Water lifting system based on off-grid wind-solar power generation integrated converter and control method

Abstract

The invention provides a water lifting system based on an off-grid type wind-solar power generation integrated converter and a control method, and relates to the field of converters, the system comprises a solar power generation module, a wind power generation module, the wind-solar power generation integrated converter and a water lifting module, the solar power generation module and the wind power generation module are electrically connected with the input end of the wind-solar power generation integrated converter, and the output end of the wind-solar power generation integrated converter is electrically connected with the water lifting module; the wind and light power generation integrated converter comprises three switch channels, the solar power generation module and the wind power generation module are electrically connected with the water lifting module through the three switch channels, and the wind and light power generation integrated converter has the advantages that wind-light-water lifting integration is achieved, the topological structure of the wind and light power generation integrated converter is simplified, and it can be guaranteed that wind and light water lifting is stable, reliable and efficient.

Description

Technical Field

[0001] The present invention relates to the field of converters, and in particular to a water pumping system and a control method based on an off-grid wind-solar power generation integrated converter. Background Art

[0002] Water is the most lacking in places with inconvenient transportation and difficult line laying, such as border posts and remote pastoral areas. Most of the water used in border posts is transported back by border guards from streams dozens of kilometers away; herders on the grassland cannot live without water all year round. In winter, they will break the ice on the river surface and take the ice home to use after melting. In summer, they will also fetch water from the river. Most of the current herders use diesel generators to drive water pumps to draw water from deep wells, but this method is too expensive. Therefore, the present invention uses local wind energy and solar energy and other natural resources to generate electricity and then drive water pumps to draw water to solve the problem of long-term stable and reliable water extraction for households. Solar energy and wind energy are relatively mature energy sources among renewable energy sources, and they have strong complementarity in time and region. It is mainly reflected in the strong light and weak wind during the day, weak light but strong wind at night; strong light and weak wind in summer, strong light but strong wind in winter. Therefore, the rational use of local wind energy and solar energy for complementary power generation and water extraction to solve the problem of large-scale water use by users, such as pasture irrigation and livestock drinking water, is the best choice.

[0003] Most of the existing wind-solar hybrid water pumping devices use three converters for coordinated control. The power generated by the photovoltaic module is boosted to the voltage level required by the DC bus through DC-DC controllable conversion, and the power generated by the wind turbine is rectified to the voltage level required by the DC bus through AC-DC controllable rectification. The DC bus then provides power through the inverter to provide controllable AC power to the water pump for water pumping. This structure requires three converters, which need to be coordinated and controlled, use more power devices, and have a high investment cost.

[0004] Therefore, a water pumping system and control method based on an off-grid wind-solar integrated power generation converter is needed to achieve wind-solar-water pumping integration, which not only simplifies the topological structure of the wind-solar complementary converter, but also ensures that the wind-solar water pumping can operate stably, reliably and efficiently. Summary of the invention

[0005] The present invention provides a water pumping system based on an off-grid wind-solar integrated power generation converter, comprising a solar power generation module, a wind power generation module, a wind-solar integrated power generation converter and a water pumping module, wherein the solar power generation module and the wind power generation module are electrically connected to the input end of the wind-solar integrated power generation converter, and the output end of the wind-solar integrated power generation converter is electrically connected to the water pumping module; the wind-solar integrated power generation converter comprises three switch channels, and the solar power generation module and the wind power generation module are electrically connected to the water pumping module through the three switch channels.

[0006] Further, the three switch channels include a first switch channel, a second switch channel and a third switch channel, wherein the first switch channel includes a first switch tube, a second switch tube and a third switch tube connected in parallel, the second switch channel includes a fourth switch tube, a fifth switch tube and a sixth switch tube connected in parallel, the third switch channel includes a seventh switch tube, an eighth switch tube and a ninth switch tube connected in parallel, the first switch tube, the fourth switch tube and the seventh switch tube are connected in series to form a first bridge arm, the second switch tube, the fifth switch tube and the eighth switch tube are connected in series to form a second bridge arm, and the third switch tube, the sixth switch tube and the ninth switch tube are connected in series to form a third bridge arm; the positive electrode of the polar capacitor is electrically connected to the collectors of the first switch tube, the second switch tube and the third switch tube, and the negative electrode of the polar capacitor is electrically connected to the emitters of the first switch tube, the second switch tube and the third switch tube; The solar power generation module is electrically connected to one end of the inductor, the other end of the inductor is electrically connected to the anodes of the first diode, the second diode and the third diode connected in parallel, the cathode of the first diode is electrically connected to the connection node of the first switch tube and the fourth switch tube, the cathode of the second diode is electrically connected to the connection node of the second switch tube and the fifth switch tube, and the cathode of the third diode is electrically connected to the connection node of the third switch tube and the sixth switch tube; the water pumping module is electrically connected to the connection node of the first switch tube and the fourth switch tube, the connection node of the second switch tube and the fifth switch tube, and the connection node of the third switch tube and the sixth switch tube; the wind power generation module is electrically connected to the connection node of the fourth switch tube and the seventh switch tube, the connection node of the fifth switch tube and the eighth switch tube, and the connection node of the sixth switch tube and the ninth switch tube.

[0007] Furthermore, the integrated wind-solar power generation converter also includes a switch control component, which is used to: determine the current operating condition, wherein the current operating condition is one of light but no wind, wind but no light, and wind and light; and control the states of the three switch channels according to the current operating condition.

[0008] Furthermore, the switch control component controls the states of the three switch channels according to the current operating conditions, including: when the current operating condition is light but no wind, controlling the seventh switch tube, the eighth switch tube and the ninth switch tube to be in the on state, and controlling the switch states of the first switch tube, the second switch tube and the third switch tube to complement the switch states of the fourth switch tube, the fifth switch tube and the sixth switch tube, respectively.

