DC bus voltage signal-based optical storage DC micro-grid converter cooperative control system

Abstract

The invention discloses an optical storage DC micro-grid converter cooperative control system based on a DC bus voltage signal, and belongs to the technical field of power system safety, and the system comprises a photovoltaic converter and an energy storage converter. The photovoltaic converter obtains a first duty ratio according to an input voltage, an input current, an output voltage, an output current and a DC bus voltage high-voltage threshold value, and switches to a maximum power point tracking mode or a high DC bus voltage regulation mode according to the first duty ratio; and the energy storage converter obtains a second duty ratio according to the input voltage, the input current, the output voltage, the output current and the direct-current bus voltage low-voltage threshold value, and switches to a constant-voltage charging mode, a constant-current charging mode or a low-direct-current bus voltage adjusting mode according to the second duty ratio. According to the system, buffeting and deadlock problems of multi-mode switching can be improved, and multi-mode smooth switching is realized.

Description

Technical Field

[0001] The present invention belongs to the technical field of power system safety, and in particular relates to a photovoltaic energy storage DC microgrid converter collaborative control system based on a DC bus voltage signal. Background Art

[0002] In a photovoltaic-storage DC microgrid, energy storage and photovoltaics are the main energy sources, and their performance depends largely on the power management strategy. Although energy storage batteries have a certain DC bus voltage regulation capability, their regulation capability is very limited due to the limitations of the state of charge and the charge / discharge power. In order to better utilize photovoltaic energy, the need for photovoltaic converters to coordinate with the DC bus voltage regulation is becoming increasingly prominent.

[0003] In a photovoltaic-storage DC microgrid based on communication interconnection, the reference power and mode management of each converter are scheduled through communication. A stable and low-latency communication strategy is the key to the stable operation of the system, which not only increases the system cost but also reduces the system reliability.

[0004] The photovoltaic-storage-DC microgrid converter cooperative control strategy based on the DC bus voltage signal adjusts the operation mode of the energy storage converter and the photovoltaic converter by detecting the DC bus voltage signal. It is a photovoltaic-storage-DC microgrid converter cooperative control strategy that does not rely on communication. However, the existing photovoltaic-storage-DC microgrid converter cooperative control strategy based on the DC bus voltage signal has jitter and deadlock problems in multi-mode switching during application. Summary of the invention

[0005] The object of the present invention is to provide a photovoltaic-storage DC microgrid converter collaborative control system based on a DC bus voltage signal, which can improve the jitter and deadlock problems of multi-mode switching and achieve multi-mode smooth switching.

[0006] In order to achieve the above object, the present invention provides the following technical solutions: In a first aspect, the present invention provides a photovoltaic-storage DC microgrid converter coordinated control system based on a DC bus voltage signal, comprising a photovoltaic converter and an energy storage converter; The photovoltaic converter obtains the maximum power point current limit value of the photovoltaic array according to its input voltage and input current, obtains the first control signal according to its output voltage and output current and the DC bus voltage high voltage threshold, obtains the given value of its input current according to the first control signal and the maximum power point current limit value of the photovoltaic array, obtains the second control signal according to its input current and the given value of the input current, obtains the first duty cycle according to the second control signal, and switches to the maximum power point tracking mode or the high DC bus voltage regulation mode according to the first duty cycle; The energy storage converter obtains a third control signal according to its input voltage and the energy storage reference voltage, obtains a maximum energy storage charging current limit value according to the third control signal and the energy storage constant current charging current setting value, obtains a fourth control signal according to its output voltage and output current and the DC bus voltage low voltage threshold, obtains a given value of its input current according to the fourth control signal and the maximum energy storage charging current limit value, obtains a fifth control signal according to its input current and the given value of the input current, obtains a second duty cycle according to the fifth control signal, and switches to a constant voltage charging mode, a constant current charging mode or a low DC bus voltage regulation mode according to the second duty cycle.

[0007] In combination with the first aspect, further, the photovoltaic converter includes: The maximum power point tracking solar controller is used to obtain the maximum power point current limit value of the photovoltaic array according to the input voltage and input current of the photovoltaic converter; A first proportional-integral controller, used for obtaining a first control signal according to an output voltage and an output current of the photovoltaic converter and a high-voltage threshold of a DC bus voltage; A first variable limiter, used to obtain a given value of the input current of the photovoltaic converter according to the first control signal and the current limit value of the maximum power point of the photovoltaic array; A second proportional-integral controller, used for obtaining a second control signal according to an input current of the photovoltaic converter and a given value of the input current; A first pulse width modulator, configured to obtain a first duty cycle according to a second control signal; The energy storage converter includes: A third proportional-integral controller, used for obtaining a third control signal according to the input voltage of the energy storage converter and the energy storage reference voltage; A second variable limiter, used to obtain a maximum energy storage charging current limit value according to a third control signal and an energy storage constant current charging current setting value; A fourth proportional-integral controller, used for obtaining a fourth control signal according to the output voltage and output current of the energy storage converter and the DC bus voltage low voltage threshold; A third variable limiter, used to obtain a given value of the input current of the energy storage converter according to the fourth control signal and the maximum charging current limit value of the energy storage; a fifth proportional-integral controller, used for obtaining a fifth control signal according to an input current of the energy storage converter and a given value of the input current; The second pulse width modulator is used to obtain a second duty cycle according to a fifth control signal.

