Grid-connected power detection method and detection system for three-phase four-wire photovoltaic grid-connected energy storage system

Abstract

The invention provides a grid-connected power detection method and detection system for a three-phase four-wire photovoltaic grid-connected energy storage system. The method comprises the following steps: obtaining a total reactive power instruction according to a grid-connected total active power instruction and a reactive power control mode; calculating to obtain single-phase active power and single-phase reactive power of the power grid; performing closed-loop control according to the total reactive power instruction, the single-phase active power and the single-phase reactive power to obtain a control signal of closed-loop output; and performing grid-connected control on the inverter according to the control signal to obtain grid-connected active and reactive output. According to the method, starting from power definition, phase current is projected to a phase voltage direction and an orthogonal direction, deformation of product sum and difference is utilized, and active current and reactive current are averagely extracted through a periodic sliding window to obtain active power and reactive power, so that three-phase active and reactive independent decoupling control is realized; and the method can adapt to working conditions of unbalanced power grids and unbalanced power requirements.

Description

Technical Field

[0001] The present invention belongs to the technical field of three-phase grid-connected energy storage systems, and particularly relates to a method and a detection system for detecting grid-connected power of a three-phase four-wire photovoltaic grid-connected energy storage system. Background Art

[0002] In the existing reactive power control methods of three-phase grid-connected energy storage inverters, the unified detection and control of the total three-phase active power and the total reactive power are mostly carried out. For example, the currently widely used three-phase reactive power detection and control algorithms mainly have the following limitations: ① Under the condition of unbalanced three-phase power grid, since there is a negative sequence component in the power grid at this time, in the positive sequence dq coordinate system, the unified calculation of the three-phase active and reactive feedback powers will generate an AC component with twice the power grid fundamental frequency, which brings difficulties to power control. ② Even under the condition of a balanced power grid, when it is necessary to compensate for unbalanced power in the three-phase power grid, due to the disadvantages of unified calculation, an AC component with twice the frequency will still be generated. For another example, currently, the single-phase active power and reactive power are also adopted. Since the orthogonal voltage and current data of the virtual method are obtained from the real phase voltage and current, there are still the following defects: ① Therefore, under the conditions of large grid harmonic content, non-standard sinusoidal grid voltage, or grid fluctuation transient conditions, there is an error between the calculated single-phase power and the actual instantaneous power. ② The process of calculating power by virtual orthogonal voltage and current is relatively cumbersome and has certain limitations. The method of storing a 1 / 4 cycle will bring feedback lag and transient distortion; the derivative method will amplify the grid harmonics during the calculation of power under the condition of large grid background harmonics, which will interfere with the calculation. The power independent calculation method is used to independently control the power to achieve the three-phase decoupling of the unbalanced power grid and unbalanced power. Summary of the Invention

[0003] To solve this problem, the present invention proposes a method and a detection system for detecting grid-connected power of a three-phase four-wire photovoltaic grid-connected energy storage system, which can realize the independent decoupling control of three-phase active power and reactive power and enhance the adaptability of the system to various grid conditions.

[0004] In the first aspect, a method for detecting grid-connected power of a three-phase four-wire photovoltaic grid-connected energy storage system according to the present invention includes:

[0005] The front-stage DC converter performs MPPT tracking to generate the total grid-connected active power command, and obtains the total reactive power command according to the total grid-connected active power command and the reactive power control mode;

[0006] The voltage and current information of the power grid is collected through a sampling circuit, and the single-phase active power and single-phase reactive power of the power grid are calculated;

[0007] Closed-loop control is performed according to the total reactive power command, the single-phase active power, and the single-phase reactive power to obtain a control signal output by the closed loop;

[0008] Grid connection control of the inverter is performed according to the control signal to obtain the active and reactive power outputs during grid connection.

[0009] Among them, the reactive power control mode includes a fixed reactive power control mode and a fixed power factor control mode.

