51 results about "Series impedance" patented technology

The invention relates to the technical field of new energy grid-connected control, in particular to a fault stage transient stability analysis method and system for a following-constructed network type converter series-parallel system, and the method comprises the steps: enabling a constructed network type converter to be equivalent to a controlled voltage source series impedance, enabling a following network type converter to be equivalent to a controlled current source, and enabling the controlled current source to be equivalent to a controlled voltage source series impedance; the whole series-parallel system is equivalent to a scene in which double voltage sources and a single current source are jointly connected in parallel to a PCC point, and a series-parallel system model is constructed; according to the series-parallel system model, respectively representing an active power coupling term of the network-building type converter and a voltage coupling term of the network-following type converter under the condition of considering parallel connection of the network-following type converter and the network-building type converter; according to the coupling term, remodeling an active loop control structure of the network-constructing converter and a phase-locked loop synchronization structure of the network-following converter, and obtaining a transient analysis model of the series-parallel system considering the coupling term; the transient stability of the hybrid system in the power grid fault stage is analyzed through the transient analysis model, and the influence on the transient stability is effectively represented.

A converter station AC filter group circuit breaker abnormal arcing modeling analysis method comprises the following steps: firstly, carrying out time mark alignment, amplitude calibration and filtering de-noising on wave recording signals such as AC bus voltage and filter branch current to obtain high-quality input data; then, combining a primary wiring diagram, enabling an alternating current system to be equivalent to an ideal power supply and series impedance, enabling circuit breaker arcing to be equivalent to arc resistance changing along with time, and constructing an equivalent circuit model comprising the power supply, the impedance, a capacitor, an electric reactor and dynamic arc resistance; establishing a state space equation according to a voltage and current constraint relation, and performing time domain solution by adopting a two-step two-order or three-order diagonal implicit Runge-Kutta method to obtain voltage and current responses of the whole process of the fault; on this basis, the arc resistance change is inversed according to the ratio of arc voltage to current, the current zero passage is identified through the resistance symbol change at adjacent moments, and the zero passage section is smoothed; and finally, the inversion result is verified again by means of the simplified equivalent model.

A filter circuit, a filter and a communication device relate to the technical field of communication. The filter circuit includes a series branch connected between the first port and the second port and including a series resonance circuit and a series impedance element connected in series with each other, wherein the series resonance circuit includes a series resonator; and a parallel branch connected between a parallel node and a ground potential and including a parallel resonance circuit and a parallel impedance element connected in series with each other, wherein the parallel resonance circuit includes a parallel resonator, and the parallel node is located on a connection path of the first port and the second port; wherein the resonance frequency of the series resonator is less than the resonance frequency of the parallel resonator.

The invention discloses a cable parameter calculation method considering material frequency change and temperature change characteristics. The cable parameter calculation method comprises the following steps: 1, measuring the temperature change and frequency change characteristics of a cable material in a laboratory; 2, establishing a corresponding relation between impedance and admittance of a cable material and temperature and frequency; 3, setting a neural network model, and training a neural network by using the actually measured data in the step 1 to obtain a corresponding relationship between the impedance and the admittance in the step 2 and the temperature and the frequency; 4, modeling a cable system, and writing a voltage and current equation along the cable; 5, obtaining the impedance and admittance of each cable material at the current temperature and frequency by using the neural network trained in the step 3, and substituting the impedance and admittance into a voltage and current equation to solve the equation; and 6, for a new cable structure, solving an impedance matrix and an admittance matrix of the corresponding cable according to the step 4. According to the method, the influence of the frequency and the temperature on the series impedance and the parallel admittance matrix of the cable is comprehensively considered, so that the calculation result is more practical, and the method has great engineering value.

