CN105244916A - Flow state evaluation method for power grid with UPFC based on standardized Euclidean distance - Google Patents

Abstract

The invention discloses a flow state evaluation method for a power grid with a UPFC based on standardized Euclidean distance. The flow state evaluation method is characterized by comprising the following steps that step one, a power grid flow optimization model considering the UPFC is established; step two, standardization processing is performed on load rate data of each line according to the optimal flow calculation result; step three, standardization processing is performed on the line load rate data under the working condition in view of a certain operation working condition to be evaluated; and step four, Euclidean distance between the working condition to the evaluated and the ideal optimal working condition is calculated, and the calculation result acts as the flow state evolution indicator under the working condition. An optimization objective is formulated from the two angles of line load balancing degree and line loss, the flow state evolution indicator is defined as the standardized Euclidean distance between the actual flow and the ideal flow, and finally different operation modes are evaluated according to the size of the indicator value.

Description

A kind of based on standardization Euclidean distance containing UPFC electric network swim method for evaluating state

Technical field

The present invention relates to a kind of based on standardization Euclidean distance containing UPFC electric network swim method for evaluating state.

Background technology

THE UPFC (UPFC) is a kind of typical flexible transmission device, can by injecting series voltage, the voltage of controls transfer circuit, impedance and transmission angle independently, can also meritorious and reactive power trend selectively on control circuit, effectively improve the stability of electric power system, be with a wide range of applications.In Practical Project, often need to evaluate the different flow state of electrical network containing UPFC, formulate preferably UPFC control strategy.At present, existing trend appraisal procedure is mostly from the angle of balanced circuit load factor, judge the relative superior or inferior between different running method according to the size of line load equilibrium degree, there is the defect that target is single, and the departure degree of actual trend distance optimal load flow cannot be reflected.

Summary of the invention

For the problems referred to above, the invention provides a kind of based on standardization Euclidean distance containing UPFC electric network swim method for evaluating state, optimization aim is formulated from line load equilibrium degree and line loss two angles, the evaluation index of definition flow state is the standardization Euclidean distance between actual trend and desirable trend, finally assesses different operational modes according to the size of index value.

For realizing above-mentioned technical purpose, reach above-mentioned technique effect, the present invention is achieved through the following technical solutions:

Based on standardization Euclidean distance containing a UPFC electric network swim method for evaluating state, it is characterized in that, comprise the following steps:

Step 1, foundation take into account the electric network swim Optimized model of UPFC:

With system operation conditions and UPFC performance parameter for constraints, the highest with line load equilibrium degree, line loss is minimum for optimization aim, calculates the electrical network optimal load flow containing UPFC;

Step 2, according to optimal load flow result of calculation, standardization is carried out to each line load rate data;

Step 3, for certain operating condition to be evaluated, standardization is carried out to the line load rate data under this operating mode;

Step 4, calculate Euclidean distance between operating mode to be evaluated and desirable optimum operating condition, result of calculation is as the flow state evaluation index under this operating mode.

Preferably, also comprise step 5, the trend evaluation index of all operating modes to be evaluated is sorted, the corresponding operating mode flow state optimum that index value is minimum.

Preferably, in step 1, system cloud gray model constraints comprises:

Node power equilibrium equation:

$\left\{\begin{array}{c}{P}_{Gi}-P_{Di}-U_i\underset{j=1}{\overset{n}{\Σ}}{U}_j(G_{ij}{\mathrm{cos\θ}}_{ij}+B_{ij}{\mathrm{sin\θ}}_{ij})=0\\ Q_{Gi}-Q_{Di}-U_i\underset{j=1}{\overset{n}{\Σ}}{U}_j(G_{ij}{\mathrm{cos\θ}}_{ij}-B_{ij}{\mathrm{sin\θ}}_{ij})=0\end{array}\right.$

Generated power is exerted oneself limit value and idle limit value of exerting oneself:

$\left\{\begin{array}{c}{P}_{Gi\min }\≤P_{Gi}\≤P_{Gimax}\\ Q_{Gi\min }\≤Q_{Gi}\≤Q_{Gimax}\end{array}\right.$

