Duty cycle loop control method of bipolar multi-phase staggered constant current source

Abstract

The invention belongs to the technical field of converter control, and relates to a duty cycle loop control method of a bipolar multi-phase staggered constant current source, which comprises a double closed-loop controller and a proportional voltage controller, the double-closed-loop controller uses average inductive current control, and the inductive current controller can realize self-current-sharing of inductive current; output current controllers of the upper buck and the lower buck are combined into one output current controller, so that loop calculation in a control process is reduced; the proportional voltage controller stabilizes the input voltage by adding an additional duty ratio compensation value when the davg1 and the davg2 deviate, so that the proportional control of the input voltage is achieved; according to the control method disclosed by the invention, the system can still keep a stable operation state in the face of inductance and load parameter difference, and the problems of voltage unbalance and output current fluctuation are effectively avoided.

Description

Technical Field

[0001] This invention belongs to the field of converter control technology, specifically relating to a duty cycle loop control method for a bipolar multiphase interleaved constant current source. Background Technology

[0002] The primary applications of bipolar multiphase interleaved buck converters are electric vehicle charging and hydrogen electrolysis. Their modeling and control algorithm design mainly target resistive loads and electrolyzer loads, with constant voltage and constant power control being the primary control methods. Due to unequal currents flowing into and out of the midpoint of the bipolar multiphase interleaved buck converter, input voltage imbalance occurs, resulting in unequal voltage stresses on the upper and lower multiphase interleaved bucks. Currently, control methods for input voltage equalization can be mainly divided into three categories: duty cycle phase shifting, duty cycle offsetting, and external voltage balancer methods.

[0003] In the duty cycle phase shifting method, the output voltage controller is mainly used to output the duty cycle values ​​of the upper and lower sets of multi-phase interleaved bucks. d The phase shift controller is mainly used to output the duty cycle and phase shift angle of the upper and lower sets of multi-phase interleaved bucks. λ This achieves the goal of equalizing the input voltage. In the duty cycle offset method, based on the duty cycle reference value obtained by the output voltage controller, a duty cycle offset is obtained through the voltage equalization controller, thus making the duty cycles of the upper and lower multi-phase interleaved bucks different, thereby achieving voltage equalization. In the external voltage balancer method, a voltage balancer is added to the front stage of the topology, specifically for controlling input voltage equalization.

[0004] Because inductance values ​​cannot be made exactly the same during manufacturing, uneven current distribution can occur between phases in a multiphase buck converter without control. Currently, there are two main methods for current sharing in multiphase interleaved buck converters: average inductor current control and average current bus control. Average current bus control uses a dual closed-loop controller with an outer voltage loop and an inner current loop. However, the inner current loop uses the average inductor current, which cannot achieve self-current sharing; therefore, this method requires an additional current sharing controller. Average inductor current control uses a dual closed-loop controller with an outer voltage loop and an inner current loop. The inner current loop uses the inductor current as the control variable, thus achieving self-current sharing without the need for an additional current bus.

[0005] Furthermore, existing control methods for bipolar multiphase interleaved buck converters have the following shortcomings: 1. Currently, all bipolar multiphase interleaved buck converters are constant voltage sources, and there is no precedent for using them as constant current sources. 2. Currently, the loads of bipolar multiphase interleaved buck converters are mostly resistive loads or electrolytic cell loads, and they have not yet been applied to diode loads. 3. Currently, the input voltage uses equalization control, and proportional voltage control where the input voltage is proportional to the output voltage has not yet appeared.

[0006] Therefore, a control method for a bipolar multiphase interleaved buck converter that is voltage-balanced, has good current-sharing performance, and can operate stably is needed to solve the above-mentioned technical problems. Summary of the Invention

[0007] This invention provides the following technical solution: a duty cycle loop control method for a bipolar multiphase interleaved constant current source, comprising: a dual closed-loop controller and a proportional voltage controller; the dual closed-loop controller achieves precise control of the output current through average inductor current control; the dual closed-loop controller includes an output current controller and an inductor current controller, the output current controller achieves precise current control by monitoring the output current and comparing it with a reference value, and adjusting the conduction time of the switching device; the inductor current controller dynamically adjusts the switching state by monitoring the inductor current and comparing it with a target value to maintain the stability of the inductor current; the inductor current controller is also used for voltage equalization.

[0008] The output current controller ensures that the power supply output current is stable at the set value by adjusting the power supply output current; the inductor current controller maintains the stability of the inductor current by adjusting the current in the inductor; the output current controllers of the upper and lower buck circuits are combined into one output current controller.