[0010] Preferably, the calculation of the power to obtain the single-phase active power and single-phase reactive power of the power grid includes:

[0011] Calculating the active power, the formula is: P = U rms ·I rms ·cos(Δθ);

[0012] Calculating the reactive power, the formula is: Q = U rms ·I rms ·sin(Δθ);

[0013] I 有功 = I rms ·cos(Δθ) P = U rms ·I 有功

[0014] Define: I 无功 = I rms ·sin(Δθ); obtain: Q = U rms ·I 无功 ;

[0015] In the formula, U is the amplitude of the phase voltage; θ g is the phase of the phase voltage; I is the amplitude of the phase current; θ i is the phase of the phase current; is the effective value of the phase voltage; the phase voltage leads the phase current by Δθ = θ g - θ i ; the effective value of the phase current phase current phase θ i = θ g - Δθ; the phase voltage expression is U·cos(θ g ) ; the phase current expression is I·cos(θ i ).

[0016] Preferably, the calculation of the power to obtain the single-phase active power and single-phase reactive power of the power grid further includes: performing a sliding window calculation on the voltage effective value U rms Sliding window calculation:

[0017] Sliding window calculation expression:

[0018] Among them, U(n) is the sampled value of the phase voltage of the current system, n = (0, 1, ……, N), is the number of sampling points in a phase voltage cycle, is the sliding window calculation process; among them, the accumulated sum Each time when calculating, first subtract the corresponding sampling moment U(n) of the phase voltage in the previous cycle 2 旧值 , and then add the current sampling update value U(n) 2 .

[0019] Preferably, the power calculation to obtain the single-phase active power and single-phase reactive power of the power grid further includes: performing the calculation of the active current I 有功 Calculation:

[0020] Current expression: I 电流 = I·cos(θ i ), substituting θ i = θ g -Δθ into it to obtain I 电流 = I·cos(θ g -Δθ);

[0021] Multiply the current by the cosine value of the voltage phase to get:

[0022]

[0023] Perform the sliding window average calculation of the phase voltage cycle on I 有功变形 ; among them is the 2-fold frequency sine AC component of the phase voltage, and the average value is 0; the remaining sliding window period average value; the sliding window calculation expression is:

[0024]

[0025] Among them, I 电流 (n) is the current sampling current value, cos(θ g ) is the cosine value output by the phase-locked loop of the current phase voltage, is the number of sampling points in a phase voltage cycle;

[0026] Preferably, the power calculation to obtain the single-phase active power and single-phase reactive power of the power grid further includes: performing the calculation of the reactive current I 无功 Calculation:

[0027] Current expression: I 电流 = I·cos(θ i ), substituting θ i = θ g -Δθ into it to obtain:

[0028] I 电流 = I·cos(θ g -Δθ);

[0029] Multiply the current by the sine value of the voltage phase to get:

[0030]

[0031] For I 无功变形 perform a phase voltage periodic sliding window average calculation, where is the second harmonic sinusoidal AC component of the phase voltage, with an average value of 0; the remaining sliding window period average value to obtain I 无功 The sliding window calculation expression of is:

[0032]

[0033] where, I 电流 (n) is the current sampled current value, sin(θ g ) is the sinusoidal value output by the current phase voltage phase-locked loop, is the number of sampling points in a phase voltage period.

[0034] Preferably, the total reactive power command and the single-phase active power and single-phase reactive power are subjected to closed-loop control to obtain a closed-loop output control signal, including:

[0035] Adjust the reactive power output by the system to reach the given total reactive power command;

[0036] Calculate the reactive power error;

[0037] Through the three-phase independent controller, perform reactive power regulation so that the reactive power converges to the total reactive power command, and output the a-phase control signal, b-phase control signal and c-phase control signal to the inverter.

[0038] In a second aspect, the present invention also proposes a three-phase four-wire photovoltaic grid-connected energy storage system grid-connected power detection system, and the detection system includes:

[0039] A power command generation module, configured to track and generate a grid-connected total active power command, and obtain a total reactive power command according to the grid-connected total active power command and the reactive power control mode;

[0040] A power feedback calculation module, which collects the voltage and current information of the power grid through a sampling circuit, and performs power calculation to obtain the single-phase active power and single-phase reactive power of the power grid;

[0041] The three-phase independent controller performs closed-loop control according to the total reactive power command and the single-phase active power and single-phase reactive power to obtain a closed-loop output control signal;

[0042] A grid-connected inverter, configured to perform grid-connected control on the inverter according to the control signal to obtain grid-connected active and reactive power outputs.

