Medium voltage fast flexible power electronic voltage regulating device

Abstract

The utility model relates to a kind of medium voltage fast flexible power electronic voltage regulating device, it is related to voltage regulating technical field technical field, solve the problem of slow response, single function, low reliability of existing voltage regulating device.The utility model uses AC-AC two-stage conversion topology, combined with Dyn11 voltage reduction and Yd11 voltage increasing transformer combination and double bypass protection framework, integrates voltage current double loop control and TTA harmonic detection algorithm, solve the problem of slow response, single function, low reliability of existing voltage regulating device, can simultaneously realize fast voltage regulating, harmonic suppression and uninterrupted power supply, applicable to remote area, rural power grid and city network table area, with wide application prospect.

Description

Technical Field

[0001] This utility model relates to the field of voltage regulation technology, specifically to a medium-voltage fast flexible power electronic voltage regulator. Background Technology

[0002] With the continuous advancement of medium- and low-voltage distribution network construction, electricity load is growing rapidly, and distribution lines are constantly extending. The number of long-distance, heavily loaded power supply lines is increasing, leading to more prominent power quality problems such as low voltage at the line ends, large voltage fluctuations, three-phase imbalance, and excessive voltage harmonics. Especially in remote areas such as Xinjiang, and in rural and urban power grid areas, the voltage quality problems in the distribution network are further exacerbated by factors such as excessively large power supply radius, dispersed load distribution, significant seasonal load fluctuations, and large-scale grid connection of distributed energy sources. This results in the load-end power supply voltage failing to meet national standards, directly affecting users' normal production and daily electricity consumption, and posing greater challenges to power supply reliability and grid safety. Currently, there is an urgent need for a medium-voltage voltage management device that is fast-responding, highly accurate, functionally integrated, and reliable in operation to address the prominent problem that existing technologies cannot adapt to complex distribution network conditions.

[0003] Currently, voltage regulation and power quality management in 10kV distribution networks mainly employ three technical methods: mechanical or contactless on-load tap changers, line series tap changers, and reactive power compensation devices. However, all of these methods have significant limitations and defects. Traditional on-load tap changers suffer from arcing during regulation, slow response speed, and inability to make frequent adjustments. While contactless on-load tap changers offer some improvement, they are still limited by the voltage withstand capability of components, resulting in a small regulation range. High-low voltage isolation designs are prone to causing control system breakdown, and circulating currents can easily burn out components during switching. Furthermore, they lack reactive power compensation capabilities, which can exacerbate the risk of voltage drops in the main grid when the system has a large reactive power deficit. Line series tap changers can increase the voltage at the end of the line, but they further lower the voltage at the beginning of the line. Under low load conditions, they are prone to overvoltage damage to equipment. Their large size and weight make installation and maintenance inconvenient, and they have poor resistance to load fluctuations. Conventional reactive power compensation devices can only improve low voltage caused by reactive power loss and cannot solve voltage problems caused by active power loss. They can manage current harmonics but cannot suppress voltage harmonics. Overall, their response speed is slow, and they cannot achieve rapid and accurate compensation for transient voltages. In summary, existing technologies generally suffer from problems such as limited functionality, low reliability, complex control, and poor adaptability. They are unable to simultaneously meet the comprehensive needs of rapid voltage regulation, harmonic suppression, reactive power compensation, and uninterrupted power supply during faults, and cannot meet the requirements of high-quality voltage management in new distribution networks. Utility Model Content

[0004] To address the technical problems of existing 10kV distribution network voltage regulation devices, such as slow response, limited functionality, low reliability, and inability to simultaneously achieve rapid voltage regulation, harmonic suppression, and uninterrupted power supply, this utility model provides a medium-voltage fast flexible power electronic voltage regulation device, comprising: an input isolating switch, an output isolating switch, a high-voltage bypass switch, a step-down transformer, a low-voltage molded case circuit breaker, a step-up transformer, and a low-voltage power unit.

[0005] The input terminal of the input isolating switch is connected to a 10kV power grid, and the output terminal is connected to the primary side of the step-down transformer.

