CN113162045A - Inverter control method and device containing nonlinear load island microgrid harmonic suppression - Google Patents
Inverter control method and device containing nonlinear load island microgrid harmonic suppression Download PDFInfo
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Abstract
The invention discloses a method and a device for controlling an inverter containing nonlinear load island microgrid harmonic suppression. And obtaining the fundamental wave and harmonic component of the inverter voltage outer ring reference value by adopting fundamental wave and harmonic component decoupling control. The fundamental wave domain adopts virtual synchronous motor control, and the harmonic wave domain adopts a control mode of combining self-adaptive harmonic compensation and harmonic virtual impedance, so that the harmonic wave current output by the inverter can be automatically distributed according to the capacity of the inverter to inhibit harmonic wave circulation, and the restraint of PCC voltage harmonic wave component is realized.
Description
Technical Field
The invention belongs to the technical field of power electronics, and particularly relates to a control method of an inverter containing nonlinear load island microgrid harmonic suppression, and further relates to a control device of the inverter containing nonlinear load island microgrid harmonic suppression.
Background
With the increasing shortage of traditional energy and the aggravation of environmental problems, distributed power generation such as photovoltaic, wind power and fuel cells is rapidly developed, and micro-grids composed of distributed power generation, energy storage, local loads and the like are more and more widely applied. The micro-grid often contains nonlinear loads, and inter-inverter harmonic circulation and micro-grid PCC (grid common point) voltage harmonic distortion are easily caused when the micro-grid operates in an off-grid island. Harmonic circulation may affect stable operation of the inverter and even damage, and it is necessary to distribute the output harmonic current between the inverters to suppress the circulation. National standards and IEEE standards both stipulate that the Total Harmonic Distortion (THD) of the grid voltage is not more than 5%, and when the PCC voltage harmonic of the microgrid is serious, the normal work of electrical equipment in the microgrid can be influenced, so that the PCC voltage harmonic component caused by nonlinear load is restrained, and the electric energy quality of the microgrid is ensured.
Applying an active power filter to the microgrid can effectively suppress harmonics, but this increases the cost of the microgrid system. The control strategy for realizing the harmonic suppression of the island microgrid by the inverter is mainly divided into two modes of distributed autonomous control without a communication line and layered control based on the communication line. The inter-inverter harmonic circulating current and the output voltage distortion are influenced by the output impedance of the inverter and the impedance of a feeder line, the circulating current suppression is realized by adopting virtual impedance mostly under the autonomous control without an interconnection communication line, but the circulating current suppression is easily influenced by the impedance of the feeder line when the virtual impedance is smaller, and the PCC voltage distortion is easily increased when the virtual impedance is larger. The hierarchical control based on the communication lines can effectively reduce the influence of the feeder line impedance on current distribution and inhibit the harmonic distortion of the PCC voltage of the microgrid. However, the hierarchical control based on the communication line can increase the hardware complexity of the microgrid system, reduce the reliability, and is not beneficial to the increase of the parallel inverters so as to facilitate the expansion of the microgrid.
Disclosure of Invention
The invention aims to overcome the defects in the prior art and provides an inverter control method for suppressing the harmonic of a microgrid with a nonlinear load island.
In order to solve the technical problem, the invention provides an inverter control method for suppressing harmonic waves of a micro-grid of an island containing a nonlinear load, which comprises the following steps:
acquiring output voltage and output current of an inverter and PCC voltage of a microgrid, and respectively carrying out fundamental wave and harmonic wave separation on the acquired voltage and current to obtain corresponding fundamental wave and harmonic wave components;
calculating to obtain instantaneous active power and reactive power of the fundamental wave domain inverter based on the obtained fundamental wave components of the output voltage and the output current of the inverter, and controlling the instantaneous active power and the reactive power of the fundamental wave domain inverter by adopting a virtual synchronous motor to obtain fundamental wave components of voltage outer ring reference voltage;
introducing a self-adaptive harmonic compensation loop to be combined with the harmonic virtual impedance based on the obtained PCC voltage and the harmonic component of the inverter output current to obtain the harmonic component of the voltage outer ring reference voltage;
and calculating to obtain voltage outer ring reference voltage based on the obtained fundamental wave and harmonic component of the voltage outer ring reference voltage, and aiming at the voltage outer ring reference voltage, adopting inverter voltage outer ring current inner ring double-ring control to obtain control voltage of the inverter three-phase inverter bridge.
