A district-level DC street lamp system

Abstract

The present invention relates to the technical field of AC-DC hybrid distribution networks, and particularly to a substation-level DC street lamp system. The system includes a power grid, a filter, a bidirectional converter, a supercapacitor array, a DC bus, a DC street lamp unit, and a control module. The DC street lamp unit includes 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 to the filter through a main grid connection breaker. The high-voltage side of the bidirectional converter is connected to the filter, and the low-voltage side of the bidirectional converter is connected to the DC bus through the supercapacitor array. 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 state signal of the power switching tube of the bidirectional converter, the voltage signal of the DC bus, and the state feedback signal of the main grid connection breaker. When it is determined that the current first working mode is the off-grid mode, the control module controls the main grid connection breaker to disconnect, and the voltage of the DC 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 networks, and particularly to a substation-level DC street lamp system. Background Art

[0002] Smart street lamps are a new type of urban infrastructure. As the most natural Internet of Things platform in a smart city, guided by information technology, they can achieve the "street lamp +" mode. However, the DC street lamp systems in related technologies cannot operate off-grid.

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

[0004] An embodiment of the present invention provides a substation-level DC street lamp system that can operate off-grid.

[0005] An embodiment of the present invention provides a substation-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. 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 connection breaker. The high-voltage side of the bidirectional converter is connected to the filter. The filter is used to filter out harmonics in 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 mutually connected in parallel 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 connection 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 state signal of the power switch tube of the bidirectional converter, the voltage signal of the DC bus, and the state feedback signal of the main grid connection 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 substation-level DC street lamp system is the off-grid mode, the control module controls the main grid connection breaker to disconnect and makes the voltage of the DC bus provided by the energy storage module.

[0008] According to the district-level DC street lamp system provided by the embodiments of the present invention, the DC street lamp unit includes an energy storage module, a photovoltaic module, a street lamp module, and a charging pile module. The control module is used to determine the current first working mode of the district-level DC street lamp system according to the collected voltage signal of the power grid, the state signal of the power switching tube 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 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 disconnect, and makes the voltage of the DC bus provided by the energy storage module, so that off-grid operation can be realized. BRIEF DESCRIPTION OF THE DRAWINGS

[0009] In order to more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the following will briefly introduce the drawings required for use in the description of the embodiments or the prior art. Obviously, the drawings in the following description are some embodiments of the present invention. For those of ordinary skill in the art, without creative efforts, other drawings can also be obtained based on these drawings.

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

[0011] Reference Numerals:

[0012] 1 - Power grid; 2 - Filter; 3 - Bidirectional converter; 4 - Supercapacitor array; 5 - DC bus. DETAILED DESCRIPTION OF THE EMBODIMENTS

[0013] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the following will clearly and completely describe the technical solutions in the embodiments of the present invention with reference to the drawings in the embodiments of the present invention. Obviously, the described embodiments are some, but not all, of the embodiments of the present invention. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative efforts fall within the scope of protection of the present invention.

[0014] As Figure 1 shown, the embodiments of the present invention provide 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). The DC street lamp unit includes an energy storage module, a photovoltaic module, a street lamp module, and a charging pile module, where:

[0015] The output terminal of the power grid 1 is connected to the filter 2 through the main grid connection 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 lamp module, and the charging pile module are connected in parallel with each other 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 lamp unit, and the main grid connection breaker 6 respectively. The control module is used to determine the current first working mode of the district-level DC street lamp system according to the collected voltage signal of the power grid 1, the state signal of the power switch tubes of the bidirectional converter 3, the voltage signal of the DC bus 5, and the status feedback signal of the main grid connection breaker 6. The first working mode includes the grid-connected mode and the 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 connection breaker 6 to disconnect, and makes the voltage of the DC bus 5 provided by the energy storage module.

[0017] In this embodiment, the DC street lamp unit includes an energy storage module, a photovoltaic module, a street lamp module, and a charging pile module. The control module is used to determine the current first working mode of the district-level DC street lamp system according to the collected voltage signal of the power grid 1, the state signal of the power switch tubes of the bidirectional converter 3, the voltage signal of the DC bus 5, and the status feedback signal of the main grid connection breaker 6. 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 connection 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 realized.

[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 methods such as photovoltaic, electric vehicle charging, and energy storage, and actively responds to the load changes brought about by carrying multiple devices. It is becoming a development trend of smart city construction, mainly reflected in energy efficiency improvement, new energy coupling, and intelligent management and control. The scale and urban coverage rate 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. Applying low-voltage DC power supply technology to transform municipal street lamps and build DC charging piles for electric vehicles will be conducive to promoting the popularization of electric vehicles, widely absorbing new energy power generation such as photovoltaic, and finally realizing energy conservation and emission reduction at a higher level and the formation of an urban intelligent charging network.

[0020] In an embodiment of the present invention, the energy storage module includes an energy storage inverter, an energy storage battery pack, and an energy storage grid-connected breaker; the photovoltaic module includes a photovoltaic inverter, a photovoltaic battery pack, and a photovoltaic grid-connected breaker; the street lamp module includes a street lamp inverter, a street lamp, and a street lamp grid-connected breaker; the charging pile module includes a charging pile inverter, a charging pile, and a charging pile grid-connected 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 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 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 breaker; 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 breaker.

[0022] When it is determined that the current working mode of the substation-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 breaker, which is beneficial for subsequent control of the on / off of different modules according to different modes, so as to realize the effective regulation of the DC street lamp.

[0024] In an embodiment of the present invention, several power switch tubes (such as IGBTs) are provided in the bidirectional inverter 3, the energy storage inverter, the photovoltaic inverter, the street lamp inverter, and the charging pile inverter, and the power switch tubes are used to adjust the input power and output power of each module.

