CN113381414B - Multi-mode comprehensive control method of dynamic voltage restorer based on super capacitor energy storage - Google Patents
Multi-mode comprehensive control method of dynamic voltage restorer based on super capacitor energy storage Download PDFInfo
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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
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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
- H02J3/28—Arrangements for balancing of the load in a network by storage of energy
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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
- H02J7/00—Circuit arrangements for charging or depolarising batteries or for supplying loads from batteries
- H02J7/0068—Battery or charger load switching, e.g. concurrent charging and load supply
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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
- H02J7/00—Circuit arrangements for charging or depolarising batteries or for supplying loads from batteries
- H02J7/02—Circuit arrangements for charging or depolarising batteries or for supplying loads from batteries for charging batteries from ac mains by converters
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- H—ELECTRICITY
- H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
- H02M—APPARATUS FOR CONVERSION BETWEEN AC AND AC, BETWEEN AC AND DC, OR BETWEEN DC AND DC, AND FOR USE WITH MAINS OR SIMILAR POWER SUPPLY SYSTEMS; CONVERSION OF DC OR AC INPUT POWER INTO SURGE OUTPUT POWER; CONTROL OR REGULATION THEREOF
- H02M1/00—Details of apparatus for conversion
- H02M1/14—Arrangements for reducing ripples from dc input or output
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- H—ELECTRICITY
- H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
- H02M—APPARATUS FOR CONVERSION BETWEEN AC AND AC, BETWEEN AC AND DC, OR BETWEEN DC AND DC, AND FOR USE WITH MAINS OR SIMILAR POWER SUPPLY SYSTEMS; CONVERSION OF DC OR AC INPUT POWER INTO SURGE OUTPUT POWER; CONTROL OR REGULATION THEREOF
- H02M3/00—Conversion of dc power input into dc power output
- H02M3/02—Conversion of dc power input into dc power output without intermediate conversion into ac
- H02M3/04—Conversion of dc power input into dc power output without intermediate conversion into ac by static converters
- H02M3/10—Conversion of dc power input into dc power output without intermediate conversion into ac by static converters using discharge tubes with control electrode or semiconductor devices with control electrode
- H02M3/145—Conversion of dc power input into dc power output without intermediate conversion into ac by static converters using discharge tubes with control electrode or semiconductor devices with control electrode using devices of a triode or transistor type requiring continuous application of a control signal
- H02M3/155—Conversion of dc power input into dc power output without intermediate conversion into ac by static converters using discharge tubes with control electrode or semiconductor devices with control electrode using devices of a triode or transistor type requiring continuous application of a control signal using semiconductor devices only
- H02M3/156—Conversion of dc power input into dc power output without intermediate conversion into ac by static converters using discharge tubes with control electrode or semiconductor devices with control electrode using devices of a triode or transistor type requiring continuous application of a control signal using semiconductor devices only with automatic control of output voltage or current, e.g. switching regulators
- H02M3/158—Conversion of dc power input into dc power output without intermediate conversion into ac by static converters using discharge tubes with control electrode or semiconductor devices with control electrode using devices of a triode or transistor type requiring continuous application of a control signal using semiconductor devices only with automatic control of output voltage or current, e.g. switching regulators including plural semiconductor devices as final control devices for a single load
- H02M3/1584—Conversion of dc power input into dc power output without intermediate conversion into ac by static converters using discharge tubes with control electrode or semiconductor devices with control electrode using devices of a triode or transistor type requiring continuous application of a control signal using semiconductor devices only with automatic control of output voltage or current, e.g. switching regulators including plural semiconductor devices as final control devices for a single load with a plurality of power processing stages connected in parallel
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- H—ELECTRICITY
- H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
- H02M—APPARATUS FOR CONVERSION BETWEEN AC AND AC, BETWEEN AC AND DC, OR BETWEEN DC AND DC, AND FOR USE WITH MAINS OR SIMILAR POWER SUPPLY SYSTEMS; CONVERSION OF DC OR AC INPUT POWER INTO SURGE OUTPUT POWER; CONTROL OR REGULATION THEREOF
- H02M7/00—Conversion of ac power input into dc power output; Conversion of dc power input into ac power output
- H02M7/66—Conversion of ac power input into dc power output; Conversion of dc power input into ac power output with possibility of reversal
- H02M7/68—Conversion of ac power input into dc power output; Conversion of dc power input into ac power output with possibility of reversal by static converters
- H02M7/72—Conversion of ac power input into dc power output; Conversion of dc power input into ac power output with possibility of reversal by static converters using discharge tubes with control electrode or semiconductor devices with control electrode
- H02M7/79—Conversion of ac power input into dc power output; Conversion of dc power input into ac power output with possibility of reversal by static converters using discharge tubes with control electrode or semiconductor devices with control electrode using devices of a triode or transistor type requiring continuous application of a control signal
- H02M7/797—Conversion of ac power input into dc power output; Conversion of dc power input into ac power output with possibility of reversal by static converters using discharge tubes with control electrode or semiconductor devices with control electrode using devices of a triode or transistor type requiring continuous application of a control signal using semiconductor devices only
