129results about How to "Improve output power quality" patented technology

The invention relates to a distributed photovoltaic energy storage system and an energy management method. The system comprises a photovoltaic cell array and an energy storage cell component; a converter device comprises a photovoltaic cell direct current conversion module, an energy storage cell direct current conversion module, a rectification conversion module, a grid-connected inverter module and an off-grid inverter module; the energy management system is connected with each module; a layered control strategy is applied to optimize operation of the distributed photovoltaic energy storage system; a central decision-making level makes an operating strategy of the whole system according to current energy conditions and feeding characteristics of each power supply; a centralized control level monitors states of distributed power supplies in real time and takes corresponding control measures under different energy conditions; and a local executing level selectively cuts a part of loads or stores surplus electricity into an energy storage cell according to the load requirement of an actual system and the energy conditions. Photovoltaic power generation and energy storage technologies are sufficiently combined, so that the photovoltaic and the energy storage are intelligently controlled, and the energy management efficiency, the power supply reliability, power quality and the like of the system are effectively improved.

The invention belongs to the technical field of the power quality control of wind power generation, in particular a double-fed aerogenerator excitation system based on the hybrid stored energy of a super capacitor and a storage battery. The system is characterized by comprising a rotor side converter 3, a net side converter 4, a chopper A5, a chopper B7, a super capacitor 6, a storage battery 8, a bilateral switch as well as a limiting resistor Rl and a direct current side capacitor C, wherein a hybrid stored energy device comprising the chopper A5, the chopper B7, the supper capacitor 6 and the storage battery 8 is connected to both ends of the direct current capacitor in parallel; the rotor side converter 3 is responsible for providing excitation power to an aerogenerator; the net side converter 4 is responsible for transmitting power exchanging with the output end of the rotor side of the aerogenerator, and exactly controlling the charge and discharge power of the storage battery and the super capacitor by controlling the chopper A5 and the chopper B7 so as to compensate external power fluctuation. The invention has the advantages that the aerogenerator generates stable electrical energy under the condition of the frequent fluctuation of the aerogenerator, the safe stability of large-scale synchronization running of a wind farm is improved, and the excitation system can also be widely used in ocean power generation such as wave-actuated power generation and tidal power generation.

The utility model provides a wind farm super capacitor energy storage type unified power quality conditioner which comprises a compensation transformer, a series connection compensator, a parallel connection compensator, a current limiting circuit, a super capacitor group, a bidirectional DC/DC chopper circuit, a signal acquisition conditioning circuit, a control circuit and a driving circuit. The conditioner has two control modes which are a power regulating mode and a low voltage ride through mode. In the power regulating mode, the wind power unit assembly output power quality can be improved, in the low voltage ride through mode, namely in a fault condition, the blower outlet voltage can be maintained and is not reduced, and the current influence on a blower system is avoided until the voltage is recovered and the low voltage ride through is realized. Electric energy generated by the blower in a fault stage can be stored in the super capacitor group, the energy is transmitted to the power grid after a power grid is recovered to a normal state, and the waste of the electric energy is avoided. The conditioner has versatility and can be applied to wind farms of various blower generations of a fixed speed induction generator (FSIG), a permanent magnet synchronous generator (PMSG) and a double-fed induction generator (DFIG).

The invention discloses a photovoltaic micro-inverter based on secondary-side reference current reconstruction, a control system and a control method. A topological structure of a staggered flyback laser photovoltaic micro-inverter based on the secondary-side reference current reconstruction is adopted. The control system comprises the staggered flyback laser photovoltaic micro-inverter based on the secondary-side reference current reconstruction, a direct current voltage and current sampling module, a driving circuit, a secondary-side pulse current sampling module, an alternating current sampling and phase locking module and a signal processing unit. The control method is an indirect control method approximate to grid-connected current direct control, primary-side reference current based on the secondary-side reference current reconstruction is adopted to control connection and disconnection of a primary-side switching tube of a flyback converter, and the control method effectively avoids the problem of slow control response, low tracking accuracy and the like in a direct control method, can guarantee same frequency and same phase of output current and public power grid voltage, reduces total harmonic distortion of grid-connected current substantially, and improves output power quality.

