Electric energy conversion device and method connected with multiple wave energy generators

Abstract

The invention relates to the technical field of energy conversion, and discloses an electric energy conversion device and method connected with multiple wave energy generators, electric energy conversion is performed through an electric energy conversion module, a three-winding transformer in the electric energy conversion module is used for performing voltage conversion on alternating current electric energy, and a higher harmonic current channel is provided; the high-order harmonic current can form circulating current in the triangular winding, so that transmission of harmonic waves is restrained, the quality of converted electric energy is further improved, meanwhile, a rectification current component after rectification operation is collected through the generator main control module, motor closed-loop control is carried out on the rectification current component, and the conversion efficiency is improved. And performing same-speed, same-direction and equal-torque regulation and control on the two synchronous generators according to the generated motor operation data, so that the two synchronous generators are consistent in phase, same in rotating speed and same in rotating direction, phase shift difference is realized, harmonic waves of current / voltage are effectively reduced, and the electric energy quality is improved.

Description

Technical Field

[0001] The present invention relates to the technical field of energy conversion, and in particular to an electric energy conversion device and method for connecting multiple wave energy generators. Background Art

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

[0003] At present, rectifiers are usually adapted to synchronous generator operation. However, when multiple synchronous units are connected to each other, the power processing capacity of a single rectifier is limited, and it is difficult to meet the requirements of starting, running and speed regulation of multiple motors at the same time. In terms of current quality, due to the differences in electrical characteristics of multiple motors and the diversity of load changes, a single rectifier cannot be effectively adjusted, resulting in low quality of power converted by the generator, which cannot meet the modern industrial and power application scenarios with high requirements for power quality. Summary of the invention

[0004] The present invention provides an electric energy conversion device and method for accessing multiple wave energy generators, which solves the technical problem of how to improve the quality of converted electric energy generated by renewable energy.

[0005] A first aspect of the present invention provides an electric energy conversion device connected to multiple wave energy generators, comprising an electric energy conversion module and a generator main control module that are communicatively connected to each other;

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

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

[0008] The three-winding transformer is used to perform voltage conversion on AC power and provide a high-order harmonic current channel;

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

[0010] The generator main control module is used to use the rectified current component after the rectification operation to perform motor closed-loop control, and to regulate the two synchronous generators according to the generated motor operation data.

[0011] Optionally, the regulation is specifically to regulate the two synchronous generators at 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 tertiary winding of the three-winding transformer.

[0015] Optionally, the two synchronous generators and the rectifier are both 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 operation data includes motor speed data and rotor position angle data;

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

[0019] The rotor position angle submodule is used to generate the 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 current zero-crossing period time difference and perform an inverse operation to obtain the frequency locking speed component;

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

[0023] Optionally, the rotor position angle submodule includes a phase locking unit;

[0024] The phase-locked unit is used to perform an integration operation on the frequency-locked rotation speed component to generate the rotor position angle data.

[0025] Optionally, the speed processing unit includes a speed operation subunit, a speed outer loop subunit, a current operation subunit, a current inner loop subunit, a first processing subunit and a second processing subunit which are sequentially communicatively connected;

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

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

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

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

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

[0031] The second processing subunit is used for performing a multiplication operation on 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 link submodule;

[0033] The modulation link submodule is used to perform a modulation operation on the motor operation data to generate a switch drive signal for controlling the rectifier to start or stop power conversion.

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

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

[0036] Performing rectification operation on the rectified current component after receiving the rectification operation to generate motor operation data;

[0037] The electric energy conversion module is regulated at the same speed, direction and torque according to the motor operation data, and electric energy conversion is performed.

