Multi-wave energy conversion device and method based on direct-current series structure

Abstract

The invention relates to the technical field of energy conversion, and discloses a multi-wave energy conversion device and method based on a direct-current series structure, and the device comprises the steps: carrying out the motor closed-loop control of a rectification current component after rectification operation through a generator main control module, and generating motor operation data for controlling two synchronous generators; the problem that a single driving circuit is difficult to drive two or more synchronous generators can be solved; meanwhile, the synchronous generators generate power through mechanical transmission, and when the rectifier and the synchronous generators comprising the mechanical transmission are integrated, the two synchronous generators are regulated and controlled according to the obtained motor operation data, so that the problem that the adjustability of the mechanical transmission is ignored in rectification operation is solved. And on the direct current side, the two uncontrolled rectifiers are connected in series, direct current ripples are mutually counteracted, and high-quality rectified voltage can be provided, so that high-quality electric energy is obtained.

Description

Technical Field

[0001] The present invention relates to the technical field of energy conversion, and in particular to a multi-wave energy conversion device and method based on a direct current series structure. Background Art

[0002] As a key type of renewable energy, new energy has the characteristics of abundant resources, wide distribution and high energy flow density. Taking wave energy power generation devices as an example, they need to operate stably for a long time in harsh marine environments. In the utilization of wave energy, conversion efficiency and cost are the key factors restricting its large-scale application. Therefore, lightweight, easy to control and highly integrated multi-wave energy conversion devices based on DC series structure have become an important development trend.

[0003] At present, the traditional control method of driving two synchronous generators with a single rectifier is to directly connect the two synchronous generators to the rectifier. However, when two synchronous generators are operated in parallel, they will face many problems. The output characteristics of each generator such as voltage, frequency, and phase sequence often differ, which will cause ripples during power conversion. Ripple will interfere with the stable transmission and use of power, reduce power quality, affect the normal operation of electrical equipment, and increase equipment losses. This is an urgent problem to be solved in modern industrial and power application scenarios with high requirements for power quality. Summary of the invention

[0004] The present invention provides a multi-wave energy conversion device and method based on a DC series structure, which solves the technical problem of how to improve the quality of converted electric energy of renewable energy power generation.

[0005] A first aspect of the present invention provides a conversion device, comprising:

[0006] It includes an electric energy conversion module and a generator main control module which are communicatively connected to each other;

[0007] The electric energy conversion module includes two synchronous generators, a double-winding transformer and two rectifiers;

[0008] The synchronous generator is used to convert mechanical energy into AC electrical energy;

[0009] The double-winding transformer is used to convert the voltage of AC power and provide a high-order harmonic current channel and leakage inductance filtering capability;

[0010] The rectifier is used to rectify the AC power after voltage conversion to generate DC power;

[0011] The generator main control module is used to use the rectified current component after the rectification operation to perform motor closed-loop control, and to regulate the two synchronous generators according to the generated motor operation data.

[0012] Optionally, the regulation is specifically to perform the same-speed, reverse-direction and equal-torque regulation on the two synchronous generators.

[0013] Optionally, the double-winding transformer is a DY type double-winding transformer;

[0014] The two synchronous generators are respectively connected to the primary winding and the secondary winding of the double-winding transformer;

[0015] The two rectifiers are respectively connected to the primary winding and the secondary winding of the double-winding transformer;

[0016] The two rectifiers are connected in series;

[0017] A coupling inductor is provided between the two rectifiers and the dual-winding transformer, and the coupling inductor is used to filter out high-order harmonics of the rectifiers.

[0018] Optionally, the two synchronous generators and the two rectifiers are both communicatively connected to the generator main control module;

[0019] The generator main control module includes a speed submodule and a position angle submodule;

[0020] The motor operation data includes motor speed data and rotor position angle data;

[0021] The speed submodule is used to generate the motor speed data for regulating the motor speed of the synchronous generator according to the rectified current component;

[0022] The position angle submodule is used to generate the rotor position angle data for regulating the rotor position of the synchronous generator.

[0023] Optionally, the speed submodule includes an inverse operation unit and a speed calculation unit that are communicatively connected to each other;

[0024] The inverse operation unit is used to obtain the current zero-crossing cycle time difference, and perform an inverse operation based on the current zero-crossing cycle time difference to generate a frequency-locked speed component;

[0025] The speed calculation unit is used to obtain the motor speed data according to the frequency-locked speed component, in combination with the rectified current component and a preset reference speed component.

[0026] Optionally, the position angle submodule includes an integral operation unit;

[0027] The integral operation unit is used to perform an integral operation on the frequency-locked speed component to generate the rotor position angle data.

