Control method and device of grid-connected inverter

Abstract

The embodiment of the invention discloses a control method and device for a grid-connected inverter. The method comprises the following steps: acquiring a first grid-connected sampling current of the grid-connected inverter; obtaining a first target difference value according to the first grid-connected sampling current and the grid-connected set current; obtaining a target compensation value based on the adjustment of the first target difference value; determining a second output value of a grid-connected current loop according to the target compensation value, the power grid sampling voltage and a first output value of a proportional resonance controller; determining a pulse width modulation signal of a corresponding duty ratio based on the second output value and the bus voltage of the grid-connected inverter; and on-off of each transistor of the grid-connected inverter is controlled based on the pulse width modulation signal. According to the method and the device, the technical problem that in the prior art, current oscillation is easily caused when static errors are reduced by adjusting transfer function parameters, and then components are damaged is solved, and the technical effects that the static errors of the inverter are accurately compensated, and the components are prevented from being damaged by the current oscillation are achieved.

Description

Technical Field

[0001] The embodiments of the present invention relate to the technical field of inverter control, and in particular to a control method and device for a grid-connected inverter. Background Art

[0002] In PR (Proportional Resonant) control, the gain changes with the transfer function parameter K. i But in practical applications, if K i If it is too small, static error will occur and the inverter's grid-connected current will never be able to track the given current.

[0003] The existing solution is generally to increase K i , thereby speeding up the adjustment speed of the control loop to reduce the static error, but this will cause current oscillation problems and damage the components of the inverter. Summary of the invention

[0004] The embodiments of the present invention provide a control method and device for a grid-connected inverter, which solves the technical problem in the prior art that reducing static errors by adjusting transfer function parameters easily causes current oscillation and thus damages components.

[0005] An embodiment of the present invention provides a control method for a grid-connected inverter, the control method comprising:

[0006] Obtaining a first grid-connected sampling current of the grid-connected inverter;

[0007] Obtaining a first target difference according to the first grid-connected sampling current and the grid-connected set current;

[0008] Based on the adjustment of the first target difference, a target compensation value is obtained;

[0009] Determine a second output value of the grid-connected current loop according to the target compensation value, the grid sampling voltage and the first output value of the proportional resonant controller;

[0010] Determine a pulse width modulation signal of a corresponding duty cycle based on the second output value and the bus voltage of the grid-connected inverter;

[0011] The on and off of each transistor of the grid-connected inverter is controlled based on the pulse width modulation signal.

[0012] Further, based on the adjustment of the first target difference, obtaining the target compensation value includes:

[0013] The first target difference is input into a proportional-integral controller for adjustment to obtain the target compensation value.

[0014] Further, obtaining a first target difference according to the first grid-connected sampling current and the grid-connected set current includes:

[0015] Converting the first grid-connected sampling current into a parameter in a dq coordinate system to obtain a second grid-connected sampling current;

[0016] The second grid-connected sampling current is subtracted from the grid-connected set current to obtain the first target difference.

[0017] Further, obtaining a first target difference according to the first grid-connected sampling current and the grid-connected set current includes:

[0018] Multiplying the grid-connected setting current by the grid phase to obtain the grid-connected setting alternating current quantity;

[0019] The first target difference is obtained by subtracting the first grid-connected sampling current from the grid-connected set AC quantity.

[0020] Further, determining the second output value of the grid-connected current loop according to the target compensation value, the grid sampling voltage and the first output value of the proportional resonant controller includes:

[0021] determining a first output value of the proportional resonant controller;

[0022] The grid sampling voltage is used as a feedforward signal, and the target compensation value is used as a compensation signal, and the first output value is jointly adjusted to determine the second output value of the grid-connected current loop.

[0023] Further, determining the first output value of the proportional resonant controller includes:

[0024] Multiplying the grid-connected setting current by the grid phase to obtain the grid-connected setting alternating current quantity;

[0025] Subtract the grid-connected set AC quantity from the first grid-connected sampled current to obtain a second target difference;

[0026] The second target difference is input into the proportional resonant controller to obtain the first output value.

