A constant current control method for dimmer based on sliding mode control

Abstract

The present invention relates to a dimmer constant current control method based on sliding mode control, comprising the following steps: S1: obtaining a smaller duty cycle of the leading arm and the lagging arm of the H-bridge; S2: obtaining the deviation signal e and the sliding film variable S of the sliding film control; S3: obtaining the output u of the dimmer constant current controller based on the sliding film control; S4: setting the control parameters of the dimmer constant current based on the sliding film control. The dimmer constant current control method based on sliding mode control of the present invention has a fast response due to the introduction of sliding mode control, is insensitive to corresponding parameter changes and disturbances, does not require system online identification, and is simple in physical implementation. The method of the present invention can improve the input power factor, improve the output waveform quality, and improve the stability and real-time performance of the constant current dimmer.

Description

Technical Field

[0001] The invention relates to a dimmer, and in particular to a dimmer constant current control method based on sliding mode control. Background Art

[0002] The constant current dimmer is the main control equipment in the airport navigation lighting system. It provides AC constant current power for the navigation lighting circuit. The stability and fast response of the constant current dimmer are the key to the high-quality operation of the entire airport navigation lighting system.

[0003] With the development of society, the market has put forward higher requirements for sinusoidal constant current dimmers, which are manifested in: the input and output currents are both sinusoidal waves with low harmonic content; they have good adaptability to loads of different natures and extreme working conditions such as load short circuit, secondary open circuit of isolation transformer, etc., and have good dimming speed and high input power factor; low noise, energy saving, environmental protection, continuous and reliable, and stable operation.

[0004] Most traditional control algorithms use PI (PID), but the sine wave constant current dimmer control system itself has uncertain system model structure, frequent random interference such as load changes, etc., which makes the system often have problems such as untimely adjustment, large harmonic components, and low power factor during operation, which seriously affects the power supply quality of airport navigation lights. Summary of the invention

[0005] In view of this, it is necessary to provide a dimmer constant current control method based on sliding mode control to address the above problems. This method can improve the stability and real-time performance of the constant current dimmer.

[0006] In order to solve the problems existing in the prior art, the present invention adopts the following technical solutions:

[0007] A dimmer constant current control method based on sliding mode control comprises the following steps:

[0008] S1: Obtain a smaller duty cycle for the leading arm and lagging arm of the H-bridge;

[0009] S2: Obtain the deviation signal e and synovial variable S of the synovial control;

[0010] S3: Obtain the output u of the dimmer constant current controller based on sliding film control;

[0011] S4: Setting of constant current control parameters of dimmer based on sliding film control.

[0012] Furthermore, the S1 comprises the following steps:

[0013] S11: Initially set a smaller duty cycle for the leading arm and lagging arm of the H-bridge, initially about 8%;

[0014] S12: Calculate the actual regulation duty cycle based on the measured current and the target current.

[0015] Further, the S2 comprises the following steps:

[0016] S21: Take e as the deviation (tracking deviation / system deviation), e=detected relevant physical signal-expected command signal (set value);

[0017] S22: Calculate the deviation change value Δe, Δe=deviation formed this time-deviation formed by last sampling;

[0018] S23: Take the sliding mode variable S = Δe + c × e;

[0019] S24: Determine the range of the sign function sign(S).

[0020] Further, the S3 comprises the following steps:

[0021] S31: Obtain sliding mode control expression as u=-k 1 ×Sk 2 ×Δe-k 3 ×sign(S), where k 1 , k 2 , k 3 , c is the parameter to be adjusted,

[0022] S32: Discretize the sliding mode control expression approximately as follows: u(T) = -k 1 ×S(T)-k 2 ×(e(T)-e(T-Δt))-k 3 ×sign(S(T)), where u(T) is the control output at the current moment; e(T-Δt) is the deviation formed by the last sampling; S(T) is the sliding mode variable value at the current moment, which is expressed as S(T)=e(T)-e(T-Δt)+c×e(T); sign(S(T)) is the sign function value at the current moment.

[0023] Further, the S4 comprises the following steps:

[0024] S41: Set k first 1 =1, and assign a larger c value, while k 2 =k 3 =0, observe the simulation or experimental waveform;

[0025] S42: If there is a certain tracking trend but the overshoot is large, keep the value of c unchanged while gradually increasing k 1 and k 3 The value of

[0026] S43: According to step S42, if the adjustment effect tends to track the input, keep k 1 , k 3 , c parameter value remains unchanged, and k is gradually increased 2 value until the observed simulation or experimental waveform reaches the expected target.

