361 results about "Harmonic pollution" patented technology

The invention relates to an intelligent control device of a high power energy saving electromagnetic stove, and the method thereof, The intelligent control device comprises a controllable rectifying and filtering module, a contravariant module and a microcomputer controlling module, which is characterized in that a three-phase alternating current power supply is rectified into an adjustable direct current power supply through the controllable rectifying and filtering module ; the direct current power supply is inverted into a high frequency alternating current power supply through the contravariant module, and then the electric energy is converted into electromagnetic energy to be radiated to the bottom of a cookware, and vortex flow is generated, and the cookware can be heated because of the thermal effect of the vortex flow; the microcomputer controlling module is the core of the entire system, which is used for collecting data and transmitting control information to each module; the device adopts a series of advanced control policies, such as the trigger control of the rectifier bridge of an PI regulator, the intelligent self-adaptive constant power control, the intelligent soft-start control, the intelligent cookware detection control, etc., and thereby the working stability and the security of the electromagnetic stove are enhanced. The harmonic pollution of the equipment to the electric network can be reduced to the utmost extent when the electric energy of the electromagnetic stove is saved, and the electromagnetic stove is suitable for various kitchens and dining rooms.

The invention discloses a testing device and a testing method of flexible direct-current transmission modular multilevel converter (MMC) converter valve operating. Large current needing to be checked is produced through energy exchange between two groups of valve module submodule capacitors and a load electric reactor, accurate alternating current-direct current overlaying current stress can be obtained through respective adjustment of alternating component amplitude and phase difference of output voltage of two valve modules, and adjusting modes are simple and flexible. A charging source is only used for building working voltage of two sample valve submodules at the beginning of the test, energy supplementation power sources are used for building working voltage of two auxiliary valves at the beginning of the test, only less active loss is supplemented in the test process later, the two energy supplementation power sources respectively share one half of system loss, and requirements for power capacity of a test circuit are greatly lowered. In addition, the two energy supplementation power sources can offset harmonic waves of grid-connected current of the two energy supplementation power sources through difference of connection modes of transformers of the two energy supplementation power sources to a great degree, and harmonic wave pollution to power grids is reduced.

The invention discloses a storage battery reduction charge-discharge converter circuit, belonging to the technical field of storage battery reduction. The structure is characterized in that an alternating-current power supply, a three-phase-voltage-type PWM (pulse width modulation) converter, a direct-current bus, a dual-direction DC / DC (direct-current / direct-current) converter module and a storage battery module are connected in series. The storage battery reduction charge-discharge converter circuit provided by the invention has the beneficial effects that the three-phase-voltage-type PWM converter has high power coefficient and low harmonic pollution, dual-direction DC / DC converter module improves the conversion efficiency, dynamic property and power density of a storage battery reduction charge-discharge device, and the volume and weight of a reduction charge-discharge device are reduced; and at the same time, the utilization efficiency of energy is improved, thus the safety, reliability and economy of the system are improved effectively.

The invention relates to a single-phase universal electric energy quality controller for power supply for electrified railways, and belongs to the technical field of flexible AC power transmission and distribution; the invention comprises a single-phase multi-coil transformer composed of a primary coil and n secondary coils, so that the secondary coils of the transformer can be connected in parallel with n voltage sources of current transformers; n capacitors are connected with n voltage source current transformers, so as to form a single-phase chain-type H-bridge current transformer with n chains; the AC terminal of the H-bridge current transformer is directly connected with the traction grid through a reactor. The invention has the functions of active power control, reactive power compensation and harmonic compensation, so as to resolve three-phase voltage unbalance, voltage fluctuation, low power factor and harmonic pollution and so on that exist in ER traction transformer stations, effectively lower the capacity of traction transformers, increase ER transport capacity and transportation capability. Moreover, the invention is characterized in small occupied area, little loss and low cost, in order to gain perfect harmonic suppression characteristics and dynamic response features, and provide convenience in industrial production and improve device reliability.

