CN113783189A - Control method and device for virtual synchronous machine to cope with power grid voltage unbalance - Google Patents
Control method and device for virtual synchronous machine to cope with power grid voltage unbalance Download PDFInfo
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- H—ELECTRICITY
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Abstract
本申请公开一种虚拟同步机应对电网电压不平衡的控制方法及装置，所述方法包括：对虚拟同步机输出的有功功率和无功功率中的二倍基频振荡分量进行抑制，得到负序电压作用量1；将所述负序电压作用量1与目标坐标系下的基本电压作用量进行叠加，得到最终电压作用量；对所述最终电压作用量进行调制，以生成虚拟同步机控制所需的驱动信号。本申请在不增加系统成本基础上，通过对有功功率和无功功率中二倍基频振荡分量的抑制，可以使虚拟同步机在模拟同步机实现有功调频和无功调压输出特性的同时，减少在电网电压跌落时的过流风险，提高应对电网电压不对称跌落的应对能力。
The present application discloses a control method and device for a virtual synchronous machine to cope with grid voltage unbalance. The method includes: suppressing the double fundamental frequency oscillation component in the active power and reactive power output by the virtual synchronous machine to obtain a negative sequence Voltage action amount 1; superimpose the negative sequence voltage action amount 1 with the basic voltage action amount in the target coordinate system to obtain the final voltage action amount; modulate the final voltage action amount to generate a virtual synchronous machine control system. required drive signal. On the basis of not increasing the system cost, by suppressing the double fundamental frequency oscillation component in the active power and reactive power, the virtual synchronous machine can simulate the synchronous machine to realize the output characteristics of active frequency regulation and reactive voltage regulation, and at the same time, Reduce the risk of overcurrent when the grid voltage drops, and improve the ability to cope with asymmetric drops in the grid voltage.
Description
Technical Field
The application relates to the technical field of power electronics, in particular to a control method and device for a virtual synchronous machine to cope with power grid voltage unbalance.
Background
Most of traditional new energy grid-connected units work in a controlled current source CSC mode running along with a power grid and do not actively participate in frequency adjustment of the power grid. Existing research results show that the CSC operation mode can cause the grid inertia to decrease, which brings a serious challenge to the safe operation of the power system in the context of high-permeability new energy grid connection.
Only if the power grid is safe and stable, the clean energy can improve the self viability. Under the situation of large-scale access of new energy power generation, the control idea of 'only managing power generation and no matter a power grid' in the past is increasingly difficult to meet the requirement of stable operation of a power system. The grid voltage amplitude and frequency supporting capacity is certain, the capacity of a service grid is enhanced by means of a flexible and controllable power electronic technology, and the grid voltage amplitude and frequency supporting capacity are both used for maintaining the safety and stability of the current grid and are also the requirements of a new grid-connected guide rule on future new energy power generation. In this context, VSG (Virtual Synchronous Generator) technology has been developed and has become a hotspot of research and attention in the industry. The new energy generator set adopts a virtual synchronous machine technology, so that the new energy generator set can autonomously participate in the operation and management of the power grid according to the operation mechanism of the synchronous machine, and can make corresponding response under the abnormal conditions of the voltage/frequency and active/reactive power of the power grid so as to deal with the operation transient state and dynamic stability problems of the power grid and resist the interference caused by external disturbance. The beneficial effects of the method are preliminarily proved in research.
However, the current VSG technology focuses mainly on how to realize the simulation of the external characteristics of the synchronous generator and the grid-connected stability of the virtual synchronous machine, and has few influences on common conditions such as unbalanced grid voltage and background harmonic contained in the grid voltage, and the corresponding strategy is relatively deficient. When a new energy unit adopting the VSG operation mode encounters a grid voltage drop fault, although the VSG operation mode is switched back to the CSC operation mode to cope with the unit overcurrent, the VSG operation characteristic of the unit can be lost, and the risk of operation instability or overcurrent also exists when the VSG operation mode is switched between the two operation modes.
