mysql stopped working. What is the reason?

Question

MySQL

Hello, worked under openserver and mysql. At one point, sites on the local site stopped loading at all, and then the server itself stopped starting.
Here's what's in the logs:

190626 14:34:56 [Note] c:\openserver\modules\database\MySQL-5.5\bin\mysqld.exe (mysqld 5.5.45-log) starting as process 6364 ...
190626 14:34:56 [Note] Plugin 'FEDERATED' is disabled.
c:\openserver\modules\database\MySQL-5.5\bin\mysqld.exe: Table 'mysql.plugin' doesn't exist
190626 14:34:56 [ERROR] Can't open the mysql.plugin table. Please run mysql_upgrade to create it.
190626 14:34:56 InnoDB: The InnoDB memory heap is disabled
190626 14:34:56 InnoDB: Mutexes and rw_locks use Windows interlocked functions
190626 14:34:56 InnoDB: Compressed tables use zlib 1.2.3
190626 14:34:56 InnoDB: Initializing buffer pool, size = 20.0M
190626 14:34:56 InnoDB: Completed initialization of buffer pool
190626 14:34:56 InnoDB: highest supported file format is Barracuda.
InnoDB: Log scan progressed past the checkpoint lsn 463248949
190626 14:34:56  InnoDB: Database was not shut down normally!
InnoDB: Starting crash recovery.
InnoDB: Reading tablespace information from the .ibd files...
InnoDB: Restoring possible half-written data pages from the doublewrite
InnoDB: buffer...
InnoDB: Doing recovery: scanned up to log sequence number 463250320
190626 14:34:57  InnoDB: Starting an apply batch of log records to the database...
InnoDB: Progress in percents: 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60 61 62 63 64 65 66 67 68 69 70 71 72 73 74 75 76 77 78 79 80 81 82 83 84 85 86 87 88 89 90 91 92 93 94 95 96 97 98 99 
InnoDB: Apply batch completed
190626 14:34:58  InnoDB: Waiting for the background threads to start
190626 14:34:59 InnoDB: 5.5.45 started; log sequence number 463250320
190626 14:34:59 [Note] Server hostname (bind-address): '192.168.18.158'; port: 3306
190626 14:34:59 [Note]   - '192.168.18.158' resolves to '192.168.18.158';
190626 14:34:59 [Note] Server socket created on IP: '192.168.18.158'.
190626 14:34:59 [ERROR] Fatal error: Can't open and lock privilege tables: Table 'mysql.host' doesn't exist

Please help