[0043] Preferably, the power feedback calculation module further includes: a phase-locked module, a voltage and current sampling module, and a power calculation unit;

[0044] The phase-locked module is used to lock the grid frequency to obtain synchronous sampled voltage and current;

[0045] The voltage and current sampling module performs real-time voltage and current sampling, sends the voltage to the phase-locked module, and sends the current to the power calculation unit;

[0046] The power calculation unit is used to calculate single-phase active power and single-phase reactive power.

[0047] In a third aspect, the present invention further provides a three-phase four-wire photovoltaic grid-connected energy storage system, and the three-phase four-wire photovoltaic grid-connected energy storage system uses the detection system described in the second aspect to detect the grid-connected power of the three-phase four-wire photovoltaic grid-connected energy storage system.

[0048] Compared with the prior art, the present invention has the following beneficial effects:

[0049] Starting from the power definition, the present invention projects the phase current onto the phase voltage direction and the orthogonal direction, then uses the deformation of the product-to-sum formula, and finally extracts the active current and reactive current through periodic sliding window averaging to obtain the active and reactive power, realizing independent decoupling control of three-phase active and reactive power, and can adapt to unbalanced power grids and working conditions with unbalanced power demands. Further, the detection algorithm of the present invention uses mains power periodic sliding window averaging to calculate the components required for power calculation, which can reflect the change of grid-connected power within one mains power cycle, facilitating the real-time control of grid-connected power.

[0050] In summary, the active and reactive power detection and control algorithm enables the three-phase four-wire grid-connected energy storage system to have stronger adaptability and faster control response ability. BRIEF DESCRIPTION OF THE DRAWINGS

[0051] Figure 1 is a schematic diagram of the grid-connected power detection method of the three-phase four-wire photovoltaic grid-connected energy storage system of the present invention.

[0052] Figure 2 is a schematic diagram of the grid-connected power detection system of the three-phase four-wire photovoltaic grid-connected energy storage system of the present invention.

[0053] Figure 3 is a schematic diagram of the projection coordinates of voltage and current in the voltage direction of the present invention. DETAILED DESCRIPTION OF THE EMBODIMENTS

[0054] The following description is used to disclose the present invention so that those skilled in the art can implement the present invention. The preferred embodiments described below are only examples, and those skilled in the art can think of other obvious variations.

[0055] Example 1, as Figure 1-2 shown, a grid-connected power detection method for a three-phase four-wire photovoltaic grid-connected energy storage system according to the present invention. The present invention starts from the power definition and derives using the product-to-sum relationship of trigonometric functions. The calculation method does not require virtual data, which can ensure the accuracy and stability of the data calculation results. At the same time, the sliding window calculation can be used to accelerate the reactive power feedback and reduce the reactive power control tracking time. Specifically, the method includes:

[0056] The front-stage DC converter performs MPPT tracking to generate the total grid-connected active power command, and obtains the total reactive power command according to the total grid-connected active power command and the reactive power control mode;

[0057] Collect the voltage and current information of the power grid through the sampling circuit, and perform power calculation to obtain the single-phase active power and single-phase reactive power of the power grid;

[0058] Perform closed-loop control according to the total reactive power command, the single-phase active power, and the single-phase reactive power to obtain the control signal of the closed-loop output;

[0059] Perform grid-connected control on the inverter according to the control signal to obtain the grid-connected active and reactive power outputs.

[0060] Among them, the reactive power control mode includes a fixed reactive power control mode and a fixed power factor control mode.

[0061] Preferably, obtaining the total reactive power command according to the total grid-connected active power command and the reactive power control mode specifically includes:

[0062] 1. Obtain the total grid-connected active power command

[0063] Total active power command: The system obtains the total active power command through external input or internal calculation. This command represents the active power that the system requires the grid-connected inverter to provide, and is usually determined by factors such as load demand, grid conditions, or the maximum output power of the power generation system.

[0064] This command is often dynamically adjusted according to real-time load changes, the conditions of power generation resources (such as photovoltaic cells), etc.

[0065] 2. Select the reactive power control mode

[0066] There can be several different choices for the reactive power control mode. Common reactive power control modes include:

[0067] Power factor control mode: The system adjusts the reactive power to make the power factor of the power grid close to 1 (i.e., the reactive power is minimized) to improve the power transmission efficiency.

