A Resonance Suppression Method for LCL-type Energy Storage Converters Based on Passive SMC

Abstract

This invention discloses a resonance suppression method for LCL-type energy storage converters based on passive SMC (Smooth Mode Control), comprising: 1. sampling the converter's machine-side current and capacitor voltage; 2. injecting appropriate dissipation damping according to the sufficient conditions for passive control stability; 3. designing a suitable sliding mode surface to obtain the controller output signal; 4. performing an inverse d-q transform on the controller output signal to obtain the modulation wave signal; 5. combining an SVPWM modulation strategy to output the pulse drive signal for the switching devices. This invention utilizes the strong robustness of sliding mode control and the energy dissipation characteristics of passive control to jointly reduce the influence of resonance, thereby improving the system stability.

Description

Technical Field

[0001] This invention relates to a resonance suppression method for LCL-type energy storage converters based on passive SMC, belonging to the field of energy storage converter control. Background Technology

[0002] With the expansion of battery cell capacity and the increase in voltage levels, high-voltage, high-capacity energy storage systems have become the future development trend. Depending on the power rating and cost of the energy storage converter, the AC output side of the bridge arm mainly uses two types of filters: L-type and LCL-type. Among them, the filter capacitor in the LCL filter provides a low-damping path for high-frequency harmonic currents, exhibiting a strong suppression effect on high-frequency harmonic components in the AC current. Moreover, it is smaller and cheaper than the L-type filter, thus its widespread application. However, as a low-damping third-order system, the resonant network formed by the LCL filter inevitably experiences resonance problems, threatening the stable operation of the entire energy storage system.

[0003] As can be seen from the resonance mechanism of a single energy storage converter, the main reason for system resonance is the inherent resonance of the LCL filter as a third-order underdamped system. Therefore, the influence of resonance can be suppressed by appropriately increasing the energy dissipation at the resonance point. Currently, the passive damping method of filter capacitor series resistor suffers from high power loss and is difficult to use long-term. The active damping method of capacitor current proportional feedback is widely used due to its significant resonance damping effect; however, it suffers from problems such as dependence on sampler accuracy and high-frequency interference reducing sensor lifespan, making long-term stable application difficult.

[0004] Therefore, it is of great significance to study the resonant optimization control strategy of LCL-type energy storage converter. Summary of the Invention

[0005] In view of the shortcomings of the prior art, the present invention proposes a resonance suppression method for LCL type energy storage converter based on passive SMC, aiming to enhance the anti-interference capability of the current loop through sliding mode variable structure control and reduce resonance energy by introducing passive dissipation characteristics, thereby ensuring the stable operation of the energy storage converter and meeting the requirement that the total harmonic content is not greater than 5%.

[0006] To achieve the above-mentioned objectives, the present invention adopts the following technical solution:

[0007] The present invention provides a resonance suppression method for LCL-type energy storage converters based on passive SMC, characterized by the following steps:

[0008] Step 1: Establish sufficient conditions for the passive control stability of the LCL type energy storage converter using equation (1):

[0009] (1)

[0010] In equation (1), It is the error vector of the machine-side inductor current of the LCL type energy storage converter, and is obtained by equation (2); yes The derivative; yes Transpose of; It is a diagonal matrix composed of the machine-side inductance parameters of the LCL type energy storage converter in the dq coordinate system;

[0011] (2)

[0012] In equation (2), It is the d-axis component of the inductor current on the machine side of the LCL type energy storage converter; It is the q-axis component of the inductor current on the machine side of the LCL type energy storage converter; It is the d-axis balance point of the inductor current on the machine side of the LCL type energy storage converter; It is the q-axis equilibrium point of the inductor current on the machine side of the LCL type energy storage converter;

[0013] Step 2: Obtain the passive output signal of the LCL type energy storage converter using equation (3). :

[0014] (3)

[0015] In equation (3), It is a symmetrical matrix composed of the machine-side inductors of an LCL-type energy storage converter; It is the parasitic resistance of the machine-side inductor of the LCL type energy storage converter; It is a diagonal matrix composed of dissipation damping of LCL type energy storage converter;

