CN102801160A - Dynamic trend controller based on voltage magnitude and phase angle control and control method thereof - Google Patents

Abstract

A dynamic power flow controller based on voltage amplitude and phase angle control and its control method, including: a controllable three-phase transformer, a first power unit, a second power unit, a measurement and control module, a series winding unit, and an input voltage mutual inductance Transformer, output voltage transformer and output current transformer: the secondary side of the controllable three-phase transformer includes the main joint, positive tap, negative tap, and each phase outputs two sets of independent windings with a transformation ratio of N, of which 0 <N<0.2; the series winding unit of each phase is formed by series connection of the other two phases of the controllable three-phase transformer and each independent winding with opposite voltage polarity. The invention realizes the decoupling control of active power and reactive power, improves the dynamic adjustment ability and power transmission ability of power system power flow, improves the stability and reliability of the system, etc., and has the advantages of low cost, independent control of active power and reactive power, and reliable high sex characteristics.

Description

Dynamic Power Flow Controller Based on Voltage Amplitude and Phase Angle Control and Its Control Method

technical field

The invention relates to the technical field of flexible power transmission, in particular to a dynamic power flow controller based on voltage amplitude and phase angle control and a control method thereof.

Background technique

With the interconnection of large-scale power systems, the access of intermittent new energy sources such as wind power, and the use of various new equipment, the possibility of grid operation at the edge of the stability limit has greatly increased. Therefore, the flexibility of grid operation, controllability of power flow and grid stability are becoming increasingly important, and they are also the goals pursued by smart grids. In an increasingly complex power grid, being able to simultaneously control the voltage and current of the line will become the key to the problem.

In order to control the voltage and current of the line, the conventional method is to adjust the excitation of the generator, transformer tap and reactive power compensation device through offline optimal power flow calculation and state estimation to meet the dual constraints of voltage and current. But in a complex network, this is such a challenging problem that in practice no controller can control a complex network in real time.

There are some new methods that can simultaneously control the amplitude and phase of the node voltage of the line, and realize the control of active power and reactive power by controlling the phase and amplitude of the node voltage. Devices that can provide such functions include FACTS equipment, such as united power flow control (UPFC) and static synchronous series compensator (static synchronous series compensator, SSSC). Reactive power compensation devices such as SVC and STATCOM can control the node voltage amplitude through reactive power support. Although the FACTS device has entered into the formative stage, the economics of the above-mentioned devices have yet to be tested. Phase shifters can provide real power flow control, but cannot control voltage, and this control is sluggish. Solid-state transformers, also known as power electronic transformers, can control voltage amplitude and phase angle, but require the use of a large number of high-power power electronic switching devices, and research and development are still at the stage of theoretical research. In response to the above problems, a low-cost controllable network transformer (controllable network transformer, CNT) was proposed, and the required power electronic switching capacity is only a small part of the transformer capacity. It can control the amplitude and phase angle of the output voltage, but the control range of the voltage phase angle is relatively small and the control of the voltage amplitude and phase angle cannot achieve decoupling. In addition, in order to eliminate the low-frequency harmonics generated by this method, a larger Big cost.

However, the current FACTS technology also has great limitations: the cost of the FACTS device is high, and it is difficult to popularize and apply; there are adverse effects between the FACTS device and power equipment and other controllers; the loss of the FACTS device itself is large; the complexity of the FACTS device The control structure and the requirements for corresponding auxiliary equipment such as communication facilities put forward stricter requirements for the operation and control of the power grid; additional problems caused by device failures; system stability problems caused by series connection, etc. The application in the power grid is very limited.

Contents of the invention

In view of the above problems, the object of the present invention is to provide a dynamic power flow controller and its control method based on a controllable three-phase transformer independently controlled by voltage amplitude and phase angle. The three-phase transformer realizes the decoupling control of the active power and reactive power of the transmission line through the independent control of the phase angle and amplitude of the output voltage of the controllable three-phase transformer, and has the characteristics of low cost and high reliability.

Technical solution of the present invention is as follows:

A dynamic power flow controller based on voltage amplitude and phase angle control, characterized in that the dynamic power flow controller includes: a controllable three-phase transformer, a first power unit, a second power unit, a measurement and control module, and a series winding unit , input voltage transformer, output voltage transformer and output current transformer:

The secondary side of the controllable three-phase transformer includes a main joint, a positive tap, a negative tap, and each phase outputs two sets of independent windings with a transformation ratio of N, wherein 0<N<0.2;

The series winding unit of each phase is formed by series connection of the other two phases of the controllable three-phase transformer and a set of independent windings with opposite voltage polarities;

The first power unit is composed of a first switching power tube, a second switching power tube, a first filter inductor, a first filter capacitor and a second filter capacitor;

The second power unit is composed of a third switching power tube, a third switching power tube, a second filter inductor, a third filter capacitor and a fourth filter capacitor;

The first switching power tube, the second switching power tube, the third switching power tube and the fourth switching power tube are all composed of two insulated gate bipolar transistors in reverse series;

One end of the first switch power tube is connected to the positive tap of the secondary side of the controllable three-phase transformer, one end of the second switch power tube is connected to the negative tap, and the other end of the first group of switch power tubes One end is connected to the other end of the second group of switching power tubes and the connection point is connected to one end of the first filter inductance, and the other end of the first filter inductance is respectively connected to one end of the series winding unit, the fourth switch One end of the power tube is connected to one end of the second filter capacitor, the other end of the second filter capacitor is connected to the secondary main connector of the controllable three-phase transformer, and the other end of the series winding unit is connected to the third switching power One end of the tube is connected, the other end of the third switching power tube is connected to the other end of the fourth switching power tube and the connection point is connected to one end of the second filter inductor, and the other end of the second filter inductor is connected to the output power supply or load,

