Hybrid power flow controller and starting method and circuit of cascaded H-bridge current converter of hybrid power flow controller

Abstract

The invention relates to a hybrid power flow controller and a starting method and circuit of a cascaded H-bridge converter of the hybrid power flow controller, and belongs to the technical field of power electronics. The method comprises the steps that the hybrid power flow controller operates in a phase-shifting transformer mode, a phase-shifting transformer selects a proper gear to be connected into a power grid, and the phase voltage peak value of the secondary side of a parallel transformer of the phase shifter reaches a set range; controlling the phase-shifting transformer to charge the cascaded H-bridge current converter until the voltage of the sub-module of the cascaded H-bridge current converter reaches the rated direct-current voltage; the charging circuit is disconnected, the cascaded H-bridge converter is unlocked, the modulation wave of the cascaded H-bridge converter is limited to 0, the cascaded H-bridge converter is controlled to be put into use, and the cascaded H-bridge converter and the phase-shifting transformer are jointly operated; and issuing a constant DC voltage and constant power control unlocking instruction of the cascaded H-bridge converter. The circuit and the hybrid power flow controller comprise a phase-shifting transformer and a switch module, and normal starting of a cascaded H-bridge converter is realized by controlling switching of an electrical switch in the switch module. The cost is reduced, and the economical efficiency is higher.

Description

Technical Field

[0001] The present invention relates to the technical field of power electronics, and in particular to a starting method and a circuit of a hybrid power flow controller and a cascaded H-bridge converter thereof. Background Art

[0002] With the rapid development of new energy, the proportion of new energy access to the power grid is increasing. However, due to the uneven distribution of power grid currents and the limitation of line thermal stability limits, the power grid has experienced transmission bottlenecks and idle power transmission capacity. Therefore, the use of safe, reliable and economical power flow controller equipment can improve the current power grid's power flow control capabilities. Improving the power grid's carrying capacity for new energy is an important direction for upgrading traditional AC power grids to flexible power grids.

[0003] The hybrid power flow controller is a power flow controller that combines a passive phase-shifting transformer with an active cascade H-bridge converter. The hybrid power flow controller uses the advantages of large adjustment capacity of the phase-shifting transformer and fast adjustment speed and high precision of the cascade H-bridge converter to achieve flexible and continuous control of line power flow over a large range. However, the cascade H-bridge converter in this hybrid power flow controller often uses an externally excited power supply when starting. This externally excited starting method requires additional configuration of an externally excited starting circuit. Therefore, this externally excited starting method is costly. Summary of the invention

[0004] The object of the present invention is to provide a hybrid power flow controller and a starting method and circuit of a cascaded H-bridge converter thereof, so as to solve the problem of high cost of the existing separately excited starting method.

[0005] The present invention provides a method for starting a cascaded H-bridge converter based on a hybrid power flow controller to solve the above technical problems, and is implemented according to the following steps: 1) Control the phase-shifting transformer in the hybrid power flow controller to connect to the grid and operate independently, and adjust the gear of the phase-shifting transformer so that the peak value of the secondary side phase voltage of the parallel transformer of the phase-shifting transformer is between the sum of the power-on voltages of each submodule of the cascaded H-bridge converter and the sum of the rated DC voltages of each submodule of the cascaded H-bridge converter; 2) Turn on the charging circuit between the phase-shifting transformer and the cascaded H-bridge converter, and control the phase-shifting transformer to charge the cascaded H-bridge converter until the submodule voltage of the cascaded H-bridge converter reaches the rated DC voltage of the submodule; 3) disconnecting the charging circuit, unlocking the cascaded H-bridge converter and limiting its modulation wave to 0, controlling the cascaded H-bridge converter to be put into operation and operate in conjunction with the phase-shifting transformer; 4) Send the unlocking command of the constant DC voltage and constant power control of the cascaded H-bridge converter.

