CN112467891B - IPT system efficiency optimization method based on full-bridge half-bridge switching - Google Patents

Abstract

The invention discloses an IPT system based on full-bridge and half-bridge switching and an efficiency optimization method thereof, belonging to the technical field of wireless charging, and aims to solve the problem of low efficiency of an inductive wireless power supply system under light load conditions. It includes the following steps: a. Establishing the fundamental wave equivalent model of the IPT system based on full-bridge and half-bridge switching; b. Analyzing the SS compensation IPT system efficiency model based on full-bridge and half-bridge switching; c. SS compensation IPT system control strategy. The method can switch the system to a half-bridge inverter mode and a full-bridge inverter mode when the system works under light load or heavy load, and can effectively improve energy transmission efficiency under light load conditions. The invention is applicable to an IPT system based on full-bridge and half-bridge switching and an efficiency optimization method thereof.

Description

An IPT system efficiency optimization method based on full-bridge and half-bridge switching

Technical Field

The present invention belongs to the technical field of wireless charging, and in particular relates to an IPT system based on full-bridge and half-bridge switching and an efficiency optimization method thereof.

Background Art

Inductance Power Transfer (IPT) technology is a power supply method that uses electromagnetic fields as a transmission medium to transfer energy from a power source to a load through magnetic coupling. IPT technology was first proposed by Professor M.Soljacic of the Massachusetts Institute of Technology and his research team. In 2008, it was listed by the Massachusetts Institute of Technology Technology Review as one of the top ten emerging technologies that will affect future development. The introduction of this technology has opened up a new direction for wireless power supply research and has triggered a research boom among scholars and companies in related fields at home and abroad. In recent years, research on IPT technology has achieved certain results. Due to its safety, reliability and flexibility, it has been widely used in electric vehicles, medical electronic equipment, consumer electronics and other fields, providing an efficient and reliable technical path for contactless power supply and wireless battery charging of electrical equipment.

The IPT system is mainly composed of an inverter, a resonant network, a magnetic coupling mechanism, and a rectifier. In most applications, due to changes in the power demand of the electrical equipment or changes in the battery charging state, the system load changes greatly, and it is necessary to dynamically close the loop of the receiving end converter to adapt to the system output power and voltage requirements. At the same time, in order to improve the economy and efficiency of the IPT system, while meeting the system output power and voltage requirements, the system volume and energy transmission efficiency should be considered.

Summary of the invention

The purpose of the present invention is to change the problem of low efficiency of the inductive wireless power supply system under light load conditions, and propose an IPT system based on full-bridge and half-bridge switching and its efficiency optimization method. The system switches the working mode of the inverter to ensure the load power demand while controlling the phase shift angle of the active rectifier at the receiving end and the AC voltage and current phase angle difference, thereby reducing the system converter switching loss and coil loss under light load conditions and improving the system energy transmission efficiency.

The technical solution adopted by the present invention is as follows:

An IPT system based on full-bridge and half-bridge switching includes a DC side voltage source U _in , a transmitting end, and a receiving end. The transmitting end includes a full-bridge inverter composed of four MOS tubes. Q ₁ , Q ₂ , Q ₃ , and Q ₄ are respectively four MOS tube switching signals of the transmitting end. The switching frequency of Q ₁ , Q ₂ , Q ₃ , and Q ₄ is f. The transmitting end is connected in parallel with a capacitor C _l1 and a capacitor C _l2 used as a third bridge arm. The transmitting end is also electrically connected to a switch S. The switch S is controlled to be closed/opened to realize the switching of the full-bridge and half-bridge inverters. The receiving end includes an active rectifier composed of four MOS tubes. Q ₅ , Q ₆ , Q ₇ , and Q ₈ are respectively four MOS tube switching signals of the receiving end. The switching frequency of Q ₅ , Q ₆ , Q ₇ , and Q ₈ is f. The receiving end is also electrically connected to a DC side filter capacitor C _d and a system load resistor R. It also includes a transmitting coil self-inductance L ₁ and a receiving coil self-inductance L ₂ , the mutual inductance M between the transmitting coil and the receiving coil, the compensation capacitor C ₁ of the self-inductance of the transmitting coil, the compensation capacitor C ₂ of the self-inductance of the receiving coil, and the compensation network of the compensation capacitor C ₁ and the compensation capacitor C ₂ adopts a series resonant compensation network structure.

An IPT system efficiency optimization method based on full-bridge and half-bridge switching comprises the following steps:

a. Establish the fundamental wave equivalent model of the IPT system based on full-bridge and half-bridge switching;

b. Analyze the efficiency model of SS compensation IPT system based on full-bridge and half-bridge switching;

c. Analyze the control strategy of the SS compensation IPT system based on full-bridge and half-bridge switching.

