CN203895987U

CN203895987U - Alternating-current chopper

Info

Publication number: CN203895987U
Application number: CN201420316435.2U
Authority: CN
Inventors: 刘幼林; 杨振; 徐海杰; 仲隽伟
Original assignee: SHANGHAI YINGTONG ELECTRIC Co Ltd
Current assignee: SHANGHAI YINGTONG ELECTRIC Co Ltd
Priority date: 2014-06-13
Filing date: 2014-06-13
Publication date: 2014-10-22
Anticipated expiration: 2024-06-13

Abstract

Disclosed in the utility model is an alternating-current chopper comprising three compensation circuits with identical structures. A first terminal of each compensation circuit is connected with a first terminal of a compensation input capacitor and is connected to a three-phase alternating-current power grid voltage by a compensator input reactor; and a second terminal, a third terminal, a fourth terminal of each compensation circuit are connected to second terminals, third terminals, and fourth terminals of other compensation circuits respectively and correspondingly. Second terminals of all compensation input capacitors are connected with second terminals of compensation input capacitors of other compensation circuits. The compensation circuits include AC-AC converters, each of which is formed by two IGBTs with source electrodes and drain electrodes in series connection. A diode is connected in an anti-parallel mode between the source electrode and the drain electrode of each IGBT; a buffer circuit is connected in parallel between a first terminal and a second terminal of each AC-AC converter and is formed by parallel connection of a resistor and a capacitor; a first terminal of a transformer secondary side is connected to the first terminal of the AC-AC converter by one compensation capacitor; and a first terminal of a transformer primary side is connected between the two IGBTs in series connection. No low-order harmonics are generated and the reactive currents of the capacitor output can be adjusted continuously.

Description

AC chopper

Technical field

The utility model relates to power domain, particularly relates to a kind of AC three-phase chopper that can realize the adjusting of capacitive reactive power current continuity.

Background technology

Great majority load consume reactive power in electric power system, if exist a large amount of reactive powers to flow in supply line, can cause mains supply ability to be not fully utilized, and causes a large amount of energy losses simultaneously.Therefore reactive power compensation is the energy-saving and cost-reducing requisite measure of electric power system, in load or burden without work, inductive load accounts for the overwhelming majority at present, and these loads constantly change idle demand, so reactive-load compensator main task is to provide continuously adjustable capacitive reactive power in actual applications.

Along with the development of power electronic technology, the static compensator (SVC) of thyristor-controlled reactor (TCR) and thyristor switchable capacitor (TSC) form is widely used.It has the advantages such as machinery-free weares and teares, response speed is very fast, but TCR can produce low-order harmonic, needs extra filter, and TSC is grading control, can not regulate continuously.Provide continuously adjustable capacitive reactive power need to take the form of TCR+ fixed capacitor (FC) or TCR+TSC.Another utilizes pulse-width modulation (PWM) the type SVC of self-turn-off device, by the duty of control switch, recently regulate the equivalent reactance of reactor, compare with TCR that to produce harmonic wave little, fast response time, could realize capacitive reactive power and regulate continuously but need coordinate with FC and TSC equally.And this by the idle continuous regulative mode of offsetting capacitive reactive power of continuous adjusting perception, reduced the utilance of compensating element,, increased loss.Although the static reacance generator (SVG) based on voltage-type or current mode bridge-type unsteady flow structure proposing in recent years has more satisfactory compensation characteristic, the control of this compensator than aforesaid SVC complexity many, installation cost is also very high.

Utility model content

The technical problems to be solved in the utility model is to provide a kind of static reacance AC chopper that low-order harmonic can be realized continuous control capacittance electric current that do not produce.

For solving the problems of the technologies described above, chopper of the present utility model, comprising:

Three compensating circuits that structure is identical, the first end of each compensating circuit connects the first end of a compensation input capacitance and respectively by a compensator input reactance access three-phase alternating current electrical network voltage, each compensating circuit second end, the 3rd end and the 4th end are connected respectively the second end, the 3rd end and the 4th end of other compensating circuits;

Describedly respectively compensate the second end of input capacitance and compensation input capacitance second end of other compensating circuits is connected;

Described compensating circuit comprises: the AC-AC converter that two IGBT of source drain series connection form, inverse parallel one diode between the source electrode of each IGBT and drain electrode, between the first end of described AC-AC converter and the second end, be parallel with a buffer circuit, described buffer circuit is comprised of a resistance and a Capacitance parallel connection, one transformer secondary first end connects the first end of described AC-AC converter by a building-out capacitor, described transformer primary side first end is connected between two IGBT of series connection;

The first end of described AC-AC converter is as the first end of described compensating circuit, the second end of described AC-AC converter is as the second end of described compensating circuit, described transformer primary side the second end is the 3rd end of circuit by way of compensation, and described transformer secondary the second end is the 4th end of circuit by way of compensation.

Preferably, described transformer is 1:1 transformer.

The utility model utilizes AC-AC converter and transformer to regulate continuously the voltage on building-out capacitor, directly realize the continuous adjusting of capacitive reactive power, in the utility model, the capacity of transformer can be set to 25% of capacitance, does not produce low-order harmonic, and control simply, be easy to realize.

Accompanying drawing explanation

Below in conjunction with accompanying drawing and embodiment, the present invention is further detailed explanation:

Fig. 1 is the structural representation of the utility model one embodiment.

