Energy router AC side grid-connected and off-grid smooth switching control method and system

Abstract

The invention provides an energy router AC side grid-connected and off-grid smooth switching control method and system, and the method comprises the steps: controlling a voltage loop to be always in an operation state and not to enter a saturation state, and controlling the output power of a grid-connected control module to be the same as the output power of the voltage loop, when the energy router is switched between the grid-connected state and the off-grid state, the operation state is switched in a smooth transition manner; wherein the output end of the off-grid control module and the output end of the grid-connected control module are connected with the input end of the inverter in a current loop sharing mode, and the output end of the voltage loop is connected with the output end of the grid-connected control module in series and then connected to the input end of the voltage loop. Because the voltage loop is always in an operation state and does not enter a saturation state, the voltage loop does not enter the saturation state during off-grid or grid-connected switching operation, so that a buffer effect can be achieved, the output of the voltage loop at the switching moment is ensured to be the same as the output of the grid-connected control module before switching, and smooth transition switching between off-grid and grid-connected is realized.

Description

Technical Field

[0001] The present invention belongs to the technical field of power grid control, and in particular relates to a method and system for controlling smooth on-grid and off-grid switching of an AC side of an energy router. Background Art

[0002] In the process of transformation from traditional power grid to energy internet, the operation control strategy of energy routers and their networking coordination and energy dispatching methods are the basis for the operation of energy internet. Through energy routers, the power supply demand on the user side will gradually develop from the single power supply mode of traditional power grid to traditional power grid, distributed new energy generation and energy storage system.

[0003] The operation control strategy of the existing energy router will cause current shock during the switching process between on-grid and off-grid. Summary of the invention

[0004] In order to overcome the above-mentioned deficiencies of the prior art, in a first aspect, the present invention proposes a method for controlling the smooth switching of the AC side of an energy router on and off the grid, the method comprising:

[0005] Based on the received energy router operation status switching instruction, the inverter controls the selection of the off-grid control module or the grid-connected control module to achieve the switching between grid-connected and off-grid;

[0006] Control the voltage loop to always be in an operating state and not enter a saturation state, and control the output power of the grid-connected control module to be the same as the output power of the voltage loop, so that the energy router can smoothly transition to switch the operating state when switching between grid-connected and grid-off;

[0007] Among them, the output end of the off-grid control module and the output end of the grid-connected control module are connected to the input end of the inverter in the form of a common current loop, the output end of the inverter is connected to the AC side of the energy router, the AC side of the energy router is connected to the power grid, the output end of the off-grid control module is forwardly connected to the voltage loop between the current loop, and the output end of the voltage loop is connected in series with the output end of the grid-connected control module and then connected to the input end of the voltage loop.

[0008] Preferably, the control voltage loop is always in an operation state and does not enter a saturation state, and the output power of the grid-connected control module is controlled to be the same as the output power of the voltage loop, including:

[0009] The output power of the grid-connected control module is controlled as a given instruction, and the difference between the given instruction and the output power of the voltage loop is used as the input signal of the voltage loop. The input signal is output after being subjected to proportional-integral operation by the voltage loop, so that the voltage loop is always in an operation state and does not enter a saturation state;

[0010] Based on the fact that the voltage loop is always in an operation state and does not enter a saturation state, the output power of the grid-connected control module is controlled to be consistent with the output power of the voltage loop.

[0011] Preferably, a first switch is connected between the grid-connected control module and the current loop, and a second switch is connected between the voltage loop and the current loop;

[0012] A third switch is connected between the off-grid control module and the voltage loop;

[0013] After the connection point between the output of the voltage loop and the second switch and the connection point between the first switch and the current loop are connected, a fourth switch is connected to the input end of the voltage loop.

[0014] Preferably, based on the received energy router operation state switching instruction, the inverter controls the selection of the off-grid control module or the grid-connected control module to implement the grid-connected and off-grid switching, including:

[0015] If the energy router operation state switching instruction is a grid-connected operation instruction, the inverter controls the first switch and the fourth switch to be closed, and the second switch and the third switch to be opened, so as to select the grid-connected control module; or

[0016] If the energy router operation state switching instruction is an off-grid operation instruction, the inverter controls the first switch and the fourth switch to be opened, and the second switch and the third switch to be closed, so as to select the off-grid control module and realize off-grid switching.

[0017] Preferably, a current decoupling controller and a pulse width modulation controller are sequentially connected between the current loop and the input end of the inverter;

[0018] Before the inverter controls the selection of the off-grid control module or the grid-connected control module based on the received energy router operation state switching instruction to implement the grid-connected and off-grid switching, the method further includes:

[0019] The two-phase electrical signal of the current loop is converted into a three-phase electrical control signal by using the current decoupling controller, and the three-phase electrical control signal is used as a modulation wave to compare with a fixed carrier wave;

[0020] When the modulated wave is higher than the carrier wave, the pulse width modulation controller outputs a high level, and the high level is used as an input signal of the inverter to drive the inverter to operate;

[0021] When the modulation wave is lower than the carrier wave, the pulse width modulation controller outputs a low level, and the low level is used as an input signal of the inverter to drive the inverter to operate.

[0022] Preferably, the energy router comprises an AC converter and a plurality of DC converters, the output end of the AC converter is connected to the input end of each DC converter; the input end of the AC converter is connected to the output end of the inverter;

[0023] The output ends of the multiple DC converters are respectively connected to the DC load, the photovoltaic array, and the energy storage battery.

