H-bridge series-parallel active support type SVG system and control method

Abstract

The invention discloses an H-bridge series-parallel active support type SVG system and a control method, and relates to the technical field of active support type SVGs, the H-bridge series-parallel active support type SVG system is formed by three-phase star connection of a chain structure, each phase is formed by connecting an H-bridge power module and a super capacitor power module in series, the H-bridge power module and the super capacitor power module are both controlled by the power control module; the H-bridge power module is used for providing reactive power support for the static var generator system and maintaining the stability of the voltage of the power grid by adjusting the reactive power injected into the power grid; and the super capacitor power module is used for providing active support for the static var generator system so as to realize frequency active support of the static var generator system to a power grid. According to the invention, the configuration scheme of the active support type SVG super capacitor is simplified, the overall configuration is more flexible, and the expandability is stronger.

Description

Technical Field

[0001] The present invention relates to the technical field of active support type SVG, and in particular to an H-bridge hybrid active support type SVG system and a control method. Background Art

[0002] The salient feature of the new power system is that new energy occupies a major position in the power structure. As the proportion of new energy power generation devices increases to a certain extent, the stable operation of the power system after encountering similar disturbances is at great risk. The active support technology of the converter can comprehensively solve the problem of large-scale new energy development and improve the stable operation of large-scale new energy power generation bases without conventional power support. Due to the speed advantage of the power electronic control system, its rapid response performance even exceeds that of traditional generators, and its external characteristics can be shaped by control characteristics.

[0003] By configuring a certain proportion of active support SVG in specific situations of large new energy bases, it can play a role similar to that of a phase regulator. While meeting the conditions for new energy access, it can also control the overvoltage level within the specified range, thereby ensuring the stable operation of the power grid connected to new energy under severe shocks and improving the new energy absorption capacity.

[0004] Conventional SVG devices cannot effectively support the frequency fluctuations of the power grid because they do not have enough energy storage elements. Active support SVG can provide inertia response support for the system under frequency fluctuations by adding parallel power storage elements - supercapacitors on the DC side of all chain link H-bridge power modules, thereby improving the overall support capacity of SVG for the power grid. At the same time, the current method of directly connecting supercapacitors in parallel on the DC side of the H-bridge power module has problems such as low supercapacitor power utilization and high configuration costs; in addition, the utilization rate of supercapacitors can be improved through a two-level topology configuration, but there are also problems such as multiple control units and low efficiency of complex control systems.

[0005] Currently, no effective solution has been proposed for the problems in the related technologies. Summary of the invention

[0006] In view of the problems in the related art, the present invention proposes an H-bridge hybrid active support type SVG system and a control method to overcome the above technical problems existing in the existing related art.

[0007] To this end, the specific technical solution adopted by the present invention is as follows:

[0008] According to one aspect of the present invention, an H-bridge hybrid active support type SVG system is provided. The H-bridge hybrid active support type SVG system is connected in a three-phase star shape through a chain structure, and each phase is composed of an H-bridge power module and a super capacitor power module connected in series, and the H-bridge power module and the super capacitor power module are both controlled by a power control module;

[0009] Among them, the H-bridge power module is used to provide reactive power support for the static VAR generator system and maintain the stability of the grid voltage by adjusting the reactive power injected into the grid;

[0010] Supercapacitor power module, used to provide active support for the static VAR generator system, so as to realize the active frequency support of the static VAR generator system to the power grid;

[0011] The power control module is used to control the operation of the H-bridge power module and the supercapacitor power module.

[0012] Preferably, the power control module includes an active and reactive power calculation module, a phase-locked loop module, a supercapacitor charging and discharging control module, a DC voltage stabilization control module, a reactive power control module, an active power control module and an intra-phase voltage equalization control module;

[0013] Among them, the active and reactive power calculation module is used to calculate the active power command and reactive power command of the power grid;

[0014] A phase-locked loop module is used to keep the output of the static VAR generator system consistent with the grid phase;

[0015] A supercapacitor charge and discharge control module is used to control the charge and discharge process of the supercapacitor to avoid overcharge and over-discharge of the supercapacitor;

[0016] A DC voltage regulation control module is used to compare the average DC voltage of the H-bridge power module with a preset voltage and then perform proportional-integral regulation to generate an active power regulation amount of the H-bridge power module;

[0017] The reactive power control module is used to compare the reactive power command with the instantaneous reactive power of the grid and then perform proportional-integral regulation to generate the total reactive power control amount of the static reactive generator system;

[0018] Active power control module, used to compare the active power command with the instantaneous active power of the grid, and then perform proportional-integral regulation to generate the active power control amount of the supercapacitor power module;

[0019] The intra-phase voltage balancing control module is used to distribute the total reactive power control amount of the static VAR generator system to the intra-phase voltage balancing control module as reactive power regulation voltage output based on a preset distribution coefficient.

