Comprehensive conditioning device for electric energy quality of tail end line of low-voltage distribution network

Abstract

The invention relates to the technical field of power distribution equipment, in particular to a low-voltage distribution network tail end line power quality comprehensive conditioning device which comprises a low-voltage flexible compensation assembly, a main circuit and a control circuit. The main circuit comprises a transformer, a filter assembly, a filter reactor, a first three-level inverter and a second three-level inverter; a primary winding of the transformer is connected in series between an input power supply and a load; the low-voltage flexible compensation assembly is linearly connected between the transformer and the load; according to the invention, a series and parallel three-level inverter technology is adopted; the two converters are controlled in real time through the control circuit, so that various electric energy quality adjusting functions such as reactive compensation, harmonic compensation, unbalance compensation and low-voltage compensation can be realized, and the effect of an electric energy quality treatment scheme is greatly improved.

Description

Technical Field

[0001] The present invention relates to the technical field of power distribution equipment, and in particular to a low-voltage distribution network terminal line power quality comprehensive conditioning device. Background Art

[0002] At present, the power quality problems existing in the distribution station area mainly include: low power factor, unbalanced three-phase load, excessive system harmonic content and low voltage at the end; power quality problems will cause adverse consequences such as increased line losses and equipment accidents, affecting power supply reliability.

[0003] The existing method for managing power quality mainly controls the three-phase load imbalance problem by manually changing the line and adjusting the load. This method can temporarily solve the three-phase load imbalance problem, but it has high labor costs, requires cutting off the power supply to users, and cannot adapt to the changing laws of load in the long term. Therefore, the existing power quality management solution is not effective. Summary of the invention

[0004] In view of the problems existing in the prior art, the present invention is proposed.

[0005] To solve the above technical problems, the present invention provides the following technical solutions: a low-voltage distribution network terminal line power quality comprehensive conditioning device, comprising a low-voltage flexible compensation component, a main circuit and a control circuit; the main circuit comprises a transformer, a filter component, a filter reactor, a first three-level inverter and a second three-level inverter; the primary winding of the transformer is connected in series between the input power supply and the load; the low-voltage flexible compensation component is linearly connected between the transformer and the load; the third-level inverter is connected in series to the power grid after passing through the filter component and the secondary winding of the transformer, the second three-level inverter is connected in parallel with the load after passing through the filter reactor, and the control signal input end of the first three-level inverter and the control signal input end of the second three-level inverter are respectively electrically fused to the control signal output end of the control circuit.

[0006] As a preferred solution of the low-voltage distribution network terminal line power quality comprehensive conditioning device described in the present invention, wherein: the control circuit includes an acquisition unit, a preprocessing unit and a main control unit, the acquisition unit includes a grid voltage detection circuit, a load circuit detection circuit, an output circuit detection circuit and a DC bus voltage detection circuit; the preprocessing unit includes a conditioning circuit and an analog-to-digital converter, and the main control unit includes a digital signal processor, an FPGA chip, a PWM pulse blocking module and a PWM output module.

[0007] As a preferred solution of the low-voltage distribution network terminal line power quality comprehensive conditioning device described in the present invention, wherein: the output end of the grid voltage detection circuit, the output end of the load circuit detection circuit, the output end of the output circuit detection circuit and the output end of the DC bus voltage detection circuit are electrically connected to the input end of the conditioning circuit respectively; the output end of the conditioning circuit is electrically connected to the input end of the analog-to-digital converter; the output end of the analog-to-digital converter is electrically connected to the input end of the digital signal processor, the output end of the digital signal processor is electrically connected to the input end of the FPGA chip, the output end of the FPGA chip is electrically connected to the input end of the PWM pulse blocking module, and the output end of the PWM pulse blocking module is electrically connected to the input end of the PWM output module.

[0008] As a preferred solution of the low-voltage distribution network terminal line power quality comprehensive conditioning device described in the present invention, wherein: the control circuit also includes a zero-crossing detection circuit and a protection circuit, the output end of the zero-crossing detection circuit is electrically connected to the input end of the digital signal processor, and the output end of the protection circuit is electrically connected to the input end of the PWM pulse blocking module.

