A photovoltaic energy storage coordinated DC bus voltage stabilization unit, DC bus voltage stabilization control method and power quality regulator

Abstract

The present invention discloses a photovoltaic storage coordinated DC bus voltage stabilization unit, a DC bus voltage stabilization control method and a power quality conditioner, comprising a PV photovoltaic array and a lithium battery pack; a Boost boost module is connected between the PV photovoltaic array and the lithium battery pack; voltage and current acquisition modules are arranged at both ends of the Boost boost module, and an energy control module is also connected between the two voltage and current acquisition modules; the energy control module is also connected to the Boost boost module through a driving module; the present invention uses a PV photovoltaic array and a lithium battery pack, and utilizes the continuous charging of the PV photovoltaic array to ensure the effective output of the lithium battery pack power, which can effectively reduce the DC bus instability problem caused by the temporary drop of the AC power supply during current harmonic compensation, and greatly improves the effectiveness and stability of current harmonic control; and through the energy control module, the output voltage of the Boost boost module is compensated to ensure that the voltage output by the Boost boost module is constant, thereby realizing voltage stabilization control of the DC bus.

Description

Technical Field

[0001] The present invention relates to the technical field of electric energy regulation, and in particular to a photovoltaic energy storage coordinated DC bus voltage stabilization unit, a DC bus voltage stabilization control method and a power quality regulator. Background Art

[0002] Microgrids, which integrate loads, power sources and their regulation means, are one of the most important new energy grid forms in the new power system besides the main grid. Among the renewable energy sources connected to microgrids, photovoltaic power generation and wind power generation are developing fastest. From the perspective of power quality, microgrids composed of multiple groups of photovoltaic and wind power will easily cause power quality problems in distribution networks containing microgrids due to the complexity and uncertainty of distributed power sources compared with traditional distribution networks. At present, with the insufficient acceptance capacity of the power grid, the access of large-scale or high-power distributed renewable energy has some impact on the power quality of the existing distribution network. Since renewable energy sources such as photovoltaic and wind power are easily affected by weather, they are prone to voltage fluctuations, resulting in large random fluctuations in grid-connected voltage and poor adjustability. In addition, when microgrids are connected to the grid, large impact currents will be generated, resulting in deviations in grid frequency, grid voltage fluctuations and flickers, causing changes in the power flow in the feeder, affecting the steady-state voltage distribution and reactive power characteristics, making the grid uncontrollable and the peak-shaving capacity margin larger. At the same time, the presence of a large number of single-phase distributed power sources in microgrids also increases the three-phase imbalance of the distribution network.

[0003] At present, the power quality management technologies widely used in traditional distribution networks at home and abroad mainly include: (1) dynamic reactive power compensation technology, such as static reactive power compensator (SVC); (2) active power filtering technology, such as active power filter (APF); (3) dynamic voltage recovery technology, such as dynamic voltage restorer (DVR). SVC can solve the problems of voltage drop and three-phase imbalance caused by insufficient reactive power in the system, APF can solve the problems of current harmonics and three-phase imbalance, and DVR can solve the problems of voltage swell and voltage harmonics. At present, most power management equipment tends to focus on a specific indicator, and can basically meet the power management requirements under the condition of stable distribution network. However, for the power quality management of distribution network containing microgrid, the loose combination of single or multiple power quality management devices can no longer meet the requirements.

[0004] Based on the above situation, the present invention proposes a photovoltaic and energy storage coordinated DC bus voltage stabilization unit, a DC bus voltage stabilization control method and a power quality conditioner, which can effectively solve the above problems. Summary of the invention

[0005] The object of the present invention is to provide a photovoltaic energy storage coordinated DC bus voltage stabilization unit, a DC bus voltage stabilization control method and a power quality conditioner.

[0006] The present invention is achieved through the following technical solutions:

[0007] A photovoltaic energy storage coordinated DC bus voltage stabilization unit comprises a PV photovoltaic array and a lithium battery pack; a Boost module is connected between the PV photovoltaic array and the lithium battery pack; voltage and current acquisition modules are provided at both ends of the Boost module, and an energy control module is also connected between the two voltage and current acquisition modules; the energy control module is also connected to the Boost module through a drive module.

