Multi-inverter parallel improved reactive droop control method and system

Abstract

The invention discloses a multi-inverter parallel connection improved reactive droop control method and system, and relates to the technical field of inverter operation voltage regulation, and the method comprises the steps: obtaining first data of the output side of an inverter, and calculating second data outputted in real time according to the first data of the output side of the inverter; performing droop control on the second data to obtain given values of frequency and voltage, obtaining PWM given voltage through voltage and current double-closed-loop control according to the given values of the voltage, and performing dynamic adjustment on the PWM given voltage through energy storage adjustment; the phase of the inverter 1 is collected in real time through SOGI-PLL pre-synchronization and serves as phase input of the inverter 2. Through the improvement of the variable reactive droop coefficient, the drop phenomenon of the system voltage is relieved, the stability of the output voltage of the inverter is kept, the influence of voltage fluctuation on the system is reduced, and the electric energy quality of the system is improved.

Description

Technical Field

[0001] The invention relates to the technical field of inverter operation voltage regulation, and in particular to an improved reactive power droop control method and system for multiple inverters in parallel. Background Art

[0002] With the rapid development of society, people's living standards must also develop and improve rapidly. As an important part of society, the stability and reliability of the power system are important topics of global research. The balanced distribution of output power affects the stability and service life of the inverter. In a system where multiple inverters are running in parallel, the way to control the load depends on the capacity parameters of each inverter. Therefore, the current research focus in the industry is on the reasonable distribution of the output power of a multi-inverter parallel system running in isolated grid mode.

[0003] The multi-inverter parallel structure has high design flexibility, which helps to expand capacity as needed. At the same time, a single inverter can also be replaced and repaired independently, and the design complexity and construction cost are relatively small. However, the parallel structure will also cause uneven power distribution due to the mismatch of equivalent line impedance, resulting in problems such as circulating current and system instability. The internal power loop, internal voltage loop, and current loop used in droop control together constitute a multi-inverter parallel control system, and their coordinated work can effectively suppress high-frequency oscillations and damping. However, in the traditional droop control method, the amplitude fluctuation of the grid voltage and the instability of the frequency will be detrimental to the uniformity of power distribution between inverters, and also slow down the system's response capability.

[0004] When multiple inverters are operated in parallel, this method can effectively improve the degree of reactive power distribution, reduce the occurrence of overload operation of a single inverter, and thus significantly reduce the loss of inverter bridge power devices. At the same time, this method can also improve the system voltage drop phenomenon and improve the stability of parallel operation of multiple inverters. Previously, Zhang Heng et al. published a study on the improved droop control of inverter parallel operation in electrical engineering technology. They added an integral link on the basis of the traditional reactive voltage droop equation, and corrected the droop coefficient to a linear function containing power, and achieved a certain reactive power distribution and improvement of system voltage drop. On this basis, this patent adds a SOGI-PLL pre-synchronization module to reduce the circulating current and overload caused by phase differences between multiple inverters. Summary of the invention

[0005] The purpose of this section is to summarize some aspects of embodiments of the present invention and briefly introduce some preferred embodiments. Some simplifications or omissions may be made in this section and the specification abstract and the invention title of this application to avoid blurring the purpose of this section, the specification abstract and the invention title, and such simplifications or omissions cannot be used to limit the scope of the present invention.

[0006] In view of the above existing problems, the present invention is proposed.

[0007] Therefore, the present invention provides a method and system for improving reactive power droop control of multiple inverters in parallel, which can solve the problems mentioned in the background technology.

[0008] In order to solve the above technical problems, the present invention provides the following technical solutions:

[0009] In a first aspect, the present invention provides an improved reactive droop control method for multiple inverters in parallel, comprising: acquiring first data on an inverter output side, and calculating second data output in real time according to the first data on the inverter output side;

[0010] The second data is used to obtain given values ​​of frequency and voltage through droop control, and a PWM given voltage is obtained through voltage and current double closed-loop control according to the given value of voltage;

[0011] The phase of inverter 1 is acquired in real time through SOGI-PLL pre-synchronization and used as the phase input of inverter 2.

[0012] As a preferred solution of the improved reactive droop control method for multiple inverters in parallel according to the present invention, wherein: the first data includes voltage data, current data, temperature data, humidity data, inverter fault data, grid frequency data and inverter output harmonic data;

[0013] The second data includes active power data and reactive power data;

[0014] Calculating the second data output in real time includes:

[0015]

[0016] Among them, P and Q are the active power and reactive power output by the inverter respectively. is the power factor angle, X is the line reactance, U is the inverter output voltage, and E is the grid-side voltage;

[0017] An environmental parameter compensation mechanism is introduced to compensate the second data output in real time, and the calculation formula is as follows:

[0018]

[0019]

[0020] Among them, Pa is the active power after compensation, Q a is the reactive power after replenishment, α is the temperature compensation coefficient, β is the humidity compensation coefficient, T is temperature, and H is humidity.