[0006] Furthermore, the implementation method of step 2) controlling the phase-shifting transformer to charge the cascaded H-bridge converter until the sub-module voltage of the cascaded H-bridge converter reaches the rated DC voltage is: controlling the phase-shifting transformer to charge the cascaded H-bridge converter uncontrolled, and when the sub-module voltage of the cascaded H-bridge converter reaches the power-on voltage of the cascaded H-bridge converter sub-module, gradually cutting off the cascaded H-bridge converter sub-module so that the sub-module voltage of the cascaded H-bridge converter reaches the rated DC voltage.

[0007] Furthermore, when the cascaded H-bridge converter submodules are gradually removed, the calculation formula for the number of removed cascaded H-bridge converter submodules is: In the formula, N c is the number of submodules removed from the cascaded H-bridge converter. U 2p is the peak value of the secondary side phase voltage of the parallel transformer of the phase-shifting transformer, U dc is the rated DC voltage of the cascaded H-bridge converter submodule, N is the number of cascaded H-bridge converter submodules.

[0008] Furthermore, in step 4), if the voltage of the cascaded H-bridge converter submodule does not reach the rated DC voltage, a fixed DC voltage control is first performed, and the voltage setting value of the fixed DC voltage control is the rated DC voltage, and the power setting value is 0. After the voltage of the cascaded H-bridge converter submodule reaches the rated DC voltage, the power setting value is given according to the actual control requirements.

[0009] The beneficial effect of the starting method of the present invention is that the present invention adopts the phase-shifting transformer in the hybrid power flow controller as the starting power supply of the cascade H-bridge converter, and by selecting the appropriate gear of the phase-shifting transformer, controlling the connection relationship between the phase-shifting transformer and the cascade H-bridge converter, and allowing the secondary voltage of the phase-shifting transformer to charge the cascade H-bridge converter uncontrolled, the cascade H-bridge converter is enabled to enter normal startup without affecting the normal operation of the three-phase on-load phase-shifting transformer. This starting method is a self-excitation starting method. Compared with the method of starting the cascade H-bridge converter with an externally excited power supply, there is no need to set up an additional starting circuit, which is low in cost and more economical.

[0010] The present invention provides a starting circuit of a cascaded H-bridge converter based on a hybrid power flow controller to solve the above technical problems, comprising a phase-shifting transformer and a switch module in the hybrid power flow controller, wherein the head end and / or the end end of the secondary winding of the shunt transformer in the phase-shifting transformer is connected to the input end of the switch module, the switch module comprises two output ends, the first output end is grounded, and the second output end is used to connect to the AC side of the cascaded H-bridge converter; the voltage regulating tap contact on the secondary winding of the shunt transformer is connected to the AC side of the cascaded H-bridge converter through the first switch; the switch module is used to ground the head end or the end end of the secondary winding of the shunt transformer when adjusting the peak value of the secondary side phase voltage of the shunt transformer, and is used to connect the head end or the end end of the secondary winding of the shunt transformer to the AC side of the cascaded H-bridge converter when controlling the cascaded H-bridge converter and the phase-shifting transformer to operate jointly, and the first switch is used to close when the cascaded H-bridge converter needs to be charged.

[0011] Further, when the beginning and the end of the secondary winding of the parallel transformer are both connected to the input end of the switch module, the switch module includes a second switch, a third switch, a fourth switch and a fifth switch, the second switch and the third switch are connected in series, the end of the second switch not connected in series serves as the first input end of the switch module to connect the beginning of the secondary winding of the parallel transformer, and the end of the third switch not connected in series serves as the second input end of the switch module to connect the end of the secondary winding of the parallel transformer; the series point between the second switch and the third switch is respectively connected to one end of the fourth switch and the fifth switch, the other end of the fourth switch is grounded as the first output end, and the other end of the fifth switch is used as the second output end for connecting to the AC side of the cascaded H-bridge converter.