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

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

[0027] In an embodiment of the present invention, the control module is further configured to determine the current second operating mode of the substation-level DC street lamp system according to the voltage signal of the DC bus 5, the status feedback signal of the energy storage grid-connected circuit breaker, the status signal of the power switching tubes of the energy storage converter, the status feedback signal of the photovoltaic grid-connected circuit breaker, the status signal of the power switching tubes of the photovoltaic converter, the status feedback signal of the street lamp grid-connected circuit breaker, the status signal of the power switching tubes of the street lamp converter, the status feedback signal of the charging pile grid-connected circuit breaker, and the status signal of the power switching tubes of the charging pile converter. The second operating mode includes a normal mode and a fault mode.

[0028] In this embodiment, the substation-level DC street lamp system not only has a first operating mode but also has a second operating mode. In this way, the operating scenarios of the substation-level DC street lamp system can be made more diverse, thereby enabling more diverse and targeted control.

[0029] In an 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 status signal of the power switching tubes of the energy storage converter, the status feedback signal of the photovoltaic grid-connected circuit breaker, the status signal of the power switching tubes of the photovoltaic converter, the status feedback signal of the street lamp grid-connected circuit breaker, the status signal of the power switching tubes of the street lamp converter, the status feedback signal of the charging pile grid-connected circuit breaker, and the status signal of the power switching tubes of the charging pile converter are all normal, the substation-level DC street lamp system is in the normal mode; otherwise, it is in the fault mode.

[0030] In an embodiment of the present invention, when the substation-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 the full operating state;

[0031] When the substation-level DC street lamp system 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 substation-level DC street lamp system is in the off-grid mode, if the control module detects that the power grid 1 returns to normal, it controls the substation-level DC street lamp system to return to the grid-connected mode.

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

[0034] Control the photovoltaic converter to receive and amplify the output electric energy of the photovoltaic battery pack, and input the amplified maximum power electric energy in sequence according to the order that the street lamp converter is for street lamps, the charging pile converter is for charging piles, the energy storage converter is for the energy storage battery pack, and the bidirectional converter 3 module is for the power grid 1.

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

[0036] If the maximum power electric energy obtained by amplification can successively satisfy the electric energy input to the street lamp by the street lamp inverter and the electric energy input to the charging pile by the charging pile inverter and there is still remaining output electric energy, then control the energy storage inverter to charge the energy storage battery pack. At this time, first charge the supercapacitor and then charge the storage battery;

[0037] If the maximum power electric energy obtained by amplification cannot meet the requirements of the street lamp inverter and the charging pile inverter, then control the energy storage inverter to discharge the energy storage battery pack. At this time, the supercapacitor supplies power first. When the electric energy of the supercapacitor is insufficient, the storage battery supplies power to the supercapacitor, the street lamp and the charging pile in sequence; if the energy storage battery pack still cannot meet the requirements of the street lamp inverter and the charging pile inverter after discharging, then control the bidirectional converter module 3 to obtain electric energy from the power grid 1.

[0038] In this embodiment, the supercapacitor and the storage battery can be connected in parallel through a Buck - Boost type DC / DC bidirectional power conversion. When the power generation power of the photovoltaic battery pack 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 storage battery is not affected. In this way, the storage battery can always be in an optimized charge - discharge working state, is little affected by external factors, thereby improving the working environment of the storage battery, reducing the charge - discharge times of the storage battery, and prolonging the service life of the storage battery.

[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 actual relationship or order between these entities or operations. Moreover, the terms "include", "comprise" or any other variant thereof are intended to cover non - exclusive inclusion, so that a process, method, article or device including a series of elements not only includes those elements, but also includes other elements not expressly listed, or also includes elements inherent to such process, method, article or device. Without further limitation, an element defined by the statement "including a..." does not exclude the existence of additional identical elements in the process, method, article or device including the said element.

[0040] Finally, it should be noted that: the above - mentioned are only the preferred embodiments of the present invention, which are only used to illustrate the technical solutions of the present invention and are not used to limit the protection scope of the present invention. Any modifications, equivalent replacements, improvements, etc. made within the spirit and principle of the present invention are all included within 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; 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 an off-grid mode, the voltage of the DC bus is provided by the energy storage battery pack; The control module is also used to determine the current second working mode of the district-level DC street lamp system according to the collected voltage signal of the DC bus, the state feedback signal of the energy storage grid-connected circuit breaker, the power switch tube state signal of the energy storage converter, the state feedback signal of the photovoltaic grid-connected circuit breaker, the power switch tube state signal of the photovoltaic converter, the state feedback signal of the street lamp grid-connected circuit breaker, the power switch tube state signal of the street lamp converter, the state feedback signal of the charging pile grid-connected circuit breaker and the power switch tube state signal of the charging pile converter, wherein the second working mode includes a normal mode and a fault mode; When the voltage signal of the DC bus, the state feedback signal of the energy storage grid-connected circuit breaker, the power switch tube state signal of the energy storage converter, the state feedback signal of the photovoltaic grid-connected circuit breaker, the power switch tube state signal of the photovoltaic converter, the state feedback signal of the street light grid-connected circuit breaker, the power switch tube state signal of the street light converter, the state feedback signal of the charging pile grid-connected circuit breaker and the power switch tube state signal of the charging pile converter are all normal, the substation-level DC street light system is in normal mode, otherwise it is in fault mode; 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 has returned to normal, the control module controls the district-level DC street lamp system to be in the on-grid mode again; 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 lamp inverter for the street lamp, 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; 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.

2. The district-level DC streetlight system according to claim 1, 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.

3. The district-level DC streetlight system according to claim 1, 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.

4. The district-level DC streetlight system according to claim 1, 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.

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