CN112977097B - Flexible intelligent body and solar unmanned aerial vehicle distributed hybrid energy system - Google Patents

Flexible intelligent body and solar unmanned aerial vehicle distributed hybrid energy system Download PDF

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CN112977097B
CN112977097B CN202110314900.3A CN202110314900A CN112977097B CN 112977097 B CN112977097 B CN 112977097B CN 202110314900 A CN202110314900 A CN 202110314900A CN 112977097 B CN112977097 B CN 112977097B
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flexible
controller
power
mppt
energy
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CN112977097A (en
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郑好银
张晓辉
席涵宇
张江浩
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Beijing Institute of Technology BIT
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    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B60—VEHICLES IN GENERAL
    • B60L—PROPULSION OF ELECTRICALLY-PROPELLED VEHICLES; SUPPLYING ELECTRIC POWER FOR AUXILIARY EQUIPMENT OF ELECTRICALLY-PROPELLED VEHICLES; ELECTRODYNAMIC BRAKE SYSTEMS FOR VEHICLES IN GENERAL; MAGNETIC SUSPENSION OR LEVITATION FOR VEHICLES; MONITORING OPERATING VARIABLES OF ELECTRICALLY-PROPELLED VEHICLES; ELECTRIC SAFETY DEVICES FOR ELECTRICALLY-PROPELLED VEHICLES
    • B60L50/00—Electric propulsion with power supplied within the vehicle
    • B60L50/50—Electric propulsion with power supplied within the vehicle using propulsion power supplied by batteries or fuel cells
    • B60L50/60—Electric propulsion with power supplied within the vehicle using propulsion power supplied by batteries or fuel cells using power supplied by batteries
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B60—VEHICLES IN GENERAL
    • B60L—PROPULSION OF ELECTRICALLY-PROPELLED VEHICLES; SUPPLYING ELECTRIC POWER FOR AUXILIARY EQUIPMENT OF ELECTRICALLY-PROPELLED VEHICLES; ELECTRODYNAMIC BRAKE SYSTEMS FOR VEHICLES IN GENERAL; MAGNETIC SUSPENSION OR LEVITATION FOR VEHICLES; MONITORING OPERATING VARIABLES OF ELECTRICALLY-PROPELLED VEHICLES; ELECTRIC SAFETY DEVICES FOR ELECTRICALLY-PROPELLED VEHICLES
    • B60L50/00—Electric propulsion with power supplied within the vehicle
    • B60L50/50—Electric propulsion with power supplied within the vehicle using propulsion power supplied by batteries or fuel cells
    • B60L50/60—Electric propulsion with power supplied within the vehicle using propulsion power supplied by batteries or fuel cells using power supplied by batteries
    • B60L50/66—Arrangements of batteries
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B60—VEHICLES IN GENERAL
    • B60L—PROPULSION OF ELECTRICALLY-PROPELLED VEHICLES; SUPPLYING ELECTRIC POWER FOR AUXILIARY EQUIPMENT OF ELECTRICALLY-PROPELLED VEHICLES; ELECTRODYNAMIC BRAKE SYSTEMS FOR VEHICLES IN GENERAL; MAGNETIC SUSPENSION OR LEVITATION FOR VEHICLES; MONITORING OPERATING VARIABLES OF ELECTRICALLY-PROPELLED VEHICLES; ELECTRIC SAFETY DEVICES FOR ELECTRICALLY-PROPELLED VEHICLES
    • B60L53/00—Methods of charging batteries, specially adapted for electric vehicles; Charging stations or on-board charging equipment therefor; Exchange of energy storage elements in electric vehicles
    • B64D27/40—
    • 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
    • H02J7/00—Circuit arrangements for charging or depolarising batteries or for supplying loads from batteries
    • H02J7/0013—Circuit arrangements for charging or depolarising batteries or for supplying loads from batteries acting upon several batteries simultaneously or sequentially
    • 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
    • H02J7/00—Circuit arrangements for charging or depolarising batteries or for supplying loads from batteries
    • H02J7/0047—Circuit arrangements for charging or depolarising batteries or for supplying loads from batteries with monitoring or indicating devices or circuits
    • H02J7/0048—Detection of remaining charge capacity or state of charge [SOC]
    • 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
    • H02J7/00—Circuit arrangements for charging or depolarising batteries or for supplying loads from batteries
    • H02J7/007—Regulation of charging or discharging current or voltage
    • H02J7/00712—Regulation of charging or discharging current or voltage the cycle being controlled or terminated in response to electric parameters
    • H02J7/00714—Regulation of charging or discharging current or voltage the cycle being controlled or terminated in response to electric parameters in response to battery charging or discharging current
    • 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
    • H02J7/00—Circuit arrangements for charging or depolarising batteries or for supplying loads from batteries
    • H02J7/007—Regulation of charging or discharging current or voltage
    • H02J7/007188—Regulation of charging or discharging current or voltage the charge cycle being controlled or terminated in response to non-electric parameters
    • H02J7/007192—Regulation of charging or discharging current or voltage the charge cycle being controlled or terminated in response to non-electric parameters in response to temperature
    • H02J7/007194—Regulation of charging or discharging current or voltage the charge cycle being controlled or terminated in response to non-electric parameters in response to temperature of the battery
    • 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
    • H02J7/00—Circuit arrangements for charging or depolarising batteries or for supplying loads from batteries
    • H02J7/34—Parallel operation in networks using both storage and other dc sources, e.g. providing buffering
    • H02J7/35—Parallel operation in networks using both storage and other dc sources, e.g. providing buffering with light sensitive cells
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B60—VEHICLES IN GENERAL
    • B60L—PROPULSION OF ELECTRICALLY-PROPELLED VEHICLES; SUPPLYING ELECTRIC POWER FOR AUXILIARY EQUIPMENT OF ELECTRICALLY-PROPELLED VEHICLES; ELECTRODYNAMIC BRAKE SYSTEMS FOR VEHICLES IN GENERAL; MAGNETIC SUSPENSION OR LEVITATION FOR VEHICLES; MONITORING OPERATING VARIABLES OF ELECTRICALLY-PROPELLED VEHICLES; ELECTRIC SAFETY DEVICES FOR ELECTRICALLY-PROPELLED VEHICLES
    • B60L2200/00—Type of vehicles
    • B60L2200/10—Air crafts
    • 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
    • Y02B10/00—Integration of renewable energy sources in buildings
    • Y02B10/10—Photovoltaic [PV]
    • 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
    • Y02T—CLIMATE CHANGE MITIGATION TECHNOLOGIES RELATED TO TRANSPORTATION
    • Y02T10/00—Road transport of goods or passengers
    • Y02T10/60—Other road transportation technologies with climate change mitigation effect
    • Y02T10/70—Energy storage systems for electromobility, e.g. batteries
    • 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
    • Y02T—CLIMATE CHANGE MITIGATION TECHNOLOGIES RELATED TO TRANSPORTATION
    • Y02T10/00—Road transport of goods or passengers
    • Y02T10/60—Other road transportation technologies with climate change mitigation effect
    • Y02T10/7072—Electromobility specific charging systems or methods for batteries, ultracapacitors, supercapacitors or double-layer capacitors
    • 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
    • Y02T—CLIMATE CHANGE MITIGATION TECHNOLOGIES RELATED TO TRANSPORTATION
    • Y02T90/00—Enabling technologies or technologies with a potential or indirect contribution to GHG emissions mitigation
    • Y02T90/10—Technologies relating to charging of electric vehicles
    • Y02T90/14—Plug-in electric vehicles

Abstract

The invention discloses a distributed hybrid energy system of a flexible intelligent body and a solar unmanned aerial vehicle; the flexible intelligent body is a core module of the distributed hybrid energy system and is formed by packaging a power generation module and an energy storage module, the power generation module outputs peak power of a flexible photovoltaic module mainly through a flexible MPPT controller, and the energy storage module realizes energy output and storage of a lithium battery under monitoring and management of a BMS. BMS controller through I 2 And the C bus transmits data to the flexible MPPT controller, so that communication between the top-level energy controller of the active energy management strategy and the flexible MPPT controller is realized through the CAN bus. The advantage of the transient quick response of the capacitor is utilized to make up the defect of slow response of the lithium battery, thereby being beneficial to relieving the stress of the lithium battery and maintaining the stable voltage of the bus. The invention aims to provide a distributed hybrid energy system of a flexible intelligent body and a solar unmanned aerial vehicle, which improves the performance of related products.