[0008] Preferably, the Boost module includes a transformer T, one side of the transformer T is connected to a low-voltage circuit, and the other side of the transformer T is connected to a high-voltage circuit.

[0009] Preferably, the low voltage circuit includes a low voltage power supply U l , low voltage power supply U l The positive electrode passes through the first inductor L i and boost leakage inductance L s Connected to the input end of the primary side of the transformer T, the output end of the primary side of the transformer T is connected to the low voltage power supply U through the second capacitor C2 l The negative pole of the first inductor L i One end of the first MOS tube V T1 The first capacitor C1 is connected to one end of the second capacitor C2; the first inductor L i The same end of the second MOS tube V T2 Connected to the other end of the second capacitor C2; the first MOS tube V T1 A first diode V is connected in parallel with D1 and the first filter capacitor C r1 ; The second MOS tube V T2 A second diode V D2 and the second filter capacitor C r2 .

[0010] Preferably, the high voltage circuit includes a high voltage power supply U h , high voltage power supply U h The positive electrode passes through the third MOS tube V T3 Connected to the input terminal of the secondary side of transformer T; high voltage power supply U h The negative electrode is connected to the output end of the secondary side of the transformer T through the fourth capacitor C4; the high voltage power supply U h The positive electrode is also connected to the output end of the secondary side of the transformer T through the third capacitor C3; the high voltage power supply U h The negative electrode also passes through the fourth MOS tube V T4 Connected to the input terminal of the secondary side of transformer T; high voltage power supply U h There is a rectifier capacitor C in parallelo ; The third MOS tube V T3 A third diode V is connected in parallel with D3 And the third filter capacitor C r3 ; The fourth MOS tube V T4 A fourth diode V D4 And the fourth filter capacitor C r4 .

[0011] Preferably, the energy control module includes an operational amplifier, an analog linear isolation chip, an A / D conversion chip, a DSP chip and a D / A conversion chip; the DSP chip is also connected to the SRAM memory.

[0012] A DC bus voltage stabilization control method includes the following contents:

[0013] Photovoltaic power generation: The energy released by sunlight is absorbed by the PV array and converted into DC electricity;

[0014] Charging of lithium battery pack: By connecting the Boost module at the output end of the PV array, the output voltage is increased to charge the lithium battery pack;

[0015] Voltage and current collection: The current and voltage at both ends of the Boost module are collected through the voltage and current collection module connected to both ends of the Boost module, and the collected current and voltage are transmitted to the energy control module;

[0016] Power distribution: The voltage, current and power collected in real time by the voltage and current acquisition module are used with the help of the power supply circuit and peripheral circuit, and the constant voltage control algorithm is used to perform voltage compensation on the Boost module.

[0017] Preferably, when the lithium battery pack is charged, one side of the transformer in the Boost module is the low voltage side, and the other side is the high voltage side. The low voltage side transmits power P0 to the high voltage side, which is expressed as formula (1):

[0018]

[0019] Among them, U1 is the low-voltage side input voltage, ω is the switching angular frequency, L s is the leakage inductance of the step-up transformer, and θ is the phase difference between the half-bridge conduction angles in the low-voltage side and the high-voltage side.

[0020] Preferably, in electric energy distribution, the GPC algorithm is selected to implement the MPPT function, and a controlled autoregressive integral moving average model is added to the GPC algorithm as a prediction model, and the identified model parameters and information are provided to the GPC algorithm in real time, thereby triggering the triangular carrier to enable the drive module to output maximum power.

[0021] Preferably, the electric energy distribution also includes the following contents:

[0022] The output voltage is stabilized by using a dual-loop control strategy of voltage outer loop and current inner loop to obtain the transfer function shown in equation (2):

[0023]

[0024] Among them, K dcl is the integral constant of the DC bus voltage PI regulator.

[0025] A power quality conditioner comprises a series active filter, a parallel active filter and the above-mentioned photovoltaic energy storage coordinated DC bus voltage stabilization unit.

