A buck converter system based on droop control and a control method thereof

Abstract

This disclosure provides a control method for a Buck converter system based on droop control, the method comprising: based on the output current i of the Buck converter system... o droop coefficient R d Output voltage rated value V bus Droop control is applied to the Buck converter system to obtain the desired voltage value. Based on this desired voltage value, the output voltage value v of the Buck converter system is obtained. dc Voltage control is applied to the Buck converter system to obtain the desired current value. Based on this desired current value, the output current i of the Buck converter system is obtained. o The Buck converter system is current controlled to obtain the drive signal d; the Buck converter system is then controlled to operate based on the drive signal d.

Description

Technical Field

[0001] This disclosure relates to the field of power technology, and in particular to a Buck converter system based on droop control and its control method. Background Technology

[0002] Buck converters are widely used due to their simple structure, high conversion efficiency, and low operating cost. In a Buck converter, the load is connected to the DC bus via a closed-loop controlled converter, forming a constant power load. However, when a constant power load is connected to the Buck converter, the load exhibits negative admittance at its input, which amplifies disturbances such as positive feedback, leading to a decrease in system stability. Summary of the Invention

[0003] Therefore, the purpose of this disclosure is to propose a Buck converter system based on droop control and its control method.

[0004] To achieve the above objectives, in a first aspect, this disclosure provides a control method for a Buck converter system based on droop control, comprising:

[0005] Output current based on Buck converter system i o Sag coefficient R d Output voltage rating V bus Droop control is applied to the Buck converter system to obtain the desired voltage value. ;

[0006] Based on voltage expectation Output voltage value of Buck converter system v dc Voltage control is applied to the Buck converter system to obtain the desired current value. ;

[0007] Based on current expectation Output current of Buck converter system i o Current control is applied to the Buck converter system to obtain the drive signal d;

[0008] The Buck converter system operates based on the drive signal d.

[0009] On the other hand, this disclosure provides a Buck converter system based on droop control, which is controlled by the method described in the first aspect.

[0010] As can be seen from the above, the Buck converter system and its control method based on droop control provided in this disclosure can increase the positive admittance of the system by adding a differential element to the traditional droop control strategy, thereby increasing the system stability margin and improving system stability without adding passive components. Attached Figure Description

[0011] To more clearly illustrate the technical solutions in this disclosure or related technologies, the accompanying drawings used in the description of the embodiments or related technologies will be briefly introduced below. Obviously, the accompanying drawings described below are only embodiments of this disclosure. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0012] Figure 1 This is a schematic main circuit diagram of a Buck converter system according to an embodiment of the present disclosure.

[0013] Figure 2 This is a control principle diagram of a Buck converter system based on droop control according to an embodiment of the present disclosure.

[0014] Figure 3 This is a schematic diagram of the steady-state waveforms of the output voltage and output current of a Buck converter system according to an embodiment of the present disclosure.

[0015] Figure 4 This is a schematic diagram of the steady-state waveforms of the output voltage and output current of a Buck converter system under a traditional droop control strategy.

[0016] Figure 5 This is a waveform diagram of the output voltage and output current of a Buck converter system according to an embodiment of the present disclosure under disturbance conditions.

[0017] Figure 6 This is a schematic diagram of the output voltage and output current of a Buck converter system under disturbance conditions using a traditional droop control strategy. Detailed Implementation

[0018] To make the objectives, technical solutions, and advantages of this disclosure clearer, the following detailed description is provided in conjunction with specific embodiments and the accompanying drawings.

[0019] It should be noted that, unless otherwise defined, the technical or scientific terms used in the embodiments of this disclosure should have the ordinary meaning understood by one of ordinary skill in the art to which this disclosure pertains. The terms "first," "second," and similar terms used in the embodiments of this disclosure do not indicate any order, quantity, or importance, but are merely used to distinguish different components. Terms such as "comprising" or "including" mean that the element or object preceding the word encompasses the elements or objects listed following the word and their equivalents, without excluding other elements or objects. Terms such as "connected" or "linked" are not limited to physical or mechanical connections, but can include electrical connections, whether direct or indirect.

[0020] In microgrids, droop control is commonly used for energy distribution and system control. However, the output admittance of Buck converters based on traditional droop control is zero at high frequencies. When a constant power load with negative admittance is connected to the Buck converter, the system risks non-positive admittance, leading to system oscillations or other instabilities. Therefore, improving the stability of Buck converters based on droop control has become an urgent technical problem to be solved.

