5968 results about "Grid voltage" patented technology

A method for controlling dynamic power factor or the reactive power of a wind farm is provided. The wind farm comprises a number of wind turbines connected to a utility grid driven with a requested power factor or a requested reactive power. The wind turbine output voltage is controlled to a specific voltage set point. In the method, the wind farm power factor is measured and compared with the power factor requested for the utility grid, or the wind farm reactive power is measured and compared with the reactive power requested for the utility grid, respectively; the ratio of the wind farm voltage to the utility grid voltage is adjusted, and the output voltage of the individual wind turbines is regulated to correspond to the specific voltage set point; the steps are repeated until the power factor of the wind farm electricity corresponds to the requested reactive power.

Power conversion apparatus and methods are presented for providing electrical power to a grid or other load in which a synchronous machine is driven by a wind turbine or other prime mover to provide generator power to a switching type current source converter (CSC), with a current source rectifier (CSR) of the CSC being switched to provide d-axis control of the synchronous machine current based on grid power factor feedback, and with a current source inverter (CSI) of the CSC being switched to provide leading firing angle control and selective employment of dumping resists to dissipate excess generator energy in a fault mode when a grid voltage drops below a predetermined level.

A wind turbine 36 has a back-to-back AC/DC/AC power electronic converter chain in which the grid side converter 48 is connected in series with DFIG stator windings 64.

The machine side converter 56 is fed from the rotor windings 54 of the DFIG 44.

Series connection of the grid side converter 48 enables voltage sag ride-through capability via control of the stator flux.

In the event of a grid voltage sag, the series converter allows for a controlled response in the stator flux and electromagnetic shaft torque, protects the machine side converter and enables continued power delivery to the grid.

The invention discloses an organic electroluminesence display panel and a display device. A first preset voltage is written into a grid of a drive transistor through a data writing unit; drive current of the drive transistor is received through a detection unit; the drive current is computed through a detection line, and the grid voltage of the drive transistor is adjusted until the changing quantity of the voltage on the detection line becomes a preset value, so that the changing quantity of the drive voltage of a light emitting device is computed through computing the changing quantity of the grid voltage of the drive transistor, and thus the ageing condition corresponding to the light emitting device is obtained. An original gray value corresponding to each sub-pixel is compensated according to the ageing condition of the light emitting device in each sub-pixel, so that the uniformity of the brightness of the display panel is improved. Furthermore, a plurality of sub-pixels belonging to one pixel group in the display panel share one detection line, so that the wiring number in the display panel can be reduced, and thus the number of signal channels of a drive chip can be reduced, and the area of the drive chip is decreased to reduce the production cost.

The invention relates to a control method which can be applied to an active-clamp flyback miniature photovoltaic grid-connected inverter device. The active-clamp flyback miniature photovoltaic grid-connected inverter device comprises a flyback converter and a power frequency polarity conversion circuit. In the device, a current reference is used for controlling a flyback primary-side current peak value so that the device can output a half-wave sinusoidal current, and the output voltage is clamped by a grid voltage. When the instantaneous power is lower, a constant frequency current discontinuous mode in combined with a variable frequency current critical continuous mode is adopted in the flyback control method. When the flyback converter works in a variable frequency current critical discontinuous mode, an auxiliary switching tube can be conducted for a period of time when the secondary-side current of the flyback converter reaches zero, the conduction time can be accurately controlled by a digital chip, thus realizing the leakage inductance energy feedback and the soft switch of a master switching tube under the condition of wide-range output voltages and different instantaneous powers and greatly improving the efficiency under the condition of full loads.

The present invention relates to a photovoltaic three phase synchronization control method realizing maximum power tracking swiftly and stably, which belongs to the technical field photovoltaic power generating control. The method includes the steps as follows: judging the DeltaP/DeltaV value according to the power difference DeltaP between the current time k and the previous time and the voltage difference DeltaV; working out the Iref(k) when the photovoltaic array produces the maximum power; using the Iref(k) to adjust the uq* under the coordinates in vectorial synchronous rotation with the electric network voltage; acquiring six ways of space vectorial SVPWM impulse series according to the rotation angle degree Theta of the three phase electric network voltage, with the aim to control the inverter in order to ensure that the output current of the photovoltaic inverter has the same phase position as that of the mains voltage while ensuring the photovoltaic array is realizing the maximum power output tracking. The power factor is 1. The present invention also can adjust the Idref(k) according to local load requirements, therefore achieving adjustment to the power factor, with low synchronization current harmonic wave distortion factor.

