CN212063505U - Active power balancing device for micro-grid - Google Patents

Abstract

The utility model discloses an active power balancing device for a micro-grid, which comprises an active power balancing main circuit, a detection circuit and a control circuit; the active power balance main circuit comprises an A-phase inverter, a B-phase inverter, a C-phase inverter, three groups of isolation transformers and double active bridge converters, wherein the A-phase inverter, the B-phase inverter and the C-phase inverter have the same structure and parameters, the three groups of isolation transformers have the same structure and parameters, and the double active bridge converters are connected with filter inductors in parallel and have adjustable number; the detection circuit comprises a current transformer, a voltage transformer, a frequency locking ring and a data acquisition module; the control circuit comprises a power balance control module of the A-phase inverter, the B-phase inverter and the C-phase inverter and a direct-current voltage control module of the high-voltage side of the double-active bridge type converter. The utility model discloses can realize the power balance distribution between the little electric wire netting simultaneously, three-phase DG's among the unbalanced alternating current little electric wire netting three-phase output is balanced and voltage quality's improvement, guarantees the reliable of the interconnected little electric wire netting of unbalanced alternating current-direct current, high-efficient operation.

Description

Active power balancing device for micro-grid

Technical Field

The utility model belongs to the technical field of power transmission and distribution technique and specifically relates to an initiative power balancing unit for little electric wire netting.

Background

The increasing demand for energy and the increasing demand for reliability, safety and flexibility of power supply coupled with concerns about environmental pollution and climate change have driven the development of modern power systems towards distributed generation. The micro-grid as a special distributed power generation system will play a very critical role in the future smart grid. The micro-grid system can be operated in a grid-connected mode and an isolated island mode, and can provide safe, flexible and reliable power supply and high-quality and diversified electric energy services. In a microgrid, a Distributed Generation (DG) system is typically connected to the microgrid via a power electronic converter device. One of the main tasks of a power electronic converter is to control the output of power. Controlling the distribution of load power among the DGs in an accurate and coordinated manner is one of the keys to the proper operation of the microgrid. The power balance control of the alternating current-direct current hybrid interconnected micro-grid is a hot spot of current research.

Currently, in the research of an alternating current-direct current hybrid microgrid, a single-phase system or a three-phase balance system is mainly considered in the alternating current microgrid. However, in an actual ac microgrid, a three-phase DG system and a single-phase DG system coexist widely, a three-phase load and a single-phase load coexist widely, and permeability is higher and higher, and installation capacities and installation positions of the DG and the load are determined by a user, so that the ac microgrid system is often an unbalanced system, and capacity and load demand of each phase of the DG are unbalanced. This causes unbalanced three-phase DG output power of the system, and the system voltage quality is poor, seriously influences the system operation reliability and the high-efficient integration and utilization of renewable energy. The current research only solves the problem of power balance of a system in which DGs in a micro-grid are all three-phase DGs, and does not solve the problem of power balance of an unbalanced system containing the three-phase DGs and the single-phase DGs at the same time, particularly the unbalanced AC/DC interconnected micro-grid system. All the above requirements are to develop an active power balancing device which can be used for an unbalanced AC/DC interconnected microgrid to realize three-phase DG power balance between the microgrid and inside the unbalanced AC microgrid, so as to ensure reliable operation of a system and efficient integrated utilization of renewable energy.

SUMMERY OF THE UTILITY MODEL

The utility model discloses aim at solving one of the technical problem that exists among the prior art at least. Therefore, the utility model provides an initiative power balancing unit for little electric wire netting can realize the power balance distribution between little electric wire netting simultaneously, and the improvement of three-phase DG's three-phase output balance and voltage quality in the unbalanced alternating current little electric wire netting guarantees reliable, the high-efficient operation of unbalanced alternating current-direct current interconnected little electric wire netting.

