CN107565614B - Alternating current-direct current hybrid power system - Google Patents
Alternating current-direct current hybrid power system Download PDFInfo
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- CN107565614B CN107565614B CN201610513316.XA CN201610513316A CN107565614B CN 107565614 B CN107565614 B CN 107565614B CN 201610513316 A CN201610513316 A CN 201610513316A CN 107565614 B CN107565614 B CN 107565614B
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Abstract
The invention discloses an alternating current-direct current hybrid power system which comprises an alternating current power supply (01), an alternating current bus (02), an alternating current feeder (03), an alternating current switch (04), an alternating current/direct current converter device (05), an arc extinction device (06), a fault current damping device (07), a direct current positive bus (101) voltage measuring device (51), a direct current negative bus (102) voltage measuring device (52) and a grounding current measuring device (08). And a transformer is not connected between the AC/DC converter device (05) and the AC power supply (01) in the AC/DC hybrid power system, so that the overall investment and the occupied area of the system can be reduced.
Description
Technical Field
The invention relates to an alternating current and direct current hybrid power system, and belongs to the technical field of alternating current and direct current power supply.
Background
The power transmission and distribution technology of the alternating current power grid is mature, and the control and protection mechanism is clear. The direct current power grid can realize flexible control of transmission power, is suitable for the access of a direct current power supply and a direct current load, and can be used as an important supplement of an urban power supply system. The alternating current-direct current hybrid power supply system is constructed in a specific area, so that higher-quality power supply can be provided, a distributed power supply and a direct current load can be better accommodated, the power and voltage control capability of an alternating current distribution system is improved, the safety and stability level of the system is improved, and the loss is reduced.
The voltage source type converter can realize AC/DC conversion, the active power and the reactive power of the converter can be independently decoupled and controlled, and the converter is a core device for constructing an AC/DC hybrid power supply system. The voltage source converter device is mostly connected with an alternating current power grid by adopting a connecting transformer, on one hand, the connecting transformer can realize fault isolation between alternating current and direct current systems, and on the other hand, the transformer can realize matching of the voltage of the alternating current system and the voltage of the valve side of the voltage source converter device. The urban power supply system has higher requirements on the volume and the occupied area of the power device, and a compact design scheme is required when the voltage source converter device is applied to the urban power supply system. If a connecting transformer between the converter device and the alternating current system can be omitted, the overall investment and the occupied area of the system can be reduced.
In order to solve the problems that the urban alternating current power distribution system has large capacitance current to the ground, the current flowing through a fault point after single-phase grounding is large, and intermittent arc light grounding overvoltage is easy to generate, the urban power grid generally adopts a resonance grounding mode, namely an arc suppression coil is arranged at a neutral point. When single-phase grounding occurs, the inductive current generated by the arc suppression coil compensates the capacitance current of the fault point. The arc suppression coil has obvious effects of suppressing intermittent arc overvoltage and ferromagnetic resonance overvoltage, reducing the accident trip rate of a circuit, and reducing personal casualties and equipment damage.
The voltage source type inverter generally uses a method of connecting a high-resistance ground on a transformer side or a high-resistance ground on a direct current side. When the voltage source type converter device is directly connected to the ac system, the converter device may share a ground system with the ac system. When the alternating current system adopts the arc suppression coil to be grounded, and the current conversion device and the alternating current system share the ground, namely after the direct current side of the current conversion device has a ground fault, a neutral point of the alternating current system generates direct current bias voltage, fault current with bias can be generated on the arc suppression coil at the moment, even if the current conversion device is locked, three-phase alternating current voltage can still be conducted alternately through a freewheeling diode of the current converter, the situation that the alternating current switch cannot be disconnected due to the fact that phase current lacks a zero crossing point can occur at the moment, and the direct current ground fault of the current conversion device cannot be isolated by the system. A large fault current flows through each of the arc suppression device, the converter device, and the ac line, and in the serious case, the arc suppression coil, the converter device, and other devices are damaged. Therefore, appropriate measures need to be taken to cope with this, and an appropriate system scheme is proposed.
