A control method for optimizing dynamic performance of parallel inverters

Abstract

The application relates to the technical field of inverter control, and discloses a control method for optimizing the dynamic performance of parallel operation of inverters, which introduces active power feedforward of parallel operation as a given value through a voltage effective value loop of an original control loop, does not need to change a core control architecture, guarantees loop stability and parallel operation current sharing precision, and is excellent in engineering adaptability. The method updates active power in real time through a sliding window algorithm, shortens an active power transmission period of a CAN bus to 1 ms, relies on a fast feedforward mechanism to make the control loop respond to load mutation in real time, automatically compensates for inverter output voltage drop, significantly shortens voltage effective value recovery time, and greatly improves system transient dynamic performance. Meanwhile, quantitative compensation is realized based on an active power mean value of the parallel operation system and a control coefficient designed accurately, voltage deviation caused by active droop and virtual impedance is effectively offset, output voltage steady-state precision is guaranteed, and the feedforward values of the inverters are consistent, further ensuring parallel operation current sharing performance.

Description

Technical Field

[0001] This invention relates to the field of inverter control technology, and in particular to a control method for optimizing the dynamics of inverter parallel operation. Background Technology

[0002] In power electronic systems, parallel operation of inverters is an important way to increase power supply capacity and improve power supply reliability. Currently, traditional linear or T-shaped inverters generally adopt current sharing strategies such as amplitude droop and virtual impedance during parallel control to ensure balanced current distribution among the inverters.

[0003] However, the aforementioned traditional current sharing strategy has obvious technical defects: under sudden load changes (such as instantaneous full load), the dynamic response performance of the inverter voltage is poor, and the recovery time of the effective voltage value is too long. It is difficult to meet the relevant test standards for inverter parallel operation and the dynamic performance requirements in actual engineering applications, thus limiting the application of inverter parallel operation systems in scenarios with high requirements for dynamic response.

[0004] Therefore, there is an urgent need to develop a new inverter parallel control method that can significantly improve the voltage dynamic response speed and recovery characteristics of the system under transient load changes without compromising the original parallel current sharing performance.

[0005] The above information is provided as background information only to aid in understanding the present invention, and does not constitute an assertion or admission that any of the above content can be used as prior art relative to the present invention. Summary of the Invention

[0006] This invention provides a control method for optimizing the dynamics of inverter parallel operation, in order to solve the problems existing in the prior art.

[0007] To achieve the above objectives, the present invention provides the following technical solution: A control method for optimizing the dynamics of inverter parallel operation, the method comprising: The effective reference setting value of inverter output voltage RMS_REF, the parallel current sharing amplitude adjustment Para_Amp_Shr, the self-active droop P_Droop, and the parallel active power feedforward are used as the reference values ​​for the effective voltage value loop. The voltage RMS value reference Vrms_Ref output by the voltage RMS value loop, the inverter voltage phase, the IdcLoopOut output by the DC component current loop, and the VrmsLoopOut output by the voltage RMS value loop are used as the references for the instantaneous voltage loop. Based on the real-time voltage reference Vinv_Ref, the real-time voltage feedback Vinv_f, the virtual impedance, and the bus voltage feedforward coefficient, a modulation wave duty cycle is generated to control the operation of the switching transistors in the inverter.

[0008] Furthermore, in the control method for optimizing the parallel operation dynamics of the inverter, the calculation formula for the effective voltage reference Vrms_Ref is as follows: Vrms_Ref RMS_REF Para_Amp_Shr P_Droop Parallel active power feedforward.

[0009] Furthermore, in the control method for optimizing the parallel operation dynamics of inverters, the parallel active power feedforward is based on the average active power of all inverters on the parallel bus. and control coefficient constitute.

[0010] Furthermore, in the control method for optimizing the parallel operation dynamics of inverters, the control coefficient The design is based on: ; ; ; Where P_Droop is the self-active droop, K_Droop is the droop coefficient, and P N Z represents the active power of each inverter, K represents the virtual impedance coefficient, IoutReal represents the instantaneous value of the output current, Vbus_Ref represents the rated value of the input BUS voltage, and RMS_REF represents the effective reference setting value of the inverter output voltage.

[0011] Furthermore, in the control method for optimizing the parallel operation dynamics of the inverters, the inverter voltage phase is a sine wave, and the calculation formula is as follows: ; Where θ is the output angle of the phase-locked loop (PLL), Para_Ang_Shr is the parallel current sharing phase adjustment, and Q_Droop is its own reactive power droop.

