New energy power generation system and converter control method therefor, and converter controller

Abstract

NOT VISIBLE DUE TO STATUS OF PATENT

Description

New energy power generation system and converter control method and converter controller thereof

[0001] This application claims priority to Chinese patent application number 202311750213.1, filed on December 18, 2023, entitled “Reactive power generation system and converter control method and converter controller”, and Chinese patent application number 202311749953.3, filed on December 18, 2023, entitled “New energy power generation system and converter control method and converter controller”, the disclosures of which are incorporated herein by reference. Technical Field

[0002] The present disclosure generally relates to the field of renewable energy power generation technology, and more specifically, to a renewable energy power generation system and a converter control method and a converter controller thereof. Background Art

[0003] For a new power system dominated by renewable energy, increasing the proportion of renewable energy and the grid's absorption capacity, while ensuring safe and stable grid operation, are priorities for technological research and development. While the renewable energy industry, represented by wind power, has maintained rapid growth in recent years, the wind power industry still faces numerous technical challenges that need to be addressed and improved, starting with grid connection stability.

[0004] Currently, wind farms around the world operate using a "centralized dispatch, decentralized control" approach. Centralized dispatch means that power is uniformly distributed among the wind turbines (hereinafter referred to as wind turbines) within the site by a higher-level centralized control center. Decentralized control involves each wind turbine using an independent control unit for data collection and grid connection / disconnection control. Each wind turbine is a separate entity. Under special operating conditions such as low voltage ride-through and high voltage ride-through, wind turbines can interfere with each other, resulting in a weak combined power effect and limited fault ride-through capability. This poses a risk of grid disconnection, especially in weak grid conditions.

[0005] Summary of the Invention

[0006] An exemplary embodiment of the present disclosure provides a new energy power generation system and a converter control method and a converter controller thereof, which can effectively solve the stability problem of grid-connected operation of the new energy power generation system.

[0007] According to a first aspect of an embodiment of the present disclosure, a converter control method for a new energy power generation system is provided, the converter control method comprising: acquiring the three-phase voltage value of the station grid-connected point in real time and inputting it into a phase-locked loop to obtain a phase-locked angle, and determining a first reference phase angle based on the phase-locked angle; based on the first reference phase angle, performing coordinate transformation on the grid-side inductor current value of the converter to obtain dq-axis positive and negative sequence inductor current value, and performing coordinate transformation on the grid-side three-phase voltage value of the converter to obtain dq-axis positive and negative sequence grid-side voltage value; based on the dq-axis positive and negative sequence inductor current value and the dq-axis positive and negative sequence grid-side voltage value, determining the dq-axis grid-side voltage reference value; based on the dq-axis grid-side voltage reference value and the first reference phase angle, generating a PWM signal for controlling the grid-side three-phase power module of the converter.

[0008] According to a second aspect of an embodiment of the present disclosure, a computer-readable storage medium storing a computer program is provided. When the computer program is executed by a processor, it prompts the processor to execute the converter control method of the new energy power generation system as described above.

[0009] According to a third aspect of an embodiment of the present disclosure, a converter controller for a new energy power generation system is provided, the converter controller comprising: a processor; and a memory storing a computer program, wherein when the computer program is executed by the processor, the processor is prompted to execute the converter control method for the new energy power generation system as described above.

[0010] According to a fourth aspect of an embodiment of the present disclosure, a new energy power generation system is provided, which includes a converter and the converter controller as described above.

[0011] According to the exemplary embodiment of the present disclosure, the new energy power generation system and its converter control method and converter controller are introduced into the converter grid-side control of the new energy power generation system by the transformer substation grid-connected point voltage. The flexible grid-connected characteristics of the converter are utilized to coordinate and intensively control the decentralized new energy power generation system, so that the new energy power generation system group (for example, a wind turbine group) has the dynamic properties of synchronous control, synchronous response, and synchronous execution, so as to maximize the group effect and combined force of the new energy power generation system, thereby improving the fault ride-through capability and grid-connected stability of the new energy power generation system. In addition, a reactive closed-loop control algorithm based on the voltage orientation of the station grid-connected point is proposed. The voltage phase-locked angle of the station grid-connected point directly participates in the synchronous control of the converter current inner loop of each new energy power generation system, so that the reactive output direction of the new energy power generation system in the same new energy station is consistent, maximizing the group effect and combined force of the new energy power generation system, thereby realizing reactive synchronous control of the new energy station.

[0012] In the following description, some aspects and / or advantages of the general inventive concept of the present disclosure will be set forth, and some aspects and / or advantages will be known through the following description or implementation of the general inventive concept of the present disclosure. BRIEF DESCRIPTION OF THE DRAWINGS

[0013] These and / or other aspects and advantages of the present application will become more clear and easier to understand from the following detailed description of the embodiments of the present application in conjunction with the accompanying drawings, in which:

[0014] FIG1 shows a flow chart of a converter control method for a new energy power generation system according to an exemplary embodiment of the present disclosure;

[0015] FIG2 shows a schematic diagram of a topological structure of a wind turbine converter according to an exemplary embodiment of the present disclosure;

[0016] FIG3 shows a timing diagram of a station grid connection point and a local control of a converter according to an exemplary embodiment of the present disclosure;

[0017] FIG4 shows a schematic diagram of a phase-locked loop design and coordinate transformation of voltage and current according to an exemplary embodiment of the present disclosure;

[0018] 5 is a flowchart illustrating a method for determining a dq axis grid-side voltage reference value based on dq axis positive and negative sequence inductor current values ​​and dq axis positive and negative sequence grid-side voltage values ​​according to an exemplary embodiment of the present disclosure;

[0019] FIG6 shows a flow chart of a method for determining a dq axis grid side voltage reference value according to an exemplary embodiment of the present disclosure;

[0020] FIG7 shows a schematic diagram of a voltage outer loop according to an exemplary embodiment of the present disclosure;

[0021] FIG8 shows a schematic diagram of a reactive closed loop according to an exemplary embodiment of the present disclosure;

[0022] FIG9 shows a schematic diagram of a current inner loop according to an exemplary embodiment of the present disclosure;

[0023] FIG10 shows a low voltage ride through simulation waveform according to an exemplary embodiment of the present disclosure;