Description

Flexible intelligent body and solar unmanned aerial vehicle distributed hybrid energy system
Technical Field
The invention relates to the field of power electronics and automation control, in particular to a distributed hybrid energy system of a flexible intelligent body and a solar unmanned aerial vehicle.
Background
The solar unmanned aerial vehicle has the characteristics of zero emission, no pollution, low noise and good stealth performance, is favored in military and civil applications, and relates to various aspects such as border military patrol, spark detection, emergency search and rescue, geological environment monitoring, communication relay platform construction and the like. The photovoltaic array is constructed by utilizing the light solar cell module, photovoltaic peak power is output through the single MPPT controller, and the centralized configuration scheme is easy to cause the inconsistency of the solar cell operation due to the shielding of the outside and the accumulation of dust, so that the power-voltage characteristic curve of the solar cell has obvious nonlinearity and a plurality of peak points, and the power mismatch problem of the system is serious. The distributed energy system is based on the solar cell module, and the module-level MPPT controller is designed, so that the defects of the centralized system are greatly relieved. The lithium battery is used as a typical power source of the unmanned aerial vehicle, redundant energy is stored except for supplying power to a load, so that the endurance capacity is improved, and the solar unmanned aerial vehicle rarely manages the charge and discharge of the lithium battery to ensure the safety of the whole unmanned aerial vehicle, so that the service life of the lithium battery is seriously reduced. With the development of power electronics technology, gaN MOSFET driving technology has matured, and according to high-frequency power electronics technology, higher energy density is realized, and the advantages of light weight, thin thickness, softness, flexibility, good heat dissipation and the like of a flexible circuit board are utilized, so that in a distributed energy system, the energy density of the system is improved, maintainability is improved, and one of the overall design goals of a solar unmanned aerial vehicle is realized by light weight and flexible design. The reliability and the robustness of the unmanned aerial vehicle energy system are improved, redundancy design is carried out, the safety is guaranteed, a stable data communication protocol is established, and the like, which are important research contents of the flexible intelligent body and the solar unmanned aerial vehicle distributed hybrid energy system in response to the current hot spot problem (development of the electric unmanned aerial vehicle).
Disclosure of Invention
The invention aims to overcome the defects in the prior art, and provides a distributed hybrid energy system of a flexible intelligent body and a solar unmanned aerial vehicle.
A flexible agent comprising: a power generation module and an energy storage module;
wherein the power generation module includes: a flexible photovoltaic module and a flexible MPPT controller; the flexible photovoltaic module is formed by assembling a plurality of flexible solar battery monomers;
wherein, the energy storage module includes: a flexible lithium battery, a flexible BMS controller; the flexible lithium battery is used for providing energy for a load and storing energy transmitted by the flexible photovoltaic assembly (the flexible lithium battery with large-dimension range bending can provide energy for the load and store residual solar energy except for load requirements in real time under the control of the flexible BMS controller); the flexible BMS controller is used for on-line calculation of the SOC of the flexible lithium battery (regarding the content of the SOC calculated by the BMS controller, refer to the prior literature: liyang. Electric automobile lithium battery modeling and SOC calculation method research [ D ]. Changchun: jilin university, 2020.), monitoring of charge and discharge current, monitoring and control of temperature of the lithium battery and heating control (the function of heating the lithium battery to a constant temperature by utilizing an electric heating wire is achieved, and the energy output of the lithium battery is not greatly influenced when the unmanned aerial vehicle works in a high and cold environment);
The output end of the power generation module is connected with the flexible lithium battery of the load and the energy storage module respectively;
the flexible MPPT controller is used for controlling the flexible photovoltaic module to supply power to a load (namely controlling output voltage and output current), and controlling the flexible photovoltaic module to charge the flexible lithium battery (namely controlling output current to the flexible photovoltaic module to the flexible lithium battery);
the output end of the energy storage module is connected with a load so that the flexible lithium battery can supply power for the load; the input end of the energy storage module is connected with the output end of the power generation module so as to store the energy remained outside the load power supply requirement of the flexible photovoltaic module;
the flexible MPPT controller is used for controlling the flexible photovoltaic module to supply power to the load and controlling the flexible photovoltaic module to supply energy to the flexible lithium battery;
the output end of the energy storage module is connected with a load so that the flexible lithium battery can supply power for the load;
the BMS controller transmits the current SOC, charging and discharging current and lithium battery temperature data of the flexible lithium battery to the flexible MPPT controller;
and the MPPT controller controls the output current of the flexible photovoltaic module to the flexible lithium battery according to the SOC and the charging current transmitted by the BMS controller.
Further, the method for controlling the output current of the flexible photovoltaic module by the flexible MPPT controller is as follows:
s1, calculating an adjusted current I down ：
I down ＝I mppt_out,0 -I load -I chg_max
Wherein I is mppt_out，0 For the output current before adjustment of the power generation module, I load For the load current to be applied,I chg_max presetting a maximum charging current for the flexible lithium battery;
S2:
s2-1, if I down If the current is less than or equal to 0, the flexible MPPT controller does not adjust the output current of the power generation module;
s2-2, if I down When the current is larger than 0, the flexible MPPT controller adjusts the output current of the power generation module, and the current output of the flexible photovoltaic module is reduced by adopting a fixed-period variable step length, and the specific mode is as follows:
step 1, adjustment:
first, step 1 size I is calculated using the following formula step (1)：
In the above, the soc H Taking 0.85 of SOC as the upper limit value of the rated SOC of the lithium battery L Taking 0.65 as a rated SOC lower limit value; secondly, the MPPT controller controls the current of the power generation module:
I mppt_out，1 ＝I mppt_out，0 -I step (1)
in the above, I mppt_out，1 The current after the first step of the power generation module is adjusted;
again, confirm whether continued adjustment is needed:
when (when)Step 2, no adjustment is performed;
when (when)Step 2, adjusting;
……
step k adjustment:
first, the k-th step size I is calculated by the following formula step (k)：
Secondly, according to the size I of the kth step length calculated in the kth step step (k) The MPPT controller controls the current of the power generation module:
I mppt_out，k ＝I mppt_out，k-1 -I step (k)
I mppt_out，k-1 、I mppt_out，k The current after the k-1 step and the k step of the power generation module are respectively adjusted;
again, confirm whether continued adjustment is needed:
when (when)The k+1 step adjustment is not performed;
when (when)Then the k +1 step adjustment is performed.
