Magnetic fluid wave energy generator output power control system

Abstract

The application discloses a kind of magnetic fluid wave energy generator output power control systems, control system is by a plurality of identical control module parallel composition, each module includes full-bridge Boost circuit, voltage current sampling link, power control compensation link, commutation control link, PWM modulation link and drive link.Input end of all modules is connected after parallel magnetic fluid wave energy generator output, and output end is connected after parallel through pre-charge circuit DC bus;The control circuit of each module is according to the input voltage current signal collected and is tracked to the output power automatic control by table lookup method, or according to output voltage current signal and is manually controlled to the output power, simultaneously according to input voltage signal and is commutated control.The control system can not only realize the output power control of output waveform regular or irregular magnetic fluid wave energy generator, so that the output of magnetic fluid wave energy generator matches wave output in real time, improves wave energy conversion efficiency, but also efficient and reliable and easy to maintain.

Description

TECHNICAL FIELD

[0001] The application belongs to the field of new energy power generation control, and particularly relates to a control system for output power of a magneto-fluid wave energy generator. BACKGROUND

[0002] Wave energy has the characteristics of wide distribution, large reserves (about 7 x 10 10 kW), and high energy density (about 2-3 kW / m 2 ). Wave energy generation is of great significance for power supply to users on the sea and islands, solving the energy crisis, and achieving the dual-carbon goal. Based on the characteristics that the damping characteristics of the magneto-fluid generator match the wave characteristics, the Institute of Electrical Engineering of the Chinese Academy of Sciences first proposed a scheme of applying the magneto-fluid generator to wave energy generation in China, and developed a magneto-fluid wave energy generation device. The device has the advantages of high reliability, compact structure, and high power density, and almost no mechanical transmission components. However, according to different driving modes, the magneto-fluid wave energy generator outputs irregular or regular wave-shaped, low-voltage (10 1 V order of magnitude), large-current (10 4 A order of magnitude), and low-frequency (10 -1 Hz order of magnitude) alternating current. Irrespective of irregular or regular wave-shaped electrical energy output, the electrical energy needs to be converted before being supplied to users.

[0003] At present, the output power control system of the MHD wave energy generator is relatively less, the Institute of Electrical Engineering of Chinese Academy of Sciences proposes a two-stage circuit of uncontrolled rectification plus synchronous rectification Boost for the output characteristics of the MHD wave energy generator, the circuit can realize the function of rectification and voltage increase, the front stage adopts uncontrolled rectification, and the natural commutation can be realized simply and reliably regardless of the irregular or regular waveform of the output power; the rear stage adopts the synchronous rectification technology, although the on-state loss can be reduced, but the power devices are turned on at the same time in the scheme, including two diodes, the on-state resistance of the diode is larger than that of the controlled device in the synchronous rectification Boost circuit, so the on-state loss of the scheme is larger for the low-voltage and large-current occasions. Nanjing University of Aeronautics and Astronautics proposes a high-gain bridgeless PFC circuit for the output characteristics of the MHD wave energy generator, the circuit adopts a bridgeless structure, and uses a controlled device instead of a diode, thereby reducing the on-state loss of the circuit, and the coupling inductance is further used to improve the circuit gain, but the circuit can only be used for the input of regular sine wave, and the actual output of the MHD wave energy generator is irregular random wave or relatively regular square wave, so the circuit is not suitable for the actual MHD wave energy generator. Beijing University of Technology proposes a Boost circuit with a diode-capacitor voltage doubling link, the main purpose of the circuit is to perform DC voltage increase, and the circuit is mainly used for the MHD wave energy generator with unidirectional motion and DC output, and the actual MHD wave energy generator is reciprocating motion, and the output is alternating current, so the circuit is not suitable for the actual MHD wave energy generator. In addition, the above-mentioned circuits mainly perform input PFC control or output constant voltage control, and the two controls cannot control the output power of the generator, the output power of the generator is determined by the load, but the load power cannot match the input wave power in real time, so that the wave energy is wasted or the power supply is insufficient. SUMMARY

[0004] To solve the above technical problems, the present application provides a MHD wave energy generator output power control system, which can realize efficient rectification and voltage increase conversion of the MHD wave energy generator with regular or irregular output waveform, and can also realize the control of the output power of the MHD wave energy generator, adjust the output of the generator to match the input wave output, maximize the conversion of wave energy into usable electric energy, and improve the wave energy conversion rate.

