CN113572388A - Piezoelectric energy collecting device and control method - Google Patents
Piezoelectric energy collecting device and control method Download PDFInfo
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- H—ELECTRICITY
- H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
- H02N—ELECTRIC MACHINES NOT OTHERWISE PROVIDED FOR
- H02N2/00—Electric machines in general using piezoelectric effect, electrostriction or magnetostriction
- H02N2/18—Electric machines in general using piezoelectric effect, electrostriction or magnetostriction producing electrical output from mechanical input, e.g. generators
- H02N2/186—Vibration harvesters
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- H—ELECTRICITY
- H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
- H02J—CIRCUIT ARRANGEMENTS OR SYSTEMS FOR SUPPLYING OR DISTRIBUTING ELECTRIC POWER; SYSTEMS FOR STORING ELECTRIC ENERGY
- H02J7/00—Circuit arrangements for charging or depolarising batteries or for supplying loads from batteries
- H02J7/32—Circuit arrangements for charging or depolarising batteries or for supplying loads from batteries for charging batteries from a charging set comprising a non-electric prime mover rotating at constant speed
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- H—ELECTRICITY
- H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
- H02M—APPARATUS FOR CONVERSION BETWEEN AC AND AC, BETWEEN AC AND DC, OR BETWEEN DC AND DC, AND FOR USE WITH MAINS OR SIMILAR POWER SUPPLY SYSTEMS; CONVERSION OF DC OR AC INPUT POWER INTO SURGE OUTPUT POWER; CONTROL OR REGULATION THEREOF
- H02M3/00—Conversion of dc power input into dc power output
- H02M3/02—Conversion of dc power input into dc power output without intermediate conversion into ac
- H02M3/04—Conversion of dc power input into dc power output without intermediate conversion into ac by static converters
- H02M3/10—Conversion of dc power input into dc power output without intermediate conversion into ac by static converters using discharge tubes with control electrode or semiconductor devices with control electrode
- H02M3/145—Conversion of dc power input into dc power output without intermediate conversion into ac by static converters using discharge tubes with control electrode or semiconductor devices with control electrode using devices of a triode or transistor type requiring continuous application of a control signal
- H02M3/155—Conversion of dc power input into dc power output without intermediate conversion into ac by static converters using discharge tubes with control electrode or semiconductor devices with control electrode using devices of a triode or transistor type requiring continuous application of a control signal using semiconductor devices only
- H02M3/156—Conversion of dc power input into dc power output without intermediate conversion into ac by static converters using discharge tubes with control electrode or semiconductor devices with control electrode using devices of a triode or transistor type requiring continuous application of a control signal using semiconductor devices only with automatic control of output voltage or current, e.g. switching regulators
- H02M3/157—Conversion of dc power input into dc power output without intermediate conversion into ac by static converters using discharge tubes with control electrode or semiconductor devices with control electrode using devices of a triode or transistor type requiring continuous application of a control signal using semiconductor devices only with automatic control of output voltage or current, e.g. switching regulators with digital control
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Abstract
The invention provides a piezoelectric energy collection device and a control method, which relate to the technical field of micro-energy collection and comprise the following steps: the device comprises a piezoelectric collector, a rectifying circuit, a DC/DC Boost booster circuit, a sampling circuit, an MPPT controller, an optical coupling isolation circuit, a driving circuit, a direct current load, a storage battery and a PC; the piezoelectric collector is connected with the rectifying circuit; the rectifying circuit is connected with the DC/DC Boost circuit; the direct-current load and the storage battery are connected with the DC/DC Boost circuit; the sampling circuit is connected with the MPPT controller; the MPPT controller is connected with the optical coupling isolation circuit and the driving circuit; the driving circuit is connected with the DC/DC Boost circuit; the PC is connected with the MPPT controller, the output voltage nonlinearity problem that piezoelectric energy collection exists, and the circuit collection efficiency is lower, can cause certain vibration energy loss, the not efficient problem of energy collection.
Description
Technical Field
The invention relates to the technical field of micro-energy collection, in particular to a piezoelectric energy collection device and a control method.
