1078results about How to "Reduce harmonic content" patented technology

An AC driven LED light string assembly is provided possessing reduced harmonic distortion and improved electrical efficiency when one or more series blocks of LED lamps is employed. In one embodiment, there is provided an LED light string employing a capacitor coupled in parallel across the light string AC input, or end connector terminals. According to another embodiment, LED light strings are to be manufactured with a substantially equal number of light strings produced with all LEDs in forward bias (anode first) and reverse bias (cathode first). This allows true randomness when large numbers of single series block LED light strings are connected in an end-to-end manner. It is possible to apply this concept to single LED lamps having two chips where one chip is powered in reverse bias to the second chip; thereby providing self-canceling harmonics within the single LED lamp.

The invention provides a wind energy and solar energy grid-connected generation system and a control method thereof. The wind energy and solar energy grid-connected generation system comprises a generation unit, an inversion unit, a grid-connecting unit, a main control unit and a detection unit. Each unit is effectively controlled by an integrated control unit which is formed by a digital signal processor (DSP), and operating state parameters of the system are predicted by a neural network, so the defect that the grid-connected system changes due to execution delaying of a control instructionis overcome, and the operating stability of the system is improved. Island detection adopts an active and passive detection mode, so the capacity for anti-island operation of the system is improved. The invention has the advantages that: inverted electric energy is supplied to an electricity grid and can be locally supplied to local alternating current and direct current loads, so the load pressure of the electricity grid is reduced, and the capacity for stable operation of the electricity grid can be improved; and when the output electric energy of the system is smaller than a local load, the electricity grid can supply power to the local load of the system, so the local load is supplied with power doubly by power supplies of the system and the electricity grid, and the time for uninterrupted power supply of the power supplies is prolonged.

The invention discloses a charging-discharging system for a V2G bilateral power conversion electric automobile and a control method thereof, which belong to the technical field of intelligent power grids. In the charging-discharging system, a single-phase or three-phase voltage PWM (Pulse Width Modulation) converter (VSC) is taken as a first-grade power conversion circuit, so that energy conversion between an alternating-current power grid and a first direct-current bus is realized; and a symmetric half-bridge LLC (Logical Link Control) resonant bilateral direct current-direct current (DC / DC) converter is taken as a second-grade power conversion circuit, so that energy conversion between a direct-current bus and a power battery pack is realized. The charging-discharging system has the beneficial effects that: the current of the converter power grid side of the first-grade power conversion circuit is approximate to sine wave, so that the harmonic content is small; and the converting efficiency, dynamic performance and power density of the second-grade power conversion circuit are increased, the volume and weight of a charging-discharging device of the electric automobile are reduced, and the safety, reliability and economic efficiency of the system are improved effectively.

The invention relates to a power distribution network fault arc extinction method by connecting a neutral point to the ground through multi-level converter. The power distribution network fault arc extinction method is characterized in that the cascade H-bridge multi-level converter is adopted and directly connected at the position of the neutral point of a power distribution network through a reactor; at the initial moment when the power distribution network has a single-phase earth fault, synthetic operation is conducted to generate offset currents needed to be injected (img file='69356dest_path_image001. TIF'wi'19' he'=25' / ), then the offset currents are quickly put into the multi-level converter, the multi-level converter is controlled by aid of the current tracking control algorithm and the PWM (Pulse-Width Modulation) modulation strategy to generate offset currents (img file='652784dest_path_image001. TIF'wi'19' he'=25' / ), and the offset currents are put into the neutral point of the power distribution network so as to compensate grounding total currents of the fault point. In addition, the fault phase voltage is forced to be 0 constantly so the instantaneous grounding fault can be cleared automatically, and further the technical problem of the existing fault arc extinction technology of poor arc extinction effect can be solved.

