CN105914831B - Magnetic coupling resonant radio energy transmission system parameters design method based on SS topologys - Google Patents

Abstract

The invention discloses a parameter design method of a magnetic coupling resonant wireless power transmission system based on SS topology. In order to solve the problem of excessive peak power of the traditional two-stage charging, the method switches from constant current charging to constant voltage charging of a battery. The constant power charging stage is introduced; at the same time, in order to ensure the safe operation of the system and the high transmission efficiency, the input current of the primary side resonant network and the phase shift angle of the inverter are limited, and the three charging stages and the safe operation range are used to limit two The parameter relationship of the coupling coil inductance is determined to determine the value range of the two coupling coil inductances, which provides a reliable design criterion for the design of the resonant network parameters and ensures the safety and efficiency of the battery charging process. The invention satisfies the requirement that the magnetic coupling resonant wireless power transmission system is used for full-range charging of storage batteries.

Description

Parameter Design Method of Magnetically Coupled Resonant Wireless Power Transfer System Based on SS Topology

technical field

The invention relates to a parameter design method of a magnetic coupling resonance wireless power transmission system, in particular to a parameter design method of a magnetic coupling resonance wireless power transmission system based on SS topology.

Background technique

According to its realization principle, wireless power transmission technology can be divided into two categories: near field and far field. Near-field technology is easy to achieve higher efficiency and greater power, so it is widely used in wireless charging of electric vehicles, smart devices, robots, drones, implanted medical equipment, etc., and the magnetic field in near-field technology Coupled resonant technology can better meet performance requirements. When charging commonly used batteries, wireless chargers have the following requirements for their charging characteristics:

1) Constant charging current. The first stage of the battery charging process is constant current charging. The charger charges the battery with a constant current at the maximum current, and the charging voltage of the battery gradually rises.

2) Constant maximum charging power. The second stage of the battery charging process is power charging. The charger charges the battery with a constant power at the maximum power, and the charging voltage of the battery gradually rises.

3) Constant charging voltage. The third stage of the battery charging process is constant voltage charging. The charger charges the battery at a constant voltage with the maximum voltage, and the charging current of the battery gradually decreases until it reaches the floating charge state.

4) Safe operating current. For the entire wireless power transfer system, in order to ensure the safe operation of the system, it is necessary to set a safe upper limit for the input current.

5) Reasonable total harmonic distortion (THD). In order to ensure that the THD value of the square wave output by the primary inverter of the wireless power transfer system is not too large and to obtain high transmission efficiency, it is necessary to set a lower limit for the phase shift angle of the front-end inverter.

Since the position of the primary and secondary coils is fixed when charging the battery, the coupling coefficient of the two resonant coils of the system can be regarded as a constant value during the entire charging process, and the voltage and current of the battery change with time during the charging process, so the The charging process is regarded as a variable resistance that changes with time. During the wireless power transmission process, the change of the load resistance will affect the output characteristics of the system. At the same time, in order to achieve the requirements of safe operation, a reasonable resonant network is required. The parameters enable the wireless power transfer system to meet the corresponding output characteristics and safety requirements in the above three different charging states. However, the current parameter design method is only for a fixed load resistance or selection of resonant network parameters based on experience, and there is no discussion of a parameter design method that combines the above charging characteristics of the battery.

Therefore, there is a need for a parameter design method that can meet the battery charging characteristics and safety requirements.

Contents of the invention

The purpose of the present invention is to overcome the above-mentioned shortcomings of the prior art, and provide a parameter design method of a magnetic coupling resonant wireless power transmission system based on SS topology, which can meet the characteristics and safety requirements of three-stage battery charging.

