Intelligent expressway through direct current power supply system and key parameter calculation method thereof

Abstract

The intelligent expressway through direct current power supply system comprises one of a through power supply line, a local side machine, a far-end inverter, a far-end chopper, a T-connection terminal and a T-connection box which are electrically connected with one another; the invention relates to a key parameter calculation method of a smart highway through direct current power supply system. Wire cross section calculation of a through power supply line is verified according to temperature rise, short-circuit thermal stability, voltage loss and economic technology of a wire. As a plurality of power supplies penetrate through the power supply cable, when a certain power supply fails, other power supplies can still be used for normal operation of the equipment; a unified power supply system is adopted, equipment access management is facilitated, and application is more flexible; new equipment is convenient to access, and when the equipment is added, a T-connection terminal can be connected to a through power supply line; power supply access is convenient, and a cut-through power supply line is accessed through chopping; the system has strong expansibility, and the newly built highway through power supply line can be connected to the existing through power supply line. According to the invention, beneficial technical support is provided for stable, economical and reliable power supply of the expressway.

Description

Technical Field

[0001] The present invention relates to the field of power supply technology, and in particular to a smart highway through-going DC power supply system and a method for calculating key parameters thereof. Background Art

[0002] With the construction of smart highways, more and more power-consuming equipment needs to be deployed along the highways. In the existing technology, the general way to supply power to power-consuming equipment is that the substations set up at highway toll stations, service areas, etc. use the laid power cables to supply power to remote devices such as cameras and fill lights along the line in AC mode. Due to technical limitations, it has the disadvantages of small power supply radius, large cable cross-sectional area, poor economy, and few external power grid access points in remote areas, making it difficult to obtain power locally.

[0003] In addition, as the number and power of smart devices along highways increase, the cross-section of cables is required to be larger. Therefore, during the renovation, the renovation project is often accompanied by the renovation of power cables, which is costly. In addition, in areas not covered by the original power lines, new power cables need to be laid. Sometimes the terminal voltage and other parameters are difficult to meet the equipment requirements, which further increases the difficulty of the project. In addition, in recent years, the application of new energy power supply forms such as solar energy and wind energy to power electrical equipment on highways has gradually matured. However, the existing AC power supply mode of highways and the traditional power supply topology are difficult to meet the direct access of new energy sources, and the technical difficulty is high. Summary of the invention

[0004] In order to overcome the existing power supply mode for electrical equipment on highways, due to technical limitations, there are disadvantages as described in the background. The present invention provides a power supply for electromechanical equipment such as intelligent monitoring, communication, ventilation, etc. on highways. Under the joint action of relevant equipment and methods, it can solve the problems of difficulty in local power supply for newly added electromechanical equipment on highways, poor accessibility of new energy power sources, and difficulty in upgrading and transforming existing power supply systems. It has a safe, reliable, low-cost, and highly expandable power supply effect for electromechanical equipment along the smart highway, and also has the advantage of little interference with communication lines. The smart highway through-connected DC power supply system and its key parameter calculation method are also provided.

[0005] The technical solution adopted by the present invention to solve its technical problem is: The through-connected DC power supply system of a smart highway is characterized in that it includes a through-connected power supply line, a local machine, a remote inverter, a remote chopper and one of a T-terminal and a T-junction box; the through-connected power supply cable is laid along the highway, and the through-connected power supply line cables are laid in pipelines and pipe corridors; the local machine is installed in a power supply room where there is access to an external power supply at a highway toll station or service area; the remote inverter is installed at power loads such as smart lamp poles, ETC gantries, tunnel fans, and tunnel lighting, and the remote chopper is installed at a new energy power source including a wind turbine and a solar generator; one of the T-terminal and the T-junction box is installed at the point where the remote inverter and the remote chopper are connected to the through-connected power supply cable; when there is no new energy power supply access, the local machine takes the substation set up in the toll station or service area as the starting point, the local machine is powered by an AC power supply, and the rectifier is electrically connected to the DC bus, The DC bus is electrically connected to the through power supply line, and the remote inverter is electrically connected to the through power supply line through a T-terminal and a T-junction box; when the local terminal has access to a new energy power source, the local terminal takes the substation set up in the toll station and service area as the starting point, and the local terminal is powered by AC, and the rectifier is electrically connected to the DC bus, the DC bus is electrically connected to the through power supply line, and the remote inverter is electrically connected to the through power supply line through a T-terminal and a T-junction box. The new energy power source is boosted to the rated voltage of the power supply line through a remote chopper, and is electrically connected to the through power supply line through a T-terminal and a T-junction box; a method for calculating key parameters of a through DC power supply system for a smart highway, and the conductor cross-section calculation of the through power supply line is based on the temperature rise, short-circuit thermal stability, voltage loss, and economic and technical conditions of the conductor. The selected cross-section is verified and determined according to the most unfavorable conditions.