[0024] FIG11 shows a flow chart of a converter control method for a new energy power generation system according to another exemplary embodiment of the present disclosure;

[0025] FIG12 shows a flow chart of a method for determining a reactive closed-loop feedback amount according to an exemplary embodiment of the present disclosure;

[0026] FIG13 shows a flow chart of a method for determining a q-axis grid-side voltage reference value according to an exemplary embodiment of the present disclosure;

[0027] FIG14 shows a flow chart of a converter control method for a new energy power generation system according to another exemplary embodiment of the present disclosure;

[0028] FIG15 shows a schematic diagram of reactive power control of a station according to an exemplary embodiment of the present disclosure;

[0029] FIG16 shows a schematic diagram of a current inner loop according to another exemplary embodiment of the present disclosure. DETAILED DESCRIPTION

[0030] Reference will now be made in detail to the embodiments of the present disclosure, examples of which are illustrated in the accompanying drawings, wherein like reference numerals refer to like parts throughout. The embodiments are described below with reference to the drawings in order to explain the present disclosure.

[0031] It should be noted that the terms "first," "second," and the like in the specification and claims of the present disclosure and the above-mentioned drawings are used to distinguish similar objects and are not necessarily used to describe a specific order or precedence. It should be understood that the numbers used in this manner are interchangeable where appropriate so that the embodiments of the present disclosure described herein can be implemented in an order other than those illustrated or described herein. The embodiments described in the following exemplary embodiments do not represent all embodiments consistent with the present disclosure. Instead, they are merely examples of apparatus and methods consistent with certain aspects of the present disclosure as detailed in the appended claims.

[0032] It should be noted that the phrase "at least one of the items" in this disclosure includes three types of parallel situations: "any one of the items", "a combination of any multiple items of the items", and "all of the items". For example, "including at least one of A and B" includes the following three parallel situations: (1) including A; (2) including B; (3) including A and B. For another example, "performing at least one of step 1 and step 2" includes the following three parallel situations: (1) performing step 1; (2) performing step 2; and (3) performing steps 1 and 2.

[0033] FIG1 shows a flow chart of a converter control method of a new energy power generation system according to an exemplary embodiment of the present disclosure.

[0034] As an example, the types of renewable energy power generation systems may include, but are not limited to, wind turbines and / or photovoltaic power generation systems. It should be understood that the types of renewable energy power generation systems may also be other types, and this disclosure does not limit this. In other words, the application scenarios of the converter control method for renewable energy power generation systems according to the exemplary embodiments of this disclosure are not limited to wind farms and can also be applied to other types of renewable energy stations.

[0035] Taking a wind turbine generator system as a renewable energy power generation system and a back-to-back dual PWM converter as an example, the topology of the wind turbine converter can be shown in Figure 2. The wind turbine converter can include a grid-side inverter and a machine-side rectifier. The DC side of the grid-side inverter is connected to the generator of the wind turbine generator via the machine-side rectifier. The AC side of the grid-side inverter is connected to the low-voltage side of the transformer via a filter (i.e., the grid-side filter). The high-voltage side of the transformer is connected to the PCC point of the substation (i.e., the common connection point after all the converter equipment in the station is connected). For example, the grid-side filter can be an LC filter or an LCL filter.

[0036] As an example, the converter control method of the new energy power generation system according to the exemplary embodiment of the present disclosure may be executed by a controller of the converter of the new energy power generation system (ie, a converter controller).

[0037] 1 , in step S101 , the three-phase voltage value of the station grid connection point is obtained in real time and input into a phase-locked loop to obtain a phase-locked angle, and a first reference phase angle is determined based on the phase-locked angle.

[0038] As an example, the most recently acquired three-phase voltage value of the station grid connection point may be input into a phase-locked loop (PLL) to obtain a phase-locked angle, and the first reference phase angle may be determined based on the phase-locked angle.

[0039] The station grid connection point transmits the real-time collected data (including but not limited to the three-phase voltage value at the station grid connection point) via a high-speed communication bus to each renewable energy power generation system within the renewable energy station that is connected to the power grid via the station grid connection point. Accordingly, the step of obtaining the three-phase voltage value at the station grid connection point in real time may include: receiving the three-phase voltage value at the station grid connection point in real time.

[0040] As an example, the data collection moments (ie, sampling points) of the converter and the station grid connection point are the same. In other words, the converter and the station grid connection point are sampled synchronously.

[0041] As shown in Figure 3, as an example, the data synchronization acquisition period of the converter and the station grid connection point is consistent with the converter control period T s (ie, the execution period of the converter control method) is the same length, and the length of the switching period T of the grid-side three-phase power module is the control period T s Twice the length of dThis represents the communication delay from the substation PCC to the converter controller (i.e., the transmission delay of the three-phase voltage value at the station grid connection point from the station grid connection point to the converter controller). Specifically, it is the time difference between the time when the three-phase voltage value at the station grid connection point is received locally and the time when the three-phase voltage value at the station grid connection point is collected. It should be understood that the data synchronization collection period is not limited to the same length as the control period, and the transmission delay is not limited to less than the control period. For example, a transmission delay of less than 1ms is sufficient.

[0042] Taking into account the transmission delay of the three-phase voltage value at the station grid connection point and the phase angle difference of the transformer through which the converter is connected to the station grid connection point, the phase-locked angle can be compensated to obtain a more accurate first reference phase angle. As an example, the first reference phase angle can be obtained by compensating the phase-locked angle based on the transmission delay of the three-phase voltage value at the station grid connection point and the phase difference between the high-voltage and low-voltage sides of the transformer.

[0043] As an example, the sum of the phase-locking angle, the first compensation angle used to compensate for the phase difference between the high and low voltage sides of the transformer, and the second compensation angle used to compensate for the transmission delay of the three-phase voltage value at the station grid connection point can be used as the first reference phase angle.

[0044] For example, the first reference phase angle θ can be calculated by the following formula: pcc :

[0045] θ pcc =θ0+δ θ0 +δ θ1

[0046] Where θ0 represents the phase-locking angle, δ θ0 represents the first compensation angle, δ θ1 Indicates the second compensation angle.

