CN117277855A

CN117277855A - Network-structured converter with front-stage power supply universality and control method thereof

Info

Publication number: CN117277855A
Application number: CN202311253959.1A
Authority: CN
Inventors: 冀肖彤; 柳丹; 胡四全; 贺之渊; 熊平; 康逸群; 肖繁; 邓万婷; 陈孝明; 曹侃; 蔡萱; 王伟; 熊亮雳; 江克证; 徐驰; 李猎; 叶畅; 胡畔
Original assignee: State Grid Smart Grid Research Institute Co ltd; XJ Electric Co Ltd; State Grid Hubei Electric Power Co Ltd
Current assignee: State Grid Smart Grid Research Institute Co ltd; XJ Electric Co Ltd; State Grid Hubei Electric Power Co Ltd
Priority date: 2023-09-27
Filing date: 2023-09-27
Publication date: 2023-12-22
Anticipated expiration: 2043-09-27
Also published as: CN117277855B

Abstract

The application provides a grid-connected converter with a front-stage power supply wide adaptability and a control method thereof, which are used for solving the problem that the existing grid-connected converter grid-connected control method is limited in application scene due to the fact that the front-stage power supply is completely relied on to control direct-current voltage. The control method of the DC voltage control device adopts the parallel inertia control channel and the forward damping control channel to control the DC voltage, and simultaneously autonomously generates the output frequency reference, the phase reference and the voltage amplitude reference of the converter, so that the converter has networking capability and is not dependent on a DC side front-stage power supply to control the DC voltage, and is widely applicable to front-stage power supplies adopting various topologies and different control strategies. The invention can expand the application scene of the grid-built converter, can be used in the fields of new energy power generation and energy storage and the field of flexible direct current transmission, and can effectively promote the large-scale popularization and application of the grid-built converter, thereby having great significance for improving the stability of an electric power system.

Description

Network-structured converter with front-stage power supply universality and control method thereof

Technical Field

The application relates to the technical field of power systems, in particular to a network-structured converter with a front-stage power source wide adaptability and a control method thereof.

Background

At present, the low-carbon transformation of energy sources is obviously accelerated, and a novel power system of high-proportion new energy sources and high-proportion power electronic equipment has become a development trend. On one hand, new energy power generation represented by wind power and photovoltaic shows explosive growth. On the other hand, energy storage as an important technology and basic equipment for constructing a new power system is also in an explosive situation. The power system morphology is transitioning from synchronous machine-dominated to high-proportion power electronics.

At present, a grid-connected (grid-connected) control architecture is widely used in practical engineering, synchronization between the converter and a power grid is realized through a phase-locked loop (PLL), and a voltage source exists in a system for constructing voltage for grid-connected points of the grid-connected control architecture. In conventional power systems, the voltage source is provided by a synchronous generator/synchronous regulator. However, as the new energy power generation device is connected to the power grid in a large scale through the converter, the duty ratio of the synchronous generator in the system is gradually reduced, so that the strength of the power grid is continuously reduced, the voltage supporting capability is seriously insufficient, and the stability problem of the power system is increasingly complex. Particularly, when the power generation units in the novel power system in the future are all composed of power electronic converters, if the converters are controlled by a follow-up grid type, no voltage source construction voltage exists in the system, and obviously, the system cannot normally operate.

The grid construction technology can build a voltage source for supporting a large power grid to stably run through the control characteristics of the converter, realizes the effects of quickly adjusting frequency and voltage, increasing inertia and short-circuit capacity, inhibiting broadband oscillation and the like, and is an important means for supporting a novel power system taking new energy as a main body. The novel energy storage represented by electrochemical energy storage has flexible bidirectional regulation and millisecond-level rapid response capability, and the engineering application of the network construction control technology is realized at present.

However, the existing grid-type current transformer mainly focuses on controlling the voltage and power of the ac side, and the objective of maintaining the voltage stability of the dc side of the current transformer is handed to the front-stage power source, so that the existing grid-type current transformer can only be used in cooperation with the front-stage power source having the capability of controlling the dc voltage. When the existing grid-formed control is applied to an energy storage system, a flexible direct current transmission system and a new energy power generation system, a front-stage control energy storage battery is required to be charged and discharged rapidly to maintain stable direct current voltage, or a front-stage new energy power supply is required to give up tracking control on the maximum power of new energy, the reserved allowance is used for maintaining the constant direct current voltage, or a front-stage needs to be provided with a large-capacity energy storage device for maintaining the constant direct current voltage, or the direct current side of a flexible direct current converter is required to have the other end of the flexible direct current converter to stabilize the direct current voltage, so that the operation life of the energy storage battery is seriously reduced, the power generation benefit of the new energy is reduced, and the control flexibility of the converter at the two ends of the flexible direct current is reduced.

Therefore, the current grid-connected converter is subjected to direct-current side matching power supply elbow in engineering application, and popularization of grid-connected control technology in the fields of flexible direct-current power transmission systems, wind power, photovoltaic new energy sources, energy storage and the like is severely limited.

Disclosure of Invention

In view of this, the embodiment of the application provides a grid-connected inverter with a front-stage power supply and a control method thereof, which realize the control of direct-current voltage through a parallel inertia control channel and a forward damping control channel, release the dependence of the grid-connected inverter on the voltage stabilizing capability of a direct-current side front-stage power supply, and effectively widen the application scenario of the grid-connected inverter.

In a first aspect, the present application provides a method for controlling a grid-connected converter, the grid-connected converter being configured to convert a dc voltage output by a dc side power supply into a three-phase output voltage, the method comprising: determining a DC voltage and a DC voltage U output by a DC side power supply _dc And a DC voltage command value U _dcref Is a direct current voltage difference of (2). Wherein (1)>. Direct current voltage difference->The input inertia-damping control module is used for respectively processing the direct-current voltage difference through the parallel forward damping channel and the inertia control channel to determine the phase reference value theta of the three-phase output voltage _mod Frequency reference value f _mod . Based on the phase reference value theta _mod Output voltage amplitude reference value E _mod Determining a modulation wave u of a three-phase output voltage _mod(a,b,c) So that the grid-formed converter adjusts the three-phase output voltage u based on the modulation wave _(a,b,c) . Determining a phase reference value θ of a three-phase output voltage _mod Frequency reference value f _mod The method comprises the following steps: direct current voltage difference->Inputting an inertia control path to, in the inertia control path: inertia coefficient k based on inertia controller _inertia Process DC voltage difference->And combining the rated frequency value f of the three-phase output voltage ₀ Determining a frequency reference value f _mod . Based on the frequency reference value f _mod Determining a first phase θ ₁ . Direct current voltage difference->Inputting the forward damping channel to be in the forward damping channel: damping coefficient D based on damping controller _damp Process DC voltage difference->Determining the second phase θ ₂ . Based on the first phase theta ₁ Second phase θ ₂ Determining a phase reference value θ _mod . Wherein,；/>；/>；/>。

preferably, determining the dc voltage output from the dc side power supply and the dc voltage difference between the dc voltage and the dc voltage command value includes: and inputting a sampling value of the direct-current voltage output by the direct-current side power supply into a low-pass filter, and determining a filtering result of the direct-current voltage. The DC voltage command value is subtracted from the DC voltage filtering result to obtain a DC voltage difference.