[0005] To achieve the above purpose, the technical scheme adopted by the present application is as follows:

[0006] The application discloses a magneto-fluid wave energy generator output power control system which is composed of multiple same control modules in parallel, each of the control modules comprises a full-bridge Boost circuit, a voltage and current sampling link, a power control compensation link, a commutation control link, a PWM modulation link and a driving link, input ends of all the control modules are connected to an output end of the magneto-fluid wave energy generator in parallel, and output ends of all the control modules are connected to a DC bus capable of absorbing power through a pre-charge circuit in parallel.

[0007] Further, the full-bridge Boost circuit comprises an input inductor L, a first switch S1, a second switch S2, a third switch S3, a fourth switch S4 and an output filter capacitor C; wherein the first to fourth switches S1, S2, S3 and S4 are all full-controlled devices with low conduction loss to form a full-bridge circuit, the first and second switches S1 and S2 are connected in series to form a first bridge arm, and a connecting point of the first and second switches S1 and S2 is used as a first input end of the full-bridge circuit; the third and fourth switches S3 and S4 are connected in series to form a second bridge arm, and a connecting point of the third and fourth switches S3 and S4 is used as a second input end of the full-bridge circuit; one end of the input inductor L is used as a first input end of the full-bridge Boost circuit, the other end of the input inductor L is connected to the first input end of the full-bridge circuit, the second input end of the full-bridge circuit is used as a second input end of the full-bridge Boost circuit, and the output filter capacitor C is connected in parallel to an output end of the full-bridge circuit; the first input end and the second input end of the full-bridge circuit and the full-bridge Boost circuit can be interchanged, and the voltage at the first input end of the full-bridge Boost circuit is defined as the input power positive direction when the voltage is positive.

[0008] Further, in the full-bridge Boost circuit, only two switches are in the simultaneous conduction state at each moment; when the input AC power U in is positive, the first and second switches S1 and S2 are in the complementary conduction state, the third switch S3 is in the constant-off state, and the fourth switch S4 is in the constant-on state, at this moment, the input inductor L, the first, second and fourth switches S1, S2 and S4 and the output filter capacitor C form a synchronous rectification Boost circuit; when the input AC power U in is negative, the third and fourth switches S3 and S4 are in the complementary conduction state, the first switch S1 is in the constant-off state, and the second switch S2 is in the constant-on state, at this moment, the input inductor L, the second, third and fourth switches S2, S3 and S4 and the output filter capacitor C form a synchronous rectification Boost circuit.

[0009] Further, the pre-charge circuit is used to eliminate the impact on the output filter capacitor C when the DC bus starts, which is connected in series between the positive terminal of the output filter capacitor C and the positive output terminal of the MHD wave energy generator output power control system after being connected in parallel with the power resistor R and the solid-state relay KM; the solid-state relay KM is initially in an open state, the DC bus charges the output filter capacitor C through the power resistor R, when the voltage across the output filter capacitor C reaches the DC bus voltage, the solid-state relay KM is controlled to be closed, the current flows through the solid-state relay KM, and the MHD wave energy generator output power system is shut down, and the solid-state relay KM is opened.

[0010] Further, the voltage and current sampling links are arranged at the input and output terminals of the full-bridge Boost circuit. The voltage and current sampling link at the input terminal can measure positive and negative voltage and current, the positive input terminal of the input voltage sampling link is connected to the first input terminal of the full-bridge Boost circuit, and the negative input terminal of the input voltage sampling link is connected to the second input terminal of the full-bridge Boost circuit; the input current sampling link is arranged at the first input terminal of the full-bridge Boost circuit, and it is defined that the current flowing from the first input terminal to the second input terminal is positive. The voltage and current sampling link at the output terminal can measure positive voltage and current, the positive input terminal of the output voltage sampling link is connected to the positive output terminal of the full-bridge Boost circuit, and the negative input terminal of the output voltage sampling link is connected to the negative output terminal of the full-bridge Boost circuit; the output current sampling link is arranged at the positive output terminal of the full-bridge Boost circuit, and it is defined that the current flowing from the output positive terminal to the output negative terminal is positive. The measured voltage and current signals are input into the power control compensation link and the commutation control link as the feedback signals of the closed-loop control and the reference signals of the commutation control.

[0011] Further, the power control compensation link includes two modes, the first mode controls the output current of the MHD wave energy generator to perform output power automatic tracking control according to the input voltage signal through a lookup table method, and the second mode performs output power manual control according to the output voltage and current signals.

