Intra-day rolling scheduling method for integrated heat and electricity system

This is a continuation of International Application No. PCT/CN2017/114465 filed Dec. 4, 2017, which claims priority to Chinese Patent Application No. 201710989015.9, filed Oct. 22, 2017, the entire disclosures of which are incorporated herein by reference.

The present disclosure relates to an intra-day rolling scheduling method for an integrated heat and electricity system, belongs to the field of operation and control technologies for a power grid with a plurality of energy forms.

The multi-energy system may include a plurality of energy flow subsystems. The energy may refer to such as electricity, heat, cold, gas, or transportation. The multi-energy system has considerable benefits, such as reducing energy consumption, improving overall energy efficiency, and reducing total energy costs, but improves the control complex.

The integrated heat and electricity system is one of the multi-energy systems. The integrated heat and electricity system may include a power grid and a heating network, in which coupling components such as combined heat and power units, heat pumps, and circulating pumps may couple the power grid and the heating network. However, there coupling components bring about new requirements on operation and control on the integrated heat and electricity system, such as the intra-day rolling scheduling on the integrated heat and electricity system needs to consider these coupling components comprehensively.

The intra-day rolling scheduling method for the integrated heat and electricity system, provided by the present disclosure, may include the following: establishing an objective function for scheduling of the integrated heat and electricity system, the objective function aiming to make operating costs of the integrated heat and electricity system to be a minimum, the integrated heat and electricity system comprising combined heat and power units, thermal power units, heat pumps, and circulating pump; establishing constraints for a steady-state safe operation of the integrated heat and electricity system; and solving the objective function based on the constraints by an interior point method, to obtain an active power and a heating power of each combined heat and power unit, an active power of each thermal power unit, a heating power of each heat pump, and an active power consumed by each circulating pump, as an intra-day rolling scheduling scheme of the integrated heat and electricity system.

FIG. 1 is a block diagram of an integrated heat and electricity system according to an embodiment of the present disclosure.

FIG. 2 is a flowchart of an intra-day rolling scheduling method for an integrated heat and electricity system according to an embodiment of the present disclosure.

The integrated heat and electricity system is shown in FIG. 1 . The integrated heat and electricity system may include a power grid and a heating network. Coupling components such as combined heat and power units, heat pumps, and circulating pumps may couple the power grid and the heating network.

The intra-day rolling scheduling method for the integrated heat and electricity system, provided by the present disclosure, may include: establishing ( 110 ) an objective function for scheduling of the integrated heat and electricity system, the objective function aiming to make operating costs of the integrated heat and electricity system to be a minimum, the integrated heat and electricity system comprising combined heat and power units, thermal power units, heat pumps, and circulating pump; establishing ( 120 ) constraints for a steady-state safe operation of the integrated heat and electricity system; and solving ( 130 ) the objective function based on the constraints by an interior point method, to obtain an active power and a heating power of each combined heat and power unit, an active power of each thermal power unit, a heating power of each heat pump, and an active power consumed by each circulating pump, as an intra-day rolling scheduling scheme of the integrated heat and electricity system.

In detail, the intra-day rolling scheduling method for the integrated heat and electricity system, provided by the present disclosure, may include the following steps.

(1) An objective function for optimal scheduling of the integrated heat and electricity system may be established by a formula of:

min ⁢ ∑ t = 1 16 ⁢ ( ∑ b = 1 N ⁢ F ⁢ ( p b , t , ⁢ q b , t ) + ∑ x = 1 N TU ⁢ F TU ⁡ ( p x , t ) ) ⁢ Δ ⁢ t ,

where, p b,t represents an active power of a b th combined heat and power unit in the integrated heat and electricity system at a t th scheduling period, q b,t represents a heating power of the b th combined heat and power unit in the integrated heat and electricity system at the t th scheduling period, N represents a number of combined heat and power units in the integrated heat and electricity system, F(p b,t ,q b,t ) represents a running cost of the b th combined heat and power unit in the integrated heat and electricity system at the t th scheduling period, p x,t represents an active power of an x th thermal power unit in the integrated heat and electricity system at the t th scheduling period, N TU represents a number of thermal power units in a power grid in the integrated heat and electricity system, F TU (p x,t ) represents a running cost of the x th thermal power unit in the power grid in the integrated heat and electricity system, Δt represents an interval between two neighboring scheduling periods, and a value of Δt is 15 minutes.

