CN106941258B - Power factor control method and device applied to current converter - Google Patents
Power factor control method and device applied to current converter 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
- H02J3/18—Arrangements for adjusting, eliminating or compensating reactive power in networks
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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
- Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
- Y02E—REDUCTION OF GREENHOUSE GAS [GHG] EMISSIONS, RELATED TO ENERGY GENERATION, TRANSMISSION OR DISTRIBUTION
- Y02E40/00—Technologies for an efficient electrical power generation, transmission or distribution
- Y02E40/30—Reactive power compensation
Abstract
The invention provides a power factor control method and a device applied to a current converter, wherein a reactive power reference value is obtained by controlling a power factor: setting a power factor reference value, carrying out PI regulation on the difference between the power factor reference value and the power factor measured value to obtain a reactive power reference value, and adding the reactive power reference value and a set value of reactive power to obtain a final reactive power reference value; and carrying out fixed reactive power adjustment on the reactive power reference value to obtain a current reference value. The power factor control method can improve the power factor of the access point and reduce the influence of a harmonic source on an alternating current system and a flexible direct current converter on the premise of not increasing an alternating current filter.
Description
Technical Field
The invention belongs to the technical field of direct current transmission, and particularly relates to a power factor control method and device applied to a current converter.
Background
Since the flexible direct-current transmission technology based on the Modular Multilevel Converter (MMC) is provided, the flexible direct-current transmission system is rapidly developed in the engineering application of domestic power systems and shows good technical characteristics. Compared with the conventional direct-current transmission technology, the flexible direct-current transmission system has two degrees of freedom in control, active power and reactive power output by the converter can be independently controlled through dq decoupling of the inner ring controller, the problem of commutation failure does not exist, power can be supplied to a passive system, and the flexible direct-current transmission system has a great development prospect.
Reactive power is an important factor in the operation of power systems, and most network elements and loads consume reactive power, and most consumer loads also consume reactive power, such as transformers, large numbers of induction motors, gas discharge lamps, electric fans, refrigerators, air conditioners, loads, etc., which need to absorb not only active power from the power system, but also reactive power to generate the alternating magnetic field necessary for the devices to maintain normal operation, and reactive power is not useless power and creates the necessary conditions for energy exchange, transmission, and conversion.
Therefore, in order to transmit active power, a certain phase difference is required between voltages of a power transmitting terminal and a power receiving terminal, in order to transmit reactive power, a certain amplitude difference is required between voltages of both terminals, reactive power is consumed when the active power is transmitted, and if it is unreasonable that all the reactive power required to be consumed is provided by a generator and is transmitted over a long distance, the reactive power is generated at a place where the reactive power is required to be consumed, so that reactive power compensation, namely reactive power control, is required.
Wherein, the power factor is an important factor influencing the reactive power, the power factor is the ratio of the active power and the apparent power, the change rate of the power factor directly influences the ratio of the active power and the reactive power of the system, in view of the characteristics of power production, the height of the power factor has important influence on the full utilization of power generation, power supply and power utilization equipment, the saving of electric energy and the improvement of voltage quality, therefore, the power industry enterprises pay particular attention to the management of the power factor to the majority of users, especially the majority of industrial users, and compensate the reactive power, for example, the reactive power is controlled by adopting a constant reactive power mode, but when the constant reactive power control mode is adopted, because the control of the power factor is not considered, the enabling control of the current converter is not flexible, the control function is single, and when an alternating current filter is not added on the alternating current side of the current converter, if the power factor is not reasonably controlled, the effect of the harmonic power supply on the ac system and the flexible dc converter will be increased.
Disclosure of Invention
The invention aims to provide a power factor control method and a power factor control device applied to a converter, which are used for solving the problems that the control of the converter is not flexible enough and the control function is single because the regulation of the power factor is not considered when a flexible direct current converter adopts constant reactive power to carry out reactive power voltage regulation.
In order to achieve the purpose, the technical scheme of the invention is as follows:
a power factor control method applied to a converter obtains a reactive power reference value by controlling a power factor: setting a power factor reference value COS thetarefReference value of power factor COS thetarefAnd actual power factor value COS thetameasObtaining a reactive power reference value Q through PI regulationcosθ_refReference value Q of reactive powercosθ_refWith set value Q of reactive powerac_setAdding the obtained values to obtain a final reactive power reference value Qac_ref_final(ii) a For reactive power reference value Qac_ref_finalAnd adjusting the constant reactive power to obtain a current reference value.
Further, the reactive power reference value Qcosθ_refBy referencing the power factor to value COS thetarefThe difference with the power factor measured value is obtained by multiplying the power factor measured value by +/-1 through PI regulation, wherein +/-1 is selected from the reactive power measured value Qac_measAnd determining that the inductive power is 1 if the reactive power is detected, and the capacitive power is-1 if the reactive power is detected.
Further, if the power factor control is not needed, the reactive power reference value Q is setcosθ_refIs reduced to 0.
