Control method of DC / DC converter of two-stage energy storage converter

Abstract

The present invention relates to the technical field of energy storage converter control, and specifically discloses a control method for a DC / DC converter of a two-stage energy storage converter, comprising: S1: simulating the DC / DC converter of the two-stage energy storage converter as a virtual DC motor, adding armature voltage compensation, and establishing a virtual DC motor control model; S2: obtaining the bus voltage of the DC / DC converter and calculating the rate of change of the bus voltage; and S3: adjusting the moment of inertia and armature voltage compensation coefficient of the virtual DC motor control model based on the rate of change of the bus voltage to achieve control of the DC / DC converter. The present invention establishes a virtual DC motor control model and adds armature voltage compensation control to reduce bus voltage fluctuations, thereby improving the bus voltage's anti-disturbance and dynamic recovery capabilities.

Description

Technical Field

[0001] The present invention relates to the technical field of energy storage converter control, and in particular to a control method for a DC / DC converter of a two-stage energy storage converter. Background Art

[0002] Two-stage energy storage converters incorporate an additional DC / DC converter in the front stage, creating a constant-voltage DC bus between the front and rear converters. This facilitates stable operation of the rear-stage DC / AC converter and allows for greater flexibility in configuring the energy storage battery's capacity, power, and voltage level. Therefore, two-stage energy storage converters are widely used in microgrids containing renewable energy generation, often combined with vanadium redox flow batteries (VFBs) with lower voltage levels on the low-voltage side to mitigate fluctuations in renewable energy generation.

[0003] To control the DC-side bus voltage of a two-stage energy storage converter, the front-stage DC / DC converter typically uses PI dual closed-loop control to achieve bidirectional energy flow and maintain bus voltage stability. However, when the operating conditions of the downstream DC / AC converter change or are subject to load disturbances, especially when braking motor loads, the feedback energy can easily cause transient bus voltage fluctuations, resulting in overvoltage on the bus capacitors or instability or even damage to downstream electrical equipment. While traditional dual closed-loop control can ultimately eliminate the effects of load disturbances, it still exhibits a certain degree of hysteresis, resulting in large transient bus voltage fluctuations that adversely affect the stable operation of the two-stage energy storage converter.

[0004] Traditional bus voltage fluctuation suppression relies on a load current feedforward control strategy. The control concept is to calculate the current required by the preceding converter based on the power demand of the following converter, and then feed this current directly into the inner current loop as a reference current. This feedforward control bypasses the slower-response outer voltage loop, thereby directly controlling the current loop to quickly suppress bus voltage fluctuations. Alternatively, model predictive control can be used to establish a predictive model and objective function for the inner current loop in a dual closed-loop control system, thereby selecting the optimal switching state.

[0005] In existing technologies, neither load current feedforward control nor model predictive control fundamentally address the reason why bus voltage fluctuates significantly when disturbed, namely, the low inertia and weak damping characteristics of the bus port. Therefore, to increase the inertia and damping of the bus port and improve its ability to suppress load disturbances, some researchers have proposed a virtual DC motor control (VDCM) strategy for use in the control of the preceding DC / DC converter. For example, Chinese invention patent application publication number CN118249415A discloses a method and system for virtual inertia network control of a photovoltaic grid-connected system based on a limited Sigmoid function. The method involves simulating the dynamic characteristics of a synchronous generator rotor, introducing virtual inertia into the photovoltaic grid-connected converter unit, and establishing a virtual inertia control equation for the photovoltaic grid-connected system. The method also analyzes the response of the AC side frequency and its rate of change during load fluctuations to clarify the design principles of the virtual inertia parameters. A variant of the Sigmoid function with limited amplitude is used to construct the virtual inertia control parameters based on adaptive frequency recovery requirements. Combined with the control logic of the photovoltaic grid-connected converter, an adaptive virtual inertia network control scheme for the photovoltaic grid-connected system based on a limited Sigmoid function is obtained. However, this method struggles to achieve good dynamic performance for the bus voltage while achieving both inertia and damping support. Therefore, how to implement virtual DC motor control to better enhance bus voltage immunity and dynamic recovery capabilities remains a key technical challenge in this field. Summary of the Invention

[0006] The present invention aims to address the long bus voltage recovery time problem of traditional virtual DC motor control, which achieves both inertia and damping support. To this end, the present invention provides a control method for a DC / DC converter in a two-stage energy storage inverter. This method establishes a virtual DC motor control model and incorporates armature voltage compensation control to reduce bus voltage fluctuations. Furthermore, the method uses a sigmoid function to perform adaptive parameter adjustment, improving the bus voltage's anti-disturbance and dynamic recovery capabilities.

