Unbalanced power control method and device and three-phase inverter

Abstract

The invention relates to the technical field of electronic power, and discloses an unbalanced power control method and device and a three-phase inverter, the method is applied to a controller of the three-phase inverter, and the method comprises the following steps: obtaining a power grid voltage, an AC side output current and an ammeter power corresponding to each phase line of the three-phase inverter; performing positive sequence extraction and phase locking calculation based on the power grid voltage to obtain a positive sequence component angle; converting the output current and the power grid voltage by using the positive sequence component angle to obtain a current component and a power grid voltage component under the dq0 coordinate system; further, based on a feed network point power limit value, a positive sequence component angle and the like, determining a current given value under the dq0 coordinate system; and finally, performing loop control processing on each parameter under the dq0 coordinate system to obtain a three-phase modulation signal. The method does not need to directly extract the positive and negative sequence components of the alternating current side output current, namely, does not need to add a negative sequence loop, and reduces the calculation amount, the occupation of calculation resources and the like.

Description

Technical Field

[0001] The present application relates to the field of power electronics technology, and in particular to an unbalanced power control method, device and three-phase inverter. Background Art

[0002] For the scenario of photovoltaic energy storage grid-connected system, there is often a three-phase imbalance phenomenon, so it is necessary to adopt a corresponding unbalanced control algorithm to deal with it. For example, the traditional solution mainly includes an unbalanced control algorithm based on positive and negative sequence separation and decoupling control. However, since the algorithm includes positive and negative sequence separation of grid voltage and inductor current, phase locking based on positive sequence grid voltage, decoupling control based on positive and negative zero sequence separation, and considering that both positive and negative sequences are based on fundamental wave extraction, the algorithm also needs to add additional suppression strategies for each current harmonic, so the overall control calculation is complicated and requires more computing resources. Summary of the invention

[0003] In view of this, the embodiments of the present application provide an unbalanced power control method, device and three-phase inverter, which can effectively solve the problem of complicated calculations and occupying more computing resources in existing solutions.

[0004] In a first aspect, an embodiment of the present application provides an unbalanced power control method, which is applied to a controller of a three-phase inverter, comprising:

[0005] Obtaining the grid voltage, AC side output current and meter power corresponding to each phase line of the three-phase inverter;

[0006] Based on the grid voltage corresponding to each phase line, positive sequence extraction and phase-locked calculation are performed to obtain the grid voltage positive sequence component angle;

[0007] Using the positive sequence component angle of the grid voltage, coordinate transformation is performed on the AC side output current corresponding to each phase line to obtain the current component in the dq0 coordinate system;

[0008] Using the grid voltage positive sequence component angle, coordinate transformation is performed on the grid voltage corresponding to each phase line to obtain the grid voltage component in the dq0 coordinate system;

[0009] Determine the current amplitude given value corresponding to each phase line and the power phase angle corresponding to each phase line based on the grid voltage corresponding to each phase line, the meter power corresponding to each phase line and the feeder point power limit value corresponding to each phase line;

[0010] Determine a current given value in the dq0 coordinate system based on the current amplitude given value corresponding to each of the phase lines, the grid voltage positive sequence component angle and the power phase angle corresponding to each of the phase lines;

[0011] The current given value in the dq0 coordinate system, the current component in the dq0 coordinate system and the grid voltage component in the dq0 coordinate system are processed by loop control to obtain a three-phase modulation signal for driving and controlling each phase bridge arm of the three-phase inverter.

[0012] In a second aspect, an embodiment of the present application provides an unbalanced power control device, which is applied to a controller of a three-phase inverter, including:

[0013] A data acquisition module, used to obtain the grid voltage, AC side output current and meter power corresponding to each phase line of the three-phase inverter;

[0014] A positive sequence extraction and phase locking module, used to perform positive sequence extraction and phase locking calculation based on the grid voltage corresponding to each phase line, to obtain the grid voltage positive sequence component angle;

[0015] A current component calculation module, used to perform coordinate transformation on the AC side output current corresponding to each phase line using the positive sequence component angle of the grid voltage, to obtain the current component in the dq0 coordinate system;

[0016] A voltage component calculation module, used to perform coordinate transformation on the grid voltage corresponding to each phase line using the grid voltage positive sequence component angle to obtain the grid voltage component in the dq0 coordinate system;

[0017] A power calculation module, used to determine the current amplitude given value corresponding to each phase line and the power phase angle corresponding to each phase line based on the grid voltage corresponding to each phase line, the meter power corresponding to each phase line and the feeder point power limit value corresponding to each phase line;

[0018] A current given value calculation module, used to determine the current given value in the dq0 coordinate system based on the current amplitude given value corresponding to each phase line, the grid voltage positive sequence component angle and the power phase angle corresponding to each phase line;

[0019] The control signal acquisition module is used to process the current given value in the dq0 coordinate system, the current component in the dq0 coordinate system and the grid voltage component in the dq0 coordinate system through loop control to obtain a three-phase modulation signal for driving and controlling each phase bridge arm of the three-phase inverter.

[0020] In a third aspect, an embodiment of the present application provides a three-phase inverter, the three-phase inverter comprising a controller and a memory, the memory storing a computer program, and the controller being used to execute the computer program to implement the unbalanced power control method.

[0021] The embodiments of the present application have the following beneficial effects:

[0022] The unbalanced power control method of the present application only extracts and locks the positive sequence of the grid voltage corresponding to each phase line of the three-phase inverter to obtain the positive sequence component angle of the grid voltage, and then transforms the AC side output current and grid voltage of the three-phase inverter into current components and grid voltage components in the dq0 coordinate system according to the positive sequence component angle of the grid voltage, and further calculates the current given value in the dq0 coordinate system, and finally uses the current component, grid voltage component and current given value in the dq0 coordinate system to obtain the three-phase modulation signal. Since there is no need to directly extract the positive and negative sequence of the AC side output current, there is no need to add a negative sequence loop, which reduces the amount of calculation and thus reduces the occupation of computing resources. BRIEF DESCRIPTION OF THE DRAWINGS

[0023] In order to more clearly illustrate the technical solutions of the embodiments of the present application, the drawings required for use in the embodiments will be briefly introduced below. It should be understood that the following drawings only show certain embodiments of the present application and therefore should not be regarded as limiting the scope. For ordinary technicians in this field, other related drawings can be obtained based on these drawings without paying creative work.