[0028] Optionally, the speed calculation unit includes a speed difference calculation subunit, a speed feedback adjustment subunit, a current difference calculation subunit, a current feedback adjustment subunit, a target current calculation subunit and a motor speed generation submodule which are sequentially communicatively connected;

[0029] The speed difference calculation subunit is used to generate an error speed by calculating the difference between the preset reference speed component and the frequency-locked speed component;

[0030] The speed feedback regulation subunit is used to generate a reference current component by inputting the error speed into a preset speed regulator for feedback regulation based on a preset speed outer loop transfer function;

[0031] The current difference calculation subunit is used to generate an error current by calculating the difference between the reference current component and the rectified current component;

[0032] The current feedback regulation subunit is used to input the error current into a preset current regulator for feedback regulation based on a preset current inner loop transfer function to generate a duty cycle parameter;

[0033] The target current calculation subunit is used to generate target current data by calculating the product between the duty cycle parameter and a preset first transfer function;

[0034] The motor speed generating submodule is used to generate the motor speed data by calculating the product between the target current data and a preset second transfer function.

[0035] Optionally, the generator main control module further includes a drive signal generation submodule;

[0036] The drive signal generation submodule is used to perform a modulation operation on the motor operation data to generate a switch drive signal for controlling the rectifier to start or stop power conversion.

[0037] Optionally, the rectifier is a diode uncontrolled rectifier.

[0038] The second aspect of the present invention provides a conversion method applied to the multi-wave energy conversion device based on a DC series structure, comprising:

[0039] Performing rectification operation on the rectified current component after receiving the rectification operation to generate motor operation data;

[0040] According to the motor operation data, the electric energy conversion module is regulated in the same speed, reverse direction and equal torque, and electric energy conversion is performed.

[0041] It can be seen from the above technical solutions that the present invention has the following advantages:

[0042] The present invention proposes a multi-wave energy conversion device based on a DC series structure based on a double-winding transformer, and adopts a generator main control module to perform motor closed-loop control on the rectified current component after the rectification operation, and generates motor operation data for controlling two synchronous generators, which can solve the problem that a single drive circuit is difficult to drive two or more synchronous generators; at the same time, the synchronous generator of the present invention generates electricity through mechanical transmission. When the rectifier is integrated with the synchronous generator including mechanical transmission, if the adjustability of the mechanical transmission is ignored, it may cause the electrical and mechanical parts to be difficult to match. The present invention uses the acquired motor operation data to regulate the two synchronous generators, specifically by adjusting the operating parameters of the synchronous generator, such as speed and torque, to solve the problem of ignoring the adjustability of the mechanical transmission in the rectification operation, and introduce a low-frequency AC transformer on the motor side to provide a channel for harmonics, improve the motor current quality, and avoid the harmonic current of the diode from being connected in series with the synchronous generator. On the DC side, two uncontrolled rectifiers are connected in series, and the DC ripples cancel each other out, which can provide a higher quality rectified voltage, thereby obtaining high-quality electric energy. BRIEF DESCRIPTION OF THE DRAWINGS

[0043] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings required for use in the embodiments or the description of the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying creative labor.

[0044] Figure 1 This is a schematic structural diagram of a multi-wave energy conversion device based on a DC series structure according to an embodiment of the present invention;

[0045] Figure 2 A schematic diagram of the structure of a rotation speed calculation unit according to an embodiment of the present invention;

[0046] Figure 3 A schematic diagram of voltage and current waveforms according to an embodiment of the present invention;

[0047] Figure 4 is a comparison diagram of the total harmonic distortion THD of the generator current and the diode side current in an embodiment of the present invention;

[0048] Figure 5 The present invention is a flowchart of the steps of a conversion method applied to a multi-wave energy conversion device based on a DC series structure according to an embodiment of the present invention. DETAILED DESCRIPTION

[0049] The embodiment of the present invention provides a multi-wave energy conversion device and method based on a DC series structure, which is used to solve the technical problem of how to improve the quality of converted electric energy of renewable energy power generation.

[0050] In order to make the purpose, features and advantages of the present invention more obvious and easy to understand, the technical solutions in the embodiments of the present invention will be clearly and completely described below in conjunction with the drawings in the embodiments of the present invention. Obviously, the embodiments described below are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0051] In wave energy power generation technology, the energy storage wave energy DC power generation system mainly includes wave energy collector, hydraulic accumulator, energy distribution unit, gearbox, permanent magnet synchronous generator, rectifier and DC bus. The wave energy is collected into the hydraulic accumulator through the collector, and then transmitted to each permanent magnet synchronous generator through the energy distribution unit and gearbox, and finally collected into the DC bus through the rectifier. Among them, the permanent magnet synchronous generator and the rectifier are combined into a multi-wave energy conversion device based on the DC series structure, and the Boost-PFC type rectifier topology is a more suitable solution for wave energy generator sets, which can realize the effective adjustment of motor current and frequency. At present, the Boost-PFC type rectifier is usually adapted to the operation of wave energy permanent magnet synchronous generators. However, when multiple wave energy permanent magnet synchronous units are DC-connected, the solution of parallel connection to the medium voltage DC bus or series connection to the high voltage DC bus is often adopted, which is easy to cause problems such as high cost and low power density.