[0012] In the first mode, first, the current value corresponding to the maximum output power is obtained as the reference value of the current closed-loop control according to the absolute value of the input voltage and the previously measured volt-ampere characteristic curve table of the MHD wave energy generator at the maximum output power, then the error signal is obtained by comparing the current reference value with the absolute value of the measured current, and then the error signal is sent to the PI controller for error compensation, and the PWM modulated control signal is obtained after the compensated signal is limited.

[0013] In the second mode, the actual output power is obtained according to the output voltage and current signals, the obtained actual output power value is compared with the set power value to obtain an error signal, the error signal is sent to a PI controller for error compensation, the compensated signal is limited in amplitude, the limited signal is taken as a reference value of current closed-loop control, the current reference value is compared with the measured input current absolute value to obtain an error signal, and finally the current error signal is sent to the PI controller for error compensation, and the compensated signal is limited in amplitude to obtain the PWM modulated control signal.

[0014] Further, the commutation control link is used for continuously sampling and storing the input voltage, judging the size of the continuous n input voltage values, wherein n>1; if the continuous n input voltage values are greater than or equal to the positive voltage threshold Vp, wherein Vp>0, it is determined that the input voltage is positive at this time; if the continuous n input voltage values are less than or equal to the negative voltage threshold Vn, wherein Vn<0, it is determined that the input voltage is negative at this time; if the continuous n input voltage values are greater than the negative voltage threshold Vn and less than the positive voltage threshold Vp, it is determined that the input voltage is 0 at this time; otherwise, it is determined that the input voltage is in the original direction; then the size of the next continuous n input voltage values is judged, and the commutation control is continuously and rolling judged.

[0015] Further, the PWM modulation link comprises a first PWM output PWM1 and a second PWM output PWM2, the first PWM output PWM1 is a PWM signal generated by taking the control signal from the power control compensation link as a modulation signal, and the second PWM output PWM2 is a constant high level output; when it is determined that the input voltage is positive, the first PWM output PWM1 outputs the modulated PWM signal, and the second PWM output PWM2 outputs a constant high level; when it is determined that the input voltage is negative, the first PWM output PWM1 outputs a constant high level, and the second PWM output PWM2 outputs the modulated PWM signal; when it is determined that the input voltage is zero, the first and second PWM outputs PWM1 and PWM2 are closed.

[0016] Further, the driving link comprises a first driving module and a second driving module both working in a half-bridge mode, the first driving module and the second driving module can both output two paths of complementary PWM waves with dead zones controlled by input signals; the output signal of the first driving module is controlled by PWM1, and the output signal of the second driving module is controlled by PWM2; when the input voltage is determined to be positive, the first driving module outputs two paths of complementary PWM waves with dead zones to control the complementary conduction of the first switch S1 and the second switch S2, the second driving module outputs one path of constant high level and one path of constant low level, the constant high level controls the constant conduction of the fourth switch S4, and the constant low level controls the constant closing of the third switch S3; when the input voltage is determined to be negative, the first driving module outputs one path of constant high level and one path of constant low level, the constant high level controls the constant conduction of the second switch S2, and the constant low level controls the constant closing of the first switch S1, the second driving module outputs two paths of complementary PWM waves with dead zones to control the complementary conduction of the third switch S3 and the fourth switch S4; when the input voltage is determined to be zero, the first driving module and the second driving module are both disabled, and the first switch S1, the second switch S2, the third switch S3 and the fourth switch S4 are all closed.

[0017] The present application has the following advantages:

[0018] The present application solves some problems in the practical application of the output power control system of the magnetic fluid wave energy generator, and can be used in the actual magnetic fluid wave energy generation system, and has the following advantages:

[0019] (1) The modular design is adopted, the large current output by the magnetic fluid wave energy generator is distributed to multiple control modules, the efficiency of the control system can be improved, the number of parallel modules can be determined according to the output parameters of the magnetic fluid wave energy generator, considering the control system efficiency, weight, volume and cost, and several modules are reserved as redundant backup, the system has high reliability and is convenient to maintain;

[0020] (2) The full-bridge Boost circuit is adopted, only two full-controlled devices are turned on at the same time each time, and no coupling inductor is contained, not only the conduction loss is reduced and the system efficiency is improved, but also the irregular or regular waveforms of electric energy can be converted, and the corresponding commutation control strategy is proposed;

