Three-phase four-bridge-arm inversion topological structure for distribution network direct-current voltage regulation device

Abstract

The utility model relates to a three-phase four-bridge-arm inversion topological structure for a distribution network direct-current voltage regulation device. The three-phase four-bridge-arm inversion topological structure comprises a three-phase four-wire alternating-current power grid, a load Load, a rectifier REC and an inverter INV. A novel direct-current power transmission mode is adopted. In the device, a rectifier REC and an inverter INV both adopt the same three-phase four-bridge-arm topology, the rectifier REC inputs a three-phase four-wire system, the voltage is boosted into 750V direct current through AC / DC conversion, the 750V direct current is remotely transmitted to the inverter INV side, the inverter INV is converted into alternating current through DC / AC conversion, the alternating current is merged into the tail end of a power grid line, the voltage of the tail end of the power grid line is governed, and if the voltage of the user side of the tail end of the power grid is lower than 220Vac, the inverter INV is switched to the 750V direct current. According to the device, the terminal voltage can be boosted to 220Vac to be supplied to a user side, so that the power utilization stability of the user side is ensured, namely, the low-voltage treatment of the terminal of the power grid is realized.

Description

Technical Field

[0001] The utility model relates to the technical field of power conversion, in particular to a three-phase four-leg inverter topology structure for a distribution network DC voltage regulation device. Background Technique

[0002] Due to the increase in household appliances and the increase in power consumption load among electricity customers, and the increasing requirements for power quality. Especially for rural scattered users, due to the long power supply radius and small wire diameter, low voltage and unbalanced three-phase loads often occur, resulting in a decrease in user satisfaction; because this type of user is relatively scattered, according to the low-voltage substation governance plan, adding new distribution transformer points, replacing large wire diameter conductors, and changing two-phase power supply to four-phase power supply increase the investment in the power grid and do not achieve the expected effect.

[0003] For example, the document with the publication number CN113824121B discloses a structure for suppressing common-mode interference applied to a flexible DC integrated voltage regulation device. The invention solves the problem of suppressing common-mode interference in the flexible DC integrated voltage regulation device, realizes the isolation of common-mode interference signals while adjusting the grid voltage, and achieves the goal of adjusting the power quality.

[0004] However, in the past conventional DC power transmission, T-type three-level is used for power conversion. During the power conversion process, situations such as uneven three-phase current sharing and bus voltage bias often occur. In the past equipment, it was often necessary to add a balancing circuit to suppress the bias voltage and uneven current sharing, increasing the complexity and cost of the system. Content of the Utility Model

[0005] (1) Technical Problems to be Solved

[0006] To solve the above technical problems, the utility model provides a three-phase four-leg inverter topology structure for a distribution network DC voltage regulation device.

[0007] (2) Technical Solutions

[0008] Based on this, the utility model provides the following technical solutions: A three-phase four-leg inverter topology structure for a distribution network DC voltage regulation device, including a three-phase four-wire AC power grid, a load Load, a rectifier REC, and an inverter INV. The three-phase four-wire AC power grid is connected to the load Load through a branch cable. Four output terminals of the rectifier REC are connected to the front ends of the four legs ABCN of the three-phase four-wire AC power grid. Four output terminals of the inverter INV are connected to the ends of the four legs ABCN of the three-phase four-wire AC power grid. The line between the rectifier REC and the inverter INV uses DC flexible DC power transmission;

[0009] The inverter INV is composed of 16 IGBT tubes. Four IGBT tubes are arranged on each of the four bridge arms ABCN. Each bridge arm consists of four IGBT tubes and two diodes. The midpoint is led out and divided into an upper bridge arm and a lower bridge arm. On the upper and lower sides of the A bridge arm, IGBT tube QA1, IGBT tube QA2, IGBT tube QA3, and IGBT tube QA4 are respectively connected. On the upper and lower sides of the B bridge arm, IGBT tube QB1, IGBT tube QB2, IGBT tube QB3, and IGBT tube QB4 are respectively connected. On the upper and lower sides of the C bridge arm, IGBT tube QC1, IGBT tube QC2, IGBT tube QC3, and IGBT tube QC4 are respectively connected. On the upper and lower sides of the N bridge arm, IGBT tube QN1, IGBT tube QN2, IGBT tube QN3, and IGBT tube QN4 are respectively connected. The ends of the four bridge arms ABCN of the three-phase four-wire AC power grid are respectively connected to inductors LA2, LB2, LC2, and LN2.

