Improved droop control method combining high-order dynamic inertia and dynamic virtual impedance

Abstract

The invention discloses an improved droop control method combining high-order dynamic inertia and dynamic virtual impedance, which comprises the following steps: firstly, configuring parameters of a distributed power supply and initial control parameters of droop control, and initializing initial values of the dynamic inertia and the virtual impedance; collecting voltage, current, frequency and power change data of each distributed power supply in the micro-grid in real time through a sensor; adjusting the cut-off frequency and the damping ratio of the dynamic inertia link; the virtual resistor and the virtual inductor are adjusted, and virtual impedance is dynamically obtained; and analyzing feedback data and iteratively optimizing dynamic inertia and virtual impedance parameters. According to the improved droop control method combining the high-order dynamic inertia and the dynamic virtual impedance, the dynamic inertia parameters and the virtual impedance characteristics of the micro-grid system are adjusted in real time; the method has the advantages that the influence of power fluctuation on operation of the micro-grid system can be reduced, the decoupling capability between distributed power supplies is improved, and the dynamic performance and stability of the micro-grid system are improved.

Description

Technical Field

[0001] The invention relates to a simulation experiment platform, in particular to an improved droop control method combining high-order dynamic inertia and dynamic virtual impedance. Background Art

[0002] Microgrid refers to a small power generation and distribution system consisting of distributed generation (DG), energy storage devices, energy conversion devices, loads, monitoring and protection devices, etc. Distributed generation, energy storage devices, loads, etc. are all connected to the DC bus, and the DC network is then connected to the external AC grid through a power electronic inverter (inverter).

[0003] Droop control simulates the droop characteristics of synchronous generators in traditional power systems. The working principle of droop control is: the inverter detects the size of its own output power and decouples the active power and reactive power; the output frequency and voltage amplitude reference values ​​are obtained according to the droop characteristics, so as to reasonably distribute the active and reactive power of the system. A common application of droop control is "active frequency regulation and reactive voltage regulation". For inverter power grid-connected systems, the droop characteristics are used: (1) the inverter active power output decreases and the output frequency increases; the inverter active power output increases and the output frequency decreases; (2) the inverter capacitive reactive power output decreases and the voltage increases; the inverter capacitive reactive power output increases and the voltage decreases.

[0004] The traditional droop control strategy is widely used in microgrids. It simulates the steady-state characteristics of synchronous generators and adjusts the voltage amplitude and angular frequency according to the reactive power and active power. However, this strategy has the problem of insufficient inertia (such as voltage inertia and angular frequency inertia), which makes the voltage and angular frequency of distributed power units susceptible to power fluctuations. At the same time, the traditional droop control strategy is prone to reduce the power regulation accuracy between power sources under the coupling resistance-inductance characteristics, affecting the stability of the microgrid.

[0005] ‌Virtual impedance‌ is a virtual element introduced into the power electronic system. By adding a virtual impedance to the original line, the line impedance is made approximately inductive, thereby reducing the unbalanced impedance between devices. It is mainly used to improve the dynamic response and stability of the system and reduce the coupling between distributed power units. By adjusting the parameters of the virtual impedance, the line can be made more inductive, thereby achieving power decoupling, improving the distribution of reactive power, reducing the circulating current between inverters, and improving the quality of power output. However, using virtual impedance alone is difficult to solve the impact of power fluctuations on voltage and angular frequency, and the system stability still needs to be further improved.

[0006] Therefore, an improved control strategy is urgently needed to enhance the stability of the system and reduce the impact of power fluctuations on the operation of the microgrid. Summary of the invention

[0007] The present invention aims to avoid the deficiencies in the above-mentioned prior art and provide an improved droop control method combining high-order dynamic inertia and dynamic virtual impedance to reduce the impact of power fluctuations on the operation of a microgrid system and improve the dynamic performance and stability of the microgrid system.

[0008] The present invention adopts the following technical solutions to solve the technical problems.

