Hybrid converter control method for offshore wind power

Abstract

A hybrid converter control method for offshore wind power, an apparatus, a device and a storage medium. The method comprises the following steps: S1, assigning a reference initial value for an effective value of an alternating current bus voltage of a hybrid converter, an operating angular frequency of the hybrid converter, and a reference value of an MMC direct current voltage, and acquiring an alternating current bus voltage of the hybrid converter, an effective value of the alternating current bus voltage of the hybrid converter, and an MMC direct current voltage; S2, calculating d-axis and q-axis components of the alternating current bus voltage of the hybrid converter in a dq rotating coordinate system; S3, calculating a reference value of the effective value of the alternating current bus voltage of the hybrid converter; S4, calculating a reference value of an MMC modulation voltage in the dq rotating coordinate system; S5, calculating an MMC modulation voltage in a three-phase stationary coordinate system; and S6, on the basis of the MMC modulation voltage in the three-phase stationary coordinate system, performing pulse width modulation to obtain trigger pulses for IGBTs of the MMC, thereby implementing steady-state control on the hybrid converter.

Description

A Hybrid Converter Control Method for Offshore Wind Power Technical Field

[0001] This invention relates to the field of offshore wind power DC transmission technology, specifically to a control method, apparatus, computer equipment, and storage medium for a large-scale offshore wind power transmission system using a hybrid DC transmission system cascaded with diode rectifier units and modular multilevel converters (DRU-MMC). Background Technology

[0002] As the scale of offshore wind farms continues to expand, the problems of large size and heavy weight of flexible DC transmission schemes for offshore wind power are becoming increasingly prominent. Among the many lightweight offshore wind power transmission technologies, the hybrid converter transmission scheme based on diode rectifier units and modular multilevel converters has attracted widespread attention due to its independent active and reactive power regulation capabilities, autonomous voltage build-up capabilities, and high technological maturity. Hereinafter, the diode rectifier unit is abbreviated as DRU, and the modular multilevel converter is abbreviated as MMC. Among them, the cascaded transmission scheme of DRU and MMC has advantages over the parallel transmission scheme of DRU and MMC, with MMC having lower voltage levels, lower insulation requirements, and fewer sub-modules, making it more suitable for the construction of future large-scale offshore wind power point-to-point DC transmission projects.

[0003] To reduce transmission losses and lower investment costs, in cascaded DRU and MMC power transmission schemes, the DRU typically transmits most of the active power, while the MMC handles reactive power compensation and a small portion of the active power transmission. DRU transmission characteristics show that, with the same transformer ratio, its transmitted active power is proportional to the AC bus voltage. Therefore, to control the distribution of active power between the MMC and DRU, the outer loop of the MMC control typically employs an active-voltage loop. However, under this control, the PCC bus voltage cannot be precisely controlled at its rated value, and to ensure the DRU power always follows its reference value, the bus voltage fluctuates significantly. To improve system reliability and reduce AC bus voltage fluctuation, constant bus voltage control has been proposed for the MMC control structure of hybrid converters. However, under this scheme, the DRU transmitted power cannot be stably controlled at 1 p.u., requiring power devices to maintain a larger margin. Furthermore, because the bus voltage is fixed, all fluctuations in wind power are borne by the MMC, resulting in significant DC voltage fluctuations in the MMC. Summary of the Invention

[0004] To address the shortcomings of existing DRU and MMC cascaded transmission schemes, such as large DC voltage fluctuations and large power device capacities in the MMC, this invention proposes a hybrid converter control method, device, computer equipment, and storage medium for offshore wind power. Simultaneously, it ensures that the MMC has the function of establishing offshore AC voltage and frequency and compensating for system reactive power. Using this invention, stable control of offshore wind power dual-terminal DRU and MMC cascaded DC systems can be achieved, reducing the difficulty of voltage insulation design for offshore wind power dual-terminal DRU and MMC cascaded DC systems, reducing power device margin requirements, and facilitating the lightweight and low-cost development of offshore wind power DC transmission systems.

[0005] The first objective of this invention is to provide a hybrid converter control method for offshore wind power, wherein the hybrid converter includes a diode rectifier unit (DRU) and a modular multilevel converter (MMC); the AC side of the DRU and the AC side of the MMC are connected in parallel at the AC bus, and the DC side of the DRU and the DC side of the MMC are connected in series; the hybrid converter control method includes the following steps:

[0006] S1. Given the initial reference value of the effective value of the AC bus voltage of the hybrid converter, the operating angular frequency ω of the hybrid converter, and the reference value of the MMC DC voltage, obtain the AC bus voltage, the effective value of the AC bus voltage of the hybrid converter, and the MMC DC voltage;

[0007] S2. Transform the AC bus voltage of the hybrid converter from the abc stationary three-phase coordinate system to the dq rotating coordinate system to obtain the d-axis and q-axis components of the AC bus voltage of the hybrid converter.

