32 results about "Superposition theorem" patented technology

The invention discloses a method for predicting electrical properties of deformed log-periodic antennae based on an electromechanical coupling model, aiming to mainly solve the problem of electromechanical separation in the log-periodic antennae. The method comprises the following steps: building a finite element model based on the structural design parameters of the log-periodic antennae, loading dead load, random wind and other environmental loads and carrying out finite element analysis to obtain the structure displacement field of the log-periodic antennae; utilizing the analysis results to obtain current distribution of oscillator units in the log-periodic antennae and phase difference caused by the positions and deflection of the oscillator units and computing the far field patternsof the log-periodic antennae according to the superposition theorem; and obtaining the electrical property parameters of the log-periodic antennae to realize electromechanical coupling analysis of the log-periodic antennae. The method can help the log-periodic antenna structural design personnel improve the antenna design and manufacturing quality.

The invention discloses an evaluation method for distance protection performance of a mixed direct current feeding alternating current system. The method comprises the following steps: utilizing the characteristics of a mixed multi-feed direct current transmission system to enable a conventional direct current transmission system and a flexible direct current transmission system before the fault to be equivalent to a constant current source; enabling the conventional direct current transmission system and the flexible direct current transmission system after the fault to be equivalent to a controlled current source; subtracting the constant current source in a network before the fault from the controlled current source in the network under a normal condition after the fault equivalent to the conventional direct current transmission system and the flexible direct current transmission system in a fault component network; and adopting a transient state principle for acquiring a short circuit current at a fault point, thereby utilizing a superposition theorem to acquire the variation of voltage and current on a protecting mounting position in the fault component network, further acquiring the measured impedance and verifying the protection sensitivity. The defects of an evaluation scheme for the distance protection performance characteristics in a mixed multi-feed direct current transmission system model and an alternating current system connected with the mixed multi-feed direct current transmission system model in a traditional electrical power system equivalent model can be overcome.

The invention discloses a loop closing power supply operation risk assessment method for a power distribution network. The method comprises the steps of 1: analyzing the type of a loop closing mode; 2: properly adjusting values and power factors of loads on two sides of a loop closing point; 3: ensuring a sum of the loads on the two sides of the loop closing point not to exceed a rated load of oneof switches on the two sides; 4: according to a superposition theorem, calculating line power flow after loop closing, and calculating a phase difference and a voltage of the two sides of the loop closing point; and 5: calculating a loop closing impact current and a loop closing steady-state current, performing safety check on all devices on the loop by utilizing the loop closing impact current and the loop closing steady-state current, and judging whether the loop closing can be performed or not. According to the method, the power supply reliability can be improved; better services can be provided for users; the power supply reliability of the power distribution network can be enhanced; the power supply flexibility of the power distribution network is ensured; the economy of power distribution network operation is improved; and remarkable social and economic benefits are achieved.

The invention provides a calculation method for high-frequency harmonic power flow of an active power distribution network, aiming at the problems of how to calculate the high-frequency harmonic power flow of the active power distribution network, and no related calculation methods in the prior art. The calculation method comprises the steps of 1) obtaining a high-frequency harmonic impedance model of each component; 2) performing equivalence on high-frequency background harmonics and voltage source and current source type grid-connected inverters; 3) calculating harmonic voltages of to-be-calculated nodes of the active power distribution network during separate action after equivalence; and 4) obtaining the high-frequency harmonic power flow of the to-be-calculated nodes by utilizing a superposition theorem. According to the method, the high-frequency harmonic power flow of the active power distribution network is obtained by utilizing an equivalent high-frequency harmonic model of the active power distribution network and the superposition theorem in electrotechnics, so that high-frequency harmonic power flow distribution can be mastered more accurately and harmonic control measures can be better established for reducing harmonic control cost and influence on a power system; and therefore, the method has a very important effect for research and development of the active power distribution network.

The invention relates to a power frequency electric field acquisition method based on the periphery of a high-voltage power transmission line, and the method comprises the following steps: S10, enabling the power transmission line to be simplified meeting the engineering precision requirement in order to facilitate the calculation and analysis of the electric field distribution around the power transmission line; S20, calculating a potential coefficient matrix of the power transmission line by resetting analog charges and matching point positions in the simplified model of the power transmission line; and S30, calculating the charges of the wire per unit length according to the potential coefficient matrix and the voltage vector, obtaining an electric field generated by the charges by using a superposition theorem, finally verifying the calculation precision, and repeating the step S20 if the calculation precision does not meet the requirements. Compared with the prior art, the methodhas the advantages of relatively high calculation precision and the like.

