CN104767215A - Multifunctional DVR and dynamic regulation control method thereof - Google Patents

Multifunctional DVR and dynamic regulation control method thereof Download PDF

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Publication number
CN104767215A
CN104767215A CN201510144226.3A CN201510144226A CN104767215A CN 104767215 A CN104767215 A CN 104767215A CN 201510144226 A CN201510144226 A CN 201510144226A CN 104767215 A CN104767215 A CN 104767215A
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voltage
dvr
preset
power grid
threshold
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CN104767215B (en
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胡子珩
姚森敬
曹军威
张华赢
孙杰
王淼
乐健
杨金涛
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Shenzhen Power Supply Co ltd
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Shenzhen Power Supply Co ltd
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    • H—ELECTRICITY
    • H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
    • H02J—CIRCUIT ARRANGEMENTS OR SYSTEMS FOR SUPPLYING OR DISTRIBUTING ELECTRIC POWER; SYSTEMS FOR STORING ELECTRIC ENERGY
    • H02J3/00—Circuit arrangements for ac mains or ac distribution networks
    • H02J3/12—Circuit arrangements for ac mains or ac distribution networks for adjusting voltage in ac networks by changing a characteristic of the network load
    • H—ELECTRICITY
    • H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
    • H02H—EMERGENCY PROTECTIVE CIRCUIT ARRANGEMENTS
    • H02H9/00—Emergency protective circuit arrangements for limiting excess current or voltage without disconnection
    • H02H9/02—Emergency protective circuit arrangements for limiting excess current or voltage without disconnection responsive to excess current

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  • Engineering & Computer Science (AREA)
  • Power Engineering (AREA)
  • Inverter Devices (AREA)

Abstract

The invention provides a multifunctional DVR which is arranged between a power grid system side and a load side and comprises a bypass system, a filter capacitor, a filter inductor, an inverter and a control unit, wherein the bypass system is connected with the filter capacitor; the positive electrode of the filter capacitor is connected with the power grid system side, and the negative electrode of the filter capacitor is connected with the power grid load side; the bypass system is bridged on two ends of the filter capacitor and is also connected with one end of the control unit; the positive pole of the inverter is connected with the filter inductor in series and then is connected with the positive pole of the filter capacitor, the negative pole of the inverter is connected with the negative pole of the filter capacitor, and the control end of the inverter is connected with the other end of the control unit. The embodiment of the invention not only has the voltage drop compensation function, but also can automatically realize the fault current limiting or low voltage compensation function according to the actual requirement, thereby improving the cost performance of the DVR and promoting the industrial application and popularization degree of the DVR.

Description

Multifunctional DVR and dynamic regulation control method thereof
Technical Field
The invention relates to the technical field of dynamic voltage regulators, in particular to a multifunctional DVR and a dynamic regulation control method thereof.
Background
A Dynamic Voltage Regulator (DVR) is a device connected in series in a power grid, and the device can be used as a Voltage source connected in series in the power grid when the Voltage of the power grid drops, and the Voltage of a load terminal is regulated by controlling the output Voltage of the device, so as to achieve the purpose of protecting a sensitive load from the influence of Voltage disturbance.
In the prior art, because the actual voltage drop is mostly caused by the fault in the medium-voltage distribution network, a scheme that the DVR governs the voltage drop on one feeder line or a plurality of feeder lines at the same time is often adopted, the scheme is more economical compared with the distributed low-voltage compensation, and is more feasible compared with the high-voltage compensation technology, and the defect is that: the voltage drop compensation function can be realized, the problem of low use efficiency exists, the voltage drop caused by the downstream fault can not be compensated, and the large-scale industrial application and market popularization are not facilitated.
Therefore, there is a need for a multifunctional and multi-purpose DVR, which not only has the voltage drop compensation function, but also has other functions, so as to further improve the cost performance of the DVR and promote the industrial application and popularization degree of the DVR.
Disclosure of Invention
The technical problem to be solved by the embodiments of the present invention is to provide a multi-functional DVR and a dynamic adjustment control method thereof, which not only have a voltage drop compensation function, but also can automatically implement a fault current limiting or low voltage compensation function according to actual requirements, thereby improving the cost performance of the DVR, and promoting the industrial application and popularization degree of the DVR.
In order to solve the technical problem, an embodiment of the present invention provides a multi-functional DVR, where the DVR is arranged between a power grid system side and a load side, and includes a bypass system, a filter capacitor, a filter inductor, an inverter, and a control unit; wherein,
the positive electrode of the filter capacitor is connected with the power grid system side, and the negative electrode of the filter capacitor is connected with the power grid load side;
the bypass system is bridged on two ends of the filter capacitor and is also connected with one end of the control unit;
and the positive electrode of the inverter is connected with the filtering inductor in series and then is connected with the positive electrode of the filtering capacitor, the negative electrode of the inverter is connected with the negative electrode of the filtering capacitor, and the control end of the inverter is connected with the other end of the control unit.
