Multi-port energy router device for rail transit

Abstract

The invention provides a multi-port energy router device for rail transit, which belongs to the technical field of rail transit power supply and energy management, and comprises a photovoltaic controller unit for converting direct current of a photovoltaic power generation unit and transmitting the direct current to a rail transit direct current traction network for train traction and train auxiliary equipment to use electricity, braking energy of the train is converted and transmitted to a photovoltaic power generation unit side; the photovoltaic grid-connected inverter unit is used for converting the direct current of the photovoltaic power generation unit into alternating current and transmitting the alternating current to a 400V power grid in the station; the energy storage bidirectional DC / DC converter unit transmits train braking energy and surplus energy of the photovoltaic power generation unit to the energy storage unit, converts electric energy in the energy storage unit and transmits the converted electric energy to a rail transit direct current traction network; and the system control unit is used for controlling the photovoltaic controller unit, the photovoltaic grid-connected inverter unit and the energy storage bidirectional DC / DC converter unit and improving the energy consumption rate and the braking energy recovery rate.

Description

TECHNICAL FIELD

[0001] The present application belongs to the technical field of rail transit power supply and energy management, and particularly relates to a multi-port energy router device for rail transit. BACKGROUND

[0002] With the deepening of urbanization, rail transit has become the backbone of urban public transportation due to its large capacity, high efficiency and low pollution. However, its huge operating energy consumption, especially traction energy consumption, also brings high operating costs and heavy environmental burden. At the same time, the proposal of the "double carbon" strategic goal puts forward higher requirements for the green and low-carbon development of rail transit.

[0003] Currently, there are two major energy flow problems in the rail transit system that need to be optimized: Low regenerative braking energy recovery rate: urban rail trains start and stop frequently, and can generate a large amount of regenerative energy during braking. In the traditional mode, this part of energy is mainly dissipated in the form of heat through the on-board resistor, not only causing energy waste, but also exacerbating the tunnel temperature rise, leading to increased air conditioning energy consumption; although there are applications of inverter feedback devices, there is still room for improvement in flexibility, economy and efficiency.

[0004] Insufficient photovoltaic new energy consumption capacity: In order to reduce dependence on the power grid, photovoltaic power generation systems have been installed on many field sections and station roofs; however, the current mainstream solution is to directly integrate photovoltaic power generation into the station 400V low-voltage distribution system, which has obvious limitations: Energy cannot be directly and efficiently utilized: the electricity generated by photovoltaic power is preferentially supplied to low-voltage loads such as station lighting and air conditioning, and cannot be directly utilized by the 1500V or 750V rail transit direct-current traction network; when the station's own load is low, it is easy to produce "abandoned light" phenomenon, and the photovoltaic consumption rate is low. Cannot be optimized with braking energy: there is complementary potential in the timing of photovoltaic power generation and train regenerative braking, but the traditional separate system cannot achieve coordination and mutual aid between the two, and the overall energy efficiency of the system is not optimal.

[0005] In summary, the braking energy recovery device and photovoltaic grid-connected system in the existing rail transit are independent of each other, forming an energy island, and cannot achieve global optimization and maximize the use of energy, making it difficult to meet the development needs of rail transit for green, low-carbon and high-efficiency energy saving. SUMMARY

[0006] In view of the above-mentioned deficiencies in the prior art, the present application provides a multi-port energy router device for rail transit, which solves the problems of waste of regenerative braking energy, low photovoltaic new energy consumption rate, and inability to optimize braking energy recovery and photovoltaic utilization systems to form an energy island, resulting in low overall energy utilization efficiency in rail transit.

[0007] In order to achieve the above object, the technical scheme adopted by the present application is as follows: a multi-port energy router device for rail transit, comprising: a photovoltaic controller unit, a photovoltaic grid-connected inverter unit, a storage bidirectional DC / DC converter unit, a system control unit, and an external storage unit and a photovoltaic power generation unit; The photovoltaic controller unit is used to control the electricity output by the photovoltaic power generation unit by using an MPPT algorithm, to convert and transmit the direct current of the photovoltaic power generation unit to the rail transit direct-current traction network, and to convert and transmit the braking energy of the train to the photovoltaic power generation unit side for the power consumption of the photovoltaic grid-connected inverter unit. The photovoltaic grid-connected inverter unit is used to convert the direct current of the photovoltaic power generation unit into alternating current, and to transmit the alternating current to the 400V power grid in the station. The storage bidirectional DC / DC converter unit is used to transmit the train braking energy and the surplus energy of the photovoltaic power generation unit to the storage unit, and to convert and transmit the electrical energy in the storage unit to the rail transit direct-current traction network. The system control unit is used to establish a communication connection with the photovoltaic controller unit, the photovoltaic grid-connected inverter unit, and the storage bidirectional DC / DC converter unit, and to execute an automatic power distribution control strategy based on the traction network voltage according to the comparison between the traction network voltage and the voltage threshold.