[0027] The advantages and beneficial effects of the present invention are:

[0028] The invention discloses a dimmer constant current control method based on sliding mode control. Due to the introduction of sliding mode control, the response is fast, the corresponding parameter changes and disturbances are insensitive, no system online identification is required, and the physical implementation is simple. The method of the invention can improve the input power factor, improve the output waveform quality, and improve the stability and real-time performance of the constant current dimmer. BRIEF DESCRIPTION OF THE DRAWINGS

[0029] The present invention will be further described below in conjunction with the accompanying drawings and specific embodiments:

[0030] Figure 1 This is the control system block diagram of the sine wave constant current dimmer;

[0031] Figure 2 It is a flow chart of a dimmer constant current control method based on sliding mode control;

[0032] Figure 3 This is a schematic diagram of the capacitive open circuit test simulation circuit;

[0033] Figure 4 It is a test waveform of a dimmer based on sliding mode control when the dynamic capacitor is open circuit;

[0034] Figure 5 It is a test waveform of a dimmer based on sliding mode control when the inductive load is switched from 100% to 50%;

[0035] Figure 6 The current output waveform of a dimmer based on sliding mode control at 70Ω and 140Ω loads. DETAILED DESCRIPTION

[0036] The following will be combined with the drawings in the embodiments of the present application to clearly and completely describe the technical solutions in the embodiments of the present application. Obviously, the described embodiments are only part of the embodiments of the present application, not all of the embodiments. Based on the embodiments in the present application, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of this application.

[0037] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as those commonly understood by those skilled in the art to which this application belongs. The terms used herein in the specification of this application are only for the purpose of describing specific embodiments and are not intended to limit this application.

[0038] like Figure 1 The sinusoidal wave constant current dimmer control system shown, usually traditional control algorithms mostly use PI (PID), but the sinusoidal wave constant current dimmer control system itself has uncertain system model structure, frequent random interference such as load changes, etc., which makes the system often have problems such as untimely adjustment, large harmonic components, and low power factor during operation, which seriously affects the power supply quality of airport navigation lights. Therefore, the present application provides a dimmer constant current control method based on sliding mode control to improve the stability and real-time performance of the constant current dimmer.

[0039] It should be noted that the constant current control method provided in this application is designed for the airport navigation light dimmer, but its application scenario is not limited to the airport navigation light dimmer, such as Figure 2 As shown, the method comprises the following steps:

[0040] S1: Obtain a smaller duty cycle for the leading arm and lagging arm of the H-bridge;

[0041] S2: Obtain the deviation signal e and synovial variable S of the synovial control;

[0042] S3: Obtain the output u of the dimmer constant current controller based on sliding film control;

[0043] S4: Setting of constant current control parameters of dimmer based on sliding film control.

[0044] Furthermore, step 1 includes the following steps:

[0045] S11: Initially set the H-bridge leading arm and lagging arm to a smaller duty cycle, initially around 8%.

[0046] S12: Calculate the actual adjustment duty cycle according to the measured current and the target current. The specific implementation is carried out in steps. The step number selection range is 20 to 30 steps. The target duty cycle is reached in a successive approximation manner.

[0047] Further, step 2 includes the following steps:

[0048] S21: Take e as the deviation (tracking deviation / system deviation), e = detected related physical signal - expected command signal (set value). The deviation here is reflected in the difference between the duty cycle corresponding to the current state of the system and the step duty cycle calculated based on the measured voltage, current, load characteristics and other parameters.

[0049] S22: Calculate the deviation change value Δe, Δe=deviation formed this time-deviation formed in the previous sampling.

[0050] S23: According to the system requirements, the sliding mode variable S=Δe+c×e is taken, where c is the parameter to be adjusted.

[0051] S24: Determine the range of the sign function sign(S), according to the value of the synovial variable, which is specifically: when S>0, sign(S)=1; when S<0, sign(S)=-1; when S=0, sign(S)=0.

[0052] Further, step 3 includes the following steps:

[0053] S31: According to the parameters of step 2, the sliding mode control expression is obtained as u=-k 1 ×Sk 2 ×Δe-k 3 ×sign(S), where k 1 , k 2 , k 3 , c is the parameter to be adjusted,

[0054] S32: Discretize the sliding mode control expression approximately as follows: u(T) = -k 1 ×S(T)-k 2 ×(e(T)-e(T-Δt))-k 3 ×sign(S(T)), where u(T) is the control output at the current moment; e(T-Δt) is the deviation formed by the last sampling; S(T) is the sliding mode variable value at the current moment, which is expressed as S(T)=e(T)-e(T-Δt)+c×e(T); sign(S(T)) is the sign function value at the current moment.

[0055] Further, step 4 includes the following steps:

[0056] S41: Set k first 1 =1, and assign a larger c value, while k 2 =k 3 =0, observe the simulation or experimental waveform;

[0057] S42: If there is a certain tracking trend but the overshoot is large, keep the value of c unchanged while gradually increasing k 1 and k 3 The value of

[0058] S43: According to step S42, if the adjustment effect tends to track the input, k can be maintained. 1 , k 3 , c parameter value remains unchanged, and k is gradually increased 2 value until the observed simulation or experimental waveform reaches the expected target.

