CN117039905A - Energy storage device control system with unbalanced voltage compensation function for transformer area - Google Patents
Energy storage device control system with unbalanced voltage compensation function for transformer area 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
- H02J3/12—Circuit arrangements for ac mains or ac distribution networks for adjusting voltage in ac networks by changing a characteristic of the network load
- H02J3/16—Circuit arrangements for ac mains or ac distribution networks for adjusting voltage in ac networks by changing a characteristic of the network load by adjustment of reactive power
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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
- H02J3/26—Arrangements for eliminating or reducing asymmetry in polyphase networks
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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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- 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
- Y02E40/50—Arrangements for eliminating or reducing asymmetry in polyphase networks
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Abstract
The invention discloses a control system of a district energy storage device with an unbalanced voltage compensation function, which belongs to the field of power grid voltage management and comprises a negative sequence voltage loop module, a positive sequence current loop module, a zero sequence voltage loop module and an abc/dq conversion module. The negative sequence voltage loop module and the positive sequence current loop module obtain d and q axis control amounts according to the negative sequence d and q axis voltage reference values and the positive sequence active and reactive power reference values; the zero-sequence current loop module and the zero-sequence voltage loop module determine 0-axis control quantity according to the zero-sequence voltage reference value, and the abc/dq conversion module converts the d-axis control quantity, the q-axis control quantity and the 0-axis control quantity into three-phase modulation waves so as to control the energy storage device. The energy storage device is controlled by the controller through obtaining reactive power and active power reference values for treating low voltage and zero sequence and negative sequence voltage reference values for treating unbalance, so that the degree of low voltage or three-phase unbalance of the voltage at the tail end of the power grid is reduced.
Description
Technical Field
The invention belongs to the field of power grid voltage management, and particularly relates to a control system of a district energy storage device with an unbalanced voltage compensation function.
Background
In the existing power grid, the distribution transformer is in an asymmetric running state due to unbalanced three-phase load. When the distribution transformer is in an asymmetric running state, unbalanced three-phase voltage can cause the increase of loss of the transformer, overlarge zero sequence current and increase of local metal part temperature rise, and even the transformer is burnt out, so that the safe running of a power system is seriously threatened.
The treatment method aiming at low voltage is based on the static reactive compensator to carry out treatment, and can realize voltage compensation under the condition that the impedance of the line is inductive, but the treatment effect of the power grid of the transformer area aiming at the characteristic that the line is resistive is not ideal.
The control method for unbalance is to control based on load current detection, and balance of three-phase voltage is realized by compensating load unbalance current. However, the scheme can only be installed at the head end of the transformer area to detect three-phase load current, and cannot give consideration to low voltage at the tail end of the transformer area.
In summary, the existing voltage unbalance management has the defect that the low voltage and the three-phase unbalance cannot be managed simultaneously.
Disclosure of Invention
The invention aims to provide a control system of a district energy storage device with an unbalanced voltage compensation function, which is used for solving the technical problem that the treatment of voltage unbalance in the prior art cannot be realized at the same time as the treatment of low voltage and the treatment of three-phase unbalance.
In order to achieve the above purpose, the technical scheme of the control system of the energy storage device of the transformer area with the unbalanced voltage compensation function provided by the invention is as follows:
a control system of a district energy storage device with an unbalanced voltage compensation function comprises a negative sequence voltage loop module, a positive sequence current loop module, a negative sequence current loop module, a zero sequence voltage loop module and an abc/dq conversion module; the negative sequence voltage loop module takes negative sequence d and q axis voltages and negative sequence d and q axis voltage reference values based on the tail end of the platform area as input, and outputs a negative sequence alpha axis current reference value and a negative sequence beta axis current reference value after PI regulation and inverse park transformation; the positive and negative sequence current loop module takes d and q axis induction current reference values and d and q axis induction currents as input, outputs the d and q axis induction current reference values through PI regulation and PR control, and determines d axis control quantity and q axis control quantity by utilizing the output, positive sequence d and q axis voltages and d and q axis induction voltage crossover operators, wherein the d and q axis induction current reference values are determined by the output of the negative sequence voltage loop module and positive sequence active power reference values and negative sequence reactive power reference values respectively; the zero-sequence voltage ring module takes the zero-sequence voltage and the zero-sequence voltage reference value as input and outputs the zero-sequence current reference value through PR control; the zero sequence current loop module takes the output of the zero sequence voltage loop module as input, outputs a three-time zero sequence current reference value through PR control, and determines a 0-axis control quantity according to the output; the abc/dq conversion module converts the d-axis control quantity, the q-axis control quantity and the 0-axis control quantity into three-phase modulation waves, so that the control of the energy storage device is realized.