[0024] Preferably, the off-grid control module is a constant voltage and frequency controller, and the grid-connected control module is a constant power controller.

[0025] In the second aspect, the present invention also proposes a control system for smooth on-grid and off-grid switching of the AC side of an energy router, including an energy router, an inverter, a current loop, a voltage loop, a on-grid control module, an off-grid control module, and a control module;

[0026] The inverter is used to control the selection of the off-grid control module or the grid-connected control module based on the received operation state switching instruction of the energy router to realize the switching between grid connection and off-grid;

[0027] The control module is used to control the voltage loop to always be in an operating state and not enter a saturated state, and to control the output power of the grid-connected control module to be the same as the output power of the voltage loop, so that the energy router can smoothly transition to switch the operating state when switching between grid-connected and off-grid;

[0028] The output end of the off-grid control module and the output end of the grid-connected control module are connected to the input end of the inverter in a manner of sharing the current loop. The output end of the inverter is connected to the AC side of the energy router, and the AC side of the energy router is connected to the power grid. The voltage loop is forwardly connected between the output end of the off-grid control module and the current loop, and the output end of the voltage loop is connected in series with the output end of the grid-connected control module and then connected to the input end of the voltage loop.

[0029] The control module is specifically used for:

[0030] The output power of the grid-connected control module is controlled as a given instruction, and the difference between the given instruction and the output power of the voltage loop is used as the input signal of the voltage loop. The input signal is output after being subjected to proportional-integral operation by the voltage loop, so that the voltage loop is always in an operation state and does not enter a saturation state;

[0031] Based on the fact that the voltage loop is always in an operation state and does not enter a saturation state, the output power of the grid-connected control module is controlled to be consistent with the output power of the voltage loop.

[0032] Preferably, a first switch is connected between the grid-connected control module and the current loop, and a second switch is connected between the voltage loop and the current loop;

[0033] A third switch is connected between the off-grid control module and the voltage loop;

[0034] After the connection point between the output of the voltage loop and the second switch and the connection point between the first switch and the current loop are connected, a fourth switch is connected to the input end of the voltage loop.

[0035] The inverter is specifically used for:

[0036] If the energy router operation state switching instruction is a grid-connected operation instruction, the first switch and the fourth switch are controlled to be closed, and the second switch and the third switch are controlled to be opened, so as to select the grid-connected control module; or

[0037] If the energy router operation state switching instruction is an off-grid operation instruction, the first switch and the fourth switch are controlled to be opened, and the second switch and the third switch are controlled to be closed, so as to select the off-grid control module and realize off-grid switching.

[0038] Preferably, a current decoupling controller and a pulse width modulation controller are sequentially connected between the current loop and the input end of the inverter;

[0039] The current decoupling controller is used to convert the two-phase electrical signal of the current loop into a three-phase electrical control signal, and the three-phase electrical control signal is used as a modulated wave to be compared with a fixed carrier wave;

[0040] When the modulated wave is higher than the carrier wave, the pulse width modulation controller is used to output a high level, and use the high level as an input signal of the inverter to drive the inverter to operate;

[0041] When the modulation wave is lower than the carrier wave, the pulse width modulation controller is used to output a low level, and the low level is used as the input signal of the inverter to drive the inverter to operate.

[0042] Preferably, the energy router comprises an AC converter and a plurality of DC converters, the output end of the AC converter is connected to the input end of each DC converter; the input end of the AC converter is connected to the output end of the inverter;

[0043] The output ends of the multiple DC converters are respectively connected to the DC load, the photovoltaic array, and the energy storage battery.

[0044] Preferably, the off-grid control module is a constant voltage and frequency controller, and the grid-connected control module is a constant power controller.

[0045] In a third aspect, the present invention application further proposes an electronic device, comprising: at least one processor and a memory; the memory and the processor are connected via a bus;

[0046] The memory is used to store one or more programs;

[0047] When the one or more programs are executed by the at least one processor, the energy router AC side on-grid and off-grid smooth switching control method is implemented.

[0048] In a fourth aspect, the present invention application further proposes a readable storage medium having an execution program stored thereon, and when the execution program is executed, the energy router AC side on-grid and off-grid smooth switching control method is implemented.

[0049] Compared with the closest prior art, the present invention has the following beneficial effects:

[0050] A method and system for controlling smooth on-grid and off-grid switching of an AC side of an energy router of the present invention comprises: based on a received energy router operation state switching instruction, an inverter controls the selection of an off-grid control module or a grid-connected control module to realize on-grid and off-grid switching; controlling a voltage loop to always be in an operation state and not enter a saturation state, and controlling the output power of the grid-connected control module to be the same as the output power of the voltage loop, so that the energy router smoothly transitions to switch the operation state when on-grid and off-grid switching occurs; wherein the output end of the off-grid control module and the output end of the grid-connected control module are connected to the input end of the inverter in a manner of a common current loop, the output end of the inverter is connected to the AC side of the energy router, the AC side of the energy router is connected to the power grid, the output end of the off-grid control module is forwardly connected to the voltage loop between the current loop, and the output end of the voltage loop is connected in series with the output end of the grid-connected control module and then connected to the input end of the voltage loop. Since the voltage loop is always in an operating state and does not enter a saturated state, the voltage loop does not enter a saturated state during off-grid or grid-connected switching operation, which can play a buffering role and ensure that the output of the voltage loop at the switching moment is the same as the output of the grid-connected control module before switching, thereby achieving smooth transition switching between off-grid and grid-connected. BRIEF DESCRIPTION OF THE DRAWINGS