[0008] In combination with the first aspect, further, when the DC bus voltage is greater than the first reference value of the DC bus voltage and less than or equal to the DC bus voltage high voltage threshold, the first proportional integral controller is in an activated state, the photovoltaic converter is switched to a high DC bus voltage regulation mode, the third proportional integral controller is in an activated state and the fourth proportional integral controller is in a saturated state, and the energy storage converter is switched to a constant voltage charging mode; When the DC bus voltage is greater than the second reference value of the DC bus voltage and less than or equal to the first reference value of the DC bus voltage, the first proportional-integral controller is in a saturated state, and the photovoltaic converter switches to the maximum power point tracking mode. If the energy storage capacity is greater than a preset threshold, the third proportional-integral controller is in an activated state and the fourth proportional-integral controller is in a saturated state, and the energy storage converter switches to a constant voltage charging mode. Otherwise, the third proportional-integral controller is in a saturated state and the fourth proportional-integral controller is in a saturated state, and the energy storage converter switches to a constant current charging mode. When the DC bus voltage is greater than or equal to the DC bus voltage low voltage threshold and less than or equal to the DC bus voltage second reference value, the first proportional integral controller is in a saturated state, the photovoltaic converter switches to a maximum power point tracking mode, the third proportional integral controller is in a saturated state and the fourth proportional integral controller is in an activated state, and the energy storage converter switches to a low DC bus voltage regulation mode; When the DC bus voltage is greater than the DC bus voltage high voltage threshold or less than the DC bus voltage low voltage threshold, all converters stop running.

[0009] In combination with the first aspect, further, when the first proportional integral controller is in an activated state, the first variable limiter is in an unactivated state, and a given value of the input current of the photovoltaic converter is a first control signal; When the first proportional-integral controller is in a saturated state, the first variable limiter is in a start-up state, and the given value of the input current of the photovoltaic converter is the current limit value of the maximum power point of the photovoltaic array.

[0010] In combination with the first aspect, further, when the third proportional-integral controller is in an activated state and the fourth proportional-integral controller is in a saturated state, the second variable limiter is in an unactivated state and the third variable limiter is in an activated state, the maximum charging current limit value of the energy storage is the third control signal, and the given value of the input current of the energy storage converter is the maximum charging current limit value of the energy storage; When the third proportional-integral controller is in a saturated state and the fourth proportional-integral controller is in a saturated state, the second variable limiter is in an activated state and the third variable limiter is in an activated state, the maximum charging current limit value of the energy storage is the energy storage constant current charging current setting value, and the given value of the input current of the energy storage converter is the maximum charging current limit value of the energy storage; When the third proportional-integral controller is in a saturated state and the fourth proportional-integral controller is in an activated state, the second variable limiter is in a started state and the third variable limiter is in a non-started state, the energy storage maximum charging current limit value is the energy storage constant current charging current setting value, and the given value of the input current of the energy storage converter is the fourth control signal.

[0011] In combination with the first aspect, further, the high voltage threshold of the DC bus voltage is 104% of the rated value of the DC bus voltage, the low voltage threshold of the DC bus voltage is 96% of the rated value of the DC bus voltage, the first reference value of the DC bus voltage is 102% of the rated value of the DC bus voltage, and the second reference value of the DC bus voltage is 98% of the rated value of the DC bus voltage.

[0012] In combination with the first aspect, further, the bandwidth of the first proportional integral controller is greater than the bandwidth of the maximum power point tracking solar controller.

[0013] In a second aspect, the present invention provides a photovoltaic converter, comprising: The maximum power point tracking solar controller is used to obtain the maximum power point current limit value of the photovoltaic array according to the input voltage and input current of the photovoltaic converter; A first proportional-integral controller, used for obtaining a first control signal according to an output voltage and an output current of the photovoltaic converter and a high-voltage threshold of a DC bus voltage; A first variable limiter, used to obtain a given value of the input current of the photovoltaic converter according to the first control signal and the current limit value of the maximum power point of the photovoltaic array; A second proportional-integral controller, used for obtaining a second control signal according to an input current of the photovoltaic converter and a given value of the input current; A first pulse width modulator, configured to obtain a first duty cycle according to a second control signal; The photovoltaic converter is switched to a maximum power point tracking mode or a high DC bus voltage regulation mode according to the first duty cycle.

[0014] In a third aspect, the present invention provides an energy storage converter, comprising: A third proportional-integral controller, used for obtaining a third control signal according to the input voltage of the energy storage converter and the energy storage reference voltage; A second variable limiter, used to obtain a maximum energy storage charging current limit value according to a third control signal and an energy storage constant current charging current setting value; A fourth proportional-integral controller, used for obtaining a fourth control signal according to the output voltage and output current of the energy storage converter and the DC bus voltage low voltage threshold; A third variable limiter, used to obtain a given value of the input current of the energy storage converter according to the fourth control signal and the maximum charging current limit value of the energy storage; a fifth proportional-integral controller, used for obtaining a fifth control signal according to an input current of the energy storage converter and a given value of the input current; a second pulse width modulator, configured to obtain a second duty cycle according to a fifth control signal; The energy storage converter switches to a constant voltage charging mode, a constant current charging mode or a low DC bus voltage regulation mode according to the second duty cycle.

