Series voltage division type non-isolated power flow controller, control method and related device

Abstract

The invention discloses a series voltage-dividing type non-isolated power flow controller, a control method and a related device, the power flow controller comprises a voltage-dividing capacitor, a first voltage source type converter and a second voltage source type converter, and the voltage-dividing capacitor and the first voltage source type converter are connected in series and then are connected with a first alternating current power grid in parallel; the second voltage source type converter is connected in series with a second alternating current power grid; and the direct current bus in the first voltage source type converter and the direct current bus in the second voltage source type converter are the same direct current bus. According to the invention, voltage division is carried out through the voltage division capacitor, the voltage of the AC side of the first voltage source type converter can be reduced, the DC bus voltage is reduced, the modulation ratio is increased when the DC bus voltage is reduced, and thus harmonic waves are reduced; and power transmission under different power factor angles can be realized under the condition that the amplitudes and phases of the power grids at the two ends are not equal.

Description

TECHNICAL FIELD

[0001] The application relates to a series voltage division type non-isolated power flow controller, a control method and related devices, and belongs to the technical field of electric power. BACKGROUND

[0002] In a new power system, a large number of distributed power sources are connected to a distribution network, and the distribution network becomes active, active, and bidirectional. The flexible interconnection technology combines power electronic flexible control technology with optimal design of the distribution network framework, can provide fast and accurate active and reactive power control, power loss support and power quality management functions between distribution network lines and between transformer areas, and provides an effective technical means for tapping the power supply potential of the distribution network and improving power supply reliability. Therefore, the low-voltage distribution network flexible interconnection network multi-level access to large-scale distributed power sources can maximize the power supply potential of distributed renewable energy sources, effectively improve the reliability, economy and environmental protection of the overall operation of the distribution system, and is an important technical route to solve the high proportion of distributed power sources in the distribution network. The existing low-voltage transformer area flexible interconnection equipment directly takes power from the power grid using a half-bridge or full-bridge topology structure, and has the problems of high DC bus voltage and large transmission current harmonic. SUMMARY

[0003] The application provides a series voltage division type non-isolated power flow controller, a control method and related devices, which solves the problems disclosed in the background.

[0004] According to one aspect of the application, a series voltage division type non-isolated power flow controller is provided, the power flow controller is arranged between a first alternating current power grid and a second alternating current power grid, the power flow controller comprises a voltage division capacitor, a first voltage source type converter and a second voltage source type converter, the voltage division capacitor and the first voltage source type converter are connected in series and connected in parallel with the first alternating current power grid, the second voltage source type converter is connected in series with the second alternating current power grid, and a direct current bus inside the first voltage source type converter and a direct current bus inside the second voltage source type converter are the same direct current bus.

[0005] Further, the first voltage source type converter comprises a first LC filter circuit, a full-bridge circuit and a direct current bus, the full-bridge circuit and the direct current bus are connected in parallel, the midpoint of the first bridge arm and the midpoint of the second bridge arm of the full-bridge circuit are connected to the two ends of the first LC filter circuit, and the filter capacitor in the first LC filter circuit and the voltage division capacitor are connected in series and connected in parallel with the first alternating current power grid.

[0006] Further, the second voltage source type converter comprises a second LC filter circuit, and a half-bridge circuit and a direct current bus connected in parallel, and the midpoint of the bridge arm in the half-bridge circuit and the midpoint of the direct current bus are connected in series with the second alternating current power grid through the second LC filter circuit.

[0007] According to one aspect of the present application, a control method of a series voltage division type non-isolated power flow controller is provided, the power flow controller being the power flow controller described above, and the method comprising: For the first voltage source converter, a reference value of a filter inductor current in the first voltage source converter is calculated according to the first AC grid voltage, a preset value of the DC bus voltage and a DC bus capacitor voltage, and a control signal of a switching tube in the first voltage source converter is generated according to the reference value and an actual value of the filter inductor current in the first voltage source converter; For the second voltage source converter, a reference value of a filter inductor current in the second voltage source converter is calculated according to the second AC grid voltage, a grid-side current on the second AC grid side, a preset value of a second AC grid transmission active power and a preset value of a second AC grid transmission reactive power, and a control signal of a switching tube in the second voltage source converter is generated according to the reference value and an actual value of the filter inductor current in the second voltage source converter.

