Intensive transient disturbance regulation circuit

Abstract

The application relates to an intensive transient disturbance regulation circuit, which comprises a three-phase bridge arm unit, a common DC side unit and a zero sequence bridge arm unit; the three-phase bridge arm unit is connected with each phase power supply branch of a three-phase power grid, a common neutral end of the common DC side unit and an input end of the zero sequence bridge arm unit, and an output end of the zero sequence bridge arm unit is grounded; the zero sequence bridge arm unit is used for generating a first current for offsetting a fault zero sequence component based on a power grid voltage, a power grid current and a common neutral end voltage of the three-phase power grid; the three-phase bridge arm unit is used for determining a three-phase reactive compensation current based on the common neutral end voltage and the first current input by the zero sequence bridge arm unit, and sending the three-phase reactive compensation current to a corresponding phase distribution line of the three-phase power grid; and the common DC side unit is used for providing common DC voltage support for the three-phase bridge arm unit and the zero sequence bridge arm unit. The zero sequence disturbance of the distribution network can be inhibited, and the voltage deviation and power fluctuation problems caused by the power grid transient disturbance can be weakened.

Description

Technical Field

[0001] This application relates to the field of power distribution network technology, and in particular to an intensive transient disturbance control circuit. Background Technology

[0002] Against the backdrop of energy transition and the expansion and upgrading of distribution networks, the complex structure and diverse operation modes of distribution networks, coupled with the high proportion of transient disturbances, can easily lead to problems such as overvoltage, equipment burnout, and phase-to-phase short circuits.

[0003] Traditional technologies generally include transient disturbance control equipment, which mainly includes directly grounded type, single-phase converter grounded type and arc suppression coil grounded type. However, existing equipment only optimizes reactive power compensation or transient control capacity separately, and does not achieve multi-mode active capacity collaborative optimization, resulting in insufficient integration. Summary of the Invention

[0004] Therefore, it is necessary to provide a compact transient disturbance control circuit that can improve the compactness of the circuit and address the above-mentioned technical problems.

[0005] In a first aspect, this application provides a compact transient disturbance control circuit, which includes: a three-phase bridge arm unit, a common DC side unit, and a zero-sequence bridge arm unit; the three-phase bridge arm unit is respectively connected to each phase power supply branch of the three-phase power grid, the common neutral terminal of the common DC side unit, and the input terminal of the zero-sequence bridge arm unit, and the output terminal of the zero-sequence bridge arm unit is grounded;

[0006] The zero-sequence bridge arm unit is used to generate a first current to cancel the zero-sequence component of a fault, based on the grid voltage, grid current, and common neutral terminal voltage of the three-phase power grid.

[0007] The three-phase bridge arm unit is used to determine the three-phase reactive power compensation current based on the common neutral terminal voltage and the first current input to the zero-sequence bridge arm unit, and to send the three-phase reactive power compensation current to the corresponding phase distribution line of the three-phase power grid.

[0008] The common DC side unit is used to provide a common DC voltage support for the three-phase bridge arm unit and the zero-sequence bridge arm unit.

[0009] In one embodiment, the three-phase bridge arm unit includes: a first bridge arm, a second bridge arm, and a third bridge arm; the three-phase power grid access unit includes: a first phase, a second phase, and a third phase; the first phase, the second phase, and the third phase are AC lines with phases differing by 120° sequentially.

[0010] The input terminal of the first bridge arm is connected to the first phase, the input terminal of the second bridge arm is connected to the second phase, and the input terminal of the third bridge arm is connected to the third phase.

[0011] In one embodiment, each phase arm of the three-phase bridge arm unit includes a passive voltage divider capacitor and a first downstream power unit. One end of the passive voltage divider capacitor is connected to the corresponding phase line of the three-phase power grid, and the other end of the passive voltage divider capacitor is connected to the input terminal of the downstream power unit. The output terminal of the downstream power unit is connected to the common DC side unit.

[0012] The passive voltage divider capacitor is used to divide the voltage in series with the first power unit to reduce the voltage stress on the power switch.

[0013] In one embodiment, each phase arm of the three-phase bridge arm unit further includes a filter inductor connected in series between the corresponding phase line of the three-phase power grid and the passive voltage divider capacitor.

[0014] The filter inductor is used to filter out high-frequency harmonics, suppress instantaneous inrush currents, and protect the downstream power units.

[0015] In one embodiment, the first power unit includes an NPC three-level bridge arm and a cascaded power module; the filter inductor, the passive voltage divider capacitor and the cascaded power module are connected in series, and the NPC three-level bridge arm and the common DC side unit form an NPC circuit.

[0016] In one embodiment, the zero-sequence bridge arm unit includes a passive voltage divider inductor and a second power unit. The input terminal of the second power unit is connected to the common neutral terminal of the common DC side unit, and the output terminal of the second power unit is connected to one end of the passive voltage divider inductor. The other end of the passive voltage divider inductor is grounded.

[0017] The passive voltage divider inductor is used to share the zero-sequence circuit voltage, reduce the voltage stress of the second power unit, and suppress inrush current and harmonics.

[0018] In one embodiment, the second power unit includes an NPC three-level bridge arm and a cascaded power module; the cascaded power module is connected in series with the passive voltage divider inductor, and the NPC three-level bridge arm and the common DC side unit form an NPC circuit.

[0019] In one embodiment, the cascaded power module is a cascaded H-bridge power module.

