阅读说明：本技术 用于储能变流器的并离网动作切换的控制方法及系统 (Control method and system for grid-connected and off-grid action switching of energy storage converter ) 是由 曾广磊 周盼 刘幼林 徐海杰 于 2021-05-21 设计创作，主要内容包括：本发明提供了用于储能变流器的并离网动作切换的控制方法及系统,其能够在储能变流器并入电网的情况下,通过对电网的输出电压信号进行检测来确定电网中的谐波电压成分参数,由于电网输出的电压信号中谐波电压占比高低会直接影响电网的供电质量,而通过分析该谐波电压成分参数,能够准确地判断电网的供电有效性,这样能够便于指示储能变流器与电网进行适应的并网/离网切换动作,从而便于电网的实时供电状态,实现储能变流器的智能化和自动化并网/离网动作切换以及提高电网输电工作的稳定性和可靠性。(The invention provides a control method and a system for grid-connected/off-grid action switching of an energy storage converter, which can determine harmonic voltage component parameters in a power grid by detecting output voltage signals of the power grid under the condition that the energy storage converter is merged into the power grid, can accurately judge the power supply effectiveness of the power grid by analyzing the harmonic voltage component parameters because the harmonic voltage in the voltage signals output by the power grid directly influences the power supply quality of the power grid, can conveniently indicate the energy storage converter to carry out adaptive grid-connected/off-grid switching action with the power grid, thereby being convenient for the real-time power supply state of the power grid, realizing the intelligent and automatic grid-connected/off-grid action switching of the energy storage converter and improving the stability and reliability of power transmission work of the power grid.)

1. The control method for grid-connected and off-grid action switching of the energy storage converter is characterized by comprising the following steps of:

step S1, detecting an output voltage signal of the power grid within a preset time period under the condition that the energy storage converter is incorporated into the power grid, and determining harmonic voltage component parameters in the voltage signal output by the power grid according to the output voltage signal;

step S2, determining the actual output power state of the power grid in the preset time period according to the harmonic voltage component parameters, and judging the power supply effectiveness of the power grid according to the actual output power state;

and step S3, according to the power supply effectiveness judgment result of the power grid, indicating the energy storage converter and the power grid to carry out grid connection/grid disconnection switching action.

2. The control method for grid-connected and off-grid action switching of an energy storage converter as claimed in claim 1, characterized in that:

in step S1, when the energy storage converter is incorporated into the power grid, detecting an output voltage signal of the power grid within a preset time period, and determining, according to the output voltage signal, a harmonic voltage component in the voltage signal output by the power grid specifically includes:

step S101, detecting an output voltage signal of a power grid within a preset time period when an energy storage converter is merged into the power grid;

step S102, analyzing the output voltage signal, thereby determining a fundamental voltage component and a plurality of higher harmonic voltage components contained in the output voltage signal;

step S103, determining a fundamental voltage amplitude corresponding to the fundamental voltage component and a higher-order harmonic voltage amplitude corresponding to each higher-order harmonic voltage component in the preset time period, and taking the fundamental voltage amplitudes and the higher-order harmonic voltage amplitudes as the harmonic voltage component parameters.

3. The control method for grid-connected and off-grid action switching of an energy storage converter as claimed in claim 2, characterized in that:

in step S2, determining an actual output power state of the power grid within the preset time period according to the harmonic voltage component parameter, and determining the power supply validity of the power grid according to the actual output power state specifically includes:

step S201, calculating the output power state of the power grid within the preset time period according to the fundamental wave voltage amplitude corresponding to the fundamental wave voltage component and the high order harmonic voltage amplitude corresponding to each high order harmonic voltage component, so as to determine a fundamental wave output power value corresponding to the power grid under the condition of outputting the fundamental wave voltage and a high order harmonic output power value corresponding to the power grid under the condition of outputting the high order harmonic voltage;

step S202, adding the fundamental wave output power value and the high-order harmonic output power value to obtain an actual output power value of the power grid in the preset time period;

step S203, comparing the actual output power value with a preset power output threshold, if the actual output power value is greater than or equal to the preset power output threshold, judging that the power grid is currently in a power supply valid state, otherwise, judging that the power grid is currently in a power supply invalid state.

4. A control method for grid-connected and off-grid action switching of an energy storage converter as claimed in claim 3, characterized by:

in step S201, calculating an output power state of the power grid during the preset time period according to the fundamental voltage amplitude corresponding to the fundamental voltage component and the higher-order harmonic voltage amplitude corresponding to each higher-order harmonic voltage component, so as to determine a fundamental output power value corresponding to the power grid when the power grid outputs the fundamental voltage and a higher-order harmonic output power value corresponding to the power grid when the power grid outputs the higher-order harmonic voltage specifically include:

step S2011, determining a fundamental wave output power value corresponding to the fundamental wave voltage component by using the following formula (1),

in the above formula (1), P_LRepresenting a fundamental wave output power value corresponding to the fundamental wave voltage component, U (ω t) representing the sum of input voltage vectors of all loads in the power grid, ω representing the input voltage vectors of all loads in the power grid and corresponding angular frequencies, L representing a total inductance value of the loads in the power grid after series-parallel connection, C representing a total capacitance value of all loads in the power grid after series-parallel connection, R representing a total resistance value of all loads in the power grid after series-parallel connection, and t representing the corresponding transmission time of the fundamental wave voltage in the power grid;

step S2012, determining a higher harmonic output power value corresponding to the higher harmonic voltage component by using the following formula (2),