The invention belongs to the technical field of key power supply conversion in an aviation airborne starting power converter, and discloses a novel matrix LLC secondary side resonant topology. On the basis of an LLC resonant topology circuit, a resonant cavity is placed on the secondary side of a transformer, a matrix transformer with the primary side connected in parallel and the secondary side connected in series is adopted, and the matrix transformer comprises n parallel H-bridge inversion units on the low-voltage side, a high-frequency matrix transformer, the LLC resonant cavity on the high-voltage side and a full-bridge uncontrollable rectification circuit. The matrix transformer is composed of n transformer units, primary sides of which are connected in parallel and secondary sides of which are connected in series. A primary winding of each transformer unit is connected with the H-bridge DC-AC inverter circuit. According to the matrix LLC secondary side resonant topology, by controlling the switching frequency of the H-bridge power MOS tube, square wave signals with different frequencies are obtained, the series impedance of the resonant capacitor and the resonant inductor is changed, the partial voltage at the two ends of the excitation inductor is adjusted, gain control over the resonant cavity is achieved, and the purpose of adjusting the output load voltage is achieved.

A computer-implemented method and system includes a head-mounted wearable device having two current electrodes that delivers an input alternating current over a range of frequencies to a subject during at least one intervention. The head-mounted wearable device includes at least two sense electrodes that collect voltage difference measurements in response to the input alternating current. A measurement validation module applies a Hilbert transform or a Cramer-Kronig test to the voltage difference measurements to generate a validated time-series impedance spectrum. A head fluid dynamics module fits the validated time-series impedance spectrum to an electrical circuit model to determine a glymphatic flow response to the at least one intervention.

The invention discloses a harmonic interaction characteristic analysis method and device based on chaotic characteristics, equipment, a storage medium and a program product. The method comprises the following steps: obtaining harmonic impedance corresponding to a plurality of harmonic sources respectively; determining series impedance and parallel admittance of the power transmission line between the first harmonic source and the second harmonic source based on a pre-constructed equivalent circuit model of the power transmission line between the multiple harmonic sources, and determining equivalent connection impedance between the first harmonic source and the second harmonic source based on the series impedance and the parallel admittance; inputting the first harmonic impedance corresponding to the first harmonic source, the second harmonic impedance corresponding to the second harmonic source, the equivalent connection impedance and the Lyapunov exponent into a preset chaotic interaction factor calculation model to obtain a chaotic interaction factor between the first harmonic source and the second harmonic source; and determining an interaction characteristic analysis result between the first harmonic source and the second harmonic source based on the chaos interaction factor. Therefore, the stability of the multi-harmonic source system is improved.

This invention discloses a method for calculating the steady-state voltage and circulating current of the sheath based on a distributed model of a multi-loop terrestrial cable. The method includes: 1. Obtaining the factors affecting the steady-state induced voltage and circulating current of the sheath of a multi-loop single-core terrestrial cable; 2. Establishing a distributed parameter model per unit length of the multi-loop single-core terrestrial cable, thereby obtaining the linear equation matrix describing the entire multi-loop terrestrial cable system; 3. Calculating the series impedance of the multi-loop single-core terrestrial cable lines in the system's linear equation matrix; 4. Calculating the parallel admittance between the multi-loop single-core terrestrial cable lines in the system's linear equation matrix; 5. Constructing the impedance matrix and admittance matrix to complete the system's linear equation matrix; 6. Determining the boundary conditions of the system's linear equation matrix; 7. Solving the system's linear equation matrix to obtain the values ​​of the steady-state induced voltage and circulating current; 8. Calculating the steady-state induced voltage and circulating current of the sheath of a multi-loop single-core terrestrial cable with the same arrangement. This invention eliminates repetitive modeling and simulation calculations, improves the model's adaptability, and has significant engineering value.

The present invention discloses a calculation method for sheath induced voltage and circulating current of a multi-circuit cable system. First, this method calculates the calculation models of the series impedance matrix and the shunt admittance matrix per unit length of the cable line; subsequently, according to the telegraph equation in the frequency domain, series approximation is performed on the multi-circuit micro-segment cable lines under different grounding methods to construct the node admittance matrix of the micro-segment cable lines; then, a variety of cascade formulas are derived to obtain the complete node admittance matrix of the multi-circuit full-line cable system; according to the boundary conditions and the complete node admittance matrix of the multi-circuit cable system, the cable line micro-segments are subdivided, and the calculation models of the induced voltage and circulating current of the metal sheath of the multi-circuit cable under different grounding methods are constructed segment by segment. The present invention can accurately describe the distribution of sheath induced voltage and circulating current in the multi-circuit cable system, laying a solid foundation for the subsequent research on cable loss reduction measures.

