Sensitivity analysis method for flexible direct-current traction power supply system

Abstract

The invention provides a sensitivity analysis method for a flexible direct-current traction power supply system, and belongs to the technical field of flexible direct-current traction power supply systems, and the method comprises the steps: obtaining the sensitivity degrees of different variables through the differential relation between the physical quantities of a site and a measurement node under a given operation state of the traction power supply system; comprising relations between converter voltage and catenary power as well as between traction unit output power and catenary tidal current. By analyzing a sensitivity calculation result, visual and efficient decision support is provided for power dispatching personnel, and an operator can quickly determine a key control variable and adjust a control strategy according to the key control variable, so that optimization and improvement of system performance are realized.

Description

Technical Field

[0001] The present invention belongs to the technical field of flexible direct current traction power supply systems, and in particular relates to a sensitivity analysis method for flexible direct current traction power supply systems. Background Art

[0002] At present, urban rail traction power supply systems at home and abroad mainly use power monitoring technology based on diode rectifier units and static monitoring of operating status. This traditional technical solution is highly dependent on the urban distribution network. Due to the frequent start and stop of trains, the utilization rate of distribution network and traction system equipment is low, the traction power supply voltage fluctuates violently, the energy distribution of the traction network is extensive, and the train regenerative braking energy cannot be efficiently utilized within the traction system.

[0003] As an emerging technology, the flexible DC traction power supply system based on fully controlled bidirectional converters and intelligent collaborative control can flexibly regulate the energy of the traction power supply system, actively respond to the needs of the urban distribution network, and fundamentally change the operation mechanism of the traction power supply system. Although its excellent performance and reliability face many challenges in practical applications, sensitivity analysis technology provides strong support for dispatchers. This analysis method deeply analyzes the subtle effects of various system parameters on the overall performance, allowing dispatchers to quickly understand the inherent connection between control objectives and complex control variables, and combine comprehensive information to accurately select the optimal control variables and degree of regulation. Subsequently, through the distribution of efficient strategies (covering control modes and clear goals) to the collaborative controller, the voltage / power value of the traction unit can be accurately adjusted, thereby optimizing the system design and significantly improving system performance. Summary of the invention

[0004] In view of the deficiencies in the prior art, the present invention provides a sensitivity analysis method for a flexible DC traction power supply system. By real-time calculation of the injected power, line loss and node voltage of each node, the impact of changes in control quantities in the traction power supply system on system performance is accurately evaluated, which facilitates operating personnel to quickly adjust the control strategy and optimize and improve system performance.

[0005] The present invention achieves this object through the following technical solutions: A sensitivity analysis method for a flexible DC traction power supply system comprises the following steps: S1: According to the actual network topology and operating status of the flexible DC traction power supply system, the obtained physical quantities are classified to determine the independent parameter variables, state variables, control variables, and output variables; S2: The steady-state equilibrium condition of the traction power supply system is represented by several nonlinear network equations. The power flow equation of the traction power supply system is constructed, and the sensitivity matrix equation is obtained using the Newton-Raphson method. S3: Analyze the small changes in the state variables and output variables of the system when the control variables of the traction power supply system change slightly under a given operating state, including: the relationship between the change in the active power of the traction system and the change in the voltage, the relationship between the change in the active network loss and the change in the voltage of the traction system, and the relationship between the change in the active network loss and the change in the active power of the traction system; S4: Compare the sensitivities of different control variables corresponding to the same state variable / output variable, and sort them according to the sensitivity values, determine the key control variables that affect the state variable / output variable, and adjust the control strategy accordingly to optimize and improve system performance.

[0006] Furthermore, in step S1, the variables are divided into the following four categories according to their mathematical functions: Independent parameter variables: including line admittance parameters , ; State variables: including the voltage and phase angle of the load node, and the phase angle of the generator node voltage; Control variables: including active power and reactive power of load nodes, active power and voltage of generator nodes, voltage and phase angle of balance nodes; Output variables: including reactive power of generator nodes, active power and reactive power of balancing nodes, system active loss and reactive loss.

