Abstract: Has given the non-contact loose coupling induction electrical energy transmission basic principle, discussed the influence system electrical energy transmission key aspect. In view of the different application situation, to original vice-side has carried on the compensation design, raises the electrical energy transmission efficiency and reduces electric power supply’s voltage electric current fixed quantity. And has carried on the discussion to the system stability and the controllability question. Finally, analyzes based on the above, gives the non-contact loose coupling induction electrical energy transmission system’s general layout method.
Key word: Non-contact type; Induction electrical energy transmission; Loose coupling; System design
Introduction
The contact electrical energy transmission through electric interlocks and so on plug - plug realizes the electrical energy transmission, obtained the widespread use in the electrical energy transmission domain. But along with the current collector to request and so on power supply quality, security, reliability unceasing enhancements, this traditional electrical energy transmission method inherent flaw, already enabled the numerous application situations to accept the contact electrical energy transmission, urgent need novel electrical energy transmission method [1].
In the mine pit, the petroleum drill pick and so on situations, uses the contact electrical energy transmission, because the contact friction produces the small electric spark, very possibly causes explodes, creates heavy accident [2]. In submarine situation, contact electrical energy transmission existence electric shock potential hazard [3]. When gives the mobile equipment supplies power, generally selects the sliding contact power supply method, this way has such as the glide in the use to wear, flaw [4][5] and so on touch spark, carbon deposit and unsafe exposed conductor. When gives the aeroseal instrumentation equipment internal electrical power supply, the contact electrical energy transmission needs to use the special coupling design, the cost is high, and guarantees equipment’s gas tight [6] with difficulty.
In order to solve the traditional contact type electrical energy transmission not to be able the question which is accepted by the numerous application situations, needs one novel electrical energy transmission method urgently. Therefore, the non-contact induction electrical energy transmission arises at the historic moment, becomes the current electrical energy transmission domain a big research hot spot. This article has first given this kind of novel electrical energy transmission method basic principle, has analyzed the influence system electrical energy transmission key aspect; Then revolves to raise the system electrical energy transmission efficiency and to reduce electric power supply’s voltage electric current fixed quantity request, in view of the different application situation, to original vice-side has carried on the corresponding compensation design; Have carried on the discussion to system’s stability and the controllability question. Finally, analyzes based on the above, gives the non-contact induction electrical energy transmission system’s general layout method.
1 non-contact induction electrical energy transmission system
Non-contact induction electrical energy transmission system’s modular design as shown in Figure 1. The system two major part is composed of the primary side electric circuit and the vice-side electric circuit. The primary side electric circuit with between the vice-side electric circuit has section of crevices, relates through the magnetic field coupling. The primary side electric circuit transforms the electrical energy into the magnetic field launch, after passing through this section of air gaps, the vice-side electric circuit through accepts the installment, the circle chain magnetic line of force, accepts the magnetic field energy, and through the corresponding capacity regulator installment, transforms the electrical energy form which may use directly for the application situation load, thus realized the non-contact electrical energy transmission (in article load with resistance to express that simplified analysis). The magnetic coupling equipment may use many kinds of forms. Fundamental mode like chart 2(a) the primary side winding and the vice-side winding circle separately on the separation ferrite core; Figure 2(b) the primary side uses the spatial core winding, the vice-side winding circles on the ferrite core; Figure 2(c) the primary side uses the long electric cable, the vice-side winding circles on the ferrite core.
In this non-contact induction electrical energy transmission system, between original vice-side electric circuit big air gap existence, on the one hand causes the original vice-side radio contact, has made up the traditional contact type electrical energy transmission inherent flaw. On the other hand the big air gap’s existence enables the system constitution the magnetic coupling relations to belong to the loose coupling (from this, this kind of novel electrical energy transmission technology usually is also called loose coupling induction electrical energy transmission technology, records is LCIPT), leakage and initiation quite, even was higher than the initiation, has limited the electrical energy transmission size and the transmission efficiency. Therefore, usually needs in original vice-side to use the compensating network to promote the electrical energy transmission the size and the transmission efficiency, simultaneously reduces the power source converter’s voltage electric current stress. Moreover in this system’s analysis, because the magnetic coupling installment is the loose coupling, therefore, usually uses in the magnetic elements analysis the transformer model no longer being suitable, must use in the coupling inductance model analysis this system’s electromagnetism relations, simultaneously considers the leakage inductance and the magnetizing inductance to the system work influence.
