45results about How to "Achieving Maximum Power Tracking" patented technology

The invention discloses a variable speed constant frequency wind power generation system integrated with an energy storing device and control methods. A variable pitch draught fan is connected with a variable pump through a coupler, the variable pump, a one-way valve A, a two-position two-way electromagnetic directional valve B, a variable motor and an oil filter are sequentially connected through hydraulic pipelines to form a loop-locked main hydraulic speed regulation loop, the variable motor is connected with a power generator or an electromotor through a clutch A, the energy storing device comprises a pump or a motor and a high-pressure gas storage tank, and the power generator or the electromotor is connected with the pump or the motor through a clutch B. A wind generating set and the energy storing device are integrated, the displacement of the variable pump and the displacement of the variable motor are independently regulated, maximum power tracing of a wind turbine can be achieved, it can be guaranteed that the output rotating speed of the variable motor is constant, the output frequency of the power generator is stable, different control methods are adopted for different types of wind power, the influences of the time and climate change on wind power generation are effectively avoided, the wind energy utilization rate is greatly increased, and wind electricity quality is improved.

The invention discloses a multi-phase direct-drive permanent-magnet wind power generation variable current integrated system and a control method thereof. The system comprises a multi-phase direct-drive permanent-magnet wind power generator and a modular multilevel inverter, wherein the quantity of three-phase windings of the multi-phase direct-drive permanent-magnet wind power generator is 6n (n is equal to 1, 2, 3 and so on), the modular multilevel inverter comprises six three-phase bridge arms, each bridge arm comprises n sub-modules and a filter inductor, each sub-module comprises a PWM (Pulse Width Modulation) rectifier, two IGBTs (Insulated Gate Bipolar Transistors) and a capacitor, the two IGBTs are connected in series and then are connected in parallel with the capacitor and a DC side of the PWM rectifier, and an AC side of the PWM rectifier is connected with one of the three-phase windings of the multi-phase direct-drive permanent-magnet wind power generator. In the wind power generation system, modular series-parallel connection is performed on three-phase branches, each three-phase winding of the wind power generator is controlled, thus, maximum wind energy capturing and high-voltage direct grid connection of a multi-phase permanent-magnet synchronous motor can be achieved, and a grid-connection transformer is omitted.

The invention discloses a hybrid modulation strategy based power balance control method for a cascade H-bridge inverter and aims to solve a problem of incapability of stable operation of a system due to input power imbalance of a photovoltaic battery panel on a DC side of the photovoltaic inverter. The method includes steps of 1, master DC side voltage control used for realizing maximal power point voltage tracking by H-bridge unit DC side voltages and obtaining a system active current command value; 2, grid side current decoupling control capable realizing independent control of active current and reactive current and generating inverter total modulation wave voltage; 3, inter-unit power balance control including determining the correct switching states of each H-bridge unit so as to realize the power balance control among the H-bridge units and the maximal power tracking of the H-bridge units through DC side voltage error ranking of the H-bridge units. The method can be suitable for different kinds of working conditions. By adopting the method, stable operation of the cascade H-bridge photovoltaic inverter in a comparatively large range and system power generation capacity can be guaranteed.

The invention relates to a self-adaptation sliding mode control strategy for a permanent magnet synchronous wind power generation system. The self-adaptation sliding mode control strategy is technically characterized in that mathematic models of various components of a wind power generation system power generator side are established; an interfered PMSG model with uncertain parameters is established; a Terminal sliding mode surface is constructed; a rotation speed self-adaptation Terminal sliding mode controller is constructed; and a current self-adaptation Terminal sliding mode controller is constructed. On the basis of influences from inherent nonlinearity, uncertainty, outside interference and other factors of the permanent magnet synchronous wind power system, the Terminal sliding mode control theory and the self-adaptation technology are combined, the self-adaptation Terminal sliding mode control strategy is formed, maximum power tracing for a permanent magnet synchronous draught fan is achieved, the maximum wind energy below the rated wind speed can be captured, vibration can be effectively restrained, and good self-adaptability and robustness are achieved.

The invention discloses a photovoltaic cell multiple-peak maximum power tracing method and system based on a particle swarm. The data values of voltage and current output by a photovoltaic cell underthe partial shaded condition are obtained, particles are initialized to a possible voltage value, the maximum power point of the particles is iteratively continually updated, a historical optimal position and a global optimal position of an individual are looked for, therefore, the multi-peak maximum power point obtained under the complicated partial shaded condition is determined, and after a corresponding ending condition is reached, searching of the maximum power point is ended. Compared with a traditional maximum power tracing method, the maximum power tracing method can prevent searchingfrom trapping in local optimum, the tracing precision and speed are ensured, oscillation loss generated in the tracing process is reduced, and the method more conforms to reality.

