Series converter, control method and related device

Abstract

The invention discloses a series converter, a control method and a related device, an H-bridge converter is connected in series on each interconnecting line, the H-bridge converter is a full-control device, when a fault occurs, a power device can be immediately locked through control, so that fault current cannot flow through, the fault range is prevented from being expanded, and the reliability of the system is improved. Through DC side voltage outer loop control and inner loop current control, the output power of the H-bridge converter can be controlled, so that the flexible mutual aid power between two AC systems can be changed.

Description

Technical Field

[0001] The invention relates to a series converter, a control method and a related device, and belongs to the technical field of power electronic switch topology and control of an AC / DC hybrid power distribution network. Background Art

[0002] Under the background of dual carbon, a large number of intermittent and fluctuating distributed power sources are connected, and the distribution network faces many challenges such as efficient consumption of new energy, reliable load power supply, and flexible power flow control. The flexible interconnection device based on power electronic conversion technology has multiple functions such as power regulation, voltage support, and fault isolation. It has become an important means to support the efficient consumption of new energy and safe and stable operation of distribution networks, and promote the evolution of traditional distribution networks to AC and DC flexible interconnected distribution systems.

[0003] Flexible interconnection devices in distribution networks (specifically flexible interconnection converters) are usually divided into parallel and series types. The parallel type usually provides back-to-back full-power transfer, which can achieve four-quadrant control, and all the power of the line flows through the power devices; the series type changes the line power flow characteristics through devices connected in series in the line, and part of the power of the line flows through the power devices.

[0004] Compared with the parallel type, the biggest disadvantage of the traditional series converter is that it cannot achieve fault isolation through its own circuit. When a fault occurs in the power grid at one end, the fault range may be magnified because the series converter cannot be blocked in time. Summary of the invention

[0005] The present invention provides a series converter, a control method and related devices, which solve the problems disclosed in the background technology.

[0006] According to one aspect of the present disclosure, a series converter is provided, which is arranged between interconnected AC systems. The series converter includes a controller and an H-bridge converter. The controller controls the power devices of the H-bridge converter. The H-bridge converter is connected in series on each interconnected line.

[0007] According to another aspect of the present disclosure, a control method of a series converter is provided, wherein the series converter is the above-mentioned series converter, and the method comprises: If an overcurrent is detected in the interconnected line, all power devices of the corresponding H-bridge converter are controlled to be locked; If it is detected that all interconnected lines have no overcurrent, the output power of all H-bridge converters is controlled to change the flexible mutual aid power of the interconnected AC system.

[0008] In some embodiments of the present disclosure, controlling the output power of all H-bridge converters includes: The series converter is equivalent to a static VAR generator, and the DC side voltage outer loop control method and the inner loop current control method are used in sequence to control the output power of all H-bridge converters.

[0009] In some embodiments of the present disclosure, a DC side voltage outer loop control method includes: Calculate the voltage difference between the mean value of the three-phase DC side voltage and the reference value; The voltage difference is controlled by PI proportional integral to obtain the active power given value of AC / DC switching.

[0010] In some embodiments of the present disclosure, an inner loop current control method includes: Performing Park transformation on the output and reactive power given value of the DC side voltage outer loop control method to obtain an output bridge arm current given value; wherein the output bridge arm current given value includes each phase current given value; For each phase current given value, the current difference between the phase current given value and the corresponding measured current is calculated, and the current difference is subjected to PI proportional integral control to obtain the phase voltage given value; Perform PMW modulation on the voltage set value of each phase to obtain the control signal of each phase; Each phase of the H-bridge converter is controlled by using each phase control signal and a complementary signal of the each phase control signal.

[0011] In some embodiments of the present disclosure, the control signal and the complementary signal of the control signal are both gate signals of power devices of the H-bridge converter; The i-phase control signal controls the first power device of the first bridge arm and the fourth power device of the second bridge arm in the i-phase H-bridge converter, and the complementary signal of the i-phase control signal controls the second power device of the first bridge arm and the third power device of the second bridge arm in the i-phase H-bridge converter; wherein, i=A, B, C.

