Efficient power supply guarantee device based on photovoltaic panel

Abstract

The invention relates to a converter technology, which can be used for efficiently extracting electric energy of a solar panel, converting the obtained energy, transmitting the converted energy to an industrial power grid and providing load service for consumers. The invention discloses an efficient power supply guarantee device based on a photovoltaic panel. Comprising a solar cell panel unit, a current and voltage sensor unit of the solar cell panel unit, a DC / DC converter, a DC bus, an inverter, a current and voltage sensor unit at the output end of the converter, a DC / DC converter control unit, an inverter control unit, a control and switch microcontroller, and a current and voltage sensor unit of the DC bus. The invention relates to a DC / DC converter, which comprises a solar panel, a DC / DC converter, an LC filter, a radio interference filter and a load current and voltage sensor unit, and is characterized by further comprising a voltage pulse unit arranged between the solar panel and the DC / DC converter, and a control unit of the DC / DC converter has an additional function of controlling the voltage pulse unit. The technical result obtained by using the proposed device is that more energy is obtained from the solar panel device, the reliability of supplying power to the user is improved, and the flexibility and functionality of the user energy system are improved.

Description

Technical Field

[0001] The present invention relates to inverter technology, which can be used to efficiently extract the electrical energy of solar panels, convert and transmit the obtained energy to the industrial power grid, and provide load services for consumers. It can also use the energy obtained from the power grid to charge rechargeable batteries and supercapacitors, and convert it into industrial frequency AC voltage as needed, thereby providing consumers with a guaranteed uninterrupted power supply. Background Art

[0002] A device known in the prior art is powered by solar cells, comprising a solar module, a first DC-DC converter, a rechargeable battery, a second DC-DC converter, a controller and a load (RU2503120 A device powered by solar cells, IPCH02M3 / 156, December 27, 2013).

[0003] This device has the following disadvantages:

[0004] 1. Use traditional methods to track the maximum power point under uniform illumination;

[0005] 2. Unable to communicate with the industrial grid to ensure that batteries are charged during severe weather conditions and power cannot be released to the grid.

[0006] The power devices known in the prior art include solar cells, energy storage devices, DC / DC converters, DC / AC converters, and automatic circuit breakers (RU2397593 A power device and a control method thereof, IPCH02J7 / 35, H01L31 / 00, August 20, 2010).

[0007] This device has the following disadvantages:

[0008] 1. It is impossible to release the electricity obtained by solar panels into the industrial power grid;

[0009] 2. Use traditional methods to track the maximum power point under uniform illumination.

[0010] A device and method for tracking the maximum power point of an inverter when using a solar panel is known in the prior art, wherein the device includes a solar panel, an inverter, a system controller and a load. (US7158395B2 Method and device for tracking the maximum power point of an inverter, such as in photovoltaic applications, IPCH02M7 / 44, January 2, 2007).

[0011] This device has the following disadvantages:

[0012] 1. The traditional maximum power point is tracked based on the volt-ampere characteristic (VAC) of the solar panel cell, which drifts with temperature changes and uniform changes in light, resulting in inefficiency in the power extracted from the solar panel cell;

[0013] 2. In the event of a power outage in the grid, such equipment cannot be used as a backup power source.

[0014] A power conversion system with a maximum power point tracking function is also known in the prior art, the system comprising a maximum power point tracking (MPPT) device, a DC bus, a power converter and a converter controller. (US20130027997A1 Maximum power point tracking of a power conversion system and method thereof, IPCH02M7 / 44, January 31, 2013).

[0015] This device has the following disadvantages:

[0016] The traditional maximum power point is tracked based on the volt-ampere characteristic (VAC) of the solar panel cell, which drifts with temperature changes and uniform changes in light, resulting in insufficient power extracted from the solar panel cell;

[0017] There is no energy storage capability (batteries or supercapacitors), so this system cannot be used to power loads during grid failures or when the solar panel output is low.

[0018] In terms of technical essence, guaranteed power supply equipment based on renewable energy sources (RES) is closest to the required solution (RU207387U1, October 26, 2021). The patent tracks all areas on the VAC, if there is partial shading and a power peak occurs in the left branch of the VAC. When this point is reached, traditional methods are used to extract energy from the solar panel (SP). For example, there is a boost converter that extracts current from the solar panel so that the product of the current and voltage of the solar panel reaches a maximum. This is similar to a rheostat, and by choosing the position of the rheostat knob (impedance), the maximum energy can be obtained from the solar panel.

