CN108879679A - A kind of multiple target Power Quality Comprehensive Treatment Device for medium voltage distribution network - Google Patents

Abstract

The invention discloses a multi-objective power quality comprehensive treatment device for medium-voltage distribution network. single-phase energy storage type conversion unit, single-phase energy storage type conversion unit includes 2n first units and n second units, the first unit includes sequentially connected single-phase full-bridge AC-DC converter, power supply side bidirectional DC ‑DC converter, energy storage device and load side bidirectional DC‑DC converter, the second unit includes a three-phase six-arm DC‑AC converter. The invention is mainly used in medium-voltage distribution networks with medium-level (10kV or 35kV) voltage levels. It can suppress harmonic currents on the load side, balance the three-phase currents of distribution transformers, improve transformer utilization, dynamically compensate load reactive power, and improve distribution efficiency. The network power factor can be quickly compensated for the active power of the load, and the stability and reliability of the user's power supply voltage can be improved.

Description

A multi-objective power quality comprehensive control device for medium voltage distribution network

technical field

The invention relates to the technical field of power systems, in particular to a multi-objective power quality comprehensive treatment device for medium-voltage distribution networks.

Background technique

As a secondary energy source that is economical, practical, clean, convenient, and easy to control and convert, electric energy has become an important basis for economic development and people's lives. With the wide application of power electronic equipment, various non-linear, impulsive, fluctuating and asymmetrical loads have increased substantially, resulting in problems such as unbalanced three-phase voltage, voltage sag, harmonics, low power factor, negative sequence Power quality problems such as high current content. At the same time, due to the large variation range of the distribution network load, it is difficult to adjust the distribution network voltage, and the power supply voltage is high or low, and even the voltage exceeds the limit. Therefore, how to effectively improve power quality is a common concern of power supply departments, power users and power equipment manufacturers.

For this reason, various current quality control devices are currently installed on the user side to suppress the user's harmonic current, negative sequence current, etc. from polluting the grid; at the same time, various voltage quality control devices are installed between the power supply system and the user, Provide high-quality power supply voltage for electrical equipment. However, when multiple power quality problems coexist in a power supply area, multiple different target control devices need to be used together. At present, due to the lack of coordination between multiple devices, it may cause repeated compensation for some power quality problems. Or interact with each other, so that the governance of power quality cannot achieve the desired effect. In addition, there may be repeated installation of power quality control devices with similar functions, resulting in waste of control funds.

Contents of the invention

The technical problem to be solved by the present invention is to provide a multi-objective, synchronous and integrated power quality management device for the above-mentioned problems in the prior art, which can solve various power quality problems existing on the power supply side and the user side at the same time. Carry out comprehensive treatment, so as to improve the quality of power supply to sensitive loads and restrain its power pollution to the distribution network.

In order to solve the problems of the technologies described above, the technical solution adopted in the present invention is:

The invention provides a multi-objective power quality comprehensive treatment device for medium-voltage distribution network, which includes three-phase parallel transformers, three single-phase series transformers corresponding to each phase of ABC three-phases, and three single-phase transformers. An energy storage type conversion unit, the single-phase energy storage type conversion unit includes 2n first units and n second units, the first unit includes sequentially connected single-phase full-bridge AC-DC converters, bidirectional power supply side A DC-DC converter, an energy storage device, and a load-side bidirectional DC-DC converter, the second unit includes a three-phase six-leg DC-AC converter, and the single-phase full-bridge AC-DC of all 2n first units The AC ports of the converters are cascaded in sequence to form a chain structure, and are connected to the low-voltage windings of the three-phase parallel transformer through the AC ports at the beginning and end of the chain respectively, and the high-voltage windings of the three-phase parallel transformer are connected to the medium-voltage distribution network The DC port of the single-phase full-bridge AC-DC converter in each first unit is sequentially connected through the power supply side bidirectional DC-DC converter and one end of the energy storage device, and the other end of the energy storage device is connected to the load side bidirectional The low-voltage ports of the DC-DC converters are connected, and the high-voltage ports of the load-side bidirectional DC-DC converters of the 2n first units are connected in parallel with each other, and then respectively connected with the three-phase six-arm DC-AC converters of the n second units. The DC ports are connected one by one, and each phase of the AC ports of the three-phase six-leg DC-AC converters of the n second units is respectively connected to an outlet terminal of a single-phase series transformer, and the three single-phase series The other outgoing terminals of the transformers are connected to ground in parallel, and the high-voltage windings of the three single-phase series transformers are respectively connected in series in corresponding phases of the medium-voltage distribution network.