[0012] The beneficial effect of the starting circuit of the present invention is that the present invention adopts the phase-shifting transformer in the hybrid power flow controller as the starting power supply of the cascade H-bridge converter, and by selecting the appropriate gear of the phase-shifting transformer, controlling the switching mode of the electrical switch in the switch module, and allowing the secondary voltage of the phase-shifting transformer to charge the cascade H-bridge converter uncontrolled, the cascade H-bridge converter is enabled to enter normal startup without affecting the normal operation of the three-phase on-load phase-shifting transformer. The starting circuit belongs to a self-excited starting circuit. Compared with the method of starting the cascade H-bridge converter with an externally excited power supply, there is no need to set up an additional starting circuit, which is low in cost and more economical.

[0013] The hybrid power flow controller provided by the present invention to solve the above technical problems includes a phase-shifting transformer, a cascaded H-bridge converter and a switch module. The head end and / or the end of the secondary winding of the parallel transformer in the phase-shifting transformer is connected to the input end of the switch module. The switch module includes two output ends, the first output end is grounded, and the second output end is connected to the AC side of the cascaded H-bridge converter; the voltage regulating tap contact on the secondary winding of the parallel transformer is connected to the AC side of the cascaded H-bridge converter through the first switch; the switch module is used to ground the head end or the end of the secondary winding of the parallel transformer when adjusting the peak value of the secondary side phase voltage of the parallel transformer, and is used to connect the head end or the end of the secondary winding of the parallel transformer to the AC side of the cascaded H-bridge converter when controlling the cascaded H-bridge converter and the phase-shifting transformer to operate jointly, and the first switch is used to close when the cascaded H-bridge converter needs to be charged.

[0014] Further, when the beginning and the end of the secondary winding of the parallel transformer are both connected to the input end of the switch module, the switch module includes a second switch, a third switch, a fourth switch and a fifth switch, the second switch and the third switch are connected in series, the end of the second switch not connected in series serves as the first input end of the switch module to connect the beginning of the secondary winding of the parallel transformer, and the end of the third switch not connected in series serves as the second input end of the switch module to connect the end of the secondary winding of the parallel transformer; the series point between the second switch and the third switch is respectively connected to one end of the fourth switch and the fifth switch, the other end of the fourth switch is grounded as the first output end, and the other end of the fifth switch is connected to the AC side of the cascaded H-bridge converter as the second output end.

[0015] The beneficial effects of the hybrid power flow controller of the present invention are as follows: when starting the cascaded H-bridge converter, the hybrid power flow controller of the present invention uses the phase-shifting transformer of the hybrid power flow controller itself as the starting power supply of the cascaded H-bridge converter, and by selecting the appropriate gear of the phase-shifting transformer, controlling the switching mode of the electrical switch in the switch module, and allowing the secondary voltage of the phase-shifting transformer to charge the cascaded H-bridge converter uncontrolled, the cascaded H-bridge converter is enabled to enter normal startup without affecting the normal operation of the three-phase on-load phase-shifting transformer. The hybrid power flow controller of the present invention is a hybrid power flow controller with a self-excited starting circuit. Compared with other hybrid power flow controllers that use an externally excited power supply to start the cascaded H-bridge converter, there is no need to set up an additional starting circuit, so the cost is low and the economy is higher. BRIEF DESCRIPTION OF THE DRAWINGS

[0016] Figure 1 It is a schematic diagram of the topological structure of an existing hybrid power flow controller; Figure 2 is a flow chart of a method for starting a cascaded H-bridge converter based on a hybrid power flow controller according to an embodiment of the present invention; Figure 3 is a schematic diagram of the topological structure of a hybrid power flow controller according to an embodiment of the present invention; Figure 4 It is a circuit structure schematic diagram of a starting circuit of a cascaded H-bridge converter based on a hybrid power flow controller according to an embodiment of the present invention. DETAILED DESCRIPTION

[0017] The specific implementation of the present invention will be further described below in conjunction with the accompanying drawings.