An embodiment of the utility model provides an active power balancing unit for microgrid, is applied to the interconnected microgrid of unbalanced alternating current-direct current, characterized in that, the said device includes active power balancing main circuit, detection circuit and control circuit;

the active power balance main circuit comprises an A-phase inverter, a B-phase inverter, a C-phase inverter, three groups of isolation transformers and L-shaped connection filter inductors, wherein the A-phase inverter, the B-phase inverter and the C-phase inverter have the same structure and parameters, the three groups of isolation transformers have the same structure and parameters, and the two active bridge converters are connected in parallel and have adjustable number;

the detection circuit comprises a current transformer, a voltage transformer, a frequency locking ring and a data acquisition module;

the control circuit comprises a power balance control module of the A-phase inverter, the B-phase inverter and the C-phase inverter and a direct-current voltage control module of the high-voltage side of the double-active bridge converter.

The utility model discloses an initiative power balancing unit for little electric wire netting has following beneficial effect at least: the method can realize the power balance distribution among the micro-grids, the three-phase output power balance of the three-phase DG in the unbalanced alternating current micro-grid and the improvement of the voltage quality at the same time, and ensure the reliable and efficient operation of the unbalanced alternating current-direct current interconnected micro-grid.

According to other embodiments of the present invention, the active power balance device for a microgrid comprises a three-phase ac plastic-shell circuit breaker, an unbalanced ac microgrid public connection point bus, and a dc microgrid public connection point bus;

the high-voltage direct-current sides of the A-phase inverter, the B-phase inverter and the C-phase inverter are connected together;

one end of the double-active bridge converter is connected with an inverter high-voltage direct-current bus, and the other end of the double-active bridge converter is connected with the direct-current microgrid common connection point bus;

the A-phase inverter, the B-phase inverter and the C-phase inverter are respectively formed by connecting single-phase bridge inverter circuits with adjustable numbers in parallel;

one ends of the three groups of isolation transformers are respectively connected with the alternating current sides of the A-phase inverter, the B-phase inverter and the C-phase inverter, and the other ends of the three groups of isolation transformers form a three-phase four-wire system port and are connected to a public connection point bus of the unbalanced alternating current microgrid;

the high-voltage side and the low-voltage side of the double-active bridge converter are connected in parallel.

Drawings

Fig. 1 is a schematic structural diagram of an embodiment of an active power balancing apparatus for a microgrid according to an embodiment of the present invention;

fig. 2 is a schematic structural diagram of another embodiment of an active power balancing apparatus for a microgrid according to an embodiment of the present invention;

fig. 3 is a schematic structural diagram of an embodiment of a detection circuit according to the present invention;

fig. 4 is a communication topology connection diagram of an active power balancing apparatus for a microgrid in an embodiment of the present invention.

Wherein, 1-unbalanced AC micro-grid, 2-unbalanced AC micro-grid common connection point bus, 3-active power balancing device, 4-DC micro-grid, 5-DC micro-grid common connection point bus, 6-DC micro-grid load, 7-distributed generation of DC micro-grid, 8-DC breaker, 9-three-phase AC plastic shell breaker, 10-unbalanced AC micro-grid three-phase load, 11-unbalanced AC micro-grid three-phase DG, 12-unbalanced AC micro-grid C-phase load, 13-unbalanced AC micro-grid C-phase DG, 14-unbalanced AC micro-grid B-phase load, 15-unbalanced AC micro-grid B-phase DG, 16-unbalanced AC micro-grid A-phase load, 17-unbalanced AC micro-grid A-phase, 18-single-phase plastic shell breaker, 19-active power balancing device main circuit, 20-control circuit of active power balancing device, 21-detection circuit of active power balancing device; 22-connection filter inductor, 23-isolation transformer, 24-A phase inverter, 25-active power balancing device high-voltage side direct current bus capacitor, 26-single phase inverter main circuit forming A phase inverter main circuit, 27-double active bridge type DC/DC converter, 28-double active bridge type DC/DC main circuit structure, 29-high voltage side direct current bus voltage detection module of active power balancing device, 30-low voltage side direct current interface of active power balancing device (connected to direct current microgrid PCC bus through CB 2), 31-alternating current microgrid PCC bus frequency and direct current microgrid PCC bus direct current voltage detection module, 32-C phase inverter, 33-single phase inverter main circuit forming C phase inverter main circuit, 34-single phase inverter main circuit forming B phase inverter, 35-B phase inverter, 36-ac side interface of active power balancing device (connected to unbalanced ac microgrid PCC bus through CB 1); 37-three-phase DG of alternating current microgrid selected to communicate with active power balancing device, 38-DG in microgrid, 39-direct current voltage control module, 40-power balance control module, 41-voltage transformer, 42-communication line, 43-control algorithm module for balancing output active power and reactive power of three-phase DG in unbalanced alternating current microgrid, 44-current transformer, 45-inverter high-voltage side direct current bus, 46-DG of direct current microgrid selected to communicate with active power balancing device, 47-microgrid internal communication topology link, 48-microgrid-to-microgrid communication topology link.