[0021] In view of this, embodiments of the present disclosure provide a Buck converter system and control method based on droop control, which improves the positive admittance of the system by adding a differential element to the traditional droop control strategy, thereby improving the system stability.

[0022] See Figure 1 , Figure 1 A schematic main circuit diagram of a Buck converter system according to an embodiment of the present disclosure is shown. Figure 1 In this system, the Buck converter system 100 may include: a DC voltage source 110, a Buck converter circuit 120, and a constant power load 130 connected in sequence. The input voltage of the DC voltage source 110 is... v s .

[0023] In some embodiments, the Buck converter circuit 120 includes:

[0024] A controllable power switching device VT, the first terminal of which is connected to the positive terminal of a DC voltage source 110;

[0025] The inductor has an equivalent internal resistance r and an inductor L. The first terminal of the equivalent internal resistance r is connected to the second terminal of the controllable power switching device VT, and the first terminal of the inductor L is connected to the second terminal of the equivalent internal resistance r.

[0026] Capacitor C, the first terminal of capacitor C is connected to the second terminal of inductor L, and the second terminal of capacitor C is connected to the negative terminal of DC voltage source 110;

[0027] Diode VD, the cathode of diode VD is connected to the first terminal of controllable power switching device VT, and the anode of diode VD is connected to the negative terminal of DC voltage source 110.

[0028] In some embodiments, a constant power load (CPL) 130 is connected in parallel across capacitor C.

[0029] Specifically, such as Figure 1 As shown, the control terminal of the controllable power switching device VT (such as IGBT, MOSFET, etc.) receives the drive signal from the controller. d The output current of the Buck converter system 100 is the same as the output current of the inductor L. i o The output voltage of the Buck converter system 100 is the output voltage of capacitor C. v dc The voltage across the constant power load 130 can also be the output voltage of the inductor L. v dc .

[0030] See Figure 2 , Figure 2 A control principle diagram of a Buck converter system based on droop control according to an embodiment of the present disclosure is shown. Figure 2 In this context, the control process of a Buck converter system based on droop control can include droop control 210, voltage loop control 220, and current loop control 230. The droop control 210 includes output current... i o Sag coefficient R d Output voltage rating V bus The voltage loop control 220 includes the output voltage. v dc Expected output voltage Differential gain element G F ( s Voltage PI controller G v ( s The current loop control 230 includes the output current. i o Expected output voltage Current PI controller G i ( s ).

[0031] According to embodiments of this disclosure, a control method for a Buck converter system based on droop control may include:

[0032] Output current based on Buck converter system i o Sag coefficient R d Output voltage rating V bus Droop control is applied to the Buck converter system to obtain the desired voltage value. ;

[0033] Based on voltage expectation Output voltage value of Buck converter system v dc Voltage control is applied to the Buck converter system to obtain the desired current value. ;

[0034] Based on current expectation Output current of Buck converter system i o Current control is applied to the Buck converter system to obtain the drive signal d;

[0035] The Buck converter system operates based on the drive signal d.

[0036] In some embodiments, based on the output current of the Buck converter system i o Sag coefficient R d Output voltage rating V bus Droop control is applied to the Buck converter system to obtain the desired voltage value. ,include:

[0037] Output current based on Buck converter system i o and droop coefficient R d The first voltage is obtained;

[0038] Based on the first voltage and output voltage ratings V bus The difference yields the expected voltage value. .

[0039] In some embodiments, based on the output current of the Buck converter system i o and droop coefficient R d Obtaining the first voltage may include:

[0040] First voltage V1 = droop coefficient R d Output current of the ×Buck converter system i o .

[0041] In some embodiments, based on the first voltage and the output voltage rating V bus The difference yields the expected voltage value. This may include: expected voltage value = Output voltage rating V bus - First voltage V1.

[0042] In some embodiments, based on the expected voltage value Output voltage value of Buck converter system v dc Voltage control is applied to the Buck converter system to obtain the desired current value. ,include:

[0043] Output voltage value based on Buck converter system v dc and differential gain G F ( s The second voltage is obtained;

[0044] Based on the second voltage and the expected voltage value The difference yields the third voltage;

[0045] Based on the third voltage and voltage proportional-integral coefficient G v ( s Obtain the expected value of the current. .

[0046] In some embodiments, based on the output voltage value of the Buck converter system v dc and differential gain G F ( s The second voltage is obtained, including:

[0047] Second voltage V2 = Output voltage value v dc × Differential gain G F ( s ).

[0048] Among them, differential gain G F ( s )=k F s +1, k F The differential coefficients of the proportional-differential component are... s It is a differential operator.

