Reactive power control method and device of new energy power generation system

Abstract

The invention provides a reactive power control method and device for a new energy power generation system. The reactive power control method comprises the following steps: acquiring a three-phase voltage value of a station grid-connected point in real time, inputting the three-phase voltage value 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 inductive current value of the converter to obtain a dq-axis positive and negative sequence inductive current value, and performing coordinate transformation on the grid-side three-phase voltage value of the converter to obtain a q-axis positive and negative sequence grid-side voltage value; determining a q-axis inductive current reference value based on a reactive instruction value issued by the new energy station controller and the reactive closed-loop feedback quantity of the converter; determining a q-axis network side voltage reference value based on the dq-axis positive and negative sequence inductance current value, the q-axis positive and negative sequence network side voltage value and the q-axis inductance current reference value; and generating a PWM signal for controlling a grid-side three-phase power module of the converter based on the q-axis grid-side voltage reference value and the first reference phase angle.

Description

Technical Field

[0001] The present disclosure generally relates to the field of renewable energy power generation technology, and more specifically, to a reactive power control method and device for a renewable energy power generation system. Background Art

[0002] As the capacity of new energy grid connection continues to increase, the problems of unstable grid voltage and increased line losses caused by the access of new energy to the grid are becoming increasingly prominent. The quality of power has a significant impact on the stability of the grid, the safe operation of power equipment, and industrial and agricultural production. New energy power generation is characterized by randomness (instability) and uncontrolledness. The short-term fluctuations in the output of new energy power generation are significant. The changes in the power generation power of new energy may cause fluctuations in the voltage and frequency of the grid system, and even cause the grid system to become unstable. Therefore, new energy reactive power compensation 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.

[0003] 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, the reactive capacity and regulation capability of wind turbines are utilized. If the voltage regulation needs of the power grid system cannot be met, reactive compensation devices such as SVG (Static Var Generator) need to be installed. However, this method has two shortcomings: first, the AVC system has a large regulation step, mostly in minutes or seconds, which makes it difficult to meet the randomness of wind turbines and the rapid voltage fluctuations 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 compensation devices, resulting in high reactive compensation costs. Summary of the invention

[0004] An exemplary embodiment of the present disclosure provides a reactive power control method and device 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 in the same new energy station.

[0005] According to a first aspect of an embodiment of the present disclosure, a reactive power control method for a new energy power generation system is provided, the reactive power control method comprising: acquiring a three-phase voltage value at a station grid connection 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 a grid-side inductor current value of a converter to obtain a dq-axis positive and negative sequence inductor current value, and performing coordinate transformation on a grid-side three-phase voltage value of the converter to obtain a q-axis positive and negative sequence grid-side voltage value; determining a q-axis inductor current reference value based on a reactive command value issued by a new energy station controller and a reactive closed-loop feedback amount of the converter; determining a q-axis grid-side voltage reference value based on the dq-axis positive and negative sequence inductor current value, the q-axis positive and negative sequence grid-side voltage value, and the q-axis inductor current reference value; and generating a PWM signal for controlling a grid-side three-phase power module of the converter based on the q-axis grid-side voltage reference value and the first reference phase angle.

[0006] Optionally, the reactive power control method further includes: determining a reactive closed-loop feedback quantity used to characterize the equivalent reactive power value injected by the converter into the station grid-connected point based on the three-phase voltage value of the station grid-connected point, the three-phase current value on the grid side of the converter and the first reference phase angle.

[0007] Optionally, based on the three-phase voltage value of the station grid-connected point, the three-phase current value of the grid-side of the converter and the first reference phase angle, the step of determining the reactive closed-loop feedback amount includes: based on the first reference phase angle, performing a coordinate transformation on the three-phase voltage value of the station grid-connected point to obtain the dq axis station grid-connected point voltage value, and performing a coordinate transformation on the three-phase current value on the grid-side to obtain the dq axis grid-side current value; determining the reactive closed-loop feedback amount based on the dq axis station grid-connected point voltage value, the dq axis grid-side current value and the voltage transformation ratio of the transformer; wherein the converter is connected to the station grid-connected point via the transformer.

[0008] Optionally, based on the reactive closed-loop feedback amount and the reactive command value, 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 amount into a first PI controller; 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 capacitance value of the converter, determining the q-axis inductor current reference value; wherein the d-axis positive-sequence grid-side voltage value is obtained by coordinate transformation of the grid-side three-phase voltage value of the converter based on the first reference phase angle.