Figure 3 gives the magnetic coupling installment to use the coupling inductance model the system equivalent circuit diagram. The original vice-side magnetic coupling installment’s mutual inductance records is M.
Supposes the primary side to use in the magnetic field launch the high frequency current carrying conductor circle adopting the angular frequency for Omega, the electric current effective value is the Ip alternating current. According to the coupling relations, the vice-side electric circuit will accept in the coil to induce the voltage
Voc=jωMIp (1)
Corresponding, the Norton equivalent circuit short-circuit current is
In the formula: Ls is the vice-side inductance.
If the vice-side coil’s quality factor is Qs, under above parameter, the maximum work which rate the vice-side coil can obtain is
May see from type (3), enhances the electrical energy transmission the size to be possible through to increase Omega, Ip, M and Qs or reduce Ls. But receives the application situation machinery installment and the cost restriction, in the LCIPT system, the M value is generally small, moreover, once after the magnetic coupling installment design completes, M and the Ls value basically fixed. What can make the adjustment is the product quantity (ωIp2Qs). Considered from the engineering design angle that in the parameter choice design, Qs will not surpass generally 10, otherwise the system active status to the variation of load, the part parameter variation and the frequency shift will be sensitive, the system will be very difficult stably. From this what to transmits the electrical energy size adjustment redundancy to be biggest is the product ωIp2. From this relationship obvious frequency and emission current relations: Raises the frequency Omega, may reduce primary side electric current Ip, vice versa. In the transmission equal electrical energy and the other related quantity invariable situation, uses the high frequency LCIPT system with to use the low frequency LCIPT system to compare, needs the emission current reduces greatly, the power source converter electric current stress and the system cost reduce greatly. Therefore LCIPT is quite suitable to use the high frequency system. But is restricted in present power electronic technology level and the magnetic field launch related standard, the system frequency is restricted. According to the application situation’s difference, the frequency range which the system uses generally between 10kHz~100kHz.
Figure 4
2 system compensations
nearby 2.1 compensates
In loose coupling induction electrical energy transmission system, if vice-side accepts the coil to be directly connected with the load, the system output voltage and the electric current could change along with the variation of load, have limited the power delivery.
Therefore, must to vice-side carry on the effective compensation design. As shown in Figure 4, the basic compensation analysis situs has the electric capacity series compensation and the electric capacity shunt compensation two forms.
In the electric capacity series compensation electric circuit, the vice-side network’s impedance is
The output is
When the compensation electric capacity Cs value satisfies with vice-side inductance Ls when the system operating frequency place resonance, the vice-side network induction reactance and the capacitance disappear mutually, is the pure resistance, the output voltage has nothing to do with the load, equivalent in output voltage for vice-side open-circuit voltage constant pressure source, theoretically the electrical energy transmission is not limited.
The electric capacity shunt compensation electric circuit vice-side network’s conductance is
The output is
In the formula: Isc is the vice-side short-circuit current.
When the compensation electric capacity Cs value satisfies with vice-side inductance Ls when the system operating frequency place resonance, the vice-side network conductance and the accommodation disappear mutually, is the pure electric conductance, the output current has nothing to do with the load, was equal to that the vice-side short-circuit current, the electrical energy transmission is not limited theoretically.
In order to cause the vice-side resonance frequency is the system frequency, compensates electric capacity’s value to satisfy-like (5) and type (7) imaginary component is zero.
In the loose coupling induction electrical energy transmission system, the vice-on the one hand electric circuit to the primary side electric circuit’s work’s influence, may use the vice-on the other hand electric circuit to reflect that expressed to primary side electric circuit’s reflection impedance Zr.
In the formula: Zs corresponds the vice-side network impedance, sees type (5) and type (7), reflected that the impedance result is listed in table 1 (ω0 for system frequency).
Table 1 original vice-adopts when the different compensation analysis situs compensation electric capacity and reflection resistance value
|
Vice-side compensates the analysis situs |
Vice-side compensates the electric capacity Cs value |
Vice-side electric circuit reflection to primary side impedance |
|
| Resistance | Reactance | ||
|
Electric capacity series compensation |
1/(ω02Ls) |
(ω02M2) /R |
0 |
|
Electric capacity shunt compensation |
1/(ω02Ls) |
(M2R)/Ls2 |
- (ω02M2) /Ls |
2.2 primary side compensations
In the LCIPT system, the primary side current carrying conductor circle average effective value high high-frequency current, has been possible to use the PWM working the converter to obtain this high-frequency current directly, converter’s voltage electric current fixed quantity is high, the system cost is high. Therefore, must take the essential compensation measure, comes to reduce the converter voltage electric current fixed quantity effectively. With vice-side compensates similarly, according to electric capacity put in circuit’s connection mode, may also use the series compensation and the shunt compensation two kind of basic compensating circuits.
