1763results about How to "Improve power quality" patented technology

The present invention relates to a micro-power source for successfully implementing a microgrid and to a control method for realizing smooth reconnection between the microgrid and an upper electric power system and smooth switching between the control modes of the micro-power source. A micro-power source sectionalizes an electric power system into an upper electric power system and a lower electric power system, and enables the lower electric power system to be independently operated in an island mode and to smoothly switch between a grid-connected mode and the island mode. As a result, a hierarchical microgrid is implemented with sectionalized sub-microgrids. One of the merits of the hierarchical microgrid is that each consumer group can be supplied with high quality power regardless of the power quality of the other consumer groups, and various types of services independently.

A brushless generator with permanent-magnet multi-pole rotor disks and coreless stator winding disks includes integral electronics to efficiently generate regulated DC current and voltage from shaft input power over a broad speed range. Its power rating is scalable, and it incurs no cogging torque, or friction from gearing. Integral power control electronics includes high-frequency pulse-width-modulated boost regulation, which provides regulated current at requisite voltage over its broad speed range. A main embodiment to produce DC power at widely variable speeds includes signal processing so output power varies according to the third power of speed. A version for use with vertical-axis wind turbines has a relatively large diameter to facilitate a large number of poles. Combined boost-regulation, zero cogging torque, and no gearing, enable a wide speed range, for better power quality and higher wind energy yields. An alternate embodiment is intended to produce DC power from a variety of shaft drive sources, with selectable shaft torque.

The invention belongs to the field of power converter control and relates to a model prediction control method of a voltage source type rectifier when a network voltage is unbalanced. The model prediction control method of the voltage source type rectifier when the network voltage is unbalanced comprises the steps of converting three-phase network voltage and a three-phase current into network voltage and a current which are under a two-phase static coordinate system through an abc / alpha beta coordinate, obtaining network positive sequence voltage and negative sequence voltage by carrying positive and negative sequence component separation of the network voltage under the two-phase static coordinate system, calculating reference values of active power, calculating current reference values of the rectifier under the two-phase static coordinate system, and carrying out model prediction current control and selecting an optimal on-off state. The model prediction control method of the voltage source type rectifier when the network voltage is unbalanced is capable of quickly and precisely tracing the current under the two-phase static coordinate and effectively eliminating fluctuation of direct current side voltage at the same time, power quality of the system is improved, a reliable network-connected operation of the rectifier when transient state network voltage is unbalance is achieved, and dynamics and stability of the whole system are improved.

The invention relates to a method for suppressing an output harmonic wave and a direct current component of a single-phase grid-combined photovoltaic inverter. In the invention, an original voltage and current detection device and a digital controller in a photovoltaic grid-combined generation system are utilized, and the controls to the Boost circuit duty ratio and an inverter are increased on the basis of an original control algorithm. A phase current signal output by the inverter is subjected to single-phase conversion, actually output current is compared with a reference value, and a difference value is subjected to PI regulation to obtain a voltage control command of a fundamental wave and a harmonic wave; a direct current component detection value obtained by calculating the phase current signal and a given calibration currents difference value are processed to obtain a direct current component suppression voltage command; and after a control command of instantaneous fundamentalwave voltage, a control command of instantaneous harmonic wave voltage and the direct current component suppression voltage command are added and processed to obtain a control command used for the inverter. The invention realizes the control of the active and reactive current of the inverter, the elimination of the designated harmonic wave and the suppression of the direct current component and can effectively improve the electric energy quality of the grids.

The invention discloses a control system for measuring the energy consumption of urban rail transit and an evaluation method. The control system comprises a vehicle-mounted energy consumption control unit, a data management unit and a ground energy consumption control unit. The control system has the beneficial effects that the system is a multi-path sampling energyconsumption metering system; drive control is carried out by adopting a permanent-magnet synchronous DC motor; a double-energy control module is built by using a super capacitor and a lithium battery for vehicle-mounted energy conversion control; train force analysis and modeling are not needed; a large quantity of nonlinear analysis or intelligent optimization calculation is not needed; traction energy consumption, regenerative braking energy and auxiliary energy consumption can be measured and monitored by directly utilizing collected voltage and current data; the control system has the functions of real-time storage and display of energy consumption data; the energy consumption data can be uploaded to the ground energy consumption control unit through the data management unit; the labor cost is reduced; the control system has a fault detection function; and the fault can be accurately reported when the system fails.