[0009] Optionally, 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 includes: determining the 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; determining the 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; and taking the sum of the q-axis positive-sequence grid-side voltage reference value and the q-axis negative-sequence grid-side voltage reference value as the q-axis grid-side voltage reference value.

[0010] Optionally, the data collection time of the converter is the same as that of the station grid-connected point; and / or, the transmission delay of the three-phase voltage value of the station grid-connected point from the station grid-connected point to the converter is less than 1ms.

[0011] Optionally, the reactive power control method further includes: when switching from the site reactive power synchronous control mode to the local reactive power control mode, inputting the grid-side three-phase voltage value of the converter into the phase-locked loop to obtain a second reference phase angle; based on the second 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 values, and performing coordinate transformation on the grid-side three-phase voltage value to obtain q-axis positive and negative sequence grid-side voltage values; determining the q-axis inductor current reference value based on the local reactive power reference value and the reactive value of the converter; determining 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; generating a PWM signal for controlling the grid-side three-phase power module based on the q-axis grid-side voltage reference value in the local reactive power control mode and the second reference phase angle.

[0012] Optionally, the reactive power control method further includes: determining the difference between the target setting value of the grid-side line voltage effective value of the converter and the 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; wherein, based on the local reactive power reference value and the reactive power value of the converter, the step of determining the q-axis inductor current reference value includes: inputting the difference between the local reactive power reference value and the reactive power value of the converter into a third PI controller; determining 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 capacitance value of the converter; wherein, the d-axis positive-sequence grid-side voltage value is obtained by coordinate transformation of the grid-side three-phase voltage value of the converter based on the second reference phase angle.

[0013] 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, the processor is prompted to execute the reactive power control method of the new energy power generation system as described above.

[0014] According to a third aspect of an embodiment of the present disclosure, a converter controller for a renewable 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 reactive power control method for the renewable energy power generation system as described above.

[0015] According to the reactive power control method and device of the renewable energy power generation system of the exemplary embodiment of the present disclosure, a reactive closed-loop control algorithm based on the voltage orientation of the station grid-connected point is proposed. The voltage phase-locking angle of the station grid-connected point is directly involved in the synchronous control of the converter current inner loop of each renewable energy power generation system, so that the reactive power output direction of the renewable energy power generation system in the same renewable energy station is consistent, and the group effect and combined force of the renewable energy power generation system are maximized, thereby realizing the reactive synchronous control of the renewable energy station.

[0016] In the following description, some aspects and / or advantages of the general inventive concept will be set forth, and some other aspects and / or advantages will be known through the following description or the implementation of the general inventive concept. BRIEF DESCRIPTION OF THE DRAWINGS

[0017] These and / or other aspects and advantages of the present application will become clearer and easier to understand from the following detailed description of the embodiments of the present application in conjunction with the accompanying drawings, in which:

[0018] Figure 1 A flowchart showing a reactive power control method of a new energy power generation system according to an exemplary embodiment of the present disclosure;

[0019] Figure 2 A schematic diagram showing a topological structure of a wind turbine converter according to an exemplary embodiment of the present disclosure is shown;

[0020] Figure 3 A timing diagram showing local control of a station grid connection point and a converter according to an exemplary embodiment of the present disclosure is shown;

[0021] Figure 4 A schematic diagram showing coordinate transformation according to an exemplary embodiment of the present disclosure is shown;

[0022] Figure 5 A flow chart showing a method for determining a reactive closed-loop feedback amount according to an exemplary embodiment of the present disclosure;

[0023] Figure 6A flow chart showing a method for determining a q-axis grid-side voltage reference value according to an exemplary embodiment of the present disclosure;

[0024] Figure 7 A flowchart showing a reactive power control method of a new energy power generation system according to another exemplary embodiment of the present disclosure;

[0025] Figure 8 A schematic diagram showing reactive power control of a station according to an exemplary embodiment of the present disclosure is shown;

[0026] Fig. 9 A schematic diagram showing local reactive power control according to an exemplary embodiment of the present disclosure;

[0027] Fig.10 A schematic diagram showing a current inner loop according to an exemplary embodiment of the present disclosure. DETAILED DESCRIPTION

[0028] 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 will be described below with reference to the drawings in order to explain the present disclosure.