[0010] Preferably, the voltage of the DC flexible DC transmission is 750V.

[0011] Preferably, the collectors of IGBT tube QA1, IGBT tube QB1, IGBT tube QC1, and IGBT tube QN1 are connected to the upper end of the bus capacitor Cop. The emitters of IGBT tube QA2, IGBT tube QB2, IGBT tube QC2, and IGBT tube QN2 are connected to the lower end of the bus capacitor Cop. The bus capacitor Cop is connected to the upper end of the bus voltage Vdc.

[0012] Preferably, the collectors of IGBT tube QA3, IGBT tube QB3, IGBT tube QC3, and IGBT tube QN3 are connected to the upper end of the bus capacitor Cdw. The emitters of IGBT tube QA4, IGBT tube QB4, IGBT tube QC4, and IGBT tube QN4 are connected to the lower end of the bus capacitor Cdw. The bus capacitor Cdw is connected to the lower end of the bus voltage Vdc.

[0013] Preferably, the emitter of IGBT tube QA2 and the collector of IGBT tube QA3 are connected to the left end of inductor LA1. The emitter of IGBT tube QB2 and the collector of IGBT tube QB3 are connected to the left end of inductor LB1. The emitter of IGBT tube QC2 and the collector of IGBT tube QC3 are connected to the left end of inductor LC1. The emitter of IGBT tube QN2 and the collector of IGBT tube QN3 are connected to the left end of inductor LN1.

[0014] Preferably, the inductor LA1 is connected to the left end of the inductor LA2, the inductor LB1 is connected to the left end of the inductor LB2, the inductor LC1 is connected to the left end of the inductor LC2, and the inductor LN1 is connected to the left end of the inductor LN2.

[0015] Preferably, the circuit between the inductor LA1 and the inductor LA2 is connected to a filter capacitor CA, the circuit between the inductor LB1 and the inductor LB2 is connected to a filter capacitor CB, the circuit between the inductor LC1 and the inductor LC2 is connected to a filter capacitor CC, the circuit between the inductor LN1 and the inductor LN2 is connected to a filter capacitor CN, and the filter capacitor CA, filter capacitor CB, filter capacitor CC, and filter capacitor CN are connected in series with each other.

[0016] Preferably, the IGBT tube uses a 1200V / 100A SIC for power conversion, namely DC / AC, the equipment has a rated output line voltage of 380V, an output voltage frequency of 50HZ, and a DC bus voltage of 750V.

[0017] Preferably, the bus capacitor Cop and the bus capacitor Cdw use multiple 450V / 820uF electrolytic capacitors to stabilize the voltage and ensure the output of power. The filter inductor is a 10mH ferrite inductor, and the filter capacitor is a 440VAC 2.5uF film capacitor. The switching frequency of the semiconductor power tube is 20kHZ, where the inductor and bus capacitor serve as lift-voltage, the diode in the bridge arm serves to clamp the voltage, and the body diode serves to freewheel.

[0018] (3) Beneficial effects

[0019] Compared with the prior art, the present invention provides a three-phase four-bridge-leg inverter topology structure for a distribution network DC voltage regulator, which has the following beneficial effects:

[0020] This distribution network DC voltage regulator uses a three-phase, four-leg inverter topology and a novel DC transmission method (flexible DC). In this device, both the rectifier REC and the inverter INV utilize the same three-phase, four-leg topology. The rectifier REC input is three-phase, four-wire, and the voltage is boosted to 750V DC through AC / DC conversion. This voltage is then transmitted over long distances to the inverter INV. The inverter INV then converts this voltage to AC through DC / AC conversion and is incorporated into the end of the grid line to manage the voltage at the end. If the voltage at the end user side of the grid is lower than 220Vac, this device can boost the voltage to 220Vac to supply the user side, ensuring stable power consumption at the user side. This is known as low-voltage management at the end of the grid. BRIEF DESCRIPTION OF THE DRAWINGS

[0021] Figure 1 This is a schematic diagram of the overall circuit connection of the utility model;

[0022] Figure 2 This is a schematic diagram of the circuit connection of the inverter of the present utility model.