[0015] In a fourth aspect, the present invention provides a method for coordinated control of a photovoltaic-storage DC microgrid converter based on a DC bus voltage signal, comprising: According to the input voltage and input current of the photovoltaic converter, the maximum power point current limit value of the photovoltaic array is obtained; Acquire a first control signal according to the output voltage and output current of the photovoltaic converter and the high voltage threshold of the DC bus voltage; Obtaining a given value of the input current of the photovoltaic converter according to the first control signal and the maximum power point current limit value of the photovoltaic array; Acquire a second control signal according to an input current of the photovoltaic converter and a given value of the input current; Acquire a first duty cycle according to the second control signal; According to the first duty cycle, controlling the photovoltaic converter to switch to a maximum power point tracking mode or a high DC bus voltage regulation mode; Obtaining a third control signal according to an input voltage of the energy storage converter and an energy storage reference voltage; Obtaining a maximum energy storage charging current limit value according to the third control signal and the energy storage constant current charging current setting value; Obtaining a fourth control signal according to the output voltage and output current of the energy storage converter and the DC bus voltage low voltage threshold; Obtaining a given value of the input current of the energy storage converter according to the fourth control signal and the maximum charging current limit value of the energy storage; Acquire a fifth control signal according to an input current of the energy storage converter and a given value of the input current; acquiring a second duty cycle according to a fifth control signal; According to the second duty cycle, the energy storage converter is controlled to switch to a constant voltage charging mode, a constant current charging mode or a low DC bus voltage regulation mode.

[0016] Compared with the prior art, the present invention has the following beneficial effects: The present invention provides a photovoltaic-energy storage DC microgrid converter collaborative control system based on a DC bus voltage signal, in which the photovoltaic converter can switch to a maximum power point tracking mode or a high DC bus voltage regulation mode according to a DC bus voltage high voltage threshold, and the energy storage converter can switch to a constant voltage charging mode, a constant current charging mode or a low DC bus voltage regulation mode according to a DC bus voltage low voltage threshold.

[0017] The photovoltaic-storage-DC microgrid converter collaborative control system based on a DC bus voltage signal provided by the present invention controls the photovoltaic converter to switch to a maximum power point tracking mode or a high DC bus voltage regulation mode through a first variable limiter based on the DC bus voltage signal, controls the energy storage converter to switch to a low DC bus voltage regulation mode or a constant voltage / constant current charging mode through a third variable limiter, and controls the energy storage converter to switch to a constant voltage charging mode or a constant current charging mode through a second variable limiter. Under the premise of not relying on communication, different operating modes are unified in the same control loop, which can avoid switching of the control loop during mode switching, improve mode switching performance, improve oscillation and overshoot of the DC bus voltage during mode switching, and achieve multi-mode smooth switching.

[0018] The photovoltaic-storage DC microgrid converter collaborative control system based on the DC bus voltage signal provided by the present invention sets the bandwidth of the first proportional-integral controller to be greater than the bandwidth of the maximum power point tracking solar controller. When the power fluctuates, the first proportional-integral controller responds first. BRIEF DESCRIPTION OF THE DRAWINGS

[0019] Figure 1 It is a structural schematic diagram of a photovoltaic-storage DC microgrid converter cooperative control system based on a DC bus voltage signal provided in an embodiment of the present application; Figure 2 It is a schematic diagram of a photovoltaic-storage DC microgrid operation mode based on a DC bus voltage signal provided by an embodiment of the present invention; Figure 3 It is a schematic diagram of the variable amplitude limiting coordinated control of the photovoltaic converter provided by an embodiment of the present invention; Figure 4 It is a schematic diagram of variable amplitude limiting coordinated control of energy storage converter provided by an embodiment of the present invention; Figure 5 It is a schematic diagram of a high DC bus voltage regulation mode of a photovoltaic converter provided by an embodiment of the present invention; Figure 6 is a schematic diagram of a maximum power point tracking mode of a photovoltaic converter provided by an embodiment of the present invention; Figure 7 Schematic diagram of a constant voltage charging mode of an energy storage converter provided by an embodiment of the present invention; Figure 8 Schematic diagram of a constant current charging mode of an energy storage converter provided by an embodiment of the present invention; Fig. 9 It is a schematic diagram of a low DC bus voltage regulation mode of an energy storage converter provided in an embodiment of the present invention. DETAILED DESCRIPTION

[0020] The technical solution of the present application is further described in detail below in conjunction with specific implementation methods.

[0021] The embodiments of the present application are described in detail below, and examples of the embodiments are shown in the accompanying drawings, wherein the same or similar reference numerals throughout represent the same or similar elements or elements with the same or similar functions. The embodiments described below with reference to the accompanying drawings are exemplary and are only used to explain the present application, and should not be construed as limitations on the present application. In the absence of conflict, the embodiments of the present application and the technical features in the embodiments may be combined with each other.

[0022] The present application embodiment provides a photovoltaic storage DC microgrid converter coordinated control system based on a DC bus voltage signal, such as Figure 1 As shown, it includes a photovoltaic converter, an energy storage converter, a grid-side converter and a load converter connected to a direct current bus (DC Bus).

[0023] In this embodiment, the photovoltaic converter, energy storage converter, grid-side converter and load converter are all connected to the DC bus to form a common bus structure. If the grid-side converter is connected to the photovoltaic-storage DC microgrid, the photovoltaic-storage DC microgrid is in grid-connected mode, and the DC bus voltage is determined by the grid-side converter; if the grid-side converter is not connected to the photovoltaic-storage DC microgrid, the photovoltaic-storage DC microgrid is in island mode. By coordinating the operation modes of the photovoltaic converter and the energy storage converter, the purpose of maintaining the stability of the photovoltaic-storage DC microgrid is achieved.

