CN113258775A - Active damping control method for direct-current micro-grid - Google Patents

Active damping control method for direct-current micro-grid Download PDF

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Publication number
CN113258775A
CN113258775A CN202110631482.0A CN202110631482A CN113258775A CN 113258775 A CN113258775 A CN 113258775A CN 202110631482 A CN202110631482 A CN 202110631482A CN 113258775 A CN113258775 A CN 113258775A
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converter
grid
direct
battery
direct current
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尹子晨
彭超
蔡明君
唐欣
柴金超
李勇
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Changsha University of Science and Technology
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Changsha University of Science and Technology
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    • H—ELECTRICITY
    • H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
    • H02M—APPARATUS FOR CONVERSION BETWEEN AC AND AC, BETWEEN AC AND DC, OR BETWEEN DC AND DC, AND FOR USE WITH MAINS OR SIMILAR POWER SUPPLY SYSTEMS; CONVERSION OF DC OR AC INPUT POWER INTO SURGE OUTPUT POWER; CONTROL OR REGULATION THEREOF
    • H02M3/00—Conversion of dc power input into dc power output
    • H02M3/02—Conversion of dc power input into dc power output without intermediate conversion into ac
    • H02M3/04—Conversion of dc power input into dc power output without intermediate conversion into ac by static converters
    • H02M3/10—Conversion of dc power input into dc power output without intermediate conversion into ac by static converters using discharge tubes with control electrode or semiconductor devices with control electrode
    • H02M3/145—Conversion of dc power input into dc power output without intermediate conversion into ac by static converters using discharge tubes with control electrode or semiconductor devices with control electrode using devices of a triode or transistor type requiring continuous application of a control signal
    • H02M3/155—Conversion of dc power input into dc power output without intermediate conversion into ac by static converters using discharge tubes with control electrode or semiconductor devices with control electrode using devices of a triode or transistor type requiring continuous application of a control signal using semiconductor devices only
    • H02M3/156—Conversion of dc power input into dc power output without intermediate conversion into ac by static converters using discharge tubes with control electrode or semiconductor devices with control electrode using devices of a triode or transistor type requiring continuous application of a control signal using semiconductor devices only with automatic control of output voltage or current, e.g. switching regulators
    • H02M3/158—Conversion of dc power input into dc power output without intermediate conversion into ac by static converters using discharge tubes with control electrode or semiconductor devices with control electrode using devices of a triode or transistor type requiring continuous application of a control signal using semiconductor devices only with automatic control of output voltage or current, e.g. switching regulators including plural semiconductor devices as final control devices for a single load
    • 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
    • H02J3/00—Circuit arrangements for ac mains or ac distribution networks
    • H02J3/12—Circuit arrangements for ac mains or ac distribution networks for adjusting voltage in ac networks by changing a characteristic of the network load
    • H02J3/14—Circuit arrangements for ac mains or ac distribution networks for adjusting voltage in ac networks by changing a characteristic of the network load by switching loads on to, or off from, network, e.g. progressively balanced loading
    • H02J3/144—Demand-response operation of the power transmission or distribution network
    • 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
    • H02J3/00—Circuit arrangements for ac mains or ac distribution networks
    • H02J3/24—Arrangements for preventing or reducing oscillations of power in networks
    • 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
    • H02J3/00—Circuit arrangements for ac mains or ac distribution networks
    • H02J3/28—Arrangements for balancing of the load in a network by storage of energy
    • H02J3/32—Arrangements for balancing of the load in a network by storage of energy using batteries with converting means
    • 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
    • H02J3/00—Circuit arrangements for ac mains or ac distribution networks
    • H02J3/36—Arrangements for transfer of electric power between ac networks via a high-tension dc link
    • 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
    • H02J3/00—Circuit arrangements for ac mains or ac distribution networks
    • H02J3/38—Arrangements for parallely feeding a single network by two or more generators, converters or transformers
    • H—ELECTRICITY
    • H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