The invention discloses a single-phase cascade H-bridge grid-connected inverter control method under the weak grid and aims to realize stable operation of a cascaded photovoltaic inverter under the extremely weak grid. The method comprises following steps of (1) of DC side voltage control, the DC side voltage of each H-bridge unit is realized to track the maximum power point voltage; (2) of droopcontrol, a grid side current control command is obtained through a droop control equation and an AC voltage loop; and (3) of network side current control, independent control of the active current andthe reactive current can be realized, and an inverter modulation signal is generated. The method is advantaged in that advantages of both the droop control strategy and maximum power tracking are integrated, not only can the stable operation range of the cascaded H-bridge PV grid-connected inverter be expanded, but also maximum power tracking of each H-bridge unit can be realized.

The invention discloses a three-port direct-current converter device and a hybrid modulation method and closed loop control method of the three-port direct-current converter device. The direct-current converter device comprises a main circuit and a control circuit, wherein the main circuit comprises a double-input full-bridge inverter, a high-frequency transformer, a half-bridge full-control rectifier and a voltage stabilization capacitor; the control circuit comprises a storage battery voltage sampling circuit, a storage battery current sampling circuit, a photovoltaic battery voltage sampling circuit, a photovoltaic battery current sampling circuit, a full-bridge inverter current sampling circuit and an output voltage sampling circuit, the output end of the storage battery voltage sampling circuit, the output end of the storage battery current sampling circuit, the output end of the photovoltaic battery voltage sampling circuit, the output end of the photovoltaic battery current sampling circuit, the output end of the full-bridge inverter current sampling circuit and the output end of the output voltage sampling circuit are connected to a digital signal processor, and the signal output end of the digital signal processor is connected with a first MOS transistor driving circuit, a second MOS transistor driving circuit, a third MOS transistor driving circuit, a fourth MOS transistor driving circuit, a fifth IGBT driving circuit and a sixth IGBT driving circuit. According to the three-port direct-current converter device, cost is saved, and the three-port direct-current converter device can be used in electrical equipment.

The invention discloses a solar CVT (Constant-Voltage Transformer) control method based on temperature detection, which comprises a photovoltaic cell array, a DC / DC (Direct Current / Direct Current) converter, a photovoltaic voltage detection circuit, a PI (Proportional-Integral) adjuster, a PWM (Pulse-Width Modulation) controller, an isolation driving circuit, a temperature sensor and an arithmetic circuit are provided, wherein the photovoltaic cell array is connected with the DC / DC converter; the temperature sensor, the arithmetic circuit, the PI adjuster, the PWM controller and the isolation driving circuit are connected between the photovoltaic cell array and the DC / DC converter sequentially; and the photovoltaic voltage detection circuit is connected in parallel between the photovoltaic cell array and the DC / DC converter, and connected with the PI adjuster. A temperature of a photovoltaic cell is detected by the temperature sensor; a set voltage value of a maximum power point is adjusted in real time according to the detected temperature and the voltage-temperature characteristic of the measured maximum power point of the photovoltaic cell; and the method is simple in structure, low in cost and high in practicability.

The invention discloses a multiple-input fly-back photovoltaic grid-connected inverter. The inverter comprises a plurality of fly-back circuits, a plurality of photovoltaic assemblies, a clamping capacitor, an output filter circuit, an inversion circuit and an electric network. The each fly-back circuit comprises a positive input terminal and a negative input terminal, a clamping terminal, and a positive output terminal and a negative output terminal. The positive input terminal and the negative input terminal of the each fly-back circuit are connected with the positive output terminal and the negative output terminal of the photovoltaic assembly respectively. The clamping terminals of all the fly-back circuits are connected with one end of the clamping capacitor. The output terminals of all the fly-back circuits are connected with each other in parallel and are connected with the output filter circuit. The photovoltaic grid-connected inverter of the invention can be connected with a plurality of photovoltaic assemblies simultaneously. Through one inverter, maximum power tracking of all the photovoltaic assemblies can be realized. All the fly-back circuits share the clamping capacitor, the output filter circuit and the inversion circuit. The inverter has the following advantages that: cost is low; generating efficiency is high; grid-connected current harmonics are low and so on.