[0027] Further, determining the second output value of the grid-connected current loop according to the target compensation value, the grid sampling voltage and the first output value of the proportional resonant controller includes:

[0028] Inputting the first target difference into the proportional resonant controller to obtain the first output value;

[0029] The grid sampling voltage is used as a feedforward signal, and the target compensation value is used as a compensation signal, and the first output value is jointly adjusted to determine the second output value of the grid-connected current loop.

[0030] Furthermore, before multiplying the grid-connected setting current by the grid phase to obtain the grid-connected setting alternating current quantity, the control method further includes:

[0031] Obtaining a sampling voltage of the power grid;

[0032] The grid sampling voltage is phase-locked to obtain the grid phase.

[0033] Further, determining a pulse width modulation signal with a corresponding duty cycle based on the second output value and the bus voltage of the grid-connected inverter includes:

[0034] The second output value is divided by the bus voltage of the grid-connected inverter to obtain the pulse width modulation signal of the corresponding duty cycle.

[0035] An embodiment of the present invention further provides a control device for a grid-connected inverter, the control device comprising:

[0036] A current acquisition unit, used for acquiring a first grid-connected sampling current of the grid-connected inverter;

[0037] a difference determination unit, configured to obtain a first target difference according to the first grid-connected sampled current and the grid-connected set current;

[0038] a compensation value determining unit, configured to obtain a target compensation value based on an adjustment of the first target difference value;

[0039] An output value determination unit, configured to determine a second output value of the grid-connected current loop according to the target compensation value, the grid sampling voltage, and the first output value of the proportional resonant controller;

[0040] a control signal determining unit, configured to determine a pulse width modulation signal of a corresponding duty cycle based on the second output value and the bus voltage of the grid-connected inverter;

[0041] A transistor control unit is used to control the on and off of each transistor of the grid-connected inverter based on the pulse width modulation signal.

[0042] The embodiment of the present invention discloses a control method and device for a grid-connected inverter, the method comprising: obtaining a first grid-connected sampling current of the grid-connected inverter; obtaining a first target difference according to the first grid-connected sampling current and the grid-connected set current; obtaining a target compensation value based on the adjustment of the first target difference; determining a second output value of the grid-connected current loop according to the target compensation value, the grid sampling voltage and the first output value of the proportional resonant controller; determining a pulse width modulation signal of a corresponding duty cycle based on the second output value and the bus voltage of the grid-connected inverter; and controlling the on and off of each transistor of the grid-connected inverter based on the pulse width modulation signal. The present application determines the compensation value by the difference between the sampling current and the set current, and compensates the proportional resonant control based on the compensation value, thereby solving the technical problem in the prior art that the static error is easily caused by adjusting the transfer function parameters to reduce the static error, thereby causing damage to the components, and achieving the technical effect of accurately compensating the static error of the inverter and avoiding the damage of the components caused by the current oscillation. BRIEF DESCRIPTION OF THE DRAWINGS

[0043] Figure 1 This is a control principle block diagram of a grid-connected inverter provided by an embodiment of the present invention;

[0044] Figure 2 is the G of the PR controller provided in the embodiment of the present invention PR (s) amplitude-frequency characteristic curve;

[0045] Figure 3 is a flow chart of a control method for a grid-connected inverter provided by an embodiment of the present invention;

[0046] Figure 4 This is a control principle block diagram of an outer loop compensation using the effective value of current provided by an embodiment of the present invention;

[0047] Figure 5 This is a control principle block diagram of an outer loop compensation using AC error provided by an embodiment of the present invention;

[0048] Figure 6 It is a structural diagram of a control device for a grid-connected inverter provided in an embodiment of the present invention. DETAILED DESCRIPTION

[0049] The present invention will be further described in detail below in conjunction with the accompanying drawings and embodiments. It is to be understood that the specific embodiments described herein are only used to explain the present invention, rather than to limit the present invention. It should also be noted that, for ease of description, only parts related to the present invention, rather than all structures, are shown in the accompanying drawings.

