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

Abstract

The application 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. A generator main control module is used to perform motor closed-loop control on the rectified current component after rectification operation, and motor operation data for controlling two synchronous generators is generated, so that the problem that a single driving circuit is difficult to drive two or more synchronous generators can be solved. Meanwhile, the synchronous generator of the application generates electricity through mechanical transmission, and when the rectifier and the synchronous generator containing mechanical transmission are integrated, the motor operation data obtained by the application is used to regulate and control the two synchronous generators, so that the problem that the adjustability of mechanical transmission is ignored during rectification operation is solved. On the direct-current side, the two uncontrolled rectifiers are connected in series, the direct-current ripples are offset to each other, a high-quality rectification voltage can be provided, and high-quality electric energy can be obtained.

Description

TECHNICAL FIELD

[0001] The present application 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

[0002] New energy is a kind of key renewable energy, which has the characteristics of abundant resources, wide distribution and large energy flow density. For example, the wave energy generation device needs to operate stably in the harsh marine environment for a long time. In the utilization of wave energy, conversion efficiency and cost are the key elements restricting its large-scale application. Therefore, a light, easy-to-control and efficient multi-wave energy conversion device based on a direct current series structure has become an important development trend.

[0003] At present, the control mode of the traditional single rectifier driving two synchronous generators is to directly connect the two synchronous generators into the rectifier. However, when the two synchronous generators are operated side by side, many problems will be encountered. There are often differences in output characteristics such as voltage, frequency and phase sequence between the generators, which will cause ripple phenomenon during power conversion. The ripple will interfere with stable power transmission and use, reduce power quality, affect the normal operation of electrical equipment and increase equipment loss, which is a problem that needs to be solved in modern industry and power application scenarios with high requirements for power quality. SUMMARY

[0004] The present application provides a multi-wave energy conversion device and method based on a direct current series structure, which solves the technical problem of how to improve the conversion power quality of new energy generation.

[0005] The first aspect of the present application provides a conversion device, comprising:

[0006] The conversion device comprises an electric energy conversion module and a generator main control module connected in communication with each other;

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

[0008] The synchronous generator is used to convert mechanical energy into alternating current energy;

[0009] The double-winding transformer is used to transform the voltage of the alternating current energy, and provide a high-order harmonic current channel and a leakage inductance filtering capability;

[0010] The rectifier is used to rectify the alternating current energy after voltage transformation to generate direct current energy;

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

[0012] Optionally, the regulating specifically comprises regulating the two synchronous generators at the same speed in opposite directions and with equal torque.

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

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

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

[0016] The two rectifiers are connected in series.

[0017] A coupling inductance is arranged between the two rectifiers and the double-winding transformer, and the coupling inductance is used to filter high-order harmonics of the rectifiers.

[0018] Optionally, the two synchronous generators and the two rectifiers are in communication connection with the generator master control module.

[0019] The generator master control module comprises a rotating speed sub-module and a position angle sub-module.

[0020] The motor operation data comprises motor rotating speed data and rotor position angle data.

[0021] The rotating speed sub-module is used to generate the motor rotating speed data for regulating the motor rotating speed of the synchronous generator according to the rectified current component.

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

[0023] Optionally, the rotating speed sub-module comprises a mutual inverse operation unit and a rotating speed calculation unit in communication connection with each other.

[0024] The mutual inverse operation unit is used to obtain a current zero-crossing period difference, and perform mutual inverse operation based on the current zero-crossing period difference to generate a frequency-locked rotating speed component.

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

[0026] Optionally, the position angle sub-module comprises an integral operation unit.

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

[0028] Optionally, the rotation speed calculation unit comprises rotation speed difference value calculation subunit, rotation speed feedback adjustment subunit, current difference value calculation subunit, current feedback adjustment subunit, target current calculation subunit and motor rotation speed generation sub-module connected in sequence.

[0029] The rotation speed difference value calculation subunit is used for generating error rotation speed by calculating the difference value between the preset reference rotation speed component and the locked frequency rotation speed component.

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

[0031] The current difference value calculation subunit is used for generating error current by calculating the difference value between the reference current component and the rectified current component.

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

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

[0034] The motor rotation speed generation sub-module is used for generating the motor rotation speed data by calculating the product between the target current data and a preset second transfer function.

