CN102354972B - Output-side-switching-based dynamic power flow control device and control method for controllable transformer - Google Patents

Abstract

The invention discloses an output-side-switching-based dynamic power flow control device for a controllable transformer. The device consists of the controllable transformer, a power unit, a measurement and control module, a bypass switch, an input voltage transformer, an output voltage transformer and an output current transformer. In a dynamic power flow control method, the switching-on and switching-off of an output side/secondary tapping point of the controllable transformer are controlled by utilizing a fast switching-on/off power electronic switch, a frequency doubling signal is injected into a pulse width modulation signal of the power electronic switch of the controllable transformer by adopting a direct current signal, and the amplitude of the direct current signal and the amplitude and initial phase of the frequency doubling signal in the pulse width modulation signal are changed, thereby changing the phase and amplitude of output voltage of the controllable transformer and realize active power adjustment and passive power adjustment. The switching-on of the tapping point of the controllable transformer is controlled, thereby realizing adjustment control over the dynamic power flow of a power grid. The device and the method have the characteristics of low cost and high dynamic power flow control reliability.

Description

Dynamic power flow control device and the control method thereof of outlet side switch controllable transformer

Technical field

The present invention relates to the flexible transmission technical field, particularly a kind of dynamic power flow control device and control method thereof of the controllable transformer based on the outlet side switch.

Background technology

Along with the use of the interconnected and various new equipments of large-scale power system, make generating, transmission of electricity more economical, also increased scale and the complexity of electric power system simultaneously efficiently, operation of power networks also greatly increases in the possibility at stability limit edge.Therefore, the flexibility of operation of power networks, trend controllability and grid stability become the problem that more and more presses for solution.

Therefore, the demand that produces of the transmission system operating pressure of 21 century may be summarized to be following 3 aspects:

(1) increase ability to transmit electricity: thus because the increase of electricity consumption increases the transmission of electric energy demand, the situation of line construction reduction makes the requirement that improves ability to transmit electricity more outstanding on the other hand.

(2) keep system stability: serious power system accident causes severe impairment can for the social life in the vast service area, as interruption of communication, cut off the water and electricity supply, communication paralysis, financial circulation are damaged, the precise machining process process is impaired, computerized information is lost etc., directly influences user's normal electricity consumption.Therefore, still can keep the stability of a system when how in electric power system, to make longer distance carry more electric power, become another vital task of management and running personnel.

(3) optimize the system operation: because service conditions changes and the change frequency of the power delivery that electricity market determines increases fast, system controls and becomes more complicated, need the trend of total system be optimized.This optimization need be taken all factors into consideration the situation of overall situation operation in increasing area.In addition, electricity market requirement system by one specific " contract path " go to control flow of power to, control has the higher ability of controlling to trend to require electrical network, and this is difficult to accomplish in AC transmission system, because wherein the electric power in each " path " all is to be determined by the electrical characteristic of other all power transmission lines.

Flexible AC transmitting system (the Flexible Alternate Current Transmission System that arises at the historic moment at the demand, be designated hereinafter simply as FACTS) technology, fundamentally changed ac grid system substantially only rely in the past mechanical type, at a slow speed, the situation of interruption and coarse control and optimisation technique measure.The FACTS device simultaneously or control voltage, impedance and phase angle on the transmission line is selectively realized meritorious and reactive power flow control, for ac grid system provides rapidly, continuously and accurate control and the ability of optimizing trend.Under the prerequisite that does not change system's power generation mode and network topology structure, can utilize the FACTS device to improve the stability of system, improve the ability to transmit electricity of system, and alleviate the clogged conditions of system to a certain extent.

But also there is significant limitation in present FACTS technology: FACTS unit engineering cost height, apply difficulty; There is ill-effect between FACTS device and power equipment and other controllers; The loss of FACTS device self is big; The complicated control structure of FACTS device and to the requirement of corresponding auxiliary devices such as communications facility has proposed more strict requirement to operation and the control of electrical network; The additional problem that plant failure is brought; Stability of a system problem that the series connection access causes etc. is very restricted its application in electrical network.