When the voltage of the power grid is unbalanced, the output power of the VSG generates pulsation with twice fundamental frequency of the power grid (hereinafter referred to as twice fundamental frequency), and the pulsation amplitude is increased along with the increase of the unbalance degree of the power grid and the generating power of the unit. The ripple of the double fundamental frequency is reflected to the amplitude of the modulation wave of the VSG through the power regulating loop, so that the modulation wave is distorted, and finally, the output voltage and the current of the VSG are distorted. To suppress the influence of the pulsating quantity in the feedback power on the output voltage, the existing VSG control scheme must make the bandwidths of the active loop and the reactive loop sufficiently low [ documents "wuheng, raney wave, chongchang, etc. ] the modeling and parameter design of the power loop of the virtual synchronous generator [ J ], the chinese electro-mechanical engineering report, 2015, 35 (24): 6508-. Therefore, the flexibility of the VSG frequency modulation link design and the dynamic response capability of the frequency modulation are limited. In addition to the problem of output voltage and current distortion, when the output current is not subjected to closed-loop control, negative-sequence current is introduced due to unbalanced network voltage, and overcurrent risk and challenge are brought to the VSG. The document "Sara Yazdani, Mehdi fendowsi, mass Davari, et al," Advanced Current-Limiting and Power-spring Control in a PV-Based Grid-Forming Inverter Under underlying baseband Grid Conditions, "IEEE Transactions on Power Electronics, vol.8, No.2, pp.1084-1096, june.2020" is connected in parallel to the regulators of the active frequency modulation and reactive voltage regulation Control loops, respectively, to help to suppress the negative sequence Current and reduce the overcurrent risk of the VSG. However, the outputs of the resonant regulators of the active frequency modulation loop and the reactive power controller circuit of the method are respectively superposed on the frequency command and the output voltage command of the VSG, and the mismatch of the output amplitude and the phase of the resonant regulators of the two power control loops inevitably brings contradiction of negative sequence current suppression and current distortion.
Disclosure of Invention
The method and the device aim at limiting the output current of the grid-connected virtual synchronous machine operating in the VSG mode when the grid voltage falls asymmetrically, reduce the overcurrent risk of the grid-connected virtual synchronous machine, and improve the operation capacity of the grid-connected virtual synchronous machine for coping with unbalanced grid voltage.
In one aspect of the present application, a method for controlling a virtual synchronous machine to cope with a grid voltage imbalance is provided, where the method includes:
inhibiting a double fundamental frequency oscillation component in active power and reactive power output by the virtual synchronous machine to obtain a negative sequence voltage action amount 1;
superposing the negative sequence voltage acting quantity 1 with a basic voltage acting quantity under a target coordinate system to obtain a final voltage acting quantity;
and modulating the final voltage acting quantity to generate a driving signal required by the virtual synchronous machine control.
In another aspect of the present application, a control device for a virtual synchronous machine to cope with a voltage imbalance of a power grid is provided, which includes:
the frequency doubling suppression module is used for suppressing double fundamental frequency oscillation components in active power and reactive power output by the virtual synchronous machine to obtain a negative sequence voltage action amount 1;
the synthesis module is used for superposing the negative sequence voltage acting quantity 1 and a basic voltage acting quantity under a target coordinate system to obtain a final voltage acting quantity;
and the modulation module is used for modulating the final voltage acting quantity so as to generate a driving signal required by the virtual synchronous machine control.