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

[0039] The present invention proposes an electric energy conversion device connected to a multi-wave power generator based on a three-winding transformer, and electric energy conversion is performed through an electric energy conversion module, wherein the three-winding transformer in the electric energy conversion module is used to perform voltage conversion on the AC electric energy and provide a high-order harmonic current channel. The high-order harmonic current can form a circulating current inside the triangle winding, thereby suppressing the transmission of harmonics and further improving the quality of converted electric energy. At the same time, the rectified current component after the rectification operation is collected through the generator main control module, and the rectified current component is controlled by the motor closed-loop. According to the generated motor operation data, the two synchronous generators are controlled at the same speed, direction and torque, so that the two synchronous generators have the same phase, the same speed and the same rotation direction. A three-winding transformer is introduced on the motor side, wherein the D11 side is connected to an uncontrolled rectifier to suppress the transmission of harmonics. Combined with the mechanical system to control the synchronous generators to run at the same speed, direction and torque, the two synchronous generators PMSG1 and PMSG2 are connected to the d11 and yn sides respectively. The three-winding transformer staggers the phases of the two synchronous generators and then converges them to achieve phase shift difference, effectively reduce the harmonics of current / voltage, and improve the power quality. BRIEF DESCRIPTION OF THE DRAWINGS

[0040] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings required for use in the embodiments or the description of the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying creative labor.

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

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

[0043] Figure 3 A schematic diagram of voltage and current waveforms according to an embodiment of the present invention;

[0044] Figure 4 is a comparison diagram of the total harmonic distortion THD of the generator current and the diode side current in an embodiment of the present invention;

[0045] Figure 5 The present invention is a flowchart of the steps of a conversion method of an electric energy conversion device connected to multiple wave energy generators according to an embodiment of the present invention. DETAILED DESCRIPTION

[0046] The embodiment of the present invention provides an electric energy conversion device and method for connecting multiple wave power generators, which are used to solve the technical problem of how to improve the quality of converted electric energy generated by renewable energy.

[0047] In order to make the purpose, features and advantages of the present invention more obvious and easy to understand, the technical solutions in the embodiments of the present invention will be clearly and completely described below in conjunction with the drawings in the embodiments of the present invention. Obviously, the embodiments described below are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0048] At present, in the wave energy power generation technology, usually only a Boost-PFC type rectifier is used to drive a single wave energy permanent magnet synchronous generator, and the two form a complete set of equipment. Therefore, when multiple wave energy permanent magnet synchronous generators are in operation, multiple Boost-PFC type rectifiers are required to drive and operate, and are connected to the DC bus in series or parallel. However, this will consume a lot of cost and space.

[0049] Lightweight and low-cost and efficient 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 machines is an important development direction at present. The traditional single driver drives two synchronous machines, and the two synchronous machines are directly connected to the Boost-PFC rectifier. However, the randomness of the motor operation affects the overall grid-connected quality and operating 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 machine to meet the power quality requirements, which is bound to cause a large motor circulating current.

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

[0051] In summary, in the prior art, Boost-PFC type rectifiers are usually adapted to operate wave energy permanent magnet synchronous generators. However, when multiple wave energy permanent magnet synchronous generators are connected in parallel to a medium voltage DC bus or in series to a high voltage DC bus, the solution is often adopted, which easily leads to problems such as high cost and low power density.

[0052] In the scheme of driving multiple synchronous motors with a single motor drive circuit, they are usually directly connected and a more complex control scheme is adopted, which results in higher cost, increased control difficulty, decreased robustness and other problems.

[0053] The coordination between the mechanical part control and the electrical part control is relatively low, which is limited to the coordinated management of power / energy and has not been delegated to the specific speed control.

[0054] The present invention is based on a topological structure in which a single rectifier main circuit connected to a D11d11yn three-winding transformer drives multiple synchronous motors, and solves the problems of relatively complex control schemes that easily lead to high costs, increased control difficulty, and reduced robustness.

[0055] The mechanical system control and the electrical system control that consider the electrical characteristics and motor motion characteristics operate in coordination to solve the problems of random dispersion of operation and complex and difficult control structures.

