A power conversion device and method for connecting a multi-wave energy generator.

Abstract

This invention relates to the field of energy conversion technology and discloses a power conversion device and method for connecting multi-wave energy generators. The invention performs power conversion through a power conversion module, which utilizes a three-winding transformer to transform the voltage of AC power and provides a path for high-order harmonic currents. These high-order harmonic currents can form circulating currents within the delta windings, thereby suppressing harmonic transmission and further improving the quality of the converted power. Simultaneously, the generator main control module collects the rectified current components after rectification and performs closed-loop motor control on these components. Based on the generated motor operating data, the two synchronous generators are controlled to operate at the same speed, in the same direction, and with equal torque, ensuring that the two synchronous generators are in phase, have the same speed, and rotate in the same direction. This achieves phase shift, effectively reducing current / voltage harmonics and thus improving power quality.

Description

Technical Field

[0001] This invention relates to the field of energy conversion technology, and in particular to an energy conversion device and method for connecting a multi-wave energy generator. Background Technology

[0002] New energy sources, as a key type of renewable energy, possess characteristics such as abundant resources, wide distribution, and high energy flux 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 key factors restricting its large-scale application. Therefore, lightweight, easy-to-control, and highly integrated power conversion devices that integrate multiple wave energy generators have become an important development trend.

[0003] Currently, rectifiers are typically adapted to operate with a single synchronous generator. However, when multiple synchronous generators converge their DC power, the power handling capacity of a single rectifier is limited, making it difficult to simultaneously meet the starting, running, and speed regulation requirements of multiple motors. Regarding current quality, due to the differences in electrical characteristics among multiple motors and the diversity of load variations, a single rectifier cannot effectively regulate the current, resulting in low-quality power converted by the generator, which cannot meet the high power quality requirements of modern industrial and power applications. Summary of the Invention

[0004] This invention provides a power conversion device and method for multi-wave energy generators, solving the technical problem of how to improve the quality of converted power from new energy power generation.

[0005] The first aspect of the present invention provides a power conversion device for multi-wave energy generator access, comprising a power conversion module and a generator main control module that are interconnected.

[0006] The power conversion module includes two synchronous generators, a three-winding transformer, and a rectifier;

[0007] The synchronous generator is used to convert mechanical energy into alternating current electrical energy;

[0008] The three-winding transformer is used to transform AC power voltage and provide a path for high-order harmonic current.

[0009] The rectifier is used to rectify the AC power after voltage transformation to generate DC power;

[0010] 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.

[0011] Optionally, the regulation specifically involves regulating the two synchronous generators to the same speed, in the same direction, and with equal torque.

[0012] Optionally, the three-winding transformer is a DDY type three-winding transformer;

[0013] The two synchronous generators are respectively connected to the primary winding and the secondary winding of the three-winding transformer;

[0014] The rectifier is connected to the third winding of the three-winding transformer.

[0015] Optionally, both synchronous generators and the rectifier are communicatively connected to the generator main control module;

[0016] The generator main control module includes a speed submodule and a rotor position angle submodule;

[0017] The motor operating data includes motor speed data and rotor position angle data;

[0018] The speed submodule is used to generate motor speed data for regulating the synchronous generator motor speed based on the rectified current component;

[0019] The rotor position angle submodule is used to generate rotor position angle data for regulating the rotor position of the synchronous generator.

[0020] Optionally, the speed submodule includes a frequency locking unit and a speed processing unit that are communicatively connected to each other;

[0021] The frequency locking unit is used to obtain the time difference of the current zero-crossing cycle and perform a reciprocal operation to obtain the frequency locking speed component;

[0022] The speed processing unit is used to generate the motor speed data based on the rectified current component, the frequency-locked speed component, and the preset reference speed component.

[0023] Optionally, the rotor position submodule includes a phase-locked unit;

[0024] The phase-locked unit is used to perform integral calculations on the locked frequency speed component to generate the rotor position angle data.

[0025] Optionally, the speed processing unit includes a speed calculation subunit, a speed outer loop subunit, a current calculation subunit, a current inner loop subunit, a first processing subunit, and a second processing subunit that are connected in sequence via communication.

