阅读说明：本技术 微网逆变器控制方法、系统、存储介质及计算设备 (Microgrid inverter control method and system, storage medium and computing equipment ) 是由 周子奇 冯炜 过亮 庄圣伦 孙素娟 孔祥梅 曲慧星 钱爽 单馨 张平 徐志英 于 2021-05-26 设计创作，主要内容包括：本发明公开了一种微网逆变器控制方法,包括对电容电压、电网相电压、注入负荷电流和注入电网电流进行采样；将采样的电容电压、电网相电压、注入负荷电流和注入电网电流输入预先设计的新单环控制模型,进行微网逆变器控制；其中,新单环控制模型为：在传统单环控制模型的基础上,将上一采样周期的调制电压按反馈比例系数反馈回控制环路中。同时公开了相应的系统。本发明将上一采样周期的调制电压按反馈比例系数反馈回控制环路中,从而偏移临界频率,实现对谐振频率变化的鲁棒性。(The invention discloses a micro-grid inverter control method which comprises the steps of sampling capacitor voltage, grid phase voltage, injected load current and injected grid current; inputting the sampled capacitor voltage, the power grid phase voltage, the injected load current and the injected power grid current into a pre-designed new single-ring control model to control the micro-grid inverter; wherein, the new single-ring control model is as follows: on the basis of the traditional single-ring control model, the modulation voltage of the previous sampling period is fed back to the control loop according to the feedback proportionality coefficient. A corresponding system is also disclosed. The invention feeds back the modulation voltage of the last sampling period to the control loop according to the feedback proportion coefficient, thereby shifting the critical frequency and realizing the robustness to the change of the resonant frequency.)

1. The microgrid inverter control method is characterized by comprising the following steps:

sampling the capacitor voltage, the power grid phase voltage, the injected load current and the injected power grid current;

inputting the sampled capacitor voltage, the power grid phase voltage, the injected load current and the injected power grid current into a pre-designed new single-ring control model to control the micro-grid inverter; wherein, the new single-ring control model is as follows: on the basis of the traditional single-ring control model, the modulation voltage of the previous sampling period is fed back to the control loop according to the feedback proportionality coefficient.

2. The microgrid inverter control method of claim 1, characterized in that: the new single-ring control model is characterized in that on the basis of the traditional single-ring control model, the difference value of the PR control output of the sampling period and the modulation voltage of the last sampling period fed back according to the feedback proportion coefficient is used as the modulation voltage of the sampling period.

3. The microgrid inverter control method of claim 1, characterized in that: the specific process of designing a new single-loop control model is,

constructing a new single-ring control model;

carrying out stability analysis on the new single-ring control model to obtain a constraint condition of a feedback proportionality coefficient;

and obtaining the control parameters of the new single-ring control model according to the constraint condition of the feedback proportionality coefficient and the preset upper limit of the resonance frequency.

4. The microgrid inverter control method of claim 1, characterized in that: the stability analysis is carried out on the new single-ring control model to obtain the constraint condition of the feedback proportionality coefficient, the specific process is,

and performing w transformation on the denominator of the open-loop transfer function of the new single-loop control model, and obtaining the constraint condition of the feedback proportionality coefficient according to the Laus criterion.

5. The microgrid inverter control method of claim 4, characterized in that: the open-loop transfer function of the new single-loop control model is,

wherein z represents a z domain; t is_o(z) is the open loop transfer function; g_PR(z) is the transfer function of the PR control; p is feedbackA proportionality coefficient; k_PWMModulating the equivalent gain coefficient for PWM; l is₁The micro-grid inverter side inductor is adopted; l is_gA microgrid inverter network side inductor; t is_sIs a sampling period; omega_rgThe resonant frequency of the LCL filter.

6. The microgrid inverter control method of claim 4, characterized in that: the constraint condition of the feedback proportionality coefficient is,

wherein, P is a feedback proportionality coefficient.