[0009] Furthermore, the switch control component controls the states of the three switch channels according to the current working conditions, including: when the current working condition is that there is light but no wind, the seventh switch tube, the eighth switch tube and the ninth switch tube are controlled to be in the on state; the target port voltage is obtained according to the port voltage and port current of the solar power generation module; the target port voltage is closed-loop controlled to obtain a DC bias signal injected into the modulation wave; on the basis of the asynchronous motor vector control, the q-axis current of the asynchronous motor of the water pumping module is adjusted to control the DC side voltage in a closed loop, and the asynchronous motor is obtained after the current loop output is inversely transformed by 3 / 2. A modulation signal of the motor; based on the modulation signal of the asynchronous motor, a tripled harmonic signal is obtained; a DC bias signal, the modulation signal of the asynchronous motor and the tripled harmonic signal are superimposed to obtain the modulation signals of the first switch tube, the second switch tube and the third switch tube; the modulation signals of the first switch tube, the second switch tube and the third switch tube are compared with the triangular carrier operation to control the switching states of the first switch tube, the second switch tube and the third switch tube, and the switching states of the first switch tube, the second switch tube and the third switch tube are controlled to complement the switching states of the fourth switch tube, the fifth switch tube and the sixth switch tube respectively.

[0010] Further, the switch control component controls the states of the three switch channels according to the current working condition, including: when the current working condition is wind without solar power or wind with solar power, controlling the switch states of the first bridge arm, the second bridge arm and the third bridge arm according to the following first constraint condition: , in, The first bridge arm The switch state of the switch tube is When the switch is in the on state, ,otherwise , The second bridge arm The switching state of the switch tube, The third bridge arm The switching state of the switch tube, .

[0011] Furthermore, the modulation reference waves of the first switch channel and the third switch channel are: , in, is the modulation reference wave of the first switch channel, is the modulation wave reference amplitude of the first switch channel, is the angular frequency of the modulation reference wave of the first switching channel, is the initial phase of the modulation reference wave of the first switching channel, is the offset of the first switch channel, is the modulation reference wave of the third switch channel, is the modulation wave reference amplitude of the third switch channel, is the angular frequency of the modulation reference wave of the third switching channel, The initial phase of the modulation reference wave of the third switching channel, is the offset of the third switch channel.

[0012] Further, the offset of the first switch channel, the offset of the third switch channel, the reference amplitude of the modulation wave of the first switch channel, and the reference amplitude of the modulation wave of the third switch channel satisfy the following second constraint condition: , .

[0013] Furthermore, the switch control component controls the states of the three switch channels according to the current working condition, including: when the current working condition is windy but without light, the states of the three switch channels are controlled for the purpose of achieving maximum power output operation of the wind turbine.

[0014] The present invention provides a water lifting control method based on an off-grid wind-solar integrated power generation converter, which is applied to the above-mentioned water lifting system based on an off-grid wind-solar integrated power generation converter, including: determining a current operating condition, wherein the current operating condition is one of light but no wind, wind but no light, and wind and light; when the current operating condition is light but no wind, controlling the seventh switch tube, the eighth switch tube, and the ninth switch tube to be in a conducting state, and controlling the switching states of the first switch tube, the second switch tube, and the third switch tube to be complementary to the switching states of the fourth switch tube, the fifth switch tube, and the sixth switch tube, respectively; when the current operating condition is wind but no light or wind and light, controlling the switching states of the first bridge arm, the second bridge arm, and the third bridge arm according to the first constraint condition and the second constraint condition.

[0015] Compared with the prior art, the water pumping system and control method based on the off-grid wind-solar power generation integrated converter provided by the present invention have at least the following beneficial effects: 1. Connecting the electricity generated by wind and solar energy and the water pump to a converter reduces the number of power devices, reduces energy loss, and makes full use of the complementary characteristics of the two renewable energy sources to achieve efficient use of energy. The system can provide stable power supply under the conditions of wind but no light, light but no wind, and wind and light, ensuring the continuous operation of the water pumping system. It can generate electricity from wind energy at night and on rainy days when there is no sunlight, and from solar energy on sunny days. When there is both wind and sun, both can play a role at the same time, realizing the all-weather power generation function, which is more economical, scientific and practical than using wind turbines and solar energy alone.

[0016] 2. Through integrated design, the number of converters is reduced, thereby reducing system costs, simplifying system structure, and improving overall system reliability.

[0017] 3. Make full use of wind energy and solar energy, two clean and renewable energy sources, to reduce dependence on traditional fossil energy, reduce carbon emissions and environmental pollution, and have significant environmental benefits. In addition, the present invention can reasonably configure the system capacity according to the user's power load and resource conditions, which can ensure the reliability of the system power supply and reduce the cost of the power generation system.

[0018] 4. Able to realize energy conversion and management between different ports, with high efficiency and wide working range. BRIEF DESCRIPTION OF THE DRAWINGS

[0019] This specification will be further described in the form of exemplary embodiments, which will be described in detail by the accompanying drawings. These embodiments are not restrictive, and in these embodiments, the same number represents the same structure, wherein: Figure 1 It is a module schematic diagram of a water pumping system based on an off-grid wind-solar power generation integrated converter according to some embodiments of this specification; Figure 2 It is a structural schematic diagram of a water pumping system based on an off-grid wind-solar power generation integrated converter according to some embodiments of this specification; Figure 3 is a schematic diagram of an equivalent circuit under light-on but no wind conditions according to some embodiments of this specification; Figure 4 This is a circuit diagram of the "011" state operation under the condition of light but no wind as shown in some embodiments of this specification; Figure 5 This is a working circuit diagram of the "001" state under the condition of light but no wind as shown in some embodiments of this specification; Figure 6 This is a working circuit diagram of the "000" state under the condition of light but no wind as shown in some embodiments of this specification; Figure 7 This is a circuit diagram of the "111" state operation under the condition of light but no wind as shown in some embodiments of this specification; Figure 8 It is a control strategy block diagram under the condition of light but no wind shown in some embodiments of this specification; Fig. 9 is a schematic diagram of an equivalent circuit under windy but no-light conditions according to some embodiments of this specification; Fig.10 It is a schematic diagram of the working circuit of the combination 9 under windy but no-light conditions shown in some embodiments of this specification; Fig.11 It is a schematic diagram of the working circuit of the combination 15 under windy but no-light conditions shown in some embodiments of this specification; Fig.12 is a schematic diagram of a modulation waveform of a switch tube under windy but no solar conditions according to some embodiments of this specification; Fig.13 It is a control strategy block diagram under windy but no-light conditions according to some embodiments of this specification; Fig.14 It is a schematic diagram of the working circuit of the combination 9 under windy but no-light conditions shown in some embodiments of this specification; Fig.15 It is a schematic diagram of the working circuit of the combination 15 under windy but no-light conditions shown in some embodiments of this specification; Fig.16 It is a schematic diagram of a simulated waveform under a light-on but no-wind condition according to some embodiments of this specification; Fig.17 is a schematic diagram of a simulated waveform under windy but sunless working conditions according to some embodiments of this specification; Fig.18 is a schematic diagram of a simulated waveform under windy and solar conditions according to some embodiments of this specification; Fig.19 It is a flow chart of a water lifting control method based on an off-grid wind-solar power generation integrated converter according to some embodiments of this specification; Fig. 20 It is a flow chart of a water lifting control method based on an off-grid wind-solar power generation integrated converter as shown in some embodiments of this specification. DETAILED DESCRIPTION