The beneficial effects are that: the control system comprises a negative sequence voltage loop module, a positive sequence current loop module, a negative sequence current loop module, a zero sequence voltage loop module, an abc/dq conversion module and an overload wave stacking module. The negative sequence voltage loop module and the positive sequence current loop module determine d and q axis control amounts according to the negative sequence d and q axis voltage reference values and the positive sequence active and reactive power reference values; the zero-sequence current loop module and the zero-sequence voltage loop module determine 0-axis control quantity according to the zero-sequence voltage reference value, and the abc/dq conversion module converts the d-axis control quantity, the q-axis control quantity and the 0-axis control quantity into three-phase modulation waves to control the energy storage device. According to the technical scheme, reactive power and active power reference values for treating low voltage and zero sequence voltage reference values and negative sequence voltage reference values for treating three-phase imbalance are obtained simultaneously, and an abc/dq conversion module converts d-axis control quantity, q-axis control quantity and 0-axis control quantity into three-phase modulation waves so as to control an energy storage device, so that the low voltage or the three-phase imbalance degree of the voltage at the tail end of a power grid is eliminated or relieved.
As a further improvement, the device also comprises a midpoint potential control module, wherein the midpoint potential control module takes the negative value of the bus voltage difference as input and adjusts and outputs a midpoint current reference value through PI; and determining the 0-axis control quantity by using the output and the output of the zero-sequence current loop module.
The beneficial effects are that: the neutral current potential control module converts the bus voltage difference into a neutral current reference value, and the reference value and the input of the zero sequence current loop module are utilized to determine the 0-axis control quantity.
As a further improvement, the determination basis of the d-axis control amount and the q-axis control amount is: the d-axis control quantity is determined by the positive sequence d-axis voltage, the PI regulated d-axis voltage output by the positive sequence current loop and the positive sequence current loop, and the difference value between the PR controlled d-axis voltage and the q-axis inductance voltage; the q-axis control quantity is determined by the positive sequence q-axis voltage, the q-axis voltage after PI adjustment output by the positive sequence current loop and the positive sequence current loop, and the difference value between the q-axis voltage and the d-axis inductance voltage after PR control.
As a further improvement, the process of obtaining the negative sequence voltage reference value and the zero sequence voltage reference value is as follows: the acquisition process of the negative sequence d, q axis voltage reference value and the zero sequence voltage reference value comprises the following steps: acquiring the negative sequence d and q axis inductance voltage of the power grid terminal voltage; when the negative sequence d-axis voltage is not equal to 0, determining a negative sequence d-axis voltage reference value by utilizing the negative sequence d-axis current, the negative sequence virtual impedance and the q-axis inductance voltage, so as to reduce the negative sequence d-axis voltage; when the negative sequence q-axis voltage is not equal to 0, determining a negative sequence q-axis voltage reference value by utilizing the negative sequence q-axis current, the negative sequence virtual impedance and the d-axis inductance voltage, so as to reduce the negative sequence q-axis voltage; when the zero sequence voltage is not equal to 0, the zero sequence current and the zero sequence virtual impedance and the zero sequence inductance voltage are utilized to determine the zero sequence voltage reference value, so that the zero sequence voltage is reduced.
The beneficial effects are that: the end voltage of a normal power grid should only have positive sequence voltage, if the existence of zero sequence or negative sequence voltage indicates that the end voltage is unbalanced, the end voltage needs to be balanced by eliminating the zero sequence and the negative sequence as much as possible. The problem of unbalanced terminal voltage is solved through the calculation, and the safety of the power grid is ensured.