[0035] Optionally, the generator master control module further comprises a driving signal generation sub-module.

[0036] The driving signal generation sub-module is used for modulating the motor operation data to generate a switch driving signal for controlling the start or stop of the power conversion of the rectifier.

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

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

[0039] The rectified current component after the rectification operation is subjected to the rectification operation to generate motor operation data.

[0040] The power conversion module is subjected to the same-speed reverse and equal-torque regulation according to the motor operation data, and the power conversion is performed.

[0041] From the above technical solutions, the present application has the following advantages:

[0042] The application provides a multi-wave energy conversion device based on a DC series structure and a double-winding transformer, a motor main control module is used to perform motor closed-loop control on a rectified current component after rectification, motor operation data for controlling two synchronous generators is generated, and the problem that a single drive circuit is difficult to drive two or more synchronous generators can be solved. BRIEF DESCRIPTION OF DRAWINGS

[0043] In order to more clearly illustrate the technical solutions in the embodiments of the present application or the prior art, the following will briefly introduce the drawings needed to be used in the embodiments or the prior art description. Obviously, the drawings in the following description only show some embodiments of the present application, and for those skilled in the art, other drawings can also be obtained from these drawings without creative labor.

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

[0045] Figure 2 FIG. 2 is a structural schematic diagram of a speed calculation unit according to an embodiment of the present application;

[0046] Figure 3 FIG. 3 is a voltage and current waveform schematic diagram according to an embodiment of the present application;

[0047] Figure 4 FIG. 4 is a total harmonic distortion (THD) comparison diagram of a generator current and a diode side current according to an embodiment of the present application;

[0048] Figure 5 FIG. 5 is a step flowchart 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 application. DETAILED DESCRIPTION

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

[0050] In order to make the application purposes, features and advantages of the present application more obvious and easy to understand, the technical solutions in the embodiments of the present application will be described clearly and completely below in combination with the drawings in the embodiments of the present application. Obviously, the embodiments described below are only some of the embodiments of the present application, rather than all the embodiments. Based on the embodiments in the present application, all other embodiments obtained by those of ordinary skill in the art without creative labor fall within the scope of the present application.

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

[0052] On the other hand, the regulation of the motor current quality is usually realized through the closed-loop control of the converter. The control scheme for improving the power quality usually adopts schemes such as increasing the complexity of the control structure or increasing the feedback variables. However, the existing schemes will greatly increase the cost of control and debugging. Therefore, simple topology structure adjustment and mechanical control are also important means and trends for realizing the improvement of power quality.

[0053] In summary, in the prior art, the Boost-PFC type rectifier is usually single adapted to the operation of the wave energy permanent magnet synchronous generator. However, when the multi-wave energy permanent magnet synchronous machine set is DC collected, the scheme of parallel connection to the medium voltage DC bus or series connection to the high voltage DC bus is often used, which is easy to cause problems such as high cost and low power density.

[0054] The control scheme for improving the power quality usually adopts schemes such as increasing the complexity of the control structure or increasing the feedback variables. However, the existing schemes will greatly increase the cost of materials, control and debugging.

[0055] The single motor drive circuit is difficult to drive multiple motors, and does not have the condition of high motor current quality operation.

[0056] The application is based on a single rectifier Boost PFC circuit driven by two synchronous generators, even multiple synchronous generators, connected with a DY type double-winding transformer, which reduces the complexity of the topology and the difficulty of control and the cost of equipment.

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

[0058] Therefore, the application provides a multi-wave energy conversion device based on a DC series structure based on a double-winding transformer, which uses a generator master module to perform motor closed-loop control on the rectified current component after 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 application generates electricity through mechanical transmission, and when the rectifier and the synchronous generator containing mechanical transmission are integrated, if the adjustability of mechanical transmission is ignored, it may be difficult to match the electrical and mechanical parts. For example, in a system in which a generator is driven by an engine through a belt drive, and then the generator outputs alternating current which is converted into direct current by 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 reduced rectification efficiency. Therefore, the application regulates the two synchronous generators by using the obtained motor operation data, specifically by adjusting the operating parameters of the synchronous generators, such as speed and torque. The problem of ignoring the adjustability of mechanical transmission in rectification operation is solved, and the double-winding transformer of the application provides a high-order harmonic current channel and leakage inductance filtering capability, thereby improving the power quality and solving the problem of low motor current quality in traditional wave energy generation multi-machine DC grid connection.