[0019] A disadvantage of this device is that it tracks several local areas on the VAC of the solar panel installation and drifts with changes in temperature and uniform changes in light, and it also tracks the occurrence of the maximum power point at partial shading and extracts power at this point, resulting in inefficiencies in extracting power from the solar panel installation. Summary of the invention

[0020] The technical problem to be solved by the present invention is to improve the efficiency of the device consisting of a solar panel (SP) unit and a converter, track the real maximum power point under actual operating conditions; transmit the received electrical energy to the grid and the load, and charge the energy storage unit from the solar panel unit and the grid. This improves the efficiency of extracting electrical energy from the solar panel unit and improves the reliability of power supply to users.

[0021] The technical results achieved using the proposed device are obtaining more energy from the solar panel device, improving the reliability of power supply to the user, and increasing the flexibility and functionality of the user's energy system.

[0022] In addition, the device also improves the reliability of power supply to users, which is mainly achieved by using an energy storage device, which receives energy from solar panels and the power grid according to a specific algorithm. When the power grid fails or the energy received from the solar panels is reduced, the energy from the energy storage device is added to the energy received from the solar panels on the common DC bus, which is then converted into AC power and supplied to the users, thereby ensuring uninterrupted power supply to the users.

[0023] The technical problems solved by the present invention and the technical achievements achieved are: a high-efficiency power supply guarantee device based on photovoltaic panels includes a solar panel unit, a current and voltage sensor unit of the solar panel unit, a DC / DC converter, a DC bus, an inverter, a current and voltage sensor unit at the output end of the converter, a DC / DC converter control unit, an inverter control unit, a control and switch microcontroller, a current and voltage sensor unit of the DC bus, an LC filter and a radio interference filter, and a current and voltage sensor unit of the load, wherein the device also includes a voltage pulse unit installed between the solar panel and the DC / DC converter, and the control unit of the DC / DC converter has an additional function of controlling the voltage pulse unit.

[0024] In addition, the device includes a bidirectional DC / DC converter for charging / discharging the rechargeable battery and the rechargeable battery.

[0025] In addition, the device includes a bidirectional DC / DC converter for the supercapacitor unit and charging / discharging the supercapacitor unit. BRIEF DESCRIPTION OF THE DRAWINGS

[0026] Figure 1. Structural block diagram of a high-efficiency power supply guarantee device based on photovoltaic panels;

[0027] Figure 2. The volt-ampere characteristics of a solar panel family depend on changes in temperature and uniform illumination of the panel.

[0028] Figure 3. The essence of the perturb-and-observe approach to maximum power point tracking.

[0029] Figure 4. Simplified diagram of a solar panel;

[0030] Figure 5. A possible implementation scheme;

[0031] Fig. 6. Schematic diagram of possible series (a) and parallel (b) connections of solar panels. DETAILED DESCRIPTION

[0032] A photovoltaic panel-based high-efficiency power supply guarantee device comprises a solar panel unit, a voltage pulse unit, a current and voltage sensor unit of the solar panel unit, a DC / DC converter, a DC bus, a current and voltage sensor unit of the DC bus, a reversible inverter, an LC filter, a current and voltage sensor unit at the output end of the converter, a radio interference filter, a current and voltage sensor unit of a load, a load, a controlled grid switch, a current and voltage sensor unit of a grid, a grid, a control unit of a DC / DC converter and a voltage pulse unit, a control unit of a reversible inverter, and a microprocessor control and switch unit.

[0033] In addition, the device may also include a rechargeable battery (RB) and a bidirectional DC / DC converter for charging / discharging the rechargeable battery, a super capacitor unit (SCU) and a bidirectional DC / DC converter for charging / discharging the super capacitor unit, and a control unit of the RB and the SCU.

[0034] Using a diagram to explain the claimed solution, FIG1 shows a block diagram of a highly efficient power supply guarantee device based on photovoltaic panels.

[0035] The figure shows a solar panel unit (1), a current and voltage sensor unit (2) of the solar panel unit, a DC / DC converter (3), a DC bus (4), a current and voltage sensor unit (5) of the DC bus, a reversible inverter (6), an LC filter (7), a current and voltage sensor unit (8) at the output of the converter, a radio interference filter (9), a current and voltage sensor unit (10) of the load, a load (11), a controlled grid switch (12), a current and voltage sensor unit (13) of the grid, a grid (14), a control unit (15) of the DC / DC converter and a voltage pulse unit, a control unit (16) of the reversible inverter, a microprocessor control and switch unit (17), a bidirectional DC / DC converter for charging / discharging a rechargeable battery (18), a rechargeable battery (RB) (19), a bidirectional DC / DC converter for charging / discharging a supercapacitor unit (20), a supercapacitor unit (SCU) (21), a voltage pulse unit (22), a control unit of the RB, and an SCU (23).