[0016] Step 3: Determine whether equation (1) is true. If it is true, proceed to step 4; otherwise, change the dissipation damping. The value of is determined, and the machine-side inductor current of the LCL energy storage converter is resampled, thereby adjusting the error vector. After the update is performed, return to step 2 and execute it sequentially;

[0017] Step 4: Design the sliding surface of the LCL type energy storage converter using equation (4). :

[0018] (4)

[0019] In equation (4), These are the two sliding surface coefficients of the LCL-type energy storage converter; It is the operator symbol for the fractional integral of an LCL-type energy storage converter, where α is the order of the fractional integral; It is the error vector for reconstructing the passive output signal of the LCL type energy storage converter, and is obtained from equation (5):

[0020] (5)

[0021] Step 5: Obtain the control signal of the LCL type energy storage converter using equation (6). :

[0022] (6)

[0023] In equation (6), This is the machine-side inductance value of the LCL type energy storage converter; It is the robustness coefficient of the LCL type energy storage converter; These are the coefficients of the exponential approach term of the LCL-type energy storage converter; sat is the saturation function. It is the capacitor voltage of the LCL type energy storage converter; It is a coupling component caused by the dq transform;

[0024] Step 6: [Regarding...] After performing the dq inverse transformation, a three-phase modulation signal is obtained. The three-phase modulation signal is then processed using the SVPWM modulation strategy to output the pulse drive signal for the switching devices in the LCL type energy storage converter, thereby suppressing the resonance of the LCL type energy storage converter.

[0025] The present invention provides an electronic device, including a memory and a processor, wherein the memory is used to store a program that supports the processor in executing the LCL-type energy storage converter resonance suppression method, and the processor is configured to execute the program stored in the memory.

[0026] The present invention discloses a computer-readable storage medium, wherein a computer program is stored on the computer-readable storage medium, and the computer program is executed by a processor to perform the steps of the LCL-type energy storage converter resonance suppression method.

[0027] Compared with the prior art, the present invention has the following beneficial effects:

[0028] 1. This invention uses sliding mode variable structure control based on improving system robustness, which enhances the robustness of the current loop of the energy storage converter, while reducing the sensitivity of the control loop to parameter changes.

[0029] 2. By combining passive control and utilizing the passive dissipation characteristics, this invention achieves the purpose of reducing energy at the resonance point, thereby improving the stability of the LCL type energy storage converter.

[0030] 3. By combining SMC and passive control, this invention simplifies the complex controller expression of traditional SMC and reduces the amplitude of chattering. Attached Figure Description

[0031] Figure 1 This is a schematic diagram of the energy storage three-level converter structure in an embodiment of the present invention;

[0032] Figure 2 This is a control loop model for a three-level converter.

[0033] Figure 3 The output current waveform of a traditional PI-controlled converter;

[0034] Figure 4 The converter output current waveform for a passive SMC;

[0035] Figure 5 The output current THD diagram for a passive SMC converter. Detailed Implementation

[0036] In this embodiment, in order to solve Figure 1 This paper addresses the resonance problem of an LCL-type energy storage converter and proposes a resonance suppression method based on a passive SMC (Smooth Mode Controller). First, the machine-side current and capacitor voltage of the LCL-type energy storage converter are sampled. Second, the state equation in the dq coordinate system is rewritten in Euler-Lagrange form, and passive dissipation analysis is performed, injecting appropriate dissipation damping. Next, a fractional-order sliding mode surface is designed, and combined with the circuit state equation, the control expression is obtained. Finally, the controller output is inversely dq transformed to obtain a three-phase modulated wave, and the pulse drive signal of the switching devices is output using an SVPWM modulation strategy to achieve the goals of suppressing resonance, stabilizing the system, and enhancing system robustness. Specifically, this resonance suppression method includes:

[0037] Step 1: Establish sufficient conditions for the passive control stability of the LCL type energy storage converter using equation (1):

[0038] (1)

[0039] In equation (1), It is the error vector of the machine-side inductor current of the LCL type energy storage converter, and is obtained by equation (2); It is the derivative of the machine-side inductor current error vector of the LCL type energy storage converter; It is the transpose of the error vector of the machine-side inductor current of the LCL type energy storage converter; It is a diagonal matrix composed of the machine-side inductance parameters of the LCL type energy storage converter in the dq coordinate system;

[0040] (2)

[0041] In equation (2), It is the d-axis component of the inductor current on the machine side of the LCL type energy storage converter; It is the q-axis component of the inductor current on the machine side of the LCL type energy storage converter; It is the d-axis balance point of the inductor current on the machine side of the LCL type energy storage converter; It is the q-axis equilibrium point of the inductor current on the machine side of the LCL type energy storage converter.