There is provided a low-noise amplifier circuit (200a:200g) for a full-duplex radio transceiver, the low-noise amplifier circuit (200a:200g) comprising: an input port (Vin) for receiving a signal from an antenna; a first signal path operatively connected to the input port (Vin) and comprising a series impedance (Z1) and a first transistor (M1) operatively connected in series with each other for providing a positive polarity of the received signal at a first differential output (+Vout) of the low-noise amplifier circuit (200a:200g); a second signal path operatively connected to the input port (Vin) and comprising a second transistor (M2) for providing a negative polarity of the received signal at a second differential output (-Vout) of the low-noise amplifier circuit (200a:200g); a cancellation circuit (iC1, iC2) operatively connected to the first signal path for injecting a cancellation current in the first signal path; and a Self- Interference-Signal control circuit configured to receive channel and cross- interference information and to control the cancellation circuit (ic1, ic2) based on the received channel and cross-interference information.

The invention relates to an analysis method and device for current-carrying unbalance degree limitation information and computer equipment. The method comprises the following steps: acquiring actual impedance parameters of equidirectional parallel cables, constructing and adjusting a cable unbalance degree optimization model based on the actual impedance parameters through a dynamic programming algorithm, obtaining a cable unbalance degree model, and identifying a target cable series connection impedance value; and calculating a current-carrying unbalance degree based on the target cable series connection impedance value, adjusting the target cable series connection impedance value through a preset adjustment strategy, and returning to execute the above steps to obtain the current-carrying unbalance degree corresponding to each target cable series connection impedance value, thereby identifying limit information and a real impedance parameter of the current-carrying unbalance degree. And returning to iteratively execute the above steps to obtain the current-carrying unbalance degree limitation information of the same-direction parallel cables. By adopting the method, the limit analysis accuracy of the current-carrying imbalance of the laid cable can be improved.

The present invention discloses a resonant shunt impedance measurement device and its control system. The resonant shunt impedance measurement device comprises an LC series resonant branch, a capacitor-coupled series impedance measurement device (SIMD), and a bypass switch. The LC series resonant branch, the SIMD, and the bypass switch are connected in parallel. The LC series resonant branch flows through the steady-state current of most of the system to be measured without affecting the injection of the disturbance voltage. The control of the resonant shunt impedance measurement device consists of three parts: signal processing, reference generation, and PR-based dual closed-loop control. This control can achieve the control objectives of controllable disturbance voltage output amplitude and minimizing the fundamental current flowing through the SIMD. The present invention can achieve the goal of almost no fundamental current flowing through the SIMD across the entire frequency band, increase the switching frequency of the impedance measurement device, and reduce the size, cost, and loss of the impedance measurement device.

A filter circuit, a filter, and a communication device, relating to the technical field of communications. The filter circuit comprises: a series branch, connected between a first port and a second port and comprising a series resonant circuit and a series impedance element which are connected in series, the series resonant circuit comprising a series resonator; and a parallel branch, connected between a parallel node and a ground potential and comprising a parallel resonant circuit and a parallel impedance element which are connected in series, the parallel resonant circuit comprising a parallel resonator, and the parallel node being located on a connecting path of the first port and the second port, wherein the resonant frequency of the series resonator is less than the resonant frequency of the parallel resonator.

