76results about How to "Reduce output harmonics" patented technology

The invention discloses a permanent magnet synchronous motor drive control system and method of a cascaded multilevel converter and belongs to the technical field of power electronic control. According to the system and the method, the problems that the safety and the comfort level of new energy electric vehicles are affected due to the fact that traction motors on the existing new energy electric vehicles are a lot in output harmonic wave and low in output power quality are solved. According to the system, a traditional framework of a traction motor driver is abandoned, a series-connection cascaded type and parallel-connection cascaded type multilevel converter based topological structure and a control technology are put forward, high-performance drive control of a motor can be realized, in addition, the problem of single direct current power supply is solved, meanwhile, the control method is optimized, and a more reasonable multilevel current waveform output design is put forward according to different requirements of the embedded permanent magnet synchronous motor for current harmonic waves in low speed, medium speed and high speed processes. The system is applicable to occasions requiring high-efficiency and high-performance output and provision of energy sources by the single power supply, such as the new energy vehicles and the like.

A medium and high voltage power conversion method is as follows: ① convert the input medium and high voltage AC into N channels of AC; ② convert N channels of AC into the same number of high frequency AC; Or step-down processing, and then superimposed after rectification-inverter circuit transformation, and output alternating current of required frequency and amplitude. The device includes a symmetrical and identical input conversion stage, an output conversion stage (all of which are connected in series with the same power conversion modules of N stages) and an intermediate isolation transformer stage composed of N high-frequency transformers. The output of each power conversion module Both are coupled to the output conversion stage via a high frequency transformer. The invention utilizes the potential superposition principle to realize the application of the low-voltage power electronic device in the medium-high voltage system. Through the intermediate AC-DC-AC conversion technology and the intermediate high-frequency transformer coupling, a static power conversion device is designed to convert the input AC into a voltage output with continuously adjustable amplitude and frequency. Realize forced voltage balance between devices and reduce harmonic components in the output waveform.

The invention discloses a reactive power control circuit of a single-phase photovoltaic inverter. The reactive power control circuit comprises a bus voltage supporting capacitor, a single-phase full-bridge inversion circuit, a filtering inductor, an EMC (Electro Magnetic Compatibility) filtering circuit, a sampling circuit, a power switch pipe driving circuit and a DSP (Digital Signal Processor), wherein the DSP consists of a PLL (Phase Locked Loop) control module, a voltage outer ring PI control module, a current inner ring PI feedforward control module and a sinusoidal PWM (Pulse-Width Modulation) wave sending control module, and an input signal of the sinusoidal PWM wave sending control module of the DSP further includes a current inner ring current given amount Ig. The invention further provides a reactive power control method of the single-phase photovoltaic inverter. The method not only can be used for judging whether the voltage Uac of a power grid is larger than zero, and comparing the absolute value of a PWM wave sending control input modulation wave Upwm with a given triangular carrier wave Uc, but also can be used for judging whether the given current inner ring current amount Ig is larger than zero. Not only can the conduction loss of a power switching tube be reduced, and the conversion efficiency of the inverter is improved, but also the current waveform can be continuous, an output harmonic wave is reduced, and the pollution on a harmonic wave of a power grid is reduced.