332 results about "Dc capacitor" patented technology

The invention relates to a networking type three-level converter control system and a dynamic configuration method thereof, the networking type three-level converter control system comprises a redundant main control unit, a function unit, a six-phase power unit and a chopping unit, the redundant main control unit is connected with the function unit through an optical fiber, the function unit is respectively connected with the six-phase power unit and the chopping unit through optical fibers, and the chopping unit is connected with the six-phase power unit. The chopping unit is connected with the two ends of the direct current capacitor side of the inversion unit of the six-phase power unit; the main control unit and the pulse distribution unit are compact in sampling and modularized in design, small in occupied space, comprehensive in function, high in expandability and excellent in control performance, a dynamic configuration method is adopted, the redundant main control unit can be replaced on line, no power-on sequence requirement exists between the main control unit and each functional unit, and the power-on reliability is high. According to the invention, parameters of the pulse distribution unit can be forcibly updated on line, each functional module is independent, a more complex control system can be combined, and the system is convenient to use and maintain and is suitable for application occasions of complex control systems such as a network-forming converter and the like.

The invention discloses a fault ride-through test method for an offshore wind power flexible direct output system, and the method comprises the steps: building a fault equivalent circuit of the offshore wind power flexible direct output system, analyzing the operation characteristics of an AC power grid side under a low-voltage fault, and determining the incidence relation between the DC side excess energy and the power grid voltage drop; establishing a model representing each component in the fault equivalent circuit, wherein the components at least comprise a machine-side converter, a grid-side converter, a direct-current capacitor and an unloading resistor; when a low-voltage fault of an alternating-current power grid side is detected, executing the following cooperative control based on the model: synchronously starting unloading resistance control and reactive power support control, wherein an unloading resistor dissipates excess energy of a direct-current side through a direct-current chopper; the grid-side converter injects a capacitive reactive current which is deeply matched with the voltage drop of the power grid so as to improve the voltage of a grid-connected point; and if the direct-current voltage continuously exceeds the preset threshold value, starting power prompt drop control, and reducing the output power of the unit according to a gradient until the system recovers to be stable.

The invention relates to the technical field of power system control, in particular to a direct-current capacitor self-synchronizing grid-connected control strategy method, system, equipment and medium, a direct-current capacitor energy dynamic model is established based on an actual energy balance relation, a direct-current voltage signal is acquired in real time, and a synchronous compensation signal is calculated based on the acquired direct-current voltage signal; performing phase compensation and gain adjustment on the synchronous compensation signal through a correction link based on the calculated synchronous compensation signal, adjusting the internal frequency of the inverter based on the synchronous compensation signal after phase compensation and gain adjustment, controlling the DC voltage through the internal frequency of the inverter, and establishing a self-synchronization control model; and based on the self-synchronization control model, establishing an adaptive control algorithm, generating a damping coefficient and a virtual inertia coefficient through the adaptive control algorithm, and dynamically adjusting control parameters according to the damping coefficient and the virtual inertia coefficient.

The invention discloses a two-stage multi-mode bidirectional inverter circuit, which comprises a direct-current power supply DC, an alternating-current power supply AC, a DC / DC circuit, a direct-current voltage-dividing capacitor Cb1, a direct-current voltage-dividing capacitor Cb2, a DC / AC circuit and a controller, and is characterized in that a negative electrode of a second port of the DC / DC circuit is connected with a negative electrode of the direct-current voltage-dividing capacitor Cb1 and a negative electrode of a direct-current port of the DC / AC circuit; a middle point of a second port of the DC / DC circuit is connected with a negative electrode of a direct-current voltage-dividing capacitor Cb1 and a positive electrode of a direct-current voltage-dividing capacitor Cb2, and is connected to an alternating-current neutral line N; the AC port of the DC / AC circuit is connected with an AC live wire L1 and an AC live wire L2. The controller stably outputs voltage or current by controlling the DC / DC circuit and the DC / AC circuit, and bidirectional electric energy conversion is achieved. According to the invention, direct-current capacitance and additional circuits do not need to be increased, the size of the device is reduced, the system cost is reduced, the conversion efficiency is improved, and the device can be widely applied to new energy power generation and energy storage and other industrial and civil bidirectional power conversion systems so as to meet the global power supply and consumption requirements.

