682 results about "Electrical network frequency" patented technology

The invention provides a method and apparatus for an energy storage system to participate in power grid frequency control. The method comprises the steps of monitoring power grid frequency and charged states of an energy storage system in real time; if a power grid frequency offset exceeds a maximum frequency deviation, determining the energy storage system to participate into power grid primary frequency modulation according to deviation directions and the charged states; when a primary frequency modulation starting condition is satisfied, calculating virtual inertia response, a primary variable sagging control power adjustment value and a primary frequency modulation active control instruction; according to the primary frequency modulation active control instruction, carrying out primary adjusting of active power output of the energy storage system; starting secondary frequency modulation after time delay to determine a secondary frequency modulation instruction; according to the virtual inertia response, the primary variable sagging control power adjustment value and the secondary frequency modulation instruction, determining a secondary frequency modulation active control instruction; and according to the secondary frequency modulation active control instruction, carrying out secondary adjusting of the active output power of the energy storage system. Through adoption of the method and apparatus of the invention, coordination and cooperation between the energy storage system and other machine sets in aspects of primary frequency modulation and secondary frequency modulation can be well solved.

Systems, apparatus, and methods are provided for maintaining the state of charge of energy storage devices such as batteries, flywheel, capacitors, or other technologies that are energetically coupled with the electricity grid to support ancillary services. To reliably respond to requests to regulate the grid, the charge on the energy storage device is sustained or restored to a specified range in a manner that optimizes the readiness of the energy storage device to supply ancillary services in light of the condition of the grid. A state of charge (SOC) of the energy storage device and the grid frequency may be monitored. When a request from the operator to regulate the grid frequency is not being serviced, the charge of the energy storage device may be increased or decreased so that the charge may be sustained within the specific range. Once the SOC falls outside of the first range, charge may be added to or removed from the energy storage device when the grid frequency has appropriate values, e.g. if the grid frequency is respectively above a first setpoint or below a second setpoint.

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.

A method and system allows for substantially real-time monitoring of the operational dynamics of power plants and other components comprising an AC power grid, by using information collected from a network of power grid frequency detection and reporting devices. The invention allows for the substantially real-time detection and reporting of certain power grid events such as power plant trips.

A wind farm (10) may include a plurality of variable speed wind turbines (12, 14, 16). A centralized controller (50) may be configured to selectively adjust a respective electrical output power from each of the wind turbines. The controller may include a monitor (52) configured to monitor a correlation between a deviation from a grid frequency and a wind power change. The controller may be configured to adjust a response of the electrical output power based on the monitored correlation. The electrical output power response may be configured to meet a grid frequency regulation notwithstanding of random occurrences of wind power changes.

The invention provides a coordination control method capable of enabling a super-capacitor energy storage system to participate in electric power primary frequency modulation, wherein the super-capacitor energy storage system is arranged on the bus side of a generator set which needs cooperation. A decision optimizing module obtains a frequency from a synchronous vector measurement unit, and the frequency deviation is obtained through the difference between the frequency and a 50Hz frequency. If the deviation exceeds a frequency dead band, the same motion instructions are simultaneously sent to a traditional generator set and the super-capacitor energy storage system. When the super-capacitor energy storage system participates in primary frequency modulation, the opportunity motion and the motion depth of the super-capacitor energy storage system are determined through the decision optimizing module according to partition of typical working conditions, the conversion from the frequency deviation to the power is achieved through a power-frequency conversion module, the charging / discharging control of the super-capacitor energy storage system is achieved through a PCS control module, and finally the traditional generator set is assisted in participating in the primary frequency modulation process. According to the coordination control scheme, the transient state performance and the steady-state performance of the primary frequency modulation can be obviously improved, frequent starting of the traditional generator set is reduced, and the power system frequency can be rapidly kept stable.

The invention presents a structure for the conversion of direct current electric power into alternating current electric power, characterised in that it is simple, highly efficient and minimises the problem of electromagnetic compatibility. The circuit includes, in its first preferred embodiment, six switching elements governed by a command unit, four switches forming an H-bridge (T1, T2, T3, T4) and two auxiliary switches (T5D, T6D), and two auxiliary diodes (Daux1 and Daux2). The elements of the H-bridge switch at grid frequency, whereas T5D and T6D switch at high frequency by means of pulse width modulation (PWM), or other appropriate modulation techniques. The voltage of these auxiliary switching elements (T5D, T6D) is limited topologically to half the direct current input voltage (Vin), thereby reducing switching losses and resulting in a high performance converter.