According to the control method and device for the virtual synchronous machine to cope with the power grid voltage unbalance, on the basis of not increasing the system cost, through restraining the double fundamental frequency oscillation component in the active power and the reactive power, the virtual synchronous machine can reduce the overcurrent risk when the power grid voltage drops and improve the coping capability of coping with the power grid voltage asymmetrical drop while simulating the synchronous machine to realize the active frequency modulation and reactive voltage regulation output characteristics;
specifically, on one hand, when the voltage of the power grid is unbalanced, the double-frequency pulsating component of the output power of the virtual synchronous machine can be effectively inhibited, so that the output current of the virtual synchronous machine is limited, and the overcurrent risk is reduced; on the other hand, the current distortion problem does not need to be solved by limiting the bandwidths of the active frequency modulation loop and the reactive power loop, so that the design flexibility of the active power controller and the reactive power controller is improved;
compared with the existing VSG control method, the output current waveform obtained by control is better under the same current limiting requirement; under the requirement of the same output power quality, the current-limiting capacity can be stronger; in addition, the existing control method is generally provided for the virtual synchronous machine with a voltage and current double inner ring control structure, and the embodiment of the application meets the current limiting control requirement of the virtual synchronous machine without inner ring control under the unbalanced power grid voltage.
Drawings
Fig. 1 is a schematic block diagram of a control principle of a virtual synchronous machine provided in an embodiment of the present application when a grid voltage is unbalanced;
fig. 2 is a schematic diagram illustrating active power and reactive power control of a virtual synchronous machine according to an embodiment of the present disclosure;
fig. 3 is a schematic diagram of frequency doubling suppression provided in an embodiment of the present application;
FIG. 4 is a schematic diagram illustrating the final voltage contribution generated according to an embodiment of the present disclosure;
fig. 5 is a schematic diagram of a quadrature signal generator according to an embodiment of the present application;
fig. 6 is a schematic block diagram of a control principle of a virtual synchronous machine when a grid voltage is unbalanced according to another embodiment of the present application;
FIG. 7 is a virtual schematic diagram of negative sequence impedance provided in accordance with another embodiment of the present application;
FIG. 8 is a schematic diagram illustrating the final voltage contribution generation provided by another embodiment of the present application;
FIG. 9 is a schematic diagram of a second-order generalized integrator provided in an embodiment of the present application;
FIG. 10 is a simulation diagram illustrating a case where neither the negative sequence voltage acting amount 1 nor the negative sequence voltage acting amount 2 is added to the basic voltage acting amount according to the embodiment of the present application;
FIG. 11 is a simulation diagram illustrating the negative sequence voltage acting amount 1 superimposed on the basic voltage acting amount according to an embodiment of the present application;
FIG. 12 is a simulation diagram showing the negative sequence voltage acting amount 1 and the negative sequence voltage acting amount 2 superimposed on the basic voltage acting amount according to the embodiment of the present application;
fig. 13 is a schematic diagram of a control method for a virtual synchronous machine to cope with grid voltage imbalance according to an embodiment of the present application.
The implementation, functional features and advantages of the objectives of the present application will be further explained with reference to the accompanying drawings.
Detailed Description
In order to make the technical problems, technical solutions and advantageous effects to be solved by the present application clearer and clearer, the present application is further described in detail below with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are merely illustrative of the present application and are not intended to limit the present application.
In the description of the present application, it is to be understood that the terms "center", "upper", "lower", "front", "rear", "left", "right", and the like, indicate orientations or positional relationships based on the orientations or positional relationships shown in the drawings, are only for convenience in describing the present application and simplifying the description, and do not indicate or imply that the referred device or element must have a specific orientation, be constructed in a specific orientation, and be operated, and thus, should not be construed as limiting the present application. Furthermore, the terms "first" and "second" are used for descriptive purposes only and are not to be construed as indicating or implying relative importance.