Summary of the invention

At the problems referred to above, the purpose of this invention is to provide a kind of dynamic power flow control device and control method thereof of the controllable transformer based on the outlet side switch, low cost, high reliability characteristics that this device has based on the controllable transformer of outlet side switch.It will improve trend adjusting, ability to transmit electricity, the stability of a system, reliability of electric power system etc., make China's electrical network really become strong intelligent grid.

Technical solution of the present invention is as follows:

A kind of dynamic power flow control device of the controllable transformer based on the outlet side switch, its characteristics are that the formation of this dynamic power flow control device comprises controllable transformer, power cell, measurement and control module, by-pass switch, input voltage instrument transformer, output voltage instrument transformer and output current transformer:

The secondary of described controllable transformer comprises major joint and plus tapping head minus tapping head;

Described power cell is connected on the plus tapping head of controllable transformer secondary, between minus tapping head and out-put supply or the load, this power cell is by first group power, second group power, filter inductance and filter capacitor are formed, described first group power and second group power constitute by 2 insulated gate bipolar transistors (abbreviating IGBT as) differential concatenation, one end of described first group power and second group power connects plus tapping head and the minus tapping head of described controllable transformer secondary respectively, one end of the described filter inductance of another termination of described first group power and second group power, the described out-put supply of another termination or the load of this filter inductance, described filter capacitor is connected between the plus tapping head and minus tapping head of described controllable transformer secondary, and the control end of described first group power and second group power links to each other with the corresponding controling end of control module with described measurement;

Described by-pass switch is connected between the major joint and out-put supply or load of described controllable transformer secondary:

One side of described input voltage instrument transformer links to each other with the former limit of controllable transformer input voltage main circuit, and voltage signal output end links to each other with the voltage signal input port of control module with described measurement;

One side of described output voltage instrument transformer links to each other with controllable transformer secondary output voltage main circuit, and output links to each other with the voltage signal input port of control module with described measurement;

Described output current transformer is serially connected in the output main circuit of controllable transformer, and its current signal output end links to each other with the current signal input port of control module with described measurement;

Described measurement links to each other with described first group power and the control end of second group power and the control end of described by-pass switch of described power cell respectively with the control signal output of control module, and this measurement links to each other with host computer with control module.

Described measurement and control module are digital signal processor, single-chip microcomputer or computer.

A kind of dynamic power flow control device that utilizes described controllable transformer based on the outlet side switch carries out the control method of dynamic power flow, and it is following concrete rapid that its characteristics are that this method comprises:

1) described measurement and control module are carried out initialization to measuring with control, send signal to by-pass switch and turn-off by-pass switch, receive the set-point Q of the given reactive power of host computer ₀Set-point P with active power ₀

2) described measurement and control module receive the input voltage V that described input voltage instrument transformer 5, described output voltage instrument transformer and described output current transformer are imported respectively _In, output voltage V _Out, output current I, output voltage and output current angle β, receive distant place line voltage V _{Electrical network 2}Information and transmission line reactance value L:

V _{Electrical network 2}=V ₂Sin (ω ₀T+ α), V wherein ₂Be its amplitude, α is its phase angle;

Calculate active power P, the reactive power Q of actual measurement by following formula:

$P=\frac{1}{\sqrt{2}}{V}_{\mathrm{out}}I\cos \mathrm{\β}$

$Q=\frac{1}{\sqrt{2}}{V}_{\mathrm{out}}I\sin \mathrm{\β};$

3) according to active power P ₀And reactive power Q ₀, according to following formula, calculate output voltage phase angle theta and the output voltage amplitude V of controllable transformer _Out:

$P_0=\frac{V_2{V}_{\mathrm{out}}}{{\mathrm{\ω}}_{0}L}\sin (\mathrm{\α}-\mathrm{\θ})$