in the above formula (2), P_H,ARepresenting the A-th harmonic output power value, Z, corresponding to the higher harmonic voltage component_NRepresents the impedance corresponding to the nth order harmonic, I_naRepresenting the harmonic current of the order n, theta, corresponding to the a-th resonance source in the power grid_nRepresenting the phase angle, alpha, of the harmonic current of order n_nRepresenting the phase angle, beta, of the harmonic voltage of the n order_nRepresenting the phase angle, U, of the harmonic voltage of order n_NThe method comprises the steps of representing nominal voltage of a power grid, wherein t represents the corresponding transmission moment of high-order harmonic voltage in the power grid;

step S2013, determining a fundamental wave output standard power value corresponding to the fundamental wave voltage component by using the following formula (3),

in the above-mentioned formula (3),indicating the fundamental wave output standard power value, f, corresponding to the fundamental wave voltage component₀Represents the fundamental frequency and takes the value of 50Hz, t represents the corresponding transmission moment of the fundamental voltage in the power grid, U (2 pi f)₀t) represents the fundamental frequency f₀Corresponding angular frequency 2 pi f₀The lower load input voltage vector sum;

step S2014, utilizing the following formula (4), outputting power value P according to the fundamental wave_LThe fundamental wave outputs a standard power valueJudging whether to filter the load in the power grid or not,

in the above formula (4), δ represents a determination value of whether or not to perform filtering processing on the load in the power grid, u () represents a step function, and when the value in the parentheses is greater than or equal to 0, the function value of the step function is 1, and when the value in the parentheses is less than 0, the function value of the step function is 0, and when δ is 1, it represents that filtering processing on the load in the power grid is not necessary, and when δ is 0, it represents that filtering processing on the load in the power grid is necessary.

5. The control method for grid-connected and off-grid action switching of an energy storage converter as claimed in claim 4, characterized in that:

in step S2014, when it is determined that the filtering process needs to be performed on the load in the power grid, the input voltage after the control filtering of the load by the power grid loop is determined by using the following formula (5),

in the above equation (5), U' (ω)_it) represents the input voltage of the power grid loop after control filtering of the ith load，U(ω_it) represents the input voltage of the network loop to the ith load before filtering for controlling the ith load, omega_iRepresenting the angular frequency, f, of the input voltage of the ith load in the network loop₀The fundamental frequency is represented, the value of the fundamental frequency is 50Hz, u () represents a step function, the value of the step function is 1 when the value in the brackets is greater than or equal to 0, and the value of the step function is 0 when the value in the brackets is less than 0.

6. A control method for grid-connected and off-grid action switching of an energy storage converter as claimed in claim 3, characterized by:

in the step S3, instructing, according to the result of the power supply validity judgment of the power grid, the energy storage converter and the power grid to perform grid connection/grid disconnection switching specifically includes:

step S301, when the power grid is judged to be in a power supply effective state currently, indicating the energy storage converter to be connected into the power grid, and indicating the energy storage converter to serve as a voltage source to output power;

step S302, when the power grid is judged to be in a power supply invalid state currently, the energy storage converter and the power grid are indicated to perform off-grid action, and the energy storage converter is indicated to serve as a current source to output power.

7. The control system is used for switching the grid-connected action and the off-grid action of the energy storage converter and is characterized by comprising a voltage signal detection module, a voltage signal analysis module, a power grid output power determination module, a power grid power supply state judgment module and an energy storage converter switching action module; wherein the content of the first and second substances,

the voltage signal detection module is used for detecting an output voltage signal of the power grid within a preset time period when the energy storage converter is incorporated into the power grid;

the voltage signal analysis module is used for determining harmonic voltage component parameters in the voltage signal output by the power grid according to the output voltage signal;

the power grid output power determining module is used for determining the actual output power state of the power grid in the preset time period according to the harmonic voltage component parameter;

the power supply state judgment module of the power grid is used for judging the power supply effectiveness of the power grid according to the actual output power state;

the energy storage converter switching action module is used for indicating the energy storage converter and the power grid to carry out grid connection/grid disconnection switching action according to the power supply effectiveness judgment result of the power grid.

8. The control system for grid-connected and off-grid action switching of an energy storage converter as claimed in claim 7, wherein:

the voltage signal analysis module determines harmonic voltage component parameters in the voltage signal output by the power grid according to the output voltage signal, and specifically includes:

analyzing the output voltage signal to determine a fundamental voltage component and a number of higher order harmonic voltage components contained in the output voltage signal;

and then determining the fundamental voltage amplitude corresponding to the fundamental voltage component and the high-order harmonic voltage amplitude corresponding to each high-order harmonic voltage component in the preset time period, and taking the fundamental voltage amplitude and the high-order harmonic voltage amplitude as the harmonic voltage component parameters.

9. The control system for grid-connected and off-grid action switching of an energy storage converter as claimed in claim 8, wherein:

the determining, by the power grid output power determining module, the actual output power state of the power grid within the preset time period according to the harmonic voltage component parameter specifically includes:

according to the fundamental wave voltage amplitude corresponding to the fundamental wave voltage component and the high order harmonic wave voltage amplitude corresponding to each high order harmonic wave voltage component, calculating the output power state of the power grid in the preset time period, and accordingly determining a fundamental wave output power value corresponding to the power grid under the condition of outputting the fundamental wave voltage and a high order harmonic wave output power value corresponding to the power grid under the condition of outputting the high order harmonic wave voltage; then, the fundamental wave output power value and the high-order harmonic output power value are added, so that an actual output power value of the power grid in the preset time period is obtained;

and the number of the first and second groups,

the power supply state judgment module judges the power supply effectiveness of the power grid according to the actual output power state, and specifically comprises the following steps:

and comparing the actual output power value with a preset power output threshold, if the actual output power value is greater than or equal to the preset power output threshold, judging that the power grid is currently in a power supply valid state, and otherwise, judging that the power grid is currently in a power supply invalid state.

