A serial micro-grid communication-free adaptive virtual inertia control method and device

Abstract

This invention discloses a communication-free adaptive virtual inertial control method and device for a series-connected microgrid. The method includes: calculating active and reactive power based on the voltage and current information of the i-th inverter; obtaining the angular frequency differential term based on the active and reactive power, combined with locally acquired angular frequency, damping coefficient, rated inertia coefficient, and control coefficient; obtaining the angular frequency reference value of the i-th inverter based on the angular frequency differential term and the rated angular frequency; setting the voltage amplitude reference value of the i-th inverter to its rated value; and obtaining the sinusoidal voltage reference value of the i-th inverter; and adjusting the i-th inverter using the voltage outer loop and current inner loop based on the sinusoidal voltage reference value to achieve communication-free control of the entire system. This invention can suppress dynamic power oscillations, thereby improving the dynamic performance of the system and providing users with high-quality power.

Description

Technical Field

[0001] This invention relates to a communication-free adaptive virtual inertial control method and device for a series-connected microgrid, belonging to the field of smart grid technology. Background Technology

[0002] Virtual synchronous machine (VSM) technology is widely used in power grids to provide inertial support and damping effects, effectively suppressing power oscillations and enhancing system stability. Furthermore, parallel and series connections are two fundamental forms of complex networks. Parallel VSM systems have been extensively studied, with numerous publications revealing the power oscillation mechanism and proposing numerous power oscillation suppression methods.

[0003] Furthermore, series systems based on H-bridge inverters are widely used in high-voltage power networks. Although a great deal of research has been done on the underlying self-synchronization control methods for series power network systems, these methods cannot guide the overall control of the system from the physical concepts of damping and inertia to suppress dynamic power oscillations.

[0004] Therefore, establishing a series-type virtual synchronous machine model and proposing a communication-free adaptive virtual inertial control method and device for series-type microgrids is of great significance for improving the dynamic performance of series-type microgrid systems, enhancing system stability, and providing users with high-quality power. Summary of the Invention

[0005] The technical problem to be solved by the present invention is to provide a communication-free adaptive virtual inertial control method and device for a series microgrid, which is used to suppress power oscillations, improve the dynamic performance of the series microgrid system, enhance system stability, and provide users with high-quality power, thereby solving the technical problems existing in the prior art.

[0006] The technical solution adopted in this invention is: a communication-free adaptive virtual inertial control method and device for a series-connected microgrid, the method comprising the following steps:

[0007] Step 1: Calculate the active power and reactive power based on the voltage and current information of the i-th inverter.

[0008] Step 2: Based on the active power and reactive power from Step 1, and combined with the locally acquired angular frequency, damping coefficient, rated inertia coefficient, and control coefficient, obtain the differential term of the angular frequency.

[0009] Step 3: Based on the angular frequency differential term in Step 2 and the rated angular frequency, obtain the angular frequency reference value of the i-th inverter, set the voltage amplitude reference value of the i-th inverter to the rated value, and obtain the sinusoidal voltage reference value of the i-th inverter.

[0010] Step 4: Based on the sinusoidal voltage reference value described in Step 3, adjust the i-th inverter using the outer voltage loop and inner current loop.

[0011] The method for calculating the differential term of the i-th inverter angular frequency in step 2 is as follows:

[0012] According to the active power P i and reactive power Q i Combined with locally acquired angular frequency ω i Damping coefficient D, rated inertia coefficient J 0i And the control coefficient k, to obtain the differential term dω of the i-th inverter angular frequency. Di / dt, its expression is:

[0013]

[0014] In the formula ω com,i P is the angular frequency of the line current. * P is the rated active power. Di =P i -P * ;ω * The rated angular frequency, ω Di ω is a transition variable. Di =ω i -ω * ; sgn(·) is a symbolic function.

[0015] Based on the angular frequency differential term described in step 2, and then based on the rated angular frequency, the angular frequency reference value of the i-th inverter is obtained, and its expression is:

[0016]

[0017] ω i =ω * +ω Di

[0018] The voltage amplitude reference value of the i-th inverter is set to the rated value, and the expression is:

[0019] V i =V *

[0020] Based on the voltage amplitude reference and the voltage phase angle reference, obtain the sinusoidal voltage reference of the i-th inverter.