[0059] Please refer to Figure 1 and Figure 2 The application provides a multi-wave energy conversion device based on a DC series structure, which comprises an electrical energy conversion module and a generator master module in communication with each other.

[0060] The electrical energy conversion module comprises two synchronous generators, a double-winding transformer and two rectifiers.

[0061] The synchronous generator is used for converting mechanical energy into alternating current energy.

[0062] The double-winding transformer is used for voltage transformation of the alternating current energy and provides a high-order harmonic current channel and leakage inductance filtering capability.

[0063] The rectifier is used for rectification operation on the voltage-transformed alternating current energy to generate direct current energy.

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

[0065] It should be noted that, please refer to Figure 1 , Figure 1 The structure diagram of the multi-wave energy conversion device based on the DC series structure, the two M on the left side of the figure refer to two synchronous generators, PMSG1 and PMSG2 respectively, the two synchronous generators are connected through the gear box rotating shaft, the controller in the gear box is in communication connection with the generator master control module, used for receiving and regulating the two synchronous generators according to the motor operation data, the right side of the two synchronous generators is respectively connected with the delta (D) connection of the primary winding side of the DY type double-winding transformer and the star (Y) connection of the secondary winding side, the AC side of the two rectifiers is also respectively connected with the delta (D) connection of the primary winding side of the DY type double-winding transformer and the star (Y) connection of the secondary winding side, under this connection mode, for high harmonic currents, especially 3 times and multiple of 3 harmonic currents, the circulating current is formed in the delta connection winding. Because the delta connection winding is closed itself, these harmonic currents can circulate inside the delta winding, thereby providing a low impedance channel for high harmonic currents; the leakage inductance of the transformer is the inductance generated due to 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 harmonic currents, due to the high frequency, the leakage inductance presents a large inductance, when the high harmonic current tries to pass through the transformer, the large leakage inductance will limit the size of the harmonic current, playing a filtering role. The main circuit of the rectifier DC side is connected with a DC bus, the rectifier main circuit includes a current transformer or a Hall current sensor, an inductor, a diode, a capacitor and an IGBT element; the current transformer or the Hall current sensor between the rectifier main circuit and the DC bus is provided with an inductor in series, the end of the inductor away from the current transformer or the Hall current sensor is respectively connected with the IGBT element and the diode, the end of the diode away from the inductor is connected with the capacitor, and the end of the capacitor away from the diode is connected with the DC bus.

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

[0067] Please refer to Figure 1 and Figure 2 The generator master control module includes a speed sub-module and a position angle sub-module, the speed sub-module includes a reciprocal operation unit and a speed calculation unit, Figure 2A structural schematic diagram of the rotating speed calculation unit, the rotating speed calculation unit comprises a rotating speed difference value calculation subunit, a rotating speed feedback adjustment subunit, a current difference value calculation subunit, a current feedback adjustment subunit, a target current calculation subunit and a motor rotating speed generation sub-module which are sequentially communicatively connected, Figure 2 plant i1 and plant i2 respectively refer to the target current calculation subunit and the motor rotating speed generation sub-module.

[0068] The multi-wave energy conversion device based on a direct-current series structure comprises a mechanical system and an electrical system. The mechanical system comprises a gear box, which is used to provide torque to a synchronous generator and to realize reverse following control on other generators. Taking wave energy generation as an example, in an actual wave energy generation device, wave energy is collected by a collector, stored in a hydraulic accumulator, and further converted into torque for a wave energy permanent magnet synchronous motor through an energy distribution unit and a gear box shaft. In the present application, a gear box interconnecting two synchronous generators is added, and the torque, rotating speed and rotating direction phase of the two interconnected generators are the same according to the motor operation data.

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

[0070] It is worth mentioning that the generator main control module refers to a control main loop connected to the main circuit of the rectifier, specifically referring to a Boost-PFC circuit connected to the direct-current side of the rectifier, which is used to drive the two synchronous generators.