Background
The continuous development of low-power integrated circuit technology enables wireless sensors, wearable devices and the like to be widely applied. At present, wireless sensors and wearable equipment are mainly powered by batteries, and the batteries have a series of problems of short endurance time, limited service life, complex maintenance and replacement, high cost and the like, and the energy collection technology is considered by industry to be the most potential battery replacement technology in the future of the field, and becomes the hot spot of domestic and foreign research in recent years.
When the piezoelectric vibration energy collector is influenced by external vibration to generate stress strain, the piezoelectric material generates polarization phenomenon and gathers charges on the surface by utilizing the positive piezoelectric effect of the piezoelectric material, and the charge energy can be collected and stored through the energy management circuit and can be used as a power supply for supplying energy.
The energy collection technology based on the vibration energy is a hot spot concerned at home and abroad at present, and is also a new technology for solving the problem that the node energy supply is more effective, the structure of the current piezoelectric energy collection device is simpler, the output voltage nonlinearity exists for piezoelectric energy collection, the circuit collection efficiency is lower, and certain vibration energy loss can be caused, so that how to efficiently collect the vibration energy becomes a problem which needs to be solved urgently.
Disclosure of Invention
Technical problem to be solved
Aiming at the defects of the prior art, the invention provides a piezoelectric energy collecting device, which solves the problems of output voltage nonlinearity, low circuit collecting efficiency, certain vibration energy loss and low energy collecting efficiency of the piezoelectric energy collecting device in the background technology.
(II) technical scheme
In order to achieve the purpose, the invention is realized by the following technical scheme: a piezoelectric energy harvesting device, comprising: the device comprises a piezoelectric collector 1, a rectifying circuit 2, a DC/DCboost booster circuit 3, a sampling circuit 4, an MPPT controller 5, an optical coupling isolation circuit 6, a driving circuit 7, a direct current load, a storage battery 8 and a PC 9;
the piezoelectric collector 1 is connected with the rectifying circuit 2;
the rectification circuit 2 is connected with the DC/DC Boost booster circuit 3;
the direct current load and the storage battery 8 are connected with the DC/DC Boost booster circuit 3;
the sampling circuit 4 is connected with the MPPT controller 5;
the MPPT controller 5 is connected with the optical coupling isolation circuit 6 and the driving circuit 7;
the driving circuit 7 is connected with the DC/DC Boost circuit 3;
the PC 9 is connected to the MPPT controller 5.
Preferably, the piezoelectric collector 1 comprises: the device comprises a base 1-1, a supporting layer 1-2, a substrate 1-3, a substrate tail end mass block 1-4, an acceleration sensor 1-5, a data acquisition card 1-6 and a piezoelectric cantilever beam 1-7;
the piezoelectric cantilever beams 1-7 are fixedly arranged between the base plate 1-3 and the supporting layer 1-2, and the mass block 1-4 at the tail end of the base plate is arranged at the non-fixed end of the piezoelectric cantilever beams 1-7;
the base 1-1 is directly or indirectly connected with the support layer 1-2, the substrate 1-3, the substrate tail end mass block 1-4, the acceleration sensor 1-5 and the piezoelectric cantilever beam 1-7 and used for fixing the components;
the acceleration sensor 1-5 is connected with the data acquisition card 1-6.
Preferably, the piezoelectric cantilever 1-7, comprises: 1-7-1 parts of a first double-crystal piezoelectric ceramic piece, 1-7-2 parts of a second double-crystal piezoelectric ceramic piece, 1-7-3 parts of a voltage output positive electrode of a piezoelectric collector and 1-7-4 parts of a voltage output negative electrode of the piezoelectric collector;
the first double-crystal piezoelectric ceramic plate 1-7-1 and the second double-crystal piezoelectric ceramic plate 1-7-2 are symmetrically bonded on the substrate 1-3;
the first double-crystal piezoelectric ceramic piece 1-7-1 and the second double-crystal piezoelectric ceramic piece 1-7-2 are connected in parallel, one lead is respectively led out in a welding mode, and the other ends of the two leads are welded and shorted to serve as voltage output positive electrodes 1-7-3 of the piezoelectric collector;
and a lead is welded on the surface of the substrate 1-3 and is used as a voltage output negative electrode 1-7-4 of the piezoelectric collector.