[0068] Reactive power command control mode: According to the set reactive power target, directly control the inverter to output a certain amount of reactive power.

[0069] Voltage control mode: The system controls the reactive power output by the inverter to regulate the grid voltage and ensure the stability of the grid voltage.

[0070] 3. Calculate the total reactive power command

[0071] The total reactive power command is usually calculated based on the total active power command and the selected reactive power control mode. The core idea of the calculation is to determine the reactive power output according to the active power demand, combined with the goal or strategy of reactive power control. The calculation process may include the following steps:

[0072] Power factor target: If the power factor control mode is adopted, the system will set a target power factor (for example, 0.95 or 1.0), and calculate the required reactive power through the total active power command. Usually, the relationship between the power factor, active power, and reactive power is given by the following formula:

[0073] Q = P × tan(arccos(power factor));

[0074] Where P is the total active power, Q is the reactive power, and the power factor is usually between 0 and 1.

[0075] If the voltage control mode is selected, the system may dynamically adjust the reactive power output according to the voltage demand of the grid to maintain the stability of the grid voltage. At this time, the total reactive power command may be adjusted according to the voltage and the requirements of the grid.

[0076] In practical applications, the grid load may change. Therefore, the total reactive power command may be adjusted in real time according to the change of the grid load. For example, when the load increases, more reactive power may be required to stabilize the voltage. The inverter will adjust the output according to the real-time grid voltage and power feedback information to ensure consistency with the total reactive power command. In dynamic situations (such as load changes or grid voltage fluctuations), the system will continuously monitor and adjust the total reactive power command in real time according to the feedback information.

[0077] After calculating the total reactive power command, the control system will generate corresponding control signals, which will be transmitted to the inverter to guide the inverter to output the corresponding reactive power.

[0078] Preferably, as Figure 3 shown, the power calculation to obtain the single-phase active power and single-phase reactive power of the grid includes:

[0079] Active power: It can be regarded as the product of the effective value of the voltage and the projection of the effective value of the current in the voltage direction.

[0080] To calculate the active power, the formula is: P = U rms ·Irms · cos(Δθ);

[0081] Reactive power: It can be regarded as the product of the effective value of voltage U rms and the effective value of current I rms and the projection product in the direction perpendicular to the voltage by 90°.

[0082] To calculate the reactive power, the formula is:

[0083]

[0084] Summary expression:

[0085] P = U rms · I rms · cos(Δθ)

[0086] Q = U rms · I rms · sin(Δθ);

[0087] Furthermore, define:

[0088] I 有功 = I rms · cos(Δθ)

[0089] I 无功 = I rms · sin(Δθ)

[0090] Get:

[0091] P = U rms · I 有功

[0092] Q = U rms · I 无功 .

[0093] To solve the active power and reactive power from the above expressions, it is necessary to calculate the values of the three components U rms , I 有功 , I 无功 .

[0094] In the formula, U is the amplitude of the phase voltage; θ g is the phase of the phase voltage; I is the amplitude of the phase current; θ i is the phase of the phase current; is the effective value of the phase voltage; the voltage leads the current phase the effective value of the phase current the phase of the phase current θ i = θ g - Δθ; the phase voltage expression is U · cos(θ g ); the phase current expression is I · cos(θ i ).

[0095] Preferably, the power calculation to obtain the single-phase active power and single-phase reactive power of the power grid further includes: calculating the effective voltage U rms Sliding window calculation:

[0096] Sliding window calculation expression:

[0097] where U(n) is the sampled value of the phase voltage of the current system, n = (0, 1, ……, N), is the number of sampling points in a phase voltage cycle, is the sliding window calculation process; among them, the sum subtracts the sampled value U(n) at the corresponding sampling moment in the previous cycle of the phase voltage each time during calculation 2 旧值 , and then adds the current sampling update value U(n) 2 .

[0098] Preferably, the power calculation to obtain the single-phase active power and single-phase reactive power of the power grid further includes: calculating the active current I 有功 Calculation:

[0099] Current expression: I 电流 = I·cos(θ i ), substituting θ i = θ g -Δθ gives I 电流 = I·cos(θ g -Δθ);

[0100] To obtain the active current, multiply the current by the cosine value of the voltage phase to get:

[0101]

[0102] As known before, I 有功 = I rms ·cos(Δθ), perform sliding window average calculation on I 有功变形 in the phase voltage cycle, where is the double-frequency sine AC component of the phase voltage, and its average value is 0; the remaining sliding window period average value.