[0021] (3) The method of controlling the output power of the generator by controlling the output current of the generator is adopted, not only the PFC of the output electric energy of the generator can be realized, but also the automatic current sharing of multiple modules in parallel can be realized; by directly controlling the output power of the generator, the power output by the generator is first output to the DC bus, and then the DC bus supplies power to the user, a buffer link is added, different control modes can be realized to automatically track the maximum power output by the generator, the conversion rate of wave energy is improved, the control flexibility is improved. BRIEF DESCRIPTION OF DRAWINGS

[0022] Figure 1 The schematic diagram of the output power control system of the magnetic fluid wave energy generator of the present application;

[0023] Figure 2 The automatic tracking control schematic diagram of the power control compensation link of the present application;

[0024] Figure 3 The manual control schematic diagram of the power control compensation link of the present application;

[0025] Figure 4 The commutation control program flow chart of the present application;

[0026] Figure 5 The drive control signal timing chart of the present application. DETAILED DESCRIPTION

[0027] In order to make the purpose, technical solutions and advantages of the present application more clear and understandable, the present application is further described in detail below in combination with the drawings and examples. It should be understood that the specific examples described herein are only used to explain the present application and do not limit the present application. In addition, the technical features involved in each embodiment of the present application described below can be combined with each other as long as they do not conflict with each other.

[0028] As shown in Figure 1 The output power control system of the magnetic fluid wave energy generator of the present application is composed of a plurality of identical control modules connected in parallel, each control module includes a full-bridge Boost circuit, a voltage and current sampling link, a power control compensation link, a commutation control link, a PWM modulation link and a drive link, the input ends of all control modules are connected in parallel and then connected to the output end of the magnetic fluid wave energy generator, and the output ends thereof are connected in parallel and then connected to a DC bus capable of absorbing power through a pre-charge circuit. The output power control system of the magnetic fluid wave energy generator of the present application controls the output power of the magnetic fluid wave energy generator by controlling the output current of the magnetic fluid wave energy generator, the output voltage of the control system is clamped by the DC bus, the output current size is determined by the input power size of the control system, and the output power is absorbed by the DC bus.

[0029] The number N of parallel modules can be determined by the following relationship:

[0030]

[0031] Where R on is the on-resistance of the power device, R L is the parasitic resistance of the input inductor L, and R l is the parasitic resistance of the connecting line, I ZThe formula is: Iout=ηIref, where Iout is the rated output current of the MHD wave energy generator, η is the system design efficiency without considering the switching loss, and Vin is the system input voltage. As can be seen from the formula, when the output parameters of the MHD wave energy generator, the on-resistance and the parasitic resistance are determined, the more the number of parallel modules, the greater the system efficiency. However, too many parallel modules will increase the weight, volume and cost of the system, and when the number of parallel modules reaches a certain number, the system efficiency will not be significantly improved. Therefore, the number of parallel modules N can be determined by comprehensively considering the system efficiency, weight, volume and cost. After determining N, in order to improve the system reliability, 2-3 modules can be added as redundant backup.

[0032] The full-bridge Boost circuit includes an input inductor L, a first switch S1, a second switch S2, a third switch S3, a fourth switch S4, and an output filter capacitor C. Since the output voltage of the generator is very low and the output current is very large, in order to reduce the on-resistance loss of the control system, the first to fourth switches S1, S2, S3 and S4 are all composed of MOSFETs with low on-resistance to form a full-bridge circuit. The source of the first switch S1 is connected to the drain of the second switch S2 to form a first bridge arm, and the connection point thereof serves as a first input terminal of the full-bridge circuit. The source of the third switch S3 is connected to the drain of the fourth switch S4 to form a second bridge arm, and the connection point thereof serves as a second input terminal of the full-bridge circuit. The drain of the first switch S1 is connected to the drain of the third switch S3, and the connection point thereof serves as a positive output terminal of the full-bridge circuit. The source of the second switch S2 is connected to the source of the fourth switch S4, and the connection point thereof serves as a negative output terminal of the full-bridge circuit. The parasitic resistance R L The parasitic resistance R C The parasitic resistance R

[0033] Only two switches are in a simultaneous conduction state at each moment, which reduces the on-resistance loss and is very suitable for low-voltage and large-current applications. When the input AC power U in When the input AC power U inWhen the input voltage is negative, the third and fourth switch tubes S3 and S4 are in complementary conduction state, the first switch tube S1 is in constant off state, and the second switch tube S2 is in constant on state, at this time, the input inductor L, the second, third and fourth switch tubes S2, S3 and S4 and the output filter capacitor C form a high-efficiency synchronous rectification Boost circuit.