Preferably, the cut-off frequency of the low-pass filter is configured to be 1/10-1/2 of the switching frequency of the grid-structured converter so as to filter out high-frequency ripples in the direct-current voltage.

Preferably, the method further comprises: a desired equivalent rotational inertia value J and a desired damping ratio ζ are determined. Determining an inertia coefficient k of the inertia controller based on the desired equivalent rotational inertia value J _inertia Based on inertia coefficient k _inertia The desired damping ratio ζ determines a damping coefficient D of the forward damping controller _damp 。

Wherein,；/>the method comprises the steps of carrying out a first treatment on the surface of the C is the capacitance value between the DC side power supply and the grid-structured converter, and A is the synchronization coefficient between the grid-structured converter and the power grid.

Preferably, determining the modulated wave of the three-phase output voltage based on the output voltage amplitude reference value and the phase reference value includes: determining a reference value U for the DC voltage for modulation _dcmod . DC voltage reference value U for modulation _dcmod Output voltage amplitude reference value E _mod Determining the amplitude U of a modulated wave _mod 。

Wherein,. Based on the amplitude U of the modulated wave _mod Phase reference value θ _mod Determining a modulated wave u _mod(a,b,c) 。

Wherein,。

u _moda 、u _modb u _modc Is the phase component of the modulated wave.

Preferably, determining the dc voltage reference value for modulation includes: the DC voltage is inputted to a low-pass filter for low-pass filtering, and the filtered DC voltage is used as a DC voltage reference value for modulation.

Preferably, the method further comprises determining the output voltage magnitude reference value using a droop control strategy. Determining the output voltage amplitude reference value using the droop control strategy includes: determining an output voltage amplitude U _o And reactive power Q. Based on the output voltage amplitude U _o Output voltage amplitude command value U _ref Reactive power Q and reactive power command value Q _ref Determining an output voltage amplitude reference value E by adopting a droop control strategy _mod 。

Wherein,，k _q is the reactive droop coefficient, k in the droop control strategy _u Is the voltage droop coefficient in the droop control strategy.

Preferably, adjusting the three-phase output voltage based on the modulated wave includes: and determining the topological structure and the modulation strategy of the network-structured current transformer. And determining a driving signal of a switching tube of the network-structured converter based on the modulation wave and the modulation strategy so that the network-structured converter performs electric energy conversion based on the driving signal.

In a second aspect, the present application provides an apparatus for controlling a grid-connected converter for converting a dc voltage of a dc side power supply into a three-phase output voltage, the apparatus comprising: the detection module is used for determining the direct-current voltage output by the direct-current side power supply and the direct-current voltage U _dc And a DC voltage command value U _dcref Is a direct current voltage difference of (2) . Wherein,. A phase determination module for applying a DC voltage difference +.>The input inertia-damping control module is used for respectively processing the direct-current voltage difference through the parallel forward damping channel and the inertia control channel to determine the phase reference value theta of the three-phase output voltage _mod Frequency reference value f _mod . A modulation module for based on the phase reference value theta _mod Output voltage amplitude reference value E _mod Determining a modulation wave u of a three-phase output voltage _mod(a,b,c) So that the grid-formed converter adjusts the three-phase output voltage u based on the modulation wave _(a,b,c) 。

The phase determining module is specifically configured to: voltage difference of direct currentInputting an inertia control path to, in the inertia control path: inertia coefficient k based on inertia controller _inertia Process DC voltage difference->And combining the rated frequency value f of the three-phase output voltage ₀ Determining a frequency reference value f _mod . Based on the frequency reference value f _mod Determining a first phase θ ₁ . Direct current voltage difference->Inputting the forward damping channel to be in the forward damping channel: damping coefficient D based on damping controller _damp Process DC voltage difference->Determining the second phase θ ₂ ,. Based on the first phase theta ₁ Second phase θ ₂ Determining a phase basisQuasi value theta _mod . Wherein,；/>；/>；/>。

preferably, the apparatus further comprises an amplitude determination module for determining the output voltage amplitude reference value using a droop control strategy. The amplitude determining module is specifically configured to: determining an output voltage amplitude U _o And reactive power Q. Based on the output voltage amplitude U _o Output voltage amplitude command value U _ref Reactive power Q and reactive power command value Q _ref Determining an output voltage amplitude reference value E by adopting a droop control strategy _mod 。

Wherein,，k _q is the reactive droop coefficient, k, of the droop control strategy _u Is the voltage droop coefficient of the droop control strategy.

In a third aspect, the present application provides a grid-connected converter, comprising: the three-phase converter is used for converting the direct-current voltage output by the direct-current side power supply into three-phase output voltage; and a control circuit for executing the grid-formation type converter control method according to the first aspect to determine the modulated wave and superimpose the modulated wave on the three-phase output voltage.

In a fourth aspect, the present application provides a computer-readable storage medium, where a computer program is stored, where the computer program, when executed by a computer, implements the grid-formation converter control method according to the first aspect.

According to the networking converter with the front-stage power supply wide adaptability and the control method thereof, the parallel inertia control channel and the forward damping control channel are adopted to control the direct-current voltage and automatically generate the output frequency reference, the phase reference and the voltage amplitude reference of the converter, so that the converter has networking capability and is independent of the front-stage power supply to control the direct-current voltage, and the networking converter can be widely suitable for the front-stage power supply adopting various topologies and different control strategies. Therefore, the application scene of the grid-built converter is expanded, so that the grid-built converter can be used in the fields of new energy power generation and energy storage and the field of flexible direct current transmission, the large-scale popularization and application of the grid-built converter are effectively promoted, and the grid-built converter has important significance for improving the stability of a power system dominated by power electronics.

Drawings

In order to more clearly illustrate the technical solutions of the embodiments of the present invention, the drawings that are needed in the embodiments will be briefly described below, it being understood that the following drawings only illustrate some embodiments of the present invention and therefore should not be considered as limiting the scope, and other related drawings may be obtained according to these drawings without inventive effort for a person skilled in the art.

Fig. 1 is a schematic diagram of an application scenario of a grid-based power system according to some embodiments of the present application.

Fig. 2 is an exemplary flowchart of a method for controlling a converter according to some embodiments of the present application.

Fig. 3 is a schematic structural diagram of an equivalent control circuit in a converter according to some embodiments of the present application.

Fig. 4 is an exemplary flowchart of a method for determining a modulated wave according to some embodiments of the present application.