[0008] Further, the reference value of the filter inductor current in the first voltage source converter is calculated according to the first AC grid voltage, the preset value of the DC bus voltage and the DC bus capacitor voltage, comprising: a phase of the first AC grid voltage is obtained by phase locking the first AC grid voltage; a difference between the preset value of the DC bus voltage and the DC bus capacitor voltage is calculated, and a proportional integral control is performed on the difference; a result of the proportional integral control is multiplied by the phase of the first AC grid voltage to obtain the reference value of the filter inductor current in the first voltage source converter.

[0009] Further, the reference value of the filter inductor current in the second voltage source converter is calculated according to the second AC grid voltage, the grid-side current on the second AC grid side, the preset value of the second AC grid transmission active power and the preset value of the second AC grid transmission reactive power, comprising: a modulus value S tran and a phase angle φ tran of a second AC grid transmission complex power are calculated according to the second AC grid voltage U G2 and the grid-side current I G2 on the second AC grid side; a modulus value S set and a phase angle φ set of a second AC grid transmission complex power preset value are calculated according to the preset value P set of the second AC grid transmission active power and the preset value Q set of the second AC grid transmission reactive power; the modulus value S tran is calculated according to the modulus value S seta modulus value difference, and performing proportional-integral control on the modulus value difference; calculating a phase angle φ tran a phase angle difference, and performing proportional-integral control on the phase angle difference; set a phase angle difference, and performing proportional-integral control on the phase angle difference; multiplying the proportional-integral control result of the modulus value difference and the proportional-integral control result of the phase angle difference to obtain a reference value of the filter inductor current in the second voltage source type converter.

[0010] Further, according to the reference value and the actual value of the filter inductor current in the first voltage source type converter, a control signal of the switching tube in the first voltage source type converter is generated, including: calculating a difference between the reference value and the actual value of the filter inductor current in the first voltage source type converter, and sequentially performing proportional-resonance control and pulse width modulation on the difference between the reference value and the actual value of the filter inductor current in the first voltage source type converter to obtain the control signal of the switching tube in the first voltage source type converter; According to the reference value and the actual value of the filter inductor current in the second voltage source type converter, a control signal of the switching tube in the second voltage source type converter is generated, including: calculating a difference between the reference value and the actual value of the filter inductor current in the second voltage source type converter, and sequentially performing proportional-resonance control and pulse width modulation on the difference between the reference value and the actual value of the filter inductor current in the second voltage source type converter to obtain the control signal of the switching tube in the second voltage source type converter.

[0011] According to an aspect of the present application, a control device of a series voltage division type non-isolated power flow controller is provided, the power flow controller being the power flow controller described above, and the device comprising: a first control module, configured to calculate, for the first voltage source type converter, a reference value of a filter inductor current according to a first alternating current grid voltage, a preset value of a direct current bus voltage and a direct current bus capacitor voltage, and generate a control signal of a switching tube in the first voltage source type converter according to the reference value and an actual value of the filter inductor current in the first voltage source type converter; a second control module, configured to calculate, for the second voltage source type converter, a reference value of a filter inductor current according to a second alternating current grid voltage, a grid side current on a second alternating current grid side, a preset value of a second alternating current grid transmission active power and a preset value of a second alternating current grid transmission reactive power, and generate a control signal of a switching tube in the second voltage source type converter according to the reference value and an actual value of the filter inductor current in the second voltage source type converter.

[0012] According to another aspect of the present application, a computer-readable storage medium is provided, the computer-readable storage medium storing one or more programs including instructions which, when executed by a computing device, cause the computing device to perform the control method of the series voltage division type non-isolated power flow controller.

[0013] According to another aspect of the present application, a computer device is provided, comprising one or more processors, and one or more memories, one or more programs being stored in the one or more memories and configured to be executed by the one or more processors, the one or more programs including instructions for performing the control method of the series voltage division type non-isolated power flow controller.

