CN115954857A - Crane off-grid type direct current micro-grid system for capturing and utilizing various types of new energy and control method - Google Patents

Abstract

The invention provides a crane off-grid wind-solar storage direct current micro-grid system for capturing and utilizing various types of new energy and an energy control method. This equipment energy storage system can store multiple energy: the device comprises a crane, a wind power generation system, a photovoltaic system and an energy storage system, wherein the crane is used for supplying power to the crane during operation. The control method comprises the steps of formulating a wind power generation control strategy, a photovoltaic power generation control strategy and a window type direct current bus voltage coordination control strategy based on the SOC charge state of a lithium battery to adapt to energy storage and energy supply control under the working condition of the crane, so that the consumption of commercial power is saved, the utilization rate of clean energy is improved, and the energy-saving and efficient functions are strong.

Description

Crane off-grid type direct current micro-grid system for capturing and utilizing various types of new energy and control method

Technical Field

The invention relates to the technical field of crane control, in particular to an off-grid type direct current micro-grid system for a crane and a control method for capturing and utilizing various types of new energy.

Background

When the crane motor driven by variable frequency speed regulation lifts a cargo and transfers the cargo, the feedback brake is adopted, the motor can be in a regeneration state, and the direct current bus of the frequency converter is connected into the energy storage device to store the electric quantity, so that the energy recovery and utilization can be realized. The off-grid wind-solar storage direct-current micro-grid system structure comprises an alternating-current type and a direct-current type, and a wind power generation system, a photovoltaic power generation system and an energy storage system in the direct-current type structure are connected through a common direct-current bus and have a similar structure with a crane frequency converter direct-current bus system. In view of this,

a wind power generation system and a photovoltaic power generation system are added on a direct-current bus of a crane frequency converter to form a wind-light storage direct-current micro-grid system for a crane for capturing various types of new energy, the system can recover and utilize regenerated electric quantity generated by crane feedback braking, and capture new energy such as wind energy, solar energy and the like, and can independently supply power for the crane without consuming commercial power in energy supply. And aiming at the difference between the power fluctuation and the common direct current micro-grid during the operation of the crane and the energy consumption, the feedback electric energy is generated at the same time, so that the voltage fluctuation of the bus is larger, a bus working voltage mode of a window voltage mode is established, and a control strategy is established.

Disclosure of Invention

The invention discloses an off-grid wind-solar storage direct current micro-grid system and an energy control method for a crane, which are used for capturing and utilizing various types of new energy, so that the electric energy of commercial power is saved and wind power and photoelectric clean energy are efficiently utilized when the crane works; meanwhile, the text provides a control method for the system, which comprises the following steps: the method comprises the steps of adopting an improved MPPT algorithm to control wind power generation, adopting the improved MPPT algorithm to control photovoltaic power generation and adopting a window type direct current bus voltage coordination control strategy based on the SOC state of charge of a lithium battery.

In order to solve the technical problems, the invention adopts the following technical scheme:

a hoist off-grid wind-solar storage direct current micro-grid system for capturing and utilizing various types of new energy comprises: the system comprises a frequency converter direct current bus system, a crane mechanical lifting system, an energy storage system, a wind power generation system, a photovoltaic power generation system and a control system;

wherein, converter direct current bus system includes: the system comprises a frequency converter, a primary direct current voltage bus, a No. 1 bidirectional DCDC direct current converter and a secondary direct current voltage bus; the secondary direct-current voltage bus is used for connecting the energy storage system, the wind power generation system and the photovoltaic power generation system; the frequency converter is used for driving the three-phase alternating current asynchronous motor in a frequency conversion mode, leading out a primary direct current bus, absorbing electric quantity generated by feedback braking of the three-phase alternating current asynchronous motor and transmitting the electric quantity to a secondary direct current bus.

Further, the energy storage system includes: the system comprises a super capacitor bank, a lithium battery pack and a No. 2 bidirectional DCDC direct current converter; the lithium battery pack is used for storing and releasing electric energy and is connected to a secondary direct current bus through a No. 2 DCDC direct current converter; the super capacitor group is formed by connecting a plurality of single capacitors in series and in parallel and is used for frequently absorbing and releasing electric energy and maintaining the voltage of the secondary direct current bus within the range of a set value Umin-Umax.

Further, the wind power generation system includes: the system comprises a wind driven generator, a three-phase controllable rectifier and a No. 3 bidirectional DCDC direct current converter; the wind driven generator is used for wind power generation, and is rectified into direct current through the three-phase controllable rectifier, and the direct current is connected to a secondary direct current bus through the No. 3 bidirectional DCDC direct current converter.

Further, the photovoltaic power generation system includes: a photovoltaic array and a No. 4 bidirectional DCDC direct current converter; the photovoltaic array is used for solar power generation and is connected to a secondary direct current bus through a No. 4 bidirectional DCDC direct current converter.

Further, the control system includes: the system comprises an MCGS touch screen, a PLC programmable logic controller, a frequency converter and an encoder; the MCGS touch screen is used as an upper computer for man-machine interaction, the PLC is used as a core controller for crane frequency converter drive control and micro-grid electrical control, the MCGS touch screen and the PLC are communicated through an Ethernet, and the PLC, the frequency converter and the encoder are communicated through a Modbus-RTU.

