Power generation and distribution topology circuit structure for realizing grid connection by using high-voltage variable-frequency power supply

Abstract

The utility model provides a power generation and distribution topology circuit structure for realizing grid connection by using a high-voltage variable-frequency power supply, which relates to the technical field of high-voltage frequency converters and high-voltage variable-frequency power supplies and comprises a power generation bus section, a power generation bus section PT, a lightning arrester, a high-speed alternating-current generator, a high-voltage pre-charging cabinet and the like. The power generation bus section is respectively connected with the power generation bus section PT, the lightning arrester and the two switch cabinets, one switch cabinet is connected with the high-speed alternating-current generator, the other switch cabinet is connected with the high-voltage pre-charging cabinet, the high-voltage pre-charging cabinet is connected with the high-voltage variable-frequency power supply device, and the high-voltage variable-frequency power supply device is connected with the reactor cabinet; the commercial power bus section is respectively connected with the commercial power bus section PT, the lightning arrester and at least more than three switch cabinets, one switch cabinet is connected with the reactor cabinet, and the other switch cabinet is connected with a commercial power supply system; the utility model can utilize the voltage and frequency regulation function of the high-voltage variable-frequency power supply to realize the synchronous undisturbed grid connection between the power generation network with different frequencies and the commercial power supply system.

Description

Technical Field

[0001] The utility model relates to the technical field of high-voltage frequency converters and high-voltage variable-frequency power supplies, and in particular to a power generation and distribution topology circuit structure that utilizes a high-voltage variable-frequency power supply to achieve grid connection. Background Art

[0002] Since the scale and capacity of new energy systems are relatively small when generating electricity, they are basically installed directly at the user end in a modular and decentralized manner. They can operate independently or in conjunction with the grid.

[0003] Because high-speed motors have high speeds and are much smaller than ordinary power motors, they are connected to the prime mover, eliminating the traditional reduction mechanism, and have small rotational inertia. Therefore, they have the advantages of high motor power density, effective material saving, high transmission efficiency, low noise, and fast dynamic response. Therefore, the use of high-speed generators is an important choice for new energy systems such as biomass power generation and distributed energy. However, when using high-speed generators, the power generation frequency is often higher than the industrial frequency 50Hz (not 50Hz), making it impossible for the power generation grid to be directly connected to the mains power grid. Certain technical means must be used to convert the frequency and voltage of the power generation system into the same frequency and voltage as the mains before it can be connected to the grid.

[0004] To better illustrate the problem, let's take a small steam turbine power generation project for small biomass power generation, distributed energy and other markets as an example. The input voltage of its high-speed generator bus section is 6kV or 10kV, the frequency is 75-100Hz, and the power supply is 2MW-8MW; the rated voltage of the mains power supply system bus section is 6kV or 10kV, and the frequency is 50Hz; it is required that the generating bus can be connected to the mains power frequency power supply network.

[0005] Existing technical solution: adopting the technical method of AC-DC-AC conversion, the power supply of the power generation system is first split into two groups of power supplies at different angles through a rectifier transformer (generally an oil-immersed transformer) and then transmitted to a high-voltage rectifier device for rectification into DC (generally 12-pulse rectification), filtered and stored through an intermediate DC link, and then inverted into AC power with the same frequency as the mains through an inverter, and then boosted to the same voltage as the mains through a step-up transformer, and finally the power generation network is connected to the industrial frequency mains network through a synchronization device to jointly provide power for the power load.

[0006] The biggest disadvantage of the above existing technical solutions is that each link is relatively independent, the integrated control system and protection are quite complicated, and the transformer and reactor are in long-term operation, which greatly increases the loss of the entire system, thereby causing a large amount of power loss. The equipment price of the overall solution is relatively expensive, and the overall cost performance is not high.

[0007] In summary, there are areas for improvement, and the utility model proposes a power generation and distribution topology circuit structure that utilizes a high-voltage variable-frequency power supply to achieve grid connection. Utility Model Content

[0008] In view of the shortcomings of the prior art, the utility model aims to propose a power generation and distribution topology circuit structure that uses a high-voltage variable-frequency power supply to achieve grid connection. The specific scheme is as follows:

[0009] A power generation and distribution topology circuit structure that uses a high-voltage variable-frequency power supply to achieve grid connection, the circuit structure comprising a power generation bus section, a power generation bus section PT and a lightning arrester, a high-speed AC generator, a high-voltage pre-charging cabinet, a high-voltage variable-frequency power supply device, a reactor cabinet, a mains bus section, a mains bus section PT and a lightning arrester, and a switch cabinet;

