Smoothing capacitor for a power converter

Abstract

The application relates to a permanent magnet synchronous generator rotor position and rotating speed estimation method based on SMO, which comprises the following steps: when a permanent magnet synchronous generator starts from zero speed, a sliding mode state observer is not started; the rotor position and rotating speed of the permanent magnet synchronous generator are extracted according to an established PMSG extended back electromotive force model; the rotor position and rotating speed meeting a set stable condition are taken as initial states of a previous beat before the sliding mode state observer is started, and the sliding mode state observer is started; the back electromotive force is estimated by using the sliding mode state observer; a Lyapunov function is constructed according to a current error, so that a sliding mode gain coefficient meets a stable condition of the sliding mode state observer; and the rotor rotating speed and position information are extracted from the estimated back electromotive force. The application effectively shortens a steady state regulation time, avoids possible overshoot, oscillation and other phenomena in a process of transition from an initial state to a stable state, and improves the stability of a permanent magnet synchronous generator vector control system.

Description

Technical Field

[0001] This invention relates to the field of sensorless permanent magnet synchronous generator (PMSG) technology, and more particularly to a method for estimating the rotor position and speed of a PMSG based on a SMO. Background Technology

[0002] Permanent magnet synchronous generators (PMSGs) possess advantages such as simple structure, high torque-to-inertia ratio, high power density, fast dynamic response, strong overload capacity, and a wide constant power range. Therefore, PMSGs are widely used in aerospace, electric vehicles, and industrial control. PMSG vector control systems require rotor position and speed information, which is typically obtained from position sensors. This increases system cost and reduces system reliability; therefore, sensorless PMSG technology has gained significant attention.

[0003] Common methods for estimating rotational speed and position include the Kalman filter method, model reference adaptive method, flux linkage estimation method, and sliding mode observer method. The sliding mode observer (SMO) is characterized by its simple algorithm, ease of engineering implementation, and strong system robustness. It estimates the back electromotive force (EMF) of the permanent magnet synchronous generator (PMSG) using SMO, thereby extracting the rotor's position and rotational speed information from the EMF. The initial state of the sliding mode observer is typically set to zero vector by default. When SMO is enabled, the transition from the initial state to the steady state requires a certain amount of time. This process may involve overshoot, oscillations, and other phenomena, leading to a decrease in the stability of the permanent magnet synchronous generator vector control system. Summary of the Invention

[0004] Based on the above analysis, the present invention aims to provide a method for estimating the rotor position and speed of a permanent magnet synchronous generator based on SMO, which solves problems such as overshoot and oscillation during the transition from zero initial state to steady state.

[0005] The technical solution provided by this invention is:

[0006] This invention discloses a method for estimating the rotor position and speed of a permanent magnet synchronous generator based on SMO, comprising:

[0007] When a permanent magnet synchronous generator starts from zero speed, the sliding mode state observer is not activated.

[0008] The rotor position and speed of the permanent magnet synchronous generator were extracted based on the established PMSG extended back EMF model.

[0009] The rotor position and speed that meet the stability conditions are used as the initial state of the sliding mode state observer in the previous step before it is activated.

[0010] The back electromotive force is estimated using a sliding mode state observer;

[0011] Based on the current error, a Lyapunov function is constructed to make the sliding mode gain coefficient satisfy the stability condition of the sliding mode state observer.

[0012] Rotor speed and position information are extracted from the estimated back electromotive force.

[0013] Furthermore, the step of extracting the rotor position and speed of the permanent magnet synchronous generator based on the established PMSG extended back EMF model includes:

[0014] Establish a mathematical model for the DQ axis of the PMSG;

[0015] An extended back electromotive force model of IPSMG is established by inverse Park transformation;

[0016] The α and β axis back electromotive forces E are obtained from the IPSMG extended back electromotive force model. α and E β ;

[0017] Based on the back electromotive force E of the α and β axes α and E β Extract rotor speed and position information.