The invention discloses a photovoltaic maximum power tracing system and method based on P-U curvature characteristics. The method includes the following steps: sampling the output voltage and the output current of a photovoltaic cell panel in real time; calculating curvature changes corresponding to P-U curves output by the photovoltaic cell panel in real time; determining the duty ratio change direction of a Boost circuit in the next step according to the direction of the curvature changes and the direction of changes of the voltage output by the photovoltaic cell panel; sending the adjusted duty ratio to the Boost circuit to control the output voltage of the photovoltaic cell panel to be adjusted in the maximum power output direction. By means of the photovoltaic maximum power tracing system and method, the tracing direction is determined with the method of calculating the curvature increments of the P-U curves output by the photovoltaic cell panel in real time, maximum power point tracing of a photovoltaic cell is achieved, the response speed is high, rapid tracing control is easily achieved, and the photovoltaic maximum power tracing system and method are suitable for areas with the high external environmental change speeds; in addition, shocks nearby the maximum power point are small, and power losses nearby the maximum power point are fewer.

The invention relates to a maximum power tracing method. The maximum power tracing method optimizes and adjusts a conventional maximum power tracing algorithm on the basis of power prediction, that is, current maximum power tracing disturbance is modified and optimized through power prediction when an original maximum power tracing algorithm is reserved. The maximum power tracing method can overcome the defects of the conventional maximum power tracing algorithm and solve the problems such as misjudgment and local maximum power. The maximum power tracing method reserves the original maximum power tracing algorithm to the limit, and thus facilitates transplant of optimization algorithms under different platforms and different maximum power tracing methods.

The invention discloses a solar grid-connected inverter with a maximum power point tracking (MPPT) system. The solar grid-connected inverter comprises a cabinet-type container box body (22) of a metal structure, a door lock (18) and a door (19). Working state indicating lights (17) and an LCD (Liquid Crystal Display) screen (21) are arranged on the surface of the door (19), and a cooling fan (20) is arranged on the lateral face of the box body. The solar grid-connected inverter is characterized in that all unit circuits are arranged in the cabinet container box body of the metal structure, a photovoltaic grid-connected system which takes a DSP (Digital Signal Processing) microprocessor (12) as a main control chip has rapid operational capability and rich peripheral resources so as to provide a favorable platform for the entire control system, and an MPPT control algorithm which has the tacking object of making a load acquire maximum power is adopted to realize the tracking of a maximum power point.

The invention provides a modularized photovoltaic energy storage system, wherein the output ends of energy storage cell units are connected with direct current bus input ends of half-bridge modules to form multiple energy storage cells; the alternating current output sides of the multiple energy storage units are connected in series and then connected with electric reactors in series to form a one-phase half-bridge arm; two half-bridge arms are connected in series to form a one-phase overall bridge arm, and three bridge arms form three-phase bridge arms in the manner; the upper ends of the three bridge arms are connected to form the direct current bus positive end of the photovoltaic energy storage system; the lower ends of the three bridge arms are connected to form the direct current bus negative end of the photovoltaic energy storage system; the connecting points of the upper bridge arm and the lower bridge arm of the three-phase bridge arms, namely the three middle points of the three bridge arms are led out to form an alternating current port of the photovoltaic energy storage system; and the output positive end and the output negative end of a photovoltaic group string are connected with the direct current bus negative end and the direct current bus negative end of the photovoltaic energy storage system for transmitting voltage. The modularized photovoltaic energy storage system is based on a modularized multi-level structure; the modularized photovoltaic energy storage system is provided with the alternating current port, the direct current port and the cell port, so that the modularized photovoltaic energy storage system can be connected with a photovoltaic module, an energy storage cell and an alternating current power grid at the same time.

The invention provides a device and a method for power system MPPT control for a satellite, and solves a problem that an existing power system used for a satellite is difficult to track maximum power of a microsatellite. The forward power signal output end of a solar cell array is connected with the anode of a first diode, the cathode of the first diode is connected with the power tracking signal input end of a MPPT control circuit, the cathode of a second diode, and the forward power signal input end of a load. The power signal output end of the MPPT control circuit is connected with the anode of a second diode and the anode of a lithium ion battery pack. The cathode of the lithium ion battery pack is connected with ground. The negative power signal output end of the solar cell array is connected with the negative power signal input end of the load and ground at the same time. The device and the method are suitable for power system control used for satellites.