[0020] Preferably, the front stage of the supercapacitor power module is connected to the two bridge arm H-bridge power modules, the rear stage of the supercapacitor power module is staggered in parallel with the DC converter, and the DC output of the H-bridge power module is connected to the input end of the DC converter, and the output end of the DC converter is connected to the supercapacitor module.

[0021] Preferably, the DC voltage regulation control module performs proportional-integral regulation after comparing the average DC voltage of the H-bridge power module with the preset voltage, and generates the active power regulation amount of the H-bridge power module, including:

[0022] The average DC voltage of the H-bridge power module is compared with the DC voltage regulation instruction, and the comparison result is input into the proportional-integral regulator, and the proportional-integral regulator is used to output the active power regulation amplitude;

[0023] Based on the active power regulation amplitude and the predefined grid phase-locking angle, the active power regulation amount of the H-bridge power module is generated.

[0024] Preferably, the calculation formula of the active control amount of the H-bridge power module is:

[0025]

[0026] Where U dcm_out Indicates the active power regulation amplitude output by the proportional-integral regulator; u mda 、u mdb 、u mdc They respectively represent the phase active control quantity of each phase H-bridge power module; θ represents the grid phase-locking angle.

[0027] Preferably, the reactive power control module performs proportional-integral regulation after comparing the reactive power command with the instantaneous reactive power of the grid, and generates the total reactive power control amount of the static VAR generator system, including:

[0028] Compare the reactive power command with the system reactive power, and input the comparison result into the proportional-integral regulator, and output the reactive power adjustment amplitude through the proportional-integral regulator;

[0029] Based on the reactive power regulation amplitude, the grid phase-locking angle and the grid amplitude, the total reactive power regulation amount of the static reactive power generator system is generated;

[0030] Based on the predefined allocation coefficient, the total reactive power control amount of the static VAR generator system is allocated to the intra-phase voltage balancing control module as the reactive power regulation voltage output.

[0031] Preferably, the calculation formula for reactive power regulation voltage output is:

[0032]

[0033] In the formula, u mqa 、u mqb and u mqc Both represent reactive power regulated voltage output; U Q_out represents the reactive power regulation amplitude; θ represents the grid phase-locking angle; U m Indicates the power grid amplitude.

[0034] Preferably, the active power control module performs proportional-integral regulation after comparing the active power instruction with the instantaneous active power of the grid, and generates the active power control amount of the supercapacitor power module, including:

[0035] Based on the change of grid frequency, the primary frequency modulation, inertia response adjustment and supercapacitor charge are calculated in sequence to obtain the active power command;

[0036] The active power command is compared with the system active power, and the comparison result is input into the proportional-integral regulator, and the active power adjustment amplitude is output through the proportional-integral regulator;

[0037] Based on the active power regulation amplitude and the grid phase-locking angle, the active power regulation quantity of the supercapacitor power module is generated.

[0038] Preferably, the calculation formula of the active power instruction is:

[0039]

[0040] Where P ref Indicates the active power reference value, K pc Indicates the supercapacitor voltage loop proportional coefficient; K pi Indicates the integral coefficient of the supercapacitor voltage loop; U cref Indicates the supercapacitor voltage reference value; U c Indicates the supercapacitor voltage value; K f Indicates the active frequency modulation coefficient; P N Indicates rated active power; f N Indicates the rated frequency of the power grid; T j represents the inertia response time constant; df / dt represents the rate of change of the power grid frequency; K en It indicates the adjustable charge coefficient of the supercapacitor; Δf indicates the difference between the actual frequency and the rated grid frequency.

[0041] According to another aspect of the present invention, a control method for an H-bridge hybrid active support type SVG system is provided. The control method for the H-bridge hybrid active support type SVG system includes:

[0042] Use H-bridge power modules to provide reactive power support for the static VAR generator system and maintain grid voltage stability by adjusting the reactive power injected into the grid;

[0043] Use supercapacitor power modules to provide active support for the static VAR generator system, so as to realize the active frequency support of the static VAR generator system to the power grid;

[0044] Connect the DC converter to the supercapacitor power module and control the DC bus voltage to remain stable when the supercapacitor is charged and discharged;

[0045] The intra-phase voltage equalization control module is used to control the DC voltage balance between the H-bridge power module and the supercapacitor power module respectively.