10. The control system for grid-connected and off-grid action switching of an energy storage converter as claimed in claim 9, wherein:

the energy storage converter switching action module indicates the energy storage converter and the power grid to carry out grid connection/grid disconnection switching actions according to the power supply effectiveness judgment result of the power grid, and the method specifically comprises the following steps:

when the power grid is judged to be in a power supply effective state currently, indicating the energy storage converter to be connected into the power grid, and indicating the energy storage converter to serve as a voltage source to output power;

and when the power grid is judged to be in a power supply invalid state currently, the energy storage converter is indicated to perform off-grid action with the power grid, and the energy storage converter is indicated to serve as a current source to output power.

Technical Field

The invention relates to the technical field of intelligent power grid control, in particular to a control method and a control system for grid-connected and off-grid action switching of an energy storage converter.

Background

At present, a power grid, especially a micro-grid, is widely applied to a distributed power supply system, and can provide a stable and reliable distributed power supply for different load devices. In order to ensure the sustainable power supply operation of the power grid, an energy storage converter is usually configured to perform grid connection or grid disconnection switching operation with the power grid, so that under abnormal conditions such as a fault or power failure of the power grid, the energy storage converter is instructed to perform adaptive grid connection/grid disconnection switching, thereby maintaining the normal power supply of the power grid. In the prior art, the grid-connected/off-grid action switching of the energy storage converter is only simple switching-in and switching-off action conversion, and the energy storage converter cannot be instructed to carry out intelligent and automatic action switching according to the current real-time power supply state of the power grid, so that the working stability and controllability of the power grid are greatly reduced.

Disclosure of Invention

The invention provides a control method and a system for grid-connected and off-grid action switching of an energy storage converter, which are used for detecting an output voltage signal of a power grid in a preset time period under the condition that the energy storage converter is incorporated into the power grid, determining a harmonic voltage component parameter in the voltage signal output by the power grid according to the output voltage signal, then determining the actual output power state of the power grid in the preset time period according to the harmonic voltage component parameter, judging the power supply effectiveness of the power grid according to the actual output power state, and finally indicating the energy storage converter and the power grid to carry out grid-connected/off-grid switching action according to the power supply effectiveness judgment result of the power grid; therefore, the control method and the system for switching the grid-connected and grid-disconnected actions of the energy storage converter can determine the harmonic voltage component parameters in the power grid by detecting the output voltage signal of the power grid under the condition that the energy storage converter is merged into the power grid, the power supply quality of the power grid can be directly influenced due to the harmonic voltage in the voltage signal output by the power grid, and the power supply effectiveness of the power grid can be accurately judged by analyzing the harmonic voltage component parameters, so that the energy storage converter can be conveniently indicated to perform the adaptive grid-connected/grid-disconnected switching actions with the power grid, the real-time power supply state of the power grid is facilitated, the intelligent and automatic grid-connected/grid-disconnected action switching of the energy storage converter is realized, and the stability and the reliability of the power transmission work of the power grid are improved.

The invention provides a control method for grid-connected and off-grid action switching of an energy storage converter, which is characterized by comprising the following steps of:

step S1, detecting an output voltage signal of the power grid within a preset time period under the condition that the energy storage converter is incorporated into the power grid, and determining harmonic voltage component parameters in the voltage signal output by the power grid according to the output voltage signal;

step S2, determining the actual output power state of the power grid in the preset time period according to the harmonic voltage component parameters, and judging the power supply effectiveness of the power grid according to the actual output power state;

step S3, according to the power supply effectiveness judgment result of the power grid, indicating the energy storage converter and the power grid to carry out grid connection/grid disconnection switching action;

further, in step S1, when the energy storage converter is incorporated into the power grid, detecting an output voltage signal of the power grid within a preset time period, and determining, according to the output voltage signal, a harmonic voltage component in the voltage signal output by the power grid specifically includes:

step S101, detecting an output voltage signal of a power grid within a preset time period when an energy storage converter is merged into the power grid;

step S102, analyzing the output voltage signal, thereby determining a fundamental wave voltage component and a plurality of high-order harmonic voltage components contained in the output voltage signal;

step S103, determining a fundamental voltage amplitude corresponding to the fundamental voltage component and a higher harmonic voltage amplitude corresponding to each higher harmonic voltage component in the preset time period, and taking the fundamental voltage amplitude and the higher harmonic voltage amplitude as the harmonic voltage component parameters;

further, in step S2, determining an actual output power state of the power grid within the preset time period according to the harmonic voltage component parameter, and determining the power supply effectiveness of the power grid according to the actual output power state specifically includes:

step S201, calculating the output power state of the power grid within the preset time period according to the fundamental wave voltage amplitude corresponding to the fundamental wave voltage component and the high order harmonic voltage amplitude corresponding to each high order harmonic voltage component, so as to determine a fundamental wave output power value corresponding to the power grid under the condition of outputting the fundamental wave voltage and a high order harmonic output power value corresponding to the power grid under the condition of outputting the high order harmonic voltage;

step S202, adding the fundamental wave output power value and the high-order harmonic output power value to obtain an actual output power value of the power grid in the preset time period;

step S203, comparing the actual output power value with a preset power output threshold, if the actual output power value is greater than or equal to the preset power output threshold, judging that the power grid is currently in a power supply valid state, otherwise, judging that the power grid is currently in a power supply invalid state;

further, in step S201, calculating an output power state of the power grid during the preset time period according to the fundamental voltage amplitude corresponding to the fundamental voltage component and the higher-order harmonic voltage amplitude corresponding to each higher-order harmonic voltage component, so as to determine a fundamental output power value corresponding to the power grid when the fundamental voltage is output and a higher-order harmonic output power value corresponding to the power grid when the higher-order harmonic voltage is output specifically include:

step S2011, determining a fundamental wave output power value corresponding to the fundamental wave voltage component by using the following formula (1),

in the above formula (1), P_LRepresenting a fundamental wave output power value corresponding to the fundamental wave voltage component, U (ω t) representing the sum of input voltage vectors of all loads in the power grid, ω representing the input voltage vectors of all loads in the power grid and corresponding angular frequencies, L representing a total inductance value of the loads in the power grid after series-parallel connection, and C representing all negative inductance values in the power gridThe total capacitance value of the loads after series-parallel connection is carried out, R represents the total resistance value of all the loads after series-parallel connection in the power grid, and t represents the corresponding transmission moment of fundamental voltage in the power grid;

step S2012, determining a higher harmonic output power value corresponding to the higher harmonic voltage component by using the following formula (2),

in the above formula (2), P_H,ARepresenting the A-th harmonic output power value, Z, corresponding to the higher harmonic voltage component_NRepresents the impedance corresponding to the nth order harmonic, I_naRepresenting the n-order harmonic current, theta, corresponding to the a-th resonant source in the power grid_nRepresenting the phase angle, alpha, of the harmonic current of order n_nPhase angle, beta, representing the voltage of the n-th harmonic_nRepresenting the phase angle, U, of the harmonic voltage of order n_NThe method comprises the steps of representing nominal voltage of a power grid, wherein t represents the corresponding transmission moment of high-order harmonic voltage in the power grid;

step S2013, determining a fundamental wave output standard power value corresponding to the fundamental wave voltage component by using the following formula (3),

in the above-mentioned formula (3),representing a fundamental output standard power value, f, corresponding to said fundamental voltage component₀Represents the fundamental frequency and takes the value of 50Hz, t represents the corresponding transmission moment of the fundamental voltage in the power grid, U (2 pi f)₀t) represents the fundamental frequency f₀Corresponding angular frequency 2 pi f₀The lower load input voltage vector sum;

step S2014, utilizing the following formula (4), outputting power value P according to the fundamental wave_LThe fundamental wave output standard power valueJudging whether to filter the load in the power grid or not,

in the above formula (4), δ represents a determination value of whether or not to perform filtering processing on a load in the power grid, u () represents a step function, where a function value of the step function is 1 when a value in parentheses is greater than or equal to 0, and the function value of the step function is 0 when a value in parentheses is less than 0, and if δ is 1, it represents that filtering processing on the load in the power grid is not required, and if δ is 0, it represents that filtering processing on the load in the power grid is required;

further, in step S2014, when it is determined that the filtering process needs to be performed on the load in the power grid, the input voltage after the control filtering of the load by the power grid loop is determined by using the following formula (5),

in the above equation (5), U' (ω)_it) represents the input voltage, U (ω), of the network loop after control filtering of the ith load_it) represents the input voltage of the network loop to the ith load before filtering for controlling the ith load, omega_iRepresenting the angular frequency, f, of the input voltage of the ith load in the network loop₀The fundamental frequency is represented, the value of the fundamental frequency is 50Hz, u () represents a step function, the value of the step function is 1 when the value in brackets is greater than or equal to 0, and the value of the step function is 0 when the value in brackets is less than 0;

further, in step S3, according to the result of determining the power supply validity of the power grid, instructing the energy storage converter and the power grid to perform grid connection/grid disconnection switching specifically includes:

step S301, when the power grid is judged to be in a power supply effective state currently, indicating the energy storage converter to be kept incorporated into the power grid, and simultaneously indicating the energy storage converter to serve as a voltage source to output power;

step S302, when the power grid is judged to be in a power supply invalid state currently, the energy storage converter is indicated to perform off-grid action with the power grid, and the energy storage converter is indicated to serve as a current source to output power.

The invention also provides a control system for switching the grid-connected and off-grid actions of the energy storage converter, which is characterized by comprising a voltage signal detection module, a voltage signal analysis module, a power grid output power determination module, a power grid power supply state judgment module and an energy storage converter switching action module; wherein the content of the first and second substances,

the voltage signal detection module is used for detecting an output voltage signal of the power grid within a preset time period when the energy storage converter is incorporated into the power grid;

the voltage signal analysis module is used for determining harmonic voltage component parameters in the voltage signal output by the power grid according to the output voltage signal;

the power grid output power determining module is used for determining the actual output power state of the power grid within the preset time period according to the harmonic voltage component parameter;

the power grid power supply state judgment module is used for judging the power supply effectiveness of the power grid according to the actual output power state;

the energy storage converter switching action module is used for indicating the energy storage converter and the power grid to carry out grid connection/grid disconnection switching action according to the power supply effectiveness judgment result of the power grid;

further, the determining, by the voltage signal analysis module, the harmonic voltage component parameter in the voltage signal output by the power grid according to the output voltage signal specifically includes:

analyzing the output voltage signal to determine a fundamental voltage component and a number of higher order harmonic voltage components contained in the output voltage signal;

then determining a fundamental voltage amplitude corresponding to the fundamental voltage component and a high-order harmonic voltage amplitude corresponding to each high-order harmonic voltage component in the preset time period, and taking the fundamental voltage amplitude and the high-order harmonic voltage amplitude as the harmonic voltage component parameters;

further, the determining, by the power grid output power determining module, an actual output power state of the power grid within the preset time period according to the harmonic voltage component parameter specifically includes:

according to the fundamental wave voltage amplitude corresponding to the fundamental wave voltage component and the high order harmonic wave voltage amplitude corresponding to each high order harmonic wave voltage component, calculating the output power state of the power grid in the preset time period, and accordingly determining a fundamental wave output power value corresponding to the power grid under the condition of outputting the fundamental wave voltage and a high order harmonic wave output power value corresponding to the power grid under the condition of outputting the high order harmonic wave voltage;

