WO2018133232A1 - 直流微电网系统及其控制方法 - Google Patents

直流微电网系统及其控制方法 Download PDF

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Publication number
WO2018133232A1
WO2018133232A1 PCT/CN2017/081703 CN2017081703W WO2018133232A1 WO 2018133232 A1 WO2018133232 A1 WO 2018133232A1 CN 2017081703 W CN2017081703 W CN 2017081703W WO 2018133232 A1 WO2018133232 A1 WO 2018133232A1
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Prior art keywords
unit
grid
micro
energy storage
storage battery
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PCT/CN2017/081703
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English (en)
French (fr)
Inventor
唐文强
任鹏
文武
黄猛
南树功
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珠海格力电器股份有限公司
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Publication of WO2018133232A1 publication Critical patent/WO2018133232A1/zh

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    • H—ELECTRICITY
    • H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
    • H02J—CIRCUIT ARRANGEMENTS OR SYSTEMS FOR SUPPLYING OR DISTRIBUTING ELECTRIC POWER; SYSTEMS FOR STORING ELECTRIC ENERGY
    • H02J1/00—Circuit arrangements for dc mains or dc distribution networks
    • H02J1/10—Parallel operation of dc sources
    • H—ELECTRICITY
    • H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
    • H02J—CIRCUIT ARRANGEMENTS OR SYSTEMS FOR SUPPLYING OR DISTRIBUTING ELECTRIC POWER; SYSTEMS FOR STORING ELECTRIC ENERGY
    • H02J1/00—Circuit arrangements for dc mains or dc distribution networks
    • H02J1/14—Balancing the load in a network

Definitions

  • the present invention relates to the field of microgrid technology, and in particular to a DC microgrid system and a control method thereof.
  • the microgrid technology based on new energy power generation technology has developed rapidly.
  • the DC microgrid has become a research and research advantage.
  • the application of hotspots, as well as the trend of continuous DC power promotes the development of household electricity to more efficient DC, and the combination of new energy generation technology and DC power distribution DC microgrid technology will be a direction of future development.
  • the electric energy flows from the power generation end to the power supply side, while the energy exchange between the distributed new energy, the power grid, the load and the energy storage in the micro power grid system based on new energy utilization is different from
  • the energy of a traditional power grid system flows in one direction, and there are multiple modes or modes of operation of the microgrid system.
  • the DC bus is the intermediary of the system energy exchange.
  • the multiple distributed energy, energy storage, load and grid in the DC microgrid are connected to the DC bus through the power electronic converter, in the DC microgrid system.
  • the energy exchange of multiple units through the DC bus ensures that the DC bus voltage stability is important for the stable operation of the system.
  • the invention provides a DC microgrid system and a control method thereof for improving the stability of the DC bus voltage.
  • the present invention provides a DC microgrid system, comprising: a micro-source unit composed of a photovoltaic power generation unit and a wind power generation unit, a DC load unit, a grid interface unit, and a storage unit.
  • the battery unit and the DC bus wherein the micro-source unit, the DC load unit, the grid interface unit, and the energy storage battery unit are connected to the DC bus through the power electronic device, and the energy exchange is realized through the DC bus, and the DC micro-grid system passes through the micro-source unit.
  • the DC load unit, the grid interface unit, the respective controllers of the energy storage battery unit, and the microgrid central controller MGCC are jointly controlled, and the microgrid central controller MGCC is an upper controller with respect to the respective controllers.
  • the wind power generation unit uses a power electronic device including a rectifying and boosting converter to connect to the DC bus Pick up.
  • wind power unit is controlled by the maximum power tracking MPPT controller.
  • the photovoltaic power generation unit is connected to the DC bus connection using power electronics including a boost converter.
  • the photovoltaic power generation unit is controlled by the maximum power tracking MPPT controller.
  • the energy storage battery unit is connected to the DC bus connection by using power electronics including a buck-boost converter.
  • the energy storage battery unit is connected to the DC bus connection by using power electronics including a buck-boost converter.
  • the energy storage battery unit is controlled by a charge and discharge controller.
  • the grid interface unit controls the grid to connect to the DC bus connection using power electronics including a three-phase full-bridge inverter.
  • the grid interface unit is controlled by a four-quadrant rectifier controller.
  • the DC load unit is a secondary pure DC load unit.
  • the power electronics device comprises: a DC/DC converter, and/or an AC/DC converter.
  • the DC microgrid system includes a grid-connected working mode and an off-grid working mode, wherein the DC grid system is connected to the external grid system when the DC grid system is in the grid-connected working mode, and the external grid is used as a compensation energy source to suppress the micro-source unit to generate electricity.
  • a control method of a DC microgrid system includes: a micro-source unit composed of a photovoltaic power generation unit and a wind power generation unit, a DC load unit, a power grid interface unit, The energy storage battery unit and the DC bus, wherein the micro source unit, the DC load unit, the grid interface unit, and the energy storage battery unit are connected to the DC bus through the power electronic device, and the method comprises: through the micro source unit, the DC load unit, and the grid interface unit.
  • the respective controllers of the energy storage battery unit and the central controller of the system microgrid jointly control each unit of the DC microgrid system to realize energy exchange through the DC bus, wherein the microgrid central controller MGCC is an upper controller relative to the respective controller.
  • the DC microgrid system includes a grid-connected working mode and an off-grid working mode, wherein the DC grid system is connected to the external grid system when the DC grid system is in the grid-connected working mode, and the external grid is used as a compensation energy source to suppress the micro-source unit to generate electricity.
  • the method includes : Pre-coding and coding the working states of the micro-source unit, the DC load unit, the grid interface unit, and the energy storage battery unit; and working on the system composed of the micro-source unit, the DC load unit, the grid interface unit, and the energy storage battery unit.
  • the status is encoded and identified.
  • the working states of the micro-source unit, the DC load unit, the grid interface unit, and the energy storage battery unit are coded in advance, including: working the micro-source unit, the DC load unit, the grid interface unit, and the energy storage battery unit.
  • the DC bus energy inflow and outflow and the inflow and outflow direction are used as the basis to determine its working state; the working status of the micro-source unit, DC load unit, grid interface unit and energy storage battery unit is coded and identified.
  • the working states of the micro-source unit, the DC load unit, the grid interface unit, and the energy storage battery unit are coded, including: when the micro-source unit energy does not flow into the DC bus, the code is the first identifier, and the micro-source unit is characterized. When the micro-source unit energy flows into the DC bus, the code is the second identifier, which indicates that the micro-source unit is in the access working state; when the DC load unit and the DC bus have no energy interaction, the code is the first identifier.
  • the DC load cell is characterized as being in the disconnected working state; when the DC bus energy is flown into the DC load cell, the code is the third identifier, which indicates that the DC load cell is in the access working state; when the energy of the energy storage battery cell does not flow into the DC bus, the code is The first identifier indicates that the energy storage battery unit is in a disconnected working state; when the energy of the energy storage battery unit flows into the DC bus, the code is a second identifier, indicating that the energy storage battery unit is in a charging working state; and the DC bus energy is flown into the energy storage battery.
  • the energy storage battery unit When the unit is coded as the third identifier, the energy storage battery unit is in charge State; when the grid interface unit energy does not flow into the DC bus, the code is the first identifier, indicating that the grid interface unit is in the disconnected working state, the DC microgrid system is in the off-grid working mode; when the grid interface unit energy flows into the DC bus, the encoding For the second identifier, the grid interface unit is in the access working state, and the DC microgrid system is in the grid-connected working mode; when the DC bus energy flows into the grid interface unit, the code is the third identifier, and the grid interface unit is in the power working state. .
  • the first identifier is 00
  • the second identifier is 11
  • the third identifier is 01.
  • the system working states of the micro-source unit, the DC load unit, the grid interface unit, and the energy storage battery unit are coded and identified, including: the micro-source unit, the DC load unit, the grid interface unit, and the energy storage battery.