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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
- H02J2207/00—Indexing scheme relating to details of circuit arrangements for charging or depolarising batteries or for supplying loads from batteries
- H02J2207/20—Charging or discharging characterised by the power electronics converter
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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
- H02J2207/00—Indexing scheme relating to details of circuit arrangements for charging or depolarising batteries or for supplying loads from batteries
- H02J2207/50—Charging of capacitors, supercapacitors, ultra-capacitors or double layer capacitors
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- Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
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- Y02E—REDUCTION OF GREENHOUSE GAS [GHG] EMISSIONS, RELATED TO ENERGY GENERATION, TRANSMISSION OR DISTRIBUTION
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- Y02E40/30—Reactive power compensation
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Abstract
The invention discloses a multi-mode comprehensive control method of a dynamic voltage restorer based on super-capacitor energy storage, which is applied to the dynamic voltage restorer based on super-capacitor energy storage and comprises the following control modes: super capacitor charging mode: when the dynamic voltage restorer works in a super capacitor mode, energy is taken from a power grid and stored in the super capacitor, and the method comprises the following steps: when the voltage of the power grid is detected to be stable, the voltage of the AC-DC side is kept constant through a voltage outer ring, a current inner ring and a power feedforward link, and then the super capacitor is charged with constant power through a DC-DC circuit; voltage compensation mode: when the dynamic voltage restorer works in a voltage compensation mode, the super capacitor discharges to compensate the voltage drop of the power grid, and the method comprises the following steps: when the voltage of the power grid is detected to drop, the dropping voltage is compensated through the AC-DC inverter, and the voltage of the DC-DC high-voltage side is kept constant through the voltage outer ring, the circuit inner ring and the power feedforward link. The invention improves the voltage compensation precision and the response speed of the super-capacitor energy storage type dynamic voltage restorer, and is beneficial to enhancing the stability of the power supply voltage at the load end.
Description
Technical Field
The invention relates to the technical field of power grid protection, in particular to a voltage compensation control method of a dynamic voltage restorer based on super-capacitor energy storage under the condition of power grid voltage drop.
Background
The voltage drop is a dynamic power quality problem with the highest occurrence frequency, the most serious influence and the largest economic loss, and the statistical results of the power company in Guanxi Japan show that: most voltage dips are faults within 20% of the drop amplitude and within 100ms of duration. Although dynamic power quality degradation does not last long, the consequences and economic losses to sensitive equipment and sensitive users are severe.
The energy storage type DVR (Dynamic Voltage Restorer) has the characteristics of high energy density, quick charge and discharge, long service life, no pollution and the like. Research on DVR is very active in many countries of the world since 1998, and especially in developed countries like america, days, and germany, etc., work on this aspect has been done earlier. However, the type of fault that may occur in the grid voltage is complex and difficult to detect, and the DVR, as a device for compensating for voltage sag, has high requirements for dynamic response of a control strategy.
Therefore, the research on a feasible super-capacitor energy storage type dynamic voltage restorer control method is particularly important for popularizing the application of the energy storage system in the electric energy and voltage drop suppression of the power distribution network.
Disclosure of Invention
The invention provides a multi-mode comprehensive control method of a dynamic voltage restorer based on super-capacitor energy storage, which is used for solving the technical problems that the type of faults possibly occurring in the voltage of a power grid is complex and the detection is difficult, and the dynamic response to a control strategy is difficult to meet the use requirement by adopting a DVR (digital video recorder) as a device for compensating voltage drop.
In order to solve the technical problems, the technical scheme provided by the invention is as follows:
a multi-mode comprehensive control method of a dynamic voltage restorer based on super-capacitor energy storage is applied to the dynamic voltage restorer comprising the following components: the system comprises a transformer, an LC filter circuit, an inverter H-bridge unit, a direct-current side capacitor, a Buck-Boost unit and a super capacitor array; the method comprises the following control modes:
charging mode of the super capacitor: when the dynamic voltage restorer works in a super capacitor mode, energy is taken from a power grid and stored in the super capacitor, and the method comprises the following steps: when the voltage of the power grid is detected to be stable, the voltage of the AC-DC side is kept constant through a voltage outer ring, a current inner ring and a power feedforward link, and then the super capacitor is charged with constant power through a DC-DC circuit;
voltage compensation mode: when the dynamic voltage restorer works in a voltage compensation mode, the super capacitor discharges to compensate the voltage drop of the power grid, and the method comprises the following steps: when the voltage of the power grid is detected to drop, the AC-DC inverter compensates the drop voltage, and then the voltage of the DC-DC high-voltage side is kept constant through the voltage outer ring, the circuit inner ring and the power feedforward link.