[0012] Furthermore, in the control method for optimizing the parallel operation dynamics of the inverter, the calculation formula for VrmsLoopOut of the voltage RMS output is: ; Wherein, Regulator() is the PI regulation algorithm configured in the voltage RMS loop, Vrms_Ref is the voltage RMS reference, and Vrms is the voltage RMS feedback.

[0013] Furthermore, in the control method for optimizing the parallel operation dynamics of the inverter, the calculation formula for the real-time voltage reference Vinv_Ref is as follows: .

[0014] Furthermore, in the control method for optimizing the parallel operation dynamics of inverters, the calculation formula for the real-time voltage feedback Vinv_f is as follows: ; in, VdcLoopOut is the output of the DC component loop of the voltage, representing the instantaneous inverter voltage.

[0015] Furthermore, in the control method for optimizing the parallel operation dynamics of the inverter, the DC component loop of the current is used to eliminate the DC component of the output current; The DC component loop is used to eliminate the DC component in the inverter voltage.

[0016] Furthermore, in the control method for optimizing the parallel operation dynamics of inverters, the average active power... The calculation methods include: Each inverter calculates its own active power based on the inverter voltage Vinv and inverter current Iinv of one power frequency cycle, and uses a sliding window algorithm to update the active power in real time. Each inverter, acting as a slave unit, transmits its updated active power data to the master inverter via the CAN bus at a 1ms transmission cycle. The master inverter then calculates the average active power value. .

[0017] Compared with the prior art, the present invention has the following beneficial effects: The present invention provides a control method for optimizing the dynamics of inverter parallel operation. By introducing the active power feedforward of parallel operation into the voltage effective value loop of the original control loop of the inverter as a given value, there is no need to modify the core control architecture of the inverter. While ensuring the stability of the control loop, it does not affect the parallel current sharing accuracy between each inverter. It has excellent engineering adaptability and can be directly applied to the upgrade and transformation of existing inverter parallel operation systems. The active power is updated in real time by using a sliding window algorithm, and the active power transmission cycle of the CAN bus is shortened to 1ms. A fast feedforward mechanism is introduced to enable the control loop to respond to load change conditions in real time. The parallel active power feedforward can automatically compensate for the voltage drop of the inverter output, significantly shorten the recovery time of the effective voltage value, and greatly improve the dynamic performance of the system under transient conditions. Based on the average active power of the parallel system and the precisely designed control coefficient K This enables quantitative compensation of the effective value of the inverter voltage, effectively offsetting the voltage deviation caused by active power droop and virtual impedance, ensuring the steady-state accuracy of the inverter output voltage. At the same time, since the average active power obtained by each inverter is consistent and the feedforward is the same, the parallel current sharing performance is further guaranteed.

[0018] The present invention has other features and advantages, which will be apparent from or will be set forth in detail in the accompanying drawings and the following detailed description, which together serve to explain the particular principles of the invention. Attached Figure Description

[0019] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0020] Figure 1 This is a schematic diagram of the three-level one-word topology provided in an embodiment of the present invention; Figure 2 This is a flowchart illustrating a control method for optimizing the dynamics of inverter parallel operation provided in an embodiment of the present invention; Figure 3 This is a schematic diagram of the inverter control loop diagram provided in an embodiment of the present invention; Figure 4 yes Figure 3 An enlarged view of the left side of the image; Figure 5 yes Figure 3 An enlarged view of the right side of the image; Figure 6 This is a schematic diagram of CAN bus data processing provided in an embodiment of the present invention. Detailed Implementation

[0021] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0022] Example 1

[0023] Please refer to Figure 2This is a flowchart illustrating a control method for optimizing the parallel operation dynamics of inverters according to Embodiment 1 of the present invention. The method employs a three-level, one-line topology, such as... Figure 1 As shown, the input side is connected to the DC voltage rectified by the power grid, and the output side is connected to a three-phase AC load. The control loop diagram of this method is as follows. Figure 3-5 As shown. Taking single-phase output as an example, the method specifically includes the following steps: S101, use the inverter output voltage effective reference setting value RMS_REF, the parallel current sharing amplitude adjustment Para_Amp_Shr, the self-active droop P_Droop, and the parallel active power feedforward as the given value of the voltage effective value loop. It should be noted that the outermost loop is the voltage RMS loop, and its main function is to regulate the RMS value of the inverter voltage. The voltage RMS feedback Vrms is obtained by averaging the sum of the squares of the inverter voltage Vinv over one power frequency cycle (20ms).

[0024] S102, take the voltage effective value reference Vrms_Ref output by the voltage effective value loop, the inverter voltage phase, the IdcLoopOut output by the DC component current loop, and the VrmsLoopOut output by the voltage effective value loop as the given information for the instantaneous voltage loop; It should be noted that the inner loop is the instantaneous voltage loop, and the goal of this instantaneous voltage loop is to make the actual inverter voltage accurately track the reference value.

