A method for transient control of module voltage in a wideband and wide-voltage device

Abstract

This invention discloses a method for transient control of module voltage in a wideband and wide-voltage device. The wideband and wide-voltage device of this invention includes an input transformer, a converter valve, and an output transformer. The converter valve adopts a three-phase independent configuration, with each phase consisting of multiple cascaded dual H-bridge modules. Each dual H-bridge module includes an active front-end H-bridge and an inverter H-bridge. The control methods for the active front-end H-bridge and the inverter H-bridge are improved and optimized: the active front-end H-bridge employs a constant DC voltage control strategy to achieve real-time balance of the module's DC side voltage; the inverter H-bridge employs a carrier phase-shift modulation strategy. By simultaneously controlling the active front-end H-bridge and the inverter H-bridge, this invention promotes the rapid dissipation of voltage accumulation within the module, effectively suppresses voltage rise, and rapidly suppresses voltage fluctuations under transient conditions, preventing overvoltage damage and ensuring the safe and stable operation of the module under transient conditions.

Description

Technical Field

[0001] This invention belongs to the field of power electronic power system technology, and specifically relates to a module voltage transient control strategy for a wideband and wide voltage device. Background Technology

[0002] Currently, power electronic equipment covers categories such as power frequency AC, DC, and low frequency AC. In the future, the application of power electronic equipment such as medium frequency AC will also be a trend. The wideband and wide voltage device is an experimental testing device with low frequency, power frequency, medium frequency AC, and DC multiplexing functions, and has been put into operation in some flexible low frequency transmission demonstration projects.

[0003] In flexible low-frequency power transmission demonstration projects, low-frequency wind turbines, modular multilevel matrix converters (M3Cs), and wideband wide-voltage devices form a three-terminal low-frequency interconnected system on the low-frequency side. If the M3C is blocked, the wind turbine's power can only be transmitted to the grid through the wideband wide-voltage device, requiring the wideband side of the device to switch from constant active and reactive power control to constant voltage and frequency control. When the wind turbine's power switches instantaneously, the delay in the controller's action can easily lead to overvoltage in the module, and in severe cases, even damage the module. Summary of the Invention

[0004] To address the problems existing in the prior art, this invention provides a method for transient control of module voltage in a wideband and wide-voltage device. By simultaneously controlling the active front-end H-bridge and the inverter H-bridge, it promotes the rapid dissipation of voltage accumulation within the module, effectively suppressing voltage rise and ensuring the safe and stable operation of the module under transient conditions.

[0005] Therefore, the present invention adopts the following technical solution: a module voltage transient control method for a wideband wide-voltage device, wherein the wideband wide-voltage device includes an input transformer, a converter valve, and an output transformer; one end of the input transformer is connected to an input system, and the other end is connected to one end of the converter valve, the other end of the converter valve is connected to one end of the output transformer, and the other end of the output transformer is connected to a wideband AC system; the converter valve adopts a three-phase independent configuration, each phase being composed of multiple cascaded dual H-bridge modules, wherein the dual H-bridge module includes an active front-end H-bridge and an inverter H-bridge; the module voltage transient control method includes:

[0006] Meanwhile, the control methods of the active front-end H-bridge and the inverter H-bridge are improved and optimized: the active front-end H-bridge adopts a constant DC voltage control strategy to achieve real-time balance of the DC side voltage of the module; the inverter H-bridge adopts a carrier phase-shift modulation strategy.

[0007] Furthermore, the constant DC voltage control strategy is as follows: DC voltage reference value U dcr DC voltage measurement value U dcmThe difference is calculated, and the difference is compared with a high-frequency triangular modulation wave after passing through a PI controller to generate a trigger pulse signal for the IGBT in the active front-end H-bridge, thereby realizing constant DC voltage control of the active front-end H-bridge.

[0008] Furthermore, the proportional coefficient of the PI controller is K. p The integral coefficient is T i ; proportionality coefficient K p and integral coefficient T i The derivative dU with the measured DC voltage value dcm / dt, DC voltage measurement value U dcm The relevant functions are defined as follows:

[0009] 1) When the DC voltage begins to change during the transient process until dU dcm When / dt reaches its first zero-crossing point, K p and T i The value of K is determined using the following formula, where K pr The proportionality coefficient is the rated proportionality coefficient, k1, k2, and k3 are proportionality constants, and T is the proportionality coefficient. ir t1, t2, and t3 are the rated integral coefficients, t1, t2, and t3 are proportional constants, D1 is the voltage differential setting coefficient, and M1 is the voltage deviation setting coefficient.