[0020] In order to more clearly illustrate the technical solutions of the embodiments of this specification, the following is a brief introduction to the drawings required for the description of the embodiments. Obviously, the drawings described below are only some examples or embodiments of this specification. For ordinary technicians in this field, this specification can also be applied to other similar scenarios based on these drawings without creative work. Unless it is obvious from the language environment or otherwise explained, the same reference numerals in the figures represent the same structure or operation.

[0021] Figure 1 is a schematic diagram of a module of a water pumping system based on an off-grid wind-solar integrated converter according to some embodiments of this specification, such as Figure 1 As shown, the water pumping system based on the off-grid wind-solar integrated power generation converter may include a solar power generation module, a wind power generation module, a wind-solar integrated power generation converter and a water pumping module.

[0022] The solar power generation module may include a photovoltaic array, the wind power generation module may include a wind wheel and a permanent magnet synchronous motor, and the water pumping module may include an asynchronous motor.

[0023] Figure 2 is a schematic diagram of a water pumping system based on an off-grid wind-solar integrated power generation converter according to some embodiments of this specification, such as Figure 2 As shown, the integrated wind-solar power generation converter includes three switch channels, and the solar power generation module and the wind power generation module are electrically connected to the water pumping module through the three switch channels.

[0024] like Figure 2 As shown, the three switch channels include a first switch channel, a second switch channel and a third switch channel, wherein the first switch channel includes a first switch tube G11, a second switch tube G12 and a third switch tube G13 connected in parallel, the second switch channel includes a fourth switch tube G21, a fifth switch tube G22 and a sixth switch tube G23 connected in parallel, and the third switch channel includes a seventh switch tube G31, an eighth switch tube G32 and a ninth switch tube G33 connected in parallel. The first switch tube G11, the fourth switch tube G21 and the seventh switch tube G31 are connected in series to form a first bridge arm, the second switch tube G12, the fifth switch tube G22 and the eighth switch tube G32 are connected in series to form a second bridge arm, and the third switch tube G13, the sixth switch tube G23 and the ninth switch tube G33 are connected in series to form a third bridge arm.

[0025] like Figure 2 As shown, the positive electrode of the polarity capacitor C is electrically connected to the collectors of the first switch tube G11, the second switch tube G12 and the third switch tube G13, and the negative electrode of the polarity capacitor C is electrically connected to the emitters of the first switch tube G11, the second switch tube G12 and the third switch tube G13.

[0026] like Figure 2 As shown, the solar power generation module is electrically connected to one end of the inductor L1, the other end of the inductor L1 is electrically connected to the anodes of the first switch tube G11, the second switch tube G12 and the third switch tube G13 connected in parallel, the cathode of the first diode D1 is electrically connected to the connection node of the first switch tube G11 and the fourth switch tube G21, the cathode of the second diode D2 is electrically connected to the connection node of the second switch tube G12 and the fifth switch tube G22, and the cathode of the third diode D3 is electrically connected to the connection node of the third switch tube G13 and the sixth switch tube G13.

[0027] like Figure 2 As shown, the water pumping module is electrically connected to a connection node between the first switch tube G11 and the fourth switch tube G21 , a connection node between the second switch tube G21 and the fifth switch tube G22 , and a connection node between the third switch tube G13 and the sixth switch tube G23 .

[0028] like Figure 2 As shown, the wind power generation module is electrically connected to the connection node between the fourth switch tube G21 and the seventh switch tube G31, the connection node between the fifth switch tube G22 and the eighth switch tube G32, and the connection node between the sixth switch tube G23 and the ninth switch tube G33.

[0029] The wind-solar integrated converter also includes a switch control component for: Determine a current working condition, wherein the current working condition is one of: solar power but no wind, wind but no solar power, and wind and solar power; Control the status of the three switch channels according to the current working conditions.

[0030] Specifically, the three working conditions are: Working condition 1: Realize independent wind power generation and water pumping under the condition of sunlight but no wind.

[0031] Working condition 2: Realize independent photovoltaic power generation and water pumping under the condition of wind but no sunlight.

[0032] Working condition three: wind-solar complementary power generation and water pumping are achieved under the condition of wind and solar power.

[0033] By designing corresponding modulation strategies, it is possible to achieve independent wind power generation and water pumping under conditions with wind but no sun, independent photovoltaic power generation and water pumping under conditions with sun but no wind, and wind-solar complementary power generation and water pumping under conditions with wind and sun, thereby meeting the requirements of stable and efficient water pumping operation under different working conditions and realizing the integrated application of wind-solar-water pumping of the three-port converter.

[0034] In some embodiments, the switch control component controls the states of the three switch channels according to the current working conditions, including: Figure 3 Schematic diagram of an equivalent circuit under the condition of light without wind according to some embodiments of this specification. Figure 3 As shown, when the current working condition is that there is light but no wind, the seventh switch tube G31, the eighth switch tube G32 and the ninth switch tube G33 are controlled to be in the on state, and the switch states of the first switch tube G11, the second switch tube G12 and the third switch tube G13 are controlled to complement the switch states of the fourth switch tube G21, the fifth switch tube G22 and the sixth switch tube G23 respectively.