[0047] As an example, the first compensation angle can be determined based on a phase difference between the high-voltage and low-voltage sides of a transformer. For example, the phase difference between the high-voltage and low-voltage sides of a transformer may be related to the transformer model, the connection relationship between the high-voltage and low-voltage sides of the transformer, and the like. For example, the phase difference between the high-voltage and low-voltage sides of a transformer may be 30°.

[0048] As an example, the second compensation angle may be determined based on the transmission delay of the three-phase voltage value at the station grid connection point. For example, the transmission delay may be related to the length of the communication line and the communication rate.

[0049] In step S102, based on the first reference phase angle, coordinate transformation is performed on the grid-side inductor current value of the converter to obtain dq-axis positive and negative sequence inductor current values, and coordinate transformation is performed on the grid-side three-phase voltage value of the converter to obtain dq-axis positive and negative sequence grid-side voltage values.

[0050] The grid-side inductor current value is the current value flowing through the filter inductor in the grid-side filter.

[0051] The phase-locked loop and coordinate transformation design is shown in FIG4. Combined with FIG3, when performing coordinate transformation on the data collected in the current data synchronization acquisition period (including but not limited to the grid-side inductor current value and the grid-side three-phase voltage value), due to communication delay, the three-phase voltage value of the station grid connection point collected in the current data synchronization acquisition period has not been received, so the first reference phase angle θ used is pcc It is based on the three-phase voltage value u of the station grid connection point collected in the previous data synchronization collection cycle (that is, the most recently received) a 、u b 、u c The phase angle is obtained by compensating the phase-locked angle.

[0052] As an example, step S102 may include: based on the first reference phase angle, performing a calculation on the grid-side inductor current value i of the converter acquired the most recently. la 、i lb 、i lc Perform coordinate transformation to obtain the dq axis positive and negative sequence inductor current values (i.e., the d-axis positive sequence component, q-axis positive sequence component, d-axis negative sequence component, and q-axis negative sequence component of the grid-side inductor current value); the most recently collected grid-side three-phase voltage value v of the converter a 、v b 、v c Perform coordinate transformation to obtain the dq axis positive and negative sequence grid side voltage values (That is, the d-axis positive-sequence component, q-axis positive-sequence component, d-axis negative-sequence component, and q-axis negative-sequence component of the three-phase voltage value on the grid side).

[0053] In step S103 , a dq axis grid-side voltage reference value is determined based on the dq axis positive and negative sequence inductor current values ​​and the dq axis positive and negative sequence grid-side voltage values.

[0054] It should be understood that other appropriate methods can be used to determine the dq axis grid side voltage reference value, and the present disclosure does not limit this. The following will describe step S103 in conjunction with specific exemplary embodiments, which will not be expanded here.

[0055] In step S104 , a PWM signal for controlling a grid-side three-phase power module of the converter is generated based on the dq-axis grid-side voltage reference value and the first reference phase angle.

[0056] It should be understood that the first reference phase angle is used to perform coordinate transformation in the process of generating the PWM signal.

[0057] As an example, the grid-side inverter of the converter may include multiple three-phase power modules with the same structure (i.e., grid-side three-phase power modules). The three-phase power module may also be referred to as a three-level bridge arm, a three-level topology, an IGBT module, etc. As an example, each three-phase power module may include multiple switching transistors (IGBTs) and diodes connected in anti-parallel thereto.

[0058] As an example, the PWM pulse signal calculation method is not limited to SVPWM.

[0059] According to an exemplary embodiment of the present disclosure, the voltage at the grid-connected point of the station is integrated into the synchronization algorithm for controlling the converter of the renewable energy power generation system group. Based on the high-speed synchronous control system, the grid-side control action rhythm of the converter of the renewable energy power generation system group is consistent, so that the output direction of the renewable energy power generation systems in the same renewable energy station is consistent, thereby improving the fault ride-through capability and operation stability of the renewable energy power generation system under the power grid.

[0060] 5 shows a flowchart of a method for determining a dq-axis grid-side voltage reference value based on dq-axis positive and negative sequence inductor current values ​​and dq-axis positive and negative sequence grid-side voltage values ​​according to an exemplary embodiment of the present disclosure.

[0061] 5 , in step S201 , a d-axis inductor current reference value is determined based on a DC voltage target setting value of the converter and the most recently acquired DC voltage value and q-axis positive-sequence grid-side voltage value.

[0062] As an example, the difference between the DC voltage target setting value of the converter and the most recently collected DC voltage value can be input into the fourth PI controller, and then the d-axis inductor current reference value is determined based on the output value of the fourth PI controller, the q-axis positive-sequence grid-side voltage value, the grid voltage angular frequency, and the grid-side filter capacitance value of the converter.

[0063] As an example, the d-axis inductor current reference value can be obtained by the method shown in Figure 7, Indicates the DC voltage target setting value, V dc Indicates the most recently collected DC voltage value (i.e., DC voltage measurement value). The control deviation is adjusted by the fourth PI controller, plus the feedforward amount Get the d-axis inductor current reference value I d_ref , where ω represents the grid voltage angular frequency (for example, 2π*50 Hz), and C represents the capacitance value of the filter capacitor in the grid-side filter (that is, the grid-side filter capacitance value).

[0064] In step S202, a q-axis inductor current reference value is determined based on a target setting value of the grid-side line voltage effective value of the converter, the most recently acquired grid-side line voltage effective value, the most recently acquired converter reactive power value, and the d-axis positive-sequence grid-side voltage value.

[0065] As an example, the difference between the target setting value of the effective value of the grid-side line voltage of the converter and the effective value of the grid-side line voltage collected most recently can be input into the second PI controller, and then the q-axis inductor current reference value is determined based on the output value of the second PI controller, the reactive value of the converter collected most recently, the d-axis positive sequence grid-side voltage value, the grid voltage angular frequency, and the grid-side filter capacitance value of the converter.

[0066] As an example, the q-axis inductor current reference value can be obtained as shown in Figure 8, Indicates the target setting value of the grid-side line voltage effective value, V rms Indicates the most recently collected effective value of the grid-side line voltage (i.e., the effective value of the grid-side line voltage measured and calculated). The control deviation is adjusted by the second PI controller to obtain the reactive reference value Q cmd ', Q represents the most recently acquired reactive value of the converter (i.e., reactive measurement value), and then through PI reactive closed loop and feedforward control, the q-axis inductor current reference value I is obtained. q_ref , where k represents the inertia coefficient.