[0020] In one embodiment, the NPC three-level bridge arm includes a first power device, a second power device, a third power device and a fourth power device, as well as a first clamping diode and a second clamping diode;

[0021] The first power device, the second power device, the third power device, and the fourth power device are connected in series; the first terminal of the first clamping diode is connected to the second terminal of the second clamping diode;

[0022] The connection point of the first power device and the second power device is connected to the second end of the first clamping diode, and the connection point of the third power device and the fourth power device is connected to the first end of the second clamping diode;

[0023] The connection point between the first terminal of the first clamping diode and the second clamping diode is connected to the common neutral terminal of the common DC side unit.

[0024] In one embodiment, the common DC side unit includes a first DC capacitor and a second DC capacitor connected in series, and the common neutral terminal is the midpoint of the connection between the first DC capacitor and the second DC capacitor.

[0025] In one embodiment, the intensive transient disturbance control circuit further includes: a grounding branch, which includes: the line-to-ground capacitance, the line-to-ground resistance, and the fault resistance;

[0026] Each phase of the three-phase power grid access unit is connected to a set of line-to-ground capacitors and line-to-ground resistors and then grounded. The line-to-ground capacitors and the corresponding line-to-ground resistors are connected in parallel.

[0027] One end of the fault resistor is connected to any phase of the three-phase power grid access unit, and the other end of the fault resistor is grounded.

[0028] The aforementioned intensive transient disturbance control circuit includes: a three-phase bridge arm unit, a common DC side unit, and a zero-sequence bridge arm unit; the three-phase bridge arm unit is connected to each phase power supply branch of the three-phase power grid, the common neutral terminal of the common DC side unit, and the input terminal of the zero-sequence bridge arm unit, respectively, and the output terminal of the zero-sequence bridge arm unit is grounded; the zero-sequence bridge arm unit is used to generate a first current to offset the zero-sequence component of the fault based on the grid voltage, grid current, and common neutral terminal voltage of the three-phase power grid; the three-phase bridge arm unit is used to determine the three-phase reactive power compensation current based on the common neutral terminal voltage and the first current input to the zero-sequence bridge arm unit, and send the three-phase reactive power compensation current to the corresponding phase distribution line of the three-phase power grid; the common DC side unit is used to provide common DC voltage support for the three-phase bridge arm unit and the zero-sequence bridge arm unit. By coordinating the three-phase bridge arm unit, the common DC side unit, and the zero-sequence bridge arm unit to generate the first current, the zero-sequence disturbance of the distribution network can be suppressed, and the voltage deviation and power fluctuation caused by the transient disturbance of the grid can be reduced. The three-phase bridge arm unit can adaptively determine the three-phase reactive power compensation current and feed it into each phase distribution line respectively, which can balance the load difference of the three-phase grid in real time. Moreover, the common DC side unit provides a common DC voltage support for the three-phase bridge arm unit and the zero-sequence bridge arm unit, eliminating the need for separate independent DC power supply circuits. This simplifies the overall circuit topology, reduces equipment hardware costs and size, and ensures the stability of the operating voltage of each unit, thereby improving the overall operating stability and adaptability of the circuit. Attached Figure Description

[0029] To more clearly illustrate the technical solutions in the embodiments of this application or related technologies, the drawings used in the description of the embodiments of this application or related technologies will be briefly introduced below. Obviously, the drawings described below are only some embodiments of this application. For those skilled in the art, other related drawings can be obtained based on these drawings without creative effort.

[0030] Figure 1 This is a schematic diagram of the structure of a compact transient disturbance control circuit in one embodiment;

[0031] Figure 2 This is a schematic diagram of the structure of a compact transient disturbance control circuit in another embodiment;

[0032] Figure 3 This is a schematic diagram of the structure of a compact transient disturbance control circuit in another embodiment;

[0033] Figure 4 This is an equivalent schematic diagram of phase A of the power grid during normal operation of ITCE in one embodiment;

[0034] Figure 5 This is a phasor diagram of phase A voltage and current during normal operation of the power grid in one embodiment;

[0035] Figure 6 This is an equivalent schematic diagram of a power grid transient disturbance in one embodiment;

[0036] Figure 7 This is a phasor diagram of phase A voltage and current during a transient disturbance in the power grid in one embodiment;

[0037] Figure 8 This is a phasor diagram of phase B voltage and current during a transient disturbance in the power grid in one embodiment;

[0038] Figure 9 This is a phasor diagram of phase C voltage and current during a transient disturbance in the power grid in one embodiment;

[0039] Figure 10 This is a phasor diagram of the voltage and current of the fourth arm of the power grid during a transient disturbance in one embodiment.

[0040] Figure 11 This is a schematic diagram of the structure of a compact transient disturbance control circuit in another embodiment.

[0041] Explanation of reference numerals in the attached figures:

[0042] 10: Three-phase bridge arm unit; 20: Common DC side unit; 30: Zero-sequence bridge arm unit;

[0043] 40: Grounding branch; 101: First bridge arm; 102: Second bridge arm;

[0044] 103: Third bridge arm; 104: Passive voltage divider capacitor; 105: First power unit;

[0045] 106: Filter inductor; 201: First DC capacitor; 202: Second DC capacitor;

[0046] 301: Passive voltage divider inductor; 302: Second power stage unit; 401: Line-to-ground capacitance;

[0047] 402: Line-to-ground resistance; 403: Fault resistance; 500: NPC three-level bridge arm;

[0048] 600: Cascaded power module; 501: First power device; 502: Second power device;

[0049] 503: Third power device; 504: Fourth power device; 505: First clamping diode;

[0050] 506: Second clamping diode. Detailed Implementation

[0051] To make the objectives, technical solutions, and advantages of this application clearer, the following detailed description is provided in conjunction with the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are merely illustrative and not intended to limit the scope of this application.