The first filter capacitor is connected between the positive tap and the negative tap of the secondary side of the controllable three-phase transformer, and the third filter capacitor is connected between the third switching power tube and the fourth switching power tube. Between the two ends that are not connected, one end of the fourth filter capacitor is connected to the connection point of the two series windings in the series winding unit, and the other end of the fourth filter capacitor is connected to the output power supply or load end,

One side of the input voltage transformer is connected to the primary side input voltage main circuit of the controllable three-phase transformer, and the voltage signal output terminal is connected to the voltage signal input port of the measurement and control module;

One side of the output voltage transformer is connected to the secondary output voltage main circuit of the controllable three-phase transformer, and the voltage signal output terminal is connected to the voltage signal input port of the measurement and control module;

The output current transformer is connected in series in the output main circuit of the controllable three-phase transformer, and its current signal output terminal is connected to the current signal input port of the measurement and control module;

The control signal output terminals of the measurement and control module are respectively connected to the control terminals of the first switching power tube, the second switching power tube, the third switching power tube, and the fourth switching power tube. The upper computer is connected.

The measurement and control module is a digital signal processor, a single-chip microcomputer or a computer.

Using the dynamic power flow controller to control the output voltage amplitude and phase angle is characterized in that the method includes the following specific steps:

1) Assuming that the positive and negative tap ratios of the controllable three-phase transformer are (1+N) and (1-N) respectively, the three-phase input voltages of the controllable three-phase transformer are:

V _ain =sin(ω ₀ t)

V _bim =sin(ω ₀ t+120°) (1)

V _cin =sin(ω ₀ t-120°)

Among them, V _ain is the input voltage of phase A, V _bin is the input voltage of phase B, and V _cin is the input voltage of phase C;

2) Adjust the duty cycle of the first switching power tube, the second switching power tube, the third switching power tube and the fourth switching power tube through pulse width modulation:

Let the duty cycle of the first switching power tube and the second switching power tube be D ₁ , let the duty cycle of the third switching power tube and the fourth switching power tube be D ₂ , where 0≤D ₁ ≤1,0 ≤D ₂ ≤1;

When D ₁ =1, S ₁ is on and S ₂ is off; when D ₁ =0, S ₂ is on and S ₁ is off; when D ₂ =1, S ₃ is on and S ₄ is off , when D ₂ =0, S ₄ is turned on and S ₃ is turned off;

3) Calculate the output voltage of phase A, the formula is as follows:

V _aout =V _ain [(1+N)D ₁ +(1-N)(1-D ₁ )] (2)

+(NV _bin -NV _cin )D ₂

4) Substitute V _ain , V _bin , and V _cin in step 1) into formula (2) to get:

${\mathrm{<span\; class="notranslate">\; V</span>}}_{\mathrm{<span\; class="notranslate">\; aout</span>}}<span\; class="notranslate">\; =</span><span\; class="notranslate">\; [</span><span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; 1</span>}<span\; class="notranslate">\; +</span>\mathrm{<span\; class="notranslate">\; N</span>}<span\; class="notranslate">\; )</span>{\mathrm{<span\; class="notranslate">\; D.</span>}}_{\mathrm{<span\; class="notranslate">\; 1</span>}}<span\; class="notranslate">\; +</span><span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; 1</span>}<span\; class="notranslate">\; -</span>\mathrm{<span\; class="notranslate">\; N</span>}<span\; class="notranslate">\; )</span><span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; 1</span>}<span\; class="notranslate">\; -</span>{\mathrm{<span\; class="notranslate">\; D.</span>}}_{\mathrm{<span\; class="notranslate">\; 1</span>}}<span\; class="notranslate">\; )</span><span\; class="notranslate">\; ]</span>\mathrm{<span\; class="notranslate">\; sin</span>}<span\; class="notranslate">\; (</span>{\mathrm{<span\; class="notranslate">\; \&omega;</span>}}_{\mathrm{<span\; class="notranslate">\; 0</span>}}\mathrm{<span\; class="notranslate">\; t</span>}<span\; class="notranslate">\; )</span>$ $<span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; 3</span>}<span\; class="notranslate">\; )</span>$

$<span\; class="notranslate">\; +</span>\sqrt{\mathrm{<span\; class="notranslate">\; 3</span>}}\mathrm{<span\; class="notranslate">\; N</span>}{\mathrm{<span\; class="notranslate">\; D.</span>}}_{\mathrm{<span\; class="notranslate">\; 2</span>}}\mathrm{<span\; class="notranslate">\; cos</span>}<span\; class="notranslate">\; (</span>{\mathrm{<span\; class="notranslate">\; \&omega;</span>}}_{\mathrm{<span\; class="notranslate">\; 0</span>}}\mathrm{<span\; class="notranslate">\; t</span>}<span\; class="notranslate">\; )</span>$

5) The output voltage amplitude is:

