CN115642599B - Harmonic current suppression method, control device and power generation system - Google Patents
Harmonic current suppression method, control device and power generation system Download PDFInfo
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- 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
- Y02E40/40—Arrangements for reducing harmonics
Abstract
The invention discloses a harmonic current suppression method, a control device and a power generation system, relates to the field of harmonic suppression of power generation systems, and aims to obtain three-phase bridge arm current and three-phase capacitor voltage, further determine two-axis reference current and two-axis reference voltage, extract harmonic current according to the two-axis reference current and a preset harmonic current compensation strategy, determine two-axis harmonic current compensation quantity for harmonic compensation, feed the two-axis harmonic current compensation quantity into control over a controllable switch module, and determine three-phase control signals output to the controllable switch module based on power grid angular frequency, power grid voltage phase, two-axis reference current, two-axis reference voltage, two-axis harmonic current compensation quantity and a preset current loop control strategy. Therefore, harmonic current is extracted based on the three-phase bridge arm current and fed back to the three-phase control signal to realize harmonic current compensation, so that the harmonic current can be inhibited from being fed into a power grid, SVG or a current sensor for collecting capacitance current is not needed, the cost is saved, and the harmonic treatment cost of the whole power generation system is reduced.
Description
Technical Field
The invention relates to the technical field of harmonic suppression of power generation systems, in particular to a harmonic current suppression method, a control device and a power generation system.
Background
The grid-connected inverter is widely applied to the field of photovoltaic power generation, and specifically, please refer to fig. 1, where fig. 1 is a schematic structural diagram of a power generation system using the grid-connected inverter in the prior art. In fig. 1, the Direct current output by the photovoltaic array sequentially passes through a multi-path unidirectional DC-DC converter (Direct current-Direct current), a photovoltaic grid-connected inverter, an LCL filter circuit (the LCL filter circuit includes bridge side inductors La, lb, and Lc, middle capacitor branches Ca, cb, and Cc, and grid side inductors Lsa, lsb, and Lsc), and the filtered three-phase alternating current is transmitted to the secondary side of the transformer, and then is coupled to the source side of the transformer by the secondary side of the transformer, and finally fed into the power grid.
No matter the inverter is a photovoltaic grid-connected inverter or an energy storage grid-connected inverter, the inverter comprises an inverter circuit consisting of a plurality of switching tubes, and alternating current obtained by inversion is matched with an LCL filter circuit for filtering. In the grid-connected process, because of the existence of the LCL resonant peak, harmonic current near a resonant point frequency band can appear, and in order to inhibit the harmonic current from being fed into a power grid, the following modes are mainly adopted in the prior art:
the first method is to deploy a Static Var Generator (SVG) at the public end of the power grid at the source side of the transformer, but the price of the SVG itself is very high, which increases the cost of the whole power generation system; in addition, in the method, the current of the corresponding position of the secondary side of the transformer needs to be collected and transmitted to the SVG, but in a production field, the distance between the secondary side and the source side of the transformer is far, usually about 2 kilometers, and a sampling circuit is difficult to arrange, so that the use of the method is limited.
The second mode is that on the basis of collecting bridge arm side currents ia, ib and ic and capacitor branch circuit voltages Va, vb and Vc, three current sensors are additionally arranged and are respectively used for collecting a current ica flowing through a capacitor Ca, a current icb flowing through a capacitor Cb and a current icc flowing through a capacitor Cc on a capacitor branch circuit, harmonic current compensation is realized by using the currents ica, icb and icc on the capacitor branch circuit, and a PWM control signal output to a switching tube in the inverter circuit by a PWM controller is determined based on the 6 current values and the 3 voltage values in cooperation with a corresponding control strategy, but the additionally arranged current sensors still increase the cost of the whole power generation system and are not beneficial to practical application.
Therefore, how to provide a solution to the above technical problem is a problem that needs to be solved by those skilled in the art.
Disclosure of Invention
The invention aims to provide a harmonic current suppression method, a control device and a power generation system, wherein harmonic current is extracted based on three-phase bridge arm current and fed back to a three-phase control signal to realize harmonic current compensation, so that harmonic current can be favorably suppressed and fed into a power grid, SVG with higher price is not needed, a current sensor for collecting capacitance current in a filter module is not needed to be additionally arranged, the cost is saved, the investment cost and the maintenance cost of harmonic management of the whole power generation system are also reduced, the market competitiveness is improved, and the practical application is facilitated.
In order to solve the above technical problem, the present invention provides a harmonic current suppression method, which is applied to a control module in a power generation system, wherein the power generation system further includes a direct current output device, a grid-connected inverter, a filtering module and a transformer, which are sequentially connected, the grid-connected inverter includes a controllable switch module, the controllable switch module is connected with the control module, and the harmonic current suppression method includes:
obtaining three-phase bridge arm current corresponding to bridge arm side inductance in the filtering module;
acquiring three-phase capacitor voltage corresponding to a capacitor in the filtering module;
determining the angular frequency and the voltage phase of the power grid according to the three-phase capacitor voltage;
determining two-axis reference currents corresponding to the three-phase bridge arm currents and two-axis reference voltages corresponding to the three-phase capacitor voltages based on the power grid voltage phase, the three-phase bridge arm currents, the three-phase capacitor voltages and a preset coordinate transformation strategy;
extracting harmonic current according to the two-axis reference current and a preset harmonic current compensation strategy to determine two-axis harmonic current compensation quantity;
and determining a three-phase control signal for outputting to the controllable switch module based on the power grid angular frequency, the power grid voltage phase, the two-axis reference current, the two-axis reference voltage, the two-axis harmonic current compensation quantity and a preset current loop control strategy.
Preferably, the two-axis reference voltage comprises a d-axis reference voltage and a q-axis reference voltage; the two-axis harmonic current compensation quantity comprises a d-axis harmonic current compensation quantity and a q-axis harmonic current compensation quantity;
determining a three-phase control signal for outputting to the controllable switch module based on the power grid angular frequency, the power grid voltage phase, the two-axis reference current, the two-axis reference voltage, the two-axis harmonic current compensation amount and a preset current loop control strategy, including:
determining the d-axis actual control output quantity based on the power grid angular frequency, the two-axis reference current, the d-axis reference voltage, the inductance value of the bridge arm side inductor, the d-axis harmonic current compensation quantity and a preset d-axis current loop control strategy;
determining a q-axis actual control output quantity based on the power grid angular frequency, the two-axis reference current, the q-axis reference voltage, the inductance value, the q-axis harmonic current compensation quantity and a preset q-axis current loop control strategy;
inputting the d-axis actual control output quantity, the q-axis actual control output quantity and the power grid voltage phase as input items into a pre-designed dq-abc conversion model to obtain an a-phase duty ratio, a b-phase duty ratio and a c-phase duty ratio output by the dq-abc conversion model;
and determining an a-phase PWM signal, a b-phase PWM signal and a c-phase PWM signal which are output to the controllable switch module based on the a-phase duty ratio, the b-phase duty ratio and the c-phase duty ratio.
