CN201829945U

CN201829945U - Transformer direct-current magnetic biasing compensating device with reactive compensation function

Info

Publication number: CN201829945U
Application number: CN2010205759025U
Authority: CN
Inventors: 白保东; 刘宗伟; 张志佳
Original assignee: Shenyang University of Technology
Current assignee: Shenyang University of Technology
Priority date: 2010-10-26
Filing date: 2010-10-26
Publication date: 2011-05-11
Anticipated expiration: 2020-10-26

Abstract

The utility model relates to a transformer direct-current magnetic biasing compensating device with a reactive compensation function, comprising a PWM (Pulse Width Modulation) rectifier which is connected with a power grid by a reactor, the PWM rectifier serving as an alternating current side is connected with a direct current side in parallel, the direct current side, a transformer, a neutral line Hall current sensor and a CPU (Central Processing Unit) are sequentially connected; PLLs (Phase Locking Loops) are connected between the power grid and the CPU and between the reactor and the CPU. In the utility model, on the basis of static reactive compensation, a structure for inhibiting direct-current magnetic biasing is additionally arranged, the study on restraining direct-current magnetic biasing is considered in a large power grid, direct-current magnetic biasing is inhibited, normal operation of the power grid is not affected, so as to realize two efficacies by one device, reduce the cost of the device for inhibiting direct-current magnetic biasing, obtain certain economic benefit and have great valuable significance for the whole electric power system.

Description

Transformer DC magnetic bias compensation arrangement with no-power compensation function

Technical field: the present invention relates to field of power electronics, specifically refer to a kind of device that not only can be used to improve power factor of electric network but also can suppress the transformer neutral point D.C. magnetic biasing.

Background technology: along with power electronic technology, developing rapidly of computer technology and control theory is gradually improved high voltage dc transmission technology.Asynchronous aspect such as be connected between high-power long distance power transmission, submarine cable and AC system, direct current transportation has many unique advantages.Low by 1996, the DC engineering that has put into operation in the world just has 56, and transmission line capability reaches 54.166GW.Along with the electric power development general policy of China's " transferring electricity from the west to the east, north and south is confession mutually, national network ", the direct current transportation technology will play an important role in nationwide integrated power grid is interconnected.Direct current transportation has at present obtained significant progress and application in China, the Zhoushan 100KV submarine cable direct current transportation of China from building up voluntarily is so far successively to build up Three Gorges to Changzhou 500KV DC transmission engineering, day wide 500KV DC transmission engineering, expensive wide 500KV DC transmission engineering.Direct current transportation is to have very big economic benefit under certain condition.Yet find that in actual motion when DC transmission system adopted the earth as the operational mode in loop, huge direct current constituted the loop with the earth, can near AC system be exerted an influence when flowing through from the earth.Its influence to AC system mainly is caused by near the transformer DC magnetic bias of the neutral-point solid ground earth electrode.

In high voltage direct current transmission, circuit generally all adopts the mode of one pole ground return circuit to move, for example a day wide power transmission network adopts this operational mode exactly, during the operation of direct current one pole ground return circuit, the part AC transformer can be subjected to the influence of D.C. magnetic biasing, can make the vibration of electrical network interior section transformer aggravate, and noise increases, the exciting current distortion, similar incidents occurred always after three wide DC power transmission line put into operation.In expensive wide DC line, the monitoring record in May, 2004 shows that under the expensive wide DC power transmission line one pole ground return circuit operational mode, spring city station owner's transformer neutral point direct current reaches 34.5A, and noise reaches 93.9dB, and harmonic voltage resultant distortion rate reaches 2.1%.Three Gorges dragon's fountain---the flat 500kV DC transmission system of Jiangsu political affairs is since in December, 2002 debugging and trial run, and noise rise significantly (rising 20dB) all appears in two groups of 500KVA main transformers of Changzhou Wu Nan transformer station.

In addition, except high voltage direct current transmission project can cause the D.C. magnetic biasing phenomenon, the earth magnetism magnetic storm equally also can cause the D.C. magnetic biasing of transformer.By document as can be seen, cause the geomagnetic induction current (GIC) in addition of power transformer D.C. magnetic biasing.When geomagnetic storm took place, magnetic field that electrode current produces and magnetic field of the earth interacted and produce induced potential (ESP) at the earth's surface, and this induced potential can reach every kilometer 1～10V or higher.This ground potential will be brought out geomagnetic induction current between the grounding transformer in the particularly east-west transmission line in long-distance transmission system.This faradic frequency is compared to be similar to the 50Hz power frequency of AC system and is regarded direct current as between 0.001～0.1Hz.