[0024] Figure 1 A schematic structural diagram of a three-phase inverter according to an embodiment of the present application is shown;

[0025] Figure 2 A flow chart of an unbalanced power control method according to an embodiment of the present application is shown;

[0026] Figure 3 A schematic diagram showing a positive-sequence grid voltage phase locking according to an embodiment of the present application is shown;

[0027] Figure 4 A schematic diagram showing coordinate transformation of output current components according to an embodiment of the present application is shown;

[0028] Figure 5 A schematic diagram showing coordinate transformation of grid voltage components according to an embodiment of the present application is shown;

[0029] Figure 6 A flow chart showing a calculation of a given value of a d-axis current according to an embodiment of the present application is shown;

[0030] Figure 7 A flow chart of an unbalanced power control loop according to an embodiment of the present application is shown;

[0031] Figure 8 A schematic diagram of the structure of a photovoltaic energy storage grid-connected system according to an embodiment of the present application is shown;

[0032] Fig. 9 A schematic diagram of power distribution when the power limit of a feeder point is 0 is shown;

[0033] Fig.10 A schematic diagram of power distribution after a load change is shown;

[0034] Fig.11 Shows the Fig.10 Output waveform of each phase when unbalanced power control is performed;

[0035] Fig.12 A structural schematic diagram of an unbalanced power control device according to an embodiment of the present application is shown.

[0036] Description of main component symbols:

[0037] 10- three-phase inverter; 11- controller; 12- memory; 13- inverter bridge circuit;

[0038] 100-unbalanced power control device; 110-data acquisition module; 120-positive sequence extraction and phase locking module; 130-current component calculation module; 140-voltage component calculation module; 150-power calculation module; 160-current set value calculation module; 170-control signal acquisition module. DETAILED DESCRIPTION

[0039] The technical solutions in the embodiments of the present application will be described clearly and completely below in conjunction with the drawings in the embodiments of the present application. Obviously, the described embodiments are only part of the embodiments of the present application, rather than all of the embodiments.

[0040] The components of the embodiments of the present application generally described and shown in the drawings herein may be arranged and designed in various configurations. Therefore, the following detailed description of the embodiments of the present application provided in the drawings is not intended to limit the scope of the application claimed for protection, but merely represents the selected embodiments of the present application. Based on the embodiments of the present application, all other embodiments obtained by those skilled in the art without making creative work belong to the scope of protection of the present application.

[0041] Hereinafter, the terms "including", "having" and their cognates used in various embodiments of the present application are intended only to indicate specific features, numbers, steps, operations, elements, components or a combination of the foregoing items, and should not be understood as first excluding the existence of one or more other features, numbers, steps, operations, elements, components or a combination of the foregoing items or increasing the possibility of one or more features, numbers, steps, operations, elements, components or a combination of the foregoing items. In addition, the terms "first", "second", "third" and the like are only used to distinguish descriptions and cannot be understood as indicating or implying relative importance.

[0042] Unless otherwise defined, all terms (including technical terms and scientific terms) used herein have the same meanings as those generally understood by those skilled in the art to which the various embodiments of the present application belong. The terms (such as those defined in generally used dictionaries) will be interpreted as having the same meanings as the contextual meanings in the relevant technical field and will not be interpreted as having idealized meanings or overly formal meanings unless clearly defined in the various embodiments of the present application.

[0043] In conjunction with the accompanying drawings, some embodiments of the present application are described in detail below. In the absence of conflict, the following embodiments and features in the embodiments can be combined with each other.

[0044] The present application proposes a three-phase inverter 10, which can be applied to different fields such as industry, agriculture and home. Taking home as an example, it can be applied to photovoltaic energy storage grid-connected systems installed in homes. Figure 1 As shown, the three-phase inverter 10 includes a controller 11, a memory 12, and an inverter bridge circuit 13 for realizing power conversion, wherein the inverter bridge circuit 13 is composed of three bridge arms consisting of at least 6 power switch tubes, and the memory 12 stores a computer program. The controller 11 runs the computer program to enable the three-phase inverter 10 to execute the unbalanced power control method of the embodiment of the present application.

[0045] Among them, the controller 11 can be an integrated circuit chip with signal processing capabilities. The controller can be a general-purpose processor, including a central processing unit (CPU), a graphics processing unit (GPU) and a network processor (NP), a digital signal processor (DSP), an application-specific integrated circuit (ASIC), a field-programmable gate array (FPGA) or other programmable logic devices, discrete gates or transistor logic devices, discrete hardware components. At least one of the general-purpose processor can be a microprocessor or the processor can also be any conventional processor, etc., which can implement or execute the disclosed methods, steps and logic block diagrams in the embodiments of the present application.

[0046] The memory 12 may be, but is not limited to, a random access memory (RAM), a read only memory (ROM), a programmable read-only memory (PROM), an erasable programmable read-only memory (EPROM), an electrically erasable read-only memory (EEPROM), etc. The memory is used to store a computer program, and the processor may execute the computer program accordingly after receiving an execution instruction.

[0047] Based on the three-phase inverter 10 of the above structure, the unbalanced power control method applied to the three-phase inverter 10 proposed in the present application does not need to directly separate the positive and negative sequence components of the grid voltage and the inductor current like the traditional solution, but only extracts the positive sequence component of the grid voltage, and combines the voltage phase lock and unbalanced loop control algorithm at the same time to calculate the power control of each phase of the three-phase inverter 10, which can achieve compatible balanced and unbalanced power control while reducing the complexity of the overall control calculation, thereby reducing the occupation of computing resources. In addition, combined with the single-phase anti-backflow strategy, this method can also meet the anti-backflow requirements, etc.

[0048] The unbalanced power control method according to the embodiment of the present application is described in detail below.