[0103] Therefore, the sliding window calculation expression is:

[0104]

[0105] where, I 电流 (n) is the current sampled current value, cos(θ g ) is the cosine value output by the phase-locked loop of the current phase voltage, is the number of sampling points in a phase voltage cycle.

[0106] Preferably, the power calculation to obtain the single-phase active power and single-phase reactive power of the power grid further includes: performing reactive current I 无功 Calculation:

[0107] Current expression: I 电流 = I·cos(θ i ), substituting θ i = θ g -Δθ gives:

[0108] I 电流 = I·cos(θ g -Δθ);

[0109] To obtain the reactive current, multiply the current by the sine value of the voltage phase to get:

[0110]

[0111] As known before, I 无功 = I rms ·sin(Δθ), perform a phase voltage cycle sliding window average calculation on I 无功变形 , where is the 2nd harmonic sinusoidal AC component of the phase voltage, and the average value is 0; the remaining sliding window period average value gives the sliding window calculation expression of I 无功 as:

[0112]

[0113] where, I 电流 (n) is the current sampled current value, sin(θ g ) is the sine value output by the current phase voltage phase-locked loop, is the number of sampling points in a phase voltage cycle.

[0114] Since U rms , I 有功 , I 无功 in the power calculation process are all calculated by the sliding window average method, while taking into account the accuracy and stability of the data calculation results, the power change situation can be reflected within the mains cycle, and the control response of the active and reactive power can be accelerated.

[0115] Preferably, the total reactive power command and the single-phase active power and single-phase reactive power are closed-loop controlled to obtain a closed-loop output control signal, including:

[0116] Define the target and input quantity

[0117] Target: Adjust the reactive power output by the system to reach the given total reactive power command.

[0118] Input quantity:

[0119] Single-phase active power: The measured or calculated active power.

[0120] Single-phase reactive power: The measured or calculated reactive power.

[0121] Total reactive power command: The reactive power command provided by the superior control system or external signal.

[0122] Real-time sampling of single-phase active power and single-phase reactive power:

[0123] P1 = Single-phase active power measured in real time;

[0124] Q1 = Single-phase reactive power measured in real time;

[0125] Compare the total reactive power command with the actual reactive power:

[0126] e Q = Q ref - Q1;

[0127] eQ is the reactive power error; Q ref is the three-phase total reactive power setting.

[0128] Reactive power control logic:

[0129] Q ref : Three-phase total reactive power setting;

[0130] P x = Single-phase active power measured in real time (x = a, b, c);

[0131] Q x = Single-phase reactive power measured in real time (x = a, b, c);

[0132] The single-phase reactive power setting is distributed in the following ways:

[0133] Uniform equal distribution of single-phase reactive power setting:

[0134] Single-phase reactive power setting is distributed according to the actual active power:

[0135] Reactive power control, independent control of three-phase reactive power:

[0136] Q x_err : Single-phase reactive power control error;

[0137] Q x_err = Q x-ref - Q x ;

[0138] Single-phase reactive power Q x Independently track the single-phase reactive power reference Q x-ref , the single-phase reactive power converges to the single-phase reactive power reference, so that the three-phase total reactive power converges to the three-phase total reactive power command.

[0139] The reactive power is regulated by a three-phase independent controller, so that the reactive power converges to the total reactive power command, and the control signals of phase a, phase b, and phase c are output to the inverter. The goal of the closed-loop control is to continuously adjust the system output by real-time monitoring the reactive power and comparing it with the target value until the actual reactive power reaches the target total reactive power. This process depends on a suitable control algorithm (such as a PI controller) and a fast-response regulating device.

[0140] Starting from the power definition, the present invention projects the phase current onto the phase voltage direction and the orthogonal direction, then uses the deformation of the product-to-sum formula, and finally extracts the active current and reactive current by means of periodic sliding window averaging to obtain the active and reactive power, realizing the independent decoupling control of three-phase active and reactive power, and can adapt to the working conditions of unbalanced power grids and unbalanced power demands. Moreover, the present invention uses the mains cycle sliding window averaging to calculate the components required for power calculation, which can reflect the change of the grid-connected power within one mains cycle, and is beneficial to the real-time control of the grid-connected power.