The invention provides a power transmission method and system for realizing real-time tracking internal resistance matching. The method comprises the steps: carrying out modeling and selection on a Boost circuit boosting module of a two-stage three-phase grid-connected photovoltaic power generation system, and obtaining an equivalent model and a simplified equivalent model of an inverter DC side for an inverter circuit; defining photovoltaic cell internal resistance RST, equivalent input resistance ROUT of the inverter input side and duty ratio DST of a photovoltaic inverter under a standard condition, and calculating photovoltaic cell internal resistance variation delta R1, which changes with the outside world, and duty ratio delta D, which is adjusted with the change of the delta R1; andby changing the delta D, finding real-time match with the photovoltaic cell internal resistance delta R, and realizing photovoltaic power generation maximum power tracking. On the basis of the methodprovided by the invention, the invention further provides the power transmission system for realizing real-time tracking internal resistance matching. On the premise of ensuring tracking accuracy andstability, the method and system realize simplicity and rapidity of a power transmission algorithm for realizing real-time tracking internal resistance matching.

The invention relates to a photovoltaic micro-inverter power generation system based on a multi-winding high-frequency magnetic coupling system. The photovoltaic micro-inverter power generation system comprises a grid-connected system, a plurality of photovoltaic cell panels and a control unit, wherein each photovoltaic cell panel is connected to a bus capacitor through a boost topology; each bus capacitor is connected with a primary side winding of a multi-winding transformer through an H bridge inverter circuit; a secondary side winding of the multi-winding transformer is connected with a back-to-back H bridge inverter circuit; the control unit is set to be in information interaction with the grid-connected system, so that the voltages of the multiple bus capacitors are balanced, the voltages of the direct-current bus capacitors are balanced and the power grid side input power factor is 1, and the back-to-back H bridge inverter circuit is controlled to output alternating current of power frequency. The photovoltaic micro-inverter power generation system is small in size, light in weight, low in cost and capable of independently controlling each photovoltaic cell panel to track largest power points, has remarkable economic benefits and thus is suitable for popularized application.

The invention discloses a wind power generation maximum power tracking method of a speedless sensor. The method comprises the steps of: 1) obtaining maximum wind power through an experiment to capture a relation curve with the rotating speed of a motor; 2) performing the modeling analysis for the electromagnetic torque of a generator; 3) analyzing a transmission chain model in a maximum power tracking state; 4) determining a relation between an optimal output power and synchronous speed of an induction motor, and building a lookup table; and 5) designing an adaptive controller for a system. The method can realize the maximum power tracking of a wind driven generator in low wind speed without measuring the rotating speed of the wind driven generator, the wind magnitude and the direction. As the magnitude and the direction of wind are difficult to be invariable under the influence of various factors, the accurate measuring process is complex, and the system cost is increased. Therefore, the method effectively solves the measuring difficulties in the measurement of wind magnitude and direction in a conventional wind power generation system, and reduces the system cost to a certain extent.

The invention discloses a piezoelectric expandable energy collection interface circuit based on MPPT. The piezoelectric expandable energy collection interface circuit comprises expandable piezoelectric transducers, expandable peak detection switches, an LC resonant inductor, a rectifying circuit, a rectifying capacitor, a DC-DC conversion chip and an energy storage capacitor, wherein the number ofthe expandable peak detection switches corresponds to the number of the piezoelectric transducers, and the maximum power point tracking (MPPT) module is composed of a peak voltage tracking circuit and a hysteresis voltage comparator. The expandable piezoelectric transducers, the expandable peak detection switches, the LC resonant inductor, the rectifying circuit and the rectifying capacitor forman expandable series synchronous switch inductor energy collection interface circuit. The maximum power point tracking (MPPT) module detects peak open-circuit voltage of the piezoelectric transducersand voltage at two ends of the rectifying capacitor during normal operation of the expandable series synchronous switch inductance energy collection interface circuit, and keeps the voltage of the rectifying capacitor near the maximum output power by controlling the DC-DC conversion chip. The circuit can be completely self-powered, so that the energy collection efficiency is greatly improved.

The invention discloses a method and device for establishing a photovoltaic cell simulation model considering local shading. The method comprises the steps of obtaining standard parameters of a photovoltaic cell; determining equivalent series resistance, equivalent parallel resistance, P-N junction effect current and P-N junction effect reverse saturation current of the photovoltaic cell simulation model according to the standard parameters of the photovoltaic cell; according to the standard parameters, the equivalent series resistance, the equivalent parallel resistance, photo-generated current, the P-N junction effect current, the P-N junction effect reverse saturation current and an avalanche breakdown voltage, determining output load current of the photovoltaic cell simulation model; based on the equivalent series resistance, the equivalent parallel resistance, equivalent diode P-N junction direction saturation current and the output load current, establishing the photovoltaic cellsimulation model considering the local shading; the equivalent parallel resistance is connected in parallel with a reverse current source, and a bypass diode is connected in parallel between the positive and negative electrodes of a photovoltaic cell assembly. The device is used for implementing the method.