$\mathrm{<span\; class="notranslate">\; A</span>}<span\; class="notranslate">\; =</span>\sqrt{{<span\; class="notranslate">\; [</span><span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; 1</span>}<span\; class="notranslate">\; +</span>\mathrm{<span\; class="notranslate">\; N</span>}<span\; class="notranslate">\; )</span>{\mathrm{<span\; class="notranslate">\; D.</span>}}_{\mathrm{<span\; class="notranslate">\; 1</span>}}<span\; class="notranslate">\; +</span><span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; 1</span>}<span\; class="notranslate">\; -</span>\mathrm{<span\; class="notranslate">\; N</span>}<span\; class="notranslate">\; )</span><span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; 1</span>}<span\; class="notranslate">\; -</span>{\mathrm{<span\; class="notranslate">\; D.</span>}}_{\mathrm{<span\; class="notranslate">\; 1</span>}}<span\; class="notranslate">\; )</span><span\; class="notranslate">\; ]</span>}^{\mathrm{<span\; class="notranslate">\; 2</span>}}<span\; class="notranslate">\; +</span>{<span\; class="notranslate">\; (</span>\sqrt{\mathrm{<span\; class="notranslate">\; 3</span>}}\mathrm{<span\; class="notranslate">\; N</span>}{\mathrm{<span\; class="notranslate">\; D.</span>}}_{\mathrm{<span\; class="notranslate">\; 2</span>}}<span\; class="notranslate">\; )</span>}^{\mathrm{<span\; class="notranslate">\; 2</span>}}}<span\; class="notranslate">\; -</span><span\; class="notranslate">\; -</span><span\; class="notranslate">\; -</span><span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; 4</span>}<span\; class="notranslate">\; )</span>$

6) The output voltage phase shift angle θ is:

$\mathrm{<span\; class="notranslate">\; \&theta;</span>}<span\; class="notranslate">\; =</span>{\mathrm{<span\; class="notranslate">\; the\; tan</span>}}^{<span\; class="notranslate">\; -</span>\mathrm{<span\; class="notranslate">\; 1</span>}}<span\; class="notranslate">\; (</span>\frac{\sqrt{\mathrm{<span\; class="notranslate">\; 3</span>}}\mathrm{<span\; class="notranslate">\; N</span>}{\mathrm{<span\; class="notranslate">\; D.</span>}}_{\mathrm{<span\; class="notranslate">\; 2</span>}}}{<span\; class="notranslate">\; [</span><span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; 1</span>}<span\; class="notranslate">\; +</span>\mathrm{<span\; class="notranslate">\; N</span>}<span\; class="notranslate">\; )</span>{\mathrm{<span\; class="notranslate">\; D.</span>}}_{\mathrm{<span\; class="notranslate">\; 1</span>}}<span\; class="notranslate">\; +</span><span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; 1</span>}<span\; class="notranslate">\; -</span>\mathrm{<span\; class="notranslate">\; N</span>}<span\; class="notranslate">\; )</span><span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; 1</span>}<span\; class="notranslate">\; -</span>{\mathrm{<span\; class="notranslate">\; D.</span>}}_{\mathrm{<span\; class="notranslate">\; 1</span>}}<span\; class="notranslate">\; )</span><span\; class="notranslate">\; ]</span>}<span\; class="notranslate">\; )</span><span\; class="notranslate">\; -</span><span\; class="notranslate">\; -</span><span\; class="notranslate">\; -</span><span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; 5</span>}<span\; class="notranslate">\; )</span>$

The amplitude and phase angle of the output voltage can be changed by changing the duty cycle _D1 and _D2 . Usually N<0.2, therefore, the amplitude adjustment mainly depends on D ₁ , and the phase angle adjustment mainly depends on D ₂ .

When N=0.1, it is approximately available, and the voltage amplitude control range is:

0.9≤A≤1.1 (6)

The voltage phase angle control range is:

7) The dynamic power flow controller is connected in series between two power grids, the input end of the dynamic power flow controller is connected to the first power grid (11), and the output end of the dynamic power flow controller is connected to the second power grid ( 21) connection, and transmit power to the second grid (21) through the dynamic power flow controller and the transmission line;

8) Let the transmission line reactance between the output of the dynamic power flow controller and the grid 2 be JωL;

9) The relationship between the active power P and reactive power Q transmitted by the dynamic power flow controller and the phase shift angle θ of the output voltage of the dynamic power flow controller is as follows:

$\mathrm{<span\; class="notranslate">\; P</span>}<span\; class="notranslate">\; =</span>\frac{{\mathrm{<span\; class="notranslate">\; V</span>}}_{\mathrm{<span\; class="notranslate">\; 2</span>}}\mathrm{<span\; class="notranslate">\; A</span>}{\mathrm{<span\; class="notranslate">\; <figure-callout\; id="1"\; label="V"\; filenames="HDA00002013109700012.png,HDA00002013109700041.png"\; state="\{\{state\}\}">V</figure-callout></span>}}_{\mathrm{<span\; class="notranslate">\; 1</span>}}}{\mathrm{<span\; class="notranslate">\; \&omega;\; L</span>}}\mathrm{<span\; class="notranslate">\; sin</span>}<span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; \&delta;</span>}<span\; class="notranslate">\; +</span>\mathrm{<span\; class="notranslate">\; \&theta;</span>}<span\; class="notranslate">\; )</span><span\; class="notranslate">\; -</span><span\; class="notranslate">\; -</span><span\; class="notranslate">\; -</span><span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; 8</span>}<span\; class="notranslate">\; )</span>$