On March 13rd, 1989; the bias current that magnetic storm causes has caused having a power failure on a large scale of Quebec, CAN electrical network; cause is that bias current makes transformer core sharply saturated; harmonic wave heightens; cause the protective relaying maloperation of electrical network SVC device to be done, a large amount of capacitors are out of service, the system voltage collapse; finally lose the 9500MW load, nearly 9 hours of grid disconnection.Therefore, the inhibition method and the measure of the D.C. magnetic biasing phenomenon of research transformer are that thing must gone to safe operation of power system.

In electrical network, a lot of transformers all can be subjected to the influence of DC magnetic bias current, and affected transformer has plenty of near the converter direct current grounding pole, and what have but is away from direct current grounding pole ^[6], what also have but is in east-west transmission line.But any is arranged is sure, that be exactly the transformer DC magnetic bias phenomenon be to cause by the direct current that flows into its neutral point.Direct current produces potential difference between two grounding transformers, electric current is flowed into by a transformer grounding neutral point, flows out from another transformer neutral point.The direct current that flows through Transformer Winding causes that the magnetic bias of transformer causes transformer core saturated, and the exciting current distortion produces a large amount of harmonic waves, and reactive loss increases, even may cause that also system voltage seriously reduces, system relay misoperation or the like.So the inhibition of researching DC magnetic bias is imperative.

But only the inhibition of researching DC magnetic bias is far from being enough, this problem should be put into big network system considers, not only suppressed D.C. magnetic biasing but also do not influenced network system normally to move, perhaps can also do bigger contribution for network system, such as the present invention, on the basis of Static Var Compensator, increase the structure that suppresses D.C. magnetic biasing.

In sum, D.C. magnetic biasing is that outer room is imposed on transformer, so not still with the inhibition of researching DC magnetic bias, also restraining device will be embedded in the static reacance power compensator, to reach two kinds of effect purposes of a device, this is to have great practical significance to electric power system.

Summary of the invention:

Goal of the invention: the invention provides a kind of device, the DC-DC converter that will be used to suppress D.C. magnetic biasing is connected in parallel on the PWM rectifier DC side that is used for static reactive, and purpose is to reduce the cost of the device that is used to suppress magnetic bias.

Technical scheme: the present invention implements by the following technical programs:

Have the transformer DC magnetic bias compensation arrangement of no-power compensation function, it is characterized in that: described device comprises the PWM rectifier that is connected by reactor with electrical network, and the PWM rectifier is to be connected to form by the three-phase commutation bridge that IGBT and fly-wheel diode constitute; The PWM rectifier is as the AC side and the DC side parallel of whole device, wherein DC side comprises that electric capacity, resistance, DC-DC converter compose in parallel, insert diverter switch between resistance and DC-DC converter, wherein the DC-DC converter is connected to form by IGBT, fly-wheel diode; A circuit of DC-DC converter connects ground wire, and another link tester is crossed choke and is connected with transformer, and transformer is connected with CPU by neutral line Hall current sensor; Be connected by first PLL phase-locked loop circuit between electrical network and the CPU; Insert second PLL phase-locked loop circuit between reactor and the CPU.

DC side is composed in parallel by electric capacity, resistance, protective circuit, DC-DC converter, inserts diverter switch between protective circuit and resistance; Wherein protective circuit is connected to form by resistance, IGBT, fly-wheel diode.

Advantage and effect: the present invention is by increasing the structure that suppresses D.C. magnetic biasing on the basis of static reactive, to put into big network system to the research that D.C. magnetic biasing suppresses considers, both suppressed D.C. magnetic biasing, do not influence the normal operation of network system again, realized the purpose of two kinds of effects of a device, reduced the cost that suppresses the magnetic bias device, obtained certain economic benefits, whole electric power system has been had great practical significance.

Description of drawings:

Fig. 1 is a structural representation of the present invention;

Description of reference numerals:

1: electrical network, 2: reactor, 3: first PLL phase-locked loop circuit, 4:PWM rectifier, 5:IGBT, 6: DC side, 7: protective circuit, 8: diverter switch, 9: choke, 10:DC-DC converter, 11: transformer, 12: neutral line Hall current sensor, 13:CPU, 14: fly-wheel diode, 15: the second PLL phase-locked loop circuits.

Embodiment:

Below in conjunction with accompanying drawing the present invention is specifically described:

Fig. 1 is a structural representation of the present invention, and as shown in the figure, electrical network 1 is connected with PWM rectifier 4 by reactor 2, and PWM rectifier 4 is to be connected to form by the three-phase commutation bridge that six IGBT5 and fly-wheel diode 14 constitute; PWM rectifier 4 is in parallel with DC side 6, here the AC side of PWM rectifier 4 as whole device; DC side 6 is composed in parallel successively by an electric capacity, resistance, protective circuit 7, a DC-DC converter 10, inserts diverter switch 8 between resistance and protection circuit 7; Wherein protective circuit 7 is connected to form by resistance, IGBT5, fly-wheel diode 14, and DC-DC converter 10 is connected to form by four IGBT5, fly-wheel diode 14; A circuit of DC-DC converter 10 connects ground wire, and another link tester is crossed choke 9 and is connected with transformer 11, and transformer 11 is connected with CPU13 by neutral line Hall current sensor 12; Be connected by first PLL phase-locked loop circuit 3 between electrical network 1 and the CPU13; Insert second PLL phase-locked loop circuit 15 between reactor 2 and the CPU13.