[0014] The present application has the following beneficial effects: the present application can reduce the voltage on the AC side of the first voltage source type converter through voltage division by the voltage division capacitor, thereby reducing the DC bus voltage, and the increased modulation ratio caused by the reduced DC bus voltage can further reduce the harmonics; and the first voltage source type converter of the present application is connected in parallel with the first AC power grid to form a rectifier circuit, and the second voltage source type converter is connected in series with the second AC power grid to form an inverter circuit, the voltage on the DC bus and the output end is controlled through the control of the switching tube in the voltage source type converter, the control of the power transmission is realized, and the power transmission under different power factor angles can be realized in the case that the amplitudes and phases of the two end power grids are not equal. BRIEF DESCRIPTION OF DRAWINGS

[0015] Figure 1 the structure block diagram of the series voltage division type non-isolated power flow controller; Figure 2 the structure schematic diagram of the series voltage division type non-isolated power flow controller; Figure 3 the principle diagram of the control method of the series voltage division type non-isolated power flow controller; Figure 4 the block diagram of the control device of the series voltage division type non-isolated power flow controller. DETAILED DESCRIPTION

[0016] The technical solutions in the embodiments of the present application will be clearly and completely described below with reference to the drawings in the embodiments of the present application. Obviously, the described embodiments are only a part of the embodiments of the present application, rather than all the embodiments of the present application. The following description of at least one exemplary embodiment is actually only illustrative, but not as any limitation on the present application and its application or use. Based on the embodiments in the present application, all other embodiments obtained by those of ordinary skill in the art without creative labor fall within the scope of the present application.

[0017] Unless otherwise specifically stated, the relative arrangement of parts and steps, numerical expressions, and numerical values set forth in the various examples disclosed herein are only to be used for descriptive purposes and do not limit the scope of the present application.

[0018] It should be understood, of course, that the dimensions of the various elements shown in the figures are chosen primarily to facilitate recognition of the various components, and that actual

[0019] Techniques, methods, and apparatus known to those of ordinary skill in the relevant art can not be discussed in detail herein. However, where appropriate, such techniques, methods, and apparatus can be considered part of the present disclosure.

[0020] In all of the compositions and methods shown and discussed herein, any specific numerical value, as explicitly stated or as implied by its context, should be interpreted as merely an example for the purpose of illustration and not as a limitation. Thus, other examples of the example embodiments can have different values.

[0021] It should be noted that like reference numerals in the various figures indicate like elements, and that, unless specifically stated otherwise, a description of an item in one figure can also apply to the same item in another figure.

[0022] In addition, in the description of the embodiments of the present application, the terms "first", "second", and the like are used only to distinguish one item from another, and do not imply or suggest a relative importance. Thus, the features defined with "first", "second" can explicitly or implicitly include one or more features.

[0023] A voltage-source converter (VSC) is a power electronic device that can convert DC voltage to AC voltage. By controlling the voltage and frequency on the AC side, VSC can achieve flexible power regulation and grid control functions. The core components of VSC include fully controlled power electronic devices such as insulated gate bipolar transistors or gate turn-off thyristors, which can switch at high frequencies to achieve DC to AC conversion. VSC is commonly used in power system stability control, renewable energy grid connection, smart grid, etc.

[0024] The embodiments of the present application provide a series voltage division type non-isolated power flow controller based on a voltage source converter, aiming to build a power flow controller by two series voltage source converters, so as to solve the problems of high DC bus voltage and large transmission current harmonics of the existing structure.

[0025] Referring to Figure 1 , Figure 1is a structure block diagram of a series voltage division type non-isolated power flow controller provided by the embodiment of the application, the power flow controller is used for connecting two AC power grids, can realize bidirectional scheduling of energy of the two AC power grids, the two AC power grids can be defined as a first AC power grid and a second AC power grid respectively, the power flow controller can at least include a voltage division capacitor, a first voltage source type converter and a second voltage source type converter, the voltage division capacitor and the first voltage source type converter are connected in series and are connected in parallel with the first AC power grid, the second voltage source type converter is connected in series with the second AC power grid, a DC bus inside the first voltage source type converter and a DC bus inside the second voltage source type converter are the same DC bus.