[0007] Further, step S3 is specifically as follows: Assuming there are t traction depot nodes and s train nodes, the traction depot nodes are sorted first and then the train nodes, then the sensitivity in the traction power supply system is specifically in the following form: The power flow equation as the basic equation is the node power balance equation: ; in, P i Representation Node The active power, Representation Node The voltage, Representation Node The voltage, , The admittance matrix representing the network topology, Representation Node and nodes The conductivity value between Put the above formula at the operating point P 0 and U 0 Taylor series expansion is performed at , and the second-order and higher-order terms are omitted. ; Among them, , represents the Jacobian matrix; Then the sensitivity relationship between the node power change and the node voltage change is expressed as: ; in, , , Representation Node The self-conductance of The sensitivity relationship between the change in active network loss and the change in node voltage is: ; in, , P L It indicates the total loss of power lines and equipment components in the system during normal operation. ; The slight increase rate of active network loss is expressed as: ; in, .

[0008] The present invention also provides a computer program product, comprising a computer program / instruction, wherein the computer program / instruction implements the aforementioned method when executed by a processor.

[0009] The present invention also provides a computer-readable storage medium, on which a computer program is stored, and when the computer program is executed by a processor, the aforementioned method is implemented.

[0010] The present invention also provides an electronic device, comprising a processor, a memory, and a computer program stored in the memory and capable of running on the processor, wherein the computer program implements the aforementioned method when executed by the processor.

[0011] The present invention also provides a sensitivity analysis device for a flexible DC traction power supply system, which is used to implement the aforementioned method, including: State equation building module, used to establish the power flow equation of the flexible DC traction power supply system state; Sensitivity calculation module, used to calculate the sensitivity of the control variable to the state variable / output variable; The strategy analysis module is used to rank and analyze the sensitivity of each control variable that affects the same state variable / output variable, determine the key control variables that affect the state variable / output variable, and provide suggestions for adjusting the control strategy accordingly.

[0012] Compared with the prior art, the present invention has the following beneficial effects: The sensitivity analysis method of a flexible DC traction power supply system provided by the present invention can convert the node injection power, line loss and node voltage parameters in the flexible DC traction power supply system into a linear and one-to-one relationship. By using the differential relationship between the physical quantities of the station and the measurement node under a given operating state of the traction power supply system, the sensitivity between different variables, such as the relationship between the converter voltage and the contact network power, and the relationship between the output power of the traction unit and the contact network flow, is obtained. By analyzing the sensitivity calculation results, it is used to assist power dispatchers in intuitively judging the connection between the control target and many control quantities in a short time, providing intuitive and efficient decision support for power dispatchers. Operators can quickly determine and select the most appropriate control quantity and control degree, and adjust the control strategy accordingly, and send the strategy (control mode, control target) to the collaborative controller to adjust the traction unit, set the voltage / power value, and optimize and improve the system performance. BRIEF DESCRIPTION OF THE DRAWINGS

[0013] Figure 1 The figure is a flow chart of an embodiment of the present invention. DETAILED DESCRIPTION

[0014] The exemplary embodiments of the present invention will be described in more detail below with reference to the accompanying drawings. Although exemplary embodiments of the present invention are shown in the accompanying drawings, it should be understood that the present invention can be implemented in various forms and should not be limited by the embodiments set forth herein. On the contrary, these embodiments are provided in order to enable a more thorough understanding of the present invention and to be able to fully convey the scope of the present invention to those skilled in the art. It should be noted that, in the absence of conflict, the embodiments of the present invention and the features in the embodiments can be combined with each other. The present invention will be described in detail below with reference to the accompanying drawings and in conjunction with the embodiments.

[0015] The present invention provides an embodiment of a sensitivity analysis method for a flexible DC traction power supply system, the process is as follows: Figure 1 As shown, the following steps are included: S1: According to the actual network topology and operating status of the flexible DC traction power supply system, the variables can be divided into the following four categories according to the mathematical functions of each variable: 1) Independent parameter variables: including line admittance parameters , Unchanged quantity.

[0016] 2) State variables: including the voltage and phase angle of the load node, and the phase angle of the generator node voltage.

[0017] 3) Control variables: including active power and reactive power of load nodes, active power and voltage of generator nodes, voltage and phase angle of balancing nodes; 4) Output variables: including reactive power of generator nodes, active power and reactive power of balancing nodes, and system active loss and reactive loss.

[0018] S2: The steady-state equilibrium condition of the traction power supply system is represented by several nonlinear network equations. The sensitivity matrix equation is obtained by using the Newton-Raphson method: 1) The steady-state equilibrium condition of the traction power supply system can be expressed by n nonlinear network equations. Under a certain operating state, this equation is expressed as:

[0019] in, represents the column vector of controlled variables (dependent variables); represents the column vector of the control variable (independent variable). Since the number and form of the equations that make up the above formula depend on how to choose and The form and number of equations will also vary depending on the coordinate system (polar or rectangular).