The invention relates to the field of electric energy quality monitoring, aiming to solve the problem that user-side harmonic pollution can not be correctly obtained in the prior art. The invention provides a method and a system for monitoring the user-side harmonic pollution. The method comprises the following steps of: collecting current data of a user-side electrifying apparatus by utilizing a current collecting device; collecting public connection point voltage data by utilizing a voltage collecting device; transmitting the current data and the public connection point voltage data to a system terminal; calculating the current data of emission harmonic of the user-side electrifying apparatus and an impedance value of the harmonic of the electrifying apparatus at the system terminal by utilizing a partial least-squares regression algorithm to acquire active power of the emission harmonic of the user-side electrifying apparatus; and sending alarming information when the active power of the emission harmonic exceeds the preset threshold. The invention has the advantages of conveniently monitoring the pollution to power grid by the user-side electrifying apparatus to reduce fluctuation of the power supply quality of the power grid.

A high-voltage big-power frequency converter without harmonic wave pollution has an energy feedback device, a precharged circuit of bypass circuit and an easily changeable air filtering net added on the existing big-power and high-voltage frequency converter of power module unit in series connection. The said energy feedback device mainly consists of the feedback bridge control circuit and the feedback bridge connected in antiparallel at the side of rectifying bridge for each power module unit, the said bypass circuit includes the precharged circuit, silicon control and diode rectifying bridge which are connected in parallel at the said of each power module unit, the said air filtering net is mainly composed of the front panel and the filtering net supporting mechanism with the front panel having air ventilation holes on it.

The invention relates to a unified power energy quality controller based on the serial-connection multiplicity of transformers and a chain structure, which belongs to the technical filed of flexible AC transmission and distribution of an electric power system and the power electronic. The unified power quality controller comprises a single-phase serial-connection multiple transformer bank and a single-phase chain H bridge converter, wherein the transformer bank consists of m single-phase transformers which form the serial-connection multiple transformer bank together with n voltage source converters connected with n secondary windings of m single-phase transformers respectively; the single-phase chain H bridge converter is provided with n chains and is formed by connecting n DC voltage supporting units and n power source converters, and an AC port of the n-chain single-phase chain H bridge converter is directly connected with the electric fence through a reactor, m and n are signless integrals equal to or more than 2, and m is less than or equal to n. The invention can realize accurate current control, has high dynamic responding speed, and can solve the problems of the traction substation of an electrified railway that the three-phase voltage is unstable and fluctuates, the power factor is low and the harmonic pollution exists, and the like.

The invention relates to an energy-efficient bidirectional power flow transducer provided with a topological structure for dual PWM frequency conversion main circuit, combining three-phase PWM rectifying with three-phase PWM inverting to achieve a four-quadrant controlled transducer and realize bidirectional energy transmission between the power network and the motor. The power network can directly get electric energy feedback and braking torque can be adjusted automatically when power generation is delivered so that environmental protection and power saving can be realized. The great improvement of power factor both can effectively inhibit electromagnetic interference, harmonic pollution and can reduce switching loss. The entire systemis provided with double closed loop vector controlled scheme and adaptive function, is characterized in good static and dynamic performance and low frequency starting.

The invention provides lift energy feedback, reactive compensation and switched-off emergency running method and system. The system comprises an energy feedback module, a reactive compensation module and a lift switched-off emergency running module. The energy feedback module comprising an inverted circuit, a control circuit and a filter circuit and the reactive compensation module can feed back energy generated when a lift brakes to a power grid and generate reactive current for compensating reactive power when the lift is in an electric running state; and a lift switched-off emergency running circuit can ensure that lift control power is taken over by the switching of a switch under abnormal power supply of the power grid, run the lift to the leveling position and open a car door and a hall door so that a passenger safely walks out of the lift. The system has the advantages of simple structure, reliable running, less loss, low cost, high power factor and no harmonic pollution on the power grid and integrates various functions of lift frequency converter plug-in type energy feedback, reactive compensation, emergency leveling, and the like.

