Micro-inverse topology control method

Abstract

The invention discloses a micro-inverse topology control method, and the method comprises the steps: carrying out the collection and processing of an analog signal through a DSP, converting the collected voltage value into an actual value, obtaining a DC input voltage, an AC voltage, and a voltage at a capacitor C5, and calculating an effective value of the AC voltage; pLL phase locking is carried out on the AC voltage to obtain a voltage instantaneous angle theta, and active power and reactive power are calculated; and calculating transient output power Psun according to the active power, the reactive power, the voltage instantaneous angle theta and the effective value of the AC voltage, calculating the transient output power Psun according to the effective value to judge the power flow direction, and obtaining an angle through PLL phase locking to perform gate-level switching. Through control of the first MOS tube Q1 and the second MOS tube Q2, bidirectional flow of effective power is realized, the working states of the MOS tubes and the silicon controlled rectifier are accurately controlled according to the change of alternating voltage # imgabs0 # and the positive and negative of transient output power Psun, and the system efficiency is improved.

Description

Technical Field

[0001] The present invention relates to the technical field of micro-inverter topologies, and particularly to a micro-inverter topology control method. Background Art

[0002] In traditional photovoltaic power generation systems, common topology structures are usually designed for unidirectional power flow, that is, power can only flow from the DC side (photovoltaic module side) to the AC side (grid side). The characteristic of this topology structure is that it can only achieve the output of active power and cannot absorb or consume power. Specifically, energy is converted from photovoltaic modules into alternating current by an inverter and then injected into the grid, but the system cannot absorb energy from the grid or provide reactive power compensation.

[0003] However, with the wide application of photovoltaic power generation systems and the continuous improvement of grid requirements, the limitations of traditional unidirectional power flow topology structures have gradually emerged. Modern power systems have put forward higher requirements for photovoltaic power generation systems, especially in terms of reactive power compensation. The grid requires that the photovoltaic system can not only output active power but also provide reactive power support when necessary to improve the voltage stability, power factor, and harmonic problems of the grid. Summary of the Invention

[0004] Based on this, in order to solve the problem that the existing topology structure is designed for unidirectional power flow and cannot absorb energy from the grid or provide reactive power compensation, the present invention provides a micro-inverter topology control method.

[0005] The present invention provides a micro-inverter topology control method, including:

[0006] Using a DSP to collect and process analog signals, converting the collected voltage values into actual values, obtaining the DC input voltage, AC voltage, and voltage at capacitor C5, and calculating the effective value of the AC voltage;

[0007] Performing PLL phase locking on the AC voltage to obtain the voltage instantaneous angle θ, and calculating the active power and reactive power;

[0008] Calculating the transient output power P according to the active power, reactive power, voltage instantaneous angle θ, and the effective value of the AC voltage sun , calculating the transient output power P according to the effective value sun Judging the power flow direction, and performing gate-level switching by obtaining an angle through PLL phase locking.

[0009] The calculation of the active power and reactive power includes,

[0010] The output active power P is calculated by MPPT out , according to the active power P out and the power factor PF to calculate the reactive power Qout , the reactive power Q out The calculation of

[0011] .

[0012] The output power P of the transient of the effective value calculation sun The calculation of

[0013] According to the active power P out , the effective value U of the AC voltage rms and the instantaneous voltage angle θ to calculate the instantaneous active current value I you and the instantaneous active current value I wu ,

[0014] ;

[0015] ;

[0016] According to the instantaneous active current value I you and the instantaneous active current value I wu calculate the transient current target value ,

[0017] ;

[0018] According to the transient current target value and the AC voltage effective value, calculate the output power P of the transient sun ,

[0019] .

[0020] According to the output power P of the transient of the effective value calculation sun The operation of judging the power flow direction includes

[0021] When , the power flow direction is from the DC side to the AC side;

[0022] When , the power flow direction is from the AC side to the DC side.