Further, if the power factor control is not needed, the reactive power reference value Q is setcosθ_refDecreasing to 0 at a set slope.
The invention also provides a power factor control device applied to the converter, which comprises a power factor controller and a reactive power controller, wherein the power factor controller is used for adjusting the power factor to obtain a reactive power reference value: setting a power factor reference value COS thetarefReference value of power factor COS thetarefAnd actual power factor value COS thetameasObtaining a reactive power reference value Q through PI regulationcosθ_refReference value Q of reactive powercosθ_refWith set value Q of reactive powerac_setAdding the obtained values to obtain a final reactive power reference value Qac_ref_finalAnd the reactive power controller is used for adjusting the reactive power reference value to obtain a current reference value.
Further, in the power factor controller, the reactive power reference value Qcosθ_refBy referencing the power factor to value COS thetarefThe difference with the power factor measured value is obtained by multiplying the power factor measured value by +/-1 through PI regulation, wherein +/-1 is selected from the reactive power measured value Qac_measAnd determining that the inductive power is 1 if the reactive power is detected, and the capacitive power is-1 if the reactive power is detected.
Further, if the power factor control is not needed, the reactive power reference value Q is setcosθ_refIs reduced to 0.
Further, if the power factor control is not needed, the reactive power reference value Q is setcosθ_refDecreasing to 0 at a set slope.
The invention has the beneficial effects that:
the invention obtains the reactive power reference value by controlling the power factor: setting a power factor reference value, carrying out PI regulation on the difference between the power factor reference value and the power factor measured value to obtain a reactive power reference value, and adding the reactive power reference value and a set value of reactive power to obtain a final reactive power reference value; and carrying out fixed reactive power adjustment on the reactive power reference value to obtain a current reference value. The invention adjusts the power factor of the AC access point of the converter, increases the control function of the converter, makes the control function more flexible and is suitable for a plurality of application occasions.
Drawings
Fig. 1 is a structural diagram of a flexible dc converter;
FIG. 2 is a submodule circuit diagram of an MMC converter;
FIG. 3 is a schematic block diagram of a dual-loop controller of the flexible DC converter;
fig. 4 is a schematic block diagram of a power factor controller of the flexible dc converter.
Detailed Description
The following further describes embodiments of the present invention with reference to the drawings:
the embodiment of the power factor control method applied to the converter comprises the following steps:
the invention provides a power factor control method applied to a converter, which aims to control the power factor of an AC access point of the converter.
The flexible direct current converter of this embodiment adopts an MMC topology structure, as shown in fig. 1, the converter includes three-phase bridge arms, each phase of bridge arm includes an upper bridge arm and a lower bridge arm, each bridge arm includes a corresponding bridge arm inductance and N MMC sub-modules connected in series, the upper bridge arm and the lower bridge arm are connected in series through the corresponding bridge arm inductance, the number of the MMC sub-modules included in the upper bridge arm and the lower bridge arm is the same, wherein each MMC sub-module adopts a half-bridge structure, as shown in fig. 2, each half-bridge sub-module includes 2 IGBTs, 2 anti-parallel diodes, 1 energy storage capacitor and a resistor, and as other implementation modes, the converter sub-modules may also adopt a full-.
The reactive power control method of the flexible direct current converter provided by the embodiment is as shown in fig. 3 and fig. 4, and includes overall double-loop control of the flexible direct current converter and power factor control added on the basis of reactive power control. Wherein, the outer loop is the power loop, including deciding direct current voltage control, deciding active power control, deciding reactive power control and deciding alternating voltage control, and the inner loop is the current loop, adds through PI regulation term, feedforward term and decoupling term and obtains the modulation voltage reference value, specifically does:
active power control selects constant direct current voltage control or constant active power control power according to requirementsOuter loop control, constant reactive power control selected by reactive power control, and d-axis inner loop current reference value I obtained by current inner loop control of active powerd_refObtaining a q-axis inner loop current reference value I by the current inner loop control of the reactive power controlq_refD-axis inner ring current reference value Id_refAnd the q-axis inner ring current reference value is respectively obtained by the d-axis modulation voltage axis reference value U through the inner ring current controllerd_refAnd q-axis reference value Uq_refConverting the d axis and the q axis to obtain a three-phase modulation voltage reference value Ua_ref、Ub_ref、Uc_ref. The reference value of the outer ring controller is increased by a certain slope, so that the corresponding controlled quantity in the system is changed smoothly.