Fig. 5 is a schematic structural diagram of an output voltage amplitude reference value determining module according to some embodiments of the present application.

Fig. 6 is a schematic structural diagram of a converter control system according to some embodiments of the present application.

Fig. 7A, 7B, and 7C are schematic diagrams of parameters in a simulation verification process provided in some embodiments of the present application.

Detailed Description

The following description of the technical solutions in the embodiments of the present application will be made clearly and completely with reference to the drawings in the embodiments of the present application, and it is apparent that the described embodiments are only some embodiments of the present application, not all embodiments. All other embodiments, which can be made by one of ordinary skill in the art without undue burden from the present disclosure, are within the scope of the present disclosure.

Summary of the application

A power electronic converter (also known as an inverter) is an electrical energy conversion device constructed based on power semiconductor devices (e.g., thyristors, power MOSFETs, IGBTs, etc.) and conventional electrical components (e.g., capacitors, inductors, and associated control circuitry, etc.). The power electronic converter may convert electrical energy from one form to another. For example, power electronic converters can convert direct current into three-phase alternating current.

In a traditional power grid, the synchronous generator is a dominant power generation unit, and the strong voltage stabilizing capability of the synchronous generator enables the whole voltage of the power grid to be stable, so that the synchronous generator can serve as an equivalent strong voltage source to provide stable voltage for a traditional grid-following converter. The converters are thus generally controlled by a grid, i.e. the power electronic converter can convert energy based on a voltage-oriented current source.

However, in the "dual high" power system, the new energy power equipment generally uses a flexible dc mode to transmit power, and no synchronous machine is provided. In the power system, the synchronous machine duty ratio is gradually reduced, so that the voltage stability and the frequency stability of the power grid are reduced. If the converter still adopts the following-net control, the converter can easily generate interaction oscillation with the power grid with reduced voltage intensity.

In the related art, to ensure the stability of the power system, the converter may employ grid-formation control. The grid-structured converter can be used for controlling the alternating current output voltage of the converter, so that the converter externally shows controlled current source characteristics. Therefore, the grid-structured converter has stronger stability in the occasion with lower power grid strength. The network-structured control simulates the characteristics of a synchronous generator and can automatically provide power support for a power grid when the load demand of the alternating current side changes.

In practical use, the grid-formed converter generally needs to rely on a stably controlled pre-stage dc voltage and control based on active power on the ac side (i.e., the dc side power of the grid-formed converter is equal to the ac side power) to achieve synchronization with the grid.

When the grid-built converter is connected with a front-stage direct-current power supply without direct-current voltage control energy, when alternating-current side power oscillates (for example, a load is directly carried to form an island, and the power of the load fluctuates), in order to ensure that the direct-current side power of the grid-built converter is equal to alternating-current side power, the grid-built converter directly influences direct-current voltage, so that the grid-built converter oscillates along with the oscillation of the alternating-current side power. In the oscillation process, the direct-current voltage fluctuation is possibly overlarge and exceeds the safety range due to the power fluctuation, so that the converter triggers overvoltage/undervoltage protection to stop.

Therefore, conventional grid-formation control generally requires a power supply or a converter for controlling the dc voltage to be arranged in a front stage on the dc side. If the direct-current side power supply or the converter adopts non-constant direct-current voltage control such as constant power control, constant current control or droop control, the traditional grid-structured converter cannot be connected with the prior-stage equipment. This severely limits the spread of applications for networking converters.

In order to solve the technical problems, the control method of the DC voltage control device adopts the parallel inertia control channel and the forward damping control channel to control the DC voltage, and simultaneously, the output frequency reference, the phase reference and the voltage amplitude reference of the converter are autonomously generated, so that the converter has the networking capability and does not depend on a DC side front-stage power supply to control the DC voltage. The method enables the grid-built converter to adapt to the direct current side power supply with various topologies and different control strategies, solves the problem that the traditional grid-built control method is limited in many scenes because the direct current side pre-stage power supply is completely relied on to control the direct current voltage, enables the grid-built converter to be applied to the field of new energy power generation and the field of flexible direct current power transmission, effectively promotes the large-scale popularization and application of the grid-built converter, and has important significance for improving the stability of the power system dominated by power electronics. Various non-limiting embodiments of the present application will now be described in detail with reference to the accompanying drawings.

Exemplary application scenarios

As shown in fig. 1, the power system 100 may include a dc side power supply 110, a grid-connected converter 120, and a load 130, which are sequentially connected to each other, as shown in fig. 1.

When supplying power, the electric energy generated by the dc side power supply 110 is converted into three-phase ac power by the grid-connected converter 120 to meet the requirements of the load 130, and is transmitted to the load 130 (such as a power supply grid). That is, the grid-connected converter 120 may convert the dc voltage (hereinafter referred to as dc voltage) u supplied from the dc power supply 110 _dc Converted into three-phase alternating voltage u _(a,b,c) 。

If the grid converter 120 is a conventional grid converter, the conventional grid converter may be controlled based on power, i.e., the dc side power (also referred to as the input power of the dc side power supply) P of the power at the load 130 _in And consistent. When the dc side power supply 110 does not have the voltage regulation function and the power of the load 130 is changed, the dc voltage u _dc And may vary with load 130 load/power fluctuations, which may cause excessive dc voltage fluctuations, out of safety range, and cause the converter to trigger over-voltage/under-voltage protection and shut down.

The fact that the dc side power supply 110 does not have a voltage regulation function is understood to mean that the dc side power supply 110 or a power electronic converter built therein adopts a control strategy and involves control of the dc voltage. As shown in fig. 1, the dc side power supply 110 may further include a source side energy source 111 and a front stage converter 112.

Wherein the source side energy source 111 is used for storing and/or supplying energy. The source side energy source 111 may be generally a clean energy source, such as wind power equipment, solar power equipment, and the like. The pre-stage converter 112 may be used as a device for converting the source-side energy source 111, and may generate the aforementioned direct-current voltage u _dc . DC side power supply 110 is alignedCurrent voltage u _dc Is typically embodied in a control strategy configured within the pre-inverter 112. If the pre-stage converter 112 adopts an unstable DC voltage control strategy such as constant power control, constant current control or droop control, the DC side power supply 110 will lack the DC voltage u _dc Is provided.

To overcome the foregoing, the grid-connected inverter 120 may include a control circuit 121 and a three-phase inverter 122 to enable the grid-connected inverter 120 to be widely used in dc-side power supplies 110 with different control strategies/topologies. Wherein the three-phase current transformer 122 can be used to convert the DC voltage u _dc Converted into three-phase output voltage u _(a,b,c) . The control circuit 121 may be based on a DC voltage u _dc A modulated wave of the three-phase output voltage is generated to mitigate the effects of power fluctuations or other parameter fluctuations at the load 130 on the dc side power supply 110.