[0023] The primary side of the transformer is electrically connected to the drain of the first MOS transistor Q1, and the source of the first MOS transistor Q1 is electrically connected to the photovoltaic panel;

[0024] The secondary side of the transformer is electrically connected to the source of the second MOS transistor Q2.

[0025] When , the first MOS transistor Q1 is turned on and the second MOS transistor Q2 is turned off;

[0026] When When the second MOS transistor Q2 is turned on, the first MOS transistor Q1 is turned off.

[0027] When it is, the critical point strategy is adopted to calculate the on-time and off-time of the first MOS transistor Q1,

[0028] ;

[0029] ;

[0030] ;

[0031] Among them, represents the off-time of the first MOS transistor Q1, represents the on-time of the first MOS transistor Q1, represents a complete switching cycle of the first MOS transistor Q1, represents the transient current target the absolute value of the value, represents the primary inductance value of the transformer, n represents the ratio of the number of turns of the primary side to the number of turns of the secondary side of the transformer, represents the DC input voltage, represents the voltage at the capacitor C5;

[0032] When it is, the critical point strategy is adopted to calculate the on-time and off-time of the second MOS transistor Q2,

[0033] ;

[0034] ;

[0035] ;

[0036] Among them, represents the off-time of the second MOS transistor Q2, represents the on-time of the second MOS transistor Q2, represents a complete switching cycle of the second MOS transistor Q2, represents the secondary inductance value of the transformer.

[0037] When the AC voltage changes from negative to positive and it is, the gate signals for turning on the third thyristor D3 and the fourth MOS transistor Q4 are given. If it is at this time, control the first MOS transistor Q1 to turn on for a time and then turn off for a time; When When it is time, turn off the first MOS transistor Q1 and control the second MOS transistor Q2 to conduct. Turn off after a certain time time.

[0038] When the AC voltage changes from positive to negative and at a certain time, give the gate signals for the fifth thyristor D5 and the third MOS transistor Q3 to conduct. If at this time , control the first MOS transistor Q1 to conduct Turn off after a certain time time; when occurs, turn off the first MOS transistor Q1 and control the second MOS transistor Q2 to conduct Turn off after a certain time time;

[0039] When the AC voltage value starts to increase from the negative peak and is greater than at a certain time, turn off the first MOS transistor Q1 and the second MOS transistor Q2, wait for 80 us, then let the inductor on the transformer discharge, and then turn off the third thyristor D3 and the fourth MOS transistor Q4.

[0040] Beneficial effects: Through the control of the first MOS transistor Q1 and the second MOS transistor Q2, the present invention realizes the bidirectional flow of effective power. According to the change of the AC voltage and the positive and negative of the transient output power Psun, the conduction and turn-off of the MOS transistors and the third thyristor D3 and the fifth thyristor D5 are precisely controlled. Through precise timing control, the switching loss is reduced and the system efficiency is improved. Realizing the positive and negative circulation of energy can output reactive power while outputting active power, and has the function of reactive power compensation for the power grid.

[0041] It should be understood that the content described in this part is not intended to identify the key or important features of the embodiments of the present invention, nor is it used to limit the scope of the present invention. Other features of the present invention will become easily understood through the following description. Brief Description of the Drawings

[0042] The drawings are used to better understand the present solution and do not constitute a limitation to the present invention. Among them:

[0043] Figure 1 is a schematic diagram of the topological structure provided by the present invention;

[0044] Figure 2 is provided according to the present invention , control the first MOS transistor Q1 to conduct Turn off after a certain time time, Current flow diagram during the time period;

[0045] Figure 3 is provided according to the present invention , turn on the first MOS transistor Q1 and turn it off after time. When the current flow diagram of the time period;

[0046] Figure 4 is provided according to the present invention When, turn off the first MOS transistor Q1 and turn on the second MOS transistor Q2 and turn it off after time. When the current flow diagram of the time period;

[0047] Figure 5 is provided according to the present invention When, turn off the first MOS transistor Q1 and turn on the second MOS transistor Q2 and turn it off after time. When the current flow diagram of the time period;