As a further improvement, the calculation formula of the negative sequence d-axis voltage reference value and the negative sequence Q-axis voltage reference value is as follows:
wherein u is dn_ref Is a negative sequence d-axis voltage reference value, u qn_ref Is a negative sequence q-axis voltage reference value, R n i dn Is negative-sequence d-axis virtual impedance, R n i qn Negative sequence q-axis virtual impedance ωL n i qn For q-axis inductance voltage ωL n i dn Is the d-axis inductance voltage.
The beneficial effects are that: the negative sequence d-axis voltage reference value and the negative sequence q-axis voltage reference value are calculated through the formula, and data guidance is provided for eliminating the negative sequence voltage.
As a further improvement, the zero sequence voltage reference value is equal to the sum of the zero sequence d-axis voltage and the zero sequence Q-axis voltage, and the calculation formula of the zero sequence d-axis voltage and the zero sequence Q-axis voltage is as follows:
wherein u is dz_ref To increase the zero sequence d-axis voltage after the zero sequence virtual impedance, u qz_ref To increase zero sequence virtual impedance, the zero sequence q-axis voltage is R z i dz Is zero sequence d-axis virtual impedance, R z i qz Zero sequence q-axis virtual impedance ωL z i qz For zero sequence q-axis voltage ωL z i dz Is zero sequence d-axis voltage.
The beneficial effects are that: and calculating a zero sequence d-axis voltage reference value and a zero sequence q-axis voltage reference value through the formula to provide data support for acquiring the zero sequence voltage reference value.
As a further improvement, the process of obtaining the positive sequence reactive power and the positive sequence active power is as follows: when the positive sequence voltage is smaller than the set voltage compensation value, determining positive sequence active power according to the positive sequence voltage and the set voltage compensation value, and controlling the discharge to raise the power grid voltage by utilizing the positive sequence active power; when the positive sequence voltage is larger than the set voltage discharge value, determining positive sequence reactive power according to the positive sequence voltage and the set voltage discharge value, and controlling charging by utilizing the positive sequence reactive power to reduce the power grid voltage; the set voltage compensation value is smaller than the set voltage discharge value.
The beneficial effects are that: when the terminal voltage is too high or too low, the damage to the power grid can be generated, so that the corresponding active or reactive power is calculated according to the difference value between the voltage and the set voltage compensation value or the set voltage discharge value, the terminal voltage is raised or lowered, and the hidden danger of the too high or too low voltage is eliminated.
As a further improvement, the calculation equation for the positive sequence active power and the positive reactive power is as follows:
wherein P is ref Is positive order active power, K p Is a constant power factor, U gp Is of positive sequence voltage, U set To set the voltage compensation value, U char To set a voltage discharge value.
Wherein P is ref Is positive order active power, K p Is of constant power factor, K pf To set the power factor, U gp Is of positive sequence voltage, U set To set the voltage compensation value, U char To set a voltage discharge value.
The beneficial effects are that: to eliminate the potential hazard of too high or too low voltage, a data base is provided.
As a further improvement, the process of determining d and q-axis induction current reference values by the output of the negative sequence voltage loop module and the reference value of positive sequence active power reference value and positive sequence reactive power reference value respectively comprises the following steps: dividing the positive sequence active power reference value by the positive sequence d-axis voltage to obtain a positive sequence d-axis current reference value, and determining a d-axis inductance current reference value by the positive sequence d-axis current reference value and the negative sequence alpha-axis current reference value; the positive sequence reactive power reference value is divided by the positive sequence d-axis voltage to obtain a positive sequence q-axis current reference value, and the positive sequence q-axis current reference value and the negative sequence beta-axis current reference value determine a q-axis inductance current reference value.
The beneficial effects are that: the reference value of the positive sequence active power and the reference value of the positive sequence reactive power can be better integrated into the control, and the problem of low voltage of the end voltage of the power grid can be solved by the shift length through the processing.
As a further improvement, the inverse park transformation of the negative sequence voltage loop module is a double frequency inverse park transformation; PR control of the positive and negative sequence current loop module is 2 PR control times.