In the control circuit 121, the control circuit 121 may determine the dc voltage of the dc side power supply and the dc voltage difference between the dc voltage and the dc voltage command value. And inputting the direct-current voltage difference into an inertia-damping control module to determine a phase reference value and a frequency reference value of the three-phase output voltage. Then, a modulation wave of the three-phase output voltage is determined based on the phase reference value and the output voltage amplitude reference value, so that the grid-structured converter adjusts the three-phase output voltage based on the modulation wave. The inertia-damping control module comprises parallel forward damping channels and inertia control channels. More on the method of controlling the networked converter may be found in fig. 2 and its associated description, and more on the internal structure of the control circuit 121 may be found in fig. 3 and its associated description.

Exemplary converter control methods

Fig. 2 is an exemplary flowchart of a method for controlling a converter according to some embodiments of the present application. The process P200 shown in fig. 2 may be performed by related devices (e.g., the grid-connected inverter 120, the built-in processor of the grid-connected inverter 120, and the control device 640).

As shown in fig. 2, P200 may include the steps of:

s210, determining a direct current voltage difference between the direct current voltage and a direct current voltage command value of the direct current side power supply. In some embodiments, S210 may be performed by the detection module 641.

S220, inputting the direct-current voltage difference into an inertia-damping control module, and enabling the direct-current voltage difference to be processed by a parallel forward damping channel and an inertia control channel respectively to determine a phase reference value and a frequency reference value of the three-phase output voltage. In some embodiments, S220 may be performed by phase determination module 642.

And S230, determining a modulation wave of the three-phase output voltage based on the phase reference value and the output voltage amplitude reference value, so that the grid-structured converter adjusts the three-phase output voltage based on the modulation wave. In some embodiments, S230 may be performed by the modulation module 643.

In the foregoing P200, the dc side power source may refer to a dc source (such as the foregoing dc side power source 110) for converting a grid-formed converter. A grid-tied converter implementing the aforementioned P2000 may be used to convert the dc output signal of the dc side power supply into a three-phase output voltage (i.e., a three-phase ac signal).

The DC voltage may refer to the actual voltage provided by the DC side power supply to the grid-connected converter (such as the DC voltage u shown in FIG. 1 _dc ). The direct voltage command value may refer to a desired magnitude of the direct voltage, i.e. a theoretical supply voltage of the direct voltage when supplying power. The DC voltage difference is the difference between the DC voltage and the DC voltage command value.

The inertia-damping control module may refer to a control module of a forward damping channel and an inertia control channel which are arranged in parallel, wherein the forward damping channel and the inertia control channel may independently process the direct current differential pressure at the same time to determine a corresponding channel result. The forward damping channel may be configured with a damping controller and the inertia control channel may be configured with an inertia controller.

The reference value is understood to be a stable and dimensionally meaningful parameter. The phase reference value may refer to a fixed phase value that can resolve a phase in a subsequent or other control link. The frequency reference value may refer to a fixed frequency value that can be resolved for different frequencies in a subsequent or other control link.

The reference value may generally be used as a reference value in the control process. For example, the frequency reference value may be used as a reference for adjusting the three-phase output frequency in the energy conversion link of the grid-connected converter, and the three-phase output voltage is controlled based on the frequency reference value and the rated frequency value (such as the ac frequency, 50 Hz) so that the signal frequency thereof is close to the rated frequency value.

The output voltage amplitude reference value is similar to the phase reference value and the frequency reference value, and is a fixed voltage value for reflecting the voltage amplitude. Here, the output voltage amplitude reference value may generally reflect the amplitude of the output voltage.

The modulated wave may refer to an adjustment signal for the three-phase output voltage. The modulated wave may be in a form corresponding to the three-phase output voltage and may also have three phases. In the subsequent processing, the modulated wave may be superimposed on the three-phase output voltage based on the topology of the grid-formed converter and the control strategy to adjust the three-phase output voltage based on the direct current voltage.

In some embodiments, the aforementioned S210 may be performed by a sensor detecting the dc side voltage. The voltage of the grid-connected converter on the direct current side can be obtained in real time through the sensor to serve as the direct current voltage.

In some embodiments, the aforementioned dc voltages may also be presented as complex frequency domain functions. Then, when executing the foregoing S210, the time domain function of the dc voltage may be obtained based on the sensor, and then the time domain function may be converted into a complex frequency domain response based on a preset algorithm (such as an interpolation fast fourier transform algorithm).

In some embodiments, the foregoing S220 may be characterized as a process of dc voltage differential based on the forward damping channel and a process of dc voltage differential by the inertia control channel. The phase reference value may be a superposition of a forward damping channel processing result and an inertia control channel processing result. The frequency reference value may be an intermediate result in the inertia control path. Specific calculation processes and loop structures can be seen in fig. 3 and related descriptions.

In some embodiments, the foregoing S230 may be performed by determining relevant parameters of the modulated wave. The modulation wave mainly comprises a phase and a modulation wave amplitude, the modulation wave amplitude can be determined based on an output voltage amplitude reference value, and the phase can be determined based on the phase reference value. For more on determining the modulated wave see fig. 4 and its associated description.

In some embodiments, the modulated wave may be superimposed in the three-phase output voltage when the modulated wave is determined. When the topology structure of the grid-structured converter and the modulation strategy thereof are overlapped, the topology structure of the grid-structured converter and the modulation strategy thereof need to be determined first. And determining a driving signal of a switching tube of the grid-connected converter based on the modulation wave and the modulation strategy so as to enable the grid-connected converter to perform electric energy conversion based on the driving signal. The topology structure may refer to an equivalent circuit diagram of the grid-connected converter for electric energy conversion, the modulation strategy may refer to control parameters and control methods of the grid-connected converter for electric energy conversion, and the driving signals of the switching tubes may refer to voltage application values and application time of each switching tube (such as a transistor) integrated in the grid-connected converter, so that each switching tube integrated in the grid-connected converter can realize electric energy conversion based on corresponding requirements.

The foregoing superimposition process may be adaptively performed based on actual conditions. As just one example, when a three-phase converter within/mated with a grid-type converter is a two-level topology. After the modulation is obtained by the control method disclosed by P200, the modulation can be compared with a triangular carrier with the amplitude of 1 to carry out PWM modulation so as to obtain a signal for driving the switching tube.

Therefore, the control method of the DC voltage control device adopts the parallel inertia control channel and the forward damping control channel to control the DC voltage, and simultaneously, the output frequency reference, the phase reference and the voltage amplitude reference of the converter are generated autonomously, so that the converter has the networking capability and does not depend on a DC side front-stage power supply to control the DC voltage. The method enables the grid-built converter to adapt to the direct current side power supply with various topologies and different control strategies, solves the problem that the traditional grid-built control method is limited in many scenes because the direct current side pre-stage power supply is completely relied on to control the direct current voltage, enables the grid-built converter to be applied to the field of new energy power generation and the field of flexible direct current power transmission, effectively promotes the large-scale popularization and application of the grid-built converter, and has important significance for improving the stability of the power system dominated by power electronics.