The embodiment of the application relates to the following variables and definitions:
uoabc: virtual synchronous machine grid-connected point voltage
ioabc: virtual synchronous machine grid-connected current
iLabc: bridge arm output current
Zl: grid side impedance
Zv_neg: virtual negative sequence impedance
Kneg: gain of virtual impedance versus port negative sequence voltage
Zv_negmin: minimum set value of virtual impedance
Pvsc、Qvsc: the active power and the reactive power output by the virtual synchronous machine;
θvsc: output of active power controllerPhase position
Eref: amplitude of basic voltage action quantity output by reactive power controller
ωg: grid voltage angular frequency
ω0: rated angular frequency of network voltage
uneg_x_1、uneg_y_1: x-and y-axis components of negative sequence voltage applied quantity 1
unp、unq: output of virtual synchronous machine active and reactive power double fundamental frequency component suppression regulator
unp_qsg：unpOf orthogonal signals
unq_qsg：unqOf orthogonal signals
uneg_d_1、uneg_q_1: d-axis component and q-axis component of negative sequence voltage action quantity 1 output by virtual synchronous machine active and reactive power double fundamental frequency component suppression regulator
Uneg_omNegative component modulus of voltage of grid-connected point of virtual synchronous machine
Uom: virtual synchronous machine grid-connected point voltage modulus
iox、ioy: x, y axis components of output current of virtual synchronous machine
ineg_x、ineg_y: x-axis and y-axis components of negative sequence output current of virtual synchronous machine
uneg_x_2、uneg_y_2: x, y axis components of negative sequence virtual impedance voltage
evscref_x、evscref_y: x, y axis components of final voltage applied quantity
evscref_α、evscref_β: alpha and beta axis components of final voltage applied quantity
Fig. 1 to fig. 5 are schematic diagrams illustrating output current balance control of a virtual synchronous machine when a grid voltage is unbalanced according to an embodiment of the present application.
Fig. 2 is a schematic diagram of a power control module according to an embodiment of the present disclosure.
As shown in fig. 2, power controlThe input of the module is active power P calculated according to the voltage of the grid-connected point of the virtual synchronous machine and the output current of the virtual synchronous machinevscAnd reactive power Qvsc(ii) a The output of the power control module is the phase theta of the virtual synchronous machinevscAmplitude E of basic voltage applied quantityref. Phase thetavscAnd the amplitude E of the basic voltage applied quantityrefCan be calculated by the following formulas:
Eref＝GQR(Qref-Qvsc)+Uom (2)
in the formula, J is the inertia coefficient of the active power regulator, and D is the damping coefficient; gQRBeing a reactive power regulator, UomThe voltage modulus of the grid-connected point of the virtual synchronous machine is obtained.
Fig. 3 is a schematic diagram of a frequency doubling suppression module according to an embodiment of the present application.
The input of the frequency doubling suppression module is active power P calculated according to the voltage and the output current of the grid-connected point of the virtual synchronous machinevscAnd reactive power Qvsc(ii) a The output is the x-axis component u and the y-axis component u of the negative sequence voltage acting quantity 1neg_x_1、uneg_y_1。
Specifically, firstly, a resonance regulator with center frequency of double fundamental frequency is used for respectively regulating double fundamental frequency oscillation components in active power and reactive power to obtain output u of the regulatornpAnd unq(ii) a Then, the orthogonal signal generators shown in FIG. 5 are used to obtain unpOf (d) orthogonal component unp_qsgAnd unqOf (d) orthogonal component unq_qsg(ii) a Then synthesizing d-axis component u of negative sequence voltage action quantity 1 required by inhibiting double fundamental frequency oscillation component in active power and reactive power according to formula (3)neg_d_1And q-axis component uneg_q_1。
The transfer function of the output-to-input characteristic of a resonant regulator whose center frequency is twice the (grid) fundamental frequency, which is required in practice, is:
in the formula, KrAnd ωcrGain and bandwidth, omega, respectively, of a resonant regulatorgThe angular frequency is corresponding to the fundamental frequency of the power grid.