(2) Equality constraints for a steady-state safe operation of the power grid and the heating network in the integrated heat and electricity system may be set, which may include the following.

(2-1) A power flow constraint of the power grid in the integrated heat and electricity system is denoted by formulas of:

where, P i,t represents an injected active power of a i th node of the power grid in the integrated heat and electricity system at the t th scheduling period, i,t represents an injected reactive power of the i th node of the power grid in the integrated heat and electricity system at the t th scheduling period, θ i,t represents a voltage phase angle of the i th node at the t th scheduling period, θ j,t , represents a voltage phase angle of the j th node at the t th scheduling period, U i,t represents a voltage amplitude of the i th node at the t th scheduling period, U j,t represents a voltage amplitude of the j th node at the t th scheduling period, G ij represents a real part of an element at i th row and j th column in a node admittance matrix Y of the power grid, B ij represents an imaginary part of the element at i th row and j th column in the node admittance matrix Y of the power grid, the node admittance matrix Y of the power grid is obtained from an energy management system of the integrated heat and electricity system, and n represents a number of nodes of the power grid.

(2-2) A pipe pressure loss constraint of the heating network in the integrated heat and electricity system is denoted by a formula of:

Δ H l,t =S l m l,t |m l,t |,t =1,2, . . . ,16,

where, ΔH l,t represents a pressure loss of a l th pipe of the heating network in the integrated heat and electricity system at the t th scheduling period, S l represents a resistance characteristic coefficient, a range of S l is 10 Pa/(kg/s) 2 ≤S l ≤500 Pa/(kg/s) 2 , and m l,t represents a mass flow rate of the l th pipe at the t th scheduling period.

(2-3) A hydraulic characteristic constraint of a circulating pump of the heating network in the integrated heat and electricity system is denoted by a formula of:

H P,t =H 0 −S p m P,t 2 t= 1,2, . . . ,16,

where, H P,t represents a head of delivery of the circulating pump at the t th scheduling period, H 0 represents a static head of delivery of the circulating pump, S p represents a resistance coefficient of the circulating pump, H 0 and S p are obtained from a factory manual of the circulating pump, and m P,t represents a mass flow rate that flowing through the circulating pump at the t th scheduling period.

(2-4) A pipe heating loss constraint of the heating network in the integrated heat and electricity system is denoted by a formula of:

T e , l , t = ( T h , l , t - T a , l , t ) ⁢ e - λ ⁢ ⁢ L l C p ⁢ m l , t + T a , l , t , t = 1 , 2 , … ⁢ , 16 ,

where, T e,l,t represents a tail-end temperature of the l th pipe of the heating network at the t th scheduling period, T h,l,t represents a head-end temperature of the l th pipe at the t th scheduling period, T a,l,t represents an ambient temperature of the l th pipe at the t th scheduling period, m l,t represents the mass flow rate of the l th pipe at the t th scheduling period, L l represents a length of the l th pipe, C p represents a specific heat capacity of water, a value of the specific heat capacity is 4182 Joules/(kg·° C.), λ represents a heat transfer coefficient per unit length of the pipe, λ is obtained from the energy management system of the integrated heat and electricity system, and e represents a natural logarithm.

(2-5) A temperature constraint of a junction node of a plurality of pipes of the heating network in the integrated heat and electricity system is denoted by a formula of:

where, m l,t represents the mass flow rate of the l th pipe at the t th scheduling period, T e,l,t represents the tail-end temperature of the l th pipe of the heating network at the t th scheduling period, T h,l,t represents the head-end temperature of the l th pipe at the t th scheduling period, S n out represents a set of all pipe numbers flowing out of a n th node of the heating network, S n in represents a set of all pipe numbers flowing into the n th node of the heating network, and J,n,t represents a heating power of the n th node of the heating network at the t th scheduling period.