[0049] Figure 2 A flow chart of an unbalanced power control method according to an embodiment of the present application is shown. Exemplarily, the unbalanced power control method comprises the following steps:

[0050] S110 , obtaining the grid voltage, AC side output current and meter power corresponding to each phase line of the three-phase inverter 10 .

[0051] The AC side of the three-phase inverter 10 is used to connect to three-phase AC power (such as a power grid, etc.), and the output current of the AC side is also called the inductor current. This is because the AC side of the three-phase inverter 10 is provided with an output filter unit, and the output filter unit is mainly composed of an inductor and a capacitor. Therefore, the current flows through the inductor and then outputs. Figure 2 As shown, various electrical loads and electricity meters are usually arranged between the three-phase inverter 10 and the power grid, wherein the electricity meter can be a single-phase meter or a three-phase meter, which is used to perform power monitoring and electricity billing on the electrical loads of each phase.

[0052] Exemplarily, when the three-phase inverter 10 operates in a grid-connected system, the three-phase inverter 10 will obtain the grid voltage, the output current on the AC side and the meter power corresponding to each phase line in real time, and then calculate the power reference value of each phase of the three-phase inverter 10 to achieve separate control of the power of each phase.

[0053] S120, performing positive sequence extraction and phase-locking calculation based on the grid voltage corresponding to each phase line to obtain the grid voltage positive sequence component angle.

[0054] In this embodiment, the positive sequence of the grid voltage is extracted only on the three-phase line to obtain the positive sequence component of the grid voltage, and then the phase of the positive sequence component of the grid voltage is locked by using a phase-locked loop.

[0055] In one embodiment, phase locking can be achieved using αβ0 coordinate transformation, exemplarily, as Figure 3 As shown in the figure, positive sequence extraction refers to the grid voltage of each phase line (denoted as Ug a , Ug b , Ug c ) is transformed from the three-phase abc coordinate system to the αβ0 coordinate system (also known as Clark transformation) to obtain the corresponding voltage conversion component (denoted as Ug α , Ug β , Ug 0 ), and then extract the positive sequence component of the grid voltage (denoted as Ug α+ and Ug β+ ); finally, the PI closed-loop control is used to phase-lock the positive-sequence component of the grid voltage, that is, the phase-locked calculation of the positive-sequence component of the grid voltage is realized. Figure 3 The locked phase shown is the above-mentioned grid voltage positive sequence component angle θ. It can be understood that the αβ0 coordinate system is a coordinate system fixed on the stator, wherein the α axis in the αβ0 coordinate system coincides with the a axis in the abc coordinate system.

[0056] S130, using the grid voltage positive sequence component angle to perform coordinate transformation on the AC side output current corresponding to each phase line to obtain the current component in the dq0 coordinate system. The current component in the dq0 coordinate system includes the d-axis current component, the q-axis current component and the 0-axis current component.

[0057] For example, in one embodiment, Figure 4 As shown, by a 、i b 、i c ) is transformed from the abc coordinate system to the αβ0 coordinate system, and the corresponding current component (denoted as i α 、i β 、i 0); Then, the positive sequence component angle θ is used to transform the current component from the αβ0 coordinate system to the dq0 coordinate system (also called Park transformation), thereby obtaining the d-axis current component, the q-axis current component and the 0-axis current component (referred to as i d 、i q 、i 0 ). The only difference between the αβ0 coordinate system and the dq0 coordinate system is that the αβ0 coordinate system is fixed on the stator, while the dq0 coordinate system is fixed on the rotor.

[0058] S140, using the grid voltage positive sequence component angle to transform the grid voltage corresponding to each phase line to obtain the grid voltage component in the dq0 coordinate system. The grid voltage component in the dq0 coordinate system includes the d-axis grid voltage component, the q-axis grid voltage component and the 0-axis grid voltage component.

[0059] In one embodiment, Figure 5 As shown in the figure, the grid voltage positive sequence component angle θ can be used to transform the grid voltage component in the αβ0 coordinate system to the dq0 coordinate system, and the d-axis grid voltage component, q-axis grid voltage component and 0-axis grid voltage component (respectively denoted as Ug d , Ug q , Ug 0 It can be understood that the 0-axis grid voltage component is equal in the αβ0 coordinate system and the dq0 coordinate system.

[0060] S150, based on the grid voltage corresponding to each phase line, the meter power corresponding to each phase line and the feeding point power limit value corresponding to each phase line, determine the current amplitude given value corresponding to each phase line and the power phase angle corresponding to each phase line.

[0061] In order to avoid the reverse flow phenomenon of the output current corresponding to each phase line of the three-phase inverter 10, in this embodiment, when calculating the power reference value of each phase of the three-phase inverter 10, the limiting strategy of the single-phase feeding point power will be combined, so as to achieve the three-phase unbalanced control and single-phase reverse flow prevention purposes at the same time.

[0062] In one embodiment, step S150 includes the following sub-steps (not shown in the figure):

[0063] S210, based on the difference between the meter power corresponding to each phase line and the preset feeder power limit value corresponding to each phase line, the real-time acquired active power set value corresponding to each phase line in the three-phase inverter 10 is iterated to obtain an updated active power set value corresponding to each phase line.

[0064] Exemplarily, the three-phase inverter 10 obtains the reverse current limiting power value (denoted as P) issued by the energy control system (EMS) connected to it for communication. limit_tot), and the average value is calculated to obtain the reverse power of the feeder points corresponding to the three phase lines, that is, the above-mentioned feeder point power limit value (which can be recorded as P limita , P limitb , P limitC ). Then, calculate the meter power corresponding to each phase line (denoted as P metera , P meterb , P meterc ) and the power limit value of the feeder point of the corresponding phase line. Finally, according to the obtained power given value (denoted as P) corresponding to each phase line of the three-phase inverter 10 setouta , P setoutb , P setoutc ), the above difference of each phase line is used to iterate the power given value to obtain the updated active power given value corresponding to each phase line. This is because the power of the load will change in real time, so continuous iteration is required to obtain the latest power limit value of each phase line, so as to ensure the timeliness and reliability of system protection.