Preferably, the two-axis reference current includes a d-axis reference current and a q-axis reference current;
determining the actual d-axis control output quantity based on the power grid angular frequency, the two-axis reference current, the d-axis reference voltage, the inductance value of the bridge arm side inductor, the d-axis harmonic current compensation quantity and a preset d-axis current loop control strategy, wherein the determining step comprises the following steps:
inputting a d-axis current deviation value as an input item to a pre-designed d-axis current regulating module, and taking an output item of the d-axis current regulating module as a d-axis original control output value, wherein the d-axis current deviation value is a difference value between a d-axis preset reference current and a d-axis reference current;
determining a d-axis regulation control output quantity based on a first preset relational expression, the d-axis original control output quantity, the d-axis reference voltage serving as a first voltage feedforward, the power grid angular frequency, the inductance value of the bridge arm side inductor and the q-axis reference current;
the first preset relational expression is as follows:
wherein the content of the first and second substances,
adjusting a control output for the d-axis>
For the d-axis reference voltage, < >>
For said d-axis original control output amount>
Reference current for the q axis->
For the grid angular frequency->
An inductance value of the bridge arm side inductor;
and determining the difference value between the d-axis adjusting control output quantity and the d-axis harmonic current compensation quantity as a d-axis actual control output quantity.
Preferably, the method further comprises the following steps:
acquiring direct-current voltage output to the grid-connected inverter by the direct-current output device;
the step of determining the d-axis preset reference current comprises the following steps:
and inputting a voltage deviation amount as an input item to a pre-designed voltage regulation module, and taking an output item of the voltage regulation module as the d-axis preset reference current, wherein the voltage deviation amount is a difference value between the preset reference direct-current voltage and the direct-current voltage.
Preferably, the two-axis reference current comprises a d-axis reference current and a q-axis reference current;
determining a q-axis actual control output quantity based on the power grid angular frequency, the two-axis reference current, the q-axis reference voltage, the inductance value, the q-axis harmonic current compensation quantity and a preset q-axis current loop control strategy, and including:
inputting a q-axis current deviation value as an input item to a pre-designed q-axis current regulating module, and taking an output item of the q-axis current regulating module as a q-axis original control output quantity, wherein the q-axis current deviation value is a difference value between a q-axis preset reference current and a q-axis reference current;
determining q-axis regulation control output quantity based on a second preset relational expression, the q-axis original control output quantity, the q-axis reference voltage serving as second voltage feedforward, the power grid angular frequency, the inductance value and the d-axis reference current;
the second preset relational expression is as follows:
wherein the content of the first and second substances,
adjusting a control output for the q-axis>
For the q-axis reference voltage £ v>
For said q-axis original control output quantity>
Reference current for the d axis>
For the grid angular frequency->
Is the inductance value;
and determining the difference value between the q-axis adjusting control output quantity and the q-axis harmonic current compensation quantity as a q-axis actual control output quantity.
Preferably, the control module comprises a pre-designed PLL phase-locked loop;
determining the angular frequency and the voltage phase of the power grid according to the three-phase capacitor voltage, comprising the following steps:
and inputting the three-phase capacitor voltage as an input item to the PLL to obtain the grid angular frequency and the grid voltage phase output by the PLL.
Preferably, the control module comprises a pre-designed abc-to-dq conversion model;
determining two-axis reference currents corresponding to the three-phase bridge arm current and two-axis reference voltages corresponding to the three-phase capacitor voltage based on the power grid voltage phase, the three-phase bridge arm current, the three-phase capacitor voltage and a preset coordinate transformation strategy, wherein the determining comprises the following steps:
inputting the power grid voltage phase and the three-phase bridge arm current as input items to the abc-to-dq conversion model to obtain a d-axis reference current and a q-axis reference current which are output by the abc-to-dq conversion model and serve as two-axis reference currents;
and inputting the power grid voltage phase and the three-phase capacitor voltage as input items to the abc-to-dq conversion model to obtain d-axis reference voltage and q-axis reference voltage which are output by the abc-to-dq conversion model and serve as two-axis reference voltage.
Preferably, the harmonic current extraction is performed according to the two-axis reference current and a preset harmonic current compensation strategy to determine the two-axis harmonic current compensation amount, and the method includes:
inputting the two-axis reference current as an input item to a pre-designed harmonic current extraction module to obtain two-axis harmonic current extraction quantity output by the harmonic current extraction module;
and inputting the two-axis harmonic current extraction quantity serving as an input item into a pre-designed compensation coefficient module to obtain the two-axis harmonic current compensation quantity output by the compensation coefficient module.
In order to solve the above technical problem, the present invention further provides a control device, including:
a memory for storing a computer program;
a processor for implementing the steps of the harmonic current suppression method as described above when executing the computer program.
In order to solve the technical problem, the invention also provides a power generation system, which comprises a direct current output device, a grid-connected inverter, a filtering module and a transformer which are connected in sequence, and the power generation system also comprises the control device;
the grid-connected inverter comprises a controllable switch module, and the controllable switch module is connected with the control device.
The application provides a harmonic current suppression method, a control device and a power generation system, three-phase bridge arm current corresponding to a bridge arm side inductor in a filter module and three-phase capacitor voltage corresponding to a capacitor are obtained, power grid angular frequency and power grid voltage phase are determined according to the three-phase capacitor voltage, two-axis reference current and two-axis reference voltage are determined based on the power grid voltage phase, the three-phase bridge arm current, the three-phase capacitor voltage and a preset coordinate transformation strategy, harmonic current extraction is performed according to the two-axis reference current and the preset harmonic current compensation strategy to determine two-axis harmonic current compensation amount for harmonic compensation, the two-axis harmonic current compensation amount is fed into control over a controllable switch module, namely three-phase control signals for output to the controllable switch module are determined based on the power grid angular frequency, the power grid voltage phase, the two-axis reference current, the two-axis reference voltage, the two-axis harmonic current compensation amount and the preset current loop control strategy.