Preferably, the materials, sizes and shapes of the first double-crystal piezoelectric ceramic plate 1-7-1 and the second double-crystal piezoelectric ceramic plate 1-7-2 are completely consistent.
Preferably, the stress direction and the coupling electric field direction of the first double-crystal piezoelectric ceramic plate 1-7-1 and the second double-crystal piezoelectric ceramic plate 1-7-2 are the same.
Preferably, the number of the piezoelectric cantilevers 1-7 can be 1 or more.
Preferably, the MPPT controller 5 further includes: a PWM generator.
The present invention also provides a piezoelectric energy harvesting control method according to the energy harvesting device as described in any one of the above, including:
the piezoelectric collector collects energy of the vibration source and converts the energy into electric energy, and measures and outputs alternating voltage;
the alternating voltage output by the piezoelectric collector is rectified by a rectifying circuit and then outputs direct-current voltage;
the direct current voltage output by the rectification circuit passes through a DC/DCboost booster circuit and outputs direct current voltage with adjustable magnitude;
the direct-current voltage output by the rectifying circuit and the direct-current voltage output by the DC/DC Boost circuit are transmitted to a sampling circuit, and the sampling circuit measures a voltage U and a current value I;
the MPPT method comprises the steps that the micro-integral relation between the voltage U and the current value I measured by the sampling circuit is judged through the MPPT algorithm of the conductance incremental method, the MPPT controller outputs corresponding pulse width modulation information numbers, the duty ratio of a switching device in the DC/DC Boost booster circuit is adjusted through the driving circuit, and the output voltage of the DC/DC Boost booster circuit is adjusted.
Preferably, the MPPT algorithm by the conductance incremental method determines a micro-integral relationship between the voltage and the current measured by the sampling circuit, and the MPPT controller outputs a corresponding pulse width modulation information number, specifically:
when dI/dU is > -I/U, the piezoelectric collector works on the left side of the maximum power point, and the output voltage is increased by adjusting PWM waves with higher duty ratio to approach the maximum power point;
when dI/dU is equal to-I/U, the piezoelectric collector works at the left side of the maximum power point without adjustment;
when dI/dU is less than-I/U, the piezoelectric collector works at the right side of the maximum power point, and the output voltage is reduced to approach the maximum power point by outputting PWM waves with reduced duty ratio.
Preferably, the direct-current voltage output by the rectifying circuit passes through a DC/DC Boost circuit to output a direct-current voltage with adjustable magnitude, and the direct-current voltage can also be input into a direct-current load and a storage battery to store electric energy.
(III) advantageous effects
The invention provides a piezoelectric energy collecting device and a control method. The method has the following beneficial effects: the base in the piezoelectric energy collecting device is connected with a vibration source, the number and the installation position of the piezoelectric ceramic pieces can be conveniently installed and debugged according to the actual external vibration source requirement, and the piezoelectric energy collecting device has strong environmental adaptability; the invention adopts the piezoelectric energy collecting circuit with the MPPT controller, the sampling circuit has high precision and high speed, the DC/DC conversion circuit has good switching frequency characteristic, the controller control has good real-time and accuracy, and the duty ratio of a switching device in the DC/DC conversion circuit can be adjusted by judging the micro-integral relation between the voltage U and the current I measured by the sampling circuit, so that the output voltage can be fed back and regulated, the working voltage of the piezoelectric collector is always maintained at the maximum power point, and the high-efficiency collection of energy is realized.
Drawings
Fig. 1 is a schematic system structure diagram of a piezoelectric energy harvesting device provided by the present invention;
fig. 2 is a structural view of a piezoelectric energy harvesting device provided by the present invention;
FIG. 3 is a structural diagram of a piezoelectric cantilever of a piezoelectric energy harvesting device according to the present invention;
FIG. 4 is a circuit diagram of a piezoelectric energy harvesting device in accordance with the present invention;
fig. 5 is a schematic diagram of an electromechanical coupling mode of a bimorph piezoelectric ceramic piece of the piezoelectric energy harvesting device according to the present invention;
FIG. 6 is a schematic flow chart of a piezoelectric energy harvesting control method according to the present invention;
fig. 7 is a schematic diagram of an MPPT controller of the present invention.