  • the coded identifiers corresponding to the working states of the unit are combined according to a preset order to form a coded identifier of the working state of the system, and the coded identifier of each system working state corresponds to a system working state.
  • the micro-source unit, the DC load unit, the grid interface unit, the respective controllers of the energy storage battery unit, and the central controller of the system micro-grid jointly control the energy exchange of each unit of the DC micro-grid system through the DC bus, including: in DC When the microgrid system is in the grid-connected working mode, the external grid is used as a compensation energy source to suppress the output fluctuation and load fluctuation control of the micro-source unit to ensure the stability of the bus voltage, and the energy storage battery unit only responds to the control strategy of the MGCC.
  • the micro-source unit, the DC load unit, the grid interface unit, the respective controllers of the energy storage battery unit, and the central controller of the system micro-grid jointly control the energy exchange of each unit of the DC micro-grid system through the DC bus, including: in DC When the microgrid system is in the off-grid mode, the energy storage battery unit is used as a compensation energy source to suppress the output fluctuation and load fluctuation of the micro-source unit to ensure the stability of the bus voltage.
  • a pure DC microgrid system structure which comprises a micro-source unit (power generation unit) for photovoltaic power generation and wind power generation, a DC load unit, a grid interface unit, an energy storage battery unit and a DC bus, and a DC microgrid system.
  • the energy exchange is realized by the DC bus, and the stable operation of the system is ensured by the stable control of the DC bus; the system operation control is completed by the controller of each unit and the control of the system MGCC (micro-grid central controller), each unit passes through the power electronic device and The DC bus is connected, and the unit controller realizes the power conversion flow by controlling the power electronic device.
  • MGCC micro-grid central controller
  • the MGCC control maintains the stable operation of the whole system by monitoring and controlling the operation state of the system, and the DC microgrid system provides DC power.
  • Provide solutions for new energy utilization such as wind power generation and photovoltaic power generation, reduce the conversion of new energy power generation, improve the efficiency of power utilization, and at the same time stabilize the control of the DC bus to ensure stable operation of the system.
  • FIG. 1 is an optional structural block diagram of a DC microgrid system according to an embodiment of the present invention.
  • FIG. 2 is an optional structural diagram of a grid-connected microgrid system in a control method of a direct current microgrid system according to an embodiment of the present invention
  • FIG. 3 is an optional operational state flow diagram of a grid-connected microgrid system in a control method of a direct current microgrid system according to an embodiment of the present invention
  • FIG. 4 is an optional operational state flow diagram of a grid-connected DC microgrid system for energy storage and discharge in a control method of a DC microgrid system according to an embodiment of the present invention
  • FIG. 5 is an optional operational state flow diagram of a grid-connected DC microgrid system for energy storage charging in a control method of a DC microgrid system according to an embodiment of the present invention
  • FIG. 6 is an optional operational state flow diagram of an upper layer control grid-connected DC microgrid system in a control method of a direct current microgrid system according to an embodiment of the present invention
  • FIG. 7 is a schematic structural diagram of an off-grid DC microgrid system in a control method of a DC microgrid system according to an embodiment of the present invention
  • FIG. 8 is a schematic structural diagram of an off-grid DC microgrid system in a control method of a DC microgrid system according to an embodiment of the present invention
  • FIG. 9 is a flow chart showing an optional operation strategy of a DC microgrid system according to an embodiment of the present invention.
  • the DC microgrid system includes a micro-source unit composed of a photovoltaic power generation unit 201 and a wind power generation unit 202. 20, a DC load unit 21, a grid interface unit 22, an energy storage battery unit 23 and a DC bus 24, wherein the micro-source unit 20, the DC load unit 21, the grid interface unit 22, and the energy storage battery unit 23 pass through the power electronics 25
  • the DC busbar 24 is connected, and energy exchange is realized through the DC busbar 24, and the DC microgrid system passes through the micro-source unit 20, the DC load unit 21, and the power grid interface.
  • the unit 22, the respective controllers of the energy storage battery unit 23, and the microgrid central controller MGCC are jointly controlled, and the microgrid central controller MGCC is an upper controller with respect to the respective controllers.
  • a pure DC microgrid system structure comprising a micro-source unit (power generation unit) for photovoltaic power generation and wind power generation, a DC load unit, a grid interface unit, an energy storage battery unit, and a DC bus.
  • the DC microgrid system realizes energy exchange through the DC bus, and ensures stable operation of the system through stable control of the DC bus; the system operation control is completed by the controller of each unit and the control of the system MGCC (microgrid central controller), each unit passes
  • the power electronic device is connected with the DC bus, and the unit controller realizes the power conversion flow by controlling the power electronic device.
  • the MGCC control maintains the stable operation of the whole system by monitoring and controlling the operation state of the system, and the DC microgrid system provides DC power, New energy utilization such as wind power generation and photovoltaic power generation provides solutions to reduce the conversion of new energy power generation and improve the efficiency of power utilization.
  • the DC bus is stably controlled to ensure stable operation of the system.
  • the wind power unit is connected to the DC bus connection using power electronics including a rectifying and boosting converter.
  • the wind power unit is controlled by the maximum power tracking MPPT controller.
  • the photovoltaic power unit is connected to the DC bus using power electronics including a boost converter.
  • the photovoltaic unit is controlled by the maximum power tracking MPPT controller.
  • the energy storage battery unit is connected to the DC bus connection by using power electronics including a buck-boost converter.
  • the energy storage battery unit is connected to the DC bus connection by using power electronics including a buck-boost converter.
  • the energy storage battery unit is controlled by a charge and discharge controller.
  • the grid interface unit controls the grid to connect to the DC bus using power electronics including a three-phase full-bridge inverter.
  • the grid interface unit is controlled by a four-quadrant rectifier controller.
  • the DC load unit is a secondary pure DC load unit.
  • power electronics include: DC/DC converters, and/or AC/DC converters.
  • the DC microgrid system includes the grid-connected working mode and the off-grid working mode.
  • the DC grid system is connected to the external grid system when the DC grid system is in the grid-connected working mode, and the external grid is used as the compensation energy source to suppress the micro-source.
  • the optional Embodiment 2 of the present invention further provides a control method of the DC microgrid system, where the DC microgrid system comprises: a photovoltaic power generation unit and a wind power generation unit.
  • the micro-source unit, the DC load unit, the grid interface unit, the energy storage battery unit, and the DC bus wherein the micro-source unit, the DC load unit, the grid interface unit, and the energy storage battery unit are connected to the DC bus through the power electronic device, and the method includes: The micro-source unit, the DC load unit, the grid interface unit, the respective controllers of the energy storage battery unit and the central controller of the system micro-grid jointly control the energy exchange of each unit of the DC micro-grid system through the DC bus, wherein the micro-grid central controller
  • the MGCC is an upper controller with respect to its respective controller.
  • the DC microgrid system includes a grid-connected working mode and an off-grid working mode, wherein the DC grid system is connected to the external grid system when the DC grid system is in the grid-connected working mode, and the external grid is used as a compensation energy source to suppress the micro-source unit to generate electricity.
  • the battery unit acts as a compensating energy source to suppress fluctuations in power generation output and load fluctuations of the micro-source unit.
  • the respective units of the DC microgrid system are collectively controlled to realize energy through the DC bus through the micro-source unit, the DC load unit, the grid interface unit, the respective controllers of the energy storage battery unit, and the central controller of the system micro-grid.
  • the method includes: coding and identifying each working state of the micro source unit, the DC load unit, the grid interface unit, and the energy storage battery unit in advance; and working the micro source unit, the DC load unit, the grid interface unit, and the energy storage battery unit.
  • the system working state composed of states is coded and identified.
