337B - Power supply reliability-based power system energy and standby combined scheduling method - Google Patents
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Abstract
The invention relates to a power system energy and standby combined scheduling method based on power supply reliability, and belongs to the technical field of power system scheduling. The scheduling method of the invention takes the minimum sum of the energy cost, the standby cost and the risk loss cost of the power system as a target, takes the expectation of insufficient power as a reliability index for constraint, and optimizes the obtained operation mode of the power system; the method determines the system standby capacity according to the real-time load level and the startup combination of the power system, effectively relieves the system standby pressure, fully utilizes the power generation resources, saves the running standby cost of the system, and improves the running economy of the power system. The method can be used for the combined economic dispatching of the energy and the reserve of the large power grid, can obviously improve the reliability of the system operation with smaller cost increment, and has important practical significance and good application prospect.
Description
Technical Field
The invention relates to a power system energy and standby combined scheduling method based on power supply reliability, and belongs to the technical field of power system scheduling.
Background
The reserve capacity of the power system is the reserve capacity beyond the guaranteed system load, and is the extra active capacity required by meeting load prediction errors, unexpected shutdown of equipment, new energy source prediction deviation and the like, so that the system is guaranteed to be in a new stable operation state in a smooth transition mode when being disturbed in a certain range. In the conventional reserve capacity reservation method, in order to ensure safe and reliable operation of the system, extreme conditions such as large fluctuation of load or unexpected shutdown of equipment are generally considered, a constant reserve capacity is reserved, and the capacity is determined according to a fixed proportion of the maximum power generation load or the maximum equipment capacity of the system. With the deepening of the electric power marketization degree and the development of the standby market, the economy of system operation is more and more emphasized, the economic cost is mainly considered in the configuration of the standby capacity, the standby requirement is precisely determined by combining the electric energy market trading result and the power grid operation state, and the generated output and the standby output of the unit are jointly optimized by taking the minimum total system operation cost as a target.
In recent years, the construction of ultra-high voltage transmission lines continuously expands the scale of a power grid, continuously strengthens the coupling of the power grid among regions, increasingly highlights the integrated situation of a large power grid, and improves the capabilities of unified optimization scheduling of the whole power grid and realization of optimization configuration of resources in a wider range. Meanwhile, the operation characteristics of the power grid are also changed profoundly, the transmission and receiving ends of the extra-high voltage power grid and the alternating current and direct current are strongly coupled, and the overall safety and stability of the power grid are affected by local faults caused by unit shutdown. In addition, with the expansion of the power supply scale of the power grid, the number of large networked market users is increased, the real-time demand of the load is more sensitive to the electricity price, and the electricity utilization behavior has great uncertainty. In order to ensure the safe and stable operation of the system and improve the power supply reliability of a large power grid, the reserve capacity needs to be increased to cope with the power supply shortage caused by load fluctuation and equipment failure.
The influence of uncertain factors such as load fluctuation, unit faults and the like is comprehensively considered, a reasonable system spare capacity configuration method is formulated, the safe and stable operation of the system is guaranteed, the economical efficiency is considered, and the method is a key concern in the dispatching operation of the current power system. Some research achievements have been achieved at home and abroad by a method for determining reserve capacity based on uncertain factors and operation cost, but the following problems still exist in consideration of the requirements of safe and economic operation of a power system: under the traditional operation standby management mode only considering reliability, the reserved standby capacity has low utilization efficiency, so that the power generation resource is seriously wasted, and the system has to bear higher standby cost and electric energy opportunity cost, so that the economy is poorer; the method for determining the reserve capacity through the combined optimization of the electric energy and the reserve capacity has higher accuracy and smaller reserve capacity, and once load deviation or equipment failure which is more serious than expected occurs, greater power failure loss is caused and certain risk cost needs to be borne; quantitative evaluation on the risk or reliability of system operation is not considered, and the reliability and economy in the power grid operation process are balanced by lack of uniform economy indexes.
Disclosure of Invention
The invention aims to provide a power system energy and standby combined scheduling method based on power supply reliability, which comprehensively considers factors such as load prediction deviation, a power grid real-time operation mode, system reliability indexes and the like, minimizes the system operation total cost and risk loss cost, and determines the energy and standby capacity of a power system from the two aspects of reliability and economy.
