District-level direct-current street lamp system

Abstract

The invention relates to the technical field of alternating-current and direct-current hybrid power distribution networks, in particular to a district-level direct-current street lamp system. The system comprises a power grid, a filter, a bidirectional converter, a super capacitor array, a DC bus, a DC street lamp unit and a control module, the DC street lamp unit comprises an energy storage module, a photovoltaic module, a street lamp module and a charging pile module, the output end of the power grid is connected with the filter through a total grid-connected circuit breaker, and the high-voltage side of the bidirectional converter is connected with the filter. The low-voltage side of the bidirectional converter is connected with the direct-current bus through the super capacitor array; the control module is used for judging a current first working mode of the district-level direct-current street lamp system according to a collected voltage signal of a power grid, a state signal of a power switch tube of the bidirectional converter, a voltage signal of the direct-current bus and a state feedback signal of the total grid-connected circuit breaker; and the control module controls the main grid-connected circuit breaker to be switched off, and the voltage of the direct-current bus is provided by the energy storage module.

Description

Technical Field

[0001] The present invention relates to the technical field of AC / DC hybrid distribution network, and in particular to a district-level DC street lamp system. Background Art

[0002] Smart street lights are a new type of urban infrastructure. As the most natural IoT platform for smart cities, they can realize the "street light +" model with information technology as the guide. However, the DC street light system in related technologies cannot achieve off-grid operation.

[0003] Therefore, there is an urgent need to provide a district-level DC street lamp system to solve the above technical problems. Summary of the invention

[0004] The embodiment of the present invention provides a district-level DC street lamp system that can achieve off-grid operation.

[0005] An embodiment of the present invention provides a district-level DC street lamp system, including a power grid, a filter, a bidirectional converter, a supercapacitor array, a DC bus, a DC street lamp unit and a control module, wherein the DC street lamp unit includes an energy storage module, a photovoltaic module, a street lamp module and a charging pile module, wherein:

[0006] The output end of the power grid is connected to the filter through a main grid-connected circuit breaker, the high-voltage side of the bidirectional converter is connected to the filter, the filter is used to filter out harmonics in the three-phase alternating current, the low-voltage side of the bidirectional converter is connected to the DC bus through the supercapacitor array, the high-voltage sides of the energy storage module, the photovoltaic module, the street lamp module and the charging pile module are connected in parallel with each other through the DC bus, the control module is electrically connected to the power grid, the bidirectional converter, the DC bus, the DC street lamp unit and the main grid-connected circuit breaker respectively, the control module is used to determine the current first working mode of the substation-level DC street lamp system according to the collected voltage signal of the power grid, the power switch tube state signal of the bidirectional converter, the voltage signal of the DC bus and the state feedback signal of the main grid-connected circuit breaker, the first working mode includes a grid-connected mode and an off-grid mode;

[0007] When it is determined that the current first working mode of the district-level DC street lamp system is the off-grid mode, the control module controls the main grid-connected circuit breaker to be disconnected, and the voltage of the DC bus is provided by the energy storage module.

[0008] According to the substation-level DC street light system provided by an embodiment of the present invention, the DC street light unit includes an energy storage module, a photovoltaic module, a street light module and a charging pile module. The control module is used to determine the current first operating mode of the substation-level DC street light system based on the collected voltage signal of the power grid, the power switch tube status signal of the bidirectional converter, the voltage signal of the DC bus and the status feedback signal of the main grid-connected circuit breaker. When it is determined that the current first operating mode of the substation-level DC street light system is the off-grid mode, the control module controls the main grid-connected circuit breaker to disconnect and makes the voltage of the DC bus provided by the energy storage module, so that off-grid operation can be achieved. BRIEF DESCRIPTION OF THE DRAWINGS

[0009] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings required for use in the embodiments or the description of the prior art will be briefly introduced below. Obviously, the drawings described below are some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying creative work.

[0010] Figure 1 It is a circuit diagram of a district-level DC street lamp system provided by an embodiment of the present invention.

[0011] Reference numerals:

[0012] 1-power grid; 2-filter; 3-bidirectional converter; 4-supercapacitor array; 5-DC bus. DETAILED DESCRIPTION

[0013] In order to make the purpose, technical solutions and advantages of the embodiments of the present invention clearer, the technical solutions in the embodiments of the present invention will be clearly and completely described below in conjunction with the drawings in the embodiments of the present invention. Obviously, the described embodiments are part of the embodiments of the present invention, rather than all the embodiments. Based on the embodiments in the present invention, all other embodiments obtained by ordinary technicians in this field without making creative work are within the scope of protection of the present invention.