$\mathrm{<span\; class="notranslate">\; Q</span>}<span\; class="notranslate">\; =</span>\frac{{\mathrm{<span\; class="notranslate">\; <figure-callout\; id="2"\; label="V"\; filenames="HDA00002013109700012.png,HDA00002013109700032.png"\; state="\{\{state\}\}">V</figure-callout></span>}}_{\mathrm{<span\; class="notranslate">\; 2</span>}}^{\mathrm{<span\; class="notranslate">\; 2</span>}}<span\; class="notranslate">\; -</span>{\mathrm{<span\; class="notranslate">\; V</span>}}_{\mathrm{<span\; class="notranslate">\; 2</span>}}\mathrm{<span\; class="notranslate">\; A</span>}{\mathrm{<span\; class="notranslate">\; <figure-callout\; id="1"\; label="V"\; filenames="HDA00002013109700012.png,HDA00002013109700041.png"\; state="\{\{state\}\}">V</figure-callout></span>}}_{\mathrm{<span\; class="notranslate">\; 1</span>}}\mathrm{<span\; class="notranslate">\; cos</span>}<span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; \&delta;</span>}<span\; class="notranslate">\; +</span>\mathrm{<span\; class="notranslate">\; \&theta;</span>}<span\; class="notranslate">\; )</span>}{\mathrm{<span\; class="notranslate">\; \&omega;\; L</span>}}<span\; class="notranslate">\; -</span><span\; class="notranslate">\; -</span><span\; class="notranslate">\; -</span><span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; 9</span>}<span\; class="notranslate">\; )</span>$

Where V ₁ and V ₂ are the voltage amplitudes of the first power grid and the second power grid respectively, and δ is the angle difference between V ₂ and V ₁ .

It can be seen from formulas (8) and (9) that the active power P is mainly related to the output voltage θ of the controllable three-phase transformer, and the reactive power Q is mainly related to the output voltage amplitude A of the controllable three-phase transformer, namely The active power P output by the controllable three-phase transformer is mainly related to the duty cycle _D2 , while the reactive power Q is mainly related to the duty cycle _D1 ;

Therefore, the adjustment of the active power and reactive power output by the dynamic power flow controller is realized by adjusting the duty cycle D ₁ and D ₂ . Due to the control of the conduction of the tap of the controllable three-phase transformer, the capacity of the control switch power tube IGBT is only a part of the capacity of the controllable three-phase transformer, so the cost is low, so as to realize the control of dynamic power flow with low cost and high reliability .

Compared with prior art, characteristics of the present invention are as follows:

1. The switching power tube only needs to control the conduction of the controllable three-phase transformer tap, so the cost is low, and the problem of high cost of the existing FACTS device is overcome;

2. Through the independent control of the phase angle and amplitude of the output voltage of the dynamic power flow controller, the decoupling control of the active power and reactive power of the transmission line is realized;

3. The output voltage does not contain low-order harmonics, and the quality is good.

Description of drawings

Fig. 1 is a connection diagram of a dynamic power flow controller based on voltage amplitude and phase angle control of the present invention connected in series in two power grids.

Fig. 2 is a schematic structural diagram of a dynamic power flow controller based on voltage amplitude and phase angle control according to the present invention.

Fig. 3 is the voltage vector schematic diagram of the principle of changing the voltage phase angle of the present invention, wherein a shows how to obtain the voltage component perpendicular to A from the B and C two-phase voltages; b is the output voltage vector adjustment range as shown in the dotted line box shown.

Fig. 4 is a schematic diagram of output voltage harmonic analysis in the present invention. In the figure, the ordinate Mag is the voltage amplitude, and the abscissa Frequency is the frequency.

Fig. 5 is a simulation diagram of voltage and current waveforms of power electronic switching devices when the present invention works, in which IGBT is an insulated gate transistor, and Diode is an anti-parallel diode of IGBT.

Fig. 6 is a schematic diagram of input and output voltage waveforms of the present invention.

Fig. 7 is a schematic diagram of reactive power control simulation in the present invention, in which Q is reactive power.

Fig. 8 is a schematic diagram of active power control simulation of the present invention, in which P is active power.

Detailed ways

The present invention will be further described below in conjunction with the embodiments and accompanying drawings, but the protection scope of the present invention should not be limited thereby.

Please refer to FIG. 2 first. FIG. 2 is a schematic structural diagram of the dynamic power flow controller of the present invention. As shown in the figure, a controllable three-phase transformer device with independent control of voltage amplitude and phase angle includes: a controllable three-phase transformer 1 , the first power unit 2, the second power unit 8, the measurement and control module 3, the series winding unit 4, the input voltage transformer 5, the output voltage transformer 6 and the output current transformer 7 constitute:

The secondary side of the controllable three-phase transformer 1 includes a main connector 12, a positive tap 13, a negative tap 11, and each phase outputs two sets of independent windings with a transformation ratio of N, wherein 0<N<0.2;

The series winding unit 4 of each phase is formed by serially connecting the other two phases of the controllable three-phase transformer 1 and each group of independent windings with opposite voltage polarities;

The first power unit 2 is composed of a first switching power tube S ₁ , a second switching power tube S ₂ , a first filter inductor L _f1 , a first filter capacitor C _f1 and a second filter capacitor C _f ;

The second power unit 8 is composed of a third switching power tube _S3 , a third switching power tube _S4 , a second filter inductor L _f2 , a third filter capacitor C _f3 and a fourth filter capacitor C _f4 ;

The first switching power transistor S ₁ , the second switching power transistor S ₂ , the third switching power transistor S ₃ and the fourth switching power transistor S ₄ are all composed of two insulated gate bipolar transistors in reverse series (Fig. not shown in);