$Q_0=\frac{V_2^2-V_2{V}_{\mathrm{out}}\cos (\mathrm{\α}-\mathrm{\θ})}{{\mathrm{\ω}}_{0}L},$

Wherein: L is the reactance value of transmission line;

ω ₀Be 50 or the corresponding angular frequency of 60Hz;

V ₂Be distant place line voltage V _{Electrical network 2}Amplitude;

4) calculate pulse width modulation duty D:

1., according to controllable transformer input voltage V _In, output voltage phase angle theta and amplitude V _Out, by the direct current signal COEFFICIENT K in the pulse-width signal of following formula calculating insulated gate bipolar transistor ₀, two frequency-doubled signal COEFFICIENT K ₂And initial phase

Wherein: V ₁Be controllable transformer input voltage V _InAmplitude, N is controllable transformer tap no-load voltage ratio;

2., according to the direct current signal COEFFICIENT K ₀, two frequency-doubled signal COEFFICIENT K ₂And initial phase

According to following formula, calculate pulse width modulation duty D:

5) according to pulse width modulation duty D, to the conducting of insulated gate bipolar transistor pulse-width signal control insulated gate bipolar transistor;

6) repeating step 2) to 5), according to the pulse width modulation duty D that obtains, by the conducting realization of control insulated gate bipolar transistor the adjusting of the dynamic power flow of electrical network is controlled.

When above-mentioned power cell was worked, by-pass switch turn-offed, when above-mentioned power tube is deactivated, and the by-pass switch conducting.

The control principle of its power and the index of modulation is derived as follows:

IGBT pulse-width signal D is:

In the following formula, 0≤D≤1, K ₀Be direct current signal amplitude, K ₂Be two frequency-doubled signal amplitudes, ω ₀Be electrical network input voltage fundamental frequency, Be two frequency-doubled signal initial phase angles;

If the input voltage V of controllable transformer _InFor:

V _in＝V ₁sin(ω ₀t) (2)

In the following formula, V ₁Peak value for the controllable transformer input voltage;

If the positive and negative tap no-load voltage ratio of controllable transformer outlet side (secondary) is respectively (1+N) and (1-N), the then output voltage V of controllable transformer _OutFor:

V _out＝V _in ^*(1+N)(1-D)+(1-N)D (3)

So,

Filter 3 subharmonic, namely get the output voltage that only contains the first-harmonic amount

Wherein,

A＝1+N-2NK ₀，B＝NK ₂ (6)

Therefore, controllable transformer output voltage amplitude, initial phase angle theta are relevant with amplitude and the initial phase angle thereof of IGBT pulse-width modulation direct current signal amplitude, two frequency-doubled signals;

The initial phase angle of output voltage is:

(5) formula shows, the controllable transformer output voltage amplitude depends primarily on direct current signal amplitude K in the IGBT pulse-width signal ₀

Suppose that electrical network 1 links to each other with transmission line to electrical network 2 transmissions of electricity by controllable transformer, the induction reactance of transmission line is j ω L, and the voltage of electrical network 2 bus ends is:

V _{Electrical network 2}=V ₂Sin (ω ₀T+ α) (8)

Then the relation of the active power P of controllable transformer place transmission line and reactive power Q and controllable transformer output voltage is as follows:

$P=\frac{V_2{V}_{\mathrm{out}}}{\mathrm{\ω}L}\sin (\mathrm{\α}-\mathrm{\θ})---\left(9\right)$

$Q=\frac{V_2^2-V_2{V}_{\mathrm{out}}\cos (\mathrm{\α}-\mathrm{\θ})}{\mathrm{\ω}L}---\left(10\right)$

In the above-mentioned formula, active power, reactive power, voltage equivalent all adopt per unit value to calculate, and voltage magnitude is near 1.0.Can find out that from (9), (10) two formulas active power P is main relevant with the initial phase angle theta of controllable transformer output voltage fundamental component, reactive power Q is then main relevant with the controllable transformer output voltage amplitude; That is the amplitude K of main and IGBT pulse-width modulation two frequency-doubled signals of transmission line active power P, ₂And initial phase angle