[0012] According to another aspect of the present disclosure, a control device for a series converter is provided, wherein the series converter is the above-mentioned series converter, and the control device comprises: The locking control module controls all power devices of the corresponding H-bridge converter to lock if an overcurrent is detected in the interconnected line; The output power control module controls the output power of all H-bridge converters and changes the flexible mutual aid power of the interconnected AC system if it is detected that all interconnected lines have no overcurrent.

[0013] In some embodiments of the present disclosure, in the output power control module, the output power of all H-bridge converters is controlled, including: The series converter is equivalent to a static VAR generator, and the DC side voltage outer loop control method and the inner loop current control method are used in turn to control the output power of all H-bridge converters.

[0014] According to another aspect of the present disclosure, a computer-readable storage medium is provided, which stores one or more programs, the one or more programs including instructions, which, when executed by a computing device, cause the computing device to execute a control method for a series converter.

[0015] According to another aspect of the present disclosure, 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 executing a control method for a series converter.

[0016] The beneficial effects achieved by the present invention are as follows: 1. The present invention connects an H-bridge converter in series on each interconnected line. The H-bridge converter is a fully controlled device. When a fault occurs, the power device can be immediately locked by control so that the fault current cannot flow through, thereby avoiding the expansion of the fault range; 2. The present invention can control the output power of the H-bridge converter through the DC side voltage outer loop control and the inner loop current control, thereby changing the flexible mutual assistance power between the two AC systems. BRIEF DESCRIPTION OF THE DRAWINGS

[0017] Figure 1 It is a structural schematic diagram of a series converter; Figure 2 is a flow chart of a control method for a series converter; Figure 3 It is a schematic diagram of a single-phase circuit of a series converter; Figure 4 It is the equivalent schematic diagram of the single-phase circuit of the series converter; Figure 5 Schematic diagram of equivalent reactive power compensation for single-phase circuit of series converter Figure 6 This is the control block diagram of the H-bridge converter under normal conditions; Figure 7 A block diagram of a control device for a series converter. DETAILED DESCRIPTION

[0018] The following will be combined with the drawings in the embodiments of the present disclosure to clearly and completely describe the technical solutions in the embodiments of the present disclosure. It is obvious that the described embodiments are only part of the embodiments of the present disclosure, rather than all the embodiments. The following description of at least one exemplary embodiment is actually only illustrative and is by no means intended to limit the present disclosure and its application or use. Based on the embodiments in the present disclosure, all other embodiments obtained by ordinary technicians in this field without making creative work are within the scope of protection of the present disclosure.

[0019] Unless otherwise specified, the relative arrangement of components and steps, the numerical expressions and numerical values ​​set forth in these embodiments do not limit the scope of the present disclosure.

[0020] At the same time, it should be understood that for the convenience of description, the sizes of the various parts shown in the drawings are not drawn according to the actual proportional relationship.

[0021] Technologies, methods, and equipment known to ordinary technicians in the relevant art may not be discussed in detail, but where appropriate, the technologies, methods, and equipment should be considered part of the specification.

[0022] In all examples shown and discussed herein, any specific values ​​should be interpreted as merely exemplary and not as limiting. Therefore, other examples of the exemplary embodiments may have different values.

[0023] In order to solve the problem that a traditional series converter cannot achieve fault isolation through its own circuit, the present disclosure proposes a series converter, a control method and related devices.

[0024] Figure 1 This is a schematic diagram of an embodiment of a series converter disclosed in the present invention. The series converter is specifically arranged between interconnected AC systems and may include a controller (not shown) and an H-bridge converter. The controller controls the power devices of the H-bridge converter. The H-bridge converter is connected in series on each interconnected line.

[0025] It should be noted that the interconnected AC system is generally the interconnection between two sections of the AC power grid, specifically the interconnection between three-phase lines. Therefore, there are three H-bridge converters here, namely, the A-phase H-bridge converter, the B-phase H-bridge converter and the C-phase H-bridge converter. The structures of the three are the same, all of which include an H-bridge composed of a field effect transistor with a damping diode and a capacitor connected in parallel with the bridge arm. Each bridge arm includes two field effect transistors connected in series. The input and output of the H-bridge converter are respectively located at the midpoints of the two bridge arms. The input and output of the H-bridge converter are connected in series to the interconnection line through an inductor.