[0067] In step S203 , a dq axis grid-side voltage reference value is determined based on the d-axis inductor current reference value, the q-axis inductor current reference value, the dq axis positive and negative sequence inductor current values, and the dq axis positive and negative sequence grid-side voltage values.

[0068] It should be understood that the dq-axis grid-side voltage reference value can be determined using an appropriate method based on the d-axis inductor current reference value, the q-axis inductor current reference value, the dq-axis positive-sequence and negative-sequence inductor current values, and the dq-axis positive-sequence and negative-sequence grid-side voltage values, and this disclosure is not limited thereto. An exemplary embodiment of step S203 will be described below in conjunction with FIG6 and will not be expanded upon here.

[0069] FIG6 shows a flowchart of a method for determining a dq axis grid-side voltage reference value according to an exemplary embodiment of the present disclosure.

[0070] 6 , in step S301 , a d-axis positive-sequence grid-side voltage reference value is determined based on the d-axis inductor current reference value, the dq-axis positive-sequence inductor current value, and the d-axis positive-sequence grid-side voltage value.

[0071] As an example, the difference between the d-axis inductor current reference value and the d-axis positive-sequence inductor current value can be input into the fifth PI controller, and then the d-axis positive-sequence grid-side voltage reference value is determined based on the output value of the fifth PI controller, the q-axis positive-sequence inductor current value, the d-axis positive-sequence grid-side voltage value, the grid-side filter inductance value, and the grid voltage angular frequency.

[0072] In step S302 , a q-axis positive-sequence grid-side voltage reference value is determined based on the q-axis inductor current reference value, the dq-axis positive-sequence inductor current value, and the q-axis positive-sequence grid-side voltage value.

[0073] As an example, the difference between the q-axis inductor current reference value and the q-axis positive-sequence inductor current value can be input into the sixth PI controller, and then the q-axis positive-sequence grid-side voltage reference value is determined based on the output value of the sixth PI controller, the d-axis positive-sequence inductor current value, the q-axis positive-sequence grid-side voltage value, the grid-side filter inductance value, and the grid voltage angular frequency.

[0074] In step S303 , a d-axis negative-sequence grid-side voltage reference value is determined based on the dq-axis negative-sequence inductor current value and the d-axis negative-sequence grid-side voltage value.

[0075] As an example, the difference between 0 and the d-axis negative-sequence inductor current value can be input into the seventh PI controller, and then the d-axis negative-sequence grid-side voltage reference value is determined based on the output value of the seventh PI controller, the q-axis negative-sequence inductor current value, the d-axis negative-sequence grid-side voltage value, the grid-side filter inductance value, and the grid voltage angular frequency.

[0076] In step S304 , a q-axis negative-sequence grid-side voltage reference value is determined based on the dq-axis negative-sequence inductor current value and the q-axis negative-sequence grid-side voltage value.

[0077] As an example, the difference between 0 and the q-axis negative-sequence inductor current value can be input into the eighth PI controller, and then the q-axis negative-sequence grid-side voltage reference value is determined based on the output value of the eighth PI controller, the d-axis negative-sequence inductor current value, the q-axis negative-sequence grid-side voltage value, the grid-side filter inductance value, and the grid voltage angular frequency.

[0078] In step S305 , a dq-axis grid-side voltage reference value is determined based on the d-axis positive- and negative-sequence grid-side voltage reference value and the q-axis positive- and negative-sequence grid-side voltage reference value.

[0079] As an example, the sum of the d-axis positive and negative sequence grid side voltage reference values ​​can be used as the d-axis grid side voltage reference value V d_ref .

[0080] As an example, the sum of the q-axis positive and negative sequence grid-side voltage reference values ​​can be used as the q-axis grid-side voltage reference value V q_ref .

[0081] As shown in Figure 9, the current inner loop design adopts separate control of positive and negative sequences. L represents the inductance value of the filter inductor in the grid-side filter (that is, the grid-side filter inductance value). For the positive sequence design, the dq axis reference value of the positive sequence grid-side voltage is obtained through PI closed loop and feedforward control. and In the negative sequence design, the target current value of the current loop dq axis is set to 0, and the negative sequence grid side voltage dq axis reference value is obtained through PI closed loop and feedforward control. and After summing with the positive sequence calculated value, the pulse is output through the SVPWM mode.

[0082] It should be understood that the voltage outer loop design, reactive power loop design, and current inner loop design in the above embodiments may also adopt other design forms.

[0083] According to an exemplary embodiment of the present disclosure, a station-level synchronization control method is proposed for the grid-connected side of the converter. The PCC point voltage phase-locked angle directly participates in the synchronization control of the inner and outer loops of the converters of each new energy power generation system, so that the new energy power generation system group has the effect of synchronization control.

[0084] According to the exemplary embodiments of the present disclosure, it is possible to solve the stability problem of the grid-connected operation of the new energy power generation system when the proportion of the new energy grid is high and the grid is weak, thereby effectively increasing the proportion of the new energy grid.

[0085] According to the converter control method of the new energy power generation system of the exemplary embodiment of the present disclosure, the power grid to which the new energy power generation system is connected via the station grid connection point may include a weak power grid characterized by a system short circuit capacity ratio (SCR) within a predetermined range.

[0086] According to the converter control method of the new energy power generation system of the exemplary embodiment of the present disclosure, the new energy power generation system group has the dynamic properties of synchronous control, synchronous response, and synchronous execution. Figure 10 shows a set of PSCAD (Power Systems Computer Aided Design, electromagnetic transient simulation software) simulation data of low voltage ride-through capability, where the SCR (Short Circuit Ratio, system short-circuit capacity ratio) indicator is the minimum boundary value of SCR under the premise that low voltage ride-through can be passed. The simulation data shows that the converter control method of the new energy power generation system according to the exemplary embodiment of the present disclosure can adapt to lower SCR, and the fault ride-through capability is significantly enhanced compared with the conventional control method.

[0087] Under the same grid conditions, PSCAD and RTDS (Real Time Data Simulator) simulation data show that the converter control method of the new energy power generation system according to the exemplary embodiment of the present disclosure is expected to increase the proportion of new energy by more than 15% while ensuring the stable operation of the grid.