[0050] It should be noted that the terms "first", "second", etc. in the specification, claims and drawings of the present invention are used to distinguish different objects, rather than to limit a specific order. The following embodiments of the present invention can be implemented separately, or in combination with each other, and the embodiments of the present invention do not impose specific limitations on this.

[0051] Figure 1 1 is a control principle block diagram of a grid-connected inverter provided by an embodiment of the present invention. Figure 1 As shown in the figure, for the full-bridge grid-connected inverter, proportional resonant control (PR control) is used for its control, where I dref is the grid-connected setting current, the grid-connected setting current I dref The target grid-connected current is set at the DC component setting value of the d-axis. The grid sampling voltage Volt is phase-locked (PLL) to obtain the grid phase sin (Q). The grid-connected setting current I dref Multiply by sin(Q) to get the AC quantity I given by the grid current cref , I cref Subtract the actual sampled grid-connected current I c After that, it passes through the PR controller and the grid sampling voltage Volt to obtain the output Loopout of the grid-connected current loop. Finally, the output Loopout of the grid-connected current loop is divided by the bus voltage Bus to obtain a pulse width modulation signal (Pulse width modulation, PWM). The pulse width modulation signal is used to drive the four IGBTs (Insulate-Gate Bipolar Transistor) of the full bridge to achieve the grid-connected current I c regulation.

[0052] Among them, the PR controller G PR The transfer function of (s) is: kp is the proportional gain coefficient, that is, the proportional part of the proportional resonance, is the resonant part of proportional resonance, w c is the cut-off frequency, w0 is the resonant frequency, at the fundamental frequency w0, the gain of the PR controller can be obtained by k i Adjustment, k i The larger the value, the greater the gain at w0; k i The smaller it is, the smaller the gain at w0; but in other frequency bands, the gain approaches zero.

[0053] Figure 2 is the G of the PR controller provided in the embodiment of the present invention PR (s) amplitude-frequency characteristic curve. Figure 2 , w c=18,w0=2*3.14*50,kp=1.0,k i =0.2, at the fundamental wave w0, there is a relatively large gain (the frequency corresponding to the highest point of the amplitude in the figure is the fundamental wave w0, and the amplitude is the gain), and the gain of other frequency bands approaches zero; reduce k i , the PR control gain can be reduced, but if the PR control gain is reduced, there will be a static error, and the grid-connected setting current cannot reach the given I dref If you want the grid-connected current to reach a given I dref , k needs to be increased i To increase the gain of the PR controller, but k i The larger it is, the more severe the current oscillation will be.

[0054] To solve the above problems, an embodiment of the present invention provides a control method for a grid-connected inverter.

[0055] Figure 3 It is a flow chart of a control method of a grid-connected inverter provided by an embodiment of the present invention.

[0056] like Figure 3 As shown, the control method of the grid-connected inverter specifically includes the following steps:

[0057] S101, obtaining a first grid-connected sampling current of a grid-connected inverter.

[0058] Specifically, the first grid-connected sampling current I c It is the current value output by the grid-connected inverter to the grid side (Grid), and its value can be collected by a current sampling device.

[0059] S102, obtaining a first target difference according to the first grid-connected sampling current and the grid-connected set current.

[0060] Specifically, after obtaining the first grid-connected sampling current I c Afterwards, the first grid-connected sampling current I c And the grid-connected setting current I dref Convert them into quantities in the same coordinate system, for example, both are AC quantities, or both are DC quantities, and then make a difference between the two to obtain the first target difference I between the two err For example, in this embodiment, the grid-connected current I dref Directly set it as the DC component on the D axis, then the first grid-connected sampling current I c Divide by the grid phase sin(Q) to get the first grid-connected sampling current I c The DC component of the D axis, or the grid-connected setting current I dref Multiply by the grid phase sin(Q) to get the grid-connected setting current I drefIn other embodiments, if the grid-connected current I dref What is set directly is the amount of exchange, and the two can also be compared directly.

[0061] S103, obtaining a target compensation value based on the adjustment of the first target difference.