[0007] The present invention provides a control method for a DC / DC converter of a two-stage energy storage converter, and the technical solution adopted is as follows: comprising the following steps:

[0008] S1: The DC / DC converter of the two-stage energy storage converter is simulated as a virtual DC motor, and armature voltage compensation is added to establish a virtual DC motor control model;

[0009] S2: Obtain the bus voltage of the DC / DC converter and calculate the rate of change of the bus voltage;

[0010] S3: According to the rate of change of the bus voltage, the compensation coefficient of the moment of inertia and armature voltage of the virtual DC motor control model is adjusted to realize the control of the DC / DC converter.

[0011] Furthermore, after adding armature voltage compensation, the armature equation of the virtual DC motor control model is:

[0012]

[0013] Where, is the output voltage, is the armature voltage, is the compensation coefficient, is the reference voltage, is the armature current, is the armature resistance.

[0014] Furthermore, when the rate of change of the bus voltage does not exceed the threshold value of the bus voltage deviation, the moment of inertia and the compensation coefficient are maintained at inherent values;

[0015] When the bus voltage change rate exceeds the bus voltage deviation threshold, the values ​​of the moment of inertia and the compensation coefficient are changed simultaneously according to the value of the bus voltage change rate.

[0016] Furthermore, the moment of inertia and the compensation coefficient are adaptively adjusted based on the Sigmoid function.

[0017] Furthermore, the adaptive adjustment function of the moment of inertia for:

[0018]

[0019] in, is the upper limit of the moment of inertia, is the lower limit of the moment of inertia, is the inertia independent variable, is the inertia growth rate, is the midpoint of inertia;

[0020] Adaptive adjustment function of compensation coefficient for:

[0021]

[0022] in, is the upper limit of the compensation coefficient, is the lower limit of the compensation coefficient, is the compensation coefficient growth rate, is the compensation coefficient independent variable, is the midpoint of the compensation coefficient.

[0023] Furthermore, the inertia independent variable Expressed as:

[0024]

[0025] in, is a symbolic function, is the rate of change of bus voltage, is the bus voltage difference, is the threshold value of bus voltage deviation;

[0026] Inertia growth rate Expressed as:

[0027]

[0028] in, To achieve the system The minimum required bus voltage change rate;

[0029] Midpoint of inertia Expressed as:

[0030]

[0031] in, is the inherent moment of inertia.

[0032] Furthermore, the upper limit of the moment of inertia is 0.12, the lower limit of the moment of inertia is 0.02, the inherent moment of inertia is 0.06, the upper limit of the compensation coefficient is 1.5, the lower limit of the compensation coefficient is 0.5, and the inherent compensation coefficient is 1.

[0033] Furthermore, during the bus voltage fluctuation process, the adjustment method of the moment of inertia and the compensation coefficient is as follows:

[0034] During the period t0~t1, the bus voltage is disturbed and drops from the steady-state value to the valley value. The moment of inertia and compensation coefficient should be increased.

[0035] During the t1~t2 period, the bus voltage begins to recover from the valley value to the steady-state value, and the moment of inertia and compensation coefficient should be reduced;

[0036] During the t2~t3 period, the bus voltage rises from the steady-state value to the peak value, and the moment of inertia and compensation coefficient should be increased;

[0037] During the t3~t4 period, the bus voltage returns to a steady-state value, and the moment of inertia and compensation coefficient should be reduced;

[0038] Among them, t0 is the moment when the bus voltage begins to drop, t1 is the moment when the bus voltage drops to the valley value, t2 is the moment when the bus voltage returns to the steady-state value, t3 is the moment when the bus voltage rises to the peak value, and t4 is the moment when the bus voltage returns to the steady-state value.

[0039] Furthermore, the small signal model analysis method is used to analyze the virtual DC motor control model to obtain the adjustment method of the moment of inertia and compensation coefficient.