Further, the hardware carrier of the flexible MPPT controller is a flexible circuit board (when the power of the single board controller is more than 10W and less than 50W, the overall thickness is not more than 2mm, when the power is more than 50W, the overall thickness is not more than 3mm, and the power ratio mass is more than 5W/g (which can be regarded as the definition of the flexible controller of the application)).
The layout of the flexible circuit board is that the digital control part and the power conversion part are respectively arranged at two sides of the flexible area, and the lead wire passing through the flexible area adopts a straight line form.
Further, the flexible circuit board realizes the synchronous voltage reduction function, and the maximum power determination mode is as follows:
for the Buck topology structure, the inductance of the passive device is an important factor influencing the overall thickness of the digital power supply, and the influence of the thickness of the flexible digital energy controller on the power of the flexible digital energy controller can be studied by inquiring the parameter of a given inductance. Increasing the switching frequency, the controller power density increases, but switching losses are exacerbated, and the above equation becomes extremely important for quantitative analysis of the relationship between overall thickness, power class, and power consumption of a flexible controller.
Further, the flexible MPPT controller employs: top-signal1-signal2-Bottom four-layer FPC, top layer is the installation surface of the component, signal1 is used for applying the ground copper in a large area, play and reduce the area of backflow loop, reduce the high-frequency EMI problem of the switching power supply self, signal2 is used for arrangement of the sensitive signal wire, and cooperate with Top layer to carry on the widening of the main circuit wire of the power, bottom can apply the ground copper in a large area, and carry on the strengthening of the main circuit wire of the power in the appropriate position, the turning department of the signal wire adopts the arc to be excessive; the MPPT controller can be a composite unit of current collecting source buck-boost conversion and lithium battery charge-discharge management, and is a typical switching problem of respective controllers corresponding to an input MPPT loop, an output voltage ring and an output current ring, except for realizing the tracking of the maximum power point of a solar battery;
the influence of the switching frequency on the junction temperature of the power device under the rated working condition is considered, the size of a passive device in the power topology is optimized, and the flexibility of the controller is improved. When the power circuit is laid out, the power circuit elements are placed in the nearest principle, the Top layer is used as the unique patch layer, a special flexible area is reserved between the power circuit module and the control circuit module according to circuit flexibility constraint, and wires without electrical properties are placed in corner areas of the FPC, so that the power circuit is prevented from being torn.
A distributed hybrid energy system of a solar unmanned aerial vehicle comprises a plurality of flexible intelligent bodies, a top-layer energy controller and a capacitor which are connected in series-parallel;
wherein, top layer energy controller includes: the embedded microprocessor is communicated with the flexible MPPT controllers in each flexible intelligent agent through the CAN bus to obtain the input and output voltage and current of the current flexible MPPT controllers, and the SOC and charge and discharge current of the flexible lithium battery.
The top-layer energy controller performs active energy management according to an online energy management strategy and issues a control command to the MPPT controller;
the capacitor is connected to the direct current bus, (the capacitor is used for relieving the stress of the flexible lithium battery, the characteristic of the transient quick response of the capacitor is utilized for compensating the characteristic of the slow response of the lithium battery), and the capacitor plays a role of controlling the bus voltage after the system enters a steady state.
Further, the interference degree of the top-layer energy controller on the flexible intelligent body is divided into four different modes:
the unmanned aerial vehicle is in the ground test state and defined as an offline mode;
the normal operation state of the solar unmanned aerial vehicle is defined as an on-line mode, the solar unmanned aerial vehicle needs to rely on a top-layer energy controller to carry out data communication with a flexible intelligent body, and a main energy management strategy is operated in real time to finish energy distribution, so that the safety state of the whole system needs to be monitored in real time;
The offline mode of the unmanned aerial vehicle is used for system debugging and maintenance;
when no fault occurs in the system, the state is a normal mode;
the energy system monitors the fault signal, and at the moment, the energy system enters an emergency mode from a normal mode, and in the emergency mode, the flexible intelligent body starts a redundancy scheme to protect.
The redundancy scheme adopts two sets of consistent MPPT controllers, and is divided into MMPPT and HMMPPT;
MMPPT is a main controller, HMMPPT is an auxiliary controller, hardware safety state marks of the MMPPT are monitored in real time, when the MMPPT has a short circuit event, an MMPPT bypass circuit plays a role in cutting the MMPPT from the circuit, and the HMMPPT plays a role of the MMPPT;
when the MMPPT is in a circuit breaking event, the HMPPT is directly connected into the circuit, plays the role of the MMPPT, and does not need to wait, (the rated power of an MPPT controller in the flexible intelligent body is far smaller than the load power of a distributed energy system and the upper limit power of all lithium batteries), and the characteristic of quick response of the capacitor is enough to ensure the influence of the off-line state waiting time of HMMPT millisecond level on the overall safety of the system).
Further, in the data transmission mode between the top-level energy controller and the flexible intelligent agent, roles of the master and the slave can be adjusted according to the received command, the top-level energy controller with the highest priority issues the command one by one in a query mode, then enters the receiving mode, and the slave responds according to the received identifier and the command format and the rule base. The communication mode avoids the defect that a host command cannot be responded in time under the condition of multiple slaves, and the command issuing time interval can be flexibly configured in the time domain, so that the extremely high requirement of continuous refreshing of slow response task data on a data storage medium is avoided.
Further, the design method of the distributed hybrid energy system is as follows:
under the constraint of considering load power, the power density of the flexible MPPT controller and the whole thickness of the FPC, the serial-parallel quantity of the lithium batteries is optimized to establish a distributed hybrid energy system;
p in the following rate The equality constraint of (2) means that under a certain light intensity condition, the sum of the power provided by the solar battery and the power provided by the current SOC lithium battery can meet the power requirement of a load;
J＝n sbat +n pbat
taking J as a parameter, and taking n corresponding to the minimum time of J sbat ，n pbat ；
Further, by establishing the reliability function R (t) through MTTF (mean time before failure), the influence of the number of photovoltaic modules, MPPT controllers, on the reliability can be analyzed:
λ p lambda is the failure rate of the photovoltaic module d For the failure rate of the power level of the flexible MPPT controller, t is the number of working years, and n is the MPPT controller in the single group stringM is the number of parallel strings in the distributed system.
Adopt the aforesaid flexible agent distributed hybrid energy system's solar unmanned aerial vehicle, flexible photovoltaic module pastes in the wing surface, and flexible MPPT controller and flexible BMS controller carry out modularization integrated design, flexible MPPT controller and flexible BMS controller after the modularization integration are combined with flexible lithium cell, hugs closely flexible photovoltaic module, installs in the wing skin inboard.
A solar unmanned aerial vehicle adopts the flexible intelligent body to supply energy to the unmanned aerial vehicle.
The application has the beneficial effects that:
first, the main technical problems solved by the present application are summarized as follows:
(1) The novel distributed hybrid energy system topology structure is provided for the solar unmanned aerial vehicle, constraint and optimization targets considered in the design of the distributed energy system are clarified, the serious power mismatch problem existing in the centralized system is relieved through the distributed topology structure, and the distributed energy design method makes up for a non-optimal scheme of the current energy system design;
(2) The output current of the solar battery is regulated according to the step length of the SOC of the lithium battery to control the charging current of the lithium battery, the lithium battery is heated in a low-temperature environment, a capacitor is introduced into a distributed energy topology, the service life of the lithium battery is greatly prolonged, and the charging current control mode of the lithium battery has great perfection on the functions of the current electric unmanned aerial vehicle BMS;
(3) The flexible intelligent body has the advantages that the flexible intelligent body is made of flexible materials, the defects that the current controller is heavy, poor in flexibility, large in cable loss and extremely inconvenient in assembly installation and layout are overcome, in addition, from the aspects of design and manufacturing of the FPC digital power supply, the flexibility of the FPC is improved, the power density is improved, and the gap of the FPC in the field of the digital power supply is made up;
(4) In the aspect of energy management, four different working modes are provided for the working priority of the top-layer energy controller and the bottom-layer energy controller;
(5) Aiming at the problem of the execution time of tasks, a CAN bus inquiry communication mode capable of changing the data receiving and transmitting rate is provided, the transmission failure rate of multi-controller data is avoided, and the gap of the current solar unmanned aerial vehicle power system redundancy scheme is made up by the double MPPT controller redundancy scheme.