[0071] In the embodiment of the present application, when responding to the received electric energy conversion request, mechanical energy is converted into alternating current electric energy by the synchronous generator, the alternating current electric energy is subjected to voltage transformation by using the three-winding transformer, and a high-order harmonic current channel is provided, the high-order harmonic current can form a circulating current inside the delta winding, thereby inhibiting the transmission of harmonics, and further improving the quality of the converted electric energy, then the alternating current electric energy subjected to voltage transformation is subjected to rectification operation by the rectifier to generate direct current electric energy, but due to the difference in electrical characteristics of multiple motors and the diversity of load changes, a single rectifier cannot effectively regulate, resulting in low quality of the electric energy converted by the generator, therefore, the rectified current component after the rectification operation is collected by the generator master control module, and the motor closed-loop control is performed on the rectified current component, the two synchronous generators are controlled at the same speed in opposite directions and with equal torque according to the generated motor operation data, so that the two synchronous generators are consistent in phase and have the same speed and opposite rotation directions, since the rotation speeds of the two synchronous generators are set to be the same in opposite directions, the generated voltage phase sequence and phase are opposite. Therefore, a low-frequency alternating current transformer is introduced on the motor side to provide a channel for harmonics and improve the motor current quality to avoid the harmonic current of the diode from entering the synchronous generator. On the DC side, two uncontrolled rectifiers are connected in series, the DC ripple is offset, and a high-quality rectified voltage can be provided to obtain high-quality electric energy.

[0072] Referring to Figure 1 and Figure 2 The present application provides a multi-wave energy conversion device based on a DC series structure, and the regulation and control is specifically equal torque control of the two synchronous generators at the same speed in opposite directions.

[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 master control module, and the two synchronous generators rotate at the same speed in opposite directions, so that the generated voltage phase sequence and phase are opposite. Therefore, a low-frequency alternating current transformer is introduced on the motor side to provide a channel for harmonics and improve the motor current quality to avoid the harmonic current of the diode from entering the motor. On the DC side, two uncontrolled rectifiers are connected in series, the DC ripple is offset, and a high-quality rectified voltage can be provided.

[0074] Referring to Figure 1 and Figure 2 The present application provides a multi-wave energy conversion device based on a DC series structure, and the regulation and control is specifically equal torque control of the two synchronous generators at the same speed in opposite directions.

[0075] The two synchronous generators are connected to the primary winding and the secondary winding of the double-winding transformer, respectively.

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

[0077] The two rectifiers are connected in series.

[0078] Coupling inductors are arranged between the two rectifiers and the double-winding transformer, and are used to filter high-order harmonics of the rectifiers.

[0079] It should be noted that 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, and 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. In this connection mode, for high-order harmonic currents, especially 3 times and multiples of 3 times harmonic currents, circulating currents are formed in the triangle-connected winding on the primary side. Since the triangle-connected winding is closed in itself, 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 due to 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 inductance, which will limit the size of the harmonic current when the high-order harmonic current tries to pass through the transformer, thereby playing a filtering role and improving the quality of the converted electric energy.

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

[0081] Please refer to Figure 1 and Figure 2 The application provides a multi-wave energy conversion device based on a direct-current series structure, two synchronous generators and two rectifiers are in communication connection with a generator master control module.

[0082] The generator master control module comprises a rotating speed sub-module and a position angle sub-module.

[0083] The motor operation data comprises motor rotating speed data and rotor position angle data.

[0084] The rotating speed sub-module is used to generate motor rotating speed data for regulating and controlling the rotating speed of the synchronous generator motor according to the rectified current component.

[0085] The position angle sub-module is used to generate rotor position angle data for regulating and controlling the position of the rotor of the synchronous generator.

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

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

[0088] Referring to Figure 1 and Figure 2 The application provides a multi-wave energy conversion device based on a DC series structure, and the rotation speed sub-module comprises a reciprocal operation unit and a rotation speed calculation unit which are communicatively connected to each other.

[0089] The reciprocal operation unit is configured to obtain a current zero-crossing period time difference and perform reciprocal operation based on the current zero-crossing period time difference to generate a locked-frequency rotation speed component.

[0090] The rotation speed calculation unit is configured to obtain motor rotation speed data by processing the locked-frequency rotation speed component in combination with the rectified current component and a preset reference rotation speed component.