[0018] The basic idea of ​​the present invention is: Figure 1 The hybrid power flow controller shown in the figure no longer uses a separately excited power supply and no longer configures a separately excited starting circuit when starting the cascaded H-bridge converter therein. Instead, the phase-shifting transformer in the hybrid power flow controller is used as a starting power supply, so that the cascaded H-bridge converter can enter normal startup without affecting the normal operation of the phase-shifting transformer.

[0019] Embodiment of a startup method for cascaded H-bridge converter based on hybrid power flow controller Based on the above basic ideas, Figure 2 As shown, the startup method of the cascaded H-bridge converter based on the hybrid power flow controller of the present invention is implemented according to the following steps: 1) Control the phase-shifting transformer in the hybrid power flow controller to connect to the grid and operate independently, and adjust the gear of the phase-shifting transformer so that the peak value of the secondary side phase voltage of the parallel transformer of the phase-shifting transformer is between the sum of the power-on voltages of each sub-module of the cascaded H-bridge converter and the sum of the rated DC voltages of each sub-module of the cascaded H-bridge converter.

[0020] Controlling the phase-shifting transformer in the hybrid power flow controller to connect to the grid and operate independently means operating the hybrid power flow controller in the phase-shifting transformer mode, that is, only the phase-shifting transformer in the hybrid power flow controller is put into operation, and the cascaded H-bridge converter is disconnected from the mobile transformer and is not put into operation. Then, the phase-shifting transformer selects a suitable gear to connect to the grid, so that the peak value of the secondary side phase voltage of the parallel transformer of the phase shifter reaches the range of the following formula: (1) In the formula, U po is the power-on voltage of the cascaded H-bridge converter submodule, U 2p is the peak value of the secondary side phase voltage of the phase shifter parallel transformer, U dc is the rated DC voltage of the cascaded H-bridge converter submodule, and N is the number of the cascaded H-bridge converter submodules.

[0021] 2) Turn on the charging circuit between the phase-shifting transformer and the cascaded H-bridge converter, and control the phase-shifting transformer to charge the cascaded H-bridge converter until the submodule voltage of the cascaded H-bridge converter reaches the rated DC voltage of the submodule.

[0022] As a preferred implementation, in step 2), when controlling the phase-shifting transformer to charge the cascaded H-bridge converter, first control the phase-shifting transformer to charge the cascaded H-bridge converter uncontrolled until the voltage of the cascaded H-bridge converter submodule reaches the power-on voltage, and the uncontrolled charging voltage value of the cascaded H-bridge converter is u c Satisfies formula (2): (2) When the submodule voltage reaches the power-on voltage, the submodule is in a controllable state. At this time, the cascaded H-bridge converter is charged with equalized voltage, and the cascaded H-bridge converter submodules are gradually removed so that the submodule voltage reaches the rated DC voltage. The calculation of the number of submodules removed is shown in formula (3).

[0023] (3) In the formula, N c The number of cascaded H-bridge converter submodules removed.

[0024] 3) Disconnect the charging circuit, unlock the cascaded H-bridge converter and limit its modulation wave to 0, control the cascaded H-bridge converter to be put into operation, and operate in conjunction with the phase-shifting transformer. That is, at this time, the hybrid power flow controller operates in a hybrid operation mode in which the phase-shifting transformer and the cascaded H-bridge converter operate in conjunction with each other.

[0025] 4) Send the unlocking command of the constant DC voltage and constant power control of the cascaded H-bridge converter.

[0026] In step 4), if the voltage of the cascaded H-bridge converter submodule does not reach the rated DC voltage, a fixed DC voltage control is performed first. The voltage setting value of the fixed DC voltage control is the rated DC voltage, and the power setting value is 0. After the voltage of the cascaded H-bridge converter submodule reaches the rated DC voltage, the power setting value is given according to the actual control requirements.

