Medium-pressure optical storage, charging and discharging station

Abstract

The invention discloses a medium-voltage optical storage charging and discharging station, and relates to the field of charging stations for electric automobiles, and in the charging and discharging station, a medium-voltage transformer substation is arranged in a charging pile end to form a power transformation and charging integrated structure; the medium-voltage switch control protection cabinet is connected with a network side power supply through a medium-voltage cable; the medium-voltage switch control protection cabinet is connected with the converter transformer; the converter transformer is connected with the high-efficiency bidirectional converter through the low-voltage switch control protection cabinet; and the control system is respectively connected with the converter transformer, the low-voltage switch control protection cabinet and the efficient bidirectional converter. According to the invention, the line loss can be effectively reduced, and the safety and the conversion efficiency are improved.

Description

Technical Field

[0001] The present invention relates to the field of charging stations for electric vehicles, and in particular to a medium-voltage photovoltaic storage charging and discharging station. Background Art

[0002] Existing electric vehicle charging stations all consist of two parts: an independently installed medium-voltage substation and an independently installed charging pile. The existing solutions have the following problems:

[0003] First, the low-voltage line loss is large. In most scenarios, the actual distance between the medium-voltage substation and the charging pile is about tens of meters to hundreds of meters. The line loss of the low-voltage cable L connecting the medium-voltage substation and the charging pile is ΔP = I2*R, where R is the body resistance of the low-voltage cable, and I is the power supply current flowing through the low-voltage cable L.

[0004] If the charging power is 1000kW charging station, take the distance between its 10kV substation and the 380V charging pile as 50 meters, the phase current of its low-voltage cable is about 1500A. The low-voltage cable is selected according to the regulations, and the loss of the three cables is calculated to be ΔP=3*(IL)2*RL=3*(1500)2*RL=11kW. The square term of current affects the loss.

[0005] Therefore, reducing the phase current of the cable makes a significant contribution to reducing the line consumption of the charging station.

[0006] Second, the module efficiency is low. The existing rectifier modules are converted from traditional rectifier modules in communication systems. This type of module focuses on power quality, and its overall conversion efficiency is not very high. The efficiency of a single module at rated load is 91%-95%, and the actual efficiency of multiple modules in parallel output will be reduced.

[0007] Therefore, changing the circuit topology of the rectifier module and improving the efficiency of the rectifier module is also an effective way to improve the efficiency of the charging station.

[0008] Third, the system has poor safety. The existing three-phase power supply circuit is a Y-type three-phase power supply circuit with center point grounding. Due to the center point grounding, there is a high safety risk of touching the phase line; the rectifier module of the existing charging pile has input rectification, DC / DC and three working units. The circuit is not isolated from the power grid, and only relies on the high-frequency output transformer of the DC / DC to achieve electrical isolation and insulation between the DC output OUT and the power grid. The primary insulation spacing of the high-frequency output transformer is small, and its withstand voltage insulation level is only 3000V-5000V, which poses a certain safety risk. This insulation measure at the output terminal is called back-end insulation. The existing Y-type three-phase power supply circuit with center point grounding is used in the existing module solution with back-end insulation measures, which poses a certain safety risk.

[0009] Based on the problems of the prior art, a new electric vehicle charging station is provided. Summary of the invention

[0010] The purpose of the present invention is to provide a medium-voltage photovoltaic storage charging and discharging station, which can effectively reduce line losses and improve safety and conversion efficiency.

[0011] To achieve the above object, the present invention provides the following solutions:

[0012] A medium-voltage photovoltaic storage charging and discharging station, characterized in that the medium-voltage photovoltaic storage charging and discharging station places a medium-voltage substation inside a charging pile end to form an integrated structure of power transformation and charging; the medium-voltage photovoltaic storage charging and discharging station comprises: a medium-voltage switch control and protection cabinet, a converter transformer, a low-voltage switch control and protection cabinet, a high-efficiency bidirectional converter and a control system;

[0013] The medium-voltage switch control protection cabinet is connected to the grid-side power supply through a medium-voltage cable; the medium-voltage switch control protection cabinet is connected to the converter transformer; the converter transformer is connected to the high-efficiency bidirectional converter through the low-voltage switch control protection cabinet; the control system is respectively connected to the converter transformer, the low-voltage switch control protection cabinet and the high-efficiency bidirectional converter; the current of the charging power flowing through the medium-voltage cable is reduced to I H =I L *(V L / V H ); where I L is the current of the low voltage cable, I H is the current of the medium voltage cable, V L is the voltage of the low voltage cable, V H is the voltage of the medium voltage cable;

[0014] The control system performs corresponding control according to the multi-channel sensor signals in each circuit of the medium voltage switch control protection cabinet, the converter transformer, the low voltage switch control protection cabinet and the high-efficiency bidirectional converter.

[0015] Optionally, the output circuit of the variable current power supply is a triangle or Y neutral point ungrounded system.

[0016] Optionally, an electromagnetic shielding layer is provided between the low voltage winding and the medium voltage winding of the converter transformer.

[0017] Optionally, the circuit TOP of the converter module adopts a single-stage bidirectional converter circuit.