[0091] It should be noted that the main circuit on the DC side of the rectifier is a Boost circuit, and the two permanent magnet synchronous motors are driven by the Boost circuit.

[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] Referring to Figure 1 and Figure 2 The application provides a multi-wave energy conversion device based on a DC series structure, and the position angle sub-module comprises an integral operation unit.

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

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

[0096] Referring to Figure 1 and Figure 2The application provides a multi-wave energy conversion device based on a direct current series structure, and a rotating speed calculation unit comprises a rotating speed difference value calculation subunit, a rotating speed feedback adjustment subunit, a current difference value calculation subunit, a current feedback adjustment subunit, a target current calculation subunit and a motor rotating speed generation subunit which are sequentially connected in communication.

[0097] The rotating speed difference value calculation subunit is used for generating an error rotating speed by calculating the difference value between the preset reference rotating speed component and the frequency-locked rotating speed component.

[0098] In the embodiment of the application, the preset reference rotating speed component and the frequency-locked rotating speed component are subjected to difference value operation to obtain the error rotating speed.

[0099] The rotating speed feedback adjustment subunit is used for inputting the error rotating speed into a preset rotating speed regulator based on a preset rotating speed outer loop transfer function to perform feedback adjustment and generate a reference current component.

[0100] In the embodiment of the application, the error rotating speed is inputted into a rotating speed regulator (a PI or PID regulator) to perform feedback adjustment, that is, a proportional-integral (PI) or proportional-integral-derivative (PID) control algorithm is used for processing, and then the reference current component is calculated to obtain the reference current component. .

[0101] In the specific implementation, for the convenience of method implementation, the above process can be converted into a formula encapsulation form, wherein the calculation method of the reference current component may be as follows:

[0102]

[0103] In the formula, Iref represents the reference current component, Ia represents the rectified current component, and Kp represents the rotating speed outer loop transfer function.

[0104] The current difference value calculation subunit is used for generating an error current by calculating the difference value between the reference current component and the rectified current component.

[0105] In the embodiment of the application, the reference current component and the rectified current component are subjected to difference value operation to obtain the error current.

[0106] The current feedback adjustment subunit is used for inputting the error current into a preset current regulator based on a preset current inner loop transfer function to perform feedback adjustment and generate a duty cycle parameter.

[0107] ​In the embodiment of the present application, the error current is input into the current inner loop for feedback regulation, that is, the error current is input into a current regulator (PI or PID regulator), and a proportional-integral (PI) or proportional-integral-derivative (PID) control algorithm is used for processing, and then duty cycle calculation is performed to obtain the duty cycle parameter.

[0108] In a specific implementation, for the convenience of implementing the method, the above process can be converted into a formula encapsulation form, wherein the duty cycle parameter The calculation method of the target current data

[0109]

[0110] In the formula, I represents the error current, Kp represents a proportional coefficient, and Ki represents an integral coefficient. represents a current inner loop transfer function.

[0111] The target current calculation subunit is configured to generate target current data by calculating the product of the duty cycle parameter and a preset first transfer function.

[0112] In a specific implementation, for the convenience of implementing the method, the above process can be converted into a formula encapsulation form, wherein the target current data The calculation method of the target current data

[0113]

[0114] In the formula, I represents the error current, Kp represents a proportional coefficient, and Ki represents an integral coefficient. represents a preset first transfer function, and specifically refers to a transfer function from a duty cycle to an inductor current.

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

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

[0117] In a specific implementation, for the convenience of implementing the method, the above process can be converted into a formula encapsulation form, wherein the motor speed data The calculation method of the motor speed data

[0118]

[0119] In the formula, I represents the error current, Kp represents a proportional coefficient, and Ki represents an integral coefficient. represents a preset second transfer function, and specifically refers to a transfer function from an inductor current to a motor speed.

[0120] Referring to Figure 1 The generator master control module further includes a drive signal generation submodule.

[0121] The drive signal generation submodule is used for modulating the motor operation data to 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 rectifier main circuit refers to the drive signal generation submodule, specifically the modulation link, which is used to determine whether the synchronous generator is in the preset standard operation data range according to the motor operation data. 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 there is a deviation, and a switch drive signal for turning off the IGBT is generated.

[0123] Please refer to Figure 1 and Figure 2 The present application provides a multi-wave energy conversion device based on a direct current series structure, and the rectifier is a diode uncontrolled rectifier.