Preferably, in the dynamic voltage restorer, an LC filter circuit is connected in series with the output end of the inversion H-bridge unit, a primary side of a transformer is connected in parallel with a capacitor C in the LC filter circuit, and a secondary side of the transformer is connected to a power grid; the three independent inverter H bridge units are connected in a direct current parallel connection mode and an alternating current isolation transformer connection mode; the three independent Buck-Boost units are connected in parallel by adopting a mode that high-voltage ends are directly connected in parallel and low-voltage ends are connected in parallel in an interleaving mode through inductors.
Preferably, in the super capacitor charging mode, the PWM signal is obtained by the following two ways:
1) when the fault diagnosis unit detects that the voltage of the power grid is stable and the voltage of the AC-DC direct current side is lower than the working voltage, the fault diagnosis unit obtains electricity from the power grid and subtracts the actual electricity from the reference value of the working voltage of the AC-DC direct current sidePress U dc And the effective value u of the voltage on the primary side of the transformer, which is obtained by calculating the power feedforward link orms Obtaining a first charging instruction; the power feedforward calculation equation is: u. of orms ＝u sc *i sc /i orms Wherein u is sc Is the super capacitor voltage i sc For the Buck-Boost unit inductor current, i orms Is the effective value of the primary side current of the transformer; the first charging command is: u. of ref ＝(200-U dc )+u orms ；
A first charging instruction u ref Minus the primary side voltage u of the transformer o Through G 1 (s) after signal processing, obtaining a filter capacitor current i ck ；
Filtering the capacitor current i ck Plus a primary side current i of the transformer o Then subtract the filter inductor current i L And through G 2 (s) after signal processing, obtaining filter inductance voltage u L ；
Will filter the inductive voltage u L Plus the filter capacitor voltage u ck The sum of which is divided by the actual voltage U dc Obtaining a modulation signal, and obtaining a PWM signal through a unipolar frequency multiplication modulation strategy;
2) when the fault diagnosis unit detects that the voltage of the power grid is stable, the voltage of the AC-DC side is equal to the working voltage and the voltage of the super capacitor is lower than the working voltage, the super capacitor is charged at constant power to obtain a second charging instruction i ref (ii) a The second charging command is i ref ＝1000/u sc ；u sc Is the super capacitor voltage;
a second charging instruction i ref Subtracting the inductance current i of the Buck-Boost unit sc Through G 2 After the(s) signal is processed, the filter inductance voltage u is obtained L ’；
Will filter the inductive voltage u L ', plus a supercapacitor voltage u sc The sum of both divided by the actual voltage U dc And obtaining a modulation signal, and obtaining a PWM signal through a unipolar frequency multiplication modulation strategy.
Preferably, in the voltage compensation mode, the PWM signal is obtained by:
3) when the fault diagnosis unit detects the voltage drop of the power grid, the super capacitor discharges to compensate the voltage of the power grid, so that the load voltage is stable:
for the DC-DC part, the command is calculated by subtracting the actual voltage from the reference value of the working voltage at the AC-DC side, and the actual voltage is subjected to G 1 After the(s) signal is processed, the inductance current i of the Buck-Boost unit is obtained sc And the Buck-Boost unit inductive current i obtained by calculating the power feedforward link sc Obtaining a compensation command i ref ；
Will compensate the instruction i ref Subtracting the inductance current i of the Buck-Boost unit sc Through G 2 After the(s) signal is processed, the filter inductance voltage u is obtained L ’；
Will filter the inductive voltage u L ', plus a supercapacitor voltage u sc The sum of both is then divided by U dc Obtaining a modulation signal, and obtaining a PWM signal through a single-pole frequency multiplication modulation strategy;
for the AC-DC part, the instruction is calculated by subtracting the actual voltage of the power grid from the reference voltage of the load, and the calculation formula is as follows: u. of ref ＝v Lref -v s ；
The obtained compensation instruction u ref Minus the primary side voltage u of the transformer o Through G 1 (s) after signal processing, obtaining a filter capacitor current i ck ；
Filtering the capacitor current i ck Plus a primary side current i of the transformer o Then subtract the filter inductor current i L And through G 2 (s) after signal processing, obtaining a filter inductance voltage u L ；
Filter the voltage u of the inductor L ', plus a supercapacitor voltage u sc The sum of which is divided by the actual voltage U dc And obtaining a modulation signal, and obtaining a PWM signal through a single-pole frequency multiplication modulation strategy.