[0052] On the other hand, the regulation of the current quality of the DC motor is usually achieved through the closed-loop control of the converter. The control scheme to improve the power quality usually adopts the scheme of increasing the complexity of the control structure or increasing the feedback variable. However, the existing scheme will greatly increase the cost of control and debugging. Therefore, simple topology adjustment and mechanical control are also important means and trends to achieve the improvement of power quality.

[0053] In summary, in the prior art, Boost-PFC type rectifiers are usually adapted to operate wave energy permanent magnet synchronous generators. However, when multiple wave energy permanent magnet synchronous generators are connected in parallel to a medium voltage DC bus or in series to a high voltage DC bus, the solution is often adopted, which easily leads to problems such as high cost and low power density.

[0054] Control solutions to improve power quality usually adopt solutions such as increasing the complexity of the control structure or adding feedback variables. However, existing solutions will greatly increase the cost of materials, control and commissioning.

[0055] A single motor drive circuit has difficulty driving multiple motors and does not have the quality to operate with high motor current.

[0056] The present invention is based on a single rectifier Boost PFC circuit connected to a DY-type double-winding transformer to drive two synchronous generators or even multiple synchronous generators, thereby reducing the complexity of topology, the difficulty of control and the cost of equipment.

[0057] The DY type double-winding transformer is a low-frequency transformer. The low-frequency transformer is connected across the synchronous generator to provide a harmonic channel and further improve the power quality.

[0058] Therefore, the present invention proposes a multi-wave energy conversion device based on a DC series structure based on a double-winding transformer, and uses a generator main control module to perform motor closed-loop control on the rectified current component after the rectification operation, and generates motor operation data for controlling two synchronous generators, which can solve the problem that a single drive circuit is difficult to drive two or more wave energy permanent magnet synchronous generators; at the same time, the synchronous generator of the present invention generates electricity through mechanical transmission. When the rectifier is integrated with the synchronous generator including mechanical transmission, if the adjustability of the mechanical transmission is ignored, it may cause the electrical and mechanical parts to be difficult to match. For example, in a system where the engine drives the generator through a belt drive, and then the generator outputs AC power that is converted into DC power through a rectifier, if the transmission ratio of the mechanical transmission cannot be adjusted, the generator may not be able to operate at the optimal speed, thereby affecting the input voltage and current characteristics of the rectifier, resulting in a reduction in rectification efficiency. Therefore, the present invention uses the acquired motor operation data to regulate the two synchronous generators, specifically by adjusting the operating parameters of the synchronous generator, such as speed and torque. The problem of the adjustability of ignoring mechanical transmission in rectification operation is solved, and the double-winding transformer of the present invention provides a high-order harmonic current channel and leakage inductance filtering capability, thereby improving the quality of electric energy and solving the problem of low motor current quality in traditional wave power generation multi-machine DC grid connection.

[0059] See also Figure 1 and Figure 2 , the present invention provides a multi-wave energy conversion device based on a DC series structure, including an electric energy conversion module and a generator main control module that are communicatively connected to each other;

[0060] The power conversion module includes two synchronous generators, a two-winding transformer and two rectifiers;

[0061] Synchronous generators are used to convert mechanical energy into AC electrical energy;

[0062] The double-winding transformer is used to convert the voltage of AC power and provide high-order harmonic current channels and leakage inductance filtering capabilities;

[0063] The rectifier is used to rectify the AC power after voltage conversion to generate DC power;

[0064] The generator master control module is used to perform motor closed-loop control using the rectified current component after the rectification operation, and to regulate the two synchronous generators according to the generated motor operation data.

[0065] Please note that Figure 1 , Figure 1 This is a structural schematic diagram of a multi-wave energy conversion device based on a DC series structure. The two M's on the left side of the figure refer to two synchronous generators, PMSG1 and PMSG2 respectively. The two synchronous generators are connected through a gearbox shaft. A controller is provided in the gearbox that is communicated with the generator main control module to receive and regulate the two synchronous generators according to the motor operation data. The right sides of the two synchronous generators are respectively connected to the primary winding side triangle (D) connection and the secondary winding side star (Y) connection of the DY type double-winding transformer. The AC sides of the two rectifiers are also respectively connected to the primary winding side triangle (D) connection and the secondary winding side star (Y) connection of the DY type double-winding transformer. Under this connection mode, for high-order harmonic currents, especially the third and multiple harmonic currents of 3, a circulating current is formed in the winding connected in the triangle on the primary side. Since the triangle-connected winding is closed, these harmonic currents can circulate inside the triangle winding, thus providing a low-impedance channel for high-order harmonic currents; the leakage inductance of the transformer is the inductance generated by the incomplete coupling between the primary winding and the secondary winding of the transformer. When the current passes through the transformer, the leakage inductance will hinder the change of the current. For high-order harmonic currents, due to their high frequency, the leakage inductance presents a large inductive reactance. When the high-order harmonic current tries to pass through the transformer, the large leakage inductive reactance will limit the size of the harmonic current and play a filtering role. The main circuit on the DC side of the rectifier is connected to the DC bus, and the main circuit of the rectifier includes a current transformer or a Hall current sensor, an inductor, a diode, a capacitor and an IGBT element; a current transformer or a Hall current sensor is arranged between the main circuit of the rectifier and the DC bus, and the current transformer or the Hall current sensor is connected in series with an inductor, and the end of the inductor away from the current transformer or the Hall current sensor is respectively connected to the IGBT element and the diode, and the end of the diode away from the inductor is connected to the capacitor, and the end of the capacitor away from the diode is connected to the DC bus.