[0088] Furthermore, as the capacity of renewable energy grids continues to increase, problems such as unstable grid voltage and increased line losses caused by renewable energy integration are becoming increasingly prominent. Power quality has a significant impact on grid stability, the safe operation of power equipment, and industrial and agricultural production. Renewable energy generation is characterized by randomness (instability) and uncontrollability, and its output fluctuates significantly over short periods. These fluctuations in renewable energy power generation can cause fluctuations in grid voltage and frequency, and even lead to grid instability. Therefore, reactive power compensation for renewable energy is extremely important for improving grid-connected power quality, reducing grid losses, and enhancing grid operational stability and safety. For example, at present, the mainstream reactive power control of wind power systems is based on the AVC (Automatic Voltage Control) system. On the one hand, it utilizes the reactive capacity and regulation capability of wind turbines. If the voltage regulation needs of the power grid system cannot be met, it is necessary to install reactive power compensation devices, such as SVG (Static Var Generator). However, this method has two shortcomings: first, the adjustment step of the AVC system is large, mostly in minutes or seconds, which makes it difficult to meet the randomness of wind turbines and the rapid fluctuations in voltage at the site grid connection point caused by power changes; on the other hand, the output changes of wind turbines in the same wind farm are not synchronized, the reactive capacity and regulation capability of the wind turbines themselves are not fully utilized, and they are highly dependent on additional reactive power compensation devices, resulting in high reactive power compensation costs.

[0089] Therefore, an exemplary embodiment of the present disclosure also provides a converter control method for a new energy power generation system, which can effectively solve the problem of reactive power regulation asynchrony caused by output changes of the new energy power generation system within the same new energy station.

[0090] Figure 11 shows a flow chart of a converter control method for a new energy power generation system according to an exemplary embodiment of the present disclosure. Figure 11 shows a converter control method in a station reactive power synchronization control mode.

[0091] As shown in FIG. 11 , step S103 in FIG. 1 may specifically include step S1031 and step S1032 .

[0092] 11 , in step S101 , the three-phase voltage value of the station grid connection point is obtained in real time and input into a phase-locked loop to obtain a phase-locked angle, and a first reference phase angle is determined based on the phase-locked angle.

[0093] In step S102, based on the first reference phase angle, coordinate transformation is performed on the grid-side inductor current value of the converter to obtain dq-axis positive and negative sequence inductor current values, and coordinate transformation is performed on the grid-side three-phase voltage value of the converter to obtain dq-axis positive and negative sequence grid-side voltage values.

[0094] In step S1031, a q-axis inductor current reference value is determined based on the reactive power command value issued by the new energy station controller and the reactive closed-loop feedback value of the converter.

[0095] As an example, the converter control method of the new energy power generation system according to the exemplary embodiment of the present disclosure may further include: determining a reactive closed-loop feedback quantity Q for characterizing the equivalent reactive value injected by the converter into the station grid point based on the three-phase voltage value of the station grid point, the three-phase current value of the grid side of the converter, and the first reference phase angle. pcc This reactive power quantity uses the equivalent reactive value injected into the PCC node, which has a certain compensation effect on the loss of the power supply transformer and transmission line, and can improve the power supply efficiency.

[0096] According to an exemplary embodiment of the present disclosure, a calculation method for adaptive compensation of reactive loss of output impedance of a new energy power generation system is proposed, that is, the equivalent reactive power Q injected into the PCC node pcc Calculation method.

[0097] An exemplary embodiment of a method for determining a reactive closed-loop feedback amount will be described below in conjunction with FIG. 12 , which will not be expanded here.

[0098] As an example, the total reactive power demand of the new energy station can be determined based on the target set value of the line voltage effective value of the station grid connection point and the measured and calculated value of the line voltage effective value of the station grid connection point. Then, the total reactive power demand is allocated, and the reactive power command value of each new energy power generation system in the new energy station is determined and issued. Indicates the target setting value of the effective value of the PCC line voltage, U rms It represents the measured and calculated value of the effective value of the line voltage at the PCC point. LPF represents the low-pass filter. The control deviation is adjusted by the PI controller to obtain the reactive reference set value Q ref , that is, the total reactive power demand of the new energy station, then the hierarchical principle allocation mechanism can be adopted to issue the corresponding reactive power instruction Q cmd As an example, the allocation mechanism may include but is not limited to an equal power factor allocation mechanism. It should be understood that other appropriate allocation mechanisms may also be used, and the present disclosure does not limit this.

[0099] As an example, the reactive power command value Q cmd and reactive closed-loop feedback Q pcc The difference between the two is input into the first PI controller; then, based on the d-axis positive sequence grid side voltage value The output value of the first PI controller, the grid voltage angular frequency and the grid-side filter capacitor value of the converter are used to determine the q-axis inductor current reference value I q_ref .

[0100] As an example, the q-axis inductor current reference value I can be obtained by the method shown in FIG15. q_ref , where ω represents the grid voltage angular frequency (for example, 2π*50 Hz), C represents the capacitance value of the filter capacitor in the grid-side filter (that is, the grid-side filter capacitance value), and k represents the inertia coefficient.

[0101] In step S1032 , a q-axis grid-side voltage reference value is determined based on the dq-axis positive-sequence inductor current values, the q-axis positive-sequence grid-side voltage values, and the q-axis inductor current reference value.

[0102] It should be understood that the q-axis grid-side voltage reference value may be determined in an appropriate manner, and the present disclosure does not limit this. An exemplary embodiment of step S1032 will be described below in conjunction with FIG13 , which will not be expanded here.

[0103] In step S104 , a PWM signal for controlling a grid-side three-phase power module of the converter is generated based on the dq-axis grid-side voltage reference value and the first reference phase angle.

[0104] As an example, the d-axis grid-side voltage reference value can be determined in the following manner: based on the DC voltage target setting value and DC voltage value (i.e., DC voltage measurement value) of the converter, and the q-axis positive-sequence grid-side voltage value, the d-axis inductor current reference value is determined; then, based on the d-axis inductor current reference value, the d-axis positive- and negative-sequence grid-side voltage values, and the dq-axis positive- and negative-sequence inductor current values, the d-axis grid-side voltage reference value is determined.