  • the working states of the micro-source unit, the DC load unit, the grid interface unit, and the energy storage battery unit are coded in advance, including: the micro-source unit, the DC load unit, the grid interface unit, and the energy storage battery unit are in operation According to the DC bus energy inflow and outflow and the inflow and outflow direction, determine the working state; encode the working status of the micro-source unit, DC load unit, grid interface unit and energy storage battery unit
  • the working states of the micro-source unit, the DC load unit, the grid interface unit, and the energy storage battery unit are coded, including: when the micro-source unit energy does not flow into the DC bus, the code is the first identifier, and the micro-source unit is characterized. When the micro-source unit energy flows into the DC bus, the code is the second identifier, which indicates that the micro-source unit is in the access working state; when the DC load unit and the DC bus have no energy interaction, the code is the first identifier.
  • the DC load cell is characterized as being in the disconnected working state; when the DC bus energy is flown into the DC load cell, the code is the third identifier, which indicates that the DC load cell is in the access working state; when the energy of the energy storage battery cell does not flow into the DC bus, the code is The first identifier indicates that the energy storage battery unit is in a disconnected working state; when the energy of the energy storage battery unit flows into the DC bus, the code is a second identifier, indicating that the energy storage battery unit is in a charging working state; and the DC bus energy is flown into the energy storage battery.
  • the energy storage battery unit When the unit is coded as the third identifier, the energy storage battery unit is in charge State; when the grid interface unit energy does not flow into the DC bus, the code is the first identifier, indicating that the grid interface unit is in the disconnected working state, the DC microgrid system is in the off-grid working mode; when the grid interface unit energy flows into the DC bus, the encoding For the second identifier, the grid interface unit is in the access working state, and the DC microgrid system is in the grid-connected working mode; when the DC bus energy flows into the grid interface unit, the code is the third identifier, and the grid interface unit is in the power working state. .
  • the first identifier is 00
  • the second identifier is 11
  • the third identifier is 01.
  • the system working state of each working state of the micro-source unit, the DC load unit, the grid interface unit, and the energy storage battery unit is coded, including: the micro-source unit, the DC load unit, and the grid interface unit.
  • the coded identifiers corresponding to the working states of the energy storage battery unit are combined according to a preset sequence to form a coded identifier of the working state of the system, and the coded identifier of each system working state corresponds to a system working state.
  • the micro-source unit, the DC load unit, the grid interface unit, the respective controllers of the energy storage battery unit, and the central controller of the system micro-grid jointly control the energy exchange of each unit of the DC micro-grid system through the DC bus, including: in DC When the microgrid system is in the grid-connected working mode, the external grid is used as a compensation energy source to suppress the output fluctuation and load fluctuation control of the micro-source unit to ensure the stability of the bus voltage, and the energy storage battery unit only responds to the control strategy of the MGCC.
  • the micro-source unit, the DC load unit, the grid interface unit, the respective controllers of the energy storage battery unit, and the central controller of the system micro-grid jointly control the energy exchange of each unit of the DC micro-grid system through the DC bus, Including: When the DC microgrid system is in the off-grid working mode, the energy storage battery unit is used as a compensation energy source to suppress the output fluctuation and load fluctuation of the micro-source unit to ensure the stability of the bus voltage.
  • DC microgrid systems usually include distributed energy sources such as wind power generation and photovoltaic power generation, DC loads, energy storage batteries, grid access units and DC busbars.
  • Wind power generation uses a rectification + Boost converter to connect to the DC bus, through MPPT. (Maximum Power Point Tracking) controller control;
  • photovoltaic power generation uses Boost converter to connect to DC bus, controlled by MPPT controller;
  • energy storage battery uses Boost/Buck (boost-buck) converter to connect DC bus Controlled by the charge and discharge controller;
  • the grid is connected to the DC bus through a three-phase full-bridge inverter, and four-quadrant rectification control is used to realize bidirectional flow of electric energy;
  • the MGCC is controlled as an upper controller, which communicates with the underlying controller and can be Send the corresponding control instructions.
  • the DC microgrid system is divided into two modes: grid-connected and off-grid.
  • the DC microgrid systems in the two modes have different control methods and operating characteristics.
  • the invention relates to a pure DC microgrid system structure, which comprises a micro-source unit for photovoltaic power generation and wind power generation, a secondary pure DC load unit, a grid interface unit, an energy storage battery unit and a DC bus, and each unit of the DC micro-grid system
  • a pure DC microgrid system structure which comprises a micro-source unit for photovoltaic power generation and wind power generation, a secondary pure DC load unit, a grid interface unit, an energy storage battery unit and a DC bus, and each unit of the DC micro-grid system
  • the whole control system is divided into two layers, which are the access controller of each unit and the MGCC controller of the system.
  • the grid-connected DC microgrid and the off-grid DC microgrid have different operating characteristics.
  • the grid-connected microgrid system is connected to the municipal grid system, and the municipal grid is used as a stable compensation energy to suppress the output fluctuation and load fluctuation of the new energy generation.
  • the DC bus voltage is stable and the system is stable.
  • the off-grid microgrid system usually uses energy storage as a stable compensation energy to suppress the output fluctuation of the new energy generation, thus ensuring the stability of the load side output and stable operation of the system.
  • the grid-connected DC microgrid system is shown in Figure 2.
  • PV is the photovoltaic unit
  • Wind is the wind power unit
  • Bat is the energy storage battery unit
  • Grid is the grid access unit
  • Load is the DC load unit.
  • the DC BUS is a DC bus.
  • the grid is the main link of the stable operation of the system to ensure the stability of the bus voltage, and the energy storage only responds to the optimal scheduling strategy of the upper layer control (MGCC).
  • MGCC upper layer control
  • the DC micro-grid system operation status is classified and divided, and the system operation status is integrated by identifying each unit and system status. .
  • the energy of each unit is referenced to the DC bus inflow and outflow of the system.
  • the “11” state indicates that the current (energy) flows into the DC bus
  • the “01” state indicates that the current (energy) flows out of the DC bus.
  • the “00” state indicates There is no interaction with the DC bus.
  • Table 1 The specific status table of each unit is shown in Table 1:
  • the grid-connected microgrid system adopts the strategy of operating the grid stable system, and the energy storage only responds to the upper-layer scheduling strategy.
  • the energy storage participates in the dispatch, there are 22 operating states of the grid-connected DC microgrid system, as shown in Table 2:
  • the essence of the stable operation of the grid-connected DC microgrid system is real-time switching of the operating state to ensure that the DC bus voltage is stable to meet the system energy balance.
  • 22 operating states can be divided into three levels. The operating states of these three levels are shown in Figure 3.
  • the flow chart of the system operation state is shown in Figure 4.
  • the flow chart of the system operation state is shown in Figure 5.
  • the upper layer control of the system mainly controls the energy storage. To achieve system energy optimization, this optimization comes from the upper system's judgment on the electricity price during the electricity consumption period and the system load habits. For example, for a home user's DC microgrid system, it is in the morning to wake up, lunch, dinner and evening. The peak of electricity consumption, the upper layer controls the energy storage discharge; for the sunny day, from 9:00 to 15:00, it is the peak of power generation.
  • the upper layer can control the energy storage and charge, and the energy storage is used when the standby power peak is used.
  • the invention is mainly directed to the system stable operation strategy, and involves specific upper-level scheduling optimization control, which is not described too much here.
  • the upper-layer scheduling control strategy mainly controls the energy storage according to the demand.
  • the energy storage can be regarded as a power generation device.
  • the upper control flow chart is shown in Fig. 6.
  • the control of the bottom layer includes the control of each unit's own controller, including MPPT control of photovoltaic power generation, MPPT control of wind power generation, DC load DC/DC control and grid-connected DC/AC four-quadrant rectification control.
  • the bottom control core is connected to the grid.
  • the DC/AC four-quadrant rectification control is the key to maintaining stable operation of the DC bus voltage.
  • the off-grid microgrid system is shown in Figure 7.
  • the off-grid microgrid system usually uses energy storage as a stable compensation energy to suppress the output fluctuation of new energy generation, thus ensuring the stability of the load side output and stable operation of the system.
