Four-switch buck-boost with phase compensation based disturbance efficiency extremum search method

Abstract

This invention provides a disturbance efficiency extremum search method with phase compensation based on a four-switch Buck-Boost converter and a Buck-Boost converter device, belonging to the field of power electronics. It proposes combining disturbance efficiency extremum search with phase compensation and PI control to adjust three variables: the duty cycle Da and Db of the two arms of the four-switch Buck-Boost converter, and the phase difference of the control pulse. This invention discovers the relationship between the duty cycle and the converter efficiency when the converter is operating in three modes. Furthermore, an improved extremum search algorithm is used to find the minimum point of the input current. The algorithm is found to be fast and has adaptive step size adjustment, effectively finding the maximum point of the operating efficiency of the four-switch Buck-Boost converter.

Description

Technical Field

[0001] This invention belongs to the field of power electronics, specifically relating to a method for searching the extremum of disturbance efficiency with phase compensation based on a four-switch Buck-Boost converter and a Buck-Boost converter device. Background Technology

[0002] With the continuous development of the automotive industry, traditional linear voltage regulators are gradually being replaced by high-efficiency DC-DC converters. As the number of converters increases, the choice of converter topology significantly impacts efficiency and vehicle energy consumption. The four-switch Buck-Boost converter, a non-isolated step-up / step-down DC-DC converter, is characterized by its simple circuit structure and high voltage stress on its switching devices. Therefore, improving its efficiency is a persistent research topic. To find the efficiency extrema of the converter, many related extremum search algorithms have been proposed, such as the steepest descent method based on gradients, the classical extremum search algorithm based on perturbations, and the extremum search algorithm based on sliding mode. Many improvements have been proposed based on these extremum search algorithms. After exploring the relationship between the duty cycle of the control pulses of different arms and the phase difference between the control pulses of the arms and the operating efficiency of the four-switch Buck-Boost DC-DC converter, this invention proposes to apply an improved perturbation efficiency extremum algorithm with phase compensation to the four-switch Buck-Boost converter. The perturbation extremum algorithm with phase compensation can effectively improve the efficiency of a four-switch Buck-Boost converter operating in one of the three modes, bringing it to its efficiency extremum. This extremum search algorithm effectively improves the operating efficiency of the four-switch Buck-Boost converter. Summary of the Invention

[0003] To address the shortcomings of existing technologies, this invention provides a perturbation efficiency extremum search method with phase compensation for online optimization of the control duty cycle. Based on a four-switch Buck-Boost switching model, it combines perturbation efficiency extremum search with phase compensation and PI control to adjust the duty cycles Da and Db of the two half-bridges and control the pulse phase difference. Three variables are used to enable the converter to operate in a three-mode state. In this mode, the start times of the A and B phase bridge arm pulses are the same, while the phase difference is automatically determined by the A and B phase pulses. When the output power is constant, the value of Da is adjusted, and then the value of Db is adjusted via PI control to maintain a constant output power, corresponding to a converter efficiency. Furthermore, it was found that when the converter operates in three modes, there exists a Da / Db combination that maximizes the converter's operating efficiency. Therefore, this invention proposes using an extreme value search algorithm with phase compensation to control Da in a four-switch Buck-Boost converter to find the point of highest operating efficiency.

[0004] To achieve the above objectives, the technical solution of the present invention is as follows:

[0005] An extremum search algorithm with phase compensation based on a four-switch Buck-Boost converter includes the following steps:

[0006] Step 1: Set an initial Da value and input it into the four-switch Buck-Boost converter to control the A-phase bridge arm, then proceed to Step 2;

[0007] Step 2: Sample the input current signal Iin, then proceed to step 3;

[0008] Step 3: Phase shift the sampled input current signal Iin, and then proceed to step 4;

[0009] The input current signal Iin is phase-shifted using the following formula. In the formula, ρ represents the order of the phase shift, and a single phase shift can compensate for a maximum displacement of 0.5π.

[0010]

[0011] k w T and T are phase offset parameters, which play an important role in phase compensation. These two parameters are set in relation to the frequency w of the disturbance signal and the filter cutoff frequency w. l The relevant formula is shown below;

[0012] k w =k*w

[0013]

[0014] Step 4: Filter the phase-shifted input current signal. The purpose of the filter is to remove high-order harmonics. The filter expression is shown in the following formula. Then proceed to step 5.