In the figure: the device comprises a piezoelectric collector 1, a rectifying circuit 2, a 3DC/DCboost booster circuit, a sampling circuit 4, a 5 MPPT controller, an opto-coupler isolation circuit 6, a drive circuit 7, a direct current load 8, a storage battery 9, a PC (personal computer), a first double-crystal piezoelectric ceramic piece 1-7-1, a second double-crystal piezoelectric ceramic piece 1-7-2, a voltage output positive electrode 1-7-3 of the piezoelectric collector and a voltage output negative electrode 1-7-4 of the piezoelectric collector.
Detailed Description
The technical solution in the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings in the embodiments of the present invention.
An embodiment of the present invention provides a piezoelectric energy harvesting device, as shown in fig. 1 to 4, the piezoelectric energy harvesting device including: the device comprises a piezoelectric collector 1, a rectifying circuit 2, a DC/DCboost booster circuit 3, a sampling circuit 4, an MPPT controller 5, an optical coupling isolation circuit 6, a driving circuit 7, a direct current load, a storage battery 8 and a PC 9;
the piezoelectric collector 1 is connected with a rectifying circuit 2, and the rectifying circuit 2 is used for rectifying the output alternating current voltage of the piezoelectric collector to obtain a direct current output voltage UiAnd a DC output current Ii；
The rectification circuit 2 is connected with the DC/DC Boost booster circuit 3, and the DC/DC Boost booster circuit 3 is used for rectifying and outputting the direct current output voltage U through the rectification circuit 2iAnd a DC output current IiPerforming boosting treatment to output boosted output voltage UOOutput current IO；
The direct-current load and the storage battery 8 are connected with the DC/DCboost boosting circuit 3 and receive and store piezoelectric energy output by the DC/DC Boost boosting circuit 3;
the sampling circuit 4 collects the DC output voltage UiAnd a DC output current IiAnd boosted output voltage UOOutput current IOBoost it to the MPPT controlThe digital signal which can be identified by the controller 5, and the sampling circuit 4 is connected with the MPPT controller 5;
the MPPT controller 5 is connected with the optical coupling isolation circuit 6 and the driving circuit 7;
the driving circuit 7 is connected with the DC/DC Boost booster circuit 3, and is configured to implement feedback regulation of the MPPT controller 5 on the DC/DC Boost booster circuit 3, and regulate an output voltage so that a working voltage of the piezoelectric collector 1 is maintained at a maximum power point;
the PC 9 and the MPPT controller 5 are connected with the PC 9 to monitor the acceleration and the intensity of actual vibration in real time, and accurate data support is provided for data communication.
In one embodiment, the piezoelectric collector 1 includes: the device comprises a base 1-1, a supporting layer 1-2, a substrate 1-3, a substrate tail end mass block 1-4, an acceleration sensor 1-5, a data acquisition card 1-6 and a piezoelectric cantilever beam 1-7;
the mass blocks 1-4 on the substrate meet the requirement of the whole structure on low frequency, and the stability requirements of the piezoelectric collector 1 and the piezoelectric cantilever beams 1-7 can be ensured.
The piezoelectric cantilever beams 1-7 are fixedly arranged between the base plate 1-3 and the supporting layer 1-2, and the mass block 1-4 at the tail end of the base plate is arranged at the non-fixed end of the piezoelectric cantilever beams 1-7;
the base 1-1 is directly or indirectly connected with the support layer 1-2, the substrate 1-3, the substrate tail end mass block 1-4, the acceleration sensor 1-5 and the piezoelectric cantilever beam 1-7 and used for fixing the components;
the acceleration sensor 1-5 is connected with the data acquisition card 1-6.
In one embodiment, the base 1-1 is connected with a real-life vibration source to drive the piezoelectric collector to vibrate.
In one embodiment, the substrates 1-3 can be brass sheets of model CW 617N; the base plate 1-3 vibrates with the vibration of the base 1-1 and the support layer 1-2.