[0027] Implementation of a startup circuit for a cascaded H-bridge converter based on a hybrid power flow controller The startup circuit of the cascade H-bridge converter of the hybrid power flow controller of this embodiment includes a phase-shifting transformer and a switch module in the hybrid power flow controller, and the phase-shifting transformer includes a series transformer and a parallel transformer. The switch module includes an input end and an output end, wherein the head end and / or the end end of the secondary winding of the parallel transformer is connected to the input end of the switch module, and the switch module has two output ends, the first output end is grounded, and the second output end is used to connect the AC side of the cascade H-bridge converter; the voltage-regulating tap contact on the secondary winding of the parallel transformer is connected to the AC side of the cascade H-bridge converter through the first switch; the switch module is used to ground the head end or the end end of the secondary winding of the parallel transformer when adjusting the peak value of the secondary side phase voltage of the parallel transformer, and is used to connect the head end or the end end of the secondary winding of the parallel transformer to the AC side of the cascade H-bridge converter when controlling the cascade H-bridge converter and the phase-shifting transformer to operate in combination, and the first switch is used to close when the cascade H-bridge converter needs to be charged.

[0028] As a preferred implementation mode, Figure 3 As shown, when the beginning and the end of the secondary winding of the parallel transformer are both connected to the input end of the switch module, the switch module has two input ends, and the switch module includes a second switch, a third switch, a fourth switch and a fifth switch. The second switch and the third switch are connected in series, and the end of the second switch not connected in series serves as the first input end of the switch module to connect the beginning of the secondary winding of the parallel transformer, and the end of the third switch not connected in series serves as the second input end of the switch module to connect the end of the secondary winding of the parallel transformer; the series point between the second switch and the third switch is connected to one end of the fourth switch and the fifth switch respectively, the other end of the fourth switch is grounded as the first output end, and the other end of the fifth switch is used as the second output end for connecting to the AC side of the cascaded H-bridge converter.

[0029] Below Figure 3 Taking the startup circuit shown in FIG. 1 as an example, the steps of using the startup circuit to start the cascaded H-bridge converter are further explained: 1) Connect the double-core symmetrical phase-shifting transformer of the hybrid power flow controller to the power grid, close QS1 or QS2, close QS3, open QS4, and open QS5. When QS1 is closed and QS2 is open, the output voltage of the secondary side of the parallel transformer is consistent with the direction of the primary side, and the gear can be adjusted in the positive direction; when QS1 is open and QS2 is closed, the output voltage of the secondary side of the parallel transformer is opposite to the direction of the primary side, and the gear can be adjusted in the negative direction. Therefore, when the head and the end of the secondary winding of the parallel transformer are connected to the input end of the switch module, the phase-shifting transformer can achieve the positive and negative adjustment of the gear. If only the end of the secondary winding of the parallel transformer is connected to the input end of the switch module, only the positive adjustment of the gear can be achieved; if only the head of the secondary winding of the parallel transformer is connected to the input end of the switch module, only the negative adjustment of the gear can be achieved.

[0030] The phase-shifting transformer is adjusted so that the peak value of the secondary side phase voltage of the parallel transformer meets the following conditions: (1) In the formula, U po is the power-on voltage of the cascaded H-bridge converter submodule, U 2p is the peak value of the secondary side phase voltage of the phase shifter parallel transformer, U dc is the rated DC voltage of the cascaded H-bridge converter submodule, and N is the number of the cascaded H-bridge converter submodules.

[0031] 2) When the phase-shifting transformer is adjusted to satisfy equation (1), QS5 is closed and the cascaded H-bridge converter performs uncontrolled charging. Uncontrolled charging voltage value of cascaded H-bridge converter u c As shown in formula (2).

[0032] (2) 3) When the voltage of the cascaded H-bridge converter submodule reaches the power-on voltage, the submodule is in a controllable state, the submodule is charged with equalized voltage, and the cascaded H-bridge converter submodule is gradually removed so that the submodule voltage reaches the rated DC voltage. The number of removed submodules is calculated according to the following formula (3).