Drawings
FIG. 1 is a schematic diagram of a main circuit topology at a grid terminal voltage in a district energy storage device control system with unbalanced voltage compensation according to the present invention;
FIG. 2 is a control block diagram of a control system for a district energy storage device with unbalanced voltage compensation according to the present invention;
FIG. 3a is a schematic block diagram of active power of a control system of a district energy storage device with unbalanced voltage compensation according to the present invention;
FIG. 3b is a schematic block diagram of a low reactive power system for a district energy storage device control system with unbalanced voltage compensation according to the present invention;
FIG. 4 is a control block diagram of the alpha beta component method of the energy storage device control system with unbalanced voltage compensation function according to the present invention;
FIG. 5 is a schematic block diagram of negative sequence d, q axis voltage references of a control system of a district energy storage device with unbalanced voltage compensation function according to the present invention;
FIG. 6 is a schematic block diagram of a zero sequence voltage reference value of the energy storage device control system with unbalanced voltage compensation function according to the present invention;
FIG. 7a is a schematic diagram of a waveform of an unbalanced grid voltage before compensation of a district energy storage device control system with an unbalanced voltage compensation function according to the present invention;
FIG. 7b is a schematic diagram of a compensated balanced current waveform of the system for controlling a district energy storage device with unbalanced voltage compensation according to the present invention;
FIG. 8a is a schematic diagram of a waveform of a grid voltage of a low voltage prior to compensation of a district energy storage device control system with unbalanced voltage compensation according to the present invention;
fig. 8b is a schematic diagram of a compensated normal current waveform of the energy storage device control system with unbalanced voltage compensation according to the present invention.
Detailed Description
The present invention will be described in further detail with reference to the drawings and examples, in order to make the objects, technical solutions and advantages of the present invention more apparent. It should be understood that the particular embodiments described herein are illustrative only and are not intended to limit the invention, i.e., the embodiments described are merely some, but not all, of the embodiments of the invention. The components of the embodiments of the present invention generally described and illustrated in the figures herein may be arranged and designed in a wide variety of different configurations.
An embodiment of a control system of a district energy storage device with an unbalanced voltage compensation function is provided:
FIG. 1 shows a main circuit topology of the energy storage device of the present invention, L 1 For the inversion side filter inductance L 2 For the filter inductance of the net side, C f For filtering the capacitor bank, Z g I is the equivalent impedance of the power grid La 、i Lb 、i Lc For inductive current, i a 、i b 、i c Respectively three-phase grid-connected current, u ga 、u gb 、u gc Is the three-phase network phase voltage. In order to solve the problem of unbalanced three-phase voltage of the energy storage device of the transformer area, namely the end voltage of the power grid, a transformer area energy storage device control system with an unbalanced voltage compensation function is provided. The method comprises the following steps:
in the figure, u as shown in figure 2 dp 、u qp 、u dn 、u qn 、u z Respectively the positive sequence d-axis component and the positive sequence d-axis component of the power grid voltageSequence q-axis component, negative sequence d-axis component, negative sequence q-axis component and zero sequence voltage, P P_ref 、Q P_ref Respectively positive-sequence active power and positive-sequence reactive power reference values, u dn_ref 、u qn_ref 、u z_ref Respectively refers to a negative sequence d-axis, a negative sequence q-axis and a zero sequence voltage command, i dp_ref 、i qp_ref 、i dn_ref 、i qn_ref 、i z_ref Respectively positive sequence d-axis, positive sequence q-axis, negative sequence d-axis, negative sequence q-axis and zero sequence current instruction, i Ld 、i Lq 、i Lz Respectively the d-axis, q-axis and zero sequence components of the inductance current, delta u dc Is the voltage difference between the upper bus and the lower bus. The control system of the energy storage device of the district with unbalanced voltage compensation function comprises: the system comprises a negative sequence voltage loop module, a positive and negative sequence current loop module, a zero sequence current loop module, a midpoint potential control module, a zero sequence voltage loop module, a midpoint potential control module and an abc/dq conversion module.
The negative sequence voltage ring module is a negative sequence voltage ring module based on PI regulator and negative sequence double frequency inverse park conversion and is used for controlling the negative sequence component in the three-phase voltage.
The positive and negative sequence current loop module is based on PI and 2 PR control; the PI regulator is used for controlling a direct current positive sequence component obtained after abc/dq conversion in the inductor current, and the 2-time PR regulator is used for controlling a double frequency alternating current negative sequence component obtained after abc/dq conversion in the inductor current.