[0008] S3. Calculate the reference value of the effective value of the AC bus voltage of the hybrid converter based on the MMC DC voltage, the reference value of the MMC DC voltage, and the reference initial value of the effective value of the AC bus voltage of the hybrid converter.

[0009] S4. Calculate the reference value of the MMC modulation voltage in the dq rotating coordinate system based on the effective value of the AC bus voltage of the hybrid converter, the reference value of the effective value of the AC bus voltage of the hybrid converter, and the MMC DC voltage.

[0010] S5. Calculate the MMC modulation voltage in the three-phase stationary coordinate system based on the reference value of the MMC modulation voltage in the dq rotating coordinate system.

[0011] S6. Based on the MMC modulation voltage in the three-phase stationary coordinate system, pulse width modulation is performed on the MMC modulation voltage to obtain the trigger signals of each switching device in the MMC. The steady-state control of the hybrid converter is achieved through the trigger signals of the MMC switching devices. The modulation wave is the MMC modulation voltage in the three-phase stationary coordinate system, the carrier is a triangular carrier, and the trigger signals of each switching device in the MMC are obtained through pulse width modulation.

[0012] Further, in step S2, for ease of control, the AC bus voltage of the hybrid converter is transformed from the abc stationary three-phase coordinate system to the dq rotating coordinate system to obtain the d-axis DC component and q-axis DC component of the AC bus voltage of the hybrid converter, and the transformation matrix T 3s / 2r The expression for (ωt) is

[0013]

[0014] In the formula: ω is the operating angular frequency of the hybrid converter, and t is the operating time of the hybrid converter.

[0015] Furthermore, in step S3, the MMC DC voltage reference value U * dcm Compared with the actual value U dcm The difference is calculated, and the error is processed by the first PI controller, plus the reference initial value U of the effective value of the AC bus voltage of the hybrid converter. * v The reference value U of the effective value of the AC bus voltage of the hybrid converter is obtained. * vrms The calculation formula is

[0016]

[0017] In the formula: s is the Laplace operator, U * v K is the reference initial value for the effective value of the AC bus voltage of the hybrid converter. P1 and K I1 These are the proportional and integral parameters of the first PI controller, U. dcm and U * dcm These are the MMC DC voltage and the MMC DC voltage reference value, respectively.

[0018] Furthermore, step S4 is as follows:

[0019] S41, Set the reference value U of the effective value of the AC bus voltage of the hybrid converter. * vrms With the effective value of AC bus voltage U of the hybrid converter v The difference is calculated, and the error is processed by the second PI controller, plus half of the MMC DC voltage, E.dc / 2, to obtain the reference value U of the d-axis component of the MMC modulation voltage. * diff The calculation formula is as follows:

[0020]

[0021] In the formula: K P2 and K I2 These are the proportional and integral parameters of the second PI controller, respectively.

[0022] S42. Set the q-axis reference value of the MMC modulation voltage to zero. This is because when the phase-locked loop locks the phase of the AC grid voltage, the d-axis component of the MMC modulation voltage is equal to the amplitude of the AC voltage bus voltage, while the q-axis component of the MMC modulation voltage is equal to zero.

[0023] Further, in step S5, the d-axis reference value and q-axis reference value of the MMC modulation voltage are transformed from the dq rotating coordinate system to the abc stationary three-phase coordinate system to obtain the MMC modulation voltage in the three-phase stationary coordinate system, and the transformation matrix T is used. 2r / 3s The expression for (ωt) is

[0024]

[0025] In the formula: ω is the operating angular frequency of the hybrid converter, and t is the operating time of the hybrid converter.

[0026] A second objective of this invention is to provide a hybrid converter control device for offshore wind power, the control device comprising:

[0027] The voltage acquisition module acquires the AC bus voltage, the effective value of the AC bus voltage, and the MMC DC voltage of the hybrid converter by providing a reference initial value of the effective value of the AC bus voltage of the hybrid converter, the operating angular frequency ω of the hybrid converter, and the reference value of the MMC DC voltage.

[0028] The voltage coordinate transformation module transforms the AC bus voltage of the hybrid converter from the abc stationary three-phase coordinate system to the dq rotating coordinate system, obtaining the d-axis and q-axis components of the AC bus voltage of the hybrid converter.