Secondly, in order to implement the novel distributed energy system architecture, the technical scheme of the invention is as follows: the scheme has the advantages that the traditional centralized energy system architecture is abandoned, the photovoltaic array in the system is directly formed by directly connecting a plurality of solar cell assemblies in series to form a group string, or the group string is firstly formed and then connected in parallel to meet the total power requirement of the system, the whole photovoltaic array is connected with a heavy MPPT controller to output peak power, the scheme has the great disadvantage that if the problems of local shielding or battery aging and the like occur in the single group string, the output power of the whole array is subjected to fatal influence, the inconsistency among the group strings is considered, and when the problem of local hot spots is relieved by connecting bypass diodes in parallel, the failure and power oscillation of the traditional MPPT algorithm are caused. According to the distributed energy system, the power generation module and the energy storage module are subjected to flexibility, modularized design and layout, system power and bus voltage can be flexibly configured, the MPPT controller of the power generation module is subjected to redundancy design, the power generation module is matched with the lithium battery in the energy storage module to respond to load power requirements, and not only can energy be provided for a load in real time, but also residual solar energy except the load requirements can be stored. Considering that load fluctuation is large under unmanned aerial vehicle operation working condition, quick response of an energy system is required, the service life of the transient high-power output of the lithium battery is directly reduced, and particularly, a capacitor module is introduced into the system to prevent large-amplitude drop of bus voltage. From the aspects of energy system utilization rate and reliability, it is extremely important to realize active management of energy, and energy distribution is carried out for a top-level energy controller configured by the system, and the SOC of the current lithium battery, the output power of the solar battery and the load power are obtained in a CAN query mode. From the safety point of view, even if a single MPPT controller fails, the whole system is not paralyzed, and a redundant scheme is provided; from the aspect of energy transmission efficiency, the distributed scheme reduces the bus loss from the solar battery to the lithium battery; from the design point of view, the power level of the flexible controller is relatively low, the stress born by the components is small, and the external interference and the anti-interference capability are strong; from the aspect of layout maintenance, the flexible material is suitable for the solar unmanned aerial vehicle wing with obvious airfoil curvature, only local maintenance is needed, and large-scale monitoring is avoided;
Thirdly, the second application concept of the application aims at providing a design of distributed energy, and the main technical scheme is as follows: according to the flexible solar cell module and the flexible lithium battery, the total number of the lithium batteries is minimum under the constraint of ensuring load demand power, bus voltage, charging and discharging of the lithium batteries and the like. In the constraint, η mppt P mppt_max >V bat I chg_max The purpose is to ensure that the output power of the solar battery can realize constant current charging according to the maximum charging current, and the energy of the unmanned aerial vehicle in the climbing stage is mainly provided by a lithium battery, so that the requirement of n is met pbat I dsg_max V bus >P load_max . To increase the power level of the underlying flexible MPPT controller, the effect of the inductance on the power converter may be considered. In order to improve the adaptation of the unmanned aerial vehicle to the environment, P can be added rate Equation soft constraints to cope with changes in the environment during flight.
J＝n sbat +n pbat
Taking J as a parameter, and taking n corresponding to the minimum time of J sbat ，n pbat ；
Fourth, the third inventive concept of the present application is to provide a general design method of a distributed energy source; the utility model provides a flexible agent, solar energy unmanned aerial vehicle distributed hybrid energy system to improve energy system security, robustness, maintainability are the purpose, from distributed energy system architecture, have configured necessary flexible module, have compensatied distributed energy system in the design of bottom energy controller, the not enough in the aspect of the overall scheme optimal design.
Fifth, a fourth inventive concept of the present application is that: in order to improve the service life of the lithium battery, the lithium battery is protected, and the technical scheme of the application is as follows: firstly, a capacitor module is introduced into a distributed energy structure, and instant fluctuation of a load is responded immediately through charge and discharge of a capacitor, so that the influence of time delay of data transmission under the transient load and time delay of a top-layer energy controller running an energy management strategy on response delay of a lithium battery and a solar battery is relieved. Secondly, for the hybrid power system of the solar unmanned aerial vehicle, for safety, the charging current of the lithium battery is rarely controlled through an additional bidirectional buck-boost converter, the photovoltaic power of the solar unmanned aerial vehicle is often used as a complementary energy source of a full-machine load, if the light intensity is better in a light load environment, the charging current of the lithium battery is uncontrollable, and the lithium battery is definitely damaged greatly when the maximum power of the solar battery is output. In this case, the output current of the solar cell can be dynamically adjusted, where η 1 、η 2 、η 3 The adjustment coefficients are respectively related to the current battery SOC.
When the temperature of the lithium battery is reduced, the reaction rate of the electrode is also reduced, when the voltage of the battery is kept constant, the discharge current is reduced, the power output of the battery is also reduced, the solar unmanned aerial vehicle is used as a near space vehicle, and the low-temperature environment can have great influence on the operation of the lithium battery. The lithium battery heating system is extremely important, the outside of the lithium battery is wrapped by the flexible heating wire, and when the temperature of the lithium battery is monitored to be lower than the lower limit of the required temperature, the working current and the acting time of the heating wire can be adjusted through the PID regulator, so that the temperature of the lithium battery is controlled to be proper.
Sixth, the fifth inventive concept of the present application is to provide a flexible MPPT controller with high power density, which is innovatively embodied in: a high power density design method of an FPC digital energy controller, an FPC design method of the digital energy controller and flexibility optimization design. The flexible intelligent body suitable for the solar unmanned aerial vehicle is provided with a power generation module and an energy storage module, the MPPT controller not only has the capacity of outputting peak power to supply power to a load, but also can be used as a charger of a lithium battery, can be called a composite unit of current collecting source step-up and step-down conversion and lithium battery charging and discharging management, and is a typical switching problem of respective controllers corresponding to an input MPPT loop, an output voltage ring and an output current ring.
On structural layout, when being applied to unmanned aerial vehicle system, flexible solar cell array pastes in the wing surface, and flexible MPPT controller and flexible BMS controller carry out modularization integrated design, and combine with flexible lithium cell, hug closely flexible photovoltaic module, install in the wing skin inboard. The solar cell, MPPT controller, BMS controller, the connecting cable between the lithium cell shortens, and voltage class requirement reduces, and this kind of overall arrangement has very big help to unmanned aerial vehicle fuselage weight balance distribution.