[0105] The site reactive power synchronization control method proposed in the present disclosure can solve the problem of asynchronous output changes of new energy power generation systems (for example, wind turbines) within the same new energy site, maximize the reactive power capacity and regulation capability of the new energy power generation system itself, and reduce dependence on and cost of additional reactive power compensation equipment.

[0106] According to the exemplary embodiments of the present disclosure, relying on the communication capability of the high-speed synchronous control system, the response speed and the adjustment step size meet the randomness of the new energy power generation system and the conditions of rapid power changes. The reactive power regulation and response step size can reach milliseconds or even microseconds, which is of great significance to improving the quality of grid-connected power, reducing grid losses, and enhancing the operational stability and safety of the grid.

[0107] FIG12 shows a flowchart of a method for determining a reactive closed-loop feedback amount according to an exemplary embodiment of the present disclosure.

[0108] 12, in step S401, based on the first reference phase angle, the three-phase voltage value u of the station grid connection point is calculated. a 、u b 、u c Perform coordinate transformation to obtain the voltage value of the dq axis station grid connection point Three-phase current value on the grid side i a1 、i b1 、i c1 Perform coordinate transformation to obtain the dq axis grid side current value i d1 、i q1 .

[0109] In step S402, based on the voltage value of the dq axis station grid connection point, the dq axis grid side current value and the voltage transformation ratio T of the transformer N , determine the reactive closed-loop feedback amount.

[0110] As an example, the reactive closed-loop feedback quantity can be obtained by the method shown in Figure 15: the voltage value of the d-axis station grid connection point q-axis grid-side current value i q1 And the voltage ratio of the transformer T N The product of the three and the voltage value of the q-axis station grid connection point d-axis grid side current value i d1 And the voltage ratio of the transformer T N The product of the three and the difference between them is used as the reactive closed-loop feedback quantity. Among them, the voltage transformation ratio of the transformer is T N is the voltage transformation ratio between the low voltage side and the high voltage side.

[0111] FIG13 shows a flowchart of a method for determining a q-axis grid-side voltage reference value according to an exemplary embodiment of the present disclosure.

[0112] 13 , in step S501 , a q-axis positive-sequence grid-side voltage reference value is determined based on the q-axis inductor current reference value, the dq-axis positive-sequence inductor current value, and the q-axis positive-sequence grid-side voltage value.

[0113] As an example, the difference between the q-axis inductor current reference value and the q-axis positive-sequence inductor current value can be input into the ninth PI controller, and then the q-axis positive-sequence grid-side voltage reference value is determined based on the output value of the ninth PI controller, the d-axis positive-sequence inductor current value, the q-axis positive-sequence grid-side voltage value, the grid-side filter inductance value, and the grid voltage angular frequency.

[0114] In step S502 , a q-axis negative-sequence grid-side voltage reference value is determined based on the dq-axis negative-sequence inductor current value and the q-axis negative-sequence grid-side voltage value.

[0115] As an example, the difference between the 0 and q-axis negative sequence inductor current values ​​can be input into the tenth PI controller, and then the q-axis negative sequence grid-side voltage reference value is determined based on the output value of the tenth PI controller, the d-axis negative sequence inductor current value, the q-axis negative sequence grid-side voltage value, the grid-side filter inductance value, and the grid voltage angular frequency.

[0116] In step S503 , the sum of the q-axis positive-sequence grid-side voltage reference value and the q-axis negative-sequence grid-side voltage reference value is used as the q-axis grid-side voltage reference value.

[0117] As an example, as shown in Figure 16, the current inner loop design adopts separate control of positive and negative sequences. L represents the inductance value of the filter inductor in the grid-side filter (that is, the grid-side filter inductance value). For the positive sequence design, the positive sequence grid-side voltage q-axis reference value is obtained through PI closed loop and feedforward control. In the negative sequence design, the target current value of the current loop q axis is set to 0, and the negative sequence grid side voltage q axis reference value is obtained through PI closed loop and feedforward control. After summing with the positive sequence calculated value, the q-axis total reference voltage V q_ref .

[0118] Figure 14 shows a flow chart of a converter control method for a new energy power generation system according to another exemplary embodiment of the present disclosure. Figure 14 shows a converter control method when switching from a station reactive power synchronization control mode to a local reactive power control mode.

[0119] 14 , in step S601 , the grid-side three-phase voltage value of the converter is input into a phase-locked loop to obtain a second reference phase angle.

[0120] As an example, step S601 may include: inputting the grid-side three-phase voltage value of the converter into a phase-locked loop to obtain a phase-locked angle as the second reference phase angle.

[0121] In step S602, based on the second reference phase angle, coordinate transformation is performed on the grid-side inductor current value of the converter to obtain dq-axis positive and negative sequence inductor current values, and coordinate transformation is performed on the grid-side three-phase voltage value to obtain q-axis positive and negative sequence grid-side voltage values.

[0122] In step S603 , a q-axis inductor current reference value is determined based on the local reactive power reference value and the reactive power value of the converter.

[0123] As an example, the local reactive power reference value can be determined by the following method: Determine the target set value of the grid-side line voltage effective value of the converter and the actual value of the effective value of the grid-side line voltage V rms The difference between them is input into the second PI controller to obtain the local reactive power reference value.

[0124] In step S604, the q-axis grid-side voltage reference value in the local reactive power control mode is determined based on the dq-axis positive-sequence inductor current values ​​and the q-axis positive-sequence grid-side voltage values ​​obtained by the second reference phase angle and the q-axis inductor current reference value obtained by the local reactive power reference value.

[0125] As an example, the difference between the local reactive power reference value and the reactive power value of the converter (i.e., the actual reactive power value) can be input into the third PI controller; and the q-axis inductor current reference value is determined based on the d-axis positive-sequence grid-side voltage value obtained by the second reference phase angle, the output value of the third PI controller, the grid voltage angular frequency, and the grid-side filter capacitance value of the converter.