[0008] The present application is aimed at the problem that the existing rail transit energy router couples all ports to the general bus, resulting in limited functions, and the problem that the connection mode of the photovoltaic grid-connected path and the storage is not adapted to the core functional requirements of rail transit, i.e. the requirements of regenerative braking, network voltage stability, and large power impact, which causes insufficient photovoltaic power consumption and difficulty in effectively recovering the train regenerative braking energy by the storage unit, resulting in low energy utilization efficiency. The multi-port energy router device for rail transit provided by the present application is a decoupled topology architecture centered on the direct-current traction network and oriented to functions, which allocates the functions of photovoltaic control, storage interaction, and power grid connection to the photovoltaic controller unit, the storage bidirectional DC / DC converter unit, and the photovoltaic grid-connected inverter unit, which are three independent and functionally decoupled units, and performs function coordination through the system control unit. The control logic of the present application is clear, the response is fast, the redundancy is high, and the maintenance is easy. For the high reliability requirement of rail transit, the control logic of the present application clearly defines the division of labor of each unit, is more reliable than the complex switch matrix used in the prior art, has more direct control logic, has fewer fault risk points, and improves the power quality and operation stability of the rail transit direct-current traction network.

[0009] Further, the input end of the photovoltaic grid-connected inverter unit is connected with the low-voltage side of the photovoltaic controller unit. One end of the storage bidirectional DC / DC converter unit is connected with the rail transit direct-current traction network, i.e. the high-voltage side of the photovoltaic controller unit, and the other end is connected with the storage unit.

[0010] The further beneficial effects are that the photovoltaic grid-connected inverter unit is connected with the low-voltage side of the photovoltaic controller unit, so that the photovoltaic grid-connected inverter unit can adapt to the voltage characteristics of the photovoltaic power generation unit, reduce the photovoltaic power transmission loss, and the energy storage unit is connected to the DC traction grid side, i.e. the high-voltage side of the photovoltaic controller, through the energy storage bidirectional DC / DC converter unit, so that the regenerative braking energy of the train in the rail transit can be recovered.

[0011] Further, the automatic power distribution control strategy based on the traction grid voltage includes: a preset voltage threshold, the voltage threshold including an energy storage discharge threshold, an idle grid voltage, an inverter cutoff voltage, an inverter limit voltage, an energy storage charging threshold, and a photovoltaic output voltage given value; acquiring the grid voltage of the rail transit DC traction grid, comparing the grid voltage with the voltage threshold to obtain a grid voltage threshold comparison result; According to the grid voltage threshold comparison result, the system control unit issues control instructions to the photovoltaic controller unit, the photovoltaic grid-connected inverter unit, and the energy storage bidirectional DC / DC converter unit to perform automatic energy distribution.

[0012] The further beneficial effects are that the relative size of the preset voltage threshold and the grid voltage is used as a basis for judgment, so that the system control unit can accurately identify the real-time working condition of the rail transit DC traction grid, and based on the comparison result of the grid voltage and the threshold, the control instructions are issued to realize the automation and intelligentization of energy distribution, so that the functions of photovoltaic power consumption, regenerative braking energy recovery, energy storage peak clipping and valley filling are executed in order according to the working condition priority, reducing the waste in the process of energy conversion and transmission, and improving the energy utilization efficiency, response speed and operation stability of the whole system.

[0013] Further, the energy storage discharge threshold is used to represent the voltage critical value at which the energy storage unit starts discharging to supplement power to the rail transit DC traction grid; The idle grid voltage is used to represent the voltage size when the rectifier output of the rail transit substation is without load; The inverter cutoff voltage is used to represent the voltage critical value at which the photovoltaic grid-connected inverter unit stops outputting power to the 400V grid in the station; The inverter limit voltage is used to represent the voltage critical value at which the photovoltaic grid-connected inverter unit is allowed to reach the maximum output power; The energy storage charging threshold is used to represent the voltage critical value at which the energy storage unit starts charging to absorb the surplus energy of the rail transit DC traction grid; The photovoltaic output voltage given value is used to represent the target voltage value when the photovoltaic controller unit maintains the voltage stability of the rail transit DC traction grid.

[0014] The further beneficial effect is that: due to the large fluctuation of the train traction power, the photovoltaic power cannot be accurately obtained, so that the accurate power distribution is difficult to realize, the specific meaning and function positioning of each voltage threshold are determined by analyzing the basic control strategy of each converter, the accurate and quantifiable judgment basis is provided for the automatic power distribution control strategy based on the traction network voltage, the misjudgment or response delay problem caused by the fuzzy threshold definition in the control logic is avoided, and the system control unit can realize fine management of each unit.