[0049] In some embodiments, based on the second voltage and the expected voltage value The difference yields a third voltage, including:

[0050] Third voltage V3 = Expected voltage value -Second voltage V2.

[0051] In some embodiments, based on the third voltage and the voltage proportional-integral coefficient G v ( s Obtain the expected value of the current. Including: expected current value =Third voltage V3 × Voltage proportional-integral coefficient G v ( s ).

[0052] Among them, the voltage proportional-integral coefficient G v ( s )= k pv + k iv / s , k pv This is the voltage proportionality coefficient. k iv The voltage integral coefficient, s It is a differential operator.

[0053] In some embodiments, based on the expected current value Output current of Buck converter system i o Current control is applied to the Buck converter system to obtain the drive signal d, which includes:

[0054] Based on current expectation and the output current of the Buck converter system i o The difference yields the first current;

[0055] Based on the first current and the current proportional-integral coefficient G i ( s The driving signal d is obtained.

[0056] Among them, the current proportional-integral coefficientG i ( s )= k pi + k ii / s , k pi This is the current proportionality coefficient. k ii The current integral coefficient, s It is a differential operator.

[0057] In some embodiments, based on the expected current value and the output current of the Buck converter system i o The difference yields the first current, including:

[0058] First current I1 = expected current value -Buck converter system output current i o .

[0059] In some embodiments, based on a first current and a current proportional-integral coefficient G i ( s The driving signal d is obtained, including: driving signal d = first current I1 × current proportional-integral coefficient. G i ( s ).

[0060] Under traditional droop control, the admittance model of the Buck converter is:

[0061]

[0062] In the formula, ,

[0063] in, V s This represents the steady-state value of the input voltage.

[0064] At this point, the Buck converter admittance Y 1. The admittance values ​​at low and high frequencies are respectively:

[0065]

[0066] When a constant power load is connected to the Buck converter, the overall admittance of the Buck converter system is:

[0067] ,

[0068] in, Vdc This represents the steady-state value of the output voltage. P CPL This indicates the load power.

[0069] Under traditional droop control, the high-frequency admittance of the Buck converter is 0. Since the admittance of a constant power load is negative, the overall system admittance may be negative, leading to system instability.

[0070] This disclosure adds a proportional-derivative (PD) element to the traditional droop control strategy to improve the system stability margin and enhance system stability. According to the control method of this disclosure, the admittance of the Buck converter is:

[0071] ,

[0072] In the formula,

[0073] ,

[0074] At this point, the Buck converter admittance Y 2. The admittance values ​​at low and high frequencies are respectively:

[0075]

[0076] and Y As can be seen from the comparison, the admittance of the Buck converter under the improved control is positive at both high and low frequencies, thereby improving the system stability.

[0077] Based on the passive stability criterion, the stable controller parameter range of the Buck converter system is obtained as follows:

[0078] .

[0079] According to embodiments of this disclosure, a Buck converter system based on droop control is also provided, which is controlled by the method described in embodiments of this disclosure.

[0080] See Figures 3-4 , Figure 3 A schematic diagram of the steady-state waveforms of the output voltage and output current of a Buck converter system according to an embodiment of the present disclosure is shown. Figure 4 The diagram illustrates the steady-state waveforms of the output voltage and output current of a Buck converter system under a traditional droop control strategy. (Combined with...) Figure 1 Input voltage v s 700V, output voltage v dc 400V. Buck converter circuit parameters: inductance. L The equivalent internal resistance of the inductor is 2mH. r The capacitance is 0.01Ω.C The value is 1010uF. In comparison, it can be seen that under the traditional droop control strategy, both the output voltage and output current oscillate with equal amplitude. However, under the improved control strategy of adding a proportional-derivative element, the Buck converter system of this disclosure exhibits stable output voltage and output current, resulting in a significant improvement in the steady-state performance of the Buck converter system.

[0081] See Figures 5-6 , Figure 5 The diagram shows waveforms of the output voltage and output current of a Buck converter system according to an embodiment of the present disclosure under disturbance conditions. Figure 6 The diagram shows the waveforms of the output voltage and output current of a Buck converter system under disturbance conditions using a conventional droop control strategy. Figure 5 and Figure 6 The controller parameters are the same, consisting of 5 and Figure 6 Analysis shows that when the load power P CPL When the power output suddenly increases from 2.5kW to 5kW, the improved control causes the output voltage to drop from 400V to 394.4V before recovering to a steady state, a drop of 5.6V. In contrast, the traditional droop control strategy results in an output voltage drop of 8.6V. This comparison demonstrates that the improved control strategy of this embodiment enhances the dynamic characteristics of the system.