[0029] It should be noted that the terms "first", "second", etc. 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 sequence. It should be understood that the data used in this way can be interchanged 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 devices and methods consistent with some aspects of the present disclosure as detailed in the appended claims.

[0030] It should be noted that the phrase "at least one of the items" in the present disclosure includes three types of parallel situations: "any one of the items", "a combination of any number 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. Another example is "executing at least one of step 1 and step 2" which means the following three parallel situations: (1) executing step 1; (2) executing step 2; (3) executing step 1 and step 2.

[0031] Figure 1 A flow chart showing a reactive power control method of a new energy power generation system according to an exemplary embodiment of the present disclosure.

[0032] As an example, the type of the new energy power generation system may include but is not limited to: a wind turbine and / or a photovoltaic power generation system. It should be understood that the type of the new energy power generation system may also be other types, and the present disclosure does not limit this. In other words, the application scenario of the reactive power control method of the new energy power generation system according to the exemplary embodiment of the present disclosure is not limited to wind farms, and can also be applied to other types of new energy stations.

[0033] Taking the renewable energy power generation system as a wind turbine generator set and the wind power converter as a back-to-back dual PWM converter as an example, the topological structure of the wind power converter can be as follows: Figure 2 As shown, the wind power converter may 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 set 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., a grid-side filter), and the high-voltage side of the transformer is connected to the PCC point of the station substation (i.e., the public grid connection point after all the converter equipment in the station is collected). For example, the grid-side filter may be an LC filter or an LCL filter.

[0034] As an example, the reactive power control method of the renewable energy power generation system according to the exemplary embodiment of the present disclosure may be executed by a controller of a converter of the renewable energy power generation system (ie, a converter controller).

[0035] Reference Figure 1 In step S101, the three-phase voltage value of the station grid connection point is obtained in real time and input into the phase-locked loop to obtain the phase-locked angle, and the first reference phase angle is determined based on the phase-locked angle.

[0036] 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.

[0037] The station grid connection point sends the real-time collected data (including but not limited to the three-phase voltage value of the station grid connection point) to each new energy power generation system in the new energy station that is connected to the power grid through the station grid connection point through a high-speed communication bus. Accordingly, the step of obtaining the three-phase voltage value of the station grid connection point in real time may include: receiving the three-phase voltage value of the station grid connection point in real time.

[0038] As an example, the data collection time (ie, sampling point) of the converter and the station grid connection point is the same. In other words, the converter and the station grid connection point are sampled synchronously.

[0039] like Figure 3 As shown, as an example, the data synchronization acquisition cycle of the converter and the station grid connection point is the same as the control cycle T of the converter. s (i.e., the execution period of the converter control method) is the same as the length of the switching period T of the three-phase power module on the grid side, and the length of the control period T sTwice the length of d It indicates the communication delay from the substation PCC point to the converter controller (i.e., the transmission delay of the three-phase voltage value of the station grid connection point from the station grid connection point to the converter controller), specifically, the time deviation between the time when the three-phase voltage value of the station grid connection point transmitted from the station grid connection point is received locally and the time when the three-phase voltage value of the station grid connection point is collected. It should be understood that the data synchronization collection cycle is not limited to the same length as the control cycle, and the transmission delay is not limited to be less than the length of the control cycle. For example, the transmission delay can be less than 1ms.

[0040] 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 phase-locked angle can be compensated based on the transmission delay of the three-phase voltage value at 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.

[0041] 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 of the station grid connection point can be used as the first reference phase angle.

[0042] For example, the first reference phase angle θ can be calculated by the following formula: pcc :

[0043] θ pcc =θ 0 +δ θ0 +δ θ1

[0044] Among them, θ 0 represents the phase-locking angle, δ θ0 represents the first compensation angle, δ θ1 Indicates the second compensation angle.

[0045] As an example, the first compensation angle may be determined based on the phase difference between the high and low voltage sides of the transformer. For example, the phase difference between the high and low voltage sides of the transformer is related to the type of the transformer, the connection relationship between the high voltage side and the low voltage side of the transformer, etc. For example, the phase difference between the high and low voltage sides of the transformer may be 30 degrees.

[0046] As an example, the second compensation angle may be determined based on the transmission delay of the three-phase voltage value of the station grid connection point. For example, the transmission delay is related to the length of the communication line and the communication rate.