[0029] The first voltage reference value calculation module calculates the reference value of the effective value of the AC bus voltage of the hybrid converter based on the MMC DC voltage, the MMC DC voltage reference value, and the reference initial value of the effective value of the AC bus voltage of the hybrid converter.

[0030] The second voltage reference value calculation module calculates the reference value of the MMC modulation voltage in the dq rotating coordinate system based on the effective value of the AC bus voltage of the hybrid converter, the reference value of the effective value of the AC bus voltage of the hybrid converter, and the MMC DC voltage.

[0031] The MMC modulation voltage calculation module calculates the MMC modulation voltage in the three-phase stationary coordinate system based on the reference value of the MMC modulation voltage in the dq rotating coordinate system.

[0032] The steady-state control module uses the MMC modulation voltage in the three-phase stationary coordinate system to perform pulse width modulation to obtain the trigger signals of each switching device in the MMC. The steady-state control of the hybrid converter is achieved through the trigger signals of the MMC switching devices.

[0033] A third objective of the present invention is to provide a computer device including a processor and a memory for storing a processor-executable program, wherein when the processor executes the program stored in the memory, it implements the above-described hybrid converter control method for offshore wind power.

[0034] A fourth objective of this invention is to provide a storage medium storing a program, characterized in that, when the program is executed by a processor, it implements the aforementioned hybrid converter control method for offshore wind power.

[0035] The present invention has the following advantages and effects compared with the prior art:

[0036] (1) This invention proposes a hybrid converter control method that minimizes the fluctuation of the MMC DC voltage when the wind power fluctuates, while ensuring that the DRU transmits most of the active power of the wind farm. By adopting the control method proposed in this invention, the difficulty of DC voltage insulation design and the margin requirements of MMC power devices in offshore wind power transmission projects are reduced on the basis of stable control of the hybrid converter, thereby reducing the investment cost of the system.

[0037] (2) The capacity selection of this invention is applicable to the field of large-scale offshore wind power being transmitted to DC via hybrid converters. Through theoretical analysis and simulation examples, the effectiveness and applicability of the control method proposed in this invention have been verified. Attached Figure Description

[0038] The accompanying drawings, which are included to provide a further understanding of the invention and form part of this application, illustrate exemplary embodiments of the invention and, together with their description, serve to explain the invention and do not constitute an undue limitation thereof. In the drawings:

[0039] Figure 1 is a topology diagram of the hybrid converter for offshore wind power disclosed in this invention.

[0040] Figure 2 is a flowchart of the hybrid converter control method for offshore wind power disclosed in this invention;

[0041] Figure 3 is a control block diagram of the hybrid converter for offshore wind power disclosed in this invention;

[0042] Figure 4 is a topology diagram of the large-scale offshore wind power dual-end DRU and MMC cascaded DC transmission system disclosed in this invention.

[0043] Figure 5 shows the steady-state simulation results of a large-scale offshore wind power dual-end DRU and MMC cascaded output system using the control method disclosed in this invention.

[0044] Figure 6 shows the effective value of AC bus voltage, AC current waveform, and active power diagrams of wind field, DRU, and MMC of the hybrid converter under wind speed variation using the control method disclosed in this invention.

[0045] Figure 7 shows the electrical quantity waveforms of the system when the wind speed changes by the same amount using the constant AC voltage control method.

[0046] Figure 8 is a waveform diagram of the system DC voltage, DRU DC voltage and MMC DC voltage under wind speed variation using the control method disclosed in this invention.

[0047] Figure 9 shows the DC voltage waveform of the system when the wind speed changes by the same amount using the constant AC voltage control method.

[0048] Figure 10 is a structural block diagram of the hybrid converter control device for offshore wind power in Embodiment 3 of the present invention.

[0049] Figure 11 is a structural block diagram of the computer device in Embodiment 4 of the present invention. Detailed Implementation

[0050] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0051] Example 1

[0052] This embodiment discloses a control method for a hybrid converter for offshore wind power, which is applied to the hybrid converter shown in Figure 1. The diode rectifier unit is referred to as DRU and the modular multilevel converter is referred to as MMC. The AC side of DRU and the AC side of MMC are connected in parallel at the AC bus, and the DC side of DRU and the DC side of MMC are connected in series.