[0056] Therefore, the present invention proposes an electric energy conversion device connected to multiple wave energy generators based on a three-winding transformer, and uses a generator main control module to perform motor closed-loop control on the rectified current component after the rectification operation, and generates motor operation data for controlling two synchronous generators, which can solve the problem that a single drive circuit is difficult to drive two or more wave energy permanent magnet synchronous generators; at the same time, the motor operation data is obtained to regulate the two synchronous generators, specifically, by adjusting the operating parameters of the synchronous generator, such as speed and torque. Solve the problem of electrical mutual powder operation ignoring the adjustability of mechanical transmission. For example, if it is detected that the offset of the mechanical shaft used to drive the synchronous generator exceeds a certain threshold, the speed of the motor can be reduced to reduce the impact on the mechanical transmission components, and at the same time, the torque output of the motor is adjusted to ensure the stability of the electrical mutual powder operation.

[0057] See also Figure 1 and Figure 2 , the present invention provides an electric energy conversion device connected to multiple wave energy generators, including an electric energy conversion module and a generator main control module that are communicatively connected to each other;

[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 AC electrical energy;

[0060] The three-winding transformer is used to convert the voltage of AC power and provide a channel for high-order harmonic currents;

[0061] The rectifier is used to rectify the AC power after voltage conversion to generate DC power;

[0062] The generator master control module is used to perform motor closed-loop control using the rectified current component after the rectification operation, and to regulate the two synchronous generators according to the generated motor operation data.

[0063] Please note that Figure 1 , Figure 1The schematic diagram of the structure of the electric energy conversion device connected to multiple wave energy generators. The two M's on the left side of the figure refer to two synchronous generators, namely PMSG1 and PMSG2. The two synchronous generators are connected through the gearbox shaft. The gearbox is equipped with a controller that communicates with the generator main control module to receive and regulate the two synchronous generators according to the motor operation data. The right sides of the two synchronous generators are respectively connected to the medium-voltage side of the d11 primary winding and the low-voltage side of the yn secondary winding of the D11d11yn three-winding transformer. The high-voltage side of the D11 tertiary winding is connected to the AC side of the rectifier. For a three-phase system, the third harmonic and its multiple harmonics (such as the 6th, 9th, etc.) are in phase in the three phases. In the D11d11yn three-winding transformer, the triangle-connected windings on the high-voltage side (D), the medium-voltage side (d) and the low-voltage side (y) provide channels for high-order harmonic currents. Due to the particularity of the triangle connection, the third harmonic current can form a circulating current inside the triangle winding, thereby suppressing the transmission of harmonics. The main circuit on the DC side of the rectifier is connected to the DC bus, and the main circuit of the rectifier includes a current transformer or a Hall current sensor, an inductor, a diode, a capacitor and an IGBT element; a current transformer or a Hall current sensor is arranged between the main circuit of the rectifier and the DC bus, the current transformer or the Hall current sensor is connected in series with the inductor, the end of the inductor away from the current transformer or the Hall current sensor is respectively connected to the IGBT element and the diode, the end of the diode away from the inductor is connected to the capacitor, and the end of the capacitor away from the diode is connected to the DC bus.

[0064] It should be noted that the current transformer or the Hall current sensor is used to detect the rectified current component after rectification, and the current component specifically refers to the current periodic component.

[0065] See also 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 is a structural diagram of a speed processing unit, the speed processing unit includes a speed operation subunit, a speed outer loop subunit, a current operation subunit, a current inner loop subunit, a first processing subunit and a second processing subunit which are sequentially connected in communication. Figure 2 Plant i1 and plant i2 Respectively refer to the first processing subunit and the second processing subunit.

[0066] The electric energy conversion device connected to the multiple wave energy generators includes a mechanical system and an electrical system. The mechanical system includes a gearbox, which is used to provide torque to the synchronous generator and realize reverse following control of other generators. Taking wave energy power generation as an example, in an actual wave energy power generation device, wave energy is collected by a collector, stored in a hydraulic accumulator, and further provided to the wave energy permanent magnet synchronous motor through an energy distribution unit and a gearbox shaft. In this application, a gearbox is added to interconnect the two synchronous generators, and the torque, speed and steering phase of the two interconnected generators are the same according to the motor operation data.