Optionally, the fundamental and harmonic separation is achieved by a band pass filter.
Optionally, the calculation formula of the fundamental wave and the harmonic separation is as follows:
inverter output current ioThe fundamental wave and harmonic component calculation formula is as follows:
wherein,
and
for the inverter output current ioZeta is the band-pass filter damping coefficient, and omega is the actual value of the fundamental wave electrical angular velocity of the inverter.
Optionally, the calculating to obtain instantaneous active power and reactive power of the fundamental wave domain inverter based on the obtained fundamental wave component of the inverter output voltage and the output current includes:
based on the obtained output voltage u of the inverteroAnd an output current ioThe instantaneous active power P of the inverter in the fundamental wave domain adopted by VSG control is calculatedfAnd reactive QfThe formula is as follows:
in the formula,
for fundamental component of output voltage of inverter
The dq component of (a) of (b),
for outputting fundamental component of current to inverter
The dq component of (1).
Optionally, the virtual synchronous motor is used to control instantaneous active power and reactive power of the fundamental wave domain inverter to obtain a fundamental component of the voltage outer ring reference voltage, including:
the VSG control equation is:
in the formula, P0Rated active for the inverter, kωIs the active droop coefficient, omega is the actual value of the electrical angular velocity of the inverter, PrefGiving the inverter a reference active, ω0Rated electrical angular velocity of the inverter, J rotational inertia, D VSG damping control coefficient, U0For rated voltage amplitude of inverter, nQFor the reactive droop coefficient, Q0 is the rated reactive power of the inverter, UrefGiving a reference voltage amplitude value for the inverter; k is a radical ofuIs the PCC voltage tuning coefficient;
the fundamental domain voltage reference given by VSG is given by equation (5):
in the formula, theta is the phase angle of the inverter,
t represents the time of day and t represents the time of day,
is an initial phase angle of the inverter;
further introducing virtual impedance of fundamental wave domain
Obtaining the reference voltage u of the voltage outer ringrefFundamental component of
Comprises the following steps:
wherein the virtual impedance of the fundamental wave region
Is composed of
The resistance of the portion of (a) to be,
is composed of
The inductance section of (1).
Optionally, the step of introducing a self-adaptive harmonic compensation loop and combining the harmonic virtual impedance based on the obtained harmonic component of the PCC voltage and the inverter output current to obtain the harmonic component of the voltage outer loop reference voltage includes:
introducing a self-adaptive harmonic compensation loop based on the obtained PCC voltage and the harmonic component of the inverter output current to obtain the compensation quantity obtained by the self-adaptive harmonic compensation loop;
and introducing harmonic virtual impedance to be combined based on the compensation quantity obtained by the self-adaptive harmonic compensation loop and the harmonic component of the output current of the inverter to obtain the harmonic component of the voltage outer ring reference voltage.
Optionally, the step of introducing a self-adaptive harmonic compensation loop and combining the harmonic virtual impedance based on the obtained harmonic component of the PCC voltage and the inverter output current to obtain the harmonic component of the voltage outer loop reference voltage includes:
the adaptive harmonic compensation loop is introduced into the voltage outer loop reference voltage harmonic component, and the compensation quantity U obtained by the adaptive harmonic compensation loophExpressed as:
in the formula, khIn order to compensate the coefficient for the harmonic wave,
kihin order to adapt the harmonic compensation coefficients to the application,
is a PCC voltage upccA harmonic component of (a);
introducing harmonic domain virtual impedance, voltage outer ring reference voltage urefHarmonic component
Comprises the following steps:
in the formula,
is a harmonic domain virtual impedance.
Optionally, the adaptive harmonic compensation coefficient kihThe value range is as follows:
the adaptive harmonic compensation coefficient meets the following requirements:
wherein, U0For rated voltage amplitude of inverter, I0The inverter rated current value.
Optionally, the adaptive harmonic compensation coefficient and the harmonic virtual impedance further need to satisfy:
among a plurality of inverters, the relationship among the rated power of the inverter, the adaptive compensation coefficient and the harmonic virtual impedance is as follows:
in the formula, SnIs the rated power of the nth inverter,
is the harmonic virtual impedance, k, of the nth inverterihnIs the adaptive compensation coefficient of the nth inverter.
