A SVG circuit

Abstract

The present invention relates to an SVG circuit, comprising N DC-DC conversion units and an H-type bridge circuit composed of gate turn-off thyristors; N is a positive integer greater than 2; each of the DC-DC conversion units is connected in parallel to the H-type bridge circuit. The present invention reduces the number of switch devices used in SVG and reduces the production cost of SVG by improving the cascade half-bridge circuit.

Description

Technical Field

[0001] The invention relates to the technical field of power electronics, and in particular to an SVG circuit. Background Art

[0002] Reactive power compensation is widely used in power systems. In the process of improving the power quality of the power grid and improving the dynamic and static stability of the system, the multi-level topology has unique advantages in high-voltage and high-power scenarios. Common multi-level topologies include cascaded H-bridge, flying capacitor, diode clamp, etc.

[0003] Cascade H-bridge SVG (Static Var Generator) is widely used in medium and high voltage reactive power compensation field, but due to the large number of power switching devices used, the cost is relatively high. Summary of the invention

[0004] The object of the present invention is to provide an SVG circuit to reduce industrial costs.

[0005] To achieve the above object, the present invention provides the following solutions:

[0006] An SVG circuit comprises N DC-DC conversion units and an H-type bridge circuit composed of gate turn-off thyristors; N is a positive integer greater than 2; each of the DC-DC conversion units is connected in parallel to the H-type bridge circuit.

[0007] Optionally, the DC-DC conversion unit includes an insulated gate bipolar transistor, a capacitor, a first diode and a second diode, one end of the capacitor is connected to the anode of the first diode, the other end of the capacitor is connected to the collector of the insulated gate bipolar transistor and the cathode of the second diode, and the emitter of the insulated gate bipolar transistor and the anode of the second diode are connected to the cathode of the first diode.

[0008] Optionally, the H-type bridge circuit includes a first gate turn-off thyristor, a second gate turn-off thyristor, a third gate turn-off thyristor, and a fourth gate turn-off thyristor; the cathode of the first gate turn-off thyristor is connected to the anode of the third gate turn-off thyristor, the cathode of the second gate turn-off thyristor is connected to the anode of the fourth gate turn-off thyristor, the anode of the first gate turn-off thyristor and the anode of the second gate turn-off thyristor are connected to the cathode of the first diode in the first DC-DC conversion unit, the cathode of the third gate turn-off thyristor and the anode of the fourth gate turn-off thyristor are connected to the cathode of the first diode in the first DC-DC conversion unit, and the cathode of the third gate turn-off thyristor and the anode of the fourth gate turn-off thyristor are connected to the cathode of the first diode in the first DC-DC conversion unit. The cathode is connected to the anode of the first diode in the Nth DC-DC conversion unit; the first DC-DC conversion unit is the first DC-DC conversion unit after N DC-DC conversion units are connected in parallel, and the Nth DC-DC conversion unit is the Nth DC-DC conversion unit after N DC-DC conversion units are connected in parallel; a diode is connected in reverse parallel at both ends of each of the gate turn-off thyristors; the connection point between the cathode of the first gate turn-off thyristor and the anode of the third gate turn-off thyristor and the connection point between the cathode of the second gate turn-off thyristor and the anode of the fourth gate turn-off thyristor serve as output ends.

[0009] Optionally, the capacitor in the DC-DC conversion unit is a DC capacitor.

[0010] Optionally, the first diode in the DC-DC conversion unit is a fast recovery diode.

[0011] According to the specific embodiments provided by the present invention, the present invention discloses the following technical effects:

[0012] The present invention discloses an SVG circuit, comprising N DC-DC conversion units and an H-type bridge circuit composed of gate turn-off thyristors; N is a positive integer greater than 2; each of the DC-DC conversion units is connected in parallel to the H-type bridge circuit. The present invention reduces the number of switch devices used in SVG and reduces the production cost of SVG by improving the cascaded half-bridge circuit. BRIEF DESCRIPTION OF THE DRAWINGS

[0013] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings required for use in the embodiments will be briefly introduced below. 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 paying creative labor.

[0014] Figure 1 SVG circuit diagram provided by an embodiment of the present invention;

[0015] Figure 2This is a circuit diagram of a medium- and high-voltage reactive power compensation on-site SVG provided in an embodiment of the present invention. DETAILED DESCRIPTION

[0016] The following will be combined with the drawings in the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0017] Reactive power compensation is widely used in power systems. In the process of improving the power quality of the power grid and improving the dynamic and static stability of the system, the multi-level topology has unique advantages in high-voltage and high-power scenarios. Common multi-level topologies include cascaded H-bridge type, flying capacitor type, diode clamp type, U_cell type, etc. Table 1 is a comparison table of the number of components in various types of SVG circuits.

[0018] Table 1

[0019]

[0020] As can be seen from Table 1, a large number of switch tubes are used in various types of existing SVG circuits, resulting in high production costs.

[0021] The object of the present invention is to provide an SVG circuit to reduce industrial costs.

[0022] In order to make the above-mentioned objects, features and advantages of the present invention more obvious and easy to understand, the present invention is further described in detail below with reference to the accompanying drawings and specific embodiments.

[0023] Example 1

[0024] This embodiment provides an SVG circuit, including N DC-DC conversion units and an H-type bridge circuit composed of gate turn-off thyristors, where N is a positive integer greater than 2. The DC-DC conversion units are connected in parallel to the H-type bridge circuit.