[0021] As a preferred solution of the improved reactive droop control method for multiple inverters in parallel according to the present invention, the second data output in real time by the calculation includes:

[0022] According to the power expression of the inverter parallel system output, the unevenness of the output power G (%) is measured, and the calculation formula is as follows:

[0023]

[0024] Among them, P1 is the output power of inverter 1, P2 is the output power of inverter 2, P n is the rated power of the system.

[0025] As a preferred solution of the improved reactive droop control method for multiple inverters in parallel according to the present invention, the step of obtaining given values ​​of voltage and frequency includes:

[0026] The droop control equation is obtained by the resistance and inductance of the line impedance. When the system impedance characteristic is resistive or inductive, the droop control equation is composed of the active and reactive power sharing formula, and the calculation formula is as follows:

[0027]

[0028] Among them, f and U are the frequency and amplitude of the inverter output voltage respectively, f n , U n are the rated frequency and amplitude of the inverter output voltage, m and n are the inverter active frequency droop coefficient and reactive voltage droop coefficient, respectively. n , Q n are the rated active power and reactive power of the inverter respectively, P and Q are the output active power and reactive power of the inverter respectively.

[0029] As a preferred solution of the improved reactive droop control method of multiple inverters in parallel described in the present invention, wherein: the droop control maintains the frequency and voltage of the power grid within a predetermined range by adjusting the output power of the generator; in the reactive voltage regulation characteristic curve of the droop control, a reactive droop coefficient variable with reactive power as a variable is used to overcome the voltage drop problem.

[0030] As a preferred solution of the improved reactive power droop control method of multiple inverters in parallel according to the present invention, the calculation formula of the PWM given voltage is as follows:

[0031]

[0032] Among them, V dref 、V qref is the dq axis component given by the PWM voltage, i d 、i qis the dq axis component of the output current, R and L are the line impedances;

[0033] The dynamic adjustment of the PWM given voltage includes:

[0034] When the system starts, set the initial voltage of the energy storage system;

[0035] Initialize control algorithm parameters; obtain the current actual voltage through the voltage sensor, obtain the current temperature and humidity through the environmental sensor, and set the target voltage according to system requirements or external instructions;

[0036] Calculate the error between the current actual voltage and the target voltage to obtain the voltage error;

[0037] The temperature compensation coefficient is multiplied by the difference between the current temperature and the reference temperature, and the humidity compensation coefficient is multiplied by the difference between the current humidity and the reference humidity, and the temperature compensation value and the humidity compensation value are added together to obtain the total environmental compensation value;

[0038] Combining the voltage error and the total environmental compensation value, the energy storage system is adjusted;

[0039] If the compensated voltage error is positive, the voltage of the energy storage system is increased;

[0040] If the compensated voltage error is a negative value, reducing the voltage of the energy storage system;

[0041] The adjusted voltage is transmitted to the PWM controller, and the PWM controller adjusts the duty cycle of the PWM signal according to the adjusted voltage signal to achieve precise control of the output voltage of the load or inverter.

[0042] As a preferred solution of the improved reactive droop control method of multiple inverters in parallel according to the present invention, wherein: the phase of the acquisition inverter 1 includes:

[0043] The frequency output by the droop control unit is used as the input resonant frequency of the SOGI unit in the frequency locked loop;

[0044] The angular frequency compensation calculated by the frequency-locked loop is added to the active power-frequency link to adjust the output frequency ω of the droop control unit, and the droop control unit is combined with the SOGI-PLL to generate a closed-loop feedback;

[0045] The inverter 1 output voltage U abc By transforming the coordinate system to the dq0 coordinate system, the component U d and U q , and then import them into two SOGI-PLL units respectively;

[0046] The frequency obtained by the active power-frequency link of the inverter 1 droop control unit is used as the resonant frequency of SOGI, and the voltage component is extracted through two SOGI-PLL units;

[0047] The angular frequency error is added to the active power-frequency loop of the droop control unit of the inverter 2, and the output frequency and phase of the droop control unit are adjusted;

[0048] Through the fixed difference of line impedance, the output voltage of inverter 2 is made to track the frequency and phase of the output voltage of inverter 1, thus completing the control.

[0049] In a second aspect, the present invention provides an improved reactive droop control system for multiple inverters in parallel, which comprises: a data acquisition and calculation module, a droop control module and a pre-synchronization phase control module;

[0050] The data acquisition and calculation module is used to obtain first data on the output side of the inverter, and calculate second data output in real time according to the first data on the output side of the inverter;

[0051] The droop control module is used to obtain given values ​​of frequency and voltage by droop control of the second data, and obtain a PWM given voltage by voltage and current double closed-loop control according to the given value of voltage;

[0052] The pre-synchronization phase control module is used to collect the phase of the inverter 1 in real time through SOGI-PLL pre-synchronization, and use it as the phase input of the inverter 2.

[0053] In a third aspect, the present invention provides a computer device, including a memory and a processor, wherein the memory stores a computer program, wherein: when the processor executes the computer program, the steps of the improved reactive power droop control method for multiple inverters in parallel are implemented.