[0052] It should be noted that the terms "first," "second," etc., used in this application can be used to describe various elements, but these elements are not limited by these terms. These terms are only used to distinguish the first element from the second element. The terms "comprising" and "having," and any variations thereof, used in this application, are intended to cover non-exclusive inclusion. The term "multiple" used in this application refers to two or more. The term "and / or" used in this application refers to one of the embodiments, or any combination of multiple embodiments.

[0053] In one embodiment, such as Figure 1 As shown, a compact transient disturbance control circuit is provided, including: a three-phase bridge arm unit 10, a common DC side unit 20, and a zero-sequence bridge arm unit 30; the three-phase bridge arm unit 10 is connected to each phase power supply branch of the three-phase power grid, the common neutral terminal of the common DC side unit 20, and the input terminal of the zero-sequence bridge arm unit 30, respectively, and the output terminal of the zero-sequence bridge arm unit 30 is grounded; the zero-sequence bridge arm unit 30 is used to generate a first current to offset the zero-sequence component of the fault based on the grid voltage, grid current, and common neutral terminal voltage of the three-phase power grid; the three-phase bridge arm unit 10 is used to determine the three-phase reactive power compensation current based on the common neutral terminal voltage and the first current input to the zero-sequence bridge arm unit 30, and send the three-phase reactive power compensation current to the corresponding phase distribution line of the three-phase power grid; the common DC side unit 20 is used to provide a common DC voltage support for the three-phase bridge arm unit 10 and the zero-sequence bridge arm unit 30.

[0054] In this embodiment, the transient disturbance circuit is a medium-voltage intensive transient-disturbance control equipment (ITCE) based on passive component cooperative voltage division.

[0055] In this embodiment, as Figure 1 As shown, the intensive transient disturbance control circuit is composed of a three-phase bridge arm unit 10, a common DC side unit 20, and a zero-sequence bridge arm unit 30. The three-phase bridge arm unit 10 includes bridge arm a, bridge arm b, and bridge arm c. x U is the phase voltage of the power grid. sx I is the grid connection point voltage. sx U0 is the three-phase current of the power grid, U0 is the neutral point voltage of the power grid, and R is the voltage of the three-phase current of the power grid. f For transient disturbance resistance, I zxI0 is the output current of the three-phase bridge arm, and Ix is the transient suppression current, where x = a, b, c. The three-phase bridge arm unit 10 corresponds to the A, B, and C phase power supply branches connected to the three-phase power grid, respectively. The three-phase bridge arm unit 10 is also electrically connected to the common neutral terminal of the common DC side unit 20. The common neutral terminal is further connected to the input terminal of the zero-sequence bridge arm unit 30, and the output terminal of the zero-sequence bridge arm unit 30 is grounded.

[0056] In this embodiment, during grid operation, the grid voltage and current parameters are collected in real time, and the voltage parameters of the common neutral terminal at the common DC side unit 20 are also acquired in real time. The zero-sequence bridge arm unit 30 takes the three-phase grid voltage, three-phase grid current, and common neutral terminal voltage as inputs, and generates a compensation current with the same amplitude but opposite phase as the grid fault zero-sequence current through zero-sequence component extraction, closed-loop control, and current modulation. This compensation current is injected into the common neutral terminal to achieve dynamic cancellation of the zero-sequence current, and the zero-sequence disturbance component is suppressed in real time by relying on the first current.

[0057] Optionally, the zero-sequence bridge arm unit 30 collects the three-phase grid voltage, three-phase grid current, and common neutral terminal voltage in real time. After digital filtering and synchronous sampling, the three-phase electrical quantities are obtained. The zero-sequence voltage and fault zero-sequence current are extracted from the three-phase electrical quantities using the symmetrical component method. The fault zero-sequence current is the zero-sequence component generated by faults such as single-phase grounding, and is the target current to be canceled. Under normal operating conditions, the zero-sequence component is approximately zero, and the zero-sequence bridge arm does not output compensation current. When a single-phase grounding fault occurs, the zero-sequence voltage and fault zero-sequence current increase, and zero-sequence compensation control is initiated. Further, a closed-loop control is constructed using the zero-sequence voltage as the outer loop control quantity and the fault zero-sequence current as the inner loop control quantity, generating a first current reference command with amplitude matching and phase opposite to the fault zero-sequence current. Based on the first current reference command, the common DC side power is converted into AC compensation current. After being buffered by a passive voltage divider inductor, the AC compensation current is injected into the common neutral terminal, forming a first current opposite to the fault zero-sequence current. These currents cancel each other out on the grid side, causing the residual current at the fault point to approach zero.

[0058] In this embodiment, during operation, the three-phase bridge arm unit 10 continuously collects and monitors the real-time fluctuation status of the common neutral terminal voltage, while simultaneously receiving the first current input from the zero-sequence bridge arm unit 30. Combining the real-time fluctuation status of the common neutral terminal voltage and the first current, a three-phase reactive power compensation current adapted to the current grid operating conditions is determined. This modulated three-phase reactive power compensation current is then transmitted to the corresponding phase distribution lines of each of the three phases of the grid, thereby smoothing grid voltage fluctuations and balancing three-phase power parameters through dynamic reactive power compensation.

