CN103248066A - Direct current micro grid topology design method based on DC-DC (Direct Current-Direct Current) sectionalizers - Google Patents

Abstract

The invention provides a DC micro-grid topology design method based on a DC-DC segmenter, which belongs to the technical field of micro-grids. Multiple DC microgrid segmenters (DC-DC segmenters for short) based on high-frequency isolated DC/DC conversion are configured in the ring-shaped DC microgrid topology to replace solid-state circuit breakers. The grid structure of the DC microgrid adopts a ring structure, and the ring bus is divided into multiple sections and multiple voltage levels. Each busbar is connected by a DC-DC sectionalizer or a circuit breaker to form a multi-divided and multi-connected power supply pattern. The DC-DC sectionalizer adopts a double full-bridge topology and is AC-coupled by a high-frequency transformer. The advantages of the present invention are: significant advantages in terms of electrical isolation, power flow control, and connection to buses of different voltage levels, etc., and has the advantages of fast response speed and high sensitivity; when the DC bus or equipment fails, the DC-DC section The inverter is not affected by the instantaneous discharge of the capacitor, and the faulty bus is isolated, which can reduce the scope of power failure as much as possible and improve the reliability of the system.

Description

DC microgrid topology design method based on DC-DC segmenter

technical field

The invention relates to the technical field of micro-grids, in particular to a DC-DC micro-grid topology design method based on a DC-DC segmenter, in which a plurality of high-frequency isolated DC-DC conversion devices are configured in a ring topology instead of a solid-state circuit breaker.

Background technique

As a form of microgrid that connects distributed power and the main grid, DC microgrid can efficiently play the value and benefits of distributed power, and effectively isolate intermittent power disturbances, power quality problems and various problems in the main grid. effect of a failure. Therefore, research institutions at home and abroad have successively carried out the research and engineering practice of DC microgrid related theories. However, the DC system requires a large-capacity capacitor to eliminate the voltage ripple. When a short-circuit fault occurs, the transient current caused by the instantaneous discharge of the capacitor may cause damage to the equipment or misoperation of the switch, resulting in the failure of the selective protection function and the power outage of a large number of loads and protection equipment. Deterioration of inter-coordination capacity and other issues. At the same time, DC high-power solid-state circuit breakers are difficult to be widely used in DC microgrids due to their high cost, complex control and questionable reliability.

The invention provides a DC microgrid topology design method, in which a DC microgrid segmenter based on high-frequency isolation DC/DC conversion (referred to as DC-DC segmenter) is configured in the ring-shaped DC microgrid topology to replace the solid-state circuit breaker device. This method has significant advantages in reliable breaking of faults, electrical isolation, power flow control and connection of buses of different voltage levels. On the other hand, if such a sectionalizer can be installed on the DC bus of the complex DC microgrid to form a multi-segmented and multi-connected power supply pattern, it can minimize the impact of power outages when the DC bus or equipment fails. Ensure the normal power supply and power consumption of micro-sources and loads in the healthy section.

Contents of the invention

The purpose of the present invention is to provide a DC microgrid topology design method to optimize the performance of traditional DC microgrids in terms of reliable fault breaking, electrical isolation, power flow control, and connection of buses of different voltage levels. The DC-DC sectionalizer is configured in the ring topology of the DC microgrid to quickly detect and isolate the fault when the DC bus fails. Control bus voltage regulation and power flow.

The principle circuit diagram of the DC microgrid topology design method proposed by the present invention is shown in Figure 1. The DC microgrid grid adopts a ring structure, and the ring busbar is divided into multiple sections and multiple voltage levels. Photovoltaic power generation (8) and DC loads (4), (7), (9) are connected to the bus through DC/DC converters and circuit breakers (14), wind power generation (3), micro gas turbines (6) and AC loads (1), (3), (5) are connected to the busbar through AC/DC converter and circuit breaker (14). The DC micro grid as a whole is connected to the AC large grid (12) and the energy storage device (13) through VSCs (10) and (11) capable of bidirectional power flow. Each segment of the bus is connected by a circuit breaker (14) or a DC/DC sectionalizer (15), forming a multi-divided and multi-connected power supply pattern. As shown in Figure 2, the DC busbar (16) is connected to the busbar (17) through a DC/DC sectionalizer, and each DC/DC sectionalizer adopts a double-full-bridge topology, and is composed of a high-frequency transformer (18) for AC coupling.