[0067] In the present application, the electrical system is composed of an electric energy conversion module and a generator main control module, specifically including a synchronous generator, a three-winding transformer, a rectifier and its associated generator main control module, and a DC bus.

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

[0069] In an embodiment of the present invention, in response to receiving a power conversion request, mechanical energy is converted into AC power through a synchronous generator, and a three-winding transformer is used to perform voltage conversion on the AC power, and a high-order harmonic current channel is provided. The high-order harmonic current can form a loop inside the triangle winding, thereby suppressing the transmission of harmonics and further improving the quality of the converted power. Then, the AC power after voltage conversion is rectified by a rectifier to generate DC power. However, since the two synchronous generators will have the problem of randomness in motor operation when they are running in parallel, the quality of the converted power is reduced. Therefore, the rectified current component after the rectification operation is collected by the generator main control module, and the rectified current component is controlled by the motor closed loop. According to the generated motor operation data, the two synchronous generators are regulated at the same speed and direction and with equal torque, so that the two synchronous generators have the same phase, the same speed, and the same rotation direction. Since the speed of the two synchronous generators is set to the same speed and direction, the voltage phase sequence and phase generated by them are the same. Therefore, a D11d11yn three-winding transformer is introduced on the motor side, wherein the D11 side is connected to an uncontrolled rectifier to suppress the transmission of harmonics. Combined with the mechanical system, the synchronous generators are controlled to run at the same speed, direction and torque. The d11 and yn sides are connected to PMSG1 and PMSG2 respectively. The three-winding transformer staggers the phases of the two synchronous generators and then converges them to achieve a 30° phase shift difference, effectively reducing the harmonics of current / voltage and improving the power quality.

[0070] See also Figure 1 and Figure 2The present invention provides an electric energy conversion device connected to multiple wave energy generators, and the control is specifically to control the 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 generated electric energy frequency, voltage and current are the same, avoiding complex harmonic components caused by different amplitudes and frequencies, thereby improving the quality of electric energy.

[0072] See also Figure 1 and Figure 2 , the present invention provides an electric energy conversion device connected to multiple wave energy generators, wherein the three-winding transformer is a DDY type three-winding transformer;

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

[0074] The rectifier is connected to the tertiary winding of the 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 respectively connected to the primary winding and the secondary winding of the three-winding transformer; 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 triangle winding, thereby suppressing the transmission of harmonics and further improving the quality of converted electric energy.

[0076] See also Figure 1 and Figure 2 , the present invention provides an electric energy conversion device connected to multiple wave energy generators, wherein two synchronous generators and a rectifier are both communicatively connected to a generator main control module;

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

[0078] The motor operation data includes motor speed data and rotor position angle data;

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

[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 speed data describes the rotation speed of the synchronous generator rotor, and the motor speed data refers to the data used to adjust the rotation speed of the synchronous generator rotor. The position angle data describes the angle of the position of the rotor relative to the stator, and the rotor position angle data refers to the data used to adjust the angle of the position of the synchronous generator rotor relative to the stator.

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

[0083] See also Figure 1 and Figure 2 , the present invention provides an electric energy conversion device connected to multiple wave energy generators, wherein the speed submodule includes a frequency locking unit and a speed processing unit that are communicatively connected to each other;

[0084] The frequency locking unit is used to obtain the current zero-crossing period time difference and perform inverse calculation to obtain the frequency locking speed component;

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

[0086] It should be noted that since the current periodic component appears after rectification, it is exactly twice the speed. Therefore, by detecting the time difference between the zero-crossing points of the current periodic component and taking the inverse, the frequency, that is, the frequency-locked speed component, can be obtained. Therefore, the frequency-locked speed component is obtained by using the frequency-locked unit to obtain the current zero-crossing periodic time difference and perform an inverse operation.

[0087] 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.