[0059] Optionally, real-time fluctuations in the neutral terminal voltage can be monitored. The voltage contribution from the first current injection into the common neutral terminal is subtracted from the measured common neutral terminal voltage fluctuation, yielding the neutral terminal voltage fluctuation component caused solely by three-phase imbalance and reactive power imbalance. This neutral terminal fluctuation component is then weighted and fused with reactive power demand to obtain the three-phase reactive power compensation current matching the current grid operating conditions, thereby driving the relevant devices in the three-phase bridge arms to output compensation current.

[0060] In this embodiment, the common DC side unit 20 provides a stable common DC voltage support for the normal operation of the three-phase bridge arm unit 10 and the regulation operation of the zero-sequence bridge arm unit 30. This ensures the consistency and stability of the operating voltage of each power unit, maintains a stable overall circuit voltage operating environment, and ensures that the three-phase bridge arm unit 10 and the zero-sequence bridge arm unit 30 can continuously and reliably complete transient disturbance regulation and power compensation work, effectively improving the overall operational stability of the distribution network under normal operation and fault disturbance conditions.

[0061] The aforementioned intensive transient disturbance control circuit includes: a three-phase bridge arm unit, a common DC side unit, and a zero-sequence bridge arm unit; the three-phase bridge arm unit is connected to each phase power supply branch of the three-phase power grid, the common neutral terminal of the common DC side unit, and the input terminal of the zero-sequence bridge arm unit, respectively, and the output terminal of the zero-sequence bridge arm unit is grounded; the zero-sequence bridge arm unit is used to generate a first current to offset the zero-sequence component of the fault based on the grid voltage, grid current, and common neutral terminal voltage of the three-phase power grid; the three-phase bridge arm unit is used to determine the three-phase reactive power compensation current based on the common neutral terminal voltage and the first current input to the zero-sequence bridge arm unit, and send the three-phase reactive power compensation current to the corresponding phase distribution line of the three-phase power grid; the common DC side unit is used to provide common DC voltage support for the three-phase bridge arm unit and the zero-sequence bridge arm unit. By coordinating the three-phase bridge arm unit, the common DC side unit, and the zero-sequence bridge arm unit to generate the first current, the zero-sequence disturbance of the distribution network can be suppressed, and the voltage deviation and power fluctuation caused by the transient disturbance of the grid can be reduced. The three-phase bridge arm unit can adaptively determine the three-phase reactive power compensation current and feed it into each phase distribution line respectively, which can balance the load difference of the three-phase grid in real time. Moreover, the common DC side unit provides a common DC voltage support for the three-phase bridge arm unit and the zero-sequence bridge arm unit, eliminating the need for separate independent DC power supply circuits. This simplifies the overall circuit topology, reduces equipment hardware costs and size, and ensures the stability of the operating voltage of each unit, thereby improving the overall operating stability and adaptability of the circuit.

[0062] In one embodiment, such as Figure 2As shown, the three-phase bridge arm unit 10 includes: a first bridge arm 101, a second bridge arm 102, and a third bridge arm 103. The three-phase power grid access unit includes: a first phase, a second phase, and a third phase. The first phase, the second phase, and the third phase are AC lines with a phase difference of 120°. The input terminal of the first bridge arm 101 is connected to the first phase, the input terminal of the second bridge arm 102 is connected to the second phase, and the input terminal of the third bridge arm 103 is connected to the third phase.

[0063] In this embodiment, the input terminal of the first bridge arm 101 is electrically connected to the first phase of the three-phase power grid access unit, the input terminal of the second bridge arm 102 is electrically connected to the second phase of the three-phase power grid access unit, and the input terminal of the third bridge arm 103 is electrically connected to the third phase of the three-phase power grid access unit. Through the one-to-one matching connection between each bridge arm and the corresponding phase power supply line, the three-phase bridge arm unit 10 can collect and correspondingly regulate the electrical operating parameters of each phase of the three-phase power grid, providing a stable electrical access foundation for subsequent phase voltage regulation, reactive power compensation, and transient disturbance suppression, ensuring that each phase line can be individually responsive to operating conditions and regulated by the corresponding bridge arm unit.

[0064] In one embodiment, such as Figure 3 As shown, each phase arm in the three-phase bridge arm unit 10 includes a passive voltage divider capacitor 104 and a first downstream power unit 105. One end of the passive voltage divider capacitor 104 is connected to the corresponding phase line of the three-phase power grid, and the other end of the passive voltage divider capacitor 104 is connected to the input terminal of the downstream power unit. The output terminal of the downstream power unit is connected to the common DC side unit 20. The passive voltage divider capacitor 104 is used to divide the voltage in series with the first downstream power unit 105 to reduce the voltage stress on the power switching transistor.