[0126] As an example, the q-axis inductor current reference value in the local reactive power control mode may be determined in the manner shown in FIG8 . Indicates the target setting value of the grid-side line voltage effective value, V rms The measured value of the effective value of the line voltage on the grid side is represented by the second PI controller, which controls the deviation and obtains the local reactive power reference value Q. cmd ', and then through the reactive closed-loop PI controller and feedforward control, the q-axis inductor current reference value I is obtained q_ref When the station synchronous control mode is exited, the station reactive synchronous control is smoothly switched to the local reactive control. At this time, the reference phase angle used in the control calculation process is switched from the first reference phase angle to the second reference phase angle.

[0127] As an example, the method for determining the q-axis grid-side voltage reference value in the local reactive power control mode is similar to the method for determining the q-axis grid-side voltage reference value in the station reactive power synchronization control mode shown in FIG11 , and will not be repeated here.

[0128] In step S605 , a PWM signal for controlling the grid-side three-phase power module is generated based on the q-axis grid-side voltage reference value and the second reference phase angle in the local reactive power control mode.

[0129] It should be understood that the reactive loop design and the current inner loop design in the above embodiments may also adopt other design forms.

[0130] According to the exemplary embodiment of the present disclosure, the reactive power control of each converter of the new energy power generation system has both the capability of synchronous control of the entire field, that is, the algorithm design based on the PCC point voltage orientation, and the control effect of switching to the local safety mode when responding to abnormalities in the field control system.

[0131] According to an exemplary embodiment of the present disclosure, a method for synchronous reactive power control and switching of a station is provided, which solves the problem of asynchronous reactive power regulation caused by output changes of a new energy power generation system within the same new energy station, maximizes the reactive capacity and regulation capability of the new energy power generation system itself, and makes the response speed and regulation step meet the randomness of the new energy power generation system and the conditions of rapid power changes, thereby improving the quality of grid-connected power, enhancing the operational stability of the power grid, and reducing the dependence on and cost of additional reactive compensation equipment.

[0132] An exemplary embodiment of the present disclosure provides a computer-readable storage medium having a computer program stored thereon, which, when executed by a processor, causes the processor to execute the converter control method for a new energy power generation system as described in the exemplary embodiment above. The computer-readable storage medium is any data storage device that can store data read by a computer system. Examples of computer-readable storage media include: read-only memory, random access memory, read-only optical disc, magnetic tape, floppy disk, optical data storage device, and carrier wave (such as data storage via the Internet via a wired or wireless transmission path).

[0133] According to an exemplary embodiment of the present disclosure, a converter controller of a new energy power generation system includes: a processor and a memory, wherein the memory stores a computer program, and when the computer program is executed by the processor, it prompts the processor to execute the converter control method of the new energy power generation system as described in the above exemplary embodiment.

[0134] A new energy power generation system according to an exemplary embodiment of the present disclosure includes: a converter and a converter controller as described in the above exemplary embodiment.

[0135] Although some exemplary embodiments of the present disclosure have been shown and described, it will be appreciated by those skilled in the art that modifications may be made to these embodiments without departing from the scope and spirit of the disclosure as defined by the claims and their equivalents.

Claims

1. A converter control method for a new energy power generation system, wherein: The converter control method comprises: Acquire the three-phase voltage value of the station grid connection point in real time and input it into the phase-locked loop to obtain the phase-locked angle, and determine the first reference phase angle based on the phase-locked angle; Based on the first reference phase angle, coordinate transformation is performed on the grid-side inductor current value of the converter to obtain dq-axis positive and negative sequence inductor current values, and coordinate transformation is performed on the grid-side three-phase voltage value of the converter to obtain dq-axis positive and negative sequence grid-side voltage values; Determine a dq axis grid side voltage reference value based on the dq axis positive and negative sequence inductor current value and the dq axis positive and negative sequence grid side voltage value; Based on the dq-axis grid-side voltage reference value and the first reference phase angle, a PWM signal for controlling a grid-side three-phase power module of the converter is generated.

2. The converter control method according to claim 1, wherein: In the station reactive synchronous control mode, based on the dq axis positive and negative sequence inductor current values ​​and the dq axis positive and negative sequence grid side voltage values, the step of determining the dq axis grid side voltage reference value comprises: Determine the q-axis inductor current reference value based on the reactive power command value issued by the new energy station controller and the reactive power closed-loop feedback value of the converter; A q-axis grid-side voltage reference value is determined based on the dq-axis positive- and negative-sequence inductor current values, the q-axis positive- and negative-sequence grid-side voltage values, and the q-axis inductor current reference value.

3. The converter control method according to claim 2, wherein: The converter control method further comprises: Based on the three-phase voltage value of the station grid-connected point, the grid-side three-phase current value of the converter and the first reference phase angle, a reactive closed-loop feedback amount for characterizing the equivalent reactive value injected by the converter into the station grid-connected point is determined.

4. The converter control method according to claim 3, wherein: The step of determining the reactive closed-loop feedback amount based on the three-phase voltage value of the station grid connection point, the grid-side three-phase current value of the converter and the first reference phase angle comprises: Based on the first reference phase angle, coordinate transformation is performed on the three-phase voltage value of the station grid connection point to obtain the dq axis station grid connection point voltage value, and coordinate transformation is performed on the three-phase current value of the grid side to obtain the dq axis grid side current value; Determine the reactive closed-loop feedback amount based on the voltage value of the dq axis station grid connection point, the dq axis grid-side current value, and the voltage transformation ratio of the transformer; Wherein, the converter is connected to the station grid connection point via the transformer.

5. The converter control method according to claim 3 or 4, wherein: Based on the reactive power command value issued by the new energy station controller and the reactive power closed-loop feedback value of the converter, the step of determining the q-axis inductor current reference value includes: Inputting the difference between the reactive command value and the reactive closed-loop feedback value into a first PI controller; The q-axis inductor current reference value is determined based on the d-axis positive-sequence grid-side voltage value, the output value of the first PI controller, the grid voltage angular frequency, and the grid-side filter capacitor value of the converter.

6. The converter control method according to claim 2, wherein: Based on the dq-axis positive and negative sequence inductor current values, the q-axis positive and negative sequence grid-side voltage values, and the q-axis inductor current reference value, the step of determining the q-axis grid-side voltage reference value comprises: Determine a q-axis positive-sequence grid-side voltage reference value based on the q-axis inductor current reference value, the dq-axis positive-sequence inductor current value, and the q-axis positive-sequence grid-side voltage value; Determine a q-axis negative-sequence grid-side voltage reference value based on the dq-axis negative-sequence inductor current value and the q-axis negative-sequence grid-side voltage value; The sum of the q-axis positive-sequence grid-side voltage reference value and the q-axis negative-sequence grid-side voltage reference value is used as the q-axis grid-side voltage reference value.