Correspondingly, the invention also provides an inverter control device containing nonlinear load island microgrid harmonic suppression, which comprises:
the fundamental wave and harmonic wave separation module is used for collecting output voltage and output current of the inverter and PCC voltage of the microgrid, and respectively carrying out fundamental wave and harmonic wave separation on the collected voltage and current to obtain corresponding fundamental wave and harmonic wave components;
the fundamental component calculation module is used for calculating to obtain instantaneous active power and reactive power of the fundamental domain inverter based on the obtained fundamental components of the output voltage and the output current of the inverter, and the instantaneous active power and the reactive power of the fundamental domain inverter are controlled by adopting a virtual synchronous motor to obtain the fundamental components of the voltage outer ring reference voltage;
the harmonic component calculation module is used for introducing a self-adaptive harmonic compensation loop and combining the harmonic virtual impedance based on the obtained PCC voltage and the harmonic component of the inverter output current to obtain the harmonic component of the voltage outer loop reference voltage;
and the control voltage calculation module is used for calculating to obtain voltage outer ring reference voltage based on the obtained fundamental wave and harmonic component of the voltage outer ring reference voltage, and obtaining the control voltage of the inverter three-phase inverter bridge by adopting inverter voltage outer ring current inner ring double-ring control aiming at the voltage outer ring reference voltage.
Compared with the prior art, the invention has the following beneficial effects: according to different control requirements of the fundamental wave and harmonic component of the island microgrid inverter, the fundamental wave and the harmonic component are subjected to separation decoupling control. Aiming at the PCC voltage harmonic distortion of the island micro-grid caused by the nonlinear load and the harmonic circulation caused by the unmatched impedance and capacity of each inverter, the harmonic component is controlled in the harmonic domain by combining the self-adaptive harmonic compensation and the harmonic virtual impedance. The control method provided by the invention is simple and feasible, can realize the micro-grid harmonic suppression of the island containing the nonlinear load, and is easy to engineer.
Drawings
FIG. 1 is a diagram of a micro grid main circuit and control system including a nonlinear load island;
FIG. 2 is a schematic diagram of fundamental and harmonic component separation principles;
FIG. 3 is a VSG control system block diagram;
FIG. 4 is a block diagram of an adaptive harmonic compensation control system;
FIG. 5 is a voltage outer loop current inner loop dual loop control block diagram;
FIG. 6 is a diagram of an embodiment of a nonlinear load island microgrid system;
FIG. 7 is the harmonic content of the microgrid PCC voltage in an example embodiment;
fig. 8 is a waveform diagram of two inverter output currents in the embodiment.
Detailed Description
The invention is further described below with reference to the accompanying drawings. The following examples are only for illustrating the technical solutions of the present invention more clearly, and the protection scope of the present invention is not limited thereby.
Example 1
A main circuit and control system diagram of a micro-grid with a nonlinear load island is shown in figure 1, and U is used for each inverterdcL, C is inverter filter inductance and capacitance, the end voltage of the capacitance C is inverter output voltage uo，ZlIs the feed line impedance between the inverter and the microgrid PCC. In order to suppress harmonic waves of an island microgrid containing nonlinear loads, a control system executes the same strategy for each inverter, calculates the output of a three-phase bridge circuit according to a sampling value, and obtains a driving signal through SVPWM to drive each IGBT switch in the three-phase bridge circuit, so that the control purpose is achieved.
The invention discloses a control method of an inverter containing nonlinear load island microgrid harmonic suppression, which comprises the following steps:
the method comprises the following steps: and acquiring output voltage and output current of the inverter and PCC voltage of the microgrid, and respectively carrying out fundamental wave and harmonic wave separation on the acquired voltage and current to obtain corresponding fundamental wave and harmonic wave components.