The DVR also comprises an energy storage unit, and the energy storage unit is connected with the energy storage end of the inverter.
The embodiment of the invention also provides a method for dynamically regulating and controlling the multi-function DVR, which is realized on a power grid comprising the DVR and comprises the following steps:
acquiring system voltage and system current of the DVR connected with the side of the power grid system;
detecting the amplitude of the system voltage and the amplitude of the system current, adjusting a control mode of the DVR according to the detection result, and further outputting a control strategy corresponding to the adjusted control mode to the load side of the power grid; the control modes comprise a common voltage compensation mode, a fault current limiting mode, a low voltage compensation mode and a bypass uncompensated mode.
The specific steps of detecting the amplitude of the system voltage and the amplitude of the system current, adjusting the control mode of the DVR according to the detection result, and further outputting a control strategy corresponding to the adjusted control mode to the load side of the power grid include:
acquiring a preset first voltage threshold, a preset second voltage threshold and a preset current threshold; wherein the preset first voltage threshold is greater than the preset second voltage threshold;
when the amplitude of the detected system voltage is larger than the preset first voltage threshold value, determining that the voltage of the power grid load side is normal, adjusting the control mode of the DVR to be a bypass uncompensated mode, controlling the bypass system of the DVR to be conducted, controlling the inverter of the DVR to be pulse-locked, and enabling the DVR not to compensate the voltage of the power grid load side.
The specific steps of detecting the amplitude of the system voltage and the amplitude of the system current, adjusting the control mode of the DVR according to the detection result, and further outputting a control strategy corresponding to the adjusted control mode to the load side of the power grid further include:
acquiring a preset first voltage threshold, a preset second voltage threshold and a preset current threshold; wherein the preset first voltage threshold is greater than the preset second voltage threshold;
when the detected amplitude of the system voltage is between the preset first voltage threshold and the preset second voltage threshold, determining that the voltage of the load side of the power grid is low, adjusting the control mode of the DVR to be a low voltage compensation mode, controlling a bypass system of the DVR to be disconnected, controlling an inverter of the DVR to be pulsed on, and simulating the DVR to be a series compensation capacitor;
and calculating the reference voltage when the DVR is used as a series compensation capacitor, obtaining the output voltage of the DVR according to the calculated reference voltage, and outputting the obtained output voltage to the load side of the power grid for voltage compensation.
The specific steps of detecting the amplitude of the system voltage and the amplitude of the system current, adjusting the control mode of the DVR according to the detection result, and further outputting a control strategy corresponding to the adjusted control mode to the load side of the power grid further include:
acquiring a preset first voltage threshold, a preset second voltage threshold and a preset current threshold; wherein the preset first voltage threshold is greater than the preset second voltage threshold;
when the amplitude of the detected system voltage is smaller than the preset second voltage threshold value, determining that the voltage of the load side of the power grid falls, and further judging that the amplitude of the detected system current is larger than the preset current threshold value, adjusting the control mode of the DVR to be a fault current limiting mode, controlling a bypass system of the DVR to be disconnected, controlling an inverter of the DVR to be pulsed on, and simulating the DVR to be a fault current limiter;
and calculating the reference voltage when the DVR is used as a fault current limiter, obtaining the output voltage of the DVR according to the calculated reference voltage, and outputting the obtained output voltage to the load side of the power grid for current limiting.
The specific steps of detecting the amplitude of the system voltage and the amplitude of the system current, adjusting the control mode of the DVR according to the detection result, and further outputting a control strategy corresponding to the adjusted control mode to the load side of the power grid further include:
acquiring a preset first voltage threshold, a preset second voltage threshold and a preset current threshold; wherein the preset first voltage threshold is greater than the preset second voltage threshold;
when the amplitude of the detected system voltage is smaller than the preset second voltage threshold value, determining that the voltage of the load side of the power grid drops, and further judging that the amplitude of the detected system current is smaller than the preset current threshold value, adjusting the control mode of the DVR to be a common voltage compensation mode, controlling a bypass system of the DVR to be disconnected, controlling an inverter of the DVR to be pulse-locked, and simulating the DVR to be a voltage source;
and calculating the difference value between the system voltage and the load voltage according to the system voltage of the power grid system side and the load voltage of the power grid load side, and compensating the calculated difference value to the power grid load side as the compensation voltage of the DVR.
The preset first threshold is 93% of the nominal voltage of the power grid, and the preset second threshold is 90% of the nominal voltage of the power grid.
And the preset current threshold is 5 times of the normal current value of the power grid.