[0021] A communication-free adaptive virtual inertial control device for a series-connected microgrid includes an active power and reactive power calculation module, an angular frequency differential term acquisition module, a voltage reference acquisition module, and a voltage regulation module. The active power and reactive power calculation module is used to acquire the active and reactive power of the i-th inverter; the angular frequency differential term acquisition module is used to acquire the angular frequency differential term of the i-th inverter; the voltage reference acquisition module is used to acquire the sinusoidal voltage reference of the i-th inverter; and the voltage regulation module is used to adjust the i-th inverter to operate in voltage source mode.

[0022] The voltage regulation module includes an outer voltage loop module, an inner current loop module, and a PWM modulation module. The output terminals of the outer voltage loop module and the inner current loop module are connected to the input terminal of the PWM modulation module. The output terminal of the PWM modulation module is connected to each switch of the H-bridge inverter to control the on and off states of each switch of the H-bridge inverter.

[0023] The beneficial effects of this invention are as follows: Compared with the prior art, this invention targets series-connected microgrids. It calculates active and reactive power based on the voltage and current information of the i-th inverter; obtains the angular frequency differential term based on the active and reactive power, combined with locally acquired angular frequency, damping coefficient, rated inertia coefficient, and control coefficient; obtains the angular frequency reference value of the i-th inverter based on the angular frequency differential term and the rated angular frequency; sets the voltage amplitude reference value of the i-th inverter to the rated value; and obtains the sinusoidal voltage reference value of the i-th inverter. Based on the sinusoidal voltage reference value, the i-th inverter is adjusted using the voltage outer loop and current inner loop, achieving communication-free control of the system. According to the communication-free adaptive virtual inertial control method and device for series-connected microgrids provided by this invention, overall control can be achieved by only acquiring local information. This control method can suppress power oscillations, improve the dynamic performance of the system, enhance system stability, and provide users with high-quality power. Attached Figure Description

[0024] Figure 1 The flowchart illustrates a communication-free adaptive virtual inertial control method for suppressing power oscillations in a series-connected microgrid according to an embodiment of the present invention.

[0025] Figure 2 This is a schematic diagram of the structure according to an embodiment of the present invention;

[0026] Figure 3 This is a control block diagram according to an embodiment of the present invention;

[0027] Figure 4 The above is a simulation waveform of power oscillation under fixed inertial parameters according to an embodiment of the present invention.

[0028] Figure 5The above is a simulation waveform of frequency oscillation under fixed inertial parameters according to an embodiment of the present invention.

[0029] Figure 6 The above is a simulation waveform of power oscillation under adaptive virtual inertia according to an embodiment of the present invention.

[0030] Figure 7 The above is a simulation waveform of frequency oscillation under adaptive virtual inertia according to an embodiment of the present invention.

[0031] Figure 8 This is a schematic diagram of a communication-free adaptive virtual inertial control device for suppressing power oscillations in a series-connected microgrid according to an embodiment of the present invention. Detailed Implementation

[0032] The present invention will be further described below with reference to the accompanying drawings and specific embodiments.

[0033] Example 1: As Figure 1 As shown, a communication-free adaptive virtual inertial control method for suppressing power oscillations in a series-connected microgrid includes the following steps:

[0034] Step 1: Calculate the active power and reactive power based on the voltage and current information of the i-th inverter.

[0035] Step 2: Based on the active power and reactive power in Step 1, and combined with the locally acquired angular frequency, damping coefficient, rated inertia coefficient, and control coefficient, obtain the i-th inverter angular frequency differential term.

[0036] Step 3: Based on the angular frequency differential term in Step 2 and the set rated angular frequency, obtain the angular frequency reference value of the i-th inverter, set the voltage amplitude reference value of the i-th inverter to the rated value, and obtain the sinusoidal voltage reference value of the i-th inverter.

[0037] Step 4: Based on the sinusoidal voltage reference value in Step 3, adjust the i-th inverter using the outer voltage loop and the inner current loop to achieve communication-free power oscillation suppression control of the series microgrid.