The present invention discloses a method for selecting a grounding line and confirming a grounding point range in a low-voltage circuit, which relates to the field of power grid protection technology and includes the following steps: obtaining impedance parameters of the circuit power supply, equipment, and cable; connecting impedances in series in the circuit according to the measured parameters to make the three-phase impedances equal; installing a high-frequency current generating module and a grounding capacitor at the end of the circuit; creating a grounding impedance matching table for each device and important node according to the measured impedance parameters; the high-frequency current generating module alternately generates AC and DC currents and measures the neutral point and capacitor currents; and determining the grounding phase and grounding range by calculating the impedance based on the measured values. The present invention installs a high-frequency current generating module and a grounding capacitor at the end of the circuit. The high-frequency current generating module is activated when a fault occurs. During phase selection, each module generates high-frequency current in a sequential cycle, enters the fault phase selection and fault location logic, and can achieve accurate fault location, quickly select the grounded phase, locate the grounding point range, and improve the operational reliability of the low-voltage system.

The invention relates to a dynamic characteristic difference analysis method and system for a parallel grid-forming converter, and belongs to the technical field of converter evaluation. The method comprises the following steps: establishing a mathematical model of a double-mechanism grid-type converter grid-connected system under a dq coordinate system taking a power grid as a reference system, solving the mathematical model to obtain a voltage steady-state value and a power angle steady-state value of the converter during steady-state operation of the system; the method comprises the following steps: for an actual model of a double-mechanism grid-type converter grid-connected system, enabling a converter and a power grid to be equivalent to a voltage source model with series impedance to obtain an equivalent circuit model, and transforming and analyzing the equivalent circuit model to obtain a relational expression of output active power of each converter about a power angle, impedance and voltage; and solving the instantaneous power synchronization coefficient difference, and evaluating the influence effect of different parameters on the dynamic characteristic difference of the converter by adopting the instantaneous power synchronization coefficient difference. According to the method, the dynamic characteristic difference detection efficiency of the system is improved.

The invention discloses a method for measuring parameters of a same-tower parallel double-circuit direct-current transmission line in a high induced voltage environment, and the method comprises the steps: enabling the head ends of four polar leads to adopt a plurality of parallel combination modes, measuring series impedance when the tail ends of the four polar lines are grounded through impedance and short-circuit impedance when the tail ends are directly grounded under different parallel combination conditions under a certain non-power frequency; according to the line length, the series impedance when the tail ends of the four pole wires are grounded through impedance and the short-circuit impedance when the tail ends are directly grounded under different parallel combination conditions, characteristic impedance and propagation coefficients under different parallel combination conditions are calculated respectively, and then equivalent distribution impedance and equivalent distribution admittance are calculated; and according to the equivalent distribution impedance and the equivalent distribution admittance under different parallel combination conditions, obtaining each distribution parameter under the unit length of the line polar wire. According to the scheme, in an environment with high induced voltage, the induced voltage can be effectively suppressed, and line parameters can be accurately measured.

The invention discloses a same-tower parallel four-circuit alternating-current power transmission line parameter measurement method for inhibiting induced voltage. The method comprises the following steps: dividing a same-tower four-circuit power transmission line into five groups of wiring modes; measuring the short-circuit impedance in each wiring mode and the series impedance in a mode that the tail end of the line is grounded through impedance; calculating the characteristic impedance and the propagation coefficient in the corresponding wiring mode by using the impedance grounding series impedance measurement result and the line short-circuit impedance measurement result of the line in each wiring mode, and further calculating the distribution impedance and the distribution admittance in the corresponding mode; and finally, calculating the resistance, inductance and ground capacitance of each phase lead of the same-tower four-circuit line, the inter-phase coupling capacitance and inter-phase coupling inductance of the single-circuit line, and the coupling capacitance and coupling inductance between each phase lead of the four-circuit line through the distributed impedance and distributed admittance in each wiring mode and simultaneous equations. According to the method, the no-load power frequency induced voltage of the line can be effectively suppressed, and the line parameters can be accurately measured.