The invention discloses an online monitoring and performance assessing method for primary frequency modulation of a thermal generator set. The method divides grid frequency changes into invalid disturbance, valid disturbance, large frequency disturbance and small frequency disturbance, wherein the large frequency disturbance and the small frequency disturbance are contained in the valid disturbance. Specific performance indexes of response time, stabilization time, diversity factors of set rotating speed and the like of the primary frequency modulation of the set are quantitatively assessed, the contributed electric quantity and the correct operation rate of the primary frequency modulation under the small disturbance of the set and the diversity factors of the set rotating speed under the large disturbance of the set can be effectively calculated, and an assessing method for the performance of the primary frequency modulation of the set is further provided. The online monitoring and performance assessing method for the primary frequency modulation of the thermal generator set has the advantages that calculation and monitoring can be carried out on the operation performance of the primary frequency modulation of the set in a long period of time, the comprehensive index of the primary frequency modulation of the set is further calculated, an assessing method is quantified, and the performance of the primary frequency modulation of sets in a network can be comprehensively learned by province professionals.

The invention is applicable to the power field and provides a power grid frequency measurement method and a device. The method comprises the following steps: sampling inputted signals at equal intervals and obtaining sampled signals with equal sampling intervals; carrying out filtering treatment on the sampled signals; determining a zero crossing point of a sampled waveform according to the sampling value after the filtering treatment and storing the sampling values of front and rear sampling points of the zero crossing point; determining the number of sampling points between the adjacent zero crossing points and measuring the frequency value according to the sampling intervals, the sampling values and the sampling points. As the high-frequency filtering treatment is carried out before the base wave frequency measurement, the embodiment of the invention can effectively eliminate the interference of harmonic waves in the practical power network operation, thereby improving the detection accuracy of the zero crossing point and further improving the reliability and the accuracy of the base wave frequency measurement.

The invention discloses a primary frequency modulation electric quantity compensation refined control method and apparatus under a giant hydroelectric generating set power mode. The control method comprises the steps of obtaining a frequency difference signal between a power grid standard frequency and an actual power grid frequency obtained in real time; judging whether the frequency difference signal is outside a primary frequency modulation frequency dead zone or not, if the frequency difference signal exceeds the primary frequency modulation frequency dead zone, delaying for 0.1second and then outputting a primary frequency modulation action signal; using the frequency difference signal, and enabling a giant hydroelectric generating set speed regulator to be in a power mode; if the actual power grid frequency obtained in real time exceeds the primary frequency modulation frequency dead zone and is within in a range of a superposition value between the primary frequency modulation frequency dead zone and power dead zone equivalent power, performing superposition between a frequency compensation coefficient and the corresponding function of a frequency modulation load according to the frequency difference signal to obtain corresponding theoretical frequency modulation power; obtaining corresponding theoretical regulation power according to the frequency difference signal and the corresponding function of the frequency modulation load; and forming a PID closed loop by a new active given value and the actual power value of the giant hydroelectric generating set, and outputting a corresponding frequency modulation load instruction. By virtue of the primary frequency modulation electric quantity compensation refined control method and apparatus, the primary frequency modulation contribution rate of the giant hydroelectric generating set can be accurately controlled, the primary frequency modulation percent of pass is improved, and the electric energy quality can be improved.

An arrangement for generating a control signal for controlling a power output of a power generation system, such as a wind turbine, is provided. The power output is supplied to a utility grid. The arrangement includes a first input terminal for receiving a first input signal indicative of an actual grid frequency of the utility grid, a control circuit for generating the control signal, and an output terminal to which the control signal is supplied. The control circuit includes a bang-bang controller for generating a first power signal being indicative of a predefined amount of power to be added to the power output of the power generation system. The bang-bang controller is adapted to be activated when the first input signal falls below a first predefined threshold. The control signal depends on the first power signal.

The present invention provides a method and a device for primary frequency regulation based on bang-bang control, the method comprises: obtaining in real-time a power grid frequency of a steam turbine generator set; performing a subtraction operation on a rated power grid frequency and said power grid frequency to generate a power grid frequency difference; performing a dead zone process on the power grid frequency difference according to a dead zone fixed value to generate a frequency difference; performing a frequency difference compensation operation on the frequency difference to generate a frequency difference compensation instruction; and combining an original primary frequency regulation output instruction with the frequency difference compensation instruction and outputting the result to a steam turbine speed regulation system when a selecting switch is 1.

A system includes a plurality of switches. The plurality of switches includes a first switch connecting a first load in a plurality of loads to a power supply line. The power supply line is connected to a public utility power grid. The plurality of switches also includes a second switch connecting a second load in the plurality of loads to the power supply line. The system further includes a power measurement device configured to measure a power grid frequency at the power supply line. The system additionally includes a load control module configured to operate the second switch to disconnect the second load from the power supply line when the power grid frequency is lower than a predetermined frequency threshold.