[0014] like Figure 1 As shown, an embodiment of the present invention provides a district-level DC street lamp system, which includes a power grid 1, a filter 2, a bidirectional converter 3, a supercapacitor array 4, a DC bus 5, a DC street lamp unit (not shown in the figure) and a control module (not shown in the figure), wherein the DC street lamp unit includes an energy storage module, a photovoltaic module, a street lamp module and a charging pile module, wherein:

[0015] The output end of the power grid 1 is connected to the filter 2 through the main grid-connected circuit breaker 6, the high-voltage side of the bidirectional converter 3 is connected to the filter 2, the filter 2 is used to filter out harmonics in the three-phase alternating current, the low-voltage side of the bidirectional converter 3 is connected to the DC bus 5 through the supercapacitor array 4, the high-voltage sides of the energy storage module, the photovoltaic module, the street light module and the charging pile module are connected in parallel through the DC bus 5, the control module is electrically connected to the power grid 1, the bidirectional converter 3, the DC bus 5, the DC street light unit and the main grid-connected circuit breaker 6 respectively, and the control module is used to determine the current first working mode of the district-level DC street light system according to the collected voltage signal of the power grid 1, the power switch tube state signal of the bidirectional converter 3, the voltage signal of the DC bus 5 and the state feedback signal of the main grid-connected circuit breaker 6, and the first working mode includes a grid-connected mode and an off-grid mode;

[0016] When it is determined that the current first working mode of the district-level DC street lamp system is the off-grid mode, the control module controls the main grid-connected circuit breaker 6 to be disconnected, and the voltage of the DC bus 5 is provided by the energy storage module.

[0017] In this embodiment, the DC street light unit includes an energy storage module, a photovoltaic module, a street light module and a charging pile module. The control module is used to determine the current first operating mode of the substation-level DC street light system based on the collected voltage signal of the power grid 1, the power switch tube status signal of the bidirectional converter 3, the voltage signal of the DC bus 5 and the status feedback signal of the main grid-connected circuit breaker 6. When it is determined that the current first operating mode of the substation-level DC street light system is the off-grid mode, the control module controls the main grid-connected circuit breaker 6 to disconnect, and makes the voltage of the DC bus 5 provided by the energy storage module, so that off-grid operation can be achieved.

[0018] It should be noted that the district-level DC street lamp system provided by the embodiment of the present invention can be flexibly connected to various modes such as photovoltaics, electric vehicle charging, and energy storage, and actively respond to load changes caused by carrying multiple devices. It is becoming a development trend in smart city construction, mainly reflected in energy efficiency improvement, new energy coupling, and intelligent management and control. The scale and urban coverage of DC-powered street lamps will maintain rapid growth in the future.

[0019] The development of electric vehicles is severely restricted by the construction of infrastructure. The application of low-voltage DC power supply technology to the transformation of municipal street lamps and the construction of DC charging piles for electric vehicles will be conducive to promoting the popularization of electric vehicles, widely absorbing new energy power generation such as photovoltaics, and ultimately achieving higher levels of energy conservation and emission reduction and the formation of urban smart charging networks.

[0020] In one embodiment of the present invention, the energy storage module includes an energy storage converter, an energy storage battery group and an energy storage grid-connected circuit breaker, the photovoltaic module includes a photovoltaic converter, a photovoltaic battery group and a photovoltaic grid-connected circuit breaker, the street light module includes a street light converter, a street light and a street light grid-connected circuit breaker, and the charging pile module includes a charging pile converter, a charging pile and a charging pile grid-connected circuit breaker;

[0021] The low voltage side of the energy storage inverter is connected to the input end of the energy storage battery pack through the energy storage grid-connected circuit breaker, the low voltage side of the photovoltaic inverter is connected to the input end of the photovoltaic battery pack through the photovoltaic grid-connected circuit breaker, the low voltage side of the street lamp inverter is connected to the input end of the street lamp through the street lamp grid-connected circuit breaker, and the low voltage side of the charging pile inverter is connected to the input end of the charging pile through the charging pile grid-connected circuit breaker;

[0022] When it is determined that the current working mode of the district-level DC street lamp system is the off-grid mode, the voltage of the DC bus 5 is provided by the energy storage battery pack.