[0010]

[0011]

[0012] 2) When the DC voltage dU is in a transient process dcm After / dt reaches its first zero-crossing point, K p Restore to K pr T i Restore to T ir .

[0013] Furthermore, the K mentioned pr and T ir It is determined based on the stable operation of the wideband and wideband voltage device under steady-state conditions.

[0014] Furthermore, the K mentioned above pr Take values ​​from 1 to 10, T ir Take values ​​from 0.01 to 0.05, k1, k2, and k3 are 2, 5, and 10 respectively, t1, t2, and t3 are 0.5, 0.2, and 0.1 respectively, and D1 is U dcr / 50ms, M1 is 0.3U dcr .

[0015] Furthermore, K p and T iAs a continuous quantity rather than a sudden change, the transition time from the original parameter to the new parameter is 10ms when the parameter changes, and a linear transition method is used.

[0016] Furthermore, the inverter H-bridge, based on the original wideband AC side voltage-frequency control, adds a DC voltage control module to the AC voltage control section to form AC voltage-DC voltage slope control, as detailed below:

[0017] wideband AC voltage command value U nr AC voltage measurement value U nm The difference, and the module DC voltage reference value U dcr and the average DC voltage U of all modules dcav The difference is multiplied by the coefficient d, summed, and then input into the original AC voltage-frequency controlled PI controller; where U dcav The result is obtained by dividing the sum of the DC voltages measured by all modules by the total number of modules.

[0018] Furthermore, the coefficient d is taken as 0.1 to 0.15.

[0019] Furthermore, the frequency of the input system is the power frequency, with a value of 50Hz or 60Hz; the frequency range of the broadband AC system is 15Hz to 200Hz.

[0020] Furthermore, the input transformer is a multi-winding transformer; the converter valve, in addition to the electromagnetic coupling with the multi-winding transformer, also has two output ports per phase, one upper and one lower. The upper output port is connected to the corresponding phase of the output transformer, and the lower output port is directly connected to the lower output ports of other phases; the dual H-bridge module also includes a filter unit and a capacitor. The filter unit is composed of an inductor. The active front-end H-bridge is composed of four IGBTs and their anti-parallel diodes, and the inverter H-bridge is composed of four IGBTs and their anti-parallel diodes. One secondary side of the multi-winding transformer is connected to a filter unit in a dual H-bridge module, and then the active front-end H-bridge, capacitor, and inverter H-bridge are connected in sequence.

[0021] Compared with the prior art, the present invention has the following beneficial effects:

[0022] This invention promotes the rapid dissipation of voltage accumulation within the module by simultaneously controlling the active front-end H-bridge and the inverter H-bridge. It can effectively suppress the rise of module voltage and achieve rapid suppression of module voltage fluctuations under transient conditions, preventing overvoltage damage and ensuring the safe and stable operation of the module under transient conditions. Attached Figure Description

[0023] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0024] Figure 1 This is a schematic diagram of the structure of the broadband and wide voltage device of the present invention;

[0025] Figure 2 This is a schematic diagram of the topology of the dual H-bridge module of the present invention;

[0026] Figure 3 This is a schematic diagram of the control of the active front-end H-bridge of the present invention;

[0027] Figure 4 This is a schematic diagram of the control of the inverter H-bridge of the present invention. Detailed Implementation

[0028] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0029] Figure 1 The diagram shows the structure of a wideband AC system. As can be seen, it includes an input transformer, a converter valve, and an output transformer. One end of the input transformer is connected to the input system, and the other end is connected to one end of the converter valve. The other end of the converter valve is connected to one end of the output transformer, and the other end of the output transformer is connected to the wideband AC system. The input transformer is a multi-winding transformer. The frequency of the input system is the power frequency, typically 50Hz or 60Hz. The frequency range of the wideband AC system is wider, such as 15Hz to 200Hz.