In order to achieve the above object, the SS topology-based magnetic coupling resonant wireless power transmission system parameter design method of the present invention includes the following steps:

In the battery constant current charging stage, the minimum mutual conductance gain of the resonant network is the first boundary condition of the coupling coil inductance in the resonant network; in the battery constant voltage charging stage, the minimum voltage gain of the resonant network is the coupling coil inductance in the resonant network The second boundary condition; during the transition from the constant current charging stage of the battery to the constant voltage charging stage, that is, in the constant power charging stage of the battery, the third boundary condition of the coupling coil inductance in the resonant network is greater than or equal to the rated power of the resonant network, During the entire charging process of the battery, the fourth boundary condition of the coupling coil inductance in the resonant network is that the input current of the resonant network is less than or equal to the safe current of the resonant network; Angle is greater than or equal to the default value Taking the maximum voltage gain of the resonant network and the maximum mutual conductance gain of the resonant network as the fifth boundary condition of the coupled coil inductance in the resonant network, the first boundary condition, the second boundary condition and the third boundary condition of the coupled coil inductance in the resonant network The intersection of the fourth boundary condition and the fifth boundary condition is used as the value range of the inductance value of the coupling coil in the resonant network.

The first boundary condition of the coupling coil inductance in the resonant network is: the mutual conductance gain of the resonant network is greater than or equal to the ratio of the effective value of the resonant current of the secondary side in the resonant network to the effective value of the AC fundamental wave voltage output by the inverter when the battery is charged with constant current, The maximum charging current of the battery is determined by the characteristics of the battery itself, and the effective value of the output AC fundamental wave voltage of the inverter is determined by the input voltage of the DC side and the phase shift angle of the inverter.

The second boundary condition of the coupling coil inductance in the resonant network is: the voltage gain of the resonant network is greater than or equal to the ratio of the effective value of the fundamental voltage of the midpoint voltage of the rectifier bridge arm to the effective value of the AC fundamental voltage output by the inverter when the battery is charged at a constant voltage. The maximum charging voltage is determined by the characteristics of the battery itself.

The third boundary condition of the coupling coil inductance in the resonant network is specifically: the output power of the resonant network is greater than or equal to the rated power of the battery.

During the charging process of the battery, the mutual resistance gain of the resonant network is greater than or equal to the ratio of the effective value of the fundamental voltage of the bridge arm midpoint of the rectifier to the resonant current of the primary side in the resonant network, and the maximum value of the resonant current of the primary side in the resonant network is determined by the system current limit value Decide.

When the phase shift angle of the inverter is the smallest, the voltage gain of the resonant network is less than or equal to the ratio of the effective value of the fundamental wave voltage at the midpoint of the rectifier bridge arm to the effective value of the AC fundamental wave voltage output by the inverter, and the mutual conductance gain of the resonant network is less than or equal to the resonance The ratio of the resonant current on the secondary side of the network to the minimum value of the effective value of the AC fundamental wave voltage output by the inverter.

The present invention has the following beneficial effects:

The parameter design method of the SS topology-based magnetically coupled resonant wireless power transmission system described in the present invention, during specific operation, obtains the boundary conditions of the coupling coil inductance in the resonant network in different charging stages of the battery, and at the same time obtains the resonant network in the entire charging process of the battery The boundary conditions of the inductance of the middle coupling coil, and then the intersection of the boundary conditions is used as the value range of the inductance of the middle coupling coil, so as to combine the output characteristics of the system with the charging characteristics of the battery. The constant power charging stage is added to the voltage charging stage, that is, the third boundary condition of the coupling coil inductance in the resonant network is added with the rated power greater than or equal to the resonant network, and at the same time, the input current of the resonant network and the phase-shift voltage regulation of the inverter are added. The phase shift angle is limited. When all the limiting conditions are met, select the appropriate coupling inductance value to meet the charging characteristics and safety requirements of the battery.

Description of drawings

Fig. 1 is a structural diagram of a magnetically coupled resonant wireless power transmission system in which the primary side is connected in series with the secondary side in series in the present invention;

Figure 2(a) is an ideal battery charging curve;

Figure 2(b) is a battery charging curve limited by the maximum power;

Fig. 3(a) The transconductance gain of the resonant network varies with the per unit value of the switching frequency of the inverter when the coupling coefficient is constant;

Figure 3(b) is a diagram showing the change of the voltage gain of the resonant network with the per unit value of the switching frequency of the inverter when the coupling coefficient is constant;

Figure 3(c) is a diagram showing the change of the output power of the resonant network with the per unit value of the switching frequency of the inverter when the equivalent resistance is constant;