Seventh, a sixth inventive concept of the present application is that: the FPC flexible digital energy controller power grade is determined, and the technical scheme of the application is as follows: the energy density of the system is improved with GaN MOSFET devices supporting drive frequencies up to megahertz, considering devices with integrated driver and MOSFET packaging. The maximum power supported by the inductor can be obtained from an inductance type selection formula of the synchronous Buck circuit, and the formula is as follows:
given a certain inductor, the inductance value, the temperature rise current and the saturation current of the inductor are determined, the temperature rise current of the inductor can be used for replacing the maximum current of a load, the ripple coefficient is determined according to the ripple requirement of the output voltage, the static operating point can be adjusted near D=0.5 for amplifying the voltage range input to the output of the converter, although the switching frequency of a power device can be increased, the size of the inductor and the capacitor can be reduced, the higher the driving frequency is, the higher the temperature of the device can be increased, the operating temperature of the device can be calculated according to the control mode and the driving frequency, the higher the temperature of the device is, the requirement of an additional heat dissipation device is avoided, and finally the balance point is found between the switching frequency and the size of the power inductor and the power size of the digital energy controller.
Eighth, a seventh inventive concept of the present application is that: the technical scheme of the application is as follows: the single-sided patch is adopted, a four-layer laminated structure is adopted for design, namely the mounting surface of the component is arranged on the surface of the circuit board, the back surface is reserved as a bonding surface with other materials, and the four-layer laminated structure adopts a Top-signal1-signal2-Bottom scheme. In order to improve the flexibility of the whole FPC during layout, the layout of the power level module is required to be prioritized, components of the power converter are arranged on the Top layer by adopting the principle of a minimum loop, and the overcurrent capacity of the main loop of the power supply is determined according to the thickness of copper and the width of a lead. A certain flexible region needs to be reserved between the control circuit and the power circuit, and the region width is determined according to a bending radius r= (10-15) ×t, wherein T is the plate thickness. When the FPC digital energy controller is wired, signal1 is used for large-area ground copper, the backflow loop area is reduced, the high-frequency EMI problem of the switching power supply is reduced, signal2 is used for arrangement of sensitive signal wires, the Top layer is cooperated for widening a main circuit wire of the power supply, the Bottom can be used for large-area ground copper, the main circuit wire of the power supply is reinforced at a proper position, arc-shaped transition is adopted at turning positions of the signal wires, wires without electrical properties are placed in corner areas of the FPC, and the wires are placed and torn. In the material selection of each layer, the top layer and the bottom layer are cover films with good flexibility and high temperature resistance, and the materials used for the two adjacent conductive layers can be non-adhesive flexible media so as to improve the flexibility of the flexible circuit board.
Ninth, an eighth inventive concept of the present application is that: the interference degree of the top layer energy controller to the bottom layer energy controller is divided into four different modes, and the technical scheme of the application is as follows: the unmanned aerial vehicle is in a ground test state and is defined as an offline mode, and the solar unmanned aerial vehicle is in a normal operation state and is defined as an online mode. The offline mode of the unmanned aerial vehicle is used for system debugging and maintenance, the online mode needs to rely on a top-layer energy controller to carry out data communication with a bottom-layer flexible intelligent body, a main energy management strategy is operated in real time so as to complete energy distribution, the safety state of the whole system needs to be monitored in real time, when the system does not have any faults, the state is a normal mode, once the energy system monitors fault signals, the energy system enters an emergency mode from the normal mode at the moment, the bottom-layer flexible intelligent body can be protected by a self-starting redundancy scheme in the emergency mode, and the top-layer energy controller does not interfere with the bottom-layer flexible intelligent body any more. The four different modes embody different environmental conditions and safety states of the solar unmanned aerial vehicle, and classification of the modes is beneficial to not affecting the safety of the system in the process of active energy management. The current solar unmanned aerial vehicle energy management system mostly stays in the ground platform test demonstration stage, and the main reason is that a solution for overcoming the active energy management strategy to introduce potential risks for the system safety is not found.
And the redundant scheme of the flexible MPPT controller in the power generation module adopts two sets of consistent MPPT controllers, namely MMPPT and HMMPPT, wherein the HMMPPT is used as an auxiliary controller, and the hardware safety state mark of the MMPPT is monitored in real time. When the MMPPT has a short circuit event, the HMMPPT plays a role of the MMPPT after being cleared from the system through the bypass circuit, the rated power of an MPPT controller in the flexible intelligent body is far smaller than the load power of the distributed energy system and the upper limit power of all lithium batteries, and the characteristic of quick response of the capacitor is enough to ensure the influence of the off-line waiting state of HMMPT millisecond level on the overall safety of the system. When the MMPPT has a circuit breaking event, the HMPPT is directly connected into the circuit, and the MMPPT is played without waiting.
Tenth, a ninth inventive concept of the present application is that: data query communication mode based on CAN bus and reliability evaluation scheme of distributed energy system;
the data inquiry communication mode of the CAN bus, namely the roles of the master and the slave CAN be adjusted according to the received command, the top-level energy controller with the highest priority issues the command one by utilizing the inquiry mode, then the slave enters a receiving mode, and the slave responds according to the received identifier and the command. Because the lithium battery, the solar battery and the capacitor response load have different durations, the data transmission should take the time of executing the fast and slow tasks into consideration so as to reduce excessive repeated sampling of the data and avoid extremely high requirements of continuous refreshing of the slow response task data on a data storage medium. The communication mode avoids the defect that the host command can not be responded in time under the condition of multiple slaves, and the command issuing time interval can be flexibly configured in the time domain.
According to the reliability evaluation scheme of the distributed energy system, a reliability function R (t) of the distributed energy system is established through MTTF (mean time before failure), and the influence of the number of photovoltaic modules and MPPT controllers on reliability is analyzed. The distributed energy system architecture of the solar unmanned aerial vehicle based on the flexible intelligent bodies is characterized in that n flexible intelligent bodies are connected in series to form a group string, m group strings are connected in parallel, only the influence of a power generation module on the system reliability is considered, when a solar cell module in the flexible intelligent bodies and a flexible MPPT controller break down, the reliability that at least one flexible intelligent body breaks down in each group string is defined to be consistent with the probability that a centralized energy system controller breaks down, then the influence of the change of m and n on the reliability of the distributed energy system can be analyzed, and the difference of the reliability of the centralized energy system and the reliability of the distributed energy system is compared.
The establishment of the reliability function of the distributed energy system is beneficial to quantitatively analyzing the reliability of the system in theory, and the qualitative evaluation is not performed intuitively any more, so that a new research scheme is provided for the reliability analysis of the energy system.
Drawings
The invention is described in further detail below in connection with the embodiments in the drawings, but is not to be construed as limiting the invention in any way.
Fig. 1 is a structural diagram of a distributed hybrid energy system of a flexible intelligent body and a solar unmanned aerial vehicle in embodiment 1.
Fig. 2 is a laminated structure diagram of the 2-layer FPC digital energy controller in example 1.
Fig. 3a is a schematic diagram of a simple bending test of the digital energy controller in example 1.
Fig. 3b is a schematic diagram of the limit bending test of the digital energy controller in example 1.
Fig. 4 is a simplified schematic diagram of a GaN MOSFET-based digital energy controller of example 1.
Fig. 5 is a flexible agent implemented in example 1.
Fig. 6 is a control block diagram of the flexible digital energy controller in example 1.
Fig. 7 is a flowchart of lithium battery charge management in example 1.
Fig. 8 is a design flow chart of a distributed energy system of a solar unmanned aerial vehicle based on a flexible agent in embodiment 1.
Fig. 9 is a simplified model of the reliability study of the distributed energy system in example 1.
Detailed Description
For a clearer, more complete description of the present invention, from the standpoint of specific implementations, reference will be made to the accompanying drawings, which form a part, but not all, of the embodiments of the invention that provide a single way of carrying out the innovative concepts presented, without excluding other ways of implementing the invention already mentioned.