[0018] Furthermore, the mathematical model for the DQ axis of PMSG is as follows:

[0019]

[0020] In the formula, u d u q For d-axis and q-axis voltages; i d i q L represents the d-axis and q-axis currents. d L q For d-axis and q-axis inductance; R s ω is the stator winding resistance; e ψ is the rotor's electric angular velocity. f is the main flux linkage of the permanent magnet; p is the differential operator.

[0021] Furthermore, the extended back electromotive force model of IPSMG can be established through the inverse Park transformation as follows:

[0022]

[0023] In the formula, u α u β For α and β axis voltages; i α i β E represents the α-axis and β-axis currents. α and E βThe back electromotive force (EMF) is defined as E along the α and β axes. α and E β The expression containing rotor position information is as follows:

[0024]

[0025] In the formula, θ e This represents the rotor's electrical angular displacement.

[0026] Furthermore, according to the IPMSG extended back EMF model, at this point, the motor current is 0, and the α-β axis motor voltage is equal to the α-β axis back EMF, as expressed below:

[0027]

[0028] In the formula, u αi u βi E represents the initial values ​​of the α and β axis voltages. αi and E βi ω represents the initial values ​​of the back electromotive force along the α and β axes; ei θ is the initial value of the rotor's electric angular velocity; ei This is the initial value of the rotor's electric angular displacement.

[0029] Furthermore, the equation for the sliding mode state observer is:

[0030]

[0031] In the formula, Estimate the differential values ​​of the current along the α and β axes; Estimate the current for the α and β axes; To estimate the electric angular velocity; z α z β This is the control function.

[0032] Furthermore, the control function z α z β The expression is:

[0033]

[0034] In the formula, sign(·) is the sign function, k is the sliding mode gain coefficient, and e α e β For the α and β axis current errors.

[0035] Furthermore, we assume that the estimated electric angular velocity can converge to the actual electric angular velocity, i.e. The state equation for the current error is expressed as follows:

[0036]

[0037] In the formula, e represents the differential values ​​of the α and β axis current errors; α e β For α and β axis current errors;

[0038] Construct the Lyapunov function as follows:

[0039]

[0040] The differential form of the Lyapunov function is as follows:

[0041]

[0042] When k > max(|E α |,|E β When |), then If the sliding mode state observer is stable, then the sliding mode state observer is stable.

[0043] Furthermore, the back electromotive force observed by the sliding mode state observer is a high-frequency discontinuous signal, in z α z β After adding a low-pass filter to the control function, the estimated back electromotive force along the α and β axes is obtained. and

[0044]

[0045] In the formula, ω c is the cutoff frequency of the low-pass filter, and s is the Laplace transform operator.

[0046] Furthermore, the rotor speed for the stable condition is set to 600-1000 rpm.

[0047] This invention can achieve at least one of the following beneficial effects:

[0048] This invention estimates the back electromotive force (EMF) of the permanent magnet synchronous generator (PMSG) using a sliding mode observer (SMO), thereby extracting the rotor's position and speed information from the back EMF. Leveraging the detectable initial value of the back EMF before the start of vector control and the sliding mode observer algorithm, the rotor position and speed information obtained from the back EMF are used as the initial state for the step before the algorithm starts. This effectively shortens the steady-state adjustment time and avoids overshoot and oscillations that may occur during the transition from the initial state to the steady state, thus improving the stability of the permanent magnet synchronous generator vector control system. Attached Figure Description

[0049] The accompanying drawings are for illustrative purposes only and are not intended to limit the invention. Throughout the drawings, the same reference numerals denote the same parts.

[0050] Figure 1This is a block diagram of the sensorless vector control of a permanent magnet synchronous generator based on SMO in an embodiment of the present invention;

[0051] Figure 2 This is a flowchart of the method for estimating the rotor position and speed of a permanent magnet synchronous generator based on SMO in an embodiment of the present invention;

[0052] Figure 3 This is a flowchart illustrating the method for extracting rotor position and speed based on the established PMSG extended back EMF model in an embodiment of the present invention. Detailed Implementation

[0053] Preferred embodiments of the present invention will now be described in detail with reference to the accompanying drawings, which form part of this application and, together with the embodiments of the present invention, serve to illustrate the principles of the present invention.