[0040] The above one or more technical solutions in the embodiments of the present invention have at least one of the following technical effects:

[0041] This paper simulates a DC / DC converter as a virtual DC motor, establishes a virtual DC motor control model, and incorporates armature voltage compensation control to reduce bus voltage fluctuations. Through small-signal model analysis, the present invention analyzes the impact of different control parameters on the system from the perspectives of dynamic performance and stability, and derives a dynamic adjustment method for the control parameters based on the bus voltage fluctuation process. Combining the results of the small-signal model analysis, the present invention uses a Sigmoid function to rationally design an adaptive function for the desired controlled moment of inertia and compensation coefficient to meet the required adjustment method.

[0042] The present invention combines virtual DC motor control with parameter adaptive control. The designed control strategy combines the advantages of virtual DC motor control and adaptive control, improves the anti-disturbance performance of the bus voltage when the two-stage energy storage converter is disturbed, and effectively shortens its dynamic recovery time.

[0043] Additional aspects and advantages of the present invention will be set forth in part in the description which follows and, in part, will be obvious from the description which follows, or may be learned by practice of the present invention. BRIEF DESCRIPTION OF THE DRAWINGS

[0044] In order to more clearly illustrate the technical solutions in the present invention or the prior art, the following briefly introduces the drawings required for use in the embodiments or the description of the prior art. Obviously, the drawings described below are some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying any creative work.

[0045] Figure 1 It is a flow chart of the method provided by the present invention.

[0046] Figure 2 This is a topological diagram of the two-stage energy storage converter provided by the present invention.

[0047] Figure 3 This is a virtual DC motor control block diagram of a traditional bidirectional DC / DC converter provided by the present invention.

[0048] Figure 4 This is a block diagram of the VDCM control with armature voltage compensation provided by the present invention.

[0049] Figure 5 This is a schematic diagram of a small signal model of VDCM control after adding armature voltage compensation provided by the present invention.

[0050] Figure 6 It is a unit step response diagram of the closed-loop output impedance provided by the present invention.

[0051] Figure 7 It is the zero and pole diagram of the closed-loop transfer function provided by the present invention.

[0052] Figure 8 This is a typical dynamic response process diagram of the bus voltage when the subsequent load suddenly increases, as provided by the present invention.

[0053] Figure 9 It is a VDCM parameter adaptive control diagram of an embodiment provided by the present invention.

[0054] Figure 10 This is a dynamic response simulation diagram of the PI dual closed-loop control and armature voltage compensation VDCM provided by the present invention when the load changes suddenly.

[0055] Figure 11 This is a simulation diagram of the armature voltage compensation VDCM and the dynamic response of the method provided by the present invention when the load changes suddenly.

[0056] Figure 12 This is an adaptive curve of the moment of inertia and the compensation coefficient when the load power suddenly increases, provided by the present invention. DETAILED DESCRIPTION

[0057] To make the purpose, technical solutions and advantages of the present invention clearer, the technical solutions of the present invention will be clearly and completely described below in conjunction with the accompanying drawings of the present invention. Obviously, the embodiments described are part of the embodiments of the present invention, rather than all the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making creative work are within the scope of protection of the present invention. The following embodiments are used to illustrate the present invention, but are not used to limit the scope of the present invention.

[0058] In the description of this specification, the description with reference to the terms "one embodiment", "some embodiments", "example", "specific example", or "some examples" means that the specific features, structures or characteristics described in conjunction with the embodiment or example are included in at least one embodiment or example of the embodiment of the present invention. In this specification, the schematic representation of the above terms does not necessarily refer to the same embodiment or example. Moreover, the specific features, structures or characteristics described can be combined in any one or more embodiments or examples in a suitable manner. In addition, those skilled in the art can combine and combine different embodiments or examples described in this specification and features of different embodiments or examples without contradiction.

[0059] The following combination Figures 1 to 12 The present invention is further described in detail, and a control method of a DC / DC converter of a two-stage energy storage converter of the present invention is described:

[0060] In this embodiment, Figure 1 As shown, a control method for a DC / DC converter of a two-stage energy storage converter is provided, comprising the following steps:

[0061] S1: The DC / DC converter of the two-stage energy storage converter is simulated as a virtual DC motor, and armature voltage compensation is added to establish a virtual DC motor control model.

[0062] S2: Obtain the bus voltage of the DC / DC converter and calculate the rate of change of the bus voltage.

[0063] S3: According to the rate of change of the bus voltage, the compensation coefficient of the moment of inertia and armature voltage of the virtual DC motor control model is adjusted to realize the control of the DC / DC converter.

