36results about How to "Good for engineering practice" patented technology

The invention relates to a method used for balancing three phases of direct current side voltages of a chain power regulating device, and belongs to the technical field of the control of power electronic devices. The method comprises the following steps of: acquiring direct current side voltages of each H-bridge unit in the three phases of a chain power regulating system; filtering ripples from the direct current side voltages; taking the direct current side voltages of which the ripples are filtered as feedback signals; calculating an average value of the three phases of the direct current side voltages based on the direct current side voltages; taking difference values between the three phases of the direct current side voltages and the average value as command signals; calculating an amplitude value and a phase angle of a negative sequence voltage according to the difference values by utilizing corresponding formulae; obtaining a required negative sequence according to an electric angle of a power supply voltage at a device grid place; and after the negative sequence voltage is superposed to an output voltage command used for power control in the device, driving the device to output an alternating current voltage so as to realize the balance control of the three phases of the direct current side voltages. The method of the invention has the characteristics of software implementation, simple algorithm, obvious effect and contribution to engineering application.

The invention discloses a method for realizing the five-freedom-degree alternating current active magnetic bearing displacement self detection by utilizing a mixed kernel function support vector machine displacement predicating model. According to the method, magnetic bearing control current is used as an input sample, radial and axial displacement is used as an output sample, the sample data is collected, a mixed kernel function is selected, the performance parameters of the support vector machine are optimized through a particle swarm algorithm, the training sample and the performance parameters are utilized for training the least square support vector machine, and a non-linear predicting model is built. The predicting model is connected with a linear closed loop controller before being connected to a five-freedom-degree alternating current active magnetic bearing in series, the magnetic bearing displacement closed loop control is formed with a first and second expansion current hysteresis three-phase power inverter and a switch power amplifier, the self detection of a five-freedom-degree alternating current active magnetic bearing displacement-free sensor is realized, the cost of a magnetic bearing system is reduced, and the dynamic property of the system is improved.

The invention provides a networking radar station distribution method based on particle mechanism immune population search. The method comprises the steps that a deceived probability model and a detection range model of networking radar under deceptive interference are established; a joint optimization objective function is established, and constraint conditions of the joint optimization objective function are determined; key parameters of a networking radar system and basic parameters of search teams are initialized, and the iteration number of the particle mechanism immune population search is determined; a fitness function is determined, and the best positions of single searchers and the best positions of search teams are initialized; a vaccine is prepared by using a popularization searching method; the positions of the searchers are updated, and the vaccine is inoculated to the search teams; immune selection is conducted on the search teams through elite selection and annealing selection, and the best positions are updated; by using a population searching method, premature convergent search teams are disturbed; whether the termination standard is met or not is judged. By adopting the method, optimal radar station distribution positions can be rapidly and accurately found under the situation that trapping in local optimum does not occur.

The invention discloses a D8PSK coherent demodulation method and system, and the method comprises the steps: enabling a band-pass filter to receive a sampling modulation signal sent by AD sampling, and carrying out the band-pass filtering; processing the two paths of output signals of the band-pass filter to obtain baseband signals of an in-phase path and an orthogonal path; processing the baseband signals of the in-phase path and the orthogonal path to obtain two orthogonal paths of values of the optimal judgment sampling point of each symbol; feeding the two orthogonal paths of values of theoptimal judgment sampling point into a differential demodulation unit, a phase-locked loop unit, a frequency offset estimation unit and a frame synchronization unit at the same time; sending the differential decomposition modulation value is sent to a parallel-serial conversion unit, converting parallel input is converted into serial output, and acquiring a final demodulation sequence is obtained. A ; according to the method, a Gardner-based multi-level code element synchronization algorithm and a D8PSK difference decomposition modulation feedback-based phase synchronization algorithm are provided, so that the calculated amount is reduced to a great extent, and the engineering practice is facilitated.

The invention discloses a fuzzy control method of a direct current transmission converter based on command filtering. A fuzzy logic system is employed to approach unknown nonlinear terms in a power grid side converter system of a voltage source type direct current transmission converter system. A command filtering technology is introduced to solve the inevitable problem of 'calculation explosion'in the back-stepping control technology, the error of the filter is reduced by introducing a filtering compensation mechanism, and the command filtering technology has good inhibition effect on higherharmonics; the problems of unknown system parameters and uncertain disturbance intervention can be solved by introducing a self-adaptive control technology; under the control method of the invention,only one self-adaptive parameter exists in the controller, thereby reducing the on-line calculation burden and facilitating engineering practice. Simulation results show that the method can achieve quick and stable response to power and can achieve control of the power grid side converter.

The invention relates to a multi-component system state opportunity maintenance optimization method. When an equipment maintenance strategy is formulated, the current state of the equipment is considered, and the future degradation trend and failure probability of the equipment are also considered. Only if the future degradation trend of the equipment is accurately known, the maintenance strategycan be better formulated. Thus, multiple prediction algorithms are compared, an equipment degradation prediction and residual life prediction model for a single individual is established on the basisof analyzing a state monitoring signal of the equipment, and an opportunity state maintenance model of the multi-component equipment in a long task period is established by considering the structure of the system and the length of the task period. According to the invention, advanced signal acquisition technology and signal processing technology are used, detection and real-time prediction of thesystem are realized, and the state-based maintenance theory and method of the equipment opportunity are expanded.

The invention discloses a method for evaluating the influence of direct-current power grid topology on fault current. The method comprises the steps that firstly, an equivalent circuit of a grounding mode of a metal return wire and a ground return wire is established, and a three-dimensional mesh circuit diagram decoupling method is provided, so that the equivalent circuit is planarized; an improved high-frequency equivalent model is provided, fault current calculation methods are deduced for a radial network and a ring network respectively, the theory is popularized to an n-end network, and then the influence of topological parameters and structures on fault currents is analyzed; an evaluation index k of the influence of the topology on the fault current is provided, and the influence of the initial fault current level of the power grid topology can be effectively evaluated; the k value determines which converter stations mainly come from in the initial stage of the single-pole short-circuit fault current of the direct-current power grid. According to the evaluation method provided by the invention, tedious calculation is avoided, and the influence of topology on the fault current can be directly and quickly evaluated.

The invention provides a voltage sag detection method for a cascade type electric energy quality comprehensive treatment device. The method comprises the following steps: 1, acquiring a three-phase phase voltage instantaneous value signal of a power grid; 2, calculating a power grid voltage phase angle and a voltage component of the three-phase phase voltage of the power grid in an alpha-beta rotating coordinate system according to the instantaneous value signal of the three-phase phase voltage of the power grid; 3, calculating a voltage component under a positive and negative sequence dq coordinate system according to a result obtained by calculation in the step 1, and obtaining positive and negative sequence fundamental wave components through positive and negative sequence decoupling and high-frequency filtering; 4, according to the positive sequence fundamental component and the negative sequence fundamental component, calculating negative sequence fundamental component angle characteristic quantity and three-phase power grid voltage positive sequence fundamental component amplitude modulus length, and obtaining a characteristic value based on a voltage sag voltage threshold value; and 5, according to the negative sequence fundamental component angle characteristic quantity, the three-phase power grid voltage positive sequence fundamental component amplitude modulus length and the characteristic value, determining the power grid voltage sag and the type thereof. The method can be realized by software, the algorithm is simple, the effect is obvious, and engineering application is facilitated.