[0026] The speed calculation subunit is used to perform a difference calculation between the preset reference speed component and the frequency-locked speed component to obtain the error speed.

[0027] The outer loop subunit of the rotation speed is used to perform feedback control operation on the error rotation speed and generate a reference current component;

[0028] The current calculation subunit is used to perform a difference calculation using the reference current component and the rectified current component to obtain the error current;

[0029] The current inner loop subunit is used to perform feedback control operation on the error current and generate duty cycle parameters;

[0030] The first processing subunit is used to perform a multiplication operation between the duty cycle parameter and a preset first transfer function to obtain the target current data;

[0031] The second processing subunit is used to perform a multiplication operation between the target current data and a preset second transfer function to generate the motor speed data.

[0032] Optionally, the generator main control module further includes a modulation submodule;

[0033] The modulation submodule is used to modulate the motor operating data and generate a switching drive signal for controlling the rectifier to start or stop power conversion.

[0034] Optionally, the rectifier is a diode uncontrolled rectifier.

[0035] A second aspect of the present invention provides a power conversion method for an energy conversion device connected to a multi-wave energy generator, comprising:

[0036] The rectified current component after receiving the rectification operation is rectified to generate motor operating data.

[0037] Based on the motor's operating data, the power conversion module is controlled at the same speed, in the same direction, and with equal torque, and then the power is converted.

[0038] As can be seen from the above technical solutions, the present invention has the following advantages:

[0039] This invention proposes a power conversion device based on a three-winding transformer and a multi-wave energy generator. Power conversion is performed through a power conversion module. The three-winding transformer in the power conversion module performs voltage transformation on AC power and provides a path for high-order harmonic currents. These high-order harmonic currents can form circulating currents within the delta windings, thereby suppressing harmonic transmission and further improving the quality of the converted power. Simultaneously, the generator main control module collects the rectified current components after rectification and performs closed-loop motor control on these components. Based on the generated motor operating data, the two synchronous generators are controlled to operate at the same speed, in the same direction, and with equal torque, ensuring that the two synchronous generators are in phase, have the same speed, and rotate in the same direction. A three-winding transformer is introduced on the motor side, with an uncontrolled rectifier connected to the D11 side to suppress harmonic transmission. By combining the mechanical system to control the synchronous generators to operate at the same speed, in the same direction, and with the same torque, two synchronous generators, PMSG1 and PMSG2, are connected to the d11 and yn sides respectively. The three-winding transformer enables the phases of the two synchronous generators to be staggered and then converged, realizing phase shift difference, effectively reducing current / voltage harmonics, and improving power quality. Attached Figure Description

[0040] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0041] Figure 1 This is a schematic diagram of the structure of the power conversion device connected to the multi-wave energy generator according to an embodiment of the present invention;

[0042] Figure 2 This is a schematic diagram of the speed processing unit according to an embodiment of the present invention;

[0043] Figure 3 This is a schematic diagram of the voltage and current waveforms in an embodiment of the present invention;

[0044] Figure 4 This 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.

[0045] Figure 5 This is a flowchart illustrating the steps of a power conversion method for a power conversion device applied to a multi-wave energy generator according to an embodiment of the present invention. Detailed Implementation

[0046] This invention provides a power conversion device and method for connecting multiple wave energy generators, which is used to solve the technical problem of how to improve the quality of converted power from new energy power generation.

[0047] To make the objectives, features, and advantages of this invention more apparent and understandable, the technical solutions of the embodiments of this invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the embodiments described below are only some embodiments of this invention, and not all embodiments. Based on the embodiments of this invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of this invention.

[0048] Currently, in wave energy power generation technology, a single wave energy permanent magnet synchronous generator is typically driven by a Boost-PFC rectifier, forming a complete system. Therefore, operating multiple wave energy permanent magnet synchronous generators requires multiple Boost-PFC rectifiers, connected to the DC bus in series or parallel. However, this consumes significant costs and space.