[0026] Compared with the prior art, the present invention has the following advantages and beneficial effects:

[0027] The photovoltaic storage coordinated DC bus voltage stabilization unit, DC bus voltage stabilization control method and power quality conditioner of the present invention use PV photovoltaic arrays and lithium battery packs, and utilize the continuous charging of the PV photovoltaic arrays to ensure the effective output of the lithium battery pack power, which can effectively reduce the DC bus instability problem caused by the temporary drop of the AC power supply during current harmonic compensation, and greatly improve the effectiveness and stability of current harmonic control; provide DC power through the PV photovoltaic array, and increase the voltage of the DC power output of the PV photovoltaic array in the Boost boost module to ensure that it reaches the charging voltage of the lithium battery pack, and the lithium battery pack provides a stable voltage to charge the DC capacitor, thereby ensuring that the DC bus capacitor has a stable compensation voltage; and through the energy control module, according to the data collected by the voltage and current acquisition module at both ends of the Boost boost module, compensate the output voltage of the Boost boost module to ensure that the voltage output by the Boost boost module is constant at the set value, thereby realizing voltage stabilization control of the DC bus. BRIEF DESCRIPTION OF THE DRAWINGS

[0028] Figure 1 This is a schematic diagram of the structure of Embodiment 1 of the present invention;

[0029] Figure 2 The circuit diagram of the Boost module of the present invention;

[0030] Figure 3 This is a hardware block diagram of the energy control module of the present invention;

[0031] Figure 4 This is a DC bus constant voltage control logic diagram in Example 2 of the present invention;

[0032] Figure 5 is a DC bus constant voltage control transfer function diagram in Example 2 of the present invention;

[0033] Figure 6 This is a schematic diagram of the structure of Example 3 of the present invention. DETAILED DESCRIPTION

[0034] In order to enable those skilled in the art to better understand the technical solution of the present invention, the preferred implementation scheme of the present invention is described below in conjunction with specific embodiments. However, it should be understood that the drawings are only used for exemplary description and cannot be understood as a limitation on this patent. In order to better illustrate this embodiment, some parts of the drawings may be omitted, enlarged or reduced, and do not represent the size of the actual product. For those skilled in the art, it is understandable that some well-known structures and their descriptions in the drawings may be omitted. The positional relationship described in the drawings is only for exemplary description and cannot be understood as a limitation on this patent.

[0035] Embodiment 1:

[0036] like Figures 1 to 3 As shown, a photovoltaic energy storage coordinated DC bus voltage stabilization unit includes a PV photovoltaic array and a lithium battery pack; a Boost boost module is connected between the PV photovoltaic array and the lithium battery pack; voltage and current acquisition modules are provided at both ends of the Boost boost module, and an energy control module is also connected between the two voltage and current acquisition modules; the energy control module is also connected to the Boost boost module through a drive module.

[0037] The present invention uses a PV photovoltaic array and a lithium battery pack, and utilizes the continuous charging of the PV photovoltaic array to ensure the effective output of the lithium battery pack power, which can effectively reduce the instability problem of the DC bus caused by the temporary drop of the AC power supply during current harmonic compensation, and greatly improve the effectiveness and stability of current harmonic control; the PV photovoltaic array provides a DC power supply, and the voltage of the DC power supply output by the PV photovoltaic array is increased in the Boost boost module to ensure that the charging voltage of the lithium battery pack is reached, and the lithium battery pack provides a stable voltage to charge the DC capacitor, thereby ensuring that the DC bus capacitor has a stable compensation voltage; and through the energy control module, according to the data collected by the voltage and current collection module at both ends of the Boost boost module, the output voltage of the Boost boost module is compensated, ensuring that the voltage output by the Boost boost module is constant at a set value, thereby realizing voltage stabilization control of the DC bus.

[0038] Furthermore, in another embodiment, the Boost module includes a transformer T, one side of the transformer T is connected to a low voltage circuit, and the other side of the transformer T is connected to a high voltage circuit.

[0039] The voltage is increased or decreased by the transformer T.

[0040] Furthermore, in another embodiment, the low voltage circuit includes a low voltage power supply U l , low voltage power supply Ul The positive electrode passes through the first inductor L i and boost leakage inductance L s Connected to the input end of the primary side of the transformer T, the output end of the primary side of the transformer T is connected to the low voltage power supply U through the second capacitor C2 l The negative pole of the first inductor L i One end of the first MOS tube V T1 The first capacitor C1 is connected to one end of the second capacitor C2; the first inductor L i The same end of the second MOS tube V T2 Connected to the other end of the second capacitor C2; the first MOS tube V T1 A first diode V is connected in parallel with D1 and the first filter capacitor C r1 ; The second MOS tube V T2 A second diode V D2 and the second filter capacitor C r2 .