[0036] The working principle of the device is as follows.

[0037] The voltage and current of the solar panel unit (1) are input to the DC / DC converter (3) through the voltage pulse unit (22) and the current and voltage sensor unit of the solar panel unit (2). The voltage and current information of the solar panel is provided to the control unit of the DC / DC converter and the voltage pulse unit (15) according to a specified algorithm, and the unit generates a control signal to operate the DC / DC converter and the voltage pulse unit so as to extract the maximum power under a given temperature and light from the solar panel. The voltage pulse unit can be controlled together with the DC / DC converter by a control unit, or it can be controlled within the voltage pulse unit, but the premise is that there must be current and voltage sensors and these sensors can be used to receive data. The obtained power is fed to the DC bus (4). The voltage and current are fed from the DC bus to the reversible inverter (6) through the current and voltage sensor unit of the DC bus. In the direct conversion mode, the inverter converts the DC voltage and current into AC voltage and current by pulse width modulation (PWM) and the like. The power PWM signal is then fed to the input of the LC filter (7) and the filtered grid low frequency signal is fed to the input of the current and voltage sensor unit at the converter output (8). The signal is then fed to the input of the radio interference filter (9). Next, the output current and voltage are provided to the load (11) via the load current and voltage sensor unit (10) and to the grid (14) via the controlled grid switch (12) and the grid current and voltage sensor unit (13). The reversible inverter is controlled by the reversible inverter control unit (16), which receives current and voltage information of the DC bus and the inverter output. The overall operation of the device is controlled by a microprocessor control and switch unit (17), which receives information from the DC / DC converter control unit and the voltage pulse unit (15), the inverter control unit (16) and the current and voltage units of the converter output, the load and the grid.

[0038] Introducing an additional voltage pulse unit between the solar panel and the DC / DC converter, and designing a DC / DC converter control unit that can control the voltage pulse unit, can ensure effective extraction of electrical energy from the solar panel unit, increase the energy obtained from the solar panel unit, improve the flexibility and functionality of consumer energy systems based on such converters, and increase the reliability of power supply to consumers. By periodically applying voltage pulses to the solar panel, the voltage pulse unit (22) can "pull out" additional electrons from the solar panel, which electrons cannot reach the conductor in traditional power extraction methods and will recombine with holes in the solar panel. Compared with traditional power extraction methods, this method can obtain more energy from the SP.

[0039] The system may also have a rechargeable battery (19) and a bidirectional DC / DC converter unit for charging / discharging the rechargeable battery (18).

[0040] The system may also have a super capacitor unit (SCU) (21) and a bidirectional DC / DC converter for charging / discharging the super capacitor unit (20).

[0041] When RB and SCU are introduced into the system, ensure that the power supply system contains the control unit (23) of RB and SCU.

[0042] This makes it possible to additionally increase the reliability of the electricity supply guaranteed to the users, which reliability is provided, inter alia, by using an energy storage unit which receives energy from the solar panels and the grid according to a specified algorithm and, in the event of a grid failure or a reduction in the energy received from the solar panels, ensures uninterrupted power supply to the users by adding the energy from the energy storage unit to the energy received from the solar panels on a common DC bus, converting it into AC power and supplying it to the users.

[0043] The power supply device can also be used as a micro power source to provide renewable energy energy to the power grid, as well as a power source to supply power to users from renewable energy; it can also be used as a guaranteed power source to supply power to users when the power grid fails.

[0044] Embodiments of the device with different configurations are described below.

[0045] 1. No RB or SCU.

[0046] On the basis of parasitic reduction recombination, energy is extracted from the maximum power point of the solar panel and converted into AC voltage for the grid. Next, the microcontroller analyzes the current and voltage of the load and the grid. If the energy of the solar panel is sufficient to power the load, the inverter disconnects the grid from the load and only the solar panel is powered. If the load consumes less energy than the energy generated by the solar panel unit (SPU), the inverter delivers part of the energy received from the solar panel unit to the load and the other part to the grid. If the load consumes more energy than the solar panel unit generates, the inverter delivers all the energy received from the solar panel unit to the load and receives insufficient energy from the grid for the load. When there is no load, all the energy received from the SPU is fed into the grid.

[0047] 2. With RB and / or SCU.