In some embodiments, the present invention includes the use of one or more electric power supply system, or systems, and the electric vehicle, or vehicles, connected thereto, to provide load-based utility grid frequency regulation by varying the amount of power drawn by the vehicle or vehicles.

The invention discloses a method for measuring electric network voltage flicker, and discloses a high-accuracy rapid flicker calculating method aiming at a non-integral cycle low sampling rate by taking account of errors probably caused by harmonic waves and electric network frequency. The core of the calculating method is that: a low fixed sampling rate is adopted to perform non-integral cycle sampling on electric network voltage waveforms, a cosine window is used for performing a fast Fourier transform algorithm (FFT), then the flicker frequency component is accurately extracted through a double-spectral line interpolation algorithm and a frequency spectrum searching algorithm, and the instantaneous flicker visual sensitivity is obtained through calculation. By using the method, under the condition of non-integral cycle low sampling rate, the errors caused by frequency spectrum leakage and harmonic wave aliasing are overcome, the frequency resolution is improved, the complexity of flicker calculation is effectively simplified, and a flicker measurement result is acquired quickly. By using the method, the performance requirement of hardware of an analog-digital converter, a processor and the like is reduced, thus the cost of a flicker measuring instrument is reduced, and simultaneously the measuring accuracy is improved; and besides, the method is applicable to fast low-cost measurement of the electric network voltage flicker, and has a very good effect.

The invention provides a control system and implementation method for a photovoltaic power station to participate in primary frequency modulation. The control system is composed of a signal acquisition unit, a primary frequency modulation processing unit, an active power calculation unit, an active power distribution unit, a telecontrol communication unit, a wave recording unit, a frequency disturbance unit, an inverter control unit and other modules. According to the invention, for the actual characteristics of new energy photovoltaic power generation, the photovoltaic power station participates in primary frequency modulation of a power grid through station-level active power optimization control; when the system frequency fluctuates and crosses a threshold, the output of an inverter isincreased or decreased; without adding an additional energy storage device, the photovoltaic power station quickly participates in primary frequency modulation within a certain period of time to maximize the role of the inverter; the frequency change amplitude of the system is reduced, participation in rapid recovery of the frequency of the power grid is realized; and the system and method are applicable for the photovoltaic power station to participate in primary frequency modulation of the system..

An energy storage device system for a primary frequency modulation and automatic generation control (AGC) auxiliary regulation technology comprises a power generation set, a transformer, a power grid, a DC-AC converter and energy storage battery packs and is characterized in that a multi-port DC-DC converter is also arranged, so that connection ports of a plurality of energy storage battery packs are connected with respective port of the DC-DC converter, and at least one supercapacitor is also connected with the respective port of the DC-DC converter; and moreover, a load allocation system is used for receiving a dispatched AGC instruction or forming a load instruction according to a frequency of the power grid, the instruction is divided into two paths, one path passes through an energy management system to be connected with the multi-port DC-DC converter and the DC-AC converter, and the other path is connected with a distributed control system (DCS) and digital electric hydraulic (DEH) control system of the generation set to control the power generation set to work. Therefore, the peak load regulation capability of a power system can be improved, the primary frequency regulation ability and the AGC response capability of a coal-fired unit are improved, the stable running of a power plant is ensured, and energy is saved.

Systems and methods for improving low-load efficiency of power converters are provided. The power converter can include one or more bridge circuits having multiple switching modules, such as insulated gate bipolar transistor (IGBT) modules, connected in parallel within the same bridge circuit. The power converter is configured to convert power from an input power source, such as a photovoltaic array or a wind turbine, into output power at a grid frequency. To avoid excessive switching losses at low load conditions, the power converter can be controlled to selectively operate a subset of the switching modules within the same bridge circuit based on a load condition for the power converter. The remaining switching modules in the bridge circuit can be disabled.

The invention discloses a method and a device for locating a single-phase grounding fault of a low-current grounding system. When the low-current grounding system has the single-phase grounding fault, a signal with pilot frequency different from grid frequency is injected between a fault phase and the ground, the voltage and current of the pilot frequency signal are detected at a signal injection end, an imaginary part of complex impedance of a fault loop under the frequency, namely a reactance value is calculated, and the distance between a signal injection point and a fault point can be obtained by multiplying the reactance value by a proportional constant. The signal is only needed to be injected at one end of a power grid, and the fault distance is directly measured and calculated, so that the method is simple and practicable, has high measuring accuracy, and has great significance for shortening fault removal time and improving the power supply quality of the power grid.