Busbar voltage limit value:

U _imin≤U _i≤U _imax

Circuit transmission power limit value:

|P _l|＝|P _ij|＝|U _iU _j(G _ijcosθ _ij+B _ijsinθ _ij)-U _i ²G _ij|≤P _lmax

In formula, P _gi, Q _gifor the meritorious, idle of bus i institute running fire motor is exerted oneself; P _di, Q _dibe respectively bus i connect the meritorious, idle of load; U _i, U _jbe respectively the voltage of bus i and bus j; G _ij, B _ijfor the element of the i-th row, jth row in node admittance matrix; θ _ijfor the phase difference of voltage of bus i and bus j; P _gimin, P _gimaxbe respectively the meritorious upper and lower limit of exerting oneself of bus i institute running fire motor; Q _gimin, Q _gimaxbe respectively the idle upper and lower limit of exerting oneself of bus i institute running fire motor; U _imin, U _imaxfor bus i working voltage upper and lower limit; P _lfor the active power that circuit l carries; P _ijfor the active power that bus i and bus j institute's line road and circuit l carry; P _lmaxfor branch road l transmission power limiting value.

Preferably, in step 1, UPFC performance parameter constraints comprises:

Series connection injecting voltage limit value:

|ΔU|≤ΔU _max

Series/parallel side converter is meritorious exchanges limit value:

P _dc≤S _sh

Wherein, Δ U is series connection injecting voltage, Δ U _maxfor the upper limit of injecting voltage of connecting; P _dcfor the active power that series/parallel top-cross is changed, S _shfor the rated capacity of side in parallel converter.

The invention has the beneficial effects as follows:

The invention discloses a kind of based on standardization Euclidean distance containing UPFC electric network swim method for evaluating state, establish the desirable mark post reference point that flow state is evaluated, i.e. optimal load flow, flow state level is characterized according to the extent of deviation between actual motion point and desirable optimum point, evaluation index not only can relative superior or inferior between more different operating condition, also to the flow state proficiency assessment of specific operation self, there is reference value, and in the computational process of optimal load flow, many optimization aim choose the utilance making electrical network can improve electric equipment, also the factor of saving energy and decreasing loss is considered to a certain extent, the more objective more realistic application of evaluation result.

Accompanying drawing explanation

Fig. 1 is embodiment of the present invention grid structure schematic diagram.

Embodiment

Below in conjunction with accompanying drawing and specific embodiment, technical solution of the present invention is described in further detail, can better understand the present invention to make those skilled in the art and can be implemented, but illustrated embodiment is not as a limitation of the invention.

Based on standardization Euclidean distance containing a UPFC electric network swim method for evaluating state, comprise the following steps:

Step 1, foundation take into account the electric network swim Optimized model of UPFC:

With system operation conditions and UPFC performance parameter for constraints, the highest with line load equilibrium degree, line loss is minimum for optimization aim, calculates the electrical network optimal load flow containing UPFC;

Step 2, according to optimal load flow result of calculation, standardization is carried out to each line load rate data, and using the data after standardization as with reference to multi-C vector, characterize desirable optimal load flow state;

Step 3, for certain operating condition to be evaluated, standardization is carried out to the line load rate data under this operating mode, the multi-C vector that the data after standardization are formed, characterize the flow state under this operating mode;

Step 4, calculate Euclidean distance between operating mode to be evaluated and desirable optimum operating condition, result of calculation is as the flow state evaluation index under this operating mode.

Preferably, also comprise step 5, the trend evaluation index of all operating modes to be evaluated is sorted, the corresponding operating mode flow state that index value is less is more excellent, and the corresponding operating mode flow state that namely index value is minimum is optimum, and the maximum corresponding operating mode flow state of index value is the poorest.

General, in step 1, system cloud gray model constraints comprises node power balance, generated power exerts oneself limit value, generator reactive exerts oneself limit value, busbar voltage limit value, circuit transmission power limit value.UPFC performance parameter constraints comprises series connection injecting voltage limit value, series/parallel side is meritorious exchanges limit value.