[0064] Figure 2 This is a topological diagram of a two-stage energy storage converter, which mainly includes a DC / DC converter at the front stage and a VSC (voltage source converter) connected to the DC / DC converter. Figure 2 middle, is the low voltage side battery voltage; is the DC side filter inductor; is the bus capacitance; is the filter inductor on the AC side of the VSC; For filter inductance The equivalent resistance of The local load is connected to the common bus node PCC and is connected to the grid through the grid-connected switch STS via the isolation transformer.

[0065] To improve the busbar voltage's immunity to disturbances, a bidirectional DC / DC converter was studied and simulated as a virtual DC motor, effectively acting as a DC motor. The DC / DC converter was considered a two-port network, with a battery connected to the front end and a load connected to the back end. By simulating the external characteristics of a DC motor, this two-port network exhibits a certain amount of inertia support at its output port, thereby improving the busbar voltage's immunity to disturbances.

[0066] Assuming the number of pole pairs of the motor is 1, the mechanical equation of the DC motor is:

[0067] (1)

[0068] Where, is the rated mechanical angular velocity, is the moment of inertia, is the damping coefficient, is the mechanical torque, is the electromagnetic torque, is the angular velocity of rotation, For time.

[0069] The armature equation of a DC motor is:

[0070] (2)

[0071] Where, is the output voltage, is the armature voltage, is the armature current, is the armature resistance, is the torque coefficient, is the magnetic flux.

[0072] Mechanical power of DC motor and electromagnetic power It can be expressed as:

[0073] (3)

[0074] Where, is the output current.

[0075] Therefore, when a DC / DC converter uses virtual DC motor (VDCM) control, it is necessary to establish a connection with the DC motor's output characteristics. The DC / DC converter's port characteristics can simulate the DC motor's armature circuit to a certain extent. However, due to the lack of mechanical rotor components, simulation of the rotor's mechanical equations can only be achieved through control.

[0076] According to equations (1) to (3), the virtual DC motor control block diagram of the DC / DC converter is as follows: Figure 3 As shown in the figure, the control strategy consists of three parts: voltage regulation, VDCM control and current regulation. In voltage regulation, the PI controller Gu is used to realize the reference voltage Tracking, thereby eliminating steady-state errors; the purpose of the PI controller Gi in current regulation is the same, in order to achieve the input current The VDCM control part simulates the inertia and damping characteristics of the DC motor based on the mechanical equation and armature equation. 1 / s is the integral operator, is the reference voltage.

[0077] In order to further improve the anti-disturbance performance of the bus voltage during traditional VDCM control, the VDCM control block diagram of this embodiment with armature voltage compensation is shown in FIG. Figure 4 Without affecting the steady-state output of the system, the armature voltage E is transiently compensated to quickly adjust the output current of the converter, thereby alleviating the fluctuation of the bus voltage to a certain extent.

[0078] according to Figure 4, after adding armature voltage compensation, the armature equation of the virtual DC motor control model can be further rewritten as:

[0079] (4)

[0080] Where, is the compensation coefficient, is the reference voltage.

[0081] Applying perturbation to equation (4), we can obtain:

[0082] (5)

[0083] Where, is the output voltage change, is the armature voltage change, is the armature current variation.

[0084] Equation (5) shows that when the armature current changes, the change in bus voltage (output voltage) after adding armature voltage compensation is 1 / (k+1) times that of traditional VDCM control, and bus voltage fluctuations are better suppressed. At the same time, the compensation coefficient k is additionally introduced to jointly adjust the dynamic characteristics of VDCM with the moment of inertia J and the damping coefficient D.

[0085] The small signal model analysis method is used to analyze the influence of different control parameters on the system from the two aspects of dynamic performance and stability. The adjustment method of the moment of inertia and compensation coefficient can be obtained based on the virtual DC motor control model. The small signal model of VDCM control after armature voltage compensation is as follows: Figure 5 shown.

[0086] Figure 5 The derivation results of the main transfer functions are as follows:

[0087] (6)

[0088] (7)

[0089] (8)

[0090] (9)

[0091] (10)

[0092] in, is the transfer function of input current to duty cycle, for The disturbance component of is the disturbance component of d, d is the duty cycle, is the steady-state value of the input current, C is the capacitance value, is the DC bus voltage, s is the Laplace operator, L is the inductance value, is the transfer function of DC bus voltage to duty cycle, for The disturbance component of is the transfer function of input current to output current, for The disturbance component of is the open-loop output impedance, for The disturbance component of is the transfer function of back electromotive force to load torque, is the disturbance component of E, for The disturbance component of . is the conduction voltage drop of the switching device.