[0065] For example, if described by a formula, we have:

[0066] detaP x =P meterx -P limita , x=a,b,c;

[0067] P setoutx (t) =P setoutx (t-1) -detaP x t≥1;

[0068] In the formula, x represents the phase line, detaP x represents the difference between the meter power corresponding to each phase line of the three-phase inverter 10 and the power limit value of the feeding point, t and t-1 represent the current time and the previous time respectively, P setoutx (t) and P setoutx (t-1) They represent the power given values ​​at time t and time t-1 respectively.

[0069] It should be understood that in the grid-connected system, the power set value corresponding to each phase line can be obtained by taking the minimum value between the phase limit power values ​​set corresponding to the above-mentioned anti-backflow function and other functions (such as self-generation and self-use function, temperature derating function, grid response function, etc.).

[0070] For example, if described by a formula, we have:

[0071] P setoutx =Min(P setx ,P setx_other )x=a,b,c;

[0072] Where P setx Indicates the phase limit power value corresponding to the anti-backflow function, which corresponds to the active power; P setx_other Indicates the phase limit power value corresponding to other functions.

[0073] For example, when the system operates in the self-generation and self-use mode, if the photovoltaic energy is sufficient, the three-phase inverter 10 can output 10kW and feed it into the grid, but the phase limit power value in the anti-backflow function module is set to 0W. At this time, the output active power set value of each phase should be 0W.

[0074] S220, based on the active power given value corresponding to each phase line and the acquired reactive power given value corresponding to each phase line, calculate the apparent power corresponding to each phase line and the power phase angle corresponding to each phase line.

[0075] Furthermore, by obtaining the reactive power given value corresponding to each phase line and combining it with the updated active power given value, the apparent power and power phase angle corresponding to each phase line can be calculated. Specifically, the calculation formula is as follows:

[0076] S setx =P setx +jQ setx ,x=a,b,c

[0077]

[0078] In the formula, S setx Indicates the apparent power corresponding to each phase line, S setxm Indicates the apparent power amplitude corresponding to each phase line; P setx and Q setx Respectively represent the active power and reactive power corresponding to each phase line; j represents an imaginary number; σ setx Indicates the power phase angle corresponding to each phase line, which is related to the power factor angle δ of each phase setx are equal.

[0079] S230, calculating a given current amplitude value corresponding to each phase line according to the effective value of the grid voltage corresponding to each phase line and the amplitude of the apparent power of the corresponding phase line.

[0080] Exemplarily, it can be calculated according to the following formula:

[0081]

[0082] Where U rmsa , U rmsb , U rmsc Respectively represent the effective value of the grid voltage corresponding to the three-phase lines a, b, and c; I setam ,I setbm,I setcm They respectively represent the given current amplitude values ​​corresponding to the three-phase lines a, b, and c.

[0083] S160, based on the current amplitude given value corresponding to each phase line, the grid voltage positive sequence component angle and the power phase angle corresponding to each phase line, determine the current given value in the dq0 coordinate system. The current given value in the dq0 coordinate system includes the d-axis current given value, the q-axis current given value and the 0-axis current given value.

[0084] To obtain a given current value in the dq0 coordinate system, in one implementation, step S160 includes the following sub-steps (not shown in the figure):

[0085] S310, based on the current amplitude given value corresponding to each phase line and the power phase angle corresponding to each phase line, respectively calculate the positive sequence current given value amplitude, the negative sequence current given value amplitude, the negative sequence phase angle, the 0 sequence current given value amplitude and the 0 sequence phase angle.

[0086] Since the current lags behind the positive sequence voltage by a power factor angle δ setx Based on this, the conversion equation and conversion coefficient matrix between the current amplitude given value and the current given value in the abc coordinate system can be established. Exemplarily, if expressed by a formula, then:

[0087]

[0088] Where C represents the conversion coefficient matrix; I seta ,I setb ,I setc They respectively represent the current given values ​​corresponding to the three-phase lines a, b, and c.

[0089] Then, the conversion matrix is ​​used to transform the current given value in the abc coordinate system to obtain the positive and negative zero-sequence components of the current given value. For example, the following formula can be used to transform to obtain the corresponding positive-sequence current given value, negative-sequence current given value and zero-sequence current given value (denoted as I setp ,I setn ,I setc0 ):

[0090]

[0091] Furthermore, according to the following formula, the positive-sequence current given value amplitude, the negative-sequence current given value amplitude, the negative-sequence current given value amplitude, the 0-sequence current given value amplitude and the 0-sequence phase angle are calculated.

[0092]

[0093] in,

[0094] In the formula, θ pos ,θ neg and θ 0 Respectively represent the positive sequence phase angle, negative sequence phase angle and 0 sequence phase angle; i posm Indicates the amplitude of the positive sequence current given value, i negm Indicates the amplitude of the negative sequence current given value, i 0m Indicates the amplitude of the 0-sequence current given value; i pos_Re and i pos_Im Respectively represent the real and imaginary parts of the positive sequence current given value, i neg_Re and i neg_Im Represent the real and imaginary parts of the negative sequence current given value, i 0_Re and i 0_Im They represent the real and imaginary parts of the 0-sequence current given value respectively.

[0095] It can be understood that the real part and the imaginary part of each current given value can be directly obtained by the current given value amplitude I in the abc coordinate system. setxm and power phase angle σ setx Calculated.

[0096] S320, calculating a d-axis current given value based on the real part of the positive-sequence current given value amplitude, the negative-sequence current given value amplitude, the negative-sequence phase angle, and the grid voltage positive-sequence component angle.

[0097] Wherein, the d-axis current given value includes a first current given value component and a second current given value component, such as Figure 6 As shown, in one implementation, the first current given value component can be calculated based on the real-time bus voltage, voltage reference value and real part of the positive sequence current given value amplitude on the three-phase power grid bus. If expressed by formula, then:

[0098] i dref1 =min(i pos_Re ,Busloopout);

[0099] In the formula, i dref1 represents the first current given value component, and Busloopout represents the real-time bus voltage V bus and voltage reference value V buref The difference between is the output result after being processed by the PI controller. It is worth noting that if the first current given value component i calculated by the above-mentioned smaller method is dref1 Exceeds the set current amplitude i dlimit , then a limiting operation is performed, that is, i dlimit Assign to the first current given value component i dref1 , otherwise, if it is less than i dlimit , then the first current given value component i calculated above is retaineddref1 , no limiting operation is required.