The present invention measures the impedance of impedance elements in a state in which a measurement target, which is formed by connecting a plurality of impedance elements in series, and a non-measurement target are connected in parallel.　The present invention comprises: a measurement current supply unit 2-1 which supplies a measurement AC current Im1 between both ends of electrochemical cells C2, C3; a measurement current supply unit 2-2 which supplies a measurement AC current Im2 between both ends of electrochemical cells C7-C10; a voltage detection unit 3-1 which detects a complex terminal voltage value V1 across the electrochemical cells C2, C3; and a processing unit 4 which calculates the impedance of the electrochemical cells C2, C3 on the basis of the complex terminal voltage value V1 detected by the voltage detection unit 3-1 and a complex current value IZ1 of an AC current Iac detected by a current sensor 7-1 in a state in which the measurement AC current Im2 and the measurement AC current Im1 flowing through a power supply device PD cancel each other.

A filter circuit, a filter and a communication device relate to the technical field of communication. The filter circuit includes a series branch connected between the first port and the second port and including a series resonance circuit and a series impedance element connected in series with each other, wherein the series resonance circuit includes a series resonator; and a parallel branch connected between a parallel node and a ground potential and including a parallel resonance circuit and a parallel impedance element connected in series with each other, wherein the parallel resonance circuit includes a parallel resonator, and the parallel node is located on a connection path of the first port and the second port; wherein the resonance frequency of the series resonator is less than the resonance frequency of the parallel resonator.

The invention discloses a cable electrical parameter calculation method, system and device considering the influence of a backflow cable and a storage medium. The cable electrical parameter calculation method adopted by the invention comprises the following steps: obtaining structure parameters and material parameters of a cable and a backflow cable; calculating a series impedance matrix including the cable and the backflow cable according to the structure parameters and the material parameters of the cable and the backflow cable; obtaining a voltage drop equation according to the series impedance matrix; and in combination with the installation condition of double-end grounding of the on-site backflow cable, a voltage drop equation is simplified, and cable electrical parameters including positive-sequence resistance, positive-sequence reactance, zero-sequence resistance and zero-sequence reactance are obtained. According to the method, the current coupling influence of the backflow cable and each phase cable is considered, accurate calculation of the electrical parameters of the cable with the backflow cable is realized, and the universality is high.

This invention relates to the field of power systems and their automation technology. It provides a method for constructing a traction network simulation model based on current distribution characteristics. The method includes: establishing multi-conductor transmission line equations based on Maxwell's equations, including Gauss's law and Faraday's law; deriving a chain-like network model of the traction network based on the multi-conductor transmission line equations and a chain circuit model with multi-conductor transmission lines as the backbone and randomly connected transverse elements; simplifying the chain-like network model to obtain a simplified series impedance matrix equation and a parallel admittance parameter matrix after conductor merging; and calculating the series impedance and parallel admittance values ​​using the simplified series impedance matrix equation and the parallel admittance parameter matrix after conductor merging. This invention improves the accuracy and applicability of traction network electrical simulation and signal analysis.

The invention belongs to the technical field of new energy bundled direct current transmission, and particularly discloses a wind and light direct current transmission station impedance adjusting method, system, equipment and medium, which can configure virtual parallel impedance or virtual series impedance according to wind power and photovoltaic field station impedance and transmission end station input impedance in a wind and light direct current transmission station. The broadband oscillation stability of the wind-solar direct current sending station is optimized, and the influence on the dynamic response performance of the wind-solar direct current sending station is reduced; the virtual impedance configuration-based impedance adjusting device for the wind-light direct-current sending-out station has the advantages of high operability, high engineering applicability, clear physical concept, high visualization degree and the like, so that the virtual impedance configuration-based impedance adjusting device has extremely high practicability in engineering practice and can be applied to improvement of broadband oscillation stability of the wind-light direct-current sending-out station.

The spiral inductor of the present invention includes a substrate and a spiral wiring disposed on the substrate. A part of the spiral wiring includes a divided wiring portion, and the divided wiring portion is divided into a plurality of mutually parallel wirings when viewed from a top-down perspective. The divided wiring portion is disposed inside the spiral wiring. In the circuit of the divided wiring portion, the wirings inside and outside the divided wiring portion are alternately arranged with a second insulating layer in between, such that the wiring inside the divided wiring portion becomes the wiring on the outside after being staggered, and the wiring on the outside of the divided wiring portion becomes the wiring on the inside after being staggered. The spiral inductor can suppress the skin effect and the proximity effect, and can improve the area utilization efficiency and reduce the series impedance. In addition, the divided wiring portion is alternately arranged through the insulating layer, which can improve the Q value.