Disclosure of Invention
The invention aims to provide an alternating current-direct current hybrid power system which can meet the fault isolation requirement when a direct current ground fault occurs in the system and realize that an AC/DC converter device is directly connected to an alternating current system which is grounded by an arc suppression device without a connecting transformer.
In order to achieve the above purpose, the solution of the invention is:
an alternating current-direct current hybrid power system comprises an alternating current power supply (01), an alternating current bus (02), an alternating current feeder (03), an alternating current switch (04), an AC/DC converter device (05), an arc extinction device (06) and a direct current network (10), wherein the AC/DC converter device (05) is connected to the alternating current bus (02) through the alternating current switch (04) to realize alternating current-direct current voltage conversion and electric energy transmission;
the alternating current and direct current hybrid power system is characterized by further comprising a fault current damping device (07), a voltage measuring device (51) of a direct current positive bus (101), a voltage measuring device (52) of a direct current negative bus (102) and a grounding current measuring device (08) for collecting grounding current IGND;
the fault current damping device comprises at least one power resistor (71), a bidirectional switch (72) connected in parallel with the power resistor, and a control unit for controlling the bidirectional switch (72), wherein one end of the fault current damping device (07) is connected to the arc extinction device (06), and the other end of the fault current damping device is grounded.
The alternating current-direct current hybrid power system is characterized in that a bidirectional switch (72) connected with a power resistor (71) in parallel in the fault current damping device (07) has direct current breaking capacity, and the bidirectional switch (72) can be a fully-controlled semiconductor bidirectional switch device (BIGT) or a fully-controlled semiconductor bidirectional switch formed by semiconductor pass devices (such as IGBTs and IGCTs).
The alternating current-direct current hybrid power system is characterized in that: under the condition that the direct current side ground fault does not occur, the bidirectional switch (72) keeps triggering and conducting, and the bidirectional switch (72) bypasses the power resistor (71); after the direct current ground fault occurs, the bidirectional switch (72) is rapidly turned off and disconnected through the bidirectional switch control unit (73), and the ground current flows through a power resistor (71) of the fault current damping device.
The alternating current-direct current hybrid power system is characterized in that the AC/DC converter device (04) can be a voltage source type converter with a two-level structure, a three-level structure or a modular multi-level structure.
The alternating current-direct current hybrid power system is characterized in that the arc extinguishing device can be an arc extinguishing device with a grounding transformer or an arc extinguishing device without a transformer; the arc extinction device with the arc extinction coil damping resistor can also be an arc extinction device without the arc extinction coil damping resistor.
The invention adopts the technical scheme to obtain the beneficial effects that:
1) according to the alternating current/direct current hybrid power system, the AC/DC converter device is directly connected with the alternating current system, so that a connecting transformer is omitted, and the overall investment and manufacturing cost of the system are saved.
2) When the AC/DC converter is in failure, the arc suppression coil can compensate the grounding current, so that the clearance arc overvoltage and ferromagnetic resonance overvoltage are suppressed, the accident trip rate of the circuit is reduced, and human casualties and equipment damage are reduced. The fault current damping device does not affect the protection mechanism when the alternating current system fails.
3) When the AC/DC converter device generates a direct current side ground fault, the bidirectional switch can realize the turn-off of the forward current and the reverse current, and after the bidirectional switch is turned off, the ground current flows through the power resistor of the fault current damping device, so that the fault current flowing through the arc suppression coil and the grounding point is quickly attenuated, and conditions are provided for the isolation of the direct current side positive pole ground fault and the negative pole ground fault.
4) The invention can be widely applied to the existing urban power supply system, constructs a compact AC/DC hybrid power system and better accommodates a distributed power supply and a DC load.
Drawings
Fig. 1 is a schematic diagram of a hybrid ac/dc power system based on the prior art.
Fig. 2 is a schematic diagram of a connectionless transformer ac/dc hybrid power system.
FIG. 3 illustrates an embodiment of an AC/DC hybrid power system.