Relevant, reactive power Q is direct current signal amplitude K in the main and IGBT pulse-width signal then ₀Relevant;

Therefore, by to two frequency-doubled signal amplitude K in the IGBT pulse-width signal ₂With the initial phase angle

With direct current signal amplitude K ₀Adjusting can realize adjusting to active power and reactive power; Because the tap conducting of controllable transformer is controlled, the power tube IGBT capacity of control controllable transformer tap only is the part of controllable transformer capacity, thereby cost is low, thus the low cost of realization, the active power of high reliability and the control of reactive power.

The dynamic power flow control method that the present invention is based on the controllable transformer of outlet side switch is a kind ofly according to the electrical network demand active power and the reactive power of controllable transformer place transmission line to be controlled; Conducting and shutoff by IGBT control controllable transformer secondary tap, in the pulse-width signal direct current signal of IGBT, inject two frequency-doubled signals, by changing direct current signal amplitude in the pulse-width signal and amplitude and the initial phase of two frequency-doubled signals, thereby phase place, the amplitude of controllable transformer output voltage have been changed.

Characteristics of the present invention are as follows:

1. power tube only needs the conducting of controllable transformer tap is controlled, thereby cost is low, has overcome the expensive problem of existing FACTS device;

2. usual controllable transformer can only be by regulating the control that its tap carries out voltage magnitude, and the present invention is by injecting two frequency-doubled signals to power tube IGBT pulse-width signal, thereby realized the skew of input voltage angle, realized the control of active power;

3. of the present invention to have a cost low, the control high reliability features of dynamic power flow.

Description of drawings

Fig. 1 is the structural representation of dynamic power flow control device that the present invention is based on the controllable transformer of outlet side switch.

Fig. 2 is the dynamic power flow control schematic diagram that the present invention is based on the controllable transformer of outlet side switch.

Fig. 3 is the algorithm flow chart of dynamic power flow control of the present invention.

Fig. 4 is the dynamic power flow phase control analogous diagram that the present invention is based on the controllable transformer of outlet side switch.

Embodiment

The invention will be further described below in conjunction with embodiment and accompanying drawing, but should not limit protection scope of the present invention with this.

See also Fig. 1 earlier, Fig. 1 is the structural representation of dynamic power flow control device that the present invention is based on the controllable transformer of outlet side switch.As seen from the figure, a kind of dynamic power flow control device of the controllable transformer based on the outlet side switch comprises: controllable transformer 1, power cell 2, measurement and control module 3, by-pass switch 4, input voltage instrument transformer 5, output voltage instrument transformer 6 and output current transformer 7 constitute:

The secondary of described controllable transformer 1 comprises major joint 12 and plus tapping head 13 minus tapping heads 11;

Described power cell 2 is by the first group power S ₁, the second group power S ₂, filter inductance L _fWith filter capacitor C _fForm this power cell 2 described first group power S ₁With the second group power S ₂Constitute the described first group power S by 2 insulated gate bipolar transistor differential concatenations ₁With the second group power S ₂An end connect plus tapping head 13 and the minus tapping head 11 of described controllable transformer 1 secondary, the described first group power S respectively ₁With the second group power S ₂The described filter inductance L of another termination _fAn end, this filter inductance L _fThe described out-put supply of another termination or load, described filter capacitor C _fBe connected between the plus tapping head 13 and minus tapping head 11 of described controllable transformer 1 secondary the described first group power S ₁With the second group power S ₂Control end link to each other with the corresponding controling end of described measurement with control module 3;

Described by-pass switch 4 is connected between the major joint 12 and out-put supply or load of described controllable transformer 1 secondary;