[0015] Further: the specific numerical value of the energy storage discharge threshold, the no-load network voltage, the inverter cutoff voltage, the inverter limiting voltage, the energy storage charging threshold and the photovoltaic output voltage given value includes: The energy storage discharge threshold is lower than the no-load network voltage, and the energy storage charging threshold is higher than the no-load network voltage; The inverter limiting voltage is higher than the inverter cutoff voltage and the no-load network voltage; The photovoltaic output voltage given value is higher than the inverter limiting voltage; The numerical value also includes: When the priority of the energy storage unit charging is higher than that of the photovoltaic grid-connected inverter unit, the energy storage charging threshold is set to be lower than the inverter cutoff voltage; When the priority of the energy storage unit charging is lower than that of the photovoltaic grid-connected inverter unit, the energy storage charging threshold is set to be higher than the inverter limiting voltage; When the photovoltaic power generation unit is not allowed to charge the energy storage unit, the energy storage charging threshold is set to be higher than the photovoltaic output voltage given value.

[0016] The further beneficial effect is that: through the clear size order, the electricity generated by the photovoltaic can first meet the train traction and auxiliary power, then meet the power consumption of the photovoltaic inverter, and finally the excess power is stored in the energy storage unit, even if the fluctuation of the train traction power is large, the power consumption order will not be affected, and the operation stability and energy utilization rate of the rail transit DC traction network are ensured.

[0017] Further: according to the comparison result of the network voltage threshold, the system control unit issues control instructions to the photovoltaic controller unit, the photovoltaic grid-connected inverter unit and the energy storage bidirectional DC / DC converter unit to perform automatic energy distribution, including: When the photovoltaic power generation unit cannot meet the train traction power of rail transit, the network voltage will drop to below the no-load network voltage, or even below the energy storage discharge threshold, at this time, the energy distribution is to supply power to the train by the photovoltaic power generation unit, the substation of rail transit and the energy storage unit at the same time; When the photovoltaic power generation unit can meet the train traction power of rail transit, the grid voltage will rise, when the grid voltage is greater than the inverter cutoff voltage, the photovoltaic grid-connected inverter unit starts to operate, and with the rise of the grid voltage, the operating power of the photovoltaic grid-connected inverter unit gradually increases, at this time, when the power of the photovoltaic power generation unit cannot meet the train traction power of rail transit and the total power of the photovoltaic grid-connected inverter unit, the grid voltage will be stabilized at a certain value between the inverter cutoff voltage and the inverter limit voltage; When the photovoltaic power generation unit can meet the train traction power of rail transit and the total power of the photovoltaic grid-connected inverter unit, the grid voltage rises above the inverter cutoff voltage, and when the grid voltage reaches the energy storage charging threshold, the energy storage unit starts to charge, and before the power of the photovoltaic power generation unit cannot meet the charging power of the energy storage unit, the grid voltage is stabilized at the energy storage charging threshold; When the photovoltaic power generation unit can meet the train traction power of rail transit, the photovoltaic grid-connected inverter unit and the total power of the energy storage unit, the grid voltage is stabilized at the given value of the photovoltaic output voltage.

[0018] The above further beneficial effects are: the present application binds the grid voltage and the operation of each unit through the comparison of the grid voltage and each voltage threshold, when the photovoltaic power is insufficient, the photovoltaic power generation, substation and energy storage unit cooperate to ensure that the train traction power is met; when the photovoltaic power is sufficient, the power is consumed in layers according to the order of traction, grid connection and energy storage, which adapts to the differentiated architecture of the multi-port energy router device, can stabilize the grid voltage, avoid energy waste, and improve the system energy utilization efficiency and operation stability.

[0019] The beneficial effects of the present application are: Efficient recovery and on-site consumption of regenerative braking energy: the train regenerative braking energy is preferentially supplied to other traction trains in the same power supply area, and the surplus energy can be used to charge the energy storage system or be converted into alternating current for the station, completely eliminating resistance energy consumption; Improve the direct supply consumption rate and economic benefit of photovoltaic power: through voltage conversion, photovoltaic power can be directly injected into the DC traction grid for train traction, greatly reducing the abandoned light, significantly improving the application proportion of photovoltaic power generation in the traction system, and reducing the purchase cost; Realize the synergistic complementation and intelligent scheduling of multiple energies: through the central controller, the traction energy, photovoltaic energy, energy storage charging and discharging and grid power are scheduled in real time to smooth the load fluctuation, enhance the system stability, and maximize the overall energy efficiency and economic benefit of the system. BRIEF DESCRIPTION OF DRAWINGS

[0020] Figure 1 It is a structure schematic diagram of a multi-port energy router device for rail transit; Figure 2 It is a sequence diagram of power automatic distribution of each grid voltage threshold setting. Detailed Implementation

[0021] The specific embodiments of the present invention are described below to enable those skilled in the art to understand the present invention. However, it should be understood that the present invention is not limited to the scope of the specific embodiments. For those skilled in the art, various changes are obvious as long as they are within the spirit and scope of the present invention as defined and determined by the appended claims. All inventions utilizing the concept of the present invention are protected.