7. The microgrid inverter control method of claim 3, characterized in that: the obtained control parameters comprise feedback proportionality coefficients and parameters for PR control, and specifically meet the following conditions:

1＞P＞-1-2cos(ω_rgmaxT_s)

wherein, P is a feedback proportion coefficient; t is_sIs a sampling period; omega_rgmaxIs the upper limit of the resonance frequency;

wherein k is_pIs a proportionality coefficient for PR control; k is a radical of_rResonance coefficient, ω, for PR control_bA bandwidth controlled for PR; parameter w ═ arccos (- (1+ P)/2)]/T_sArccos represents an inverse cosine trigonometric function; s represents the laplacian operator; jw represents a pure imaginary number with amplitude w; omega_oThe angular velocity corresponding to the fundamental frequency; l is₁The micro-grid inverter side inductor is adopted; l is_gThe micro-grid inverter is a grid side inductor.

8. Microgrid inverter control system, its characterized in that includes:

the method comprises the following steps: sampling the capacitor voltage, the power grid phase voltage, the injected load current and the injected power grid current;

a control module: inputting the sampled capacitor voltage, the power grid phase voltage, the injected load current and the injected power grid current into a pre-designed new single-ring control model to control the micro-grid inverter; wherein, the new single-ring control model is as follows: on the basis of the traditional single-ring control model, the modulation voltage of the previous sampling period is fed back to the control loop according to the feedback proportionality coefficient.

9. A computer readable storage medium storing one or more programs, characterized in that: the one or more programs include instructions that, when executed by a computing device, cause the computing device to perform any of the methods of claims 1-7.

10. A computing device, comprising:

one or more processors, one or more memories, and one or more programs stored in the one or more memories and configured to be executed by the one or more processors, the one or more programs including instructions for performing any of the methods of claims 1-7.

Technical Field

The invention relates to a microgrid inverter control method, a microgrid inverter control system, a storage medium and computing equipment, and belongs to the field of new energy grid connection.

Background

Voltage source inverters based on voltage control have been widely used in many power conversion applications, such as 50/60Hz Uninterruptible Power Supplies (UPS), 400Hz Ground Power Units (GPU) for aircraft, Distributed Generation (DG), and the like. LC-type output filters are typically required in these applications to suppress the switching ripple of the inverter and to provide a high quality output voltage. If the existence of transformer leakage inductance and grid impedance is considered, the transformer leakage inductance and the grid impedance form an LCL filter together with an LC filter. The use of LCL type filters presents resonance problems which present a significant challenge to the stability of the control system. Therefore, how to design the voltage controller is related to the quality of the operation of the voltage source type inverter.

The voltage single-loop control method (short for "single-loop control method") has the advantages of simple control structure and capacity and current sensor saving, and becomes a hot spot of recent research. However, due to the inherent delay caused by the digital control, the control generates a critical frequency, and when the resonant frequency of the LCL filter is higher or lower than the critical frequency, the voltage control parameter has different design ranges, so that the traditional single-loop control method cannot realize the robustness to the resonant frequency change.

Disclosure of Invention

The invention provides a microgrid inverter control method, a microgrid inverter control system, a storage medium and computing equipment, and solves the problems disclosed in the background art.

In order to solve the technical problems, the technical scheme adopted by the invention is as follows:

the microgrid inverter control method comprises the following steps:

sampling the capacitor voltage, the power grid phase voltage, the injected load current and the injected power grid current;

inputting the sampled capacitor voltage, the power grid phase voltage, the injected load current and the injected power grid current into a pre-designed new single-ring control model to control the micro-grid inverter; wherein, the new single-ring control model is as follows: on the basis of the traditional single-ring control model, the modulation voltage of the previous sampling period is fed back to the control loop according to the feedback proportionality coefficient.

The new single-ring control model is characterized in that on the basis of the traditional single-ring control model, the difference value of the PR control output of the sampling period and the modulation voltage of the last sampling period fed back according to the feedback proportion coefficient is used as the modulation voltage of the sampling period.

The specific process of designing a new single-loop control model is,

constructing a new single-ring control model;

carrying out stability analysis on the new single-ring control model to obtain a constraint condition of a feedback proportionality coefficient;

and obtaining the control parameters of the new single-ring control model according to the constraint condition of the feedback proportionality coefficient and the preset upper limit of the resonance frequency.