The DC-DC sectionalizer in the DC microgrid connects different busbars, these busbars have different voltage levels, or active busbars with micro power supply, or passive busbars with only passive loads, or busbars There are loads on the power supply. The primary side and the secondary side of the DC-DC segmenter have four IGBTs respectively, which are respectively arranged on the primary side and the secondary side of the high-frequency isolation transformer, and have two power conversion stages. The protection and control functions are realized through the control module, which ensures the maximum transmission power point and soft switching characteristics during the commutation process of bidirectional power flow. When the system is running normally, the DC/DC sectionalizer adopts a full-control phase-shift control strategy, and its on and off are controlled by the main control PWM signal to realize the control of the exchange power between buses of different voltage levels, active and passive Bus voltage regulation. The power conversion stages on both sides of the DC/DC sectionalizer are actively controlled. When the DC bus fails, the switching function is realized by the control pulse signal of the blocking converter, and the faulty bus is quickly detected and isolated.

The advantages of the present invention are: significant advantages in terms of electrical isolation, power flow control, and connection to buses of different voltage levels, etc., and has the advantages of fast response speed and high sensitivity; when the DC bus or equipment fails, the DC-DC section The inverter is not affected by the instantaneous discharge of the capacitor, and the faulty bus is isolated, which can reduce the scope of power failure as much as possible and improve the reliability of the system.

Description of drawings

FIG. 1 is a topology diagram of a DC microgrid based on a DC-DC segmenter according to the present invention. Fig. 2 is a topology diagram of a DC-DC segmenter in a DC microgrid.

Detailed ways

The principle circuit diagram of the DC microgrid topology design method proposed by the present invention is shown in Figure 1. The DC microgrid grid adopts a ring structure, and the ring busbar is divided into multiple sections and multiple voltage levels. Photovoltaic power generation (8) and DC loads (4), (7), (9) are connected to the bus through DC/DC converters and circuit breakers (14), wind power generation (3), micro gas turbines (6) and AC loads (1), (3), (5) are connected to the busbar through AC/DC converter and circuit breaker (14). The DC micro grid as a whole is connected to the AC large grid (12) and the energy storage device (13) through VSCs (10) and (11) capable of bidirectional power flow. Each segment of the bus is connected by a circuit breaker (14) or a DC/DC sectionalizer (15), forming a multi-divided and multi-connected power supply pattern. As shown in Figure 2, the connection between the DC bus (16) and the DC bus (17) is through a DC-DC sectionalizer, and each DC/DC sectionalizer adopts a double-full-bridge topology, and is composed of a high-frequency transformer (18 ) for AC coupling.

The DC-DC sectionalizer in the DC microgrid connects different busbars, these busbars have different voltage levels, or active busbars with micro power supply, or passive busbars with only passive loads, or busbars There are loads on the power supply. The primary side and the secondary side of the DC-DC segmenter have four IGBTs respectively, which are respectively arranged on the primary side and the secondary side of the high-frequency isolation transformer, and have two power conversion stages. The protection and control functions are realized through the control module, which ensures the maximum transmission power point and soft switching characteristics during the commutation process of bidirectional power flow.

Claims (2)

1. little power network topology method for designing of the direct current based on the DC-DC sectionalizer, it is characterized in that: the little electrical network rack of direct current adopts circulus, the little source of direct current (photovoltaic generation) and load are connected to ring bus by DC/DC converter and circuit breaker, exchange little source (micro fuel engine, wind power generation) and load and are connected to ring bus by AC/DC converter and circuit breaker; The little electrical network integral body of direct current is connected with the big electrical network of interchange and energy storage device by the VSC that possesses the mobile function of power bi-directional.

2. according to the little power network topology method for designing of the described direct current based on the DC-DC sectionalizer of claim 1, it is characterized in that: the little electrical network rack of direct current adopts circulus, and ring bus is divided into multistage, a plurality of electric pressures; DC-DC sectionalizer in the little electrical network of direct current connects different buses, and formation is cut apart more, the power supply general layout of multi-joint network; Each DC-DC sectionalizer all adopts the bridge topological structure of enjoying a double blessing, and carries out AC coupled by high frequency transformer.

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