[0034] The minimum inductance value L when the inductance current is continuous can be determined by the following formula:

[0035]

[0036] where D is the duty ratio, T is the switching period, V o is the single-module output voltage, I o is the single-module output current. After the minimum inductance value is obtained by the above formula, in order to reduce the input current ripple, the actual inductance value can be selected as 1.2-2 times margin.

[0037] The size of the output filter capacitor C can be determined by the following formula:

[0038]

[0039] where D is the duty ratio, T is the switching period, I o is the single-module output current, and ΔV o is the output voltage ripple size. After the minimum capacitance is obtained by the above formula, in order to reduce the output voltage ripple, the actual capacitance value can be selected as 1.2-2 times margin.

[0040] The pre-charge circuit is used to eliminate the impact on the output filter capacitor C when the DC bus starts, which is connected in series between the positive terminal of the output filter capacitor C and the output end of the control system after being connected in parallel with the power resistor R and the solid-state relay KM; the solid-state relay KM is initially in an open state, the DC bus charges the output filter capacitor C through the power resistor R, when the voltage across the output filter capacitor C reaches the DC bus voltage, the solid-state relay KM is controlled to be closed, the current flows through the solid-state relay KM, the control system is shut down, and the solid-state relay KM is opened.

[0041] The voltage and current sampling link is arranged at the input and output ends of the full-bridge Boost circuit, the voltage and current sampling link at the input end can measure positive and negative voltage and current; the positive input end of the input voltage sampling link of the voltage and current sampling link is connected to the first input end of the full-bridge Boost circuit, and the negative input end of the input voltage sampling link of the voltage and current sampling link is connected to the second input end of the full-bridge Boost circuit; the input current sampling link of the voltage and current sampling link is arranged at the first input end of the full-bridge Boost circuit, and it is defined that the current flowing from the first input end to the second input end is positive; the voltage and current sampling link at the output end can measure positive voltage and current, the positive input end of the output voltage sampling link is connected to the positive output end of the full-bridge Boost circuit, and the negative input end of the output voltage sampling link is connected to the negative output end of the full-bridge Boost circuit; the output current sampling link is arranged at the positive output end of the full-bridge Boost circuit, and it is defined that the current flowing from the positive output end to the negative output end is positive; the measured voltage and current signals are input into the power control compensation link and the commutation control link as the feedback signals of the closed-loop control and the reference signals of the commutation control.

[0042] Reference Figure 1 The voltage and current sampling link is arranged at the input and output ends of the full-bridge Boost circuit, the voltage and current sampling link at the input end can measure positive and negative voltage and current; the positive input end of the input voltage sampling link of the voltage and current sampling link is connected to the first input end of the full-bridge Boost circuit, and the negative input end of the input voltage sampling link of the voltage and current sampling link is connected to the second input end of the full-bridge Boost circuit; the input current sampling link of the voltage and current sampling link is arranged at the first input end of the full-bridge Boost circuit, and it is defined that the current flowing from the first input end to the second input end is positive; the voltage and current sampling link at the output end can measure positive voltage and current, the positive input end of the output voltage sampling link is connected to the positive output end of the full-bridge Boost circuit, and the negative input end of the output voltage sampling link is connected to the negative output end of the full-bridge Boost circuit; the output current sampling link is arranged at the positive output end of the full-bridge Boost circuit, and it is defined that the current flowing from the positive output end to the negative output end is positive.

[0043] In the embodiment, the power control compensation link, the commutation control link and the PWM modulation link are all completed by a digital signal processor.

[0044] Reference Figure 2 And Figure 3 The power control compensation link has two modes, which can be switched by a mode switching instruction, the first mode is to control the output current of the magneto fluid wave energy generator to automatically track the output power according to the input voltage signal by a table lookup method, and the second mode is to manually control the output power according to the output voltage and current signal.

[0045] The control circuit of the first mode mainly consists of a voltage-ampere characteristic curve table when the output power of the magneto-hydrodynamic wave energy generator is maximum, a signal comparison link, a current signal error compensation control link and a limiting link, and the specific implementation steps are as follows:

[0046] Step (1): sampling and analog-digital conversion of the input voltage and current signals;

[0047] Step (2): taking absolute values of the voltage and current, and according to the absolute value of the input voltage and the voltage-ampere characteristic curve table measured in advance when the output power of the magneto-hydrodynamic wave energy generator is maximum, obtaining the current value corresponding to the maximum output power as the reference value of the current closed-loop control;

[0048] Step (3): comparing the current reference value and the measured current absolute value to obtain an error signal;

[0049] Step (4): sending the error signal to a PI controller for error compensation, and obtaining a PWM modulated control signal after limiting the compensated signal.