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

[0125] As can be seen, the wave energy generation device based on the diode uncontrolled rectifier has the problem of large harmonic energy conversion, which seriously affects the stable operation of the wave energy permanent magnet synchronous generator and the direct current voltage. Therefore, a large-scale wave energy generation device based on a diode uncontrolled rectifier needs an economical and high-efficiency wave energy permanent magnet synchronous generator current quality improvement method.

[0126] Therefore, the rectifier in the present application adopts a diode uncontrolled rectifier, and a DY type (Y-△ type) isolation transformer and a Y type coupled inductor are connected in series between the wave energy permanent magnet synchronous generator and the uncontrolled rectifier. The Y-△ type isolation transformer isolates the generator output end from the diode uncontrolled rectifier, and at the same time, the isolation transformer provides a harmonic channel and transformer leakage inductance filtering capability. The introduction of the Y type coupled inductor can filter out high-order harmonics of the alternating current side of the rectifier. The Y type coupled inductor improves the utilization rate of the magnetic core and reduces the volume and cost. The problem of excessive current harmonics on the generator side and insufficient magnetic core utilization caused by the connection mode of the traditional synchronous generator and the uncontrolled rectifier is solved.

[0127] The following provides an application example:

[0128] Compared with the traditional generator directly connected with the diode uncontrolled rectifier, the current 5th harmonic elimination effect of the generator side of the application is reduced from 0.4825 to 0.2816, and the corresponding 7th harmonic elimination effect is reduced from 0.2853 to 0.2015, as shown in Figure 3 、 Figure 4 It can be seen that the application greatly optimizes the current waveform of the generator side and solves the problem of excessive current harmonic of the generator side caused by the diode uncontrolled rectifier.

[0129] The working principle of the application is as follows:

[0130] Please refer to Figure 1 , taking wave energy generation as an example, the mechanical system of the wave energy generation system first transmits torque to the wave energy permanent magnet synchronous generator through the transmission shaft; then the gear box and other mechanical structures are used to make the rotation speeds of PMSG1 and PMSG2 opposite. Then, the wave energy permanent magnet synchronous generator sends out three-phase electricity, and the conversion from alternating current to direct current is realized through the uncontrolled rectifier. Between the two wave energy permanent magnet synchronous machines-uncontrolled rectifiers on the alternating current side of the uncontrolled rectifier, a low-frequency DY type double-winding transformer is connected in series. On the direct current side of the uncontrolled rectifier, the two uncontrolled rectifiers are connected in series, and through the Boost circuit, the main circuit of the Boost-PFC rectifier is jointly constructed. Finally, the electric energy is collected and transmitted to the DC bus.

[0131] Please refer to Figure 5 , the application provides a conversion method applied to a multi-wave energy conversion device based on a DC series structure, which comprises the following steps:

[0132] Step 101, rectifying the rectified current component after the rectification operation to generate motor operation data.

[0133] Step 102, controlling the electric energy conversion module at the same speed in the opposite direction and at the same torque according to the motor operation data, and performing electric energy conversion.

[0134] In the embodiment of the present application, when responding to the received electric energy conversion request, mechanical energy is converted into alternating current electric energy by the synchronous generator, the alternating current electric energy is subjected to voltage transformation by using the three-winding transformer, and a high-order harmonic current channel is provided, the high-order harmonic current can form a circulating current inside the delta winding, thereby inhibiting the transmission of harmonics, and further improving the quality of the converted electric energy, then the alternating current electric energy subjected to voltage transformation is subjected to rectification operation by the rectifier to generate direct current electric energy, but due to the difference in electrical characteristics of multiple motors and the diversity of load changes, a single rectifier cannot effectively regulate, resulting in low quality of the electric energy converted by the generator, therefore, the rectified current component after the rectification operation is collected by the generator master control module, and the motor closed-loop control is performed on the rectified current component, the two synchronous generators are controlled at the same speed in opposite directions and the same torque according to the generated motor operation data, so that the two synchronous generators have consistent phases, the same speed and opposite rotation directions, since the speeds of the two synchronous generators are set to be the same in opposite directions, the generated voltage phase sequence and phase are opposite. Therefore, a low-frequency alternating current transformer is introduced at the motor side to provide a channel for harmonics and improve the motor current quality to avoid the harmonic current of the diode from entering the synchronous generator. At the direct current side, two uncontrolled rectifiers are connected in series, the direct current ripple is offset, and a high-quality rectified voltage can be provided to obtain high-quality electric energy.