[0041] Through the first filter capacitor C r1 and the second filter capacitor C r2 , filter the fluctuating voltage to ensure that the voltage difference to be transformed is small, and ensure that the voltage output by the Boost module is relatively stable.

[0042] Furthermore, in another embodiment, the high voltage circuit includes a high voltage power supply U h , high voltage power supply U h The positive electrode passes through the third MOS tube V T3 Connected to the input terminal of the secondary side of transformer T; high voltage power supply U h The negative electrode is connected to the output end of the secondary side of the transformer T through the fourth capacitor C4; the high voltage power supply U h The positive electrode is also connected to the output end of the secondary side of the transformer T through the third capacitor C3; the high voltage power supply U h The negative electrode also passes through the fourth MOS tube V T4 Connected to the input terminal of the secondary side of transformer T; high voltage power supply U h There is a rectifier capacitor C in parallel o ; The third MOS tube V T3 A third diode V is connected in parallel with D3 And the third filter capacitor C r3 ; The fourth MOS tube V T4 A fourth diode V D4 And the fourth filter capacitor C r4 .

[0043] Through the third filter capacitor C r3 And the fourth filter capacitor Cr4 , filter the fluctuating voltage, reduce the fluctuation amplitude of the boosted voltage, and ensure that the voltage output by the Boost module is relatively stable.

[0044] Furthermore, in another embodiment, the energy control module includes an operational amplifier, an analog linear isolation chip, an A / D conversion chip, a DSP chip and a D / A conversion chip; the DSP chip is also connected to the SRAM memory.

[0045] The model of the operational amplifier is LM358, and the model of the DSP chip is TMS320C2802.

[0046] Embodiment 2:

[0047] like Figures 1 to 5 As shown, a DC bus voltage stabilization control method includes the following contents:

[0048] Photovoltaic power generation: The energy released by sunlight is absorbed by the PV array and converted into DC electricity;

[0049] Charging of lithium battery pack: By connecting the Boost module at the output end of the PV array, the output voltage is increased to charge the lithium battery pack;

[0050] Voltage and current collection: The current and voltage at both ends of the Boost module are collected through the voltage and current collection module connected to both ends of the Boost module, and the collected current and voltage are transmitted to the energy control module;

[0051] Power distribution: The voltage, current and power collected in real time by the voltage and current acquisition module are used with the help of the power supply circuit and peripheral circuit, and the constant voltage control algorithm is used to perform voltage compensation on the Boost module.

[0052] By collecting the voltage and current at both ends of the Boost module and calculating the power, the energy control module analyzes it and uses the power supply circuit and peripheral circuits to perform voltage compensation on the Boost module to ensure that the voltage value output by the Boost module is stable at the set voltage value, thereby achieving voltage stabilization control of the DC bus.

[0053] Furthermore, in another embodiment, when the lithium battery pack is charged, one side of the transformer in the Boost module is the low voltage side, and the other side is the high voltage side. The low voltage side transmits power P0 to the high voltage side, which is expressed as formula (1):

[0054]

[0055] Among them, U1 is the low-voltage side input voltage, ω is the switching angular frequency, L sis the leakage inductance of the step-up transformer, and θ is the phase difference between the half-bridge conduction angles in the low-voltage side and the high-voltage side.

[0056] It can be seen from formula (1) that by adjusting the phase difference between the half-bridge conduction angles on the low-voltage side and the high-voltage side, the flow direction and size of the transformer power can be adjusted; after the Boost boost module of the present application is connected to the lithium battery pack and the photovoltaic panel, its high transformation ratio can be used to establish the high voltage on the DC side of the lithium battery pack, and at the same time, the phase difference between the half-bridge conduction angles on the low-voltage side and the high-voltage side can be adjusted. When the output of the PV photovoltaic array fluctuates, the active power can be bidirectionally exchanged between the lithium battery pack and the photovoltaic panel battery.