[0026] It should be noted that the controller is not limited and various types of simulators can also be used. In this implementation, the DSP28XX series controller can be used. The controller will send a control signal to each field effect tube, specifically a signal to the gate, thereby controlling each field effect tube, thereby further controlling the H-bridge converter.

[0027] It should be noted that since the H-bridge converter is connected in series on each interconnected line, the H-bridge converter is a fully controlled device. When a fault occurs in the power grid at one end, the power device can be immediately locked through control to prevent the fault current from flowing, thereby avoiding the expansion of the fault range. And because it is a fully controlled device, energy can flow in both directions. Compared with traditional parallel converters, the DC side voltage can be lower and the overall volume can be smaller.

[0028] Figure 2 FIG. 1 is a schematic diagram of an embodiment of a control method for a series converter disclosed in the present invention. The series converter is Figure 1 The method may be implemented by a controller of the converter, and may specifically include the following steps: Step 1: If an overcurrent is detected in the interconnected line, all power devices of the corresponding H-bridge converter are controlled to be locked.

[0029] It should be noted that when a fault occurs in a power grid at one end, a fault current will often be transmitted on the interconnected line. This fault power is generally an overcurrent. Therefore, as long as an overcurrent is detected in the interconnected line, it indicates that a fault has occurred.

[0030] The current detection here can be performed using a current sensor. There are many similar detection methods, which will not be described in detail here. If an overcurrent is detected in a certain interconnected line, the controller will control all power devices of the H-bridge converter of that phase to be locked, so that the fault current cannot flow through, thereby avoiding the expansion of the fault range.

[0031] Step 2: If it is detected that all interconnected lines have no overcurrent, the output power of all H-bridge converters is controlled to change the flexible mutual aid power of the interconnected AC system.

[0032] It should be noted that if there is no overcurrent in the interconnected lines and the surface power grid is normal, the series converter can be transformed and equivalent. Figure 3~Figure 5 , Figure 3 This is a single-phase circuit diagram with the capacitor placed in the middle. We can further get Figure 4 By equivalently calculating the power supply parts on both sides of the single-phase circuit, we can get the single-phase circuit equivalent reactive power compensation circuit.

[0033] Therefore, in some embodiments, the series converter can be equivalent to a static VAR generator (SVG), and the DC side voltage outer loop control method and the inner loop current control method are used in sequence to control the output power of all H-bridge converters.

[0034] It should be noted that the DC side voltage outer loop control method may include: calculating the voltage difference between the mean value of the three-phase DC side voltage and the reference value; performing PI proportional integral control on the voltage difference to obtain the active power given value of AC / DC exchange.

[0035] See Figure 6 , the three-phase DC side voltage is Uc a , Uc b , Uc c The average value of the three-phase DC side voltage is recorded as (Uc a +Uc b +Uc c ) / 3, the given value is Uc ref , calculate Uc ref -(Uc a +Uc b +Uc c ) / 3, the voltage difference is subjected to PI proportional integral control to obtain the output of the DC side voltage outer loop control, that is, the active power given value I of the AC / DC exchange Pref .

[0036] The inner loop current control method may include: performing Park transformation on the output of the DC side voltage outer loop control method and the reactive power given value (the reactive power output by the H-bridge is unrelated to the DC side voltage) to obtain the output bridge arm current given value; wherein the output bridge arm current given value includes the current given value of each phase; for each phase current given value, calculating the current difference between the phase current given value and the corresponding measured current, performing PI proportional integral control on the current difference, and obtaining the phase voltage given value; performing PMW modulation on each phase voltage given value to obtain each phase control signal; and using each phase control signal and the complementary signal of each phase control signal to control each phase H-bridge converter.