Detailed Description

The conception and the resulting technical effects of the present invention will be described clearly and completely with reference to the following embodiments, so that the objects, features and effects of the present invention can be fully understood. Obviously, the described embodiments are only a part of the embodiments of the present invention, and not all embodiments, and other embodiments obtained by those skilled in the art without inventive labor based on the embodiments of the present invention all belong to the protection scope of the present invention.

In the description of the present invention, if an orientation description is referred to, for example, the directions or positional relationships indicated by "upper", "lower", "front", "rear", "left", "right", etc. are based on the directions or positional relationships shown in the drawings, only for convenience of description and simplification of description, and it is not intended to indicate or imply that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and thus, should not be construed as limiting the present invention. If a feature is referred to as being "disposed," "secured," "connected," or "mounted" to another feature, it can be directly disposed, secured, or connected to the other feature or indirectly disposed, secured, connected, or mounted to the other feature.

In the description of the embodiments of the present invention, if "a plurality" is referred to, it means one or more, if "a plurality" is referred to, it means two or more, if "greater than", "less than" or "more than" is referred to, it is understood that the number is not included, and if "more than", "less than" or "within" is referred to, it is understood that the number is included. If reference is made to "first" or "second", this should be understood to distinguish between features and not to indicate or imply relative importance or to implicitly indicate the number of indicated features or to implicitly indicate the precedence of the indicated features.

Referring to fig. 1, a schematic structural diagram of an active power balancing apparatus for a microgrid in the present embodiment is shown. Referring to fig. 2, another structural schematic diagram of the active power balancing apparatus for a microgrid in the present embodiment is shown. The active power balancing device 3 includes an active power balancing main circuit 19, a detection circuit 21, and a control circuit 20.

With reference to fig. 1 and 2, the active power balancing main circuit 19 includes an a-phase inverter 24, a B-phase inverter 35, and a C-phase inverter 32, which have the same structure and parameters, three sets of isolation transformers 23 and L-type connection filter inductors 22, which have the same structure and parameters, and two active bridge converters 27 connected in parallel and having adjustable number;

the detection circuit 21 comprises a current transformer 44, a voltage transformer 41, a frequency locking ring and a data acquisition module;

the control circuit 20 comprises a power balance control module 40 of an A-phase inverter, a B-phase inverter and a C-phase inverter and a direct current voltage control module 39 of the high-voltage side of the double-active bridge converter.

One end of the active power balancing device is connected with an unbalanced AC micro-grid public connection Point (PCC, Point of Common Coupling) bus 2 through a three-phase AC plastic shell breaker 9, and the other end of the active power balancing device is connected with a DC micro-grid PCC bus 5 through a DC breaker 8.

The high-voltage direct-current sides of the a-phase inverter 24, the B-phase inverter 35 and the C-phase inverter 32 are connected together;

one end of the double-active bridge type DC/DC converter 27 is connected with the inverter high-voltage direct current bus 45, and the other end is connected with the direct current microgrid common connection point bus 5;

the A-phase inverter 24, the B-phase inverter 35 and the C-phase inverter 32 are respectively formed by connecting single-phase bridge inverter circuits 26, 34 and 33 with adjustable numbers in parallel;

one end of the three groups of isolation transformers 23 is respectively connected with the alternating current sides of the A-phase inverter 24, the B-phase inverter 35 and the C-phase inverter 32, and the other end of the three groups of isolation transformers form a three-phase four-wire system port which is connected to the public connection point bus 2 of the unbalanced alternating current microgrid;

the high-voltage side and the low-voltage side of the dual-active bridge DC/DC converter 27 are both connected in parallel.