[0035] Figure 4 This is a circuit diagram of the "011" state operation under the condition of light but no wind as shown in some embodiments of this specification. Figure 5 This is a working circuit diagram of the "001" state under the condition of light but no wind shown in some embodiments of this specification, Figure 6 This is a circuit diagram of the "000" state under the condition of light but no wind as shown in some embodiments of this specification, Figure 7This is a "111" state working circuit diagram under the condition of light but no wind as shown in some embodiments of this specification, Figure 4-Figure 7 In the figure, the solid line indicates that the switch tube is in the on state, and the dotted line indicates that the switch tube is in the off state. The on state of the first switch tube G11, the second switch tube G12 and the third switch tube G13 is set to "1", and the off state is set to "0". When the circuit is working normally, the first switch tube G11, the second switch tube G12 and the third switch tube G13 have eight switch states, namely: "000", "001", "010", "011", "100", "101", "110", and "111". In its working state, the functions of the "110" and "101" states are the same as those of the "011" state; the functions of the "100" and "010" states are the same as those of the "001" state. At this time, there are only four working states, namely "011", "001", "000" and "111". As Figure 4 As shown, in the "011" state, the solar power generation module charges the inductor L1 through the first diode D1, and the capacitor C discharges at the same time, and drives the water pump to pump water through the second switch tube G12, the third switch tube G13, and the three switch tubes G21; Figure 5 As shown, in the "001" state, the photovoltaic module charges the inductor L1 through the first diode D1 and the second diode D2, and the capacitor C is discharged at the same time, and the water pump is driven to pump water through the third switch tube G13, the fourth switch tube G21, and the fifth switch tube G22; Figure 6 As shown in FIG. 1 , in the “000” state, only the photovoltaic module charges the inductor L1 through the first diode D1, the second diode D2, and the third diode D3; Figure 7 As shown, in the "111" state, the photovoltaic module charges the capacitor C through the inductor L1, the first diode D1, the second diode D2, the third diode D and the first switch tube G11, the second switch tube G12 and the third switch tube G13. It can be seen that the "001", "010", "011", "100", "101" and "110" states are all the electric energy generated by the photovoltaic module charging the inductor L1 through the first diode D1, the second diode D2 and the third diode D3, and at the same time, the capacitor C discharges and inverts the electric energy to the AC water pump to drive the water pump to pump water. The working state of the "000" switch tube is that the photovoltaic module charges the inductor L1, and only the "111" switch tube state is to charge the capacitor C with the energy stored in the inductor L1 through the diode.

[0036] Under this working condition, it is necessary to ensure that the seventh switch tube G31, the eighth switch tube G32 and the ninth switch tube G33 are always in the on state, and then the first switch tube G11, the second switch tube G12 and the third switch tube G13, the fourth switch tube G21, the fifth switch tube G22 and the sixth switch tube G23 are modulated according to eight switch states to achieve independent photovoltaic power generation and water pumping in the case of light but no wind. When using PWM modulation, firstly, the seventh switch tube G31, the eighth switch tube G32 and the ninth switch tube G33 are turned on, ensuring that the seventh switch tube G31, the eighth switch tube G32 and the ninth switch tube G33 are always in the on state. Then, the modulation wave of the first switch tube G11, the second switch tube G12 and the third switch tube G13 is compared with the carrier wave. When the modulation wave of the first switch tube G11, the second switch tube G12 and the third switch tube G13 is greater than the carrier wave, a high level is output, and the first switch tube G11, the second switch tube G12 and the third switch tube G13 are turned on. Otherwise, the first switch tube G11, the second switch tube G12 and the third switch tube G13 are turned off. The switch control signals of the fourth switch tube G21, the fifth switch tube G22 and the sixth switch tube G23 are obtained by inverting the switch control signals of the first switch tube G11, the second switch tube G12 and the third switch tube G13.

[0037] In some embodiments, the switch control component controls the states of the three switch channels according to the current working conditions, including: When the current working condition is that there is light but no wind, the seventh switch tube G31, the eighth switch tube G32 and the ninth switch tube G33 are controlled to be in the on state; According to the port voltage and port current of the solar power generation module, a target port voltage is obtained; Performing closed-loop control on the target port voltage to obtain a DC bias signal injected into the modulation wave; On the basis of asynchronous motor vector control, the q-axis current of the asynchronous motor of the water pumping module is adjusted to control the DC side voltage in a closed loop, and the modulation signal of the asynchronous motor is obtained after the output of the current loop is inversely transformed by 3 / 2. Based on the modulation signal of the asynchronous motor, a triple frequency harmonic signal is obtained; Superimposing the DC bias signal, the modulation signal of the asynchronous motor and the triple frequency harmonic signal to obtain the modulation signals of the first switch tube G11, the second switch tube G12 and the third switch tube G13; The modulation signals of the first switch tube G11, the second switch tube G12 and the third switch tube G13 are compared with the triangular carrier operation to control the switching states of the first switch tube G11, the second switch tube G12 and the third switch tube G13, and the switching states of the first switch tube G11, the second switch tube G12 and the third switch tube G13 are controlled to complement the switching states of the fourth switch tube G21, the fifth switch tube G22 and the sixth switch tube G23 respectively.

[0038] Figure 8 This is a control strategy block diagram for a working condition with light but no wind as shown in some embodiments of this specification, such as Figure 8 As shown, when only the photovoltaic array is working effectively on the power supply side, the system is in an independent photovoltaic power generation operation mode. At this time, a circuit breaker is required to separate the wind turbine from the system and keep the seventh switch tube G31, the eighth switch tube G32 and the ninth switch tube G33 in the wind-solar power generation integrated converter in the on state and always in a closed state. At this time, a single-stage two-stage control structure is adopted. The single-stage refers to a single intermediate converter topology. The two stages are composed of the photovoltaic power supply side and the asynchronous motor load measurement. The control method is implemented independently. In this control strategy, first, the port voltage U of the solar power generation module is input to the maximum power point tracking (MPPT) control unit of the solar power generation module. PV and current I PV , the port voltage required for the maximum power operation of the photovoltaic cell is obtained through calculation, and then the port voltage is closed-loop controlled to obtain the DC bias signal injected into the modulation wave; secondly, on the basis of the asynchronous motor vector control, the asynchronous motor control q-axis current i is adjusted sq , to close the loop and control the DC side voltage U dc , after the inverse 3 / 2 transformation of the current loop output, the modulation signal for asynchronous motor control is obtained; finally, by analyzing the modulation signal of the asynchronous motor, a corresponding triple frequency harmonic signal is obtained. By superimposing the DC bias signal, the asynchronous motor modulation signal and the triple frequency harmonic signal, the modulation signals of the first switch tube G11, the second switch tube G12 and the third switch tube G13 are obtained at this time, and compared with the triangular carrier operation, the switching signals of the first switch tube G11, the second switch tube G12 and the third switch tube G13 are obtained at this time.