[0054] The sensorless vector control block diagram of the SMO-based permanent magnet synchronous generator in this embodiment is as follows: Figure 1 As shown.

[0055] The bus voltage loop output value is used as the current setpoint for the q-axis current loop. d-axis current loop current setpoint The current error is obtained by subtracting the dq-axis current loop setpoint from the dq-axis current sampling, and then using a PI controller to obtain the current loop output value u. d and u q Then, the control quantity u is obtained through the inverse Park transform and the inverse Clark transform. a u b and u c The input signals to the SMO module are the initial values ​​of the α-β axis voltage, the α-β axis voltage value, and the α-β axis current value of the PMSG. The α-β axis voltage and current values ​​are used to estimate the position and rotational speed signals, while the initial value of the α-β axis voltage is used to determine the initial state of the SMO. The output signals of the SMO module are the position estimation signal and the rotational speed estimation signal.

[0056] based on Figure 1 The block diagram of sensorless vector control for a permanent magnet synchronous generator based on SMO is shown in this embodiment. This embodiment discloses a method for estimating the rotor position and speed of a permanent magnet synchronous generator based on SMO, such as... Figure 2 As shown, it includes the following steps:

[0057] Step S201: When the permanent magnet synchronous generator starts from zero speed, the sliding mode state observer is not activated;

[0058] Step S202: Extract the rotor position and speed of the permanent magnet synchronous generator based on the established PMSG extended back EMF model;

[0059] Step S203: Take the rotor position and speed that meet the set stability conditions as the initial state of the sliding mode state observer before it is turned on, and start the sliding mode state observer.

[0060] Step S204: Estimate the back electromotive force using a sliding mode state observer;

[0061] Step S205: Construct a Lyapunov function based on the current error so that the sliding mode gain coefficient satisfies the stability condition of the sliding mode state observer;

[0062] Step S206: Extract rotor speed and position information from the estimated back electromotive force.

[0063] Specifically, the method for extracting the rotor position and speed based on the established PMSG extended back EMF model in step S202 is as follows: Figure 3 As shown, it includes the following steps:

[0064] Step S301: Establish the mathematical model of the DQ axis of PMSG;

[0065] Specifically, the mathematical model for the DQ axis of PMSG is as follows:

[0066]

[0067] In the formula, u d u q The voltages along the d and q axes (V); i d i q L represents the d-axis and q-axis currents (A). d L q For d-axis and q-axis inductance (H); R s The stator winding resistance (Ω); ω e ψ is the rotor's electric angular velocity (rad / s); f is the principal flux linkage of the permanent magnet (V·s); p is the differential operator.

[0068] Step S302: Establish the IPSMG extended back electromotive force model through inverse Park transformation;

[0069] The specific IPSMG extended back EMF model is as follows:

[0070]

[0071] In the formula, u α u β For α and β axis voltages; i α i β E represents the α-axis and β-axis currents. α and E β For the back electromotive force along the α and β axes.

[0072] The above equation can be equivalent to:

[0073]

[0074] In the formula, This is the differential of the q-axis current (A / s).

[0075] Step S303: Obtain the α- and β-axis back electromotive forces E from the IPSMG extended back electromotive force model. α and E β ;

[0076] The back electromotive force E α and E β The expression containing rotor position information is as follows:

[0077]

[0078] In the formula, θ e This represents the rotor's electrical angular displacement.

[0079] Step S304: Based on the back electromotive force E along the α and β axes α and E β Extract rotor speed and position information.

[0080] Specifically, the formulas for extracting rotor speed and position information are as follows:

[0081]

[0082] The set stability condition satisfied in step S203 is that, without activating the sliding mode state observer, the permanent magnet synchronous generator accelerates from zero speed to a relatively stable speed range after starting.

[0083] Since the back electromotive force (EMF) is proportional to the rotor speed and the main flux linkage, a rotor speed that is too low will result in a low back EMF, leading to inaccurate back EMF measurement. Therefore, considering the measurability of the voltage and current of each shaft and the size of the main flux linkage of the permanent magnet, the rotor speed under stable conditions can be set to 600-1000 rpm.