[0047] 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 q-axis positive and negative sequence grid-side voltage values.

[0048] The grid-side inductor current value is the current value flowing through the filter inductor in the grid-side filter.

[0049] Phase-locked loop and coordinate transformation design Figure 4 As shown, combined Figure 3 , when the coordinate transformation is performed on the data collected in the current data synchronization collection period (including but not limited to the grid-side inductor current value and the grid-side three-phase voltage value), due to the communication delay, the three-phase voltage value of the station grid connection point collected in the current data synchronization collection period has not been received, so the first reference phase angle θ used 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.

[0050] As an example, step S102 may include: based on the first reference phase angle, calculating the grid-side inductor current value i of the converter 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 grid-side three-phase voltage value v 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).

[0051] In step S103, the 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.

[0052] As an example, the reactive power control method of the new energy power generation system according to the exemplary embodiment of the present disclosure may also include: determining the reactive closed-loop feedback quantity Q used to characterize the equivalent reactive power 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 The reactive power quantity adopts 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.

[0053] According to an exemplary embodiment of the present disclosure, a method for calculating adaptive compensation of reactive power loss of output impedance of a new energy power generation system is proposed, that is, the equivalent reactive power Q injected into the PCC nodepcc The calculation method of .

[0054] The following will be combined Figure 5 An exemplary embodiment of a method for determining a reactive closed-loop feedback amount is described below and will not be expanded here.

[0055] As an example, the total reactive power demand of the new energy station can be determined based on the target setting 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 instruction value of each new energy power generation system in the new energy station is determined and issued. Figure 8 , Indicates the target setting value of the effective value of the PCC point line voltage, U rms It represents the measured calculated value of the effective value of the line voltage at the PCC point, LPF represents the low-pass filter, and 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 command Q cmd To each new energy power generation system. 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 is not limited thereto.

[0056] As an example, the reactive power command value Q cmd And reactive closed loop feedback quantity 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 determine the q-axis inductor current reference value I q_ref .

[0057] As an example, you can Figure 8 The q-axis inductor current reference value I is obtained by the method shown in 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.

[0058] In step S104, 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.

[0059] 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. Figure 6 An exemplary embodiment of step S104 is described below, which will not be expanded here.

[0060] In step S105 , a PWM signal for controlling a grid-side three-phase power module of the converter is generated based on the q-axis grid-side voltage reference value and the first reference phase angle.

[0061] It should be understood that the first reference phase angle is used to perform coordinate transformation in the process of generating the PWM signal.

[0062] As an example, the grid-side inverter of the converter may include a plurality of 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, or an IGBT module. As an example, each three-phase power module may include a plurality of switch tubes (IGBTs) and diodes connected in reverse parallel thereto.

[0063] As an example, the PWM pulse signal calculation method is not limited to SVPWM.

[0064] As an example, a PWM signal for controlling a grid-side three-phase power module of the converter may be generated based on a q-axis grid-side voltage reference value, a d-axis grid-side voltage reference value, and a first reference phase angle.

[0065] 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.

[0066] The reactive power synchronization control method for a station proposed in the present disclosure can solve the problem of asynchronous output changes of a new energy power generation system (for example, a wind turbine generator set) within the same new energy station, 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.

[0067] 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 can 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.

[0068] Figure 5 A flow chart showing a method for determining a reactive closed-loop feedback amount according to an exemplary embodiment of the present disclosure is shown.

[0069] Reference Figure 5 In step S201, based on the first reference phase angle, the three-phase voltage value u of the station grid connection point is calculated. a 、u b 、uc Perform coordinate transformation to obtain the voltage value of the dq axis station grid connection point The 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 .

[0070] In step S202, 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.

[0071] As an example, you can Figure 8 The reactive closed-loop feedback quantity is obtained by the method shown in the figure: the voltage value of the d-axis station grid connection point is q-axis grid-side current value i q1 And the voltage ratio of the transformer T N The product of the three is 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, the difference between them is used as the reactive closed-loop feedback. 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.

[0072] Figure 6 A flow chart showing a method for determining a q-axis grid-side voltage reference value according to an exemplary embodiment of the present disclosure is shown.

[0073] Reference Figure 6 In step S301, 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.

[0074] 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 fourth PI controller, and then the q-axis positive-sequence grid-side voltage reference value is determined based on the output value of the fourth 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.