    • H02M—APPARATUS FOR CONVERSION BETWEEN AC AND AC, BETWEEN AC AND DC, OR BETWEEN DC AND DC, AND FOR USE WITH MAINS OR SIMILAR POWER SUPPLY SYSTEMS; CONVERSION OF DC OR AC INPUT POWER INTO SURGE OUTPUT POWER; CONTROL OR REGULATION THEREOF
    • H02M1/00—Details of apparatus for conversion
    • H02M1/08—Circuits specially adapted for the generation of control voltages for semiconductor devices incorporated in static converters
    • H02M1/088—Circuits specially adapted for the generation of control voltages for semiconductor devices incorporated in static converters for the simultaneous control of series or parallel connected semiconductor devices
    • 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
    • H02J2300/00—Systems for supplying or distributing electric power characterised by decentralized, dispersed, or local generation
    • H02J2300/20—The dispersed energy generation being of renewable origin
    • H02J2300/22—The renewable source being solar energy
    • H02J2300/24—The renewable source being solar energy of photovoltaic origin
    • H02J2300/26—The renewable source being solar energy of photovoltaic origin involving maximum power point tracking control for photovoltaic 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
    • H02J2300/00—Systems for supplying or distributing electric power characterised by decentralized, dispersed, or local generation
    • H02J2300/20—The dispersed energy generation being of renewable origin
    • H02J2300/28—The renewable source being wind energy
    • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
    • Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
    • Y02B—CLIMATE CHANGE MITIGATION TECHNOLOGIES RELATED TO BUILDINGS, e.g. HOUSING, HOUSE APPLIANCES OR RELATED END-USER APPLICATIONS
    • Y02B70/00—Technologies for an efficient end-user side electric power management and consumption
    • Y02B70/30—Systems integrating technologies related to power network operation and communication or information technologies for improving the carbon footprint of the management of residential or tertiary loads, i.e. smart grids as climate change mitigation technology in the buildings sector, including also the last stages of power distribution and the control, monitoring or operating management systems at local level
    • Y02B70/3225—Demand response systems, e.g. load shedding, peak shaving
    • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
    • Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
    • Y02E—REDUCTION OF GREENHOUSE GAS [GHG] EMISSIONS, RELATED TO ENERGY GENERATION, TRANSMISSION OR DISTRIBUTION
    • Y02E10/00—Energy generation through renewable energy sources
    • Y02E10/50—Photovoltaic [PV] energy
    • Y02E10/56—Power conversion systems, e.g. maximum power point trackers
    • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
    • Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
    • Y02E—REDUCTION OF GREENHOUSE GAS [GHG] EMISSIONS, RELATED TO ENERGY GENERATION, TRANSMISSION OR DISTRIBUTION
    • Y02E60/00—Enabling technologies; Technologies with a potential or indirect contribution to GHG emissions mitigation
    • Y02E60/60—Arrangements for transfer of electric power between AC networks or generators via a high voltage DC link [HVCD]
    • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
    • Y04—INFORMATION OR COMMUNICATION TECHNOLOGIES HAVING AN IMPACT ON OTHER TECHNOLOGY AREAS
    • Y04S—SYSTEMS INTEGRATING TECHNOLOGIES RELATED TO POWER NETWORK OPERATION, COMMUNICATION OR INFORMATION TECHNOLOGIES FOR IMPROVING THE ELECTRICAL POWER GENERATION, TRANSMISSION, DISTRIBUTION, MANAGEMENT OR USAGE, i.e. SMART GRIDS
    • Y04S20/00—Management or operation of end-user stationary applications or the last stages of power distribution; Controlling, monitoring or operating thereof
    • Y04S20/20—End-user application control systems
    • Y04S20/222—Demand response systems, e.g. load shedding, peak shaving

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  • Engineering & Computer Science (AREA)
  • Power Engineering (AREA)
  • Dc-Dc Converters (AREA)

Abstract

The invention discloses an active damping control method of a bidirectional DC/DC converter of a direct-current micro-grid, belonging to the field of direct-current micro-grids. The method comprises the steps of establishing a direct current micro-grid model, simplifying the direct current micro-grid model, establishing a small-signal model, measuring signals, controlling active damping and solving the duty ratio. The invention adopts a virtual resistance control method to perform impedance remodeling, and reduces the amplitude of the output impedance of the bidirectional DC/DC converter to be far smaller than that of the output impedance of the load converter. The low-frequency amplitude of the output impedance is not changed, a hardware circuit is not added, the loss is not increased, the tidal current distribution of a system is not changed, the stability of the direct-current micro-grid is improved, and the safe and stable operation of the direct-current micro-grid is facilitated.