Example 1: as shown in fig. 1, a flexible intelligent body, solar unmanned aerial vehicle distributed hybrid energy system includes: a plurality of flexible intelligent bodies, capacitors, loads and top-layer energy controllers. The flexible intelligent body is a core part of the distributed energy system of the solar unmanned aerial vehicle, has the advantages of flexibility, light weight and high efficiency, and is formed by packaging a power generation module and an energy storage module.
Wherein the power generation module includes: a flexible photovoltaic module and a flexible MPPT controller; the flexible photovoltaic module is formed by assembling a plurality of flexible solar battery monomers;
wherein, the energy storage module includes: a flexible lithium battery, a flexible BMS controller; the flexible lithium battery is used for providing energy for a load and storing energy transferred by the flexible photovoltaic module; the flexible BMS controller is used for on-line calculation of the SOC of the flexible lithium battery, monitoring of charge and discharge current and constant temperature control in a low-temperature environment;
the flexible MPPT controller is used for controlling the flexible photovoltaic module to supply power to the load and controlling the flexible photovoltaic module to charge the flexible lithium battery; the BMS controller is used for charging and discharging the SOC of the current battery, and the lithium battery temperature data passes through I 2 The C bus is uploaded to the flexible MPPT controller. For flexible MPPT controllers, flexible BMS controllers (hereinafter, on describing the hardware structure of the controller, referred to as flexible controllers):
The difference between the flexible controller and the rigid controller is mainly represented by the material of the circuit board and the lamination structure.
Fig. 2 is a laminated structure diagram of the 2-layer FPC controller in embodiment 1, which is composed of a top layer a, a middle layer B, and a bottom layer a from top to bottom;
the top layer A and the bottom layer A are the same in material;
the top layer a includes: covering film A1 and glue A2;
the intermediate layer B includes: a flexible board base material B;
the bottom layer A comprises: covering film A1 and glue A2;
the covering film has the functions of tearing prevention, short circuit prevention and the like, has the characteristics of strong heat resistance, quick heat dissipation and the like, is beneficial to improving the efficiency of the controller, and has the same function as the ink of the rigid circuit board;
the flexible base material is also called as flexible copper clad laminate, and is mainly responsible for conducting, insulating and supporting three aspects, and besides some basic performances of the rigid copper clad laminate, the flexible base material also has the characteristics of flexibility, thickness thinness and the like, and is used for high-performance ultra-fine circuits and high-dimensional stability devices. From top to bottom: copper plating layer B1, copper foil B2, substrate B3, copper foil B4, copper plating layer B5, upper and lower copper foils of the soft board substrate are wiring layers, and the thickness can be designed according to the overcurrent size and the line width of the main current path. The actual copper foil thickness has certain errors due to various process precision, and can be compensated by a copper plating mode;
The overall thickness of the FPC flexible controller is determined by the thickness of the substrate and the thickness of the device, the thickness of the substrate can be adjusted within the allowable range of material properties, the FPC template manufactured for the laminated structure shown in fig. 2 is shown in fig. 3, the overall thickness of the controller is only 2mm, and compared with a rigid circuit board, the quality of the FPC flexible controller is negligible. The bending diagrams are shown in fig. 3a and 3 b: the simple bending situation shown in fig. 3a is applicable to a curved structure with an excessively slow curvature; the extreme bending situation shown in fig. 3b is suitable for attachment to a barrel structure having a larger curved surface structure.
As can be seen from the two bending examples, the bending radius depends on the size of the non-device space, and if the whole board is uniformly arranged with rigid devices, the flexibility of the FPC will be severely affected and the function of the system will be directly affected. Special wiring considerations should be made when designing FPC digital power controllers.
The PCB circuit board of the flexible controller shown in fig. 3: in the layout, the digital control part and the power conversion part are respectively arranged at two sides of the flexible area, the lead wire passing through the flexible area adopts a straight line form, poor contact caused by the increase of bending times of the lead wire in a curve form is avoided, and part of the lead wire adopts arc connection to have similar effect, so that the flexibility of the FPC is enhanced, copper is applied to a large area in a blank area without electrical property, and the EMC performance of the circuit can be improved. In addition, the FPC controller can not use devices such as pins and bus bars like the rigid controller, so that the connection of the FPC and other circuits is difficult, particularly for a power circuit, the selection of an interface is required to meet the suitability requirement and the grade requirement of voltage and current, the reinforcement at the interface becomes a necessary means, and the crease and crack at the interface can be prevented by using PET, PI, back glue, metal or resin reinforcing plates through the reinforcement laminating and reinforcement pressing technology.
Besides the laminated structure, flexibility and FPC design scheme, the flexible controller improves the power density and the efficiency, and generally, the known conditions of the design are parameters such as input and output voltage and current of the controller, proper topological configuration is selected, the passive device can be selected according to volt-second balance and ampere-second balance, and particularly, the inductance of the step-down controller is selected according to the following formula:
the distributed energy system, the bus voltage, the output voltage and current of the flexible controller and the number of the flexible controllers are mutually coupled, so that the design of the distributed hybrid energy system of the solar unmanned aerial vehicle based on the flexible intelligent body is a continuous iterative process, the inductor is a main device for determining the flexibility and the power density of the flexible controller, various types of inductors can be selected according to the height requirement, the steady-state working condition of the controller is reversely deduced by utilizing the inductance value and the temperature rise current, and in the embodiment 1, the above formula is deformed to obtain the maximum power expression of the controller under given parameters:
the GaN MOSFET is utilized, the switching frequency can be controlled between 500Khz and 1Mhz, the conventional digital power supply relying on the Si MOSFET is mostly 100-200 kHz, when the switching frequency is increased by 3-5 times, the size of the inductor is reduced, and the inductance value is reduced, which is one of the important methods for the miniaturization design of the flexible controller.
Fig. 4 is a simplified schematic diagram of a digital energy controller based on GaN MOSFET in example 1, and integrated with GaN MOSFET and driver, integrated with LMG5200 MOSFET and additional inductor, capacitor, to form a synchronous Buck converter, with 36V input, 25.2V,3a output at 500Khz driving frequency, without additional heat sink, with a system efficiency as high as 98.5%. For the flexible MPPT controller, in the scheme design, the output end of the flexible MPPT controller has a wider MPP range as far as possible, and the flexible MPPT controller can adapt to the dynamic voltage of a lithium battery. While the above description has not been provided in detail with respect to the design of a multi-layer FPC for a flexible digital power controller, it will be apparent to those skilled in the art that the above description is sufficient to describe the context of the flexible FPC controller of the present invention.
Fig. 5 shows a flexible intelligent agent in embodiment 1, wherein the MPPT controller and the BMS are both flexible circuit boards (i.e., the aforementioned FPC flexible controller); the flexible photovoltaic module and the flexible lithium battery are used as matched power supplies of the controller, and the flexible photovoltaic module and the flexible lithium battery are not unique in selection. The material has the characteristics of light weight and flexibility, has the characteristics of light weight, miniaturization and high energy density after being designed, and has great application value in a distributed energy system, and the integrated package has great value in the aspect of wearable equipment. In the flexible intelligent agent, the function of the flexible MPPT controller is that the function of controlling the charging management of the lithium battery is realized besides the peak power of the solar battery.