The zero sequence current loop module is a zero sequence voltage loop module based on primary PR control; the method is used for controlling zero sequence components in the three-phase power grid voltage.
The zero sequence current loop module is based on 1 PR and 3 PR zero sequence current loop modules, wherein 1 PR is used for tracking fundamental wave components, and 3 PR is used for eliminating three components in zero sequence current under unbalanced power grid voltage.
The midpoint point position control is based on the midpoint point position control of the PI regulator, and midpoint potential balance is ensured.
The specific steps for controlling the end voltage of the power grid through the steps are as follows:
1) Detecting positive sequence d-axis voltage, positive sequence q-axis voltage, negative sequence d-axis voltage, negative sequence q-axis voltage, zero sequence voltage and bus voltage difference of the terminal voltage of the transformer area, and obtaining positive sequence active power reference value, positive sequence reactive power reference value, negative sequence d-axis voltage reference value, negative sequence q-axis voltage reference value and zero sequence voltage reference value of the terminal voltage of the transformer area.
The process for obtaining the positive sequence reactive power and the positive sequence active power comprises the following steps: when the positive sequence voltage is smaller than the set voltage compensation value, positive sequence active power is determined according to the positive sequence voltage and the set voltage compensation value, and the positive sequence active power is used for controlling the discharge to raise the power grid voltage. And when the positive sequence voltage is larger than the set voltage discharge value, determining positive sequence reactive power according to the positive sequence voltage and the set voltage discharge value, and controlling charging by utilizing the positive sequence reactive power to reduce the power grid voltage. The set voltage compensation value is smaller than the set voltage discharge value. As shown in fig. 3a and 3b, the positive-sequence active power reference value is P P-ref The reference value of the positive sequence reactive power is Q P-ref Wherein u is set U is set for the voltage compensation target of the power grid char To allow the charging voltage set point, P limit For active power limit, Q limit For reactive power limit, U gp Is a positive sequence voltage.
Specifically, the equation for calculating the positive-order active power is as follows:
wherein P is ref Is positive order active power, K p Is a constant power factor, U gp Is of positive sequence voltage, U set To set the voltage compensation value, U char To set a voltage discharge value.
The reactive power calculation formula is as follows:
wherein P is ref Is positive order active power, K p Is a constant power factorNumber, K pf To set the power factor, U gp Is of positive sequence voltage, U set To set the voltage compensation value, U char To set a voltage discharge value.
The acquisition process of the negative sequence voltage reference value and the zero sequence voltage reference value comprises the following steps: and acquiring q-axis inductance voltage and d-axis inductance voltage of the end voltage of the power grid. When the negative sequence d-axis voltage is not equal to 0, determining a negative sequence d-axis voltage reference value by using the negative sequence d-axis current, the negative sequence d-axis virtual impedance negative sequence and the d-axis inductance voltage, so as to reduce the negative sequence voltage; when the negative sequence q-axis voltage is not equal to 0, determining a negative sequence q-axis voltage reference value by using the negative sequence q-axis current, the negative sequence q-axis virtual impedance and the q-axis inductance voltage, thereby reducing the negative sequence voltage. When the zero sequence voltage is not equal to 0, the zero sequence current and the zero sequence virtual impedance and the zero sequence inductance voltage are utilized to determine the zero sequence voltage reference value, so that the zero sequence voltage is reduced.
Specifically, as shown in FIG. 5, the negative sequence current d and q-axis current pass through virtual impedance to obtain d and q-axis voltage drop Deltau dn And Deltau qn Negative sequence voltage reference 0 minus deltau dn And Deltau qn Then obtaining the negative sequence d and q axis voltage reference value u dn_ref And u qn_ref . The calculation formulas of the negative sequence d-axis voltage reference value and the negative sequence Q-axis voltage reference value are as follows:
wherein u is dn_ref Is a negative sequence d-axis voltage reference value, u qn_ref Is a negative sequence q-axis voltage reference value, R n i dn Is negative-sequence d-axis virtual impedance, R n i qn Negative sequence q-axis virtual impedance ωL n i qn For q-axis inductance voltage ωL n i dn Is the d-axis inductance voltage.