The invention relates to a high-frequency high-voltage switching power supply for electric precipitation. Three-phase alternating-current is input and converted into direct current by a three-phase rectifier filter circuit and then the direct current passes through a high-frequency inverter circuit; a series-parallel connection resonant soft switching circuit is connected between two inverter bridge arms in the high-frequency inverter circuit; the output of the series-parallel connection resonant soft switching circuit is boosted by a high-frequency pulse transformer, the boosted output passes through a high voltage silicon rectifier stack to form high-voltage direct current and the high-voltage direct current is input into an electric precipitator; a DSP controller outputs a control signal to the high-frequency inverter circuit; the input side of the electric precipitator is connected with a voltage and current detection circuit; the detection circuit detects voltage and current and inputs a signal into the DSP controller; the high-frequency inverter circuit is adjusted by the DSP controller; and the DSP controller is connected with an upper computer through a CAN interface so asto realize optimal control. The switching power supply is used for electric precipitation equipment and has the advantages of small volume, light weight, light harmonic pollution, high power factor, high conversion efficiency, and capability of generating waveforms meeting various working condition requirements of the electric precipitation equipment so as to realize energy conservation and emission reduction.

The invention discloses a novel electric propulsion system. The system comprises an internal combustion engine, an electric generator, an electric distribution system, a propulsion motor and a propeller, wherein the electric generator is in cable connection with the propulsion motor through the electric distribution system; the propulsion motor is connected with the propeller through a clutch and a speed reducer; both the electric generator and the propulsion motor are synchronous motors; and the propeller is an adjustable pitch propeller. The novel electric propulsion system effectively solves the problems of high investment cost, electric loss, severe harmonic pollution, difficult maintenance and high failure risk due to the adoption of a variable frequency technique by the electric propulsion system in the prior art and also solves the problems of high voltage drop in a system power grid and big torque born by a starting transient mechanical shaft due to the high starting transient current in the electric propulsion system in the prior art. The novel electric propulsion system has little investment, convenient installation and maintenance, a low running cost, high system reliability, low failure risk in a use process and a remarkable economic benefit.

The invention discloses a method for computing harmonic impedance of a system based on maximum likelihood estimation theory. The method is characterized by comprising the following steps: collecting bus voltage instantaneous value of common coupling point and current instantaneous value of user access system, and establishing a relation between harmonic voltage phasor and harmonic current phasor; on the basis of defining a complex covariance, deriving to obtain a probability density function of unary complex normal distribution so as to obtain a maximum likelihood estimation function; establishing the maximum likelihood estimation theory of complex field estimated by the harmonic impedance of system; utilizing an extreme value theory to solve the maximum likelihood estimation function so as to obtain the estimated value of harmonic impedance of the system finally. The method has the beneficial effects that the method for computing harmonic impedance of the system based on maximum likelihood estimation theory is capable of relatively accurately computing equivalent harmonic impedance of the system and has important meanings for further solving the problem of harmonic pollution and improving the management level of electric energy quality.

The invention relates to an electric split-phase non-interruption flexible connection-compensation device and method for a traction electric network, belonging to the technical fields of railway transportation equipment and electric power and electronics. The device comprises a two-phase back-to-back converter set and three position sensors, wherein the two-phase back-to-back converter set comprises two single-phase converter sets Va and Vb sharing a DC side capacitor set, and two single-phase reduction transformer sets Ta and Tb respectively connected with AC sides of the two single-phase converter sets Va and Vb, or a single-phase reduction transformer set Ta or Tb connected with the AC side of the single-phase converter set Va or Vb, and also comprises three electric quantity sensors, a killer switch, a controllable fling-cut switch and a main controller. The device can work in two modes, and realizes that an electric locomotive passes through split phases without interruption and with loads. The device has functions of active power transfer, reaction power compensation and harmonic compensation, and can solve the problems of three-phase voltage imbalance, voltage fluctuation, low power factor, harmonic pollution and the like in a traction substation.