[0065] In this embodiment, each phase arm of the three-phase bridge arm unit 10 is equipped with a passive voltage divider capacitor 104 and a first power supply unit 105. The passive voltage divider capacitor 104 and the first power supply unit 105 are connected in series in each phase arm circuit. One end of the passive voltage divider capacitor 104 is connected to the corresponding phase power supply line of the three-phase power grid, and the other end of the passive voltage divider capacitor 104 is connected to the input terminal of the first power supply unit 105. The output terminal of the first power supply unit 105 is electrically connected to the common DC side unit 20. Under normal grid operation and transient disturbance conditions, the passive voltage divider capacitor 104 can form a series voltage divider relationship with the first downstream power unit 105 to share the power frequency voltage and transient overvoltage applied on the line side, thereby distributing the circuit voltage and reducing the instantaneous voltage stress borne by each power switching device inside the first downstream power unit 105. This prevents the power devices from aging, breaking down, or being damaged due to long-term exposure to excessively high voltage. At the same time, it can buffer the impact of grid voltage fluctuations on the downstream power unit, improving the operational safety and service life of the power devices.

[0066] In the above-mentioned embodiments, passive voltage divider capacitors are set in each phase circuit of the three-phase bridge arm and connected in series with the first downstream power unit. Through coordinated series voltage division, the normal voltage and transient overvoltage of the power grid can be distributed, reducing the voltage stress on the downstream power switching transistors; at the same time, it can buffer the disturbance impact of power grid voltage fluctuations on the downstream power unit.

[0067] In one embodiment, such as Figure 3 As shown, each phase arm of the three-phase bridge arm unit 10 also includes a filter inductor 106, which is connected in series between the corresponding phase line of the three-phase power grid and the passive voltage divider capacitor 104. The filter inductor 106 is used to filter out high-frequency harmonics, suppress instantaneous inrush current, and protect the downstream power unit.

[0068] In this embodiment of the application, each phase arm of the three-phase bridge arm unit 10, in addition to the passive voltage divider capacitor 104 and the first downstream power unit, is also provided with a filter inductor 106. The filter inductor 106 is connected in series between the corresponding phase power supply line of the three-phase power grid and the passive voltage divider capacitor 104 to form a front-end access structure.

[0069] Optional, such as Figure 3 As shown, the first power unit includes an NPC three-level bridge arm 500 and a cascaded power module 600; the filter inductor 106, the passive voltage divider capacitor 104 and the cascaded power module 600 are connected in series, and the NPC three-level bridge arm 500 and the common DC side unit 20 form an NPC circuit.

[0070] In this embodiment, the electrical energy of each phase of the three-phase power grid is first connected to the filter inductor 106. After harmonic mitigation and current buffering by the filter inductor 106, it is then transmitted to the passive voltage divider capacitor 104 to complete the circuit voltage division. Subsequently, it is connected to the cascaded power module 600 for power conversion processing, and finally connected to the common DC side unit 20 via the NPC three-level bridge arm 500.

[0071] Optionally, the cascaded power module 600 is a cascaded H-Bridge (CHB) power module.

[0072] In this embodiment, when the power grid is operating normally, the ITCE operates in reactive power compensation mode. At this time, the zero-sequence bridge arm unit 30 is not in operation, and the three-phase bridge arm unit 10 compensates the power grid for reactive power. Taking phase A as an example, the equivalent schematic diagram of phase A is as follows: Figure 4 As shown. The active section, composed of the NPC module and the CHB module, can be equivalent to a controlled voltage source Ua, and thus, combined with... Figure 2 The output voltage of the active part of ITCE can be obtained as shown in Equation 1:

[0073] (Equation 1)

[0074] in, This refers to the voltage phasor of phase A of the power grid, which is the voltage phasor of the first phase in the three-phase power grid access unit. This is the electromotive force phasor of phase A power supply, i.e., the equivalent electromotive force of the grid power supply. This is the voltage drop phasor of the filter inductor, i.e., the voltage of the filter inductor in the three-phase bridge arm; This is the voltage drop phasor of the passive voltage divider capacitor, i.e., the voltage of the passive voltage divider capacitor in the three-phase bridge arm; The angular frequency of the power grid; This is the inductance value of the filter inductor; This is the capacitance value of the passive voltage divider capacitor; The current in phase A is the phasor current filter inductor and the voltage divider capacitor. To compare the voltage divider effect of the auxiliary capacitor, the output voltage of the active section of the conventional equipment is given by Equation 2:

[0075] (Equation 2)

[0076] Furthermore, according to Figure 2 Equations 1 and 2 can be used to draw voltage and current phasor diagrams for ITCE and conventional equipment, respectively, as follows: Figure 5 As shown, (a) is the phasor diagram of ITCE, and (b) is the phasor diagram of conventional equipment. According to... Figure 5 It can be seen that when the power grid is operating normally, ITCE can effectively share the output voltage of the three-phase bridge arm by using auxiliary capacitors, thereby reducing the voltage sharing of the active part and the number of sub-modules cascaded.

[0077] In the above-mentioned embodiments, a filter inductor is connected in series between the phase line and the voltage divider capacitor to filter out high-frequency harmonics in the circuit, optimize the current waveform, and suppress instantaneous inrush current, thus protecting the downstream power unit.

[0078] In one embodiment, such as Figure 3 As shown, the zero-sequence bridge arm unit 30 includes a passive voltage divider inductor 301 and a second power stage unit 302. The input terminal of the second power stage unit 302 is connected to the common neutral terminal of the common DC side unit 20, and the output terminal of the second power stage unit is connected to one end of the passive voltage divider inductor 301. The other end of the passive voltage divider inductor 301 is grounded. The passive voltage divider inductor 301 is used to share the zero-sequence circuit voltage, reduce the voltage stress of the second power stage unit 302, and suppress inrush current and harmonics.