[0009] As a preferred solution of the low-voltage distribution network terminal line power quality comprehensive conditioning device described in the present invention, it further includes a bypass circuit; the bypass circuit includes a first contactor, a second contactor and a third contactor; the normally open contact of the first contactor is connected in series between the input power supply and the primary winding of the transformer, the normally open contact of the second contactor is connected in series between the filter inductor and the load, and the normally open contact of the third contactor is connected in series between the input power supply and the load.

[0010] As a preferred solution of the low-voltage distribution network terminal line power quality comprehensive conditioning device described in the present invention, wherein: the power quality comprehensive management device also includes a circuit breaker and a DC capacitor; the circuit breaker is connected in series between the input power supply and the normally open contact of the third contactor; the DC capacitor is connected in parallel to the common DC end of the first three-level inverter and the second three-level inverter.

[0011] As a preferred solution of the low-voltage distribution network terminal line power quality comprehensive conditioning device described in the present invention, wherein: the DC capacitor includes a first DC capacitor and a second DC capacitor, the first DC capacitor and the second DC capacitor are connected in series; the connection line between the first DC capacitor and the second DC capacitor is electrically fused to the neutral line of the input power supply.

[0012] As a preferred solution of the low-voltage distribution network terminal line power quality comprehensive conditioning device of the present invention, wherein: the transformer includes a first single-phase transformer, a second single-phase transformer and a third single-phase transformer, the filter component includes a first inductor, a second inductor, a third inductor, a first capacitor C1, a second capacitor and a third capacitor; the filter reactor includes a fourth inductor, a fifth inductor, a sixth inductor, a seventh inductor, an eighth inductor, a ninth inductor, a fourth capacitor, a fifth capacitor and a sixth capacitor;

[0013] The first three-level inverter includes a first three-level inverter circuit, a second three-level inverter circuit and a third three-level inverter circuit; the second three-level inverter includes a fourth three-level inverter circuit, a fifth three-level inverter circuit and a sixth three-level inverter circuit; the first three-level inverter circuit, the second three-level inverter circuit, the third three-level inverter circuit, the fourth three-level inverter circuit, the fifth three-level inverter circuit and the sixth three-level inverter circuit have the same structure; the first three-level inverter circuit includes a first insulated gate bipolar transistor, a second insulated gate bipolar transistor, a third insulated gate bipolar transistor and a fourth insulated gate bipolar transistor; a diode is connected between the collector and the emitter of the first insulated gate bipolar transistor, the second insulated gate bipolar transistor, the third insulated gate bipolar transistor and the fourth insulated gate bipolar transistor; the emitter of the first insulated gate bipolar transistor is connected to the collector of the second insulated gate bipolar transistor and the collector of the third insulated gate bipolar transistor respectively; the emitter of the third insulated gate bipolar transistor is connected to the emitter of the fourth insulated gate bipolar transistor.

[0014] As a preferred solution of the low-voltage distribution network terminal line power quality comprehensive conditioning device described in the present invention, wherein: the analog-to-digital converter includes three analog-to-digital converter chips, and the model of the analog-to-digital converter chip is AD7656; the zero-crossing detection circuit, the conditioning circuit, the protection circuit and the analog-to-digital converter are all arranged on a first circuit board; the digital signal processor, the FPGA chip, the PWM pulse blocking module and the PWM output module are all arranged on a second circuit board.

[0015] As a preferred solution of the low-voltage distribution network terminal line power quality comprehensive conditioning device described in the present invention, it also includes: a device control system, an SVG main circuit and a capacitor group; the device control system includes a first pulse amplification drive board, and the first pulse amplification drive board is electrically fused to the SVG main circuit; the device control system is connected to the second pulse amplification drive board through a thyristor switching signal to electrically fuse the capacitor group; a thyristor module for identifying the thyristor switching signal is arranged inside the capacitor group.