[0006] Furthermore, the voltage of the through power supply line is selected between 400VDC and 1800VDC, preferably 750V DC.

[0007] Furthermore, the output voltage of the remote inverter is AC 220VAC.

[0008] Furthermore, the capacities of the local terminal and the remote inverter are determined according to load requirements.

[0009] Furthermore, the cross-section of the conductor that passes through the power supply line is selected according to the temperature rise, and the formula used is as follows: 、I<=K1K2K3I 0， In the formula, I js Calculate the current for the maximum load, K 1 is the correction coefficient under different laying methods, K 2 is the correction factor when multiple circuits are laid in parallel. K 3 is the correction coefficient under different soil thermal resistance coefficients, I0 is the rated current carrying capacity A of the cable under standard laying conditions.

[0010] Furthermore, the cross-section of the conductor that passes through the power supply line is selected according to the short-circuit thermal stability, and the formula used is as follows: , where S min The minimum cross-sectional area of ​​the conductor that meets the short-circuit thermal stability requirement. Q t is the thermal effect of short-circuit current; C is the thermal stability coefficient of the conductor, I k is the maximum initial value of the three-phase symmetrical short-circuit current at the short-circuit point, t k is the short circuit duration, which is the protection action time t b Full disconnection time of circuit breaker t l sum.

[0011] Furthermore, the cross-section of the conductor that passes through the power supply line is selected according to the voltage drop within the allowable range, and the formula used is as follows: , where ∆ u% is the percentage of line voltage loss, ∆ up% is the percentage of voltage loss per 1kW•km of three-phase line, P i is the active load (kW); l i is the line length.

[0012] Furthermore, when the cross-section of the conductor that passes through the power supply line is selected according to economic conditions, the formula used is as follows: , where Sec is the optimal economic cross-section, j is the economic current density of the conductor; Ijs is the maximum load calculation current.

[0013] The beneficial effects of the present invention are as follows: compared with the existing solutions, the present invention has the following advantages: since the through-power supply cable has multiple power supply lines, when a power failure occurs, other power supplies can still provide normal operation of the equipment, so that the reliability is higher; the use of a unified power supply system facilitates equipment access management and is more flexible in application; new equipment is easy to access, and when the equipment is added, a T-terminal can be used to access the through-power supply line; power supply access is convenient, and the new energy power supply is generally a DC output, which can be connected to the through-power supply line through chopping; the system has strong expandability, and the newly built highway through-power supply line can be connected to the existing through-power supply line. The present invention provides favorable technical support for the stable, economical and reliable power supply of highways. In summary, the present invention has good application prospects. BRIEF DESCRIPTION OF THE DRAWINGS

[0014] Figure 1It is a schematic diagram of the composition of the DC power supply system for the intelligent highway of the present invention.

[0015] Figure 2 It is a schematic diagram of the DC power supply system of the smart highway when the new energy power supply is connected.

[0016] Figure 3 It is a schematic diagram of laying the direct current power supply system for powering the smart highway of the present invention on the side of the smart highway.

[0017] Figure 4 It is a schematic diagram of the expansion of the DC power supply system for the intelligent highway of the present invention. DETAILED DESCRIPTION

[0018] Figure 1 , 2 As shown in , 3 and 4, the through-connected DC power supply system of the smart highway includes a through-connected power supply line, a local machine, a remote inverter, a remote chopper and a T-terminal or a T-junction box; the through-connected power supply cable is laid along the highway, and the through-connected power supply line is laid in pipelines and pipe corridors; the local machine is installed in a power supply room in places with external power access conditions such as highway toll stations or service areas; the remote inverter is installed at power loads such as smart lamp poles, ETC gantries, tunnel fans, tunnel lighting, etc., and the remote chopper is installed at new energy power sources including wind turbines and solar generators; the T-terminal or T-junction box is installed at the place where the remote inverter and the remote chopper are connected to the through-connected power supply cable; when there is no new energy power access, the local machine takes the substation set up in the toll station or service area as the starting point, and the local machine uses 380V AC is the power source, the rectifier is electrically connected to the DC bus, the DC bus is electrically connected to the through power supply line, and the remote inverter is electrically connected to the through power supply line through a T-terminal or a T-junction box; when the local terminal has access to a new energy power source, the substation set up in the toll station or service area is used as the starting point, the local terminal uses 380V AC as the power source, the rectifier is electrically connected to the DC bus, the DC bus is electrically connected to the through power supply line, the remote inverter is electrically connected to the through power supply line through a T-terminal or a T-junction box, the new energy power source is boosted to the rated voltage of the power supply line through a remote chopper, and is electrically connected to the through power supply line through a T-terminal or a T-junction box; in the key parameter calculation method of the through DC power supply system of the smart highway, the conductor cross-section of the through power supply line is checked according to the temperature rise, short-circuit thermal stability, voltage loss, economic and technical conditions of the conductor, and is determined according to the most unfavorable conditions.