[0022] Example 1 like Figure 1 As shown, a multi-port energy router device for rail transit includes: a photovoltaic controller unit, a photovoltaic grid-connected inverter unit, an energy storage bidirectional DC / DC converter unit, a system control unit, and external energy storage units and photovoltaic power generation units; The photovoltaic (PV) controller unit uses the MPPT algorithm to control the output power of the PV power generation unit. It converts the DC power from the PV power generation unit and transmits it to the rail transit DC traction network for train traction and auxiliary equipment. It also converts the train's braking energy and transmits it to the PV power generation unit to power the PV grid-connected inverter unit. The main function of the PV controller unit is voltage conversion and regulation. Connecting the PV power generation unit and the rail transit DC traction network, it converts the output power from the PV power generation unit to power the rail transit DC traction network for train traction and auxiliary systems. Simultaneously, it converts the train's braking energy to power the 400V grid within the station. Depending on the specific configuration of the PV power generation unit and the voltage level of the rail transit DC traction network, the PV controller unit typically employs a simple and efficient two-level or three-level bidirectional DC / DC converter topology. It uses a maximum power point tracking (MPPT) algorithm to continuously adjust the operating point, ensuring the PV array of the PV power generation unit always operates near its maximum power point. This maximizes the capture of solar energy and improves the system's energy efficiency.

[0023] The photovoltaic grid-connected inverter unit is used for converting direct current of a photovoltaic power generation unit into alternating current and transmitting the alternating current to a 400V power grid in a station; the main function is to serve as an intelligent interface between a photovoltaic array and the 400V power grid in the station, and the most important function is to convert direct current generated by the photovoltaic power generation unit into sinusoidal alternating current with the same frequency and phase as the 400V power grid in the station, and meanwhile, the photovoltaic grid-connected inverter unit has a grid-connected protection function; when the power grid is powered off due to a fault or maintenance, the photovoltaic grid-connected inverter unit immediately detects and stops power supply to the 400V power grid in the station, thereby preventing island effect from occurring and endangering safety of maintenance personnel and equipment operation; the photovoltaic grid-connected inverter unit has various structures such as an isolated structure or a non-isolated structure, which can be selected according to requirements, and meanwhile, the photovoltaic grid-connected inverter unit can track a maximum power point of the photovoltaic array through a maximum power point tracking algorithm, so that the photovoltaic array can obtain more energy in the change of sunlight and temperature and the energy utilization rate is improved.

[0024] The energy storage bidirectional DC / DC converter unit is used for transmitting train braking energy and surplus energy of the photovoltaic power generation unit to an energy storage unit and converting and transmitting electric energy in the energy storage unit to a rail transit direct-current traction network; the energy storage bidirectional DC / DC converter unit can absorb regenerative braking energy of the train and energy output by the photovoltaic power generation unit and transmit the energy to the energy storage unit, and meanwhile, the energy storage bidirectional DC / DC converter unit can boost the energy stored in the energy storage unit and feed back the energy to the rail transit direct-current traction network when the train starts or accelerates, so as to provide auxiliary power for the train; the energy storage bidirectional DC / DC converter unit cooperates with the photovoltaic controller unit, so that the voltage fluctuation of the direct-current power grid caused by frequent start and stop of the train can be effectively inhibited, and the power supply quality and system stability are improved. Compared with the conventional energy router in which all ports are coupled to a general bus, in the energy router architecture of the present application, the photovoltaic grid-connected inverter unit is connected to an output side of the photovoltaic controller unit, i.e., a low-voltage side of the photovoltaic controller, and the energy storage unit is connected to the rail transit direct-current traction network side through the energy storage bidirectional DC / DC converter unit, i.e., a high-voltage side of the photovoltaic controller, so that the rated power of the photovoltaic controller unit is reduced, the cost of the multi-port energy router is reduced, and the connection mode is determined by different functions to be borne, the energy storage unit of the present application is not only used for storing electric energy output by the photovoltaic power generation unit, but also can recover regenerative braking energy of the train in the rail transit.

[0025] The system control unit is used for establishing a communication connection with the photovoltaic controller unit, the photovoltaic grid-connected inverter unit and the energy storage bidirectional DC / DC converter unit, and performing an automatic power distribution control strategy based on traction network voltage according to comparison of the traction network voltage and a voltage threshold; the system control unit is a control center of the multi-port energy router and has functions such as multi-modal operation and seamless switching control, global optimization and energy management strategy, system-level protection and coordination, state monitoring and advanced perception, external communication and cooperation and the like.