The embodiment of the invention has the following beneficial effects:
in the embodiment of the invention, the DVR automatically adjusts the current working control mode according to the system voltage and the system current at the system side, and calculates the output voltage of the DVR and outputs the output voltage to the load side of the power grid for voltage compensation or current limitation by combining the externally presented impedance characteristics (such as a series compensation capacitor, a fault current limiter and a voltage source), so that the DVR not only has the voltage drop compensation function, but also can automatically realize the fault current limiting or low voltage compensation function according to the actual requirement, the cost performance of the DVR is improved, and the industrial application and popularization degree of the DVR are promoted.
Drawings
In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below, and it is obvious that the drawings in the following description are only some embodiments of the present invention, and it is within the scope of the present invention for those skilled in the art to obtain other drawings based on the drawings without inventive exercise.
Fig. 1 is a circuit diagram of a multi-function DVR according to an embodiment of the present invention;
FIG. 2 is a flowchart of a method for multi-function DVR dynamic adjustment control according to a second embodiment of the invention;
fig. 3 is a logic block diagram of a multi-function DVR control strategy according to a second embodiment of the present invention;
fig. 4 is a voltage waveform diagram of the multi-function DVR as a virtual capacitor for low voltage compensation according to the second embodiment of the present invention;
fig. 5 is a three-phase voltage waveform diagram of the system in the event of a downstream fault in the installation line of the multi-function DVR according to the second embodiment of the invention;
fig. 6 is a waveform diagram of a three-phase short-circuit current of the system when a downstream fault occurs in a multi-function DVR mounting line according to the second embodiment of the present invention;
fig. 7 is a three-phase voltage waveform diagram of a system when the multifunctional DVR is used as a virtual inductor for limiting a fault current according to the second embodiment of the present invention;
fig. 8 is a waveform diagram of three-phase currents of a system when the multifunctional DVR is used as a virtual inductor for limiting a fault current according to the second embodiment of the present invention.
Detailed Description
In order to make the objects, technical solutions and advantages of the present invention more apparent, the present invention will be described in further detail with reference to the accompanying drawings.
As shown in fig. 1, a multi-functional DVR according to a first embodiment of the present invention is disposed between a grid system side and a load side, and includes a bypass system M and a filter capacitor CfFilter inductor LfAn inverter N and a control unit P; wherein,
filter capacitor CfThe positive pole (+) of the positive pole is connected with the power grid system side, and the negative pole (-) is connected with the power grid load side;
the bypass system M is bridged with the filter capacitor CfAnd also connected to one end of the control unit P;
the positive pole (+) of the inverter N is connected with the filter inductor L in seriesfRear and filter capacitor CfIs connected with the positive pole (+) and the negative pole (-) is connected with the filter capacitor CfIs connected to the other end of the control unit P, and the control terminal a1 is connected to the other end of the control unit P.
In order to ensure the voltage stability of the inverter N, the DVR further includes an energy storage unit E, and the energy storage unit E is connected to the energy storage terminal a2 of the inverter N.
It should be noted that, in FIG. 1, isFor the system current flowing through DVR, CfAnd LfFilter capacitor and filter inductor, i, of the DVR device, respectivelycAnd iLAre respectively a capacitor CfCurrent in and inductance LfOf the inverter N output is uinvThe voltage output from DVR is udvrThe grid system side voltage is upccThe voltage at the load side of the power grid is uload。
The working principle of the multifunctional DVR in the first embodiment of the invention is as follows: according to the system voltage u of the DVR connecting power grid system sidepccAnd system current isAnd controlling the working states of the bypass system M and the inverter N by combining the externally presented impedance characteristics (such as series compensation capacitor, fault current limiter and voltage source) so as to change the u of the output voltagedvrThe voltage compensation or current limitation is carried out on the load side of the power grid, so that the DVR not only has the voltage drop compensation function, but also can automatically realize the fault current limiting or low voltage compensation function according to the actual requirement.
As shown in fig. 2, a method for dynamically adjusting and controlling a multi-function DVR, provided by the second embodiment of the present invention, is implemented on a power grid including a DVR according to the first embodiment of the present invention, and includes:
step S101, obtaining system voltage and system current of a power grid system side connected to the DVR;
the specific process is that the system voltage u of the DVR connecting power grid system side in figure 1 is detectedpccAnd system current is；
Step S102, detecting the amplitude of the system voltage and the amplitude of the system current, adjusting the control mode of the DVR according to the detection result, and further outputting a control strategy corresponding to the adjusted control mode to the load side of the power grid; the control modes comprise a common voltage compensation mode, a fault current limiting mode, a low voltage compensation mode and a bypass uncompensated mode.
The specific process is that the system voltage u is detectedpccTo determine the system voltage upccWhether a voltage sag occurs and the system voltage upccWhether there is a low voltage, and further, at the system voltage upccWhen voltage drop occurs, the system current i is detectedsTo determine whether a DVR downstream malfunction has occurred.