FIG. 6 is a control block diagram of the flexible digital energy controller in example 1, which has an input voltage control loop, an output voltage control loop, and an output current control loop, wherein the control scheme is used in the distributed energy system to determine the working state according to the SOC of the lithium battery and the load power demand, and when the SOC is smaller and the load power is smaller, the output current control is performed and the charging is performed according to the maximum charging current when the voltage of the lithium battery is lower; when the SOC is smaller and the load power is larger, the problem of load power supply needs to be considered preferentially, so that the load power supply works at the maximum power point; when the SOC is large and the load power is small, the MPPT controller can control the output current, and the lithium battery is charged to a full-charge state as much as possible, and then the output voltage is controlled; when the SOC is large and the load power is large, the MPPT controller needs to work at the maximum power point.
For a distributed energy system of a solar unmanned aerial vehicle, the control strategy needs to give priority to the safety of the system. When the load power requirement is not considered, an adaptive control strategy can be adopted, namely three control loops work simultaneously, and the loop with the smallest output of the PI controller has the highest output priority in priority judgment.
When the load is lighter, the main energy output by the solar battery is used for charging the lithium battery, if the charging current is not controlled, the performance of the lithium battery is reduced due to the charging with a large current, fig. 7 is a flowchart of the lithium battery charging management in embodiment 1, when the output current of the MPPT controller needs to be restrained except for providing the load current, the part larger than the maximum charging current of the lithium battery, the controller output current is limited cycle by cycle according to the SOC of the lithium battery, and when in the offline mode, the smaller the SOC is, the larger the corresponding output current limiting step is. In the on-line mode, the power supply to the load is prioritized, so that the battery should be charged to the full state in a short time when the battery is not in the rated SOC state.
The communication mode between the flexible intelligent agent and the top-layer energy controller is CAN query communication, the top-layer energy controller issues commands and data one by utilizing the query mode, then the top-layer energy controller enters a receiving mode, and the slave responds according to the received identifier and command format and the rule base. The command comprises uploading specific data, switching the control mode of the flexible agent, and the issued data comprises the data of the adjacent controllers, so that the communication between the flexible agents in the distributed system is indirectly realized. Because the lithium battery, the solar battery and the capacitor response load have different durations, the data transmission should take the time of executing the fast and slow tasks into consideration so as to reduce excessive repeated sampling of the data and avoid extremely high requirements of continuous refreshing of the slow response task data on a data storage medium. The communication mode avoids the defect that the host command can not be responded in time under the condition of multiple slaves, and the command issuing time interval can be flexibly configured in the time domain.
The main failure modes of the MPPT controller include short circuit and open circuit, when short circuit occurs, the auxiliary controller cannot be directly connected to the circuit, the fault controller needs to be isolated from the circuit, and when open circuit occurs, the auxiliary controller can be directly connected to the circuit. The MMPPT controller monitors the state signal of the controller in a fixed period on software, once a fault signal is generated, the controller immediately pulls up a certain IO port, an optocoupler is driven through the IO port, the optocoupler controls a MOSFET (metal oxide semiconductor field effect transistor), and the MMPPT can be timely cut off from a circuit and is timely connected into the circuit. The rated power of the MPPT controller in the flexible intelligent body is far smaller than the load power of the distributed energy system and the upper limit power of all lithium batteries, and the characteristic of quick response of the capacitor is enough to ensure the influence of the off-line state waiting time of HMMPT millisecond level on the overall safety of the system. When the MMPPT has a circuit breaking event, the HMPPT is directly connected into the circuit, and the MMPPT is played without waiting.
FIG. 8 is an implementationIn the design flow chart of the distributed energy system of the solar unmanned aerial vehicle based on the flexible intelligent agent in the example 1, given known design parameters include bus voltage, maximum load power, single voltage of lithium battery, maximum charging current and other data, inductance parameters affecting the flexible MPPT controller are imported, N is used for replacing the number of the inductances, then the maximum supportable power of the inductances is calculated, the power is larger than the maximum charging power of the lithium battery, if the maximum supportable power is met, the number of the lithium batteries which are required in parallel connection can be calculated according to the maximum load, and P can be increased to improve the adaptation of the unmanned aerial vehicle to the environmental change rate Equation soft constraint if the solar light intensity is from ideal 1000W/m 2 Reduced to 500W/m 2 The rated SOC of the lithium battery is 0.75, the unmanned aerial vehicle can continue to maintain safe flight, and w can be considered in the design of a distributed scheme 1 ＝0.5,w 2 =0.75 to cope with changes in the environment during flight. When P rate When the power is larger than the cruising power of the unmanned aerial vehicle, the current serial-parallel connection structure of the lithium batteries can meet the requirements of the distributed energy system, and when N calculation is completed, the design scheme of the distributed energy with the least quantity of the lithium batteries is finally output, including the design working condition parameters of the flexible intelligent body.
According to the distributed hybrid energy system of the flexible intelligent bodies and the solar unmanned aerial vehicle, n flexible intelligent bodies are connected in series to form a group string, m group strings are connected in parallel, fig. 9 is a simplified model for researching the reliability of the distributed energy system in embodiment 1, only the influence of a power generation module on the reliability of the system is considered, when a solar cell module and a flexible MPPT controller in the flexible intelligent bodies are in faults, the reliability of at least one flexible intelligent body in each group string is defined to be consistent with the probability of the faults of the centralized energy system controller, when one MPPT controller in each string is in faults, the strings where the flexible intelligent bodies are located are considered to be invalid, when one solar cell module in each string is in faults, only the system reliability is reduced, the influence of the change of m, n and the number of working years on the reliability of the distributed energy system is not caused, and the advantages and disadvantages of the reliability of the centralized energy system and the distributed energy system are compared.
The reliability function of the distributed energy system is established, so that the reliability of the system can be quantitatively analyzed theoretically.
TABLE 1 symbology used in the present application
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The above examples are provided for convenience of description of the present application and are not to be construed as limiting the application in any way, and any person skilled in the art will make partial changes or modifications to the application by using the disclosed technical content without departing from the technical features of the application.

Claims (8)

1. A flexible agent, comprising: the power generation module and the energy storage module;
wherein the power generation module includes: a flexible photovoltaic module and a flexible MPPT controller; the flexible photovoltaic module is formed by assembling a plurality of flexible solar battery monomers;
wherein, the energy storage module includes: a flexible lithium battery, a flexible BMS controller; the flexible lithium battery is used for providing energy for a load and storing energy transferred by the flexible photovoltaic module; the flexible BMS controller is used for on-line calculation of the SOC of the flexible lithium battery, monitoring of charging and discharging currents and monitoring and control of the temperature of the lithium battery;
The output end of the power generation module is connected with the load and the input end of the energy storage module respectively;
the flexible MPPT controller is used for controlling the flexible photovoltaic module to supply power to the load and controlling the flexible photovoltaic module to supply energy to the flexible lithium battery;
the output end of the energy storage module is connected with a load so that the flexible lithium battery can supply power for the load;
the BMS controller transmits the current SOC, charging and discharging current and lithium battery temperature data of the flexible lithium battery to the flexible MPPT controller;
the MPPT controller controls the current output by the flexible photovoltaic module to the flexible lithium battery according to the SOC and the charging current transmitted by the BMS controller;
the method for controlling the output current of the flexible photovoltaic module by the flexible MPPT controller comprises the following steps:
s1, calculating an adjusted current I down ：
I down ＝I mppt_out,0 -I load -I chg_max
Wherein I is mppt_out，0 For the output current before adjustment of the power generation module, I load For load current, I chg_max Presetting a maximum charging current for the flexible lithium battery;
S2:
s2-1, if I down If the current is less than or equal to 0, the flexible MPPT controller does not adjust the output current of the power generation module;
s2-2, if I down When the current is larger than 0, the flexible MPPT controller adjusts the output current of the power generation module, and the current output of the flexible photovoltaic module is reduced by adopting a fixed-period variable step length, and the specific mode is as follows:
Step 1, adjustment:
first, step 1 size I is calculated using the following formula step (1)：
In the above, the soc H Taking 0.85 of SOC as the upper limit value of the rated SOC of the lithium battery L Taking 0.65 as a rated SOC lower limit value; second, MPPT controlThe controller controls the current of the power generation module:
I mppt_out，1 ＝I mppt_out，0 -I step (1)
in the above, I mppt_out，1 The current after the first step of the power generation module is adjusted;
again, confirm whether continued adjustment is needed:
when (when)Step 2, no adjustment is performed;
when (when)Step 2, adjusting;
……
step k adjustment:
first, the k-th step size I is calculated by the following formula step (k)：
Secondly, according to the size I of the kth step length calculated in the kth step step (k) The MPPT controller controls the current of the power generation module:
I mppt_out，k ＝I mppt_out，k-1 -I step (k)
I mppt_out，k-1 、I mppt_out，k the current after the k-1 step and the k step of the power generation module are respectively adjusted;
again, confirm whether continued adjustment is needed:
when (when)The k+1 step adjustment is not performed;
when (when)Then the k +1 step adjustment is performed.