The invention relates to a high power factor DCM Boost PFC converter comprising a main power circuit and a control circuit. The main power circuit comprises an input voltage source vin, an EMI filter, a diode rectification circuit RB, a Boost inductor Lb, a switch tube Qb, a diode Db, an output capacitor Co and a load RLd. The high power factor DCM Boost PFC converter is characterized in that the control circuit adopts an output signal which adopts duty ratio as changing rule to drive the switch tube Qb. Adopting the varying duty ratio control, the high power factor DCM Boost PFC converter can improve the PF value to about 1 in the AC input voltage range of 90-265 V, increase the inductance capacity, obviously decrease the inductive current ripple, obviously reduce the effective value of the inductive current and correspondingly reduce the effective value of the current of the switch tube, has high input power factor and small output voltage ripple and contains less input current harmonic waves. The conduction loss of the high power factor DCM Boost PFC converter is reduced, and the efficiency is improved.

Disclosed are a grid-connected converter device of a direct-drive wind power system and a corresponding power coordination control method. The converter device is composed of basic converter units of a Boost circuit based on ac-side energy storage; the structure sufficiently utilizes the equivalent inductance of a power generator stator winding, avoids an external inductor in traditional dc voltage booster circuit, and reduces power loss and equipment cost. Two converter proposals, including a diode rectification mode and a PWM rectification mode are designed; converter topologies with two capacity grades, including medium and small power converter topology, megawatt grade high power converter topology, and relative extension structures are designed, such as a parallel connection converter and an H bridge cascade structure converter; wherein, the converter with the H bridge cascade structure is applicable to grids with high capacity and high voltage, and can obviously reduce the harmonic content in grid-connected current; meanwhile, the control method performing feedback through three closed loops is designed, so the input power and output power of the converter are balanced instantaneously, the dc bus voltage maintains stable, and the grid-connected current wave is sine.

The invention discloses a control method of a four-phase permanent magnet fault-tolerant motor. In the method, a control mode can be automatically decided according to the diagnosed situation of a system failure; when the system is at a normal state, an SVPWM control is adopted; when the system has a phase-lacking failure, a fault-tolerant torque control is adopted; different fault-tolerant control proposals are adopted according to different types of phase-lacking failures. The control method realizes that the four-phase permanent magnet fault-tolerant motor can operate with high performance under the normal condition and the phase-lacking condition, overcomes the deficiency that the stable performance of the system when in normal working is reduced in the traditional fault-tolerant control system which adopts current for regulating PWM for realizing current tracing for the convenience of fault-tolerant control, establishes a mathematical model of the four-phase permanent magnet fault-tolerant motor under a rotating coordinate system, successfully applies an SVPWM strategy to the four-phase permanent magnet fault-tolerant motor and enhances the dynamic and static performances and reliability of the control system of the four-phase permanent magnet fault-tolerant motor.

The invention relates to a permanent-magnet synchronous motor torque ripple suppression method based on coordinate transformation harmonic compensation. Three-phase current is acquired and converted into stator current in a two-phase static coordinate system; the stator current in the two-phase static coordinate system is transformed to fifth, seventh, eleventh and thirteenth harmonic rotating coordinate systems; direct-current component is extracted from fifth, seventh, eleventh and thirteenth harmonic current in the corresponding coordinate systems through a low-pass filter; a second-order low-pass digital filter based on speed adaptation is designed to extract harmonic of a specific order; and on the basis, a proportional integral current controller with cross coupling is designed to complete harmonic current suppression ultimately, thus suppressing torque ripple. Compared with the prior art, the harmonic content of output current can be reduced, and torque ripple, vibration noise and other negative effects of a permanent-magnet synchronous motor for electric vehicles can be reduced on the basis of permanent-magnet synchronous motor vector control.

The multi-level DC / AC converter, comprising: an input (5,7) connectable to a direct voltage source (3), with a first connection (5) and a second connection (7) between which can be applied an input voltage (Vi); a half-bridge with a first controlled switch (21) and a second controlled switch (25) between which is positioned an output (U) of the converter; a first connecting branch (15) between the first controlled switch (21) and the first connection (5) and a second connecting branch (17) between the second controlled switch (25) and the second connection (7); a third controlled switch (59) associated to the first controlled switch (21), connectable in series to the first controlled switch to generate an output voltage exceeding a first limit value (Vi / 2); a fourth controlled switch (61) associated to the second controlled switch (25), connectable in series to said second controlled switch to generate an output voltage below a second limit value (−Vi / 2).