One end of the first switching power tube _S1 is connected to the positive tap 13 of the secondary side of the controllable three-phase transformer 1, and one end of the second switching power tube _S2 is connected to the negative tap 11. The other end of one group of switching power tubes _S1 is connected to the other end of the second group of switching power tubes _S2 , and the connection point is connected to one end of the first filter inductance L _f1 , and the other end of the first filter inductance L _f2 One end is respectively connected to one end of the series winding unit 4, one end of the fourth switching power transistor _S4 , and one end of the second filter capacitor C _f2 , and the other end of the second filter capacitor C _f2 is connected to the controllable three-phase The secondary main connector 12 of the transformer 1 is connected, the other _end of the series winding unit 4 is connected to one end of the third switching power tube S3, and the other end of the third switching power tube _S3 is connected to the fourth switching power tube The other end of _S4 is connected and the connection point is connected to one end of the second filter inductance L _f2 , and the other end of the second filter inductance L _f2 is connected to the output power supply or load,

The first filter capacitor C _f1 is connected between the positive tap 13 and the negative tap 11 of the secondary side of the controllable three-phase transformer 1, and the third filter capacitor C _f3 is connected across the third switch Between the disconnected ends of the power tube _S3 and the fourth switching power tube _S4 , one end of the fourth filter capacitor C _f4 is connected to the connection point of the two series windings in the series winding unit 4, and the fourth filter The other end of the capacitor C _f4 is connected to the output power supply or load end,

One side of the input voltage transformer 5 is connected to the primary input voltage main circuit of the controllable three-phase transformer, and the voltage signal output terminal is connected to the voltage signal input port of the measurement and control module 3;

One side of the output voltage transformer 6 is connected to the secondary output voltage main circuit of the controllable three-phase transformer, and the voltage signal output terminal is connected to the voltage signal input port of the measurement and control module 3;

The output current transformer 7 is connected in series in the output main circuit of the controllable three-phase transformer, and its current signal output terminal is connected with the current signal input port of the measurement and control module 3;

The control signal output terminals of the measurement and control module 3 are respectively connected with the control of the first switching power transistor S _{1 ,} the second switching power transistor S ₂ , the third switching power transistor S ₃ and the fourth switching power transistor S ₄ The measurement and control module 3 is connected to the host computer.

The measurement and control module 3 is a digital signal processor, a single-chip microcomputer or a computer.

The method for controlling output voltage amplitude and phase angle by using a dynamic power flow controller is characterized in that the method includes the following specific steps:

1) Suppose the positive and negative tap ratios of the controllable three-phase transformer are (1+N) and (1-N) respectively, and the three-phase input voltages of the controllable three-phase transformer are respectively:

V _ain =sin(ω ₀ t)

V _bin =sin(ω ₀ t+120°) (1)

V _cin =sin(ω ₀ t-120°)

2) Adjust the duty cycle of switches S ₁ , S ₂ and S ₃ , S ₄ through PWM technology. Let the duty cycle of S ₁ and S ₂ be D ₁ , let the duty cycle of S ₃ and S ₄ be D ₂ , 0≤D ₁ ≤1, 0≤D ₂ ≤1. When D ₁ =1, S ₁ is on and S ₂ is off; when D ₁ =0, S ₂ is on and S ₁ is off; when D ₂ =1, S ₃ is on and S ₄ is off , when D ₂ =0, S ₄ is turned on and S ₃ is turned off.

3) The output voltage of phase A can be obtained as:

V _aout =V _ain [(1+N)D ₁ +(1-N)(1-D ₁ )] (2)

+(NV _bin -NV _cin )D ₂

4) Substitute V _ain , V _bin , and V _cin into:

${\mathrm{<span\; class="notranslate">\; V</span>}}_{\mathrm{<span\; class="notranslate">\; aout</span>}}<span\; class="notranslate">\; =</span><span\; class="notranslate">\; [</span><span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; 1</span>}<span\; class="notranslate">\; +</span>\mathrm{<span\; class="notranslate">\; N</span>}<span\; class="notranslate">\; )</span>{\mathrm{<span\; class="notranslate">\; D.</span>}}_{\mathrm{<span\; class="notranslate">\; 1</span>}}<span\; class="notranslate">\; +</span><span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; 1</span>}<span\; class="notranslate">\; -</span>\mathrm{<span\; class="notranslate">\; N</span>}<span\; class="notranslate">\; )</span><span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; 1</span>}<span\; class="notranslate">\; -</span>{\mathrm{<span\; class="notranslate">\; D.</span>}}_{\mathrm{<span\; class="notranslate">\; 1</span>}}<span\; class="notranslate">\; )</span><span\; class="notranslate">\; ]</span>\mathrm{<span\; class="notranslate">\; sin</span>}<span\; class="notranslate">\; (</span>{\mathrm{<span\; class="notranslate">\; \&omega;</span>}}_{\mathrm{<span\; class="notranslate">\; 0</span>}}\mathrm{<span\; class="notranslate">\; t</span>}<span\; class="notranslate">\; )</span>$ $<span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; 3</span>}<span\; class="notranslate">\; )</span>$

$<span\; class="notranslate">\; +</span>\sqrt{\mathrm{<span\; class="notranslate">\; 3</span>}}\mathrm{<span\; class="notranslate">\; N</span>}{\mathrm{<span\; class="notranslate">\; D.</span>}}_{\mathrm{<span\; class="notranslate">\; 2</span>}}\mathrm{<span\; class="notranslate">\; cos</span>}<span\; class="notranslate">\; (</span>{\mathrm{<span\; class="notranslate">\; \&omega;</span>}}_{\mathrm{<span\; class="notranslate">\; 0</span>}}\mathrm{<span\; class="notranslate">\; t</span>}<span\; class="notranslate">\; )</span>$

It can be seen from the above formula that, in addition to the sine component that is consistent with the input phase, the output voltage also contains a cosine component that is 90 degrees out of phase with it.