[0026] The present application adopts a decoupling topology with a DC traction network as the core, and distributes the functions of photovoltaic control, energy storage interaction and grid connection to three independent units, controls according to the grid voltage and each voltage threshold through the cooperation of the system control unit, and has clear control logic, fast response and easy maintenance, is more reliable than the complex switch matrix used in the traditional method, has fewer fault points, and ensures the power quality and operation stability of the DC traction network.

[0027] In an embodiment of the present application, the control strategies of the photovoltaic controller unit, the photovoltaic grid-connected inverter unit, the energy storage bidirectional DC / DC converter unit and the system control unit are as follows respectively: The control strategy of the photovoltaic controller unit: the photovoltaic controller unit mainly adopts MPPT control, but the control structure adopts a double closed-loop control structure with an outer ring of the rail transit DC traction network voltage ring and an inner ring of the photovoltaic power generation unit current ring, and can stabilize the DC traction network voltage. The control strategy of the photovoltaic grid-connected inverter unit: the control strategy of the photovoltaic grid-connected inverter unit also adopts a double closed-loop control structure of voltage and current, and both double closed loops control the voltage and current signals on the 400V output side as control targets.

[0028] The control strategy of the bidirectional energy storage DC / DC converter unit: the bidirectional energy storage DC / DC converter unit adopts a double closed-loop control structure, in which the voltage ring is a high-voltage side voltage ring, and the inner ring is a low-voltage side current ring. The bidirectional energy storage DC / DC converter sets two voltage given values of the charging threshold and the discharging threshold, and determines the charging and discharging mode of the energy storage unit by judging the relationship between the two threshold values and the bus voltage.

[0029] The control strategy of the system control unit is an automatic power distribution control strategy based on the traction network voltage, and the control target is to transmit the power generated by the photovoltaic power generation unit to the rail transit DC traction network through the photovoltaic controller first, for train traction power and train auxiliary equipment power; the surplus energy of the photovoltaic power generation unit is transmitted to the 400V grid in the station through the photovoltaic grid-connected inverter unit, for train station ventilation, lighting lamp auxiliary equipment power, and if there is still surplus energy, it is stored in the energy storage unit through the bidirectional energy storage DC / DC converter unit for subsequent power consumption, to realize the smooth consumption of photovoltaic new energy and improve the energy utilization rate.

[0030] In an embodiment of the present application, the automatic power distribution control strategy based on the traction network voltage includes: The preset voltage threshold value includes an energy storage discharge threshold value, a no-load network voltage, an inverter cutoff voltage, an inverter limit voltage, an energy storage charging threshold value and a photovoltaic output voltage given value; The network voltage of the rail transit direct-current traction network is collected, and the network voltage is compared with the voltage threshold value to obtain a network voltage-voltage threshold value comparison result. According to the network voltage-voltage threshold value comparison result, the system control unit issues a control instruction to the photovoltaic controller unit, the photovoltaic grid-connected inverter unit and the energy storage bidirectional DC / DC converter unit to perform automatic energy distribution.

[0031] In actual engineering, the train traction electric power fluctuates greatly, and the photovoltaic power cannot be accurately obtained, so that accurate power distribution is difficult to achieve. Based on the basic control strategy of the photovoltaic controller unit, the photovoltaic grid-connected inverter unit and the energy storage bidirectional DC / DC converter unit, an automatic power distribution control strategy of the multi-port energy router based on the network voltage of the rail transit direct-current traction network is proposed. The control threshold values of the photovoltaic controller unit, the photovoltaic grid-connected inverter unit and the energy storage bidirectional DC / DC converter unit are set according to the network voltage of the rail transit direct-current traction network, and the size of the threshold value needs to meet certain restrictions. Figure 2 As shown in the figure, the power automatic distribution network voltage threshold value setting sequence diagram includes an energy storage discharge threshold value , a no-load network voltage , an inverter cutoff voltage , an inverter limit voltage , an energy storage charging threshold value and a photovoltaic output voltage given value .

[0032] The no-load network voltage is used to represent the voltage size when the rectifier output of the rail transit substation is no load. When the network voltage is lower than the no-load network voltage, it indicates that the substation supplies power to the rail transit direct-current traction network. When the network voltage is higher than the no-load network voltage, it indicates that the substation does not supply power to the rail transit direct-current traction network. Currently, 24-pulse rectifiers are used in subway substations, which can only realize single-phase energy transmission. The no-load network voltage is the voltage size when the rectifier output is no load. When the network voltage is lower than the no-load network voltage, the 24-pulse rectifier will supply power to the traction network. When the network voltage is higher than the no-load network voltage due to train braking or photovoltaic power generation unit, the 24-pulse rectifier will not supply power to the traction network temporarily.