then, the fundamental wave output power value and the high-order harmonic output power value are added, so that an actual output power value of the power grid in the preset time period is obtained;

and the number of the first and second groups,

the power supply state judgment module judges the power supply effectiveness of the power grid according to the actual output power state, and specifically comprises the following steps:

comparing the actual output power value with a preset power output threshold, if the actual output power value is greater than or equal to the preset power output threshold, judging that the power grid is currently in a power supply valid state, otherwise, judging that the power grid is currently in a power supply invalid state;

further, the energy storage converter switching action module judges a result according to the power supply effectiveness of the power grid, and instructs the energy storage converter and the power grid to perform grid connection/grid disconnection switching actions specifically includes:

when the power grid is judged to be in a power supply effective state currently, indicating the energy storage converter to be connected into the power grid, and indicating the energy storage converter to serve as a voltage source to output power;

and when the power grid is judged to be in a power supply invalid state currently, the energy storage converter is indicated to perform off-grid action with the power grid, and the energy storage converter is indicated to serve as a current source to output power.

Compared with the prior art, the control method and the system for grid-connected and off-grid action switching of the energy storage converter detect the output voltage signal of the power grid within a preset time period under the condition that the energy storage converter is merged into the power grid, determine the harmonic voltage component parameter in the voltage signal output by the power grid according to the output voltage signal, then determine the actual output power state of the power grid within the preset time period according to the harmonic voltage component parameter, judge the power supply effectiveness of the power grid according to the actual output power state, and finally instruct the energy storage converter to perform grid-connected/off-grid switching action with the power grid according to the power supply effectiveness judgment result of the power grid; therefore, the control method and the system for grid-connected/off-grid action switching of the energy storage converter can determine the harmonic voltage component parameter in the power grid by detecting the output voltage signal of the power grid under the condition that the energy storage converter is merged into the power grid, the power supply quality of the power grid can be directly influenced due to the fact that the proportion of the harmonic voltage in the voltage signal output by the power grid is high or low, the power supply effectiveness of the power grid can be accurately judged by analyzing the harmonic voltage component parameter, and therefore the energy storage converter and the power grid can be conveniently indicated to carry out adaptive grid-connected/off-grid switching action, the real-time power supply state of the power grid is facilitated, the intelligent and automatic grid-connected/off-grid action switching of the energy storage converter is achieved, and the stability and the reliability of power transmission work of the power grid are improved.

Additional features and advantages of the invention will be set forth in the description which follows, and in part will be obvious from the description, or may be learned by practice of the invention. The objectives and other advantages of the invention will be realized and attained by the structure particularly pointed out in the written description and claims hereof as well as the appended drawings.

The technical solution of the present invention is further described in detail by the accompanying drawings and embodiments.

Drawings

In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings used in the description of the embodiments or the prior art will be briefly described below, it is obvious that the drawings in the following description are only some embodiments of the present invention, and for those skilled in the art, other drawings can be obtained according to these drawings without any creative effort.

Fig. 1 is a schematic flow chart of a control method for grid-connected and off-grid action switching of an energy storage converter according to the present invention.

Fig. 2 is a schematic structural diagram of a control system for grid-connected and off-grid action switching of an energy storage converter provided by the invention.

Detailed Description

The technical solutions in the embodiments of the present invention will be described clearly and completely with reference to the accompanying drawings in the embodiments of the present invention, and it is obvious that the described embodiments are only a part of the embodiments of the present invention, and not all of the embodiments. All other embodiments, which can be derived by a person skilled in the art from the embodiments given herein without making any creative effort, shall fall within the protection scope of the present invention.

Fig. 1 is a schematic flowchart of a control method for switching between grid-connected and grid-disconnected operations of an energy storage converter according to an embodiment of the present invention. The control method for switching grid-connected and off-grid actions of the energy storage converter comprises the following steps:

step S1, detecting the output voltage signal of the power grid in a preset time period under the condition that the energy storage converter is merged into the power grid, and determining harmonic voltage component parameters in the voltage signal output by the power grid according to the output voltage signal;

step S2, determining the actual output power state of the power grid in the preset time period according to the harmonic voltage component parameters, and then judging the power supply effectiveness of the power grid according to the actual output power state;

and step S3, according to the power supply effectiveness judgment result of the power grid, indicating the energy storage converter and the power grid to carry out grid connection/grid disconnection switching action.

The beneficial effects of the above technical scheme are: according to the control method for grid-connected/off-grid action switching of the energy storage converter, under the condition that the energy storage converter is merged into a power grid, harmonic voltage component parameters in the power grid are determined by detecting output voltage signals of the power grid, the power supply quality of the power grid can be directly influenced due to the fact that the proportion of harmonic voltage in the voltage signals output by the power grid is high or low, the power supply effectiveness of the power grid can be accurately judged by analyzing the harmonic voltage component parameters, therefore, the energy storage converter can be conveniently indicated to carry out adaptive grid-connected/off-grid switching action with the power grid, the real-time power supply state of the power grid is facilitated, intelligent and automatic grid-connected/off-grid action switching of the energy storage converter is achieved, and the stability and reliability of power transmission work of the power grid are improved.

Preferably, in step S1, when the energy storage converter is incorporated into the power grid, detecting an output voltage signal of the power grid within a preset time period, and determining, according to the output voltage signal, a harmonic voltage component in the voltage signal output by the power grid specifically includes:

step S101, detecting an output voltage signal of a power grid within a preset time period when an energy storage converter is merged into the power grid;

step S102, analyzing the output voltage signal, thereby determining a fundamental voltage component and a plurality of high-order harmonic voltage components contained in the output voltage signal;

step S103, determining a fundamental voltage amplitude corresponding to the fundamental voltage component and a higher harmonic voltage amplitude corresponding to each higher harmonic voltage component in the preset time period, and taking the fundamental voltage amplitude and the higher harmonic voltage amplitude as the harmonic voltage component parameters.