[0042] Step 2: Obtain the passive output signal of the LCL type energy storage converter using equation (3). :

[0043] (3)

[0044] In equation (3), It is a symmetrical matrix composed of the machine-side inductors of an LCL-type energy storage converter; It is the parasitic resistance of the machine-side inductor of the LCL type energy storage converter; It is a diagonal matrix composed of dissipation damping of LCL type energy storage converter.

[0045] Step 3: Determine whether equation (1) is true. If it is true, proceed to step 4; otherwise, select a new dissipation damper. The parameter values ​​are sampled, and the machine-side inductor current of the LCL energy storage converter in the new cycle is sampled to determine the new error vector. Then return to step 2 and execute sequentially;

[0046] Taking an LCL-type energy storage converter as an example, the relationship between the machine-side inductor current and the converter bridge output voltage is established based on Kirchhoff's laws:

[0047] (4)

[0048] (5)

[0049] (6)

[0050] In equations (4) to (6), and These are the three-phase output voltage of the converter and the inductor current flowing through the bridge arm side, respectively. This is the voltage across the converter's filter capacitor; It is the machine-side inductance value of the LCL type energy storage converter.

[0051] Rewrite the circuit equations and perform dq decomposition:

[0052] (7)

[0053] Rewrite in Euler-Lagrange form:

[0054] (8)

[0055] In equation (8), , , .

[0056] Let the damping dissipation of the injection be: Combine equation (3) to determine whether equation (1) holds true. If it holds true, it means that the dissipation damping value is appropriate and can make the error energy function converge, that is, the control system is stable. If it does not hold true, the damping value needs to be redesigned and the machine-side inductor current of the LCL energy storage converter in the new cycle needs to be resampled to determine the error vector of the next cycle. Then return to step 2 and execute sequentially.

[0057] Step 4: Design the sliding surface of the LCL type energy storage converter using equation (9) :

[0058] (9)

[0059] In equation (9), It is the sliding surface coefficient of the LCL type energy storage converter; It is the operator symbol for the fractional integral of the LCL type energy storage converter, where α is the order of the fractional integral, and in this embodiment, the value ranges from 0.8 to 1.2. It is the error vector for reconstructing the passive output signal of the LCL type energy storage converter, and is obtained from equation (10):

[0060] (10)

[0061] Using equation (11) to select the reaching law:

[0062] (11)

[0063] Step 5: Obtain the control signal of the LCL type energy storage converter using equation (12). :

[0064] (12)

[0065] In equation (12), It is the robustness coefficient of the LCL type energy storage converter, and its magnitude affects the system's anti-interference capability. is the coefficient of the exponential approach term of the LCL type energy storage converter, and its magnitude determines how fast the control system reaches the sliding surface; sat is the saturation function, defined as in equation (13); It is the capacitor voltage of the LCL type energy storage converter; It is the coupling component caused by the dq transformation.

[0066] (13)

[0067] In equation (13), It is the smoothing term coefficient. Replacing sign(S) in conventional sliding mode control with the sat(S) function can reduce the amplitude of chattering and eliminate chattering when the system interference is low.

[0068] Combining equations (7) and (12) with the simplified calculations based on the parameters of this embodiment, the passive sliding mode controller is derived using equation (14):

[0069] (14)

[0070] Step 6: [Regarding...] After performing the dq inverse transform, a three-phase modulation signal is obtained. This signal is then processed using an SVPWM modulation strategy to output pulse drive signals for the switching devices in the LCL energy storage converter, thereby suppressing resonance in the LCL energy storage converter. The control flowchart in this embodiment is as follows: Figure 2 As shown;

[0071] The main parameters in this embodiment are shown in Table 1:

[0072] Table 1 shows the main parameters in this embodiment:

[0073]

[0074] In this embodiment, an electronic device includes a memory and a processor. The memory stores a program that supports the processor in executing the above-described method, and the processor is configured to execute the program stored in the memory.

