PI control system for realizing lci driving synchronous motor load disturbance observation compensation

Abstract

The application provides a PI control system for realizing LCI driving synchronous motor load disturbance observation compensation, which is used on an LCI driving synchronous motor and comprises a double closed loop PI control structure for controlling the rotating speed of the LCI driving synchronous motor, and further comprises a Luenberger observer arranged on the double closed loop PI control structure; the Luenberger observer observes the load torque change of the LCI driving synchronous motor and feeds the observed value to the outer loop PI control of the double closed loop PI control structure; the double closed loop PI control structure feeds the outer loop according to the observed value to realize compensation control on the torque variable of the LCI driving synchronous motor, so that the LCI driving synchronous motor can adopt the discontinuous commutation mode at low speed or the load commutation mode at high speed to ensure the stable operation state; wherein the observed value is determined by the state quantity of the LCI driving synchronous motor, including the rotor position and the rotating speed. Through the compensation control, the application can improve the anti-step load disturbance capacity of the LCI driving synchronous motor during the operation process and ensure the operation state to be always in the best state.

Description

Technical Field

[0001] This invention relates to the field of motor control technology, and in particular to a PI control system for realizing load disturbance observation compensation of LCI driven synchronous motor. Background Technology

[0002] A Load Commutated Inverter (LCI) is a high-power synchronous motor drive device. Due to its advantages such as higher efficiency, lower cost, simpler structure, and larger capacity, it is often used in high-power applications such as synchronous condensers, pumped storage, large gas turbines, and air compressors, playing a crucial role in industrial production and the safety of national defense infrastructure. However, due to the semi-controlled nature of thyristors, LCIs also suffer from a series of problems, including large steady-state errors and slow dynamic response.

[0003] Currently, LCI is a rectifier-inverter topology based on semi-controlled thyristors, enabling the corresponding LCI-driven synchronous motor soft-start topology, such as... Figure 1 As shown. An inductor is installed on the DC bus to stabilize the DC current. The difference between the given mechanical speed and the detected mechanical speed is used as the outer loop input, and the difference between the given output DC bus current and the detected DC bus current is used as the inner loop input, thus forming a double closed-loop control structure for the LCI-driven synchronous motor, as shown. Figure 2 As shown. In Figure 2 In the middle loop, the outer loop is a speed loop PI control, and the inner loop is a current loop PI control. Their control effect allows the error between the motor speed and the given speed to approach zero; where w m i is the given motor speed; d α is the given value of the DC bus current; α is the conduction rectification angle in the system rectifier circuit.

[0004] In practical applications of LCI drive synchronous motor control systems, step load changes represent the most demanding load control requirement for the motor, necessitating higher demands on dynamic response capabilities. However, existing dual-closed-loop control structures for LCI drive synchronous motors exhibit poor dynamic response to load disturbances when load and speed changes occur, resulting in weak anti-interference capabilities and an inability to guarantee optimal operating conditions. Therefore, it is necessary to provide a new solution that can improve the ability of LCI drive synchronous motors to resist step load disturbances during operation through compensation control, ensuring that the operating state is always optimal. Summary of the Invention

[0005] The technical problem to be solved by the embodiments of the present invention is to provide a PI control system for realizing load disturbance observation compensation of LCI driven synchronous motor, which can improve the ability of LCI driven synchronous motor to resist step load disturbance during operation through compensation control, and ensure that the operating state is always in the optimal state.

[0006] To address the aforementioned technical problems, embodiments of the present invention provide a PI control system for compensating for load disturbances in an LCI-driven synchronous motor. This system, used on an LCI-driven synchronous motor, includes a dual-closed-loop PI control structure for controlling the speed of the LCI-driven synchronous motor, and further includes a Lumberjack observer disposed on the dual-closed-loop PI control structure.

[0007] The Luneburger observer is used to observe the load torque changes of the LCI-driven synchronous motor and feeds the measured observation values ​​forward to the outer loop PI control of the dual closed-loop PI control structure. This allows for compensation control of the torque variables of the LCI-driven synchronous motor, enabling it to maintain stable operation by using intermittent commutation at low speeds or load commutation at high speeds. The observed values ​​are determined by the state variables of the LCI-driven synchronous motor, including rotor position and speed.

[0008] The Luneburger observer utilizes the product of the feedforward coefficient h and the observed value for feedforward control of the outer loop; wherein,

[0009] The feedforward coefficient h is the pole obtained by solving the characteristic equation of the Loenberger when all real parts are negative; the expression of the characteristic equation is:

[0010] Feedback matrix h = [h1 h2]; T L The externally applied load torque, i.e., the observed load torque; J is the moment of inertia of the LCI-driven synchronous motor; w m The speed of the synchronous motor driven by LCI; T e B1 is the electromagnetic torque of the LCI-driven synchronous motor, and B1 is the viscous friction coefficient of the LCI-driven synchronous motor. It is the first derivative of the rotational speed of the LCI-driven synchronous motor.