[0054] In a fourth aspect, the present invention provides a computer-readable storage medium having a computer program stored thereon, wherein: when the computer program is executed by a processor, the steps of an improved reactive power droop control method for multiple inverters in parallel are implemented.

[0055] Compared with the prior art, the beneficial effect of the present invention is that by correcting the reactive droop coefficient to a variable containing power, the inverter can more accurately distribute reactive power when operating in parallel, avoiding the problem of some inverters bearing too much or too little reactive power, thereby improving the operating efficiency and stability of the system. The improved reactive droop coefficient helps to balance the loads of each inverter and avoid the situation where a single inverter is overloaded; this helps to extend the service life of the equipment and reduce equipment damage and maintenance frequency; through the improvement of the variable reactive droop coefficient, the voltage drop phenomenon of the system is effectively alleviated. This helps to maintain the stability of the output voltage of the inverter, reduce the impact of voltage fluctuations on the system, and improve the power quality of the system. BRIEF DESCRIPTION OF THE DRAWINGS

[0056] In order to more clearly illustrate the technical solutions of the embodiments of the present invention, the following briefly introduces the drawings required for use in the description of the embodiments. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without creative work.

[0057] Figure 1 A method flow chart of a method and system for improving reactive power droop control of multiple inverters in parallel provided by an embodiment of the present invention;

[0058] Figure 2 An internal structural diagram of a computer device for an improved reactive power droop control method and system for multiple inverters in parallel provided by an embodiment of the present invention;

[0059] Figure 3 A basic control principle block diagram of a multi-inverter parallel improved reactive power droop control method and system provided by an embodiment of the present invention;

[0060] Figure 4 A core reactive power droop control module of a multi-inverter parallel improved reactive power droop control method and system provided by an embodiment of the present invention;

[0061] Figure 5 A SOGI principle block diagram of an improved reactive power droop control method and system for multiple inverters in parallel provided by an embodiment of the present invention;

[0062] Figure 6 An improved reactive droop control method and system for parallel connection of multiple inverters provided by an embodiment of the present invention is that when the load is increased by 5kW suddenly at 3s, and then removed at 4s, the inverter outputs active power diagram;

[0063] Figure 7An improved reactive power droop control method and system for multi-inverter parallel connection provided by an embodiment of the present invention is improved. Before running for 3s, a 5kW load is suddenly added, and then removed at 4s, and the inverter outputs reactive power diagram;

[0064] Figure 8 An improved reactive power droop control method and system for parallel connection of multiple inverters provided by an embodiment of the present invention is improved. After running for 3s, a 5kW load is suddenly added and then removed at 4s. The inverter outputs reactive power diagram;

[0065] Fig. 9 An improved reactive power droop control method and system for parallel connection of multiple inverters provided in one embodiment of the present invention is shown in the diagram of the grid-side output voltage after the load is suddenly increased by 5kW at 3s and then removed at 4s. DETAILED DESCRIPTION

[0066] In order to make the above-mentioned purposes, features and advantages of the present invention more understandable, the specific implementation methods of the present invention are described in detail below in conjunction with the drawings of the specification. Obviously, the described embodiments are part of the embodiments of the present invention, but not all of them. Based on the embodiments of the present invention, all other embodiments obtained by ordinary persons in the art without creative work should fall within the scope of protection of the present invention.

[0067] In the following description, many specific details are set forth to facilitate a full understanding of the present invention, but the present invention may also be implemented in other ways different from those described herein, and those skilled in the art may make similar generalizations without violating the connotation of the present invention. Therefore, the present invention is not limited to the specific embodiments disclosed below.

[0068] Secondly, the term "one embodiment" or "embodiment" as used herein refers to a specific feature, structure, or characteristic that may be included in at least one implementation of the present invention. The term "in one embodiment" that appears in different places in this specification does not necessarily refer to the same embodiment, nor does it refer to a separate or selective embodiment that is mutually exclusive with other embodiments.

[0069] Example 1

[0070] Reference Figure 1-Figure 2 , which is the first embodiment of the present invention, and provides a method for improving reactive power droop control of multiple inverters in parallel, comprising:

[0071] The present application provides a method that can effectively solve the above-mentioned problems. Next, multiple embodiments will be combined to explain in detail how to implement the improved reactive power droop control method of multiple inverters in parallel;

[0072] Figure 1A method flow chart of a method and system for improving reactive power droop control of multiple inverters in parallel is shown, including:

[0073] S1: Acquire first data on the output side of the inverter, and calculate second data output in real time according to the first data on the output side of the inverter;

[0074] Further, the first data includes voltage data, current data, temperature data, humidity data, inverter fault data, grid frequency data, and inverter output harmonic data;

[0075] The second data includes active power data and reactive power data;

[0076] Further, calculating the second data output in real time includes:

[0077]

[0078] Among them, P and Q are the active power and reactive power output by the inverter respectively. is the power factor angle, X is the line reactance, U is the inverter output voltage, and E is the grid-side voltage;