The beneficial effects of the above technical scheme are: according to the control method for grid-connected/off-grid action switching of the energy storage converter, under the condition that the energy storage converter is merged into a power grid, harmonic voltage component parameters in the power grid are determined by detecting output voltage signals of the power grid, the power supply quality of the power grid can be directly influenced due to the fact that the proportion of harmonic voltage in the voltage signals output by the power grid is high or low, the power supply effectiveness of the power grid can be accurately judged by analyzing the harmonic voltage component parameters, therefore, the energy storage converter can be conveniently indicated to carry out adaptive grid-connected/off-grid switching action with the power grid, the real-time power supply state of the power grid is facilitated, intelligent and automatic grid-connected/off-grid action switching of the energy storage converter is achieved, and the stability and reliability of power transmission work of the power grid are improved.

Preferably, in step S2, determining an actual output power state of the power grid within the preset time period according to the harmonic voltage component parameter, and determining the power supply effectiveness of the power grid according to the actual output power state specifically includes:

step S201, calculating the output power state of the power grid in the preset time period according to the fundamental wave voltage amplitude corresponding to the fundamental wave voltage component and the high order harmonic voltage amplitude corresponding to each high order harmonic voltage component, so as to determine the fundamental wave output power value corresponding to the power grid under the condition of outputting the fundamental wave voltage and the high order harmonic output power value corresponding to the power grid under the condition of outputting the high order harmonic voltage;

step S202, adding the fundamental wave output power value and the high-order harmonic output power value to obtain an actual output power value of the power grid in the preset time period;

step S203, comparing the actual output power value with a preset power output threshold, if the actual output power value is greater than or equal to the preset power output threshold, determining that the power grid is currently in a power supply valid state, otherwise, determining that the power grid is currently in a power supply invalid state.

The beneficial effects of the above technical scheme are: because the output power provided by the fundamental wave voltage and the output power provided by the high-order harmonic voltage have different functions in the electric energy output of the power grid, the actual output power value of the power grid in the preset time period is obtained by adding the fundamental wave output power value and the high-order harmonic output power value, the current power output condition of the power grid can be accurately represented, and whether the current power supply state of the power grid is effective or not can be accurately quantitatively judged in a threshold comparison mode.

Preferably, in step S201, calculating the output power state of the power grid during the preset time period according to the fundamental wave voltage amplitude corresponding to the fundamental wave voltage component and the higher-order harmonic voltage amplitude corresponding to each higher-order harmonic voltage component, so as to determine the fundamental wave output power value corresponding to the power grid when the fundamental wave voltage is output and the higher-order harmonic output power value corresponding to the power grid when the higher-order harmonic voltage is output specifically include:

in step S2011, a fundamental output power value corresponding to the fundamental voltage component is determined by using the following formula (1),

in the above formula (1), P_LThe fundamental wave output power value corresponding to the fundamental wave voltage component is represented, U (ω t) represents the input voltage vector sum of all loads in the power grid, ω represents the input voltage vector sum of all loads in the power grid and the corresponding angular frequency, L represents the total inductance value of the loads in the power grid after series-parallel connection, C represents the total capacitance value of all loads in the power grid after series-parallel connection, R represents the total resistance value of all loads in the power grid after series-parallel connection, and t represents the moment when the fundamental wave voltage in the power grid correspondingly transmits, and the moment t is the transmission moment corresponding to the alternating current in the power grid as the fundamental wave voltage corresponds to the alternating current transmitted in the power grid;

in step S2012, a higher harmonic output power value corresponding to the higher harmonic voltage component is determined using the following formula (2),

in the above formula (2), P_H,ARepresenting the A-th harmonic output power value, Z, corresponding to the higher harmonic voltage component_NRepresents the impedance corresponding to the nth order harmonic, I_naRepresenting the harmonic current of the order n, theta, corresponding to the a-th resonance source in the power grid_nRepresenting the phase angle, alpha, of the harmonic current of order n_nRepresenting the phase angle, beta, of the harmonic voltage of the n order_nRepresenting the phase angle, U, of the harmonic voltage of order n_NThe method includes the steps that a nominal voltage of a power grid is represented, the nominal voltage can be, but is not limited to, 220V or 380V, t represents the time when a high-order harmonic voltage in the power grid correspondingly transmits, and the time t is the transmission time of an alternating current in the corresponding power grid because the high-order harmonic voltage corresponds to the alternating current transmitted in the power grid; since the power grid usually includes several transmission lines, each transmission line will have both fundamental harmonic and several higher harmonics, the fundamental harmonic has a fundamental harmonic source corresponding to the transmission line, and each higher harmonic has a higher harmonic source corresponding to the transmission line, the above parameter Z_N、I_na、θ_n、α_n、β_nRespectively corresponding to the parameters of each harmonic source in the power transmission line;

step S2013, determining a fundamental output standard power value corresponding to the fundamental voltage component by using the following formula (3),

in the above-mentioned formula (3),indicating the fundamental wave output standard power value, f, corresponding to the fundamental wave voltage component₀Representing the fundamental frequency and having a value of 50Hz, t representing the moment of transmission of the fundamental voltage in the network, which is the moment of transmission of the alternating current in the network, U (2 pi f), since this fundamental voltage corresponds to the alternating current transmitted in the network₀t) represents the fundamental frequency f₀Corresponding angular frequency 2 pi f₀The lower load input voltage vector sum;

in step S2014, the power value P is outputted according to the fundamental wave using the following formula (4)_LThe fundamental wave outputs a standard power valueDetermining whether to filter a load in a power gridThe wave processing is carried out on the mixture of the water and the air,

in the above formula (4), δ represents a determination value of whether or not to perform filtering processing on the load in the power grid, u () represents a step function, where the function value of the step function is 1 when the value in parentheses is greater than or equal to 0, the function value of the step function is 0 when the value in parentheses is less than 0, if δ is 1, it represents that filtering processing on the load in the power grid is not necessary, and if δ is 0, it represents that filtering processing on the load in the power grid is necessary.

