Direct-current bus voltage robustness control method based on super-local model

Abstract

The invention provides a DC bus voltage robustness control method based on a hyper-local model, and the method employs the hyper-local model to replace an original nonlinear time-varying model for a DC bus voltage control system, thereby simplifying a system model. The total unknown disturbance quantity of the system is observed by using the extended state observer, and the observed total disturbance quantity is used as a feedforward quantity to control the DC bus voltage, so that the influence of the change of the operating point of the system on the control performance of the DC bus voltage is reduced. Finally, a sliding mode control method is designed based on the total disturbance quantity observed by the hyper-local model and the extended state observer, and rapid control of the DC bus voltage can be realized. Compared with the prior art, the robustness and anti-interference performance of the direct-current bus voltage control system of the permanent magnet synchronous generator are remarkably improved, and the method has the advantages of being simple in design and easy to apply and popularize.

Description

Technical Field

[0001] The invention belongs to the technical field of DC bus voltage control of permanent magnet synchronous generators, and in particular relates to a DC bus voltage robustness control method based on a super-local model. Background Art

[0002] At present, the traditional PI control is still widely used in the field to achieve the temperature control of the DC bus voltage of the permanent magnet synchronous generator. However, since the DC bus voltage control system of the permanent magnet synchronous generator is a nonlinear and time-varying system, the performance of PI control will be affected by the change of the system operating point (PMSG speed, load power and DC bus voltage). When the system operating point changes, the control effect of PI control will decrease, and even seriously affect the stability. In order to improve the control effect of the DC bus voltage when the system operating point changes, nonlinear control methods are introduced in some existing technologies, such as active disturbance rejection control (ADRC), two-degree-of-freedom (TDOF) control and sliding mode control (SMC). Among these methods, ADRC is a global linearization method, but its fixed parameter characteristics make it impossible to meet the control requirements during load switching; TDOF control can independently adjust two sets of control parameters to optimize the dynamic performance of the DC bus voltage and enhance the ability to resist load disturbances, but the existing TDOF control generally ignores the impact of motor speed changes on the DC bus voltage control performance; SMC is widely used in PMSG systems due to its fast response capability and strong robustness, but the inherent jitter problem greatly limits its application. Therefore, there is an urgent need for a permanent magnet synchronous generator DC bus voltage control method that is robust to the system operating point. Summary of the invention

[0003] In view of this, in order to solve the technical problems existing in the art, the present invention provides a DC bus voltage robustness control method based on a super local model, which specifically includes the following steps:

[0004] Step 1: Real-time acquisition of phase current, speed and DC bus voltage data of the permanent magnet synchronous generator DC bus voltage control system during operation;

[0005] Step 2: Considering the power and loss of the permanent magnet synchronous generator, a mathematical model of the DC bus voltage control system of the permanent magnet synchronous generator is established, and the power equation of the system is derived from the mathematical model; the system is regarded as a single-input single-output system, and a first-order hyperlocal model of the system is established based on the power equation;

[0006] Step 3: Design an extended state observer for the established hyperlocal model, and observe the total disturbance of the hyperlocal model by inputting the data collected in step 1 into the extended state observer;

[0007] Step 4: Design a DC bus voltage sliding mode controller based on the hyperlocal model, including designing a corresponding sliding mode surface and a sliding mode approach rate, so that the output value of the voltage outer loop, i.e., the q-axis command current, can be obtained based on the total disturbance provided by the extended state observer;

[0008] Step 5: Input the q-axis command current obtained in step 4 into the current inner loop to obtain the dq-axis reference voltage of the permanent magnet synchronous generator, and input it into the space vector pulse width modulation (SVPWM) module to obtain the switching signal of the inverter, thereby driving the permanent magnet synchronous generator to operate.