In one embodiment, the acceleration sensor 1-5 is fixed on the base 1-3 by means of bolt connection, the type of the sensor can be selected from piezoelectric acceleration sensors of CA-YD-185 of Shanghai Denko, the obtained vibration acceleration data is transmitted to a data acquisition card, and then the acceleration and the intensity of actual vibration are monitored in real time by the PC 9, so that accurate data support is provided.
In one embodiment, the piezoelectric cantilever 1-7, comprises: 1-7-1 parts of a first double-crystal piezoelectric ceramic piece, 1-7-2 parts of a second double-crystal piezoelectric ceramic piece, 1-7-3 parts of a voltage output positive electrode of a piezoelectric collector and 1-7-4 parts of a voltage output negative electrode of the piezoelectric collector;
the first double-crystal piezoelectric ceramic plate 1-7-1 and the second double-crystal piezoelectric ceramic plate 1-7-2 are symmetrically bonded on the substrate 1-3;
the first double-crystal piezoelectric ceramic piece 1-7-1 and the second double-crystal piezoelectric ceramic piece 1-7-2 are connected in parallel, one lead is respectively led out in a welding mode, and the other ends of the two leads are welded and shorted to serve as voltage output positive electrodes 1-7-3 of the piezoelectric collector;
and a lead is welded on the surface of the substrate 1-3 and is used as a voltage output negative electrode 1-7-4 of the piezoelectric collector. The output voltage of the piezoelectric collector is the voltage difference measured between the voltage output positive electrode 1-7-3 and the voltage output negative electrode 1-7-4 of the piezoelectric collector.
In one embodiment, the materials, sizes and shapes of the first double-crystal piezoelectric ceramic plate 1-7-1 and the second double-crystal piezoelectric ceramic plate 1-7-2 are completely consistent;
the selectable models of the double-crystal piezoelectric ceramic piece are as follows: product of PZT-5H.
As shown in fig. 5, in an embodiment, the stress direction and the coupling electric field direction of the first and second piezoelectric ceramic sheets 1-7-1 and 1-7-2 are both 1, and in this operating mode, the energy collection efficiency is higher, the response is severe when the external vibration is sensed, and a large deformation is generated when the external vibration is slight.
As shown in FIG. 2, in one embodiment, the number of the piezoelectric cantilevers 1-7 can be 1 or more.
Because the internal resistance of the piezoelectric collector 1 is large, usually hundreds of kilohms, the output voltage between the voltage output positive electrode 1-7-3 and the output negative electrode 1-7-4 is high, the current is small, and for the convenience of storage and utilization, the output voltage needs to be rectified, filtered and subjected to DC-DC Boost conversion, and the circuit diagram of the piezoelectric energy collecting device is shown in fig. 4.
In one embodiment, the rectifier circuit 2 includes: diode D1Diode D2Diode D3Diode D4And a filter capacitor C1；
Diode D1And diode D3Series, diode D2And diode D4Said diode D1Diode D3And diode D2Diode D4And a filter capacitor C1Are connected in parallel;
when the alternating voltage output by the piezoelectric collector 1 is larger than the filter capacitor C1Two terminal voltage, diode D2And D3On, D1And D4Cutting off; in the same way, the alternating voltage output by the piezoelectric collector 1 is smaller than the filter capacitor C1Two terminal voltage, diode D1And D4On, D2And D3Cutting off; the output voltage is direct current after passing through the rectifier bridge.
As shown in fig. 4, a Boost circuit is adopted as the DC/DC Boost circuit 3, in order to improve the efficiency of energy conversion, and at the same time, a DC voltage with adjustable magnitude can be provided. The components are as follows: energy storage inductor L, switching device IGBT, freewheeling diode VD and filter capacitor C3；
The working principle of the DC/DC Boost booster circuit 3 is as follows:
the S1 switching element IGBT is conducted at the beginning, all the voltage obtained after passing through the rectifying circuit is added to the energy storage inductor L and flows through the inductor current idA linear increase; at the same time, the freewheeling diode VD is reversely biased and is in a cut-off state, and the load is provided with a filter capacitor C3And (5) supplying power.