[0033] (3) In the formula, N c The number of removed voltage-sharing charging modules of the cascaded H-bridge converter.

[0034] 4) Disconnect QS5, unlock the cascaded H-bridge converter and limit the modulation wave to 0, then close QS4, and after closing QS4, disconnect QS3, and the hybrid phase shifter works in the hybrid operation mode.

[0035] 5) Send the unlocking command of the constant DC voltage and constant power control of the cascaded H-bridge converter.

[0036] If the voltage of the cascaded H-bridge converter submodule does not reach the rated DC voltage, fixed DC voltage control is performed first. The voltage setting value of the fixed DC voltage control is the rated DC voltage, and the power setting value is 0. After the voltage of the cascaded H-bridge converter submodule reaches the rated DC voltage, the power setting value is given according to the actual control requirements.

[0037] A hybrid power flow controller embodiment The hybrid power flow controller of this embodiment includes a phase-shifting transformer, a cascaded H-bridge converter and a switch module. When the cascaded H-bridge converter is started, the phase-shifting transformer and the switch module serve as a starting circuit of the cascaded H-bridge converter. The specific composition structure of the starting circuit and the connection relationship with the cascaded H-bridge converter are detailed in the starting circuit in the starting circuit embodiment of the cascaded H-bridge converter based on the hybrid power flow controller, which will not be described in detail here. Figure 4 The circuit shown only shows the circuit structure when the starting circuit is set on one phase of the three-phase on-load phase-shifting transformer, and the other two phases are not shown. In actual application, the starting circuit will be set on all three phases of the three-phase on-load phase-shifting transformer.

Claims

1. A method for starting a cascaded H-bridge converter based on a hybrid power flow controller, characterized in that: This method is implemented by following the steps below: 1) Control the phase-shifting transformer in the hybrid power flow controller to connect to the grid and operate independently, and adjust the gear of the phase-shifting transformer so that the peak value of the secondary side phase voltage of the parallel transformer of the phase-shifting transformer is between the sum of the power-on voltages of each submodule of the cascaded H-bridge converter and the sum of the rated DC voltages of each submodule of the cascaded H-bridge converter; 2) Turn on the charging circuit between the phase-shifting transformer and the cascaded H-bridge converter, and control the phase-shifting transformer to charge the cascaded H-bridge converter until the submodule voltage of the cascaded H-bridge converter reaches the rated DC voltage of the submodule; 3) disconnecting the charging circuit, unlocking the cascaded H-bridge converter and limiting its modulation wave to 0, controlling the cascaded H-bridge converter to be put into operation and operate in conjunction with the phase-shifting transformer; 4) Send the unlocking command of the constant DC voltage and constant power control of the cascaded H-bridge converter.

2. The method for starting a cascaded H-bridge converter based on a hybrid power flow controller according to claim 1, characterized in that: The implementation method of step 2) controlling the phase-shifting transformer to charge the cascaded H-bridge converter until the submodule voltage of the cascaded H-bridge converter reaches the rated DC voltage is: controlling the phase-shifting transformer to charge the cascaded H-bridge converter uncontrolled, and when the submodule voltage of the cascaded H-bridge converter reaches the power-on voltage of the cascaded H-bridge converter submodule, gradually cutting off the cascaded H-bridge converter submodule so that the submodule voltage of the cascaded H-bridge converter reaches the rated DC voltage.

3. The startup method of the cascaded H-bridge converter based on the hybrid power flow controller according to claim 2, characterized in that: When the cascaded H-bridge converter sub-modules are gradually removed, the calculation formula for the number of cascaded H-bridge converter sub-modules removed is: In the formula, N c is the number of submodules removed from the cascaded H-bridge converter. U 2p is the peak value of the secondary side phase voltage of the parallel transformer of the phase-shifting transformer, U dc is the rated DC voltage of the cascaded H-bridge converter submodule, N is the number of cascaded H-bridge converter submodules.