[0066] It should be noted that the current transformer or the Hall current sensor is used to detect the rectified current component after rectification, and the current component specifically refers to the current periodic component.

[0067] See also Figure 1 and Figure 2 The generator main control module includes a speed submodule and a position angle submodule. The speed submodule includes a mutual inverse operation unit and a speed calculation unit. Figure 2: is a structural diagram of a speed calculation unit, which includes a speed difference calculation subunit, a speed feedback adjustment subunit, a current difference calculation subunit, a current feedback adjustment subunit, a target current calculation subunit and a motor speed generation submodule which are sequentially connected in communication. Figure 2 Plant i1 and plant i2 They refer to the target current calculation subunit and the motor speed generation submodule respectively.

[0068] The multi-wave energy conversion device based on the DC series structure includes a mechanical system and an electrical system. The mechanical system includes a gearbox, which is used to provide torque to the synchronous generator and realize reverse following control of other generators. Taking wave energy power generation as an example, in an actual wave energy power generation device, wave energy is collected by a collector, stored in a hydraulic accumulator, and further provided to the wave energy permanent magnet synchronous motor through an energy distribution unit and a gearbox shaft. In this application, a gearbox is added to interconnect two synchronous generators, and the torque, speed and steering phase of the two interconnected generators driven by the motor operation data are the same.

[0069] In the present application, the electrical system is composed of an electric energy conversion module and a generator main control module, specifically including a synchronous generator, a three-winding transformer, a rectifier and its associated generator main control module, and a DC bus.

[0070] It is worth mentioning that the generator main control module refers to the main control circuit connected to the rectifier main circuit, specifically refers to the Boost-PFC circuit connected to the DC side of the rectifier to drive the two synchronous generators.

[0071] In an embodiment of the present invention, in response to receiving a power conversion request, mechanical energy is converted into AC power through a synchronous generator, and a three-winding transformer is used to perform voltage conversion on the AC power, and a high-order harmonic current channel is provided. The high-order harmonic current can form a loop inside the triangle winding, thereby suppressing the transmission of harmonics and further improving the quality of the converted power. Then, the AC power after voltage conversion is rectified by a rectifier to generate DC power. However, due to the differences in electrical characteristics of multiple motors and the diversity of load changes, a single rectifier cannot be effectively adjusted, resulting in low power quality converted by the generator. Therefore, the rectified current component after the rectification operation is collected by the generator main control module, and the rectified current component is controlled by the motor closed loop. According to the generated motor operation data, the two synchronous generators are reversed at the same speed and with equal torque, so that the two synchronous generators have the same phase, the same speed, and the opposite rotation direction. Since the speed of the two synchronous generators is set to be reversed at the same speed, the voltage phase sequence and phase generated by them are opposite. Therefore, a low-frequency AC transformer is introduced on the motor side to provide a channel for harmonics, improve the quality of motor current, and avoid the harmonic current of the diode from being series-connected into the synchronous generator. On the DC side, two uncontrolled rectifiers are connected in series, and the DC ripples cancel each other out, which can provide a higher quality rectified voltage and thus obtain high quality electrical energy.

[0072] See also Figure 1 and Figure 2 The present invention provides a multi-wave energy conversion device based on a DC series structure, and the control is specifically to control the two synchronous generators in the same speed, reverse direction and with equal torque.

[0073] It should be noted that the mechanical system provides the same torque to the two synchronous generators according to the motor operation data generated by the generator main control module, and makes the two synchronous generators run in opposite directions at the same speed, so the voltage sequence and phase generated by them are opposite. Therefore, a low-frequency AC transformer is introduced on the motor side to provide a channel for harmonics, improve the quality of motor current, and avoid the harmonic current of the diode from entering the motor. On the DC side, two uncontrolled rectifiers are connected in series, and the DC ripples cancel each other out, which can provide a higher quality rectified voltage.