[0046] The beneficial effects of the present invention are:

[0047] 1. The present invention cascades m H-bridge power modules and n supercapacitor power modules per phase and then connects them in series as a whole, meeting the 35kV direct access requirements of new energy stations, thereby simplifying the configuration scheme of active support type SVG supercapacitors, making the overall configuration more flexible and more scalable. At the same time, the charge utilization rate of the supercapacitor is higher, and the overall system solution is more cost-effective.

[0048] 2. The present invention separates the supercapacitor from the H-bridge power module by adopting a two-stage topology configuration, thereby avoiding the problem of low power utilization caused by direct parallel connection. The two-stage topology structure can accurately control the charging and discharging of the supercapacitor, thereby more efficiently utilizing its energy storage capacity and reducing unnecessary power waste.

[0049] 3. The two-level topology structure in the present invention enables the system to have more flexible power control capabilities. Reactive and active power control can be performed in different modules respectively, reducing the load pressure of a single module and improving the operational reliability of the system. Since the supercapacitor can quickly respond to changes in the grid frequency, it can instantly provide or absorb active power, achieve frequency support for the grid, and thus optimize the stability of the grid. BRIEF DESCRIPTION OF THE DRAWINGS

[0050] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings required for use in the embodiments will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying creative work.

[0051] Figure 1 is a system topology diagram of an H-bridge parallel-parallel active support type SVG system according to an embodiment of the present invention;

[0052] Figure 2 is a principle block diagram of an H-bridge parallel-parallel active support type SVG system according to an embodiment of the present invention;

[0053] Figure 3 is a schematic diagram of a power control module in an H-bridge parallel-parallel active support type SVG system according to an embodiment of the present invention;

[0054] Figure 4 is a flow chart of a control method of an H-bridge parallel-parallel active support type SVG system according to an embodiment of the present invention;

[0055] Figure 5 It is a voltage output vector diagram of an H-bridge parallel-parallel active-support type SVG in an H-bridge parallel-parallel active-support type SVG system according to an embodiment of the present invention;

[0056] Figure 6 It is a principle block diagram of the first m-level DC voltage stabilization control module in an H-bridge parallel-parallel active support type SVG system according to an embodiment of the present invention;

[0057] Figure 7 It is a principle block diagram of a reactive power control module in an H-bridge parallel-parallel active support type SVG system according to an embodiment of the present invention;

[0058] Figure 8 It is a principle block diagram of a rear n-stage active power control module in an H-bridge parallel-parallel active support type SVG system according to an embodiment of the present invention;

[0059] Fig. 9 The present invention is a block diagram of the principle of a rear n-stage supercapacitor power module in an H-bridge parallel-parallel active support type SVG system according to an embodiment of the present invention.

[0060] In the figure:

[0061] 1. H-bridge power module; 2. Supercapacitor power module; 3. Power control module; 301. Active and reactive power calculation module; 302. Phase-locked loop module; 303. Supercapacitor charge and discharge control module; 304. DC voltage regulation control module; 305. Reactive power control module; 306. Active power control module; 307. Intra-phase voltage equalization control module. DETAILED DESCRIPTION

[0062] To further illustrate each embodiment, the present invention provides drawings, which are part of the disclosure of the present invention and are mainly used to illustrate the embodiments. They can be used in conjunction with the relevant descriptions in the specification to explain the operating principles of the embodiments. With reference to these contents, ordinary technicians in this field should be able to understand other possible implementation methods and advantages of the present invention.

[0063] According to an embodiment of the present invention, an H-bridge parallel-parallel active support type SVG system and a control method are provided.

[0064] The present invention will now be further described with reference to the accompanying drawings and specific embodiments. Figure 1-Figure 2 As shown, according to an H-bridge hybrid active support type SVG (Static Var Generator) system of an embodiment of the present invention, the H-bridge hybrid active support type SVG system is connected in a three-phase star shape through a chain structure, and each phase is composed of a plurality of H-bridge power modules 1 and a plurality of supercapacitor power modules 2 connected in series, and the H-bridge power module 1 and the supercapacitor power module 2 are both controlled by a power control module 3.

[0065] It should be noted that the H-bridge hybrid active support type SVG system is composed of a three-phase star connection in a chain structure and is directly connected to the power grid through an inductor; the three-phase chain structure is composed of two groups of converters connected in series, the first converter is composed of m H-bridge power modules 1 cascaded, and the second converter is composed of n supercapacitor power modules 2 cascaded.