[0062] Specifically, after obtaining the first target difference I err After that, it is sent to the control compensation branch connected in parallel with the proportional resonant controller on the control loop. The control compensation branch uses the set controller to adjust the first target difference I err Adjustment is performed to obtain a target compensation value. The controller on the control compensation branch can be set as needed. In one embodiment, the controller for controlling the compensation branch is a proportional integral controller (PI controller).

[0063] S104, determining a second output value of the grid-connected current loop according to the target compensation value, the grid sampling voltage, and the first output value of the proportional resonant controller.

[0064] Specifically, the grid sampling voltage is the voltage output by the grid-connected inverter to the grid side. After obtaining the target compensation value, it is combined with the first output value of the proportional resonant controller (PR controller) on the control loop and the grid sampling voltage to obtain the second output value of the grid-connected current loop.

[0065] S105, determining a pulse width modulation signal of a corresponding duty cycle based on the second output value and the bus voltage of the grid-connected inverter.

[0066] S106, controlling the on and off of each transistor of the grid-connected inverter based on the pulse width modulation signal.

[0067] Specifically, after obtaining the second output value of the grid-connected current loop, a modulated pulse width signal is obtained based on the second output value of the grid-connected current loop divided by the bus voltage, and finally each transistor of the grid-connected inverter is driven by the pulse width modulation signal to achieve dynamic regulation of the first grid-connected sampling current.

[0068] In the embodiments of the present invention, see Figure 1 , the control loop refers to the grid-connected setting current I dref The grid phase sin(Q) is obtained by phase locking with the grid sampling voltage Volt to obtain the given AC quantity I of the grid-connected current. cref , I cref Subtract the actual sampled grid-connected current I cAfter that, it passes through the PR controller and the grid sampling voltage Volt to obtain the output Loopout of the grid-connected current loop, and divides Loopout by the bus voltage Bus to obtain the pulse width modulation signal. Finally, the pulse width modulation signal is used to drive the four IGBTs of the full bridge to realize the grid-connected current I c The control compensation branch refers to a branch connected in parallel with the PR controller (as shown below). Figure 4 and Figure 5 The control branch shown is provided with a PI controller).

[0069] The present application adds a control compensation branch outside the control loop of the proportional resonant controller, and compensates the output value of the proportional resonant controller based on the output of the control compensation branch. That is, the present application adjusts the first target difference obtained based on the first grid-connected sampling current and the grid-connected set current through the added control compensation branch, thereby obtaining a target compensation value, and the target compensation value is used to compensate the output value of the proportional resonant controller, so that the second output value of the final output is the target control amount, thereby achieving the goal of ... i Under the present circumstances, the controlled grid-connected current reaches the grid-connected set current, the static error is eliminated, and the technical problem that the static error can be easily caused by adjusting the transfer function parameters to reduce the static error in the prior art is solved, which in turn causes damage to components. The technical effect of accurately compensating for the static error of the inverter and avoiding damage to components caused by current oscillation is achieved.

[0070] On the basis of the above technical solutions, S103, based on the adjustment of the first target difference, obtaining the target compensation value specifically includes: inputting the first target difference into a proportional-integral controller for adjustment to obtain the target compensation value.

[0071] Preferably, the controller on the control compensation branch can be a proportional-integral controller. Experiments have shown that by adjusting the first target difference using a proportional-integral controller, the error compensation value, i.e., the above-mentioned target compensation value, can be obtained quickly and accurately to achieve compensation for the static error.

[0072] In an optional implementation manner, S102 specifically includes:

[0073] The first grid-connected sampling current is converted into a parameter in a dq coordinate system to obtain a second grid-connected sampling current; and the second grid-connected sampling current is subtracted from the grid-connected setting current to obtain a first target difference.

[0074] Figure 4 The present invention provides a control principle block diagram of an outer loop compensation using the effective value of current.

