Coordinated control method and system for photovoltaic and energy storage microgrid based on improved droop control based on SoC

Abstract

The present invention discloses a photovoltaic storage microgrid coordinated control method and system based on SoC improved droop control. The method includes, when the DC bus voltage is less than the upper limit threshold of the DC bus voltage, controlling each photovoltaic storage microgrid unit to work in the first mode, the photovoltaic array uses the variable step size perturbation observation method to achieve maximum power point tracking, and the energy storage battery uses the droop control equation of secondary voltage compensation to adjust the DC bus voltage; when the DC bus voltage is greater than or equal to the upper limit threshold of the DC bus voltage, controlling each photovoltaic storage microgrid unit to work in the second mode, the photovoltaic array uses the voltage stabilization control method to adjust the DC bus voltage, and the energy storage battery is in an idle state or a constant charging state. The solution provided by the present invention can improve the utilization rate of photovoltaic power generation, while avoiding overcharging and over-discharging of energy storage batteries, extending the service life of the battery, realizing seamless switching of the photovoltaic storage microgrid mode, and ensuring the safe and stable operation of the photovoltaic storage microgrid.

Description

Technical Field

[0001] The present invention relates to the technical field of photovoltaic power generation, and in particular to a photovoltaic storage microgrid coordinated control method and system based on SoC improved droop control. Background Art

[0002] Solar energy is considered to be one of the most economical and environmentally friendly energy sources. Photovoltaic power generation has shown great application potential in the field of new energy power generation due to its advantages of cleanliness, environmental protection and high efficiency. However, photovoltaic power generation is affected by factors such as weather, light intensity and temperature, and its output has problems such as intermittent, volatile and uncontrollable. The energy storage system can not only store excess electrical energy, but also release the stored electrical energy to power the load when the power generation capacity is weak, so as to achieve peak shaving and valley filling, and well solve the problem of intermittent photovoltaic power generation. When photovoltaic power generation and energy storage are used together, a photovoltaic storage microgrid is formed.

[0003] In order to obtain the maximum power from the photovoltaic system and improve the conversion efficiency of photovoltaics, it is necessary to ensure that the system operates at the maximum power point (MPP), and the maximum power point tracking (MPPT) control method came into being. The MPPT control method enables the photovoltaic system to operate at the maximum power output state by changing the operating voltage under different weather conditions.

[0004] In a photovoltaic-storage microgrid, in order to fully utilize photovoltaic power generation, the photovoltaic port generally adopts MPPT control, while energy storage generally adopts droop control to maintain the constant DC bus voltage. The photovoltaic-storage DC microgrid system using droop control has good reliability and plug-and-play performance, which is more convenient for system expansion. Of course, droop control also has limitations, and the DC bus voltage will deviate from the rated value as the power changes. Summary of the invention

[0005] In order to solve the technical problem that the DC bus voltage of a photovoltaic and energy-storage microgrid deviates from the rated value as the power changes when using traditional droop control, an embodiment of the present invention provides a photovoltaic and energy-storage microgrid coordinated control method and system based on SoC improved droop control.

[0006] The technical solution of the embodiment of the present invention is achieved as follows:

[0007] The embodiment of the present invention provides a photovoltaic storage microgrid coordinated control method based on SoC improved droop control, which is applied to a photovoltaic storage microgrid coordinated control system based on SoC improved droop control. The system includes multiple photovoltaic storage microgrid units and DC loads, each of which includes a photovoltaic array and an energy storage battery; each photovoltaic array is connected to a DC bus of the DC load through a DC boost converter, and each energy storage battery is also connected to the DC bus of the DC load through a bidirectional DC-DC converter. The method includes:

[0008] Obtaining a DC bus voltage, and determining whether the DC bus voltage is greater than an upper limit threshold of the DC bus voltage;

[0009] When the DC bus voltage is less than the DC bus voltage upper limit threshold, each photovoltaic storage microgrid unit is controlled to operate in the first mode, the photovoltaic array in the first mode uses the variable step size perturbation observation method to achieve maximum power point tracking, and the energy storage battery in the first mode uses the droop control equation of the secondary voltage compensation to adjust the DC bus voltage; the droop control equation of the secondary voltage compensation is:

[0010]

[0011] in, is the DC bus reference voltage, is the DC bus rated voltage, is the secondary voltage compensation, is the droop coefficient, Output current for the bidirectional DC / DC converter of the energy storage battery; is the upper threshold voltage of the DC bus, is the rated value of the discharge current of the energy storage battery;

[0012] When the DC bus voltage is greater than or equal to the DC bus voltage upper limit threshold, each photovoltaic storage microgrid unit is controlled to operate in a second mode, the photovoltaic array in the second mode uses a voltage stabilization control method to adjust the DC bus voltage, and the energy storage battery in the second mode is in an idle state or a constant charging state.

[0013] The embodiment of the present invention provides a photovoltaic storage microgrid coordinated control system based on SoC improved droop control, the system comprising a plurality of photovoltaic storage microgrid units and a DC load, each of the photovoltaic storage microgrid units comprising a photovoltaic array and an energy storage battery; each of the photovoltaic arrays is connected to the DC bus of the DC load via a DC boost converter, and each of the energy storage batteries is also connected to the DC bus of the DC load via a bidirectional DC-DC converter;

[0014] When the DC bus voltage is less than the DC bus voltage upper limit threshold, each of the photovoltaic storage microgrid units operates in the first mode. The photovoltaic array in the first mode uses the variable step size perturbation observation method to achieve maximum power point tracking, and the energy storage battery in the first mode uses the droop control equation of the secondary voltage compensation to adjust the DC bus voltage; the droop control equation of the secondary voltage compensation is:

[0015]

[0016] in, is the DC bus reference voltage, is the DC bus rated voltage, is the secondary voltage compensation, is the droop coefficient, Output current for the bidirectional DC / DC converter of the energy storage battery; is the upper threshold voltage of the DC bus, is the rated value of the discharge current of the energy storage battery;

[0017] Each of the photovoltaic and energy storage microgrid units operates in a second mode when the DC bus voltage is greater than or equal to the DC bus voltage upper limit threshold. The photovoltaic array in the second mode uses voltage regulation control to adjust the DC bus voltage, and the energy storage battery in the second mode is in an idle state or a constant charging state.