[0016] Beneficial effects of the present invention: The low-voltage distribution network terminal line power quality comprehensive conditioning device proposed in the present invention includes a low-voltage flexible compensation component, a main circuit and a control circuit; the main circuit includes a transformer, a filter component, a filter inductor, a first three-level inverter and a second three-level inverter; the first three-level inverter is connected in series to the power grid; the second three-level inverter is connected in parallel at the load end, and the control signal input end of the first three-level inverter and the control signal input end of the second three-level inverter are respectively electrically connected to the control signal output end of the control circuit; the present invention adopts series and parallel three-level inverter technology; through the control circuit to control the two converters in real time, it can realize reactive compensation, harmonic compensation, unbalance compensation and low voltage compensation and other power quality adjustment functions, which greatly improves the effect of the power quality management solution. BRIEF DESCRIPTION OF THE DRAWINGS

[0017] In order to more clearly illustrate the technical solutions of the embodiments of the present invention, the following briefly introduces the drawings required for describing the embodiments. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without creative work. Among them:

[0018] Figure 1 It is a schematic diagram of the component structure in the present invention.

[0019] Figure 2 It is the electrical wiring diagram of the present invention. DETAILED DESCRIPTION

[0020] In order to make the above-mentioned objects, features and advantages of the present invention more obvious and easy to understand, the specific implementation methods of the present invention are described in detail below in conjunction with the accompanying drawings.

[0021] In the following description, many specific details are set forth to facilitate a full understanding of the present invention, but the present invention may also be implemented in other ways different from those described herein, and those skilled in the art may make similar generalizations without violating the connotation of the present invention. Therefore, the present invention is not limited to the specific embodiments disclosed below.

[0022] Secondly, the term "one embodiment" or "embodiment" as used herein refers to a specific feature, structure, or characteristic that may be included in at least one implementation of the present invention. The term "in one embodiment" that appears in different places in this specification does not necessarily refer to the same embodiment, nor is it a separate or selective embodiment that is mutually exclusive with other embodiments.

[0023] As attached Figure 1As shown, in one embodiment of a low-voltage distribution network terminal line power quality comprehensive conditioning device proposed by the present invention, the low-voltage distribution network terminal line power quality comprehensive conditioning device is linearly connected between the input power supply and the load; the low-voltage distribution network terminal line power quality comprehensive conditioning device includes a low-voltage flexible compensation component, a main circuit and a control circuit; the main circuit includes a transformer, a filter component, a filter reactor, a first three-level inverter and a second three-level inverter; the primary winding of the transformer is connected in series between the input power supply and the load; the low-voltage flexible compensation component is electrically fused between the transformer and the load; the first three-level inverter is connected in series to the power grid after passing through the filter component and the secondary winding of the transformer, the second three-level inverter is connected in parallel with the load after passing through the filter reactor, and the control signal input end of the third-level inverter and the control signal input end of the second three-level inverter are respectively electrically fused to the control signal output end of the control circuit; the low-voltage flexible compensation device is used to perform continuous reactive power compensation on the outlet side of the transformer.

[0024] The low-voltage distribution network terminal line power quality comprehensive conditioning device proposed in the present invention includes a low-voltage flexible compensation component, a main circuit and a control circuit; the main circuit includes a transformer, a filter component, a filter inductor, a first three-level inverter and a second three-level inverter; the first three-level inverter is connected in series to the power grid; the second three-level inverter is connected in parallel at the load end, and the control signal input end of the first three-level inverter and the control signal input end of the second three-level inverter are respectively electrically connected to the control signal output end of the control circuit; the present invention adopts series and parallel three-level inverter technology; through the control circuit to control the two converters in real time, it can realize the reactive compensation, harmonic compensation, unbalance compensation and low voltage compensation and other power quality adjustment functions, which greatly improves the effect of the power quality management scheme.