[0051] Figure 1 A flow chart of a method for smoothly switching an AC side of an energy router on and off the grid provided by the present invention;

[0052] Figure 2A connection circuit diagram of the energy router provided by the present invention;

[0053] Figure 3 A control block diagram of a grid-connected and off-grid switching method based on a change in a current loop instruction provided by the present invention;

[0054] Figure 4 The on-grid and off-grid switching control block diagram provided by the present invention;

[0055] Figure 5 A schematic diagram of a circuit in which the inverter provided by the present invention may have a switch S1 inside and a switch S2 outside;

[0056] Figure 6 A circuit diagram of a three-phase full-bridge inverter provided in the present invention that connects a power grid to a DC bus;

[0057] Figure 7 A control block diagram of a grid-connected and off-grid switching method based on PWM signal changes provided by the present invention;

[0058] Figure 8 The inverter output and the three-phase voltage and current waveform of the power grid provided by the present invention;

[0059] Fig. 9 The power and DC voltage waveform of the system provided by the present invention;

[0060] Fig.10 A schematic diagram of the operation of an electronic device provided in the present invention application. DETAILED DESCRIPTION

[0061] The specific implementation methods of the present invention are further described in detail below with reference to the accompanying drawings.

[0062] Embodiment 1:

[0063] like Figure 1 As shown, the present invention proposes a method for controlling smooth switching of an AC side of an energy router on and off the grid, the method comprising:

[0064] Step 1: Based on the received energy router operation state switching instruction, the inverter controls the selection of an off-grid control module or a grid-connected control module to implement the switching between grid connection and off-grid connection;

[0065] Step 2: Control the voltage loop to always be in the operation state and not enter the saturation state, and control the output power of the grid-connected control module to be the same as the output power of the voltage loop, so that the energy router can smoothly transition to switch the operation state when switching between grid-connected and off-grid;

[0066] Among them, the output end of the off-grid control module and the output end of the grid-connected control module are connected to the input end of the inverter in the form of a common current loop, the output end of the inverter is connected to the AC side of the energy router, the AC side of the energy router is connected to the power grid, the output end of the off-grid control module is forwardly connected to the voltage loop between the current loop, and the output end of the voltage loop is connected in series with the output end of the grid-connected control module and then connected to the input end of the voltage loop.

[0067] In the above-mentioned steps 1 and 2, a first switch may be connected between the grid-connected control module and the current loop, and a second switch may be connected between the voltage loop and the current loop; a third switch may be connected between the off-grid control module and the voltage loop; and a fourth switch may be connected between the output of the voltage loop and the connection point between the second switch and the connection point between the first switch and the current loop and the input end of the voltage loop after the connection is made between the output of the voltage loop and the connection point between the second switch and the connection point between the first switch and the current loop.

[0068] In the above step 1: when the inverter controls the selection of the off-grid control module or the grid-connected control module based on the received energy router operation state switching instruction to implement the grid-connected and off-grid switching, it may include:

[0069] If the energy router operation state switching instruction is a grid-connected operation instruction, the inverter controls the first switch and the fourth switch to be closed, and the second switch and the third switch to be opened, so as to select the grid-connected control module; or

[0070] If the energy router operation state switching instruction is an off-grid operation instruction, the inverter controls the first switch and the fourth switch to be opened, and the second switch and the third switch to be closed, so as to select the off-grid control module and realize off-grid switching.

[0071] like Figure 2 , Figure 3 As shown, in the above step 1 and step 2, a current decoupling controller and a pulse width modulation controller may be connected in sequence between the current loop and the input end of the inverter; Figure 2 , Figure 3 , Figure 4 , Figure 6 In, f n Indicates frequency, U n Indicates voltage, P ref is the reference value set by the system, Q ref is the reference value set by the system, U ref is the reference voltage, U dref is the reference voltage vector on the d-axis, U qref is the reference voltage vector on the q axis, U d is the voltage on the d-axis, Uq is the voltage on the q axis, i dref is the reference current component on the d reference coordinate axis, i qref is the reference current component on the reference coordinate q axis, i Ld is the d-axis current, i Lq is the q-axis current, ω angular frequency, θ phase angle, ωL f is the product of angular frequency and filter inductance, ωC f is the product of the angular frequency and the capacitance value of the LC filter connected to the inverter terminals, Indicates the integral action.

[0072] Before the inverter controls the selection of the off-grid control module or the grid-connected control module based on the received energy router operation state switching instruction to implement the grid-connected and off-grid switching, the method further includes:

[0073] The two-phase electrical signal of the current loop is converted into a three-phase electrical control signal by using the current decoupling controller, and the three-phase electrical control signal is used as a modulation wave to compare with a fixed carrier wave;

[0074] When the modulated wave is higher than the carrier wave, the pulse width modulation controller outputs a high level, and the high level is used as an input signal of the inverter to drive the inverter to operate;

[0075] When the modulation wave is lower than the carrier wave, the pulse width modulation controller outputs a low level, and the low level is used as an input signal of the inverter to drive the inverter to operate.