[0075] In step S302, 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.

[0076] As an example, the difference between the 0 and q-axis negative-sequence inductor current values ​​can be input into the fifth PI controller, and then the q-axis negative-sequence grid-side voltage reference value is determined based on the output value of the fifth 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.

[0077] In step S303, 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 taken as the q-axis grid-side voltage reference value.

[0078] As an example, Fig.10 As shown, 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 .

[0079] Figure 7 A flowchart showing a reactive power control method of a new energy power generation system according to another exemplary embodiment of the present disclosure is shown. Figure 7 The reactive power control method in the case of switching from the station reactive power synchronization control mode to the local reactive power control mode is shown.

[0080] Reference Figure 7 In step S401, the grid-side three-phase voltage value of the converter is input into a phase-locked loop to obtain a second reference phase angle.

[0081] As an example, step S401 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.

[0082] In step S402, 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.

[0083] In step S403, 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.

[0084] As an example, the local reactive power reference value can be determined by: determining 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.

[0085] In step S404, the q-axis grid-side voltage reference value in the local reactive power control mode is determined 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.

[0086] 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 can be 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.

[0087] As an example, you can Fig. 9 The illustrated method determines the q-axis inductor current reference value in the local reactive power control mode. Indicates the target setting value of the effective value of the grid-side line voltage, V rms It represents the measured and calculated value of the effective value of the grid-side line voltage. The control deviation is obtained by the PI controller to obtain the local reactive power reference set 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.

[0088] 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 Fig.10 The method for determining the q-axis grid-side voltage reference value in the station reactive synchronous control mode shown is similar and will not be repeated here.

[0089] In step S405, 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.

[0090] 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.

[0091] According to the exemplary embodiments of the present disclosure, the reactive 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 PCC point voltage orientation, and the control effect of switching to the local safety mode when the field control system is abnormal.

[0092] 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, makes the response speed and regulation step size meet the randomness of the new energy power generation system and the conditions of rapid power changes, improves the quality of grid-connected power, enhances the operational stability of the power grid, and reduces the dependence on and cost of additional reactive compensation equipment.

[0093] An exemplary embodiment of the present disclosure provides a computer-readable storage medium storing a computer program, which, when executed by a processor, causes the processor to execute the reactive power control method of a new energy power generation system as described in the above exemplary embodiment. The computer-readable storage medium is any data storage device that can store data read out by a computer system. Examples of computer-readable storage media include: read-only memory, random access memory, read-only optical disk, magnetic tape, floppy disk, optical data storage device, and carrier wave (such as data transmission through the Internet via a wired or wireless transmission path).

[0094] According to the exemplary embodiment of the present disclosure, the inverter controller of the renewable 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 reactive power control method of the renewable energy power generation system as described in the above exemplary embodiment.

[0095] 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.

[0096] 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 present disclosure as defined by the claims and their equivalents.

Claims

1. A reactive power control method for a new energy power generation system, characterized in that: The reactive power 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 q-axis positive and negative sequence grid-side voltage values; 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; Determine a q-axis grid-side voltage reference value 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; Based on the q-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 reactive power control method according to claim 1, characterized in that: The reactive power 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.

3. The reactive power control method according to claim 2, characterized in that: 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.

4. The reactive power control method according to claim 2 or 3, characterized in that: The step of determining the q-axis inductor current reference value based on the reactive closed-loop feedback amount and the reactive command value comprises: Inputting the difference between the reactive command value and the reactive closed-loop feedback value into a first 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 first 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 first reference phase angle.

5. The reactive power control method according to claim 1, characterized in that: 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.

6. The reactive power control method according to claim 1, characterized in that: The data collection time of the converter is the same as that of the station grid connection point; 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.

7. The reactive power control method according to claim 1, characterized in that: The reactive power 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, 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; 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.

8. The reactive power control method according to claim 7, characterized in that: The reactive power control method further comprises: 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.

9. A computer-readable storage medium storing a computer program, characterized in that: When the computer program is executed by a processor, the processor is prompted to execute the reactive power control method for a new energy power generation system as claimed in any one of claims 1 to 8.

10. A current converter controller for a new energy power generation system, characterized in that: The current converter controller comprises: processor; A memory storing a computer program, which, when executed by a processor, prompts the processor to execute the reactive power control method for a new energy power generation system as claimed in any one of claims 1 to 8.

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