CN103972916A - Micro-grid operation method for stabilizing fluctuation of wind and light power by energy storing device - Google Patents

Abstract

The invention relates to a micro-grid operation method for stabilizing the fluctuation of wind and light power by an energy storing device, belongs to the technical field of intelligent micro-grids, and aims to solve the problems that the output power with fluctuation, randomness and intermittence of wind power generation units and photovoltaic power generation units of a current micro-grid influences the stable operation of the micro-grid. The micro-grid operation method specifically comprises the following steps: determining structure parameters and operation parameters of a micro-grid according to a micro-grid system; selecting active output of each distributive power supply and power of electricity bought from or sold to a large power grid of the micro-grid as control variables, and obtaining an operation cost function of the micro-grid according to the control variables, wherein the operation cost function is taken as a target function of operation of the micro-grid; obtaining a mathematic model of the energy storing device for stabilizing the fluctuation of wind and light power and a constraint condition of operation of the micro-grid according to the target function; and obtaining a micro-grid operation method adopted after the fluctuation of power is stabilized by an improved differential evolutionary algorithm. The micro-grid operation method is applied to the micro-grid system.

Description

Utilize energy storage device to stabilize micro-operation of power networks method of honourable power fluctuation

Technical field

The invention belongs to intelligent micro-grid technical field.

Background technology

Along with the high speed development of human society, the mankind strengthen the demand of the energy, and to the improving constantly of living environment quality requirement, the micro-electrical network that contains combined type new forms of energy has obtained people and more and more paid close attention to simultaneously.Novel distributed power source can make full use of the generating advantage of regenerative resource, but there is very large difference in novel distributed power source and conventional power source, its main feature be wind power generation, photovoltaic generation randomness, fluctuation and intermittent make ability that micro-grid system bears disturbance relatively a little less than.In order to make full use of the generating advantage of new distribution type power supply, weaken the impact of its power fluctuation on micro-electrical network, maintenance system is stable, must comprise synchronous generator unit or the energy storage device of certain capacity in micro-grid system.Energy storage device can be realized fast charging and discharging, matches realize the power stage of stabilizing honourable power fluctuation, systems stabilisation with the renewable energy power generation such as wind power generation, photovoltaic generation unit, strengthens the schedulability energy of renewable energy system.Therefore the reasonable use of energy storage device can effectively weaken the impact that new distribution type power supply causes the stable operation of micro-electrical network.

The existing fruitful research of optimization operation to micro-electrical network at present, but according to the actual operating state of micro-electrical network, the feature such as randomness, fluctuation having for the power output of the wind power generation comprising in micro-electrical network, photovoltaic generation unit need further research and solves the impact of micro-power grid operation.

Summary of the invention

The present invention seeks in order to solve existing micro-electrical network wind power generation, photovoltaic generation unit power output has fluctuation, randomness and intermittence, and then affect the problem of the stable operation of micro-electrical network, a kind of micro-operation of power networks method of utilizing energy storage device to stabilize honourable power fluctuation is provided.

Micro-operation of power networks method of utilizing energy storage device to stabilize honourable power fluctuation of the present invention, the detailed process of the method is:

Step 1, determine structural parameters and the operational factor of micro-electrical network according to the system of micro-electrical network;

Step 2, the meritorious output of choosing each distributed power source in micro-grid system and micro-electrical network to large electrical network purchase, the power of sale of electricity is as control variables, obtain the operating cost function of micro-electrical network according to control variables, the target function using operating cost function as micro-operation of power networks;

Step 3, the target function obtaining according to step 2 obtain the Mathematical Modeling of the energy storage device for stabilizing scene fluctuation;

Step 4, under the constraints of micro-operation of power networks, utilize improve differential evolution algorithm obtain the power output of stabilizing the each distributed power source after honourable power fluctuation, be micro-operation of power networks method of stabilizing after power fluctuation.