The invention relates to an auto-stability method for camera image and the auxiliary device used in hand held state or motion state. It uses angular velocity sensor to check the angular velocity of the camera rotating round the three space axes in real-time and records synchronistical with image signal. The variance of the attitude angle between two pictures would be gained by integral in afterward process software, and the attitude angle variance related to slow-varying low frequency element in motion angular velocity is reserved, meanwhile the attitude angle variance related to dithering angle element would be eliminated. Then, the image dithering would be eliminated by translation and rotation the image. The device is made up of three same circuits. And every process circuit is connected by angular velocity checking circuit which is belonged to signal collection circuit, power lever shifting circuit which is belonged to signal process circuit, voltage / frequency transformation circuit, frequency division circuit, wave transformation circuit, signal compound and extent regulation circuit in series. The output signal is sent to the interface of camera.

The invention relates to a LCL (Lower Control Unit) filtering controlled rectifying active damping control method of electric currents on a feedback variable current side, belonging to an active rectifying method of power electronics. The method comprises the following steps: a direct current voltage control unit is used for finishing the control on a direct current voltage and producing d-shaft active currents of an electric current control unit; a q-shaft current given is used for controlling reactive components of a rectifier; a soft phase locking unit is used for locking a power grid voltage phase position and realizing the synchronous rotational transformation of the power-grid voltage and sampling currents on the variable current side; the current given and a sampling actual value are fed into the electric current control unit; the output quantity of the electric current control unit is accumulated with the electric current on the variable current side which is fed back by usinga first-order high-pass filter to generate the given quantity of a voltage space vector unit; and finally, the voltage space vector unit generates six PWM (Pulse-Width Modulation) signals to finish the control on the rectifier. The method solves the stability problem of a LCL (Low Control Unit) filtering voltage type controlled rectifier and realizes the control of the rectifier on direct-currentvoltages and currents on line side under the condition that the electric current or voltage detection of a capacitor branch is not needed.

The invention relates to a two-stage photovoltaic grid-connected control system based on the combination of pole allocation and repetitive control, which can invert the direct current output by a photovoltaic cell into alternating current well and transmit the alternating current to a power system, so that the harmonic wave content is low, the power supply quality is good, the utilization ratio of a system is high, the stability of the system can be improved to a certain extent and the properties of the whole photovoltaic system are improved. The two-stage photovoltaic grid-connected control system based on the combination of pole allocation and repetitive control has the advantages that: (1) due to the adoption of numerical control, the antijamming capacity is high and the system can achieve high precision and stability; (2) the system has clear assignment, obvious control effect, reliability and high robustness, wherein a preceding-stage Boost converter can realize maximum power tracking; and a last-stage inverter achieves direct current side voltage stabilization and grid-connected inversion; and (3) a control algorithm is advanced, wherein a dead zone effect of the inverter and the harmonic wave caused by partial non-linear loads are avoided by a repetitive control technique; and precise control is realized through the state feedback-based pole allocation.

Apparatus for providing effective amounts of high-frequency AC power to a long primary trackway (1102), used for inductive power transfer includes transconductance-pi filters (1105) for deliberate mismatching; resulting in independence of current flow and track impedance. These cause the source (1101) to appear as a voltage source and the trackway to appear as a low reactance. Shorting the output (1106) cuts the connected trackway from power without harm. The filter can cause a voltage step-up so driving a longer track. Track termination apparatus is disclosed that acts as a short circuit at only the operating frequency while terminating the track at its characteristic impedance otherwise. Half-bridge and full-bridge power supplies (1101) are described for providing effective amounts of high-frequency AC power to a long primary trackway used for inductive power transfer.

The invention discloses a mixed excitation permanent magnet flux switching motor which comprises permanent magnets, three-phase armature windings and single-phase excitation windings, wherein the single-phase excitation windings are arranged on a stator, the tooth number of the stator is 4 times number of permanent magnets; and a rotor is in a salient pole structure and has no windings or permanent magnets, thereby having high mechanical strength and being suitable for high-speed operation. An air-gap field comprises an electric excitation magnetic field generated by the excitation windings and a magnetic field generated by the permanent magnets, and is flexibly adjusted by changing an excitation current. An electric excitation magnetic line of force is closed by using an iron core connecting magnetic bridge, which is beneficial to reducing the electric field ampere-turns and lowering the electric excitation copper loss. The armature windings and the excitation windings are distributed in different stator grooves at intervals, which is beneficial to increasing the self-inductance of the armature windings and the mutual inductance of the windings and effectively inhibiting the short circuit current of a motor.