[0020] When the system is operating under given stable operating conditions, the above equation becomes:

[0021] When the running state changes, and There is a deviation and When , the steady-state equilibrium equation of the system becomes:

[0022] 2) Apply the above formula at the operating point and Perform Taylor series expansion at , and ignore the second-order and higher-order terms, and we get:

[0023] because , the above formula can be further rewritten as:

[0024] Among them, the coefficient matrix and is the Jacobian matrix, and the above formula is the basic equation of sensitivity.

[0025] 3) The control variables can be obtained from the linear model of sensitivity and the controlled variable The linear relationship is:

[0026] Among them, , represents the sensitivity matrix. The effectiveness of approximate analysis using first-order sensitivity depends on whether the system's operating state has a good degree of linearity. Under normal operating conditions, the power equation of the traction power supply system is close to linear near the operating point.

[0027] S3: Analyze the small changes in the state variables and output variables of the traction power supply system when the control variables change slightly under a given operating state, and use the differential relationship between them to express this change relationship, including: the relationship between the change in the traction power supply and the change in the voltage, the relationship between the change in the active network loss and the change in the traction voltage, and the relationship between the change in the active network loss and the change in the traction power supply; Assuming there are t traction depot nodes and s train nodes, which are arranged in the order of traction depot nodes first and then train nodes, the specific form of sensitivity in the traction power supply system is as follows: 1) The sensitivity analysis method is based on the power flow equation. The node power balance equation as the basic equation is as follows:

[0028] in, P i Representation Node Active power, Representation Node The voltage, Representation and Node related nodes j The voltage, , The admittance matrix representing the network topology, Representation Node and nodes The conductivity value between .

[0029] Put the above formula at the operating point P 0 and U 0 Taylor series expansion is performed at , and the second-order and higher-order terms are omitted.

[0030] Among them, , represents the Jacobian matrix.

[0031] 2) The sensitivity relationship between the node power change and the node voltage change is expressed as:

[0032] in, , , Representation Node The self-conductance.

[0033] For example , which means that when the voltage of the traction station 1 node rises / falls by 1V, the power of node 1 will rise / fall by 2094763.438W (theoretical value, not the actual power change of node 1, but it is approximate, all the following values ​​are approximate). If the value is negative, it means that when the voltage of the traction station 1 node rises / falls by 1V, the power of node 1 will fall / rise by the corresponding value.

[0034] at the same time, It means that the change of the voltage of the node 1 of the traction station will only affect the power of node 1, and will not change the power of nodes 2, 3, ... (0.000). Similarly, the locomotive sensitivity information can be obtained.

[0035] 3) Sensitivity relationship between active network loss change and node voltage change:

[0036] in, , P L It indicates the total loss of power lines and equipment components in the system during normal operation. .

[0037] For example If the voltage of a node in the traction station increases by 1V, the total loss will increase by 5.490W. If the voltage of a node in the traction station decreases by 1V, the total loss will decrease by 5.490W.

[0038] 4) The slight increase rate of active network loss is expressed as:

[0039] in, .

[0040] For example, It means that if the active power of traction station 1 increases / decreases by 1W, the total loss decreases / increases by 0.172W. This means that if the active power of traction station 2 increases / decreases by 1W, the total loss will increase / decrease by 5.490W. The rest of the analysis is the same as the network loss sensitivity analysis.

[0041] S4: Compare the sensitivities of different control variables corresponding to the same state variable or output variable and sort them according to the sensitivity values ​​to determine the key control variables that affect the state variable or output variable, and provide intuitive and efficient decision support for power dispatchers, so that operators can quickly determine the key control variables based on the sensitivity calculation results, and adjust the control strategy accordingly to achieve optimization and improvement of system performance.

[0042] 1) The calculation results of sensitivity will change with the system state. The movement of the locomotive changes the node admittance matrix and node voltage of the network, and the sensitivity calculation is mainly based on these two data, which causes the sensitivity calculation results to be refreshed.

[0043] 2) The sensitivity value represents the degree of change (increase or decrease) of the dependent variable caused by a unit change (increase or decrease) of the independent variable. If the operator wants to reduce network loss, by observing the network loss sensitivity, the control variable with the largest network sensitivity can be selected for parameter setting and adjustment. The larger the value of the sensitivity calculation result, the greater the impact of the node parameter on the target quantity. Improving its parameters can greatly improve the target in the predetermined direction.

[0044] 3) The decision support is presented to the power dispatcher through a visual interface, reports, etc., so that the dispatcher can make decisions based on the sensitivity calculation results.