The invention discloses a voltage source type direct-current deicing and static synchronous compensation device and a control method thereof. The voltage source type direct-current deicing and static synchronous compensation device comprises at least one basic current convertor unit. The basic current convertor unit comprises a connection electric reactor Ls, a modular multi-level current convertor MMC adopting a full-bridge sub-module, disconnecting links (K1, K2, K3 and K4), and smoothing electric reactors (Ld1 and Ld2). The voltage source type direct-current deicing and static reactive generation device can meet the requirements for deicing of power transmission lines of various voltage classes. The method for switching the voltage source type direct-current deicing and static synchronous compensation device among different function modes and the control method of the voltage source type direct-current deicing device can meet the requirement for safe and rapid deicing of the lines, no harmonic pollution at an access point is caused, and dynamic reactive power compensation can be provided for the access point. The voltage source type direct-current deicing and static synchronous compensation device can be used for a newly-constructed direct-current deicing project, can also be used for upgrading and reconstruction of the direct-current deicing device in the constructed direct-current deicing project, and has the wide application prospect.

The invention discloses a fluctuation quantity method-based user side harmonic emission level practicality estimation method, belongs to the field of power quality harmonic treatment, is used for dividing rights and liabilities of harmonic pollution on a power supply side and an electricity side and belongs to a theoretical method practicality technology. The invention provides a complete processfor estimating the user side harmonic emission level by employing a fluctuation quantity method, provides a method for quantizing deviation between a power supply side harmonic impedance amplitude estimated value and an actual value, provides power supply side harmonic impedance amplitude estimated value accuracy for engineering, and easily and quantitatively judges whether the estimated value meets the requirement on engineering accuracy. In the method, various problems which possibly exist in actual engineering are considered theoretically. The conception of the time-varying dynamic phasor-based fluctuation quantity method is stated, the conventional harmonic impedance estimated value algorithm is improved, the least squares fitting algorithm which is wider in applicability and higher in accuracy is provided to estimate power supply side harmonic impedance; therefore, a practical flow more accords with actual operating conditions of a power system.

The invention provides an optical network hybrid power supply uniterruptable power supply having a function of correcting a power factor on a network side, relates to the field of transformation of electrical energy, and solves the problems that the conventional used uniterruptable power supply has large harmonic pollution and cannot continuously operate for a long time. The power supply comprises an energy storing capacitor, a first diode, a second diode, a control component, a charge-discharge control unit, a power factor correction circuit and a solar battery module, wherein the output end of the power factor correction circuit is connected with an anode terminal of the first diode; a cathode terminal of the first diode is simultaneously connected with one end of the energy storing capacitor, a cathode terminal of the second diode, the output end of the charge-discharge control unit and the input end of the control component; an anode terminal of the second diode is connected with the output end of the solar battery module; and the other end of the energy storing capacitor is simultaneously connected with the input end of the power factor correction circuit, the input end of the charge-discharge control unit, the input end of the solar battery module and the input end of the control component. The power supply can be widely used in the field of the transformation of the electrical energy.

The invention relates to the technical field of wind power generation, in particular to a wind power generation-combined ordered charge and discharge coordinated control system of a pure electric vehicle. The system is characterized in that: information of each charging station is transmitted to a power grid dispatching center, the power grid dispatching center judges the state of the current power system to generate a corresponding charging control mode, and then, the information is transmitted to a charging station concentrated coordination monitoring system to carry out information interaction; the power gird dispatching center transmits a pitch peak instruction to each dynamic battery, namely a dynamic battery group, through a communication network of the charging station concentrated coordination monitoring system; and the dynamic battery group receives the pitch peak instruction to realize pitch peak and feeds back residual electric quantity to a power grid at the same time. According to the system disclosed by the invention, an advantage complementation relation among wind power generation, charge and discharge of the electric vehicle and power gird stabilization is realized and coordinated; the acceptability of wind and electricity is improved; the harmonic pollution caused by disordered charge of the pure electric vehicles and the adverse influence on the power grid are reduced to the greatest extent, and the utilization efficiency of wind and electricity and the stabilization level of the power grid are improved.