Drawings
In order to more clearly illustrate the technical solutions in the embodiments of the present invention, the drawings needed in the prior art and the embodiments will be briefly described below, and it is obvious that the drawings in the following description are only some embodiments of the present invention, and it is obvious for those skilled in the art to obtain other drawings without creative efforts.
Fig. 1 is a schematic structural diagram of a power generation system using a grid-connected inverter in the prior art;
FIG. 2 is a flow chart of a harmonic current suppression method according to the present invention;
FIG. 3 is a schematic diagram of a power generation system according to the present invention;
FIG. 4 is a logic control block diagram corresponding to a harmonic current suppression method according to the present invention;
FIG. 5 is a logic control block diagram corresponding to another harmonic current suppression method provided by the present invention;
fig. 6 is a structural block diagram of a d-axis current loop small-signal model corresponding to a harmonic current suppression method provided by the present invention;
FIG. 7 is a structural diagram of a q-axis current loop small-signal model corresponding to a harmonic current suppression method according to the present invention;
FIG. 8 is a comparison graph of the amplitude-frequency characteristics of the grid-side d-axis current before and after harmonic current compensation according to the present invention;
FIG. 9 is a phase-frequency characteristic comparison graph of the grid-side d-axis current before and after harmonic current compensation according to the present invention;
fig. 10 is a schematic structural diagram of a control device according to the present invention.
Detailed Description
The core of the invention is to provide a harmonic current suppression method, a control device and a power generation system, wherein harmonic current is extracted based on three-phase bridge arm current and fed back to a three-phase control signal to realize harmonic current compensation, so that the harmonic current can be favorably suppressed and fed into a power grid, SVG with higher price is not needed, a current sensor for collecting capacitance current in a filter module is not needed to be additionally arranged, the cost is saved, the investment cost and the maintenance cost of harmonic management of the whole power generation system are reduced, the market competitiveness is improved, and the practical application is facilitated.
In order to make the objects, technical solutions and advantages of the embodiments of the present invention clearer, the technical solutions in the embodiments of the present invention will be clearly and completely described below with reference to the drawings in the embodiments of the present invention, and it is obvious that the described embodiments are some, but not all embodiments of the present invention. All other embodiments, which can be derived by a person skilled in the art from the embodiments given herein without making any creative effort, shall fall within the protection scope of the present invention.
Referring to fig. 1, fig. 2 and fig. 3, fig. 1 is a schematic structural diagram of a power generation system using a grid-connected inverter in the prior art, fig. 2 is a flowchart of a harmonic current suppression method provided by the present invention, and fig. 3 is a schematic structural diagram of a power generation system provided by the present invention.
In the embodiment, considering the harmonic suppression method in the prior art, or the SVG is deployed at the public end of the power grid at the source side of the transformer, but the price of the SVG is very high, the cost is increased, and the sampling circuit in the method is difficult to arrange, so that the use of the method is limited; or, three additional current sensors are additionally arranged and are respectively used for collecting the current ica flowing through the capacitor Ca, the current icb flowing through the capacitor Cb and the current icc flowing through the capacitor Cc on the capacitor branch circuit, and further determining the PWM control signal output to the switching tube in the inverter circuit by the PWM controller based on 6 current values and 3 voltage values, but the additional current sensors still increase the cost. In order to solve the technical problem, the application provides a harmonic current suppression method, which is used for extracting harmonic current based on three-phase bridge arm current and feeding the harmonic current back to a three-phase control signal to realize harmonic current compensation and is beneficial to suppressing the harmonic current to feed into a power grid.
The harmonic current suppression method is applied to a control module in a power generation system, the power generation system further comprises a direct current output device, a grid-connected inverter, a filtering module and a transformer which are sequentially connected, the grid-connected inverter comprises a controllable switch module, and the controllable switch module is connected with the control module, and the harmonic current suppression method comprises the following steps:
s11: acquiring three-phase bridge arm current corresponding to bridge arm side inductance in a filtering module;
specifically, the direct current output device includes, but is not limited to, a photovoltaic array or a battery pack; the grid-connected inverter comprises but is not limited to a photovoltaic grid-connected inverter or an energy storage grid-connected inverter, and the specific circuit structure of the controllable switch module in the grid-connected inverter is not particularly limited; the filtering module is specifically connected with a secondary side of a transformer, the secondary side of the transformer is coupled with a source side of the transformer, and the source side is connected with a power grid and used for feeding electric energy into the power grid; referring to fig. 3, fig. 3 is a schematic structural diagram of a power generation system according to the present invention, where the filter module may be an LCL filter module shown in fig. 3 (that is, the filter module includes a first bridge arm side inductor La, a second bridge arm side inductor Lb, a third bridge arm side inductor Lc, a first capacitor Ca, a second capacitor Cb, a third capacitor Cc, a first network side inductor Lsa, a second network side inductor Lsb, and a third network side inductor Lsc), and of course, the filter module may also be an Lc filter module (that is, an Lc circuit obtained by removing the above network side inductors), which is not particularly limited herein;
the three-phase arm currents, that is, the first-phase arm current ia (the current flowing through the first arm-side inductor La), the second-phase arm current ib (the current flowing through the second arm-side inductor Lb), and the third-phase arm current ic (the current flowing through the third arm-side inductor Lc, which are marked in fig. 3) can be obtained in step S11.
It should be further noted that fig. 3 is a schematic structural diagram only, in order to illustrate the sequential connection relationship between the LCL filter module and the transformer and the power grid, and the secondary side of the transformer and the source side of the transformer are coupled and represented by two intersecting circles; in fig. 3, the controllable switch module is schematically illustrated in the form of a rectangular frame containing the controllable switch therein, and the controllable switch module is denoted by reference numeral 1; PWMA, PWMB, and PWMC in fig. 3 represent three-phase control signals input to the controllable switching modules.
S12: acquiring three-phase capacitor voltage corresponding to a capacitor in the filtering module;
specifically, the three-phase capacitor voltage is a first-phase capacitor voltage Va (a branch voltage corresponding to the first capacitor Ca), a second-phase capacitor voltage Vb (a branch voltage corresponding to the second capacitor Cb), and a third-phase capacitor voltage Vc (a branch voltage corresponding to the third capacitor Cc, which is marked in fig. 3).