[0037] See Figure 6 , the reactive power given value is I Qref , to I Pref and I Qref Perform Park transformation (i.e. C in the figure) 23 ), obtain the output bridge arm current given value I Lref , I Lref It contains the given values ​​of the three-phase currents A, B, and C. The given values ​​are compared with the actual measured three-phase currents I L Subtraction, that is, subtract the given current value of phase A from the actual measured value of phase A, subtract the given current value of phase B from the actual measured value of phase B, and subtract the given current value of phase C from the actual measured value of phase C. The current difference of each phase is controlled by PI proportional integral to obtain the given voltage value of each phase. ref Indicates that u ref The control gate signal g of the three-phase H-bridge converter is obtained directly through PMW modulation, and each phase of the H-bridge converter is controlled through the gate signal and the corresponding complementary signal; wherein the PWM modulation here is a pulse width modulation, and specifically bipolar PWM control can be adopted.

[0038] The specific control is: the i-phase control signal controls the first power device of the first bridge arm and the fourth power device of the second bridge arm in the i-phase H-bridge converter, the two power devices controlled by the control signal are a pair of tubes with the same gate signal, and the complementary signal of the i-phase control signal controls the second power device of the first bridge arm and the third power device of the second bridge arm in the i-phase H-bridge converter; wherein, i=A, B, C.

[0039] by Figure 1 Taking the structure in as an example, the A-phase control signal controls V1 and V4 tubes, and the control signals of V2 and V3 tubes are the complementary signals of V1 and V4 tubes; the B-phase control signal controls V5 and V8 tubes, and the control signals of V6 and V7 tubes are the complementary signals of V8 and V8 tubes; the C-phase control signal controls V9 and V12 tubes, and the control signals of V10 and V11 tubes are the complementary signals of V9 and V12 tubes.

[0040] The output power of the H-bridge converter can be controlled by the DC side voltage outer loop control and the inner loop current control, thereby changing the flexible mutual power between the two AC systems.

[0041] The parallel low-voltage flexible interconnection device is converted into a series flexible interconnection through circuit equivalent, which reduces the capacitor voltage and the size of the equipment. After phase control, each phase is controlled independently, and it is impossible to achieve unified control of the DC side voltage and the output positive and negative sequence. Therefore, the SVG control method is used to control the topology to avoid the uncertainty of phase control.

[0042] Figure 7 is a schematic diagram of an embodiment of a control device for a series converter disclosed in the present invention, Figure 7 An embodiment of the invention is a virtual device that can be loaded and executed by a controller of a series converter, and includes a locking control module and an output power control module.

[0043] The locking control module of the embodiment is configured to control all power devices of the corresponding H-bridge converter to lock if an overcurrent of the interconnected line is detected.

[0044] The output power control module of the embodiment is configured to control the output power of all H-bridge converters and change the flexible mutual aid power of the interconnected AC system if it is detected that all interconnected lines have no overcurrent.

[0045] In the output power control module, the output power of all H-bridge converters is controlled, including: the series converter is equivalent to a static VAR generator, and the DC side voltage outer loop control method and the inner loop current control method are used in sequence to control the output power of all H-bridge converters.

[0046] Similar to the above method, the device can control the output power of the H-bridge converter through the DC side voltage outer loop control and the inner loop current control, thereby changing the flexible mutual assistance power between the two AC systems.

[0047] Based on the same technical solution, the present disclosure also relates to a computer-readable storage medium, which 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 a control method for a series converter.

[0048] Based on the same technical solution, the present disclosure also relates to a computer device, comprising 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, and the one or more programs include instructions for executing a control method of a series converter.

[0049] Those skilled in the art should understand that the method, apparatus, or computer program product provided by the embodiments of the present invention may be in the form of a complete hardware embodiment, a complete software embodiment, or an embodiment combining software and hardware. Moreover, the present invention may 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 codes.

[0050] The present invention is described with reference to flowcharts and / or block diagrams of methods, devices (systems), and computer program products according to embodiments of the present invention. It should be understood that each process and / or block in the flowchart and / or block diagram, as well as the combination of processes and / or blocks in the flowchart and / or block diagram, can be implemented by computer program instructions. These computer program instructions can be provided to a processor of a general-purpose computer, a special-purpose computer, an embedded processor, or other programmable data processing device to produce a machine, so that the instructions executed by the processor of the computer or other programmable data processing device generate instructions for implementing the processes in the flowchart and / or block diagram. Figure 1 A process or multiple processes and / or boxes Figure 1 A device that provides the functions specified in a block or multiple blocks.