[0015]

[0016] Wherein, the cutoff frequency of the filter is w h After passing through the above filter, the estimated value of the converter input current Iin is obtained;

[0017] Step 5: Multiply the estimated value of the input current signal Iin by the sinusoidal disturbance signal, the expression of which is shown in the following formula, and then proceed to step 6;

[0018] α*sin(wt)

[0019] Among them, the disturbance signal parameters are the amplitude coefficient α and the signal period w, which are sinusoidal disturbance signal parameters. The magnitude of parameter α will affect the fluctuation amplitude of the final convergence extremum, and parameter w can affect the speed of the entire system's search for the extremum.

[0020] Step 6: Filter the signal obtained by multiplying the input current estimate with the disturbance signal to remove higher harmonics. The transfer function of the low-pass filter is shown in the following formula. Then proceed to step 7.

[0021]

[0022] Among them, w l This is the cutoff frequency of the low-pass filter, and it should be less than w when setting the parameters;

[0023] Step 7: After processing in steps 4 to 6, the gradient estimation information of the input current signal Iin can be obtained. Then, this signal is passed through an optimizer, which performs proportional integration on the signal to obtain the estimated coordinates of the current extreme point. The transfer function of the optimizer is shown in the following equation. Then, proceed to step 8.

[0024]

[0025] Where k is the scaling parameter of the optimizer; the larger the value, the faster the convergence to the extreme value.

[0026] Step 8: Introduce an error into the estimated extreme coordinates. The error perturbation is the same as the expression in Step 5. Then, input the Da estimate with the superimposed perturbation into the converter. The converter will be in a new steady state under the new Da. The new state corresponds to a new operating efficiency and a new input current Iin. Then, transfer the new input current signal to Step 1 to start a new round of iteration. This continues until the extreme point between the converter Da and the input current Iin is found. At this point, the converter is at the efficiency maxima, and the purpose of efficiency optimization is completed.

[0027] Furthermore, the four-switch Buck-Boost converter operates in a mode where the switching times of the left and right bridge arms are the same, that is, the start times of the PWM square waves Va and Vb controlled by Da and Db are the same. At this time, there are three operating modes of the converter.

[0028] Furthermore, this invention proposes applying a phase-shifted, perturbation-based extremum search to a three-modal, four-switch Buck-Boost model to optimize the optimal switch duty cycle combination. A PI controller is used to adjust the duty cycle Db of the right phase arm, and the control variable for the perturbation-based extremum search is the duty cycle Da of the left arm, with the output variable being the input current Iin of the four-switch Buck-Boost model. Through the aforementioned PI controller and extremum search model, the extremum of the input current can be optimized while maintaining constant output power, thus ensuring the converter's conversion power is at its optimal state.

[0029] Furthermore, the parameter settings of the various parts of the aforementioned disturbance-based extremum search algorithm with phase shift exhibit the following relationship: the entire control system is divided into three parts: a four-switch Buck-Boost converter, a sinusoidal disturbance signal part, and an output signal filter part. The time scales of these three parts follow a sequentially decreasing trend, and it is this separation of the three time scales that ensures the stability of the extremum search. The algorithm parameter settings are summarized as follows, where w and δ are small positive constants, and w... h w l k are positive coefficients of the same order as w*δ.

[0030] w h =O(w*δ)

[0031] w l =O(w*δ)

[0032] k = O(w*δ)

[0033] Furthermore, the topology of the aforementioned four-switch Buck-Boost converter includes the following components: an inductor (L), an input regulating capacitor (C1), an output regulating capacitor (C2), four MOSFET switches (S1, S2, S3, S4), an output resistor (R), and an input power supply (V). in Four MOSFETs form a full bridge and are connected in parallel through an inductor. The lower ends of the two half-bridges are connected to the negative terminal of the power supply. The output capacitor C2 is connected in parallel with the output resistor.

[0034] Furthermore, the algorithm is based on the premise that the output voltage of the converter is constant. By using PI regulation to keep the output voltage constant, the output power is also constant.

[0035] Furthermore, the present invention generates a control PWM wave through a triangular wave comparison method, so the value of Da can be controlled by controlling the upper limit of the comparison.