The invention discloses a VIENNA rectifier neutral point potential alternating-direct-current component balance control method which can reduce design capacity of a capacitor on a direct-current side and a filter on an alternating-current side and save cost of a tri-level VIENNA rectifier. On the basis of common mode component injection modulation, a common mode component direct-current compensation coefficient and an alternating-current compensation coefficient are modified dynamically, so that the problem of neutral point unbalance of direct-current and alternating-current components is solved; more importantly, the method guarantees uniformity between triphase alternating-current side harmonic distortion rate and SVPWM while substantially inhibiting neutral point potential low-frequency oscillation in conventional modulation methods and improving quality of output power and can be popularized and applied in the field of battery testing, charging facilities and driving systems.

The invention relates to a control system and a control method of a permanent magnet synchronous motor of a series-connected cascade-type multi-level converter and belongs to the field of power electronic control technology, and solves the problem that traction motors are huge in harmonic wave output and low in output power quality in the existing new energy electric cars, so that safety and comfortableness of new energy electric cars are affected. In the invention, traditional traction motor driver structure is abandoned, topology of the series-connected reaction type multi-level converter is provided, high-performance drive control of the motor can be realized and the problem of single direct-current power supply is solved, the control method is optimized, and more reasonable multi-level current wave form output design is provided according to different requirements of current harmonics to built-in permanent magnet synchronous motors in low speed, middle speed and high speed. The control system and the control method of the permanent magnet synchronous motor of the series-connected cascade-type multi-level converter are applicable to new energy automobiles which need high-efficiency and high-performance output, and single power to supply energy source.

The invention provides an electrified railway through-type traction power supply system, and belongs to the technical field of railway traction power supply systems. The traction power supply system is characterized in that the output end of a connection transformer CT is connected with an alternating current side of a three-phase MMC rectifier through a filter inductance Ls, and a direct currentside DC is connected with a direct current bus; the input end of a single-phase MMC inverter is connected with the direct current bus, the output side is connected with a single-phase step-down transformer SDT primary winding, and single-phase alternating current, with output voltage of 27.5 kV, of the secondary side of the single-phase step-down transformer is connected into a railway traction network to supply power to trains. The alternating current side of a AC-DC transformer of wind power generation WP is connected with the output of a fan, the direct current output side is connected thedirect current bus, one side of a DC-DC converter of photovoltaic power generation PV is connected with the output of a photovoltaic panel, the other side of the DC-DC converter of the photovoltaic power generation PV is connected with the direct current bus; and one side of a DC-DC converter of an energy storage system NS is connected with a hybrid energy storage system formed by a storage battery and a super capacitor, and the other side of the DC-DC converter of the energy storage system NS is connected with the direct current bus.

The invention discloses a method of load shedding of a floating wind turbine generator system based on semi-active structure control of a magneto rheological damper. The method includes the following steps: (1) analyzing the structure of the magneto rheological damper, obtaining a force-displacement relationship of the magneto rheological damper; (2) establishing an equation of motion of a multi-degree of freedom system of an offshore floating wind turbine generator system which is configured with the magneto rheological damper, and establishing equations of motion of the wind turbine generator system and the magneto rheological damper; (3) controlling the magneto rheological damper through a LQR controller and a Fuzzy controller so as to reduce the pitch angle of the floating wind turbine generator system and the longitudinal displacement of a nacelle. According to the invention, the method overcomes the defects of passive control and active control in structural control of a damper, requires less extra energy, requires simple apparatus and is not less susceptible to stability loss, can effectively reduce total load of the floating wind turbine generator system, guarantees stability of a platform, and further increases service life and energy quality of output electricity of a wind turbine generator.