The groundwork of whole device partly is AC side and DC side, AC side can compensate the reactive power of electrical network 1, by DC side transformer 11 is suppressed by the magnetic bias that the neutral point direct current electric current causes, wherein AC side is a voltage type PWM rectifier 4, only allow it operate in rectification state, promptly not only from electrical network 1 absorbing reactive power but also absorb the state of active power, the active power that absorbs is used to reduce line loss and suppresses D.C. magnetic biasing, and the reactive power of absorption is used to improve the power factor (PF) of electrical network 1; The DC side major part is a DC-DC converter 10, can change output voltage along with the bias current size of neutral point, thereby the neutral point direct current magnetic bias of transformer 11 is suppressed.

When the D.C. magnetic biasing phenomenon takes place in transformer 11, by neutral line Hall current sensor 12 detection signal is sent into CPU13, CPU13 control its switch 8 is with protective circuit 7 then, DC-DC converter 10 is linked into DC side 6, begin to produce DC power supply and suppress D.C. magnetic biasing, PWM rectifier 4 is in rectification state under the current state, can only be operated in three, four-quadrant, wherein PWM rectifier 4 is equivalent to inductance when three quadrants, PWM rectifier 4 is equivalent to electric capacity when four-quadrant, not only can absorb active power but also can absorbing reactive power, wherein active power is much larger than reactive power, when the needs potential compensation, the active power energy consumption increases, detection signal feeds back to the control core CPU 13 of reactive power compensation, DC-DC converter 10 just can utilize this active power to suppress D.C. magnetic biasing, this moment, the effect of protective circuit 7 was when the voltage on the dc bus surpasses safety value, IGBT conducting on the excess voltage protection, by this circuit earial drainage, the unnecessary electric energy on the bus distributes with the form of heat; When transformer 11 non DC bias phenomenons produce; by neutral line Hall current sensor 12 detection signal is sent into CPU13; CPU13 control its switch 8 disconnects; protective circuit 7, DC-DC converter 10 are excised from DC side 6; PWM rectifier 4 is operated near under the pure electric capacity state at this moment, i.e. the negative semiaxis of Y-axis.

The three-phase commutation bridge that six IGBT5 are constituted is connected on the electrical network 1 by reactor 2, then by first PLL phase-locked loop circuit 3, according to instantaneous reactive power theory, real component in the detection of grid 1 and idle component draw the reactive current of required generation simultaneously, again by second PLL phase-locked loop circuit 15 sensed current signal, according to instantaneous reactive power theory, resistance value in conjunction with known reactor 2, calculate the active current that potential compensation consumed, with above by first PLL phase-locked loop circuit 3, second two detection signal input CPU13 that PLL phase-locked loop circuit 15 is drawn, produce the relative trigger pulse, reach the double effects of reactive power compensation and potential compensation.

So, when the whole device of control, realize both having guaranteed that PWM rectifier 4 is operated in four-quadrant, regulate DC-DC converter 10 output available powers again.

Claims

1. the transformer DC magnetic bias compensation arrangement that has no-power compensation function, it is characterized in that: described device comprises the PWM rectifier (4) that is connected by reactor (2) with electrical network (1), and PWM rectifier (4) is to be connected to form by the three-phase commutation bridge that IGBT (5) and fly-wheel diode (14) constitute; PWM rectifier (4) is in parallel with DC side (6) as the AC side of whole device, wherein DC side (6) comprises that electric capacity, resistance, DC-DC converter (10) compose in parallel, insert diverter switch (8) between resistance and DC-DC converter (10), wherein DC-DC converter (10) is connected to form by IGBT (5), fly-wheel diode (14); A circuit of DC-DC converter (10) connects ground wire, and another link tester is crossed choke (9) and is connected with transformer (11), and transformer (11) is connected with CPU (13) by neutral line Hall current sensor (12); Be connected by first PLL phase-locked loop circuit (3) between electrical network (1) and the CPU (13); Insert second PLL phase-locked loop circuit (15) between reactor (2) and the CPU (13).

2. according to the described transformer DC magnetic bias compensation arrangement of claim 1 with no-power compensation function, it is characterized in that: DC side (6) is composed in parallel by electric capacity, resistance, protective circuit (7), DC-DC converter (10), inserts diverter switch (8) between protective circuit (7) and resistance; Wherein protective circuit (7) is connected to form by resistance, IGBT (5), fly-wheel diode (14).