SK7495Y1 - Electronic photovoltaic panels switch for electric heating elements and other electrical loads - Google Patents

Abstract

Electronic switch (11) of photovoltaic panels (1) for electrical heating elements and other electrical loads (3) consists of IGBT transistor (2), the control electrode (2.1) of which is connected to the control circuits (7) the input power electrode (2.2) is connected through the load (3), then through the second contact of the safety thermostat (4.2) and through the main fuse (13) to the potential of the DC+ of the photovoltaic panels (1) and the output force electrode (2.3) is connected to the potential of the DC- of the photovoltaic panels (1). The control circuit (7) of the IGBT transistor (2) are connected to the power supply circuits (8), to the supply of the control circuits (7) and through the supply circuits (8) are connected to the means for fusing in the order of the auxiliary fuse (14), then through the auxiliary fuse (14) to the second contact (4.2) of the safety thermostat (4) and to the main fuse (13). The control circuits (7) are further connected through the connectors HLI, HL2 to the LED diodes (9) and (10) for signaling the state of the electronic switch (11) and to the terminals T+ and T- to the control contact (5.1) of the thermostat (5) connected in the series with the first contact (4.1) of the safety thermostat (4). The electronic switch (11) is provided with arc extinguishing circuits (6.1) and (6.2).

Description

The technical solution deals with electronic switch of direct current produced by photovoltaic panels, which is further used for heating of domestic hot water (DHW) or for switching of other suitable electric load (eg floor, wall or ceiling heating by resistive wires).

BACKGROUND OF THE INVENTION

DHW heating with photovoltaic panels without MPPT (maximum power point tracking) is described in utility model no. 5788. Its essence is that the water is heated by mechanically connecting direct and alternating current while ensuring electrical temperature control and the safety of the water heating device. The DC circuit ensures the power utilization of the device and the AC circuit ensures the safety of the device.

Photovoltaic panels in the existing water heating systems are connected to the DHW heater by means of electromechanical contacts (power relays, contactors), while the extinguishing of the direct electric arc is achieved by different ways of connection of individual contacts.

The disadvantage of all the existing solutions is that the coils of the power relays and contactors are supplied from the AC network, therefore, in the event of a power failure, the DHW heating does not work and it is not possible to use these solutions in island systems. Another disadvantage is the high tanning of the contacts of the power elements when the DC current is expanded, which is associated with their limited lifetime.

The aim of the present solution is to heat the hot water by means of an electronic switch, that is, to replace the electromechanical switch used so far, thus achieving a longer lifetime and higher reliability than the electromechanical switch and the necessity to use an external power supply of the electromechanical switch.

The essence of the technical solution

The essence of the technical solution lies in the electronic switching of the power supplied to the electric heater of the DHW heater (or other suitable electrical load). The control input of the electronic switch is the contact of the control thermostat of the DHW heater, with which the first of the two contacts of the safety thermostat is connected in series and create the control signal of the electronic switch.

The second of the two safety thermostat contacts is connected in series with the electronic switch, and therefore the solution maintains the requirements for direct safe shutdown when the critical temperature in the DHW heater is reached (before the safe temperature is exceeded).

The control voltage is max. 20 V _DC and the control current is max. 250 mA, and therefore the thermostat contacts do not burn. The control contact is also connected to the first of the two contacts of the safety thermostat (it opens when the critical DHW temperature is reached). This ensures that the power of the heater is switched off quickly even when the safety thermostat contacts are opened. As a result, at the second contact of the safety thermostat, which is directly connected in the power circuit of the heating element, only an arc that opens only for max. 1 ms (response speed of electronic switch + maximum possible time shift of both safety thermostat contacts). The safety thermostat is normally designed for switching off the AC voltage and current, therefore it has to handle an arc lasting up to 10 ms. Since the electronic switch ensures the duration of this arc max. 1 ms, the safety thermostat is also several times less loaded, resulting in an extension of its service life.

Electronic switch of photovoltaic panels is realized by IGBT (IGBT) - Insulated Gate Bipolar Transistor - bipolar transistor with isolated gate is a transistor designed for a wide range of switching powers and a high switching frequency, whose advantages are low on-state losses, low excitation power and wide range operating voltage and current). The IGBT transistor control electrode is connected to the electronic switch control circuits, the IGBT transistor input power electrode is connected through the load, the second safety thermostat contact, and the main fuse to the DC + photovoltaic panel potential, and the IGBT transistor output electrode is connected to the DC photovoltaic potential panels.

The control circuitry of the electronic switch is coupled to the supply circuitry for supplying the control circuitry, and through the supply circuitry, the control circuitry is further coupled to the means for securing it in the order of the auxiliary fuse and the auxiliary fuse for the second contact of the safety thermostat.