[0066] The first converter is used to provide reactive power support for the static VAR generator system and maintain the stability of the grid voltage by adjusting the reactive power injected into the grid.

[0067] The second converter is used to provide active power support for the static VAR generator system, so as to realize active frequency support of the static VAR generator system to the power grid.

[0068] The H-bridge power module 1 includes four switch devices, a driver and a DC support capacitor.

[0069] Among them, the supercapacitor power module 2 includes a front-stage two-bridge-arm H-bridge power module 1 and a rear-stage staggered parallel DC-DC converter (equivalent to a DC converter). The DC of the H-bridge power module 1 is connected to the DC-DC converter, and the output of the DC-DC converter is connected to the supercapacitor module.

[0070] The first converter and the second converter are connected in series to meet the 35kV direct access requirements of the new energy station. The first converter provides reactive power support for the system, and the second converter provides active power support for the system to meet the system's active support for the voltage and frequency of the power grid.

[0071] The number m of H-bridge power modules 1 in the chain structure satisfies that the voltage level after the m individual H-bridge power modules 1 are connected in series can directly match the voltage level of the access grid, thereby satisfying the maximum capacitive reactive power output of the system.

[0072] The number n of supercapacitor power modules 2 in the chain structure satisfies that under the rated current of the system, the total adjustable active power of the 3n supercapacitor power modules 2 in three phases is not less than the maximum active power regulation requirement of the system configuration design.

[0073] The supercapacitor power module 2 is composed of a supercapacitor, a charge management module and a heat dissipation module, and is installed and placed directly near the DC-DC converter.

[0074] The adjustable active power includes consuming active power from the grid and sending active power to the grid to interact with the supercapacitor.

[0075] The power control module 3 is used to control the operation of the H-bridge power module 1 and the supercapacitor power module 2.

[0076] It should be noted that if Figure 3As shown, the power control module 3 includes an active and reactive power calculation module 301, a phase-locked loop module 302, a supercapacitor charge and discharge control module 303, a reactive power control module 305, an active power control module 306, a DC voltage regulation control module 304 and two groups of grouped phase balancing control modules of different cascade modules (equivalent to two groups of phase voltage equalization control modules 307). The first converter composed of the first m-stage modules realizes reactive power regulation of the system, and the second converter composed of the latter n-stage modules realizes active power regulation of the system.

[0077] The active and reactive power calculation module 301 is used to calculate the active power command and reactive power command of the power grid.

[0078] It should be noted that the input of the active and reactive power calculation module 301 is the three-phase grid connection point voltage e abc , three-phase grid-connected point current e abc , the output is active power P and reactive power Q.

[0079] The phase-locked loop module 302 is used to keep the output of the static VAR generator system consistent with the phase of the power grid.

[0080] It should be noted that the input of the phase-locked loop module 302 is the three-phase grid voltage e abc , the output is the voltage amplitude U m and the phase-locking angle θ.

[0081] The supercapacitor charge and discharge control module 303 is used to control the charge and discharge process of the supercapacitor to avoid overcharge and overdischarge of the supercapacitor.

[0082] It should be noted that the supercapacitor charge and discharge control module 303 has n power module DC voltage stabilization indicators U as input. dcn_ref , its single power module DC voltage U dcn_j , the output is the modulation instruction of the back-end DC-DC converter.

[0083] In order to avoid overcharging and over-discharging of the supercapacitor during the adjustment process, the supercapacitor adjustable charge coefficient K is set. en As follows, and the limit is 0≤K en ≤1:

[0084]

[0085] In the formula, K en is the adjustable charge coefficient of the supercapacitor, U max The maximum voltage allowed for charging the supercapacitor, U min The minimum discharge voltage allowed for the supercapacitor, U cref is the normal given value of supercapacitor, U c Indicates the supercapacitor voltage value.

[0086] The output of the supercapacitor voltage PI loop for active power regulation sets a limit of 10% of the rated active power to ensure the system's active power response and regulation capability to grid frequency disturbances to the greatest extent.

[0087] The principle block diagram of the supercapacitor charge and discharge control module 303 is as follows: Fig. 9 As shown in FIG. 1 , it is composed of a DC bus voltage stabilization regulation PI regulator (Proportional-Integral Controller), a current inner loop PI regulator and a branch current equalization PI regulator. The current inner loop output is added to the branch current equalization loop and the modulation ratio S of each branch is obtained by limiting. Dn_j1 , S Dn_j2 .