[0009] The proportional voltage controller averages the buck duty cycle of the upper and lower channels. d avg1 , d avg2 During offset, the input voltage is stabilized by adding an additional duty cycle compensation value, thus achieving proportional control of the input voltage.

[0010] The modeling methods for the above control methods include: Modeling: Large-signal and small-signal modeling of the bipolar multiphase interleaved buck constant current source; The large-signal model is established that, under the condition of proportional voltage, the average duty cycle of the upper and lower multiphase interleaved bucks is the same in steady state. The small signal model is established as follows: (7) Preferably, the circuit topology controlled by the control method includes: an input power supply. V in ,capacitance Cin1 , C in2 , C o1 , C o2 ,inductance L 1~ L 6. Switching transistor Q 1a ~ Q 6a Switching transistor Q 1b ~ Q 6b The circuit connection of the circuit topology is as follows: capacitor C in1 , C in2 The two ends of the series connection are respectively connected to the input power supply. V in Both ends; switching transistor Q 1a , Q 1b The two ends of the series connection are respectively connected to capacitors. C in1 At both ends, the switching transistor Q 2a , Q 2b The two ends of the series connection are respectively connected to capacitors. C in1 At both ends, the switching transistor Q 3a , Q 3b The two ends of the series connection are respectively connected to capacitors. C in1 Both ends; switching transistor Q 4a , Q 4b The two ends of the series connection are respectively connected to capacitors. C in2 At both ends, the switching transistor Q 5a , Q 5b The two ends of the series connection are respectively connected to capacitors. C in2 At both ends, the switching transistor Q 6a , Q 6b The two ends of the series connection are respectively connected to capacitors. C in2 The two ends of the inductor; L 1. Capacitor C o1 Series inductor L1 is connected to the floating end of the switching transistor. Q 1a , Q 1b Connection nodes, inductors L 1. Capacitor C o1 series capacitor C o1 floating terminal capacitor C in1 , C in2 Connection nodes; inductors L The two ends of 2 are connected to the switching transistors respectively. Q 2a , Q 2b Connection nodes and inductors L 1. Capacitor C o1 Connection nodes, inductors L The two ends of 3 are connected to the switching transistors respectively. Q 3a , Q 3b Connection nodes and inductors L 1. Capacitor C o1 Connection nodes; inductors L 4. Capacitor C o2 Series inductor L 4 is connected to the floating end of the switch transistor. Q 4a , Q 4b Connection nodes, inductors L 4. Capacitor C o2 series capacitor C o2 floating terminal capacitor C in1 , C in2 Connection nodes; inductors L The two ends of 5 are connected to the switching transistors respectively. Q 5a , Q 5b Connection nodes and inductors L 4. Capacitor C o2 Connection nodes, inductors L The two ends of 6 are connected to the switching transistors respectively. Q 6a , Q 6b Connection nodes and inductors L 4. CapacitorC o2 The connection node.

[0011] Preferably, in the proportional voltage controller, the input signal d avg1 , d avg2 After passing through an adder, the signal is multiplied by 0.5 to obtain the intermediate signal d. bus In a proportional voltage controller, the intermediate signal d bus With input signal d avg1 Subtraction, through a transfer function G d (s), finally obtaining the output signal d com .

[0012] Preferably, in the output current controller, the two input signals are the actual output current I. o1 and I o2 I o1 and I o2 The signals are superimposed using an adder; the other input signal is then amplified by a gain of 2 and combined with I. o1 and I o2 Subtracting the superposition results, the final difference signal is obtained through G. io (s) Calculate the duty cycle d.

[0013] Preferably, the inductor current controller includes six independent inductor current control modules, each consisting of a multiplier and a transfer function block G. iL (s) Composition; Inductor current control modules correspond to inductor current I respectively. L1 ~I L6 Each inductor current control module multiplies the input signal with the corresponding inductor current via a multiplier, and then passes the result through the transfer function block G. iL (s) is processed.

[0014] The beneficial effects of this invention are: 1. This invention maintains stable input voltage during multi-phase Buck converter operation, preventing voltage imbalance. Simultaneously, the converter's output current remains stable at the set reference current with minimal ripple, achieving excellent current sharing.