As shown in fig. 6, the zero-sequence current is passed through an all-pass filter to obtain a virtual beta-axis component, the virtual impedance is increased by inverse Park transformation, and finally the voltage drop deltau is obtained dz And Deltau qz Alpha-axis component of zero sequence virtual impedance voltage drop obtained by coordinate transformation of componentsQuantity Deltau αz Zero sequence voltage reference 0 minus deltau αz Zero sequence voltage reference value u z_ref 。
The zero sequence voltage reference value is equal to the sum of the zero sequence d-axis voltage and the zero sequence Q-axis voltage. The calculation formulas of the zero sequence d-axis voltage and the zero sequence Q-axis voltage are as follows:
wherein u is dz_ref Is zero sequence d-axis voltage reference value, u qz_ref Is zero sequence q axis voltage reference value, R z i dz Is zero sequence d-axis virtual impedance, R z i qz Zero sequence q-axis virtual impedance ωL z i qz For zero sequence q-axis voltage ωL z i dz Is zero sequence d-axis voltage.
After the data of the positive sequence active power reference value, the positive sequence reactive power reference value, the negative sequence d-axis voltage reference value, the negative sequence q-axis voltage reference value and the zero sequence voltage reference value are obtained, the data are used for regulating the end voltage of the power grid, so that the end voltage of the power grid reaches an equilibrium state.
2) The negative sequence voltage loop module and the positive sequence current loop module determine d and q axis control quantities Td and Tq according to the negative sequence d and q axis voltage reference values and the positive sequence active and reactive power reference values.
In which the d-axis control amount and the q-axis control amount are determined in a similar manner, the d-axis control amount is taken as an example, and the negative sequence voltage loop module is based on the negative sequence d-axis voltage U at the end of the region as shown in FIG. 2 dn And negative sequence d-axis voltage reference value U dn-ref The difference of the two is taken as input, and i is obtained through PI adjustment dn-ref ，i dn-ref After reverse park transformation, negative sequence alpha-axis current reference value i is output nα-ref 。
The positive and negative sequence current loop module refers to the d-axis inductance current reference value i Ld-ref With d-axis inductance current i Ld The difference is taken as an input, output is performed through PI regulation and PR control, and the output and positive sequence d-axis voltage U are utilized dp And q-axis inductance voltage ωLi Lq Determining a d-axis control quantity Td, the d-inductance current reference value i Ld-ref From output i of negative sequence voltage loop module nα-ref And positive sequence active power reference value P p-ref Determining; specifically, positive sequence active power reference value P p-ref Divided by positive sequence d-axis voltage U dp Obtaining a positive sequence d-axis current reference value i Ldp-ref Positive sequence d-axis current reference i Ldp-ref And negative sequence alpha-axis current reference value i nα-ref Determining d-axis inductance current reference value i Ld-ref 。
Wherein u is at the time of abc/dq transformation as shown in FIG. 4 α And u β Respectively the alpha beta component and the u component of the power grid voltage α_P 、u β_P 、u α_N 、u β_N U respectively α And u β The corresponding positive and negative sequence components, i.e., the process of converting the alpha and beta axes into corresponding positive and negative sequence data, are shown.
3) And the midpoint potential control module, the zero-sequence current loop module and the zero-sequence voltage loop module determine a 0-axis control quantity To according To the zero-sequence voltage reference value.
Next, as shown in fig. 2, the zero sequence voltage loop module will zero sequence voltage U z And zero sequence voltage reference value u z_ref d is used as input, and the zero sequence current reference value i is output through PR control z_ref . Zero sequence current loop module will i z_ref And i Lz And outputting a three-time zero sequence current reference value through PR control. The neutral point potential control module controls the bus voltage difference delta u dc Takes as input the negative value of (c), and the output midpoint current reference value is adjusted through PI. And determining the 0-axis control quantity by using the output and the output of the zero-sequence current loop module.
4) Finally, the abc/dq conversion module converts the d-axis control quantity, the q-axis control quantity and the 0-axis control quantity into three-phase modulation waves, and the energy storage device is controlled by the three-phase modulation waves to regulate the state of the end voltage of the power grid.