[0053] Based on the hybrid converter disclosed above, the flowchart of a control method for a hybrid converter for offshore wind power disclosed in this embodiment is shown in Figure 2, and the control block diagram is shown in Figure 3. The MMC DC voltage reference value U * dcm Compared with the actual value U dcm The difference is calculated, and the error is processed by the first PI controller, plus the reference initial value U of the effective value of the AC bus voltage of the hybrid converter. * v This yields the reference value U of the effective value of the AC bus voltage. * rms Reference value of AC bus voltage RMS value U * rms Compared with the actual value U v The difference is calculated, and the error is processed by the second PI controller, plus the MMC DC voltage E. dc Half of this value is used to obtain the reference value U of the d-axis component of the MMC modulated voltage. * diff The q-axis reference value of the MMC modulation voltage is set to zero. The hybrid converter control method includes the following steps:

[0054] S1. Given the initial reference value of the effective value of the AC bus voltage of the hybrid converter, the operating angular frequency of the hybrid converter, and the reference value of the MMC DC voltage, obtain the AC bus voltage, the effective value of the AC bus voltage, and the MMC DC voltage of the hybrid converter;

[0055] S2. Transform the AC bus voltage of the hybrid converter from the abc stationary three-phase coordinate system to the dq rotating coordinate system, using the transformation matrix T. 3s / 2r The expression for (ωt) is

[0056]

[0057] In the formula: ω is the operating angular frequency of the hybrid converter, and t is the operating time of the hybrid converter.

[0058] S3, Reference value of the effective value of the AC bus voltage of the hybrid converter U * vrms The calculation formula is

[0059]

[0060] In the formula: s is the Laplace operator; U * v K is the reference initial value for the effective value of the AC bus voltage of the hybrid converter. P1 and K I1 These are the proportional and integral parameters of the first PI controller, respectively; U dcm and U *dcm These are the MMC DC voltage and its reference value.

[0061] S4. Based on the effective value of the AC bus voltage of the hybrid converter, the reference value of the effective value of the AC bus voltage of the hybrid converter, and the MMC DC voltage, calculate the reference value of the MMC modulation voltage in the dq rotating coordinate system. The process includes:

[0062] S41. Based on the effective value U of the AC bus voltage of the hybrid converter v Reference value U of the effective value of AC bus voltage of hybrid converter * vrms and MMC DC voltage E dc Reference value U of the d-axis component of the MMC modulated voltage * diff The calculation formula is as follows:

[0063]

[0064] In the formula: K P2 and K I2 These are the proportional and integral parameters of the second PI controller, respectively.

[0065] S42. Set the q-axis reference value of the MMC modulation voltage to zero. This is because when the phase-locked loop locks the phase of the AC grid voltage, the d-axis component of the MMC modulation voltage is equal to the amplitude of the AC voltage bus voltage, while the q-axis component of the MMC modulation voltage is equal to zero.

[0066] S5. Transform the MMC modulated voltage from the dq rotating coordinate system to the abc stationary three-phase coordinate system. The transformation matrix T is as follows: 2r / 3s The expression for (ωt) is

[0067]

[0068] In the formula: ω is the operating angular frequency of the hybrid converter, and t is the operating time of the hybrid converter.

[0069] S6. Based on the reference value of the MMC modulation voltage in the abc static three-phase coordinate system, the trigger signals of each switching device in the MMC are controlled by pulse width modulation to achieve steady-state control of the hybrid converter.

[0070] The pulse width modulation (PWM) method is referenced in the book *Principles and Applications of High Voltage Direct Current Transmission (2nd Edition)*, authored by Zhang Yongjun, Liu Ziwen, and Xiao Huangqing in 2021. The PWM consists of six arms: Arm 1, Arm 2, Arm 3, Arm 4, Arm 5, and Arm 6. Each arm comprises N sub-modules. The high-voltage terminal of the N sub-modules connected in series in each arm is the D-port. The D-ports of Arms 1, 2, and 3 are connected to the positive DC terminal, while the D-ports of Arms 4, 5, and 6 are connected to the negative DC terminal. The low-voltage terminals of the N sub-modules connected in series correspond to the S-ports of the corresponding arms. The S-ports of Arms 1 and 4 are connected to the phase a AC line; the S-ports of Arms 2 and 5 are connected to the phase b AC line; and the S-ports of Arms 3 and 6 are connected to the phase c AC line. The pulse width modulation steps for the above MMC are as follows: N triangular carriers of equal amplitude but unequal width are introduced, and the phase θ of each carrier is... i Represented as

[0071]

[0072] The MMC bridge arm modulation voltage is compared with these N carriers to obtain the number N submodules that need to be deployed in that bridge arm. on Based on the voltage ranking results of each submodule in this bridge arm and the polarity of the bridge arm current, select N in this bridge arm. on Each sub-module is activated and generates a corresponding trigger pulse.