Because the power factor has a certain influence on the control process of the constant reactive power control mode, the power factor is additionally controlled in the constant reactive power control mode, as shown in fig. 4, X in the figure can be +1 or-1, and the specific control process is as follows: setting a power factor reference value COS thetarefThen, power factor control is enabled, and the power factor reference value COS theta is setrefAnd power factor measured value COS thetameasPerforming PI control, and multiplying the inductive or capacitive reactive power required by the system by +/-1 to obtain a reactive power reference value Q output by the power factor controllercosθ_refThe specific process for determining whether X takes +1 or-1 is as follows: qac_measIs a real measurement of reactive power, if Q is detectedac_measIf not less than 0, the output-1 is multiplied by the output of PI to obtain Qcosθ_ref(ii) a If Q is detectedac_meas<0, the output +1 is multiplied by the output of PI to obtain Qcosθ_refThat is, if the detected reactive power is capacitive-1, and if the detected reactive power is inductive +1, the output of PI is multiplied by-1 or +1 to obtain Qcosθ_refThen add the setpoint Q of the reactive power controller itselfac_setObtaining the final reactive power reference value Qac_ref_finalBy means of a pair Qac_ref_finalPerforming constant reactive power control to obtain a current command value, wherein Qac_ref_finalThe output range of the power converter is self-adaptively changed according to the system capacity and the current active power measured value. In a power factor control enabled stateNext, if it is not necessary to control the power factor any more, an operation of prohibiting the power factor control can be performed. After power factor control is forbidden, the reactive power reference value Qcosθ_refAnd reducing to 0 with a certain slope so as to avoid sudden change of the reactive power of the system.
The invention also provides a power factor control device applied to the converter, which comprises a power factor controller and a reactive power controller, wherein the power factor controller is used for adjusting the power factor to obtain a reactive power reference value: setting a power factor reference value, carrying out PI adjustment on the difference between the power factor reference value and the power factor measured value to obtain a reactive power reference value, adding the reactive power reference value and a set value of reactive power to obtain a final reactive power reference value, and adjusting the reactive power reference value by a reactive power controller to obtain a current reference value. The control device is utilized to adjust the power factor of the AC access point of the converter, and the control function of the converter is increased, so that the control function is more flexible, and the control device is suitable for a plurality of application occasions.
The power factor control device is actually a software architecture, and each module and unit in the power factor control device is a process or program corresponding to the control method. Therefore, the control device will not be described in detail.
The specific embodiments are given above, but the present invention is not limited to the above-described embodiments. The basic idea of the present invention lies in the above basic scheme, and it is obvious to those skilled in the art that no creative effort is needed to design various modified models, formulas and parameters according to the teaching of the present invention. Variations, modifications, substitutions and alterations may be made to the embodiments without departing from the principles and spirit of the invention, and still fall within the scope of the invention.
Claims (6)
1. A power factor control method applied to a converter is characterized in that a reactive power reference value is obtained by controlling a power factor: setting a power factor reference value COS thetarefReference value of power factor COS thetarefAnd actual power factor value COS thetameasObtaining a reactive power reference value Q through PI regulationcosθ_refReference value Q of reactive powercosθ_refWith set value Q of reactive powerac_setAdding the obtained values to obtain a final reactive power reference value Qac_ref_final(ii) a For reactive power reference value Qac_ref_finalAdjusting the constant reactive power to obtain a current reference value;
the reactive power reference value Qcosθ_refBy referencing the power factor to value COS thetarefThe difference with the power factor measured value is obtained by multiplying the power factor measured value by +/-1 through PI regulation, wherein +/-1 is selected from the reactive power measured value Qac_measAnd determining that the inductive power is 1 if the reactive power is detected, and the capacitive power is-1 if the reactive power is detected.
2. The power factor control method applied to the inverter according to claim 1, wherein the reactive power reference value Q is set if the power factor control is not requiredcosθ_refIs reduced to 0.
3. The power factor control method applied to the inverter according to claim 2, wherein the reactive power reference value Q is set if the power factor control is not requiredcosθ_refDecreasing to 0 at a set slope.
4. A power factor control device applied to a converter is characterized by comprising a power factor controller and a reactive power controller, wherein the power factor controller is used for adjusting a power factor to obtain a reactive power reference value: setting a power factor reference value COS thetarefReference value of power factor COS thetarefAnd actual power factor value COS thetameasObtaining a reactive power reference value Q through PI regulationcosθ_refReference value Q of reactive powercosθ_refWith set value Q of reactive powerac_setAdding the obtained values to obtain a final reactive power reference value Qac_ref_finalThe reactive power controller is used for adjusting the reactive power reference value to obtain a current reference value;
in the power factor controller, the reactive power reference value Qcosθ_refBy referencing the power factor to value COS thetarefThe difference with the power factor measured value is obtained by multiplying the power factor measured value by +/-1 through PI regulation, wherein +/-1 is selected from the reactive power measured value Qac_measAnd determining that the inductive power is 1 if the reactive power is detected, and the capacitive power is-1 if the reactive power is detected.
5. The apparatus of claim 4, wherein the reactive power reference value Q is set if the power factor control is not requiredcosθ_refIs reduced to 0.
6. The apparatus of claim 5, wherein the reactive power reference value Q is set if the power factor control is not requiredcosθ_refDecreasing to 0 at a set slope.
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| CN114938039B (en) * | 2022-06-14 | 2023-03-24 | 深圳市优优绿能股份有限公司 | Reactive power regulation method and system for single-phase grid-connected inverter and computer storage medium |
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