6results about How to "Improve harmonic characteristics" patented technology

The invention provides a nine-level inverter topological structure and a modulation method thereof, the topological structure comprises a load end, and a first direct-current voltage source, a second direct-current voltage source and a third direct-current voltage source which are respectively connected with the load end, and the output voltage ratio among the first direct-current voltage source, the second direct-current voltage source and the third direct-current voltage source is 2: 1: 1. By configuring an insulated gate bipolar transistor and a power diode, the number of switching tubes is reduced, and the inverter is ensured not to have the problems of power backward flowing and instantaneous peak voltage, so that the power backward flowing phenomenon caused by the fact that the current of a high-voltage power unit reversely flows into a low-voltage power unit and the instantaneous peak voltage during inductive loading are avoided; the stability of circuit output power is ensured, the design is simplified, and a step wave and carrier wave laminated hybrid modulation method is used, so that the low switching loss of a high-voltage power unit and the excellent harmonic characteristic of the output voltage of the inverter are ensured.

The present invention discloses a cross-coupling filter, including a minimum resonant structure, which is composed of four resonators, in which two resonators in the same row form a group, and the two resonators in the same row are mainly electrically coupled or magnetically coupled; the two resonators in the same column are electromagnetically mixed coupled; and the coupling polarities of the two groups of resonators in the two rows of resonant units are opposite, and at least one cross coupling is formed. The present invention realizes miniaturization and light weight in structural characteristics, and realizes low loss and good harmonic characteristics in electrical performance.

The present invention discloses a harmonic suppression method, device, equipment and storage medium. By setting a harmonic voltage droop control strategy, a first relationship between harmonic power and harmonic impedance is determined; based on the first relationship, the actual harmonic power in the power grid is converted into a first harmonic impedance, and based on the first harmonic impedance and the harmonic voltage droop control strategy, the harmonic voltage value of a target feeder in the power grid is calculated; it is judged whether the harmonic voltage value satisfies multiple harmonic power balances, and when it is determined that multiple harmonic power balances are satisfied, the harmonic power balance impedance values ​​of each feeder are obtained, and the multiple harmonic impedances of the target feeder are obtained at the same time, and the compensation impedance is calculated according to the harmonic impedance and the harmonic power balance impedance values ​​of each feeder, and the harmonic impedance of the target feeder is compensated based on the compensation impedance; compared with the prior art, the technical solution of the present invention can improve the overall harmonic suppression level of the power grid and ensure the stable operation and quality of the power system.

The present invention discloses a direct power prediction control method without a grid voltage sensor based on MRAS, which adopts model reference adaptation (MRAS) to identify the grid-side inductance in real time, reduces the volume and cost of the system, and makes up for the excessive dependence of traditional model predictive control (MPC) on system parameters, so that the control is more stable and reliable, has stronger anti-interference ability to AC voltage, and has good harmonic characteristics; at the same time, the control method without a grid voltage sensor eliminates the grid-side voltage sensor, reduces the system volume, and saves system cost.

The invention discloses an H-bridge low-frequency switch control method of a cascaded half-bridge converter, which is characterized in that a direct-current side adopts an in-phase carrier laminated modulation strategy, zero level duration is increased at a signal zero crossing point, the action times of a direct-current side switching device near the zero crossing point are reduced, and the switching loss of an H-bridge under closed-loop control is effectively inhibited. An alternating current side phase control algorithm is provided for multiple bridge arms, the bridge arms are divided into a leading group and a lagging group, control signals of sub-modules are redistributed based on fundamental wave phases, meanwhile, two groups of phase-complementary power frequency control signals are distributed for H bridges of the bridge arms, and on the premise that the output characteristics of the converter are not affected, the control signals of the sub-modules are distributed to the H bridges of the bridge arms. All H-bridge switching tubes only act twice in a fundamental wave period, strict power frequency switching and zero voltage switching are achieved, and switching loss is reduced to the minimum. And meanwhile, a battery online energy balancing function based on SOC sorting is integrated, so that the reliability of the converter is improved and the service life of the converter is prolonged on the premise of keeping relatively high output waveform quality, and the switching frequency of an H bridge under closed-loop control is reduced.

The present application belongs to the field of rail transit conversion technology application, and particularly relates to a novel multi-topology conversion inverter and a control method thereof. The present application solves the technical problem that the basic main circuit topology structure of the three-phase inverter is determined in the design, and cannot be changed according to the actual situation or working condition. When a switching device in the power module is damaged, the three-phase inverter has to be stopped, resulting in power loss, and having a great influence on the reliability and operation efficiency of the locomotive. The present application optimizes the design of the three-phase inverter main topology, adopts modular design, reduces the types of power modules, reduces the inventory of spare parts, and the main topology structure of the three-phase inverter can be flexibly changed according to the demand. When a switching device is damaged, the normal operation of the three-phase inverter can still be realized through topology switching. The present application is redundantly designed for different application environments and application requirements, and improves the reliability and operation efficiency of the three-phase inverter.