CN-118868618-B - Modulation method for critical conduction of Boost circuit and electronic equipment

Abstract

The invention discloses a modulation method for critical conduction of a Boost circuit and electronic equipment. The Boost circuit critical conduction modulation method is applied to a two-stage photovoltaic inverter, the two-stage photovoltaic inverter comprises a front-stage Boost circuit, the front-stage Boost circuit comprises a first Boost inductor, a first switching tube and a first freewheeling diode, the Boost circuit critical conduction modulation method comprises the steps of calculating a carrier cycle of the first switching tube according to a reference current of the first Boost inductor and a Boost duty ratio of the front-stage Boost circuit, calculating a carrier value of the first switching tube according to the carrier cycle of the first switching tube, determining a carrier of the first switching tube according to the carrier value of the first switching tube, and comparing the carrier of the first switching tube with the Boost duty ratio of the front-stage Boost circuit to generate a switching signal of the first switching tube. The invention reduces the loss, has simple circuit structure, does not increase the cost and has high reliability.

Inventors

• CAO XUEQIAN
• ZHOU XU
• ZHANG YULIN

Assignees

• 上海正泰电源系统有限公司
• 深圳正泰电源系统有限公司

Dates

Publication Date

20260505

Application Date

20240703

Claims (10)

1. 1. The modulation method for critical conduction of the Boost circuit is applied to a two-stage photovoltaic inverter and is characterized in that the two-stage photovoltaic inverter comprises a front-stage Boost circuit, the front-stage Boost circuit comprises a first Boost inductor, a first switching tube and a first free-wheeling diode, the first switching tube is connected with a photovoltaic module and a rear-stage inverter circuit, the first Boost inductor is connected between the photovoltaic module and the first switching tube, and the first free-wheeling diode is connected between the first switching tube and the rear-stage inverter circuit; the modulation method for critical conduction of the Boost circuit comprises the following steps: calculating the carrier period of the first switching tube according to the reference current of the first Boost inductor and the Boost duty ratio of the front-stage Boost circuit; calculating the carrier value of the first switching tube according to the carrier period of the first switching tube; and determining the carrier wave of the first switching tube according to the carrier wave value of the first switching tube, and comparing the carrier wave of the first switching tube with the boosting duty ratio of the front-stage Boost circuit to generate a switching signal of the first switching tube.
2. 2. The method of claim 1, wherein the carrier period of the first switching tube is calculated as follows: Wherein, T b is the carrier period, L b1 is the first Boost inductor, I Lbref is the reference current of the first Boost inductor, d is the Boost duty cycle of the front-stage Boost circuit, and V pv is the photovoltaic input voltage.
3. 3. The method of claim 1, wherein said calculating the carrier value of the first switching tube from the carrier period of the first switching tube comprises: Judging whether the carrier flag bit is equal to 1, if so, accumulating the carrier value of the first switching tube; if not, the carrier value of the first switching tube is subtracted.
4. 4. The method of claim 3, wherein the accumulating the carrier values of the first switching tube further comprises: Judging whether the accumulated carrier value is greater than or equal to 1, if so, making the carrier value equal to 1 and the carrier flag bit equal to 0; and if not, generating the carrier wave of the first switching tube.
5. 5. A method according to claim 3, wherein the subtracting the carrier value of the first switching tube further comprises: judging whether the carrier value after the accumulation is smaller than or equal to 0, if so, enabling the carrier value to be equal to 0 and enabling the carrier flag bit to be equal to 1; and if not, generating the carrier wave of the first switching tube.
6. 6. The method of claim 1, wherein the pre-stage Boost circuit further comprises a second Boost inductor, a second switching tube, and a second freewheeling diode, the second switching tube being connected with the photovoltaic module and the post-stage inverter circuit, the second Boost inductor being connected between the photovoltaic module and the second switching tube, the second freewheeling diode being connected between the second switching tube and the post-stage inverter circuit; after the carrier of the first switching tube is determined according to the carrier value of the first switching tube, establishing a master-slave relation to generate the carrier of the second switching tube.
7. 7. The method of claim 6, wherein after generating the carrier of the second switching tube by establishing the master-slave relationship, further comprising comparing the carrier of the second switching tube with a Boost duty cycle of the pre-Boost circuit to generate the switching signal of the second switching tube.
8. 8. The method of claim 6, wherein the carrier wave of the first switching tube and the carrier wave of the second switching tube are triangular or saw-tooth waves.
9. 9. The method of claim 1, wherein comparing the carrier of the first switching tube with the Boost duty cycle of the pre-stage Boost circuit to generate the switching signal of the first switching tube comprises: The carrier wave of the first switching tube is larger than the boosting duty ratio of the front-stage Boost circuit, and a switching signal of the first switching tube is generated to be in a high level; and the carrier wave of the first switching tube is smaller than the boosting duty ratio of the front-stage Boost circuit, and the switching signal of the first switching tube is generated to be low level.
10. 10. An electronic device, comprising: One or more processors; A memory for storing one or more programs; When the one or more programs are executed by the one or more processors, the one or more processors implement the modulation method of Boost circuit critical conduction as claimed in any one of claims 1-9.