[0079] In this embodiment, the zero-sequence bridge arm unit 30 is internally provided with a passive voltage divider inductor 301 and a second power stage unit 302. The input terminal of the second power stage unit 302 is electrically connected to the common neutral terminal of the common DC side unit 20. The output terminal of the second power stage unit 302 is connected to one end of the passive voltage divider inductor 301, and the other end of the passive voltage divider inductor 301 is grounded, thereby forming a complete zero-sequence control path.

[0080] Optional, such as Figure 3 As shown, the second power unit 302 includes an NPC three-level bridge arm 500 and a cascaded power module 600; the cascaded power module 600 is connected in series with the passive voltage divider inductor 301, and the NPC three-level bridge arm 500 and the common DC side unit 20 form an NPC circuit.

[0081] In this embodiment, during operation, the zero-sequence charge at the common neutral terminal is buffered and divided by the passive voltage divider inductor 301 and cascaded with the power module 600 for power conversion, and the zero-sequence current is modulated and output through the NPC three-level bridge arm 500 in conjunction with the common DC side unit 20, thereby realizing real-time control of the zero-sequence component.

[0082] Optionally, the cascaded power module 600 is a cascaded H-bridge power module.

[0083] In this embodiment, when a transient disturbance occurs in the power grid, the ITCE operates in transient disturbance control mode. The ITCE simultaneously compensates for reactive current and suppresses transient current, effectively suppressing the current at the transient fault point and ensuring that the power grid still operates at unity power factor during the transient disturbance. To facilitate obtaining the voltage-current relationship when each bridge arm simultaneously outputs reactive current and transient suppression current, and further analyze the impact of passive components on the voltage withstand of the active module, the active part is equivalent to a voltage source, resulting in the equivalent schematic diagram as shown below. Figure 6 As shown.

[0084] Furthermore, regarding Figure 6 The KCL equation for point D is shown in Equation 3:

[0085] (Equation 3)

[0086] in, , , ,and According to Equation 3, the transient suppression current... It can be represented as The ITCE simultaneously compensates for reactive current and suppresses current in the grid. At this time, the three-phase output current can be expressed as... ,in , , These are the three-phase output currents; , , These are the reactive currents output by the three phases; R is the reactive current of the three-phase output; f This is the fault resistor.

[0087] Furthermore, according to Figure 6 It can be seen that the output voltage of the active part of the ITCE three-phase bridge arm is as shown in Equation 4:

[0088] (Equation 4)

[0089] in, This is used to simplify the formula and facilitate subsequent analysis of the partial pressure effect.

[0090] To compare the voltage-dividing effect of the auxiliary capacitor, the output voltage of the active part of the three-phase bridge arm in a traditional system is given by Equation 5:

[0091] (Equation 5)

[0092] Thus, the three-phase bridge arm voltage and current phasor diagrams of ITCE and conventional equipment are obtained respectively, such as Figure 7 , Figure 8 , Figure 9 As shown. Figure 7 (a) is the phasor diagram of ITCE, and (b) is the phasor diagram of conventional equipment. Figure 8 (a) is the phasor diagram of ITCE, and (b) is the phasor diagram of conventional equipment. Figure 9 (a) is the phasor diagram of ITCE, and (b) is the phasor diagram of conventional equipment.

[0093] In this embodiment of the application, for phase A, With E a The included angle is -60°. With E a The included angle is 180°. With E a The included angle is 120°. With E a The included angle is 0°, so when At this time, the auxiliary capacitor can reduce the output voltage of the active section. Under normal circumstances, the transient suppression current in phase A of ITCE is much smaller than the reactive power compensation current, that is... Therefore, ITCE can effectively reduce the voltage borne by the active part of the A-phase bridge arm by using auxiliary capacitors, such as Figure 7 As shown; for phase B, With E b The included angle is 60°. With E b The included angle is 180°. With E b The included angle is -120°. With E b With an included angle of 0°, the situation is similar to phase A. ITCE utilizes an auxiliary capacitor to effectively reduce the voltage borne by the active portion of the phase B bridge arm, such as... Figure 8 As shown; for the C phase, With E c The included angle is 180°. With E c With an included angle of 0°, the ITCE effectively reduces the voltage borne by the active part of the C-phase bridge arm using auxiliary capacitors, regardless of the magnitude of transient suppression current and reactive power compensation current. In summary, when a transient disturbance occurs, and the ITCE simultaneously compensates for reactive current and transient suppression current to the grid, the ITCE effectively reduces the voltage shared by the active part and the number of cascaded submodules by utilizing auxiliary capacitors.

[0094] In this embodiment of the application, KVL equations are written for the zero-sequence bridge arm element 30, which yields... ,in, This is the output voltage of the fourth bridge arm of the ITCE. To compare the voltage division effect of the arc suppression coil, the output voltage of the active part of the fourth bridge arm in conventional equipment is... ,according to Figure 6 The KVL equations for the zero-sequence bridge arm element 30 can be used to plot the voltage and current phasor diagrams of the fourth bridge arm for both ITCE and conventional equipment, as shown below. Figure 10 As shown, (a) is the phasor diagram of ITCE, and (b) is the phasor diagram of conventional equipment. According to... Figure 10 It can be seen that when the power grid experiences transient disturbances, ITCE can effectively reduce the voltage sharing of the active part of the fourth bridge arm and the number of cascaded submodules by utilizing the arc suppression inductor.