The invention discloses a reactive power control circuit of a single-phase photovoltaic inverter. The reactive power control circuit comprises a bus voltage supporting capacitor, a single-phase full-bridge inversion circuit, a filtering inductor, an EMC (Electro Magnetic Compatibility) filtering circuit, a sampling circuit, a power switch pipe driving circuit and a DSP (Digital Signal Processor), wherein the DSP consists of a PLL (Phase Locked Loop) control module, a voltage outer ring PI control module, a current inner ring PI feedforward control module and a sinusoidal PWM (Pulse-Width Modulation) wave sending control module, and an input signal of the sinusoidal PWM wave sending control module of the DSP further includes a current inner ring current given amount Ig. The invention further provides a reactive power control method of the single-phase photovoltaic inverter. The method not only can be used for judging whether the voltage Uac of a power grid is larger than zero, and comparing the absolute value of a PWM wave sending control input modulation wave Upwm with a given triangular carrier wave Uc, but also can be used for judging whether the given current inner ring current amount Ig is larger than zero. Not only can the conduction loss of a power switching tube be reduced, and the conversion efficiency of the inverter is improved, but also the current waveform can be continuous, an output harmonic wave is reduced, and the pollution on a harmonic wave of a power grid is reduced.

The invention provides a parameter design method for a high-voltage high-capacity VSC (voltage source converter). The VSC is connected with an electric grid through an LCL (lower control limit) filter, the LCL filter comprises an electric grid side electric reactor, a valve side reactor and a filter capacitor, and the filter capacitor is connected in parallel between the valve side reactor and the electric grid side electric reactor. The problems for filtering out harmonic waves filled into the electric grid by the VSC and inhibiting the converter main loop resonance led in by the LCL filter are solved through setting the parameters of the LCL filter and a controller of the VSC. Compared with the simple experience algorithm and the complicated calculating method of the existing LCL filter, the method has the advantages that the parameter of the filter is designed according to the operation characteristics of the VSC and the frequency-domain characteristics of the LCL filter, simplicity is realized, the implementation is easy, the engineering construction can be realized, the theoretical basis is full, the harmonic pollution to the electric grid is low, and the grid-connected electric energy quality requirement of the national standard on the VSC can be met.

The invention discloses a topological structure of a wind-hydrogen-water-electricity hybrid energy system and a control method of the wind-hydrogen-water-electricity hybrid energy system. Firstly, the topological structure of the wind-hydrogen-water-electricity hybrid energy system based on a permanent-magnet synchronous wind generator, a water storage tank, an electrolytic tank, a fuel cell and a load is constructed; the permanent-magnet synchronous wind generator is in grid-connected operation; the system works in a wind-electricity grid-connected generation operation mode or a surplus wind-electricity hydrogen production operation mode; stable control is achieved by a central controller; the permanent-magnet synchronous wind generator is off-grid operation; the system works in an abandoned wind hydrogen production operation mode or a fuel cell power generation operation mode; and stable control is achieved by the central controller. According to the topological structure and the control method, waste of wind energy can be reduced; the abandoned wind utilization capacity is improved; the quality of grid-connected electric energy is improved; harmonic pollution in a power grid is reduced; the comprehensive utilization efficiency of energy sources is improved; and the energy complementary operation ability of wind energy, hydrogen energy, water and electric energy is achieved.

The invention discloses a distribution method based on waveform matching for harmonic voltage responsibility. The distribution method comprises the steps of: step 10) acquiring harmonic test data, and forming a harmonic data sequence; step 20) setting basic matching parameters; step 30) calculating an Euclidean distance, wherein normalization processing is performed on the harmonic data sequence which is formed in the step 10) according to a sequence of subsequences based on the basic matching parameters set in the step 20) to obtain harmonic sample data, and the Euclidean distance between a harmonic voltage and a harmonic current in the harmonic sample data is calculated; step 40) screening the subsequences, wherein similarity of each subsequence is calculated, and the subsequence with the similarity not less than a set value is screened out; step 50) and distributing harmonic responsibility, wherein system-side equivalent harmonic impedances of the screened subsequences is estimated by adopting a least square method, and a mean value of the equivalent harmonic impedances is utilized for calculating the harmonic voltage responsibility. The distribution method can quantify harmonic pollution liability of a feeder by utilizing harmonic amplitude data, and is suitable for engineering practice.