Description

Active damping control method for direct-current micro-grid
Technical Field
The invention relates to an active damping control method applied to a direct-current micro-grid storage battery bidirectional DC/DC converter, which is used for impedance remodeling and reducing the output impedance peak value of the storage battery bidirectional DC/DC converter so as to improve the stability of a system and belongs to the field of direct-current micro-grids.
Background
With the development of economy, the demand of people for electric power is increasing day by day. Most of the traditional power grids use fossil fuel as primary energy, which causes problems of greenhouse effect, environmental pollution and the like. In order to solve the above problems, scientists at home and abroad put forward the concept of micro-grid. The micro-grid is composed of a distributed power generation unit, an energy storage unit and a load, and a power electronic converter is mainly used for energy conversion and control in the micro-grid so as to meet the requirements of local loads on reliability and safety. The device can be used as an independent whole and can be operated in a grid-connected mode or an island mode. According to the distribution mode, the micro-grid can be divided into an alternating current micro-grid and a direct current micro-grid. Compared with an alternating-current micro-grid, the direct-current micro-grid has the main advantages that frequency and phase do not need to be tracked, only the direct-current bus voltage needs to be controlled, the line cost and the loss are low, the problems of reactive loss and stability do not need to be considered, and the operation reliability of the grid is higher.
With the development of the system structure of the direct-current micro-grid and the increase of the load types, the requirements on the reliability of the design and the stability of the operation of the direct-current micro-grid are gradually improved, and the research on the system stability is more important and complex. Firstly, a direct-current microgrid comprises a large number of electronic devices, and when the direct-current microgrid is in a working state, the mutual influence among control parameters of the devices can cause high-frequency oscillation of the microgrid; and secondly, the energy storage, the micro source and the load in the micro grid are connected with the direct current bus in parallel through the converter, different control structures or different control strategies are selected to ensure that the output equivalent impedance of the converter is different, and the voltage of the bus is possibly vibrated due to mismatching of the impedance.
At present, measures for improving the stability of the direct-current micro-grid mainly include an active damping method and a passive damping method. The passive damping method improves the stability of the system, but requires additional hardware devices, increases the volume, cost and loss required by the system, and has low conversion efficiency. Although the existing active damping method is easy to realize without adding a hardware circuit and without loss, the output impedance of the converter in a low frequency band is increased, and the steady-state power flow distribution of a system is influenced.
Disclosure of Invention
The invention provides an active damping control method of a bidirectional DC/DC converter of a storage battery of a direct-current micro-grid. The purpose is to solve the problem that the output equivalent impedance of a converter is different due to the fact that different control structures or different control strategies are selected in a direct-current micro-grid, bus voltage is vibrated, and the system is unstable.
In order to achieve the above object, an embodiment of the present invention provides an active damping control method for a bidirectional DC/DC converter of a DC microgrid battery, including:
step 1, building a direct current microgrid model: the direct current microgrid comprises a distributed power generation unit, an energy storage unit and a load unit. The distributed power generation unit is generally composed of renewable energy sources such as a fan and photovoltaic energy sources, and is connected to a direct current bus through an AC/DC or DC/DC converter; the energy storage unit is mainly energy storage equipment such as a storage battery and a super capacitor and is connected to the direct current bus through the bidirectional DC/DC converter; the load unit can be roughly divided into an alternating current load and a direct current load, and is connected to a direct current bus through a corresponding AC/DC or DC/DC converter; the distributed power generation unit, the energy storage unit and the load unit contained in the direct-current micro-grid all comprise a current transformer, a control system and a measuring element; the input ends of control systems of a distributed power generation unit, an energy storage unit and a load unit contained in the direct-current micro-grid are respectively connected with the output ends of the corresponding measuring elements, and the output ends of the control systems are connected with the input ends of the corresponding converters; the measuring elements in the direct-current micro-grid mainly comprise a voltage sensor and a current sensor on the direct-current bus side of a distributed power generation unit, an energy storage unit and a load unit, a voltage sensor and a current sensor on the distributed power supply side, the storage battery side and the constant-power load side and the like.