[0048] Figure 6 is provided according to the present invention , turn on the first MOS transistor Q1 and turn it off after time. When the current flow diagram of the time period;

[0049] Figure 7 is provided according to the present invention When, turn off the first MOS transistor Q1 and turn on the second MOS transistor Q2 and turn it off after time. When the current flow diagram of the time period;

[0050] Figure 8 is the waveform diagram of the alternating voltage and the transient current target provided according to the present invention. Detailed implementation manners

[0051] The following describes exemplary embodiments of the present invention with reference to the accompanying drawings, including various details of the embodiments of the present invention to facilitate understanding. It should be considered merely exemplary. Therefore, those of ordinary skill in the art should recognize that various changes and modifications can be made to the embodiments described herein without departing from the scope and spirit of the present invention. Similarly, for clarity and conciseness, the description of well-known functions and structures is omitted below.

[0052] The present invention provides a micro-inverter topology control method (the topology is as shown in Figure 1 ), including:

[0053] S1: Using a DSP to collect and process analog signals, converting the collected voltage values into actual values, obtaining the DC input voltage, AC voltage, and the voltage at capacitor C5, and calculating the effective value of the AC voltage.

[0054] S2: Performing PLL phase-locking on the AC voltage to obtain the instantaneous voltage angle θ, and calculating the active power and reactive power. It should be noted that:

[0055] The calculation of active power and reactive power includes

[0056] The output active power P is calculated by MPPT out , and the reactive power Q is calculated according to the active power P out and the power factor PF out . The calculation of the reactive power Q out includes

[0057] .

[0058] The calculation of the transient output power P in the effective value calculation includes sun :

[0059] According to the active power P out , the effective value U of the AC voltage rms , and the instantaneous voltage angle θ, calculate the instantaneous value of the active current I you and the instantaneous value of the active current I wu ,

[0060] ;

[0061] ;

[0062] According to the instantaneous value of the active current I you and the instantaneous value of the active current I wu calculate the transient current target value ,

[0063] ;

[0064] S3: Calculate the transient output power P according to the active power, reactive power, voltage instantaneous angle θ, and the effective value of the AC voltage sun , judge the power flow according to the transient output power P calculated by the effective value sun , and perform gate-level switching by obtaining the angle through PLL phase-locking. It should be noted that:

[0065] According to the transient current target value and the effective value of the AC voltage calculate the transient output power P sun ,

[0066] .

[0067] Calculate the transient output power P according to the effective value sun The operation of judging the power flow direction includes

[0068] When , the power flow direction is from the DC side to the AC side;

[0069] When , the power flow direction is from the AC side to the DC side.

[0070] The primary side of the transformer is electrically connected to the drain of the first MOS transistor Q1, and the source of the first MOS transistor Q1 is electrically connected to the photovoltaic panel;

[0071] The secondary side of the transformer is electrically connected to the source of the second MOS transistor Q2.

[0072] The present invention realizes the bidirectional flow of effective power through the control of the first MOS transistor Q1 and the second MOS transistor Q2.

[0073] When , the first MOS transistor Q1 is turned on and the second MOS transistor Q2 is turned off;

[0074] When , the second MOS transistor Q2 is turned on and the first MOS transistor Q1 is turned off.

[0075] The present invention can flexibly switch the power flow direction according to the transient output power P sun When , the first MOS transistor Q1 is turned on and the second MOS transistor Q2 is turned off, and the power flow direction is from the DC side to the AC side;

[0076] When , the second MOS transistor Q2 is turned on and the first MOS transistor Q1 is turned off, and the power flow direction is from the AC side to the DC side.

[0077] Only need to directly control the on and off of the first MOS transistor Q1 and the second MOS transistor Q2 according to the positive and negative of the transient output power P sun , the logic is simple and clear, reducing the complexity of the control system and the demand for computing resources.

[0078] By judging the power flow direction in real time and switching the on and off working states of the first MOS transistor Q1 and the second MOS transistor Q2, the system can quickly respond to power changes, improving the dynamic response ability and stability of the system.