[0088] The specific operation is as follows: n power modules (equivalent to n supercapacitor power modules 2) DC voltage regulation instruction U dcn_ref With its single power module DC voltage U dcn_j After comparison, the DC bus voltage is stabilized and PI regulator is used to generate i ref ; Compare with the branch current mean value through the current inner loop PI regulator to obtain the current inner loop output; branch current i out_j1 、i out_j2 After the branch current average is output by the branch current PI regulator, the current inner loop output is superimposed and the back-end DC-DC converter modulation instruction S is obtained after the limiting process. Dn_j1 , S Dn_j2 .

[0089] The DC voltage stabilization control module 304 is used to compare the average DC voltage of the H-bridge power module 1 with a preset voltage and then perform proportional-integral regulation to generate an active power control amount of the H-bridge power module 1 .

[0090] It should be noted that the DC voltage stabilization control module 304 takes as input the DC voltage stabilization instructions U of m power modules (equivalent to m H-bridge power modules 1). dcm_ref , the average DC voltage of m power modules is U dcm_avg , phase-locking angle θ; the output is multiplied by the distribution coefficient k1 and added to the output of the reactive power control module 305 to obtain the total DC voltage stabilization instruction of the m power modules; the actual voltage value of the single power module is added to the total DC voltage stabilization instruction of the m power modules through the first group of intra-phase voltage control modules 307 to obtain the modulation instruction S of the single power module ma / b / c .

[0091] The DC voltage regulation control module 304 performs proportional-integral regulation after comparing the average DC voltage of the H-bridge power module 1 with the preset voltage, and generates the active control amount of the H-bridge power module 1, including:

[0092] The average DC voltage of the H-bridge power module 1 is compared with the DC voltage regulation instruction, and the comparison result is input into the proportional-integral regulator, and the proportional-integral regulator is used to output the active power regulation amplitude.

[0093] Based on the active power regulation amplitude and the predefined grid phase-locking angle, the active power regulation amount of the H-bridge power module 1 is generated.

[0094] It should be noted that the DC voltage regulation control module is Figure 6 As shown, according to the average DC voltage U of m power modules dcm_avg With m power module DC voltage regulation instructions U dcm_ref , through the PI regulator output active regulation amplitude U dcm_out , and then generate the active control quantity u of the first m modules with the grid phase-locking angle θ mda 、u mdb 、u mdc , and its calculation formula is:

[0095]

[0096] Where U dcm_out Indicates the active power regulation amplitude output by the proportional-integral regulator; u mda 、u mdb 、u mdc They represent the active control amount of each phase H-bridge power module respectively; θ represents the grid phase-locking angle.

[0097] The reactive power control module 305 is used to compare the reactive power instruction with the instantaneous reactive power of the grid and then perform proportional-integral regulation to generate the total reactive power control amount of the static VAR generator system.

[0098] It should be noted that the reactive power control module 305 has a reactive power control instruction Q as input. ref , system reactive power Q, voltage amplitude U m and the grid phase-locking angle θ; the outputs are multiplied by the allocation coefficients k1 and k2 respectively and superimposed on the outputs of the DC voltage stabilization control module 304 and the active power control module 306.

[0099] The reactive power control module 305 performs proportional-integral regulation after comparing the reactive power command with the instantaneous reactive power of the grid, and generates the total reactive power control amount of the static VAR generator system, including:

[0100] The reactive power command is compared with the system reactive power, and the comparison result is input into the proportional-integral regulator, and the reactive power adjustment amplitude is output through the proportional-integral regulator.

[0101] Based on the reactive power regulation amplitude, the grid phase-locking angle and the grid amplitude, the total reactive power regulation amount of the static VAR generator system is generated.

[0102] Based on the predefined allocation coefficient, the total reactive power control amount of the static VAR generator system is allocated to the intra-phase voltage sharing control module 307 as reactive power regulation voltage output.

[0103] It should be noted that the reactive power control module is Figure 7 As shown, according to the reactive power control instruction Q ref After comparing with the system reactive power Q, the reactive power adjustment amplitude U is output through the PI regulator. Q_out , and the grid phase-locking angle θ and the grid amplitude U m Generate the total reactive power control amount of the system; use the set distribution coefficients k1 and k2 to distribute the total reactive power control amount of the system to two groups of cascade modules, and their reactive power regulation voltage outputs are u mqa 、u mqb 、u mqc and u nqa 、u nqb 、u nqc , which can ensure that the n-level module of the second converter can maintain the DC bus voltage stability even at low power. The calculation formula for reactive power regulation voltage output is:

[0104]

[0105] In the formula, u mqa 、u mqb 、u mqc and u nqa 、u nqb 、u nqc Both represent reactive power regulated voltage output; U Q_out represents the reactive power regulation amplitude; θ represents the grid phase-locking angle; U m Indicates the power grid amplitude.