[0018] The embodiments of the present invention have the following beneficial effects:

[0019] This embodiment divides the photovoltaic storage microgrid into two modes of operation. In the first mode, the photovoltaic array operates in the MPPT mode with a variable step size perturbation observation method to achieve maximum power tracking, so as to improve the utilization rate of photovoltaic power generation. The energy storage battery adopts an improved droop control based on the battery remaining capacity SoC (i.e., the droop control equation of the secondary voltage compensation). By introducing the secondary voltage compensation amount, the DC bus voltage is compensated according to the SoC of the energy storage battery, so that the DC bus voltage is maintained near the rated value under power changes and is within the threshold range, thereby ensuring the normal operation of the photovoltaic storage microgrid. In the second mode, the photovoltaic array uses voltage stabilization control to adjust the DC bus voltage to the upper limit threshold of the bus voltage, and the energy storage battery is in an idle state or a constant charging state. The two modes realize seamless switching automatically according to the relationship between the bus voltage and the upper limit threshold of the bus voltage, thereby realizing the coordinated control of the photovoltaic storage microgrid and ensuring the safe and stable operation of the photovoltaic storage microgrid. BRIEF DESCRIPTION OF THE DRAWINGS

[0020] Figure 1 It is a flow chart of a photovoltaic-storage microgrid coordinated control method based on SoC improved droop control according to an embodiment of the present invention;

[0021] Figure 2 This is a schematic diagram of the operation mode of a photovoltaic port according to an embodiment of the present invention;

[0022] Figure 3 This is a system power distribution block diagram of the photovoltaic storage microgrid in two modes of the embodiment of the present invention;

[0023] Figure 4 It is a flow chart of an improved droop control algorithm based on SoC adopted by the energy storage port in an embodiment of the present invention;

[0024] Figure 5 A schematic diagram of the relationship between the bus reference voltage and the SoC according to an embodiment of the present invention;

[0025] Figure 6 This is a schematic diagram of the structure of a photovoltaic-storage DC microgrid according to an embodiment of the present invention;

[0026] Figure 7 This is a control block diagram used by the energy storage port in an embodiment of the present invention;

[0027] Figure 8 This is a control block diagram used by the photovoltaic port of an embodiment of the present invention;

[0028] Fig. 9 1 is a diagram showing the internal structure of a computer device according to an embodiment of the present invention. DETAILED DESCRIPTION

[0029] The present invention will be described in further detail below with reference to the accompanying drawings and embodiments.

[0030] The embodiment of the present invention provides a photovoltaic storage microgrid coordinated control method based on SoC improved droop control, which is applied to a photovoltaic storage microgrid coordinated control system based on SoC improved droop control, wherein the system comprises a plurality of photovoltaic storage microgrid units and a DC load, wherein each photovoltaic storage microgrid unit comprises a photovoltaic array and an energy storage battery; each photovoltaic array is connected to a DC bus of the DC load via a DC boost converter, and each energy storage battery is also connected to a DC bus of the DC load via a bidirectional DC-DC converter, such as Figure 1 As shown, the method includes:

[0031] Step 101: Obtain a DC bus voltage, and determine whether the DC bus voltage is greater than an upper limit threshold of the DC bus voltage;

[0032] When the DC bus voltage is less than the DC bus voltage upper limit threshold, step 102 is performed: each photovoltaic storage microgrid unit is controlled to operate in the first mode, the photovoltaic array in the first mode uses a variable step size perturbation observation method to achieve maximum power point tracking, and the energy storage battery in the first mode uses a droop control equation of secondary voltage compensation to adjust the DC bus voltage; the droop control equation of secondary voltage compensation is:

[0033]

[0034] in, is the DC bus reference voltage, is the DC bus rated voltage, is the secondary voltage compensation, is the droop coefficient, Output current for the bidirectional DC / DC converter of the energy storage battery; is the upper threshold voltage of the DC bus, is the rated value of the discharge current of the energy storage battery;

[0035] When the DC bus voltage is greater than or equal to the DC bus voltage upper limit threshold, execute step 103: control each photovoltaic storage microgrid unit to operate in a second mode, the photovoltaic array in the second mode uses a voltage stabilization control method to adjust the DC bus voltage, and the energy storage battery in the second mode is in an idle state or a constant charging state.

[0036] In this embodiment, the operation modes of the photovoltaic microgrid are divided into two types according to the level of the DC bus voltage. In the first mode (the DC bus voltage Less than the DC bus voltage upper threshold ), the photovoltaic array uses the variable step size perturbation observation method to achieve MPPT (maximum power point tracking), so that photovoltaic power generation can be fully utilized. The energy storage battery uses the improved droop control based on SoC (i.e., the droop control equation of quadratic voltage compensation) to adjust the DC bus voltage and keep it within the threshold range, ensuring the normal operation of the photovoltaic storage microgrid; in the second mode (DC bus voltage Greater than or equal to the DC bus voltage upper threshold ), the PV array uses voltage regulation control to adjust the DC bus voltage, and the energy storage battery is in an idle state or a constant charging state.