The invention relates to a mechanical and electrical integrated photovoltaic direct-current high-power submersible pump which comprises a submersible pump, a direct-current motor, a solar power supply component and a controller, wherein an upper end of a shell of the direct-current motor is fixedly connected with a lower end of a pump body; the upper end of a rotor shaft of the direct-current motor is connected with the lower end of a pump shaft through a coupler; the controller and the output end of the solar power supply component are connected with an input cable of the direct-current motor; and the controller is connected with a water level sensor. The controller is utilized to realize the automatic over-current protection for the direct-current motor, the maximum power tracking for the solar power supply component, the rotating speed abnormal protection for the motor, the dry striking protection for the water pump, the double-water-level detection and automatic stopping and the prevention for the backwater restarting of the pipeline. The motor has a permanent magnetic brushless position-sensor-free structure; after a stator and a rotor are respectively subjected to plastic package, the water flow is utilized to realize cooling; a graphite bearing is used for realizing water lubrication, so that the heating problem is solved; and the mechanical and electrical integrated photovoltaic direct-current high-power submersible pump has the advantages of high power of the motor, no noise, full automation, high reliability, excellent suitability of supplied water volume for evaporation capacity, high flow, high lift and all-weather unattended running.

The invention provides a ship photovoltaic power generation grid-connected system. The system comprises a solar photovoltaic power generation device which is used for photovoltaic power generation, acapacitance filter which is connected with the solar photovoltaic power generation device and used for converting the pulse direct current output by the solar photovoltaic power generation device intosmooth direct current, an improved high-boost-ratio ship photovoltaic power generation grid-connected Z-source inverter which is a cascaded switch inductance type Z-source inverter and is used for modulating direct current into alternating current through SPWM pulse width modulation; the ship power grid is connected with the output end of the improved high-boost-ratio ship photovoltaic power generation grid-connected Z-source inverter. According to the improved high-boost-ratio grid-connected Z-source inverter ship photovoltaic power generation system, the change fluctuation of the current ship photovoltaic power generation output alternating voltage voltage is effectively reduced, the quality of the output alternating voltage voltage is improved, and the stability of ship grid connectionis ensured.

The invention discloses an integrated photovoltaic module taking a printed circuit board (PCB) as a bottom plate. The integrated photovoltaic module comprises a PCB bottom plate, photovoltaic cell pieces, printed circuits, an inversion control circuit and two output sockets, wherein the printed circuits are arranged on a front surface of the PCB bottom plate and are used for connecting the photovoltaic cell pieces, a plurality of photovoltaic cell pieces are sequentially arranged on the front surface of the PCB bottom plate, positive leads and negative leads of all photovoltaic cell pieces arewelded on corresponding welding points on the printed circuits to form a photovoltaic cell string comprising the photovoltaic cell pieces, an output of the photovoltaic cell string is an output port,the inversion control circuit is printed at the top of a reverse surface of the PCB bottom plate, an input end of the inversion control circuit is connected with the output port, and an output end ofthe inversion control circuit is connected with the two output sockets. By the integrated photovoltaic module, the production efficiency and the product quality of the photovoltaic module are improved; and meanwhile, the photovoltaic cells and the inversion control circuit are integratedly designed, maximum power tracking of each photovoltaic module can be achieved, maximum energy utilization isachieved, and great convenience is brought to application.

The invention discloses a DC synthesis maximal power matching circuit and a digital control method thereof. The method comprises that S1) it is supposed that n=0, the duty ratio is controlled as 0, and an equivalent input voltage VI is detected; S2) a theoretical duty ratio is calculated, and the duty ratio is controlled as the theoretical duty ratio; S3) the equivalent input voltage is detected and recorded; S4) whether the equivalent input voltage is within the interval of [1 / 2VI-alpha, 1 / 2VI+alpha] is determined, if NO, a step S5) is turned to, and otherwise, a step S6) is turned to; S5) whether the equivalent input voltage is greater than 1 / 2 VI is determined, if YES, the duty ratio is increased and the step S3) is returned to, and otherwise, the duty ratio is decreased and the step S3) is returned to; and S6) the duty ratio at this time is recorded as Dn, whether the duty ratio Dn is within the interval of [D0-beta, D0+beta] is determined, if YES, it is supposed that n=n+1 and thestep S3) is returned to, and otherwise, the step S1) is returned to. According to the circuit and method, the difficulty in tracking the maximal power due to a DC synthesis circuit is micro and cannot be measured accurately is overcome, the circuit and method are not limited to a Boost topology structure, and requirement of maximal power matching and transmitting of different low-power circuits can be met.