Finally, u is converted by a negative sequence voltage acting quantity 1 coordinate conversion moduleneg_d_1And uneg_q_1Converting into a target coordinate system xy to obtain x-axis and y-axis components u of the negative sequence voltage acting quantity 1neg_x_1、uneg_y_1。
When the target coordinate system is a dq coordinate system, the transformation formula of the negative sequence voltage acting amount 1 coordinate transformation module is as follows:
when the target coordinate system is an alpha beta coordinate system, the transformation formula of the negative sequence voltage acting quantity 1 coordinate transformation module is as follows:
fig. 4 is a schematic diagram of a voltage application quantity synthesis module according to an embodiment of the present application.
As shown in FIG. 4, the voltage applied quantity synthesis module applies the x-axis component u and the y-axis component u of the negative sequence voltage applied quantity 1neg_x_1、uneg_y_1Superposed on the basic voltage acting quantity to obtain the alpha and beta axis components e of the final voltage acting quantityvscref_α、evscref_β。
Specifically, the phase theta output by the module is controlled according to the active power and the reactive power of the virtual synchronous machinevscAnd basic voltage ofAmplitude E of doserefConverting the basic voltage acting quantity into an xy coordinate system through a basic voltage acting quantity coordinate conversion module to obtain x-axis and y-axis components e of the basic voltage acting quantityref_x_0、eref_y_0。
Corresponding to the frequency doubling suppression module, when the target coordinate system is a dq coordinate system, the conversion formula of the basic voltage acting quantity coordinate conversion module is as follows:
when the target coordinate system is an alpha beta coordinate system, the transformation formula of the basic voltage acting quantity coordinate transformation module is as follows:
secondly, the x-axis component u and the y-axis component u of the negative sequence voltage applied quantity 1 are measuredneg_x_1、uneg_y_1Superposed to the x-and y-axis components e of the applied basic voltage quantities, respectivelyref_x_0、eref_y_0To obtain the x-axis component e and the y-axis component e of the final voltage acting quantityvscref_x、evscref_yThe integrated formula is:
finally, the x-axis component e and the y-axis component e of the final voltage acting quantity are converted by a final voltage acting quantity coordinate conversion modulevscref_x、evscref_yConverting into alpha beta coordinate system to obtain alpha and beta axis components e of final voltage action quantityvscref_α、evscref_β。
When the target coordinate system is a dq coordinate system, the transformation formula of the final voltage acting amount coordinate transformation module is as follows:
when the target coordinate system is an alpha beta coordinate system, the transformation formula of the final voltage acting quantity coordinate transformation module is as follows:
the modulation module applies alpha and beta axis components e of the final voltagevscref_α、evscref_βThe PWM driving signals required by the virtual synchronous machine control are generated through PWM modulation, for example, a three-phase space vector modulation method is adopted.
Fig. 10 shows a simulation result that when the negative sequence voltage acting amount 1 and/or the negative sequence voltage acting amount 2 are not superimposed on the basic voltage acting amount, the grid voltage single phase drops by 20% and continues for 0.5s in the operation process of the virtual synchronous machine, and then the normal operation is recovered.
Fig. 11 shows the simulation result in which the negative sequence voltage applied amount 1 is added to the basic voltage applied amount. Compared with fig. 10, when the grid voltage is unbalanced, the double-frequency ripple component of the output power of the virtual synchronous machine can be effectively suppressed, so that the output current of the virtual synchronous machine is limited, and the overcurrent risk is reduced.
Fig. 6 to 8 are schematic diagrams illustrating output current balance control of a virtual synchronous machine when a grid voltage is unbalanced according to another embodiment of the present application.
Different from the examples of fig. 1 to 5, the virtual synchronous machine further comprises a negative sequence impedance virtualization module, wherein the negative sequence impedance virtualization module is used for virtualizing negative sequence impedance at the output end of the virtual synchronous machine so as to restrain negative sequence current.