Preferably, G 1 (s) the expression is:
G 2 (s) the expression is:
G 2 the expression(s) is:
G 1 the expression(s) is:
wherein, K p1 And K p2 All are proportional amplification factors; k is i1 And K i2 Are all integral amplification factors.
The invention has the following beneficial effects:
1. according to the multimode comprehensive control method of the dynamic voltage restorer based on the super capacitor energy storage, disclosed by the invention, through double closed-loop control based on power feedforward, on one hand, DC-DC output inductive current ripples are reduced, the service life of the super capacitor is prolonged, and on the other hand, the multimode comprehensive control method is matched with the short-time high-power charging and discharging characteristics of the super capacitor, so that the voltage dip is favorably inhibited, and the power quality of a power grid is improved.
2. In a preferred scheme, the circuit topology of the dynamic voltage restorer based on super-capacitor energy storage effectively inhibits the influence of sudden voltage drop of a power grid on a sensitive load through power feedforward and voltage-current double closed-loop control; the three H-bridge units form the DC-AC converter, the control is simple, the control freedom degree is high, split-phase voltage compensation can be realized, and the unbalanced voltage compensation capability is good; the DC-DC converter adopts a staggered parallel Buck-Boost structure, so that the power transmission capacity of the converter is improved, the output inductive current ripple is reduced, less harmonic current flows into the super capacitor energy storage unit, and the service life of the super capacitor is prolonged; the super-capacitor energy storage unit has the characteristic of short-time high-power charging and discharging, voltage drop caused by power fluctuation can be inhibited, and the power quality of a power grid is improved.
In addition to the above-described objects, features and advantages, the present invention has other objects, features and advantages. The present invention will be described in further detail below with reference to the accompanying drawings.
Drawings
The accompanying drawings, which are incorporated in and constitute a part of this application, illustrate embodiments of the invention and, together with the description, serve to explain the invention and not to limit the invention. In the drawings:
fig. 1 is a control flow chart of an H-bridge single-phase inverter unit according to a preferred embodiment of the present invention;
FIG. 2 is a system bode plot of filter capacitance variation in accordance with a preferred embodiment of the present invention;
FIG. 3 is a system bode plot of filter inductance variation for a preferred embodiment of the present invention;
FIG. 4 is a block diagram of the instruction calculation of the multi-modal integrated control method of the dynamic voltage restorer based on super capacitor energy storage according to the preferred embodiment of the present invention;
FIG. 5 is a control block diagram of a multi-modal integrated control method of a dynamic voltage restorer based on super capacitor energy storage according to a preferred embodiment of the present invention;
FIG. 6 shows the proportional amplification factor K of the AC-DC voltage loop PI regulator according to the preferred embodiment of the present invention p1 A system bode plot of variation;
FIG. 7 shows the proportional amplification factor K of the AC-DC current loop PI regulator according to the preferred embodiment of the present invention p2 A system bode plot of variation;
FIG. 8 shows the integral amplification factor K of the AC-DC voltage loop PI regulator according to the preferred embodiment of the present invention i1 A system bode plot of variation;
FIG. 9 shows the integral amplification factor K of the AC-DC current loop PI regulator according to the preferred embodiment of the present invention i2 A system bode plot of variation;
FIG. 10 shows the proportional amplification factor K of the PI regulator for DC-DC voltage loop in accordance with the preferred embodiment of the present invention p1 A system bode plot of variation;
FIG. 11 shows the proportional amplification factor K of the DC-DC current loop PI regulator according to the preferred embodiment of the present invention p2 A system bode plot of variation;
FIG. 12 shows the integral amplification factor K of the DC-DC voltage loop PI regulator according to the preferred embodiment of the present invention i1 A system bode plot of variation;
FIG. 13 shows the integral amplification factor K of the DC-DC current loop PI regulator in accordance with the preferred embodiment of the present invention i2 A system bode plot of variation;
fig. 14 is a schematic topology diagram of a supercapacitor energy storage dynamic voltage restorer according to a preferred embodiment of the present invention.
Detailed Description
Embodiments of the invention will be described in detail below with reference to the drawings, but the invention can be implemented in many different ways as defined and covered by the claims.
