Current Sharing Method for Four-Phase Interleaved Parallel High-Gain Boost Converter

Abstract

The present invention discloses a current sharing method for a four-phase interleaved parallel high-gain Boost converter. Under the condition of average phase shift, based on the principle of capacitor charge and discharge balance, a current sharing method for a four-phase interleaved parallel high-gain Boost converter is designed to expand the duty cycle range of current sharing for each phase of the converter. Compared with the current sharing strategies of other multi-phase interleaved parallel high-gain Boost converters, the control strategy design and online implementation are simpler. Based on this current sharing method, a discrete mathematical model of a periodic converter with a unified structure description can be established for the design of the converter model predictive control strategy.

Description

Technical Field

[0001] The present invention belongs to the technical field of power electronics, and particularly relates to a current sharing method for a four-phase interleaved parallel high-gain Boost converter. Background Art

[0002] For a traditional Boost boost converter, due to the existence of parasitic parameters of components and the equivalent series impedance of the circuit, when the duty cycle value reaches a certain level, its voltage gain will no longer increase. Generally, it is only used in some low-power and low-voltage application scenarios. With the development of multiple power conversion fields such as energy storage systems and photovoltaic power generation in the new energy industry, the Boost converter plays an important role in energy conversion and transmission. These fields all require a converter with high efficiency and high boost capability to boost the voltage to the required voltage level;

[0003] A multi-phase interleaved parallel high-gain Boost converter, also known as an extended duty cycle boost converter, is a non-isolated converter with high boost capability. Under traditional phase shift control, each phase of the multi-phase Boost high-gain converter is evenly phase-shifted. The converter will enter different working regions as the duty cycle changes, and the automatic current sharing characteristic of each phase of the converter only exists within a limited duty cycle range [(M - 1) / M, 1), where M is the number of phases. Therefore, the four-phase interleaved parallel high-gain Boost converter can only achieve automatic current sharing among phases within the range of [3 / 4, 1);

[0004] The limited automatic current sharing range greatly restricts the application range of the converter. To improve the application ability of the converter, a current sharing strategy for the multi-phase interleaved parallel high-gain Boost converter has been proposed. The method of adjusting the duty cycle of each phase according to the working region to achieve current sharing among phases is only applicable to converters with a lower number of phases (three phases and below). For converters with a higher number of phases (more than three phases), such a method is difficult to apply. The variable phase shift current sharing control strategy applicable to converters with a higher number of phases can achieve current sharing among phases within a wide duty cycle range. However, since the phase shift angles of each phase are different, it will increase the difficulty of designing a periodic voltage control strategy for the converter system based on a model. Because based on the variable phase shift current sharing control strategy, during the dynamic regulation process of the converter or when the duty cycle is set differently, the working mode division of each cycle is not unified. Therefore, a discrete mathematical model with a unified structure description for each cycle cannot be constructed, and model-based predictive control design for the converter cannot be carried out. Summary of the Invention

[0005] The object of the present invention is to provide a current sharing method for a four-phase interleaved parallel high-gain Boost converter, so as to solve the problems existing in the prior art that the existing current sharing strategies for multi-phase interleaved parallel high-gain Boost converters are complex in design and implementation, and a periodic discrete mathematical model with a unified structure description cannot be established based on the current sharing strategy for model predictive control strategy design.

[0006] The technical solution adopted by the present invention is a current sharing method for a four-phase interleaved parallel high-gain Boost converter, which is specifically implemented according to the following steps:

[0007] Step 1, set the interval range of the four-phase duty cycles and perform average phase shift triggering for the four phases;

[0008] Step 2, divide the working process of the converter in one cycle into 8 modes;

[0009] Step 3, analyze the charging and discharging times and charging and discharging currents of the capacitors in each mode obtained in Step 2 respectively;

[0010] Step 4, establish the charge and discharge balance equations of each capacitor in one cycle respectively;

[0011] Step 5, solve the charge and discharge balance equations established in Step 4 simultaneously to obtain the setting method of the duty cycle of each of the four phases.