[0036] In summary, after adopting the above technical solution, the beneficial effects achieved by the present invention are as follows:

[0037] This invention proposes a perturbation extremum algorithm with phase shift based on a four-switch Buck-Boost switching model, combined with a PI controller to adjust Da, Db, and... This paper describes a converter efficiency optimization problem implemented using three variables with the same initial time across three operating modes. Due to the characteristics of this operating mode, the problem is transformed into finding the minimum input power, i.e., the minimum input current Iin, by adjusting Da. This successfully reduces the three-variable problem to a single-variable extremum problem. Based on this problem, an optimized perturbation-based extremum search algorithm is used to find the optimal Da value, and Db is adjusted using PI control to keep the output power constant. The value is determined by this working mode. Calculated.

[0038] This invention discovers the relationship between duty cycle and converter efficiency under a certain operating mode. An improved classical extremum search algorithm is used to find the minimum point of Iin. This algorithm is characterized by its high speed and adaptive step size adjustment, and can effectively find the point of highest operating efficiency for the Buck-Boost converter. Attached Figure Description

[0039] Figure 1 This is a schematic diagram of a four-switch Buck-Boost converter.

[0040] Figure 2 This is a mode diagram showing the operation of a four-switch Buck-Boost converter where the output voltage is less than the input voltage.

[0041] Figure 3 This is a mode diagram showing the operation of a four-switch Buck-Boost converter where the output voltage is greater than the input voltage.

[0042] Figure 4 This is a flowchart of a perturbation extremum search algorithm with phase shift.

[0043] Figure 5 This provides the algorithmic framework for the extreme value search algorithm.

[0044] Figure 6 This represents the conduction state when both Va and Vb are enabled.

[0045] Figure 7 This represents the circuit conduction state when Va is off and Vb is on.

[0046] Figure 8 The circuit conduction state when Va is on and Vb is off.

[0047] Figure 9 This represents the circuit conduction state when both Va and Vb are off.

[0048] Figure 10 The upper limit of Da and the input current Iin are determined by the extreme value algorithm search when the input is 10V, the output is constant at 4V, and the output load is 4Ω.

[0049] Figure 11 With a 10V input and a constant output of 4V, the output voltage Vo is regulated by a PI controller when the output load is 4Ω. Detailed Implementation

[0050] The specific embodiments of the present invention are described below to enable those skilled in the art to better understand the present invention.

[0051] The topology of the Buck-Boost converter is as follows: Figure 1 As shown, the device includes the following components: an inductor (L), an input regulating capacitor (C1), an output regulating capacitor (C2), four MOSFET switches (S1, S2, S3, S4), an output resistor (R), and an input power supply (V). in );

[0052] Figure 2 The operating mode of the converter proposed in this invention when the output voltage is less than the input voltage is described, as shown in the figure. At this time, the output voltage is less than the input voltage, and the control pulses for Va and Vb are turned on at the same time. When S1 and S4 are turned on, the inductor current rises, and the circuit state is as follows. Figure 6 As shown, when S1 is off and S4 is on, the inductor current decreases, and the circuit state at this time is as follows. Figure 7 As shown. When both S1 and S4 are off, the inductor current remains constant, and the circuit state is as follows. Figure 9 As shown.

[0053] Figure 3 The operating mode of the converter proposed in this invention when the output voltage is greater than the input voltage is described, as shown in the figure. In this mode, the output voltage is greater than the input voltage, and the control pulses for Va and Vb are turned on at the same time. When S1 and S4 are turned on, the inductor and power supply charge the output load, and the inductor current decreases. The circuit state at this time is as follows: Figure 6 As shown, when S1 is on and S4 is off, the power supply charges the inductor, and the inductor current increases. The circuit state at this time is as follows: Figure 8 As shown. When both S1 and S4 are off, the inductor current remains constant, and the circuit state is as follows. Figure 9 As shown.

[0054] Figure 10 It describes a 10V input, a constant output of 4V, and an output load R. o The algorithm controls Da and the input current Iin when the Ω is 4Ω. From... Figure 10 As Da is continuously adjusted, its input current I... in The current continuously decreases. The minimum input current is 0.43A, and Da is approximately 1.78 / 2 = 0.89. It can be seen that the algorithm quickly adjusts according to the gradient value and converges to the minimum current value. Its efficiency has effectively increased from approximately 80% initially to 93%.