[0050] The control circuit of the second mode mainly consists of a signal comparison link, a power signal error compensation control link, a current signal error compensation control link and a limiting link, and the specific implementation steps are as follows:

[0051] Step (1): sampling and analog-digital conversion of the output voltage and current signals;

[0052] Step (2): multiplying the output voltage and current to obtain the output power, comparing the obtained power value with the set power value to obtain an error signal;

[0053] Step (3): sending the error signal to a PI controller for error compensation, and taking the limited signal as the reference value of the current closed-loop control;

[0054] Step (4): comparing the current reference value and the measured current absolute value to obtain an error signal;

[0055] Step (5): sending the error signal to a PI controller for error compensation, and obtaining a PWM modulated control signal after limiting the compensated signal.

[0056] Reference Figure 4 The specific implementation steps of the commutation control link are as follows:

[0057] Step (1): defining a floating-point array a[n] containing n elements, a commutation control flag C_flag, a commutation retention flag B_flag, a positive voltage threshold Vp and a negative voltage threshold Vn, and assigning initial values to all variables;

[0058] Step (2): Sampling and analog-digital conversion of input voltage, continuous sampling, and input voltage sample values are stored in array a[n] from back to front in turn;

[0059] Step (3): Determine the size of the continuous n input voltage values, if the continuous n input voltage values are greater than or equal to the forward voltage threshold Vp (Vp> 0), C_flag=1; if the continuous n input voltage values are less than or equal to the negative voltage threshold Vn (Vn<0), C_flag=2; if the continuous n input voltage values are greater than the negative voltage threshold Vn and less than the positive voltage threshold Vp, C_flag=0; otherwise, C_flag=B_flag;

[0060] Step (4): Determine the size of the next continuous n input voltage values, and continuously roll the determination to control the commutation.

[0061] The greater the number n, the absolute value of the positive voltage threshold Vp and the absolute value of the negative voltage threshold Vn, the more sluggish and stable the commutation is; the smaller the absolute value of the three numbers, the more sensitive and the more likely to appear oscillation.

[0062] The PWM modulation link includes first and second PWM outputs, the first PWM output is a PWM signal generated by the control signal output by the control compensation link as a modulation signal, and the second PWM output is a constant high level output; the two PWM outputs are defined as PWM1 and PWM2 respectively, when C_flag=1, the first PWM output PWM1 outputs the modulated PWM signal, and the second PWM output PWM2 outputs a constant high level; when C_flag=2, the first PWM output PWM1 outputs a constant high level, and the second PWM output PWM2 outputs the modulated PWM signal; when C_flag=0, the PWM output is closed.

[0063] Reference Figure 5The driving link adopts two driving modules working in half-bridge mode, the two driving modules are defined as a first driving module and a second driving module, the output signal of the first driving module is controlled by PWM1 in the PWM modulation link, and the output signal of the second driving module is controlled by PWM2 in the PWM modulation link; when C_flag=1, the first driving module outputs two complementary PWM waves with a dead zone to control the complementary conduction of the first switch S1 and the second switch S2, the second driving module outputs a constant high level and a constant low level, the constant high level controls the fourth switch S4 to be constantly turned on, and the constant low level controls the third switch S3 to be constantly turned off; when C_flag=2, the first driving module outputs a constant high level and a constant low level, the constant high level controls the second switch S2 to be constantly turned on, and the constant low level controls the first switch S1 to be constantly turned off, and the second driving module outputs two complementary PWM waves with a dead zone to control the complementary conduction of the third switch S3 and the fourth switch S4; when C_flag=0, the first driving module and the second driving module are disabled, and the first to fourth switches S1, S2, S3 and S4 are all turned off.

[0064] Those skilled in the art should understand that the embodiments of the present application can be provided as a method, a system or a computer program product. The present application can take the form of an entirely hardware embodiment, an entirely software embodiment or an embodiment combining software and hardware. And the present application can take the form of a computer program product implemented on one or more computer-usable storage media (including but not limited to disk storage, CD-ROM, U disk) containing computer-usable program code.