S2 TonAt the moment, the switching tube is turned off, iLThe power flows to the output side through a freewheeling diode VD4, and the power of the power supply and the capacity of the energy storage inductor L flow to a load and a filter capacitor C3Transfer to the capacitor C3And (6) charging.
The voltage applied to the inductor L is Uin-UoBecause of Uo＞UinTherefore idThe linearity decreases. Wherein T isonThe time of the switch tube conducting in a time period is.
Time S3T, where T is the cycle time iLA minimum value is reached. Starting a new time period, the above S1 and S2 are repeated. Can adjust the conduction time T of the switch tube in one period TonTo control the magnitude of the output voltage.
In order to keep the DC/DCBoost boost circuit 3 working in CCM (continuous current), the energy storage inductor L is calculated according to the following formula:
Considering the impact current when the circuit works, the limit parameter selection of the switching device needs to have a certain allowance, and the IGBT type selection of the switching device meets the following requirements:
with the type selection requirement of the IGBT, the fly-wheel diode VD should satisfy the following conditions in consideration of the peak current, surge voltage and the like when the circuit works:
selection and output of capacitor versus pulsating quantity DeltaUcIs related to the design requirements, filter capacitor C3And (3) calculating:
because the output characteristics of the piezoelectric ceramic pieces in the piezoelectric collector 1 are nonlinear, the piezoelectric voltage and current of the whole piezoelectric ceramic piece are influenced by the length of the cantilever beam substrate 1-3, the width and thickness of the piezoelectric ceramic pieces, the external load impedance and other factors to a great extent.
When the corresponding conditions change, the output characteristics and the output power of the entire piezoelectric collector 1 also change, resulting in a loss of power.
The invention adopts the Maximum Power Point Tracking (MPPT) technology, and adjusts the output of the piezoelectric collector 1 by adopting the MPPT device, so that the piezoelectric energy collecting device always works at the maximum power point, the energy generated by the piezoelectric collector 1 is effectively utilized, and the conversion efficiency of the piezoelectric energy is improved.
In one embodiment, the MPPT controller 5 further includes: a PWM generator; the MPPT controller 5 outputs a PWM (pulse width modulation) signal to control the DC/DC Boost booster circuit 3 through the voltage value at the maximum power point, and the output voltage can be adjusted by adjusting the duty ratio of a switching device IGBT (insulated gate bipolar transistor) in the DC/DC Boost booster circuit 3, so that the working voltage of the piezoelectric collector 1 is maintained at the maximum power point, and the maximum power tracking distributed control is realized.
The PWM control signal output from the MPPT controller 5 cannot directly drive the switching device IGBT power switching tube in the DC/DC Boost voltage Boost circuit 3, and needs to be driven by the driving circuit 7, and the MOSFET tube driving usually adopts a push-and-pull circuit structure or a dedicated MOSFET driving chip.
As shown in fig. 6 to 7, an embodiment of the present invention further provides a piezoelectric energy harvesting control method, where the energy harvesting device according to any one of the preceding claims includes:
the piezoelectric collector collects energy of the vibration source and converts the energy into electric energy, and measures and outputs alternating voltage;
the alternating voltage output by the piezoelectric collector is rectified by a rectifying circuit and then outputs direct-current voltage;
the direct-current voltage output by the rectification circuit passes through a DC/DC Boost booster circuit and outputs direct-current voltage with adjustable magnitude;
the direct-current voltage output by the rectifying circuit and the direct-current voltage output by the DC/DC Boost circuit are transmitted to a sampling circuit, and the sampling circuit measures a voltage U and a current value I;
the MPPT method comprises the steps that the micro-integral relation between the voltage U and the current value I measured by the sampling circuit is judged through the MPPT algorithm of the conductance incremental method, the MPPT controller outputs corresponding pulse width modulation information numbers, the duty ratio of a switching device in the DC/DC Boost booster circuit is adjusted through the driving circuit, and the output voltage of the DC/DC Boost booster circuit is adjusted.