[0030] The converter valve adopts a three-phase independent design, with each phase consisting of multiple cascaded double H-bridge modules. In addition to the electromagnetic coupling with the multi-winding transformer, each phase also has two output ports: the upper output port is connected to the corresponding phase of the output transformer, and the lower output port is directly connected to the lower output ports of other phases.

[0031] Figure 2The diagram shows the topology of a dual H-bridge module. As can be seen, the module contains a filter unit, an active front-end H-bridge, capacitors, and an inverter H-bridge. The filter unit is composed of inductors, the active front-end H-bridge consists of four IGBTs and their anti-parallel diodes, and the inverter H-bridge also consists of four IGBTs and their anti-parallel diodes. One secondary winding of the multi-winding transformer is connected to the filter unit within a dual H-bridge module, and then sequentially connected to the active front-end H-bridge, capacitors, and inverter H-bridge.

[0032] The transient control method for module voltage of wideband and widevoltage devices requires simultaneous improvement and optimization of the control strategies of the active front-end H-bridge and the inverter H-bridge: the active front-end H-bridge adopts a constant DC voltage control strategy to achieve real-time balance of the DC side voltage of the module; the inverter H-bridge adopts a carrier phase-shift modulation strategy.

[0033] Figure 3 The diagram shows a constant DC voltage control scheme for an active front-end H-bridge. As can be seen from the diagram, the control strategy is as follows: DC voltage reference value U... dcr DC voltage measurement value U dcm The difference is calculated, and after passing through a PI controller, it is compared with a high-frequency triangular modulated wave to generate trigger pulse signals for the four IGBTs in the active front-end H-bridge, thus achieving constant DC voltage control of the active front-end H-bridge. Within the PI controller, the proportional coefficient is Kp, and the integral coefficient is Ti; both are derivatives of the measured DC voltage dU. dcm / dt, DC voltage measurement value U dcm The relevant functions are defined as follows:

[0034] (1) When the DC voltage begins to change during the transient process until dU dcm When / dt reaches its first zero crossing, Kp and Ti are determined using the following formula, where K pr The proportionality coefficient is the rated proportionality coefficient, k1, k2, and k3 are proportionality constants, and T is the proportionality coefficient. ir t1, t2, and t3 are the rated integral coefficients, t1, t2, and t3 are proportional constants, D1 is the voltage differential setting coefficient, and M1 is the voltage deviation setting coefficient.

[0035]

[0036]

[0037] (2) When the DC voltage dU is in the transient process dcm After / dt reaches its first zero crossing, Kp recovers to K. pr T i Restore to T ir .

[0038] K pr and T irGenerally, K is determined based on the stable operation of the wideband and wideband voltage device under steady-state conditions. pr A value of 1 to 10 can be used, T ir The range can be 0.01 to 0.05. k1, k2, and k3 are 2, 5, and 10 respectively, and t1, t2, and t3 are 0.5, 0.2, and 0.1 respectively. D1 is U dcr / 50ms, M1 is 0.3U dcr Kp and T i As a continuous quantity rather than a sudden change, the transition time from the original parameter to the new parameter is 10ms when the parameter changes, and a linear transition method is used.

[0039] Figure 4 The diagram shows the control schematic of an inverter H-bridge. Based on the original wideband AC side voltage-frequency control, the inverter H-bridge adds a DC voltage control module to the AC voltage control section, forming AC voltage-DC voltage slope control. As shown in the figure, the wideband AC voltage command value U... nr AC voltage measurement value U nm The difference, and the module DC voltage reference value U dcr and the average DC voltage U of all modules dcav The difference is multiplied by a coefficient d, summed, and then input into the original AC voltage-frequency controlled PI controller. Where U dcav The value is obtained by summing the DC voltages measured from all modules and dividing by the total number of modules. The coefficient d should generally not be too large, as an excessively large value can easily cause severe overvoltage or undervoltage in a broadband AC system. Generally, d can be taken as 0.1 to 0.15.

[0040] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, and not to limit them; although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some of the technical features; and these modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the spirit and scope of the technical solutions of the embodiments of the present invention.