[0009] The present invention discloses an improved droop control method combining high-order dynamic inertia and dynamic virtual impedance, comprising the following steps:

[0010] Step 1: Configure the parameters of each distributed power source in the microgrid system and the initial control parameters of the droop control, and initialize the initial values ​​of the high-order dynamic inertia link and the dynamic virtual impedance link;

[0011] Step 2: Use sensors to collect the voltage U, current I, angular frequency ω of each distributed power source in the microgrid system and the power change data of the inverter in real time;

[0012] Step 3: Adjust the cutoff angular frequency ω and damping ratio ζ of the high-order dynamic inertia link;

[0013] Step 4: In the dynamic virtual impedance link, adjust the virtual resistance and virtual inductance to dynamically obtain the virtual impedance;

[0014] Step 5: Analyze the feedback data and iteratively optimize the dynamic inertia and virtual impedance parameters.

[0015] The improved droop control method combining high-order dynamic inertia and dynamic virtual impedance of the present invention is also characterized in that:

[0016] Further, in step 1, the parameters of the distributed power source include basic impedance parameters and filter parameters;

[0017] The initial control parameters of the droop control include a reactive power droop coefficient Kv and an active power droop coefficient Kw.

[0018] Furthermore, in step 1, the high-order dynamic inertia link includes a dynamic voltage inertia model and a dynamic angular frequency inertia model.

[0019] Furthermore, the dynamic voltage inertia model H v (s, t) is expressed by the following formula (1);

[0020] (1)

[0021] In the formula (1), ω s(t) is the cutoff angular frequency that changes with time t in the dynamic voltage inertia model, ω s0 is the initial cutoff angular frequency of the dynamic voltage inertia model, k1 and k2 are the adjustment coefficients of the dynamic voltage inertia model, ζ0 is the initial damping ratio of the dynamic voltage inertia model, ζ(t) is the damping ratio that changes with time t in the dynamic voltage inertia model; ΔP(t) is the real-time inverter output active power fluctuation, which changes with time t; ΔQ(t) is the real-time inverter output reactive power fluctuation, which changes with time t; S represents the Laplace transform parameter.

[0022] Furthermore, the dynamic angular frequency inertia model H ω (s, t) is expressed by the following formula (2);

[0023] (2)

[0024] In the formula (2), ω s1 (t) is the cutoff angular frequency that changes with time t in the dynamic angular frequency inertial model, ω s10 is the initial cutoff angular frequency of the dynamic angular frequency inertia model, k3 and k4 are the adjustment coefficients of the dynamic angular frequency inertia model, ζ 10 is the initial damping ratio of the dynamic angular frequency inertia model, ζ1(t) is the damping ratio that changes with time t in the dynamic angular frequency inertia model, ΔP(t) is the real-time inverter output active power fluctuation, which changes with time t; ΔQ(t) is the real-time inverter output reactive power fluctuation, which changes with time t; S represents the Laplace transform parameter.

[0025] Furthermore, in step 4, the following formula (3) is used to calculate and obtain the dynamic virtual impedance Z vi (s, t);

[0026] (3)

[0027] In the formula (3), R vi (s, t) is the virtual resistance value that changes with time t, L vi (s, t) is the virtual inductance value that changes with time t, j represents the imaginary unit, k r (t) and k l (t) are the dynamic adjustment coefficient of resistance and the dynamic adjustment coefficient of inductance respectively; R0 is the basic resistance, L0 is the basic inductance; ω is the cut-off angular frequency; ΔP(t) is the real-time inverter output active power fluctuation, which changes with time t; ΔQ(t) is the real-time inverter output reactive power fluctuation, which changes with time t; S in (s, t) represents the Laplace transform parameter, and t is time.

[0028] Furthermore, the following formula (4) is used to calculate the resistance dynamic adjustment coefficient k: r (t);

[0029] (4)

[0030] In the formula (4), k r0 is the initial resistance adjustment coefficient; α r is the sensitivity of the resistance adjustment coefficient, which indicates the influence of active power change on the resistance adjustment; ΔP(t) is the real-time inverter output active power fluctuation, which changes with time t.

[0031] Furthermore, the following formula (5) is used to calculate the inductance dynamic adjustment coefficient k: l (t);

[0032] (5)

[0033] In the formula (5), k l0 is the initial inductance adjustment coefficient; α l is the sensitivity of the inductance adjustment coefficient, which indicates the impact of reactive power changes on inductance adjustment; ΔQ(t) is the real-time inverter output reactive power fluctuation, which changes with time t.