The utility model discloses a circuit structure in an electric connector, the electric connector and a phased-array antenna, which are applied to the field of electric connectors, and comprise a first circuit end connected with a first external end in a conducting manner and a second circuit end connected with a second external end in a conducting manner, a multi-section impedance matcher is arranged between the first circuit end and the second circuit end; the impedance matcher comprises at least one series impedance matcher connected in series in the circuit structure, and at least one impedance matching branch; one end of the impedance matching branch is connected between the first circuit end and the second circuit end; the impedance matching branch comprises a short-circuit impedance matching branch and / or an open-circuit impedance matching branch. According to the utility model, the multi-section impedance matchers are arranged in the circuit structure of the electric connector, the impedance matching branch sections are additionally arranged in the circuit structure of the electric connector, and reflected waves generated by the impedance matching branch sections are subtracted from reflected waves on a main circuit, so that the bandwidth range of matched radio-frequency signals can be widened, and the signal transmission bandwidth of the electric connector is improved.

Circuit arrangement (10) for operating at least a first and a second LED string, comprising: - a rectifier (14) having a first (14a) and a second rectifier terminal (14b) for coupling to an AC voltage source (12) or a DC voltage source (11), and a third (14c) and a fourth rectifier terminal (14d) for providing a rectifier output voltage (Urect); - a voltage equalisation longitudinal impedance (24); - at least one first (100) and one second load subgroup (200), each having a first (102, 202) and a second terminal (104, 204), wherein a bridging element (120, 220) is connected between the first and the second terminal, and each having a coupling element (110, 210) designed as a four-pole with a first (106, 206) and a second primary terminal (108, 208), as well as with a first (112, 212) and a second secondary terminal (114, 214), wherein the first primary terminal (106, 206) is electrically connected to the first terminal (102, 202) and the second primary terminal (108, 208) is electrically connected to the second terminal (104, 204), wherein the first LED string (D100 to D155), which has a first number of LEDs connected in series, between the secondary terminals (112,114) of the coupling element (110) of the first load subgroup (100) and the second LED string (D200 to D227), which has a second number of LEDs connected in series,is connected between the secondary terminals (212,214) of the coupling element (210) of the second load subgroup (200); , - a control device (20) which is designed to control the bridging elements (120, 220) as a function of a voltage difference between the respectively associated first terminal (102, 202) and an auxiliary DC voltage source (22) related to the third rectifier terminal (14c), and as a function of a respective LED string voltage which is applied between the first (102, 202) and the second terminal (104, 204) when the respectively associated bridging element (120, 220) blocks a short-circuit current flow between the two terminals (102, 104, 202, 204); - wherein the second terminal of a higher load subgroup, which is not a lowest load subgroup, is electrically connected to the first terminal of a next lower load subgroup, wherein the first terminal of a highest load subgroup is electrically coupled to the fourth rectifier terminal (14d) and the voltage compensation longitudinal impedance (24) is connected between the second terminal of a lowest load subgroup and the third rectifier terminal (14c); - a voltage divider device (26) connected between the third (14c) and the fourth (14d) rectifier terminal for providing a control signal (28) to the voltage compensation series impedance (24), wherein the voltage divider device (26) is designed to control a current with a current value (Ireg) as a function of an instantaneous value of the rectifier output voltage (Urect) through the series-coupled load subgroups (100, 200) by means of the control signal (28);characterized in that the control device (20) is designed, when the circuit arrangement (10) is operated on a DC voltage source (11), to permanently control at least a first bridging element of the bridging elements of the load subgroups into a short-circuit state and to permanently control at least a second bridging element of the bridging elements of the load subgroups into a state in which the second bridging element blocks a short-circuit current flow between the first and the second terminal of the associated load subgroup.;

A remodeling control method and device for improving the voltage support capability of a grid-type SVG converter, the method comprising: obtaining the internal potential phase and internal potential amplitude of the SVG converter based on a virtual excitation control SVG converter model, based on the internal potential phase and internal potential amplitude, converting the SVG converter into a voltage source series impedance form as a simplified SVG converter model, obtaining adjustable parameters based on the simplified SVG converter model, and adjusting the adjustable parameters to improve the voltage support capability of the SVG converter. The method and device provided by the embodiments of the present invention can increase the rate at which the SVG converter outputs reactive power during transient periods, can improve the voltage support capability of the SVG converter, and improve the voltage strength of the power system.