  • the state-of-the-art DC microgrid state coding method is also adopted, and the energy storage-based DC microgrid system strategy is adopted.
  • the energy storage is used to ensure real-time power balance, and energy storage is used as a stable operation of the system.
  • the stable operation status of the off-grid microgrid system is shown in Table 4:
  • Micro source load Energy storage Power grid system status Status description 1 00 00 00 00 00000000 System stop 2 00 01 11 00 00011100 Energy storage ⁇ load 3 11 00 01 00 11000100 Micro-source ⁇ energy storage 4 11 01 01 00 11010100 Micro source ⁇ load+energy storage 5 11 01 00 00 11010000 Micro source ⁇ load 6 11 01 11 00 11011100 Micro source + energy storage ⁇ load
  • the system operates stably through real-time switching of five operating modes, and its operating state is shown in Figure 9.
  • the off-grid DC microgrid system has a relatively simple operating state, only two levels of state, the first level of five modes of operation switching, the second level, when the energy storage is full or lack of power, the MGCC needs to perform micro-source output or load.
  • Control, off-grid DC microgrid operating state is shown in Figure 8.
  • the off-grid DC microgrid system realizes stable operation of the system through operation state switching, and the energy storage battery maintains the DC bus voltage stability;
  • the MGCC controller needs to achieve system energy balance through load control and micro-source output power control according to the energy storage state, and the corresponding control state can be switched from the corresponding state.
  • the operation strategy of the DC microgrid is as shown in Figure 9. After the system starts running, it is detected whether it is connected to the network. If yes, it is determined whether the SOC (State of Charge) is greater than a preset upper threshold. If it is greater than, Explain that the energy storage is sufficient, limit the energy storage and charging, and then the grid-connected self-operating mode. If it is not greater than, continue to judge whether the energy storage SOC is less than the lower threshold. If yes, it indicates that the energy storage is insufficient, the energy storage discharge is limited, and then the process ends. After the system starts running, if the detection is not connected to the network, it is determined whether the energy storage SOC is greater than a preset upper threshold. If yes, the load operation mode is tracked.
  • SOC State of Charge
  • the off-grid self-operation mode determines that the current energy storage is insufficient, and after removing the unimportant load, it is determined whether the energy storage SOC is less than the preset lower limit threshold, and if not less than, the off-network self-running mode is still performed, if If it is less than, then the new energy source is controlled to charge only the energy storage part, the DC side load is disconnected, and then the process ends.
  • the system operation realizes the system operation through the upper layer control and the lower layer control.
  • the upper layer control In the grid connection state, the upper layer control only needs to judge the energy storage state to the energy storage control.
  • the upper and lower thresholds for the energy storage judgment need to be configured according to the capacity of each unit of the system.
  • the system self-operating mode is automatically controlled by the underlying controller; in the off-grid operating state, the upper layer control needs to control the power storage device and the load to determine the energy storage state, and the upper and lower thresholds for energy storage judgment are required.
  • the system self-run mode is automatically controlled by the underlying controller.