As shown in fig. 7, first, the output current of the virtual synchronous machine is transformed to the target coordinate system xy by the current coordinate transformation module to obtain the x-axis component i and the y-axis component i thereofox、ioy；
When the target coordinate system is a dq coordinate system, the transformation formula of the current coordinate transformation module is as follows:
when the target coordinate system is an alpha beta coordinate system, the transformation formula of the current coordinate transformation module is as follows:
secondly, extracting i by using a negative sequence component extraction moduleoxAnd ioyNegative sequence current component of (1) to obtain ineg_xAnd ineg_y；
When the target coordinate system is a dq coordinate system, the negative sequence component extraction module may be implemented by a band-pass filter whose center frequency is twice the fundamental frequency of the power grid, and a transfer function of output to input characteristics of the band-pass filter is as follows:
in the formula, ωcbIs the bandwidth, omega, of a band-pass filtergThe angular frequency is corresponding to the fundamental frequency of the power grid.
When the target coordinate system is an α β coordinate system, the negative sequence component extraction module can be implemented by using a second-order generalized integrator-based negative sequence component extraction module shown in fig. 9.
Finally, extracting the negative sequence current component ineg_xAnd ineg_yRespectively associated with a specific virtual impedance Zv_negMultiplying to obtain x-axis and y-axis components u of the negative sequence voltage acting quantity 2neg_x_2、uneg_y_2。
Virtual impedance Zv_negAnd the modulus of the negative sequence component of the grid voltage increases.
In this example, Zv_negSet as follows:
Zv_neg＝Zv_negmin+KnegUneg_om (11)
in the formula, Zv_negmin>0 is the minimum set value of the virtual impedance, KnegGain, U, for a virtual impedance > 0neg_omGrid connection for virtual synchronous machineThe negative sequence voltage component modulus of the dot voltage.
As shown in FIG. 8, the voltage applied quantity synthesis module applies the x-axis component u and the y-axis component u of the negative sequence voltage applied quantity 2neg_x_2uneg_y_2And x-and y-axis components u of negative sequence voltage applied quantity 1neg_x_1、uneg_y_1Superposed to the basic voltage acting quantity output by the power control module to obtain the alpha and beta axis components e of the final voltage acting quantityvscref_α、evscref_β。
Specifically, the phase theta output by the module is controlled according to the active power and the reactive power of the virtual synchronous machinevscAnd the amplitude E of the applied quantity of the basic voltagerefConverting the basic voltage acting quantity into an xy coordinate system through a basic voltage acting quantity coordinate conversion module to obtain x-axis and y-axis components e of the basic voltage acting quantityref_x_0、eref_y_0。
When the target coordinate system is a dq coordinate system, the transformation formula of the basic voltage acting quantity coordinate transformation module is as follows:
when the target coordinate system is an alpha beta coordinate system, the transformation formula of the basic voltage acting quantity coordinate transformation module is as follows:
secondly, the x-axis component u and the y-axis component u of the negative sequence voltage acting quantity 2 are combinedneg_x_2、uneg_y_2And x-and y-axis components u of negative sequence voltage applied quantity 1neg_x_1、uneg_y_1Superposed to the x-and y-axis components e of the applied basic voltage quantities, respectivelyref_x_0、eref_y_0To obtain the x-axis component e and the y-axis component e of the final voltage acting quantityvscref_x、evscref_yThe integrated formula is:
finally, the x-axis component e and the y-axis component e of the final voltage acting quantity are converted by a final voltage acting quantity coordinate conversion modulevscref_x、evscref_yConverting into alpha beta coordinate system to obtain alpha and beta axis components e of final voltage action quantityvscref_α、evscref_β。
When the target coordinate system is a dq coordinate system, the transformation formula of the final voltage acting amount coordinate transformation module is as follows:
when the target coordinate system is an alpha beta coordinate system, the transformation formula of the final voltage acting quantity coordinate transformation module is as follows:
the modulation module applies alpha and beta axis components e of the final voltagevscref_α、evscref_βThe PWM driving signals required by the virtual synchronous machine control are generated through PWM modulation, for example, a three-phase space vector modulation method is adopted.