[0076] In the above step 2, the control voltage loop is always in an operation state and does not enter a saturation state, and the output power of the grid-connected control module is controlled to be the same as the output power of the voltage loop, which may include:

[0077] The output power of the grid-connected control module is controlled as a given instruction, and the difference between the given instruction and the output power of the voltage loop is used as the input signal of the voltage loop. The input signal is output after being subjected to proportional-integral operation by the voltage loop, so that the voltage loop is always in an operation state and does not enter a saturation state;

[0078] Based on the fact that the voltage loop is always in an operation state and does not enter a saturation state, the output power of the grid-connected control module is controlled to be consistent with the output power of the voltage loop.

[0079] In the above step 1 and step 2, the energy router may include an AC converter and a plurality of DC converters, the output end of the AC converter is connected to the input end of each DC converter; the input end of the AC converter is connected to the output end of the inverter;

[0080] The output ends of the multiple DC converters are respectively connected to the DC load, the photovoltaic array, and the energy storage battery.

[0081] An energy storage battery, used to store and release energy for the energy router during operation;

[0082] The photovoltaic array includes photovoltaic units, which are used to boost the low-voltage direct current generated by the photovoltaic units to the voltage required by the energy router and control the power output of the photovoltaic units.

[0083] The off-grid control module can be selected as a constant voltage and frequency controller, and the grid-connected control module can be selected as a constant power controller.

[0084] In summary, the method for smooth switching between the grid-connected and off-grid operating modes of the energy router AC side proposed in the present invention ensures that the inverter output will not suddenly change during the state switching process, solves the current shock problem during the grid-connected and off-grid switching process, and realizes the smooth switching of the grid operation mode and the safe operation of the system.

[0085] Embodiment 2:

[0086] The present invention application also proposes an energy router AC side grid-connected and off-grid smooth switching control system, including an energy router, an inverter, a current loop, a voltage loop, a grid-connected control module, an off-grid control module, and a control module;

[0087] The inverter is used to control the selection of an off-grid control module or a grid-connected control module based on the received energy router operation state switching instruction to achieve grid-connected and off-grid switching;

[0088] The control module is used to control the voltage loop to always be in an operating state and not enter a saturated state, and to control the output power of the grid-connected control module to be the same as the output power of the voltage loop, so that the energy router can smoothly transition to switch the operating state when switching between grid-connected and off-grid;

[0089] The output end of the off-grid control module and the output end of the grid-connected control module are connected to the input end of the inverter in the form of a common current loop. The output end of the inverter is connected to the AC side of the energy router, and the AC side of the energy router is connected to the power grid. The output end of the off-grid control module is forwardly connected to the voltage loop between the current loop, and the output end of the voltage loop is connected in series with the output end of the grid-connected control module and then connected to the input end of the voltage loop.

[0090] The control module is specifically used for:

[0091] The output power of the grid-connected control module is controlled as a given instruction, and the difference between the given instruction and the output power of the voltage loop is used as the input signal of the voltage loop. The input signal is output after being subjected to proportional-integral operation by the voltage loop, so that the voltage loop is always in an operation state and does not enter a saturation state;

[0092] Based on the fact that the voltage loop is always in an operation state and does not enter a saturation state, the output power of the grid-connected control module is controlled to be consistent with the output power of the voltage loop.

[0093] Further, a first switch is connected between the grid-connected control module and the current loop, and a second switch is connected between the voltage loop and the current loop;

[0094] A third switch is connected between the off-grid control module and the voltage loop;

[0095] After the connection point between the output of the voltage loop and the second switch and the connection point between the first switch and the current loop are connected, a fourth switch is connected to the input end of the voltage loop.

[0096] The inverter is specifically used for:

[0097] If the energy router operation state switching instruction is a grid-connected operation instruction, the first switch and the fourth switch are controlled to be closed, and the second switch and the third switch are controlled to be opened, so as to select the grid-connected control module; or

[0098] If the energy router operation state switching instruction is an off-grid operation instruction, the first switch and the fourth switch are controlled to be opened, and the second switch and the third switch are controlled to be closed, so as to select the off-grid control module and realize off-grid switching.

[0099] Furthermore, a current decoupling controller and a pulse width modulation controller are sequentially connected between the current loop and the input end of the inverter;

[0100] The current decoupling controller is used to convert the two-phase electrical signal of the current loop into a three-phase electrical control signal, and the three-phase electrical control signal is used as a modulated wave to be compared with a fixed carrier wave;

[0101] When the modulated wave is higher than the carrier wave, the pulse width modulation controller is used to output a high level, and use the high level as an input signal of the inverter to drive the inverter to operate;

[0102] When the modulation wave is lower than the carrier wave, the pulse width modulation controller is used to output a low level, and the low level is used as the input signal of the inverter to drive the inverter to operate.

[0103] Furthermore, the energy router includes an AC converter and a plurality of DC converters, the output end of the AC converter is connected to the input end of each DC converter; the input end of the AC converter is connected to the output end of the inverter;

[0104] The output ends of the multiple DC converters are respectively connected to the DC load, the photovoltaic array, and the energy storage battery.

[0105] Furthermore, the off-grid control module is a constant voltage and frequency controller, and the grid-connected control module is a constant power controller.

[0106] Embodiment 3:

[0107] The present invention application also proposes a specific use case of a method for smoothly switching an energy router on and off the AC side:

[0108] Step 1: The inverter controls the selection of an off-grid control module or a grid-connected control module to achieve switching between grid connection and off-grid connection;

[0109] Step 2: During the switching process, the voltage loop is always in the operation state and does not enter the saturation state, so there will be no desaturation shock problem, so that the energy router can smoothly transition and switch the operating state when switching between on-grid and off-grid.