[0075] Specifically, see Figure 4 , the first grid-connected sampling current I c Converted into the parameter in the dq coordinate system, the second grid-connected sampling current is obtained. The second grid-connected sampling current is actually the first grid-connected sampling current I c The actual d-axis current I in the dq coordinate system d , and then the second grid-connected sampling current I d And the grid-connected setting current I dref Difference, get the first target difference I err Then use the PI (proportional integral) controller to control the first target difference I err Adjust to get the target compensation value Pi Out .

[0076] Among them, the first grid-connected sampling current I c Convert to get the second grid-connected sampling current I d The formula is: d =I α *sin(Q)-I β *cos(Q),I α =I c , I β The first grid-connected sampling current I c The current is delayed by 90 degrees, and Q is the phase-locked mains angle of the phase-locked loop PLL.

[0077] It should be noted that when using the PI controller to control the first target difference I err During the adjustment process, the frequency domain transfer function of the PI controller is: The timing formula is: i (t) = kp*e(t)+k i ∫e(t)dt. The integral term accumulates the error. When there is a steady-state error in the control system, the error continues to accumulate in the integral term until the output value is consistent with the set value (that is, the second grid-connected sampling current is consistent with the grid-connected set current I dref is consistent, or is the first grid-connected sampling current I c The AC quantity I given by the grid current cref This “memory” mechanism enables the integral control to compensate for the steady-state error even though the proportional controller alone is not sufficient to eliminate the error.

[0078] like Figure 4 As shown, when the second grid-connected sampling current I d And the grid-connected setting current I dref When there is an error between the two, the error accumulates in the integral term, and the target compensation value Pi of the loop output Out Increases, the modulation duty cycle of the pulse width modulation signal increases, acting on the full-bridge circuit, and finally makes the first grid-connected sampling current Ic Increase until the actual grid-connected current is consistent with the given grid-connected current, that is, the first grid-connected sampling current I c The current value represented and the grid-connected setting current I dref The current represented is consistent, that is, the second grid-connected sampling current is consistent with the grid-connected setting current I dref is consistent, or is the first grid-connected sampling current I c The AC quantity I given by the grid current cref This effectively eliminates the static error and achieves the goal of increasing k without increasing i The static error is eliminated.

[0079] In another optional implementation, S102 further includes: multiplying the grid-connected setting current by the grid phase to obtain the grid-connected setting alternating current; and subtracting the first grid-connected sampling current from the grid-connected setting alternating current to obtain a first target difference.

[0080] Figure 5 The invention provides a control principle block diagram of using AC error to perform outer loop compensation.

[0081] Specifically, see Figure 5 , the grid-connected current I can be set dref Multiply it by the grid phase sin(Q) to get the grid-connected AC quantity I cref Finally, the first grid-connected sampling current I c And grid-connected setting AC quantity I cref Make a difference and get the first target difference I err The first target difference I is sent to the control compensation branch and the PI controller is used to control the first target difference I err Adjust to get the target compensation value Pi Out .

[0082] Specifically, when the first grid-connected sampling current I c Set the AC quantity I cref When there is a static error between the two, the static error accumulates in the integral term, and the target compensation value Pi output by the loop Out Increases, the modulation duty cycle of the pulse width modulation signal increases, acting on the full-bridge circuit, and finally makes the first grid-connected sampling current I c Increase until the first grid-connected sampling current I c And the grid-connected setting current I dref The current represented is consistent, which effectively eliminates the static error and achieves the goal of increasing k i The static error is eliminated.

[0083] In an optional implementation, S104, determining the second output value of the grid-connected current loop according to the target compensation value, the grid sampling voltage, and the first output value of the proportional resonant controller includes:

[0084] Determine a first output value of the proportional resonant controller; use the grid sampling voltage as a feedforward signal and the target compensation value as a compensation signal to jointly adjust the first output value to determine a second output value of the grid-connected current loop.

[0085] Specifically, we first need to set the current I based on the grid connection dref Multiply it by the grid phase sin(Q) to get the grid-connected AC quantity I cref , set the grid-connected AC quantity I cref The first grid-connected sampling current I c The difference is sent to the proportional resonant controller to determine the first output value PRout; then the grid sampling voltage Volt and the target compensation value Pi are used to Out The first output value PRout is jointly adjusted to obtain a second output value Loopout of the grid-connected current loop.