Exemplary equivalent control Circuit

Fig. 3 is a schematic structural diagram of an equivalent control circuit in a converter according to some embodiments of the present application. That is, the control circuit shown in fig. 3 may be a control circuit that is equivalently generated by the grid-connected converter based on a built-in control strategy.

As shown in fig. 3, an inertia-damping control module 310 may be included in the control circuit 121. Wherein the input of the inertia-damping control module 310 is a DC voltage differenceI.e. DC voltage U _dc And a DC voltage command value U _dcref Is a difference between (a) and (b). The output may be a phase reference value θ _mod 。

Further, as shown in FIG. 3, inertia-damping control module 310 may include an inertia control channel 311, a forward damping channel determination 312. Wherein the inertia control channel 311 is further provided with an inertia controller 313 and an integration unit 314, and a nominal frequency value f is introduced in the calculation process ₀ . The intermediate output of the inertia control path 311 is the frequency reference value f _mod The channel output is the first phase theta ₁ . A damping controller 315 is disposed within forward damping channel acknowledgement 312. The channel output of forward damping channel determination 312 is the second phase θ ₂ 。

Based on the above circuit configuration, θ when determining the phase reference value _mod The method can be performed based on the following steps:

First, a direct current voltage difference is input to an inertia control channel to determine a first phase and a frequency reference value.

Second, the direct voltage difference is input to the forward damping channel to determine a second phase.

Finally, a phase reference value is determined based on the first phase and the second phase.

In the inertia control passage 311:the DC voltage difference Deltau may be processed based on the inertia controller 313 _dcfil And combining the rated frequency value f of the three-phase output voltage ₀ Determining a frequency reference value f _mod The method comprises the steps of carrying out a first treatment on the surface of the Based on the frequency reference value f _mod Determining a first phase θ ₁ 。

In the forward damping channel 312: the dc voltage difference deltau may be processed based on the damping controller 315 _dcfil Determining the second phase θ ₂ 。

Based on the above processing procedure, the frequency reference value is determined based on the formula:

。

based on the above processing procedure, the phase reference value is determined based on the following formula:

。

the foregoing integration section is described as an integration unit 314 having a transfer function of 1/s in the frequency domain.

In practical design, the desired inertia value and the desired damping ratio of the equivalent rotation may be introduced through the foregoing inertia coefficient and damping coefficient, so that the grid-configured converter 120 has a certain anti-mutation capability corresponding to the equivalent rotation on the ac side (load 130 side), thereby resisting the influence of mutation on parameters (especially, direct current side power supply parameters). In some embodiments, the desired value of the equivalent rotation may be determined based on parameters of the ac synchronous machine rotor such that a portion of the parameters of the grid-tied converter 120 on the ac side are proximate to the ac synchronous machine rotor.

Thus, the inertia coefficient and the damping coefficient can be determined based on the aforementioned desired inertia value and desired damping ratio. Wherein the desired inertial value of the equivalent rotation and the desired damping ratio may be determined first. And determining an inertia coefficient of the inertia controller based on the desired inertia value. Finally, a damping coefficient of the forward damping controller is determined based on the inertia coefficient and the desired damping ratio. Wherein the inertia coefficient is inversely related to the inertia value.

In some embodiments, the inertia coefficient is determined based on the following formula:

. Wherein k is _inertia Is the inertia coefficient, U _dcref The direct-current voltage command value is C, the capacitance value between the direct-current side power supply and the grid-connected converter is C, and J is the expected inertia value.

The damping coefficient is determined based on the following formula:

. Wherein D is _damp Is the damping coefficient, ζ is the expected damping ratio, and A is the synchronization coefficient of the grid-structured converter and the power grid.

In some embodiments, to counteract the interference of the high frequency components in the dc voltage, the control circuit 121 may further include a low pass filter 340. At this time, a sampling value of the dc voltage output from the dc side power supply may be input to the low-pass filter 340 to determine a filtering result of the dc voltage; and determining a DC voltage difference Deltau based on the filtering result of the DC voltage and the DC voltage command value _dcfil 。

In some embodiments, the low pass filter 340 is a low band pass filter with a cutoff frequency that is the upper frequency limit of the low pass filter 340. The cut-off frequency of the low-pass filter 340 may be configured to be 1/10-1/2 of the switching frequency of the grid-connected transformer, so as to filter out high-frequency ripple in the dc voltage difference.

In determining the phase reference value θ _mod After that, as further shown in fig. 3, the control circuit 121 may further include an output voltage amplitude reference value determination module 320 and a modulated wave generation module 330.

The output voltage amplitude reference value determining module 320 is used for determining an output voltage amplitude reference value E _mod . The output voltage amplitude reference value determination module 320 may determine the input parameters according to actual needs. Output voltage amplitude reference value determination module 320Will generally be based on a specific output signal and employ a corresponding control strategy.

In some embodiments, the output voltage amplitude reference value determination module 320 inputs an output parameter of the ac side three-phase output voltage and a corresponding parameter reference value (such as reactive power and a reference value thereof). Fig. 5 of the present application provides an output voltage magnitude reference value determination module 320 formed based on voltage power, as more fully described with reference to fig. 5 and related description.

The aforementioned modulated wave generation module 330 may be a virtual device for determining modulated waves. Wherein the input of the modulation wave generation module 330 may be the output voltage amplitude reference value E _mod DC voltage reference value U for modulation _dcmod The output may be a modulated wave u _mod(a,b,c) 。

When the DC side power source is used for supplying DC voltage u _dc When the control capability is provided, the DC voltage reference value U for modulation _dcmod Can directly adopt the direct current voltage command value U _dcref . When the DC side power source is used for supplying DC voltage u _dc Without control capability, e.g. direct-current voltage command value U _dcref DC voltage reference value U for modulation _dcmod May result in the modulated wave not reflecting the DC voltage u _dc Is a variation of (c). Thus, in some embodiments, the voltage may be based on the DC voltage u _dc Determining a reference value U for the DC voltage for modulation _dcmod 。

In some embodiments, to determine the DC voltage reference value U for modulation _dcmod DC voltage u _dc Can be processed by a low-pass filter 340 before being input into the control circuit 121 as a DC voltage reference value U for modulation _dcmod 。

In some embodiments, to further improve the filtering accuracy, the dc voltage reference value U _dcmod Low-pass filter and determining the dc voltage difference deltau _dcfil The low-pass filters of the (2) can be independently arranged and the band-pass range can be independently arranged, so that the control precision is improved.