[0018] Optionally, the single-stage bidirectional converter circuit is a two-level circuit or a three-level circuit structure.

[0019] Optionally, the medium-voltage photovoltaic storage charging and discharging station further includes: a photovoltaic access port and an energy storage access port; the photovoltaic access port and the energy storage access port are both connected to the converter transformer.

[0020] Optionally, the medium-voltage photovoltaic storage charging and discharging station further includes: a DC terminal of a bidirectional converter; the DC terminal of the bidirectional converter is correspondingly connected to the high-efficiency bidirectional converter.

[0021] According to the specific embodiments provided by the present invention, the present invention discloses the following technical effects:

[0022] A medium-voltage photovoltaic storage charging and discharging station provided by the present invention places a medium-voltage substation inside the charging pile end to form an integrated structure of substation and charging, thereby reducing the length of the low-voltage cable and effectively reducing line loss.

[0023] The present invention adopts a power supply method with a triangle or Y neutral point not grounded; an electromagnetic shielding layer is arranged between the low-voltage winding and the medium-voltage winding of the converter transformer to eliminate the floating potential of the low-voltage power supply circuit, enhance the withstand voltage insulation strength of the low-voltage winding relative to the medium-voltage winding, and effectively improve safety;

[0024] The present invention adopts a high-efficiency single-stage bidirectional conversion circuit, which can improve the conversion efficiency and realize the V2G function of charging and discharging of the charging pile. BRIEF DESCRIPTION OF THE DRAWINGS

[0025] 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 will be briefly introduced below. Obviously, the drawings described below are only 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.

[0026] Figure 1 A schematic diagram of the structure of a medium-voltage photovoltaic storage and charging / discharging station provided in Example 1 of the present invention;

[0027] Figure 2 It is a schematic diagram of a system principle block diagram of a charging station in the prior art;

[0028] Figure 3 It is a schematic diagram of the structure of a single-stage bidirectional converter circuit. DETAILED DESCRIPTION

[0029] The following will be combined with the drawings in the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0030] The purpose of the present invention is to provide a medium-voltage photovoltaic storage charging and discharging station, which can effectively reduce line losses and improve safety and conversion efficiency.

[0031] In order to make the above-mentioned objects, features and advantages of the present invention more obvious and easy to understand, the present invention is further described in detail below with reference to the accompanying drawings and specific embodiments.

[0032] like Figure 1 As shown, a medium-voltage photovoltaic storage charging and discharging station provided by the present invention places a medium-voltage substation inside the charging pile end to form an integrated structure of power transformation and charging; Figure 2 It is the existing technology. Figure 2 In the middle, G is the grid-side power supply point, H is the medium-voltage cable, L is the low-voltage cable, OUT is the charging pile output, 12 is the medium-voltage cabinet, 13 is the distribution transformer, 14 is the low-voltage cabinet, 16 is the substation, and 15 is the three-level sorting module, i.e. the charging pile.

[0033] The medium voltage photovoltaic storage charging and discharging station 20 includes: a medium voltage switch control protection cabinet 21, a converter transformer 24, a low voltage switch control protection cabinet 22, a high efficiency bidirectional converter 231 ... 23NS and a control system 25;

[0034] The medium-voltage switch control protection cabinet 21 is connected to the grid-side power supply through a medium-voltage cable; the medium-voltage switch control protection cabinet 21 is connected to the converter transformer 24; the converter transformer 24 is connected to the high-efficiency bidirectional converter 231 ... 23NS through the low-voltage switch control protection cabinet 22; the control system 25 is respectively connected to the converter transformer 24, the low-voltage switch control protection cabinet 22 and the high-efficiency bidirectional converter 231 ... 23NS; the current of the charging power flowing through the medium-voltage cable is reduced to I H =I L *(V L / V H ); where I L is the current of the low voltage cable, I H is the current of the medium voltage cable, V L is the voltage of the low voltage cable, V H is the voltage of the medium voltage cable.

[0035] Among them, the medium voltage switch control protection cabinet 21 and the converter transformer 24 constitute a converter power supply system; the low voltage switch control protection cabinet 22 and the high-efficiency bidirectional converter 231 ... 23NS constitute a converter system;

[0036] The control system realizes control of the current conversion power supply system and the current conversion system according to the signals of multiple multi-channel sensors respectively arranged in each circuit of the current conversion power supply system and the current conversion system;

[0037] During charging, the power transmission path is that the grid-side power G passes through the ring network metering cabinet 1 in turn to the power conversion power supply system and the power conversion system of the medium-voltage photovoltaic storage charging and discharging station 20, and then outputs the required multi-channel DC power OT1...OTN;

[0038] During discharge, the power transmission path is that the external on-board battery power is sent back to the converter system through OT1...OTN. The converter system converts the DC power into industrial frequency power, which is then stepped up by the converter transformer 24 and sent back to the grid.