The positive sequence d-axis voltage, the positive sequence q-axis voltage, the negative sequence d-axis voltage and the negative sequence q-axis voltage component have the same meaning as the positive sequence d-axis component, the positive sequence q-axis component, the negative sequence d-axis component and the negative sequence q-axis component. The instruction data mentioned by the partial data has the same meaning as the corresponding reference value data.
The invention is characterized in thatThe invention also has better effect in practical application, as shown in fig. 7a and 7b, and is an unbalanced voltage treatment RTDS experimental waveform adopting the compensation method provided by the invention. It can be seen that the three-phase network phase voltage u before the compensation method is put into operation a 、u b 、u c Peak values are 255 v,320v,326v, respectively; after 3.6s of the compensation method, the phase voltage u of the three-phase power grid a 、u b 、u c The peak changes were 315v,316v,321v. The compensation algorithm can effectively reduce the voltage unbalance of the three-phase power grid.
Similarly, as shown in fig. 8a and 8b, the RTDS test waveforms for the low voltage governance using the control and system according to the present invention are shown. It can be seen that the three-phase network phase voltage u before the compensation method is put into operation a 、u b 、u c Peak values are 314v,316v,322v, respectively; after 1.1s of the compensation method is put into, the phase voltage u of the three-phase power grid a 、u b 、u c The peak values are changed to 322V,323V and 330V respectively, so that the compensation of the voltages of the phases is realized.
It should be noted that the above-mentioned embodiments are merely preferred embodiments of the present invention, and the present invention is not limited to the above-mentioned embodiments, but may be modified without inventive effort or equivalent substitution of some of the technical features thereof by those skilled in the art. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present invention should be included in the protection scope of the present invention.
Claims (10)
1. The control system is characterized by comprising a negative sequence voltage loop module, a positive sequence current loop module, a negative sequence current loop module, a zero sequence voltage loop module and an abc/dq conversion module;
the negative sequence voltage loop module takes negative sequence d and q axis voltages and negative sequence d and q axis voltage reference values based on the tail end of the platform area as input, and outputs a negative sequence alpha axis current reference value and a negative sequence beta axis current reference value after PI regulation and inverse park transformation; the positive and negative sequence current loop module takes d and q axis induction current reference values and d and q axis induction currents as input, outputs the d and q axis induction current reference values through PI regulation and PR control, and determines d axis control quantity and q axis control quantity by utilizing the output, positive sequence d and q axis voltages and d and q axis induction voltage crossover operators, wherein the d and q axis induction current reference values are determined by the output of the negative sequence voltage loop module and positive sequence active power reference values and negative sequence reactive power reference values respectively;
the zero-sequence voltage ring module takes the zero-sequence voltage and the zero-sequence voltage reference value as input and outputs the zero-sequence current reference value through PR control; the zero sequence current loop module takes the output of the zero sequence voltage loop module as input, outputs a three-time zero sequence current reference value through PR control, and determines a 0-axis control quantity according to the output;
the abc/dq conversion module converts the d-axis control quantity, the q-axis control quantity and the 0-axis control quantity into three-phase modulation waves, so that the control of the energy storage device is realized.
2. The control system of a district energy storage device with unbalanced voltage compensation function according to claim 1, further comprising a midpoint potential control module, wherein the midpoint potential control module takes a negative value of a bus voltage difference as an input, and outputs a midpoint current reference value through PI adjustment; and determining the 0-axis control quantity by using the output and the output of the zero-sequence current loop module.
3. The control system of a district energy storage device with unbalanced voltage compensation function according to claim 1, wherein the determination basis of the d-axis control amount and the q-axis control amount is: the d-axis control quantity is determined by the positive sequence d-axis voltage, the PI regulated d-axis voltage output by the positive sequence current loop and the positive sequence current loop, and the difference value between the PR controlled d-axis voltage and the q-axis inductance voltage;
the q-axis control quantity is determined by the positive sequence q-axis voltage, the q-axis voltage after PI adjustment output by the positive sequence current loop and the positive sequence current loop, and the difference value between the q-axis voltage and the d-axis inductance voltage after PR control.