Further, the control system is configured to: (1) real-time data reading: reading real-time voltage Usc of a super capacitor bank, reading real-time voltage ULi and state of charge SOC of a lithium battery, reading real-time output voltage Uw, current Iw and power Pw of a wind driven generator, and reading real-time output voltage Upv, current Ipv and power Ppv of a photovoltaic array; (2) history data recording and reading: recording and reading historical total power generation amount Ew of the wind driven generator, recording and reading historical total power generation amount Epv of the photovoltaic array, recording and reading total power consumption Ec of a commercial power of the crane and recording and reading total power consumption Eave of an energy storage system of the crane; (3) displaying the real-time energy flow state: displaying a wind power generation energy flow route in real time, displaying a photovoltaic power generation energy flow route in real time, displaying a crane power consumption energy flow route, and displaying a crane feedback braking power transmission energy flow route in real time; and (4) controlling the rotating speed of the motor: displaying the real-time rotating speed of the motor, and writing in the given rotating speed to control the motor drive; (5) communication switch interface control: the button inching controls the communication contactor switch between the devices, the device contactor switch includes: the PLC, the DCDC communication switch and the super capacitor are connected into a second-level bus contactor switch.

The invention also provides a crane off-grid wind-solar storage direct-current micro-grid control method for capturing and utilizing various types of new energy, wherein the wind power generation system adopts an MPPT output mode and adopts a variable-step MPPT mountain climbing search control algorithm to realize that the wind power generator is always output at the maximum power point; the photovoltaic power generation system adopts two modes of MPPT output and power reduction constant voltage output, the MPPT output mode is realized through a variable step length MPPT disturbance observation algorithm, the power reduction constant voltage output mode is realized through a voltage outer ring current inner ring double closed loop PI control algorithm, the frequency converter direct current bus system adopts a constant voltage or high-voltage side window voltage control mode, and the energy storage system adopts a high-voltage side window voltage control mode for control.

Furthermore, the bidirectional DCDC direct-current converter No. 1 adopts a high-voltage side window voltage control mode, the high-voltage side is connected with a frequency converter bus to set window voltage (Ulow 1, uup 1), the low-voltage side is connected with a secondary direct-current bus, and the working logic is as follows: when the high-voltage side U < Ulow1, the high-voltage side draws current from the low-voltage side to maintain the voltage in a window voltage interval, and when the high-voltage side U > Uup1, the high-voltage side transmits current from the low-voltage side to maintain the voltage in the window voltage interval;

the No. 2 bidirectional DCDC direct current converter adopts a high-voltage side window voltage control mode, and the high-voltage side is connected with a secondary direct current bus to set window voltage (U) ^l _ow ² ，U _up ² ) The low-voltage side is connected with a lithium battery, and the working logic is as follows: when the high-voltage side U<U ^l _ow ² When the voltage is in the window voltage range, the high-voltage side draws current from the low-voltage side, and when the voltage is in the window voltage range, the high-voltage side U>U _up ² When the voltage is within the window voltage range, the high-voltage side transmits current from the low-voltage side to maintain the voltage;

the low-voltage side of the No. 3 bidirectional DCDC direct-current converter is connected with the direct current output after rectification of the wind driven generator, the high-voltage side is connected with the secondary direct-current bus, the low-voltage side is connected with the high-voltage side in an output mode, and the low-voltage side of the No. 3 bidirectional DCDC direct-current converter is set to have the rated output voltage U of the wind driven generator _wind ；

The low-voltage side of the No. 4 bidirectional DCDC direct current converter is connected with the direct current output of the photovoltaic array, the high-voltage side is connected with the secondary direct current bus, the low-voltage side is output to the high-voltage side in a low-voltage side output mode, and the set voltage of the No. 4 DCDC low-voltage side is the rated output voltage U of the photovoltaic array _pv 。

Further, the wind power generation system adopts a variable-step MPPT mountain climbing search control algorithm, and the specific steps are as follows:

step1: starting a system, initializing the output power value of the current period to be 0, the disturbance duty ratio value to be 0 and the initial duty ratio value to be D;

step2: sampling a current value I (k) and a voltage value U (k) of the current period k, and calculating output power P (k) = I (k) × I (k) at the current sampling time point; calculating the output power change delta P = P (k) -P (k-1) of the current sampling period k and the last sampling period k-1;

step3: comparing whether the power change value delta P is larger than or equal to a set minimum power change value e, if so, skipping Step4 to execute Step5, and if not, executing Step4;

step4: comparing whether the current duty ratio disturbance value delta D is smaller than or equal to the set minimum duty ratio disturbance value Dmin, if so, enabling the duty ratio disturbance value delta D = Dmin, and if not, enabling the duty ratio disturbance value to be reduced by half, namely enabling the duty ratio disturbance value delta D =1/2 delta D;

step5: and comparing whether the product of the duty ratio disturbance value delta D and the output power change value delta P is larger than zero. If the result is yes, the maximum power point is not reached, the current direction disturbance needs to be continued, and the disturbance duty ratio delta D value is kept unchanged; if the result is negative, the maximum power point is disturbed, the next period needs to be disturbed in an ultra-opposite direction, and the disturbance duty ratio delta D = -delta D of the next period is made.