Fig. 4 shows an embodiment of a bidirectional switch formed by reverse series connection of IGBT elements.
Fig. 5 shows an example of a bidirectional switch including IGBT elements and diode elements.
FIG. 6 is a schematic diagram of a ground current path when the bi-directional switch is on.
Fig. 7 is a schematic diagram of the ground current path when the bi-directional switch is off.
Detailed Description
The present invention will be described in detail below with reference to the accompanying drawings. It is to be understood, however, that the drawings are provided solely for the purposes of promoting an understanding of the invention and that they are not to be construed as limiting the invention.
Fig. 1 is an example of a hybrid AC/DC power system based on the prior art, in which a connecting transformer (041) is arranged between an AC power source (01) and an AC/DC converter device (05), and a grounding device (042) is arranged between the connecting transformer (041) and the AC/DC converter device (05) to provide a reference potential for the AC/DC converter device (05). The connection transformer between the alternating current power supply (01) and the AC/DC converter device (05) increases the overall investment and the occupied area of the system. Fig. 2 is a prior art connectionless transformer-based AC-DC hybrid power system, which includes an AC power supply (01), an AC bus (02), an AC feeder (03), an AC switch (04), an AC/DC converter (05), and an arc suppression device (06). A transformer is not connected between an alternating current power supply (01) and an AC/DC converter device (05), under the condition of direct-current single-pole ground fault, a fault current path is formed by an alternating current power grid through a freewheeling diode and an arc suppression coil of the converter, direct-current bias voltage appears at two ends of the arc suppression coil, fault current with direct-current bias flows through an alternating current switch (04), the breaking capacity of the alternating current switch (04) is exceeded, the alternating current switch (04) cannot normally open a brake, and the fault is isolated. Larger fault current flows on the arc extinction coil, the arc extinction coil damping resistance protection unit (65) can short-circuit the arc extinction coil damping resistance (64), at the moment, the damping of a fault loop is smaller, and the attenuation time of the fault current flowing through the alternating current switch (04) is longer.
Fig. 3 shows a 10kV ac/dc hybrid power system according to an embodiment of the invention. The alternating current-direct current hybrid power system comprises a 10kV alternating current power supply (01), an alternating current bus (02), a 10kV alternating current feeder (03), an alternating current switch (04), an AC/DC converter device (05), an arc extinction device (06), a fault current damping device (07) and a grounding current measuring device (08), wherein a voltage measuring element (51) is configured on a direct current side positive bus (101) of the AC/DC converter device (05) to measure the voltage UdcP of the direct current side positive bus of the converter to the ground; arranging a voltage measuring element (52) on a direct current side negative bus (102) of an AC/DC converter device (05) to measure the voltage UdcN of the direct current side negative bus of the converter to the ground; a ground measuring device is disposed between the damping device and the ground point to detect a ground current IGND.
The ac feeder (03) shown in fig. 3 is used to supply power to an ac load; the AC/DC converter device (05) is used for alternating current-direct current voltage conversion and realizing power transmission of an alternating current system and a direct current system, an alternating current voltage connection of the AC/DC converter device (05) is connected to the alternating current switch (04), and a direct current voltage connection of the AC/DC converter device (05) is connected to the direct current load (10). In the embodiment, the converter of the AC/DC converter device (05) adopts a voltage source type converter with a modular multilevel structure. One end of the alternating current switch (04) is connected with the alternating current voltage end of the current converter, and the other end of the alternating current switch is connected with the 10kV alternating current bus (02). In this embodiment, there is no transformer connected between the AC/DC converter (05) and the AC power supply (01).