The invention discloses a modulating method and a control device of a soft direct current power transmission modularized multi-level transverter. The method comprises the steps of controlling the power as well as voltage and current in a closed-loop mode to obtain three-phase modulation waves; and according to the three-phase modulation wave or the modulation wave and the sub-module number, issued by a direct current control protective system, and the sub-module number put into each bridge arm and the interpolation increment of the putting number of each bridge arm sub-module, obtained by calculating the rated voltage of the sub-modules, overlapping a high-frequency interpolation increment on the sub-module number put on the low-frequency bridge arm by a high-frequency FPGA (field programmable gate array), thus obtaining the high-frequency bridge arm modulation command and realizing the high-level number output. The modulating method and the control device of the soft direct current power transmission modularized multi-level transverter can meet the modulation demands of the soft direct current power transmission modularized multi-level transverter, and can save software and hardware resources, and break through the limitations such as long control period, low frequency and low output level number of traditional digital controllers such as a DSP (digital signal processor), thus realizing the high-level number or even whole-level output under the low-frequency control, obviously reducing the output voltage harmonic waves and improving output electric energy quality.

The invention discloses a coordination control method applied to a flywheel energy storage matrix system of a wind power plant. The method comprises the following steps of: (1) establishing a wind power plant flywheel energy storage matrix topological structure; (2) establishing a control system of a flywheel energy storage matrix; (3.1) performing flywheel energy storage matrix system discharge control, wherein when Prfw is less than or equal to POmaxj, a flywheel energy storage unit j is solely connected, and when Prfw is more than or equal to POmax1, first m flywheel energy storage units with the highest rotation speed need to be selected one by one; and (3.2) performing flywheel energy storage matrix charge control, wherein when the absolute value of Prfw is less than or equal to PImaxj, the flywheel energy storage unit j is solely connected for energy storage, and when the absolute value of Prfw is more than or equal to PImaxn, first m flywheel energy storage units with the lowest rotation speed need to be selected one by one. By virtue of the coordination control method, the advantages of the flywheel energy storage matrix system is given full play more effectively, the unit switching loss and operation loss are reduced, the stability of the flywheel energy storage matrix system and a power system is ensured, and thus the quality of electric energy output from wind power is improved.

The invention provides an MMC slave module capacitance voltage balance control method suitable for carrier phase shifting modulation. According to the invention, pulses in a carrier period are divided into first half period pulses and second half period pulses based on traditional carrier phase shifting modulation so that a ranking rule of pulse duty ratio in half a carrier period can be obtained. Dynamic ranking is performed on all slave module capacitance voltage in each half carrier period. Pulses in the half carrier periods are reallocated according to the magnitude of the capacitance voltage, so that dynamic balance of slave module capacitance voltage is realized. According to the invention, slave module capacitance voltage balance can be realized without changing prior modulation waves and the modulation effect totally equals to that carrier phase shifting modulation. No external loop current is generated at the same time of realizing the slave module capacitance voltage balance, so that output current quality is ensured.

The invention provides a three-level active triple harmonic injection matrix converter with a T-shaped structure. The three-level active triple harmonic injection matrix converter comprises a rectification-stage circuit, a triple harmonic injection circuit, an inversion-stage circuit and an input LC filter, wherein the rectification-stage circuit is used for rectifying an alternating current input from a three-phase AC input voltage provided by a three-phase AC power supply to a six-pulse DC voltage, the triple harmonic injection circuit is used for generating triple harmonic from a direct current and injecting the triple harmonic to the rectification-stage circuit, the inversion-stage circuit is used for converting the direct current to the alternating current, and the input LC filter comprises a filtering inductor and a filtering capacitor and is used for filtering and providing a neutral point of an inversion stage in the inversion-stage circuit. The three-level active triple harmonic injection matrix converter has the advantages of better control performance, lower common-mode level and higher system efficiency, the control range of input reactive power is expanded, synchronous modulation is not needed, higher output power quality is also provided, and an output waveform is improved.