[0049] Lightweight design and low-cost, high-efficiency integration are important trends in large-scale wave energy power generation devices. Therefore, using a single driver to drive two or more wave energy permanent magnet synchronous generators is a current important development direction. The traditional scheme of using a single driver to drive two synchronous generators directly connects the two generators to a Boost-PFC rectifier. However, the randomness of motor operation affects the overall grid connection quality and operational stability of the system. Furthermore, effective motor power / speed control can be achieved through current-weighted feedback of each generator. However, this type of control scheme sacrifices the operating power of the synchronous generators to meet power quality requirements, inevitably resulting in significant circulating current in the motors.

[0050] On the other hand, mechanical torque control and electrical control are usually disconnected. They only interact within the energy management system through energy / power, and are not adapted to specific speed control. This greatly limits the development potential of a single driver to drive two or more wave energy permanent magnet synchronous machines.

[0051] In summary, in existing technologies, Boost-PFC rectifiers are typically adapted for single-use wave energy permanent magnet synchronous generators. However, when multiple wave energy permanent magnet synchronous generators are connected to the DC bus, parallel connection to the medium-voltage DC bus or series connection to the high-voltage DC bus is often used, which can easily lead to problems such as high cost and low power density.

[0052] In schemes where a single motor drive circuit drives multiple synchronous motors, direct connection is usually used, along with a relatively complex control scheme, which results in higher costs, increased control difficulty, and decreased robustness.

[0053] The coordination between mechanical and electrical control is relatively low, limited to power / energy coordination management, and not extended to specific speed control.

[0054] This invention addresses the problem of complex control schemes that can lead to higher costs, increased control difficulty, and decreased robustness by using a single rectifier main circuit connected to a D11d11yn three-winding transformer to drive multiple synchronous motors.

[0055] The mechanical system control and electrical system control are coordinated to consider the electrical characteristics and motor motion characteristics, thus solving the problems of random and dispersed operation and complex and difficult control structure.

[0056] Therefore, this invention proposes a power conversion device based on a three-winding transformer and multiple wave energy generators. It employs a generator main control module to perform closed-loop motor control on the rectified current component after rectification, generating motor operating data for controlling two synchronous generators. This solves the problem that a single drive circuit cannot drive two or more wave energy permanent magnet synchronous generators. Simultaneously, the acquired motor operating data is used to regulate the two synchronous generators, specifically by adjusting their operating parameters, such as speed and torque. This addresses the issue of neglecting the adjustability of mechanical transmission during electrical mutual-pulverization operation. For example, if the offset of the mechanical shaft driving the synchronous generator exceeds a certain threshold, the motor speed can be reduced to decrease the impact on the mechanical transmission components, while simultaneously adjusting the motor's torque output to ensure the stability of electrical mutual-pulverization operation.

[0057] Please see Figure 1 and Figure 2 The present invention provides a power conversion device for multi-wave energy generator access, comprising a power conversion module and a generator main control module that are interconnected.

[0058] The power conversion module includes two synchronous generators, a three-winding transformer, and a rectifier;

[0059] Synchronous generators are used to convert mechanical energy into alternating current (AC) electrical energy.

[0060] Three-winding transformers are used to transform AC power voltage and provide a path for high-order harmonic currents.

[0061] A rectifier is used to rectify alternating current (AC) power after voltage conversion to generate direct current (DC) power.

[0062] 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 based on the generated motor operating data.