[0023] In this embodiment, each module is provided with a grid-connected circuit breaker, so that the on and off of different modules can be controlled according to different modes in the subsequent process, thereby realizing effective regulation of the DC street lamp.

[0024] In one embodiment of the present invention, a number of power switching tubes (such as IGBTs) are provided in the bidirectional converter 3, the energy storage converter, the photovoltaic converter, the street light converter and the charging pile converter, and the power switching tubes are used to adjust the input power and output power of each module.

[0025] In one embodiment of the present invention, the filter 2 includes three filter reactors (i.e., L21, L22, and L23), three filter capacitors (i.e., C1, C2, and C3) and three grid-connected reactors (i.e., L11, L12, and L13). The three filter reactors are respectively connected in series with the three-phase AC output terminals of the bidirectional converter 3, one end of the three filter capacitors is connected to form a common end, and the other ends are respectively connected to the three filter reactors, and the three grid-connected reactors are respectively connected in series with the three filter reactors and then connected to the main grid-connected circuit breaker 6.

[0026] In one embodiment of the present invention, when the voltage signal of the power grid 1, the power switch tube status signal of the bidirectional converter 3, the voltage signal of the DC bus 5 and the status feedback signal of the main grid-connected circuit breaker 6 are all normal, the substation-level DC street lamp system is in grid-connected mode, otherwise it is in off-grid mode.

[0027] In one embodiment of the present invention, the control module is also used to determine the current second operating mode of the substation-level DC street lamp system based on the collected voltage signal of the DC bus 5, the status feedback signal of the energy storage grid-connected circuit breaker, the power switch tube status signal of the energy storage inverter, the status feedback signal of the photovoltaic grid-connected circuit breaker, the power switch tube status signal of the photovoltaic inverter, the status feedback signal of the street lamp grid-connected circuit breaker, the power switch tube status signal of the street lamp inverter, the status feedback signal of the charging pile grid-connected circuit breaker and the power switch tube status signal of the charging pile inverter. The second operating mode includes a normal mode and a fault mode.

[0028] In this embodiment, the district-level DC street lamp system not only has a first working mode, but also has a second working mode, which can enrich the working scenarios of the district-level DC street lamp system, thereby achieving richer and more targeted regulation.

[0029] In one embodiment of the present invention, when the voltage signal of the DC bus 5, the status feedback signal of the energy storage grid-connected circuit breaker, the power switch tube status signal of the energy storage inverter, the status feedback signal of the photovoltaic grid-connected circuit breaker, the power switch tube status signal of the photovoltaic inverter, the status feedback signal of the street light grid-connected circuit breaker, the power switch tube status signal of the street light inverter, the status feedback signal of the charging pile grid-connected circuit breaker and the power switch tube status signal of the charging pile inverter are all normal, the substation-level DC street light system is in normal mode, otherwise it is in fault mode.

[0030] In one embodiment of the present invention, when the district-level DC street lamp system is in the grid-connected mode and the normal mode, the control module controls the bidirectional converter 3, the energy storage converter, the photovoltaic converter, the street lamp converter and the charging pile converter to be in full operation;

[0031] When the DC street lamp system at the substation level is in the grid-connected mode and the fault mode, the control module controls the faulty converter and circuit breaker to be turned off;

[0032] When the district-level DC street lamp system is in the off-grid mode, if the control module detects that the power grid 1 has returned to normal, it controls the district-level DC street lamp system to be in the on-grid mode again.

[0033] In one embodiment of the present invention, when the district-level DC street lamp system is in the grid-connected mode and the normal mode, the control module specifically performs the following operations:

[0034] The photovoltaic inverter is controlled to receive and amplify the output electric energy of the photovoltaic battery group, and the amplified maximum power electric energy is input in sequence according to the order of street light inverter for street light, charging pile inverter for charging pile, energy storage inverter for energy storage battery group, and bidirectional inverter 3 module for power grid 1.