The invention discloses a robust control method based on SSR-KDF for a grid-connected inverter. An output signal of a direct current bus voltage control ring, which is controlled by PI, serves as a reference value for output current of the grid-connected inverter, a tracking value of an actual value of the output current and a differential signal are extracted from an output end of the grid-connected inverter and serve as an input signal of a grid-connected inverter controller to be input into the gird-connected inverter controller, an indirect control signal of the grid-connected inverter is output and obtained after calculation, and the reference value for the output current of the inverter is subtracted from the indirect control signal of the grid-connected inverter to obtain actual control quantity of the inverter so as to control the grid-connected inverter. By the robust control method, running stability of a system is improved, halting failure caused by factors such as uncertainty on a system structure is avoided, grid-connected power quality is improved, and harmonic distortion of output electric energy of the grid-connected inverter is effectively reduced.

The invention discloses a novel voltage type multi-level inverter. When the number of input power sources is expanded from n to n+1, the number of power switch tubes is increased from 2n+2 to 2n+4, wherein n is an integer not smaller than 1, similarly hereinafter; and when voltage of the input power sources is the same, the number of output levels changes from 2n+1 to 2n+3, namely when one power source is added, two power switch tubes and two levels are added. Compared with an existing classic multi-level inverter, the novel voltage type multi-level inverter enables the used power switch tubes and isolation driving to be less, a clamping diode and a flying capacitor and the like are not required, part of the power switch tubes are be in a low-frequency working state, on-off times is little, and switching loss is reduced. According to the novel voltage type multi-level inverter, one-dimensional space vector modulation is adopted, a modulation method is simple, the computing speed is quick, redundant vectors are reasonably utilized, quality of electric energy output by the inverter is improved, and the novel inverter meets the technical requirements of renewable energy and new energy power generation and is suitable for multi-input power source occasions.

The invention relates to the fields of new energy power generation and energy management thereof, specifically to a microgrid current conversion and energy storage apparatus and an energy management method therefor. The microgrid current conversion and energy storage apparatus comprises a six-switch seven-level single-phase inverter unit, a bidirectional DC/AC converter unit for a storage battery, a bidirectional DC/AC converter unit for a supercapacitor, a micro current converter energy storage apparatus control and energy management unit, a photovoltaic MPPT unit, a storage battery charging-discharging management unit, a supercapacitor charging-discharging management unit and a load management unit. By adoption of the microgrid current conversion and energy storage apparatus and the energy management method therefor, photovoltaic energy can be converted into electric energy to be connected to a power grid; power fluctuation balance of the system through peak-load shifting can be realized by the energy storage apparatus according to the energy flowing condition of the system; by adoption of the six-switch seven-level single-phase inverter, the apparatus is less in required power switching devices, low in switching loss, and high in output electric energy quality; the energy storage apparatus adopts the bidirectional DC/AC converters, so that compared with the conventional current converter, the energy storage apparatus has the advantages of less switching devices, wide voltage output range, simple SPWM modulation and the like; and therefore, the energy storage apparatus has wide application prospect in the microgrid application field.

The invention relates to the technical field of a power electronics technology, a digital signal processing technology and a control technology, in particular to an optimal carrier frequency-based design method of an inverter. The method comprises the following steps of (1) building an inverter hardware circuit; (2) building an inverter loss model and an output harmonic distortion model, building an efficiency optimization model by employing a carrier frequency as a variable and solving the optimal carrier frequency under different power by employing the efficiency optimization model; and (3) applying the optimal carrier frequency obtained in the step (2) to the inverter by employing software programming, and finishing the design of the inverter. By the inverter designed by the design method, the inverter loss can be reduced to different extents under the premise of ensuring that the quality of power output by the inverter is good enough; the efficiency is improved; and especially the inverter has more significant efficiency promotion than an ordinary fixed-frequency inverter during low-power output.

An electric generating system using a solar cell improves the quality of output power by including a converter for converting an output voltage generated from the solar cell into a DC voltage in a pulse shape. An inverter converts the DC voltage in the pulse shape into an AC voltage and applies the AC voltage to a power system and a control device for determining whether an erroneous operation of the electric generating system using the solar cell is generated or not based on an output voltage of the solar cell, an output current of the solar cell and a voltage of the power system. At least one inverter switching device among a plurality of inverter switching devices performs a switching at a frequency higher than a frequency during a normal operation at an interval where the erroneous operation is generated.