[0079] It should be noted that traditional inverter control systems usually only focus on limited operating parameters, making it difficult to fully reflect the working status of the inverter, resulting in insufficient control accuracy and response speed. The present invention can more accurately calculate real-time power data by comprehensively acquiring the operating data of the inverter, thereby improving the accuracy and real-time performance of the control. Calculating the second data (active power and reactive power) can provide a more accurate real-time operating status and provide accurate data support for subsequent control algorithms. For example, by calculating active power and reactive power in real time, dynamic adjustment of the inverter output power can be achieved to ensure the stability and efficiency of the system operation. Assuming that the output voltage of the inverter fluctuates during operation, the actual active and reactive power changes can be quickly calculated through real-time voltage data and current data, so that the output of the inverter can be adjusted in time to avoid power imbalance or overload;

[0080] Furthermore, an environmental parameter compensation mechanism is introduced to compensate the second data output in real time to improve the calculation accuracy. The calculation formula is as follows:

[0081]

[0082]

[0083] Among them, Pa is the active power after compensation, Q a is the reactive power after replenishment, α is the temperature compensation coefficient, β is the humidity compensation coefficient, T is the temperature, and H is the humidity;

[0084] When T and H are zero, the compensation factor is 1, and the formula degenerates into the original active power and reactive power calculation formula;

[0085] It should be noted that the temperature compensation coefficient α and the humidity compensation coefficient β in the present invention are defined according to experimental data, and the specific calculation formula is as follows:

[0086]

[0087] Among them, k T is the proportional constant of the effect of temperature change on power, ΔP T is the power change measured under temperature change, P0 is the reference power value;

[0088]

[0089] Among them, k H is the proportional constant of the effect of humidity change on power, ΔP H is the power change measured under humidity change, P0 is the reference power value;

[0090] The data collection method is as follows:

[0091] Measure active power and reactive power changes under different temperature and humidity conditions in the laboratory or on site;

[0092] Record the reference power value P0 (power measured under standard conditions);

[0093] Measure the effect of temperature change ΔT and humidity change ΔH on power and get ΔP T and ΔP H ;

[0094] Calculate the temperature compensation coefficient α and humidity compensation coefficient β.

[0095] Specifically, assuming that kT=0.01 and kH=0.02 are determined through experiments or models, and that ΔPT=5kW under a certain temperature change, ΔPH=3kW under a certain humidity change, and the reference power P0=100kW, the calculation result of the temperature compensation coefficient can be obtained as follows:

[0096]

[0097] The calculation result of humidity compensation coefficient is:

[0098]

[0099] S2: obtaining given values ​​of voltage and frequency by droop control of the second data;

[0100] Furthermore, according to the power expression of the inverter parallel system output, the unevenness of the output power G (%) is measured, and the calculation formula is as follows:

[0101]

[0102] Among them, P1 is the output power of inverter 1, P2 is the output power of inverter 2, P n is the system rated power;

[0103] Furthermore, the droop control equation depends on the resistance and inductance of the line impedance. When the system impedance characteristic is resistive or inductive, the droop control equation is composed of the active and reactive power sharing formula, and the calculation formula is as follows:

[0104]

[0105] Among them, f and U are the frequency and amplitude of the inverter output voltage respectively, f n , U n are the rated frequency and amplitude of the inverter output voltage, m and n are the inverter active frequency droop coefficient and reactive voltage droop coefficient, respectively. n , Q n are the rated active power and reactive power of the inverter respectively, P and Q are the output active power and reactive power of the inverter respectively.

[0106] Furthermore, the droop control adjusts the output voltage and frequency of each distributed power source according to the active-frequency and reactive-voltage characteristic curves;

[0107] Maintain the frequency and voltage of the power grid within a predetermined range by adjusting the output power of the generator;

[0108] The system's active power shortage causes the system frequency to drop. The frequency drop stimulates the synchronous generator sets to generate more active power. Similarly, the change in reactive power will also cause the voltage to change, so that the active and reactive output power at different frequencies can be reasonably distributed.

[0109] Furthermore, it can be seen from the reactive voltage regulation characteristic curve in the droop control unit that the traditional fixed reactive droop coefficient will bring about certain voltage drop problems, while the reactive droop coefficient variable with reactive power as the variable can overcome this problem well;

[0110] The droop coefficient is adjusted in real time with the change of reactive power, thereby improving the reactive droop adjustment speed and accuracy. The adjustment method includes: when the reactive power increases, the reactive droop coefficient decreases; when the reactive power decreases, the reactive droop coefficient increases.

[0111] It should be noted that in the traditional method, the control of voltage and frequency often relies on fixed preset values, which is difficult to cope with changes in actual operation. However, the present invention can dynamically adjust the given values ​​of voltage and frequency according to real-time data through droop control, thereby improving the response speed and adaptability of the system. For example, when the load of the power grid changes, by adjusting the given values ​​of voltage and frequency in real time, it can quickly adapt to the changes and maintain the stability of the system.

[0112] In a multi-inverter parallel system, the uneven output power of each inverter will cause system instability. The present invention ensures the balance and stability of system operation by measuring and adjusting power distribution. If the output power of an inverter in the system is obviously too high, the power unevenness can be reduced by adjusting its output, thereby improving the overall stability of the system.