[0079] When occurs, the critical point strategy is adopted to calculate the on - time and off - time of the first MOS transistor Q1,

[0080] ;

[0081] ;

[0082] ;

[0083] wherein, represents the off - time of the first MOS transistor Q1, represents the on - time of the first MOS transistor Q1, represents a complete switching cycle of the first MOS transistor Q1, represents the absolute value of the transient current target value, represents the primary inductor value of the transformer, n represents the ratio of the number of turns of the primary winding to the number of turns of the secondary winding of the transformer, represents the DC input voltage, represents the voltage at capacitor C5;

[0084] When occurs, the critical point strategy is adopted to calculate the on - time and off - time of the second MOS transistor Q2,

[0085] ;

[0086] ;

[0087] ;

[0088] wherein, represents the off - time of the second MOS transistor Q2, represents the on - time of the second MOS transistor Q2, represents a complete switching cycle of the second MOS transistor Q2, represents the secondary inductor value of the transformer.

[0089] As Figure 8 shown, when the AC voltage changes from negative to positive and occurs, the gate signals for turning on the third thyristor D3 and the fourth MOS transistor Q4 are given. If at this time , control the first MOS transistor Q1 to turn on for a time and then turn off for a time ( the current direction during the Figure 2 time period is as shown, the current direction during theFigure 3 as shown); when occurs, turn off the first MOS transistor Q1 and control the second MOS transistor Q2 to conduct and turn it off after time ( the current direction during the Figure 4 time period is as shown in the current direction during the Figure 5 time period is as shown);

[0090] When the AC voltage changes from positive to negative and occurs, give the gate signals for the fifth thyristor D5 and the third MOS transistor Q3 to conduct. If is the case at this time, control the first MOS transistor Q1 to conduct and turn it off after time ( the current direction during the Figure 2 time period is as shown in the current direction during the Figure 6 time period is as shown); when occurs, turn off the first MOS transistor Q1 and control the second MOS transistor Q2 to conduct and turn it off after time ( the current direction during the Figure 7 time period is as shown in the current direction during the Figure 5 time period is as shown);

[0091] When the value of the AC voltage starts to increase from the negative peak value and is greater than , turn off the first MOS transistor Q1 and the second MOS transistor Q2, wait for 80 us, then let the inductor on the transformer discharge, and then turn off the third thyristor D3 and the fourth MOS transistor Q4.

[0092] According to the change of the AC voltage and the positive and negative of the transient output power P sun , precisely control the conduction and turn-off of the MOS transistors and the third thyristor D3 and the fifth thyristor D5. Through precise timing control, the switching loss is reduced and the system efficiency is improved.

[0093] When power needs to be transmitted from the PV side of the photovoltaic panel to the grid side, the first MOS transistor Q1 conducts, and the excitation inductor of the transformer stores energy and the current rises linearly. When the first MOS transistor Q1 is turned off, since there is no discharge circuit on the primary side for the energy on the excitation inductor, it will automatically flow through the discharge circuit on the secondary side. When the current flows through the discharge circuit on the secondary side, the fifth capacitor C5 will be charged, resulting in an increase in the voltage at the fifth capacitor C5. Since the voltage of the fifth capacitor C5 is clamped by the AC voltage, the output current will flow through the AC voltage circuit. When power needs to flow from the AC side to the DC side, the second MOS transistor Q2 conducts to store energy in the transformer excitation inductor. When the second MOS transistor Q2 is turned off, the current on the excitation inductor charges the first capacitor C1 through the circuit on the side of the first capacitor C1.

[0094] As described above, it is only the specific implementation manner of the present invention, but the protection scope of the present invention is not limited thereto. Any changes or substitutions within the technical scope disclosed by the present invention should be covered within the protection scope of the present invention. Therefore, the protection scope of the present invention should be subject to the protection scope of the claimed rights.