[0006] The step-down transformer adopts a Dyn11 connection, and the secondary side of the step-down transformer is connected to the input terminal of the low-voltage molded case circuit breaker.

[0007] The output terminal of the low-voltage molded case circuit breaker is connected to the input terminal of the low-voltage power unit;

[0008] The output terminal of the low-voltage power unit is connected to the primary side of the step-up transformer;

[0009] The step-up transformer adopts a Yd11 connection, and the secondary side of the step-up transformer is connected to the input terminal of the output isolating switch;

[0010] The output terminal of the output isolating switch is used to connect to the load;

[0011] The high-voltage bypass switch is connected between the output terminal of the input isolating switch and the input terminal of the output isolating switch;

[0012] The low-voltage power unit includes: a soft-start circuit, an input LCL filter unit, a PWM rectifier, a PWM inverter, an output LCL filter unit, a low-voltage contactor bypass unit, and a low-voltage thyristor bypass unit.

[0013] The soft start circuit is connected in series between the low-voltage molded case circuit breaker and the input LCL filter unit;

[0014] The AC side of the PWM rectifier is connected to the output terminal of the low-voltage molded case circuit breaker through the input LCL filter unit, and the DC side of the PWM rectifier and the DC side of the PWM inverter share a DC bus.

[0015] The AC side of the PWM inverter is connected to the primary side of the step-up transformer via the output LCL filter unit; the low-voltage contactor bypass unit is connected across the output terminal of the output LCL filter unit and the primary side of the step-up transformer.

[0016] The low-voltage thyristor bypass unit consists of two sets of delta-connected thyristors, which are connected in parallel.

[0017] The low-voltage thyristor bypass unit and the low-voltage contactor bypass unit are connected in parallel and are connected together across the output terminal of the output LCL filter unit and the primary side of the step-up transformer.

[0018] Furthermore, the soft-start circuit includes a soft-start AC contactor and a soft-start resistor, wherein the soft-start AC contactor is connected in parallel with the soft-start resistor.

[0019] Furthermore, each of the two sets of delta-connected thyristors contains three thyristors, corresponding to phases A, B, and C of the three-phase AC power supply, respectively.

[0020] Furthermore, a DC support capacitor is connected between the DC side of the PWM rectifier and the DC side of the PWM inverter.

[0021] Furthermore, the high-voltage bypass switch is a high-voltage bypass circuit breaker.

[0022] The beneficial effects of this utility model are as follows: 1. This utility model adopts a two-stage converter topology, which can simultaneously address steady-state and transient voltage problems such as overvoltage, undervoltage, voltage drop, and voltage surge in the power grid, and can quickly and accurately stabilize the load-side voltage within the national standard range.

[0023] 2. This utility model is equipped with a dual protection architecture of high-voltage bypass and low-voltage bypass. The low-voltage bypass adopts a structure of two sets of delta-connected thyristors and contactors connected in parallel, which can achieve uninterrupted switching in case of fault. At the same time, it adopts a combination of Dyn11 step-down transformer and Yd11 step-up transformer to achieve automatic phase matching between inverter output voltage and grid, eliminating the need for complex phase calculations, reducing control complexity and system fault risk. Attached Figure Description

[0024] Figure 1 This is the overall main circuit topology diagram of the medium-voltage fast flexible power electronic voltage regulating device of this utility model;

[0025] Figure 2 This is a diagram of the internal circuit topology of the low-voltage power unit of this invention. Detailed Implementation

[0026] The technical solution of this utility model will be further described below with reference to embodiments, but it is not limited thereto. Any modifications or equivalent substitutions to the technical solution of this utility model that do not depart from the spirit and scope of this utility model should be covered within the protection scope of this utility model. In the following embodiments, process equipment or devices not specifically specified are all conventional equipment or devices in the art. Unless specifically indicated, the technical means used in the embodiments of this utility model are all conventional means well known to those skilled in the art.