Further, the photovoltaic power generation system adopts a variable step MPPT disturbance observation control algorithm, and the method comprises the following specific steps:

step1: starting a system, initializing the output power value of the current period to be 0, and initializing the disturbance voltage value to be delta U;

step2: sampling the output voltage U (k) and the output current I (k) of the photovoltaic array in the current period k, and calculating the current output power P (k) = U (k) × I (k);

step3: comparing with the value of the last sampling period k-1, calculating a voltage variation dU = U (k) -U (k-1) and a power variation dP = P (k) -P (k-1), and calculating a value alpha =1-exp (- | dP |) of the current time-varying factor;

step4: a comparison is made as to whether the value of dU × dP is greater than zero. If the current voltage does not reach the maximum power point, keeping the current disturbance direction and enabling the disturbance voltage value to be alpha delta U; if the result is negative, the current voltage is positioned at the left side of the maximum power point, and voltage disturbance needs to be applied towards the opposite direction, so that the disturbance voltage value is-alpha delta U;

step5: let U (k-1) = U (k), P (k-1) = P (k), return to Step2, execute the control flow of the next cycle.

Compared with the prior art, the invention at least comprises the following beneficial effects:

according to the invention, the wind power generation system and the photovoltaic power generation system are added on the variable-frequency drive crane, so that the functions of the crane are not limited to storing and recovering the electric quantity fed back and braked by the motor, but also the electric quantity generated by wind and light power generation can be captured and stored, and the stored electricity can be used for independently supplying power to the crane during working and running through the frequency converter, so that the consumption of commercial power is efficiently saved, and the utilization rate of clean energy is improved; in the control method provided by the invention, the MPPT control algorithm innovation of wind power generation based on improved variable-step hill-climbing search and the MPPT control algorithm innovation of photovoltaic power generation based on improved variable-step disturbance observation can improve the response time of wind power generation and maximum power point capture of photovoltaic power generation, reduce overshoot and ensure higher stability of maximum output power; the window type direct current bus voltage coordination control strategy based on the SOC state of charge of the lithium battery can well adjust the power balance control between the voltage power fluctuation caused in the crane operation energy utilization process and the output of wind power generation and photovoltaic power generation, and always maintain the bus voltage in a balanced state. More references are provided for the energy-saving technical scheme of the hoisting machinery, more information is provided for the system application of the wind-solar-storage direct-current micro-grid on the crane, and the control method is improved on the traditional micro-grid control to adapt to the working condition of the crane.

Drawings

In order to more clearly illustrate the technical solutions in the embodiments of the present invention, the drawings required to be used in the description of the embodiments are briefly introduced below, and it is obvious that the drawings in the description below are only some embodiments of the present invention, and it is obvious for those skilled in the art that other drawings can be obtained according to the drawings without creative efforts.

FIG. 1 is a diagram of the composition and information flow of a wind-light storage direct current micro-grid system for a crane for capturing and utilizing various types of new energy according to the present invention;

FIG. 2 is an energy flow schematic diagram and an information diagram of energy utilization and regenerative electric energy recycling of regenerative braking, wind power generation utilization and solar power generation utilization in the working process of a hoisting motor in the invention;

FIG. 3 is a schematic diagram of an improved variable step size mountain climbing search wind power generation MPPT control algorithm of the present invention;

FIG. 4 is a schematic diagram of an improved variable step disturbance observation wind power generation MPPT control algorithm of the present invention; (ii) a

FIG. 5 is a flow chart of a window type DC bus voltage coordination control strategy based on the SOC state of charge of the lithium battery according to the method of the present invention;

FIG. 6 is a diagram illustrating exemplary functions of a UI control interface according to the invention.

Detailed Description

The technical solutions in the embodiments of the present invention will be clearly and completely described below with reference to the drawings in the embodiments of the present invention, and it is obvious that the described embodiments are only a part of the embodiments of the present invention, and not all of the embodiments. All other embodiments, which can be derived by a person skilled in the art from the embodiments given herein without making any creative effort, shall fall within the protection scope of the present invention.

It is to be noted that the experimental methods described in the following embodiments are all conventional methods unless otherwise specified, and the reagents and materials, if not otherwise specified, are commercially available; in the description of the present invention, the terms "lateral", "longitudinal", "up", "down", "front", "back", "left", "right", "vertical", "horizontal", "top", "bottom", "inner", "outer", etc., indicate orientations or positional relationships based on the orientations or positional relationships shown in the drawings, are only for convenience in describing the present invention and simplifying the description, and do not indicate or imply that the device or element being referred to must have a particular orientation, be constructed and operated in a particular orientation, and thus, should not be construed as limiting the present invention.

Furthermore, the terms "horizontal", "vertical", "suspended" and the like do not imply that the components are absolutely horizontal or suspended, but may be slightly inclined. For example, "horizontal" merely means that the direction is more horizontal than "vertical" and does not mean that the structure must be perfectly horizontal, but may be slightly inclined.

In the description of the present application, it should also be noted that, unless expressly stated or limited otherwise, the terms "disposed," "mounted," "connected," and "connected" are to be construed broadly and can include, for example, fixed connections, detachable connections, or integral connections; can be mechanically or electrically connected; they may be connected directly or indirectly through intervening media, or they may be interconnected between two elements. The specific meaning of the above terms in this application will be understood to be a specific case for those of ordinary skill in the art.