Step 2, simplifying a direct-current microgrid model: wind, light and other intermittent distributed power supplies adopt a maximum power tracking strategy to utilize renewable energy sources to the maximum extent. For a converter adopting power control, because the converter has similar external characteristics with a constant power load, the converter can be regarded as a special type of constant power load with negative output power when being modeled. Therefore, the direct current microgrid can be simplified into an equivalent model comprising a bidirectional DC/DC converter, a resistive load and a constant power load.
Step 3, establishing a small signal model: and establishing a small signal model of the bidirectional DC/DC converter by a state space averaging method to obtain the output impedance of the bidirectional DC/DC converter. The parameters of the controller are designed by adopting a double closed loop control strategy combining a bus voltage outer loop and an inductive current inner loop. According to the Middlebrook impedance criterion, in order to ensure the stability of the cascade system, the output impedance Z of the source converter is required to be satisfiedbcAnd load converter impedance ZLImpedance ratio of (T)m＝Zbc(s)/ZLThe Nyquist curve of(s) does not contain a point (-1, 0). The stability of the system is changed by changing the impedance of the source converter so that it does not intersect the load converter.
Step 4, signal measurement: measuring DC bus voltage u in DC micro-grid by DC bus side voltage sensordcMeasuring the input voltage u of the battery by means of a battery-side voltage sensorbMeasuring the input current i of the battery by means of a battery-side current sensorbAnd a direct current bus side current idc。
And 5, active damping control: the method of the parallel virtual resistance corrects the output impedance of the power supply side. The parallel resistor on the side of the bidirectional DC/DC converter of the storage battery can improve the stability of a cascade system, but the physical resistor can increase the cost and the resistance value cannot be flexibly valued. A virtual resistance control method is provided through equivalent transformation of a control structure to improve the stability of the system. The control is only to add a feedforward path on the basis of the original control, and the method is simple and feasible and is convenient to realize. Measuring DC bus voltage u in DC micro-grid by DC bus side voltage sensordcMultiplying by a factor k (k 1/R)vD) The output of the PI controller is fed back to the voltage loop for comparison to generate the given value of the current loop。
Step 6, duty ratio is obtained: and calculating to obtain the duty ratio D of the storage battery DC/DC converter, and sending a control signal to a switching tube of the storage battery DC/DC converter for PWM modulation control.
The scheme of the invention has the following beneficial effects:
the invention adopts an active damping control method of a bidirectional DC/DC converter of a storage battery of a direct-current micro-grid. The amplitude of the output impedance of the bidirectional DC/DC converter is reduced to be far smaller than that of the output impedance of the load converter, the low-frequency amplitude of the output impedance is not changed, the tidal current distribution of a system is not changed, a hardware circuit does not need to be added, the advantages of no loss are achieved, and the stability of the direct-current micro-grid is improved.
Drawings
FIG. 1 is a topological structure diagram of a direct current microgrid
FIG. 2 is a topology structure diagram of an energy storage bidirectional DC/DC converter
FIG. 3 is a control block diagram of an energy storage bidirectional DC/DC converter
FIG. 4 is a diagram of the DC bus voltage waveform for PI-only control
FIG. 5 is a voltage waveform diagram of an active damping control bus with added virtual resistors
Detailed Description
In order to make the technical problems, technical solutions and advantages of the present invention more apparent, the following detailed description is given with reference to the accompanying drawings and specific embodiments.