[0010] The generating bus section is used for input voltage of 6kV or 10kV and frequency of 75-100Hz, and is respectively connected to the generating bus section PT and lightning arrester, and two switch cabinets, one of which is connected to the high-speed AC generator, and the other is connected to the high-voltage pre-charging cabinet, which is then connected to the high-voltage variable frequency power supply device, which is then connected to the reactor cabinet;

[0011] The rated voltage of the mains bus section is 6kV or 10kV, the frequency is 50Hz, and it is connected to the mains bus section PT and lightning arrester, and at least three switch cabinets, one of which is connected to the reactor cabinet, and another is connected to the mains power supply system;

[0012] Among them, each switch cabinet is equipped with a withdrawable vacuum circuit breaker.

[0013] Further, the high voltage pre-charging cabinet includes a fixed vacuum circuit breaker, a current limiting resistor;

[0014] The fixed vacuum circuit breaker is connected to both ends of the current limiting resistor.

[0015] Further, the high-voltage variable-frequency power supply device includes a phase-shifting transformer, a power unit and a control system;

[0016] The phase-shifting transformer is connected in series with the current-limiting resistor, and the power unit and the control system are further connected in series with the phase-shifting transformer.

[0017] Further, the reactor cabinet includes a reactor and a bypass switch, and the bypass switch is configured as a fixed vacuum circuit breaker 2;

[0018] The reactor is connected in series with the power unit and the control system, and the bypass switch is connected in parallel to both ends of the reactor.

[0019] Furthermore, the high voltage variable frequency power supply device is used for outputting a voltage of 6 kV or 10 kV and a frequency of 50 Hz.

[0020] Furthermore, the capacity of the high voltage variable frequency power supply device is 10MVA.

[0021] Compared with the prior art, the beneficial effects of the utility model are as follows:

[0022] (1) The utility model directly utilizes the voltage and frequency regulation functions of the mature and stable cascade high-voltage transformer to achieve simultaneous and disturbance-free grid connection between power generation grids of different frequencies and the city power supply system, that is, to achieve grid connection of power supply systems of the same voltage but different frequencies. Without reducing the safety and stability of the overall system, the overall cost of the high-voltage variable-frequency power supply is reduced, the overall volume is reduced, and the overall cost performance is very high.

[0023] (2) The reactor in the variable frequency power supply circuit only operates for a short period of time when connected to the grid, usually only a few minutes, which improves the overall system efficiency of the variable frequency power supply, reduces system losses, and saves some electricity.

[0024] (3) By utilizing cascaded high-voltage inverter technology, the variable frequency power supply has minimal harmonic pollution to the power generation bus and the mains power supply bus, with a high input power factor and good output waveform quality. There is no additional heating caused by harmonics, and there is no need to add input and output filters. BRIEF DESCRIPTION OF THE DRAWINGS

[0025] Figure 1 It is a single line diagram of the utility model;

[0026] Figure 2 This is the topological structure diagram of the high-voltage inverter.

[0027] Figure numerals: 1. Power generation bus section; 2. Power generation bus section PT and lightning arrester; 3. High-speed AC generator; 4. High-voltage pre-charging cabinet; 41. Fixed vacuum circuit breaker 1; 42. Current limiting resistor; 5. High-voltage variable frequency power supply device; 51. Phase-shifting transformer; 52. Power unit and control system; 6. Reactor cabinet; 61. Reactor; 62. Fixed vacuum circuit breaker 2; 7. Mains bus section; 8. Mains bus section PT and lightning arrester; 9. Switch cabinet; 10. Pull-out vacuum circuit breaker. DETAILED DESCRIPTION

[0028] The present invention will be further described in detail below in conjunction with the embodiments and drawings, but the implementation methods of the present invention are not limited thereto.

[0029] In order to achieve the project requirements, the utility model proposes a power generation and distribution topology circuit structure that uses a high-voltage variable-frequency power supply to achieve grid connection. A small steam turbine high-speed generator outputs a high-voltage and high-frequency power supply, which is connected to the factory's industrial frequency power grid synchronously and without disturbance after voltage and frequency regulation by the high-voltage variable-frequency power supply.

[0030] Specifically, the circuit structure includes a generating bus section 1, a generating bus section PT and a lightning arrester 2, a high-speed AC generator 3, a high-voltage pre-charging cabinet 4, a high-voltage frequency conversion power supply device 5, a reactor cabinet 6, a mains bus section 7, a mains bus section PT and a lightning arrester 8, and a switch cabinet 9.