As shown in fig. 1, the present embodiment includes a crane off-grid wind-solar storage dc micro-grid system for capturing and utilizing multiple types of new energy, including: the system comprises a frequency converter direct current bus system 1, a crane mechanical lifting system 2, an energy storage system 3, a wind power generation system 4, a photovoltaic power generation system and a control system 5;

in this embodiment, the converter dc bus system 1 includes: a frequency converter 10 (1.1 KW), a primary direct current voltage bus 11 (about 580-610V), a first bidirectional DCDC direct current converter 12 (5 KW) and a secondary direct current voltage bus 13 (about 180-210V); the secondary direct-current voltage bus 13 is used for connecting the energy storage system 3, the wind power generation system 4 and the photovoltaic power generation system 5;

the crane lifting mechanism comprises: a three-phase alternating current asynchronous motor 14 (380V 400W), a three-level gear reduction box 15 (reduction ratio 42.5) and a lifting appliance 16 (maximum lifting mass 200 kg); a three-phase alternating current asynchronous motor 14 (380V 400W) for providing output torque and regenerative braking to generate electric energy, and a lifting appliance 16 of a hook type for connecting goods;

the energy storage system includes: a super capacitor group 17 (320V 20 AH), a lithium battery group 18 (96V 20 AH), and a second bidirectional DCDC direct current converter 19 (4 KW); the super capacitor bank 17 and the lithium battery bank 18 are used for storing and releasing electric energy and are controlled to be connected to a secondary direct current bus (about 180-210V) through a second bidirectional DCDC direct current converter;

the wind power generation system includes: a wind driven generator 20 (1000W 96V), a three-phase controllable rectifier 21 (2 KW) and a three-way bidirectional DCDC direct current converter 22 (4 KW); the wind driven generator 20 is used for wind power generation, and is rectified into direct current through a three-phase controllable rectifier 21 and is controlled to be connected to a secondary direct current bus through a three-phase bidirectional DCDC direct current converter 22 (4 KW);

a photovoltaic power generation system includes: a photovoltaic array 23 (400W 120V) and a four-way DCDC direct current converter 24 (4 KW); the photovoltaic array 23 is used for solar power generation and is controlled to be connected to the secondary direct current bus 13 (about 180-210V) through a fourth DCDC direct current converter 24.

As shown in fig. 2, when the crane works, the wind power generation system 4 and the photovoltaic power generation system 5 can directly supply power to the crane mechanical lifting system 2 through the direct current bus, redundant electric quantity is stored in the energy storage system 3, the energy storage system 3 can directly supply power to the crane mechanical lifting system 2, and regenerated electric quantity generated by the lifting motor through feedback braking can be recovered and stored in the energy storage system 3;

the frequency converter 10 is used for driving a three-phase alternating current asynchronous motor 14 in a frequency conversion manner, leading out a primary direct current bus 11, absorbing electric quantity generated by feedback braking of the three-phase alternating current asynchronous motor 14 and transmitting the electric quantity to a secondary direct current bus 13;

the first bidirectional DCDC DC converter 12 adopts a high-voltage side window voltage control mode, and the high-voltage side is connected with a first-level bus of the frequency converter 11 to set a window voltage (U) _low1 ，U _up1 ) = (580v, 610v), the low-voltage side is connected with the secondary direct current bus 13, and the working logic is as follows: when the high-voltage side U<580V, the high-voltage side draws current from the low-voltage side to maintain the voltage in the window voltage interval, and when the high-voltage side U is in the voltage interval>When the voltage is 610V, the high-voltage side transmits current from the low-voltage side, so that the voltage is maintained in a window voltage interval;

the super capacitor group 17 is formed by connecting a plurality of single capacitors in series and in parallel, and is used for frequently absorbing and releasing electric energy and maintaining the voltage of the secondary direct current bus 13 at a set value U _min ～U _max A range;

the second bidirectional DCDC DC converter 19 adopts a high-voltage side window voltage control mode, and the high-voltage side is connected with a second-level DC bus 13 to set a window voltage (U) _low2 ，U _up2 ) = (180v, 210v), the low voltage side is connected with 18 lithium batteries, and the working logic is: when the high-voltage side U<When the voltage is 180V, the high-voltage side draws current from the low-voltage side to maintain the voltage in a window voltage interval, and when the high-voltage side U is in a voltage range of U>At 210V, the high-pressure side is from lowThe voltage side transmits current to maintain the voltage in a window voltage interval;

the wind driven generator 20 adopts an improved variable step MPPT hill climbing search control algorithm for power generation control, a wind turbine is controlled to work at the maximum power point all the time, wind energy is utilized to the maximum extent, and the power generation efficiency is highest;

the three-phase controllable rectifier 21 rectifies three-phase alternating current output by the wind driven generator into stable direct current, the low-voltage side of the third bidirectional DCDC direct current converter 22 is connected with the rectified direct current output of the wind driven generator, the high-voltage side is connected with the second-level direct current bus 13, a low-voltage side to high-voltage side output mode is adopted, and the low-voltage side of the third bidirectional DCDC direct current converter 22 is set to have the rated output voltage U of the wind driven generator 20 _wind ＝96V；

Furthermore, the photovoltaic array 23 is formed by connecting photovoltaic modules in series and parallel, the power generation control of the photovoltaic array adopts an improved variable-step MPPT disturbance observation control algorithm, the photovoltaic array is controlled to work at the maximum power point all the time, the solar power is utilized to the maximum extent for power generation, and the power generation efficiency is highest;

the low-voltage side of the fourth DCDC direct-current converter 24 is connected with the direct-current output of the photovoltaic array, the high-voltage side is connected with the secondary direct-current bus, a low-voltage side to high-voltage side output mode is adopted, and the set voltage of the low-voltage side of the fourth DCDC is the rated output voltage Upv =120V of the photovoltaic array;

furthermore, the control system comprises a hardware component and a software component