Concrete electric network swim Optimized model is as follows:

Node power equilibrium equation:

$\left\{\begin{array}{c}{P}_{Gi}-P_{Di}-U_i\underset{j=1}{\overset{n}{\Σ}}{U}_j(G_{ij}{\mathrm{cos\θ}}_{ij}+B_{ij}{\mathrm{sin\θ}}_{ij})=0\\ Q_{Gi}-Q_{Di}-U_i\underset{j=1}{\overset{n}{\Σ}}{U}_j(G_{ij}{\mathrm{cos\θ}}_{ij}-B_{ij}{\mathrm{sin\θ}}_{ij})=0\end{array}\right.$

Generated power is exerted oneself limit value and idle limit value of exerting oneself:

$\left\{\begin{array}{c}{P}_{Gi\min }\≤P_{Gi}\≤P_{Gimax}\\ Q_{Gi\min }\≤Q_{Gi}\≤Q_{Gimax}\end{array}\right.$

Busbar voltage limit value:

U _imin≤U _i≤U _imax

Circuit transmission power limit value:

|P _l|＝|P _ij|＝|U _iU _j(G _ijcosθ _ij+B _ijsinθ _ij)-U _i ²G _ij|≤P _lmax

In formula, P _gi, Q _gifor the meritorious, idle of bus i institute running fire motor is exerted oneself; P _di, Q _dibe respectively bus i connect the meritorious, idle of load; U _i, U _jbe respectively the voltage of bus i and bus j; G _ij, B _ijfor the element of the i-th row, jth row in node admittance matrix; θ _ijfor the phase difference of voltage of bus i and bus j; P _gimin, P _gimaxbe respectively the meritorious upper and lower limit of exerting oneself of bus i institute running fire motor; Q _gimin, Q _gimaxbe respectively the idle upper and lower limit of exerting oneself of bus i institute running fire motor; U _imin, U _imaxfor bus i working voltage upper and lower limit; P _lfor the active power that circuit l carries; P _ijfor the active power that bus i and bus j institute's line road (i.e. circuit l) are carried; P _lmaxfor branch road l transmission power limiting value.

Series connection injecting voltage limit value:

|ΔU|≤ΔU _max

Series/parallel side converter is meritorious exchanges limit value:

P _dc≤S _sh

Wherein, Δ U is series connection injecting voltage, Δ U _maxfor the upper limit of injecting voltage of connecting; P _dcfor the active power that series/parallel top-cross is changed, S _shfor the rated capacity of side in parallel converter.

The optimization aim expression formula that line load equilibrium degree is the highest is:

minE

Wherein, E is line load equilibrium degree index, and computing formula is:

$E=\sqrt{\frac{1}{n}\underset{i=1}{\overset{n}{\Σ}}{({\mathrm{\α}}_i-\stackrel{\‾}{\mathrm{\α}})}^2}$

Wherein, n is the number of lines of electrical network, α _ibe the load factor of i-th circuit, for the mean value of load factor, computing formula is:

$\stackrel{\‾}{\mathrm{\α}}=\frac{1}{n}\underset{i=1}{\overset{n}{\Σ}}{\mathrm{\α}}_i$

The minimum optimization aim expression formula of line loss is:

$\begin{array}{cc}min& \underset{i=1}{\overset{n}{\Σ}}{I_i}^2{R}_i\end{array}$

Wherein, n is the number of lines of electrical network, I _ibe the electric current of i-th branch road, R _ibe the resistance of i-th branch road.