[0088] See also Figure 1 and Figure 2 , the present invention provides an electric energy conversion device connected to multiple wave energy generators, the rotor position angle submodule includes a phase locking unit;

[0089] The phase-locked unit is used to perform integration operation on the frequency-locked speed component to generate rotor position angle data.

[0090] It should be noted that, since the phase is the integral of the frequency, the phase-locked unit is used to perform an integral operation on the frequency-locked speed component to generate the rotor position angle data.

[0091] See also Figure 1 and Figure 2 , the present invention provides an electric energy conversion device connected to multiple wave energy generators, wherein the speed processing unit includes a speed operation subunit, a speed outer loop subunit, a current operation subunit, a current inner loop subunit, a first processing subunit and a second processing subunit which are sequentially connected in communication;

[0092] The speed calculation subunit is used to perform difference calculation using a preset reference speed component and a frequency-locked speed component to obtain an error speed;

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

[0094] The speed outer loop subunit is used to perform feedback control operation on the error speed to generate a reference current component;

[0095] In the embodiment of the present invention, the error speed is input into the speed outer loop for feedback control operation, that is, the error speed is input into the speed regulator (PI or PID regulator), and the proportional-integral (PI) or proportional-integral-derivative (PID) control algorithm is used for processing, and then the reference current component is calculated, so as to obtain the reference current component .

[0096] In a specific implementation, in order to facilitate the implementation of the method, the above process can be converted into a formula encapsulation form, where the reference current component The calculation method can be as follows:

[0097]

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

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

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

[0101] The current inner loop subunit is used to perform feedback control operation on the error current to generate a duty cycle parameter;

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

[0103] In the specific implementation, in order to facilitate the implementation of the method, the above process can be converted into a formula encapsulation form, where the duty cycle parameter The calculation method can be as follows:

[0104]

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

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

[0107] In the specific implementation, in order to facilitate the implementation of the method, the above process can be converted into a formula encapsulation form, where the target current data The calculation method can be as follows:

[0108]

[0109] In the formula, It represents a preset first transfer function, specifically refers to a transfer function from duty cycle to 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 on the target current data and a preset second transfer function to generate motor speed data.

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

[0113]

[0114] In the formula, It represents a preset second transfer function, specifically refers to a transfer function from the inductor current to the motor speed.

[0115] See also Figure 1 , the present invention provides an electric energy conversion device connected to multiple wave energy generators, the generator main control module also includes a modulation link submodule;

[0116] The modulation link submodule is used to modulate the motor operation data and generate a switch drive signal for controlling the rectifier to start or stop power conversion.

[0117] It should be noted that Figure 1 The M in the main circuit of the medium rectifier refers to the modulation link sub-module, specifically the modulation link, which is used to determine whether the synchronous generator operated according to the motor operating data is in the preset standard operating data range. If it is, a switch drive signal for turning on the IGBT is generated to maintain the current motor state. If it is not, it indicates that a deviation has occurred, and a switch drive signal for turning off the IGBT is generated.

[0118] See also Figure 1 and Figure 2The present invention provides an electric energy conversion device connected to multiple wave energy generators, wherein the rectifier is a diode uncontrolled rectifier.

[0119] It should be noted that, at present, 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 them, the PWM rectifier has high controllability, but it is expensive, occupies a large volume, has insufficient reliability, and the trigger signal is easily interfered when operating in an offshore environment. The diode uncontrolled rectifier has high reliability and can significantly reduce the investment cost of the offshore converter station, but it will cause excessive harmonics in the current at the output end of the generator, which will lead to serious distortion of the current on the AC side of the rectifier. Using inductor filtering is an effective and practical method to improve the quality of electric energy, but the current single inductor has problems such as large volume and low utilization rate of iron core materials.