[0093] according to Figure 5 , we can get and The relationship between is shown in formula (11), that is, the closed-loop output impedance of the system . and The relationship between is shown in formula (12), that is, the closed-loop transfer function of the system , reflecting the ability to track the bus voltage.

[0094] (11)

[0095] (12)

[0096] in:

[0097] (13)

[0098] (14)

[0099] in, is the transfer function of the current regulator, is the open-loop output impedance, is the disturbance component of the reference voltage, is the transfer function of the voltage regulator. is the first intermediate parameter is the second intermediate parameter.

[0100] Based on formula (11), the unit step response of the closed-loop output impedance of the system can be obtained when different control parameters change, as shown in Figure 6 As shown:

[0101] exist Figure 6 In the case of a unit increase in output current, the bus voltage is disturbed and there will be a transient drop. Figure 6 (a) and Figure 6 As shown in (b), increasing the moment of inertia J can suppress the transient drop of bus voltage to a certain extent, but too large a value of J will lead to overshoot and increased response time when bus voltage recovers. Increasing the damping coefficient D can better suppress overshoot when bus voltage recovers and shorten the dynamic adjustment time. In addition, Figure 6 In (c), as the compensation coefficient k increases, the bus voltage drop and recovery overshoot can be well suppressed compared with the moment of inertia J. Figure 6 middle, is the DC bus voltage change.

[0102] In order to ensure that the system has good tracking and stability, the closed-loop dominant zero and pole diagrams are drawn according to formula (12) under the traditional virtual DC motor control, that is, when armature voltage compensation is not used, J = 0.06, D takes 2~10, and D = 4, J takes 0.01~0.14, as shown in the following figure: Figure 7 (a) and Figure 7 As shown in (b), and after adopting armature voltage compensation, J=0.06, D=4, k takes 0~2, the VDCM closed-loop zero and pole diagram is as follows: Figure 7 (c) and Figure 7 As shown in (d).

[0103] Depend on Figure 7 As shown in (a), the system has a pair of dominant poles P1 and P2. As the moment of inertia J increases, the dominant poles change from two negative real roots to a pair of conjugate complex roots and gradually approach the origin, resulting in an increase in the system overshoot and response time. Figure 7 In (b), the increase in the damping coefficient D will cause the pair of conjugate complex roots to move toward the negative real axis, becoming two negative real roots again, and the dominant pole P1 moves along the negative real axis to the imaginary axis, resulting in a reduction in the system overshoot. The compensation coefficient k is similar to the conjugate pole distribution of the damping D, as shown in Figure 7 As shown in (c), a pair of conjugate zeros will be brought about near it. Although the existence of the conjugate zeros will not affect the transient response component of the system, it determines the proportion of its transient component. When the conjugate zeros and conjugate poles are close to each other, the oscillation characteristics generated by the conjugate poles are further weakened, that is, the overshoot of the system is reduced. Figure 7 (d) is Figure 7 Enlarged view of point (d) in (c).

[0104] Taking the sudden increase of load or power of the subsequent VSC as an example, the typical dynamic response process of the bus voltage is as follows: Figure 8 shown. Figure 8The dynamic response process of bus voltage can be divided into five stages: 0~t0, t0~t1, t1~t2, t2~t3, t3~t4. Among them, the 0~t0 stage belongs to the initial steady-state stage; in the t0~t1 stage, the bus voltage is disturbed and drops from the steady-state value (0) to the valley value. At this time, the J and k values ​​should be increased to provide inertia support for the system, so as to better suppress the drop of bus voltage; in the t1~t2 stage, the bus voltage starts to rise from the valley value. Restore to steady-state value. During the bus voltage recovery phase, the J and k values ​​should be reduced, and smaller J and k values ​​should be used to avoid overshoot when the voltage recovers and reduce the dynamic response time of this phase. During the t2~t3 phase, the bus voltage rises from the steady-state value to the peak value. , similar to the t0~t1 stage, it is the stage where the bus voltage error becomes larger, and the J and k values ​​should be increased, and larger J and k values ​​should be used; in the t3~t4 stage, the bus voltage returns to the steady-state value, which is similar to the t1~t2 stage, it is the voltage recovery stage, and the J and k values ​​should be reduced, and smaller J and k values ​​should be used. Among them, t0 is the moment when the bus voltage begins to drop, t1 is the moment when the bus voltage drops to the valley value, t2 is the moment when the bus voltage returns to the steady-state value, t3 is the moment when the bus voltage rises to the peak value, and t4 is the moment when the bus voltage returns to the steady-state value. The above content shows the adjustment method of the moment of inertia and compensation coefficient during the bus voltage fluctuation process. Based on Figure 8 According to the above analysis, the dynamic adjustment method of J and k when the DC bus voltage fluctuates is shown in Table 1.