The invention provides a direct current grid fault current complex frequency domain calculation method. In the technical field of power transmission and distribution, a direct current grid is used asan effective means to collect new energy sources such as wind power and photovoltaic energy resources, and the calculation of fault currents is of great significance for operation such as equipment type selection, protection design and parameter optimization. The fault current complex frequency domain calculation method is suitable for monopole and bipolar faults and is not affected by the transition resistance, the alternating current feed of the alternating current side after the fault and the direct current feed of a remote sound branch are fully considered, for the alternating current feedof a converter station, a superposition theorem is used for dividing the direct current grid into a normal network and a fault additional network, and the normal network and the fault additional network are solved separately; and for the direct current feed of a normal line branch, an external node of the fault additional network is statically equivalent, and an equivalent circuit is subjected tofault current solution in a complex frequency domain.

The invention belongs to the technical field of stability analysis of power systems and particularly relates to a position function-based out-of-step and oscillation center positioning and migration tracking system and method under multi-frequency oscillation. The method comprises the steps of connecting power supplies at three sides to a point through three lines to build a three-machine equivalent system model; obtaining a voltage vector expression of any point under the simultaneous action of the power supplies at three sides according to a superposition theorem; setting position functionsof oscillation centers according to line impedance ratios; rewriting the voltage vector expression of any point into a form of modulus and phase, expanding the expression into a quadratic function, calculating a partial derivative and then obtaining an expression of the position of the oscillation center at any side according to a trigonometric function relationship and a mean value inequality; and analyzing the influences of three factors, namely relative power angles of systems, impedance structure parameters and power supply voltage amplitudes of the systems on the oscillation centers, obtaining conditions of appearing of an out-of-step center at various sides, obtaining a criterion according to the trigonometric function relationship of one voltage vector and then determining the position of the out-of-step center.

The invention discloses a finite array antenna analysis method. The method includes the following steps that the subarray solving scale is determined according to solving precision; full-wave solving is carried out on determined subarrays with a moment method; medium and large arrays are extrapolated according to the subarray solving result; in the process of solving subarray radiation fields, the subarray radiation fields are assumed to be radiation far fields, and an array antenna pattern is obtained. According to the method, based on the local effect of array antenna unit radiation fields and the electromagnetic field superposition principle, the numerical simulation issue of medium and large array antennas is simplified into full-wave solving of the subarrays according to the solving precision, then all unit radiation fields in the large arrays are equivalent to the unit radiation fields at corresponding positions in the subarrays, and finally based on the superposition theorem, the total radiation field is calculated, so that full-array matrix filling and the operation of solving the system of linear equations in the calculation process are omitted; besides, the radiation field calculation issue of the large arrays is transformed into the unit radiation field calculation issue of the small arrays, so that the calculation amount is effectively reduced, and the implementation difficulty is lowered.

The invention relates to a frequency full-response analytical model considering an initial state of a system. The model is characterized in that S1, a dynamic frequency full-response model is established according to a linearized model of each element of a power system and is simplified; S2, the initial state and input of the system are respectively ignored based on the full-response model in theS1, and analytic expressions of the frequency offset and the zero state response and zero input response of the power increment of a low-pressure cylinder in a steam turbine in the time period from tito ti+1 after a sudden change point i are obtained; S3, according to the superposition theorem, a full-response expression of the system frequency offset in the time period from ti to ti+1 after thesudden change point i is obtained through the S2; S4, i is made to be 1, and the process turns to a S5; S5, an analytical expression of the system frequency offset and the power increment of the low-pressure cylinder in the steam turbine in the time period from ti to ti+1 is solved; S6; if i is less than n, i is made to be equal to i+1, and the process turns to the S5; otherwise, the process turnsto a S7; and S7, an analytical expression of the whole dynamic frequency response process of the system is obtained. The model is advantaged in that the frequency response process of the system wheninput such as low-frequency load shedding and unit protection generator tripping occurs or parameters change suddenly when the frequency falls can be analyzed.

The application provides an active power control method and system based on voltage sensitivity subareas; the method comprises the following steps: equivalently transforming the whole feed line in a distribution network system into a plurality of two-port network cascade so as to obtain a complex two-port transmission parameter matrix; respectively calculating voltage sensitivity photovoltaic contributed on other photovoltaic user grid connected point by each photovoltaic user grid connected point according to a superposition theorem and the complex two-port transmission parameter matrix, thus obtaining a voltage sensitivity matrix; dividing each the photovoltaic user grid connected point on the feed line into one or more voltage autonomous control area according to the voltage sensitivity matrix; when the feed line voltage exceeds a limit, calculating the active power reduction quantity of each the photovoltaic user grid connected point according to the voltage sensitivity of each the photovoltaic user grid connected point in the voltage autonomous control area to which the photovoltaic user grid connected point with the exceeded voltage is located.

The invention discloses an equivalent three-phase short circuit calculation method which considers an outer network ground branch circuit and sensitivity information. Firstly, whole-network basic data including system element parameters, a topology structure and a trend calculation result under a normal running condition is input, then based on a sensitivity consistency equivalent method, an equivalent network is constructed, through a sensitivity weighing method, ground branch circuit admittance parameters are deducted, and according to trend, sensitivity and power transfer characteristic consistency, other parameters are solved. Finally, an improved equivalent method is applied to three-phase short circuit calculation, through the adoption of a node impedance method and a superposition theorem and based on the trend calculation result, a short circuit point current under a three-phase short circuit fault of an inner network, all node short circuit voltages and all branch circuit short circuit currents are calculated.