[0095] In the above-mentioned embodiments, by connecting a passive voltage divider inductor to the zero-sequence circuit, the voltage of the zero-sequence circuit can be shared, the voltage stress of the second power unit can be reduced, and the circuit inrush current and high-frequency harmonics can be suppressed to protect the internal power devices.

[0096] In one embodiment, such as Figure 3As shown, the aforementioned NPC three-level bridge arm 500 includes a first power device 501, a second power device 502, a third power device 503, and a fourth power device 504, as well as a first clamping diode 505 and a second clamping diode 506; the first power device 501, the second power device 502, the third power device 503, and the fourth power device 504 are connected in series; the first end of the first clamping diode 505 is connected to the second end of the second clamping diode 506; the connection point of the first power device 501 and the second power device 502 is connected to the second end of the first clamping diode 505, and the connection point of the third power device 503 and the fourth power device 504 is connected to the first end of the second clamping diode 506; the connection point of the first end of the first clamping diode 505 and the second clamping diode 506 is connected to the common neutral terminal of the common DC side unit 20.

[0097] In this embodiment, the first power device 501, the second power device 502, the third power device 503, and the fourth power device 504 are connected in series in a preset order to form a power switch link; the first end of the first clamping diode 505 and the second end of the second clamping diode 506 are connected to each other to form a clamping branch. The connection node between the first power device 501 and the second power device 502 is electrically connected to the second end of the first clamping diode 505; the connection node between the third power device 503 and the fourth power device 504 is connected to the first end of the second clamping diode 506; the connection node between the first end of the first clamping diode 505 and the second clamping diode 506 is directly connected to the common neutral terminal of the common DC side unit 20, forming a complete clamping and power conversion circuit.

[0098] In the above-mentioned embodiments, by deploying four sets of power devices and two sets of clamping diodes, an NPC three-level bridge arm structure is constructed, which effectively realizes three-level voltage output and power conversion, and reduces the voltage stress of power devices.

[0099] In one embodiment, such as Figure 3 As shown, the common DC side unit 20 includes a first DC capacitor 201 and a second DC capacitor 202 connected in series, and the common neutral terminal is the connection midpoint between the first DC capacitor 201 and the second DC capacitor 202.

[0100] In this embodiment, the common DC side unit 20 is equipped with a first DC capacitor 201 and a second DC capacitor 202, which are connected in series. The midpoint between the first DC capacitor 201 and the second DC capacitor 202 constitutes the common neutral terminal of the common DC side unit 20. After being connected in series, the first DC capacitor 201 and the second DC capacitor 202 jointly bear the DC bus voltage, forming the upper and lower DC bus potentials in the form of voltage division. The common neutral terminal provides a unified neutral point potential reference for the three-phase bridge arm unit 10 and the zero-sequence bridge arm unit 30, and at the same time provides a stable midpoint clamping potential support for the NPC three-level bridge arm 500, so that each power unit can rely on the common neutral terminal to complete the potential reference, zero-sequence circulating current control and three-level potential clamping operation.

[0101] In the above-mentioned embodiments, a common DC side unit is formed by connecting the first DC capacitor and the second DC capacitor in series, and the midpoint of the connection between the two capacitors is used as the common neutral terminal. The structure is simple and regular, and no additional neutral point construction device is required.

[0102] In one embodiment, such as Figure 11 As shown, the above-mentioned intensive transient disturbance control circuit also includes: a grounding branch 40, which includes: a line-to-ground capacitor 401, a line-to-ground resistor 402, and a fault resistor 403; each phase of the three-phase power grid access unit is connected to a set of line-to-ground capacitors 401 and line-to-ground resistors 402 and then grounded, and the line-to-ground capacitors 401 and the corresponding line-to-ground resistors 402 are connected in parallel; one end of the fault resistor 403 is connected to any phase of the three-phase power grid access unit, and the other end of the fault resistor 403 is grounded.

[0103] In the embodiments of this application, C 0x The line-to-ground capacitance is 401, r 0x The line-to-ground resistance 402 is used for the first, second, and third phases of the three-phase power grid access unit. Each phase is connected to a corresponding set of line-to-ground capacitors 401 and line-to-ground resistors 402. The line-to-ground capacitors 401 and line-to-ground resistors 402 within each set are arranged in parallel. The overall structure after parallel connection is then connected to the grounding terminal, achieving a reliable connection between each phase of the three-phase power grid and ground. The fault resistor 403 adopts a single-point connection method. One end of the fault resistor 403 can be selectively connected to any phase line of the three-phase power grid access unit, while the other end is grounded. This is used to simulate a single-phase ground fault scenario in the power grid, ensuring that the circuit can form a complete grounding path under both normal operation and fault conditions.

[0104] In the embodiments of this application, the above-mentioned grounding branch not only ensures the ground insulation monitoring requirements during normal power grid operation, but also provides a stable path for zero-sequence current regulation under fault conditions, thereby improving the practicality and reliability of the intensive transient disturbance regulation circuit.

[0105] The technical features of the above embodiments can be combined in any way. For the sake of brevity, not all possible combinations of the technical features in the above embodiments are described. However, as long as there is no contradiction in the combination of these technical features, they should be considered to be within the scope of this application.