Exemplary modulated wave determination methods

Fig. 4 is an exemplary flowchart of a method for determining a modulated wave according to some embodiments of the present application. The process P400 described in fig. 4 may be performed by the modulation module 643.

As shown in fig. 4, P400 may include the steps of:

s410, determining a direct-current voltage reference value for modulation.

S420, determining the amplitude of the modulation wave based on the direct current voltage reference value for modulation and the output voltage amplitude reference value.

S430, determining the modulation wave based on the amplitude of the modulation wave and a phase reference value, wherein the initial phase of the modulation wave is the phase reference value, and the amplitude of the modulation wave is the amplitude of the modulation wave.

Based on the above procedure, the modulation amplitude value is determined based on the formula:

。

the modulated wave is determined based on the formula:

. Wherein u is _mod(a,b,c) Is a modulated wave, u _moda 、u _modb U _modc Is the phase component of the modulated wave.

Exemplary output Voltage amplitude reference value determination Module

Fig. 5 is a schematic structural diagram of an output voltage amplitude reference value determining module according to some embodiments of the present application. The output voltage amplitude reference value determining module 320 shown in fig. 5 may reflect a droop control strategy based on the reactive power Q and the output voltage amplitude U _o Is controlled by the control process of (a). Wherein, based on the reactive power Q and the output voltage amplitude U _o Control may be performed by the amplitude determination module 644.

As shown in fig. 5, the voltage reference value determination module 320 may include a power control module 321 and a voltage control module 322. Wherein the power control module 321 may be configured with a reactive droop coefficient in a power-voltage droop control strategy and the voltage control module 322 may be configured with a voltage droop coefficient in a power-voltage droop control strategy.

Based on the structure shown in fig. 5, the output voltage amplitude and reactive power may be determined first when determining the voltage reference value. The output voltage amplitude voltage control module 322 is further configured to process the output voltage amplitude U based on the output voltage amplitude, the output voltage amplitude command value, the reactive power, and the reactive power command value using a power-voltage droop control strategy _o Output voltage amplitude command value U _ref

Based on the above procedure, the output voltage amplitude reference value is determined based on the following formula:

。

wherein k is _q Is the reactive droop coefficient (gain coefficient of the power control module 321), k in the power-voltage droop control strategy _u Is the voltage droop coefficient (gain coefficient of the voltage control block 322) in the power-voltage droop control strategy. k (k) _q And k _u The value of (2) may be designed based on the desired ratio of steady-state reactive bias to steady-state voltage bias.

It should be noted that, in practice, other possible control strategies may be used to determine the output voltage amplitude reference value E _mod . For example, the voltage amplitude reference value E may be determined based on the active portion, the reactive portion, and based on a similar control process of the output voltage _mod 。

Exemplary converter control System

As shown in fig. 6, the converter control system 600 may include a power electronic converter 610 and a processor 620, wherein the power electronic converter 610 may refer to the grid-configured converter 120 described above, and is not described herein.

The processor 620 may be a processing device having computing power and capable of controlling the power electronic converter 610. For example, the processor 620 may be a collection of related components of the power electronic converter 610 having computing capabilities. For another example, the processor 620 may be an external controller of the power electronic converter 610.

The processor 620 may perform the methods of controlling the power electronic converter 610 provided by embodiments of the present application.

In some embodiments, the power system converter control system 600 may also include a storage medium 630. The storage medium 630 may store a computer program therein. When the computer program is invoked by a processor (processor 620), the method for controlling the power electronic converter 610 provided in the embodiments of the present application is implemented.

In some embodiments, the aforementioned processor 620 may form a control device 640 of a grid-tied converter with the storage medium 630 and be configured within the power electronic converter 610. The control device 640 may include a plurality of functional modules, so that the power electronic converter 610 performs a plurality of related functions in the present application.

As shown in fig. 6, the control device 640 may include an output detection module 641, a phase determination module 642, and a modulation module 643.

The detection module 610 may be configured to determine a dc voltage output by the dc side power supply and a dc voltage difference between the dc voltage and a dc voltage command value.

The phase determining module 642 may be configured to input the dc voltage difference to the inertia-damping control module, and process the dc voltage difference through the parallel forward damping channel and the inertia control channel respectively to determine a phase reference value and a frequency reference value of the three-phase output voltage.

The modulation module 643 may be configured to determine a modulated wave of the three-phase output voltage based on the phase reference value and the output voltage amplitude reference value, such that the grid-formed converter adjusts the three-phase output voltage based on the modulated wave.

Wherein the phase determination module 642 may also be used in an inertia-damping control module: inputting the direct current voltage difference into an inertia control channel to be in the inertia control channel: processing the direct current voltage difference based on the inertia controller, and determining a frequency reference value by combining the rated frequency value of the three-phase output voltage; determining a first phase based on the frequency reference value; inputting a dc voltage difference into the forward damping channel to be in the forward damping channel: the second phase is determined based on the damping controller processing the dc voltage difference.

In some embodiments, the control device 640 may also include an amplitude determination module 644. The amplitude determination module 644 may be used to determine the output voltage amplitude reference value using a droop control strategy, among other things.

Control example of grid-structured converter

The simulation of the network-structured converter can be performed based on simulation tools such as Matlab/Simulink and the like. The simulation model of the current transformer can be built in a related environment based on simulation tools such as Matlab/Simulink, so that the control method of the networking current transformer is verified.

In the simulation, a grid-connected system of the grid-connected converter comprising a direct-current side power supply, a converter thereof, a grid-connected converter and a power grid can be built, so that the actual application effect of the proposed grid-connected converter control method is verified, and the model topological diagram is consistent with that of fig. 1.

The relevant parameters of the control circuit (e.g., control circuit 121) of the grid-connected converter are configured as follows:

rated frequency f ₀ =50 Hz, dc voltage command value U _dcref =700V, voltage droop coefficient k _u =0.1, reactive sag coefficient k _q =1e ^-4 Rotor inertia analog control parameter k _inertia =0.126, ac voltage amplitude command value U _ref =311V, damping coefficient D _damp =5e ^-3 Reactive power command Q _ref =0 kvar。

In the simulation model, the DC-side power converter adopts droop to control the input power P of the DC-side power supply _in Let P _in And the output frequency of the converter is regulated in a sagging relation. The grid-connected converter is controlled by adopting the control method disclosed by the patent.

Based on the above simulation environment, relevant parameters determined by the simulation process may be presented in fig. 7A, 7B, 7C. Wherein each image comprises a function of the direct voltage udc, the output active power Pe, the reactive power Q, the frequency reference value f in time sequence.

FIG. 7A can be reflected at 0.5s, DC side power P _in And when the time sequence change of the output parameters of the grid-structured converter is abrupt, the time sequence change schematic diagram of the output parameters of the grid-structured converter based on the control method is shown. Wherein at 0.5s the dc side supply power Pi may be increased from 5 kW to 10 kW. The abrupt change of the power of the direct current side power supply can reflect the power change condition of the direct current side power supply without the direct current voltage control capability caused by the change of the load power.