[0039] Fig. 20 is a flow chart of a water pumping control method based on an off-grid wind-solar power generation integrated converter according to some embodiments of this specification, such as Fig. 20 As shown, specifically, MPPT uses the optimized conductivity increment method to obtain that the i-th step size is the calculation result of the absolute value of the previous step size plus or minus the current step size coefficient multiplied by dP / dU, that is, the change in the previous step size plus or minus the step size. Suppose the variable step size coefficient is , the step size change is , then the step length The expression is: , , in, is the step size of the i-th iteration, is the step size of the i-1th iteration, is the variable step size coefficient of the i-th iteration, It is the reciprocal of power P to voltage U. is the step size change, is the initial adjustment value of the variable step size coefficient, is the number of iterations.

[0040] The mathematical model equation of the asynchronous motor in the dq coordinate system can be transformed, and the voltage equation is: , in, is the d-axis component of the stator voltage, is the stator resistance, is the d-axis component of the stator current, is the d-axis component of the stator flux, is the synchronous angular velocity, is the q-axis component of the stator flux, is the q-axis component of the stator current, is the q-axis component of the stator voltage, is the d-axis component of the rotor voltage, is the rotor flux, is the q-axis component of the rotor voltage, is the rotor angular velocity, is the d-axis component of the rotor current, is the q-axis component of the rotor current.

[0041] The magnetic flux equation is: , in, is the stator-rotor mutual inductance, is the stator self-inductance, is the rotor self-inductance, is the d-axis component of the rotor flux, is the q-axis component of the rotor flux.

[0042] After simplification, the rotor current can be obtained: , Finally, it is simplified to: , The torque equation is: , in, is the leakage inductance coefficient, are the rotor time constant and the stator time constant, is the pole pair number, is the electromagnetic torque.

[0043] From the above, we can see that after adopting rotor magnetic field orientation, Depend on Decide; Depend on and When the asynchronous motor runs below the rated speed, it can be controlled Make the rotor flux Keep constant, on this basis Depend on The only decision is thus made through , By limiting them separately, the asynchronous motor can be controlled.

[0044] The control of electromagnetic torque of asynchronous motor is the control of active power of motor. In off-grid system, in order to achieve power balance of the system, the asynchronous motor can be used to consume the active power generated by the system. Based on this, the DC voltage can be stabilized by controlling the asynchronous motor isq, thereby balancing the system power.

[0045] In some embodiments, the switch control component controls the states of the three switch channels according to the current working conditions, including: When the current working condition is wind without solar power or wind with solar power, the switch states of the first bridge arm, the second bridge arm and the third bridge arm are controlled according to the following first constraint condition: , in, is the switching state of the jth switch tube of the first bridge arm. When the jth switch tube of the first bridge arm is in the on state, ,otherwise , is the switching state of the jth switch tube of the second bridge arm, is the switching state of the jth switch tube of the third bridge arm, , that is, only two switching tubes can be turned on in each bridge arm at the same time.

[0046] The on state of the switch tube is recorded as "1", and the off state is recorded as "0". Therefore, there are three combinations of the three switch tube states in each bridge arm, namely "110", "101", and "011". There are 27 combinations of the three bridge arms, as shown in Table 1.

[0047]

[0048] Fig. 9 is a schematic diagram of an equivalent circuit under windy but no-light conditions according to some embodiments of this specification, such as Fig. 9As shown, in the working condition 2 when there is wind but no sun, the first switch tube G11, the second switch tube G12, the third switch tube G13, the fourth switch tube G21, the fifth switch tube G22 and the sixth switch tube G23 constitute the upper converter, and the fourth switch tube G21, the fifth switch tube G22 and the sixth switch tube G23, the seventh switch tube G31, the eighth switch tube G32 and the ninth switch tube G33 constitute the lower converter. From the switch combination state analysis in Table 1, it can be seen that combination 1 to combination 8 meet the switch tube conduction conditions under the working condition 1 when there is sun but no wind. Fig.10 is a schematic diagram of the working circuit of the combination 9 under windy but no-light conditions according to some embodiments of this specification, Fig.11 is a schematic diagram of the working circuit of the combination 15 under windy but no light conditions shown in some embodiments of this specification, such as Fig.10 and Fig.11 As shown, the conduction conditions of the switch tubes of combination 9 to combination 27 can meet the working condition 2.

[0049] Under the condition of wind but no sun, the modulation reference wave of the first switch tube G11, the second switch tube G12 and the third switch tube G13 is The modulation reference wave of the seventh switch tube G31, the eighth switch tube G32 and the ninth switch tube G33 is , Mc is a triangular carrier. and The modulation signals of the fourth switch tube G21, the fifth switch tube G22 and the sixth switch tube G23 are respectively compared with Mc, and the modulation signals of the fourth switch tube G21, the fifth switch tube G22 and the sixth switch tube G23 are generated through an exclusive OR logic operation. However, in order to ensure that the modulation signals of the first switch tube G11, the second switch tube G12 and the third switch tube G13 and the seventh switch tube G31, the eighth switch tube G32 and the ninth switch tube G33 do not overlap, it is necessary to ensure that the modulation signals of the first switch tube G11, the second switch tube G12 and the third switch tube G13 are always greater than or equal to the modulation signals of the seventh switch tube G31, the eighth switch tube G32 and the ninth switch tube G33. and Add offset m respectively 1 、m 2 .

[0050] In some embodiments, the modulation reference waves of the first switch channel and the third switch channel are: , in, is the modulation reference wave of the first switch channel, is the modulation wave reference amplitude of the first switch channel, is the angular frequency of the modulation reference wave of the first switching channel, is the initial phase of the modulation reference wave of the first switching channel, is the offset of the first switch channel, is the modulation reference wave of the third switch channel, is the reference amplitude of the modulation wave of the third switch channel, is the angular frequency of the modulation reference wave of the third switching channel, is the initial phase of the modulation reference wave of the third switching channel, is the offset of the third switch channel.

[0051] in, and Divide the carrier equally so that The modulation interval is [0, 1], The modulation interval is [-1, 0], the offset of the first switch channel, the offset of the third switch channel, the modulation wave reference amplitude of the first switch channel and the modulation wave reference amplitude of the third switch channel meet the following second constraint condition: , .