[0019] Figure 1 , 2As shown in Figures 3 and 4, the voltage of the through power supply line is between 400VDC and 1800VDC, preferably 750V DC. The output voltage of the remote inverter is 220VAC AC. The capacity of the local terminal and the remote inverter is determined according to the load demand.

[0020] Figure 1 , 2 As shown in 3 and 4, the cross-section of the conductor that runs through the power supply line is selected according to the temperature rise. The heating temperature generated by the conductor when passing the normal maximum load current should not exceed its maximum temperature during normal operation. The working temperature of the cable in different environments will be different. The cable cross-section should be selected according to the worst heat dissipation environment along the line. The application formula is as follows, , I<=K1K2K3I0, where I js is the maximum load calculation current (A); K1 is the correction coefficient under different laying methods; K2 is the correction coefficient when multiple circuits are laid in parallel; K3 is the correction coefficient under different soil thermal resistance coefficients; I0 is the rated current carrying capacity of the cable under standard laying conditions (A).

[0021] Figure 1 , 2 As shown in Figures 3 and 4, the cross-section of the conductor that runs through the power supply line is selected according to the short-circuit thermal stability. When the short-circuit current flows through the conductor, a thermal effect will be generated accordingly. The thermal effect causes the conductor temperature to rise sharply, accelerating the aging of the conductor insulation layer or directly damaging the insulation layer. The conductor cross-section meets the following conditions: , where S min The minimum cross-sectional area of ​​the conductor that meets the short-circuit thermal stability requirement (mm2); Q t is the short-circuit current thermal effect (kA 2 ·s); C is the thermal stability coefficient of the conductor; I k is the initial value of the maximum three-phase symmetrical short-circuit current at the short-circuit point; t k is the short circuit duration, which is the protection action time t b Full disconnection time of circuit breaker t l Specifically, the four judgment methods depend on the distribution of load. The load is determined according to the design plan. The four methods are determined according to the most unfavorable situation, generally determined by the first and fourth methods.

[0022] Figure 1 , 2As shown in , 3, and 4, the cross-section of the conductor that runs through the power supply line is selected according to the voltage drop within the allowable range. Since the conductor itself has impedance, a voltage drop will occur when the load current passes through the distribution line. The terminal voltage requirement is selected according to the voltage requirement on the input side of the remote inverter. The formula used is as follows, , where ∆u% is the percentage of line voltage loss (%); ∆ up% is the percentage of voltage loss per 1kW•km of three-phase line (% / kW•km); P i is the active load (kW); l i is the line length (km).

[0023] Figure 1 , 2 As shown in Figures 3 and 4, the cross-section of the conductor that runs through the power supply line is selected according to economic conditions. Under the technical conditions of conductor temperature rise, thermal stability and voltage drop, the cable cross-section should also be determined based on the principle of minimizing the sum of the initial investment cost of the cable and the accumulated power loss during operation during the cable life cycle. The formula is as follows: , where Sec is the best economic cross section (mm2); j is the economic current density of the conductor (A / mm2); Ijs is the maximum load calculation current (A). The cable conductor cross section should be selected according to the voltage loss and economic current density first, and then other technical conditions should be checked. The cable can be laid along the line and can be laid in parallel with the communication line (the laying method has nothing to do with the load size. This scheme uses DC power supply, which does not affect the communication line and is determined according to the on-site conditions.) Figure 1 , 2 As shown in Figures 3 and 4, the present invention uses the above technical solution to select the conductor cross-section of a power supply line for a section of highway. The highway section is 20 km long and has 25 smart lamp poles. The load spacing of each smart pole is controlled according to 800m. The load size is 600W, and the input voltage range of the DC / AC inverter is DC400V~750V; the output voltage is AC220V. According to the single-core aluminum cable, cross-linked polyethylene (XLPE) insulation selection calculation, the cable cross-section is 35mm 2 . The present invention has multiple power supply lines in the through-power supply cable. When a power failure occurs, other power supplies can still provide normal operation of the equipment, so the reliability is higher; a unified power supply system is adopted, which is convenient for equipment access management and more flexible in application; new equipment can be easily accessed, and when equipment is added, a T-terminal can be used to access the through-power supply line; power supply access is convenient, and new energy power supplies are generally DC outputs, which can be connected to the through-power supply line through chopping; the system has strong expandability, and the newly built highway through-power supply line can be connected to the existing through-power supply line. The present invention provides favorable technical support for the stable, economical and reliable power supply of highways.