[0025] Figure 1 The SVG circuit diagram provided by the embodiment of the present invention is as follows: Figure 1As shown, the DC-DC conversion unit includes an insulated gate bipolar transistor V, a capacitor C, a first diode VD1 and a second diode VD2, one end of the capacitor C is connected to the anode of the first diode VD1, the other end of the capacitor C is connected to the collector of the insulated gate bipolar transistor V and the cathode of the second diode VD2, and the emitter of the insulated gate bipolar transistor V and the anode of the second diode VD2 are connected to the cathode of the first diode VD1. The second diode VD2 in the DC-DC conversion unit plays the role of voltage clamping, ensuring that the capacitor C discharges normally and controlling the disconnection of the insulated gate bipolar transistor V of the switching device. By charging and discharging the capacitor C, DC / DC conversion is achieved.

[0026] The H-type bridge circuit includes a first gate turn-off thyristor VT1, a second gate turn-off thyristor VT2, a third gate turn-off thyristor VT3, and a fourth gate turn-off thyristor VT4. The cathode of the first gate turn-off thyristor VT1 is connected to the anode of the third gate turn-off thyristor VT3, the cathode of the second gate turn-off thyristor VT2 is connected to the anode of the fourth gate turn-off thyristor VT4, the anode of the first gate turn-off thyristor VT1 and the anode of the second gate turn-off thyristor VT2 are connected to the cathode of the first diode VD1 in the first DC-DC conversion unit, and the cathode of the third gate turn-off thyristor VT3 and the cathode of the fourth gate turn-off thyristor VT4 are connected to the anode of the first diode VD1 in the Nth DC-DC conversion unit. The first DC-DC conversion unit is the first DC-DC conversion unit after N DC-DC conversion units are connected in parallel, and the Nth DC-DC conversion unit is the Nth DC-DC conversion unit after N DC-DC conversion units are connected in parallel. A diode is connected in reverse parallel at both ends of each gate turn-off thyristor. The cathode connection point of the first gate turn-off thyristor VT1 and the anode connection point of the third gate turn-off thyristor VT3 and the cathode connection point of the second gate turn-off thyristor VT2 and the anode connection point of the fourth gate turn-off thyristor VT4 serve as output terminals.

[0027] Preferably, the capacitor C in the DC-DC conversion unit is a DC capacitor.

[0028] Preferably, the first diode VD1 in the DC-DC conversion unit is a fast recovery diode.

[0029] This circuit is used in the field of medium and high voltage reactive power compensation. By turning on and off the IGBT insulated gate bipolar transistor, the DC side voltage can be converted into a step-shaped steamed bun wave to complete the DC / DC conversion. Then through the H-bridge circuit, the inverter process is realized to complete the DC / AC conversion. This process can generate reactive current to achieve reactive power compensation for the system. Figure 2 The circuit diagram of the medium and high voltage reactive power compensation site SVG provided by the embodiment of the present invention is as follows: Figure 2As shown, by adding an inductor where the SVG circuit is connected to the grid, it can be used on-site for medium and high voltage reactive power compensation.

[0030] According to the specific embodiments provided by the present invention, the present invention discloses the following technical effects:

[0031] The present invention reduces the number of switch devices used in SVG by improving the cascade half-bridge circuit, while achieving reactive power compensation without affecting the compensation quality, thereby reducing the production cost of SVG to the maximum extent.

[0032] The various embodiments in this specification are described in a progressive manner, and each embodiment focuses on the differences from other embodiments. The same or similar parts between the various embodiments can be referenced to each other.

[0033] This article uses specific examples to illustrate the principles and implementation methods of the present invention. The above examples are only used to help understand the core idea of ​​the present invention. At the same time, for those skilled in the art, according to the idea of ​​the present invention, there will be changes in the specific implementation methods and application scope. In summary, the content of this specification should not be understood as limiting the present invention.

Claims

1. An SVG circuit, characterized in that: It comprises N DC-DC conversion units and an H-type bridge circuit composed of gate turn-off thyristors; N is a positive integer greater than 2; each of the DC-DC conversion units is connected in parallel to the H-type bridge circuit; The DC-DC conversion unit includes an insulated gate bipolar transistor, a capacitor, a first diode and a second diode, one end of the capacitor is connected to the anode of the first diode, the other end of the capacitor is connected to the collector of the insulated gate bipolar transistor and the cathode of the second diode, and the emitter of the insulated gate bipolar transistor and the anode of the second diode are connected to the cathode of the first diode; The H-type bridge circuit includes a first gate turn-off thyristor, a second gate turn-off thyristor, a third gate turn-off thyristor, and a fourth gate turn-off thyristor; the cathode of the first gate turn-off thyristor is connected to the anode of the third gate turn-off thyristor, the cathode of the second gate turn-off thyristor is connected to the anode of the fourth gate turn-off thyristor, the anode of the first gate turn-off thyristor and the anode of the second gate turn-off thyristor are connected to the cathode of the first diode in the first DC-DC conversion unit, the cathode of the third gate turn-off thyristor and the cathode of the fourth gate turn-off thyristor are connected to the cathode of the first diode in the first DC-DC conversion unit, and the cathode of the third gate turn-off thyristor and the cathode of the fourth gate turn-off thyristor are connected to the cathode of the first diode in the first DC-DC conversion unit. Connecting the anode of the first diode in the Nth DC-DC conversion unit; the first DC-DC conversion unit is the first DC-DC conversion unit after N DC-DC conversion units are connected in parallel, and the Nth DC-DC conversion unit is the Nth DC-DC conversion unit after N DC-DC conversion units are connected in parallel; a diode is connected in reverse parallel at both ends of each gate turn-off thyristor; the cathode of the first gate turn-off thyristor and the anode connection point of the third gate turn-off thyristor and the cathode of the second gate turn-off thyristor and the anode connection point of the fourth gate turn-off thyristor serve as output ends; The capacitor in the DC-DC conversion unit is a DC capacitor.

2. The SVG circuit according to claim 1, characterized in that: The first diode in the DC-DC conversion unit is a fast recovery diode.

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