Advantage of the present invention: micro-operation of power networks method of utilizing energy storage device to stabilize honourable power fluctuation of the present invention, the impact of fluctuation, randomness and the intermittent feature that the regenerative resource such as wind power generation, photovoltaic generation comprising can be for micro-grid system actual motion time has on micro-grid system operation.According to wind-powered electricity generation, the real-time power output of photovoltaic generation, calculate its fluctuation situation with respect to a upper scheduling moment power output, if exceed the maximum fluctuation scope of permission, energy storage device discharges and recharges to stabilize power fluctuation; When energy storage device is stated target in realization, also need according to the sale of electricity electricity price situation of purchasing of whole micro-grid system supply and demand situation and the large electrical network that is connected with it, energy storage device rationally discharges and recharges so that realize micro-grid system owner and obtains greatest benefit.

Brief description of the drawings

Fig. 1 is the structural representation of micro-electrical network;

Fig. 2 is the real-time output power curve figure of wind power generation, photovoltaic generation;

Fig. 3 is the output power curve figure that stabilizes wind power generation after honourable power fluctuation, photovoltaic generation;

Fig. 4 is that the energy storage device that blower fan bus connects discharges and recharges power;

Fig. 5 is that the energy storage device that photovoltaic generator bus connects discharges and recharges power.

Embodiment

Embodiment one: below in conjunction with Fig. 1, present embodiment is described, utilizes energy storage device to stabilize micro-operation of power networks method of honourable power fluctuation described in present embodiment, the detailed process of the method is:

Step 1, determine structural parameters and the operational factor of micro-electrical network according to the system of micro-electrical network;

Step 2, the meritorious output of choosing each distributed power source in micro-grid system and micro-electrical network to large electrical network purchase, the power of sale of electricity is as control variables, obtain the operating cost function of micro-electrical network according to control variables, the target function using operating cost function as micro-operation of power networks;

Step 3, the target function obtaining according to step 2 obtain the Mathematical Modeling of the energy storage device for stabilizing scene fluctuation;

Step 4, under the constraints of micro-operation of power networks, utilize improve differential evolution algorithm obtain the power output of stabilizing the each distributed power source after honourable power fluctuation, be micro-operation of power networks method of stabilizing after power fluctuation.

In present embodiment, described structural parameters comprise bus parameter and line parameter circuit value; Described operational factor comprise each distributed power source service data, load data and scheduling time interval.

Embodiment two: present embodiment is described further execution mode one, described in step 2, micro-operation of power networks cost comprises that fuel cost, charges for disposing pollutants, operation and maintenance cost and large electrical network purchase sale of electricity expense, operating cost is expressed as target function:

$F=\underset{T=1}{\overset{M}{\mathrm{\Σ}}}[\underset{i=1}{\overset{N}{\mathrm{\Σ}}}(C_{\mathrm{OP}}\left(P_{\mathrm{Gi}}\right)+C_{\mathrm{ES}}\left(P_{\mathrm{Gi}}\right)+C_{\mathrm{OM}}\left(P_{\mathrm{Gi}}\right))+C_b\·P_{\mathrm{bgrid}}-C_s\·P_{\mathrm{sgrid}}]$

Wherein: N represents number of power sources, i represents i power supply, C _oPrepresent the fuel cost of distributed power source i, C _eSrepresent the discharge fee of distributed power source i, C _oMrepresent the operation and maintenance cost of distributed power source i, C _brepresent large electrical network power purchase price, unit is unit/kWh, C _srepresent large electrical network sale of electricity price, unit is kWh, P _githe energy output that represents power supply i in certain period, unit is kWh, P _bgridthe electric energy that represents power purchase in certain period, unit is kWh, P _sgridthe electric energy that represents sale of electricity in certain period, unit is kWh; M represents period number; T represents a certain period of scheduling.