[0037] This embodiment improves the traditional droop control and proposes an improved droop control method based on the battery remaining capacity SoC (i.e., the droop control equation of secondary voltage compensation) to achieve the DC bus voltage maintained at the rated threshold under power changes and coordinated control of the photovoltaic storage microgrid.

[0038] Specifically, before introducing the solution of this embodiment, a traditional droop control method is first introduced.

[0039] The traditional droop control equation is When the DC bus voltage is higher than the expected value When the DC bus voltage is lower than the expected value, it means that the bus voltage is high, the system power is in excess, and the energy storage battery needs to be charged to store energy; when the DC bus voltage is lower than the expected value When the bus voltage is low, the system needs more power, and the energy storage battery needs to release energy to stabilize the bus voltage. From the traditional droop control equation, it can be seen that when the energy storage battery current changes, if the DC bus voltage is not compensated twice, the DC bus voltage will deviate from the rated value. If the DC bus voltage deviates from the threshold range of the rated value, the photovoltaic storage microgrid will not operate normally.

[0040] Based on this, this embodiment improves the traditional droop control method, proposes an improved droop control method based on the battery remaining capacity SoC, introduces a secondary voltage compensation amount, and compensates the DC bus voltage according to the battery remaining capacity SoC of the energy storage battery, so as to achieve the DC bus voltage maintained near the rated value under power changes and within the threshold range, thereby ensuring the safe and stable operation of the photovoltaic storage microgrid.

[0041] In order to reduce the degree to which the DC bus voltage deviates from the rated value, the control equation of the improved droop control based on the battery remaining capacity SoC proposed in this embodiment is specifically: , is the secondary voltage compensation, The DC bus voltage is compensated according to the remaining battery capacity SoC of the energy storage battery, so that the DC bus voltage is maintained near the rated value and within the threshold range, ensuring the safe and stable operation of the photovoltaic storage microgrid.

[0042] Specifically, the present embodiment can further divide the improved droop control equation according to the battery remaining capacity SoC of the energy storage battery. The present embodiment can divide the state of charge of the energy storage battery into three types according to the battery remaining capacity SoC, corresponding to three different droop control equations respectively. Different droop control equations calculate and determine the reference voltage of the DC bus according to the battery remaining capacity SoC.

[0043] The first one:

[0044] When the remaining battery capacity of the energy storage battery is greater than a preset first threshold, the energy storage battery is in a high SoC state (HSS).

[0045] The droop control equation of the secondary voltage compensation is:

[0046]

[0047] in, is the DC bus reference voltage, is the DC bus rated voltage, is the droop coefficient, Output current of the bidirectional DC / DC converter for the energy storage battery, is the upper threshold voltage of the DC bus, is the rated value of the energy storage battery discharge current, is the secondary voltage compensation, is the remaining capacity of the energy storage battery, ;

[0048] Second type:

[0049] When the remaining battery capacity of the energy storage battery is greater than a preset second threshold value and less than or equal to a preset first threshold value, the energy storage battery is in a nominal SoC State (NSS).

[0050] The droop control equation of the secondary voltage compensation is:

[0051]

[0052] in, is the DC bus reference voltage, is the DC bus rated voltage, is the droop coefficient, Output current of the bidirectional DC / DC converter for the energy storage battery, is the upper threshold voltage of the DC bus, is the rated value of the energy storage battery discharge current, is the secondary voltage compensation, is the remaining capacity of the energy storage battery, ;

[0053] The third type:

[0054] When the remaining battery capacity of the energy storage battery is greater than a preset third threshold value and less than or equal to a preset second threshold value, the energy storage battery is in a low SoC state (LSS).

[0055] The droop control equation of the secondary voltage compensation is:

[0056]

[0057] in, is the DC bus reference voltage, is the DC bus rated voltage, is the droop coefficient, Output current of the bidirectional DC / DC converter for the energy storage battery, is the upper threshold voltage of the DC bus, is the rated value of the energy storage battery discharge current, is the secondary voltage compensation, is the remaining capacity of the energy storage battery, , is the lower threshold voltage of the DC bus.

[0058] In practical applications, the preset first threshold, preset second threshold, and preset third threshold can all be set based on the actual situation. For example, the preset first threshold can be set to 90%, the preset second threshold can be set to 35%, and the preset third threshold can be set to 25%.

[0059] That is, when the SoC of the energy storage battery > 90%, , the droop control equation is ; when 35% < SoC < 90% of the energy storage battery, , the droop control equation is ; when 25% < SoC < 35% of the energy storage battery, , the droop control equation is .

[0060] In addition, for the case where the remaining battery capacity of the energy storage battery is less than or equal to the preset third threshold, the DC bus voltage can be set to the lower threshold voltage of the DC bus.

[0061] That is, when SoC is lower than 25%, the battery will be in the charging mode and always have a reference voltage . Therefore, in this embodiment, by improving the traditional droop control method, the energy storage battery adjusts the DC bus voltage within a limited range, ensuring the normal operation of the photovoltaic energy storage microgrid. That is, when working in the first mode, the DC bus voltage is maintained between the upper threshold and the lower threshold values.

[0062] In addition, on the basis of the DC bus voltage regulation, this embodiment can also use a current limiter based on the SoC of the energy storage battery to limit the charging and discharging current of the energy storage battery, avoiding over-discharge of the energy storage battery when SoC is low and over-charging when SoC is high, reducing the damage to the energy storage battery caused by overcharging and over-discharging, and prolonging the service life of the battery.