[0065] The embodiments of the present application are described above in combination with the drawings, but the present application is not limited to the above specific embodiments, the above specific embodiments are illustrative rather than limiting, and those skilled in the art can make many forms under the inspiration of the present application without departing from the purpose of the present application and the scope protected by the claims, which all belong to the protection scope of the present application.

Claims

1. A magnetohydrodynamic wave energy generator output power control system, characterized in that: Each control module comprises a full-bridge Boost circuit, a voltage and current sampling link, a power control compensation link, a commutation control link, a PWM modulation link and a driving link, input ends of all the control modules are connected in parallel and then connected to an output end of a magneto-hydrodynamic wave energy generator, output ends of all the control modules are connected in parallel and then connected to a DC bus capable of absorbing power through a pre-charging circuit; the magneto-hydrodynamic wave energy generator output power control system controls the output power of the magneto-hydrodynamic wave energy generator by controlling the output current of the magneto-hydrodynamic wave energy generator, the output voltage of the magneto-hydrodynamic wave energy generator output power control system is clamped by the DC bus, the output current size is determined by the input power size of the magneto-hydrodynamic wave energy generator output power control system, and the output power is absorbed by the DC bus; The full-bridge Boost circuit comprises an input inductor L, first, second, third and fourth switching tubes S1, S2, S3 and S4, and an output filter capacitor C; wherein the first to fourth switching tubes S1, S2, S3 and S4 are all full-controlled devices with low conduction loss and form a full-bridge circuit, the first and second switching tubes S1 and S2 are connected in series to form a first bridge arm, and a connection point thereof serves as a first input end of the full-bridge circuit; the third and fourth switching tubes S3 and S4 are connected in series to form a second bridge arm, and a connection point thereof serves as a second input end of the full-bridge circuit; one end of the input inductor L serves as a first input end of the full-bridge Boost circuit, the other end of the input inductor L is connected to the first input end of the full-bridge circuit, the second input end of the full-bridge circuit serves as a second input end of the full-bridge Boost circuit, and the output filter capacitor C is connected in parallel to an output end of the full-bridge circuit; it is specified that when the first input end voltage of the full-bridge Boost circuit is positive, it is a positive input power; In the full-bridge Boost circuit, only two switching tubes are in simultaneous conduction state at each moment; when the input AC power U in is positive, the first and second switching tubes S1 and S2 are in complementary conduction state, the third switching tube S3 is in constant off state, and the fourth switching tube S4 is in constant on state, at this moment, the input inductor L, the first, second, fourth switching tubes S1, S2 and S4 and the output filter capacitor C form a synchronous rectification Boost circuit; when the input AC power U in is negative, the third and fourth switching tubes S3 and S4 are in complementary conduction state, the first switching tube S1 is in constant off state, and the second switching tube S2 is in constant on state, at this moment, the input inductor L, the second, third and fourth switching tubes S2, S3 and S4 and the output filter capacitor C form a synchronous rectification Boost circuit.

2. A system for controlling the output power of a magneto-hydrodynamic wave energy converter according to claim 1, characterised in that: The pre-charging circuit is used to eliminate the impact of the DC bus on the output filter capacitor C during startup, and is connected in series between the positive electrode end of the output filter capacitor C and the positive output end of the magneto-hydrodynamic wave energy generator output power control system after being connected in parallel with a power resistor R and a solid-state relay KM; the solid-state relay KM is initially in an open state, the DC bus charges the output filter capacitor C through the power resistor R, when the voltage across the output filter capacitor C reaches the DC bus voltage, the solid-state relay KM is controlled to be closed, current flows through the solid-state relay KM, the magneto-hydrodynamic wave energy generator output power control system is shut down, and the solid-state relay KM is opened.

3. A system for controlling the output power of a magneto-hydrodynamic wave energy converter according to claim 1, characterized in that: The voltage and current sampling link is arranged at the input and output ends of the full-bridge Boost circuit, and the voltage and current sampling link at the input end can measure positive and negative voltage and current; the positive input end of the input voltage sampling link is connected to the first input end of the full-bridge Boost circuit, and the negative input end of the input voltage sampling link is connected to the second input end of the full-bridge Boost circuit; The input current sampling link is arranged at the first input end of the full-bridge Boost circuit, and is defined as positive when flowing from the first input end to the second input end; the voltage and current sampling link of the output end can measure the forward voltage and current, the positive input end of the output voltage sampling link is connected to the positive output end of the full-bridge Boost circuit, and the negative input end of the output voltage sampling link is connected to the negative output end of the full-bridge Boost circuit; the output current sampling link is arranged at the positive output end of the full-bridge Boost circuit, and is defined as positive when flowing from the positive output end to the negative output end; the measured voltage and current signals are input into the power control compensation link and the commutation control link as the feedback signals of the closed-loop control and the reference signals of the commutation control.