[0113] The traditional fixed droop control equation is not effective under different line impedances. The present invention improves the adaptability and control accuracy of the system by adjusting the droop control equation according to the actual line impedance characteristics. When the line impedance changes, the stability and accuracy of the inverter output power can be ensured by adjusting the droop control equation.

[0114] S3: According to the voltage given value, the PWM given voltage is obtained through the voltage and current double closed-loop control, and the PWM given voltage is dynamically adjusted through energy storage regulation;

[0115] Furthermore, the PWM given voltage is obtained through voltage and current double closed-loop control according to the voltage given value. The calculation formula is as follows:

[0116]

[0117] Among them, V dref 、V qref is the dq axis component given by the PWM voltage, i d 、i q is the dq axis component of the output current, R and L are the line impedances.

[0118] Furthermore, dynamically adjusting the PWM given voltage includes:

[0119] When the system starts, set the initial voltage of the energy storage system;

[0120] Initialize control algorithm parameters, including gain coefficient, temperature compensation coefficient, humidity compensation coefficient, etc.;

[0121] The current actual voltage is obtained through the voltage sensor, the current temperature and humidity are obtained through the environmental sensor, and the target voltage is set according to system requirements or external instructions;

[0122] Calculate the error between the current actual voltage and the target voltage to obtain the voltage error;

[0123] The temperature compensation coefficient is multiplied by the difference between the current temperature and the reference temperature, and the humidity compensation coefficient is multiplied by the difference between the current humidity and the reference humidity, and the temperature compensation value and the humidity compensation value are added together to obtain the total environmental compensation value;

[0124] Combining the voltage error and the total environmental compensation value, the energy storage system is adjusted;

[0125] If the compensated voltage error is positive, increase the voltage of the energy storage system (charge);

[0126] If the compensated voltage error is negative, reduce the voltage of the energy storage system (discharge);

[0127] The adjusted voltage is transmitted to the PWM controller, and the PWM controller adjusts the duty cycle of the PWM signal according to the adjusted voltage signal to achieve precise control of the output voltage of the load or inverter.

[0128] S4: The phase of inverter 1 is collected in real time through SOGI-PLL pre-synchronization and used as the phase input of inverter 2.

[0129] Furthermore, collecting the phase of inverter 1 includes:

[0130] The frequency output by the droop control unit is used as the input resonant frequency of the SOGI unit in the frequency locked loop;

[0131] The angular frequency compensation calculated by the frequency-locked loop is added to the active power-frequency link to adjust the output frequency ω of the droop control unit, as shown in Figure 4 As shown, the droop control unit and SOGI-PLL are combined to generate a closed-loop feedback.

[0132] Furthermore, the inverter 1 output voltage U abc By transforming the coordinate system to the dq0 coordinate system, the component U d and U q , and then import them into two SOGI-PLL units respectively;

[0133] The frequency obtained by the active power-frequency link of the inverter 1 droop control unit is used as the resonant frequency of SOGI, and the voltage component is extracted through two SOGI-PLL units;

[0134] The angular frequency error is added to the active power-frequency loop of the droop control unit of the inverter 2, and the output frequency and phase of the droop control unit are adjusted;

[0135] Through the fixed difference of line impedance, the output voltage of inverter 2 is made to track the frequency and phase of the output voltage of inverter 1.

[0136] It should be noted that the phase synchronization in the traditional method usually relies on fixed preset values ​​or delayed sampling, which makes it difficult to cope with the frequency and phase changes in actual operation. However, the present invention can cope with these changes more flexibly by real-time acquisition and synchronization of phases, thereby improving the stability and response speed of the system. For example, when the load of the power grid changes, the real-time synchronization of phases can quickly adapt to the changes, maintain the stability of the system, and avoid power imbalance and harmonic problems.

[0137] The traditional fixed frequency control method is not flexible enough to deal with dynamic load changes, while the present invention can dynamically adjust the frequency and phase through a closed-loop feedback mechanism to ensure the stable operation of the system. For example, in the case of a sudden increase in load, the system can quickly adjust the frequency through a closed-loop feedback mechanism to avoid large fluctuations in the grid frequency.

[0138] The traditional three-phase voltage processing method is highly complex and difficult to achieve real-time control. However, the present invention simplifies the voltage processing process through coordinate system transformation, improving the real-time performance and accuracy of control. For example, when a power grid fails, the voltage component can be quickly extracted and the phase can be adjusted through coordinate system transformation and SOGI-PLL processing to ensure the stable operation of the system.

[0139] In summary, the present invention uses SOGI-PLL pre-synchronization technology, combines real-time data to dynamically adjust the given values ​​of phase and frequency, adopts a closed-loop feedback mechanism to improve the control accuracy of frequency and phase, and simplifies the voltage processing process through coordinate system transformation. These technical measures not only solve the problems of low control accuracy and slow response speed in traditional methods, but also improve the stability and adaptability of the system, providing technical support for achieving efficient and stable inverter parallel operation.