[0052] Fig.12 is a schematic diagram of a modulation waveform of a switch tube under windy but no solar conditions according to some embodiments of this specification, such as Fig.12 As shown in FIG. 1 , the waveform required for the water pump to lift water is normalized, and after the offset correction, it is satisfied that it is in the modulation interval of [0, 1] as the modulation waveform of the first switch tube G11, the second switch tube G12 and the third switch tube G13, and then compared with the triangular carrier. When it is greater than the carrier, the first switch tube G11, the second switch tube G12 and the third switch tube G13 are turned on, otherwise they are turned off; similarly, the seventh switch tube G31, the eighth switch tube G32 and the ninth switch tube G33 obtain the modulation waveform in the same way. The shape is formed and made within the interval of [-1, 0], and then compared with the triangular carrier. When it is less than the carrier, the seventh switch tube G31, the eighth switch tube G32 and the ninth switch tube G33 are turned on, otherwise they are turned off; the on-off signals of the fourth switch tube G21, the fifth switch tube G22 and the sixth switch tube G23 are obtained by the on-off signals of the first switch tube G11, the second switch tube G12 and the third switch tube G13 and the on-off signals of the seventh switch tube G31, the eighth switch tube G32 and the ninth switch tube G33 through exclusive OR operation.

[0053] In some embodiments, the switch control component controls the states of the three switch channels according to the current working conditions, including: When the current working condition is that there is wind but no sun, the states of the three switch channels are controlled for the purpose of achieving maximum power output of the wind turbine.

[0054] Fig.13 This is a control strategy block diagram for wind-free working conditions according to some embodiments of this specification, such as Fig.13As shown, similar to the control target under the condition of solar power but no wind, the purpose under the condition of solar power but no wind is still to achieve the maximum power output of the wind turbine. The power output of the wind turbine is related to the tip speed ratio. When the wind speed is determined, the tip speed ratio is related to the speed of the wind turbine. That is, it is only necessary to adjust the speed of the wind turbine to a certain value to achieve the maximum power operation of the wind turbine. Both permanent magnet synchronous motors and asynchronous motors are rotating elements. Unlike the DC control of solar power generation modules, the control methods of permanent magnet synchronous motors and asynchronous motors under the condition of solar power but no wind are both AC control with variable voltage and frequency. The control of asynchronous motors can be consistent with the control of asynchronous motors under the condition of solar power but no wind, that is, on the basis of vector control, by controlling the asynchronous motors, the power of the asynchronous motors can be controlled by the AC control of the motors. sq To achieve the control of the DC capacitor voltage, so as to balance the system power. Since the permanent magnet synchronous motor has no slip frequency, the system decoupling is more convenient, so its control is simpler than that of the asynchronous motor, so it can still control the speed of the fan by controlling the q-axis current on the basis of vector control, thereby realizing the control of the fan power. Through the closed-loop control, the voltage waveform required by the water pump is output, and the modulation signals of the first switch tube G11, the second switch tube G12 and the third switch tube G13 of the converter are obtained by comparing with the triangular carrier, and the modulation signals of the seventh switch tube G31, the eighth switch tube G32 and the ninth switch tube G33 of the converter are obtained by comparing the voltage waveform triangular carrier output by the fan side control, and then the switch signals of the fourth switch tube G21, the fifth switch tube G22 and the sixth switch tube G23 are obtained by the "exclusive or" operation.

[0055] The specific implementation method of rotor magnetic field oriented vector control is: first, after the rotor flux is oriented, coordinate transformation is performed to establish a mathematical model; second, let , so that the motor stator current is fully used for motor torque control, and The system has a linear relationship, the dynamic response is fast and easy to control, the torque output reaches the maximum, and the working efficiency is greatly improved. Considering the control requirements of the selected permanent magnet synchronous generator, the The rotor magnetic field oriented vector control method is adopted; finally, by adjusting The size of can realize the control of the electromagnetic torque of the motor, and then realize the control of the fan speed, that is, by adjusting The size of the variable can be used to control the motor speed.

[0056] Under working condition 3, with wind and light, the equivalent circuit is as follows Figure 2The first switch tube G11, the second switch tube G12, the third switch tube G13, the fourth switch tube G21, the fifth switch tube G22 and the sixth switch tube G23 constitute the upper converter, and the fourth switch tube G21, the fifth switch tube G22 and the sixth switch tube G23, the seventh switch tube G31, the eighth switch tube G32 and the ninth switch tube G33 constitute the lower converter. Fig.14 is a schematic diagram of the working circuit of the combination 9 under windy but no-light conditions according to some embodiments of this specification, Fig.15 is a schematic diagram of the working circuit of the combination 15 under windy but no-light conditions shown in some embodiments of this specification, Fig.14 , Fig.15 Combined with the switch combination state analysis in Table 1, it can be seen that the conduction conditions of the switch tubes of combination 9 to combination 27 can meet the working condition 3. Compared with the working condition with wind but no light, the working condition with wind and light has an additional path for the photovoltaic module to charge the capacitor C through the inductor L1 and the first diode D1, the second diode D2, and the third diode D3. The modulation strategy of the switch tube is the same as the modulation method under the working condition with wind but no light.

[0057] When wind and light work together, the overall control method of the system is: the wind turbine control system input power on the power supply side adopts the MPPT power outer loop and the rotor flux orientation i sd =0 asynchronous motor vector inner loop control structure. The sinusoidal waveform output by the wind turbine after control is used as the modulation wave signal of the three tubes under the three-port converter; the solar power generation module outputs the correction value by optimizing the variable step length conductance increment method, which is injected into the trigger signal for adjustment as a DC bias to control the opening and closing of the first switch tube G11, the second switch tube G12 and the third switch tube G13, and the on-off signal of the fourth switch tube G21, the fifth switch tube G22 and the sixth switch tube G23 is obtained by the on-off signal of the first switch tube G11, the second switch tube G12 and the third switch tube G13 and the on-off signal of the seventh switch tube G31, the eighth switch tube G32 and the ninth switch tube G33 through XOR operation. Among them, the asynchronous motor adopts rotor flux vector control, and the q-axis outer ring is a voltage ring.

[0058] The following simulation test is combined to verify the beneficial effects of the water pumping system based on the off-grid wind-solar integrated converter.