[0048] When the system has RB and / or SCU, the general operation algorithm described above will not be changed, but there will be more changes in the system operation. When the load consumes part of the energy provided by the SPU, the remaining energy will be used to charge the RB and / or SCU. Once they are fully charged, the energy will be delivered to the grid. If the grid voltage fails, the control and switch microcontroller disconnects the grid from the system and the load, and the SPU supplies power to the user. If the energy provided by the SPU is insufficient, the DC bus will obtain the stored energy from the RB and / or SCU, which will then be converted into an AC voltage of industrial frequency to supply power to the user. If the energy received from the SPU is not enough to power the load and keep the RB and / or SCU charged for a certain time interval, the inverter will operate in reverse mode according to the specified algorithm (for example, at night) to charge the DC bus from the industrial grid, and then the voltage converter will charge the RB and SCU to the specified level.

[0049] The following describes the operation of the solar panel installation under various operating conditions. Figure 2 shows the series of volt-ampere characteristics of the solar panel, which depends on the temperature of the panel and the change of uniform irradiance. The volt-ampere characteristic (VAC) has a traditional form - first, the power increases linearly with the increase of voltage, then reaches an extreme value, after which the received power decreases with the increase of the solar panel voltage. In this case, we can see that according to the VAC value of the solar panel, there is only one extreme value, which drifts along the VAC value in a limited area with the change of temperature and the uniform change of irradiance.

[0050] As the temperature increases, the voltage at the maximum power point decreases. The extreme value of the power function on VAC moves to the lower left. When the temperature decreases, the voltage at the extreme point increases, and the maximum power point on VAC moves upward and to the right. When the uniform illumination of the panel decreases, the current at the maximum power point decreases, and the power extreme value moves downward. When the uniform illumination of the panel increases, the current increases, so the maximum power point moves upward.

[0051] There are several known algorithms for maximum power point tracking. These include, for example, the perturb and observe method or the increase conductivity method. The essence of the perturb and observe method is shown in Figure 3. The voltage and current are measured on the solar panel unit (SPU). The power point Р0 is calculated. Then, the output voltage of the SPU is changed by controlling the converter (positive voltage increment). The current and voltage are measured. In this way, the power point Р1 is determined. Р1 is compared with Р0, and if Р1 is greater, the voltage increment is maintained and the next step is taken. The voltage is increased on the panel unit. The current is measured. The power point Р2 is calculated. Next, the Р3 and Р4 points are also calculated. If the new power point is lower than the previous power point, the increment sign changes from positive to negative. There is also an adaptive algorithm whose increment step size is not constant, but varies depending on the distance of the extreme value. When approaching the extreme value, the step size is reduced to reduce the ripple of the power extracted from the solar panel unit.

[0052] Therefore, under the condition of stable temperature change and uniform illumination change on solar panels, the traditional maximum power point search algorithm can track the extreme drift of VAC of solar panels in a given area.

[0053] Virtually all existing methods of extracting power from solar panels are equivalent to connecting an inverter to the solar panel, which ensures that DC current is extracted from the solar panel at the maximum power point at VAC by automatically adjusting "its impedance".

[0054] Modern industrially produced solar panels extract energy using the traditional ("varistor") method with an efficiency of between 18% and 23%. In other words, 1 kilowatt of solar photon energy produces 180-230 watts of electrical energy on the equivalent load converter.

[0055] The rest of the energy of the solar radiation is lost in the SP. The following are the main processes that lead to the inefficiency of solar cells: reflection of some of the radiation by the semiconductor surface, absorption of inactive photons, parasitic recombination of non-equilibrium carriers, etc.

[0056] Figure 4 is a simplified view of the operation of the SP. In Figure 4, light falls on the SP and propagates to the "n" region, the "p" region, and the loss region. In the loss region, the energy of the photon is transferred to the electron-hole pair. They are separated. Under the influence of the internal magnetic field, the electron moves up through the "n" region to the conductor and then into the load. After entering the load, the electron returns to the SP on the "p" region side through the conductor and recombine with the hole.

[0057] This is how the energy of photons is converted into electrical energy.

[0058] After the electrons and holes are separated by sunlight, some of the electrons cannot reach the conductor and therefore cannot reach the load. During the movement of electrons and holes, parasitic recombination occurs in the loss region and partially in the "n" and "p" regions. Therefore, due to the parasitic recombination process, most of the energy received by the solar cell from sunlight cannot reach the load.

[0059] To reduce the energy losses caused by parasitic recombination, we introduce a pulse voltage unit between the SP and the load. The purpose is to apply a positive potential in the "n" region of the SP and a negative potential in the "p" region using short pulses (with a certain rising and falling edge) with a certain amplitude, frequency, peak-to-average ratio and duration. The purpose is to allow the electrons and holes that receive energy from the photons to obtain an additional pulse when moving from the loss zone to the conductor. Under the action of these voltage pulses, the probability of parasitic recombination is reduced, the number of electrons reaching the conductor and the load is increased, and therefore the energy obtained from the solar panel and the efficiency of the solar cell converter system are improved.