[0140] Furthermore, the present embodiment also provides a multi-inverter parallel improved reactive power droop control system, comprising: a data acquisition and calculation module, a droop control module and a pre-synchronization phase control module;

[0141] The data acquisition and calculation module is used to obtain first data on the output side of the inverter, and calculate second data output in real time according to the first data on the output side of the inverter;

[0142] The droop control module is used to obtain the given values ​​of frequency and voltage by droop control of the second data, and obtain the PWM given voltage by voltage and current double closed-loop control according to the given value of voltage;

[0143] The pre-synchronization phase control module is used to collect the phase of inverter 1 in real time through SOGI-PLL pre-synchronization and use it as the phase input of inverter 2.

[0144] This embodiment also provides a computer device, which may be a terminal, and its internal structure diagram may be as shown in FIG. Figure 2 As shown. The computer device includes a processor, a memory, a communication interface, a display screen and an input device connected through a system bus. Among them, the processor of the computer device is used to provide computing and control capabilities. The memory of the computer device includes a non-volatile storage medium and an internal memory. The non-volatile storage medium stores an operating system and a computer program. The internal memory provides an environment for the operation of the operating system and the computer program in the non-volatile storage medium. The communication interface of the computer device is used to communicate with an external terminal in a wired or wireless manner, and the wireless manner can be achieved through WIFI, an operator network, NFC (near field communication) or other technologies. When the computer program is executed by the processor, a comprehensive evaluation method suitable for orderly access of large-scale distributed power sources is implemented. The display screen of the computer device can be a liquid crystal display screen or an electronic ink display screen, and the input device of the computer device can be a touch layer covered on the display screen, or a key, trackball or touchpad set on the computer device housing, or an external keyboard, touchpad or mouse.

[0145] This embodiment further provides a computer-readable storage medium, on which a computer program is stored. When the computer program is executed by a processor, the following steps are implemented:

[0146] Acquire first data on the output side of the inverter, and calculate second data output in real time according to the first data on the output side of the inverter;

[0147] The second data is controlled by droop to obtain given values ​​of frequency and voltage, and a PWM given voltage is obtained by voltage and current double closed-loop control according to the given value of voltage;

[0148] The phase of inverter 1 is acquired in real time through SOGI-PLL pre-synchronization and used as the phase input of inverter 2.

[0149] Example 2

[0150] Reference Figure 1 - Figure 2 , which is the second embodiment of the present invention, and this embodiment provides an improved reactive power droop control method for multiple inverters in parallel. In order to verify the beneficial effects of the present invention, scientific demonstration is carried out through economic benefit calculation and simulation experiments.

[0151] In this experiment, in order to verify the effectiveness of the improved reactive power droop control method of multiple inverters in parallel, an experimental device was established, including two parallel inverter systems. The experimental environment simulates typical power grid operating conditions, and the experimental data is processed through real-time acquisition and calculation. The specific steps are as follows:

[0152] Experimental setup: The experimental platform includes two parallel inverters (Inverter 1 and Inverter 2), a data acquisition module, a droop control unit, a SOGI-PLL unit, and a load simulator. The rated power of the inverter is 10kW, and the experiment is carried out under different load conditions.

[0153] Data acquisition: The data acquisition module is used to obtain the first data on the inverter output side, including voltage data (V), current data (I), temperature data (T), humidity data (H), inverter fault data, grid frequency data (f) and inverter output harmonic data (Harmonic). These data are monitored and recorded in real time through sensors.

[0154] Real-time data calculation: Based on the collected first data, calculate the second data output in real time, including active power (P) and reactive power (Q).

[0155] Droop control: The calculated active power and reactive power data are used to obtain the given values ​​of frequency and voltage through droop control. The droop control equation is as follows:

[0156] PWM given voltage calculation: According to the given value of voltage, the PWM given voltage is obtained through voltage and current double closed-loop control.

[0157] Phase synchronization and adjustment: The phase of inverter 1 is collected in real time through SOGI-PLL pre-synchronization and used as the phase input of inverter 2. The output voltage Uabc of inverter 1 is transformed into the components Ud and Uq in the dq0 coordinate system through the coordinate system, and then imported into two SOGI-PLL units for processing. By adjusting the phase and frequency of inverter 2, its output voltage tracks the output voltage of inverter 1.

[0158] Data recording and analysis: Under different load conditions, record the changes of various parameters. The experimental data are recorded in Tables 1 and 2, which respectively show the active power and reactive power data under different load conditions, as well as the changes of frequency and voltage.

[0159] Table 1 Active power and reactive power data under different load conditions

[0160]

[0161]

[0162] Table 2 Frequency and voltage data under different load conditions

[0163]

[0164] From the data in Table 1 and Table 2, it can be seen that under different load conditions, the inverter parallel system can effectively maintain the frequency and voltage of the power grid within the predetermined range. The specific analysis is as follows:

[0165] Active power and reactive power distribution: Under light load conditions, the active power and reactive power of the two inverters are basically the same, indicating that the system can distribute the load evenly. Under heavy load conditions, the active power and reactive power of the two inverters can also be consistent, which verifies that the method of the present invention has good power distribution capabilities under different load conditions.