4. The system according to claim 1, wherein the process of obtaining the negative sequence d, q axis voltage reference value and the zero sequence voltage reference value is: acquiring the negative sequence d and q axis inductance voltage of the power grid terminal voltage;
when the negative sequence d-axis voltage is not equal to 0, determining a negative sequence d-axis voltage reference value by utilizing the negative sequence d-axis current, the negative sequence virtual impedance and the q-axis inductance voltage, so as to reduce the negative sequence d-axis voltage;
when the negative sequence q-axis voltage is not equal to 0, determining a negative sequence q-axis voltage reference value by utilizing the negative sequence q-axis current, the negative sequence virtual impedance and the d-axis inductance voltage, so as to reduce the negative sequence q-axis voltage;
when the zero sequence voltage is not equal to 0, the zero sequence current and the zero sequence virtual impedance and the zero sequence inductance voltage are utilized to determine the zero sequence voltage reference value, so that the zero sequence voltage is reduced.
5. The system according to claim 4, wherein the negative sequence d-axis voltage reference value and the negative sequence q-axis voltage reference value are calculated as follows:
wherein u is dn_ref Is a negative sequence d-axis voltage reference value, u qn_ref Is a negative sequence q-axis voltage reference value, R n i dn Is negative-sequence d-axis virtual impedance, R n i qn Negative sequence q-axis virtual impedance ωL n i qn For q-axis inductance voltage ωL n i dn Is the d-axis inductance voltage.
6. The system according to claim 4, wherein the zero sequence voltage reference value is equal to a sum of a zero sequence d-axis voltage and a zero sequence q-axis voltage, and the calculation formula of the zero sequence d-axis voltage and the zero sequence q-axis voltage is as follows:
wherein u is dz_ref To increase the zero sequence d-axis voltage after the zero sequence virtual impedance, u qz_ref To increase zero sequence virtual impedance, the zero sequence q-axis voltage is R z i dz Is zero sequence d-axis virtual impedance, R z i qz Zero sequence q-axis virtual impedance ωL z i qz For zero sequence q-axis voltage ωL z i dz Is zero sequence d-axis voltage.
7. The control system of a district energy storage device with unbalanced voltage compensation function according to claim 1, wherein the process of obtaining positive-sequence reactive power and positive-sequence active power is: when the positive sequence voltage is smaller than the set voltage compensation value, determining positive sequence active power according to the positive sequence voltage and the set voltage compensation value, and controlling the discharge to raise the power grid voltage by utilizing the positive sequence active power;
when the positive sequence voltage is larger than the set voltage discharge value, determining positive sequence reactive power according to the positive sequence voltage and the set voltage discharge value, and controlling charging by utilizing the positive sequence reactive power to reduce the power grid voltage;
the set voltage compensation value is smaller than the set voltage discharge value.
8. The system of claim 7, wherein the equation for calculating the positive sequence active power and the positive reactive power is as follows:
wherein P is ref Is positive order active power, K p Is a constant power factor, U gp Is of positive sequence voltage, U set To set the voltage compensation value, U char Setting a voltage discharge value;
wherein P is ref Is positive order active power, K p Is of constant power factor, K pf To set the power factor, U gp Is of positive sequence voltage, U set To set the voltage compensation value, U char To set a voltage discharge value.
9. The control system of a district energy storage device with unbalanced voltage compensation function according to any one of claims 1 to 8, wherein the d, q axis inductor current reference value is: dividing the positive sequence active power reference value by the positive sequence d-axis voltage to obtain a positive sequence d-axis inductance current reference value, wherein the sum of the positive sequence d-axis inductance current reference value and the negative sequence alpha-axis current reference value is the d-axis inductance current reference value; the positive sequence reactive power reference value is divided by the positive sequence d-axis voltage to obtain a positive sequence q-axis current reference value, and the positive sequence q-axis current reference value and the negative sequence beta-axis current reference value determine a q-axis inductance current reference value.
10. The control system of a district energy storage device with unbalanced voltage compensation function according to any one of claims 1 to 8, wherein the inverse park transformation of the negative sequence voltage loop module is a double frequency inverse park transformation; PR control of the positive and negative sequence current loop module is 2 PR control times.
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