[0024] In this embodiment, the DC bus voltage is used as an information carrier to identify the operation mode of the photovoltaic and energy storage DC microgrid. Figure 2 As shown, is the rated value of DC bus voltage, is the DC bus voltage high voltage threshold, is the DC bus voltage low voltage threshold. According to the different DC bus voltages and power flows in the photovoltaic storage DC microgrid, the photovoltaic storage DC microgrid is divided into five operating modes: Mode I is the off-grid energy storage discharge mode; Mode II is the off-grid energy storage charging mode; Mode III is the off-grid photovoltaic constant voltage mode; Mode IV is the grid-connected inverter mode; Mode V is the grid-connected rectification mode. Modes I and II stabilize the DC bus voltage through energy storage droop, Mode III stabilizes the DC bus voltage through photovoltaic droop, and Mode IV and Mode V stabilize the DC bus voltage through the grid-side converter. For DC power supply systems below 1.5kV, the voltage deviation range is -20%~+5% of the rated value of the DC bus voltage.

[0025] In this embodiment, Figure 1 As shown, the photovoltaic converter is provided with: Maximum power point tracking solar controller MPPT is used to adjust the input voltage of the photovoltaic converter and input current , obtain the maximum power point current limit value of the photovoltaic array ; The first proportional integral controller PI 1 , used to adjust the output voltage of the photovoltaic converter and output current And the DC bus voltage high voltage threshold , obtain the first control signal ; The first variable limiter is used to adjust the amplitude according to the first control signal And the maximum power point current limit of the photovoltaic array , get the given value of the input current of the photovoltaic converter ; The second proportional integral controller PI 2 , used to adjust the input current of the photovoltaic converter And the given value of input current , obtain the second control signal ; The first pulse width modulator PWM 1 , for use according to the second control signal , get the first duty cycle ; The photovoltaic converter is configured according to a first duty cycle Switch to maximum power point tracking mode or high DC bus voltage regulation mode.

[0026] Specifically, Figure 3 As shown, the maximum power point current limit value of the photovoltaic array As the upper limit value of the first variable limiter. Affected by environmental factors such as light and temperature, the upper limit value of the first variable limiter is not fixed, but is dynamically adjusted as environmental conditions change.

[0027] In this embodiment, the first variable limiter is used to control the smooth switching of the operation mode of the photovoltaic converter, and the internal control loop of the photovoltaic converter remains unchanged, which can effectively avoid the sudden change of the duty cycle during the traditional mode switching.

[0028] In this embodiment, Figure 1 As shown, the energy storage converter is provided with: The third proportional integral controller PI 3 , used to adjust the input voltage of the energy storage converter And energy storage reference voltage , obtain the third control signal ; The second variable limiter is used to adjust the amplitude according to the third control signal And the energy storage constant current charging current setting value , obtain the maximum charging current limit value of energy storage ; Fourth proportional integral controller PI 4 , used to adjust the output voltage of the energy storage converter and output current And the DC bus voltage low voltage threshold , obtain the fourth control signal ; The third variable limiter is used to adjust the amplitude according to the fourth control signal And the maximum charging current limit of energy storage , get the given value of the input current of the energy storage converter ; Fifth proportional integral controller PI 5 , used to adjust the input current of the energy storage converter And the given value of input current , obtain the fifth control signal ; The second pulse width modulator PWM 2 , for use according to the fifth control signal , get the second duty cycle ; The energy storage converter is configured according to the second duty cycle Switch to constant voltage charging mode, constant current charging mode or low DC bus voltage regulation mode.

[0029] Specifically, Figure 4 As shown, the energy storage constant current charging current setting value As the lower limit of the second variable limiter, the maximum charging current limit value of the energy storage As the lower limit value of the third variable limiter. In practical applications, Specific settings can be made according to energy storage charging needs.

[0030] In this embodiment, the second variable limiter and the third variable limiter control the smooth switching of the operation mode of the energy storage converter, and the internal control loop of the energy storage converter remains unchanged, which can effectively avoid the sudden change of the duty cycle during the traditional mode switching.

[0031] Based on the DC bus voltage stratification rule, , , and take the first reference value of DC bus voltage as The second reference value of DC bus voltage is ,set up is the DC bus voltage.

[0032] (1) When When the photovoltaic storage DC microgrid is in an overvoltage state, all converters stop running.

[0033] (2) When When Figure 2 In the middle mode III, the DC bus voltage is greater than the rated value of the DC bus voltage, indicating that the grid-side converter is not connected to the photovoltaic storage DC microgrid, and the photovoltaic storage DC microgrid is in the island mode. It also indicates that the power generated by the system is greater than the power required by the load, and the energy storage capacity is greater than the preset threshold, and the excess energy cannot be absorbed. At this time, the first proportional integral controller is in an active state, the photovoltaic converter switches to the high DC bus voltage regulation mode, the third proportional integral controller is in an active state and the fourth proportional integral controller is in a saturated state, and the energy storage converter switches to the constant voltage charging mode.

[0034] Specifically, Figure 5 As shown, when the first proportional integral controller is in an activated state, the first variable limiter is in an unactivated state, and the given value of the input current of the photovoltaic converter is the first control signal, that is, At this time, based on Get the first duty cycle The feedback is fed back to the gate of the MOS tube in the photovoltaic converter, so that the photovoltaic converter switches to a high DC bus voltage regulation mode.