The invention provides a power system energy and standby combined scheduling method based on power supply reliability, which comprises the following steps:
(1) Predicting the load value of the power system in 24 hours on the current scheduling day, which comprises the following specific steps:
(1-1) recording the current scheduling date as D, acquiring the actual load value of the power system 60 days before the current scheduling date from the power system scheduling center, and calculating the load increase rate of the power system of each historical scheduling date D at the scheduling time t compared with the last time t-1
Wherein: d represents a historical scheduling day, D = D-60, …, D-1,t represents a scheduling time, t =1,2, …,24,
the actual load value of the system at the dispatching time t on the historical dispatching day d;
(1-2) scheduling according to each historical scheduling day 60 days before the current scheduling day of the step (1-1)Scaled power system load growth rate
Calculating the average value of the system load increase rate of the power system at the scheduling time t compared with the last scheduling time t-1
(1-3) acquiring the actual load value of the 24 th scheduling time of the day (D-1) before the current scheduling date from the power system scheduling center
To be provided with
As the reference load, the average load increase rate at each scheduling time obtained in the step (1-2) is used
Sequentially calculating the predicted value of the load of the power system at the scheduling time t on the current scheduling day D
(2) Determining the reserve capacity requirement of the power system on the current scheduling day, wherein the specific process is as follows:
(2-1) determining a load reserve capacity demand of the power system on the current scheduling day, comprising the steps of:
(2-1-1) obtaining the predicted value of the system load at the scheduling time t 60 days before the current scheduling date from the power system scheduling center
And the actual value
Calculating the system load prediction deviation of the historical scheduling day d at the scheduling time t
(2-1-2) forecasting deviation of load of the power system at dispatching time t according to the historical dispatching day d obtained in the step (2-1-1)
Calculating the maximum load prediction deviation of the power system at the scheduling time t on the current scheduling day
(2-1-3) calculating the maximum load prediction deviation of the power system at the scheduling time t on the current scheduling day according to the step (2-1-2)
And (1) calculating the system load predicted value of the current scheduling day D at the scheduling time t
Determining the load reserve capacity requirement of the current dispatching day D power system at the dispatching time t
(2-2) determining the emergency reserve capacity demand of the power system on the current scheduling day, comprising the steps of:
(2-2-1) setting the active power of a generator set i planned to be started in the power system on the current dispatching day at the dispatching time t
And the load demand of the power system at the scheduling time t is met:
in the formula: i represents the generator sets planned to be started up in the power system, n is the number of the generator sets planned to be started up and is obtained from a power system dispatching center,
obtained according to the step (1-3);
active power G of each generator set at each scheduling time i,t The active power vector G of all the generator sets at each scheduling moment is obtained according to the scheduling time sequence;
(2-2-2) according to the active power G of all the generator sets on the current scheduling day given in the step (2-2-1) i,t Calculating the maximum power generation shortage of the power system possibly caused by the fault outage of the single generator set at the scheduling time t, and taking the maximum power generation shortage of the power system as the accident reserve capacity requirement of the power system at the scheduling time t on the current scheduling day
(2-3) load reserve capacity requirement calculated according to the step (2-1-3)To find
Calculating the accident reserve capacity requirement calculated in the step (2-2-2)
Obtaining the reserve capacity R of the power system at the dispatching time t on the current dispatching day t ：
(3) Calculating the expected power shortage as a reliability index of the power system, wherein the calculation steps are as follows:
(3-1) by S i Representing the working state of the generator set i, setting two states of failure and operation of each generator set, wherein the failure of the generator sets is an independent event, and S i Is a discrete random variable:
obtaining fault rates lambda of all generator sets from power system dispatching center i And a repair rate parameter μ i Calculating the probability u of failure and outage of the generator set i i And probability of normal operation a i ：
(3-2) calculating the system power supply shortage caused by the failure outage of the generator set as the expected power shortage of the power system at the scheduling time t:
wherein:
x t represents the state of the power system at the scheduled time t, x t ＝(S 1 ,S 2 …,S n )，S i Is a random variable, x t Is a random vector, X represents the state space of the power system at the scheduling time t,
I f (x t ) The state function of the power system at the scheduling time t is shown as the following expression:
L C (x t ) Indicating that the power system is in fault system state x t Then, the minimum load reduction value required for restoring the power system to a static safe operation point is determined according to a single fault safety criterion specified in the power system that at most 1 generator set fails, and if the generator set i fails at this time, the following steps are performed:
L C (x t )＝G i,t
in the formula: g i,t The active power of the generator set i given in the step (2-2-1) at the scheduling time t;
P(x t ) Is x t Of a probability distribution function, P (x) t ) Representing power system state x t I.e. considering that the states of all generator sets are random variables independent of each other, only when a generator set i fails down:
in the formula: symbol Π denotes the multiplication by multiplication, P (S) i ) Indicating that genset i is in state S i Probability of (u) i 、a i The probability of failure outage and the probability of normal operation of the generator set i calculated in the step (3-1) respectivelyRate;
(4) A power system energy and standby combined scheduling model based on power supply reliability is constructed as follows:
(4-1) an objective function of the power system energy and backup joint scheduling model based on supply reliability expects an EW to be minimized for the total cost of power system operation:
in the formula: g i,t The active power of the generator set i at the scheduling time t is obtained; r i,t The reserve capacity of the generator set i at the scheduling time t is a decision variable of the joint scheduling model; EWG t The expectation of the total cost of normal operation of all the generator sets of the power system at the scheduling time t, the quantity to be solved, the EWL t The expected risk loss cost of the power system at the scheduling time t is the amount to be solved;
total cost expectation EWG for normal operation of all units of power system at scheduling time t t The calculation formula of (2) is as follows:
in the formula: n is the number of generator sets planned to be started and is obtained from a power system dispatching center; WG (WG) t The total cost of normal operation of all the generator sets of the power system at the scheduling time t, the waiting quantity a i For the probability of normal operation, alpha, of the generator set i calculated in step (3-1) i 、β i Respectively acquiring the energy price and the standby price of the generator set i from the trading center of the power system;
risk loss cost expectation EWL of power system at scheduling time t t The calculation formula is as follows:
in the formula: gamma ray VOLL For the unit power failure loss of the power system, u is obtained from a power system dispatching center i Is the probability that the generator set i is in the fault outage state at the scheduling time t, a j Is the probability that the generator set j is in the normal operation state, u i And a j Calculated in the step (3-1);
(4-2) constraints of the power system energy and standby joint scheduling model based on the power supply reliability include:
(4-2-1) power system circuit active power flow constraint:
|z k,t |≤z k,max
in the formula: z is a radical of k,max The method comprises the steps that the transmission capacity limit of a power transmission line in a power system is obtained from a power system dispatching center; z is a radical of formula k,t The method is characterized in that the method is a method for determining the power flow of a power transmission line k at a scheduling time t in a power system:
wherein, g i,k Acquiring a power transmission distribution factor of the generator set i to the power transmission line k from a power system dispatching center; g i,t The active power of the generator set i at the scheduling time t, the amount to be solved, g i,k Acquiring a power transmission distribution factor of the node load j to the power transmission line k from a power system dispatching center; PF (particle Filter) j,t And acquiring a load predicted value of the current scheduling day node j at the scheduling time t from the power system scheduling center.
(4-2-2) power system active power supply and demand balance constraint:
l is the number of network lines of the power system, obtained from the power system dispatching center, delta k Obtaining the line loss rate of the transmission line k from a power system dispatching center, PF t Obtaining a load predicted value of the power system at the dispatching time t on the current dispatching day through the step (1-3);
(4-2-3) power system reserve capacity constraint:
wherein R is t Obtaining the standby requirement of the power system at the dispatching time t through the step (2-3);
(4-2-4) upper and lower limit constraints of the power system generator set output:
(4-2-5) the climbing capability of the power system generator set is restrained:
wherein,
respectively considering the maximum active power of the climbing constraint for the generator set i at the scheduling time t, and acquiring the maximum active power from a power system scheduling center;
(4-2-6) the reliability index constraint of the power system, wherein the expression formula is as follows:
in the formula, EDNS t The EDNS is calculated from the step (3-2) for the power system at the dispatching time t to expect the power shortage max The power system dispatching center is used for safely meeting the expected upper limit of power shortage of the power system all day after the dispatching daySetting an operation requirement;
(5) Solving a power system energy and standby combined scheduling model which is composed of the objective function and the constraint condition and is based on power supply reliability by using a Lagrange relaxation method, and solving to obtain the optimal active power G of each generator set in the current scheduling day i,t And spare capacity R i,t ；
(6) Obtaining an active power optimization result G of all generator sets of the power system at the scheduling time t according to the step (5) i,t And spare capacity optimization result R i,t Constructing an active power vector G' according to a scheduling time sequence;
(7) Setting a convergence judgment parameter epsilon, comparing the active power vector G 'with the active power vector G in the step (2-2-1), if G' -G | is less than epsilon, calculating convergence, and comparing the active power G of each generator set in the step (6) i,t And reserve capacity R i,t As a result of joint scheduling of the energy and the reserve of the power system, joint scheduling of the energy and the reserve of the power system based on power supply reliability is realized; if | G k+1 -G k If | ≦ ε, the result does not converge and let G = G', return to step (2-2-1).