5) The output voltage amplitude is:

$\mathrm{<span\; class="notranslate">\; A</span>}<span\; class="notranslate">\; =</span>\sqrt{{<span\; class="notranslate">\; [</span><span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; 1</span>}<span\; class="notranslate">\; +</span>\mathrm{<span\; class="notranslate">\; N</span>}<span\; class="notranslate">\; )</span>{\mathrm{<span\; class="notranslate">\; D.</span>}}_{\mathrm{<span\; class="notranslate">\; 1</span>}}<span\; class="notranslate">\; +</span><span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; 1</span>}<span\; class="notranslate">\; -</span>\mathrm{<span\; class="notranslate">\; N</span>}<span\; class="notranslate">\; )</span><span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; 1</span>}<span\; class="notranslate">\; -</span>{\mathrm{<span\; class="notranslate">\; D.</span>}}_{\mathrm{<span\; class="notranslate">\; 1</span>}}<span\; class="notranslate">\; )</span><span\; class="notranslate">\; ]</span>}^{\mathrm{<span\; class="notranslate">\; 2</span>}}<span\; class="notranslate">\; +</span>{<span\; class="notranslate">\; (</span>\sqrt{\mathrm{<span\; class="notranslate">\; 3</span>}}\mathrm{<span\; class="notranslate">\; N</span>}{\mathrm{<span\; class="notranslate">\; D.</span>}}_{\mathrm{<span\; class="notranslate">\; 2</span>}}<span\; class="notranslate">\; )</span>}^{\mathrm{<span\; class="notranslate">\; 2</span>}}}<span\; class="notranslate">\; -</span><span\; class="notranslate">\; -</span><span\; class="notranslate">\; -</span><span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; 4</span>}<span\; class="notranslate">\; )</span>$

6) The output voltage phase shift angle θ is:

$\mathrm{<span\; class="notranslate">\; \&theta;</span>}<span\; class="notranslate">\; =</span>{\mathrm{<span\; class="notranslate">\; the\; tan</span>}}^{<span\; class="notranslate">\; -</span>\mathrm{<span\; class="notranslate">\; 1</span>}}<span\; class="notranslate">\; (</span>\frac{\sqrt{\mathrm{<span\; class="notranslate">\; 3</span>}}\mathrm{<span\; class="notranslate">\; N</span>}{\mathrm{<span\; class="notranslate">\; D.</span>}}_{\mathrm{<span\; class="notranslate">\; 2</span>}}}{<span\; class="notranslate">\; [</span><span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; 1</span>}<span\; class="notranslate">\; +</span>\mathrm{<span\; class="notranslate">\; N</span>}<span\; class="notranslate">\; )</span>{\mathrm{<span\; class="notranslate">\; D.</span>}}_{\mathrm{<span\; class="notranslate">\; 1</span>}}<span\; class="notranslate">\; +</span><span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; 1</span>}<span\; class="notranslate">\; -</span>\mathrm{<span\; class="notranslate">\; N</span>}<span\; class="notranslate">\; )</span><span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; 1</span>}<span\; class="notranslate">\; -</span>{\mathrm{<span\; class="notranslate">\; D.</span>}}_{\mathrm{<span\; class="notranslate">\; 1</span>}}<span\; class="notranslate">\; )</span><span\; class="notranslate">\; ]</span>}<span\; class="notranslate">\; )</span><span\; class="notranslate">\; -</span><span\; class="notranslate">\; -</span><span\; class="notranslate">\; -</span><span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; 5</span>}<span\; class="notranslate">\; )</span>$

When N=0.1, it is approximately available, and the voltage amplitude control range is:

0.9≤A≤1.1 (6)

The voltage phase angle control range is:

The amplitude and phase angle of the output voltage can be changed by changing the duty cycle _D1 and _D2 . Usually N<0.2, therefore, the amplitude adjustment mainly depends on D ₁ , and the phase angle adjustment mainly depends on D ₂ .

7) The dynamic power flow controller is connected in series between the two power grids, the input end of the dynamic power flow controller is connected to the first power grid (11), and the output end of the dynamic power flow controller is connected to the second power grid 21 via the output line connected to transmit electricity to the second grid 22 through the dynamic power flow controller and the transmission line;

8) Let the transmission line reactance between the output of the dynamic power flow controller and the second grid 22 be jωL;

9) The relationship between the active power P and reactive power Q transmitted by the dynamic power flow controller and the phase shift angle θ of the output voltage of the dynamic power flow controller is as follows:

$\mathrm{<span\; class="notranslate">\; P</span>}<span\; class="notranslate">\; =</span>\frac{{\mathrm{<span\; class="notranslate">\; V</span>}}_{\mathrm{<span\; class="notranslate">\; 2</span>}}\mathrm{<span\; class="notranslate">\; A</span>}{\mathrm{<span\; class="notranslate">\; <figure-callout\; id="1"\; label="V"\; filenames="HDA00002013109700012.png,HDA00002013109700041.png"\; state="\{\{state\}\}">V</figure-callout></span>}}_{\mathrm{<span\; class="notranslate">\; 1</span>}}}{\mathrm{<span\; class="notranslate">\; \&omega;\; L</span>}}\mathrm{<span\; class="notranslate">\; sin</span>}<span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; \&delta;</span>}<span\; class="notranslate">\; +</span>\mathrm{<span\; class="notranslate">\; \&theta;</span>}<span\; class="notranslate">\; )</span><span\; class="notranslate">\; -</span><span\; class="notranslate">\; -</span><span\; class="notranslate">\; -</span><span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; 8</span>}<span\; class="notranslate">\; )</span>$