[0100] And, based on the negative sequence current set value amplitude, the negative sequence phase angle and the grid voltage positive sequence component angle, calculate the second current set value component i dref2 If expressed by formula, we have:

[0101] i dref2 =i negm cos(2θ+θ neg ).

[0102] Finally, the sum of the first current given value component and the second current given value component is taken as the d-axis current given value, i.e., dref =i dref1 +i dref2 .

[0103] S330, calculating a q-axis current given value based on an imaginary part of a positive-sequence current given value amplitude, a negative-sequence current given value amplitude, a negative-sequence phase angle, and a grid voltage positive-sequence component angle.

[0104] For example, the q-axis current given value can be calculated according to the following formula:

[0105] i qref =i pos_Im -i negm sin(2θ+θ neg )+i comp ;

[0106] Among them, i comp =w*C*U d ;

[0107] In the formula, i qref Indicates the given value of the q-axis current, i comp represents the compensation amount of the reactive power generated by the output capacitor of the three-phase inverter 10, w represents the angular frequency, C represents the capacitance of the output capacitor, and U d Represents the terminal voltage of the output capacitor.

[0108] S340, calculating a 0-axis current given value based on a 0-sequence current given value amplitude, a 0-sequence phase angle, and a grid voltage positive-sequence component angle.

[0109] For example, the 0-axis current given value i can be calculated according to the following formula: 0ref :

[0110] i 0ref =i 0m cos(θ+θ 0 ).

[0111] S170, the current given value in the dq0 coordinate system, the current component in the dq0 coordinate system and the grid voltage component in the dq0 coordinate system are processed by loop control to obtain a three-phase modulation signal for driving and controlling each phase bridge arm of the three-phase inverter 10. The loop includes a d-axis loop, a q-axis loop and a 0-axis loop.

[0112] It can be understood that the output current and grid voltage corresponding to each phase line of the three-phase inverter 10 can be decomposed into corresponding positive and negative zero-sequence components. In order to achieve unbalanced control of each phase, this embodiment converts the unbalanced power control instruction into a positive and negative zero-sequence current set value instruction, so that only the positive and negative zero-sequence components of the current set value need to be controlled separately.

[0113] In one implementation, the three components of the current given value, namely, the positive sequence, negative sequence and zero sequence, can be tracked and controlled separately in the dq0 coordinate system. It is worth noting that, since it can be known through the dq0 transformation that the positive sequence component is expressed as a DC quantity, the negative sequence component is expressed as a double frequency, and the zero sequence component is expressed as a fundamental frequency, in order to achieve zero static error control of the positive, negative and zero sequence components of the current given value, this embodiment first locally adjusts the structure of each loop.

[0114] Exemplarily, for the d-axis loop and the q-axis loop, in order to achieve zero-static error tracking of the negative-sequence double-frequency current given value, for example, the d-axis loop and the q-axis loop each add a double-frequency resonant controller based on their original PI (proportional-integral) control.

[0115] Furthermore, in order to suppress the current harmonic components, Kalman filters are also set in the d-axis loop and the q-axis loop respectively to suppress the second-order harmonics such as the 4th, 6th and 8th in the d-axis and q-axis, so as to make the sinusoidality of the grid-connected current better.

[0116] For the 0-axis loop, in order to achieve zero-static error tracking of the 0-axis fundamental frequency current given value, a fundamental frequency resonance controller is added to the 0-axis loop based on the original proportional resonance (PR) control.

[0117] The expression of the resonant controller is as follows:

[0118]

[0119] In the formula, K r is the resonant gain, ω c is the resonant bandwidth, ω 0 is the resonant frequency.

[0120] Therefore, for the above-mentioned double frequency resonant controller, the resonant frequency of the resonant controller should satisfy ω 0=2π*100. For the above fundamental frequency resonant controller, the resonant frequency of the resonant controller should satisfy ω 0 =2π*50. It is understandable that the resonance gain and resonance bandwidth of the resonance controller in different axis loops can be adaptively adjusted according to actual control requirements, which is not limited here.

[0121] Based on the above loop structure, in one implementation, the loop control process in step S170 includes the following sub-steps (not shown in the figure):

[0122] S410, the d-axis current given value, the d-axis current component, the q-axis current component and the d-axis grid voltage component are processed by a d-axis loop to obtain a d-axis loop output value.

[0123] In one embodiment, the d-axis loop includes a proportional integral resonant controller (ie, PIR) and a Kalman filter arranged in parallel. Figure 7 As shown in the figure, the d-axis current given value and the d-axis current component can be subtracted to obtain the d-axis deviation; the d-axis deviation is input into the PIR controller to obtain the d-axis adjustment amount; the d-axis deviation is input into the Kalman and is adjusted by the corresponding coefficient K p Adjustment is performed to obtain the d-axis harmonic suppression amount; then, the d-axis mutual inductance is determined based on the q-axis current component; finally, the d-axis adjustment amount, d-axis harmonic suppression amount, d-axis mutual inductance and d-axis grid voltage component are calculated to obtain the d-axis loop output value.

[0124] S420, the q-axis current given value, the d-axis current component, the q-axis current component and the q-axis grid voltage component are processed by the q-axis loop to obtain a q-axis loop output value.

[0125] In one embodiment, the q-axis loop also includes a proportional integral resonant controller (ie, PIR) and a Kalman filter arranged in parallel. For example, after obtaining a given value of the q-axis current, Figure 7 As shown in the figure, the q-axis current given value and the q-axis current component can be subtracted to obtain the q-axis deviation; then, the q-axis deviation is input into the PIR controller to obtain the q-axis adjustment amount; at the same time, the q-axis deviation is also input into the Kalman and the corresponding coefficient K is used to calculate the q-axis adjustment amount. p Adjustment is performed to obtain the q-axis harmonic suppression amount; then, the q-axis mutual inductance is determined based on the d-axis current component; finally, the q-axis adjustment amount, the q-axis harmonic suppression amount, the q-axis mutual inductance and the q-axis grid voltage component are calculated to obtain the q-axis loop output value.