With reference to fig. 1 and fig. 2, the detection circuit 21 of the active power balancing device 3 detects the frequency of the PCC bus 2 of the unbalanced ac microgrid 1 and the dc voltage of the bus 5 of the point of common connection of the dc microgrid 4 through the detection module 31 for detecting the frequency of the PCC bus 2 of the unbalanced ac microgrid and the dc voltage of the PCC bus of the dc microgrid, and calculates to obtain the active power instruction reference values of the single-phase inverter main circuits 26,33,34 constituting the a-phase inverter 24, the B-phase inverter 35 and the C-phase inverter 32 of the active power balancing device main circuit 19, which realize active power balance among the microgrids by the power balance control module 40 of the control circuit 20 in the active power balancing device 3; three-phase DG11, A-phase DG17, B-phase DG15 and C-phase DG13 in the unbalanced AC microgrid 1 establish communicated communication topological connection, a control algorithm module 43 for balancing the output active power and the reactive power of the three-phase DG11 in the unbalanced AC microgrid 1 calculates the active power and the reactive power regulating quantity of single-phase inverter main circuits 26,33 and 34 forming an active power balancing device main circuit 19, a B-phase inverter 35 and a C-phase inverter 32, which realize the balance of the output power of the three-phase DG11 in the unbalanced AC microgrid 1, and transmits active power and reactive power regulating quantity signals through a communication line 42 connected with a detection circuit 21 in the active power balancing device 3 through a three-phase DG 11; the power balance control module 40 of the control circuit 20 in the active power balancing device 3 controls the single-phase inverter main circuits 26,33 and 34 of the phase-A inverter 24, the phase-B inverter 35 and the phase-C inverter 32 which form the active power balancing device main circuit 19 to transmit power to the unbalanced AC microgrid 1 through the isolation transformer 23 and the connection filter inductor 22 according to the obtained active power and reactive power instruction reference values and the adjustment quantities; meanwhile, the DC voltage control module 39 controls the DC/DC converter main circuit 28 in the dual active bridge DC/DC converter 27 according to the voltage of the capacitor 25 of the high-side DC bus 45 detected by the high-side DC bus voltage detection module 29 of the active power balancing device, and performs power transmission and DC voltage regulation through the low-voltage side DC interface 30 of the active power balancing device.

Referring to fig. 4, a communication topology connection diagram of an active power balancing apparatus for a microgrid in an embodiment of the present invention is shown. The unbalanced ac microgrid 1 (unbalanced ac microgrids p and q) and the dc microgrid 4 (dc microgrid i and j) establish communication topology links 47 between DG38 inside the microgrid, select DG46 in the dc microgrid 4 and three-phase DG37 in the ac microgrid 1, establish communication topology links 48 between the microgrids, and enable the active power balancing device 3 to communicate with the unbalanced ac microgrid 1 and the dc microgrid 4.

With reference to fig. 1 to 4, the power balance control module 40 controls the transmission power of the a-phase inverter 24, the B-phase inverter 35, and the C-phase inverter 32 according to the voltage frequency of the busbar 2 at the point of common connection of the unbalanced ac microgrid, the active power and reactive power balance adjustment amount commands to be transmitted by the a-phase, B-phase, and C-phase inverters uploaded by the three-phase DG37 of the unbalanced ac microgrid, and the inductor current at the ac side of the active power balancing device.