[0015] 2. Total input voltage of the converter of this invention V in When a disturbance occurs, the system can operate stably both before and after the change. Attached Figure Description

[0016] Figure 1 This is a schematic diagram of the constant current source principle of the duty cycle loop control method of a bipolar multiphase interleaved constant current source according to the present invention. Figure 2 This is a diagram illustrating the average inductor current control method of the proportional voltage controller of the present invention; Figure 3 This is a waveform diagram of the input voltage imbalance without the addition of a proportional voltage controller according to the present invention; Figure 4 This is the steady-state waveform diagram of the present invention without considering the differences in inductance and load parameters; Figure 5 This is a transient waveform diagram of the present invention without considering differences in inductance and load parameters; Figure 6 This is a steady-state waveform diagram of the present invention considering the differences in inductance and load parameters. Detailed Implementation

[0017] The related technologies of the present invention will be clearly and completely described below with reference to the accompanying drawings of the embodiments of the present invention. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative effort are within the scope of protection of the present invention.

[0018] like Figures 1-6 As shown in the figure, this embodiment first performs large-signal modeling and small-signal modeling for a bipolar multiphase interleaved buck constant current source. Figure 1 The circuit topology and notation system used in this embodiment are as follows: V in1 and V in2 These represent the input voltages of the upper and lower bucks, respectively. I Lk Represents the inductor current of each circuit. V o1 and V o2 These represent the output voltages of the upper and lower buck converters, respectively. I o1 and I o2 These represent the output current of the upper and lower paths, respectively. C in1 and C in2 These represent the input capacitors of the upper and lower buck circuits, respectively. L k These represent the inductance values ​​of each circuit. C o1 and C o2 These represent the output capacitors of the upper and lower buck circuits, respectively. V inThis represents the input voltage of a bipolar multiphase interleaved buck.

[0019] Since the actual load of the laser power supply is a pump source, its load characteristics are similar to those of a diode. Therefore, a diode load is used instead in the analysis. To enable subsequent topology modeling, the diode load needs to be modeled first. The load characteristics of the diode can be described by equation (1), where... V 1 and V 2 represents the cutoff voltage of the upper and lower Buck diode loads. R 1 and R 2 represents the on-resistance of the upper and lower Buck diode loads.

[0020] (1) The large-signal model of this topology is established below. Since the output power equals the input power, equation (2) can be obtained. Because the inputs of this topology are cascaded, therefore... I in1 = I in2 Furthermore, because constant current control is performed... I o1 = I o2 Therefore, equation (3) can be further obtained from equation (2), which means that the input voltage is proportional to the output voltage. Therefore, equal voltage control can no longer be used in the control process, but proportional voltage control should be used instead.

[0021] (2) (3) The steady-state equation for a bipolar multiphase interleaved buck can be obtained from the steady-state formula of a regular buck, as shown in equation (4). Wherein, D 1avg and D 2avg These represent the average duty cycle values ​​of the upper and lower multiphase interleaved bucks in steady state. Combining equations (3) and (4), we can obtain equation (5) in steady state, which means that under the condition of proportional voltage, the average duty cycle values ​​of the upper and lower multiphase interleaved bucks in steady state should be the same.

[0022] (4) (5) The following establishes a small-signal model for this topology, and the state-averaged equation for this topology is shown in equation (6), where r LkLet be the inductance and resistance of each phase. Then, linearization is performed near the steady-state point to obtain the small-signal model of the topology, as shown in equation (7).

[0023] (6) (7) Since the differences in inductance, inductance resistance, and diode load characteristics are small in actual circuits, it is assumed that the inductance and inductance resistance values ​​of each phase are the same, and the diode load characteristics of the upper and lower bucks are also the same, in order to simplify the derivation process. Under this premise, after rearranging equation (7), several important conclusions can be obtained as shown in equations (8)-(10).

[0024] (8) in, V inavg This represents the average input voltage of the upper and lower buck converters. d avg1 and d avg2 This represents the average duty cycle of the upper and lower bucks.

[0025]

[0026] (9) Equations (8)-(9) are mainly the conclusions obtained for the first buck. The conclusions for the second buck are similar and are not given here. From equation (8), the disturbance value of the input voltage of the first buck can be found. Only the difference between the average duty cycle of the upper and lower bucks The disturbance value of the total input voltage of the converter This is relevant. Therefore, without considering the total input voltage disturbance, it can be controlled... To control the input voltage of the upper and lower bucks to prevent them from... Figure 3 The voltage instability condition is shown.