[0038] This invention proposes a communication-free adaptive virtual inertial control method and device for a series-connected microgrid. Based on the voltage and current information of the i-th inverter, active power and reactive power are calculated. Based on the active and reactive power, and combined with locally acquired angular frequency, damping coefficient, rated inertia coefficient, and control coefficient, an angular frequency differential term is obtained. Based on the angular frequency differential term and the rated angular frequency, an angular frequency reference value for the i-th inverter is obtained. The voltage amplitude reference value for the i-th inverter is set to its rated value, and a sinusoidal voltage reference value for the i-th inverter is obtained. Based on the sinusoidal voltage reference value, the i-th inverter is adjusted using an outer voltage loop and an inner current loop to achieve system control. The communication-free adaptive virtual inertial control method for suppressing power oscillations in a series-connected microgrid provided by this invention can effectively suppress system power oscillations, improve system dynamic performance, enhance system stability, and improve power quality.

[0039] For series-connected microgrids, active and reactive power can be calculated based on the collected local voltage and current information.

[0040] For the differential term dω of the i-th inverter angular frequency Di / dt, based on active power P i and reactive power Q i Combined with locally acquired angular frequency ω i Damping coefficient D, rated inertia coefficient J 0i And the control coefficient k, to obtain the differential term dω of the i-th inverter angular frequency. Di / dt, its expression is:

[0041]

[0042] In the formula ω com,i P is the angular frequency of the line current. * P is the rated active power. Di =P i -P * ;ω * The rated angular frequency, ω Di ω is a transition variable. Di =ω i -ω * ; sgn(·) is a symbolic function.

[0043] As an optional embodiment, the expression for the angular frequency reference quantity is: ω i =ω * +ω Di ,in

[0044] The voltage amplitude reference value of the i-th inverter is set to the rated value, and the expression is:

[0045] V i =V *

[0046] Based on the voltage amplitude reference and the voltage phase angle reference, a voltage reference is synthesized as a vector, thus obtaining the sinusoidal voltage reference for the i-th inverter.

[0047] It should be noted that the method proposed in this invention is applicable to... Figure 2 The diagram shows a series-connected microgrid structure, and the control block diagram of this method is shown below. Figure 3 As shown in Table 1, the number of series inverters in the series-type microgrid system is not limited. Specifically, in this embodiment, the relevant circuit parameter values ​​are shown in Table 1. The series-type microgrid system includes three inverter modules, each corresponding to a local controller. The inverters are DC / AC based inverters. Each inverter output is connected to an LC filter. The LC filters are connected in series to the load via the line impedance (inductive). Each inverter includes an active power and reactive power calculation module, an angular frequency differential term acquisition module, a voltage reference acquisition module, and a voltage regulation module (including an outer voltage loop, an inner current loop, and a PWM modulation module).

[0048] Table 1 Relevant Circuit Parameter Values

[0049]

[0050]

[0051] To construct the voltage reference value for the i-th inverter, it is first necessary to obtain the active power and reactive power of the i-th inverter.

[0052] After obtaining the active power and reactive power, it is necessary to obtain the angular frequency differential term of the i-th inverter. Specifically, in this embodiment, the angular frequency differential term dω of the i-th inverter is... Di / dt is:

[0053]

[0054] In the formula ω i The angular frequency is the locally acquired frequency, D is the damping coefficient, and J is the damping coefficient. 0i ω is the rated inertia coefficient, k is the adaptive control coefficient, and ω is the ω value. com,i P is the angular frequency of the line current. * P is the rated active power. Di =P i -P * ω * The rated angular frequency, ω Di =ω i -ω *sgn(·) is a symbolic function.

[0055] Among them, the sinusoidal voltage reference quantity of the i-th inverter is constructed based on the angular frequency differential term.

[0056] Solving for the differential terms of the angular frequency in the 102 terms yields the angular frequency deviation of the i-th inverter, expressed as follows: In this embodiment, the set rated angular frequency ω * The voltage angular frequency reference value of the i-th inverter is expressed as ω. i =ω * +ω Di Then, according to the established expression for the rated voltage reference value, V i =V * Based on the obtained voltage angular frequency reference and voltage amplitude reference, the sinusoidal voltage reference of the i-th inverter is synthesized.

[0057] Based on the inverter's voltage reference value, the voltage corresponding to the inverter is adjusted. Voltage outer loop and current inner loop control are employed to track the given voltage reference value, ensuring the corresponding inverter operates in voltage source mode.