The beneficial effects of the above technical scheme are: by using the formulas (1) and (2), the fundamental wave output power value corresponding to the power grid under the condition of outputting fundamental wave voltage and the high-order harmonic output power value corresponding to the power grid under the condition of outputting high-order harmonic voltage can be accurately calculated; and the stable fundamental voltage output power is calculated by using a formula (3) according to the national fundamental frequency within the upper and lower ranges of 5HZ, the stable fundamental voltage output power exceeding the range is calculated as a power supply invalid state, the corresponding fundamental output power value of the power grid under the condition of outputting the fundamental voltage is calculated, the order number of the high-order harmonic is fixed within the range of 2 to 40 by using a formula (4), unnecessary evading calculation can be directly abandoned and planned as the power supply invalid state, and then the corresponding high-order harmonic output power value under the condition of outputting the high-order harmonic voltage is calculated.

Preferably, in step S2014, when it is determined that the filtering process needs to be performed on the load in the power grid, the input voltage after the control filtering of the load by the power grid loop is determined by using the following formula (5),

in the above equation (5), U' (ω)_it) represents the input voltage, U (ω), of the network loop after control filtering of the ith load_it) represents the input voltage of the network loop to the ith load before filtering for controlling the ith load, omega_iRepresenting the angular frequency, f, of the input voltage of the ith load in the network loop₀The frequency of the fundamental wave is represented, the value of the fundamental wave is 50Hz, u () represents a step function, the value of the step function is 1 when the value in the brackets is greater than or equal to 0, and the value of the step function is 0 when the value in the brackets is less than 0.

The beneficial effects of the above technical scheme are: the input voltage of the power grid loop after the control filtering of the load is determined through the formula (5), so that the operation frequency of the power grid can be guaranteed to be stable after all the loads are merged into the power grid, the normal operation of the power grid is prevented from being interfered by harmonic wave influence, and the fault probability of the power grid is reduced.

Preferably, in step S3, instructing, according to the result of the determination of the power supply effectiveness of the power grid, the energy storage converter to perform grid connection/grid disconnection switching with the power grid specifically includes:

step S301, when the power grid is judged to be in a power supply effective state currently, indicating the energy storage converter to be merged into the power grid, and indicating the energy storage converter to serve as a voltage source to output power;

step S302, when the power grid is judged to be in the power supply invalid state currently, the energy storage converter is indicated to perform off-grid action with the power grid, and the energy storage converter is indicated to serve as a current source to output power.

The beneficial effects of the above technical scheme are: when the power grid is judged to be in the effective power supply state currently, the fact that the power supply performance of the power grid can be improved effectively after the energy storage converter is merged into the power grid is shown, at the moment, the grid connection state between the energy storage converter and the power grid should be kept continuously, the energy storage converter is indicated to serve as a voltage source to output power, and therefore the power supply stability of the power grid is improved to the maximum extent. When the power grid is judged to be in a power supply invalid state at present, the fact that the power supply performance of the power grid is deteriorated after the energy storage converter is merged into the power grid is shown, at the moment, the energy storage converter and the power grid should be separated from the power grid, and the energy storage converter is indicated to serve as a current source to output power, so that independent and effective power supply of the energy storage converter to loads of other equipment is guaranteed.

Fig. 2 is a schematic structural diagram of a control system for grid-connected and off-grid operation switching of an energy storage converter according to an embodiment of the present invention. The control system for grid-connected and off-grid action switching of the energy storage converter comprises a voltage signal detection module, a voltage signal analysis module, a power grid output power determination module, a power grid power supply state judgment module and an energy storage converter switching action module; wherein the content of the first and second substances,

the voltage signal detection module is used for detecting an output voltage signal of the power grid within a preset time period when the energy storage converter is incorporated into the power grid;

the voltage signal analysis module is used for determining harmonic voltage component parameters in the voltage signal output by the power grid according to the output voltage signal;

the power grid output power determining module is used for determining the actual output power state of the power grid in the preset time period according to the harmonic voltage component parameter;

the power supply state judgment module of the power grid is used for judging the power supply effectiveness of the power grid according to the actual output power state;

the energy storage converter switching action module is used for indicating the energy storage converter and the power grid to carry out grid connection/grid disconnection switching action according to the power supply effectiveness judgment result of the power grid.

The beneficial effects of the above technical scheme are: the control system for grid-connected/off-grid action switching of the energy storage converter can determine harmonic voltage component parameters in a power grid by detecting output voltage signals of the power grid under the condition that the energy storage converter is merged into the power grid, the power supply quality of the power grid can be directly influenced due to the fact that the proportion of harmonic voltage in the voltage signals output by the power grid is high or low, the power supply effectiveness of the power grid can be accurately judged by analyzing the harmonic voltage component parameters, therefore, the energy storage converter can be conveniently indicated to carry out adaptive grid-connected/off-grid switching action with the power grid, the real-time power supply state of the power grid is facilitated, intelligent and automatic grid-connected/off-grid action switching of the energy storage converter is achieved, and the stability and reliability of power transmission work of the power grid are improved.

