31 results about "P v curve" patented technology

The invention discloses a maximal power tracing and catching photovoltaic controlled method with self-adaptive searching algorithm, which comprises the following steps: setting initial step-length; monitoring the voltage and the current of the i time solar battery array; evaluating the i time power; getting voltage change quantity delta Ui and power change delta Pi of the i time and the i-1 time; judging whether the delta Ui is 0; backing to sample if delta Ui=0; evaluating slope delta Pi / delta Ui of P-V curve if delta Ui is not equal to 0; judging whether delta Pi / delta Ui absolute value is not less than the setting accuracy E; un-changing dutycycle of buck circuit switching tube if |delta Pi / delta Vi|=E. This invention does not need device to test light intensity and temperature, which can decrease the cost of solar electric power generation system.

The invention belongs to the field of a power supply system and automatics thereof and is applicable to wide area information based quiescent voltage unstability prediction of power grid real-time states and working conditions after a predicted accident. The method comprises the steps of: (1) integrating the PMU (Power Management Unit) node distribution information and actual grid structure of the power grid and dividing the power grid into a plurality of generating areas and load areas; (2) carrying out P-V curve computation on the basis of SCADA (Supervisory Control And Data Acquisition) measurement information and state estimation results to obtain critical voltage of each node at the moment of voltage breakdown; (3) carrying out Q-V model analysis computation on a trend the voltage ofwhich is close to breakdown to obtain all participation factors installed with PMU nodes; (4) weighting the voltage margin of each node in real time to be used as a compressive voltage margin index according to real voltage data detected by a PMU by taking the PMU node participation factors as weight; and (5) when the compressive voltage margin index is relatively small, using the sensitivity of the reactive power loss change of a receiving section in a load area to transmission active power as a real-time proof for calculating voltage unstability.

The invention discloses a power transmission-distribution network integrating voltage stability assessment method based on distributed calculation. The power transmission-distribution network integrating voltage stability assessment method based on distributed calculation comprises the following steps: (A) defining loads and generation increase modes of a power transmission network and a power distribution network, and resolving the global voltage stability assessment problem of the power transmission network and the power distribution network into three parts, namely an independent power transmission network calculation sub-problem, an independent power distribution network calculation sub-problem and common connection point information interaction; (B) carrying out continuous power flow prediction by the power transmission network employing a tangent prediction method, calculating various node state variables, various common connection point state variables and predicted values of load parameters of the power transmission network, and judging whether the tangent slope symbols of front and rear points of a P-V curve are opposite or not; and (C) finishing continuous power flow correction link calculation by distributed alternate iteration of the power flow of the power transmission network and power distribution network, and judging whether the power flow meets the convergence condition of distributed calculation or not, if so, turning to the step (B), or else, continuing the step (C). Therefore, distributed calculation of the whole power network load margin is realized.

The invention discloses a method for measuring the large-deformation uniaxial constitutive relationship of a material based on the energy principle and the P-V curve obtained by stretching a central circular hole plate sample. The quasi-static tensile test was carried out on the central circular hole plate sample to obtain the continuous P-V curve, and the elastic stiffness S, characteristic load P* and displacement exponent m were determined through the curve, and then the large deformation uniaxial constitutive relationship of the material was obtained. The present invention is applicable to ductile materials with isotropic strengthening and whose constitutive relation conforms to the power law, wherein the structure of the central circular hole plate sample has particularity, that is, during the tensile test, the material unit at the center point of the circular hole edge of the sample It is in a uniaxial stress state before the necking occurs. Compared with the straight sample, the invention is easier to implement, and the obtained uniaxial stress-strain relationship has a wider range, which is of great significance to engineering structure design and safety assessment.

The invention discloses a method for obtaining uniaxial stress-strain relation of a material through a small punch test. After a continuous load-displacement curve of a stamped wafer sample is obtained, power-law fitting is conducted on the stage III of the P-V curve, obtained load characteristics and displacement indexes are introduced to a Hollomon equation so as to obtain the uniaxial stress-strain relation of the material. The method is suitable for ductile and power-law isotropic hardening materials, the uniaxial stress-strain relation of the material can be obtained only by cutting out a small wafer sample from an existing member in special circumstances such as high temperature and irradiation, and accordingly the degradation properties of the material are assessed. The method has weaker destructiveness on the existing member, achieves the micro-damage detection, sample processing and testing principles are simpler, obtained results have higher accuracy, the shortcoming that a traditional uniaxial drawing test is largely limited by material size and the like is overcome, and the cost lower. The method has the greater advantages in testing of precious-metal servicing micro-force materials establishing constitutive relation of minimally invasive wafers and other small samples.

The invention discloses a multi-step size based photovoltaic power generation system maximum power tracking control method. The multi-step size based photovoltaic power generation system maximum power tracking control method comprises the steps of firstly setting an initial disturbance step size; utilizing a function M=V*abs (dP / dV) to conduct demarcation on a photovoltaic cell P-V curve, taking step size d1 in a left-side region of a maximum power point when a value of a function dM / dV is greater than 0; taking step size d1*M / P when the value of the function dM / dV is smaller than 0; taking step size d2 in a right-side region of the maximum power point when a value of the function M is greater than power P; taking step size d2*M / P when the value of the function is smaller than the power P; The multi-step size based photovoltaic power generation system maximum power tracking control method is simple and practical, and the proportional relation of an initial fixed step size can be determined by utilizing photovoltaic cell panel parameters provided by a manufacturer. The problem that steady accuracy and dynamic tracking speed cannot be simultaneously considered in most of maximum power tracking controls is solved by means of the method.

The invention relates to a method and system for realizing static voltage stability monitoring in a power system. The method includes: constructing a power flow equation corresponding to the direct power flow method, and solving the initial transitional operation state of the system according to the power flow equation; detecting the solved initial transitional operation state to judge whether the preset switching condition is met, and if so, constructing a continuous The extended power flow equation corresponding to the power flow method, according to the extended power flow equation, solves the stable transitional operating state of the system; generates the system P-V curve according to the solved initial transitional operating state and stable transitional operating state, and then obtains the static voltage stability when the power system load changes Power limit value and voltage threshold value information. The invention not only increases the speed of P-V curve generation, but also ensures the accuracy of P-V curve generation, and can quickly and accurately obtain the power limit value and voltage critical value information of static voltage stability when the power system load changes.