95results about How to "Improve the ability of low voltage ride through" patented technology

The invention discloses a double-fed type wind generating set low-voltage-ride-through control method based on an electromagnetic transient algorithm. The double-fed type wind generating set low-voltage-ride-through control method is characterized in that when falling fault happens to power grid voltages, a control system controls double-fed motor stator flux linkage decoupling, transient state compensating current computing and composition and rotor current loop closing, so that a low-voltage-ride-through purpose of a double-fed type wind generating set is achieved. According to the requirement that transient state voltage impact at a double-fed motor rotor end is lowered when a power grid falls, transient state compensating currents are injected into the double-fed motor rotor end, the angle of the double-fed motor rotor end is set, so that the transient state voltages at the rotor end is optimally controlled when the power grid voltages fall, and accordingly impact from the transient state voltages on the double-fed type wind generating set when the voltages fall is lowered, and meanwhile decay speed of stator direct current flux linkage can be increased, a transient state process of a system is shortened, and influence from a flux linkage negative sequence component on the wind generating set is lowered. Accordingly, through the low-cost high-reliability control method, the voltage fault range which the double-fed type wind generating set can ride through is expanded, and the low-voltage-ride-through performance of the double-fed type wind generating set is greatly improved.

The invention relates to a double-fed wind driven generator system and a low-voltage through control method. According to the double-fed wind driven generator and the low-voltage through control method on the basis of a Crowbar circuit and a battery energy storage device, the low-voltage through capability can be effectively improved under the condition of large-range voltage drop, the double-fed wind driven generator system can be still kept to be connected with a power grid, and the stability of a wind power system is improved.

The invention discloses a low voltage ride through control method of a grid-connected photovoltaic power generation system. The method comprises the following steps of: firstly, establishing a mathematical model of a photovoltaic inverter when the power grid is unbalanced; secondly, analyzing current control on an alternating current side, and when the voltage of the power grid drops asymmetrically, controlling the photovoltaic inverter with the control target of eliminating 2 times power frequency fluctuation of the active power; and thirdly, forcing an output current of the photovoltaic inverter to follow a current command value given in advance within a switching period so as to suppress voltage fluctuation on the direct current side. According to the invention, the voltage fluctuation on the direct current side can be reduced, the voltage across the direct current side remains stable, and the stable operation of the integrated system is ensured.

The invention relates to the technical field of control over wind power plants with energy storage systems, and discloses a central-control-system-based energy storage type wind power plant. The energy storage system is added on the basis of the conventional wind power plant. A central control system integrates the monitoring of an energy storage battery system, an energy conversion system, fans of the whole plant, a booster station and box type transformers of the whole plant. A power grid scheduling interface is arranged to realize totally integrated control over the energy storage type wind power plant. A central control system platform realizes a power prediction function, an energy management function, a power grid direct scheduling function and an entire-wind power plant low-voltage ride through function. A problem about the grid connection of conventional wind power generation is solved, the quality of grid-connected electric energy of the wind power generation is improved, and the real-time performance, accuracy and safety of the control over the energy storage type wind power plant are improved.

The invention discloses a power control device and method used for low voltage ride through of a direct-drive permanent magnetic synchronous wind driven generator. The device comprises a generator speed measuring module, a direct current voltage measuring module, a generator terminal voltage measuring module, a generator terminal current measuring module, a grid measurement voltage measuring module, a grid measurement current measuring module, a maximum power tracking and controlling module, a grid measurement power measuring module, a wind speed measuring module, a pitch angle measuring module and a power coordination control module. The invention further provides the power control method, active power and reactive power of a unit in a temporarily stable state period can be coordinated and controlled, so that the direct-drive wind driven generator effectively achieves low voltage ride through in a maximum power tracking area and a power limiting area, and the unit can provide dynamic reactive support for a power grid in a low-voltage transient state period. The power control device and method can use the control means of the direct-drive wind driven generator self sufficiently and reasonably without adding unloading hardware, and the power control method is easy to implement and remarkable in effect.