[0027] Example 1, combined with Figure 1 This embodiment describes a medium-voltage fast flexible power electronic voltage regulating device, comprising: an input isolating switch, an output isolating switch, a high-voltage bypass switch, a step-down transformer, a low-voltage molded case circuit breaker, a step-up transformer, and a low-voltage power unit;

[0028] The input terminal of the input isolating switch is connected to a 10kV power grid, and the output terminal is connected to the primary side of the step-down transformer.

[0029] The step-down transformer adopts a Dyn11 connection, and the secondary side of the step-down transformer is connected to the input terminal of the low-voltage molded case circuit breaker.

[0030] The output terminal of the low-voltage molded case circuit breaker is connected to the input terminal of the low-voltage power unit;

[0031] The output terminal of the low-voltage power unit is connected to the primary side of the step-up transformer;

[0032] The step-up transformer adopts a Yd11 connection, and the secondary side of the step-up transformer is connected to the input terminal of the output isolating switch;

[0033] The output terminal of the output isolating switch is used to connect to the load;

[0034] The high-voltage bypass switch is connected between the output terminal of the input isolating switch and the input terminal of the output isolating switch;

[0035] The low-voltage power unit includes: a soft-start circuit, an input LCL filter unit, a PWM rectifier, a PWM inverter, an output LCL filter unit, a low-voltage contactor bypass unit, and a low-voltage thyristor bypass unit.

[0036] The soft start circuit is connected in series between the low-voltage molded case circuit breaker and the input LCL filter unit;

[0037] The AC side of the PWM rectifier is connected to the output terminal of the low-voltage molded case circuit breaker through the input LCL filter unit, and the DC side of the PWM rectifier and the DC side of the PWM inverter share a DC bus.

[0038] The AC side of the PWM inverter is connected to the primary side of the step-up transformer via the output LCL filter unit; the low-voltage contactor bypass unit is connected across the output terminal of the output LCL filter unit and the primary side of the step-up transformer.

[0039] The low-voltage thyristor bypass unit consists of two sets of delta-connected thyristors, which are connected in parallel.

[0040] The low-voltage thyristor bypass unit and the low-voltage contactor bypass unit are connected in parallel and are connected together across the output terminal of the output LCL filter unit and the primary side of the step-up transformer.

[0041] Specifically, the device described in this utility model is connected in series to a 10kV power distribution line. The control unit monitors the grid voltage in real time, and the compensation voltage is generated by the PWM rectification and inverter unit. The compensation voltage is then injected into the grid through the step-up transformer to achieve rapid treatment and reactive power compensation of line overvoltage, undervoltage, and voltage harmonics. The high and low voltage bypass units can ensure uninterrupted power supply to the load when the device fails. Figure 1 The connection relationship and overall topology layout of the high-voltage side switch, dual transformers and low-voltage power unit of the device described in this utility model are clarified. Figure 2 The detailed circuit topology diagram of the low-voltage power unit shows the two-stage power conversion and bypass structure on the low-voltage side of the device: from the input side to the output side, it includes a soft-start circuit, an input LCL filter unit, a PWM rectifier, a DC support capacitor, a PWM inverter, and an output LCL filter unit. At the same time, a low-voltage thyristor bypass unit and a low-voltage contactor bypass unit are configured to form a dual low-voltage bypass, clearly showing the complete link of the low-voltage power conversion, the filtering link, and the dual bypass design for fault protection.

[0042] Furthermore, the soft-start circuit includes a soft-start AC contactor and a soft-start resistor, wherein the soft-start AC contactor is connected in parallel with the soft-start resistor.

[0043] Specifically, the soft-start resistor is used to limit the starting inrush current when the device is powered on. After startup, the soft-start AC contactor closes to short-circuit the resistor, allowing the device to enter a stable operating state and ensuring safe startup of the equipment.

[0044] Furthermore, each of the two sets of delta-connected thyristors contains three thyristors, corresponding to phases A, B, and C of the three-phase AC power supply, respectively.