4. The method for starting a cascaded H-bridge converter based on a hybrid power flow controller according to claim 1, characterized in that: In step 4), if the voltage of the cascaded H-bridge converter submodule does not reach the rated DC voltage, a fixed DC voltage control is first performed, and the voltage setting value of the fixed DC voltage control is the rated DC voltage, and the power setting value is 0. After the voltage of the cascaded H-bridge converter submodule reaches the rated DC voltage, the power setting value is given according to the actual control requirements.

5. A startup circuit of a cascaded H-bridge converter based on a hybrid power flow controller, characterized in that: The circuit includes a phase-shifting transformer and a switch module in a hybrid power flow controller. The head end and / or the end of the secondary winding of the parallel transformer in the phase-shifting transformer is connected to the input end of the switch module. The switch module includes two output ends, the first output end is grounded, and the second output end is used to connect to the AC side of the cascaded H-bridge converter; the voltage-regulating tap contact on the secondary winding of the parallel transformer is connected to the AC side of the cascaded H-bridge converter through a first switch; the switch module is used to ground the head end or the end of the secondary winding of the parallel transformer when adjusting the peak value of the secondary side phase voltage of the parallel transformer, and is used to connect the head end or the end of the secondary winding of the parallel transformer to the AC side of the cascaded H-bridge converter when controlling the cascaded H-bridge converter and the phase-shifting transformer to operate jointly, and the first switch is used to close when the cascaded H-bridge converter needs to be charged.

6. The starting circuit of the cascaded H-bridge converter based on the hybrid power flow controller according to claim 5, characterized in that: When the head end and the end of the secondary winding of the parallel transformer are both connected to the input end of the switch module, the switch module includes a second switch, a third switch, a fourth switch and a fifth switch, the second switch and the third switch are connected in series, the end of the second switch not connected in series is used as the first input end of the switch module to connect the head end of the secondary winding of the parallel transformer, and the end of the third switch not connected in series is used as the second input end of the switch module to connect the end of the secondary winding of the parallel transformer; the series point between the second switch and the third switch is respectively connected to one end of the fourth switch and the fifth switch, the other end of the fourth switch is grounded as the first output end, and the other end of the fifth switch is used as the second output end for connecting to the AC side of the cascaded H-bridge converter.

7. A hybrid power flow controller, characterized in that: The hybrid power flow controller includes a phase-shifting transformer, a cascaded H-bridge converter and a switch module. The head end and / or the end of the secondary winding of the parallel transformer in the phase-shifting transformer is connected to the input end of the switch module. The switch module includes two output ends, the first output end is grounded, and the second output end is connected to the AC side of the cascaded H-bridge converter; the voltage regulating tap contact on the secondary winding of the parallel transformer is connected to the AC side of the cascaded H-bridge converter through a first switch; the switch module is used to ground the head end or the end of the secondary winding of the parallel transformer when adjusting the peak value of the secondary side phase voltage of the parallel transformer, and is used to connect the head end or the end of the secondary winding of the parallel transformer to the AC side of the cascaded H-bridge converter when controlling the cascaded H-bridge converter and the phase-shifting transformer to operate jointly, and the first switch is used to close when the cascaded H-bridge converter needs to be charged.

8. The hybrid power flow controller according to claim 7, characterized in that: When the head end and the end of the secondary winding of the parallel transformer are both connected to the input end of the switch module, the switch module includes a second switch, a third switch, a fourth switch and a fifth switch, the second switch and the third switch are connected in series, the end of the second switch not connected in series is used as the first input end of the switch module to connect the head end of the secondary winding of the parallel transformer, and the end of the third switch not connected in series is used as the second input end of the switch module to connect the end of the secondary winding of the parallel transformer; the series point between the second switch and the third switch is connected to one end of the fourth switch and the fifth switch respectively, the other end of the fourth switch is grounded as the first output end, and the other end of the fifth switch is connected to the AC side of the cascaded H-bridge converter as the second output end.

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