The direct current voltage control module 39 controls the dual-active bridge DC/DC converter 27 to adjust the direct current voltage at the high-voltage side of the active power balancing device 3 through the high-voltage side voltage detection module 29 according to the detected direct current voltage at the high-voltage side of the dual-active bridge DC/DC converter 27;

the voltage frequency of the bus 2 at the public connection point of the unbalanced alternating-current microgrid is obtained by the voltage detected by the voltage transformer 41 through a frequency locking ring;

the active power and reactive power balance regulating quantity instruction is obtained by calculating in a three-phase DG11 system after detecting voltage and current and calculating power through a voltage transformer 41 and a current transformer 44 of a three-phase DG11 and a single-phase DG (an unbalanced AC microgrid C-phase DG13, an unbalanced AC microgrid B-phase DG15 and an unbalanced AC microgrid A-phase DG17)) which are in communication connection in an unbalanced AC microgrid.

In this embodiment, the active power balancing device 3 can simultaneously achieve the balance of active power between the micro grids and the balance of active power and reactive power output by the three-phase DG11 in the unbalanced ac micro grid 1.

The active power and the reactive power transmitted by the active power balancing device are respectively calculated as

Active power:

reactive power:

wherein, P_IC,k(t) active power transmitted by the active power balancing device, Q_IC,k(t) is a reactive power set value transmitted by the active power balancing device,

the A-phase active power transmitted by the active power balancing device is controlled by the A-phase active power instruction reference value for realizing the balance of the active power between the micro grids

And A-phase active power balance regulating quantity delta p for realizing three-phase DG active power output balance in unbalanced alternating-current micro-grid_IC,k,a(t) two parts;

the B-phase active power transmitted by the active power balancing device is controlled by a B-phase active power instruction reference value for realizing the balance of the active power between the micro grids

And realizing the balance of three-phase DG active power output in the unbalanced AC micro-gridB phase active power balance adjustment quantity Δ p_IC,k,b(t) two parts;

the C-phase active power transmitted by the active power balancing device is controlled by a C-phase active power instruction reference value for realizing the balance of the active power between the micro grids

And C-phase active power balance regulating variable for realizing three-phase DG active power output balance in unbalanced alternating current micro-grid

Two parts are formed;

a-phase reactive power transmitted for the active power balance device is commanded by the A-phase reactive power reference value

And A-phase reactive power balance regulating quantity delta q for realizing three-phase DG reactive power output balance in unbalanced alternating current micro-grid_IC,k,a(t) two parts;

b-phase reactive power transmitted for active power balancing devices, with reference value commanded by the B-phase reactive power

And B-phase reactive power balance regulating quantity delta q for realizing three-phase DG reactive power output balance in unbalanced alternating current micro-grid_IC,k,b(t) two parts;

c-phase reactive power transmitted for active power balancing devices, with reference value commanded by C-phase reactive power

And C-phase reactive power balance regulating quantity delta q for realizing three-phase DG reactive power output balance in unbalanced alternating current micro-grid_IC,k,c(t) two parts; a, B, C three-phase reactive power instruction reference value of active power balancing device satisfies

Specifically, the step of realizing the balance of the active power between the micro grids is as follows:

step 110: initializing;

step 120: checking whether the communication is normal, if so, executing step 130, otherwise, continuing to scan and wait;

step 130: collecting direct-current voltage of a bus of a common connection point of a direct-current microgrid and unbalanced alternating-current microgrid frequency;

step 140: transmitting the collected direct current voltage and alternating current frequency to a power balance control device connected with the direct current voltage and alternating current frequency;

step 150: normalizing the received direct current voltage and the received alternating current frequency according to a formula (3):

wherein x is the voltage V of the DC micro-grid bus_dcAnd an unbalanced ac microgrid frequency f;

step 160: the control algorithm for performing active power balance between the micro grids is shown as a formula (4), and then the reference value of each phase transmission active power instruction of the active power balance device A, B, C is obtained by using the formulas (5) to (7):

phase a active power command reference value:

b phase active powerInstruction reference value:

c-phase active power command reference value:

step 170: setting reactive power command reference values transmitted by each phase of the active power balancing device A, B, C:

the method for realizing the balance of the active power and the reactive power output by the three-phase DG in the unbalanced AC microgrid comprises the following steps:

step 210: initializing;

step 220: selecting a single-phase DG from the unbalanced alternating-current microgrid, and connecting the single-phase DG with all other three-phase DGs through communication cables to form a communicated communication topology;