[0110] In step 1 and step 2, the off-grid control module is a constant voltage and frequency controller, and the grid-connected control module is a constant power controller.

[0111] In the above step 1, when connected to the grid, the inverter uses a constant power controller (PQ controller) to respond to the dispatch instruction and inject the specified power into the grid or absorb the specified power from the grid. When operating off the grid, the inverter uses a constant voltage frequency controller (U / f controller) to perform U / f control to provide a stable current for the load connected to the energy router. The two working modes of grid-connected operation and off-grid operation need to be able to switch smoothly, so that the energy router can work stably in both grid-connected and off-grid operation modes.

[0112] The control method of the current loop is shared by both grid-connected and off-grid operation modes. Figure 3 As shown. The constant voltage frequency controller used in off-grid operation is the same as the current loop in the constant power controller used in grid-connected operation. The two current loops are combined into one, and the two control methods share the same current loop. The current loop has a proportional integral controller. Due to the role of the proportional integral controller (PI) controller in the current loop, it can play a certain calculation buffer role and reduce the current impact caused by command switching.

[0113] In the above step 2, based on the fact that the voltage loop is always in the operation state and does not enter the saturation state, its control block diagram is as follows: Figure 4 As shown. When the system is connected to the grid, the first switch k1 and the fourth switch k4 are closed, and the second switch k2 and the third switch k3 are disconnected. At this time, the inverter transmits power to the grid under the control of the constant power controller. At the same time, the output of the constant power controller is used as a given instruction, and the output of the voltage loop is used as the input signal of the voltage loop after the difference is made. The output can be voltage or power, and it is output after the PI operation of the voltage loop. In this way, during the grid-connected operation, the voltage and frequency output on the AC side can be kept constant, and the AC load can continue to work. The voltage loop in control is always in an operating state and does not enter a saturation state, and the output of the voltage loop is consistent with the output of the constant power controller. In this way, when the system receives an off-grid operation instruction, the output of the voltage loop at the moment of switching is the same as the output of the constant power controller before switching, and there will be no jump in the instruction, and there will be no desaturation overshoot problem, which can ensure smooth transition switching of the system.

[0114] like Figure 4 As shown, during the switching process, when the first switch K1, the second switch K2, the third switch K3, and the fourth switch K4 change from receiving the control command signal of the constant voltage frequency controller to receiving the control command signal of the constant power controller when connected to the grid, to the moment when the first switch K1, the second switch K2, the third switch K3, and the fourth switch K4 are switched, the system of the present invention is in an off-grid operation state under the control of the constant power controller. During this period, since the system has only one current loop control, the output voltage will be uncontrolled, and the magnitude of the output voltage is determined by the three-phase load and the output current carried by the inverter. If during this period, the amplitude of the grid voltage is greatly different from the voltage determined by the load and the output current, a short-term voltage fluctuation will occur. One method to suppress this voltage fluctuation is to control the given instruction of the constant power controller to match the load power during the switching process.

[0115] During the operation of the energy router, the switching from grid-connected to off-grid can be divided into two categories. The first category is to participate in the dispatching of the power system and to disconnect from the power grid in a planned manner. This planned off-grid operation is a positive one that can enable various forms of new energy to participate in the dispatching and operation of the power system and optimize the power supply structure of the power grid. The other is that during the grid-connected operation, if there is a failure in the equipment or the power grid, it is necessary to separate the equipment from the power grid to ensure the safety of the equipment or personnel. This unplanned off-grid operation has a strong uncertainty and poses a great threat to the safe operation of the equipment or the power system. Therefore, this unplanned grid-connected to off-grid switching action requires the equipment to have a relatively strong protection capability. The present invention belongs to a planned grid-connected and off-grid operation with clear off-grid operation instructions.

[0116] like Figure 5 As shown: For planned grid-connected and off-grid operation, the inverter may have a switch S1 inside and a switch S2 outside. The inverter of the present invention uses a three-phase full-bridge inverter to connect the grid to the DC bus; when the energy router is operating in an off-grid state, the software control inside the inverter selects switch S1 to select the off-grid control module, and the hardware switch S2 outside the inverter is in an off-grid operation state, and the system is disconnected from the grid. When a grid-connected command signal is received, switch S1 is switched from the off-grid control module to the grid-connected control module, and switch S2 is switched from off-grid operation to grid-connected operation, connecting the energy router to the grid. In the most ideal state, switches S1 and S2 are switched at the same time, but in the actual state, the switching of switch S1 is a pure software operation process. Taking the commonly used DSP model TMS320F28335 as an example, the process can be completed in a few microseconds or even shorter; however, the switching of switch S2 involves the process from the issuance of software instructions to the completion of the action of the hardware switch. The action process of commonly used contactors is mostly in the order of tens of milliseconds, which lags far behind the action process of switch S1. Figure 6 Middle,U dc is the DC bus voltage, C is the capacitance, U ia , U ib , U ic is the output voltage of the three-phase half-bridge, i ia 、i ib 、i ic is the output current of the three-phase half-bridge, L1 is the filter inductor, C1 is the filter capacitor, R1, R L is a resistor, PCC is a switch, U oa , U ob , U oc is the voltage at the inverter bridge port after filtering by inductance and capacitance, i oa 、i ob 、i oc is the current after the inverter bridge voltage is filtered by the inductor and capacitor, E ga 、E gb 、E gc is the grid voltage, Z g is the grid impedance.