[0074] See also Figure 1 and Figure 2 , the present invention provides a multi-wave energy conversion device based on a DC series structure, wherein the double-winding transformer is a DY type double-winding transformer;

[0075] Two synchronous generators are connected to the primary winding and secondary winding of a double-winding transformer respectively;

[0076] The two rectifiers are respectively connected to the primary winding and the secondary winding of the double-winding transformer;

[0077] Two rectifiers are connected in series;

[0078] A coupling inductor is arranged between the two rectifiers and the double-winding transformer, and the coupling inductor is used to filter out high-order harmonics of the rectifier.

[0079] It should be noted that the right sides of the two synchronous generators are connected to the primary winding side of the DY type double winding transformer in a triangle (D) connection and the secondary winding side in a star (Y) connection, and the AC sides of the two rectifiers are also connected to the primary winding side of the DY type double winding transformer in a triangle (D) connection and the secondary winding side in a star (Y) connection. In this connection mode, for high-order harmonic currents, especially the third and multiple harmonic currents, a loop current is formed in the winding connected in the triangle on the primary side. Since the winding connected in the triangle is closed, these harmonic currents can circulate inside the triangle winding, thereby providing a low-impedance channel for high-order harmonic currents; the leakage inductance of the transformer is the inductance generated by the incomplete coupling between the primary winding and the secondary winding of the transformer. When the current passes through the transformer, the leakage inductance will hinder the change of the current. For high-order harmonic currents, due to their high frequency, the leakage inductance presents a large inductive reactance. When the high-order harmonic current tries to pass through the transformer, the large leakage inductance will limit the size of the harmonic current and play a filtering role, thereby improving the quality of the converted electric energy.

[0080] It is worth mentioning that the introduction of Y-type coupled inductors can filter out high-order harmonics on the AC side of the rectifier. Y-type coupled inductors improve the utilization of the magnetic core and reduce the size and cost.

[0081] See also Figure 1 and Figure 2 , the present invention provides a multi-wave energy conversion device based on a DC series structure, wherein two synchronous generators and two rectifiers are both communicatively connected to a generator main control module;

[0082] The generator main control module includes a speed submodule and a position angle submodule;

[0083] The motor operation data includes motor speed data and rotor position angle data;

[0084] The speed submodule is used to generate motor speed data for regulating the speed of the synchronous generator motor according to the rectified current component;

[0085] The position angle submodule is used to generate rotor position angle data for regulating the rotor position of the synchronous generator.

[0086] It should be noted that the speed data describes the rotation speed of the synchronous generator rotor, and the motor speed data refers to the data used to adjust the rotation speed of the synchronous generator rotor. The position angle data describes the angle of the position of the rotor relative to the stator, and the rotor position angle data refers to the data used to adjust the angle of the position of the synchronous generator rotor relative to the stator.

[0087] It should be noted that the speed submodule is used to generate motor speed data for regulating the speed of the synchronous generator motor according to the rectified current component detected by the rectifier main circuit, and the position angle submodule is used to generate rotor position angle data for regulating the rotor position of the synchronous generator.

[0088] See also Figure 1 and Figure 2 , the present invention provides a multi-wave energy conversion device based on a DC series structure, the speed submodule includes a mutual inverse operation unit and a speed calculation unit that are connected to each other in communication;

[0089] The inverse operation unit is used to obtain the current zero-crossing cycle time difference, and perform an inverse operation based on the current zero-crossing cycle time difference to generate a frequency-locked speed component;

[0090] The speed calculation unit is used to obtain the motor speed data according to the frequency-locked speed component, the rectified current component and the preset reference speed component.

[0091] It should be noted that the main circuit on the DC side of the rectifier is a Boost circuit, which drives two permanent magnet synchronous motors. Due to the series structure of the uncontrolled rectifier, the inductive current fluctuation amplitude of the Boost circuit increases, and the current frequency is twice the motor rotation frequency. Therefore, by detecting the time difference between the zero-crossing points of the current periodic component and taking the inverse, the frequency, that is, the frequency-locked speed component, can be obtained. Therefore, the current zero-crossing period time difference is obtained by the reciprocal operation unit, and the reciprocal operation is performed based on the current zero-crossing period time difference to generate the frequency-locked speed component.

[0092] It is worth mentioning that the current zero-crossing period time difference refers to the time difference between the zero-crossing points of the current periodic component.

[0093] See also Figure 1 and Figure 2 , the present invention provides a multi-wave energy conversion device based on a DC series structure, the position angle submodule includes an integral operation unit;

[0094] The integral operation unit is used to perform integral operation on the frequency-locked speed component to generate rotor position angle data.

[0095] It should be noted that, since the phase is the integral of the frequency, an integral operation unit is used to perform an integral operation on the frequency-locked speed component to generate rotor position angle data.