The control system hardware includes: the system comprises 1 frequency converter, 2 MCGS touch screens, 4 bidirectional DCDC direct current converters, 2 PLC programmable logic controllers, a plurality of wires and cables, 2 switches, 2 RS485 converters, 3 encoders, a plurality of contactors, a plurality of relays, a plurality of emergency stop switches and a plurality of fuses;

the control system software comprises: the method comprises the following steps of realizing PLC control frequency converter driving motor codes, realizing PLC electrical safety control system codes, realizing MCGS touch screen human-computer interaction UI interface, realizing MCGS touch screen, frequency converter and Modbus _ RTU communication codes among the PLCs, and realizing the Modbus _ TCP communication codes between the PLCs and the 4 bidirectional DCDC direct current converters;

the control algorithm and the control strategy in the embodiment include: the method comprises the following steps of searching a wind power generation MPPT control algorithm based on improved variable-step climbing, observing the wind power generation MPPT control algorithm based on improved variable-step disturbance, and carrying out window type direct current bus voltage coordination control strategy based on the SOC state of charge of a lithium battery;

as shown in fig. 3, the MPPT control algorithm for wind power generation based on improved variable step climbing search is implemented as follows: the improved wind power generation output MPPT control algorithm has the advantages that a wind power generation characteristic curve is shown in fig. 3- (a), a control principle is shown in fig. 3- (b), and a control flow is shown in fig. 3- (c). The control algorithm is realized by the following steps:

step1: starting a system, initializing the output power value of the current period to be 0, the disturbance duty ratio value to be 0 and the initial duty ratio value to be D;

step2: sampling a current value I (k) and a voltage value U (k) of a current period k, and calculating output power P (k) = I (k) × I (k) of a current sampling time point; calculating the output power change delta P = P (k) -P (k-1) of the current sampling period k and the last sampling period k-1;

step3: comparing whether the power change value delta P is larger than or equal to a set minimum power change value e, if so, skipping Step4 to execute Step5, and if not, executing Step4;

step4: comparing whether the current duty ratio disturbance value delta D is smaller than or equal to the set minimum duty ratio disturbance value D _min If yes, making the duty ratio disturbance value delta D = D _min If the duty ratio disturbance value is reduced by half, the result is that the delta D =1/2 delta D;

step5: and comparing whether the product of the duty ratio disturbance value delta D and the output power change value delta P is larger than zero. If the result is yes, the maximum power point is not reached, the current direction disturbance needs to be continued, and the disturbance duty ratio delta D value is kept unchanged; if the result is negative, the maximum power point is disturbed, the next period needs to be disturbed in an ultra-opposite direction, and the disturbance duty ratio delta D of the next period is enabled to be = -delta D;

step6: let P (k-1) = P (k), return to Step2, execute the control flow of the next cycle.

As shown in FIG. 4, the MPPT control algorithm for wind power generation based on improved variable step disturbance observation is realized as follows: the MPPT control algorithm of the improved photovoltaic power generation output is characterized in that characteristic curves among photovoltaic power generation output power, illumination intensity and output voltage are shown in fig. 4- (a), the MPPT disturbance observation algorithm method control principle is shown in fig. 4- (b), and the control flow is shown in fig. 4- (c). The improved photovoltaic power generation MPPT control algorithm is realized by the following steps:

step1: starting a system, initializing the output power value of the current period to be 0, and initializing the disturbance voltage value to be delta U;

step2: sampling the output voltage U (k) and the output current I (k) of the photovoltaic array in the current period k, and calculating the current output power P (k) = U (k) × I (k);

step3: comparing with the value of the last sampling period k-1, calculating a voltage variation dU = U (k) -U (k-1) and a power variation dP = P (k) -P (k-1), and calculating a value alpha =1-exp (- | dP |) of the current time-varying factor;

step4: comparing whether the value of dU + dP is larger than zero, if so, indicating that the current voltage does not reach the maximum power point, and keeping the current disturbance direction to enable the disturbance voltage value to be alpha delta U; if the result is negative, the current voltage is positioned on the left side of the maximum power point, and voltage disturbance needs to be applied towards the reverse direction, so that the disturbance voltage value is-alpha delta U;

step5: let U (k-1) = U (k), P (k-1) = P (k), return to Step2, execute the control flow of the next cycle.

As shown in fig. 5, the window type dc bus voltage coordination control strategy based on the SOC state of charge of the lithium battery is implemented as follows: different from the generating line constant voltage control method of fixed voltage value, this embodiment provides a window voltage control mode, is about to the operating voltage of second grade direct current bus no longer sets up to fixed voltage value, but changes into two window voltage value control, can effectual reduction lithium cell group charge-discharge number of times, and at hoist lifting machinery system operation under any operating mode, the little electric wire netting of scene storage can both keep steady operation, and clean energy utilization efficiency maximize specifically includes:

(1) The wind power generation system has an output control mode: MPPT output mode;

(2) The photovoltaic power generation system has two output control modes: an MPPT output mode and a power reduction constant voltage output mode;

(3) The working voltage of the secondary direct current bus is set as window voltage (Ulow, uup) = (180V, 210V), the charge state of the lithium battery is between 10 and 90 percent when the lithium battery is charged and discharged and works in voltage stabilization

When the wind-solar-storage direct-current micro-grid system supplies power to the crane, the wind-solar-storage direct-current micro-grid system is divided into 4 basic operation states:

(1) State 1: the super capacitor is used for stabilizing voltage, when the SOC of the lithium battery is more than or equal to 10% and less than or equal to 90%, and the bus voltage is more than or equal to 180V and less than or equal to 210V, the secondary direct current bus voltage is stabilized by self absorption and release of electric quantity of the super capacitor, and the wind power generation MPPT output mode and the photovoltaic power generation MPPT output mode are adopted;

(2) And 2, state: the method comprises the following steps that a lithium battery is stabilized, when the SOC of the lithium battery is more than or equal to 10% and less than or equal to 90%, a super capacitor can not maintain the voltage of a bus to be stable by self absorption and self release of electric quantity, when Udc is less than or equal to 180V, the lithium battery discharges to charge a secondary direct current bus and the super capacitor, the bus is maintained in a window voltage range, when Udc is more than or equal to 210V, the lithium battery absorbs the surplus electric quantity of the bus and the super capacitor, the bus is maintained in the window voltage range, a wind power generation MPPT output mode and a photovoltaic generation MPPT output mode are adopted;

(3) State 3: when the SOC of the lithium battery is larger than or equal to 90%, the lithium battery is close to a full charge state, the surplus electric quantity of the bus cannot be absorbed, the electric quantity generated by the power supply needs to be reduced, the photovoltaic power generation is changed into a reduced power constant voltage output mode to maintain the voltage of the bus at 210V, and the output of the wind driven generator is closed.

(4) And 4: and in a power-off energy storage mode, when the SOC of the lithium battery is less than or equal to 10 percent and the photovoltaic power generation can not work at night generally, the power generated by the photoelectric wind power generation is less than the power consumed by the crane, or the power supply of the microgrid system is not in demand, the power supply of the microgrid needs to be cut off, and the power is changed into the mains supply of the power grid to supply power to the crane. The electric quantity generated by wind and light is stored in a lithium battery and a super capacitor until the SOC is more than or equal to 60 percent, and the wind and light power generation system is switched back to the state 2 to work.

The embodiment is embodied as follows:

(1) A second bidirectional DCDC converter (4 KW) 19 controls the charge and discharge of the super capacitor bank 17 to maintain the voltage 13 of the secondary direct current bus to be stabilized in a certain range (180V-210V);

(2) When the voltage of the second-stage direct-current bus 13 is lower than 180V, a second bidirectional DCDC converter (4 KW) 19 draws electric quantity from a lithium battery pack (96V 120W) 18 at a low-voltage side, a third DCDC converter (4 KW) 22 controls a wind driven generator (96V 1000W) 20 to output electric energy to the second-stage direct-current bus 13 at the maximum point power, a fourth DCDC converter (4 KW) 24 controls a photovoltaic array (120V 400W) 23 to output electric energy to the second-stage direct-current bus 13 at the maximum point power, and the voltage of the second-stage direct-current bus 13 is in a range of (180V-210V);

(3) When the voltage of the secondary direct current bus 13 is higher than 210V, the electric quantity of a super capacitor group 17 on the secondary bus 13 is conveyed to a lithium battery group (96V 20 AH) 18 on a low-voltage side by a second bidirectional DCDC converter (4 KW) 19 for storage, a third DCDC converter (4 KW) 22 controls a wind driven generator 20 (96V 1000W) to cut off and output electric energy to the secondary direct current bus 13, a fourth DCDC converter (4 KW) 24 controls a photovoltaic array (120V 400W) 23 to cut off and output electric energy to the secondary direct current bus 13, a power reduction constant voltage control strategy mode is changed, and the voltage of the secondary direct current bus 13 is 210V;

(4) Controlling the charging and discharging of the lithium battery pack (18), and when the charging SOC of the lithium battery pack (96V 20 AH) 18 is less than 10%, cutting off the discharging of the lithium battery by a second bidirectional DCDC converter (4 KW) 19 to keep charging; when the charge SOC of the lithium battery pack (96V 20 AH) 18 is equal to 100%, the second bidirectional DCDC converter (4 KW) 19 cuts off the charging of the lithium battery and keeps discharging.

As shown in fig. 6, further, the touch screen human-computer interaction control interface function is characterized by comprising: (1) real-time data reading: reading real-time voltage Usc of a super capacitor bank, reading real-time voltage ULi and state of charge SOC of a lithium battery, reading real-time output voltage Uw, current Iw and power Pw of a wind driven generator, and reading real-time output voltage Upv, current Ipv and power Ppv of a photovoltaic array; (2) history data recording and reading: recording and reading historical total power generation amount Ew of the wind driven generator, recording and reading historical total power generation amount Epv of the photovoltaic array, recording and reading total power consumption Ec of a commercial power of the crane and recording and reading total power consumption Eave of an energy storage system of the crane; (3) displaying the real-time energy flow state: displaying a wind power generation energy flow route in real time, displaying a photovoltaic power generation energy flow route in real time, displaying a crane power consumption energy flow route, and displaying a crane feedback braking power transmission energy flow route in real time; and (4) controlling the rotating speed of the motor: displaying the real-time rotating speed of the motor, and writing the real-time rotating speed into a given rotating speed to control the motor drive; (5) communication switch interface control: the button inching controls the communication contactor switch between the equipment, equipment contactor switch includes: the PLC, the DCDC communication switch and the super capacitor are connected to a second-level bus contactor switch;

further, in the example of the invention, the generated energy Ew of the 4 wind power generation system, the generated energy Epv of the 5 photovoltaic power generation system, the power consumption Ei of the commercial power for supplying power to the crane mechanical lifting system independently, and the power consumption Es and Ec of the wind-solar-storage micro-grid and the commercial power for supplying power to the crane mechanical lifting system together are measured in the dimension of 2 hours. Test data records, characterized in that the results show: the recycling rate of regenerative electric energy of regenerative braking of the system reaches 62.4%, the utilization rate of wind power and photoelectricity during the lifting operation of the crane reaches 86.67%, and the electric power consumption of the commercial power is saved by 28.57% compared with a device which is not connected with the access inlet renewable energy and the regenerative energy capturing and comprehensive utilizing device under the same working condition.