The invention discloses a power assembly and a liquid cooling converter, the power assembly comprises a capacitor module and a power module, in the capacitor module, a direct current capacitor pool comprises a first capacitor pool and a second capacitor pool, a capacitor busbar comprises a first busbar and a second busbar, and planes where the first busbar and the second busbar are located are intersected or parallel; in the power module, a mounting base body is provided with a first mounting surface and a second mounting surface which are deviated from each other, the first mounting surface is close to a first busbar, and the second mounting surface is close to a second busbar; the power tube group comprises a plurality of switching devices, and part of the switching devices are connected with the capacitor busbar through wiring components and are divided into first switches and second switches according to the connection relation with polar plates with different polarities on the capacitor busbar; each first switch is located on the first mounting surface and is connected with the first busbar through a wiring component, and each second switch is located on the second mounting surface and is connected with the second busbar through a wiring component. The structure of the power assembly can reduce stray inductance generated during operation.

The invention discloses a direct black-start method and system for a grid-forming type permanent magnet direct-drive wind turbine generator, and the method comprises the steps: starting a rotor-side converter, accelerating a permanent magnet direct-drive fan to a given rotating speed, continuously charging a direct current side when the rotating speed rises until a rated voltage is reached, and maintaining the capacitor voltage of the direct current side through machine-side control; a grid-side converter is started, and inertia support is provided for the system through control of the virtual synchronous machine; a load is accessed, and a virtual synchronous machine and a linear active-disturbance-rejection technology are combined to improve the stability of a network construction type system. According to the method, the autonomous frequency and voltage supporting capacity of the direct-driven wind turbine generator are improved, the direct-driven wind turbine generator can independently serve as a black-start power supply to participate in power grid black-start, and the black-start process can be effectively achieved for a regional power grid lacking a conventional black-start power supply.

This application discloses a power electronic transformer wherein each phase includes a plurality of power conversion modules. Each power conversion module includes a rectifier AC / DC circuit, a direct current bus capacitor, and a direct current-direct current DC / DC circuit. In each power conversion module, an output end of the AC / DC circuit is connected to an input end of the DC / DC circuit; the direct current bus capacitor is connected in parallel to the output end of the AC / DC circuit; and input ends of all the AC / DC circuits are connected in series, and output ends of all the DC / DC circuits are connected in parallel. The power electronic transformer includes a relatively small quantity of power conversion modules, thereby reducing occupied space and costs.

The invention discloses an energy storage type SOP black-start method, system and device based on improved VSG network construction control and a medium, and relates to the field of power grid black-start, and the method comprises the steps: an energy storage type converter MMC carries out the active and reactive control based on an improved VSG network construction control strategy; a non-fault side MMC is controlled to firstly close an isolation circuit breaker and slowly charge a direct-current capacitor, and when the voltage reaches a set threshold value, a current-limiting resistor is quitted; the fault side MMC is started by the same step as the non-fault side MMC; after synchronization is completed, AC circuit breakers between the non-fault side MMC and the feeder load and between the fault side MMC and the feeder load are closed respectively; based on the collected power grid power data, MMC output parameters are adjusted to meet the power grid connection condition, the control mode is switched according to the grid connection state, and the black start process is ended. And by arranging the black start resistor for current-limiting charging and sub-module voltage balance control, the phenomena of overcurrent and voltage unbalance in the black start process are avoided.