The power system energy and standby combined scheduling method based on the power supply reliability has the following advantages:
1. compared with the traditional constant spare capacity determining method, the scheduling method can effectively relieve the spare pressure of the system, fully utilize power generation resources and save the running spare cost of the system, thereby improving the running economy of the power system.
2. The scheduling method provided by the invention aims at minimizing the sum of the energy cost, the standby cost and the risk loss cost of the power system, restrains the power shortage expectation as a reliability index, optimizes the obtained power system operation mode, can effectively reduce the risk loss cost of the system, and improves the operation reliability of the power system.
3. According to the method, the reliable iteration of the power system energy and reserve combined scheduling model and the reserve capacity demand problem is considered, the reserve capacity and active power distribution of the generator set can be fully coordinated, and therefore the safety and stability of the system can be improved by increasing smaller economic cost.
Drawings
Fig. 1 is a flow chart of a power system energy and standby joint scheduling method based on power supply reliability according to the present invention.
Detailed Description
The power system energy and standby combined scheduling method based on power supply reliability, provided by the invention, has a flow diagram as shown in fig. 1, and comprises the following steps:
(1) Predicting the load value of the power system in 24 hours on the current scheduling day, which comprises the following specific steps:
(1-1) recording the current scheduling date as D, acquiring the actual load value of the power system 60 days (D-60-D-1) before the current scheduling date from the power system scheduling center, and calculating the load increase rate of the power system at the previous time t-1 of the scheduling time t of each historical scheduling date D
Wherein: d represents a historical scheduling day, D = D-60, …, D-1,t represents a scheduling time, t =1,2, …,24,
the actual load value of the system at the scheduling time t on the historical scheduling day d;
(1-2) electric power system load increase rate at each scheduling time according to each historical scheduling day 60 days before the current scheduling day of the step (1-1)
Calculating the average value of the system load increase rate of the power system at the dispatching time t compared with the last dispatching time t-1
(1-3) acquiring the actual load value of the 24 th scheduling time of the day (D-1) before the current scheduling date from the power system scheduling center
To be provided with
As the reference load, the average load increase rate at each scheduling time obtained in the step (1-2) is used
Sequentially calculating the predicted value of the load of the power system at the scheduling time t on the current scheduling day D
(2) Determining the reserve capacity requirement of the power system on the current scheduling day, wherein the specific process is as follows:
(2-1) determining the load reserve capacity requirement of the power system on the current scheduling day, wherein the load reserve capacity is set as required for balancing instant load fluctuation and load prediction error, and the method comprises the following steps:
(2-1-1) obtaining the predicted value of the system load at the scheduling time t 60 days before the current scheduling date from the power system scheduling center
And the actual value
Calculating the system load prediction deviation of the historical scheduling day d at the scheduling time t
(2-1-2) predicting the load deviation of the power system at the scheduling time t according to the historical scheduling day d obtained in the step (2-1-1)
Calculating the maximum load prediction deviation of the power system at the current scheduling day scheduling time t
(2-1-3) calculating the maximum load prediction deviation of the power system at the scheduling time t on the current scheduling day according to the step (2-1-2)
And the system load predicted value of the current scheduling day D at the scheduling time t calculated in the step (1-3)
Determining the load reserve capacity requirement of the current dispatching day D power system at the dispatching time t
(2-2) determining the accident reserve capacity requirement of the power system on the current scheduling day, wherein the accident reserve capacity is the power generation capacity required to be set for ensuring normal power supply when power generation and power transmission and transformation equipment in the power system fails, and the method comprises the following steps:
(2-2-1) according to the system load prediction condition of the power system on the current scheduling day, setting the active power G of a generator set i planned to be started in the power system on the current scheduling day at the scheduling time t i,t And the load demand of the power system at the scheduling time t is met:
in the formula: i represents the generator sets planned to be started up by the power system, n is the number of the generator sets planned to be started up, and is obtained from a power system dispatching center,
obtained according to the step (1-3);
active power G of each generator set at each scheduling time i,t The active power vector G of all the generator sets at each scheduling moment is obtained according to the scheduling time sequence;
(2-2-2) according to the active power G of all the generator sets on the current scheduling day given in the step (2-2-1) i,t Calculating the maximum power generation shortage of the power system possibly caused by the fault outage of the single generator set at the scheduling time t, and taking the maximum power generation shortage of the power system as the accident reserve capacity requirement of the power system at the scheduling time t on the current scheduling day