Preferably, the determining, by the voltage signal analysis module, the harmonic voltage component parameter in the voltage signal output by the power grid according to the output voltage signal specifically includes:

analyzing the output voltage signal to determine a fundamental voltage component and a plurality of higher harmonic voltage components contained in the output voltage signal;

and then determining the fundamental voltage amplitude corresponding to the fundamental voltage component and the high-order harmonic voltage amplitude corresponding to each high-order harmonic voltage component in the preset time period, and taking the fundamental voltage amplitude and the high-order harmonic voltage amplitude as the harmonic voltage component parameters.

The beneficial effects of the above technical scheme are: because the power grid can be provided with different types of nonlinear electronic elements, when the energy storage converter is incorporated into the power grid, the energy storage converter can interact with the nonlinear electronic elements to enable the voltage fluctuation inside the power grid to be generated, so that the higher harmonic voltage component in the voltage signal output by the power grid is increased, when the proportion of the higher harmonic voltage component in the voltage signal output by the power grid is increased to a certain degree, the output power quality of the power grid can be seriously influenced, and reliable basis can be provided for the follow-up accurate analysis of the effectiveness of the power supply state of the power grid by analyzing the output voltage signal of the power grid.

Preferably, the determining, by the power grid output power determining module, an actual output power state of the power grid within the preset time period according to the harmonic voltage component parameter specifically includes:

according to the fundamental wave voltage amplitude corresponding to the fundamental wave voltage component and the high order harmonic wave voltage amplitude corresponding to each high order harmonic wave voltage component, calculating the output power state of the power grid in the preset time period, and accordingly determining the fundamental wave output power value corresponding to the power grid under the condition of outputting the fundamental wave voltage and the high order harmonic wave output power value corresponding to the power grid under the condition of outputting the high order harmonic wave voltage;

then, the fundamental wave output power value and the high-order harmonic output power value are added, so that an actual output power value of the power grid in the preset time period is obtained;

and the number of the first and second groups,

the power supply state judgment module judges the power supply effectiveness of the power grid according to the actual output power state, and specifically comprises the following steps:

and comparing the actual output power value with a preset power output threshold, if the actual output power value is greater than or equal to the preset power output threshold, judging that the power grid is currently in a power supply valid state, and if not, judging that the power grid is currently in a power supply invalid state.

The beneficial effects of the above technical scheme are: because the output power provided by the fundamental wave voltage and the output power provided by the high-order harmonic voltage have different functions in the electric energy output of the power grid, the actual output power value of the power grid in the preset time period is obtained by adding the fundamental wave output power value and the high-order harmonic output power value, the current power output condition of the power grid can be accurately represented, and whether the current power supply state of the power grid is effective or not can be accurately quantitatively judged in a threshold comparison mode.

Preferably, the energy storage converter switching action module instructs, according to the power supply validity judgment result of the power grid, the energy storage converter and the power grid to perform grid connection/grid disconnection switching actions specifically includes:

when the power grid is judged to be in a power supply effective state currently, indicating the energy storage converter to be connected into the power grid, and indicating the energy storage converter to serve as a voltage source to output power;

and when the power grid is judged to be in the power supply invalid state currently, the energy storage converter is indicated to perform off-grid action with the power grid, and the energy storage converter is indicated to serve as a current source to output power.

The beneficial effects of the above technical scheme are: when the power grid is judged to be in the effective power supply state currently, the fact that the power supply performance of the power grid can be improved effectively after the energy storage converter is merged into the power grid is shown, at the moment, the grid connection state between the energy storage converter and the power grid should be kept continuously, the energy storage converter is indicated to serve as a voltage source to output power, and therefore the power supply stability of the power grid is improved to the maximum extent. When the power grid is judged to be in a power supply invalid state at present, the fact that the power supply performance of the power grid is deteriorated after the energy storage converter is merged into the power grid is shown, at the moment, the energy storage converter and the power grid should be separated from the power grid, and the energy storage converter is indicated to serve as a current source to output power, so that independent and effective power supply of the energy storage converter to loads of other equipment is guaranteed.

As can be seen from the content of the above embodiment, in the control method and system for grid-connected and grid-disconnected operation switching of the energy storage converter, when the energy storage converter is incorporated into a power grid, an output voltage signal of the power grid within a preset time period is detected, a harmonic voltage component parameter in the voltage signal output by the power grid is determined according to the output voltage signal, then an actual output power state of the power grid within the preset time period is determined according to the harmonic voltage component parameter, then power supply validity of the power grid is determined according to the actual output power state, and finally, the energy storage converter and the power grid are instructed to perform grid-connected/grid-disconnected switching operation according to a power supply validity determination result of the power grid; therefore, the control method and the system for grid-connected/off-grid action switching of the energy storage converter can determine the harmonic voltage component parameter in the power grid by detecting the output voltage signal of the power grid under the condition that the energy storage converter is merged into the power grid, the power supply quality of the power grid can be directly influenced due to the high-low proportion of the harmonic voltage in the voltage signal output by the power grid, and the power supply effectiveness of the power grid can be accurately judged by analyzing the harmonic voltage component parameter, so that the energy storage converter can be conveniently indicated to perform adaptive grid-connected/off-grid switching action with the power grid, the real-time power supply state of the power grid is facilitated, the intelligent and automatic grid-connected/off-grid action switching of the energy storage converter is realized, and the stability and the reliability of power transmission work of the power grid are improved.

It will be apparent to those skilled in the art that various changes and modifications may be made in the present invention without departing from the spirit and scope of the invention. Thus, if such modifications and variations of the present invention fall within the scope of the claims of the present invention and their equivalents, the present invention is intended to include such modifications and variations.