[0057] Furthermore, in another embodiment, in electric energy distribution, the GPC algorithm is selected to implement the MPPT function, and a controlled autoregressive integral moving average model is added to the GPC algorithm as a prediction model, and the identified model parameters and information are provided to the GPC algorithm in real time, thereby triggering the triangular carrier to enable the driving module to output maximum power.

[0058] A controlled autoregressive integral moving average model is added to the traditional GPC method as a prediction model to form an optimized GPC algorithm, which is called the improved generalized predictive control algorithm, namely the P-GPC control algorithm. In the Boost module, the P-GPC control algorithm is used to implement the MPPT control logic according to the voltage and current output by the PV photovoltaic array, and the reference voltage value of the photovoltaic cell working point is set. The error value is generated compared with the actual output voltage of the photovoltaic cell. After adjustment by the P-GPC algorithm, it is compared with the high-frequency triangular carrier. If it is greater than 0, S is turned on, otherwise S is turned off, so that the photovoltaic array voltage can work stably, and the P-GPC algorithm is used to control its output power to reach the maximum value. P-GPC combines the advantages of predictive control and adaptive control to achieve optimal control of MPPT.

[0059] Furthermore, in another embodiment, the electric energy distribution further includes the following:

[0060] The output voltage is stabilized by using a dual-loop control strategy of voltage outer loop and current inner loop to obtain the transfer function shown in equation (2):

[0061]

[0062] Among them, K dcl is the integral constant of the DC bus voltage PI regulator.

[0063] like Figure 4 In the process, a dual-loop control strategy of voltage outer loop and current inner loop is adopted, and the output DC voltage is kept stable at U by voltage PI outer loop control. dc , DC bus reference voltage U dcref =Udc , and U dcref is the output voltage after the boost circuit is boosted, I dc is the output current after boost, U dcref and U dc The voltage outer loop is formed, forming a DC voltage PI control loop, and the generated current I dR Current I dc The DC bus voltage U is generated by the inner loop PI controller, PWM signal generation and IGBT driver in sequence. dc .

[0064] For the DC bus voltage PI regulator, the current loop is approximately replaced by a first-order inertia link as shown in equation (3):

[0065]

[0066] T v is the equivalent inertia time constant, then the transfer function of the DC bus voltage control is as follows: Figure 5 shown.

[0067] Figure 5 Medium dc K is the DC bus voltage sampling delay time constant, dcp is the proportional constant of the DC bus voltage PI regulator, K dcl is the integral constant of the DC bus voltage PI regulator, and the open-loop forward transfer function of the control system is as follows:

[0068]

[0069] In formula (2), due to τ dc , T v are very small, τ dc =0.000Is,T v =0.0005s.

[0070] According to the principle of merging small inertia links, equation (4) is simplified to equation (5):

[0071]

[0072] In formula (5), K is set pwm =2, and let K dcP / K dcl =T pwm After achieving zero-pole cancellation, we can obtain equation (2):

[0073]

[0074] Embodiment 3:

[0075] like Figure 6As shown, a power quality conditioner includes a series active filter, a parallel active filter and the above-mentioned photovoltaic energy storage coordinated DC bus voltage stabilization unit.

[0076] A photovoltaic and energy-storage collaborative DC bus voltage stabilization control unit is added to control the voltage across the DC bus voltage stabilization capacitor to ensure better voltage stabilization control effect.

[0077] Based on the description and drawings of the present invention, those skilled in the art can easily manufacture or use the photovoltaic energy storage coordinated DC bus voltage stabilization unit, DC bus voltage stabilization control method and power quality conditioner of the present invention, and can produce the positive effects recorded in the present invention.

[0078] The above description is only a preferred embodiment of the present invention and does not limit the present invention in any form. Any simple modification or equivalent change made to the above embodiment based on the technical essence of the present invention shall fall within the protection scope of the present invention.