[0024] The above shows and describes the basic principles and main features of the present invention and the advantages of the present invention. It is obvious to those skilled in the art that the present invention is not limited to the details of the above exemplary embodiments, and the present invention can be implemented in other specific forms without departing from the spirit or basic features of the present invention. Therefore, no matter from which point of view, the embodiments should be regarded as exemplary and non-restrictive. The scope of the present invention is defined by the appended claims rather than the above description, and it is intended that all changes falling within the meaning and scope of the equivalent elements of the claims are included in the present invention.

[0025] In addition, it should be understood that although the present specification is described according to the implementation mode, the implementation mode does not only include an independent technical solution. This narrative method of the specification is only for the sake of clarity. Those skilled in the art should regard the specification as a whole. The technical solutions in each embodiment can also be appropriately combined to form other implementation modes that can be understood by those skilled in the art.

Claims

1. The smart highway runs through the DC power supply system, which is characterized by It includes a through power supply line, a local machine, a remote inverter, a remote chopper and one of a T-terminal and a T-junction box; the through power supply cable is laid along the highway, and the through power supply line cables are laid in pipelines and pipe corridors; the local machine is installed in a power supply room where there is access to an external power supply at a highway toll station or service area; the remote inverter is installed at power loads such as smart lamp poles, ETC gantries, tunnel fans, and tunnel lighting, and the remote chopper is installed at a new energy power source including a wind turbine and a solar generator; one of the T-terminal and the T-junction box is installed at the point where the remote inverter and the remote chopper are connected to the through power supply cable; when there is no new energy power supply access, the local machine takes the substation set up in the toll station or service area as the starting point, the local machine is powered by an AC power supply, the rectifier is electrically connected to the DC bus, and the DC bus is connected to the through power supply line The remote inverter is electrically connected to the through power supply line through a T-terminal and a T-junction box; when the local terminal has access to a new energy power source, the substation set up in the toll station and service area is used as the starting point, the local terminal is powered by AC, and the rectifier is electrically connected to the DC bus, the DC bus is electrically connected to the through power supply line, the remote inverter is electrically connected to the through power supply line through a T-terminal and a T-junction box, the new energy power source is boosted to the rated voltage of the power supply line through a remote chopper, and is electrically connected to the through power supply line through a T-terminal and a T-junction box; the key parameter calculation method of the through DC power supply system of the smart highway, the conductor cross-section calculation of the through power supply line is verified according to the temperature rise, short-circuit thermal stability, voltage loss, and economic and technical conditions of the conductor, and the selected cross-section is determined according to the most unfavorable conditions.

2. The intelligent highway through-connection DC power supply system according to claim 1 is characterized in that: The voltage of the through power supply line is selected between 400VDC and 1800VDC, preferably 750V DC.

3. The intelligent highway through-connection DC power supply system according to claim 1 is characterized in that: The output voltage of the remote inverter is 220VAC.

4. The intelligent highway through-connection DC power supply system according to claim 1 is characterized in that: The capacity of the local unit and remote inverter is determined according to the load demand.

5. The key parameter calculation method of the intelligent highway through DC power supply system according to claim 1 is characterized in that: The cross-section of the conductor that runs through the power supply line is selected according to the temperature rise. The formula used is as follows: 、I<=K1K2K3I 0， In the formula, I js Calculate the current for the maximum load, K 1 is the correction coefficient under different laying methods, K 2 is the correction factor when multiple circuits are laid in parallel. K 3 is the correction coefficient under different soil thermal resistance coefficients, I 0 is the rated current carrying capacity A of the cable under standard laying conditions.

6. The key parameter calculation method of the intelligent highway through DC power supply system according to claim 5 is characterized in that: The cross-section of the conductor that runs through the power supply line is selected according to the short-circuit thermal stability. The formula used is as follows: , where S min The minimum cross-sectional area of ​​the conductor that meets the short-circuit thermal stability requirement. Q t is the thermal effect of short-circuit current; C is the thermal stability coefficient of the conductor, I k is the maximum initial value of the three-phase symmetrical short-circuit current at the short-circuit point, t k is the short circuit duration, which is the protection action time t b Full disconnection time of circuit breaker t l sum.

7. The key parameter calculation method of the intelligent highway through-going DC power supply system according to claim 5 is characterized in that: The cross-section of the conductor that runs through the power supply line is selected according to the voltage drop within the allowable range. The formula used is as follows: , where ∆ u% is the percentage of line voltage loss, ∆ up% is the percentage of voltage loss per 1kW•km of three-phase line, P i is the active load (kW); l i is the line length.

8. The key parameter calculation method of the intelligent highway through-going DC power supply system according to claim 1 is characterized in that: The cross-section of the conductor that runs through the power supply line is selected according to economic conditions. The formula used is as follows: , where Sec is the optimal economic cross-section, j is the economic current density of the conductor; Ijs is the maximum load calculation current.

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