[0033] The energy storage charging threshold value is used to represent the voltage critical value of the energy storage unit starting charging to absorb the surplus energy of the rail transit direct-current traction network. When the network voltage is lower than the energy storage charging threshold value, it indicates that the train is in traction state and needs the energy storage unit to discharge to supply power to the rail transit direct-current traction network. When the network voltage is higher than the energy storage charging threshold value, it indicates that the train is in braking state and needs the energy storage unit to charge to absorb the surplus energy. The energy storage discharge threshold is used to represent a voltage threshold for the energy storage unit to start discharging to supplement power of the rail transit DC traction network. When the network voltage is between the energy storage charging threshold and the energy storage discharge threshold, it indicates that the traction train and the braking train in the entire subway system are in a relatively balanced state, and the energy of the train braking can be absorbed by the traction train, so that the energy storage unit does not need to act. The energy storage charging threshold and the energy storage discharge threshold realize efficient recycling of the train regenerative braking energy, smooth the power peak of the power grid, and stabilize the operating network voltage of the rail transit DC traction network.

[0034] The inverter limit voltage is used to represent a voltage threshold when the photovoltaic grid-connected inverter unit reaches the maximum output power. When the network voltage is higher than the inverter limit voltage, the photovoltaic grid-connected inverter unit runs at full power to supply power to the 400V power grid in the station. When the network voltage is lower than the inverter cutoff voltage, the photovoltaic grid-connected inverter stops running. When the network voltage is between the inverter limit voltage and the inverter cutoff voltage, the maximum running power of the photovoltaic grid-connected inverter can be calculated, and in the case of stable output voltage, the running power is linearly related to the output current. The photovoltaic inverter unit adopts a current inner loop, so the current limit value in the control is calculated by the formula .

[0035] The inverter cutoff voltage is used to represent a voltage threshold for the photovoltaic grid-connected inverter unit to stop outputting electric energy to the 400V power grid in the station. When the network voltage is higher than the inverter cutoff voltage, the photovoltaic grid-connected inverter starts to invert the output electric energy of the photovoltaic power generation unit to the 400V power grid in the station from 0kW. As the network voltage rises, the inverter power gradually increases until the inverter limit voltage, and the power of the photovoltaic grid-connected inverter reaches the maximum. The range from the inverter cutoff voltage to the inverter limit voltage is an important stage for automatic power distribution of the entire system. When the network voltage is in this range, it indicates that the power generation of the photovoltaic power generation unit at this time can meet the train traction power and auxiliary equipment power consumption, but cannot meet the power consumption of the photovoltaic grid-connected inverter unit.

[0036] The photovoltaic output voltage given value is used to represent a target voltage value when the photovoltaic controller unit maintains the voltage stability of the rail transit DC traction network. When the power generation of the photovoltaic power generation unit can meet the train traction power, the power consumption of the photovoltaic grid-connected inverter unit and the demand of the energy storage unit, the network voltage will be stabilized at the photovoltaic output voltage given value. At the same time, if the train braking power is large, the network voltage is higher than the photovoltaic output voltage given value, the photovoltaic controller unit will convert the braking energy to the photovoltaic power generation side and transmit it to the 400V power grid in the station by the photovoltaic grid-connected inverter unit, thereby improving the utilization rate of energy and maintaining the stable operation of the system.

[0037] In the specific embodiments of the present application, the energy storage discharge threshold, the no-load network voltage, the inverter cutoff voltage, the inverter limit voltage, the energy storage charging threshold and the photovoltaic output voltage given value need to be calculated according to the formulaFigure 2 The shown numerical size order is set to realize that the power generation of the photovoltaic power generation unit first meets the train traction power and auxiliary equipment power, then meets the photovoltaic grid-connected inverter unit power, and finally, if there is excess power, the power is stored in the energy storage unit; through the clear size order, the power generated by the photovoltaic can first meet the train traction and auxiliary power, then meet the power of the photovoltaic inverter, and finally, if there is excess power, the power is stored in the energy storage unit, even if the train traction power fluctuates greatly, it will not affect the power sequence, ensuring the operation stability and energy utilization rate of the rail transit DC traction network.

[0038] The specific numerical size of the energy storage discharge threshold, the no-load network voltage, the inverter cutoff voltage, the inverter limit voltage, the energy storage charging threshold, and the photovoltaic output voltage given value includes: The energy storage discharge threshold is lower than the no-load network voltage, and the energy storage charging threshold is higher than the no-load network voltage; The inverter limit voltage is higher than the inverter cutoff voltage and the no-load network voltage; The photovoltaic output voltage given value is higher than the inverter limit voltage; According to the different priorities, the numerical size further includes: When the priority of the energy storage unit charging is higher than that of the photovoltaic grid-connected inverter unit, the energy storage charging threshold is set to be lower than the inverter cutoff voltage; When the priority of the energy storage unit charging is lower than that of the photovoltaic grid-connected inverter unit, the energy storage charging threshold is set to be higher than the inverter limit voltage; When the photovoltaic power generation unit is not allowed to charge the energy storage unit, the energy storage charging threshold is set to be higher than the photovoltaic output voltage given value.