Correspondingly, when the power grid is judged to have the problems, the DVR carries out voltage compensation or downstream line current limiting by setting a corresponding control mode to realize the purpose of automatic regulation controlAnd when the grid voltage is determined to be stable, the DVR automatically restores to a normal working state. Thus, the DVR will be correspondingly set with four modes, including: a normal voltage compensation mode, a fault current limiting mode, a low voltage compensation mode and a bypass uncompensated mode; wherein, the common voltage compensation mode and the fault current limiting mode are used for the voltage u of the power grid systempccWhen voltage drop occurs, the low-voltage compensation mode is used for the voltage u of the power grid systempccWhen the voltage is low, the bypass uncompensated mode is used for the voltage u of the power grid systempccWhen stable.
It should be noted that the system voltage u is determinedpccThe conditions of voltage drop, low voltage and normal recovery are that the system voltage u passespccIs respectively compared with a preset first voltage threshold value and a preset second voltage threshold value to determine the amplitude value of the DVR, and the condition for judging that the downstream fault occurs in the DVR is that the system voltage u is determined firstlypccVoltage sag occurs and further system current isIs compared with a preset current threshold value.
In some embodiments, the preset first voltage threshold is set to be greater than the preset second voltage threshold, the preset first threshold is 93% of the nominal voltage of the power grid, the preset second threshold is 90% of the nominal voltage of the power grid, and the preset current threshold is 5 times of the normal current value of the power grid. According to the system voltage upccAmplitude of>The grid system voltage u is determined by a preset first threshold value (93% of the nominal grid voltage)pccThe stability is realized, and the compensation on the load side of the power grid is not needed; according to a preset second threshold (i.e. 90% of the nominal voltage of the network)<System voltage upccAmplitude of<A preset first threshold value is used for judging the voltage u of the power grid systempccThe low voltage phenomenon exists, and low voltage compensation is needed to be carried out on the load side of the power grid; according to the system voltage upccAmplitude of<A preset second threshold value is used for judging the voltage u of the power grid systempccA drop occurs, at which time it is dependent on the system current isAmplitude of>And (4) judging that the DVR has downstream fault and needs to be judged according to a preset current threshold (namely 5 times of the normal current value of the power grid)Limiting the current of the load side of the power grid; likewise, at the grid system voltage upccWhen falling, according to the system current isAmplitude of<And (4) judging that the DVR does not have downstream faults by a preset current threshold value, and only carrying out ordinary compensation on the load side of the power grid.
In summary, the specific implementation manners of the four modes of the DVR and the compensation manner on the load side of the power grid are as follows:
(a) bypass uncompensated mode
Acquiring a preset first voltage threshold, a preset second voltage threshold and a preset current threshold; the preset first voltage threshold is greater than the preset second voltage threshold;
when the detected system voltage upccWhen the amplitude of the voltage is larger than a preset first voltage threshold value, it is determined that the voltage of the load side of the power grid is normal, the control mode of the DVR is adjusted to be a bypass uncompensated mode, a bypass system M (shown in figure 1) of the DVR is controlled to be conducted, an inverter N (shown in figure 1) of the DVR is controlled to be pulse-locked, and the DVR does not compensate the voltage of the load side of the power grid.
The specific process is that the DVR is controlled to be kept in a bypass state, so that the DVR is equivalent to a conductor in a power grid line and the system voltage u at the side of a power grid system is keptpccTo the load voltage u of the load side of the networkloadAre equal.
(b) Low voltage compensation mode
Acquiring a preset first voltage threshold, a preset second voltage threshold and a preset current threshold; the preset first voltage threshold is greater than the preset second voltage threshold;
when the detected system voltage upccWhen the amplitude value of the voltage is between a preset first voltage threshold value and a preset second voltage threshold value, determining that the voltage of the load side of the power grid is low, adjusting the control mode of the DVR to be a low voltage compensation mode, controlling a bypass system M (shown in figure 1) of the DVR to be disconnected, controlling an inverter N (shown in figure 1) of the DVR to be pulsed on, and simulating the DVR to be a low voltage compensation modeA series compensation capacitor;
calculating a reference voltage u when DVR is used as a series compensation capacitorrefAnd based on the calculated reference voltage urefTo obtain the output voltage u of DVRdvrAnd the obtained output voltage u is compared withdvrAnd outputting the voltage compensation to the load side of the power grid.
The specific process is that when the DVR is used as a series compensation capacitor, the virtual capacitor size C0At this time, the current flowing through the DVR and the DVR output voltage need to satisfy the volt-ampere characteristic of the capacitance, and the reference voltage u is calculated according to the volt-ampere characteristicrefControlling the output voltage u of the DVR by a composite control strategydvrAnd (6) outputting. Therefore, as shown in fig. 3, fig. 1 needs to be transformed into a corresponding logic block diagram for calculation.