(2-3) the reserve capacity must satisfy both the load deviation and the supply capacity requirement for equipment failure, and therefore, the load reserve capacity requirement calculated according to step (2-1-3)
Calculating the accident reserve capacity requirement calculated in the step (2-2-2)
Obtaining the reserve capacity R of the power system at the dispatching time t on the current dispatching day t ：
(3) Calculating the expected power shortage as a reliability index of the power system, wherein the calculation steps are as follows:
(3-1) by S i Representing the working state of the generator set i, setting two states of failure and operation of each generator set, wherein the failure of the generator sets is an independent event, and S i Is a discrete random variable:
obtaining fault rates lambda of all generator sets from power system dispatching center i And a repair rate parameter μ i And calculating the probability u of failure outage of the generator set i i And probability of normal operation a i ：
(3-2) calculating the system power supply shortage caused by the failure outage of the generator set as the expected power shortage of the power system at the scheduling time t:
wherein:
x t represents the state of the power system at the scheduled time t, x t ＝(S 1 ,S 2 …,S n )，S i Is a random variable, x t Is a random vector, X represents the state space of the power system at the scheduling time t,
I f (x t ) The state function of the power system at the scheduling time t is shown as the following expression:
L C (x t ) Indicating that the power system is in fault system state x t Then, the minimum load reduction value required for restoring the power system to a static safe operation point is determined according to a single fault safety criterion specified in the power system that at most 1 generator set fails, and if the generator set i fails at this time, the following steps are performed:
L C (x t )＝G i,t
in the formula: g i,t The active power of the generator set i given in the step (2-2-1) at the scheduling time t;
P(x t ) Is x t Of a probability distribution function, P (x) t ) Representing power system state x t I.e. considering that the states of all generator sets are random variables independent of each other, only when a generator set i fails down:
in the formula: symbol Π denotes the multiplication by two, P (S) i ) Indicating that genset i is in state S i Probability of (u) i 、a i Respectively calculating the probability of failure shutdown and the probability of normal operation of the generator set i in the step (3-1);
(4) A power system energy and standby combined scheduling model based on power supply reliability is constructed as follows:
(4-1) an objective function of the power system energy and backup joint scheduling model based on supply reliability expects an EW to be minimized for the total cost of power system operation:
in the formula: g i,t The active power of the generator set i at the scheduling time t is obtained; r i,t The reserve capacity of the generator set i at the scheduling time t is used as a decision variable of the joint scheduling model; EWG t For the total cost expectation of normal operation of all generator sets of the power system at the scheduling time t, the waiting quantity, EWL t The expected risk loss cost of the power system at the scheduling time t is the amount to be solved;
total cost expectation EWG for normal operation of all units of power system at scheduling time t t The calculation formula of (2) is as follows:
in the formula: n is the number of generator sets planned to be started and is obtained from a power system dispatching center; WG (WG) t The total cost of normal operation of all the generator sets of the power system at the scheduling time t, the waiting quantity a i For the probability of normal operation, alpha, of the generator set i calculated in step (3-1) i 、β i Respectively acquiring the energy price and the standby price of the generator set i from the trading center of the power system;
risk loss cost expectation EWL of power system at scheduling time t t The calculation formula is as follows:
in the formula: gamma ray VOLL For power system unit power failureLoss, obtained from the electric power system dispatch center, u i Is the probability that the generator set i is in the fault outage state at the scheduling time t, a j Is the probability that the generator set j is in the normal operation state, u i And a j Calculated in the step (3-1);
(4-2) constraints of the power system energy and standby joint scheduling model based on the power supply reliability include:
(4-2-1) power system circuit active power flow constraint:
|z k,t |≤z k,max
in the formula: z is a radical of k,max The method comprises the steps that the transmission capacity limit of a power transmission line in a power system is obtained from a power system dispatching center; z is a radical of k,t The method is characterized in that the method is a method for determining the power flow of a power transmission line k at a scheduling time t in a power system:
wherein, g i,k Acquiring a power transmission distribution factor of a generator set i to the power transmission line k from a power system dispatching center; g i,t Active power of the generator set i at the scheduling time t, the amount to be solved, g i,k Acquiring a power transmission distribution factor of the node load j to the power transmission line k from a power system dispatching center; PF (particle Filter) j,t And acquiring a load predicted value of the current scheduling day node j at the scheduling time t from the power system scheduling center.