The invention provides an active damping control method of a bidirectional DC/DC converter of a storage battery of a direct-current micro-grid, aiming at the problems that energy storage, a micro source and a load in the micro-grid are connected with a direct-current bus in parallel through converters, different control structures or different control strategies are selected to ensure that the output equivalent impedances of the converters are different, and the voltage of the bus is likely to vibrate due to mismatching of the impedances.
As shown in fig. 1 to 3, an embodiment of the present invention provides an active damping control method for a bidirectional DC/DC converter of a DC microgrid battery, including: step 1, building a direct current microgrid model: the direct current microgrid comprises a distributed power generation unit, an energy storage unit and a load unit;step 2, simplifying a direct current micro-grid model, wherein wind and light can be seen as a special type of constant power load with negative output power during modeling; step 3, establishing a small signal model: and establishing a small signal model of the bidirectional DC/DC converter by a state space averaging method to obtain the output impedance of the bidirectional DC/DC converter. Step 4, signal measurement: measuring DC bus voltage u in DC micro-grid by DC bus side voltage sensordcMeasuring the input voltage u of the battery by means of a battery-side voltage sensorbMeasuring the input current i of the battery by means of a battery-side current sensorbAnd a direct current bus side current idc. And 5, active damping control: the method of the parallel virtual resistance corrects the output impedance of the power supply side. The resistor is connected in parallel on the side of the bidirectional DC/DC converter of the storage battery, so that the stability of a cascade system can be improved.
Wherein, the step 2 specifically comprises: wind, light and other intermittent distributed power supplies adopt a maximum power tracking strategy to utilize renewable energy sources to the maximum extent. For a converter adopting power control, because the converter has similar external characteristics with a constant power load, the converter can be regarded as a special type of constant power load with negative output power when being modeled. Therefore, the direct current microgrid can be simplified into an equivalent model comprising a bidirectional DC/DC converter, a resistive load and a constant power load.
Wherein, the step 3 specifically comprises: and establishing a small signal model of the bidirectional DC/DC converter by a state space averaging method to obtain the output impedance of the bidirectional DC/DC converter. The parameters of the controller are designed by adopting a double closed loop control strategy combining a bus voltage outer loop and an inductive current inner loop. The effect of the parallel resistance on the bi-directional DC/DC output impedance in the cascade system is then analyzed. According to the Middlebrook impedance criterion, in order to ensure the stability of the cascade system, the output impedance Z of the source converter is required to be satisfiedbcAnd load converter impedance ZLImpedance ratio of (T)m＝Zbc(s)/ZLThe Nyquist curve of(s) does not contain a point (-1, 0). The stability of the system is changed by changing the impedance of the source converter so that it does not intersect the load converter.
Wherein the content of the first and second substances,the step 4 specifically includes: measuring DC bus voltage u in DC micro-grid by DC bus side voltage sensordcMeasuring the input voltage u of the battery by means of a battery-side voltage sensorbMeasuring the input current i of the battery by means of a battery-side current sensorbAnd a direct current bus side current idc。
Wherein, the step 5 specifically comprises: a virtual resistance control method is provided through equivalent transformation of a control structure to improve the stability of the system. As shown in fig. 3, the control is only to add a feedforward path on the basis of the original control, and the method is simple and feasible and is convenient to implement. Measuring DC bus voltage u in DC micro-grid by DC bus side voltage sensordcMultiplying by a factor k (k 1/R)vD) And feeding back the output of the voltage loop PI controller for comparison to generate a given value of the current loop.
Wherein, the step 6 specifically comprises: and calculating to obtain the duty ratio D of the storage battery DC/DC converter, and sending a control signal to a switching tube of the storage battery DC/DC converter for PWM modulation control.
In order to verify the feasibility of an active damping control strategy and the theoretical correctness of the active damping control strategy, the active damping control method of the direct-current microgrid storage battery bidirectional DC/DC converter provided by the embodiment of the invention is subjected to simulation verification based on a Matlab/simulink simulation platform. The parameter settings in the simulation are shown in table 1.