Claims

1. A module voltage transient control method for a wide-bandwidth voltage device, the wide-bandwidth voltage device comprising an input transformer, a converter valve and an output transformer; one end of the input transformer is connected to an input system, the other end is connected to one end of the converter valve, the other end of the converter valve is connected to one end of the output transformer, the other end of the output transformer is connected to a wide-bandwidth alternating current system; the converter valve adopts a three-phase independent mode, each phase is composed of a plurality of double-H bridge modules in cascade, the double-H bridge module comprises an active front-end H bridge and an inverter H bridge; characterized in that, The module voltage transient control method comprises: The control method of the active front-end H-bridge and the inverter H-bridge is improved and optimized: the active front-end H-bridge adopts a constant DC voltage control strategy to realize real-time balancing of the module DC side voltage; and the inverter H-bridge adopts a carrier phase-shifted modulation strategy. The direct current voltage control strategy is as follows: a direct current voltage reference value U dcr and a direct current voltage measurement value U dcm The difference is compared with a high-frequency triangular modulation wave after a PI controller, a trigger pulse signal of an IGBT in the active front-end H-bridge is generated, and the direct current voltage control of the active front-end H-bridge is realized. The PI controller, the proportional coefficient is K p , the integral coefficient is T i ; the proportional coefficient K p and the integral coefficient T i is the function related to the differential of the direct current voltage measurement value dU dcm / dt , the direct current voltage measurement value U dcm , and the specific definition is as follows: 1) when the direct voltage starts to change during the transient process until dU dcm / dt the first zero crossing occurs, K p and T i is determined using the following equation, wherein K pr is a rated proportional factor, k 1, k 2 and k 3 are proportional constants, T ir is a rated integral factor, t 1, t 2 and t 3 are proportional constants, D 1 is a voltage differential setting factor, M 1 is a voltage deviation setting factor; 2) when the direct voltage is in the transient process dU dcm / dt after the first zero-crossing, K p recovered to K pr , T i recovered to T ir .

2. The method of claim 1, wherein, The K pr And T ir According to the steady state of the wide frequency and wide voltage device stable operation to determine.

3. The method of claim 2, wherein, The K pr Take 1~10, T ir Take 0.01~0.05, k 1, k 2 and k 3 are 2, 5 and 10, t 1, t 2 and t 3 are 0.5, 0.2 and 0.1, D 1 is U dcr / 50ms, M 1 is 0.3 U dcr .

4. The method of claim 1, wherein, K p and T i The parameters are continuous variables, not discrete variables. When the parameters change, the transition time from the old parameters to the new parameters is 10 ms, and the transition is linear.

5. The method of claim 1, wherein, The inverter H-bridge adds a module DC voltage control in the original wide-frequency AC side voltage-frequency control to form an AC voltage-DC voltage slope control, and the specific process is as follows: The difference between the wideband AC voltage command value U nr and the AC voltage measurement value U nm , and the difference between the module DC voltage reference value U dcr and the average value of all module DC voltages U dcav multiplied by a coefficient d, are added together and then input into a PI controller of the original AC voltage-frequency control; wherein U dcav is obtained by dividing the sum of all module DC voltage measurements by the total number of modules.

6. The method of module voltage transient control of claim 5, wherein, The coefficient d is 0.1-0.

15.

7. The method of claim 1, wherein, The frequency of the input system is a power frequency, and the value is 50Hz or 60Hz; and the frequency range of the wide-frequency AC system is 15Hz-200Hz.

8. The method of module voltage transient control of claim 1, wherein, The input transformer is a multi-winding transformer; the converter valve further comprises upper and lower output ports in addition to the electromagnetic coupling relationship with the multi-winding transformer, wherein the upper output port is connected with a corresponding phase of the output transformer, and the lower output port is directly connected with the lower output port of another phase; the double-H-bridge module further comprises a filter unit and a capacitor, the filter unit is composed of an inductor, the active front-end H-bridge is composed of four IGBTs and their anti-parallel diodes, the inverter H-bridge is composed of four IGBTs and their anti-parallel diodes, one secondary side of the multi-winding transformer is connected with the filter unit in one double-H-bridge module, and then the active front-end H-bridge, the capacitor and the inverter H-bridge are sequentially connected.

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