The electronic switch control circuits are further coupled via the HL1, HL2 connectors to the green LED and the red LED to indicate the status of the electronic switch.

SK 7495-1

Furthermore, the control circuits of the electronic switch are connected at terminals T + and T- to the control contact of the control thermostat, which is connected in series with the first contact of the safety thermostat.

The photovoltaic panel electronic switch further comprises a quenching circuit interconnected, the first quenching circuit being connected in parallel to the heater and the second quenching circuit at the ESTOP1, ESTOP2 terminals connected to the second safety thermostat contact, the photovoltaic panels being connected to the DC + terminal via the main fuse. to the second arc quench circuit.

The state of the whole circuit is signaled by two LEDs. The green LED connected to the HLI connector indicates the status of the circuit under voltage (UNDER VOLTAGE) and the red LED connected to the HL2 connector indicates that all conditions are met, thus switching on the IGBT transistor and electronic switch

- HEAT status.

The electric heater is connected to the switch by means of terminals Z1 +, Z1-. The excitation of the IGBT transistor is provided by control circuits which evaluate the control contact signal of the control thermostat and the first of the pair of safety thermostat contacts at the terminals T +, T-. The control circuits also sense the input voltage of the photovoltaic panels at the DC +, DC- terminals. The switch (IGBT transistor) is in the on state only when the condition of sufficient supply voltage on the photovoltaic panels for the power and control circuits is fulfilled and at the same time the condition of the control thermostat control contact and both safety thermostat contacts are met. The IGBT transistor is in the open state when the control thermostat control contact or the first safety thermostat contact is in the open state. The second contact of the safety thermostat is opened when the emergency state of reaching the critical temperature in the DHW heater (or reaching the critical state of another electrical load) is disconnected and at the same time the load is disconnected from the DC voltage of the photovoltaic panels. The IGBT and the load are opened when the low voltage condition of the photovoltaic panels is met, or when the control thermostat contact or the safety thermostat contacts are open.

The electronic switch of the photovoltaic panels is equipped with arc quenching circuits to eliminate voltage peaks when the load is switched off, it is also equipped with a main fuse to protect the electronic switch, IGBT transistor and load, and an auxiliary fuse to protect the power circuits and control circuits.

The electronic switch using the IGBT transistor according to the present invention is therefore based on a different physical principle than the mechanical switch and has the advantage that by interrupting the current flowing in the circuit, the arc will switch off in less than 1 ms. Therefore, not only the electronic switch itself, but also the mechanical contacts in the circuit have a long service life.

Another advantage of the switch is the supply of control circuits directly from the photovoltaic panels, eliminating the need for external power supply. At the same time, there can be no condition when the external power supply fails, even if the exposure is sufficient.

Other advantages of this technical solution are:

- use of a standard control thermostat with a contact designed for switching AC voltage and current;

- use of a standard safety thermostat with contacts designed to switch AC voltage and current;

- practically unlimited service life of the control thermostat contact as well as the safety thermostat contacts;

- Maintained functionality even in the event of grid failure, since the switch is powered directly from the photovoltaic panels.

Electronic transistor tripping is fast and does not cause the contacts to burn. Therefore, not only the electronic switch itself, but also the thermostatic contact has practically unlimited service life.

BRIEF DESCRIPTION OF THE DRAWINGS

Figure 1 shows a block diagram of an electronic switch circuit with an IGBT transistor, its individual parts, and the connections between them.

Figure 2 shows an exemplary embodiment of a photovoltaic system for DHW heating using an electronic direct current switch together with a DHW heater.

EXAMPLES

The electronic switch 11 of the photovoltaic panels for electric heaters and other electrical loads 3 consists of an IGBT transistor 2 whose input power electrode 2.2 is connected to the electrical load 3 via terminal Z1 - and the output power electrode 2.3 is connected to the DC-terminal. The control electrode 2.1 of the transistor 2 is connected to the control circuits 7 which control the operation of the electronic switch 11. To the control

The LEDs 9 and 10 are used to indicate the status of the electronic switch 11 through the HLI, HL2 connectors, the green LED 9 on the HLI connector indicating the UNDER VOLTAGE condition and the red LED 10 on the HL2 connector indicating the HEATING status. Furthermore, the control contacts 7 of the control thermostat 5 are connected in series with the contact 4.1 of the safety thermostat 4 to the control circuits 7 by means of terminals Τ-, T +. The control circuits 7 are powered by power circuits 8 secured by fuse 14. Photovoltaic panels 1 are connected on DC + and DC- terminals. The DC + terminal is followed by a main fuse 13, which secures the IBGT transistor 2 and the second contact 4.2 of the safety thermostat 4, which disconnects the power supply if the maximum safety temperature inside the heater is exceeded. In parallel to the load 3 and the second contact 4.2 of the safety thermostat 4, quenching circuits 6.1, 6.2 are connected, which, together with the operation of the transistor 2, prevent the occurrence of voltage peaks and a long-lasting electric arc when switching the load 3.