One side of described input voltage instrument transformer 5 links to each other with the former limit of controllable transformer input voltage main circuit, and voltage signal output end links to each other with the voltage signal input port of control module 3 with described measurement;

Described output voltage instrument transformer 6, one sides link to each other with controllable transformer secondary output voltage main circuit, and output links to each other with the voltage signal input port of control module 3 with described measurement;

Described output current transformer 7 is serially connected in the output main circuit of controllable transformer, and its current signal output end links to each other with the current signal input port of control module 3 with described measurement;

The control signal output of described measurement and control module 3 respectively with the described first group power S of described power cell ₁With the second group power S ₂Control end and the control end of described by-pass switch 4 link to each other, this measurement links to each other with host computer with control module 3.

Described measurement and control module 3 are digital signal processor, single-chip microcomputer or computer.

To system shown in Figure 2, based on the dynamic power flow control workflow of the controllable transformer of outlet side switch as shown in Figure 3, utilize the dynamic power flow control device of above-mentioned controllable transformer based on the outlet side switch to carry out electrical network dynamic power flow control method, this method comprises following concrete rapid:

1) initialization is carried out in 3 pairs of measurements of described measurement and control module and control, sends signal to by-pass switch 4 and turn-offs by-pass switch, receives the set-point Q of the given reactive power of host computer ₀Set-point P with active power ₀

2) described measurement and control module 3 receive the input voltage V that described input voltage instrument transformer 5, described output voltage instrument transformer 6 and described output current transformer 7 are imported respectively _In, output voltage V _Out, output current I, output voltage and output current angle β, receive distant place line voltage V _{Electrical network 2}Information and transmission line reactance value L:

V _{Electrical network 2}=V ₂Sin (ω ₀T+ α), V wherein ₂Be its amplitude, α is its phase angle; Calculate active power P, the reactive power Q of actual measurement by following formula:

$P=\frac{1}{\sqrt{2}}{V}_{\mathrm{out}}I\cos \mathrm{\β}$

$Q=\frac{1}{\sqrt{2}}{V}_{\mathrm{out}}I\sin \mathrm{\β};$

3) according to active power P ₀And reactive power Q ₀, according to following formula, calculate output voltage phase angle theta and the output voltage amplitude V of controllable transformer _Out:

$P_0=\frac{V_2{V}_{\mathrm{out}}}{{\mathrm{\ω}}_{0}L}\sin (\mathrm{\α}-\mathrm{\θ})$

$Q_0=\frac{V_2^2-V_2{V}_{\mathrm{out}}\cos (\mathrm{\α}-\mathrm{\θ})}{{\mathrm{\ω}}_{0}L},$

Wherein: L is the reactance value of transmission line;

ω ₀Be 50 or the corresponding angular frequency of 60Hz;

V ₂Be distant place line voltage V _{Electrical network 2}Amplitude;

4) calculate pulse width modulation duty D:

1., according to controllable transformer input voltage V _In, output voltage phase angle theta and amplitude V _Out, by the direct current signal COEFFICIENT K in the pulse-width signal of following formula calculating insulated gate bipolar transistor ₀, two frequency-doubled signal COEFFICIENT K ₂And initial phase

Wherein: V ₁Be controllable transformer input voltage V _InAmplitude, N is controllable transformer tap no-load voltage ratio;

2., according to the direct current signal COEFFICIENT K ₀, two frequency-doubled signal COEFFICIENT K ₂And initial phase

According to following formula, calculate pulse width modulation duty D:

5) according to pulse width modulation duty D, to the conducting of insulated gate bipolar transistor pulse-width signal control insulated gate bipolar transistor;

6) repeating step 2) to 5), according to the pulse width modulation duty D that obtains, by the conducting realization of control insulated gate bipolar transistor the adjusting of the dynamic power flow of electrical network is controlled.