[0105] Table 1 Adjustment method of J and k when bus voltage fluctuates

[0106]

[0107] In order to smoothly change the control parameters of the VDCM, this embodiment uses the Sigmoid function to design the VDCM parameter adaptive adjustment function. It can be expressed as:

[0108] (15)

[0109] Where, It is a variable that characterizes the degree of bus voltage fluctuation; is the midpoint of the Sigmoid function; is the upper limit of the function range, is the lower limit of the function range; is the growth rate, is the natural base. Since the upper and lower limits can only be reached at infinity on the x-axis, the upper limit is used as an approximation. and lower limit approximation Instead. Among them, , .

[0110] At this point, the problem of parameter adaptation for the virtual DC motor is transformed into designing a suitable Sigmoid function so that the parameters J and k vary within a certain range. The moment of inertia and compensation coefficient are adaptively adjusted based on the Sigmoid function.

[0111] According to the stability analysis, the inherent moment of inertia of this embodiment is =0.06, inherent damping coefficient =4, inherent compensation coefficient = 1. The value range of the moment of inertia J is between 0.02 and 0.12, and the value of the compensation coefficient k is between 0.5 and 1.5. The system can maintain stability and has good dynamic performance.

[0112] Upper and lower limits of moment of inertia J: When the bus voltage is disturbed, the J value needs to be flexibly selected and adjusted according to the voltage fluctuation so that the bus voltage has a certain inertia to resist the disturbance and has a good dynamic response. In addition, the selection of moment of inertia J should be based on the premise of system stability, that is:

[0113] (16)

[0114] in, is the upper limit of the moment of inertia, is the lower limit of the moment of inertia.

[0115] Inertia independent variable and inertia growth rate Selection: When the bus voltage is slightly disturbed and the resulting voltage deviation is small, you can rely on its own inherent moment of inertia Adjust; when the disturbance is large, the bus voltage deviation exceeds , it is necessary to reasonably adjust the J value according to the voltage fluctuation. It can be expressed as:

[0116] (17)

[0117] in, is a symbolic function, is the rate of change of bus voltage, is the bus voltage difference, is the threshold value of bus voltage deviation, which can be determined according to the deviation standard of bus voltage. In this embodiment, =5V.

[0118] In the initial stage of bus voltage disturbance, the voltage change rate is large, so it is hoped that the system will provide a larger moment of inertia J to suppress voltage fluctuations. =1, the domain of the Sigmoid function is [-4.6,4.6], that is , Therefore, the bus voltage change rate can be Determine the inertia growth rate by :

[0119] (18)

[0120] in, To achieve the system The minimum required bus voltage change rate, is the midpoint of inertia.

[0121] Midpoint of inertia Determination: The midpoint of the Sigmoid function must ensure that the independent variable = 0, J is equal to its initial value, that is, the inherent moment of inertia of the system when it is in a steady state , corresponding to The calculation is as follows:

[0122] (19).

[0123] Adaptive law of the complete VDCM parameter J: According to equations (16) to (19), the complete adaptive regulation function of the moment of inertia J is It can be expressed as:

[0124] (20).

[0125] Similarly, the adaptive adjustment function of the compensation coefficient k of the armature voltage is Consistent with J, it is expressed as follows:

[0126] (twenty one)

[0127] Where, is the upper limit of the compensation coefficient, is the lower limit of the compensation coefficient, is the compensation coefficient growth rate, is the compensation coefficient independent variable, is the midpoint of the compensation coefficient. Each parameter is calculated in the same way as J.