[0055] Figure 11 for Figure 11 The waveform of the output voltage Vo shows that when the four-switch Buck-Boost converter operates at... Figure 9Under operating conditions, when the extreme value search algorithm adjusts Da, the PI controller can adjust Db to keep the output voltage constant. It can be seen that the output voltage is constant at 4V with an error within 0.05V. Therefore, under this premise, the extreme value search algorithm can maximize the converter's operating efficiency by finding the minimum input current.

Claims

1. A disturbance efficiency extremum search control method based on a four-switch Buck-Boost converter with phase compensation, characterized in that, Includes the following steps: Step 1: Set an initial duty cycle for phase A bridge arm. D a The value is input into the four-switch Buck-Boost converter to control the A-phase bridge arm; then proceed to step 2; Step 2: Sample the input current signal I in Then proceed to step 3; Step 3: Sample the input current signal I in Phase shift is performed on the input current signal. I in The phase shift operation is performed using the transfer function shown below, and then proceed to step 4; (𝑘 𝑤 𝑇s+1) ρ / (𝑇s+1) ρ Where, in the formula ρ Let be the order of the phase shift, 𝑘 𝑤 , where and are parameters of phase shift; when ρ When = 1, a single-phase offset can compensate for a maximum displacement of 0.5π; 𝑤 The parameters and play a crucial role in phase compensation. These parameters are set in relation to the disturbance signal frequency and the filter cutoff frequency . l The relevant formula is shown below; 𝑘 𝑤 = 𝑘 ∗ 𝑤 𝑇 = 1 / 𝑤 l Step 4: Filter the phase-shifted input current signal. The purpose of the filter is to remove high-order harmonics. The filter expression is shown in the following formula. Then proceed to step 5. s / (s + 𝑤 h ) The filter cutoff frequency is 𝑤 h After passing through the above filter, the converter input current signal is obtained. I in The estimated value; Step 5: Input current signal I in The estimated value is multiplied by the sinusoidal disturbance signal, the expression of which is shown below, and then proceeds to step 6; α ∗ sin (𝑤t) Among them, the disturbance signal parameters are the amplitude coefficient α and the disturbance signal frequency φ, which are sinusoidal disturbance signal parameters; the magnitude of the disturbance signal amplitude coefficient α will affect the fluctuation amplitude of the final convergence extremum, and the disturbance signal frequency φ will affect the speed at which the entire system searches for the extremum; Step 6: Filter the signal obtained by multiplying the input current estimate with the disturbance signal to remove higher harmonics. The transfer function of the low-pass filter is shown in the following formula. Then proceed to step 7. 𝑤 l / ( s + 𝑤 l ) The filter cutoff frequency is 𝑤 l When setting the parameters, the frequency should be less than the frequency of the disturbance signal, φ. Step 7: After processing in steps 4 to 6, the input current signal can be obtained. I in The gradient estimation information is obtained, and then the signal is passed through the optimizer, that is, the signal is proportionally integrated to obtain the estimated coordinates of the current extreme point; the transfer function of the optimizer is shown in the following formula, and then proceed to step 8; 𝑘 / s Where, 𝑘 is the scaling parameter of the optimizer; the larger the value, the faster it converges to the extreme value. Step 8: Introduce an error into the estimated extreme value coordinates, with the error perturbation expressed in the same way as in Step 5; then, superimpose the perturbation on the duty cycle of the A-phase bridge arm. D a The estimated input is fed into the converter, and the converter operates at the new duty cycle of phase A bridge arm. D a The system will then enter a new stable state; this new state corresponds to new operating efficiency and also to a new input current signal. I in Then, the new input current signal is transferred to step 1 to start a new round of iteration; until the duty cycle of phase A bridge arm is optimized. D a With input current signal I in The process ends at the extreme point between these points, at which point the converter is at its efficiency maximum, thus achieving the goal of efficiency optimization.

2. The disturbance efficiency extremum search control method based on a four-switch Buck-Boost converter with phase compensation as described in claim 1, characterized in that, The four-switch Buck-Boost converter operates in a mode where the switching times of the A and B bridge arms are the same, i.e., the duty cycle of the A phase bridge arm is... D a B-phase bridge arm duty cycle D b Controlled PWM square wave V a V b The starting times are the same, and at this time, there are three operating modes of the converter.