[0035] like Figure 7 As shown, when the third proportional-integral controller is in an activated state and the fourth proportional-integral controller is in a saturated state, the second variable limiter is in an unactivated state and the third variable limiter is in an activated state, the maximum charging current limit value of the energy storage is the third control signal, that is, , the given value of the input current of the energy storage converter is the maximum charging current limit value of the energy storage, that is, At this time, based on Get the second duty cycle The feedback is fed back to the gate of the MOS tube in the energy storage converter, so that the energy storage converter switches to a constant voltage charging mode.

[0036] (3) When When Figure 2 In mode IV and mode V, the DC bus voltage is stable near the rated value of the DC bus voltage, indicating that the grid-side converter is connected to the photovoltaic storage DC microgrid, and the photovoltaic storage DC microgrid is in the grid-connected mode. At this time, the first proportional integral controller is in a saturated state, and the photovoltaic converter switches to the maximum power point tracking mode. If the energy storage capacity is greater than the preset threshold, the third proportional integral controller is in an activated state and the fourth proportional integral controller is in a saturated state, and the energy storage converter switches to a constant voltage charging mode. Otherwise, the third proportional integral controller is in a saturated state and the fourth proportional integral controller is in a saturated state, and the energy storage converter switches to a constant current charging mode.

[0037] Specifically, Figure 6As shown, when the first proportional integral controller is in a saturated state, the first variable limiter is in a start-up state, and the given value of the input current of the photovoltaic converter is the maximum power point current limit value of the photovoltaic array, that is, At this time, based on Get the first duty cycle The feedback is fed back to the gate of the MOS tube in the photovoltaic converter, so that the photovoltaic converter switches to the maximum power point tracking mode.

[0038] like Figure 8 As shown, when the third proportional-integral controller is in a saturated state and the fourth proportional-integral controller is in a saturated state, the second variable limiter is in an activated state and the third variable limiter is in an activated state, the maximum charging current limit value of the energy storage is the energy storage constant current charging current setting value, that is , the given value of the input current of the energy storage converter is the maximum charging current limit value of the energy storage, that is, At this time, based on Get the second duty cycle The feedback is fed back to the gate of the MOS tube in the energy storage converter, so that the energy storage converter switches to a constant current charging mode.

[0039] (4) When When Figure 2 In Mode I and Mode II, the DC bus voltage is less than the rated value of the DC bus voltage, indicating that the grid-side converter is not connected to the photovoltaic storage DC microgrid, and the photovoltaic storage DC microgrid is in island mode. It also indicates that the power emitted by the system is less than the power required by the load, and the photovoltaic needs to output the maximum power. At this time, the first proportional integral controller is in a saturated state, the photovoltaic converter switches to the maximum power point tracking mode, the third proportional integral controller is in a saturated state and the fourth proportional integral controller is in an activated state, and the energy storage converter switches to the low DC bus voltage regulation mode.

[0040] Specifically, Fig. 9 As shown, when the third proportional-integral controller is in a saturated state and the fourth proportional-integral controller is in an activated state, the second variable limiter is in an activated state and the third variable limiter is in an unactivated state, the maximum charging current limit value of the energy storage is the energy storage constant current charging current setting value, that is , the given value of the input current of the energy storage converter is the fourth control signal, that is, At this time, based on Get the second duty cycle The feedback is fed back to the gate of the MOS tube in the energy storage converter, so that the energy storage converter switches to a low DC bus voltage regulation mode.

[0041] (5) When When , the photovoltaic storage DC microgrid is in an overload state, and all converters stop running.

[0042] The photovoltaic-energy-storage DC microgrid converter collaborative control system based on the DC bus voltage signal provided in this embodiment keeps the internal control loops unchanged for the photovoltaic converter and the energy storage converter when the operating mode is switched, which can improve the stability of the system during mode switching and achieve smooth switching of multiple modes.

[0043] In a possible embodiment, the bandwidth of the first proportional-integral controller is greater than the bandwidth of the maximum power point tracking solar controller. Therefore, when power fluctuates, the first proportional-integral controller responds first.

[0044] In one possible embodiment, Figure 1 As shown, the photovoltaic converter includes a photovoltaic and a first MOS tube , and the first capacitor , the second capacitor , the first resistor , First Inductor and diode , Connected to both ends of the photovoltaic , Sequentially in series One end and Between the drain electrodes, One end through connect The drain, The other end of the connection The output current of the photovoltaic converter Through the first sampling resistor Input the first proportional integral controller PI 1 The first pulse width modulator PWM 1 Output connection of the gate. Figure 1 middle, represents the photovoltaic current, represents the input impedance of the photovoltaic converter, Represents the input impedance of the grid-side converter.

[0045] In one possible embodiment, Figure 1 As shown, the energy storage converter includes energy storage, a second MOS tube And the third MOS tube , and the third capacitor , the fourth capacitor , the second resistor and the second inductor , Connected to both ends of the energy storage, , Sequentially in series One end and Between the drain electrodes, One end of the connection The drain, The other end of the connection The source of The source connection The output current of the energy storage converter Through the second sampling resistor Input the fourth proportional integral controller PI 4 The second pulse width modulator PWM 2 Output connection The gate of the of the gate. Figure 1 middle, represents the energy storage current, represents the input impedance of the energy storage converter, Represents the input impedance of the load transformer.