[0063] Specifically, in the traditional current limiter, regardless of which of the three states the SoC of the energy storage battery is in, the maximum discharge current and the maximum charging current are both set to the rated value. This charging and discharging current limit that does not consider the SoC state of the energy storage battery is not friendly to the energy storage battery and may cause over-discharge of the energy storage battery when SoC is low and over-charging when SoC is high, thereby causing damage to the battery and shortening the battery life.

[0064] In order to avoid over-discharge of the energy storage battery when SoC is low and over-charging when SoC is high, this embodiment also uses a current limiting method based on the SoC of the energy storage battery to adjust the charging and discharging current of the energy storage battery, preventing over-discharge of the energy storage battery when SoC is low and over-charging when SoC is high.

[0065] Specifically, the current limiting method based on the energy storage battery SoC is:

[0066] The current reference value of the battery is calculated as follows:

[0067] For low state of charge LSS: ;

[0068] For high state of charge HSS: ;

[0069] At rated state of charge NSS, the maximum discharge current and maximum charging current Set to the nominal value, that is: and . and These are the rated values ​​of discharge current and charge current respectively.

[0070] When the battery is in a low state of charge (LSS), the battery power is low and the battery is still discharging, the discharge current of the battery should be reduced, that is, the maximum discharge current should be less than the maximum discharge current at the rated state of charge (NSS); therefore, this embodiment sets To limit the discharge current of the energy storage battery.

[0071] When the battery is in a high state of charge (HSS), the battery SoC is relatively high, that is, the battery power is high and the battery is still charging, the battery charging current should be reduced, that is, its maximum charging current should be less than the maximum charging current in the rated state of charge (NSS); therefore, this embodiment sets To limit the charging current of the energy storage battery. This charging and discharging method is friendly to the battery.

[0072] That is, this embodiment reasonably limits the maximum charge and discharge current of the battery in the three modes according to the SoC of the battery, thereby avoiding over-discharge of the energy storage battery when the SoC is low and over-charge when the SoC is high, reducing damage to the battery caused by over-discharge and over-charge, and extending the battery life.

[0073] In addition, based on the regulation of the DC bus voltage and the charge and discharge current of the energy storage battery, this embodiment can further regulate the power of the photovoltaic microgrid.

[0074] Specifically, in the first mode, the power regulation method of the photovoltaic storage microgrid can be:

[0075] like ,but , that is, the photovoltaic power generation outputs at the maximum power, the energy storage battery maintains the DC bus voltage constant while providing the power shortage of the DC load, and the energy storage battery is in a discharging state; if ,but That is, the photovoltaic power generation outputs at the maximum power, the energy storage battery maintains the DC bus voltage constant while absorbing the power shortage of the photovoltaic power generation, and the energy storage battery is in a charging state. They are respectively the maximum power of photovoltaic power generation, DC load power, energy storage battery power and the maximum charging power of the energy storage battery.

[0076] In the second mode, the power regulation method of the photovoltaic storage microgrid can be:

[0077] like ,but , that is, the photovoltaic array uses voltage regulation control to adjust the DC bus voltage to the bus voltage upper limit threshold The photovoltaic array also provides power for the DC loads if the energy storage battery is charged. is the power of photovoltaic power generation.

[0078] The present embodiment provides a method for coordinated control of a photovoltaic and energy storage microgrid based on improved droop control of SoC. In the first mode, the photovoltaic port adopts the MPPT control method of the variable step size perturbation observation method to achieve maximum power tracking to improve the utilization rate of photovoltaic power generation; the energy storage port adopts improved droop control based on SoC, introduces secondary voltage compensation, and compensates the DC bus voltage according to the SoC of the energy storage battery, so that the DC bus voltage is maintained near the rated value under power changes and within the threshold range, thereby ensuring the normal operation of the photovoltaic and energy storage microgrid. In the second mode, the photovoltaic array uses voltage stabilization control to adjust the DC bus voltage to the upper limit threshold of the bus voltage, and the energy storage battery is in an idle state or a constant charging state. The two modes realize seamless switching automatically according to the relationship between the bus voltage and the upper limit threshold of the bus voltage, thereby realizing coordinated control of the photovoltaic and energy storage microgrid and ensuring the safe and stable operation of the photovoltaic and energy storage microgrid.

[0079] At the same time, this embodiment also uses a current limiting method based on the energy storage battery SoC to limit the charge and discharge current of the energy storage battery, thereby preventing the energy storage battery from over-discharging when the SoC is low and over-charging when the SoC is high, reducing the damage to the energy storage battery caused by over-charging and over-discharging, and extending the battery life.

[0080] A specific embodiment will be used for description below.

[0081] This embodiment provides a photovoltaic energy storage microgrid coordinated control method based on SoC improved droop control, the method comprising the following contents:

[0082] 1. Obtain the DC bus voltage of the photovoltaic storage microgrid , compare it with the bus voltage upper threshold When the bus voltage Less than the bus voltage upper threshold When the PV-storage microgrid operates in Mode 1 (i.e., the first mode); when the bus voltage is greater than or equal to the upper threshold of the bus voltage the PV-storage microgrid operates in Mode 2 (i.e., the second mode).

[0083] 2. In Mode 1, at this time, the maximum power of PV generation is less than the DC load demand and the maximum charging capacity of the energy storage battery. The PV array will implement MPPT (Maximum Power Point Tracking) by the variable step-size perturbation and observation method to make full use of PV power generation. The specific control implementation is shown by Figure 2 . The energy storage battery uses the improved droop control based on SoC to adjust the DC bus voltage and keep it within the threshold range.