S13: determining the angular frequency and the voltage phase of the power grid according to the three-phase capacitor voltage;
s14: determining two-axis reference currents corresponding to the three-phase bridge arm currents and two-axis reference voltages corresponding to the three-phase capacitor voltages based on a power grid voltage phase, the three-phase bridge arm currents, the three-phase capacitor voltages and a preset coordinate transformation strategy;
specifically, the angular frequency and the voltage phase of the power grid, which need to be used subsequently, are determined according to the step S13, and then based on the step S14, two axis reference currents (i.e., a d axis reference current and a q axis reference current) corresponding to the three-phase bridge arm current and two axis reference voltages (i.e., a d axis reference voltage and a q axis reference voltage) corresponding to the three-phase capacitor voltage can be determined.
S15: extracting harmonic current according to the two-axis reference current and a preset harmonic current compensation strategy to determine two-axis harmonic current compensation quantity;
s16: and determining a three-phase control signal for outputting to the controllable switch module based on the power grid angular frequency, the power grid voltage phase, the two-axis reference current, the two-axis reference voltage, the two-axis harmonic current compensation quantity and a preset current loop control strategy.
Specifically, a preset harmonic current compensation strategy and a preset current loop control strategy are designed in advance, the extraction of harmonic current is realized according to the step S15, and then two-axis harmonic current compensation quantities (namely, a d-axis harmonic current compensation quantity and a q-axis harmonic current compensation quantity) for harmonic current compensation are determined; taking the two-cycle harmonic current compensation quantity as one of the determination references of the three-phase control signal to achieve the purpose of inhibiting harmonic current; the three-phase control signals are essentially controllable switch drive signals, i.e., the PWMA, PWMB, and PWMC signals described above in fig. 3.
In summary, the present application provides a harmonic current suppression method, which extracts a harmonic current according to a two-axis reference current and a preset harmonic current compensation strategy to determine a two-axis harmonic current compensation amount for harmonic compensation, and feeds the two-axis harmonic current compensation amount into a control of a controllable switch module, i.e., to determine a three-phase control signal finally used for output to the controllable switch module. Compared with the prior art, the harmonic current is extracted based on the three-phase bridge arm current and fed back to the three-phase control signal to realize harmonic current compensation, so that the harmonic current can be inhibited from being fed into a power grid, a high-price SVG (scalable vector graphics) is not required to be adopted, a current sensor for collecting the capacitance current in the filtering module is not required to be additionally arranged, the cost is saved, the investment cost and the maintenance cost for harmonic treatment of the whole power generation system are reduced, the market competitiveness is improved, and the practical application is facilitated.
On the basis of the above-described embodiment:
as a preferred embodiment, the two-axis reference voltage includes a d-axis reference voltage and a q-axis reference voltage; the two-axis harmonic current compensation quantity comprises a d-axis harmonic current compensation quantity and a q-axis harmonic current compensation quantity;
based on electric wire netting angular frequency, electric wire netting voltage phase place, diaxon reference current, diaxon reference voltage, diaxon harmonic current offset and predetermine the current loop control strategy, confirm the three-phase control signal who is used for exporting to controllable switch module, include:
determining the actual d-axis control output quantity based on the angular frequency of the power grid, the two-axis reference current, the d-axis reference voltage, the inductance value of the bridge arm side inductor, the d-axis harmonic current compensation quantity and a preset d-axis current loop control strategy;
determining a q-axis actual control output quantity based on the power grid angular frequency, the two-axis reference current, the q-axis reference voltage, the inductance value, the q-axis harmonic current compensation quantity and a preset q-axis current loop control strategy;
inputting the d-axis actual control output quantity, the q-axis actual control output quantity and the power grid voltage phase as input items into a pre-designed dq-to-abc conversion model to obtain an a-phase duty ratio, a b-phase duty ratio and a c-phase duty ratio output by the dq-to-abc conversion model;
and determining an a-phase PWM signal, a b-phase PWM signal and a c-phase PWM signal which are output to the controllable switch module based on the a-phase duty ratio, the b-phase duty ratio and the c-phase duty ratio.
In this embodiment, an implementation manner for determining the three-phase control signal is given, which is specifically described above and is not described herein again. It should be noted that the dq conversion abc model is essentially coordinate conversion dq conversion abc, and a specific mathematical expression corresponding to the model is determined according to an actual requirement, which is not particularly limited herein; the specific manner of determining the a-phase PWM signal, the b-phase PWM signal, and the c-phase PWM signal may be: as an illustration, please refer to fig. 4, in which fig. 4 is a logic control block diagram corresponding to a harmonic current suppression method provided by the present invention. Wherein da represents the a-phase duty ratio, db represents the b-phase duty ratio, and dc represents the c-phase duty ratio; PWMA represents an a-phase PWM signal, PWMB represents a b-phase PWM signal, and PWMC represents a c-phase PWM signal; the rectangular box marked dq/abc represents the dq-to-abc model, and the rectangular box marked PWM modulation represents the PWM modulation module;
representing the grid voltage phase.
As a preferred embodiment, the two-axis reference current includes a d-axis reference current and a q-axis reference current;
determining the actual d-axis control output quantity based on the power grid angular frequency, the two-axis reference current, the d-axis reference voltage, the inductance value of the bridge arm side inductor, the d-axis harmonic current compensation quantity and a preset d-axis current loop control strategy, wherein the method comprises the following steps:
inputting the d-axis current deviation value serving as an input item into a pre-designed d-axis current regulating module, and taking an output item of the d-axis current regulating module as a d-axis original control output value, wherein the d-axis current deviation value is a difference value between a d-axis preset reference current and a d-axis reference current;
determining d-axis regulation control output quantity based on a first preset relational expression, d-axis original control output quantity, d-axis reference voltage serving as first voltage feedforward, power grid angular frequency, inductance value of bridge arm side inductance and q-axis reference current;
the first predetermined relationship is:
wherein, the first and the second end of the pipe are connected with each other,
adjusting a control output for the d-axis>
Is d-axis reference voltage,. According to the standard voltage>
Is the original control output quantity of the d-axis,
for q-axis reference current, for>
For the angular frequency of the grid>
The inductance value of the bridge arm side inductor;
and determining the difference value between the d-axis regulation control output quantity and the d-axis harmonic current compensation quantity as the d-axis actual control output quantity.