Furthermore, the steps of establishing the equivalent model in step a are as follows:

Step 1. List the matrix equation according to the fundamental wave equivalent circuit:

Step 2. Calculate the impedance matrix of the equation group based on the self-impedance and mutual impedance of each loop:

Step 3. Calculate the current expressions of the transmitting coil and the receiving coil:

Step 4. Calculate the rectifier output DC voltage:

Step 5. Calculate the rectifier input DC current:

Step 6. Calculate the equivalent impedance Z _L as

Furthermore, the steps of efficiency model analysis in step b are as follows:

Step 1. Calculate the output voltage _U1 and output current _I1 of the full-bridge inverter:

Step 2. Calculate the magnitude of the currents _I1 and _I2 in the transmitter and receiver coils in full-bridge inverter mode:

Step 3. Calculate the output voltage _U1 and output current _I1 of the half-bridge inverter:

Step 4. Calculate the magnitude of the currents _I1 and _I2 in the transmitting and receiving coils in the half-bridge inverter mode:

Furthermore, the steps of control strategy analysis in step c are as follows:

Step 1. In full-bridge inverter mode, when the system output voltage U _out is constant, calculate the rectifier phase shift angle α as:

Step 2. In the half-bridge inverter mode, when the system output voltage U _out is constant, calculate the rectifier phase shift angle α as:

In summary, due to the adoption of the above technical solution, the beneficial effects of the present invention are:

1. In the present invention, according to the working condition of the system (heavy load/light load), the system inverter is switched between full bridge and half bridge to reduce the switching loss and coil loss of the system converter under light load conditions, and improve the energy transmission efficiency of the system. To adjust the system gain. While ensuring the output power and voltage of the system, the system reduces the switching loss of the active rectifier and the reactive component of the system current under light load conditions. The experimental results show that compared with the traditional IPT system, the proposed IPT system can effectively improve the energy transmission efficiency of the system under a wide load range, providing a good reference for the design of the IPT system.

2. In the present invention, by controlling the phase shift angle of the active rectifier at the receiving end and the phase angle difference of the converted voltage and current, the ZVS operation of the system converter is achieved while maintaining the stability of the system output voltage.

BRIEF DESCRIPTION OF THE DRAWINGS

In order to more clearly illustrate the technical solutions of the embodiments of the present invention, the following briefly introduces the drawings required for use in the embodiments. It should be understood that the following drawings only illustrate certain embodiments of the present invention and should not be regarded as limiting the scope. For those skilled in the art, other related drawings can be obtained based on these drawings without creative work, among which:

Figure 1 is a structural diagram of an IPT system based on full-bridge and half-bridge switching;

FIG2 is a fundamental wave equivalent circuit diagram of an IPT system based on SS compensation topology;

FIG3 is a waveform diagram of the AC voltage, current and converter drive signal of the SS compensated IPT system.

DETAILED DESCRIPTION

In order to make the purpose, technical solutions and advantages of the embodiments of the present invention clearer, the technical solutions in the embodiments of the present invention will be clearly and completely described below in conjunction with the drawings in the embodiments of the present invention. Obviously, the described embodiments are part of the embodiments of the present invention, not all of the embodiments. Generally, the components of the embodiments of the present invention described and shown in the drawings here can be arranged and designed in various different configurations.

Therefore, the following detailed description of the embodiments of the present invention provided in the accompanying drawings is not intended to limit the scope of the claimed invention, but merely represents selected embodiments of the present invention. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

It should be noted that reference numerals and letters denote similar items in the following drawings, and therefore, once an item is defined in one drawing, further definition and explanation thereof is not required in subsequent drawings.

In the description of the present invention, it should be noted that the terms "center", "upper", "lower", "left", "right", "vertical", "horizontal", "inside", "outside", etc. indicate positions or positional relationships based on the positions or positional relationships shown in the accompanying drawings, or the positions or positional relationships in which the invented product is usually placed when in use. They are only simplified descriptions for the convenience of describing the present invention, and do not indicate or imply that the device or element referred to must have a specific position, be constructed and operated in a specific position, and therefore cannot be understood as limiting the present invention. In addition, the terms "first", "second", "third", etc. are only used to distinguish the descriptions, and cannot be understood as indicating or implying relative importance.

In addition, the terms "horizontal", "vertical" and the like do not mean that the components are required to be absolutely horizontal or suspended, but can be slightly tilted. For example, "horizontal" only means that its direction is more horizontal than "vertical", and does not mean that the structure must be completely horizontal, but can be slightly tilted.