[0106] The embodiments described above are merely illustrative of several implementation methods of this application, and while the descriptions are specific and detailed, they should not be construed as limiting the scope of this patent application. It should be noted that those skilled in the art can make various modifications and improvements without departing from the concept of this application, and these all fall within the protection scope of this application. Therefore, the protection scope of this application should be determined by the appended claims.

Claims

1. A compact transient disturbance control circuit, characterized in that, The intensive transient disturbance control circuit includes: a three-phase bridge arm unit, a common DC side unit, and a zero-sequence bridge arm unit; the three-phase bridge arm unit is respectively connected to each phase power supply branch of the three-phase power grid, the common neutral terminal of the common DC side unit, and the input terminal of the zero-sequence bridge arm unit, and the output terminal of the zero-sequence bridge arm unit is grounded; The zero-sequence bridge arm unit is used to generate a first current to cancel the zero-sequence component of a fault, based on the grid voltage, grid current, and common neutral terminal voltage of the three-phase power grid. The three-phase bridge arm unit is used to determine the three-phase reactive power compensation current based on the common neutral terminal voltage and the first current input to the zero-sequence bridge arm unit, and to send the three-phase reactive power compensation current to the corresponding phase distribution line of the three-phase power grid. The common DC side unit is used to provide common DC voltage support for the three-phase bridge arm unit and the zero-sequence bridge arm unit.

2. The intensive transient disturbance control circuit according to claim 1, characterized in that, The three-phase bridge arm unit includes: a first bridge arm, a second bridge arm, and a third bridge arm; the three-phase power grid access unit includes: a first phase, a second phase, and a third phase; the first phase, the second phase, and the third phase are AC lines with phases differing by 120° sequentially. The input terminal of the first bridge arm is connected to the first phase, the input terminal of the second bridge arm is connected to the second phase, and the input terminal of the third bridge arm is connected to the third phase.

3. The intensive transient disturbance control circuit according to claim 2, characterized in that, Each phase arm in the three-phase bridge arm unit includes a passive voltage divider capacitor and a first downstream power unit. One end of the passive voltage divider capacitor is connected to the corresponding phase line of the three-phase power grid, and the other end of the passive voltage divider capacitor is connected to the input terminal of the downstream power unit. The output terminal of the downstream power unit is connected to the common DC side unit. The passive voltage divider capacitor is used to divide the voltage in series with the first power unit to reduce the voltage stress on the power switch.

4. The intensive transient disturbance control circuit according to claim 3, characterized in that, Each phase arm in the three-phase bridge arm unit also includes a filter inductor, which is connected in series between the corresponding phase line of the three-phase power grid and the passive voltage divider capacitor. The filter inductor is used to filter out high-frequency harmonics, suppress instantaneous inrush currents, and protect the downstream power units.

5. The intensive transient disturbance control circuit according to claim 4, characterized in that, The first power unit includes an NPC three-level bridge arm and a cascaded power module; the filter inductor, the passive voltage divider capacitor and the cascaded power module are connected in series, and the NPC three-level bridge arm and the common DC side unit form an NPC circuit.

6. The intensive transient disturbance control circuit according to claim 1, characterized in that, The zero-sequence bridge arm unit includes a passive voltage divider inductor and a second power unit. The input terminal of the second power unit is connected to the common neutral terminal of the common DC side unit, and the output terminal of the second power unit is connected to one end of the passive voltage divider inductor. The other end of the passive voltage divider inductor is grounded. The passive voltage divider inductor is used to share the zero-sequence circuit voltage, reduce the voltage stress of the second power unit, and suppress inrush current and harmonics.

7. The intensive transient disturbance control circuit according to claim 6, characterized in that, The second power unit includes an NPC three-level bridge arm and a cascaded power module; the cascaded power module is connected in series with the passive voltage divider inductor, and the NPC three-level bridge arm and the common DC side unit form an NPC circuit.

8. The intensive transient disturbance control circuit according to claim 5 or 7, characterized in that, The cascaded power module is a cascaded H-bridge power module.

9. The intensive transient disturbance control circuit according to claim 5 or 7, characterized in that, The NPC three-level bridge arm includes a first power device, a second power device, a third power device, and a fourth power device, as well as a first clamping diode and a second clamping diode; The first power device, the second power device, the third power device, and the fourth power device are connected in series; the first terminal of the first clamping diode is connected to the second terminal of the second clamping diode; The connection point of the first power device and the second power device is connected to the second end of the first clamping diode, and the connection point of the third power device and the fourth power device is connected to the first end of the second clamping diode; The connection point between the first terminal of the first clamping diode and the second clamping diode is connected to the common neutral terminal of the common DC side unit.

10. The intensive transient disturbance control circuit according to claim 1, characterized in that, The common DC side unit includes a first DC capacitor and a second DC capacitor connected in series, and the common neutral terminal is the midpoint of the connection between the first DC capacitor and the second DC capacitor.

11. The intensive transient disturbance control circuit according to claim 1, characterized in that, The intensive transient disturbance control circuit further includes: a grounding branch, which includes: the line-to-ground capacitance, the line-to-ground resistance, and the fault resistance; Each phase of the three-phase power grid access unit is connected to a set of line-to-ground capacitors and line-to-ground resistors and then grounded. The line-to-ground capacitors and the corresponding line-to-ground resistors are connected in parallel. One end of the fault resistor is connected to any phase of the three-phase power grid access unit, and the other end of the fault resistor is grounded.

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