[0045] The present invention can compile the above content into a computer program to realize intelligent analysis and facilitate information extraction and decision-making processing for power dispatchers.

[0046] The present invention has been described in detail above through embodiments, but the contents described are only exemplary embodiments of the present invention and cannot be considered to limit the scope of implementation of the present invention. The protection scope of the present invention is defined by the claims. Anyone who utilizes the technical solution described in the present invention, or a technician in the field, inspired by the technical solution of the present invention, designs a similar technical solution within the essence and protection scope of the present invention to achieve the above technical effects, or makes equal changes and improvements to the scope of application, shall still belong to the scope of protection covered by the patent of the present invention. It should be noted that in order to make a clear statement, the description of some components and processes that have no direct and obvious connection with the scope of protection of the present invention but are known to those skilled in the art are omitted in the description of the present invention.

Claims

1. A sensitivity analysis method for a flexible DC traction power supply system, characterized in that: The steps include: S1: According to the actual network topology and operating status of the flexible DC traction power supply system, the obtained physical quantities are classified to determine the independent parameter variables, state variables, control variables, and output variables; S2: The steady-state equilibrium condition of the traction power supply system is represented by several nonlinear network equations. The power flow equation of the traction power supply system is constructed, and the sensitivity matrix equation is obtained using the Newton-Raphson method. S3: Analyze the small changes in the state variables and output variables of the system when the control variables of the traction power supply system change slightly under a given operating state, including: the relationship between the change in the active power of the traction system and the change in the voltage, the relationship between the change in the active network loss and the change in the voltage of the traction system, and the relationship between the change in the active network loss and the change in the active power of the traction system; S4: Compare the sensitivities of different control variables corresponding to the same state variable / output variable, and sort them according to the sensitivity values, determine the key control variables that affect the state variable / output variable, and adjust the control strategy accordingly to optimize and improve system performance.

2. The sensitivity analysis method of the flexible DC traction power supply system according to claim 1 is characterized in that: In step S1, the variables are divided into the following four categories according to their mathematical functions: Independent parameter variables: including line admittance parameters , ; State variables: including the voltage and phase angle of the load node, and the phase angle of the generator node voltage; Control variables: including active power and reactive power of load nodes, active power and voltage of generator nodes, voltage and phase angle of balancing nodes; Output variables: including reactive power of generator nodes, active power and reactive power of balancing nodes, system active loss and reactive loss.

3. The sensitivity analysis method of the flexible DC traction power supply system according to claim 1 is characterized in that: Step S3 is as follows: Assuming there are t traction depot nodes and s train nodes, the traction depot nodes are arranged first and then the train nodes. The sensitivity in the traction power supply system is specifically in the following form: The power flow equation as the basic equation is the node power balance equation: ; in, P i Representation Node The active power, Representation Node The voltage, Representation Node The voltage, , The admittance matrix representing the network topology, Representation Node and nodes The conductivity value between Put the above formula at the operating point P 0 and U 0 Taylor series expansion is performed at , and the second-order and higher-order terms are omitted. ； Among them, , represents the Jacobian matrix; Then the sensitivity relationship between the node power change and the node voltage change is expressed as: ; in, , , Representation Node The self-conductance of The sensitivity relationship between the change in active network loss and the change in node voltage is: ； in, , P L It indicates the total loss of power lines and equipment components in the system during normal operation. ; The slight increase rate of active network loss is expressed as: ; in, .

4. A computer program product comprising a computer program / instructions, characterized in that When the computer program / instructions are executed by a processor, the method according to any one of claims 1 to 3 is implemented.

5. A computer-readable storage medium, characterized in that: The computer-readable storage medium stores a computer program, and when the computer program is executed by a processor, the method according to any one of claims 1 to 3 is implemented.

6. An electronic device, characterized in that: The method comprises a processor, a memory, and a computer program stored in the memory and capable of running on the processor, wherein when the computer program is executed by the processor, the method according to any one of claims 1 to 3 is implemented.

7. A sensitivity analysis device for a flexible DC traction power supply system, characterized in that: The device is used to implement the method according to any one of claims 1 to 3, comprising: State equation building module, used to establish the power flow equation of the flexible DC traction power supply system state; Sensitivity calculation module, used to calculate the sensitivity of the control variable to the state variable / output variable; The strategy analysis module is used to rank and analyze the sensitivity of each control variable that affects the same state variable / output variable, determine the key control variables that affect the state variable / output variable, and provide suggestions for adjusting the control strategy accordingly.

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