3. The disturbance efficiency extremum search control method based on a four-switch Buck-Boost converter with phase compensation as described in claim 1, characterized in that, A perturbation-based extremum search with phase shift is applied to a three-mode four-switch Buck-Boost converter to optimize the optimal switch duty cycle combination. A PI controller is used to adjust the duty cycle of the B-phase bridge arm. D b The control variable for the extremum search based on the disturbance is the duty cycle of phase A bridge arm. D a The output variable is the input current signal of the four-switch Buck-Boost converter. I in The above-mentioned PI controller and extreme value search model can optimize the extreme value of the input current under the premise of keeping the output power constant, so that the converter's conversion power is in an extreme state.

4. The disturbance efficiency extremum search control method based on a four-switch Buck-Boost converter with phase compensation as described in claim 3, characterized in that, The parameter settings of the various parts of the algorithm have the following relationship: The entire control system is divided into three parts: a four-switch Buck-Boost converter, a sinusoidal disturbance signal part, and an output signal filter part; the time scales of the three parts follow a sequentially decreasing trend, and it is the separation of the three time scales that ensures the stability of the extreme value search; the algorithm parameter settings are summarized as follows, where and are small positive constants, and ... ℎ , l , where is the coefficient of the same order as , , and . 𝑤 ℎ = 𝑂(𝑤 ∗ 𝛿) 𝑤 l = 𝑂(𝑤 ∗ 𝛿) 𝑘 = 𝑂(𝑤 ∗ 𝛿) .

5. The disturbance efficiency extremum search control method based on a four-switch Buck-Boost converter with phase compensation as described in claim 1, characterized in that, The topology of the aforementioned four-switch Buck-Boost converter includes the following components: inductor L Input voltage regulator capacitor C 1. Output voltage regulator capacitor C 2. Four MOSFET switching transistors S 1 , S 2 、S 3 、S 4 Output resistance R Input power 𝑉 𝑖𝑛 Four MOSFETs are combined to form a full bridge and connected in parallel through an inductor. The lower ends of the two half-bridges are connected to the negative terminal of the power supply, and the output voltage regulator is connected to the capacitor. C 2 and output resistance R in parallel.

6. The disturbance efficiency extremum search control method based on a four-switch Buck-Boost converter with phase compensation as described in claim 1, characterized in that, A disturbance efficiency extremum search control method based on a four-switch Buck-Boost converter with phase compensation is based on the premise that the output voltage of the converter is constant. By using PI regulation to keep the output voltage constant, the output power is also constant.

7. The disturbance efficiency extremum search control method based on a four-switch Buck-Boost converter with phase compensation as described in claim 1, characterized in that, The control PWM wave is generated by comparing triangular waves, so the duty cycle of phase A bridge arm is controlled by controlling the upper limit of the comparison. D a The value of .

8. The disturbance efficiency extremum search control method based on a four-switch Buck-Boost converter with phase compensation as described in claim 1, characterized in that, Based on the switching model of a four-switch Buck-Boost converter, a perturbation extremum algorithm with phase shift is proposed, combined with a PI controller to adjust the duty cycle of the A-phase bridge arm. D a B-phase bridge arm duty cycle D b Including three variables, a method for optimizing the efficiency of a four-switch Buck-Boost converter with the same start time was implemented. Based on the characteristic that the duty cycles of the A and B arms of the four-switch Buck-Boost converter start at the same time, the efficiency optimization problem in the operating mode where the duty cycles of the A and B arms of the four-switch Buck-Boost converter start at the same time is transformed into adjusting the duty cycle of the A phase arm. D a Find the minimum value of the input power, which is the input current signal. I in The minimum value; The problem was successfully reduced from a three-variable problem to a single-variable extremum problem. For the efficiency optimization problem under a working mode with the same duty cycle start time, an optimized perturbation-based extremum search algorithm was used to find the optimal duty cycle of phase A bridge arm. D a The value is determined, and the duty cycle of phase B is adjusted via PI. D b To keep the output power constant, the value of ∅ is determined by ∅ = ( ) in this operating mode. D b - D a The result is calculated as ) / 2.

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