The above embodiments are merely illustrative of the technical solutions of the present invention. The method and apparatus of the present invention are not limited to the embodiments described above, but rather are subject to the scope defined by the claims. Any modification, supplement or equivalent replacement by a person skilled in the art on the basis of this embodiment is within the scope of the invention as claimed in the claims.

Claims (10)

1. The utility model provides a hoist off-grid type scene of polymorphic type new forms of energy is caught and is stored up direct current little grid system, its characterized in that includes: the system comprises a frequency converter direct current bus system, a crane mechanical lifting system, an energy storage system, a wind power generation system, a photovoltaic power generation system and a control system;

wherein, converter direct current bus system includes: the system comprises a frequency converter, a primary direct current voltage bus, a No. 1 bidirectional DCDC direct current converter and a secondary direct current voltage bus; the secondary direct-current voltage bus is used for connecting the energy storage system, the wind power generation system and the photovoltaic power generation system; the frequency converter is used for driving the three-phase alternating current asynchronous motor in a frequency conversion mode, leading out a primary direct current bus, and absorbing electric quantity generated by feedback braking of the three-phase alternating current asynchronous motor to be transmitted to a secondary direct current bus.

2. The crane off-grid wind-solar energy storage direct-current micro-grid system for multi-type new energy capture and utilization according to claim 1, wherein the energy storage system comprises: the system comprises a super capacitor bank, a lithium battery pack and a No. 2 bidirectional DCDC direct current converter; the lithium battery pack is used for storing and releasing electric energy and is connected to a secondary direct current bus through a No. 2 DCDC direct current converter; the super capacitor group is formed by connecting a plurality of single capacitors in series and parallel and is used for frequently absorbing and releasing electric energy and maintaining the voltage of the secondary direct current bus within the range of a set value Umin-Umax.

3. The crane off-grid wind-solar storage direct current micro-grid system for multi-type new energy capture and utilization according to claim 1, wherein the wind power generation system comprises: the system comprises a wind driven generator, a three-phase controllable rectifier and a No. 3 bidirectional DCDC direct current converter; the wind driven generator is used for wind power generation, and is rectified into direct current through the three-phase controllable rectifier, and the direct current is connected to a secondary direct current bus through the No. 3 bidirectional DCDC direct current converter.

4. The crane off-grid wind-solar storage direct current micro-grid system for multi-type new energy capture and utilization according to claim 1, wherein the photovoltaic power generation system comprises: a photovoltaic array, a No. 4 bidirectional DCDC direct current converter; the photovoltaic array is used for solar power generation and is connected to a secondary direct current bus through a No. 4 bidirectional DCDC direct current converter.

5. The crane off-grid wind-solar storage direct current micro-grid system for multi-type new energy capture and utilization according to claim 1, wherein the control system comprises: the system comprises an MCGS touch screen, a PLC programmable logic controller, a frequency converter and an encoder; the MCGS touch screen is used as an upper computer for man-machine interaction, the PLC is used as a core controller for crane frequency converter drive control and micro-grid electrical control, the MCGS touch screen and the PLC are communicated through an Ethernet, and the PLC, the frequency converter and the encoder are communicated through a Modbus-RTU.

6. The crane off-grid wind-solar storage direct current micro-grid system for multi-type new energy capture and utilization according to claim 5, wherein the control system is used for: (1) real-time data reading: reading real-time voltage Usc of a super capacitor bank, reading real-time voltage ULi and state of charge SOC of a lithium battery, reading real-time output voltage Uw, current Iw and power Pw of a wind driven generator, and reading real-time output voltage Upv, current Ipv and power Ppv of a photovoltaic array; (2) history data recording and reading: recording and reading historical total power generation amount Ew of the wind driven generator, recording and reading historical total power generation amount Epv of the photovoltaic array, recording and reading total power consumption Ec of a commercial power of the crane and recording and reading total power consumption amount Eave of an energy storage system of the crane; (3) displaying the real-time energy flow state: displaying a wind power generation energy flow route in real time, displaying a photovoltaic power generation energy flow route in real time, displaying a crane power consumption energy flow route, and displaying a crane feedback braking power transmission energy flow route in real time; (4) controlling the rotating speed of the motor: displaying the real-time rotating speed of the motor, and writing the real-time rotating speed into a given rotating speed to control the motor drive; (5) communication switch interface control: the button inching controls the communication contactor switch between the devices, the device contactor switch includes: the PLC, the DCDC communication switch and the super capacitor are connected into a second-level bus contactor switch.