[0058] This embodiment proposes a communication-free adaptive virtual inertial control method for a series-connected microgrid. Based on the voltage and current information of the i-th inverter, active and reactive power are calculated. The angular frequency differential term is obtained based on the active and reactive power, combined with locally acquired angular frequency, damping coefficient, rated inertia coefficient, and control coefficient. An angular frequency reference value for the i-th inverter is obtained based on the angular frequency differential term and the rated angular frequency. The voltage amplitude reference value of the i-th inverter is set to its rated value, and a sinusoidal voltage reference value for the i-th inverter is obtained. Based on the sinusoidal voltage reference value, the i-th inverter is adjusted using an outer voltage loop and an inner current loop, achieving communication-free control of the entire system. The communication-free adaptive virtual inertial control method and device for a series-connected microgrid provided by this invention can suppress dynamic power oscillations, thereby improving the dynamic performance of the system and providing users with high-quality power.

[0059] Based on the series-type microgrid structure adopted in this embodiment, simulation verification was performed with 3 series inverters, rated active power of 1000W, rated voltage amplitude of 311 / 3V, damping coefficient of 100, rated inertia coefficient of 20 for the first inverter, rated inertia coefficient of 30 for the second inverter, rated inertia coefficient of 25 for the third inverter, and adaptive control parameter of 20.

[0060] For a configuration with 3 series inverters, a rated active power of 1000W, and a rated voltage amplitude of 311 / 3V, the active power waveform obtained from an experiment using simulation software when the adaptive control parameter k is set to 0 is shown below. Figure 4 As shown in the figure. The horizontal axis represents time in seconds (s), and the vertical axis represents the corresponding value in milliseconds (W).

[0061] The frequency waveform obtained from the experiment using simulation software with the adaptive control parameter k set to 0 is shown below. Figure 5 As shown in the figure. The horizontal axis represents time in seconds, and the vertical axis represents output active power in watts (W).

[0062] For the method of setting the adaptive control parameter k to 20, the active power waveform obtained by simulation software is as follows. Figure 6 As shown in the figure. The horizontal axis represents time in seconds, and the vertical axis represents output active power in watts (W).

[0063] The frequency waveform obtained from the experiment using simulation software with the adaptive control parameter k set to 20 is shown below. Figure 7 As shown in the figure. The horizontal axis represents time in seconds (s), and the vertical axis represents the corresponding frequency value in Hz.

[0064] Comparison of simulated waveforms Figure 4 With simulated waveforms Figure 6 Simulation waveform Figure 5 With simulated waveforms Figure 7 The proposed adaptive virtual inertial control method can suppress power oscillations and frequency oscillations in the system.

[0065] Therefore, the method for obtaining reference frequency and reference voltage proposed in this invention enables communication-free control operation of series-connected microgrids, suppresses power oscillations in the system, and improves the dynamic performance of the system.

[0066] Example 2: As Figure 8As shown, a communication-free adaptive virtual inertial control device for suppressing power oscillations in a series-connected microgrid is disclosed. This communication-free control device includes an active power and reactive power calculation module, an angular frequency differential term acquisition module, a voltage reference acquisition module, and a voltage regulation module. The active power and reactive power calculation module is used to acquire the active power and reactive power of the i-th inverter; the angular frequency differential term acquisition module is used to acquire the angular frequency differential term of the i-th inverter; the voltage reference acquisition module is used to acquire the sinusoidal voltage reference of the i-th inverter; and the voltage regulation module is used to adjust the i-th inverter to operate in voltage source mode. Specifically, the active power and reactive power calculation module is used to execute step 1 of the communication-free adaptive virtual inertial control method for suppressing power oscillations in a series-connected microgrid in Embodiment 1; the angular frequency differential term acquisition module and the voltage reference acquisition module are used to execute steps 2-3 of Embodiment 1, respectively; and the voltage regulation module is used to execute step 4 of Embodiment 1.

[0067] The voltage regulation module of the i-th inverter includes an outer voltage loop, an inner current loop, and a PWM modulation module, thus forming a dual closed-loop voltage source automatic control system. The output terminals of the outer voltage loop and the inner current loop are connected to the input terminal of the PWM modulation module, and the output terminal of the PWM modulation module is connected to each switch of the H-bridge inverter to control the on and off of each switch of the H-bridge inverter.

[0068] The present invention provides a communication-free adaptive virtual inertial control method and device for a series microgrid, which can suppress power oscillations, improve dynamic performance, enhance stability, and provide users with high-quality power.