[0128] According to equations (20) and (21), the virtual DC motor parameter adaptive control strategy proposed in this embodiment is as follows: Figure 9When the bus voltage is disturbed, the moment of inertia J and the compensation coefficient k can be adaptively adjusted according to the rate of change of the voltage. This improves the system's anti-disturbance capability while also taking into account its dynamic characteristics, allowing the bus voltage to recover to a steady-state value more quickly.

[0129] In summary, when the bus voltage change rate does not exceed the bus voltage deviation threshold, the moment of inertia and compensation coefficient are kept at their inherent values. When the bus voltage change rate exceeds the bus voltage deviation threshold, the moment of inertia and compensation coefficient are changed simultaneously according to the value of the bus voltage change rate; specifically, the adaptive adjustment function is used to adjust the moment of inertia and compensation coefficient. and adaptive adjustment function Adjust the values ​​of the moment of inertia and compensation coefficient.

[0130] To verify the feasibility and effectiveness of this embodiment, a simulation model of a bidirectional DC / DC converter using virtual DC motor control was built in MATLAB / Simulink. The control part was implemented using an S-Function, and the relevant control parameters are shown in Table 2.

[0131] Table 2 System simulation parameters

[0132]

[0133] Figure 10 (a) and (b) show the simulation comparison waveforms of traditional PI dual closed-loop control and armature voltage compensation VDCM when the load power suddenly increases and decreases. Figure 10 In (a), at 1 second, the load power suddenly increases from 5kW to 10kW, causing the bus voltage to be disturbed and begin to drop. Using traditional PI dual-closed-loop control, although the bus voltage recovers quickly, at approximately 110ms, the initial voltage drop peaks at approximately 25V. However, using only the armature voltage compensation (VDCM) in this method—fixing the moment of inertia and compensation coefficient to inherent values ​​and not adaptively adjusting the VDCM parameters based on a sigmoid function—the bus voltage drop is reduced to only 17V, but the voltage recovery time is increased to approximately 200ms. Figure 10 In (b), at 1s, the load power suddenly drops from 15kW to 10kW. As can be seen from the figure, the armature voltage compensation VDCM can still effectively suppress the bus voltage fluctuation.

[0134] Therefore, the above simulation comparison shows that compared to traditional PI dual closed-loop control, armature voltage compensation (VDCM) can provide additional rotational inertia and damping for the bidirectional DC / DC converter, thereby improving the bus port's anti-disturbance performance and effectively suppressing voltage fluctuations. However, the introduction of inertia, damping, and compensation coefficients increases the dynamic recovery time of the bus voltage.

[0135] Figure 11 (a) and (b) are the simulated waveforms of the bus voltage when the load power suddenly increases and decreases using the armature voltage compensation VDCM and this method (armature voltage compensation + parameter adaptive VDCM), respectively. Figure 11 In (a), at 1 second, the load power suddenly increases from 5 kW to 10 kW. Using armature voltage compensation (VDCM), the bus voltage drops by approximately 17 V, with a recovery time of approximately 200 ms. However, using this method, the bus voltage drop is further suppressed to only 11 V. Furthermore, the bus voltage recovery time is shortened to only 140 ms. Figure 11 In (b), the load power suddenly decreases from 15kW to 10kW in 1s. This method can still effectively suppress bus voltage fluctuations and shorten the dynamic voltage recovery time.

[0136] When the power suddenly increases, the parameter adaptive VDCM control is adopted, and the dynamic adjustment curves of the moment of inertia J and the compensation coefficient k are as follows: Figure 12 As shown in (a) and (b). In the initial stage, , the moment of inertia is maintained When the voltage fluctuates greatly, , the moment of inertia is adaptively adjusted along with the bus voltage change rate, and when Greater than When , the moment of inertia J takes the maximum value to improve the bus voltage's anti-disturbance capability or accelerate the voltage recovery time. The adaptive curve of the compensation coefficient k is similar.

[0137] Therefore, it can be seen that in this method, based on the armature voltage compensation VDCM control, the fluctuation of the bus voltage is further suppressed through the adaptive adjustment of the moment of inertia and the compensation coefficient, and better dynamic recovery characteristics are obtained.

[0138] Through the above experimental comparison, it can be seen that the present invention designs a reasonable parameter adaptive adjustment function through the armature voltage compensation strategy and the Sigmoid function, which solves the problem that the proposed VDCM control is difficult to obtain good dynamic performance while obtaining inertia and damping support, and further improves the anti-disturbance and dynamic recovery capabilities of the bus voltage.