4. A system for controlling the output power of a magneto-hydrodynamic wave energy converter according to claim 1, characterized in that: The power control compensation link comprises two modes, in the first mode, the output current of the MFC wave energy generator is controlled by the lookup table method according to the input voltage signal to perform the output power automatic tracking control, and in the second mode, the output power is manually controlled according to the output voltage and current signals. In the first mode, firstly, the current value corresponding to the maximum output power is obtained according to the input voltage absolute value and the previously measured volt-ampere characteristic curve table of the MFC wave energy generator at the maximum output power, as the reference value of the current closed-loop control, then the error signal is obtained by comparing the current reference value with the measured current absolute value, then the error signal is sent to the PI controller for error compensation, and the amplitude-limited signal is obtained after the compensated signal is amplitude-limited, and the PWM-modulated control signal is obtained. In the second mode, firstly, the actual output power value is obtained according to the output voltage and current signals, then the error signal is obtained by comparing the obtained actual output power value with the set power value, then the error signal is sent to the PI controller for error compensation, and the amplitude-limited signal is obtained after the compensated signal is amplitude-limited, then the amplitude-limited signal is used as the reference value of the current closed-loop control, the current reference value is compared with the measured input current absolute value to obtain the error signal, and finally the current error signal is sent to the PI controller for error compensation, and the PWM-modulated control signal is obtained after the amplitude-limited signal is amplitude-limited.

5. A system for controlling the output power of a magneto-hydrodynamic wave energy converter according to claim 1, characterized in that: The commutation control link is used for continuously sampling and storing the input voltage, and judging the size of the continuous n input voltage values, wherein n>1. If the continuous n input voltage values are greater than or equal to the forward voltage threshold Vp, wherein Vp>0, it is determined that the input voltage is forward at this time; if the continuous n input voltage values are less than or equal to the negative voltage threshold Vn, wherein Vn<0, it is determined that the input voltage is negative at this time; if the continuous n input voltage values are greater than the negative voltage threshold Vn and less than the forward voltage threshold Vp, it is determined that the input voltage is 0 at this time; otherwise, it is determined that the input voltage is in the original direction; then the size of the next continuous n input voltage values is judged, and the commutation control is continuously and rolling judged.

6. A system for controlling the output power of a magneto-hydrodynamic wave energy converter according to claim 5, characterised in that: The PWM modulation link comprises a first PWM output PWM1 and a second PWM output PWM2; when the input voltage is determined to be positive, the first PWM output PWM1 outputs a PWM signal generated by taking the control signal from the power control compensation link as a modulation signal, and the second PWM output PWM2 outputs a constant high level; when the input voltage is determined to be zero, the first and second PWM outputs PWM1 and PWM2 are closed; when the input voltage is determined to be reverse, the first PWM output PWM1 outputs a high level, and the second PWM output PWM2 outputs a PWM signal generated by taking the control signal from the power control compensation link as a modulation signal.

7. A system for controlling the output power of a magneto-hydrodynamic wave energy converter according to claim 6, characterised in that: The driving link comprises a first driving module and a second driving module both working in a half-bridge mode, and the first and second driving modules can both output two paths of complementary PWM waves with a dead zone controlled by an input signal; the output signal of the first driving module is controlled by PWM1, and the output signal of the second driving module is controlled by PWM2; when the input voltage is determined to be positive, the first driving module outputs two paths of complementary PWM waves with a dead zone to control the complementary conduction of the first and second switching tubes S1 and S2, the second driving module outputs a constant high level to control the constant conduction of the fourth switching tube S4 and a constant low level to control the constant closing of the third switching tube S3; when the input voltage is determined to be negative, the first driving module outputs a constant high level to control the constant conduction of the second switching tube S2 and a constant low level to control the constant closing of the first switching tube S1, and the second driving module outputs two paths of complementary PWM waves with a dead zone to control the complementary conduction of the third and fourth switching tubes S3 and S4; when the input voltage is determined to be zero, the first and second driving modules are both disabled, and the first to fourth switching tubes S1, S2, S3 and S4 are all closed.

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