[0106] Under the joint action of the m-level module and the n-level module, the reactive power regulation voltage output is stable, and the distribution coefficient is as follows:

[0107]

[0108] Wherein, k1 and k2 represent the distribution coefficients.

[0109] The active power control module 306 is used to compare the active power instruction with the instantaneous active power of the grid and then perform proportional-integral regulation to generate the active power control amount of the supercapacitor power module 2.

[0110] It should be noted that the active power control module 306 takes as input the active power command P ref , system active power P, phase-locking angle θ, output and reactive power control module output multiplied by the distribution coefficient k2 are added to obtain the total DC voltage stabilization instruction of n power modules; the actual voltage value of a single power module is added to the total DC voltage stabilization instruction of n power modules through the second group of intra-phase voltage equalization control modules 307 to obtain the modulation instruction S of a single power module na / b / c.

[0111] The active power control module 306 performs proportional-integral regulation after comparing the active power command with the instantaneous active power of the grid, and generates the active power control amount of the supercapacitor power module 2, including:

[0112] Based on the change of grid frequency, the primary frequency modulation, inertia response adjustment and supercapacitor charge are calculated in sequence to obtain the active power command.

[0113] It should be noted that the active power control module is Figure 8 As shown, according to the active power instruction P ref After comparing with the system active power P, the active power adjustment amplitude U is output through the PI regulator. P_out , whose output is phase-locked with the grid to generate the three-phase active control quantity u of the n super-capacitor control modules of the second converter nda 、u ndb 、u ndc , and its calculation formula is:

[0114]

[0115] Active power command P ref According to the change of grid frequency, frequency modulation, inertia response adjustment and stable supercapacitor charge are calculated, and the calculation formula is:

[0116]

[0117] Where P ref Indicates the active power reference value, K pc Indicates the supercapacitor voltage loop proportional coefficient; K pi Indicates the integral coefficient of the supercapacitor voltage loop; U cref Indicates the supercapacitor voltage reference value; U c Indicates the supercapacitor voltage value; K f Indicates the active frequency modulation coefficient; P NIndicates rated active power; f N Indicates the rated frequency of the power grid; T j represents the inertia response time constant; df / dt represents the rate of change of the power grid frequency; K en It indicates the adjustable charge coefficient of the supercapacitor; Δf indicates the difference between the actual frequency and the rated grid frequency.

[0118] The active power command is compared with the system active power, and the comparison result is input into the proportional-integral regulator, and the active power adjustment amplitude is output through the proportional-integral regulator.

[0119] Based on the active power regulation amplitude and the grid phase-locking angle, the active power regulation amount of the supercapacitor power module 2 is generated.

[0120] The intra-phase voltage balancing control module 307 is used to distribute the total reactive power control amount of the static VAR generator system to the intra-phase voltage balancing control module 307 as reactive power regulation voltage output based on a preset distribution coefficient.

[0121] It should be noted that if Figure 5 As shown in the figure, the voltage output vector diagram of H-bridge hybrid active support type SVG, the system grid-connected reactive current is i q , the active current entering the grid is i d , the grid voltage is e d 、e q The main function of the first m-level module is to adjust the system reactive power. Its output voltage d and q axis components are u d1 、u q1 The main function of the latter n-stage module is to adjust the system active power. Its output voltage d and q axis components are u d2 、u q 2 .

[0122] The system grid current i is obtained by coordinate transformation to obtain the system grid reactive current i q And the active current i d ; Output voltage d-axis component u of the first m-stage module d1 , q-axis component u q1 Through vector calculation, the output voltage u1 of the first m-level module is obtained; the d-axis component u of the output voltage of the next n-level module is obtained. d2 , q-axis component u q2 The output voltage u2 of the rear n-stage modules is obtained through vector operation; the output voltage u1 of the first m-stage modules and the output voltage u2 of the rear n-stage modules are obtained through vector operation to obtain the total output voltage u.