[0034] The present invention also discloses an electronic device, comprising at least one processor and a memory communicatively connected to the at least one processor; wherein the memory stores instructions executable by the at least one processor, and the instructions are executed by the at least one processor so that the at least one processor can execute the improved droop control method combining high-order dynamic inertia and dynamic virtual impedance.

[0035] The present invention also discloses a non-transitory computer-readable storage medium storing computer instructions, wherein the computer instructions are used to enable the computer to execute the improved droop control method combining high-order dynamic inertia and dynamic virtual impedance.

[0036] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0037] The invention discloses an improved droop control method combining high-order dynamic inertia and dynamic virtual impedance, which combines high-order dynamic inertia and dynamic virtual impedance to enhance the dynamic performance and stability of a microgrid system; firstly, the parameters of a distributed power source and the initial control parameters of the droop control are configured, and the initial values ​​of the dynamic inertia and the virtual impedance are initialized; the voltage, current, frequency and power change data of each distributed power source in the microgrid are collected in real time by sensors; the cutoff frequency and damping ratio of the dynamic inertia link are adjusted; the virtual resistance and virtual inductance are adjusted, and the virtual impedance is dynamically obtained; the feedback data is analyzed and the dynamic inertia and virtual impedance parameters are iteratively optimized.

[0038] The improved droop control method combining high-order dynamic inertia and dynamic virtual impedance of the present invention has the advantages of reducing the impact of power fluctuations on the operation of the microgrid system, improving the decoupling capability between distributed power sources, and improving the dynamic performance and stability of the microgrid system by adjusting the dynamic inertia parameters and virtual impedance characteristics of the microgrid system in real time. BRIEF DESCRIPTION OF THE DRAWINGS

[0039] Figure 1 The block diagram of an improved droop control method combining high-order dynamic inertia and dynamic virtual impedance of the present invention.

[0040] Figure 2 This is a high-order dynamic inertia control principle diagram of an improved droop control method combining high-order dynamic inertia and dynamic virtual impedance of the present invention.

[0041] Figure 3 This is a dynamic virtual impedance control principle diagram of an improved droop control method combining high-order dynamic inertia and dynamic virtual impedance of the present invention.

[0042] The present invention will be further described below through specific implementation modes in conjunction with the accompanying drawings. DETAILED DESCRIPTION

[0043] See also Figure 1 to Figure 3 The present invention discloses an improved droop control method combining high-order dynamic inertia and dynamic virtual impedance, comprising the following steps:

[0044] Step 1: Configure the parameters of each distributed power source in the microgrid system and the initial control parameters of the droop control, and initialize the initial values ​​of the high-order dynamic inertia link and the dynamic virtual impedance link;

[0045] Configure the basic impedance, filter parameters and initial control parameters of the distributed power source, and initialize the initial values ​​of dynamic inertia and virtual impedance;

[0046] Step 2: Use sensors to collect the voltage U, current I, angular frequency ω of each distributed power source in the microgrid system and the power change data of the inverter in real time (including the active power fluctuation ΔP(t) and reactive power fluctuation ΔQ(t) of the inverter, and the dynamic virtual impedance Z calculated by ΔP(t) and ΔQ(t) vi (s, t));

[0047] Step 3: Adjust the cutoff angular frequency ω and damping ratio ζ of the high-order dynamic inertia link;

[0048] According to the active power fluctuation ΔP(t) and the reactive power fluctuation ΔQ(t), the cutoff angular frequency ω and the damping ratio ζ of the dynamic inertia link are adjusted to enhance the suppression capability of the output voltage U and angular frequency ω fluctuation of each distributed power source, and the phase signal θ and the command voltage signal Vref of the inverter are output;

[0049] Step 4: In the dynamic virtual impedance link, adjust the virtual resistance and virtual inductance to dynamically obtain the virtual impedance;

[0050] Calculate and adjust virtual resistance and virtual inductance in real time, dynamically obtain virtual impedance, optimize power decoupling through voltage control links, and reduce mutual interference between distributed power sources;

[0051] Step 5: Analyze the feedback data and iteratively optimize the dynamic inertia and virtual impedance parameters.

[0052] An improved droop control strategy is implemented to analyze feedback data in real time and iteratively optimize dynamic inertia and virtual impedance parameters to ensure system stability and robustness.