A kind of power device parallel type power module and capacitor charging and discharging method, power module includes two or more than pressure type power device, the two or more than pressure type power device adopts the physical form of half bridge group string upper and lower parallel;The half bridge group string of the pressure type power device is connected in parallel by silicon pile composite busbar;Each power module is provided with pneumatic short-circuit switch, in the case of multiple power module series connection, the pneumatic short-circuit switch is connected in series with all DC capacitors, and charging and discharging is carried out through the ground loop of flexible AC transmission equipment AC, DC valve side;The pneumatic short-circuit switch is connected with gas driving pipeline, and the gas driving pipeline is connected with valve-based gas pressurizing device.The power module can effectively improve the capacity of flexible AC transmission equipment, so that it has short-time frequency modulation capacity output, provides technical scheme support for new power system construction, and guarantees system safety and stability;The provided capacitor charging and discharging method can improve maintenance efficiency and enhance product reliability.

A first voltage control circuitry controls a first representative value, i.e., an average-value corresponding value of DC capacitor voltages of all converter cells to follow an overall voltage command value. A phase balance control circuitry controls second representative values, i.e., average-value corresponding values of DC capacitor voltages of the converter cells in leg circuits for respective phases to follow the first representative value. A positive-negative balance control circuitry controls deviations of third representative values, i.e., average-value corresponding values of the DC capacitor voltages of the converter cells in the positive and negative arms of the leg circuits for respective phases to become zero between the positive and negative arms. An individual balance control circuitry controls DC capacitor voltages of all the converter cells to follow the third representative values.

The present invention discloses a UPQC topology and a series-parallel side coordinated control method thereof, including: a series side unit, a DC capacitor and a parallel side unit; the series side unit includes a series transformer, a series coupling capacitor, a first filter and a series converter connected in series in sequence; the parallel side unit includes a parallel converter, a second filter and a parallel transformer connected in series in sequence; the series converter, the DC capacitor and the parallel converter are connected in parallel with each other; the first filter includes a first inductor and a first capacitor connected in series, and the second filter includes a second inductor; the series converter includes four insulated gate bipolar transistors; the parallel converter includes four insulated gate bipolar transistors. The present invention can effectively improve the utilization rate of the series side device, and can use the series side converter to reduce the rated capacity of the parallel side converter, further reducing the active capacity of the device.

The invention provides a resistance voltage division control redundancy power supply circuit for a multi-level converter power sub-module, and relates to the technical field of power supply of the multi-level converter power sub-module. The resistor voltage division control redundancy power supply circuit comprises n voltage division resistors which are connected in series and are connected with a high-voltage direct-current capacitor in parallel; one end of the first through-current unit is connected with a connection point of the (k-1) th divider resistor and the kth divider resistor; one end of the second through-flow unit is connected with a connection point of the (j-1) th divider resistor and the jth divider resistor, and the other end of the second through-flow unit is connected with an energy storage capacitor of the bypass switch; one end of the resistance voltage division control branch is connected with one end of the first through-current unit, and the other end is connected with the negative electrode of the high-voltage direct-current capacitor; and two ends of the redundant power supply and energy taking module are respectively connected with the other end of the first through-current unit and the negative electrode of the high-voltage direct-current capacitor. In the low-voltage pre-charging stage of the multi-level converter power sub-module, starting of redundant power supply is achieved, black module faults are avoided, and the system reliability is improved.

The invention provides a direct-current capacitance determination method for a flexible interconnection device of a three-port intensive low-voltage power distribution network, the flexible interconnection device comprises three alternating-current ports and a direct-current port, each alternating-current port is connected with a power grid through an alternating-current feeder line, and the direct-current port comprises a plurality of direct-current capacitors; the method comprises the following steps: respectively determining active power and reactive power of three alternating-current feeder lines, and respectively determining current and modulation voltage of three alternating-current ports according to the active power and the reactive power of the three alternating-current feeder lines; according to the current and the modulation voltage of the three alternating current ports, determining a current instantaneous value of a direct current capacitor without a current direct current component in a fundamental wave period; determining the capacitance value of the direct current capacitor according to the capacitor voltage ripple limit value and the current instantaneous value of the direct current capacitor; the scene of multiple alternating current ports is considered, and the adjusting effect of the power flow is improved.