In the ac/dc hybrid power system shown in fig. 3, the arc suppression device (06) includes a grounding transformer (061), an isolator (62), an arc suppression coil (63), an arc suppression coil damping resistor (64), an arc suppression coil damping resistor protection unit (65), and the like. The grounding transformer of the arc suppression device (06) is connected to a three-phase alternating current power supply, a neutral point is led out through the grounding transformer, and the grounding transformer is connected to the arc suppression coil (63) through an isolation switch. One end of the arc suppression coil (63) is connected to the isolating switch, the other terminal of the arc suppression coil is connected to an arc suppression coil damping resistor (64), and an arc suppression coil damping resistor protection unit (65) is connected with two ends of an arc suppression damping resistor (064) in parallel. The winding of the grounding transformer (061) connected with the alternating current power supply (1) adopts Z-shaped wiring, and the grounding transformer (061) can only be a primary winding and can also be additionally provided with a secondary winding according to the requirement. When the AC power supply (01) has a neutral point, the arc suppression device (06) does not need to use a grounding transformer, and the arc suppression coil (63) is directly connected to the neutral point of the AC power supply (01). The arc suppression coil damping resistor (64) is used for limiting the displacement voltage UN of the neutral point to be less than 15% of the phase voltage when the series resonance occurs in the system. When the system is in single-phase grounding, a large current flows through a neutral point, and then the arc suppression coil damping resistor (64) is in short circuit through an arc suppression coil damping resistor protection unit (65).
The fault current damping device in the ac/dc hybrid power system shown in fig. 3 includes at least one power resistor (71), a bidirectional switch (72) connected in parallel with the power resistor, and a control unit (73) for controlling the bidirectional switch (72). One end of the fault current damping device (07) is connected to the arc extinction device (06), and the other end is grounded. The bidirectional switch (72) is a semiconductor switch (BIGT) capable of reverse conduction. The bidirectional switch connected with the power resistor in parallel has bidirectional current breaking capacity, and can also be a bidirectional switch with bidirectional current breaking capacity formed by combining controllable semiconductor devices. Fig. 4 shows another example of the bidirectional switch in the fault current damping device of the present invention, the bidirectional switch is formed by connecting two IGBT units in series in reverse, and each IGBT unit can be turned on and off by a control signal. Fig. 5 shows another example of the bidirectional switch in the damping device of the present invention, which is composed of 1 IGBT cell and 4 diode cells.
The invention is implemented in the situation that the DC fault does not occur, the bidirectional switch is conducted, the grounding current flows through the power resistor of the bidirectional switch (as shown in figure 6) and is bypassed by the bidirectional switch (72), and the arc extinction device can compensate the fault current when the AC system is in the grounding fault; after a direct current ground fault occurs, the bidirectional switch is rapidly turned off through the bidirectional switch control unit (73), and ground current flows through a power resistor (71) of the fault current damping device (shown in figure 7), so that the fault current is rapidly attenuated.
The AC/DC converter device (04) in the alternating current and direct current hybrid power system can be a voltage source type converter with a two-level structure, a three-level structure or a modular multi-level structure.
The above examples are only for illustrating the technical idea of the present invention, and the scope of the present invention should not be limited thereto, and all equivalent changes and modifications based on the technical solution of the present invention should not be excluded from the scope of the present invention.