According to different control requirements of fundamental wave and harmonic component of an island microgrid inverter, separation decoupling control is carried out on the fundamental wave and the harmonic component. In the embodiment of the invention, the inverter outputs the current ioThe fundamental wave and the harmonic wave separation of (2) are realized by adopting a band-pass filter, fig. 2 is a schematic diagram of the fundamental wave and the harmonic wave separation method, as shown in fig. 2, zeta is a damping coefficient of the band-pass filter, omega is an actual value of the electrical angular velocity of the inverter (the electrical angular velocity is used for simulating a synchronous generator due to the control of the inverter),
and
for the inverter output current ioThe fundamental wave and harmonic components of the physical quantity are denoted by f, and the harmonic components of the physical quantity are denoted by h.
Inverter output current ioThe fundamental wave and harmonic component calculation formula is as follows:
the fundamental and harmonic components of the voltage are separated equally,
and
for inverter output voltage uoThe fundamental and harmonic components of (a) and (b),
and
is a PCC voltage upccThe fundamental and harmonic components of (a).
The traditional controlled inverter has the same fundamental wave domain and harmonic wave domain output impedance, is difficult to meet different control requirements of fundamental wave and harmonic wave components, and has difficult ideal control effect under nonlinear load. According to the invention, the fundamental wave and harmonic components of the voltage outer ring reference value are respectively obtained by adopting the decoupling control of the fundamental wave domain and the harmonic domain, the output characteristic is improved, and the stable operation capability of the island micro-grid under the nonlinear load is improved.
Step two: fundamental wave domain: based on the obtained output voltage u of the inverteroAnd an output current ioCalculating to obtain instantaneous active power and reactive power of the fundamental wave domain inverter, controlling the instantaneous active power and reactive power of the fundamental wave domain inverter by adopting a virtual synchronous motor (VSG) to obtain a fundamental wave domain voltage reference value, introducing fundamental wave domain virtual impedance based on the fundamental wave domain voltage reference value and the fundamental wave component of the output current of the inverter to obtain electric powerThe fundamental component of the outer loop reference voltage is suppressed.
In order to improve the stability of the droop control of the fundamental wave domain, the VSG control is adopted to obtain the fundamental wave component of the voltage outer ring reference voltage
The rotor motion and stator excitation regulation characteristics of the synchronous generator are simulated, so that the inverter has frequency modulation and voltage regulation characteristics similar to those of the synchronous generator. FIG. 3 is a block diagram of a VSG control system, the VSG control strategy being as follows:
according to a decoupling control principle, the inverter output voltage u obtained based on the step oneoAnd an output current ioThe instantaneous active power P of the inverter in the fundamental wave domain adopted by VSG control is calculatedfAnd reactive QfThe formula is as follows:
in the formula,
for fundamental component of output voltage of inverter
The dq component of (a) of (b),
for outputting fundamental component of current to inverter
The dq component of (1).
Simulating the primary frequency modulation characteristic, the rotor motion equation and the stator excitation regulation characteristic of the synchronous motor to obtain a VSG control equation as follows:
in the formula, P0The inverter is rated to have active power,kωis the active droop coefficient, omega is the actual value of the electrical angular velocity of the inverter, PrefGiving the inverter a reference active, ω0Rated electrical angular velocity of the inverter, J rotational inertia, D VSG damping control coefficient, U0For rated voltage amplitude of inverter, nQIs a reactive sag factor, Q0Rated reactive, U, for the inverterrefGiven a reference voltage amplitude, k, for the inverteruThe PCC voltage tuning coefficient.
The fundamental wave domain voltage reference value given by VSG can be obtained according to the formula (5)
Comprises the following steps:
in the formula, theta is the phase angle of the inverter,
t represents the time of day and t represents the time of day,
is the inverter initial phase angle.
In order to inhibit the circulation of the parallel inverters and enhance the stability of the system, the fundamental wave domain virtual impedance is further introduced
To improve the output characteristics of the inverter to obtain the reference voltage u of the voltage outer ringrefFundamental component of
Comprises the following steps:
wherein the virtual impedance of the fundamental wave region
Is composed of
The resistance of the portion of (a) to be,
is composed of
The inductance section of (1). To improve the droop characteristics of the inverter, the fundamental wave output impedance needs to be strong.