(2-6) A coupling constraint between the power grid and the heating network coupled by combined heat and power units in the integrated heat and electricity system is denoted by formulas of:

p b,t =Σ k=1 NK b α b,t k P b k ,q b,t =Σ k=1 NK b α b,t k b k ,t= 1,2, . . . ,16,

where, p b,t represents the active power of the b th combined heat and power unit at the t th scheduling period, q b,t represents the heating power of the b th combined heat and power unit at the t th scheduling period, (P b k , b k ) represents the k th vertex of an approximate convex polygon in a running feasible region of the b th combined heat and power unit, α b,t k represents a k th combination coefficient of the b th combined heat and power unit at the t th scheduling period, Σ k=1 NK b α b,t k =1, 0≤α b,t k ≤1, NK b represents a number of vertexes of the approximate polygon in the running feasible region of the b th combined heat and power unit, and the approximate polygon in the running feasible region of the combined heat and power unit is obtained from a factory instruction of the combined heat and power unit.

(2-7) A coupling constraint between the power grid and the heating network coupled by a circulating pump in the integrated heat and electricity system is denoted by a formula of:

P P , t = m P , t ⁢ g ⁢ H P , t 1 ⁢ 0 6 ⁢ η P , t = 1 , 2 , … ⁢ , 16 ,

where, P P,t represents an active power consumed by the circulating pump at the t th scheduling period, g represents an acceleration of gravity, η P represents an efficiency of the circulating pump, a value of η P ranges from 0 to 1, m P,t represents the mass flow rate that flowing through the circulating pump at the t th scheduling period, and H P,t represents the head of delivery of the circulating pump at the t th scheduling period.

(2-8) A coupling constraint between the power grid and the heating network coupled by a heat pump in the integrated heat and electricity system is denoted by a formula of:

P hp,t =C hp hp,t ,t= 1,2, . . . ,16,

where, hp,t represents a heating power emitted by the heat pump in the integrated heat and electricity system at the t th scheduling period, P hp,t represents an electric power consumed by the heat pump at the t th scheduling period, C hp represents a heat generation efficiency of the heat pump, and C hp is obtained from a factory manual of the heat pump.

(3) Inequality constraints for a steady-state safe operation of the power grid and a heating network in the integrated heat and electricity system may be set, which may include the following.

(3-1) The voltage amplitude U i,t of the i th node of the power grid in the integrated heat and electricity system at the t th scheduling period is between a set upper and lower limits U i , Ū i of safe operating voltage of the power grid, in which, U i is 0.95 times a rated voltage of the i th node, and Ū i is 1.05 times the rated voltage of the i th node, i.e.:

U i ≤U i,t ≤Ū i ,t= 1,2, . . . ,16.

(3-2) A transmission capacity S l,t of a l th branch of the power grid in the integrated heat and electricity system at the t th scheduling period is less than or equal to a set maximum value S l of the transmission capacity for safe operating of the power grid, i.e.:

S l,t ≤ S l ,t= 1,2, . . . ,16.

(3-3) Ramp constraints of active powers of combined heat and power units of the power grid of the integrated heat and electricity system are denoted by a formula of:

−Δ p b down ·Δt≤p b,t −p b,t-1 ≤Δp b up ·Δt,t= 1,2, . . . ,16,

where, Δp b up represents an upward ramp rate of the active power of the b th combined heat and power unit, Δp b down represents a downward ramp rate of the active power of the b th combined heat and power unit, Δp b up and Δp b down are obtained from a factory instruction of the combined heat and power unit, Δt represents the interval between two neighboring scheduling periods, p b,t represents the active power of the b th combined heat and power unit at the t th scheduling period, and p b,t-1 represents the active power of the b th combined heat and power unit at the (t−1) th scheduling period.