[0053] The improved droop control method combining high-order dynamic inertia and dynamic virtual impedance of the present invention includes a high-order dynamic inertia link and a dynamic virtual impedance link; in the high-order dynamic inertia link, a dynamic second-order inertia model is introduced to slow down the rate of change of voltage and angular frequency, and the system's anti-interference ability to power fluctuations is improved by filtering out high-frequency noise and transient fluctuations; in the dynamic virtual impedance link, the virtual impedance characteristics of distributed power sources are adjusted in real time to reduce power coupling between distributed power sources and optimize power distribution accuracy. The present invention can significantly improve the dynamic performance of a microgrid, reduce the impact of power fluctuations on voltage and angular frequency, and improve the decoupling ability between distributed power sources, thereby enhancing the stability and robustness of the microgrid.

[0054] In specific implementation, in step 1, the parameters of the distributed power source include basic impedance parameters and filter parameters;

[0055] The initial control parameters of the droop control include a reactive power droop coefficient Kv and an active power droop coefficient Kw.

[0056] The basic impedance parameters include: R0 is a basic resistance, and L0 is a basic inductance.

[0057] During specific implementation, in step 1, the high-order dynamic inertia link includes a dynamic voltage inertia model and a dynamic angular frequency inertia model.

[0058] The initial values ​​of the initial high-order dynamic inertia link and the dynamic virtual impedance link include the following parameters: ω s0 is the initial cutoff angular frequency of the dynamic voltage inertia model, ζ0 is the initial damping ratio of the dynamic voltage inertia model, ω s10 is the initial cutoff angular frequency of the dynamic angular frequency inertial model, ζ 10 is the initial damping ratio of the dynamic angular frequency inertia model, R0 is the basic resistance, and L0 is the basic inductance.

[0059] In the present invention, the dynamic voltage inertia model optimizes voltage stability according to the fluctuations of active power P and reactive power Q by adjusting the cutoff angular frequency ω and the damping ratio ζ in real time; the dynamic angular frequency inertia model reduces the impact of power fluctuations on system frequency and improves the robustness of frequency regulation by dynamically adjusting the angular frequency cutoff value and the damping ratio.

[0060] In specific implementation, the dynamic voltage inertia model H v (s, t) is expressed by the following formula (1);

[0061] (1)

[0062] In the formula (1), ω s (t) is the cutoff angular frequency that changes with time t in the dynamic voltage inertia model, ω s0 is the initial cutoff angular frequency of the dynamic voltage inertia model, k1 and k2 are the adjustment coefficients of the dynamic voltage inertia model, ζ0 is the initial damping ratio of the dynamic voltage inertia model, ζ(t) is the damping ratio that changes with time t in the dynamic voltage inertia model; ΔP(t) is the real-time inverter output active power fluctuation, which changes with time t; ΔQ(t) is the real-time inverter output reactive power fluctuation, which changes with time t; S represents the Laplace transform parameter.

[0063] In specific implementation, the dynamic angular frequency inertia model H ω (s, t) is expressed by the following formula (2);

[0064] (2)

[0065] In the formula (2), ω s1 (t) is the cutoff angular frequency that changes with time t in the dynamic angular frequency inertial model, ωs10 is the initial cutoff angular frequency of the dynamic angular frequency inertia model, k3 and k4 are the adjustment coefficients of the dynamic angular frequency inertia model, ζ 10 is the initial damping ratio of the dynamic angular frequency inertia model, ζ1(t) is the damping ratio that changes with time t in the dynamic angular frequency inertia model, ΔP(t) is the real-time inverter output active power fluctuation, which changes with time t; ΔQ(t) is the real-time inverter output reactive power fluctuation, which changes with time t; S represents the Laplace transform parameter.

[0066] In the specific implementation, in step 4, the following formula (3) is used to calculate and obtain the dynamic virtual impedance Z vi (s, t);

[0067] (3)

[0068] In the formula (3), R vi (s, t) is the virtual resistance value that changes with time t, L vi (s, t) is the virtual inductance value that changes with time t, j represents the imaginary unit, k r (t) and k l (t) are the dynamic adjustment coefficient of resistance and the dynamic adjustment coefficient of inductance respectively; R0 is the basic resistance, L0 is the basic inductance; ω is the cut-off angular frequency; ΔP(t) is the real-time inverter output active power fluctuation, which changes with time t; ΔQ(t) is the real-time inverter output reactive power fluctuation, which changes with time t; S in (s, t) represents the Laplace transform parameter, and t is time.