The control thermostat 5 of the DHW heater 12 is set to the desired maximum temperature at which the control contact 5.1 of the thermostat 5 opens. The control circuits 7 evaluate the state of the terminals Τ-, T +, while measuring the DC voltage of the panels. When the PV panel voltage drops (below approx. 40 V _DC ), the control circuits 7 automatically open the IGBT transistor 2. The maximum voltage of the photovoltaic panels 1 is limited by the connected varistor (up to approx. 560 V _DC ).

The IGBT transistor 2 is in the on state, and thus the electronic switch 11 is in the on state only when the condition of sufficient supply voltage on the photovoltaic panels 1 for the supply circuits 8 and the control circuits 7 is fulfilled and the control contact 5.1 of the control contact 5.1 is fulfilled. thermostat 5 and the first contact 4.1 of the safety thermostat 4. The second contact 4.2 of the safety thermostat 4 is connected in series with the DC power supply at the terminals ESTOP1, ESTOP2. When it is opened, when the critical temperature in the DHW heater is reached, load 3 is automatically disconnected from the DC voltage of the photovoltaic panels 1. The quenching circuits 6.1 and 6.2 eliminate the voltage peaks generated when the load is switched off. LED 9 on the HLI connector (under voltage indication) and red LED 10 on the HL2 connector (heating indication).

When the water temperature set on the control thermostat 5 reaches the control thermostat control contact 5.1, it opens, causing the electronic switch 11 to open. The red LED 10 on the HL2 connector goes out and only the green LED 9 on the HLI connector is lit. If the control thermostat 5 fails and the water temperature in the DHW heater 12 rises to a critical value, the contacts of the safety thermostat 4 are opened and the entire circuit of the electronic switch JT is disconnected and the green LED 9 on the HLI connector is disconnected. the red LED 10 on the HL2 connector is off. Both LEDs are off even if the voltage on the photovoltaic panels 11 is zero or very low due to zero or low intensity of solar radiation.

Industrial usability

The electronic switch makes it possible to replace the electromechanical switch used for connecting to the DHW heater or other suitable electrical load and disconnecting the photovoltaic panels. The use of an electronic switch achieves a longer lifetime and greater reliability than an electromechanical switch, while eliminating the need to use an external power supply for the electromechanical switch, since the electronic switch is powered directly from photovoltaic panels.

PROTECTION REQUIREMENTS

Claims (3)

L Electronic switch (11) for photovoltaic panels (1) for electric heaters and other electrical loads (3), characterized in that it consists of an IGBT transistor (2) whose control electrode (2.1) is connected to control circuits (7) , the input power electrode (2.2) is connected via the electrical load (3), the second safety thermostat contact (4.2) and the main fuse (13) to the DC + photovoltaic panel potential (1) and the output power electrode (2.3) is connected to potential of DC photovoltaic panels (1), from the control circuits (7) of the IGBT transistor (2), which are connected to the following elements: to the power circuits (8) to power the control circuits (7) and through the power circuits (8) control circuits (7) connected to the means for securing them in sequence to the auxiliary fuse (14), then via the auxiliary fuse (14) to the second contact (4.2) of the safety thermostat (4) and to the main fuse (13), via HL connectors I, HL2 to the green LED (9) and the red LED (10) to indicate the status of the electronic switch (11), to the T + and T- terminals to the control contact (5.1) of the control thermostat (5) connected in series with the first contact ( 4.1) a safety thermostat (4), connected to the arc quenching circuits (6.1), (6.2), the first arc quenching circuit (6.1) being connected in parallel to the electrical load (3) and the second arc quenching circuit (6.2) on the ESTOP1 terminals, SK 7495-1 EST0P2 connected to the second contact of the safety thermostat (4.2), whereby the photovoltaic panels (1) are connected to the second arc circuit (6.2) on the DC + terminal via the main fuse (13). The photovoltaic panel electronic switch (11) according to claim 1, characterized in that the second contact (4.2) of the safety thermostat (4) is opened when the critical temperature in the heater is reached. 5 (12) and at the same time the electrical load (3) is disconnected from the DC voltage of the photovoltaic panels (1). The photovoltaic panel electronic switch (11) according to claim 1, characterized in that the IGBT (2) and the electrical load (3) are opened at low voltage of the photovoltaic panels (1) or at the contact (5.1) of the control thermostat (5). ) or open contacts (4.1), (4.2) of the safety thermostat (4). The photovoltaic panel electronic switch (11) according to claim 1, characterized in that it is provided with arc-quenching circuits (6.1), (6.2) to eliminate the voltage peaks when the electrical load (3) is switched off. 15 2 drawings