The invention discloses a coordination control and optimization method for battery energy accumulation and photovoltaic power generation based on a co-direct current bus in synchronization and independent operation modes, which supports the access of various types of storage batteries and photovoltaic battery boards through the free combination of the co-direct current bus of a DC (Direct Current)/DC converter, the automatic intelligent charge-discharge management of a storage battery branch and the maximum power tracing management of a photovoltaic battery board branch, wherein the branches are completely independently controlled to realize optimization management; the energy collected by a direct current bus is interacted with the energy of a power grid or an independent load through a post DC/AC (Alternating Current) converter; the DC/AC converter adopts a method for carrying out directional vector control on the voltage of the power grid and modulating the space vector pulse widthof the voltage in the course of the synchronization operation in an active and reactive complete decoupling control mode; and V/f control is adopted in the course of the independent operation to provide a constant voltage and frequency reference to an alternating current bus. The result of an experiment proves that the invention can realize the coordination complementary control and the autonomous optimization management of photovoltaic power storage and has the advantages of good generality, practicality and application prospects.

This invention deals with an advanced Real-time Grid Monitoring System (RTGMS) suitable for both single-phase and three-phase electric power systems. This invention provides an essential signal processing block to be used as a part of complex systems either focused on supervising and diagnosing power systems or devoted to control power processors interacting with the grid. This invention is based on a new algorithm very suitable for real-time characterization of the grid variables under distorted and unbalanced grid conditions. The main characteristic of this invention is the usage of a frequency-locked loop, based on detecting the grid frequency, for synchronizing to the grid variables. It results in a very robust system response in relation to existing technique based on the phase-angle detection since grid frequency is much more stable variable than the grid voltage/current phase-angle, mainly during grid faults. Moreover, the algorithm supporting this invention is very efficient and can be implemented in regular industrial microprocessors. These features make the RTGMS object of this invention ideal to be applied in the control of distributed generation systems (DGS), flexible AC transmission systems (FACTS), power quality conditioners (PQC) and uninterruptible power supplies (UPS). In all these systems, the fast and precise real time detection of the voltage and/or current sequence components under grid fault conditions is a crucial matter.

Enclosed is an active and reactive coordination control method for permanent-magnet direct-driven wind turbines in the low-voltage ride-through process. Two different control strategies are employed for a grid side converter according to amplitude change of power grid voltage: when the power grid voltage is in a normal state, the grid side converter is in an active-priority maximum power tracing control mode so that the wind turbines capture wind energy to the maximum extent; when the power grid voltage is beyond the normal range, the grid side converter is in an active priority control mode so that the dynamic reactive current which is injected into an electricity system meets the requirements of grid combining. An engine side converter is in a direct-current voltage control mode based on rotor energy storage, power unbalance of the direct-current side of the engine side converter is relieved and the direct-current voltage is stabilized by utilizing the self rotating speed of the permanent-magnet direct-driven wind turbines and the change of the kinetic energy. The active and reactive coordination control for the wind turbines before or after the sudden change of the power grid voltage is realized according to the amplitude change of the power grid voltage, the fluctuation of the direct-current bus voltage is restrained by releasing or storing the rotor kinetic energy, so that the low-voltage ride-through capability of the permanent-magnet direct-driven wind turbines is improved, reactive power support is rapidly and accurately provided for the power grid, and certain support is given to restoration of the power grid voltage.

The invention discloses a parallel structure and a control method for a photovoltaic power generation grid-connected inverter and belongs to the technical field of renewable energy sources. A topological circuit structure of the photovoltaic power generation grid-connected inverter is divided into a parallel structure of single-phase voltage type pulse-width modulation (PWM) inverters and a parallel structure of three-phase voltage type PWM inverters; and in the control method, an outer ring regulator of a control circuit of the parallel voltage type PWM inverters is independent based on a power grid voltage-oriented vector control technology in a control mode of voltage outer ring and current inner ring so as to form a common unified outer ring regulator; control strategies of various inverters are simplified into single closed loop current control so as to achieve the consistency of energy flow directions of the parallel voltage type PWM inverters and avoid ring current; and the parallel current sharing of the voltage type PWM inverters is realized. Therefore, multiple modules of the voltage type PWM inverters are connected in parallel to realize high-power modularized large-scale application.

The invention belongs to the field of power converter control and relates to a model prediction control method of a voltage source type rectifier when a network voltage is unbalanced. The model prediction control method of the voltage source type rectifier when the network voltage is unbalanced comprises the steps of converting three-phase network voltage and a three-phase current into network voltage and a current which are under a two-phase static coordinate system through an abc / alpha beta coordinate, obtaining network positive sequence voltage and negative sequence voltage by carrying positive and negative sequence component separation of the network voltage under the two-phase static coordinate system, calculating reference values of active power, calculating current reference values of the rectifier under the two-phase static coordinate system, and carrying out model prediction current control and selecting an optimal on-off state. The model prediction control method of the voltage source type rectifier when the network voltage is unbalanced is capable of quickly and precisely tracing the current under the two-phase static coordinate and effectively eliminating fluctuation of direct current side voltage at the same time, power quality of the system is improved, a reliable network-connected operation of the rectifier when transient state network voltage is unbalance is achieved, and dynamics and stability of the whole system are improved.