[0086] Optionally, determining a first output value of the proportional resonant controller comprises:

[0087] The grid-connected setting current is multiplied by the grid phase to obtain the grid-connected setting AC quantity; the grid-connected setting AC quantity is subtracted from the first grid-connected sampling current to obtain a second target difference; the second target difference is input into the proportional resonant controller to obtain a first output value.

[0088] Specifically, see Figure 4 and Figure 5 As shown, the grid-connected setting current I dref Multiply it by the grid phase sin(Q) to get the grid-connected AC quantity I cref , set the grid-connected AC quantity I cref The first grid-connected sampling current I c The second target difference is obtained by subtracting, and finally the second target difference is sent to the proportional resonant controller to obtain the first output value PRout.

[0089] In another optional implementation, S104, determining the second output value of the grid-connected current loop according to the target compensation value, the grid sampling voltage, and the first output value of the proportional resonant controller includes:

[0090] The first target difference is input into the proportional resonant controller to obtain a first output value; the grid sampling voltage is used as a feedforward signal, and the target compensation value is used as a compensation signal to jointly adjust the first output value to determine a second output value of the grid-connected current loop.

[0091] Specifically, see Figure 5 , after obtaining the first target difference I err After that, the first target difference I can be directly err The proportional resonant controller is sent to determine the first output value PRout; then the grid sampling voltage Volt and the target compensation value Pi are used Out The first output value PRout is jointly adjusted to obtain the second output value Loopout of the grid-connected current loop, thereby achieving the effect of reducing the amount of calculation.

[0092] Optionally, before multiplying the grid-connected setting current by the grid phase to obtain the grid-connected setting AC quantity, the control method further includes: acquiring a grid sampling voltage; and performing phase locking on the grid sampling voltage to obtain a grid phase.

[0093] Specifically, see 4 and Figure 5 The grid voltage measured by the grid connection is collected by the voltage collection device (V) to obtain the grid sampling voltage Volt, and then the grid sampling voltage Volt is phase-locked (PLL) to obtain the grid phase sin (Q).

[0094] Optionally, S105, determining a pulse width modulation signal of a corresponding duty cycle based on the second output value and the bus voltage of the grid-connected inverter includes: dividing the second output value by the bus voltage of the grid-connected inverter to obtain a pulse width modulation signal of a corresponding duty cycle.

[0095] Specifically, see Figure 4 and Figure 5 After obtaining the second output value Loopout of the grid-connected current loop, the second output value Loopout is divided by the bus voltage Bus to obtain a pulse width modulation signal PWM, and the pulse width modulation signal PWM is used to control the output of each transistor in the full-bridge inverter to achieve the first grid-connected sampling current I c regulation.

[0096] Figure 6 It is a structural diagram of a control device for a grid-connected inverter provided in an embodiment of the present invention.

[0097] like Figure 6 As shown, the control device of the grid-connected inverter specifically includes:

[0098] A current acquisition unit 61, used to acquire a first grid-connected sampling current of the grid-connected inverter;

[0099] A difference determination unit 62, configured to obtain a first target difference according to the first grid-connected sampled current and the grid-connected set current;

[0100] a compensation value determination unit 63, configured to obtain a target compensation value based on an adjustment of the first target difference value;

[0101] An output value determination unit 64, configured to determine a second output value of the grid-connected current loop according to a target compensation value, a grid sampling voltage, and a first output value of a proportional resonant controller;

[0102] A control signal determination unit 65, configured to determine a pulse width modulation signal of a corresponding duty cycle based on the second output value and the bus voltage of the grid-connected inverter;

[0103] The transistor control unit 66 is used to control the on and off of each transistor of the grid-connected inverter based on the pulse width modulation signal.

[0104] Optionally, the compensation value determining unit 63 is specifically configured to:

[0105] The first target difference is input into the proportional-integral controller for adjustment to obtain a target compensation value.