A brushless generator with permanent-magnet multi-pole rotor disks and stator winding disks in their axial magnetic field includes integral electronics to efficiently generate regulated DC current and voltage from mechanical input power over a broad speed range. All power for the electronics is provided by rectifier diodes from its stator windings. Differential amplifiers provide stator voltage feedback signals. Its power rating is scalable, depending on the number of its disks. Having no iron cores and no gears, it incurs no cogging torque, and no gear friction. Integral power control electronics includes high-frequency pulse-width-modulated boost regulation, which provides regulated current at requisite voltage over its broad speed range. A main wind-powered embodiment to produce DC power for a constant voltage DC load over a broad speed range includes signal processing so output power varies according to the third power of speed. Combined boost-regulation, zero cogging torque, and no gearing, enable a wide speed range, for better power quality and higher wind energy yields.

The invention discloses a parallel active filter based on a modularization multi-level converter and a control method of the parallel active filter and belongs to the technical field of power harmonic suppression in a medium-high voltage high-power occasion. The problem that an existing parallel active filter cannot carry out harmonic combination compensation effectively, so that power distribution network electric energy quality is poor is solved. The filter comprises the modularization multi-level converter, a current transformation unit, a harmonic current detecting unit, a current controller, a capacitor C and a power grid electric reactor LS. The modularization multi-level converter is of a half-bridge-type topological structure, and an upper bridge arm and a lower bridge arm of the modularization multi-level converter respectively comprise n submodules SMn. According to the control method, a carrier phase-shifting modulation method is used, so that under the same switch frequency, equivalent switch frequency is high, switching loss is reduced, meanwhile, a capacitive coupling voltage sharing and ring current suppression strategy is used, and capacitor voltages and direct current bus voltages of the submodules are kept stable. The parallel active filter is used for harmonic suppression of a power grid.

The invention relates to a megawatt wind generating set combination control policy. When the wind speed of a wind generator fluctuates at rated wind speed, a torque control policy and feather control policy simultaneously remain in operation state, so as to realize undisturbed switching between a feather PID controller and a torque PID controller. The invention makes the best of the integral saturation characteristic of PID algorithm, so that switching between the torque PID controller and the feather PID controller is smooth and sensitive, mutual interference between the feather controller and the torque controller in the previous switch mode switching process while only one controller is ensured to operate at the same time, drastic fluctuation of wind generator power when the wind speedfluctuates at the rated wind speed is avoided, further load impact is reduced, electric energy quality is improved, reliability of the wind generating set is improved, and operation performance of the wind generating set is improved.

The invention discloses a photovoltaic fault diagnosis system and method based on theoretical calculation and data analysis. The diagnosis system comprises a data acquisition sub system, a data storage sub system, a data mining sub system, a system modeling prediction sub system, a fault decision-making sub system and a fault display feedback sub system. According to the photovoltaic fault diagnosis system and method based on theoretical calculation and data analysis, starting from the perspective of a whole electric field, the operation conditions of all unit equipment in the electric field are analyzed, and the operation conductions of all the unit equipment are judged in real time in combination with the predicted value of a system model; meanwhile, the fault decision-making system makes the fault diagnosis system have the autonomous leaning function through an intelligent algorithm, and the fault judgment accuracy of the system can be increased continuously; meanwhile, the photovoltaic fault diagnosis system can store the electric field real-time data, electric field external environment data, unit model prediction data, fault source and other data in real time, and the system is made to have the fault retrospection function; the electric field operation safety level is increased, and the electric field power quality is improved.