Preferably, the second unit further includes a three-phase filter inductor, the three-phase filter inductor is connected in series to the AC port of the three-phase six-leg DC-AC converter, and the three-phase filter inductor includes a A filter inductor for each phase of the AC port of the three-phase six-leg DC-AC converter.

Preferably, a single-phase filter inductor is connected in series between the AC port of the chain head in the chain structure and each phase line of the low-voltage winding of the three-phase parallel transformer.

Preferably, the energy storage device is a supercapacitor, or a lithium battery, or a storage battery.

Preferably, the single-phase full-bridge AC-DC converter, the power supply-side bidirectional DC-DC converter, the load-side bidirectional DC-DC converter, and the three-phase six-arm DC-AC converter are all based on full-control switching devices the converter.

Preferably, the full control switching device is one of an insulated gate bipolar power transistor IGBT, an electron injection enhanced gate transistor IEGT, an integrated gate commutated thyristor IGCT and a turn-off thyristor GTO.

The multi-objective power quality comprehensive treatment device for medium-voltage distribution network of the present invention has the following advantages: the present invention includes three-phase parallel transformers and three single-phase series transformers corresponding to each phase of the ABC three-phases and three single-phase energy storage type conversion unit, single-phase energy storage type conversion unit includes 2n first units and n second units, the first unit includes sequentially connected single-phase full-bridge AC-DC converter, power supply side bidirectional DC -DC converters, energy storage devices, and load-side bidirectional DC-DC converters, the second unit includes three-phase six-leg DC-AC converters, and controls the working status and power supply of each single-phase full-bridge AC-DC converter On the one hand, it can control the harmonic current generated by the load side and the unbalanced three-phase current on the load side, and on the other hand, it can quickly and dynamically compensate the reactive power to ensure the stability of the grid side voltage. Operation; by controlling the working status of all three-phase six-arm DC-AC converters, the working status of the load-side bidirectional DC-DC converter, combined with energy storage devices, it can control the voltage sag, voltage harmonics and The three-phase voltage is unbalanced, which improves the voltage stability and reliability of the user side.

Description of drawings

FIG. 1 is a schematic structural diagram of a circuit principle of an embodiment of the present invention.

Fig. 2 is a schematic structural diagram of a circuit principle of a single-phase energy storage type conversion unit in an embodiment of the present invention.

Legend: 1. Single-phase energy storage conversion unit; 11. Single-phase full-bridge AC-DC converter; 111. Single-phase filter inductor; 12. Bidirectional DC-DC converter on the power supply side; 13. Energy storage device; 14 1. Load-side bidirectional DC-DC converter; 15. Three-phase six-leg DC-AC converter; 16. Three-phase filter inductor; 2. Three-phase parallel transformer; 3. Single-phase series transformer.

Detailed ways

As shown in Figures 1 and 2, this embodiment provides a multi-objective power quality comprehensive management device for medium-voltage distribution networks, including a three-phase parallel transformer 2 and three phases corresponding to each of the ABC three-phases. single-phase series transformer 3 and three single-phase energy storage conversion units 1 (refer to Fig. 1, respectively 1#1~1#3), the single-phase energy storage conversion unit 1 includes 2n first units and n A second unit, the first unit includes a single-phase full-bridge AC-DC converter 11 connected in sequence, a power supply side bidirectional DC-DC converter 12, an energy storage device 13 and a load side bidirectional DC-DC converter 14, the second The unit includes a three-phase six-leg DC-AC converter 15, and the AC ports of the single-phase full-bridge AC-DC converters 11 of all 2n first units are sequentially cascaded to form a chain structure, and are connected through the chain head and the chain respectively. The AC port at the tail is connected to the low-voltage winding of the three-phase parallel transformer 2, the high-voltage winding of the three-phase parallel transformer 2 is connected to the medium-voltage distribution network, and the single-phase full-bridge AC-DC converter 11 in each first unit The DC port is sequentially connected to one end of the bidirectional DC-DC converter 12 on the power supply side and the energy storage device 13, and the other end of the energy storage device 13 is connected to the low-voltage port of the bidirectional DC-DC converter 14 on the load side. The loads of 2n first units The high-voltage ports of the side bidirectional DC-DC converter 14 are connected in parallel with each other and then respectively connected to the DC ports of the three-phase six-arm DC-AC converters 15 of n second units one by one, and the three-phase Each phase of the AC port of the six-arm DC-AC converter 15 is connected to one outlet terminal of a single-phase series transformer 3, and the other outlet terminals of the three single-phase series transformers 3 are connected to each other in parallel to the ground. The high-voltage windings of the single-phase series-connected transformers 3 are respectively connected in series in corresponding phases of the medium-voltage distribution network. It should be noted that, as shown in FIG. 1 , the number of 2n first units and n second units included in the single-phase energy storage type conversion unit 1 is exemplified by a plurality (n≥3). Undoubtedly, the number of them can also be one or two as required, and the principle is the same as in this embodiment, so the number n can be extended to n≧1.