[0084] 3. In Mode 1, the power distribution method of the system is as follows: If , then , that is, the PV generation outputs at the maximum power, and the energy storage battery provides the power deficit of the DC load while maintaining the constant DC bus voltage, and the energy storage battery is in the discharging state; if , then , that is, the PV generation outputs at the maximum power, and the energy storage battery absorbs the power deficit of the PV generation while maintaining the constant DC bus voltage, and the energy storage battery is in the charging state. Where are the maximum power of PV generation, DC load power, energy storage battery power, and the maximum charging power of the energy storage battery respectively. The specific power distribution method is shown by Figure 3 .

[0085] 4. The reference value of the DC bus reference voltage is determined by this droop control method based on SoC. The SoC algorithm is used as the main control. In order to track the reference voltage value, a voltage and current controller is adopted to achieve constant voltage and constant current control.

[0086] According to the high and low SoC of the energy storage battery, the energy storage battery is divided into three states. When 25% < SoC < 35%, it is in the low state of charge (Low SoC State, LSS) at this time; when 35% < SoC < 90%, it is in the nominal state of charge (Nominal SoC State, NSS) at this time; when SoC > 90%, it is in the high state of charge (High SoC State, HSS) at this time. The three SoC states correspond to three different droop control equations respectively. Different droop control equations determine the reference voltage of the DC bus according to SoC, as shown by Figure 4 ; The relationship between the bus reference voltage and SoC is shown by Figure 5 ;

[0087] When the SoC of the energy storage battery > 90%, the droop control equation is ;

[0088] When 35% < SoC < 90% of the energy storage battery, the droop control equation is ;

[0089] When 25% < SoC < 35% of the energy storage battery, the droop control equation is ;

[0090] Among them, is the rated voltage of the DC bus, is the output current of the bidirectional DC / DC converter of the energy storage battery, is the droop coefficient. a, b, c are the SoC droop coefficients, which are defined as the following formulas respectively:

[0091] , , , .

[0092] , , are the upper threshold voltage, lower threshold voltage and rated voltage of the DC bus respectively.

[0093] 5. In order to avoid over-discharging of the energy storage battery at low SoC and over-charging at high SoC, a current limiter based on the SoC of the energy storage battery is also used, and the current reference value of the battery is limited as follows;

[0094] For LSS: ;

[0095] For HSS: ;

[0096] In the NSS mode, the maximum discharge current and the maximum charge current are set to the rated values, that is: and . and are the rated values of the discharge current and charge current respectively. When SoC is lower than 25%, the battery will be in the charging mode and always have the reference voltage .

[0097] Through the above-mentioned SoC-based droop control method, the energy storage battery regulates the DC bus voltage within a limited range, that is, when working in Mode 1, the DC bus voltage is maintained between the upper threshold and the lower threshold.

[0098] 6. In mode 2, the maximum power of photovoltaic power generation is greater than the DC load demand and the maximum charging capacity of the energy storage battery. The photovoltaic array uses voltage regulation control to adjust the DC bus voltage, and the energy storage battery is in an idle state or constant charging state. Adjust the DC bus voltage to the bus voltage upper limit threshold .

[0099] 7. In mode 2, the system power allocation method is: ,but , that is, the photovoltaic array uses voltage regulation control to adjust the DC bus voltage to the bus voltage upper limit threshold The photovoltaic array also provides power for the DC loads if the energy storage battery is charged. is the power of photovoltaic power generation.

[0100] The two modes can be switched seamlessly according to the relationship between the bus voltage and the upper threshold of the bus voltage, thereby achieving coordinated control of the photovoltaic and energy storage microgrid and ensuring the safe and stable operation of the photovoltaic and energy storage microgrid.

[0101] The beneficial effects of this embodiment are:

[0102] Compared with the traditional photovoltaic storage microgrid coordinated control method, the control method proposed in this embodiment divides the photovoltaic storage microgrid into two modes of operation. In mode 1, the photovoltaic array operates in the MPPT mode with a variable step size perturbation observation method to achieve maximum power tracking, so as to improve the utilization rate of photovoltaic power generation. The energy storage battery adopts an improved droop control based on SoC, introduces a secondary voltage compensation amount, and compensates the DC bus voltage according to the SoC of the energy storage battery, so as to achieve the DC bus voltage maintained near the rated value under power changes and within the threshold range. At the same time, a current limiter based on the SoC of the energy storage battery is used to limit the charging and discharging current of the energy storage battery, so as to avoid over-discharging of the energy storage battery when the SoC is low and over-charging when the SoC is high, thereby reducing the damage to the energy storage battery caused by over-charging and over-discharging, and extending the service life of the battery; in mode 2, the photovoltaic array uses voltage stabilization control to adjust the DC bus voltage to the upper limit threshold of the bus voltage, and the energy storage battery is in an idle state or a constant charging state. The two modes can be switched seamlessly according to the relationship between the bus voltage and the upper limit threshold of the bus voltage, thereby realizing coordinated control of the photovoltaic and energy storage microgrid and ensuring the safe and stable operation of the photovoltaic and energy storage microgrid.