[0026] It should be noted that the voltage source type converter mainly includes an LC filter circuit, a full-controlled power electronic device and a DC bus, wherein the full-controlled power electronic device can adopt a full-bridge circuit or a half-bridge circuit.

[0027] In some embodiments, the first voltage source type converter can adopt a full-bridge circuit, and the second voltage source type converter can adopt a half-bridge circuit, and the specific structure is that the first voltage source type converter includes a first LC filter circuit, a full-bridge circuit and a DC bus, the full-bridge circuit and the DC bus are connected in parallel, the midpoint of a first bridge arm and the midpoint of a second bridge arm of the full-bridge circuit are connected with the two ends of the first LC filter circuit, and a filter capacitor in the first LC filter circuit and a voltage division capacitor are connected in series and connected in parallel with the first AC power grid; the second voltage source type converter includes a second LC filter circuit, and a half-bridge circuit and a DC bus connected in parallel, and the midpoint of a bridge arm in the half-bridge circuit and the midpoint of the DC bus are connected in series with the second AC power grid through the second LC filter circuit.

[0028] Taking the first voltage source type converter and the second voltage source type converter with the above structure as an example, the specific structure of the power flow controller can be referred to Figure 2 , wherein G1 and G2 are the first AC power grid and the second AC power grid respectively, T a1 ~ T a4 are all switching tubes, T a1 and T a2 constitute a first bridge arm of the full-bridge circuit of the first voltage source type converter, T a3 and T a4 constitute a second bridge arm of the full-bridge circuit of the first voltage source type converter, C dc1 and C dc2 are both DC bus capacitors, C dc1 and C dc2 have equal voltage amplitudes (so that the voltage on the DC side is equal whether the upper tube is turned on or the lower tube is turned on, which is half of the DC bus voltage), C P and L P are a filter capacitor and a filter inductor respectively, C div is a voltage division capacitor, and C Pand L P The first LC filter circuit constitutes the first voltage source type converter, C P and L div are connected in series and are connected in parallel with G1; T b1 ~ T b2 are all switching tubes, T b1 and T b2 The bridge arm constitutes the second voltage source type converter half-bridge circuit, the second voltage source type converter and the first voltage source type converter share the same DC bus, C S and L S are filter capacitor and filter inductor respectively, C S and L S The second LC filter circuit constitutes the second voltage source type converter, and the second voltage source type converter is connected in series with G2.

[0029] Figure 2 In the structure, the first voltage source type converter AC side voltage phase is consistent with the G1 voltage, which can be expressed as: ; In the formula, is the voltage of C P , is the G1 voltage, is the capacitance value of C P and C div .

[0030] Because the first voltage source type converter adopts full-bridge circuit, the minimum value of the DC bus voltage is .

[0031] The modulation ratio of the second voltage source type converter can be expressed as: ; In the formula, M S is the modulation ratio, and U DC is the DC bus voltage.

[0032] Of course, the above-mentioned first voltage source type converter and second voltage source type converter can also all adopt full-bridge, or all adopt half-bridge, or the first voltage source type converter adopts half-bridge and the second voltage source type converter adopts full-bridge.

[0033] Because of the existence of the voltage dividing capacitor, the AC side voltage of the first voltage source converter is C PThe voltage on the DC bus capacitor is smaller than the G1 voltage without the voltage dividing capacitor, and thus the minimum voltage on the DC bus capacitor can be reduced, that is, the DC bus voltage is reduced. According to relevant standards, the voltage difference between the two power grids is usually less than 10%, and thus the output port voltage of the second voltage source type converter is usually small, which corresponds to a lower modulation ratio. Too low modulation ratio will introduce a large amount of harmonics. The above power flow controller reduces the DC bus voltage through the voltage dividing capacitor, increases the modulation ratio, and thus reduces the harmonics. The first voltage source type converter of the above power flow controller is connected in parallel with the first AC power grid to form a rectifier circuit, and the second voltage source type converter is connected in series with the second AC power grid to form an inverter circuit. By controlling the switching tubes in the voltage source type converters, the voltages of the DC bus and the output port are controlled to realize the control of power transmission. The power transmission can be realized under different power factor angles in the case that the amplitudes and phases of the two power grids are not equal. The power flow controller is suitable for fast and accurate active and reactive power control between distribution network lines and between transformer areas, is helpful for flexible transmission of electric energy between distribution network lines and between transformer areas, and has a wide application prospect in the field of power system power flow control.