In the description of the present invention, it is also necessary to explain that, unless otherwise clearly specified and limited, the terms "set", "install", "connect", and "connect" should be understood in a broad sense, for example, it can be a fixed connection, a detachable connection, or an integral connection; it can be a mechanical connection or an electrical connection; it can be a direct connection, or it can be indirectly connected through an intermediate medium, or it can be the internal communication of two components. For ordinary technicians in this field, the specific meanings of the above terms in the present invention can be understood according to specific circumstances.

An IPT system efficiency optimization method based on full-bridge and half-bridge switching comprises the following steps:

a. Establish the fundamental wave equivalent model of the IPT system with basic full-bridge and half-bridge switching;

b. Analyze the efficiency model of SS compensation IPT system based on full-bridge and half-bridge switching;

c. Analyze the control strategy of SS compensation IPT system based on full-bridge and half-bridge switching;

Furthermore, the steps of establishing the fundamental wave equivalent model of the IPT system of basic full-bridge and half-bridge switching in step a are as follows:

The series compensation IPT system based on full-bridge and half-bridge inverter switching is shown in Figure 1. U _in is the DC side voltage source. The transmitter uses a full-bridge inverter composed of four MOS tubes. Q ₁ -Q ₄ is its switching signal and the switching frequency is f. Two capacitors C _l1 and C _l2 are connected in parallel on the left side as the third bridge arm, where point a of the left MOS tube bridge arm is connected to the midpoint of the capacitor bridge arm through a switch S. The switch S can be controlled to switch the full-bridge and half-bridge inverters. L ₁ and L ₂ are the self-inductance of the transmitting coil and the receiving coil respectively, and M is the mutual inductance between the two coils. _{C 1} and C ₂ are the compensation capacitors of the self-inductance of the transmitting coil and the receiving coil respectively, and the compensation network adopts a series resonant (SS) compensation network structure. The receiving end uses an active rectifier composed of four MOS tubes. Q ₅ -Q ₈ is its switching signal and the switching frequency is f. _{C d} is the DC side filter capacitor and R is the system load resistor.

In the two working modes, the fundamental wave model of the AC side of the SS compensation IPT system based on full-bridge and half-bridge inverter can be equivalent to the same circuit, as shown in Figure 2.

When _L1 , _L2 resonate with _C1 , _C2 respectively, the relationship between the resonant network parameters and the switching frequency satisfies:

Ignoring parasitic resistance and switching loss, the matrix equation can be listed based on the fundamental wave equivalent circuit:

The impedance matrix of the system of equations consists of the self-impedance and mutual impedance of each loop:

Where ω = 2πf is the system operating angular frequency, and Z _L is the load equivalent impedance. Substituting equation (3) into equation (2), we can get the current expressions of the transmitting coil and the receiving coil:

The voltage and current waveforms of the system's transmitting and receiving ends, as well as the drive waveforms of the inverter and rectifier are shown in Figure 3. The receiving end uses an active rectifier, and its input voltage and current are expressed as:

Among them, _U2 is the voltage effective value of _u2 , _I2 is the current effective value of _i2 , _φv is the phase difference between the inverter output voltage and the rectifier input voltage; _φi is the phase difference between the inverter output current and the rectifier input current, and the relationship between them is:

Among them, β is the phase angle difference between the inverter output voltage and current. In addition, by controlling the phase shift angle α between the left and right bridge arms of the rectifier to adjust the output voltage amplitude, the rectifier output DC voltage can be expressed as:

In order to reduce the switching loss of the IPT system, the zero voltage switching (ZVS) state can be achieved by adjusting the phase angle difference β between the voltage and current at the rectifier input. At this time, the rectifier input DC current can be expressed as:

In order to ensure the soft switching state of the switch tube, β and α should satisfy:

It can be seen from formula (10) that in order to achieve a wide range of ZVS, the phase angle difference β needs to increase with the increase of the rectifier phase shift angle α. However, the increase of β will lead to an increase in reactive current at the transmitter, reducing the energy transmission efficiency of the system. When β = α/2, it is exactly the minimum phase angle difference required to achieve ZVS operation. In the subsequent modeling, this analysis will be based on this. At this time, Z _L can be expressed as:

Furthermore, the steps of analyzing the SS compensation IPT system model based on the full-bridge inverter in step b are as follows:

Depending on the state of switch S, the inverter will work in two modes. When S is disconnected and _Q1 ~ _Q4 output four complementary PWM waveforms, the inverter works in full-bridge inverter mode. Let the inverter output voltage phase be the reference phase, then its output voltage and current are:

Among them, _U1 is the voltage effective value of _u1 , and _I1 is the current effective value of _i1 . When the primary and secondary sides of the system are completely resonant, the phase angle difference between the rectifier input voltage and current is also β. The size of _U1 and _I1 can be calculated by the following formula:

Substituting equations (11), (14) and (15) into equation (4), we can obtain the magnitudes of the currents _I1 and _I2 in the transmitting and receiving coils:

When S is closed, _Q2 and _Q4 output two complementary PWM waveforms. When the signals of _Q1 and _Q3 are locked, the inverter works in half-bridge inverter mode. At this time, the size of _U1 and _I1 can be calculated by the following formula:

Substituting equations (18) and (19) into equation (4), we can obtain the magnitudes of the currents _I1 and _I2 in the transmitting and receiving coils:

Furthermore, the steps of analyzing the SS compensation IPT system model based on the half-bridge inverter in step c are as follows:

From equations (6), (8), (11) and (14), when the system output voltage _Uout is constant, the calculation formula for the rectifier phase shift angle α can be obtained:

It can be seen from equations (16) and (17) that in order to keep the system output voltage _Uout constant, the rectifier phase shift angle α will increase with the increase of the load resistance R. At the same time, the magnitude of the transmitting coil current _I1 will decrease with the increase of the load resistance R.

From equations (6), (8), (11) and (18), when the system output voltage U _out is constant, the calculation formula for the rectifier phase shift angle α can be obtained:

It can be seen from formula (21) that when the inverter works in the half-bridge inverter mode, under the condition of satisfying the system output voltage U _out , the rectifier phase shift angle α is smaller than when the inverter works in the full-bridge inverter mode, and thus the system switching loss and coil loss will also be smaller.

During the implementation of the present invention, when the inverter works in the full-bridge inverter mode, the system can obtain a larger receiving coil current _I2 , which is suitable for the heavy-load output mode of the IPT system; however, when the system is under light-load conditions, α and β need to be increased to adapt to the system power output requirements, which will increase the system power loss under light-load conditions; and when the inverter works in the half-bridge inverter mode, the receiving coil current _I2 is smaller, which can effectively reduce the system power loss under light-load conditions, but the maximum output power of the system is smaller at this time. In order to ensure the system power requirements under heavy-load conditions and improve the energy transmission efficiency of the system under light-load conditions, the working mode of the inverter can be switched, and the full-bridge inverter mode can be used under heavy load, and the half-bridge inverter mode can be used under light load.

The above are the embodiments of the present invention. The above are the preferred embodiments of the present invention. If the preferred implementation methods in each preferred embodiment are not obviously self-contradictory or based on a preferred implementation method, each preferred implementation method can be arbitrarily superimposed and used in combination. The embodiments and the specific parameters in the embodiments are only for the purpose of clearly describing the verification process of the invention, and are not used to limit the patent protection scope of the present invention. The patent protection scope of the present invention is still subject to its claims. Any equivalent structural changes made by using the contents of the description and drawings of the present invention should be included in the protection scope of the present invention.

Claims (1)

1. A method for optimizing the efficiency of an IPT system based on full-bridge and half-bridge switching, characterized in that it comprises the following steps: a. Establish the fundamental wave equivalent model of the IPT system based on full-bridge and half-bridge switching; b. Analyze the efficiency model of SS compensation IPT system based on full-bridge and half-bridge switching; c. Analyze the control strategy of SS compensation IPT system based on full-bridge and half-bridge switching; The steps of establishing the equivalent model in step a are as follows: Step 1. List the matrix equation according to the fundamental wave equivalent circuit:

Step 2. Calculate the impedance matrix of the equation group based on the self-impedance and mutual impedance of each loop:

Step 3. Calculate the current expressions of the transmitting coil and the receiving coil:

Step 4. Calculate the rectifier output DC voltage:

Step 5. Calculate the rectifier input DC current:

Step 6. Calculate the equivalent impedance Z _L as

The steps of efficiency model analysis in step b are as follows: Step 1. Calculate the output voltage _U1 and output current _I1 of the full-bridge inverter:

Step 2. Calculate the magnitude of the currents _I1 and _I2 in the transmitter and receiver coils in full-bridge inverter mode:

Step 3. Calculate the output voltage _U1 and output current _I1 of the half-bridge inverter:

Step 4. Calculate the magnitude of the currents _I1 and _I2 in the transmitting and receiving coils in the half-bridge inverter mode:

The steps of control strategy analysis in step c are as follows: Step 1. In full-bridge inverter mode, when the system output voltage U _out is constant, calculate the rectifier phase shift angle α as:

Step 2. In the half-bridge inverter mode, when the system output voltage U _out is constant, calculate the rectifier phase shift angle α as:

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