The invention discloses a model predictive control-based virtual inertia adjustment method and system for power electronic equipment. The method comprises the following steps of: respectively calculating an output power reference value and an output power adjustment amount of each power emitting node in a power grid before and after load power change; obtaining an output power prediction sequence in a certain time range in the future by taking minimization of a power loss function and a direct current loss function of the power electronic equipment in an adjustment process as a target through model prediction control; taking an output power predicted value obtained by calculation at the first moment as optimal control at the current moment, and mapping the optimal control back to a PWM control signal; and adjusting the output power of the power electronic equipment to a corresponding power reference value by cyclically repeating model predictive control and mapping PWM control signals. According to the method, the loss in the power adjustment process is effectively reduced while the power electronic equipment is ensured to provide the required virtual inertia, the stability of the direct-current capacitor voltage is maintained, and the dynamic stability and the energy utilization efficiency of a power grid system are improved.

The invention relates to a network construction type STATCOM (static synchronous compensator) analysis model based on DC capacitance dynamics, and belongs to the technical field of power distribution networks. The invention aims to realize the simulation of the synchronization characteristic of a synchronous machine by utilizing the similarity between the dynamic state of the direct current capacitor and the dynamic state of a generator rotor, namely a grid-building STATCOM analysis model based on the dynamic state of the direct current capacitor for the self-synchronous control of the direct current capacitor. The control structure of the internal frequency of the STATCOM on the direct current voltage is adjusted, a voltage equation under a synchronous coordinate system is deduced according to the superposition theorem and a topological graph, and the equivalent synchronous machine is obtained according to the equivalent principle, so that an equivalent rotor motion equation of the equivalent synchronous machine is obtained. According to the control mode, the internal frequency of the equipment can be adjusted to realize synchronization with the power grid, and stable operation of the direct-current side is ensured by controlling the direct-current voltage.

The invention discloses a magnetic flux coupling regulation type hybrid transformer and a control method thereof, and relates to the technical field of power distribution network voltage regulation equipment. The magnetic flux coupling regulation and control type hybrid transformer is composed of three three-column four-winding transformers and a voltage source type back-to-back converter. The three three-column four-winding transformers are the same in structure, and four windings are respectively an input winding, an output winding, an energy taking winding and a voltage regulating winding. The back-to-back converter is composed of a rectification unit, an inversion unit and a direct current capacitor. The rectification unit realizes stable control of DC voltage through controlling port current, and carries out reactive power and harmonic compensation on an input port of the hybrid transformer. And the inversion unit realizes flexible adjustment of the voltage of the output winding port of the hybrid transformer by controlling the output voltage of the inversion side. The method has the characteristic that the line fault current does not directly flow through the converter, and can reduce the voltage and current resistance level of a converter power device and the equipment protection difficulty, thereby reducing the cost of the hybrid transformer.

The invention specifically discloses an optical storage system dynamic damping control method based on direct current capacitor energy, and relates to the technical field of new energy. The method comprises the following steps: firstly, acquiring a direct-current bus voltage value, photovoltaic output voltage and current, energy storage battery voltage and current, LC filter inductive current and grid-connected point voltage and current in the current optical storage system; then, the photovoltaic system and the energy storage system are adjusted to operate cooperatively, the photovoltaic system achieves maximum power point tracking through a disturbance observation method, and the energy storage system stabilizes the direct-current bus voltage through a voltage-current double closed loop; secondly, based on a dynamic damping control strategy of direct-current capacitor energy, introducing a difference value between actual direct-current capacitor energy and a reference value into a network construction control active control loop through a direct-current damping coefficient; and finally, performing network construction control by combining an inverter virtual synchronous generator control technology. According to the method, existing hardware resources are effectively utilized, a complex algorithm is not needed, the dynamic performance of the system is remarkably improved, and the method has high adaptability and wide application prospects.

