46results about How to "Reduce dynamic loss" patented technology

The invention relates to a method for preparing a vertical double-diffusion MOS transistor, which comprises the following steps: firstly, simultaneously growing thick insulating layers at a position beside a channel region on the surface of an epitaxial layer in the horizontal direction and on a buffering isolation oxide layer of a device layer at the position; and secondly, finishing the preparations of a source electrode, a drain electrode and a grid electrode of the vertical double-diffusion MOS transistor by adopting a conventional process method. The introduction of the thick insulating layers increases the relative distance between a polysilicon gate and the epitaxial layer, namely increases the distance two pole plates of a grate-drain capacitor, so under the condition of not changing the polysilicon grate area and not increasing the on-resistance of a device, the method effectively reduces the grate-drain capacitance of the device, greatly shortens the time for charging and discharging the grate-drain capacitor in the switching process of the MOS transistor, improves the switching speed of the MOS transistor, reduces the dynamic loss of the MOS transistor, and greatly improves the performance of the device.

The invention relates to a directly-driven wind power generation system and a mode for modulating an SPWM inversion control signal in the system. The directly-driven wind power generation system is characterized in that a high-inductance permanent magnet synchronous generator is arranged and coaxially connected with a wind turbine; an alternating current signal output end of the high-inductance permanent magnet generator is connected in series with a triphase uncontrollable rectifier; direct current output by the triphase uncontrollable rectifier is used as an input signal of a subsequent current type inverter; an output signal of the current type inverter is filtered by a wave filter and fed to an alternating current network as sinusoidal current; the current type inverter consists of a fully-controlled power electronic switch and a current source type full-bridge inverting circuit; and the fully-controlled power electronic switch uses a sinusoidal pulse-width modulating signal SPWM as a control signal. Under the condition of a low wind speed, the directly-driven wind power generation system can also generate power without needing a direct current capacitor of the convertor, simplifies a controlling system, improves the generating efficiency of the whole machine and reduces the cost.

The invention provides a reactive power control method and device of a four-quadrant current source converter. The reactive power control method comprises the steps of obtaining a reference current imaginary part value and an actual current imaginary part value at an AC (Alternating Current) side of the four-quadrant current source converter; obtaining a triggering angle control quantity based on the difference value between the reference current imaginary part value and the actual current imaginary part value; and controlling the reactive power of the four-quadrant current source converter by adjusting the triggering angle control quantity. The reactive power control method and device of the four-quadrant current source converter solve the problems in the prior art that relatively big switching loss is resulted when a PWM control technology is adopted for reactive power control of the current source converter and relatively great stress may be generated for a switch device by the current source type converter when the current is cut off at a high frequency.

The invention relates to a silicon carbide split-gate MOSFET integrated with a high-speed freewheeling diode and a preparation method thereof, belonging to the technical field of power semiconductor devices. The MOSFET of the present invention adopts the design of the split gate to reduce the switching loss of the device. In order to prevent the gate oxygen reliability problem caused by the split gate structure, a P-type buried layer is added to reduce the electric field intensity of the polysilicon edge gate oxide layer. Furthermore, an N-type conduction layer is added to introduce current from the channel to the drift region of the device. In addition, in order to reduce the turn-on voltage drop of the silicon carbide MOSFET parasitic body diode and introduce a unipolar conduction mode, a high-speed freewheeling diode based on a MOS structure is introduced on the other side of the MOSFET cell. Compared with the traditional method, the present invention The high-speed freewheeling diode uses the surface tailing of the P-type buried layer to form a channel region, that is, the conduction voltage drop of the high-speed freewheeling diode is reduced as much as possible without adding additional versions.

The invention relates to a reverse conduction type IGBT gate pre-desaturation driving method based on current threshold judgment, using an external power MOSFET in the reverse conduction type IGBT gate to achieve flexible conversion of the drive level, and the drive circuit can be monitored in real time The operation mode of the reverse conduction IGBT, and the average current flowing through the circuit is obtained through the current measurement method, so as to judge whether it is necessary to change the gate voltage to optimize the dynamic and static characteristics of the internal integrated diode of the reverse conduction IGBT, thereby reducing the three-phase The dynamic and static loss of the inverter system can improve the system efficiency. After calculation, applying this pre-desaturated gate drive circuit to the three-phase inverter can increase the system capacity by about 30% while keeping the volume unchanged. Reducing 10%-15% loss release, 1MW class three-phase inverter can save 10%-12% of electric energy.

The invention discloses a heterospolar type permanent magnet bias mixed radial magnetic bearing. The heterospolar type permanent magnet bias mixed radial magnetic bearing comprises a stator assembly and a rotor assembly. The rotor assembly comprises a rotary shaft and a rotor iron core arranged outside the rotary shaft. The stator assembly comprises auxiliary magnetic poles, a stator iron core, permanent magnets and excitation coils. Stator magnetic poles with the number of the multiple of four are distributed on the inner surface of the stator iron core evenly at intervals in the circumferential direction. One auxiliary magnetic pole is arranged between every two adjacent stator magnetic poles. One permanent magnet is embedded between each stator magnetic pole and the adjacent auxiliary magnetic pole. The magnetizing directions of every two adjacent permanent magnets are opposite. One set of excitation coils are arranged in a groove between every two adjacent stator magnetic poles. Work air gaps are arranged between the surfaces, toward the axes, of the stator magnetic poles and the auxiliary magnetic poles, and the outer surface of the rotor iron core. An electrical excitation magnetic path of the magnetic bearing does not pass the permanent magnets, additional air gaps do not exist, the auxiliary magnetic poles effectively solve the problem that the stator yoke thickness is large, the stator outer diameter can be reduced, and the space utilization ratio is increased.