[0166] Frequency and voltage stability: Under different load conditions, the system frequency and voltage change little, the maximum frequency error does not exceed 0.06Hz, and the maximum voltage error does not exceed 0.7V, indicating that the method of the present invention can effectively maintain the frequency and voltage stability of the power grid. This is due to the application of droop control and SOGI-PLL pre-synchronization technology, which ensures the accuracy of inverter phase synchronization and frequency adjustment.

[0167] Effect of droop control: By adjusting the output power of the generator, the system can overcome the voltage drop problem, especially under heavy load conditions, the voltage error is still maintained in a small range. This verifies the effectiveness of the method of the present invention in dealing with large load fluctuations.

[0168] Innovation and advantages: Compared with the prior art, the method of the present invention improves the response speed and stability of the system through the combination of multi-parameter data acquisition, real-time calculation and droop control. In particular, under the application of SOGI-PLL pre-synchronization technology, high-precision phase synchronization and frequency adjustment are achieved, effectively overcoming the phase drift and frequency fluctuation problems in the prior art.

[0169] It should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention rather than to limit it. Although the present invention has been described in detail with reference to the preferred embodiments, those skilled in the art should understand that the technical solutions of the present invention may be modified or replaced by equivalents without departing from the spirit and scope of the technical solutions of the present invention, which should all be included in the scope of the claims of the present invention.

[0170] Those skilled in the art will appreciate that the embodiments of the present application can be provided as methods, systems, or computer program products. Therefore, the present application can adopt the form of complete hardware embodiments, complete software embodiments, or embodiments in combination with software and hardware. Moreover, the present application can adopt the form of a computer program product implemented on one or more computer-usable storage media (including but not limited to disk storage, CD-ROM, optical storage, etc.) that contain computer-usable program code. The scheme in the embodiments of the present application can be implemented in various computer languages, for example, object-oriented programming language Java and literal scripting language JavaScript, etc.

[0171] The present application is described with reference to the flowcharts and / or block diagrams of the methods, devices (systems), and computer program products according to the embodiments of the present application. It should be understood that each process and / or box in the flowchart and / or block diagram, as well as the combination of the processes and / or boxes in the flowchart and / or block diagram, can be implemented by computer program instructions. These computer program instructions can be provided to a processor of a general-purpose computer, a special-purpose computer, an embedded processor, or other programmable data processing device to generate a machine, so that the instructions executed by the processor of the computer or other programmable data processing device generate instructions for implementing the processes in the flowchart and / or block diagram. Figure 1 A process or multiple processes and / or boxes Figure 1 A device that provides the functions specified in a block or multiple blocks.

[0172] These computer program instructions may also be stored in a computer-readable memory capable of directing a computer or other programmable data processing device to operate in a specific manner, so that the instructions stored in the computer-readable memory produce an article of manufacture comprising an instruction device, which implements the process Figure 1 A process or multiple processes and / or boxes Figure 1 A function specified in one or more boxes.

[0173] These computer program instructions can also be loaded onto a computer or other programmable data processing device so that a series of operating steps are executed on the computer or other programmable device to produce a computer-implemented process, thereby providing instructions for implementing the process. Figure 1 A process or multiple processes and / or boxes Figure 1 The steps for the functions specified in one or more boxes.

[0174] Although the preferred embodiments of the present application have been described, those skilled in the art may make other changes and modifications to these embodiments once they have learned the basic creative concept. Therefore, the appended claims are intended to be interpreted as including the preferred embodiments and all changes and modifications falling within the scope of the present application.

[0175] Obviously, those skilled in the art can make various changes and modifications to the present application without departing from the spirit and scope of the present application. Thus, if these modifications and variations of the present application fall within the scope of the claims of the present application and their equivalents, the present application is also intended to include these modifications and variations.

Claims

1. An improved reactive power droop control method for multiple inverters in parallel, Features: The method comprises acquiring first data at an output side of an inverter, and calculating second data output in real time according to the first data at the output side of the inverter; The second data is used to obtain given values ​​of frequency and voltage through droop control, and a PWM given voltage is obtained through voltage and current double closed-loop control according to the given value of the voltage, and the PWM given voltage is dynamically adjusted through energy storage regulation; The phase of inverter 1 is acquired in real time through SOGI-PLL pre-synchronization and used as the phase input of inverter 2.

2. The improved reactive power droop control method for multiple inverters in parallel as claimed in claim 1, Features: The first data includes voltage data, current data, temperature data, humidity data, inverter fault data, grid frequency data, and inverter output harmonic data; The second data includes active power data and reactive power data; Calculating the second data output in real time includes: Among them, P and Q are the active power and reactive power output by the inverter respectively. is the power factor angle, X is the line reactance, U is the inverter output voltage, and E is the grid-side voltage; An environmental parameter compensation mechanism is introduced to compensate the second data output in real time, and the calculation formula is as follows: Among them, Pa is the active power after compensation, Q a is the reactive power after replenishment, α is the temperature compensation coefficient, β is the humidity compensation coefficient, T is temperature, and H is humidity.