The invention discloses a charging system for an unmanned aircraft. The charging system is characterized by comprising a power-taking device, an electric energy transmitting device, an electric energy receiving device and an aircraft-mounted battery, wherein an overhead transmission line is arranged on the power-taking device; the electric energy transmitting device is for converting power frequency alternating current into high-frequency alternating current; the electric energy receiving device is arranged on the unmanned aircraft; electric energy transmission is realized in a wireless manner between the electric energy receiving device and the electric energy transmitting device; the aircraft-mounted battery is arranged on the unmanned aircraft, is used for supplying power to the unmanned aircraft, and is connected in series to a current loop of the electric energy receiving device. Compared with the prior art, an electric unmanned aircraft charging system based on an alternating-current power transmission overhead line provided by the invention has the advantages that a full-autonomous and safe charging way is realized for the unmanned aircraft, and the distance per charge of the unmanned aircraft is prolonged. Meanwhile, a high-frequency inductive constant-current charging circuit based on an unstable alternating-current power supply is provided, so that unmanned charging operation is fully realized, the dependence of the unmanned aircraft on a ground base or a mobile base station is reduced, labor operation is reduced, and labor cost is reduced.

The invention provides a virtual synchronous generator virtual inertia and virtual damping coefficient adaptive control method, which relates to the technical field of smart grid and intelligent algorithms. Firstly, the inverter based on the virtual synchronous generator is modeled, and the correlation between the output frequency of the inverter and the virtual inertia J and the virtual damping coefficient D is obtained. Then the fitness function of the adaptive control method of virtual inertia J and virtual damping coefficient D based on the improved particle swarm optimization algorithm isdetermined. Finally, the improved particle swarm optimization algorithm is applied to the active power. In the frequency control part, the real-time adaptive control of virtual inertia J and virtualdamping coefficient D is realized in order to minimize the frequency deviation and stabilize the system. The invention provides a virtual synchronous generator virtual inertia and virtual damping coefficient real-time adaptive control method, which fully utilizes the characteristics of the virtual inertia and introduces the virtual damping coefficient, so that the inverter is more stable and the frequency offset is smaller.

The invention discloses an energy storing device for supplying valley current at the peak of electricity supply. The energy storing device comprises an electric return circuit formed by connecting the electronic components, wherein, a two-way converter is connected with a storage battery pack, a controller and a detection circuit; the controller is connected with a human-machine interface; the two-way converter is a voltage-type three-phase half-bridge rectifier/converter comprising three single-phase half-bridge converter bridge arms; the controller has a double-CPU structure with DSP (digital signal processing) chips and single-chip; the human-machine interface is a liquid crystal display (LCD) module; the detection circuit adopts the commercial power input detection, the converter output detection and the storage battery detection; and a hall sensor is used for sampling voltages and currents. By charging the storage battery when the electricity price is lower at the valley of the power supply and partially or fully discharging the load from the storage battery through inversion, the invention can solve the problem of the imbalance between supply and demand of the electric energy and achieve the effect of 'peak load shifting' as the effective supplement to the national grid.

A relay apparatus includes a plurality of connecting terminals, such as a modem connecting terminal, a power line connecting terminal, an electric appliance connecting terminal and an antenna line connecting terminal; a selector that selects at least one connecting terminal from among the plurality of connecting terminals to transmit and receive a communication signal; and a control circuit that controls the selector. The relay apparatus further includes a first communication filter that passes signals in a frequency band used for communication by a power line communication modem and that blocks signals in other frequency bands, and a second communication filter that passes signals in a frequency band used for communication by another electric appliance and that blocks signals in other frequency bands.

The invention discloses a grid-connected control method and system based on a virtual synchronous generator. The method comprises the steps as follows: simulating synchronous impedance with a synchronous impedance method based on cascade connection of an order-reduced resonator and a three-order generalized integrator to improve stability of the system, inhibit current deviation formed by load disturbance and realize power equalization, and inhibiting imbalance of output voltage and harmonic component by using quasi-proportional resonance controller. An order-reduced resonator phase-locked loop is combined with a quasi-synchronous parallel algorithm, asymmetry of grid voltage and output voltage of an inverter as well as the effect of harmonic waves on detection accuracy is avoided, the frequency, amplitude and phase of the output voltage of the virtual synchronous inverter track grid voltage quickly without static errors by the aid of the quasi-synchronous parallel algorithm, so that flexible off-grid/grid-connected switching is realized, the power supply reliability of the system is improved, and the electric energy quality is improved.