[0073] As shown in Figure 4, a large-scale offshore wind power dual-terminal DRU and MMC cascaded DC transmission system includes: an offshore wind farm, an onshore converter, a hybrid converter, a DC submarine cable, and an AC power grid; in the figure, U v For the AC bus voltage of the hybrid converter, I v U is the AC current of the hybrid converter, P is the active power of the hybrid converter, Q is the reactive power of the hybrid converter, and U is the AC current of the hybrid converter. dc For the DC voltage of the hybrid converter, I dc This represents the DC current of the hybrid converter. The hybrid converter includes a DRU and an MMC, as shown in Figure 1.

[0074] Each wind farm uses a direct-drive wind turbine with a single unit capacity of 2MW. The wind farms are connected to the offshore converter station via two 66kV submarine cables. The wind farm's rated active power is 1000MW, and the system DC voltage level is ±320kV. The DRU uses a 12-pulse rectifier bridge with a rated DC voltage of 480kV. The offshore MMC uses a half-bridge submodule with a rated DC voltage of 160kV. The onshore MMC uses a full-bridge submodule with a rated DC voltage of 640kV. Each MMC has 320 submodules per arm. The system capacity baseline is 750MVA, the AC voltage baseline is 66kV, and the DC voltage baseline is 640kV. The active power transmitted by the DRU is set to 3 / 4 of the active power generated by the wind farm. A simulation model of a large-scale offshore wind power dual-end DRU and MMC cascaded DC transmission system with a hybrid converter is established based on PSCAD / EMTDC.

[0075] Referring to step S1 in Example 1, a reference initial value U is given as the effective value of the AC bus voltage of the hybrid converter. * v Given a 1p.u. hybrid converter operating angular frequency ω of 100π and a given MMC DC voltage reference value U. * dcm For 1p.u. Referring to step S2 in Example 1, the AC bus voltage of the hybrid converter is transformed from the abc stationary three-phase coordinate system to the dq rotating coordinate system. Referring to step S3 in Example 1, the proportional parameter K of the first PI controller... P1 and integration parameter K I1 The reference value U of the effective value of the AC bus voltage of the hybrid converter was calculated by setting the values ​​to 0.4 and 0.08 respectively. * rms The value is 0.983. Referring to step S4 in Example 1, the proportional parameter K of the second PI controller is... P2 and integration parameter K I2 The reference value U of the d-axis component of the MMC modulation voltage was calculated by setting the values ​​to 2.5 and 0.01 respectively. * diff The reference value for the q-axis component of the MMC modulation voltage is set to 0, with a value of 0.955. Referring to step S5 in Example 1, the MMC modulation voltage is transformed from the dq rotating coordinate system to the abc stationary three-phase coordinate system. Based on the MMC modulation voltage waveform, the trigger signals of each switching device in the MMC are controlled by pulse width modulation, ultimately achieving steady-state control of the hybrid converter. During steady-state operation of the hybrid converter, its AC bus voltage, AC current, DC voltage, DC current, and transmission power are shown in Figure 5. As can be seen from Figure 5, this invention can achieve stable control of a cascaded DC system of a dual-terminal DRU and an MMC for offshore wind power.

[0076] Example 2

[0077] Based on the hybrid converter control method and simulation model for offshore wind power disclosed in Embodiment 1, this embodiment will compare the effects of the control method disclosed in this invention with those of traditional control methods. Strategy 1 is the control method disclosed in this invention, and Strategy 2 is a traditional constant AC voltage amplitude control method.

[0078] The simulation control timing is as follows: it is assumed that the system has reached steady state at t = 3.5s. The initial wind speed is 12m / s, the wind speed slowly decreases to 8m / s at t = 4s, and the wind speed slowly recovers to 12m / s at t = 6s.

[0079] Figure 6 shows the RMS value of the AC bus voltage, AC current waveform, and active power diagrams of the wind farm, DRU, and MMC for the system using Strategy 1 when wind speed changes. Figure 7 shows the corresponding electrical quantity changes for the system using Strategy 2 when wind speed changes by the same amount. Figure 8 shows the DC voltage waveforms of the system, DRU DC voltage, and MMC DC voltage for Strategy 1 when wind speed changes. Figure 9 shows the corresponding three DC voltage waveforms for Strategy 2 when wind speed changes.