[0126] S430, the 0-axis current given value, the 0-axis current component and the 0-axis grid voltage component are processed by the 0-axis loop to obtain a 0-axis loop output value.

[0127] In one embodiment, the 0-axis loop includes two proportional resonant controllers arranged in parallel. Figure 7 As shown, the 0-axis current given value and the 0-axis current component can be subtracted to obtain the 0-axis deviation; then, the 0-axis deviation is input into the two PR controllers respectively to obtain the 0-axis harmonic first suppression amount and the 0-axis harmonic second suppression amount; finally, the 0-axis harmonic first suppression amount, the 0-axis harmonic second suppression amount and the 0-axis grid voltage component are calculated to obtain the 0-axis loop output value.

[0128] S440 , coordinate transformation and signal modulation are performed on the d-axis loop output value, the q-axis loop processing and the 0-axis loop output value to obtain a three-phase modulation signal for driving and controlling each phase bridge arm of the three-phase inverter 10 .

[0129] Therefore, after the corresponding loop output values ​​are calculated using the d-axis loop, q-axis loop and 0-axis loop, they are transformed from the dq0 coordinate system to the three-phase abc coordinate system and further pulse width modulated to obtain a three-phase modulated signal (denoted as u ma 、u mb 、u mc ), and finally, the corresponding phase bridge arm in the three-phase inverter 10 is driven and controlled by using the modulation signal of each phase to realize power control.

[0130] In order to better understand the unbalanced power control method of the present application, a specific description is given below in conjunction with a photovoltaic energy storage grid-connected system including a three-phase inverter.

[0131] like Figure 8 As shown, the photovoltaic energy storage grid-connected system includes a Boost converter for photovoltaic MPPT tracking and boosting, a bidirectional DC-DC converter for controlling the battery charging and discharging power, and a bidirectional AC-DC converter for controlling the photovoltaic PV and the power grid to exchange active power, wherein the bidirectional AC-DC converter is used to realize bidirectional energy exchange, that is, including rectification and inversion functions. It can be understood that the three-phase inverter 10 in the present application can be a unidirectional AC-DC converter or the above-mentioned bidirectional AC-DC converter, which is not limited here.

[0132] The photovoltaic energy storage grid-connected system can have multiple working modes, such as self-generation and self-use mode, AC power replenishment mode, grid dispatching mode, etc. Among them, the self-generation and self-use mode means that the power output of the energy storage photovoltaic system, on the premise of meeting the household load, supplies the excess power to the grid or charges the battery; the AC power replenishment mode means that when the battery power drops to the corresponding condition, it is necessary to replenish the battery through the grid; and the grid dispatching mode means that the grid requires the energy storage system to feed or absorb active power / reactive power according to instructions.

[0133] like Fig. 9 As shown in the figure, when the photovoltaic energy storage grid-connected system operates in the self-generation and self-use mode, if the current power of each phase load R is: P loada =3000W, P loadb =2000W, P loadc = 1000W. Due to single-phase reverse flow prevention, the EMS sets the power limit of each phase feed point to 0W. Then the power consumption of each load comes from the energy storage converter (PCS) including photovoltaic PV and batteries. If the load changes at this time, such as Fig.10 As shown, it becomes P loada =1500W, P loadb =1000W, P loadc =500W, at this time, the power fed into the grid will be: P metera =1500W, P meterb =1000W, P meterc =500 Therefore, through calculation, it can be known that the new active power given value corresponding to each phase line is:

[0134] P seta =3000-1500=1500W

[0135] P setb =2000-1000=1000W

[0136] P setc =1000-500=500W.

[0137] Assume that the effective values ​​of the grid voltages corresponding to the phase lines of the three-phase inverter 10 are U rmsa =210V, U rmsb =230V, U rmsc =240V (here is to take the unbalanced power grid as an example), then, by adopting the steps of the unbalanced power control method of the above embodiment, the current given value in the dq0 coordinate system can be calculated:

[0138] i dref =i dref1 +i dref2

[0139]

[0140] i qref =0-2.069sin(2θ+0.463)+i comp ;

[0141] i 0ref =2.069cos(θ-0.463).

[0142] Therefore, the current component in the dq0 coordinate system and the grid voltage component in the dq0 coordinate system are combined through Figure 7 The loop control process shown in FIG. 1 calculates the three-phase PWM signal and controls each phase bridge arm of the three-phase inverter 10 respectively. The waveform of each phase active power control is as follows: Fig.11 The effective values ​​of the grid voltage corresponding to each phase line shown include: 11-1 represents U rmsb , 11-2 means U rmsc , 11-3 means U rmsa , the output current corresponding to each phase line includes: 11-4 represents I b , 11-5 means I c , 11-6 means I a It can be seen that even in the case of an unbalanced power grid, the unbalanced power control method of the present application can still achieve accurate control of single-phase power imbalance, thereby achieving optimal power usage of the photovoltaic energy storage grid-connected system.

[0143] Fig.12 A structural schematic diagram of an unbalanced power control device 100 according to an embodiment of the present application is shown. Exemplarily, the unbalanced power control device 100 is applied to a controller of a three-phase inverter 10, including:

[0144] The data acquisition module 110 is used to obtain the grid voltage, AC side output current and meter power corresponding to each phase line of the three-phase inverter 10;

[0145] The positive sequence extraction and phase locking module 120 is used to perform positive sequence extraction and phase locking calculation based on the grid voltage corresponding to each phase line to obtain the grid voltage positive sequence component angle;

[0146] The current component calculation module 130 is used to perform coordinate transformation on the AC side output current corresponding to each phase line using the positive sequence component angle of the grid voltage to obtain the current component in the dq0 coordinate system;

[0147] The voltage component calculation module 140 is used to perform coordinate transformation on the grid voltage corresponding to each phase line using the grid voltage positive sequence component angle to obtain the grid voltage component in the dq0 coordinate system;

[0148] The power calculation module 150 is used to determine the current amplitude given value corresponding to each phase line and the power phase angle corresponding to each phase line based on the grid voltage corresponding to each phase line, the meter power corresponding to each phase line and the feeder point power limit value corresponding to each phase line;

[0149] A current given value calculation module 160 is used to determine the current given value in the dq0 coordinate system based on the current amplitude given value corresponding to each phase line, the grid voltage positive sequence component angle and the power phase angle corresponding to each phase line;

[0150] The control signal acquisition module 170 is used to process the current given value in the dq0 coordinate system, the current component in the dq0 coordinate system and the grid voltage component in the dq0 coordinate system through loop control to obtain a three-phase modulation signal for driving and controlling each phase bridge arm of the three-phase inverter 10.