In this embodiment, the determination of the actual control output of the d-axis is givenThe specific way, which is specifically described above, is not described herein again. It should be noted that, referring to fig. 4, fig. 4 shows a schematic control block diagram of the determination step corresponding to the d-axis actual control output quantity, in fig. 4, idRef represents a d-axis preset reference current, id represents a d-axis reference current,
the variable-frequency converter is configured to represent a grid angular frequency, L represents inductance values of bridge arm side inductors (specifically, in practical application, since the inductance values of the first bridge arm side inductor La, the second bridge arm side inductor Lb and the third bridge arm side inductor Lc are all the same, one of the inductance values is selected as the inductance value of the bridge arm side inductor, for example, the inductance value of the first bridge arm side inductor La is selected), gid represents a d-axis current regulation module (which is essentially a d-axis current regulator, which may be a PID controller, and regulates output of the controller by regulating a proportional coefficient and/or an integral coefficient and/or a differential coefficient, and of course, may also be a PID controller + a resonant controller, and regulates output of the controller by regulating a corresponding coefficient, which is not particularly limited herein and is determined according to actual requirements), and the converter>
Represents a q-axis reference current>
Represents d-axis reference voltage, deltaD represents d-axis harmonic current compensation amount, and/or>
And d-axis regulation control output quantity is shown.
As a preferred embodiment, the method further comprises the following steps:
acquiring direct-current voltage output to a grid-connected inverter by a direct-current output device;
d-axis preset reference current determination step, comprising:
and inputting the voltage deviation amount as an input item to a pre-designed voltage regulation module, and taking an output item of the voltage regulation module as a d-axis preset reference current, wherein the voltage deviation amount is a difference value between a preset reference direct current voltage and a direct current voltage.
In this embodiment, a step of determining a preset reference current of the d-axis is given, it should be noted that the voltage regulation module, which is essentially a voltage regulator, including but not limited to a PID regulator, regulates the output of the controller by regulating a proportional coefficient and/or an integral coefficient and/or a differential coefficient, and is not particularly limited herein and is determined according to actual requirements; the preset reference direct-current voltage is set according to actual requirements. Referring to fig. 4, fig. 4 is a schematic control block diagram of the determining step corresponding to the d-axis preset reference current, where in fig. 4, gvbus represents the voltage regulating module, vbus represents the dc voltage (Vbus is also shown in fig. 3 as the dc voltage input to the grid-connected inverter), and VbusRef represents the preset reference dc voltage.
As a preferred embodiment, the two-axis reference current includes a d-axis reference current and a q-axis reference current;
based on electric wire netting angular frequency, diaxon reference current, q axle reference voltage, inductance value, q axle harmonic current compensation volume and predetermine q axle current loop control strategy, confirm the actual control output volume of q axle, include:
the q-axis current deviation value is used as an input item and is input into a pre-designed q-axis current regulating module, an output item of the q-axis current regulating module is used as a q-axis original control output quantity, and the q-axis current deviation value is a difference value between a q-axis preset reference current and a q-axis reference current;
determining q-axis regulation control output quantity based on a second preset relational expression, q-axis original control output quantity, q-axis reference voltage serving as second voltage feedforward, power grid angular frequency, inductance value and d-axis reference current;
the second predetermined relationship is:
wherein, the first and the second end of the pipe are connected with each other,
adjusting a control output for the q axis>
Is a q-axis reference voltage>
For the original control of an output for the q axis>
Is a d-axis reference current, is greater than or equal to>
For the angular frequency of the grid>
Is an inductance value;
and determining the difference value between the q-axis adjusting control output quantity and the q-axis harmonic current compensation quantity as a q-axis actual control output quantity.
In this embodiment, a determination manner of the q-axis actual control output quantity is given, which is specifically described above and is not described herein again. It should be noted that, referring to fig. 4, fig. 4 shows a control block diagram of the determination step corresponding to the q-axis actual control output quantity, in fig. 4, iqRef represents a q-axis preset reference current (a specific value of which may be determined according to an actual requirement), giq represents a q-axis current regulation module (which is essentially a q-axis current regulator, may be a PID controller, and regulates the controller output by regulating a proportional coefficient and/or an integral coefficient and/or a differential coefficient, or may be a PID controller + a resonant controller, and likewise regulates the controller output by regulating a corresponding coefficient, which is not particularly limited and is determined according to an actual requirement),
represents a q-axis reference voltage, deltaQ represents a q-axis harmonic current compensation amount, and/or>
And d-axis regulation control output quantity is shown. It can be seen that finally the d-axis actual control output quantity, the q-axis actual control output quantity and the grid voltage phase are input to the dq conversion abc model for determining the duty ratio.
As a preferred embodiment, the control module comprises a pre-designed PLL phase-locked loop;
determining the power grid angular frequency and the power grid voltage phase according to the three-phase capacitor voltage, comprising the following steps of:
and inputting the three-phase capacitor voltage serving as an input item into the PLL to obtain the grid angular frequency and the grid voltage phase output by the PLL.
In this embodiment, a step of determining the angular frequency and the phase of the power grid voltage is given, that is, three-phase capacitor voltages (a first-phase capacitor voltage Va, a second-phase capacitor voltage Vb, and a third-phase capacitor voltage Vc) are input to a PLL phase-locked loop, so as to obtain the angular frequency and the phase of the power grid voltage.
As a preferred embodiment, the control module comprises a pre-designed abc-to-dq transformation model;
determining two-axis reference current corresponding to the three-phase bridge arm current and two-axis reference voltage corresponding to the three-phase capacitor voltage based on a power grid voltage phase, the three-phase bridge arm current, the three-phase capacitor voltage and a preset coordinate transformation strategy, wherein the method comprises the following steps:
inputting the power grid voltage phase and the three-phase bridge arm current as input items into an abc-to-dq conversion model to obtain d-axis reference current and q-axis reference current which are output by the abc-to-dq conversion model and serve as two-axis reference current;
and inputting the phase of the power grid voltage and the three-phase capacitor voltage as input items into the abc-to-dq conversion model to obtain d-axis reference voltage and q-axis reference voltage which are output by the abc-to-dq conversion model and serve as two-axis reference voltage.
In this embodiment, an implementation manner for determining the two-axis reference voltage and the two-axis reference current is given, and it should be noted that the abc to dq conversion model is essentially coordinate conversion abc to dq, and a corresponding specific mathematical expression thereof is determined according to an actual requirement, such as Clark conversion or Park conversion, and is not particularly limited herein.
As a preferred embodiment, the harmonic current extraction is performed according to the two-axis reference current and a preset harmonic current compensation strategy to determine the two-axis harmonic current compensation amount, including:
inputting the two-axis reference current as an input item to a pre-designed harmonic current extraction module to obtain two-axis harmonic current extraction quantity output by the harmonic current extraction module;
and inputting the two-axis harmonic current extraction quantity as an input item to a pre-designed compensation coefficient module to obtain the two-axis harmonic current compensation quantity output by the compensation coefficient module.