[0031] Among them, the power generation bus section 1 in the utility model is used for input voltage of 6kV or 10kV and frequency of 75-100Hz. After passing through the high-voltage frequency conversion power supply device 5, the output voltage is 6kV or 10kV and the frequency is 50Hz. Through the synchronous reactor cabinet 6, it is connected to the mains bus section 7 without disturbance, and jointly provides power for the power load.

[0032] Among them, the rated voltage of the mains bus section 7 in the utility model is 6kV or 10kV, the frequency is 50Hz, and the output voltage and frequency of the variable frequency power supply device must be the same frequency, amplitude and phase as the mains power supply system.

[0033] In this regard, the connection relationship of the circuit structure is specifically as follows: the power generation bus section 1 is respectively connected to the power generation bus section PT and the arrester 2, and two switch cabinets 9, one of which is connected to the high-speed AC generator 3, and the other switch cabinet 9 is connected to the high-voltage pre-charging cabinet 4, and the high-voltage pre-charging cabinet 4 is further connected to the high-voltage variable frequency power supply device 5, and the high-voltage variable frequency power supply device 5 is further connected to the reactor cabinet 6;

[0034] The mains bus section 7 is respectively connected to the mains bus section PT and the arrester 8, and at least three switch cabinets 9, one of which is connected to the reactor cabinet 6, and another of which is connected to the mains power supply system.

[0035] For ease of description, the primary single-line diagram of the utility model is as follows Figure 1 As shown, in Figure 1 The specific contents are as follows:

[0036] QF1~n are withdrawable vacuum circuit breakers 10 in the switch cabinet 9. Each switch cabinet 9 is provided with a withdrawable vacuum circuit breaker 10. Since there are two switch cabinets 9 cooperating with the power generation bus section 1, Figure 1 It can be seen that from left to right they are QF1 and QF2, QF1 is used to connect to the high-speed AC generator 3, and QF2 is used to connect to the high-voltage pre-charging cabinet 4; there are a large number of switch cabinets 9 cooperating with the mains bus section 7, which are QF3, QF4, QF5...QFn from left to right, and QF3 is used to connect to the reactor cabinet 6.

[0037] 1QF is a fixed vacuum circuit breaker 41, R is a current limiting resistor 42, the fixed vacuum circuit breaker 41 is connected in parallel to both ends of the current limiting resistor 42, and 1QF and R together constitute a high-voltage pre-charging cabinet 4, which is used to limit the transformer excitation surge current and the charging current of the inverter when the inverter is powered on.

[0038] VFD is a high-voltage variable frequency power supply device 5, which includes a phase-shifting transformer 51, a power unit and a control system 52. The phase-shifting transformer 51 is a part of the high-voltage frequency converter. The phase-shifting transformer 51 is connected in series with the current-limiting resistor 42, and the power unit and the control system 52 are connected in series with the phase-shifting transformer 51. The capacity of the high-voltage variable frequency power supply device 5 is 10MVA, which meets the power generation capacity requirement.

[0039] L is a reactor 61, which is used to limit the grid circulation when the variable frequency power supply is connected to the grid, and avoid the impact on the frequency converter and the grid power supply; 2QF is a fixed vacuum circuit breaker 62, that is, a bypass switch. The reactor 61 is connected in series with the power unit and the control system 52, and the bypass switch is connected to both ends of the reactor 61. L and 2QF together constitute the reactor cabinet 6, which serves as the bypass reactor 61 after the high-voltage variable frequency power supply device 5 is connected to the grid.

[0040] It should be noted that the high-voltage frequency converter in the high-voltage frequency conversion power supply device 5 of the present invention adopts a multi-level topology structure in which several low-voltage power units are connected in series. Figure 2 The structure of the inverter can ensure that the voltage and current waveforms on its input and output sides are very close to sine waves, and the harmonic distortion rate is very small.

[0041] like Figure 2 As shown, the low voltage power unit is Figure 2 The right part of the low-voltage power unit includes units A1-An, units B1-Bn, units C1-Cn, Figure 2 The left side of is a phase-shifting transformer 51, and each low-voltage power unit corresponds to a phase-shifting transformer 51 connected in series.