The invention discloses a rotor gravity unloading type magnetic bearing composite motor comprising an external stator, an armature winding, a permanent magnet, a rotor, a magnetic isolation aluminum ring, an internal stator and a suspension control winding. The armature winding is wound in external stator slots. The magnetic isolation aluminum ring is embedded in the rotor. A Halbach type permanent magnet array is surface-mounted on the surface of the rotor. The internal stator has seven internal stator poles including two opposite bias flux magnetic poles, four radial suspension control poles and one gravity direction rotor weight unloading pole. Radial magnetized permanent magnets are surface-mounted on the surface of the bias flux magnetic poles. The suspension control winding is wound on the four suspension control poles. Coupling between the suspension winding and the armature winding in the conventional magnetic suspension motor can be eliminated, and the influence of the rotor weight on suspension control in the conventional suspension motor can also be greatly solved so that the rotor is enabled to stably work at the central balance position without increasing suspension control current, and low power consumption and stable suspension of the magnetic bearing composite motor can be realized.

The invention relates to an electric current reconstructing and over-modulating device of an air conditioning frequency converter, which is characterized by comprising an electric current reconstructing device, a vector controller, a pulse width modulation (PWM) frequency converter, a direct current side electric current sensor, an electric motor and a coder. The electric current reconstructing device comprises an SVPWM over-modulating module, a pulse width modulation (PWM) signal adjusting module, a direct current sampling module and an alternating current reconstructing module. An electric current reconstructing and over modulating method of the air conditioning frequency converter comprises the steps: sampling the direct current side electric current of the pulse width modulation (PWM)frequency converter at twice by the electric current reconstructing device; counting an approach vector switch action time which meets a minimum sampling time request according to the two sampling values; sampling the direct current side electric current at twice again in the approach vector switch action time; and reconstructing three phase alternating current according to the sampling values ofthe direct current at twice, thereby realizing the closed loop control of the pulse width modulation (PWM) frequency converter. The modulating method can be widely used for the field in reconstructingand over-modulating the electric current of the frequency converter in air conditionings and electric vehicles.

A reactive power compensation device based on novel modular multilevel topology and a control method thereof relate to a high-voltage and large-power reactive power compensation device. In the prior art, compensation in a high-voltage and large-power field is limited and an inhibiting ability to circulation is insufficient. The invention aims at solving the above problems. A three-phase alternating-current power supply, a resistance-inductance load, a MMC converter, a signal detection circuit, a control circuit and a driving circuit are included. The MMC converter comprises three bridge arms which share a same structure and are connected in parallel. Each bridge arm comprises an upper bridge arm and a lower bridge arm which are symmetrical about a middle point of the bridge arm and are connected in series. Each upper bridge arm comprises a resistor, an inductor, several half-bridge units and an H bridge unit which are connected in series. The inductor of each upper bridge arm and an inductor of each lower bridge arm are connected in series. The middle points of the three bridge arms of the converter are connected in parallel between the three-phase alternating-current power supply and the load through a lead. By using the device and the method in the invention, power-grid reactive power can be compensated; a three-phase imbalance problem of a system is solved; effects of supporting a power grid voltage and inhibiting the circulation are achieved.

The invention relates to a default phase fault tolerance driving system of an open winding motor. A head end and a tail end of a common three-phase motor winding are cascaded with two nominal electrical level inverters; after a fault happens in a one-phase winding open circuit, two switches on a fault phase upper bridge arm are online locked; two switching tubes of a lower bridge arm are normally driven by 1; and through the modulation of phase current reconstruction and effective redundancy switch vector reconstruction, a stable torque output is retained, the default phase fault tolerance operation of the driving system is realized and the requirements on the system continuous operation capability of the high-reliability application field such as electric automobiles are satisfied. Through the design of dual power supply, the danger of a common-mode voltage and a zero-sequence current to electric components and motors is eliminated. The device comprises a primary direct-current voltage source (1), a primary capacitor (2), a primary inverter (3), a secondary direct-current voltage source (4), a secondary capacitor (5), a secondary inverter (6), a three-phase motor (7) and a redundant switch vector (8); the primary inverter is connected to the head end of the three-phase motor winding and the secondary inverter is connected to the tail end of the motor winding.