[0011] The Luneburger observer is a digital signal processor or microcontroller used to acquire and analyze the speed, rotor position, current and voltage of the LCI-driven synchronous motor.

[0012] Both the intermittent commutation method and the load commutation method control the thyristor's leading commutation angle in the LCI to achieve the switching of the thyristor, thereby ensuring the control and adjustment of the LCI-driven synchronous motor speed.

[0013] Implementing the embodiments of the present invention has the following beneficial effects:

[0014] Compared to the traditional dual-closed-loop PI control structure, this invention uses a Luenberger observer to observe the load disturbances of the LCI driven synchronous motor and adopts a feedforward control strategy to compensate for the system. This aims to ensure that the LCI driven synchronous motor can still operate quickly and stably when the load changes. It not only has better control effects such as smaller speed drop during loading and shorter settling time, but also improves the ability of the LCI driven synchronous motor to resist step load disturbances during operation through compensation control, ensuring that the operating state is always in the optimal state. Attached Figure Description

[0015] 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, obtaining other drawings based on these drawings without creative effort still falls within the scope of the present invention.

[0016] Figure 1 This is a diagram of the soft-start topology of an LCI-driven synchronous motor in the prior art;

[0017] Figure 2 This is a schematic diagram of the traditional dual-closed-loop PI control used in the existing technology for driving synchronous motors with LCI;

[0018] Figure 3 This is a schematic diagram of a PI control system for load disturbance observation compensation of an LCI-driven synchronous motor, provided by an embodiment of the present invention.

[0019] Figure 4 The following is a logic circuit diagram of the Lumberjack observer in a PI control system for realizing load disturbance observation compensation of LCI driven synchronous motor, provided in an embodiment of the present invention;

[0020] Figure 5 This is a graph showing the variation of applied load torque in an application scenario of a PI control system for realizing load disturbance observation compensation of an LCI-driven synchronous motor, as provided in an embodiment of the present invention.

[0021] Figure 6 The graph shows the torque variation observed by the Lumberjack observer in an application scenario of a PI control system for compensating for load disturbances in an LCI-driven synchronous motor, as provided in this embodiment of the invention.

[0022] Figure 7 The waveform diagrams of the Luneburg observer based on different feedforward coefficients in an application scenario of a PI control system for realizing load disturbance observation compensation of LCI driven synchronous motor provided in an embodiment of the present invention. Detailed Implementation

[0023] To make the objectives, technical solutions, and advantages of the present invention clearer, the present invention will be further described in detail below with reference to the accompanying drawings.

[0024] like Figure 3 As shown in the figure, a PI control system for load disturbance observation compensation of an LCI-driven synchronous motor is proposed in an embodiment of the present invention. This system is used on an LCI-driven synchronous motor and includes a dual-closed-loop PI control structure for controlling the speed of the LCI-driven synchronous motor. It also includes a Luneburger observer disposed on the dual-closed-loop PI control structure.

[0025] The Luneburger observer is used to observe the load torque changes of the LCI-driven synchronous motor and feed the measured observations forward to the outer loop PI control of the dual closed-loop PI control structure. The observed values ​​are determined by the state variables of the LCI-driven synchronous motor, including rotor position and speed.

[0026] At this point, the dual-closed-loop PI control structure performs feedforward control on the outer loop based on the observations of the Luneburg observer. This compensates for the torque variable of the LCI-driven synchronous motor, enabling the LCI-driven synchronous motor to operate stably at low speeds using intermittent commutation or at high speeds using load commutation. Both intermittent and load commutation methods control the thyristor's commutation angle in the LCI to control and adjust the motor's speed. It should be noted that the working principle of dual-closed-loop PI control for synchronous motors is a common technique in this field and will not be elaborated further here.

[0027] In this embodiment of the invention, a Luneburger observer is used to observe changes in load torque, thereby employing feedforward control to compensate for system changes, thereby improving system dynamic performance and enhancing system anti-interference capability.

[0028] The Romberg observer is a relatively mature state observer built based on the system's state equations. Its feedback is derived from the error between the observed and actual quantities of the system. By introducing a feedback matrix and appropriately configuring the roots of the system's characteristic equations, the feedback error is reduced, making the observed values ​​closer to reality. Since there are errors between the observer model and the actual motor model, the output of the state equations also contains errors. To further increase the observer's accuracy and make its error approach zero in the shortest possible time, a feedback matrix h is added to feed the error output back to the input. At this point, the observer approximates the actual operating condition of the motor to the greatest extent possible.

[0029] At this point, the Luneburger observer uses the product of the feedforward coefficient h and the observed value to perform feedforward control on the outer loop; whereby the feedforward coefficient h is the pole obtained by solving the characteristic equation preset in the Luneburger observer when all the real parts are negative, so as to ensure the stability of the system.