[0063] It should be noted that you should refer to [link / reference]. Figure 1 , Figure 1This is a schematic diagram of the power conversion device connected to a multi-wave energy generator. The two M's on the left side of the diagram refer to two synchronous generators, PMSG1 and PMSG2, respectively. The two synchronous generators are connected to each other through a gearbox shaft. The gearbox contains a controller that communicates with the generator main control module to receive and regulate the two synchronous generators based on the generator's operating data. The right sides of the two synchronous generators are connected to the medium-voltage side of the d11 primary winding and the low-voltage side of the yn secondary winding of a D11d11yn type three-winding transformer, respectively. The high-voltage side of the D11 tertiary winding is connected to the AC side of the rectifier. For a three-phase system, the 3rd harmonic and its multiples (such as the 6th, 9th, etc.) are in phase in the three phases. In the D11d11yn type three-winding transformer, the delta-connected windings on the high-voltage side (D), medium-voltage side (d), and low-voltage side (y) provide a path for higher harmonic currents. Due to the special nature of the delta connection, the 3rd harmonic current can form a circulating current inside the delta winding, thereby suppressing the transmission of harmonics. The main circuit on the DC side of the rectifier is connected to a DC bus. The main circuit of the rectifier includes a current transformer or Hall current sensor, an inductor, a diode, a capacitor, and an IGBT element. A current transformer or Hall current sensor is installed between the main circuit of the rectifier and the DC bus. An inductor is connected in series with the current transformer or Hall current sensor. An IGBT element and a diode are connected to the end of the inductor away from the current transformer or Hall current sensor, respectively. A capacitor is connected to the end of the diode away from the inductor. The end of the capacitor away from the diode is connected to the DC bus.

[0064] It should be noted that current transformers or Hall current sensors are used to detect the rectified current components after rectification, specifically the periodic components of the current.

[0065] Please see Figure 1 and Figure 2 The generator main control module includes a speed submodule and a rotor position angle submodule. The speed submodule includes a frequency locking unit and a speed processing unit. Figure 2 This is a schematic diagram of the speed processing unit. The speed processing unit includes a speed calculation subunit, a speed outer loop subunit, a current calculation subunit, a current inner loop subunit, a first processing subunit, and a second processing subunit, which are connected in sequence via communication. Figure 2 plant i1 and plant i2 These refer to the first processing subunit and the second processing subunit, respectively.

[0066] The power conversion device connected to multiple wave energy generators includes a mechanical system and an electrical system. The mechanical system includes a gearbox, which provides torque to the synchronous generator and enables reverse following control of other generators. Taking wave energy generation as an example, in actual wave energy generation devices, wave energy is collected by a trap, stored in a hydraulic accumulator, and further supplied with torque to the wave energy permanent magnet synchronous motor through an energy distribution unit and the gearbox shaft. In this application, a gearbox interconnecting two synchronous generators is added, driving the two interconnected generators to have the same torque, speed, and rotation phase based on motor operating data.

[0067] In this application, the electrical system consists of a power 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.

[0068] It is worth mentioning that the generator main control module refers to the main control circuit connected to the rectifier main circuit. Specifically, it refers to the Boost-PFC circuit connected to the DC side of the rectifier, which is used to drive the two synchronous generators.

[0069] In this embodiment of the invention, upon receiving a power conversion request, mechanical energy is converted into AC power by a synchronous generator. A three-winding transformer is then used to perform voltage transformation on the AC power, providing a path for high-order harmonic currents. These high-order harmonic currents can form circulating currents within the delta windings, thereby suppressing harmonic transmission and further improving the quality of the converted power. The voltage-transformed AC power is then rectified by a rectifier to generate DC power. However, due to the randomness of motor operation when two synchronous generators are running in parallel, the quality of the converted power is reduced. Therefore, the generator main control module collects the rectified current component after rectification and performs closed-loop motor control on it. Based on the generated motor operating data, the two synchronous generators are controlled to operate at the same speed, in the same direction, and with equal torque, ensuring that the two synchronous generators are in phase, have the same speed, and rotate in the same direction. Since the two synchronous generators are set to operate at the same speed and in the same direction, the voltage phase sequence and phase they generate are the same. Therefore, a three-winding transformer (D11d11yn) is introduced on the motor side, with an uncontrolled rectifier connected to the D11 side to suppress harmonic transmission. By combining the mechanical system to control the synchronous generators to operate at the same speed, in the same direction, and with the same torque, PMSG1 and PMSG2 are connected to the d11 and yn sides respectively. The three-winding transformer enables the phases of the two synchronous generators to be staggered and then converged, achieving a 30° phase shift difference, effectively reducing current / voltage harmonics and improving power quality.