[0025] In addition, the uplink control circuit includes a collection unit, a preprocessing unit and a main control unit. The collection unit includes: a grid voltage detection circuit, a load circuit detection circuit, an output circuit detection circuit and a DC bus voltage detection circuit. The preprocessing unit includes: a conditioning circuit and an analog-to-digital converter. The main control unit includes a digital signal processor (i.e., a DSP chip), an FPGA chip, a PWM pulse blocking module and a PWM output module. Specifically, the input power here can be a three-phase four-wire AC grid with a rated voltage of 380V, a frequency of 50Hz, and a voltage fluctuation range of -40% to +20%.

[0026] At the same time, the output end of the grid voltage detection circuit, the output end of the load circuit detection circuit, the output end of the output circuit detection circuit and the output end of the DC bus voltage detection circuit are electrically connected to the input end of the conditioning circuit respectively; the output end of the conditioning circuit is electrically connected to the input end of the analog-to-digital converter; the output end of the analog-to-digital converter is electrically connected to the input end of the digital signal processor, the output end of the digital signal processor is electrically fused to the input end of the FPGA chip, the output end of the FPGA chip is electrically fused to the input end of the PWM pulse blocking module, and the output end of the PWM pulse blocking module is electrically fused to the input end of the PWM output module.

[0027] Specifically, the control circuit also includes a zero-crossing detection circuit and a protection circuit. The output end of the zero-crossing detection circuit is electrically connected to the input end of the digital signal processor, and the output end of the protection circuit is electrically fused to the input end of the PWM pulse blocking module.

[0028] In addition, the comprehensive power quality management device also includes a bypass circuit; the bypass circuit includes a first contactor, a second contactor and a third contactor; the normally open contact of the first contactor is connected in series between the input power supply and the primary winding of the transformer, the normally open contact of the second contactor is connected in series between the filter inductor and the load, and the normally open contact of the third contactor is connected in series between the input power supply and the load.

[0029] At the same time, the comprehensive power quality management device also includes a circuit breaker and a DC capacitor; the circuit breaker is connected in series between the input power supply and the normally open contact of the third contactor; the DC capacitor is connected in parallel to the common DC terminal of the first three-level inverter and the second three-level inverter.

[0030] Specifically, the DC capacitor includes a first DC capacitor and a second DC capacitor, and the first DC capacitor and the second DC capacitor are connected in series; a connection line between the first DC capacitor and the second DC capacitor is electrically connected to a neutral line of an input power supply.

[0031] Specifically, this embodiment adopts series and parallel three-level inverter technology, and controls two converters in real time through a control circuit, thereby realizing various power quality regulation functions such as reactive power compensation, harmonic compensation, unbalance compensation and low voltage compensation.

[0032] In addition, the transformer includes a first single-phase transformer, a second single-phase transformer and a third single-phase transformer, the filter component includes a first inductor, a second inductor, a third inductor, a first capacitor C1, a second capacitor and a third capacitor; the filter reactor includes a fourth inductor, a fifth inductor, a sixth inductor, a seventh inductor, an eighth inductor, a ninth inductor, a fourth capacitor, a fifth capacitor and a sixth capacitor, the first three-level inverter includes a first three-level inverter circuit, a second three-level inverter circuit and a third three-level inverter circuit; the second three-level inverter includes a fourth three-level inverter circuit, a fifth three-level inverter circuit and a sixth three-level inverter circuit; the first three-level inverter circuit, the second three-level inverter circuit, the third three-level inverter circuit, the fourth three-level inverter circuit, the first three-level inverter circuit, the second three-level inverter circuit, the third three-level inverter circuit, the fourth three-level inverter circuit, the The fifth three-level inverter circuit has the same structure as the sixth three-level inverter circuit; the third level inverter circuit includes a first insulated gate bipolar transistor, a second insulated gate bipolar transistor, a third insulated gate bipolar transistor and a fourth insulated gate bipolar transistor (IGBT unit); a diode is connected between the collector and the emitter of the first insulated gate bipolar transistor, the second insulated gate bipolar transistor, the third insulated gate bipolar transistor and the fourth insulated gate bipolar transistor; the emitter of the first insulated gate bipolar transistor is connected to the collector of the second insulated gate bipolar transistor and the collector of the third insulated gate bipolar transistor respectively; the emitter of the third insulated gate bipolar transistor is connected to the emitter of the fourth insulated gate bipolar transistor.