[0123] like Figure 4 As shown, according to another embodiment of the present invention, a control method of an H-bridge hybrid active support type SVG system is also provided. The control method of the H-bridge hybrid active support type SVG system includes:

[0124] S1, using H-bridge power module 1 to provide reactive power support for the static VAR generator system, and maintaining the stability of the grid voltage by adjusting the reactive power injected into the grid;

[0125] S2, using the supercapacitor power module 2 to provide active support for the static VAR generator system, so as to realize the active frequency support of the static VAR generator system to the power grid;

[0126] S3, connecting the DC converter to the supercapacitor power module 2, and controlling the voltage of the DC bus to remain stable when the supercapacitor is charged and discharged;

[0127] S4. Use the intra-phase voltage balance control module 307 to control the DC voltage balance between the H-bridge power module 1 and the supercapacitor power module 2 respectively.

[0128] It should be noted that the control method of the H-bridge hybrid active support type SVG system includes: DC voltage stabilization control of the first m cascaded H-bridge power modules and system reactive power support control; the latter n power modules are divided into two stages, front and rear, the front-stage H-bridge power module 1 is connected in series with n supercapacitor power modules 2, and connected to the power grid to realize active power support control and partial reactive power support, and the rear-stage staggered parallel DC-DC converter is connected to the supercapacitor to maintain the stability of the intermediate DC bus voltage through supercapacitor charging and discharging control; two groups of phase intra-voltage equalization control respectively control the balance of the first m series H-bridge power modules 1 and the latter n supercapacitor power modules 2.

[0129] In summary, by means of the above technical solution of the present invention, the present invention is cascaded by m H-bridge power modules 1 and n supercapacitor power modules 2 per phase and then connected in series as a whole, meeting the 35kV direct access requirements of the new energy station, thereby simplifying the configuration scheme of the active support type SVG supercapacitor, the overall configuration is more flexible, the scalability is stronger, and the charge utilization rate of the supercapacitor is higher, and the overall system solution is more cost-effective. The present invention separates the supercapacitor from the H-bridge power module 1 by adopting a two-stage topology configuration, avoiding the low power utilization problem caused by direct parallel connection, and the two-stage topology structure can accurately control the charging and discharging of the supercapacitor, thereby more efficiently utilizing its energy storage capacity and reducing unnecessary power waste. The two-stage topology structure in the present invention enables the system to have more flexible power control capabilities, and reactive and active power control can be performed in different modules respectively, reducing the load pressure of a single module, and improving the operational reliability of the system. Since the supercapacitor can quickly respond to changes in the frequency of the power grid, it can provide or absorb active power in an instant, and realize the frequency support of the power grid, thereby optimizing the stability of the power grid.

[0130] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc. made within the spirit and principle of the present invention should be included in the protection scope of the present invention.

Claims

1. An H-bridge hybrid active support type SVG system, characterized in that: The H-bridge hybrid active support type SVG system is connected in a three-phase star shape with a chain structure, and each phase is composed of an H-bridge power module and a super capacitor power module connected in series, and both the H-bridge power module and the super capacitor power module are controlled by a power control module; Wherein, the H-bridge power module is used to provide reactive power support for the static VAR generator system and maintain the stability of the grid voltage by adjusting the reactive power injected into the grid; The supercapacitor power module is used to provide active support for the static VAR generator system, so as to realize active frequency support of the static VAR generator system to the power grid; The power control module is used to control the operation of the H-bridge power module and the supercapacitor power module.

2. The H-bridge hybrid active support type SVG system according to claim 1, characterized in that: The power control module includes an active and reactive power calculation module, a phase-locked loop module, a supercapacitor charging and discharging control module, a DC voltage stabilization control module, a reactive power control module, an active power control module and an intra-phase voltage equalization control module; The active and reactive power calculation module is used to calculate the active power command and reactive power command of the power grid; The phase-locked loop module is used to keep the output of the static VAR generator system consistent with the phase of the power grid; The supercapacitor charge and discharge control module is used to control the charge and discharge process of the supercapacitor to avoid overcharging and over-discharging of the supercapacitor; The DC voltage stabilization control module is used to compare the average DC voltage of the H-bridge power module with the preset voltage and then perform proportional-integral regulation to generate the active power regulation amount of the H-bridge power module; The reactive power control module is used to compare the reactive power command with the instantaneous reactive power of the grid and then perform proportional-integral regulation to generate the total reactive power control amount of the static VAR generator system; The active power control module is used to compare the active power instruction with the instantaneous active power of the grid and then perform proportional-integral regulation to generate the active power control amount of the supercapacitor power module; The intra-phase voltage balancing control module is used to distribute the total reactive power control amount of the static VAR generator system to the intra-phase voltage balancing control module as reactive power regulation voltage output based on a preset distribution coefficient.