[0117] like Figure 6 As shown: The inverter with AC port is a key component for realizing the conversion of direct current to alternating current (AC / DC) of the energy router while ensuring the power quality, stability and interconnection with the grid. Its task is to ensure the coordinated interaction between the energy router and the external grid. Figure 7As shown, the output end of the inverter is connected to the DC load, the photovoltaic array, and the energy storage battery. The energy storage battery is used to store and release energy during the operation of the energy router. The photovoltaic array includes a photovoltaic unit, which is used to boost the low-voltage DC power generated by the photovoltaic unit to the voltage required by the energy router and control the power output of the photovoltaic unit.

[0118] Based on the above, a simulation test is carried out on the method of the present invention:

[0119] The DC bus voltage is maintained stable by energy storage batteries, and voltage and current dual closed-loop control is adopted; the photovoltaic array in the photovoltaic unit is controlled by Maximum Power Point Tracking (MPPT) technology, and the DC converter (DC / DC) in the energy router adopts voltage outer loop and current dual closed-loop control, which can output stable DC voltage for DC loads.

[0120] The time nodes are set as shown in Table 1. At the beginning of the simulation, the energy storage battery is started, the voltage of the energy storage battery is boosted, the system DC bus voltage is established to be 750V and maintained constant; at the same time, the inverter is started in the off-grid operation mode, the system carries a constant load of 4kW, and when it is 0.01s, the photovoltaic array control operation is started. The photovoltaic panels in the photovoltaic array use the photovoltaic cell model (SunPower) in the visual simulation tool (Simulink) library, model SPR-305E-WHT-D, the ambient temperature is set to 25℃, the light intensity is 1000W / m2, and the simulation runs as follows:

[0121] At 0.05s, the DC converter is started with load.

[0122] At 0.1s, the inverter is started and the DC load is loaded with 2kW.

[0123] At 0.15s, the environmental conditions were changed, the light intensity was reduced to 500W / m2, and the ambient temperature remained unchanged.

[0124] At 0.2s, the inverter switches from off-grid operation to grid-connected operation.

[0125] At 0.25s, the inverter power command increases to 7kW, and at 0.3s, the inverter power command is reduced to 4kW.

[0126] At 0.35s, the environmental conditions were changed again and the light intensity was restored to 1000W / m2.

[0127] At 0.4s, the inverter switches from grid-connected operation to off-grid operation.

[0128] The simulation ends at 0.5s.

[0129] Table 1 Energy router simulation time node settings

[0130]

[0131]

[0132] Simulation results, such as Figure 8 (a) Figure 8 (b) is the inverter output voltage and current waveform, Figure 8 (c) is the grid current waveform. Figure 8 (a) Figure 8 It can be seen from (b) and 8(c) that:

[0133] At t5=0.2s, the inverter switches from off-grid to grid-connected operation, and the output voltage and current of the inverter have no impact and distortion, achieving smooth switching.

[0134] At t6=0.25s, the inverter power command gradually increases to 7kW, and the inverter output current gradually and steadily rises. Figure 8 In (c), the grid-connected current also gradually increases, and the system transmits 3kW of power to the grid through the inverter.

[0135] At t7=0.3s, the inverter output power command gradually recovered to 4kW, and the output current and grid-connected current decreased steadily, indicating that the inverter worked stably during the power addition and subtraction process.

[0136] At t9=0.4s, the grid-connected operation is switched to off-grid operation, and the inverter output voltage and current have no impact and distortion, and smooth switching is also achieved. The whole process is smooth and stable, without current impact, which proves that the control method of the shared current loop and voltage loop adopted can achieve smooth switching of the AC side inverter of the energy router from grid-connected to off-grid operation, and ensure the stability of the voltage and current on the AC side.

[0137] like Fig. 9 Figure 5 is the system power and DC voltage waveform, where Figures (a) to (f) are the PV unit output power, energy storage unit power (charging is positive, discharging is negative), inverter output power when connected to the grid, DC load power, system 750V DC bus voltage and 220V DC load voltage, respectively.

[0138] from Fig. 9 The power balance state of the system can be clearly seen.

[0139] From system startup to t4=0.15s, the photovoltaic output power is 12kW, of which 4kW is provided to the AC load by the inverter output, and 7kW is used to charge the energy storage battery to store electrical energy.

[0140] At t4, due to the decrease in light intensity, the photovoltaic output power is reduced to 6kW, and the energy storage battery charging power is reduced to 2kW. Due to the sudden decrease in photovoltaic power, the input and output power of the system are unbalanced, the output power is greater than the input power, and the DC bus voltage drops. Subsequently, the system of the present invention is quickly adjusted to a normal value.

[0141] At t5=0.2s, the DC load interface converter is suddenly loaded with 2kW from no load, the input power of the energy storage battery is reduced to 0, and charging stops.

[0142] At t6=0.25s, the grid-connected inverter gradually increased its power output. At this time, the light intensity was still low, and the energy storage battery began to discharge with a discharge power of 3kW.

[0143] At t7=0.3s, the inverter output power gradually decreases, and the energy storage battery discharge power also gradually decreases and returns to 0 and stops discharging.