[0096] See also Figure 1 and Figure 2, the present invention provides a multi-wave energy conversion device based on a DC series structure, the speed calculation unit includes a speed difference calculation subunit, a speed feedback adjustment subunit, a current difference calculation subunit, a current feedback adjustment subunit, a target current calculation subunit and a motor speed generation submodule which are sequentially connected in communication;

[0097] The speed difference calculation subunit is used to generate an error speed by calculating the difference between a preset reference speed component and a frequency-locked speed component;

[0098] In the embodiment of the present invention, a preset reference speed component is used. The frequency-locked speed component Perform difference calculation to obtain the error speed.

[0099] The speed feedback regulation subunit is used to generate a reference current component by using an error speed input to a preset speed regulator for feedback regulation based on a preset speed outer loop transfer function;

[0100] In the embodiment of the present invention, the error speed is input into the speed outer loop for feedback regulation, that is, the error speed is input into the speed regulator (PI or PID regulator), and the proportional-integral (PI) or proportional-integral-derivative (PID) control algorithm is used for processing, and then the reference current component is calculated, so as to obtain the reference current component .

[0101] In a specific implementation, in order to facilitate the implementation of the method, the above process can be converted into a formula encapsulation form, where the reference current component The calculation method can be as follows:

[0102]

[0103] In the formula, represents the speed outer loop transfer function.

[0104] The current difference calculation subunit is used to generate an error current by calculating the difference between the reference current component and the rectified current component;

[0105] In the embodiment of the present invention, the reference current component is used and the rectified current component Perform difference calculation to obtain the error current.

[0106] The current feedback regulation subunit is used to generate a duty cycle parameter by inputting an error current into a preset current regulator for feedback regulation based on a preset current inner loop transfer function;

[0107] In an embodiment of the present invention, an error current is input into a current inner loop for feedback regulation, that is, the error current is input into a current regulator (PI or PID regulator), processed using a proportional-integral (PI) or proportional-integral-derivative (PID) control algorithm, and then the duty cycle is calculated to obtain a duty cycle parameter.

[0108] In the specific implementation, in order to facilitate the implementation of the method, the above process can be converted into a formula encapsulation form, where the duty cycle parameter The calculation method can be as follows:

[0109]

[0110] In the formula, represents the current inner loop transfer function.

[0111] The target current calculation subunit is used to generate target current data by calculating the product between the duty cycle parameter and the preset first transfer function;

[0112] In the specific implementation, in order to facilitate the implementation of the method, the above process can be converted into a formula encapsulation form, where the target current data The calculation method can be as follows:

[0113]

[0114] In the formula, It represents a preset first transfer function, specifically refers to a transfer function from duty cycle to inductor current.

[0115] It is worth mentioning that the target current data refers to the inductor current.

[0116] The motor speed generating submodule is used to generate motor speed data by calculating the product between the target current data and a preset second transfer function.

[0117] In the specific implementation, in order to facilitate the implementation of the method, the above process can be converted into a formula package, where the motor speed data The calculation method can be as follows:

[0118]

[0119] In the formula, It represents a preset second transfer function, specifically refers to a transfer function from the inductor current to the motor speed.

[0120] See also Figure 1 , the present invention provides a multi-wave energy conversion device based on a DC series structure, the generator main control module also includes a drive signal generation submodule;

[0121] The drive signal generation submodule is used to modulate the motor operation data and generate a switch drive signal for controlling the rectifier to start or stop power conversion.

[0122] It should be noted that Figure 1 The M in the main circuit of the medium rectifier refers to the drive signal generation submodule, specifically the modulation link, which is used to determine whether the synchronous generator operated according to the motor operation data is in the preset standard operation data interval. If it is, a switch drive signal for turning on the IGBT is generated to maintain the current motor state. If it is not, it indicates that a deviation has occurred, and a switch drive signal for turning off the IGBT is generated.

[0123] See also Figure 1 and Figure 2 The present invention provides a multi-wave energy conversion device based on a DC series structure, wherein the rectifier is a diode uncontrolled rectifier.

[0124] It should be noted that, at present, taking wave energy power generation as an example, the output end of the wave energy permanent magnet synchronous generator is directly connected to the diode uncontrolled rectifier or PWM rectifier. Among them, the PWM rectifier is expensive, occupies a large area, has low reliability, and is very prone to faulty operation caused by component failure in the offshore operation environment. The diode uncontrolled rectifier has a simple structure, low cost, and can achieve high redundancy operation, but it will cause serious distortion of the current at the output end of the generator, which will cause harmonic pollution on the AC side of the rectifier.

[0125] It can be seen that the power conversion of wave energy power generation devices based on diode uncontrolled rectifiers has the problem of large harmonics, which seriously affects the stable operation of wave energy permanent magnet synchronous generators and DC voltage. Therefore, large-scale wave energy power generation devices based on diode uncontrolled rectifiers require economical and energy-efficient methods to improve the current quality of wave energy permanent magnet synchronous generators.