[0059] Fig.16 is a schematic diagram of a simulated waveform under a light-on, no-wind working condition according to some embodiments of this specification, such as Fig.16As shown in the figure, in the simulation, the rated output power of photovoltaic power generation P1 is 5kW, the actual power of water pumping P3 is 5kW, and the voltage across the DC capacitor is controlled to be 1100V. In the simulation, as the light intensity changes, the photovoltaic output power changes accordingly. By controlling the converter, the voltage across the DC capacitor remains basically unchanged, and the water pump power changes with the photovoltaic output power, and the waveforms of the two coincide. The simulation shows that the water pump power always changes with the photovoltaic output power, which well realizes the photovoltaic power generation and water pumping under the condition of light but no wind.

[0060] Fig.17 is a schematic diagram of a simulated waveform under windy but no-light conditions according to some embodiments of this specification, such as Fig.17 As shown, in the simulation, the wind turbine output power P2 is 10kW, the actual water pump power P3 is 10kW, and the voltage across the DC capacitor is controlled to be 1100V. It can be seen from the simulation waveform that when the wind speed is very small, the power generated by the wind turbine is also very small, and the water pump power is also very small. At this time, the water pump cannot perform water extraction work; when the wind speed gradually increases, the power generated by the wind turbine also increases, and the water pump power also increases, and the water pump can perform water extraction work well. When the wind speed gradually decreases, the power generated by the wind turbine also decreases, and the water pump power also decreases. By controlling the converter, the voltage control across the DC capacitor remains basically unchanged, and the water pump power changes with the power output of the wind turbine, and the waveforms of the two coincide. The simulation shows that the water pump power always changes with the change of the output power of the wind turbine, which well realizes the independent wind power generation and water extraction under the condition of wind and no light.

[0061] Fig.18 is a schematic diagram of a simulated waveform under wind and solar conditions according to some embodiments of this specification, such as Fig.18As shown, the photovoltaic output power P1 is 5kW, the wind turbine output power P2 is 10kW, the actual water pump power P3 is 15kW, and the voltage across the DC capacitor is controlled to be 1100V. It can be seen from the simulation waveform that the wind turbine output power changes with the wind speed, and the photovoltaic output power changes with the light intensity. When the wind speed is very small and the light intensity is strong, the wind turbine output power is small and the photovoltaic output power is large. At this time, the water pump starts to work. When the wind speed increases and the light intensity decreases, the wind turbine output power increases, the photovoltaic output power decreases, the sum of the wind turbine and photovoltaic output power increases, and the water pump power continues to increase. Subsequently, the light intensity increases, the photovoltaic output power increases, and the water pump power reaches the rated power. When the light intensity increases and the wind speed decreases, the wind turbine output power decreases, the photovoltaic output power increases, and the sum of the wind turbine and photovoltaic output power remains basically unchanged. At this time, the water pump can still stably carry out water extraction. By controlling the converter, the voltage across the DC capacitor remains basically unchanged, and the water pump power can follow the sum of the power output of the wind turbine and the power output of the photovoltaic power plant, and the waveforms of the two coincide. Simulation shows that the water pump output power always changes with the changes in the output power of the wind turbine and the photovoltaic power plant, thus realizing the wind-solar complementary power generation and water pumping under wind and solar conditions.

[0062] Depend on Figure 16-Figure 18 It can be seen that the actual power of the water pump based on the off-grid wind-solar integrated converter follows the changes of the input photovoltaic and wind power, ensuring the energy balance at all times, verifying the correctness and feasibility of the water pump based on the off-grid wind-solar integrated converter, and reflecting the characteristics of wind, light and water pump integrated into one. Compared with other off-grid wind-solar power generation water pumping devices, it uses 2 fewer converters, which reduces the economic cost of the system and improves the system efficiency.

[0063] Fig.19 is a flow chart of a water pumping control method based on an off-grid wind-solar power generation integrated converter according to some embodiments of this specification, such as Fig.19 As shown, the water lifting control method based on the off-grid wind-solar power generation integrated converter may include the following steps.

[0064] Step 1910, determining a current operating condition, wherein the current operating condition is one of solar power without wind, wind without solar power, and wind and solar power; Step 1920, when the current working condition is that there is solar power but no wind, the seventh switch tube, the eighth switch tube and the ninth switch tube are controlled to be in the on state, and the switch states of the first switch tube, the second switch tube and the third switch tube are controlled to complement the switch states of the fourth switch tube, the fifth switch tube and the sixth switch tube respectively; Step 1930, when the current working condition is wind without solar power or wind with solar power, the switch states of the first bridge arm, the second bridge arm and the third bridge arm are controlled according to the first constraint condition and the second constraint condition.

[0065] The water lifting control method based on the off-grid wind-solar integrated power generation converter can be applied to the water lifting system based on the off-grid wind-solar integrated power generation converter. For more descriptions of the water lifting control method based on the off-grid wind-solar integrated power generation converter, please refer to the relevant descriptions of the water lifting system based on the off-grid wind-solar integrated power generation converter, which will not be repeated here.

[0066] Finally, it should be understood that the embodiments described in this specification are only used to illustrate the principles of the embodiments of this specification. Other variations may also fall within the scope of this specification. Therefore, as an example and not a limitation, alternative configurations of the embodiments of this specification may be considered consistent with the teachings of this specification. Accordingly, the embodiments of this specification are not limited to the embodiments explicitly introduced and described in this specification.

Claims

1. A water pumping system based on an off-grid wind-solar integrated converter, characterized in that: It includes a solar power generation module, a wind power generation module, a wind-solar power generation integrated converter and a water pumping module, wherein the solar power generation module and the wind power generation module are electrically connected to the input end of the wind-solar power generation integrated converter, and the output end of the wind-solar power generation integrated converter is electrically connected to the water pumping module; The wind-solar power generation integrated converter comprises three switch channels, and the solar power generation module and the wind power generation module are electrically connected to the water pumping module via the three switch channels.