[0039] In the specific embodiments of the present application, according to the network voltage threshold comparison result, the system control unit issues control instructions to the photovoltaic controller unit, the photovoltaic grid-connected inverter unit, and the energy storage bidirectional DC / DC converter unit to automatically distribute energy, including: When the photovoltaic power generation unit cannot meet the train traction power of rail transit, the network voltage will drop to below the no-load network voltage, or even below the energy storage discharge threshold, at this time, the energy distribution is to supply power to the train by the photovoltaic power generation unit, the substation of rail transit, and the energy storage unit at the same time; When the photovoltaic power generation unit can meet the train traction power of rail transit, the network voltage will rise, when the network voltage is greater than the inverter cutoff voltage, the photovoltaic grid-connected inverter unit starts to operate, and with the rise of the network voltage, the operating power of the photovoltaic grid-connected inverter unit gradually increases, at this time, when the power of the photovoltaic power generation unit cannot meet the train traction power of rail transit and the total power of the photovoltaic grid-connected inverter unit operation, the network voltage will be stabilized at a certain value between the inverter cutoff voltage and the inverter limit voltage; When the photovoltaic power generation unit can meet the power of the train traction of the rail transit and the whole power of the photovoltaic grid-connected inverter unit, the grid voltage is lifted above the inverter cutoff voltage, and when the grid voltage reaches the energy storage charging threshold, the energy storage unit starts charging, and before the power of the photovoltaic power generation unit cannot meet the charging power of the energy storage unit, the grid voltage is stabilized at the energy storage charging threshold; When the photovoltaic power generation unit can meet the power of the train traction of the rail transit, the photovoltaic grid-connected inverter unit and the energy storage unit, the grid voltage is stabilized at the photovoltaic output voltage given value.

[0040] The system control unit is the upper control unit of the photovoltaic controller unit, the photovoltaic grid-connected inverter unit and the energy storage bidirectional DC / DC converter unit, can regulate and control the whole multi-port energy router device, at the same time, the system control unit can modify the voltage threshold, has stronger adaptability, and better realizes the control strategy according to the actual situation of the engineering site.

[0041] The beneficial effects of the present application are: Realize efficient recovery and on-site consumption of regenerative braking energy: the train regenerative braking energy is preferentially supplied to other traction trains in the same power supply area, the surplus energy can charge the energy storage system or be inverted into alternating current for the station, and the resistance energy consumption is completely eliminated; Improve the direct supply consumption rate and economic benefits of photovoltaic: through voltage conversion, the photovoltaic energy can be directly injected into the direct current traction network for train traction, greatly reducing the light abandonment, significantly improving the application proportion of photovoltaic power generation in the traction system, and reducing the power purchase cost; Realize the collaborative complementation and intelligent scheduling of multiple energies: through the central controller, the traction energy, photovoltaic energy, energy storage charging and discharging and grid energy are scheduled in real time, the load fluctuation is suppressed, the system stability is enhanced, and the maximization of the overall energy efficiency and economic benefits of the system is realized.

Claims

1. A multi-port energy router device for rail transit, characterized in that, The application relates to a rail transit power supply system based on photovoltaic energy storage, which comprises a photovoltaic controller unit, a photovoltaic grid-connected inverter unit, a storage bidirectional DC / DC converter unit, a system control unit, an external storage unit and a photovoltaic power generation unit. The photovoltaic controller unit is used for controlling the electricity output by the photovoltaic power generation unit by adopting an MPPT algorithm, transforming the direct current of the photovoltaic power generation unit to the rail transit direct-current traction network, and transforming the braking energy of the train to the photovoltaic power generation unit side for the photovoltaic grid-connected inverter unit to use electricity. The photovoltaic grid-connected inverter unit is used for converting the direct current of the photovoltaic power generation unit into alternating current and transmitting the alternating current to the 400V power grid in the station. The storage bidirectional DC / DC converter unit is used for transmitting the braking energy of the train and the surplus energy of the photovoltaic power generation unit to the storage unit and transforming the electric energy in the storage unit to the rail transit direct-current traction network. The system control unit is used for establishing a communication connection with the photovoltaic controller unit, the photovoltaic grid-connected inverter unit and the storage bidirectional DC / DC converter unit and executing an automatic power distribution control strategy based on the traction network voltage according to the comparison between the traction network voltage and the voltage threshold value. The input end of the photovoltaic grid-connected inverter unit is connected with the low-voltage side of the photovoltaic controller unit.