[0151] It can be understood that the device of this embodiment corresponds to the unbalanced power control method of the above embodiment, and the options in the above embodiment are also applicable to this embodiment, so they will not be described repeatedly here.

[0152] The present application also provides a computer-readable storage medium for storing the computer program used in the above three-phase inverter 10. For example, the computer-readable storage medium includes: a USB flash drive, a mobile hard disk, a read-only memory (ROM), a random access memory (RAM), a magnetic disk or an optical disk, and other media that can store program codes.

[0153] In several embodiments provided in the present application, it should be understood that the disclosed devices and methods can also be implemented in other ways. The device embodiments described above are merely schematic. For example, the flowcharts and structure diagrams in the accompanying drawings show the possible architecture, functions and operations of the devices, methods and computer program products according to multiple embodiments of the present application. In this regard, each box in the flowchart or block diagram can represent a module, a program segment or a part of a code, and the module, a program segment or a part of a code contains one or more executable instructions for implementing the specified logical function. It should also be noted that in an alternative implementation, the functions marked in the box can also occur in a different order from the order marked in the accompanying drawings. For example, two consecutive boxes can actually be executed substantially in parallel, and they can sometimes be executed in the opposite order, depending on the functions involved. It should also be noted that each box in the structure diagram and / or the flow diagram, and the combination of boxes in the structure diagram and / or the flow diagram, can be implemented with a dedicated hardware-based system that performs a specified function or action, or can be implemented with a combination of dedicated hardware and computer instructions.

[0154] In addition, the functional modules or units in the various embodiments of the present application may be integrated together to form an independent part, or each module may exist separately, or two or more modules may be integrated to form an independent part.

[0155] If the functions are implemented in the form of software function modules and sold or used as independent products, they can be stored in a computer-readable storage medium. Based on this understanding, the technical solution of the present application, or the part that contributes to the prior art, or the part of the technical solution, can be embodied in the form of a software product, which is stored in a storage medium and includes several instructions for a computer device (which can be a smart phone, a personal computer, a server, or a network device, etc.) to perform all or part of the steps of the methods described in the various embodiments of the present application.

[0156] The above description is only a specific implementation manner of the present application, but the protection scope of the present application is not limited thereto. Any technician familiar with the technical field can easily think of changes or substitutions within the technical scope disclosed in the present application, which should be included in the protection scope of the present application.

Claims

1. An unbalanced power control method, applied to a controller of a three-phase inverter, characterized in that: include: Obtaining the grid voltage, AC side output current and meter power corresponding to each phase line of the three-phase inverter; Based on the grid voltage corresponding to each phase line, positive sequence extraction and phase-locked calculation are performed to obtain the grid voltage positive sequence component angle; Using the positive sequence component angle of the grid voltage, coordinate transformation is performed on the AC side output current corresponding to each phase line to obtain the current component in the dq0 coordinate system; Using the grid voltage positive sequence component angle, coordinate transformation is performed on the grid voltage corresponding to each phase line to obtain the grid voltage component in the dq0 coordinate system; Determine the current amplitude given value corresponding to each phase line and the power phase angle corresponding to each phase line based on the grid voltage corresponding to each phase line, the meter power corresponding to each phase line and the feeder point power limit value corresponding to each phase line; Determine a current given value in the dq0 coordinate system based on the current amplitude given value corresponding to each of the phase lines, the grid voltage positive sequence component angle and the power phase angle corresponding to each of the phase lines; The current given value in the dq0 coordinate system, the current component in the dq0 coordinate system and the grid voltage component in the dq0 coordinate system are processed by loop control to obtain a three-phase modulation signal for driving and controlling each phase bridge arm of the three-phase inverter.

2. The unbalanced power control method according to claim 1, characterized in that: The loop includes a d-axis loop, a q-axis loop and a 0-axis loop; the current given value in the dq0 coordinate system includes a d-axis current given value, a q-axis current given value and a 0-axis current given value; the current component in the dq0 coordinate system includes a d-axis current component, a q-axis current component and a 0-axis current component; the grid voltage component in the dq0 coordinate system includes a d-axis grid voltage component, a q-axis grid voltage component and a 0-axis grid voltage component; The current given value in the dq0 coordinate system, the current component in the dq0 coordinate system and the grid voltage component in the dq0 coordinate system are subjected to loop control processing to obtain a three-phase modulation signal for driving and controlling each phase bridge arm of the three-phase inverter, including: Processing the d-axis current given value, the d-axis current component, the q-axis current component and the d-axis grid voltage component through the d-axis loop to obtain a d-axis loop output value; Processing the q-axis current given value, the d-axis current component, the q-axis current component and the q-axis grid voltage component through the q-axis loop to obtain a q-axis loop output value; Processing the 0-axis current given value, the 0-axis current component and the 0-axis grid voltage component through the 0-axis loop to obtain a 0-axis loop output value; The d-axis loop output value, the q-axis loop processing and the 0-axis loop output value are subjected to coordinate transformation and signal modulation to obtain a three-phase modulation signal for driving and controlling each phase bridge arm of the three-phase inverter.

3. The unbalanced power control method according to claim 2, characterized in that: The d-axis loop and the q-axis loop both include a proportional-integral resonant controller and a Kalman filter arranged in parallel; The step of processing the d-axis current given value, the d-axis current component, the q-axis current component and the d-axis grid voltage component through the d-axis loop to obtain a d-axis loop output value includes: After subtracting the d-axis current given value from the d-axis current component, a d-axis deviation is obtained; Inputting the d-axis deviation into the proportional-integral resonant controller to obtain a d-axis adjustment amount; Inputting the d-axis deviation into the Kalman filter to obtain a d-axis harmonic suppression amount; Determining a d-axis mutual inductance based on the q-axis current component; The d-axis adjustment amount, the d-axis harmonic suppression amount, the d-axis mutual inductance and the d-axis grid voltage component are calculated to obtain the d-axis loop output value.