[0141] Embodiment 2, the present invention also proposes a grid-connected power detection system for a three-phase four-wire photovoltaic grid-connected energy storage system, and the detection system includes:

[0142] A power command generation module, configured to track and generate a grid-connected total active power command, and obtain a total reactive power command according to the grid-connected total active power command and the reactive power control mode;

[0143] A power feedback calculation module, which collects the voltage and current information of the power grid through a sampling circuit, and calculates the power to obtain the single-phase active power and single-phase reactive power of the power grid;

[0144] The three-phase independent controller performs closed-loop control according to the total reactive power command, the single-phase active power, and the single-phase reactive power to obtain the control signals output by the closed-loop;

[0145] A grid-connected inverter, configured to perform grid-connected control on the inverter according to the control signal to obtain grid-connected active and reactive power outputs.

[0146] Preferably, the power feedback calculation module further includes: a phase-locked module, a voltage and current sampling module, and a power calculation unit;

[0147] The phase-locked module is used to lock the grid frequency to obtain synchronous sampling voltage and current;

[0148] The voltage and current sampling module performs real-time voltage and current sampling, sends the voltage to the phase-locked module, and sends the current to the power calculation unit;

[0149] The power calculation unit is used to calculate the single-phase active power and the single-phase reactive power.

[0150] Embodiment 3: The present invention also provides a three-phase four-wire photovoltaic grid-connected energy storage system. The three-phase four-wire photovoltaic grid-connected energy storage system uses the detection system described in the second aspect to detect the grid-connected power of the three-phase four-wire photovoltaic grid-connected energy storage system.

[0151] The foregoing has shown and described the basic principles, main features, and advantages of the present invention. Those skilled in the art should understand that the present invention is not limited by the above embodiments. What is described in the above embodiments and the specification is only the principle of the present invention. Without departing from the spirit and scope of the present invention, the present invention will have various changes and improvements, and these changes and improvements all fall within the scope of the present invention claimed. The scope of protection claimed by the present invention is defined by the appended claims and their equivalents.

Claims

1. A grid-connected power detection method for a three-phase four-wire photovoltaic grid-connected energy storage system, characterized in that, The method includes: The pre-stage DC converter performs MPPT tracking to generate the total grid-connected active power command, and obtains the total reactive power command according to the total grid-connected active power command and the reactive power control mode; The voltage and current information of the power grid is collected through a sampling circuit, and the single-phase active power and single-phase reactive power of the power grid are obtained through power calculation; Closed-loop control is performed according to the total reactive power command, the single-phase active power, and the single-phase reactive power to obtain the control signal of the closed-loop output; Grid-connected control of the inverter is performed according to the control signal to obtain grid-connected active and reactive power outputs.

2. The grid-connected power detection method of the three-phase four-wire photovoltaic grid-connected energy storage system according to claim 1, wherein The obtaining of the single-phase active power and single-phase reactive power of the power grid through power calculation includes: Calculate the active power, and the formula is: P = U rms ·I rms ·cos(Δθ); Calculate the reactive power, and the formula is: Q = U rms ·I rms ·sim(Δθ); Definition: Obtained: Wherein, U is the amplitude of the phase voltage; θ g is the phase of the phase voltage; I is the amplitude of the phase current; θ i is the phase of the phase current; is the effective value of the phase voltage; the phase angle by which the voltage leads the current is Δθ = θ g - θ i ; the effective value of the phase current The phase of the phase current θ i = θ g - Δθ; the expression of the phase voltage is U·cos(θ g ); the expression of the phase current is I·cos(θ i ).

3. The grid-connected power detection method for a three-phase four-wire photovoltaic grid-connected energy storage system according to claim 2, wherein, The power calculation to obtain the single-phase active power and single-phase reactive power of the power grid further includes: performing a root-mean-square voltage U rms Sliding window calculation: Sliding window calculation expression: where U(n) is the sampled value of the phase voltage of the current system, n = (0, 1, ……, N), is the number of sampling points in one phase voltage period, is the sliding window calculation process; among them, the cumulative sum subtracts the sampled value U(n) at the corresponding sampling moment in the previous phase voltage period each time during calculation 2 旧值 , and then adds the current sampled update value U(n) 2 .