The invention discloses an isolated direct current converter applicable for a medium-voltage direct current system and a control method thereof. The direct current converter is of a modularized combined structure for a plurality of power modules through serial connection during input and parallel connection during output, and each power module consists of a switching circuit and an isolated switching circuit cascade connection. Each switching circuit consists of a switching switch, a switching power device and a short circuit prevention diode, and is used for controlling the switching and elimination of the corresponding control module, so that redundant operation and rapid fault isolation of the system are realized; when an external fault appears, the fault can be quickly eliminated, andwhen an internal fault of the module appears, the fault module can be quickly eliminated, so that normal operation of the converter is guaranteed; simultaneously, input and output voltage matching ofeach module can be guaranteed, so that the stress of voltage and current on the power device is reduced; and after the fault is eliminated, the converter also can be quickly used. The converter disclosed by the invention is high in reliability and long in service life, and is applicable for the applications such as long-distance underwater electric energy supply, interconnection of direct currentmicrogrids with different voltage levels and electrolytic aluminum and sea water desalination industries.

The invention provides a wind farm active power control method. The active power output of a wind farm is dynamically adjusted online by means of variable pitch and startup-shutdown according to a scheduling order of a power grid and under the premise of ensuring the service life of fans, considering the working conditions of fans and reducing fan failure. According to the control method put forward by the invention, a set value can be tracked quickly and accurately, and the generation power can be limited below a limit value by overshooting. When a unit is shut down due to failure, a target generation power can be allocated according to the failure state of the unit to make the real-time generation power quickly restore to a target value. Through centralized control on wind turbine generator units in a wind farm by use of the power control method, the quality of electric energy output by the wind farm is improved, the stability of the output power of the wind farm is ensured, and the adverse impact of the randomness and volatility of wind power generation on the power grid is reduced.

The invention discloses a ZSC-SMES topological structure comprising an AC side three-phase bridge circuit, a Z source impedance network and a chopper connected in sequence. The input end of the AC side three-phase bridge circuit is connected to a three-phase power grid. The invention also discloses an AC/DC side control method. The Z source impedance network is introduced on the basis of a traditional VSC which enables the fault through state in the VSC to become the normal working state of the ZSC, so that the fault caused by the through state is avoided. A controller on the AC side of a converter is designed based on the passive theory, the dynamic response capability and the robustness of the system are improved through an energy shaping and damping injection method, and the output power quality of the converter is improved. Based on the dynamic evolution theory, the controller on the DC side of the converter is designed, so that the voltage at two ends of a magnet is evenly distributed, the operating state of the magnet is improved, and the system safe operation is guaranteed.

The invention discloses a modular multilevel topological structure based on a coupling inductor double step-down type submodule and a control method thereof. Each of upper and lower bridge arms of the topological structure respectively comprises N coupling inductor double step-down type sub-modules capable of outputting three levels, so that output voltage distortion caused by bridge arm direct connection and dead zones of a traditional half-bridge sub-module is avoided, and the output electric energy quality and the power density of the converter are effectively improved. In a single-phase topology, the far ends of the upper bridge arm and the lower bridge arm are used as a common direct current end of a converter; the submodules of the upper bridge arm and the lower bridge arm are connected with a coupling inductor in series, and the midpoint of the coupling inductor is led out and connected with an external alternating current system. In addition, in the control method of the topological structure, the voltage loop is used for adjusting a common-mode voltage, the current loop is used for adjusting the common-mode and differential-mode current, and a current loop for controlling the common-mode current of the sub-module is additionally arranged to obtain a certain direct-current bias, so that the sub-module keeps a current continuous working condition, the dynamic performance of the topological structure is improved, and the safe and reliable operation of the topological structure is ensured.