2. The water pumping system based on the off-grid wind-solar power generation integrated converter according to claim 1 is characterized in that: The three switch channels include a first switch channel, a second switch channel and a third switch channel, wherein the first switch channel includes a first switch tube, a second switch tube and a third switch tube connected in parallel, the second switch channel includes a fourth switch tube, a fifth switch tube and a sixth switch tube connected in parallel, the third switch channel includes a seventh switch tube, an eighth switch tube and a ninth switch tube connected in parallel, the first switch tube, the fourth switch tube and the seventh switch tube are connected in series to form a first bridge arm, the second switch tube, the fifth switch tube and the eighth switch tube are connected in series to form a second bridge arm, and the third switch tube, the sixth switch tube and the ninth switch tube are connected in series to form a third bridge arm; The positive electrode of the polarity capacitor is electrically connected to the collectors of the first switch tube, the second switch tube and the third switch tube, and the negative electrode of the polarity capacitor is electrically connected to the emitters of the first switch tube, the second switch tube and the third switch tube; The solar power generation module is electrically connected to one end of the inductor, the other end of the inductor is electrically connected to the anodes of the first diode, the second diode and the third diode connected in parallel, the cathode of the first diode is electrically connected to the connection node of the first switch tube and the fourth switch tube, the cathode of the second diode is electrically connected to the connection node of the second switch tube and the fifth switch tube, and the cathode of the third diode is electrically connected to the connection node of the third switch tube and the sixth switch tube; The water pumping module is electrically connected to a connection node between the first switch tube and the fourth switch tube, a connection node between the second switch tube and the fifth switch tube, and a connection node between the third switch tube and the sixth switch tube; The wind power generation module is electrically connected to a connection node between the fourth switch tube and the seventh switch tube, a connection node between the fifth switch tube and the eighth switch tube, and a connection node between the sixth switch tube and the ninth switch tube.

3. The water pumping system based on the off-grid wind-solar power generation integrated converter according to claim 2 is characterized in that: The wind-solar power generation integrated converter further includes a switch control component for: Determine a current operating condition, wherein the current operating condition is one of solar power but no wind, wind but no solar power, and wind and solar power; The states of the three switch channels are controlled according to the current working conditions.

4. The water pumping system based on the off-grid wind-solar power generation integrated converter according to claim 3 is characterized in that: The switch control component controls the states of the three switch channels according to the current working conditions, including: When the current working condition is that there is light but no wind, the seventh switch tube, the eighth switch tube and the ninth switch tube are controlled to be in the on state, and the switch states of the first switch tube, the second switch tube and the third switch tube are controlled to complement the switch states of the fourth switch tube, the fifth switch tube and the sixth switch tube respectively.

5. The water pumping system based on the off-grid wind-solar power generation integrated converter according to claim 4 is characterized in that: The switch control component controls the states of the three switch channels according to the current working conditions, including: When the current working condition is that there is light but no wind, the seventh switch tube, the eighth switch tube and the ninth switch tube are controlled to be in a conducting state; Obtaining a target port voltage according to the port voltage and port current of the solar power generation module; Performing closed-loop control on the target port voltage to obtain a DC bias signal injected into the modulation wave; On the basis of asynchronous motor vector control, the q-axis current of the asynchronous motor of the water pumping module is adjusted to control the DC side voltage in a closed loop, and the modulation signal of the asynchronous motor is obtained after the output of the current loop is inversely transformed by 3 / 2. Based on the modulation signal of the asynchronous motor, a triple frequency harmonic signal is obtained; Superimposing a DC bias signal, a modulation signal of the asynchronous motor and a triple frequency harmonic signal to obtain modulation signals of the first switch tube, the second switch tube and the third switch tube; The modulation signals of the first switch tube, the second switch tube and the third switch tube are compared with the triangular carrier operation to control the switching states of the first switch tube, the second switch tube and the third switch tube, and the switching states of the first switch tube, the second switch tube and the third switch tube are controlled to complement the switching states of the fourth switch tube, the fifth switch tube and the sixth switch tube respectively.

6. The water pumping system based on the off-grid wind-solar integrated converter according to claim 4 or 5, characterized in that: The switch control component controls the states of the three switch channels according to the current working conditions, including: When the current working condition is wind without solar power or wind with solar power, the switch states of the first bridge arm, the second bridge arm and the third bridge arm are controlled according to the following first constraint condition: ， in, The first bridge arm The switch state of the switch tube is When the switch is in the on state, ,otherwise , The second bridge arm The switching state of the switch tube, The third bridge arm The switching state of the switch tube, .

7. The water pumping system based on the off-grid wind-solar integrated converter according to claim 6 is characterized in that: The modulation reference waves of the first switch channel and the third switch channel are: ， in, is the modulation reference wave of the first switch channel, is the modulation wave reference amplitude of the first switch channel, is the angular frequency of the modulation reference wave of the first switching channel, is the initial phase of the modulation reference wave of the first switching channel, is the offset of the first switch channel, is the modulation reference wave of the third switch channel, is the modulation wave reference amplitude of the third switch channel, is the angular frequency of the modulation reference wave of the third switching channel, is the initial phase of the modulation reference wave of the third switching channel, is the offset of the third switch channel.

8. The water pumping system based on the off-grid wind-solar integrated power generation converter according to claim 7 is characterized in that: The offset of the first switch channel, the offset of the third switch channel, the reference amplitude of the modulation wave of the first switch channel, and the reference amplitude of the modulation wave of the third switch channel satisfy the following second constraint condition: ， 。 9. The water pumping system based on the off-grid wind-solar integrated converter according to any one of claims 3 to 5, characterized in that: The switch control component controls the states of the three switch channels according to the current working conditions, including: When the current working condition is that there is wind but no sun, the states of the three switch channels are controlled for the purpose of achieving maximum power output operation of the wind turbine.

10. A water pumping control method based on an off-grid wind-solar integrated converter, characterized in that: The water pumping system based on the off-grid wind-solar power generation integrated converter as claimed in any one of claims 2 to 9 comprises: Determine a current operating condition, wherein the current operating condition is one of solar power but no wind, wind but no solar power, and wind and solar power; When the current working condition is that there is light but no wind, the seventh switch tube, the eighth switch tube and the ninth switch tube are controlled to be in the on state, and the switch states of the first switch tube, the second switch tube and the third switch tube are controlled to complement the switch states of the fourth switch tube, the fifth switch tube and the sixth switch tube respectively; When the current working condition is wind without solar power or wind with solar power, the switching states of the first bridge arm, the second bridge arm and the third bridge arm are controlled according to the first constraint condition and the second constraint condition.

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