[0126] Therefore, the rectifier in the present invention adopts a diode uncontrolled rectifier, and a DY type (Y-△ type) isolation transformer and a Y type coupling inductor are connected in series between the wave energy permanent magnet synchronous generator and the AC side of the uncontrolled rectifier. The Y-△ type isolation transformer isolates the output end of the generator from the diode uncontrolled rectifier, and the isolation transformer provides a harmonic channel and transformer leakage inductance filtering capability. The introduction of the Y type coupling inductor can filter out the higher harmonics on the AC side of the rectifier. The Y type coupling inductor improves the utilization rate of the magnetic core and reduces the volume and cost. It solves the problem of excessive harmonics on the generator side current and insufficient utilization of the magnetic core caused by the connection method between the traditional synchronous generator and the uncontrolled rectifier.

[0127] The following is an application example:

[0128] Compared with the conventional method of directly connecting the generator to the diode uncontrolled rectifier, the fifth harmonic elimination effect of the generator side current of the present invention is reduced from 0.4825 to 0.2816, and the corresponding seventh harmonic elimination effect is reduced from 0.2853 to 0.2015. Figure 3 , Figure 4 It can be seen that the present invention greatly optimizes the current waveform on the generator side and solves the problem of excessive harmonics on the generator side current caused by the diode uncontrolled rectifier.

[0129] Working principle of the present invention:

[0130] See also Figure 1 Taking wave energy power generation as an example, the mechanical system of the wave energy power generation system first transmits torque to the wave energy permanent magnet synchronous generator through the transmission shaft; then the mechanical structure such as the gearbox is used to make the rotation speed of PMSG1 and PMSG2 opposite. Subsequently, the wave energy permanent magnet synchronous generator emits three-phase electricity, and the conversion of AC to DC is realized through the uncontrolled rectifier. On the AC side of the uncontrolled rectifier, a low-frequency DY-type double-winding transformer is connected between the two wave energy permanent magnet synchronous motors-uncontrolled rectifiers. On the DC side of the uncontrolled rectifier, the two uncontrolled rectifiers are connected in series, and then the main circuit of the Boost-PFC rectifier is constructed together through the Boost circuit. Finally, the electrical energy is collected and transmitted to the DC bus.

[0131] See also Figure 5 The present invention provides a conversion method for a multi-wave energy conversion device based on a DC series structure, comprising:

[0132] Step 101: Perform rectification operation on the rectified current component after receiving the rectification operation to generate motor operation data.

[0133] Step 102: According to the motor operation data, the electric energy conversion module is regulated in the same speed and reverse direction with equal torque, and electric energy conversion is performed.

[0134] In an embodiment of the present invention, in response to receiving a power conversion request, mechanical energy is converted into AC power through a synchronous generator, and a three-winding transformer is used to perform voltage conversion on the AC power, and a high-order harmonic current channel is provided. The high-order harmonic current can form a loop inside the triangle winding, thereby suppressing the transmission of harmonics and further improving the quality of the converted power. Then, the AC power after voltage conversion is rectified by a rectifier to generate DC power. However, due to the differences in electrical characteristics of multiple motors and the diversity of load changes, a single rectifier cannot be effectively adjusted, resulting in low power quality converted by the generator. Therefore, the rectified current component after the rectification operation is collected by the generator main control module, and the rectified current component is controlled by the motor closed loop. According to the generated motor operation data, the two synchronous generators are reversed at the same speed and with equal torque, so that the two synchronous generators have the same phase, the same speed, and the opposite rotation direction. Since the speed of the two synchronous generators is set to be reversed at the same speed, the voltage phase sequence and phase generated by them are opposite. Therefore, a low-frequency AC transformer is introduced on the motor side to provide a channel for harmonics, improve the quality of motor current, and avoid the harmonic current of the diode from being series-connected into the synchronous generator. On the DC side, two uncontrolled rectifiers are connected in series, and the DC ripples cancel each other out, which can provide a higher quality rectified voltage and thus obtain high quality electrical energy.

[0135] Those skilled in the art can clearly understand that, for the convenience and brevity of description, the specific working processes of the systems, devices and units described above can refer to the corresponding processes in the aforementioned method embodiments and will not be repeated here.

[0136] In the several embodiments provided in the present application, it should be understood that the disclosed systems, devices and methods can be implemented in other ways. For example, the device embodiments described above are only schematic. For example, the division of the units is only a logical function division. There may be other division methods in actual implementation, such as multiple units or components can be combined or integrated into another system, or some features can be ignored or not executed. Another point is that the mutual coupling or direct coupling or communication connection shown or discussed can be an indirect coupling or communication connection through some interfaces, devices or units, which can be electrical, mechanical or other forms.