[0082] As can be seen, compared with traditional droop control, the control method according to the embodiments of this disclosure adds a proportional-derivative element to the traditional droop control strategy to improve the system stability margin and improve the stability of the Buck converter system.

[0083] Those skilled in the art should understand that the discussion of any of the above embodiments is merely exemplary and is not intended to imply that the scope of this disclosure (including the claims) is limited to these examples; within the framework of this disclosure, the technical features of the above embodiments or different embodiments can also be combined, the steps can be implemented in any order, and there are many other variations of different aspects of the embodiments of this disclosure as described above, which are not provided in detail for the sake of brevity.

[0084] Additionally, to simplify the description and discussion, and to avoid obscuring the embodiments of this disclosure, the provided drawings may or may not show well-known power / ground connections to integrated circuit (IC) chips and other components. Furthermore, the apparatus may be shown in block diagram form to avoid obscuring the embodiments of this disclosure, and this also takes into account the fact that the details of implementation of these block diagram apparatuses are highly dependent on the platform on which the embodiments of this disclosure will be implemented (i.e., these details should be fully understood by those skilled in the art). While specific details (e.g., circuits) have been set forth to describe exemplary embodiments of this disclosure, it will be apparent to those skilled in the art that the embodiments of this disclosure can be implemented without these specific details or with variations thereof. Therefore, these descriptions should be considered illustrative rather than restrictive.

[0085] This disclosure is intended to cover all such substitutions, modifications, and variations that fall within the broad scope of the appended claims. Therefore, any omissions, modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of this disclosure should be included within the scope of protection of this disclosure.

Claims

1. A control method for a Buck converter system based on droop control, characterized in that, include: Output current based on Buck converter system i o Sag coefficient R d Output voltage rating V bus Droop control is applied to the Buck converter system to obtain the desired voltage value. v dc * This includes: the output current of a Buck converter-based system. i o and droop coefficient R d Obtain the first voltage; based on the first voltage and the output voltage rating. V bus The difference yields the expected voltage value. v dc * ; Based on voltage expectation v dc * Output voltage value of Buck converter system v dc Voltage control is applied to the Buck converter system to obtain the desired current value i. o * ,include: Output voltage value based on Buck converter system v dc and differential gain G F ( s The second voltage is obtained, including: Second voltage = Output voltage value v dc × Differential gain G F ( s ); where, differential gain G F ( s )= k F s +1, k F The differential coefficients of the proportional-differential component are... s It is a differential operator; Based on the second voltage and the expected voltage value v dc * The difference yields the third voltage; based on the third voltage and the voltage proportional-integral coefficient... G v ( s The desired current value i is obtained. o * ; Based on the expected current i o * Output current of Buck converter system i o Current control is applied to the Buck converter system to obtain the drive signal d, which includes: based on the desired current value i o * and the output current of the Buck converter system i o The difference yields the first current; based on the first current and the current proportional-integral coefficient... G i ( s The driving signal d is obtained; where the current proportional-integral coefficient is... G i ( s )= k pi + k ii / s , k pi This is the current proportionality coefficient. k ii The current integral coefficient; The Buck converter system operates based on the drive signal d.

2. The method according to claim 1, characterized in that, Output current based on Buck converter system i o and droop coefficient R d To obtain the first voltage, the following steps are taken: First voltage = droop coefficient R d Output current of the ×Buck converter system i o .

3. The method according to claim 1, characterized in that, Based on the third voltage and voltage proportional-integral coefficient G v ( s The desired current value i is obtained. o * This includes: the expected current value i o * =Third voltage V3 × Voltage proportional-integral coefficient G v ( s ); Among them, the voltage proportional-integral coefficient G v ( s )= k pv + k iv / s , k pv This is the voltage proportionality coefficient. k iv The voltage integral coefficient, s It is a differential operator.

4. The method according to claim 1, characterized in that, Based on the expected current i o * and the output current of the Buck converter system i o The difference yields the first current, including: First current I1 = expected current i o * -Buck converter system output current i o。 5. The method according to claim 4, characterized in that, Based on the first current and the current proportional-integral coefficient G i ( s The driving signal d is obtained, including: driving signal d = first current I1 × current proportional-integral coefficient. G i ( s ).

6. A Buck converter system based on droop control, characterized in that, Control is performed using the method described in any one of claims 1-5.

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