[0069] Use formula (3) to calculate and adjust the virtual resistance R in real time vi (s, t) and virtual inductance L vi (s, t), dynamically obtain virtual impedance Z vi (s, t), optimize power decoupling through voltage control link and reduce mutual interference between distributed power sources; dynamic virtual impedance optimizes the power decoupling performance of the system according to load changes and the output status of distributed power sources by dynamically adjusting the real-time characteristics of resistance and inductance.

[0070] In specific implementation, the following formula (4) is used to calculate the resistance dynamic adjustment coefficient k r (t);

[0071] (4)

[0072] In the formula (4), k r0 is the initial resistance adjustment coefficient; α ris the sensitivity of the resistance adjustment coefficient, which indicates the influence of active power change on the resistance adjustment; ΔP(t) is the real-time inverter output active power fluctuation, which changes with time t.

[0073] In specific implementation, the following formula (5) is used to calculate the inductance dynamic adjustment coefficient k: l (t);

[0074] (5)

[0075] In the formula (5), k l0 is the initial inductance adjustment coefficient; α l is the sensitivity of the inductance adjustment coefficient, which indicates the impact of reactive power changes on inductance adjustment; ΔQ(t) is the real-time inverter output reactive power fluctuation, which changes with time t.

[0076] According to the real-time changes in system status and load conditions, k in formula (3) is calculated by formula (4) and formula (5) respectively. r (t) and k l (t).

[0077] The present invention also discloses an electronic device, comprising at least one processor and a memory communicatively connected to the at least one processor; wherein the memory stores instructions executable by the at least one processor, and the instructions are executed by the at least one processor so that the at least one processor can execute the improved droop control method combining high-order dynamic inertia and dynamic virtual impedance.

[0078] The present invention also discloses a non-transitory computer-readable storage medium storing computer instructions, wherein the computer instructions are used to enable the computer to execute the improved droop control method combining high-order dynamic inertia and dynamic virtual impedance.

[0079] The improved droop control method of the present invention, which combines high-order dynamic inertia with dynamic virtual impedance, realizes innovative design in voltage inertia, angular frequency inertia and dynamic virtual impedance, significantly improves the dynamic performance and stability of the microgrid, and has broad application potential in both isolated island and grid-connected operation.

[0080] It will be apparent to those skilled in the art that the invention is not limited to the details of the exemplary embodiments described above and that the invention can be implemented in other specific forms without departing from the spirit or essential features of the invention. Therefore, the embodiments should be considered exemplary and non-limiting in all respects, and the scope of the invention is defined by the appended claims rather than the foregoing description, and it is intended that all variations falling within the meaning and scope of the equivalent elements of the claims be included in the invention. Any reference numeral in a claim should not be considered as limiting the claim to which it relates.

[0081] In addition, it should be understood that although the present specification is described according to implementation modes, not every implementation mode contains only one independent technical solution. This description of the specification is only for the sake of clarity. Those skilled in the art should regard the specification as a whole. The technical solutions in each embodiment may also be appropriately combined to form other implementation modes that can be understood by those skilled in the art.

Claims

1. An improved droop control method combining high-order dynamic inertia and dynamic virtual impedance, characterized in that: The steps include: Step 1: Configure the parameters of each distributed power source in the microgrid system and the initial control parameters of the droop control, and initialize the initial values ​​of the high-order dynamic inertia link and the dynamic virtual impedance link; Step 2: Use sensors to collect the voltage U, current I, angular frequency ω of each distributed power source in the microgrid system and the power change data of the inverter in real time; Step 3: Adjust the cutoff angular frequency ω and damping ratio ζ of the high-order dynamic inertia link; Step 4: In the dynamic virtual impedance link, adjust the virtual resistance and virtual inductance to dynamically obtain the virtual impedance; Step 5: Analyze the feedback data and iteratively optimize the dynamic inertia and virtual impedance parameters.

2. The improved droop control method combining high-order dynamic inertia and dynamic virtual impedance according to claim 1 is characterized in that: In the step 1, the parameters of the distributed power source include basic impedance parameters and filter parameters; The initial control parameters of the droop control include a reactive power droop coefficient Kv and an active power droop coefficient Kw.