The invention discloses a capacitor-clamped three-level dual-buck half-bridge inverter which comprises a first three-level duck circuit, a second three-level duck circuit, a direct-current power-supply input circuit and a load circuit, wherein each three-level duck circuit comprises two power switching tubes, two power diodes, a clamping capacitor and an inductor, and +1, -1 and 0 three-state levels are output by an inverter bridge under the actions of controlling the switching tubes and clamping the clamping capacitor, thereby realizing the three-level dual-buck half-bridge inverter. The invention has the advantages that the advantage that a DBI circuit has not problems of through bridge arms or backward recovery of switching tube body diodes is inherited; the advantage that a three-level convertor per se has small output voltage harmonic content is reserved; compared with a traditional half-bridge inverter, the voltage stress of power devices is reduced; and the whole circuit structure is simpler and easy to realize.

The invention relates to an open winding type permanent magnet motor driven reconstructed vehicle-mounted charging system for an electric vehicle. The system comprises a single-phase AC power supply,a rectifier bridge, an input filtering capacitor, three-phase voltage inverters, a three-phase permanent magnet motor winding, an output filtering capacitor, a storage battery and mode switches. The charging system sufficiently utilizes original double three-phase inverters, the permanent magnet motor winding, control and sensor units and the like of electric vehicles, and total integration of functions such as motor driving, high-power factor charging, harmonic control and the like is realized by optimizing topology to complete rectification, inversion and power factor correction. During charging, two three-phase voltage inverters are reconstructed into a three-phase cascading Buck-Boost circuit; the permanent magnet motor winding serves as an energy storage inductor of the three-phase cascading Buck-Boost circuit. By means of the charging system, the cost of a device can be effectively reduced and high-power factor charging can be realized.

The invention provides a rotor punching structure for a permanent-magnet servo motor, and the structure comprises a rotor punching body. The peripheral surface of the rotor punching body is provided with permanent magnet tanks, and the interior of each permanent magnet tank is provided with a permanent magnet in an embedded manner. The external circle of the rotor punching body above the permanent magnet tanks is not concentric with the internal circle of a stator. The rotor punching body above the permanent magnet tanks is provided with magnetic isolation holes which are arranged horizontally, and the rotor punching body below the permanent magnet tanks is provided with an axial cooling channel. The permanent magnet tanks are radially arranged in a layered manner, and magnetic isolation tanks are respectively disposed between the adjacent permanent magnet tanks. Magnetic isolation bridges are disposed among the magnetic isolation tanks and the permanent magnet tanks. Through the improvement of the rotor punching structure and the control of the direction of a magnetic field, the nonlinear impact, caused by the coupling of quadrature-axis and direct-axis magnetic circuits, on motor parameters is reduced, and the space of a rotor punching is used fully for placing permanent magnets as many as possible. Moreover, the capability of resistance to demagnetizing and the overbearing capability of the permanent-magnet servo motor are improved, and the operation performance of the permanent-magnet servo motor is effectively improved.

The invention discloses a three-level three-phase four-bridge arm converter which comprises a direct-current part, a converting part, a converting part controller, a fourth bridge arm and a fourth bridge arm controller, wherein the converting part is a diode clamp type three-level inverter, the fourth bridge arm is a T-type three-level structure, the exchange of energy at a direct-current side and an alternating-current side is realized by controlling the states of first three bridge arm power switching tubes of the converting part, and a neutral point voltage at the direct-current side is changed by controlling the state of a power switching tube of the fourth bridge arm to realize the balance of neutral point potential. The fourth bridge arm of the three-level three-phase four-bridge arm converter adopts a T-type three-level topology and omits 2 clamp diodes compared with the diode clamp-type three-level inverter, thus saving the cost, and being more balanced in power loss and higher in efficiency; the control of neutral point balance is not affected by a power factor, the modulation degree and a modulation strategy; and as the deviation permission range of the neutral point voltage at the direct-current side is controllable, the permission range can be adjusted according to actual working conditions to improve the efficiency of a system.