[0051] These computer program instructions may also be stored in a computer-readable memory capable of directing a computer or other programmable data processing device to operate in a specific manner, so that the instructions stored in the computer-readable memory produce an article of manufacture including an instruction device, which implements the process Figure 1 A process or multiple processes and / or boxes Figure 1 A function specified in one or more boxes.

[0052] These computer program instructions can also be loaded onto a computer or other programmable data processing device so that a series of operating steps are executed on the computer or other programmable device to produce a computer-implemented process, thereby providing instructions for implementing the process. Figure 1 A process or multiple processes and / or boxes Figure 1 The steps for the functions specified in one or more boxes.

[0053] The above are merely embodiments of the present invention and are not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc. made within the spirit and principles of the present invention are included in the scope of the claims of the present invention to be approved.

Claims

1. A series converter, characterized in that: The series converter is arranged between interconnected AC systems. The series converter includes a controller and an H-bridge converter. The controller controls the power devices of the H-bridge converter. The H-bridge converter is connected in series on each interconnected line.

2. A control method for a series converter, characterized in that: The series converter is the series converter according to claim 1, and the method comprises: If an overcurrent is detected in the interconnected line, all power devices of the corresponding H-bridge converter are controlled to be locked; If it is detected that all interconnected lines have no overcurrent, the output power of all H-bridge converters is controlled to change the flexible mutual aid power of the interconnected AC system.

3. The control method of the series converter according to claim 2, characterized in that: Controls the output power of all H-bridge converters, including: The series converter is equivalent to a static VAR generator, and the DC side voltage outer loop control method and the inner loop current control method are used in turn to control the output power of all H-bridge converters.

4. The control method of the series converter according to claim 3, characterized in that: The DC side voltage outer loop control method comprises: Calculate the voltage difference between the mean value of the three-phase DC side voltage and the reference value; The voltage difference is controlled by PI proportional integral to obtain the active power given value of AC / DC switching.

5. The control method of the series converter according to claim 3 or 4, characterized in that: The inner loop current control method comprises: Performing Park transformation on the output and reactive power given value of the DC side voltage outer loop control method to obtain an output bridge arm current given value; wherein the output bridge arm current given value includes each phase current given value; For each phase current given value, the current difference between the phase current given value and the corresponding measured current is calculated, and the current difference is subjected to PI proportional integral control to obtain the phase voltage given value; Perform PMW modulation on the voltage set value of each phase to obtain the control signal of each phase; Each phase of the H-bridge converter is controlled by using each phase control signal and a complementary signal of the each phase control signal.

6. The control method of the series converter according to claim 5, characterized in that: The control signal and the complementary signal of the control signal are both gate signals of the power devices of the H-bridge converter; The i-phase control signal controls the first power device of the first bridge arm and the fourth power device of the second bridge arm in the i-phase H-bridge converter, and the complementary signal of the i-phase control signal controls the second power device of the first bridge arm and the third power device of the second bridge arm in the i-phase H-bridge converter; wherein, i=A, B, C.

7. A control device for a series converter, characterized in that: The series converter is the series converter according to claim 1, and the control device comprises: The locking control module controls all power devices of the corresponding H-bridge converter to lock if an overcurrent is detected in the interconnected line; The output power control module controls the output power of all H-bridge converters and changes the flexible mutual aid power of the interconnected AC system if it is detected that all interconnected lines have no overcurrent.

8. The control device for a series converter according to claim 7, characterized in that: In the output power control module, the output power of all H-bridge converters is controlled, including: The series converter is equivalent to a static VAR generator, and the DC side voltage outer loop control method and the inner loop current control method are used in turn to control the output power of all H-bridge converters.

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 any one of the methods described in claims 2 to 7.

10. A computer device, characterized in that: include: One or more processors, and one or more memories, one or more programs are stored in the one or more memories and are configured to be executed by the one or more processors, and the one or more programs include instructions for executing any of the methods described in claims 2 to 7.

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