3. The H-bridge hybrid active support type SVG system according to claim 1, characterized in that: The front stage of the supercapacitor power module is connected to the two bridge arm H-bridge power modules, the rear stage of the supercapacitor power module is staggered in parallel with the DC converter, and the DC output of the H-bridge power module is connected to the input end of the DC converter, and the output end of the DC converter is connected to the supercapacitor module.

4. The H-bridge hybrid active support type SVG system according to claim 2, characterized in that: The DC voltage stabilization control module performs proportional-integral regulation after comparing the average DC voltage of the H-bridge power module with the preset voltage to generate the active power regulation amount of the H-bridge power module, including: The average DC voltage of the H-bridge power module is compared with the DC voltage regulation instruction, and the comparison result is input into the proportional-integral regulator, and the proportional-integral regulator is used to output the active power regulation amplitude; Based on the active power regulation amplitude and the predefined grid phase-locking angle, the active power regulation amount of the H-bridge power module is generated.

5. The H-bridge parallel-parallel active support type SVG system according to claim 4, characterized in that: The calculation formula of the active control amount of the H-bridge power module is: Where U dcm_out Indicates the active power regulation amplitude output by the proportional-integral regulator; u mda 、u mdb 、u mdc They respectively represent the phase active control quantity of each phase H-bridge power module; θ represents the grid phase-locking angle.

6. The H-bridge hybrid active support type SVG system according to claim 2, characterized in that: The reactive power control module performs proportional-integral regulation after comparing the reactive power command with the instantaneous reactive power of the grid to generate the total reactive power control amount of the static VAR generator system, including: Compare the reactive power command with the system reactive power, and input the comparison result into the proportional-integral regulator, and output the reactive power adjustment amplitude through the proportional-integral regulator; Based on the reactive power regulation amplitude, the grid phase-locking angle and the grid amplitude, the total reactive power regulation amount of the static reactive power generator system is generated; Based on the predefined allocation coefficient, the total reactive power control amount of the static VAR generator system is allocated to the intra-phase voltage balancing control module as the reactive power regulation voltage output.

7. The H-bridge hybrid active support type SVG system according to claim 6, characterized in that: The calculation formula of the reactive power regulation voltage output is: In the formula, u mqa 、u mqb and u mqc Both represent reactive power regulated voltage output; U Q_out represents the reactive power regulation amplitude; θ represents the grid phase-locking angle; U m Indicates the power grid amplitude.

8. The H-bridge hybrid active support type SVG system according to claim 2, characterized in that: The active power control module performs proportional-integral regulation after comparing the active power command with the instantaneous active power of the grid, and generates the active power control amount of the supercapacitor power module, including: Based on the change of grid frequency, the primary frequency modulation, inertia response adjustment and supercapacitor charge are calculated in sequence to obtain the active power command; The active power command is compared with the system active power, and the comparison result is input into the proportional-integral regulator, and the active power adjustment amplitude is output through the proportional-integral regulator; Based on the active power regulation amplitude and the grid phase-locking angle, the active power regulation quantity of the supercapacitor power module is generated.

9. The H-bridge parallel-parallel active support type SVG system according to claim 8, characterized in that: The calculation formula of the active power instruction is: Where P ref Indicates the active power reference value, K pc Indicates the supercapacitor voltage loop proportional coefficient; K pi Indicates the integral coefficient of the supercapacitor voltage loop; U cref Indicates the supercapacitor voltage reference value; U c Indicates the supercapacitor voltage value; K f Indicates the active frequency modulation coefficient; P N Indicates rated active power; f N Indicates the rated frequency of the power grid; T j represents the inertia response time constant; df / dt represents the rate of change of the grid frequency; K en It indicates the adjustable charge coefficient of the supercapacitor; Δf indicates the difference between the actual frequency and the rated grid frequency.

10. A control method for an H-bridge parallel-parallel active support type SVG system, used to implement voltage control of the H-bridge parallel-parallel active support type SVG system according to any one of claims 1 to 9, characterized in that: The control method of the H-bridge hybrid active support type SVG system includes: Use H-bridge power modules to provide reactive power support for the static VAR generator system and maintain grid voltage stability by adjusting the reactive power injected into the grid; Use supercapacitor power modules to provide active support for the static VAR generator system, so as to realize the active frequency support of the static VAR generator system to the power grid; Connect the DC converter to the supercapacitor power module and control the DC bus voltage to remain stable when the supercapacitor is charged and discharged; The intra-phase voltage equalization control module is used to control the DC voltage balance between the H-bridge power module and the supercapacitor power module respectively.

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