[0035] In one embodiment of the present invention, the energy storage battery pack adopts the form of hybrid energy storage of supercapacitors and batteries;

[0036] If the maximum power electric energy obtained by amplification satisfies the street lamp inverter for the street lamp and the charging pile inverter for the charging pile, and there is still remaining output electric energy, the energy storage inverter is controlled to charge the energy storage battery pack, and at this time, the supercapacitor is charged first, and then the battery is charged;

[0037] If the maximum power electricity obtained by amplification cannot meet the needs of the street light inverter and the charging pile inverter, the energy storage inverter is controlled to discharge the energy storage battery group. At this time, the supercapacitor supplies power first. When the power of the supercapacitor is insufficient, the battery supplies power to the supercapacitor, the street light and the charging pile in turn; if the energy storage battery group still cannot meet the needs of the street light inverter and the charging pile inverter after discharge, the bidirectional inverter 3 module is controlled to obtain power from the power grid 1.

[0038] In this embodiment, the supercapacitor and the battery can be connected in parallel through Buck-Boost DC / DC bidirectional power conversion. When the power generation of the photovoltaic battery group is very large, the supercapacitor stores most of the electric energy and releases the electric energy when the system output power is low; when the load power pulsates, the supercapacitor outputs current in time so that the charging process of the battery is not affected. In this way, the battery can always be in an optimized charging and discharging working state, and is less affected by external factors, thereby improving the working environment of the battery, reducing the number of battery charging and discharging times, and extending the battery life.

[0039] It should be noted that, in this article, relational terms such as first and second are only used to distinguish one entity or operation from another entity or operation, and do not necessarily require or imply any such actual relationship or order between these entities or operations. Moreover, the terms "include", "comprise" or any other variants thereof are intended to cover non-exclusive inclusion, so that the process, method, article or equipment including a series of elements includes not only those elements, but also includes other elements not explicitly listed, or also includes elements inherent to such process, method, article or equipment. In the absence of more restrictions, the elements defined by the statement "comprise one..." do not exclude the existence of other identical factors in the process, method, article or equipment including the elements.

[0040] Finally, it should be noted that the above is only a preferred embodiment of the present invention, which is only used to illustrate the technical solution of the present invention, and is not used to limit the protection scope of the present invention. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present invention are included in the protection scope of the present invention.

Claims

1. A district-level DC streetlight system, characterized in that: It includes a power grid, a filter, a bidirectional converter, a supercapacitor array, a DC bus, a DC street light unit and a control module. The DC street light unit includes an energy storage module, a photovoltaic module, a street light module and a charging pile module, wherein: The output end of the power grid is connected to the filter through a main grid-connected circuit breaker, the high-voltage side of the bidirectional converter is connected to the filter, the filter is used to filter out harmonics in the three-phase alternating current, the low-voltage side of the bidirectional converter is connected to the DC bus through the supercapacitor array, the high-voltage sides of the energy storage module, the photovoltaic module, the street lamp module and the charging pile module are connected in parallel with each other through the DC bus, the control module is electrically connected to the power grid, the bidirectional converter, the DC bus, the DC street lamp unit and the main grid-connected circuit breaker respectively, the control module is used to determine the current first working mode of the substation-level DC street lamp system according to the collected voltage signal of the power grid, the power switch tube state signal of the bidirectional converter, the voltage signal of the DC bus and the state feedback signal of the main grid-connected circuit breaker, the first working mode includes a grid-connected mode and an off-grid mode; When it is determined that the current first working mode of the district-level DC street lamp system is the off-grid mode, the control module controls the main grid-connected circuit breaker to be disconnected, and the voltage of the DC bus is provided by the energy storage module.

2. The district-level DC streetlight system according to claim 1, characterized in that: The energy storage module includes an energy storage converter, an energy storage battery pack and an energy storage grid-connected circuit breaker, the photovoltaic module includes a photovoltaic converter, a photovoltaic battery pack and a photovoltaic grid-connected circuit breaker, the street light module includes a street light converter, a street light and a street light grid-connected circuit breaker, and the charging pile module includes a charging pile converter, a charging pile and a charging pile grid-connected circuit breaker; The low voltage side of the energy storage inverter is connected to the input end of the energy storage battery group through the energy storage grid-connected circuit breaker, the low voltage side of the photovoltaic inverter is connected to the input end of the photovoltaic battery group through the photovoltaic grid-connected circuit breaker, the low voltage side of the street lamp inverter is connected to the input end of the street lamp through the street lamp grid-connected circuit breaker, and the low voltage side of the charging pile inverter is connected to the input end of the charging pile through the charging pile grid-connected circuit breaker; When it is determined that the current working mode of the district-level DC street lamp system is the off-grid mode, the voltage of the DC bus is provided by the energy storage battery pack.