7. The converter control method according to claim 1, wherein: The data collection time of the converter is the same as that of the station grid connection point; And / or, the data synchronization acquisition period of the converter and the station grid connection point is the same as the control period of the converter, and the switching period of the grid-side three-phase power module is twice the control period; And / or, the transmission delay of the three-phase voltage value of the station grid connection point from the station grid connection point to the converter is less than 1 ms.

8. The converter control method according to claim 2, wherein: The converter control method further comprises: In case of switching from the station reactive power synchronous control mode to the local reactive power control mode, inputting the grid-side three-phase voltage value of the converter into a phase-locked loop to obtain a second reference phase angle; Based on the second reference phase angle, the grid-side inductor current value of the converter is transformed to obtain the dq axis positive and negative sequence inductor current value, and the grid-side three-phase voltage value is transformed to obtain the q Shaft positive and negative sequence grid side voltage value; Determining a q-axis inductor current reference value based on a local reactive power reference value and a reactive power value of the converter; Determine the q-axis grid-side voltage reference value in the local reactive power control mode based on the dq-axis positive- and negative-sequence inductor current values ​​and the q-axis positive- and negative-sequence grid-side voltage values ​​obtained by the second reference phase angle and the q-axis inductor current reference value obtained by the local reactive power reference value; Based on the q-axis grid-side voltage reference value and the second reference phase angle in the local reactive power control mode, a PWM signal for controlling the grid-side three-phase power module is generated.

9. The converter control method according to claim 8, wherein: The converter control method further includes: determining a difference between a target set value of the grid-side line voltage effective value of the converter and an actual value of the grid-side line voltage effective value, and inputting the difference into a second PI controller to obtain the local reactive power reference value; The step of determining the q-axis inductor current reference value based on the local reactive power reference value and the reactive power value of the converter comprises: inputting the difference between the local reactive power reference value and the reactive power value of the converter into a third PI controller; Determine the q-axis inductor current reference value based on the d-axis positive-sequence grid-side voltage value, the output value of the third PI controller, the grid voltage angular frequency, and the grid-side filter capacitor value of the converter; The d-axis positive-sequence grid-side voltage value is obtained by performing coordinate transformation on the grid-side three-phase voltage value of the converter based on the second reference phase angle.

10. The converter control method according to claim 1, wherein: The data collection time point of the converter is the same as that of the station grid connection point; The step of determining the first reference phase angle based on the phase-locking angle includes: compensating the phase-locking angle based on the transmission delay of the three-phase voltage value of the station grid connection point and the phase difference between the high and low voltage sides of the transformer to obtain the first reference phase angle; Wherein, the converter is connected to the station grid connection point via the transformer; The transmission delay is the transmission delay of the three-phase voltage value of the station grid connection point from the station grid connection point to the converter.

11. The converter control method according to claim 10, wherein: Based on the transmission delay of the three-phase voltage value of the station grid connection point and the phase difference between the high and low voltage sides of the transformer, the phase lock angle is compensated to obtain the first reference phase angle, which includes: The phase locking angle, the first compensation angle for compensating the phase difference between the high and low voltage sides, and the first compensation angle for compensating The sum of the three second compensation angles of the transmission delay is used as the first reference phase angle.

12. The converter control method according to any one of claims 1, 10-11, wherein: The system short-circuit capacity ratio SCR of the power grid to which the new energy power generation system is connected via the station grid connection point is within a predetermined range.

13. The converter control method according to claim 1, wherein: The step of determining a dq axis grid side voltage reference value based on the dq axis positive and negative sequence inductor current value and the dq axis positive and negative sequence grid side voltage value comprises: Determine a d-axis inductor current reference value based on a DC voltage target setting value of the converter, a collected DC voltage value, and a q-axis positive-sequence grid-side voltage value; Determine a q-axis inductor current reference value based on a target setting value of the grid-side line voltage effective value of the converter, the collected grid-side line voltage effective value, the reactive value of the converter, and the d-axis positive-sequence grid-side voltage value; A dq axis grid side voltage reference value is determined based on the d axis inductor current reference value, the q axis inductor current reference value, the dq axis positive and negative sequence inductor current values, and the dq axis positive and negative sequence grid side voltage values.

14. The converter control method according to claim 13, wherein: Based on the d-axis inductor current reference value, the q-axis inductor current reference value, the dq-axis positive and negative sequence inductor current values, and the dq-axis positive and negative sequence grid-side voltage values, the step of determining the dq-axis grid-side voltage reference value includes: Determine a d-axis positive-sequence grid-side voltage reference value based on the d-axis inductor current reference value, the dq-axis positive-sequence inductor current value, and the d-axis positive-sequence grid-side voltage value; Determine a q-axis positive-sequence grid-side voltage reference value based on the q-axis inductor current reference value, the dq-axis positive-sequence inductor current value, and the q-axis positive-sequence grid-side voltage value; Determine a d-axis negative-sequence grid-side voltage reference value based on the dq-axis negative-sequence inductor current value and the d-axis negative-sequence grid-side voltage value; Determine a q-axis negative-sequence grid-side voltage reference value based on the dq-axis negative-sequence inductor current value and the q-axis negative-sequence grid-side voltage value; The dq-axis grid-side voltage reference value is determined based on the d-axis positive- and negative-sequence grid-side voltage reference value and the q-axis positive- and negative-sequence grid-side voltage reference value.

15. A computer-readable storage medium storing a computer program, wherein: When the computer program is executed by a processor, the processor is prompted to execute the converter control method for a new energy power generation system according to any one of claims 1 to 14.

16. A current converter controller for a new energy power generation system, wherein: The current converter controller comprises: processor; A memory storing a computer program, which, when executed by a processor, prompts the processor to execute the converter control method for a new energy power generation system as described in any one of claims 1 to 14.

17. A new energy power generation system, wherein: The new energy power generation system includes a converter and a converter controller as claimed in claim 16.