In the complex frequency domain, the current-voltage characteristics of capacitance and resistance can be expressed as: u ═ i/C0s；u＝R0i; wherein s represents a differential operator, C0Is a virtual capacitance value, R0Is a virtual resistance value;
according to the detected system current isSetting the virtual impedance as Z(s), calculating the reference voltage u of DVR according to the formula (1)ref：
uref＝Z(s)is (1)；
In fig. 3, the transfer function of the DVR composite control is derived, as shown in equation (2):
<math> <mrow> <msub> <mi>u</mi> <mi>dvr</mi> </msub> <mo>=</mo> <mfrac> <mrow> <mrow> <mrow> <mo>(</mo> <msub> <mi>K</mi> <mi>PWM</mi> </msub> <mrow> <mo>(</mo> <msub> <mi>K</mi> <mi>P</mi> </msub> <mo>+</mo> <mn>1</mn> <mo>)</mo> </mrow> <mo>)</mo> </mrow> <mi>s</mi> <mo>+</mo> <msub> <mi>K</mi> <mi>PWM</mi> </msub> <msub> <mi>K</mi> <mi>i</mi> </msub> <mo>)</mo> </mrow> <msub> <mi>u</mi> <mi>ref</mi> </msub> <mo>-</mo> <msub> <mi>L</mi> <mi>f</mi> </msub> <msup> <mi>s</mi> <mn>2</mn> </msup> <msub> <mi>i</mi> <mi>s</mi> </msub> </mrow> <mrow> <msub> <mi>L</mi> <mi>f</mi> </msub> <msub> <mi>C</mi> <mi>f</mi> </msub> <msup> <mi>s</mi> <mn>3</mn> </msup> <mo>+</mo> <mi>k</mi> <mo>&CenterDot;</mo> <msub> <mi>K</mi> <mi>PWM</mi> </msub> <msub> <mi>C</mi> <mi>f</mi> </msub> <msup> <mi>s</mi> <mn>2</mn> </msup> <mo>+</mo> <mrow> <mo>(</mo> <msub> <mi>K</mi> <mi>PWM</mi> </msub> <msub> <mi>K</mi> <mi>P</mi> </msub> <mo>+</mo> <mn>1</mn> <mo>)</mo> </mrow> <mi>s</mi> <mo>+</mo> <msub> <mi>K</mi> <mi>PWM</mi> </msub> <msub> <mi>K</mi> <mi>i</mi> </msub> </mrow> </mfrac> <mo>-</mo> <mo>-</mo> <mo>-</mo> <mrow> <mo>(</mo> <mn>2</mn> <mo>)</mo> </mrow> <mo>;</mo> </mrow> </math>
in the formula (2), KPWMIs the loss factor of the inverter, KP，KiFor adjusting the parameters for PI, the transfer function isk is the current feedback coefficient.
At this time, when the external output characteristic of the DVR is controlled to be a resistance-capacitance series circuit, the system current i flowssWhile, the reference voltage urefCan be transformed from formula (1) to formula (3):
u ref = R 0 i s + i s C 0 s - - - ( 3 ) ;
substituting formula (3) into formula (2) to obtain formula (4):
<math> <mrow> <msub> <mi>u</mi> <mi>dvr</mi> </msub> <mo>=</mo> <mfrac> <mrow> <mrow> <mo>(</mo> <msub> <mi>b</mi> <mn>3</mn> </msub> <msup> <mi>s</mi> <mn>3</mn> </msup> <mo>+</mo> <msub> <mi>b</mi> <mn>2</mn> </msub> <msup> <mi>s</mi> <mn>2</mn> </msup> <mo>+</mo> <msub> <mi>b</mi> <mn>1</mn> </msub> <mi>s</mi> <mo>+</mo> <msub> <mi>b</mi> <mn>0</mn> </msub> <mo>)</mo> </mrow> <msub> <mi>i</mi> <mi>s</mi> </msub> </mrow> <mrow> <msub> <mi>L</mi> <mi>f</mi> </msub> <msub> <mi>C</mi> <mi>f</mi> </msub> <msup> <mi>s</mi> <mn>4</mn> </msup> <mo>+</mo> <mi>k</mi> <mo>&CenterDot;</mo> <msub> <mi>K</mi> <mi>PWM</mi> </msub> <msub> <mi>C</mi> <mi>f</mi> </msub> <msup> <mi>s</mi> <mn>3</mn> </msup> <mo>+</mo> <mrow> <mo>(</mo> <msub> <mi>K</mi> <mi>PWM</mi> </msub> <msub> <mi>K</mi> <mi>P</mi> </msub> <mo>+</mo> <mn>1</mn> <mo>)</mo> </mrow> <msup> <mi>s</mi> <mn>2</mn> </msup> <mo>+</mo> <msub> <mi>K</mi> <mi>PWM</mi> </msub> <msub> <mi>K</mi> <mi>i</mi> </msub> <mi>s</mi> </mrow> </mfrac> <mo>-</mo> <mo>-</mo> <mo>-</mo> <mrow> <mo>(</mo> <mn>4</mn> <mo>)</mo> </mrow> <mo>;</mo> </mrow> </math>
in the formula (4), b3＝-Lf，b2＝R0KPWM(KP+1)， b 0 = K PWM K i C 0 ;
Obtaining the output voltage u of DVR according to the formula (4)dvrAnd the obtained output voltage u is compared withdvrAnd outputting the voltage compensation to the load side of the power grid.