The invention relates to a building photovoltaic grid connected system which comprises a plurality of photovoltaic buildings accessed into a power distribution grid through a plurality of access points, and is characterized by comprising an energy storage station and a power-adjustable photovoltaic power station, wherein an electric energy quality coordinated control system and a plurality of electric energy quality adjustment devices are used for adjusting and controlling electric energy quality input into a plurality of low voltage systems; power distribution grid relay protection devices, anti-islanding protection devices and counting measurement and control devices are arranged in a plurality of low voltage systems; and the anti-islanding protection devices and the counting measurement and control devices are arranged at eahc access point of the photovoltaic buildings. By adopting the building photovoltaic grid connected system, short-time power fluctuation in a power distribution grid region can be relieved, and the stability of a power grid can be improved; furthermore, the harmonic content and the voltage fluctuation degree are reduced, and the quality of electric energy is controlled; the power distribution grid relay protection devices and the anti-islanding protection devices ensure security of equipment and safety of human; and the counting measurement and control devices are distributed for different systems, so that automatic and intelligent running management is realized.

The invention discloses a comprehensive control method for a high-power efficient energy consuming high-frequency switching power supply. The high-power efficient energy consuming high-frequency switching power supply comprises a three-phase current inverter and a high-frequency DC / DC (Direct Current to Direct Current) converter, wherein the high-frequency DC / DC converter consists of a single-phase full-bridge inverter, a high-frequency coupling transformer and a low-voltage rectifier which are connected in series in sequence; the input end of the three-phase current inverter is connected with a group of three-phase capacitors connected in a Y form, and is connected with a power grid through a three-phase inductor L; and the three-phase current inverter is connected with the single-phase full-bridge inverter of the high-frequency DC / DC converter. According to the method, quick response of a system is realized, change of a load is tracked quickly, efficient power consumption of the system is realized, and the voltage and current distortion factors of the system are decreased.

The invention discloses a bifunctional direct current ice melting apparatus based on a voltage source type current converter and an ice melting method thereof. The direct current ice melting apparatus is characterized in that: the apparatus is in a bifunctional working mode. More particularly, in an ice-melting mode, the apparatus is in a rectification working state and can provide enough direct currents to carry out ice melting on an icing line; and in a non-ice melting mode, a corresponded switch switching and controlling strategy is utilized, so that the apparatus is in an inversion working state and is used as a static synchronous compensator (STATCOM) for operation; and thus, system reactive compensation is realized. Compared with a current source type ice melting apparatus, the provided novel apparatus enables an ice melting power to be increased, reactive power consumption to be reduced and harmonic output to be optimized; besides, the main characteristic of the apparatus is as follows: a dual mode working performance is designed; that is, energy-saving economic objectives of three-phase uniform ice melting and ice melting current minimization can be achieved in minimum ice melting time under an ice melting mode.

The invention discloses a multitooth magnetic bridge type hybrid excitation magnetic flux switching motor. Permanent magnets, an armature winding and a single-phase excitation winding are installed on a stator; the tooth number of the stator is four times of the number of the permanent magnets; and part of a rotor part is a salient pole, and a rotor has no winding or permanent magnets and has simple and firm structure. An air gap magnetic field comprises an electric excitation magnetic field generated by the excitation winding and a magnetic field generated by the permanent magnets and is adjusted by changing the magnitude and the direction of excitation current, thereby improving the rotating speed operating range and the magnetic weakening capability of the motor. An electric excitation magnetic force line is connected with a magnetic bridge for closing after penetrating through an iron core at the top of the permanent magnets, which is beneficial to reducing the electric excitation ampere turns. The invention has parallel connecting structure of the excitation winding and the permanent magnet in space, bipolarity of phase magnetic flux, large magnetic chain change amplitude value and higher torque output capability and power density and is suitable for a low-speed straight application occasion.