[0025] S103. Based on the real-time voltage value reference Vinv_Ref, the real-time voltage value feedback Vinv_f, the virtual impedance, and the bus voltage feedforward coefficient, generate the duty cycle of the modulation wave to control the operation of the switching transistors in the inverter.

[0026] It should be noted that the key point of this embodiment of the invention is the introduction of parallel active power feedforward, specifically, the introduction of parallel active power feedforward on the given voltage effective value loop in the original control loop, in order to improve the dynamic response capability of the system.

[0027] In one embodiment of this example, the formula for calculating the effective voltage value reference Vrms_Ref is as follows: Vrms_Ref RMS_REF Para_Amp_Shr P_Droop Parallel active power feedforward.

[0028] In one embodiment of this invention, the parallel active power feedforward is the average active power of all inverters on the parallel bus. and control coefficient constitute.

[0029] The control coefficient The design is based on: ; ; ; Where P_Droop is the self-active droop, K_Droop is the droop coefficient, and P N Z represents the active power of each inverter, K represents the virtual impedance coefficient, IoutReal represents the instantaneous value of the output current (which is basically equal to the inverter current Iinv), Vbus_Ref represents the rated value of the input BUS voltage, and RMS_REF represents the effective reference setting value of the inverter output voltage.

[0030] It should be noted that Vbus_Ref, K_Droop, K, and RMS_REF are all known fixed parameters in the original control strategy, while , Both IoutReal and IoutReal are measurable / calculable quantities related to system power, therefore the control coefficients can be determined using the above equation. Perform accurate tuning.

[0031] In one embodiment of this invention, the inverter voltage phase is sinusoidal, and the calculation formula is as follows: ; Where θ is the output angle of the phase-locked loop (PLL), Para_Ang_Shr is the parallel current sharing phase adjustment, and Q_Droop is its own reactive power droop.

[0032] In one embodiment of this example, the formula for calculating VrmsLoopOut, the output of the voltage RMS loop, is as follows: ; Wherein, Regulator() is the PI regulation algorithm configured in the voltage RMS loop, which is a classic algorithm in power electronic control to achieve zero steady-state error voltage regulation and improve steady-state accuracy; Vrms_Ref is the voltage RMS reference, and Vrms is the voltage RMS feedback.

[0033] In one embodiment of this example, the formula for calculating the real-time voltage reference Vinv_Ref is as follows: .

[0034] In one embodiment of this invention, the formula for calculating the real-time voltage feedback Vinv_f is as follows: ; in, VdcLoopOut is the output of the DC component loop of the voltage, representing the instantaneous inverter voltage.

[0035] It should be noted that the DC component loop of the current is used to eliminate the DC component of the output current; The DC component loop is used to eliminate the DC component in the inverter voltage.

[0036] In one embodiment of this example, the average active power The calculation methods include: Each inverter calculates its own active power based on the inverter voltage Vinv and inverter current Iinv of one power frequency cycle (20ms), and uses a sliding window algorithm to update the active power in real time. Each inverter, acting as a slave unit, transmits its updated active power data to the master inverter via the CAN bus at a 1ms transmission cycle. The master inverter then calculates the average active power value. .

[0037] It should be noted that, as Figure 6 As shown, to improve dynamic response, this embodiment of the invention adds CAN mailbox communication, shortening the transmission cycle from the conventional 20ms to 1ms. Specifically, in the DSP, one CAN mailbox is used to poll and send active power data with a 1ms transmission cycle, while two CAN mailboxes are used for receiving, ensuring high-speed transmission without affecting the normal communication of the original 20ms cycle data. When the load changes abruptly (such as a three-phase load being instantaneously connected), the active power can be quickly detected and calculated, and the parallel active power feedforward quickly compensates for the effective value of the inverter voltage.

[0038] Although this invention frequently uses terms such as voltage RMS loop and parallel active power feedforward, the possibility of using other terms is not excluded. These terms are used merely for the convenience of describing and explaining the essence of this invention; interpreting them as any additional limitation would contradict the spirit of this invention.