[0084] Using the rotor position and speed of the permanent magnet synchronous generator under these stable conditions as the initial state before the sliding mode state observer is activated, the sliding mode state observer is started. This avoids overshoot and oscillation phenomena that occur when using the sliding mode state observer for vector control during the transition of the permanent magnet synchronous generator rotor from zero speed to steady state, thus improving the stability of the permanent magnet synchronous generator vector control system. Furthermore, it effectively shortens the steady-state settling time and improves the efficiency of regulation.

[0085] When the PMSG rotor is running stably and vector control and sliding mode observer algorithms are not enabled, the initial state of the SMO is determined. According to the PMSG extended back EMF model, at this time, the motor current is 0, and the α-β axis motor voltage is equal to the α-β axis back EMF, as expressed below:

[0086]

[0087] In the formula, u αi u βi E represents the initial values ​​(V) of the α and β axis voltages. αi and E βi ω represents the initial values ​​(V) of the back electromotive force along the α and β axes; ei θ is the initial value of the rotor's electric angular velocity (rad / s); ei This is the initial value (rad) of the rotor's electrical angular displacement.

[0088] Specifically, the PSMG extended back electromotive force model in this embodiment is mathematically transformed to obtain the following state equation:

[0089]

[0090] In the formula, Let be the differential values ​​of the α and β axis currents (A / s).

[0091] The SMO design is as follows:

[0092]

[0093] In the formula, Estimate the differential values ​​of the current (A / s) for the α and β axes; Estimate the current (A) for the α and β axes; To estimate the electric angular velocity (rad / s); z α z β The control function has the following expression:

[0094]

[0095] In the formula, sign(·) is the sign function.

[0096] Specifically, in step S205, a Lyapunov function is constructed based on the current error to make the sliding mode gain coefficient satisfy the stability condition of the sliding mode state observer.

[0097] Assuming the estimated electric angular velocity converges to the actual electric angular velocity, i.e. The state equation for the current error is expressed as follows:

[0098]

[0099] In the formula, e represents the differential values ​​of the α and β axis current errors; α e β For α and β axis current errors;

[0100] Construct the Lyapunov function as follows:

[0101]

[0102] The differential form of the Lyapunov function is as follows:

[0103]

[0104] When the sliding mode gain coefficient k > max(|E α |,|E β When |), then Then the sliding mode state observer is stable.

[0105] Specifically, in step S206, after the sliding mode state observer stabilizes, the observed back electromotive force is a high-frequency discontinuous signal, at z α z β After adding a low-pass filter to the control function, the estimated back electromotive force along the α and β axes is obtained. and

[0106]

[0107] In the formula, ω c is the cutoff frequency of the low-pass filter, and s is the Laplace transform operator.

[0108] Finally, the rotor speed and position information are extracted from the estimated back electromotive force after filtering out high-frequency signals, using the following formula:

[0109]

[0110] In summary, this embodiment estimates the back electromotive force (EMF) of the PMSG using the SMO (Sliding Mode Observer) algorithm, thereby extracting the rotor position and speed information from the back EMF. Utilizing the detectable initial value of the back EMF before the start of vector control and the sliding mode observer algorithm, the rotor position and speed information obtained from the back EMF are used as the initial state for the step before the algorithm starts. This effectively shortens the steady-state adjustment time and avoids overshoot and oscillations that may occur during the transition from the initial state to the steady state, thus improving the stability of the permanent magnet synchronous generator vector control system.

[0111] The above description is only a preferred embodiment of the present invention, but the scope of protection of the present invention is not limited thereto. Any changes or substitutions that can be easily conceived by those skilled in the art within the scope of the technology disclosed in the present invention should be included within the scope of protection of the present invention.