[0012] The characteristics of the present invention also lie in:

[0013] Among them, in Step 1, the four-phase duty cycles are d 1 , d 2 , d 3 and d 4 , and the interval ranges of d 1 , d 2 , d 3 and d 4 are all (2 / 4, 3 / 4), and average phase shift triggering is performed for the four phases, and the phase shift angle θ is 90°;

[0014] Among them, in Step 2, the working process of the converter in one cycle is divided into 8 modes, which are 1011, 1001, 1101, 1100, 1110, 0110, 0111 and 0011 respectively;

[0015] Among them, Step 3 is specifically as follows: The switching capacitors in the converter circuit are C 1 , C 2 and C 3 , and the charging and discharging times and charging and discharging currents of the switching capacitors C 1 , C 2 and C 3 in the 8 modes are respectively:

[0016] "1011" mode: Capacitor C 1 discharges, and the discharge current is i L2 , capacitor C 2 charges, and the charging current is i L2 , and the mode duration is d 3 T - T / 2;

[0017] "1001" mode: Capacitor C 1 discharges, and the discharge current is i L2 , capacitor C 2 discharges, and the discharge current is i L3 , capacitor C 3 charges, and the charging current is (i L2 +i L3 ), and the mode duration is 3T / 4 - d 3 T;

[0018] "1101" mode: Capacitor C 2 discharges, and the discharge current is i L3 , capacitor C 3 charges, and the charging current is i L3 , and the mode duration is d 4 T - T / 2;

[0019] "1100" mode: Capacitor C 2 discharges, and the discharge current is i L3 , capacitor C 3 discharges, and the discharge current is i L4 , and the mode duration is 3T / 4 - d 4 T;

[0020] "1110" mode: Capacitor C 3 discharges, and the discharge current is i L4 , and the mode duration is d 1 T - T / 2;

[0021] "0110" mode: Capacitor C 1 charges, and the charging current is i L1 , capacitor C 3 discharges, and the discharge current is i L4 , and the mode duration is 3T / 4 - d 1 T;

[0022] "0111" mode: Capacitor C 1 charges, and the charging current is i L1 , and the mode duration is d 2 T - T / 2;

[0023] "0011" mode: Capacitor C 1 discharges, and the discharge current is iL2 , capacitor C 2 is charged, and the charging current is (i L1 + i L2 ), and the modal duration is 3T / 4 - d 2 T;

[0024] Among them, the charge-discharge balance equations in step 4 are respectively:

[0025] The charge-discharge balance equation of capacitor C 1 is as shown in Equation (1):

[0026]

[0027] The charge-discharge balance equation of capacitor C 2 is as shown in Equation (2):

[0028]

[0029] The charge-discharge balance equation of capacitor C 3 is as shown in Equation (3):

[0030]

[0031] Among them, the charge-discharge balance equations in step 5 are respectively: By simultaneously solving the charge-discharge balance equations (1) to (3) established in step 4, a method for setting the duty cycle of each phase is obtained. As shown in Equation (4), the current sharing method of the four-phase interleaved parallel high-gain Boost converter with the duty cycle range in (2 / 4, 3 / 4) under the average phase shift is obtained:

[0032]

[0033] The beneficial effects of the present invention are:

[0034] The current sharing method of the four-phase interleaved parallel high-gain Boost converter of the present invention is a current sharing method of a four-phase interleaved parallel high-gain Boost converter designed based on the principle of capacitor charge-discharge balance under the condition of average phase shift, which expands the duty cycle range of current sharing of each phase of the converter. Compared with the current sharing strategies of other multi-phase interleaved parallel high-gain Boost converters, the control strategy design and online implementation are simpler. Based on this current sharing method, a periodic converter discrete mathematical model with a unified structure description can be established for the design of the converter model predictive control strategy. BRIEF DESCRIPTION OF THE DRAWINGS

[0035] Figure 1 is the circuit of the four-phase interleaved parallel high-gain Boost converter in the current sharing method of the four-phase interleaved parallel high-gain Boost converter of the present invention;

[0036] Figure 2The trigger signal waveform of the average phase shift of the duty cycle of the converter in the range of (2 / 4, 3 / 4) in the current sharing method of the four-phase interleaved parallel high-gain Boost converter of the present invention;

[0037] Figure 3 The four-phase current sharing inductor current waveform of the average phase shift of the duty cycle of the converter in the range of (2 / 4, 3 / 4) in the current sharing method of the four-phase interleaved parallel high-gain Boost converter of the present invention. Detailed implementation manners

[0038] The present invention will be described in detail below with reference to the accompanying drawings and specific implementation manners.