Fig. 10 shows a simulation result that when the negative sequence voltage acting amount 1 and/or the negative sequence voltage acting amount 2 are not superimposed on the basic voltage acting amount, the grid voltage single phase drops by 20% and continues for 0.5s in the operation process of the virtual synchronous machine, and then the normal operation is recovered.
Fig. 12 shows the simulation result in which the negative sequence voltage applied amount 1 and the negative sequence voltage applied amount 2 are added to the basic voltage applied amount. Compared with fig. 10, when the grid voltage is unbalanced, the double-frequency ripple component of the output power of the virtual synchronous machine can be effectively suppressed, so that the output current of the virtual synchronous machine is limited, and the overcurrent risk is reduced.
Fig. 13 is a schematic diagram of a control method for a virtual synchronous machine to cope with grid voltage imbalance according to an embodiment of the present application.
As shown in fig. 13, the method includes:
step S11, inhibiting the double fundamental frequency oscillation component in the active power and the reactive power output by the virtual synchronous machine to obtain a negative sequence voltage acting amount 1;
step S12, overlapping the negative sequence voltage acting quantity 1 with a basic voltage acting quantity under a target coordinate system to obtain a final voltage acting quantity;
and step S13, modulating the final voltage acting quantity to generate a driving signal required by the virtual synchronous machine control.
In one example, the suppressing the double fundamental frequency oscillation component in the active power and the reactive power output by the virtual synchronous machine to obtain the negative sequence voltage acting amount 1 includes:
adjusting the two-fold fundamental frequency oscillation component in the active power and the reactive power output by the virtual synchronous machine to obtain an adjustment component;
obtaining an orthogonal component of the adjustment component by an orthogonal signal generator;
and obtaining the negative sequence voltage acting quantity 1 according to the adjusting component and the orthogonal component thereof.
In one example, the phase and the amplitude of the basic voltage acting quantity of the virtual synchronous machine are subjected to coordinate transformation, and the basic voltage acting quantity in the target coordinate system is obtained.
In an example, the method further comprises:
calculating active power and reactive power output by the virtual synchronous machine according to the voltage of the grid-connected point of the virtual synchronous machine and the output current of the virtual synchronous machine;
and calculating the phase and the amplitude of the basic voltage acting quantity of the virtual synchronous machine according to the active power and the reactive power output by the virtual synchronous machine.
In an example, the superimposing the negative-sequence voltage applied quantity 1 and the basic voltage applied quantity in the target coordinate system to obtain the final voltage applied quantity further includes:
extracting a negative sequence current component in the output current of the virtual synchronous machine; multiplying the negative sequence current component by a specific virtual impedance to obtain a negative sequence voltage acting quantity 2;
superposing the negative sequence voltage acting quantity 1 and a basic voltage acting quantity under a target coordinate system to obtain a final voltage acting quantity, wherein the steps of:
and superposing the negative sequence voltage acting quantity 1, the negative sequence voltage acting quantity 2 and the basic voltage acting quantity under the target coordinate system to obtain the final voltage acting quantity.
In one example, the virtual impedance includes at least one of a resistive impedance, an inductive impedance, and a resistive-inductive impedance.
In one example, the virtual impedance is proportional to a negative sequence voltage component modulus of the virtual synchronous machine grid-connected point voltage.
In an example, the output current of the virtual synchronous machine comprises a grid-connected point current or a bridge arm current.
In one example, the extracting a negative-sequence current component in an output current of a virtual synchronous machine includes:
carrying out coordinate transformation on the output current of the virtual synchronous machine to obtain a current component under a target coordinate system;
and extracting the current component under the target coordinate system to obtain the negative sequence current component.
In one example, the target coordinate system includes a dq coordinate system or an α β coordinate system.
The preferred embodiments of the present application have been described above with reference to the accompanying drawings, and are not intended to limit the scope of the claims of the application accordingly. Any modifications, equivalents and improvements which may occur to those skilled in the art without departing from the scope and spirit of the present application are intended to be within the scope of the claims of the present application.