3. The improved reactive power droop control method for multiple inverters in parallel as claimed in claim 2, Features: The second data output in real time by the calculation includes: According to the power expression of the inverter parallel system output, the unevenness of the output power G (%) is measured, and the calculation formula is as follows: Among them, P 1 is the output power of inverter 1, P 2 is the output power of inverter 2, P n is the rated power of the system.

4. The improved reactive power droop control method for multiple inverters in parallel as claimed in claim 3, Features: The step of obtaining given values ​​of voltage and frequency includes: The droop control equation is obtained by the resistance and inductance of the line impedance. When the system impedance characteristic is resistive or inductive, the droop control equation is composed of the active and reactive power sharing formula, and the calculation formula is as follows: Among them, f and U are the frequency and amplitude of the inverter output voltage respectively, f n , U n are the rated frequency and amplitude of the inverter output voltage, m and n are the inverter active frequency droop coefficient and reactive voltage droop coefficient, respectively. n , Q n are the rated active power and reactive power of the inverter respectively, P and Q are the output active power and reactive power of the inverter respectively.

5. The improved reactive power droop control method for multiple inverters in parallel as claimed in claim 4, Features: The droop control maintains the frequency and voltage of the power grid within a predetermined range by adjusting the output power of the generator; in the reactive voltage regulation characteristic curve of the droop control, a reactive droop coefficient variable with reactive power as a variable is used to overcome the voltage drop problem.

6. The improved reactive power droop control method for multiple inverters in parallel as claimed in claim 5, Features: The calculation formula of the PWM given voltage is as follows: Among them, V dref 、V qref is the dq axis component given by the PWM voltage, i d 、i q is the dq axis component of the output current, R and L are the line impedances; The dynamic adjustment of the PWM given voltage includes: When the system starts, set the initial voltage of the energy storage system; Initialize control algorithm parameters; obtain the current actual voltage through the voltage sensor, obtain the current temperature and humidity through the environmental sensor, and set the target voltage according to system requirements or external instructions; Calculate the error between the current actual voltage and the target voltage to obtain the voltage error; The temperature compensation coefficient is multiplied by the difference between the current temperature and the reference temperature, and the humidity compensation coefficient is multiplied by the difference between the current humidity and the reference humidity, and the temperature compensation value and the humidity compensation value are added together to obtain the total environmental compensation value; Combining the voltage error and the total environmental compensation value, the energy storage system is adjusted; If the compensated voltage error is positive, increase the voltage of the energy storage system; If the compensated voltage error is a negative value, reducing the voltage of the energy storage system; The adjusted voltage is transmitted to the PWM controller, and the PWM controller adjusts the duty cycle of the PWM signal according to the adjusted voltage signal to achieve precise control of the output voltage of the load or inverter.

7. The improved reactive power droop control method for multiple inverters in parallel as claimed in claim 6, Features: The phase of the acquisition inverter 1 includes: The frequency output by the droop control unit is used as the input resonant frequency of the SOGI unit in the frequency locked loop; The angular frequency compensation calculated by the frequency-locked loop is added to the active power-frequency link to adjust the output frequency ω of the droop control unit, and the droop control unit is combined with the SOGI-PLL to generate a closed-loop feedback; The inverter 1 output voltage U abc By transforming the coordinate system to the dq0 coordinate system, the component U d and U q , and then import them into two SOGI-PLL units respectively; The frequency obtained by the active power-frequency link of the inverter 1 droop control unit is used as the resonant frequency of SOGI, and the voltage component is extracted through two SOGI-PLL units; The angular frequency error is added to the active power-frequency loop of the droop control unit of the inverter 2, and the output frequency and phase of the droop control unit are adjusted; Through the fixed difference of line impedance, the output voltage of inverter 2 is made to track the frequency and phase of the output voltage of inverter 1, thus completing the control.

8. An improved reactive power droop control system for multiple inverters in parallel, based on the improved reactive power droop control method for multiple inverters in parallel as claimed in any one of claims 1 to 7, Features: It includes a data acquisition and calculation module, a droop control module and a pre-synchronization phase control module; The data acquisition and calculation module is used to obtain first data on the output side of the inverter, and calculate second data output in real time according to the first data on the output side of the inverter; The droop control module is used to obtain given values ​​of frequency and voltage by droop control of the second data, and obtain a PWM given voltage by voltage and current double closed-loop control according to the given value of voltage; The pre-synchronization phase control module is used to collect the phase of the inverter 1 in real time through SOGI-PLL pre-synchronization, and use it as the phase input of the inverter 2.

9. A computer device comprising a memory and a processor, wherein the memory stores a computer program. Features: When the processor executes the computer program, the steps of the improved reactive power droop control method for multiple inverters in parallel according to any one of claims 1 to 7 are implemented.

10. A computer-readable storage medium having a computer program stored thereon, Features: When the computer program is executed by a processor, the steps of the improved reactive power droop control method for multiple inverters in parallel according to any one of claims 1 to 7 are implemented.

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