The invention provides a transformer DC capacitor state monitoring device and method based on an FPGA, and relates to the technical field of capacitor state monitoring. The device comprises a voltage acquisition module used for synchronously acquiring voltage analog signals at two ends of a DC capacitor in a plurality of MMC modules and performing analog-to-digital conversion; the current acquisition module is used for synchronously acquiring bridge arm current analog signals of a plurality of MMC modules and performing analog-to-digital conversion; the master control FPGA module is respectively connected with the voltage acquisition module and the current acquisition module, and is used for receiving and caching the digitized voltage signal and current signal, respectively calculating a real-time capacitance value of a direct-current capacitor in each MMC module based on a parallel sliding window and a hardware acceleration real-time capacitance value tracking algorithm, and outputting the real-time capacitance value of the direct-current capacitor in each MMC module; the degradation state of each direct-current capacitor is evaluated according to the real-time capacitance value; and the communication module is connected with the master control FPGA module and is used for uploading the degradation state data to an upper computer. According to the method, the real-time performance of monitoring can be remarkably improved while the calculation precision is ensured.

The invention discloses a power module. The power module comprises a direct current busbar, a radiator, an IGBT module I and an IGBT module II, the IGBT module I and the IGBT module II are respectively arranged on a mounting surface I and a mounting surface II of the radiator; the direct-current busbar comprises a direct-current busbar I, a direct-current busbar II, a direct-current busbar III and a direct-current busbar IV; the two ends of a fourth direct-current busbar are connected with the first IGBT module and the second IGBT module respectively, and the middle of the fourth direct-current busbar is connected with the middle of a third direct-current busbar. The two ends of the direct current busbar III are respectively connected with the direct current busbar I and the direct current busbar II; the direct current busbar I and the mounting surface I as well as the direct current busbar II and the mounting surface II are oppositely arranged and parallel to each other; the first direct current capacitor assembly is connected with the first direct current busbar, and the second direct current capacitor assembly is connected with the second direct current busbar. The influence of stray inductance is reduced by optimizing a current path, and the voltage spike at the switching moment is reduced due to the reduction of the stray inductance, so that the switching loss is reduced.

The present invention relates to the technical field of pumped-storage units, and particularly to a starting control method for a full-power variable-speed pumped-storage unit converter, including: when the unit starts, keeping the grid-side circuit breaker and the machine-side circuit breaker in the off state; controlling the excitation device to generate an initial excitation current; controlling the guide vane opening through the governor to control the speed increase of the motor, and judging the currently required operating state. If it is the power generation state, the machine-side converter enters the power control mode to complete the start; if it is the pumping state, closing the guide vane, the machine-side converter enters the braking and decelerating state. After the motor speed drops to 0, it drives the pump-turbine to increase speed in the reverse direction and enters the pumping working condition mode to complete the start. Through this control method, the additional DC capacitor charging circuit of the traditional full-power converter can be omitted, reducing the unit cost.

The invention relates to an expandable distributed voltage controller, and relates to the technical field of power grid electric energy management, the expandable distributed voltage controller comprises a series-parallel module comprising a parallel converter, a first series converter, a first DC capacitor and an isolation transformer, the DC side of the parallel converter is connected with the DC side of the first series converter through the first DC capacitor, and the DC side of the first series converter is connected with the isolation transformer through the isolation transformer; the alternating current side of the series converter is connected in series to the power grid side through the isolation transformer; and the series connection module comprises a second series connection converter, a second direct current capacitor and an isolation transformer, the second direct current capacitor is arranged on the direct current side of the second series connection converter, and the second series connection converter is connected to the load and / or the grid connection position in series through the isolation transformer. A plurality of problems can be solved while the power quality problem of the power grid is governed, so that the application range is wider.

The invention discloses a cooperative control method for suppressing transient overvoltage of a hybrid wind power plant, and the method comprises the steps: judging whether a fault occurs or not through monitoring a grid-connected bus voltage effective value and a DC capacitor voltage in real time; when the fault signal meets the synchronous trigger logic, switching the GFM-PMSG of the network-forming type fan to constant voltage control; and when the fault signal meets the low-voltage logic of the grid-connected point, the grid-following type fan GFL-PMSG is switched from steady-state control to low-voltage ride-through control, and meanwhile, a grid-connected bus reactive power compensator is cut off, and advanced reactive power cut-off control is carried out. According to the method, the problem of transient overvoltage caused by sudden change of voltage amplitude and phase of the GFM-PMSG of the grid-forming fan during a fault period, control lag of the GFM-PMSG and incapability of realizing instantaneous adjustment by reactive compensation equipment can be solved.