Figure 3(d) is a diagram showing the change of the mutual resistance gain of the resonant network with the per unit value of the switching frequency of the inverter when the coupling coefficient is constant;

Fig. 4 is the boundary condition diagram of the coupling inductance value obtained in embodiment one;

Fig. 5(a) is a curve diagram of charging voltage, charging current and charging power changing with time in a steady state when constant current charging is performed at point A;

Fig. 5(b) is a curve diagram of charging voltage, charging current and charging power changing with time in steady state when constant power charging is performed at point B;

Fig. 5(c) is a curve diagram of charging voltage, charging current and charging power changing with time in a steady state when constant power charging is performed at point C;

FIG. 5( d ) is a graph showing the time-varying curves of charging voltage, charging current, and charging power in a steady state when constant voltage charging is performed at point D. FIG.

Detailed ways

The present invention is described in further detail below in conjunction with accompanying drawing:

The parameter design method of the magnetic coupling resonant wireless power transmission system based on the SS topology of the present invention comprises the following steps:

In the battery constant current charging stage, the minimum mutual conductance gain of the resonant network is the first boundary condition of the coupling coil inductance in the resonant network; in the battery constant voltage charging stage, the minimum voltage gain of the resonant network is the coupling coil inductance in the resonant network The second boundary condition; during the transition from the constant current charging stage of the battery to the constant voltage charging stage, that is, in the constant power charging stage of the battery, the third boundary condition of the coupling coil inductance in the resonant network is greater than or equal to the rated power of the resonant network, During the entire charging process of the battery, the fourth boundary condition of the coupling coil inductance in the resonant network is that the input current of the resonant network is less than or equal to the safe current of the resonant network; The angle is greater than or equal to the preset value π/4, taking the maximum voltage gain of the resonant network and the maximum mutual conductance gain of the resonant network as the fifth boundary condition of the coupled coil inductance in the resonant network, and the first boundary condition of the coupled coil inductance in the resonant network The intersection of the second boundary condition, the third boundary condition, the fourth boundary condition and the fifth boundary condition is used as the value range of the inductance value of the coupling coil in the resonant network.

It should be noted that the first boundary condition of the coupling coil inductance in the resonant network is: the mutual conductance gain of the resonant network is greater than or equal to the effective value of the resonant current of the secondary side in the resonant network and the AC fundamental wave voltage output by the inverter when the battery is charged with a constant current. The ratio of the effective value, the maximum charging current of the battery is determined by the characteristics of the battery itself, and the effective value of the output AC fundamental wave voltage of the inverter is determined by the input voltage of the DC side and the phase shift angle of the inverter;

The second boundary condition of the coupling coil inductance in the resonant network is: the voltage gain of the resonant network is greater than or equal to the ratio of the effective value of the fundamental voltage of the midpoint voltage of the rectifier bridge arm to the effective value of the AC fundamental voltage output by the inverter when the battery is charged at a constant voltage. The maximum charging voltage is determined by the characteristics of the battery itself;

The third boundary condition of the coupling coil inductance in the resonant network is specifically: the output power of the resonant network is greater than or equal to the rated power of the battery;

During the charging process of the battery, the mutual resistance gain of the resonant network is greater than or equal to the ratio of the effective value of the fundamental voltage of the bridge arm midpoint of the rectifier to the effective value of the resonant current of the primary side in the resonant network, and the maximum value of the resonant current of the primary side in the resonant network is limited by the system current Determined by the amplitude, the voltage gain of the resonant network is less than or equal to the ratio of the effective value of the fundamental wave voltage at the midpoint of the rectifier bridge arm to the effective value of the AC fundamental wave voltage output by the inverter, and the mutual conductance gain of the resonant network is less than or equal to the resonance of the secondary side in the resonant network The ratio of the current to the minimum value of the effective value of the AC fundamental wave voltage output by the inverter, and the minimum value of the effective value of the AC fundamental wave voltage output by the inverter is determined by the minimum phase shift angle of the inverter.

The invention can simultaneously meet the requirements of different charging states when charging the storage battery, and the charging stages of the storage battery successively include a constant current charging stage, a constant power charging stage and a constant voltage charging stage.