[0046] An embodiment of the present application provides a method for collaboratively controlling a photovoltaic-energy-storage DC microgrid converter based on a DC bus voltage signal, wherein the converter includes a photovoltaic converter, an energy storage converter, a grid-side converter, and a load converter connected to the DC bus.

[0047] The method for coordinated control of a photovoltaic-storage DC microgrid converter based on a DC bus voltage signal provided in this embodiment specifically includes the following steps: Step 1.1: According to the input voltage and input current of the photovoltaic converter, use the maximum power point tracking solar controller to obtain the maximum power point current limit value of the photovoltaic array; Step 1.2: Obtain a first control signal using a first proportional-integral controller according to the output voltage and output current of the photovoltaic converter and the high voltage threshold of the DC bus voltage; Step 1.3: according to the first control signal and the current limit value of the maximum power point of the photovoltaic array, using the first variable limiter, obtain a given value of the input current of the photovoltaic converter; Step 1.4: obtaining a second control signal by using a second proportional-integral controller according to an input current of the photovoltaic converter and a given value of the input current; Step 1.5: Obtain a first duty cycle using a first pulse width modulator according to a second control signal; Step 1.6: According to the first duty cycle, controlling the photovoltaic converter to switch to a maximum power point tracking mode or a high DC bus voltage regulation mode; Step 2.1: Obtain a third control signal using a third proportional-integral controller according to the input voltage of the energy storage converter and the energy storage reference voltage; Step 2.2: According to the third control signal and the energy storage constant current charging current setting value, using the second variable limiter, obtain the energy storage maximum charging current limit value; Step 2.3: according to the output voltage and output current of the energy storage converter and the DC bus voltage low voltage threshold, using a fourth proportional integral controller to obtain a fourth control signal; Step 2.4: according to the fourth control signal and the maximum charging current limit value of the energy storage, using the third variable limiter, obtain a given value of the input current of the energy storage converter; Step 2.5: obtaining a fifth control signal by using a fifth proportional-integral controller according to the input current of the energy storage converter and a given value of the input current; Step 2.6: Obtain a second duty cycle using a second pulse width modulator according to the fifth control signal; Step 2.7: According to the second duty cycle, the energy storage converter is controlled to switch to a constant voltage charging mode, a constant current charging mode or a low DC bus voltage regulation mode.

[0048] In this embodiment, when the DC bus voltage is greater than the first reference value of the DC bus voltage and less than or equal to the high voltage threshold of the DC bus voltage, the first proportional-integral controller is in an activated state, the photovoltaic converter switches to a high DC bus voltage regulation mode, the third proportional-integral controller is in an activated state and the fourth proportional-integral controller is in a saturated state, and the energy storage converter switches to a constant voltage charging mode.

[0049] When the DC bus voltage is greater than the second reference value of the DC bus voltage and less than or equal to the first reference value of the DC bus voltage, the first proportional-integral controller is in a saturated state, and the photovoltaic converter switches to the maximum power point tracking mode. If the energy storage capacity is greater than a preset threshold, the third proportional-integral controller is in an activated state and the fourth proportional-integral controller is in a saturated state, and the energy storage converter switches to a constant voltage charging mode. Otherwise, the third proportional-integral controller is in a saturated state and the fourth proportional-integral controller is in a saturated state, and the energy storage converter switches to a constant current charging mode.

[0050] When the DC bus voltage is greater than or equal to the DC bus voltage low voltage threshold and less than or equal to the DC bus voltage second reference value, the first proportional-integral controller is in a saturated state, the photovoltaic converter switches to a maximum power point tracking mode, the third proportional-integral controller is in a saturated state and the fourth proportional-integral controller is in an activated state, and the energy storage converter switches to a low DC bus voltage regulation mode.

[0051] When the DC bus voltage is greater than the DC bus voltage high voltage threshold or less than the DC bus voltage low voltage threshold, all converters stop running.

[0052] Specifically, when the first proportional-integral controller is in an activated state, the first variable limiter is in an inactive state, and the given value of the input current of the photovoltaic converter is the first control signal.

[0053] When the first proportional-integral controller is in a saturated state, the first variable limiter is in a start-up state, and the given value of the input current of the photovoltaic converter is the current limit value of the maximum power point of the photovoltaic array.

[0054] When the third proportional-integral controller is in an activated state and the fourth proportional-integral controller is in a saturated state, the second variable limiter is in an unactivated state and the third variable limiter is in an activated state, the maximum energy storage charging current limit value is the third control signal, and the given value of the input current of the energy storage converter is the maximum energy storage charging current limit value.

[0055] When the third proportional-integral controller is in a saturated state and the fourth proportional-integral controller is in a saturated state, the second variable limiter is in a startup state and the third variable limiter is in a startup state, the maximum energy storage charging current limit value is the energy storage constant current charging current setting value, and the given value of the input current of the energy storage converter is the energy storage maximum charging current limit value.

[0056] When the third proportional-integral controller is in a saturated state and the fourth proportional-integral controller is in an activated state, the second variable limiter is in a started state and the third variable limiter is in a non-started state, the energy storage maximum charging current limit value is the energy storage constant current charging current setting value, and the given value of the input current of the energy storage converter is the fourth control signal.