[0106] Optionally, the difference determination unit 62 includes:

[0107] A first conversion subunit, used for converting the first grid-connected sampling current into a parameter in a dq coordinate system to obtain a second grid-connected sampling current;

[0108] The first difference subunit is used for making a difference between the second grid-connected sampling current and the grid-connected setting current to obtain a first target difference value.

[0109] Optionally, the difference determination unit 62 further includes:

[0110] A calculation subunit, used for multiplying the grid-connected setting current by the grid phase to obtain the grid-connected setting AC quantity;

[0111] The second difference subunit is used to make a difference between the first grid-connected sampling current and the grid-connected set AC quantity to obtain a first target difference value.

[0112] Optionally, the output value determination unit 64 includes:

[0113] A first calculation subunit, used to determine a first output value of the proportional resonant controller;

[0114] The second calculation subunit is used to use the grid sampling voltage as a feedforward signal and the target compensation value as a compensation signal to jointly adjust the first output value to determine the second output value of the grid-connected current loop.

[0115] Optionally, the first computing subunit is specifically configured to:

[0116] Multiply the grid-connected setting current by the grid phase to obtain the grid-connected setting AC quantity;

[0117] Subtract the grid-connected set AC quantity from the first grid-connected sampling current to obtain a second target difference value;

[0118] The second target difference is input into the proportional resonant controller to obtain a first output value.

[0119] Optionally, the output value determination unit 64 further includes:

[0120] a third calculation subunit, configured to input the first target difference into the proportional resonant controller to obtain a first output value;

[0121] The fourth calculation subunit is used to use the grid sampling voltage as a feedforward signal and the target compensation value as a compensation signal to jointly adjust the first output value to determine the second output value of the grid-connected current loop.

[0122] Optionally, before the first calculation subunit multiplies the grid-connected setting current by the grid phase to obtain the grid-connected setting AC quantity, the output value determination unit 64 further includes:

[0123] A voltage acquisition subunit, used to acquire a sampling voltage of a power grid;

[0124] The phase locking subunit is used to phase lock the grid sampling voltage to obtain the grid phase.

[0125] Optionally, the control signal determination unit 65 is specifically configured to:

[0126] The second output value is divided by the bus voltage of the grid-connected inverter to obtain a pulse width modulation signal with a corresponding duty cycle.

[0127] The control device for the grid-connected inverter provided in the embodiment of the present invention has the same technical features as the control method for the grid-connected inverter provided in the above embodiment, and therefore can also solve the same technical problems and achieve the same technical effects.

[0128] An embodiment of the present invention further provides a grid-connected inverter, which includes the control device for the grid-connected inverter in any of the above embodiments.

[0129] The grid-connected inverter provided in the embodiment of the present invention includes the control device of the grid-connected inverter in the above embodiment. Therefore, the grid-connected inverter provided in the embodiment of the present invention also has the beneficial effects described in the above embodiment, which will not be described in detail here.

[0130] In the description of the embodiments of the present invention, unless otherwise clearly specified and limited, the terms "installed", "connected", and "connected" should be understood in a broad sense, for example, it can be a fixed connection, a detachable connection, or an integral connection; it can be a mechanical connection or an electrical connection; it can be a direct connection or an indirect connection through an intermediate medium, or it can be the internal communication of two components. For ordinary technicians in this field, the specific meanings of the above terms in the present invention can be understood according to specific circumstances.

[0131] Finally, it should be noted that the above are only preferred embodiments of the present invention and the technical principles used. Those skilled in the art will understand that the present invention is not limited to the specific embodiments described herein, and that various obvious changes, readjustments and substitutions can be made by those skilled in the art without departing from the scope of protection of the present invention. Therefore, although the present invention has been described in more detail through the above embodiments, the present invention is not limited to the above embodiments, and may include more other equivalent embodiments without departing from the concept of the present invention, and the scope of the present invention is determined by the scope of the appended claims.