$\mathrm{<span\; class="notranslate">\; Q</span>}<span\; class="notranslate">\; =</span>\frac{{\mathrm{<span\; class="notranslate">\; <figure-callout\; id="2"\; label="V"\; filenames="HDA00002013109700012.png,HDA00002013109700032.png"\; state="\{\{state\}\}">V</figure-callout></span>}}_{\mathrm{<span\; class="notranslate">\; 2</span>}}^{\mathrm{<span\; class="notranslate">\; 2</span>}}<span\; class="notranslate">\; -</span>{\mathrm{<span\; class="notranslate">\; V</span>}}_{\mathrm{<span\; class="notranslate">\; 2</span>}}\mathrm{<span\; class="notranslate">\; A</span>}{\mathrm{<span\; class="notranslate">\; <figure-callout\; id="1"\; label="V"\; filenames="HDA00002013109700012.png,HDA00002013109700041.png"\; state="\{\{state\}\}">V</figure-callout></span>}}_{\mathrm{<span\; class="notranslate">\; 1</span>}}\mathrm{<span\; class="notranslate">\; cos</span>}<span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; \&delta;</span>}<span\; class="notranslate">\; +</span>\mathrm{<span\; class="notranslate">\; \&theta;</span>}<span\; class="notranslate">\; )</span>}{\mathrm{<span\; class="notranslate">\; \&omega;\; L</span>}}<span\; class="notranslate">\; -</span><span\; class="notranslate">\; -</span><span\; class="notranslate">\; -</span><span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; 9</span>}<span\; class="notranslate">\; )</span>$

Where V ₁ and V ₂ are the voltage amplitudes of the first power grid and the second power grid respectively, and δ is the angle difference between V ₂ and V ₁ .

It can be seen from formulas (8) and (9) that the active power P is mainly related to the output voltage θ of the controllable three-phase transformer, and the reactive power Q is mainly related to the output voltage amplitude A of the controllable three-phase transformer, namely The active power P output by the controllable three-phase transformer is mainly related to the duty cycle _D2 , while the reactive power Q is mainly related to the duty cycle _D1 ;

Therefore, the adjustment of the active power and reactive power output by the dynamic power flow controller is realized by adjusting the duty cycle D ₁ and D ₂ . Due to the control of the conduction of the tap of the controllable three-phase transformer, the capacity of the control switch power tube IGBT is only a part of the capacity of the controllable three-phase transformer, so the cost is low, so as to realize the control of dynamic power flow with low cost and high reliability .

Figure 3 is a voltage vector diagram of the principle of phase shifting and amplitude changing of the output voltage of the dynamic power flow controller. Fig. 4 is a schematic diagram of the harmonic analysis of the output voltage of the present invention. It can be seen that the output voltage does not contain low-order harmonics, but only switching frequency harmonics. Therefore, it is easy to filter out, because the first and second groups of power units contain high-frequency The filter circuit filters out high-frequency harmonics, so that the controllable three-phase transformer outputs high-quality voltage waveforms.

Figure 5 is a simulation diagram of the voltage of the controllable three-phase transformer power electronic switching device when N=0.1, D ₁ =0.5, D ₂ =0. The figure shows that the operating voltage of the power electronic switching device is a small part of the controllable three-phase transformer , which is 20% (2N times). It can be seen from the simulation figure 6 that the phase shift is about 11 degrees, and the output amplitude increases by 10%, which is consistent with the above analysis results.

The dynamic power flow control simulation is as follows:

The model used in the simulation is shown in Figure 3, the amplitudes of V1 and V2 are both 35kV, and V ₁ is 20° ahead of V ₂ .

Keeping D ₂ =0, D ₁ changes from 0 to 1 with a step increase of 0.25, the change of reactive power transmitted by the line is shown in Figure 7.

Keeping D ₁ =0.5, D ₂ changes from 0 to 1 by increasing 0.25 per step, and the change of active power transmitted by the line is shown in Figure 8.

It can be known from the above simulation results that changing the modulation parameters D ₁ and D ₂ can dynamically control the active power and reactive power output by the dynamic power flow controller.

Claims (3)

1. dynamic power flow controller and control method thereof based on the control of voltage magnitude and phase angle; It is characterized in that this dynamic power flow controller comprises: controlled three-phase transformer (1), first power cell (2), second power cell (8), measurement constitute with control module (3), the winding element of connecting (4), input voltage instrument transformer (5), output voltage instrument transformer (6) and output current transformer (7):

The secondary of described controlled three-phase transformer (1) comprises major joint (12), plus tapping head (13), minus tapping head (11), and every phase independent winding that to export 2 groups of no-load voltage ratios separately be N, and wherein 0 < N < 0.2;

The series connection winding element (4) of every phase is formed by other two phases and each opposite 1 group of independent winding serial connection of polarity of voltage of controlled three-phase transformer (1);

Described first power cell (2) is by the first switching power tube (S ₁), second switch power tube (S ₂), the first filter inductance (L _F1) the first filter capacitor (C _F1) and the second filter capacitor (C _F2) form;