The invention relates to a method for improving a double-fed converter low voltage ride through performance. The method is characterized in that a current transformer on a power grid side and a current transformer on a motor side are respectively subjected to different force pulse control according to overcurrent degree. The method comprises the following steps of: after detecting overcurrent, finding a maximum current phase and a current sign thereof, if the maximum current phase is larger than 0, conducting a whole switching period through a phase lower switch tube, and controlling by utilizing 0 voltage, and if the maximum current phase is less than 0, conducting the whole switching period through a phase upper switch tube, and controlling by utilizing full direct-current voltage; judging the overcurrent degree, wherein when the overcurrent is slightly larger, non-overcurrent two phases output a normal PWM (Pulse-Width Modulation) signal, and restrain the overcurrent, when the overcurrent is still larger, non-overcurrent two phase output is opposite to the maximum current, and the increasing of the overcurrent is restrained extremely; for the current transformer on the motor side, when the overcurrent is larger, blocking a three-phase pulse; and if the current is increased to trigger a Crowbar threshold value, inputting into a Crowbar circuit so as to protect a power electronic device.

The invention belongs to the field of direct drive type permanent-magnet synchronous wind power/wave power generation and power electronics control and relates to a power inverter for a reconfigurable direct drive type permanent-magnet synchronous generating system, comprising a three-phase bridge diode rectifier circuit, a motor side reconfigurable control circuit, a Buck-Boost direct current control circuit, a network side reconfigurable control circuit and an inverter circuit which are sequentially connected, wherein the motor side reconfigurable control circuit comprises three bidirectional controllable diodes and two redundant rectifier diode bridge arms, motor sides of the three bidirectional controllable diodes are connected in parallel, the two redundant rectifier diode bridge arms are connected in series, the network side reconfigurable control circuit comprises two redundant MOSFET (Metal Oxide Semiconductor Field Effect Transistor)/IGBT (Insulated Gate Bipolar Translator) bridge arms and three bidirectional controllable diodes, the two redundant MOSFET/IGBT bridge arms are connected in series and are then connected with the output end of the Buck-Boost direct current control circuit, and network sides of the three bidirectional controllable diodes are connected in parallel. The power inverter can lower the control complexity of the motor sides and can also fulfill the functions of self-adaptation voltage boosting and depressing.

The invention discloses a complex optimal control method for reactive power of a wind power system in a grid voltage sag fault. The method comprises the following steps: reading grid voltage data provided by grid voltage real-time monitoring equipment in real time; judging whether a wind turbine generator has reactive current requirements or not; if so, providing reactive compensation for a grid system through a static synchronous compensator, calculating a voltage deviation value [delta]U between the grid voltage U<pcc> and the preset reference voltage U<pccref>, and judging whether the voltage deviation value [delta]U is greater than a first preset threshold U<ref1> or not; and if so, starting a static reactive compensation mode of a grid-side converter, and enabling the grid-side converter and the static synchronous compensator to synchronously provide reactive compensation to the grid system. According to the complex optimal control method, the voltage of a grid-connected common connection point can be stabilized; and the low-voltage ride through capability of a wind power generation system is enhanced.

A low voltage ride-through system of a double-fed asynchronous wind generating unit based on a dynamic voltage restorer (DVR) is characterized by comprising the double-fed asynchronous wind generating unit and the DVR. The low voltage ride-through system has the advantages that low voltage ride-through capacity of a DFIG unit is improved, and fluctuation of stator voltages can be also reduced and even eliminated through the DVR and an injection transformer.

The invention relates to a low voltage ride-through control method of a permanent magnetic direct drive wind power system under unbalanced network voltage. The control method includes the concrete steps that first, the phase theta

and the phase theta<n> of positive and negative sequence voltages are acquired; second, through the positive and negative sequence voltage phases, voltages and currents of a three-phase network are converted in a dq coordinate system, and positive and negative sequence voltages and currents in the dq coordinate system are obtained; third, through the positive and negative sequence network currents and parameters of a network connection reactor, the active power consumption direct current component deltaP<0>, the cosine component deltaP<c2> and the sine component deltaP<s2> on the network connection reactor are calculated; fourth, the reference value of the direct current component of active power output by an inverter and the reference value of the direct current component of reactive power output by the inverter are acquired; fifth, through the obtained reference values of power, the positive and negative sequence components of the output current of the inverter are calculated; sixth, switching signals are obtained through the positive and negative sequence components of the output current, and the output current and the output power of the inverter are controlled through the switching signals. Compared with the prior art, the low voltage ride-through control method of the permanent magnetic direct drive wind power system under unbalanced network voltage has the advantages of being efficient, easy and convenient to operate and the like.