[0060] It is worth noting that the duration of the voltage pulse is in the microsecond unit or less, so the energy consumed to generate the voltage pulse is an order of magnitude less than the energy of the electrons, which do not lose energy in the parasitic recombination process and are fed to the load. In addition, for a positive polarity voltage pulse applied to the SP "n" region, the SP's pn junction is equivalent to a closed diode.

[0061] When this "control" voltage is applied, a large number of electrons that have gained energy from photons but have previously recombined with holes and failed to reach the load will leave the "n" layer of the SP, thereby increasing the useful energy and efficiency of the SP to 1.2-1.5 times that of traditional ("rheological") power extraction methods. In a way, this principle can be vividly likened to the working principle of field effect transistors, that is, the electric field of the gate controls the opening of the channel and the power current through the pn junction of the field effect transistor, and no current is actually wasted.

[0062] There are many circuit methods to realize the method of improving the efficiency of the SP conversion system. FIG5 shows one possible implementation.

[0063] FIG5 shows a solar panel SP1, a storage capacitor C1, a boost voltage converter consisting of a capacitor C2, a choke L1, a diode D1, a key K1, a pulse source consisting of a transformer Tr1, a capacitor C3, a key K2, a power supply U1 and a common control device UU1.

[0064] The control device UU1 generates control signals for the buttons K1 and K2. When the button K2 is switched to the off state for a short time, a current pulse passes through the primary winding 1 of the transformer Tr1. A voltage pulse is generated on the secondary winding of the transformer Tr1. The positive polarity voltage pulse is applied to the "n" area of ​​the solar panel SP1 through the capacitor C1, and the negative polarity voltage pulse is applied to the "p" area of ​​the solar panel SP1 through the capacitor C1. At the same time, the button K1 is periodically opened according to the specified operation algorithm, thereby generating a voltage on the capacitor C2. Next, the voltage on the capacitor C2 is provided to the load or voltage inverter.

[0065] The light falling on the solar panel SP1 separates electrons and holes. The electrons move along the circuit and charge the capacitor C1. At the same time, a positive voltage pulse of given frequency, duration, amplitude, rising edge and falling edge is applied to the "n" area of ​​the solar panel through the pulse transformer Tr1; therefore, the parasitic recombination probability of electrons and holes is reduced, and more electrons excited by the photons reach the conductor and charge the capacitor C1. Then, the boost converter (L1, K1, D1, C2) increases the voltage to the level required by the load or voltage inverter.

[0066] Transformer Tr1 may or may not use a ferromagnetic core.

[0067] Figure 6 shows possible series (a) and parallel (b) schematic diagrams of solar panels, taking two solar panels as an example. When the solar panels are connected as a unit, diodes are connected in parallel with the solar panels to bypass the current when the solar panels are partially shaded. To prevent these diodes from shunting the pulse signals applied to the solar panels, series chokes (L2-L4) are installed between each diode (D2-D4). These DC chokes have almost no impedance, and when partially shaded, DC current will pass through the diodes. In this case, when transformer Tr1 (Figure 5) generates voltage pulses lasting microseconds or shorter, the D2-D4 chokes have high wave impedance and will not shunt these pulses.

[0068] This solution can improve the energy obtained from solar panel arrays under actual operating conditions. This is critical for both off-grid and grid-connected systems as it ultimately affects the energy obtained from solar panels and the payback period of the entire system.

Claims

1. A photovoltaic panel-based high-efficiency power supply guarantee device, comprising a solar panel unit, a current and voltage sensor unit of the solar panel unit, a DC / DC converter, a DC bus, an inverter, a current and voltage sensor unit at the output end of the converter, a DC / DC converter control unit, an inverter control unit, a control and switch microcontroller, a current and voltage sensor unit of the DC bus, an LC filter and a radio interference filter, and a current and voltage sensor unit of the load, characterized in that , also includes a voltage pulse unit installed between the solar cell panel and the DC / DC converter, wherein the control unit of the DC / DC converter has an additional function of controlling the voltage pulse unit.

2. The high-efficiency power supply guarantee device based on photovoltaic panels according to claim 1 is characterized in that: Includes a bidirectional DC / DC converter for charging and discharging rechargeable batteries.

3. The high-efficiency power supply guarantee device based on photovoltaic panels according to claim 1 is characterized in that: Includes a bidirectional DC / DC converter for supercapacitor cells and charging / discharging the supercapacitor cells.