[0070] Please see Figure 1 and Figure 2The present invention provides a power conversion device for connecting multiple wave energy generators, wherein the control is specifically performed by controlling two synchronous generators at the same speed, in the same direction and with equal torque.

[0071] It should be noted that the mechanical system provides the same torque to the two synchronous generators based on the motor operation data generated by the generator main control module, and makes the two synchronous generators run at the same speed. That is, the frequency, voltage and current of the generated electrical energy are the same, avoiding complex harmonic components caused by different amplitudes and frequencies, thereby improving the power quality.

[0072] Please see Figure 1 and Figure 2 The present invention provides an energy conversion device for connecting a multi-wave energy generator, wherein the three-winding transformer is a DDY type three-winding transformer;

[0073] Two synchronous generators are connected to the primary and secondary windings of a three-winding transformer, respectively.

[0074] The rectifier is connected to the third winding of a three-winding transformer.

[0075] It should be noted that the three-winding transformer is a DDY type three-winding transformer; the two synchronous generators are connected to the primary and secondary windings of the three-winding transformer respectively; the rectifier is connected to the tertiary winding of the three-winding transformer, and the high-order harmonic current can form a circulating current inside the delta winding, thereby suppressing the transmission of harmonics and further improving the quality of the converted electrical energy.

[0076] Please see Figure 1 and Figure 2 The present invention provides a power conversion device for multi-wave energy generator access, wherein two synchronous generators and a rectifier are all communicatively connected to the generator main control module;

[0077] The generator main control module includes a speed submodule and a rotor position angle submodule;

[0078] Motor operating data includes motor speed data and rotor position angle data;

[0079] The speed submodule is used to generate motor speed data for regulating the synchronous generator motor speed based on the rectified current component;

[0080] The rotor position angle submodule is used to generate rotor position angle data for controlling the rotor position of the synchronous generator.

[0081] It should be noted that the rotational speed data describes the speed of the synchronous generator rotor, while the motor speed data refers to the data used to adjust the rotational speed of the synchronous generator rotor. The position angle data describes the angle of the rotor's position relative to the stator; the rotor position angle data refers to the data used to adjust the angle of the synchronous generator rotor's position relative to the stator.

[0082] It should be noted that the speed submodule is used to generate motor speed data for regulating the synchronous generator motor speed based on the rectified current component detected by the rectifier main circuit, and the rotor position angle submodule is used to generate rotor position angle data for regulating the synchronous generator rotor position.

[0083] Please see Figure 1 and Figure 2 The present invention provides a power conversion device for multi-wave energy generator access, wherein the speed submodule includes a frequency locking unit and a speed processing unit that are interconnected.

[0084] The frequency locking unit is used to obtain the time difference of the current zero-crossing cycle and perform reciprocal calculations to obtain the frequency locking speed component;

[0085] The speed processing unit is used to generate motor speed data based on the rectified current component, the frequency-locked speed component, and the preset reference speed component.

[0086] It should be noted that since a periodic current component appears after rectification, which is exactly twice the rotational speed, the frequency, i.e. the frequency-locked rotational speed component, can be obtained by detecting the time difference between the zero-crossing points of the periodic current component and taking its reciprocal. Therefore, the frequency-locked rotational speed component can be obtained by using the frequency-locking unit to obtain the time difference of the current zero-crossing period and performing the inverse operation.

[0087] It is worth mentioning that the zero-crossing cycle time difference of current refers to the time difference between the zero-crossing points of the periodic components of current.

[0088] Please see Figure 1 and Figure 2 The present invention provides a power conversion device for multi-wave energy generator access, wherein the rotor position sub-module includes a phase-locked unit;

[0089] The phase-locked unit is used to perform integral calculations on the frequency-locked speed components to generate rotor position angle data.

[0090] It should be noted that since phase is the integral of frequency, the rotor position angle data is generated by integrating the frequency-locked rotational speed component using the phase-locked unit.

[0091] Please see Figure 1 and Figure 2 The present invention provides a power conversion device for multi-wave energy generator access, wherein the speed processing unit includes a speed calculation subunit, a speed outer loop subunit, a current calculation subunit, a current inner loop subunit, a first processing subunit, and a second processing subunit that are connected in sequence via communication.