In the electric capacity series compensation electric circuit, power source’s loaded impedance is
On electric capacity voltage compensation primary side winding’s voltage, thus reduced power source’s voltage fixed quantity.
In the electric capacity shunt compensation electric circuit, power source’s load admittance is
The charging current has compensated in the primary side winding’s electric current, thus reduced power source’s electric current nominal value. When design guarantee type (10) and type (11) the imaginary component in the system resonance frequency place is zero, may reduce power source’s voltage electric current fixed quantity effectively, enables the voltage electric current with the phase, the input to have the high power factor. Its result is listed in table 2.
The primary side adopts what kind of compensating circuit, is very big to the application situation’s dependence. When the primary side uses the long electric cable, the electric cable terminal voltage will be very high, suits uses the series compensation, will reduce the supply voltage stress; When the primary side uses the concentrated winding, for the magnetic field launch need, the request high electric current, suits generally uses the shunt compensation, reduces supply current stress [7].
3 system stabilities and control
In the LCIPT system, original vice-side uses when the electric capacity compensates, the system is a fourth-order system, in the certain circumstances, will present divergent phenomenon [8]. Vice-side electric circuit’s quality factor Qs is specially smaller than in primary side electric circuit’s quality factor Qp, when or both quite, the system is very possible not to be unstable, this time must carry on the thorough stability analyses to the system. At the same time, in the LCIPT system, the control plan’s reasonable choice is stable to the system and electrical energy through-put capacity is essential. At present, often uses two kind of basic control plans: The permanent frequency control and the frequency conversion control [9].
The permanent frequency control is advantageous to circuit element’s choice, but the permanent frequency control correspondence’s question is, in electric circuit practical work electric capacity inevitably because will lose produces the temperature rise, will cause the electric capacity to drop, the vice-side practical work resonance frequency will elevate, the original vice-side electric circuit different harmony, will enable the electrical energy transmission to suffer injury [10]. The frequency conversion control may through the real-time control primary side resonance frequency, cause it to track the vice-side acceptor frequency, causes the original vice-side electric circuit same harmony, obtains the biggest electrical energy transmission. But in the frequency conversion control, between the mains input voltage and the input current phase angle and the frequency relations very possibly presents the divergent phenomenon, causes the system not to be unstable. Therefore, must perform the strict limit to the original vice-side quality factor.
4 LCIPT system designs
Regarding the close coupling induction electrical energy transmission system, the original vice-on the one hand electrical energy relations may be approximate with the original vice-on the other hand ratio-turn transformation relations indicated that thus its system design may divide into three independent sectors: The primary side electric circuit, close coupling magnetism, the vice-side electric circuit, carries on the design separately. The close coupling magnetism’s design also has the mature design procedure to be possible to depend on.
But in the loose coupling induction electrical energy transmission system, the original vice-side electric circuit’s work dependence is very big, if type (3) shows, the original vice-side electrical energy transmission relations decided by many variables, these variables must act according to the existing power electron level, and related design experience primary election some values, then the basis correlation formula carries on the next step the computation, fixed parameter. In the entire design process, many variables which appears must carry on the choice, but these variables isolate by no means that but has certain restriction relations. Therefore, the loose coupling induction electrical energy transmission system’s design must be much more complex than the close coupling induction electrical energy transmission system. Here each variable meaning which presents the loose coupling induction electrical energy transmission system, and the selection method gives a showing, and draws the corresponding flow chart, as shown in Figure 5, with the aim of understanding. The design procedure is as follows.
4.1 choice frequencies
The selective system operating frequency is the LCIPT system design first step, may see from type (3), the frequency size’s selection, with power source’s complex degree, the cost and the system electrical energy transmission size has the close relation. Wants the overall evaluation application situation to the system volume weight request, the present power electron level and system-related’s design experience selects the frequency. Considered on the present power electron level and the system cost that chooses between 10kHz~100kHz the frequency to be quite reasonable. Along with the power electron level’s unceasing progress, the system frequency hopes to further enhance, thus causes the system volume to be smaller, the weight to be lighter.