[0144] At t8 = 0.35s, the light intensity returns to the initial level, and the photovoltaic output power becomes 12kW. At this time, the inverter still carries 4kW AC load, the DC load is 2kW, and the energy storage battery is charged at 6kW. Due to the sudden change of the photovoltaic unit power, the system power is temporarily unbalanced, and the DC bus voltage rises in a small range but quickly returns to the normal value of 750V. In the entire power variation range, the system DC bus voltage remains relatively stable, and there is no particularly large range of changes, indicating that the power balance of the system of the present invention is relatively stable, and the 220V DC load voltage remains stable, which can provide a stable DC voltage and power to the DC load to ensure the normal operation of the load.

[0145] The present invention mainly studies the smooth switching control of the energy router on and off the AC side to achieve a smooth transition between the two working states. The control method can enable the energy router to work stably in both the on-grid and off-grid operating modes, and the two operating modes need to be able to switch smoothly. Ensure that the load power supply is normal and stable during the switching process between the on-grid and off-grid operating states, and reduce the voltage and current impact on the power grid and local equipment.

[0146] What those skilled in the art should know is that: as a distribution point for energy and information, energy routers can conveniently collect and analyze electric energy data. With the trend of vigorously developing smart grids, massive data will provide model guarantees for electric energy dispatching and intelligent grids. However, the development of energy routers is not yet very mature. As energy and information distribution nodes, the stable operation of energy routers themselves is related to the stable operation of the entire energy Internet. How to cooperate with traditional power grids is a hot topic of research. Therefore, it is imperative to study the stable operation of energy routers themselves and provide favorable technical support for the construction of energy Internet.

[0147] Embodiment 4:

[0148] like Fig.10 As shown, the present invention also provides an electronic device, which may be a computer device, a single-chip device, an intelligent mobile device, etc. The electronic device in this embodiment may include a processor, a memory, a transceiver component, etc. The memory, the processor, and the transceiver component are connected via a bus; the memory may be used to store an execution program, and an exemplary execution program may include instructions; the processor is used to execute the instructions stored in the memory. The memory may also be used to store data, which may be called and / or modified when the instructions are executed.

[0149] The processor may be a central processing unit (CPU), or other general-purpose processors, digital signal processors (DSP), application-specific integrated circuits (ASIC), field-programmable gate arrays (FPGA) or other programmable logic devices, discrete gates or transistor logic devices, discrete hardware components, etc. It is the computing core and control core of the terminal, which is suitable for implementing one or more instructions, and is specifically suitable for loading and executing one or more instructions in a storage medium to implement the corresponding method flow or corresponding function, so as to implement the steps of a method for smooth on-grid and off-grid switching control of an energy router AC side in the above embodiment.

[0150] Embodiment 5:

[0151] Based on the same inventive concept, the present invention also provides a readable storage medium, specifically an electronic device readable storage medium (Memory), which is a memory device in an electronic device for storing programs and data. It is understandable that the storage medium here may include both a built-in storage medium in an electronic device and an extended storage medium supported by the electronic device. The storage medium provides a storage space, which stores the operating system of the terminal. In addition, one or more instructions suitable for being loaded and executed by a processor are also stored in the storage space, and these instructions may be one or more execution programs (including program codes). It should be noted that the storage medium here may be a high-speed RAM memory or a non-volatile memory, such as at least one disk memory. The processor loads and executes one or more instructions stored in the storage medium, which can implement the steps of a method for smoothly switching between the AC side and off-grid of an energy router in the above embodiment.

[0152] Those skilled in the art will appreciate that the embodiments of the present invention application can be provided as methods, systems, or computer program products. Therefore, the present invention application can adopt the form of a complete hardware embodiment, a complete software embodiment, or an embodiment in combination with software and hardware. Moreover, the present invention application can adopt the form of a computer program product implemented on one or more computer-usable storage media (including but not limited to disk storage, CD-ROM, optical storage, etc.) that contain computer-usable program code.

[0153] The present invention application is described with reference to the flowcharts and / or block diagrams of the methods, devices (systems), and computer program products according to the embodiments of the present invention application. It should be understood that each process and / or block in the flowchart and / or block diagram, as well as the combination of the processes and / or blocks in the flowchart and / or block diagram, can be implemented by computer program instructions. These computer program instructions can be provided to a processor of a general-purpose computer, a special-purpose computer, an embedded processor, or other programmable data processing device to generate a machine, so that the instructions executed by the processor of the computer or other programmable data processing device generate instructions for implementing the processes in the flowchart and / or block diagram. Figure 1 A process or multiple processes and / or boxes Figure 1 A device that provides the functions specified in a block or multiple blocks.

[0154] These computer program instructions may also be stored in a computer-readable memory capable of directing a computer or other programmable data processing device to operate in a specific manner, so that the instructions stored in the computer-readable memory produce an article of manufacture comprising an instruction device, which implements the process Figure 1 A process or multiple processes and / or boxes Figure 1 A function specified in one or more boxes.

[0155] These computer program instructions can also be loaded onto a computer or other programmable data processing device so that a series of operating steps are executed on the computer or other programmable device to produce a computer-implemented process, thereby providing instructions for implementing the process. Figure 1 A process or multiple processes and / or boxes Figure 1 A step that specifies a function in one or more boxes.