The stability analysis is carried out on the new single-ring control model to obtain the constraint condition of the feedback proportionality coefficient, the specific process is,

and performing w transformation on the denominator of the open-loop transfer function of the new single-loop control model, and obtaining the constraint condition of the feedback proportionality coefficient according to the Laus criterion.

The open-loop transfer function of the new single-loop control model is,

wherein z represents a z domain; t is_o(z) is the open loop transfer function; g_PR(z) is the transfer function of the PR control; p is a feedback proportionality coefficient; k_PWMModulating the equivalent gain coefficient for PWM; l is₁The micro-grid inverter side inductor is adopted; l is_gA microgrid inverter network side inductor; t is_sIs a sampling period; omega_rgThe resonant frequency of the LCL filter.

The constraint condition of the feedback proportionality coefficient is,

wherein, P is a feedback proportionality coefficient.

The obtained control parameters comprise feedback proportionality coefficients and parameters for PR control, and specifically meet the following conditions:

1＞P＞-1-2cos(ω_rgmaxT_s)

wherein, P is a feedback proportion coefficient; t is_sIs a sampling period; omega_rgmaxIs the upper limit of the resonance frequency;

wherein k is_pIs a proportionality coefficient for PR control; k is a radical of_rResonance coefficient, ω, for PR control_bA bandwidth controlled for PR; parameter w ═ arccos (- (1+ P)/2)]/T_sArccos represents an inverse cosine trigonometric function; s represents the laplacian operator; jw represents a pure imaginary number with amplitude w; omega_oThe angular velocity corresponding to the fundamental frequency; l is₁The micro-grid inverter side inductor is adopted; l is_gThe micro-grid inverter is a grid side inductor.

Microgrid inverter control system includes:

the method comprises the following steps: sampling the capacitor voltage, the power grid phase voltage, the injected load current and the injected power grid current;

a control module: inputting the sampled capacitor voltage, the power grid phase voltage, the injected load current and the injected power grid current into a pre-designed new single-ring control model to control the micro-grid inverter; wherein, the new single-ring control model is as follows: on the basis of the traditional single-ring control model, the modulation voltage of the previous sampling period is fed back to the control loop according to the feedback proportionality coefficient.

The invention achieves the following beneficial effects: 1. according to the invention, the modulation voltage of the last sampling period is fed back to the control loop according to the feedback proportional coefficient, so that the critical frequency is deviated, and the robustness to the change of the resonant frequency is realized; 2. when the single-ring control model is designed, the stability of the control model when the resonant frequency of the filter is smaller than the maximum value can be ensured only by setting the upper limit of the resonant frequency and designing the parameters of the controller on the basis, and the design is simple; 3. the feedback loop of the single-loop control model only uses an internal variable, and an additional sensor is not needed.

Drawings

Fig. 1 is a schematic diagram of microgrid inverter control according to the present invention;

FIG. 2 is an equivalent block diagram of a single loop control model according to the present invention;

FIG. 3 is a single-phase waveform of converter output capacitor voltage and injected grid current corresponding to a first set of control parameters;

FIG. 4 is a single-phase waveform of converter output capacitor voltage and injected grid current corresponding to a second set of control parameters;

FIG. 5 is a single-phase waveform of the converter output capacitor voltage and the injected grid current corresponding to the third set of control parameters;

fig. 6 is a single-phase waveform of the converter output capacitor voltage and the injected grid current corresponding to the fourth set of control parameters.

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.

The microgrid inverter control method comprises the following steps:

step 1, sampling capacitor voltage, grid phase voltage, injected load current and injected grid current;

step 2, inputting the sampled capacitor voltage, the power grid phase voltage, the injected load current and the injected power grid current into a pre-designed new single-ring control model to control the micro-grid inverter; wherein, the new single-ring control model is as follows: on the basis of the traditional single-ring control model, the modulation voltage of the previous sampling period is fed back to the control loop according to the feedback proportionality coefficient.