4. The grid-connected power detection method for the three-phase four-wire photovoltaic grid-connected energy storage system according to claim 3, wherein, The power calculation to obtain the single-phase active power and single-phase reactive power of the power grid further includes: calculating the active current I 有功 Calculation: Current expression: I 电流 = I·cos(θ i ), substituting θ i = θ g -Δθ gives I 电流 = I·cos(θ g -Δθ); Multiplying the current by the cosine value of the voltage phase to obtain: For I 有功变形 perform phase voltage periodic sliding window averaging calculation; where is the 2nd harmonic sinusoidal AC component of the phase voltage, with an average value of 0; the remaining sliding window period average value; the sliding window calculation expression is: Among them, I 电流 (n) is the current sampled current value, cos(θ g ) is the cosine value output by the phase voltage phase-locked loop, is the number of sampling points in one phase voltage period.

5. The grid-connected power detection method for the three-phase four-wire photovoltaic grid-connected energy storage system according to claim 4, characterized in that, The power calculation to obtain the single-phase active power and single-phase reactive power of the power grid further includes: calculating the reactive current I 无功 Calculation: Current expression: I 电流 = I·cos(θ i ), substituting θ i = θ g - Δθ gives: I 电流 = I·cos(θ g -Δθ); Multiplying the current by the sine value of the voltage phase to obtain: For I 无功变形 perform a phase voltage periodic sliding window average calculation, where is the second harmonic sinusoidal AC component of the phase voltage, and its average value is 0; the remaining sliding window period average value gives I 无功 The sliding window calculation expression of is: Among them, I 电流 (n) is the current sampled current value, sin(θ g ) is the sine value output by the phase voltage phase-locked loop, is the number of sampling points in one phase voltage period.

6. The grid-connected power detection method for a three-phase four-wire photovoltaic grid-connected energy storage system according to claim 1, characterized in that, The reactive power control mode includes a fixed reactive power control mode and a fixed power factor control mode.

7. The grid-connected power detection method of the three-phase four-wire photovoltaic grid-connected energy storage system according to claim 1, characterized in that The closed-loop control of the total reactive power command, the single-phase active power, and the single-phase reactive power to obtain the control signal of the closed-loop output includes: Adjusting the reactive power output by the system to reach the given total reactive power command; Calculating the reactive power error; The three-phase independent controller performs reactive power regulation so that the reactive power converges to the total reactive power command, and outputs the a-phase control signal, b-phase control signal, and c-phase control signal to the inverter.

8. A detection system adopting the grid-connected power detection method of the three-phase four-wire photovoltaic grid-connected energy storage system according to any one of claims 1-7, characterized in that, The detection system includes: A power command generation module, which is used to track and generate the total grid-connected active power command, and obtain the total reactive power command according to the total grid-connected active power command and the reactive power control mode; A power feedback calculation module, which collects the voltage and current information of the power grid through a sampling circuit, and performs power calculation to obtain the single-phase active power and single-phase reactive power of the power grid; The three-phase independent controller performs closed-loop control according to the total reactive power command, the single-phase active power, and the single-phase reactive power to obtain the control signal of the closed-loop output; A grid-connected inverter, which is used to perform grid-connected control of the inverter according to the control signal to obtain grid-connected active and reactive power outputs.

9. The detection system according to claim 8, wherein The power feedback calculation module further includes: a phase-locked module, a voltage and current sampling module, and a power calculation unit; The phase-locked module is used to lock the grid frequency to obtain synchronous sampling voltage and current; the voltage and current sampling module performs real-time voltage and current sampling, and sends the voltage to the phase-locked module and the current to the power calculation unit; The power calculation unit is used to calculate the single-phase active power and single-phase reactive power.

10. A three-phase four-wire photovoltaic grid-connected energy storage system, characterized in that, The three-phase four-wire photovoltaic grid-connected energy storage system uses the detection system described in any one of claims 8-9 to detect the grid-connected power of the three-phase four-wire photovoltaic grid-connected energy storage system.

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