The invention provides a five-electrical level inverter and belongs to the technical field of inverters. The structure of the inverter comprises an input direct current power supply, an input dividing capacitor, a three-electrical level bridge arm, a two-electrical level bridge arm, an output filter circuit and a load. The three-electrical level bridge arm consists of four switch tubes and only two switch tubes switch at high frequency at the same moment; the two-electrical level bridge arm consists of two switch tubes and the switching frequencies and output voltages of the two switch tubes are equal; as only two switch tubes of the inverter switch at high frequency at the same moment, the switching power consumption is small and the switching efficiency is high; the maximum voltage stresses of all switching tubes of the inverter are equal to an input voltage, the voltage stress of the switching tubes is low, and compared with the conventional five-electrical level inverter, the five-electrical level inverter uses fewer switching tubes, a simpler topological structure and simpler control; and due to multiple electrical level output, the volume of the output filter is reduced greatly. The inverter is suitable to be used on medium / high-voltage and high-power application occasions. In addition, the inverter has a promising application prospect in fields such as new energy interconnected power generation.

The invention discloses a mixed permanent magnetic pole-alternating and magnetic flux-switching memory motor and a winding switching magnetism-weakening control method thereof. The mixed permanent magnetic pole-alternating and magnetic flux-switching memory motor comprises a salient rotor and a stator, wherein the stator contains stator cores, aluminium-nickel-cobalt permanent magnets, neodymium-iron-boron permanent magnets, centralized armature windings and pulsed magnetism-adjusting windings; iron core edges of two adjacent outer U-shaped units and tangentially-magnetized long-stripped neodymium-iron-boron permanent magnets form a first permanent magnetic pole, while the circumferentially-inward (outward) and parallel-magnetized V-shaped embedded aluminium-nickel-cobalt permanent magnets and inner U-shaped units form a second permanent magnetic pole; mixed magnetic poles are in alternating polarity distribution; when the motor runs at a low speed, the pulsed magnetism-adjusting windings are in direct-current pulsed working state, while in a high-speed weak-magnetism area, the pulsed magnetism-adjusting windings are converted into alternating-current armature windings. Requirements on performance in a low-speed area and in the high-speed area can be met at the same time; influence of an armature reaction field on the aluminium-nickel-cobalt permanent magnets with low coercivity is small; the utilization rate of permanent magnetism, the torque density, and the reliability of system operation are high.

The invention relates to a bi-directional power flow controlled multi-level mutual balance solid state transformer and a realization method thereof. The solid state transformer is a three-phase solid state transformer which is designed by using a mutual balance structure, and uses an AC-DC-AC three step type transform structure. A high voltage level, an isolation level and a low voltage level are comprised. The high voltage level and the isolation level are transformers with the same three-phase structure and are composed of sub units. The low voltage level is a single whole module which realizes an automatic mutual balance structure. Three-phase sub units of the high voltage level are connected in a star mode. The low voltage level is an alternating current output end with a three-phase four-wire wiring mode. The solid state transformer can realize power bi-directional flow. The whole three-phase system uses an independent structure, which is convenient for three-phase independent control and modular production. Through the direct current bus parallel module of the low voltage level, a three-phase electric power automatic mutual balance function is realized, so that the practical problem of the solid state transformer is solved.

The invention discloses a mixed type multi-level current converter with direct-current fault ride-through capability and a working method. The current converter is based on a dislocation stacking theory and comprises a three-phase bridge rectifier circuit; each bridge arm of the three-phase bridge rectifier circuit comprises a dislocation stacking module, a cascading double-sub-module assembly, a half-bridge sub-module assembly and an electric reactor which are cascaded to one another; when a fault occurs, a discharging process before locking of the current converter is an oscillating discharging process under known initial conditions; and after the current converter is locked, equivalent capacitance values of the bridge arms are changed, if and only if backward voltages of cascading capacitors of the bridge arms are always greater than an alternating-current line voltage amplitude value in any loop states, a short-circuiting current is reduced to zero by the inverting blocking characteristic of diodes, and the direct-current fault is eliminated. The direct-current fault is eliminated in a self-limited manner by locking the current converter, and an extra high-voltage and direct-current circuit breaker is not required. The mixed type multi-level current converter with the direct-current fault ride-through capability is suitable for a common overhead circuit, and can be used for the fields of multi-terminal direct-current network establishment, new energy grid connection, passive network power supply and the like.