The control method feeds back the modulation voltage of the previous sampling period to the control loop according to the feedback proportion coefficient, so that the critical frequency is deviated, the robustness to the change of the resonant frequency is realized, and the feedback loop of the single-loop control model only uses an internal variable without an additional sensor.

Conventional single loop controlI.e. directly to the filter capacitor voltage u of the LC filter_ckAnd (3) controlling: phase voltage u to capacitor_ckGrid e_gPhase voltage e of_gkCurrent i injected into the load_lkAnd current i injected into the grid_gkSampling (consistent with step 1 of the present application); to sampled electric network e_gPhase voltage e of_gkCurrent i injected into the load_lkAnd current i injected into the grid_gkProcessing to obtain a reference voltage u_ck_re_f(ii) a Will u_ckAnd u_ck__refDirectly comparing, directly outputting a modulation voltage reference value through a PR controller, delaying a sampling period, and inputting a corresponding duty ratio into an inverter Q₁～Q₆In (1).

As shown in fig. 1 and 2, the specific modification of the conventional single loop control model here is as follows: on the basis of a traditional single-ring control model, the difference value of the PR control output of the sampling period and the modulation voltage of the previous sampling period fed back according to the feedback proportionality coefficient is used as the modulation voltage of the sampling period.

Based on the improved principle, the specific process of designing the new single-ring control model is as follows:

1) constructing a new single-ring control model;

the method comprises the following steps of controlling the microgrid inverter under a two-phase static coordinate system, constructing a new single-ring control model based on a traditional single-ring control model, wherein the corresponding open-loop transfer function of the model is as follows:

wherein z represents a z domain; t is_o(z) is the open loop transfer function; g_PR(z) is the transfer function of the PR control; p is a feedback proportionality coefficient; k_PWMModulating the equivalent gain coefficient for PWM; l is₁The micro-grid inverter side inductor is adopted; l is_gA microgrid inverter network side inductor; t is_sIs a sampling period;

ω_rgfor the resonant frequency of the LCL filter, the specific expression is:

wherein, C_fIs the capacitance value f of the filter capacitor of the LC filter in FIG. 1_rgFor LC filters in weak networks e_gResonant frequency at connection;

PR control is proportional resonance control, and the s-domain expression of the transfer function is as follows:

wherein k is_pIs a proportionality coefficient for PR control; k is a radical of_rResonance coefficient, ω, for PR control_bA bandwidth controlled for PR; omega_oThe angular velocity corresponding to the fundamental frequency; f. of_oThe fundamental frequency of the power grid;

the feedback proportionality coefficient and the parameter of PR control are mainly designed in the model.

2) Regarding the load current as external disturbance, performing stability analysis on the new single-ring control model to obtain a constraint condition of a feedback proportionality coefficient, wherein the specific process is as follows:

carrying out w transformation on the denominator of the open-loop transfer function of the new single-loop control model, and obtaining the constraint conditions of the feedback proportionality coefficient according to the Laus criterion as follows:

wherein, P is a feedback proportionality coefficient.

3) Obtaining control parameters of the new single-ring control model according to the constraint condition of the feedback proportionality coefficient and a preset upper limit of the resonant frequency, wherein the control parameters specifically comprise the feedback proportionality coefficient and parameters for PR control;

presetting the expected resonant frequency at [ omega ]_rgmin,ω_rgmax]And (3) internal variation, combining the constraint conditions of the feedback proportionality coefficient, wherein the obtained feedback proportionality coefficient needs to meet the following conditions:

1＞P＞-1-2cos(ω_rgmaxT_s)

wherein, ω is_rgmaxIs the upper limit of the resonance frequency;

the parameters of the PR control need to satisfy the following conditions:

wherein, the parameter w ═ arccos (- (1+ P)/2)]/T_sArccos represents an inverse cosine trigonometric function; s represents laplacian, denoted as s ═ jw; jw represents a pure imaginary number with amplitude w, by which T can be represented_o(z) from the frequency domain to the complex domain, thereby facilitating the calculation of the controller parameters. And (3) substituting the control parameters meeting the conditions into the model constructed in the step 1), so as to obtain a complete new single-ring control model.