Embodiment three: present embodiment is described further execution mode one, the energy storage device Mathematical Modeling of obtaining according to target function described in step 3 is:

$|P_{\mathrm{py}}\left(t\right)-P_{\mathrm{py}}(t-1)|\≤S\·\mathrm{\λ}$

P _ess(t)＝P _py(t)-P _max(t)

Wherein: P _py(t) represent the power output after the t moment stabilizes; P _py(t-1) represent the power output after wind-powered electricity generation was stabilized in the t-1 moment; P _max(t) represent the peak power output that the t moment exports; P _ess(t) what represent energy storage device discharges and recharges power; S table

Show installed capacity; λ represents the maximum rate of change of energy storage device power output;

Work as P _ess(t), when >0, energy storage device electric discharge, works as P _ess(t) when <0, energy storage device charging;

Energy storage device meets at the capacity in t moment:

C _ess(t)＝C _ess(t-1)(1-δ)-P _ess(t)·η·△t

Wherein: C _ess(t), C _ess(t-1) represent respectively the capability value of t and t-1 moment energy storage device, unit is kWh; δ is the self discharge current rate of energy storage device; η is the efficiency for charge-discharge of energy storage device; △ t represents the changing value in t and t-1 moment;

After energy storage device discharges and recharges, capacity is at { C _essmin, C _essmaxbetween, after charging, capacity is greater than C _essmaxtime, energy storage device stops charging, and capacity and the charge power of energy storage device are as follows:

$\left\{\begin{array}{c}{P}_{\mathrm{ess}}=-\frac{C_{\mathrm{ess}\max }-C_{\mathrm{ess}}(t-1)(1-\mathrm{\&delta;})}{\mathrm{\&Delta;t}\&CenterDot;\mathrm{\&eta;}}\\ C_{\mathrm{ess}}\left(t\right)=C_{\mathrm{ess}\max }\end{array}\right.$

After energy storage device electric discharge, capacity is less than C _essmintime, energy storage device stops electric discharge, and capacity and the discharge power of energy storage device are as follows:

$\left\{\begin{array}{c}{P}_{\mathrm{ess}}=-\frac{C_{\mathrm{ess}\min }-C_{\mathrm{ess}}(t-1)(1-\mathrm{\&delta;})}{\mathrm{\&Delta;t}\&CenterDot;\mathrm{\&eta;}}\\ C_{\mathrm{ess}}\left(t\right)=C_{\mathrm{ess}\min }\end{array}\right.$

Energy storage device is in the situation that meeting above-mentioned condition, and the condition that discharges and recharges power is

$\left\{\begin{array}{c}{P}_{c,\min }\&le;P_{c,\mathrm{ess}}\left(t\right)\&le;P_{c,\max }\\ P_{f,\min }\&le;P_{f,\mathrm{ess}}\left(t\right)\&le;P_{f,\max }\end{array}\right.$

Wherein: P _{c, ess}(t) expression energy storage device is at the charge power in t moment, P _{c, min}and P _{c, max}represent respectively lower limit and the upper limit of charge power; P _{f, ess}(t) expression energy storage device is at the discharge power in t moment, P _{f, min}and P _{f, max}represent respectively lower limit and the upper limit of discharge power.

In present embodiment, energy storage device discharge and recharge according to being: first, in the time that the active power value of wind-powered electricity generation and photovoltaic output is greater than the maximum fluctuation value of its permission, energy storage device charging, until energy storage device is charged to its maximum capacity, device stops charging, the principle output that remaining active power is not wasted according to the energy; The second, in the time that the active power value of wind-powered electricity generation and photovoltaic output is less than the maximum fluctuation value of its permission, energy storage device electric discharge, until energy storage device discharges into its minimum capacity value, next scheduling moment energy storage device does not discharge.