As shown in fig. 7A, when the power of the dc side source is disturbed, the grid-structured converter control method can dynamically buffer the changed power by dynamically adjusting the dc voltage, and then slowly send the power to the power grid, and finally, the dc voltage and the frequency are adjusted to the rated value 1pu. The output active power increases. The control method disclosed by the invention can maintain the DC voltage of the grid-built converter stable and output stable power and frequency even though the DC side power supply does not control the DC voltage and even if the DC side power supply generates power fluctuation. Furthermore, it should be noted that the reactive power output decreases with an increase in the active power due to the line power transfer characteristic, where the change in reactive power is caused by the increase in active power due to the line characteristic, instead of the control method disclosed in the present invention.

Fig. 7B may reflect a power command of 10 kW for the dc side power supply, but the time-series variation of the output parameters of the grid-configured converter is shown when the grid frequency is suddenly changed at 0.5 seconds.

As shown in fig. 7B, in the network configuration control method disclosed by the invention, when the frequency of the power grid is rapidly changed, the output frequency of the network configuration converter is not suddenly changed, but a certain inertia is kept to slowly change to the same value as the new frequency of the power grid, which shows that the network configuration control itself has the network configuration capability of providing frequency, inertia support and the like. Simultaneously, with the regulation of the direct current voltage and the frequency of the grid-connected converter, the active power output by the grid-connected converter is gradually reduced, and finally the grid-connected converter is arranged on the gridWhen the mode converter and the power grid are regulated to be in frequency synchronization, the active power output by the mode converter is reduced to a new steady state value, and the reactive power is changed to a new value along with the power transmission characteristic of the line. The steady-state value of the active power is reduced by the input power P of the DC side power supply _in Is controlled to have a droop relationship with the output frequency of the grid-tied converter.

In general, the simulation results of fig. 7A and 7B demonstrate that the disclosed grid-formed converter control method can maintain the dc bus voltage of the grid-formed converter stable and maintain the grid-formed capability to regulate the output frequency and power when the grid frequency changes rapidly, so that the frequency is smoothly regulated to the same value as the grid frequency.

The present application further simulates dc side power supplies using different strategies, and based on the same conditions as in fig. 7B, when the dc side power supply uses constant power control, the time sequence change of the output parameters of the grid-configured converter is shown in fig. 7C.

As can be seen from comparing fig. 7B with fig. 7C, when the dc side power supply adopts different control strategies, the grid-structured converter disclosed by the invention can still maintain the stability of the dc voltage, the output frequency and the power when the grid frequency changes rapidly, and the output frequency still shows inertia regulation characteristics, and finally is regulated to a value consistent with the grid frequency through smooth regulation.

In contrast, since the droop control is no longer adopted by the direct-current side power supply at this time, the output active power is no longer reduced at steady state. In the dynamic process, the grid-built converter still reduces the output active power to participate in the power regulation of the power grid, and the disclosed grid-built control method is proved to be capable of comprehensively considering the characteristics of the source side and the grid side, participating in the regulation of the grid side as much as possible, providing frequency and power support for the grid side and having the grid-built capability. In addition, the dc voltage is slightly higher than the nominal value in this case, but still within a safe and controllable range. Since the disclosed control method obtains the modulation wave by dividing the output voltage reference value by 1/2 times of the direct current voltage for modulation, the influence of the direct current voltage change on the output reactive power is effectively counteracted in the link of generating the modulation wave.

As is clear from fig. 7B and 7C, in fig. 7C, the steady-state value of the reactive power to be output is the same as the reactive power value at the rated dc voltage, although the dc voltage is higher than the rated dc voltage. A comparison of fig. 7C and fig. 7B demonstrates, on the one hand, that the disclosed control method is suitable for different dc side power sources, and on the other hand, that the necessity and advantage of the design of the disclosed control method to obtain the modulated wave by dividing the output voltage reference value by 1/2 times the dc voltage for modulation.

Those of ordinary skill in the art will appreciate that the various illustrative elements and algorithm steps described in connection with the embodiments disclosed herein may be implemented as electronic hardware, or combinations of computer software and electronic hardware. Whether such functionality is implemented as hardware or software depends upon the particular application and design constraints imposed on the solution. Skilled artisans may implement the described functionality in varying ways for each particular application, but such implementation decisions should not be interpreted as causing a departure from the scope of the present application. It will be clear to those skilled in the art that, for convenience and brevity of description, specific working procedures of the above-described systems, apparatuses and units may refer to corresponding procedures in the foregoing method embodiments, and are not repeated herein.

In the several embodiments provided in this application, it should be understood that the disclosed systems, devices, and methods may be implemented in other manners. For example, the apparatus embodiments described above are merely illustrative, e.g., the division of the units is merely a logical function division, and there may be additional divisions when actually implemented, e.g., multiple units or components may be combined or integrated into another system, or some features may be omitted or not performed. Alternatively, the coupling or direct coupling or communication connection shown or discussed with each other may be an indirect coupling or communication connection via some interfaces, devices or units, which may be in electrical, mechanical or other form.

The units described as separate units may or may not be physically separate, and units shown as units may or may not be physical units, may be located in one place, or may be distributed on a plurality of network units. Some or all of the units may be selected according to actual needs to achieve the purpose of the solution of this embodiment. In addition, each functional unit in each embodiment of the present application may be integrated in one processing unit, or each unit may exist alone physically, or two or more units may be integrated in one unit.

The functions, if implemented in the form of software functional units and sold or used as a stand-alone product, may be stored in a computer-readable storage medium. Based on such understanding, the technical solution of the present application may be embodied essentially or in a part contributing to the prior art or in a part of the technical solution, in the form of a software product stored in a storage medium, including several instructions for causing a computer device (which may be a personal computer, a server, or a network device, etc.) to perform all or part of the steps of the methods described in the embodiments of the present application. And the aforementioned storage medium includes: a usb disk, a removable hard disk, a Read-Only Memory (ROM), a random access Memory (RAM, random Access Memory), a magnetic disk, or an optical disk, or other various media capable of storing program verification codes.

It should be noted that in the description of the present application, the terms "first," "second," "third," and the like are used for descriptive purposes only and are not to be construed as indicating or implying relative importance. Furthermore, in the description of the present application, unless otherwise indicated, the meaning of "a plurality" is two or more.

The foregoing description of the preferred embodiments of the present invention is not intended to limit the invention to the precise form disclosed, and any modifications, equivalents, and alternatives falling within the spirit and principles of the present invention are intended to be included within the scope of the present invention.