The invention discloses a method and system for expanding network construction control to DC bus voltage control, and relates to the technical field of intelligent power grid control, and the method comprises the steps: generating a grid-connected phase angle needed by park conversion through a DC capacitor voltage self-synchronization controller; generating a reference voltage amplitude by using a reactive droop controller; converting the acquired three-phase voltage and current signals into two-phase dq-axis voltage and current signals; a current instruction value required by the current inner loop control module is obtained through the voltage outer loop control module, and a modulation voltage signal is obtained through the current inner loop control module. GFM control is expanded to direct-current bus voltage control, dynamic balance of voltage and power is achieved by controlling the power angle of the converter, potential conflicts between traditional GFM control and direct-current voltage control are avoided, the robustness of the system is improved, the system can adapt to wider power grid conditions including a strong power grid and a weak power grid, and the system can be widely applied to power grid control. And normal operation can still be maintained when an alternating-current power grid is lost.

The present invention belongs to the technical field of power electronic converters and discloses a medium-voltage distribution network flexible interconnection switch topology and control method. The medium-voltage distribution network flexible interconnection switch topology provided by the present invention includes three connected reactors L1, three connected reactors L3, two chain-type STATCOMs, two three-phase isolation transformers, two three-phase LC filters, two three-phase inverter circuits, and a DC port. Back-to-back three-phase converters are introduced at the ends of the chain-type STATCOMs of two feeders. Through the back-to-back three-phase converters, active power flow mutualization between the two medium-voltage chain-type STATCOMs, that is, between two different feeders, can be achieved. The present invention can achieve DC capacitor voltage balancing of the chain-type STATCOM submodules of the two feeders. Compared with the BTB-VSC commonly used in existing medium-voltage distribution network flexible interconnection demonstration projects, this solution has lower cost, simpler topology, easier control, and does not need to consider the active and reactive power decoupling issues between interconnected feeders, making it easy to promote and apply on a large scale.

The invention relates to the technical field of power systems, and particularly discloses a high-voltage cascade valve hall type energy storage direct current side double-frequency current suppression method, which comprises the following steps of S1, acquiring the current of a branch where a battery cluster is located and / or the current of a battery stack direct current bus; s2, performing second harmonic extraction on the current of the branch and / or the current of the direct current bus to obtain a second harmonic generation harmonic current component; s3, performing difference calculation on the reference value of the double-frequency harmonic current component and the double-frequency harmonic current component to obtain a modulation signal; s4, inputting the modulation signal into a full-current controller, adjusting the output target voltage of the battery pack, and acting on a loop of a direct-current capacitor of a half-bridge sub-module and / or a full-bridge sub-module to realize suppression of a double-frequency harmonic current component; according to the invention, the extracted double-frequency harmonic current component is compared with the preset reference value to generate the modulation signal, and the battery pack is adjusted by using the modulation signal to output the target voltage, so that suppression of the double-frequency harmonic current component is realized.

The invention relates to the technical field of all-condition equivalent testing of flexible direct current capacitors, and discloses an all-condition equivalent testing method and system for a flexible direct current capacitor. The preset working condition voltage is adjusted according to the waveform consistency judgment result of the sample so as to equivalently simulate the alternating-current and direct-current superposed voltage and pulse power characteristics in actual operation; and collecting the surface temperature and leakage current of the sample, and finally generating an electric heating performance parameter curve through comparison and judgment with a preset threshold value. By dynamically adjusting the working condition voltage and strictly monitoring the waveform consistency, the pulse power intensity of large-current charging and discharging of the capacitor in each working period in actual operation is effectively reproduced, and the performance change under the real operation working condition is comprehensively reflected by combining environmental parameter simulation and real-time monitoring of temperature and current. The technical problems that in the prior art, the pulse power intensity of the capacitor in the continuous charging and discharging process along with large current in each work period during operation is difficult to reflect, and the real operation condition cannot be comprehensively reflected are solved.