As an example, as shown in fig. 4, the DVR is controlled as a virtual capacitor for the simulation effect of low voltage compensation, and as seen from fig. 4, the DVR outputs a voltage as a virtual capacitor from 0.5s, and the voltage amplitude is increased from 7.5kV to 8.0kV, so that the problem of low voltage can be effectively solved, and the voltage loss of the inductive power transmission and distribution line can be reduced.
(c) Fault current limiting mode
Acquiring a preset first voltage threshold, a preset second voltage threshold and a preset current threshold; the preset first voltage threshold is greater than the preset second voltage threshold;
when the detected system voltage upccWhen the amplitude is smaller than the preset second voltage threshold value, determining the voltage drop of the load side of the power grid, and further judging the detected system current isWhen the amplitude value of the current limiting circuit is larger than a preset current threshold value, the control mode of the DVR is adjusted to be a fault current limiting mode, a bypass system M of the DVR is controlled to be disconnected, an inverter N of the DVR is controlled to be opened in a pulse mode, and the DVR is simulated to be a fault current limiter;
calculating reference voltage u when DVR is used as fault current limiterrefAnd based on the calculated reference voltage urefTo obtain the output voltage u of DVRdvrAnd applying said obtained output voltage udvrAnd outputting the current to the load side of the power grid for current limiting.
The specific process is that when the DVR is used as a fault current limiter, the size L of the virtual inductor is0At this time, the current flowing through the DVR and the DVR output voltage need to satisfy the current-voltage characteristic of the inductance, and the reference voltage u is calculated according to the current-voltage characteristicrefControlling the output voltage u of the DVR by a composite control strategydvrThe output, and therefore, correspondingly, is also calculated using the logic block diagram of fig. 3.
In the complex frequency domainIn (1), the current-voltage characteristics of the inductor and the resistor can be expressed as: u ═ sL0i；u＝R0i; wherein s represents a differential operator, L0Is a virtual inductance value, R0Is a virtual resistance value;
at this time, when the external output characteristic of the DVR is controlled to be a resistance-inductance series circuit, the system current i flowssWhile, the reference voltage urefCan be transformed from formula (1) to formula (5):
uref＝(R0+L0)sis (5)；
substituting formula (5) into formula (2) to obtain formula (6):
<math> <mrow> <msub> <mi>u</mi> <mi>dvr</mi> </msub> <mo>=</mo> <mfrac> <mrow> <mrow> <mo>(</mo> <msub> <mi>a</mi> <mn>2</mn> </msub> <msup> <mi>s</mi> <mn>2</mn> </msup> <mo>+</mo> <msub> <mi>a</mi> <mn>1</mn> </msub> <mi>s</mi> <mo>+</mo> <msub> <mi>a</mi> <mn>0</mn> </msub> <mo>)</mo> </mrow> <msub> <mi>i</mi> <mi>s</mi> </msub> </mrow> <mrow> <msub> <mi>L</mi> <mi>f</mi> </msub> <msub> <mi>C</mi> <mi>f</mi> </msub> <msup> <mi>s</mi> <mn>3</mn> </msup> <mo>+</mo> <mi>k</mi> <mo>&CenterDot;</mo> <msub> <mi>K</mi> <mi>PWM</mi> </msub> <msub> <mi>C</mi> <mi>f</mi> </msub> <msup> <mi>s</mi> <mn>2</mn> </msup> <mo>+</mo> <mrow> <mo>(</mo> <msub> <mi>K</mi> <mi>PWM</mi> </msub> <msub> <mi>K</mi> <mi>P</mi> </msub> <mo>+</mo> <mn>1</mn> <mo>)</mo> </mrow> <mi>s</mi> <mo>+</mo> <msub> <mi>K</mi> <mi>PWM</mi> </msub> <msub> <mi>K</mi> <mi>i</mi> </msub> </mrow> </mfrac> <mo>-</mo> <mo>-</mo> <mo>-</mo> <mrow> <mo>(</mo> <mn>6</mn> <mo>)</mo> </mrow> <mo>;</mo> </mrow> </math>
in the formula (6), a2＝KPWM(KP+1)L0-Lf，a1＝KPWM(KiL0+(Kp+1)R0)，a0＝KPWMKiR0；
Obtaining the output voltage u of DVR according to the formula (6)dvrAnd the obtained output voltage u is compared withdvrAnd outputting the current to the load side of the power grid for current limiting.