Claims (10)
1. A method for controlling a virtual synchronous machine to cope with grid voltage imbalance, the method comprising:
inhibiting a double fundamental frequency oscillation component in active power and reactive power output by the virtual synchronous machine to obtain a negative sequence voltage action amount 1;
superposing the negative sequence voltage acting quantity 1 with a basic voltage acting quantity under a target coordinate system to obtain a final voltage acting quantity;
and modulating the final voltage acting quantity to generate a driving signal required by the virtual synchronous machine control.
2. The method according to claim 1, wherein the suppressing the double fundamental frequency oscillation component in the active power and the reactive power output by the virtual synchronous machine to obtain the negative sequence voltage acting amount 1 comprises:
adjusting the two-fold fundamental frequency oscillation component in the active power and the reactive power output by the virtual synchronous machine to obtain an adjustment component;
obtaining an orthogonal component of the adjustment component by an orthogonal signal generator;
and obtaining the negative sequence voltage acting quantity 1 according to the adjusting component and the orthogonal component thereof.
3. The method according to claim 1, wherein the phase and the amplitude of the fundamental voltage acting quantity of the virtual synchronous machine are subjected to coordinate transformation to obtain the fundamental voltage acting quantity in the target coordinate system.
4. The method of claim 3, further comprising:
calculating active power and reactive power output by the virtual synchronous machine according to the voltage of the grid-connected point of the virtual synchronous machine and the output current of the virtual synchronous machine;
and calculating the phase and the amplitude of the basic voltage acting quantity of the virtual synchronous machine according to the active power and the reactive power output by the virtual synchronous machine.
5. The method according to claim 1, wherein the step of superimposing the negative-sequence voltage applied quantity 1 with the basic voltage applied quantity in the target coordinate system to obtain the final voltage applied quantity further comprises:
extracting a negative sequence current component in the output current of the virtual synchronous machine; multiplying the negative sequence current component by a specific virtual impedance to obtain a negative sequence voltage acting quantity 2;
superposing the negative sequence voltage acting quantity 1 and a basic voltage acting quantity under a target coordinate system to obtain a final voltage acting quantity, wherein the steps of:
and superposing the negative sequence voltage acting quantity 1, the negative sequence voltage acting quantity 2 and the basic voltage acting quantity under the target coordinate system to obtain the final voltage acting quantity.
6. The method of claim 5, wherein the virtual impedance comprises at least one of a resistive impedance, an inductive impedance, and a resistive-inductive impedance.
7. The method of claim 5, wherein the virtual impedance is proportional to a negative sequence voltage component modulus of a virtual synchronous machine grid-connected point voltage.
8. The method of claim 5, wherein the output current of the virtual synchronous machine comprises a grid-connected point current or a bridge arm current.
9. The method of claim 5, wherein extracting a negative sequence current component in an output current of the virtual synchronous machine comprises:
carrying out coordinate transformation on the output current of the virtual synchronous machine to obtain a current component under a target coordinate system;
and extracting the current component under the target coordinate system to obtain the negative sequence current component.
10. A control apparatus for a virtual synchronous machine to cope with grid voltage imbalance, comprising:
the frequency doubling suppression module is used for suppressing double fundamental frequency oscillation components in active power and reactive power output by the virtual synchronous machine to obtain a negative sequence voltage action amount 1;
the synthesis module is used for superposing the negative sequence voltage acting quantity 1 and a basic voltage acting quantity under a target coordinate system to obtain a final voltage acting quantity;
and the modulation module is used for modulating the final voltage acting quantity so as to generate a driving signal required by the virtual synchronous machine control.
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| CN114243784A (en) * | 2021-12-27 | 2022-03-25 | 西南交通大学 | The balanced current output control method of virtual synchronous machine under the condition of unbalanced voltage |
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