[0034] Embodiments of the present application also provide a control method based on the above power flow controller, that is, a control method of the above series voltage dividing type non-isolated power flow controller. The control method can be executed by a control device, which can be a terminal device or a server. The terminal device can include but is not limited to a mobile phone, a computer, etc., and the embodiments of the present application do not make any limitation. The server can be a physical server, a server cluster composed of multiple physical servers, or a distributed system, and can also be a cloud server providing cloud services, cloud databases, cloud computing, big data, and artificial intelligence platforms, etc. The embodiments of the present application do not make any limitation. Optionally, the control method can also be executed by multiple electronic devices with computing power in cooperation. For the convenience of description, the following embodiments are described by the control device.

[0035] Referring to Figure 3 , Figure 3 is a schematic diagram of a control method of a series voltage dividing type non-isolated power flow controller provided by the embodiments of the present application. The control method can be executed by a control device, and the control method is mainly the control of the switching tubes in the first voltage source type converter and the second voltage source type converter. Therefore, the method can at least include a control method for the first voltage source type converter and a control method for the second voltage source type converter.

[0036] The control method for the first voltage source type converter: according to the first AC power grid voltage, the preset value of the DC bus voltage, and the DC bus capacitor voltage, the reference value of the filter inductor current in the first voltage source type converter is calculated, and according to the reference value and the actual value of the filter inductor current in the first voltage source type converter, the control signal of the switching tube in the first voltage source type converter is generated.

[0037] It should be noted that the first AC grid voltage and the DC bus capacitor voltage are both actual values, that is, the values ​​actually collected by the voltage measuring device, and the preset value of the DC bus voltage is a manually set value, which can specifically be the amplitude of the first AC grid voltage.

[0038] In some embodiments, calculating a reference value of the filter inductor current in the first voltage source converter may include the following steps: 1) Phase-locking the first AC grid voltage to obtain the phase of the first AC grid voltage.

[0039] In the figure, the first AC grid voltage is represented by U G1 , U G1 It can be phase-locked by a second-order generalized integral phase-locked loop to obtain U G1 phase.

[0040] 2) Calculate the difference between the preset value of the DC bus voltage and the DC bus capacitor voltage, and perform proportional-integral control on the difference.

[0041] In the figure, the preset value of DC bus voltage is represented as U DC_set , the DC bus capacitor voltage is expressed as U DC (It is C dc1 Voltage and C dc2 The sum of the voltages), U DC_set with U DC The difference is input into the PI (Proportional Integral) controller.

[0042] 3) Multiplying the result of proportional-integral control by the phase of the first AC grid voltage to obtain a reference value I of the filter inductor current in the first voltage source converter pref .

[0043] Furthermore, it is necessary to calculate the reference value I of the filter inductor current in the first voltage source converter. pref and the actual value I Lp Specifically, the difference is input into the PR (Proportional Resonant, proportional resonance) controller, and the output of the PR controller is subjected to PWM (Pulse Width Modulation, pulse width modulation) to obtain the control signal T of the first voltage source converter switch tube. ax .

[0044] in the case of Figure 2 The full-bridge first voltage source converter shown in FIG. ax Control T a1 、Ta2 , T a3 and T a4 the on-off of the switch.

[0045] For the first voltage source converter, the on-off of the switch is controlled by accurate tracking of the internal filter inductor current reference value, so as to maintain the stability of the DC bus voltage.

[0046] For the control method of the second voltage source converter: according to the second AC grid voltage, the grid-side current of the second AC grid side, the preset value of the active power transmitted by the second AC grid and the preset value of the reactive power transmitted by the second AC grid, the reference value of the filter inductor current in the second voltage source converter is calculated, and the control signal of the switch in the second voltage source converter is generated according to the reference value and the actual value of the filter inductor current in the second voltage source converter.