[0039] The present invention provides a current sharing method for a four-phase interleaved parallel high-gain Boost converter. The circuit of the four-phase interleaved parallel high-gain Boost converter is as Figure 1 shown, Figure 1 wherein, U in is the input voltage of the converter circuit, L 1 , L 2 , L 3 , L 4 are inductors, i L1 , i L2 , i L3 , i L4 are inductor currents, VD 1 , VD 2 , VD 3 , VD 4 are diodes, S 1 , S 2 , S 3 , S 4 are power switch devices, C 1 , C 2 , C 3 are switching capacitors, U C1 , U C2 , U C3 are switching capacitor voltages, C out is the output filter capacitor, U Cout is the output filter capacitor voltage, and R is the load; The specific implementation is carried out according to the following steps:

[0040] Step 1, set the ranges of the four-phase duty cycles d 1 , d 2 , d 3 and d 4 to be all (2 / 4, 3 / 4), and perform four-phase trigger average phase shift with a phase shift angle θ of 90°; As Figure 2 shown, Figure 2 wherein, 1 represents high level, 0 represents low level, T is the switching period, and d 1 is the first-phase power switch device S1 Duty cycle of, d 2 is the second-phase power switch device S 2 Duty cycle of, d 3 is the third-phase power switch device S 3 Duty cycle of, d 4 is the fourth-phase power switch device S 4 Duty cycle of, θ is the phase-shift angle;

[0041] Step 2: According to the Figure 2 trigger setting, the working process of the converter in one cycle is divided into 8 modes, which are 1011, 1001, 1101, 1100, 1110, 0110, 0111, and 0011 respectively;

[0042] Step 3: Analyze the Figure 1 capacitors C 1 , C 2 and C 3 charging and discharging times and charging and discharging currents as follows:

[0043] "1011" mode: Capacitor C 1 discharges, and the discharge current is i L2 , capacitor C 2 charges, and the charging current is i L2 , and the mode duration is d 3 T - T / 2;

[0044] "1001" mode: Capacitor C 1 discharges, and the discharge current is i L2 , capacitor C 2 discharges, and the discharge current is i L3 , capacitor C 3 charges, and the charging current is (i L2 + i L3 ), and the mode duration is 3T / 4 - d 3 T;

[0045] "1101" mode: Capacitor C 2 discharges, and the discharge current is i L3 , capacitor C 3 charges, and the charging current is i L3 , and the mode duration is d 4 T - T / 2;

[0046] "1100" mode: Capacitor C 2 discharges, and the discharge current is i L3 , capacitor C 3 discharges, and the discharge current is i L4 , and the mode duration is 3T / 4 - d 4T;

[0047] "1110" mode: Capacitor C 3 discharges, and the discharge current is i L4 , and the mode duration is d 1 T - T / 2;

[0048] "0110" mode: Capacitor C 1 charges, and the charging current is i L1 , and capacitor C 3 discharges, and the discharge current is i L4 , and the mode duration is 3T / 4 - d 1 T;

[0049] "0111" mode: Capacitor C 1 charges, and the charging current is i L1 , and the mode duration is d 2 T - T / 2;

[0050] "0011" mode: Capacitor C 1 discharges, and the discharge current is i L2 , and capacitor C 2 charges, and the charging current is (i L1 +i L2 ), and the mode duration is 3T / 4 - d 2 T;

[0051] Step 4, respectively establish the charge-discharge balance equations of capacitors C 1 , C 2 and C 3 within one period:

[0052] The charge-discharge balance equation of capacitor C 1 is shown in Equation (1):

[0053]

[0054] The charge-discharge balance equation of capacitor C 2 is shown in Equation (2):

[0055]

[0056] The charge-discharge balance equation of capacitor C 3 is shown in Equation (3):

[0057]

[0058] Step 5: Simultaneously solve the charge-discharge balance equations (1)-(3) established in Step 4 to obtain the setting method for the duty cycle of each of the four phases, as shown in Equation (4), and thus obtain the current sharing method for the four-phase interleaved parallel high-gain Boost converter with the duty cycle range within (2 / 4, 3 / 4) under average phase shift:

[0059]

[0060] Figure 3 is the inductor current waveform of the four-phase interleaved parallel high-gain Boost converter with the duty cycle range within (2 / 4, 3 / 4) under the current sharing strategy of the present invention; the converter operating period T = 5 μs, the four-phase trigger signals have an average phase shift, the phase shift angle θ = 90°, the converter input power supply U in = 4 V, and the duty cycles of the four phases are d 1 = 0.65, d 2 = d 3 = d 4 = 0.7; Figure 3 The inductor current waveform in shows that by adopting the current sharing strategy of the present invention, the inductor current sharing can be achieved under the condition of average phase shift when the converter duty cycle is within the range of (2 / 4, 3 / 4). That is, by adopting the current sharing strategy of the present invention, the duty cycle range for the current sharing of the four phases of the four-phase interleaved parallel high-gain Boost converter under the average phase shift strategy can be extended from [3 / 4, 1) to (2 / 4, 1).