[0075] In this embodiment, a computer-readable storage medium stores a computer program, which is executed by a processor to perform the steps of the above method.

[0076] To illustrate the effectiveness of the proposed method in suppressing LCL resonance, simulations were used to compare and analyze the LCL resonance suppression effects of the traditional PI converter and the proposed method. This example uses a T-type three-level energy storage converter. Figure 3 The output current waveform of a traditional PI-controlled converter is severely distorted. Figure 4 The converter output current waveform of the method proposed in this invention is stable and has good waveform quality. Figure 5The THD diagram of the output current proposed in this invention shows a THD of 1.41%. This demonstrates the effectiveness of the proposed method in suppressing LCL resonance.

Claims

1. A method for suppressing resonance in an LCL-type energy storage converter based on passive SMC, characterized in that, Includes the following steps: Step 1: Establish sufficient conditions for the passive control stability of the LCL type energy storage converter using equation (1): (1) In equation (1), It is the error vector of the machine-side inductor current of the LCL type energy storage converter, and is obtained by equation (2); yes The derivative; yes Transpose of; It is a diagonal matrix composed of the machine-side inductance parameters of the LCL type energy storage converter in the dq coordinate system; (2) In equation (2), It is the d-axis component of the inductor current on the machine side of the LCL type energy storage converter; It is the q-axis component of the inductor current on the machine side of the LCL type energy storage converter; It is the d-axis balance point of the inductor current on the machine side of the LCL type energy storage converter; It is the q-axis equilibrium point of the inductor current on the machine side of the LCL type energy storage converter; Step 2: Obtain the passive output signal of the LCL type energy storage converter using equation (3). : (3) In equation (3), It is a symmetrical matrix composed of the machine-side inductors of an LCL-type energy storage converter; It is the parasitic resistance of the machine-side inductor of the LCL type energy storage converter; It is a diagonal matrix composed of dissipation damping of LCL type energy storage converter; Step 3: Determine whether equation (1) is true. If it is true, proceed to step 4; otherwise, change the dissipation damping. The value of is determined, and the machine-side inductor current of the LCL energy storage converter is resampled, thereby adjusting the error vector. After the update is performed, return to step 2 and execute it sequentially; Step 4: Design the sliding surface of the LCL type energy storage converter using equation (4). : (4) In equation (4), These are the two sliding surface coefficients of the LCL-type energy storage converter; It is the operator symbol for the fractional integral of an LCL-type energy storage converter, where α is the order of the fractional integral; It is the error vector for reconstructing the passive output signal of the LCL type energy storage converter, and is obtained from equation (5): (5) Step 5: Obtain the control signal of the LCL type energy storage converter using equation (6). : (6) In equation (6), This is the machine-side inductance value of the LCL type energy storage converter; It is the robustness coefficient of the LCL type energy storage converter; These are the coefficients of the exponential approach term of the LCL-type energy storage converter; sat is the saturation function. It is the capacitor voltage of the LCL type energy storage converter; It is a coupling component caused by the dq transform; Step 6: [Regarding...] After performing the dq inverse transformation, a three-phase modulation signal is obtained. The three-phase modulation signal is then processed using the SVPWM modulation strategy to output the pulse drive signal for the switching devices in the LCL type energy storage converter, thereby suppressing the resonance of the LCL type energy storage converter.

2. An electronic device, comprising a memory and a processor, characterized in that, The memory is used to store a program that supports the processor in executing the LCL-type energy storage converter resonance suppression method of claim 1, and the processor is configured to execute the program stored in the memory.

3. A computer-readable storage medium storing a computer program, characterized in that, The computer program, when run by the processor, executes the steps of the LCL-type energy storage converter resonance suppression method according to claim 1.

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