[0092] The speed calculation subunit is used to perform difference calculation between a preset reference speed component and a frequency-locked speed component to obtain the error speed.

[0093] In this embodiment of the invention, a preset reference rotational speed component is used. With frequency-locked speed component Perform the difference calculation to obtain the error speed.

[0094] The outer loop subunit for rotational speed is used to perform feedback control on the error rotational speed and generate a reference current component.

[0095] In this embodiment of the invention, feedback control is performed using an error speed input speed outer loop. That is, the error speed is input into the speed regulator (PI or PID regulator), processed using a proportional-integral (PI) or proportional-integral-derivative (PID) control algorithm, and then the reference current component is calculated to obtain the reference current component. .

[0096] In practical implementation, to simplify the method, the above process can be converted into a formulaic encapsulation, where the reference current component... The calculation method can be as follows:

[0097]

[0098] In the formula, This represents the outer loop transfer function for rotational speed.

[0099] The current calculation subunit is used to perform difference calculation using the reference current component and the rectified current component to obtain the error current;

[0100] In this embodiment of the invention, a reference current component is used. and rectified current component Perform the difference calculation to obtain the error current.

[0101] The inner current loop subunit is used to perform feedback control on the error current and generate duty cycle parameters.

[0102] In this embodiment of the invention, feedback control is performed using the error current input current inner loop. That is, the error current input current regulator (PI or PID regulator) is processed using a proportional-integral (PI) or proportional-integral-derivative (PID) control algorithm, and then the duty cycle is calculated to obtain the duty cycle parameter.

[0103] In practical implementation, to simplify the method, the above process can be converted into a formula, where the duty cycle parameter... The calculation method can be as follows:

[0104]

[0105] In the formula, This represents the transfer function of the inner current loop.

[0106] The first processing subunit is used to perform a multiplication operation between the duty cycle parameter and a preset first transfer function to obtain the target current data;

[0107] In practical implementation, to facilitate the method's implementation, the above process can be converted into a formulaic encapsulation, where the target current data... The calculation method can be as follows:

[0108]

[0109] In the formula, This indicates the preset first transfer function, specifically the transfer function from the duty cycle to the inductor current.

[0110] It is worth mentioning that the target current data refers to the inductor current.

[0111] The second processing subunit is used to perform a multiplication operation between the target current data and a preset second transfer function to generate motor speed data.

[0112] In practical implementation, to simplify the method, the above process can be converted into a formula encapsulated in the form of motor speed data. The calculation method can be as follows:

[0113]

[0114] In the formula, This indicates a preset second transfer function, specifically referring to the transfer function from inductor current to motor speed.

[0115] Please see Figure 1 The present invention provides a power conversion device for multi-wave energy generator access, wherein the generator main control module further includes a modulation sub-module;

[0116] The modulation submodule is used to modulate the motor operating data and generate switching drive signals for controlling the rectifier to start or stop the power conversion.

[0117] It should be noted that, Figure 1 In the main circuit of the rectifier, M refers to the modulation stage submodule, specifically the modulation stage, which is used to determine whether the synchronous generator is within the preset standard operating data range based on the motor operating data. If it is, a switching drive signal to turn on the IGBT is generated to maintain the current motor state. If it is not, it indicates a deviation, and a switching drive signal to turn off the IGBT is generated.

[0118] Please see Figure 1 and Figure 2The present invention provides a power conversion device for multi-wave energy generator connection, wherein the rectifier is a diode uncontrolled rectifier.

[0119] It should be noted that, currently, taking wave energy power generation as an example, the stator side of the wave energy permanent magnet synchronous generator is connected to a diode uncontrolled rectifier or a PWM rectifier. Among these, the PWM rectifier offers high controllability, but it is expensive, bulky, and lacks reliability; its trigger signal is highly susceptible to interference when operating in a marine environment. Diode uncontrolled rectifiers offer high reliability and can significantly reduce the investment cost of offshore converter stations, but they can cause excessive harmonics in the generator output current, leading to severe distortion of the rectifier's AC current. Using inductive filtering is an effective and practical method to improve power quality; however, currently, single inductors suffer from large size and low core material utilization.