[0120] The power conversion of wave energy power generation devices based on diode uncontrolled rectifiers has the problem of large harmonics, which seriously affects the stable operation of wave energy permanent magnet synchronous generators and DC voltages. In addition, each motor in the traditional way needs to be matched with an inductor and a converter, resulting in material waste and insufficient core utilization. Therefore, large-scale wave energy power generation devices based on diode uncontrolled rectifiers require a generator-side harmonic suppression method that is small in size and consumes less materials.

[0121] Therefore, the rectifier in the present invention adopts a diode uncontrolled rectifier, and a D11d11yn type three-winding transformer is connected in series between two permanent magnet synchronous generators and the uncontrolled rectifier. The two permanent magnet synchronous generators are connected to the d11 side and the yn side 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 channel for high-order harmonics, so that the high-order harmonic current on the AC side of the uncontrolled rectifier only flows inside the three-winding transformer, thereby improving the current quality of the permanent magnet synchronous generator. The dual motors save half of the diode switching devices through the cascade of the three-winding transformer, and the single core and multiple windings improve the utilization rate of the core, solving the problems of excessive harmonics on the generator side and insufficient utilization of the core caused by the traditional diode rectifier. And a single uncontrolled rectifier is realized to drive two permanent magnet synchronous generators at the same time.

[0122] The following is an application example:

[0123] Compared with the conventional method of directly connecting the generator to the diode uncontrolled rectifier, the synchronous generator side current 5th harmonic elimination effect of the present invention is reduced from 0.0353 to 0.0329, and the corresponding 7th harmonic elimination effect is reduced from 0.0138 to 0.0127. Figure 3 , Figure 4 It can be seen that the present invention greatly optimizes the current waveform on the generator side and solves the problem of excessive harmonics on the generator side current caused by uncontrolled rectification of diodes.

[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 generated electric energy frequency, voltage and current are the same, avoiding complex harmonic components caused by different amplitudes and frequencies.

[0126] 2. The three-winding transformer staggers the phases of the two synchronous generators and then converges them, effectively reducing harmonics.

[0127] 3. Phase control of current loop.

[0128] See also Figure 5 The present invention provides a conversion method for an electric energy conversion device connected to multiple wave energy generators, comprising:

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

[0130] Step 102: According to the motor operation data, the electric energy conversion module is regulated to have the same speed, direction and torque, and performs electric energy conversion.

[0131] In an embodiment of the present invention, in response to receiving a power conversion request, mechanical energy is converted into AC power through a synchronous generator, and a three-winding transformer is used to perform voltage conversion on the AC power, and a high-order harmonic current channel is provided. The high-order harmonic current can form a loop inside the triangle winding, thereby suppressing the transmission of harmonics and further improving the quality of the converted power. Then, the AC power after voltage conversion is rectified by a rectifier to generate DC power. However, since the two synchronous generators will have the problem of randomness in motor operation when they are running in parallel, the quality of the converted power is reduced. Therefore, the rectified current component after the rectification operation is collected by the generator main control module, and the rectified current component is controlled by the motor closed loop. According to the generated motor operation data, the two synchronous generators are regulated at the same speed and direction and with equal torque, so that the two synchronous generators have the same phase, the same speed, and the same rotation direction. Since the speed of the two synchronous generators is set to the same speed and direction, the voltage phase sequence and phase generated by them are the same. Therefore, a D11d11yn three-winding transformer is introduced on the motor side, wherein the D11 side is connected to an uncontrolled rectifier to suppress the transmission of harmonics. Combined with the mechanical system, the synchronous generators are controlled to run at the same speed, direction and torque. The d11 and yn sides are connected to PMSG1 and PMSG2 respectively. The three-winding transformer staggers the phases of the two synchronous generators and then converges them to achieve a 30° phase shift difference, effectively reducing the harmonics of current / voltage and improving the power quality.

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

[0133] In the several embodiments provided in the present application, it should be understood that the disclosed systems, devices and methods can be implemented in other ways. For example, the device embodiments described above are only schematic. For example, the division of the units is only a logical function division. There may be other division methods in actual implementation, such as multiple units or components can be combined or integrated into another system, or some features can be ignored or not executed. Another point is that the mutual coupling or direct coupling or communication connection shown or discussed can be an indirect coupling or communication connection through some interfaces, devices or units, which can be electrical, mechanical or other forms.