2. The multi-port energy router device for rail transit according to claim 1, wherein, One end of the storage bidirectional DC / DC converter unit is connected with the rail transit direct-current traction network, that is, the high-voltage side of the photovoltaic controller unit, and the other end is connected with the storage unit. The automatic power distribution control strategy based on the traction network voltage comprises the following steps:

3. The multi-port energy router device for rail transit according to claim 1, wherein, presetting a voltage threshold value, wherein the voltage threshold value comprises a storage discharge threshold value, an idle network voltage, an inverter cutoff voltage, an inverter limiting voltage, a storage charging threshold value and a photovoltaic output voltage given value; collecting the network voltage of the rail transit direct-current traction network, comparing the network voltage with the voltage threshold value and obtaining a network voltage threshold value comparison result; according to the network voltage threshold value comparison result, the system control unit issues a control instruction to the photovoltaic controller unit, the photovoltaic grid-connected inverter unit and the storage bidirectional DC / DC converter unit to perform automatic energy distribution. The storage discharge threshold value is used for indicating the voltage critical value at which the storage unit starts discharging to supplement power to the rail transit direct-current traction network.

4. The multi-port energy router device for rail transportation of claim 3, wherein, The idle network voltage is used for indicating the voltage size when the rectifier output of the rail transit substation is without load. The inverter cutoff voltage is used for indicating the voltage critical value at which the photovoltaic grid-connected inverter unit stops outputting electric energy to the 400V power grid in the station. The inverter limiting voltage is used for indicating the voltage critical value at which the photovoltaic grid-connected inverter unit is allowed to reach the maximum output power. The storage charging threshold value is used for indicating the voltage critical value at which the storage unit starts charging to absorb the surplus energy of the rail transit direct-current traction network. The photovoltaic output voltage given value is used for indicating the target voltage value when the photovoltaic controller unit maintains the voltage stability of the rail transit direct-current traction network. The specific numerical values of the storage discharge threshold value, the idle network voltage, the inverter cutoff voltage, the inverter limiting voltage, the storage charging threshold value and the photovoltaic output voltage given value comprise the following steps:

5. The multi-port energy router device for rail transportation of claim 4, wherein, the storage discharge threshold value is lower than the idle network voltage, and the storage charging threshold value is higher than the idle network voltage; the inverter limiting voltage is higher than the inverter cutoff voltage and the idle network voltage. ​ The photovoltaic output voltage setpoint is higher than the inverter limiting voltage; The numerical value also includes: When the charging priority of the energy storage unit is higher than that of the photovoltaic grid-connected inverter unit, the energy storage charging threshold is set to be lower than the inverter cutoff voltage. When the charging priority of the energy storage unit is lower than that of the photovoltaic grid-connected inverter unit, the energy storage charging threshold is set to be higher than the inverter limiting voltage. When photovoltaic power generation units are not allowed to charge energy storage units, the energy storage charging threshold is set to be higher than the given value of photovoltaic output voltage.

6. The multi-port energy router device for rail transportation of claim 3, wherein, Based on the grid voltage threshold comparison result, the system control unit sends control commands to the photovoltaic controller unit, the photovoltaic grid-connected inverter unit, and the energy storage bidirectional DC / DC converter unit to perform automatic energy distribution, including: When the photovoltaic power generation unit cannot meet the traction power demand of the rail transit train, the grid voltage will drop to below the no-load grid voltage, or even below the energy storage discharge threshold. At this time, the energy distribution is that the photovoltaic power generation unit, the rail transit substation, and the energy storage unit simultaneously supply power to the train. When the photovoltaic power generation unit can meet the traction power demand of rail transit trains, the grid voltage will rise. When the grid voltage is greater than the inverter cutoff voltage, the photovoltaic grid-connected inverter unit starts to operate. As the grid voltage rises, the operating power of the photovoltaic grid-connected inverter unit gradually increases. At this time, when the power of the photovoltaic power generation unit cannot meet the traction power demand of rail transit trains and the full operating power of the photovoltaic grid-connected inverter unit, the grid voltage will stabilize at a certain value between the inverter cutoff voltage and the inverter limiting voltage. When the photovoltaic power generation unit can meet the power requirements of the rail transit train traction and the full power of the photovoltaic grid-connected inverter unit, the grid voltage rises above the inverter cutoff voltage. When the grid voltage reaches the energy storage charging threshold, the energy storage unit starts charging. Before the power of the photovoltaic power generation unit can meet the charging power of the energy storage unit, the grid voltage stabilizes at the energy storage charging threshold. When the photovoltaic power generation unit can meet the full power requirements of the rail transit train traction power supply, the photovoltaic grid-connected inverter unit, and the energy storage unit, the grid voltage is stabilized at the given value of the photovoltaic output voltage.

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