Referring to fig. 14, it is a schematic diagram of a topology structure of the super capacitor energy storage dynamic voltage restorer in this embodiment, and the super capacitor energy storage dynamic voltage restorer in this embodiment includes: the system comprises a power grid connecting end, a load, a transformer, an LC filter circuit, an inversion H-bridge unit, a direct-current side capacitor, a Buck-Boost unit and a super capacitor array. The LC filter circuit is connected in series with the output end of the inverter H bridge unit, the primary side of the transformer is connected in parallel with a capacitor C in the LC filter circuit, and the secondary side of the transformer is connected to a power grid; the three independent inverter H bridge units are connected in a direct current parallel connection mode and an alternating current isolation transformer connection mode; the three independent Buck-Boost units are connected in parallel by adopting a mode that high voltage ends are directly connected in parallel and low voltage ends are connected in parallel in an interleaved mode through inductors. The circuit topology effectively inhibits the influence of sudden voltage drop of a power grid on a sensitive load through power feedforward and voltage and current double closed-loop control; the three H-bridge units form the DC-AC converter, the control is simple, the control freedom degree is high, split-phase voltage compensation can be realized, and the unbalanced voltage compensation capability is good; the DC-DC converter adopts a staggered parallel Buck-Boost structure, so that the power transmission capacity of the converter is improved, the output inductive current ripple is reduced, less harmonic current flows into the super capacitor energy storage unit, and the service life of the super capacitor is prolonged; the super-capacitor energy storage unit has the characteristic of short-time high-power charging and discharging, voltage drop caused by power fluctuation can be inhibited, and the power quality of a power grid is improved.
According to the multi-mode comprehensive control method of the dynamic voltage restorer based on the super capacitor energy storage, disclosed by the invention, through reasonably designing the super capacitor energy storage type filtering parameters and the double closed loop control parameters based on power feedforward, on one hand, DC-DC output inductive current ripples are reduced, the service life of the super capacitor is prolonged, and on the other hand, the short-time high-power charging and discharging characteristics of the super capacitor are matched, so that the voltage dip is favorably inhibited, and the power quality of a power grid is improved.
The parameters of the super-capacitor energy storage type filter circuit are designed as follows:
FIG. 1 is a control flow chart of an H-bridge single-phase inverter unit. Wherein, K pwm Is the equivalent gain of the bridge PWM. Let G 1 (s)＝K p1 +K i1 /s,G 2 (s)＝K p2 +K i2 /s，Z1＝sL 1 ，Z 2 ＝sL 2 +R，Z 3 ＝1/sC k ，K pwm ＝1。u ck (s) and u ck * The open-loop transfer between(s) is:
assuming that the switching frequency of the power device is 10kHz, the input direct-current voltage U dc 200V, L1 ═ 1mH, C ═ 20 μ F, L2 ═ 6.67mH, and R ═ 3.63 Ω. It can be seen from fig. 2 that the system is always in a steady state, but as the capacitance value of the capacitor decreases, the phase angle margin of the system rises first and then falls, and the peak is reached around C-20 e-6F, while the amplitude margin monotonically decreases. Meanwhile, the influence of the change of the capacitance value of the filter capacitor on the low frequency band and the high frequency band of the Burde diagram is small, the change trend of the middle frequency band is similar, and the cut-off frequency is gradually increased along with the reduction of the capacitance value of the filter capacitor. In the final simulation, the filter capacitor C is selected to be 20e-6F in the embodiment, so that on one hand, high stability of the system is guaranteed, and on the other hand, the system has high rapidity due to high cut-off frequency.
From FIG. 3 can be seenIt is seen that the system is always in steady state, but as the inductance value decreases, the phase angle margin rises first and then falls, at L 1 The phase angle margin reaches the maximum at 1 e-3H; and the margin of the amplitude of each curve is similar. Meanwhile, the influence of the change of the inductance value of the filter inductor on the low frequency band of the Bode diagram is small; the rapidity of the intermediate frequency band is weakened along with the reduction of the inductance value; for the high frequency band, the high frequency interference resistance is gradually weakened along with the reduction of the inductance value. In the final simulation, L is selected in the embodiment 1 The 2e-3H can ensure that the system has certain rapidity and higher anti-interference capability and also can ensure high stability of the system.
Based on the parameters of the dynamic voltage restorer and the super-capacitor energy storage type filter circuit, the multi-mode comprehensive control method of the dynamic voltage restorer based on super-capacitor energy storage comprises the following two control modes:
charging mode of the super capacitor: when the dynamic voltage restorer works in a super capacitor mode, energy is taken from a power grid and is stored in the super capacitor, and the method comprises the following steps: when the voltage of the power grid is detected to be stable, the voltage of the AC-DC direct current side is maintained to be constant through a voltage outer ring, a current inner ring and a power feedforward link, and then the super capacitor is charged with constant power through a DC-DC circuit;
voltage compensation mode: when the dynamic voltage restorer works in a voltage compensation mode, the super capacitor discharges to compensate the voltage drop of the power grid, and the method comprises the following steps: when the voltage of the power grid is detected to drop, the dropping voltage is compensated through the AC-DC inverter, and the voltage of the DC-DC high-voltage side is kept constant through the voltage outer ring, the circuit inner ring and the power feedforward link.