[0080] As shown in Figures 6 and 8, using Strategy 1, the MMC DC voltage can be precisely controlled at 1 p.u. (160 kV) when wind power changes. Therefore, the active power transmitted by the DRU is always controlled to 0.75 times the power generated by the wind farm, and the DRU bears all the fluctuations in wind power. Although the PCC bus voltage cannot be precisely controlled at the rated value, the bus voltage fluctuation is small and acceptable. During wind speed changes, the bus voltage fluctuates between 62.3 kV and 65.1 kV, with a fluctuation rate of 4.2%; the system DC voltage fluctuates between 621.6 kV and 672.0 kV, with a ripple of 7.9%; and the MMC DC voltage fluctuates between 155.3 kV and 163.0 kV, with a ripple of only 4.8%.

[0081] As shown in Figures 7 and 9, using Strategy 2, the AC bus voltage fluctuation is very small when wind power changes, and it can be precisely controlled at 66kV. However, the DRU transmission power cannot be stably controlled at its set value. The simulation shows that the DRU transmission power is too high throughout the process. Since the bus voltage is fixed, the wind power fluctuation is entirely borne by the MMC, resulting in significant MMC DC voltage fluctuation. During wind speed changes, the bus voltage fluctuates between 65.9kV and 66.3kV, with a fluctuation rate of 0.56%; the system DC voltage fluctuates between 620.2kV and 671.4kV, with a ripple of 8.0%; and the MMC DC voltage fluctuates between 129.8kV and 153.4kV, with a ripple of 14.7%. Table 1 shows the comparison results of the above electrical quantities for the DRU-MMC cascaded DC systems using Strategy 1 and Strategy 2.

[0082] Table 1. Comparison of electrical quantities of DRU-MMC cascaded DC systems using the present invention and other control methods.

[0083]

[0084] In summary, the control proposed in this embodiment can reduce MMC DC voltage fluctuations and avoid MMC overmodulation problems. It has advantages such as small device margin requirements, low difficulty in equipment insulation design, and low control difficulty.

[0085] Example 3

[0086] As shown in Figure 10, based on the control method for a hybrid converter for offshore wind power disclosed in Embodiment 1 above, this embodiment further provides a control device for a hybrid converter for offshore wind power.

[0087] The device includes a voltage acquisition module 101, a voltage coordinate transformation module 102, a first voltage reference value calculation module 103, a second voltage reference value calculation module 104, an MMC modulation voltage calculation module 105, and a steady-state control module 106. The specific functions of each module are as follows:

[0088] The voltage acquisition module 101 acquires the AC bus voltage, the effective value of the AC bus voltage, and the MMC DC voltage of the hybrid converter by giving a reference initial value of the effective value of the AC bus voltage of the hybrid converter, the operating angular frequency ω of the hybrid converter, and the reference value of the MMC DC voltage.

[0089] Voltage coordinate transformation module 102 transforms the AC bus voltage of the hybrid converter from the abc stationary three-phase coordinate system to the dq rotating coordinate system, and obtains the d-axis component and q-axis component of the AC bus voltage of the hybrid converter.

[0090] The first voltage reference value calculation module 103 calculates the reference value of the effective value of the AC bus voltage of the hybrid converter based on the MMC DC voltage, the MMC DC voltage reference value, and the reference initial value of the effective value of the AC bus voltage of the hybrid converter.

[0091] The second voltage reference value calculation module 104 calculates the reference value of the MMC modulation voltage in the dq rotating coordinate system based on the effective value of the AC bus voltage of the hybrid converter, the reference value of the effective value of the AC bus voltage of the hybrid converter, and the MMC DC voltage.

[0092] MMC modulation voltage calculation module 105 calculates the MMC modulation voltage in the three-phase stationary coordinate system based on the reference value of the MMC modulation voltage in the dq rotating coordinate system.

[0093] The steady-state control module 106 obtains the trigger signals of each switching device in the MMC by pulse width modulation of the MMC modulation voltage in the three-phase stationary coordinate system, and realizes the steady-state control of the hybrid converter through the trigger signals of the MMC switching devices.

[0094] The specific implementation of each module in this embodiment can be found in Embodiment 1 above, and will not be repeated here. It should be noted that the device provided in this embodiment is only illustrated by the division of the above functional modules. In practical applications, the above functions can be assigned to different functional modules as needed, that is, the internal structure can be divided into different functional modules to complete all or part of the functions described above.