[0120] Wave energy generation devices based on diode uncontrolled rectifiers suffer from significant harmonic distortion during power conversion, severely impacting the stable operation of wave energy permanent magnet synchronous generators and DC voltage. Furthermore, traditional methods require matching inductors and converters for each generator, resulting in material waste and insufficient core utilization. Therefore, large-scale wave energy generation devices based on diode uncontrolled rectifiers require generator-side harmonic suppression methods that are compact and require minimal materials.

[0121] Therefore, the rectifier in this invention employs a diode uncontrolled rectifier. A D11d11yn type three-winding transformer is connected in series between the two permanent magnet synchronous generators and the uncontrolled rectifier. The two permanent magnet synchronous generators are connected to the d11 and yn sides of the three-winding transformer, and the uncontrolled rectifier is connected to the D11 side of the three-winding transformer. The proposed D11d11yn type three-winding transformer provides a current path for high-order harmonics, ensuring that the high-order harmonic current on the AC side of the uncontrolled rectifier flows only within the three-winding transformer, thus improving the current quality of the permanent magnet synchronous generators. The cascaded connection of the two motors through the three-winding transformer saves half of the diode switching devices, and the single-core multi-winding improves the core utilization rate, solving the problems of excessive generator-side current harmonics and insufficient core utilization caused by traditional diode rectifiers. Furthermore, it enables a single uncontrolled rectifier to simultaneously drive two permanent magnet synchronous generators.

[0122] Here is an example application:

[0123] Compared to the traditional method of directly connecting a generator to a diode-controlled rectifier, the present invention reduces the 5th harmonic of the synchronous generator side current from 0.0353 to 0.0329, and the corresponding 7th harmonic reduction effect is from 0.0138 to 0.0127. Figure 3 , Figure 4 As shown, this invention significantly optimizes the current waveform on the generator side and solves the problem of excessive generator-side current harmonics caused by uncontrolled diode rectification.

[0124] It should be noted that the harmonic elimination of the present invention includes the following aspects:

[0125] 1. The mechanical system provides the same torque and makes the two synchronous machines run at the same speed, that is, the frequency, voltage and current of the generated electrical energy are the same, avoiding complex harmonic components caused by different amplitudes and frequencies.

[0126] 2. The three-winding transformer allows the phases of the two synchronous generators to be staggered and then converged, effectively reducing harmonics.

[0127] 3. Phase modulation of the current loop.

[0128] Please see Figure 5 The present invention provides a power conversion method for a power conversion device applied to a multi-wave energy generator, comprising:

[0129] Step 101: Rectify the rectified current component after receiving the rectification operation to generate motor operating data.

[0130] Step 102: Based on the motor operating data, the power conversion module is adjusted to operate at the same speed, in the same direction, and with equal torque, and then the power is converted.

[0131] In this embodiment of the invention, upon receiving a power conversion request, mechanical energy is converted into AC power by a synchronous generator. A three-winding transformer is then used to perform voltage transformation on the AC power, providing a path for high-order harmonic currents. These high-order harmonic currents can form circulating currents within the delta windings, thereby suppressing harmonic transmission and further improving the quality of the converted power. The voltage-transformed AC power is then rectified by a rectifier to generate DC power. However, due to the randomness of motor operation when two synchronous generators are running in parallel, the quality of the converted power is reduced. Therefore, the generator main control module collects the rectified current component after rectification and performs closed-loop motor control on it. Based on the generated motor operating data, the two synchronous generators are controlled to operate at the same speed, in the same direction, and with equal torque, ensuring that the two synchronous generators are in phase, have the same speed, and rotate in the same direction. Since the two synchronous generators are set to operate at the same speed and in the same direction, the voltage phase sequence and phase they generate are the same. Therefore, a three-winding transformer (D11d11yn) is introduced on the motor side, with an uncontrolled rectifier connected to the D11 side to suppress harmonic transmission. By combining the mechanical system to control the synchronous generators to operate at the same speed, in the same direction, and with the same torque, PMSG1 and PMSG2 are connected to the d11 and yn sides respectively. The three-winding transformer enables the phases of the two synchronous generators to be staggered and then converged, achieving a 30° phase shift difference, effectively reducing current / voltage harmonics and improving power quality.