The invention provides a harmonic source identification method which comprises the following steps: performing responsibility allocation on harmonic pollution through the harmonic voltage emission level of a user, wherein the harmonic voltage emission level of the user at a time is represented through the variable quantity of harmonic voltage or current at a time at a point of common coupling before and after the user accesses to a power system; positioning an accurate point of a harmonic source through harmonic emission level evaluation to the maximum extent. The method has the benefits that an algorithm provided by the invention can quickly determine the harmonic source, is high in accuracy and practicality, and has very good project utilization values.

The invention discloses a mixed induction type active electric power filter system. The mixed induction type active electric power filter system comprises a rectifier transformer, a filtering branch, a rectifier and the other filtering branch, wherein the other filtering branch comprises three passive filters and a voltage source inverter, the passive filters are connected to the voltage source inverter, the primary side of the rectifier transformer is connected to a three-phase power grid through connecting impedor, an epitaxy winding of the secondary side of the rectifier transformer is connected with the rectifier, and the passive filters are connected to three junction points between a delta winding and the epitaxy winding of the secondary side of the rectifier transformer in parallel respectively. According to the mixed induction type active electric power filter system, influence of frequency fluctuation of the power grid side and the high-capacity nonlinear load side on electric power filtering performance is eliminated; meanwhile, the problems that serious harmonic pollution, high additional loss of a master device, high vibration and noise, low system power factor and low system operation efficiency are caused by harmonic waves and idle work to an industrial power distribution and consumption system are effectively solved on the premise that electric power quality on the power grid side meets the national standard of China.

In the transformer, line side windings connected in star type continuous form is adopted in inner side. Structure of outer side is three groups divided, N groups phase shifted cake typed line side windings. The invented transformer solves issues of harmonic polluting on power grid and harmonic wastage, possessing advantages: reliable operation, simple maintenance, small harmonic current at power grid side, low noise, low heat generated, high power factor. When being applied to high voltage frequency control, the invention solves issues: heating of motor, torque ripple, influence of dv / dr and common mode voltage on insulation of motor. The invention can reaches ideal effect of harmonic elimination even if out of balanced currents occurred, providing advantages of approximate to sinusoidal waveform output, high conversion efficiency etc.

The invention is an energy feedback power unit used in series power unit-type high voltage inverter and implementing four-quadrant operating ability, and its control circuit comprises: filter circuit composed of three-phase capacitors and three-phase reactors, three-phase synchronous rectifier bridge composed of IGBTs, DC filter circuit composed of capacitors, unit inverter bridge composed of IGBTs, and synchronous rectification control circuit and unit inversion control circuit controlling the operating states of the three-phase synchronous rectifier bridge and unit inverter bridge, respectively. And it has rectifying and energy feedback functions, and simple structure, low losses, easy to implement, low-cost, having high power factor but no harmonic pollution to electric network. And the high voltage transformer composed by it has all functional characteristics of common high voltage transformers and ability to convert kinetic energy or potential energy into electric power to feed back to the electric network on the conditions of fast system braking or weight dropping.

The invention discloses a high-performance four-quadrant frequency converter which achieves the purposes that output direct current voltage is controllable, harmonic content of current at the network side is small, the energy can flow in double directions, intermittent operation law is realized and the energy is saved. The direct current side voltage can be kept at a set value by control no matter the frequency converter is in heavy load or light load, and even energy feeds back. The control method comprises the steps of carrying out unified coordinate control on the combination of a rectifier and an inverter, and carrying out feedforward control by the information at the inverter side to obtain good direct current bus voltage control performance and rapid dynamic response speed by the rectifier. The purpose of intermittent operation is achieved by matching the operation law of the rectifier with the operation law of a motor at the inverter side; and bidirectional flow of energy can be achieved so as to save electric energy. The high-performance four-quadrant frequency converter has the characteristics that the harmonic content of the current at the network side is low, the sine degree is high, harmonic pollution on a power grid does not exist, the rectifier runs by the unit power factor, an automatic booster function is achieved, and the voltage stability of the direct current bus can be controlled.