[0103] In order to implement the method of the embodiment of the present invention, the embodiment of the present invention also provides a photovoltaic storage microgrid coordinated control system based on SoC improved droop control, such as Figure 6As shown, the system includes a plurality of photovoltaic storage microgrid units and DC loads, each of the photovoltaic storage microgrid units includes a photovoltaic array and an energy storage battery; each of the photovoltaic arrays is connected to the DC bus of the DC load through a DC boost converter, and each of the energy storage batteries is also connected to the DC bus of the DC load through a bidirectional DC-DC converter;

[0104] When the DC bus voltage is less than the DC bus voltage upper limit threshold, each of the photovoltaic storage microgrid units operates in the first mode. The photovoltaic array in the first mode uses the variable step size perturbation observation method to achieve maximum power point tracking, and the energy storage battery in the first mode uses the droop control equation of the secondary voltage compensation to adjust the DC bus voltage; the droop control equation of the secondary voltage compensation is:

[0105]

[0106] in, is the DC bus reference voltage, is the DC bus rated voltage, is the secondary voltage compensation, is the droop coefficient, Output current for the bidirectional DC / DC converter of the energy storage battery; is the upper threshold voltage of the DC bus, is the rated value of the discharge current of the energy storage battery;

[0107] Each of the photovoltaic and energy storage microgrid units operates in a second mode when the DC bus voltage is greater than or equal to the DC bus voltage upper limit threshold. The photovoltaic array in the second mode uses voltage regulation control to adjust the DC bus voltage, and the energy storage battery in the second mode is in an idle state or a constant charging state.

[0108] Furthermore, the energy storage battery in this embodiment uses the droop control equation of the secondary voltage compensation to adjust the DC bus voltage through the voltage and current controller. The photovoltaic array implements MPPT through the voltage and current controller and uses the voltage stabilization control method to adjust the DC bus voltage.

[0109] Here, the control block diagram adopted by the energy storage port is shown in Figure 7 , the control block diagram used by the photovoltaic port is shown in Figure 8 .

[0110] The above-mentioned system provided in this embodiment belongs to the same concept as the above-mentioned method embodiment. The specific implementation process thereof is detailed in the method embodiment and will not be repeated here.

[0111] In order to implement the method of the embodiment of the present invention, the embodiment of the present invention also provides a computer program product, which includes computer instructions, and the computer instructions are stored in a computer-readable storage medium. The processor of the computer device reads the computer instructions from the computer-readable storage medium, and the processor executes the computer instructions, so that the computer device performs the steps of the above method.

[0112] Based on the hardware implementation of the above program modules, and in order to implement the method of the embodiment of the present invention, the embodiment of the present invention further provides an electronic device (computer device). Specifically, in one embodiment, the computer device may be a terminal, and its internal structure diagram may be as follows: Fig. 9 As shown. The computer device includes a processor A01, a network interface A02, a display screen A04, an input device A05 and a memory (not shown in the figure) connected through a system bus. Among them, the processor A01 of the computer device is used to provide computing and control capabilities. The memory of the computer device includes an internal memory A03 and a non-volatile storage medium A06. The non-volatile storage medium A06 stores an operating system B01 and a computer program B02. The internal memory A03 provides an environment for the operation of the operating system B01 and the computer program B02 in the non-volatile storage medium A06. The network interface A02 of the computer device is used to communicate with an external terminal through a network connection. When the computer program is executed by the processor A01, the method of any one of the above embodiments is implemented. The display screen A04 of the computer device can be a liquid crystal display screen or an electronic ink display screen, and the input device A05 of the computer device can be a touch layer covered on the display screen, or a key, trackball or touchpad set on the computer device housing, or an external keyboard, touchpad or mouse, etc.

[0113] Those skilled in the art will understand that Fig. 9 The structure shown in the figure is only a block diagram of a part of the structure related to the solution of the present application, and does not constitute a limitation on the computer device to which the solution of the present application is applied. The specific computer device may include more or fewer components than those shown in the figure, or combine certain components, or have a different arrangement of components.

[0114] The device provided by the embodiment of the present invention includes a processor, a memory, and a program stored in the memory and executable on the processor. When the processor executes the program, the method of any one of the above embodiments is implemented.

[0115] Those skilled in the art will appreciate that the embodiments of the present application may be provided as methods, systems, or computer program products. Therefore, the present application may adopt the form of a complete hardware embodiment, a complete software embodiment, or an embodiment combining software and hardware. Moreover, the present application may 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.) containing computer-usable program codes.

[0116] The present 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 application. It should be understood that each process and / or box in the flowchart and / or block diagram, as well as the combination of the processes and / or boxes 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.

[0117] 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.

[0118] 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 The steps for the functions specified in one or more boxes.

[0119] In a typical configuration, a computing device includes one or more processors (CPU), input / output interfaces, network interfaces, and memory.

[0120] The memory may include non-permanent memory in a computer-readable medium, random access memory (RAM) and / or non-volatile memory in the form of read-only memory (ROM) or flash RAM. The memory is an example of a computer-readable medium.

[0121] Computer readable media include permanent and non-permanent, removable and non-removable media that can be implemented by any method or technology to store information. Information can be computer readable instructions, data structures, program modules or other data. Examples of computer storage media include, but are not limited to, phase change memory (PRAM), static random access memory (SRAM), dynamic random access memory (DRAM), other types of random access memory (RAM), read-only memory (ROM), electrically erasable programmable read-only memory (EEPROM), flash memory or other memory technology, compact disk read-only memory (CD-ROM), digital versatile disk (DVD) or other optical storage, magnetic cassettes, magnetic tape disk storage or other magnetic storage devices or any other non-transmission media that can be used to store information that can be accessed by a computing device. As defined herein, computer readable media does not include temporary computer readable media (transitory media), such as modulated data signals and carrier waves.