In the embodiment, the step of determining the harmonic current compensation amount of the two shafts is provided, so that the harmonic current extraction mode in the embodiment is simple and easy to implement, and complicated state equations and differential links are not required to be designed. Specifically, the two-axis reference current comprises a d-axis reference current and a q-axis reference current, the d-axis reference current is used as an input item and is input to a harmonic current extraction module, an output item of the harmonic current extraction module is a d-axis harmonic current extraction amount at the moment, the d-axis harmonic current extraction amount is used as an input item and is input to a pre-designed compensation coefficient module, and an output item of the compensation coefficient module is a d-axis harmonic current compensation amount at the moment; and inputting the q-axis reference current as an input item to a harmonic current extraction module, wherein the output item of the harmonic current extraction module is the q-axis harmonic current extraction amount, the q-axis harmonic current extraction amount is input as an input item to a pre-designed compensation coefficient module, and the output item of the compensation coefficient module is the q-axis harmonic current compensation amount.
More specifically, referring to fig. 5, fig. 5 is another logic control block diagram corresponding to the harmonic current suppression method, where id represents a d-axis reference current, iq represents a q-axis reference current, id _ ripple represents a d-axis harmonic current extraction amount, iq _ ripple represents a q-axis harmonic current extraction amount, deltaD represents a d-axis harmonic current compensation amount, deltaQ represents a q-axis harmonic current compensation amount, gc(s) represents the compensation coefficient module, and Ge(s) represents the harmonic current extraction module.
It should be noted that the compensation coefficient module is still a PID controller per se, and the specific form is not limited, preferably, only a proportional link is adopted, and the design of the compensation coefficient module is realized by adjusting a proportional coefficient; the harmonic current extraction module is essentially a filter structure, namely a filter, specifically a sliding window filter, so as to extract harmonic current, specifically according to actual requirements.
It can be understood that the specific design steps of the d-axis current adjusting module, the q-axis current adjusting module, the voltage adjusting module, the compensation coefficient module and the harmonic current extracting module may be as follows: obtaining a certain amount of three-phase bridge arm current and three-phase capacitor voltage, analyzing the frequency domain characteristics of the network side current (such as drawing a baud chart for analysis), and realizing parameter adjustment of each module until a satisfactory control effect is achieved, namely, the harmonic current is effectively inhibited, the control parameters are easy to adjust, the development difficulty is reduced, the debugging time is short, and the control method is simple, effective and not easily interfered by the field environment; the network side current may specifically be a network side d-axis current or a network side q-axis current, and taking the LCL filter module as an example, the network side d-axis current or the network side q-axis current may be obtained by converting abc to dq conversion model through a first phase network side current flowing through a first network side inductor Lsa, a second phase network side current flowing through a second network side inductor Lsb, and a third phase network side current flowing through a third network side inductor Lsc.
As a further analysis of the above embodiments to prove the effectiveness of the method provided by the present application, a linear analysis is now performed on the entire power generation system including the LCL filter module shown in fig. 3 to establish a small signal model corresponding to a d-axis current loop from a d-axis preset reference current to a grid-side d-axis current and a small signal model corresponding to a q-axis current loop from a q-axis preset reference current to a grid-side q-axis current, specifically, refer to fig. 6 and 7, fig. 6 is a structural block diagram of a small signal model of a d-axis current loop corresponding to a harmonic current suppression method provided by the present invention, and fig. 7 is a structural block diagram of a small signal model of a q-axis current loop corresponding to a harmonic current suppression method provided by the present invention.
In FIG. 6, the reference current is preset from the d-axis
D-axis current to the network side->
The connection of the middle parts is as shown in fig. 6, and the nodes and links of the parts are explained and explained: />
Is a d-axis current error signal>
For d-axis current adjusting module, based on the current value of the d-axis current adjusting module>
For d-axis current regulation, based on the measured value>
For the gain of the PWM modulation module>
The d-axis voltage value on the bridge arm side (i.e. the first phase voltage at the position ia of the first bridge arm side inductor side, the second phase voltage at the position ib of the second bridge arm side inductor Lb side and the third phase voltage at the position ic of the third bridge arm side inductor Lc side in fig. 3 are obtained through an abc-to-dq conversion model), and (i) is/are (i) the voltage value on the bridge arm side>
For the terminal voltage of the first bridge leg side inductance La on the d axis, in combination>
Is a d-axis reference current, is greater than or equal to>
For the current of the first capacitance Ca on the d-axis>
For the voltage at the upper end of the d-axis of the first capacitor Ca, < >>
For the disturbance variable of the d-axis voltage of the power grid in the small-signal model>
The voltage of the first network side inductor Lsa at the upper end of the d axis is obtained; />
Multiply the perturbation amount of the q-axis reference current in the small signal model by ^ er>
Can be regarded as a disturbance in the small-signal model, a disturbance of 0 can be disconnected, (represented in fig. 6 in the form of a cross, wherein here &>
*/>
The reason why the components correspond to the addition operation is that the d-axis adjusting control output quantity is based on the direct consideration of the coupling quantity of the inductor and capacitor in the LCL model in FIG. 6>
In the determination of
Correspondingly, the subtraction operation is caused because the coupling quantity needs to be decoupled in the actual calculation process, so the operation is opposite); />
As a harmonic current extraction module->
Is entered into the device>
As an output item +>
Is entered into the device>
Is d-axis harmonic current compensation quantity->
。
In FIG. 7, the reference current is preset from the q-axis
Q-axis current on the network side->
The connection of the middle parts is as shown in fig. 7, and the nodes and links of the parts are explained and explained: />
For a q-axis current error signal>
For q-axis current regulating module, based on the comparison of the measured values>
For q-axis current regulation, for>
Is the gain of the PWM modulation module>
The q-axis voltage value on the bridge arm side (i.e. the first phase voltage at the position ia of the first bridge arm side inductor side, the second phase voltage at the position ib of the second bridge arm side inductor Lb and the third phase voltage at the position ic of the third bridge arm side inductor Lc in fig. 3 are obtained by an abc-to-dq conversion model), and (i) is/are (i) the voltage value on the bridge arm side>
For the terminal voltage of the first leg-side inductance La on the q-axis, < >>
For q-axis reference current, is greater than or equal to>
For the current of the first capacitor Ca on the q-axis, <' >>
For the upper voltage on the q-axis of the first capacitor Ca>
For disturbance values of the grid q-axis voltage in the small-signal model>
The voltage of the upper end of the q axis of the first network side inductor Lsa is measured; />
Multiply ^ er on the disturbance of the d-axis reference current in the small signal model>
Can be regarded as a disturbance in the small-signal model, a disturbance of 0 can be disconnected (represented in fig. 7 in the form of a fork, wherein here £ er>
*/>