The invention discloses a sequential active frequency support method for an offshore wind power flexible direct current sending-out system, and the method comprises the steps: constructing a dynamic coupling relation between the frequency of an onshore alternating current system and the direct current voltage at a receiving end converter station through a direct current voltage synchronous control technology; the grid-connected power of a receiving end converter station is adjusted in real time according to the frequency change of an onshore alternating-current power grid by setting a proper direct-current voltage and frequency coupling coefficient. In a sending end converter station, additional control based on direct current voltage-frequency is added. And according to the fluctuation of the direct-current voltage, the frequency given value of the offshore alternating-current collection system is adjusted in real time, so that the stored energy of the sub-module capacitor of the sending-end converter station is released, and short-time frequency support is realized. In addition, the control strategy of the offshore wind turbine generator is improved, and fan virtual inertia control and primary frequency modulation control are introduced; and the frequency modulation function is realized by fully releasing the DC capacitor of the wind turbine generator and the stored energy of the rotor. The frequency change of the alternating current system can be quickly responded, and the stability is enhanced.

The invention relates to the technical field of power grid control, in particular to a control parameter design method and device for a multi-scene active support type networking SVG (Static Var Generator), and the method comprises the steps: determining the target power grid strength and an active support demand based on a short-circuit ratio and an inertia ratio; determining a parameter steady-state reference value and a boundary of the network-forming static var compensator; the short-circuit ratio and the inertia ratio are dynamically mapped to the virtual impedance, the voltage regulation coefficient and the frequency modulation coefficient of the network-forming type static var compensator; and based on the parameter steady-state reference value, the boundary, the virtual impedance, the voltage regulation coefficient and the frequency modulation coefficient, comprehensively determining a direct-current system value according to a direct-current capacitance value and a system inertia demand, and generating control parameters of the multi-scene active support network-forming static var compensator. Therefore, the problems of inertia deficiency, poor frequency stability and the like of a power grid system due to the fact that network construction SVG control mainly adopts fixed parameters or a parameter adjustment principle is determined from a short circuit ratio single dimension in related technologies are solved.

The invention provides a grid-connected frequency modulation control strategy based on photovoltaic power prediction so as to solve the problems of stability and safety of a power system under high-proportion photovoltaic grid connection. According to the strategy, new parameters representing characteristics of a traditional synchronous generator set and a photovoltaic system are introduced, and a control strategy of a power grid side inverter is improved based on actual grid-connected working conditions. Meanwhile, a frequency dynamic response model considering the photovoltaic penetration influence is established, and the inertia response of the synchronous generator set is accurately simulated by introducing the dynamic characteristics of a power grid side direct current capacitor. And by adjusting the virtual inertia and the adjustment factor, the anti-disturbance capability of the photovoltaic system is enhanced. In combination with historical photovoltaic power generation data, the photovoltaic power is predicted by adopting data normalization, feature selection, SOM clustering analysis, singular spectrum analysis and a full-connection network model, and the prediction accuracy is improved. And the control strategy is combined with the power prediction result to realize efficient and stable frequency modulation control of the grid-connected photovoltaic system.

The invention discloses a device and a method for suppressing frequency doubling fluctuation of direct-current side current of an inverter. The device comprises a full-bridge converter, an output filter, a direct-current side capacitor and a control device, wherein the suppression device is connected in series between a direct-current power source and a direct-current capacitor of the inverter; the control device is used for generating PWM (Pulse Width Modulation) waves according to the real-time parameters of the direct-current power source and the suppression device, and controlling the switching conversion of the full-bridge converter based on the PWM waves, so that the full-bridge converter outputs frequency doubling voltage opposite to the equivalent frequency doubling voltage of the inverter, and the voltage of the direct-current side capacitor is maintained to be a stable value; and the output filter is used for filtering the output signal of the full-bridge converter. Based on the mode that the device is connected between the direct current capacitor and the direct current power source of the inverter in series, borne voltage is reduced, and suppression of frequency doubling fluctuation of current on the direct current side of the inverter can be achieved with low cost.