In the above control method, the power feedforward-based double closed-loop control parameters of the present embodiment are designed as follows:
the command computation block diagram of the AC-DC section and DC-DC section charging and compensation is contained in fig. 4. Wherein u dc Is an AC-DC side voltage, u sc Is the super capacitor voltage i sc For the Buck-Boost unit inductor current, i o Is the primary side current of the transformer; u. u Lref Is a load reference voltage, u s For a certain single-phase mains voltage, u o To becomeThe transformer primary side voltage.
A control block diagram for charging and compensation of the AC-DC section and the DC-DC section is included in fig. 5.
In the implementation, in the super capacitor charging mode, the PWM signal is obtained in the following two ways:
1) when the fault diagnosis unit detects that the voltage of the power grid is stable and the voltage of the AC-DC side is lower than the working voltage, power is taken from the power grid, and the actual voltage U is subtracted from the reference value (200V in the embodiment) of the working voltage of the AC-DC side dc And the effective value u of the voltage on the primary side of the transformer, which is obtained by calculating the power feedforward link orms Obtaining a first charging instruction; the power feed-forward calculation equation is: u. u orms ＝u sc *i sc /i orms Wherein u is sc Is the super capacitor voltage, i sc For the inductor current of Buck-Boost unit, i orms The effective value of the primary side current of the transformer; the first charging command is: u. of ref ＝(200-U dc )+u orms ；
A first charging command u ref Minus the primary side voltage u of the transformer o Through G 1 (s) after signal processing, obtaining a filter capacitor current i ck ；G 1 (s) the expression is:
wherein, K p1 Is a scale factor; k i1 Is the integral amplification factor.
Filter the capacitor current i ck Plus a primary side current i of the transformer o Then subtract the filter inductor current i L And through G 2 (s) after signal processing, obtaining a filter inductance voltage u L ；G 2 (s) the expression is:
K p2 is a scale factor; k i2 Is the integral amplification factor.
Will filter the inductive voltage u L Plus the filter capacitor voltage u ck The sum of which is divided by the actual voltage U dc To obtainModulating the signal, and obtaining a PWM signal through a unipolar frequency multiplication modulation strategy;
2) when the fault diagnosis unit detects that the voltage of the power grid is stable, the voltage of the AC-DC side is equal to the working voltage and the voltage of the super capacitor is lower than the working voltage, the super capacitor is charged at constant power to obtain a second charging instruction i ref (ii) a In this embodiment, the charging power is 1kW, and the second charging command is i ref ＝1000/u sc ；u sc Is the super capacitor voltage;
a second charging instruction i ref Subtracting the inductance current i of the Buck-Boost unit sc Through G 2 After the(s) signal is processed, the filter inductance voltage u is obtained L ’；
Will filter the inductive voltage u L ', plus a supercapacitor voltage u sc The sum of both divided by the actual voltage U dc And obtaining a modulation signal, and obtaining a PWM signal through a unipolar frequency multiplication modulation strategy.
In the implementation, in the voltage compensation mode, the PWM signal is obtained by:
3) when the fault diagnosis unit detects the voltage drop of the power grid, the super capacitor discharges to compensate the voltage of the power grid, so that the load voltage is stable:
for the DC-DC part, the command is calculated by subtracting the actual voltage from the reference value of the working voltage at the AC-DC side, and the actual voltage is subjected to G 1 After the(s) signal is processed, the inductance current i of the Buck-Boost unit is obtained sc And the Buck-Boost unit inductive current i obtained by calculating the power feedforward link sc Obtaining a compensation command i ref ；G 1 The expression(s) is:
K p1 is a scale factor; k i1 Is the integral amplification factor.
Will compensate the instruction i ref Subtracting the inductance current i of the Buck-Boost unit sc Through G 2 After the(s) signal is processed, the filter inductance voltage u is obtained L ’；G 2 The expression(s) is:
K p2 is a scale factor; k i2 Is the integral amplification factor.
Filter the voltage u of the inductor L ', plus a supercapacitor voltage u sc The sum of both is then divided by U dc Obtaining a modulation signal, and obtaining a PWM signal through a single-pole frequency multiplication modulation strategy;
for the AC-DC part, the instruction is calculated by subtracting the actual voltage of the power grid from the load reference voltage, and the calculation formula is as follows: u. of ref ＝v Lref -v s ；
The obtained compensation instruction u ref Subtracting the primary side voltage u of the transformer o Through G 1 (s) after signal processing, obtaining a filter capacitance current i ck ；
Filter the capacitor current i ck Plus the primary current i of the transformer o Then subtract the filter inductor current i L And through G 2 (s) after signal processing, obtaining a filter inductance voltage u L ；
Filter the voltage u of the inductor L ', plus a supercapacitor voltage u sc The sum of which is divided by the actual voltage U dc And obtaining a modulation signal, and obtaining a PWM signal through a single-pole frequency multiplication modulation strategy.