[0033] The input power supply is connected to the load in sequence through the circuit breaker, the normally open contact of the first contactor and the normally open contact of the second contactor; the normally open contact of the first contactor and the normally open contact of the second contactor are connected to the normally open contact of the third contactor at both ends; the primary winding of the first single-phase transformer is connected in series to the A-phase line between the normally open contact of the first contactor and the normally open contact of the second contactor; the primary winding of the second single-phase transformer is connected in series to the B-phase line between the normally open contact of the first contactor and the normally open contact of the second contactor; the primary winding of the third single-phase transformer is connected in series to the C-phase line between the normally open contact of the first contactor and the normally open contact of the second contactor; one end of the secondary winding of the first single-phase transformer is connected to the input The first single-phase transformer is connected to the neutral line of the input power supply; the other end of the secondary winding of the first single-phase transformer is connected in series with the first inductor and then connected to the connection line between the emitter of the first insulated gate bipolar transistor and the collector of the second insulated gate bipolar transistor in the first three-level inverter circuit; one end of the secondary winding of the second single-phase transformer is connected to the neutral line of the input power supply; the other end of the secondary winding of the second single-phase transformer is connected in series with the second inductor and then connected to the connection line between the emitter of the first insulated gate bipolar transistor and the collector of the second insulated gate bipolar transistor in the second three-level inverter circuit; one end of the secondary winding of the third single-phase transformer is connected to the neutral line of the input power supply; the other end of the secondary winding of the third single-phase transformer is connected in series with the third inductor and then connected to the The emitter of the first insulated gate bipolar transistor and the collector of the second insulated gate bipolar transistor in the third three-level inverter circuit are connected; the two ends of the secondary winding of the first single-phase transformer are connected in parallel with the first capacitor, and the two ends of the secondary winding of the second single-phase transformer are connected in parallel with the second capacitor; the two ends of the secondary winding of the third single-phase transformer are connected in parallel with the third capacitor; one end of the seventh inductor is connected to the A-phase line between the primary winding of the first single-phase transformer and the normally open contact of the second contactor; the other end of the seventh inductor is connected in series with the fourth inductor and the first resistor in sequence, and then connected to the line between the emitter of the first insulated gate bipolar transistor and the collector of the second insulated gate bipolar transistor in the third level inverter circuit; One end of the fourth capacitor is connected to the connection line between the seventh inductor and the fourth inductor; the other end of the fourth capacitor is connected to the neutral line of the input power supply; the first switch is connected in parallel to both ends of the first resistor; one end of the eighth inductor is connected to the B-phase line between the primary winding of the second single-phase transformer and the normally open contact of the second contactor; the other end of the eighth inductor is connected in series with the fifth inductor and the second resistor in sequence, and then connected to the connection line between the emitter of the first insulated gate bipolar transistor and the collector of the second insulated gate bipolar transistor in the fifth three-level inverter circuit; one end of the fifth capacitor is connected to the connection line between the eighth inductor and the fifth inductor; the other end of the fifth capacitor is connected to the neutral line of the input power supply; the second switch is connected in parallel to both ends of the second resistor.