  • one of the inventions created by the present invention is to propose a pure DC microgrid system structure, including a micro-source unit for photovoltaic power generation and wind power generation, a 2-stage pure DC load unit, a grid interface unit, Energy storage battery unit and DC bus, DC microgrid system realizes energy exchange through DC bus, and ensures stable operation of the system through stable control of DC bus; system operation control is completed by controller of each unit and system MGCC control, each unit Through the connection of the power electronic device and the DC bus, the unit controller realizes the power conversion flow by controlling the power electronic device, and the MGCC control maintains the stable operation of the whole system by monitoring and controlling the operation state of the system; due to the micro-source output power such as wind power generation and photovoltaic power generation With the change of environment, the DC load is affected by the user factor, the energy storage battery is controlled by scheduling, the system has multiple operating states, the system running state code and the running state flow graph analysis, and a DC microgrid system based on running state control

Abstract

一种直流微电网系统及其控制方法，其中，系统包括：光伏发电单元(201)和风力发电单元(202)组成的微源单元(20)、直流负荷单元(21)、电网接口单元(22)、储能电池单元(23)和直流母线(24)，其中，微源单元、直流负荷单元、电网接口单元、储能电池单元通过电力电子器件(25)与直流母线连接，通过直流母线实现能量交换，直流微电网系统通过微源单元、直流负荷单元、电网接口单元、储能电池单元各自的控制器以及微电网中央控制器MGCC共同控制，微电网中央控制器MGCC相对于各自的控制器为上层控制器。本方案实现了直流母线稳定控制，保证系统稳定运行。

Description

直流微电网系统及其控制方法
相关申请
本发明申请要求2017年01月18日申请的，申请号为201710035731.3，名称为“直流微电网系统及其控制方法”的中国专利申请的优先权，在此将其全文引入作为参考。
技术领域
本发明涉及微电网技术领域，具体而言，涉及一种直流微电网系统及其控制方法。
背景技术
随着化石能源储量不断减少，环境问题日益突出，促使新能源技术的快速发展和广泛应用，以新能源发电技术为基础的微电网技术快速发展，直流微电网以其本身技术应用优势成为研究和应用的热点，同时电器不断直流化的趋势，促使家庭用电向效率更高的直流化方向发展，将新能源发电技术和直流配电结合的直流微电网技术将是未来发展的一个方向。
传统的配电系统中电能由发电端到用电端单向流动，而以新能源利用为基础的微电网系统中分布式新能源、电网、负载和储能之间存在能量交互，有别于传统电网系统的能量单向流动，微电网系统运行存在多种运行模式或者方式。对于直流微电网系统来说，直流母线是系统能量交换的中介，直流微电网中的多种分布式能源、储能、负载和电网通过电力电子变流装置接入直流母线，直流微电网系统中多个单元通过直流母线实现能量交换，保证直流母线电压稳定对系统稳定运行有着重要意义。
针对相关技术中如何提高直流母线电压的稳定的问题，目前尚未提出有效地解决方案。
发明内容
本发明提供了一种直流微电网系统及其控制方法，以提高直流母线电压的稳定。
为解决上述技术问题，根据本公开实施例的一个方面，本发明提供了一种直流微电网系统，包括：光伏发电单元和风力发电单元组成的微源单元、直流负荷单元、电网接口单元、储能电池单元和直流母线，其中，微源单元、直流负荷单元、电网接口单元、储能电池单元通过电力电子器件与直流母线连接，通过直流母线实现能量交换，直流微电网系统通过微源单元、直流负荷单元、电网接口单元、储能电池单元各自的控制器以及微电网中央控制器MGCC共同控制，微电网中央控制器MGCC相对于各自的控制器为上层控制器。
进一步地，风力发电单元采用包括整流和升压变换器的电力电子器件接入直流母线连 接。
进一步地，风力发电单元通过最大功率追踪MPPT控制器控制。
进一步地，光伏发电单元采用包括升压变换器的电力电子器件接入直流母线连接。
进一步地，光伏发电单元通过最大功率追踪MPPT控制器控制。
进一步地，储能电池单元采用包括升降压变换器的电力电子器件接入直流母线连接。
进一步地，储能电池单元采用包括升降压变换器的电力电子器件接入直流母线连接。
进一步地，储能电池单元通过充放电控制器控制。
进一步地，电网接口单元控制电网采用包括三相全桥逆变器的电力电子器件接入直流母线连接。
进一步地，电网接口单元通过四象限整流控制器控制。
进一步地，直流负荷单元为二级纯直流负荷单元。
进一步地，电力电子器件包括：DC/DC交换器，和/或，AC/DC交换器。
进一步地，直流微电网系统包括并网工作形态和离网工作形态，其中，在直流微电网系统处于并网工作形态时接入外部电网系统，将该外部电网作为补偿能源以抑制微源单元发电输出波动和负载波动；在直流微电网系统处于离网工作形态时未接入外部电网系统，将储能电池单元作为补偿能源以抑制微源单元发电输出波动和负载波动。
根据本公开实施例的另一方面，提供了一种直流微电网系统的控制方法，直流微电网系统包括：由光伏发电单元和风力发电单元组成的微源单元、直流负荷单元、电网接口单元、储能电池单元和直流母线，其中，微源单元、直流负荷单元、电网接口单元、储能电池单元通过电力电子器件与直流母线连接，方法包括：通过微源单元、直流负荷单元、电网接口单元、储能电池单元各自的控制器以及系统微电网中央控制器共同控制直流微电网系统各个单元通过直流母线实现能量交换，其中，微电网中央控制器MGCC相对于各自的控制器为上层控制器。
进一步地，直流微电网系统包括并网工作形态和离网工作形态，其中，在直流微电网系统处于并网工作形态时接入外部电网系统，将该外部电网作为补偿能源以抑制微源单元发电输出波动和负载波动；在直流微电网系统处于离网工作形态时未接入外部电网系统，将储能电池单元作为补偿能源以抑制微源单元发电输出波动和负载波动。
进一步地，在通过微源单元、直流负荷单元、电网接口单元、储能电池单元各自的控制器以及系统微电网中央控制器共同控制直流微电网系统各个单元通过直流母线实现能量交换之前，方法包括：预先对微源单元、直流负荷单元、电网接口单元、储能电池单元各个工作状态进行编码标识；将微源单元、直流负荷单元、电网接口单元、储能电池单元各个工作状态组成的系统工作状态进行编码标识。
进一步地，预先对微源单元、直流负荷单元、电网接口单元、储能电池单元各个工作状态进行编码标识，包括：将微源单元、直流负荷单元、电网接口单元、储能电池单元工作过 程中对直流母线能量流入流出与否以及流入流出方向为依据，确定其工作状态；对微源单元、直流负荷单元、电网接口单元、储能电池单元各个工作状态进行编码标识
进一步地，对微源单元、直流负荷单元、电网接口单元、储能电池单元各个工作状态进行编码标识，包括：将微源单元能量不流入直流母线时，编码为第一标识，表征微源单元处于断开工作状态；将微源单元能量流入直流母线时，编码为第二标识，表征微源单元处于接入工作状态；将直流负荷单元与直流母线无能量交互时，编码为第一标识，表征直流负荷单元处于断开工作状态；将直流母线能量流入直流负荷单元时，编码为第三标识，表征直流负荷单元处于接入工作状态；将储能电池单元能量不流入直流母线时，编码为第一标识，表征储能电池单元处于断开工作状态；将储能电池单元能量流入直流母线时，编码为第二标识，表征储能电池单元处于充电工作状态；将直流母线能量流入储能电池单元时，编码为第三标识，表征储能电池单元处于充电工作状态；将电网接口单元能量不流入直流母线时，编码为第一标识，表征电网接口单元处于断开工作状态，直流微电网系统处于离网工作形态；将电网接口单元能量流入直流母线时，编码为第二标识，表征电网接口单元处于接入工作状态，直流微电网系统处于并网工作形态；将直流母线能量流入电网接口单元时，编码为第三标识，表征电网接口单元处于用电工作状态。