By dsp controller voltage, electric current are sampled, calculate active power and the reactive power of transmission line, according to host computer given active power and reactive power value, according to initial phase angle and the amplitude of formula (9) and (10) calculating controllable transformer output voltage, according to the DC component K in formula (5) and the corresponding IGBT pulse-width signal of (6) calculating ₀, two frequency-doubled signal amplitude K ₂With the initial phase angle Thereby derive IGBT pulse-width signal D.Turn-off by-pass switch, carry out conducting control by the IGBT power tube of IGBT pulse-width signal D, make the voltage of the corresponding band of controllable transformer output phase deviation, the high-frequency switching signal that produces during power tube IGBT work is by the filter circuit filtering.Difference by actual measurement active power and reactive power and set-point, active power and reactive power are carried out closed-loop control, regulate IGBT pulse-width signal D, make actual measurement active power consistent with set-point with reactive power, thereby the trend of transmission line is controlled.

IGBT when work be owing to comprise two frequency-doubled signals in its pulse-width signal, then in transmission line, can produce triple-frequency harmonics, though harmonic content is little, also can be as required, in addition filtering, thus make that the quality of controllable transformer output voltage is higher.

Fig. 4 is N=0.15, K ₀=K ₂=0.5,

The time controllable transformer output voltage analogous diagram, V among the figure _Out1Be fundamental voltage output of voltage, V _InBe input supply voltage, V _Out3Be the contained triple-frequency harmonics of output voltage.From analogous diagram 4, found out the output voltage phase shift 4.25 the degree, output amplitude is constant, and is consistent with above-mentioned analysis result.

When out of service, described measurement and control module 3 are sent instruction, switch-off power pipe IGBT, and conducting by-pass switch 4 is so dynamic power flow control is out of service.

Claims (2)

1. dynamic power flow control device based on the controllable transformer of outlet side switch is characterized in that this device comprises: controllable transformer (1), power cell (2), measurement and control module (3), by-pass switch (4), input voltage instrument transformer (5), output voltage instrument transformer (6) and output current transformer (7) constitute:

The secondary of described controllable transformer (1) comprises major joint (12) and plus tapping head (13) minus tapping head (11);

Described power cell (2) is by the first group power (S ₁), the second group power (S ₂), filter inductance (L _f) and filter capacitor (C _f) form the described first group power (S of this power cell (2) ₁) and the second group power (S ₂) constitute the described first group power (S by 2 insulated gate bipolar transistor differential concatenations ₁) the plus tapping head (13) of the described controllable transformer of a termination (1) secondary, the second group power (S ₂) the minus tapping head (11) of the described controllable transformer of a termination (1) secondary, the described first group power (S ₁) and the second group power (S ₂) the described filter inductance (L of another termination _f) an end, this filter inductance (L _f) another termination out-put supply or load, described filter capacitor (C _f) be connected between the plus tapping head (13) and minus tapping head (11) of described controllable transformer (1) secondary the described first group power (S ₁) and the second group power (S ₂) control end link to each other with the corresponding controling end of described measurement with control module (3);

Described by-pass switch (4) is connected between the major joint (12) and out-put supply or load of described controllable transformer (1) secondary;

One side of described input voltage instrument transformer (5) links to each other with the former limit of controllable transformer input voltage main circuit, and voltage signal output end links to each other with the voltage signal input port of described measurement with control module (3);

Described output voltage instrument transformer (6), a side links to each other with controllable transformer secondary output voltage main circuit, and voltage signal output end links to each other with the voltage signal input port of described measurement with control module (3);

Described output current transformer (7) is serially connected in the output main circuit of controllable transformer, and its current signal output end links to each other with the current signal input port of described measurement with control module (3);

The control signal output of described measurement and control module (3) respectively with the described first group power (S of described power cell ₁) link to each other with the control end of second group power (S2) and the control end of described by-pass switch (4), this measurement links to each other with host computer with control module (3).

2. the dynamic power flow control device of the controllable transformer based on the outlet side switch according to claim 1 is characterized in that described measurement and control module (3) are digital signal processor, single-chip microcomputer or computer.

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