[0009] Furthermore, the mathematical model of the DC bus voltage control system of the permanent magnet synchronous generator established in step 2 specifically includes:

[0010] P m =P cooper_loss +P iron_loss +P converter_loss +P C +P L

[0011] P m =-ω m T e

[0012]

[0013] P L =v dc i L

[0014] Where P m is the output power of the prime mover; P copper_loss and P iron_loss Respectively represent the copper loss and iron loss of the permanent magnet synchronous generator; P converter_loss Represents the power loss of the PWM rectifier; P C Represents the power absorbed by the DC bus capacitor; P L Represents load power; i d 、i q are dq axis current respectively; C represents the DC bus capacitance, R s is the stator resistance; i L Represents the load current; ω m is the mechanical angular velocity of the rotor, T e Represents the electromagnetic torque of the permanent magnet synchronous generator, and its expression is:

[0015] T e =1.5pψ f i q

[0016] In the formula, Ψ fis the permanent magnet flux of the motor rotor; p is the number of motor pole pairs;

[0017] The following power equation is derived from the above mathematical model:

[0018]

[0019] The basic equation of the first-order hyperlocal model is:

[0020]

[0021] In the formula, y represents the state variable, the superscript · represents the first-order derivative of the corresponding parameter, u is the control variable, α is the coefficient selected according to the control system, and F represents the total unknown disturbance;

[0022] Therefore, the super-local model of the DC bus voltage control system of the permanent magnet synchronous generator can be expressed as:

[0023]

[0024] In the formula, Ψ fn and C n are the nominal values ​​of the motor rotor permanent magnet flux and the DC bus capacitance respectively.

[0025] Furthermore, the specific form of the extended state observer designed in step 3 is as follows:

[0026]

[0027] in, Yes dc The observed value of is the observed value of the total unknown disturbance F;

[0028] The extended state observer is rewritten in matrix form:

[0029]

[0030] Among them, A, B and C are coefficient matrices respectively, and L is the feedback gain matrix, and their values ​​are as follows:

[0031]

[0032] The feature matrix can be obtained as:

[0033]

[0034] By taking the determinant of the characteristic matrix, we get the following characteristic equation:

[0035] |sI-(A-LC)|=s 2 +β 1 s+β2 =0

[0036] By setting β 1 =2ω 0 , To simplify the extended state observer gain, we get the following characteristic equation:

[0037]

[0038] Among them, ω 0 is the bandwidth of the expanded state observer, which is used to adjust the convergence speed of the observer.

[0039] Furthermore, the specific form of the sliding surface designed in step 4 is as follows:

[0040]

[0041] The sliding mode approach rate is designed as:

[0042]

[0043] In the formula, ε and k are the approach rate coefficients respectively;

[0044] Based on the sliding mode surface and sliding mode approach rate, the following differential expression of DC bus voltage is derived:

[0045]

[0046] According to the hyperlocal model and the differential expression, the q-axis command current is obtained as follows:

[0047]

[0048] The DC bus voltage robustness control method based on the hyperlocal model provided by the present invention adopts a hyperlocal model to replace the original nonlinear time-varying model for the DC bus voltage control system, thereby simplifying the system model; an extended state observer is used to observe the total unknown disturbance of the system, and the observed total disturbance is used as a feedforward to control the DC bus voltage, thereby reducing the impact of the system operating point change on the DC bus voltage control performance. Finally, based on the hyperlocal model and the total disturbance observed by the extended state observer, a sliding mode control method is designed to achieve rapid control of the DC bus voltage. Compared with other existing technologies, the present invention significantly improves the robustness and anti-disturbance performance of the permanent magnet synchronous generator DC bus voltage control system, and has the advantages of simple design and easy promotion and application. BRIEF DESCRIPTION OF THE DRAWINGS

[0049] Figure 1 A flowchart of the method provided by the present invention;

[0050] Figure 2 The control of the DC bus voltage and the observed effect of the system disturbance in the example of the present invention are shown. DETAILED DESCRIPTION

[0051] The technical solution of the present invention will be described clearly and completely below in conjunction with the accompanying drawings. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0052] The DC bus voltage robustness control method based on the ultra-local model provided by the present invention is as follows: Figure 1 As shown, the specific steps include:

[0053] Step 1: Real-time acquisition of phase current, speed and DC bus voltage data of the permanent magnet synchronous generator DC bus voltage control system during operation;

[0054] Step 2: Considering the power and loss of the permanent magnet synchronous generator, a mathematical model of the DC bus voltage control system of the permanent magnet synchronous generator is established, and the power equation of the system is derived from the mathematical model; the system is regarded as a single-input single-output system, and a first-order hyperlocal model of the system is established based on the power equation;

[0055] Step 3: Design an extended state observer for the established hyperlocal model, and observe the total disturbance of the hyperlocal model by inputting the data collected in step 1 into the extended state observer;

[0056] Step 4: Design a DC bus voltage sliding mode controller based on the hyperlocal model, including designing a corresponding sliding mode surface and a sliding mode approach rate, so that the output value of the voltage outer loop, i.e., the q-axis command current, can be obtained based on the total disturbance provided by the extended state observer;

[0057] Step 5: Input the q-axis command current obtained in step 4 into the current inner loop to obtain the dq-axis reference voltage of the permanent magnet synchronous generator, and input it into the space vector pulse width modulation (SVPWM) module to obtain the switching signal of the inverter, thereby driving the permanent magnet synchronous generator to operate.