4.2 choose the loose coupling induction installment
The close coupling induction installment (for example widely uses transformer) the structure is restricted in the existing ferrite core structure generally, thus the structural style is limited. But the loose coupling induction installment the ferrite core structure limit, according to each kind of application situation’s need, possibly will actually not be appeared many kinds of structural styles. To a great extent, these loose couplings induce the equipment to depend upon the related design experience to choose. Determined after loose coupling induction installment structure, must demarcate some basic parameters, like original vice-side coil inductance quantity, coupling coefficient, mutual inductance and so on.
4.3 choice primary side electric current Ip
In the LCIPT system, the transmission electrical energy size, the primary side power source converter’s cost with uses in the magnetic field launch the primary side electric current Ip direct correlation. Generally starts from the relatively small magnitude of current to select Ip, thus corresponds power source’s low electric current stress. If after computation, this Ip magnitude of current does not satisfy the system electrical energy transmission request, may further increase the magnitude of current, carries on the computation confirmation again, satisfies the request until the system design.
4.4 determine the (VocIsc) value
According to electromagnetism installment which chooses, when the primary side electric current for chooses Ip, tests vice-side accepts the coil open-circuit voltage Voc and short-circuit current Isc. Determined that this product (VocIsc) may also use one to accept the coil same number of windings with the design to accept the coil to complete light-sized, avoids because of accepting the coil current fixed quantity insufficiently to do over. Certainly, may also use the corresponding electromagnetic field simulation software package to carry on the simulation design. But simulation design process quite complex [11].
4.5 determined that vice-side compensates
nearby 4.5.1 compensates the rank
When the vice-side electric circuit does not compensate, the load can obtain the maximum work rate transmission is equal to (VocIsc/2)[11]. If the load needs the performance number to surpass this value, then vice-side needs to use the compensating circuit, vice-side electric circuit’s quality factor available -like (12) calculates.
In the formula: P is to the load transmission power.
Thus vice-side needs V · A fixed quantity is
If the vice-side actual VA fixed quantity is higher than type (13) predicted value, the system may transmit the power which needs. Otherwise, this design cannot transmit needs power P, must to design makes the corresponding adjustment to increase the power delivery ability. Generally may consider following 4 ways:
- - overstrikeing accepts the coil winding wire diameter or increases the ferrite core cross-sectional area;
- - increases the primary side electric current;
- - the improvement electromagnetism installment’s coupling degree, enhances mutual inductance value M;
- - raises the system frequency suitably.
The 1st kind of plan increased the vice-side cost; The 2nd kind of plan increased the primary side cost; The 3rd kind of plan increased the loose coupling induction installment cost; The 4th kind of plan has the power electronic technology limit. In the actual design, should the overall evaluation performance and the cost choice performance-to-price ratio best plan takes the most superior design.
nearby 4.5.2 compensates the analysis situs
After the vice-side VA fixed quantity satisfies the design requirements, next step must determine that vice-side compensates the analysis situs form which uses specifically. Compensates the analysis situs the choice to rely on the concrete application situation. The shunt compensation correspondence current supply characteristic, suits in situations and so on battery charger; The series compensation corresponds to the potential source characteristic, is suitable in situations and so on motor-driven power supply.
4.6 definite primary side compensations
After vice-compensates the design completes, design primary side compensation. According to the known primary side electric current and the loose coupling induction installment primary side winding inductance quantity, may determine the primary side winding terminal voltage. Thus calculates the primary side VA fixed quantity, divides this VA fixed quantity with the actual transmission power, may obtain the primary side quality factor Qp size. As mentioned above, the primary side compensating circuit form is also decided is decided the application situation. When the primary side uses the long electric cable, suits uses the series compensation; When the primary side uses the concentrated winding, suits uses the shunt compensation.
4.7 system stabilities and control investigation
Last step must carries on the investigation to the system stability and the control, whether is the system in the practical application situation most essential one step which uses. As stated above, if Qp<Qs must carry on the thorough stability analyses to the system. If the system cannot guarantee that controls stably in all working condition, must make the adjustment to the system parameters. The commonly used method including increases the primary side electric current, to improve the loose coupling induction installment the structure or the change system frequency and so on.
5 conclusions
In the article has given the loose coupling induction electrical energy transmission basic principle, based on the system compensation design and the systems control question’s discussion, has given the loose coupling induction electrical energy transmission system’s generality design method, this system’s design relies on to a great extent the designer to each design parameter between the interdependence understanding, those who need the special attention is after various parameters design completes, must carries on the comprehensive inspection to overall system’s stability and the controllability, guarantees the system design the validity.