进一步地，第一标识为00，第二标识为11，第三标识为01。
进一步地，将微源单元、直流负荷单元、电网接口单元、储能电池单元各个工作状态组成的系统工作状态进行编码标识，包括：将微源单元、直流负荷单元、电网接口单元、储能电池单元各个工作状态对应的编码标识按照预设顺序进行组合，组成系统工作状态的编码标识，每个系统工作状态的编码标识对应一种系统工作状态。
进一步地，通过微源单元、直流负荷单元、电网接口单元、储能电池单元各自的控制器以及系统微电网中央控制器共同控制直流微电网系统各个单元通过直流母线实现能量交换，包括：在直流微电网系统处于并网工作形态时，将该外部电网作为补偿能源抑制微源单元发电输出波动和负载波动控制，以保证母线电压稳定，储能电池单元仅响应MGCC的控制策略。
进一步地，通过微源单元、直流负荷单元、电网接口单元、储能电池单元各自的控制器以及系统微电网中央控制器共同控制直流微电网系统各个单元通过直流母线实现能量交换，包括：在直流微电网系统处于离网工作形态时，将储能电池单元作为补偿能源以抑制微源单元发电输出波动和负载波动，以保证母线电压稳定。
在本发明中，提出一种纯直流微电网系统结构，包含光伏发电和风力发电的微源单元(发电单元)、直流负荷单元、电网接口单元、储能电池单元和直流母线，直流微电网系统通过直流母线实现能量交换，通过对直流母线稳定控制保证系统稳定运行；系统运行控制通过每个单元的控制器和系统MGCC(微电网中央控制器)控制共同完成，每个单元通过电力电子器件与直流母线连接，单元控制器通过对电力电子器件控制实现电能变换流动，MGCC控制通过对系统运行状态监测控制调度维持整个系统稳定运行，该直流微电网系统提供直流化用电， 为风力发电和光伏发电等新能源利用提供解决方案，减少新能源发电转换环节，提高电能利用效率，同时对直流母线稳定控制，保证系统稳定运行。
附图说明
图1是本发明根据实施例的直流微电网系统的一种可选的结构框图；
图2是本发明根据实施例的直流微电网系统的控制方法中并网型微电网系统的一种可选的结构示意图；
图3是本发明根据实施例的直流微电网系统的控制方法中并网型微电网系统一种可选的运行状态流图；
图4是本发明根据实施例的直流微电网系统的控制方法中储能放电时并网型直流微电网系统一种可选的运行状态流图；
图5是本发明根据实施例的直流微电网系统的控制方法中储能充电时并网型直流微电网系统一种可选的运行状态流图；
图6是本发明根据实施例的直流微电网系统的控制方法中上层控制并网型直流微电网系统一种可选的运行状态流图；
图7是本发明根据实施例的直流微电网系统的控制方法中离网型直流微电网系统一种可选的结构示意图；
图8是本发明根据实施例的直流微电网系统的控制方法中离网型直流微电网系统一种可选的结构示意图；以及
图9是本发明根据实施例的直流微电网系统一种可选的运行策略流程示意图。
具体实施方式
这里将详细地对示例性实施例进行说明，其示例表示在附图中。下面的描述涉及附图时，除非另有表示，不同附图中的相同数字表示相同或相似的要素。以下示例性实施例中所描述的实施方式并不代表与本发明相一致的所有实施方式。相反，它们仅是与如所附权利要求书中所详述的、本发明的一些方面相一致的装置和方法的例子。
实施例1
下面结合附图对本发明提供的直流微电网系统进行说明。
图1示出本发明的实施例的直流微电网系统的一种可选的结构框图，如图1所示，该直流微电网系统包括：光伏发电单元201和风力发电单元202组成的微源单元20、直流负荷单元21、电网接口单元22、储能电池单元23和直流母线24，其中，微源单元20、直流负荷单元21、电网接口单元22、储能电池单元23通过电力电子器件25与直流母线24连接，通过直流母线24实现能量交换，直流微电网系统通过微源单元20、直流负荷单元21、电网接口 单元22、储能电池单元23各自的控制器以及微电网中央控制器MGCC共同控制，微电网中央控制器MGCC相对于各自的控制器为上层控制器。
在本发明的上述实施方式中，提出一种纯直流微电网系统结构，包含光伏发电和风力发电的微源单元(发电单元)、直流负荷单元、电网接口单元、储能电池单元和直流母线，直流微电网系统通过直流母线实现能量交换，通过对直流母线稳定控制保证系统稳定运行；系统运行控制通过每个单元的控制器和系统MGCC(微电网中央控制器)控制共同完成，每个单元通过电力电子器件与直流母线连接，单元控制器通过对电力电子器件控制实现电能变换流动，MGCC控制通过对系统运行状态监测控制调度维持整个系统稳定运行，该直流微电网系统提供直流化用电，为风力发电和光伏发电等新能源利用提供解决方案，减少新能源发电转换环节，提高电能利用效率，同时对直流母线稳定控制，保证系统稳定运行。
进一步地，作为优选，风力发电单元采用包括整流和升压变换器的电力电子器件接入直流母线连接。风力发电单元通过最大功率追踪MPPT控制器控制。光伏发电单元采用包括升压变换器的电力电子器件接入直流母线连接。光伏发电单元通过最大功率追踪MPPT控制器控制。储能电池单元采用包括升降压变换器的电力电子器件接入直流母线连接。储能电池单元采用包括升降压变换器的电力电子器件接入直流母线连接。储能电池单元通过充放电控制器控制。电网接口单元控制电网采用包括三相全桥逆变器的电力电子器件接入直流母线连接。电网接口单元通过四象限整流控制器控制。
优选地，直流负荷单元为二级纯直流负荷单元。
此外，电力电子器件包括：DC/DC交换器，和/或，AC/DC交换器。
具体工作过程中，直流微电网系统包括并网工作形态和离网工作形态，其中，在直流微电网系统处于并网工作形态时接入外部电网系统，将该外部电网作为补偿能源以抑制微源单元发电输出波动和负载波动；在直流微电网系统处于离网工作形态时未接入外部电网系统，将储能电池单元作为补偿能源以抑制微源单元发电输出波动和负载波动。
实施例2
基于上述实施例1中提供的直流微电网系统，本发明可选的实施例2还提供了一种直流微电网系统的控制方法，直流微电网系统包括：由光伏发电单元和风力发电单元组成的微源单元、直流负荷单元、电网接口单元、储能电池单元和直流母线，其中，微源单元、直流负荷单元、电网接口单元、储能电池单元通过电力电子器件与直流母线连接，方法包括：通过微源单元、直流负荷单元、电网接口单元、储能电池单元各自的控制器以及系统微电网中央控制器共同控制直流微电网系统各个单元通过直流母线实现能量交换，其中，微电网中央控制器MGCC相对于各自的控制器为上层控制器。
进一步地，直流微电网系统包括并网工作形态和离网工作形态，其中，在直流微电网系统处于并网工作形态时接入外部电网系统，将该外部电网作为补偿能源以抑制微源单元发电输出波动和负载波动；在直流微电网系统处于离网工作形态时未接入外部电网系统，将储能 电池单元作为补偿能源以抑制微源单元发电输出波动和负载波动。
在一个优选的实施方式中，在通过微源单元、直流负荷单元、电网接口单元、储能电池单元各自的控制器以及系统微电网中央控制器共同控制直流微电网系统各个单元通过直流母线实现能量交换之前，方法包括：预先对微源单元、直流负荷单元、电网接口单元、储能电池单元各个工作状态进行编码标识；将微源单元、直流负荷单元、电网接口单元、储能电池单元各个工作状态组成的系统工作状态进行编码标识。
进一步地，预先对微源单元、直流负荷单元、电网接口单元、储能电池单元各个工作状态进行编码标识，包括：将微源单元、直流负荷单元、电网接口单元、储能电池单元工作过程中对直流母线能量流入流出与否以及流入流出方向为依据，确定其工作状态；对微源单元、直流负荷单元、电网接口单元、储能电池单元各个工作状态进行编码标识
进一步地，对微源单元、直流负荷单元、电网接口单元、储能电池单元各个工作状态进行编码标识，包括：将微源单元能量不流入直流母线时，编码为第一标识，表征微源单元处于断开工作状态；将微源单元能量流入直流母线时，编码为第二标识，表征微源单元处于接入工作状态；将直流负荷单元与直流母线无能量交互时，编码为第一标识，表征直流负荷单元处于断开工作状态；将直流母线能量流入直流负荷单元时，编码为第三标识，表征直流负荷单元处于接入工作状态；将储能电池单元能量不流入直流母线时，编码为第一标识，表征储能电池单元处于断开工作状态；将储能电池单元能量流入直流母线时，编码为第二标识，表征储能电池单元处于充电工作状态；将直流母线能量流入储能电池单元时，编码为第三标识，表征储能电池单元处于充电工作状态；将电网接口单元能量不流入直流母线时，编码为第一标识，表征电网接口单元处于断开工作状态，直流微电网系统处于离网工作形态；将电网接口单元能量流入直流母线时，编码为第二标识，表征电网接口单元处于接入工作状态，直流微电网系统处于并网工作形态；将直流母线能量流入电网接口单元时，编码为第三标识，表征电网接口单元处于用电工作状态。
优选地，第一标识为00，第二标识为11，第三标识为01。
在一个实施方式中，上述将微源单元、直流负荷单元、电网接口单元、储能电池单元各个工作状态组成的系统工作状态进行编码标识，包括：将微源单元、直流负荷单元、电网接口单元、储能电池单元各个工作状态对应的编码标识按照预设顺序进行组合，组成系统工作状态的编码标识，每个系统工作状态的编码标识对应一种系统工作状态。