Thereby maintaining the operating voltage of the piezoelectric collector at the maximum power point, and realizing maximum power tracking distributed control.
As shown in fig. 7, the output characteristic curve of the piezoelectric energy collector P-U is a single-peak curve, which is continuous and conductive in a certain range. When the derivative value dP/dU is 0, the function takes an extreme value, and the extreme value point is the maximum power output point; then
Preferably, the MPPT algorithm by the conductance incremental method determines a calculus relationship between the voltage U and the current value I measured by the sampling circuit, and the MPPT controller outputs a corresponding pulse width modulation information number, specifically:
when dI/dU is > -I/U, the piezoelectric collector works on the left side of the maximum power point, and the output voltage is increased by adjusting PWM waves with higher duty ratio to approach the maximum power point;
when dI/dU is equal to-I/U, the piezoelectric collector works at the left side of the maximum power point without adjustment;
when dI/dU is less than-I/U, the piezoelectric collector works at the right side of the maximum power point, and the output voltage is reduced to approach the maximum power point by outputting PWM waves with reduced duty ratio.
Preferably, the direct-current voltage output by the rectifying circuit passes through a DC/DC Boost circuit to output a direct-current voltage with adjustable magnitude, and the direct-current voltage can also be input into a direct-current load and a storage battery to store electric energy.
In summary, the present invention provides a piezoelectric energy harvesting device and a control method thereof. The method has the following beneficial effects:
the base in the piezoelectric energy collecting device is connected with a vibration source, the number and the installation position of the piezoelectric ceramic pieces can be conveniently installed and debugged according to the actual external vibration source requirement, and the piezoelectric energy collecting device has strong environmental adaptability; the invention adopts the piezoelectric energy collecting circuit with the MPPT controller, the sampling circuit has high precision and high speed, the DC/DC conversion circuit has good switching frequency characteristic, the controller control has good real-time and accuracy, and the duty ratio of a switching device in the DC/DC conversion circuit can be adjusted by judging the micro-integral relation between the voltage U and the current value I measured by the sampling circuit, so that the output voltage can be fed back and regulated, the working voltage of the piezoelectric collector is always maintained at the maximum power point, and the high-efficiency collection of energy is realized.
Although embodiments of the present invention have been shown and described, it will be appreciated by those skilled in the art that changes, modifications, substitutions and alterations can be made in these embodiments without departing from the principles and spirit of the invention, the scope of which is defined in the appended claims and their equivalents.
Claims (10)
1. A piezoelectric energy harvesting device, characterized by: the method comprises the following steps: the device comprises a piezoelectric collector (1), a rectifying circuit (2), a DC/DC Boost circuit (3), a sampling circuit (4), an MPPT controller (5), an optical coupling isolation circuit (6), a driving circuit (7), a direct current load, a storage battery (8) and a PC (personal computer) (9);
the piezoelectric collector (1) is connected with the rectifying circuit (2);
the rectifying circuit (2) is connected with the DC/DC Boost boosting circuit (3);
the direct-current load and the storage battery (8) are connected with the DC/DC Boost booster circuit (3);
the sampling circuit (4) is connected with the MPPT controller (5);
the MPPT controller (5) is connected with the optical coupling isolation circuit (6) and the driving circuit (7);
the drive circuit (7) is connected with the DC/DC Boost circuit (3);
and the PC (9) is connected with the MPPT controller (5).
2. A piezoelectric energy harvesting apparatus according to claim 1, wherein: the piezoelectric collector (1) comprises: the device comprises a base (1-1), a supporting layer (1-2), a substrate (1-3), a substrate tail end mass block (1-4), an acceleration sensor (1-5), a data acquisition card (1-6) and a piezoelectric cantilever beam (1-7);
the piezoelectric cantilever beams (1-7) are fixedly arranged between the base plate (1-3) and the supporting layer (1-2), and the base plate tail end mass block (1-4) is arranged at the non-fixed end of the piezoelectric cantilever beams (1-7);
the base (1-1) is directly or indirectly connected with the supporting layer (1-2), the base plate (1-3), the base plate tail end mass block (1-4), the acceleration sensor (1-5) and the piezoelectric cantilever beam (1-7) and used for fixing the components;
the acceleration sensor (1-5) is connected with the data acquisition card (1-6).