[0122] It can be understood that the memory of the embodiment of the present invention can be a volatile memory or a non-volatile memory, and can also include both volatile and non-volatile memories. Among them, the non-volatile memory can be a read-only memory (ROM), a programmable read-only memory (PROM), an erasable programmable read-only memory (EPROM), an electrically erasable programmable read-only memory (EEPROM), a magnetic random access memory (FRAM), a flash memory, a magnetic surface memory, an optical disc, or a compact disc read-only memory (CD-ROM); the magnetic surface memory can be a disk memory or a tape memory. The volatile memory can be a random access memory (RAM), which is used as an external cache. By way of example and not limitation, many forms of RAM are available, such as static random access memory (SRAM), synchronous static random access memory (SSRAM), dynamic random access memory (DRAM), synchronous dynamic random access memory (SDRAM), double data rate synchronous dynamic random access memory (DDRSDRAM), enhanced synchronous dynamic random access memory (ESDRAM), synchronous link dynamic random access memory (SLDRAM, SyncLink Dynamic Random Access Memory), and direct RAMbus random access memory (DRRAM, Direct Rambus Random Access Memory).The memories described in the embodiments of the present invention are intended to include, but are not limited to, these and any other suitable types of memories.

[0123] It should also be noted that the terms "include", "comprises" or any other variations thereof are intended to cover non-exclusive inclusion, so that a process, method, commodity or device including a series of elements includes not only those elements, but also other elements not explicitly listed, or also includes elements inherent to such process, method, commodity or device. In the absence of more restrictions, the elements defined by the sentence "comprises a ..." do not exclude the existence of other identical elements in the process, method, commodity or device including the elements.

[0124] The above are only embodiments of the present application and are not intended to limit the present application. For those skilled in the art, the present application may have various changes and variations. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present application should be included within the scope of the claims of the present application.

Claims

1. A coordinated control method for photovoltaic and energy storage microgrids based on SoC improved droop control, characterized in that: A photovoltaic storage microgrid coordinated control system applied to improved droop control based on SoC, the system comprising a plurality of photovoltaic storage microgrid units and a DC load, each of the photovoltaic storage microgrid units comprising a photovoltaic array and an energy storage battery; each of the photovoltaic arrays is connected to a DC bus of the DC load via a DC boost converter, and each of the energy storage batteries is also connected to a DC bus of the DC load via a bidirectional DC-DC converter, the method comprising: Obtaining a DC bus voltage, and determining whether the DC bus voltage is greater than an upper limit threshold of the DC bus voltage; When the DC bus voltage is less than the DC bus voltage upper limit threshold, each photovoltaic storage microgrid unit is controlled to operate in the first mode, the photovoltaic array in the first mode uses the variable step size perturbation observation method to achieve maximum power point tracking, and the energy storage battery in the first mode uses the droop control equation of the secondary voltage compensation to adjust the DC bus voltage; the droop control equation of the secondary voltage compensation is: in, is the DC bus reference voltage, is the DC bus rated voltage, is the secondary voltage compensation, is the droop coefficient, Output current for the bidirectional DC / DC converter of the energy storage battery; is the upper threshold voltage of the DC bus, is the rated value of the discharge current of the energy storage battery; When the DC bus voltage is greater than or equal to the DC bus voltage upper limit threshold, each photovoltaic storage microgrid unit is controlled to operate in a second mode, the photovoltaic array in the second mode uses a voltage stabilization control method to adjust the DC bus voltage, and the energy storage battery in the second mode is in an idle state or a constant charging state; The energy storage battery in the first mode uses a droop control equation of secondary voltage compensation to adjust the DC bus voltage, including: When the remaining battery capacity of the energy storage battery is greater than a preset first threshold, the energy storage battery is in a high charge state, and the droop control equation of the secondary voltage compensation is: in, is the DC bus reference voltage, is the DC bus rated voltage, is the droop coefficient, Output current of the bidirectional DC / DC converter for the energy storage battery, is the upper threshold voltage of the DC bus, is the rated value of the energy storage battery discharge current, is the secondary voltage compensation, is the remaining capacity of the energy storage battery, ; When the remaining battery capacity of the energy storage battery is greater than the preset second threshold value and less than or equal to the preset first threshold value, the energy storage battery is in the rated charge state, and the droop control equation of the secondary voltage compensation is: in, is the DC bus reference voltage, is the DC bus rated voltage, is the droop coefficient, Output current of the bidirectional DC / DC converter for the energy storage battery, is the upper threshold voltage of the DC bus, is the rated value of the energy storage battery discharge current, is the secondary voltage compensation, is the remaining capacity of the energy storage battery, ; When the remaining battery capacity of the energy storage battery is greater than the preset third threshold value and less than or equal to the preset second threshold value, the energy storage battery is in a low charge state, and the droop control equation of the secondary voltage compensation is: in, is the DC bus reference voltage, is the DC bus rated voltage, is the droop coefficient, Output current of the bidirectional DC / DC converter for the energy storage battery, is the upper threshold voltage of the DC bus, is the rated value of the energy storage battery discharge current, is the secondary voltage compensation, is the remaining capacity of the energy storage battery, , is the lower threshold voltage of the DC bus.

2. The photovoltaic energy storage microgrid coordinated control method based on SoC improved droop control according to claim 1 is characterized in that: The energy storage battery in the first mode uses a droop control equation of secondary voltage compensation to adjust the DC bus voltage, including: When the remaining battery capacity of the energy storage battery is less than or equal to a preset third threshold value, the DC bus voltage is adjusted to a lower threshold voltage of the DC bus.