[0137] As described above, the above embodiments are only used to illustrate the technical solutions of the present invention, rather than to limit the same. Although the present invention has been described in detail with reference to the aforementioned embodiments, those skilled in the art should understand that the technical solutions described in the aforementioned embodiments may still be modified, or some of the technical features thereof may be replaced by equivalents. However, these modifications or replacements do not deviate the essence of the corresponding technical solutions from the spirit and scope of the technical solutions of the embodiments of the present invention.

Claims

1. A multi-wave energy conversion device based on a DC series structure, characterized in that: It includes an electric energy conversion module and a generator main control module which are communicatively connected to each other; The electric energy conversion module includes two synchronous generators, a double-winding transformer and two rectifiers; The synchronous generator is used to convert mechanical energy into AC electrical energy; The double-winding transformer is used to perform voltage conversion on AC power; The rectifier is used to rectify the AC power after voltage conversion to generate DC power; The generator main control module is used to use the rectified current component after the rectification operation to perform motor closed-loop control, and to regulate the two synchronous generators according to the generated motor operation data.

2. The multi-wave energy conversion device based on a DC series structure according to claim 1 is characterized in that: The control is specifically to control the two synchronous generators in the same speed, reverse direction and with equal torque.

3. The multi-wave energy conversion device based on a DC series structure according to claim 1 is characterized in that: The double-winding transformer is a DY type double-winding transformer; The two synchronous generators are respectively connected to the primary winding and the secondary winding of the double-winding transformer; The two rectifiers are respectively connected to the primary winding and the secondary winding of the double-winding transformer; The two rectifiers are connected in series; A coupling inductor is provided between the two rectifiers and the dual-winding transformer, and the coupling inductor is used to filter out high-order harmonics of the rectifiers.

4. The multi-wave energy conversion device based on a DC series structure according to claim 1 is characterized in that: The two synchronous generators and the two rectifiers are both communicatively connected to the generator main control module; The generator main control module includes a speed submodule and a position angle submodule; The motor operation data includes motor speed data and rotor position angle data; The speed submodule is used to generate the motor speed data for regulating the motor speed of the synchronous generator according to the rectified current component; The position angle submodule is used to generate the rotor position angle data for regulating the rotor position of the synchronous generator.

5. The multi-wave energy conversion device based on a DC series structure according to claim 4 is characterized in that: The speed submodule includes an inverse operation unit and a speed calculation unit that are communicatively connected to each other; The inverse operation unit is used to obtain the current zero-crossing cycle time difference, and perform an inverse operation based on the current zero-crossing cycle time difference to generate a frequency-locked speed component; The speed calculation unit is used to obtain the motor speed data according to the frequency-locked speed component, in combination with the rectified current component and a preset reference speed component.

6. The multi-wave energy conversion device based on a DC series structure according to claim 5 is characterized in that: The position angle submodule includes an integral operation unit; The integral operation unit is used to perform an integral operation on the frequency-locked speed component to generate the rotor position angle data.

7. The multi-wave energy conversion device based on a DC series structure according to claim 5 is characterized in that: The speed calculation unit includes a speed difference calculation subunit, a speed feedback adjustment subunit, a current difference calculation subunit, a current feedback adjustment subunit, a target current calculation subunit and a motor speed generation submodule which are sequentially connected in communication; The speed difference calculation subunit is used to generate an error speed by calculating the difference between the preset reference speed component and the frequency-locked speed component; The speed feedback regulation subunit is used to generate a reference current component by inputting the error speed into a preset speed regulator for feedback regulation based on a preset speed outer loop transfer function; The current difference calculation subunit is used to generate an error current by calculating the difference between the reference current component and the rectified current component; The current feedback regulation subunit is used to input the error current into a preset current regulator for feedback regulation based on a preset current inner loop transfer function to generate a duty cycle parameter; The target current calculation subunit is used to generate target current data by calculating the product between the duty cycle parameter and a preset first transfer function; The motor speed generating submodule is used to generate the motor speed data by calculating the product between the target current data and a preset second transfer function.

8. The multi-wave energy conversion device based on a DC series structure according to claim 4 is characterized in that: The generator main control module also includes a drive signal generation submodule; The drive signal generation submodule is used to perform a modulation operation on the motor operation data to generate a switch drive signal for controlling the rectifier to start or stop power conversion.

9. The multi-wave energy conversion device based on a DC series structure according to any one of claims 1 to 8, characterized in that: The rectifier is a diode uncontrolled rectifier.

10. A conversion method for a multi-wave energy conversion device based on a DC series structure according to any one of claims 1 to 9, characterized in that: include: Performing rectification operation on the rectified current component after receiving the rectification operation to generate motor operation data; According to the motor operation data, the electric energy conversion module is regulated in the same speed, reverse direction and equal torque, and electric energy conversion is performed.

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