[0139] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, rather than to limit it. Although the present invention has been described in detail with reference to the aforementioned embodiments, those skilled in the art should understand that they can still modify the technical solutions described in the aforementioned embodiments, or make equivalent replacements for some of the technical features therein. However, these modifications or replacements do not deviate the essence of the corresponding technical solutions from the spirit and scope of the technical solutions of the various embodiments of the present invention.

Claims

1. A control method for a DC / DC converter of a two-stage energy storage converter, characterized in that: The following steps are involved: S1: The DC / DC converter of the two-stage energy storage converter is simulated as a virtual DC motor, and armature voltage compensation is added to establish a virtual DC motor control model; S2: Obtain the bus voltage of the DC / DC converter and calculate the rate of change of the bus voltage; S3: According to the change rate of the bus voltage, the compensation coefficient of the moment of inertia and armature voltage of the virtual DC motor control model is adjusted to realize the control of the DC / DC converter; Adaptive adjustment function of moment of inertia for: in, is the upper limit of the moment of inertia, is the lower limit of the moment of inertia, is the inertia independent variable, is the inertia growth rate, is the midpoint of inertia; Adaptive adjustment function of compensation coefficient for: in, is the upper limit of the compensation coefficient, is the lower limit of the compensation coefficient, is the compensation coefficient growth rate, is the compensation coefficient independent variable, is the midpoint of the compensation coefficient.

2. The control method of a DC / DC converter of a two-stage energy storage converter according to claim 1, characterized in that: After adding armature voltage compensation, the armature equation of the virtual DC motor control model is: Where, is the output voltage, is the armature voltage, is the compensation coefficient, is the reference voltage, is the armature current, is the armature resistance.

3. The control method of a DC / DC converter of a two-stage energy storage converter according to claim 1 or 2, characterized in that: When the bus voltage change rate does not exceed the bus voltage deviation threshold, the moment of inertia and compensation coefficient are maintained at inherent values; When the bus voltage change rate exceeds the bus voltage deviation threshold, the values ​​of the moment of inertia and the compensation coefficient are changed simultaneously according to the value of the bus voltage change rate.

4. The control method of a DC / DC converter of a two-stage energy storage converter according to claim 3, characterized in that: The moment of inertia and compensation coefficient are adaptively adjusted based on the Sigmoid function.

5. The control method of a DC / DC converter of a two-stage energy storage converter according to claim 1, characterized in that: Inertia independent variable Expressed as: in, is a symbolic function, is the rate of change of bus voltage, is the bus voltage difference, is the threshold of bus voltage deviation; Inertia growth rate Expressed as: in, To achieve the system The minimum required bus voltage change rate; Midpoint of inertia Expressed as: in, is the inherent moment of inertia.

6. The control method of a DC / DC converter of a two-stage energy storage converter according to claim 5, characterized in that: The upper limit of the moment of inertia is 0.12, the lower limit of the moment of inertia is 0.02, the inherent moment of inertia is 0.06, the upper limit of the compensation coefficient is 1.5, the lower limit of the compensation coefficient is 0.5, and the inherent compensation coefficient is 1.

7. The control method of a DC / DC converter of a two-stage energy storage converter according to claim 1, characterized in that: During bus voltage fluctuation, the adjustment method of the moment of inertia and compensation coefficient is: During the period t0~t1, the bus voltage is disturbed and drops from the steady-state value to the valley value. The moment of inertia and compensation coefficient should be increased. During the t1~t2 period, the bus voltage begins to recover from the valley value to the steady-state value, and the moment of inertia and compensation coefficient should be reduced; During the t2~t3 phase, the bus voltage rises from the steady-state value to the peak value, and the moment of inertia and compensation coefficient should be increased; During the t3~t4 period, the bus voltage returns to a steady-state value, and the moment of inertia and compensation coefficient should be reduced; Among them, t0 is the moment when the bus voltage begins to drop, t1 is the moment when the bus voltage drops to the valley value, t2 is the moment when the bus voltage returns to the steady-state value, t3 is the moment when the bus voltage rises to the peak value, and t4 is the moment when the bus voltage returns to the steady-state value.

8. The control method of a DC / DC converter of a two-stage energy storage converter according to claim 7, characterized in that: The small signal model analysis method is used to analyze the virtual DC motor control model to obtain the adjustment method of the moment of inertia and compensation coefficient.

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