7. A crane off-grid wind-solar storage direct-current micro-grid control method for capturing and utilizing various new energy is characterized by comprising the following steps: the wind power generation system adopts an MPPT output mode and adopts a variable step length MPPT hill climbing search control algorithm to realize that the wind power generator is always output at the maximum power point; the photovoltaic power generation system adopts two modes of MPPT output and power reduction constant voltage output, the MPPT output mode is realized through a variable step length MPPT disturbance observation algorithm, the power reduction constant voltage output mode is realized through a voltage outer ring current inner ring double closed loop PI control algorithm, the frequency converter direct current bus system adopts a constant voltage or high-voltage side window voltage control mode, and the energy storage system adopts a high-voltage side window voltage control mode for control.

8. The method for controlling the crane off-grid wind-solar-storage direct-current micro-grid for capturing and utilizing the multiple types of new energy according to claim 7, wherein the method comprises the following steps:

no. 1 two-way DCDC direct current converter adopts high-pressure side window voltage control mode, and the high-pressure side is connected the converter bus and is set for window voltage (Ulow 1, uup 1), and the low pressure side is connected second grade direct current bus, and its working logic is: when the high-voltage side U < Ulow1, the high-voltage side draws current from the low-voltage side to maintain the voltage in a window voltage interval, and when the high-voltage side U > Uup1, the high-voltage side transmits current from the low-voltage side to maintain the voltage in the window voltage interval;

the No. 2 bidirectional DCDC direct current converter adopts a high-voltage side window voltage control mode, and the high-voltage side is connected with a secondary direct current bus to set window voltage (U) ^l _ow ² ，U _up ² ) The low-voltage side is connected with a lithium battery, and the working logic is as follows: when the high-voltage side U<U ^l _ow2 When the voltage is in the window voltage range, the high-voltage side draws current from the low-voltage side, and when the voltage is in the window voltage range, the high-voltage side U>U _up ² When the voltage is in the window voltage interval, the high-voltage side transmits current from the low-voltage side to maintain the voltage;

the low-voltage side of the No. 3 bidirectional DCDC direct-current converter is connected with the direct current output after the rectification of the wind driven generator, the high-voltage side is connected with the secondary direct-current bus, the low-voltage side is connected with the high-voltage side in an output mode, and the set voltage of the No. 3 DCDC low-voltage side is the rated output voltage U of the wind driven generator _wind ；

The low-voltage side of the No. 4 bidirectional DCDC direct current converter is connected with the direct current output of the photovoltaic array, the high-voltage side is connected with the secondary direct current bus, the low-voltage side is output to the high-voltage side in a low-voltage side output mode, and the set voltage of the No. 4 DCDC low-voltage side is the rated output voltage U of the photovoltaic array _pv 。

9. The method for controlling the crane off-grid wind-solar-storage direct-current micro-grid for capturing and utilizing the multiple types of new energy according to claim 7, wherein the method comprises the following steps: the wind power generation system adopts a variable-step MPPT mountain climbing search control algorithm, and the specific steps are as follows:

step1: starting a system, initializing the output power value of the current period to be 0, the disturbance duty ratio value to be 0 and the initial duty ratio value to be D;

step2: sampling a current value I (k) and a voltage value U (k) of a current period k, and calculating output power P (k) = I (k) × I (k) of a current sampling time point; calculating the output power change delta P = P (k) -P (k-1) of the current sampling period k and the last sampling period k-1;

step3: comparing whether the power change value delta P is larger than or equal to a set minimum power change value e, if so, skipping Step4 to execute Step5, and if not, executing Step4;

step4: comparing whether the current duty ratio disturbance value delta D is smaller than or equal to the set minimum duty ratio disturbance value Dmin, if so, enabling the duty ratio disturbance value delta D = Dmin, and if not, enabling the duty ratio disturbance value to be reduced by half, namely enabling the duty ratio disturbance value delta D =1/2 delta D;

step5: comparing whether the product of the duty ratio disturbance value delta D and the output power change value delta P is larger than zero; if the result is yes, the maximum power point is not reached, the current direction disturbance needs to be continued, and the disturbance duty ratio delta D value is kept unchanged; if the result is negative, the maximum power point is disturbed, the next period needs to be disturbed in an ultra-opposite direction, and the disturbance duty ratio delta D = -delta D of the next period is made.

10. The method for controlling the crane off-grid wind-solar-storage direct-current micro-grid for capturing and utilizing the multiple types of new energy according to claim 7, wherein the method comprises the following steps: the photovoltaic power generation system adopts a variable step MPPT disturbance observation control algorithm, and the method comprises the following specific steps:

step1: starting a system, initializing the output power value of the current period to be 0, and initializing the disturbance voltage value to be delta U;

step2: sampling the output voltage U (k) and the output current I (k) of the photovoltaic array in the current period k, and calculating the current output power P (k) = U (k) × I (k);

step3: comparing with the value of the last sampling period k-1, calculating the voltage variation dU = U (k) -U (k-1) and the power variation dP = P (k) -P (k-1), and calculating the value alpha =1-exp (| dP |) of the current time-varying factor;

step4: comparing whether the value of dU + dP is larger than zero, if so, indicating that the current voltage does not reach the maximum power point, and keeping the current disturbance direction to enable the disturbance voltage value to be alpha delta U; if the result is negative, the current voltage is positioned on the left side of the maximum power point, and voltage disturbance needs to be applied towards the reverse direction, so that the disturbance voltage value is-alpha delta U;

step5: let U (k-1) = U (k), P (k-1) = P (k), return to Step2, execute the control flow of the next cycle.

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