[0027] According to equation (9), the output current disturbance value of the first buck can be found. Only the average duty cycle of the first-way buck and the input voltage disturbance value of the first buck Therefore, when designing an output current controller, the average duty cycle can be controlled. To adjust the output current.

[0028] Based on the above conclusions, this implementation method uses the following... Figure 2The control method shown in the figure uses average inductor current control in the dual closed-loop controller. (Refer to...) Figure 6 The inductor current controller can achieve self-equalization of inductor current.

[0029] According to equation (5), it can be found that the average duty cycle of the upper and lower bucks is the same in steady state, that is... D avg1 = D avg2 ,therefore Figure 2 The output current controllers of the upper and lower buck circuits are combined into a single output current controller, reducing loop calculations in the control process.

[0030] In order to solve the voltage imbalance problem, Figure 2 A proportional voltage controller has been added, which can... d avg1 and d avg2 During offset, an additional duty cycle compensation value is added to stabilize the input voltage, thereby achieving proportional control of the input voltage and preventing offsetting. Figure 3 The voltage imbalance shown is illustrated.

[0031] Without adding an additional proportional voltage controller, the following will occur: Figure 3 The input voltage imbalance shown will eventually lead to the collapse of the entire control system.

[0032] Figure 4 This diagram illustrates the steady-state input voltage, output current, and inductor current waveforms of the upper and lower multiphase buck converters, without considering differences in inductance and load parameters. The diagram shows that the input voltages of the upper and lower buck converters remain stable during operation, without exhibiting the characteristics seen in other diagrams. Figure 3 The voltage imbalance problem is shown. Meanwhile, the converter's output current remains stable at the set reference current of 60A, with a ripple of only 0.0001A. The six-phase inductor currents in the diagram achieve good current sharing.

[0033] Figure 5 This demonstrates the total input voltage of the converter without considering differences in inductance and load parameters. V in The waveforms of dynamic input voltage, output current, and inductor current of the upper and lower multiphase buck converters during a disturbance are shown in the figure. The total input voltage of the converter at 50ms is also shown. V in The voltage was increased from 800V to 900V. It can be seen that the system operates stably both before and after the change. Furthermore, because this control method is a dual-closed-loop control, its dynamic performance is good, significantly reducing the overshoot of the output current during transient processes when the input voltage changes.

[0034] Figure 6 This demonstrates the steady-state input voltage, output current, and inductor current waveforms of the upper and lower multiphase Buck converters, considering differences in inductance and load parameters. (The inductor and resistor are then discussed.) r L1 Compared to other inductors and resistors, increasing the resistance by 10% will reduce the on-resistance of the diode load in the first multiphase buck converter. R 1 increases by 10%. Because... R 1 compared to R 2 increased by 10%, therefore controlling the output current I o1 and I o2 Under the same conditions, the output voltage can be obtained according to equation (1). V o1 Should be greater than V o2 Therefore, the input voltage can be obtained according to the proportional voltage relationship (3). V in1 It should also be greater than V in2 As can be seen from the graph, the input voltage V in1 and V in2 It can satisfy the proportional voltage relationship and remain stable during operation, with a stable output current. I o1 and I o2 All currents can be kept stable at the set 60A, with a ripple of only 0.0001A. The inductor current can also achieve good current sharing effect and is not affected by the difference in inductor parameters.

[0035] In summary, the duty cycle loop control method for the bipolar multiphase interleaved constant current source of this invention demonstrates excellent performance and stability in practical applications. Its unique proportional voltage control design ensures stable system operation even when faced with differences in inductance and load parameters, effectively avoiding voltage imbalance and output current fluctuations. Particularly when the total input voltage is disturbed, this control method rapidly adjusts the duty cycle through a dual closed-loop control strategy, ensuring a smooth transition of the output current, significantly reducing overshoot, and improving the system's dynamic response. Furthermore, this control method simplifies the control structure and reduces loop calculations by merging the output current controller, further enhancing the overall system efficiency and reliability. Therefore, this duty cycle loop control method for the bipolar multiphase interleaved constant current source has broad application prospects and significant practical value in the field of power electronics.

[0036] It should be emphasized that the above are merely preferred embodiments of the present invention and are not intended to limit the present invention in any way. Any simple modifications, equivalent changes and alterations made to the above embodiments based on the technical essence of the present invention shall still fall within the scope of the technical solution of the present invention.