Claims (5)
1. The utility model provides an alternating current-direct current hybrid power system, includes alternating current power supply (01), alternating current bus (02), alternating current feeder (03), AC switch (04), AC/DC current conversion device (05), arc extinguishing device (06), direct current network (10), its characterized in that:
the AC/DC converter device (05) is connected to an AC bus (02) through an AC switch (04) to realize AC/DC voltage conversion and electric energy transmission; the alternating current bus (02) is connected to an alternating current power supply (01), and the alternating current feeder line (03) is an alternating current outgoing branch line of the alternating current bus (02); the arc suppression device (06) is connected to the alternating current bus (02); the direct current network is connected to an AC/DC converter device (05);
the alternating current-direct current hybrid power system further comprises a fault current damping device (07), wherein the fault current damping device (07) comprises at least one power resistor (71), a bidirectional switch (72) connected with the power resistor in parallel and a control unit used for controlling the bidirectional switch (72), one end of the fault current damping device (07) is connected to an arc extinction device (06), one end of the fault current damping device is grounded, when the alternating current system is in single-phase grounding, the bidirectional switch (72) of the fault current damping device (07) is conducted, grounding current flows through the bidirectional switch (72), the power resistor is bypassed by the bidirectional switch (72), and the arc extinction device (06) compensates fault current in the case of grounding fault of the alternating current system; after a direct current ground fault occurs, the bidirectional switch is quickly turned off through a control unit (73) of the bidirectional switch of the fault current damping device (07), the ground current flows through a power resistor (71) of the fault current damping device, the fault current flowing through an arc suppression coil and a grounding point is quickly attenuated, and conditions are provided for isolating a direct current side positive pole ground fault from a negative pole ground fault;
the alternating current-direct current hybrid power system further comprises an AC/DC converter device (05) and a voltage measuring device (51) of a direct current positive bus (101), and the voltage measuring device is used for measuring the voltage UdcP of the direct current positive bus of the AC/DC converter device to the ground; the voltage measuring device (52) comprises an AC/DC converter device (05) direct current negative bus (102), and is used for measuring the voltage UdcN of the direct current negative bus of the AC/DC converter device to the ground; and a ground current measuring device (08) between the damping device and the ground point for detecting the ground current IGND.
2. The ac-dc hybrid power system according to claim 1, wherein the bidirectional switch (72) connected in parallel with the power resistor (71) in the fault current damping device (07) has a dc current breaking capability, and the bidirectional switch (72) is a semiconductor-type bidirectional switch formed by a fully-controlled semiconductor device.
3. The ac-dc hybrid power system of claim 1, wherein: the AC/DC converter device is a voltage source type converter device with a two-level structure, a three-level structure or a modular multi-level structure.
4. The ac-dc hybrid power system of claim 1, wherein: the arc extinguishing device is an arc extinguishing device with a grounding transformer or an arc extinguishing device without a grounding transformer.
5. The ac-dc hybrid power system of claim 1, wherein: arc extinguishing device (06) is the arc extinguishing device who takes arc suppression coil damping resistance, arc extinguishing device (06) are including grounding transformer (61), isolator (62), arc suppression coil (63), arc suppression coil damping resistance (64), arc suppression coil damping resistance protection unit (65), grounding transformer (61) of arc extinguishing device (06) are connected to alternating current power supply (01), grounding transformer is connected to arc suppression coil (63) through isolator (61), another terminal of arc suppression coil (63) is connected to arc suppression coil damping resistance (64), arc suppression coil damping resistance protection unit (65) connect in parallel in arc suppression coil damping resistance (64) both ends, arc extinguishing device perhaps is the arc extinguishing device who does not take arc suppression coil damping resistance.
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Citations (1)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN201533158U (en) * | 2009-11-25 | 2010-07-21 | 安徽山川电力技术有限公司 | Overvoltage restraining and inrush current limiting circuit |
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| US8339055B2 (en) * | 2009-08-03 | 2012-12-25 | Intersil Americas Inc. | Inrush current limiter for an LED driver |
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| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN201533158U (en) * | 2009-11-25 | 2010-07-21 | 安徽山川电力技术有限公司 | Overvoltage restraining and inrush current limiting circuit |
Non-Patent Citations (1)
| Title |
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| 中性点经消弧线圈接地系统中柔性环网控制装置接地故障分析;姜田贵，等;《电力建设》;20160531;第37卷(第5期);146－152 * |
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Effective date of registration: 20190203 Address after: 211102 Suyuan Avenue, Jiangning District, Nanjing, Jiangsu Province, No. 69 Applicant after: Nanrui Relay Protection Electricity Co., Ltd., Nanjing Applicant after: Nanjing Nari-Relays Engineering Technology Co., Ltd. Applicant after: State Grid Zhejiang Electric Power Co., Ltd. Hangzhou power supply company Address before: 211106 Suyuan Avenue, Jiangning District, Nanjing, Jiangsu Province, No. 69 Applicant before: Nanrui Relay Protection Electricity Co., Ltd., Nanjing Applicant before: Nanjing Nari-Relays Engineering Technology Co., Ltd. |
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