As an example, as shown in fig. 5 to 8, wherein fig. 5 and 6 are simulation waveforms when a fault occurs downstream of the DVR device, fig. 7 and 8 control the DVR as a virtual inductor for the simulation effect of fault current limiting. As seen from fig. 5 and 6, at 0.5s, the downstream of the DVR has a fault, the system voltage drops from 8.3kV to 3.4kV, and the short-circuit current is nearly 60kA, and as seen from fig. 7 and 8, the DVR is output as a virtual reactance, so that the fault current can be limited, and the system voltage can be restored to a normal value.
(d) Common voltage compensation mode
Acquiring a preset first voltage threshold, a preset second voltage threshold and a preset current threshold; the preset first voltage threshold is greater than the preset second voltage threshold;
when the detected system voltage upccWhen the amplitude value of the voltage drop is less than the preset second voltage threshold value, the voltage drop of the load side of the power grid is determined, and further judgment is madeOutput the detected system current isWhen the amplitude value of the voltage reference is smaller than the preset current threshold value, the control mode of the DVR is adjusted to be a common voltage compensation mode, a bypass system M of the DVR is controlled to be disconnected, an inverter N of the DVR is controlled to be locked in a pulse mode, and the DVR is simulated to be a voltage source;
according to the system voltage u of the network system sidepccTo the load voltage u of the load side of the networkloadCalculating the system voltage upccTo the load voltage uloadAnd compensating the calculated difference to a load side of the power grid as the compensation voltage of the DVR.
The specific process is to control the DVR as a voltage source and to set Δ u (system voltage u)pcc-load voltage uload) And compensating the load side of the power grid.
The embodiment of the invention has the following beneficial effects:
in the embodiment of the invention, the DVR automatically adjusts the current working control mode according to the system voltage and the system current at the system side, and calculates the output voltage of the DVR and outputs the output voltage to the load side of the power grid for voltage compensation or current limitation by combining the externally presented impedance characteristics (such as a series compensation capacitor, a fault current limiter and a voltage source), so that the DVR not only has the voltage drop compensation function, but also can automatically realize the fault current limiting or low voltage compensation function according to the actual requirement, the cost performance of the DVR is improved, and the industrial application and popularization degree of the DVR are promoted.
It will be understood by those skilled in the art that all or part of the steps in the method for implementing the above embodiments may be implemented by relevant hardware instructed by a program, and the program may be stored in a computer-readable storage medium, such as ROM/RAM, magnetic disk, optical disk, etc.
The above disclosure is only for the purpose of illustrating the preferred embodiments of the present invention, and it is therefore to be understood that the invention is not limited by the scope of the appended claims.

Claims (9)

1. A multifunctional DVR is characterized in that the DVR is arranged between a power grid system side and a load side and comprises a bypass system, a filter capacitor, a filter inductor, an inverter and a control unit; wherein,
the positive electrode of the filter capacitor is connected with the power grid system side, and the negative electrode of the filter capacitor is connected with the power grid load side;
the bypass system is bridged on two ends of the filter capacitor and is also connected with one end of the control unit;
and the positive electrode of the inverter is connected with the filtering inductor in series and then is connected with the positive electrode of the filtering capacitor, the negative electrode of the inverter is connected with the negative electrode of the filtering capacitor, and the control end of the inverter is connected with the other end of the control unit.
2. The DVR of claim 1, wherein the DVR further comprises an energy storage unit, and wherein the energy storage unit is coupled to the energy storage terminal of the inverter.
3. A method for dynamic regulation control of a multi-function DVR, implemented on a power grid comprising a DVR as claimed in claim 1 or 2, the method comprising:
acquiring system voltage and system current of the DVR connected with the side of the power grid system;
detecting the amplitude of the system voltage and the amplitude of the system current, adjusting a control mode of the DVR according to the detection result, and further outputting a control strategy corresponding to the adjusted control mode to the load side of the power grid; the control modes comprise a common voltage compensation mode, a fault current limiting mode, a low voltage compensation mode and a bypass uncompensated mode.
4. The method of claim 3, wherein the steps of detecting the magnitude of the system voltage and the magnitude of the system current, adjusting the control mode of the DVR according to the detection result, and further outputting a control strategy corresponding to the adjusted control mode to the load side of the power grid comprise:
acquiring a preset first voltage threshold, a preset second voltage threshold and a preset current threshold; wherein the preset first voltage threshold is greater than the preset second voltage threshold;
when the amplitude of the detected system voltage is larger than the preset first voltage threshold value, determining that the voltage of the power grid load side is normal, adjusting the control mode of the DVR to be a bypass uncompensated mode, controlling the bypass system of the DVR to be conducted, controlling the inverter of the DVR to be pulse-locked, and enabling the DVR not to compensate the voltage of the power grid load side.