3. A piezoelectric energy harvesting apparatus according to claim 2, wherein: the piezoelectric cantilever (1-7) comprises: the piezoelectric ceramic plate comprises a first double-crystal piezoelectric ceramic plate (1-7-1), a second double-crystal piezoelectric ceramic plate (1-7-2), a piezoelectric collector voltage output positive electrode (1-7-3) and a piezoelectric collector voltage output negative electrode (1-7-4);
the first double-crystal piezoelectric ceramic piece (1-7-1) and the second double-crystal piezoelectric ceramic piece (1-7-2) are symmetrically bonded on the substrate (1-3);
the first double-crystal piezoelectric ceramic piece (1-7-1) and the second double-crystal piezoelectric ceramic piece (1-7-2) are connected in parallel, one lead is respectively led out in a welding mode, and the other ends of the two leads are welded and shorted to serve as voltage output positive electrodes (1-7-3) of the piezoelectric collector;
and a lead is welded on the surface of the substrate (1-3) and is used as a voltage output negative electrode (1-7-4) of the piezoelectric collector.
4. A piezoelectric energy harvesting apparatus according to claim 3, wherein: the first double-crystal piezoelectric ceramic piece (1-7-1) and the second double-crystal piezoelectric ceramic piece (1-7-2) are completely consistent in material, size and shape.
5. A piezoelectric energy harvesting apparatus according to claim 4, wherein: the stress direction and the coupling electric field direction of the first double-crystal piezoelectric ceramic piece (1-7-1) and the second double-crystal piezoelectric ceramic piece (1-7-2) are the same.
6. A piezoelectric energy harvesting apparatus according to claim 5, wherein: the number of the piezoelectric cantilever beams (1-7) can be 1 or more.
7. A piezoelectric energy harvesting apparatus according to claim 1, wherein: the MPPT controller (5) further comprises: a PWM generator.
8. A piezoelectric energy harvesting control method according to the harvesting apparatus according to any one of claims 1 to 7, comprising:
the piezoelectric collector collects energy of the vibration source and converts the energy into electric energy, and measures and outputs alternating voltage;
the alternating voltage output by the piezoelectric collector is rectified by a rectifying circuit and then outputs direct voltage:
the direct-current voltage output by the rectification circuit passes through a DC/DC Boost booster circuit and outputs direct-current voltage with adjustable magnitude;
the direct-current voltage output by the rectifying circuit and the direct-current voltage output by the DC/DC Boost circuit are transmitted to a sampling circuit, and the sampling circuit measures a voltage U and a current value I;
the MPPT method comprises the steps that the micro-integral relation between the voltage U and the current value I measured by the sampling circuit is judged through the MPPT algorithm of the conductance incremental method, the MPPT controller outputs corresponding pulse width modulation information numbers, the duty ratio of a switching device in the DC/DC Boost booster circuit is adjusted through the driving circuit, and the output voltage of the DC/DC Boost booster circuit is adjusted.
9. The piezoelectric energy collection control method according to claim 8, wherein the MPPT algorithm by the conductance incremental method determines a micro-integral relationship between a voltage U and a current I measured by the sampling circuit, and the MPPT controller outputs a corresponding pulse width modulation information number, specifically:
when dI/dU > -I/U, the piezoelectric collector works at the left side of the maximum power point, and the output voltage is increased by adjusting PWM waves with higher duty ratio to approach the maximum power point;
when dI/dU is equal to-I/U, the piezoelectric collector works at the left side of the maximum power point without adjustment;
when dI/dU < -I/U, the piezoelectric collector works at the right side of the maximum power point, and the output voltage is reduced by outputting PWM waves with reduced duty ratio to approach the maximum power point.
10. The piezoelectric energy collection control method according to claim 8, wherein the direct-current voltage output by the rectifying circuit passes through a DC/DC Boost voltage boosting circuit to output a direct-current voltage with adjustable magnitude, and the direct-current voltage can be further input into a direct-current load and a storage battery for electric energy storage.
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