[0023] In the figure: three-phase four-wire AC power grid, load - Load, rectifier - REC, inverter - INV, IGBT transistor - QA1, IGBT transistor - QA2, IGBT transistor - QA3, IGBT transistor - QA4, IGBT transistor - QB1, IGBT transistor - QB2, IGBT transistor - QB3, IGBT transistor - QB4, IGBT transistor - QC1, IGBT transistor - QC2, IGBT transistor - QC3, IGBT transistor - QC4, IGBT transistor - QN1, IGBT transistor - QN2, IGBT transistor - QN3, IGBT transistor - QN4, inductor - LA1, inductor - LB1, inductor - LC1, inductor - LN1, inductor - LA2, inductor - LB2, inductor - LC2, inductor - LN2, bus capacitor - Cop, bus voltage - Vdc, bus capacitor - Cdw, filter capacitor - CA, filter capacitor - CB, filter capacitor - CC, filter capacitor - CN. Specific implementation mode

[0024] Next, the technical solutions in the embodiments of the present utility model will be clearly and completely described in conjunction with the accompanying drawings in the embodiments of the present utility model. Obviously, the described embodiments are only a part of the embodiments of the present utility model, rather than all the embodiments. All other embodiments obtained by those of ordinary skill in the art based on the embodiments of the present utility model without making creative efforts shall fall within the protection scope of the present utility model.

[0025] Please refer to Figure 1 - Figure 2, a three-phase four-leg inverter topology for a distribution network DC voltage regulation device, including a three-phase four-wire AC power grid, a load Load, a rectifier REC, and an inverter INV. The three-phase four-wire AC power grid is connected to the load Load through a branch cable. Four output terminals of the rectifier REC are connected to the front ends of the four legs ABCN of the three-phase four-wire AC power grid, and four output terminals of the inverter INV are connected to the ends of the four legs ABCN of the three-phase four-wire AC power grid. The line between the rectifier REC and the inverter INV uses DC flexible DC transmission; the inverter INV is composed of 16 IGBT tubes, with 4 IGBT tubes arranged on each of the four legs ABCN. Each leg consists of 4 IGBT tubes and 2 diodes. The midpoint is led out and divided into an upper leg and a lower leg. On the upper and lower sides of the A leg, IGBT tube QA1, IGBT tube QA2, IGBT tube QA3, and IGBT tube QA4 are respectively connected. On the upper and lower sides of the B leg, IGBT tube QB1, IGBT tube QB2, IGBT tube QB3, and IGBT tube QB4 are respectively connected. On the upper and lower sides of the C leg, IGBT tube QC1, IGBT tube QC2, IGBT tube QC3, and IGBT tube QC4 are respectively connected. On the upper and lower sides of the N leg, IGBT tube QN1, IGBT tube QN2, IGBT tube QN3, and IGBT tube QN4 are respectively connected. The ends of the four legs ABCN of the three-phase four-wire AC power grid are respectively connected to inductors LA2, LB2, LC2, and LN2.

[0026] In this embodiment, the voltage of the DC flexible DC transmission is 750V, aiming to reduce the loss of the AC line. The whole device is connected in parallel to the power grid, with higher safety, and has functions such as low voltage at the end, voltage imbalance, and bus bias voltage.

[0027] In this embodiment, the collectors of IGBT transistors QA1, QB1, QC1, and QN1 are connected to the upper end of the bus capacitor Cop. The emitters of IGBT transistors QA2, QB2, QC2, and QN2 are connected to the lower end of the bus capacitor Cop. The bus capacitor Cop is connected to the upper end of the bus voltage Vdc. The collectors of IGBT transistors QA3, QB3, QC3, and QN3 are connected to the upper end of the bus capacitor Cdw. The emitters of IGBT transistors QA4, QB4, QC4, and QN4 are connected to the lower end of the bus capacitor Cdw. The bus capacitor Cdw is connected to the lower end of the bus voltage Vdc. The emitter of IGBT transistor QA2 and the collector of IGBT transistor QA3 are connected to the left end of inductor LA1. The emitter of IGBT transistor QB2 and the collector of IGBT transistor QB3 are connected to the left end of inductor LB1. The emitter of IGBT transistor QC2 and the collector of IGBT transistor QC3 are connected to the left end of inductor LC1. The emitter of IGBT transistor QN2 and the collector of IGBT transistor QN3 are connected to the left end of inductor LN1. The left end of inductor LA1 is connected to the left end of inductor LA2. The left end of inductor LB1 is connected to the left end of inductor LB2. The left end of inductor LC1 is connected to the left end of inductor LC2. The left end of inductor LN1 is connected to the left end of inductor LN2. A filter capacitor CA is connected to the line between inductor LA1 and inductor LA2. A filter capacitor CB is connected to the line between inductor LB1 and inductor LB2. A filter capacitor CC is connected to the line between inductor LC1 and inductor LC2. A filter capacitor CN is connected to the line between inductor LN1 and inductor LN2. The filter capacitors CA, CB, CC, and CN are connected in series with each other.