The invention provides a commutation failure prediction method considering waveform distortion and DC current change for an AC and DC interconnection system. The method comprises the following steps:establishing an AC-DC system commutation process mathematical model according to a DC commutation principle; decomposing three-phase components of a converter bus voltage based on discrete Fourier transform, and predicting a commutation voltage in a commutation process; predicting a direct current of the commutation process based on the superposition theorem; finally, predicting whether commutation failure occurs or not by comparing the extinction angle prediction value with the inherent limit extinction angle of a valve. The method can quickly predict the occurrence of commutation failure after a system fault, facilitates the timely making and taking of emergency control measures, and is of great significance to the maintenance of the stable operation of a power system.

Provided is an AC/DC hybrid micro-grid grid connection robust control method taking uncertainty into consideration. The method includes the following steps: on the basis of the superposition theorem,establishing an AC/DC hybrid micro-grid grid connection mathematical model and a feed-forward system mathematical model in accordance with an AC/DC hybrid micro-grid grid connection topological structure; independently controlling a DC sub-micro-grid and providing a reference voltage to a filter capacitor in an AC/DC hybrid micro-grid; and constructing an AC/DC hybrid micro-grid grid connection robust controller and AC/DC hybrid micro-grid grid connection is achieved, so the robust performance of the AC/DC hybrid micro-grid is improved. The method of the invention avoids overcurrents in grid connection points during AC/DC hybrid micro-grid grid connection, realizes seamless switching, and enables AC/DC hybrid microgrids still to be normally connected in a condition of certain parameter perturbation.

The invention discloses a zero-dynamic DC output voltage control method and system of a current source converter. According to the invention, a power grid voltage feedforward control item and a DC side output current feedforward control item are effectively calculated through the instantaneous power theory, the small signal model analysis, the superposition theorem and other methods; the zero-dynamic DC output voltage control method of the current source converter is provided on such basis, and by adopting the DC output voltage and power grid voltage feedforward control technology, the methodcan realize stable DC output voltage, and can realize zero-dynamic adjustment of the output voltage under the condition that the power grid voltage fluctuates; furthermore, no matter under the condition of balanced drop or unbalanced drop of the power grid voltage, zero dynamic adjustment of the DC output voltage can be realized by adopting the method, the power supply quality of the current source converter is effectively improved, and the method is simple in implementation process and has a great practical engineering application value.

The invention belongs to the technical field of frequency response measurement, and discloses a frequency response measurement system and method based on synchronous discrete Fourier transform. The system includes a synchronous waveform generator, a to-be-measured linear system, a signal conditioning circuit, a synchronous analog-to-digital converter and a calculation control unit. The characteristic that a discrete Fourier transform result has a real part and an imaginary part at the same time is utilized, a superposition theorem is utilized, a superposition signal of a plurality of sine sub-signals is input, and the amplitude-frequency response and the phase-frequency response of the to-be-measured linear system on a plurality of frequency points are obtained at a time through system synchronization and synchronous discrete Fourier transform. The measurement system and method provided by the invention have the advantages of simple measurement system and high measurement efficiency.

The invention discloses a method for estimating single particle crosstalk among multiple lines, which belongs to the technical field of crosstalk measurement and comprises the following steps of: 1, determining lumped RC coupling interconnection line model parameters; 2, constructing a single particle crosstalk equivalent circuit; 3, calculating the response voltage of the disturbed line under theindependent action of each disturbed line; 4, establishing a disturbed line comprehensive single particle crosstalk estimation model; and step 5, determining crosstalk peak voltage and pulse width. According to the invention, the admittance rule is defined; the SET equivalent circuit, the voltage basic law, the substitution theorem and the superposition theorem are utilized to establish the method for estimating the single-particle crosstalk between the multiple lines, the analytical expression of the peak voltage and the pulse width of the single-particle crosstalk is given through derivation operation and Taylor formula expansion, and the waveform and the noise peak of the single-particle crosstalk between the multiple lines can be accurately estimated.

The invention provides a short-circuit current calculation method for a multiphase power distribution network containing a negative sequence current injection IIDG, and the method comprises the steps: building an IIDG sequence component equivalent model through analyzing the relation between the IIDG fault current and an employed control strategy; a sequence equivalent model of the unbalanced multiphase power distribution network is established by adopting a method of introducing a virtual node, a virtual line and a compensation current; a sequence node voltage equation of the multi-phase power distribution network containing the IIDG is constructed, the relation between the IIDG output current and the corresponding node voltage and the relation between the decoupling compensation current and the corresponding node voltage are revealed, and an iterative correction short-circuit current calculation method based on the superposition theorem is provided. According to the method, the feasibility and effectiveness of the calculation method are verified through simulation comparison, the calculation speed is obviously improved, and meanwhile the convergence speed of iteration errors is higher.