[0156] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention application rather than to limit its protection scope. Although the present invention application is described in detail with reference to the above embodiments, ordinary technicians in the relevant field should understand that after reading the present invention application, those skilled in the art can still make various changes, modifications or equivalent substitutions to the specific implementation methods of the application, but these changes, modifications or equivalent substitutions are all within the protection scope of the claims to be approved.

Claims

1. A method for controlling smooth switching of an energy router on and off the AC side, characterized in that: The method comprises: Based on the received energy router operation status switching instruction, the inverter controls the selection of the off-grid control module or the grid-connected control module to achieve the switching between grid-connected and off-grid; Control the voltage loop to always be in an operating state and not enter a saturation state, and control the output power of the grid-connected control module to be the same as the output power of the voltage loop, so that the energy router can smoothly transition to switch the operating state when switching between grid-connected and grid-off; Among them, the output end of the off-grid control module and the output end of the grid-connected control module are connected to the input end of the inverter in the form of a common current loop, the output end of the inverter is connected to the AC side of the energy router, the AC side of the energy router is connected to the power grid, the output end of the off-grid control module is forwardly connected to the voltage loop between the current loop, and the output end of the voltage loop is connected in series with the output end of the grid-connected control module and then connected to the input end of the voltage loop.

2. The method according to claim 1, characterized in that The control voltage loop is always in an operation state and does not enter a saturation state, and the output power of the grid-connected control module is controlled to be the same as the output power of the voltage loop, including: The output power of the grid-connected control module is controlled as a given instruction, and the difference between the given instruction and the output power of the voltage loop is used as the input signal of the voltage loop. The input signal is output after being subjected to proportional-integral operation by the voltage loop, so that the voltage loop is always in an operation state and does not enter a saturation state; Based on the fact that the voltage loop is always in an operation state and does not enter a saturation state, the output power of the grid-connected control module is controlled to be consistent with the output power of the voltage loop.

3. The method according to claim 1, characterized in that A first switch is connected between the grid-connected control module and the current loop, and a second switch is connected between the voltage loop and the current loop; A third switch is connected between the off-grid control module and the voltage loop; After the connection point between the output of the voltage loop and the second switch and the connection point between the first switch and the current loop are connected, a fourth switch is connected to the input end of the voltage loop.

4. The method according to claim 3, characterized in that The inverter controls the selection of the off-grid control module or the grid-connected control module based on the received energy router operation state switching instruction to implement the grid-connected and off-grid switching, including: If the energy router operation state switching instruction is a grid-connected operation instruction, the inverter controls the first switch and the fourth switch to be closed, and the second switch and the third switch to be opened, so as to select the grid-connected control module; or If the energy router operation state switching instruction is an off-grid operation instruction, the inverter controls the first switch and the fourth switch to be opened, and the second switch and the third switch to be closed, so as to select the off-grid control module and realize off-grid switching.

5. The method according to claim 1, characterized in that A current decoupling controller and a pulse width modulation controller are connected in sequence between the current loop and the input end of the inverter; Before the inverter controls the selection of the off-grid control module or the grid-connected control module based on the received energy router operation state switching instruction to implement the grid-connected and off-grid switching, the method further includes: The two-phase electrical signal of the current loop is converted into a three-phase electrical control signal by using the current decoupling controller, and the three-phase electrical control signal is used as a modulation wave to compare with a fixed carrier wave; When the modulated wave is higher than the carrier wave, the pulse width modulation controller outputs a high level, and the high level is used as an input signal of the inverter to drive the inverter to operate; When the modulation wave is lower than the carrier wave, the pulse width modulation controller outputs a low level, and the low level is used as an input signal of the inverter to drive the inverter to operate.

6. The method according to claim 1, characterized in that The energy router includes an AC converter and a plurality of DC converters, wherein the output end of the AC converter is connected to the input end of each DC converter; the input end of the AC converter is connected to the output end of the inverter; The output ends of the multiple DC converters are respectively connected to the DC load, the photovoltaic array, and the energy storage battery.

7. The method according to any one of claims 1 to 4, characterized in that: The off-grid control module is a constant voltage and frequency controller, and the grid-connected control module is a constant power controller.

8. An energy router AC side on-grid and off-grid smooth switching control system, characterized by: Including energy router, inverter, current loop, voltage loop, grid-connected control module, off-grid control module, control module; The inverter is used to control the selection of the off-grid control module or the grid-connected control module based on the received operation state switching instruction of the energy router to realize the switching between grid connection and off-grid; The control module is used to control the voltage loop to always be in an operating state and not enter a saturated state, and to control the output power of the grid-connected control module to be the same as the output power of the voltage loop, so that the energy router can smoothly transition to switch the operating state when switching between grid-connected and off-grid; The output end of the off-grid control module and the output end of the grid-connected control module are connected to the input end of the inverter in a manner of sharing the current loop. The output end of the inverter is connected to the AC side of the energy router, and the AC side of the energy router is connected to the power grid. The voltage loop is forwardly connected between the output end of the off-grid control module and the current loop, and the output end of the voltage loop is connected in series with the output end of the grid-connected control module and then connected to the input end of the voltage loop.

9. An electronic device, characterized in that: include: at least one processor and memory; The memory and the processor are connected via a bus; The memory is used to store one or more programs; When the one or more programs are executed by the at least one processor, the energy router AC side on-grid and off-grid smooth switching control method is implemented.

10. A readable storage medium, characterized in that: An execution program is stored thereon, and when the execution program is executed, the energy router AC side on-grid and off-grid smooth switching control method is implemented.

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