Claims

1. A control method for a grid-connected inverter, characterized in that: The control method comprises: Obtaining a first grid-connected sampling current of the grid-connected inverter; Obtaining a first target difference according to the first grid-connected sampling current and the grid-connected set current; Based on the adjustment of the first target difference, a target compensation value is obtained; Determine a second output value of the grid-connected current loop according to the target compensation value, the grid sampling voltage and the first output value of the proportional resonant controller; Determine a pulse width modulation signal of a corresponding duty cycle based on the second output value and the bus voltage of the grid-connected inverter; The on and off of each transistor of the grid-connected inverter is controlled based on the pulse width modulation signal.

2. The control method of the grid-connected inverter according to claim 1, characterized in that: Based on the adjustment of the first target difference, obtaining the target compensation value includes: The first target difference is input into a proportional-integral controller for adjustment to obtain the target compensation value.

3. The control method of the grid-connected inverter according to claim 1, characterized in that: Obtaining a first target difference according to the first grid-connected sampling current and the grid-connected set current includes: Converting the first grid-connected sampling current into a parameter in a dq coordinate system to obtain a second grid-connected sampling current; The second grid-connected sampling current is subtracted from the grid-connected set current to obtain the first target difference.

4. The control method of the grid-connected inverter according to claim 1, characterized in that: Obtaining a first target difference according to the first grid-connected sampling current and the grid-connected set current includes: Multiplying the grid-connected setting current by the grid phase to obtain the grid-connected setting alternating current quantity; The first target difference is obtained by subtracting the first grid-connected sampling current from the grid-connected set AC quantity.

5. The control method of the grid-connected inverter according to claim 1, characterized in that: Determining the second output value of the grid-connected current loop according to the target compensation value, the grid sampling voltage and the first output value of the proportional resonant controller comprises: determining a first output value of the proportional resonant controller; The grid sampling voltage is used as a feedforward signal, and the target compensation value is used as a compensation signal, and the first output value is jointly adjusted to determine the second output value of the grid-connected current loop.

6. The control method of the grid-connected inverter according to claim 5, characterized in that: Determining a first output value of the proportional resonant controller comprises: Multiplying the grid-connected setting current by the grid phase to obtain the grid-connected setting alternating current quantity; Subtract the grid-connected set AC quantity from the first grid-connected sampled current to obtain a second target difference; The second target difference is input into the proportional resonant controller to obtain the first output value.

7. The control method of the grid-connected inverter according to claim 4, characterized in that: Determining the second output value of the grid-connected current loop according to the target compensation value, the grid sampling voltage and the first output value of the proportional resonant controller comprises: Inputting the first target difference into the proportional resonant controller to obtain the first output value; The grid sampling voltage is used as a feedforward signal, and the target compensation value is used as a compensation signal, and the first output value is jointly adjusted to determine the second output value of the grid-connected current loop.

8. The control method of the grid-connected inverter according to claim 6 or 7, characterized in that: Before multiplying the grid-connected setting current by the grid phase to obtain the grid-connected setting AC quantity, the control method further includes: Obtaining the grid sampling voltage; The grid sampling voltage is phase-locked to obtain the grid phase.

9. The control method of the grid-connected inverter according to claim 1, characterized in that: Determining a pulse width modulation signal with a corresponding duty cycle based on the second output value and the bus voltage of the grid-connected inverter includes: The second output value is divided by the bus voltage of the grid-connected inverter to obtain the pulse width modulation signal of the corresponding duty cycle.

10. A control device for a grid-connected inverter, characterized in that: The control device comprises: A current acquisition unit, used for acquiring a first grid-connected sampling current of the grid-connected inverter; a difference determination unit, configured to obtain a first target difference according to the first grid-connected sampled current and the grid-connected set current; a compensation value determining unit, configured to obtain a target compensation value based on an adjustment of the first target difference value; An output value determination unit, configured to determine a second output value of the grid-connected current loop according to the target compensation value, the grid sampling voltage, and the first output value of the proportional resonant controller; a control signal determination unit, configured to determine a pulse width modulation signal of a corresponding duty cycle based on the second output value and the bus voltage of the grid-connected inverter; A transistor control unit is used to control the on and off of each transistor of the grid-connected inverter based on the pulse width modulation signal.

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