The invention discloses a permanent magnetic direct-driven wind turbine generator set reinforced low-voltage ride through control method on the condition of a power grid asymmetrical fault, wherein the method relates to controlling of a network-side converter and a machine-side converter of the permanent magnetic direct-driven wind turbine generator set. According to the method, based on sufficient consideration for capacity of a converter and operation condition of the set, positive-sequence and negative-sequence dq axis current given instruction of the network-side converter of the permanentmagnetic direct-driven wind turbine generator set are obtained; and furthermore a network-side converter PWM driving signal through spatial vector modulation of the obtained positive-sequence controlvoltage and the negative-sequence control voltage ualphagamma<+><+> and ualphagamma<-><-> and DC bus voltage Udc, so that the permanent magnetic direct-driven wind turbine generator set can suppressvoltage unbalance of a grid connecting point and maximally supply active current to the power grid, thereby remarkably improving low-voltage ride through capability of the permanent magnetic direct-driven wind turbine generator set on the condition of the power grid asymmetrical fault and electric energy quality of the connected power grid.

The invention discloses a method for using a unified power flow controller in wind turbine generator grid-connected operation, and belongs to the technical field of power electronics. An active and inactive independent control system is established on the series side of a UPFC, compensating voltage is output to an electric transmission line, the power flow distribution capability of the system for optimizing a wind power gird-connected system is researched, and a model is established in Matlab/Simulink software. Simulation results indicate that the UPFC can obviously improve the low voltage ride through capability and optimized power flow distribution of the wind power grid-connected system based on powerful reactive compensation capability and power flow control capability of the UPFC.

The invention relates to a PSCAD modeling and simulation method for a grid-connected inverter during an unsymmetrical failure of a power grid and belongs to the technical field of PSCAD modeling and simulation methods. The technical problem to be solved is providing a PSCAD modeling and simulation method for a grid-connected inverter under a positive-negative dual-sequence independent control strategy. The technical scheme comprises following steps: first, the positive-negative sequence voltage and current of the three-phase voltage and current of the AC side of the grid-connected inverter are separated; the three-phase positive and negative voltage and current are converted to a [alpha][beta] axis to obtain reference values of positive-negative sequence current of a dq axis; then the PI parameter of current inner loop and voltage outer loop is calculated. The method is suitable for electrical power systems.

The invention discloses a superconducting magnetic energy storage based double-fed fan low voltage ride-through method in the technical field of double-fed fan equipment. The method includes the following steps: a superconducting magnetic energy storage system is established; whether a double-fed fan is in a failure state is judged, a voltage source inverter is in a hot standby state and does notperform energy exchange with a rotor winding when the double-fed fan is operated in a non-fault state, and a DC-DC converter executes smooth output power control; and the DC-DC converter performs voltage stabilization control on a capacitor after a fault occurs, the voltage source inverter executes transient voltage control and current back tracking control, and a double-fed fan rotor side inverter executes transient voltage control and current back tracking control. Therefore, the problem of unstable energy output of the double-fed fan can be improved, and the low voltage ride-through capabilities of the double-fed fan can be enhanced.

The invention relates to a reactive compensation and vector control method for a doubly-fed wind turbine generator, and belongs to the technical field of operation and control of doubly-fed wind turbine generators in new energy power generation. In order to avoid off-grid operation of the doubly-fed wind turbine generator caused by voltage drop of a power grid, the output reactive power of a gridside is adjusted in a reactive power compensation mode by changing a grid side converter control method on the one hand; and on the other hand, in consideration of transient characteristics of a stator flux linkage during a voltage drop period, a rotor side converter adds a stator flux linkage change item caused by the voltage drop on the basis of the traditional vector control method, and the DCside overvoltage and the rotor side overcurrent are suppressed during the voltage drop period and after the fault is removed so as to help the recovery of the system voltage. For research of a grid-side and rotor-side converter cooperative control method, off-grid operation of the doubly-fed wind turbine generator caused by the voltage drop of the power grid can be effectively avoided, the systemfault voltage is helped to be recovered, and the stability of the power grid is maintained.