3. The district-level DC streetlight system according to claim 2, characterized in that: The bidirectional converter, the energy storage converter, the photovoltaic converter, the street light converter and the charging pile converter are all provided with a plurality of power switch tubes, and the power switch tubes are used to adjust the input electric energy power and the output electric energy power of each module.

4. The district-level DC streetlight system according to claim 2, characterized in that: The filter includes three filter reactors, three filter capacitors and three grid-connected reactors. The three filter reactors are respectively connected in series with the three-phase AC output ends of the bidirectional converter. One ends of the three filter capacitors are connected to form a common end, and the other ends are respectively connected to the three filter reactors. The three grid-connected reactors are respectively connected in series with the three filter reactors and then connected to the main grid-connected circuit breaker.

5. The district-level DC streetlight system according to claim 2, characterized in that: When the voltage signal of the power grid, the power switch status signal of the bidirectional converter, the voltage signal of the DC bus and the status feedback signal of the main grid-connected circuit breaker are all normal, the substation-level DC street lamp system is in grid-connected mode, otherwise it is in off-grid mode.

6. The district-level DC streetlight system according to any one of claims 2-5, characterized in that: The control module is also used to determine the current second operating mode of the substation-level DC street lamp system based on the collected voltage signal of the DC bus, the status feedback signal of the energy storage grid-connected circuit breaker, the power switch tube status signal of the energy storage inverter, the status feedback signal of the photovoltaic grid-connected circuit breaker, the power switch tube status signal of the photovoltaic inverter, the status feedback signal of the street light grid-connected circuit breaker, the power switch tube status signal of the street light inverter, the status feedback signal of the charging pile grid-connected circuit breaker and the power switch tube status signal of the charging pile inverter. The second operating mode includes a normal mode and a fault mode.

7. The district-level DC streetlight system according to claim 6, characterized in that: When the voltage signal of the DC bus, the status feedback signal of the energy storage grid-connected circuit breaker, the power switch tube status signal of the energy storage inverter, the status feedback signal of the photovoltaic grid-connected circuit breaker, the power switch tube status signal of the photovoltaic inverter, the status feedback signal of the street light grid-connected circuit breaker, the power switch tube status signal of the street light inverter, the status feedback signal of the charging pile grid-connected circuit breaker and the power switch tube status signal of the charging pile inverter are all normal, the substation-level DC street light system is in normal mode, otherwise it is in fault mode.

8. The district-level DC streetlight system according to claim 7, characterized in that: When the district-level DC street lamp system is in the grid-connected mode and the normal mode, the control module controls the bidirectional converter, the energy storage converter, the photovoltaic converter, the street lamp converter and the charging pile converter to be in full operation state; When the substation-level DC street lamp system is in a grid-connected mode and a fault mode, the control module controls the faulty converter and circuit breaker to be turned off; When the district-level DC street lamp system is in the off-grid mode, if the control module detects that the power grid returns to normal, it controls the district-level DC street lamp system to be in the on-grid mode again.

9. The district-level DC streetlight system according to claim 8, characterized in that: When the district-level DC street lamp system is in the grid-connected mode and the normal mode, the control module specifically performs the following operations: Control the photovoltaic inverter to receive and amplify the output electric energy of the photovoltaic battery group, and input the amplified maximum power electric energy in the order of the street light inverter for the street light, the charging pile inverter for the charging pile, the energy storage inverter for the energy storage battery group, and the bidirectional inverter module for the power grid.

10. The district-level DC streetlight system according to claim 9, characterized in that: The energy storage battery pack adopts the form of hybrid energy storage of super capacitor and battery; If the maximum power electric energy obtained by amplification satisfies the remaining output electric energy after the street lamp converter inputs electric energy to the street lamp and the charging pile converter inputs electric energy to the charging pile, the energy storage converter is controlled to charge the energy storage battery pack, and the supercapacitor is charged first, and then the storage battery is charged; If the amplified maximum power electric energy cannot meet the needs of the street light inverter and the charging pile inverter, the energy storage inverter is controlled to discharge the energy storage battery group. At this time, the supercapacitor supplies power first. When the power of the supercapacitor is insufficient, the battery supplies power to the supercapacitor, the street light and the charging pile in turn; if the energy storage battery group still cannot meet the needs of the street light inverter and the charging pile inverter after discharge, the bidirectional inverter module is controlled to obtain power from the power grid.

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