[0028] In this application, the IGBT transistors are selected as 1200V / 100A SIC for power conversion, i.e., DC / AC. The rated output line voltage of the device is 380V, the output voltage frequency is 50HZ, the DC bus is 750V. The bus capacitors Cop and Cdw are selected as multiple 450V / 820uF electrolytic capacitors to stabilize the voltage and ensure power output. The filter inductor is a 10mH ferrite inductor, and the filter capacitor is a 2.5uF thin-film capacitor of 440VAC. The switching frequency of the semiconductor power transistor is 20kHz. Among them, the inductor and the bus capacitor are used for voltage boosting, the diode in the bridge arm is used for voltage clamping, and the body diode is used for freewheeling.

[0029] In a typical embodiment of the present application, taking phase A as an example:

[0030] For positive voltage and negative current (V>0, I<0), after the IGBT tube QA3 is turned on, the current flows from the IGBT tube QA3 and the lower diode of the arm to the neutral point to achieve commutation. At the same time, the body diode of the IGBT tube QA1 recovers reversely; after the IGBT tube QA3 is turned off, the current is continued by the IGBT tube QA1 and the body diode of the IGBT tube QA2.

[0031] For positive voltage and positive current (V>0, I>0), the IGBT tubes QA1 and QA2 are turned on, and the current flows from the IGBT tubes QA1 and QA2 to the AC side. After the IGBT tube QA1 is turned off, the current is continued by the IGBT tube QA2 and the upper diode to the AC terminal.

[0032] For negative voltage and positive current (V<0, I>0), in this case, when flowing out of the topology from the AC terminal, when a negative pulse is output, the current flows out from the negative terminal through the diode; when a zero pulse is output, the current flows to the AC terminal through the IGBT tube QA2 and the diode.

[0033] For negative voltage and negative current (V<0, I<0), after the IGBT tube QA4 is turned off, the current is continued by the IGBT tube QA3 and the lower arm diode to the neutral point; after the IGBT tube QA4 is turned on, the current is commutated by the IGBT tubes QA3 and QA4, and at the same time, the lower arm diode recovers reversely.

[0034] For example, when the upper tube of the phase A arm is turned on and the lower tube is turned off, the voltage VA = E, and the switching mode of this arm is defined as 1; when the upper arm is turned off and the lower arm is turned on, VA = 0, and the switching mode of this arm is defined as 0. According to the complementary mode of the upper and lower arms, 16 switching modes can be arranged, and there is a corresponding voltage at the midpoint A of each arm with respect to the g point; SA, SB, SC, SN. The voltages of the A / B / C arms with respect to N are E(SA - SN), E(SB - SN), E(SC - SN).

[0035] The purpose of three-phase balance is achieved according to the sampling of the voltage of each phase and the duty cycle regulation.

[0036] This device mainly uses a three-phase four-arm as the main topology to convert alternating current into direct current through a rectifier, use direct current for high-voltage transmission, and the line loss is much smaller than that of alternating current transmission. Then, the inverter side converts the direct current back into alternating current and incorporates it into the end-user side of the power grid. If the voltage at the end-user side of the power grid is lower than 220Vac, this device can boost the end voltage to 220Vac to supply the user side, ensuring the stable power consumption of the user side, that is, the low-voltage governance of the end of the power grid.

[0037] Although embodiments of the present utility model have been shown and described, those of ordinary skill in the art can understand that various changes, modifications, substitutions, and variations can be made to these embodiments without departing from the principle and spirit of the present utility model. The scope of the present utility model is defined by the appended claims and their equivalents.