Claims

1. A duty cycle loop control method for a bipolar multiphase interleaved constant current source, characterized by, Comprise: Double closed-loop controller, proportional voltage controller; The double closed-loop controller realizes accurate control of output current through average inductance current control; the double closed-loop controller comprises an output current controller and an inductance current controller, the output current controller realizes accurate control of current by monitoring output current and comparing with a reference value to adjust the on-time of a switching device, the inductance current controller dynamically adjusts switching state by monitoring inductance current and comparing with a target value to maintain stability of inductance current, and the inductance current controller is also used for voltage equalization; The output current controller adjusts the current output by the power supply to ensure that the output current of the power supply is stable at a set value; the inductance current controller adjusts the current in the inductance to maintain stability of the inductance current; The output current controllers of the upper and lower buck circuits are combined into one output current controller; The proportional voltage controller stabilizes the input voltage by increasing an additional duty cycle compensation value when the input voltage is shifted d avg1 、 d avg2 The proportional voltage controller stabilizes the input voltage by increasing an additional duty cycle compensation value when the input voltage is shifted 2. The duty cycle loop control method of a bipolar multiphase interleaved constant current source according to claim 1, wherein, The control method controls a circuit topology including: an input power source V in a capacitor C in1 , C in2 , C o1 , C o2 an inductor L 1- L 6, a switch tube Q 1a - Q 6a a switch tube Q 1b - Q 6b ; the circuit connection of the circuit topology is that: the two ends of the capacitor C in1 , C in2 after being connected in series are connected to the two ends of the input power source V in ; the two ends of the switch tube Q 1a , Q 1b after being connected in series are connected to the two ends of the capacitor C in1 , the two ends of the switch tube Q 2a , Q 2b after being connected in series are connected to the two ends of the capacitor C in1 , the two ends of the switch tube Q 3a , Q 3b after being connected in series are connected to the two ends of the capacitor C in1 ; the two ends of the switch tube Q 4a , Q 4b after being connected in series are connected to the two ends of the capacitor C in2 , the two ends of the switch tube Q 5a , Q 5b after being connected in series are connected to the two ends of the capacitor C in2 , the two ends of the switch tube Q 6a , Q 6b after being connected in series are connected to the two ends of the capacitor C in2 end of 1; inductor L 1, capacitor C o1 inductor after series connection L 1, switch tube connected to open end of Q 1a , Q 1b connection node of 1; inductor L 1, capacitor C o1 capacitor after series connection C o1 capacitor connected to open end of 1 C in1 , C in2 connection node of 1; inductor L 2, switch tube connected to each end of Q 2a , Q 2b connection node of 1 and inductor L 1, capacitor C o1 connection node of 1; inductor L 3, switch tube connected to each end of Q 3a , Q 3b connection node of 1 and inductor L 1, capacitor C o1 connection node of 1; inductor L 4, capacitor C o2 inductor after series connection L 4, switch tube connected to open end of Q 4a , Q 4b connection node of 1; inductor L 4, capacitor C o2 capacitor after series connection C o2 capacitor connected to open end of 1 C in1 , C in2 connection node of 1; inductor L 5, switch tube connected to each end of Q 5a , Q 5b connection node of 1 and inductor L 4, capacitor C o2 connection node of 1; inductor L 6, switch tube connected to each end of Q 6a , Q 6b Connection node and inductance of L 4, Capacitance C o2 Connection node.

3. The duty cycle loop control method of a bipolar multiphase interleaved constant current source according to claim 1, wherein, In the proportional voltage controller, the input signal d avg1 , d avg2 passes through an adder and is then multiplied by 0.5 to obtain an intermediate signal d bus ; In the proportional voltage controller, the intermediate signal d bus is formed by subtracting the input signal d avg1 from a transfer function G d (s) and finally the output signal d com is obtained.

4. The duty cycle loop control method of a bipolar multiphase interleaved constant current source according to claim 1, wherein, The output current controller, two input signals are actual output current I o1 and I o2 , the I o1 and I o2 superimposed by an adder; another input signal after a gain of 2 amplifier, and I o1 and I o2 superimposed result minus the final difference signal through G io (s) to calculate the duty cycle d.

5. The duty cycle loop control method of a bipolar multiphase interleaved constant current source according to claim 1, wherein, The inductance current controller includes six independent inductance current control modules, each of which is composed of a multiplier and a transfer function block G iL (s) consisting of; The inductance current control module corresponds to inductance current I L1 ~I L6 ; Each inductor current control module multiplies the input signal by the corresponding inductor current through a multiplier iL (s) is processed.

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