Embodiment one

Referring to Figure 1, taking the 250W low-power charging platform as an example, the ideal voltage source of 80V in the front stage passes through the inverter to invert the DC power to generate a high-frequency AC square wave voltage to drive the resonant network on the transmitting side. The resonant network on the transmitting side generates a high-frequency electromagnetic field. The resonant network on the receiving side induces a high-frequency electromagnetic field to generate a high-frequency AC voltage, which is finally charged to the battery after being rectified by a rectifier.

2(a) is the ideal battery charging curve. The battery is charged with a constant current in section A-B, the charging current remains unchanged, and the charging voltage gradually increases with time. When charging at a constant voltage in section B-C, the charging voltage remains unchanged, and the charging current increases with time. The time gradually decreases, and the equivalent resistance of the battery increases gradually in both cases; Figure 2(b) shows the charging curve of the battery limited by the maximum power: the battery is charged at a constant power in the B-C section, and the charging voltage gradually rises. The charging current decreases gradually, the charging power remains constant, and the equivalent resistance increases gradually.

The transconductance gain of the resonant network varies with the per unit value of the switching frequency of the inverter when the coupling coefficient is constant. See Figure 3(a). The frequency remains constant, that is, the mutual conductance gain of the resonant network will not change with the change of load resistance at this time, and when the effective value of the AC fundamental voltage output by the inverter and the switching frequency of the inverter are constant, the mutual conductance gain of the resonant network It is only related to the inductance value of the coupling coil in the resonant network and the coupling coefficient between the primary coil and the secondary coil, so as to obtain the boundary condition of the coupling coil inductance value under different coupling coefficients when the mutual conductance gain is required.

The change of the voltage gain of the resonant network with the per unit value of the switching frequency of the inverter when the coupling coefficient is constant is shown in Figure 3(b). , the voltage gain of the resonant network will not change with the change of load resistance, and the voltage gain of the resonant network is only related to the inductance value of the coupling coil, so that the boundary condition of the inductance value of the coupling coil when the voltage gain of the resonant network is satisfied is obtained.

The output power of the resonant network changes with the per unit value of the switching frequency of the inverter when the equivalent resistance is constant. See Figure 3(c). When the switching frequency of the inverter is equal to the resonant frequency of the SS resonant network, the resonant network The output power decreases with the increase of the coupling coefficient between the primary coil and the secondary coil. In the constant power charging stage of the battery, under the condition of the maximum coupling coefficient, the output power of the resonant network must not be less than the rated charging power of the battery, so that The boundary condition of coupling coil inductance value is obtained when the output power required by the storage battery is met.

Refer to Figure 3(d) for the change of the mutual resistance gain of the resonant network with the per unit value of the switching frequency of the inverter when the coupling coefficient is constant. The mutual resistance gain of the resonant network is equal to that of the SS resonant network when the switching frequency of the inverter is equal to At the resonant frequency, the mutual resistance gain of the resonant network does not change with the change of the load resistance, and when the effective value of the inverter output AC fundamental voltage and the switching frequency of the inverter are constant, the mutual resistance gain of the resonant network is only the same as that of the coupling coil The inductance value is related to the coupling coefficient of the primary coil and the secondary coil, so as to obtain the boundary condition of the coupling coil inductance value under different coupling coefficients when the mutual resistance gain of the resonant network meets the requirements.

In order to illustrate the effectiveness of the present invention, the system design indicators in Table 1 are used to design the parameters of the wireless power transmission system of SS topological magnetic coupling resonance.

Table 1

The boundary conditions of the coupling inductance value obtained according to the above parameter design method are shown in Figure 4. The dotted horizontal line is the boundary condition that the primary and secondary inductance needs to satisfy when the maximum phase shift angle and the minimum phase shift angle meet the voltage gain condition. The inductance should be above the dotted horizontal line with a phase shift angle of π and the phase shift angle is The dotted line is below the dot horizontal line; the dotted line is the boundary condition that the primary and secondary inductance needs to satisfy when the mutual conductance gain condition is satisfied under different coupling coefficients and the maximum phase shift angle and the minimum phase shift angle. Below the dotted line of the upper limit of the gain and above the dotted line of the lower limit of the mutual conductance gain; the dotted line is the boundary condition that the primary and secondary inductance needs to satisfy when the two transition points B and C meet the rated power conditions during constant power charging, and the secondary inductance should be Below the two-point line; the solid line is the boundary condition that the primary and secondary side inductance needs to meet when the system meets the mutual resistance gain condition at different operating points under different coupling coefficients, and the secondary side inductance should be above the three solid lines . Through the constraints of multiple conditions, it can be obtained that the value range of the inductance of the primary coil and the inductance of the secondary coil is the shaded area in the figure.