A power grid frequency flexible operation system is provided. The system comprises a generating unit, which includes a base-load unit and a peak-load unit; a high voltage direct-current (HVDC) transmission unit, which transmits the power generated in the generating unit as direct current (DC) power; and a load, which is supplied with the power generated by the generating unit; wherein the high-voltage direct current (HVDC) transmission unit comprises a converter, which transforms to direct current (DC) power, alternating current (AC) power generated in the generating unit and having a first frequency variation allowance range; an inverter, which is connected to the converter and transforms the direct current (DC) power to alternating current (AC) power having a second frequency variation allowance range, wherein the first frequency variation allowance range is larger than the second frequency variation allowance range.

The invention discloses an interconnection power grid primary frequency modulation responding performance assessment method, comprising steps of eliminating the affect of an AGC order through subtracting the change of the AGC order in power change of a power generator unit when the primary frequency modulation parameter and the indexes of the power generator unit are analyzed, assessing an accuracy index psi 1 of a primary frequency modulation responding characteristic, assessing a fast performance index psi 2 of the primary frequency modulation responding characteristic, assessing a stability performance index psi 3 of the primary frequency modulation responding characteristic, and assessing a robustness index psi 4 of the primary frequency modulation responding characteristic. The invention establishes the primary modulation frequency responding characteristic assessment index from four respects of accuracy, fastness, stability and robustness of the interconnection power grid primary frequency modulation control effect, provides the method for objectively evaluating the primary modulation frequency responding effect, analyzes the responding characteristics of the power grid primary modulation frequency responding characteristic. When the frequency of the interconnection power grid is changed, the power generator unit or the load spontaneously or continuously inhibits the change of the frequency.

The invention discloses a primary frequency modulation control method and system for a photovoltaic power station based on multi-master station coordination control. The method comprises the steps that the active power of the grid-connected point of the photovoltaic power station is collected in real time; since AGC load shedding control reserves power reserve capacity for the photovoltaic power station, the active power of the grid-connected point of the photovoltaic power station is active power Pref when the photovoltaic power station has the load shedding level described in the description; when the grid frequency exceeds the artificial dead zone DB disturbance of primary frequency modulation, a PFC control system calculates the active power variation delta P after frequency fluctuation, and the target value Pset=Pref+ delta P is given to the active power issued to an inverter group; and the active power of the photovoltaic power station is changed to achieve primary frequency modulation. The scheme simply needs to upgrade the algorithm of the control software of a conventional photovoltaic power station inverter, and adds a PFC master station coordination mechanism based on the existing AGC function of the power station, so as to realize multi-master station coordination control of AGC and PFC. Cost can be maximized. The primary frequency modulation function of the photovoltaic power station is used to speed up the frequency recovery of a grid.

The invention belongs to the technical field of wind power generation, and discloses a comprehensive control system adopting a doubly-fed wind generator participated in power grid primary frequency modulation. The control system comprises a rotor rotary speed control module, a simulation inertia control module, a droop control module, a rotary speed protection and power determination module and apitch angle control module. After the wind generator is participated in frequency modulation, the power grid inertia is equivalently enlarged, so that the doubly-fed asynchronous wind generator can have inertia response on the power grid frequent as the conventional synchronous generator, thereby lowering change rate of the power grid frequency; and by controlling the rotary speed and the pitch angle, the wind generator output is lowered, so that the wind generator has certain active backup capacity to be participated in primary frequency modulation, thereby lowering steady-state error of thefrequency.

The invention provides an auxiliary primary frequency modulation and optimization control method for battery energy storage systems. The auxiliary primary frequency modulation and optimization control method is characterized by comprising the following steps: obtaining the power shortage and the power grid frequency deviation change rate of primary frequency modulation; obtaining the modulation proportional coefficient of the battery energy storage system; computing the output power value of the battery energy storage system, determining the amendment opportunity and the amendment degree of the battery in a charging state, and amending. According to the method provided by the invention, the deficiency that a generator unit is insufficient in power change is made up; and the energy storage system is rapid in response speed, thus facilitating the faster recovery of power grid frequency. After the frequency modulation is completed, on the premise that the power grid frequency is not caused to cross a dead zone, SOC of the battery is corrected, next smooth frequency modulation process is ensured, the situation of time-of-use electricity price is comprehensively considered, charging cost for energy storage is reduced, and back discharge proceeds are increased.