[0047] It should be noted that the second AC grid voltage and the grid-side current of the second AC grid side are actual values, i.e. values actually collected by the voltage measurement device, and the preset value of the active power transmitted by the second AC grid and the preset value of the reactive power transmitted by the second AC grid are artificial values, which are set according to the use environment of the controller and the power to be transmitted.

[0048] In some embodiments, calculating the reference value of the filter inductor current in the second voltage source converter can include the following steps: S1) according to the second AC grid voltage U G2 and the grid-side current I G2 of the second AC grid side, the modulus S tran and the phase angle φ tran of the complex power transmitted by the second AC grid are calculated; according to the preset value P set of the active power transmitted by the second AC grid and the preset value Q set of the reactive power transmitted by the second AC grid, the modulus S set and the phase angle φ set of the preset value of the complex power transmitted by the second AC grid are calculated. S2) the modulus difference of modulus S tran and modulus S set is calculated, and the modulus difference is controlled by proportional integral control; the phase angle difference of phase angle φ tran and phase angle φ set is calculated, and the phase angle difference is controlled by proportional integral control.

[0049] As in the control method of the first voltage source converter, the difference is directly input to the PI controller.

[0050] S5) Multiplying the proportional-integral control result of the modulus difference with the proportional-integral control result of the phase angle difference to obtain a reference value I of the filter inductor current in the second voltage source converter sref .

[0051] Furthermore, it is necessary to calculate the reference value I of the filter inductor current in the second voltage source converter. sref and the actual value I Ls Specifically, the difference is input into the PR controller, and the output of the PR controller is PWMed to obtain the control signal T of the second voltage source converter switch tube. bx .

[0052] in the case of Figure 2 The full-bridge second voltage source converter shown in FIG. bx Control T b1 and T b2 The on and off.

[0053] For the second voltage source converter, the on-off of the switch tube is controlled by accurately tracking the reference value of the internal filter inductor current, thereby achieving control of the output voltage and further achieving control of the transmission power.

[0054] In the power flow controller, a first voltage source converter is connected in parallel with a first AC power grid to form a rectifier circuit. By accurately tracking the reference value of the internal filter inductor current of the first voltage source converter, the on-off of the switch tube of the first voltage source converter is controlled, and the stability of the DC bus voltage is controlled. A second voltage source converter is connected in series with a second AC power grid to form an inverter circuit. By accurately tracking the reference value of the internal filter inductor current of the second voltage source converter, the on-off of the switch tube of the second voltage source converter is controlled, and the voltage at the output end is controlled to achieve power transmission control. When the amplitude and phase of the power grids at both ends are unequal, power transmission under different power factor angles can be achieved.

[0055] See also Figure 4 , Figure 4 This is a block diagram of a control device of a series voltage-dividing non-isolated power flow controller provided in an embodiment of the present application. Figure 4 The embodiment is a virtual device that can be loaded and executed by a computer device, the computer device can include the above-mentioned control device, and the device can include at least a first control module and a second control module. When used to execute the above-mentioned control method, it can: The first control module is configured to calculate a reference value of a filter inductor current in the first voltage source converter according to the first AC grid voltage, a preset value of the DC bus voltage and a DC bus capacitor voltage, and generate a control signal of a switch tube in the first voltage source converter according to the reference value and an actual value of the filter inductor current in the first voltage source converter.

[0056] The second control module is configured to calculate a reference value of a filter inductor current in the second voltage source converter according to the second AC grid voltage, a grid-side current on the second AC grid side, a preset value of the second AC grid transmitted active power and a preset value of the second AC grid transmitted reactive power, and generate a control signal of a switch tube in the second voltage source converter according to the reference value and an actual value of the filter inductor current in the second voltage source converter.

[0057] The device can accurately track the reference value of the filter inductor current in the first voltage source converter, control the on-off of the switch tube in the first voltage source converter, control the stability of the DC bus voltage, accurately track the reference value of the filter inductor current in the second voltage source converter, control the on-off of the switch tube in the second voltage source converter, and control the voltage at the output end, so as to realize the control of power transmission, and realize power transmission under different power factor angles in the case that the magnitudes and phases of the two AC grids are not equal.