进一步地，通过微源单元、直流负荷单元、电网接口单元、储能电池单元各自的控制器以及系统微电网中央控制器共同控制直流微电网系统各个单元通过直流母线实现能量交换，包括：在直流微电网系统处于并网工作形态时，将该外部电网作为补偿能源抑制微源单元发电输出波动和负载波动控制，以保证母线电压稳定，储能电池单元仅响应MGCC的控制策略。
进一步地，通过微源单元、直流负荷单元、电网接口单元、储能电池单元各自的控制器以及系统微电网中央控制器共同控制直流微电网系统各个单元通过直流母线实现能量交换， 包括：在直流微电网系统处于离网工作形态时，将储能电池单元作为补偿能源以抑制微源单元发电输出波动和负载波动，以保证母线电压稳定。
下面结合具体实例来对上述方案进行进一步说明，以便更好的理解本方案：
直流微电网系统通常包含风力发电、光伏发电等分布式能源，直流负载，储能电池，电网接入单元和直流母线，风力发电采用整流+Boost(升压)变换器接入直流母线，通过MPPT(Maximum Power Point Tracking，最大功率点跟踪)控制器控制；光伏发电采用Boost变换器接入直流母线，通过MPPT控制器控制；储能电池采用Boost/Buck(升降压)变换器接入直流母线，通过充放电控制器控制；电网通过三相全桥逆变器接入直流母线，采用四象限整流控制，可实现电能双向流动；MGCC控制为上层控制器，与底层控制器相互通信并可以下发相应的控制指令。直流微电网系统分为并网型和离网型两种模式，两种模式下的直流微电网系统具有不同的控制方法和运行特点。
本发明提出的一种纯直流微电网系统结构，包含光伏发电和风力发电的微源单元、二级纯直流负荷单元、电网接口单元、储能电池单元和直流母线，直流微电网系统每个单元通过电力电子器件与直流母线连接，整个系统控制通过每个单元控制和MGCC控制器实现，整个控制系统分为两层，分别为每个单元的接入控制器和系统的MGCC控制器。并网型直流微电网和离网型直流微电网具有不同的运行特点，并网型微电网系统接入市电网系统，采用市电网作为稳定的补偿能源抑制新能源发电输出波动和负载波动，从而保证直流母线电压稳定和系统稳定运行；离网型微电网系统通常采用储能作为稳定的补偿能源抑制新能源发电输出波动，从而保证负载侧输出的稳定和系统稳定运行。
并网型直流微电网系统如图2所示，在图2中，PV为光伏发电单元，Wind为风力发电单元，Bat为储能电池单元，Grid为电网接入单元部分，Load为直流负载单元部分，DC BUS为直流母线。并网型直流微电网系统中，电网作为系统稳定运行的主要环节保证母线电压稳定，储能仅响应上层控制(MGCC)的优化调度策略。为了方便上层控制识别系统运行状态情况以及对系统运行状态进行下一步策略判断和控制，对直流微电网系统运行状态进行归类和划分，通过对各个单元和系统状态进行标识，整合出系统运作状态。具体状态分析，将各个单元能量对于系统以直流母线流入和流出为参考，“11”状态表示电流(能量)流入直流母线，“01”状态表示电流(能量)流出直流母线，“00”状态表示与直流母线无交互，各个单元具体状态表如表1所示：
Figure PCTCN2017081703-appb-000001
Figure PCTCN2017081703-appb-000002
表1
并网型微电网系统采用以电网稳定系统运行为主，储能仅响应上层调度的策略。当储能参与调度时，并网型直流微电网系统运行状态有22种，如表2所示：
序号 微源 负载 储能 电网 系统状态 系统状态说明
1 00 00 01 11 00000111 电网→储能
2 00 00 00 00 00000000 系统待机
3 00 00 11 01 00001101 储能→电网
4 00 01 01 11 00010111 电网→负载+储能
5 00 01 00 11 00010011 电网→负载
6 00 01 11 01 00011101 储能→电网+负载
7 00 01 11 00 00011100 储能→负载
8 00 01 11 11 000111111 储能+电网→负载
9 11 00 01 01 11000101 微源→储能+电网
10 11 00 01 00 11000100 微源→储能
11 11 00 01 11 11000111 微源+电网→储能
12 11 00 00 01 11000001 微源→电网
13 11 00 11 01 11001101 微源+储能→电网
14 11 01 01 01 11010101 微源→负载+储能+电网
15 11 01 01 00 11010100 微源→负载+储能
16 11 01 01 11 11010111 微源+电网→负载+储能
17 11 01 00 01 11010001 微源→负载+电网
18 11 01 00 00 11010000 微源→负载
19 11 01 00 11 11010011 微源+电网→负载
20 11 01 11 01 11011101 微源+储能→负载+电网
21 11 01 11 00 11011100 微源+储能→负载
22 11 01 11 11 11011111 微源+储能+电网→负载
表2
并网型直流微电网系统稳定运行的本质是运行状态实时切换，以保证直流母线电压稳定满足系统能量平衡。对于以上22种运行状态分析，将22种运行状态可以划分为三个层次，这三个层次运行状态如图3所示。
当上层控制不对储能下达调度指令时(即储能处于待机状态)，系统由底层控制处于自运行状态，并网型直流微电网系统基本运行状态如表3所示。
Figure PCTCN2017081703-appb-000003
Figure PCTCN2017081703-appb-000004
表3并网型直流微电网系统基本运行状态
上层控制对储能下达放电指令时，系统运行状态流图如图4所示，上层控制对储能下达充电指令时，系统运行状态流图如图5所示，系统上层控制主要对储能控制来实现系统能量优化，这种优化来源于上层系统对于用电时段电价及系统负荷使用习惯的判断，比如对于一个家庭用户的直流微电网系统，在早上起床、中午午餐、晚餐及傍晚等时段是用电高峰，上层控制储能放电；对于晴天的上午9点到15点都是发电的高峰，可以在发电量富余情况下上层控制储能充电，将能量存储以备用电高峰时使用，本发明主要针对系统稳定运行策略，涉及到具体上层调度优化控制，此处不作过多说明。上层调度控制策略主要根据需求对储能控制，当储能放电时可以将储能看作一个发电设备，当储能放电是可以看作一个用电设备，上层控制流图如图6所示。
对于底层控制包含每个单元自带控制器的控制，包含光伏发电的MPPT控制、风力发电的MPPT控制、直流负荷DC/DC控制和并网DC/AC四象限整流控制，底层控制核心为并网DC/AC四象限整流控制，是保持直流母线电压稳定运行的关键。
离网型微电网系统如图7所示，离网型微电网系统通常采用储能作为稳定的补偿能源抑制新能源发电输出波动，从而保证负载侧输出的稳定和系统稳定运行。
对于离网型直流微电网系统运行策略分析，同样采用并网型直流微电网的状态编码方法，采用基于储能的直流微电网系统策略，采用储能保证实时功率平衡，储能作为系统稳定运行的主要环节。离网型微电网系统稳定运行状态如表4所示：
序号 微源 负载 储能 电网 系统状态 状态说明
1 00 00 00 00 00000000 系统停止
2 00 01 11 00 00011100 储能→负载
3 11 00 01 00 11000100 微源→储能
4 11 01 01 00 11010100 微源→负载+储能
5 11 01 00 00 11010000 微源→负载
6 11 01 11 00 11011100 微源+储能→负载
表4离网型微电网运行状态
对于离网型微电网系统，通过5种运行模式实时切换实现系统稳定运行，其运行状态如图9所示。
离网型直流微电网系统运行状态相对简单，仅仅只有2个层次状态，第1层次5种运行模式切换，第2层次，当储能处于充满或者缺电状态需要MGCC对微源输出或者负荷进行控制，离网型直流微电网运行状态如图8所示。
运行状态图分析：
1.离网型直流微电网系统通过运行状态切换实现系统稳定运行，储能电池维持直流母线电压稳定；
2.离网型直流微电网系统运行状态MGCC控制器需根据储能状态情况通过负荷控制和微源输出功率控制来实现系统能量平衡，相应的控制状态可以从对应的状态切换。
直流微电网运行策略如图9所示，在系统运行开始后，检测是否为并网，若是，则判断储能SOC(State of Charge，荷电状态)是否大于预设的上限阈值，若大于，说明储能足够，限制储能充电，然后并网自运行模式，若不大于，继续判断储能SOC是否小于下限阈值，若是，说明储能不够，限制储能放电，然后结束该流程。在系统运行开始后，若检测不为并网，则判断储能SOC是否大于预设的上限阈值，若是，跟踪负荷运行模式，否则，继续判断储能SOC是否大于预设运行阈值，若大于，则离网自运行模式，若不大于，判定当前储能不充足，切除不重要的负荷后，继续判断储能SOC是否小于预设下限阈值，若不小于，仍进行离网自运行模式，若小于，则控制新能源发电仅给储能部分充电，直流侧负荷断开，然后结束进程。