Embodiment four: present embodiment is described further execution mode one, the constraints of micro-operation of power networks comprises power flow equation constraint, inequality constraints and purchases sale of electricity constraint described in step 4;

Power flow equation constraint, is equality constraint, is expressed as:

$\left\{\begin{array}{c}{P}_{\mathrm{Hi}}-P_{\mathrm{Di}}-V_i\underset{j=1}{\overset{n}{\mathrm{\&Sigma;}}}{V}_j(G_{\mathrm{ij}}\cos {\mathrm{\&theta;}}_{\mathrm{ij}}+B_{\mathrm{ij}}\sin {\mathrm{\&theta;}}_{\mathrm{ij}})=0\\ Q_{\mathrm{Hi}}-Q_{\mathrm{Di}}-V_i\underset{j=1}{\overset{n}{\mathrm{\&Sigma;}}}{V}_j(G_{\mathrm{ij}}\sin {\mathrm{\&theta;}}_{\mathrm{ij}}-B_{\mathrm{ij}}\cos {\mathrm{\&theta;}}_{\mathrm{ij}})=0\end{array}\right.$

Wherein: P _hirepresent the active power of distributed power source i; Q _hirepresent the reactive power of distributed power source i; P _direpresent the load active power of distributed power source i; Q _direpresent the reactive load power of distributed power source i; N represents node sum; J represents the connected node of i; θ i _jrepresent what represents the voltage phase angle between i and j; V _jrepresent the voltage magnitude of node j; Gi _jand Bi _jall represent the element in node admittance matrix;

Inequality constraints comprises units limits, node voltage Filters with Magnitude Constraints and the capacity of trunk constraint of distributed power source, is expressed as:

$\left\{\begin{array}{c}{P}_{\mathrm{Ki}}^{\min }\&le;P_{\mathrm{Ki}}\&le;P_{\mathrm{Ki}}^{\max }\\ Q_{\mathrm{Ki}}^{\min }\&le;Q_{\mathrm{Ki}}\&le;Q_{\mathrm{Ki}}^{\max }\\ V_{\mathrm{Ki}}^{\min }\&le;V_i\&le;V_{\mathrm{Ki}}^{\max }\\ S_{\mathrm{ij}}\&le;S_{\mathrm{ij}}^{\max }\end{array}\right.$

Wherein: P _kirepresent the meritorious output of distributed power source i; Q _kirepresent the idle output of distributed power source i; V _irepresent the voltage magnitude of distributed power source i; S _ijrepresent the apparent power of circuit; Superscript max is the higher limit of represented variable; Superscript min is the lower limit of represented variable;

Purchase sale of electricity constraint, be expressed as:

$\left\{\begin{array}{c}{P}_{b,\min }\&le;P_b\&le;P_{b,\max }\\ P_{c,\min }\&le;P_c\&le;P_{c,\max }\end{array}\right.$

Wherein: P _brepresent power purchase, P _crepresent sale of electricity; The max of subscript is the higher limit of represented variable; The min of subscript is the lower limit of represented variable.

For the micro-grid system structure chart of Fig. 1, adopt the result of method acquisition of the present invention as shown in Figure 3, compared with Fig. 2, wind-powered electricity generation, photovoltaic power output nearly smooth, Fig. 4 and Fig. 5 have provided respectively the power that discharges and recharges of energy storage device that wind power generation and photovoltaic generation unit bus connect.This shows: the present invention can effectively weaken honourable power fluctuation to the basis of micro-grid system stable operation on, realize the optimization operation of micro-grid system.

Claims (4)

1. utilize energy storage device to stabilize micro-operation of power networks method of honourable power fluctuation, it is characterized in that, the detailed process of the method is:

Step 1, determine structural parameters and the operational factor of micro-electrical network according to the system of micro-electrical network;

Step 2, the meritorious output of choosing each distributed power source in micro-grid system and micro-electrical network to large electrical network purchase, the power of sale of electricity is as control variables, obtain the operating cost function of micro-electrical network according to control variables, the target function using operating cost function as micro-operation of power networks;

Step 3, the target function obtaining according to step 2 obtain the Mathematical Modeling of the energy storage device for stabilizing scene fluctuation;

Step 4, under the constraints of micro-operation of power networks, utilize improve differential evolution algorithm obtain the power output of stabilizing the each distributed power source after honourable power fluctuation, be micro-operation of power networks method of stabilizing after power fluctuation.