(4-2-2) power system active power supply and demand balance constraint:
l is the number of network lines of the power system, obtained from the power system dispatching center, delta k Obtaining the line loss rate of the transmission line k from a power system dispatching center, PF t Obtaining a load predicted value of the power system at the dispatching time t on the current dispatching day through the step (1-3);
(4-2-3) power system reserve capacity constraint:
wherein R is t Obtaining the standby requirement of the power system at the dispatching time t through the step (2-3);
(4-2-4) restraining the upper limit and the lower limit of the output of the generator set of the power system:
(4-2-5) the climbing capability of the power system generator set is restrained:
wherein,
respectively considering the maximum active power of the climbing constraint for the generator set i at the scheduling time t, and acquiring the maximum active power from a power system scheduling center;
(4-2-6) the reliability index constraint of the power system, wherein the expression formula is as follows:
in the formula, EDNS t The EDNS is calculated from the step (3-2) for the power system at the dispatching time t to expect the power shortage max Setting an expected upper limit of power shortage of the power system in the whole day of a dispatching day according to a safe operation requirement by a power system dispatching center;
(5) By using a lagrangian relaxation method, a power system energy and standby combined scheduling model based on power supply reliability and composed of the objective function and the constraint condition is solved, and taking a certain scheduling time as an example, the lagrangian function can be written as:
α,β,λ i,max ,λ i,min ,μ i,max ,μ i,min ,τ k,max ,τ k,min and ω is the lagrange multiplier. Analyzing the resolvable structure of the equation by using a dual theorem to form a two-layer maximum-minimum optimization problem:
by utilizing Lagrange multiplier transfer parameters, the two-layer problem is repeatedly iterated to construct a feasible solution, and the optimal active power G of each generator set in the current scheduling day can be obtained through solving i,t And reserve capacity R i,t ；
(6) Obtaining an active power optimization result G of all generator sets of the power system at the scheduling time t according to the step (5) i,t And spare capacity optimization result R i,t Constructing an active power vector G' according to a scheduling time sequence;
(7) Setting a convergence judgment parameter epsilon, comparing the active power vector G 'with the active power vector G in the step (2-2-1), if G' -G | is less than epsilon, calculating convergence, and comparing the active power G of each generator set in the step (6) i,t And reserve capacity R i,t As a power system energy and standby combined scheduling result, power system energy and standby combined scheduling based on power supply reliability is realized; if | G k+1 -G k If | ≦ ε, the result does not converge and let G = G', return to step (2-2-1).
Obviously, the method adopted in the implementation steps proposed by the method can be flexibly selected and customized according to needs, and the expandability is strong. Therefore, the above implementation steps are only used for illustrating and not limiting the technical solution of the present invention. Any modification or partial replacement without departing from the spirit and scope of the present invention should be covered in the claims of the present invention.