Step three: harmonic domain: based on the harmonic component of the PCC voltage and the inverter output current, a self-adaptive harmonic compensation loop is introduced to be combined with the harmonic virtual impedance to obtain the harmonic component of the voltage outer loop reference voltage
The harmonic component of the harmonic domain is controlled by combining adaptive harmonic compensation and harmonic virtual impedance, harmonic virtual impedance can effectively realize harmonic current distribution, and the adaptive harmonic compensation loop can effectively inhibit PCC voltage harmonic distortion to eliminate the influence of the harmonic virtual impedance on PCC electric energy quality. And the suppression of the micro-grid PCC voltage harmonic component and the inverter harmonic circulating current is realized.
The adaptive harmonic compensation loop is introduced into the voltage outer loop reference voltage harmonic component, and the compensation quantity U obtained by the adaptive harmonic compensation loophExpressed as:
in the formula, khIn order to compensate the coefficient for the harmonic wave,
kihin order to adapt the harmonic compensation coefficients to the application,
is a PCC voltage upccThe harmonic component of (a).
Introducing harmonic domain virtual impedance, voltage outer ring reference voltage urefHarmonic component
Comprises the following steps:
in the formula,
is a harmonic domain virtual impedance.
Adaptive harmonic compensation control as shown in fig. 4, can be obtained by equation (9)
Increase will result in khAlso increases due to khTo pair
Function of
Conversely, it can be lowered
To pair
Can effectively realize the pair
Inhibition of (3). Will kihThe arrangement is in a reasonable range, and the distribution control effect of harmonic current can be ensured. This step then requires k to be obtainedihAnd
the value range of (a).
And due to
According to the inverter voltage outer loop current inner loop double loop control system of fig. 5, it can be obtained:
obtaining the steady state according to the final value theorem
Comprises the following steps:
since the national standard and the IEEE standard stipulate that the grid voltage THD should not be greater than 5%, that is:
in a microgrid, a plurality of inverters are often connected in parallel, and harmonic circulation among the inverters needs to be restrained. In the following analysis of this step, in order to distinguish the physical quantities of the inverters, the inverter numbers are added to the physical subscripts, for example:
is the output current harmonic component of the jth inverter,
is the output current harmonic component of the kth inverter.
Suppressing inter-inverter harmonic circulation requires distributing inter-inverter output harmonic currents according to inverter capacity. And (3) making the ratio w of the rated power of the j and k inverters in the microgrid, wherein the distribution control target of the inter-inverter harmonic current is as follows:
by substituting formula (15) for formula (12), it is possible to obtain:
in the formula,
is the harmonic virtual impedance, Z, of the jth inverterljIs the feed line impedance, k, between the jth inverter and the PCCihjFor the adaptive harmonic compensation coefficient of the jth inverter,
is the harmonic virtual impedance, Z, of the kth inverterlkIs the feed line impedance between the kth inverter and the PCC, kihkAnd the adaptive harmonic compensation coefficient of the kth inverter.
And due to
Neglecting ZlThe influence of (a) is given by equation (16):
according to formula (17):
according to the equation (18), the relationship among the rated power of the inverter, the adaptive compensation coefficient and the harmonic virtual impedance can be obtained by:
in the formula, SnIs the rated power of the nth inverter,
is the harmonic virtual impedance, k, of the nth inverterihnIs the adaptive compensation coefficient of the nth inverter. The subscript n here denotes the nth inverter, and the same is true for the preceding variables without the subscript n.
Thus, by combining formula (14) and formula (19), k can be obtainedihAnd
the value of (2).
Step four: obtaining voltage outer ring reference voltage based on fundamental wave and harmonic component of voltage outer ring reference voltage
Obtaining the output u of the inverter three-phase inverter bridge through the outer ring current and inner ring double-ring control of the inverter voltageinv。
The inverter voltage outer loop current inner loop double loop control is shown in FIG. 5, Gu(s) is a voltage outer loop regulator by outputting a voltage u to the inverteroThe regulation control gives a current reference value i of the current inner loopref，Gi(s) is a current inner loop regulator by applying a capacitive current icThe regulation control of the three-phase inverter gives an output u of the inverter three-phase inverter bridgeinv，urefIs a voltage outer loop reference voltage value, irefIs a current inner loop reference value, icAs a value of capacitance current, iLFor filtering the inductor current, KpwmThe gain of the inverter three-phase inverter bridge is obtained.