[0134] As described above, the above embodiments are only used to illustrate the technical solutions of the present invention, rather than to limit the same. Although the present invention has been described in detail with reference to the aforementioned embodiments, those skilled in the art should understand that the technical solutions described in the aforementioned embodiments may still be modified, or some of the technical features thereof may be replaced by equivalents. However, these modifications or replacements do not deviate the essence of the corresponding technical solutions from the spirit and scope of the technical solutions of the embodiments of the present invention.

Claims

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

2. The electric energy conversion device connected to the multi-wave energy generator according to claim 1 is characterized in that: The control specifically involves controlling the two synchronous generators at the same speed, in the same direction and with the same torque.

3. The electric energy conversion device connected to the multi-wave energy generator according to claim 1 is characterized in that: The three-winding transformer is a DDY type three-winding transformer; The two synchronous generators are respectively connected to the primary winding and the secondary winding of the three-winding transformer; The rectifier is connected to the tertiary winding of the three-winding transformer.

4. The electric energy conversion device connected to multiple wave energy generators according to claim 1 is characterized in that: The two synchronous generators and the rectifier are both 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 operation data includes motor speed data and rotor position angle data; The speed submodule is used to generate the motor speed data for regulating the motor speed of the synchronous generator according to the rectified current component; The rotor position angle submodule is used to generate the rotor position angle data for regulating the rotor position of the synchronous generator.

5. The electric energy conversion device connected to multiple wave energy generators according to claim 4 is characterized in that: The speed submodule includes a frequency locking unit and a speed processing unit that are communicatively connected to each other; The frequency locking unit is used to obtain the current zero-crossing period time difference and perform an inverse operation to obtain the frequency locking speed component; The speed processing unit is used to generate the motor speed data according to the rectified current component, the frequency-locked speed component and the preset reference speed component.

6. The electric energy conversion device connected to the multi-wave energy generator according to claim 5 is characterized in that: The rotor position angle submodule includes a phase locking unit; The phase-locked unit is used to perform an integration operation on the frequency-locked rotation speed component to generate the rotor position angle data.

7. The electric energy conversion device connected to the multi-wave energy generator according to claim 5 is characterized in that: The speed processing unit comprises a speed operation subunit, a speed outer loop subunit, a current operation subunit, a current inner loop subunit, a first processing subunit and a second processing subunit which are sequentially connected in communication; The speed calculation subunit is used to perform a difference calculation using the preset reference speed component and the frequency-locked speed component to obtain an error speed; The speed outer loop subunit is used to perform feedback control operation on the error speed to generate a reference current component; The current operation subunit is used to perform a difference operation using the reference current component and the rectified current component to obtain an error current; The current inner loop subunit is used to perform feedback control operation on the error current to generate a duty cycle parameter; The first processing subunit is used to perform a multiplication operation using the duty cycle parameter and a preset first transfer function to obtain target current data; The second processing subunit is used for performing a multiplication operation on the target current data and a preset second transfer function to generate the motor speed data.

8. The electric energy conversion device connected to multiple wave energy generators according to claim 4 is characterized in that: The generator main control module also includes a modulation link submodule; The modulation link submodule is used to perform a modulation operation on the motor operation data to generate a switch drive signal for controlling the rectifier to start or stop power conversion.

9. The electric energy conversion device connected to multiple wave energy generators according to any one of claims 1 to 8, characterized in that: The rectifier is a diode uncontrolled rectifier.

10. A conversion method for an electric energy conversion device connected to a multi-wave energy generator as claimed in any one of claims 1 to 9, characterized in that: include: Performing rectification operation on the rectified current component after receiving the rectification operation to generate motor operation data; The electric energy conversion module is regulated at the same speed, direction and torque according to the motor operation data, and electric energy conversion is performed.

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