In step 2, if electrical network has n bar circuit, the vector that original load factor is formed is α (α ₁, α ₂..., α _n), be η (η after standardization ₁, η ₂..., η _n), η _ibe the load factor after i-th line standard, computing formula is:

${\mathrm{\η}}_i=\frac{{\mathrm{\α}}_i-\stackrel{\‾}{\mathrm{\α}}}{s}$

Wherein, α _ifor the original load factor of the circuit before standardization, for the mean value of original load factor, computing formula is:

$\stackrel{\‾}{\mathrm{\α}}=\frac{1}{n}\underset{i=1}{\overset{n}{\Σ}}{\mathrm{\α}}_i$

S is the standard deviation of original load factor, and computing formula is:

$s=\sqrt{\frac{1}{n}\underset{i=1}{\overset{n}{\Σ}}{({\mathrm{\α}}_i-\stackrel{\‾}{\mathrm{\α}})}^2}.$

In step 4, for operating mode j to be evaluated, flow state evaluation index d _jbe defined as the flow state η of operating mode j _j(η _j1, η _j2..., η _jn) and desirable flow state η (η ₁, η ₂..., η _n) between Euclidean distance, computing formula is:

$d_j=\sqrt{\underset{i=1}{\overset{n}{\Σ}}{({\mathrm{\η}}_{ji}-{\mathrm{\η}}_i)}^2}$

η _jifor the normalized load rate of i-th circuit of operating mode j to be evaluated, computing formula is:

${\mathrm{\η}}_{ji}=\frac{{\mathrm{\α}}_{ji}-{\stackrel{\‾}{\mathrm{\α}}}_j}{s_j}=\frac{{\mathrm{\α}}_{ji}-\frac{1}{n}\underset{i=1}{\overset{n}{\Σ}}{\mathrm{\α}}_{ji}}{\sqrt{\frac{1}{n}\underset{i=1}{\overset{n}{\Σ}}{({\mathrm{\α}}_{ji}-\frac{1}{n}\underset{i=1}{\overset{n}{\Σ}}{\mathrm{\α}}_{ji})}^2}}$

Wherein, α _jifor i-th line standardization load factor before treatment of operating mode j; s _jfor the line load rate standard deviation under operating mode j.

Below for the grid structure in Fig. 1, wherein, embodiment is IEEE9 node system, assuming that UPFC is installed on branch road 1, then optimization aim is that line load equilibrium degree is the highest, line loss is minimum, and expression formula is respectively:

Line load equilibrium degree is the highest: minE

Wherein $E=\sqrt{\frac{1}{n}\underset{i=1}{\overset{n}{\Σ}}{\left({\mathrm{\α}}_i-\stackrel{\‾}{\mathrm{\α}}\right)}^2}=\sqrt{\frac{1}{n}\underset{i=1}{\overset{n}{\Σ}}{\left({\mathrm{\α}}_i-\frac{1}{n}\underset{i=1}{\overset{n}{\Σ}}{\mathrm{\α}}_i\right)}^2}=\sqrt{\frac{1}{6}\underset{i=1}{\overset{6}{\Σ}}{\left({\mathrm{\α}}_i-\frac{1}{6}\underset{i=1}{\overset{6}{\Σ}}{\mathrm{\α}}_i\right)}^2}$

α _iit is the load factor of i-th branch road;

Line loss is minimum: $\begin{array}{cc}min& \underset{i=1}{\overset{6}{\Σ}}{I_i}^2{R}_i\end{array}$

Wherein, I _ibe the electric current of i-th branch road, R _ibe the resistance of i-th branch road;

Therefore, optimization aim is comprehensively:

$\left\{\begin{array}{c}min\sqrt{\frac{1}{6}\underset{i=1}{\overset{6}{\Σ}}{({\mathrm{\α}}_i-\frac{1}{6}\underset{i=1}{\overset{6}{\Σ}}{\mathrm{\α}}_i)}^2}\\ min\underset{i=1}{\overset{6}{\Σ}}{I_i}^2{R}_i\end{array}\right.$

According to optimal load flow result of calculation, line load rate vector is α (α ₁, α ₂..., α ₆), obtain vectorial η (η after standardization ₁, η ₂..., η ₆) characterize desirable optimal load flow state, wherein:

In like manner can be obtained by course of standardization process, the flow state vector that operating mode j to be evaluated is corresponding is η _j(η _j1, η _j2..., η _j6), wherein ${\mathrm{\η}}_{ji}=\frac{{\mathrm{\α}}_{ji}-{\stackrel{\‾}{\mathrm{\α}}}_j}{s_j}=\frac{{\mathrm{\α}}_{ji}-\frac{1}{6}\underset{i=1}{\overset{6}{\Σ}}{\mathrm{\α}}_{ji}}{\sqrt{\frac{1}{6}\underset{i=1}{\overset{6}{\Σ}}{({\mathrm{\α}}_{ji}-\frac{1}{6}\underset{i=1}{\overset{6}{\Σ}}{\mathrm{\α}}_{ji})}^2}}$

The flow state evaluation index d of definition operating mode j _jfor η _jand the Euclidean distance between η, expression formula is: $d_j=\sqrt{\underset{i=1}{\overset{6}{\Σ}}{({\mathrm{\η}}_{ji}-{\mathrm{\η}}_i)}^2}$

Suppose the difference due to UPFC controling parameters, there are 2 operating conditions to be evaluated, calculate its flow state evaluation index and be respectively d ₁and d ₂if, d ₁> d ₂, then operating mode 2 is more close to desirable optimum operating condition, and trend distribution is better than operating mode 1; If d ₁< d ₂, then operating mode 1 is more close to desirable optimum operating condition, and trend distribution is better than operating mode 2.

The invention discloses a kind of based on standardization Euclidean distance containing UPFC electric network swim method for evaluating state, establish the desirable mark post reference point that flow state is evaluated, i.e. optimal load flow, flow state level is characterized according to the extent of deviation between actual motion point and desirable optimum point, evaluation index not only can relative superior or inferior between more different operating condition, also to the flow state proficiency assessment of specific operation self, there is reference value, and in the computational process of optimal load flow, many optimization aim choose the utilance making electrical network can improve electric equipment, also the factor of saving energy and decreasing loss is considered to a certain extent, the more objective more realistic application of evaluation result.

These are only the preferred embodiments of the present invention; not thereby the scope of the claims of the present invention is limited; every utilize specification of the present invention and accompanying drawing content to do equivalent structure or equivalent flow process conversion; or be directly or indirectly used in the technical field that other are relevant, be all in like manner included in scope of patent protection of the present invention.

Claims (6)

1. based on standardization Euclidean distance containing a UPFC electric network swim method for evaluating state, it is characterized in that, comprise the following steps:

Step 1, foundation take into account the electric network swim Optimized model of UPFC:

With system operation conditions and UPFC performance parameter for constraints, the highest with line load equilibrium degree, line loss is minimum for optimization aim, calculates the electrical network optimal load flow containing UPFC;

Step 2, according to optimal load flow result of calculation, standardization is carried out to each line load rate data;

Step 3, for certain operating condition to be evaluated, standardization is carried out to the line load rate data under this operating mode;

Step 4, calculate Euclidean distance between operating mode to be evaluated and desirable optimum operating condition, result of calculation is as the flow state evaluation index under this operating mode.

2. according to claim 1 a kind of based on standardization Euclidean distance containing UPFC electric network swim method for evaluating state, it is characterized in that, also comprise step 5, the trend evaluation index of all operating modes to be evaluated is sorted, the corresponding operating mode flow state optimum that index value is minimum.

3. according to claim 2 a kind of based on standardization Euclidean distance containing UPFC electric network swim method for evaluating state, it is characterized in that, in step 1, system cloud gray model constraints comprises:

Node power equilibrium equation:

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

Generated power is exerted oneself limit value and idle limit value of exerting oneself:

$\left\{\begin{array}{c}{P}_{Gi\min }\&le;P_{Gi}\&le;P_{Gimax}\\ Q_{Gi\min }\&le;Q_{Gi}\&le;Q_{Gimax}\end{array}\right.$

Busbar voltage limit value:

U _imin≤U _i≤U _imax

Circuit transmission power limit value:

|P _l|＝|P _ij|＝|U _iU _j(G _ijcosθ _ij+B _ijsinθ _ij)-U _i ²G _ij|≤P _lmax

In formula, P _gi, Q _gifor the meritorious, idle of bus i institute running fire motor is exerted oneself; P _di, Q _dibe respectively bus i connect the meritorious, idle of load; U _i, U _jbe respectively the voltage of bus i and bus j; G _ij, B _ijfor the element of the i-th row, jth row in node admittance matrix; θ _ijfor the phase difference of voltage of bus i and bus j; P _gimin, P _gimaxbe respectively the meritorious upper and lower limit of exerting oneself of bus i institute running fire motor; Q _gimin, Q _gimaxbe respectively the idle upper and lower limit of exerting oneself of bus i institute running fire motor; U _imin, U _imaxfor bus i working voltage upper and lower limit; P _lfor the active power that circuit l carries; P _ijfor the active power that bus i and bus j institute's line road and circuit l carry; P _lmaxfor branch road l transmission power limiting value.

4. according to claim 2 a kind of based on standardization Euclidean distance containing UPFC electric network swim method for evaluating state, it is characterized in that, in step 1, UPFC performance parameter constraints comprises:

Series connection injecting voltage limit value:

|ΔU|≤ΔU _max

Series/parallel side converter is meritorious exchanges limit value:

P _dc≤S _sh

Wherein, Δ U is series connection injecting voltage, Δ U _maxfor the upper limit of injecting voltage of connecting; P _dcfor the active power that series/parallel top-cross is changed, S _shfor the rated capacity of side in parallel converter.

5. according to claim 2 a kind of based on standardization Euclidean distance containing UPFC electric network swim method for evaluating state, it is characterized in that, in step 2, if electrical network has n bar circuit, the vector that original load factor is formed is α (α ₁, α ₂..., α _n), be η (η after standardization ₁, η ₂..., η _n), η _ibe the load factor after i-th line standard, computing formula is:

${\mathrm{\&eta;}}_i=\frac{{\mathrm{\&alpha;}}_i-\stackrel{\&OverBar;}{\mathrm{\&alpha;}}}{s}$

Wherein, α _ifor the original load factor of the circuit before standardization, for the mean value of original load factor, computing formula is:

$\stackrel{\&OverBar;}{\mathrm{\&alpha;}}=\frac{1}{n}\underset{i=1}{\overset{n}{\&Sigma;}}{\mathrm{\&alpha;}}_i$

S is the standard deviation of original load factor, and computing formula is:

$s=\sqrt{\frac{1}{n}\underset{i=1}{\overset{n}{\&Sigma;}}{({\mathrm{\&alpha;}}_i-\stackrel{\&OverBar;}{\mathrm{\&alpha;}})}^2}.$

6. according to claim 5 a kind of based on standardization Euclidean distance containing UPFC electric network swim method for evaluating state, it is characterized in that, in step 4, for operating mode j to be evaluated, flow state evaluation index d _jbe defined as the flow state η of operating mode j _j(η _j1, η _j2..., η _jn) and desirable flow state η (η ₁, η ₂..., η _n) between Euclidean distance, computing formula is:

$d_j=\sqrt{\underset{i=1}{\overset{n}{\&Sigma;}}{({\mathrm{\&eta;}}_{ji}-{\mathrm{\&eta;}}_i)}^2}$

η _jifor the normalized load rate of i-th circuit of operating mode j to be evaluated, computing formula is:

${\mathrm{\&eta;}}_{ji}=\frac{{\mathrm{\&alpha;}}_{ji}-{\stackrel{\&OverBar;}{\mathrm{\&alpha;}}}_j}{s_j}=\frac{{\mathrm{\&alpha;}}_{ji}-\frac{1}{n}\underset{i=1}{\overset{n}{\&Sigma;}}{\mathrm{\&alpha;}}_{ji}}{\sqrt{\frac{1}{n}\underset{i=1}{\overset{n}{\&Sigma;}}{({\mathrm{\&alpha;}}_{ji}-\frac{1}{n}\underset{i=1}{\overset{n}{\&Sigma;}}{\mathrm{\&alpha;}}_{ji})}^2}}$

Wherein, α _jifor i-th line standardization load factor before treatment of operating mode j; s _jfor the line load rate standard deviation under operating mode j.