Step five: inverter three-phase inverter bridge output voltage u obtained through the stepsinvAnd finally, the control target of the invention, namely the suppression of the PCC voltage harmonic component of the microgrid and the harmonic circulation of the inverter, is realized by driving the switch of each power tube of the inverter bridge of the inverter through SVPWM.
According to the invention, the fundamental wave and the harmonic component are subjected to separation decoupling control to obtain the fundamental wave and the harmonic component of the inverter voltage outer ring reference voltage, so that different control requirements of the fundamental wave and the harmonic component are met. And the harmonic domain combines adaptive harmonic compensation and harmonic virtual impedance to realize the suppression of the PCC voltage harmonic component of the microgrid and the harmonic circulation of the inverter.
Example 2
The control method provided by the invention is subjected to simulation verification by Matlab/Simulink modeling, a nonlinear load island microgrid simulation model is shown in FIG. 6, two inverters are adopted for simulation, an inverter INV1 and an inverter INV2 are connected in parallel, each inverter adopts the strategy of the invention, k1And k2Being relay switches, Zl1And Zl2Is the line impedance (these two impedances are equal, namely Z in Table 1l) Table 1 shows the main simulation parameters, Zload1For three-phase linear load, the DC side of three-phase uncontrolled rectifier bridge is connected with Zload2Constituting a nonlinear load.
TABLE 1 Main parameters
From the harmonic content diagram of the PCC voltage of the microgrid in the embodiment of fig. 7, the adoption of the control strategy of the invention can realize that the power quality of the islanding microgrid reaches the standard under the nonlinear load. As can be seen from the two inverter output current waveform diagrams in fig. 8, the output current of the inverter INV2 is 2 times of that of the inverter INV1, the same frequency and phase are achieved, and the harmonic content is close, which indicates that the inter-inverter harmonic current can be distributed according to the rated power of the inverter, and the harmonic circulation can be effectively suppressed.
Example 3
Based on the same inventive concept as embodiment 1, the inverter control device with nonlinear load island microgrid harmonic suppression of the invention comprises:
the fundamental wave and harmonic wave separation module is used for collecting output voltage and output current of the inverter and PCC voltage of the microgrid, and respectively carrying out fundamental wave and harmonic wave separation on the collected voltage and current to obtain corresponding fundamental wave and harmonic wave components;
the fundamental component calculation module is used for calculating to obtain instantaneous active power and reactive power of the fundamental domain inverter based on the obtained fundamental components of the output voltage and the output current of the inverter, and the instantaneous active power and the reactive power of the fundamental domain inverter are controlled by adopting a virtual synchronous motor to obtain the fundamental components of the voltage outer ring reference voltage;
the harmonic component calculation module is used for introducing a self-adaptive harmonic compensation loop and combining the harmonic virtual impedance based on the obtained PCC voltage and the harmonic component of the inverter output current to obtain the harmonic component of the voltage outer loop reference voltage;
and the control voltage calculation module is used for calculating to obtain voltage outer ring reference voltage based on the obtained fundamental wave and harmonic component of the voltage outer ring reference voltage, and obtaining the control voltage of the inverter three-phase inverter bridge by adopting inverter voltage outer ring current inner ring double-ring control aiming at the voltage outer ring reference voltage.
The specific implementation process of each module of the device of the invention refers to the specific implementation process of each step in embodiment 1.
As will be appreciated by one skilled in the art, embodiments of the present application may be provided as a method, system, or computer program product. Accordingly, the present application may take the form of an entirely hardware embodiment, an entirely software embodiment or an embodiment combining software and hardware aspects. Furthermore, the present application may take the form of a computer program product embodied on one or more computer-usable storage media (including, but not limited to, disk storage, CD-ROM, optical storage, and the like) having computer-usable program code embodied therein.
The present application is described with reference to flowchart illustrations and/or block diagrams of methods, apparatus (systems), and computer program products according to embodiments of the application. It will be understood that each flow and/or block of the flow diagrams and/or block diagrams, and combinations of flows and/or blocks in the flow diagrams and/or block diagrams, can be implemented by computer program instructions. These computer program instructions may be provided to a processor of a general purpose computer, special purpose computer, embedded processor, or other programmable data processing apparatus to produce a machine, such that the instructions, which execute via the processor of the computer or other programmable data processing apparatus, create means for implementing the functions specified in the flowchart flow or flows and/or block diagram block or blocks.