The invention provides a dynamic reactive power reserve optimization method for improving transient voltage stability of an alternating-current and direct-current power grid. The method comprises the steps of determining a key fault set and a key node set which influence the transient voltage stability of a power system, and sequentially ranking nodes; adjusting reactive power output of dynamic reactive power compensation equipment and calculating the trajectory sensitivity of the dynamic reactive power compensation equipment; ranking m dynamic reactive power compensation equipment and calculating the weight coefficients of the nodes in the dynamic reactive power compensation equipment; calculating the capacities of the dynamic reactive power compensation equipment, establishing a dynamic reactive power reserve optimization model and solving the dynamic reactive power reserve optimization model. The dynamic reactive power reserve optimization method for improving the transient voltage stability of the alternating-current and direct-current power grid provides auxiliary decision-making support for improving the transient voltage stability of the multi-direct-current-drop-point power grid, and has great importance in improving the allowance of the transient voltage stability of the large-scale alternating-current and direct-current power grid, establishing a smooth power transmission passage between a transmitting end and a receiving end, improving the transmission capacity of the alternating-current and direct-current power transmission passage and improving the operation economy and the power quality of the power grid.

The invention discloses a method for outputting active power by using a smoothing permanent-magnet direct-driving wind power generating system of a direct-current-side flywheel energy storage unit. The method comprises the following steps of: controlling a motor-side converter; controlling a grid-side converter; and controlling an energy-storage-unit-side converter. By cooperated control of the motor-side converter, the grid-side converter and the energy-storage-unit-side converter, a wind power generator set can generate relatively-smoothed active output in the situation of change of a wind speed, and operating requirements of frequency modulation and voltage regulation of the system are met. The method has the advantages that: 1, based on the requirement of power smoothing control, maximum wind energy tracking control is realized; and 2, the network-side active power is smoothed, the quality of electric energy is improved, and the grid-connected operating characteristic of the wind power generating system is improved.

The present invention discloses a decentralized cooperative economic dispatching method comprising a multi-microgrid active distribution system. The method comprises the following steps: (1) establishing a distributed power supply optimization operation model, solving an optimal scheduling model, calculating a microgrid node electricity price, considering a micro gas turbine in a microgrid, a fuel cell, output force characteristics and energy consumption characteristics of an energy storage device and wind power and photovoltaic random output force characteristics, and employing a prime-dual interior point method to calculate each node electricity price of the microgrid; (2) designing a multi-microgrid decentralized cooperative optimal scheduling frame to determine the size of each distributed power supply output force; and (3) researching the active distribution system optimal scheduling model and the solution method thereof considering the influence of multi-microgrid access. The decentralized cooperative economic dispatching method comprising the multi-microgrid active distribution system improve the electric energy quality and peak load shaving capability of the distribution system through depending on the support of the microgrid layer and network reconstruction while economic operation so as to provide valuable reference for allowing the microgrid system to access the distribution system optimal scheduling.

The invention dsiclsoes a microgrid system with an asymmetric non-linear load and a power balancing control method. The system comprises a plurality of DG units connected in parallel and line impedors connected with all DG units. The line impedors are connected to a microgrid bus by PCC points. A three-phase balancing resistive load, an asymmetric linear load, and a diode rectifier non-linear load of a load unit are connected to the microgrid bus by PCC points. A measurement module for measuring voltage fundamental wave positive sequence and negative sequence components and harmonic wave components of the PCC points is also connected to the microgrid bus. The microgrid bus is connected with a 10-kV main power grid by a static switch and a transformer successively. According to the invention, reactive and harmonic power balancing of the microgrid is realized by using a selective virtual impedance based on the virtual fundamental positive and negative sequence impedance and the virtual variable harmonic impedance; a harmonic and unbalancing voltage compensation controller enables equal division of an unbalanced power and a harmonic power to be realized; and a problem of unbalancing of the harmonic wave and the voltage of the microgrid can be solved.