[0030] The characteristic equation is expressed as follows:

[0031] Feedback matrix h = [h1 h2]; T L The externally applied load torque, i.e., the observed load torque; J is the moment of inertia of the LCI-driven synchronous motor; w m The speed of the synchronous motor driven by LCI; T e B1 is the electromagnetic torque of the LCI-driven synchronous motor, and B1 is the viscous friction coefficient of the LCI-driven synchronous motor. It is the first derivative of the rotational speed of the LCI-driven synchronous motor.

[0032] In this embodiment of the invention, the Luneburg observer is a digital signal processor or microcontroller used to acquire and analyze the speed, rotor position, current, and voltage of an LCI-driven synchronous motor. Specifically, it involves selecting appropriate h1 and h2 values ​​and constructing the Luneburg observer based on the speed, position, current, and voltage (e.g., ...). Figure 4 (As shown). At this time, the observed load change is multiplied by h and applied to the outer speed loop to enhance the robustness and load disturbance resistance of the LCI-driven synchronous motor.

[0033] In one example, the simulation model applies a load reduction of 6000 on the LCI-driven synchronous motor at 4.5s and 5.5s of system operation; a load reduction of 4000 on the LCI-driven synchronous motor at 6.5s and 7.5s of system operation; and a load reduction of 2000 on the LCI-driven synchronous motor at 8.5s and 9.5s of system operation. The torque load transformation output waveforms of the system at these three different operating times are as follows: Figure 5As shown.

[0034] Based on the constructed Luneburger observer, the estimated load change curve largely reflects the changes in motor loading and unloading during operation. Based on the load changes, feedforward compensation is applied to the system to enhance its robustness and anti-interference characteristics. At this point, the changed torque estimated by the constructed Luneburger observer is as follows: Figure 6 As shown.

[0035] Based on the estimated torque change, feedforward is applied to the outer speed loop to suppress the impact of load disturbances on the stable operation of the motor. Within a certain range, increasing the feedforward coefficient improves the control effect on motor speed; however, excessively large feedforward coefficients can cause motor speed instability. Therefore, selecting an appropriate feedforward coefficient for the system is crucial. Different feedforward coefficients also have different control effects on the motor. For example... Figure 7 As shown.

[0036] Implementing the embodiments of the present invention has the following beneficial effects:

[0037] Compared to the traditional dual-closed-loop PI control structure, this invention uses a Luenberger observer to observe the load disturbances of the LCI driven synchronous motor and adopts a feedforward control strategy to compensate for the system. This aims to ensure that the LCI driven synchronous motor can still operate quickly and stably when the load changes. It not only has better control effects such as smaller speed drop during loading and shorter settling time, but also improves the ability of the LCI driven synchronous motor to resist step load disturbances during operation through compensation control, ensuring that the operating state is always in the optimal state.

[0038] The above description is merely a preferred embodiment of the present invention and should not be construed as limiting the scope of the invention. Therefore, any equivalent variations made in accordance with the claims of the present invention are still within the scope of the present invention.

Claims

1. A PI control system for load disturbance observation compensation of an LCI-driven synchronous motor, used on an LCI-driven synchronous motor, comprising a dual closed-loop PI control structure for controlling the speed of the LCI-driven synchronous motor, characterized in that, Also includes: The Luneburg observer is configured on the dual-closed-loop PI control structure; wherein... The Lumberjack observer is used to observe the load torque changes of the LCI-driven synchronous motor and feeds the measured observation values ​​forward to the outer loop PI control of the dual closed-loop PI control structure. This allows for compensation control of the torque variables of the LCI-driven synchronous motor, enabling it to maintain stable operation by using intermittent commutation at low speeds or load commutation at high speeds. The observed values ​​are determined by the state variables of the LCI-driven synchronous motor, including rotor position and speed. The Luenberger observer utilizes feedforward coefficients h The product of the observed values ​​and the external loop is used for feedforward control; where, The feedforward coefficient h The poles are obtained when all real parts of the predefined characteristic equation in the Luneburg observer are negative; the expression of the characteristic equation is: ; Feedback matrix ; ; ; ; ; ; T L The externally applied load torque, i.e., the observed load torque; J The moment of inertia of the LCI-driven synchronous motor; w m The speed of the synchronous motor driven by LCI; , T e For the electromagnetic torque of the LCI-driven synchronous motor, The viscous friction coefficient of the LCI-driven synchronous motor; It is the first derivative of the rotational speed of the LCI-driven synchronous motor.

2. The PI control system for load disturbance observation compensation of LCI-driven synchronous motor as described in claim 1, characterized in that, The Luneburger observer is a digital signal processor or microcontroller used to acquire and analyze the speed, rotor position, current and voltage of the LCI-driven synchronous motor.

3. The PI control system for load disturbance observation compensation of LCI-driven synchronous motor as described in claim 1, characterized in that, Both the intermittent commutation method and the load commutation method achieve the switching of the thyristors by controlling the magnitude of the leading commutation angle of the thyristors in the LCI, thereby ensuring the control and adjustment of the speed of the synchronous motor driven by the LCI.

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