Claims

1. Current sharing method for four-phase interleaved parallel high-gain Boost converter Characterized in that It is specifically implemented according to the following steps: Step 1, set the interval range of the four-phase duty cycle, and perform average phase shift triggering for the four phases; The duty cycles of the four phases are respectively d 1 , d 2 , d 3 and d 4 , d 1 , d 2 , d 3 and d 4 , and the interval ranges of d , d , d , and d are all (2 / 4, 3 / 4). The four-phase trigger has an average phase shift, and the phase shift angle θ is 90 o ; Step 2, divide the working process of the converter in one cycle into 8 modes; In step 2, the working process of the converter in one cycle is divided into 8 modes, which are 1011, 1001, 1101, 1100, 1110, 0110, 0111 and 0011 respectively; Step 3, analyze the charging and discharging time and charging and discharging current of the capacitor in each mode obtained in step 2 respectively; Step 3 is specifically as follows: The switching capacitors in the converter circuit are C 1 , C 2 and C 3 . In 8 modes, the charging / discharging times and charging / discharging currents of the switching capacitors C 1 , C 2 and C 3 are respectively: "1011" mode: Capacitor C 1 discharges, and the discharge current is i L2 , and capacitor C 2 charges, and the charging current is i L2 , and the mode duration is d 3 T - T / 2; "1001" mode: Capacitor C 1 discharges, and the discharge current is i L2 , capacitor C 2 discharges, and the discharge current is i L3 , capacitor C 3 charges, and the charging current is ( i L2 + i L3 ), and the mode duration is 3T / 4 - d 3 T; "1101" mode: Capacitor C 2 discharges, and the discharge current is i L3 , and capacitor C 3 charges, and the charging current is i L3 , and the mode duration is d 4 T - T / 2; "1100” mode: Capacitor C 2 discharges, and the discharge current is i L3 , and capacitor C 3 discharges, and the discharge current is i L4 , and the mode duration is 3T / 4 - d 4 T; "1110” mode: Capacitor C 3 discharges, and the discharge current is i L4 , and the mode duration is d 1 T - T / 2; "0110” mode: Capacitor C 1 is charged, and the charging current is i L1 . Capacitor C 3 is discharged, and the discharging current is i L4 . The mode duration is 3T / 4 - d 1 T; "0111" mode: Capacitor C 1 is charged, and the charging current is i L1 , and the mode duration is d 2 T - T / 2; "0011” mode: Capacitor C 1 discharges, and the discharge current is i L2 , and capacitor C 2 charges, and the charging current is ( i L1 + i L2 ), and the mode duration is 3T / 4 - d 2 T; Step 4, establish the charge and discharge balance equations of each capacitor in one cycle respectively; The charge and discharge balance equations are respectively: Capacitor C 1 The charge-discharge balance equation is as shown in Equation (1): 　　　　　　　　　（1） Capacitor C 2 The charge and discharge balance equation is shown in Equation (2) as follows: 　　（2） Capacitor C 3 The charge and discharge balance equation is shown in Equation (3) as follows: 　　（3） Step 5, solve the charge and discharge balance equations established in step 4 simultaneously to obtain the setting method of the duty cycle of each of the four phases; The charge and discharge balance equations are respectively: Solve the charge and discharge balance equations (1) to (3) established in step 4 simultaneously to obtain the setting method of the duty cycle of each of the four phases. As shown in formula (4), the current sharing method of the four-phase interleaved parallel high-gain Boost converter with the duty cycle range within (2 / 4, 3 / 4) under average phase shift is obtained: 　　　　　　　　　　（4） Under the average phase shift strategy, the duty cycle range of current sharing of the four phases of the four-phase interleaved parallel high-gain Boost converter can be extended from [3 / 4, 1) to (2 / 4, 1).

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