[0135] Those skilled in the art can clearly understand that, for the convenience and brevity of description, the specific working processes of the above-described system, device and unit can refer to the corresponding processes in the foregoing method embodiments, which will not be repeated here.

[0136] In several embodiments provided in the present application, it should be understood that the disclosed system, device and method 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, and actual implementation can have another division manner, for example, a plurality of units or components can be combined or integrated into another system, or some features can be ignored or not executed. In addition, the coupling or direct coupling or communication connection between the units shown or discussed can be indirect coupling or communication connection through some interface, device or unit, and can be electrical, mechanical or other forms.

[0137] The above-described embodiments are only used to illustrate the technical solutions of the present application, rather than limit them; although the present application has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that: it can still modify the technical solutions recorded in the foregoing embodiments, or make equivalent replacement for some technical features; and these modifications or replacements do not make the essence of the corresponding technical solutions deviate from the spirit and scope of the technical solutions of the embodiments of the present application.

Claims

1. A multi-wave energy conversion device based on a DC series structure, characterized in that, This includes a power conversion module and a generator main control module that are interconnected. The power conversion module includes two synchronous generators, a dual-winding transformer, and two rectifiers; The synchronous generator is used to convert mechanical energy into alternating current electrical energy; The dual-winding transformer is used to perform voltage transformation on alternating current. The dual-winding transformer is a DY-type dual-winding transformer; The two synchronous generators are respectively connected to the primary winding and the secondary winding of the dual-winding transformer; The two rectifiers are respectively connected to the primary winding and the secondary winding of the dual-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 the high-order harmonics of the rectifiers. The rectifier is used to rectify the AC power after voltage transformation to generate DC power; The generator main control module is used to perform closed-loop control of the motor using the rectified current component after rectification operation, 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-DC series structure according to claim 1, characterized in that, The regulation specifically involves regulating the two synchronous generators at the same speed, in opposite directions, and with equal torque.

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

4. The multi-wave energy conversion device based on a DC-DC series structure according to claim 3, characterized in that, The speed submodule includes a reciprocal operation unit and a speed calculation unit that are interconnected. The reciprocal operation unit is used to obtain the current zero-crossing cycle time difference and perform reciprocal operation based on the current zero-crossing cycle time difference to generate frequency-locked speed components. The speed calculation unit is used to process and obtain the motor speed data based on the locked frequency speed component, combined with the rectified current component and the preset reference speed component.

5. The multi-wave energy conversion device based on a DC-DC series structure according to claim 4, characterized in that, The position angle submodule includes an integration calculation unit; The integral calculation unit is used to perform integral calculation on the frequency-locked speed component to generate the rotor position angle data.

6. The multi-wave energy conversion device based on a DC-DC series structure according to claim 4, 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 connected in sequence via 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 adjustment subunit is used to perform feedback adjustment based on the preset speed outer loop transfer function and the error speed input preset speed regulator to generate a reference current component. 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 perform feedback regulation based on the preset current inner loop transfer function and the error current input to the preset current regulator to generate duty cycle parameters. 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; The motor speed generation submodule is used to generate the motor speed data by calculating the product between the target current data and a preset second transfer function.

7. The multi-wave energy conversion device based on a DC series structure according to claim 3, characterized in that, The generator main control module also includes a drive signal generation submodule; The drive signal generation submodule is used to modulate the motor operating data to generate a switching drive signal for controlling the rectifier to start or stop power conversion.

8. The multi-wave energy conversion device based on a DC-DC series structure according to any one of claims 1-7, characterized in that, The rectifier is a diode uncontrolled rectifier.

9. A conversion method for a multi-wave energy conversion device based on a DC-DC series structure as described in any one of claims 1-8, characterized in that, include: The rectified current component after receiving the rectification operation is rectified to generate motor operating data. Based on the motor operating data, the power conversion module is controlled to operate at the same speed and in the opposite direction with equal torque, and then the power is converted.

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