[0095] Example 4

[0096] This embodiment provides a computer device, which can be a computer, as shown in FIG11. It includes a processor 1102, a memory, an input device 1103, a display 1104, and a network interface 1105 connected via a system bus 1101. The processor provides computing and control capabilities. The memory includes a non-volatile storage medium 1106 and internal memory 1107. The non-volatile storage medium 1106 stores an operating system, computer programs, and a database. The internal memory 1107 provides an environment for the operation of the operating system and computer programs in the non-volatile storage medium. When the processor 1102 executes the computer programs stored in the memory, it implements the control method for a hybrid converter for offshore wind power proposed in Embodiment 1 above, as follows:

[0097] S1. Given the initial reference value of the effective value of the AC bus voltage of the hybrid converter, the operating angular frequency ω of the hybrid converter, and the reference value of the MMC DC voltage, obtain the AC bus voltage, the effective value of the AC bus voltage of the hybrid converter, and the MMC DC voltage;

[0098] S2. Transform the AC bus voltage of the hybrid converter from the abc stationary three-phase coordinate system to the dq rotating coordinate system to obtain the d-axis and q-axis components of the AC bus voltage of the hybrid converter.

[0099] S3. Calculate the reference value of the effective value of the AC bus voltage of the hybrid converter based on the MMC DC voltage, the reference value of the MMC DC voltage, and the reference initial value of the effective value of the AC bus voltage of the hybrid converter.

[0100] S4. Calculate the reference value of the MMC modulation voltage in the dq rotating coordinate system based on the effective value of the AC bus voltage of the hybrid converter, the reference value of the effective value of the AC bus voltage of the hybrid converter, and the MMC DC voltage.

[0101] S5. Calculate the MMC modulation voltage in the three-phase stationary coordinate system based on the reference value of the MMC modulation voltage in the dq rotating coordinate system.

[0102] S6. Based on the MMC modulation voltage in the three-phase stationary coordinate system, pulse width modulation is performed using the MMC modulation voltage to obtain the trigger signals of each switching device in the MMC. The steady-state control of the hybrid converter is realized through the trigger signals of the MMC switching devices.

[0103] Example 5

[0104] This embodiment provides a storage medium, which is a computer-readable storage medium, storing a computer program. When the computer program is executed by a processor, it implements a control method for a hybrid converter for offshore wind power according to Embodiment 1 above, as follows:

[0105] S1. Given the initial reference value of the effective value of the AC bus voltage of the hybrid converter, the operating angular frequency ω of the hybrid converter, and the reference value of the MMC DC voltage, obtain the AC bus voltage, the effective value of the AC bus voltage of the hybrid converter, and the MMC DC voltage;

[0106] S2. Transform the AC bus voltage of the hybrid converter from the abc stationary three-phase coordinate system to the dq rotating coordinate system to obtain the d-axis and q-axis components of the AC bus voltage of the hybrid converter.

[0107] S3. Calculate the reference value of the effective value of the AC bus voltage of the hybrid converter based on the MMC DC voltage, the reference value of the MMC DC voltage, and the reference initial value of the effective value of the AC bus voltage of the hybrid converter.

[0108] S4. Calculate the reference value of the MMC modulation voltage in the dq rotating coordinate system based on the effective value of the AC bus voltage of the hybrid converter, the reference value of the effective value of the AC bus voltage of the hybrid converter, and the MMC DC voltage.

[0109] S5. Calculate the MMC modulation voltage in the three-phase stationary coordinate system based on the reference value of the MMC modulation voltage in the dq rotating coordinate system.

[0110] S6. Based on the MMC modulation voltage in the three-phase stationary coordinate system, pulse width modulation is performed using the MMC modulation voltage to obtain the trigger signals of each switching device in the MMC. The steady-state control of the hybrid converter is realized through the trigger signals of the MMC switching devices.

[0111] The storage medium described in this embodiment can be a disk, optical disk, computer memory, random access memory (RAM), USB flash drive, portable hard drive, etc.

[0112] The above embodiments are preferred embodiments of the present invention, but the embodiments of the present invention are not limited to the above embodiments. Any changes, modifications, substitutions, combinations, or simplifications made without departing from the spirit and principle of the present invention shall be considered equivalent substitutions and shall be included within the protection scope of the present invention.