step 230: checking whether the communication is normal, if so, executing step 240, otherwise, continuing to scan and wait;

step 240: executing a distributed power balance control algorithm such as a formula (9) and a formula (10) in the three-phase DG system to obtain A, B, C active power and reactive power balance adjustment quantity of each phase in the three-phase DG:

active power balance adjustment amount:

reactive power balance adjustment quantity:

step 250: and (2) executing equations (11) and (12) in the three-phase DG system to obtain A, B, C estimated values of the balance average adjustment quantity of the active power and the reactive power of each phase in the three-phase DG:

active power balance adjustment quantity estimation value:

reactive power balance adjustment quantity estimation value:

step 260: and (3) executing the formulas (13) and (14) to obtain the active power and reactive power regulating quantity commands which need to be transmitted by each phase A, B, C of the active power balancing device:

an active power regulating quantity instruction:

reactive power regulating variable instruction:

step 270: and realizing power balance control according to the active power and reactive power regulating quantity instructions.

The parameters of equations (9) and (10) in step 240 are designed according to the linear matrix inequality (15):

wherein the content of the first and second substances,

H＝L_M+g_Mp is a symmetric positive definite matrix, mu>0 and I are unit matrixes with equivalent dimensions.

The utility model provides an initiative power balancing unit for balanced little electric wire netting power of unbalanced alternating current-direct current interconnection can independently cooperate a plurality of little electric wire netting and little electric wire netting inside DG unit simultaneously, realize between little electric wire netting and the balanced little electric wire netting inside three-phase DG of unbalance exerting oneself, effectively solved the balanced problem of the equal unbalanced power of actual little electric wire netting power and load that is not considered at present to improve system voltage quality, improve the reliability and the renewable energy integration of system operation, very high practical value has.

The embodiments of the present invention have been described in detail with reference to the accompanying drawings, but the present invention is not limited to the above embodiments, and various changes can be made without departing from the spirit of the present invention within the knowledge of those skilled in the art. Furthermore, the embodiments of the present invention and features of the embodiments may be combined with each other without conflict.

Claims (2)

1. An active power balancing device for a microgrid is applied to an unbalanced alternating current-direct current interconnected microgrid and is characterized by comprising an active power balancing main circuit, a detection circuit and a control circuit;

the active power balance main circuit comprises an A-phase inverter, a B-phase inverter, a C-phase inverter, three groups of isolation transformers and L-shaped connection filter inductors, wherein the A-phase inverter, the B-phase inverter and the C-phase inverter have the same structure and parameters, the three groups of isolation transformers have the same structure and parameters, and the two active bridge converters are connected in parallel and have adjustable number;

the detection circuit comprises a current transformer, a voltage transformer, a frequency locking ring and a data acquisition module;

the control circuit comprises a power balance control module of the A-phase inverter, the B-phase inverter and the C-phase inverter and a direct-current voltage control module of the high-voltage side of the double-active bridge converter.

2. The active power balance device for the micro-grid according to claim 1, wherein one end of the active power balance control device is connected with the unbalanced AC micro-grid common connection point bus through a three-phase AC molded case circuit breaker, and the other end of the active power balance control device is connected with the DC micro-grid common connection point bus through a DC circuit breaker;

the high-voltage direct-current sides of the A-phase inverter, the B-phase inverter and the C-phase inverter are connected together;

one end of the double-active bridge converter is connected with an inverter high-voltage direct-current bus, and the other end of the double-active bridge converter is connected with the direct-current microgrid common connection point bus;

the A-phase inverter, the B-phase inverter and the C-phase inverter are respectively formed by connecting single-phase bridge inverter circuits with adjustable numbers in parallel;

one ends of the three groups of isolation transformers are respectively connected with the alternating current sides of the A-phase inverter, the B-phase inverter and the C-phase inverter, and the other ends of the three groups of isolation transformers form a three-phase four-wire system port and are connected to a public connection point bus of the unbalanced alternating current microgrid;

the high-voltage side and the low-voltage side of the double-active bridge converter are connected in parallel.

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