The invention belongs to the technical field of power system simulation, and discloses an interpolation-free hybrid line simulation model of accurate zero sequence impedance and a construction method thereof, the model comprises a decoupling module, a parallel compensation module and a series synthesis module; the decoupling module is used for enabling the electromagnetic propagation delay time to be equal to the simulation step length of a simulation program and realizing interpolation-free calculation decoupling at the two ends of the line; the parallel compensation module is used for compensating introduced additional parallel susceptance and inter-phase capacitance in an original physical model of the introduced line; and the series synthesis module is used for synthesizing the residual series impedance of the line, so that the total series positive-sequence impedance and zero-sequence impedance of the equivalent model are matched with a preset target value under the fundamental frequency. According to the method, calculation decoupling without interpolation can be provided for a short line, and full-sequence network parameters including zero-sequence components can be accurately simulated, so that the requirement of modern power distribution network high-fidelity parallel simulation can be well met.

The application belongs to the field of power systems and relates to a series virtual impedance method for improving grid-connected current quality of a static synchronous reactive compensator under a weak power grid. In view of the problems that the existing methods cannot simultaneously achieve stability and harmonic suppression and the THD of grid-connected current increases and the quality of grid-connected current decreases due to harmonics in a weak power grid, the application constructs a grid-connected system with a three-level diode clamped STATCOM as a core, designs a harmonic suppression module containing a multi-resonant controller and a series virtual inductor, superimposes the harmonic suppression module and an original virtual series impedance to form a composite series virtual impedance, injects the composite series virtual impedance into a shunt impedance correction feedforward path, and realizes closed-loop control of grid-connected current. The method can effectively suppress characteristic harmonics, reduce THD, ensure stable operation of the system under a weak power grid, and has good dynamic performance and is easy to implement.

The invention discloses an SVG virtual impedance adaptive switching control method and system. The method mainly comprises a virtual series impedance control link, a virtual parallel impedance control link and an SVG double-closed-loop control link. The oscillation frequency of a new energy station is monitored through VMD and HT conversion, an optimal virtual impedance control loop is put into use, and the output of a virtual impedance control link is used as a compensation amount to be compensated to an original double-closed-loop control structure of the SVG, so that the SVG obtains a more excellent oscillation suppression effect in a broadband range. And the limitation that a single virtual impedance control method is difficult to adapt to the multi-band oscillation suppression requirement is overcome. The method can be widely applied to wind power, photovoltaic and other new energy grid-connected systems containing the SVG, and an effective solution is provided for broadband oscillation suppression and safe and stable operation of the new energy grid-connected systems.

The invention relates to a plasma radio frequency power source and a radio frequency system. The plasma radio frequency power source comprises a radio frequency power amplifier module; the impedance compression unit comprises at least one impedance compression network, and the impedance compression network is provided with a series branch circuit or a parallel branch circuit, or both of the series branch circuit and the parallel branch circuit. The radio frequency power amplifier module, the matcher and the impedance compression unit are sequentially connected in series, the output end of the impedance compression unit is used as a load cavity connecting port, and the impedance compression unit is used for compressing impedance of a load cavity to be within a matchable impedance range of the matcher. According to the invention, the impedance compression unit is arranged between the matcher and the cavity, so that different and large-range changing load impedances of a plurality of cavities can be compressed to a narrow range, the design requirement on the matcher is reduced, and the requirements on larger-range impedance matching capability and higher matching speed of a radio frequency system in different processes can be met; and the product cost is reduced and the product structure is miniaturized.