According to the range of inductance values in Figure 4, the primary inductor L ₁ is selected as 116.86μH, the secondary inductor L ₂ is 116.86μH, the primary capacitor C ₁ is 30nF, and the secondary capacitor C ₂ is 30nF. On the charging curve of the battery, when the system operates at point A for constant voltage charging, refer to Figure 5(a), when the system operates at points B and C for constant power charging, refer to Figure 5(b) and Figure 5(c), and the system operates at See Figure 5(d) for constant voltage charging at point D.

Claims (3)

1. a kind of magnetic coupling resonant radio energy transmission system parameters design method based on SS topologys, which is characterized in that including Following steps：

In accumulator constant-current charging phase, using the minimum mutual conductance gain of resonant network as resonant network in coupling coil inductance One boundary condition；In accumulator constant voltage charging phase, using the minimum voltage gain of resonant network as resonant network in coupling coil The second boundary of inductance；In accumulator constant-current charging phase to during constant voltage charging phase transition, i.e., in accumulator The invariable power charging stage, using the rated power more than or equal to resonant network as resonant network in coupling coil inductance third boundary Condition, in the entire charging process of accumulator, the safe current that resonant network is less than or equal to the input current of resonant network is 4th boundary condition of coupling coil inductance in resonant network；Shifting in entire charging process when inverter progress phase-shift voltage regulating Phase angle is more than or equal to preset valueUsing the maximum voltage gain of resonant network and the maximum mutual conductance gain of resonant network as Resonance Neural Network 5th boundary condition of coupling coil inductance in network, by the First Boundary Condition of coupling coil inductance, the second side in resonant network Boundary's condition, third boundary condition, the 4th boundary condition and the 5th boundary condition intersection are as coupling coil inductance in resonant network The value range of value；

The First Boundary Condition of coupling coil inductance is in resonant network：It is permanent that the mutual conductance gain of resonant network is more than or equal to accumulator When current charge in resonant network secondary side the ratio between resonance current virtual value and inverter output AC fundamental voltage virtual value, electric power storage The maximum charging current in pond is determined that the output exchange fundamental voltage virtual value of inverter is defeated by DC side by accumulator self character Enter voltage to determine with inverter phase shifting angle；

The second boundary of coupling coil inductance is in resonant network：It is permanent that the voltage gain of resonant network is more than or equal to accumulator The ratio between rectifier bridge arm mid-point voltage fundamental wave virtual value and inverter output AC fundamental voltage virtual value when pressure charging, accumulator Maximum charging voltage determined by accumulator self character；

The third boundary condition of coupling coil inductance is specially in resonant network：The output power of resonant network, which is more than, is equal to resonance The rated power of network.

2. the magnetic coupling resonant radio energy transmission system parameters design method according to claim 1 based on SS topologys, It is characterized in that, in battery charging process, the mutual resistance gain of resonant network is more than or equal to rectifier bridge arm mid-point voltage fundamental wave The ratio between the resonance current of virtual value and primary side in resonant network, the maximum value of the resonance current of primary side is by system electricity in resonant network Ductility limit amplitude determines.

3. the magnetic coupling resonant radio energy transmission system parameters design method according to claim 1 based on SS topologys, It is characterized in that, when inverter phase shifting angle minimum, the voltage gain of resonant network is less than or equal to rectifier bridge arm mid-point voltage The mutual conductance gain of the ratio between fundamental wave virtual value and inverter output AC fundamental voltage virtual value, resonant network is less than or equal to Resonance Neural Network The ratio between the minimum value of the resonance current and inverter output AC fundamental voltage virtual value on secondary side in network.