2. utilize according to claim 1 energy storage device to stabilize micro-operation of power networks method of honourable power fluctuation, it is characterized in that, described in step 2, micro-operation of power networks cost comprises that fuel cost, charges for disposing pollutants, operation and maintenance cost and large electrical network purchase sale of electricity expense, operating cost is expressed as target function:

$F=\underset{T=1}{\overset{M}{\mathrm{\&Sigma;}}}[\underset{i=1}{\overset{N}{\mathrm{\&Sigma;}}}(C_{\mathrm{OP}}\left(P_{\mathrm{Gi}}\right)+C_{\mathrm{ES}}\left(P_{\mathrm{Gi}}\right)+C_{\mathrm{OM}}\left(P_{\mathrm{Gi}}\right))+C_b\&CenterDot;P_{\mathrm{bgrid}}-C_s\&CenterDot;P_{\mathrm{sgrid}}]$

Wherein: N represents number of power sources, i represents i power supply, C _oPrepresent the fuel cost of distributed power source i, C _eSrepresent the discharge fee of distributed power source i, C _oMrepresent the operation and maintenance cost of distributed power source i, C _brepresent large electrical network power purchase price, unit is unit/kWh, C _srepresent large electrical network sale of electricity price, unit is kWh, P _githe energy output that represents power supply i in certain period, unit is kWh, P _bgridthe electric energy that represents power purchase in certain period, unit is kWh, P _sgridthe electric energy that represents sale of electricity in certain period, unit is kWh; M represents period number; T represents a certain period of scheduling.

3. utilize according to claim 1 energy storage device to stabilize micro-operation of power networks method of honourable power fluctuation, it is characterized in that, the energy storage device Mathematical Modeling of obtaining according to target function described in step 3 is:

$|P_{\mathrm{py}}\left(t\right)-P_{\mathrm{py}}(t-1)|\&le;S\&CenterDot;\mathrm{\&lambda;}$

P _ess(t)＝P _py(t)-P _max(t)

Wherein: P _py(t) represent the power output after the t moment stabilizes; P _py(t-1) represent the power output after wind-powered electricity generation was stabilized in the t-1 moment; P _max(t) represent the peak power output that the t moment exports; P _ess(t) what represent energy storage device discharges and recharges power; S represents installed capacity; λ represents the maximum rate of change of energy storage device power output;

Work as P _ess(t), when >0, energy storage device electric discharge, works as P _ess(t) when <0, energy storage device charging;

Energy storage device meets at the capacity in t moment:

C _ess(t)＝C _ess(t-1)(1-δ)-P _ess(t)·η·△t

Wherein: C _ess(t), C _ess(t-1) represent respectively the capability value of t and t-1 moment energy storage device, unit is kWh; δ is the self discharge current rate of energy storage device; η is the efficiency for charge-discharge of energy storage device; △ _trepresent _twith _t- ₁the changing value in moment;

After energy storage device discharges and recharges, capacity is at { C _essmin, C _essmaxbetween, after charging, capacity is greater than C _essmaxtime, energy storage device stops charging, and capacity and the charge power of energy storage device are as follows:

$\left\{\begin{array}{c}{P}_{\mathrm{ess}}=-\frac{C_{\mathrm{ess}\max }-C_{\mathrm{ess}}(t-1)(1-\mathrm{\&delta;})}{\mathrm{\&Delta;t}\&CenterDot;\mathrm{\&eta;}}\\ C_{\mathrm{ess}}\left(t\right)=C_{\mathrm{ess}\max }\end{array}\right.$

After energy storage device electric discharge, capacity is less than C _essmintime, energy storage device stops electric discharge, and capacity and the discharge power of energy storage device are as follows:

$\left\{\begin{array}{c}{P}_{\mathrm{ess}}=-\frac{C_{\mathrm{ess}\min }-C_{\mathrm{ess}}(t-1)(1-\mathrm{\&delta;})}{\mathrm{\&Delta;t}\&CenterDot;\mathrm{\&eta;}}\\ C_{\mathrm{ess}}\left(t\right)=C_{\mathrm{ess}\min }\end{array}\right.$