These computer program instructions may also be stored in a computer-readable memory that can direct a computer or other programmable data processing apparatus to function in a particular manner, such that the instructions stored in the computer-readable memory produce an article of manufacture including instruction means which implement the function specified in the flowchart flow or flows and/or block diagram block or blocks.
These computer program instructions may also be loaded onto a computer or other programmable data processing apparatus to cause a series of operational steps to be performed on the computer or other programmable apparatus to produce a computer implemented process such that the instructions which execute on the computer or other programmable apparatus provide steps for implementing the functions specified in the flowchart flow or flows and/or block diagram block or blocks.
The above description is only a preferred embodiment of the present invention, and it should be noted that, for those skilled in the art, several modifications and variations can be made without departing from the technical principle of the present invention, and these modifications and variations should also be regarded as the protection scope of the present invention.
Claims (10)
1. A control method of an inverter containing nonlinear load island microgrid harmonic suppression is characterized by comprising the following processes:
acquiring output voltage and output current of an inverter and PCC voltage of a microgrid, and respectively carrying out fundamental wave and harmonic wave separation on the acquired voltage and current to obtain corresponding fundamental wave and harmonic wave components;
calculating to obtain instantaneous active power and reactive power of the fundamental wave domain inverter based on the obtained fundamental wave components of the output voltage and the output current of the inverter, and controlling the instantaneous active power and the reactive power of the fundamental wave domain inverter by adopting a virtual synchronous motor to obtain fundamental wave components of voltage outer ring reference voltage;
introducing a self-adaptive harmonic compensation loop to be combined with the harmonic virtual impedance based on the obtained PCC voltage and the harmonic component of the inverter output current to obtain the harmonic component of the voltage outer ring reference voltage;
and calculating to obtain voltage outer ring reference voltage based on the obtained fundamental wave and harmonic component of the voltage outer ring reference voltage, and aiming at the voltage outer ring reference voltage, adopting inverter voltage outer ring current inner ring double-ring control to obtain control voltage of the inverter three-phase inverter bridge.
2. The method for controlling the inverter with the harmonic suppression of the micro-grid of the nonlinear load island according to claim 1, wherein the fundamental wave and the harmonic separation are realized by a band-pass filter.
3. The method for controlling the inverter with the nonlinear load island microgrid harmonic suppression function as claimed in claim 2, characterized in that a calculation formula of the fundamental wave and harmonic separation is as follows:
inverter output current ioThe fundamental wave and harmonic component calculation formula is as follows:
wherein,
and
for the inverter output current ioZeta is the band-pass filter damping coefficient, and omega is the actual value of the fundamental wave electrical angular velocity of the inverter.
4. The method for controlling the inverter with nonlinear load island microgrid harmonic suppression function according to claim 1, wherein the step of calculating the instantaneous active power and reactive power of the fundamental wave domain inverter based on the obtained fundamental wave components of the inverter output voltage and the output current comprises the following steps:
based on the obtained output voltage u of the inverteroAnd an output current ioThe instantaneous active power P of the inverter in the fundamental wave domain adopted by VSG control is calculatedfAnd reactive QfThe formula is as follows:
in the formula,
for fundamental component of output voltage of inverter
The dq component of (a) of (b),
for outputting fundamental component of current to inverter
The dq component of (1).
5. The method for controlling the inverter with nonlinear load island microgrid harmonic suppression function according to claim 1, characterized in that the virtual synchronous machine control is adopted for instantaneous active power and reactive power of the fundamental wave domain inverter to obtain a fundamental wave component of a voltage outer ring reference voltage, and the method comprises the following steps:
instantaneous active power P based on fundamental wave domain inverterfAnd reactive QfThe VSG control equation is:
in the formula, P0Rated active for the inverter, kωIs the active droop coefficient, omega is the actual value of the electrical angular velocity of the inverter, PrefGiving the inverter a reference active, ω0Rated electrical angular velocity of the inverter, J rotational inertia, D VSG damping control coefficient, U0For rated voltage amplitude of inverter, nQIs a reactive sag factor, Q0Rated reactive, U, for the inverterrefGiving a reference voltage amplitude value for the inverter; k is a radical ofuIs the PCC voltage tuning coefficient;
the fundamental domain voltage reference given by VSG is given by equation (5):
in the formula, theta is the phase angle of the inverter,
t represents the time of day and t represents the time of day,
is an initial phase angle of the inverter;
further introducing virtual impedance of fundamental wave domain
Obtaining fundamental component of voltage outer ring reference voltage
Comprises the following steps:
wherein the virtual impedance of the fundamental wave region
Is composed of
The resistance of the portion of (a) to be,
is composed of
The inductance section of (1).