5. The method of claim 3, wherein the steps of detecting the magnitude of the system voltage and the magnitude of the system current, adjusting the control mode of the DVR according to the detection result, and further outputting a control strategy corresponding to the adjusted control mode to the load side of the power grid further comprise:
acquiring a preset first voltage threshold, a preset second voltage threshold and a preset current threshold; wherein the preset first voltage threshold is greater than the preset second voltage threshold;
when the detected amplitude of the system voltage is between the preset first voltage threshold and the preset second voltage threshold, determining that the voltage of the load side of the power grid is low, adjusting the control mode of the DVR to be a low voltage compensation mode, controlling a bypass system of the DVR to be disconnected, controlling an inverter of the DVR to be pulsed on, and simulating the DVR to be a series compensation capacitor;
and calculating the reference voltage when the DVR is used as a series compensation capacitor, obtaining the output voltage of the DVR according to the calculated reference voltage, and outputting the obtained output voltage to the load side of the power grid for voltage compensation.
6. The method of claim 3, wherein the steps of detecting the magnitude of the system voltage and the magnitude of the system current, adjusting the control mode of the DVR according to the detection result, and further outputting a control strategy corresponding to the adjusted control mode to the load side of the power grid further comprise:
acquiring a preset first voltage threshold, a preset second voltage threshold and a preset current threshold; wherein the preset first voltage threshold is greater than the preset second voltage threshold;
when the amplitude of the detected system voltage is smaller than the preset second voltage threshold value, determining that the voltage of the load side of the power grid falls, and further judging that the amplitude of the detected system current is larger than the preset current threshold value, adjusting the control mode of the DVR to be a fault current limiting mode, controlling a bypass system of the DVR to be disconnected, controlling an inverter of the DVR to be pulsed on, and simulating the DVR to be a fault current limiter;
and calculating the reference voltage when the DVR is used as a fault current limiter, obtaining the output voltage of the DVR according to the calculated reference voltage, and outputting the obtained output voltage to the load side of the power grid for current limiting.
7. The method of claim 3, wherein the steps of detecting the magnitude of the system voltage and the magnitude of the system current, adjusting the control mode of the DVR according to the detection result, and further outputting a control strategy corresponding to the adjusted control mode to the load side of the power grid further comprise:
acquiring a preset first voltage threshold, a preset second voltage threshold and a preset current threshold; wherein the preset first voltage threshold is greater than the preset second voltage threshold;
when the amplitude of the detected system voltage is smaller than the preset second voltage threshold value, determining that the voltage of the load side of the power grid drops, and further judging that the amplitude of the detected system current is smaller than the preset current threshold value, adjusting the control mode of the DVR to be a common voltage compensation mode, controlling a bypass system of the DVR to be disconnected, controlling an inverter of the DVR to be pulse-locked, and simulating the DVR to be a voltage source;
and calculating the difference value between the system voltage and the load voltage according to the system voltage of the power grid system side and the load voltage of the power grid load side, and compensating the calculated difference value to the power grid load side as the compensation voltage of the DVR.
8. The method according to any one of claims 4 to 7, wherein the preset first threshold is 93% of the nominal voltage of the power grid and the preset second threshold is 90% of the nominal voltage of the power grid.
9. The method according to any one of claims 4 to 7, wherein the preset current threshold is 5 times the grid normal current value.
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Cited By (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
CN106229982A (en) * 2016-09-30 2016-12-14 浙江百固电气科技股份有限公司 Quality of power supply intelligent comprehensive optimizes device
CN110391664A (en) * 2019-04-30 2019-10-29 江苏谷峰电力科技股份有限公司 Suitable for remote 10kV distribution end low-voltage controlling device and method
CN110867951A (en) * 2019-12-02 2020-03-06 国网江苏省电力有限公司徐州供电分公司 Composite DVR topological structure based on cross power supply and light storage dual power supply

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Publication number Priority date Publication date Assignee Title
CN202550574U (en) * 2012-03-30 2012-11-21 上海市电力公司 Voltage regulator
CN104052062B (en) * 2014-06-10 2016-01-20 江苏大学 Based on the dynamic electric voltage recovery device compensating control method that minimum active power is injected

Cited By (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
CN106229982A (en) * 2016-09-30 2016-12-14 浙江百固电气科技股份有限公司 Quality of power supply intelligent comprehensive optimizes device
CN110391664A (en) * 2019-04-30 2019-10-29 江苏谷峰电力科技股份有限公司 Suitable for remote 10kV distribution end low-voltage controlling device and method
CN110391664B (en) * 2019-04-30 2021-10-08 江苏谷峰电力科技股份有限公司 Low-voltage treatment device and method suitable for long-distance 10kV distribution network tail end
CN110867951A (en) * 2019-12-02 2020-03-06 国网江苏省电力有限公司徐州供电分公司 Composite DVR topological structure based on cross power supply and light storage dual power supply

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