系统运行通过上层控制和下层控制配合实现系统运行，在并网状态下，上层控制只需要判断储能状态对储能控制，对于储能判断的上限和下限阀值需要根据系统各个单元容量配置情况来设定，系统自运行模式由底层控制器自动控制实现；离网运行状态下，上层控制需要对需要判断储能状态对于发电装置和负荷进行控制，对于储能判断的上限和下限阀值需要根据系统各个单元容量配置情况来设定，系统自运行模式由底层控制器自动控制实现。
从以上描述中可以看出，本发明创造的发明点之一在于：提出一种纯直流微电网系统结构，包含光伏发电和风力发电的微源单元、2级纯直流负荷单元、电网接口单元、储能电池单元和直流母线，直流微电网系统通过直流母线实现能量交换，通过对直流母线稳定控制保证系统稳定运行；系统运行控制通过每个单元的控制器和系统MGCC控制共同完成，每个单元通过电力电子器件与直流母线连接，单元控制器通过对电力电子器件控制实现电能变换流动，MGCC控制通过对系统运行状态监测控制调度维持整个系统稳定运行；由于风力发电和光伏发电等微源输出功率随环境变化，直流负荷受用户因素影响，储能电池受到调度控制，系统存在多种运行状态，对系统运行状态编码和对运行状态流图分析，提出一种基于运行状态控制的直流微电网系统控制方法，通过对系统运行状态切换控制实现直流母线电压稳定控制，从而保证系统能量平衡，实现系统稳定运行。
本领域技术人员在考虑说明书及实践这里公开的发明后，将容易想到本发明的其它实施方案。本申请旨在涵盖本发明的任何变型、用途或者适应性变化，这些变型、用途或者适应性变化遵循本发明的一般性原理并包括本发明未发明的本技术领域中的公知常识或惯用技术手段。说明书和实施例仅被视为示例性的，本发明的真正范围和精神由下面的权利要求指出。
应当理解的是，本发明并不局限于上面已经描述并在附图中示出的精确结构，并且可以在不脱离其范围进行各种修改和改变。本发明的范围仅由所附的权利要求来限制。

Claims (22)

  1. 一种直流微电网系统，其特征在于，包括：光伏发电单元和风力发电单元组成的微源单元、直流负荷单元、电网接口单元、储能电池单元和直流母线，其中，所述微源单元、直流负荷单元、电网接口单元、储能电池单元通过电力电子器件与所述直流母线连接，通过所述直流母线实现能量交换，所述直流微电网系统通过所述微源单元、直流负荷单元、电网接口单元、储能电池单元各自的控制器以及微电网中央控制器MGCC共同控制，所述微电网中央控制器MGCC相对于所述各自的控制器为上层控制器。
  2. 根据权利要求1所述的系统，其特征在于，所述风力发电单元采用包括整流和升压变换器的电力电子器件接入所述直流母线连接。
  3. 根据权利要求1所述的系统，其特征在于，所述风力发电单元通过最大功率追踪MPPT控制器控制。
  4. 根据权利要求1所述的系统，其特征在于，所述光伏发电单元采用包括升压变换器的电力电子器件接入所述直流母线连接。
  5. 根据权利要求1所述的系统，其特征在于，所述光伏发电单元通过最大功率追踪MPPT控制器控制。
  6. 根据权利要求1所述的系统，其特征在于，所述储能电池单元采用包括升降压变换器的电力电子器件接入所述直流母线连接。
  7. 根据权利要求1所述的系统，其特征在于，所述储能电池单元采用包括升降压变换器的电力电子器件接入所述直流母线连接。
  8. 根据权利要求1所述的系统，其特征在于，所述储能电池单元通过充放电控制器控制。
  9. 根据权利要求1所述的系统，其特征在于，所述电网接口单元控制电网采用包括三相全桥逆变器的电力电子器件接入所述直流母线连接。
  10. 根据权利要求1所述的系统，其特征在于，所述电网接口单元通过四象限整流控制器控制。
  11. 根据权利要求1所述的系统，其特征在于，所述直流负荷单元为二级纯直流负荷单元。
  12. 根据权利要求1所述的系统，其特征在于，所述电力电子器件包括：DC/DC交换器，和/或，AC/DC交换器。
  13. 根据权利要求1所述的系统，其特征在于，所述直流微电网系统包括并网工作形态和离网工作形态，其中，
    在所述直流微电网系统处于并网工作形态时接入外部电网系统，将该外部电网作为补偿能源以抑制所述微源单元发电输出波动和负载波动；
    在所述直流微电网系统处于离网工作形态时未接入外部电网系统，将所述储能电池单元作为补偿能源以抑制所述微源单元发电输出波动和负载波动。
  14. 一种直流微电网系统的控制方法，其特征在于，所述直流微电网系统包括：由光伏发电单元和风力发电单元组成的微源单元、直流负荷单元、电网接口单元、储能电池单元和直流母线，其中，所述微源单元、直流负荷单元、电网接口单元、储能电池单元通过电力电子器件与所述直流母线连接，所述方法包括：
    通过所述微源单元、直流负荷单元、电网接口单元、储能电池单元各自的控制器以及系统微电网中央控制器共同控制所述直流微电网系统各个单元通过所述直流母线实现能量交换，其中，所述微电网中央控制器MGCC相对于所述各自的控制器为上层控制器。
  15. 根据权利要求14所述的方法，其特征在于，所述直流微电网系统包括并网工作形态和离网工作形态，其中，
    在所述直流微电网系统处于并网工作形态时接入外部电网系统，将该外部电网作为补偿能源以抑制所述微源单元发电输出波动和负载波动；
    在所述直流微电网系统处于离网工作形态时未接入外部电网系统，将所述储能电池单元作为补偿能源以抑制所述微源单元发电输出波动和负载波动。
  16. 根据权利要求15所述的方法，其特征在于，在所述通过所述微源单元、直流负荷单元、电网接口单元、储能电池单元各自的控制器以及系统微电网中央控制器共同控制所述直流微电网系统各个单元通过所述直流母线实现能量交换之前，所述方法包括：
    预先对所述微源单元、直流负荷单元、电网接口单元、储能电池单元各个工作状态进行编码标识；
    将所述微源单元、直流负荷单元、电网接口单元、储能电池单元各个工作状态组成的系统工作状态进行编码标识。
  17. 根据权利要求16所述的方法，其特征在于，所述预先对所述微源单元、直流负荷单元、电网接口单元、储能电池单元各个工作状态进行编码标识，包括：
    将所述微源单元、直流负荷单元、电网接口单元、储能电池单元工作过程中对所述直流母线能量流入流出与否以及流入流出方向为依据，确定其工作状态；
    对所述微源单元、直流负荷单元、电网接口单元、储能电池单元各个工作状态进行编码标识
  18. 根据权利要求17所述的方法，其特征在于，所述对所述微源单元、直流负荷单元、电网接口单元、储能电池单元各个工作状态进行编码标识，包括：
    将所述微源单元能量不流入所述直流母线时，编码为第一标识，表征所述微源单元处于断开工作状态；将所述微源单元能量流入所述直流母线时，编码为第二标识，表征所述微源单元处于接入工作状态；
    将所述直流负荷单元与所述直流母线无能量交互时，编码为第一标识，表征所述直流负 荷单元处于断开工作状态；将所述直流母线能量流入所述直流负荷单元时，编码为第三标识，表征所述直流负荷单元处于接入工作状态；
    将所述储能电池单元能量不流入所述直流母线时，编码为第一标识，表征所述储能电池单元处于断开工作状态；将所述储能电池单元能量流入所述直流母线时，编码为第二标识，表征所述储能电池单元处于充电工作状态；将所述直流母线能量流入所述储能电池单元时，编码为第三标识，表征所述储能电池单元处于充电工作状态；
    将所述电网接口单元能量不流入所述直流母线时，编码为第一标识，表征所述电网接口单元处于断开工作状态，所述直流微电网系统处于离网工作形态；将所述电网接口单元能量流入所述直流母线时，编码为第二标识，表征所述电网接口单元处于接入工作状态，所述直流微电网系统处于并网工作形态；将所述直流母线能量流入所述电网接口单元时，编码为第三标识，表征所述电网接口单元处于用电工作状态。
  19. 根据权利要求18所述的方法，其特征在于，所述第一标识为00，所述第二标识为11，所述第三标识为01。
  20. 根据权利要求18所述的方法，其特征在于，所述将所述微源单元、直流负荷单元、电网接口单元、储能电池单元各个工作状态组成的系统工作状态进行编码标识，包括：
    将所述微源单元、直流负荷单元、电网接口单元、储能电池单元各个工作状态对应的编码标识按照预设顺序进行组合，组成系统工作状态的编码标识，每个所述系统工作状态的编码标识对应一种系统工作状态。
  21. 根据权利要求15所述的方法，其特征在于，所述通过所述微源单元、直流负荷单元、电网接口单元、储能电池单元各自的控制器以及系统微电网中央控制器共同控制所述直流微电网系统各个单元通过所述直流母线实现能量交换，包括：
    在所述直流微电网系统处于并网工作形态时，将该外部电网作为补偿能源抑制所述微源单元发电输出波动和负载波动控制，以保证母线电压稳定，储能电池单元仅响应所述MGCC的控制策略。
  22. 根据权利要求15所述的方法，其特征在于，所述通过所述微源单元、直流负荷单元、电网接口单元、储能电池单元各自的控制器以及系统微电网中央控制器共同控制所述直流微电网系统各个单元通过所述直流母线实现能量交换，包括：
    在所述直流微电网系统处于离网工作形态时，将所述储能电池单元作为补偿能源以抑制所述微源单元发电输出波动和负载波动，以保证母线电压稳定。
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