Claims

1. A photovoltaic energy storage coordinated DC bus voltage stabilization unit, characterized in that: It includes a PV photovoltaic array and a lithium battery pack; a Boost module is connected between the PV photovoltaic array and the lithium battery pack; voltage and current acquisition modules are provided at both ends of the Boost module, and an energy control module is also connected between the two voltage and current acquisition modules; the energy control module is also connected to the Boost module through a drive module; The Boost module includes a transformer T, one side of the transformer T is connected to a low voltage circuit, and the other side of the transformer T is connected to a high voltage circuit; The low voltage circuit includes a low voltage power supply U l , low voltage power supply U l The positive electrode passes through the first inductor L i and boost leakage inductance L s Connected to the input end of the primary side of the transformer T, the output end of the primary side of the transformer T is connected to the low voltage power supply U through the second capacitor C2 l The negative pole of the first inductor L i One end of the first MOS tube V T1 The first capacitor C1 is connected to one end of the second capacitor C2; the first inductor L i The same end of the second MOS tube V T2 Connected to the other end of the second capacitor C2; the first MOS tube V T1 A first diode V is connected in parallel with D1 and the first filter capacitor C r1 ; The second MOS tube V T2 A second diode V D2 and the second filter capacitor C r2 ; The high voltage circuit includes a high voltage power supply U h , high voltage power supply U h The positive electrode passes through the third MOS tube V T3 Connected to the input terminal of the secondary side of transformer T; high voltage power supply U h The negative electrode is connected to the output end of the secondary side of the transformer T through the fourth capacitor C4; the high voltage power supply U h The positive electrode is also connected to the output end of the secondary side of the transformer T through the third capacitor C3; the high voltage power supply U h The negative electrode also passes through the fourth MOS tube V T4 Connected to the input terminal of the secondary side of transformer T; high voltage power supply U h There is a rectifier capacitor C in parallel o ; The third MOS tube V T3 A third diode V is connected in parallel with D3 And the third filter capacitor C r3 ; The fourth MOS tube V T4 A fourth diode V is connected in parallel with D4 And the fourth filter capacitor C r4 .

2. The photovoltaic energy storage coordinated DC bus voltage stabilizing unit according to claim 1 is characterized in that: The energy control module comprises an operational amplifier, an analog linear isolation chip, an A / D conversion chip, a DSP chip and a D / A conversion chip; the DSP chip is also connected to the SRAM memory.

3. A DC bus voltage stabilization control method, characterized in that: The photovoltaic energy storage coordinated DC bus voltage stabilizing unit as described in claim 1 or 2 comprises the following contents: Photovoltaic power generation: The energy released by sunlight is absorbed by the PV array and converted into DC electricity; Charging of lithium battery pack: By connecting the Boost module at the output end of the PV array, the output voltage is increased to charge the lithium battery pack; Voltage and current collection: The current and voltage at both ends of the Boost module are collected through the voltage and current collection module connected to both ends of the Boost module, and the collected current and voltage are transmitted to the energy control module; Power distribution: The voltage, current and power collected in real time by the voltage and current acquisition module are used with the help of the power supply circuit and peripheral circuit, and the constant voltage control algorithm is used to perform voltage compensation on the Boost module.

4. The DC bus voltage stabilization control method according to claim 3 is characterized in that: When the lithium battery pack is charged, one side of the transformer in the Boost module is the low voltage side, and the other side is the high voltage side. The low voltage side transmits power P0 to the high voltage side, which is expressed as formula (1): Among them, U1 is the low-voltage side input voltage, ω is the switching angular frequency, L s is the leakage inductance of the step-up transformer, and θ is the phase difference between the half-bridge conduction angles in the low-voltage side and the high-voltage side.

5. The DC bus voltage stabilization control method according to claim 3, characterized in that: In power distribution, the GPC algorithm is selected to realize the MPPT function, and a controlled autoregressive integral moving average model is added to the GPC algorithm as a prediction model. The identified model parameters and information are provided to the GPC algorithm in real time, thereby triggering the triangular carrier to enable the drive module to output maximum power.

6. The DC bus voltage stabilization control method according to claim 3, characterized in that: The distribution of electric energy also includes the following: The output voltage is stabilized by using a dual-loop control strategy of voltage outer loop and current inner loop to obtain the transfer function shown in equation (2): Among them, K dcl is the integral constant of the DC bus voltage PI regulator.

7. A power quality conditioner, characterized in that: It comprises a series active filter, a parallel active filter and the photovoltaic energy storage coordinated DC bus voltage stabilization unit as described in claim 1 or 2.

Images