As shown in Figure 1 and Figure 2, the second unit also includes a three-phase filter inductor 16, the three-phase filter inductor 16 is connected in series with the AC port of the three-phase six-leg DC-AC converter 15, and the three-phase filter inductor 16 It includes a filter inductor connected in series with each phase of the AC port of the three-phase six-leg DC-AC converter 15 .

As shown in FIG. 1 and FIG. 2 , a single-phase filter inductor 111 is connected in series between the AC port at the head of the chain and each phase line of the low-voltage winding of the three-phase parallel transformer 2 in the chain structure.

Referring to Fig. 2, the chain structure formed by cascading the single-phase full-bridge AC-DC converters 11 of all 2n first units passes through the AC ports a and b of the chain head and the chain tail respectively and the low voltage of the three-phase parallel transformer 2. The windings are connected. Taking the single-phase full-bridge AC-DC converter 11 at the head of the chain as an example, the positive pole c1 of the DC port of the single-phase full-bridge AC-DC converter 11 and the high-voltage port d1 of the single-phase full-bridge AC-DC converter 12 The low-voltage port e1 of the single-phase full-bridge AC-DC converter 12 is connected to one end f1 of the energy storage device 13, and the other end g1 of the energy storage device 13 is connected to the end g1 of the load-side bidirectional DC-DC converter 14. Low pressure port h 1 is connected. Moreover, the high-voltage port i 1 of the load side bidirectional DC-DC converter 14 in the single-phase full-bridge AC-DC converter 11 of the chain head and the load-side bidirectional DC-DC- The high-voltage ports i2 of the DC converter 14 are connected in parallel with each other and then respectively connected to the DC port j1 of the three-phase six-arm DC-AC converter 15 of the first second unit among the n second units, the three-phase six-bridge The AC port k1 of the arm DC-AC converter 15 is connected to one terminal l1 of the three-phase filter inductor 16, and the other terminal o1 of the three-phase filter inductor 16 is connected to the single-phase series transformer 3 of phase A One outlet terminal of A\B\C three-phase single-phase series transformer 3 is connected in parallel with each other, and the high voltage of three single-phase series transformer 3 of A\B\C three-phase The windings are respectively connected in series in corresponding phases of the medium voltage distribution network.

In this embodiment, the energy storage device 13 may use a supercapacitor, or a lithium battery, or a storage battery as required.

In this embodiment, the single-phase full-bridge AC-DC converter 11, the power supply side bidirectional DC-DC converter 12, the load side bidirectional DC-DC converter 14, and the three-phase six-leg DC-AC converter 15 are all based on A converter with fully controlled switching devices.

In this embodiment, the full control switching device is one of an insulated gate bipolar power transistor IGBT, an electron injection enhanced gate transistor IEGT, an integrated gate commutated thyristor IGCT and a turn-off thyristor GTO.

The multi-objective power quality comprehensive management device used in the medium-voltage distribution network in this embodiment is mainly used for intermediate (10kV or 35kV) voltage levels, and this embodiment is used for the work of the multi-objective power quality comprehensive management device in the medium-voltage distribution network The principle is as follows: On the one hand, by controlling the working state of each single-phase full-bridge AC-DC converter 11 and the working state of the bidirectional DC-DC converter 12 on the power supply side, on the one hand, it can control the harmonic current generated by the load side and the load side On the other hand, it can quickly and dynamically compensate the reactive power to ensure the stable operation of the grid side voltage; on the other hand, by controlling the working status and load of all three-phase six-leg DC-AC converters 15 The working state of the side-side bidirectional DC-DC converter 14, combined with the energy storage device 13, can control the voltage sag, voltage harmonics and three-phase voltage imbalance on the power supply side, and improve the voltage stability and reliability of the user side, thereby The purpose of comprehensive management of multi-objective power quality of the medium-voltage distribution network can be realized.