[0034] One end of the ninth inductor is connected to the C-phase line between the primary winding of the third single-phase transformer and the normally open contact of the second contactor; the other end of the ninth inductor is connected in series with the sixth inductor and the third resistor in sequence, and then connected to the connection line between the emitter of the first insulated gate bipolar transistor and the collector of the second insulated gate bipolar transistor in the sixth three-level inverter circuit; one end of the sixth capacitor is connected to the connection line between the ninth inductor and the sixth inductor; the other end of the sixth capacitor is connected to the zero line of the input power supply; the third switch is connected in parallel to both ends of the third resistor; the The collector is respectively connected to the collector of the first insulated gate bipolar transistor in the second three-level inverter circuit, the collector of the first insulated gate bipolar transistor in the third three-level inverter circuit, the collector of the first insulated gate bipolar transistor in the fourth three-level inverter circuit, the collector of the first insulated gate bipolar transistor in the fifth three-level inverter circuit, and the collector of the first insulated gate bipolar transistor in the sixth three-level inverter circuit; the emitter of the second insulated gate bipolar transistor in the first three-level inverter circuit is respectively connected to the emitter of the second insulated gate bipolar transistor in the second three-level inverter circuit, The emitter of the second insulated gate bipolar transistor in the third three-level inverter circuit, the emitter of the second insulated gate bipolar transistor in the fourth three-level inverter circuit, the emitter of the second insulated gate bipolar transistor in the fifth three-level inverter circuit, and the emitter of the second insulated gate bipolar transistor in the sixth three-level inverter circuit are connected; the collector of the fourth insulated gate bipolar transistor in the first three-level inverter circuit, the collector of the fourth insulated gate bipolar transistor in the second three-level inverter circuit, the collector of the fourth insulated gate bipolar transistor in the third three-level inverter circuit, the collector of the fourth insulated gate bipolar transistor in the fourth three-level inverter circuit The collector of the fourth insulated gate bipolar transistor, the collector of the fourth insulated gate bipolar transistor in the fifth three-level inverter circuit, and the collector of the fourth insulated gate bipolar transistor in the sixth three-level inverter circuit are all connected to the neutral line of the input power supply; at least one DC capacitor is connected in parallel between the collector of the first insulated gate bipolar transistor and the emitter of the second insulated gate bipolar transistor in the first three-level inverter circuit; the DC capacitor includes a first DC capacitor and a second DC capacitor connected in series, and the connection line between the first DC capacitor and the second DC capacitor is connected to the neutral line of the input power supply.

[0035] The coil of the first contactor, the coil of the second contactor, the coil of the third contactor, the first switch, the second switch and the third switch are all electrically fused to the control circuit in the control circuit; the gates of all the insulated gate bipolar transistors in the first three-level inverter circuit, the second three-level inverter circuit, the third three-level inverter circuit, the fourth three-level inverter circuit, the fifth three-level inverter circuit and the sixth three-level inverter circuit are all electrically fused to the control circuit in the control circuit.

[0036] Specifically, this solution adopts a full digital control method of DSP+FPGA, which improves the real-time performance of the entire device.

[0037] In addition, the analog-to-digital converter includes three analog-to-digital converter chips (i.e., AD chips), the model of the analog-to-digital converter chip is AD7656; the zero-crossing detection circuit, conditioning circuit, protection circuit and analog-to-digital converter are all arranged on the first circuit board; the digital signal processor, FPGA chip, PWM pulse blocking module and PWM output module are all arranged on the second circuit board.

[0038] At the same time, the low-voltage flexible compensation device includes a device control system, an SVG main circuit and a capacitor group; the device control system includes a first pulse amplification drive board, and the first pulse amplification drive board is electrically fused to connect the SVG main circuit; the device control system is connected to the second pulse amplification drive board through a thyristor switching signal to electrically fuse the capacitor group; a thyristor module for identifying the thyristor switching signal is arranged inside the capacitor group.

[0039] Specifically, the main circuit has a bypass function that can automatically cut off the device when a device fails without affecting the back-end power supply; the coupling part adopts an LCT filter structure to better reduce switching subharmonics, and the inverter part adopts a bidirectional three-level inverter circuit to increase the switching frequency and realize six-directional power flow.

[0040] Specifically, the distributed SVG circuit can include several groups of SVG compensation circuits, the number of which can be set according to the actual load quantity of the region, and each group of SVG compensation circuits can be individually connected to the three-phase power of the distribution transformer in the substation area. Since the load units in different regions are different, the number of corresponding distributed SVG circuits is also different, that is, the distributed SVG circuit and the actual load quantity of the region are adapted to each other. The distributed SVG circuit can solve the three-phase imbalance problem and low voltage problem on the load side of each branch user.