Claims

1. A micro-inverter topology control method, characterized in that, Including: Using a DSP to collect and process analog signals, converting the collected voltage values into actual values, obtaining the DC input voltage, AC voltage, and the voltage at capacitor C5, and calculating the effective value of the AC voltage; Performing PLL phase locking on the AC voltage to obtain the instantaneous voltage angle θ, and calculating the active power and reactive power; Calculate the transient output power P according to the active power, reactive power, instantaneous angle θ of the voltage, and the effective value of the AC voltage sun , calculate the transient output power P according to the effective value sun Judge the power flow direction, and obtain the angle through PLL phase-locking for gate-level switching 2. The micro-inverter topology control method according to claim 1, wherein: The calculation of active power and reactive power includes The output active power P is calculated by MPPT out , and the reactive power Q is calculated according to the active power P out and the power factor PF out , the calculation of the reactive power Q out includes 。 3. A micro-inverter topology control method according to claim 2, characterized in that: The calculation of the output power P sun in the transient of the effective value calculation includes According to the active power P out , the effective value U of the alternating voltage rms and the instantaneous voltage angle θ, calculate the instantaneous value I of the active current you and the instantaneous value I of the active current wu , ； ； According to the instantaneous value I of the active current you and the instantaneous value I of the active current wu calculate the target value of the transient current , ； According to the transient current target value and the effective value of the AC voltage calculate the transient output power P sun , 。 4. A micro-inverter topology control method according to claim 3, characterized in that: Calculate the output power P of the transient according to the effective value sun The operation of judging the power flow direction includes When occurs, the power flow is from the DC side to the AC side; When the power flow is from the AC side to the DC side.

5. A micro-inverter topology control method according to any one of claims 1-4, characterized in that: The primary side of the transformer is electrically connected to the drain of the first MOS transistor Q1, and the source of the first MOS transistor Q1 is electrically connected to the photovoltaic panel; The secondary side of the transformer is electrically connected to the source of the second MOS transistor Q2.

6. The micro-inverter topology control method according to claim 5, characterized in that: When the first MOS transistor Q1 is turned on and the second MOS transistor Q2 is turned off; When the second MOS transistor Q2 is turned on and the first MOS transistor Q1 is turned off.

7. A micro-inverter topology control method according to claim 6, characterized in that: When is reached, the on-time and off-time of the first MOS transistor Q1 are calculated using the critical point strategy, ； ； ； Among them, represents the turn-off time of the first MOS transistor Q1, represents the turn-on time of the first MOS transistor Q1, represents a complete switching cycle of the first MOS transistor Q1, represents the transient current target the absolute value of the value, represents the primary inductance value of the transformer, and n represents the ratio of the number of turns of the primary winding to the number of turns of the secondary winding of the transformer, represents the DC input voltage, represents the voltage at capacitor C5; When is reached, the critical point strategy is used to calculate the on-time and off-time of the second MOS transistor Q2. ； ； ； Among them, represents the turn-off time of the second MOS transistor Q2, represents the turn-on time of the second MOS transistor Q2, represents a complete switching cycle of the second MOS transistor Q2, represents the inductance value of the secondary side of the transformer.

8. A micro-inverter topology control method according to claim 7, characterized in that: When the AC voltage changes from negative to positive and at this time, a gate signal for turning on the third thyristor D3 and the fourth MOS transistor Q4 is given. If at this time , control the first MOS transistor Q1 to turn on and turn it off after time; When occurs, turn off the first MOS transistor Q1 and control the second MOS transistor Q2 to conduct and turn it off after time.

9. A micro-inverter topology control method according to claim 7 or 8, characterized in that: When the AC voltage changes from positive to negative and at this time, a gate signal for turning on the fifth thyristor D5 and the third MOS transistor Q3 is given. If at this time , control the first MOS transistor Q1 to turn on and turn it off after time; When occurs, turn off the first MOS transistor Q1 and control the second MOS transistor Q2 to conduct and turn it off after time; When the AC voltage value starts to increase from the negative peak and is greater than , turn off the first MOS transistor Q1 and the second MOS transistor Q2, wait for 80 μs, then discharge the inductor on the transformer and turn off the third thyristor D3 and the fourth MOS transistor Q4.

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