The invention discloses an MMC (modular multiple converter) type multi-port power electronic transformer applied to an alternating current/direct current hybrid power distribution network. The multi-port power electronic transformer comprises an input level, a middle level and an output level, and are equipped with four kinds of universal interfaces: a high-voltage alternating current interface, a high-voltage direct current interface, a low-voltage alternating current interface and a low-voltage direct current interface; the input level refers to the MMC; the middle level refers to an isolating dual active full-bridge DC/DC converter; and the output level refers to a three-phase four-wire-system full-bridge inverter. Except the basic functions of voltage transformation, isolation, energy transfer and the like as a common transformer, the transformer provided by the invention can realize access of voltages of various forms with the multiple working modes, can perform functions of power flow control, electric quality adjustment and the like; and therefore, an intelligent power distribution network interface with higher applicability is configured.

The invention relates to an electric stepless speed-variable dual-power wind generator, wherein the electric stepless speed changer (2) comprises a stator (2.1), an outer rotor (2.2), an inner rotor (2.3), and a sliding ring (2.4). The wind turbine (1) via an input axle (6) is connected with the rotor (2.3), the sliding ring (2.4) is mounted on the axle (6), the circumference of the rotor (2.3) is disposed with the rotor (2.2), the circumference of the rotor (2.2) is disposed with the stator (2.1) which via an output axle (7) is connected to a generator (3), the rotor (2.3) is disposed with a multi-phase winding to connect a first power converter (5) via the sliding ring (2.4) and an electric brush, the stator (2.1) is arranged with a multi-phase winding and connected with a second power converter (4), the first and second power converters (4, 5) are connected with one direct-current power.

The invention provides a cascade megawatt photovoltaic grid-connected inverter, wherein a topology structure of the cascade megawatt photovoltaic grid-connected inverter is composed of two levels, namely a DC/DC (direct current/direct current) isolation level and a DC/AC (direct current/alternating current) output level; the structures of three phases of circuits are the same; the output ends of a power inverter group of each single-phase of DC/DC output level are connected in a star shape; the input sides of power units of each single-phase level are provided with independent PV (photovoltaic) modules of the same structure; the DC/DC isolation level comprises high-frequency DC/AC, a high-frequency transformer and high-frequency AC/DC nodes of each single-phase for realizing isolation and boosting, and reducing the consumption of a switch tube via action of a resonant soft switch; the output level power transformer set adopts a bridge type inverter circuit; and the single-phase output level power units are connected with each other in a cascade mode. Based output cascade, the device can realize megawatt grid connection; as a high-frequency chain technology is used, the traditional low frequency transformer is omitted, and the power density is high; and compared with the existing photovoltaic grid-connected inverter structure, the device provided by the invention has the advantages of high energy conversion efficiency, excellent output energy quality, certain fault-tolerant capability and the like.

The invention provides a composite energy storage system, which consists of a supercapacitor and a storage battery, wherein the composite energy storage formed by the supercapacitor and the storage battery has both power type and energy type characteristics; through the combined use, the charging and discharging times of the storage battery can be effectively reduced; in addition, the utilization rate of the energy storage system can be improved. According to an energy management and control optimization method matched with the composite energy storage, the total power of the composite energy storage is distributed through a low-pass filter, so that the supercapacitor and the storage battery respectively share a high-frequency component and a low-frequency component in the fluctuating power; through the two-way DC/DC1 converter constant-power control on the storage battery, the two-way DC/DC2 converter constant bus voltage control on the supercapacitor, and control strategies of the two-way DC/AC converter, the network loss of a power distribution network is reduced; the utilization efficiency of new energy sources is improved; the power fluctuation during micro power grid interconnection is effectively inhibited; the electric energy quality of a region electric network is improved; in an offline state, the stability of the voltage and the frequency of a micro power grid system can be ensured; the power balance generated during grid connection/off-grid switching is fast compensated.