The invention relates to a safety level evaluation method a power grid, comprising the following steps of: firstly determining a supposed accident list, and sequentially disconnecting elements of the supposed accident list; after a certain element is disconnected, carrying out topological structure analysis and load flow calculation on a system, and then calculating a power grid loss load risk evaluation index, a power grid overload risk evaluation index, a power grid low voltage risk evaluation index and a power grid voltage collapse risk evaluation index; repeating the process till all the elements of the supposed accident list are completely calculated; and then calculating a system single-risk evaluation index and a system total-risk evaluation index. The invention introduces a risk theory and a utility theory to the safety evaluation of the power grid, separately diagnoses the safety of the system from different side surfaces, further obtains the risk evaluation index of the whole system by an analytic hierarchy process (AHP), obtains simple and clear results and has better discrimination and can reflect the occurrence possibility of different accidental accidents and severity degree of a consequence caused by the accidental accidents.

The utility model relates to a voltage type source rectifier stable control system and method based on LCL filter wave, belonging to the source rectifying technical range of electronic technology. The system comprises a DC voltage control cell, a current control cell, an active damp control cell and a voltage space vector generating cell. the utility model produces six PWM signals to gain the current signal of the filter wave capacitor branch directly or indirectly, outputs the reference value of the damp voltage and achieves the stable control on the system. The method provides an adjustable sine control on the DC voltage output and input current through the active damp vector control of the voltage type source rectifier stable control system, the damp voltage reference value outputted by the active damp vector control cell, and the network voltage to execute summation operation. The utility model has the advantages of controllable DC voltage, low aberrance rate of the network input current, high power factor, satisfying the requirement of energy double-redirection flowing, and achieving the stability of the system without increasing the quantity of hardware damp resistance.

The invention discloses a robust dicyclic photovoltaic grid-connected control method based on power feedforward, which mainly comprises three parts: proportion integration (PI) control of exocyclic voltage, dead-beat control of endocyclic robust predictive current and power feedforward control, wherein the exocyclic PI control of the voltage is used for stabilizing the capacitive voltage of a direct-current side; the dead-beat control of the endocyclic robust predictive current is used for carrying out linear prediction on the voltage of a power grid at a next control period and carrying out non-linear prediction on grid-connected current by advanced control so as to obtain the command value of the grid-connected current at the next period; and then, PWM (pulse-width modulation) and grid-connected control are realized by the dead-beat control. According to the robust dicyclic photovoltaic grid-connected control method based on the power feedforward, a photovoltaic grid-connected inverter has higher robustness, wider stability margin and quicker dynamic response, and the requirement of grid-connected running of an inverter is better met.

The present invention relates to a method for increasing a total reactive power capability of a cluster of wind turbines operationally connected to a grid. The method comprises the steps of generating a voltage value representative of a grid voltage level, determining a total required reactive power value based on the voltage value, and activating at least one wind turbine in said cluster to increase the total reactive power capability from a present value to the required total reactive power value by a predetermined amount. Moreover, the present invention relates to a system suitable for carrying out the before-mentioned method.

A power compensation apparatus for a renewable energy system includes a plurality of converter modules positioned between any two phases of a three-phase AC electrical grid, each converter module including a plurality of inverter circuits connected in series. Each inverter circuit includes an energy storage unit for providing a direct current (DC) voltage; a capacitor connected to the energy storage unit; and an H-bridge circuit converting the DC voltage into an alternating current (AC) voltage. The converter modules perform reactive power compensation and active power regulation on the electrical grid in a delta connection. A plurality of converter modules are respectively positioned between any two phases of the electrical grid in a delta connection, so as to keep the voltage of the electrical grid continuously stable when the voltage of the electrical grid fluctuates, and also compensate load current when system load is not balanced.

Disclosed is a controller of a grid coupled type doubly-fed induction generator having a multi-level converter topology, which can control the doubly-fed induction generator having a high voltage specification and can perform a fault ride-through function, an anti-islanding function and a grid voltage synchronization function required for a dispersed power generation facility. The controller makes a H-bridge multi-level converter generate a three-phase voltage waveform resulted from the structure that single-phase converters each being composed of a 2-leg IGBT are stacked in a serial manner, and controls a rotor current so as to make the rotor coil of the doubly-fed induction generator in charge of a slip power only. The boost converter is composed of a 3-leg IGBT and a boost inductor generating a direct current voltage of its source required for the H-bridge multi-level converter.

Systems and methods are disclosed to control voltage profiles of a power grid by forming an autonomous voltage control model with one or more neural networks as Deep Reinforcement Learning (DRL) agents; training the DRL agents to provide data-driven, real-time and autonomous grid control strategies; and coordinating and optimizing reactive power controllers to regulate voltage profiles in the power grid with a Markov decision process (MDP) operating with reinforcement learning to control problems in dynamic and stochastic environments.