[0132] Those skilled in the art will clearly understand that, for the sake of convenience and brevity, the specific working processes of the systems, devices, and units described above can be referred to the corresponding processes in the foregoing method embodiments, and will not be repeated here.

[0133] In the several embodiments provided in this application, it should be understood that the disclosed systems, apparatuses, and methods can be implemented in other ways. For example, the apparatus embodiments described above are merely illustrative; for instance, the division of units is only a logical functional division, and in actual implementation, there may be other division methods. For example, multiple units or components may be combined or integrated into another system, or some features may be ignored or not executed. Furthermore, the coupling or direct coupling or communication connection shown or discussed may be an indirect coupling or communication connection between apparatuses or units through some interfaces, and may be electrical, mechanical, or other forms.

[0134] The above-described embodiments are only used to illustrate the technical solutions of the present invention, and are not intended to limit it. Although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some of the technical features. Such modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the spirit and scope of the technical solutions of the embodiments of the present invention.

Claims

1. A power conversion device for use with a multi-wave energy generator, 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 three-winding transformer, and a rectifier; The two synchronous generators are respectively connected to the medium-voltage side of the d11 primary winding and the low-voltage side of the yn secondary winding of the D11d11yn type three-winding transformer; The rectifier is connected to the high-voltage side of the D11 tertiary winding of the D11d11yn type three-winding transformer; The synchronous generator is used to convert mechanical energy into alternating current electrical energy; The three-winding transformer is used to perform voltage transformation on AC power. 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 power conversion device connected to the multi-wave energy generator according to claim 1, characterized in that, The regulation specifically refers to regulating the two synchronous generators to the same speed, in the same direction, and with equal torque.

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

4. The power conversion device connected to the multi-wave energy generator according to claim 3, characterized in that, The speed submodule includes a frequency locking unit and a speed processing unit that are interconnected. The frequency locking unit is used to obtain the time difference of the current zero-crossing cycle and perform a reciprocal operation to obtain the frequency locking speed component; The speed processing unit is used to generate the motor speed data based on the rectified current component, the frequency-locked speed component, and the preset reference speed component.

5. The power conversion device connected to the multi-wave energy generator according to claim 4, characterized in that, The rotor position submodule includes a phase-locked unit; The phase-locked unit is used to perform integral calculations on the locked frequency speed component to generate the rotor position angle data.

6. The power conversion device connected to the multi-wave energy generator according to claim 4, characterized in that, The speed processing unit includes a speed calculation subunit, a speed outer loop subunit, a current calculation subunit, a current inner loop subunit, a first processing subunit, and a second processing subunit that are connected in sequence via communication. The speed calculation subunit is used to perform a difference calculation between the preset reference speed component and the frequency-locked speed component to obtain the error speed. The outer loop subunit of the rotation speed is used to perform feedback control operation on the error rotation speed and generate a reference current component; The current calculation subunit is used to perform a difference calculation using the reference current component and the rectified current component to obtain the error current; The current inner loop subunit is used to perform feedback control operation on the error current and generate duty cycle parameters; The first processing subunit is used to perform a multiplication operation between the duty cycle parameter and a preset first transfer function to obtain the target current data; The second processing subunit is used to perform a multiplication operation between the target current data and a preset second transfer function to generate the motor speed data.

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

8. The power conversion device connected to a multi-wave energy generator according to any one of claims 1-7, characterized in that, The rectifier is a diode uncontrolled rectifier.

9. A conversion method for an energy conversion device applied to a multi-wave energy generator 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's operating data, the power conversion module is controlled at the same speed, in the same direction, and with equal torque, and then the power is converted.

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