[0058] In a preferred embodiment of the present invention, the mathematical model of the DC bus voltage control system of the permanent magnet synchronous generator established in step 2 specifically includes:

[0059] P m =P cooper_loss +P iron_loss +P converter_loss +P C +P L

[0060] P m =-ω m T e

[0061]

[0062] P L =v dc i L

[0063] Where P m is the output power of the prime mover; P copper_loss and P iron_loss Respectively represent the copper loss and iron loss of the permanent magnet synchronous generator; P converter_loss Represents the power loss of the PWM rectifier; P C Represents the power absorbed by the DC bus capacitor; P L Represents load power; i d 、i q are dq axis current respectively; C represents the DC bus capacitance, R s is the stator resistance; i L Represents the load current; ω m is the mechanical angular velocity of the rotor, T e Represents the electromagnetic torque of the permanent magnet synchronous generator, and its expression is:

[0064] T e =1.5pψ f i q

[0065] In the formula, Ψ f is the permanent magnet flux of the motor rotor; p is the number of motor pole pairs;

[0066] The following power equation is derived from the above mathematical model:

[0067]

[0068] The basic equation of the first-order hyperlocal model is:

[0069]

[0070] In the formula, y represents the state variable, the superscript · represents the first-order derivative of the corresponding parameter, u is the control variable, α is the coefficient selected according to the control system, and F represents the total unknown disturbance;

[0071] Therefore, the super-local model of the DC bus voltage control system of the permanent magnet synchronous generator can be expressed as:

[0072]

[0073]

[0074] In the formula, Ψ fn and C n are the nominal values ​​of the motor rotor permanent magnet flux and the DC bus capacitance respectively.

[0075] In a preferred embodiment of the present invention, the specific form of designing the extended state observer in step 3 is as follows:

[0076]

[0077] in, Yes dc The observed value of is the observed value of the total unknown disturbance F;

[0078] The extended state observer is rewritten in matrix form:

[0079]

[0080] Among them, A, B and C are coefficient matrices respectively, and L is the feedback gain matrix, and their values ​​are as follows:

[0081]

[0082] The feature matrix can be obtained as:

[0083]

[0084] By taking the determinant of the characteristic matrix, we get the following characteristic equation:

[0085] |sI-(A-LC)|=s 2 +β 1 s+β 2 =0

[0086] By setting β 1 =2ω 0 , To simplify the extended state observer gain, we get the following characteristic equation:

[0087]

[0088] Among them, ω 0 is the bandwidth of the expanded state observer, which is used to adjust the convergence speed of the observer.

[0089] In a preferred embodiment of the present invention, the specific form of designing the sliding surface in step 4 is as follows:

[0090]

[0091] The sliding mode approach rate is designed as:

[0092]

[0093] In the formula, ε and k are the approach rate coefficients respectively;

[0094] Based on the sliding mode surface and sliding mode approach rate, the following differential expression of DC bus voltage is derived:

[0095]

[0096] According to the hyperlocal model and the differential expression, the q-axis command current is obtained as follows:

[0097]

[0098] The method provided by the present invention can significantly improve the robustness and anti-interference performance of the DC bus voltage control method to the system operating point. In a preferred embodiment of the present invention, the tracking waveform of the DC bus voltage and the total disturbance observed by the ESO are given when the permanent magnet synchronous generator operates at 1000r / min, the DC bus voltage command value is 160V, and the load power steps from 0.5 times the rated load power to the rated load power. Figure 2 As shown in the figure, it can be seen that: 1. In the steady-state condition before and after the load power step, the DC bus voltage accurately tracks the voltage command value; 2. The load power step only causes a 3% voltage drop and quickly recovers to the command value; 3. The total disturbance observed by the ESO can quickly follow the change of the load power, and in the steady-state condition, the total disturbance remains stable. Figure 2 The results show that when the system operating point changes, the ESO can quickly observe the change of load power and perform feedforward compensation on the DC bus voltage control method according to the method provided by the present invention, thereby achieving robustness to changes in the system operating point and always achieving excellent DC bus voltage control performance.

