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 relates to a photovoltaic charger control device which comprises a photovoltaic voltage sampling unit, an output current sampling unit, an output voltage sampling unit, an MPPT unit, a first voltage controller, a voltage stabilizing control given unit, a second voltage controller, an amplitude limiting control unit, a current controller and a PWM generator. A photovoltaic charger control method comprises the steps that an MPPT control ring, a voltage stabilizing control ring, two voltage inner rings and a current control outer ring are adopted, the MPPT control ring output minimum value and the voltage stabilizing control ring output minimum value are selected as the given Iref of the current control outer ring, the output current value Ibuck of a photovoltaic charger is used as the feedback of the current control outer ring, the current control outer ring outputs the driving duty ratio to the PWM generator, and the PWM generator generates PWM driving signals to drive a switch tube of a main circuit of the photovoltaic charger to work. According to the photovoltaic charger control device and method, it is ensured that the photovoltaic voltage is always on the right side of a polar plate P-V curve, no output current jumping occurs, and it is ensured that photovoltaic energy is used more efficiently.

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 novel MPPT algorithm and a method for obtaining hardware for the novel MPPT algorithm. The novel MPPT algorithm comprises the steps that the open-circuit voltage of a solar cell panel and the battery voltage at present are sampled and measured; when the open-circuit voltage of the solar cell panel is higher than the battery voltage, tracking is started, and a master control unit outputs PSMC1A, PSMC1B and PSMC2A; the PSMC1A outputs PWM1 through an AND logic circuit, and the PSMC1B and PSMC2A output PWM2 through the AND logic circuit; the PWM1 and the PWM2 output PWMH and PWML respectively through a driving circuit unit; a synchronous rectification unit is driven by the PWMH and the PWML to scan the P-V curve of the solar cell panel, and the maximum power point of the solar cell panel is obtained by sampling output current in real time through a comparison current sampling unit. According to the novel MPPT algorithm and the method for obtaining the hardware for the novel MPPT algorithm, the maximum power point of the solar cell panel can be found accurately and rapidly, limitation of the environmental factors such as illumination, temperature and shadow shading is avoided, the tracking speed is high, and the efficiency is high.

The invention relates to an overheat protection device and method of an inverter. The overheat protection method comprises the following steps of: detecting real-time temperature of a power device of the inverter in the operation process; judging whether the real-time temperature is greater than a first preset temperature; and if so, boosting the maximum power tracking output voltage to the right side of a maximum power point of a P-V curve, carrying out amplitude-limiting on active current giving and reducing the active current giving, wherein the output power of the inverter is reduced by reduction of the active current giving so that the temperature of the power device is reduced. When a first judgment module judge that the real-time temperature is less than the first preset temperature, the detection module continues detect. The overheat protection device and method disclosed by the invention have the advantages of capabilities of carrying out rapid control on the temperature in real time, avoiding larger fluctuation of the output power of the inverter, controlling the output power of the inverter to be zero without poweroff and effectively prolonging the grid-connected generation time of the inverter.

The invention discloses a three-phrase power-distributing network continuation power flow analysis of the distributed power supply, and belongs to the technical field of electrical power system static voltage stability analysis. According to the three-phrase power-distributing network continuation power flow analysis, by the introducing of the increasing relation between the active power output of load parameter simulation distributed power supply and the load power, a three-phrase power-distributing network continuation power flow equation with the load parameter is established, and a P-V curve of the three-phrase power-distributing network is traced with the method of prediction-parameterization-method correction. The invention also provides an identification method of branch-point type when the distributed power supply is connected. The grid-connected injection current spillage of the distributed power supply in the continuation power flow analyzing process is considered, a node-type bilateral switching logic is adopted to conduct the process, and the running state of the distributed power supply is more close to a real situation, so that the P-V curve of the three-phrase power-distributing network can be traced accurately, the voltage collapse critical point can be calculated accurately, and the branch-point type can be identified accurately.

A method for obtaining a continuous power flow of an electric power system is provided. The method comprises: establishing first power flow equations for PQ buses, and establishing second power flow equations for PV buses; establishing power flow equations according to the first flow equations, the second power flow equations, and a voltage magnitude and a voltage phase of a balance bus; choosing a bus having a fastest voltage drop as a parameterization bus, and defining a parameterization variable according to a voltage magnitude of the parameterization bus and the load growth factor; defining an equality constraint equation according to the parameterization variable, and generating an extended power flow equation according to the equality constraint equation and the power flow equations; solving the extended power flow equation by a plurality of iterations to obtain a plurality of load summations; generating a P-V curve according to the plurality of load summations.

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.