It can be seen from fig. 6 that the system is always in steady state, but with the scaling factor K p1 The amplitude margin and the phase angle margin of the system are gradually increased, and the stability of the system is enhanced. But the rapidity of the system is gradually deteriorated. In the final simulation, K is selected in the compromise of the embodiment in order to take stability and rapidity into consideration p1 ＝2。
It can be seen from fig. 7 that the system is always in steady state, but with the scaling factor K p2 And when the amplitude is reduced, the phase angle margin of the system is gradually reduced, and the amplitude margin is gradually increased. At the same time, it can be seen that when K p2 When 300, 200 and 100 are taken, respectively, the Bode plot cut-off frequency changes very little, so K p2 In these three cases, the influence on the system rapidity is small, and the same is true for K p2 When taking 50 and 10 respectively, the system rapidity is greatly influencedIs small. In the final simulation, this embodiment selects K p2 100, the system is fast and stable.
From FIG. 8, the integral amplification factor K can be seen i1 When varied, mainly affects the low frequency band of the Bode diagram, i.e. the steady-state accuracy, and K i1 In the process of gradually decreasing from 0.8 to 0, the steady-state accuracy gradually deteriorates. And for mid and high bands, K i1 The change in (c) has no effect on the system. Therefore, in the final simulation, K is selected in the embodiment i1 ＝0.8。
From FIG. 9, it can be seen that the integral amplification factor K i2 When varied, mainly affects the low frequency band of the Bode diagram, i.e. the steady-state accuracy, and K i2 In the process of gradually decreasing from 0.8 to 0, the steady-state accuracy gradually deteriorates. And for mid and high bands, K i2 The change in (c) has substantially no effect on the system. Therefore, in the final simulation, K is selected in the embodiment i2 ＝0.8。
It can be seen from fig. 10 that the system is always in a closed loop steady state with the scaling factor K p1 The phase angle margin gradually rises and then decreases, the amplitude margin gradually increases, the cut-off frequency gradually decreases, namely, the rapidity is weakened, and the anti-interference capability is gradually enhanced in a high frequency band. While steady state accuracy is at k p The lowest when it is 10. This example selects K p1 6, both guarantee higher stability and rapidity, steady state precision and interference killing feature are better moreover.
It can be seen from fig. 11 that the system is always in closed loop steady state with K p2 The amplitude margin is basically kept unchanged, but the phase angle margin is gradually increased, and the cut-off frequency is not greatly changed, so that the system rapidity is not greatly influenced, and the anti-interference capability is gradually enhanced, therefore, the embodiment selects K p2 ＝0.01。
It can be seen from fig. 12 that the system is always in closed loop steady state with K i1 There is no significant change in the amplitude margin, while the phase angle margin is gradually increased. While steady-state accuracy gradually decreases and rapidity increases. Therefore, this embodiment selects K i1 2, the system is ensured to have greater stability and higher steady-state precision and rapidity.
It can be seen from FIG. 13 that the system is always in closed loop steady state with K i2 The margin of amplitude is slightly increased, the margin of phase angle rises first and then falls, at K i2 The maximum is reached at 0.1. For low frequency band, K i2 The system has the best steady state accuracy when the frequency is 0.01, and the middle frequency band and the high frequency band K i2 Does not have too great an effect, therefore K is selected in this embodiment i2 ＝0.01。
In conclusion, the voltage compensation precision and the response speed of the super-capacitor energy storage type dynamic voltage restorer are improved, and the stability of the power supply voltage at the load end is enhanced.
The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention, and various modifications and changes may be made by those skilled in the art. Any modification, equivalent replacement, or improvement made within the spirit and principle of the present invention should be included in the protection scope of the present invention.