Claims

1. The utility model provides a network-structured converter control method with preceding stage power source wide adaptability, characterized in that, network-structured converter is used for converting direct current voltage that direct current side power source output into three-phase output voltage, and the method includes:

determining the DC voltage output by the DC side power supply and the DC voltage U _dc And a DC voltage command value U _dcref Is a direct current voltage difference of (2)Wherein->；

Differential the DC voltageThe input inertia-damping control module is used for respectively processing the direct current voltage difference through the parallel forward damping channel and the inertia control channel to determine the phase reference value theta of the three-phase output voltage _mod Frequency reference value f _mod ；

Based on the phase reference value theta _mod Output voltage amplitude reference value E _mod Determining a modulation wave u of the three-phase output voltage _mod(a,b,c) So that the grid-formed converter adjusts the three-phase output voltage u based on the modulation wave _(a,b,c) ；

The phase reference value theta for determining the three-phase output voltage _mod Frequency reference value f _mod The method comprises the following steps:

differential the DC voltageInputting the inertia control path to: inertia coefficient k based on inertia controller _inertia Treating the DC voltage difference->And combining the rated frequency value f of the three-phase output voltage ₀ Determining the frequency reference value f _mod The method comprises the steps of carrying out a first treatment on the surface of the Based onThe frequency reference value f _mod Determining a first phase θ ₁ ；

Differential the DC voltageInputting the forward damping channel, and in the forward damping channel: damping coefficient D based on damping controller _damp Treating the DC voltage difference->Determining the second phase θ ₂ ；

Based on the first phase theta ₁ The second phase theta ₂ Determining the phase reference value θ _mod ；

Wherein,；/>；/>；/>。

2. the method of claim 1, wherein determining the dc voltage output by the dc side power supply and the dc voltage difference between the dc voltage and a dc voltage command value comprises:

inputting a sampling value of the direct-current voltage output by the direct-current side power supply into a low-pass filter, and determining a filtering result of the direct-current voltage;

and subtracting the direct-current voltage command value from the filtering result of the direct-current voltage to obtain the direct-current voltage difference.

3. The method according to claim 2, wherein the cut-off frequency of the low-pass filter is configured to be 1/10-1/2 of the switching frequency of the grid-formed converter to filter out high-frequency ripple in the dc voltage.

4. The method according to claim 1, wherein the method further comprises:

determining a desired equivalent rotational inertia value J and a desired damping ratio ζ;

determining an inertia coefficient k of the inertia controller based on the desired equivalent rotational inertia value J _inertia ；

Wherein,c is the capacitance value between the direct-current side power supply and the grid-connected converter;

based on the inertia coefficient k _inertia And the desired damping ratio ζ determines a damping coefficient D of the forward damping controller _damp ；

Wherein,and A is the synchronization coefficient of the grid-structured converter and the power grid.

5. The method of claim 1, wherein the determining the modulated wave of the three-phase output voltage based on the output voltage amplitude reference value and the phase reference value comprises:

determining a reference value U for the DC voltage for modulation _dcmod ；

Based on the DC voltage reference value U for modulation _dcmod The output voltage amplitude reference value E _mod Determining the amplitude U of a modulated wave _mod ；

Based on the amplitude U of the modulated wave _mod The phase reference value θ _mod Determining the modulated wave u _mod(a,b,c) ；

Wherein,；/>，u _moda 、u _modb u _modc Is the phase component of the modulated wave.

6. The method of claim 5, wherein determining a dc voltage reference value for modulation comprises:

and inputting the direct current voltage into a low-pass filter for low-pass filtering, and taking the filtered direct current voltage as a direct current voltage reference value for modulation.

7. The method according to claim 1, wherein the method further comprises:

determining the output voltage amplitude reference value by adopting a droop control strategy comprises the following steps:

determining an output voltage amplitude U _o And reactive power Q;

based on the output voltage amplitude U _o Output voltage amplitude command value U _ref The reactive power Q and the reactive power command value Q _ref Determining an output voltage amplitude reference value E by adopting the droop control strategy _mod ；

Wherein,，k _q is the reactive droop coefficient, k, in the droop control strategy _u Is the voltage droop coefficient in the droop control strategy.

8. The method of claim 1, wherein said adjusting said three-phase output voltage based on said modulated wave comprises:

determining the topological structure and the modulation strategy of the network-structured converter;

And determining a driving signal of a switching tube of the grid-connected converter based on the modulation wave and the modulation strategy so that the grid-connected converter performs electric energy conversion based on the driving signal.

9. An apparatus for controlling a grid-tied converter for converting a dc voltage of a dc side power source to a three-phase output voltage, the apparatus comprising:

a detection module for determining the DC voltage output by the DC side power supply and the DC voltage U _dc And a DC voltage command value U _dcref Is a direct current voltage difference of (2)Wherein->；

A phase determining module for differentiating the DC voltageThe input inertia-damping control module is used for respectively processing the direct current voltage difference through the parallel forward damping channel and the inertia control channel to determine the phase reference value theta of the three-phase output voltage _mod Frequency reference value f _mod ；

A modulation module for based on the phase reference value theta _mod Output voltage amplitude reference value E _mod Determining a modulation wave u of the three-phase output voltage _mod(a,b,c) So that the grid-formed converter adjusts the three-phase output voltage u based on the modulation wave _(a,b,c) ；

The phase determining module is specifically configured to:

differential the DC voltage Inputting the inertia control path, and in the inertia control path: inertia coefficient k based on inertia controller _inertia Treating the DC voltage difference->And combining the rated frequency value f of the three-phase output voltage ₀ Determining the frequency reference value f _mod The method comprises the steps of carrying out a first treatment on the surface of the Based on the frequency reference value f _mod Determining a first phase θ ₁ ；

Differential the DC voltageInputting the forward damping channel to be in the forward damping channel: damping coefficient D based on damping controller _damp Treating the DC voltage difference->Determining the second phase θ ₂ ；

Wherein,；/>；/>；/>。

10. the apparatus of claim 9, wherein the apparatus further comprises:

the amplitude determining module is used for determining the output voltage amplitude reference value by adopting a droop control strategy;

the amplitude determining module is specifically configured to:

determining an output voltage amplitude U _o And reactive power Q;

based on the transportationOutput voltage amplitude U _o Output voltage amplitude command value U _ref The reactive power Q and the reactive power command value Q _ref Determining an output voltage amplitude reference value E by adopting the droop control strategy _mod ；

11. A grid-tied converter having a pre-power source wide adaptability, the grid-tied converter comprising:

the three-phase converter is used for converting the direct-current voltage output by the direct-current side power supply into three-phase output voltage; and

a control circuit for performing the method for controlling a grid-connected converter according to any one of claims 1 to 8 to determine a modulation wave and superimpose the modulation wave on the three-phase output voltage so that the grid-connected converter has a front-stage power source universality.

12. A computer-readable storage medium storing a computer program which, when executed by a computer, implements the grid-connected inverter control method according to any one of claims 1 to 8.