A solar battery array variable step-size MPPT control circuit and a control method, the method comprising a current sampling circuit, an MPPT control circuit, a hysteresis loop comparison circuit, and a step-size switching circuit. The current sampling circuit is used to collect the output current of the solar cell array, and the MPPT control circuit is used to realize the tracking of the maximum power point; the hysteresis comparison circuit is used to increase the anti-interference ability of the step switching circuit; the step switching circuit is used for MPPT tracking step switch. The circuit realizes that when the current of the solar cell array is small, the maximum power point is tracked with a larger step size, and when the current of the solar cell array is large, the maximum power point is tracked with a smaller step size, which improves the maximum power point of the solar cell array Tracking accuracy.

The invention relates to a maximum power tracking device of a photovoltaic grid-connected inverter control system. The maximum power tracking device is provided with an MPPT module of a photovoltaic string port, a voltage regulator and a current regulator. And the matching relation of the multi-path photovoltaic string connected with the MPPT line is re-determined by comparing a plurality of open-circuit voltages of the multi-path photovoltaic string connected with the MPPT line with the voltages of a plurality of maximum power points, and the multi-path photovoltaic string connected with the MPPT line is switched between a working state and a standby state. The method can flexibly and intelligently select the tracking mode of a plurality of MPPT to the multi-path photovoltaic module, achieves the maximum power tracking of the multi-path photovoltaic module, and improves the working efficiency of a photovoltaic grid-connected inverter.

The invention discloses a tidal energy control system, which comprises a tidal energy power generation device, a hardware circuit topology and a control module, and is characterized in that the hardware circuit topology comprises an uncontrolled rectification circuit and a Boost converter circuit, and the Boost converter circuit is connected in parallel with a hybrid semiconductor parallel device; the control module comprises a variable step frequency adaptive filtering controller, a maximum power tracking controller and a high-performance prediction controller. Maximum power point capturing of output power is achieved through a self-adaptive maximum power control strategy, and meanwhile smooth processing is conducted on tidal energy output power on the premise that power is not lost too much; the high-efficiency, low-harmonic-content and high-power-factor operation of the power converter is realized by establishing a cost function containing device loss, harmonic content and power factors through a high-performance predictive control method. Therefore, the tidal power generation device can meet high-performance and high-stability power supply requirements in the island, coast or offshore power generation process.

The invention discloses a photovoltaic cell multiple-peak maximum power tracing method and system based on a particle swarm. The data values of voltage and current output by a photovoltaic cell underthe partial shaded condition are obtained, particles are initialized to a possible voltage value, the maximum power point of the particles is iteratively continually updated, a historical optimal position and a global optimal position of an individual are looked for, therefore, the multi-peak maximum power point obtained under the complicated partial shaded condition is determined, and after a corresponding ending condition is reached, searching of the maximum power point is ended. Compared with a traditional maximum power tracing method, the maximum power tracing method can prevent searchingfrom trapping in local optimum, the tracing precision and speed are ensured, oscillation loss generated in the tracing process is reduced, and the method more conforms to reality.

The invention discloses a method and a system for realizing an optimal value of charging current of a storage battery in an off-network charging system. The method comprises the following steps: A, selecting an initial output current reference value, outputting operation results by a digital regulator, feeding the operation results into a pulse width regulator to generate a control signal, and obtaining an actual output current value by current feedback; B, calculating the change direction of the current according to the actual output current value and the initial output circuit reference value, calculating and updating the current disturbance direction results of next MPPT (maximum power point tracking) by combining the current disturbance direction of this MPPT; C, updating the output current reference value at fixed step length according to the calculated current disturbance direction results of next MPPT, and obtaining maximal charging current by repeatedly updating. According to the method and the system for realizing the optimal value of the charging current of the storage battery in the off-network charging system, measurement for voltage and current signals is cancelled, so that the maximum power tracking of a PV (photovoltaic) component can be realized by only needing to measure the charging current of the storage battery, and therefore, the hardware cost is lowered, and the requirements of processor performances are lowered.