3. The photovoltaic energy storage microgrid coordinated control method based on SoC improved droop control according to claim 2 is characterized in that: The energy storage battery in the first mode also controls the charge and discharge current of the energy storage battery in the following manner, including: When the energy storage battery is in a low charge state, the maximum charging current of the energy storage battery is set to the rated value of the charging current of the energy storage battery, and the maximum discharging current of the energy storage battery is set to: in, is the maximum discharge current, is the rated value of the energy storage battery discharge current, The remaining capacity of the energy storage battery; When the energy storage battery is in a high charge state, the maximum discharge current of the energy storage battery is set to the rated value of the energy storage battery discharge current, and the maximum charge current of the energy storage battery is set to: in, is the maximum charging current, is the rated value of the energy storage battery charging current, The remaining capacity of the energy storage battery; When the energy storage battery is in a rated charge state, the maximum charging current of the energy storage battery is set to the rated value of the charging current of the energy storage battery, and the maximum discharging current of the energy storage battery is set to the rated value of the discharging current of the energy storage battery.

4. The photovoltaic energy storage microgrid coordinated control method based on SoC improved droop control according to claim 3 is characterized in that: The energy storage battery and the photovoltaic array in the first mode also use the following method to distribute power, including: When the maximum power of photovoltaic power generation is less than the DC load power, the photovoltaic array outputs at the maximum power, and the output power of the energy storage battery is the difference between the DC load power and the maximum power output of the photovoltaic array; When the maximum power of the photovoltaic power generation is greater than the DC load power and less than the sum of the DC load power and the maximum charging power of the energy storage battery, the photovoltaic array outputs at the maximum power, and the energy storage battery absorbs power equal to the difference between the maximum power output by the photovoltaic array and the DC load power.

5. The photovoltaic energy storage microgrid coordinated control method based on SoC improved droop control according to claim 4 is characterized in that: The energy storage battery and the photovoltaic array in the second mode also use the following method to distribute power, including: When the maximum power of the photovoltaic power generation is greater than the sum of the DC load power and the maximum charging power of the energy storage battery, the photovoltaic array output power is the sum of the DC load and the energy storage battery absorption power.

6. The photovoltaic energy storage microgrid coordinated control method based on SoC improved droop control according to claim 1 is characterized in that: The photovoltaic array in the second mode uses a voltage stabilization control method to regulate the DC bus voltage, including: In the second mode, the PV array controls the DC bus voltage to be an upper threshold voltage of the DC bus.

7. A photovoltaic storage microgrid coordinated control system based on SoC improved droop control, characterized in that: The system includes a plurality of photovoltaic storage microgrid units and DC loads, each of which includes a photovoltaic array and an energy storage battery; each photovoltaic array is connected to the DC bus of the DC load via a DC boost converter, and each energy storage battery is also connected to the DC bus of the DC load via a bidirectional DC-DC converter; When the DC bus voltage is less than the DC bus voltage upper limit threshold, each of the photovoltaic storage microgrid units operates in the first mode. The photovoltaic array in the first mode uses the variable step size perturbation observation method to achieve maximum power point tracking, and the energy storage battery in the first mode uses the droop control equation of the secondary voltage compensation to adjust the DC bus voltage; the droop control equation of the secondary voltage compensation is: in, is the DC bus reference voltage, is the DC bus rated voltage, is the secondary voltage compensation, is the droop coefficient, Output current for the bidirectional DC / DC converter of the energy storage battery; is the upper threshold voltage of the DC bus, is the rated value of the discharge current of the energy storage battery; Each of the photovoltaic and energy storage microgrid units operates in a second mode when the DC bus voltage is greater than or equal to the DC bus voltage upper limit threshold, the photovoltaic array in the second mode uses voltage stabilization control to adjust the DC bus voltage, and the energy storage battery in the second mode is in an idle state or a constant charging state; The energy storage battery in the first mode uses a droop control equation of secondary voltage compensation to adjust the DC bus voltage, including: When the remaining battery capacity of the energy storage battery is greater than a preset first threshold, the energy storage battery is in a high charge state, and the droop control equation of the secondary voltage compensation is: in, is the DC bus reference voltage, is the DC bus rated voltage, is the droop coefficient, Output current of the bidirectional DC / DC converter for the energy storage battery, is the upper threshold voltage of the DC bus, is the rated value of the energy storage battery discharge current, is the secondary voltage compensation, is the remaining capacity of the energy storage battery, ; When the remaining battery capacity of the energy storage battery is greater than the preset second threshold value and less than or equal to the preset first threshold value, the energy storage battery is in the rated charge state, and the droop control equation of the secondary voltage compensation is: in, is the DC bus reference voltage, is the DC bus rated voltage, is the droop coefficient, Output current of the bidirectional DC / DC converter for the energy storage battery, is the upper threshold voltage of the DC bus, is the rated value of the energy storage battery discharge current, is the secondary voltage compensation, is the remaining capacity of the energy storage battery, ; When the remaining battery capacity of the energy storage battery is greater than the preset third threshold value and less than or equal to the preset second threshold value, the energy storage battery is in a low charge state, and the droop control equation of the secondary voltage compensation is: in, is the DC bus reference voltage, is the DC bus rated voltage, is the droop coefficient, Output current of the bidirectional DC / DC converter for the energy storage battery, is the upper threshold voltage of the DC bus, is the rated value of the energy storage battery discharge current, is the secondary voltage compensation, is the remaining capacity of the energy storage battery, , is the lower threshold voltage of the DC bus.

8. The photovoltaic energy storage microgrid coordinated control system based on SoC improved droop control according to claim 7 is characterized in that: The energy storage battery in the first mode uses a droop control equation of quadratic voltage compensation to regulate the DC bus voltage through a voltage and current controller.

9. The photovoltaic energy storage microgrid coordinated control system based on SoC improved droop control according to claim 7 is characterized in that: The photovoltaic array in the second mode regulates the DC bus voltage using a voltage and current controller using a voltage regulation control method.

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