[0058] The application also relates to a computer readable storage medium storing one or more programs, the one or more programs including instructions that, when executed by a computing device, cause the computing device to perform the control method of the series voltage division type non-isolated power flow controller.

[0059] The application also relates to a computer device including one or more processors and one or more memories, one or more programs being stored in the one or more memories and configured to be executed by the one or more processors, the one or more programs including instructions for performing the control method of the series voltage division type non-isolated power flow controller.

[0060] Those skilled in the art should understand that the embodiments of the application can be provided as a method, a system or a computer program product. Therefore, the application can be in the form of an entirely hardware embodiment, an entirely software embodiment or an embodiment combining software and hardware aspects. Moreover, the application can be in the form of a computer program product implemented on one or more computer usable storage media (including but not limited to disk storage, CD-ROM, optical storage etc.) containing computer usable program code.

[0061] The computer program instructions can also be loaded onto a computer or other programmable data processing apparatus to cause a series of operational steps to be performed on the computer or other programmable apparatus to produce a computer-implemented process such that the instructions which execute on the computer or other programmable apparatus provide steps for implementing the functions specified in the flowchart block or blocks. Figure 1 one or more flow or blocks. Figure 1 one or more flow or blocks.

[0062] These computer program instructions can also be stored in a computer readable memory that can direct a computer or other programmable data processing apparatus to function in a particular manner, such that the instructions stored in the computer readable memory produce an article of manufacture including instructions which implement the function specified in the flowchart block or blocks. Figure 1 one or more flow or blocks. Figure 1 one or more flow or blocks.

[0063] The computer program instructions can also be loaded onto a computer or other programmable data processing apparatus to cause a series of operational steps to be performed on the computer or other programmable apparatus to produce a computer-implemented process such that the instructions which execute on the computer or other programmable apparatus provide steps for implementing the functions specified in the flowchart block or blocks. Figure 1 one or more flow or blocks. Figure 1 one or more flow or blocks.

[0064] The above merely provides an embodiment of the present application, but is not intended to limit the present application. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present application shall fall within the scope of the claims of the present application.

Claims

1. A series voltage-dividing non-isolated power flow controller, characterized in that: The power flow controller is arranged between the first AC power grid and the second AC power grid. The power flow controller includes a voltage-dividing capacitor, a first voltage source converter and a second voltage source converter. The voltage-dividing capacitor and the first voltage source converter are connected in series and then in parallel with the first AC power grid. The second voltage source converter is connected in series with the second AC power grid. The DC bus inside the first voltage source converter and the DC bus inside the second voltage source converter are the same DC bus.

2. The power flow controller according to claim 1, characterized in that: The first voltage source converter includes a first LC filter circuit, a full-bridge circuit and the DC bus, the full-bridge circuit and the DC bus are connected in parallel, the midpoint of the first bridge arm and the midpoint of the second bridge arm of the full-bridge circuit are connected to the two ends of the first LC filter circuit, and the filter capacitor in the first LC filter circuit and the voltage divider capacitor are connected in series and then connected in parallel with the first AC power grid.

3. The power flow controller according to claim 1, characterized in that: The second voltage source converter includes a second LC filter circuit, a half-bridge circuit and a DC bus in parallel, and the midpoint of the bridge arm in the half-bridge circuit and the midpoint of the DC bus are connected in series with the second AC power grid through the second LC filter circuit.

4. A control method for a series voltage-dividing non-isolated power flow controller, characterized in that: The power flow controller is the power flow controller according to any one of claims 1 to 3, and the method comprises: For the first voltage source converter, calculating a reference value of a filter inductor current in the first voltage source converter based on the first AC grid voltage, a preset value of the DC bus voltage, and the DC bus capacitor voltage, and generating a control signal for a switch in the first voltage source converter based on the reference value and an actual value of the filter inductor current in the first voltage source converter; For the second voltage source converter, a reference value of the filter inductor current in the second voltage source converter is calculated based on the second AC grid voltage, the grid-side current on the second AC grid side, a preset value of the active power transmitted by the second AC grid, and a preset value of the reactive power transmitted by the second AC grid. A control signal for the switch tube in the second voltage source converter is generated based on the reference value and an actual value of the filter inductor current in the second voltage source converter.