[0059] The present invention introduces sliding mode control, has fast response, is insensitive to corresponding parameter changes and disturbances, can improve input power factor, improve output waveform quality, and improve the stability and real-time performance of the constant current dimmer.

[0060] 1. Under capacitive load:

[0061] like Figure 3 As shown, Figure 3 The capacitive open circuit test simulation circuit is shown in Figure 2. The system parameters except the control parameters are set as follows: the input sinusoidal AC input voltage Vms=380V, the effective value of the signal is 220v, the frequency is f=50Hz, RL=114Ω, and the capacitance C=7uf.

[0062] First, switch S is placed in position 1, the dimmer modulates the light level to level 5, and the output current effective value is Ims = 6.6A. At this time, close S to position 2. After detecting a sudden change in load, the dimmer immediately converges the duty cycle to 0, and tries to restore the output. Within 1 cycle (20ms), it detects that the load capacitive circuit is open, completely shuts off the output, and alarms. The current waveform is as follows Figure 4 .from Figure 4 It can be seen that with the sliding film control technology, the system tracks the input after 2 sampling cycles under capacitive load (open circuit) and enters the system shutdown state. The maximum value of the system adjustment process current is 20.31mA, the minimum value is 3.125mA, and the mean square value is 12.03mA. After 2 sampling cycles, the system output is stable.

[0063] 2. In the case of inductive load:

[0064] The system parameters other than the control parameters are set as follows: AC input voltage Vms = 380V, grid frequency f = 50Hz, initial load is inductive full load 7.5Kw, load lagging power factor PF = 0.6. Turn the dimmer to level 5, the output current effective value Ims = 6.6A, and then 50% of the load is short-circuited through the external switch. After the dimmer detects the sudden change in load, it immediately reduces the output duty cycle, and the current impact is controllable. After 8 cycles, the output reaches a stable target current again. The waveform is as follows Figure 5 As shown. Figure 5 It can be obtained that the maximum current during the system adjustment process is 17.14A and the minimum current is -18.30A. After 2 sampling cycles, the system output is stable at 6.6A.

[0065] 3. Under resistive load:

[0066] The system parameters other than the control parameters are set as follows: AC input voltage Vms = 380V, grid frequency f = 50Hz, initial load is resistive load 70 ohms and 140 ohms, duty cycle is modulated from 0 to 100%, the system output is as follows Figure 6 As shown in the figure, the sliding film control technology is adopted, and the system output waveform is close to the smooth input sine wave. Under the condition of not allowing the duty cycle, the stability of the output current is well guaranteed. When the dimmer is turned to level 5, the output current effective value Ims=6.6A.

[0067] The above-mentioned embodiments only express the implementation methods of the present application, and the descriptions thereof are relatively specific and detailed, but they cannot be understood as limiting the scope of the invention patent. It should be pointed out that, for ordinary technicians in this field, several variations and improvements can be made without departing from the concept of the present application, and these all belong to the protection scope of the present application. Therefore, the protection scope of the patent of the present application shall be subject to the attached claims.

Claims

1. A dimmer constant current control method based on sliding mode control, characterized in that: The following steps are involved: S1: Get the duty cycle of the leading arm and the lagging arm of the H bridge; S2: Obtain the deviation signal e and synovial variable S of the synovial control; S3: Obtain the output u of the dimmer constant current controller based on sliding film control; S4: Constant current control parameter setting of dimmer based on sliding film control; The S2 comprises the following steps: S21: Take e as the deviation (tracking deviation / system deviation), e=detected relevant physical signal-expected command signal (set value); S22: Calculate the deviation change value Δe, Δe=deviation formed this time-deviation formed by last sampling; S23: Take the sliding mode variable S = Δe + c × e, c is the parameter to be adjusted; S24: Determine the range of the sign function sign(S); The S3 comprises the following steps: S31: The sliding mode control expression is obtained as u=-k1×S-k2×Δe-k3×sign(S), where k1, k2, k3 are parameters to be adjusted; S32: The sliding mode control expression is approximately discretized as: u(T) = -k1×S(T)-k2×(e(T)-e(T-Δt))-k3×sign(S(T)), where u(T) is the control output at the current moment; e(T-Δt) is the deviation formed by the last sampling; S(T) is the sliding mode variable value at the current moment, which is expressed as S(T) = e(T)-e(T-Δt)+C×e(T); sign(S(T)) is the sign function value at the current moment.

2. A dimmer constant current control method based on sliding mode control according to claim 1, characterized in that: The S1 comprises the following steps: S11: Initially set the duty cycle of the leading arm and the lagging arm of the H-bridge, initially 8%; S12: Calculate the actual regulation duty cycle based on the measured current and the target current.

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