Description of reference numerals

Ua, Ub, Uc are three-phase alternating current electrical network voltage

Lfa, Lfb, Lfc are the first～three compensator input reactances

Cfa, Cfb, Cfc are the first～three compensator input capacitances

Ta, Tb, Tc are transformers

Ca, Cb, Cc are building-out capacitors.

S1-S6 is the first～six IGBT

1,2,3 is the first～three compensating circuits

11～14 is first of the first compensating circuit～four ends

21～24 is first of the second compensating circuit～four ends

31～34 is first of the 3rd compensating circuit～four ends

D1～D6 is diode

R1～R3 is the first～three resistance

C1～C3 is the first～three electric capacity

Embodiment

As shown in Figure 1, chopper one of the present utility model is implemented, and comprising:

Three compensating circuits 1 that structure is identical, 2, 3, the first～three that compensating circuit 1, 2, 3 its first ends 11 separately, 21, 31 are connected respectively the first～three compensation input capacitance Cfa, Cfb, the first end of Cfc also passes through respectively by the first～three compensator input reactance Lfa, Lfb, Lfc accesses respectively three-phase alternating current electrical network voltage U a, Ub, Uc, it is the second end 12 separately, 22, 32 the 3rd ends 13, 23, the 33 and the 4th end 14, 24, 34 are connected respectively the second end 12 of other compensating circuits, 22, 32, the 3rd end 13, 23, the 33 and the 4th end 14, 24, 34, 12,22 are connected with 32, and 13,23 are connected with 33, and 14,24 are connected with 34

The second end interconnection of the first～three compensation input capacitance Cfa, Cfb, Cfc;

First compensating circuit 1 of take is example, compensating circuit 1 comprises: the AC-AC converter that an IGBT S1 of source drain series connection and the 4th IGBTS4 form, the drain electrode of the one IGBT S1 is as the first end of an AC-AC converter, the source electrode of the 4th IGBT S4 is as the second end of an AC-AC converter

Inverse parallel one diode D1, D4 respectively between its source electrode separately of the one IGBT S1, the 4th IGBT S4 and drain electrode, form diode cathode and connect its corresponding IGBT drain electrode, and diode anode connects the structure of its corresponding IGBT source electrode;

Between the first end of the one AC-AC converter and the second end, be parallel with the first buffer circuit, the first buffer circuit is composed in parallel by the first resistance R 1 and the first capacitor C 1, the first transformer Ta secondary first end Ta1 connects the first end of described AC-AC converter by the first building-out capacitor Ca, the first former limit of transformer Ta3 first end is connected between two IGBTS1 and S4 of series connection;

The first end of described AC-AC converter is as the first end 11 of described compensating circuit, the second end of described AC-AC converter is as the second end 12 of described compensating circuit, described transformer primary side the second end Ta4 is the 3rd end 13 of circuit by way of compensation, and described transformer secondary the second end Ta4 is the 4th end 14 of circuit by way of compensation;

In the present embodiment, the first～three transformer Ta, Tb, Tc are 1:1 transformer;

During the utility model work, Lfa, Lfb, Lfc and Cfa, Cfb, Cfc are compensator input reactance and capacitor, and they have formed the high order harmonic component in high pass filter filtering compensator input current.Lfa, Lfb, Lfc can utilize transformer leakage reactance to replace in the situation that electrical network connects by step-down transformer at compensator, and Cfa, Cfb, Cfc are the compensation condenser groups of fixed capacity.Ta, Tb, Tc are that no-load voltage ratio is the transformer of 1:1, play former, the effect of secondary isolation.Ca, Cb, Cc are building-out capacitor, connect, for load provides required reactive power with transformer secondary.S1-S6 and anti-paralleled diode thereof form AC-AC converter, and the first～three IGBT S1, S2, S3 act as main switch, and the four～six S4, S5, S6 act as auxiliary switch.S1, S2, S3 periodically turn on and off former limit and the three-phase alternating current system of transformer, and S4, S5, S6 allow the primary current afterflow of transformer at S1, S2, S3 blocking interval, so the relation of S1, S2, S3 and S4, S5, S6 turn-on and turn-off is complementary.When switch state, in order to prevent that two switches conducting simultaneously of same brachium pontis from causing power supply short circuit, must arrange certain Dead Time.In order to provide current path to transformer primary side in Dead Time, guarantee that transformer primary side electric current is in dead band

In time, do not suddenly change, on brachium pontis, install the buffer circuit being formed by resistance and Capacitance parallel connection additional.In a switch periods, AC-AC converter has three kinds of mode of operations like this: effective model, bypass mode and afterflow pattern.

The first compensating circuit (Ua phase) of take is example, in the situation that ignoring Dead Time, when main switch is opened, line voltage is added in transformer primary side by main switch S1, when auxiliary switch S4 opens, the former limit of transformer and line voltage disconnect, and its original edge voltage is 0, now transformer primary side electric current is by auxiliary continued flow switch afterflow, and transformer primary side comprises first-harmonic and harmonic wave two parts.Its fundametal compoment and S1 duty ratio are linear, and the ON time of S1 is set by different duty ratios, can obtain different output voltages, finally compensate the electric current of different capabilities.

Below through the specific embodiment and the embodiment the utility model is had been described in detail, but these not form restriction of the present utility model.In the situation that not departing from the utility model principle, those skilled in the art also can make many distortion and improvement, and these also should be considered as protection range of the present utility model.

Claims

1. an AC chopper, is characterized in that, comprising:

2. chopper as claimed in claim 1, is characterized in that, comprising: described transformer is 1:1 transformer.