[0057] In this embodiment, the high voltage threshold of the DC bus voltage is 104% of the rated value of the DC bus voltage, the low voltage threshold of the DC bus voltage is 96% of the rated value of the DC bus voltage, the first reference value of the DC bus voltage is 102% of the rated value of the DC bus voltage, and the second reference value of the DC bus voltage is 98% of the rated value of the DC bus voltage.

[0058] In this embodiment, the bandwidth of the first proportional-integral controller is greater than the bandwidth of the maximum power point tracking solar controller.

[0059] The photovoltaic-storage-DC microgrid converter collaborative control method based on the DC bus voltage signal provided in the embodiment of the present application has the corresponding beneficial effects of the photovoltaic-storage-DC microgrid converter collaborative control system based on the DC bus voltage signal.

[0060] The above are only preferred implementations of the present application. It should be pointed out that for ordinary technicians in this technical field, several improvements and modifications can be made without departing from the technical principles of the present application. These improvements and modifications should also be regarded as the scope of protection of the present application.

Claims

1. A photovoltaic energy storage DC microgrid converter coordinated control system based on DC bus voltage signal, characterized in that: Including photovoltaic converter and energy storage converter; The photovoltaic converter obtains the maximum power point current limit value of the photovoltaic array according to its input voltage and input current, obtains the first control signal according to its output voltage and output current and the DC bus voltage high voltage threshold, obtains the given value of its input current according to the first control signal and the maximum power point current limit value of the photovoltaic array, obtains the second control signal according to its input current and the given value of the input current, obtains the first duty cycle according to the second control signal, and switches to the maximum power point tracking mode or the high DC bus voltage regulation mode according to the first duty cycle; The energy storage converter obtains a third control signal according to its input voltage and the energy storage reference voltage, obtains a maximum energy storage charging current limit value according to the third control signal and the energy storage constant current charging current setting value, obtains a fourth control signal according to its output voltage and output current and the DC bus voltage low voltage threshold, obtains a given value of its input current according to the fourth control signal and the maximum energy storage charging current limit value, obtains a fifth control signal according to its input current and the given value of the input current, obtains a second duty cycle according to the fifth control signal, and switches to a constant voltage charging mode, a constant current charging mode or a low DC bus voltage regulation mode according to the second duty cycle.

2. The photovoltaic energy storage DC microgrid converter coordinated control system based on DC bus voltage signal according to claim 1 is characterized in that: Photovoltaic converters include: The maximum power point tracking solar controller is used to obtain the maximum power point current limit value of the photovoltaic array according to the input voltage and input current of the photovoltaic converter; A first proportional-integral controller, used for obtaining a first control signal according to an output voltage and an output current of the photovoltaic converter and a high-voltage threshold of a DC bus voltage; A first variable limiter, used to obtain a given value of the input current of the photovoltaic converter according to the first control signal and the current limit value of the maximum power point of the photovoltaic array; A second proportional-integral controller, used for obtaining a second control signal according to an input current of the photovoltaic converter and a given value of the input current; A first pulse width modulator, configured to obtain a first duty cycle according to a second control signal; The energy storage converter includes: A third proportional-integral controller, used for obtaining a third control signal according to the input voltage of the energy storage converter and the energy storage reference voltage; A second variable limiter, used to obtain a maximum energy storage charging current limit value according to a third control signal and an energy storage constant current charging current setting value; A fourth proportional-integral controller, used for obtaining a fourth control signal according to the output voltage and output current of the energy storage converter and the DC bus voltage low voltage threshold; A third variable limiter, used to obtain a given value of the input current of the energy storage converter according to the fourth control signal and the maximum charging current limit value of the energy storage; a fifth proportional-integral controller, used for obtaining a fifth control signal according to an input current of the energy storage converter and a given value of the input current; The second pulse width modulator is used to obtain a second duty cycle according to a fifth control signal.

3. The photovoltaic-storage-DC microgrid converter coordinated control system based on the DC bus voltage signal according to claim 2 is characterized in that: When the DC bus voltage is greater than the first reference value of the DC bus voltage and less than or equal to the high voltage threshold of the DC bus voltage, the first proportional-integral controller is in an activated state, the photovoltaic converter is switched to a high DC bus voltage regulation mode, the third proportional-integral controller is in an activated state and the fourth proportional-integral controller is in a saturated state, and the energy storage converter is switched to a constant voltage charging mode; When the DC bus voltage is greater than the second reference value of the DC bus voltage and less than or equal to the first reference value of the DC bus voltage, the first proportional-integral controller is in a saturated state, and the photovoltaic converter switches to the maximum power point tracking mode. If the energy storage capacity is greater than a preset threshold, the third proportional-integral controller is in an activated state and the fourth proportional-integral controller is in a saturated state, and the energy storage converter switches to a constant voltage charging mode. Otherwise, the third proportional-integral controller is in a saturated state and the fourth proportional-integral controller is in a saturated state, and the energy storage converter switches to a constant current charging mode. When the DC bus voltage is greater than or equal to the DC bus voltage low voltage threshold and less than or equal to the DC bus voltage second reference value, the first proportional integral controller is in a saturated state, the photovoltaic converter switches to a maximum power point tracking mode, the third proportional integral controller is in a saturated state and the fourth proportional integral controller is in an activated state, and the energy storage converter switches to a low DC bus voltage regulation mode; When the DC bus voltage is greater than the DC bus voltage high voltage threshold or less than the DC bus voltage low voltage threshold, each converter stops running.