(3-4) Ramp constraints of heating powers of combined heat and power units of the power grid of the integrated heat and electricity system are denoted by a formula of:

−Δ q b down ·Δt≤q b,t −q b,t-1 ≤Δq b up ·Δt,t= 1,2, . . . ,16,

where, Δq b up represents an upward ramp rate of the heating power of the b th combined heat and power unit, Δq b down represents a downward ramp rate of the heating power of the b th combined heat and power unit, Δq b up and Δq b down are obtained from a factory instruction of the combined heat and power unit, Δt represents the interval between two neighboring scheduling periods, q b,t represents the heating power of the b th combined heat and power unit at the t th scheduling period, and q b,t-1 represents the heating power of the b th combined heat and power unit at the (t−1) th scheduling period.

(3-5) Ramp constraints of active powers of thermal power units of the power grid of the integrated heat and electricity system are denoted by a formula of:

Δ−p x down ·Δt≤p x,t −p x,t-1 ≤Δp x up ·Δt,t= 1,2, . . . ,16,

where, Δp x up represents an upward ramp rate of the active power of the x th thermal power unit, Δp x down represents a downward ramp rate of the active power of the x th thermal power unit, Δp x up and Δp x down are obtained from a factory instruction of the thermal power unit, Δt represents the interval between two neighboring scheduling periods, p x,t represents the active power of the x th thermal power unit at the t th scheduling period, and p x,t-1 represents the active power of the x th thermal power unit at the (t−1) th scheduling period.

(3-6) The active power p b,t of the b th combined heat and power unit at the t th scheduling period is between a set upper and lower limits p b and p b of the active power of the b th combined heat and power unit, i.e.,

p b ≤p b,t ≤ p b ,t= 1,2, . . . ,16.

(3-7) The heating power q b,t of the b th combined heat and power unit at the t th scheduling period is between a set upper and lower limits q b and q b of the heating power of the b th combined heat and power unit, i.e.,

q b ≤q b,t ≤ q b ,t= 1,2, . . . ,16.

(3-8) The active power p x,t of the x th thermal power unit at the t th scheduling period is between a set upper and lower limits p x , and p x of the active power of the x th thermal power unit, i.e.,

p x ≤p x,t ≤ p x ,t= 1,2, . . . ,16.

(3-9) The mass flow rate m l,t of the l th pipe at the t th scheduling period is less than or equal to an upper limit m l of the mass flow rate for safe operation of the heating network, i.e.:

0≤ m l,t ≤ m l ,t= 1,2, . . . ,16.

(3-10) A return water temperature T i,t of an i th heat exchange station in the heating network at the t th scheduling period is between a set upper and lower limits T and T of the return water temperature for safe operation of the heating network, i.e.:

T ≤T i,j ≤ T ,t =1,2, . . . ,16.

(4) Using an interior point method, the equation in the above step (1) is used as the objective function, and all equations in the above step (2) and step (3) are used as the constraints, to solve to obtain the active power and the heating power of each combined heat and power unit, the active power of each thermal power unit, the heating power of each heat pump, and the active power consumed by each circulating pump, as the intra-day rolling scheduling scheme of the integrated heat and electricity system, realizing the intra-day rolling scheduling of the integrated heat and electricity system.

The intra-day rolling scheduling method for the integrated heat and electricity system, proposed by the present disclosure, has the characteristics and effects as follows. The method considers the mutual influence of the integrated heat and electricity system and realizes the intra-day rolling scheduling method for the integrated heat and electricity system. This method can continuously modify the current intra-day rolling scheduling plan to obtain a more accurate intra-day rolling scheduling scheme. Compared with independent optimization analysis of the power grid and the heating system, it may get a better scheduling scheme (lower total operating cost), and improve scheduling flexibility. The method can be applied to the formulation of the intra-day rolling scheduling method for the integrated heat and electricity system, which is beneficial to improving the energy efficiency of the integrated heat and electricity system and reducing operating costs.