Claims (1)
1. A power system energy and standby combined scheduling method based on power supply reliability is characterized by comprising the following steps:
(1) Predicting the load value of the power system in 24 hours on the current scheduling day, which comprises the following specific steps:
(1-1) recording the current scheduling date as D, acquiring the actual load value of the power system 60 days before the current scheduling date from the power system scheduling center, and calculating the load increase rate of the power system at the previous time t-1 of each historical scheduling date D in comparison with the scheduling time t
Wherein: d represents historical schedule day, D = D-60, …, D-1,t represents schedule time, t =1,2, …,24,
the actual load value of the system at the dispatching time t on the historical dispatching day d;
(1-2) the load increase rate of the power system at each scheduling time according to each historical scheduling day 60 days before the current scheduling day in the step (1-1)
Calculating the average value of the system load increase rate of the power system at the dispatching time t compared with the last dispatching time t-1
(1-3) acquiring the actual load value of the 24 th scheduling time of the day (D-1) before the current scheduling date from the power system scheduling center
To be provided with
As the reference load, the average load increase rate at each scheduling time obtained in the step (1-2) is used
Sequentially calculating the predicted value of the load of the power system at the scheduling time t on the current scheduling day D
(2) Determining the reserve capacity requirement of the power system on the current scheduling day, wherein the specific process is as follows:
(2-1) determining the load reserve capacity demand of the power system on the current scheduling day, comprising the steps of:
(2-1-1) obtaining the predicted value of the system load 60 days before the current scheduling day at the scheduling time t from the power system scheduling center
And actual value
Calculating the system load prediction deviation of the historical scheduling day d at the scheduling time t
(2-1-2) forecasting deviation of load of the power system at dispatching time t according to the historical dispatching day d obtained in the step (2-1-1)
Calculating the maximum load prediction deviation of the power system at the scheduling time t on the current scheduling day
(2-1-3) according to the load prediction deviation of the power system at the scheduling time t maximum on the current scheduling day calculated in the step (2-1-2)
And (1) calculating the system load predicted value of the current scheduling day D at the scheduling time t
Determining the load reserve capacity requirement of the current dispatching day D power system at the dispatching time t
(2-2) determining the emergency reserve capacity demand of the power system on the current scheduling day, comprising the steps of:
(2-2-1) setting active power G of generator set i planned to be started in power system on current dispatching day at dispatching time t i,t And the load demand of the power system at the scheduling time t is met:
in the formula: i represents the generator sets planned to be started up in the power system, n is the number of the generator sets planned to be started up and is obtained from a power system dispatching center,
obtained according to the step (1-3);
active power G of each generator set at each scheduling time i,t The active power vector G of all the generator sets at each scheduling moment is obtained according to the scheduling time sequence;
(2-2-2) according to the active power G of all the generator sets on the current scheduling day given in the step (2-2-1) i,t Calculating the maximum power generation shortage of the power system possibly caused by the fault outage of the single generator set at the scheduling time t, and taking the maximum power generation shortage of the power system as the accident reserve capacity requirement of the power system at the scheduling time t on the current scheduling day
(2-3) the load reserve capacity demand calculated according to the step (2-1-3)
Calculating the accident reserve capacity requirement calculated in the step (2-2-2)
Obtaining the reserve capacity R of the power system at the dispatching time t on the current dispatching day t ：
(3) Calculating the expected power shortage as a reliability index of the power system, wherein the calculation steps are as follows:
(3-1) by S i Representing the working state of the generator set i, setting two states of failure and operation of each generator set, wherein the failure of the generator sets is an independent event, and S i Is a discrete random variable:
obtaining fault rates lambda of all generator sets from power system dispatching center i And a repair rate parameter μ i And calculating the probability u of failure outage of the generator set i i And probability of normal operation a i ：
(3-2) calculating the system power supply shortage caused by the failure outage of the generator set as the expected power shortage of the power system at the scheduling time t:
wherein:
x t represents the state of the power system at the scheduled time t, x t ＝(S 1 ,S 2 …,S n )，S i Is a random variable, x t Is a random vector, X represents the state space of the power system at the scheduling time t,
I f (x t ) The state function of the power system at the scheduling time t is shown as the following expression:
L C (x t ) Indicating that the power system is in fault system state x t Then, the minimum load reduction value required for restoring the power system to a static safe operation point is determined according to a single fault safety criterion specified in the power system that at most 1 generator set fails, and if the generator set i fails at this time, the following steps are performed:
L C (x t )＝G i,t
in the formula: g i,t The active power of the generator set i given in the step (2-2-1) at the scheduling time t;
P(x t ) Is x t Of a probability distribution function, P (x) t ) Representing power system state x t I.e. considering that the states of all generator sets are random variables independent of each other, only when a generator set i fails down:
in the formula: symbol Π denotes the multiplication by multiplication, P (S) i ) Indicating that genset i is in state S i Probability of (u) i 、a i Respectively calculating the probability of failure outage and the probability of normal operation of the generator set i in the step (3-1);
(4) A power system energy and standby combined scheduling model based on power supply reliability is constructed as follows:
(4-1) an objective function of the power system energy and backup joint scheduling model based on supply reliability expects an EW to be minimized for the total cost of power system operation:
in the formula: g i,t The active power of the generator set i at the scheduling time t is obtained; r i,t The reserve capacity of the generator set i at the scheduling time t is used as a decision variable of the joint scheduling model; EWG t For the total cost expectation of normal operation of all generator sets of the power system at the scheduling time t, the waiting quantity, EWL t The expected risk loss cost of the power system at the scheduling time t is the amount to be solved;
total cost expectation EWG for normal operation of all units of power system at scheduling time t t The calculation formula of (2) is as follows:
in the formula: n is the number of generator sets planned to be started and is obtained from a power system dispatching center; WG (WG) t The total cost of normal operation of all the generator sets of the power system at the scheduling time t, the waiting quantity a i For the probability of normal operation, alpha, of the generator set i calculated in step (3-1) i 、β i Respectively acquiring an energy price and a standby price of the generator set i from a trading center of the power system;
risk loss cost expectation EWL of power system at scheduling time t t The calculation formula is as follows:
in the formula: gamma ray VOLL For the unit power failure loss of the power system, u is obtained from a power system dispatching center i For generator set i in dispatchingProbability of moment t being in a fault shutdown state, a j Is the probability that the generator set j is in the normal operation state, u i And a j Calculated in the step (3-1);
(4-2) constraints of the power system energy and standby joint scheduling model based on the power supply reliability include:
(4-2-1) power system circuit active power flow constraint:
|z k,t |≤x k,max
in the formula: z is a radical of k,max The method comprises the steps that the transmission capacity limit of a power transmission line in a power system is obtained from a power system dispatching center; z is a radical of formula k,t The method is characterized in that the method is a method for controlling the power flow of a power transmission line k in a power system at a scheduling time t:
wherein, g i,k Acquiring a power transmission distribution factor of the generator set i to the power transmission line k from a power system dispatching center; g i,t The active power of the generator set i at the scheduling time t, the amount to be solved, g i,k Acquiring a power transmission distribution factor of the node load j to the power transmission line k from a power system dispatching center; PF (particle Filter) j,t Acquiring a load predicted value of a current scheduling day node j at a scheduling time t from a power system scheduling center;
(4-2-2) power system active power supply and demand balance constraint:
l is the number of network lines of the power system, obtained from the power system dispatching center, delta k Obtaining the line loss rate of the transmission line k from a power system dispatching center, PF t Obtaining a load predicted value of the power system at the dispatching time t on the current dispatching day through the step (1-3);
(4-2-3) power system reserve capacity constraint:
wherein R is t Obtaining the standby requirement of the power system at the dispatching time t through the step (2-3);
(4-2-4) restraining the upper limit and the lower limit of the output of the generator set of the power system:
(4-2-5) the climbing capability of the power system generator set is restrained:
wherein,
respectively considering the maximum active power of the climbing constraint for the generator set i at the scheduling time t, and acquiring the maximum active power from a power system scheduling center;
(4-2-6) the reliability index constraint of the power system, wherein the expression formula is as follows:
in the formula, EDNS t The EDNS is calculated from the step (3-2) for the power system at the dispatching time t to expect the power shortage max Setting an expected upper limit of power shortage of the power system in the whole day of the dispatching day by the dispatching center of the power system according to the safe operation requirement；
(5) Solving a power system energy and standby combined scheduling model which is composed of the objective function and the constraint condition and is based on power supply reliability by using a Lagrange relaxation method, and solving to obtain the optimal active power G of each generator set in the current scheduling day i,t And spare capacity R i,t ；
(6) Obtaining an active power optimization result G of all generator sets of the power system at the scheduling time t according to the step (5) i,t And spare capacity optimization result R i,t Constructing an active power vector G' according to a scheduling time sequence;
(7) Setting a convergence judgment parameter epsilon, comparing the active power vector G 'with the active power vector G in the step (2-2-1), and if G' -G is not visible<E, calculating convergence, and calculating the active power G of each generator set in the step (6) i,t And spare capacity R i,t As a power system energy and standby combined scheduling result, power system energy and standby combined scheduling based on power supply reliability is realized; if | G k+1 -G k If | ≦ ε, the result does not converge and let G = G', return to step (2-2-1).
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