5. The method according to claim 4, characterized in that Calculating a reference value of a filter inductor current in the first voltage source converter according to the first AC grid voltage, a preset value of the DC bus voltage, and the DC bus capacitor voltage, including: performing phase locking on the first AC grid voltage to obtain a phase of the first AC grid voltage; Calculating a difference between a preset value of the DC bus voltage and the DC bus capacitor voltage, and performing proportional-integral control on the difference; The result of the proportional-integral control is multiplied by the phase of the first AC grid voltage to obtain a reference value of the filter inductor current in the first voltage source converter.

6. The method according to claim 4, characterized in that Calculating a reference value of a filter inductor current in the second voltage source converter according to the second AC grid voltage, the grid-side current of the second AC grid, a preset value of active power transmitted by the second AC grid, and a preset value of reactive power transmitted by the second AC grid includes: According to the second AC grid voltage U G2 and the grid-side current I of the second AC grid side G2 , calculate the modulus S of the complex power transmitted by the second AC power grid tran and phase angle φ tran ; According to the preset value P of the active power transmitted by the second AC power grid set and the preset value Q of reactive power transmitted by the second AC grid set , calculate the module value S of the second AC power grid transmission complex power preset value set and phase angle φ set ; Calculate the modulus S tran With the modulus value S set The module value difference is obtained by performing proportional integral control on the module value difference; Calculate the phase angle φ tran and phase angle φ set A phase angle difference value is obtained, and proportional-integral control is performed on the phase angle difference value; A proportional-integral control result of the modulus difference is multiplied by a proportional-integral control result of the phase angle difference to obtain a reference value of the filter inductor current in the second voltage source converter.

7. The method according to claim 4, characterized in that Generating a control signal for a switch in the first voltage source converter according to a reference value and an actual value of a filter inductor current in the first voltage source converter includes: calculating a difference between a reference value and an actual value of a filter inductor current in the first voltage source converter, and sequentially performing proportional resonant control and pulse width modulation on the difference between the reference value and the actual value of the filter inductor current in the first voltage source converter to obtain a control signal for a switch in the first voltage source converter; Generating a control signal for a switch in the second voltage source converter according to a reference value and an actual value of a filter inductor current in the second voltage source converter includes: A difference between a reference value and an actual value of a filter inductor current in the second voltage source converter is calculated, and proportional resonance control and pulse width modulation are sequentially performed on the difference between the reference value and the actual value of the filter inductor current in the second voltage source converter to obtain a control signal for a switch tube in the second voltage source converter.

8. A control device of a series voltage-dividing non-isolated power flow controller, characterized in that: The power flow controller is the power flow controller according to any one of claims 1 to 3, and the device comprises: a first control module, configured to calculate, for the first voltage source converter, a reference value of a filter inductor current in the first voltage source converter based on the first AC grid voltage, a preset value of the DC bus voltage, and the DC bus capacitor voltage, and generate a control signal for a switch in the first voltage source converter based on the reference value and an actual value of the filter inductor current in the first voltage source converter; a second control module configured to calculate, for the second voltage source converter, a reference value of a filter inductor current in the second voltage source converter based on the second AC grid voltage, the grid-side current on the second AC grid side, a preset value of active power transmitted by the second AC grid, and a preset value of reactive power transmitted by the second AC grid, and to generate a control signal for a switch in the second voltage source converter based on the reference value and an actual value of the filter inductor current in the second voltage source converter.

9. A computer-readable storage medium, characterized in that The computer-readable storage medium stores one or more programs, and the one or more programs include instructions. When the instructions are executed by a computing device, the computing device executes the method according to any one of claims 4 to 7.

10. A computer device, characterized in that: include: One or more processors, and one or more memories, one or more programs stored in the one or more memories and configured to be executed by the one or more processors, the one or more programs including instructions for executing any one of the methods of claims 4 to 7.

Images