The reason why the components correspond to the subtraction operation is that fig. 7 directly considers the coupling amount of the inductor and the capacitor in the LCL model, whereas the q-axis adjusting control output amount £ is greater than or equal to the q-axis adjusting control output amount in the present application>
In the determination of
Correspondingly, the reason of the addition operation is that the coupling quantity needs to be decoupled in the actual calculation process, so the operation is opposite); />
As harmonic current extraction module>
In combination with an input of (2), in combination with a selection of a selection number>
As a compensation factor module>
In combination with an input of (2), in combination with a selection of a selection number>
Is q-axis harmonic current compensation quantity->
。
Because the small signal model of the d-axis current loop and the small signal model of the q-axis current loop are analyzed in the same way, the small signal model of the d-axis current loop is taken as an example to perform the following analysis:
without extracting module by harmonic current
And compensation coefficientModule->
Determining d-axis harmonic current compensation
The transfer function at participation is:
in the presence of harmonic current extraction modules
And a compensation coefficient module>
Determining d-axis harmonic current compensation
The transfer function at participation is: />
Further, a baud graph of the grid-side d-axis current is drawn to prove the effectiveness of the method provided by the application, and circuit topology parameters are selected as follows:
=1250, the inductance of first arm-side inductor La is 100 microhenry, the inductance of first grid-side inductor Lsa is 10 microhenry, the capacitance of first capacitor is 13.2 microfarads,the compensation coefficient module taking a proportion element, i.e. <' > i>
=20000, the harmonic current extraction module takes a sliding window filter with a cut-off frequency of 8khz, i.e. </or >>
Comprises the following steps:
then, a frequency domain characteristic comparison graph of the grid side d-axis current before and after the harmonic current compensation is performed according to the method in the present application can be obtained, specifically referring to fig. 8 and 9, fig. 8 is a comparison graph of the amplitude-frequency characteristic of the grid side d-axis current before and after the harmonic current compensation is performed according to the present invention; fig. 9 is a comparison diagram of phase-frequency characteristics of the grid-side d-axis current before and after harmonic current compensation according to the present invention. As can be seen from fig. 8, after the harmonic compensation is added, the gain of the harmonic peak of the LCL is reduced to less than 0dB, and although the gain of the low frequency band is also reduced, the gain can be corrected at the low frequency band by the design parameters of the d-axis current adjusting module; as can be seen from fig. 9, after the harmonic compensation is added, the phase from 100Hz to around the harmonic point 15khz is improved, the current loop bandwidth is usually designed to be around 1 to 2khz, and the compensated phase increases the system stability around the bandwidth, thereby verifying the effectiveness of the harmonic current suppression method in the present application.
Referring to fig. 10, fig. 10 is a schematic structural diagram of a control device according to the present invention.
The control device includes:
a memory 21 for storing a computer program;
a processor 22 for implementing the steps of the harmonic current suppression method as described above when executing the computer program.
For the introduction of the control device provided in the present invention, please refer to the embodiment of the harmonic current suppression method, which is not described herein again.
The invention also provides a power generation system, which comprises the direct current output device, the grid-connected inverter, the filtering module and the transformer which are connected in sequence, and the control device;
the grid-connected inverter comprises a controllable switch module, and the controllable switch module is connected with the control device.
For the introduction of the power generation system provided in the present invention, please refer to the embodiment of the harmonic current suppression method, which is not described herein again.
The embodiments in the present description are described in a progressive manner, each embodiment focuses on differences from other embodiments, and the same and similar parts among the embodiments are referred to each other. The device disclosed by the embodiment corresponds to the method disclosed by the embodiment, so that the description is simple, and the relevant points can be referred to the method part for description. Relational terms such as first and second, and the like may be used solely to distinguish one entity or action from another entity or action without necessarily requiring or implying any actual such relationship or order between such entities or actions. Also, the terms "comprises," "comprising," or any other variation thereof, are intended to cover a non-exclusive inclusion, such that a process, method, article, or apparatus that comprises a list of elements does not include only those elements but may include other elements not expressly listed or inherent to such process, method, article, or apparatus. Without further limitation, an element defined by the phrases "comprising a," "8230," "8230," or "comprising" does not exclude the presence of additional like elements in a process, method, article, or apparatus that comprises the element.
Those of skill would further appreciate that the various illustrative components and algorithm steps described in connection with the embodiments disclosed herein may be implemented as electronic hardware, computer software, or combinations of both, and that the components and steps of the various examples have been described above generally in terms of their functionality in order to clearly illustrate this interchangeability of hardware and software. Whether such functionality is implemented as hardware or software depends upon the particular application and design constraints imposed on the implementation. Skilled artisans may implement the described functionality in varying ways for each particular application, but such implementation decisions should not be interpreted as causing a departure from the scope of the present invention. Various modifications to these embodiments will be readily apparent to those skilled in the art, and the generic principles defined herein may be applied to other embodiments without departing from the spirit or scope of the invention. Thus, the present invention is not intended to be limited to the embodiments shown herein but is to be accorded the widest scope consistent with the principles and novel features disclosed herein.
Claims (10)
1. A harmonic current suppression method is characterized by being applied to a control module in a power generation system, wherein the power generation system further comprises a direct current output device, a grid-connected inverter, a filtering module and a transformer which are sequentially connected, the grid-connected inverter comprises a controllable switch module, and the controllable switch module is connected with the control module, and the harmonic current suppression method comprises the following steps:
acquiring three-phase bridge arm current corresponding to bridge arm side inductance in the filter module;
acquiring three-phase capacitor voltage corresponding to a capacitor in the filtering module;
determining the angular frequency and the voltage phase of the power grid according to the three-phase capacitor voltage;
determining two-axis reference currents corresponding to the three-phase bridge arm currents and two-axis reference voltages corresponding to the three-phase capacitor voltages based on the power grid voltage phase, the three-phase bridge arm currents, the three-phase capacitor voltages and a preset coordinate transformation strategy;
extracting harmonic current according to the two-axis reference current and a preset harmonic current compensation strategy to determine two-axis harmonic current compensation quantity;
and determining a three-phase control signal for outputting to the controllable switch module based on the power grid angular frequency, the power grid voltage phase, the two-axis reference current, the two-axis reference voltage, the two-axis harmonic current compensation quantity and a preset current loop control strategy.