4. The unbalanced power control method according to claim 3, characterized in that: The step of processing the q-axis current given value, the d-axis current component, the q-axis current component and the q-axis grid voltage component through the q-axis loop to obtain a q-axis loop output value includes: After subtracting the q-axis current given value from the q-axis current component, a q-axis deviation is obtained; Inputting the q-axis deviation into the proportional-integral resonant controller to obtain a q-axis adjustment amount; Inputting the q-axis deviation into the Kalman filter to obtain the q-axis harmonic suppression amount; Determining a q-axis mutual inductance based on the d-axis current component; The q-axis adjustment amount, the q-axis harmonic suppression amount, the q-axis mutual inductance and the q-axis grid voltage component are calculated to obtain the q-axis loop output value.

5. The unbalanced power control method according to claim 3, characterized in that: The 0-axis loop includes two proportional resonant controllers arranged in parallel; The step of processing the 0-axis current given value, the 0-axis current component and the 0-axis grid voltage component through the 0-axis loop to obtain a 0-axis loop output value includes: After subtracting the 0-axis current given value from the 0-axis current component, a 0-axis deviation is obtained; Inputting the 0-axis deviation into the two proportional resonant controllers respectively, to obtain a 0-axis harmonic first suppression amount and a 0-axis harmonic second suppression amount respectively; The 0-axis harmonic first suppression amount, the 0-axis harmonic second suppression amount and the 0-axis grid voltage component are calculated to obtain the 0-axis loop output value.

6. The unbalanced power control method according to claim 1, characterized in that: The determining of the current amplitude given value corresponding to each phase line and the power phase angle corresponding to each phase line based on the grid voltage corresponding to each phase line, the electric meter power corresponding to each phase line and the feeder point power limit value corresponding to each phase line comprises: Based on the difference between the meter power corresponding to each phase line and the preset feeder point power limit value corresponding to each phase line, respectively iterate the active power given value corresponding to each phase line in the three-phase inverter obtained in real time to obtain the updated active power given value corresponding to each phase line; Based on the active power given value corresponding to each phase line and the acquired reactive power given value corresponding to each phase line, calculate the apparent power corresponding to each phase line and the power phase angle corresponding to each phase line; The current amplitude given value corresponding to each phase line is calculated according to the effective value of the grid voltage corresponding to each phase line and the amplitude of the apparent power of the corresponding phase line.

7. The unbalanced power control method according to claim 1, characterized in that: The determining of the current given value in the dq0 coordinate system based on the current amplitude given value corresponding to each of the phase lines, the grid voltage positive sequence component angle and the power phase angle corresponding to each of the phase lines comprises: Based on the current amplitude given value corresponding to each phase line and the power phase angle corresponding to each phase line, respectively calculate the positive sequence current given value amplitude, the negative sequence current given value amplitude, the negative sequence phase angle, the 0 sequence current given value amplitude and the 0 sequence phase angle; Calculate the d-axis current given value based on the real part of the positive-sequence current given value amplitude, the negative-sequence current given value amplitude, the negative-sequence phase angle and the grid voltage positive-sequence component angle; Calculate the q-axis current given value based on the imaginary part of the positive-sequence current given value amplitude, the negative-sequence current given value amplitude, the negative-sequence phase angle and the grid voltage positive-sequence component angle; The 0-axis current given value is calculated based on the 0-sequence current given value amplitude, the 0-sequence phase angle and the grid voltage positive sequence component angle.

8. The unbalanced power control method according to claim 7, characterized in that: The calculating of the d-axis current given value based on the real part of the positive-sequence current given value amplitude, the negative-sequence current given value amplitude, the negative-sequence phase angle and the grid voltage positive-sequence component angle comprises: Calculate a first current given value component based on the real-time bus voltage on the three-phase power grid bus, the voltage reference value and the real part of the positive sequence current given value amplitude; Calculating a second current given value component based on the negative sequence current given value amplitude, the negative sequence phase angle and the grid voltage positive sequence component angle; The sum of the first current set value component and the second current set value component is used as the d-axis current set value.

9. An unbalanced power control device, applied to a controller of a three-phase inverter, characterized in that: include: A data acquisition module, used to obtain the grid voltage, AC side output current and meter power corresponding to each phase line of the three-phase inverter; A positive sequence extraction and phase locking module, used to perform positive sequence extraction and phase locking calculation based on the grid voltage corresponding to each phase line, to obtain the grid voltage positive sequence component angle; A current component calculation module, used to perform coordinate transformation on the AC side output current corresponding to each phase line using the positive sequence component angle of the grid voltage, to obtain the current component in the dq0 coordinate system; A voltage component calculation module, used to perform coordinate transformation on the grid voltage corresponding to each phase line using the grid voltage positive sequence component angle to obtain the grid voltage component in the dq0 coordinate system; A power calculation module, used to determine the current amplitude given value corresponding to each phase line and the power phase angle corresponding to each phase line based on the grid voltage corresponding to each phase line, the meter power corresponding to each phase line and the feeder point power limit value corresponding to each phase line; A current given value calculation module, used to determine the current given value in the dq0 coordinate system based on the current amplitude given value corresponding to each phase line, the grid voltage positive sequence component angle and the power phase angle corresponding to each phase line; The control signal acquisition module is used to process the current given value in the dq0 coordinate system, the current component in the dq0 coordinate system and the grid voltage component in the dq0 coordinate system through loop control to obtain a three-phase modulation signal for driving and controlling each phase bridge arm of the three-phase inverter.

10. A three-phase inverter, characterized in that: The three-phase inverter comprises a controller and a memory, wherein the memory stores a computer program, and the controller is configured to execute the computer program to implement the unbalanced power control method according to any one of claims 1 to 8.

Images