Through the process, when the single-ring control model is designed, only the upper limit of the resonant frequency needs to be set, and the stability of the control model when the resonant frequency of the filter is smaller than the maximum value can be ensured by designing the controller parameters on the basis, so that the design is simpler compared with the design of the traditional model.

The method is applied to a distributed power generation system, a specific control schematic diagram is shown in figure 1, a new model is shown in figure 2, wherein the grid voltage e is collected firstly_gkCurrent i injected into the grid_gkCurrent i injected into the load_lkGenerating the reference voltage u of the alpha-beta axis of the capacitor by a certain strategy_{c_ref}(u_{cα_ref},u_{cβ_ref}) Feedback voltage u of capacitance voltage alpha beta axis_c(u_cα、u_cβ) From the voltage u of the capacitor phase_ckThe samples are obtained by Clark transformation, u_{c_ref}And u_cPerforming PR control by taking difference, wherein the output of the PR controller is different from the modulation voltage of the last period fed back according to the feedback proportionality coefficient P, and the obtained output is the modulation voltage u_m(u_mα、u_mβ) And PWM modulation output is carried out after one sampling period is delayed, and the corresponding output voltage of the inverter side is u_con。

In FIG. 1S₁And S₂Representing a load switch and a grid-connected switch; q₁～Q₆Represents a power device; u shape_dcRepresenting the inverter dc bus voltage.

Microgrid inverter inductor L in fig. 1₁Inductance value of 1mH, filter capacitor C_fThe capacitance value is 10 muF, and the sum of the power grid impedance and the transformer leakage inductance is assumed to be changed between 0.2mH and 1 mH; then the resonance frequency can be calculated to be [2250Hz,3900Hz]The interval varies. The sampling frequency is 10kHz, then-1-2 cos (omega) can be calculated_rgmaxT_s) 0.54, so that P may be 0.9.

Since the amplitude of the resonant component of PR control is negligible at high frequencies, P is brought to be available:

get k_pIs-0.5, and k is taken in consideration of the actual dynamic response performance requirement on the capacitor voltage_rIs 100;

the simulation test is carried out by four groups of simulation experiments, each group of simulation parameters are shown in table 1, wherein 1 and 2 groups adopt the control parameters; 3. the 4 groups are parameters of the traditional method (P under the traditional method is considered as 0), and PR control parameters under the two methods are the same, and the difference is only that the value of P is different.

TABLE 1 simulation parameters

As shown in fig. 2(a) and 2(b), it is explained that resonance is suppressed at this time, thereby ensuring stable operation of the control; when the conventional method is used, as shown in FIG. 2(c) and FIG. 2(d), only L can be measured_gThe operation is stable under the condition of 1 mH; when the impedance of the power grid is changed to 0.2mH, the stable operation of the system cannot be ensured by adopting the same control parameters, and the capacitor voltage and the power grid current are seen to generate high-frequency oscillation and gradually diverge. It can be found that the adoption of the control method has better effect on the impedance change of the power gridRobustness, thus verifying the effectiveness of the proposed method.

Microgrid inverter control system includes:

the method comprises the following steps: sampling the capacitor voltage, the power grid phase voltage, the injected load current and the injected power grid current;

a control module: inputting the sampled capacitor voltage, the power grid phase voltage, the injected load current and the injected power grid current into a pre-designed new single-ring control model to control the micro-grid inverter; wherein, the new single-ring control model is as follows: on the basis of the traditional single-ring control model, the modulation voltage of the previous sampling period is fed back to the control loop according to the feedback proportionality coefficient.

A computer readable storage medium storing one or more programs, the one or more programs comprising instructions, which when executed by a computing device, cause the computing device to perform a microgrid inverter control method.

A computing device comprising one or more processors, one or more memories, and one or more programs stored in the one or more memories and configured to be executed by the one or more processors, the one or more programs including instructions for performing a microgrid inverter control method.

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 present invention is not limited to the above embodiments, and any modifications, equivalent replacements, improvements, etc. made within the spirit and principle of the present invention are included in the scope of the claims of the present invention which are filed as the application.