[0041] Importantly, it should be noted that the construction and arrangement of the present application shown in a plurality of different exemplary embodiments are only exemplary. Although only a few embodiments are described in detail in this disclosure, it should be readily understood by those who refer to this disclosure that many modifications are possible (e.g., the size, scale, structure, shape and proportion of various elements, as well as parameter values ​​(e.g., temperature, pressure, etc.), mounting arrangements, use of materials, color, directional changes, etc.) without substantially departing from the novel teachings and advantages of the subject matter described in the application. For example, the element shown as integrally formed can be composed of multiple parts or elements, the position of the element can be inverted or otherwise changed, and the nature or number or position of the discrete element can be changed or changed. Therefore, all such modifications are intended to be included in the scope of the present invention. The order or sequence of any process or method steps can be changed or reordered according to alternative embodiments. In the claims, any "device plus function" clause is intended to cover the structure described herein that performs the function, and is not only structurally equivalent but also equivalent structure. Without departing from the scope of the present invention, other replacements, modifications, changes and omissions can be made in the design, operating conditions and arrangement of the exemplary embodiments. Therefore, the invention is not limited to a specific embodiment, but extends to numerous modifications still falling within the scope of the appended claims.

[0042] Additionally, in order to provide a concise description of exemplary embodiments, all features of an actual embodiment (ie, those features that are not relevant to the best mode presently contemplated for carrying out the invention or those that are not relevant to implementing the invention) may not be described.

[0043] It should be understood that in the development of any actual implementation, as in any engineering or design project, numerous implementation-specific decisions may be made. Such a development effort may be complex and time-consuming, but for those of ordinary skill having the benefit of this disclosure, without undue experimentation, the development effort will be a routine task of design, fabrication, and production.

[0044] It should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention rather than to limit it. Although the present invention has been described in detail with reference to the preferred embodiments, those skilled in the art should understand that the technical solutions of the present invention may be modified or replaced by equivalents without departing from the spirit and scope of the technical solutions of the present invention, which should all be included in the scope of the claims of the present invention.

Claims

1. A low-voltage distribution network terminal line power quality comprehensive conditioning device, characterized by: include, Low voltage flexible compensation components, main circuit and control circuit; The main circuit includes a transformer, a filter assembly, a filter reactor, a first three-level inverter and a second three-level inverter; The primary winding of the transformer is connected in series between the input power supply and the load; The low-voltage flexible compensation component is linearly connected between the transformer and the load; The first three-level inverter is connected in series to the power grid after passing through the filter component and the secondary winding of the transformer, the second three-level inverter is connected in parallel to the load after passing through the filter reactor, and the control signal input end of the first three-level inverter and the control signal input end of the second three-level inverter are respectively electrically fused to the control signal output end of the control circuit.

2. The low-voltage distribution network terminal line power quality comprehensive conditioning device according to claim 1, characterized in that: The control circuit includes a collection unit, a preprocessing unit and a main control unit, and the collection unit includes: A grid voltage detection circuit, a load circuit detection circuit, an output circuit detection circuit and a DC bus voltage detection circuit; the preprocessing unit includes a conditioning circuit and an analog-to-digital converter, and the main control unit includes a digital signal processor, an FPGA chip, a PWM pulse blocking module and a PWM output module.

3. The low-voltage distribution network terminal line power quality comprehensive conditioning device as claimed in claim 2, characterized in that: The output end of the grid voltage detection circuit, the output end of the load circuit detection circuit, the output end of the output circuit detection circuit and the output end of the DC bus voltage detection circuit are electrically connected to the input end of the conditioning circuit respectively; the output end of the conditioning circuit is electrically connected to the input end of the analog-to-digital converter; the output end of the analog-to-digital converter is electrically connected to the input end of the digital signal processor, the output end of the digital signal processor is electrically connected to the input end of the FPGA chip, the output end of the FPGA chip is electrically connected to the input end of the PWM pulse blocking module, and the output end of the PWM pulse blocking module is electrically connected to the input end of the PWM output module.