[0039] The output circuit of the inverter power supply is a triangle or Y neutral point ungrounded system. An electromagnetic shielding layer M is set on the outside of the low-voltage winding of the converter transformer 24. The electromagnetic shielding layer M needs to be reliably grounded to eliminate the induced floating potential of the low-voltage circuit and enhance the dielectric strength of the low-voltage winding to the energy storage winding, the photovoltaic winding and the medium-voltage winding. The photovoltaic and energy storage are independent windings, respectively, and the outer layer of the electromagnetic shielding layer M is wound around the outer layer of the independent windings of the photovoltaic and energy storage. An electromagnetic shielding layer N is set, and the magnetic shielding layer N needs to be reliably grounded. The medium-voltage winding is placed on the outside of the magnetic shielding layer N. The low-voltage output and the photovoltaic, energy storage, and medium-voltage wire packages are all radially multi-cake-shaped or axially layered. The medium-voltage, photovoltaic, and energy storage are connected to the corresponding windings respectively.

[0040] The circuit TOP of the converter module adopts a single-stage bidirectional converter circuit. Figure 3 As shown, the power part TOP of the converter circuit is a two-level circuit or a three-level circuit structure.

[0041] The charging power of passenger cars ranges from 60-600kW, and that of commercial vehicles ranges from 240-3000kW. Energy conservation and consumption reduction of charging stations themselves are extremely important technical means to improve the efficiency of charging operations, and are also issues that urgently need to be addressed by the rapidly developing electric vehicle charging facilities. Taking a 1000kW substation as an example, if the substation is 50 meters away from a 380V charging pile, if the present invention is adopted, the low-voltage line loss can be reduced from 11kW to 0.2kW, and the amount of electricity saved nationwide can be equivalent to the power generation of dozens of power plants.

[0042] The medium-voltage photovoltaic storage charging and discharging station also includes: a photovoltaic access port F and an energy storage access port S; the photovoltaic access port F and the energy storage access port S are both connected to the converter transformer.

[0043] The medium-voltage photovoltaic storage charging and discharging station also includes: DC terminals OT1...OTN of the bidirectional converter; the DC terminals OT1...OTN of the bidirectional converter are correspondingly connected to the high-efficiency bidirectional converters 231...23NS.

[0044] The technical features of the above embodiments may be combined arbitrarily. To make the description concise, not all possible combinations of the technical features in the above embodiments are described. However, as long as there is no contradiction in the combination of these technical features, they should be considered to be within the scope of this specification.

[0045] The principles and implementation methods of the present invention are described in this article using specific examples. The description of the above embodiments is only used to help understand the method and core idea of ​​the present invention. At the same time, for those skilled in the art, according to the idea of ​​the present invention, there will be changes in the specific implementation methods and application scope. In summary, the content of this specification should not be understood as limiting the present invention.

Claims

1. A medium-voltage solar energy storage charging and discharging station, characterized in that: The medium-voltage photovoltaic storage charging and discharging station places the medium-voltage substation inside the charging pile end to form an integrated structure of power transformation and charging; the medium-voltage photovoltaic storage charging and discharging station includes: a medium-voltage switch control and protection cabinet, a converter transformer, a low-voltage switch control and protection cabinet, a high-efficiency bidirectional converter and a control system; The medium-voltage switch control protection cabinet is connected to the grid-side power supply through a medium-voltage cable; the medium-voltage switch control protection cabinet is connected to the converter transformer; the converter transformer is connected to the high-efficiency bidirectional converter through the low-voltage switch control protection cabinet; the control system is respectively connected to the converter transformer, the low-voltage switch control protection cabinet and the high-efficiency bidirectional converter; the current of the charging power flowing through the medium-voltage cable is reduced to I H =I L *(V L / V H );where I L is the current of the low voltage cable, I H is the current of the medium voltage cable, V L is the voltage of the low voltage cable, V H is the voltage of the medium voltage cable; The control system performs corresponding control according to the multi-channel sensor signals in each circuit of the medium voltage switch control protection cabinet, the converter transformer, the low voltage switch control protection cabinet and the high-efficiency bidirectional converter.

2. A medium-voltage solar energy storage charging and discharging station according to claim 1, characterized in that: The output circuit of the variable current power supply is a triangle or Y neutral point ungrounded system.

3. A medium-voltage photovoltaic charging and discharging station according to claim 1, characterized in that: An electromagnetic shielding layer is arranged between the low voltage winding and the medium voltage winding of the converter transformer.

4. A medium-voltage photovoltaic charging and discharging station according to claim 1, characterized in that: The circuit TOP of the converter module adopts a single-stage bidirectional converter circuit.

5. A medium-voltage solar energy storage charging and discharging station according to claim 4, characterized in that: The single-stage bidirectional converter circuit is a two-level circuit or a three-level circuit structure.

6. A medium-voltage photovoltaic charging and discharging station according to claim 1, characterized in that: The medium-voltage photovoltaic storage charging and discharging station also includes: a photovoltaic access port and an energy storage access port; the photovoltaic access port and the energy storage access port are both connected to the converter transformer.

7. A medium-voltage photovoltaic charging and discharging station according to claim 1, characterized in that: The medium-voltage photovoltaic storage charging and discharging station also includes: DC terminals of the bidirectional converter; the DC terminals of the bidirectional converter are correspondingly connected to the high-efficiency bidirectional converter.

Images