Claims

1. A hybrid converter control method for offshore wind power, wherein the hybrid converter includes a diode rectifier unit and a modular multilevel converter (MMC), the diode rectifier unit is abbreviated as DRU and the modular multilevel converter is abbreviated as MMC, the AC side of the DRU and the AC side of the MMC are connected in parallel at the AC bus, and the DC side of the DRU and the DC side of the MMC are connected in series, characterized in that, The hybrid converter control method includes the following steps: S1. Given the initial reference value of the effective value of the AC bus voltage of the hybrid converter, the operating angular frequency ω of the hybrid converter, and the reference value of the MMC DC voltage, obtain the AC bus voltage, the effective value of the AC bus voltage of the hybrid converter, and the MMC DC voltage; S2. Transform the AC bus voltage of the hybrid converter from the abc stationary three-phase coordinate system to the dq rotating coordinate system to obtain the d-axis and q-axis components of the AC bus voltage of the hybrid converter. S3. Based on the MMC DC voltage, the MMC DC voltage reference value, and the initial reference value of the effective value of the hybrid converter AC bus voltage, calculate the reference value of the effective value of the hybrid converter AC bus voltage; where the reference value U of the effective value of the hybrid converter AC bus voltage is... * vrms The calculation formula is In the formula: s is the Laplace operator, U * v K is the reference initial value for the effective value of the AC bus voltage of the hybrid converter. P1 and K I1 These are the proportional and integral parameters of the first PI controller, U. dcm and U * dcm These are the MMC DC voltage and the MMC DC voltage reference value, respectively. S4. Based on the effective value of the AC bus voltage of the hybrid converter, the reference value of the effective value of the AC bus voltage of the hybrid converter, and the MMC DC voltage, calculate the reference value of the MMC modulation voltage in the dq rotating coordinate system; the process of step S4 is as follows: S41. Based on the effective value U of the AC bus voltage of the hybrid converter v Reference value U of the effective value of AC bus voltage of hybrid converter * vrms and MMC DC voltage E dc Reference value U of the d-axis component of the MMC modulated voltage * diff The calculation formula is as follows: In the formula: K P2 and K I2 These are the proportional and integral parameters of the second PI controller, respectively. S42. Set the q-axis reference value of the MMC modulation voltage to zero; S5. Calculate the MMC modulation voltage in the three-phase stationary coordinate system based on the reference value of the MMC modulation voltage in the dq rotating coordinate system. S6. Based on the MMC modulation voltage in the three-phase stationary coordinate system, pulse width modulation is performed using the MMC modulation voltage to obtain the trigger signals of each switching device in the MMC. The steady-state control of the hybrid converter is realized through the trigger signals of the MMC switching devices.

2. The hybrid converter control method for offshore wind power according to claim 1, characterized in that, In step S2, the AC bus voltage of the hybrid converter is transformed from the abc stationary three-phase coordinate system to the dq rotating coordinate system, and the transformation matrix T is used. 3s / 2r The expression for (ωt) is In the formula: ω is the operating angular frequency of the hybrid converter, and t is the operating time of the hybrid converter.

3. The hybrid converter control method for offshore wind power according to claim 1, characterized in that, In step S5, the AC bus voltage of the hybrid converter is transformed from the dq rotating coordinate system to the abc stationary three-phase coordinate system, and the transformation matrix T is used. 2r / 3s The expression for (ωt) is In the formula: ω is the operating angular frequency of the hybrid converter, and t is the operating time of the hybrid converter.

4. A control device for a hybrid converter control method for offshore wind power according to any one of claims 1 to 3, characterized in that, The control device includes: The voltage acquisition module acquires the AC bus voltage, the effective value of the AC bus voltage, and the MMC DC voltage of the hybrid converter by providing a reference initial value of the effective value of the AC bus voltage of the hybrid converter, the operating angular frequency ω of the hybrid converter, and the reference value of the MMC DC voltage. The voltage coordinate transformation module transforms the AC bus voltage of the hybrid converter from the abc stationary three-phase coordinate system to the dq rotating coordinate system, obtaining the d-axis and q-axis components of the AC bus voltage of the hybrid converter. The first voltage reference value calculation module calculates the reference value of the effective value of the AC bus voltage of the hybrid converter based on the MMC DC voltage, the MMC DC voltage reference value, and the reference initial value of the effective value of the AC bus voltage of the hybrid converter. The second voltage reference value calculation module calculates the reference value of the MMC modulation voltage in the dq rotating coordinate system based on the effective value of the AC bus voltage of the hybrid converter, the reference value of the effective value of the AC bus voltage of the hybrid converter, and the MMC DC voltage. The MMC modulation voltage calculation module calculates the MMC modulation voltage in the three-phase stationary coordinate system based on the reference value of the MMC modulation voltage in the dq rotating coordinate system. The steady-state control module uses the MMC modulation voltage in the three-phase stationary coordinate system to perform pulse width modulation to obtain the trigger signals of each switching device in the MMC. The steady-state control of the hybrid converter is achieved through the trigger signals of the MMC switching devices.

5. A computer device, comprising a processor and a memory for storing a processor-executable program, characterized in that, When the processor executes the program stored in the memory, it implements the hybrid converter control method for offshore wind power as described in any one of claims 1-3.

6. A storage medium storing a program, characterized in that, When the program is executed by the processor, it implements the hybrid converter control method for offshore wind power as described in any one of claims 1-3.

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