The invention discloses a converter, a control method thereof and a wind power generation system. The converter comprises an electrical light conversion module, an electrical light conversion controller connected with the electrical light conversion module, a photoelectric conversion module and a photoelectric conversion controller connected with the photoelectric conversion module, wherein one end of the electrical light conversion module is in circuit connection with a wind power generation unit, the other end of the electrical light conversion module is in light path connection with the photoelectric conversion module, the other end of the photoelectric conversion module is connected with the electrical power network, the electrical light conversion controller is connected with the wind power generation unit, the photoelectric conversion controller is connected with the electrical power network, the electrical light conversion module is controlled by the electrical light conversion controller to adjust side energy of the wind power generation unit, and the photoelectric conversion module is controlled through the photoelectric conversion controller to adjust the side energy of the electrical power network. According to the converter, through electrical light conversion and photoelectric conversion, electrical decoupling at wind power generation sides and electrical power network sides can be realized, harmonic waves are reduced, and low and high voltage ride through capabilities of the wind power generation unit can be improved.

The invention discloses a photovoltaic grid-connected inverter which is composed of MPPT, a controller, a PV array, a filter, a power grid, a voltage and current detection module and a topological circuit structure. The PV array is connected with the topological circuit structure through a capacitor. The signal output end of the PV array is connected with the signal input end of the controller through the MPPT. The output end of the controller is connected with the topological circuit structure. The topological circuit structure is connected with the filter. The filter is connected with the input end of the voltage and current detection circuit through the power grid. The output end of voltage and current detection is connected with the signal input end of the controller. Compared with the inverters in the prior art, a novel phase lock technology and a nonlinear control strategy are adopted to improve the performance of the photovoltaic grid-connected inverter on the basis of deeply researching the mathematical model of the photovoltaic grid-connected inverter and the control strategy of the photovoltaic grid-connected inverter under the asymmetric power grid so as to improve the capacity of low voltage ride through on the basis of reasonable reactive compensation.

The invention discloses a low-voltage ride through method of a winding type brushless double-fed wind power generator set. The low-voltage ride through method comprises the following steps of S1, calculating a voltage amplitude and a voltage drop depth of a power grid; S2, switching a control strategy of a power generator to a low-voltage ride through control strategy from a normal control strategy if the power grid drops; S3, detecting a current of a control winding of the brushless double-fed power generator in real time, calculating the size of reactive current which shall be injected to the power grid according to the voltage drop depth of the power grid if the current amplitude of the control winding is smaller than a threshold value of the rated current of the control winding, taking the reactive current as a current loop instruction of the control winding, and injecting the reactive current to the power grid to help recovery the voltage of the power grid by a machine-side current converter; S4, detecting the voltage of the power grid in real time, and judging whether a fault of the power grid is eliminated or not; and S5, switching the low-voltage ride through control strategy of the winding type brushless double-fed power generator to the normal control strategy. By the low-voltage ride through method, extra hardware is not additionally arranged, and the low-voltage ride through capability of the power generator can be improved.

The invention discloses a doubly-fed induction wind driven generator transient current tracking control method under power grid faults, and belongs to the technical field of wind power generation. A rotor current instruction feedforward component related with a rotor transient current instruction is attached to a current loop of a rotor side converter, so as to improve a capability of the original current loop in tracking an alternating current instruction, thereby fully excavating characteristics corresponding to the transient current instruction, and enhancing low voltage ride through capacity of the doubly-fed induction wind driven generator. The control method provided by the invention has the advantages that the structure is simple, implementation is easy, stability of the original current loop is not changed, and in addition, the method has relatively high robustness in power grid frequency fluctuation and doubly-fed induction wind driven generator parameter drift.

The invention discloses an energy storage type electric energy quality regulator for a wind power generation system. The energy storage type electric energy quality regulator comprises a three-phase full-bridge DC-AC converter, a three-phase half-bridge DC-AC converter, a two-way DC-DC converter and an energy storage device. One outgoing line terminal of an alternating current port of each phase of the three-phase full-bridge DC-AC converter is connected with an outgoing line terminal of the corresponding phase in a wind power generation set, and the other outgoing line terminal is connected with a connecting terminal of the corresponding phase in the low-voltage side of a boosting transformer. Direct current ports of all phases of the three-phase full-bridge DC-AC converter are connected with a direct current port of the three-phase half-bridge DC-AC converter, and three alternating current ports of the three-phase half-bridge DC-AC converter are connected with a connecting port in the low-voltage side of the boosting transformer. The energy storage device is connected with the alternating current ports of the three-phase half-bridge DC-AC converter through the two-way DC-DC converter. The energy storage type electric energy quality regulator can smooth the power fluctuation of wind power and improve the low voltage ride-through capacity of the wind power.