[0099] It should be understood that the size of the serial numbers of the steps in the embodiment of the present invention does not mean the order of execution. The execution order of each process should be determined by its function and internal logic, and should not constitute any limitation on the implementation process of the embodiment of the present invention.

[0100] Although embodiments of the present invention have been shown and described, it will be appreciated by those skilled in the art that various changes, modifications, substitutions and variations may be made to the embodiments without departing from the principles and spirit of the present invention, and that the scope of the present invention is defined by the appended claims and their equivalents.

Claims

1. A DC bus voltage robustness control method based on a super local model, characterized in that: The specific steps include: Step 1: Real-time acquisition of phase current, speed and DC bus voltage data of the permanent magnet synchronous generator DC bus voltage control system during operation; Step 2: Considering the power and loss of the permanent magnet synchronous generator, a mathematical model of the DC bus voltage control system of the permanent magnet synchronous generator is established, and the power equation of the system is derived from the mathematical model; the system is regarded as a single-input single-output system, and a first-order hyperlocal model of the system is established based on the power equation; Step 3: Design an extended state observer for the established hyperlocal model, and observe the total disturbance of the hyperlocal model by inputting the data collected in step 1 into the extended state observer; Step 4: Design a DC bus voltage sliding mode controller based on the hyperlocal model, including designing a corresponding sliding mode surface and a sliding mode approach rate, so that the output value of the voltage outer loop, i.e., the q-axis command current, can be obtained based on the total disturbance provided by the extended state observer; Step 5: Input the q-axis command current obtained in step 4 into the current inner loop to obtain the dq-axis reference voltage of the permanent magnet synchronous generator, and input it into the space vector pulse width modulation module to obtain the switching signal of the inverter, thereby driving the permanent magnet synchronous generator to operate.

2. The method according to claim 1, characterized in that: The mathematical model of the DC bus voltage control system of the permanent magnet synchronous generator established in step 2 specifically includes: P m =P cooper_loss +P iron_loss +P converter_loss +P C +P L P m =-ω m T e P L =v dc i L Where P m is the output power of the prime mover; P copper_loss and P iron_loss Respectively represent the copper loss and iron loss of the permanent magnet synchronous generator; P converter_loss Represents the power loss of the PWM rectifier; P C Represents the power absorbed by the DC bus capacitor; P L Represents load power; i d 、i q are dq axis current respectively; C represents the DC bus capacitance, R s is the stator resistance; i L Represents the load current; ω m is the mechanical angular velocity of the rotor, T e Represents the electromagnetic torque of the permanent magnet synchronous generator, and its expression is: T e =1.5pψ f i q In the formula, Ψ f is the permanent magnet flux of the motor rotor; p is the number of motor pole pairs; The following power equation is derived from the above mathematical model: The basic equation of the first-order hyperlocal model is: In the formula, y represents the state variable, the superscript · represents the first-order derivative of the corresponding parameter, u is the control variable, α is the coefficient selected according to the control system, and F represents the total unknown disturbance; Therefore, the super-local model of the DC bus voltage control system of the permanent magnet synchronous generator can be expressed as: In the formula, Ψ fn and C n are the nominal values ​​of the motor rotor permanent magnet flux and the DC bus capacitance respectively.

3. The method according to claim 1, characterized in that: The specific form of designing the extended state observer in step 3 is as follows: in, Yes dc The observed value of is the observed value of the total unknown disturbance F; The extended state observer is rewritten in matrix form: Among them, A, B and C are coefficient matrices respectively, and L is the feedback gain matrix, and their values ​​are as follows: The feature matrix can be obtained as: By taking the determinant of the characteristic matrix, we get the following characteristic equation: |sI-(A-LC)|=s 2 +β1s+β2=0 By setting β1 = 2ω0, To simplify the extended state observer gain, we get the following characteristic equation: Among them, ω0 is the bandwidth of the extended state observer, which is used to adjust the convergence speed of the observer.

4. The method according to claim 1, characterized in that: The specific form of the sliding surface designed in step 4 is as follows: The sliding mode approach rate is designed as: In the formula, ε and k are the approach rate coefficients respectively; Based on the sliding mode surface and sliding mode approach rate, the following differential expression of DC bus voltage is derived: According to the hyperlocal model and the differential expression, the q-axis command current is obtained as follows:

Images