[0045] Specifically, the two sets of delta-connected thyristors are connected to the corresponding A, B, and C phases in three phases. The two sets are connected in parallel to form redundant protection, which can realize the rapid bypass conduction of the three-phase circuit on the low-voltage side when the device fails, meet the requirements of ultra-fast bypass switching, and ensure uninterrupted power supply to the load.

[0046] Furthermore, a DC support capacitor is connected between the DC side of the PWM rectifier and the DC side of the PWM inverter.

[0047] Specifically, the DC support capacitor is used to stabilize the voltage of the common DC bus, filter out DC ripple, and provide instantaneous energy support for the PWM rectifier and PWM inverter, ensuring the stable and reliable operation of the two-stage converter unit.

[0048] Furthermore, the high-voltage bypass switch is a high-voltage bypass circuit breaker.

[0049] Furthermore, a DC support capacitor is connected between the DC side of the PWM rectifier and the DC side of the PWM inverter.

[0050] The DC support capacitor is used to stabilize the voltage of the common DC bus, filter out DC ripple, and provide instantaneous energy support for the PWM rectifier and PWM inverter, ensuring the stable and reliable operation of the two-stage converter unit.

Claims

1. A medium-voltage fast flexible power electronic voltage regulating device, characterized in that, include: Input isolating switch, output isolating switch, high-voltage bypass switch, step-down transformer, low-voltage molded case circuit breaker, step-up transformer and low-voltage power unit; The input terminal of the input isolating switch is connected to a 10kV power grid, and the output terminal is connected to the primary side of the step-down transformer. The step-down transformer adopts a Dyn11 connection, and the secondary side of the step-down transformer is connected to the input terminal of the low-voltage molded case circuit breaker. The output terminal of the low-voltage molded case circuit breaker is connected to the input terminal of the low-voltage power unit; The output terminal of the low-voltage power unit is connected to the primary side of the step-up transformer; The step-up transformer adopts a Yd11 connection, and the secondary side of the step-up transformer is connected to the input terminal of the output isolating switch; The output terminal of the output isolating switch is used to connect to the load; The high-voltage bypass switch is connected between the output terminal of the input isolating switch and the input terminal of the output isolating switch; The low-voltage power unit includes: a soft-start circuit, an input LCL filter unit, a PWM rectifier, a PWM inverter, an output LCL filter unit, a low-voltage contactor bypass unit, and a low-voltage thyristor bypass unit. The soft start circuit is connected in series between the low-voltage molded case circuit breaker and the input LCL filter unit; The AC side of the PWM rectifier is connected to the output terminal of the low-voltage molded case circuit breaker through the input LCL filter unit, and the DC side of the PWM rectifier and the DC side of the PWM inverter share a DC bus. The AC side of the PWM inverter is connected to the primary side of the step-up transformer via the output LCL filter unit; the low-voltage contactor bypass unit is connected across the output terminal of the output LCL filter unit and the primary side of the step-up transformer. The low-voltage thyristor bypass unit consists of two sets of delta-connected thyristors, which are connected in parallel. The low-voltage thyristor bypass unit and the low-voltage contactor bypass unit are connected in parallel and are connected together across the output terminal of the output LCL filter unit and the primary side of the step-up transformer.

2. The medium-voltage fast flexible power electronic voltage regulating device according to claim 1, characterized in that, The soft-start circuit includes a soft-start AC contactor and a soft-start resistor, wherein the soft-start AC contactor is connected in parallel with the soft-start resistor.

3. The medium-voltage fast flexible power electronic voltage regulating device according to claim 1, characterized in that, The two sets of delta-connected thyristors each contain three thyristors, corresponding to phases A, B, and C of the three-phase AC power supply, respectively.

4. The medium-voltage fast flexible power electronic voltage regulating device according to claim 1, characterized in that, A DC support capacitor is also connected between the DC side of the PWM rectifier and the DC side of the PWM inverter.

5. A medium-voltage fast flexible power electronic voltage regulating device according to claim 1, characterized in that, The high-voltage bypass switch is a high-voltage bypass circuit breaker.

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