[0069] As an alternative embodiment, such as Figure 8 As shown, the voltage reference acquisition module is specifically used for the i-th inverter in a series microgrid. It obtains the angular frequency differential term based on the calculation of active power and reactive power, and then obtains the angular frequency reference of the i-th inverter. Based on the set voltage amplitude reference, it obtains the voltage reference excluding the i-th inverter through the voltage amplitude reference and the voltage angular frequency reference.

[0070] The above description is merely a specific embodiment of the present invention, but the scope of protection of the present invention is not limited thereto. Any variations or substitutions that can be easily conceived by those skilled in the art within the scope of the technology disclosed in the present invention should be included within the scope of protection of the present invention. Therefore, the scope of protection of the present invention should be determined by the scope of protection of the claims.

Claims

1. A communication-free adaptive virtual inertial control method for a series-connected microgrid, wherein the series-connected microgrid includes inverters connected in series, characterized in that: The method includes the following steps: Step 1: Calculate the active power and reactive power based on the voltage and current information of the i-th inverter; Step 2: Based on the active power and reactive power described in Step 1, and combined with the locally acquired angular frequency, damping coefficient, rated inertia coefficient, and control coefficient, obtain the i-th inverter angular frequency differential term; Step 3: Based on the angular frequency differential term described in Step 2, and based on the rated angular frequency, obtain the angular frequency reference value of the i-th inverter, set the voltage amplitude reference value of the i-th inverter to the rated value, and obtain the sinusoidal voltage reference value of the i-th inverter. Step 4: Based on the sinusoidal voltage reference value described in Step 3, adjust the i-th inverter using the outer voltage loop and the inner current loop to achieve coordinated control of the system without communication. The method for calculating the differential term of the i-th inverter angular frequency in step 2 is as follows: Based on active power and reactive power Combined with locally acquired angular frequency Damping coefficient Rated inertia coefficient and control coefficients Obtain the differential term of the i-th inverter angular frequency. Its expression is: ， In the formula The angular frequency of the line current; Rated active power, ; The rated angular frequency, As a transitional variable, ; It is a symbolic function.

2. The non-communication adaptive virtual inertial control method for a series-connected microgrid according to claim 1, characterized in that: The calculation method for the sinusoidal voltage reference value of the i-th inverter in step 3 includes: Based on the angular frequency differential term described in step 2, and then based on the rated angular frequency, obtain the angular frequency reference value for the i-th inverter. Its expression is: ， ， The voltage amplitude reference value of the i-th inverter is set to the rated value, and the expression is: ， In the formula, This is a reference value for voltage amplitude. Given the rated voltage amplitude, the sinusoidal voltage reference value of the i-th inverter is obtained based on the voltage amplitude reference value and the angular frequency reference value.

3. A communication-free adaptive virtual inertial control device for a series-connected microgrid, wherein the series-connected microgrid includes inverters connected in series, characterized in that: The control device includes, The active power and reactive power calculation module is used to calculate the active power and reactive power of the i-th inverter. The angular frequency differential term acquisition module, based on active power and reactive power, combined with locally acquired angular frequency, damping coefficient, rated inertia coefficient and control coefficient, is used to obtain the i-th inverter angular frequency differential term; The method for calculating the differential term of the i-th inverter angular frequency is as follows: Based on active power and reactive power Combined with locally acquired angular frequency Damping coefficient Rated inertia coefficient and control coefficients Obtain the differential term of the i-th inverter angular frequency. Its expression is: ， In the formula The angular frequency of the line current; Rated active power, ; The rated angular frequency, As a transitional variable, ; It is a symbolic function; The voltage reference acquisition module obtains the angular frequency reference of the i-th inverter based on the angular frequency differential term and the rated angular frequency, and sets the voltage amplitude reference of the i-th inverter to the rated value to obtain the sinusoidal voltage reference of the i-th inverter. The voltage regulation module, based on a sinusoidal voltage reference, uses an outer voltage loop and an inner current loop to regulate the i-th inverter.

4. The series-connected microgrid non-communication adaptive virtual inertial control device according to claim 3, characterized in that: The voltage regulation module includes an outer voltage loop module, an inner current loop module, and a PWM modulation module. The output of the outer voltage loop module is connected to the input of the PWM modulation module, and the output of the PWM modulation module is connected to each switching transistor of the H-bridge inverter.

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