2. The flexible agent of claim 1, wherein the hardware carriers of the flexible MPPT controller and the flexible BMS controller are flexible circuit boards;
the layout of the flexible circuit board is as follows: the digital control part and the power conversion part are respectively arranged at two sides of the flexible region, and the wire passing through the flexible region adopts a straight line form.
3. The flexible intelligent agent according to claim 1, wherein the flexible MPPT controller implements a synchronous step-down function, and the maximum power determination method is as follows:
wherein: l is inductance value, r is ripple coefficient, fsw is switching frequency, I o For maximum load current, D is the duty cycle.
4. The flexible agent of claim 1, wherein the flexible MPPT controller employs: top-signal1-signal2-Bottom four-layer FPC, top layer is the installation surface of the component, signal1 is used for applying the ground copper in a large area, in order to reduce the loop area of the main circuit, reduce the self high-frequency EMI problem of the switching power supply, signal2 is used for arranging the sensitive signal wire, and cooperate with Top layer to widen the main circuit wire of the power supply, bottom can apply the ground copper in a large area, and carry on the reinforcement of the main circuit wire of the power supply in the appropriate position, the turning department of the signal wire adopts the arc to be excessive;
considering the influence of the switching frequency on the junction temperature of the power device under the rated working condition, optimizing the size of a passive device in the power topology, and improving the flexibility of the controller; when the power circuit is laid out, the power circuit elements are placed in the nearest principle, the Top layer is used as the unique patch layer, a special flexible area is reserved between the power circuit module and the control circuit module according to circuit flexibility constraint, and wires without electrical properties are placed in corner areas of the FPC, so that the power circuit is prevented from being torn.
5. A distributed hybrid energy system of a solar unmanned aerial vehicle, which is characterized by comprising a plurality of flexible intelligent bodies, a top-layer energy controller and a capacitor which are connected in series-parallel;
wherein, top layer energy controller includes: the embedded microprocessor is communicated with the flexible MPPT controllers in each flexible intelligent agent through the CAN bus to obtain the input and output voltage and current of the current flexible MPPT controllers, and the SOC, charge and discharge current and temperature of the flexible lithium battery;
the top-layer energy controller performs active energy management according to an online energy management strategy and issues a control command to the MPPT controller;
the capacitor is connected into the direct current bus, the capacitor is used for relieving the stress of the flexible lithium battery, the characteristic of slow response of the lithium battery is made up by utilizing the characteristic of transient quick response of the capacitor, and the capacitor plays a role of controlling the bus voltage after the system enters a steady state.
6. The solar unmanned aerial vehicle distributed hybrid energy system of claim 5, wherein the degree of interference of the top-level energy controller to the flexible agent is in four different modes:
the unmanned aerial vehicle is in the ground test state and defined as an offline mode;
The normal operation state of the solar unmanned aerial vehicle is defined as an on-line mode, the solar unmanned aerial vehicle needs to rely on a top-layer energy controller to carry out data communication with a flexible intelligent body, and a main energy management strategy is operated in real time to finish energy distribution, so that the safety state of the whole system needs to be monitored in real time;
the offline mode of the unmanned aerial vehicle is used for system debugging and maintenance;
when no fault occurs in the system, the state is a normal mode;
the energy system monitors a fault signal, and enters an emergency mode from a normal mode at the moment, and in the emergency mode, the flexible intelligent body starts a redundancy scheme for protection;
the redundancy scheme adopts two sets of consistent MPPT controllers, and is divided into MMPPT and HMMPPT;
MMPPT is a main controller, HMMPPT is an auxiliary controller, hardware safety state marks of the MMPPT are monitored in real time, when the MMPPT has a short circuit event, an MMPPT bypass circuit plays a role, and after the MMPPT is cut off from the circuit, the HMMPPT plays a role of the MMPPT;
when the MMPPT is in a circuit breaking event, the HMPPT is directly connected into the circuit, plays the role of the MMPPT, does not need to wait, and the rated power of an MPPT controller in the flexible intelligent body is far smaller than the load power of a distributed energy system and the upper power limit of all lithium batteries, so that the influence of the off-line state waiting time of HMMPT millisecond level on the overall safety of the system is ensured by the characteristic of quick response of the capacitor.
7. The solar unmanned aerial vehicle distributed hybrid energy system of claim 6, wherein in a data transmission mode between the top-level energy controller and the flexible intelligent agent, roles of the master and the slave can be adjusted according to received commands, the top-level energy controller with the highest priority issues commands one by using a query mode, then enters a receiving mode, responds according to a rule base by the received identifier and command format; the communication mode avoids the defect that a host command cannot be responded in time under the condition of multiple slaves, and the command issuing time interval can be flexibly configured in the time domain, so that the extremely high requirement of continuous refreshing of slow response task data on a data storage medium is avoided.
8. The solar unmanned aerial vehicle distributed hybrid energy system of claim 6, wherein the design method of the distributed hybrid energy system is as follows:
under the constraint of considering load power, the power density of the flexible MPPT controller and the whole thickness thereof, optimizing the serial-parallel quantity of lithium batteries so as to establish a distributed hybrid energy system;
p in the following rate The equality constraint of (2) means that under a certain light intensity condition, the power provided by the solar cell is equal to the current SOC The sum of the power provided by the lithium battery can meet the power requirement of the load under the condition;
J＝n sbat +n pbat
taking J as a parameter, and taking n corresponding to the minimum time of J sbat ，n pbat ；
The physical meaning of the variables in the constraint is:
n sbat for the number of lithium batteries connected in series, n pbat The number of the parallel lithium batteries is n smppt For MPPT serial number, n pmppt The MPPT parallel number is used;
V bat rated for lithium battery, V bus Is the bus voltage;
w 1 the power weight coefficient of the solar battery is more than 0 and less than w 1 < 1, related to irradiance, 0.5;
w 2 the power weight coefficient of the lithium battery is more than 0 and less than w 2 < 1, regarding the rated SOC of the lithium battery, 0.75 was taken.
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