Described second power cell (8) is by the 3rd switching power tube (S ₃), the 3rd switching power tube (S ₄), the second filter inductance (L _F2) the 3rd filter capacitor (C _F3) and the 4th filter capacitor (C _F4) form;

The described first switching power tube (S ₁), second switch power tube (S ₂), the 3rd switching power tube (S ₃) and the 4th switching power tube (S ₄) constitute by 2 insulated gate bipolar transistor differential concatenations;

The described first switching power tube (S ₁) the plus tapping head (13) of the described controlled three-phase transformer of a termination (1) secondary, described second switch power tube (S ₂) a termination minus tapping head (11), this first group of switching power tube (S ₁) the other end and second group of switching power tube (S ₂) the other end link to each other and this tie point and the described first filter inductance (L _F1) an end link to each other this first filter inductance (L _F1) the other end respectively with an end, the 4th switching power tube (S of the described winding element of connecting (4) ₄) an end, the second filter capacitor (C _F2) an end link to each other the second filter capacitor (C _F2) the other end link to each other the other end of described series connection winding element (4) and the 3rd switching power tube (S with the secondary major joint (12) of described controlled three-phase transformer (1) ₃) an end link to each other described the 3rd switching power tube (S ₃) other end and the 4th switching power tube (S ₄) other end continuous and this tie point and the described second filter inductance (L _F2) an end link to each other this second filter inductance (L _F2) the other end connect out-put supply or load,

The described first filter capacitor (C _F1) be connected between the plus tapping head (13) and minus tapping head (11) of described controlled three-phase transformer (1) secondary described the 3rd filter capacitor (C _F3) be connected across the 3rd switching power tube (S ₃) and the 4th switching power tube (S ₄) between the disjunct two ends, described the 4th filter capacitor (C _F4) an end and series connection winding element (4) in the tie points of 2 serial connection windings link to each other the 4th filter capacitor (C _F4) the other end connect out-put supply or load end,

One side of described input voltage instrument transformer (5) links to each other with the former limit of controlled three-phase 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 controlled three-phase 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 controlled three-phase 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 ends of described measurement and control module (3) respectively with the described first switching power tube (S ₁) second switch power tube (S ₂), the 3rd switching power tube (S ₃) and the 4th switching power tube (S ₄) control end link to each other, this measurement links to each other with host computer with control module (3).

2. dynamic power flow controller according to claim 1 is characterized in that described measurement and control module (3) are digital signal processor, single-chip microcomputer or computer.

3. utilize the described dynamic power flow controller of claim 1 to carry out the control method of output voltage amplitude and phase angle, it is characterized in that this method comprises following concrete steps:

1) establish the positive and negative tap no-load voltage ratio of controlled three-phase transformer and be respectively (1+N) and (1-N), controlled three-phase transformer three-phase input voltage is respectively:

V _ain=sin(ω ₀t)

V _bin=sin(ω ₀t+120°) (1)

V _cin=sin(ω ₀t-120°)

Wherein, V _AinBe A phase input voltage, V _BinBe B phase input voltage, V _CinBe C phase input voltage;

2) through pulse-width modulation the duty ratio of first switching power tube, second switch power tube, the 3rd switching power tube and the 4th switching power tube is regulated:

If the duty ratio of first switching power tube and second switch power tube is D ₁, the duty ratio of establishing the 3rd switching power tube and the 4th switching power tube is D ₂, wherein, 0≤D ₁≤1,0≤D ₂≤1;

3) calculate A phase output voltage, formula is following:

V _aout=V _ain[(1+N)D ₁+(1-N)(1-D ₁)] (2)

+(NV _bin-NV _cin)D ₂

4) with V in the step 1) _Ain, V _Bin, V _CinSubstitution formula (2) obtains:

$V_{\mathrm{aout}}=[(1+N)D_1+(1-N)(1-D_1)]\sin \left({\mathrm{\&omega;}}_{0}t\right)$ $\left(3\right)$

$+\sqrt{3}N{D}_2\cos \left({\mathrm{\&omega;}}_{0}t\right)$

5) output voltage amplitude is:

$A=\sqrt{{[(1+N)D_1+(1-N)(1-D_1)]}^2+{\left(\sqrt{3}N{D}_2\right)}^2}---\left(4\right)$

6) output voltage phase shift angle θ is:

$\mathrm{\&theta;}={\tan }^{-1}\left(\frac{\sqrt{3}N{D}_2}{[(1+N)D_1+(1-N)(1-D_1)]}\right)---\left(5\right)$

7) described dynamic power flow controller is serially connected between two electrical networks; Input termination first electrical network (11) of dynamic power flow controller; The output of this dynamic power flow controller is connected with second electrical network (21) through outlet line, transmits electricity to second electrical network (22) through this dynamic power flow controller and transmission line;

The output and the transmission line reactance between second electrical network of 8) establishing the dynamic power flow controller are j ω L;

9) then the relation of the active power P of dynamic power flow controller transmission and reactive power Q and dynamic power flow controller output voltage phase shift angle θ is following:

$P=\frac{V_{2}A{V}_1}{\mathrm{\&omega;L}}\sin (\mathrm{\&delta;}+\mathrm{\&theta;})---\left(8\right)$

$Q=\frac{V_2^2-V_{2}A{V}_1\cos (\mathrm{\&delta;}+\mathrm{\&theta;})}{\mathrm{\&omega;L}}---\left(9\right)$

V wherein ₁And V ₂Be respectively the voltage magnitude of first electrical network and second electrical network, δ is V ₂With V ₁Differential seat angle.

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