2. The harmonic current suppression method according to claim 1, wherein the two-axis reference voltages include a d-axis reference voltage and a q-axis reference voltage; the two-axis harmonic current compensation quantity comprises a d-axis harmonic current compensation quantity and a q-axis harmonic current compensation quantity;
determining a three-phase control signal for outputting to the controllable switch module based on the power grid angular frequency, the power grid voltage phase, the two-axis reference current, the two-axis reference voltage, the two-axis harmonic current compensation amount and a preset current loop control strategy, including:
determining the actual d-axis control output quantity based on the power grid angular frequency, the two-axis reference current, the d-axis reference voltage, the inductance value of the bridge arm side inductor, the d-axis harmonic current compensation quantity and a preset d-axis current loop control strategy;
determining a q-axis actual control output quantity based on the power grid angular frequency, the two-axis reference current, the q-axis reference voltage, the inductance value, the q-axis harmonic current compensation quantity and a preset q-axis current loop control strategy;
inputting the d-axis actual control output quantity, the q-axis actual control output quantity and the power grid voltage phase as input items into a pre-designed dq-abc conversion model to obtain an a-phase duty ratio, a b-phase duty ratio and a c-phase duty ratio output by the dq-abc conversion model;
and determining an a-phase PWM signal, a b-phase PWM signal and a c-phase PWM signal which are output to the controllable switch module based on the a-phase duty ratio, the b-phase duty ratio and the c-phase duty ratio.
3. The harmonic current suppression method according to claim 2, wherein the two-axis reference currents include a d-axis reference current and a q-axis reference current;
determining the actual d-axis control output quantity based on the power grid angular frequency, the two-axis reference current, the d-axis reference voltage, the inductance value of the bridge arm side inductor, the d-axis harmonic current compensation quantity and a preset d-axis current loop control strategy, wherein the determining step comprises the following steps:
inputting a d-axis current deviation value as an input item to a pre-designed d-axis current regulating module, and taking an output item of the d-axis current regulating module as a d-axis original control output value, wherein the d-axis current deviation value is a difference value between a d-axis preset reference current and a d-axis reference current;
determining d-axis regulation control output quantity based on a first preset relational expression, the d-axis original control output quantity, the d-axis reference voltage serving as a first voltage feedforward, the power grid angular frequency, the inductance value of the bridge arm side inductor and the q-axis reference current;
the first preset relational expression is as follows:
wherein the content of the first and second substances,
adjusting a control output for the d-axis>
For the d-axis reference voltage, < >>
For the d-axis original control output, <' >>
Reference current for the q axis->
For the grid angular frequency>
The inductance value of the bridge arm side inductor;
and determining the difference value between the d-axis adjusting control output quantity and the d-axis harmonic current compensation quantity as a d-axis actual control output quantity.
4. The harmonic current suppression method according to claim 3, further comprising:
acquiring direct-current voltage output to the grid-connected inverter by the direct-current output device;
the step of determining the d-axis preset reference current comprises the following steps:
and inputting a voltage deviation amount as an input item to a pre-designed voltage regulation module, and taking an output item of the voltage regulation module as the d-axis preset reference current, wherein the voltage deviation amount is a difference value between a preset reference direct current voltage and the direct current voltage.
5. The harmonic current suppression method according to claim 2, wherein the two-axis reference currents include a d-axis reference current and a q-axis reference current;
determining a q-axis actual control output quantity based on the power grid angular frequency, the two-axis reference current, the q-axis reference voltage, the inductance value, the q-axis harmonic current compensation quantity and a preset q-axis current loop control strategy, and the method comprises the following steps:
inputting a q-axis current deviation value serving as an input item into a pre-designed q-axis current regulating module, and taking an output item of the q-axis current regulating module as a q-axis original control output quantity, wherein the q-axis current deviation value is a difference value between a q-axis preset reference current and a q-axis reference current;
determining q-axis regulation control output quantity based on a second preset relational expression, the q-axis original control output quantity, the q-axis reference voltage serving as second voltage feedforward, the power grid angular frequency, the inductance value and the d-axis reference current;
the second preset relational expression is as follows:
wherein, the first and the second end of the pipe are connected with each other,
adjusting a control output for the q-axis>
Reference voltage for the q axis>
For said q-axis original control output quantity>
Reference current for the d-axis->
For the grid angular frequency>
Is the inductance value;
and determining the difference value between the q-axis adjusting control output quantity and the q-axis harmonic current compensation quantity as a q-axis actual control output quantity.
6. The harmonic current suppression method of claim 1, wherein the control module comprises a pre-designed PLL phase-locked loop;
determining the angular frequency and the voltage phase of the power grid according to the three-phase capacitor voltage, comprising the following steps:
and inputting the three-phase capacitor voltage as an input item to the PLL, so as to obtain the grid angular frequency and the grid voltage phase output by the PLL.
7. The harmonic current suppression method of claim 1, wherein the control module comprises a pre-designed abc-to-dq conversion model;
determining two-axis reference currents corresponding to the three-phase bridge arm current and two-axis reference voltages corresponding to the three-phase capacitor voltage based on the power grid voltage phase, the three-phase bridge arm current, the three-phase capacitor voltage and a preset coordinate transformation strategy, wherein the determining comprises the following steps:
inputting the power grid voltage phase and the three-phase bridge arm current as input items to the abc-to-dq conversion model to obtain d-axis reference current and q-axis reference current which are output by the abc-to-dq conversion model and serve as two-axis reference current;
and inputting the power grid voltage phase and the three-phase capacitor voltage as input items to the abc-to-dq conversion model to obtain d-axis reference voltage and q-axis reference voltage which are output by the abc-to-dq conversion model and serve as two-axis reference voltage.
8. The method for harmonic current suppression according to any one of claims 1 to 7, wherein performing harmonic current extraction based on the two-axis reference current and a preset harmonic current compensation strategy to determine a two-axis harmonic current compensation amount comprises:
inputting the two-axis reference current as an input item to a pre-designed harmonic current extraction module to obtain two-axis harmonic current extraction quantity output by the harmonic current extraction module;
and inputting the two-axis harmonic current extraction quantity serving as an input item into a pre-designed compensation coefficient module to obtain the two-axis harmonic current compensation quantity output by the compensation coefficient module.
9. A control device, characterized by comprising:
a memory for storing a computer program;
a processor for implementing the steps of the harmonic current suppression method as claimed in any one of claims 1 to 8 when executing the computer program.
10. A power generation system comprising a dc power output device, a grid-connected inverter, a filter module, and a transformer, which are connected in sequence, and further comprising the control device according to claim 9;
the grid-connected inverter comprises a controllable switch module, and the controllable switch module is connected with the control device.
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