Claims (4)
1. A multi-mode comprehensive control method of a dynamic voltage restorer based on super-capacitor energy storage is applied to the dynamic voltage restorer comprising the following components: the system comprises a transformer, an LC filter circuit, an AC-DC inverter, a direct current side capacitor, a DC-DC circuit and a super capacitor array; the method is characterized by comprising the following control modes:
charging mode of the super capacitor: when the dynamic voltage restorer works in a super capacitor mode, energy is taken from a power grid and stored in the super capacitor, and the method comprises the following steps: when the voltage of the power grid is detected to be stable, the voltage of the direct current side of the AC-DC inverter is kept constant through a voltage outer ring, a current inner ring and a power feedforward link, and then the super capacitor is charged with constant power through a DC-DC circuit;
voltage compensation mode: when the dynamic voltage restorer works in a voltage compensation mode, the super capacitor discharges to compensate the voltage drop of the power grid, and the method comprises the following steps: when the voltage of a power grid is detected to drop, the dropping voltage is compensated through the AC-DC inverter, and the voltage of the high-voltage side of the DC-DC circuit is kept constant through the voltage outer ring, the circuit inner ring and the power feedforward link;
in the charging mode of the super capacitor, a PWM signal is obtained through the following two modes:
1) when the fault diagnosis unit detects that the voltage of the power grid is stable and the voltage of the direct current side of the AC-DC inverter is lower than the working voltage, power is taken from the power grid, and the actual voltage U is subtracted from the reference value of the working voltage of the direct current side of the AC-DC inverter dc And the effective value u of the voltage on the primary side of the transformer, which is obtained by calculating the power feedforward link orms Obtaining a first charging instruction;
a first charging instruction u ref Minus the primary side voltage u of the transformer o Through G 1 (s) after signal processing, obtaining a filter capacitor current i ck ；
Filtering the capacitor current i ck Plus a primary side current i of the transformer o Then subtract the filter inductor current i L And through G 2 (s) after signal processing, obtaining a filter inductance voltage u L ；
Will filter the inductive voltage u L Plus the filter capacitor voltage u ck The sum of which is divided by the actual voltage U dc Obtaining a modulation signal, and obtaining a PWM signal through a single-pole frequency multiplication modulation strategy;
2) when the fault diagnosis unit detects that the voltage of the power grid is stable, the direct-current side voltage of the AC-DC inverter is equal to the working voltage and the voltage of the super capacitor is lower than the working voltage, the super capacitor is charged at constant power to obtain a second charging instruction i ref ；
A second charging instruction i ref Subtracting the inductor current i of the DC-DC circuit sc Through G 2 After the(s) signal is processed, the filter inductance voltage u is obtained L ’；
Will filter the inductive voltage u L ', plus a supercapacitor voltage u sc The sum of both divided by the actual voltage U dc And obtaining a modulation signal, and obtaining a PWM signal through a single-pole frequency multiplication modulation strategy.
2. The multi-modal integrated control method for the supercapacitor energy storage based dynamic voltage restorer according to claim 1, wherein in the dynamic voltage restorer, an LC filter circuit is connected to an output end of an AC-DC inverter in series, a primary side of a transformer is connected with a capacitor C in the LC filter circuit in parallel, and a secondary side of the transformer is connected to a power grid; the three independent AC-DC inverters are connected in a direct current parallel connection mode and an alternating current isolation transformer connection mode; the three independent DC-DC circuits are connected in parallel by adopting a mode that high-voltage ends are directly connected in parallel and low-voltage ends are connected in parallel in an interleaving mode through inductors.
3. The multi-modal integrated control method for the supercapacitor energy storage based dynamic voltage restorer according to claim 1, wherein the voltage compensation mode obtains the PWM signal by:
3) when the fault diagnosis unit detects the voltage drop of the power grid, the super capacitor discharges to compensate the voltage of the power grid, so that the load voltage is stable:
for the DC-DC part, the command is calculated by subtracting the actual voltage from the reference value of the working voltage at the DC side of the AC-DC inverter through G 1 '(s) after signal processing, obtaining the inductive current i of the DC-DC circuit sc And the inductance current i of the DC-DC circuit is obtained by adding the calculation of a power feedforward link sc Obtaining a compensation command i ref ’；
Will compensate the instruction i ref ', subtracting the inductor current i of the DC-DC circuit sc Through G 2 After the(s) signal is processed, the filter inductance voltage u is obtained L ’；
Filter the voltage u of the inductor L ', plus a supercapacitor voltage u sc The sum of both is then divided by U dc Obtaining a modulation signal, and obtaining a PWM signal through a unipolar frequency multiplication modulation strategy;
for the AC-DC inverter part, the instruction is calculated by subtracting the actual voltage of the power grid from the load reference voltage, and the calculation formula is as follows: u. of ref ’＝v Lref -v s ；
The obtained compensation command u ref ', minus the transformer primary side voltage u o Through G 1 (s) after signal processing, obtaining a filter capacitance current i ck ；
Filtering the capacitor current i ck Plus a primary side current i of the transformer o Then subtract the filter inductor current i L And through G 2 (s) after signal processing, obtaining a filter inductance voltage u L ；
Will filter the inductive voltage u L ', plus a supercapacitor voltage u sc The sum of which is divided by the actual voltage U dc And obtaining a modulation signal, and obtaining a PWM signal through a unipolar frequency multiplication modulation strategy.
4. The multi-modal integrated control method of the supercapacitor energy storage based dynamic voltage restorer according to claim 1 or 3,
G 1 (s) the expression is:
G 2 (s) the expression is:
G 2 the expression(s) is:
G 1 the expression(s) is:
wherein, K p1 And K p2 All are proportional amplification factors; k i1 And K i2 Are all integral amplification factors.
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