6. The method of claim 1, wherein the step of obtaining the harmonic component of the voltage outer loop reference voltage by introducing an adaptive harmonic compensation loop and combining a harmonic virtual impedance based on the obtained PCC voltage and the harmonic component of the inverter output current comprises:
introducing a self-adaptive harmonic compensation loop based on the obtained PCC voltage and the harmonic component of the inverter output current to obtain the compensation quantity obtained by the self-adaptive harmonic compensation loop;
and introducing harmonic virtual impedance to be combined based on the compensation quantity obtained by the self-adaptive harmonic compensation loop and the harmonic component of the output current of the inverter to obtain the harmonic component of the voltage outer ring reference voltage.
7. The method of claim 1, wherein the step of obtaining the harmonic component of the voltage outer loop reference voltage by introducing an adaptive harmonic compensation loop and combining a harmonic virtual impedance based on the obtained PCC voltage and the harmonic component of the inverter output current comprises:
the adaptive harmonic compensation loop is introduced into the voltage outer loop reference voltage harmonic component, and the compensation quantity U obtained by the adaptive harmonic compensation loophExpressed as:
in the formula, khIn order to compensate the coefficient for the harmonic wave,
kihin order to adapt the harmonic compensation coefficients to the application,
is a PCC voltage upccA harmonic component of (a);
outputting a current harmonic component for the inverter;
introducing harmonic domain virtual impedance, voltage outer ring reference voltage urefHarmonic component
Comprises the following steps:
in the formula,
is a harmonic domain virtual impedance.
8. The method for controlling the inverter with the harmonic suppression of the microgrid of the nonlinear load island as claimed in claim 7, characterized in that the adaptive harmonic compensation coefficient kihThe value range is as follows:
the adaptive harmonic compensation coefficient meets the following requirements:
wherein, U0For rated voltage amplitude of inverter, I0The inverter rated current value.
9. The method for controlling the inverter with the harmonic suppression of the micro-grid of the nonlinear load island according to claim 7, wherein the adaptive harmonic compensation coefficient and the harmonic virtual impedance further satisfy the following requirements:
among a plurality of inverters, the relationship among the rated power of the inverter, the adaptive compensation coefficient and the harmonic virtual impedance is as follows:
in the formula, SnIs the rated power of the nth inverter,
is the harmonic virtual impedance, k, of the nth inverterihnIs the adaptive compensation coefficient of the nth inverter.
10. An inverter control device containing nonlinear load island microgrid harmonic suppression is characterized by comprising:
the fundamental wave and harmonic wave separation module is used for collecting output voltage and output current of the inverter and PCC voltage of the microgrid, and respectively carrying out fundamental wave and harmonic wave separation on the collected voltage and current to obtain corresponding fundamental wave and harmonic wave components;
the fundamental component calculation module is used for calculating to obtain instantaneous active power and reactive power of the fundamental domain inverter based on the obtained fundamental components of the output voltage and the output current of the inverter, and the instantaneous active power and the reactive power of the fundamental domain inverter are controlled by adopting a virtual synchronous motor to obtain the fundamental components of the voltage outer ring reference voltage;
the harmonic component calculation module is used for introducing a self-adaptive harmonic compensation loop and combining the harmonic virtual impedance based on the obtained PCC voltage and the harmonic component of the inverter output current to obtain the harmonic component of the voltage outer loop reference voltage;
and the control voltage calculation module is used for calculating to obtain voltage outer ring reference voltage based on the obtained fundamental wave and harmonic component of the voltage outer ring reference voltage, and obtaining the control voltage of the inverter three-phase inverter bridge by adopting inverter voltage outer ring current inner ring double-ring control aiming at the voltage outer ring reference voltage.
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