The invention provides a method for simulating and analyzing automatic generation control of an electrical power system containing wind power. The method comprises the following steps of building a power grid model to which the wind power is connected, building a simulation platform external interface model, performing formatting processing to data changing with time in a power grid and inputting the data into the simulation platform external interface model, setting a simulation parameter and performing dynamic operation simulation, building a control performance index assessing and analyzing model, preserving and processing result data to a control performance index. The method is used for studying impact analysis of wind power connection to power grid dynamic frequency modulation, the simulation time can be calculated from second level to hour level and higher than hour level, and monitoring variables include power system frequency, interconnection power, conventional generator set power, wind farm power and the like and are used for quantitatively analyzing influence on power grid frequency control performance under the conditions of different wind power and providing reasonable suggestions for adjustment of a control method of an automatic generation control system. The method facilitates in-advance early warning of safe and stable operation risks of the power system after large-scale wind power is connected to the power system.

The invention relates to the technical field of thermal power set coordination control, and discloses a thermal power set primary frequency modulation and AGC coordination control method. The method comprises the following steps: step one, determining whether a power network has a high frequency or a low frequency, and determining whether an AGC system increases a load or decreases the load; step two, when the high frequency and an increased load are simultaneously one, outputting the increased load and holding signals; step three, when the low frequency and a decreased load are simultaneously one, outputting the decreased load and the holding signals; step four, triggering the increased load, locking a load increasing instruction of AGC, and prioritizing a load decreasing instruction of a primary frequency modulation function; step five, triggering the decreased load, locking a load decreasing instruction of the AGC, and prioritizing a load increasing instruction of the primary frequency modulation function; step six, superposing a power compensation amount on the basis of an original AGC instruction; and step seven, after primary frequency modulation is brought into play, and the AGC system recovering a power adjustment function of a positive direction and a negative direction. According to the invention, power network frequency control is better safeguarded, and the risk of worsening a power network frequency accident is reduced.

The invention discloses a detection method for grid frequency, which mainly comprises the following steps of: (1) connecting a test power supply to a detection circuit, wherein the test power supply can generate a string of square wave signals corresponding to the grid frequency of the test power supply after being subjected to voltage reducing treatment by the detection circuit; (2) obtaining a time difference value Delta t1 of the square wave signals from rising edge interruption to first falling edge interruption by a micro-controller; (3) comparing a sine wave half-cycle time value T0 corresponding to the frequency of 200HZ with the value of Delta t1 to determine whether to store or not; (4) as described in the step (2), obtaining a time difference value Delta t2 of the square wave signals from rising edge interruption to first falling edge interruption by the micro-controller; (5) comparing the sine wave half-cycle time value T0 corresponding to the frequency of 200HZ with the value of Delta t2 to determine whether to store or not; and (6) calculating a cycle actual time value T and grid frequency according to the values of Delta t1 and Delta t2. With the adoption of the detection method, both the standard sine wave input grid frequency and the voltage stabilization precision difference grid frequency can be detected.

The invention discloses a control method for an electric automobile participating in grid frequency modulation based on V2G technology. A charge / discharge circuit is a two-stage converter circuit, which comprises a PWM rectification circuit and a matched LC filter and a Buck-Boost conversion circuit, wherein the two circuits are connected through a DC bus capacitor; the PWM rectification circuit rectifies a network voltage into a 700V DC voltage, AC-side harmonic waves are filtered through the LC filter, and the PWM rectification circuit is connected with a power grid through a network-side inductor; and the Buck-Boost conversion circuit converts the 700V DC voltage into a 60V DC voltage, and is connected with an electric automobile directly. The method adopts an AC / DC control module and a DC / DC control module, and meanwhile, enables a frequency modulation control module to be embedded into the DC / DC control module; and charge and discharge power reference values of a power battery are given through the frequency modulation control module, and a current transformer makes a response to realize primary and secondary frequency modulation of the power grid.

The invention discloses an energy storage control system used for wind electric power regulation and control. A wind electric field is connected with a high-voltage bus through a first boosting transformer, and an energy storage system is connected with the high-voltage bus through a second boosting transformer. The high-voltage bus is connected with an alternating-current power grid. The energy storage system comprises an energy storage medium, a power converter and the energy storage control system. The energy storage medium is connected with the second boosting transformer through the power converter. The energy storage control system collects wind electric field real-time power, the charged state of the energy storage medium and power grid frequency information and outputs control signals to the power converter. The grid-connected wind electric power characteristics are improved by the energy storage technology, the fluctuation of the wind electric power is inhibited, the frequency change of the power grid is simultaneously responded, and inertia response characteristics of a common set are simulated; in addition, energy storage control system can be flexibly switched to a frequency control mode and participate in primary frequency modulation of the power grid, so that the negative influences of wind power grid connection on the grid frequency are effectively reduced.