Claims

1. A method for estimating the rotor position and speed of a permanent magnet synchronous generator based on SMO, characterized in that, The method comprises the following steps: When the permanent magnet synchronous generator starts from zero speed, a sliding mode state observer is not started; The rotor position and speed of the permanent magnet synchronous generator are extracted according to the established PMSG extended back electromotive force model; The rotor position and speed meeting the stable condition are set as the initial state of the previous frame before the sliding mode state observer is started, and the sliding mode state observer is started; The back electromotive force is estimated by using the sliding mode state observer; The Lyapunov function is constructed according to the current error, so that the sliding mode gain coefficient meets the stable condition of the sliding mode state observer; Assume estimated electrical angular velocity can converge to the actual electrical angular velocity ω e i.e. The state equation of the current error is expressed as follows: wherein is the α, β axis current error differential value; e α , e β is the α, β axis current error; L d , L q is the d, q axis inductance; R s is the stator winding resistance; ω e is the rotor electrical angular velocity; E α and E β is the α, β axis back electromotive force; z α , z β is the control function; The Lyapunov function is constructed as follows: The differential form of the Lyapunov function is as follows: When k > max(|E α |,|E β |), then then the sliding mode state observer is stable; The rotor speed and position information are extracted from the estimated back electromotive force.

2. The method for estimating the rotor position and speed of the permanent magnet synchronous generator according to claim 1, wherein The rotor position and speed of the permanent magnet synchronous generator are extracted according to the established PMSG extended back electromotive force model, which comprises the following steps: The D-Q axis mathematical model of the PMSG is established; The IPSMG extended back electromotive force model is established through inverse Park transformation; The back EMF E of the α, β axes is obtained from the extended back EMF model of the IPSMG α and E β ; According to the α, β axis back electromotive force E α and E β Extracting the rotor speed and position information.

3. The method for estimating the rotor position and speed of the permanent magnet synchronous generator according to claim 1, wherein The D-Q axis mathematical model of the PMSG is as follows: wherein u d , u q are d, q-axis voltages; i d , i q are d, q-axis currents; L d , L q are d, q-axis inductances; R s is the stator winding resistance; ω e is the rotor electrical angular velocity; ψ f is the permanent magnet flux linkage; and p is the differential operator.

4. The method for estimating the rotor position and speed of the permanent magnet synchronous generator according to claim 1, wherein The IPSMG extended back electromotive force model can be established through inverse Park transformation as follows: In the formula, u α u β For α and β axis voltages; i α i β E represents the α-axis and β-axis currents. α and E β The back electromotive force (EMF) is defined as E along the α and β axes. α and E β The expression containing rotor position information is as follows: In the formula, θ e is the rotor electrical angular displacement.

5. The method for estimating the rotor position and speed of the permanent magnet synchronous generator according to claim 4, wherein According to the IPSMG extended back electromotive force model, at this time, the motor current is 0, the α-β axis motor voltage value is equal to the α-β axis back electromotive force, and the expression is as follows: wherein u αi , u βi are the initial values of the α, β axis voltages; E αi and E βi are the initial values of the α, β axis back electromotive forces; ω ei is the initial value of the rotor electric angular velocity; and θ ei is the initial value of the rotor electric angular displacement.

6. The method for estimating the rotor position and speed of the permanent magnet synchronous generator according to claim 1, wherein The sliding mode state observer equation is as follows: wherein is the α, β axis estimated current differential value; is the α, β axis estimated current; is the estimated electrical angular velocity; z α , z β is the control function.

7. The method for estimating the rotor position and speed of the permanent magnet synchronous generator according to claim 6, wherein Control function z α , z β The expression for z is: In the formula, the function sign(·) is a sign function, k is a sliding mode gain coefficient, e α , e β is an α, β axis current error.

8. The method for estimating the rotor position and speed of the permanent magnet synchronous generator according to claim 7, wherein The back EMF observed by the sliding mode state observer is a high frequency discontinuous signal, in z α , z β After adding a low-pass filter to the control function, the estimated back EMF in α, β axes is obtained and where ω c is the low-pass filter cutoff frequency and s is the Laplace transform operator.

9. The method for estimating the rotor position and speed of the permanent magnet synchronous generator according to any one of claims 1-8, wherein The rotor speed of the stable condition is set to 600-1000 revolutions / second.

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