[0039] The present invention provides a control method for optimizing the dynamics of inverter parallel operation. By introducing the active power feedforward of parallel operation into the voltage effective value loop of the original control loop of the inverter as a given value, there is no need to modify the core control architecture of the inverter. While ensuring the stability of the control loop, it does not affect the parallel current sharing accuracy between the inverters. It has excellent engineering adaptability and can be directly applied to the upgrade and transformation of existing inverter parallel operation systems. The active power is updated in real time by using a sliding window algorithm, and the active power transmission cycle of the CAN bus is shortened to 1ms. A fast feedforward mechanism is introduced to enable the control loop to respond to load change conditions in real time. The parallel active power feedforward can automatically compensate for the voltage drop of the inverter output, significantly shorten the recovery time of the effective voltage value, and greatly improve the dynamic performance of the system under transient conditions. Based on the average active power of the parallel system and the precisely designed control coefficient K This enables quantitative compensation of the effective value of the inverter voltage, effectively offsetting the voltage deviation caused by active power droop and virtual impedance, ensuring the steady-state accuracy of the inverter output voltage. At the same time, since the average active power obtained by each inverter is consistent and the feedforward is the same, the parallel current sharing performance is further guaranteed.

[0040] Finally, it should be noted that although the above embodiments have been described in the description and drawings of this invention, this should not limit the scope of patent protection of this invention. Any technical solutions that are based on the essential concept of this invention, utilize the content described in the description and drawings of this invention to make equivalent structural or procedural substitutions or modifications, as well as the direct or indirect application of the technical solutions of the above embodiments to other related technical fields, are all included within the scope of patent protection of this invention.

Claims

1. A control method for optimizing the dynamic performance of inverters operating in parallel, characterized in that, The method includes: The effective reference setting value of inverter output voltage RMS_REF, the parallel current sharing amplitude adjustment Para_Amp_Shr, the self-active droop P_Droop, and the parallel active power feedforward are used as the reference values ​​for the effective voltage value loop. The voltage RMS value reference Vrms_Ref output by the voltage RMS value loop, the inverter voltage phase, the IdcLoopOut output by the DC component current loop, and the VrmsLoopOut output by the voltage RMS value loop are used as the references for the instantaneous voltage loop. Based on the real-time voltage reference Vinv_Ref, the real-time voltage feedback Vinv_f, the virtual impedance, and the bus voltage feedforward coefficient, a modulation wave duty cycle is generated to control the operation of the switching transistors in the inverter.

2. The control method for optimizing the dynamic performance of parallel inverters according to claim 1, characterized in that, The formula for calculating the effective voltage reference Vrms_Ref is as follows: Vrms_Ref RMS_REF Para_Amp_Shr P_Droop Parallel active power feedforward.

3. The control method for optimizing the dynamic performance of parallel inverters according to claim 1, characterized in that, The parallel active power feedforward is the average active power of all inverters on the parallel bus. and control coefficient constitute.

4. The control method for optimizing the dynamic performance of parallel inverters according to claim 3, characterized in that, The control coefficient The design is based on: ； ； ； Where P_Droop is the self-active droop, K_Droop is the droop coefficient, and P N Z represents the active power of each inverter, K represents the virtual impedance coefficient, IoutReal represents the instantaneous value of the output current, Vbus_Ref represents the rated value of the input BUS voltage, and RMS_REF represents the effective reference setting value of the inverter output voltage.

5. The control method for optimizing the dynamic performance of parallel inverters according to claim 1, characterized in that, The inverter voltage phase is sinusoidal, and the calculation formula is as follows: ； Where θ is the output angle of the phase-locked loop (PLL), Para_Ang_Shr is the parallel current sharing phase adjustment, and Q_Droop is its own reactive power droop.

6. The control method for optimizing the dynamic performance of parallel inverters according to claim 1, characterized in that, The formula for calculating VrmsLoopOut, the output of the voltage RMS loop, is as follows: ； Wherein, Regulator() is the PI regulation algorithm configured in the voltage RMS loop, Vrms_Ref is the voltage RMS reference, and Vrms is the voltage RMS feedback.

7. The control method for optimizing the dynamic performance of parallel inverters according to claim 5, characterized in that, The formula for calculating the real-time voltage reference Vinv_Ref is as follows: 。 8. The control method for optimizing the dynamic performance of parallel inverters according to claim 1, characterized in that, The formula for calculating the real-time voltage feedback Vinv_f is as follows: ； in, VdcLoopOut is the output of the DC component loop of the voltage, representing the instantaneous inverter voltage.

9. The control method for optimizing the dynamic performance of parallel inverters according to claim 8, characterized in that, The DC component loop is used to eliminate the DC component of the output current. The DC component loop is used to eliminate the DC component in the inverter voltage.

10. The control method for optimizing the dynamic performance of parallel inverters according to claim 3, characterized in that, The average active power The calculation methods include: Each inverter calculates its own active power based on the inverter voltage Vinv and inverter current Iinv of one power frequency cycle, and uses a sliding window algorithm to update the active power in real time. Each inverter, acting as a slave unit, transmits its updated active power data to the master inverter via the CAN bus at a 1ms transmission cycle. The master inverter then calculates the average active power value. .

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