[0042] The number of low-voltage power units of a high-voltage inverter is related to the voltage level on the output side. The configuration table is as follows:

[0043] Inverter output voltage level Power unit voltage level Number of power units in series 6kV 720V Level 5 10kV 720V Level 8

[0044] It should be noted that in the present invention, the input side power supply of the high-voltage variable frequency power supply device 5 is 10kV (or 6kV), the input frequency is 75-100Hz, and it is sent to the 10kV (or 6kV), 50Hz system bus through the power switch QF3 and the high-voltage pre-charging cabinet 4. The input side switch of the high-voltage variable frequency power supply device 5 is QF2, which supplies power to the high-voltage variable frequency power supply device 5, and the synchronous inductor 61 and its bypass circuit breaker 2QF configured on the output side of the high-voltage variable frequency power supply device 5. When the high-voltage variable frequency power supply device 5 receives the instruction to output a constant voltage and frequency to the 50Hz system bus, the high-voltage variable frequency power supply device 5 has a complete power supply disturbance-free grid-connected switching function. After meeting certain voltage difference and frequency difference thresholds, it automatically detects its phase and realizes the disturbance-free and 50Hz grid-connected function. This function has been built into the high-voltage variable frequency power supply device 5.

[0045] The variable frequency power supply has perfect output and self-fast disconnection, overcurrent, overvoltage, undervoltage, overheating and other protection functions. The protection action directly blocks the variable frequency output and can jump the upper power switch. At the same time, it has certain input side overcurrent, overvoltage, undervoltage and other protection functions. The protection action jumps the upper power switch and forms a perfect system protection together with the upper switch comprehensive protection.

[0046] The above is only a preferred embodiment of the present invention. The protection scope of the present invention is not limited to the above embodiments. All technical solutions under the concept of the present invention belong to the protection scope of the present invention. It should be pointed out that for ordinary technicians in this technical field, some improvements and modifications without departing from the principle of the present invention should also be regarded as the protection scope of the present invention.

Claims

1. A power generation and distribution topology circuit structure for grid connection using a high-voltage variable-frequency power supply, characterized in that: The circuit structure comprises a power generation bus section (1), a power generation bus section PT and a lightning arrester (2), a high-speed AC generator (3), a high-voltage pre-charging cabinet (4), a high-voltage variable frequency power supply device (5), a reactor cabinet (6), a mains bus section (7), a mains bus section PT and a lightning arrester (8), and a switch cabinet (9); The power generation bus section (1) is used for inputting a voltage of 6 kV or 10 kV and a frequency of 75-100 Hz, and is respectively connected to the power generation bus section PT and a lightning arrester (2) and two switch cabinets (9), one of which is connected to a high-speed AC generator (3), and the other switch cabinet (9) is connected to a high-voltage pre-charging cabinet (4), which is further connected to a high-voltage variable frequency power supply device (5), which is further connected to a reactor cabinet (6); The rated voltage of the mains bus section (7) is 6 kV or 10 kV, the frequency is 50 Hz, and it is respectively connected to the mains bus section PT and the lightning arrester (8), and at least three switch cabinets (9), one of which is connected to the reactor cabinet (6), and another of which is connected to the mains power supply system; Wherein, each switch cabinet (9) is provided with a withdrawable vacuum circuit breaker (10).

2. The power generation and distribution topology circuit structure for grid connection using a high-voltage variable-frequency power supply according to claim 1 is characterized in that: The high-voltage pre-charging cabinet (4) comprises a fixed vacuum circuit breaker (41) and a current-limiting resistor (42); A fixed vacuum circuit breaker (41) is connected in parallel to both ends of a current limiting resistor (42).

3. The power generation and distribution topology circuit structure for grid connection using a high-voltage variable-frequency power supply according to claim 2 is characterized in that: The high-voltage variable-frequency power supply device (5) comprises a phase-shifting transformer (51), a power unit and a control system (52); The phase-shifting transformer (51) is connected in series with the current-limiting resistor (42), and the power unit and control system (52) is further connected in series with the phase-shifting transformer (51).

4. The power generation and distribution topology circuit structure for grid connection using a high-voltage variable-frequency power supply according to claim 3 is characterized in that: The reactor cabinet (6) comprises a reactor (61) and a bypass switch, wherein the bypass switch is configured as a second fixed vacuum circuit breaker (62); The reactor (61) is connected in series with the power unit and the control system (52), and the bypass switch is connected in parallel to both ends of the reactor (61).

5. The power generation and distribution topology circuit structure for grid connection using a high-voltage variable-frequency power supply according to claim 3 is characterized in that: The high-voltage variable-frequency power supply device (5) is used for outputting a voltage of 6 kV or 10 kV and a frequency of 50 Hz.

6. The power generation and distribution topology circuit structure for grid connection using a high-voltage variable-frequency power supply according to claim 3 is characterized in that: The capacity of the high-voltage variable-frequency power supply device (5) is 10MVA.

Images