4. The photovoltaic-storage-DC microgrid converter coordinated control system based on the DC bus voltage signal according to claim 3 is characterized in that: When the first proportional-integral controller is in an activated state, the first variable limiter is in an inactive state, and the given value of the input current of the photovoltaic converter is the first control signal; When the first proportional-integral controller is in a saturated state, the first variable limiter is in a start-up state, and the given value of the input current of the photovoltaic converter is the current limit value of the maximum power point of the photovoltaic array.

5. The photovoltaic-storage-DC microgrid converter coordinated control system based on DC bus voltage signal according to claim 3 is characterized in that: When the third proportional-integral controller is in an activated state and the fourth proportional-integral controller is in a saturated state, the second variable limiter is in an unactivated state and the third variable limiter is in an activated state, the maximum charging current limit value of the energy storage is the third control signal, and the given value of the input current of the energy storage converter is the maximum charging current limit value of the energy storage; When the third proportional-integral controller is in a saturated state and the fourth proportional-integral controller is in a saturated state, the second variable limiter is in an activated state and the third variable limiter is in an activated state, the maximum charging current limit value of the energy storage is the energy storage constant current charging current setting value, and the given value of the input current of the energy storage converter is the maximum charging current limit value of the energy storage; When the third proportional-integral controller is in a saturated state and the fourth proportional-integral controller is in an activated state, the second variable limiter is in a started state and the third variable limiter is in a non-started state, the energy storage maximum charging current limit value is the energy storage constant current charging current setting value, and the given value of the input current of the energy storage converter is the fourth control signal.

6. The photovoltaic-storage-DC microgrid converter coordinated control system based on DC bus voltage signal according to claim 3 is characterized in that: The high voltage threshold of the DC bus voltage is 104% of the rated value of the DC bus voltage, the low voltage threshold of the DC bus voltage is 96% of the rated value of the DC bus voltage, the first reference value of the DC bus voltage is 102% of the rated value of the DC bus voltage, and the second reference value of the DC bus voltage is 98% of the rated value of the DC bus voltage.

7. The photovoltaic-storage-DC microgrid converter coordinated control system based on the DC bus voltage signal according to claim 2 is characterized in that: The bandwidth of the first proportional-integral controller is greater than the bandwidth of the maximum power point tracking solar controller.

8. A photovoltaic converter, characterized in that: include: The maximum power point tracking solar controller is used to obtain the maximum power point current limit value of the photovoltaic array according to the input voltage and input current of the photovoltaic converter; A first proportional-integral controller, used for obtaining a first control signal according to an output voltage and an output current of the photovoltaic converter and a high-voltage threshold of a DC bus voltage; A first variable limiter, used to obtain a given value of the input current of the photovoltaic converter according to the first control signal and the current limit value of the maximum power point of the photovoltaic array; A second proportional-integral controller, used for obtaining a second control signal according to an input current of the photovoltaic converter and a given value of the input current; A first pulse width modulator, configured to obtain a first duty cycle according to a second control signal; The photovoltaic converter is switched to a maximum power point tracking mode or a high DC bus voltage regulation mode according to the first duty cycle.

9. An energy storage converter, characterized in that: include: A third proportional-integral controller, used for obtaining a third control signal according to the input voltage of the energy storage converter and the energy storage reference voltage; A second variable limiter, used to obtain a maximum energy storage charging current limit value according to a third control signal and an energy storage constant current charging current setting value; A fourth proportional-integral controller, used for obtaining a fourth control signal according to the output voltage and output current of the energy storage converter and the DC bus voltage low voltage threshold; A third variable limiter, used to obtain a given value of the input current of the energy storage converter according to the fourth control signal and the maximum charging current limit value of the energy storage; a fifth proportional-integral controller, used for obtaining a fifth control signal according to an input current of the energy storage converter and a given value of the input current; a second pulse width modulator, configured to obtain a second duty cycle according to a fifth control signal; The energy storage converter switches to a constant voltage charging mode, a constant current charging mode or a low DC bus voltage regulation mode according to the second duty cycle.

10. A method for coordinated control of a photovoltaic-storage DC microgrid converter based on a DC bus voltage signal, characterized in that: include: According to the input voltage and input current of the photovoltaic converter, the maximum power point current limit value of the photovoltaic array is obtained; Acquire a first control signal according to the output voltage and output current of the photovoltaic converter and the high voltage threshold of the DC bus voltage; Obtaining a given value of the input current of the photovoltaic converter according to the first control signal and the maximum power point current limit value of the photovoltaic array; Acquire a second control signal according to an input current of the photovoltaic converter and a given value of the input current; Acquire a first duty cycle according to the second control signal; According to the first duty cycle, controlling the photovoltaic converter to switch to a maximum power point tracking mode or a high DC bus voltage regulation mode; Obtaining a third control signal according to the input voltage of the energy storage converter and the energy storage reference voltage; Obtaining a maximum energy storage charging current limit value according to the third control signal and the energy storage constant current charging current setting value; Obtaining a fourth control signal according to the output voltage and output current of the energy storage converter and the DC bus voltage low voltage threshold; Obtaining a given value of the input current of the energy storage converter according to the fourth control signal and the maximum charging current limit value of the energy storage; Acquire a fifth control signal according to an input current of the energy storage converter and a given value of the input current; acquiring a second duty cycle according to a fifth control signal; According to the second duty cycle, the energy storage converter is controlled to switch to a constant voltage charging mode, a constant current charging mode or a low DC bus voltage regulation mode.

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