3. The improved droop control method combining high-order dynamic inertia and dynamic virtual impedance according to claim 1 is characterized in that: In the step 1, the high-order dynamic inertia link includes a dynamic voltage inertia model and a dynamic angular frequency inertia model.

4. The improved droop control method combining high-order dynamic inertia and dynamic virtual impedance according to claim 3 is characterized in that: The dynamic voltage inertia model H v (s, t) is expressed by the following formula (1); （1） In the formula (1), ω s (t) is the cutoff angular frequency that changes with time t in the dynamic voltage inertia model, ω s0 is the initial cutoff angular frequency of the dynamic voltage inertia model, k1 and k2 are the adjustment coefficients of the dynamic voltage inertia model, ζ0 is the initial damping ratio of the dynamic voltage inertia model, ζ(t) is the damping ratio that changes with time t in the dynamic voltage inertia model; ΔP(t) is the real-time inverter output active power fluctuation, which changes with time t; ΔQ(t) is the real-time inverter output reactive power fluctuation, which changes with time t; S represents the Laplace transform parameter.

5. The improved droop control method combining high-order dynamic inertia and dynamic virtual impedance according to claim 3 is characterized in that: The dynamic angular frequency inertia model H ω (s, t) is expressed by the following formula (2); （2） In the formula (2), ω s1 (t) is the cutoff angular frequency that changes with time t in the dynamic angular frequency inertial model, ω s10 is the initial cutoff angular frequency of the dynamic angular frequency inertia model, k3 and k4 are the adjustment coefficients of the dynamic angular frequency inertia model, ζ 10 is the initial damping ratio of the dynamic angular frequency inertia model, ζ1(t) is the damping ratio in the dynamic angular frequency inertia model that changes with time t, ΔP(t) is the real-time inverter output active power fluctuation, which changes with time t; ΔQ(t) is the real-time inverter output reactive power fluctuation, which changes with time t; S represents the Laplace transform parameter.

6. The improved droop control method combining high-order dynamic inertia and dynamic virtual impedance according to claim 1 is characterized in that: In step 4, the dynamic virtual impedance Z is calculated using the following formula (3): vi (s, t); （3） In the formula (3), R vi (s, t) is the virtual resistance value that changes with time t, L vi (s, t) is the virtual inductance value that changes with time t, j represents the imaginary unit, k r (t) and k l (t) are the dynamic adjustment coefficient of resistance and the dynamic adjustment coefficient of inductance respectively; R0 is the basic resistance, L0 is the basic inductance; ω is the cut-off angular frequency; ΔP(t) is the real-time inverter output active power fluctuation, which changes with time t; ΔQ(t) is the real-time inverter output reactive power fluctuation, which changes with time t; S in (s, t) represents the Laplace transform parameter, and t is time.

7. The improved droop control method combining high-order dynamic inertia and dynamic virtual impedance according to claim 6 is characterized in that: The following formula (4) is used to calculate the resistance dynamic adjustment coefficient k r (t); （4） In the formula (4), k r0 is the initial resistance adjustment coefficient; α r is the sensitivity of the resistance adjustment coefficient, which indicates the influence of active power change on the resistance adjustment; ΔP(t) is the real-time inverter output active power fluctuation, which changes with time t.

8. The improved droop control method combining high-order dynamic inertia and dynamic virtual impedance according to claim 6, characterized in that: The dynamic adjustment coefficient k of inductance is calculated using the following formula (5): l (t); （5） In the formula (5), k l0 is the initial inductance adjustment coefficient; α l is the sensitivity of the inductance adjustment coefficient, which indicates the impact of reactive power changes on inductance adjustment; ΔQ(t) is the real-time inverter output reactive power fluctuation, which changes with time t.

9. An electronic device comprising at least one processor and a memory in communication with the at least one processor; wherein: The memory stores instructions executable by the at least one processor, and the instructions are executed by the at least one processor to enable the at least one processor to execute the improved droop control method combining high-order dynamic inertia and dynamic virtual impedance as described in any one of claims 1-8.

10. A non-transitory computer-readable storage medium storing computer instructions, characterized in that: The computer instructions are used to enable the computer to execute the improved droop control method combining high-order dynamic inertia and dynamic virtual impedance according to any one of claims 1-8.

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