The above descriptions are only preferred implementations of the present invention, and the protection scope of the present invention is not limited to the above-mentioned embodiments, and all technical solutions under the idea of the present invention belong to the protection scope of the present invention. It should be pointed out that for those skilled in the art, some improvements and modifications without departing from the principles of the present invention should also be regarded as the protection scope of the present invention.

Claims (6)

1. a kind of multiple target Power Quality Comprehensive Treatment Device for medium voltage distribution network, which is characterized in that including parallel three phase Type transformer（2）And respectively correspond three single-phase series type transformers of each phase in ABC three-phase（3）And three single-phase storages It can type converter unit（1）, the single-phase accumulation energy type converter unit（1）Including 2n first unit and n second unit, described Unit one includes the single-phase full bridge AC-DC converter being sequentially connected（11）, supply side bidirectional DC-DC converter（12）, energy storage dress It sets（13）And load side bidirectional DC-DC converter（14）, the second unit includes six bridge arm DC-AC converter of three-phase （15）, the single-phase full bridge AC-DC converter of all 2n first units（11）AC port successively cascade connection be in chain knot Structure and the AC port and Three-Phase Parallel transformer for passing through first-in-chain(FIC) and last-of-chain respectively（2）Low pressure winding be connected, parallel three phase Type transformer（2）High-voltage winding be connected with medium voltage distribution network, single-phase full bridge AC-DC converter in each first unit（11） DC port pass sequentially through supply side bidirectional DC-DC converter（12）, energy storage device（13）One end be connected, energy storage dress It sets（13）The other end and load side bidirectional DC-DC converter（14）Low-pressure port is connected, and the load side of 2n first unit is double To DC-DC converter（14）Become respectively with six bridge arm DC-AC of the three-phase of n second unit again after high pressure port is parallel with one another two-by-two Parallel operation（15）DC port be connected one by one, the six bridge arm DC-AC converter of three-phase of n second unit（15）AC port Each phase respectively with a single-phase series type transformer（3）An outlet terminal be connected, and three single-phase series type transformers （3）Another outlet terminal ground connection parallel with one another, three single-phase series type transformers（3）High-voltage winding be connected in series respectively In the correspondence phase of medium voltage distribution network.

2. the multiple target Power Quality Comprehensive Treatment Device according to claim 1 for medium voltage distribution network, feature exist In the second unit further includes three-phase filter inductance（16）, the three-phase filter inductance（16）It is serially connected in six bridge arm DC- of three-phase AC converter（15）AC port on, and the three-phase filter inductance（16）Including being serially connected with six bridge arm DC-AC of three-phase transformation Device（15）The each phase of AC port filter inductor.

3. the multiple target Power Quality Comprehensive Treatment Device according to claim 1 for medium voltage distribution network, feature exist In：The AC port of first-in-chain(FIC) and Three-Phase Parallel transformer in the chain structure（2）Low pressure winding each phase line on It is connected in series with single-phase filter inductance（111）.

4. the multiple target Power Quality Comprehensive Treatment Device according to claim 1 for medium voltage distribution network, feature exist In：The energy storage device（13）For supercapacitor or lithium battery or battery.

5. the multiple target Power Quality Comprehensive Treatment Device according to claim 1 for medium voltage distribution network, feature exist In：The single-phase full bridge AC-DC converter（11）, supply side bidirectional DC-DC converter（12）, load side bidirectional DC-DC converter Device（14）, six bridge arm DC-AC converter of three-phase（15）It is the converter based on full control switching device.

6. the multiple target Power Quality Comprehensive Treatment Device according to claim 5 for medium voltage distribution network, feature exist In：The full control switching device is insulated gate bipolar translator power tube IGBT, electron injection enhancement gate transistor IEGT, integral gate One of commutated thyristor IGCT and turn-off thyristor GTO.