4. The low-voltage distribution network terminal line power quality comprehensive conditioning device as claimed in claim 3, characterized in that: The control circuit also includes a zero-crossing detection circuit and a protection circuit. The output end of the zero-crossing detection circuit is electrically connected to the input end of the digital signal processor, and the output end of the protection circuit is electrically connected to the input end of the PWM pulse blocking module.

5. The low-voltage distribution network terminal line power quality comprehensive conditioning device as claimed in claim 4, characterized in that: It also includes a bypass circuit; the bypass circuit includes a first contactor, a second contactor and a third contactor; the normally open contact of the first contactor is connected in series between the input power supply and the primary winding of the transformer, the normally open contact of the second contactor is connected in series between the filter inductor and the load, and the normally open contact of the third contactor is connected in series between the input power supply and the load.

6. The low-voltage distribution network terminal line power quality comprehensive conditioning device as claimed in claim 5, characterized in that: The comprehensive power quality control device also includes a circuit breaker and a DC capacitor; the circuit breaker is connected in series between the input power supply and the normally open contact of the third contactor; the DC capacitor is connected in parallel to the common DC terminal of the first three-level inverter and the second three-level inverter.

7. The low-voltage distribution network terminal line power quality comprehensive conditioning device according to claim 6, characterized in that: The DC capacitor includes a first DC capacitor and a second DC capacitor, and the first DC capacitor and the second DC capacitor are connected in series; the connection line between the first DC capacitor and the second DC capacitor is electrically fused to the neutral line of the input power supply.

8. The low-voltage distribution network terminal line power quality comprehensive conditioning device according to claim 7, characterized in that: The transformer includes a first single-phase transformer, a second single-phase transformer and a third single-phase transformer, the filter component includes a first inductor, a second inductor, a third inductor, a first capacitor C1, a second capacitor and a third capacitor; the filter reactor includes a fourth inductor, a fifth inductor, a sixth inductor, a seventh inductor, an eighth inductor, a ninth inductor, a fourth capacitor, a fifth capacitor and a sixth capacitor; The first three-level inverter includes a first three-level inverter circuit, a second three-level inverter circuit and a third three-level inverter circuit; the second three-level inverter includes a fourth three-level inverter circuit, a fifth three-level inverter circuit and a sixth three-level inverter circuit; the first three-level inverter circuit, the second three-level inverter circuit, the third three-level inverter circuit, the fourth three-level inverter circuit, the fifth three-level inverter circuit and the sixth three-level inverter circuit have the same structure; the first three-level inverter circuit includes a first insulated gate bipolar transistor, a second insulated gate bipolar transistor, a third insulated gate bipolar transistor and a fourth insulated gate bipolar transistor; a diode is connected between the collector and the emitter of the first insulated gate bipolar transistor, the second insulated gate bipolar transistor, the third insulated gate bipolar transistor and the fourth insulated gate bipolar transistor; the emitter of the first insulated gate bipolar transistor is connected to the collector of the second insulated gate bipolar transistor and the collector of the third insulated gate bipolar transistor respectively; the emitter of the third insulated gate bipolar transistor is connected to the emitter of the fourth insulated gate bipolar transistor.

9. The low-voltage distribution network terminal line power quality comprehensive conditioning device according to claim 8, characterized in that: The analog-to-digital converter includes three analog-to-digital converter chips, and the model of the analog-to-digital converter chip is AD7656; the zero-crossing detection circuit, the conditioning circuit, the protection circuit and the analog-to-digital converter are all arranged on a first circuit board; the digital signal processor, the FPGA chip, the PWM pulse blocking module and the PWM output module are all arranged on a second circuit board.

10. The low-voltage distribution network terminal line power quality comprehensive conditioning device according to claim 9, characterized in that: It also includes a device control system, an SVG main circuit and a capacitor group; the device control system includes a first pulse amplification drive board, and the first pulse amplification drive board is electrically fused to the SVG main circuit; the device control system is connected to the second pulse amplification drive board through a thyristor switching signal to electrically fuse the capacitor group; a thyristor module for identifying the thyristor switching signal is arranged inside the capacitor group.

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