Claims

1. A three-phase four-leg inverter topology for a distribution network DC voltage regulation device, characterized in that: It includes a three-phase four-wire AC power grid, a load, a rectifier (REC), and an inverter (INV). The three-phase four-wire AC power grid is connected to the load through a branch cable. Four output terminals of the rectifier (REC) are connected to the front-end ABCN four arms of the three-phase four-wire AC power grid. Four output terminals of the inverter (INV) are connected to the end ABCN four arms of the three-phase four-wire AC power grid. The line between the rectifier (REC) and the inverter (INV) uses DC flexible DC power transmission. The inverter (INV) is composed of 16 IGBT tubes. Four IGBT tubes are arranged on each of the ABCN four arms. Each arm is composed of 4 IGBT tubes and 2 diodes. On the upper and lower sides of the A arm, IGBT tube (QA1), IGBT tube (QA2), IGBT tube (QA3), and IGBT tube (QA4) are connected respectively. On the upper and lower sides of the B arm, IGBT tube (QB1), IGBT tube (QB2), IGBT tube (QB3), and IGBT tube (QB4) are connected respectively. On the upper and lower sides of the C arm, IGBT tube (QC1), IGBT tube (QC2), IGBT tube (QC3), and IGBT tube (QC4) are connected respectively. On the upper and lower sides of the N arm, IGBT tube (QN1), IGBT tube (QN2), IGBT tube (QN3), and IGBT tube (QN4) are connected respectively. The end ABCN four arms of the three-phase four-wire AC power grid are respectively connected to inductor (LA2), inductor (LB2), inductor (LC2), and inductor (LN2).

2. A three-phase four-leg inverter topology for a distribution network DC voltage regulation device according to claim 1, characterized in that: The voltage of the DC flexible DC power transmission is 750V.

3. A three-phase four-leg inverter topology for a distribution network DC voltage regulation device according to claim 1, characterized in that: The collectors of IGBT tube (QA1), IGBT tube (QB1), IGBT tube (QC1), and IGBT tube (QN1) are connected to the upper end of the bus capacitor (Cop). The emitters of IGBT tube (QA2), IGBT tube (QB2), IGBT tube (QC2), and IGBT tube (QN2) are connected to the lower end of the bus capacitor (Cop). The bus capacitor (Cop) is connected to the upper end of the bus voltage (Vdc).

4. A three-phase four-leg inverter topology for a distribution network DC voltage regulation device according to claim 1, characterized in that: The collectors of IGBT tube (QA3), IGBT tube (QB3), IGBT tube (QC3), and IGBT tube (QN3) are connected to the upper end of the bus capacitor (Cdw). The emitters of IGBT tube (QA4), IGBT tube (QB4), IGBT tube (QC4), and IGBT tube (QN4) are connected to the lower end of the bus capacitor (Cdw). The bus capacitor (Cdw) is connected to the lower end of the bus voltage (Vdc).

5. A three-phase four-leg inverter topology for a distribution network DC voltage regulation device according to claim 1, characterized in that: The emitter of the IGBT transistor (QA2), the collector of the IGBT transistor (QA3) are connected to the left end of the inductor (LA1). The emitter of the IGBT transistor (QB2), the collector of the IGBT transistor (QB3) are connected to the left end of the inductor (LB1). The emitter of the IGBT transistor (QC2), the collector of the IGBT transistor (QC3) are connected to the left end of the inductor (LC1). The emitter of the IGBT transistor (QN2), the collector of the IGBT transistor (QN3) are connected to the left end of the inductor (LN1).

6. The three-phase four-leg inverter topology for a distribution network DC voltage regulation device according to claim 5, wherein: The left end of the inductor (LA1) is connected to the left end of the inductor (LA2). The left end of the inductor (LB1) is connected to the left end of the inductor (LB2). The left end of the inductor (LC1) is connected to the left end of the inductor (LC2). The left end of the inductor (LN1) is connected to the left end of the inductor (LN2).

7. A three-phase four-leg inverter topology for a distribution network DC voltage regulation device according to claim 6, characterized in that: A filter capacitor (CA) is connected to the line between the inductor (LA1) and the inductor (LA2). A filter capacitor (CB) is connected to the line between the inductor (LB1) and the inductor (LB2). A filter capacitor (CC) is connected to the line between the inductor (LC1) and the inductor (LC2). A filter capacitor (CN) is connected to the line between the inductor (LN1) and the inductor (LN2). The filter capacitors (CA), (CB), (CC), and (CN) are connected in series with each other.

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