Energy storage device is in the situation that meeting above-mentioned condition, and the condition that discharges and recharges power is

$\left\{\begin{array}{c}{P}_{c,\min }\&le;P_{c,\mathrm{ess}}\left(t\right)\&le;P_{c,\max }\\ P_{f,\min }\&le;P_{f,\mathrm{ess}}\left(t\right)\&le;P_{f,\max }\end{array}\right.$

Wherein: P _{c, ess}(t) expression energy storage device is at the charge power in t moment, P _{c, min}and P _{c, max}represent respectively lower limit and the upper limit of charge power; P _{f, ess}(t) expression energy storage device is at the discharge power in t moment, P _{f, min}and P _{f, max}represent respectively lower limit and the upper limit of discharge power.

4. utilize according to claim 1 energy storage device to stabilize micro-operation of power networks method of honourable power fluctuation, it is characterized in that, the constraints of micro-operation of power networks comprises power flow equation constraint, inequality constraints and purchases sale of electricity constraint described in step 4;

Power flow equation constraint, is equality constraint, is expressed as:

$\left\{\begin{array}{c}{P}_{\mathrm{Hi}}-P_{\mathrm{Di}}-V_i\underset{j=1}{\overset{n}{\mathrm{\&Sigma;}}}{V}_j(G_{\mathrm{ij}}\cos {\mathrm{\&theta;}}_{\mathrm{ij}}+B_{\mathrm{ij}}\sin {\mathrm{\&theta;}}_{\mathrm{ij}})=0\\ Q_{\mathrm{Hi}}-Q_{\mathrm{Di}}-V_i\underset{j=1}{\overset{n}{\mathrm{\&Sigma;}}}{V}_j(G_{\mathrm{ij}}\sin {\mathrm{\&theta;}}_{\mathrm{ij}}-B_{\mathrm{ij}}\cos {\mathrm{\&theta;}}_{\mathrm{ij}})=0\end{array}\right.$

Wherein: P _hirepresent the active power of distributed power source i; Q _hirepresent the reactive power of distributed power source i; P _direpresent the load active power of distributed power source i; Q _direpresent the reactive load power of distributed power source i; N represents node sum; J represents the connected node of i; θ i _jrepresent what represents the voltage phase angle between i and j; V _jrepresent the voltage magnitude of node j; Gi _jand Bi _jall represent the element in node admittance matrix;

Inequality constraints comprises units limits, node voltage Filters with Magnitude Constraints and the capacity of trunk constraint of distributed power source, is expressed as:

$\left\{\begin{array}{c}{P}_{\mathrm{Ki}}^{\min }\&le;P_{\mathrm{Ki}}\&le;P_{\mathrm{Ki}}^{\max }\\ Q_{\mathrm{Ki}}^{\min }\&le;Q_{\mathrm{Ki}}\&le;Q_{\mathrm{Ki}}^{\max }\\ V_{\mathrm{Ki}}^{\min }\&le;V_i\&le;V_{\mathrm{Ki}}^{\max }\\ S_{\mathrm{ij}}\&le;S_{\mathrm{ij}}^{\max }\end{array}\right.$

Wherein: P _kirepresent the meritorious output of distributed power source i; Q _kirepresent the idle output of distributed power source i; V _irepresent the voltage magnitude of distributed power source i; Si _jrepresent the apparent power of circuit; Superscript max is the higher limit of represented variable; Superscript min is the lower limit of represented variable;

Purchase sale of electricity constraint, be expressed as:

$\left\{\begin{array}{c}{P}_{b,\min }\&le;P_b\&le;P_{b,\max }\\ P_{c,\min }\&le;P_c\&le;P_{c,\max }\end{array}\right.$

Wherein: P _brepresent power purchase, P _crepresent sale of electricity; The max of subscript is the higher limit of represented variable; The min of subscript is the lower limit of represented variable.