The invention discloses a design of a reflective wave strip sheet with a single-stage diffraction characteristic and a manufacturing method thereof. The reflective wave strip sheet comprises a transparent substrate; and multiple high-reflectivity circular elements which are formed on the aforementioned transparent substrate. The aforementioned circular elements are randomly distributed in elliptical rings of the reflective wave strip sheet and are not intersected. Radiuses of the circular elements change along with size of width of the elliptical rings. The range of the radiuses of the elements arranged between the (n-1)th and nth (n is an integer greater than 1) rings is [rnmax, rnmin], wherein rnmax=(an-an-1) / 2, rnmin=(bn-bn-1) / 2, an in the formula is the long axis of the nth ring line, and bn is the short axis of the nth ring line. The reflective wave strip sheet only has zero-order and positive and negative one-order diffraction so that high-order diffraction can be effectively inhibited and harmonic pollution can be eliminated. Meanwhile, the reflective wave strip sheet has a binary structure characteristic so that the reflective wave strip sheet is easy to manufacture and realize. The reflective wave strip sheet with the single-stage diffraction characteristic has characteristics of integrating dispersion, focusing and higher harmonic inhibition so that the reflective wave strip sheet can act as an optical element for leading edge science, such as soft X-ray light source focusing, monochromatization and spectral analysis.

The invention discloses an automatic power grid resonance detection method based on active injection current. For the problems of harmonic pollution due to a nonlinear load in a power system and resonance easy occurring when a reactive compensating capacitor is connected in the power system, an active power quality regulating device connected in the power grid in parallel is used for compensating the harmonic, and meanwhile, the active power quality regulating device is used for injecting reactive and harmonic combined current of a specific waveform into the power grid to automatically detect the resonance angular frequency and the damping coefficient of the power grid; for a single-phase system, the rectangular wave current of 180 degrees is injected; for a three-phase system, the rectangular wave current of 120 degrees is injected. According to the automatic power grid resonance detection method based on the active injection current, the resonance detection combined model of the optimal weight algorithm is established according to the harmonic voltage and the harmonic current of the power grid and spectral characteristics of the harmonic power, and then the resonance angular frequency and the damping degree of the power grid can be judged quickly and accurately; as a result, application basis is provided for the damping control of the power grid resonance and the power quality of the power system is further improved.

A harmonic energy metering error analytic device comprises a harmonic data collection part used for inputting the harmonic data collected by power network into an electric energy data analytic part, an electric energy metering error data analytic part comprising a model storage module and an error analysis module and an error analytic result output part used for outputting or storing the error data analytic result acquired from the electric energy metering error data analytic part; wherein the model storage module is used for storing metering error models and model functions corresponding to the models of electric energy meters; the error analysis module is used for deriving the theoretical error data to be analyzed of the input harmonic data and deriving the error of each harmonic measurement and the total error. The harmonic energy metering error analytic device can provide quantitative data basis for power supply department to retrieve electric energy metering error loss and control harmonic pollution.

The invention belongs to the technical field of frequency converters and provides a four-quadrant frequency converter. According to the four-quadrant frequency converter, a frequency converter is arranged between a power grid and an induction motor; an energy feedback unit is arranged at a direct current (DC) busbar side of the frequency converter; a negative pole end DC- of a direct current busbar on the frequency converter is electrically connected with the DC- of the energy feedback unit; the DC+ on the frequency converter is electrically connected with DC+ of the energy feedback unit; three-phase alternating current output of the energy feedback unit is connected to input sides R, S and T of the frequency converter in parallel; a PE (Protecting Earthing) terminal of the energy feedback unit is reliably connected to the ground; when the busbar voltage of the frequency converter is detected by the energy feedback unit to be up to a set valve, feedback electric energy is converted to power frequency and transferred to the power grid to carry out energy saving regulation. The four-quadrant frequency converter provided by the invention has the advantages that through an external energy feedback device, the electric energy produced by the motor is added to the input end to the frequency converter after feedback and an electric reactor is additionally arranged to avoid the harmonic pollution, so that the power factor is greatly improved and the efficient utilization ratio of the electric energy is realized.