TABLE 1 energy storage converter parameters
Figure BDA0003103723270000051
In order to verify the influence of the active damping control method based on the virtual resistor, simulation is respectively carried out under the condition of only PI control and the condition of adding active damping control, the initial load power is 6kW, 2kW is increased every second, the simulation time is 3s, and the waveforms of the simulation result are respectively shown in fig. 4 and 5. In the case of only PI control, the dc bus voltage oscillates sharply with an increase in load, and when t is 3s, the bus voltage oscillates, and the system is unstable. And the bus voltage added with the active damping control is kept stable.
According to the active damping control method of the bidirectional DC/DC converter of the storage battery of the direct-current microgrid, disclosed by the embodiment of the invention, the amplitude of the output impedance of the bidirectional DC/DC converter is reduced to be far smaller than that of the output impedance of the load converter without increasing a hardware circuit and loss, the low-frequency amplitude of the output impedance is not changed, the power flow distribution of a system is not changed, and the stability of the direct-current microgrid is improved.
While the foregoing is directed to the preferred embodiment of the present invention, it will be understood by those skilled in the art that various changes and modifications may be made without departing from the spirit and scope of the invention as defined in the appended claims.

Claims (6)

1. A direct current micro-grid active damping control method is characterized by comprising the following steps:
step 1, building a direct current microgrid model: the direct current microgrid comprises a distributed power generation unit, an energy storage unit and a load unit;
step 2, simplifying a direct-current microgrid model: during modeling, wind and light can be considered as a special type of constant power load with negative output power;
step 3, establishing a small signal model: establishing a small signal model of the bidirectional DC/DC converter by a state space averaging method to obtain the output impedance of the bidirectional DC/DC converter;
step 4, signal measurement: measuring DC bus voltage u in DC micro-grid by DC bus side voltage sensordcMeasuring the input voltage u of the battery by means of a battery-side voltage sensorbMeasuring the input current i of the battery by means of a battery-side current sensorbAnd a direct current bus side current idc；
And 5, active damping control: the method for connecting the virtual resistors in parallel corrects the output impedance of the power supply side, and the resistors are connected in parallel on the side of the bidirectional DC/DC converter of the storage battery, so that the stability of the cascade system can be improved.
2. The active damping control method applied to the direct current microgrid according to claim 1, characterized in that the step 2 specifically comprises:
a maximum power tracking strategy is adopted by wind, light and other intermittent distributed power sources, and for a converter adopting power control, the converter has similar external characteristics with a constant power load, so that the converter can be regarded as a special type of constant power load with negative output power during modeling.
3. The active damping control method applied to the direct current microgrid according to claim 2, characterized in that the step 3 specifically comprises:
the method comprises the steps of establishing a small signal model of the bidirectional DC/DC converter through a state space averaging method to obtain the output impedance of the bidirectional DC/DC converter, analyzing the influence of parallel resistors on the bidirectional DC/DC output impedance in a cascade system, judging the stability of the system, and changing the stability of the system through a method of changing the impedance of a source level converter to enable the impedance of the source level converter to be not intersected with a load converter.
4. The active damping control method applied to the direct current microgrid according to claim 3, characterized in that the step 4 specifically comprises:
measuring DC bus voltage u in DC micro-grid by DC bus side voltage sensordcMeasuring the input voltage u of the battery by means of a battery-side voltage sensorbMeasuring the input current i of the battery by means of a battery-side current sensorbAnd a direct current bus side current idc。
5. The active damping control method applied to the direct current microgrid according to claim 4, characterized in that the step 5 specifically comprises:
a virtual resistance control method is provided through equivalent transformation of a control structure to improve the stability of a system, and the control only adds a feedforward path on the basis of the original control and transmits voltage through a direct current bus sideSensor measuring DC bus voltage u in DC micro-griddcMultiplying by a factor k (k 1/R)vD) And feeding back the output of the voltage loop PI controller for comparison to generate a given value of the current loop.
6. The active damping control method applied to the direct current microgrid according to claim 5, characterized in that the step 6 specifically comprises:
and calculating to obtain the duty ratio D of the storage battery DC/DC converter, and sending a control signal to a switching tube of the storage battery DC/DC converter for PWM modulation control.
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