Description

Modulation method for critical conduction of Boost circuit and electronic equipment Technical Field The embodiment of the invention relates to the technical field of photovoltaic power generation, in particular to a modulation method for critical conduction of a Boost circuit and electronic equipment. Background Boost circuits are widely used in the communication field, renewable energy systems, automotive electronics and other fields due to their simple structure, easy control and high reliability. In recent years, the development of Boost circuits has been accelerated due to the development and application of wide bandgap semiconductor devices. However, the increase of the switching frequency will increase the switching loss proportionally, exacerbating the switching tube heating, resulting in reduced converter efficiency and reliability. Therefore, the switching loss is an important factor influencing the high-frequency and high-efficiency operation of the Boost circuit, and the research of the soft switching implementation method of the power switch device has important theoretical and application significance. The Boost circuit may operate in three different modes, namely a continuous conduction mode (Continuous Conduction Mode, CCM), a critical conduction mode (Boundary Conduction Mode, BCM), and an intermittent conduction mode (Discontinuous Conduction Mode, DCM). The critical conduction mode is that the current flowing through the inductor linearly drops to zero in one switching cycle, and then the switch is turned on again, so that the inductor current linearly rises. The Boost circuit in critical conduction mode has the characteristic that the free wheeling diode zero current (Zero current switch, ZCS) is turned off. When the current flowing through the freewheeling diode is reduced to zero crossing, the diode is naturally turned off, and meanwhile the switching tube ZCS is turned on, so that the conduction loss of the switching tube is reduced. Therefore, the power loss is effectively reduced, and the reliability of the switching tube and the freewheeling diode is greatly improved. The peak inductor current and the peak current flowing through the switching tube are twice the peak input current, so the method is not suitable for high-power occasions. For a Boost circuit in CCM, since the inductor current is continuous and cannot flow reversely, an auxiliary circuit is added to transfer the inductor current to other branches, so that conditions are provided for zero-current soft switching (Zero Current Switching, ZCS) of the main switching tube. In high power applications, the method is widely used. However, for medium and small power applications, the introduction of auxiliary circuits increases the cost of the Boost circuit, makes the circuit structure more complex, and reduces the reliability of the Boost circuit while causing additional loss. When the inductance current of the Boost circuit working under BCM and DCM is 0, the main switching tube is turned on, so that the switching loss can be reduced under the condition of no auxiliary circuit. Fig. 1 is a Boost circuit for a power factor corrector, and referring to fig. 1, fig. 1 exemplarily shows a case where the Boost circuit is a single-phase Boost circuit. In addition, interleaved parallel Boost circuits under BCM are also commonly used in power factor correction (Power Factor Correction, PFC) circuits. However, in this application, the effective value of the input voltage and the output voltage are approximately constant, and when the on-time of the switching tube is a constant value, the input current is proportional to the input voltage, and the input current naturally takes a sinusoidal shape, that is, power factor correction is achieved. For a two-stage photovoltaic inverter, the input voltage of the PV side (photovoltaic component) and the bus voltage of the output side of the front-stage Boost circuit are not constant voltage values, and if BCM conduction is to be realized, the conduction time of a switching tube and the switching frequency are changed, so that a common modulation method of carrier wave and modulation wave contrast cannot be adopted. Currently, there is a lack of BCM modulation methods based on the pre-Boost circuits used in two-stage photovoltaic inverters. Disclosure of Invention The invention provides a modulation method and electronic equipment for critical conduction of a Boost circuit, which have smaller inductance ripple, lower inductance current stress, lower loss, simple circuit structure, no increase of cost and high reliability. According to one aspect of the invention, the invention provides a modulation method for critical conduction of a Boost circuit, which is applied to a two-stage photovoltaic inverter, wherein the two-stage photovoltaic inverter comprises a front-stage Boost circuit, the front-stage Boost circuit comprises a first Boost inductor, a first switching tube and a first freewheeling dio